WARM-UP METHOD AND SYSTEM FOR WARMING UP EXHAUST PURIFICATION CATALYST
A warm-up system for warming up an exhaust purification catalyst arranged in an exhaust passage of an engine equipped with a turbocharger. The warm-up system includes an electric motor coupled to a turbine of the turbocharger, and control device that operates the electric motor to apply counter torque to the turbine when the exhaust purification catalyst needs to be warmed up.
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The present invention relates to a warm-up method and system for warming up a catalyst for purifying exhaust gas, and more particularly, to a warm-up method and system capable of speeding up activation of the exhaust purification catalyst of an internal combustion engine equipped with a turbocharger.
BACKGROUND ARTA motor vehicle mounted with an internal combustion engine such as a diesel engine or a gasoline engine uses a catalytic converter containing a catalyst, for example, a three-way catalyst, for purifying the exhaust gas. The reducing ability of such an exhaust purification catalyst is activated at elevated temperatures, and therefore, temperature control is important for the proper functioning of the exhaust purification catalyst. Immediately after the start of the engine, however, the temperature of the exhaust gas is low, so that a certain period of time (warm-up time) is needed to activate the exhaust purification catalyst. To remove the drawback, various methods have been adopted so far, such as a method of using a heater to heat the exhaust purification catalyst and a method of setting a relatively high idling speed immediately after the start of the engine.
Meanwhile, some internal combustion engines are equipped with turbochargers with a view to increasing the engine output. The turbocharger is a device whereby the energy of the exhaust gas is recovered with the use of a turbine to drive a compressor so that compressed air may be supplied to the engine to increase the output. In turbocharged internal combustion engines, the catalytic converter containing an exhaust purification catalyst is generally arranged downstream of the turbocharger. As a consequence of such arrangement of the turbocharged internal combustion engine, the amount of heat supplied to the exhaust purification catalyst is liable to decrease because of the recovery of the exhaust energy by the turbocharger and the heat capacity of the turbocharger itself, requiring a relatively long warm-up time compared with internal combustion engines not equipped with turbochargers. In the case of the turbocharged internal combustion engine, therefore, it is important that the warm-up time be reduced as short as possible.
For example, Patent Document 1 identified below discloses turbocharger control means whereby a determination is made as to whether or not the catalytic converter needs to be warmed up, and when the warm-up of the catalytic converter is needed, the control means controls the rotating speed of the turbine such that a pressure difference between the exhaust gas flowing into the turbine and the exhaust gas flowing out of the turbine falls within a predetermined range. With the turbocharger control means, when the catalytic converter needs to be warmed up, the control means decreases the pressure difference between the exhaust gas flowing into the turbine of the turbocharger and the exhaust gas flowing out of the turbine so as to fall within the predetermined range, so that the resistance exerted by the turbine against the flow of the exhaust gas lessens, thereby decreasing the exhaust heat energy needed to rotate the turbine. Consequently, the consumption of the exhaust heat energy by the turbine is restrained. Since the exhaust gas of sufficiently high temperature can be supplied to the catalytic converter when the catalytic converter needs to be warmed up, the catalytic converter can be warmed up in a short time, thus improving the warm-up efficiency.
Prior Art Document
- Patent Document 1: Japanese Laid-open Patent Publication No. 2007-278252
The turbocharger control means disclosed in Patent Document 1 is, however, based on the technical concept that loss in the amount of heat generated by the internal combustion engine is reduced as small as possible so that the saved heat energy may be appropriated to the warm-up of the exhaust purification catalyst. There is naturally a limit to the extent to which the loss in the heat amount can be reduced. Also, complicated process is required to control the difference between the turbine inflow and outflow exhaust pressures to a level close to zero in a short period of time. Further, a certain length of time is needed to bring the difference between the turbine inflow and outflow exhaust pressures to a level close to zero, and there is a limit to the extent to which the warm-up time can be shortened.
The present invention was created to solve the above problems, and an object thereof is to provide an exhaust purification catalyst warm-up method and system whereby a warm-up time required to warm up an exhaust purification catalyst is shortened by employing a simple procedure, thus making it possible to speed up the activation of the exhaust purification catalyst.
Means for Solving the ProblemsThe present invention provides a warm-up method for warming up an exhaust purification catalyst arranged in an exhaust passage of an internal combustion engine equipped with a turbocharger, the warm-up method being characterized in that temperature of an exhaust gas in the exhaust passage is raised by applying counter torque to a turbine of the turbocharger.
When the counter torque is applied, the exhaust gas may be recirculated from an upstream side of the turbine back to a downstream side of a compressor of the turbocharger.
