Vehicle braking control device

Abstract

To provide a brake control device of a vehicle which can reduce a sense of discomfort of a driver when the driver steps on a brake pedal in a state where brake torque is generated with an automatic brake function.SOLUTION: A brake control device (150) of a vehicle comprises an electric brake booster (10) and a brake fluid pressure control unit (30), and executes brake control by setting the sum of automatic brake request torque (T_req_in) and driver request brake torque (T_dri) to target brake torque (T_tgt) when the driver steps on the brake pedal (3) while receiving a brake request signal (S_brk) with the automatic brake function. Control units (90, 100) advance a valve body (15) of the electric brake booster (10) in such a range that does not increase the pressure (P_mc) in a master cylinder (5) before the driver steps on the brake pedal (3) after receiving the brake request signal (S_brk) with the automatic brake function.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Recent vehicles are equipped with an automatic braking function. One known automatic braking function is a function in which a driving assistance device, also known as an ADAS (Advanced Driver-Assistance System), automatically generates a brake torque based on information about the area ahead of the vehicle detected by a camera or sensor mounted on the vehicle. Known automatic braking functions include an automatic braking function of an ACC (Adaptive Cruise Control) that automatically drives a vehicle while maintaining a target distance from a preceding vehicle, and an emergency braking function that avoids a collision with an obstacle or reduces the impact.

[0003] Another known automatic braking function is a function that automatically generates braking torque when the driver releases the accelerator pedal while it is depressed in electric vehicles and hybrid electric vehicles (hereinafter collectively referred to as "electric vehicles").

[0004] Electric vehicles use two types of brake torque generation functions: hydraulic brakes, which generate braking torque at the wheels by controlling the brake fluid pressure at each wheel using a brake fluid pressure control unit equipped with an electric oil pump and an electromagnetic control valve, and regenerative brakes, which generate braking torque at the wheels by generating electricity in a motor using the rotational torque of the wheels. In regenerative brakes, the rotational kinetic energy of the wheels is converted into electricity and charged into the battery.

[0005] When the automatic braking function of the electric vehicle is activated, regenerative braking is used preferentially to increase the power generation efficiency (hereinafter also referred to as "regenerative efficiency") of the regenerative brake, but the deceleration torque that can be obtained by regenerative braking is limited depending on the specifications of the motor. If the required deceleration torque exceeds the maximum deceleration torque that can be obtained by regenerative braking, the required deceleration torque can be satisfied by further controlling the brake hydraulic control unit to generate hydraulic brake torque. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-047807 Summary of the Invention [Problem to be solved by the invention]

[0007] Here, hydraulic brake systems have been put into practical use that include an electric brake booster that uses the output torque of an electric motor as a brake booster that boosts the brake pedal force applied by the driver and pressurizes the brake fluid in a master cylinder that supplies brake fluid to a brake fluid pressure control unit.In a hydraulic brake system with an electric brake booster, hydraulic brake torque can be generated by an automatic braking function without moving the brake pedal by controlling the brake fluid pressure control unit to generate hydraulic brake torque without operating the electric brake booster.

[0008] In an electric vehicle equipped with such a hydraulic brake system, one method for setting a target brake torque when the driver depresses the brake pedal while the automatic braking function is activated is a method (hereinafter also referred to as a "selective method") in which the target brake torque is set to the larger torque value of the brake torque required by the automatic braking function (hereinafter also referred to as "automatic braking required torque") or the brake torque required according to the amount of depression of the brake pedal by the driver (hereinafter also referred to as "driver required brake torque"). Another setting method is a method (hereinafter also referred to as an "add-on method") in which the driver required brake torque is added to the automatic braking required torque. With the selective setting method, there is a time lag between when the driver depresses the brake pedal and when the driver required brake torque exceeds the automatic braking required torque, which may cause the driver to feel uncomfortable. On the other hand, with the add-on setting method, the brake torque increases when the driver depresses the brake pedal, so the driver does not feel uncomfortable.

[0009] However, with the add-on setting method, when the driver further depresses the brake pedal while the automatic brake function is generating hydraulic brake torque in addition to regenerative brake torque, the electric brake booster is activated to increase the pressure in the master cylinder (hereinafter also referred to as "master cylinder pressure"), and the brake hydraulic pressure control unit is activated to quickly increase the pressure in the wheel cylinders of the wheels (hereinafter also referred to as "brake hydraulic pressure"). Because the rotation speed of the electric oil pump depends on the master cylinder pressure, when the driver depresses the brake pedal and the master cylinder pressure increases, the rotation speed of the electric oil pump increases, which may increase the driving noise and load of the electric oil pump. Therefore, the driver may feel uncomfortable when the driving noise and load of the electric oil pump increase when they depress their own brake pedal.

[0010] On the other hand, with the selective setting method, when the driver depresses the brake pedal while the automatic braking function is activated, the master cylinder pressure increases due to the activation of the electric brake booster, but the target brake torque is maintained until the driver-requested brake torque exceeds the automatic braking-requested torque. After the driver-requested brake torque exceeds the automatic braking-requested torque, the brake fluid pressure increases due to the increase in master cylinder pressure, and the target brake torque can be achieved without activating the brake fluid pressure control unit. Therefore, there is no risk of an increase in the driving noise or load of the electric oil pump.

[0011] However, because the rigidity between the brake fluid pressure control unit and the master cylinder is very high, the master cylinder pressure rapidly rises to the brake fluid pressure with a slight pedal stroke when using the selective setting method. This causes the driver to experience a large reaction force immediately after starting to depress the brake pedal, which may prevent the driver from properly depressing the brake pedal. Furthermore, because the brake pedal force varies depending on the brake fluid pressure at the start of brake pedal depression, there is a problem that the pedal feel is not consistent depending on the automatic brake request torque and the regenerative brake torque. Furthermore, with the selective setting method, the regenerative brake torque must be reduced as the driver-requested brake torque increases. This reduces regenerative efficiency and, as mentioned above, may cause a discomfort to the driver due to the time lag between when the driver depresses the brake pedal and when the vehicle deceleration increases.

[0012] The present invention aims to provide a braking control device for a vehicle that improves the above-mentioned problem that can occur when a driver depresses the brake pedal while braking torque is being generated by an automatic braking function. [Means for solving the problem]

[0013] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a control unit (90, 100) for controlling a hydraulic brake system (1) including an electric brake booster (10) that drives an electric motor (11) to advance a valve body (15) and advance a piston (6, 7) of a master cylinder (5) to boost a brake pedal (3) depression force by a driver to pressurize brake fluid in the master cylinder (5), and a brake fluid pressure control unit (30) that adjusts brake fluid pressure (P_whl) generated in each wheel, and the control unit (90, 100) controls a braking request signal (S_br) by an automatic braking function. In a vehicle braking control device (150), an automatic brake request torque (T_req_in) is set to a target brake torque (T_tgt) while a braking request signal (S_brk) by the automatic brake function is received, and when the driver depresses the brake pedal (3) while a braking request signal (S_brk) by the automatic brake function is received, the control unit (90, 100) sets the sum of the automatic brake request torque (T_req_in) and a driver request brake torque (T_dri) to the target brake torque (T_tgt) and executes brake control. By doing so, Before the driver depresses the brake pedal (3) , by operating the electric brake booster (10) in advance, The valve body (15) of the electric brake booster (10) is opened within a range that does not increase the pressure (P_mc) in the master cylinder (5). To the master cylinder (5) side A braking control system for a forward moving vehicle is provided. [Effects of the Invention]

[0014] As described above, according to the present invention, in a vehicle hydraulic brake system including an electric brake booster and a brake hydraulic control unit, it is possible to reduce the discomfort felt by the driver when the driver depresses the brake pedal while brake torque is being generated by the automatic braking function. [Brief explanation of the drawings]

[0015] [Figure 1]1 is an explanatory diagram showing an example of the configuration of a hydraulic brake system to which a vehicle brake control device according to an embodiment of the present invention can be applied; [Figure 2] FIG. 2 is a partial cross-sectional view showing the internal structure of the electric brake booster. [Figure 3] 2 is a block diagram showing a functional configuration of a braking control device for a vehicle according to the embodiment; FIG. [Figure 4] FIG. 2 is an explanatory diagram showing a basic operation when ACC control is performed. [Figure 5] FIG. 10 is an explanatory diagram showing a conventional operation when the brake pedal is depressed while ACC control is being executed. [Figure 6] FIG. 10 is an explanatory diagram showing a conventional operation when the brake pedal is depressed while ACC control is being executed. [Figure 7] 4 is an explanatory diagram showing the operation when the brake pedal is depressed during execution of ACC control according to the first example of the present embodiment. FIG. [Figure 8] 5 is a flowchart showing an operation when the brake pedal is depressed during execution of ACC control according to a first example of the present embodiment. [Figure 9] FIG. 10 is an explanatory diagram showing the operation when the brake pedal is depressed during execution of ACC control according to a second example of the present embodiment. [Figure 10] 10 is a flowchart showing an operation when the brake pedal is depressed during execution of ACC control according to a second example of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In this specification and drawings, components having substantially the same functional configurations are designated by the same reference numerals, and redundant description will be omitted.

[0017] <1. Example of hydraulic brake system configuration> First, a configuration example of a hydraulic brake system to which the vehicle brake control device according to this embodiment can be applied will be described.

