Method and system for particulate filter regeneration

Abstract

A particulate filter regeneration system is provided for regenerating a filter at low vehicular speeds. The power source is selectively coupled to a transmission unit so that the transmission unit can be at least partially decoupled from the power source. An exhaust passage having a particulate filtering device is configured to release exhaust from the power source into the atmosphere. In addition, a controller is configured to determine at least one power source parameter indicative of an exhaust temperature, at least partially decouple the power source from the transmission unit in response to the determination, and increase a power source speed in response to the determination.

Description

TECHNICAL FIELD

The present disclosure is directed to a particulate filter system and, more particularly, to a particulate filter system having regeneration capabilities at low engine speeds.

BACKGROUND

Engines, including diesel engines, gasoline engines, natural gas engines, and other engines known in the art, may exhaust a complex mixture of air pollutants. The air pollutants may be composed of gaseous and solid material, which include particulate matter. Particulate matter may include unburned carbon particles, which are also called soot.

Due to increased attention on the environment, exhaust emission standards have become more stringent. The amount of particulates emitted from an engine may be regulated depending on the type of engine, size of engine, and/or class of engine. One method that has been implemented by engine manufacturers to comply with the regulation of particulate matter exhausted to the environment has been to remove the particulate matter from the exhaust flow of an engine with a device called a particulate filter. A particulate filter is a device designed to trap particulate matter and consists of a wire mesh medium or a porous ceramic substrate. However, the use of the particulate filter for extended periods of time may cause the particulate matter to build up in the wire mesh or porous ceramic substrate, thereby causing the functionality of the filter and engine performance to decrease.

The functionality of particulate filters can be improved by implementing regeneration. Regeneration is the process of increasing the temperature of the exhaust system until the organic components of the particulate matter such as the soot and the soluble organic fraction (SOF) that accumulated in the filter, burn off. If the engine exhaust does not reach the temperature required for regeneration within the filter, an additional component is necessary to raise the temperature within the filter. In some systems this component is an outside heat source that heats the filter media or the engine exhaust before it reaches the filter. Alternatively, a catalyst is sometimes used to lower the regeneration temperature necessary to oxidize the soot and the SOF. However, these additional components are expensive, inefficient, and unreliable.

U.S. Pat. No. 6,978,602, issued to Ohtake et al. (hereinafter the '602 patent) discloses a system that addresses the issues stated above. The '602 patent discloses temporarily increasing the engine idle speed if regeneration is required when the vehicle is stopped. By increasing the engine idle speed, the temperature and oxygen level of the exhaust that passes through the particulate filter are increased eliminating the need for additional components in situations where the vehicle is stopped.

While the method disclosed in the '602 patent may effectively reduce the need for additional components when the vehicle is stopped, increasing the engine idle speed may be problematic. In particular, while the engine is operating at idle speed, the operator must apply a braking force to keep the vehicle from moving. Increasing the idle speed requires a greater braking force, which in turn places a greater physical demand on the operator. Additionally, the increased braking force may increase the wear on the brakes. Furthermore, elevating the engine idle speed at low vehicular speeds may raise the vehicle's speed above the desired rate.

The disclosed particulate filter system is directed to overcoming one or more of the problems set forth above.

SUMMARY OF THE INVENTION

In one aspect, the present disclosure is directed toward a particulate filter regeneration system. The particulate filter regeneration system includes a power source selectively coupled to a transmission unit so that the transmission unit can be at least partially decoupled from the power source. In addition, the particulate filter regeneration system has an exhaust passage including a particulate filtering device configured to release exhaust from the power source into the atmosphere. Furthermore, the particulate filter regeneration system includes a controller configured to determine at least one power source parameter indicative of an exhaust temperature, at least partially decouple the power source from the transmission unit in response to the determination, and increase a power source speed in response to the determination.

