Assist control device

Abstract

To provide an assist control device which can enhance a start property and an acceleration property at steep slope while restraining a clutch from generating heat.SOLUTION: An assist control device executes control on a hybrid vehicle which comprises: an engine; a transmission configured to shift rotation of the engine and transmit the rotation to drive wheels; a clutch configured to cut off or connect a power transmission path between the transmission and the engine; and a motor generator which is capable of transmitting power to the drive wheels. The assist control device comprises: a hybrid control unit (HCU) which executes climbing assist control of outputting climbing assist torque from the motor generator for the drive wheels when an execution condition is satisfied, the execution condition being that a road surface is on an uphill road having a gradient equal to or greater than a prescribed gradient, the clutch is in a disengaged state including a half-engaged state, and there is no request for gear shifting. The HCU stops the climbing assist control on condition that vehicle speed reaches a prescribed vehicle speed or more.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Patent Document 1 discloses a hybrid vehicle in which, when the clutch is in a half-clutch state, the electric motor is controlled to generate a starting assist torque equal to the difference between the driver-requested torque requested by the driver and the idling torque generated by the engine when idling.

[0003] In the hybrid vehicle disclosed in Patent Document 1, when the road is uphill with a gradient of at least a predetermined gradient, the correction unit corrects the assist start torque, which is a threshold value used to determine whether or not to assist the engine with the driving force of the electric motor, in accordance with the gradient so that the assist start torque is larger than the assist start torque on a flat road. Furthermore, when the road is uphill with a gradient of at least a predetermined gradient, the correction unit corrects the assist full torque, which is the upper limit of the torque of the electric motor when assisting the engine with the driving force of the electric motor, in accordance with the gradient so that the assist full torque is smaller than the assist full torque on a flat road.

[0004] As a result, in the hybrid vehicle disclosed in Patent Document 1, when the gradient of an uphill road is steep, the assist start torque is intentionally increased, and only the torque that is insufficient in the engine is compensated for by the electric motor, and basic power (torque) is generated by the engine, thereby preventing excessive discharge of the battery and shortening the period in which the clutch is in a half-engine state. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2012 / 053596 Brochure Summary of the Invention [Problem to be solved by the invention]

[0006] However, in the hybrid vehicle described in Patent Document 1, when the gradient of an uphill road is large, the assist torque acting on the clutch output shaft is small, so the clutch is engaged with a high load on the clutch output shaft, resulting in a large amount of heat generated by the clutch. To reduce this heat generation, it is necessary to reduce the amount of change in torque transmitted from the clutch input shaft to the clutch output shaft, thereby lengthening the period of time the clutch is in the half-clutch state. In this case, the transition time from the half-clutch state to the engaged state becomes longer, impairing the vehicle's starting and acceleration on steep uphill roads.

[0007] Furthermore, in the hybrid vehicle described in Patent Document 1, frequent engine assistance by the electric motor on flat roads can cause a decrease in SOC. When the SOC decreases, the torque that can be output by the electric motor is limited, and even if engine assistance is attempted on steep uphill roads, the desired assist torque cannot be output, which can result in a loss of starting and acceleration performance of the vehicle.

[0008] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide an assist control device that can improve starting and acceleration performance on steep gradients while suppressing heat generation in the clutch. [Means for solving the problem]

[0009] In order to achieve the above-mentioned object, the present invention provides an assist control device for a vehicle equipped with an engine, a transmission that changes the speed of the engine and transmits it to the drive wheels, a clutch that disconnects or connects the power transmission path between the transmission and the engine, and a motor that can transmit power to the drive wheels, and the control unit executes hill climbing assist control that outputs assist torque from the motor to the drive wheels when the execution conditions are met, with the road being an uphill road with a predetermined gradient or higher, the clutch being in a disengaged state including a half-engaged state, and there being no request for a gear change, and the control unit is configured to stop the hill climbing assist control when the vehicle speed, which is the speed of the vehicle, becomes equal to or higher than the predetermined vehicle speed. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an assist control device that can improve starting and acceleration performance on steep gradients while suppressing heat generation in the clutch. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing the configuration of a hybrid vehicle according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing the functions of the HCU of the hybrid vehicle according to one embodiment of the present invention. [Figure 3] FIG. 3 is a flowchart showing the flow of a hill climbing assist determination process executed by the HCU of the hybrid vehicle according to one embodiment of the present invention. [Figure 4] FIG. 4 is a flowchart showing the flow of acceleration assist determination processing executed by the HCU of the hybrid vehicle according to one embodiment of the present invention. [Figure 5] FIG. 5 is a time chart showing an example of a case where hill climbing assist control is executed in a hybrid vehicle according to an embodiment of the present invention. [Figure 6] FIG. 6 is a flowchart showing the flow of a shift assist determination process executed by the HCU of the hybrid vehicle according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0012] An assist control device according to one embodiment of the present invention is an assist control device for a vehicle that includes an engine, a transmission that changes the speed of the engine rotation and transmits it to the drive wheels, a clutch that disconnects or connects the power transmission path between the transmission and the engine, and a motor that can transmit power to the drive wheels, and is equipped with a control unit that executes climbing assist control that outputs assist torque from the motor to the drive wheels when the execution conditions are met, with the execution conditions being that the road is an uphill road with a predetermined gradient or higher, the clutch is in a disengaged state including a half-engaged state, and there is no request for a gear change, and the control unit stops the climbing assist control when the vehicle speed, which is the speed of the vehicle, reaches or exceeds the predetermined vehicle speed.

[0013] As a result, the assist control device according to one embodiment of the present invention can improve starting and acceleration performance on steep gradients while suppressing heat generation in the clutch. [Example]

[0014] An assist control device according to an embodiment of the present invention will be described below with reference to the drawings.

[0015] As shown in Fig. 1, a hybrid vehicle 1 includes an engine 2, a transmission 3 as a gearbox, a motor generator 4 as a motor, drive wheels 5, an HCU (Hybrid Control Unit) 10 that comprehensively controls the hybrid vehicle 1, an ECM (Engine Control Module) 11 that controls the engine 2, a TCM (Transmission Control Module) 12 that controls the transmission 3, an ISGCM (Integrated Starter Generator Control Module) 13, an INVCM (Inverter Control Module) 14, a low-voltage BMS (Battery Management System) 15, and a high-voltage BMS 16. The engine 2 and the motor generator 4 constitute a drive source that transmits power to a drive shaft 23 as a drive shaft. The HCU 10 according to this embodiment constitutes a control unit.

[0016] In this embodiment, the engine 2 is an internal combustion engine. The engine 2 is formed with a plurality of cylinders. In this embodiment, the engine 2 is configured to perform a series of four strokes for each cylinder, which are an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke.

[0017] An ISG (Integrated Starter Generator) 20 and a starter 21 are connected to the engine 2. The ISG 20 is connected to a crankshaft 18 of the engine 2 via a power transmission member such as a belt or chain. The ISG 20 functions as an electric motor that rotates when supplied with electric power, thereby driving the engine 2 to rotate, and also functions as a generator that converts the rotational force input from the crankshaft 18 into electric power.

