Vehicle control device

Abstract

To prevent an internal combustion engine from being stopped when a connection and disconnecting clutch is put into a connected state under a situation where an electric motor cannot be driven.SOLUTION: A vehicle control device executes: slip control in which a connecting and disconnecting clutch is engaged with indicated hydraulic pressure to enable the connecting and disconnecting clutch to be engaged through a hydraulic control mechanism set as indicated hydraulic pressure to maintain a rotation speed of an internal combustion engine at a higher rotation speed than a lower limit rotation speed for avoiding stoppage of the internal combustion engine after starting up the internal combustion engine with a starter; and engagement completion control in which the indicated hydraulic pressure to enable the connecting and disconnecting clutch to be engaged through the hydraulic control mechanism is increased from the indicated hydraulic pressure in the slip control to indicated hydraulic pressure to complete engagement of the connecting and disconnecting clutch when a difference between the rotation speed of the internal combustion engine and a rotation speed of an electric motor is smaller than a predetermined threshold.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a vehicle control device. [Background technology]

[0002] Conventionally, vehicles have been known that have an internal combustion engine and an electric motor as power sources on a power transmission path, and are equipped with a disconnecting clutch that disconnects the transmission of torque between them (see, for example, Patent Document 1). In such vehicles, when the power of the internal combustion engine is transmitted to the drive wheels, the disconnecting clutch is engaged. As a result, the power of the internal combustion engine is transmitted to the drive wheels via an output shaft of the electric motor. In other words, in order to make the vehicle capable of running using the driving force of the internal combustion engine, the disconnecting clutch needs to be engaged even when the electric motor is not operating.

[0003] Patent Document 1 discloses a vehicle control device that allows the vehicle to run in a situation where the electric motor cannot be driven. This vehicle control device starts the internal combustion engine with a starter and gradually engages a disconnecting clutch. The disconnecting clutch gradually increases the rotation speed of the electric motor to match the rotation speed of the electric motor and the rotation speed of the internal combustion engine. As a result, the driving force of the internal combustion engine becomes capable of being transmitted to the drive wheels even in a situation where the electric motor cannot be driven, and the vehicle becomes capable of running. In Patent Document 1, the rotation torque of the engine is increased in conjunction with the engagement control of the disconnecting clutch. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2020-093731 A Summary of the Invention [Problem to be solved by the invention]

[0005] Incidentally, in the power transmission path, a rotating element such as a transmission is arranged downstream of the electric motor in the power transmission direction. For this reason, when the rotation of the internal combustion engine is transmitted to the electric motor in a stopped state via a disconnecting clutch, it is assumed that the influence of the drag torque and rotation inertia of the rotating elements after the electric motor will affect the rotation state of the internal combustion engine. For this reason, depending on how the disconnecting clutch is engaged, the rotation speed of the internal combustion engine may suddenly drop and the internal combustion engine may stop. Here, the vehicle is placed in various situations, and the state of the hydraulic oil in each part at the start of the internal combustion engine is not uniform. For example, in a vehicle left overnight in an extremely cold place, it is assumed that the hydraulic oil has leaked from the oil passage for operating the disconnecting clutch, and further, the viscosity of the hydraulic oil has increased. In Patent Document 1, the rotation torque of the internal combustion engine is increased in conjunction with the engagement control of the disconnecting clutch. However, even if the rotation torque of the internal combustion engine is increased, the rotation speed of the internal combustion engine may drop and the internal combustion engine may stop depending on the situation in which the vehicle is placed.