[0018] FIG. 1 is a schematic diagram showing an example of the configuration of a hydraulic brake system 1 for a vehicle. The vehicle hydraulic brake system 1 shown in Fig. 1 is a brake system for a four-wheel electric vehicle (including a hybrid electric vehicle). The hydraulic brake system 1 is configured as a brake system that includes two brake systems, each of which controls the brake torque of one front wheel and one rear wheel as a set.

[0019] The hydraulic brake system 1 may be a brake system of so-called X-pipe type, in which two brake systems each control the brake torque of one of the front wheels (left or right) and the rear wheel diagonally opposite the front wheel as a pair. Alternatively, the hydraulic brake system 1 may be a brake system of so-called H-pipe type, in which one system brakes the left front and rear wheels and the other system brakes the right front and rear wheels. The hydraulic brake system may also be a brake system for vehicles other than four-wheeled vehicles.

[0020] The hydraulic brake system 1 includes an electric brake booster 10, a master cylinder 5, and a brake hydraulic pressure control unit 30. The hydraulic brake system 1 also includes a hydraulic control device 90 that controls the brake hydraulic pressure control unit 30, and a booster control device 100 that controls the electric brake booster 10. The hydraulic control device 90 and the booster control device 100 are each partially or entirely configured with a microcomputer or microprocessor unit including an arithmetic processing device such as a CPU (Central Processing Unit). The hydraulic control device 90 and the booster control device 100 may be partially or entirely configured with updatable firmware or the like, or may be a program module executed by commands from the CPU or the like.

[0021] The hydraulic pressure control device 90 and the booster control device 100 are configured to be able to communicate with each other via a communication bus 140 such as a CAN (Controller Area Network). The hydraulic pressure control device 90 and the booster control device 100 are also configured to be able to communicate with the driving assistance device 110 and the motor control device 130 via the communication bus 140.

[0022] In the hydraulic brake system 1, the depression force applied to the brake pedal 3 is amplified by an electric brake booster 10 and transmitted to a master cylinder 5, which serves as a hydraulic pressure generation source. A reservoir tank 4 is attached to the top of the master cylinder 5, supplying brake fluid to the master cylinder 5. Within the master cylinder 5, two pressure chambers, a primary chamber 8 and a secondary chamber 9, are formed, which are separated by a primary piston 6 and a secondary piston 7. When the driver depresses the brake pedal 3, the primary piston 6 and the secondary piston 7 are pressed, pressurizing the brake fluid stored in the primary chamber 8 and the secondary chamber 9, and the brake fluid is supplied into a brake fluid pressure control unit 30.

[0023] The electric brake booster 10 is connected to the brake pedal 3 via an input shaft 13. The pedal force amplified by the electric brake booster 10 is transmitted to the master cylinder 5 via a push rod 14 that abuts against the primary piston 6. Axial movement of the primary piston 6 also causes the secondary piston 7 to move axially. This pressurizes the brake fluid in the primary chamber 8 and the secondary chamber 9.

[0024] FIG. 2 is a cross-sectional view partially showing the internal structure of the electric brake booster 10. As shown in FIG. The electric brake booster 10 includes a push rod 14, a valve body 15, a return spring 18, a plunger 16, a displacement sensor 80, and an assist mechanism 20. The plunger 16 is connected to an input shaft that is linked to a brake pedal (not shown), and moves forward and backward in accordance with the amount of brake pedal operation. A key member 17 is fixed to the plunger 16.

[0025] The assist mechanism 20 receives output from an electric motor (not shown) to move the valve body 15 forward toward the master cylinder 5. The electric motor may be, for example, a brushless DC-DC motor including a stator as a fixed element and a rotor as a movable element. The electric motor operates by receiving a supply of power (current) controlled by the booster control device 100. The electric motor is capable of rotating forward to move the valve body 15 forward and rotating reverse to move the valve body 15 backward by switching the direction of the current.

[0026] The assist mechanism 20 includes a reduction gear 21, a hub 22, a spindle nut 23, a spindle 24, and a valve body 15. The hub 22 is fixed to the spindle nut 23, and the rotational output of the electric motor is reduced in speed via the reduction gear 21 and transmitted to the hub 22 and the spindle nut 23. A support plate 25 that holds the valve body 15 is attached to the tip of the spindle 24. The valve body 15 and the support plate 25 are capable of moving relative to the plunger 16 and key member 17. The push rod 14 is connected to the front part (master cylinder side) of the valve body 15 by a retainer 26 via a reaction disc 27.

[0027] The spindle 24 moves forward or backward relative to the spindle nut 23 depending on the rotation direction of the electric motor 11, i.e., the rotation direction of the spindle nut 23. When the spindle 24 moves forward toward the master cylinder, the valve body 15 is pushed forward via the support plate 25 and moves forward against the biasing force of the return spring 18. This pressurizes the brake fluid in the master cylinder. When the spindle 24 moves backward, the valve body 15 moves backward due to the biasing force of the return spring 18.

[0028] The displacement sensor 80 detects the amount of relative displacement of the plunger 16 with respect to the valve body 15 and outputs a sensor signal to the booster control device 100. Specifically, the displacement sensor 80 includes a magnet 81 fixed to the key member 17, which moves back and forth together with the plunger 16, and an electrode 83 fixed to the valve body 15 in a position facing the magnet 81. The key member 17 and the valve body 15 are capable of relative displacement, and the displacement sensor 80 outputs to the booster control device 100 a current whose magnitude corresponds to a change in the magnetic field that accompanies the relative displacement between the key member 17 and the valve body 15. The amount of relative displacement between the key member 17 and the valve body 15 corresponds to the amount of relative displacement between the plunger 16 and the valve body 15.

[0029] The booster control device 100 detects the amount of relative displacement of the plunger 16 with respect to the valve body 15 based on the magnitude of the current input from the displacement sensor 80. In the booster control device 100, the current value input from the displacement sensor 80 when the electric brake booster 10 is in an inoperative state is used as a reference value when the amount of relative displacement is zero. When the driver depresses the brake pedal, the plunger 16 moves forward relative to the valve body 15, and the displacement sensor 80 outputs a current according to the amount of relative displacement to the booster control device 100.

[0030] The booster control device 100 supplies power (current) to the stator of the electric motor 11 in accordance with the amount of relative displacement of the plunger 16 with respect to the valve body 15. When the driver depresses the brake pedal and the plunger 16 is displaced forward relative to the valve body 15, the booster control device 100 rotates the electric motor in the forward direction to move the valve body 15 forward. Conversely, when the driver releases the brake pedal and the plunger 16 is displaced backward relative to the valve body 15, the booster control device 100 rotates the electric motor in the reverse direction to move the valve body 15 backward.

[0031] Returning to FIG. 1 , a first hydraulic circuit 31 and a second hydraulic circuit 32 extend from hydraulic ports respectively communicating with the primary chamber 8 and secondary chamber 9 of the master cylinder 5 toward hydraulic brakes 38a to 38d of each of the wheels RF, LR, LF, and RR. The hydraulic circuits of the vehicle brake system 1 according to this embodiment are of an X-piping type, and brake fluid is supplied to the wheel cylinder of hydraulic brake 38a of the right front wheel RF and the wheel cylinder of hydraulic brake 38b of the left rear wheel LR via the first hydraulic circuit 31. Brake fluid is also supplied to the wheel cylinder of hydraulic brake 38c of the left front wheel LF and the wheel cylinder of hydraulic brake 38d of the right rear wheel RR via the second hydraulic circuit 32. This allows each of the hydraulic brakes 38a to 38d to generate braking force on each of the wheels RF, LR, LF, and RR by hydraulic pressure.

[0032] The brake fluid pressure control unit 30 includes a first fluid pressure circuit 31 and a second fluid pressure circuit 32 having the same configuration. Brake fluid is supplied to the first fluid pressure circuit 31 and the second fluid pressure circuit 32 from the master cylinder 5. Below, the first fluid pressure circuit 31 will be briefly described, and a description of the second fluid pressure circuit 32 will be omitted.

[0033] The first hydraulic circuit 31 includes solenoid valves, such as a normally open, linearly controllable circuit control valve 36a, a normally closed, on / off controlled suction valve 34a, normally open, linearly controllable pressure increase valves (adjustment valves) 58aa, 58ba, and normally closed, on / off controlled pressure reduction valves 54aa, 54ba. The first hydraulic circuit 31 also includes a pump 44a driven by a pump motor 46, a low-pressure accumulator 71a, and a damper 73a. The number of pumps 44a is not limited to one.

[0034] A first pressure increase valve 58aa and a first pressure reduction valve 54aa provided adjacent to the hydraulic brake 38a of the right front wheel RF are used for ABS (Antilock Brake System) control or ESP (Electronic Stability Program) control of the right front wheel RF. A second pressure increase valve 58ba and a second pressure reduction valve 54ba provided adjacent to the hydraulic brake 38b of the left rear wheel LR are used for ABS control or ESP control of the left rear wheel LR.

[0035] The first pressure-increasing valve 58aa for the right front wheel RF is located between the circuit control valve 36a and the hydraulic brake 38a for the right front wheel RF. The linearly controllable first pressure-increasing valve 58aa continuously adjusts the flow rate of brake fluid from the circuit control valve 36a to the wheel cylinder of the hydraulic brake 38a for the right front wheel RF. When the first pressure-increasing valve 58aa is closed, the first pressure-increasing valve 58aa allows brake fluid to flow from the hydraulic brake 38a to the circuit control valve 36a, while also providing a bypass flow path with a check valve that restricts reverse flow.

