Pressure fluid vehicle brake anti-lock system with independent right-left control

Claim 2

Pressure fluid brake anti-lock system for vehicles having separate left and right braking systems at left and right sides of the vehicle comprising left and right inlet valves (14, 114) to admit pressurized brake fluid to left and right wheel brakes, respectively, and means (23, 123) respectively controlling operation of said valves; left and right drain valves (19, 119) to drain pressurized brake fluid from the left and right wheel brakes, respectively, and drain control means (25, 125) respectively controlling operation of the drain valves; left and right anti-lock control systems including left and right means (32-42; 132-142) to sense, respectively, left and right wheel rate-of-change of speed and independently controlling respective selective operation of said left valves and said right valves, in accordance with respective rate of change of wheel speed, to provide for independent control cycles including pressure rise and pressure drop in the respective left and right braking systems; said anti-lock system further comprising a pulse source (46); common means (44, 45) sensing deceleration of any one of the wheels above a predetermined limit, said common deceleration sensing means (44, 45) controlling connection (E; 43, 143) of said pulse source (46) to at least one of the valves associated with the brakes on the other side of the vehicle with respect to the side where deceleration above a predetermined limit has been sensed to permit only intermittent, pulsed, gradual increase of brake pressure at said other side of the veHicle after the common sensing means has sensed a wheel rate of change of speed of any one wheel indicative of imminent brake locking, and to control subsequent rate of pressure change in both systems by the pulses derived from said pulse source.

Claim 3

System according to claim 1 wherein said pulse source (46) is connected to intermittently energize the inlet valves of both said brake systems to permit flow of pressurized brake fluid to the respective brake only in intermittent pulses.

Claim 4

System according to claim 1 wherein the deceleration sensing means includes a bistable flip-flop (45) connected to control operation of the pulse source (46); and means (44) connected to have control inputs applied to said flip-flop (45) which are energized upon opening of any one of the drain valves (19, 119).

Claim 5

System according to claim 3 wherein the vehicle has a switch (29) operating upon operation of the brake control of the vehicle; and wherein the switch (29) is connected to the reset input of the flip-flop (45) to reset the flip-flop when the brake is not operated and the switch is open to thereby disable further operation of the pulse source (46).

Claim 6

System according to claim 3 comprising a fail-safe reset circuit (48) connected to the reset input of the flip-flop (45), the fail-safe reset circuit comprising a timing circuit (FIG. 3; 480, 484, 485, 487) connected to the rate-of-change sensing means associated with at least one of the wheels and starting a timing interval if the rate of change of speed of the respective wheel or wheels exceeded a predetermined level.

Claim 7

System according to claim 5 wherein the rate of change of speed sensing means comprises a plurality of threshold switches (39, 40, 41; 139, 140, 141) sensing different values of rate of change of wheel speed, said system further comprising a reset OR gate (49) having its input connected to at least two of said rate of speed change threshold sensors.

Claim 8

System according to claim 1 wherein the rate of speed change sensing means comprises a tachometer generator providing an output signal representative of wheel speed; a low pass filter means (36) connected to said tachometer generator to deliver a dc signal representative of wheel speed; a differentiator (37) connected to said low pass filter means to deliver a rate of change of speed signal; and at least one threshold switch (39) connected to the differentiator and responding to a predetermined value of wheel deceleration.

Claim 9

System according to claim 7 wherein said threshold switch has a switching hysteresis and changes state upon a first value of wheel deceleration, and then changes state back at a second value of wheel rate of change of speed.

Claim 10

System according to claim 7 wherein three threshold switches (39, 40, 41) are provided, the first threshold switch (39) responding to a high value of wheel deceleration (b1), the second threshold switch (40) responding to about zero rate of change of wheel speed (b2), and the third threshold switch (41) responding to wheel acceleration (b3), the second threshold switch (40) being connected to said differentiator (37); a second low pass filter (38) connected to said differentiator (37), the first and third threshold switches (39, 41) being connected to said second low pass filter (38).

Claim 11

System according to claim 1 wherein the note of speed change sensing means comprises means deriving a signal representative of wheel rate of change speed; and three threshold switches (39, 40, 41), the first threshold switch (39) responding to a high value of wheel deceleration (b1); a second threshold switch (40) responding to about zero rate of change of wheel speed (b2); and a third threshold switch (41) responding to a small value of wheel acceleration (b3).

Claim 12

System according to claim 10 further comprising a low pass filter (38) connected between the first and third threshold switches (39, 41) and the means deriviNg the rate of speed change signal.

Claim 13

System according to claim 10 further comprising an AND gate (42) connected to the output of the first and second threshold switches (39, 40) the output of the AND gate controlling the drain valve solenoid (25).

Claim 14

System according to claim 10 wherein the pulse source (46) is common to anti-lock systems at both sides of the vehicle and the inlet valves (14, 114) have operating solenoids (23, 123) and are normally open and close upon energization of the respective inlet solenoid (23, 123); the drain valves (19, 119) have operating solenoids (25, 125) and are normally closed and open upon energization of the respective outlet solenoid (25, 125), each said brake system further comprising respective disjunctive logic gates (43, 143) connected in series with the respective inlet solenoid (23, 123); each respective gate (43, 143) having applied thereto; the output of the respective first and third threshold switches (39, 41; 139, 141); the output of the common pulse source (46); and a signal indicative of energization of the respective drain valve solenoid (25, 125) to permit independent operation of the respective inlet valve solenoid (23, 123), and to interlock the respective solenoids of the respective inlet valves of the drain valves.

