JP7363466B2 - Brake control device - Google Patents

Description

The present invention relates to a brake control device.

The brake control device is, for example, a device that includes a pump driven by the rotation of a motor and uses the drive of the pump to adjust the pressure of the wheel cylinder, that is, the braking force. Here, Japanese Patent Laid-Open No. 11-93859 describes a pump drive device that periodically switches the rotational direction of a motor in a startup operation mode and then switches to a steady operation mode. According to this, minute foreign matter accumulated in the gear of the pump is crushed and removed by the vibration generated each time the rotational direction of the motor is switched.

Japanese Patent Application Publication No. 11-93859

Incidentally, the torque of the motor required to drive the pump varies depending on the hydraulic pressure (load pressure) generated in the flow path between the discharge port of the pump that discharges fluid and the check valve. By reducing this load pressure, the torque required for the motor can be reduced. According to this, it is possible to start the motor quickly, and furthermore, it is possible to reduce the size of the motor.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a brake control device that can reduce the load pressure of a pump.

The braking control device of the present invention includes a motor whose rotation direction can be changed in two directions, forward and reverse, and which is driven according to the rotation of the motor, and when the motor rotates in the forward direction, fluid is sucked from a suction port and fluid is drawn from a discharge port. disposed between a pump that discharges fluid from the pump , a first flow path connected to the discharge port of the pump, and a second flow path, the fluid flowing from the second flow path to the first flow path; a check valve that prevents the above, a control unit that controls driving of the motor, and a leakage amount prediction unit that predicts an amount of fluid leaking from the discharge port to the suction port of the pump, the control unit In order to reduce the load pressure, which is the hydraulic pressure in the first flow path, at a predetermined timing when the state of the motor is changed from a normal rotation state in which it is rotating in the forward direction to a stopped state, the motor is reversely rotated. In addition to executing load reduction control to rotate the motor in the forward direction, the control unit may cause the motor to rotate after the number of rotations in the positive direction of the motor reaches 0, depending on the leakage amount predicted by the leakage amount prediction unit. Set the time to rotate in the opposite direction.

According to the present invention, by executing the load reduction control, the fluid in the first flow path is sucked into the pump from the discharge port and discharged from the suction port. Thereby, the hydraulic pressure, that is, the load pressure in the first flow path can be reduced. By lowering the load pressure when starting the motor next time, the starting torque required for the motor is reduced. According to the present invention, the motor can be started quickly.

FIG. 1 is a configuration diagram of a brake control device according to a first embodiment. It is a time chart for explaining load reduction control of a 1st embodiment. FIG. 2 is a conceptual diagram for explaining the pump of the first embodiment. FIG. 2 is a conceptual diagram for explaining the pump of the first embodiment. It is a block diagram which shows a part of brake control apparatus of 2nd Embodiment. It is a time chart for explaining load reduction control of a 2nd embodiment.

Embodiments of the present invention will be described below based on the drawings. Each figure used in the explanation is a conceptual diagram. As shown in FIG. 1, the brake control device 1 of the first embodiment is incorporated into a vehicle brake device 100. Specifically, the vehicle braking device 100 includes a brake pedal 11, a booster 12, a master cylinder 13, a reservoir 14, a brake switch 15, a stroke sensor 16, and a brake control device 1. . This brake control device 1 includes an actuator 5 and a brake ECU 6. Each part of the vehicle braking device 100 will be briefly explained below, and then the brake control device 1 will be explained in detail.

The brake pedal 11 is an operation member that allows the driver to operate the brake. The brake switch 15 is a sensor that detects whether or not the brake pedal 11 is operated. The stroke sensor 16 is a sensor that detects the stroke (operation amount) of the brake pedal 11. Brake switch 15 and stroke sensor 16 output detection signals to brake ECU 6. The booster 12 is, for example, a vacuum booster that uses the engine's intake negative pressure to assist the brake operation force.

The master cylinder 13 is a device that generates master pressure according to the operation of the brake pedal 11. The reservoir 14 is a member for storing fluid and replenishing the master cylinder 13 with the fluid.

The actuator 5 is a device that adjusts the hydraulic pressure of the wheel cylinder 54 (hereinafter referred to as "wheel pressure") based on the master pressure supplied from the master cylinder 13. Actuator 5 is arranged between master cylinder 13 and wheel cylinder 54. Actuator 5 adjusts wheel pressure according to instructions from brake ECU 6. Depending on the wheel pressure, for example, a disc brake device or a drum brake device (not shown) provided on each wheel Wf, Wr is driven, and a braking force is generated on each wheel Wf, Wr.