[0036] The first pressure-reducing valve 54aa for the right front wheel RF is a solenoid valve that can be switched between a fully open and a fully closed state, and is located between the wheel cylinder of the hydraulic brake 38a for the right front wheel RF and the low-pressure accumulator 71a. When the first pressure-reducing valve 54aa is open, it reduces the pressure of brake fluid supplied to the wheel cylinder of the hydraulic brake 38a for the right front wheel RF. By repeatedly opening and closing the valve intermittently, the first pressure-reducing valve 54aa can adjust the flow rate of brake fluid flowing from the wheel cylinder of the hydraulic brake 38a for the right front wheel RF to the low-pressure accumulator 71a.

[0037] The second pressure-increasing valve 58ba for the left rear wheel LR is provided between the circuit control valve 36a and the hydraulic brake 38b for the left rear wheel LR. The linearly controllable second pressure-increasing valve 58ba continuously adjusts the flow rate of brake fluid from the circuit control valve 36a to the wheel cylinder of the hydraulic brake 38b for the left rear wheel LR. When the second pressure-increasing valve 58ba is closed, it allows brake fluid to flow from the hydraulic brake 38b to the circuit control valve 36a, while also providing a bypass flow path with a check valve that restricts reverse flow.

[0038] The second pressure-reducing valve 54ba for the left rear wheel LR is a solenoid valve that can be switched between a fully open and a fully closed state, and is located between the wheel cylinder of the hydraulic brake 38b for the left rear wheel LR and the low-pressure accumulator 71a. When the second pressure-reducing valve 54ba is open, it reduces the pressure of the brake fluid supplied to the wheel cylinder of the hydraulic brake 38b for the left rear wheel LR. By repeatedly opening and closing the valve intermittently, the second pressure-reducing valve 54ba can adjust the flow rate of brake fluid flowing from the wheel cylinder of the hydraulic brake 38b for the left rear wheel LR to the low-pressure accumulator 71a.

[0039] The circuit control valve 36a is provided to establish or block communication between the pressure increase valves 58aa, 58ba and the master cylinder 5. The suction valve 34a is provided to establish or block communication between the master cylinder 5 and the suction side of the pump 44a. A hydraulic pressure sensor 33 is provided in the lines between the circuit control valve 36a and the master cylinder 5, as well as between the suction valve 34a and the master cylinder 5. These are similar to the components of a conventional brake hydraulic control unit 30, so detailed description thereof will be omitted.

[0040] The second hydraulic circuit 32 controls a hydraulic brake 38c for the front left wheel LF and a hydraulic brake 38d for the rear right wheel RR. The second hydraulic circuit 32 is configured in the same manner as the first hydraulic circuit 31, except that the wheel cylinder of the hydraulic brake 38a for the front right wheel RF in the description of the first hydraulic circuit 31 is replaced with the wheel cylinder of the hydraulic brake 38c for the front left wheel LF, and the wheel cylinder of the hydraulic brake 38b for the rear left wheel LR is replaced with the wheel cylinder of the hydraulic brake 38d for the rear right wheel RR.

[0041] In the following description, these will be collectively referred to as the suction valve 34, the circuit control valve 36, the pressure increase valve 58, and the pressure reduction valve 54, respectively.

[0042] <2. Vehicle Braking Control Device> So far, an example of the configuration of the hydraulic brake system 1 to which a vehicle braking control device can be applied has been described. Next, an example of the configuration of a vehicle braking control device according to this embodiment will be described.

[0043] (2-1. Configuration example) FIG. 3 is a block diagram showing an example of a functional configuration related to the automatic braking function of the ACC, among the configurations of the vehicle braking control device 150 according to this embodiment. The vehicle braking control device 150 includes a driving assistance device 110, a hydraulic pressure control device 90, a booster control device 100, and a motor control device 130. The driving assistance device 110, the hydraulic pressure control device 90, the booster control device 100, and the motor control device 130 are each configured with a microcomputer or microprocessor unit including an arithmetic processing device such as a CPU or a GPU (Graphics Processing Unit). Some or all of these devices may be configured with updatable firmware, or may be program modules executed by commands from the CPU, etc. In addition, each device includes a drive circuit and a memory element such as a RAM or a ROM, not shown.

[0044] In this embodiment, the automatic braking function of the ACC is implemented by the hydraulic control device 90, the booster control device 100, and the motor control device 130 communicating with each other to control the driving of the brake hydraulic control unit 30, the electric brake booster 10, and the drive motor 121, based on a braking request signal S_brk transmitted from the driving assistance device 110. The hydraulic control device 90 and the booster control device 100 control hydraulic brake torque, and the motor control device 130 controls regenerative brake torque.

[0045] In addition, all or part of the driving assistance device 110, hydraulic control device 90, booster control device 100, and motor control device 130 may be configured as a single control device, or may be further configured as multiple control devices.

[0046] (2-1-1. Driving assistance devices) The driving assistance device 110 is configured to be able to acquire information detected by a sensor device 111 for detecting information on the environment ahead of the vehicle, such as other vehicles, pedestrians, bicycles, and obstacles ahead of the vehicle. The sensor device 111 includes, for example, at least one of a camera, radar, and LiDAR. The driving assistance device 110 is configured to be able to execute emergency brake control to avoid collision of the host vehicle with other vehicles, obstacles, etc. or to reduce the impact of a collision, in addition to ACC control to automatically drive the host vehicle while maintaining at least a target inter-vehicle distance between the host vehicle and a preceding vehicle.

[0047] While ACC control is being performed, the driving assistance device 110 determines whether braking is necessary and calculates the required braking torque indication value (automatic braking request torque) based on information detected by sensor equipment 111 such as a camera, radar, LiDAR, etc., and transmits a braking request signal S_brk indicating information on the automatic braking request torque T_req_in to the hydraulic control device 90 and the motor control device 130.

[0048] Specifically, the driving assistance device 110 calculates the inter-vehicle distance D between the host vehicle and the preceding vehicle and the relative speed dV of the host vehicle with respect to the preceding vehicle based on information detected by the sensor device 111. The driving assistance device 110 determines whether braking is required based on the calculated inter-vehicle distance D and relative speed dV. For example, the driving assistance device 110 determines that braking is required when the inter-vehicle distance D between the host vehicle and the preceding vehicle becomes less than a braking start threshold D_brk_thr set according to the host vehicle's speed V, relative speed dV, and target inter-vehicle distance D_tgt. The target inter-vehicle distance D_tgt may be a variable value set according to the host vehicle's speed V. Note that the method by which the driving assistance device 110 determines whether braking is required is not particularly limited.

[0049] Furthermore, the driving assistance device 110 calculates the automatic brake request torque T_req_in based on the vehicle speed V of the host vehicle, the relative speed dV, and the difference dD between the inter-vehicle distance D and the target inter-vehicle distance D_tgt. The rate of change of the inter-vehicle distance D when braking torque is applied to the vehicle may differ depending on the relative speed dV. Furthermore, the braking torque for decelerating the vehicle may differ depending on the vehicle speed V. For this reason, the driving assistance device 110 may calculate the automatic brake request torque T_req_in by referring to map information in which the automatic brake request torque T_req_in is preset according to the vehicle speed V, the relative speed dV, and the difference dD between the inter-vehicle distance. Note that the method of calculating the automatic brake request torque T_req_in by the driving assistance device 110 is not particularly limited.

[0050] (2-1-2. Motor control device) The motor control device 130 includes a regenerative braking target torque setting unit 131 and a control unit 133. Part or all of the regenerative braking target torque setting unit 131 and the control unit 133 are functions realized by a microcomputer executing a program. The motor control device 130 is configured to be able to acquire a braking request signal S_brk including information on an automatic braking request torque T_req_in transmitted from the driving assistance device 110. The motor control device 130 is also configured to be able to acquire information on the number of rotations N_whl of the wheels detected by wheel speed sensors (not shown).

[0051] The motor control device 130 controls the drive of the inverter 123 to control the drive motor 121. The motor control device 130 converts DC power supplied from the battery 125 into AC power and supplies it to the drive motor 121, causing the drive motor 121 to output drive torque (power running). In this case, the control unit 133 controls the drive of the inverter 123 based on a target drive torque that is set based on information such as the accelerator opening and required acceleration.

[0052] Furthermore, when the vehicle decelerates, the motor control device 130 converts the AC power output from the drive motor 121 into DC power and supplies it to the battery 125, thereby generating regenerative braking torque (regenerative driving). In this case, the control unit 133 controls the driving of the inverter 123 based on a regenerative braking target torque that is set based on information about the amount of brake pedal operation and the required deceleration. If the inverter 123 includes a step-up / step-down circuit, the control unit 133 converts the AC power output from the drive motor 121 into DC power when the vehicle decelerates, and drives the step-up circuit to boost the voltage up to the battery charging voltage.

[0053] With regard to the automatic braking function by the ACC, when the regenerative braking target torque setting unit 131 receives a braking request signal S_brk by the ACC from the driving assistance device 110, it sets the automatic braking request torque T_req_in to the regenerative braking target torque T_reg_tgt. However, when the automatic braking request torque T_req_in exceeds the maximum regenerative torque T_reg_pot of the drive motor 121, the regenerative braking target torque setting unit 131 sets the maximum regenerative torque T_reg_pot to the regenerative braking target torque T_reg_tgt. Furthermore, when the rotation speed of a wheel decreases as the vehicle speed decreases, the regenerative braking target torque setting unit 131 sets the regenerative torque that depends on the rotation speed N_whl of that wheel to the regenerative braking target torque T_reg_tgt.

