Engine with EGR system
The engine with an EGR device addresses the challenge of maintaining starting and exhaust performance during startup by controlling the EGR valve and exhaust gas recirculation based on engine states, enhancing starting performance and exhaust treatment.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- MITSUBISHI MOTORS CORP
- Filing Date
- 2022-12-21
- Publication Date
- 2026-06-03
AI Technical Summary
Existing engines face challenges in maintaining starting performance and exhaust performance during startup due to inaccurate control of the EGR valve, especially when sensors for intake air amount and air-fuel ratio are not accurately detected, leading to potential decreases in both starting and exhaust performance.
An engine with an EGR device that includes an exhaust gas purification device, an EGR passage connecting the exhaust and intake passages, and an EGR valve, controlled by an adjustment means and a control unit to manage the ratio of exhaust gases and the EGR valve opening based on engine operating states, ensuring appropriate recirculation and suppression of exhaust discharge during startup.
This solution effectively suppresses exhaust gas discharge to the outside while ensuring starting performance by recirculating unburned gases and residual oxygen to the intake passage, improving engine starting performance and exhaust treatment efficiency.
Smart Images
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Abstract
Description
Technical Field
[0005] , ,
[0004]
[0001] The present invention relates to an exhaust gas purification technology for an engine equipped with an EGR device.
Background Art
[0002] When the engine is started, since the fuel injection amount is set large to improve the starting performance, there is a problem that the exhaust state at the time of engine start deteriorates. In contrast, in Patent Document 1, an EGR passage that connects the exhaust passage on the downstream side of the exhaust gas purification device and the intake passage, and a flow rate change mechanism that changes the ratio between the flow rate of the exhaust discharged from the exhaust passage and the flow rate of the exhaust flowing into the EGR passage are provided. When the NOx concentration discharged from the air purification device is high, an EGR system is proposed that controls the flow rate change mechanism so that the ratio of the flow rate of the exhaust flowing into the EGR passage is larger than the ratio of the flow rate of the exhaust discharged from the exhaust passage.
Prior Art Documents
Patent Documents
[0003]
Patent Document 1
Summary of the Invention
Problems to be Solved by the Invention
[0004] [ However, when the engine is started, depending on the operating state of the engine, it may not be appropriate to increase the flow rate of the exhaust flowing into the EGR passage. For example, immediately after the engine is started, sensors for detecting the intake air amount and the air-fuel ratio of the exhaust at the time of starting may not be able to detect accurately, the EGR valve may not be controlled appropriately, and there is a risk of a decrease in starting performance or exhaust performance.
[0005] The present invention has been made to solve such problems, and its objective is to provide an engine equipped with an EGR device that suppresses the discharge of exhaust gases to the outside during startup while ensuring starting performance. [Means for solving the problem]
[0006] To achieve the above objective, the engine with an EGR device according to claim 1 of the present invention comprises: an exhaust gas purification device provided in the exhaust passage; an EGR passage connecting the exhaust passage downstream of the exhaust gas purification device and the intake passage; and an EGR valve for adjusting the opening degree of the EGR passage, wherein the engine with an EGR device comprises: an adjustment means for adjusting the ratio of exhaust gases between the side of the exhaust gas purification device downstream of the exhaust gas purification device and the EGR passage side of the exhaust passage; and a control unit that controls the ratio of exhaust gases between the side of the exhaust gas purification device downstream of the exhaust gas purification device and the EGR passage side of the exhaust passage and the opening degree of the EGR valve based on the operating state at engine startup. The control unit controls the adjustment means so that the proportion of exhaust from the EGR passage side of the exhaust passage is greater than the proportion of exhaust from the EGR passage side of the exhaust purification device downstream of the exhaust gas purification device, from the time the engine starts cranking until complete combustion, and also controls the EGR valve to open the EGR passage. It is characterized by the following:
[0007] This allows the adjustment means to control the discharge of exhaust gases to the downstream side of the exhaust gas purification device in the exhaust passage and to the EGR passage side, and the EGR valve to control the recirculation of exhaust gases from the EGR passage to the intake passage. Furthermore, by controlling the adjustment means and the EGR valve based on the engine's operating state, it is possible to achieve both suppression of exhaust gas discharge to the outside and ensure engine starting performance according to the engine's operating state.