[0006] Therefore, the present invention aims to provide a vehicle control device disclosed in this specification that prevents the internal combustion engine from stopping when the disconnecting clutch is connected in a situation where the electric motor cannot be driven. [Means for solving the problem]

[0007] The above object can be achieved by a control device for a vehicle including an internal combustion engine, an electric motor connected to a power transmission path between the internal combustion engine and drive wheels so as to be capable of transmitting power, a disconnecting clutch provided in the power transmission path and which is brought into a released state to disconnect the internal combustion engine from the electric motor, a starter for starting the internal combustion engine, and a hydraulic control mechanism for controlling the hydraulic pressure supplied to the disconnecting clutch, the control device performing a slip control for engaging the disconnecting clutch by the hydraulic control mechanism after the internal combustion engine is started by the starter, as a command hydraulic pressure for engaging the disconnecting clutch, which command hydraulic pressure maintains the rotational speed of the internal combustion engine at a rotational speed higher than a lower limit rotational speed that avoids a stop of the internal combustion engine, and an engagement completion control for increasing the command hydraulic pressure for engaging the disconnecting clutch by the hydraulic control mechanism from the command hydraulic pressure in the slip control to a command hydraulic pressure at which engagement of the disconnecting clutch is completed, when the difference between the rotational speed of the internal combustion engine and the rotational speed of the electric motor becomes smaller than a predetermined threshold value.

[0008] In the above-mentioned vehicle control device, a configuration can be adopted in which, after the internal combustion engine is started by the starter, preparatory control is further implemented prior to the slip control in order to increase the hydraulic pressure in the hydraulic control mechanism that engages the disconnecting clutch from the hydraulic pressure before the starter is driven.

[0009] In the above vehicle control device, the command oil pressure in the preparatory control may be set to be equal to or higher than the command oil pressure at the start of the slip control.

[0010] Furthermore, in the above-mentioned vehicle control device, the end of the period in which the preparatory control is carried out can be a time when at least one of a drop in the rotation speed of the internal combustion engine or an increase in the rotation speed of the electric motor is detected.

[0011] In the above vehicle control device, the command oil pressure in the slip control may be given by a pulse wave that repeats an increase and a decrease in the command oil pressure.

[0012] Furthermore, the above-mentioned vehicle control device can be configured to, during the slip control, when the internal combustion engine speed falls below a lower limit avoidance speed which is set to a value higher than the lower limit avoidance speed, reduce the command oil pressure for engaging the disconnecting clutch from the command oil pressure when a speed below the lower limit avoidance speed is indicated.

[0013] In the above-described control device for a vehicle, the command oil pressure in the engagement completion control may be set in accordance with a rotational torque of the internal combustion engine. Effect of the Invention

[0014] According to the present invention, when the disconnecting clutch is brought into the connected state in a situation in which the electric motor cannot be driven, it is possible to prevent the internal combustion engine from stopping. [Brief description of the drawings]

[0015] [Figure 1] FIG. 1 is a schematic diagram of a hybrid vehicle equipped with a vehicle control device according to an embodiment. [Diagram 2] FIG. 2 is a flowchart showing an example of K0 clutch engagement control executed by the vehicle control device (ECU) of the embodiment. [Diagram 3] FIG. 3 is a time chart showing the transition of each value when the K0 clutch engagement control is performed by the vehicle control device (ECU) of the embodiment. [Figure 4] FIG. 4 is an explanatory diagram showing an example of a command pressure for the engagement oil pressure of the K0 clutch in slip control included in the K0 clutch engagement control. [Diagram 5] FIG. 5 is a flowchart showing another example of the K0 clutch engagement control. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. However, in the drawings, the dimensions, ratios, and the like of each part may not be illustrated to be completely consistent with the actual ones. In addition, some details may be omitted in some drawings. Furthermore, the scale of each element depicted in each drawing may differ from one another.

[0017] [General configuration of hybrid vehicle] FIG. 1 is a schematic diagram of a hybrid vehicle 1. In the hybrid vehicle 1, a K0 clutch 14, a motor generator 15, a torque converter 18, and a transmission 19 are provided in this order on a power transmission path from an engine 10, which corresponds to an internal combustion engine, to drive wheels 13. The engine 10 and the motor generator 15 are mounted on the hybrid vehicle 1 as a driving source for traveling. The engine 10 is an example of an internal combustion engine, and is, for example, an in-line three-cylinder gasoline engine, but the number of cylinders and the arrangement of the cylinders are not limited thereto. It may also be a diesel engine that uses diesel as fuel. The K0 clutch 14, the motor generator 15, the torque converter 18, and the transmission 19 are provided in a transmission unit 11. The transmission unit 11 and the left and right drive wheels 13 are drive-coupled via a differential 12.