The turbocharger may include turbine flow rate adjusting means for adjusting a flow rate of the exhaust gas flowing into the turbine. In this case, when the counter torque is applied to the turbine, the turbine flow rate adjusting means may be controlled such that energy loss of the exhaust gas is lessened, or may be controlled such that the exhaust gas is recirculated from the upstream side of the turbine back to the downstream side of the compressor of the turbocharger.
The present invention also provides a warm-up system for warming up an exhaust purification catalyst arranged in an exhaust passage of an internal combustion engine equipped with a turbocharger, the warm-up system being characterized by comprising: load means coupled to a turbine of the turbocharger; and control means for operating the load means to apply counter torque to the turbine when the exhaust purification catalyst needs to be warmed up.
The control means may control the load means in accordance with an output of a sensor for detecting a rotating speed of the turbine or a pressure in the exhaust passage.
The warm-up system may further comprise: an exhaust gas recirculation device for recirculating an exhaust gas of the engine from an upstream side of the turbine back to a downstream side of a compressor of the turbocharger; and control means for operating the exhaust gas recirculation device to recirculate the exhaust gas when the exhaust purification catalyst needs to be warmed up.
Also, the warm-up system may further comprise: turbine flow rate adjusting means for adjusting a flow rate of the exhaust gas flowing into the turbine; and control means for operating the turbine flow rate adjusting means to lessen energy loss of the exhaust gas when the exhaust purification catalyst needs to be warmed up.
The warm-up system may further comprise: an exhaust gas recirculation device for recirculating the exhaust gas from the upstream side of the turbine back to the downstream side of the compressor of the turbocharger; turbine flow rate adjusting means for adjusting the flow rate of the exhaust gas flowing into the turbine; and control means for operating the exhaust gas recirculation device and the turbine flow rate adjusting means to recirculate the exhaust gas when the exhaust purification catalyst needs to be warmed up.
Effect of the InventionWith the exhaust purification catalyst warm-up method and system according to the present invention, when the exhaust purification catalyst needs to the warmed up such as at the start of the engine, the turbine of the turbocharger is applied with counter torque, so that the exhaust gas discharged from the internal combustion engine slows down and takes more time to travel, making it possible to raise the temperature of the exhaust gas in a portion of the exhaust passage between the internal combustion engine and the turbine. Accordingly, the exhaust gas of high temperature can be supplied to the exhaust purification catalyst, whereby the warm-up time is shortened and the exhaust purification catalyst is activated in a short time.
According to the present invention, counter torque has only to be applied to the turbine. Thus, complicated process such as pressure control is unnecessary; nevertheless, it is possible to activate the exhaust purification catalyst in a short time by means of a simple control procedure.
Embodiments of the present invention will be described below with reference to
The exhaust purification catalyst warm-up system illustrated in
The turbocharger 1 is a device whereby exhaust gas energy is recovered by means of the turbine 1t to drive a compressor 1c so that compressed air may be supplied to the engine 2 to increase the engine output. The compressor 1c has an inlet connected to an intake passage 6 for letting in air from the outside, and has an outlet connected to an engine-side intake passage 6e for supplying the compressed air to the engine 2. An intercooler for cooling the compressed air may be arranged in the engine-side intake passage 6e. The turbine 1t has an inlet connected to an engine-side exhaust passage 3e for conveying the exhaust gas discharged from the engine 2, and has an outlet connected to an exhaust passage 3 for emitting the exhaust gas to the outside.
The turbocharger 1 shown in
The turbine 1t is provided with a sensor 1s (e.g., rotary encoder or the like) for detecting the rotating speed of the turbine. The sensor 1s is electrically connected to the control means 5, and in accordance with the output from the sensor 1s, the control means 5 controls the electric motor 1m to generate counter torque such that the rotating speed of the turbine 1t becomes equal to a predetermined rotating speed. Since the start-up operation of the engine 2 is a rated operation, the amount of counter torque to be applied to the turbine 1t may be set in advance according to the type or size of the engine 2 or turbocharger 1, thereby omitting the sensor 1s.
The engine 2 is, for example, a diesel engine or gasoline engine mounted on a motor vehicle or the like. The amount of the compressed air to be supplied and the amount of the fuel to be supplied are controlled in accordance with operating conditions of the engine 2. Such control operation is carried out by an electronic control unit (ECU) mounted on the vehicle. Operation of the engine 2 is controlled by means of air-fuel ratio (air mass/fuel mass). During normal operation, for example, the air-fuel ratio is controlled to a ratio close to the stoichiometric air-fuel ratio (with which the reaction of oxygen in the air with fuel takes place with neither of the two being too much or deficient) to cause the exhaust purification catalyst 4 to function effectively. In some cases, the air-fuel ratio is controlled to a ratio (economical air-fuel ratio) higher than the stoichiometric air-fuel ratio in order to improve the fuel efficiency as well as to reduce toxic substances contained in the exhaust gas. Also, at the start of the engine 2, the air-fuel ratio is controlled to produce a relatively rich air-fuel mixture so as to increase the engine output. The electronic control unit (ECU) serves also as the control means 5 of the warm-up system of the present invention.
