CN114379523A - Vehicle brake control device - Google Patents

Abstract

Provided is a brake control device for a vehicle, which can reduce the possibility that the deceleration of the vehicle due to the automatic braking function of an ACC will continue to exceed a predetermined limit value for a long time. A brake control device for a vehicle is provided with target brake torque setting units (91, 101) and control units (93, 103), wherein the target brake torque setting units (91, 101) set a target brake torque (T _ out) on the basis of information (T _ req _ in) of a brake request, the information (T _ req _ in) of the brake request being set on the basis of a target vehicle-to-vehicle distance between the vehicle and a preceding vehicle, the control units (93, 103) control the braking force of the vehicle on the basis of the target brake torque (T _ out), and the target brake torque setting units (91, 101) set a limit brake torque (T _ lim) having a value smaller than an instruction brake torque (T _ req _ in) to the target brake torque (T _ out) when a deceleration (Ax) of the vehicle exceeds a predetermined limit value (Ax _ lim).

Description

Vehicle brake control device

Technical Field

The present invention relates to a brake control device for a vehicle.

Background

Recent vehicles are equipped with an automatic braking function. The automatic braking function is as follows: a driving Assistance device, also called ADAS (Advanced Driver-Assistance System), transmits an instruction of a braking request to a brake hydraulic pressure control device based on information on the front side of the vehicle detected by a camera or a sensor mounted on the vehicle, and automatically pressurizes a brake hydraulic pressure. As the automatic braking function, there are known an acc (adaptive Cruise control) automatic braking function for automatically moving a vehicle while maintaining a vehicle-to-vehicle distance from a preceding vehicle to a target vehicle-to-vehicle distance, and an emergency braking function for avoiding a collision with an obstacle or the like or for reducing an impact.

Specifically, in the automatic braking function, the driving assistance device determines whether braking is necessary or not and calculates the necessary braking torque based on information detected by the camera and the sensor, and transmits a signal indicating information on the braking request and the braking torque to the brake hydraulic pressure control device. The brake hydraulic pressure control device receives a signal indicating a braking request and information on braking torque from the driving assistance device, switches the control mode in accordance with the type of the automatic braking function or the emergency braking function of the ACC device, converts the received information on braking torque into brake hydraulic pressure, and transmits a drive command to an actuator for adjusting the brake hydraulic pressure. As a result, the electric motor provided in the brake fluid pressure control device operates, and the brake fluid pressure of each wheel rises to generate a braking force.

Patent document 1: japanese patent laid-open No. 2018-227532.

In the automatic braking function of the ACC, unlike the emergency braking function, control is required so that the deceleration does not exceed a predetermined limit value as much as possible in order to suppress unstable behavior of the vehicle body due to sudden deceleration of the vehicle. In contrast, it is conceivable to set an upper limit to the braking torque set by the driving assistance device, but since the braking force generated by the vehicle is affected by various factors, if only the braking torque set by the driving assistance device is limited, the deceleration may exceed the limit value for a long time.

Disclosure of Invention

The present invention has been made in view of the above problems, and provides a brake control device for a vehicle that can reduce the possibility that the deceleration of the vehicle due to the automatic braking function of the ACC continues to exceed a predetermined limit value for a long time.

In order to solve the above-described problems, according to an aspect of the present invention, there is provided a brake control device for a vehicle, including a target brake torque setting unit that sets a target brake torque based on information of a brake request set based on a target vehicle-to-vehicle distance between the vehicle and a preceding vehicle, and a control unit that controls a brake force of the vehicle based on the target brake torque, wherein the target brake torque setting unit sets a limit brake torque having a smaller value than the brake torque corresponding to the information of the brake request as the target brake torque when a deceleration of the vehicle exceeds a predetermined limit value.

Effects of the invention

As described above, according to the present invention, it is possible to reduce the possibility that the deceleration of the vehicle exceeds the predetermined limit value for a long time due to the automatic braking function of the ACC.

Drawings

Fig. 1 is an explanatory diagram showing a configuration example of a brake system to which a vehicle brake control device according to embodiment 1 of the present invention can be applied.

Fig. 2 is a block diagram showing a configuration example of a brake hydraulic pressure control device constituting the vehicle brake control device of the embodiment.

Fig. 3 is a flowchart showing an example of an automatic braking control process performed by the vehicle braking control device according to the embodiment.

Fig. 4 is a flowchart showing an example of a target braking torque setting process performed by the vehicle braking control device according to the embodiment.

Fig. 5 is an explanatory diagram illustrating an operation of the vehicle brake control device according to the embodiment.

Fig. 6 is a block diagram showing a configuration example of an assist device control device constituting the vehicle brake control device of the embodiment.

Detailed Description

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the present specification and the drawings, the same reference numerals are given to components having substantially the same functional configuration, and overlapping description is omitted.

< 1. embodiment No. 1 >

< 1-1. structural example of brake System >

First, a configuration example of a brake system to which a vehicle brake control device according to embodiment 1 of the present invention can be applied will be described with reference to fig. 1.

Fig. 1 is a schematic diagram showing a configuration example of a brake system 1 of a vehicle. A brake system 1 of a vehicle shown in fig. 1 is a brake system for a four-wheeled vehicle. The brake system 1 includes two brake systems, each of which is configured to control braking force by combining one front wheel and one rear wheel.

The brake system 1 may be a so-called X-pipe type brake system in which two brake systems each control braking force by using a pair of a front wheel on the left and right and a rear wheel located diagonally to the front wheel. Alternatively, the brake system 1 may be a so-called H-pipe type brake system in which one system brakes the left front and rear wheels and the other system brakes the right front and rear wheels. The brake system may be a brake system of a vehicle other than a four-wheel vehicle.

The brake system 1 includes a booster 10, a master cylinder 14, and a brake hydraulic unit 20. The brake system 1 further includes a hydraulic control device 90 that controls the brake hydraulic unit 20, and a booster control device 100 that controls the booster 10. A part or all of the hydraulic control device 90 and the booster control device 100 are constituted by a microcomputer or a microprocessor Unit including an arithmetic Processing device such as a Central Processing Unit (CPU), for example. A part or all of the hydraulic control device 90 and the booster control device 100 may be configured to be updatable, such as firmware, or may be a program module or the like that is executed in accordance with a command from a central processing unit or the like.

The hydraulic control device 90 and the booster control device 100 are configured to be able to communicate with each other via a communication bus 120 such as a control Area Network (Controller Area Network), for example. The hydraulic control device 90 and the booster control device 100 are configured to be able to communicate with the driving assistance device 110 via a communication bus 120. The driving assistance device 110 is configured to be able to acquire information detected by a sensor device 111 for detecting information of other vehicles, pedestrians, bicycles, obstacles, and the like in front of the vehicle, and an environment in front of the vehicle. The sensor machine 111 comprises, for example, at least one of a camera or radar, a lidar.

