JP2020019335A - Brake control device and brake control method - Google Patents

Abstract

To provide a brake control device capable of inhibiting the unintended stop of motor rotation or the impossibility of the restart of the motor rotation.SOLUTION: Brake control devices (3, 9) capable of controlling wheel cylinder pressure comprise: a pump (6) capable of sucking in a hydraulic fluid and discharging it to a liquid passage (31) connected to a wheel cylinder (21); an electric motor (60) for driving the pump (6); and an electronic control unit (9) that can control the number of revolutions of the motor (60) by PWM control and that is constituted to continuously drive the motor (60) by setting a duty factor at 100%, when discharge-side liquid pressure of the pump (6) is higher than predetermined first liquid pressure.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a brake control device.

  BACKGROUND ART Conventionally, a brake control device including a pump driven by an electric motor and capable of controlling a hydraulic pressure of a brake cylinder of a wheel is known. For example, the device described in Patent Literature 1 can execute PWM (Pulse Width Modulation) control that modulates the width of a pulse output to a motor.

JP 2000-313325 A

  If the hydraulic pressure on the discharge side of the pump is higher than normal during the control of the rotation speed of the motor by the PWM control, a load larger than expected, for example, a large load exceeding the motor specification, acts on the pump. sell. If the load suddenly fluctuates in this state, the PWM control cannot cope with this fluctuation, and the motor may stop unintentionally.

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

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

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

  ADVANTAGE OF THE INVENTION According to this invention, the stop of an unintended motor can be suppressed and the performance of a brake control apparatus can be improved.

1 shows a brake system of an embodiment together with a hydraulic circuit. 6 is a flowchart illustrating a motor control process according to the embodiment. 6 is a time chart illustrating transition of each variable when executing motor control according to the embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the specification and the drawings, components having substantially the same function and structure are denoted by the same reference numerals, and redundant description is omitted.

<1. Configuration 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.

  The brake system 1 is a hydraulic system for a four-wheeled vehicle, and includes a master brake cylinder (hereinafter, master cylinder) 14 connected to a brake pedal 10 as a brake operation input element, and hydraulic brakes 2a to 2b for each wheel. A hydraulic cylinder 3 (hereinafter referred to as a wheel cylinder) 21a to 21d provided in 2d, 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 a hydraulic unit 3 And an electronic control unit (ECU) 9 for controlling the operation. The brake control device has a hydraulic unit 3 and an ECU 9.

  The brake system 1 according to the present embodiment does not include a booster that amplifies the depression force of the brake pedal 10 by using a negative pressure of the engine or the like, but may include the booster described above. The brake operation input element is not limited to the brake pedal 10 as long as the driver can input a request for vehicle braking.

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

  The master cylinder 14 has two pressure chambers 13a, 13b defined by both pistons 12a, 12b. The volume of each pressure chamber 13a, 13b changes according to the stroke amount of the piston rod 11. The piston rod 11 is provided with a stroke sensor 81 for detecting a stroke amount that is an axial displacement amount of the piston rod 11.

  Hydraulic oil is supplied to each of the pressure chambers 13a and 13b from the reservoir tank 16. The hydraulic oil functions as a hydraulic fluid for generating a hydraulic pressure. The coil springs 15a and 15b disposed in the pressure chambers 13a and 13b function as return springs that bias the pistons 12a and 12b toward the initial positions.

  The hydraulic unit 3 includes two hydraulic circuits 30a and 30b. One hydraulic circuit 30a is connected to one pressure chamber 13a of the master cylinder 14, and the other hydraulic circuit 30b is connected to the other pressure chamber 13b of the master cylinder 14.

  When the primary piston 12a and the secondary piston 12b are pressed and moved via the piston rod 11 by operating the brake pedal 10, 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-type piping system, and the pressure chambers 13a and 13b of the master cylinder 14 are located at diagonal positions of the vehicle via hydraulic circuits 30a and 30b. It is connected to a set of one front wheel and one rear wheel. Hydraulic oil is supplied to the wheel cylinder 21a of the right front wheel (FR) and the wheel cylinder 21b of the left rear wheel (RL) via a hydraulic circuit 30a. 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 a hydraulic circuit 30b.

