Anti-lock brake control systems for multi-axle vehicles

• US 4,270,808 A
• Filed: 04/16/1979
• Issued: 06/02/1981
• Est. Priority Date: 04/22/1978
• Status: Expired due to Term

• Current Assignee: Grau Limited
• Original Assignee: Girling Limited (ZF International UK Ltd.)
• Inventors: Brearley, Malcolm
• Primary Examiner(s): Miller, J. D.
• Assistant Examiner(s): Eisenzopf, Reinhard J.
• Application Number:
  US06/030,433
• Time in Patent Office: 778 Days
• Field of Search: 303/92, 303/20
• US Class Current: 303/122.05
• CPC Class Codes: B60T 2270/406 Test-mode; Self-diagnosis
• CPC Class Codes: B60T 8/885 using electrical circuitry

Abstract

Anti-skid brake control systems are described in which anti-skid brake control modules associated with the braked axles are each provided with a failsafe circuit and these failsafe circuits are connected in cascade fashion to form a chain so that an input signal applied to a first failsafe circuit will propagate through the chain of failsafe circuits to the output of the last failsafe circuit only if the wiring connecting the modules is correct, the failsafe circuits are themselves operating correctly and electrical power is being supplied to each module, a warning being given to the driver of the vehicle if the output signal from the last failsafe circuit fails. In a previously proposed system the warning given is only produced in the event of a fault, and there is no positive indication of correct operation of the system at switch on. Circuits are here described in which the vehicle ignition switch is arranged to apply a fault pulse to the input of the first failsafe circuit in the chain at switch-on of the ignition and the response of the output of the last failsafe circuit to the pulse is monitored by a suitable monitor unit. Some of the failsafe circuits incorporate switch-off circuits which are so arranged that, on the occurence of a fault in the chain upstream of that failsafe circuit, the switch-off circuits operate an inhibit device to inhibit operation of one or more of the brake release circuits which are downstream of the point at which the fault exists.

Claims

1. A multi-axle wheeled vehicle comprising a respective brake for each axle, a respective speed sensor associated with each axle, a respective brake release means associated with each axle and responsive to the respective speed sensor to release the respective brake on the occurrence of a skid condition at that axle, a respective inhibit means associated with each brake release means and being operable by inhibit operation of that brake release means, a respective fault detection circuit associated with each brake release means and being responsive to a fault condition in that brake release means to operate the respective inhibit means so as to inhibit operation of the associated brake release means, a respective signal repeater circuit associated with each brake release means and having an input and an output, means connecting the inputs and outputs of the signal repeater circuits in series to form a chain so that a signal applied to the input of the first repeater circuit in said chain will normally be propagated along said chain to the output of the last repeater circuit in said chain, each signal repeater circuit being responsive to the respective fault detection circuit so as to interrupt the passage of said signal along said chain upon the occurrence of said fault condition, and a respective shutdown connection means associated with each inhibit means and for optional connection to the input of the respective signal repeater circuit so that, when connected, an interruption in said signal at said input due to a fault upstream thereof along said chain causes said inhibit means to be operated to inhibit operation of the associated brake release means, whereby in the event of said fault condition occurring in one of said brake release means, operation of selected brake release means downstream thereof is inhibited.

2. A multi-axle wheeled vehicle as claimed in claim 1, including a warning device responsive to the absence of said signal at the output of the last signal repeater circuit in said chain, and a switch arranged to apply to the input of the first signal repeater circuit in said chain on each operation of said vehicle a test pulse in the form of an interruption of said signal in order to check whether said signal is being propagated through said chain to said warning device.

3. A multi-axle wheeled vehicle as claimed in claim 2, including a delay device arranged to provide a delay between operation of said switch and application of said test pulse to the input of the first signal repeater circuit in said chain.

4. A multi-axle wheeled vehicle as claimed in claim 3, in which said delay device is adapted to provide a delay of about 0.05 seconds.

5. A wheeled vehicle having at least four axles and comprising a respective brake for each axle, a respective speed sensor associated with each axle, a respective brake release means associated with each axle and responsive to the respective speed sensor to release the respective brake on the occurrence of a skid condition at that axle, a respective inhibit means associated with each brake release means and being operable to inhibit operation of that brake release means, a respective fault detection circuit associated with each brake release means and being responsive to a fault condition in that brake release means to operate the respective inhibit means so as to inhibit operation of the associated brake release means, a respective signal repeater circuit associated with each brake release means and having an input and an output, first means connecting the inputs and outputs of the signal repeater circuits of at least two of the forward axles of said vehicle in series to form a first chain so that a first signal applied to the input of the first repeater circuit in said first chain will normally be propagated along said first chain to the output of the last repeater circuit in said first chain, second means connecting the inputs and outputs of the signal repeater circuits of at least two of the rearward axles of said vehicle in series to form a second chain so that a signal applied to the input of the first repeater circuit in said second chain will normally be propagated along said second chain to the output of the last repeater circuit in said second chain, each signal repeater circuit being responsive to the respective fault detection circuit so as to interrupt the passage of the respective signal along the respective chain upon the occurrence of said fault condition, and a respective shutdown connection means associated with each inhibit means and for optional connection to the input of the respective signal repeater circuit so that, when connected, a interruption in the respective signal at said input due to a fault upstream thereof along the respective chain causes said inhibit means to be operated to inhibit operation of the associated brake release means, whereby in the event of said fault condition occurring in one of said brake release means, operation of selected brake release means downstream thereof is inhibited.