Anti-skid control with fail-safe function

• US 4,789,938 A
• Filed: 02/26/1986
• Issued: 12/06/1988
• Est. Priority Date: 03/25/1985
• Status: Expired due to Fees

• Current Assignee: Nippondenso Co., Ltd. (DENSO Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Original Assignee: Nippondenso Co., Ltd. (DENSO Corporation), Toyota Jidosha Kabushiki Kaisha (Toyota Motor Corporation)
• Inventors: Masaki, Shoichi, Hirano, Satoshi, Asami, Ken, Sakai, Kazunori, Maehata, Hiromi, Okuda, Yutaka
• Primary Examiner(s): Chin, Gary
• Application Number:
  US06/833,230
• Time in Patent Office: 1,014 Days
• Field of Search: 364/426, 364/565, 364/566, 303/92, 303/93, 303/94, 303/95, 180/197, 361/238
• US Class Current: 701/76
• CPC Class Codes: B60T 8/885 using electrical circuitry
• CPC Class Codes: B60T 8/94 on a fluid pressure regulator

Abstract

In an anti-skid control system for a motor vehicle there is provided a fail-safe control system for providing a compensation for a proper vehicle braking operation against the occurrence of failure of a hydraulic pressure control valve. The fail-safe control system includes a device for monitoring a control signal for controlling the operation of the control valve so that the hydraulic pressure applied to a wheel braking cylinder is regulated for preventing a wheel of the vehicle from skidding. The monitoring device detects the occurrence of failure of the control valve when the control signal indicative of one of the operation modes of the control valve is continuously generated more than a predetermined time period. In response to the detection, the fail-safe control system switches a directional control valve to the passage-opening condition so that the hydraulic pressure from a master cylinder can directly be applied to the wheel braking cylinder, thereby enabling the braking operation to be controlled by a vehicle driver.

Claims

1. A braking system with an anti-skid device for a motor vehicle, comprising:

a master cylinder operatively coupled to a brake pedal of said vehicle;

at least two braking cylinders each associated with a wheel of the vehicle and each responsive to a hydraulic pressure developed in said master cylinder, each for braking said associated wheel of said vehicle;

hydraulic pressure passage means, provided between said master cylinder and said two wheel braking cylinders, said hydraulic pressure passage means including a single directional control valve having at least a first passage opening position and a second passage closing position to open and close said hydraulic pressure passage means, respectively, said single directional control valve being arranged to be common for all of said wheel braking cylinders;

a hydraulic pressure supplying device connected through a number of hydraulic pressure control valves to said at least two wheel braking cylinders, the number of said hydraulic pressure control valves being determined in accordance with the number of said wheel braking cylinders;

means for detecting a speed of at least one of said vehicle wheels and generating a signal corresponding to the detected speed of said wheel;

comparing means, responsive to said signal from said wheel speed detecting means, for comparing the detected speed with a predetermined reference speed;

first control means for determining if anti-skid control for said vehicle should be performed, in accordance with said comparing of said comparing means, and generating first and second control signals, said first control signal being supplied from said first control means to said single directional control valve to command said single directional control valve to switch from said passage-opening position to said passage-closing position, and said second control signals being supplied to said hydraulic pressure control valves to control the hydraulic pressures to be applied to said wheel braking cylinders on the basis of a hydraulic pressure from said hydraulic pressure supplying device so as to approach predetermined values, respectively; and

second control means, coupled to said first control means, for receiving said second control signals to monitor operating conditions of each of said hydraulic pressure control valves to determine any of said hydraulic pressure control valves to be in an abnormal condition when each of said second control signals indicative of a specific valve-operating mode being successively supplied to said second control means for a predetermined time period, said second control means generating a third control signal in response to the abnormal condition of at least one of said hydraulic pressure control valves to command said single directional control valve to be switched to the passage-opening condition.

2. A braking system with an anti-skid device for a motor vehicle, comprising:

a master cylinder operatively coupled to a brake pedal of said vehicle;

at least two wheel braking cylinders each associated with a wheel of the vehicle and each responsive to a hydraulic pressure developed in said master cylinder for braking at least two wheels of said vehicle;

hydraulic pressure passage means provided between said master cylinder and said two wheel braking cylinders, said hydraulic pressure passage means including a single directional control valve having at least a first passage open position and a second passage closing position to open and close said hydraulic pressure passage means, respectively, said single directional control valve being arranged to be common for all of said wheel braking cylinders;

a hydraulic pressure supplying device connected through at least two hydraulic pressure control valves to said at least two wheel braking cylinders, the number of said hydraulic pressure control valves being determined in accordance with the number of said wheel braking cylinders;

means for detecting a speed of at least one of said vehicle wheels;

means for detecting an acceleration of said at least one vehicle wheel;

comparing means for comparing said wheel speed and said wheel acceleration with a predetermined reference speed and a predetermined reference wheel acceleration;

first control means for determining if anti-skid control for said vehicle should be performed in accordance with said comparing of said comparing means and generating first and second signals, said first control signal being supplied therefrom to said single directional control valve to switch said single directional control valve from said passage-opening position to said passage-closing position and said second control signal being supplied to said hydraulic pressure control valves so that said hydraulic pressure control valves are controlled in response to said second control signals to regulate the hydraulic pressures applied to said wheel braking cylinders to prevent said vehicle wheels from being in a skidding condition, each of said control signals performing a switching operation among pressure-controlling modes of each of said hydraulic pressure control valves so as to cause a hydraulic pressure applied to each of said wheel braking cylinders to approach a predetermined value; and

second control means coupled to said first control means for receiving each of said second control signals to monitor the operating condition of each of said hydraulic pressure control valves and determining whether each of said hydraulic pressure control valves is in an abnormal condition, the abnormality of said hydraulic pressure control valve being determined when said second control signal indicative of a specific pressure-controlling mode being successively supplied to said second control means for a predetermined time period, said second control means generating a third control signal in response to said abnormal condition of said at least one hydraulic pressure control valve, so that said single directional control valve is switched to the passageopening condition.

3. A braking system as claimed in claim 2, wherein said predetermined reference wheel speed and said predetermined reference acceleration are determined on the basis of the condition of a road on which said vehicle is running.

4. A braking system as claimed in claim 3, wherein said road condition is estimated in accordance with the detected wheel speed and wheel acceleration.

5. A braking system as claimed in claim 2, wherein said second control means includes means for indicating said abnormal condition of said hydraulic pressure control valve to a driver of said vehicle.

6. A braking system as claimed in claim 2, wherein said first control means controls said hydraulic pressure control valve in accordance with the results of the comparison between the detected wheel speed and acceleration and said reference wheel speed and reference acceleration, respectively.

7. A braking system as claimed in claim 2, wherein said specific pressure controlling mode is a pressure-increasing mode for increasing the hydraulic pressure applied to said wheel braking cylinder.

8. A braking system as claimed in claim 7, wherein said second control means includes means for counting said second control signal indicative of said pressure-increasing mode generated therefrom.