[0008] especially, By recirculating exhaust gases, including unburned gases, from the EGR passage to the intake passage along with residual oxygen in the EGR passage between the start of engine cranking and complete combustion, engine starting performance can be improved.
[0009] Preferably, the intake passage is provided with an intake volume detection means for detecting the amount of intake air, and the control unit controls the adjustment means so that exhaust gas is introduced into both the downstream side of the exhaust gas purification device in the exhaust passage and the EGR passage side from the time the engine is fully ignited until the intake volume detection means can detect the amount of intake air, and also controls the EGR valve to close the EGR passage.
[0010] This allows the EGR valve to close the EGR passage until the intake volume detection means can detect the intake volume, thereby avoiding the introduction of exhaust gas into the intake passage based on the intake volume detection by the intake volume detection means, which may be inaccurate. Preferably, the exhaust passage is provided with an air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas, and the control unit controls the adjustment means so that exhaust gas is introduced into both the downstream side of the exhaust gas purification device and the EGR passage side of the exhaust passage from the time the intake air volume detection means becomes detectable when the engine starts until the air-fuel ratio detection means becomes activated and detectable, and also controls the EGR valve to open the EGR passage.
[0011] This allows exhaust resistance to be suppressed while recirculating exhaust gases containing unburned gases that flow into the EGR passage during engine startup back into the intake passage for treatment. Preferably, the above Adjustment means The control unit includes a differential pressure detection means for detecting the differential pressure between the pressure in the upstream exhaust passage and the pressure in the EGR passage, and the control unit operates from the time of engine startup, from cranking until the air-fuel ratio detection means is activated and detectable. Adjustment means If the pressure in the upstream exhaust passage is lower than the pressure in the EGR passage, the adjustment means should be controlled so that the proportion of exhaust in the EGR passage is smaller than that downstream of the exhaust gas purification device in the exhaust passage.
[0012] This prevents exhaust gases that have entered the EGR passage during engine startup from flowing back and being discharged downstream of the exhaust gas purification device in the exhaust passage. Preferably, the exhaust passage is located upstream of the EGR passage. It is connected to the exhaust passage The control unit comprises a high-pressure EGR passage connecting the intake passage and a high-pressure EGR valve for adjusting the opening degree of the high-pressure EGR passage. The control unit may open the high-pressure EGR valve when the engine is running at a predetermined high speed and low load, and close the high-pressure EGR valve and open the EGR valve when the engine is running at a predetermined high speed and high load.
[0013] This allows exhaust gases to be recirculated into the intake passage via the high-pressure EGR passage during high-speed, low-load engine operation, thereby improving exhaust performance. During high-speed, high-load engine operation, closing the high-pressure EGR valve prevents high-temperature exhaust gases from being recirculated into the intake passage. Conversely, opening the EGR valve allows exhaust gases, which tend to cool down more easily, to be recirculated, further improving exhaust performance. [Effects of the Invention]
[0014] According to the present invention, by controlling the shutter and EGR valve based on the engine operating state, it is possible to suppress the discharge of exhaust gases to the outside and ensure engine starting performance at the time of engine startup. [Brief explanation of the drawing]
[0015] [Figure 1] This is a schematic diagram of the drive system of a hybrid vehicle according to an embodiment of the present invention. [Figure 2] This is a diagram showing the configuration of the intake and exhaust systems of the engine of the hybrid vehicle according to this embodiment. [Figure 3] This flowchart shows the control procedure for storage EGR control performed in the EGR control unit. [Figure 4] This flowchart shows the control procedure for condensation control. [Figure 5] This is a flowchart showing the procedure for estimating and controlling the intake air volume. [Figure 6] This flowchart shows the air-fuel ratio estimation injection control procedure. [Modes for carrying out the invention]
[0016] Hereinafter, embodiments of the present invention will be described based on the drawings. FIG. 1 is a schematic configuration diagram of a 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 (engine with an EGR device) to generate electricity and includes an electric front motor 4 (travel motor) for driving wheels.