[0018] In this embodiment, the ISG 20 functions as an electric motor under the control of the ISGCM 13, thereby restarting the engine 2 from a stopped state caused by the idling stop function. The ISG 20 can also assist the running of the hybrid vehicle 1 by functioning as an electric motor.

[0019] The starter 21 includes a motor and a pinion gear (not shown). The starter 21 rotates the motor to rotate the crankshaft 18, thereby providing the rotational force for starting the engine 2. In this manner, the engine 2 is started by the starter 21 and is restarted by the ISG 20 from a stopped state due to the idling stop function.

[0020] The transmission 3 changes the speed of the rotation output from the engine 2 and transmits it to the drive wheels 5 via the drive shaft 23, thereby driving the drive wheels 5. The transmission 3 includes a constant mesh type speed change mechanism 25 made up of a parallel shaft gear mechanism, a clutch 26 made up of a normally closed type dry clutch, a differential mechanism 27 as a reducer, and actuators 51 and 52.

[0021] The clutch 26 is provided between the transmission mechanism 25 and the engine 2, and is adapted to disconnect or connect the power transmission path between the drive wheels 5 and the engine 2 by switching between engagement and disengagement.

[0022] The transmission 3 is configured as a so-called AMT (Automated Manual Transmission) and is capable of establishing multiple gears, including multiple forward gears and multiple reverse gears. In the transmission 3, an actuator 52 controlled by the TCM 12 switches the gears in the speed change mechanism 25, and an actuator 51 engages and disengages the clutch 26. The differential mechanism 27 transmits the power output by the speed change mechanism 25 to the drive shaft 23. The power transmitted to the drive shaft 23 is transmitted to the drive wheels 5.

[0023] The motor generator 4 is connected to a differential mechanism 27 via a power transmission member 28 such as a chain. The motor generator 4 is connected to a drive shaft 23 via the differential mechanism 27. The motor generator 4 functions as an electric motor.

[0024] In this way, the hybrid vehicle 1 forms a parallel hybrid system that can use the power of both the engine 2 and the motor generator 4 to drive the vehicle, and is designed to run using the power output by at least one of the engine 2 and the motor generator 4.

[0025] The driving modes of the hybrid vehicle 1 include at least an HEV driving mode in which the driving force of the engine 2 and the motor generator 4 is transmitted to the drive shaft 23 to drive the hybrid vehicle 1, and an EV driving mode in which fuel injection to the engine 2 is stopped to stop the engine 2 from driving and the driving force of only the motor generator 4 is transmitted to the drive shaft 23 to drive the hybrid vehicle 1 in EV driving mode.

[0026] The motor generator 4 also functions as a generator that generates electricity using the rotation of the drive wheels 5, and generates electricity as the hybrid vehicle 1 runs. Note that the motor generator 4 need only be connected to any point in the power transmission path from the engine 2 to the drive wheels 5 so as to be capable of transmitting power, and does not necessarily have to be connected to the differential mechanism 27.

[0027] The hybrid vehicle 1 includes a first power storage device 30, a low-voltage power pack 32 including a second power storage device 31, a high-voltage power pack 34 including a third power storage device 33 as a battery, a high-voltage cable 35, and a low-voltage cable 36.

[0028] The first power storage device 30, the second power storage device 31, and the third power storage device 33 are configured by rechargeable secondary batteries. The first power storage device 30 is configured by a lead battery. The second power storage device 31 is a power storage device with higher output and higher energy density than the first power storage device 30.

[0029] The second power storage device 31 can be charged in a shorter time than the first power storage device 30. In this embodiment, the second power storage device 31 is made of a lithium ion battery. However, the second power storage device 31 may also be made of a nickel-metal hydride battery.

[0030] The first power storage device 30 and the second power storage device 31 are low-voltage batteries in which the number of cells and the like are set so as to generate an output voltage of approximately 12 V. The third power storage device 33 is, for example, a lithium-ion battery.

[0031] The third power storage device 33 is a high-voltage battery in which the number of cells and the like are set so as to generate a higher voltage than the first power storage device 30 and the second power storage device 31, and generates an output voltage of, for example, 100 V. The state of the third power storage device 33, such as its remaining capacity (hereinafter referred to as "remaining battery capacity"), is managed by the high-voltage BMS 16.

[0032] The hybrid vehicle 1 is provided with a general load 37 and a protected load 38 as electrical loads. The general load 37 and the protected load 38 are electrical loads other than the starter 21 and the ISG 20.

[0033] The protected load 38 is an electrical load that requires a constant stable power supply, and includes, for example, lamps on an instrument panel (not shown).

[0034] The general loads 37 are electrical loads that are used temporarily and do not require a stable power supply compared to the protected loads 38. The general loads 37 include, for example, windshield wipers (not shown).

[0035] The low-voltage power pack 32 has switches 40, 41 and a low-voltage BMS 15 in addition to the second power storage device 31. The first power storage device 30 and the second power storage device 31 are connected via a low-voltage cable 36 so as to be able to supply power to the starter 21, the ISG 20, and a general load 37 and a protected load 38 as electrical loads. The first power storage device 30 and the second power storage device 31 are electrically connected in parallel to the protected load 38.

[0036] The switch 40 is provided in the low-voltage cable 36 between the second power storage device 31 and the protected load 38. The switch 41 is provided in the low-voltage cable 36 between the first power storage device 30 and the protected load 38.

[0037] Low-voltage BMS 15 controls the opening and closing of switches 40 and 41 to control the charging and discharging of second power storage device 31 and the supply of power to protected load 38. When engine 2 is stopped due to an idling stop, low-voltage BMS 15 closes switch 40 and opens switch 41 to supply power from high-output, high-energy-density second power storage device 31 to protected load 38.

[0038] When starting the engine 2 with the starter 21, or when restarting the engine 2 that has been stopped by idling stop control with the ISG 20, the low-voltage BMS 15 closes the switch 40 and opens the switch 41 to supply power from the first power storage device 30 to the starter 21 or the ISG 20. With the switch 40 closed and the switch 41 open, power is also supplied from the first power storage device 30 to the general load 37.

[0039] In this way, the first power storage device 30 is configured to supply power to at least the starter 21 and the ISG 20, which serve as starting devices for starting the engine 2. The second power storage device 31 is configured to supply power to at least the general load 37 and the protected load 38.

[0040] The second storage device 31 is connected so as to be able to supply power to both the general load 37 and the protected load 38, but the switches 40 and 41 are controlled by the low-voltage BMS 15 so as to supply power preferentially to the protected load 38, which requires a constant stable power supply.

[0041] The low-voltage BMS 15 may take into consideration the state of charge (remaining charge) of the first storage device 30 and the second storage device 31, as well as the operation requirements of the general load 37 and the protected load 38, and may control the switches 40, 41 differently from the example described above, giving priority to stable operation of the protected load 38.

[0042] The high-voltage power pack 34 has, in addition to the third power storage device 33, an inverter 45, an INVCM 14, and a high-voltage BMS 16. The high-voltage power pack 34 is connected to the motor generator 4 via a high-voltage cable 35 so as to be able to supply electric power to the motor generator 4.

