Vehicle driving force control apparatus

A hybrid electronic control unit sets a target vehicle speed for constant-speed driving based on setting operation of an auto cruise switch by a driver. When the target vehicle speed is set, the required torque is set such that the vehicle speed detected by a vehicle speed sensor becomes the target vehicle speed. When the required torque is set, a constant-speed driving torque map, indicating the required torque with respect to a torque command value by accelerator operation or brake operation by the driver using the required torque, and a positive maximum torque and a negative maximum torque, which the vehicle can output, is set. Further, the required torque changes using the constant-speed driving torque map according to the torque command value. In the hybrid electronic control unit, by increasing followability of torque change when changing the vehicle speed from the constant-speed driving, controllability is improved and drivability is improved.

TECHNICAL FIELD

The present invention relates to a vehicle driving force control apparatus, and especially relates to a hybrid vehicle driving force control apparatus capable of driving with an engine and an electric motor as a power source.

BACKGROUND ART

Recently, a hybrid vehicle equipped with an engine for outputting torque by burning of fuel and an electric motor for outputting the torque by supply of electricity and capable of driving by transmitting the torque of the engine and the electric motor to wheels is suggested. In such a hybrid vehicle, the wheels are driven only by the torque of the electric motor or driven by the torque of both the engine and the electric motor, by controlling driving and stopping of the engine and the electric motor according to driving condition, and the electric motor can be driven by electricity stored in a battery and when the energy of the battery decreases, the battery is charged by driving the engine.

That is to say, the hybrid vehicle is provided with the engine and the electric motor as a drive power source and with a planetary gear for combining the power of the engine and the electric motor to transmit to the wheels. Specifically, it is configured such that an output shaft of the engine is coupled to a carrier of the planetary gear and an output shaft of the electric motor is coupled to a ring gear of the planetary gear, and the power is transmitted from a sprocket coupled to the ring gear to the wheels. Also, an electricity generator is provided between the planetary gear and the engine, and a rotating shaft of the electricity generator is coupled to a sun gear of the planetary gear. Therefore, the power of the engine is divided to the wheels and the electricity generator by the planetary gear, and by controlling a rotation speed of the electricity generator, the rotation speed of the engine can be controlled. That is to say, a power dividing mechanism composed of the planetary gear has a function of converting the rotation speed of the engine and a function of dividing the power of the engine to the wheels and the electricity generator.

In the hybrid vehicle, when a driver operates an auto cruise switch to perform constant-speed driving, the drive of the engine and the electric motor is controlled such that the target vehicle speed for performing the constant-speed driving is set and deviation between the current vehicle speed and the target vehicle speed is reduced. That is to say, the vehicle is stably driven at the target vehicle speed by calculating energy in a direction to negate the deviation between the current vehicle speed and the target vehicle speed to increase and decrease the torque of the engine and increase and decrease the torque of the electric motor.

Meanwhile, such a vehicle driving control apparatus is disclosed in Patent Documents 1 to 5.

DISCLOSURE OF INVENTION

Problem to be Solved by the Invention

In the above-described conventional vehicle driving control apparatus, while the vehicle is driving, when the driver operates the auto cruise switch to start the constant-speed driving, a controller controls the vehicle driving force so as to maintain the current vehicle speed to allow the vehicle to drive. However, during the constant-speed driving of the vehicle, when the driver intends to increase the vehicle speed by depressing an accelerator pedal or to decrease the vehicle speed by depressing a brake pedal, the vehicle speed does not change appropriately according to a depression amount of the accelerator pedal and the brake pedal, so that controllability deteriorates and the driver feels discomfort.

FIG. 4is a constant-speed driving control map used for the conventional vehicle driving force control apparatus. As shown inFIG. 4, the conventional control apparatus has the constant-speed driving control map indicating required torque with respect to accelerator opening. That is to say, in a case that the driver depresses the accelerator pedal and the accelerator opening is at Acc1, when the driver operates the auto cruise switch, the control apparatus sets required torque Tr1at the time the accelerator opening is Acc1in order to maintain the current vehicle speed, and controls the vehicle according to the required torque Tr1, thereby the vehicle drives at the current vehicle speed even if the driver does not depress the accelerator pedal.