The actuator 5 performs pressure increase control to make the wheel pressure the same level as the master pressure, pressure increase control to make the wheel pressure higher than the master pressure, pressure reduction control to reduce the wheel pressure, or wheel pressure control in accordance with instructions from the brake ECU 6. Executes retention control to maintain the . The actuator 5 executes, for example, anti-skid control (also referred to as ABS control), skid prevention control (ESC control), etc. based on instructions from the brake ECU 6.

In detail, the actuator 5 includes a hydraulic circuit 5A and a motor 90 whose rotation direction can be changed in two directions: forward and reverse. The motor 90 of the first embodiment is a three-phase brushless motor. The hydraulic circuit 5A includes a first piping system 50a and a second piping system 50b. Further, a wheel speed sensor 73 is installed for each wheel Wf, Wr.

The first piping system 50a includes a flow path A, a differential pressure control valve 51, a holding valve 52, a pressure reduction flow path B, a pressure reduction valve 53, a pressure regulation reservoir 56, a reflux flow path C, and a pump 57. , a check valve 58, a damper section 59, an auxiliary flow path D, and a pressure sensor 71. In addition, in the description, the term "flow path" can be replaced with terms such as hydraulic path, oil path, pipe line, passage, or piping.

The flow path A is a flow path that connects the master cylinder 13 and the wheel cylinder 54 via the flow path 17. The differential pressure control valve 51 is a normally open type solenoid valve provided in the flow path A. Based on the magnitude of the applied control current and the drive of the pump 57, the differential pressure control valve 51 controls the hydraulic pressure in the flow path on its own wheel cylinder 54 side to be higher than the hydraulic pressure in the flow path on its own master cylinder 13 side. Make it expensive. That is, the differential pressure control valve 51 is a solenoid valve that can adjust the differential pressure between the master pressure and the wheel pressure.

The holding valve 52 is a normally open electromagnetic valve that is disposed in the flow path A and whose opening and closing are controlled by the brake ECU 6. The pressure reduction flow path B is constituted by a flow path that connects a portion of the flow path A between the holding valve 52 and the wheel cylinder 54 and the pressure regulating reservoir 56.

The pressure reducing valve 53 is a normally closed electromagnetic valve that is disposed in the pressure reducing flow path B and whose opening and closing are controlled by the brake ECU 6. The pressure regulating reservoir 56 is a so-called low pressure reservoir that includes a cylinder, a piston, and a biasing member. The reflux flow path C is a flow path that connects the decompression flow path B and the pressure regulation reservoir 56 to the branch point X. The branch point X is a portion of the flow path A between the differential pressure control valve 51 and the holding valve 52.

The pump 57 is a device that is driven according to the rotation of the motor 90 and sucks fluid from the suction port 571 and discharges it from the discharge port 572 as the motor 90 rotates in the forward direction. The pump 57 is provided in the reflux channel C. The suction port 571 is connected to the pressure regulation reservoir 56 and the pressure reduction channel B side portion of the reflux channel C. The discharge port 572 is connected to a portion of the reflux channel C on the branch point X side. The pump 57 sucks fluid from the pressure regulating reservoir 56 and discharges it to the branch point X by rotating the motor 90 in the forward direction. The pump 57 of the first embodiment is, for example, a gear pump such as a trochoid pump.

The check valve 58 is disposed between the first flow path C1 connected to the discharge port 572 of the pump 57 and the second flow path C2, and prevents fluid from flowing from the second flow path C2 to the first flow path C1. It is a valve mechanism that prevents flow. The check valve 58 allows fluid to flow from the first flow path C1 to the second flow path C2. The first flow path C1 is a portion of the reflux flow path C between the discharge port 572 and the check valve 58. The second flow path C2 is a portion of the reflux flow path C between the check valve 58 and the branch point X. The first flow path C1 forms a substantially sealed space between the check valve 58 and the discharge port 572.

The damper section 59 is a damper mechanism that can store fluid according to hydraulic pressure. The damper portion 59 is provided in a flow path branched from the first flow path C1. The damper portion 59 is provided, for example, to reduce pulsation of hydraulic pressure.

