Anti-skid brake system

Claim 2

In a hydraulic brake system for a vehicle having front and rear wheel brakes, the combination comprising, a power booster for assisting manual effort in operating said front and rear wheel brakes, a variable proportioning device in said hydraulic brake system including means for varying the ratio of front to rear braking forces as a substantially continuously varying, non-linear, predetermined function of tire-road coefficient of friction, which function approximately matches the non-linear function as defined by the Holland equation for Sf/Sr, and deceleration responsive means for detecting vehicle deceleration and for controlling said power booster in response to changes in deceleration reflecting a slip ratio at both front and rear wheels exceeding that corresponding to the peak value of tire-road coefficient of friction and return to rolling contact with the road to modulate the braking forces at both front and rear wheels about their maximum to maintain maximum vehicle deceleration without wheel lock-up.

Claim 3

The combination in a hydraulic system as defined in claim 1 wherein said power booster is a vacuum suspended power booster adapted to receive supply air at a modulated pressure, and said deceleration responsive means includes a valve for modulating the supply air pressure an thereby controlling said power booster in response to changes in deceleration.

Claim 4

The combination in a hydraulic brake system as defined in claim 2 wherein said deceleration responsive means includes signal generating means operated by said wheels, and circuit means operated by said generating means for deriving rate of change of wheel deceleration signals, and wherein said means for controlling said power booster includes means for modulating the output of said booster in response to varying rate of change signals reflecting changes in slip ratio at the wheels.

Claim 5

In an anti-skid hydraulic brake system for a vehicle having front and rear braking sub-systems, each sub-system being supplied with fluid pressure by master cylinder means and operable to apply braking forces to the front and rear wheels, respectively, of the vehicle, the combination comprising: booster means for assisting a manual force applied to operate the braking system, the output of the booster means being connected to the master cylinder means; a variable proportioning device in said hydraulic brake system including means for varying the ratio of fluid pressures in the front and rear brake sub-systems as a predetermined function of vehicle deceleration so as to achieve substantially the same slip ratio at the front wheels as at the rear wheels under any tire-road coefficient of friction condition, said proportioning device means being adjustable to compensate for changes in vehicle loading, and means for controlling said booster means including means for detecting changes in vehicle deceleration, the controlling means being adapted to i. vary the booster means output in response to the applied manual force during normal brake application resulting in braking forces producing a slip ratio less than that corresponding to the peak value of tire-road coefficient of friction, and to ii. reduce the booster means output to reduce braking forces in response to decreases in deceleration reflecting a slip ratio at both front and rear wheels exceeding that corresponding to the peak value of tire-road coefficient of friction, notwithstanding continued manual force being applied.

Claim 6

In an anti-skid hydraulic brake system for a vehicle having front and rear braking sub-systems, each sub-system being supplied with fluid pressure by master cylinder means and operable to apply braking forces to the front and rear wheels, respectively, of the vehicle, the combination comprising: booster means for assisting a manual force applied to operate the braking system, the output of the booster means being connected to the master cylinder means; a variable proportioning device in said hydraulic brake system including means for varying the ratio of fluid pressures in the front and rear brake sub-systems as a predetermined function of vehicle deceleration so as to achieve substantially the same slip ratio at the front wheels as at the rear wheels under any tire-road coefficient of friction condition, said proportioning device means being adjustable to compensate for changes in vehicle loading, and means for controlling said booster means including means for detecting changes in vehicle deceleration, the controlling means being adapted to i. vary the booster means output in response to the applied manual force during normal brake application resulting in braking forces producing a slip ratio less than that corresponding to the peak value of tire-road coefficient of friction, and to ii. reduce the booster means output to reduce braking forces in response to decreases in deceleration reflecting a slip ratio at both front and rear wheels exceeding that corresponding to the peak value of tire-road coefficient of friction, notwithstanding continued manual force being applied.