  The brake system 1 may be a front-rear piping system or the like. The brake system 1 is not limited to a four-wheeled vehicle, but may be a two-wheeled vehicle or a brake system for other vehicles.

<2. Configuration example of hydraulic circuit>
One hydraulic circuit 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 solenoid 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 are normally open type and can be linearly controlled. The pressure reducing valves 42a and 42b and the suction control valve 44 are normally closed and on / off controlled.

  The plurality of liquid paths include a supply liquid path 31, a reduced-pressure liquid path 32, a first suction liquid path 33, a second 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 13a. The other end of the supply liquid passage 31 branches into two. Each of the branch fluid paths 31a, 31b is connected to a brake pipe communicating with the wheel cylinders 21a, 21b.

  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 liquid passage parallel to the circuit control valve 41. The branch liquid passages 31a and 31b are provided with pressure increasing valves 41a and 41b, respectively. Check valves 47a and 47b are provided in a bypass liquid passage parallel to the pressure increasing valves 41a and 41b.

  One end of the decompression liquid passage 32 is connected to the accumulator 5. The other end of the decompression liquid passage 32 branches into two. The branch liquid passages 32a and 32b are connected to the pressure increase valves 41a and 41b of the branch liquid passages 31a and 31b of the supply liquid passage 31, respectively, on the side of the wheel cylinders 21a and 21b.

  One end of the first suction liquid passage 33 is connected to the accumulator 5. The other end of the first suction liquid passage 33 is connected to the suction side of the pump 6. A check valve 43 is provided in the first suction liquid passage 33.

  One end of the second suction liquid passage 34 is connected to the brake pipe communicating with the pressure chamber 13a via the supply liquid passage 31. The other end of the second suction liquid passage 34 is connected to the suction side of the pump 6 via the first suction liquid passage 33. A suction control valve 44 is provided in the second suction liquid passage 34.

  One end of the discharge liquid passage 35 is connected to the discharge side of the pump 6. The other end of the discharge liquid passage 35 is connected to the circuit control valve 41 of the supply liquid passage 31 on the side of the pressure increasing valves 41a and 41b. A damper 7 is provided in the discharge liquid path 35. A check valve 45 is provided between the damper 7 and the supply liquid passage 31 in the discharge liquid passage 35. A variable throttle 70 is provided between the damper 7 and the check valve 45 in the discharge liquid path 35.

  The circuit control valve 41 can communicate or shut off between the master cylinder 14 and the pressure-intensifying valves 41a and 41b in the supply liquid passage 31. The check valve 46 allows the movement of the hydraulic oil from the master cylinder 14 side to the wheel cylinders 21a and 21b of the right front wheel or the left rear wheel via the bypass fluid path, and prohibits the movement in the reverse direction. .

  The pressure-intensifying valve 41a is capable of adjusting the flow rate of hydraulic oil from the circuit control valve 41 side to the wheel cylinder 21a of the right front wheel via the supply liquid path 31. The check valve 47a allows movement of hydraulic oil from the hydraulic brake 2a side of the right front wheel toward the circuit control valve 41 via the bypass fluid path, and prohibits movement in the reverse direction.

  By opening the pressure reducing valve 42a, the operating oil of the wheel cylinder 21a of the right front wheel can be supplied to the accumulator 5 via the pressure reducing fluid passage 32, and thereby the pressure of the wheel cylinder 21a can be reduced.

  The same applies to the pressure increasing valve 41b and the pressure reducing valve 42b.

  The accumulator 5 accumulates the hydraulic oil or discharges the hydraulic oil to the first suction liquid passage 33 while changing the volume in accordance with the pressure of the hydraulic oil supplied through the reduced-pressure liquid passage 32. The check valve 43 permits the movement of the hydraulic oil from the accumulator 5 side to the suction side of the pump 6 via the first suction liquid passage 33, and prohibits the movement in the reverse direction.

