JP2014061795A - Vehicular braking control system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a vehicular braking control system capable of upgrading a feel of a pedal.SOLUTION: In a vehicular braking control system, a braking torque control unit that controls driving of a regenerative braking device B and brake system 10, and implements regenerative collaboration braking control so as to generate a target braking torque using a regenerative braking torque and fluid pressure braking torque includes: a regenerative braking torque increase gradient designation block that designates an increase gradient for use in increasing the regenerative braking torque along with an increase in the target braking torque. The regenerative braking torque increase gradient designation block designates the increase gradient according to a magnitude of a change in the target braking torque. If the magnitude of a change falls below a predefined magnitude-of-change set value, the regenerative braking torque increase gradient designation block sets the increase gradient to a predefined set increase gradient. If the magnitude of a change is equal to or larger than the magnitude-of-change set value, the increase gradient is set to a variable increase gradient equal to or smaller than a change rate of the magnitude of a change.

Description

  The present invention relates to a vehicular braking control device that controls braking torque of a regenerative braking device and a hydraulic braking device according to a detected total braking torque of a driver detected during braking.

2. Description of the Related Art Conventionally, a braking control device for a vehicle that performs braking by regenerative cooperative control that activates a regenerative braking device and a hydraulic braking device according to a detected total braking torque of a driver detected during braking is known (for example, a patent) Reference 1).
In this prior art, as a hydraulic braking device, an input member that moves forward and backward by operation of a brake pedal, an assist member that is arranged to be relatively movable with respect to the input member, and an electric actuator that moves the assist member forward and backward The electric booster provided with is used. This electric booster generates a brake fluid pressure boosted in the master cylinder by an assist thrust applied to the assist member by the electric actuator in accordance with the movement of the input member by the brake pedal.

JP 2007-112426 A

However, when the regenerative cooperative control is executed using the hydraulic braking device that applies assist force by the electric actuator as described above, there is a possibility that the following problem may occur.
At the time of braking in which the depression of the brake pedal is increased, in the hydraulic braking device, a master cylinder pressure reaction force and a spring reaction force act on the brake pedal.
On the other hand, during regenerative cooperative braking, when the regenerative braking torque is increased, the hydraulic braking torque may be decreased. At this time, when the master cylinder pressure reaction force acting on the brake pedal is reduced, the pedal reaction force is changed, giving the driver a sense of incongruity and possibly deteriorating the pedal feel.

  The present invention has been made paying attention to the above-described problem, and an object of the present invention is to provide a vehicle brake control device that can improve pedal feel.

In order to achieve the above object, a vehicle brake control device of the present invention includes:
A braking torque control unit that controls driving of the regenerative braking device and the braking device and performs regenerative cooperative braking control that generates a target braking torque based on the regenerative braking torque and the hydraulic braking torque is performed during the regenerative cooperative control. A regenerative braking torque increase gradient setting unit for setting an increase gradient when increasing the regenerative braking torque according to an increase in
The regenerative braking torque increase gradient setting unit sets the increase gradient to a preset increase gradient according to the change amount of the target braking torque when the change amount is less than a preset change amount setting value. When the change amount is equal to or greater than the change amount set value, the vehicular brake control device is characterized in that the increase gradient is set to a variable increase gradient that is equal to or less than the change rate of the change amount.

In the present invention, at the time of braking, the regenerative braking torque increase gradient setting unit responds to the amount of change in the target braking torque, and when the amount of change is equal to or greater than the amount of change set value, the regenerative braking torque increase gradient is changed. Set to a variable increasing slope below the rate.
For this reason, when the regenerative braking torque is increased as the target braking torque increases, the hydraulic braking torque (master cylinder pressure) can be prevented from decreasing.
Therefore, in this situation, the pedal reaction force change can be suppressed and the pedal feel can be improved as compared with the case where the hydraulic braking torque (master cylinder pressure) decreases.
On the other hand, when the change amount of the target braking torque is less than the change amount set value, the increase gradient is set to a preset increase gradient. For this reason, even if the amount of change is less than the set value, if the regenerative braking torque increase gradient is finely controlled as a variable increase gradient, the master cylinder pressure may change slightly, which may cause a sense of incongruity. Suppresses and secures a good pedal feel.

1 is a system configuration diagram of a vehicle brake control device according to a first embodiment. 1 is a cross-sectional view showing a configuration of a brake device including an electric booster applied to a vehicle brake control device of Embodiment 1. FIG. 6 is a flowchart showing a flow of processing of hydraulic braking torque (master cylinder pressure) control by a drive motor of the electric booster in the vehicle brake control device of the first embodiment. In the flowchart of FIG. 3, it is a flowchart which shows the flow of the detailed process of step S103. 4 is a flowchart showing a flow of a regenerative braking torque setting process executed by the integrated control device and the motor control unit in the vehicle brake control device of the first embodiment. 4 is a flowchart showing a flow of processing for replacement control including preload regenerative braking torque reduction control in the vehicle brake control device of the first embodiment. FIG. 6 is a characteristic diagram illustrating another example of the reference replacement vehicle speed line and the preload start vehicle speed line in the vehicle brake control device according to the first embodiment, and (a) shows the preload start vehicle speed line as the regenerative braking torque increases, and the reference replacement start This is an example in which the vehicle speed range with respect to the vehicle speed line is widened, and (b) is an example in which the preload start vehicle speed line is set substantially parallel to the reference replacement start vehicle speed line. FIG. 3 is a time chart showing an operation at the time of switching control of the vehicular braking control apparatus according to the first embodiment, where (a) shows changes in vehicle speed, (b) shows changes in regenerative braking torque and hydraulic braking torque, c) shows the change of the pedal stroke. 6 is a time chart showing an operation example of a comparative example for explaining the operation of the vehicle brake control device of the first embodiment. 3 is a time chart illustrating an operation example of the vehicle brake control device according to the first embodiment. It is a time chart which expands and shows the principal part of FIG. 6 is a flowchart showing a flow of processing in a regenerative braking torque increase gradient setting unit of the vehicle brake control device of the second embodiment. FIG. 10 is a ratio setting characteristic diagram showing a ratio setting characteristic in a regenerative braking torque increase gradient setting unit of the vehicle brake control device of the second embodiment. 6 is a time chart illustrating an operation example of the vehicle brake control device according to the second embodiment. 12 is a flowchart illustrating a processing flow in a regenerative braking torque increase gradient setting unit of the vehicle brake control device according to the third embodiment. 10 is a time chart illustrating an operation example of the vehicle brake control device of the third embodiment.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for realizing a vehicle brake control device of the present invention will be described with reference to the drawings.
(Embodiment 1)
First, the overall configuration of the vehicle brake control device according to the first embodiment will be described with reference to FIG. 1 which is a system configuration diagram of the vehicle brake control device.

  The vehicle braking control apparatus according to the first embodiment is applied to an electric vehicle in which driving wheels (wheels WH shown in FIG. 1) are driven by a motor / generator 1 (hereinafter simply referred to as a motor 1). A braking device A and a regenerative braking device B are provided.

  The hydraulic braking device A includes a brake pedal BP, a master cylinder MC, a brake control unit 2, and a VDC control unit 3, and the regenerative braking device B includes a motor control unit 4, and each control is performed by the integrated control device 5 during braking. Units 2, 3 and 4 are controlled.

  Specifically, at the time of braking, the integrated control device 5 obtains a driver request total braking torque corresponding to the braking operation. And the integrated control apparatus 5 performs regeneration cooperation control as needed at the time of braking. In this regenerative cooperative control, the hydraulic pressure of the master cylinder MC is generated by reducing the hydraulic pressure corresponding to the braking torque (regenerative braking torque) generated during the regeneration of the motor 1.

Hereinafter, the hydraulic braking device A and the regenerative braking device B will be described.
(Hydraulic braking device)
First, the hydraulic braking device A will be described.
The hydraulic braking device A includes a brake device 10 and a VDC actuator 30.
In the brake device 10, a braking fluid pressure corresponding to the depression force applied to the brake pedal BP that the driver steps on is generated in the master cylinder MC, and this braking fluid pressure is transmitted via the brake fluid pressure circuit (primary circuit 11 and secondary circuit 12). It is supplied to a wheel cylinder WC provided on each wheel WH to generate a braking force.

  Further, the brake device 10 includes an electric booster 20, and the depression force (operation amount) of the brake pedal BP is boosted at a boost ratio set in advance by the electric booster 20, and the master cylinder MC The boosted input is converted into hydraulic pressure to form a braking hydraulic pressure.