[0018] The K0 clutch 14 is provided between the engine 10 and the motor generator 15 on the power transmission path. The K0 clutch 14 is switched from a released state to an engaged state by receiving a supply of hydraulic pressure, and connects the power transmission between the engine 10 and the motor generator 15. The K0 clutch 14 is switched to a released state by stopping the supply of hydraulic pressure, and cuts off the power transmission between the engine 10 and the motor generator 15. The engaged state is a state in which both engagement elements of the K0 clutch 14 are connected and the engine 10 and the motor generator 15 have the same rotation speed. The released state is a state in which both engagement elements of the K0 clutch 14 are separated. Depending on the supply state of the engagement hydraulic pressure, the K0 clutch 14 may be in a slip state in which the rotation speed of the engine 10 side and the rotation speed of the motor generator 15 side do not match. The K0 clutch 14 corresponds to a disconnecting clutch.

[0019] The motor generator 15 is connected to the battery 16 via an inverter 17. The motor generator 15 functions as a motor that generates driving force for the vehicle in response to power supplied from the battery 16, and also functions as a generator that generates power to charge the battery 16 in response to power transmission from the engine 10 and the drive wheels 13. The power exchanged between the motor generator 15 and the battery 16 is regulated by the inverter 17. The use of the battery 16 may be restricted depending on its temperature, such as at extremely low temperatures. The temperature at which use is restricted is set for each specification of the actual vehicle. The motor generator 15 corresponds to an electric motor.

[0020] The inverter 17 is controlled by the ECU 100 described later, and converts the DC voltage from the battery 16 into an AC voltage, or converts the AC voltage from the motor generator 15 into a DC voltage. In the case of powering operation in which the motor generator 15 outputs torque, the inverter 17 converts the DC voltage of the battery 16 into an AC voltage and adjusts the power supplied to the motor generator 15. In the case of regenerative operation in which the motor generator 15 generates power, the inverter 17 converts the AC voltage from the motor generator 15 into a DC voltage and adjusts the power supplied to the battery 16. The battery 16 is mainly used as a power source for driving the hybrid vehicle 1.

[0021] The torque converter 18 is a fluid coupling having a torque amplifying function. The transmission 19 is a stepped automatic transmission that switches the gear ratio in multiple stages by changing the gear stage, but is not limited thereto and may be a continuously variable automatic transmission. The transmission 19 is provided between the motor generator 15 and the driving wheels 13 on the power transmission path. The motor generator 15 and the transmission 19 are connected via the torque converter 18. The torque converter 18 is provided with a lock-up clutch 20 that is supplied with hydraulic pressure and is engaged to directly connect the motor generator 15 and the transmission 19.

[0022] The transmission unit 11 is further provided with an electric oil pump 21 and a hydraulic control mechanism 22. The hydraulic pressure generated by the electric oil pump 21 is supplied to the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22. The hydraulic control mechanism 22 is provided with hydraulic circuits for the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20, and various hydraulic control valves for controlling the operating hydraulic pressures thereof. Note that a wet clutch may be provided instead of the torque converter 18.

[0023] The hybrid vehicle 1 includes an auxiliary battery 23 in addition to the battery 16. The hybrid vehicle 1 includes a starter 24 that starts the engine 10. The starter 24 is driven by the auxiliary battery 23. The use of the battery 16 may be restricted, for example, when the temperature of the environment in which the vehicle is placed is very low. However, even in such a case, the auxiliary battery 23 can be used, and the engine 10 can be started by the starter 24 driven by the auxiliary battery 23. The auxiliary battery 23 can also be used to drive the electric oil pump 21.

