JP2022090310A - Control device of hybrid vehicle - Google Patents

Abstract

To provide a control device of a hybrid vehicle which restrains hunting of engine rotational speed.SOLUTION: A control device of a hybrid vehicle is configured so that a motor is installed on power transmission path between an engine and wheels and at the same time so that a clutch is inserted into a portion between the engine and the motor. The control device comprises: an engine control part which executes engine drive control which includes injection increment quantity processing setting target fuel injection quantity on the basis of a fuel injection quantity obtained by adding increment quantity correction portion to fundamental fuel injection quantity of the engine when an engine rotational speed reduces to a prescribed value or less during drive of the engine; a motor control part which executes motor drive control which increases the motor rotational speed up into the target range by increasing torque of the motor when the motor rotational frequency is lower than the target range; and a determination part which determines whether or not the clutch is in complete engaging state or in slip engaging state. The control device restricts execution of the injection increment quantity processing when affirmative determination is made by the determination part.SELECTED DRAWING: Figure 4

Description

The present invention relates to a control device for a hybrid vehicle.

A hybrid vehicle is known in which a motor is installed in a power transmission path between an engine and a wheel, and a clutch is interposed in a portion between the engine and the motor in the power transmission path (see, for example, Patent Document 1). In such vehicles, the drive of both the engine and the motor is controlled and the clutch may be in a fully engaged or slip-engaged state.

Japanese Unexamined Patent Publication No. 06-323213

In engine drive control, when the engine speed drops below a predetermined value, injection increase processing is executed to increase the fuel injection amount in the engine and increase the engine speed in order to prevent engine stall. May occur. In the injection increase processing, within the range where the engine speed is within a predetermined value, the fuel injection amount increase correction amount increases as the engine speed decreases, and the fuel injection amount increase correction amount increases as the engine speed increases. Set to decrease.

For the motor, when the motor rotation speed drops below the target range determined according to the vehicle speed and accelerator pedal opening, motor drive control is executed to increase the motor torque and raise the motor rotation speed to within the target range. To. As a result, the motor rotation speed can be maintained within the target range.

When the clutch is in the fully engaged state or the slip engaged state, when the engine speed drops below a predetermined value, the engine speed is transmitted to the motor via the clutch, and the motor speed also deviates from the target range. descend. As a result, the injection increase process is executed on the engine side, and the motor rotation speed is controlled to increase on the motor side. As a result, the engine speed increases, but the increase in engine speed in this case is assisted not only by the increase in injection but also by the above-mentioned increase in motor speed.

In this state, if the engine speed increases and the injection increase amount is reduced, the engine speed may drop to an unsustainable level due to the rotation of the motor. When the engine speed decreases again in this way, the injection increase amount increases again and the engine speed increases again. As described above, the engine speed may be hunted.

Therefore, an object of the present invention is to provide a control device for a hybrid vehicle that suppresses hunting of engine speed.

The above object is a control device for a hybrid vehicle in which a motor is installed in a power transmission path between an engine and wheels and a clutch is interposed between the engine and the motor in the power transmission path. When the engine speed drops to a predetermined value or less while the engine is being driven, the engine speed falls within the range of the predetermined value or less to the basic fuel injection amount determined according to the operating state of the engine. An engine control unit that executes engine drive control, including an injection increase process that sets a target fuel injection amount based on a fuel injection amount that is added to an increase correction amount that is determined to decrease as the engine speed increases. A motor control unit that executes motor drive control that increases the torque of the motor to raise the motor rotation speed within the target range when the motor rotation speed drops below the target range, the engine drive control, and the engine drive control. The engine control unit includes a determination unit for determining whether or not the clutch is in a fully engaged state or a slip engagement state while the motor drive control is being executed, and the engine control unit makes a positive determination by the determination unit. If this is the case, it can be achieved by a hybrid vehicle control device that limits the execution of the injection increase process.

According to the present invention, it is possible to provide a control device for a hybrid vehicle in which hunting of engine speed is suppressed.