  The suction control valve 44 can communicate or shut off the communication between the master cylinder 14 and the suction side of the pump 6 in the second suction liquid passage 34.

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

  The motor 60 is an electric motor, 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 or vibration noise accompanying a change in the flow rate of hydraulic oil inside the hydraulic circuit 30a.

  The variable throttle 70 is capable of adjusting the flow rate of the working oil supplied from the pump 6 via the damper 7. The check valve 45 permits the movement of the hydraulic oil from the damper 7 side to the supply liquid path 31 via the discharge liquid path 35, and prohibits the movement in the reverse direction.

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

  A second pressure sensor 83 is provided on the right front wheel wheel cylinder 21a side of the pressure increasing valve 41a in the branch liquid passage 31a of the supply liquid passage 31. The second pressure sensor 83 can detect the pressure of the wheel cylinder 21a (the wheel cylinder pressure of the right front wheel). Note that the second pressure sensor 83 may be provided in a liquid passage 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 different from the hydraulic circuit 30a in 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. It is configured similarly to the hydraulic circuit 30a.

<3. Configuration example of electronic control unit>
Part or all of the ECU 9 may be configured by, for example, a microcomputer or a microprocessor unit. Microcomputers and the like include a central processing unit (CPU) that executes various arithmetic processes, a read-only memory (ROM) that stores various control programs, and a random access memory (RAM) that is used as a work area for storing data and executing programs. ), And an input / output interface (I / O), which may be connected to each other by a bidirectional common bus.

  Further, a part or all of the ECU 9 may be configured by an updatable device such as firmware, or may be a program module or the like executed by a command from a CPU or the like.

  The ECU 9 is connected to a stroke sensor 81, first and second pressure sensors 82 and 83, and a wheel speed sensor that detects a rotation speed (wheel speed) of each wheel via a communication line. The ECU 9 is connected to another ECU so that bidirectional communication can be performed via a communication line such as a CAN (Controller Area Network).

  The ECU 9 individually controls the wheel cylinder pressure of each wheel by controlling the driving of the solenoid valve 41 and the like, which are actuators of the hydraulic unit 3, and the motor 60 based on signals input from these sensors or other ECUs. It can be controlled.

  For example, by closing the pressure increasing valve 41a and opening the pressure reducing valve 42a, the wheel cylinder pressure of the right front wheel can be reduced. By closing the pressure increasing valve 41a and the pressure reducing valve 42a, the wheel cylinder pressure of the right front wheel can be held. By opening the pressure increasing valve 41a and closing the pressure reducing valve 42a, the wheel cylinder pressure of the right front wheel can be increased.

  The ECU 9 determines that one of the wheels is likely to be locked due to the pressure increase of the wheel cylinders 21a to 21d by the driver's brake operation, for example, in a state where the circuit control valve 41 is opened and the suction control valve 44 is closed. Is detected by a signal from a wheel speed sensor or the like. At this time, the locking tendency can be reduced by controlling the wheel cylinder pressure of the wheel by reducing, holding, or increasing the pressure as described above. Thereby, the brake control device functions as an anti-lock brake system (ABS).

  For example, the ECU 9 can adjust the flow rate of the working oil flowing from the wheel cylinder 21a to the accumulator 5 via the pressure reducing fluid passage 32 by intermittently repeating opening and closing of the pressure reducing valve 42a. By driving the pump 6, the ECU 9 can pump the hydraulic oil released to the accumulator 5 toward the master cylinder 14.

  Further, the ECU 9 drives the pump 6 and drives the pressure increasing valve 41a or the pressure reducing valve 42a, for example, in a state where the circuit control valve 41 is closed and the suction control valve 44 is opened, so that the driver brakes. The wheel cylinder pressure of each wheel can be controlled independently of the operation. As a result, brake control for controlling the motion of the vehicle, emergency brake control for avoiding collision of the vehicle, and the like can be executed as part of the electronic stability program (ESP).

