Hybrid vehicles

Abstract

To suppress outflow of exhaust gas from an exhaust emission control device at start of an engine when a traveling mode is switched and suppress generation of condensation water in an exhaust passage.SOLUTION: A vehicle enabling switching between an engine traveling mode and an EV traveling mode includes: a three-way catalyst 36 provided in an exhaust passage 35 of an engine 2; a two-way shutter 52 that adjusts an opening of the exhaust passage 35 on the downstream side of the three-way catalyst 36; and a control section that when the engine 2 is stopped in the EV traveling mode, controls the two-way shutter 52 so as to reduce an air flow rate in the exhaust passage 35 on the downstream side of the three-way catalyst 36, compared to when the engine 2 stopped due to stop of a starting state of the vehicle.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an exhaust gas purification technology for an engine mounted on a hybrid vehicle.

Background Art

[0002] Many engines are equipped with an exhaust gas purification catalyst (exhaust gas purification device) for purifying NOx and the like in the exhaust gas in the exhaust passage. The exhaust gas purification catalyst has a problem that the purification efficiency at low temperatures decreases. In contrast, Patent Document 1 proposes an engine provided with throttle portions for opening and closing the exhaust passage on the upstream side and the downstream side of the exhaust gas purification catalyst. In Patent Document 1, in a hybrid vehicle, when the operation of the engine is stopped during traveling, the exhaust passages on the upstream side and the downstream side of the exhaust gas purification catalyst are closed to confine the heat of the exhaust gas purification catalyst and suppress the temperature drop, thereby improving the exhaust gas purification performance at the start of the engine operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when the exhaust passages on the upstream side and the downstream side of the exhaust gas purification catalyst are closed when the engine operation is stopped as in Patent Document 1, for example, when the engine is stopped for a long time and the temperature of the exhaust gas purification catalyst drops, condensed water is generated from the exhaust gas confined in the exhaust passage, and there is a possibility that the exhaust passage, the exhaust gas purification device, etc. may be corroded. Particularly, in a vehicle such as a hybrid vehicle where the engine stop and start are frequently switched, it is required to suppress the emission of exhaust gas containing a large amount of unburned gas (unburned fuel) at the start of the engine, and it is also required to suppress the generation of condensed water in the exhaust passage.

[0005] The present invention has been made to solve such problems, and its objective is to provide a hybrid vehicle that suppresses the outflow of exhaust gas from the exhaust purification device when the engine is started during a driving mode switch, and also suppresses the generation of condensed water in the exhaust passage. [Means for solving the problem]

[0006] To achieve the above objective, the hybrid vehicle according to claim 1 of the present invention is a hybrid vehicle comprising an engine and a drive motor, which is switchable between an engine driving mode in which the vehicle is driven with at least the engine running and an EV driving mode in which the vehicle is driven by the drive motor with the engine stopped, and is characterized by comprising: an exhaust purification device provided in the exhaust passage of the engine; an adjustment means for adjusting the airflow rate of the exhaust passage downstream of the exhaust purification device; and a control unit that controls the adjustment means to reduce the airflow rate of the exhaust passage downstream of the exhaust purification device when the engine is stopped in the EV driving mode, so as to be less than when the engine is stopped due to the start state of the hybrid vehicle being stopped.

[0007] As a result, when the engine stops in EV driving mode, the adjustment means is controlled to reduce the airflow rate in the exhaust passage downstream of the exhaust purification device, thereby trapping heat around the exhaust purification device and suppressing the temperature drop of the exhaust purification device. Furthermore, when the engine stops due to the hybrid vehicle's startup state being stopped, the adjustment means is controlled to increase the airflow rate in the exhaust passage downstream of the exhaust purification device, thereby releasing exhaust gases from the exhaust passage and suppressing the generation of condensed water in the exhaust passage.

[0008] Preferably, the adjustment means is a shutter provided downstream of the exhaust purification device in the exhaust passage, and comprises an EGR passage connecting the position in the exhaust passage where the shutter is provided, or a position between the exhaust purification device and the shutter, and the intake passage of the engine, and an EGR valve provided in the EGR passage, and the control unit, when the engine stops in the EV driving mode, closes the shutter. Below a predetermined opening By closing it, the airflow rate in the exhaust passage downstream of the exhaust purification device is reduced, and the EGR valve is also closed. The EGR passage is then closed. It would be best to control it in that way.

[0009] As a result, when the engine stops in EV driving mode, the shutter When the opening angle is below a predetermined degree The EGR valve closes as it closes. The EGR passage is closed. Therefore, high-temperature exhaust gas flows from the EGR passage into the intake passage, suppressing heat loss from the exhaust passage and EGR passage, and also suppressing heat damage to the intake passage. Preferably, the system has an electric motor to drive the engine, and the control unit controls the system to open the shutter and the EGR valve when the engine stops due to the shutdown of the hybrid vehicle's startup state, thereby forcibly driving the engine with the electric motor in a fuel cut-off state.

[0010] This allows the exhaust gas in the exhaust passage and EGR passage to be discharged when the hybrid vehicle's startup state is stopped and the engine stops, thereby suppressing the generation of condensed water. Preferably, the control unit controls the adjustment means such that when the engine starts, the airflow rate in the exhaust passage downstream of the exhaust purification device becomes smaller than when the engine stops due to the shutdown of the hybrid vehicle's starting state.

