JP2009138615A - Control device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control device for an internal combustion engine capable of preventing the deterioration of emission even if an engine load is heavy and recovering exhaust heat at an early stage. <P>SOLUTION: The control device for the internal combustion engine is provided with a heat exchanger, an exhaust gas changeover valve, an upstream catalyst, a downstream catalyst, and a valve control means. The heat exchanger recovers heat from exhaust gas, and has a function cooling EGR gas as an EGR cooler function. The heat exchanger is positioned in an exhaust gas passage between the upstream catalyst and the downstream catalyst. The exhaust gas changeover valve adjusts the quantity of exhaust gas to the heat exchanger from the exhaust gas passage. The valve control means controls the exhaust gas changeover valve based on a downstream catalyst bed temperature and the engine load. Consequently, the prevention of the deterioration of the emission and recovery of exhaust heat at the early stage can be performed. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a control device for an internal combustion engine provided with an EGR device.

  2. Description of the Related Art Conventionally, in an internal combustion engine equipped with an exhaust gas recirculation (EGR) device that recirculates a part of exhaust gas to an intake system, a heat exchanger for recovering thermal energy from the exhaust gas is arranged. The control for passing the exhaust gas through the heat exchanger is performed by opening and closing an exhaust gas switching valve provided on the exhaust passage.

  Note that Patent Document 1 includes a connecting pipe formed between downstream catalytic converters that joins a merging portion on an exhaust passage, and one or more exhaust control valves that control exhaust gas flowing into a heat exchanger. An exhaust emission control device is described. In addition, techniques related to the present invention are described in Patent Documents 2 and 3.

JP 2007-024022 A JP 2001-280200 A JP 11-193753 A

  By the way, in the exhaust emission control device described in Patent Document 1, warming up of the upstream catalyst and warming up of the engine are preferentially executed. However, in order to further improve the emission deterioration, it is desirable to warm up the downstream catalyst so as to reach the activation temperature at an early stage. In particular, when there is an accelerator operation with a high engine load, an organic compound that cannot be purified only by the upstream catalyst is discharged from the engine, so it is necessary to warm up the downstream catalyst early. Patent Documents 1 to 3 do not discuss any of the above problems.

  The present invention has been made to solve the above-described problems, and provides a control device for an internal combustion engine that can prevent emission deterioration even when the engine load is large and can recover exhaust heat early. The purpose is to provide.

  In one aspect of the present invention, an internal combustion engine control device having an EGR device adjusts the flow of exhaust gas from an exhaust passage to the heat exchanger, and a heat exchanger having both an exhaust heat recovery function and an EGR cooler function. Based on the exhaust switching valve, the upstream catalyst disposed upstream of the heat exchanger in the exhaust passage, the downstream catalyst disposed downstream of the heat exchanger in the exhaust passage, the downstream catalyst bed temperature and the engine load amount And a valve control means for controlling the exhaust gas switching valve.

  The control device for an internal combustion engine is a control device for an internal combustion engine having an EGR device that recirculates a part of exhaust gas to an intake system. The control device for an internal combustion engine includes a heat exchanger, an exhaust gas switching valve, an upstream catalyst, a downstream catalyst, and valve control means. The heat exchanger collects heat from the exhaust gas and has a function of cooling the EGR gas as an EGR cooler function. The heat exchanger is positioned between the upstream catalyst and the downstream catalyst on the exhaust passage. The exhaust switching valve adjusts the amount of exhaust gas from the exhaust passage to the heat exchanger. The valve control means is, for example, an ECU (Electronic Control Unit), and controls the exhaust gas switching valve based on the downstream catalyst bed temperature and the engine load. When the downstream catalyst does not reach the activation temperature or when the engine load is heavy, the exhaust gas switching valve is controlled to warm up the catalyst. In other cases, the exhaust heat recovery by the heat exchanger is performed. Execute. As a result, it is possible to prevent emission deterioration and recover exhaust gas heat at an early stage.

  In one aspect of the control apparatus for an internal combustion engine, the valve control means is configured such that at least when the downstream catalyst bed temperature is equal to or lower than the first catalyst bed temperature, the exhaust switching valve and the exhaust gas pass through the downstream catalyst. It is characterized by being in the mode. In this aspect, when the downstream catalyst is equal to or lower than the first catalyst bed temperature, which is a predetermined activation temperature, the valve control means controls the exhaust gas switching valve so as to warm up the catalyst regardless of the presence or absence of EGR control. To do. Thereby, the highest priority can be given to prevention of emission deterioration.