Here, based on FIG. 2, the structure of the brake device 10 including the electric booster 20 will be described.
The brake device 10 includes a wheel cylinder WC that brakes the wheel WH, a master cylinder MC that supplies hydraulic oil to the wheel cylinder WC, a reservoir tank RES that stores hydraulic oil, and an input shaft that moves forward and backward by operating the brake pedal BP. 13. The electric booster 20 boosts the propulsive force applied to the input shaft 13. Further, the brake control unit 2 controls the electric booster 20 according to the displacement amount detected by the stroke sensor 14 that detects the displacement amount of the input shaft 13.

  The input shaft 13 is an input member that makes a stroke (advance and retreat) together with the brake pedal BP, and the primary piston 15 of the master cylinder MC is moved by the stroke of the input shaft 13. The input shaft 13 is provided with a relative displacement sensor 101 that detects a relative displacement amount with a primary piston 15 described later.

  The master cylinder MC moves the primary piston 15 as an assist member of the input shaft 13 forward and backward.

  The electric booster 20 gives a propulsion amount to the primary piston 15 according to the movement of the input shaft 13, and boosts the hydraulic pressure in the master cylinder MC (hereinafter, master cylinder pressure Pmc) by the propulsion force.

  The stroke sensor 14 is provided at one end of the input shaft 13. The stroke sensor 14 is a detection unit that detects a displacement amount of a stroke of the input shaft 13 as an operation amount of a driver's braking operation. The stroke sensor 14 outputs a detection signal corresponding to the detected displacement amount to the brake control unit 2.

The brake control unit 2 receives a detection signal from the stroke sensor 14 and transmits displacement amount information indicating the displacement amount of the stroke of the input shaft 13 according to the detection signal to the integrated control device 5 (see FIG. 1). The brake control unit 2 drives the electric booster 20 in accordance with a control command from the integrated control device 5 (applying propulsive force corresponding to the displacement amount of the input shaft 13 to the primary piston 15.
Hereinafter, the axial direction of the master cylinder MC is the x-axis direction, the bottom side of the master cylinder MC that is the left direction in the figure is the x-axis positive direction, and the brake pedal BP side is the x-axis negative direction.

The master cylinder MC is a so-called tandem type cylinder. In the cylinder 16 of the master cylinder MC, a primary piston 15 as an assist member and a secondary piston 17 are provided, and both 15 and 17 are arranged apart from each other in the axial direction by a gap L2.
In the cylinder 16, a primary hydraulic pressure chamber 16 a is formed by the end surface of the primary piston 15 on the x-axis positive direction side and the end surface of the secondary piston 17 on the x-axis negative direction side. The primary hydraulic pressure chamber 16a is connected so as to be able to communicate with the primary circuit 11.

  The volume of the primary hydraulic chamber 16a changes as the primary piston 15 and the secondary piston 17 stroke in the cylinder 16. A return spring 15b that urges the primary piston 15 toward the negative x-axis direction is installed in the primary hydraulic chamber 16a.

In the cylinder 16, a secondary hydraulic pressure chamber 16 b is formed by the bottom surface in the cylinder 16 and the end surface of the secondary piston 17 on the x-axis positive direction side. The secondary hydraulic chamber 16b is connected so as to be able to communicate with the secondary circuit 12.
The volume of the secondary hydraulic chamber 16b changes as the secondary piston 17 strokes in the cylinder 16. In the secondary hydraulic pressure chamber 16b, a return spring 17b that urges the secondary piston 17 toward the negative x-axis direction is installed.

  The primary circuit 11 is provided with a primary hydraulic pressure sensor 11S. The primary hydraulic pressure sensor 11S detects the hydraulic pressure in the primary hydraulic pressure chamber 16a and transmits hydraulic pressure information indicating the detection result to the brake control unit 2 in order to adjust the friction braking torque.

  The secondary circuit 12 is provided with a secondary hydraulic pressure sensor 12S. The secondary hydraulic pressure sensor 12S detects the hydraulic pressure in the secondary hydraulic pressure chamber 16b in order to adjust the friction braking torque, and transmits hydraulic pressure information indicating the detection result to the brake control unit 2. A VDC actuator 30 is provided in the middle of both circuits 11 and 12.

  The end of the input shaft 13 on the x axis positive direction side penetrates the partition wall 15a of the primary piston 15 and is grounded in the primary hydraulic chamber 16a. The gap between the end of the input shaft 13 and the partition wall 15a of the primary piston 15 is sealed to ensure liquid tightness, and the end of the input shaft 13 is slidable in the axial direction with respect to the partition wall 15a. Is provided.

On the other hand, the end of the input shaft 13 on the x-axis negative direction side is connected to the brake pedal BP. When the driver steps on the brake pedal BP, the input shaft 13 moves to the x-axis positive direction side, and when the driver returns the brake pedal BP, the input shaft 13 moves to the x-axis negative direction side.
Further, the input shaft 13 is formed with a large-diameter portion 13a having a diameter smaller than the outer diameter of the flange portion 13f and larger than the inner circumference of the partition wall 15a of the primary piston 15. When the brake is not operated when no brake operation is performed, a gap L1 is provided between the end surface on the x-axis positive direction side of the large diameter portion 13a and the end surface on the x-axis negative direction side of the partition wall 15a. The gap L1 enables the primary piston 15 to move relative to the input shaft 13 in the negative x-axis direction. Thereby, when the regenerative cooperative control command is received from the integrated control device 5, the brake control unit 2 can reduce the friction braking torque by the regenerative braking torque.

Further, when the input shaft 13 is relatively displaced by the gap L1 in the x-axis positive direction with respect to the primary piston 15 by the gap L1, the end surface on the x-axis positive direction side of the large diameter portion 13a and the partition wall 15a come into contact with each other. The input shaft 13 and the primary piston 15 move integrally. As a result, the hydraulic fluid in the primary hydraulic chamber 16 a is pressurized, and the pressurized hydraulic fluid is supplied to the primary circuit 11.
The secondary piston 17 moves to the x-axis positive direction side by the pressure of the primary hydraulic chamber 16a. As a result, the hydraulic fluid in the secondary hydraulic chamber 16 b is pressurized, and the pressurized hydraulic fluid is supplied to the secondary circuit 12.

  The wheel cylinder WC is a friction braking device that applies friction braking torque to the wheel WH. A piston (not shown) is moved by hydraulic fluid from the cylinder 16, and a pad (not shown) connected to the piston is a disk. The rotor DR (see FIG. 1) is pressed.

  The reservoir tank RES has at least two liquid chambers separated from each other by a partition wall (not shown). One of the fluid chambers in the reservoir tank RES is connected to the primary fluid pressure chamber 16a of the master cylinder MC via the brake circuit 18a. The other fluid chamber is connected to the secondary fluid pressure chamber 16b through the brake circuit 18b so as to be able to communicate therewith.

Next, the electric booster 20 will be described.
The electric booster 20 adjusts the displacement amount of the primary piston 15, that is, the master cylinder pressure Pmc in accordance with a control command from the brake control unit 2. The electric booster 20 includes a drive motor 21 that generates a rotational force according to the amount of displacement of the input shaft 13, a speed reducer 22 that increases the rotational force of the drive motor 21, and a rotational force of the speed reducer 22 that is used as a master cylinder MC. And a rotation-translation conversion device 23 for transmitting to the device.

  The drive motor 21 is a three-phase DC (Direct Current) brushless motor. The drive motor 21 generates a rotational torque according to the detection signal from the stroke sensor 14 in accordance with a control command from the brake control unit 2. The drive motor 21 serves as an actuator that moves the primary piston 15 forward and backward.

The speed reducer 22 decelerates the output rotation of the drive motor 21 by a pulley speed reduction method. The reduction gear 22 includes a small-diameter driving pulley 22a provided on the output shaft of the driving motor 21, a large-diameter driven pulley 22b provided on the ball screw nut 23a of the rotation-translation converter 23, and a driving pulley 22a. And a belt 22c wound around the driven pulley 22b.
The reduction gear 22 amplifies the rotational torque of the drive motor 21 in accordance with the reduction gear ratio determined by the radius ratio between the driving pulley 22 a and the driven pulley 22 b and transmits the amplified torque to the rotation-translation converter 23.

  The rotation-translation conversion device 23 converts the rotational power of the drive motor 21 into translation power, and presses the primary piston 15 with the translation power. The rotation-translation converter 23 employs a ball screw system, and includes a ball screw nut 23a, a ball screw shaft 23b, a movable member 23c, and a return spring 23d.

  A housing member HSG1 is provided on the x-axis negative direction side of the master cylinder MC, and a housing member HSG2 is provided on the x-axis negative direction side of the housing member HSG1. A ball screw nut 23a is rotatably installed on the inner periphery of the bearing BRG provided in the housing member HSG2.