[0043] Under the control of INVCM 14, inverter 45 converts AC power applied to high-voltage cable 35 into DC power applied to third power storage device 33, and vice versa. For example, when INVCM 14 powers motor generator 4, INVCM 14 converts DC power discharged from third power storage device 33 into AC power using inverter 45 and supplies the AC power to motor generator 4.

[0044] When the motor generator 4 is used for regeneration, the INVCM 14 converts the AC power generated by the motor generator 4 into DC power using the inverter 45 and charges the third power storage device 33 with the DC power.

[0045] HCU10, ECM11, TCM12, ISGCM13, INVCM14, low-voltage BMS15 and high-voltage BMS16 are each composed of a computer unit equipped with a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), flash memory for storing backup data, etc., input ports and output ports.

[0046] The ROM of these computer units stores various constants, maps, etc., as well as programs that cause the computer units to function as the HCU 10, ECM 11, TCM 12, ISGCM 13, INVCM 14, low-voltage BMS 15, and high-voltage BMS 16, respectively.

[0047] That is, by the CPU using the RAM as a working area to execute the programs stored in the ROM, these computer units function as the HCU 10, ECM 11, TCM 12, ISGCM 13, INVCM 14, low-voltage BMS 15, and high-voltage BMS 16 in this embodiment, respectively.

[0048] In this embodiment, the ECM 11 is configured to execute idling stop control. In this idling stop control, the ECM 11 stops the engine 2 when a predetermined stop condition is met, and when a predetermined restart condition is met, the ECM 11 drives the ISG 20 via the ISGCM 13 to restart the engine 2. This prevents unnecessary idling of the engine 2, thereby improving the fuel efficiency of the hybrid vehicle 1.

[0049] The hybrid vehicle 1 is provided with CAN (Controller Area Network) communication lines 48 and 49 for forming an in-vehicle LAN (Local Area Network) that conforms to standards such as CAN.

[0050] The HCU 10 is connected to the INVCM 14 and the high-voltage BMS 16 by a CAN communication line 48. The HCU 10, the INVCM 14, and the high-voltage BMS 16 transmit and receive signals such as control signals to and from each other via the CAN communication line 48.

[0051] The HCU 10 is connected to the ECM 11, TCM 12, ISGCM 13, and low-voltage BMS 15 via a CAN communication line 49. The HCU 10, ECM 11, TCM 12, ISGCM 13, and low-voltage BMS 15 mutually transmit and receive signals such as control signals via the CAN communication line 49.

[0052] The HCU 10 is connected to a wheel speed sensor 10a that detects the wheel speed of each wheel including the drive wheels 5, an accelerator opening sensor 10b that detects the operation amount of the accelerator pedal 8 as an accelerator opening, a clutch stroke sensor 10c that detects the engagement degree of the clutch 26, a crank angle sensor 10d, and an acceleration sensor 10e. The HCU 10 calculates the engine rotation speed, which is the rotation speed of the engine 2, based on the detection information from the crank angle sensor 10d.

[0053] The wheel speed sensor 10a outputs a pulse signal as a vehicle speed pulse, which pulse is generated every time the wheel rotates by a predetermined angle. The HCU 10 calculates the vehicle speed of the hybrid vehicle 1 based on this vehicle speed pulse.

[0054] The acceleration sensor 10e detects the acceleration of the hybrid vehicle 1 and outputs the detection result to the HCU 10. In this embodiment, the acceleration sensor 10e is configured to detect the acceleration of the hybrid vehicle 1, but the HCU 10 may be configured to calculate the acceleration of the hybrid vehicle 1 based on the above-mentioned vehicle speed and the change over time in the rotation speed of the motor generator 4.

[0055] Furthermore, the acceleration sensor 10e detects the gradient of the road surface on which the hybrid vehicle 1 is traveling or stopped based on the tilt of the hybrid vehicle 1 in the longitudinal direction, and outputs the detection result to the HCU 10. In this embodiment, the gradient of the road surface is detected by the acceleration sensor 10e, but the HCU 10 may also detect the gradient of the road surface based on information obtained from a map information acquisition unit 10f and a position information acquisition unit 10g, which will be described later.

[0056] As shown in FIG. 2, in addition to the above sensors, a map information acquisition unit 10f and a position information acquisition unit 10g are connected to the HCU 10.

[0057] The map information acquiring unit 10f is configured as a car navigation device, and is configured to acquire map information including uphill road information and transmit it to the HCU 10. The map information is stored in a storage medium of the car navigation device. The map information acquiring unit 10f is not limited to a car navigation device, and may be, for example, application software such as a map app installed on a mobile terminal such as a smartphone or tablet terminal.

[0058] The position information acquisition unit 10g is made up of a GPS receiver, and measures the current position of the hybrid vehicle 1 using a GPS (Global Positioning System), and transmits the measured current position to the HCU 10.

[0059] The HCU 10 functions as a road surface gradient determination unit 101 that determines whether the road surface on which the hybrid vehicle 1 is traveling or stopped is an uphill road with a predetermined gradient (e.g., 20%) or more, based on the detection results input from the acceleration sensor 10e.

[0060] The HCU 10 functions as a clutch state determination unit 102 that determines whether the clutch 26 is in a disengaged state, including a half-engaged state, or in an engaged state, including a fully engaged state, based on the detection result input from the clutch stroke sensor 10c. The disengaged state of the clutch 26 includes a disengaged state in which power is not transmitted between the engine-side friction engagement element 26a of the clutch 26 and the transmission-side friction engagement element 26b.

[0061] The partially engaged state refers to a state in which the engine-side friction engagement element 26a and the transmission-side friction engagement element 26b of the clutch 26 are engaged and rotate relative to each other with slippage occurring between them. The fully engaged state refers to an engaged state in which the engine-side friction engagement element 26a and the transmission-side friction engagement element 26b of the clutch 26 rotate together without slippage occurring.

[0062] The HCU 10 has a function as a shift request determination unit 103 that determines whether or not to perform a shift in the transmission 3 by referring to a shift map based on the accelerator opening and vehicle speed, and determines whether or not there is a request for a shift (hereinafter referred to as a "shift request") based on the result of this determination. The shift map is a relationship between the accelerator opening, vehicle speed, and shift timing that has been experimentally obtained in advance, and is stored in the ROM of the HCU 10.

[0063] The HCU 10 functions as an acceleration request determination unit 104 that determines whether an acceleration request value indicating the degree of acceleration request for the hybrid vehicle 1 is equal to or greater than a predetermined value. The predetermined values include a "first predetermined value" used to determine the execution conditions for a hill climbing assist control, which will be described later, and a "second predetermined value" used to determine the execution conditions for an acceleration assist control, which will be described later. In this embodiment, the first predetermined value is set to a value greater than the second predetermined value.

[0064] The accelerator opening can be used as the acceleration requirement value, and in this case, the first predetermined value is set to, for example, 75% of the accelerator opening. Alternatively, the depression speed of the accelerator pedal 8, i.e., the amount of change in the accelerator opening per unit time, may be used as the acceleration requirement value.