  In another aspect of the control apparatus for an internal combustion engine, the valve control means is configured such that when the downstream catalyst bed temperature is equal to or higher than the first catalyst bed temperature, the exhaust gas passes through the heat exchanger and the exhaust gas passes through the heat exchanger. The second mode is set. In this aspect, when the downstream catalyst reaches the first catalyst bed temperature, which is a predetermined activation temperature, the valve control means prioritizes exhaust heat recovery over catalyst warm-up regardless of the presence or absence of EGR control. The exhaust gas switching valve is controlled as follows. Thereby, warming up of a downstream catalyst can be performed at an early stage, preventing emission deterioration.

  In another aspect of the control apparatus for an internal combustion engine, the valve control means may be configured such that after the downstream catalyst bed temperature once reaches the first catalyst bed temperature, the downstream catalyst bed temperature is the first catalyst bed. The exhaust gas switching valve is not switched to the first mode even when the temperature is lower than the temperature. The gas discharged from the engine passes through the upstream catalyst before the downstream catalyst and the heat exchanger. Therefore, when the downstream catalyst reaches the activation temperature, the upstream catalyst has sufficiently reached the activation temperature. Therefore, in this case, it can be assumed that the upstream catalyst has been sufficiently warmed up, and exhaust gas purification is also performed by the upstream catalyst, so the valve control means prioritizes recovery of exhaust heat. To do. As a result, even in vehicles that perform intermittent operation, such as hybrid vehicles and eco-run vehicles, exhaust gas purification can be guaranteed and exhaust heat can be recovered.

  In another aspect of the control apparatus for an internal combustion engine, the valve control unit is configured such that the engine load is equal to or higher than the first engine load, and the downstream catalyst bed temperature is equal to or lower than the first catalyst bed temperature. In this case, the exhaust gas switching valve is set to the first mode. In this aspect, in principle, when the downstream catalyst bed temperature reaches the first catalyst bed temperature, the upstream catalyst bed temperature is regarded as being higher than the second catalyst bed temperature thereafter, and the exhaust gas is exhausted more than the warm-up of the downstream catalyst. Prioritize heat recovery. However, when the engine load is large, the emission of organic compounds is expected to increase from the engine. In this case, the highest priority is given to the downstream catalyst bed temperature reaching the first catalyst bed temperature. As a result, it is possible to guarantee the prevention of emission deterioration in a wider range of situations.

  Another aspect of the control apparatus for an internal combustion engine is characterized in that the valve control means uses the engine load amount as an accelerator opening amount. In this aspect, the accelerator opening amount is monitored as an engine load amount by an accelerator opening sensor or the like, and when the accelerator opening amount becomes higher than a predetermined value due to an accelerator operation that increases the engine load, the engine load amount Therefore, it is possible to give the highest priority to the downstream catalyst bed temperature reaching the first catalyst bed temperature.

  In another aspect of the control device for an internal combustion engine, the valve control means further controls the exhaust gas switching valve based on an engine water temperature. In this aspect, for example, engine protection or in-vehicle heating can be prioritized by controlling the exhaust gas switching valve in consideration of the engine water temperature.

  Another aspect of the control device for the internal combustion engine is an exhaust gas switching valve at least when the downstream catalyst bed temperature is equal to or higher than the first catalyst bed temperature and when the engine water temperature is equal to or lower than the first engine water temperature. In the second mode. In this embodiment, when the downstream catalyst has reached the activation temperature, it is considered that the catalyst has been warmed up, and the engine water temperature is prioritized. Thereby, warm-up of engine water temperature can be completed at an early stage.

  According to another aspect of the control device for an internal combustion engine, the valve control means may be configured to switch the second exhaust switching valve when the outside air temperature is equal to or lower than the first air temperature, regardless of the downstream catalyst bed temperature and the engine load. It is characterized by being in the mode. In this aspect, when the outside air temperature is extremely low, the function of the engine may be deteriorated due to freezing of the device or the like, and therefore, the increase of the engine water temperature is given top priority for safety. Thereby, the performance of deice and a defroster can be improved.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

[Internal combustion engine]
First, the configuration of the control device for an internal combustion engine according to the present embodiment will be described. FIG. 1 is a block diagram showing an example of a schematic configuration of a control device 100 for an internal combustion engine having an engine 3 according to the present embodiment. In FIG. 1, solid arrows indicate the flow of intake and exhaust, and broken arrows indicate control signals. The control device 100 for an internal combustion engine is mounted on a vehicle and uses the output of the engine 3 as a driving power source. The control device 100 for an internal combustion engine includes an engine 3, an EGR device 5, catalysts 30a and 30b, an exhaust gas switching valve 20, various sensors 25, 26 and 27, and an ECU 10 as constituent elements.