  The ball screw nut 23a is fitted to the driven pulley 22b. A hollow ball screw shaft 23b is screwed into the ball screw nut 23a. A plurality of balls are rotatably installed in the gap between the ball screw nut 23a and the ball screw shaft 23b.

  A movable member 23c is integrally provided at the end of the ball screw shaft 23b on the x-axis positive direction side, and the primary piston 15 is joined to the end surface of the movable member 23c on the x-axis positive direction side. The primary piston 15 is accommodated in the housing member HSG1. The end of the primary piston 15 on the x-axis positive direction side protrudes from the housing member HSG1 and is fitted to the inner periphery of the master cylinder MC.

  A return spring 23d is provided between the inner periphery of the housing member HSG1 and the outer periphery of the primary piston 15. The return spring 23d has an end on the x-axis positive direction side fixed to the bottom surface on the x-axis positive direction side in the housing member HSG1, and an end on the x-axis negative direction side engaged with the movable member 23c. The return spring 23d is installed to be compressed in the axial direction between the bottom surface and the movable member 23c, and urges the movable member 23c and the ball screw shaft 23b to the x-axis negative direction side.

  When the driven pulley 22b rotates, the ball screw nut 23a rotates integrally, and the ball screw shaft 23b translates in the axial direction by the rotational movement of the ball screw nut 23a. The primary piston 15 is pressed to the x-axis positive direction side via the movable member 23c by the thrust of the translational movement of the ball screw shaft 23b to the x-axis positive direction side. FIG. 2 shows a state in which the ball screw shaft 23b is maximum displaced in the negative x-axis direction when the brake is not operated. This state is the initial position of the ball screw shaft 23b.

  On the other hand, the elastic force of the return spring 23d acts on the ball screw shaft 23b in the opposite direction (x-axis negative direction side) to the translational thrust. For example, when a brake operation is performed, that is, even when the primary piston 15 is pressed in the positive x-axis direction and the master cylinder pressure Pmc is increased, the elastic force acts on the negative x-axis direction.

  A pair of springs 19 a and 19 b are disposed in an annular space 19 defined between the input shaft 13 and the primary piston 15. One end of the spring 19 a is locked to a flange portion 13 f provided on the input shaft 13, and the other end of the spring 19 a is locked to a partition wall 15 a of the primary piston 15. One end of the spring 19b is locked to the flange portion 13f, and the other end of the spring 19b is locked to the movable member 23c.

  The springs 19a and 19b urge the input shaft 13 toward the neutral position of the relative displacement of the primary piston 15 and hold the input shaft 13 and the primary piston 15 in the neutral position of relative movement when the brake is not operated. To play a role. When the input shaft 13 and the primary piston 15 are relatively displaced in any direction from the neutral position by the springs 19a and 19b, a biasing force is applied to the primary piston 15 to return the input shaft 13 to the neutral position.

Therefore, in the brake device 10, the displacement (forward and backward) of the primary piston 15 is added to the displacement of the input shaft 13 to adjust the master cylinder pressure Pmc. This hydraulic pressure adjustment is expressed by the following equation (1) ) Is performed with a pressure equilibrium relationship indicated by
Here, each element in the equation (1) of pressure equilibrium is as follows.
Pb: Hydraulic pressure Fi in the pressure chamber (primary hydraulic pressure chamber 16a) in the master cylinder MC: Input thrust Fb: Booster thrust Ai: Pressure receiving area Ab of the input shaft 13: Pressure receiving area of the primary piston 15 K: Springs 19a, 19b Spring constant ΔX: relative displacement between the input shaft 13 and the primary piston 15

The relative displacement amount ΔX is defined as ΔX = Xi−Xb, where Xi is the displacement of the input shaft 13 and Xb is the displacement of the primary piston 15. Therefore, ΔX is 0 at the neutral position of the relative movement, has a positive sign in the direction in which the primary piston 15 moves backward with respect to the input shaft 13, and has a negative sign in the opposite direction. In the pressure balance equation (1), the sliding resistance of the seal is ignored. In the pressure balance equation (1), the booster thrust Fb can be estimated from the current value of the drive motor 21.
Pb = (Fi−K × ΔX) / Ai = (Fb + K × ΔX) / Ab (1)

On the other hand, the boost ratio Bα is expressed by the following equation (2). Therefore, when Pb of the pressure balance equation (1) is substituted into the equation (2), the boost ratio Bα is expressed by the following equation (3). It becomes like the formula.
Bα = Pb × (Ab + Ai) / Fi (2)
Bα = (1−K × ΔX / Fi) × (Ab / Ai + 1) (3).

  In this case, when performing constant boost control as the background art, the rotation of the drive motor 21 is controlled (feedback control) so that the relative displacement amount ΔX becomes 0 based on the detection result of the stroke sensor 14. Then, the boost ratio Bα becomes Bα = Ab / Ai + 1, and is uniquely determined by the area ratio between the pressure receiving area Ab of the primary piston 15 and the pressure receiving area Ai of the input shaft 13 as in the vacuum booster and the background art.

  On the other hand, the relative displacement amount ΔX can be set to a predetermined negative value. In this case, the rotation of the drive motor 21 is controlled so that the absolute displacement amount of the primary piston 15 becomes larger than the absolute displacement amount of the input shaft 13 as the input shaft 13 moves in the direction of increasing the brake fluid pressure. To do. In this way, the boost ratio Bα has a magnitude of (1−K × ΔX / Fi) times, that is, the boost ratio Bα is variable, the drive motor 21 acts as a boost source, and the pedal depression force Can be greatly reduced.

  The VDC (abbreviation of Vehicle Dynamics Control) actuator 30 shown in FIG. 1 is a well-known one (see, for example, Japanese Patent Application Laid-Open No. 2004-196064). That is, the VDC actuator 30 includes a pump, a pressure increasing valve, and a pressure reducing valve, which are not shown, and can adjust the wheel cylinder pressure Pwc by increasing or decreasing it. Therefore, when the driver performs braking, it is possible to execute so-called ABS control that adjusts the wheel cylinder pressure Pwc so that the wheels WH including the driving wheels are not locked.

Further, the VDC actuator 30 incorporates a pump (not shown). Therefore, the VDC actuator 30 can generate a hydraulic braking torque on the wheels WH including the drive wheels by the braking hydraulic pressure formed by the built-in pump in a state where no braking hydraulic pressure is generated in the master cylinder MC. Then, by using this hydraulic braking torque to generate an arbitrary braking force at any of the four wheels, it is possible to execute vehicle motion control (hereinafter referred to as VDC control).
The driving of the VDC actuator 30 is controlled by the VDC control unit 3.

(Regenerative braking device)
Next, the regenerative braking device B will be described.
The regenerative braking device B converts wheel rotational energy into electric power by a motor (motor / generator) 1 that is drivingly coupled to a drive wheel (wheel WH) shown in FIG. 1 via a speed reducer and a differential 6. That is, the motor 1 is controlled through AC / DC conversion in the inverter 41 by the three-phase PWM signal from the motor control unit 4. In the EV traveling mode that requires driving of the driving wheels (wheels WH shown in FIG. 1), the motor 1 is driven as a motor by the electric power from the high-power battery 42 to rotate the driving wheels (wheels WH shown in FIG. 1). . On the other hand, in a braking mode that requires braking, regenerative braking torque control is performed to drive the motor 1 as a generator to convert vehicle kinetic energy into electric power and collect it in the high-power battery 42.

The VDC control unit 3 and the motor control unit 4 control the hydraulic braking device A and the regenerative braking device B according to a command from the integrated control device 5.
Accordingly, the motor control unit 4 controls the regenerative braking torque by the motor 1 based on the regenerative braking torque command value from the integrated control device 5.
Further, the VDC control unit 3 controls the hydraulic braking torque in the wheel cylinder WC based on command values from the integrated control device 5 and the brake control unit 2.

  The sensor group 100 includes a battery temperature sensor, a wheel speed sensor, a master cylinder pressure sensor, a wheel cylinder hydraulic pressure sensor, etc. (not shown) in addition to the stroke sensor 14 and the relative displacement sensor 101 described above. .

Further, the motor control unit 4 calculates the maximum allowable regenerative braking torque of the motor 1 from the battery temperature and the estimated charge capacity of the high-power battery 42 (hereinafter referred to as the battery SOC) and transmits it to the integrated control device 5. To do.
Further, the VDC control unit 3 transmits the input wheel speed Vw, master cylinder pressure Pmc and wheel cylinder pressure Pwc to the integrated control device 5.

(Braking torque control)
When the driver performs a braking operation, the integrated control device 5 obtains a driver-requested total braking torque Treq based on various input information. Then, based on the control of the brake control unit 2 and the motor control unit 4, the braking torque control for generating the target braking torque by the regenerative braking torque and the hydraulic braking torque is executed using the driver requested total braking torque Treq as the target braking torque. To do.