[0065] The acceleration request for the hybrid vehicle 1 described above may include an acceleration request due to the driver depressing the accelerator pedal 8, as well as an acceleration request that is made in accordance with the difference between the set vehicle speed and the actual vehicle speed when the vehicle is traveling regardless of the driver's accelerator operation, such as in cruise control or automatic driving.

[0066] The HCU 10 has a function as a battery status determination unit 105 that acquires the remaining battery capacity of the third storage device 33 from the high-voltage BMS 16, and determines whether the remaining battery capacity of the third storage device 33 is equal to or greater than a first threshold, or whether the remaining battery capacity is equal to or greater than a second threshold.

[0067] The first threshold is a lower limit value of the remaining battery charge at which the hill climbing assist control described later can be executed, and is experimentally determined in advance and stored in the ROM of the HCU 10. The second threshold is a value larger than the first threshold, and is a lower limit value of the remaining battery charge at which the acceleration assist control described later can be executed, and is experimentally determined in advance and stored in the ROM of the HCU 10.

[0068] The HCU 10 functions as an uphill road information acquisition unit 106 that acquires uphill road information on the driving route from the current location to the destination based on input information from the map information acquisition unit 10f and the position information acquisition unit 10g. The destination is a destination set in the car navigation device. When a map application is used as the map information acquisition unit 10f, the destination is a destination set in the map application. The uphill road information includes at least information such as whether or not there is an uphill road on the driving route to the destination, the gradient of the uphill road, the distance to the uphill road, and the length of the uphill road.

[0069] If the HCU10 determines, based on the uphill road information acquired as described above, that there is an uphill road with a gradient of a predetermined or greater on the travel route from the current location to the destination, it ensures that the third power storage device 33 has a remaining battery capacity equal to or greater than the first threshold value by the time the vehicle reaches the uphill road from the current location.

[0070] For example, the HCU 10 can ensure or maintain the remaining battery charge at or above the first threshold by generating electricity using the motor generator 4 or the ISG 20 to increase the remaining battery charge, or by limiting assist control other than the climbing assist control, such as acceleration assist control. Additionally, the HCU 10 may generate electricity using the ISG 20 simultaneously with assist control other than the climbing assist control, or may generate electricity using the ISG 20 by driving the engine 2.

[0071] If the HCU10 determines based on the uphill road information that there is no uphill road with a gradient of a predetermined gradient or more on the driving route from the current position to the destination, the HCU10 may prohibit each of the above processes for ensuring that the remaining battery capacity is equal to or greater than the first threshold.

[0072] The HCU 10 includes a timer 107. The timer 107 measures various times. For example, the timer 107 measures the elapsed time from the start of execution of hill climbing assist control, which will be described later.

[0073] The HCU 10 executes hill climbing assist control, which outputs assist torque from the motor generator 4 to the drive wheels 5, when the execution conditions are met: the road surface on which the hybrid vehicle 1 is traveling or stopped is an uphill road with a gradient equal to or greater than a predetermined gradient, the clutch 26 is in a disengaged state, and there is no request for a gear change. Hereinafter, the assist torque in the hill climbing assist control will be referred to as "hill climbing assist torque."

[0074] The conditions for executing the hill climbing assist control include a condition that the acceleration required value for the hybrid vehicle 1 is equal to or greater than a first predetermined value. Note that the condition that the acceleration required value for the hybrid vehicle 1 is equal to or greater than the first predetermined value does not have to be one of the conditions for executing the hill climbing assist control.

[0075] Furthermore, the conditions for executing the hill climbing assist control include the remaining battery capacity of the third power storage device 33 being equal to or greater than the first threshold. However, the remaining battery capacity of the third power storage device 33 being equal to or greater than the first threshold does not necessarily have to be one of the conditions for executing the hill climbing assist control.

[0076] Furthermore, one of the conditions for executing the hill-climbing assist control may be that the gear position or gear ratio is less than a predetermined value. As a result, when the gear position or gear ratio is large, the gear position or gear ratio is lowered to increase the output torque before execution of the hill-climbing assist control is started, thereby suppressing the assist amount and assist frequency of the hill-climbing assist torque and reducing power consumption of the third power storage device 33.

[0077] The HCU 10 stops the hill climbing assist control when any one of the following first to fourth stop conditions is met.

[0078] The first stop condition is that the clutch 26 has transitioned from a disengaged state to an engaged state. The second stop condition is that the vehicle speed is equal to or greater than a predetermined vehicle speed. The third stop condition is that the remaining battery capacity of the third power storage device 33 is less than a first threshold. The fourth stop condition is that a predetermined time has elapsed since the execution of the hill climbing assist control was initiated.

[0079] The HCU 10 can execute acceleration assist control to output assist torque from the motor generator 4 to the drive wheels 5 in response to an acceleration request for the hybrid vehicle 1. That is, the HCU 10 executes acceleration assist control on the condition that the acceleration request value for the hybrid vehicle 1 is equal to or greater than a second predetermined value. Hereinafter, the assist torque in the acceleration assist control will be referred to as "acceleration assist torque."

[0080] The acceleration assist control is executed on the condition that the remaining battery capacity of the third power storage device 33 is equal to or greater than a second threshold value that is greater than the first threshold value. Note that the remaining battery capacity of the third power storage device 33 being equal to or greater than the second threshold value does not necessarily have to be one of the execution conditions for the acceleration assist control.

[0081] Next, the flow of the hill-climbing assistance determination process executed by the HCU 10 will be described with reference to Fig. 3. The hill-climbing assistance determination process shown in Fig. 3 is repeatedly executed at predetermined time intervals.

[0082] 3, the HCU 10 determines whether or not a gear change request is present (step S1). If the HCU 10 determines in step S1 that a gear change request is present, the HCU 10 terminates the hill climbing assist determination process. If the HCU 10 determines in step S1 that a gear change request is not present, the HCU 10 determines whether or not the road surface on which the hybrid vehicle 1 is traveling or stopped is an uphill road with a gradient equal to or greater than a predetermined gradient (step S2).

[0083] If the HCU 10 determines in step S2 that the road surface is not an uphill road with a gradient of at least a predetermined value, it ends this climbing assist determination process. If the HCU 10 determines in step S2 that the road surface is an uphill road with a gradient of at least a predetermined value, it determines whether the acceleration requirement value for the hybrid vehicle 1 is at least a first predetermined value (step S3).

[0084] In step S3, the HCU 10 preferably determines whether the acceleration requirement value has changed from a state where it was less than the first predetermined value to a state where it was equal to or greater than the first predetermined value. As a result, after the climb assist control is stopped, the climb assist control is not executed unless the acceleration requirement value becomes equal to or greater than the first predetermined value again after it has become less than the first predetermined value. Therefore, even if the climb assist control is stopped when the acceleration requirement value is equal to or greater than the first predetermined value, the climb assist control is prevented from being resumed immediately thereafter.

