CN112469607A

CN112469607A - Brake control device and brake control method

Info

Publication number: CN112469607A
Application number: CN201980050924.3A
Authority: CN
Inventors: M·尚岑巴赫; 宫川秀一
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2018-07-31
Filing date: 2019-07-03
Publication date: 2021-03-09
Anticipated expiration: 2039-07-03
Also published as: DE112019003862T5; JPWO2020026051A1; JP7297757B2; WO2020026051A1; CN112469607B; JP2020019335A

Abstract

Provided is a brake control device capable of suppressing an unexpected stop or an inability to restart rotation of a motor. Brake control devices (3, 9) capable of controlling wheel cylinder pressure are provided with a pump (6), a motor (60), and an electronic control unit (9), wherein the pump (6) is capable of sucking working fluid and discharging the working fluid to a fluid path (31) connected to a wheel cylinder (21), the motor (60) is used for driving the pump (6), the motor (60) is electrically driven, and the electronic control unit (9) is configured to control the rotation speed of the motor (60) by PWM control, and when the fluid pressure on the discharge side of the pump (6) is higher than a predetermined 1 st fluid pressure, the motor (60) is continuously driven with a duty ratio of 100%.

Description

Brake control device and brake control method

Technical Field

The present invention relates to a brake control device.

Background

Conventionally, a brake control device is known which includes a pump driven by an electric motor and is capable of controlling a hydraulic pressure of a brake cylinder of a wheel. For example, the device described in patent document 1 can perform pwm (pulse Width modulation) control for modulating the Width of a pulse to be output to a motor.

Patent document 1: japanese patent laid-open No. 2000-313325.

When the rotation speed of the motor is controlled by PWM control, if the hydraulic pressure on the discharge side of the pump is in a region higher than normal, a large load exceeding an assumed load, for example, exceeding the specification of the motor acts on the pump. If the load suddenly fluctuates in this state, the PWM control cannot respond to the fluctuation, and the motor may be stopped unexpectedly.

Further, if the hydraulic pressure on the discharge side of the pump is in a higher region than normal after the motor is unexpectedly stopped, the motor may not be able to restart rotation within a predetermined time by PWM control.

Disclosure of Invention

The present invention has been made in view of the above problems, and provides a brake control device capable of improving performance by suppressing unexpected stop of a motor.

According to an aspect of the present invention, there is provided a brake control device configured to continuously drive a motor with a duty ratio of 100% when a hydraulic pressure on a discharge side of a pump is higher than a predetermined 1 st hydraulic pressure.

Effects of the invention

According to the present invention, the performance of the brake control device can be improved by suppressing an unexpected stop or the like of the motor.

Drawings

Fig. 1 shows a brake system of an embodiment together with a hydraulic circuit.

Fig. 2 is a flowchart showing a motor control process according to the embodiment.

Fig. 3 is a time chart showing changes in the respective variables during the motor control execution according to 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 redundant description is omitted.

< 1. structural example of brake System >

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

The brake system 1 is a hydraulic system for a four-wheel vehicle, and includes a master brake cylinder (hereinafter, a master cylinder) 14 connected to a brake pedal 10 as a brake operation input element, brake cylinders (hereinafter, wheel cylinders) 21a to 21d provided for hydraulic brakes 2a to 2d of each wheel, a hydraulic unit 3 provided in the middle of a brake pipe connecting the master cylinder 14 and the wheel cylinders 21a to 21d, and an Electronic Control unit (hereinafter, an ECU)9 that controls the operation of the hydraulic unit 3. The brake control device includes a hydraulic unit 3 and an ECU 9.

The brake system 1 of the present embodiment does not include a booster for amplifying the depression force of the brake pedal 10 by using the negative pressure of the engine or the like, but may include the booster. The brake operation input element is not limited to the brake pedal 10, and may be any element that allows the driver to input a request for braking the vehicle.

The master cylinder 14 is of a tandem type, and holds the primary piston 12a and the secondary piston 12b so as to be movable forward and backward. The master piston 12a is coupled to the brake pedal 10 via a piston rod 11.

The master cylinder 14 has two

pressure chambers

13a, 13b partitioned by two

pistons

12a, 12 b. The volumes of the

pressure chambers

13a and 13b change in accordance with the stroke amount of the piston rod 11. The piston rod 11 is provided with a stroke sensor 81 for detecting an axial displacement amount, i.e., a stroke amount, of the piston rod 11.

The working oil is supplied from the reservoir tank 16 to the

pressure chambers

13a and 13 b. The hydraulic oil functions as a hydraulic fluid for generating hydraulic pressure. The

coil springs

15a and 15b disposed in the

pressure chambers

13a and 13b function as return springs for biasing the

pistons

12a and 12b to the initial positions.

