Control device for engine

Abstract

To provide a control device for an engine that enables improvement of reacceleration performance of a vehicle in a circuit mode.SOLUTION: A control device for an engine has an air bypass valve for opening / closing an intake bypass passage communicating an upstream side and a downstream side of a compressor of a supercharger, and is mounted to a vehicle. The control device includes: a control section that closes the air bypass valve when a pressure ratio of pressure on the downstream side of the compressor to pressure on the upstream side of the compressor is equal to or lower than a first determination value set to a larger value as an intake air amount of the engine increases and that opens the air bypass valve when the pressure ratio exceeds the first determination value; and a switching section that switches the first determination value to a higher value when a traveling mode is a circuit mode, compared to when the traveling mode is a mode other than the circuit mode.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an engine control device. [Background technology]

[0002] For example, during deceleration, the throttle valve opening may suddenly decrease. In this case, the intake air volume decreases quickly, but the pressure downstream of the compressor may remain high. This may cause intake air to flow back toward the compressor, potentially resulting in intake surging. To avoid intake surging, the air bypass valve is opened when the pressure ratio, which is the pressure downstream of the compressor relative to the pressure upstream of the compressor, exceeds a threshold value that is set higher as the intake air volume increases. This allows intake air to flow back from the downstream side of the compressor to the upstream side via the bypass passage, reducing the pressure downstream of the compressor and avoiding intake surging (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-189907 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, when the driving mode is switched to the circuit mode, if the air bypass valve opens as described above during deceleration, there is a risk that the re-acceleration performance after deceleration will be reduced.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an engine control device that improves the re-acceleration performance of a vehicle in circuit mode. [Means for solving the problem]

[0006] The above object can be achieved by a control device for an engine mounted on a vehicle, the control device having an air bypass valve that opens and closes an intake bypass passage that connects the upstream side and downstream side of a compressor of a turbocharger, the engine control device including: a control unit that closes the air bypass valve when a pressure ratio, which is the pressure downstream of the compressor to the pressure upstream of the compressor, is equal to or smaller than a first determination value that is set to a value that increases as the amount of intake air of the engine increases, and opens the air bypass valve when the pressure ratio exceeds the first determination value; and a switching unit that, when the driving mode is a circuit mode, switches the first determination value to a value that is higher than when the driving mode is other than the circuit mode.

[0007] When the pressure ratio is equal to or less than the first determination value and equal to or less than a second determination value that is a constant value regardless of the intake air amount while the air bypass valve is open, the control unit closes the air bypass valve, and when the driving mode is the circuit mode, the switching unit may switch the second determination value to a value that is higher than when the driving mode is other than the circuit mode. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide an engine control device that improves the re-acceleration performance of a vehicle in circuit mode. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic configuration diagram of a vehicle. [Figure 2] 10 is a flowchart illustrating a determination value switching control executed by an ECU. [Figure 3] FIG. 10 is a diagram illustrating a map defining first and second determination values. [Figure 4] 4 is a flowchart illustrating an example of an air bypass valve opening / closing control executed by the ECU. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Vehicle outline] FIG. 1 is a schematic diagram of a vehicle 100. The vehicle 100 includes an engine 1, an intake passage 3, an exhaust passage 4, a turbocharger 5, an intercooler 6, a catalyst 7a, a filter 7b, an exhaust bypass passage 8, a wastegate valve 9, a transmission 21, a differential gear 23, wheels 25, and an ECU (Electronic Control Unit) 30. The engine 1 may be a gasoline engine or a diesel engine. The driving force of the engine 1 is transmitted to the wheels 25 via the transmission 21 and the differential gear 23. The vehicle 100 is an engine vehicle equipped with the engine 1 as a driving source. However, the vehicle 100 may be a hybrid vehicle equipped with a motor in addition to the engine 1 as a driving source.

[0011] The engine 1 has four cylinders 2, but the number of cylinders is not limited to this. Each cylinder 2 is provided with a fuel injection valve 2a and a spark plug 2b. An intake passage 3 and an exhaust passage 4 are connected to the engine 1. A compressor 5b of a supercharger 5 is disposed in the intake passage 3. A turbine 5a of the supercharger 5 is disposed in the exhaust passage 4. The turbine 5a and compressor 5b are coaxially connected by a shaft. The supercharger 5 supercharges the intake air to the engine 1.