  The engine 3 is supplied with air (intake air) through the intake passage 2. A throttle valve 22 that adjusts the amount of inflow into the engine is disposed in the intake passage 2. Further, an exhaust passage 4 is connected to the engine 3, and exhaust gas generated by the above-described combustion is discharged from the exhaust passage 4. Preferable examples of the engine 3 include a gasoline engine and a diesel engine.

  The control device 100 for an internal combustion engine includes an EGR device 5 that recirculates a part of the exhaust gas to the intake system. The EGR device 5 includes an EGR passage 6, a heat exchanger 7, and an EGR valve 9. The EGR passage 6 has one end connected to the exhaust passage 4 and the other end connected to the intake passage 2.

  The heat exchanger 7 functions as an EGR cooler that cools the exhaust gas that passes through the EGR passage 6 and also functions as an exhaust heat recovery device that transmits thermal energy contained in the exhaust gas to the engine coolant. That is, the heat exchanger 7 is a heat exchanger in which the functions of the EGR cooler and the exhaust heat recovery device are integrated. Specifically, the heat exchanger 7 is configured as a water-cooled type, and performs cooling using cooling water passing through the inside. That is, the heat exchanger 7 cools the exhaust gas by exchanging heat between the cooling water and the exhaust gas. The cooling water passes through the cooling water passage 8 and is circulated by a water pump (not shown).

  The EGR valve 9 is a valve for controlling the amount of exhaust gas to be recirculated (hereinafter referred to as “EGR amount”). The opening degree of the EGR valve 9 is controlled by a control signal S2 supplied from the ECU 10.

  An upstream catalyst 30 a and a downstream catalyst 30 b are disposed in the exhaust passage 4. The upstream catalyst 30 a is a small catalyst having a small volume, and is a catalyst disposed in the exhaust passage 4 downstream of the engine 3 and upstream of the first bypass passage 15. In a preferred example, the upstream catalyst 30a is preferably a NOx storage reduction catalyst that stores and purifies NOx. Hereinafter, the temperature of the upstream catalyst 30a is referred to as “upstream catalyst bed temperature”.

  The downstream catalyst 30b is a large-sized catalyst having a larger volume than the upstream catalyst 30a, and is a catalyst disposed downstream of the exhaust gas switching valve 20 in the exhaust passage 4. The downstream catalyst 30b is preferably a NOx storage reduction catalyst that stores and purifies NOx, similarly to the upstream catalyst 30a. Hereinafter, the temperature of the downstream catalyst 30b is referred to as “downstream catalyst bed temperature”, and the generic name of the upstream catalyst bed temperature and the downstream catalyst bed temperature is simply referred to as “catalyst bed temperature”.

  The first bypass passage 15 is a passage for connecting the exhaust passage 4 and the heat exchanger 7 and flowing the exhaust gas from the exhaust passage 4 to the heat exchanger 7. The second bypass passage 16 is a passage for connecting the exhaust passage 4 and the heat exchanger 7 and allowing the exhaust gas to flow from the heat exchanger 7 to the exhaust passage 4.

  The exhaust gas switching valve 20 is a valve that adjusts the flow of exhaust gas by opening and closing the second bypass passage 16 and the exhaust passage 4. The exhaust switching valve 20 is controlled to be opened and closed by a control signal S1 supplied from the ECU 10.

  Further, the control device 100 for the internal combustion engine is provided with various sensors. Specifically, an engine water temperature sensor 25 that measures the coolant temperature on the coolant passage 8 is provided in the head portion of the engine 3. The engine water temperature sensor 25 supplies a detection signal S5 corresponding to the detected coolant temperature to the ECU 10.

  The downstream catalyst 30b is provided with a catalyst bed temperature sensor 26 for measuring the downstream catalyst bed temperature. The catalyst bed temperature sensor 26 supplies the ECU 10 with a detection signal S6 corresponding to the detected downstream catalyst bed temperature.