FIG. 1 is a schematic configuration diagram of a hybrid vehicle. FIG. 2 is a schematic configuration diagram of the engine. FIG. 3 shows the fuel injection increase correction amount according to the engine speed in the injection increase process. FIG. 4 is a flowchart showing an example of control for limiting the injection increase processing executed by the ECU. FIG. 5 is a diagram showing changes in engine speed in a comparative example in which injection increase processing is executed with the K0 clutch fully engaged during drive control of the engine and motor. FIG. 6 is a diagram showing changes in the engine speed in the present embodiment in which the injection increase processing is restricted while the K0 clutch is in a fully engaged state while the engine and the motor are in drive control.

[Outline configuration of hybrid vehicle]
FIG. 1 is a schematic configuration diagram of a hybrid vehicle. The hybrid vehicle is equipped with an engine 10 and a motor 15 as a driving source for traveling. A speed change unit 11 is provided in the power transmission path from the engine 10 to the wheels 13 in the hybrid vehicle. The speed change unit 11 and the left and right wheels 13 are drive-connected via a differential 12.

The speed change unit 11 is provided with a K0 clutch 14 and a motor 15. In the speed change unit 11, the motor 15 is installed so as to be located on the power transmission path from the engine 10 to the wheels 13.

The K0 clutch 14 is installed so as to be located at a portion between the engine 10 and the motor 15 in the same power transmission path. The K0 clutch 14 receives hydraulic pressure and is in a fully engaged state to connect the power transmission between the engine 10 and the motor 15. The K0 clutch 14 is opened in response to the stop of the hydraulic pressure supply, and cuts off the power transmission between the engine 10 and the motor 15. The K0 clutch 14 is in a slip-engaged state from the start of torque transmission until it is completely engaged. In the fully engaged state, the engine 10 and the motor 15 are directly connected, so that the engine speed and the motor speed match. In the slip-engaged state and the open state, the engine speed and the motor speed do not match.

The motor 15 is connected to the vehicle-mounted battery 16 via the inverter 17. The motor 15 functions as a motor that generates the driving force of the vehicle in response to the power supplied from the vehicle-mounted battery 16, while the motor 15 generates electric power to charge the vehicle-mounted battery 16 in response to power transmission from the engine 10 and the wheels 13. It also functions as a machine. The electric power exchanged between the motor 15 and the vehicle-mounted battery 16 is adjusted by the inverter 17.

The speed change unit 11 is provided with a torque converter 18 which is a fluid joint having a torque amplification function, and a stepped automatic transmission 19 which switches a gear ratio in multiple stages by switching gear stages. In the speed change unit 11, the automatic transmission 19 is installed so as to be located on the wheel 13 side of the motor 15 in the power transmission path. Then, the motor 15 and the automatic transmission 19 are connected via the torque converter 18. The torque converter 18 is provided with a lockup clutch 20 that receives and engages with the supply of hydraulic pressure to directly connect the motor 15 and the automatic transmission 19.

Further, the speed change unit 11 is provided with an oil pump 21 and a hydraulic control mechanism 22. Then, 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 lockup clutch 20 via the hydraulic pressure control mechanism 22, respectively. The hydraulic control mechanism 22 is provided with hydraulic circuits for each of the K0 clutch 14, the torque converter 18, the automatic transmission 19, and the lockup clutch 20, and various hydraulic control valves for controlling their hydraulic pressure. Has been done.

The hybrid vehicle is provided with an ECU (Electronic Control Unit) 23 as a control device for the vehicle. The ECU 23 is an electronic control unit including an arithmetic processing circuit that performs various arithmetic processing related to vehicle travel control, and a storage device that stores control programs and data. The ECU 23 functionally realizes an engine control unit, a motor control unit, and a determination unit, which will be described in detail later.

The ECU 23 performs drive control of the engine 10 and drive control of the motor 15, which will be described in detail later. Further, the ECU 23 controls the inverter 17 to adjust the amount of electric power exchanged between the motor 15 and the vehicle-mounted battery 16 to control the torque of the motor 15. Further, the ECU 23 controls the drive of the K0 clutch 14, the lockup clutch 20, and the automatic transmission 19 through the control of the hydraulic control mechanism 22. A detection signal such as a vehicle speed or an accelerator pedal opening degree, which is the amount of depression of the accelerator pedal by the driver, is input to the ECU 23.