Claim 15

System according to claim 1 wherein the pulse source (46) is common to respective anti-lock systems at both sides of the vehicle, and the inlet valves (14, 114) are normally open, and the drain valves (19, 119) are normally closed, and each of said brake systems further comprises respective disjunctive logic gates (43, 143) connected in series with the respective inlet solenoid (23, 123); each respective gate (43, 143) having applied thereto; a signal representative of the respective wheel speed rate of change; the output of the pulse source (46); and a signal indicative of opening of the respective drain valve (19, 119), to permit independent operation of the respective inlet valve (14, 114) and interlock the respective drain valve (19, 119) and the inlet valve (14, 114).

Claim 16

Pressure fluid brake anti-lock system for vehicles having separate left and right braking systems at left and right sides of the vehicle comprising left and right inlet valves (14, 114) to admit pressurized brake fluid to left and right wheel brakes, respectively; left and right drain valves (19, 119) to drain pressurized brake fluid from the left and right brakes; left and right means (23, 25; 123, 125) controlling, selectively, closing of said left and right inlet valves and opening of said left and right drain valves; left and right wheel brake anti-lock control systems including left and right means (32-42; 132-142) to sense, respectively, left and right wheel rate-of-change of speed and independently controlling respective selective operation of said left valves and of said right valves in accordance with respective rates of change of wheel speed, to provide for independent control cycles of application of braking fluid pressure to the left and right brakes, respectively, and to control pressure maintenance and pressure drop in said respective brakes; respective separate left and right logic gates (43, 143) controlling closing of the respective left and right inlet valves (14, 114), connected to and controlled by the respective left and right control systems; a pulse source (46); common means (44, 45) including a controlled switch (45) connected to the wheel speed rate-of-change sensing means of the left control system as well as of the right control system, and sensing deceleration of any one of the wheels above a predetermined limit, indicative of imminent locking of the respective wheel, said switch (45) changing from a first to a second state upon sensing deceleration above said limit, said switch (45) being connected to and, upon change to the second state, controlling connection of said pulse sourCe (46) additionally to all of the logic gates (43, 143) to provide pulses tending to close all the inlet valves in pulsed steps independently of sensing of deceleration above said limit by a a control system other than the control system which has first sensed said deceleration above said limit, thereby inhibiting steep pressure rise in the brake at the side of the vehicle where the respective system has not sensed deceleration above said limit; said vehicle further having a switch (29) operating upon operation of the brake control of the vehicle, said switch (29) being connected to said controlled switch (45) to reset said switch to the first state when the brake is not operated to thereby prevent connection of said pulse source to said disjunctive gates upon release of the brake, and re-connection unless one of the anti-lock control systems senses deceleration of any one wheel above said limit.

Claim 17

Pressure fluid brake anti-lock system for vehicles having separate left and right braking systems at left and right sides of the vehicle comprising left and right inlet valves (14, 114) to admit pressurized brake fluid to left and right wheel brakes, respectively; left and right drain valves (19, 119) to drain pressurized brake fluid from the left and right brakes; left and right means (23, 25; 123, 125) controlling, selectively, closing of said left and right inlet valves and opening of said left and right drain valves; left and right wheel brake anti-lock control systems including left and right means (32-42; 132-142) to sense, respectively, left and right wheel rate-of-change of speed and independently controlling respective selective operation of said left valves and of said right valves in accordance with respective rates of change of wheel speed, to provide for independent control cycles of application of braking fluid pressure to the left and right brakes, respectively, and to control pressure maintenance and pressure drop in said respective brakes; respective separate left and right logic gates (43, 143) controlling closing of the respective left and right inlet valves (14, 114), connected to and controlled by the respective left and right control systems; a pulse source (46); common means (44, 45) including a controlled switch (45) connected to the wheel speed rate-of-change sensing means of the left control system as well as of the right control system, and sensing deceleration of any one of the wheels above a predetermined limit, indicative of imminent locking of the respective wheel, said switch (45) changing from a first to a second state upon sensing deceleration above said limit, said switch (45) being connected to and, upon change to the second state, controlling connection of said pulse sourCe (46) additionally to all of the logic gates (43, 143) to provide pulses tending to close all the inlet valves in pulsed steps independently of sensing of deceleration above said limit by a a control system other than the control system which has first sensed said deceleration above said limit, thereby inhibiting steep pressure rise in the brake at the side of the vehicle where the respective system has not sensed deceleration above said limit; said vehicle further having a switch (29) operating upon operation of the brake control of the vehicle, said switch (29) being connected to said controlled switch (45) to reset said switch to the first state when the brake is not operated to thereby prevent connection of said pulse source to said disjunctive gates upon release of the brake, and re-connection unless one of the anti-lock control systems senses deceleration of any one wheel above said limit.

Claim 18

System according to claim 15, wherein a single pulse source (46) is provided, said pulse source controlling pulsed closing of the inlet valves through all said logic gates (43, 143).

Claim 19

System according to claim 15, wherein the controlled switch comprises a flip-flop (45), said left and right control systems each include threshold switches sensing deceleration of the respective left and right wheels, the brakes of which are controlled, above said predetermined limit, said flip-flop (45) being connected to said threshold switches and being set upon response of any one of said threshold switches; the brake switch (29) being connected to reset the flip-flop when the brake control for the vehicle is in released, inoperated condition.

Claim 20

System according to claim 15, wherein the means controlling the respective inlet valves comprises a respective left and right inlet solenoid (23, 123), and the means controlling the respective drain valves comprise respective left and right drain solenoids (25, 125); said respective control means causing opening of the respective drain valve when wheel deceleration above the predetermined limit is sensed, all said drain valve solenoids (25, 125) being connected to said common means (44, 45) to control change of state of said switch (45) when one of said drain valve solenoids is energized, thus connecting said pulse source (46) to all said inlet pressure valve solenoids (23, 123), and prevent unmodified application of full brake fluid pressure to the wheels having control systems associated therewith which have not sensed wheel deceleration above said predetermined limit.