The driving assistance device 110 is configured to be capable of executing at least ACC control for automatically traveling the host vehicle while maintaining the inter-vehicle distance between the host vehicle and the preceding vehicle at the target inter-vehicle distance. In the present embodiment, the driving assistance device 110 is configured to be able to execute ACC control for avoiding a collision between the host vehicle and another vehicle or an obstacle or for reducing a shock at the time of the collision. The driving assistance device 110 is configured by, for example, a microcomputer or a microprocessor Unit including an arithmetic Processing device such as a central Processing Unit (cpu) or a Graphics Processing Unit (GPU). Some or all of the driving assistance device 110 may be configured to be updatable, such as firmware, or may be a program module or the like that is executed in accordance with a command from a central processing unit or the like.

In the brake system 1, the depression force applied to the brake pedal 11 is amplified by the booster 10 and transmitted to the master cylinder 14 as a hydraulic pressure generation source. A reservoir tank 60 for supplying brake fluid to the master cylinder 14 is attached to an upper portion of the master cylinder 14. In the master cylinder 14, a first chamber 47 and a second chamber 48, which are two pressurizing chambers partitioned by the first piston 43 and the second piston 44, are formed. In response to the depression operation of the brake pedal 11 by the driver, the first piston 43 and the second piston 44 are pressed, the brake fluid stored in the first chamber 47 and the second chamber 48 is pressurized, and the brake fluid is supplied into the brake fluid pressure unit 20.

The booster 10 is connected to a brake pedal 11 via an input shaft 16. The pedal force amplified by the booster 10 is transmitted to the master cylinder 14 via the push rod 13 abutting against the first piston 43. Due to the axial movement of the first piston 43, the second piston 44 also performs an axial movement. Thereby, the brake fluid in the first chamber 47 and the second chamber 48 is pressurized.

In the present embodiment, an electric booster driven by an electric motor is used as the booster 10. The electric motor may be, for example, a brushless DCDC motor including a stator as a fixed element and a rotor as a movable element. The electric motor operates by receiving electric power (electric current) supply controlled by the booster control device 100. The electric motor is a motor capable of performing forward rotation for advancing the push rod 13 and reverse rotation for retracting the push rod 13 by switching the flow of current. When the driver steps on the brake pedal 11, the booster control device 100 supplies electric power (current) to the stator of the electric motor, boosts the stepping force on the brake pedal 11, and transmits the boosted force to the master cylinder 14.

The 1 st and 2 nd hydraulic circuits 28, 30 extend from the first and second chambers 47, 48 of the master cylinder 14 to the hydraulic brakes 38a to 38d of the wheels RF, LR, LF, RR, respectively. The hydraulic circuit of the brake system 1 of the vehicle according to the present embodiment is of an X-type piping system, and brake fluid is supplied to the wheel cylinder of the hydraulic brake 38a of the right front wheel RF and the wheel cylinder of the hydraulic brake 38b of the left rear wheel LR via the 1 st hydraulic circuit 28. The brake fluid is supplied to the wheel cylinder of the hydraulic brake 38c of the front left wheel LF and the wheel cylinder of the hydraulic brake 38d of the rear right wheel RR via the 2 nd hydraulic circuit 30. Thus, the hydraulic brakes 38a to 38d can generate braking forces for the wheels RF, LR, LF, RR by hydraulic pressure.

The brake hydraulic unit 20 includes a 1 st hydraulic circuit 28 and a 2 nd hydraulic circuit 30 having the same configuration. Brake fluid is supplied from the master cylinder 14 to the 1 st and 2 nd hydraulic circuits 28 and 30. Hereinafter, the 1 st hydraulic circuit 28 will be briefly described, and the 2 nd hydraulic circuit 30 will not be described.

The 1 st hydraulic circuit 28 includes, as electromagnetic valves, a normally open and linearly controllable circuit control valve 36a, a normally closed and open/close controllable intake valve 34a, normally open and linearly controllable pressure increase valves (adjustment valves) 58aa and 58ba, and normally closed and open/close controllable pressure decrease valves 54aa and 54 ba. The 1 st hydraulic circuit 28 includes a pump 44a driven by a pump motor 96, a low pressure accumulator 71a, and a damper 73 a. In addition, the number of pumps 44a is not limited to one.

The 1 st pressure increasing valve 58aa and the 1 st pressure reducing 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 2 nd pressure increase valve 58ba and a 2 nd pressure decrease 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.

The 1 st pressure increasing valve 58aa of the right front wheel RF is provided between the circuit control valve 36a and the hydraulic brake 38a of the right front wheel RF. The 1 st pressure increasing valve 58aa, which is linearly controllable, continuously adjusts the flow rate of the brake fluid from the circuit control valve 36a side to the wheel cylinder side of the hydraulic brake 38a of the right front wheel RF. The 1 st pressure increasing valve 58aa includes a bypass flow path including a check valve that allows the brake fluid to flow from the hydraulic brake 38a side to the circuit control valve 36a side while restricting a reverse flow thereof in a state where the 1 st pressure increasing valve 58aa is closed.

The 1 st pressure reducing valve 54aa of the right front wheel RF is an electromagnetic valve capable of switching the valve only to a fully open or fully closed state, and is provided between the wheel cylinder of the hydraulic brake 38a of the right front wheel RF and the low pressure accumulator 71 a. The 1 st pressure reducing valve 54aa reduces the brake fluid supplied to the wheel cylinder of the hydraulic brake 38a of the right front wheel RF in the open state. The 1 st pressure reducing valve 54aa can adjust the flow rate of the brake fluid flowing from the wheel cylinder of the hydraulic brake 38a of the right front wheel RF to the low pressure reservoir 71a by intermittently repeating the opening and closing of the valve.

The 2 nd pressure increasing valve 58ba of the left rear wheel LR is provided between the circuit control valve 36a and the hydraulic brake 38b of the left rear wheel LR. The 2 nd pressure increase valve 58ba, which is linearly controllable, continuously adjusts the flow rate of the brake fluid from the circuit control valve 36a side toward the wheel cylinder side of the hydraulic brake 38b of the left rear wheel LR. The 2 nd pressure increasing valve 58ba is provided with a bypass flow path provided with a check valve which, in a state where the 2 nd pressure increasing valve 58ba is closed, allows the brake fluid to flow from the hydraulic brake 38b side to the circuit control valve 36a side, while restricting the flow in the reverse direction.

The 2 nd pressure reducing valve 54ba of the left rear wheel LR is an electromagnetic valve capable of switching the valve only to a fully open or fully closed state, and is provided between the wheel cylinder of the hydraulic brake 38b of the left rear wheel LR and the low pressure reservoir 71 a. The 2 nd pressure reducing valve 54ba reduces the brake fluid supplied to the wheel cylinder of the hydraulic brake 38b of the rear left wheel LR in the opened state. The 2 nd pressure reducing valve 54ba can adjust the flow rate of the brake fluid flowing from the wheel cylinder of the hydraulic brake 38b of the left rear wheel LR to the low pressure reservoir 71a by intermittently repeating the opening and closing of the valve.