[0017] The engine 2 can drive the drive shaft 8 of the front wheels 3 via the front transaxle 7, and can drive the motor generator 9 (electric motor) via the front transaxle 7 to generate electricity. Further, the engine 2 and the front wheels 3 are connected via a clutch 16 disposed in the front transaxle 7. The front motor 4 is driven by being supplied with electric power from a drive battery 11 or the motor generator 9 mounted on the vehicle 1 via a front control unit 10, and drives the drive shaft 8 of the front wheels 3 via the front transaxle 7.
[0018] The electric power generated by the motor generator 9 can charge the drive battery 11 via the front control unit 10, and can supply electric power to the front motor 4 and the rear motor 6. The drive battery 11 is composed of a secondary battery such as a lithium-ion battery. Further, the drive battery 11 includes a charge rate detection unit 11a for detecting the state of charge (SOC) of the drive battery 11.
[0019] The front control unit 10 has a function of controlling the output of the front motor 4 and controlling the power generation amount and output of the motor generator 9 based on a control signal from a 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.
[0020] 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.
[0021] 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.
[0022] 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.
[0023] 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.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] The 2-way shutter 52 allows you to change its opening degree to adjust the ratio of exhaust flowing into the storage EGR passage 51 and 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.
[0028] 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.
[0029] 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.
[0030] Furthermore, the intake passage 31 between the air cleaner 32 and the throttle valve 33 is equipped with an intake flow sensor (MAF60, intake volume detection means) 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, respectively, in the intake passage 31 on the upstream and downstream sides of the throttle valve 33.
[0031] 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, air-fuel ratio detection means) 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.
[0032] Furthermore, a differential pressure sensor (DPS65, differential pressure detection means) 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).
[0033] 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 60, 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.
[0034] 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.
[0035] 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.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] In step S50, the first control is executed. Specifically, the 2-way shutter 52 is opened to a medium position (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 motorize 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.
[0040] 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.
[0041] 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.
[0042] 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.
[0043] 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.
[0044] 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.
[0045] 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 is being performed, such as activating the catalyst heater or performing post-injection. Hereinafter, the state where the catalyst is being heated is 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.
[0046] 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.
[0047] 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.
[0048] 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.
[0049] 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.
[0050] 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.
[0051] 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.
[0052] 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.
[0053] 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.
[0054] 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 (the storage EGR passage 51 between the exhaust storage tank 54 and the storage EGR cooler 55) 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.
[0055] 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.
[0056] 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.
[0057] 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.
[0058] 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.
[0059] In step S420, the 13th control is executed. Specifically, the EGR side is closed by the 2-way shutter 52. 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 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 2-way 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.
[0060] 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, the engine 2 in this embodiment is equipped with exhaust gas purification devices such as a three-way catalytic converter 36 and a particulate filter 37 in the exhaust passage 35, and a storage EGR device 50 which has a storage EGR passage 51 that connects the exhaust passage 35 downstream of the three-way catalytic converter 36 and the particulate filter 37 to the intake passage 31, and a storage EGR valve 56 that adjusts the opening degree of the storage EGR passage 51.