The hydraulic unit 3 includes two

hydraulic circuits

30a, 30b of the system. One pressure chamber 13a of the master cylinder 14 is connected to one hydraulic circuit 30a, and the other pressure chamber 13b of the master cylinder 14 is connected to the other hydraulic circuit 30 b.

When the master piston 12a and the slave piston 12b are pushed and moved via the piston rod 11 by the operation of the brake pedal 10, the hydraulic oil is supplied from the

pressure chambers

13a and 13b to the

hydraulic circuits

30a and 30b, respectively.

The brake system 1 of the present embodiment is configured in a so-called X-pipe system, in which the

pressure chambers

13a and 13b of the master cylinder 14 are connected to a set of one front wheel and one rear wheel at diagonal positions of the vehicle via

hydraulic circuits

30a and 30 b. The hydraulic oil is supplied to the wheel cylinder 21a of the front right wheel (FR) and the wheel cylinder 21b of the rear left wheel (RL) via the hydraulic circuit 30 a. The hydraulic oil is supplied to the wheel cylinder 21c of the left front wheel (FL) and the wheel cylinder 21d of the right rear wheel (RR) via the hydraulic circuit 30 b.

The brake system 1 may be of a front-rear pipe system or the like. The brake system 1 is not limited to a four-wheel vehicle, and may be a brake system for a two-wheel vehicle or another vehicle.

< 2. example of Structure of Hydraulic Circuit

One of the hydraulic circuits 30a includes a plurality of solenoid valves, a plurality of fluid paths, a pump 6, an accumulator 5, and a damper 7.

The plurality of electromagnetic valves include a circuit control valve 41,

pressure increasing valves

41a and 41b,

pressure reducing valves

42a and 42b, and a suction control valve 44. The circuit control valve 41 and the pressure increase

valves

41a and 41b can be linearly controlled in a normally open type. The

pressure reducing valves

42a and 42b and the suction control valve 44 are opened and closed in a normally closed manner.

The plurality of liquid paths include a supply liquid path 31, a pressure-reducing liquid path 32, a 1 st suction liquid path 33, a 2 nd suction liquid path 34, and a discharge liquid path 35.

One end of the supply liquid passage 31 is connected to a brake pipe communicating with the pressure chamber 13 a. The other end of the supply liquid passage 31 is branched into two. The

branch fluid passages

31a and 31b are connected to brake pipes that communicate with the wheel cylinders 21a and 21 b.

A circuit control valve 41 is provided on the pressure chamber 13a side of the supply liquid passage 31. A check valve 46 is provided in a bypass fluid passage parallel to the circuit control valve 41. The

branch liquid paths

31a and 31b are provided with

pressure increasing valves

41a and 41b, respectively.

Check valves

47a and 47b are provided in bypass fluid paths parallel to the

pressure increasing valves

41a and 41 b.

The end of the pressure reducing liquid path 32 on one side is connected to the reservoir 5. The other end of the pressure reducing liquid passage 32 is branched into two. The

branch liquid paths

32a and 32b are connected to the side of the wheel cylinders 21a and 21b with respect to the pressure increase

valves

41a and 41b of the

branch liquid paths

31a and 31b of the supply liquid path 31, respectively.

The end on the 1 st intake path 33 side is connected to the reservoir 5. The other end of the 1 st intake liquid passage 33 is connected to the intake side of the pump 6. The 1 st intake liquid passage 33 is provided with a check valve 43.

The 2 nd suction liquid passage 34 has one end connected to a brake pipe communicating with the pressure chamber 13a via the supply liquid passage 31. The other end of the 2 nd intake liquid passage 34 is connected to the intake side of the pump 6 via the 1 st intake liquid passage 33. The 2 nd intake liquid passage 34 is provided with an intake control valve 44.

One end of the discharge liquid path 35 is connected to the discharge side of the pump 6. The other end of the discharge liquid passage 35 is connected to the

pressure increasing valves

41a and 41b with respect to the circuit control valve 41 of the supply liquid passage 31. The discharge liquid path 35 is provided with a damper 7. A check valve 45 is provided between the damper 7 of the discharge liquid passage 35 and the supply liquid passage 31. A variable orifice 70 is provided between the damper 7 and the check valve 45 in the discharge liquid passage 35.

The circuit control valve 41 can connect or disconnect the master cylinder 14 of the supply liquid path 31 and the

pressure increasing valves

41a and 41 b. The check valve 46 permits the hydraulic oil to move from the master cylinder 14 side to the wheel cylinders 21a and 21b of the right or left front wheel through the bypass fluid passage, and prohibits the hydraulic oil from moving in the opposite direction.