[0024] The hybrid vehicle 1 includes a mechanical oil pump 25. The mechanical oil pump 25 is operated by the rotation of the output shaft of the motor generator 15. Therefore, the mechanical oil pump 25 is not driven when the engine 10 and the motor generator 15 are stopped. Even if the engine 10 is running, the mechanical oil pump 25 is not driven when the motor generator 15 is stopped and the K0 clutch 14 is in a disengaged state. The mechanical oil pump 25, like the electric oil pump 21, can supply hydraulic pressure to the K0 clutch 14, the torque converter 18, the transmission 19, and the lock-up clutch 20 via the hydraulic control mechanism 22.

[0025] The hybrid vehicle 1 is provided with an ECU (Electronic Control Unit) 100 as a control device for the vehicle. The ECU 100 is an electronic control unit including a calculation processing circuit that performs various calculation processes related to vehicle driving control, and a memory that stores control programs and data.

[0026] The ECU 100 controls the operation of the engine 10 and the motor generator 15. Specifically, the ECU 100 controls the torque and rotation speed of the engine 10 by controlling the throttle opening, ignition timing, and fuel injection amount of the engine 10. The ECU 100 controls the torque and rotation speed of the motor generator 15 by controlling the inverter 17 to adjust the amount of electric power exchanged between the motor generator 15 and the battery 16. The ECU 100 also controls the operation of the K0 clutch 14, the lock-up clutch 20, and the transmission 19 through the control of the hydraulic control mechanism 22.

[0027] The ECU 100 receives signals from an ignition switch 71, a crank angle sensor 72, and a motor revolution speed sensor 73. The crank angle sensor 72 detects the rotation speed of a crankshaft of the engine 10. The motor revolution speed sensor 73 detects the rotation speed of an output shaft of the motor generator 15. When the ignition switch 71 is turned on, the ECU 100 issues a drive command to the starter 24.

[0028] The ECU 100 runs the hybrid vehicle in either a motor mode or a hybrid mode. In the motor mode, the ECU 100 releases the K0 clutch 14 and runs the vehicle using the power of the motor generator 15. At this time, the engine 10 may be stopped. In the hybrid mode, the ECU 100 switches the K0 clutch 14 to an engaged state and runs the vehicle using at least the power of the engine 10. For example, when the hybrid vehicle 1 is placed in an extremely low temperature environment and the use of the battery 16 is restricted, the ECU 100 also switches the K0 clutch 14 to an engaged state when the hybrid vehicle 1 is to be allowed to run using only the driving force of the engine 10.

[0029] [K0 clutch engagement control] Next, with reference to FIG. 2 and FIG. 3, a control in the case where the hybrid vehicle 1 transitions from a state in which both the engine 10 and the motor generator 15 are stopped to a state in which the hybrid vehicle 1 is capable of running will be described. Here, it is assumed that the hybrid vehicle 1 is stopped with both the engine 10 and the motor generator 15 stopped and then a predetermined time has passed. It is assumed that the hybrid vehicle 1 is in a state in which hydraulic pressure is lost at a location where hydraulic pressure is required due to the passage of a predetermined time after the hybrid vehicle 1 is stopped. In addition, the environment in which the hybrid vehicle 1 is placed is an extremely low temperature environment in which the use of the battery 16 is restricted. In this case, the hybrid vehicle 1 cannot operate the motor generator 15, so the engine 10 is started in order to make the hybrid vehicle 1 capable of running. Since the motor generator 15 cannot be used to start the engine 10, the engine 10 is started using the starter 24 driven by the auxiliary battery 23. When the hybrid vehicle 1 is stopped, the K0 clutch 14 is in a released state, so that the K0 clutch engagement control is performed to make the hybrid vehicle 1 capable of running. The K0 clutch engagement control will be described in detail below. Referring to Fig. 3, the K0 clutch engagement control includes a preparatory control performed in a period T1 and a slip control performed in a period T2. The K0 clutch engagement control also includes an engagement completion control (see step S6 in Fig. 2) performed at time t6, which is the end of the period T2.

