Control device for turbocharged engines

Abstract

To provide a control device of an engine with a supercharger, securing excellent sport sound.SOLUTION: A control device of an engine with a supercharger controls the ignition timing, injection quantity, and intake air amount of the engine with the supercharger loaded on a vehicle, and controls a wastegate valve disposed in a bypass passage bypassing a turbine of the supercharger. The control device of the engine with the supercharger executes torque-down control of retarding the ignition timing, when shifting from accelerator ON to accelerator OFF, by reducing the injection quantity and the intake air amount while opening the wastegate valve, and executes exhaust air sound control of further retarding the ignition timing until the finish of a top dead point between a compression stroke and an expansion stroke, and opening the wastegate valve.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a control device for an engine with a supercharger.

Background Art

[0002] There is a technique of increasing the exhaust sound by significantly retarding the ignition timing of the engine when shifting from accelerator on to accelerator off to obtain a good sports sound (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003] [[ID=2,2]]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the case of an engine with a supercharger, if the above control is executed with the wastegate valve closed, the exhaust sound may be attenuated by the turbine of the supercharger, and it may not be possible to obtain a good sports sound.

[0005] Therefore, an object of the present invention is to provide a control device for an engine with a supercharger that ensures a good sports sound.

Means for Solving the Problems

[0006] The above objective can be achieved by a control device for a supercharged engine mounted on a vehicle, which controls the ignition timing, fuel injection amount, and intake air amount of the supercharged engine, and also controls a wastegate valve provided in a bypass passage that bypasses the turbine of the supercharger, wherein when transitioning from accelerator on to accelerator off, the control device performs torque down control, which reduces the fuel injection amount and intake air amount while closing the wastegate valve and retards the ignition timing, and then performs exhaust noise control, which further retards the ignition timing to after top dead center between the compression stroke and the expansion stroke and opens the wastegate valve. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a control device for a supercharged engine that ensures a good sports sound. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of the vehicle's configuration. [Figure 2] This timing chart illustrates the torque reduction control and exhaust noise control performed by the ECU. [Modes for carrying out the invention]

[0009] [Vehicle Outline] Figure 1 is a schematic diagram of the vehicle 100. The vehicle 100 includes a supercharged engine (hereinafter simply referred to as the engine) 1, an intake passage 3, an exhaust passage 4, a supercharger 5, an intercooler 6, a catalyst 7a, a filter 7b, a bypass passage 8, a wastegate valve 9, a transmission 21, a differential 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 23. The vehicle 100 is an engine-powered vehicle equipped with the engine 1 as a power source. However, it may also be a hybrid vehicle equipped with an electric motor in addition to the engine 1 as a power source.

[0010] Engine 1 has four cylinders 2, but the number of cylinders is not limited to this. Each cylinder 2 is equipped with a fuel injector 2a and a spark plug 2b. Engine 1 is connected to an intake passage 3 and an exhaust passage 4. A compressor 5b of the supercharger 5 is located in the middle of the intake passage 3. A turbine 5a of the supercharger 5 is located in the middle of the exhaust passage 4. The turbine 5a and the compressor 5b are coaxially connected by a shaft. The supercharger 5 supercharges the intake air into engine 1.

[0011] In the middle of the exhaust passage 4, there is a bypass passage 8 that bypasses the turbine 5a, and a wastegate valve 9 that opens and closes the bypass passage 8. 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 determined according to the operating state of the engine 1. The ECU 30 controls the opening degree of the wastegate valve 9 by outputting a command value to the electric actuator 9a. The wastegate valve 9 is a normally closed type that is fully closed when the electric actuator 9a is not energized.

[0012] In the intake passage 3, an intercooler 6 for cooling the intake air is located downstream of the compressor 5b. Downstream of the intercooler 6 in the intake passage 3, a throttle valve 3a for adjusting the amount of intake air for the engine 1 is located.

[0013] In the exhaust passage 4, downstream of the turbine 5a, a catalyst 7a for purifying exhaust gases and a filter 7b for collecting exhaust gas particles are provided. The filter 7b is located downstream of the catalyst 7a. The catalyst 7a contains catalytic metals such as platinum (Pt), palladium (Pd), and rhodium (Rh), has oxygen storage capacity, and purifies NOx, HC, and CO. The filter 7b is a porous ceramic structure.

[0014] The ECU30 includes a CPU (Central Processing Unit), ROM (Read Only Memory), and RAM (Random Access Memory). The ECU30 controls the engine 1 based on information from sensors and other information stored in the ROM, according to a control program pre-stored in the ROM. The ECU30 is an example of a control device for a turbocharged engine.

[0015] The ECU 30 controls the operating state of the engine 1 based on detection signals from various sensors, including the crank angle sensor 11, the airflow meter 12, and the air-fuel ratio sensor 13. The crank angle sensor 11 detects the rotation angle of the crankshaft of the engine 1. The airflow 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 pedal position sensor 14 detects the accelerator pedal position, which is the amount the accelerator pedal is operated.