The pressure increasing valve 41a can adjust the flow rate of the hydraulic oil from the circuit control valve 41 side toward the wheel cylinder 21a of the right front wheel via the supply liquid passage 31. The check valve 47a permits the hydraulic oil to move from the hydraulic brake 2a side of the right front wheel to the circuit control valve 41 side through the bypass fluid passage, and prohibits the hydraulic oil from moving in the opposite direction.

The pressure reducing valve 42a can supply the hydraulic oil of the wheel cylinder 21a of the right front wheel to the reservoir 5 through the pressure reducing liquid passage 32 by opening the valve, thereby reducing the pressure of the wheel cylinder 21 a.

The pressure increasing valve 41b and the pressure reducing valve 42b are also the same.

The accumulator 5 accumulates or discharges the working oil to the 1 st intake liquid passage 33 while changing its volume in accordance with the pressure of the working oil supplied via the pressure reducing liquid passage 32. The check valve 43 permits the movement of the hydraulic oil from the reservoir 5 side to the suction side of the pump 6 through the 1 st suction liquid passage 33, and prohibits the movement in the opposite direction.

The suction control valve 44 can connect or disconnect the suction side of the pump 6 to or from the master cylinder 14 of the 2 nd suction liquid passage 34.

The pump 6 is driven by the motor 60, sucks the hydraulic oil from the 1 st suction liquid passage 33, and discharges the hydraulic oil to the discharge liquid passage 35. In addition, the number of pumps 6 is not limited to one. The pump 6 is, for example, a gear pump.

The motor 60 is of an electric type, for example, a brush motor. The driving state of the motor 60 is controlled by the ECU 9.

The damper 7 has a function of reducing vibration and vibration sound accompanying a change in the flow rate of the hydraulic oil in the hydraulic circuit 30 a.

The variable restrictor 70 can adjust the flow rate of the working oil supplied from the pump 6 through the damper 7. The check valve 45 permits the hydraulic oil from the damper 7 side to move toward the supply liquid passage 31 side through the discharge liquid passage 35, and prohibits the hydraulic oil from moving in the opposite direction.

A 1 st pressure sensor 82 is provided in the supply liquid passage 31 on the pressure chamber 13a side of the master cylinder 14 with respect to the circuit control valve 41. The 1 st pressure sensor 82 can detect the pressure of the pressure chamber 13a (master cylinder pressure).

The 2 nd pressure sensor 83 is provided on the side of the wheel cylinder 21a on the right front wheel side of the pressure increasing valve 41a in the branch liquid passage 31a of the supply liquid passage 31. The 2 nd pressure sensor 83 is capable of detecting the pressure of the wheel cylinder 21a (the wheel cylinder pressure of the right front wheel). The 2 nd pressure sensor 83 may be provided in a fluid path communicating with the wheel cylinder 21b of the left rear wheel.

The other hydraulic circuit 30b is supplied with hydraulic oil from the pressure chamber 13b of the master cylinder 14, and can control the wheel cylinder pressure of the left front wheel and the wheel cylinder pressure of the right rear wheel. The hydraulic circuit 30b is configured similarly to the hydraulic circuit 30a except that the wheel cylinder 21a of the right front wheel is replaced with the wheel cylinder 21c of the left front wheel and the wheel cylinder 21b of the left rear wheel is replaced with the wheel cylinder 21d of the right rear wheel in the description of the hydraulic circuit 30 a.

< 3. example of Structure of electronic control Unit

Part or all of the ECU9 may be constituted by a microcomputer, a microprocessor unit, or the like, for example. A microcomputer or the like has a Central Processing Unit (CPU) for executing various arithmetic processing, a Read Only Memory (ROM) for storing various control programs, a Random Access Memory (RAM) used as a work area for data storage and program execution, and an input/output interface (I/O), and these may be of a general configuration in which they are connected to each other by a bidirectional common bus.

The ECU9 may be partially or entirely configured to be updatable, such as firmware, or may be a program module or the like to be executed in accordance with instructions from a CPU or the like.

The ECU9 is connected via communication lines to the stroke sensor 81, the 1 st and 2

nd pressure sensors

82, 83, and a wheel speed sensor that detects the rotational speed of each wheel (wheel speed). The ECU9 is connected to another ECU so as to enable bidirectional communication via a communication line such as can (controller Area network).

The ECU9 can individually control the wheel cylinder pressure of each wheel by controlling the drive of the motor 60 and the solenoid valve 41 and the like as the actuator of the hydraulic unit 3 based on signals input from these sensors or other ECUs.