  Further, an accelerator opening sensor 27 that is a sensor for detecting an accelerator opening corresponding to an accelerator operation by the driver is provided. The accelerator opening sensor 27 supplies the ECU 10 with a detection signal S7 indicating the detected accelerator opening. The ECU 10 controls the EGR valve 9 and the exhaust gas switching valve 20 based on these detection signals S5 to S7.

  The ECU 10 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like (not shown). The ECU 10 controls the engine 3 based on detection signals supplied from various sensors. For example, the ECU 10 determines the required torque of the engine 3 based on the detection signal S7 supplied from the accelerator opening sensor 27. Then, the ECU 10 controls the engine 3 based on the determined required torque.

  The ECU 10 controls the exhaust gas switching valve 20 and the EGR valve 9 by transmitting control signals S1 and S2 to them. Therefore, the ECU 10 functions as valve control means in the present invention.

  Next, the state of the airflow of each exhaust gas, which changes by the control of the EGR valve 9 and the exhaust gas switching valve 20 performed by the ECU 10, will be described.

  FIG. 2A shows a state in which the ECU 10 controls the EGR valve 9 and the exhaust gas switching valve 20 so that the EGR valve 9 is closed and the exhaust gas switching valve 20 closes the second bypass passage 16. That is, the state 70 is a state when the ECU 10 controls the EGR valve 9 and the exhaust gas switching valve 20 so that the exhaust gas is not recirculated by the EGR device 5 and the exhaust gas switching valve 20 is positioned on the broken line 20a. Hereinafter, the state 70 is referred to as “catalyst warm-up mode”. An arrow 80 indicates the flow of exhaust. Hereinafter, controlling the exhaust gas switching valve 20 to be positioned on the broken line 20a is simply expressed as “closing the exhaust gas switching valve 20” or “putting the exhaust gas switching valve 20 in the first mode”.

  In the catalyst warm-up mode, the exhaust gas discharged from the engine 3 does not pass through the heat exchanger 7, so that the heat of the exhaust gas is not recovered by the heat exchanger 7. Therefore, the exhaust gas follows the flow of the arrow 80 and passes through the downstream catalyst 30b. Thereby, the downstream catalyst 30b is warmed up by the exhaust gas.

  FIG. 2B shows a state in which the ECU 10 controls the EGR valve 9 and the exhaust gas switching valve 20 so as to close the EGR valve 9 and open the exhaust gas switching valve 20. Hereinafter, the state 71 is referred to as a “heat recovery mode”. An arrow 81 indicates the flow of exhaust. Hereinafter, controlling the exhaust gas switching valve 20 to be positioned on the broken line 20b is expressed as “opening the exhaust gas switching valve 20” or “putting the exhaust gas switching valve 20 in the second mode”.

  In the heat recovery mode, as indicated by an arrow 81, the exhaust gas discharged from the engine 3 passes through the heat exchanger 7, whereby the heat of the exhaust gas is recovered by the heat exchanger 7.

  FIG. 3A shows a state in which the ECU 10 controls the EGR valve 9 and the exhaust gas switching valve 20 so that the EGR valve 9 is opened and the exhaust gas switching valve 20 is closed. Hereinafter, the state 72 is referred to as “EGR cooler mode”. Arrows 82a and 82b indicate the flow of exhaust.

  In the EGR cooler mode, as indicated by the arrow 82a, part of the exhaust gas discharged from the engine 3 is recirculated to the intake passage 2 by the EGR device 5 again. Thereby, the negative pressure of the intake passage 2 is relatively lowered, and the fuel consumption can be improved by the reduction of the pumping loss. Further, the exhaust gas that is not recirculated by the EGR device 5 passes through the downstream catalyst 30b without passing through the heat exchanger 7, as indicated by the arrow 82b. Thereby, the downstream catalyst 30b is warmed up by the exhaust gas.

  FIG. 3B shows a state in which the ECU 10 controls the EGR valve 9 and the exhaust gas switching valve 20 so that the EGR valve 9 is opened and the exhaust gas switching valve 20 is opened. Hereinafter, the state 73 is referred to as “heat recovery / EGR cooler mode”. Arrows 83a and 83b indicate the flow of exhaust.