[0054] The control unit 133 controls the driving of the inverter 123 based on the regenerative brake target torque T_reg_tgt set by the regenerative brake target torque setting unit 131, thereby generating a regenerative brake torque T_reg. The control unit 133 transmits information about the regenerative brake torque T_reg generated by the drive motor 121 to the hydraulic pressure control device 90. The control unit 133 may calculate the regenerative brake torque T_reg based on the rotation speed of the drive motor 121 and the output voltage of the generated power, and transmit information about the calculated regenerative brake torque T_reg to the hydraulic pressure control device 90, or may transmit information about the regenerative brake target torque T_reg_tgt to the hydraulic pressure control device 90.

[0055] In this way, while receiving the braking request signal S_brk of ACC control, the motor control device 130 compares the automatic braking request torque T_req_in with the maximum regenerative torque T_reg_pot, sets the smaller torque value as the regenerative braking target torque T_reg_tgt, and regeneratively drives the drive motor 121.

[0056] (2-1-3. Hydraulic pressure control device) The hydraulic control device 90 includes a hydraulic brake target torque setting unit 91 and a control unit 93. Part or all of the hydraulic brake target torque setting unit 91 and the control unit 93 are functions realized by a microcomputer executing a program. The hydraulic control device 90 is configured to be able to acquire a braking request signal S_brk including information on an automatic brake request torque T_req_in transmitted from the driving assistance device 110. The hydraulic control device 90 is also configured to be able to acquire information on a regenerative brake torque T_reg transmitted from the motor control device 130.

[0057] The hydraulic pressure control device 90 performs ABS control and ESP control by controlling the operation of the brake hydraulic pressure control unit 30. Furthermore, when the hydraulic pressure control device 90 receives a braking request signal S_brk for ACC control from the driving assistance device 110, it performs automatic brake control.

[0058] With regard to the automatic braking function of the ACC, the hydraulic brake target torque setting unit 91 of the hydraulic control device 90 sets the target brake torque T_tgt based on the automatic brake request torque T_req_in transmitted from the driving support device 110. Furthermore, when the driver depresses the brake pedal while receiving the braking request signal S_brk of the ACC control, the hydraulic control device 90 sets the target brake torque T_tgt to the sum of the automatic brake request torque T_req_in and the driver request brake torque T_dri (add-on type).

[0059] As described above, in the braking control device 150 of the vehicle according to this embodiment, the regenerative brake torque T_reg is used preferentially. For this reason, the hydraulic control device 90 acquires information about the regenerative brake torque T_reg transmitted from the motor control device 130, and sets the hydraulic brake target torque T_hyd_tgt to a value obtained by subtracting the regenerative brake torque T_reg from the target brake torque T_tgt. When the regenerative brake torque T_reg is zero, the target brake torque T_tgt becomes the hydraulic brake target torque T_hyd_tgt. Furthermore, when the regenerative brake torque T_reg begins to decrease after the regenerative brake torque T_reg has been generated, the hydraulic brake target torque T_hyd_tgt increases relatively.

[0060] After receiving the braking request signal S_brk of the ACC control, the control unit 93 controls the drive of the brake fluid pressure control unit 30 based on the hydraulic brake target torque T_hyd_tgt set by the hydraulic brake target torque setting unit 91 until the driver depresses the brake pedal. For example, the control unit 93 converts the hydraulic brake target torque T_hyd_tgt into a target brake fluid pressure P_tgt and controls the drive of the brake fluid pressure control unit 30, thereby controlling the brake torque of the vehicle. In this embodiment, the control unit 93 calculates the target brake fluid pressure P_tgt to be generated at each wheel based on the target brake torque T_tgt, and controls the drive of the pump motor 46 and various electromagnetic control valves of the brake fluid pressure control unit 30.

[0061] The control unit 93 may determine the target brake fluid pressure P_tgt corresponding to the hydraulic brake target torque T_hyd_tgt by referring to map information in which the relationship between the hydraulic brake target torque T_hyd_tgt and the target brake fluid pressure P_tgt is preset. The control unit 93 sets a target flow rate V_tgt of brake fluid to be supplied from the master cylinder 5 to the brake fluid pressure control unit 30 based on the calculated target brake fluid pressure P_tgt. The control unit 93 may set the target flow rate V_tgt of brake fluid by referring to map information in which the relationship between the target brake fluid pressure P_tgt and the target flow rate V_tgt is preset.

[0062] The control unit 93 may set the target flow rate V_tgt according to the difference dP between the current brake fluid pressure P_whl and the target brake fluid pressure P_tgt. The current brake fluid pressure P_whl may alternatively be a pressure value detected by the fluid pressure sensor 33. If a brake fluid pressure sensor that detects the brake fluid pressure of one of the wheel cylinders is provided in addition to the fluid pressure sensor 33, the pressure value detected by the brake fluid pressure sensor may be used instead of the fluid pressure sensor 33.

[0063] When the automatic braking function of the ACC is activated, the control unit 93 opens the pressure-increasing valve 58, closes the pressure-reducing valve 54, closes the circuit control valve 36, and opens the suction valve 34, and outputs a control signal to the drive circuit of the pump motor 46 in accordance with the set target flow rate V_tgt to drive the pumps 44a and 44b. This causes brake fluid to be supplied from the master cylinder 5 to the brake fluid pressure control unit 30, and then to the wheel cylinders of each wheel. As a result, the brake fluid pressure of each wheel increases, generating a hydraulic brake torque.

[0064] When the driver depresses the brake pedal, the control unit 93 opens the circuit control valve 36 and closes the suction valve 34, thereby stopping the operation of the pumps 44a and 44b. As a result, brake fluid is supplied from the master cylinder 5 to the brake fluid pressure control unit 30 in response to the driver's brake pedal operation, and the brake fluid pressure P_whl increases in accordance with the amount of brake pedal operation.

[0065] In this way, after receiving the braking request signal S_brk of the ACC control, the hydraulic pressure control device 90 sets the hydraulic brake target torque T_hyd_tgt to a value obtained by subtracting the regenerative brake torque T_reg from the automatic brake request torque T_req_in, and controls the driving of the brake hydraulic pressure control unit 30 to generate the brake hydraulic pressure P_whl until the driver depresses the brake pedal 3. Furthermore, after the driver starts to depress the brake pedal 3, the hydraulic pressure control device 90 stops the brake hydraulic pressure control unit 30 from applying the brake hydraulic pressure P_whl until the regenerative brake torque T_reg begins to decrease. Furthermore, if the regenerative brake torque T_reg begins to decrease after the driver starts to depress the brake pedal 3, the hydraulic pressure control device 90 resumes applying the brake hydraulic pressure P_whl by the brake hydraulic pressure control unit 30. During this period, the hydraulic pressure control device 90 transmits information about the brake hydraulic pressure P_whl detected by the hydraulic pressure sensor 33 or a brake hydraulic pressure sensor (not shown) to the booster control device 100.

[0066] (2-1-4. Booster control device) The booster control device 100 includes a control unit 101. Part or all of the functions of the control unit 101 are realized by the execution of a program by a microcomputer. The booster control device 100 is configured to be able to acquire a braking request signal S_brk including information on an automatic brake request torque T_req_in transmitted from the driving assistance device 110. The booster control device 100 is also configured to be able to acquire information on a brake fluid pressure P_whl transmitted from the fluid pressure control device 90. The booster control device 100 is also configured to be able to acquire information on a relative displacement amount d_str of the plunger 16 with respect to the valve body 15, which is detected by a displacement sensor 80 provided in the electric brake booster 10.

[0067] The control unit 101 controls the driving of the electric motor 11 based on information on the relative displacement amount d_str transmitted from the displacement sensor 80. Specifically, the control unit 101 sets the relative displacement amount d_str between the valve body 15 and the plunger 16 when the electric motor 11 is not driven as a reference value d_str_0, and when the relative displacement amount d_str changes, the control unit 101 rotates the electric motor 11 forward or reverse so that the relative displacement amount d_str becomes the reference value d_str_0. For example, the control unit 101 rotates the electric motor 11 forward or reverse at a rotation speed that corresponds to the rate of change of the relative displacement amount d_str. This causes the valve body 15 to move forward or backward, and the brake fluid in the master cylinder 5 is pressurized or depressurized. When the brake fluid in the master cylinder 5 is pressurized, brake fluid is supplied from the master cylinder 5 to the brake fluid pressure control unit 30, and hydraulic brake torque is generated on the wheels.

[0068] Furthermore, with regard to the automatic braking function of the ACC, in the braking control device 150 of the vehicle according to this embodiment, when generating hydraulic brake torque through ACC control, the control unit 101 rotates the electric motor 11 forward in advance before the driver depresses the brake pedal, thereby advancing (offsetting) the valve body 15 toward the master cylinder 5. At this time, the control unit 101 advances the valve body 15 within a range that does not increase the master cylinder pressure P_mc. In the booster control device 100, a maximum offset amount d_ofs_max is preset according to the displacement amount of the valve body 15 at which the master cylinder pressure P_mc starts to increase. Although it depends on the configuration of the electric brake booster 10, the relative displacement amount d_str of the valve body 15 at which the master cylinder pressure P_mc starts to increase is, for example, approximately 1.0 to 1.5 mm, and in this case, the maximum offset amount d_ofs_max is set to, for example, 0.5 to 0.8 mm.

