JP5922557B2 - Brake control device - Google Patents

Description

  The present invention relates to a brake control device.

  Patent Document 1 discloses a pressure regulating valve capable of adjusting a differential pressure between an upstream side and a downstream side connected to a wheel cylinder side of a hydraulic circuit in a circulation flow path for circulating a part of brake fluid discharged from the pump to the pump. A brake control device is provided. The pressure regulating valve controls the applied current so that the differential pressure between the upstream side and the downstream side becomes a target differential pressure based on the circulating flow rate of the circulating brake fluid.

JP 2010-159057 A

In the pressure regulating valve, when the flow rate is small, that is, when the pressure regulating valve opening is very small, the operation is unstable, and the valve may be closed or opened by slight pulsation of the pump. For this reason, when the amount of brake fluid discharged from the pump is small, or when the amount of brake fluid discharged from the pump is slightly higher than the amount of brake fluid supplied to the wheel cylinder, the pressure adjustment accuracy of the pressure adjustment valve There has been a problem that the fluid pressure control accuracy is deteriorated, and the hydraulic pressure control accuracy is lowered.
An object of the present invention is to provide a brake control device capable of improving the hydraulic pressure control accuracy.

In the present invention, the number of rotations of the motor is determined based on the pump discharge amount obtained by adding a predetermined discharge amount to the pump discharge amount necessary for obtaining the target wheel cylinder hydraulic pressure, and the determined rotation number A current value at which a target differential pressure is obtained is calculated by the flow of the discharged brake fluid through the pressure regulating valve, and the current applied to the pressure regulating valve is controlled.

  Therefore, in the present invention, the hydraulic pressure control accuracy can be improved.

It is a circuit block diagram of the brake control apparatus of Example 1. It is a flowchart which shows the flow of the target electric current calculation process of a gate out valve | bulb. It is a figure which shows the correlation of the electric current applied to a gate-out valve, and passage flow volume. It is a schematic diagram of the plunger front-end | tip part of a gate out valve | bulb. It is a figure which shows the correlation of valve lift amount and fluid force. 3 is a time chart illustrating a target current calculation operation of the first embodiment.

[Example 1]
First, the configuration will be described.
FIG. 1 is a circuit configuration diagram of a brake control device in a vehicle brake device.
The hydraulic circuit 1 according to the first embodiment has a piping structure called an X piping that includes two systems, a P system (first piping system) and an S system (second piping system). By adopting X piping, even if one piping system fails, the other piping system can be used to generate half of the braking force during normal operation. In addition, P attached to the end of the code | symbol of each site | part described in FIG. 1 shows P system | strain, S shows S system | strain, FL, RR, FR, RL are a left front wheel, a right rear wheel, a right front wheel, a left rear. Indicates that it corresponds to a ring. In the following description, the description of P, S or FL, RR, FR, RL is omitted when the P, S system or each wheel is not distinguished.
The hydraulic circuit 1 of the first embodiment uses a closed hydraulic circuit. Here, the “closed hydraulic circuit” refers to a hydraulic circuit that returns the brake fluid supplied to the wheel cylinder W / C to the reservoir tank RSV via the master cylinder M / C. By the way, the hydraulic circuit that can return the brake fluid supplied to the wheel cylinder W / C directly to the reservoir tank RSV without passing through the master cylinder M / C is called “Open hydraulic circuit”. That's it.
The brake pedal BP is connected to the master cylinder M / C via the input rod IR. The pedaling force of the driver is boosted by the negative pressure booster BST to generate brake fluid in the master cylinder M / C.
The wheel cylinder W / C (FL) of the left front wheel FL and the wheel cylinder W / C (RR) of the right rear wheel RR are connected to the P system, and the wheel cylinder W / C ( FR), wheel cylinder W / C (RL) of the left rear wheel RL is connected. In addition, pumps PP and PS are provided in the P system and the S system. The pumps P are, for example, gear pumps and are each driven by one motor M.