The ECU 23 drives the hybrid vehicle in any of the motor driving modes, the hybrid driving modes, and the engine driving modes. In the motor running mode, the ECU 23 releases the K0 clutch 14 and rotates the wheels 13 with the power of the motor 15. In the hybrid drive mode, the ECU 23 engages the K0 clutch 14 to rotate the wheels 13 with the power of the engine 10 and the motor 15. In the engine running mode, the ECU 23 engages the K0 clutch 14 to rotate the wheels 13 with the power of the engine 10. In the hybrid traveling mode, traveling assist by power running of the motor 15 and regenerative power generation by regenerative operation of the motor 15 are performed. The switching of the traveling mode is performed based on the required driving force of the vehicle obtained from the vehicle speed and the accelerator pedal opening degree, the charging state of the in-vehicle battery 16, and the like.

[Outline configuration of engine]
FIG. 2 is a schematic configuration diagram of the engine 10. The engine 10 is provided with a cylinder 30 that burns the air-fuel mixture. In the figure, only one of the plurality of cylinders 30 of the engine 10 is displayed. A piston 31 is housed in each cylinder 30 so as to be reciprocating. The piston 31 of each cylinder 30 is connected to the crank shaft 33, which is the output shaft of the engine 10, via a connecting rod 32. The connecting rod 32 and the crank shaft 33 constitute a crank mechanism that converts the reciprocating motion of the piston 31 into the rotational motion of the crank shaft 33. The engine 10 is provided with a crank angle sensor 34 that detects the rotation angle of the crank shaft 33.

An intake passage 35, which is an intake introduction path, is connected to each cylinder 30 of the engine 10 via an intake valve 36. An exhaust passage 37, which is an exhaust exhaust path, is connected to each cylinder 30 of the engine 10 via an exhaust valve 38. The intake passage 35 is provided with an air flow meter 39 for detecting the amount of intake air and a throttle valve 40 which is a valve for adjusting the flow rate of the intake air. The engine 10 is provided with an in-cylinder injection valve 41 for injecting fuel into the cylinders 30 in each cylinder 30. Each cylinder 30 is provided with an ignition device 42 that ignites a mixture of intake air introduced through the intake passage 35 and fuel injected by the in-cylinder injection valve 41 by spark discharge. The exhaust passage 37 is provided with a catalyst device 43 for purifying the exhaust gas.

The detection signals of the crank angle sensor 34 and the air flow meter 39 are input to the ECU 23. The ECU 23 calculates the engine rotation speed from the detection signal of the crank angle sensor 34 as a crank angle interrupt process for each rotation of the crank shaft 33 by a predetermined angle. The ECU 23 performs engine drive control through opening degree control of the throttle valve 40, fuel injection control of the in-cylinder injection valve 41, ignition control of the ignition device 42, and the like.

During engine drive control, the ECU 23 calculates the basic fuel injection amount according to the intake air amount, engine rotation speed, and target air-fuel ratio for the fuel injection amount of the in-cylinder injection valve 41, and sets the basic fuel injection amount as the target injection. Set as a quantity. The valve opening period of the in-cylinder injection valve 41 is controlled so that the actual fuel injection amount becomes the target injection amount according to the target injection amount and the fuel pressure set in this way. However, when a predetermined condition is satisfied, the ECU 23 executes the following injection increase processing.

[Injection increase processing]
The ECU 23 executes the injection increase process when the engine speed becomes the predetermined value α or less during the engine drive control. The injection increase process is a process for increasing and correcting the fuel injection amount in order to prevent engine stall when the engine speed becomes a predetermined value α or less. Specifically, it is a process of calculating the fuel injection amount as the final target injection amount by adding a predetermined increase correction amount to the basic fuel injection amount calculated as described above.