[0085] If the HCU 10 determines in step S3 that the acceleration requirement value is not equal to or greater than the first predetermined value, it ends the hill climbing assistance determination process. If the HCU 10 determines in step S3 that the acceleration requirement value is equal to or greater than the first predetermined value, it determines whether the clutch 26 is in a disengaged state, including a half-engaged state (step S4).

[0086] If the HCU 10 determines in step S4 that the clutch 26 is not disengaged, the HCU 10 ends this hill climbing assist determination process. If the HCU 10 determines in step S4 that the clutch 26 is disengaged, the HCU 10 determines whether the remaining battery capacity of the third power storage device 33 is equal to or greater than a first threshold (step S5).

[0087] If the HCU 10 determines in step S5 that the remaining battery charge of the third power storage device 33 is not equal to or greater than the first threshold, the HCU 10 ends this climbing assist determination process. If the HCU 10 determines in step S5 that the remaining battery charge of the third power storage device 33 is equal to or greater than the first threshold, the HCU 10 executes climbing assist control (step S6).

[0088] When the climbing assist control is executed in step S6, a climbing assist torque is output from the motor generator 4 to the drive wheels 5. Therefore, while the climbing assist control is being executed, the torque required of the hybrid vehicle 1 is the sum of the engine torque output from the engine 2 and transmitted to the drive shaft 23 via the clutch 26 and the transmission 3 and the climbing assist torque (hereinafter referred to as "total torque"), and is transmitted to the drive wheels 5. The climbing assist torque is set to the torque obtained by subtracting the engine torque from the required torque required of the hybrid vehicle 1.

[0089] The total torque is set to at least a torque that can ensure a driving force (hereinafter referred to as "required driving force") that allows the hybrid vehicle 1 to start or run at a predetermined acceleration on an uphill road with a predetermined gradient.

[0090] Next, the HCU 10 determines whether the clutch 26 remains disengaged during the execution of the hill-climbing assist control (step S7). If the HCU 10 determines in step S7 that the clutch 26 does not remain disengaged, the HCU 10 determines that the clutch 26 has transitioned to an engaged state, which is a fully engaged state, and therefore it is no longer necessary to output hill-climbing assist torque, and stops the hill-climbing assist control that was started in step S6 (step S11), and ends this hill-climbing assist determination process.

[0091] If the HCU 10 determines in step S7 that the clutch 26 remains disengaged, it determines whether the vehicle speed is less than a predetermined vehicle speed (step S8). If the HCU 10 determines in step S8 that the vehicle speed is not less than the predetermined vehicle speed, that is, that the vehicle speed is equal to or greater than the predetermined vehicle speed, it stops the hill climbing assist control that was started in step S6 (step S11), and ends this hill climbing assist determination process.

[0092] The predetermined vehicle speed is set to a speed lower than the target vehicle speed of the hybrid vehicle 1. The aforementioned target vehicle speed is, for example, an estimated vehicle speed estimated from the accelerator opening or gear position, or a set vehicle speed during cruise control or automatic driving. Both the estimated vehicle speed and the set vehicle speed are variable values. For this reason, it is preferable that the predetermined vehicle speed also fluctuates in conjunction with the estimated vehicle speed and the set vehicle speed. For example, the predetermined vehicle speed can be a vehicle speed that is a predetermined speed lower than the estimated vehicle speed and the set vehicle speed, or a vehicle speed obtained by multiplying the estimated vehicle speed and the set vehicle speed by a predetermined ratio (predetermined ratio < 100%).

[0093] The predetermined vehicle speed may be set to a target vehicle speed of the hybrid vehicle 1. The predetermined vehicle speed may also be changed depending on the remaining battery capacity of the third power storage device 33. For example, when the remaining battery capacity of the third power storage device 33 is equal to or greater than a predetermined threshold value that is greater than the first threshold value, the predetermined vehicle speed may be set to a target vehicle speed of the hybrid vehicle 1, and when the remaining battery capacity of the third power storage device 33 is equal to or greater than the first threshold value and less than the predetermined threshold value, the predetermined vehicle speed may be set to a speed lower than the target vehicle speed of the hybrid vehicle 1. Furthermore, the predetermined vehicle speed may also be set to a fixed value that is determined in advance through experiments, tests, or the like.

[0094] If the HCU 10 determines in step S8 that the vehicle speed is less than the predetermined vehicle speed, it determines whether the remaining battery charge of the third power storage device 33 is equal to or greater than a first threshold (step S9). If the HCU 10 determines in step S9 that the remaining battery charge of the third power storage device 33 is not equal to or greater than the first threshold, that is, that the remaining battery charge of the third power storage device 33 is less than the first threshold, it stops the climbing assist control that was started in step S6 (step S11) and ends this climbing assist determination process.

[0095] If the HCU 10 determines in step S9 that the remaining battery capacity of the third power storage device 33 is equal to or greater than the first threshold, the HCU 10 determines whether a predetermined time has elapsed since the execution of the hill climbing assist control was started in step S6 (step S10).

[0096] If the HCU 10 determines in step S10 that the predetermined time has not elapsed since the execution of the hill climbing assist control was started in step S6, the HCU 10 proceeds to step S7 and repeats the processes from step S7 to step S10 again.

[0097] If the HCU10 determines in step S10 that a predetermined time has elapsed since the execution of the hill-climbing assist control was started in step S6, the HCU10 stops the hill-climbing assist control that was started in step S6 (step S11) and ends this hill-climbing assist determination process.

[0098] Next, a flow of the acceleration assist determination process executed by the HCU 10 will be described with reference to Fig. 4. The acceleration assist determination process shown in Fig. 4 is repeatedly executed at predetermined time intervals.

[0099] 4, the HCU 10 determines whether or not the acceleration request value for the hybrid vehicle 1 is equal to or greater than a second predetermined value (step S21). The second predetermined value is smaller than the first predetermined value.

[0100] If the HCU 10 determines in step S21 that the acceleration request value is not equal to or greater than the second predetermined value, it terminates the acceleration assist determination process without executing acceleration assist control. If the HCU 10 determines in step S21 that the acceleration request value is equal to or greater than the second predetermined value, it determines whether the remaining battery capacity of the third power storage device 33 is equal to or greater than a second threshold (step S22).

[0101] If the HCU 10 determines in step S22 that the remaining battery charge of the third power storage device 33 is not equal to or greater than the second threshold, the HCU 10 ends the acceleration assist determination process without executing acceleration assist control. If the HCU 10 determines in step S22 that the remaining battery charge of the third power storage device 33 is equal to or greater than the second threshold, the HCU 10 determines whether or not the climbing assist control or the acceleration assist control is being executed (step S23).

[0102] If the HCU 10 determines in step S23 that the climbing assist control or the acceleration assist control is being executed, it ends this acceleration assist determination process without executing the acceleration assist control. If the HCU 10 determines in step S23 that the climbing assist control or the acceleration assist control is not being executed, it executes the acceleration assist control (step S24) and ends this acceleration assist determination process.