Claim 7

In an anti-skid hydraulic brake system for a vehicle having front and rear wheel braking sub-systems, each sub-system being supplied with pressure fluid by power means and operable to apply braking forces to the front and rear wheels, respectively, of the vehicle, the combination comprising: manually operated control means for controlling the output of said power means in response to applied manual force and thereby the fluid pressure in said sub-systems, a variable proportioning device in said hydraulic brake system including means for varying the ratio of fluid pressures in the front and rear brake sub-systems as a predetermined function of vehicle deceleration so as to achieve substantially the same slip ratio at the front wheels as at the rear wheels under any tire-road coefficient of friction condition, said proportioning device means being adjustable to compensate for changes in vehicle loading, and vehicle deceleration responsive means operable independently of and in conjunction with said manually operated control means for controlling said power means, i. to vary the output of said power means in response to the applied manual force during normal brake application resulting in braking forces producing a slip ratio less than that corresponding to the peak value of tire-road coefficient of friction, ii. to reduce the output of said power means to reduce braking forces in response to decreases in deceleration reflecting a slip ratio at both front and rear wheels exceeding that corresponding to the peak value of tire-road coefficient of friction, notwithstanding continued manual force being applied, iii. to reapply the output of said power means after rolling contact is reestablished between the tires and road, and iv. to repeat the cycle of events (ii) and (iii) until the vehicle is stopped.

Claim 8

In an anti-skid hydraulic brake system for a vehicle having front and rear wheel braking sub-systems, each sub-system being supplied with pressure fluid by power means and operable to apply braking forces to the front and rear wheels, respectively, of the vehicle, the combination comprising: manually operated control means for controlling the output of said power means in response to applied manual force and thereby the fluid pressure in said sub-systems, a variable proportioning device in said hydraulic brake system including means for varying the ratio of fluid pressures in the front and rear brake sub-systems as a predetermined function of vehicle deceleration so as to achieve substantially the same slip ratio at the front wheels as at the rear wheels under any tire-road coefficient of friction condition, said proportioning device means being adjustable to compensate for changes in vehicle loading, and vehicle deceleration responsive means operable independently of and in conjunction with said manually operated control means for controlling said power means, i. to vary the output of said power means in response to the applied manual force during normal brake application resulting in braking forces producing a slip ratio less than that corresponding to the peak value of tire-road coefficient of friction, ii. to reduce the output of said power means to reduce braking forces in response to decreases in deceleration reflecting a slip ratio at both front and rear wheels exceeding that corresponding to the peak value of tire-road coefficient of friction, notwithstanding continued manual force being applied, iii. to reapply the output of said power means after rolling contact is reestablished between the tires and road, and iv. to repeat the cycle of events (ii) and (iii) until the vehicle is stopped.

Claim 9

The combination in an anti-skid hydraulic brake system as defined in claim 5 wherein said power means is a booster for assisting manual force applied to operate the braking system and said variable proportioning device in said hydraulic brake system is operable to vary the ratio of fluid pressures in the front and rear brake sub-systems and the ratio Of braking forces produced thereby as a non-linear, predetermined function of vehicle deceleration, which function approximately matches in non-linear function as defined by the Holland equation for Sf/Sr.

Claim 10

In a hydraulic brake system for a wheel vehicle having front and rear wheel brakes, the combination comprising, a power booster for assisting manual effort in operating said front and rear wheel brakes, a variable proportioning device in said hydraulic brake system including means for varying the ratio of fluid pressures in the front and rear brakes as a predetermined function of tire-road coefficient of friction, which function approximately matches the Holland equation for Sf/Sr, said means being adjustable to compensate for changes in vehicle loading, and deceleration responsive means for detecting vehicle deceleration and for controlling said power booster in response to changes in deceleration reflecting impending wheel lock-up and return to rolling contact with the road to modulate the braking forces at both front and rear wheels about their maximum to maintain maximum vehicle deceleration without wheel lock-up.

Claim 11

In a hydraulic brake system for a wheel vehicle having front and rear wheel brakes, the combination comprising, a power booster for assisting manual effort in operating said front and rear wheel brakes, a variable proportioning device in said hydraulic brake system including means for varying the ratio of fluid pressures in the front and rear brakes as a predetermined function of tire-road coefficient of friction, which function approximately matches the Holland equation for Sf/Sr, said means being adjustable to compensate for changes in vehicle loading, and deceleration responsive means for detecting vehicle deceleration and for controlling said power booster in response to changes in deceleration reflecting impending wheel lock-up and return to rolling contact with the road to modulate the braking forces at both front and rear wheels about their maximum to maintain maximum vehicle deceleration without wheel lock-up.