Consistent with a further aspect of the disclosure, a method is also provided for implementing a particulate filter regeneration. The method includes sensing at least one power source parameter indicative of an exhaust gas temperature, sensing at least one power source parameter indicative of a power source speed, and sensing at least one machine parameter indicative of a travel speed of a machine. In addition, the method includes at least partially decoupling the power source from a transmission unit in response to at least the sensed parameter of the exhaust gas temperature, the sensed condition of the power source speed, and the sensed condition of the travel speed of the machine. Furthermore, the method includes increasing the power source speed in response to the sensed condition of the exhaust gas temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic illustration of an exemplary disclosed machine;

FIG. 2 is a diagrammatic illustration of an exemplary disclosed power train for used with the machine of FIG. 1; and

FIG. 3 is a flow chart depicting an exemplary method of operating the power train of FIG. 2.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary machine 10 having multiple systems and components that cooperate to accomplish a task. The tasks performed by machine 10 may be associated with a particular industry such as mining, construction, farming, transportation, power generation, or any other industry known in the art. For example, machine 10 may embody a mobile machine such as the on-highway vocational vehicle depicted in FIG. 1, a bus, an off-highway haul truck, or any other type of machine known in the art. Machine 10 may include one or more traction devices 12 operatively connected to and driven by a power train 14.

Traction devices 12 may embody wheels located on each side of machine 10 (only one side shown). Alternatively, traction devices 12 may include tracks, belts or other known traction devices. It is contemplated that any combination of the wheels on machine 10 may be driven and/or steered.

Power train 14 may be an integral package configured to generate and transmit power to traction devices 12. In particular, as shown in FIG. 2, power train 14 may include a power source 16 operable to generate a power output, a torque converter 18, a transmission unit 20 connected to receive the power output and transmit the power output in a useful manner to traction devices 12, and a controller 22 configured to regulate the operation of power source 16, torque converter 18, and transmission unit 20 in response to one or more inputs.

Power source 16 may include an internal combustion engine having multiple subsystems that cooperate to produce mechanical or electrical power output. For the purposes of this disclosure, power source 16 is depicted and described as a four-stroke diesel engine. One skilled in the art will recognize, however, that power source 16 may be any other type of internal combustion engine such as, for example, a gasoline or a gaseous fuel-powered engine. One of the subsystems included within power source 16 may be an exhaust system 24. Other subsystems included within power source 16 may be, for example, a fuel system, an air induction system, a lubrication system, a cooling system, or any other appropriate system.

Exhaust system 24 may remove or reduce the amount of pollutants in the exhaust produced by power source 16 and release the treated exhaust into the atmosphere. Exhaust system 24 may include an exhaust passage 26 which may be in fluid communication with an exhaust manifold 28 of power source 16. Exhaust system 24 may also include after-treatment devices fluidly connected to exhaust passage 26, such as a particulate filter 30 and/or a catalytic device (not shown). Such catalytic devices may include NOx absorbers, SOx absorbers, HC catalysts, CO catalysts, and any other catalytic device known in the art.

Particulate filter 30 may be any general type of exhaust filter known in the art and may include any type of filter media (not shown) known in the art, such as, for example, a ceramic foam, ceramic, sintered metal, metal foam, silicon carbide, or silicon carbide foam. The filter media (not shown) may assist in removing particulate matter like soot, soluble organic fraction (SOF), and other pollutants produced by power source 16. The filter media (not shown) may be situated horizontally, vertically, radially, or in any other configuration allowing for proper filtration. Additionally, the filter media (not shown) may be of a honeycomb, mesh, mat, or any other configuration that provides an appropriate surface area available for filtering of particulate matter. Furthermore, the filter media (not shown) may contain pores, cavities, or spaces of a size that allow exhaust gas to flow through while substantially restricting the passage of particulate matter. In an alternate embodiment, the filter media (not shown) may contain heating elements capable of heating the filter media and the exhaust during a regeneration process.

Catalytic devices typically operate efficiently only within a certain temperature range. In addition, critical functions involving after-treatment devices such as the regeneration of particulate filter 30, require that the exhaust gas be above a threshold temperature. In order to monitor the temperature of the exhaust gas flowing through the after-treatment devices, a sensor 32 may be associated with exhaust passage 26 to sense a temperature of the exhaust gas. Sensor 32 may be any type of temperature sensor mounted within exhaust passage 26. For example, sensor 32 may embody a surface-type temperature sensor that measures a wall temperature of exhaust passage 26. Alternately, sensor 32 may be a gas-type temperature sensor that directly measures the temperature of the exhaust gas within exhaust passage 26. Sensor 32 may generate an exhaust gas temperature signal and send this signal to controller 22 via a communication line as is known in the art. This temperature signal may be sent continuously, on a periodic basis, or only when prompted to do so by controller 22.