[0011] This prevents exhaust gases from being discharged into the exhaust passage downstream of the exhaust purification device when the engine is started. Preferably, the adjustment means is a shutter provided downstream of the exhaust purifier in the exhaust passage, and comprises an EGR passage connected to the position in the exhaust passage where the shutter is provided, or a position between the exhaust purifier and the shutter, and an EGR valve provided downstream of the EGR passage, wherein the control unit controls the shutter from the start of engine cranking until complete combustion. Below a predetermined opening By closing the shutter, the airflow rate in the exhaust passage downstream of the exhaust purification device is reduced and the EGR valve is opened. After complete combustion, the shutter remains closed and the EGR valve is closed. The EGR passage is then closed. It would be best to control it in that way.

[0012] This allows exhaust gases to be flowed into the EGR passage and recirculated back into the intake air from the time the engine starts cranking until complete combustion occurs, reusing the unburned gases in the exhaust. After complete combustion, the exhaust gases can be stored in the EGR passage. Preferably, the adjustment means is a shutter provided downstream of the exhaust gas purification device in the exhaust passage, and the control unit may control the shutter to open if the engine temperature is above a predetermined level when the engine starts.

[0013] This helps to prevent high-temperature exhaust gases from flowing into the intake passage via the EGR passage, thereby protecting the engine. [Effects of the Invention]

[0014] According to the present invention, in a hybrid vehicle where the engine is likely to start and stop relatively frequently due to the switching of driving modes during driving, when the engine stops in EV driving mode, exhaust gas can be confined in the exhaust passage to suppress the temperature drop of the exhaust gas purification device. As a result, when the vehicle subsequently transitions from EV driving mode to engine driving mode, the exhaust gas purification performance of the exhaust gas purification device immediately after engine start-up can be improved.

[0015] When the engine stops due to the start state of the hybrid vehicle being stopped, exhaust can be discharged from the exhaust passage to suppress the generation of condensed water in the exhaust passage upstream from the shutter, thereby protecting the exhaust purification device.

Brief Description of the Drawings

[0016] [Figure 1] It is a schematic configuration diagram of the driving system of a hybrid vehicle according to an embodiment of the present invention. [Figure 2] It is a configuration diagram of the intake and exhaust system of the engine of the hybrid vehicle according to the present embodiment. [Figure 3] It is a flowchart showing the control procedure of the storage EGR control executed in the EGR control unit. [Figure 4] It is a flowchart showing the control procedure of the condensed water countermeasure control. [Figure 5] It is a flowchart showing the intake air amount estimation control procedure. [Figure 6] It is a flowchart showing the air-fuel ratio estimation injection control procedure.

Modes for Carrying Out the Invention

[0017] Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 1 is a schematic configuration diagram of the driving system of a hybrid vehicle (hereinafter referred to as vehicle 1) according to an embodiment of the present invention. Vehicle 1 in an embodiment of the present invention is a vehicle such as a plug-in hybrid vehicle or a hybrid vehicle that drives a motor generator 9 (electric motor) by the output of an engine 2 to generate electricity and includes an electric front motor 4 (travel motor) that drives the wheels.

[0018] Engine 2 can drive the drive shaft 8 of the front wheel 3 via the front transaxle 7, and can also drive the motor generator 9 (electric motor) via the front transaxle 7 to generate electricity. In addition, engine 2 and the front wheel 3 are connected via a clutch 16 located within the front transaxle 7. The front motor 4 is powered by a drive battery 11 and a motor generator 9 mounted on the vehicle 1 via the front control unit 10, and drives the drive shaft 8 of the front wheels 3 via the front transaxle 7.

[0019] The power generated by the motor generator 9 can charge the drive battery 11 via the front control unit 10 and supply power to the front motor 4 and rear motor 6. The drive battery 11 is composed of a secondary battery such as a lithium-ion battery. The drive battery 11 is also equipped with a charge level detection unit 11a that detects the state of charge (SOC) of the drive battery 11.

[0020] The front control unit 10 has the function of controlling the output of the front motor 4 and the amount of power generated and the output of the motor generator 9 based on control signals from the hybrid control unit 20 mounted on the vehicle. The engine control unit 22 is a control device for the engine 2, and controls the fuel injection amount and timing, intake air amount, etc., of the engine 2 based on control signals (request outputs) from the hybrid control unit 20 to control the engine 2's operation. The hybrid control unit 20 is a control device for overall control of the vehicle 1. The engine control unit 22 and the hybrid control unit 20 are composed of input / output devices, storage devices (ROM, RAM, non-volatile RAM, etc.), a central processing unit (CPU), and timers, etc.

[0021] The front control unit 10, engine control unit 22, and other devices are connected to the input side of the hybrid control unit 20, and detection and operation information from these devices is input. On the other hand, the output side of the hybrid control unit 20 is connected to the front control unit 10, the engine control unit 22, the clutch 16 of the front transaxle 7, and the like.

[0022] The hybrid control unit 20 then calculates the vehicle-required output necessary for driving the vehicle 1 based on various detected quantities such as the degree of accelerator operation information of the vehicle 1 and various operational information, and sends control signals to the engine control unit 22 and the front control unit 10 to control the switching of the driving mode (EV mode, series mode, parallel mode), the output of the engine 2 and the front motor 4, the generated power and output of the motor generator, and the engagement and disengagement of the clutch 16 in the front transaxle 7.

[0023] In EV mode, engine 2 is stopped, and the vehicle is driven by motor 46. In series mode, the clutch 16 of the front transaxle 7 is disengaged, and the engine 2 drives the motor generator 9 to generate electricity, while simultaneously driving the front motor 4 to propel the vehicle. In series mode, the rotational speed of the engine 2 is set to an efficient value.

