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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
First Claim
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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.

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