The circuit control valve 36a is provided to communicate or shut off between the pressure increasing valves 58aa, 58ba and the master cylinder 14. The suction valve 34a is provided to communicate or cut off between the master cylinder 14 and the suction side of the pump 44 a. A hydraulic pressure sensor 24 is provided in a line between the master cylinder 14 and the circuit control valve 36a and the suction valve 34 a. These are the same as the constituent elements of the brake hydraulic unit 20, and therefore, detailed description thereof is omitted.

The 2 nd hydraulic circuit 30 controls the hydraulic brake 38c of the left front wheel LF and the hydraulic brake 38d of the right rear wheel RR. The 2 nd hydraulic circuit 30 is configured in the same manner as the 1 st hydraulic circuit 28, except that the wheel cylinder of the hydraulic brake 38a for the right front wheel RF is replaced with the wheel cylinder of the hydraulic brake 38c for the left front wheel LF, and the wheel cylinder of the hydraulic brake 38b for the left rear wheel LR is replaced with the wheel cylinder of the hydraulic brake 38d for the right rear wheel RR in the description of the 1 st hydraulic circuit 28.

In the braking system 1 configured as described above, when the host vehicle approaches too close to the preceding vehicle during execution of the ACC, the driving assistance device 110 generates a signal (hereinafter, also referred to as a "braking request signal") indicating a braking request for maintaining the inter-vehicle distance between the host vehicle and the preceding vehicle at a predetermined target inter-vehicle distance. In embodiment 1, the fluid pressure control device 90 that controls the brake fluid pressure unit 20 functions as a brake control device for a vehicle that: the braking force is controlled so that the deceleration of the vehicle does not continue to exceed a predetermined limit value for a long time by receiving a braking request signal transmitted from the driving assistance device 110.

< 1-2. brake control device (hydraulic control device) for vehicle

(1-2-1. structural example)

Fig. 2 is a block diagram showing a functional configuration related to automatic braking control of the ACC in the configuration of the brake system 1. In the present embodiment, the automatic braking control of the ACC line is performed by the driver assistance device 110 and the hydraulic pressure control device 90 communicating with each other, and the hydraulic pressure control device 90 controlling the brake hydraulic pressure unit 20.

The driving assistance device 110 determines whether braking is necessary or not and calculates a required braking request instruction value based on information detected by a sensor device 111 such as a camera, a radar, or a RiDAR during execution of the ACC, and transmits a braking request signal indicating information of the braking request and the braking request instruction value to the hydraulic control device 90. The indicated value of the braking request may be, for example, an indicated value of braking torque or an indicated value of brake fluid pressure. In the present embodiment, the following example will be explained: the driving assistance device 110 calculates an instruction value for the braking torque (hereinafter, also referred to as "indicated braking torque") T _ req _ in as information of an instruction value for the braking request, and transmits a braking request signal indicating the braking request S _ brk and the information of the indicated braking torque T _ req _ in to the hydraulic control device 90.

Specifically, the driving assistance device 110 obtains 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 the information detected by the sensor device 111. The driving assistance device 110 determines whether braking is necessary based on the information of the calculated inter-vehicle distance D and the calculated relative speed dV. For example, the driving assistance device 110 determines that braking is necessary when the inter-vehicle distance D between the host vehicle and the preceding vehicle is not sufficient for the braking start threshold D _ brk _ thr set in accordance with the vehicle speed V, the relative speed dV, and the target inter-vehicle distance D _ tgt of the host vehicle. The target inter-vehicle distance D _ tgt may be a variable value set in accordance with the vehicle speed V of the host vehicle. The method of determining whether braking is necessary or not by the driving assistance device 110 is not particularly limited.

The driving assistance device 110 calculates the indicated braking torque T _ req _ in based on the vehicle speed V, the relative speed dV, and the difference dD between the inter-vehicle distance D and the target inter-vehicle distance D _ tgt of the host vehicle. The speed of change of the inter-vehicle distance D in the case where the vehicle generates the braking torque differs depending on the relative speed dV. Further, the braking torque for decelerating the vehicle may differ depending on the vehicle speed V. Therefore, the driving assistance device 110 may calculate the indicated braking torque T _ req _ in by referring to map information in which the indicated braking torque T _ req _ in is set in advance in accordance with the vehicle speed V, the relative speed dV, and the difference dD between the vehicle distances. The method of calculating the indicated braking torque T _ req _ in by the driving assistance device 110 is not particularly limited.

The hydraulic control device 90 basically controls the driving of the brake hydraulic unit 20 to execute ABS control and ESP control. Further, the hydraulic pressure control device 90 sets the target braking torque T _ out based on the indicated braking torque T _ req _ in and converts the target braking torque T _ out into the target braking hydraulic pressure P _ tgt, controlling the driving of the brake hydraulic pressure unit 20, in the case where the braking request signal of the ACC has been received from the drive assist device 110. In the automatic braking control of the ACC, the hydraulic control device 90 drives at least the pump motor 96 of the brake hydraulic unit 20, and supplies brake fluid from the master cylinder 14 to the wheel cylinders of the respective wheels to increase the brake hydraulic pressure of the respective wheels, thereby generating the braking force of the vehicle.

The hydraulic control device 90 includes a target braking torque setting unit 91 and a control unit 93. The target braking torque setting unit 91 and the control unit 93 are functions realized by a microcomputer executing a program. The hydraulic control device 90 includes a drive circuit not shown in the figure and storage elements such as ram (random Access memory) and rom (read Only memory).

The hydraulic control device 90 is configured to be able to receive a braking request signal transmitted from the driving assistance device 110. The hydraulic control device 90 is configured to be able to acquire information on the acceleration G in the front-rear direction of the vehicle. The hydraulic control device 90 may obtain the information of the acceleration G by directly receiving the sensor signal from the wheel speed sensor provided in the vehicle and differentiating the detected value, or may obtain the information of the acceleration G transmitted from another control device via the communication bus 120.

The acceleration G of the vehicle calculated based on the detection value of the wheel speed sensor indicates a positive value in a state where the vehicle is accelerated in the forward direction. That is, the deceleration Ax of the vehicle means a negative acceleration G. Therefore, the deceleration Ax exceeding the predetermined limit value Ax _ lim means that the acceleration G is lower than a value obtained by inverting the positive and negative of the predetermined limit value Ax _ lim (positive value).

The target braking torque setting unit 91 is based on the driven assistance device 1The information indicating the braking torque T _ req _ in included in the braking request signal transmitted by 10 sets the target braking torque T _ out. The target braking torque setting unit 91 sets the target braking torque T _ out so that the deceleration Ax of the vehicle does not exceed the predetermined limit value Ax _ lim for a long time. The limit value Ax _ lim is an upper limit value of the deceleration Ax set to avoid instability of the vehicle behavior due to automatic braking control of the ACC, and is set to 4.8 to 5.0m/s, for example²A value within the range of (1).