  In the heat recovery / EGR cooler mode, as indicated by an arrow 83a, a part of the exhaust gas discharged from the engine 3 is returned to the intake passage 2 again by the EGR device 5. Thereby, the negative pressure of the intake passage 2 is relatively lowered, and the fuel consumption can be improved by the reduction of the pumping loss. In the heat recovery / EGR cooler mode, as indicated by arrows 83a and 83b, the exhaust gas discharged from the engine 3 passes through the heat exchanger 7 so that the heat of the exhaust gas is recovered by the heat exchanger 7. Is done.

[Exhaust gas switching valve control method 1]
Next, a specific description will be given of a method of controlling the exhaust gas switching valve 20 that is executed by the ECU 10 in accordance with a state change after the engine is started. FIG. 4 shows an example of a graph showing changes in engine speed, engine water temperature, and downstream catalyst bed temperature over time, and a graph showing the state of the exhaust switching valve corresponding thereto. The exhaust gas switching valve control method shown in FIG. 4 is hereinafter referred to as “exhaust gas switching valve control method 1”.

  In FIG. 4, the engine 3 is started at time t1. Then, until the time t2, that is, in the period A, the downstream catalyst bed temperature does not reach the predetermined activation temperature T2 (referred to herein as “first catalyst bed temperature”). In this case, there is a possibility of emission deterioration due to the downstream catalyst 30b not reaching the activation temperature. Therefore, the ECU 10 needs to warm up the downstream catalyst 30b. That is, in the period A, the ECU 10 sets the exhaust gas switching valve 20 to the first mode. As a result, the heat of the exhaust gas is not recovered by the heat exchanger 7, and the exhaust gas can be passed to the downstream catalyst 30b, so that the downstream catalyst bed temperature can be brought to the first catalyst bed temperature T2 at an early stage.

  Between time t2 and time t3, that is, during period B, the downstream catalyst bed temperature reaches the first catalyst bed temperature T2, and the warming up of the downstream catalyst 30b is completed. On the other hand, the engine water temperature does not reach a predetermined engine water temperature (hereinafter referred to as “first engine water temperature”) that is an appropriate temperature. Here, the first engine water temperature is T1. Therefore, in this case, the ECU 10 gives priority to heat recovery by the heat exchanger 7 over warming up of the downstream catalyst 30b. That is, in the period B, the ECU 10 sets the exhaust gas switching valve 20 to the second mode. In other words, the ECU 10 switches the exhaust gas switching valve 20 from the first mode to the second mode at time t2. Thereby, ECU10 can collect | recover the heat | fever of exhaust gas with the heat exchanger 7, and can raise engine water temperature at an early stage.

  After the time t3, that is, in the period C, the warm-up of the downstream catalyst 30b is completed, and the engine water temperature has reached the first engine water temperature T1 or higher. In this case, if the engine water temperature is further warmed up, the engine 3 may be adversely affected due to boiling of the engine water temperature or the like. Therefore, the ECU 10 sets the exhaust gas switching valve 20 to the first mode in the period C. That is, the ECU 10 switches the exhaust gas switching valve 20 from the second mode to the first mode at time t3. Thereby, it is possible to prevent boiling due to a rise in the engine water temperature and protect the engine 3.

  As described above, when the ECU 10 switches the exhaust gas switching valve 20, it is possible to appropriately perform warm-up of the catalyst and heat recovery by the heat exchanger 7, thereby preventing emission deterioration and protecting the engine.

[Exhaust gas switching valve control method 2]
When the control device 100 for an internal combustion engine shown in FIG. 1 is applied to a vehicle that performs intermittent operation of an engine such as a hybrid vehicle or an eco-run vehicle, the downstream catalyst bed temperature decreases due to the intermittent operation of the engine. As a result, the ECU 10 frequently switches the exhaust gas switching valve 20 as the engine is restarted. FIG. 5 is a graph showing changes in engine speed, engine water temperature, and downstream catalyst bed temperature in a hybrid vehicle, and a state of the corresponding exhaust gas switching valve when the exhaust gas switching valve control method 1 is applied. An example is shown.

  In FIG. 5, after the start of the vehicle travel start, the ECU 10 appropriately performs the travel by the motor (hereinafter referred to as “EV travel”) and the travel by the engine 3 (hereinafter referred to as “engine travel”). Switching. In particular, from the time t10 to the time t11, that is, in the period D, the downstream catalyst bed temperature is frequently lower than the first catalyst bed temperature T2 due to the switching of the travel mode described above. As a result, in the exhaust gas switching valve control method 1, since the exhaust gas switching valve 20 is switched to the first mode, heat cannot be recovered from the exhaust gas even when the engine water temperature does not reach the first engine water temperature T1. Moreover, it is conceivable that the possibility of failure of the exhaust gas switching valve 20 increases by frequently switching the exhaust gas switching valve 20.