[0024] In parallel mode, the clutch 16 of the front transaxle 7 is engaged, transmitting power from the engine 2 and the front motor 4 to drive the front wheels 3. The hybrid control unit 20 sets the driving mode to parallel mode in areas where the engine 2 is efficient, such as high speeds. In areas other than parallel mode, i.e., low to medium speeds, it switches between EV mode and series mode based on the state of charge (SOC) of the drive battery 11. The EV mode corresponds to the EV driving mode of the present invention, and the series mode and parallel mode correspond to the engine driving modes of the present invention.

[0025] Figure 2 is a diagram showing the configuration of the intake and exhaust system of engine 2 according to one embodiment of the present invention. The engine 2 according to this embodiment is, for example, an internal combustion engine such as a gasoline engine or a diesel engine having multiple cylinders. As shown in Figure 2, the intake passage 31 of the engine 2 is equipped with an air cleaner 32 and a throttle valve 33, in order from the upstream side toward the engine 2.

[0026] The exhaust passage 35 of engine 2 is equipped with, in order from engine 2 downstream, a three-way catalytic converter 36 (exhaust purification device), a particulate filter 37, and a muffler 38. Engine 2 is equipped with a high-pressure EGR device 40 that recirculates a portion of the exhaust gas to the intake side as EGR gas. The high-pressure EGR device 40 includes a high-pressure EGR passage 43 that connects the intake passage 31 downstream of the throttle valve 33 and the exhaust passage 35 upstream of the three-way catalytic converter 36, a high-pressure EGR valve 44 that opens and closes (adjusts the opening degree of) the high-pressure EGR passage 43, and a high-pressure EGR cooler 45 that cools the EGR gas passing through the high-pressure EGR passage 43.

[0027] Furthermore, in this embodiment, a storage EGR device 50 is provided in addition to the high-voltage EGR device 40. The storage EGR device 50 includes a storage EGR passage 51 (EGR passage) that connects the exhaust passage 35 between the particulate filter 37 and the muffler 38 to the downstream side of the intake passage 31 from the throttle valve 33, and a 2-way shutter 52 (adjustment means) at the branching point between the storage EGR passage 51 and the exhaust passage 35.

[0028] The 2-way shutter 52 can be opened to adjust the ratio of exhaust gas flowing into the storage EGR passage 51 and the muffler 38, that is, to adjust the airflow rate to the muffler 38. The storage EGR passage 51 is equipped with, in order from the 2-way shutter 52 side toward the intake manifold 42, an exhaust compressor 53, an exhaust storage tank 54, a storage EGR cooler 55, and a storage EGR valve 56.

[0029] The exhaust compressor 53 is an electric compressor driven by power supplied from a storage battery such as the drive battery 11, and compresses and supplies exhaust gas from the exhaust passage 35 toward the exhaust storage tank 54. The exhaust gas storage tank 54 is a storage tank for storing exhaust gas (EGR gas). As will be described later, the capacity of the exhaust gas storage tank 54 should be such that it can store the exhaust gas from the start of engine 2 until the exhaust air-fuel ratio can be measured. 。

[0030] The storage EGR cooler 55 is a cooler that cools the EGR gas passing through the storage EGR passage 51, and exchanges heat with the outside air using the airflow from the vehicle or a fan provided on the engine 2. Although the high-pressure EGR cooler 45 and the storage EGR cooler 55 are integrated, their EGR gas flow paths are different. The storage EGR valve 56 adjusts the opening degree of the storage EGR passage 51.

[0031] Furthermore, the intake passage 31 between the air cleaner 32 and the throttle valve 33 is equipped with an intake flow sensor (MAF60) for detecting intake air flow rate, and intake temperature and pressure sensors (first intake temperature and pressure sensor 61 on the upstream side and second intake temperature and pressure sensor 62 on the downstream side) for detecting intake air temperature and intake air pressure in the intake passage 31 on the upstream and downstream sides of the throttle valve 33.

[0032] The exhaust passage 35 between the exhaust manifold 41 and the three-way catalytic converter 36 is equipped with a linear air-fuel ratio sensor (LAFS63) for detecting the air-fuel ratio. Furthermore, the storage EGR passage 51 between the storage EGR cooler 55 and the storage EGR valve 56 is equipped with an EGR gas temperature and pressure sensor 64 for detecting the temperature and pressure of the EGR gas.

[0033] Furthermore, a differential pressure sensor (DPS65) is provided to detect the difference between the pressure in the storage EGR passage 51 between the exhaust storage tank 54 and the storage EGR cooler 55 and the pressure in the exhaust passage 35 between the particulate filter 37 and the 2-way shutter 52. The hybrid control unit 20 is equipped with an EGR control unit 70 (control unit).

[0034] The EGR control unit 70 controls the operation of the 2-way shutter 52, exhaust compressor 53, high-pressure EGR valve 44, and storage EGR valve 56 based on the engine operating status (running, stopped, cranking status, engine water temperature, engine rotational speed, etc.), the intake air flow sensor, the first intake air temperature and pressure sensor 61, the second intake air temperature and pressure sensor 62, the LAFS 63, the EGR gas temperature and pressure sensor 64, and the differential pressure sensor 65.

