Fail-safe system in anti-skid brake control system for automotive vehicles

• US 4,722,576 A
• Filed: 12/11/1984
• Issued: 02/02/1988
• Est. Priority Date: 12/13/1983
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Matsuda, Toshiro
• Primary Examiner(s): Caldwell, Sr., John W.
• Assistant Examiner(s): Oberley, Alvin
• Application Number:
  US06/680,523
• Time in Patent Office: 1,148 Days
• Field of Search: 303/92, 303/119, 303/100, 303/105, 303/106, 303/109, 364/426
• US Class Current: 303/122.05
• CPC Class Codes: B60T 2270/415 Short-circuit, open circuit failure
• CPC Class Codes: B60T 2270/416 Wheel speed sensor failure
• CPC Class Codes: B60T 8/4291 having means to reduce or eliminate pedal kick-back
• CPC Class Codes: B60T 8/885 using electrical circuitry
• CPC Class Codes: B60T 8/90 using a simulated speed signal to test speed responsive control means

Abstract

A fail-safe system for an automotive anti-skid control system ensures that manual control of vehicle brakes is enabled if any system components should fail. The anti-skid control system employs actuators to control the brakes automatically, the actuators being powered by a vehicle battery. The power supply to the actuators is interrupted by the fail-safe system if malfunction of any system components is detected and the control signals for operating the actuators are held to a value such that the actuators are positioned in the brake pressure increase position. Specifically, the fail-safe system checks for open or short circuits in the actuators themselves, inaccuracy or failure of any of a plurality of wheel speed sensors, excessive or insufficient battery voltage, and malfunction of major system components such as a hydraulic pump used to expedite automatic control, signal processing units, etc. The particular type of malfunction may be recorded for reference during maintenance and repair.

Claims

1. A fail-safe system for an anti-skid brake control system comprising:

a hydraulic brake circuit;

a pressure control valve disposed in said brake circuit for increasing hydraulic brake pressure in a wheel cylinder in a first position, for decreasing hydraulic brake pressure in said wheel cylinder in a second position and for holding hydraulic brake pressure in said wheel cylinder constant in a third position;

an actuator associated with said pressure control valve for operating said pressure control valve among said first, second and third positions according to a control signal, said actuator being connected to an electric power source to receive power therefrom;

a sensor for detecting wheel speed and producing a sensor signal indicative of the wheel speed;

a detector for detecting faulty operation of components of said anti-skid brake control system and producing a fault-indicative signal when faulty operation of at least one of said components is detected; and

a controller receiving said sensor signal and processing the sensor signal, deriving values of wheel acceleration and slippage, deriving said control signal in accordance with said derived values, and said controller being responsive to said fault-indicative signal to perform a first fail-safe operation to hold said control signal at a value at which said pressure control valve is in said first position and to perform a second fail-safe operation to terminate power to said actuator, such that, if said second fail-safe operation which causes termination of power fails to occur, said first fail-safe operation will still cause said pressure control valve to be operated to said first position.

2. The fail-safe system as set forth in claim 1, which further comprises a fault monitor lamp energized by said fault-indicative signal.

3. The fail-safe system as set forth in claim 1, which further comprises a memory associated with said detector for storing data identifying all faulty components in response to said fault-indicative signal.

4. The fail-safe system as set forth in claim 3, further comprising a faulty component indicator corresponding to each detected faulty component and energized when faulty operation of a corresponding one of said components is detected by said detector.

5. The fail-safe system as set forth in claim 4, wherein said detector monitors the power to said actuator and produces said fault-indicative signal when the power is interrupted.

6. The fail-safe system as set forth in claim 5, wherein said detector distinguishes between termination of power to said actuator by said controller and by external conditions, and in the former case does not produce said fault-indicative signal.

7. The fail-safe system as set forth in claim 1, wherein said detector includes means receiving said control signal and signals indicative of the response of the components of the anti-skid brake control system to the current control signal, comparing said control signal and said response-indicative signals and producing said fault-indicative signal when said responsive-indicative signals do not correspond to the current control signal.

8. A fail-safe system for an anti-skid brake control system comprising:

a hydraulic brake circuit including a wheel cylinder for applying hydraulic braking pressure for decelerating rotation of a vehicular wheel;

a pressure control valve disposed in said brake circuit for increasing hydraulic brake pressure in said wheel cylinder in a first position, and decreasing hydraulic brake pressure in said wheel cylinder in a second position;

an actuator associated with said pressure control valve for operating said pressure control valve between said first and second positions according to a control signal, said actuator being connected to an electric power source to receive power therefrom, said actuator operating said pressure control valve in said first position while in a nonactive state thereof and in said second position in an active state thereof;

a sensor for detecting wheel speed and producing a sensor signal indicative of wheel speed;

a detector for monitoring operations of components of said anti-skid brake control system and producing a fault indicative signal whenever fault in at least one of said components is detected;

a controller receiving said sensor signal and processing the sensor signal for deriving brake-controlling parameters on the basis of said sensor signal and deriving said control signal based on said sensor signal and said brake controlling parameters, and said controller performing a first fail-safe operation for disconnecting said actuator from said power source for forcing said actuator to assume said non-active state, and a second fail-safe operation for fixedly holding said control signal at a value affecting said first position of said pressure control valve, such that, if said first fail-safe operation fails to occur, said second fail-safe operation will occur.

9. A fail-safe system for an anti-skid brake control system comprising:

a hydraulic brake circuit including a wheel cylinder for applying hydraulic brake pressure to a vehicular wheel for deceleration of the latter;

a pressure control valve disposed in said brake circuit for increasing hydraulic brake pressure in said wheel cylinder in a first position and decreasing hydraulic brake pressure in said wheel cylinder in a second position;

an actuator cooperatively associated with said pressure control valve and variable in positions between a first inoperative position for positioning said pressure control valve in said first position and a second operative position for positioning said pressure control valve in said second position and connected to an electric power source, said actuator being responsive to a control signal to vary positions between said first inoperative position and said second operative position;

a sensor for detecting wheel speed and producing a sensor signal indicative of wheel speed;

a detector for monitoring operations components of said anti-skid brake control system for producing a fault indicative signal whenever fault in at least one of said components is detected; and

a controller receiving said sensor signal and processing the sensor signal for deriving brake controlling parameters on the basis of said sensor signal and deriving said control signal based on said sensor signal and said brake controlling parameters, said controller being responsive to perform a first fail-safe operation for disconnecting said actuator from said electric power source, for holding said actuator in said first inoperative position, for holding said pressure control valve in said first position, and a second fail-safe operation for fixing said control signal value at a value ordering said first position of said pressure control valve, such that, if said first fail-safe operation fails to occur, said second fail-safe operation will occur.