[0030] In step S1, the ECU 100 determines whether or not there has been a request to start the engine 10. Specifically, the ECU 100 determines whether or not the ignition switch 71 has been turned on. If the ECU 100 makes a negative determination (No) in step S1, the ECU 100 repeats the process of step S1 until it makes a positive determination (Yes) in step S1. If the ECU 100 makes a positive determination in step S1, the ECU 100 proceeds to step S2.

[0031] In step S2, the ECU 100 issues a drive command to the starter 24. As a result, the starter 24 is driven between time t1 and time t2, the rotation speed of the engine 10 increases, and the starting of the engine 10 is completed. The rotation speed of the engine 10 after starting is maintained at a preset idle rotation speed.

[0032] In step S2, the ECU 100 drives the starter 24 to start the engine 10, and then in step S3, the ECU 100 performs preparatory control for engaging the K0 clutch 14. This preparatory control is a control for increasing the hydraulic pressure in the hydraulic control mechanism 22 that engages the K0 clutch 14 prior to the slip control described in detail later, and is sometimes called packing. By performing the preparatory control, the hydraulic pressure in the oil passage that supplies hydraulic pressure to the K0 clutch 14 is increased, and the K0 clutch 14 can be immediately shifted to an engaged state. In this embodiment, the preparatory control is performed in a period T1 from time t3 to time t5. The end of the period T1, that is, time t5, can be set as a time when at least one of a drop in the rotation speed of the engine 10 or an increase in the rotation speed of the motor generator 15 is detected. This is because it can be determined that the K0 clutch 14 is in an engageable state when the rotation speed of the engine 10 drops or the rotation speed of the motor generator 15 increases. In this embodiment, the time when the drop in the rotation speed of the engine 10 is detected is defined as time t5.

[0033] In this embodiment, the length of the period T1 and the command oil pressure are set in advance according to the hardware configuration of the hybrid vehicle 1, such as the engine 10, the K0 clutch 14, and the oil pressure control mechanism 22, and the target start time. This makes it possible to appropriately increase the oil pressure state according to the configuration of the hybrid vehicle 1. The ECU 100 starts the preparatory control from time t3, so that the actual oil pressure for engaging the K0 clutch starts to gradually increase from time t4, which is delayed from time t3.

[0034] When the preparatory control executed in step S3 is completed, the ECU 100 proceeds to step S4. The ECU 100 starts slip control in step S4. The slip control is executed in a period T2 from time t5 to time t6. Until time t5, the rotation speed of the engine 10 is kept at an idle rotation speed. In contrast, the motor generator 15 is not operating, and its rotation speed is 0 (zero). The slip control gradually engages the K0 clutch 14 so as to match the rotation speeds of the engine 10 and the motor generator 15, in which such a rotation difference occurs. During this time, the rotating element of the K0 clutch 14 on the engine 10 side and the rotating element on the motor generator 15 side are in a slip state. As a result, the rotation speed of the motor generator 15 gradually increases, while the rotation speed of the engine 10 decreases as the rotation speed of the motor generator 15 increases. At this time, the rotation speed of the engine 10 is controlled to be maintained higher than the lower limit rotation speed that avoids the stop of the engine 10. Specifically, the command oil pressure for engaging the K0 clutch 14 is controlled to a value so as to maintain the engine 10 at a higher rotation speed than the lower limit rotation speed. The higher the engagement oil pressure of the K0 clutch 14, the more quickly the engine 10 can increase the rotation speed of the motor generator 15. However, on the other hand, the engine 10 is likely to drop rapidly. If the engine 10 speed drops rapidly and falls below the lower limit rotation speed, the engine 10 may stop, which is called a stalled state. Therefore, in this embodiment, the command oil pressure is set so that the engine 10 speed does not fall below the lower limit rotation speed during slip control. This prevents the engine 10 from stopping. The lower limit rotation speed is set according to the specifications of the engine 10, such as the idle speed.