[0069] Specifically, after receiving a braking request signal S_brk from the driving assistance device 110, the control unit 101 controls the driving of the electric motor 11 based on information about the brake fluid pressure P_whl transmitted from the brake fluid pressure control unit 30. A relative displacement amount d_str of the valve body 15 corresponding to the value of the brake fluid pressure P_whl is set in advance, and the control unit 101 rotates the electric motor 11 in the forward direction in accordance with the increasing rate of the received brake fluid pressure P_whl, and moves the valve body 15 forward within a range not exceeding the maximum offset amount d_ofs_max. As a result, the valve body 15 moves forward relative to the plunger 16.

[0070] Furthermore, when the driver depresses the brake pedal with the valve body 15 offset, the control unit 101 drives the electric motor 11 in accordance with the amount of depression of the brake pedal by the driver while maintaining the maximum offset amount d_ofs_max, thereby moving the valve body 15 forward. In other words, the control unit 101 sets the relative displacement amount d_str in the offset state to the offset reference value d_ofs_0 and controls the drive of the electric motor 11 so that the relative displacement amount d_str between the valve body 15 and the plunger 16 is maintained at the offset reference value d_ofs_0. As a result, the master cylinder pressure P_mc increases in accordance with the depression of the brake pedal by the driver, and brake fluid is supplied to the brake fluid pressure control unit 30, thereby increasing the brake fluid pressure P_whl.

[0071] Furthermore, if the regenerative brake torque T_reg decreases while the control unit 101 is receiving the braking request signal S_brk of the ACC control and the brake fluid pressure P_whl is applied again by the brake fluid pressure control unit 30, the control unit 101 drives the electric motor 11 to cancel the state in which the valve body 15 is offset in the forward direction. In other words, the control unit 101 rotates the electric motor 11 in the reverse direction to move the valve body 15 backward in a direction that returns the relative displacement amount d_str between the valve body 15 and the plunger 16 to zero (reference value d_str_0).

[0072] In this way, while receiving the braking request signal S_brk of ACC control, the booster control device 100 offsets the valve body 15 within a range that does not increase the master cylinder pressure P_mc if the brake fluid pressure P_whl increases before the driver depresses the brake pedal 3, based on information about the brake fluid pressure P_whl transmitted from the brake fluid pressure control unit 30. Furthermore, when the driver depresses the brake pedal 3 while receiving the braking request signal S_brk of ACC control, the booster control device 100 drives the electric motor 11 based on the relative displacement amount d_str between the valve body 15 and the plunger 16 at that time so as to maintain the relative displacement amount d_str between the valve body 15 and the plunger 16 at the offset reference value d_ofs_0 (or reference value d_str_0). Furthermore, if the regenerative braking torque T_reg that has been generated while the driver is depressing the brake pedal while receiving the braking request signal S_brk of the ACC control begins to decrease, the booster control device 100 moves the valve body 15 backward in accordance with the increase in brake fluid pressure P_whl caused by the drive of the brake fluid pressure control unit 30, thereby eliminating the offset state.

[0073] (2-2. Example of operation) Next, a specific example of the operation of the vehicle braking control device 150 according to this embodiment will be described.

[0074] (2-2-1. Detailed description of conventional operation and issues) First, before describing an example of the operation of the control processing by the vehicle braking control device according to this embodiment, the operation and problems of the control processing that has been conventionally performed will be described in detail.

[0075] Fig. 4 shows the automatic brake request torque T_req_in, brake torque T_act, regenerative brake torque T_reg, and hydraulic brake torque T_hyd when ACC control is being executed, as well as the operating states of the pump (pmp) 44, intake valve (HSV) 34, and circuit control valve (USV) 36 of the brake hydraulic control unit (ESP) 20. Fig. 4 shows an example of the basic operation when the driver does not depress the brake pedal 3 while ACC control is being executed.

[0076] At time t1, after the execution of ACC control is started, in section a where the maximum regenerative torque T_reg_pot exceeds the automatic brake request torque T_req_in, the brake torque T_act is generated by the regenerative brake torque T_reg.

[0077] At time t2, when the automatic brake request torque T_req_in exceeds the maximum regenerative torque T_reg_pot, in the subsequent section b, the brake torque T_act is generated from the regenerative brake torque T_reg and the hydraulic brake torque T_hyd. Specifically, at time t2, the intake valve 34 of the brake hydraulic pressure control unit 30 is opened, the circuit control valve 36 is closed, and the pump 44 is driven to generate the hydraulic brake torque T_hyd corresponding to the shortfall with respect to the automatic brake request torque T_req_in.

[0078] At time t3, when the automatic brake request torque T_req_in becomes constant, the driving of the pump 44 is stopped and the hydraulic brake torque T_hyd is maintained at a constant level. Thereafter, at time t4, when the regenerative brake torque T_reg begins to decrease as the vehicle decelerates, the pump 44 is driven again and the hydraulic brake torque T_hyd increases so as to compensate for the decrease in the regenerative brake torque T_reg.

[0079] At time t5, the regenerative brake torque T_reg is replaced by the hydraulic brake torque T_hyd and the regenerative brake torque T_reg becomes zero. In the following section c, the pump 44 is stopped again and the hydraulic brake torque T_hyd is maintained at a constant value. In section c, the brake torque T_act is generated by the hydraulic brake torque T_hyd.

[0080] FIG. 5 shows an example in which the driver depresses the brake pedal 3 while ACC control is being executed. FIG. 5 is an example in which the brake torque T_act is generated by the add-on formula described above, and shows the automatic brake request torque T_req_in, brake torque T_act, regenerative brake torque T_reg, brake fluid pressure P_whl, master cylinder pressure P_mc, and the operating states of the pump (pmp) 44, intake valve (HSV) 34, and circuit control valve (USV) 36 of the brake fluid pressure control unit (ESP) 20. For ease of understanding, in FIG. 5, the value of the fluid pressure (Prs) and the value of the brake torque (Trq) are shown on the same scale, and the hydraulic brake torque T_hyd is shown in terms of the brake fluid pressure P_whl.

[0081] At time t11, after the execution of ACC control is started, in section a where the maximum regenerative torque T_reg_pot exceeds the automatic brake request torque T_req_in, the brake torque T_act is generated by the regenerative brake torque T_reg.

[0082] At time t12, when the automatic brake request torque T_req_in exceeds the maximum regenerative torque T_reg_pot, in the subsequent section b, the brake torque T_act is generated from the regenerative brake torque T_reg and the brake fluid pressure P_whl. Specifically, at time t12, the suction valve 34 of the brake fluid pressure control unit 30 is opened, the circuit control valve 36 is closed, and the pump 44 is driven to generate the brake fluid pressure P_whl equivalent to the torque that is insufficient for the automatic brake request torque T_req_in. At time t13, when the automatic brake request torque T_req_in becomes constant, the drive of the pump 44 is stopped and the brake fluid pressure P_whl is maintained at a constant level.

[0083] If the driver depresses the brake pedal 3 at time t14, then in section α where the operation amount of the brake pedal 3 increases, the electric motor 11 of the electric brake booster 10 is driven to rotate in the forward direction, causing the master cylinder pressure P_mc to increase and brake fluid to be supplied from the master cylinder 5 to the brake fluid pressure control unit 30. In section α, the pump 44 of the brake fluid pressure control unit 30 is driven to supply the brake fluid from the master cylinder 5 to the wheel cylinders, causing the brake fluid pressure P_whl to increase. The brake fluid pressure P_whl is the sum of the brake fluid pressure P_whl_org generated by driving the brake fluid pressure control unit 30 and the master cylinder pressure P_mc. The generated brake torque T_act is the sum of the brake fluid pressure P_req, which corresponds to the automatic brake request torque T_req_in, and the master cylinder pressure P_mc.

[0084] Here, when the brake fluid pressure P_whl is constant, the flow rate discharged by the pump 44 is expressed by the following equation (1).

[0085]

number

[0086] Q_pmp: Discharge flow rate of pump 44 cCir: Hydraulic circuit stiffness P_whl: Brake fluid pressure P_mc: Master cylinder pressure

[0087] In other words, the rotation speed of the pump 44 of the brake fluid pressure control unit 30 depends only on the rate of increase of the master cylinder pressure P_mc. Therefore, in section α, if the driver suddenly depresses the brake pedal 3, the rotation speed of the pump 44 may become excessive, and the driving noise of the pump 44 in this case may be annoying to the driver. Furthermore, as long as the driver continues to depress the brake pedal 3, the driving of the pump 44 continues, and the load on the pump 44 increases significantly.

[0088] At time t15, when the depression amount of the brake pedal 3 becomes constant, the driving of the pump 44 of the brake fluid pressure control unit 30 is stopped, and the brake fluid pressure P_whl is maintained. Accordingly, the brake torque T_act is also maintained at a constant value. Thereafter, at time t16, when the regenerative brake torque T_reg begins to decrease as the vehicle decelerates, the pump 44 is driven again while the degree of opening of the circuit control valve 36 is reduced in order to compensate for the decrease in regenerative brake torque T_reg with the brake fluid pressure P_whl.

[0089] In section β from time t16 onwards, the brake fluid pressure P_whl increases, but the brake fluid corresponding to the increase is drawn from the master cylinder 5, causing the master cylinder pressure P_mc to decrease. As a result, the pedal feeling of the driver who is depressing the brake pedal 3 suddenly becomes lighter, and the amount of operation of the brake pedal 3 increases, even though the driver does not intend to do so. Furthermore, the increase in the brake fluid pressure P_whl is insufficient due to the decrease in master cylinder pressure P_mc, so the deceleration decreases, even though the driver does not intend to do so.