For example, the pressure increase valve 41a is closed and the pressure decrease valve 42a is opened, whereby the wheel cylinder pressure of the right front wheel can be decreased. The pressure increasing valve 41a and the pressure reducing valve 42a are closed, whereby the wheel cylinder pressure of the right front wheel can be maintained. The wheel cylinder pressure of the right front wheel can be increased by opening the pressure increasing valve 41a and closing the pressure reducing valve 42 a.

The ECU9 detects that any one of the wheels is locked due to the pressure increase of the wheel cylinders 21a to 21d caused by the braking operation of the driver, based on a signal from a wheel speed sensor or the like, for example, in a state where the circuit control valve 41 is opened and the suction control valve 44 is closed. At this time, the wheel cylinder pressure of the wheel is controlled by reducing, maintaining, or increasing the pressure as described above. This can alleviate the tendency to lock. Thus, the brake control device functions as an Antilock Brake System (ABS).

For example, the ECU9 can adjust the flow rate of the hydraulic oil flowing from the wheel cylinder 21a to the accumulator 5 via the pressure-reducing fluid passage 32 by intermittently repeating the opening and closing of the pressure-reducing valve 42 a. The ECU9 can pressure-feed the hydraulic oil discharged from the reservoir 5 to the master cylinder 14 by driving the pump 6.

The ECU9 can control the wheel cylinder pressure of each wheel without direct relation to the brake operation performed by the driver by driving the pump 6 and driving the pressure increasing valve 41a or the pressure reducing valve 42a in a state where the circuit control valve 41 is closed and the suction control valve 44 is opened, for example. As a result, it is possible to execute a brake control as a motion control for the vehicle, an emergency brake control for avoiding a collision of the vehicle, or the like as a loop of an Electronic Stability Program (ESP).

The ECU9 is configured to be able to switch between the PWM control mode and the duty 100% mode as a mode for controlling the motor 60.

The PWM control mode is a mode in which the rotation speed of the motor 60 is feedback-controlled to a predetermined value by PWM control for modulating the width of the pulse to be output to the motor 60.

The duty 100% mode is a mode in which the motor 60 is continuously driven with the duty of the pulse set to 100%.

(flow chart)

An example of the control process of the ECU9 according to the present embodiment will be described in detail with reference to fig. 2. Fig. 2 shows an example of the flow of the motor control process executed by the ECU 9. This process is repeatedly executed at a predetermined cycle.

The ECU9 reads the detected master cylinder pressure P and vehicle speed V in step S1. The vehicle speed V can be calculated from the detected wheel speed, for example. The vehicle speed V may be detected by a signal from a vehicle speed sensor provided in the vehicle.

In step S2, it is determined whether the master cylinder pressure P is higher than a predetermined value (1 st hydraulic pressure) P1. If the master cylinder pressure P is higher than the 1 st hydraulic pressure P1, the process proceeds to step S3, and if the master cylinder pressure P is equal to or lower than the 1 st hydraulic pressure P1, the process proceeds to step S6.

That is, when the ECU9 controls the rotation speed of the motor 60 by PWM control, the master cylinder pressure P acts on the pump 6 as the hydraulic pressure on the discharge side of the pump 6, and a load is generated to stop the rotation of the motor 60.

The 1 st hydraulic pressure P1 is the master cylinder pressure P that is applied to the pump 6 (motor 60) by a load with a probability of being equal to or greater than a predetermined value at the 1 st time T1 after the motor 60 stops rotating in this way, and the motor 60 can restart rotating by PWM control.

The 1 st time T1 can be set to a time that does not affect the ABS control even if the pump 6 is not operated between the 1 st time T1, for example. The probability of the predetermined value or more is, for example, 90% or more, preferably 95% or more, and more preferably 99% or more.

When the lower limit of the range of the master cylinder pressure P in which the load for stopping the rotation of the motor 60 is generated as described above is set to the 2 nd hydraulic pressure P2, the 1 st hydraulic pressure P1 is higher than the 2 nd hydraulic pressure P2.

In step S3, it is determined whether the vehicle speed V is higher than a predetermined value V1. The predetermined value V1 can be set to, for example, a vehicle speed at which the probability of the ABS control operation is less than a predetermined value. If the vehicle speed V is higher than the predetermined value V1, the routine proceeds to step S4, and if the vehicle speed V is equal to or lower than the predetermined value V1, the routine proceeds to step S6.

In step S4, the control mode of the motor 60 is set to the duty 100% mode, and the process advances to step S5.

In step S5, it is determined whether or not the ABS control is switched from on (active) to off (inactive). If the switch is made from on to off, the process proceeds to step S11, and if the switch is not made, the cycle is ended.

In step S6, it is determined whether the control mode of the motor 60 is the duty 100% mode. If the duty ratio mode is 100%, the process proceeds to step S7, and if the duty ratio mode is not 100%, the process proceeds to step S11.

