Anti-skid control system for a road surface having a split coefficient of friction

• US 5,058,018 A
• Filed: 03/26/1990
• Issued: 10/15/1991
• Est. Priority Date: 03/27/1989
• Status: Expired due to Term

• Current Assignee: Advics Company Limited (Aisin Corp.)
• Original Assignee: Aisin Seiki Co., Ltd. (Aisin Corp.)
• Inventors: Yoshida, Tsuyoshi, Tozu, Kenji, Kuwana, Kazutaka
• Primary Examiner(s): Lall, Parshotam S.
• Assistant Examiner(s): Pipala, E. J.
• Application Number:
  US07/498,658
• Time in Patent Office: 568 Days
• Field of Search: 364/426.02, 364/426.01, 303/102, 303/106, 303/109, 303/111, 303/110
• US Class Current: 701/73
• CPC Class Codes: B60T 8/1764 Regulation during travel on surface with different coefficients of friction, e.g. between left and right sides, mu-split or between front and rear
• CPC Class Codes: B60T 8/4275 Pump-back systems
• CPC Class Codes: B60T 8/505 Pressure reapplication in a mu-split situation, i.e. a situation with different coefficients of friction on both sides of the vehicle

Abstract

The invention is directed to an arrangement for controlling a braking force applied to each of right and left road wheels individually depending upon a braking condition, with a hydraulic braking pressure supplied to each of wheel brake cylinders through actuators respectively. The actuators are controlled by the braking force control system wherein output signals of wheel speed detectors are fed into first and second detecting circuits respectively by which the braking conditions of the road wheels are detected. Then, the detected signals are fed into a first driving circuit which produces driving signals fed to the actuators on the basis of an output signal fed from either of the detectors for one road wheel having a tendency to be locked first. One of the actuators provided for the road wheel on the road surface of the lower coefficient of friction is driven by a driving signal fed from the first driving circuit, whereas the other actuator is driven by a driving signal which is fed from the first driving circuit and modified thereafter by the second driving circuit in response to a value representing a vehicle speed so as to increase the hydraulic braking pressure rapidly when the vehicle is driven at low speed, consequently shortening the stopping distance.

Claims

1. An anti-skid control system for controlling a braking force applied to road wheels of an automotive vehicle, comprising:

wheel brake cylinders operatively connected to right and left road wheels, respectively, of said vehicle for applying braking force thereto;

a hydraulic pressure generator for supplying a hydraulic braking pressure to each of said wheel brake cylinders;

actuating means disposed in each hydraulic circuit communicating said hydraulic pressure generator with each of said wheel brake cylinders for individually controlling said hydraulic braking pressure supplied to each of said wheel brake cylinders;

wheel speed detecting means for detecting a rotational wheel speed of each of said road wheels and providing an output signal corresponding to said wheel speed; and

braking force control means for controlling said actuating means in response to said output signal of said wheel speed detecting means, said braking force control means including first detecting means and second detecting means for detecting each braking condition of said road wheels respectively on the basis of said output signal of said wheel speed detecting means,

first driving means for producing driving signals fed to said actuating means on the basis of an output signal fed from one of said first and second detecting means for detecting a braking condition of one of said road wheels having a tendency to be locked firstly, said first driving means including split determination means for determining if said vehicle is running on a split road surface having a different coefficient of friction where one of said road wheels is on a road surface of the higher coefficient of friction and the other of said road wheels is on a road surface of the lower coefficient of friction; and

second driving means for receiving said driving signals from said first driving means and modifying the driving signal fed to one of said actuating means provided for one of said road wheels on said road surface of the higher coefficient of friction in response to a value representing a vehicle speed immediately after said split determination means determines that said vehicle is running on said split road surface.

2. An anti-skid control system for an automotive vehicle as set forth in claim 1, wherein said first detecting means provides a first cumulative value of differences between a wheel speed of one of said road wheels and said value representing the vehicle speed during a predetermined period of time, and said second detecting means provides a second cumulative value of differences between a wheel speed of the other of said road wheels and said value representing the vehicle speed during said predetermined period of time, and wherein said split determination means comprises comparing means for comparing a difference between said first cumulative value and said second cumulative value with a predetermined value, and determining that said vehicle is running on said split road surface when said difference between said first cumulative value and said second cumulative value exceeds said predetermined value.

3. An anti-skid control system for an automotive vehicle as set forth in claim 1, wherein said second driving means includes locking condition determination means for determining if one of said road wheels on said road surface of the higher coefficient of friction tends to be locked, said second driving means modifying the driving signal fed to one of said actuating means for one of said road wheels on said road surface of the higher coefficient of friction, in response to said value representing the vehicle speed, only when one of said road wheels on said road surface of the higher coefficient of friction is determined to have no tendency to be locked.