[0090] After that, at time t17, when the regenerative brake torque T_reg becomes zero, the pump 44 is stopped again in the following section c, and the brake fluid pressure P_whl is maintained at a constant level. In section c, the brake torque T_act is generated by the brake fluid pressure P_whl.

[0091] As described above, according to the operation of the conventional add-on automatic brake torque control process, when the driver depresses the brake pedal 3 while ACC control is being executed, the driving noise of the pump 44 of the brake fluid pressure control unit 30 becomes noisy for the driver, and there is a risk of an excessive load on the pump 44. Furthermore, when the regenerative brake torque T_reg is replaced with the brake fluid pressure P_whl, the decrease in master cylinder pressure P_mc causes the driver's pedal feeling to suddenly become lighter, which may result in an unintended increase in the amount of brake pedal 3 operation or a decrease in deceleration.

[0092] 6 shows a reference example of a selection type that generates the brake torque T_act as the larger value of either the automatic brake request torque T_req_in or the driver request brake torque, rather than the add-on type, when the driver depresses the brake pedal while ACC control is being executed. The driver request brake torque is a value that is determined according to the amount of operation of the brake pedal 3 by the driver, and is reflected in the magnitude of the master cylinder pressure P_mc.

[0093] At time t21, after the execution of ACC control is started, in section a where the maximum regenerative torque T_reg_pot exceeds the automatic brake required torque T_req_in, the brake torque T_act is generated by the regenerative brake torque T_reg.

[0094] At time t22, when the automatic brake request torque T_req_in exceeds the maximum regenerative torque T_reg_pot, in the subsequent section b, the brake torque T_act is generated from the regenerative brake torque T_reg and the brake fluid pressure P_whl. Specifically, at time t22, the suction valve 34 of the brake fluid pressure control unit 30 is opened, the circuit control valve 36 is closed, and the pump 44 is driven to generate the brake fluid pressure P_whl equivalent to the torque that is insufficient for the automatic brake request torque T_req_in. At time t23, when the automatic brake request torque T_req_in becomes constant, the driving of the pump 44 is stopped and the brake fluid pressure P_whl is maintained at a constant level.

[0095] If the driver depresses the brake pedal 3 at time t24, when the brake torque T_act is selectively controlled, after the master cylinder pressure P_mc rises to the brake fluid pressure P_whl, the intake valve 34 is closed and the circuit control valve 36 is opened to generate the brake torque T_act with the brake fluid pressure P_whl. If the stiffness between the brake fluid pressure control unit 30 and the master cylinder 5 is high, even a slight operation of the brake pedal 3 will quickly raise the master cylinder pressure P_mc to the brake fluid pressure P_whl. Thereafter, in the section γ from time t24 to time t25, the regenerative brake torque T_reg is reduced as the master cylinder pressure P_mc rises, and the regenerative brake torque T_reg is replaced with the brake fluid pressure P_whl.

[0096] When the brake torque T_act is controlled by the selective method, brake fluid is not supplied to the wheel cylinders even if the master cylinder pressure P_mc increases until the master cylinder pressure P_mc exceeds the automatic brake request torque T_req_in. Therefore, the rate at which the master cylinder pressure P_mc increases is faster than when the brake torque T_act is controlled by the add-on method. As a result, the driver feels a large reaction force immediately after depressing the brake pedal 3. If the reaction force from the brake pedal 3 becomes large, some drivers may find it difficult to brake further. Furthermore, because the magnitude of the reaction force from the brake pedal 3 depends on the brake fluid pressure P_whl, i.e., the automatic brake request torque T_req_in or the regenerative brake torque T_reg, the pedal feeling may vary each time.

[0097] Furthermore, when the brake torque T_act is selectively controlled, the regenerative brake torque T_reg needs to be reduced in accordance with the increase in the master cylinder pressure P_mc in the section γ from time t24 to time t25. This reduces the regenerative efficiency and may cause the driver to feel uncomfortable because the deceleration does not increase even though the driver has started to depress the brake pedal 3.

[0098] (2-2-2. First Example of This Embodiment) Next, a first example of the control process of the vehicle braking control device 150 according to this embodiment will be described.

[0099] FIG. 7 is an explanatory diagram showing the operation of a first example. The braking control device 150 of a vehicle according to this embodiment generates a brake torque T_act by an add-on system when the driver depresses the brake pedal during ACC control. FIG. 7 shows the automatic brake request torque T_req_in, the brake torque T_act, the regenerative brake torque T_reg, the brake fluid pressure P_whl, the master cylinder pressure P_mc, the virtual master cylinder pressure P_mc_vrt, the operating states of the pump (pmp) 44, the intake valve (HSV) 34, and the circuit control valve (USV) 36 of the brake fluid pressure control unit (ESP) 20, and the relative displacement amount d_str of the valve body 15 of the electric brake booster 10. For ease of understanding, in FIG. 7, the values ​​of the fluid pressure (Prs) and the brake torque (Trq) are shown on the same scale, and the hydraulic brake torque T_hyd is shown in terms of the brake fluid pressure P_whl.

[0100] At time t31, after the execution of ACC control is started, in section a where the maximum regenerative torque T_reg_pot exceeds the automatic brake request torque T_req_in, the brake torque T_act is generated by the regenerative brake torque T_reg.

[0101] At time t32, when the automatic brake request torque T_req_in exceeds the maximum regenerative torque T_reg_pot, in the subsequent section b, the brake torque T_act is generated from the regenerative brake torque T_reg and the brake fluid pressure P_whl. Specifically, at time t32, the suction valve 34 of the brake fluid pressure control unit 30 is opened, the circuit control valve 36 is closed, and the pump 44 is driven to generate the brake fluid pressure P_whl equivalent to the torque that is insufficient for the automatic brake request torque T_req_in. At time t33, when the automatic brake request torque T_req_in becomes constant, the driving of the pump 44 is stopped and the brake fluid pressure P_whl is maintained at a constant level.

[0102] In this embodiment, in the section δ from time t32 to time t33 when the brake fluid pressure P_whl is increased by the drive of the brake fluid pressure control unit 30, the electric motor 11 is rotated forward in advance, even before the driver depresses the brake pedal, to offset the valve body 15 toward the master cylinder 5. The relative displacement d_str at this time increases as the brake fluid pressure P_whl increases. After the relative displacement d_str reaches the maximum offset d_ofs_max, the relative displacement d_str is maintained at the maximum offset d_ofs_max.

[0103] Thereafter, at time t34, when the driver depresses the brake pedal 3, the suction valve 34 is closed and the circuit control valve 36 is opened. Furthermore, during a section ε in which the amount of operation of the brake pedal 3 increases from time t34 to time t35, the offset state between the valve body 15 and the plunger 16 is used as a reference position, and as the plunger 16 advances due to the increase in the amount of operation of the brake pedal 3, the electric motor 11 is driven to rotate in the forward direction based on the relative displacement d_str between the valve body 15 and the plunger 16. This causes the master cylinder pressure P_mc to increase, and brake fluid is supplied from the master cylinder 5 to the brake fluid pressure control unit 30.

[0104] At this time, in this embodiment, the brake torque T_act is controlled by the add-on system, so the brake fluid supplied from the master cylinder 5 is supplied to the wheel cylinders via the brake fluid pressure control unit 30. If the rigidity between the brake fluid pressure control unit 30 and the master cylinder 5 is high, the master cylinder pressure P_mc quickly rises to the brake fluid pressure P_whl_org with even a slight operation of the brake pedal 3. After time t34, the brake fluid pressure P_whl becomes the sum of the brake fluid pressure P_whl_org generated by the operation of the brake fluid pressure control unit 30 and the virtual master cylinder pressure P_mc_vir that rises due to the driver's operation of the brake pedal 3.

[0105] At this time, the intake valve 34 is closed and the circuit control valve 36 is open, so the master cylinder pressure P_mc is equal to the brake fluid pressure P_whl. However, the output torque of the electric motor 11, which corresponds to the relative displacement d_str (=maximum offset d_ofs_max) of the valve body 15 when the driver begins to depress the brake pedal 3, serves as a force to assist the driver's depressing force on the brake pedal 3, and therefore the reaction force of the brake pedal 3 felt by the driver corresponds to the virtual master cylinder pressure P_mc_vir that increases due to the driver's operation of the brake pedal 3.

[0106] At time t35, when the amount of operation of the brake pedal 3 becomes constant, the amount of rotation of the electric motor 11 is maintained, thereby maintaining the position of the valve body 15 and maintaining the brake fluid pressure P_whl. Accordingly, the brake torque T_act is also maintained at a constant value. Thereafter, at time t36, when the regenerative brake torque T_reg begins to decrease as the vehicle decelerates, the suction valve 34 of the brake fluid pressure control unit 30 is opened again, the circuit control valve 36 is closed again, and the operation of the pump 44 is resumed in order to compensate for the decrease in regenerative brake torque T_reg with the brake fluid pressure P_whl.

[0107] In the section ζ from time t36 onwards, the brake fluid pressure P_whl increases, while the brake fluid corresponding to the increase is drawn from the master cylinder 5, causing the master cylinder pressure P_mc to decrease. At this time, in this embodiment, the relative displacement amount d_str (=maximum offset amount d_ofs_max) of the valve body 15, which was previously offset in the forward direction, is reduced in accordance with the decrease in the master cylinder pressure P_mc. Specifically, the electric motor 11 of the electric brake booster 10 is driven to rotate in the reverse direction, and the valve body 15 moves backward relative to the plunger 16. This prevents the driver's pedal feeling from becoming lighter due to a decrease in the master cylinder pressure P_mc and prevents an unintended decrease in the driver-requested brake torque. Furthermore, because the drive of the brake fluid pressure control unit 30 does not affect the reaction force of the brake pedal 3 felt by the driver, there is no need to estimate the driver-requested brake torque.