[0035] In this embodiment, when the engine 2 is started, the 2-way shutter 52 is moved to the muffler 38 side, increasing the opening of the passage on the storage EGR passage 51 side and decreasing the opening of the passage on the muffler 38 side, thereby directing most of the exhaust to the storage EGR passage 51 side and suppressing the outflow of exhaust from the exhaust passage 35 to the outside of the vehicle when the engine 2 is started. At this time, if it is not appropriate to introduce EGR gas into the engine 2, the storage EGR valve 56 is closed to store the exhaust in the storage EGR passage 51. Also, when the engine 2 is stopped, the 2-way shutter 52 is moved to the muffler 38 side to suppress the escape of heat from the three-way catalytic converter 36 and particulate filter 37 (hereinafter referred to as catalyst) from the exhaust passage 35 to the outside of the vehicle. At this time, if there is a possibility of condensation forming in the exhaust passage 35, the 2-way shutter 52 is moved to the storage EGR passage 51 side, and the exhaust in the exhaust passage 35 is released to the outside of the vehicle to suppress the formation of condensation.

[0036] Figure 3 is a flowchart showing the control procedure for storage EGR control in the storage EGR device 50. Figure 4 is a flowchart showing the control procedure for condensate countermeasures control. Figure 5 is a flowchart showing the intake air volume estimation control procedure. Figure 6 is a flowchart showing the air-fuel ratio estimation injection control procedure. The control shown in Figures 3 to 6 is performed in the EGR control unit 70.

[0037] Storage EGR control is repeatedly performed at predetermined intervals after the power switch of vehicle 1 is turned ON (IG-ON). As shown in Figure 3, the storage EGR control first acquires engine status (running, stopped, cranking status, engine speed, engine water temperature, etc.) from the engine control unit 22, etc., in step S10. Then proceeds to step S20.

[0038] In step S20, it is determined whether engine 2 is stopped or not. If the engine is stopped, the process proceeds to step S30. If engine 2 is running, the process proceeds to step S70. Note that engine stopped means that the fuel in the cylinders of engine 2 is not being intentionally burned, and this includes the state in which engine 2 is rotating by inertia.

[0039] In step S30, it is determined whether the engine rotational speed Ne is 0 or less. If the engine rotational speed Ne is 0 or less, the process proceeds to step S40. If the engine rotational speed Ne is greater than 0, i.e., if the engine is rotating by inertia, the process proceeds to step S200 shown in Figure 4. In step S40, it is determined whether the power switch of vehicle 1 is on or off. If the power switch is on, i.e., if engine 2 is stopped due to idle stop or EV driving, the process proceeds to step S60. If the power switch is off, i.e., if the vehicle is in a shutdown state, the process proceeds to step S50.

[0040] In step S50, the first control is executed. Specifically, the 2-way shutter 52 is opened to a medium degree (both the storage EGR passage 51 and the exhaust passage 35 on the muffler 38 side are open). In this embodiment, the opening ratio between the storage EGR passage 51 side (hereinafter referred to as the EGR side) and the muffler 38 side is set to 5:5. The storage EGR valve 56 is also closed (closing the intake side of the storage EGR passage 51). Then, this routine is returned. The first control is performed when the engine stops due to the vehicle's power being turned off. In this case, since it is expected that the engine 2 will remain stopped for a long time, the 2-way shutter 52 is controlled to open the exhaust passage 35 side in order to suppress the generation of condensed water in the exhaust passage 35. At this time, closing the storage EGR valve 56 suppresses the flow of exhaust to the intake passage 31 side. It is preferable to motor the engine 2 with the motor generator 9 at this time to promote the discharge of exhaust from the storage EGR passage 51 and the exhaust passage 35.

[0041] In step S60, the second control is executed. Specifically, the muffler side of the exhaust passage 35 is closed by the 2-way shutter 52. Note that closing the muffler side of the exhaust passage 35 means that most of the exhaust flows to the storage EGR passage 51 side (hereinafter referred to as the EGR side), and it is not necessary to completely close the muffler side of the exhaust passage 35. In this embodiment, the opening ratio between the EGR side and the muffler side is set to 9:1. The storage EGR valve 56 is also closed. Then, this routine is returned. The second control is performed when the engine stops due to idle stop or EV driving. In this case, since it is expected that the engine 2 will be restarted in a relatively short time, the muffler side of the exhaust passage 35 is closed in order to suppress the temperature drop of the catalyst. At this time, closing the storage EGR valve 56 prevents heat from the exhaust passage 35 from escaping to the intake passage 31 side.

[0042] In step S70, it is determined whether engine 2 is in a state between cranking and full combustion. If it is in a state between cranking and full combustion, the process proceeds to step S80. If it is not in a state between cranking and full combustion, i.e., if it is in the operating state after full combustion, the process proceeds to step S110. In step S80, it is determined whether the engine coolant temperature is low (for example, 80°C or below, before warming up). If the engine coolant temperature is 80°C or below, the process proceeds to step S100. If the engine coolant temperature is higher than 80°C, the process proceeds to step S90.

[0043] In step S100, the third control is executed. Specifically, the 2-way shutter 52 is set to a medium opening (both the EGR side and the muffler side are open). In this embodiment, the EGR side is set to be more open. The storage EGR valve 56 is also set to a medium opening (any opening between fully open and fully closed). Then, this routine is returned. The third control is performed in the initial stages of engine startup at low temperatures. In this case, since the catalyst is not activated and the exhaust purification efficiency is poor, most of the exhaust is directed to the EGR side, suppressing the discharge of exhaust from the exhaust passage 35 to the outside of the vehicle. At this time, the storage EGR valve 56 is opened to prevent the pressure in the storage EGR passage 51 from becoming too high. Note that in the initial stages of engine startup, there is sufficient oxygen in the storage EGR passage 51, so opening the storage EGR valve 56 has little adverse effect on engine starting performance. Note that at this time, the exhaust compressor 53 may be driven to pressurize and send exhaust to the storage EGR passage 51.