Specifically, the target braking torque setting unit 91 sets the indicated braking torque T _ req _ in to the target braking torque T _ out when the deceleration Ax of the host vehicle is equal to or less than the predetermined limit value Ax _ lim. On the other hand, when the deceleration Ax exceeds the predetermined limit value Ax _ lim, the target braking torque setting unit 91 starts the braking torque limitation mode, calculates a limited braking torque T _ lim having a smaller value than the indicated braking torque T _ req _ in, and sets the limited braking torque T _ lim to the target braking torque T _ out. That is, the driving assistance device 110 calculates the indicated braking torque T _ req _ in (N seed) as a target value for decelerating the vehicle, and the target braking torque setting unit 91 uses the deceleration Ax (m/s) of the vehicle of different units, on the other hand²) Imposes a limit on the braking torque. Thus, even if the generated braking force is disturbed by the traveling conditions of the vehicle, the possibility that the deceleration Ax exceeds the limit value Ax _ lim for a long time is reduced, and the instability of the behavior of the vehicle body can be suppressed.

The calculation method of the limit braking torque T _ lim is not particularly limited. For example, the target braking torque setting unit 91 may calculate the limit braking torque T _ lim by reducing the command braking torque T _ req _ in at a constant reduction rate when the deceleration Ax of the vehicle exceeds the predetermined limit value Ax _ lim. Specifically, when the deceleration Ax of the vehicle exceeds a predetermined limit value Ax _ lim, the target braking torque setting unit 91 sets a limit braking torque T _ lim obtained by subtracting a predetermined constant correction value T _ x from the value of the indicated braking torque T _ req _ in as the target braking torque T _ out. The target braking torque setting unit 91 sets the limit braking torque T _ lim obtained by subtracting the correction value T _ x from the target braking torque T _ out of the previous cycle as the target braking torque T _ out for each subsequent calculation cycle. The correction value T _ x in this case is set to an appropriate value so as not to rapidly decrease the deceleration Ax. By obtaining the limit braking torque T _ lim in this way, the braking torque can be easily limited without increasing the calculation load of the hydraulic control device 90. Further, since the deceleration Ax of the vehicle is not rapidly decreased, the inter-vehicle distance D from the preceding vehicle can be prevented from becoming excessively small.

However, the calculation method of the limit braking torque T _ lim is not limited to the method of subtracting the constant correction value T _ x. For example, the correction value T _ x may be a value that varies according to the deceleration state of the vehicle. Specifically, the correction value T _ x may be set to a value that increases as the difference between the deceleration Ax of the vehicle and the predetermined limit value Ax _ lim increases. Thus, the deceleration Ax of the vehicle can be suppressed to the predetermined limit value Ax _ lim or less earlier than in the case where the constant correction value T _ x is subtracted.

In the present embodiment, the target braking torque setting unit 91 is configured to compare the deceleration Ax with the limit value Ax _ lim when the deceleration Ax of the vehicle exceeds the control start threshold value Ax _0 set to a value smaller than the limit value Ax _ lim, and to limit the braking torque when the deceleration Ax exceeds the limit value Ax _ lim. This reduces the calculation load on the hydraulic control device 90 during a period in which the deceleration Ax is small without limiting the braking torque.

The target braking torque setting unit 91 may start the braking torque limitation mode when the deceleration Ax of the vehicle exceeds the limit value Ax _ lim for a predetermined time t _ thr _ st or longer. Thus, the braking torque is not limited when the deceleration Ax exceeds the limit value Ax _ lim for an extremely short time, and the braking torque can be prevented from being limited more than necessary, and the vehicle-to-vehicle distance D from the preceding vehicle can be prevented from becoming excessively small. The predetermined time t _ thr _ st is set to an appropriate value in advance by simulation or the like.

The target braking torque setting unit 91 may start the braking torque limitation mode in a state where the deceleration Ax of the vehicle exceeds the limit value Ax _ lim, and then end the braking torque limitation mode in a state where the deceleration Ax is equal to or less than the limit value Ax _ lim for a predetermined time period t _ thr _ fn or longer. This makes it possible to delay the timing of ending the limitation of the braking torque, and to suppress the deceleration Ax equal to or smaller than the limitation value Ax _ lim from exceeding the limitation value Ax _ lim again due to the end of the limitation of the braking torque. The predetermined time t _ thr _ fn is set to an appropriate value in advance by simulation or the like.

After the braking torque limit mode is ended, the target braking torque setting unit 91 may hold the limited braking torque T _ lim and hold the limited braking torque T _ lim at the target braking torque T _ out during a period in which the indicated braking torque T _ req _ in output from the driving assistance device 110 is equal to or less than the target braking torque T _ out (i.e., the limited braking torque T _ lim) set in the previous calculation cycle at the time of ending the braking torque limit mode. Thus, when the braking torque limitation mode is ended, the target braking torque T _ out can be prevented from rapidly increasing, and the indicated braking torque T _ req _ in can be transitioned to the state in which the indicated braking torque T _ req _ in is set to the target braking torque T _ out without greatly changing the target braking torque T _ out.

Further, during execution of the ABS control or the ESP control, the deceleration Ax of the vehicle obtained by differentiating the detection value of the wheel speed sensor may become excessively large, and the reliability of the value of the deceleration Ax may be lowered. Therefore, the target braking torque setting unit 91 sets the target braking torque T _ out without using the information of the deceleration Ax when the ABS control or the ESP control is executed. For example, the target braking torque setting unit 91 compares the value of the indicated braking torque T _ req _ in output from the driving assistance device 110 with the value of the target braking torque T _ out set in the previous calculation cycle, and sets the smaller one as the target braking torque T _ out of the current calculation cycle.

The control unit 93 controls the driving of the brake hydraulic unit 20 based on the target braking torque T _ out set by the target braking torque setting unit 91. Thereby, the braking force of the vehicle is controlled. In the present embodiment, the control unit 93 calculates a target brake fluid pressure P _ tgt to be generated in each wheel based on the target brake torque T _ out, and controls the driving of the pump motor 96 of the brake fluid pressure unit 20.

For example, the control unit 93 may determine the target brake fluid pressure P _ tgt corresponding to the target brake torque T _ out by referring to map information in which a relationship between the target brake torque T _ out and the target brake fluid pressure P _ tgt is set in advance. The control unit 93 sets the target flow rate V _ tgt of the brake fluid supplied from the master cylinder 14 to the brake fluid pressure unit 20 based on the calculated target brake fluid pressure P _ tgt. For example, the control unit 93 may set the target flow rate V _ tgt of the 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 set in advance.