In step S7, it is determined whether or not the master cylinder pressure P is equal to or less than the predetermined 3 rd hydraulic pressure P3. The 3 rd hydraulic pressure P3 can be set to a value lower than the 1 st hydraulic pressure P1 by the amount of fluctuation of the master cylinder pressure P predicted during the ABS control operation, for example. If the master cylinder pressure P is equal to or lower than the 3 rd hydraulic pressure P3, the process proceeds to step S8, and if the master cylinder pressure P is higher than the 3 rd hydraulic pressure P3, the process proceeds to step S4.

In step S8, a threshold T of the count value T of the timer is set. In accordance with the master cylinder pressure P read in step S1, a value greater when the master cylinder pressure P is high than when it is low can be set as the threshold value T. Thereafter, the process proceeds to step S9.

In step S9, the count value T is incremented. Thereafter, the process proceeds to step S10.

In step S10, it is determined whether or not the count value T is equal to or greater than the threshold value T. If the count value T is equal to or greater than the threshold T, the process proceeds to step S11, and if the count value T is less than the threshold T, the process proceeds to step S4.

In step S11, the control mode of the motor 60 is set to the PWM control mode. Thereafter, the cycle is ended.

< 4. example of operation of brake control device

Next, an example of the operation of the brake control device will be described with reference to fig. 3.

Fig. 3 illustrates a transition 101 of the master cylinder pressure, a transition 102 of the opening and closing of the ABS control, a transition 103 of the opening and closing of the duty 100% pattern, a transition 104 of the count value T of the timer, a transition 105 of the threshold T, a transition 106 of the rotation speed N of the motor 60, and a transition 107 of the current I of the motor 60 when the ECU9 executes the motor control according to the present embodiment.

At time t1 when the driver depresses the brake pedal 10 and the master cylinder pressure P rises, the ABS control starts to operate. At this time, since the master cylinder pressure P is equal to or less than the 1 st hydraulic pressure P1, the flow of step S1 → S2 → S6 → S11 → S1 is shown in fig. 2, and the ECU9 executes the PWM control mode. The rotation speed N of the motor 60 is controlled to a predetermined constant value.

At time t2, the master cylinder pressure P becomes higher than the 1 st hydraulic pressure P1. In the ABS control operation, the vehicle speed V is higher than a predetermined value V1. Thus, in fig. 2, which is a flow of step S1 → S2 → S3 → S4 → S5 → S1, the ECU9 executes the duty 100% mode. The motor 60 is continuously driven, and the rotation speed N is not particularly controlled.

At time t3, the master cylinder pressure P becomes equal to or lower than the 3 rd hydraulic pressure P3. Accordingly, in fig. 2, the flow of step S1 → S2 → S6 → S7 → S8 → S9 → S10 → S4 → S5 → S1 is shown, and the ECU9 continues the duty 100% mode, while setting the threshold T, and starts to count up the count value T.

Since the master cylinder pressure P is equal to or lower than the 3 rd hydraulic pressure P3 at time T4, the value corresponding to the master cylinder pressure P at each time is set to the threshold value T again, and the count-up of the count value T is continued.

At time T4, count value T reaches threshold T. Thus, the ECU9 executes the PWM control mode in the flow of step S1 → S2 → S6 → S7 → S8 → S9 → S10 → S11 → S1 in fig. 2. The rotation speed N of the motor 60 is controlled to be converged to a predetermined value again.

At time t5, the ABS control ends. In response, the ECU9 stops the motor 60.

As is clear from the above example, the ECU9 can control the rotation speed N of the motor 60 by PWM control, and is configured to continuously drive the motor 60 with the duty ratio set to 100% when the master cylinder pressure P is higher than the 1 st hydraulic pressure P1.

That is, when the rotation speed N is controlled by the PWM control, if the master cylinder pressure P is in a higher region than normal, a load exceeding an assumed load, for example, a load exceeding the specification of the motor 60 acts on the pump 6. If the load fluctuates rapidly in this state, the PWM control cannot respond to the fluctuation, and the motor 60 may be stopped unexpectedly.

Further, when the master cylinder pressure P is in a higher region than normal after the motor 60 is unexpectedly stopped, a large load acts on the pump 6, and thus there is a possibility that the motor 60 cannot start rotating again within a predetermined time by the PWM control.

Here, while the motor 60 is continuously driven at a duty ratio of 100% (that is, fully-opened rotation), even when a large load acts on the pump 6, a torque exceeding the load can be generated, and the rotation can be continued even if the load abruptly fluctuates.

The present inventors paid attention to this point, and configured that when the master cylinder pressure P is higher than the 1 st hydraulic pressure P1, the ECU9 switches the control of the motor 60 from the PWM control mode to the 100% duty mode (continuous drive).

