Monitoring circuitry for a skid control system

• US 3,920,284 A
• Filed: 05/10/1974
• Issued: 11/18/1975
• Est. Priority Date: 05/10/1974
• Status: Expired due to Term

• Current Assignee: David Thomas Klien, Eneas James Lane, Steven Geppert
• Original Assignee: David Thomas Klien, Eneas James Lane, Steven Geppert
• Inventors: Lane, Eneas James, Klien, David Thomas, Geppert, Steven
• Primary Examiner(s): Blix, Trygve M.
• Assistant Examiner(s): Kunin, Stephen G.
• Application Number:
  US05/468,929
• Time in Patent Office: 557 Days
• Field of Search: 303/21 318/563,565 324/34R,51,57R,62K,73R,133,14R 340/52B,248A,248B
• US Class Current: 303/122.06
• CPC Class Codes: B60T 2270/406 Test-mode; Self-diagnosis
• CPC Class Codes: B60T 8/885 using electrical circuitry

Abstract

A skid control system serves to control the operation of a braking system for applying braking forces to a pair of spaced apart, independently rotatable vehicle wheels. The system employs a brake control device which responds to a skid signal for controlling the braking system to release the braking forces on the wheels. Wheel speed signals are provided by sensor circuitry and are representative of the wheel speeds of the first and second wheels. Logic circuitry utilizes the wheel speed signals to determine an incipient skid condition of at least one of the wheels and, in dependence upon the determination, provides a skid signal. Monitoring circuitry is provided for use with such a skid control system for inhibiting the operation of the system. The wheel speed sensing circuits are monitored for sensor continuity and a control signal is provided when an open circuit condition is detected. This control signal is employed to disable the skid control system. Monitoring circuitry is also provided for monitoring the brake control, such as a valve solenoid, and for disabling the system when a determination is made of either an open or shorted solenoid coil. Monitoring circuitry is also provided for monitoring the time duration that a skid signal is provided by the skid signal logic circuitry and disabling the skid control system when the time duration of the skid signal is excessive.

Claims

1. A skid control system for use with a vehicle having at least first and second spaced apart independently rotatable wheels and a braking system for applying braking forces to said wheels and comprising:

brake control means responsive to a skid signal for controlling said braking system to release the braking forces on said wheels;

means for providing first and second wheel speed signals respectively representative of the wheel speeds of said first and second wheels;

logic circuit means for utilizing said first and second wheel speed signals to determine therefrom an incipient skid condition of at least one of said wheels and providing a said skid signal in dependence upon said determination;

said brake control means including energizable valve solenoid coil means for, when energized, acting upon said braking system to release braking forces on said wheels and valve driver circuit means responsive to a skid signal for energizing said valve solenoid coil means; and

monitor means for disabling said valve driver circuit means in response to detection of an erroneous operating characteristic and comprising means for applying a DC test current of a magnitude insufficient to energize said valve solenoid coil means to flow through said coil means to develop a test voltage thereacross, first test circuit means for diverting said test current to flow in a first signal path when said valve solenoid coil means develops an open circuit fault, second test circuit means for producing a signal current in a second signal path when a short circuit of said valve solenoid coil means reduces said test voltage below a predetermined threshold, means including a third current path for combining said first and second signal current paths so that either an open circuit or short circuit fault produces a fault signal current in said third current path, and circuit means for disabling said valve driver circuit means in dependence upon said fault signal current in said third path.

2. A skid control system as set forth in claim 1 including time delay means for timing a given period of time before disabling said valve driver circuit means in response to a said fault signal current.

3. A skid control system as set forth in claim 2 including fuse means associated with said valve driver means and means for permanently disabling said valve driver means by blowing said fuse means in response to a said fault signal current.

4. A skid control system as set forth in claim 1 and wherein said second test circuit means includes voltage comparator means for comparing said test voltage with a reference voltage and providing a said signal current in said second signal path when said reference voltage exceeds said test voltage, and timing means for timing a given time duration in response to a said fault signal current before disabling said valve driver circuit means.