[0061] In this embodiment, a 2-way shutter 52 is provided at the connection point between the exhaust passage 35 and the storage EGR passage 51, making it possible to adjust the opening ratio between the muffler 38 side, which is downstream of the exhaust passage 35, and the storage EGR passage 51 side. By controlling the 2-way shutter 52, the exhaust can be discharged arbitrarily to the muffler 38 side and the EGR passage side (storage EGR passage 51 side), and by controlling the storage EGR valve 56, the recirculation of exhaust from the storage EGR passage 51 to the intake passage 31 can be controlled.
[0062] Furthermore, the EGR control unit 70 is configured to control the opening degree of the storage EGR valve 56 and the opening ratio of the 2-way shutter 52 based on the operating state of the engine 2. This makes it possible to suppress the discharge of exhaust to the muffler 38 side and ensure engine starting performance at the same time, depending on the exhaust discharge situation from the engine 2. For example, from the time the engine 2 starts cranking until complete combustion, the EGR control unit 70 performs the third control in step S100, which controls the 2-way shutter 52 to open the EGR passage side more than the muffler side, and also controls the storage EGR valve 56 to open the storage EGR passage 51.
[0063] This allows exhaust gases containing unburned gas (unburned fuel), along with oxygen remaining in the storage EGR passage 51, to be recirculated from the storage EGR passage 51 to the intake passage 31 between the start of cranking of engine 2 and complete combustion, thereby improving the starting performance of engine 2. By controlling the 2-way shutter 52 to slightly open the muffler side, the increase in exhaust resistance can be suppressed and starting performance can be ensured, but the 2-way shutter 52 may also be controlled to completely close the muffler side.
[0064] Furthermore, the EGR control unit 70 performs the 10th control in step S310 from the time the engine 2 is fully ignited until the intake air flow sensor (MAF60) can detect the intake air volume. This control controls the 2-way shutter 52 so that both the muffler side and the EGR passage side are open to an intermediate degree, and controls the storage EGR valve 56 to close the storage EGR passage 51. This allows the storage EGR valve 56 to close the storage EGR passage 51 until the MAF 60 can detect the intake volume, thereby avoiding the introduction of exhaust gas (EGR gas) into the intake passage 31 based on the intake volume, which could be inaccurate.
[0065] Furthermore, from the time the MAF 60 becomes detectable until the exhaust air-fuel ratio sensor (LAFS 63) is activated and becomes detectable, the EGR control unit 70 performs the 12th control in step S410, controlling the storage EGR valve 56 to open the storage EGR passage 51, and also controlling the 2-way shutter 52 to open both the EGR passage side and the muffler side. This makes it possible to suppress exhaust resistance in the exhaust passage 35. In addition, exhaust gases that have a particularly large amount of unburned gas flowing into the storage EGR passage 51 immediately after engine start are processed by being recirculated into the intake passage 31.
[0066] Furthermore, during the period from cranking when the engine 2 is started until the LAFS 63 is activated and detectable, if the pressure in the exhaust passage 35 upstream of the 2-way shutter 52 is lower than the pressure in the storage EGR passage 51, the EGR control unit 70 performs the 13th control in step S420 and controls the 2-way shutter 52 to close the EGR passage side (opening to zero).
[0067] This prevents exhaust gas from flowing back from the storage EGR passage 51 into the exhaust passage 35 and being discharged to the muffler 38 side when the engine 2 is started. Furthermore, the engine 2 of this embodiment is equipped with a high-pressure EGR device that includes a high-pressure EGR passage 43 connecting the exhaust passage upstream of the storage EGR passage 51 to the intake passage 31, and a high-pressure EGR valve 44 for adjusting the opening degree of the high-pressure EGR passage 43.