[0044] In step S90, the fourth control is executed. Specifically, the storage EGR passage 51 is closed by the 2-way shutter 52. Note that closing the storage EGR passage 51 means that most of the exhaust flows to the muffler side of the exhaust passage 35, and it is not necessary to completely close the storage EGR passage 51. In this embodiment, the opening ratio of the EGR side and the muffler side of the 2-way shutter 52 is set to 1:9. The storage EGR valve 56 is also closed. Then, this routine is returned. The fourth control is performed in the initial stages of engine startup when the engine is hot. In this case, the opening of the muffler side of the exhaust passage 35 is increased to suppress the rise in exhaust pressure and improve engine starting performance. At this time, since the catalyst is active and the exhaust purification efficiency is considered to be sufficient, most of the exhaust is discharged outside the vehicle from the exhaust passage 35, and the flow of exhaust to the EGR side is suppressed, thereby preventing the introduction of EGR into the intake air in the initial stages of engine startup and preventing deterioration of starting performance.

[0045] In step S110, it is determined whether or not the intake air volume can be measured. This can be determined, for example, by checking whether or not the output of the intake air flow sensor (MAF60) is stable. If the intake air volume can be measured, the process proceeds to step S120. If the intake air volume cannot be measured, the process proceeds to step S300 shown in Figure 5. In step S120, it is determined whether or not the exhaust air-fuel ratio can be measured. Whether or not the exhaust air-fuel ratio can be measured can be determined, for example, by whether or not the exhaust air-fuel ratio sensor (LAFS63) is in an active state. If the exhaust air-fuel ratio can be measured, the process proceeds to step S130. If the exhaust air-fuel ratio cannot be measured, the process proceeds to step S400 shown in Figure 6.

[0046] In step S130, it is determined whether the engine is operating in a state where the catalyst is being heated or in a state where the catalyst is cooling. The state where the catalyst is being heated is a state where the catalyst is cooling, and control for heating, such as operating the catalyst heater or performing post-injection, is being carried out. Hereafter, the state where the catalyst is being heated will be included in the state where the catalyst is cooling. Whether or not the catalyst is cooling is determined by determining whether or not the engine is operating in a state where the catalyst temperature is not yet sufficiently activated, for example, when the engine temperature is below a predetermined temperature, or when the engine has not been running for a predetermined time even if the temperature is above the predetermined temperature. If the catalyst is cooling, proceed to step 140. If the catalyst is not cooling, i.e., the catalyst has finished heating, proceed to step S150.

[0047] In step S140, the fifth control is executed. Specifically, the 2WAY shutter 52 is set to a medium opening on the EGR side (the muffler side is more open). The storage EGR valve 56 is also set to a medium opening. The opening of the 2WAY shutter 52 and the storage EGR valve 56 are controlled based on the required amount of EGR. Then, this routine is returned. The fifth control is performed after the engine has started (after complete combustion) and the catalyst is in a cold state. In this case, the opening of the exhaust passage 35 on the muffler side is narrowed by the 2WAY shutter 52, and the exhaust pressure upstream of the 2WAY shutter 52, i.e., on the catalyst side, is increased to promote catalyst heating. However, the opening of the 2WAY shutter 52 is adjusted so that the exhaust pressure does not rise too high so that the engine 2 cannot produce the required output.

[0048] In step S150, it is determined whether the engine is in a warm state or not. This can be determined, for example, by whether the engine temperature is within a predetermined warm state range. If the engine is in a warm state, the process proceeds to step S160. If the engine is not in a warm state, the process proceeds to step S170. In step S160, the sixth control is executed. Specifically, the 2-way shutter 52 is set to a medium opening on the EGR side (the muffler side is more open). Also, the opening of the storage EGR valve 56 is set to a medium opening. The opening of the 2-way shutter 52 and the storage EGR valve 56 are controlled based on the required amount of EGR. Then, this routine is returned. The sixth control is performed after the engine has started (after complete combustion) and both the catalyst and the engine 2 are sufficiently warmed up. In this case, the 2-way shutter 52 should be controlled according to the required amount of EGR. At this time, it is preferable to set the 2-way shutter 52 to the EGR side (increase the opening on the muffler side) compared to the fifth control to prevent the exhaust pressure from rising too high and to ensure the output of the engine 2.

[0049] In step S170, because engine 2 is hot (hotter than the normal temperature), the EGR side is closed by the 2-way shutter 52 as a fail-safe. The storage EGR valve 56 is also closed. In other words, EGR gas is not introduced into the intake passage 31. Then, this routine returns. As shown in Figure 4, in step S200, it is determined whether the pressure in the exhaust storage tank 54 is below atmospheric pressure. Whether the pressure in the exhaust storage tank 54 is below atmospheric pressure can be determined, for example, based on the opening degree of the 2-way shutter 52, the operating time of the engine 2, or a value detected by a pressure sensor installed in the exhaust storage tank 54. If the pressure in the exhaust storage tank 54 is below atmospheric pressure, the process proceeds to step S210. If the pressure in the exhaust storage tank 54 is higher than atmospheric pressure, the process proceeds to step S230.