Thus, even in a state where the load acts on the pump 6, the motor 60 is continuously driven, and thus it is possible to suppress the motor 60 from being unexpectedly stopped or from being unable to restart rotation. Therefore, the performance of the brake control device can be improved.

In a state where a large load acts on the pump 6 and the motor 60 generates a high load, if the opening/closing control is performed by the PWM control so that the rotation speed N of the motor 60 is constant, the current I of the motor 60 becomes large on average due to the generation of a rush current.

In contrast, when the motor 60 is continuously driven, the current I may be small because the on/off control is not performed. As illustrated in fig. 3, the current I of the motor 60 is small (time t2-t4) in the duty 100% mode, compared to that in the PWM control mode (time t1-t2, time t4-t 5).

This can reduce the electric load on the vehicle by suppressing the current consumption of the motor 60. Further, by suppressing an increase in the wire diameter of the power cable of the motor 60, the capacity of the fuse, the heat resistance of the plug of the ECU9, and the like, it is possible to achieve a reduction in the size and cost of the brake control device.

The voltage of the motor 60, in other words, the torque that the motor 60 can generate, varies depending on the ambient temperature and the like. Thus, the ECU may be configured to change the timing of switching the control mode of the motor 60 (for example, the value of the 1 st hydraulic pressure P1) according to the ambient temperature or the like.

It is also considered that a parameter for switching the control of the motor 60 between the PWM control mode and the duty 100% mode is set to be equal to the induced voltage of the motor 60 in the PWM control, the length of the idle time, or the like.

However, when these parameters are used, it is difficult to accurately determine whether or not a large load exceeding the specification of the motor 60 acts on the pump 6 due to a phenomenon such as an accidental stop of the motor 60, and it is difficult to switch the control mode depending on whether or not such a large load acts.

In contrast, the ECU of the present embodiment uses the master cylinder pressure P as the parameter, and can appropriately switch the control mode depending on whether or not the large load acts on the pump 6.

The parameter may be determined whether or not the large load acts on the pump 6, and the parameter is not limited to the master cylinder pressure P, and may generally use the hydraulic pressure on the discharge side of the pump 6. Accordingly, in the present specification, the description of the master cylinder pressure P can be appropriately replaced with the hydraulic pressure on the discharge side of the pump 6.

The 1 st hydraulic pressure P1, which is a threshold value for switching the control of the motor 60 from the PWM control mode to the duty 100% mode, can be set to the master cylinder pressure P at which the rotation can be restarted by the PWM control with a probability equal to or higher than a predetermined value within the 1 st time T1 determined after the rotation of the motor 60 is stopped.

That is, when the rotation speed N of the motor 60 is controlled by the PWM control, even if the rotation of the motor 60 is unexpectedly stopped when the master cylinder pressure P is equal to or lower than the 1 st hydraulic pressure P1, the rotation can be restarted at the probability of being equal to or higher than the predetermined value at the 1 st time T1. This prevents the motor 60 from being accidentally disabled from being restarted, and allows the rotation speed control by the PWM control to be executed.

On the other hand, when the rotation speed N is controlled by the PWM control, if the master cylinder pressure P is higher than the 1 st hydraulic pressure P1 and the motor 60 stops rotating unexpectedly, the probability that the rotation can be restarted at the 1 st time T1 is less than a predetermined value. Accordingly, when the master cylinder pressure P is higher than the 1 st hydraulic pressure P1, the motor 60 is continuously driven in advance, and thus an unexpected stop of rotation of the motor 60 and an inability to restart rotation can be suppressed.

When the lower limit of the range of the master cylinder pressure P in which a load for stopping the motor 60 is generated when the rotation speed N of the motor 60 is controlled by the PWM control is set to the 2 nd hydraulic pressure P2, the 1 st hydraulic pressure P1 is higher than the 2 nd hydraulic pressure P2.

Here, when the master cylinder pressure P is equal to or higher than the 2 nd hydraulic pressure P2, it is also conceivable to switch the control of the motor 60 from the PWM control mode to the duty 100% mode. That is, it is also conceivable that the ECU9 is configured to continuously drive the motor 60 in advance before a large load such as stopping the motor 60 occurs, regardless of whether or not the rotation of the motor 60 can be restarted by PWM control. The above-described unexpected stop of the motor 60 is also avoided in this case.

In contrast, the ECU9 of the present embodiment is configured to switch the control of the motor 60 from the PWM control mode to the duty 100% mode when the master cylinder pressure P is higher than the 2 nd hydraulic pressure P1. The 1 st hydraulic pressure P1 is higher than the 2 nd hydraulic pressure P2. Thus, even if the master cylinder pressure P generates a large load to stop the motor 60, the PWM control can be continued, and the sound vibration performance of the brake control device can be improved.