The master cylinder M / C and the wheel cylinder W / C are connected by a pipeline 11 and a pipeline 12. The pipe 12P branches into pipes 12FL and 12RR, the pipe 12FL is connected to the wheel cylinder W / C (FL), and the pipe 12RR is connected to the wheel cylinder W / C (RR). The pipe line 12S branches into pipe lines 12FR and 12RL, the pipe line 12FR is connected to the wheel cylinder W / C (FR), and the pipe line 12RL is connected to the wheel cylinder W / C (RL).
On the pipeline 11, a gate-out valve (pressure regulating valve) 13 which is a normally open type proportional control valve is provided. A master cylinder hydraulic pressure sensor 5 is provided at a position closer to the master cylinder side than the gate-out valve 13S of the pipeline 11S of the S system. A pipe 14 is provided on the pipe 11 in parallel with the gate-out valve 13. A check valve 15 is provided on the pipeline 14. The check valve 15 allows the flow of brake fluid from the master cylinder M / C to the wheel cylinder W / C and prohibits the flow in the opposite direction.
A solenoid-in valve 16 that is a normally open proportional control valve corresponding to each wheel cylinder W / C is provided on the pipe line 12. A pipe line 17 is provided on the pipe line 12 in parallel with the solenoid-in valve 16. A check valve 18 is provided on the pipe line 17. The check valve 18 allows the brake fluid to flow in the direction from the wheel cylinder W / C toward the master cylinder M / C, and prohibits the flow in the opposite direction.

The discharge side of the pump P and the pipe 12 are connected by a pipe 19. A discharge valve 20 is provided on the pipeline 19. The discharge valve 20 allows the flow of brake fluid in the direction from the pump P toward the pipe 12, and prohibits the flow in the opposite direction.
A position on the master cylinder side of the gate 11 from the gate-out valve 13 and the suction side of the pump P are connected by pipes 21 and 22. A pressure regulating reservoir 23 is provided between the pipe line 21 and the pipe line 22. The pipelines 21 and 22 constitute a circulation flow path provided in a state where a part of the hydraulic circuit 1 is shared in order to circulate a part of the brake fluid discharged from the pump P to the pump P.
The position on the wheel cylinder side of the conduit 12 relative to the solenoid-in valve 16 and the pressure regulating reservoir 23 are connected by a conduit 24. The pipe 24P branches to the pipes 24FL and 24RR, and the pipe 24S branches to the pipes 24RL and 24FR and is connected to the corresponding wheel cylinder W / C.
On the conduit 24, a solenoid-out valve 25, which is a normally closed solenoid valve, is provided.
The pressure adjustment reservoir 23 includes a pressure-sensitive check valve 26. The check valve 26 prevents the brake fluid from flowing into the reservoir when a predetermined amount of brake fluid is stored or when the pressure in the pipe line 21 exceeds a predetermined pressure. Prevent high pressure from being applied to the suction side of P. The check valve 26 is opened regardless of the pressure in the pipe line 21 when the pump P is activated and the pressure in the pipe line 22 becomes low, and allows the brake fluid to flow into the reservoir. To do.

The hydraulic circuit 1 can perform automatic brake control and anti-skid (ABS) control such as ACC (adaptive cruise control) and VDC (vehicle behavior control). The brake control unit BCU sets a predetermined wheel or a target cylinder hydraulic pressure for each wheel in each control, and a gate-out valve 13, a solenoid-in valve 16, a solenoid so that each wheel cylinder hydraulic pressure becomes the target wheel cylinder hydraulic pressure. The out valve 25 and the motor M are operated to control each wheel cylinder hydraulic pressure. For example, in the case of automatic brake control such as vehicle behavior control, taking the left front wheel FL as an example, the gate out valve 13P is proportionally controlled in the closing direction and the pump PP is operated at the same time from the master cylinder M / C to the pipeline 19FL → pipe. Brake fluid is supplied to the wheel cylinder W / C (FL) via the passage 12FL. Further, the gate-out valve 13P, the solenoid-in valve 16FL or the solenoid-out valve 25FL is controlled so as to generate the target wheel cylinder hydraulic pressure corresponding to the braking force necessary for stabilizing the vehicle behavior.
During ABS control, taking the left front wheel FL as an example, the solenoid out valve 25FL connected to the wheel cylinder W / C (FL) is opened and the solenoid in valve 16 is proportionally controlled in the closing direction. The pressure is reduced by discharging the brake fluid of / C (FL) to the pressure adjusting reservoir 23. The brake fluid discharged to the reservoir 23 is returned to the master cylinder (M / C) side by operating the pump P. Further, when the left front wheel FL recovers from the locking tendency, the solenoid out valve 25 is closed to maintain the wheel cylinder hydraulic pressure. Further, the solenoid-in valve 16 is opened to increase the pressure appropriately.