However, during the constant-speed driving, when the driver tries to increase the vehicle speed by depressing the accelerator pedal, even though the accelerator opening increases, the current required torque Tr1is maintained up to the accelerator opening Acc1, and from the accelerator opening Acc1, the required torque increases according to the map, then new required torque Tr2is set with respect to accelerator opening Acc2. Therefore, even when the driver depresses the accelerator pedal, the vehicle speed does not increase until the accelerator opening is over the accelerator opening Acc1and continuity of the control is deteriorated, and the driver feels discomfort because the vehicle speed temporarily does not increase even though the accelerator pedal is depressed.

The present invention is for solving such a problem, and an object thereof is to provide the vehicle driving force control device for improving the controllability by increasing followability of the torque change when changing the vehicle speed from the constant-speed driving and to improve drivability.

Means for Solving Problem

In order to solve the above problem, and to attain the above object, a vehicle driving force controlling apparatus of the present invention includes vehicle speed detecting means for detecting a vehicle speed, target vehicle speed setting means for setting a target vehicle speed for constant-speed driving based on setting operation by a driver, constant-speed driving required torque setting means for setting required torque such that the vehicle speed detected by the vehicle speed detecting means becomes the target vehicle speed when the target vehicle speed is set by the target vehicle speed setting means, constant-speed driving torque map creating means for setting a constant-speed driving torque map indicating required torque with respect to a torque command value by accelerator operation or brake operation by the driver by using the required torque, and a positive maximum torque and a negative maximum torque, which the vehicle can output, when the required torque is set by the constant-speed driving required torque setting means, and required torque changing means for changing the required torque by using the constant-speed driving torque map according to the torque command value.

In the vehicle driving force controlling apparatus of the present invention, the constant-speed driving torque map creating means sets the constant-speed driving torque map indicating required driving force with respect to an accelerator operation amount by the driver by using the required torque and vehicle maximum driving force when the accelerator operation amount is the maximum.

In the vehicle driving force controlling apparatus of the present invention, the constant-speed driving torque map creating means sets the constant-speed driving torque map indicating required braking force with respect to a brake operation amount by the driver by using the required torque and vehicle maximum braking force when the brake operation amount is the maximum.

In the vehicle driving force controlling apparatus of the present invention, the constant-speed driving torque map is formed by a curved line smoothly connecting the positive maximum torque, the required torque, and the negative maximum torque, and a change amount at an early phase of change of the required torque by the required torque changing means is set so as to be smaller than the change amount at a late phase of the change.

In the vehicle driving force controlling apparatus of the present invention, when the required torque is changed by the required torque changing means, the constant-speed driving torque map creating means changes the constant-speed driving torque map by using the changed required torque, the positive maximum torque, and the negative maximum torque.

In the vehicle driving force controlling apparatus of the present invention, normal driving torque map indicating the required torque with respect to the torque command value is set in advance by using an original point, the positive maximum torque, and the negative maximum torque, and when the target vehicle speed is not set by the target vehicle speed setting means, the required torque changing means changes the required torque by using the normal driving torque map.

Effect of the Invention

According to the vehicle driving force control apparatus of the present invention, when the required torque is set by the constant-speed driving required torque setting means, since the constant-speed driving torque map indicating the required torque with respect to the torque command value is set by using the required torque, a positive maximum torque, and a negative maximum torque, and the required torque is changed by using the constant-speed driving torque map according to the torque command value, the torque command value is changed during the constant-speed driving, and the required torque is changed according to the torque command value when the vehicle changes the vehicle speed from the constant-speed driving, so that the followability of the torque change is improved to improve the controllability, and the drivability is improved.

EXPLANATIONS OF LETTERS OR NUMERALS

15power distribution integration mechanism

20hybrid electronic control unit (constant-speed driving required torque setting means, constant-speed driving torque map creating means, required torque changing means)

21engine electronic control unit, engine ECU

33motor electronic control unit, motor ECU

36battery electronic control unit, battery ECU

48accelerator pedal position sensor

50brake pedal stroke sensor

52auto cruise switch (target vehicle speed setting means)

BEST MODE(S) FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of a vehicle driving force control apparatus according to the present invention is described in detail with reference to the drawings. Meanwhile, the present invention is not limited by the embodiment.