[0103] Next, an example of the case where the hill climbing assist control is executed will be described with reference to the time chart of Fig. 5. The time chart of Fig. 5 shows an example of the case where the hybrid vehicle 1 starts from a stop on an uphill road with a predetermined gradient or more, and the execution condition for the hill climbing assist control is established at time t1.

[0104] 5, when the hybrid vehicle 1 is stopped in an idling state and the driver requests a start at time t1 by depressing the accelerator pedal 8, the engine speed and total torque increase according to the accelerator pedal depression amount. At this time, the clutch 26 is released from the disengaged state and the engagement state changes toward the half-engaged state.

[0105] Then, at time t2, when the clutch 26 transitions to a half-engaged state, torque begins to be transmitted from the engine-side frictional engagement element 26a to the transmission-side frictional engagement element 26b. As a result, from time t2 onwards, the clutch rotational speed begins to increase, and the difference with the engine rotational speed gradually decreases. The clutch rotational speed is the rotational speed of the transmission-side frictional engagement element 26b.

[0106] Furthermore, after time t2, the state in which the total torque of the hill climbing assist torque and the engine torque exceeds the required driving force is maintained.

[0107] Thereafter, at time t3, when the difference between the engine rotation speed and the clutch rotation speed becomes less than a set value, the clutch 26 starts to transition from the partially engaged state to the fully engaged state. This set value is set to a value that reduces the shock that occurs when the clutch 26 transitions from the partially engaged state to the fully engaged state. This shortens the time it takes for the clutch 26 to transition from the partially engaged state to the fully engaged state compared to when the set value is set to 0, thereby suppressing an increase in clutch temperature and the discharge power of the third power storage device 33. Note that this set value can also be set to 0 to eliminate the shock that occurs when the clutch 26 transitions from the partially engaged state to the fully engaged state.

[0108] The degree of clutch engagement is maintained at a predetermined level between time t2 and time t3. This degree of clutch engagement is an index showing the degree of engagement of the clutch 26. When the clutch 26 is in a partially engaged state, the higher the degree of clutch engagement, the higher the power transmission rate of the clutch 26, and the lower the degree of clutch engagement, the lower the power transmission rate of the clutch 26.

[0109] As an indicator of the degree of engagement of clutch 26, the distance between friction engagement element 26a and friction engagement element 26b, the drive amount for driving clutch 26 (the amount of current or voltage in the case of an electromagnetic clutch, or the amount of pressure oil in the case of a hydraulic clutch), or the clutch capacity may be used.

[0110] The predetermined degree of engagement is set to a value that causes the rate of temperature rise of the clutch 26 due to friction between the friction engagement elements 26a and 26b to be below the upper limit. As a result, between time t2 and time t3, that is, when the difference between the engine rotation speed and the clutch rotation speed exceeds the set value and the rate of rise in the clutch temperature increases, the predetermined degree of engagement is maintained at a constant value, thereby suppressing a sudden rise in the clutch temperature.

[0111] The predetermined degree of engagement may be a fixed value determined in advance through experiments, tests, etc., or may be set to a variable value that changes depending on the vehicle state and the external environment. When the predetermined degree of engagement is set to a variable value, for example, the predetermined degree of engagement may be set to be smaller as the difference between the engine rotation speed and the clutch rotation speed increases, or the predetermined degree of engagement may be set to be smaller as the output value of a clutch temperature sensor (not shown) or the clutch temperature (or temperature rise rate) estimated by a clutch temperature estimation unit (not shown) increases.

[0112] Thereafter, at time t4, when the clutch 26 transitions from the half-engaged state to the fully engaged state, the engine rotation speed and the clutch rotation speed are synchronized, and the clutch 26 enters the engaged state, thereby stopping the hill climbing assist control.

[0113] When the climbing assist control is stopped at time t4, the climbing assist torque may be immediately set to 0. However, if the climbing assist torque is immediately set to 0, if the amount of climbing assist torque immediately before time t4 is large, the total torque may drop suddenly, causing the driver to feel a shock or discomfort due to the torque drop.

[0114] Therefore, even if the climbing assist control is stopped, the drive of the motor generator 4 is controlled so that the climbing assist torque gradually decreases until time t5. This causes the total torque to gradually decrease. As a result, the total torque does not suddenly decrease when the climbing assist control is stopped, and it is possible to suppress the shock and discomfort that accompanies a torque decrease.

[0115] The control to gradually reduce the climbing assist torque when the climbing assist control is stopped is performed only when the assist torque amount immediately before the climbing assist control is stopped is greater than a set value or when the proportion of the assist torque amount in the total torque immediately before the climbing assist control is stopped is greater than a set value, and may be stopped if the shock or discomfort caused by the torque reduction is minimal. In addition, the control that gradually reduces the climbing assist torque when the climbing assist control is stopped may increase the rate or degree of reduction of the assist torque when the assist torque amount just before the climbing assist control is stopped is smaller than a set value or when the proportion of the assist torque amount in the total torque just before the climbing assist control is stopped is smaller than a set value.

[0116] When the climbing assist control is stopped, the climbing assist torque becomes 0. However, in the following cases, for example, it is preferable to reduce or increase the climbing assist torque to the assist torque in another assist control rather than setting it to 0: When the climbing assist torque and the assist torque in another assist control match, the climbing assist torque is maintained.

[0117] In other words, the period from time t4 to time t5 can be regarded as a transition period during which the hill-climbing assist control is gradually switched to another assist control. This prevents a sudden change in the assist torque when the hill-climbing assist control is switched to the other assist control, thereby reducing the shock and discomfort that accompanies a sudden change in the assist torque and improving the ability of the total torque to follow the target torque. In this embodiment, this transition period is set to a fixed time, but by setting the transition period longer the greater the torque difference between the hill-climbing assist torque and the assist torque in the other assist control, the shock and discomfort that accompanies a sudden change in the assist torque can be further reduced.

[0118] Also, even when the climbing assist torque is set to 0 without transitioning to another assist control, the transition period may be set longer as the climbing assist torque increases, thereby suppressing shock and discomfort caused by a sudden change in the assist torque.

[0119] For example, if the conditions for executing acceleration assist control are met while the climbing assist control is being executed and it is predicted that the acceleration assist control will be executed immediately after the climbing assist control is stopped, the climbing assist torque is gradually decreased or increased to the acceleration assist torque, and the climbing assist control is stopped when the climbing assist torque matches the acceleration assist torque. Also, if the acceleration assist torque and the climbing assist torque match when the conditions for executing the acceleration assist control are met, the climbing assist torque is maintained.

[0120] In addition, cases where the execution of acceleration assist control is predicted include, for example, cases where the execution conditions for acceleration assist control are met during climbing assist control, and cases where the execution conditions for acceleration assist control are met between the time when climbing assist control is stopped and the time when climbing assist torque transitions to 0.

[0121] As described above, the assist control device of this embodiment is configured to execute climbing assist control in which assist torque is output from the motor generator 4 to the drive wheels 5 when the execution conditions are met, with the conditions being that the road is an uphill road with a gradient of a predetermined gradient or more, the clutch 26 is in a disengaged state including a half-engaged state, and there is no request for gear shifting.