In the automatic brake control, when the pump P is operated, it is necessary to return excess brake fluid to the master cylinder side. Therefore, the brake control unit BCU slightly opens the gate-out valve 13 when the pump P is operated, and leaks excess brake fluid to the master cylinder side. At this time, to the coil of the gate-out valve 13, the differential pressure generated on the upstream side ( wheel cylinder side) and the downstream side ( master cylinder side) of the gate-out valve 13 becomes the differential pressure corresponding to the target wheel cylinder hydraulic pressure. The applied current is controlled.
Here, when the opening degree of the gate-out valve 13 is very small, there is a concern about the deterioration of the hydraulic pressure control accuracy due to the unstable operation. Therefore, in the first embodiment, the target current calculation process for the gate-out valve 13 as described below is performed with the aim of improving the hydraulic pressure control accuracy during pump operation. The brake control unit BCU includes a target W / C hydraulic pressure calculation unit (target wheel cylinder hydraulic pressure calculation unit) 30, a motor rotation number determination unit (motor rotation number determination unit) 31 as a configuration for performing the target current calculation process. And a current control unit (current control unit) 32.
The target W / C hydraulic pressure calculation unit 30 calculates the target wheel cylinder hydraulic pressure of each wheel cylinder W / C according to the traveling state of the vehicle and the like.
The motor rotation speed determination unit 31 determines the rotation speed of the motor M so that the flow rate (circulation flow rate) of the brake fluid flowing through the gate-out valve 13 is equal to or higher than a predetermined flow rate.
The current control unit 32 calculates a current value (target current) at which a target differential pressure is obtained by the flow of the brake fluid discharged at the rotation number determined by the motor rotation number determination unit 31 through the gate-out valve 13. The current applied to the coil of the gate-out valve 13 is controlled.

[Target current calculation processing]
FIG. 2 is a flowchart showing a flow of target current calculation processing of the gate-out valve 13, and each step will be described below.
In step S1, the target wheel cylinder hydraulic pressure is calculated in the target W / C hydraulic pressure calculator 30.
In step S2, the motor rotational speed determination unit 31 calculates a target fluid amount from the target wheel cylinder hydraulic pressure calculated in step S1.
In step S3, the motor rotational speed determination unit 31 calculates a necessary pump discharge amount from the target liquid amount calculated in step S2.
In step S4, the motor speed determining unit 31 calculates the target motor speed based on the ejection amount obtained by adding a predetermined pump discharge amount Q _alpha to the pump discharge amount required calculated in step S3. Here, the predetermined pump discharge amount _Qα is a flow rate through the gate-out valve 13 that exceeds the region where the gate-out valve 13 closes or opens due to slight pulsation of the pump P, that is, the region where the valve operation becomes unstable. (See FIG. 3).
In step S5, the current control unit 32 calculates the estimated pump discharge amount from the estimated motor rotation speed. The estimated motor speed can be obtained from the actual voltage and current of the motor M.