The exhaust purification catalyst 4 is, for example, a three-way catalyst. The three-way catalyst is a catalyst for removing toxic substances (mainly, hydrocarbons, carbon monoxide, and nitrogen oxides) contained in the exhaust gas. The exhaust purification catalyst 4 to be used in the present invention is, however, not limited to the three-way catalyst. The catalytic converter containing the exhaust purification catalyst 4 is provided with a detector 4s for detecting activation of the exhaust purification catalyst. The detector 4s is, for example, a thermometer or an oxygen concentration detector. Where a thermometer is used as the detector 4s, it is determined whether or not the temperature detected by the thermometer has reached a temperature at and above which the exhaust purification catalyst 4 is activated (in the case of the three-way catalyst, 200 to 300° C.). Since the temperature of the exhaust purification catalyst 4 is determined by the exhaust gas temperature, the detector 4s may be so positioned as to detect the temperature of the exhaust gas immediately upstream or downstream of the exhaust purification catalyst 4. On the other hand, where an oxygen concentration detector is used as the detector 4s, it is determined based on the output of the detector 4s whether or not the exhaust purification catalyst 4 is functioning properly. In this case, the detector 4s is preferably arranged immediately downstream of the exhaust purification catalyst 4. Alternatively, a detector for detecting the concentration of some other gas than oxygen, such as carbon dioxide, may be used.
The control means 5 is constituted by the aforementioned electronic control unit (ECU). The control means 5 is electrically connected with an ignition key 7 for starting the engine 2 and thus is capable of detecting the start of the engine 2. Also, the control means 5 is electrically connected with fuel supply means of the engine 2 to supply fuel to the engine 2 such that an air-fuel mixture formed in the engine 2 has a desired air-fuel ratio. Further, the control means 5 is electrically connected with the electric motor in to control the operation (start and stop, rotating speed, etc.) of the electric motor 1m. The control means 5 is also electrically connected with the detector 4s to determine whether or not the exhaust purification catalyst 4 has been activated. On detecting the start of the engine 2 as manipulation of the ignition key 7, the control means 5 couples the electric motor 1m and the turbine it together by a clutch and operates the electric motor 1m such that counter torque is applied to the turbine 1t. The amount of the counter torque applied to the turbine 1t by the electric motor in is controlled in accordance with, for example, the output of the sensor 1s. Also, the control means 5 determines on the basis of the signal from the detector 4s whether or not the exhaust purification catalyst 4 has been activated and, if the exhaust purification catalyst 4 is judged to have been activated, stops the electric motor 1m and disengages the clutch.
For the conventional warm-up system 1, an exhaust purification catalyst warm-up system was used which was equipped with an ordinary turbocharger having no electric motor coupled to its turbine. With the conventional warm-up system 1, the turbine rotating speed showed a curve F1, indicated by the dot-dash line in
For the conventional warm-up system 2, an exhaust purification catalyst warm-up system was used which was equipped with an electrically assisted turbocharger having an electric motor coupled to its turbine. With the conventional warm-up system 2, the turbine rotating speed showed a curve F2, indicated by the dot-dot-dash line in
With the exhaust purification catalyst warm-up system according to the present invention illustrated in
In the above description, the amount of the counter torque is controlled on the basis of the rotating speed of the turbine 1t. Alternatively, the pressure in the exhaust passage 3 (including the engine-side exhaust passage 3e) may be detected, and the amount of the counter torque applied to the turbine it may be controlled on the basis of the detected pressure, as described below.
In the first modification illustrated in
In the second modification illustrated in
Where the rotating speed of the turbine 1t is restrained, the rotating speed of the compressor 1c lowers, so that the amount of compressed air supplied to the engine 2 decreases. Since the amount of fuel supplied to the engine 2 is correspondingly decreased, the amount of heat energy retained by the exhaust gas lowers. Thus, it is generally thought that restraining the rotating speed of the turbine is not desirable as a means to accelerate the activation of the exhaust purification catalyst 4. The present invention is based on a knowledge contrary to the generally accepted thought, that is, the knowledge that although the amount of the exhaust heat energy imparted by the engine 2 lowers, the use of the turbine 1t as the resistance to the exhaust gas flow makes it possible to effectively raise the temperature of the exhaust gas in a short period of time by accumulating the exhaust heat energy generated by the engine 2. According to the present invention, therefore, not only the activation of the exhaust purification catalyst 4 can be accelerated but the fuel efficiency of the engine 2 can be improved. Also, since the exhaust purification catalyst 4 can be activated in a short time, the heat or thermal mass of the exhaust purification catalyst 4 may be small. Accordingly, the amount of the exhaust purification catalyst 4 used can be reduced, making it possible to cut down costs and also to further shorten the warm-up time.