[0108] After that, at time t37, when the regenerative brake torque T_reg becomes zero, the pump 44 is stopped again in the following section c, and the brake fluid pressure P_whl is maintained at a constant level. In section c, the brake torque T_act is generated by the brake fluid pressure P_whl. Note that in section c, the drive of the electric motor 11 is controlled in response to the driver's operation of the brake pedal 3, and the brake fluid pressure P_whl is adjusted so that the relative displacement amount d_str between the valve body 15 and the plunger 16 at time t37 is maintained.

[0109] FIG. 8 shows a flowchart of a first example of the control process of the vehicle braking control device 150 according to this embodiment. First, when the automatic braking function of the ACC becomes active, the motor control device 130 regeneratively drives the traction motor 121 and starts increasing the regenerative braking torque T_reg (step S11). Specifically, when a braking request signal S_brk due to ACC control is received from the driving assistance device 110, the regenerative braking target torque setting unit 131 of the motor control device 130 sets the automatic braking request torque T_req_in to the regenerative braking target torque T_reg_tgt. However, when the automatic braking request torque T_req_in exceeds the maximum regenerative torque T_reg_pot of the traction motor 121, the regenerative braking target torque setting unit 131 sets the maximum regenerative torque T_reg_pot to the regenerative braking target torque T_reg_tgt. The control unit 133 of the motor control device 130 controls the drive of the inverter 123 based on the set regenerative braking target torque T_reg_tgt, thereby generating the regenerative braking torque T_reg.

[0110] Next, the hydraulic pressure control device 90 determines whether the automatic brake required torque T_req_in exceeds the maximum regenerative torque T_reg_pot (step S13). If the automatic brake required torque T_req_in is equal to or less than the maximum regenerative torque T_reg_pot (S13 / No), the process returns to step S11 and the determination in step S13 is repeated until the automatic brake required torque T_req_in exceeds the maximum regenerative torque T_reg_pot.

[0111] On the other hand, if the automatic brake request torque T_req_in exceeds the maximum regenerative torque T_reg_pot (S13 / Yes), the hydraulic pressure control device 90 starts increasing the brake hydraulic pressure P_whl (step S15). Specifically, the hydraulic brake target torque setting unit 91 of the hydraulic pressure control device 90 sets the hydraulic brake target torque T_hyd_tgt to a value obtained by subtracting the regenerative brake torque T_reg from the automatic brake request torque T_req_in transmitted from the driving assistance device 110. The control unit 93 of the hydraulic pressure control device 90 controls the operation of the brake hydraulic pressure control unit 30 based on the set hydraulic brake target torque T_hyd_tgt. The control unit 93 closes the circuit control valve 36 of the brake hydraulic pressure control unit 30, opens the suction valve 34, and drives the pump 44.

[0112] Furthermore, the booster control device 100 offsets the valve body 15 of the electric brake booster 10 toward the master cylinder 5 in advance before the driver depresses the brake pedal 3 in accordance with the increase in the brake fluid pressure P_whl (step S17). Specifically, the control unit 101 of the booster control device 100 rotates the electric motor 11 in the forward direction in accordance with the increasing rate of the brake fluid pressure P_whl transmitted from the brake fluid pressure control unit 30, and moves the valve body 15 forward within a range not exceeding the maximum offset amount d_ofs_max.

[0113] Next, the booster control device 100 determines whether the relative displacement amount d_str between the valve body 15 and the plunger 16 has reached the maximum offset amount d_ofs_max (step S19). The booster control device 100 repeats the determination in step S19 until the relative displacement amount d_str between the valve body 15 and the plunger 16 reaches the maximum offset amount d_ofs_max, and if the relative displacement amount d_str between the valve body 15 and the plunger 16 has reached the maximum offset amount d_ofs_max (S19 / Yes), the booster control device 100 stops driving the electric motor 11 and holds the relative displacement amount d_str between the valve body 15 and the plunger 16 at the maximum offset amount d_ofs_max (step S21).

[0114] Next, the booster control device 100 determines whether or not the brake pedal 3 has been depressed by the driver (step S23). For example, the control unit 101 of the booster control device 100 determines whether or not the relative displacement amount d_str detected by the displacement sensor 80 has decreased below the maximum offset amount d_ofs_max. Whether or not the brake pedal 3 has been depressed by the driver may be determined based on the output of a sensor that detects the depression force on the brake pedal 3.

[0115] The booster control device 100 repeats the determination in step S23 until it is determined that the brake pedal 3 has been depressed by the driver. If the brake pedal 3 has been depressed (S23 / Yes), the hydraulic control device 90 closes the suction valve 34 of the brake hydraulic pressure control unit 30, opens the circuit control valve 36, and stops the pump 44. The booster control device 100 also controls the drive of the electric motor 11 so as to maintain the relative displacement d_str between the valve body 15 and the plunger 16 at the maximum offset d_ofs_max (step S25). As a result, the valve body 15 moves further forward, increasing the master cylinder pressure P_mc, and brake fluid is supplied to the wheel cylinders via the brake hydraulic pressure control unit 30, increasing the brake hydraulic pressure P_whl.

[0116] Next, the hydraulic pressure control device 90 determines whether the regenerative braking torque T_reg has started to decrease as the vehicle decelerates, based on the information on the regenerative braking torque T_reg transmitted from the motor control device 130 (step S27). The hydraulic pressure control device 90 repeats the determination in step S27 until the regenerative braking torque T_reg has started to decrease, and if the regenerative braking torque T_reg has started to decrease (S27 / Yes), it closes the circuit control valve 36 and opens the suction valve 34, and drives the pump 44 to increase the brake hydraulic pressure P_whl (step S29). At this time, the hydraulic pressure control device 90 increases the brake hydraulic pressure P_whl to compensate for the decrease in the regenerative braking torque T_reg.

[0117] Next, the booster control device 100 determines whether the master cylinder pressure P_mc is lower than the virtual master cylinder pressure P_mc_vrt (step S31). If the master cylinder pressure P_mc is lower than the virtual master cylinder pressure P_mc_vrt (S31 / Yes), the booster control device 100 reduces the relative displacement amount d_str of the valve body 15 that has been advanced toward the master cylinder 5 (step S33). The booster control device 100 reduces the relative displacement amount d_str of the valve body 15 in accordance with the master cylinder pressure P_mc that is reduced by the driving of the brake fluid pressure control unit 30.

[0118] Next, the hydraulic pressure control device 90 determines whether the regenerative brake torque T_reg has become zero (step S35). If the master cylinder pressure P_mc is not lower than the virtual master cylinder pressure P_mc_vrt in step S31 (S31 / No), the hydraulic pressure control device 90 skips the processing of step S33 and determines whether the regenerative brake torque T_reg has become zero (step S35).

[0119] If the regenerative brake torque T_reg has not become zero (S35 / No), the process returns to step S29, and the processes from step S29 to step S35 are repeated until the regenerative brake torque T_reg becomes zero. On the other hand, if the regenerative brake torque T_reg has become zero (S35 / Yes), the booster control device 100 stops the reverse rotation drive of the electric motor 11 and controls the drive of the electric motor 11 so as to maintain the relative displacement amount d_str at that time. As a result, the brake fluid pressure P_whl is thereafter adjusted in accordance with the amount of operation of the brake pedal 3 by the driver.

[0120] As described above, according to the first example of the control processing of the vehicle braking control device 150 of this embodiment, when automatic brake control of the ACC is executed in an add-on manner, the regenerative brake torque T_reg is used preferentially, and the brake fluid pressure P_whl is generated when the automatic brake request torque T_req_in exceeds the maximum regenerative torque T_reg_pot. At this time, in accordance with the increase in brake fluid pressure P_whl, the valve body 15 of the electric brake booster 10 is advanced (offset) toward the master cylinder 5 before the driver depresses the brake pedal 3. Furthermore, when the driver subsequently depresses the brake pedal, the drive of the electric brake booster 10 is controlled to maintain the relative displacement amount d_str in the offset state. Therefore, the output torque of the electric motor 11, which has been offset in advance, serves as a force to supplement the driver's depressing force on the brake pedal 3, thereby preventing the reaction force of the brake pedal 3 felt by the driver from becoming excessive.

[0121] In addition, when the brake fluid pressure P_whl is increased in response to the driver's depression of the brake pedal 3, the brake fluid pressure control unit 30 is not driven, thereby reducing noise caused by the driving sound of the pump 44 and alleviating the load on the pump 44.

[0122] (2-2-3. Second Example of This Embodiment) Next, a second example of the control process of the vehicle braking control device 150 according to this embodiment will be described. The second example is an example in which ACC control is performed when the maximum regenerative torque T_reg_pot is 0. This second example can also be applied to vehicles that are not equipped with a regenerative braking function.