In the present embodiment, the master cylinder 14 is connected to the supply liquid passage 31. The master cylinder 14 is capable of generating hydraulic pressure P by operation of a driver. The supply liquid path 31 is connected to the discharge liquid path 35, and functions as a liquid path on the discharge side of the pump 6. That is, the hydraulic pressure on the discharge side of the pump 6 is a hydraulic pressure that changes in accordance with the hydraulic pressure P generated by the master cylinder 14, that is, the operation of the driver.

Thus, the discharge side of the pump 6 is likely to be a large hydraulic pressure at which the motor 60 is unexpectedly stopped or cannot start rotating again. Further, the load acting on the discharge side of the pump 6 is likely to change rapidly due to the fluctuation of the master cylinder pressure P. Therefore, the above-described operational effect of switching the control mode of the motor 60 is effectively obtained.

Here, the operation of the ABS control can be said to be a situation in which the above-described large hydraulic pressure is likely to be generated by the operation of the driver. This effectively achieves the above-described operational effects during the operation of the ABS control, and can prevent the ABS function using the pump 6 from being stopped.

In the present embodiment, the reservoir 5 is connected to the 1 st intake liquid path 33. The reservoir 5 can store the working oil flowing out of the wheel cylinders 21a to 21 d. The 1 st intake liquid passage 33 functions as a liquid passage on the intake side of the pump 6.

That is, the load acting on the pump 6 also changes in accordance with the amount of the hydraulic oil stored in the reservoir 5. This is a load acting on the suction side of the pump 6. Due to this variation in load, the motor 60 may be unexpectedly stopped or may not be able to start rotating again.

This effectively achieves the above-described operational effects of switching the control mode of the motor 60. Here, during the operation of the ABS control, the liquid amount of the reservoir 5 is likely to vary, and the load acting on the suction side of the pump 6 is likely to vary. Therefore, the ABS control operates effectively to obtain the above-described operational effects.

In the ABS control, the liquid amount of the reservoir 5 varies depending on the road surface μ. Thus, the ECU may be configured to change the timing of switching the control mode of the motor 60 (for example, the value of the 1 st hydraulic pressure P1) in accordance with the estimated road surface μ.

The ECU9 may be configured to switch the control mode of the motor 60 before the start of the operation of the ABS control or after the end of the operation of the ABS control. The control mode of the motor 60 may be switched regardless of the presence or absence of the operation of the ABS control.

In the non-operation of the ABS control, the amount of the working oil in the reservoir 5 is relatively small. Therefore, even if the motor 60 is continuously driven, the hydraulic oil is supplied to the master cylinder 14 side, and there is less possibility that the driver feels a sense of discomfort or the like. Thus, steps S3 and S5 of the processing flow of fig. 2 can be omitted as appropriate.

In the example of fig. 2, steps S3 and S5 are provided, and the mode can be switched to the duty 100% mode during ABS control, thereby preventing the ABS function from being stopped.

In addition, the condition for ending the duty 100% mode is not limited to the condition of the present embodiment. For example, a part or all of steps S6 to S10 in FIG. 2 may be omitted as appropriate.

In the present embodiment, the ECU9 is configured to switch the control of the motor 60 to the PWM control when the motor 60 is continuously driven with the duty ratio set to 100%, the continuous driving is continued even if the master cylinder pressure P is equal to or lower than the 1 st hydraulic pressure P1, and the master cylinder pressure P is equal to or lower than the 3 rd hydraulic pressure P3 which is lower than the 1 st hydraulic pressure P1.

This can suppress the timing of the determination of the end of the duty 100% mode from being inappropriate due to short-term fluctuations in the master cylinder pressure P. In other words, the threshold value of the master cylinder pressure P for ending the duty 100% mode can be set to the 3 rd hydraulic pressure P3 that is lower than the 1 st hydraulic pressure P1, and thus the mode can be ended only when the master cylinder pressure P tends to decrease in a long-term view. This allows the control mode of the motor 60 to be switched with higher accuracy.

Further, by making the start threshold P1 and the end threshold P3 of the duty 100% mode different, frequent switching of the control mode can be suppressed.

The ECU9 is configured to switch the control of the motor 60 to the PWM control when a 2 nd time T2 (time T3-T4 in fig. 3) elapses after the master cylinder pressure P becomes equal to or lower than the 3 rd hydraulic pressure P3. For example, the ECU9 can determine the switching based on whether or not the count value T counted up in the control cycle exceeds the threshold value T.