Embodiment

FIG. 1is a schematic configuration diagram showing a vehicle driving force control apparatus according to one embodiment of the present invention,FIG. 2is a graph showing required torque with respect to a torque command value in the vehicle driving force control apparatus of this embodiment, andFIG. 3is a flowchart showing driving force control in a vehicle driving force control apparatus of this embodiment.

A vehicle to which the vehicle driving force control apparatus of this embodiment is applied is a hybrid vehicle equipped with an engine, an electric motor, and an electricity generator as a power source, and the engine, the electric motor, and the electricity generator are connected by a power distribution integration mechanism to distribute output of the engine to the electricity generator and driving wheels, transmits output from the electric motor to the driving wheels, and serves as a transmission regarding driving force transmitted from a drive shaft to the driving wheels through a decelerator.

That is to say, as shown inFIG. 1, a hybrid vehicle11of this embodiment has an engine12, a triaxial power distribution integration mechanism15connected to a crank shaft13as an output shaft of the engine12through a damper14, a motor (MG1)16capable of generating electricity connected to the power distribution integration mechanism15, a reduction gear18attached to a ring gear shaft17as a drive shaft connected to the power distribution integration mechanism15, a motor (MG2)19connected to the reduction gear18, and a hybrid electronic control unit20for controlling an entire power output apparatus.

The engine12is an internal-combustion engine for outputting power by hydrocarbon fuel such as gasoline and light oil, and receives an operation control command such as fuel injection control, ignition control, and intake air mass adjustment control, by an engine electronic control unit (hereinafter, referred to as an engine ECU)21for inputting signals from various sensors for detecting an operating condition of the engine12. The engine ECU21can communicate with the hybrid electronic control unit20to control the operation of the engine12by a control signal from the hybrid electronic control unit20and output data relating to the operating condition of the engine12to the hybrid electronic control unit20as needed.

The power distribution integration mechanism15has a sun gear22, which is an external-tooth gear, a ring gear23, which is an internal-tooth gear arranged concentrically with the sun gear22, a plurality of pinion gears24meshing with the sun gear22and with the ring gear23, and a carrier25for rotatably and revolvably holding the pinion gears24, and is configured as a planetary gear mechanism for performing a differential action with the sun gear22, the ring gear23, and the carrier25as rotational elements. In the power distribution integration mechanism15, the crank shaft13of the engine12is coupled to the carrier25, the motor19is coupled to the sun gear22, and the reduction gear18is coupled to the ring gear23through the ring gear shaft17, respectively. When the motor16serves as the electricity generator, the power from the engine12input from the carrier25is distributed to the sun gear22side and the ring gear23side according to a gear ratio thereof, and when the motor16serves as the electric motor, the power from the engine12input from the carrier25and the power from the motor16input from the sun gear22are integrated and output to the ring gear23side. The power output to the ring gear23is finally output to driving wheels28of the vehicle from the ring gear shaft17through a gear mechanism26and a differential gear27.

Each of the motors16and19is configured as a well-known synchronous generator-motor, which can be driven as the electricity generator and driven as the electric motor to exchange electricity with a battery31through inverters29and30. Electricity lines32connecting the inverters29and30and the battery31are configured as a positive electrode bus bar and a negative electrode bus bar commonly used by the inverters29and30, and the electricity generated by one of the motors16and19can be consumed by the other motor. Therefore, the battery31is charged and discharged by electricity generated by one of the motors16and19and by insufficient electricity. Meanwhile, if the electricity from the motors16and19is balanced, the battery31is not charged and discharged.

The drive of the motors16and19is controlled by a motor electronic control unit (hereinafter, referred to as a motor ECU)33. Signals required for controlling the drive of the motors16and19, such as signals from rotational position detection sensors34and35for detecting rotational positions of rotators of the motors16and19and phase current to be applied to the motors16and19detected by a current sensor (not shown) are input to the motor ECU33, and switching control signals to the inverters29and30are output from the motor ECU33. The motor ECU33communicates with the hybrid electronic control unit20to control the drive of the motors16and19by the control signal from the hybrid electronic control unit20and output data relating to the operating condition of the motors16and19to the hybrid electronic control unit20as needed.

