Controller for exhaust purification device of internal combustion engine

Abstract

To early increase a temperature of a catalyst located downstream of an electrically heated catalyst without using an air supply device such as an electric air pump.SOLUTION: A controller 100 for controlling an exhaust purification device of an internal combustion engine, comprises an electrically heated catalyst 12 provided in an exhaust passage 7 connected to an internal combustion engine 1, and a catalyst 14 provided in the exhaust passage 7 and located downstream of the electrically heated catalyst 12. The controller comprises control means 102, 103, and 104 for controlling the internal combustion engine to start heating the electrically heated catalyst 12 and close a throttle valve 8 provided in an intake passage 6 connected to the internal combustion engine 1 when the internal combustion engine 1 is started, and to open an EGR valve 20 provided in an EGR passage 18 that recirculates exhaust gas from the exhaust passage 7 to the intake passage 6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a control device for an exhaust gas purification device of an internal combustion engine.

Background Art

[0002] A vehicle equipped with an internal combustion engine is equipped with an exhaust gas purification device that purifies the exhaust gas discharged from the internal combustion engine. The exhaust gas purification device includes a catalyst that oxidizes and reduces toxic components contained in the exhaust gas. In order to promote oxidation and reduction by the catalyst, it is required to quickly bring the catalyst to the activation temperature.

[0003] Patent Document 1 discloses an exhaust gas purification device provided with an electric heating catalyst (EHC) in order to improve the exhaust gas purification performance immediately after the engine is started. In the exhaust gas purification device of Patent Document 1, a secondary air supply device (an electric air pump) is provided upstream of the electric heating catalyst, and secondary air is passed as a temperature medium through the electric heating catalyst heated before the engine is started, thereby raising the temperature of the three-way catalyst located downstream of the electric heating catalyst.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, for example, an electric air pump is provided as the secondary air supply device, which requires installation space, leads to a complicated structure, and may cause power consumption due to the drive of the electric air pump. It is preferable to be able to quickly raise the temperature of the catalyst located downstream of the electric heating catalyst without using an air supply device such as an electric air pump.

[0006] The present invention has been made in view of such circumstances, and an object thereof is to enable early temperature rise of a catalyst located downstream of an electric heating catalyst without using an air supply device such as an electric air pump.

Means for Solving the Problems

[0007] A control device for an exhaust gas purification device of an internal combustion engine according to the present invention is a control device for controlling an exhaust gas purification device of an internal combustion engine, the exhaust gas purification device including an electric heating catalyst provided in an exhaust passage connected to the internal combustion engine and a catalyst provided in the exhaust passage and located downstream of the electric heating catalyst. When starting the internal combustion engine, the control device includes control means for starting heating of the electric heating catalyst, closing a throttle valve provided in an intake passage connected to the internal combustion engine, and opening an EGR valve provided in an EGR passage for refluxing exhaust gas from the exhaust passage to the intake passage.

Effects of the Invention

[0008] According to the present invention, it becomes possible to raise the temperature of a catalyst located downstream of an electric heating catalyst at an early stage without using an air supply device such as an electric air pump.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0010] The control device 100 for an exhaust gas purification device of an internal combustion engine according to an embodiment of the present invention is a control device 100 that controls an exhaust gas purification device of an internal combustion engine including an electric heating catalyst 12 provided in an exhaust passage 7 connected to the internal combustion engine 1 and a catalyst 14 provided in the exhaust passage 7 and located downstream of the electric heating catalyst 12. When the internal combustion engine 1 is started, the control means 102, 103, 104 are provided to start heating the electric heating catalyst 12, close a throttle valve 8 provided in an intake passage 6 connected to the internal combustion engine 1, and open an EGR valve 20 provided in an EGR passage 18 that refluxes exhaust gas from the exhaust passage 7 to the intake passage 6. With this configuration, when the internal combustion engine 1 is started, the air warmed by the electric heating catalyst 12 passes through the catalyst 14 and heats the catalyst 14. As a result, the catalyst 14 can be heated at an early stage without using an air supply device such as an electric air pump, and the exhaust gas purification performance immediately after the start of the internal combustion engine 1 can be improved.