  The ECU 9 is configured to switch between a PWM control mode and a 100% duty mode as a mode for controlling the motor 60 and to execute the mode.

  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 that modulates the width of a pulse output to the motor 60.

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

(flowchart)
An example of the control processing by the ECU 9 of the present embodiment will be described in detail with reference to FIG. FIG. 2 shows an example of a flow of a motor control process executed by the ECU 9. This process is repeatedly executed at a predetermined cycle.

  In step S1, the ECU 9 reads the detected master cylinder pressure P and the detected vehicle speed V. The vehicle speed V can be calculated, for example, from the detected wheel speed. The vehicle speed V may be detected using 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 (first hydraulic pressure) P1. If the master cylinder pressure P is higher than the first hydraulic pressure P1, the process proceeds to step S3. If the master cylinder pressure P is equal to or less than the first hydraulic pressure P1, the process proceeds to step S6.

  That is, while the ECU 9 is controlling the rotation speed of the motor 60 by the PWM control, the master cylinder pressure P acts on the pump 6 as a hydraulic pressure on the discharge side of the pump 6 to generate a load for stopping the rotation of the motor 60. sell.

  The first hydraulic pressure P1 is such that a load that allows the motor 60 to resume rotation by the PWM control with a probability equal to or higher than a predetermined value within a predetermined first time T1 after the rotation of the motor 60 is stopped. This is the master cylinder pressure P applied to (motor 60).

  The first time T1 can be set, for example, to a time that does not hinder the ABS control even if the pump 6 does not operate during the first time T1. The probability of the predetermined value or more is, for example, 90% or more, preferably 95% or more, and more preferably 99% or more.

  As described above, when the lower limit of the range of the master cylinder pressure P that can generate the load for stopping the rotation of the motor 60 is the second hydraulic pressure P2, the first hydraulic pressure P1 is higher than the second 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 that the ABS control will operate is less than the predetermined value. If the vehicle speed V is higher than the predetermined value V1, the process proceeds to step S4. If the vehicle speed V is equal to or less than the predetermined value V1, the process proceeds to step S6.

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

  In step S5, it is determined whether the ABS control has been switched from ON (operation) to OFF (non-operation). If it has been switched from on to off, the process proceeds to step S11, and if it has not been switched, this cycle ends.

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

  In step S7, it is determined whether the master cylinder pressure P is equal to or lower than a predetermined third hydraulic pressure P3. The third hydraulic pressure P3 can be set to a value lower than the first hydraulic pressure P1 by, for example, a fluctuation of the master cylinder pressure P predicted during the ABS control operation. If the master cylinder pressure P is equal to or lower than the third hydraulic pressure P3, the process proceeds to step S8. If the master cylinder pressure P is higher than the third hydraulic pressure P3, the process proceeds to step S4.

  In step S8, a threshold value T * of the count value T of the timer is set. According to the master cylinder pressure P read in step S1, the threshold T * can be set to a larger value when the master cylinder pressure P is high than when it is low. 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 the count value T is equal to or greater than a threshold value T *. If the count value T is equal to or greater than the threshold value T *, the process proceeds to step S11. If the count value T is less than the threshold value 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 current cycle ends.

<4. Operation example of brake control device>
Next, an example of the operation of the brake control device will be described with reference to FIG.

  FIG. 3 shows a master cylinder pressure transition 101, an ABS control on / off transition 102, a 100% duty on / off transition 103, and a timer count value T transition when the ECU 9 of this embodiment executes motor control. 104, a transition 105 of the threshold value 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.

  At time t1 when the driver depresses the brake pedal 10 and the master cylinder pressure P is increasing, the ABS control starts operating. At this time, since the master cylinder pressure P is equal to or lower than the first hydraulic pressure P1, the flow of steps S1, S2, S6, S11, and S1 in FIG. 2 is performed, and the ECU 9 executes the PWM control mode. The rotation speed N of the motor 60 is controlled to converge to a predetermined constant value.