The battery31is managed by a battery electronic control unit (hereinafter, referred to as a battery ECU)36. Signals required to manage the battery31, such as inter-terminal voltage from a voltage sensor (not shown) installed between terminals of the battery31, charging/discharging current from a current sensor (not shown) attached to the electricity lines32connected to an output terminal of the battery31, and a cell temperature from a temperature sensor (not shown) attached to the battery31are input to the battery ECU36, and data relating to condition of the battery31is output to the hybrid electronic control unit20by communication as needed. Meanwhile, the battery ECU36also calculates a state of charge (SOC) based on an integrated value of the charging/discharging current detected by the current sensor in order to manage the battery31.

The hybrid electronic control unit20is configured as a microprocessor centered on a CPU41, and has a ROM42for storing a processing program, a RAM43for temporarily storing data, and an input port, and output port, and a communication port (not shown), in addition to the CPU41. An ignition signal from an ignition switch44, a shift position signal SP from a shift position sensor46for detecting an operation position of a shift lever45, accelerator opening Acc from an accelerator pedal position sensor48for detecting a depression amount of an accelerator pedal47, a pedal stroke Sp from a brake pedal stroke sensor50for detecting a depression amount of a brake pedal49, a vehicle speed V from a vehicle speed sensor51, a set signal and a cancellation signal for constant-speed driving from an auto cruise switch52provided in the vicinity of a steering wheel are input to the hybrid electronic control unit20through the input port.

When the set signal from the auto cruise switch52is input, the hybrid electronic control unit20sets the vehicle speed V at that time as a target vehicle speed Vt to set a constant-speed driving mode (auto cruise mode), and cancels the constant-speed driving mode by canceling the set target vehicle speed Vt when the cancel signal from the auto cruise switch52is input. In addition, when the accelerator opening Acc from the accelerator pedal position sensor48and the pedal stroke Sp from the brake pedal stroke sensor50are input during the constant-speed driving mode, the set target vehicle speed Vt is changed. Also, the hybrid electronic control unit20is connected to the engine ECU21, the motor ECU33, and the battery ECU36through the communication port as described above to exchange various control signals and data with the engine ECU21, the motor ECU33, and the battery ECU36.

The hybrid vehicle11of the embodiment thus configured calculates the required torque, which should be output to the ring gear shaft17as the drive shaft, based on the accelerator opening Acc corresponding to the depression amount of the accelerator pedal47by a driver and the vehicle speed V, and the drive of the engine12, and the motors16and19is controlled such that required driving force corresponding to the required torque is output to the ring gear shaft17. As the drive control of the engine12and the motors16and19, there are a torque conversion operation mode of controlling the drive of the engine12such that the driving force matching the required driving force is output from the engine12and of controlling the drive of the motors16and19such that entire driving force output from the engine12is torque-converted by the power distribution integration mechanism15and the motors16and19to be output to the ring gear shaft17, a charging/discharging operation mode of controlling the drive of the engine12such that the driving force matching a sum of the required driving force and power required for charging and discharging the battery31is output from the engine12and of controlling the drive of the motors16and19such that an entire or a part of power output from the engine12with charging and discharging of the battery31is torque-converted by the power distribution integration mechanism15and the motors16and19and the required driving force is output to the ring gear shaft17, and a motor operation mode of controlling the drive such that the driving force matching the required driving force from the motor19is output to the ring gear shaft17by stopping the drive of the engine12.

Then, a vehicle speed sensor51is applied to the hybrid vehicle11of this embodiment as vehicle speed detecting means for detecting the vehicle speed V. The hybrid electronic control unit20sets the target vehicle speed Vt for the constant-speed driving based on set operation of the auto cruise switch (target vehicle speed setting means)52by the driver. Then, when the target vehicle speed Vt is set, the hybrid electronic control unit20sets required torque Trt (constant-speed driving required torque setting means) such that the vehicle speed V detected by the vehicle speed sensor51becomes the targeted vehicle speed Vt. Next, when the required torque Trt is set, the hybrid electronic control unit20sets a constant-speed driving torque map (constant-speed driving torque map creating means) indicating the required torque Trt with respect to a torque command value by an accelerator operation or a brake operation by the driver by using the required torque Trt, and a positive maximum torque Tramax and a negative maximum torque Trbmax, which the vehicle can output. The hybrid electronic control unit20changes the required torque Trt (required torque changing means) by using the constant-driving torque map according to the torque command value.