The auxiliary flow path D is a flow path that connects the pressure adjustment hole 56a of the pressure adjustment reservoir 56 and a portion of the flow path A closer to the master cylinder 13 than the differential pressure control valve 51. The pressure regulating reservoir 56 is configured such that the valve hole 56b is closed as the amount of fluid flowing into the pressure regulating hole 56a increases due to an increase in stroke. A reservoir chamber 56c is formed on the flow path B, C side of the valve hole 56b. Pressure sensor 71 is a sensor that detects master pressure. Pressure sensor 71 transmits the detection result to brake ECU 6. The second piping system 50b has the same configuration as the first piping system 50a, so a description thereof will be omitted.

The brake ECU 6 is an electronic control unit including a CPU, memory, and the like. Various sensors such as a brake switch 15, a stroke sensor 16, a pressure sensor 71, and a wheel speed sensor 73 are connected to the brake ECU 6 via communication lines (not shown). The brake ECU 6 determines whether or not the actuator 5 needs to be operated based on the detection results of these various sensors.

The brake ECU 6 controls the wheel pressure by controlling the differential pressure control valve 51, the holding valve 52, the pressure reducing valve 53, and the motor 90. When the brake ECU 6 causes the pump 57 to operate normally, the brake ECU 6 rotates the motor 90 in the forward direction.

(load reduction control)
The brake ECU 6 includes a control section 61 and a pressure acquisition section 62. The control unit 61 controls the driving of the motor 90. Further, the control unit 61 executes load reduction control to rotate the motor 90 in the opposite direction at a predetermined timing in order to reduce the load pressure, which is the hydraulic pressure in the first flow path C1. The predetermined timing in the first embodiment is the timing at which the state of the motor 90 is shifted from a normal rotation state in which it is rotating in the normal direction to a stopped state. The control unit 61 detects a predetermined timing (that a predetermined condition is met) based on the control status of the motor 90. In this manner, the control unit 61 rotates the motor 90 in the reverse direction and then stops the motor 90 in transitioning the state of the motor 90 from the normal rotation state to the stopped state. In other words, the control unit 61 executes load reduction control when transitioning the state of the motor 90 from the normal rotation state to the stopped state.

A specific example of load reduction control will be described with reference to FIG. 2. In a state where master pressure is generated by the driver's brake operation and wheel pressure corresponding to the master pressure is generated, the second flow path pressure, which is the hydraulic pressure of the second flow path C2, is the same as the master pressure and the wheel pressure. level of fluid pressure. When the pump 57 is not driven in this state, the load pressure is 0, which is lower than the second channel pressure, but the check valve 58 prevents the fluid from flowing back toward the pump 57 side. When the motor 90 rotates in the forward direction and the pump 57 is driven when the load pressure is 0 and the second channel pressure is high, fluid is discharged from the discharge port 572 to the first channel C1, and the load pressure reaches the maximum. The pressure increases to the second flow path pressure.

As shown in the upper part of FIG. 2, conventionally, when the state of the motor 90 is transferred from a normal rotation state to a stopped state, the motor 90 is simply controlled by the brake ECU 6 so that the rotation speed of the motor 90 becomes 0. was. Therefore, the load pressure is gradually reduced by leakage from the first flow path C1 to other flow paths (leakage allowed by the configuration). A certain amount of time is required until the load pressure becomes zero.

According to this conventional configuration, when the control unit 61 rotates the motor 90 in the forward direction again under a high load pressure after the motor 90 has stopped, the rotational resistance force due to the high load pressure and the friction of the pump 57 The motor 90 is required to have enough torque to overcome the resultant force. In other words, in the conventional configuration, the output torque required of the motor 90 in order to be able to drive the motor 90 at any time is the hydraulic load torque corresponding to the maximum load pressure and the static friction torque corresponding to the static friction force of the pump 57. The total torque is greater than the total torque.

The frictional force of the pump 57 is generated by a sealing member disposed within the pump 57 (and within the motor 90). Here, the frictional force generated in the pump 57 during rotation will be briefly explained with reference to FIGS. 3 and 4. FIG. 3 corresponds to a cross-sectional view of the pump 57 taken along a plane perpendicular to the drive shaft 94 of the pump 57. FIG. 4 corresponds to a partial cross-sectional view of the pump 57 and the motor 90 taken along a plane passing through the center of the drive shaft 94 of the pump 57.

As shown in FIG. 3, the pump 57 is an internal gear pump in which an outer rotor 92 disposed within a housing 91 and an inner rotor 93 disposed inside the outer rotor 92 mesh with each other to rotate. A drive shaft 94 of the motor 90 is arranged at the center of the inner rotor 93 .

