Further improved reversing flow catalytic converter for internal combustion engines

Abstract

A further improved compact reversing flow catalytic converter with protection from overheating includes an improved valve unit which directs exhaust gases through a container filled with catalytic material to permit a bypass of catalytic material when a temperature of the material exceeds a predetermined threshold. The container defines a U-shaped gas passage that communicates with two chambers at the top of the container. The improved valve unit is mounted to the top of the container and includes two container chamber extension cavities, an improved intake cavity and an improved exhaust cavity. The improved valve unit includes an improved valve flapper and two conjoined valve walls each wall with two openings therethrough. The improved valve flapper rotates around normal central axis between a first, a second and third positions. When overheating of the catalytic material is predicted, a controller relinquishes control of the improved valve flapper and an improved center return mechanism rotates the improved valve flapper to a third position, in which each of the valve openings communicates with both inlet and exhaust ports so that the exhaust gas flow bypasses catalytic material. A fuel injection system under control of the controller is used so that measured amounts of fuel can be injected into the container reaction core to enhance oxidation. The catalytic material is thus protected from damage due to overheating. The advantage is a compact, reliable, highly efficient further improved catalytic converter that is inexpensive to manufacture, durable, and adapted for extended service life. The improved valve may driven by a stepper motor that moves and holds the valve to its three positions including bypass, forward and reverse flow. An alternate version also replaces the oxidizing flow-through monolith with an oxidizing filter trap.

Description

The present invention relates to catalytic converters for internal combustion engines, and in particular, to a further improved reversing flow catalytic converter over that disclosed in U.S. patent application Ser. No. 11/218,608 filed Aug. 29, 2005 in the name of some of the inventors herein for treating exhaust gases from internal combustion engines.

BACKGROUND OF THE INVENTION

A problem relating to catalytic converters for internal combustion engines, such as the prior art reversing flow catalytic converter for internal combustion engines disclosed in U.S. Pat. No. 6,148,613, is overheating Lean burn combustion systems for fuel-efficient vehicles are particularly hard on exhaust after-treatment systems because excessive oxygen is always present in the exhaust. For example, the exhaust of diesel dual fuel (DDF) engines, which is one type of diesel engine, normally contains more than 5% volumetric oxygen after combustion. Under partial load the surplus of oxygen in the exhaust may be higher than 10% by volume. Under such circumstances, any engine management problems that result in excessive fuel in the exhaust, will generally damage exhaust after-treatment system due to overheating.

If a fuel management problem occurs, a large amount of the excess fuel delivered to the engine can pass through it and into the engine exhaust. That fuel will burn inside the catalyst if sufficient oxygen is available and the catalyst has reached catalytic temperature. For example, the complete burning of 2% of methane in the exhaust, can raise the temperature of exhaust gases by about 420° C., in addition to the 600° C. temperature of the exhaust as it is ejected from the engine. Consequently, the rate of temperature rise in the catalyst can reach 20 to 30° C./second, if the monoliths are metallic. Besides the catalytic burning of methane, any combustible matter such as soot accumulated on the catalyst surface, will also be rapidly oxidized under such high temperatures. The burning of accumulated soot will escalate and prolong the temperature rise. The thermal wave oscillation produced by the reverse flow process will also expedite the rise of the peak temperature of the catalyst substrate. Once the catalyst temperature reaches 1200° C., a metallic substrate will begin to soften and subsequently lose mechanical strength. Further temperature rise will cause collapse of the substrate and eventual melt-down will occur when it is heated to 1400-1450° C. A detrimental uncontrolled temperature rise can damage a catalyst in less than 20 seconds.

In the prior art, when a catalyst protection mode is required for a gasoline engine, an extremely rich fuel/air mixture is delivered to the engine. Since all oxygen is basically consumed inside the engine during the over-rich combustion process, the engine exhaust contains no oxygen. The large amount of excessive fuel from the engine pulls down the catalyst temperature. In this type of catalyst protection mode, however, the carbon monoxide content of the exhaust gas is undesirably very high.

However, for lean burn systems such as diesel or dual fuel engines, the excessive fuel will not cool down the catalyst temperature because of the presence of a high concentration of oxygen in the exhaust. Furthermore, lean burn systems cannot burn stoichiometric fuel/air mixtures because of knocking restrictions. For knock-free operation of a dual fuel engine, the original compression ratio of the baseline diesel engine requires the pre-mixed natural gas/air mixture to be generally leaner than λ=1.5.

As well, the concept of the reversing flow catalytic converter has been found to offer nearly continuous oxidation of exhaust components, mainly unburned hydrocarbons and carbon monoxide, when used after natural gas or dual fuel engines, in a 13 mode test cycle. For this reason, such a catalytic converter will likely not require supplementary heat added to the converter to maintain oxidation temperature. However, for a diesel engine there are fewer hydrocarbons and CO in the exhaust stream providing less fuel in the emissions. Engine fuel will need to be added to the exhaust stream during idle and low power operation of the engine in order to maintain an oxidation temperature sufficient to convert CO and hydrocarbons (including particulates), however, a considerably lesser amount of fuel than would be required by a conventional uni-directional oxidation catalyst. For this reason, addition of fuel can also result in overheating of the catalyst, if too much fuel is added.

U.S. Pat. No. 6,148,613 discloses a prior art reversing flow catalytic converter for internal combustion engines. Such device 10 includes a valve housing 14 which reversibly directs exhaust gases through a “U” shaped passage having a catalytic material therein. A valve disk 42 having two openings 48 therein rotates around a central axis, wherein in a first position of such rotatable valve disk 42 the exhaust gases enter the exhaust cavity from an exhaust pipe and pass through one of the openings in valve disk 42 into the “U” shaped passage. In the second position of the rotatable valve disk 42, the disk 42 and corresponding openings 48 therein are rotated 90° so that each opening 48 communicates with the same cavity within the valve housing 14, but a different one of the ports communicating with the U-shaped passage, so that gas flow through the u-shaped passage is thereby able to be reversed.

Disadvantageously, prior art devices such as the type disclosed in U.S. Pat. No. 6,148,613 lack a safeguard system to protect such reversing flow catalytic converter from overheating, as may arise under any one or more of the conditions explained above.

Further, there exists a need for a continuously oxidizing filter particulate trap for diesel engine exhausts.

An improved patent application Ser. No. 11/212,608 addresses the above problems and disadvantages and presents solutions and improvements.

The improved patent however, suffers from use of a rotating compact valve that is prone to having a high degree of friction drag due to its design and requirement for low leakage of exhaust gas across the valve. For each percent of exhaust gas leakage across the valve, the effectiveness of the destruction of exhaust methane or exhaust particulates diminishes by about one percentage point. Leakage and drag at the valve are reduced in this new invention by a re-configuration of the valve rotor and stator ports from being rotated as a sliding assembly perpendicular to and rotated about a shaft, to the rotor now being a symmetrical flapper and four stator ports now being fixed in the two conjoined inner valve walls parallel to the shaft intersecting each other at the center of the valve at the shaft area, and the rotor flapper being rotated about the shaft between two stator walls with four ports. The improved valve is divided into four cavities separated from each other by the internal valve walls The valve cavities extending from container chambers one and two and constrained between valve bottom ports one and two, the two valve inner walls, the outer wall and the cover plate are now better described as extended cavities to chambers one and two of the container. The valve cavities extending from the inlet and outlet piping ports and constrained by the valve top and bottom covers and between two valve walls are now better called inlet and outlet cavities through which the flapper moves to redirect flow as directed by the controller, actuator, spring return and rotor The rotor is now better described as a symmetrical flapper without ports and the stator is now better described as two pairs of conjoined walls intersecting at the center of the valve housing, each wall section having a valve port which the flapper covers two at a time while leaving the other two completely uncovered on a cyclic basis This type of valve action occurs with very little drag even at operating temperature, and the flapper is able to cover valve ports effectively and in this manner improve exhaust component destruction efficiency. The valve action of the flapper alternately covering two ports and uncovering the other two ports on a cyclic basis, is controlled by a temperature control system and has the effect of reversing the flow of exhaust gas cyclically flowing through the monolith in the container.

The improved patent application also suffers from a neutralizing spring return design with two compressed springs such that the spring return is not force-balanced at the shaft and therefore prone to shaft wear. Therefore an improvement is made to create a force-balanced spring return with the use of four compressed springs mounted in such a way as to balance out forces on the shaft that were prevalent with the original two spring design.

The improved patent application used diesel injection as required into the inlet pipe taking exhaust gases from the diesel engine into the valve and oxidation or filter monolith and also mentioned that injection of diesel was alternately possible into the space at the central core of the monolith. It is preferred to add diesel fuel within the central core since the heat in this area is prevalently greater than in the inlet to the monolith, giving greater opportunity for complete diesel vaporization within the core thereby effecting a greater oxidation efficiency of the added fuel.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide a further improved reversing flow catalytic converter system for treating exhaust gases from an internal combustion engine, which system includes an improved compact valve structure incorporated in the converter as well as an improved safeguard system to protect the catalyst and converter from overheating and including an improved method for monolith heat addition by diesel injection into the central core of the monolith.