Also, in this embodiment, the torque command value is the accelerator opening Acc detected by the accelerator pedal position sensor48or the pedal stroke Sp detected by the brake pedal stroke sensor50. Then, the hybrid electronic control unit (constant-speed driving torque map creating means)20sets a constant-speed driving torque map curved line X indicating the required torque Trt with respect to the accelerator opening Acc of the driver by using the required torque Trt and the vehicle maximum positive torque (vehicle maximum driving force) Tramax when the accelerator opening Acc is maximum opening Accmax, as shown inFIG. 2. Also, the hybrid electronic control unit (constant-speed driving torque map)20sets a constant-speed driving torque map curved line Y indicating the required torque Trt with respect to the pedal stroke Sp of the driver by using the required torque Trt and the vehicle maximum negative torque (vehicle maximum braking force) Trbmax when the pedal stroke Sp is a maximum stroke Spmax.

In this case, the constant-speed driving torque map set by the hybrid electronic control unit20is formed by a curved line X-Y, which smoothly connects the positive maximum torque (vehicle maximum positive torque Tramax), the required torque Trt, and the negative maximum torque (vehicle maximum negative torque Trbmax), and a change amount at an early phase of the change of the required torque Trt by the hybrid electronic control unit (required torque changing means)20is set to be smaller than the change amount at a late phase of the change. Meanwhile, when the hybrid vehicle11drives a downslope, only the negative required driving force Trt, that is to say, the braking force is generated, and the constant-speed driving torque map curved line X-Y is indicated by a two-dot chain line inFIG. 2. That is to say, the constant-speed driving torque map curved line X-Y is set according to the required torque Trt set by the accelerator opening Acc and the pedal stroke Sp.

Meanwhile, the vehicle maximum torque Tramax with respect to the accelerator maximum opening Accmax and the vehicle maximum torque Trbmax with respect to the brake pedal maximum stroke Spmax are fixed values set by a specification of the hybrid vehicle11.

When the required torque Trt is changed by the hybrid electronic control unit (required torque changing means)20, the constant-speed driving torque map is changed by using the changed required torque Trt and the positive maximum torque (maximum opening Accmax), and the required torque Trt and the negative maximum torque (maximum stroke Spmax).

Also, in this embodiment, a normal driving torque map indicating the required torque Trt with respect to the torque command value, that is to say, a normal driving torque map straight line Z is set in advance by using an original point0, the positive maximum torque (maximum opening Accmax), and the negative maximum torque (maximum stroke Spmax). When the target vehicle speed Vt for the constant-speed driving is not set based on the auto cruise switch (set operation)52by the driver, the hybrid electronic control unit (required torque changing means)20changes the required torque Trt by using the normal driving torque map.

Herein, the driving force control by the driving force control apparatus of the hybrid vehicle of the above-described embodiment, especially the constant-speed driving control is described in detail with reference to a flowchart inFIG. 3. Meanwhile, a routine of the driving force control executed by the hybrid electronic control unit20shown in the flowchart inFIG. 3is repeatedly executed every predetermined time period. Also, since the operation at the time of the constant-speed driving (at the time of auto cruise) is considered, it is described on the assumption that the hybrid vehicle11is operated in the torque conversion operation mode and the charging/discharging operation mode.

In the driving force control by the hybrid vehicle driving force control apparatus of this embodiment, as shown inFIG. 3, at a step S11, the CPU41of the hybrid electronic control unit20performs processing to read data required for controlling such as the accelerator opening Acc from the accelerator pedal position sensor48, the brake pedal stroke Sp from the brake pedal stroke sensor50, the vehicle speed V from the vehicle speed sensor51, the target vehicle speed Vt, and rotation numbers Nm1and Nm2of the motors16and19. Herein, in this embodiment, the target vehicle speed Vt set based on the vehicle speed V detected by the vehicle speed sensor51and stored in a predetermined address of the RAM43is read when the set signal from the auto cruise switch52is input. Also, the rotation numbers Nm1and Nm2of the motors16and19calculated based on the rotational positions of the rotators of the motors16and19detected by the rotational position detecting sensors34and35are input from the motor ECU33by communication.