As shown in FIG. 2, a sensor 34 may be fluidly connected to exhaust passage 26 downstream of particulate filter 30. Sensor 34 may be any type of mass air flow sensor such as, for example, a hot wire anemometer or a venturi-type sensor. Sensor 34 may be configured to sense the amount of exhaust flow passing through particulate filter 30. It is contemplated that sensor 34 and sensor 32 may be combined into one sensor configured to sense the temperature and flow of the exhaust gas. Sensor 34 may generate an exhaust gas flow signal and send this signal to controller 22 via a communication line (not shown) as is known in the art. This flow signal may be sent continuously, on a periodic basis, or only when prompted to do so by controller 22.

Power source 16 may be at least partially controlled with an operator input device 36 that is configured to indicate a level of demand for machine power output. Operator input device 36 may embody any device capable of providing an electric signal signifying a desired machine power output such as, for example, an operator movable pedal having a minimum position and being movable through a range of positions to a maximum position. A sensor (not shown), such as a switch or potentiometer, may be provided to sense the position of operator input device 36 and to produce a demanded machine power signal responsive to the device's position. The desired machine power signal may be directed through controller 22 to power source 16 to control a flow of air and/or fuel into power source 16. It is contemplated that a desired machine power output may be determined in an alternative manner if desired, such as, for example, by monitoring a fuel setting, a boost pressure, an exhaust temperature, a valve timing, an output torque, or any other suitable parameter of power source 16.

A sensor 38 may be associated with power source 16 to sense a rotational speed of power source 16. In one example, sensor 38 may embody a magnetic pickup type of sensor associated with a magnet embedded within a rotational component of power source 16 such as a crankshaft or flywheel. During operation of power source 16, sensor 38 may sense the rotating magnetic field produced by the magnet and generate a signal corresponding to the rotational speed of power source 16. Sensor 38 may generate a power source speed signal and send this signal to controller 22 via a communication line (not shown) as is known in the art. This speed signal may be sent continuously, on a periodic basis, or only when prompted to do so by controller 22.

Torque converter 18 may be a hydro-mechanical device configured to couple power source 16 to transmission unit 20. In particular, torque converter 18 may conduct pressurized fluid between the output of power source 16 and the input of transmission unit 20 to thereby drive transmission unit 20, while still allowing power source 16 to rotate somewhat independently of transmission unit 20. In this arrangement, torque converter 18 may selectively absorb and multiply the torque transferred between power source 16 and transmission unit 20 by either allowing or preventing slippage between the output rotation of power source 16 and the input rotation of transmission unit 20. It is contemplated that torque converter 18 may alternatively embody a non-hydraulic device such as, for example, a mechanical diaphragm clutch.

Transmission unit 20 may include numerous components that interact to transmit power from power source 16 to traction device 12. In particular, transmission unit 20 may be a multi-speed bidirectional mechanical transmission having a neutral gear ratio, a plurality of forward gear ratios, a reverse gear ratio, and one or more clutches 40. The clutches 40 may be selectively actuated to engage predetermined combinations of gears 42 to produce a desired output gear ratio. It is contemplated that transmission unit 20 may be an automatic-type transmission, with shifting based on a power source speed, a maximum selected gear ratio, and a shift map, or a manual-type transmission, with shifting between each gear 42 directly initiated by an operator. The output of transmission unit 20 may be connected to and configured to rotatably drive traction device 12 via output shaft 44, thereby propelling machine 10.

It is contemplated that transmission unit 20 may alternately embody a hydraulic transmission having one or more pumps and hydraulic motors, a hydro-mechanical transmission having both hydraulic and mechanical components, an electric transmission having a generator and one or more electric motors, an electromechanical transmission having both electrical and mechanical components, or any other suitable transmission. It is also contemplated that transmission unit 20 may alternately embody a continuously variable transmission such as, for example, an electric transmission having a generator and an electric motor, a hydraulic transmission having a pump and a fluid motor, or any other continuously variable transmission known in the art.