The seal members are arranged at various locations within the housing 91 (and within the motor 90). For example, the first seal member 95 is an elastic member that is disposed in a recess provided in the inner circumferential surface of the housing 91 and restricts a predetermined flow of fluid around the outer circumference of the outer rotor 92. The first sealing member 95 seals a portion where the fluid has a low pressure and a portion where the fluid has a high pressure on the outer periphery of the outer rotor 92. The first seal member 95 is composed of, for example, a columnar rubber member and a resin member.

Further, as shown in FIG. 4, the second seal member 96 is an annular elastic member disposed at a predetermined position on the outer peripheral surface of the drive shaft 94. As shown in FIG. The second seal member 96 is a shaft seal and an oil seal that regulates a predetermined flow of fluid on the outer peripheral surface of the drive shaft 94 . The second seal member 96 prevents fluid from flowing into the motor 90 and from flowing out of the pump 57, for example. The second seal member 96 is, for example, a rubber O-ring. In this way, the plurality of seal members 95 and 96 generate frictional force against the rotation of the drive shaft 94.

As described above, in the conventional configuration in which load reduction control is not performed, when the motor 90 is driven again after the motor 90 has stopped, the motor 90 is affected by the rotational resistance force caused by the high load pressure and by the seal members 95 and 96. It is necessary to output torque that overcomes the resultant force with the static friction force. In other words, conventionally, the maximum output torque of the motor 90 required in the design of the actuator 5 corresponds to the resultant force of the rotational resistance force corresponding to the maximum load pressure, that is, the control maximum pressure of the wheel pressure, and the static friction force of the pump 57. do.

The dynamic frictional force of the pump 57 can be said to be the frictional force when the lubricating oil is fully functioning on the sealing members 95 and 96 (in other words, the sealing members 95 and 96 are wet). Further, the static friction force of the pump 57 can be said to be the friction force when the lubricating oil is not functioning sufficiently with respect to the seal members 95 and 96 (in other words, the seal members 95 and 96 are dry). Static friction force is greater than dynamic friction force.

In the configuration of the first embodiment, as shown in the lower part of FIG. 2, in order to stop the motor 90 rotating in the forward direction, the control unit 61 gradually reduces the rotation speed and executes load reduction control. , rotates the motor 90 in the opposite direction. The control unit 61 controls the motor 90 so that the rotation speed of the motor 90 gradually changes from a positive value to a predetermined negative value (that is, a predetermined rotation speed in the opposite direction). Further, the control unit 61 controls the rotation speed of the motor 90 so that the amount of change in the rotation speed per unit time (change gradient of the rotation speed) is constant. The control unit 61 detects the timing to stop the motor 90 based on the motor control status, such as the execution status of anti-skid control or pressurization control, and executes the load reduction control in accordance with the timing.

Further, in the load reduction control, the control unit 61 rotates the motor 90 in the reverse direction within a predetermined switching time after the number of rotations in the forward direction of the motor 90 becomes 0. The predetermined switching time corresponds to the time from when the rotation speed of the motor 90 in the forward direction becomes 0 until the frictional force of the pump 57 changes to static frictional force. In other words, the predetermined switching time corresponds to the time from when the pump 57 stops until the frictional force of the pump 57 changes from dynamic frictional force to static frictional force.

In the first embodiment, the control unit 61 continuously changes the rotation direction of the motor 90 from the forward direction to the reverse direction. That is, the control unit 61 changes the rotation direction of the motor so that the predetermined switching time becomes approximately 0. Note that the predetermined switching time can be obtained in advance through experiment, simulation, or the like. Further, a change from dynamic frictional force to static frictional force can be detected, for example, when the frictional force becomes equal to or greater than a predetermined frictional force.

Further, the control unit 61 continues the load reduction control for a predetermined duration time, and then stops the motor 90. The predetermined duration is the time during which the motor 90 is rotated in the opposite direction. The predetermined duration time may be a fixed time set in advance, or may be calculated by calculation each time the load reduction control is executed. Based on the rotation speed of the motor 90 and the predetermined duration, the amount of reduction in the load pressure can be calculated. Note that the control unit 61 can estimate the rotation angle of the motor 90, for example, from the control current value (current monitor value) of the motor 90, or can acquire it from a rotation angle sensor such as a Hall element or a resolver of the motor 90. .

