Engine control device

Abstract

To provide an engine control device that suppresses the occurrence of a torque shock due to the return of fuel injection.SOLUTION: An engine control device comprises: a determination unit that determines whether the torque required for an engine at the time when there is a request to resume fuel injection, which is stopped in the engine mounted on a vehicle as a travel power source, is less than an MBT (Minimum advance for the Best Torque) torque outputted by the engine when the ignition timing of the engine is assumed to be MBT; and a control unit that, when the required torque is equal to or greater than the MBT torque, executes first return processing to resume fuel injection while gradually advancing the ignition timing from the retarded side of the MBT to the MBT, and, when the required torque is less than the MBT torque, executes second return processing to resume fuel injection while gradually advancing the ignition timing from the retarded side of required ignition timing for achieving the required torque to the required ignition timing.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] In a return process for returning the fuel injection stopped in the engine, there is a technique of retarding the ignition timing from MBT (Minimum advance for the Best Torque) (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In such a return process, it is conceivable to secure the required torque for the engine while suppressing the torque shock by gradually advancing the ignition timing to MBT. However, there are cases where the required torque is smaller than the MBT torque, which is the output torque of the engine when the ignition timing is assumed to be MBT. In this case, for example, if the ignition timing is advanced to MBT and then retarded to the required ignition timing corresponding to the required torque, there is a risk of generating a torque shock.

[0005] Therefore, an object of the present invention is to provide an engine control device that suppresses the occurrence of torque shock due to the return of fuel injection.

Means for Solving the Problems

[0006] When there is a return request to resume the stopped fuel injection in an engine mounted as a driving power source in a vehicle, a determination unit determines whether the required torque for the engine is less than the MBT torque output by the engine when the ignition timing of the engine is assumed to be MBT (Minimum Advance for the Best Torque); and a control unit, when the required torque is equal to or greater than the MBT torque, executes a first return process of gradually advancing the ignition timing from the retarded side of the MBT to the MBT while resuming the fuel injection, and when the required torque is less than the MBT torque, executes a second return process of gradually advancing the ignition timing from the retarded side of the required ignition timing for realizing the required torque to the required ignition timing while resuming the fuel injection. The above object can be achieved by an engine control device including the determination unit and the control unit.

[0007] The control unit may advance the ignition timing so that the time from the start of the second return process until the ignition timing reaches the required ignition timing is shorter than the time from the start of the first return process until the ignition timing reaches the MBT.

[0008] When the determination by the determination unit during the execution of the second return process results in a negative determination, the control unit may shift from the second return process to the first return process.

[0009] The control unit may end the first return process when the ignition timing reaches the MBT during the execution of the first return process, and may end the second return process at the same timing as the timing when the first return process ends during the execution of the second return process.

[0010] The vehicle may be a hybrid vehicle having a motor as a driving power source and a clutch disposed between the engine and the motor.

Advantages of the Invention

[0011] According to the present invention, an engine control device capable of suppressing the generation of torque shock due to the return of fuel injection can be provided.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0013] [Schematic Configuration of Hybrid Vehicle] FIG. 1 is a schematic configuration diagram of a hybrid vehicle 1. The hybrid vehicle 1 is equipped with an engine 10 and a motor 15 as driving power sources. The engine 10 is a gasoline engine having a plurality of cylinders, but it may also be a diesel engine. A transmission unit 11 is provided on the power transmission path from the engine 10 to the drive wheels 13. The transmission unit 11 and the left and right drive wheels 13 are drivingly connected via a differential gear 12.

[0014] The transmission unit 11 is provided with a K0 clutch 14 and a motor 15. The motor 15 is provided on the power transmission path from the engine 10 to the drive wheels 13.

[0015] The K0 clutch 14 is provided between the engine 10 and the motor 15 in the same power transmission path. The K0 clutch 14 receives the supply of hydraulic pressure and becomes engaged to connect the power transmission between the engine 10 and the motor 15. The K0 clutch 14 becomes disengaged in response to the stop of the hydraulic pressure supply to cut off the power transmission between the engine 10 and the motor 15.

[0016] The motor 15 is connected to the battery 16 via the inverter 17. The battery 16 is a rechargeable secondary battery such as a nickel-metal hydride battery or a lithium-ion battery. The motor 15 functions as a motor that generates the driving force of the vehicle in response to the power supply from the battery 16. Furthermore, the motor 15 also functions as a generator that generates electric power for charging the battery 16 in response to the power transmission from the engine 10 or the drive wheels 13. The electric power exchanged between the motor 15 and the battery 16 is adjusted by the inverter 17.