[0035] During the period T2, the command oil pressure gradually increases at a rate set so that the engine 10 rotation speed does not reach the lower limit due to the drag torque and rotation inertia of the rotating elements subsequent to the motor generator 15.

[0036] Here, the command oil pressure during the slip control will be explained in more detail. Referring to FIG. 3, the command oil pressure gradually increases during the period T2 from time t5 to time t6 during which the slip control is being performed. Time t5 is the start point of the slip control. In other words, time t5 is the timing of switching from the preparatory control to the slip control. At time t5, the command oil pressure is once lowered from the command oil pressure during the preparatory control up to that point. In other words, the command oil pressure during the preparatory control is set to a command oil pressure equal to or higher than the command oil pressure at the start point of the slip control. In other words, the command oil pressure during the preparatory control is set to a command oil pressure equal to or higher than the command oil pressure at the start point of the slip control. By setting such a command oil pressure, the period T1 required for the preparatory control can be shortened, and the period for making the hybrid vehicle 1 in a state in which it can run can be shortened overall.

[0037] Here, the command oil pressure during slip control will be described with reference to FIG. 4. The command oil pressure during slip control can be a pulse wave as shown in FIG. 4. In this way, by making the command oil pressure a pulse wave that repeats rising and falling, it is possible to easily avoid the engine 10 from stopping. The rotation speed of the engine 10 is likely to decrease if the oil pressure for engaging the K0 clutch 14 increases abruptly. Therefore, by making the command oil pressure a pulse wave and setting a timing for decreasing the command oil pressure, the change in the rotation speed can be made gradual. Note that the pulse wave shown in FIG. 4 is rectangular, but the waveform of the pulse wave is not limited to this, and may be other waveforms such as a square wave or a sine wave. Furthermore, a continuous waveform other than a pulse wave or a fine step-like waveform may be used, and the waveform of the command oil pressure during slip control is not limited to a specific waveform and can be appropriately selected.

[0038] After starting slip control in step S4, the ECU 100 proceeds to step S5. In step S5, the ECU 100 determines whether the differential rotation has become smaller than a preset differential rotation threshold value Δ1. The differential rotation is the difference between the rotation speed of the engine 10 and the rotation speed of the motor generator 15. The rotation speed of the engine 10 is acquired by a crank angle sensor 72. The rotation speed of the motor generator 15 is acquired by a motor rotation speed sensor 73. The differential rotation threshold value Δ1 is set in advance in consideration of the magnitude of the shock that occurs when the K0 clutch 14 is engaged so that the rotation speed of the engine 10 and the rotation speed of the motor generator 15 match, and the performance and characteristics of the engine 10.

[0039] If the ECU 100 makes a negative determination in step S5, the ECU 100 repeats the process of step S5 until it makes a positive determination in step S5. If the ECU 100 makes a positive determination in step S5, the ECU 100 proceeds to step S6.

[0040] In step S6, the ECU 100 performs engagement completion control. The engagement completion control is a control for increasing the command hydraulic pressure for engaging the K0 clutch 14 by the hydraulic control mechanism 22 to a command hydraulic pressure at which the engagement of the K0 clutch 14 is completed. The completion of engagement means that the rotation speeds of the engine 10 and the motor generator 15 match, and the rotating elements of the K0 clutch 14 on the engine 10 side and the rotating elements on the motor generator 15 side are in a synchronized state without slipping. In this embodiment, the slip control ends at time t6, and the engagement completion control is performed. In the engagement completion control, the command hydraulic pressure increases to a full engagement hydraulic pressure. As a result, the rotation speeds of the engine 10 and the motor generator 15 match at time t7. With the above, the K0 clutch engagement control ends, and the hybrid vehicle 1 is in a state in which it can run.

[0041] Here, the command oil pressure in the engagement completion control is set according to the rotational torque of the engine 10. This makes it possible to suppress slippage in the K0 clutch 14 and to keep the engine 10 and the motor generator 15 in a connected state.