[0122] With this configuration, the assist control device according to this embodiment does not execute the climbing assist control when the gradient of the uphill road is small, thereby reducing the power consumption of the third power storage device 33 that supplies power to the motor generator 4. This makes it easier to ensure power for outputting the climbing assist torque when the gradient of the uphill road is large, thereby increasing the opportunities for executing the climbing assist torque control.

[0123] As a result, the assist control device according to this embodiment can output the necessary climbing assist torque through climbing assist torque control on steep uphill roads, thereby reducing the load acting on the transmission-side friction engagement element 26b of the clutch 26. This reduces the amount of heat generated by the clutch 26. Therefore, it is not necessary to extend the period in which the clutch 26 is in the half-engaged state in order to reduce the amount of heat generated by the clutch 26, and the transition time for the clutch 26 to transition from the half-engaged state to the fully engaged state can be shortened.

[0124] Therefore, the assist control device according to this embodiment can improve the starting and acceleration performance of the hybrid vehicle 1 on steep gradients while suppressing heat generation in the clutch 26.

[0125] The assist control device of this embodiment stops the climbing assist control when the clutch 26 transitions from a non-engaged state to an engaged state, thereby suppressing the output of unnecessary climbing assist torque and reducing power consumption of the third storage device 33.

[0126] Furthermore, with the above configuration, the assist control device according to this embodiment minimizes the period during which climbing assist control is performed, thereby suppressing heating of high-voltage components such as the inverter 45 and high-voltage cable 35 connected to the motor generator 4. This makes it possible to prevent the assist torque from being limited due to heating of the high-voltage components.

[0127] The assist control device according to this embodiment has a configuration in which the hill climbing assist control is stopped on condition that the vehicle speed reaches or exceeds a predetermined vehicle speed that is lower than the target vehicle speed of the hybrid vehicle.

[0128] With this configuration, the assist control device according to this embodiment continues to execute the hill-climbing assist control even when the clutch 26 is in a half-engaged state until the actual vehicle speed reaches a predetermined vehicle speed, thereby reducing the sluggish feeling when starting off. Furthermore, once the actual vehicle speed reaches the predetermined vehicle speed, the hill-climbing assist control is stopped, thereby reducing unnecessary power consumption. As a result, the number of opportunities to execute the hill-climbing assist control can be increased.

[0129] The assist control device according to this embodiment has a configuration in which the climbing assist control is stopped on the condition that a predetermined time has elapsed since the start of the execution of the climbing assist control.

[0130] With this configuration, the assist control device of this embodiment limits the output time of the climbing assist torque, so that the climbing assist torque is not output more than necessary or for a long period of time, thereby suppressing power consumption of the third storage device 33.

[0131] The assist control device according to this embodiment is configured to execute the climbing assist control on the condition that, after the climbing assist control is stopped, the acceleration request value changes from a state where it is less than a first predetermined value to the first predetermined value or more.

[0132] With this configuration, the assist control device according to this embodiment prevents the climbing assist control from being resumed immediately after the climbing assist control is stopped because the climbing assist control is not executed until the acceleration requirement value becomes less than the first predetermined value and then becomes equal to or greater than the first predetermined value again. As a result, the climbing assist control is not outputted more than necessary or for a long period of time, and the climbing assist control is not executed continuously, thereby suppressing power consumption of the third power storage device 33.

[0133] In the assist control device of this embodiment, the climbing assist control is executed on the condition that the remaining battery capacity of the third power storage device 33 is equal to or greater than a first threshold, and the acceleration assist control is executed on the condition that the remaining battery capacity of the third power storage device 33 is equal to or greater than a second threshold that is greater than the first threshold.

[0134] With this configuration, the assist control device according to this embodiment does not execute acceleration assist control when the remaining battery capacity of the third power storage device 33 is less than the second threshold, thereby reducing power consumption of the third power storage device 33. Furthermore, for example, when traveling on a flat road where climbing assist control is not executed, the execution of acceleration assist control is limited as described above, thereby increasing the opportunities for power generation by the motor generator 4. As a result, the remaining battery capacity of the third power storage device 33 can be increased, and the opportunities for executing climbing assist control can be increased.

[0135] The assist control device of this embodiment has a configuration in which, if it is determined that an uphill road with a gradient of a predetermined gradient or more exists on the travel route from the current location to the destination, the third power storage device 33 ensures a remaining battery capacity of a first threshold or more by the time the uphill road is reached from the current location.

[0136] With this configuration, when it is known that an uphill road with a gradient of at least a predetermined level exists on the travel route to the destination, the assist control device according to this embodiment reserves the necessary remaining battery charge in advance, thereby preventing a situation in which the uphill assist control cannot be executed due to insufficient remaining battery charge when the vehicle reaches the uphill road, thereby increasing the opportunities for executing the uphill assist control.

[0137] In this embodiment, an example has been described in which acceleration assist control is executed as an assist control other than hill climbing assist control, but this is not limiting, and gear change assist control may also be executed as another assist control. Gear change assist control is a control that suppresses engine torque loss during gear changes by outputting gear change assist torque from motor generator 4 while transmission 3 is shifting and clutch 26 is in a disengaged state based on a gear change request that changes the gear ratio of transmission 3, such as an upshift request or a downshift request, thereby improving drivability while mitigating discomfort and gear change shock felt by the occupants during gear changes.

[0138] In an example where gear shift assist control is executed, the HCU 10 executes the gear shift assist determination process shown in Fig. 6 in addition to the hill climbing assist determination process and acceleration assist determination process of this embodiment. This gear shift assist determination process is executed repeatedly at predetermined time intervals.

[0139] 6, the HCU 10 determines whether or not a gear shift request is present (step S31). If the HCU 10 determines in step S31 that a gear shift request is not present, the HCU 10 ends this gear shift assistance determination process. If the HCU 10 determines in step S31 that a gear shift request is present, the HCU 10 determines whether or not the remaining battery capacity of the third power storage device 33 is equal to or greater than a third threshold value (step S32).

[0140] The third threshold value is set to a value greater than the first threshold value and smaller than the second threshold value in this embodiment. Here, the first threshold value is a value related to whether or not to execute the hill climbing assist control, and therefore is set to the smallest value among the first threshold value, second threshold value, and third threshold value from the viewpoint of ensuring the power performance of the hybrid vehicle 1. This allows the hill climbing assist control to be executed even when the remaining battery charge is such that other assist controls are not executed.

[0141] In contrast, the second and third thresholds are set to values greater than the first threshold because the acceleration assist control and the gear change assist control are both executed from the perspective of improving drivability and therefore have lower priorities than the hill climbing assist control.

[0142] If the HCU 10 determines in step S32 that the remaining battery charge of the third power storage device 33 is not equal to or greater than the third threshold, the HCU 10 ends this shift assist determination process. If the HCU 10 determines in step S32 that the remaining battery charge of the third power storage device 33 is equal to or greater than the third threshold, the HCU 10 determines whether the clutch 26 has changed from an engaged state to a disengaged state (step S33).