The control unit 93 may set the target flow rate V _ tgt corresponding to the difference dP between the current brake liquid pressure P _ act and the target brake liquid pressure P _ tgt. The current braking hydraulic pressure P _ act can use the pressure value detected by the hydraulic pressure sensor 24 instead. When a brake fluid pressure sensor that detects the brake fluid pressure of a certain wheel cylinder is provided in addition to the fluid pressure sensor 24, the pressure value detected by the brake fluid pressure sensor may be used instead of the fluid pressure sensor 24.

The control unit 93 outputs a control signal to the drive circuit of the pump motor 96 of the brake hydraulic unit 20 based on the set target flow rate V _ tgt, and drives the pumps 44a and 44 b. Thus, the brake fluid is supplied from the master cylinder 14 into the brake fluid pressure unit 20, and the brake fluid is supplied to the wheel cylinders of the respective wheels. As a result, the brake fluid pressure of each wheel rises, and the braking force of the vehicle is generated. As described above, in the braking torque limitation mode, since the braking torque is limited when the deceleration Ax of the vehicle exceeds the limit value Ax _ lim, there is a reduced possibility that the deceleration Ax exceeds the limit value Ax _ lim for a long time.

(1-2-2. action example)

Next, a specific operation example of the hydraulic control device 90 as a vehicle brake control device according to the present embodiment will be described.

Fig. 3 and 4 are flowcharts showing a braking control process executed by the hydraulic control device 90 during execution of the ACC line. Fig. 3 is a flowchart showing a main path of a brake control process executed by the hydraulic control device 90 during execution of the ACC line. Fig. 4 is a flowchart showing a route of the target braking torque setting process. The brake control process described below is always executed during execution of the ACC.

As shown in fig. 3, first, the target braking torque setting unit 91 of the hydraulic control device 90 determines whether or not a braking request signal has been received from the driving assistance device 110 (step S11). When the braking request signal is not received (S11/no), the target braking torque setting unit 91 ends the route and returns to the start. On the other hand, when the braking request signal is received (S11/yes), the target braking torque setting unit 91 sets the target braking torque T _ out based on the indicated braking torque T _ req _ in included in the braking request signal (step S13). The process of setting the target braking torque T _ out is performed according to the flowchart shown in fig. 4.

In the flowchart shown in fig. 4, "(n)" represents a value obtained or calculated in the current calculation cycle, and "(n-1)" represents a value calculated in the previous calculation cycle. First, the target braking torque setting unit 91 acquires information on the deceleration Ax (n) of the vehicle, and determines whether or not the deceleration Ax (n) exceeds the control start threshold Ax _0 (step S21). When the deceleration Ax (n) does not exceed the control start threshold Ax _0 (no at S21), the deceleration Ax is less likely to exceed the limit value Ax _ lim, and therefore the target braking torque setting unit 91 sets the indicated braking torque T _ req _ in (n) included in the braking request signal received from the driving assistance device 110 as it is to the target braking torque T _ out (n) (step S43).

On the other hand, when the deceleration Ax (n) exceeds the control start threshold Ax _0 (S21/yes), the target braking torque setting unit 91 calculates a difference da (n) obtained by subtracting the limit value Ax _ lim from the deceleration Ax (n) (step S23). Next, the target braking torque setting unit 91 determines whether or not the difference da (n) is a positive value (step S25). In step S25, it is determined whether or not the deceleration Ax (n) of the vehicle exceeds the limit value Ax _ lim.

When the difference da (n) is a positive value (yes in S25), that is, when the deceleration Ax (n) exceeds the limit value Ax _ lim, the target braking torque setting unit 91 starts the braking torque limit mode (step S27). At this time, the target braking torque setting unit 91 may turn on the braking torque limitation mode when a predetermined time t _ thr _ st elapses since the deceleration Ax (n) exceeds the limit value Ax _ lim. When the braking torque limitation mode is on, the target braking torque setting unit 91 calculates the limited braking torque T _ lim (n) (step S29). In the example of the present embodiment, the target braking torque setting unit 91 calculates the limit braking torque T _ lim (n) by subtracting a predetermined constant correction value T _ x from the target braking torque T _ out (n-1) set in the previous cycle. Next, the target braking torque setting unit 91 sets the calculated limit braking torque T _ lim (n) to the target braking torque T _ out (n).

On the other hand, if the difference da (n) is not a positive value (S25/no), the target braking torque setting unit 91 determines whether or not the current braking torque restriction mode is on (step S33). When the braking torque restriction mode is not on (S33/no), the target braking torque setting unit 91 sets the indicated braking torque T _ req _ in (n) included in the braking request signal received from the driving assistance device 110 as it is to the target braking torque T _ out (n) (step S43).

On the other hand, when the braking torque limitation mode is on (S33/yes), the target braking torque setting unit 91 determines whether or not the predetermined time t _ thr _ fn has elapsed since the difference da (n) became 0 or less (step S35). The predetermined time t _ thr _ fn is set to delay the timing to end the restriction of the braking torque in order to prevent the deceleration Ax of the deceleration equal to or smaller than the restriction value Ax _ lim from exceeding the restriction value Ax _ lim again by the end of the restriction of the braking torque.

When the predetermined time T _ thr _ fn has not elapsed since the difference da (n) was 0 or less (S35/no), the target braking torque setting unit 91 calculates the limit braking torque T _ lim (n) by subtracting a predetermined constant correction value T _ x from the target braking torque T _ out (n-1) set in the previous cycle (step S29). Next, the target braking torque setting unit 91 sets the calculated limit braking torque T _ lim (n) to the target braking torque T _ out (n) (step S31).

In the method of calculating the limited braking torque T _ lim (n) according to the present embodiment, in the first cycle in which the braking torque limitation mode is switched from off to on, the target braking torque T _ out (n-1) set in the previous cycle is the indicated braking torque T _ req _ in (n-1), and therefore, the value obtained by subtracting the correction value T _ x from the indicated braking torque T _ req _ in (n-1) is the limited braking torque T _ lim (n). While the braking torque limitation mode continues, a value obtained by subtracting the correction value T _ x from the target braking torque T _ out (n-1) set in the previous cycle is the limited braking torque T _ lim (n). Therefore, during the period in which the braking torque limitation mode is on, the limitation braking torque T _ lim is calculated by reducing the indicated braking torque T _ req _ in at a constant reduction rate.

On the other hand, when the predetermined time t _ thr _ fn has elapsed since the difference da (n) was 0 or less (S35/yes), the target braking torque setting unit 91 turns off the braking torque restriction mode (step S37). Next, the target braking torque setting unit 91 determines whether or not the indicated braking torque T _ req _ in (n) is larger than the target braking torque T _ out (n-1) set in the previous cycle (step S39). When the indicated braking torque T _ req _ in (n) is greater than the target braking torque T _ out (n-1) (S39/yes), the deceleration Ax is lower than the limit value Ax _ lim, but the target braking torque setting unit 91 holds the target braking torque T _ out (n-1) set in the previous cycle as the target braking torque T _ out (n) of the current cycle in order to prevent the deceleration Ax from exceeding the limit value Ax _ lim again as the target braking torque T _ out (n) of the current cycle by the increase of the target braking torque T _ out due to the termination of the limitation of the braking torque (step S41).