A gear selector (not shown) may be provided for indicating a desired transmission gear ratio and direction of travel. The gear selector may be any device capable of providing an electric signal indicating a desired gear ratio and direction of travel. For example, the gear selector may be a movable lever having a neutral position, a plurality of forward gear positions, and a reverse gear position. The desired gear ratio signal may be provided to controller 22. In an automatic-type transmission, as machine travel speed increases, controller 22 may effect gear shifting in accordance with a shift map until a maximum desired gear is reached. In a manual-type transmission, controller 22 may effect the exact gear change selected by the operator as the operator makes the selection. It is contemplated that the gear selector may alternately embody a mechanical device directly effecting gear shifting.

A sensor 46 may be associated with an output of transmission unit 20 to sense a travel speed of machine 10. In one example, sensor 46 may embody a magnetic pickup type of sensor associated with a magnet embedded within a rotational component such as output shaft 44 of transmission unit 20. During operation of machine 10, sensor 46 may sense the rotating magnetic field produced by the magnet and generate a signal corresponding to the travel speed of machine 10. Sensor 46 may generate a travel speed signal and send this signal to controller 22 via a communication line (not referenced) as is known in the art. This travel speed signal may be sent continuously, on a periodic basis, or only when prompted to do so by controller 22.

Controller 22 may embody a single microprocessor or multiple microprocessors that include a means for controlling the operation of power train 14. Numerous commercially available microprocessors can be configured to perform the functions of controller 22. It should be appreciated that controller 22 could readily embody a general machine microprocessor capable of controlling numerous machine functions, an engine microprocessor, or a transmission microprocessor. Controller 22 may include a memory, a secondary storage device, a processor, and any other components for running an application. Various other circuits may be associated with controller 22, such as power supply circuitry, signal conditioning circuitry, solenoid driver circuitry, and other types of circuitry.

INDUSTRIAL APPLICABILITY

The disclosed filter regeneration system may provide a reliable and inexpensive way to implement regeneration when the vehicle is idling or stopped. In particular, the disclosed filter regeneration system may eliminate the need for peripheral regeneration devices by adjusting the engine speed to produce the desired exhaust temperature necessary for regeneration. By fully or partially decoupling the transmission from the engine, the engine speed can be increased without affecting the travel speed of the vehicle. The operation of the filter regeneration system will now be explained.

Over time, soot produced by the combustion process may collect in particulate filter 30 and may begin to impair the ability of particulate filter 30 to store particulates. As is illustrated by the method disclosed in FIG. 3, at step 100, temperature sensor 32, flow sensor 34, engine speed sensor 38, and other sensors (not shown) may sense parameters of engine 16 and/or exhaust system 24. Such parameters may include, for example, engine speed, engine temperature, exhaust flow temperature, exhaust flow pressure, and particulate matter content. At step 102, controller 22 may use the information sent from the sensors in conjunction with an algorithm or other pre-set criteria to determine whether particulate filter 30 has become saturated and is in need of regeneration.

Step 104 may be performed if controller 22 has determined that particulate filter 30 has become saturated and is in need of regeneration. At step 104, travel speed sensor 46 may sense the traveling speed of vehicle 10. At step 106, controller 22 may use the information sent from travel speed sensor 46 in conjunction with an algorithm or other pre-set criteria to determine whether vehicle 10 is stopped or moving. If vehicle 10 is stopped, step 108 may be performed. If vehicle 10 is moving, step 110 may be performed.

At step 108, controller 22 may completely disengage engine 16 from transmission 20. This may be accomplished by not allowing clutch 40 to engage with gear 42. In an alternate embodiment, controller 22 may completely disengage engine 16 from transmission 20 by allowing torque converter 18 to completely disengage from the output rotation of engine 16 and/or the input rotation of transmission 20. It should be understood that while transmission 20 is completely disengaged from engine 16, controller 22 may continually analyze signals sent by the sensor (not shown) associated with operator input device 36. Controller 22 may determine whether vehicle 10 should begin moving based on the signals from the sensor (not shown) associated with operator input device 36. If controller 22 determines that vehicle 10 should begin moving, it may perform step 108 and partially couple engine 16 with transmission 20.