[0042] In this embodiment, the engagement completion control is performed at time t6 when the differential rotation becomes smaller than the differential rotation threshold value Δ1. Therefore, in this embodiment, the period T3 from time t5 to time t7 is a rotation synchronization period in which the rotation speed of the engine 10 and the rotation speed of the motor generator 15 are synchronized. In contrast, the period in which the slip control is performed may be managed by time. In other words, the engagement completion control may be performed when a predetermined time set in advance has elapsed from time t5 when the slip control is started. In this case, it is assumed that the rotation speed of the engine 10 and the rotation speed of the motor generator 15 match before the engagement completion control is performed. However, the engagement completion control is performed thereafter, so that the hybrid vehicle 1 can be made capable of running.

[0043] [effect] According to this embodiment, the command oil pressure for engaging the K0 clutch 14 is set to a command oil pressure that maintains the engine 10 at a speed higher than the lower limit speed, thereby making it possible to prevent the engine 10 from stalling.

[0044] Also, according to this embodiment, by performing preparatory control prior to slip control, it is possible to reduce the time required to make the hybrid vehicle 1 ready to travel. Furthermore, by setting the command oil pressure in the preparatory control to a higher command oil pressure than the command oil pressure at the start of the slip control, it is possible to reduce the period of the preparatory control.

[0045] Furthermore, since the command oil pressure is given by a pulse wave, the internal combustion engine is effectively prevented from stalling.

[0046] [Variations] Next, a modified example of the vehicle control device (ECU) 100 will be described with reference to FIG. 5. The flowchart shown in FIG. 5 is a modified version of the slip control (step S4) in the flowchart shown in FIG. 2. In this modified example, feedback control is performed in the slip control. In the flowchart shown in FIG. 5, the processes in steps S1 to S3 in the flowchart shown in FIG. 2 are omitted, but in this modified example, the processes in steps S1 to S3 are similarly performed. Note that the time chart for the modified example is the same as the time chart shown in FIG. 3, and therefore the time chart shown in FIG. 3 will be referred to as appropriate in the following description.

[0047] In step S41, the ECU 100 increases the command hydraulic pressure for engaging the K0 clutch 14 (time t5 in FIG. 3). In step S42, which is executed following step S41, the ECU 100 determines whether the rotation speed of the engine 10 is equal to or lower than the lower limit avoidance rotation speed. Here, the lower limit avoidance rotation speed is a rotation speed higher than the lower limit rotation speed. When the rotation speed of the engine 10 reaches the lower limit rotation speed, the possibility of the engine 10 stopping increases, but by setting the lower limit avoidance rotation speed, it is possible to detect a state immediately before such a state is reached.

[0048] When the ECU 100 makes a positive determination in step S42, the process proceeds to step S43. In step S43, the ECU 100 reduces the command oil pressure for engaging the K0 clutch 14. This makes it possible to prevent the engine 10 speed from dropping to the lower limit speed, and as a result, makes it possible to prevent the engine 10 from stopping. The amount of reduction in the command oil pressure can be appropriately set by fitting to an actual machine or by simulation. After executing the process of step S43, the ECU 100 executes the process of step S42 again.

[0049] When the ECU 100 makes a negative determination in step S42, the process proceeds to step S44. In step S44, the ECU 100 continues to increase the command hydraulic pressure. After performing the process of step S44, the ECU 100 proceeds to step S5. Steps S5 and S6 are the same as those in the flowchart shown in FIG. 2, and the ECU 100 performs engagement completion control at time t6 in the time chart shown in FIG. 3, and ends the series of controls.

[0050] According to this modification, the command oil pressure for engaging the K0 clutch 14 is controlled while comparing the engine speed with the lower limit avoidance speed, so that the engine speed can be prevented from reaching the lower limit speed, and as a result, the engine 10 can be prevented from stalling.