  At time t2, master cylinder pressure P becomes higher than first hydraulic pressure P1. The ABS control is in operation, and the vehicle speed V is higher than the predetermined value V1. Accordingly, the flow of steps S1, S2, S3, S4, S5, and S1 in FIG. 2 is performed, and the ECU 9 executes the 100% duty mode. The motor 60 is driven continuously, and the number of revolutions N is not particularly controlled.

  At time t3, the master cylinder pressure P becomes equal to or lower than the third hydraulic pressure P3. Therefore, in FIG. 2, the flow is the sequence of steps S1, S2, S6, S7, S8, S9, S10, S4, S5, and S1, and the ECU 9 continues the duty 100% mode, sets the threshold value T *, and sets the count value. Start counting up T.

  Until the time t4, the master cylinder pressure P is equal to or lower than the third hydraulic pressure P3. Therefore, the threshold value T * is reset to a value corresponding to the master cylinder pressure P at that time, and the count value T continues to be counted up.

  At time t4, the count value T reaches the threshold value T *. Therefore, in FIG. 2, the flow is steps S1, S2, S6, S7, S8, S9, S10, S11, and S1, and the ECU 9 executes the PWM control mode. The rotation speed N of the motor 60 is controlled to converge to a predetermined value again.

  At time t5, the ABS control ends its operation. Accordingly, the ECU 9 stops the motor 60.

  As is clear from the above example, the ECU 9 can control the rotation speed N of the motor 60 by PWM control. When the master cylinder pressure P is higher than the first hydraulic pressure P1, the ECU 9 sets the duty ratio to 100% and sets the motor 60 Are configured to be continuously driven.

  That is, if the master cylinder pressure P is in a higher range than normal during the control of the rotation speed N by the PWM control, a load exceeding the expectation, for example, a large load exceeding the specification of the motor 60 acts on the pump 6. sell. If the load fluctuates rapidly in this state, the PWM control cannot cope with this fluctuation, and the motor 60 may stop unintentionally.

  Further, if the master cylinder pressure P is in a region higher than normal after the motor 60 is stopped unintentionally, a large load is applied to the pump 6 so that the PWM control causes the motor 60 to rotate within a predetermined time. It may not be possible to resume.

  Here, while the motor 60 is continuously driven at a duty of 100% (so-called fully opened), even when a large load is acting on the pump 6, a torque exceeding this load can be generated. In addition, even if the load fluctuates rapidly, rotation can be continued.

  The present inventors pay attention to this point, and when the master cylinder pressure P is higher than the first hydraulic pressure P1, the ECU 9 switches the control of the motor 60 from the PWM control mode to the 100% duty mode (continuous drive). Configured.

  Therefore, even when the load is applied to the pump 6, by continuously driving the motor 60, it is possible to prevent the motor 60 from stopping unintentionally or from being unable to restart rotation. Therefore, the performance of the brake control device can be improved.

  Further, when on / off control is performed so that the rotation speed N of the motor 60 is constant by PWM control in a state where a large load is applied to the pump 6 and a high load is generated on the motor 60, the inrush current of the motor 60 The current I increases on average.

  On the other hand, when the motor 60 is driven continuously, the current I can be small because the on / off control is not performed. As illustrated in FIG. 3, the current I of the motor 60 is smaller during the 100% duty mode (time t2 to t4) than during the PWM control mode (time t1 to t2, time t4 to t5).

  Therefore, by suppressing the current consumption of the motor 60, the power load on the vehicle can be reduced. In addition, it is possible to suppress an increase in the wire diameter of the power supply cable of the motor 60, the capacity of the fuse, or the heat resistance of the connector pins of the ECU 9, thereby making it possible to reduce the size and cost of the brake control device.

  Note that the voltage of the motor 60, in other words, the torque that can be generated by the motor 60 may vary depending on the environmental temperature and the like. Therefore, the ECU may be configured to change the switching timing (for example, the value of the first hydraulic pressure P1) of the control mode of the motor 60 according to the environmental temperature or the like.