Claim 12

In an anti-skid hydraulic brake system for a vehicle having fornt and rear wheel braking sub-systems, each sub-system being supplied with fluid pressure by master cylinder means and operable to apply braking forces to the front and rear wheels, respectively, of the vehicle, a power booster for producing an output force to operate said master cylinder means, said power booster having a power wall operable by a differential pressure across said wall to produce said output force, and manually operated valve means for controlling the differential pressure across said power wall and thereby controlling the output force produced by said booster, the combination comprising: a variable proportioning device in said hydraulic brake system including means for varying the ratio of fluid pressures in said front and rear braking sub-systems and for varying the ratio of braking forces produced thereby as a substantially continuously varying, predetermined function of tire-road coefficient of friction, which function approximately matches the non-linear function as defined by the Holland equation for Sf/Sr, so that when said brake system is operated substantially at braking forces where wheel lock-up is impending the braking forces applied to the front and rear wheels will produce substantially maximum vehicle deceleration under any given tire-road coefficient of friction and all wheels will begin to slip toward lock-up substantially simultaneously, and a deceleration responsive control means for detecting vehicle deceleration and responsive to predetermined changes in deceleration reflecting wheel slip toward lock-up, acting in conjunction with said manually operated valve means for modulating the differential pressure across said power wall to modulate the output force produced by said booster and the braking forces at both front and rear wheels about their maximum to maintain substantially maximum vehicle deceleration while preventing wheel lock-up.

Claim 13

In an anti-skid hydraulic brake system for a vehicle having fornt and rear wheel braking sub-systems, each sub-system being supplied with fluid pressure by master cylinder means and operable to apply braking forces to the front and rear wheels, respectively, of the vehicle, a power booster for producing an output force to operate said master cylinder means, said power booster having a power wall operable by a differential pressure across said wall to produce said output force, and manually operated valve means for controlling the differential pressure across said power wall and thereby controlling the output force produced by said booster, the combination comprising: a variable proportioning device in said hydraulic brake system including means for varying the ratio of fluid pressures in said front and rear braking sub-systems and for varying the ratio of braking forces produced thereby as a substantially continuously varying, predetermined function of tire-road coefficient of friction, which function approximately matches the non-linear function as defined by the Holland equation for Sf/Sr, so that when said brake system is operated substantially at braking forces where wheel lock-up is impending the braking forces applied to the front and rear wheels will produce substantially maximum vehicle deceleration under any given tire-road coefficient of friction and all wheels will begin to slip toward lock-up substantially simultaneously, and a deceleration responsive control means for detecting vehicle deceleration and responsive to predetermined changes in deceleration reflecting wheel slip toward lock-up, acting in conjunction with said manually operated valve means for modulating the differential pressure across said power wall to modulate the output force produced by said booster and the braking forces at both front and rear wheels about their maximum to maintain substantially maximum vehicle deceleration while preventing wheel lock-up.

Claim 14

In a hydraulic brake system for a vehicle, having front and rear wheel braking sub-systems, each sub-system being supplied with fluid pressure by manually operated master cylinder means and operable to apply braking forces to the front and rear wheels respectively, the combination comprising: a vacuum suspended power booster for assisting manual effort applied to operate said master cylinder means, said power booster having a power wall, a variable proportioning device in said hydraylic brake system including means for varying the ratio of fluid pressures in the front and rear brake sub-systems and for varying the ratio of braking forces produced thereby as a substantially continuously varying, non-linear, predetermined function of tire-road coefficient of friction, which function approximately matches the non-Linear function as defined by the Holland equation for Sf/Sr, so as to produce substantially maximum deceleration under various tire-road conditions, and means for controlling the differential pressure across the power wall of said booster including a manually operated booster control valve and deceleration responsive means having a valve for controlling the air supply to said booster control valve responsive to sudden decreases in deceleration reflecting impending wheel lock-up to prevent such lock-up while permitting said manually operated booster control valve to control said differential pressure upon gradual changes in deceleration.