[0017] The transmission unit 11 is provided with a torque converter 18 and an automatic transmission 19. The torque converter 18 is a fluid coupling having a torque amplification function. The automatic transmission 19 is a stepped transmission that switches the gear ratio in multiple steps. The torque converter 18 is provided between the motor 15 and the drive wheels 13 on the above-mentioned power transmission path. The automatic transmission 19 is provided between the torque converter 18 and the drive wheels 13 on the above-mentioned power transmission path. The torque converter 18 is provided with a lock-up clutch (hereinafter referred to as the LU clutch) 20 that engages upon receiving the supply of hydraulic pressure to directly connect the motor 15 and the automatic transmission 19.

[0018] The LU clutch 20 engages upon receiving the supply of hydraulic pressure to connect the power transmission between the motor 15 and the drive wheels 13. The LU clutch 20 is released in response to the stop of the hydraulic pressure supply.

[0019] The transmission unit 11 is further provided with an oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the oil pump 21 is supplied to the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the LU clutch 20 via the hydraulic control mechanism 22, respectively. The hydraulic control mechanism 22 is provided with the respective hydraulic circuits of the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the LU clutch 20, and various hydraulic control valves for controlling their operating hydraulic pressures.

[0020] The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 50 as a control device for the vehicle. The ECU 50 is an electronic control unit including an arithmetic processing circuit that performs various arithmetic processes related to the running control of the vehicle, and a memory that stores control programs and data. The ECU 50 is an example of an engine control device, and specifically, functionally realizes a determination unit and a control unit, which will be described in detail later.

[0021] Connected to the ECU 50 are an ignition switch 61, a crank angle sensor 62, an air flow meter 63, a SOC (State of Charge) sensor 64, an accelerator opening sensor 65, and a water temperature sensor 66. The ignition switch 61 detects the on / off state of the ignition. The crank angle sensor 62 detects the rotational speed of the crankshaft of the engine 10. The air flow meter 63 detects the intake air amount introduced into the engine 10. The SOC sensor 64 detects the charge rate of the battery 16. The accelerator opening sensor 65 detects the accelerator opening, which is the operation amount of the accelerator pedal. The water temperature sensor 66 detects the temperature of the cooling water that cools the engine 10.

[0022] The ECU 50 controls the driving of the engine 10 and the motor 15. Specifically, the ECU 50 controls the inverter 17 to adjust the amount of power transfer between the motor 15 and the battery 16, thereby performing torque control of the motor 15. The ECU 50 performs drive control of the K0 clutch 14, the LU clutch 20, and the automatic transmission 19 through the control of the hydraulic control mechanism 22.

[0023] The ECU 50 runs the hybrid vehicle 1 in either the motor running mode or the hybrid running mode. In the motor running mode, the ECU 50 releases the K0 clutch 14 and rotates the drive wheels 13 with the power of the motor 15. In the hybrid running mode, the ECU 50 engages the K0 clutch 14 and rotates the drive wheels 13 with the power of at least one of the engine 10 and the motor 15.

[0024] [Schematic Configuration of Engine] Figure 2 is a schematic configuration diagram of the engine 10. The engine 10 has a cylinder block 30, a cylinder head 32, a piston 33, a connecting rod 34, a crankshaft 35, an intake passage 36, an intake valve 36v, an exhaust passage 37, and an exhaust valve 37v.

[0025] The cylinder block 30 is provided with a cylindrical bore 31. The piston 33 is reciprocally accommodated within the bore 31. A combustion chamber C is defined by the wall surface of the bore 31, the lower surface of the cylinder head 32, and the top surface of the piston 33. The volume of the combustion chamber C increases and decreases with the reciprocating motion of the piston 33.

[0026] A connecting rod 34 is connected to the crankshaft 35, which is the output shaft of the engine 10. The connecting rod 34 and the crankshaft 35 convert the reciprocating motion of the piston 33 into the rotational motion of the crankshaft 35. The engine 10 is provided with the above-described crank angle sensor 62.

[0027] The intake passage 36 is connected to the combustion chamber C via the intake valve 36v. The exhaust passage 37 is connected to the combustion chamber C via the exhaust valve 37v. The above-described air flow meter 63 is provided in the intake passage 36.