At step 110, controller 22 may partially disengage engine 16 from transmission 20. This may be accomplished by allowing at least one clutch 40 to slip while engaging with gear 42. The degree to which clutch 40 is allowed to slip may be determined by a combination of engine speed and vehicle travel speed. For example, controller 22 may increase the degree to which clutch 40 disengages from the gear 42 as the actual engine speed increases above the ideal engine speed for a given travel speed of vehicle 10. In an alternate embodiment, controller 22 may partially disengage engine 16 from transmission 20 by allowing torque converter 18 to slip between the output rotation of engine 16 and the input rotation of transmission 20.

After engine 16 has been partially or completely disengaged from transmission 20, step 112 may be performed. At step 112, controller 22 may increase the engine speed. While the engine speed is increasing, step 114 may be performed. At step 114, temperature sensor 32 may sense the temperature of the exhaust.

At step 116, controller 22 may analyze signals sent by temperature sensor 32 regarding the temperature of the exhaust gas. Based on this analysis, controller 22 may determine whether the desired exhaust temperature, e.g., 600 degrees Celsius, has been reached. In an alternate embodiment, it is contemplated that controller 22 may utilize other sensory input as a substitute for the temperature signal, if desired. Such input may be associated with various engine parameters, such as, for example, fuel consumption rate, engine throttle position, intake manifold temperature, boost pressure, fuel setting, air flow, and/or any other parameter known in the art. Controller 22 may receive and analyze this input to derive the exhaust gas temperature. If the desired temperature has not been reached, controller 22 may continue increasing the engine speed. However, if the desired exhaust gas temperature has been reached, then step 118 may be performed. At step 118, controller 22 may maintain the engine speed at its current level, facilitating the regeneration process.

At step 120, temperature sensor 32, flow sensor 34, engine speed sensor 38, and other sensors (not shown) may continually send signals to controller 22 regarding parameters of engine 16 and/or exhaust system 24. Such parameters may include, for example, engine speed, engine temperature, exhaust flow temperature, exhaust flow pressure, and particulate matter content. At step 122, controller 22 may use the information sent from the sensors in conjunction with an algorithm or other pre-set criteria to determine whether the regeneration process has removed a desired amount of particulate matter from particulate filter 30. If controller 22 determines that the desired amount of particulate matter has not been removed, then controller 22 may continue the regeneration process. However, if controller 22 determines that the desired amount of particulate matter has been removed from particulate filter 30, step 124 may be performed.

At step 124, controller 22 may lower the engine speed. At step 126, controller 22 may determine whether the engine speed has been lowered to the desired rate. This determination may be based on information sent from engine speed sensor 38 and travel speed sensor 46 in conjunction with an algorithm or other pre-set criteria. If controller 22 determines that the engine speed is above the desired engine speed, then controller 22 may continue lowering the engine speed. However, if controller 22 determines that the engine speed is at the desired rate, then step 128 may be performed.

At step 128, controller 22 may complete the regeneration process by coupling the engine to the transmission. This may be accomplished either by fully reengaging clutch 40 with gear 42 or reengaging torque converter 18 with engine 16 and transmission 20.

In an alternate embodiment, it may be contemplated that regeneration may commence according to a set schedule based on fuel consumption, hours of operation, and/or other variables.

Because the disclosed system disengages the transmission from the engine when the vehicle is stopped or idling during regeneration, particulate emissions may remain within regulations at all speeds without the use of additional components that are expensive, inefficient, and unreliable. Specifically, completely or partially disengaging the transmission from the engine at slow vehicular speeds or while stopped may ensure that the vehicle's speed will not increase above a desired rate as the engine speed increases. In addition, the physical demands placed on the operator might not increase because disengaging the transmission from the engine may eliminate the need to increase the braking force as the engine speed increases. Furthermore, because an increased braking force may not be needed, the wear on the brakes may be kept to levels expected during typical use.

