BRAKE CONTROL SYSTEM AND CONTROL METHOD FOR BRAKE CONTROL SYSTEM

Abstract

A hydraulic pressure brake unit includes a power hydraulic pressure source able to generate, by a supply of power, a high hydraulic independent of a brake operation by a driver; a field system which connects the power hydraulic pressure source with both first and second wheel cylinders, regulates the hydraulic pressure of operating fluid from the power hydraulic pressure source, and applies a common hydraulic pressure to both the first and second wheel cylinders; a separator valve provided so as to be able to cut off the supply of operating fluid to the second wheel cylinder via the first system; and a second system which connects the second wheel cylinder with the power hydraulic pressure source such that operating fluid can be supplied front the power hydraulic pressure source to the second wheel cylinder regardless of weather the separator valve is open or closed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and further objects, features and advantages of the invention will become apparent from the following description of preferred embodiments with reference to the accompanying drawings, wherein like numerals are used to represent like elements and wherein:

FIG. 1 is a block diagram schematically showing a vehicle in which a brake control system according a first example embodiment of the invention has been applied;

FIG. 2 is a system diagram of a hydraulic pressure brake unit according to the first example embodiment;

FIG. 3 is a graph of braking force distribution between front and rear wheels;

FIG. 4 is a flowchart illustrating a routine of an independent control mode according to the first example embodiment; and

FIG. 5 is a flowchart illustrating a routine according to a second example embodiment.

Claims

1. A brake control system comprising: a first wheel cylinder for applying braking force to a first wheel;a second wheel cylinder for applying braking force to a second wheel;a power hydraulic pressure source able to generate, by a supply of power, a high hydraulic pressure independent of a brake operation by a driver;a first system which connects the power hydraulic pressure source with both the first and second wheel cylinders, regulates the hydraulic pressure of operating fluid from the power hydraulic pressure source, and applies a common hydraulic pressure to both the first and second wheel cylinders;a separator valve that cuts off the supply of operating fluid to the second wheel cylinder via the first system when the separator valve is closed; anda second system which connects the second wheel cylinder with the power hydraulic pressure source such that operating fluid can be supplied from the power hydraulic pressure source to the second wheel cylinder regardless of whether the separator valve is open or closed.

2. The brake control system according to claim 1, further comprising: a regenerative brake unit that applies braking force to the first wheel by regenerative control of a motor; anda control portion which increases the hydraulic pressure applied to the second wheel cylinder more than the hydraulic pressure applied to the first wheel cylinder under a predetermined condition when the braking force applied to the first wheel is a combination of regenerative braking force and hydraulic pressure braking force.

3. The brake control system according to claim 2, wherein: the second system includes a regulator that regulates the hydraulic pressure of the power hydraulic pressure source according to a brake operation by the driver and a control valve provided between the regulator and the second wheel cylinder; andthe control portion increases the hydraulic pressure applied to the second wheel cylinder by closing the separator valve to cut off the supply of operating fluid to the second wheel cylinder via the first system and supplying operating fluid that was pressure-regulated by the regulator to the second wheel cylinder by opening the control valve.

4. The brake control system according to claim 3, wherein the control portion opens the separator valve and closes the control valve to apply the hydraulic pressure of operating fluid from the power hydraulic pressure source to both the first and second wheel cylinders via the first system when the vehicle is not under the predetermined condition.

5. The brake control system according to claim 2, wherein the control portion controls the first system to generate a remaining braking force obtained by subtracting the braking force obtained through regeneration from a total required braking force that needs to be applied to the vehicle when the vehicle is not under the predetermined condition.

6. The brake control system according to claim 2, wherein the control portion increases the hydraulic pressure applied to the second wheel cylinder more than the hydraulic pressure applied to the first wheel cylinder when a braking force distribution of the second wheel is less than a predetermined value.

7. The brake control system according to claim 2, wherein the control portion increases the hydraulic pressure applied to the second wheel cylinder more than the hydraulic pressure applied to the first wheel cylinder when the vehicle is turning.

8. The brake control system according to claim 2, wherein the control portion increases the hydraulic pressure applied to the second wheel cylinder more than the hydraulic pressure applied to the first wheel cylinder when a target deceleration that exceeds a predetermined value is required.

9. The brake control system according to claim 2, wherein the control portion generates braking force to be applied to the first wheel using a combination of regenerative braking force and hydraulic pressure braking force when the separation valve is closed.

10. The brake control system according to claim 2, wherein, when the control portion increases the hydraulic pressure applied to the second wheel cylinder more than the hydraulic pressure applied to the first wheel cylinder, the control portion calculates the hydraulic pressure braking force of the second wheel cylinder, and controls the hydraulic pressure of the first system to apply a remaining braking force to the first wheel cylinder, the remaining braking force being obtained by subtracting the hydraulic pressure braking force of the second wheel cylinder and the regenerative braking force from a total required braking force that needs to be applied to the vehicle.

11. The brake control system according to claim 1, further comprising: a control portion which, when an abnormality has been detected in one of the first system and the second system, closes the separator valve to cut off the supply of operating fluid to the second wheel cylinder via the first system and supplies operating fluid to the second wheel cylinder via the second system.

12. The brake control system according to claim 11, wherein the control portion establishes which of the systems an abnormality has occurred in based on a fluctuation in the hydraulic pressure of one of the first system and the second system after closing the separator valve.

13. The brake control system according to claim 1, wherein the first wheel is the right front wheel and/or the left front wheel, and the second wheel is the right rear wheel and/or the left rear wheel.

14. A control method for a brake control system includes: a first wheel cylinder for applying braking force to a first wheel;a second wheel cylinder for applying braking force to a second wheel;a power hydraulic pressure source able to generate, by a supply of power, a high hydraulic pressure independent of a brake operation by a driver;a first system which connects the power hydraulic pressure source with both the first and second wheel cylinders, regulates the hydraulic pressure of operating fluid from the power hydraulic pressure source, and applies a common hydraulic pressure to both the first and second wheel cylinders;a separator valve that cuts off the supply of operating fluid to the second wheel cylinder via the first system when the separator valve is closed;a second system which connects the second wheel cylinder with the power hydraulic pressure source such that operating fluid can be supplied from the power hydraulic pressure source to the second wheel cylinder regardless of whether the separator valve is open or closed; anda regenerative brake unit that applies braking force to the first wheel by regenerative control of a motor,the control method comprising:increasing the hydraulic pressure applied to the second wheel cylinder more than the hydraulic pressure applied to the first wheel cylinder under a predetermined condition when the braking force applied to the first wheel is a combination of regenerative braking force and hydraulic pressure braking force.