Another object of the present invention is to provide a further improved reversing flow catalytic converter system for treating exhaust gases from an internal combustion engine which has a compact structure for efficient performance, minimal heat loss, and mechanical simplicity.

Yet another object of the present invention is to provide an improved three-way valve for a further improved reversing flow catalytic converter which overcomes the shortcomings of the prior art discussed above.

A further object of the present invention is to provide a further improved reversing flow catalytic converter having an improved bypass system to protect the further improved reversing flow catalytic converter from overheating.

A still further object of the present invention is to provide an improved three-way valve for a further improved reversing flow catalytic converter that is maintained in a neutral position to permit exhaust gases to bypass the further improved catalytic converter when the improved valve is not actuated.

A further object of the present invention is to optionally provide a further improved reversing flow catalytic converter with an oxidizing filter trap that may or may not be coated with catalytic material, to trap, hold and oxidize particulates, in place of the oxidation catalytic substrate within the further improved reversing flow catalytic converter.

A further object of the present invention is to provide a further improved reversing flow catalytic converter with an improved means of injecting a controlled amount of diesel engine fuel within the core of the further improved reversing flow catalytic converter, when required to maintain a continuous oxidation temperature. The catalytic converter monolith may or may not be coated with catalytic material, depending on the application and upon the amount of fuel normally present in the exhaust stream and additionally injected into the middle of the further improved reversing flow catalytic converter.

A still further object of the present invention is the provision of an improved force-balanced spring return design component such that the improved valve can be reliably and quickly returned to a neutral or bypass position upon detection of damaging impending temperatures within the monolith of the further improved reversing flow catalytic converter.

Accordingly, in one broad aspect of the invention, a further improved reversing flow catalytic converter for treating exhaust gases from an internal combustion engine is provided, comprising:

• • a container having a gas flow passage therein and a top end having a first chamber and a second chamber that respectively communicate with the gas flow passage;
  • a catalytic material in the gas flow passage adapted for contacting the exhaust gases that flow through the gas flow passage;
  • an improved valve for reversing an exhaust gas flow through the gas flow passage, including an improved valve housing with two extended valve cavities connecting to chambers one and two of the container and mounted to the top end of the container, an improved intake cavity and an improved exhaust cavity, the improved intake cavity adapted for connection to an exhaust gas pipe from said engine and the improved exhaust cavity adapted for connection to a tail pipe for egress of said exhaust gas from said converter; and
  • an improved valve component for reversing gas flow operably mounted to the improved valve housing, adapted to move between a first position in which the intake cavity communicates with the first valve opening and container chamber and the exhaust cavity communicates with the second valve opening and container chamber, a second position in which the intake cavity communicates with the second valve opening and container chamber and the exhaust cavity communicates with the first valve opening and container chamber, and a third position which allows the intake cavity to communicate with the exhaust cavity; and
  • a controller for controlling movement of the improved valve component between the first and second positions during normal operating temperatures for the further improved reversing flow catalytic converter and otherwise permitting movement of the improved valve component to the third position for abnormal operating temperatures.

Alternatively, in another aspect of such first aspect, the present invention comprises a further improved reversing flow catalytic converter for treating exhaust gases from an internal combustion engine is provided, comprising:

• • a container having a gas flow passage therein and a top end having a first chamber and a second chamber that respectively communicate with the gas flow passage;
  • a catalytic material in the gas flow passage adapted for contacting the exhaust gases that flow through the gas flow passage;
  • an improved valve for reversing an exhaust gas flow through the gas flow passage, including an improved valve housing with a bottom plate mounted to the top end of the container and containing two openings, one connecting to each of the first and second container chambers, and extended valve cavities within the valve connecting the container chambers to an improved intake cavity and an improved exhaust cavity, separated from the container chambers and associated extended valve cavity by two conjoined walls intersecting at the center of the valve housing, each wall section having an opening that allows communication between the container first and second chambers and connected extended valve cavities and the intake and exhaust cavities when the valve flapper is positioned to allow such communication. The improved intake cavity is adapted for connection to an exhaust gas pipe from said engine and the improved exhaust cavity is adapted for connection to a tail pipe for egress of said exhaust gas from said converter; and
  • an improved valve component for reversing gas flow operably mounted to the improved valve housing, adapted to the be moved between a first position in which the improved intake cavity communicates with the first chamber of the container through the first extended valve cavity and the improved exhaust cavity communicates with the second chamber of the container through the second extended valve cavity, a second position in which the improved intake cavity communicates with the second chamber of the container through the second extended valve cavity and the improved exhaust cavity communicates with the first chamber of the container through the first extended exhaust cavity, and a third position which allows the improved intake cavity to communicate with the improved exhaust cavity; and
  • a controller for controlling movement of the improved valve component between the first and second positions during normal operating temperatures for the further improved reversing flow catalytic converter and to the third position to permit bypass of exhaust gas without passing through said catalyst material during certain other temperatures for the further improved reversing flow catalytic converter.

Preferably, the improved valve housing has an interior cavity with two openings in the bottom plate and two transverse walls that divide the cavity into four parts, two parts that, with the outer wall and cover plate, respectively form cavity extensions of the container chambers one and two, and the other two parts that respectively connect to the engine exhaust valve inlet pipe and the engine tailpipe outlet pipe The improved valve component may include a flapper plate which is symmetrical and rotatably mounted to the center of the valve housing at the shaft, and rotates about a central axis that is perpendicular to the improved valve cover plate and the two openings therein that communicate with one of the inlet and exhaust cavities. The improved valve bottom plate has a first opening and second opening therethrough which communicate respectively with each of the two container chambers.

More preferably, the gas flow passage is formed within an interior chamber of the container, the interior chamber being separated by a transverse plate into two parts which respectively form a first chamber section and a second chamber section. The two sections communicate with each other, and each of the chamber sections communicates with one of the first and second valve openings. The container further comprises a gas permeable material which contains the catalytic material. The gas permeable material preferably comprises a plurality of monoliths having a plurality of cells extending therethrough, the monoliths being coated with a catalytic material.

According to a second aspect of the present invention, there is provided a further improved reversing flow catalytic converter for exhaust gases, the converter comprising a container which has a top end with a first chamber and a second chamber that are in fluid communication with each other so that the exhaust gases introduced into one of the first and second chambers flow through a catalytic material in the container. The improved valve structure comprises an improved valve housing including two openings in the bottom plate of the improved valve housing, opening one that connects to the first chamber of the container and opening two that connects to the second chamber of the container and two extended valve cavities, one connected to container chamber one through improved valve opening one and the other connected to chamber two through improved valve opening two, and an improved intake cavity and an improved exhaust cavity. The improved intake and exhaust cavities are separated from the container first and second chambers and their associated extended valve cavities by two conjoined walls that intersect at the center of the improved valve housing, each wall making two wall sections and each section containing one opening such that two of the four openings are blocked by the flapper alternately as dictated by the controller. The improved intake cavity is adapted for connection of an exhaust gas pipe and the improved exhaust cavity is adapted for connection of a tail pipe. An improved valve component is provided for reversing gas flow operably mounted in the valve housing. The improved valve is adapted to move the flapper between a first position in which the improved intake cavity communicates with the first container chamber through its associated extended valve cavity and the improved exhaust cavity communicates with the second container chamber through its associated extended valve cavity, and a second position in which the improved intake cavity communicates with the second container chamber through its associated extended valve cavity and the improved exhaust cavity communicates with the first container chamber through its associated extended valve cavity. The improved valve structure further includes an improved center return mechanism associated with the improved valve component for moving the improved valve component to a third position in which the improved intake cavity communicates with the improved exhaust cavity through the improved valve component when the improved valve component is not actuated to move to one of the first and second positions. Alternatively, the third position may be achieved by positive action of a controller and actuator.

According to a third aspect of the present invention, there is provided a further improved reversing flow catalytic converter for treating exhaust gases from an internal combustion engine. The catalytic converter includes a container having a gas flow passage therein and a top end having a first chamber and a second chamber which respectively communicate with the passage. A catalytic material is provided in the gas flow passage and contacts the exhaust gases which flow through the passage. The further improved catalytic converter has an improved valve for reversing the exhaust gas flow through the gas flow passage, including an improved valve housing with an improved intake cavity and an improved exhaust cavity, and two extended valve cavities mounted to the top end of the container. The improved intake cavity is adapted for connection of an exhaust gas pipe and the improved exhaust cavity is adapted for connection of a tail pipe. The improved valve also includes an improved valve component for reversing gas flow, operably mounted in the improved valve housing, and adapted to be moved between the first, second, and third positions.. In the first position, the improved intake cavity communicates with the first container chamber through its associated extended valve cavity and the improved exhaust cavity communicates with the second container chamber through its associated extended valve cavity In the second position, the improved intake cavity communicates with the second container chamber through its associated extended valve cavity and the improved exhaust cavity communicates with the first container chamber through its associated extended valve cavity. In the third position, the improved intake cavity communicates with the improved exhaust cavity. A controller controls movement of the improved valve component between the first and second positions, and movement of the improved valve component to the third position, if required to protect the catalytic material from overheating.