On the other hand, when the indicated braking torque T _ req _ in (n) is equal to or less than the target braking torque T _ out (n-1) (S39/no), the indicated braking torque T _ req _ in (n) is equal to the limit braking torque T _ lim (n-1), and the deceleration Ax can be suppressed even if the indicated braking torque T _ req _ in (n) is set as the target braking torque T _ out (n) as it is. Therefore, the target braking torque setting unit 91 sets the indicated braking torque T _ req _ in (n) included in the braking request signal received from the driving assistance device 110 to the target braking torque T _ out (n) (step S43).

Returning to fig. 3, after the target braking torque T _ out is set in step S13, the control unit 93 calculates the target braking hydraulic pressure P _ tgt based on the target braking torque T _ out (step S15). For example, the control unit 93 refers to map information in which the relationship between the target braking torque T _ out and the target braking hydraulic pressure P _ tgt is set in advance, and obtains the target braking hydraulic pressure P _ tgt corresponding to the target braking torque T _ out.

Next, the control unit 93 controls the driving of the actuator of the brake hydraulic pressure unit 20 based on the calculated target brake hydraulic pressure P _ tgt (step S17). Specifically, the control unit 93 sets the target flow rate V _ tgt of the brake fluid supplied from the master cylinder 14 to the brake fluid pressure unit 20 based on the calculated target brake fluid pressure P _ tgt, and controls the driving of the pump motor 96 of the brake fluid pressure unit 20. For example, the control unit 93 may set the target flow rate V _ tgt of the 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 set in advance.

This increases the brake fluid pressure in the wheel cylinder of each wheel, and the braking force of the vehicle can be generated. In the present embodiment, when the deceleration Ax exceeds the limit value Ax _ lim and the braking torque limit mode is set, the limit braking torque T _ lim set to a value smaller than the indicated braking torque T _ req _ in is set as the target braking torque T _ out without using the indicated braking torque T _ req _ in calculated by the driving assistance device 110 as it is. Therefore, the possibility that the deceleration Ax of the vehicle will continue to exceed the limit value Ax _ lim for a long time can be reduced. Thus, during execution of the ACC, the inter-vehicle distance to the preceding vehicle can be controlled to a predetermined target inter-vehicle distance while suppressing unstable behavior of the vehicle body.

The target braking torque setting unit 91 sets the target braking torque T _ out without using the information of the deceleration Ax when the ABS control or the ESP control is executed. For example, the target braking torque setting unit 91 compares the value of the indicated braking torque T _ req _ in (n) output from the driving assistance device 110 with the value of the target braking torque T _ out (n-1) set in the previous calculation cycle, and sets the smaller one as the target braking torque T _ out (n) of the current calculation cycle. During execution of the ABS control or the ESP control, the deceleration Ax of the vehicle obtained by differentiating the detection value of the wheel speed sensor may become excessively large, and the reliability of the value of the deceleration Ax may be lowered. Therefore, by setting the target braking torque T _ out without using the information of the deceleration Ax during execution of the ABS control or the ESP control, the possibility of instability of the behavior of the vehicle body can be reduced.

(1-2-3. Effect)

Next, the operation of the brake control process executed by the hydraulic control device 90 according to the present embodiment will be described.

Fig. 5 is a diagram for explaining the operation of the braking control process executed by the hydraulic control device 90 according to the present embodiment, and shows the temporal changes in the target braking torque T _ out set during execution of the ACC and the deceleration Ax of the vehicle.

When the inter-vehicle distance between the host vehicle and the preceding vehicle is lower than the target inter-vehicle distance or is about to be lower than the target inter-vehicle distance, the transmission of the braking request signal from the driving assistance device 110 to the hydraulic control device 90 is started at time t 1. After time T1, the indicated braking torque T _ req _ in increases, and the driving of the brake hydraulic unit 20 is controlled with the indicated braking torque T _ req _ in as the target braking torque T _ out, so that the deceleration Ax of the vehicle increases.

At time t2 when the deceleration Ax exceeds the control start threshold Ax _0, the target braking torque setting unit 91 starts calculation of a difference dA obtained by subtracting the limit value Ax _ lim from the deceleration Ax. At time t3 when deceleration Ax further increases and deceleration Ax exceeds limit value Ax _ lim, target braking torque setting unit 91 starts the timer count. At time T4 before the elapsed time from time T3 reaches predetermined time T _ thr _ st, the end of the rise of braking torque T _ req _ in is instructed, and thereafter, the value of the instructed braking torque T _ req _ in is kept constant. Accordingly, at time t4, the deceleration Ax of the vehicle is equal to or less than the limit value Ax _ lim, and therefore the target braking torque setting unit 91 resets the count value.

Then, at time t5, when deceleration Ax exceeds limit value Ax _ lim again, target braking torque setting unit 91 starts the timer count. At time T6 when the elapsed time from time T5 reaches predetermined time T _ thr _ st while deceleration Ax exceeds limit value Ax _ lim, target braking torque setting unit 91 starts the braking torque limit mode and sets limit braking torque T _ lim, which is set to a value smaller than indicated braking torque T _ req _ in, as target braking torque T _ out. In the example shown in fig. 5, the indicated braking torque T _ req _ in at the time T6 when the braking torque limitation mode is on is decreased at a constant rate of decrease to be the limitation braking torque T _ lim, and the limitation braking torque T _ lim is set to be the target braking torque T _ out.

As the braking torque is restricted, the deceleration Ax of the vehicle starts to decrease, and at time t7 when the deceleration Ax becomes the restricted value Ax _ lim, the target braking torque setting unit 91 starts the timer count. At time T8 when the elapsed time from time T7 reaches predetermined time T _ thr _ fn with deceleration Ax equal to or less than limit value Ax _ lim, target braking torque setting unit 91 turns off the braking torque limit mode, and holds target braking torque T _ out (i.e., limit braking torque T _ lim) set in the previous calculation cycle at that time, and sets the target braking torque T _ out. The magnitude relationship between the predetermined time t _ thr _ st set to turn on the braking torque restriction mode and the predetermined time t _ thr _ fn set to turn off the braking torque restriction mode is not particularly limited.

Thereafter, as the vehicle-to-vehicle distance between the host vehicle and the preceding vehicle approaches the target vehicle-to-vehicle distance, the indicated braking torque T _ req _ in decreases, and the indicated braking torque T _ req _ in becomes equal to or less than the target braking torque T _ out (the limited braking torque T _ lim) at time T9, so the target braking torque setting unit 91 ends the calculation of the limited braking torque T _ lim, and returns to the setting of setting the indicated braking torque T _ req _ in as it is to the target braking torque T _ out. At time t10, the transmission of the brake request signal from the driving assistance device 110 is stopped, and the hydraulic pressure control device 90 stops the driving of the brake hydraulic pressure unit 20.