[0012] An intake bypass passage 18 that bypasses the compressor 5b and an air bypass valve 19 that opens and closes the intake bypass passage 18 are provided in the intake passage 3. The opening degree of the air bypass valve 19 is adjusted by an electric actuator 19a that drives the air bypass valve 19. The open / closed state of the air bypass valve 19 is controlled by the ECU 30 based on the intake air amount and a pressure ratio, which will be described later.

[0013] An exhaust bypass passage 8 that bypasses the turbine 5a and a wastegate valve 9 that opens and closes the exhaust bypass passage 8 are provided in the exhaust passage 4. The opening degree of the wastegate valve 9 is adjusted by an electric actuator 9a that drives the wastegate valve 9. The opening degree of the wastegate valve 9 is feedback-controlled by the ECU 30 so that the boost pressure becomes a target boost pressure that is determined according to the operating state of the engine 1.

[0014] An intercooler 6 that cools the intake air is arranged downstream of the compressor 5b in the intake passage 3. A throttle valve 3a that adjusts the amount of intake air for the engine 1 is arranged downstream of the intercooler 6 in the intake passage 3. A catalyst 7a that purifies the exhaust and a filter 7b that collects exhaust particulates are provided downstream of the turbine 5a in the exhaust passage 4. The filter 7b is provided downstream of the catalyst 7a.

[0015] The ECU 30 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ECU 30 controls the engine 1 based on information from sensors and information previously stored in the ROM in accordance with a control program previously stored in the ROM. The ECU 30 is an example of an engine control device. The ECU 30 functionally realizes a control unit and a switching unit, which will be described later.

[0016] The ECU 30 controls the operating state of the engine 1 based on detection signals from various sensors, such as a crank angle sensor 11, an air flow meter 12, an air-fuel ratio sensor 13, and pressure sensors 15 and 16. The crank angle sensor 11 detects the rotation angle of the crankshaft of the engine 1. The air flow meter 12 detects the amount of intake air drawn into the intake passage 3. The air-fuel ratio sensor 13 detects the air-fuel ratio of the exhaust gas discharged from the engine 1. The accelerator opening sensor 14 detects the accelerator opening, which is the amount of accelerator pedal operation. The pressure sensor 15 detects the pressure upstream of the compressor 5b. The pressure sensor 16 detects the pressure downstream of the compressor 5b. The pressure sensor 15 is provided downstream of the upstream end of the intake bypass passage 18 of the intake passage 3 and upstream of the compressor 5b. The pressure sensor 16 is provided downstream of the compressor 5b and upstream of the downstream end of the intake bypass passage 18 of the intake passage 3.

[0017] Based on output signals from various sensors, the ECU 30 determines the rotation speed and load of the engine 1. Depending on the operating state determined in this manner, the ECU 30 outputs command signals to various drive circuits connected to the output ports.

[0018] The ECU 30 can switch the driving mode between normal mode, sport mode, eco mode, and circuit mode. The driver can switch the driving mode between normal mode, sport mode, and eco mode by operating the mode selector switch 20. Regarding the circuit mode, for example, when the vehicle 100 is at a circuit, the driver can switch the driving mode to circuit mode by operating a mobile terminal such as a smartphone. When the driving mode is switched to circuit mode, the control map of the vehicle 100 is switched to a control map that prioritizes driving performance corresponding to the circuit mode. This improves the driving performance of the vehicle 100 compared to driving modes other than circuit mode. Note that switching to circuit mode may also be performed by the mode selector switch 20 as described above.

[0019] [Judgment value switching control] 2 is a flowchart illustrating the determination value switching control. The ECU 30 determines whether the driving mode has been switched to the circuit mode (step S1). If the answer is No in step S1, the ECU 30 sets the first determination value to value A1 and the second determination value to value B1 (step S2). If the answer is Yes in step S1, the ECU 30 switches the first determination value to value A2, which is higher than value A1, and switches the second determination value to value B2, which is higher than value B1 (step S3). Step S3 is an example of processing executed by the switching unit.