The pressure acquisition unit 62 is configured to acquire load pressure (load pressure information). Specifically, the pressure acquisition unit 62 of the first embodiment calculates (estimates) the wheel pressure and the second flow path pressure based on the master pressure detected by the pressure sensor 71 and the control current of the differential pressure control valve 51. )do. Then, the pressure acquisition unit 62 calculates the load pressure based on the calculated second flow path pressure, the rotation speed of the motor 90 (control current value or detected value), and the driving time of the motor 90. Due to the function of the check valve 58, the maximum value of the load pressure is the second flow path pressure. The pressure acquisition unit 62 acquires the load pressure through such calculation.

Here, the control unit 61 of the first embodiment determines the time for rotating the motor 90 in the opposite direction in the load reduction control, that is, the predetermined duration time, based on the load pressure acquired by the pressure acquisition unit 62. In other words, when executing the load reduction control, the control unit 61 sets the predetermined duration time so that the lower the load pressure is, the shorter the predetermined duration time is (including the case where the predetermined duration time is set to zero). The control unit 61 can calculate, for example, by setting the fluid reduction volume according to the load pressure acquired by the pressure acquisition unit 62, and dividing the set reduction volume by the fluid conveyance volume per unit time of the pump 57. . Note that the higher the load pressure, the greater the rotational resistance force of the pump 57, and the greater the hydraulic load torque corresponding to the rotational resistance force. Further, the static friction torque corresponding to the static friction force and the kinetic friction torque corresponding to the dynamic friction force each have approximately constant values.

In this configuration, the storage unit 63 provided in the brake control device 1 may store the relationship between the load pressure and the torque required when starting the pump 57. The predetermined value of the load pressure, which is the execution threshold for the load reduction control, is set, for example, to the value of the load pressure when the maximum torque that can be generated by the motor 90 and the torque required to start the pump 57 are at the same level. may be done.

(effect)
The brake control device 1 of the first embodiment includes a motor 90, a pump 57, a control section 61, and a check valve 58, and the control section 61 rotates the motor 90 in the opposite direction at a predetermined timing. This is a device that executes load reduction control. According to this configuration, by executing the load reduction control at a predetermined timing, the fluid in the first flow path C1 is discharged to the suction port 571 side of the pump 57, and the load pressure can be reduced. When the motor 90 is started next time, the rotational resistance force due to the load pressure can be reduced. In other words, since the load pressure when starting the motor next time is low, the starting torque required for the motor is reduced. According to the first embodiment, the motor 90 can be started quickly.

Further, according to the first embodiment, the load reduction control is executed at the timing when the state of the motor 90 shifts from the normal rotation state to the stopped state. Therefore, even when the motor 90 is driven again, such as when performing anti-skid control, immediately after the motor 90 is stopped through load reduction control, the motor 90 can be started with the load pressure being low. In other words, the starting torque reduction effect can be obtained no matter when the starting command for the motor 90 is output after the time when the motor 90 stops.

According to the first embodiment, in the load reduction control, the control unit 61 rotates the motor 90 in the reverse direction within a predetermined switching time after the number of rotations in the forward direction of the motor 90 becomes 0. Thereby, the motor 90 can be rotated in the opposite direction while the frictional force of the pump 57 is a dynamic frictional force. In other words, the starting torque when rotating the motor 90 in the opposite direction can be reduced. According to this configuration, the motor 90 can be rotated in the opposite direction more reliably.

Further, according to the first embodiment, the control unit 61 determines the time (predetermined duration time) for rotating the motor 90 in the opposite direction in the load reduction control based on the load pressure acquired by the pressure acquisition unit 62. . According to this, the predetermined duration time can be set according to the load pressure, and the minimum necessary predetermined duration time can be set. For example, when the load pressure is low, the predetermined duration time can be shortened in accordance with the load pressure (for example, by setting the predetermined duration time to zero, it is also possible not to execute the load reduction control). According to this configuration, the load reduction control is executed for a time corresponding to the load pressure, unnecessary driving is suppressed, and the state of the motor 90 can be brought to a stopped state (that is, a startable state) more quickly. . Furthermore, this configuration is advantageous in terms of reducing driving noise of the motor 90 and saving power.

According to the first embodiment, when the motor 90 stops after the load pressure becomes 0 due to load reduction control, the torque required to start the motor 90 is enough to overcome the static friction force of the pump 57. Enough. Furthermore, when the load pressure reaches the maximum value due to the drive of the pump 57, the torque required for the motor 90 to continue driving is the resultant force of the rotational resistance force due to the maximum load pressure and the dynamic friction force of the pump 57 ( (hereinafter also referred to as the "first resultant force"). That is, according to the first embodiment, the motor 90 only needs to be able to output a torque that overcomes the larger of the static friction force of the pump 57 and the first resultant force.