[0016] The ECU 30 determines the rotational speed and load of the engine 1 based on the output signals from various sensors. The ECU 30 then outputs command signals to various drive circuits connected to the output ports according to the operating conditions determined in this way. The control performed by the ECU 30 in this manner includes throttle control, which adjusts the opening degree of the throttle valve 3a; fuel injection control, which adjusts the amount of fuel injected by the fuel injector 2a; and ignition timing control, which adjusts the ignition timing of the spark plug 2b.

[0017] [Torque reduction control and exhaust noise control] When the accelerator position sensor 14 detects a change from accelerator on to accelerator off, the ECU 30 performs torque reduction control and further performs exhaust noise control. Figure 2 is a timing chart showing an example of the torque reduction control and exhaust noise control performed by the ECU 30. Figure 2 shows the changes in accelerator position, intake air volume, fuel cut flag, fuel injection volume, air-fuel ratio, ignition timing, exhaust noise control flag, and the opening of the wastegate valve 9.

[0018] When the accelerator opening decreases at time t1 and shifts to an accelerator-off state where the accelerator opening becomes zero at time t2, the ECU 30 executes torque-down control. In the torque-down control, while gradually decreasing the intake air amount and the fuel injection amount, the ignition timing is temporarily advanced and then gradually controlled toward the retarded side. The intake air amount decreases to the intake air amount during idling operation. As a result, the torque of the engine 1 decreases. Note that even when the torque-down control is being executed, the wastegate valve 9 is maintained in the fully closed state, and the rotational speeds of the turbine 5a and the compressor 5b are kept high, whereby high responsiveness can be ensured with respect to an acceleration request after the execution of the torque-down control. Note that in the torque-down control, the throttle valve 3a is controlled so that the intake air amount gradually decreases regardless of the opening of the accelerator pedal 18.

[0019] At time t3 after a predetermined time has elapsed since the execution of the torque-down control, the ECU 30 executes exhaust sound control. In the exhaust sound control, the fuel injection amount is further decreased, the ignition timing is significantly retarded, and the wastegate valve 9 opens. The ignition timing in the exhaust sound control is significantly retarded until after top dead center between the compression stroke and the expansion stroke. This ignition timing is set to, for example, 20° ATDC (After Top Dead Center). By significantly retarding the ignition timing in this way, the combustion of the air-fuel mixture can be continued until the exhaust valve of the engine 1 starts to open. As a result, the exhaust sound increases, and a good sports sound is ensured.

[0020] As described above, the wastegate valve 9 opens in the exhaust sound control. As a result, it is possible to secure the exhaust flow rate that bypasses the turbine 5a as compared with when the wastegate valve 9 is closed. As a result, the attenuation of the exhaust sound by the turbine 5a is suppressed, and a good sports sound is ensured. Thus, a good sports sound can be obtained in a vehicle equipped with the turbocharged engine 1. Note that from the viewpoint of suppressing the attenuation of the exhaust sound, it is preferable that the wastegate valve 9 be in the fully open state.

[0021] At time t4 after a predetermined time has elapsed since the exhaust sound control is executed, the exhaust sound control is stopped, the fuel injection is stopped, and the original fuel cut is executed. If the rotational speed of engine 1 becomes less than or equal to the return rotational speed during the execution of the fuel cut, the ECU 30 restarts the fuel injection by the fuel injection valve 2a.

[0022] The opening degree of the throttle valve 3a in the exhaust sound control may be controlled to be the same as the opening degree during the idle operation, or may be controlled to be slightly more open than the opening degree during the idle operation, or may be controlled to be slightly more closed. The fuel injection amount in the exhaust sound control may be controlled to be the same as the injection amount during the idle operation, or may be slightly more than the injection amount during the idle operation, or may be slightly less.

[0023] In the above embodiment, the ignition timing in the exhaust sound control is set to ATDC 20°, but it is not limited thereto. If the combustion of the air-fuel mixture continues at the valve opening time of the exhaust valve, for example, the ignition timing may be between ATDC 17° and 23°, or may be between ATDC 15° and 25°.

[0024] As described above, the embodiments of the present invention have been described in detail, but the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0025] 1 Engine 2a Fuel injection valve 2b Spark plug 3a Throttle valve 4 Exhaust passage 5 Supercharger 5a Turbine 8 Bypass passage 9 Wastegate valve 14 Accelerator opening sensor 30 ECU (Control device for engine with supercharger)

Claims

[Claim 1] A control device for a supercharged engine mounted on a vehicle controls the ignition timing, fuel injection amount, and intake air amount of the supercharged engine, and also controls a wastegate valve provided in a bypass passage that bypasses the turbine of the supercharger, A control device for a supercharged engine, which, when transitioning from accelerator on to accelerator off, performs torque down control by closing the wastegate valve and reducing the fuel injection amount and intake air amount to retard the ignition timing, then performs exhaust noise control by further retarding the ignition timing to after top dead center between the compression stroke and expansion stroke and fully opening the wastegate valve, stops the exhaust noise control and stops fuel injection to perform fuel cut after a predetermined time has elapsed since the execution of the exhaust noise control, and resumes fuel injection if the rotational speed of the supercharged engine falls below the recovery rotational speed during the execution of the fuel cut.

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