In step S6, the current control unit 32 calculates the passage flow rate of the gate-out valve 13 by subtracting the target liquid amount calculated in step S2 from the estimated pump discharge amount calculated in step S5.
In step S7, the current controller 32 calculates the target current of the gate-out valve 13 from the passage flow rate calculated in step S6 and the target differential pressure between the upstream side and the downstream side of the gate-out valve 13. The target differential pressure is obtained by subtracting the master cylinder hydraulic pressure detected by the master cylinder hydraulic pressure sensor 5 from the target wheel cylinder hydraulic pressure calculated in step S1. FIG. 3 is a diagram showing the correlation between the current applied to the gate-out valve 13 and the passage flow rate. Since the gate-out valve 13 is a normally-open proportional solenoid valve, the opening degree decreases and the passing flow rate Q decreases as the applied current I increases. Such a relationship between the current I and the passage flow rate Q changes according to the differential pressure ΔP between the upstream and downstream of the gate-out valve 13. Specifically, as shown in FIG. 3, as the differential pressure ΔP increases, the correlation line shifts to the side where the current I increases. Therefore, the target current can be obtained from the passage flow rate Q and the target differential pressure by referring to the relationship of FIG.

Next, the operation will be described.
[Valve unstable operation during a leak]
FIG. 4 is a schematic diagram of the tip of the plunger of the gate-out valve. In order to leak excess brake fluid generated by pumping up to the master cylinder side, an electric current is applied to the coil of the gate-out valve to set the intermediate opening. When maintaining, the attractive force of the coil acts on the plunger in the valve closing direction, while the spring force of the spring and the fluid force due to the passage of the brake fluid act in the valve opening direction. The valve lift amount x (the axial distance between the seat and the plunger tip) is defined at a position where these three forces are balanced. Here, the valve lift amount x is approximately proportional to the flow path area, and the flow rate of the brake fluid is proportional to the flow path area when the differential pressure ΔP between the upstream side and the downstream side is constant. Therefore, when the valve lift amount x is determined, the flow rate Q of the brake fluid to be circulated is determined.
FIG. 5 is a diagram showing a correlation between the valve lift amount and the fluid force. The valve lift amount is less than a predetermined valve lift amount x _α (the flow rate Q of the gate-out valve 13 is less than the predetermined flow rate Q _α. In the case of _xα or more, the fluid force greatly changes with respect to the change in the valve lift amount. That is, when the valve lift amount x at the time of leak excess brake fluid caused by the pump up to the master cylinder side is less than x _alpha is flow in small changes in the valve lift amount x due to slight pulsation of the pump Physical strength varies greatly. Therefore, since the flow rate Q of the brake fluid largely fluctuates, there is a problem that the valve operation becomes unstable and the hydraulic pressure control accuracy decreases.

FIG. 6 is a time chart illustrating the target current calculation operation of the first embodiment.
The target W / C hydraulic pressure calculation unit 30 calculates the target wheel cylinder hydraulic pressure in the automatic brake control, and the motor rotation speed determination unit 31 sets a predetermined amount for the pump discharge amount necessary to obtain the target wheel cylinder hydraulic pressure. determining a target motor speed based on the pump discharge amount obtained by adding the discharge amount Q _alpha. The current control unit 32 calculates the passing flow rate of the gate-out valve 13 by subtracting the target fluid amount from the estimated pump discharge amount calculated from the estimated motor rotation speed, and obtains the passing differential amount and the target differential pressure for obtaining the target wheel cylinder fluid pressure. The target current is obtained from the above and the current applied to the gate-out valve 13 is controlled.
That is, in the first embodiment, as shown in FIG. 3, by maintaining the flow rate of the brake fluid flowing through the gate-out valve 13 at a predetermined flow rate Q _α exceeding the region where the valve operation is always unstable, because that can hold a predetermined valve lift x _alpha or more valve lift x, it can prevent the valve operation becomes unstable, can be improved hydraulic control accuracy.

