Control unit of brake apparatus for vehicle

Abstract

A control unit of a brake apparatus includes: a compensation braking force controlling means for controlling a compensation braking force in response to an operation of a brake operating member so that a characteristic of a total braking force relative to the operation of the brake operating member agrees with a predetermined target characteristic. The total braking force is a sum of the compensation braking force containing a pressurizing hydraulic braking force based upon at least the pressurization and a basic hydraulic pressure braking force based upon the basic hydraulic pressure. The compensation braking force controlling means includes: a judging means for judging whether the vehicle has stopped; and a limiting means for limiting the amount of pressurization via a pressure control valve when the judging means determines that the vehicle has stopped.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and additional features and characteristics of the present invention will become more apparent from the following detailed description considered with reference to the accompanying drawings, wherein:

FIG. 1 is a block view schematically illustrating a vehicle mounted with a brake apparatus according to a first embodiment of the present invention;

FIG. 2 is a view schematically illustrating a brake hydraulic pressure controller illustrated in FIG. 1;

FIG. 3 is a diagram explaining the relationship between a command electric current and a command pressure difference, the command electric current which is to be supplied to a normally open linear solenoid valve illustrated in FIG. 2 and the command pressure difference which is to be generated thereby;

FIG. 4 is a diagram explaining the relationship of a master-cylinder hydraulic pressure and a target wheel cylinder pressure relative to a pressure applied to a brake pedal in the situation where the vehicle is running;

FIG. 5 is a diagram explaining a manner where a wheel cylinder pressure is restrained in the situation where the vehicle has stopped;

FIG. 6 is a flowchart for explaining a program or routine implemented by a CPU illustrated in FIG. 1;

FIG. 7 is a diagram for explaining the relationship between the master-cylinder hydraulic pressure and the target wheel cylinder pressure, which the CPU refers to;

FIG. 8 is a diagram for explaining the relationship between a longitudinal acceleration and a road gradient, which the CPU refers to;

FIG. 9 is a diagram for explaining the relationship between the road gradient and a vehicle stopped state maintaining wheel cylinder pressure, which the CPU refers to;

FIG. 10 is a flowchart for explaining a program or routine implemented by the CPU of the brake apparatus according to a modified example of the first embodiment;

FIG. 11 is a diagram for explaining a manner where a wheel cylinder pressure is restrained by a brake apparatus for a vehicle according to a second embodiment in the situation where the vehicle has stopped;

FIG. 12 is a flowchart for explaining a routine or program implemented by a CPU of the brake apparatus according to the second embodiment; and

FIG. 13 is a diagram for explaining the relationship between a vehicle-stopped-state maintaining wheel cylinder pressure and an upper limit of a linear-valve pressure difference, which the CPU of the brake apparatus of the second embodiment refers to.

Claims

1. A control unit of a brake apparatus for a vehicle, the brake apparatus including: a basic-hydraulic-pressure generating means for generating a basic hydraulic pressure according to an operation of a brake operating member by a driver; a hydraulic pump for generating a pressurizing hydraulic pressure higher than a pressure level of the basic hydraulic pressure; and a pressure control valve for controlling an amount of pressurization to the basic hydraulic pressure by use of the pressurizing hydraulic pressure generated by the hydraulic pump, wherein a sum of the basic hydraulic pressure and the pressurization corresponds to a wheel cylinder pressure applied to a wheel cylinder so as to generate at least a hydraulic braking force,the control unit of the brake apparatus, comprising:a compensation braking force controlling means for controlling a compensation braking force in response to the operation of the brake operating member so that a characteristic of a total braking force relative to the operation of the brake operating member agrees with a predetermined target characteristic, the total braking force being a sum of at least the compensation braking force containing a pressurizing hydraulic braking force based upon the pressurization and a basic hydraulic pressure braking force based upon the basic hydraulic pressure,the compensation braking force controlling means including: a judging means for judging whether the vehicle has stopped; anda limiting means for limiting the amount of pressurization via the pressure control valve when the judging means judges that the vehicle has stopped.