[0028] The cylinder block 30 is provided with an in-cylinder injection valve 41D for directly injecting fuel into the combustion chamber C. The intake passage 36 is provided with a port injection valve 41P for injecting fuel toward the intake port. The cylinder head 32 is provided with a spark plug 42 for igniting the air-fuel mixture introduced into the combustion chamber C. Note that only one of the in-cylinder injection valve 41D and the port injection valve 41P may be provided.

[0029] The exhaust passage 37 is provided with a three-way catalyst 43 and a filter 44. The three-way catalyst 43 purifies NOx, HC, and CO in the exhaust gas. The filter 44 collects exhaust particles in the exhaust gas.

[0030] Based on the detection signals of the above-described sensors, the ECU 50 controls the driving of the engine 10 by controlling the opening degree of the throttle valve 40, the fuel injection amounts of the in-cylinder injection valve 41D and the port injection valve 41P, the ignition timing by the spark plug 42, etc.

[0031] When the fuel cut condition is satisfied during the driving of the engine 10, the ECU 50 executes fuel cut control to stop the fuel injection in the engine 10. The fuel cut condition is satisfied, for example, when the accelerator opening is zero and the engine speed is equal to or higher than a predetermined value. When the return condition is satisfied during the execution of the fuel cut control, the ECU 50 executes fuel injection return control to resume the fuel injection. The return condition is, for example, when the accelerator opening increases from zero, when the engine speed decreases to a predetermined return speed, or when the temperature of the cooling water is equal to or lower than a predetermined value and there is a heating requirement. In the fuel injection return control, the generation of torque shock due to the return of fuel injection is suppressed as described below.

[0032] [Fuel Injection Return Control] FIG. 3 is a flowchart illustrating the fuel injection return control executed by the ECU 50. This control is repeatedly executed while the ignition is on. The ECU 50 determines whether there is a return request to resume the fuel injection of the engine 10 in the fuel cut state (step S1). If the answer in step S1 is No, this control ends.

[0033] If the answer in step S1 is Yes, the ECU 50 determines whether the required torque for the engine 10 is less than the MBT torque (step S2). The MBT torque is the output torque of the engine 10 when the ignition timing is assumed to be MBT. The MBT torque is estimated by the ECU 50 based on a map defining the MBT torque according to the engine speed and the intake air amount of the engine 10. Step S2 is an example of the process executed by the determination unit.

[0034] If the answer in step S2 is No, that is, if the required torque is equal to or greater than the MBT torque, the ECU 50 executes the first return process (step S3a). The first return process is a process of returning fuel injection while gradually advancing the ignition timing from the retarded side relative to MBT to MBT. The ignition timing at the start of the first return process is set on the advanced side relative to the ignition timing at which the engine 10 may misfire. By gradually advancing the ignition timing to MBT in this way, a rapid increase in the output torque of the engine 10 is suppressed, and the occurrence of torque shock is suppressed. Note that the case where the required torque is equal to or greater than the MBT torque is, for example, the case where the accelerator pedal is depressed in the fuel cut state. Step S3a is an example of a process executed by the control unit.

[0035] Next, the ECU 50 determines whether or not the ignition timing has reached MBT (step S4a). If the answer in step S4a is No, the first return process is continued. If the answer in step S4a is Yes, the ECU 50 ends the first return process (step S5a). Note that after the end of the first return process, the ECU 50 increases the output torque of the engine 10 to the required torque by controlling the intake air amount and the fuel injection amount.

[0036] FIG. 4A is a timing chart illustrating the transition of the ignition timing in the first return process. When the first return process is started, the ignition timing gradually advances from the retarded side relative to MBT (time t1). When the ignition timing reaches MBT, the first return process ends (time t2).

[0037] If the answer in step S2 is Yes, the ECU 50 executes the second return process (step S3b). The second return process is a process of returning fuel injection while gradually advancing the ignition timing from the retarded side relative to the required ignition timing corresponding to the required torque to the required ignition timing. The required ignition timing is an ignition timing on the retarded side relative to MBT. By gradually advancing the ignition timing to the required ignition timing in this way, the occurrence of torque shock is suppressed. The ignition timing at the start of the second return process is set on the advanced side relative to the ignition timing at which the engine 10 may misfire. Step S3b is an example of a process executed by the control unit.

[0038] Here, the ECU 50 adjusts the advancing angular velocity of the ignition timing or the ignition timing at the start point of the return process so that the time from when the second return process starts until the ignition timing reaches the required ignition timing is shorter than the time from when the first return process starts until the ignition timing reaches MBT. For this reason, in the second return process, the ignition timing can be advanced to the required ignition timing in a short period, and the output torque of the engine 10 can be increased to the required torque at an early stage.