[0050] In step S210, the control that delays the decrease in engine speed by the motor generator 9 is turned off. When the fuel supply to engine 2 is stopped while engine 2 is running, the engine speed decreases. However, in the vehicle 1 of this embodiment, when the fuel supply to engine 2 is stopped, the motor generator 9 is controlled to delay the decrease in engine speed, making it possible to stop engine 2 gradually. In this step, this delay control is stopped. Then, the process proceeds to step S220.

[0051] In step S220, the seventh control is executed. Specifically, the 2-way shutter 52 is opened to a medium position (in this embodiment, the opening ratio between the EGR side and the muffler side is 5:5). The storage EGR valve 56 is also closed. Then, the process returns to the storage EGR control shown in Figure 3, and the EGR control routine is returned. The seventh control is performed when the engine 2 is rotating by inertia and exhaust gas can be introduced into the storage EGR passage 51. In this case, the storage EGR passage 51 is scavenged by opening the 2-way shutter 52 to a medium position. The storage EGR valve 56 is also closed to prevent high-temperature EGR gas from being introduced into the intake.

[0052] In step S230, the control that delays the decrease in rotational speed by the motor generator 9 is turned on. Then, the process proceeds to step S240. In step S240, it is determined whether or not exhaust gas at engine startup is being stored in the exhaust storage tank 54. Whether or not exhaust gas is being stored in the exhaust storage tank 54 can be determined, for example, based on the change in the opening degree of the 2-way shutter 52 (opening degree on the EGR side) or the opening degree of the storage EGR valve 56 from the time of engine startup. If exhaust gas at engine startup is being stored in the exhaust storage tank 54, the process proceeds to step S250. If it is not being stored, the process proceeds to step S260.

[0053] In step S250, the eighth control is executed. Specifically, the muffler side of the exhaust passage 35 is closed by the 2-way shutter 52. In this embodiment, the opening ratio between the EGR side and the muffler side is set to 9:1. Also, the storage EGR valve 56 is set between fully closed and an intermediate opening. In this embodiment, the opening of the storage EGR valve 56 is set to 10%. Then, the process returns to the storage EGR control shown in Figure 3, and the storage EGR control routine is returned. The eighth control is performed when the engine 2 is rotating by inertia, exhaust cannot be introduced into the storage EGR passage 51, and exhaust from engine startup has accumulated in the storage EGR passage 51. In this case, the muffler side of the exhaust passage 35 is closed by the 2-way shutter 52 to prevent exhaust in the storage EGR passage 51 from being discharged outside the vehicle, and the storage EGR valve 56 is slightly opened to return the exhaust to the intake side. At this time, delay control is implemented to lengthen the time the exhaust circulates, promoting exhaust purification by the catalyst.

[0054] In step S260, the ninth control is executed. Specifically, the 2WAY shutter 52 is set to a medium opening. In this embodiment, the opening ratio between the EGR side and the muffler side is set to 5:5. Also, the opening of the storage EGR valve is set to between fully closed and an intermediate opening (10% in this embodiment). Then, the process returns to the storage EGR control shown in Figure 3, and the storage EGR control routine is returned. The ninth control is performed when the engine 2 is rotating by inertia, exhaust cannot be introduced into the storage EGR passage 51, and there is no exhaust accumulated in the storage EGR passage 51 from when the engine started. In this case, since the exhaust in the storage EGR passage 51 is considered to be cleaner than in the eighth control, the opening of the muffler side of the 2WAY shutter 52 is increased compared to the eighth control, allowing some of the exhaust in the storage EGR passage 51 to flow to the muffler side and be discharged outside the vehicle.

[0055] As shown in Figure 5, in step S300, it is determined whether the pressure in the exhaust passage 35 upstream of the 2-way shutter 52 is higher than the pressure in the storage EGR passage 51. Whether the pressure upstream of the 2-way shutter 52 is higher than the pressure in the storage EGR passage 51 can be determined, for example, based on the detection value of the differential pressure sensor 65. If the pressure upstream of the 2-way shutter 52 is higher than the pressure in the storage EGR passage 51, the process proceeds to step S310. If the pressure upstream of the 2-way shutter 52 is less than or equal to the pressure in the storage EGR passage 51, the process proceeds to step S320.

[0056] In step S310, the 10th control is executed. Specifically, the 2-way shutter 52 is set to a medium opening on the muffler side. The storage EGR valve 56 is also closed. Then, the process returns to the storage EGR control shown in Figure 3, and the storage EGR control routine is returned. The 10th control is performed when the engine has finished combustion and the intake air volume cannot be measured, but exhaust gas can be introduced into the storage EGR passage 51. In this case, the 2-way shutter 52 is set to a medium opening to introduce a portion of the exhaust gas into the storage EGR passage 51. However, since the intake air volume cannot be measured and an appropriate amount of EGR introduction cannot be calculated, the storage EGR valve 56 is closed.

[0057] In step S320, the 11th control is executed. Specifically, the EGR side is closed by the 2-way shutter 52 (making the opening ratio between the EGR side and the muffler side 0:10). The storage EGR valve 56 is also closed. Then, the process returns to the storage EGR control shown in Figure 3, and the storage EGR control routine is returned. The 11th control is performed when the engine has finished combustion and the intake air volume cannot be measured, and exhaust gas cannot be introduced into the storage EGR passage 51. In this case, as with the 10th control, it is not possible to calculate an appropriate amount of EGR introduction, so the storage EGR valve 56 is closed, but since exhaust gas cannot be introduced into the storage EGR passage 51, the EGR side is closed by the 2-way shutter 52.