At a step S12, whether it is in the constant-speed driving mode is judged based on existence or nonexistence of setting of the target vehicle speed Vt by the auto cruise switch52and a setting flag of the constant-speed driving mode. Herein, when it is judged not to be in the constant-speed driving mode, the procedure shifts to a step S13to read the normal driving torque map straight line Z set in advance. On the other hand, when it is judged to be in the constant-speed driving mode at the step S12, the accelerator opening Acc (or the brake pedal stroke Sp) when the set signal is input from the auto cruise switch52is set as the torque command value at a step S14. Then, at a step S15, the above-described constant-speed driving torque map curved line X-Y is set.

Then, at a step S16, the required torque Trt is set based on current accelerator opening Acc detected by the accelerator pedal position sensor48(or brake pedal stroke Sp) or set accelerator opening Acc (or brake pedal stroke Sp) and the vehicle speed V, and required power Pet, which should be output from the engine12, is set. In this embodiment, the required torque Trt is set by defining relationship between the accelerator opening Acc (or the brake pedal stroke Sp), the vehicle speed V, and the required torque Trt in advance to store in the ROM42as a required torque setting map, and calculating corresponding required torque Trt from the stored map when the accelerator opening Acc (or the brake pedal stroke Sp) and the vehicle speed V are given. Also, the required power Pet can be calculated by adding a charging/discharging required amount Pbt of the battery31and loss to the value obtained by multiplying the set required torque Trt by the rotation number Nr of the ring gear shaft17. Meanwhile, the rotation number Nr of the ring gear shaft17can be obtained by multiplying a conversion factor k by the vehicle speed V or by dividing the rotation number Nm2of the motor19by a gear ratio Gr of the reduction gear18. The charging/discharging required amount Pbt can be set by the state of charge (SOC) of the battery31, the accelerator opening Acc (or the brake pedal stroke Sp), and the like.

When the required torque Trt and the required power Pet are set, at a step S17, a target rotation number Net and target torque Tet of the engine12are set based on the required power Pet. The target rotation number Ne and the target torque Tet are set based on an operation line and the required power Pet for allowing the engine12to efficiently operate when the required torque Trt is set in the required power Pet.

Next, at a step18, a target rotation number Nm1tof the motor16is calculated by using the set target rotation number Net, a rotation number Nr (Nm2/Gr) of the ring gear shaft17, and the gear ratio of the power distribution integration mechanism15, and a torque command Tm1tof the motor16is calculated based on the calculated target rotation number Nm1tand the current rotation number Nm1. When the target rotation number Nm1tand the torque command Tm1tof the motor16are calculated, at a step S19, a torque limit Tmax as an upper limit of the torque, which may be output from the motor19, is calculated by dividing deviation between an output limit Wout of the battery31and power consumption (generated power) of the motor16obtained by multiplying the current rotation number Nm1of the motor16by the calculated torque command Tm1tof the motor16by the rotation number Nm2of the motor19. Also, at a step S20, temporary motor torque Tm2tmpas the torque, which should be output from the motor19, is calculated by using the required torque Trt, the torque command Tm1t, and the gear ratio of the power distribution integration mechanism15. Also, at a step S21, the calculated torque limit Tmax and the temporary motor torque Tm2tmpare compared, and a smaller one is set as the torque command Tm2tof the motor19. Then, by setting the torque command Tm2tof the motor19in this manner, the required torque Trt to be output to the ring gear shaft17as the drive shaft may be set as the torque limited in a range of the output limit of the battery31. After that, at a step S22, the target rotation number Net, the target torque Tet, the torque commands Tm1tand Tm2t, and the target rotation number Num1tare transmitted.

Therefore, when the set signal is not input from the auto cruise switch52, the normal driving torque map (straight line Z) set in advance is used, and the required torque Trt is changed according to the current accelerator opening Acc detected by the accelerator position sensor48or the brake pedal stroke Sp detected by the brake pedal stroke sensor50. That is to say, when the torque command value is changed by the accelerator pedal47and the brake pedal49, the required torque Trt is changed along the normal driving torque map straight line Z shown inFIG. 2.