According to a fourth aspect of the present invention, a safeguard system is provided to inhibit overheating the further improved reversing flow catalytic converter. In addition to controlling the improved valve component for reversing flow bypass operation, the controller is also adapted to indirectly control fuel supply to the engine, in order to protect the catalytic material from overheating.

According to fifth aspect of the invention, there is provided a method for preventing overheating of the further improved reversing flow catalytic converter. The further improved reversing flow catalytic converter includes an improved valve adapted for connection of an exhaust gas pipe and a tail pipe, and associated with first and second ports of a container and their respective associated extended valve cavities for reversing exhaust gas flow through a catalytic material in the container. The method comprises steps of monitoring temperatures of the catalytic material, and controlling an improved valve mechanism to permit the exhaust gases to flow from the exhaust gas pipe to the tail pipe without passing through the catalytic material when the temperature of the catalytic converter exceeds a predetermined threshold. The method also preferably includes steps of calculating the rate of temperature rise in the catalytic material, and controlling the improved valve mechanism to permit the exhaust gases to flow from the exhaust gas pipe to the tail pipe without passing through the catalytic material when the rate of temperature rise exceeds a predetermined threshold. A further optional step adjusts engine operation to reduce total hydrocarbon and carbon monoxide volume in the exhaust gas flow.

The safeguard system in accordance with the present invention, protects the catalytic material from overheating when an abnormal rate of temperature rise is detected. The bypass of exhaust gases around the catalyst is the primary safeguard mechanism. During bypass, the exhaust gases do not flow through the monoliths in the catalytic converter. Thus, the inner catalyst is shielded from the flow of the fuel-oxygen mixture contained in the engine exhaust. Extensive testing has shown that once the exhaust flow to the catalyst is stopped by the improved bypass mechanism, the catalyst center temperature comes down quickly even if the exhaust gases are rich in both fuel and oxygen. However, if overheating occurs, the engine fuel supply is preferably adjusted to reduce the total hydrocarbon and carbon monoxide volume in the exhaust, as well as the temperature of the exhaust gases. In bypass mode, exhaust gases rich in fuel and oxygen will burn in the improved valve housing if the temperature of the improved valve housing is high enough The high temperature resulting from the burning of the fuel in the improved valve housing retards cooling of the catalyst, and may damage the improved valve structure. Therefore, control of the fuel supply is preferable when overheating occurs. Besides, in the bypass mode, the exhaust gases are not treated by the catalyst and therefore, the concentrations of hydrocarbons and carbon monoxide in the exhaust gas generally increases.

According to a sixth aspect of the invention, there is provided an option to replace the oxidation catalyst within the further improved reversing flow catalytic converter with a catalytic filter trap. In this variation of the reversing flow catalytic converter, a method is provided to entrap particulates and to hold them for a period of time to allow effective oxidation of the particulate matter when the trap is held at a continuous oxidation temperature by the temperature monitoring and control system. In this sixth aspect and as a second option, the oxidation catalyst may be replaced by a filter monolith that is not coated with catalyst.

According to a seventh aspect of the invention, there is provided a method by which diesel engine fuel may be injected through an injector valve that provides vaporized engine fuel into the central area of the further improved reversing flow catalytic converter within the flow redirection bowl. Diesel engine fuel passes into the flow redirection bowl through a bulkhead fitting into a coiled small diameter tubing section that provides sufficient heating surface to vaporize diesel fuel components into the flow redirection bowl. Diesel fuel is provided to the bulkhead fitting from a connecting pipe that connects a diesel fuel supply manifold that in turn receives diesel fuel supply from the high pressure diesel injector low pressure supply pump. The manifold contains the diesel injector, an associated flow orifice to control diesel flow, an associated check valve to block diesel flow during air purge and an associated strainer to filter diesel fuel within the manifold block before the injector. The manifold also contains an air injection solenoid valve that purges diesel fuel from the line downstream of the diesel injector by briefly injecting vehicle air into the diesel injection line when the engine is shut down. The method comprises of steps of monitoring temperature of the monolith material and controlling a fuel injector valve mounted on the flow redirection bowl of the further improved reversing flow converter to inject metered quantities of fuel required to maintain a preset oxidation temperature of the monolith material. The method includes the provision of a control interlock such that in the event of overheating for any reason, the power to the fuel injector valve will be locked out until the overheat condition is removed. Additionally, when an overheat event occurs, the engine fuel supply will be adjusted to reduce total hydrocarbons and carbon monoxide volume in the exhaust.

According to an eighth aspect of the invention, there is optionally provided, a three position valve and rotary stepper motor actuator which includes valve positions for; forward, reverse and bypass flow. In this aspect, the valve position is determined by a pneumatic or electric stepper motor that is driven by a control method similar to that described earlier for the reverse flow oxidizing catalytic converter, comprised of steps of monitoring temperature and rate of temperature rise of the oxidizing filter trap and controlling valve position such that exhaust gases are permitted to flow from the engine to the tail pipe without passing through the oxidizing filter trap when the temperature of the monolith exceeds a predetermined threshold. This is the third or bypass valve position

Other features and advantages of the invention will be more clearly understood with reference to the preferred embodiments described below.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described by way of example only, and with reference to the accompanying drawings, in which:

FIG. 1 is a side elevation view of the further improved reverse flow catalytic converter of the present invention which includes an improved bypass mechanism to control overheating of the catalytic material in the catalytic converter, an improved valve to operate with low drag and low leakage and an improved diesel fuel injection system;

FIG. 2 is a cross-sectional plan view taken along line A-A of the actuator 202 of FIG. 1 to show the structure of a rotary actuator for driving the valve;

FIG. 3a is a cross-sectional plan view taken along line B-B of the improved bypass mechanism 316 of FIG. 1 to illustrate an improved center return mechanism in a first position corresponding to that of the actuator shown in FIG. 2, and in dashed lines in a second position corresponding to a second position of the actuator shown in dashed lines in FIG. 2;

FIG. 3b is a cross-sectional plan view taken along line B-B of the improved bypass mechanism 316 of FIG. 1 to illustrate an improved center return mechanism in position for bypass mode corresponding to the actuator neutral position shown in dashed lines in FIG. 2;

FIG. 4a is a top plan view of the improved valve housing 301, showing the inlet and outlet piping with flanges and the actuator and improved spring return in a stack mounted at the center of the improved valve top cover plate.

FIG. 4b is a elevation view of the improved valve housing 301, showing the inlet and outlet piping with flanges and the actuator and improved spring return stack mounted on the improved valve top cover.

FIG. 4c is a bottom plan view of the improved valve housing 301 showing the improved valve bottom plate and its two openings to communicate with the two container chambers.

FIG. 5a is an elevational view of the oxidation catalyst or filter catalyst monolith of the further improved reverse flow catalytic converter showing the monolith and transverse separation wall of the inlet section of the can in dashed lines.

FIG. 5b shows the can top plan view of the can and monolith 302 (section E-E of FIG. 1) and FIG. 5c shows the bottom plan view of the can and monolith 302.

FIG. 6a shows the flow re-direction bowl 303 in elevational view with capillary tubing shown in dashed lines.

FIG. 6b shows the flow re-direction bowl 303 from its top plan view (section G-G of FIG. 1) showing the diesel injection capillary tubing and bulkhead fitting as well as an RTD mounted within the bowl.

FIG. 6c is a schematic showing the injection manifold 347 with its associated flow components.

FIG. 7 is a cross-sectional plan view (section C-C of FIG. 1) of the improved valve housing 301 with inlet and outlet openings in the valve cover plate superimposed in dashed lines and the flapper shown covering two wall ports.

FIG. 8a is an elevational cross-sectional view (section H-H of FIG. 7) showing wall sections 350 and 351 within the improved valve structure housing 301 in a first direction.

FIG. 8b is an elevational cross-sectional view (section J-J of FIG. 7) of the flapper 348 mounted within the improved valve structure housing 301 in a second direction.

FIG. 8c is an elevational cross-sectional view (section K-K of FOG. 7) showing wall sections 352 and 353 within the improved valve structure housing 301 in a second direction.