  A parameter used for switching the control of the motor 60 between the PWM control mode and the 100% duty mode may be an induced voltage of the motor 60 during the PWM control or the length of the duty-off time.

  However, when using these parameters, it is determined whether or not a phenomenon such as the motor 60 stopping unintentionally is caused by a large load acting on the pump 6 exceeding the specification of the motor 60. It is difficult to make an accurate determination, and it is difficult to switch the control mode depending on whether such a large load is acting.

  On the other hand, the ECU of the present embodiment can switch the control mode appropriately depending on whether the large load is acting on the pump 6 by using the master cylinder pressure P as the parameter.

  Note that the above parameters need only be able to determine whether or not the large load is acting on the pump 6, and is not limited to the master cylinder pressure P but may be a general hydraulic pressure on the discharge side of the pump 6. Therefore, in this specification, the description of the master cylinder pressure P can be appropriately read as the hydraulic pressure on the discharge side of the pump 6.

  The first hydraulic pressure P1, which is a threshold value for switching the control of the motor 60 from the PWM control mode to the 100% duty mode, has a probability of being equal to or greater than a predetermined value within a predetermined first time T1 after the motor 60 stops rotating. The master cylinder pressure P can be set so that rotation can be resumed by control.

  That is, when the rotation speed N of the motor 60 is controlled by the PWM control, and the master cylinder pressure P is equal to or lower than the first hydraulic pressure P1, even if the motor 60 stops rotating unintentionally, the predetermined time is maintained within the first time T1. The rotation can be restarted with a probability higher than the value. Therefore, the rotation speed control by the PWM control can be executed while preventing the motor 60 from being unintentionally unable to restart.

  On the other hand, when the rotation speed N is controlled by the PWM control and the master cylinder pressure P is higher than the first hydraulic pressure P1, if the motor 60 stops rotating unintentionally, there is a probability that the rotation can be restarted within the first time T1. It will be less than the predetermined value. Therefore, when the master cylinder pressure P is higher than the first hydraulic pressure P1, by continuously driving the motor 60 in advance, it is possible to suppress unintended rotation stop and inability to restart the rotation of the motor 60.

  When the lower limit of the range of the master cylinder pressure P that can generate a load for stopping the motor 60 while controlling the rotation speed N of the motor 60 by the PWM control is the second hydraulic pressure P2, the first hydraulic pressure P1 is equal to the second hydraulic pressure P2. It is higher than the pressure P2.

  Here, when the master cylinder pressure P is equal to or higher than the second hydraulic pressure P2, the control of the motor 60 may be switched from the PWM control mode to the 100% duty mode. That is, regardless of whether or not the rotation of the motor 60 can be resumed by the PWM control, the ECU 9 is configured to continuously drive the motor 60 in advance before a large load that stops the motor 60 occurs. Is also conceivable. Also in this case, the unintended stop of the motor 60 can be avoided.

  On the other hand, when the master cylinder pressure P is higher than the second hydraulic pressure P1, the ECU 9 of the present embodiment is configured to switch the control of the motor 60 from the PWM control mode to the 100% duty mode. The first hydraulic pressure P1 is higher than the second hydraulic pressure P2. Therefore, even if the master cylinder pressure P at which a large load that stops the motor 60 is generated can be maintained, 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 can generate the hydraulic pressure P by a driver's operation. 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 P generated by the master cylinder 14, that is, a hydraulic pressure that can be changed according to the driver's operation.

  Therefore, the discharge side of the pump 6 tends to have such a large hydraulic pressure that the motor 60 stops unintentionally or the rotation cannot be resumed. Further, the load acting on the discharge side of the pump 6 tends to fluctuate rapidly due to the fluctuation of the master cylinder pressure P. Therefore, the above-described operation and effect by switching the control mode of the motor 60 can be effectively obtained.