  In this braking torque control, hydraulic braking torque (master cylinder pressure Pmc) control by the drive motor 21 in the electric booster 20 by the brake control unit 2 and the integrated control device 5 will be described based on the flowchart of FIG.

In step S101, the pedal stroke amount SA detected by the stroke sensor 14 is read. In step S102, it is determined whether a regenerative cooperation flag has been generated. The regenerative cooperation flag is generated when the regenerative cooperative braking control is executed.
If it determines with YES in step S102, the target displacement amount C1 will be calculated using the target displacement amount calculation characteristic data etc. of regenerative cooperative control in step S103, and it will progress to step S105. That is, in step S103, the target displacement amount C1 of the primary piston 15 is calculated so that the braking force obtained by subtracting the regenerative braking torque from the target braking torque is generated by the hydraulic braking force.
If NO is determined in step S102, the process proceeds to step S104, the target displacement amount C2 is calculated using the target displacement amount calculation characteristic data of the variable boost control, and the process proceeds to step S105. That is, when the regenerative braking torque is not generated, the target displacement amount C2 of the primary piston 15 is obtained so as to obtain a boost ratio Bα set in advance according to the depression amount (pedal stroke amount) of the brake pedal BP. Is calculated.

  In step S105, the relative displacement detection value SB currently detected by the relative displacement sensor 101 is read, and in the next step, the relative displacement detection value SB is calculated by the target displacement amount C1, calculated in any one of steps S103 and S104. The drive motor 21 is controlled so as to be any one of C2.

Next, details of the calculation processing of the target displacement amount C1 in step S103 described above will be described based on the flowchart of FIG.
The regenerative braking command value is read from the motor control unit 4 or the integrated control device 5, the pressure reduction amount ΔP of the master cylinder pressure Pmc corresponding to the regenerative braking command value is calculated, and the process proceeds to step S202.

In step S202, the pedal stroke amount SA detected by the stroke sensor 14 is read, and the process proceeds to step S203.
In step S203, a master cylinder pressure P1 corresponding to the pedal stroke amount SA is calculated based on a relative displacement amount and a master cylinder pressure characteristic corresponding to a preset pedal stroke amount.

In the subsequent step S204, the relative displacement amount -X2 is calculated by subtracting the pressure reduction amount ΔP obtained in step S201 from the master cylinder pressure P1 obtained in step S203.
In the subsequent step S205, the relative displacement amount (−X2) is set to the target displacement amount C1, and the process proceeds to return.

  With the above processing, the amount of movement of the primary piston 15 required to reduce the master cylinder pressure Pmc by the amount of regenerative braking torque generated can be calculated as the target displacement amount C1.

Next, regenerative braking torque setting processing executed by the integrated control device 5 and the motor control unit 4 will be described with reference to the flowchart of FIG.
In step S301, after calculating the target braking torque corresponding to the pedal stroke amount SA, the process proceeds to step S302. Here, the target braking torque is set according to the detected value of the stroke sensor 14 based on the stroke amount-target braking torque characteristic shown in step S301 of FIG.

  In step S302, based on whether or not the difference between the current stroke amount and the previous stroke amount is less than a preset in-operation determination value, it is determined whether the brake pedal BP is being operated or is being depressed. . If the pedal is being held, the process proceeds to step S303, and if the brake pedal is being operated, the process proceeds to step S304. That is, in step S302, whether or not the pedal is being operated is determined based on whether or not the amount of depression of the brake pedal BP has increased or decreased and the amount of change in the amount of depression of the brake pedal BP has changed by more than a predetermined amount.

  In step S303, which proceeds when the pedal is in the depressed state, the current regeneration command value (regenerative braking torque) is calculated by adding a value based on a preset increase gradient to the previous regeneration command value, and then the process proceeds to step S306. This set increase gradient is an increase gradient shown between t5 and t6 in FIG. 10, and is set to a gently increasing gradient as shown.

  On the other hand, in step S304, which proceeds when the brake pedal is being operated in step S302, Δ target braking torque which is a target braking torque change amount corresponding to the change amount of operation of the brake pedal BP is obtained, and then the process proceeds to step S305. . That is, the target braking torque change amount (Δtarget braking torque) is obtained by subtracting the previous target braking torque from the current target braking torque calculated according to the current pedal stroke amount SA.

  In step S305, the current regeneration command value is calculated by adding the Δtarget braking torque obtained in step S304 to the previous value of the regeneration command, and then the process proceeds to step S306. In other words, the increase gradient of the current regeneration command value calculated in step S305 is set to the same increase gradient as the increase gradient of the target braking torque, as shown by the one-dot chain line in FIG. Therefore, it becomes a value obtained by multiplying the target braking torque by a coefficient of 1 or less.

  In step S306, the lower value (select low) of the current regeneration command value obtained in step S303 or S305 and the target braking torque obtained in step S301 is set as the final current regeneration command value, and the process proceeds to step S307. In step S307, the final current regeneration command value is stored as the previous value, and the process proceeds to return.

  Furthermore, in the first embodiment, the following replacement control is executed in controlling the regenerative braking torque and the hydraulic braking torque. In this switching control, when the regenerative cooperative control is executed at a low vehicle speed in the braking torque control, the regenerative braking torque is reduced from the state where only the regenerative braking torque is generated as the vehicle speed V decreases. In this control, the hydraulic braking torque is raised. In this replacement control, the braking torque is finally obtained only by the hydraulic braking torque just before the vehicle stops.

This replacement control will be described based on the flowchart of FIG.
In step S401, the driver request total braking torque Treq is calculated, and the process proceeds to the next step S402. In the first embodiment, based on the operation of the brake pedal BP of the driver detected by the stroke sensor 14, the hydraulic braking torque that can be generated in the stroke is calculated, and this is set as the driver requested total braking torque Treq. In addition, when an automatic deceleration control means such as cruise control is provided, the final high-required driver braking torque Treq may be set to a select high value with the hydraulic braking torque.

  In step S402, the calculated vehicle speed V is input, and the process proceeds to the next step S403. Here, the vehicle speed V may be obtained by applying a constant low-pass filter to the average value of the wheel speed pulse sensor obtained from the wheel speed sensor.

In step S403, the effective regenerative braking torque _TRB is input, and the process proceeds to the next step S404. The execution regenerative braking torque _TRB is a regenerative braking torque actually realized in the motor 1 based on the regenerative braking command value, and a regenerative braking command value output from the motor control unit 4 is input to this. Calculate based on.
The regenerative braking command value is formed based on the final target regenerative braking torque.
The final target regenerative braking torque is calculated based on the regenerative maximum limit value and the basic target regenerative braking torque. The regenerative maximum limit value is set based on the maximum output and current value of the motor 1 and the specification of the hydraulic braking device A that performs regenerative coordination, and is the maximum value of the regenerative braking torque that can be generated at that time. The basic target regenerative braking torque is a regenerative braking torque that is determined according to the driver-requested total braking torque within a range of a vehicle speed limit value that is a maximum regenerative braking torque that is obtained in advance according to the vehicle speed. It is.

  In step S404, after setting the reference replacement vehicle speed line, the process proceeds to step S405. The reference replacement vehicle speed line is a limit value of the regenerative braking torque set corresponding to the vehicle speed, as shown in FIG. As shown in the figure, the reference replacement vehicle speed line has a regenerative braking torque limit value set to 0 at a low vehicle speed lower limit vehicle speed Vmin or lower, and a regenerative braking torque limit value at an upper vehicle speed Vmax or higher. It is set to a constant value. Between the vehicle speeds Vmin and Vmax, the limit value of the regenerative braking torque is a first-order proportional characteristic that is proportional to the increase in the vehicle speed and goes toward the constant value.

In step S405, after setting the preload start vehicle speed line, the process proceeds to step S406.
Here, the preload start vehicle speed line will be described.
As shown by a dotted line in FIG. 7A, the preload start vehicle speed line is set with a width on the high vehicle speed side with respect to the reference replacement vehicle speed line. That is, in the first embodiment, the width of the reference switching vehicle speed line is set wider as the limit value of the regenerative braking torque is larger than the reference switching starting vehicle speed line.
The preload start vehicle speed line may be set to be substantially parallel to the reference replacement start vehicle speed line as shown in FIG. 7B.