  In FIG. 6, when a new control method of the exhaust gas switching valve 20 (hereinafter referred to as “exhaust gas switching valve control method 2”) is applied, the engine speed, the engine water temperature, and the downstream catalyst bed temperature accompanying the engine start. 2 shows an example of a graph of each change and a graph showing the state of the exhaust switching valve corresponding thereto.

  In FIG. 6, first, the ECU 10 sets the exhaust gas switching valve 20 to the first mode until the time t20 when the downstream catalyst bed temperature reaches the first catalyst bed temperature T2 after the engine 3 is started, that is, in the period E.

  From time t20 to time t21, that is, in the period F, the downstream catalyst bed temperature has reached the first catalyst bed temperature T2, so the ECU 10 sets the exhaust gas switching valve 20 to the second mode. In the period F, the downstream catalyst bed temperature may be lower than the first catalyst bed temperature T2 due to the temporary stop of the engine 3 due to switching from engine running to EV running. However, even in this case, the upstream catalyst 30a is located upstream of the heat exchanger 7 in the exhaust passage 4, so that the downstream catalyst 30b once reaches the first catalyst bed temperature T2 and is sufficiently upstream. It is considered that the activation temperature of the catalyst 30a (hereinafter referred to as “second catalyst bed temperature”) has been reached. Therefore, in this case, even if the downstream catalyst 30b does not reach the activation temperature, the upstream catalyst 30a is regarded as reaching the activation temperature, and the ECU 10 does not switch to the first mode in principle. In other words, in the exhaust gas switching valve control method 2, instead of the downstream catalyst bed temperature, the upstream catalyst bed temperature is set as a judgment target for switching the exhaust gas switching valve 20, and the downstream catalyst 30b reaches the first catalyst bed temperature T2. In this case, it is considered that the upstream catalyst 30a has sufficiently reached the second catalyst bed temperature which is the active temperature. As a result, heat recovery from the exhaust gas can be performed within a range in which the emission deterioration does not occur.

  At time t21, the accelerator opening received from the accelerator opening sensor 27 increases rapidly and exceeds a predetermined opening amount D1 (hereinafter referred to as “first opening amount”). In this case, the load on the engine 3 increases due to an increase in the accelerator opening, and as a result, a large amount of organic compounds are likely to be discharged.

  In this case, the ECU 10 prevents the deterioration of the emission by prioritizing the warming up of the downstream catalyst 30b over the recovery of the exhaust heat. That is, when the accelerator operation exceeding the first opening amount D1 is detected and the downstream catalyst 30b has not reached the first catalyst bed temperature T2, the ECU 10 moves the exhaust gas switching valve 20 from the second mode. Switch to the first mode. Thereby, even when the engine load is exceptionally high, it is possible to prevent the deterioration of the emission.

  In addition, by using the accelerator opening as an index of the engine load in this way, it can be detected that the load on the engine 3 is increased quickly, and the downstream catalyst 30b can be warmed up early.

  In addition to the accelerator opening, for example, the engine speed, the throttle valve opening, or the like may be used as an index of the engine load. A numerical value serving as an index of the engine load is defined as “engine load amount”.

  Next, at time t22, the ECU 10 switches the exhaust gas switching valve 20 to the second mode because the downstream catalyst bed temperature has reached the first catalyst bed temperature T2. Then, it is considered that the upstream catalyst bed temperature has reached the second catalyst bed temperature until time t23, that is, in the period H, and even when the downstream catalyst bed temperature becomes equal to or lower than the first catalyst bed temperature T2, the exhaust gas switching valve 20 Is not switched to the first mode, but the second mode is maintained and exhaust heat recovery is performed.

  At time t23, the ECU 10 switches the exhaust gas switching valve 20 to the first mode because the engine water temperature has reached the first engine water temperature. Then, after time t23, that is, in the period I, the exhaust heat recovery is stopped. Thereby, boiling of a cooling water etc. can be prevented and the engine 3 can be protected.

  As described above, in the exhaust gas switching valve control method 2, even when the internal combustion engine control device 100 is applied to a hybrid vehicle, the ECU 10 deteriorates emissions or exhaust heat caused by a decrease in catalyst bed temperature due to intermittent operation of the engine. Both delays in collection can be prevented.