Example

[0011] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a diagram showing a schematic configuration of a vehicle equipped with an exhaust gas purification device (hereinafter referred to as an exhaust gas purification device) of an internal combustion engine according to an embodiment. FIG. 1 is simplified for convenience of explanation to describe this embodiment, and illustration of the configuration that a vehicle normally has is omitted. In the present application, the upstream and downstream are defined based on the flow of the exhaust gas of the engine 1. The vehicle according to the embodiment includes an engine 1 as an internal combustion engine, an exhaust gas purification device 2, an EGR (Exhaust Gas Recirculation) system 3, an ECM (Engine Control Module) 100, an EHC control device 4, a battery 5, and the like.

[0012] Engine 1 is a power source for driving a vehicle. Engine 1 generates power by expanding the gas generated when fuel is burned. An intake passage 6 for introducing an air-fuel mixture is connected to Engine 1. The intake passage 6 is composed of, for example, an intake pipe. Further, an exhaust passage 7 for exhausting the exhaust gas generated by burning the air-fuel mixture to the outside is connected to Engine 1. The exhaust passage 7 is composed of, for example, an exhaust pipe.

[0013] A throttle valve 8 is provided in the intake passage 6. The throttle valve 8 adjusts the intake amount of air introduced from an air cleaner (not shown) into Engine 1.

[0014] An exhaust purification device 2 for purifying the exhaust gas discharged from Engine 1 is provided in the exhaust passage 7. The exhaust purification device 2 includes an engine-side catalytic converter 9 and an underfloor-side catalytic converter 10.

[0015] The engine-side catalytic converter 9 is disposed downstream of Engine 1 and upstream of the underfloor-side catalytic converter 10. The engine-side catalytic converter 9 includes a case 11, an electric heating catalyst (EHC) 12, an upstream catalyst 13, and a downstream catalyst 14.

[0016] The case 11 holds the electric heating catalyst 12, the upstream catalyst 13, and the downstream catalyst 14. The case 11 is, for example, a long cylindrical shape along the vertical direction and is arranged such that the central axis is parallel to the vertical direction. Further, the case 11 has a tapered shape such that the upstream end tapers as it goes toward the upper end and the downstream end tapers as it goes toward the lower end. The upper end of the case 11 is connected to an exhaust pipe connected to Engine 1, and the lower end of the case 11 is connected to an exhaust pipe connected to the underfloor-side catalytic converter 10.

[0017] The electric heating catalyst 12 is a catalyst whose catalytic reaction is promoted by being heated by energization. The electric heating catalyst 12 is heated by being supplied with electric power from the battery 5 via the EHC control device 4. The electric heating catalyst 12 has a cylindrical shape and is disposed at the vertical center within the case 11. The electric heating catalyst 12 includes a pair of electrodes 15a and 15b. The electrode 15a is connected to the EHC control device 4, and the electrode 15b is connected to the ground.

[0018] The upstream catalyst 13 is a three-way catalyst that purifies by oxidizing and reducing the toxic components contained in the exhaust gas discharged by the engine 1. The upstream catalyst 13 has a cylindrical shape and is disposed adjacent to the upstream side of the electric heating catalyst 12 within the case 11. The downstream catalyst 14 is a three-way catalyst that purifies by oxidizing and reducing the toxic components contained in the exhaust gas discharged by the engine 1. The downstream catalyst 14 has a cylindrical shape and is disposed adjacent to the downstream side of the electric heating catalyst 12 within the case 11.

[0019] The underfloor catalyst converter 10 is disposed under the vehicle floor and is located downstream of the engine-side catalyst converter 9. The underfloor catalyst converter 10 includes a case 16 and an underfloor catalyst 17. The case 16 is, for example, a long cylindrical shape along the horizontal direction and is disposed such that the central axis is parallel to the horizontal direction. The end of the case 16 on the engine 1 side is connected to the exhaust pipe connected to the engine-side catalyst converter 9, and the end of the case 16 on the side opposite to the engine 1 side is connected to the exhaust pipe connected to a muffler (not shown). The underfloor catalyst 17 is a three-way catalyst that purifies by oxidizing and reducing the toxic components contained in the exhaust gas discharged by the engine 1.