Incidentally, so that the difference between the driver request total braking torque Treq and execution regenerative braking torque T _RB acts as a friction braking torque T _FB. When the friction braking torque _TFB is applied over a certain level, the initial nonlinear region of the hydraulic braking device A is exceeded to some extent, and the pedal feel is hardly deteriorated without applying the preload by the preload regenerative braking torque reduction process. Does not occur. For this reason, in the first embodiment, in the setting of the preload start vehicle speed line in step S405, the driver-requested total braking torque Treq is equal to or greater than a preset setting value or the friction braking torque _TFB is equal to or greater than a preset setting value. In this case, the preload start vehicle speed line is matched with the reference replacement vehicle speed line. As a result, when the driver-requested total braking torque Treq is equal to or greater than a preset value or the friction braking torque _TFB is equal to or greater than a preset value, the preload regenerative braking torque reduction process described later is not executed.

In step S406, the preload start regenerative braking torque T _PRE is calculated, and then the process proceeds to step S407. That is, the preload start regenerative braking torque _TPRE is obtained from the intersection of the current vehicle speed V and the preload start vehicle speed line.
In step S407, it is determined whether or not the current execution regenerative braking torque _TRB exceeds the preload start regenerative braking torque _TPRE . If the current execution regenerative braking torque _TRB exceeds the preload start regenerative braking torque _TPRE , it is determined that the preload regenerative braking torque reduction process needs to be performed, and the process proceeds to step S408, where the preload regenerative limiting torque _TRATE is set. Calculate.
Note that the preload regenerative limiting torque T _RATE is a regenerative braking torque when the preload regenerative braking torque reduction process is executed.

On the other hand, if the execution regenerative braking torque T _RB at step S407 does not exceed beyond the preload start regenerative braking torque T _PRE, since it is not necessary to apply a preload, the upper limit value of the preload regeneration limit torque T _RATE, according to the vehicle speed The process skips step S408 and proceeds to step S409.

Note that the preload regeneration limitation torque _{T RATE} is in step S408, are those obtained from the current execution regenerative braking torque _{T RB} by subtracting the predetermined amount (Tstep), specifically, computed by the following equation (2).
T _RATE = T _RB -Tstep (2)
At step S409, the reference regeneration limit torque _{T DEC,} set from the intersection of the current vehicle speed Vref and the reference swap speed line, the process proceeds to step S410.
In step S410, after the low speed range regeneration limit torque T _VEL is determined, the process proceeds to step S411. The low speed range regeneration limit torque _TVEL is used to switch the braking torque from the regenerative braking torque to the hydraulic braking torque (friction braking torque) according to the vehicle speed in the low vehicle speed range just before the vehicle stops. Specifically, the low speed range regeneration limit torque T _VEL is determined by a select low of the preload regeneration limit torque T _RATE and the reference regeneration limit torque T _DEC . Therefore, when the preload regenerative braking torque reduction process is executed, the low speed range regenerative limit torque T _VEL is set to the preload regenerative limit torque T _RATE , and when the preload regenerative braking torque reduction process is not executed, the low speed range regenerative limit torque T _VEL = reference. Regeneration limit torque T _DEC is set.

In step S411, the regeneration limit value other than that including the low speed region regeneration limit torque _TVEL determined in step S110 is selected to determine the final regeneration limit torque. Then, this final regenerative limiting torque is transmitted to the motor control unit 4 as a regenerative braking torque command value.

By executing the swap control flow chart of FIG. 6, when the vehicle speed V is lowered at the time of braking, as shown in FIG. 8, than the time of T ₃ that the vehicle speed V reaches the reference swap vehicle speed before the point in time At (T ₂ ), the reduction of the regenerative braking torque by the preload regenerative limiting torque T _RATE is started based on the preload start vehicle speed line. Along with this, the start of the hydraulic braking torque is started.

Thereafter, execution regenerative braking torque T _RB is, from the time of T ₄ has reached the reference swap speed line, a decrease in the regenerative braking torque by the reference regeneration limitation torque T _DEC is started. Along with this, the increasing gradient of the hydraulic braking torque (master cylinder pressure Pmc) also becomes steep.

Next, the operation of the first embodiment will be described based on the time chart.
<Comparative example>
Here, in order to compare with the operation of the first embodiment, an example of the operation in the case of the prior art to which the present invention is not applied will be described with reference to FIG.

  FIG. 9 shows an example in which the braking operation is started at time t01. In this braking operation, the depression of the brake pedal BP is started at the time t01, and then the depression is gradually increased until the time t05, and the depression state is maintained after the time t05 (see the pedal stroke). ).

When such a depression operation is performed, in the brake device 10, the master cylinder pressure Pmc (hydraulic braking torque) is raised from the time point t01 in response to depression of the brake pedal BP.
Thereafter, regenerative braking is started by the regenerative braking device B from the time (t02) when the pedal stroke amount becomes SA. Further, due to the rise of the regenerative braking torque, the hydraulic braking torque (master cylinder pressure Pmc) is decreased by the amount of the rise of the regenerative braking torque. For this reason, the master cylinder pressure Pmc (hydraulic braking torque) is decreased from PMa at the time t02 and is decreased to master cylinder pressure Pmc = PMb (≈0 MPa) at the time t03. In this state, the regenerative braking torque is reduced. This is continued until the time point t04 when the preset limit value is reached. Then, after the time point t04 when the regenerative braking torque reaches the limit value, the master cylinder pressure Pmc (hydraulic braking torque) increases again according to the increase of the target braking torque, and the pedal stroke amount is kept constant. After the time t05, the master cylinder pressure Pmc is also maintained at a constant pressure (PMd).

  When such an operation is performed, the spring force and the master cylinder pressure Pmc act as reaction forces acting on the input shaft 13. That is, when the primary piston 15 is relatively displaced with respect to the input shaft 13, the springs 19a and 19b provided on the both 13 and 15 expand and contract. As a result, the spring force increases when the primary piston 15 moves in the negative x-axis direction and decreases when the primary piston 15 moves in the positive direction. Therefore, the spring force changes to SPa, SPb, SPc, and SPd as shown in the figure. On the other hand, the master cylinder pressure Pmc changes to PMa, PMb, PMc, and PMd as described above.

For this reason, the pedal reaction force, which is the resultant force, is shown by a solid line in the figure with respect to the pedal reaction force corresponding to the pedal stroke amount SA indicated by the dotted line in the figure from the time t02 to the time t05 as shown in the figure. As shown, the reaction force increases.
This change in reaction force made the driver feel uncomfortable and caused the pedal feel to deteriorate.

(Operation of Embodiment 1)
Next, the operation of the first embodiment will be described with reference to FIGS.
In the first embodiment, the braking operation is started at time t1, and the master cylinder pressure Pmc (hydraulic braking torque) rises.
At this time, the regenerative braking torque rises at time t2 as in the comparative example. However, the first embodiment differs from the comparative example in how the regenerative braking torque rises. That is, in the first embodiment, when the pedal operation is being performed in which the brake pedal BP is depressed deeply with the lapse of time from time t1 to time t5 in this way, the current regenerative command value changes to the previous value of the regenerative command and the target braking torque change A value obtained by adding the amount (Δtarget braking torque) is set (steps S4 to S6). In this case, as shown in an enlarged view in FIG. 11, an increasing gradient (variable increasing gradient) parallel to the target braking torque is obtained from the time when the regenerative braking torque rises to the time t5. That is, the regenerative braking torque is set to a value obtained by multiplying the target braking torque by a value smaller than 1.

  When controlled in this way, the master cylinder pressure Pmc is maintained at the previous value after time t2 when the regenerative braking torque rises.

Then, after the time t5 when the depression amount of the brake pedal BP is in a constant holding state, the current regeneration command value is increased with the set increase gradient by adding a value based on the set increase gradient to the previous regeneration command value.
Therefore, after t5, the increasing gradient of the regenerative braking torque becomes gentle. When the depression of the brake pedal BP disappears and the depression amount is maintained in a constant state, the regenerative braking torque is controlled to the regenerative braking torque limit value Tlim (upper limit value).

By controlling in this way, thereafter, the hydraulic braking torque (master cylinder pressure Pmc) is controlled to the difference between the target braking torque and the regenerative braking torque.
In FIGS. 10 and 11, dotted lines indicate values in the case of the comparative example described above.

  Therefore, in the first embodiment, the master cylinder pressure Pmc is maintained at the previous value without decreasing as in the conventional technique indicated by the dotted line after the time t2 when the regenerative braking torque rises. For this reason, the spring force acting on the input shaft 13 also rises gently without suddenly increasing after the time t2, as in the comparative example.

  Further, when there is no displacement in the stroke increasing direction of the brake pedal BP and the pedal is held in the depressed state, the regenerative braking torque is gradually increased thereafter (after time t5), so the master cylinder pressure Pmc is Decrease moderately.

As described above, in the first embodiment, the master cylinder pressure Pmc is held at the previous value without being decreased in order to make the increasing gradient of the regenerative braking torque coincide with the increasing gradient of the target braking torque. For this reason, the reaction force acting on the input shaft 13 increases with a substantially constant gradient without going up and down as in the comparative example (indicated by the dotted line).
Therefore, in this Embodiment 1, the deterioration of a pedal feel can be suppressed.