On the other hand, in the conventional configuration, it is necessary to be able to start the motor 90 while the load pressure is at its maximum value. Therefore, the torque required of the motor 90 is sufficient to overcome the resultant force (hereinafter also referred to as "second resultant force") of the rotational resistance force due to the maximum load pressure and the static friction force of the pump 57. The dynamic friction force is smaller than the static friction force, and the first resultant force generated in the first embodiment is smaller than the second resultant force generated in the conventional configuration. That is, according to the first embodiment, the output torque of the motor 90 can be reduced, and the motor 90 can be made smaller.

(others)
The present invention is not limited to the above embodiments. For example, the time (predetermined duration) for rotating the motor 90 in the opposite direction may be a preset constant value. For example, the predetermined duration time may be set to the time required to transition from a state where the load pressure is at a maximum value to a state where the load pressure is zero. According to this, the control unit 61 can perform load reduction control through simple calculation processing, and can reliably bring the load pressure to zero. Further, in this case, the pressure acquisition section 62 may not be provided. Note that, according to this configuration, the load reduction control can be continued even after the load pressure becomes zero, but at least the load reduction effect is exhibited.

Further, the brake control device 1 may include a pressure sensor that detects load pressure. In this case, the pressure sensor is provided, for example, in the first flow path C1. According to this configuration, the pressure acquisition unit 62 can acquire the load pressure by acquiring the detected value of the pressure sensor. Further, the predetermined duration is set so that the rotational resistance force due to the load pressure reduced by the rotation of the motor 90 in the opposite direction is smaller than the amount of variation in the frictional force of the pump 57 (the difference between the static frictional force and the dynamic frictional force). It is preferable that

(Second embodiment)
As described above, the pump 57 is structurally configured such that fluid leaks from the discharge port 572 (high pressure side) to the suction port 571 (low pressure side) due to tooth tip leakage or the like. Therefore, as shown in FIG. 5, in the brake control device 1A of the second embodiment, the brake ECU 6 includes a leak amount prediction section 64. The leakage amount prediction unit 64 predicts the amount of fluid leaking from the discharge port 572 of the pump 57 to the suction port 571 (the amount of leakage per unit time or the amount of leakage within a predetermined time). In addition, in FIG. 5, regarding the structure of the actuator 5, the display of the same structure as FIG. 1 is omitted.

The leakage amount prediction unit 64 calculates the leakage amount based on the temperature of the fluid supplied to the pump 57. The actuator 5 is provided with a temperature detection section 72 that detects the temperature of the fluid. The temperature detection unit 72 is, for example, a thermistor (temperature estimation unit) provided in the pressure sensor 71. The temperature detection unit 72 transmits the detection result to the brake ECU 6. The temperature detected by the temperature detection section 72 corresponds to (approximates) the temperature of the fluid inside the pump 57.

The leakage amount prediction unit 64 estimates the leakage amount based on the detection result of the temperature detection unit 72. The leakage amount prediction unit 64 includes a first map showing the relationship between fluid temperature and leakage amount. The leakage amount prediction section 64 determines the leakage amount from the detection result of the temperature detection section 72 and the first map. There is a correlation between fluid temperature and leakage amount. That is, the higher the temperature of the fluid, the lower the viscosity of the fluid, and the greater the amount of leakage. This correlation can be obtained by calculation, experiment, or the like. The leak amount prediction unit 64 transmits the prediction result (leak amount information) obtained from the correlation (first map) to the control unit 61.

Here, the amount of reduction in the load pressure (hydraulic pressure in the first channel C1) per unit time is determined by the amount of leakage per unit time and the rigidity of the discharge side system (the first channel C1 and the damper section 59). It can be calculated based on Stiffness is the pressure increase required to increase the volume of the system on the discharge side per unit container. The higher the stiffness, the less likely the volume of the system will change. The stiffness of the system can be obtained in advance by calculation or experiment.

There is a correlation between the amount of leakage and the amount of reduction in load pressure, and the larger the amount of leakage, the greater the amount of reduction in load pressure. By being provided with the second map showing the correlation, the control unit 61 can output the amount of reduction in load pressure in response to the input of the leakage amount. Note that the control unit 61 may calculate the reduction amount of the load pressure with respect to the input of the leakage amount based on the relational expression without using the map.