[0143] If the HCU 10 determines in step S33 that the clutch 26 has not changed from an engaged state to a disengaged state, the HCU 10 ends this shift assist determination process. If the HCU 10 determines in step S33 that the clutch 26 has changed from an engaged state to a disengaged state, the HCU 10 executes shift assist control (step S34) and ends this shift assist determination process.

[0144] When the shift assist control is executed, a shift assist torque is output from the motor generator 4 to prevent torque loss during shifting. This prevents torque loss during shifting, alleviating the discomfort and shift shock felt by occupants due to torque loss, and improving drivability.

[0145] If the conditions for executing the shift assist control are met while the climb assist control is being executed and it is predicted that the shift assist control will be executed immediately after the climb assist control is stopped, the climb assist torque is gradually reduced or increased to the shift assist torque, and the climb assist control is stopped when the shift assist torque matches the climb assist torque. Also, if the shift assist torque and the climb assist torque match when the conditions for executing the shift assist control are met, the climb assist torque is maintained.

[0146] While an embodiment of this invention has been disclosed, it will be apparent to one skilled in the art that modifications can be made thereto without departing from the scope of this invention, and it is intended that all such modifications and equivalents be included in the following claims.

[0147] For example, sudden acceleration assist control may be executed instead of or in addition to the acceleration assist control as an assist control other than the above-described hill climbing assist control. The sudden acceleration assist control is a control that aims to improve drivability by determining that sudden acceleration is required when the amount of change in an acceleration request value, such as the driver's depression speed of the accelerator pedal 8 or the required acceleration, exceeds a threshold, and generating assist torque from the motor generator 4 to increase the acceleration of the hybrid vehicle 1. The sudden acceleration assist control is executed under the condition that the remaining battery capacity of the third power storage device 33 is equal to or greater than a fourth threshold.

[0148] In this way, when multiple assist controls can be executed in addition to the hill climbing assist control, it is preferable that the first threshold value for the hill climbing assist control be set to the smallest among the threshold values for the remaining battery capacity of the third power storage device 33 that are the execution conditions for these assist controls.

[0149] As a result, the smaller the first threshold value, the higher the priority of the hill climbing assist control over other assist controls, while limiting the execution of other assist controls. This makes it possible to suppress a decrease in the remaining battery capacity of the third power storage device 33, while increasing the opportunities to charge the third power storage device 33 by making the motor generator 3 function as a generator.

[0150] As a result, the starting and acceleration performance of the hybrid vehicle 1 can be improved even on steep uphill roads where starting or acceleration would be significantly impaired without assist torque, and the anxiety felt by the driver or passengers due to the significantly long time required for starting or acceleration can be reduced.

[0151] Furthermore, among the thresholds of the remaining battery capacity of the third power storage device 33 that are the conditions for executing the assist control, it is preferable that the third threshold of the shift assist control be set smaller than the second threshold of the acceleration assist control and the fourth threshold of the sudden acceleration assist control.

[0152] As a result, the smaller the third threshold value, the higher the priority given to the hill climbing assist control and the gear change assist control over other assist controls that improve drivability, while limiting the execution of the other assist controls. This increases the opportunities to execute the hill climbing assist control and the gear change assist control, making it easier to suppress any anxiety or discomfort the driver may feel when driving uphill or changing gears on a steeply inclined road.

[0153] In this embodiment, the hill-climbing assist control is executed when the hybrid vehicle 1 is stopped on an uphill road with a gradient of at least a predetermined value and then starts moving, but the situation is not limited to this. For example, the hill-climbing assist control may be executed when the clutch 26 is transitioned from a fully engaged state to a half-engaged state to prevent the engine 2 from stalling due to the traveling load on the uphill road while the hybrid vehicle 1 is traveling at a low (very low) speed on an uphill road.

[0154] In this embodiment, a hybrid vehicle using an internal combustion engine has been described, but a vehicle using a second motor generator that generates power using battery power instead of an internal combustion engine may also be used. In this case, it is preferable that the vehicle is equipped with a fourth power storage device that supplies power to the second motor generator and a second inverter that controls the power supplied to the second motor generator. [Explanation of symbols]

[0155] 1 Hybrid vehicle (vehicle) 2 engines 3 Transmission 4 Motor generator (motor) 5 drive wheels 8 Accelerator pedal 10 HCU (control unit) 10a Wheel speed sensor 10b Accelerator opening sensor 10c Clutch stroke sensor 10d Crank angle sensor 10e Acceleration Sensor 10F Map Information Acquisition Section 10g Location information acquisition part 11 ECM 20 ISG 23 Drive shaft 26 Clutch 26a Friction engagement element on the engine side 26b Transmission-side friction engagement element 33 Third storage device (battery) 101 Road surface gradient determination unit 102 Clutch state determination unit 103 Shift request determination unit 104 Acceleration request determination section 105 Battery state determination unit 106 Uphill road information acquisition unit 107 Timer

Claims

1. The engine and a transmission that changes the speed of the rotation of the engine and transmits it to drive wheels; a clutch that connects or disconnects a power transmission path between the transmission and the engine; a motor capable of transmitting power to the drive wheels, a control unit that executes hill climbing assist control that outputs assist torque from the motor to the drive wheels when the execution conditions are met, the execution conditions being that the vehicle is traveling on an uphill road with a gradient equal to or greater than a predetermined gradient, the clutch is in a disengaged state including a half-engaged state, and there is no request for a gear change; The assist control device is characterized in that the control unit stops the hill climbing assist control on the condition that the vehicle speed, which is the speed of the vehicle, becomes equal to or greater than a predetermined vehicle speed.

2. 2. The assist control device according to claim 1, wherein the predetermined vehicle speed is set to a speed lower than a target vehicle speed of the vehicle.

3. 3. The assist control device according to claim 1, wherein the control unit stops the hill climbing assist control on condition that a predetermined time has elapsed since the start of the hill climbing assist control.

4. The execution condition further includes that an acceleration request value indicating a degree of acceleration request for the vehicle is equal to or greater than a predetermined value, 4. The assist control device according to claim 1, wherein the control unit executes the climbing assist control on the condition that, after the climbing assist control is stopped, the acceleration request value changes from a state where it is less than the predetermined value to a state where it is equal to or greater than the predetermined value.

5. the control unit is capable of executing acceleration assist control in which an acceleration assist torque is output from the motor to the drive wheels in response to an acceleration request for the vehicle, the hill climbing assist control is executed on the condition that a remaining capacity of a battery that supplies power to the motor is equal to or greater than a first threshold; 5. The assist control device according to claim 1, wherein the acceleration assist control is executed on the condition that the remaining charge of the battery is equal to or greater than a second threshold value that is greater than the first threshold value.

6. an uphill road information acquisition unit that acquires uphill road information on a travel route to a destination; 6. The assist control device according to claim 5, wherein, when it is determined that an uphill road exists on the travel route to the destination based on the uphill road information acquired by the uphill road information acquisition unit, the control unit ensures that the remaining capacity of the battery is equal to or greater than the first threshold value by the time the vehicle reaches the uphill road from its current position.

Images