Thereafter, a further reduction in vehicle speed V, the execution regenerative braking torque T _RB crosses the preload start speed line, as shown FIG. 8, while the regenerative braking torque is reduced, the swap control is started to the hydraulic braking torque increases The

  Accordingly, the regenerative braking torque is reduced to zero when the vehicle speed reaches the preset lower limit vehicle speed Vmin, and at the same time, the hydraulic braking torque increases in accordance with the decrease in the regenerative braking torque, Thus, the target braking torque is reached when the regenerative braking torque becomes zero.

As described above, in the first embodiment, when the regenerative braking torque is increased, the increasing gradient is parallel to the target braking torque so that the increasing gradient is multiplied by the target braking torque by a predetermined ratio of less than 1. Increase with. For this reason, the master cylinder pressure is maintained at the pressure at time t2 when the regenerative braking torque rises.
Therefore, as shown in FIG. 11, the reaction force (pedal reaction force) acting on the input shaft 13 is kept substantially constant and does not vary as in the comparative example shown by the dotted line. Therefore, as in the comparative example, the pedal reaction force can be prevented from changing and the pedal feel from being deteriorated, and the pedal feel can be improved.

Below, the effect of the vehicle braking control apparatus of Embodiment 1 is demonstrated.
(1) The vehicle brake control device of the first embodiment is
A regenerative braking device B for controlling a regenerative braking torque applied to the wheel WH of the vehicle;
A brake device 10 that forms a master cylinder pressure Pmc that generates a hydraulic braking torque in accordance with a driver's braking operation in the vehicle, and that can increase or decrease the master cylinder pressure Pmc by driving a drive motor 21 as an actuator;
A stroke sensor 14 serving as a target braking torque detection unit for detecting a target braking torque at the time of a braking operation, and a part for executing the processing of step S301;
Brake control unit 2 serving as a braking torque control unit that controls driving of the regenerative braking device B and the brake device 10 and performs regenerative cooperative braking control for generating a target braking torque based on the regenerative braking torque and the hydraulic braking torque, motor control Unit 4, integrated control device 5,
A vehicle brake control device comprising:
The braking torque control unit is configured to set an increasing gradient when increasing the regenerative braking torque according to the increase in the target braking torque during the regenerative cooperative control (the processing of steps S302 to S306 in FIG. 5). Part to execute)
The regenerative braking torque increase gradient setting unit sets the increase gradient according to the amount of change in the target braking torque when the amount of change is less than a preset change amount setting value (in-operation determination value). An increase gradient is set (step S303), and when the change amount is equal to or greater than the change amount setting value (operation determination value), the increase gradient is changed to a variable increase gradient equal to or less than the change rate change rate (Δtarget braking force). It is characterized by setting.
During braking, the regenerative braking torque increase gradient setting unit can change the increase gradient of the regenerative braking torque to be less than or equal to the change rate of the change amount according to the change amount of the target braking torque. Set to increasing slope.
Therefore, when the regenerative braking torque is increased as the target braking torque is increased, the hydraulic braking torque (master cylinder pressure Pmc) should not be reduced as shown in FIGS. Can do.
Therefore, as shown by the dotted line in FIGS. 10 and 11, the change in the pedal reaction force can be suppressed as compared with the hydraulic braking torque (master cylinder pressure Pmc) that decreases after the time t2. The pedal feel can be improved.
On the other hand, when the change amount of the target braking torque is less than the change amount set value, the increase gradient of the regenerative braking torque is set to a preset increase gradient as shown after time t5. For this reason, even when the amount of change is less than the set value (YES determination in step S302), if the increase gradient of the regenerative braking torque is finely controlled as the variable increase gradient, the master cylinder pressure Pmc may change slightly and give a sense of discomfort. However, by controlling to the set increase gradient, it is possible to suppress the occurrence of this uncomfortable feeling and ensure a good pedal feel.

2) The vehicle braking control device of the first embodiment is
The brake device 10 includes an input shaft 13 as an input member that moves forward and backward by operation of the brake pedal BP, a primary piston 15 as an assist member that is disposed so as to be relatively movable with respect to the input shaft 13, and a forward and backward movement of the primary piston 15. A drive motor 21 to be moved, and a spring as an urging means that is provided between the input shaft 13 and the primary piston 15 and urges the input shaft 13 toward the neutral position of the relative displacement of the primary piston 15. 19a, 19b, and generates brake fluid pressure (master cylinder pressure Pmc) boosted in the master cylinder MC by assist thrust applied to the primary piston 15 according to the movement of the input shaft 13 by the brake pedal BP. Electric double Characterized in that it comprises a device 20.
When regenerative cooperative control is performed using such an electric booster 20, when the master cylinder pressure Pmc is increased or decreased by driving the drive motor 21, the springs 19a and 19b acting on the input shaft 13 and the master cylinder pressure The reaction force due to Pmc changes, and the reaction force of the brake pedal BP changes.
Therefore, the regenerative braking torque increase gradient setting means suppresses the change in the brake pedal reaction force by setting the increase gradient to the set increase gradient and the variable increase gradient according to the amount of change in the target braking torque as described above. The pedal feel can be improved.

3) In the vehicle braking device of the first embodiment,
The regenerative braking torque increase gradient setting unit is characterized in that when the increase gradient is set to a variable increase gradient equal to or less than the change rate change rate (Δ target braking force), the change rate change rate is set. To do.
Therefore, after the time t2 when the variable increasing gradient is set, the master cylinder pressure Pmc is maintained and the pedal feel can be improved by suppressing the pedal reaction force change as compared with the case where the master cylinder pressure Pmc decreases. In addition, it is possible to ensure good regeneration efficiency as compared with the case where the master cylinder pressure Pmc increases.

(Other embodiments)
Next, a vehicle braking control device according to another embodiment will be described.
Since the other embodiment is a modification of the first embodiment, the same reference numerals as those in the first embodiment are assigned to the same components as those in the first embodiment, and the description thereof is omitted. Only the differences will be described.

(Embodiment 2)
A vehicle braking control apparatus according to the second embodiment will be described.
The second embodiment is different from the first embodiment in the process of setting the variable increase gradient shown in the first embodiment as the regenerative braking torque increase gradient setting section.
That is, in the second embodiment, the configuration corresponding to the regenerative braking torque increase gradient setting unit is different from that of the first embodiment, and the processing shown in FIG. 12 is executed instead of the processing in steps S304 and S305 in FIG. To do.

In step S2-1 in the flowchart of FIG. 12, the target braking torque and the effective regenerative braking torque _TRB are compared, and the difference ΔF between them is calculated (comparison unit). In other words, it calculates a difference ΔF from the target brake torque by subtracting the execution regenerative braking torque T _RB.

  In step S2-2, a ratio α for obtaining a variable increase gradient is set based on the difference ΔF obtained in step S2-1. That is, in the second embodiment, as shown in FIG. 13, a ratio characteristic that sets the ratio α to be smaller as the difference ΔF is smaller is set according to the difference ΔF (ratio setting unit). The ratio α is set to “1” which is the upper limit value when the difference ΔF is larger than the set value ΔF0 shown in FIG. 13, and is less than 1 in proportion to the difference ΔF when it is less than the set value ΔF0. Set to a value.

  In step S2-3, the Δ regenerative braking torque command value is set by multiplying the Δ target braking torque by the ratio α. Therefore, the current regeneration command value is set to a smaller value as the difference ΔF is smaller.

Next, the operation of the second embodiment will be described.
FIG. 14 is a time chart illustrating an operation example of the second embodiment.
In FIG. 14, the alternate long and short dash line indicates the target braking torque. That is, in this operation example, the brake pedal BP is depressed from the time point t21, and after the time point t23, the depression amount is once fixed, and then the depression amount is further slightly increased from the time point t25. A braking operation is performed with a constant depression amount.

  In FIG. 14, the operation from the time when the first depression of the brake pedal BP is started (time t21) to the time when the amount of depression is made constant (time t25) is the same as in the first embodiment. That is, when the brake pedal BP is depressed from time t21, the difference ΔF obtained by subtracting the execution regenerative braking torque from the target braking torque becomes a relatively large value, and the ratio α is set to 1 that is the upper limit value. For this reason, the regenerative braking torque (current regenerative braking torque) is started up with an increase gradient (variable increase gradient) similar to the target braking torque, and the time point t24 from the time point t23 when the depression amount of the brake pedal BP becomes constant. Up to, it increases with the set increase gradient set in step S303.

  Thereafter, the regenerative braking torque is controlled to the target braking torque after time t24 when the target braking torque is reached.