FIG. 9a is a bottom diagrammatic plan view of the bottom of the improved valve 301 showing exhaust flow paths for one position of the improved valve flapper in which exhaust gas from the engine enters the bottom inlet pipe and is redirected to the right hand side bottom plate valve opening and into the monolith and the flow that leaves the monolith enters the valve through the left hand opening of the improved valve bottom plate and is directed into the valve exhaust piping to the tail pipe. FIG. 9b is a similar improved valve 301 bottom view showing the flapper in the second position redirecting engine exhaust flow into the monolith on the left hand side and out of the monolith on the right hand side and into the valve exhaust opening into the tail pipe. FIG. 9c is a similar bottom plan view of the improved valve 301 with the flapper in the bypass position allowing direct communication from the engine exhaust to the tail pipe directly through the valve and bypassing the monolith.

FIG. 10 is a schematic plan for the control system 262 employed by the further improved reversing flow catalytic converter 300.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 illustrates a further improved catalytic converter 300 in accordance with an embodiment of the present invention which incorporates a safeguard system to inhibit overheating the catalyst monoliths, an improved valve assembly, an improved spring return and an improved monolith can and re-direction bowl with improved diesel fuel injection.

With reference to FIG. 1, the catalytic converter 300 comprises a improved container 302 and improved valve housing 301 with a similar function as described in U.S. patent application Ser. No. 11/212,608. A rotary actuator 202 and a center return mechanism 316 are mounted on the drive shaft 50 of the valve flapper parts 348 and 349. The rotary actuator 202 is controlled to periodically rotate the valve flapper parts 348 and 349 between the first and the second positions to reverse gas flow through the container 302.

As shown in FIG. 2, the rotary actuator 202 includes a housing 206 which encloses a pressure chamber 208. A moveable vane 210 is mounted to drive shaft 212 which is adapted to be connected to the shaft 50 of the valve flapper parts 348 and 349 to rotate together therewith. The housing 206 has a first opening 214 and a second opening 216 in the respective side walls of the housing 206 so that the moveable vane 210 rotates clockwise until it abuts a left stop member 218 when pressurized fluid is injected into the pressure chamber 208 through the first opening 214. This position of the moveable vane 210 corresponds to the first position of the valve flapper parts 348 and 349 as shown in FIGS. 7 and 9b, to permit the exhaust gases to flow through the container in a first direction. Similarly, the moveable vane 218 rotates counter clockwise until it abuts a right stop member 220, as shown in broken lines at the right side, when the pressurized fluid is injected into the pressure chamber 208 through the second opening 216. This position corresponds to the second position of the valve flapper parts 348 and 349, as shown in FIG. 9a, to permit the exhaust gases to flow through the container 302 in the opposite direction.

As shown in FIGS. 3a and 3b, the center return mechanism 316 includes a base block 323 having a circular bore 321 at an apex of triangular cavities 324 and 325. A swivel arm 322 is connected on both ends to a pivot shaft 358 that is rotatably mounted in the bore 321 of the base block. Four coil springs 317,318,319 and 320 are retained in the annular grooves 359 and 360, each is restrained between one end of the grooves 359 and 360 and one side of the swivel arm 322. A connector (not shown) is integrally formed with the pivot shaft 358, having a square cross-section adapted to receive a square top end of pivot shaft 212(not shown) of the rotary actuator 202. The swivel arm members 322 are adapted to swivel within the triangular cavities 324 and 325 and compress two of the springs 317, 318, 319 and 320 as they swivel. The other of the springs 317, 318, 319 and 320 are free to expand within the annular grooves. A cover 243 (not shown) is provided to retain the swivel arms 322 and springs 317, 318, 319 and 320 within the base block 323. When the pressure vane 210 of the rotary actuator 202 is at the left side, corresponding to the first position of the valve flapper 348 shown in FIGS. 7 and 9b, the swivel arm 322 of the center return mechanism 316 compresses springs 317 and 318. When the pressure vane 210 of the rotary actuator 202 pivots to the right side as shown in the broken line at the right side of FIG. 2, the valve flapper parts 348 and 349 are in the second position as shown in FIG. 9a. However, when the rotary actuator 202 is deactivated (no fluid pressure is applied to either side of the pressure vane 210), the swivel arm 322 of the center return mechanism 316 is forced by two of the springs 317 and 318, to return to the central position shown in FIG. 3b. This moves the pressure vane 210 of the rotary actuator 202 to the central position shown in broken lines in FIG. 2. It also moves the valve flapper parts 348 and 349 to the bypass position shown in FIG. 9c.

FIGS. 4a, 4b and 4c illustrate features of the improved valve housing. FIG. 4a is a plan view of the valve housing showing inlet flange 312 and inlet pipe 313 receiving exhaust gas from a diesel engine and outlet pipe 315 and outlet flange 314 discharging purified exhaust gas to the vehicle tail pipe. FIG. 4a also illustrates valve cover plate 310 and the two openings in the cover plate 329 and 328 allowing gas to pass into and out of the valve housing inlet and outlet compartments formed by valve interior walls 350, 351, 352 and 353 of FIG. 7 FIGS. 4a and 4b also show improved spring return 316 and actuator 202 mounted to the valve cover 310 and to each other by a bracket (not shown) and connected to shaft 50 that also connects to improved valve flapper parts 348 and 349 of FIG. 7. FIG. 4b also shows the outer improved valve outer assembly consisting of outer wall 330 that is welded to top flange 311 that fastens to valve cover plate 310 and valve bottom flange 309 that also is welded to outer wall 330.

FIG. 4c is is a bottom view cross-sectional along line D-D of FIG. 1 showing the valve bottom plate 309 and its two ports 326 and 327 that connect to can chambers 333 and 334 of FIG. 5b.

FIGS. 5a, 5b and 5c illustrate the further improved reversing flow catalytic converter can and substrate section 302. FIG. 5a is an elevational view of the can and substrate section 302 including can upper and lower flanges 308 and 306 respectively attached to wall section 331, and transverse wall section 335 in dashed lines and attached to flange 308 and wall 331 and sealed to the upper surface of monolith or substrate 336 surface also in dashed line. FIG. 5a also shows the preferred mountings of resistance temperature detectors (RTDs) 307, approximately ¼ and ½ of the way down the substrate on each side of the transverse wall and below the substrate 336 surface. FIG. 5b is a top plan view of the can or cross-sectional vied along line E-E of FIG. 1 showing the transverse wall 335 and the substrate 336 visible through can chamber openings 333 and 334. FIG. 5c is a bottom can or cross-sectional view along line F-F of FIG. 1 showing the exposed substrate 336 mounted flush with bottom flange 306.

FIGS. 6a, 6b and 6c illustrate the further improved reversing flow catalytic converter flow re-direction bowl 303 and diesel fuel injection capillary tubing 337 as well as a schematic showing the diesel injection block 347 with its integral components. FIG. 6a shows an elevational view of the flow re-direction bowl 303 comprised of flange 305 and bowl container 332. Also shown in FIG. 6a is a tubing bulkhead fitting 304, internal coiled tubing 337 in dashed lines supported by a bracket (not shown) and RTD 307. FIG. 6b is a plan view of cross-sectional area along line G-G of FIG. 1, showing flange 305 and bowl container 332, bulkhead fitting 304, coiled tubing 337 and RTD 307. The schematic shown in FIG. 6c reveals the manifold block 347 with internally mounted components; check valves 342, filter screen 340 and orifice 341. A diesel supply from the diesel fuel supply pump 345 enters the manifold block 347, is filtered by screen 340 before passing to a diesel injector valve 339 that is under control of converter controller 262 of FIG. 10 and then passing through a flow control orifice 341 and check valve 342 and thence out of the manifold block into tubing leading directly to bulkhead fitting 304. The manifold block 347 also contains flow passages tha direct air from vehicle air supply 346 directly to air purge solenoid 344 and then through check valve 343 and directly to tubing leading to bulkhead fitting 304. When the vehicle is shut down, the converter controller 262 will de-activate diesel injection solenoid 339 blocking diesel flow and briefly activate air purge solenoid 344 sufficient to clear diesel fuel from the tubing leading to bulkhead filling 304 and from capillary tubing 337 so that caking of the tubing is prevented.

FIG. 7 is a cross-sectional plan view along line C-C of FIG. 1 illustrating the internal wall system consisting of walls 350, 351, 352 and 353 that converge near the center of the valve and around valve shaft 50 that is connected to valve flapper sections 348 and 349. The angles subtended by the wall system are about 60 degrees in the directions of inlet opening 328 and outlet opening 329 in valve cover plate 311 and about 120 degrees in the directions of valve bottom plate 309 openings 326 and 327 that connect to can cavities 333 and 334 of FIG. 5b. As shown in FIG. 7, valve flapper section 348 completely covers the opening 354 of FIG. 8a in wall 350 and valve flapper section 349 completely covers the opening 356 of FIG. 8c in wall 352.