The control unit 61 determines the amount of reduction in load pressure per unit time from the amount of leakage per unit time. Here, a predetermined allowable time is set in the control unit 61 based on control rules required of the vehicle. The allowable time is the minimum time until the pump 57 restarts. That is, after the pump 57 in the operating state stops, the pump 57 restarts after an allowable time has elapsed at the shortest. From the viewpoint of the torque at the time of starting the motor 90, the load pressure after a permissible period of time after the pump 57 is stopped is important.

The control unit 61 can obtain the amount of leakage during the permissible time, the amount of reduction in load pressure during the permissible time, and the load pressure after the permissible time from the stop of the pump 57 by calculation or a map. For example, the control unit 61 may obtain the amount of reduction in load pressure using a map showing the relationship between the prediction result (leakage amount) and the amount of reduction in load pressure during the allowable time, or may obtain it by calculation. You may.

(Setting the execution timing of load reduction control)
The control unit 61 determines the amount of time (hereinafter referred to as "non-execution time") from when the number of rotations in the forward direction of the motor 90 becomes 0 to when the number of revolutions in the forward direction of the motor 90 is rotated in the reverse direction, depending on the amount of leakage predicted by the amount of leakage prediction section 64. (also referred to as "time"). That is, the control unit 61 sets the execution timing of the load reduction control based on the leakage amount information. The control unit 61 sets the non-execution time after the pump 57 stops based on the leak amount information received before the pump 57 stops (for example, when reducing the rotation speed).

(If the load pressure after the allowable time is 0)
The control unit 61 can calculate the load pressure after an allowable time from the stop of the pump 57 from the amount of reduction in the load pressure and the load pressure (obtained by the pressure obtaining unit 62) before the pump 57 stops. If the load pressure after the allowable time becomes 0 due to a large amount of leakage, the control unit 61 sets the non-execution time to infinity, for example, and prohibits execution of the load reduction control. It can be said that the control unit 61 determines whether the load pressure becomes equal to or less than a predetermined pressure (here, 0) within an allowable time based on the leakage amount predicted by the leakage amount prediction unit 64.

Note that a threshold value (high temperature threshold value) for the amount of leakage may be set in the control unit 61, for example. In this case, the threshold value is set to a value such that, for example, even if the load pressure is the maximum value expected, the load pressure after the allowable time is equal to or lower than the predetermined pressure (here, 0). In this case, the control unit 61 determines that the load pressure after the allowable time is 0 if the leakage amount is equal to or greater than the threshold value.

(If the load pressure after the allowable time is not 0)
Further, if the load pressure after the allowable time is not 0, the control unit 61 sets the non-execution time from the viewpoint of the torque required for reverse rotation (startup) of the motor 90. This required torque has a correlation with the load pressure. In other words, the higher the load pressure, the higher the required torque. The pump 57 is provided with side seals (not shown) that seal end faces of the outer rotor 92 and the inner rotor 93 in the axial direction. Structurally, the higher the load pressure is, the higher the sealing performance (adhesion) of the side seal becomes, and the rotational resistance force (frictional force) increases. The greater the rotational resistance, the higher the required torque.

Furthermore, the static friction force is larger than the kinetic friction force. Therefore, from the viewpoint of torque reduction, it is preferable to perform the load reduction control during a period when the load pressure is low and dynamic frictional force is generated. Here, there is a negative correlation between the temperature of the fluid (correlated with the amount of leakage) and the duration of the dynamic friction force (corresponding to the above-mentioned predetermined switching time). In other words, the higher the temperature of the fluid, the shorter the duration of the dynamic friction force. The higher the temperature of the fluid, the lower the viscosity of the fluid, and the shorter the time the fluid acts as a lubricant. In this way, the higher the temperature of the fluid, the larger the amount of leakage, but the more likely it is to become a static frictional force.

Based on this knowledge, if the load pressure after the allowable time is not 0, the control unit 61 calculates the point in time when the required torque becomes smaller than the specified value (or, for example, the point in time when the required torque becomes the minimum), and based on the calculation result, , set the non-execution time to less than the allowed time. The control unit 61 obtains the duration of the dynamic frictional force from the leakage amount using, for example, a third map showing the relationship between the leakage amount (fluid temperature) and the duration of the dynamic frictional force.

For example, if the duration of the dynamic friction force is smaller than a predetermined threshold time, the control unit 61 sets a non-execution time so that the load reduction control is executed after the duration of the dynamic friction force has passed (duration of the dynamic friction force < Non-execution time < allowable time). This is a control that prioritizes the amount of reduction in load pressure due to leakage and aims to reduce rotational resistance force by reducing load pressure, even if the frictional force becomes static frictional force. In other words, when the control unit 61 determines that the required torque in a situation where static friction force and load pressure is low pressure is smaller than the required torque in a situation where dynamic friction force and load pressure is high pressure, the control unit 61 performs the above-mentioned torque. Set the non-execution time as follows (duration of dynamic friction force < non-execution time < allowable time). The control unit 61 can use a map or calculation to determine how low the load pressure needs to be before the required torque becomes smaller than the required torque for dynamic friction force.