As shown by the broken line in fig. 5, when the indicated braking torque T _ req _ in is set as it is to the target braking torque T _ out without limiting the braking torque and the driving of the brake fluid pressure unit 20 is controlled, the state in which the deceleration Ax _ def exceeds the limit value Ax _ lim is maintained even if the indicated braking torque T _ req _ in itself decreases after the deceleration Ax exceeds the limit value Ax _ lim at time T5. Thus, if the state in which the deceleration Ax _ def exceeds the limit value Ax _ lim continues for a long time, the vehicle body behavior may become unstable due to sudden deceleration of the vehicle. In contrast, in the present embodiment, since the braking torque is restricted when the deceleration Ax of the vehicle exceeds the limit value Ax _ lim, the possibility that the deceleration Ax exceeds the limit value Ax _ lim for a long time is reduced, and unstable behavior of the vehicle body can be suppressed.

< 1-3. Effect >

As described above, according to the present embodiment, the target braking torque setting unit 91 of the hydraulic control device 90 sets the limit braking torque T _ lim, which is smaller than the indicated braking torque T _ req _ in transmitted from the driving assistance device 110, to the target braking torque T _ out when the deceleration Ax of the host vehicle exceeds the limit value Ax _ lim. The control unit 93 controls the driving of the pump motor 96 of the brake hydraulic unit 20 based on the set target braking torque T _ out. Therefore, the possibility that the deceleration Ax of the vehicle exceeds the limit value Ax _ lim for a long time is reduced, and it is possible to suppress the vehicle body behavior from becoming unstable due to rapid deceleration.

Further, according to the present embodiment, the target braking torque setting unit 91 calculates the limit braking torque T _ lim by reducing the command braking torque T _ req _ in at a constant reduction rate when the braking torque limit mode is turned on. This makes it possible to easily limit the braking torque without increasing the calculation load of the hydraulic control device 90. Further, since the deceleration Ax of the vehicle is not rapidly decreased, the inter-vehicle distance D from the preceding vehicle can be prevented from becoming excessively small.

Further, according to the present embodiment, when the deceleration Ax is equal to or less than the limit value Ax _ lim continues for the predetermined time T _ thr _ fn or longer, the target braking torque setting unit 91 turns off the braking torque limit mode, holds the target braking torque T _ out (i.e., the limit braking torque T _ lim) set in the previous calculation cycle at that time, and sets the target braking torque T _ out. This makes it possible to delay the timing of ending the limitation of the braking torque, and to suppress the deceleration Ax equal to or smaller than the limitation value Ax _ lim from exceeding the limitation value Ax _ lim again due to the end of the limitation of the braking torque.

Further, according to the present embodiment, when the deceleration Ax of the vehicle exceeds the limit value Ax _ lim for the predetermined time T _ thr _ st or longer, the target braking torque setting unit 91 starts the braking torque limit mode and sets the limit braking torque T _ lim to the target braking torque T _ out. Thus, when the deceleration Ax exceeds the limit value Ax _ lim in a very short time, the braking torque is not limited, and the vehicle-to-vehicle distance D from the preceding vehicle can be prevented from becoming too small because the braking torque is limited more than necessary.

Further, according to the present embodiment, the target braking torque setting unit 91 ends the setting of the limited braking torque T _ lim to the target braking torque T _ out when the instructed braking torque T _ req _ in is equal to or less than the limited braking torque T _ lim after the braking torque limited mode is turned on. Thus, when the braking torque limitation mode is ended, the target braking torque T _ out can be prevented from rapidly increasing, and the indicated braking torque T _ req _ in can be transitioned to the state in which the indicated braking torque T _ req _ in is set to the target braking torque T _ out without greatly changing the target braking torque T _ out.

Further, according to the present embodiment, the target braking torque setting unit 91 compares the deceleration Ax with the limit value Ax _ lim when the deceleration Ax exceeds the control start threshold value Ax _0 smaller than the limit value Ax _ lim, and sets the limit braking torque T _ lim to the target braking torque T _ out when the deceleration Ax exceeds the limit value Ax _ lim. This makes it possible to reduce the calculation load of the hydraulic control device 90 during a period in which the deceleration Ax is small, without restricting the braking torque.

< 2 > embodiment 2

Next, embodiment 2 of the present invention will be described. In embodiment 2, the booster control device 100 that controls the electric booster 10 functions as a brake control device for a vehicle that: the braking force is controlled so that the deceleration of the vehicle does not continue to exceed a predetermined limit value for a long time, in response to the braking request signal transmitted from the driving assistance device 110.

The brake system 1 of the present embodiment can have the same configuration as the brake system 1 described in embodiment 1, except that the brake control device of the vehicle that executes the automatic braking control of the ACC is the booster control device 100. Hereinafter, the description will be mainly given of the differences from embodiment 1.

Fig. 6 is a block diagram showing a functional configuration related to automatic braking control of the ACC in the configuration of the brake system 1. In the present embodiment, the automatic braking control of the ACC is executed by the driving assistance device 110 and the booster control device 100 communicating with each other, and the booster control device 100 controlling the booster 10.

As in the case of embodiment 1, during execution of the ACC, the driving assistance device 110 determines whether braking is necessary or not and calculates the instructed braking torque T _ req _ in based on information detected by the sensor device 111 such as a camera, a radar, or a RiDAR, and transmits a braking request signal indicating information of the braking request S _ brk and the instructed braking torque T _ req _ in to the booster control device 100.

The booster control device 100, having received the braking request signal of the ACC from the driving assist device 110, sets the target braking torque T _ out based on the instruction braking torque T _ req _ in, and converts the target braking torque T _ out into the target braking hydraulic pressure P _ tgt, controlling the driving of the booster 10. Specifically, the booster control device 100 drives the electric motor of the booster 10, pressurizes the brake fluid in the master cylinder 14, and supplies the brake fluid from the master cylinder 14 to the wheel cylinders of the respective wheels to increase the brake fluid pressure of the respective wheels, thereby generating the braking force of the vehicle.

The booster control device 100 includes a target braking torque setting unit 101 and a control unit 103. The target braking torque setting unit 101 and the control unit 103 are functions realized by executing a program by a microcomputer. The booster control device 100 includes a drive circuit, not shown, and a storage element such as a RAM or a ROM.

The target braking torque setting unit 101 is configured in the same manner as the target braking torque setting unit 91 of the hydraulic control device 90 described in embodiment 1. That is, the target braking torque setting unit 101 sets the target braking torque T _ out so that the deceleration Ax of the vehicle does not exceed the predetermined limit value Ax _ lim for a long time, based on the information indicating the braking torque T _ req _ in and the information of the acceleration G included in the braking request signal transmitted from the driving assistance device 110. A specific calculation method of the target braking torque T _ out may be the same as that of the target braking torque setting portion 91 of the hydraulic control device 90 described in embodiment 1.

