Brake control system for a vehicle

• US 6,206,490 B1
• Filed: 11/25/1998
• Issued: 03/27/2001
• Est. Priority Date: 11/26/1997
• Status: Expired due to Term

• Current Assignee: Advics Company Limited (Aisin Corp.)
• Original Assignee: Aisin Seiki Kabushiki Kaisha (Aisin Corp.)
• Inventors: Yokoyama, Satoshi, Fukami, Masanobu, Itoh, Takayuki, Tozu, Kenji
• Primary Examiner(s): Oberleitner, Robert J.
• Assistant Examiner(s): KRAMER, DEVON C
• Application Number:
  US09/199,374
• Time in Patent Office: 853 Days
• Field of Search: 303/10, 303/11, 303/9.62, 303/113.5, 303/186, 303/187, 303/188, 303/189
• US Class Current: 303/168
• CPC Class Codes: B60T 8/266 using valves or actuators with external control means B60T8/261 takes precedence
• CPC Class Codes: B60T 8/4872 pump-back systems

Abstract

The present invention is directed to a brake control system for a vehicle, wherein a first valve device for opening or closing a main passage, which communicates a master cylinder with wheel brake cylinders, a hydraulic pressure pump for supplying the hydraulic pressure to the main passage, and a second valve device for opening or closing an auxiliary passage, which communicates the inlet of the pressure pump with the master cylinder, are disposed in each hydraulic pressure circuit of a dual hydraulic pressure circuit system. In the case where the slip rate of at least one of the front wheels is smaller than the slip rate of at least one of the wheels belonging to a different hydraulic pressure circuit from the hydraulic pressure circuit to which the one of the front wheels belongs, when the brake pedal is being operated, the hydraulic braking pressure discharged from the pressure pump is applied to one of the wheel brake cylinders operatively mounted on at least one of the front wheels, by controlling the second valve device for example.

Claims

1. A brake control system for a vehicle comprising:

wheel brake cylinders operatively mounted on front and rear wheels of said vehicle, respectively;

a master cylinder for pressurizing brake fluid to supply hydraulic braking pressure to said wheel brake cylinders in response to depression of a brake pedal;

a pair of main passages for communicating said master cylinder with said wheel brake cylinders to provide a dual hydraulic pressure circuit system;

an auxiliary pressure source for pressurizing the brake fluid to supply the hydraulic braking pressure to said main passages;

wheel speed sensors for detecting wheel speeds of said wheels;

slip calculation means for calculating slip of said wheels on the basis of the wheel speeds detected by said wheel speed sensors; and

control means for comparing the slip of at least one of said front wheels with the slip of at least one of the wheels belonging to a hydraulic pressure circuit different from the hydraulic pressure circuit to which said at least one of said front wheels belongs, and for applying the hydraulic braking pressure discharged from said auxiliary pressure source to said wheel brake cylinder operatively mounted on said at least one of said front wheels, in the case where the slip of said at least one of said front wheels is smaller than the slip of said at least one of said wheels belonging to a different hydraulic pressure circuit from the hydraulic pressure circuit to which said at least one of said front wheels belongs, at least when said brake pedal is being operated.

2. A brake control system as set forth in claim 1, wherein said control means is adapted to equalize the hydraulic braking pressure in said wheel brake cylinders operatively mounted on said rear wheels, on the basis of one of said rear wheels having a larger slip than the other one of said rear wheels.

3. A brake control system as set forth in claim 2, wherein said control means includes modulator means disposed between said master cylinder and said wheel brake cylinders in each hydraulic pressure circuit for modulating the hydraulic braking pressure in each of said wheel brake cylinders in accordance with a pressure mode selected from at least a pressure increase mode and a pressure decrease mode.

4. A brake control system as set forth in claim 1, further comprising:

a pair of first valve means for opening or closing said main passages, respectively;

a pair of pump means disposed between said first valve means and said wheel brake cylinders in said main passages, respectively, said pump means introducing from an inlet thereof the brake fluid and pressurizing the brake fluid to supply the hydraulic braking pressure to said wheel brake cylinders;

a pair of auxiliary passages for communicating each inlet of said pump means with said master cylinder; and

a pair of second valve means for opening or closing said auxiliary passages, respectively, and

wherein said control means is adapted to control said second valve means communicated with one of said wheel brake cylinders operatively mounted on at least one of said front wheels, in the case where the slip of said at least one of said front wheels is smaller than the slip of at least one of said wheels belonging to a different hydraulic pressure circuit from the hydraulic pressure circuit to which said at least one of said front wheels belongs, at least when said brake pedal is being operated.

5. A brake control system as set forth in claim 4, wherein said control means includes modulator means disposed between said first valve means and said wheel brake cylinders in each hydraulic pressure circuit for modulating the hydraulic braking pressure in each of said wheel brake cylinders in accordance with a pressure mode selected from at least a pressure increase mode and a pressure decrease mode.

6. A brake control system as set forth in claim 5, wherein said control means is adapted to equalize the hydraulic braking pressure in said wheel brake cylinders operatively mounted on said rear wheels, on the basis of one of said rear wheels having a larger slip than the other one of said rear wheels.

7. A brake control system as set forth in claim 6, wherein said control means is adapted to calculate a first difference between the slip of the front right wheel and the slip of the rear right wheel, and calculate a second difference between the slip of the front left wheel and the slip of the rear left wheel, and wherein said control means is adapted to actuate said modulator means to reduce the first difference and the second difference to be zero, respectively.

8. A brake control system as set forth in claim 5, wherein said control means is adapted to control a duty of said second valve means with respect to said front wheels, and wherein said control means is adapted to control said modulator means with respect to said rear wheels.

9. A brake control system as set forth in claim 5, wherein said control means is adapted to turn off said second valve means immediately with respect to said front wheels, when any abnormality is found, and wherein said control means is adapted to provide a pulse pressure increase mode for a first predetermined time period before terminating the control of said modulator means with respect to said rear wheels, when any abnormality is found.

10. A brake control system as set forth in claim 9, wherein said control means is adapted to determine the abnormality, when a third difference between the slip of said front wheels exceeds a predetermined value continuously for a second predetermined time period.