4. An anti-skid control system for an automotive vehicle as set forth in claim 3, wherein said value representing the vehicle speed is an estimated vehicle speed calculated by said wheel speeds of said road wheels.

5. An anti-skid control system for an automotive vehicle as set forth in claim 3, wherein said value representing the vehicle speed is a wheel speed of one of said road wheels on said road surface of the higher coefficient of friction.

6. An anti-skid control system for an automotive vehicle as set forth in claim 3, wherein said second driving means drives said actuating means to increase the increasing speed of the hydraulic braking pressure supplied to said wheel brake cylinder for one of said road wheels on said road surface of the higher coefficient of friction.

7. An anti-skid control system for an automotive vehicle as set forth in claim 6, wherein said second driving means drives said actuating means to control the hydraulic braking pressure supplied to one of said wheel brake cylinders for one of said road wheels on said road surface of the higher coefficient of friction into the same pressure as the hydraulic braking pressure supplied to the other of said wheel brake cylinders for the other of said road wheels on said road surface of the lower coefficient of friction during a predetermined period of time immediately after the initiation of operation of said first driving means.

8. An anti-skid control system for controlling a braking force applied to road wheels of an automotive vehicle, comprising:

wheel brake cylinders operatively connected to right and left road wheels, respectively, of said vehicle for applying braking force thereto;

a hydraulic pressure generator for supplying a hydraulic braking pressure to each of said wheel brake cylinders;

actuating means disposed in each hydraulic circuit communicating said hydraulic pressure generator with each of said wheel brake cylinders for individually controlling said hydraulic braking pressure supplied to each of said wheel brake cylinders;

wheel speed detecting means for detecting a rotational wheel speed of each of said road wheels and providing an output signal corresponding to said wheel speed; and

braking force control means for controlling said actuating means in response to said output signal of said wheel speed detecting means;

wherein said braking force control means comprises;

first detecting means for detecting a braking condition of one of said road wheels on the basis of said output signal of said wheel speed detecting means and providing a first cumulative value of differences between a wheel speed of one of said road wheels and an estimated vehicle speed calculated by said wheel speed during a predetermined period of time;

second detecting means for detecting a braking condition of the other of said road wheels on the basis of said output signal of said wheel speed detecting means and providing a second cumulative value of difference between a wheel speed of the other of said road wheels and said estimated vehicle speed during said predetermined period of time;

a first driving means for producing driving signals fed to said actuating means on the basis of an output signal fed from one of said first and second detecting means for detecting a braking condition of one of said road wheels having a tendency to be locked firstly, said first driving means including split determination means for determining if said vehicle is running on a split road surface having a different coefficient of friction where one of said road wheels is on a road surface of the higher coefficient of friction and the other of said road wheels is on a road surface of the lower coefficient of friction, said split determination means including comparing means for comparing a difference between said first cumulative value and said second cumulative value with a predetermined value, and determining that said vehicle is running on said split road surface when said difference between said first cumulative value and said second cumulative value exceeds said predetermined value; and

second driving means for receiving said driving signals from said first driving means and including locking condition determination means for determining if one of said road wheels on said road surface of the higher coefficient of friction tends to be locked, said second driving means modifying the driving signal fed to one of said actuating means for one of said road wheels on said road surface of the higher coefficient of friction, in response to said estimated vehicle speed, and driving said actuating means to increase the increasing speed of the hydraulic braking pressure supplied to said wheel brake cylinder for one of said road wheels on said road surface of the higher coefficient of friction, immediately after said split determination means determines that said vehicle is running on said split road surface and only when one of said road wheels on said road surface of the higher coefficient of friction is determined to have no tendency to be locked; and

wherein said braking force control means feeds said driving signals to said actuating means through said first and second driving means when said split determination means determines that said vehicle is running on said split road surface, while said braking force control means drives each of said actuating means independently when said vehicle is not running on said split road surface.

9. An anti-skid control system for an automotive vehicle as set forth in claim 8, wherein said second driving means drives said actuating means to control the hydraulic braking pressure supplied to one of said wheel brake cylinders for one of said road wheels on said road surface of the higher coefficient of friction into the same pressure as the hydraulic braking pressure supplied to the other of said wheel brake cylinders for the other of said road wheels on said road surface of the lower coefficient of friction during a predetermined period of time immediately after the initiation of operation of said first driving means.