Claim 15

In a hydraulic brake system for a vehicle, having front and rear wheel braking sub-systems, each sub-system being supplied with fluid pressure by manually operated master cylinder means and operable to apply braking forces to the front and rear wheels respectively, the combination comprising: a vacuum suspended power booster for assisting manual effort applied to operate said master cylinder means, said power booster having a power wall, a variable proportioning device in said hydraylic brake system including means for varying the ratio of fluid pressures in the front and rear brake sub-systems and for varying the ratio of braking forces produced thereby as a substantially continuously varying, non-linear, predetermined function of tire-road coefficient of friction, which function approximately matches the non-Linear function as defined by the Holland equation for Sf/Sr, so as to produce substantially maximum deceleration under various tire-road conditions, and means for controlling the differential pressure across the power wall of said booster including a manually operated booster control valve and deceleration responsive means having a valve for controlling the air supply to said booster control valve responsive to sudden decreases in deceleration reflecting impending wheel lock-up to prevent such lock-up while permitting said manually operated booster control valve to control said differential pressure upon gradual changes in deceleration.

Claim 16

In a brake system for a vehicle having front and rear wheels, tires on said wheels, and front and rear wheel brakes, the combination comprising, manually operated means for actuating said brakes to produce front and rear braking forces, distribution means in said system including means for varying the ratio of front to rear braking forces as a substantially continuously varying non-linear predetermined function of tire-road coefficient of friction, which function approximately matches the non-linear function as defined by the Holland equation for Sf/Sr, so as to apply the maximum braking forces that the tires are capable of exerting on the road at different tire-road coefficient of friction conditions so that both front and rear wheels will slip toward lock-up substantially simultaneously, and means responsive to vehicle deceleration for opposing the operation of said manually operated means when said deceleration responsive means indicates an impending wheel lock-up condition to prevent wheel lock-up.

Claim 17

In a brake system for a vehicle having front and rear wheels, tires on said wheels, and front and rear wheel brakes, the combination comprising, manually operated means for actuating said brakes to produce front and rear braking forces, distribution means in said system including means for varying the ratio of front to rear braking forces as a substantially continuously varying non-linear predetermined function of tire-road coefficient of friction, which function approximately matches the non-linear function as defined by the Holland equation for Sf/Sr, so as to apply the maximum braking forces that the tires are capable of exerting on the road at different tire-road coefficient of friction conditions so that both front and rear wheels will slip toward lock-up substantially simultaneously, and means responsive to vehicle deceleration for opposing the operation of said manually operated means when said deceleration responsive means indicates an impending wheel lock-up condition to prevent wheel lock-up.

Claim 18

In a hydraulic brake system for a vehicle having front and rear wheels, tires on said wheels, and front and rear wheel brakes, the combination comprising, manually operated power means for actuating said brakes to produce front and rear braking forces, distribution means in said hydraulic system including means for varying the ratio of front to rear braking forces as a predetermined function of vehicle deceleration so as to achieve substantially the same tire-road coefficient of friction at the front wheels as at the rear wheels under any tire-road condition, such that at any tire-road condition both front and rear wheels will slip toward lock-up substantially simultaneously, and means responsive to vehicle deceleration for overriding the continued manual operation of said power means and reducing the output thereof to reduce braking forces when said deceleration responsive means senses reduced deceleration reflecting an impending wheel lock-up condition, to prevent wheel lock-up.

Claim 19

In a hydraulic brake system for a vehicle having front and rear wheels, tires on said wheels, and front and rear wheel brakes, the combination comprising, manually operated power means for actuating said brakes to produce front and rear braking forces, distribution means in said hydraulic system including means for varying the ratio of front to rear braking forces as a predetermined function of vehicle deceleration so as to achieve substantially the same tire-road coefficient of friction at the front wheels as at the rear wheels under any tire-road condition, such that at any tire-road condition both front and rear wheels will slip toward lock-up substantially simultaneously, and means responsive to vehicle deceleration for overriding the continued manual operation of said power means and reducing the output thereof to reduce braking forces when said deceleration responsive means senses reduced deceleration reflecting an impending wheel lock-up condition, to prevent wheel lock-up.