[0020] The EHC control device 4 supplies the electric power of the battery 5 to the electric heating catalyst 12 according to the instruction of the ECM 100. The battery 5 supplies electric power to the electric heating catalyst 12. When the engine 1 is driven, a generator (not shown) generates electricity, and the battery 5 stores the generated electric power.

[0021] The EGR system 3 includes an EGR passage 18 that recirculates exhaust gas from the exhaust passage 7 to the intake passage 6. The EGR passage 18 is connected to the intake passage 6 downstream of the throttle valve 8 and is connected to the exhaust passage 7 downstream of the downstream catalyst 14 of the engine-side catalytic converter 9. A cooling device called an EGR cooler 19 is installed on the exhaust passage 7 side of the EGR passage 18, and a valve called an EGR valve 20 is installed on the intake passage 6 side. The EGR cooler 19 cools the recirculated gas. The EGR valve 20 adjusts the flow rate of the recirculated gas.

[0022] The ECM 100 controls the engine 1, the exhaust purification device 2, and the EGR system 3. The ECM 100 includes, for example, a CPU, a RAM, a ROM, etc. Programs and predetermined information for controlling the engine 1, the exhaust purification device 2, and the EGR system 3 are stored in advance in the ROM. The RAM is a work memory that temporarily stores programs and data. The ECM 100 functions as a control device that controls the engine 1, the exhaust purification device 2, and the EGR system 3 by the CPU executing the programs stored in the memory.

[0023] Fig. 2 shows the functional configuration of the ECM 100. In this embodiment, the ECM 100 functions as a control device for the exhaust purification device to which the present invention is applied. As described above, the ECM 100 also has a function as a control device for controlling the engine 1 and the EGR system 3, but Fig. 2 shows only the functional configuration as a control device for the exhaust purification device to which the present invention is applied. The ECM 100 includes a cranking detection unit 101, an EGR valve control unit 102, a throttle valve control unit 103, a heating control unit 104, and a catalyst temperature acquisition unit 105.

[0024] The cranking detection unit 101 detects the start of cranking of the engine 1. The EGR valve control unit 102 controls the opening and closing of the EGR valve 20. When the cranking detection unit 101 detects the start of cranking of the engine 1, the EGR valve control unit 102 fully opens the EGR valve 20. The throttle valve control unit 103 controls the opening and closing of the throttle valve 8. When the cranking detection unit 101 detects the start of cranking of the engine 1, the throttle valve control unit 103 fully closes the throttle valve 8. The heating control unit 104 controls the heating of the electric heating catalyst 12. When the cranking detection unit 101 detects the start of cranking of the engine 1, the heating control unit 104 starts heating the electric heating catalyst 12. The catalyst temperature acquisition unit 105 acquires the temperature of the electric heating catalyst 12 by measurement with a temperature sensor (not shown) or calculation using a temperature estimation model.

[0025] Figure 3 is a flowchart showing an example of the process executed by the ECM 100. The flowchart in Figure 3 is executed before the engine 1 starts. In step S1, it waits until the cranking detection unit 101 detects the start of cranking of the engine 1. When the start of cranking is detected, it proceeds to step S2. In step S2, the EGR valve control unit 102 fully opens the EGR valve 20, and the throttle valve control unit 103 fully closes the throttle valve 8. In step S3, the heating control unit 104 instructs the EHC control device 4 to supply power from the battery 5 to the electric heating catalyst 12, and starts heating the electric heating catalyst 12.

[0026] In step S4, the catalyst temperature acquisition unit 105 waits until the temperature of the electric heating catalyst 12 becomes equal to or higher than the threshold value. When the temperature of the electric heating catalyst 12 becomes equal to or higher than the threshold value, it proceeds to step S5. The threshold value is preset according to the activation temperature of the electric heating catalyst 12. Although it is determined whether the temperature of the electric heating catalyst 12 becomes equal to or higher than the threshold value, the catalyst temperature acquisition unit 105 may acquire the temperature of the downstream catalyst 14 and determine whether the temperature of the downstream catalyst 14 becomes equal to or higher than the threshold value. The threshold value in this case is preset according to the activation temperature of the downstream catalyst 14. Also, it may wait until the temperatures of both the electric heating catalyst 12 and the downstream catalyst 14 become equal to or higher than their respective threshold values.