Other embodiments of the present invention will be now described.
The second embodiment illustrated in
The third embodiment illustrated in
The fourth and fifth embodiments illustrated in
The fourth embodiment illustrated in
The fifth embodiment illustrated in
The sixth and seventh embodiments illustrated in
In the sixth embodiment illustrated in
In the seventh embodiment illustrated in
The present invention is not limited to the foregoing embodiments and may be modified in various ways without departing from the spirit and scope of the invention. For example, in the second through seventh embodiments, the sensor 31 may be provided to detect the pressure in the exhaust passage 3, and in the sixth and seventh embodiments, the exhaust gas recirculation device and/or the turbine flow rate adjusting means (variable nozzle 1n, wastegate valve 1w, etc.) may be additionally used.
EXPLANATION OF REFERENCE CHARACTERS
- 1 turbocharger
- 1t turbine
- 1c compressor
- 1m electric motor
- 1s sensor
- 1n variable nozzle
- 1w wastegate valve
- 1g electric generator
- 2 engine
- 3 exhaust passage
- 3e engine-side exhaust passage
- 4 exhaust purification catalyst
- 4s detector
- 5 control means
- 6 intake passage
- 6e engine-side intake passage
- 7 ignition key
- 31 sensor
- 41 EGR passage
- 42 EGR valve
- 51 branch passage
- 52 bypass passage
- 61 storage battery
- 62 electrically operated booster
- 62c compressor
- 62m electric motor
Claims
1. A warm-up method for warming up an exhaust purification catalyst arranged in an exhaust passage of an internal combustion engine equipped with a turbocharger,
- wherein temperature of an exhaust gas in the exhaust passage is raised by applying counter torque to a turbine of the turbocharger.
2. The warm-up method according to claim 1, wherein the exhaust gas is recirculated from an upstream side of the turbine back to a downstream side of a compressor of the turbocharger.
3. The warm-up method according to claim 1, wherein the turbocharger includes a turbine flow rate adjusting device that adjusts a flow rate of the exhaust gas flowing in to the turbine, and the turbine flow rate adjusting device is controlled such that energy loss of the exhaust gas is lessened.
4. The warm-up method according to claim 1, wherein the turbocharger includes a turbine flow rate adjusting device that adjusts a flow rate of the exhaust gas flowing into the turbine, and the turbine flow rate adjusting device is controlled such that the exhaust gas is recirculated from an upstream side of the turbine back to a downstream side of a compressor of the turbocharger.
5. A warm-up system for warming up an exhaust purification catalyst arranged in an exhaust passage of an internal combustion engine equipped with a turbocharger, comprising:
- a load device coupled to a turbine of the turbocharger;
- and
- a control device that operates the load device to apply counter torque to the turbine when the exhaust purification catalyst needs to be warmed up.
6. The warm-up system according to claim 5, wherein the control device controls the load device in accordance with an output of a sensor for detecting a rotating speed of the turbine or a pressure in the exhaust passage.
7. The warm-up system according to claim 5,
- further comprising:
- an exhaust gas recirculation device for recirculating an exhaust gas of the engine from an upstream side of the turbine back to a downstream side of a compressor of the turbocharger; and
- a control device that operates the exhaust gas recirculation device to recirculate the exhaust gas when the exhaust purification catalyst needs to be warmed up.
8. The warm-up system according to claim 5,
- further comprising:
- a turbine flow rate adjusting device that adjusts a flow rate of an exhaust gas flowing into the turbine; and
- a control device that operates the turbine flow rate adjusting device to lessen energy loss of the exhaust gas when the exhaust purification catalyst needs to be warmed up.
9. The warm-up system according to claim 5,
- further comprising:
- an exhaust gas recirculation device for recirculating an exhaust gas of the engine from an upstream side of the turbine back to a downstream side of a compressor of the turbocharger;
- a turbine flow rate adjusting device that adjusts a flow rate of the exhaust gas flowing into the turbine; and
- a control device that operates the exhaust gas recirculation device and the turbine flow rate adjusting device to recirculate the exhaust gas when the exhaust purification catalyst needs to be warmed up.
Type: Application
Filed: Mar 25, 2009
Publication Date: May 12, 2011
Applicant: IHI CORPORATION (Tokyo)
Inventors: Masahiro Shimizu (Tokyo), Kazuhiko Shinagawa (Tokyo), Yoshiyuki Miyagi (Tokyo)
Application Number: 12/995,090
International Classification: F01N 3/10 (20060101); F01N 9/00 (20060101);