On the other hand, when the set signal is input from the auto cruise switch52, the constant-speed driving torque map curved line Y indicating the required torque Trt with respect to the torque command value (accelerator opening Acc or the brake pedal stroke Sp) is set by using the required torque Trt, the vehicle maximum positive torque Tramax, and the vehicle maximum negative torque Trbmax. Then, during the constant-speed driving, when the accelerator pedal47or the brake pedal49are depressed by the driver, the required torque Trt is changed according to the accelerator opening Acc or the brake pedal stroke Sp at that time. That is to say, when the torque command value is changed by the accelerator pedal47or the brake pedal49, the constant-speed driving control is not cancelled, and the required torque Trt is changed along the constant-speed driving torque map curved line X-Y shown inFIG. 2.

In this manner, in the vehicle driving force control apparatus according to this embodiment, the hybrid electronic control unit20controls to set the target vehicle speed Vt for the constant-speed driving based on the setting operation of the auto cruise switch52by the driver, when the target vehicle speed Vt is set, to set the required torque Trt such that the vehicle speed V detected by the vehicle speed sensor51becomes the target vehicle speed Vt, and when the required torque Trt is set, to set the constant-speed driving torque map indicating the required torque Vrt with respect to the torque command value by the accelerator operation or the brake operation by the driver by using the required torque Trt, and the positive maximum torque Tramax and the negative maximum torque Trbmax, which the vehicle can output, and to change the required torque Trt by using the constant-speed driving torque map according to the torque command value.

Therefore, during the constant-speed driving of the vehicle, the constant-speed driving torque map is set, so that when the accelerator opening or the brake pedal stroke as the torque command value are changed at the time of the constant-speed driving, the required torque is changed by using the constant-speed driving torque map according to the torque command value, and controllability can be improved due to improvement in followability of the torque change from the constant-speed driving state, and drivability can be improved.

Also, in the vehicle driving force control apparatus according to this embodiment, the constant-speed driving torque map indicating the required driving force with respect to the accelerator opening by the driver is set by using the vehicle maximum driving force when the required torque and the accelerator opening are the maximum. Also, by using the vehicle maximum braking force when the required torque and the brake pedal stroke are the maximum, the constant-speed driving torque map indicating the required braking force with respect to the brake pedal stroke by the driver is set.

Therefore, when there is a request to increase or decrease the speed of the vehicle from the driver during the constant-speed driving of the vehicle, it is possible to increase or decrease the speed in an early stage by the constant-speed driving torque map thereby improving controllability. In addition, in this case, the increase and decrease in speed are controlled by one constant-speed driving torque map curved line, so that integrated management of the control torque becomes possible, thereby simplifying the control program.

Also, in the vehicle driving force control apparatus according to this embodiment, the constant-speed driving torque map is formed by a curved line smoothly connecting the positive maximum torque, the required torque, and the negative maximum torque, and when the required torque is changed according to the change of the torque command value, the change amount at the early stage of the change of the required torque is set to be smaller than the change amount at the late stage of change. Therefore, when increasing or decreasing the speed from the constant-speed driving of the vehicle, the change amount at the early stage of change is small, so that acceleration shock and deceleration shock to the driver are prevented and the drivability can be improved.

Also, in the vehicle driving force control apparatus according to this embodiment, when the required torque is changed, the constant-speed driving torque map is changed by using the changed required torque, the positive maximum torque, and the negative maximum torque. Therefore, the constant-speed driving torque map is occasionally changed according to the change of the required torque, so that the followability of the torque change from the constant-speed driving state can be improved.

In addition, the vehicle driving force control apparatus according to this embodiment sets the normal driving torque map indicating the required torque with respect to the torque command value by using the original point, the positive maximum torque, and the negative maximum torque in advance, and when the target vehicle speed is not set, the required torque is changed by using the normal driving torque map. Therefore, the required torque is appropriately set by the normal driving torque map even during the normal driving, and the controllability can be improved.

Industrial Applicability

In this manner, the vehicle driving force control apparatus according to the present invention is to improve the controllability by improving the followability of the torque change when changing the vehicle speed from the constant-speed driving and to improve the drivability, and is useful in application to the hybrid vehicle capable of driving with the engine and the electric motor as the power source.