FIG. 3 shows the fuel injection increase correction amount according to the engine speed in the injection increase process. In FIG. 3, the horizontal axis indicates the engine speed [rpm], and the vertical axis indicates the increase correction amount [ml]. As shown in FIG. 3, as the engine speed decreases within the range of the predetermined value α or less, the increase correction amount is set to increase. In other words, as the engine speed increases within the range of the engine speed within the predetermined value α, the increase correction amount is set to decrease. This is because it is necessary to greatly increase the engine speed by fuel injection as the engine speed decreases within the range of the predetermined value α or less. Further, as the engine speed increases within the range of the predetermined value α or less, the amount of increase in the engine speed by fuel injection is small, and the higher the engine speed, the more in the cylinder 30. This is because the vaporization of the fuel is promoted, and the output performance of the engine 10 with respect to the fuel injection amount is also improved.

In addition, in FIG. 3, as the engine speed increases, the increase correction amount decreases linearly, but the present invention is not limited to this, and the increase correction amount may decrease in a curve or in a stepwise manner.

[Motor torque correction processing]
The ECU 23 executes the motor torque correction process during the motor drive control. In the motor torque correction process, when the motor rotation speed deviates from the target range determined according to the vehicle speed, the accelerator pedal opening, etc., the torque of the motor 15 is corrected so that the motor rotation speed falls within the target range. Is. Specifically, when the motor rotation speed is lower than the target range, the power supplied from the vehicle-mounted battery 16 to the motor 15 is increased by controlling the inverter 17. As a result, the torque of the motor 15 is increased, and the motor rotation speed is raised to within the target range. When the motor rotation speed exceeds the target range, the ECU 23 controls the inverter 17 to reduce the electric power supplied from the vehicle-mounted battery 16 to the motor 15. As a result, the torque of the motor 15 is reduced, and the motor rotation speed is reduced to within the target range. In this way, the motor rotation speed is maintained within a predetermined target range.

[Restriction on injection increase processing]
Next, the limitation of the injection increase processing will be described. FIG. 4 is a control for calculating only the basic fuel injection amount determined according to the operating state of the engine and stopping the above-mentioned injection increase process according to the engine speed as an example of the limitation of the injection increase process executed by the ECU 23. It is a flowchart which showed an example. This control is repeatedly executed during the system activation of the hybrid vehicle. The ECU 23 determines whether or not the engine 10 and the motor 15 are in drive control (step S1). During drive control of the engine 10 is a state in which the engine 10 is rotating due to fuel injection being performed by the engine 10 and combustion of the air-fuel mixture. For example, a starter motor or the like without fuel injection being performed. Does not include the state of being forcibly rotated from the outside by. The drive control of the motor 15 is a power running state in which electric power is supplied to the motor 15 to drive the motor 15, and does not include a regenerative state in which regenerative electric power is generated. If No in step S1, this control is terminated. When No in step S1, the driving mode is controlled to the motor driving mode when the operation of the engine 10 is stopped, or the engine 10 is traveling with the drive control of the motor 15 stopped. This is the case when the engine drive mode is controlled.

In the case of Yes in step S1, the ECU 23 determines whether the K0 clutch 14 is in the fully engaged state or the slip engaged state based on the output value of the sensor that detects the hydraulic pressure supplied to the K0 clutch 14 by the hydraulic control mechanism 22. It is determined whether or not (step S2). When the hydraulic pressure supplied to the K0 clutch 14 calculated from the output value of the sensor is equal to or higher than the predetermined value, it is determined to be in the fully engaged state or the slip engaged state, and when the above hydraulic pressure is less than the predetermined value. Is determined to be in the open state. Steps S1 and S2 are examples of processes executed by the determination unit that determines whether the K0 clutch 14 is in the fully engaged state or the slip engaged state while the engine drive control and the motor drive control are being executed. ..

If No in step S2, the ECU 23 determines whether or not the engine speed is equal to or less than the predetermined value α (step S3). If Yes in step S3, the ECU 23 executes the injection increase process described above (step S4). If No in step S3, or after executing the process in step S4, the ECU 23 determines whether or not the motor rotation speed is out of the target range (step S5). If Yes in step S5, the ECU 23 executes the motor torque correction process as described above (step S6). If No in step S5, or after the execution of step S6, this control is terminated. The processing of steps S3 and S4 is an example of execution by the engine control unit. The processes of steps S5 and S6 are examples of processes executed by the motor control unit.