It should also be understood that increasing the flow rate of the engine exhaust may help prevent heat-related damage to the particulate filter. During regeneration, the temperature inside the particulate filter may have a tendency to increase above safe levels. Without a means to dissipate the increased heat, the temperature of the filter may increase to point where it may be damaged. Increasing the flow rate of the engine exhaust provides a means to dissipate the buildup of heat inside the particulate filter and prevent the particulate filter from over-heating and ultimately becoming damaged.

It will be apparent to those skilled in the art that various modifications and variations can be made in the disclosed system without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents.

Claims

1. A particulate filter regeneration system, comprising:

a power source selectively coupled to a transmission unit so that the transmission unit can be at least partially decoupled from the power source;

an exhaust passage including a particulate filtering device and configured to release exhaust from the power source into the atmosphere; and

a controller configured to determine at least one power source parameter indicative of an exhaust temperature, at least partially decouple the power source from the transmission unit in response to the determination, and increase a power source speed in response to the determination.

2. The particulate filter regeneration system of claim 1, wherein the transmission unit includes a gear and an associated clutch configured to fully engage, partially engage, and fully disengage from the gear.

3. The particulate filter regeneration system of claim 2, wherein the clutch is configured to slip against the gear while partially engaged with the gear.

4. The particulate filter regeneration system of claim 3, wherein the clutch is configured to vary the degree of slippage against the gear.

5. The particulate filter regeneration system of claim 4, wherein the clutch is configure to vary the degree of slippage against the gear based on a power source speed.

6. The particulate filter regeneration system of claim 1, further including a torque converter wherein the torque converter is operationally connected to the output of the power source and the input of the transmission unit and is configured to selectively absorb a torque produced by the power source by allowing a slippage between the output of the power source and the input of the transmission unit.

7. The particulate filter regeneration system of claim 1, wherein the transmission unit is a hydro-mechanical transmission unit.

8. The particulate filter regeneration system of claim 1, wherein the transmission unit is an electromechanical transmission unit.

9. A method of implementing a particulate filter regeneration in a machine, comprising:

sensing at least one power source parameter indicative of an exhaust gas temperature;

sensing at least one power source parameter indicative of a power source speed;

sensing at least one machine parameter indicative of a travel speed of a machine;

at least partially decoupling a power source from a transmission unit in response to at least the sensed parameter indicative of the exhaust gas temperature, the sensed condition indicative of the power source speed, and the sensed condition indicative of the travel speed of the machine; and

increasing the power source speed in response to the sensed condition indicative of the exhaust gas temperature.

10. The method of claim 9, wherein the at least partially decoupling the power source from the transmission unit further includes partially disengaging a clutch associated with a gear of the transmission unit.

11. The method of claim 10, wherein the at least partially decoupling further includes partially decoupling the power source from the transmission unit when the sensed condition indicative of the temperature of the exhaust gas is below a threshold temperature.

12. The method of claim 11, wherein the threshold temperature is approximately 600 degrees Celsius.

13. The method of claim 9, wherein the at least partially decoupling the power source from the transmission unit further includes partially disengaging a torque converter from the power source.

14. The method of claim 13, wherein the at least partially decoupling further includes partially decoupling the power source from the transmission unit when the sensed condition indicative of the temperature of the exhaust gas is below a threshold temperature.

15. The method of claim 14, wherein the threshold temperature is approximately 600 degrees Celsius.

16. The method of claim 9, wherein the at least partially decoupling the power source from the transmission unit further includes completely disengaging the power source from the transmission unit.

17. The method of claim 16, wherein the at least partially decoupling further includes completely disengaging the power source from the transmission unit when the sensed condition indicative of the temperature of the exhaust gas is below a threshold temperature.

18. A method of implementing a particulate filter regeneration in a mobile machine, comprising:

determining that filter regeneration is necessary;

determining whether the machine is stopped or moving;

at least partially decoupling a transmission from an engine of the machine as a function of a degree of movement of the machine and the determination that filter regeneration is necessary; and

increasing an engine speed when the engine is at least partially decoupled from the transmission.

19. The method of claim 18, further including reducing the engine speed when a desired amount of particulate matter in the filter has been removed.

20. The method of claim 18, wherein an amount of increase in engine speed is a function of engine exhaust temperature.