FIGS. 8a, 8b and 8c all illustrate cross-sectional elevations of the internal improved valve structure of wall sections and flapper sections. FIG. 8a shows the internal cross-sectional elevation along line H-H of FIG. 7 displaying wall sections 350 and 351 and wall openings 354 and 355 respectively. This view also shows top cover plate opening 329 that connects to the inlet pipe 313 and bottom plate opening 326 that connects to can inlet cavity 334 of FIG. 5b. FIG. 8b shows the valve internal cross-sectional elevation along line J-J of FIG. 7 displaying the flapper sections 348 and 349 with connected shaft 50 and wall sections 352 and 353 in behind the flapper sections and also showing wall openings 356 and 357 in dashed lines. In this illustration, the flapper section completely seals wall opening 356 in wall section 352 and completely uncovers wall section opening 357 in wall section 353. FIG. 5c shows the valve internal cross-sectional elevation along line K-K of FIG. 7 displaying wall sections 352 and 353 along with wall section openings 356 and 357 respectively. In the position of valve flapper sections 348 and 349 shown in FIG. 7, opening 356 of wall section 352 is completely sealed by flapper section 349 and opening 357 of wall section 353 is completely uncovered. With the valve flapper position shown in FIG. 7, engine exhaust gases enter the valve housing through opening 329 and then through wall opening 355 of wall section 351 and then through opening 326 of the valve bottom plate into can cavity 334 and into the oxidation or filter monolith 336 down the left hand side in FIG. 5b and then into the flow re-direction bowl 303 of FIG. 6a and then up and into the oxidation or filter monolith right hand side of FIG. 5b and into can cavity 333 and then through valve bottom plate opening 327 and then through opening 357 of wall section 353 and out of the valve housing through top valve cover opening 328.

FIGS. 9a, 9b and 9c illustrate the valve flapper sections 348 and 349 in their three positions, for respectively forward and reverse exhaust flow through the container 302 and for bypassing the oxidation or filter catalytic material. For clearer illustration, these figures illustrate only a bottom plan schematic view of the valve housing with valve bottom plate 309 removed exposing flapper sections 348 and 349, wall sections 350, 351, 352 and 353 and valve inlet opening 329 and valve outlet 328. The four wall sections divide the interior cavity of the valve housing 301 into the intake cavity and exhaust cavity, and into two other valve cavities that are essentially extensions of the two can cavities.

When the valve flapper sections 348 and 349 are in the first position as shown in FIG. 9a, the gas flow enters intake cavity from the inlet opening 329. The gas flow passes through the valve wall opening 355 in wall section 351 to enter the container through valve bottom plate opening 326 and disperse container cavity 334 and into the cells of the catalytic material above within the container on the left hand side of the transverse wall 335. After the exhaust gas flow is forced through the catalytic material it exits on the opposite side of the container transverse wall which is on the right hand side of the transverse wall 335, and passes first through second container cavity 333 and then through the valve bottom plate opening 327 to the exhaust cavity through wall opening 357 in wall section 353. The gas flow then exits through the outlet opening 328.

As shown in FIG. 9b, when the valve flapper sections are in the second position, it is rotated about 60° counter-clockwise so that the gas flow entering the intake cavity through the inlet opening 329 passes through valve wall opening 356 in wall section 352. Therefore the gas flow must enter the container through the valve bottom plate opening 327 and first move into container cavity 333 and exit the container through container cavity 334 and then through valve bottom plate opening 325 and through valve exhaust opening 328 so that the gas flow in the container is reversed, in comparison to the gas flow shown in FIG. 9a

If during the reversing flow operation of the further improved catalytic converter 300, the temperature of the catalyst material rises too quickly or is predicted to overheat the catalytic material, a controller places the catalytic converter in bypass mode. In bypass mode, the rotary actuator is deactivated by interrupting the pressurized fluid supply (not shown) or electric power Supply. When the rotary actuator 202 is deactivated, the swivel arm 322 of the improved center return mechanism 316 is forced by two of the springs 317, 318, 319 or 320, to return to its central position as shown in FIG. 3b. Thus, the center return mechanism 316 moves the valve flapper sections 348 and 349 to the third (bypass) position which is between the first and second positions, as shown in FIG. 9c. The valve flapper sections 348 and 349 are maintained in the third position until the rotary actuator 202 is reactivated. When the valve flapper sections 348 and 349 are in the third position, the valve wall openings 354, 355, 356 and 357 communicate with both the intake cavity and the exhaust cavity. Thus, the gas flow entering the intake cavity through the inlet opening 329 passes directly through the valve wall openings, enters the valve exhaust cavity, and exits the valve outlet opening 328. Even though the valve wall openings 354, 355, 356 and 357 communicate through the first and second valve bottom plate openings 326 and 327 with the container, the gas flow through the valve wall openings does not enter the container 302 because the gas pressure at the first valve bottom plate opening 326 is equal to the gas pressure at the second valve bottom plate opening 327. Thus, when the valve flapper sections 348 and 349 are in the third position, the exhaust gases bypass the container 302.

The further improved catalytic converter 300 described above with reference to FIGS. 1 through 9c is preferably controlled by a control system, a preferred embodiment of which is illustrated in FIG. 10. During normal engine operation and normal reverse flow catalytic converter operation, a controller 250 monitors the temperature of the catalytic material in the catalytic converter. Resistance temperature detectors (RTDs) 307 attached to the catalytic converter 302 and 303, or imbedded in the catalytic material, are preferably used to measure temperatures of the catalytic material.

As long as the temperature measured is within a predetermined range, the controller controls the rotary actuator 202 to achieve cyclic reverse flow through the catalytic converter by periodically rotating valve 301 so that the reverse flow valve 301 is moved between the first and second positions. If an abnormally sharp rise in temperature is detected, or if the temperature of the catalytic material rises above a threshold that will predictably damage the catalytic material, the controller 250 enters the bypass mode. During the bypass mode, the controller 250 deactivates the rotary actuator 202. When the rotary actuator 202 is deactivated, the improved center return mechanism 316 forces the reverse flow valve 301 into the third position to cause the gas flow to bypass the catalytic converter 302/303, as described above with reference to FIG. 9c.

Exhaust flow bypass is a first safeguard action to prevent damage to the reversing flow catalytic converter. Adjusting engine fuel supply is another. Therefore, when the controller enters bypass mode, it sends a signal to the engine controller 252. The engine controller responds to the signal by adjusting the engine fuel supply to reduce total hydrocarbon and carbon monoxide volume in the exhaust gases.

As seen in FIG. 10, an auxiliary catalytic converter 254 connected in series to the engine exhaust system downstream of the reverse flow catalytic converter 302/303 may be optionally installed During bypass mode, the controller 250 activates the valve 256 to direct the exhaust flow to pass through the auxiliary catalytic converter 254, which will oxidize at least a part of the carbon monoxide and hydrocarbons during the bypass mode. The auxiliary catalytic converter may be smaller and less expensive than the reversing flow catalytic converter 300.

A look-up table 258 may be accessed at the controller 250. The look-up table 258 stores data defining a dynamic limit of a rate of rise of the temperature of the catalytic converter 300. Each time the controller 250 samples the temperature of the catalyst using the RTDs 307, the controller 250 calculates the dynamic rate of rise in the temperature and compares the dynamic rate of rise in the temperature with entries in the look-up table 258, to obtain an early indication of overheating in the catalyst. The controller 250 must promptly respond to an indication of overheating in the catalytic material. The more quickly the controller 250 responds to the prediction of overheating in the catalytic converter, the better the catalyst is protected. A quick response will protect the washcoat from damage whereas a delayed response may only protect the monolith from meltdown. The control system therefore needs to be sensitive enough to protect the washcoat most of time and invariably prevent meltdown of the monolith substrate. However, over-sensitivity will trigger catalyst protection when it is not required. Frequent triggering of unwarranted catalyst protection will compromise engine performance in the case of engine management-systems and unnecessarily increase emissions in the case where bypass protection is used.

The control algorithm used by the controller 250 therefore determines when to enter bypass mode based on catalyst temperature thresholds. Appropriate setting of the temperature thresholds will safeguard the catalyst from overheating provided there is a slow climb in catalyst temperature. However, static temperature thresholds are not sufficient to prevent the catalytic washcoat from damage if operating conditions cause a serious fuel management problem. Serious fuel management problems may result in a sustained rate of temperature rise over 20-30° C./second. Due to the inherent delay in temperature sensing and processing, and a slight delay in the response of the bypass mechanism, an early prediction of overheating is required to protect the washcoat.

It should be noted that only catalyst temperatures are used to predict overheating by the control algorithm. The catalyst temperature and the rate of temperature rise in the catalyst temperature are used by the control algorithm. The engine exhaust temperature is not measured or considered, because exhaust temperatures vary at a much greater rate than catalyst temperature variation during normal engine operating conditions.

As an example, described below is a safeguard system for preventing overheating of a reversing flow catalytic converter used for a diesel/natural gas duel fuel engine.