  In the above-described embodiment, the ECU 10 does not wait until the downstream catalyst bed temperature reaches the first catalyst bed temperature T2 from the time t21 to the time t22, that is, in the period G, even when the engine load amount becomes a predetermined amount or less. The exhaust gas switching valve 20 is set to the first mode. However, the application of the present invention is not limited to this. For example, the exhaust gas switching valve 20 may be set to the second mode regardless of the downstream catalyst bed temperature when the engine load amount becomes a predetermined amount or less. Thereby, exhaust heat can be recovered earlier.

  In addition, in the control methods 1 and 2 of the exhaust gas switching valve described above, when the vehicle is driven in an environment where the outside air temperature is particularly low, it is desirable to give top priority to the deice and the defroster such as the engine 3 for safety. Accordingly, when the outside air temperature is equal to or lower than a predetermined air temperature (hereinafter referred to as “first air temperature”), the ECU 10 sets the exhaust gas switching valve 20 to the second mode after the engine 3 is started, and sets the engine water temperature. Give rise to top priority. Thereby, safety can be given top priority in an environment where the outside air temperature is extremely low.

It is a figure which shows schematic structure of the control apparatus of an internal combustion engine. It is a figure which shows the flow of exhaust in the state which closed the EGR valve. It is a figure which shows the flow of exhaust in the state which opened the EGR valve. It is a figure which shows an example of the graph of a state change at the time of applying the control method 1 of an exhaust gas switching valve. It is a figure which shows an example of the graph of a state change at the time of applying the control method 1 of an exhaust gas switching valve with respect to a hybrid vehicle. It is a figure which shows an example of the graph of a state change at the time of applying the control method 2 of an exhaust gas switching valve with respect to a hybrid vehicle.

Explanation of symbols

3 Engine 7 Heat exchanger 9 EGR valve 10 ECU
20 Exhaust gas switching valve 30a Upstream catalyst 30b Downstream catalyst 100 Control device for internal combustion engine

Claims (9)

In a control device for an internal combustion engine having an EGR device,
A heat exchanger having both an exhaust heat recovery function and an EGR cooler function;
An exhaust gas switching valve for adjusting the flow of exhaust gas from an exhaust passage to the heat exchanger;
An upstream catalyst disposed upstream of the heat exchanger in the exhaust passage;
A downstream catalyst disposed downstream of the heat exchanger in the exhaust passage;
A control device for an internal combustion engine, comprising: valve control means for controlling the exhaust gas switching valve based on a downstream catalyst bed temperature and an engine load.   2. The internal combustion engine according to claim 1, wherein the valve control unit sets the exhaust gas switching valve to a first mode in which the exhaust gas passes through the downstream catalyst when at least the downstream catalyst bed temperature is equal to or lower than the first catalyst bed temperature. Engine control device.   The internal combustion engine according to claim 2, wherein when the downstream catalyst bed temperature is equal to or higher than the first catalyst bed temperature, the valve control means sets the exhaust gas switching valve to a second mode in which the exhaust gas passes through the heat exchanger. Control device.   After the downstream catalyst bed temperature has once reached the first catalyst bed temperature, the valve control means is configured such that the first valve of the exhaust gas switching valve even if the downstream catalyst bed temperature is equal to or lower than the first catalyst bed temperature. 4. The control device for an internal combustion engine according to claim 3, wherein switching to the mode is not performed.   The valve control means sets the exhaust gas switching valve to the first mode when the engine load is equal to or higher than the first engine load and the downstream catalyst bed temperature is equal to or lower than the first catalyst bed temperature. 4. The control apparatus for an internal combustion engine according to 4.   The control apparatus for an internal combustion engine according to claim 5, wherein the valve control means uses the engine load amount as an accelerator opening amount.   The control apparatus for an internal combustion engine according to any one of claims 1 to 6, wherein the valve control means further controls the exhaust gas switching valve based on an engine water temperature.   The valve control means sets the exhaust gas switching valve to the second mode at least when the downstream catalyst bed temperature is equal to or higher than the first catalyst bed temperature and when the engine water temperature is equal to or lower than the first engine water temperature. Item 8. The control device for an internal combustion engine according to Item 7.   The valve control means sets the exhaust gas switching valve to the second mode regardless of the downstream catalyst bed temperature and the engine load when the outside air temperature is equal to or lower than the first air temperature. The control apparatus of the internal combustion engine described in 1.

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