  Here, during the operation of the ABS control, it can be said that the large hydraulic pressure is likely to be generated by the operation of the driver. Therefore, the above-described operation and effect can be effectively obtained during the operation of the ABS control, and a situation in which the ABS function using the pump 6 stops can be prevented.

  In the present embodiment, the accumulator 5 is connected to the first suction liquid passage 33. The accumulator 5 can store the operating oil flowing out of the wheel cylinders 21a to 21d. The first suction liquid passage 33 functions as a liquid passage on the suction side of the pump 6.

  That is, the load acting on the pump 6 can also change according to the amount of hydraulic oil stored in the accumulator 5. This is a load acting on the suction side of the pump 6. Due to this change in the load, the possibility that the motor 60 stops unintentionally or the rotation cannot be restarted increases.

  Therefore, the above-described operation and effect by switching the control mode of the motor 60 can be effectively obtained. Here, during the operation of the ABS control, the liquid amount of the accumulator 5 tends to fluctuate, and the load acting on the suction side of the pump 6 tends to fluctuate. Therefore, the above-described operation and effect can be effectively obtained when the ABS control is operated.

  At the time of the ABS control, the liquid amount of the accumulator 5 may vary depending on the road surface μ. Therefore, the ECU may be configured to change the switching timing (for example, the value of the first hydraulic pressure P1) of the control mode of the motor 60 according to the estimated road surface μ.

  Note that the ECU 9 may be configured to switch the control mode of the motor 60 even before the operation of the ABS control starts or after the operation of the ABS control ends. Further, the control mode of the motor 60 may be switched regardless of the presence or absence of the operation of the ABS control.

  During the non-operation of the ABS control, the amount of hydraulic oil in the accumulator 5 is relatively small. For this reason, even if the motor 60 is continuously driven, there is little possibility that the hydraulic oil is supplied to the master cylinder 14 side to give a feeling of strangeness to the driver. Therefore, steps S3 and S5 in the processing flow of FIG. 2 can be omitted as appropriate.

  In the example of FIG. 2, steps S3 and S5 are provided so that the duty can be switched to the 100% duty mode during the ABS control, thereby preventing the stop of the ABS function.

  Note that conditions for terminating the 100% duty mode are not limited to those of the present embodiment. For example, some or all of steps S6 to S10 in FIG. 2 may be omitted as appropriate.

  In the present embodiment, the ECU 9 continues the continuous driving even when the master cylinder pressure P becomes equal to or lower than the first hydraulic pressure P1 while the motor 60 is continuously driven with the duty ratio being 100%, and the master cylinder pressure P becomes the first hydraulic pressure. When the pressure becomes equal to or lower than the third hydraulic pressure P3 lower than the pressure P1, the control of the motor 60 is switched to the PWM control.

  Therefore, it is possible to prevent the timing of the end determination of the 100% duty mode from becoming inappropriate due to the short-term fluctuation of the master cylinder pressure P. In other words, by setting the threshold value of the master cylinder pressure P for ending the 100% duty mode to the third hydraulic pressure P3 lower than the first hydraulic pressure P1, when the master cylinder pressure P tends to decrease in a long term. As long as the mode can be terminated. Thereby, the control mode of the motor 60 can be switched more accurately.

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

  In addition, the ECU 9 switches the control of the motor 60 to the PWM control when the second time T2 (time t3-t4 in FIG. 3) has elapsed since the master cylinder pressure P became equal to or lower than the third hydraulic pressure P3. It is configured. For example, the ECU 9 can determine the switching based on whether or not a count value T counted up in each control cycle exceeds a threshold value T *.

  As described above, even if the master cylinder pressure P becomes equal to or lower than the third hydraulic pressure P3, the end of the 100% duty mode is more accurately determined by switching to the PWM control after a certain period of time has elapsed, thereby controlling the control mode. Frequent switching can be suppressed more effectively.