The control unit 103 controls the driving of the booster 10 based on the target braking torque T _ out set by the target braking torque setting unit 101. Thereby, the braking force of the vehicle is controlled. In the present embodiment, the control unit 103 calculates the target brake fluid pressure P _ tgt generated in each wheel based on the target brake torque T _ out, and controls the driving of the electric motor of the booster 10 to advance the push rod 13 into the master cylinder 14.

The control unit 103 obtains the target brake fluid pressure P _ tgt based on the target brake torque T _ out with reference to map information and the like, and sets the target flow rate V _ tgt of the brake fluid supplied from the master cylinder 14 to the brake fluid pressure unit 20 based on the target brake fluid pressure P _ tgt, similarly to the control unit 93 of the fluid pressure control device 90 described in embodiment 1.

The control unit 103 outputs a control signal to a drive circuit of the electric motor of the booster 10 based on the set target flow rate V _ tgt, and moves the push rod 13 forward. Thereby, the brake fluid in the first chamber 47 and the second chamber 48 is pressurized, the brake fluid is supplied from the master cylinder 14 into the brake fluid pressure unit 20, and the brake fluid is supplied to the wheel cylinders of the respective wheels. As a result, the brake fluid pressure of each wheel rises, and the braking force of the vehicle is generated. In the present embodiment, since the braking torque is restricted even when the deceleration Ax of the vehicle exceeds the limit value Ax _ lim in the braking torque restriction mode, the possibility that the deceleration Ax exceeds the limit value Ax _ lim for a long time is reduced.

An example of operation and action of the booster control device 100 as the vehicle brake control device according to the present embodiment is the same as the example of operation and action described in embodiment 1 except that the driven actuator is not the pump motor 96 of the brake hydraulic unit 20 but the electric motor of the booster 10, and therefore detailed description thereof is omitted.

As described above, according to the present embodiment, the target braking torque setting unit 101 of the booster control device 100 sets the limit braking torque T _ lim, which is smaller than the indicated braking torque T _ req _ in transmitted from the driving assistance device 110, to the target braking torque T _ out when the deceleration Ax of the host vehicle exceeds the limit value Ax _ lim. The control unit 103 controls the driving of the electric motor of the booster 10 based on the set target braking torque T _ out. According to the booster control device 100 of the present embodiment, the same effects as those obtained according to embodiment 1 can be obtained.

Further, according to the present embodiment, the booster 10 is driven to supply the brake fluid from the master cylinder 14 to the brake fluid pressure unit 20, and the brake fluid pressure in the wheel cylinder of each wheel is increased. Therefore, the response to generation of the braking force can be improved as compared with the case where the pump motor 96 of the brake hydraulic unit 20 is driven to supply the brake fluid from the master cylinder 14 to the brake hydraulic unit 20.

While preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, the present invention is not limited to such examples. It will be apparent to those skilled in the art having a general knowledge of the technical field to which the present invention pertains that various modifications and variations can be made within the scope of the technical idea described in the claims, and they are also apparent to be within the technical scope of the present invention.

Description of the reference numerals

10 … electric booster, 13 … push rod, 14 … master cylinder, 20 … brake hydraulic unit, 43 … first piston, 44 … second piston, 47 … first chamber, 48 … second chamber, 90 … hydraulic control device, 91 … target brake torque setting unit, 93 … control unit, 100 … booster control device, 101 … target brake torque setting unit, 103 … control unit, 110 … driving assist device.

Claims (8)

1. A brake control apparatus for a vehicle,

comprises target braking torque setting units (91, 101) and control units (93, 103),

the target braking torque setting unit (91, 101) sets a target braking torque (T _ out) based on information (T _ req _ in) of a braking request, the information (T _ req _ in) of the braking request being set based on a target inter-vehicle distance between the host vehicle and the preceding vehicle,

the control unit (93, 103) controls the braking force of the vehicle on the basis of the target braking torque (T _ out),

the target braking torque setting unit (91, 101) sets a limit braking torque (T _ lim) having a value smaller than a braking torque corresponding to the braking request information (T _ req _ in) to a target braking torque (T _ out) when the deceleration (Ax) of the host vehicle exceeds a predetermined limit value (Ax _ lim).

2. The brake control apparatus of a vehicle according to claim 1,

the aforementioned information of the braking request is an indication of the braking torque (T _ req _ in),

the target braking torque setting unit (91, 101) calculates the limit braking torque (T _ lim) by reducing the indicated braking torque (T _ req _ in) at a constant reduction rate.

3. The brake control apparatus of a vehicle according to claim 2,

the target braking torque setting unit (91, 101) holds the value of the limited braking torque (T _ lim) when the deceleration (Ax) is equal to or less than the predetermined limit value (Ax _ lim) for a predetermined time (T _ thr _ fn) or longer.

4. The brake control apparatus of a vehicle according to any one of claims 1 to 3,

the target braking torque setting unit (91, 101) sets the limit braking torque (T _ lim) to the target braking torque (T _ out) when the deceleration (Ax) exceeds the predetermined limit value (Ax _ lim) for a predetermined time (T _ thr _ st) or longer.

5. The brake control apparatus of a vehicle according to any one of claims 1 to 4,

the aforementioned information of the braking request is an indication of the braking torque (T _ req _ in),

the target braking torque setting unit (91, 101) ends the setting of the limited braking torque (T _ lim) to the target braking torque (T _ out) when the indicated braking torque (T _ req _ in) is equal to or less than the limited braking torque (T _ lim) set to the target braking torque (T _ out).

6. The brake control apparatus of a vehicle according to any one of claims 1 to 5,

the target braking torque setting unit (91, 101) compares the deceleration (Ax) of the host vehicle with the predetermined limit value (Ax _ lim) when the deceleration (Ax) exceeds a control start threshold value (Ax _0) that is smaller than the predetermined limit value (Ax _ lim), and sets the limit braking torque (T _ lim) to the target braking torque (T _ out) when the deceleration (Ax) exceeds the predetermined limit value (Ax _ lim).

7. The brake control apparatus of a vehicle according to any one of claims 1 to 6,

the vehicle brake control device is a control device (90) for braking a hydraulic unit (20),

the target braking torque setting unit (91) receives a braking request signal transmitted from a driving support device (110) that outputs information (T _ req _ in) of the braking request based on the target inter-vehicle distance, and sets the target braking torque (T _ out),

the control unit (93) controls the brake hydraulic pressure unit (20) based on the target braking torque (T _ out).

8. The brake control apparatus of a vehicle according to any one of claims 1 to 6,

the brake control device for a vehicle is a control device (100) for an electric booster (10),

the target braking torque setting unit (101) receives a braking request signal transmitted from a driving support device (110) that outputs information (T _ req _ in) of the braking request based on the target inter-vehicle distance, and sets the target braking torque (T _ out),

the control unit (103) controls the electric booster (10) based on the target braking torque (T _ out).

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