[0068] The EGR control unit 70 opens the high-pressure EGR valve 44 when the engine 2 is running at high speed and under low load, and closes the high-pressure EGR valve 44 and opens the storage EGR valve 56 when the engine 2 is running at high speed and under high load. This allows exhaust gas to be recirculated to the intake passage 31 via the high-pressure EGR passage 43 when the engine is running at high RPM and low load, thereby reducing NOx in the exhaust gas. Alternatively, the storage EGR valve 56 may also be opened at this time, allowing exhaust gas to be recirculated from both the storage EGR passage 51 and the high-pressure EGR passage 43. When the engine 2 is running at high RPM and high load, closing the high-pressure EGR valve 44 prevents high-temperature exhaust gas from being recirculated to the intake manifold 42, thus protecting the engine 2. Furthermore, opening the storage EGR valve 56 allows exhaust gas, which tends to be relatively cooler, to be recirculated, further reducing NOx in the exhaust gas.
[0069] 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.
[0070] 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.
[0071] 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 an engine for driving a plug-in hybrid vehicle that can switch between EV mode, parallel mode, and series mode, it is applicable to engines for various vehicles and other applications. The present invention is broadly applicable to engines equipped with an EGR device and an exhaust gas purification device. [Explanation of symbols]
[0072] 2. Engine (Engine with EGR system) 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) 60 MAF (Intake volume detection means) 63 LAFS (Air-Fuel Ratio Detection System) 65 DPS (Differential Pressure Detection Method) 70 EGR control unit
Claims
1. Exhaust purifying device installed in the exhaust passage, An EGR passage connecting the exhaust passage and intake passage downstream of the exhaust gas purification device, An engine with an EGR device, comprising an EGR valve for adjusting the opening degree of the EGR passage, An adjustment means for adjusting the ratio of exhaust gases between the downstream side of the exhaust gas purification device in the exhaust passage and the EGR passage side, The system includes a control unit that controls the ratio of exhaust gases from the downstream side of the exhaust gas purification device in the exhaust passage to the EGR passage side and the opening degree of the EGR valve, based on the operating state at engine startup, using the adjustment means. The control unit controls the adjustment means so that, from the time the engine starts cranking until complete combustion, the proportion of exhaust from the EGR passage side of the exhaust passage is greater than that from the downstream side of the exhaust purification device, and also controls the EGR valve to open the EGR passage. An engine equipped with an EGR system, characterized by the following features.
2. The intake passage is equipped with an intake volume detection means for detecting the amount of intake air, The control unit controls the adjustment means so that exhaust gas is introduced into both the downstream side of the exhaust gas purification device in the exhaust passage and the EGR passage side, and controls the EGR valve to close the EGR passage, from the time the engine is fully ignited until the intake volume detection means can detect the intake volume. The engine with an EGR device according to feature 1.
3. The exhaust passage is equipped with an air-fuel ratio detection means for detecting the air-fuel ratio of the exhaust gas. The control unit controls the adjustment means so that exhaust gas is introduced into both the downstream side of the exhaust gas purification device and the EGR passage side of the exhaust passage, and controls the EGR valve to open the EGR passage, from the time the intake air volume detection means becomes detectable when the engine starts until the air-fuel ratio detection means becomes activated and detectable. The engine with an EGR device according to feature 2.
4. The system includes a differential pressure detection means for detecting the differential pressure between the pressure in the exhaust passage upstream of the adjustment means and the pressure in the EGR passage. The control unit controls the adjustment means such that, from the time of engine startup until the air-fuel ratio detection means is activated and detectable, the pressure in the exhaust passage upstream of the adjustment means is lower than the pressure in the EGR passage, so that the proportion of exhaust in the EGR passage is smaller than that of the exhaust gas purification device downstream of the exhaust passage. The engine with an EGR device according to feature 3.
5. A high-pressure EGR passage connects to the exhaust passage upstream of the EGR passage and connects the exhaust passage and the intake passage, The system includes a high-pressure EGR valve for adjusting the opening degree of the high-pressure EGR passage, The control unit, When the engine is operating at a predetermined high rotation speed and low load, the high-pressure EGR valve is opened. When the engine is operating at a predetermined high rotational speed and high load, the high-pressure EGR valve is closed and the EGR valve is opened. The engine with an EGR device according to feature 1.