In Example 1, the following effects are exhibited.
(1) Hydraulic circuit 1 for supplying the wheel cylinder hydraulic pressure to the wheel cylinder W / C installed on each wheel, and the target W / C liquid for calculating the target wheel cylinder hydraulic pressure of the wheel cylinder W / C The hydraulic pressure circuit 30 is driven by the rotation of the motor M, and brake fluid is discharged to the hydraulic circuit 1 with brake fluid discharged so that the wheel cylinder hydraulic pressure becomes the target wheel cylinder hydraulic pressure calculated by the target W / C hydraulic pressure calculator 30. Pump P for generating hydraulic pressure, and circulation flow paths (pipe lines 21, 22) provided in a state where a part of the hydraulic circuit 1 is shared to circulate a part of the brake fluid discharged from the pump P to the pump P. ) And the gate-out valve 13 which can adjust the differential pressure between the upstream side and the downstream side connected to the wheel cylinder side of the hydraulic circuit 1, and the circulation flow rate of the brake fluid flowing through the gate-out valve 13 is greater than or equal to a predetermined flow rate A motor speed determining unit 31 that determines the motor speed so that The target current for obtaining the target differential pressure is calculated by the flow of the brake fluid discharged at the rotation speed determined by the motor rotation speed determination unit 31 through the gate-out valve 13, and the applied current to the gate-out valve 13 is controlled. And a current control unit 32.
As a result, the gate-out valve 13 can be prevented from being used in an unstable region of the valve operation, so that the hydraulic pressure control accuracy can be improved.

(2) The predetermined flow rate Q _α is obtained by adding a predetermined rotational speed so as to avoid an unstable region with respect to the motor rotational speed for discharging the minimum pump discharge amount required to obtain the target differential pressure. This is the value obtained.
As a result, the gate-out valve 13 can be avoided from being used in an unstable region of the valve operation, so that the hydraulic pressure control accuracy can be improved.

(Other examples)
As mentioned above, although the form for implementing this invention was demonstrated based on the Example, the specific structure of this invention is not limited to the structure shown in the Example, and does not deviate from the summary of invention. Any change in the design of the range is included in the present invention.
For example, in the first embodiment, an example in which the present invention is applied to a gate-out valve has been shown. However, the present invention can adjust the differential pressure between the upstream side and the downstream side connected to the wheel cylinder side of the hydraulic circuit. It can be applied to a pressure valve and has the same effects as the embodiment.

1 Hydraulic circuit
13 Gate-out valve (pressure regulating valve)
21 Pipe line (circulation flow path)
22 Pipe line (lubricated flow path)
30 Fluid pressure calculator
31 Motor rotation speed determination unit
32 Current controller
M motor
P pump
W / C wheel cylinder

Claims (2)

A hydraulic circuit for supplying the wheel cylinder hydraulic pressure to the wheel cylinder disposed on each wheel;
A target wheel cylinder hydraulic pressure calculating section for calculating a target foil cylinder hydraulic pressure of the wheel cylinder;
A pump that is driven by the rotation of a motor and generates hydraulic pressure in the hydraulic circuit with brake fluid that is discharged so that the wheel cylinder hydraulic pressure is equal to the target wheel cylinder hydraulic pressure calculated by the target wheel cylinder hydraulic pressure calculating unit; ,
A circulation flow path provided in a state in which a part of the hydraulic circuit is shared in order to circulate a part of the brake fluid discharged from the pump to the pump;
A pressure regulating valve capable of adjusting a differential pressure between the upstream side and the downstream side connected to the wheel cylinder side of the hydraulic circuit;
A motor rotational speed determination unit that determines the rotational speed of the motor based on a discharge amount of the pump obtained by adding a predetermined discharge amount to a discharge amount of the pump necessary to obtain the target wheel cylinder hydraulic pressure ;
Controls the current applied to the pressure regulating valve by calculating a current value for obtaining the target differential pressure by the flow of the brake fluid discharged at the rotational speed determined by the motor rotational speed determining unit through the pressure regulating valve. Current controller to
A brake control device comprising: The brake control device according to claim 1, wherein
The predetermined discharge amount is a flow rate of the brake fluid flowing through the pressure regulating valve such that a change characteristic of the fluid force acting on the valve body of the pressure regulating valve with respect to a valve lift amount exceeds a non-linear region. Brake control device.

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