Three Type-K thermocouples were installed in the catalytic converter, one at each side of the boundary layers, that is, inside the catalyst substrate, and a third one at the bottom center of the container structure. Type-K thermocouples are commonly used to measure temperatures of 0° to 1250° C. in various industrial processes. For balancing control of a catalyst flow-path temperature profile, two boundary thermocouples are preferred so that heat is measured more efficiently. For catalyst overheat protection, the two boundary thermocouples and the central thermocouple are required to provide early warning of any fuel management faults. The control algorithm used by the controller 250 provides the system with the following functionality:

• • The reverse flow mode is terminated when all three thermocouples measure catalyst temperatures lower than 300° C. When any one of the three thermocouples measure a catalyst temperature higher than 350° C., the reverse flow mode is turned on.
  • The controller continuously computes rates of temperature rise in the catalyst and compares each computed rate of rise with predetermined values in the look-up table 258. The controller 250 triggers the system into bypass mode if a rate of temperature rise listed in the look-up table is exceeded by a computed rate. After entering bypass mode, the reverse flow catalyst converter is bypassed, as explained above. A prediction that the catalyst is about to overheat also triggers the engine controller 252 to switch to diesel mode. This shuts off the natural gas fuel supply and causes the engine controller to begin self-diagnostics. The engine controller 252 is also preferably programmed to operate the engine in a special diesel mode, in which the diesel injection timing is advanced as compared to normal diesel mode in order to lower engine exhaust temperature The reverse flow mode is resumed after the catalyst has cooled down to a predetermined restart threshold, 580° C., for example. If each of thermocouples indicate temperatures that are lower than the restart threshold, and a catalyst damage flag has not been set, the reverse flow mode is resumed. The controller 250 sets a damage flag when any one of the thermocouples indicates a temperature that exceeds a temperature that might damage the catalyst. If a damage flag is set, the reverse flow mode is not resumed until the catalytic material has cooled to temperature below a predetermined threshold.

The effectiveness of the safeguard system is ensured by multiple thresholds and the combination of static and dynamic temperature tracking. A performance evaluation test for the safeguard system was conducted to test the effectiveness of the catalyst temperature control and the durability of control functionality under a wide range of engine and vehicle operating conditions, including fuel management system failures. Evaluation tests demonstrated that the safeguard system reliably activated each time the controller determined that protection mode was required. For slow temperature rise, the onset of the bypass mode was triggered by either inlet or outlet catalyst temperature readings exceeding the static temperature threshold. Test results showed that the onset of bypass mode almost immediately stopped monolith temperature rise under slow temperature rise conditions. If an abnormal rate of temperature rise triggers bypass mode, the onset of bypass mode rapidly reduces and subsequently reverses the temperature rise. The tests indicted that the safeguard system reliably prevented meltdown of the catalyst under these conditions.

The protection of the catalyst washcoat is more difficult, mainly because of the narrow line between optimized working catalyst temperatures and washcoat damage temperatures. The catalyst tested worked best when bed temperatures were maintained between 580° and 640° C. and peaked at 720° C. Catalyst ageing is accelerated above 730° C. and reactivity deteriorated over 760° C. If high concentrations of hydrocarbons are present in the exhaust gases, a flame may be sustained in the valve housing for some time during bypass mode. Under such circumstances, the cavity of the valve housing is the hottest zone and conducts heat to the top of the monolith. However, the flame does not propagate to the inside of the catalyst because bypass mode stops gas flow through the catalyst. Rapidly adjusting the engine fuel supply provides improved protection for the washcoat.

The monolith material 336 of FIG. 5 can be either an oxidation substrate or a particulate filter substrate with or without a catalyst washcoat.. The replacement of the oxidation monolith with an oxidation particulate filter trap in FIG. 5 monolith 336. When used with a diesel engine, the oxidizing filter trap will trap and hold particulate matter to allow effective oxidation of the carbon kernel as well as the volatile organic fractions of the particulates.

In FIG. 6, the location and mounting of a fuel injection valve 339 is illustrated on a diesel injection manifold 347. For a dual fuel engine, it is not likely that supplementary fuel injection will be needed, but if it is deemed useful, the injector valve 339 will be one designed for gaseous fuel injection in time duration pulses. If the reverse flow oxidizing converter is to treat exhaust gases from a diesel engine, then the injector valve 339 will be one designed for diesel fuel injection as a fine mistor vapour. The injector valve 339 supply 345 and a manifold block 347 complete with filter 340, fuel flow control orifice 341 and check valve 342. The manifold block will also have an air purge system momentarily activated on engine shut down to clean out the diesel lines feeding the converter. An air supply 346 is connected to the manifold block 347 along with a check valve 343 and air purge solenoid 344. A wiring harness for power to activate the injector valve 339 and air purge solenoid 344 under command of the converter controller 250 shown in FIG. 10. Power will be applied to the injector valve 339 when the temperature profile is insufficient for oxidation and power will be locked off the injector valve 339 when the controller 250 is reacting to an overheat event. It is preferable to install diesel injector valve manifold diesel piping to bulkheads fitting 304 on the flow re-direction bowl 303. The air purge solenoid will normally not be activated and will only be momentarily activated on engine shutdown sufficient to blow all diesel fuel from the diesel injection circuit including coiled capillary tubing 337 within the flow re-direction bowl 303.

In the cases of both the oxidizing catalytic converter and the oxidizing catalytic filter, it may be feasible to reduce the amount of catalytic loading and maintain temperature at oxidizing levels by the use of incremental fuel injection by way of fuel injector valve 339. In the limit, with sufficient exhaust fuel injection, catalytic coating may not be required. The amount of catalytic material may be balanced against the amount of fuel consumed in a case by case assessment of each application

The control schematic of FIG. 10 shows a means of diesel injection with reverse flow controller 250 that can be used for the oxidizing converter or for the oxidizing particulate trap reverse flow controller. When the RTDs 307 detect a monolith temperature moving downward and approaching the catalytic light off temperature, the converter controller 250 will command the fuel injection valve 339 to pulse a metered volume of fuel into the converter re-direction bowl through bulkhead fitting 304. As the temperature moves upward from the added heat of the oxidizing fuel, the controller 250 will monitor the rate of temperature rise, and if below a selected threshold rate of rise, the controller will pulse more fuel into the converter. This action will continue until the monolith temperature is detected to be sufficiently above catalytic light off temperature to sustain continuous oxidation of particulate matter. Under conditions of catalyst overheat, the power to the fuel injector 339 will be disconnected until the overheat event is over. The control algorithm earlier described will act on both static temperature measurements and rate of temperature rise calculations for the oxidizing filter monolith in the same manner as for the oxidizing flow through catalyst monolith.

The advantages of the further improved catalytic converter described above are apparent. No plumbing is required between the converter unit and the valve unit, which makes the catalytic converter compact and inhibits heat loss between the valve and the catalyst. The valve flapper is rotated about a perpendicular axis, which provides a smooth and reliable valve operation in a minimum of space. The unique arrangement of the monolith improves catalyst life and conversion performance. And the reversing exhaust gas flow ensures maximum efficiency of conversion by keeping the catalyst material uniformly heated and in addition small incremental fuel additions help to increase catalytic activity for pollutant reduction. Furthermore, the safeguard system including the improved spring return mechanism used with the catalytic converter effectively safeguards the catalytic converter from damage due to overheating and effectively improves catalyst life. An additional advantage is the ability of the reverse flow catalytic converter to be optionally modified to work effectively and efficiently as a continuous oxidation particulate filter trap.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained. Various changes could be made in the above methods and constructions without departing from the scope of the invention, which is limited solely by the scope of the appended claims.

Claims

1. A further improved reversing flow catalytic converter for treating exhaust gases from an internal combustion engine comprising:

a container having a gas flow passage therein and a top end having a first chamber and a second chamber that respectively communicate with the gas flow passage;

a catalytic material in the gas flow passage adapted for contacting the exhaust gases that flow through the gas flow passage;

an improved valve for reversing an exhaust gas flow through the gas flow passage, including an improved valve housing with an improved intake cavity and an improved exhaust cavity, mounted to the top end of the container with extended cavities to container chambers one and two within the improved valve, the improved intake cavity adapted for connection to an exhaust gas pipe from said engine and the improved exhaust cavity adapted for connection to a tail pipe for egress of said exhaust gas from said converter; and

an improved valve component for reversing gas flow operably mounted to the improved valve housing, adapted to be moved between a first position in which the intake cavity communicates with the first container chamber through its associated extended valve cavity and the exhaust cavity communicates with the second container chamber through its associated extended valve cavity, a second position in which the intake cavity communicates with the second container chamber through its associated extended valve cavity and the exhaust cavity communicates with the first container chamber through its associated extended valve cavity, and a third position which allows the intake cavity to communicate with the exhaust cavity; and

a controller for controlling movement of the improved valve component between the first and second positions during normal operating temperatures for the catalytic converter and to the third to permit bypass of some exhaust gas without passing through said catalyst material during certain other temperatures for the further improved catalytic converter.

