Anti-lock vehicle brake system

Claim 2

An electronic control system for an anti-lock vehicle brake system containing at least one brake, said control system being responsive to an input signal from a wheel movement sensor associated with a wheel of said vehicle system, which measures change in wheel speed, said signal varying in accordance with the rate of said speed change, said electronic control system comprising: a solenoid valve mechanism connected to a brake of said antilock system for reducing brake pressure of said brake when braking takes place and wheel deceleration exceeds a reference value; a control circuit connected to said wheel movement sensor and to said solenoid valve mechanism and having a reference control circuit therein, said reference control circuit being responsive on energisation of said solenoid valve mechanism by said control circuit for progressively varying said reference value in a positive sense at a predetermined rate, said solenoid valve mechanism being held energized by said control circuit until the rate of change of said wheel speed bears a given relationship to said varying reference value.

Claim 3

The electronic control system of claim 1, further comprising a delay device connected to said reference control circuit for maintaining said reference value in an unchanged capacity for a given time after energization of said solenoid valve mechanism, said reference control circuit then being operable after said given time to change said reference value progressively in a positive sense if the wheel deceleration remains in excess of said reference value.

Claim 4

The electronic control system of claim 2, wherein said delay device comprises a monostable circuit.

Claim 5

The electronic control system of claim 1, further comprising a delay device connected to said reference control circuit for increasing the reference value of the wheel deceleration for a given time, to a new, more negative value immediately after energization of said solenoid valve mechanism, said reference control circuit being operable after said given time if the wheel deceleration remains in excess of the new reference value.

Claim 6

The electronic control system of claim 1, further comprising reset means connected to said reference control circuit for setting said reference value to a higher deceleration value for a given time at termination of anti-lock braking control action, and prior to resetting said reference value to an originaL rate commensurate with a beginning of said anti-lock braking control action.

Claim 7

The electronic control system of claim 1, further comprising reset means connected to said reference control circuit for setting said reference value to a lower acceleration value for a given time at termination of anti-lock braking control action, and prior to resetting said reference value to an original rate commensurate with a beginning of said anti-lock brake control action.

Claim 8

The electronic control system of claim 1, further comprising timing means connected to said solenoid valve mechanism for automatically terminating anti-lock braking control action after a predetermined time.

Claim 9

The electronic control system of claim 7, wherein said timing means comprises a monostable circuit.

Claim 10

The electronic control system of claim 1, wherein said control circuit comprises: an input terminal for said wheel speed signal; a transistor having a base portion, an emitter portion and a collector portion; a capacitor connected between said input terminal and the base portion of said transistor; a source of fixed potential; a resistor connected between said source of fixed potential and the base portion of said transistor, resulting base current determining said reference value; an output stage connected to said transistor and to said solenoid valve mechanism for supplying current to said solenoid valve mechanism if said transistor in common emitter connection passes no current; an input for said reference control circuit connected to said output stage; and an output for said reference control circuit connected to the base portion of said transistor.

Claim 11

The electronic control system of claim 9, wherein said control circuit further comprises a resistor connected between the base portion of said transistor and said capacitor, and transistor cut off means, said resistor for setting a fixed amount of wheel speed which must be exceeded after wheel deceleration has exceeded said reference value before said transistor is cut-off.

Claim 12

The electronic control system of claim 9, wherein said control circuit further comprises; a source of positive voltage; a resistor connected between said positive voltage source and the collector portion of said transistor, said collector portion supplying a control signal to said output stage; a null line; and a voltage divider connected between the source of positive voltage and said null line, said voltage divider having a junction point connected to the emitter portion of said transistor.

Claim 13

The electronic control system of claim 11, further comprising a delay circuit and a reset circuit connected to said reference control circuit, said delay, reset, and reference control circuits formed by a second transistor having a base portion, an emitter portion and a collector portion, said emitter portion of said second transistor being connected to the positive voltage source, said collector portion of said second transistor being connected to said null line through a resistor, and said base portion of said second transistor connected to said output stage, said second transistor being saturated when said output stage passes no current and being cut off when said output stage passes current; a resistor-capacitor network connected to said second transistor, said network comprising a first diode having an anode connected to the positive voltage source, and a cathode connected through a resistor wired in parallel with said diode, to a capacitor connected to said collector portion of said second transistor; a second resistor connected to the base portion of said former transistor; and a third resistor and a second diode in series connected between said second resistor and base portion connection and the collector portion of said former transistor, said series resistor-diode combination passing current toward said former collector portion.