Next, the operation after the time t25 when the brake pedal BP is increased as described above will be described.
Thus, when the target braking torque increases from the state where the regenerative braking torque and the target braking torque coincide with each other, the difference ΔF between the target braking torque and the effective regenerative braking torque becomes a relatively small value, and the ratio α Is also set to a relatively small value.

  For this reason, the regenerative braking torque from the time point t25 in FIG. 14 (the portion indicated by the alternate long and short dash line EX in the figure) has a gentle increase gradient compared to the increase gradient of the target braking torque. Therefore, the braking torque corresponding to the difference is compensated by the hydraulic braking torque, that is, the master cylinder pressure Pmc. Therefore, in the brake device 10, the master cylinder reaction force acting on the input shaft 13 is not reduced, and the pedal feel deterioration can be suppressed.

In the second embodiment, the difference ΔF gradually decreases due to an increase in the regenerative braking torque after the time t25, so the ratio α is gradually increased. After the time t26, the ratio α1 = 1. Set to Therefore, the regenerative braking torque increases at the same gradient as the increase gradient of the target braking torque.
Thereafter, after the time point when the increase of the brake pedal BP is stopped (time point t27), the set increasing gradient is used as the increasing gradient of the regenerative braking torque, and the regenerative braking torque converges to the target braking torque.

(Effect of Embodiment 2)
4) The vehicle braking control apparatus according to the second embodiment is
The regenerative braking torque increase gradient setting unit (the portion that executes the processes of steps S2-1 to S2-3) sets a variable increase gradient when a decrease in the regenerative braking torque is predicted when the variable increase gradient is set. In order to do this, the variable increase gradient is set to be more gradual than in the case where no prediction is made.
When the brake pedal BP is depressed again from the holding state of the brake pedal BP by the braking operation, the following pedal feel may be deteriorated.
That is, when the brake pedal BP is depressed to be in the holding state, the regenerative braking torque is 100% of the target braking torque or a state close thereto. When the brake pedal BP is depressed from this state, for example, if the regenerative braking torque is increased by a variable increasing gradient based on the ratio α, the master cylinder pressure Pmc is controlled to be close to 0 MPa, and the reaction force is insufficient. May give a sense of incongruity.
In contrast, the present embodiment 2, re-depression when the brake pedal BP as described above, according to the difference ΔF between the target braking torque and execution regenerative braking torque T _RB, as the difference ΔF is smaller, less control the ratio α By doing so, an increase in regenerative braking torque is suppressed.
Thereby, by increasing the hydraulic braking torque and surely increasing the master cylinder pressure Pmc, it is possible to suppress the pedal reaction force change and improve the pedal feel.

  When the variable increase gradient (ratio α) is set, the ratio α multiplied by the Δtarget braking torque as the amount of change may be set smaller as the difference ΔF between the target braking torque and the effective regenerative braking torque is smaller.

(Embodiment 3)
A vehicle braking control apparatus according to Embodiment 3 will be described.
The third embodiment is an example in which a control for reducing the regenerative braking torque is added before shifting to the replacement control described in the first embodiment, and the pedal feel can be further improved.

  In the third embodiment, the regenerative braking torque limit obtained by the limit value setting process shown in the flowchart of FIG. 15 in the process of obtaining the final current regenerative command value by selecting with select low in step S306 shown in the first embodiment. The value Tlim is added.

The limit value setting process shown in the flowchart of FIG. 15 will be described.
At step S501, determines whether or not the current vehicle speed V is preset reduced for determination value greater than or equal _to V _0, in the case of more than depleting determination value V ₀ the process proceeds to step S502, under reduced for determination value V ₀ In this case, the process proceeds to step S503. Note that the decrease determination value V ₀ is a value that indicates a preset low-speed traveling, and is a value that can be determined to be a time point before the shift control.
After step S502 the vehicle speed V proceeds when more than depleting determination value _{V 0,} the regenerative braking torque limit value Tlim, was set to the maximum value _{T MAX,} the process proceeds to the return. The maximum value T _MAX indicates that the regenerative braking torque limit value Tlim is not selected as the final current regenerative command value in step S306, and the maximum regenerative command value obtained in step S305 or the like is not selected. May be replaced.

In step S503 the vehicle speed V proceeds in the case of less than depleting determination value V _0, whether determined vehicle speed V is first set vehicle speed V ₁ or more set in advance, when the first predetermined vehicle speed V ₁ or more The process proceeds to step S504, and if it is less than the first set vehicle speed V1, the process proceeds to step S505. Second setting speed V ₂ and the third set speed V ₃ to the first set value V ₁ and described below, is a determination value for predicting a decrease in regenerative braking torque. That is, any of the set vehicle speeds V _{1 to} V ₃ is set on the higher speed side than the reference replacement vehicle speed line described in the first embodiment, and is directed from the first set vehicle speed V ₁ to the third set vehicle speed V ₃ . It is used to determine that the vehicle has approached the vehicle speed line for replacement and has approached the vehicle based on the predicted decrease in regenerative braking torque.

In step S504 the vehicle speed V proceeds in the case of the first set speed _{V 1} or more, after calculating the additional value ΔTlim determining the regenerative braking torque limit value Tlim, the process proceeds to step S510. In step S504, the addition value ΔTlim is calculated by the following equation (3-1).
ΔTlim = max (0, ΔT _DRQ ) / M ₁ (3-1)
Here, ΔT _DRQ is a target braking torque change amount obtained by subtracting the current value of the target braking torque from the previous value of the target braking torque. Further, max (0, ΔT _DRQ ) means a select high between the target braking torque change amount ΔT _DRQ and 0. Further, M ₁ is set to 1 in the third embodiment. Note that the relationship between M ₂ and M _3, which will be described later, used to calculate the added value ΔTlim is M ₁ = 1 <M ₂ <M ₃ .

In step S510, the execution regenerative braking torque _{T RB,} calculates a value obtained by adding the addition value ΔTlim as a regenerative braking torque limit value Tlim.

In step S505 proceeds is determined as NO at step S503, determines whether or not the current vehicle speed V is a second set speed _{V 2} or more, in the case of the second set speed _{V 2} or greater, the process proceeds to step S506, the second case lower than the set vehicle speed _{V 2} proceeds to step S507. In step S506, the addition value ΔTlim is calculated by the following equation (3-2). By larger than M ₁ used in step S504 that the value M ₂ to be used as a denominator is described above in this calculation, the additional value ΔTlim is set to a relatively small value.
ΔTlim = max (0, ΔT _DRQ ) / M ₂ (3-2)
In step S507 proceeds is determined as NO at step S505, determines whether or not the current vehicle speed V is a third set speed _{V 3} or more, in the case of the third set speed _{V 3} or greater, the process proceeds to step S508, the If less than the third set speed _{V 3} goes to step S509. In step S508, the addition value ΔTlim is calculated by the following equation (3-3). By value _{M 3} for use as the denominator in the calculation is greater than _M 1, _{M 2} used in step S504, S506 described above, the addition value ΔTlim is set to a relatively small value.
ΔTlim = max (0, ΔT _DRQ ) / M ₃ (3-3)
In step S509 that proceeds when NO is determined in step S507, the addition value ΔTlim = 0 is set, and then the process proceeds to step S510.
Then, in step S510, as described above, it sets the regenerative braking torque limit value by adding the additional value ΔTlim to perform regenerative braking torque T _RB.
That is, as the vehicle speed V approaches the reference switching vehicle speed line by the braking operation, the regenerative braking torque limit value is set such that the value added to the _effective regenerative braking torque _TRB becomes smaller, that is, the increase gradient becomes gentle. .

(Operation of Embodiment 3)
Below, the operation example of Embodiment 3 is demonstrated based on the time chart of FIG.
In this time chart, the braking operation is started at time t31. Accordingly, the master cylinder pressure Pmc (hydraulic braking torque) has risen from time t31. Then, the regenerative braking torque is raised at time t32, and the increase in the master cylinder pressure Pmc (hydraulic braking torque) is suppressed from that time. In this case, as in the first embodiment, the increase in the target braking torque is formed by the regenerative braking torque, so the master cylinder pressure Pmc is almost level. Thereby, compared with the case where master cylinder pressure Pmc falls, the reaction force with respect to the input shaft 13 is ensured, and the deterioration of the pedal feel can be suppressed as in the first and second embodiments.