2. A further improved reversing flow catalytic converter as claimed in claim 1 wherein the improved valve housing comprises an enclosed cavity with two ports in a bottom thereof and two conjoined walls that divides the cavity into four compartments that respectively form the intake cavity, the exhaust cavity, a valve extension cavity to container chamber one and a valve extension cavity to container chamber two.

3. A further improved reversing flow catalytic converter as claimed in claim 2 wherein the improved valve component includes a flapper that is symmetrical and rotatably mounted to the improved valve housing by a shaft mounted at the openings in the center of the improved valve bottom and top cover plates thereof and rotates about a central axis that is normal to the flapper, the flapper being constrained to rotating between the improved valve walls that define the inlet and exhaust cavities, each wall having a first opening and second opening therethrough which communicate respectively with one of the container chambers and its associated extended valve cavity in each of the first and second positions, and one of the intake and exhaust cavities.

4. A further improved reversing flow catalytic converter as claimed in claim 2 wherein each of the first and second openings in the improved valve walls uncovered by the flapper in the third position communicate with both the intake cavity and the exhaust cavity so that the gas flow is not forced through the catalytic material in the container.

5. A further improved reversing flow catalytic converter as claimed in claim 4 wherein the flapper further comprises a drive shaft driven by an actuator means.

6. A further improved reversing flow catalytic converter as claimed in claim 5 wherein the actuator is activated by the controller to rotate the flapper between the first and second positions, and said third position.

7. A further improved reversing flow the catalytic converter as claimed in claim 6 wherein the flapper returns to and is maintained in the third position when the actuator is deactivated by the controller.

8. A further improved reversing flow catalytic converter as claimed in claim 2 wherein the gas flow passage is formed within an interior chamber of the container, the interior chamber being separated by a transverse plate that forms a first chamber and a second chamber, the first and second chambers communicating with each other, and each of the chambers communicating with the first and second ports of the improved valve housing.

9. A further improved reversing flow catalytic converter as claimed in claim 8 wherein the catalytic material is spaced below the first and second ports of the improved valve housing to form an empty chamber between the first and second ports and the catalytic material, the empty chamber being divided by the transverse plate into two separate compartments beneath the first and second ports of the improved valve housing, respectively, the improved valve housing of the improved valve being mounted to the top of the container in an orientation so that the container transverse plate is normal to the diametrical line that bisects the angle formed by the two conjoined improved valve walls that form the inlet and exhaust cavities within the improved valve housing.

10. A further improved reversing flow catalytic converter as claimed in claim 9 wherein the improved valve flapper is positioned between the transverse walls of the inlet and exhaust cavities, the improved valve flapper being normal to both transverse walls, and each of the two openings in each of the valve walls is smaller than a half section of each of the first and second ports of the valve bottom plate.

11. A further improved reversing flow catalytic converter as claimed in claim 10 further comprising a mechanism for accurately positioning the improved valve on the top of the container and removeably securing same.

12. A further improved reversing flow catalytic converter as claimed in claim 1 further comprising a sensor device for measuring temperatures of the catalytic material.

13. A further improved reversing flow catalytic converter as claimed in claim 7 further comprising an improved center return mechanism associated with the drive shaft of the flapper to maintain the flapper in the third position, and adapted to be overridden by the actuator.

14. A further improved reversing flow catalytic converter as claimed in claim 13 wherein the improved center return mechanism comprises of a four-spring mechanism in which uneven spring forces produce a torque adapted to rotate the drive shaft until the disk is in the third position.

15. A safeguard system for a further improved reversing flow catalytic converter to inhibit overheating of a catalytic material used to treat the exhaust gases from an internal combustion engine, the further improved reversing flow catalytic converter including:

a container having a gas flow passage therein and a top end having a first chamber and a second chamber that respectively communicate with the passage;

a catalytic material in the gas flow passage adapted to contact the exhaust gases which flow through the passage; and

an improved valve mechanism for reversing an exhaust gas flow through the gas flow passage, including an improved valve housing with an improved intake cavity, an improved exhaust cavity, an extended valve cavity to chamber one of the container and an extended valve cavity to chamber two of the container, mounted to the top end of the container, the improved intake cavity adapted for connection to an exhaust gas pipe of said engine and the improved exhaust cavity being adapted for connection to a tail pipe to permit egress of exhaust gases from said further improved converter, the improved valve mechanism further including an improved valve component for reversing gas flow operably mounted to the improved valve housing, the improved valve component being actuated by an actuator to move between a first position in which the improved intake cavity communicates with the first chamber of the container through its associated extended valve cavity and the improved exhaust cavity communicates with the second chamber of the container through its associated extended valve cavity, and a second position in which the improved intake cavity communicates with the second chamber of the container and its associated extended valve cavity and the improved exhaust cavity communicates with the first chamber of the container through its associated extended valve cavity, the system comprising:

at least one temperature sensor for measuring a temperature of the catalytic material in the container; and

a controller for controlling movement of the improved valve component between the first and second positions.

16. A safeguard system as claimed in claim 15 which provides for the movement of the improved valve component to a third position in which the exhaust gas flow bypasses the catalytic material in the container.

17. A safeguard system as claimed in claim 16 wherein the controller is adapted to activate the actuator to rotate the improved valve component for a normal reversing flow operation when the temperature of the catalytic material is above a first predetermined threshold.

18. A safeguard system is as claimed in claim 17 wherein the controller is adapted to activate the actuator and resume normal reversing flow operation when the temperature of the catalytic material drops below a second predetermined threshold.

19. A safeguard system as claimed in claim 16 further comprising an improved center return mechanism for moving the improved valve component to and maintaining the improved valve component in the third position when the controller deactivates the actuator.

20. A safeguard system as claimed in claim 19 wherein the controller is adapted to deactivate the actuator to stop the normal reversing flow operation and send a signal to an engine controller to adjust the fuel supply to the engine when a rate of rise of the temperature of the catalytic material is higher than a predetermined threshold retrieved from a look-up table.

21. A safeguard system as claimed in claim 20 wherein the controller is adapted to deactivate the actuator to stop normal reversing flow operation and send a signal to an engine controller to adjust the fuel supply to the internal combustion engine when the temperature of the catalytic material exceeds a third predetermined threshold.

22. A safeguard system as claimed in claim 21 further comprising an auxiliary catalytic converter connected thereto for treating the exhaust gases only when the exhaust gases bypass the further improved reverse flow catalytic converter.

23. A method for preventing overheating of a catalytic material in the further improved reversing flow catalytic converter which is used for treating exhaust gas from an internal combustion engine which further improved converter includes an improved valve for controlling an exhaust gas flow through a catalytic material in the container, the method comprising:

monitoring a temperature of the catalytic material; and

controlling the exhaust gas flow to bypass the catalytic material when the temperature of the catalytic material is predicted to cause overheating of the catalytic material.

24. A method as claimed in claim 23 further comprising a step of:

periodically measuring the temperatures of the catalytic material;

periodically calculating a rate of rise of the temperature of the catalytic material using the temperatures measured; and

controlling the exhaust gas flow to bypass the catalytic material when the rate of rise of the temperature of the catalytic material exceeds a pre-determined threshold.

25. A method as claimed in claim 24 further comprising a step of:

adjusting engine operation to reduce oxidyzable components in the exhaust gases when the rate of rise of the temperature of the catalytic material exceeds the predetermined threshold

26. A method as claimed in claim 25 further comprising a step of:

adjusting engine operation to reduce total hydrocarbon and carbon monoxide volume in the exhaust gases when the rate of rise of the temperature of the catalytic material exceeds the predetermined threshold.

27. A method as claimed in claim 24 wherein the predetermined threshold of the rate of rise of the temperature is determined by comparing a rate of temperature rise of the catalytic material and an instant temperature of the catalytic material with corresponding entries in a look-up table.

28. A method as claimed in claim 23 further comprising a step of:

adjusting engine operation to reduce total hydrocarbon and carbon monoxide volume in the exhaust gases when the rate of rise of the temperature of the catalytic material exceeds the predetermined threshold.

29. A method as claimed in claim 23 further comprising a step of:

directing the exhaust gases through in an auxiliary catalytic converter when the exhaust gases bypass the further improved reverse flow catalytic converter.

30. A method as claimed in claim 23 further comprising a step of:

actuating and resuming normal control of the exhaust gas flow through the catalytic material in the container when an instant temperature of the catalytic material drops below the predetermined threshold.