When the control unit 61 determines that the required torque is relatively smaller if the load reduction control is executed within the duration of the dynamic friction force, the control unit 61 sets the non-execution time to be less than the duration of the dynamic friction force (less than the predetermined switching time). (non-execution time <duration of kinetic friction force). The control unit 61 may set the non-execution time to 0, for example (see FIG. 2).

According to the second embodiment, as shown in FIG. 6, if the control unit 61 determines that the load pressure after the allowable time is not 0 based on the leakage amount and the load pressure, the control unit 61 reduces the load after the set non-execution time has elapsed. Execute control. The control unit 61 executes load reduction control so that the load pressure becomes equal to or less than a predetermined pressure (here, 0) after a permissible period of time after the pump 57 is stopped. The control unit 61 may be provided with a map that outputs the optimal non-execution time when the leakage amount and load pressure are input. Further, if the control unit 61 determines that the load pressure after the allowable time is 0 based on the leakage amount and the load pressure, it does not execute the load reduction control.

(Effects of the second embodiment)
According to the second embodiment, effects similar to those of the first embodiment are exhibited. Furthermore, according to the second embodiment, by considering the amount of leakage, load reduction control can be executed at a better timing from the viewpoint of required torque. By reducing the required torque, the motor 90 or pump 57 can be made smaller. Furthermore, since the number of times high torque is applied to the pump 57 is reduced, the durability of the device is improved. Further, unnecessary implementation of load reduction control can be suppressed, and power consumption can be reduced.

Note that the configuration of the second embodiment can also be described as follows. The brake control device 1A includes a temperature detection section 72 that detects the temperature of the fluid supplied to the pump 57, and the control section 61 determines the rotation speed of the motor 90 in the forward direction based on the detection result of the temperature detection section 72. Set the time from when the time reaches 0 until the motor 90 is rotated in the opposite direction.

Furthermore, the leak amount prediction unit 64 may predict the leak amount based on, for example, the continuous operating time of the pump 57 instead of the fluid temperature. The leakage amount prediction unit 64 may store in advance the relationship between the continuous operation time of the pump 57 and the state (viscosity) of the fluid, which is obtained through experiments or calculations, for example. Further, in the description of the second embodiment, the description and drawings of the first embodiment can be referred to.

DESCRIPTION OF SYMBOLS 1... Brake control device, 57... Pump, 571... Suction port, 572... Discharge port, 58... Check valve, 61... Control section, 62... Pressure acquisition section, 64... Leakage amount prediction section.

Claims (3)

A motor that can change the rotation direction in two directions, forward and reverse.
a pump that is driven according to the rotation of the motor, and sucks fluid from a suction port and discharges it from a discharge port as the motor rotates in a positive direction ;
a check valve that is disposed between a first flow path connected to the discharge port of the pump and a second flow path, and prevents fluid from flowing from the second flow path to the first flow path; and,
a control unit that controls driving of the motor;
a leakage amount prediction unit that predicts the amount of fluid leaking from the discharge port to the suction port of the pump;
Equipped with
The control unit is configured to reduce the load pressure, which is the hydraulic pressure in the first flow path, at a predetermined timing for shifting the state of the motor from a normal rotation state in which the motor is rotating in a forward direction to a stopped state. In addition to executing load reduction control to rotate the motor in the opposite direction,
The control unit is configured to perform braking to set the time from when the number of rotations in the forward direction of the motor becomes 0 to when the motor is rotated in the reverse direction according to the leakage amount predicted by the leakage amount prediction unit. Control device. In the load reduction control, the control unit rotates the motor in the reverse direction within a predetermined switching time after the rotation speed in the forward direction of the motor becomes 0;
2. The braking control device according to claim 1 , wherein the predetermined switching time corresponds to the time from when the number of rotations in the forward direction of the motor becomes 0 until the frictional force of the pump changes to static frictional force. further comprising a pressure acquisition unit that acquires the load pressure,
The braking control device according to claim 1 or 2, wherein the control unit determines the time for rotating the motor in the opposite direction in the load reduction control based on the load pressure acquired by the pressure acquisition unit.

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