As described above, when Yes in step S1 and No in step S2, both the injection increase processing and the motor torque correction processing can be executed. That is, in response to the request for switching from the motor drive mode to the hybrid drive mode, the injection increase process and the injection increase process are performed until the engine 10 is started with the K0 clutch 14 open and the K0 clutch 14 is in the slip engagement state. The motor torque correction process can be performed.

If Yes in steps S1 and S2, the ECU 23 limits the execution of the injection increase process (step S7). Specifically, the injection increase process is stopped. Also in this case, the above-mentioned basic fuel injection amount is calculated and this basic fuel injection amount is set as the target fuel injection amount. Here, the case of Yes in steps S1 and S2 is a case where the K0 clutch 14 is in a fully engaged state and the traveling mode is controlled to a hybrid traveling mode in which the vehicle travels by the power of the engine 10 and the motor 15. .. Further, in the case of Yes in steps S1 and S2, for example, when the K0 clutch 14 is in the slip engaged state, the K0 clutch 14 is in the fully engaged state from the motor running mode in which the K0 clutch 14 is in the open state, for example. This is the case of shifting to the hybrid driving mode or the transition from the hybrid driving mode to the motor driving mode. Step S7 is an example of the process executed by the engine control unit that limits the execution of the injection increase process when the affirmative determination is made in steps S1 and S2. In this embodiment, the injection increase process is stopped by stopping the injection increase process. The execution of processing is restricted.

After the injection increase processing is stopped by step S7 in this way, the engine 10 is in drive control, but as shown in FIG. 4, the ECU 23 does not execute the processing of steps S3 and S4, and steps S5 and S6. Can only perform the processing of. That is, only the motor torque correction process can be executed without executing the injection increase process. In the case of No in step S1, when only the engine 10 is in drive control, the injection increase process described above can be executed without limitation, and only the motor 15 is in drive control. Is a state in which the motor torque correction process described above can be executed.

[Comparison example]
FIG. 5 is a diagram showing changes in engine speed in a comparative example in which the injection increase process is executed with the K0 clutch 14 in a fully engaged state during drive control of the engine 10 and the motor 15. The example of FIG. 5 shows a case where the combustion state of the engine 10 deteriorates and the engine speed decreases due to the use of low quality fuel, for example.

When the engine speed starts to decrease (time t1x) and the engine speed becomes the predetermined value α or less (time t2x), the injection increase process is executed and the motor speed is maintained at the original target speed. The amount of power supplied to the motor 15 increases. When the engine speed further decreases (time t3x), the fuel injection increase correction amount further increases, and the engine speed begins to increase as the amount of electric power supplied to the motor 15 increases. As the engine speed increases, the amount of increase correction becomes smaller. The increase in the engine speed in this case is assisted not only by the increase in injection but also by the increase in the motor speed due to the motor torque correction.

When the engine speed exceeds a predetermined value α and reaches a peak (time t4x), the increase correction amount becomes zero. In this state, the combustion state of the engine 10 is not improved, the engine speed is lowered to an extent that cannot be maintained by the rotation of the motor 15, and the engine speed is lowered again. When the engine speed decreases again in this way, the injection increase amount increases again and the engine speed starts to increase (time t5x). However, when the engine speed increases beyond the predetermined value α, the injection increase amount is set to zero again and the engine speed starts to decrease (time t6x). In this way, the engine speed may hunt. When the engine speed is hunted, the driving sound of the engine 10 may increase or decrease periodically, and the vehicle speed may become unstable.

[This Example]
FIG. 6 is a diagram showing changes in the engine speed in this embodiment in which the injection increase process is stopped while the K0 clutch 14 is in a fully engaged state while the engine 10 and the motor 15 are in drive control.

Even if the engine speed starts to decrease (time t1) and the engine speed falls below the predetermined value α (time t2), in this embodiment, the basic fuel injection amount is calculated and the engine 10 continues to be driven. However, the injection increase process described above is stopped. Therefore, the engine speed is lower than the peak value in the comparative example, but the engine speed gradually rises (time t3) and stabilizes (time t4) due to the increase in the power supply to the motor 15. In this way, since the hunting of the engine speed can be suppressed, the driving sound of the engine 10 becomes constant and the vehicle speed becomes stable. In this case, the increase injection process is restricted, but since the rotation of the engine 10 is assisted by the motor 15, the occurrence of engine stall is suppressed.