31. An improved valve structure for a further improved reversing flow catalytic converter for exhaust gases, the further improved converter having a container which has a top end with a first chamber and a second chamber which are in fluid communication with each other so that the exhaust gases introduced into one of the first and second chambers flows through a catalytic material in the container, comprising:

an improved valve housing including an improved intake cavity, an improved exhaust cavity, a valve cavity extension to chamber one of the container and a valve cavity extension to hamber two of the container, adapted to be mounted to the top end of the container, the improved intake cavity adapted for connection to an engine exhaust gas pipe of said engine and the improved exhaust cavity being adapted for connection to a tail pipe to permit egress of exhaust gases from said converter;

an improved valve component for reversing gas flow operably mounted in the improved valve housing, adapted to be moved between a first position in which the improved intake cavity communicates with the first container chamber through its associated extended valve cavity and the improved exhaust cavity communicates with the second container chamber through its associated extended valve cavity and a second position in which the improved intake cavity communicates with the second container chamber through its associated extended valve cavity and the improved exhaust cavity communicates with the first container chamber through its associated extended valve cavity.

32. An improved valve structure as claimed in claim 31 wherein the improved valve housing includes two conjoined transverse walls that divide the cavity into four compartments that respectively form the improved intake cavity, the improved exhaust cavity, the extended valve cavity to container chamber one and the extended valve cavity to container chamber two.

33. A valve structure as claimed in claim 32 wherein the improved valve component includes:

an improved valve flapper which is rotatably mounted to a bottom and a top plate of the valve housing, and rotates about a central axis that is normal to the improved valve flapper, the improved valve flapper rotating between the two conjoined walls defining the inlet and exhaust cavities and each of the two conjoined walls having a first opening and second opening therethrough which communicate respectively with each of the chambers of the container through their associated extended valve cavities, and one of the intake cavity and exhaust cavity of the valve housing.

34. An improved valve structure as claimed in claim 33 wherein the first and second chambers of the container are substantially semi-circular in plan view and the bottom plate openings of the improved valve housing are also substantially semi-circular in cross-section and oriented without offset with respect to the container chambers. Each of the four openings in the four wall sections of the two conjoined valve walls is positioned to communicate with only one of the container chambers through their associated extended valve cavities and one of the inlet or exhaust cavities when the valve flapper is in one of the first and second positions.

35. An improved valve structure as claimed in claim 34 wherein each of the openings in the improved valve conjoined wall system is adapted to communicate with both the intake port and the exhaust port when the valve component is in the third position.

36. An improved valve structure as claimed in claim 35 wherein the flapper further comprises a drive shaft affixed to the central axis, extending axially through the improved valve housing with one end projecting from the top of the improved valve housing.

37. An improved valve structure as claimed in claim 36 wherein the improved valve housing further comprises a mechanism for accurately positioning the valve housing on the top of the container and removebly securing the same.

38. An improved valve structure as claimed in claim 37 wherein the semi-circular shape of the extended valve container port cavities and the semi-circular shape of the container chambers are substantially similar, and each of the openings in the improved valve conjoined walls is slightly smaller than half the area of the semi-circular cross-section of the extended valve container ports in the bottom plate of the valve.

39. An improved valve structure as claimed in claim 38 further comprising a rotary actuator operablely associated with drive shaft at the projecting end, the rotary actuator being adapted to override the improved center return mechanism.

40. An improved valve structure as claimed in claim 39 wherein the improved center return mechanism includes a four-spring system in which uneven spring forces produce a torque adapted to rotate the drive shaft until the flapper is in the third position.

41. An improved valve structure as claimed in claim 39 wherein the improved valve component includes:

an improved center return mechanism associated with the improved valve component for moving the improved valve component to and maintaining the improved valve component in a third position in which exhaust gases are conveyed from the intake cavity to the exhaust cavity without passing through the catalytic material.

42. A further improved reversing flow catalytic converter incorporating the safeguard system as claimed in one or more of claims 15-30.

43. A further improved reversing flow catalytic converter incorporating the improved valve structure as claimed in claims 31-37.

44. A further improved revering flow catalytic converter incorporating the improved valve structure as claimed in claim 31, said further improved converter having a container that has a top end with a first chamber and a second chamber that are in fluid communication with each other so that the exhaust gases introduced into one of the first and second chambers flow through a catalytic material in the container and pass out of the container through the other second or first chamber, is substantially described.

45. A further improved reversing flow catalytic converter as claimed in claim 1 wherein the catalytic material is optionally a catalytic filter trap monolith

46. A further improved reversing flow catalytic converter as claimed in claim 45 wherein a fuel injector is affixed to a fuel manifold and diesel fuel is injected from the manifold into the container flow redirection bowl and pulses fuel into the reactor core for vaporization with time duration pulses provided from a controller with an algorithm that is based on measuring monolith static temperature and on calculating monolith rate of temperature change and reacting to increase monolith temperature by the addition of fuel when determined necessary as dictated by the algorithm.

47. A further improved reversing flow catalytic converter as claimed in claim 46 wherein the fuel injector is mounted on a manifold and the manifold also contains a fuel strainer and flow control orifice for restricting fuel flow and the manifold receives a fuel supply from the low pressure fuel supply pump feeding the diesel injector pump.

48. A further improved reversing flow catalytic converter as claimed in claim 47 wherein the fuel injector is mounted on a manifold along with a purge air supply solenoid and check valve connected such that when the engine is shut down, a pulse of vehicle air blows diesel fuel out of the injection line to prevent caking.

49. A further improved reversing flow catalytic converter as claimed in claim 45 wherein the catalytic material is optionally replaced by a filter monolith without catalytic coating.

50. A further improved reversing flow catalytic converter as claimed in claim 49 wherein a circular bottom plate is attached to the valve bottom and has two semi circular and diametrically opposed ports each subtended by an approximately 120 degree angle of opening and the openings extend from near the bottom plate center, to the inner radius of the bottom plate with the orientation of the center line diameter bifurcating the center of the two 120 degree ports being at right angles to the container transverse wall such that each port communicates only with one side of the container as divided by the container transverse plate.

51. A further improved reversing flow catalytic converter as claimed in claim 50 wherein the improved valve structure is mounted on the container in such a way that a diametrical line bifurcating the two conjoined walls defining the inlet and exhaust cavities of said improved valve structure is at normal angle, as guided by positioning pins in the container flange, to the container transverse wall.

52. A further improved catalytic converter as claimed in claim 50 wherein an improved valve flapper combined with four rectangular openings in the four wall sections of the two conjoined valve walls is provided, said walls separated at an approximately 60 degree angle of opening from the center of the valve and extending from the valve center to the valve outer wall in two diametrically opposed directions such that the flapper covers two ports when in either position one or position two and the valve port openings optimally are sealed by the flapper with minimum leakage when in cyclical operation and fully closed on either side.

53. A further improved reversing flow catalytic converter as claimed in claim 52 wherein the improved valve flapper is adapted to be rotated by a normal shaft that is connected at the flapper along the shaft length, and at the top end coupled to an electric stepper motor actuator that is attached to the improved valve structure and that rotates the valve flapper, as directed by the controller that activates the stepper motor actuator, to three operating positions, namely a position to permit:

forward flow

reverse flow

bypass flow

54. A further improved reversing flow catalytic converter as claimed in claim 53 wherein the stepper motor is a pneumatic stepper motor.

55. A further improved reversing flow catalytic converter as claimed in claim 54 wherein a controller provides power to move and position the valve flapper in each of the operating positions based on an algorithm embedded in the controller, the controller acting upon temperature measurements sent to it from sensors embedded in the filter monolith.

56. A safeguard system as claimed in claim 16 for the further improved reversing flow catalytic converter wherein the controller is adapted to move and position the improved valve flapper to a bypass position and send a signal to an engine controller to adjust the fuel supply to the internal combustion engine when a rate of rise of the temperature of the filter monolith is higher than a predetermined threshold retrieved from a look-up table embedded in the controller.

57. A safeguard system as claimed in claim 56 for the further improved reversing flow catalytic converter wherein the controller is adapted to move and hold the valve flapper to a bypass position and send a signal to an engine controller to adjust the fuel supply to an internal combustion engine when the temperature of the filter monolith exceeds a third predetermined threshold.

58. A safeguard system as claimed in claim 57 for the further improved reversing flow catalytic converter further comprising an auxiliary catalytic converter connected thereto for treating the exhaust gases only when the exhaust gases bypass the further improved reversing flow catalytic converter.

59. A safeguard system as claimed in claim 57 for the further improved reversing flow catalytic converter wherein during an overheating event said system will cause power to be blocked from the fuel injector by an interlock between the controller and injector valve.

60. An improved valve structure as claimed in claim 37 wherein the semi-circular shape of the container cavities extends over a 180 degree angle and the semi-circular shape of the valve bottom plate openings extends over a 120 degree angle, and each of the openings in the valve walls is slightly smaller than half the area of the semi-circular cross-section of each valve bottom plate port, the openings in the walls being oriented at an angle of about 60 degrees with respect to each other, this being the flapper travel zone.