In this way, even if the master cylinder pressure P is equal to or less than the 3 rd hydraulic pressure P3, switching to the PWM control is performed after a certain amount of time has elapsed, whereby the determination of the end of the 100% duty mode can be more accurately performed, and frequent switching of the control mode can be more effectively suppressed.

The ECU9 is configured to set the 2 nd time T2 (time T3-T4 in fig. 3) longer when the master cylinder pressure P is equal to or lower than the 3 rd hydraulic pressure P3 than when the master cylinder pressure P is high. For example, the threshold T is set in accordance with the master cylinder pressure P in a control cycle. The threshold T is set at a high time to a low time of the master cylinder pressure P.

This makes it possible to more accurately determine the end of the duty 100% mode.

The hydraulic circuit of the hydraulic unit is not limited to the hydraulic circuit of the embodiment, and any configuration may be employed as long as the pump 6 can discharge the hydraulic fluid to the fluid path connected to the brake cylinder of the wheel.

In addition, the respective actuators of the hydraulic unit may have any configuration. For example, the motor 60 may be a brushless motor. The pump 6 may be a piston pump or the like.

In the case of using a gear pump as in the present embodiment, it is difficult to generate a hydraulic pressure with respect to a large load, and accidental stop of the motor 60 or the like is likely to occur. This effectively achieves the above-described operational effects of switching the control mode of the motor 60.

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 the examples. It is obvious that a person having ordinary knowledge in the technical field to which the present invention belongs can conceive various modifications and alterations within the scope of the technical idea described in the claims, and it is needless to say that these also belong to the technical scope of the present invention.

Description of the reference numerals

5 reservoir, 6 pump, 60 motor, 9 electronic control unit, 14 master cylinder, 21 wheel cylinder, 31 supply fluid path.

Claims

1. A brake control device (3, 9) capable of controlling a hydraulic pressure of a brake cylinder (21) of a wheel,

comprises a pump (6), a motor (60), and a control unit (9),

the pump (6) can suck the working fluid and discharge the working fluid to a fluid path (31) connected with the brake cylinder (21),

the motor (60) is used for driving the pump (6), the motor (60) is electric,

the control unit (9) can control the rotation speed (N) of the motor (60) by PWM control using pulse width modulation, and when the hydraulic pressure (P) on the discharge side of the pump (6) is higher than a predetermined 1 st hydraulic pressure (P1), the motor (60) is continuously driven with the duty ratio set to 100%.

2. The brake control apparatus according to claim 1,

the 1 st hydraulic pressure (P1) is a hydraulic pressure (P) on the discharge side of the pump (6) at which the rotation of the motor (60) is restarted by the PWM control with a probability of being equal to or greater than a predetermined value within a predetermined 1 st time (T1) after the rotation is stopped.

3. The brake control apparatus according to claim 2,

when the lower limit of the range of the hydraulic pressure (P) on the discharge side of the pump (6) in which a load for stopping the motor (60) is generated when the rotational speed (N) of the motor (60) is controlled by the PWM control is set to a 2 nd hydraulic pressure (P2), the 1 st hydraulic pressure (P1) is higher than the 2 nd hydraulic pressure (P2).

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

a service brake cylinder (14) capable of generating a hydraulic pressure (P) by an operation of a driver is connected to the fluid passages (35, 31) on the discharge side of the pump (6).

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

a reservoir (5) capable of storing the working fluid flowing out of the brake cylinder (21) of the wheel is connected to a fluid path (33) on the suction side of the pump (6).

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

the control unit (9) is configured to continue the continuous driving even if the hydraulic pressure (P) on the discharge side of the pump (6) is equal to or less than the 1 st hydraulic pressure (P1) when the motor (60) is continuously driven with the duty ratio set to 100%,

when a 2 nd time (t3-t4) elapses from the time when the hydraulic pressure (P) on the discharge side of the pump (6) is equal to or less than a predetermined 3 rd hydraulic pressure (P3) which is lower than the 1 st hydraulic pressure (P1), the control of the motor (60) is switched to the PWM control.

7. The brake control apparatus according to claim 6,

the control unit (9) is configured to set the 2 nd time (t3-t4) to a time period when the hydraulic pressure (P) on the discharge side of the pump (6) is high than low after the hydraulic pressure (P) on the discharge side of the pump (6) is equal to or less than the 3 rd hydraulic pressure (P3).

8. A brake control method for controlling a hydraulic pressure of a brake cylinder (21) of a wheel by a hydraulic fluid discharged from a pump (6) by driving the pump (6) by a motor (60),

the rotational speed (N) of the motor (60) is controlled by PWM control of pulse width modulation,

when the hydraulic pressure (P) on the discharge side of the pump (6) is higher than a predetermined value (P1), the motor (60) is continuously driven with the duty ratio set to 100%.