[0051] 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 described in the claims. [Explanation of symbols]

[0052] 1 Hybrid vehicles 10 Engine 11. Gear unit 12 Differential 13 Drive wheels 14 K0 clutch 15 Motor generator (MG) 16 Battery 21 Electric oil pump 23 Auxiliary battery 24 Starter 25 Mechanical oil pump 100 ECU

Claims

1. A control device for a vehicle including an internal combustion engine, an electric motor connected to a power transmission path between the internal combustion engine and drive wheels so as to be capable of transmitting power, a disconnecting clutch provided in the power transmission path and disengaged to disconnect the internal combustion engine and the electric motor, a starter for starting the internal combustion engine, and a hydraulic control mechanism for controlling hydraulic pressure supplied to the disconnecting clutch, After the internal combustion engine is started by the starter, a command oil pressure for engaging the disconnecting clutch by the hydraulic control mechanism is set to an command oil pressure that maintains a rotation speed of the internal combustion engine at a rotation speed higher than a lower limit rotation speed that avoids a stop of the internal combustion engine, and a slip control is performed to engage the disconnecting clutch. an engagement completion control in which, when a difference between a rotation speed of the internal combustion engine and a rotation speed of the electric motor becomes smaller than a preset threshold value, a command oil pressure for engaging the disconnecting clutch by the hydraulic control mechanism is increased from a command oil pressure in the slip control to a command oil pressure at which the engagement of the disconnecting clutch is completed; After starting the internal combustion engine by the starter, a preparatory control is carried out to increase the hydraulic pressure in the hydraulic control mechanism that engages the disconnecting clutch from the hydraulic pressure before the starter is driven, prior to the slip control. The end of the period during which the preparatory control is performed is a time when at least one of a drop in the rotation speed of the internal combustion engine and an increase in the rotation speed of the electric motor is detected. Vehicle control device.

2. The command oil pressure in the preparation control is equal to or higher than the command oil pressure at the start of the slip control. The vehicle control device according to claim 1 .

3. The command oil pressure in the slip control is given by a pulse wave that repeats an increase and a decrease in the command oil pressure. The vehicle control device according to claim 1 or 2.

4. In the slip control, when the rotation speed of the internal combustion engine becomes equal to or lower than a lower limit avoidance rotation speed set to a value higher than the lower limit rotation speed, a command oil pressure for engaging the disconnecting clutch is reduced from a command oil pressure when a rotation speed equal to or lower than the lower limit avoidance rotation speed is indicated. The vehicle control device according to any one of claims 1 to 3.

5. The command oil pressure in the engagement completion control is set according to the rotational torque of the internal combustion engine. The vehicle control device according to any one of claims 1 to 4.

6. A control device for a vehicle including an internal combustion engine, an electric motor connected to a power transmission path between the internal combustion engine and drive wheels so as to be capable of transmitting power, a disconnecting clutch provided in the power transmission path and disengaged to disconnect the internal combustion engine and the electric motor, a starter for starting the internal combustion engine, and a hydraulic control mechanism for controlling hydraulic pressure supplied to the disconnecting clutch, After the internal combustion engine is started by the starter, a command oil pressure for engaging the disconnecting clutch by the hydraulic control mechanism is set to an command oil pressure that maintains a rotation speed of the internal combustion engine at a rotation speed higher than a lower limit rotation speed that avoids a stop of the internal combustion engine, and a slip control is performed to engage the disconnecting clutch. When a difference between the rotation speed of the internal combustion engine and the rotation speed of the electric motor becomes smaller than a preset threshold value, an engagement completion control is performed in which an instruction oil pressure for engaging the disconnecting clutch by the hydraulic control mechanism is increased from an instruction oil pressure in the slip control to an instruction oil pressure at which the engagement of the disconnecting clutch is completed, In the slip control, when the rotation speed of the internal combustion engine becomes equal to or lower than a lower limit avoidance rotation speed set to a value higher than the lower limit rotation speed, a command oil pressure for engaging the disconnecting clutch is reduced from a command oil pressure when a rotation speed equal to or lower than the lower limit avoidance rotation speed is indicated. Vehicle control device.

7. The command oil pressure in the engagement completion control is set according to the rotational torque of the internal combustion engine. The vehicle control device according to claim 6.

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