Thereafter, when the vehicle speed V decreases, the switching control for decreasing the regenerative braking torque toward 0 MPa is executed. At this time, in the third embodiment, when it is predicted that the regenerative braking torque will be reduced by the replacement control, a process of setting a limit value in which the ratio α used for setting the variable increase gradient is set to be small is performed. Run.
That is, at the time t33 when the vehicle speed V is less than the determination value V ₀ for reduction and in the range equal to or higher than the first set vehicle speed V ₁ , which is the first stage approaching the reference replacement vehicle speed Vb for executing the replacement control. By steps S504 and S510, the regenerative braking torque limit value Tlim is calculated.
In this case, the regenerative braking torque limit value Tlim is set by the select high of the target braking torque change amount ΔT _DRQ and 0. Therefore, when the vehicle speed V is lower than the decrease determination value V ₀ and the range is equal to or higher than the first set vehicle speed V ₁ , the regenerative braking torque is maintained at the target braking torque change amount ΔT _DRQ , that is, the target braking torque is maintained. Controlled to match.

Then, the vehicle speed V becomes the first set lower than the vehicle speed V _1, and second set speed V ₂ or between, i.e., in the time chart of FIG. 16, at the time of up to t34 from the time of t33, regenerative braking torque limit value Tlim is calculated in steps S506 and S510. That is, the regenerative braking torque is increased with a gentler slope than the target braking torque change amount ΔT _DRQ .

After that, when the vehicle speed V becomes less than the second set vehicle speed V ₂ and is equal to or higher than the third set vehicle speed V ₃ , that is, in the time chart of FIG. Tlim is calculated in steps S508 and S510. That is, the regenerative braking torque is further increased with a gentle slope.

Then, a just before the swap control is started, after the vehicle speed V becomes less than the third set speed V _3, i.e., since the time of t35, regenerative braking torque limit value Tlim, by the processing in step S509 0 Set to Therefore, the gradient of the regenerative braking torque is maintained at the effective regenerative braking torque, and becomes level.

Then, across the execution regenerative braking torque T _RB reference swap speed lines, the swap control is started (time point of the vehicle speed V ≦ becomes Vb t36), the regenerative braking torque, as shown in FIG. 16, a predetermined The hydraulic braking torque (master cylinder pressure Pmc) corresponding to the reduced amount is started up while being reduced at the inclination of.

  As a result, as shown in the figure, after the time t36, the regenerative braking torque is reduced to 0 MPa when the vehicle speed V reaches the lower limit vehicle speed Vmin, and the hydraulic braking torque is increased. The increase in the hydraulic braking torque is relaxed after the time point (t37) when the depression amount (target braking torque) of the brake pedal BP becomes constant.

As described above, in the third embodiment, since the master cylinder pressure Pmc does not decrease, the change in the pedal reaction force can be suppressed as in the first embodiment, and the pedal feel can be deteriorated.
Furthermore, even when the regenerative braking torque is reduced by executing the substitution control, the regenerative braking torque increase gradient is controlled more gently than the increase gradient of the target braking torque from the previous stage. Gradient change when turning from increasing to decreasing can be moderated. As a result, the change in the master cylinder pressure Pmc is suppressed, and thus the pedal feel deterioration due to the change in the master cylinder pressure Pmc can be suppressed as compared with the case where the increase gradient is not made gentle before the regenerative braking torque is reduced.

(Effect of Embodiment 3)
5) In the vehicle brake control device of Embodiment 3,
The regenerative braking torque increase gradient setting unit (the part that executes the flow of FIG. 15) variably increases the variable increase gradient when setting the variable increase gradient when a decrease in the regenerative braking torque is predicted when the variable increase gradient is set. The gradient is set more gently than in the case where the prediction is not made.
Therefore, when a decrease in the regenerative braking torque is predicted, the increase gradient is moderated in advance, and the change in the master cylinder pressure when the regenerative braking torque changes from increasing to decreasing is kept small. Can be suppressed.
Note that the regenerative braking torque increase gradient setting unit (the portion that executes the flow of FIG. 15) sets the variable increase gradient when the regenerative braking torque is predicted to decrease when the variable increase gradient is set. The ratio α for multiplying the amount of change may be set smaller than when prediction is not made.

6) In the vehicle brake control device of the third embodiment,
In setting the variable increase gradient, the regenerative braking torque increase gradient setting unit (the portion that executes the flow of FIG. 15) sets the variable increase gradient more gradually as the decrease in the regenerative braking torque approaches. It is characterized by that. Specifically, the added value ΔTlim to be added to perform regenerative braking torque T _RB to calculate the regenerative braking torque limit value Tlim, by him to approach the start timing of the swap control is set to a small value, variable The increasing slope was set gently. That is, in the third embodiment, as the vehicle speed V changes, the increasing gradient is gradually set in four steps as the time when the regenerative braking torque decrease is predicted approaches.
Therefore, when predicting a decrease in regenerative braking torque, the change in the master cylinder pressure associated with the regenerative braking torque changing from increasing to decreasing as compared to the case where the increasing gradient is set gently at only one step or less than three steps. Therefore, it is possible to further suppress the deterioration of the pedal feel by suppressing it to be smaller.
Note that the regenerative braking torque increase gradient setting unit may set the ratio α to be multiplied by the change amount to be smaller as the variable braking gradient is set closer to the timing at which the decrease in the regenerative braking torque is predicted. Good.

  As mentioned above, although the vehicle brake control apparatus of the present invention has been described based on the embodiment, the specific configuration is not limited to this embodiment, and the invention according to each claim of the claims. Design changes and additions are permitted without departing from the gist of the present invention.

  In the embodiment, an example in which the vehicle braking control device of the present invention is applied to an electric vehicle has been described. However, the application target of the present invention is a vehicle including a hydraulic braking device and a regenerative braking device. It is not limited to electric vehicles. For example, in a so-called hybrid vehicle equipped with an engine and a motor / generator as a drive source for the drive wheels, or a vehicle that can drive the drive wheels only by the driving force of the engine but can perform regenerative braking. Can also be applied.

2 Brake control unit (braking torque control unit)
4 Motor control unit (braking torque controller)
5 Integrated control device (braking torque control unit)
10 Brake device 13 Input shaft (input member)
14 Stroke sensor (Target braking torque detector)
15 Primary piston (assist member)
20 Electric Booster 21 Drive Motor (Actuator)
A fluid pressure braking device B regenerative braking apparatus BP brake pedal MC master cylinder Pmc master cylinder pressure _{T RB} perform regenerative braking torque Treq driver demand total braking torque (target braking torque)
V Vehicle speed

Claims (5)

A regenerative braking device that controls regenerative braking torque applied to the wheels of the vehicle;
A brake device capable of forming a master cylinder pressure that generates a hydraulic braking torque in accordance with execution of a braking operation of a driver in the vehicle, and capable of increasing or decreasing the master cylinder pressure by driving an actuator;
A target braking torque detector for detecting a target braking torque during the braking operation;
A braking torque control unit that controls driving of the regenerative braking device and the braking device, and performs regenerative cooperative braking control that generates the target braking torque by the regenerative braking torque and the hydraulic braking torque;
A vehicle brake control device comprising:
The braking torque control unit includes a regenerative braking torque increase gradient setting unit that sets an increase gradient when increasing the regenerative braking torque according to an increase in the target braking torque during the regenerative cooperative control,
The regenerative braking torque increase gradient setting unit sets the increase gradient to a preset increase gradient according to the change amount of the target braking torque when the change amount is less than a preset change amount setting value. The vehicular braking control apparatus is characterized in that, when the change amount is equal to or greater than the change amount set value, the increase gradient is set to a variable increase gradient equal to or less than the change rate of the change amount. The vehicle brake control device according to claim 1,
The regenerative braking torque increase gradient setting unit includes a comparison unit that compares the target braking torque with an effective regenerative braking torque that is actually generated, and at the time of setting the variable increase gradient, The vehicular braking control apparatus, wherein the variable increase gradient is set more gently as the difference between the braking torque and the effective regenerative braking torque is smaller. The vehicle brake control device according to claim 1,
The regenerative braking torque increase gradient setting unit sets the variable increase gradient to the prediction when setting the variable increase gradient when a decrease in the regenerative braking torque is predicted when the variable increase gradient is set. A vehicular braking control apparatus characterized in that it is set more gently than in a case where the above is not established. The vehicle brake control device according to claim 3, wherein
The regenerative braking torque increasing gradient setting unit sets the variable increasing gradient more gradually as the regenerative braking torque decreases nearer to a timing at which the decrease of the regenerative braking torque is predicted. Braking control device. In the vehicle brake control device according to any one of claims 1 to 4,
The brake device includes an input member that moves forward and backward by operation of a brake pedal, an assist member that is arranged to be relatively movable with respect to the input member, the actuator that moves the assist member forward and backward, the input member, and the assist member And an urging means for urging the input member toward the neutral position of the relative displacement with respect to the assist member, and according to the movement of the input member by the brake pedal A vehicular braking control apparatus comprising an electric booster that generates a brake fluid pressure boosted in a master cylinder by an assist thrust applied to the assist member.