As shown in FIG. 4 in this embodiment, the reason why the injection increase processing is restricted during the drive control of the engine 10 and the motor 15 even when the K0 clutch 14 is in the slip-engaged state is as follows. This is because the powers of the engine 10 and the motor 15 exert each other even in the slip-engaged state, and if the injection increase process is executed without limitation as described above, the engine speed may be hunted.

[others]
In the above embodiment, as a limitation of the execution of the injection increase processing, only the basic fuel injection amount is calculated and the execution of the injection increase processing itself is stopped as an example, but the present invention is not limited to this. For example, the execution of the injection increase processing may be restricted by setting the increase correction amount to be added to the basic fuel injection amount to zero at all times regardless of the engine speed and substantially not performing the injection increase processing. Further, the execution of the injection increase processing may be restricted by setting the increase correction amount to a fixed value other than zero at all times regardless of the engine speed. For example, the execution of the injection increase processing may be restricted by setting the increase correction amount to a predetermined fixed value so that the engine speed does not decrease excessively. In this case, it is conceivable to set the increase correction amount when the increase correction process is restricted to a value smaller than the maximum value of the increase correction amount when the injection increase process is not restricted, for example. It may be set to a fixed value between the intermediate value and the minimum value in the range of the increase correction that can be taken when the injection increase process is not restricted. Since the increase correction amount does not change, hunting of the engine speed can be suppressed even in such a case.

In the above engine 10, the in-cylinder injection valve 41 for directly injecting fuel into the cylinder 30 is provided, but the present invention is not limited to this, and instead of the in-cylinder injection valve 41, fuel is injected toward the intake port. A port injection valve may be provided, or both an in-cylinder injection valve 41 and a port injection valve may be provided. When both the in-cylinder injection valve 41 and the port injection valve are provided, in the injection increase processing, the increase correction amount is added to the basic injection amount which is the total injection amount of both injection valves.

The above engine 10 is a spark-ignition type gasoline engine, but may be a compression ignition type without an ignition device 42, or may be, for example, a diesel engine.

In this embodiment, the case where the hybrid vehicle is controlled by a single ECU 23 has been illustrated, but the present invention is not limited to this, and for example, the engine ECU that controls the engine 10, the motor ECU that controls the motor 15, and the K0 clutch 14 are controlled. The above-mentioned control may be executed by a plurality of ECUs such as a clutch ECU.

Although the examples of the present invention have been described in detail above, the present invention is not limited to such specific examples, and various modifications and variations are made within the scope of the gist of the present invention described in the claims. It can be changed.

10 Engine 11 Speed change unit 12 Differential 13 Wheel 14 K0 Clutch 15 Motor 16 In-vehicle battery 17 Inverter 18 Torque converter 19 Automatic transmission 20 Lock-up clutch 21 Oil pump 22 Hydraulic control mechanism 23 ECU (control device for hybrid vehicle)
30 Cylinder 34 Crank angle sensor 35 Intake passage 41 In-cylinder injection valve

Claims (1)

A control device for a hybrid vehicle in which a motor is installed in a power transmission path between an engine and wheels, and a clutch is interposed between the engine and the motor in the power transmission path.
When the engine speed drops to a predetermined value or less while the engine is being driven, the engine has a basic fuel injection amount determined according to the operating state of the engine and the engine speed is within the range of the predetermined value or less. An engine control unit that executes engine drive control, including an injection increase process that sets a target fuel injection amount based on a fuel injection amount that is added to an increase correction amount that is determined to decrease as the number of revolutions increases.
A motor control unit that executes motor drive control to increase the torque of the motor to raise the motor rotation speed to within the target range when the motor rotation speed drops below the target range.
A determination unit for determining whether or not the clutch is in a fully engaged state or a slip engaged state while the engine drive control and the motor drive control are being executed is provided.
The engine control unit is a hybrid vehicle control device that limits the execution of the injection increase processing when a positive determination is made by the determination unit.

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