  After the master cylinder pressure P becomes equal to or lower than the third hydraulic pressure P3, the ECU 9 sets the second time T2 (time t3-t4 in FIG. 3) longer when the master cylinder pressure P is high than when it is low. Is configured. For example, the threshold value T * is set according to the master cylinder pressure P for each control cycle. The threshold value T * is set longer when the master cylinder pressure P is high than when it is low.

  Therefore, the end determination of the 100% duty mode can be performed more accurately.

  In addition, the hydraulic circuit of the hydraulic unit is not limited to the one in the embodiment, and any configuration can be adopted as long as the pump 6 can discharge the hydraulic fluid to a hydraulic path connected to the brake cylinder of the wheel. is there.

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

  When a gear pump is used as in the present embodiment, it is relatively difficult to generate a hydraulic pressure for a large load, and an unintended stop of the motor 60 is likely to occur. Therefore, the above-described operation and effect by switching the control mode of the motor 60 can be effectively obtained.

  As described above, the preferred embodiments of the present invention have been described in detail with reference to the accompanying drawings, but the present invention is not limited to such examples. It is apparent that those skilled in the art to which the present invention pertains can conceive various changes or modifications within the scope of the technical idea described in the claims. It is understood that these also belong to the technical scope of the present invention.

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

Claims (8)

A brake control device (3, 9) capable of controlling a hydraulic pressure of a wheel brake cylinder (21),
A pump (6) capable of sucking hydraulic fluid and discharging the hydraulic fluid to a fluid passage (31) connected to the brake cylinder (21);
An electric motor (60) for driving the pump (6);
The rotation speed (N) of the motor (60) can be controlled by PWM control that modulates the pulse width, and the hydraulic pressure (P) on the discharge side of the pump (6) is higher than a predetermined first hydraulic pressure (P1). And a controller (9) configured to drive the motor (60) continuously when the duty ratio is 100%. The first hydraulic pressure (P1) is such that the pump () can restart rotation by the PWM control with a probability equal to or higher than a predetermined value within a predetermined first time (T1) after the rotation of the motor (60) stops. The brake control device according to claim 1, wherein the hydraulic pressure (P) on the discharge side of (6). The lower limit of the range of the hydraulic pressure (P) on the discharge side of the pump (6) that can generate a load for stopping the motor (60) while controlling the rotation speed (N) of the motor (60) by the PWM control. 3. The brake control device according to claim 2, wherein the first hydraulic pressure (P1) is higher than the second hydraulic pressure (P2), where is the second hydraulic pressure (P2). A master brake cylinder (14) capable of generating a hydraulic pressure (P) by a driver's operation is connected to a hydraulic path (35, 31) on the discharge side of the pump (6). The brake control device according to any one of claims 1 to 3. The accumulator (5) capable of storing the hydraulic fluid flowing out of the brake cylinder (21) of the wheel is connected to the fluid path (33) on the suction side of the pump (6). The brake control device according to any one of claims 4 to 4. The control unit (9) includes:
While the motor (60) is continuously driven with a duty ratio of 100%, the continuous drive is continued even if the hydraulic pressure (P) on the discharge side of the pump (6) becomes equal to or lower than the first hydraulic pressure (P1). ,
When a second time (t3-t4) has elapsed since the hydraulic pressure (P) on the discharge side of the pump (6) became equal to or lower than a predetermined third hydraulic pressure (P3) lower than the first hydraulic pressure (P1). The brake control device according to any one of claims 1 to 5, wherein the control of the motor (60) is switched to the PWM control. After the hydraulic pressure (P) on the discharge side of the pump (6) becomes equal to or lower than the third hydraulic pressure (P3), the control unit (9) controls the hydraulic pressure (P) on the discharge side of the pump (6). The brake control device according to claim 6, wherein the second time (t3-t4) is set to be longer when the value of (2) is high than when it is low. A brake control method in which a pump (6) is driven by a motor (60), and a hydraulic pressure of a brake cylinder (21) of a wheel is controlled by a hydraulic fluid discharged from the pump (6),
The number of rotations (N) of the motor (60) is controlled by PWM control for modulating a pulse width,
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 a duty ratio of 100%.