[0123] FIG. 9 is an explanatory diagram showing the operation of the second example, and corresponds to FIG. 7 shown in the first example. When ACC control starts to be executed at time t41, the brake torque T_act is generated by the brake fluid pressure P_whl because the generatable regenerative brake torque T_reg is zero. Specifically, at time t41, the intake valve 34 of the brake fluid pressure control unit 30 is opened, the circuit control valve 36 is closed, and the pump 44 is driven to generate the brake fluid pressure P_whl corresponding to the automatic brake request torque T_req_in. When the automatic brake request torque T_req_in becomes constant at time t42, the pump 44 is stopped and the brake fluid pressure P_whl is maintained constant.

[0124] In the second example, in the section η from time t41 to time t42 when the brake fluid pressure P_whl rises due to the operation of the brake fluid pressure control unit 30, as in the section δ in the first example, the electric motor 11 is rotated forward in advance to advance (offset) the valve body 15 toward the master cylinder 5 even before the driver depresses the brake pedal 3.

[0125] Thereafter, at time t43, when the driver depresses the brake pedal 3, the suction valve 34 is closed and the circuit control valve 36 is opened. Furthermore, in the section θ from time t43 to time t44 in which the amount of operation of the brake pedal 3 increases, similar to the section ε in the first example, the offset state between the valve body 15 and the plunger 16 is used as a reference position, and as the plunger 16 advances due to the increase in the amount of operation of the brake pedal 3, the electric motor 11 is driven to rotate in the forward direction based on the relative displacement d_str between the valve body 15 and the plunger 16. This increases the master cylinder pressure P_mc, and brake fluid is supplied from the master cylinder 5 to the brake fluid pressure control unit 30.

[0126] In the second example, as in the first example, even a slight operation of the brake pedal 3 causes the master cylinder pressure P_mc to quickly rise to the brake fluid pressure P_whl_org. After time t44, the brake fluid pressure P_whl is the sum of the brake fluid pressure P_whl_org generated by the operation of the brake fluid pressure control unit 30 and the virtual master cylinder pressure P_mc_vir that rises in response to the driver's operation of the brake pedal 3. At this time, the intake valve 34 is closed and the circuit control valve 36 is open, so the master cylinder pressure P_mc is equal to the brake fluid pressure P_whl. However, the output torque of the electric motor 11 corresponding to the relative displacement d_str (=maximum offset d_ofs_max) of the valve body 15 when the driver begins to press the brake pedal 3 serves as a force to assist the driver's depression force on the brake pedal 3. Therefore, the reaction force of the brake pedal 3 felt by the driver corresponds to the virtual master cylinder pressure P_mc_vir that rises in response to the driver's operation of the brake pedal 3. After time t44 when the amount of operation of the brake pedal 3 becomes constant, the brake fluid pressure P_whl is maintained at a constant level.

[0127] FIG. 10 shows a flowchart of the second example. First, when the automatic braking function of the ACC becomes active, the hydraulic control device 90 starts increasing the brake hydraulic pressure P_whl (step S16). Specifically, the hydraulic brake target torque setting unit 91 of the hydraulic control device 90 sets the automatic brake request torque T_req_in transmitted from the driving assistance device 110 as the hydraulic brake target torque T_hyd_tgt, and the control unit 93 controls the operation of the brake hydraulic pressure control unit 30 based on the set hydraulic brake target torque T_hyd_tgt. The control unit 93 closes the circuit control valve 36 of the brake hydraulic pressure control unit 30 and opens the suction valve 34, and drives the pump 44.

[0128] Thereafter, the booster control device 100 and the hydraulic pressure control device 90 execute the same processes as those in steps S17 to S25 in the first example.

[0129] As described above, according to the second example of the control processing of the vehicle braking control device 150 of this embodiment, even when the regenerative brake torque T_reg cannot be used, when the brake fluid pressure P_whl is generated in accordance with the automatic brake request torque T_req_in, the valve body 15 of the electric brake booster 10 is advanced (offset) toward the master cylinder 5 before the driver depresses the brake pedal 3. Furthermore, when the driver subsequently depresses the brake pedal 3, the drive of the electric brake booster 10 is controlled to maintain the relative displacement amount d_str in the offset state. Therefore, the output torque of the electric motor 11, which has been offset in advance, serves as a force that supplements the driver's depressing force on the brake pedal 3, making it possible to prevent the reaction force of the brake pedal 3 felt by the driver from becoming excessive.

[0130] In addition, when the brake fluid pressure P_whl is increased in response to the driver's depression of the brake pedal 3, the brake fluid pressure control unit 30 is not driven, thereby reducing noise caused by the driving sound of the pump 44 and alleviating the load on the pump 44.

[0131] <3. Effects> As described above, according to the vehicle braking control device 150 of this embodiment, when executing automatic brake control of the ACC, the valve body 15 of the electric brake booster 10 is advanced (offset) toward the master cylinder 5 in advance in accordance with the increase in brake fluid pressure P_whl even before the driver depresses the brake pedal 3. Thereafter, when the driver depresses the brake pedal 3, the vehicle braking control device 150 controls the drive of the electric brake booster 10 so as to maintain the relative displacement amount d_str (=maximum offset amount d_ofs_max) in the offset state. Therefore, the output torque of the electric motor 11, which has been offset in advance, serves as a force that supplements the driver's depressing force on the brake pedal 3, making it possible to prevent the reaction force of the brake pedal 3 felt by the driver from becoming excessive.

[0132] Furthermore, the vehicle braking control device 150 according to this embodiment does not drive the brake fluid pressure control unit 30 when increasing the brake fluid pressure P_whl in response to the driver's depression of the brake pedal 3. This reduces noise caused by the driving sound of the pump 44 and also reduces the load on the pump 44.

[0133] Furthermore, the vehicle braking control device 150 according to this embodiment generates brake torque T_act in an add-on manner when the driver depresses the brake pedal 3 while the ACC automatic brake control is being executed. Therefore, the brake torque T_act increases as the driver depresses the brake pedal 3, thereby making it possible to suppress any discomfort felt by the driver.

[0134] Furthermore, according to the vehicle braking control device 150 of this embodiment, the regenerative brake torque T_reg can be utilized to the maximum extent possible while the automatic brake control of the ACC is being executed, and a decrease in regeneration efficiency can be prevented.

[0135] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications or alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0136] For example, the above embodiment is a braking control device applicable to an electric vehicle or a hybrid electric vehicle equipped with a drive motor as a drive source for the vehicle, but the present invention is not limited to such an example. Even in a vehicle such as an engine vehicle that cannot generate regenerative braking torque, the same effects as those of the above embodiment can be obtained by controlling the drive of the electric brake booster 10 and the brake fluid pressure control unit 30 according to the second example above. [Explanation of symbols]

[0137] 1...hydraulic brake system, 3...brake pedal, 5...master cylinder, 6...primary piston, 7...secondary piston, 10...electric brake booster, 11...electric motor, 15...valve body, 30...brake fluid pressure control unit, 90...hydraulic pressure control device, 100...booster control device, 121...drive motor, 130...motor control device, 150...braking control device

Claims

1. a control unit (90, 100) for controlling a hydraulic brake system (1) including an electric brake booster (10) that drives an electric motor (11) to advance a valve body (15) and advance a piston (6, 7) of a master cylinder (5) to boost a brake pedal (3) depression force by a driver and pressurize brake fluid in the master cylinder (5), and a brake fluid pressure control unit (30) that adjusts brake fluid pressure (P_whl) generated in each wheel; a control unit (90, 100) that sets an automatic brake request torque (T_req_in) to a target brake torque (T_tgt) while receiving a braking request signal (S_brk) from an automatic brake function, and that, when the driver depresses the brake pedal (3) while receiving the braking request signal (S_brk) from the automatic brake function, sets the sum of the automatic brake request torque (T_req_in) and a driver request brake torque (T_dri) to the target brake torque (T_tgt) to execute brake control; The control unit (90, 100) By receiving a braking request signal (S_brk) from the automatic brake function, the electric brake booster (10) is activated in advance before the driver depresses the brake pedal (3), and the valve body (15) of the electric brake booster (10) is advanced toward the master cylinder (5) within a range that does not increase the pressure (P_mc) in the master cylinder (5). A vehicle braking control device characterized by:

2. The control unit (90, 100) Upon receiving a braking request signal (S_brk) from the automatic brake function, before the driver depresses the brake pedal (3), the brake fluid pressure control unit (30) is driven to increase the brake fluid pressure (P_whl) and move the valve body (15) of the electric brake booster (10) forward toward the master cylinder (5) within a range that does not increase the pressure (P_mc) in the master cylinder (5).

2. The vehicle brake control device according to claim 1.

3. The vehicle braking control device (150) The vehicle further includes a motor control device (130) that regeneratively drives the motor (121) during deceleration to generate a regenerative brake torque (T_reg), The control unit (90, 100, 130) By receiving a braking request signal (S_brk) from the automatic brake function, the regenerative brake torque (T_reg) is generated, and when the regenerative brake torque (T_reg) reaches an upper limit (T_reg_pot) before the driver depresses the brake pedal (3), the brake fluid pressure control unit (30) is driven to increase the brake fluid pressure (P_whl) and move the valve body (15) of the electric brake booster (10) toward the master cylinder (5) within a range that does not increase the pressure (P_mc) in the master cylinder (5).

3. The vehicle brake control device according to claim 2.

4. The control unit (90, 100) When the driver depresses the brake pedal (3) while receiving a braking request signal (S_brk) from the automatic brake function, the driving of the brake fluid pressure control unit (30) is stopped, and the pressure (P_mc) in the master cylinder (5) is increased to increase the brake fluid pressure (P_whl).

4. The vehicle brake control device according to claim 1, wherein the brake control device is a brake control device for a vehicle.

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