[0027] In step S5, the ECM 100 starts the engine 1 and stops cranking. After the engine 1 is started, the ECM 100 may adjust the opening degree of the EGR valve 20 and the opening degree of the throttle valve 8 while monitoring the temperature of the electric heating catalyst 12. For example, by increasing the intake air volume, overheating of the electric heating catalyst 12 can be suppressed.

[0028] As described above, when starting the engine 1, specifically when detecting the start of cranking, the heating of the electric heating catalyst 12 is started, the throttle valve 8 is closed, and the EGR valve 20 is opened. As a result, air flow is generated by the cranking of the engine 1, and as shown by the arrow in FIG. 1, the air heated by the electric heating catalyst 12 circulates through the route passing through the downstream catalyst 14, the exhaust passage 7, the EGR passage 18, the intake passage 6, the engine 1, the exhaust passage 7, and the upstream catalyst 13, and is heated again by the electric heating catalyst 12. In this way, when starting the engine 1, the air heated by the electric heating catalyst 12 passes through the downstream catalyst 14 and heats the downstream catalyst 14. As a result, without using an air supply device such as a dynamic air pump, the downstream catalyst 14, which is a catalyst located downstream of the electric heating catalyst 12, can be heated up early, and the exhaust purification performance immediately after starting the engine 1 can be improved. Note that the air heated by the electric heating catalyst 12 passes through the upstream catalyst 13 although it is after passing through the EGR passage 18, so there is also an effect of heating the upstream catalyst 13 and heating up the upstream catalyst 13 early. In addition, a part of the air heated by the electric heating catalyst 12 does not flow through the EGR passage 18 but also flows to the side of the underfloor catalyst converter 10, so there is also an effect of heating the underfloor catalyst 17 and heating up the underfloor catalyst 17 early.

[0029] As described above, the embodiments of the present invention have been described in detail with reference to the drawings. However, each embodiment merely shows a specific example in the implementation of the present invention. The technical scope of the present invention is not limited to each embodiment. The present invention can be variously modified without departing from its gist, and those are also included in the technical scope of the present invention. In this embodiment, an example in which the ECM 100 functions as a control device for an exhaust gas purification device to which the present invention is applied has been described. However, an information processing device different from the ECM 100 may function as a control device for an exhaust gas purification device to which the present invention is applied. Further, a plurality of information processing devices may cooperate to function as a control device for an exhaust gas purification device to which the present invention is applied.

Explanation of Reference Numerals

[0030] 1: Engine, 2: Exhaust gas purification device, 3: EGR system, 4: EHC control device, 5: Battery, 6: Intake passage, 7: Exhaust passage, 8: Throttle valve, 9: Engine-side catalytic converter, 10: Underfloor-side catalytic converter, 12: Electrically heated catalyst, 14: Downstream-side catalyst, 18: EGR passage, 20: EGR valve, 100: ECM, 101: Cranking detection unit, 102: EGR valve control unit, 103: Throttle valve control unit, 104: Heating control unit, 105: Catalyst temperature acquisition unit

Claims

1. A control device for controlling an exhaust gas purification device of an internal combustion engine, the exhaust gas purification device comprising an electric heating catalyst provided in an exhaust passage connected to the internal combustion engine and a catalyst provided in the exhaust passage and located downstream of the electric heating catalyst, wherein, at the start of the internal combustion engine, control means is provided for starting heating of the electric heating catalyst, closing a throttle valve provided in an intake passage connected to the internal combustion engine, and opening an EGR valve provided in an EGR passage for refluxing exhaust gas from the exhaust passage to the intake passage. The control device for the exhaust gas purification device of the internal combustion engine is characterized by this.

2. The control device for the exhaust gas purification device of the internal combustion engine according to claim 1, wherein the control means controls to close the throttle valve and open the EGR valve when detecting the start of cranking of the internal combustion engine.

3. The control device for the exhaust gas purification device of the internal combustion engine according to claim 1 or 2, wherein the EGR passage is connected to the intake passage downstream of the throttle valve and to the exhaust passage downstream of the catalyst.

Images