[0020] FIG. 3 is an example diagram of a map that defines the first and second determination values. In FIG. 3, the horizontal axis represents the intake air amount, and the vertical axis represents the pressure ratio. The pressure ratio is the pressure downstream of the compressor 5b relative to the pressure upstream of the compressor 5b. In other words, the pressure ratio is a value obtained by dividing the pressure downstream of the compressor 5b by the pressure upstream of the compressor 5b. The first determination values ​​A1 and A2 are defined to increase as the intake air amount increases. The second determination values ​​B1 and B2 are constant pressure ratio values ​​regardless of the intake air amount. The first determination value, which will be described in detail later, is used to determine whether or not to open the closed air bypass valve 19. The first and second determination values ​​are used to determine whether or not to close the open air bypass valve 19. The reason why both the first and second determination values ​​are used to close the air bypass valve 19 is that if the air bypass valve 19 is closed at a relatively high pressure ratio using only the first determination value, the boost pressure may rise suddenly, causing a shock to the vehicle 100. This will be described in more detail later.

[0021] [Air bypass valve opening / closing control] 4 is a flowchart illustrating the air bypass valve opening / closing control executed by the ECU 30. In the air bypass valve opening / closing control, the ECU 30 constantly acquires the intake air amount and the pressure ratio from the air flow meter 12 and the pressure sensors 15 and 16. The ECU 30 determines whether the pressure ratio is higher than a first determination value (step S11). If the answer is No in step S11, the ECU 30 closes the air bypass valve 19 (step S14). If the answer is Yes in step S11, the ECU 30 opens the air bypass valve 19 (step S12). This makes it possible to avoid intake surging. Step S12 is an example of processing executed by the control unit.

[0022] As described above, in the circuit mode, a value A2 higher than the value A1 is used as the first determination value. This narrows the region in which the air bypass valve 19 opens during deceleration in the circuit mode, improving re-acceleration performance. Note that using the value A2 as the first determination value in the circuit mode increases the rotation speed of the compressor 5b compared to modes other than the circuit mode. For this reason, it is preferable to set the value A2 used as the first determination value in consideration of durability resulting from such an increase in the rotation speed of the compressor 5b.

[0023] Next, the ECU 30 determines whether the pressure ratio is equal to or less than a first determination value and equal to or less than a second determination value (step S13). If the result in step S13 is No, the ECU 30 executes step S12 again. If the result in step S13 is Yes, the ECU 30 closes the opened air bypass valve 19 (step S14). Step S14 is an example of processing executed by the control unit.

[0024] If the opened air bypass valve 19 were to close at this time, the boost pressure would rise suddenly, causing a shock to the vehicle 100 and possibly worsening drivability. To prevent this deterioration in drivability, the value B1 used as the second determination value in modes other than the circuit mode is set to a relatively low value. However, in the circuit mode, it is preferable to prioritize re-acceleration performance over drivability. For this reason, the value B2 used as the second determination value in the circuit mode is set to a relatively high value. This allows the boost pressure to rise suddenly, improving re-acceleration performance.

[0025] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0026] 1 engine 3 Intake passage 5. Turbocharger 5b Compressor 18 Intake bypass passage 19 Air bypass valve 30 ECU (engine control unit, control section, switching section)

Claims

1. A control device for an engine mounted on a vehicle, the control device having an air bypass valve that opens and closes an intake bypass passage that connects an upstream side and a downstream side of a compressor of a turbocharger, a control unit that closes the air bypass valve when a pressure ratio, which is a pressure on the downstream side of the compressor to a pressure on the upstream side of the compressor, is equal to or less than a first determination value, the first determination value being set to a value that increases as the intake air amount of the engine increases, and that opens the air bypass valve when the pressure ratio exceeds the first determination value; a switching unit that, when the driving mode is a circuit mode, switches the first determination value to a higher value than when the driving mode is other than the circuit mode.

2. When the pressure ratio is equal to or less than the first determination value and equal to or less than a second determination value that is a constant value regardless of the intake air amount while the air bypass valve is open, the control unit closes the air bypass valve, The engine control device according to claim 1 , wherein when the driving mode is the circuit mode, the switching unit switches the second determination value to a higher value than when the driving mode is other than the circuit mode.

Images