2. A control unit of a brake apparatus for a vehicle according to claim 1, wherein the limiting means includes an upper limit setting means for setting an upper limit of the wheel cylinder pressure, wherein, when the judging means judges that the vehicle has stopped, the limiting means limits the amount of pressurization in a manner that the wheel cylinder pressure does not exceed the upper limit.

3. A control unit of a brake apparatus for a vehicle according to claim 2, wherein the limiting means limits the amount of pressurization to a value obtained by subtracting the basic hydraulic pressure from the upper limit while a target wheel cylinder pressure relative to the operation of the brake operating member exceeds the upper limit in a situation where the vehicle has stopped, and the target wheel cylinder corresponds to the predetermined target characteristic.

4. A control unit of a brake apparatus for a vehicle according to claim 3, wherein the control unit maintains the wheel cylinder pressure at a constant pressure value by maintaining the pressure control valve at a closed state and by stopping the hydraulic pump, and the limiting means maintains the pressure control valve at the closed state and stops the hydraulic pump after the limiting means limits the amount of pressurization to the value obtained by subtracting the basic hydraulic pressure from the upper limit while the target wheel cylinder pressure relative to the operation of the brake operating member exceeds the upper limit in a situation where the vehicle has stopped, and the target wheel cylinder corresponds to the predetermined target characteristic.

5. A control unit of a brake apparatus for a vehicle according to claim 2, wherein the upper limit setting means includes a vehicle stopped state maintaining pressure obtaining means for obtaining a vehicle stopped state maintaining wheel cylinder pressure, and the upper limit is set to be equal to or greater than the vehicle stopped state maintaining wheel cylinder pressure.

6. A control unit of a brake apparatus for a vehicle according to claim 1, wherein the limiting means includes an upper limit setting means for setting an upper limit of the amount of pressurization, and the upper limit setting means limits the amount of pressurization so as not to exceed the upper limit when the judging means judges that the vehicle has stopped.

7. A control unit of a brake apparatus for a vehicle according to claim 6, wherein the limiting means maintains the amount of pressure at the upper limit while a value, which is obtained by subtracting the basic hydraulic pressure relative to the operation of the brake operating member from the upper limit while the target wheel cylinder pressure relative to the operation of the brake operating member, exceeds the upper limit in a situation where the vehicle is being determined to have stopped.

8. A control unit of a brake apparatus for a vehicle according to claim 6, wherein the upper limit setting means includes a vehicle-stopped-state maintaining pressure obtaining means for obtaining a vehicle-stopped-state maintaining wheel cylinder pressure that is a lower limit of a wheel cylinder pressure required to maintain the vehicle in a stopped state, and the upper limit is set at a value or more, which value is obtained by subtracting a basic hydraulic pressure from the vehicle-stopped-state maintaining wheel cylinder pressure (Pwstop), the basic hydraulic pressure being a value corresponding to a case where a target wheel cylinder pressure, which corresponds to the target characteristic and is responsive to the operation of the brake operating member, agrees with the vehicle-stopped-state maintaining wheel cylinder pressure.

9. A control unit of a brake apparatus for a vehicle according to claim 5, wherein the vehicle-stopped-state maintaining pressure obtaining means includes a road gradient obtaining means for obtaining a gradient of a road on which the vehicle has stopped and determines the vehicle-stopped-state maintaining wheel cylinder pressure based upon the road gradient obtained by the road gradient obtaining means.

10. A control unit of a brake apparatus for a vehicle according to claim 8, wherein the vehicle-stopped-state maintaining pressure obtaining means includes a road gradient obtaining means for obtaining a gradient of a road on which the vehicle has stopped and determines the vehicle-stopped-state maintaining wheel cylinder pressure based upon the road gradient obtained by the road gradient obtaining means.

11. A control unit of a brake apparatus for a vehicle according to claim 9, wherein the road gradient obtaining means obtains the gradient of the road based upon an output of a longitudinal acceleration sensor detecting an acceleration of the vehicle in a longitudinal direction thereof.

12. A control unit of a brake apparatus for a vehicle according to claim 10, wherein the road gradient obtaining means obtains the gradient of the road based upon an output of a longitudinal acceleration sensor detecting an acceleration of the vehicle in a longitudinal direction thereof.