[0058] As shown in Figure 6, in step S400, similar to step S300, it is determined whether the pressure upstream of the 2WAY shutter 52 is higher than the pressure in the storage EGR passage 51. If the pressure upstream of the 2WAY shutter 52 is higher than the pressure in the storage EGR passage 51, the process proceeds to step S410. If the pressure upstream of the 2WAY shutter 52 is less than or equal to the pressure in the storage EGR passage 51, the process proceeds to step S420.

[0059] In step S410, the 12th control is executed. Specifically, the 2WAY shutter 52 is set to a medium opening on the muffler side. The storage EGR valve 56 is also opened. Then, the process returns to the storage EGR control shown in Figure 3, and the storage EGR control routine is returned. The 12th control is performed after the engine has fully combusted, when the intake air volume can be measured, the exhaust air-fuel ratio cannot be measured, and exhaust gas can be introduced into the storage EGR passage 51. In this case, the 2WAY shutter 52 is set to a medium opening to introduce a portion of the exhaust gas into the storage EGR passage 51. However, unlike the 10th control, the intake air volume can be measured, so the opening of the 2WAY shutter 52 and the storage EGR valve 56 are controlled to introduce an appropriate amount of EGR gas.

[0060] In step S420, the 13th control is executed. Specifically, the EGR side is closed by the 2WAY shutter 52. Also, the storage EGR valve 56 is opened. Then, the process returns to the storage EGR control shown in Figure 3, and the storage EGR control routine is returned. The 13th control is performed when exhaust gas cannot be introduced into the storage EGR passage 51 after the engine has finished combustion, when the intake air volume can be measured, and when the exhaust air-fuel ratio cannot be measured. In this case, since exhaust gas cannot be introduced into the storage EGR passage 51, the EGR side is closed by the 2WAY shutter 52. However, since exhaust gas remains in the storage EGR passage 51, the storage EGR valve 56 is opened according to the required EGR amount in order to introduce it into the intake passage 31.

[0061] Furthermore, in the case where a high-pressure EGR device 40 is provided as in this embodiment, if the EGR gas cannot be sufficiently cooled by the high-pressure EGR cooler 45 in the high-pressure EGR device 40 at high pressures, a storage EGR device 50 with a lower EGR gas temperature may be used as a substitute for the high-pressure EGR device 40. As described above, in the vehicle 1 according to this embodiment, the engine 2 stops when the vehicle switches from series mode or parallel mode to EV mode while in motion. When the engine stops while the power switch (ignition switch) of the vehicle 1 is ON, the second control in step S60 is performed. This closes the muffler side of the exhaust passage 35 with the 2-way shutter 52. This traps heat around the catalytic converter and suppresses the temperature drop of the catalytic converter. Therefore, when the vehicle switches from EV mode to series mode or parallel mode relatively quickly afterward, the catalytic converter remains active, allowing it to perform exhaust purification well from immediately after engine startup. Furthermore, by closing the throttle valve 33 at this time, heat escape from the intake passage 31 can also be suppressed.

[0062] Furthermore, when the engine 2 is stopped due to the power switch of vehicle 1 being turned off, the first control is performed. This sets the 2-way shutter 52 to a medium opening, opens the exhaust passage 35 to the muffler 38 side to discharge exhaust gas, suppresses the generation of condensed water in the exhaust passage 35 upstream of the 2-way shutter 52, and prevents corrosion of the catalyst. In other words, the second control controls the 2-way shutter 52 to reduce the airflow rate towards the muffler compared to the first control, thereby suppressing the temperature drop of the catalyst when the engine is stopped with the power switch of vehicle 1 turned on. Conversely, the first control controls the 2-way shutter 52 to increase the airflow rate towards the muffler compared to the second control, thereby releasing exhaust gases and suppressing the generation of condensate when the engine 2 is stopped due to the power switch of vehicle 1 being turned off.

[0063] Furthermore, the system includes a storage EGR passage 51 connecting the 2-way shutter 52 and the intake passage 31, and the storage EGR passage 51 has a storage EGR device 50 equipped with a storage EGR valve 56. When the engine 2 stops due to EV driving, the EGR valve is closed. This prevents high-temperature exhaust gas from flowing from the storage EGR passage 51 into the intake passage 31, suppressing heat loss from the exhaust passage 35 and the storage EGR passage 51, and also suppresses heat damage to the intake passage 31.

[0064] Furthermore, when engine 2 stops, the first control in step S50 is performed to open the muffler side of the 2-way shutter 52 and the storage EGR valve 56, allowing engine 2 to be motored in a fuel-cut state. This makes it possible to suppress the generation of condensate by discharging exhaust gases from the exhaust passage 35 and the storage EGR passage 51 when engine 2 stops due to power being turned off from the starting state of vehicle 1.

[0065] Furthermore, when starting engine 2, the muffler side of the 2-way shutter 52 is controlled to close (reduce the opening degree, i.e., make the opening degree on the muffler side smaller than that on the EGR side) as in the third control in step S100, the fifth control in step S140, the sixth control in step S160, the tenth control in step S310, and the twelfth control in step S410. This suppresses the discharge of exhaust gases from the exhaust passage 35 to the outside of the vehicle when starting engine 2.