[0039] In addition, the case where the required torque is less than the MBT torque is, for example, when the SOC is near the upper limit value and there is a heating requirement while decelerating by fuel cut control on a downhill slope with low coolant temperature. In this case, since the SOC is near the upper limit value, it is difficult to ensure a further deceleration by the regenerative operation of the motor 15. Also, when there is a heating requirement with low coolant temperature, the return of fuel injection of the engine 10 is required to raise the temperature of the coolant used for heating. In this case, the required torque for the engine 10 may be the minimum and less than MBT.

[0040] Next, the ECU 50 determines whether it is the end timing of the second return process (step S4b). The end timing of the second return process is the same as the end timing of the first return process. In other words, the end timing of the second return process is the timing at which the ignition timing in the first return process becomes MBT when the first return process is started simultaneously with the start of the second return process. For this reason, in the second return process, the end timing of the second return process occurs after a predetermined time from when the ignition timing reaches the required ignition time.

[0041] The determination of whether it is the end timing of the second return process is specifically executed as follows. The ECU 50 virtually calculates the ignition timing in the first return process when the first return process is started simultaneously with the start of the second return process. Next, the ECU 50 determines whether the virtual ignition timing in the first return process has become MBT. When this virtual ignition timing becomes MBT, it is determined that it is the end timing of the second return process.

[0042] If the answer is "No" in step S4b, the processes after step S2 are executed again. Thus, for example, when the accelerator pedal is depressed during the execution of the second return process and the required torque becomes equal to or greater than the MBT torque (No in step S2), the ECU 50 shifts from the second return process to the first return process (step S3a). The shift from the second return process to the first return process is realized by advancing the ignition timing from the ignition timing at the time when it is determined to be "No" in step S2 during the second return process to MBT.

[0043] If the answer is "Yes" in step S4b, the ECU 50 ends the second return process (step S5b). As described above, in the first and second return processes, the end timing is the same. In this way, the first and second return processes are made common, and an increase in the load of these processes is suppressed. Incidentally, after the end of the second return process, the ignition timing is maintained at the ignition timing at the end of the second return process as long as the required torque does not change.

[0044] FIG. 4B is a timing chart illustrating the transition of the ignition timing in the second return process. When the second return process is started, the ignition timing gradually advances from the retarded side with respect to the required ignition timing (time t1). Thereafter, the ignition timing reaches the required ignition timing (t1a). The timing (t1a) at which the ignition timing in the second return process reaches the required ignition timing is earlier than the timing (t2) at which the ignition timing in the first return process reaches MBT as shown in FIG. 4A. Also, the second return process ends at the same time as the end timing of the first return process (time t2).

[0045] As described above, even when the required torque to the engine 10 when there is a return request from fuel injection is either equal to or greater than MBT or less than MBT, the generation of torque shock due to the return of fuel injection is suppressed.

[0046] 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 changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0047] 1 Hybrid vehicle 10 Engine 15 Motor 50 ECU (Engine control unit, determination unit, control unit)

Claims

1. In an engine mounted on a vehicle as a driving power source, a determination unit that determines whether or not a required torque to the engine when there is a return request to resume stopped fuel injection is less than the MBT torque output by the engine when the ignition timing of the engine is assumed to be MBT (Minimum advance for the Best Torque); A control unit that, when the required torque is equal to or greater than the MBT torque, executes a first return process of returning the fuel injection while gradually advancing the ignition timing from the retarded side of the MBT to the MBT, and when the required torque is less than the MBT torque, gradually advances the ignition timing from the retarded side of the required ignition timing for realizing the required torque to the required ignition timing while returning the fuel injection. An engine control device comprising:

2. The control unit advances the ignition timing so that the time from the start of the second return process until the ignition timing becomes the required ignition timing is shorter than the time from the start of the first return process until the ignition timing becomes the MBT. The engine control device according to claim 1.

3. When the determination by the determination unit during the execution of the second return process is a negative determination, the control unit shifts from the second return process to the first return process. The engine control device according to claim 1.

4. When the ignition timing becomes the MBT during the execution of the first return process, the control unit ends the first return process, and ends the second return process at the same timing as the timing when the first return process ends during the execution of the second return process. The engine control device according to claim 2.

5. The vehicle is a hybrid vehicle having a motor as a driving power source and a clutch disposed between the engine and the motor. The engine control device according to any one of claims 1 to 4.

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