5. A skid control system as set forth in claim 1 and wherein said test current applying means includes resistance means connected in series with said valve solenoid coil means and exhibiting a greater resistance than that of said valve solenoid coIl means so that said test current flows through a series circuit including said resistance means and said valve solenoid coil means, said first test circuit means for diverting said test current including means for increasing the magnitude of the voltage developed across said coil means between said resistance means and said coil means from a normal low potential when there is no open circuit condition to a higher potential upon the existence of an open circuit condition, and means for applying said higher potential signal to said combining means.

6. A skid control system as set forth in claim 5 and wherein said monitor means includes means for producing a routine signal when the voltage on said valve solenoid coil means is high because of routine energization of said coil instead of an open circuit, and diode means for connecting said routine signal with said first test circuit means to prevent said fault signal current upon such routine energization, whereby false alarms are reduced.

7. A skid control system as set forth in claim 5, including time delay means for timing a given time duration in response to a said fault signal current before disabling said valve driver circuit means.

8. A skid control system for use with a vehicle having at least first and second spaced apart, independently rotatable wheels and a braking system for applying braking forces to said wheels and comprising:

brake control means responsive to a skid signal for controlling said braking system to release the braking forces on said wheels;

means for providing first and second wheel speed signals respectively representative of the wheel speed of said first and second wheels;

logic circuit means for utilizing said first and second wheel speed signals to determine therefrom an incipient skid condition of at least one of said wheels and providing a skid signal in dependence upon a said determination;

said wheel speed signal-providing means including first and second wheel speed sensors, each said wheel speed sensor comprising rotor means adapted to be mounted to a vehicle wheel for rotation therewith and stator means including at least one sensor coil means located proximate to said rotor means for providing a cyclically varying signal exhibiting a frequency dependent upon the angular velocity of said rotor means, means for conditioning said cyclically varying signal to make the amplitude of its successive cycles substantially constant, said signal-conditioning means having an input and an output and comprising means for transmitting DC signals also, and means for utilizing the conditioned frequency signal from said output to provide a said wheel speed signal;

means for monitoring the electrical continuity of a said sensor coil means and including means for applying a DC test current to said sensor coil means so as to flow therethrough and establish a DC test voltage thereacross at least while said vehicle is moving, said DC test voltage being connected with said input of said signal-conditioning means, and means connected with said output of said signal-conditioning means and responsive to a variation in the magnitude of said DC test voltage for providing a fault signal representative of a loss of electrical continuity.

9. A skid control system as set forth in claim 8 and wherein said test current applying means includes a resistor connected in series with said sensor coil means and exhibiting a resistance greater than that of said sensor coil means so that when said coil means is continuous, the test voltage developed across said coil means due to said test current is relatively small, and wherein said system further comprises control circuit means responsive to a said fault signal for effectively disabling said brake control means.

10. A skid control system as set forth in claim 9 wherein said brake control means includes valve solenoid means for, when energized, acting upon said braking system to release braking forces on said wheels, and valve driver circuIt means responsive to a said skid signal for energizing said valve solenoid means;

and wherein said control circuit means responsive to a said fault signal comprises means for disabling said valve driver circuit means so as to be non-responsive to a said skid signal.

11. A skid control system as set forth in claim 10 including time delay means responsive to a said fault signal for timing a predetermined period of time before disabling said valve driver circuit means.

12. A skid control system as set forth in claim 8 and wherein said signal conditioning means comprises amplifier means and said test current applying means includes a resistor connected in series with said sensor coil means with said resistor exhibiting a greater resistance than that of said coil means whereupon a relatively low DC test voltage is normally applied across said coil means in the absence of an open circuit condition thereof, and means for connecting the junction of said resistor and said coil means with one input of said amplifier means to provide an amplifier output signal dependent upon voltage developed across said coil means, said amplifier means providing said fault signal as a relatively extreme DC output signal in the event of an open circuit condition of said coil means.