[0066] At this time, in the third control of step S100, which is performed when engine 2 goes from cranking to complete combustion, the opening degree of the muffler side of the 2-way shutter 52 is suppressed and the EGR valve is opened. Then, after complete combustion, or more specifically from after complete combustion until the intake air volume can be measured, the tenth control of step S310 is performed, so that from the start of cranking of engine 2 until complete combustion, the exhaust is flowed into the storage EGR passage 51 and recirculated into the intake air to reuse the unburned gas in the exhaust, and after complete combustion the exhaust can be stored in the storage EGR passage 51.

[0067] Furthermore, if the engine water temperature is high when engine 2 is started, the fourth control in step S90 is performed. This increases the opening of the 2-way shutter 52 on the muffler side, suppressing the inflow of exhaust into the storage EGR passage 51, preventing high-temperature exhaust from flowing into the intake passage 31, and thus protecting engine 2. At this time, it is preferable that the storage EGR valve 56 is closed.

[0068] This concludes the description of the embodiments of the invention, but the embodiments of the invention are not limited to these embodiments. For example, in the above embodiment, the storage EGR passage 51 of the storage EGR device 50 is connected to the intake passage 31 (intake manifold 42) between the throttle valve 33 and the engine 2, but the storage EGR passage 51 may also be connected to the intake passage 31 upstream of the throttle valve 33. Furthermore, the high-pressure EGR device 40 may not be provided. Moreover, the present invention is also applicable to hybrid vehicles that do not have a storage EGR device 50.

[0069] Furthermore, the exhaust compressor 53 and exhaust storage tank 54 do not need to be provided. Furthermore, in the above embodiment, a two-way shutter 52 is provided at the point where the storage EGR passage 51 branches off from the exhaust passage 35. However, a configuration in which a shutter that adjusts the opening degree of the exhaust passage 35 is provided downstream of the exhaust purification device such as the three-way catalyst 36, and the storage EGR passage 51 is connected between the exhaust purification device and the shutter, is also possible.

[0070] Furthermore, in this embodiment, the hybrid control unit 20 is equipped with an EGR control unit 70, but the engine control unit 22 or other control units may also be equipped with control units. Furthermore, although this embodiment applies the present invention to a plug-in hybrid vehicle capable of switching between EV mode, parallel mode, and series mode, it is broadly applicable to hybrid vehicles that can switch between modes in which the engine operates, such as parallel mode and series mode, and modes in which the engine does not operate, such as EV mode. [Explanation of symbols]

[0071] 1. Vehicle (Hybrid Vehicle) 2 engines 4. Front motor (motor for driving) 9. Motor Generator (Electric Motor) 31 Intake passage 35 Exhaust passage 36. Three-way catalytic converter (exhaust gas purification device) 42 Intake manifold (intake passage) 51 Storage EGR passage (EGR passage) 52 2-Way Shutter (Shutter) 56 Storage EGR valve (EGR valve) 70 EGR Control Unit (Control Unit)

Claims

1. It is equipped with an engine and a motor for driving, At least one engine driving mode in which the engine is running, A hybrid vehicle that can switch between an EV driving mode in which the vehicle is driven by the drive motor with the engine stopped, An exhaust gas purification device provided in the exhaust passage of the aforementioned engine, An adjustment means for adjusting the airflow rate of the exhaust passage downstream of the exhaust purification device, When the engine stops due to the EV driving mode, the control unit controls the adjustment means to reduce the airflow rate in the exhaust passage downstream of the exhaust purification device compared to when the engine stops, because the starting state of the hybrid vehicle has stopped. A hybrid vehicle characterized by having the following features.

2. The adjustment means is a shutter provided downstream of the exhaust gas purification device in the exhaust passage. The system comprises an EGR passage connecting the position in the exhaust passage where the shutter is provided, or the position between the exhaust purification device and the shutter, and the intake passage of the engine, and an EGR valve provided in the EGR passage. When the engine stops due to the EV driving mode, the control unit controls the shutter to close to a predetermined opening or less, thereby reducing the airflow rate in the exhaust passage downstream of the exhaust purification device, and also controls the EGR valve to close the EGR passage. The hybrid vehicle according to claim 1, characterized by the features described above.

3. The engine has an electric motor that drives the engine, The control unit controls the engine to stop when the hybrid vehicle's startup state is terminated, by opening the shutter and the EGR valve, and by forcibly driving the engine with an electric motor in a fuel cut-off state. The hybrid vehicle according to claim 2, characterized by its features.

4. The control unit controls the adjustment means so that when the engine starts, the airflow rate in the exhaust passage downstream of the exhaust purification device is lower than when the engine stops due to the hybrid vehicle's startup state being stopped. The hybrid vehicle according to claim 1, characterized by the features described above.

5. The adjustment means is a shutter provided downstream of the exhaust gas purification device in the exhaust passage. The system comprises an EGR passage connected to the position in the exhaust passage where the shutter is provided, or to a position between the exhaust purification device and the shutter, and an EGR valve provided downstream of the EGR passage. The control unit, From the start of engine cranking until complete combustion, the shutter is closed to a predetermined opening or less to reduce the airflow rate in the exhaust passage downstream of the exhaust purification device, and the EGR valve is opened. After complete combustion, the shutter is kept closed, and the EGR valve is closed to close the EGR passage. The hybrid vehicle according to feature 4.

6. The adjustment means is a shutter provided downstream of the exhaust gas purification device in the exhaust passage. The control unit, If the engine temperature is above a predetermined level when the engine is started, the shutter is controlled to open. The hybrid vehicle according to feature 4.

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