Claim 20

In a hydraulic brake system for a vehicle having front and rear wheel brakes, the combination comprising, a power booster for assisting manual force in operating said front and rear wheel brakes to produce vehicle braking forces, said power booster having a power wall operable by a differential pressure across said wall, a variable proportioning device in said hydraulic brake system including means for varying the ratio of front to rear braking forces as a non-linear predetermined function of tire-road coefficient of friction which function approximately matches the Holland equation for Sf/Sr, and adjustable to compensate for changes in vehicle loading so that when said brakes are operated susbstantially at the skid-point where wheel lock-up is impending all wheels will tend to slip toward wheel lock-up simultaneously under any tire-road coefficient of friction condition, and deceleration responsive means for modulating the braking forces about the skid point by controlling the differential pressure across the power wall of said booster notwithstanding continued manual force being applied, to maintain vehicle deceleration while preventing wheel lock-up.

Claim 21

In a hydraulic brake system for a vehicle having front and rear wheel brakes, the combination comprising, a power booster for assisting manual force in operating said front and rear wheel brakes to produce vehicle braking forces, said power booster having a power wall operable by a differential pressure across said wall, a variable proportioning device in said hydraulic brake system including means for varying the ratio of front to rear braking forces as a non-linear predetermined function of tire-road coefficient of friction which function approximately matches the Holland equation for Sf/Sr, and adjustable to compensate for changes in vehicle loading so that when said brakes are operated susbstantially at the skid-point where wheel lock-up is impending all wheels will tend to slip toward wheel lock-up simultaneously under any tire-road coefficient of friction condition, and deceleration responsive means for modulating the braking forces about the skid point by controlling the differential pressure across the power wall of said booster notwithstanding continued manual force being applied, to maintain vehicle deceleration while preventing wheel lock-up.

Claim 22

In an anti-skid hydraulic brake system for a vehicle having Front and rear wheel braking sub-systems, each sub-system being supplied with fluid pressure by master cylinder means and operable to apply braking forces to the front and rear wheels, respectively, of the vehicle, the combination comprising: a power unit producing an output force to operate said master cylinder means, said power unit having a power wall operable by a differential pressure across said wall and connected to said master cylinder means, manually operated valve means for controlling the differential pressure across said power wall and thereby controlling the output force produced by said power unit, a variable proportioning device in said hydraulic brake system including means for varying the ratio of fluid pressures in said front and rear braking sub-systems so as to vary the ratio of braking forces as a predetermined function of vehicle deceleration, which function approximately matches the function defined by the Holland equation for Sf/Sr, to achieve susbstantially the same tire-road coefficient of friction at the front as at the rear under any tire-road coefficient of friction condition, and means for detecting vehicle deceleration and responsive to predetermined changes in deceleration reflecting wheel slip toward lock-up, acting in conjunction with said manually operated valve means for modulating the differential pressure across said power wall to prevent wheel lock-up.

Claim 23

In an anti-skid hydraulic brake system for a vehicle having Front and rear wheel braking sub-systems, each sub-system being supplied with fluid pressure by master cylinder means and operable to apply braking forces to the front and rear wheels, respectively, of the vehicle, the combination comprising: a power unit producing an output force to operate said master cylinder means, said power unit having a power wall operable by a differential pressure across said wall and connected to said master cylinder means, manually operated valve means for controlling the differential pressure across said power wall and thereby controlling the output force produced by said power unit, a variable proportioning device in said hydraulic brake system including means for varying the ratio of fluid pressures in said front and rear braking sub-systems so as to vary the ratio of braking forces as a predetermined function of vehicle deceleration, which function approximately matches the function defined by the Holland equation for Sf/Sr, to achieve susbstantially the same tire-road coefficient of friction at the front as at the rear under any tire-road coefficient of friction condition, and means for detecting vehicle deceleration and responsive to predetermined changes in deceleration reflecting wheel slip toward lock-up, acting in conjunction with said manually operated valve means for modulating the differential pressure across said power wall to prevent wheel lock-up.

Claim 24

In a hydraulic brake system for a vehicle having front and rear wheel brakes, the combination comprising: a power unit having a movable power wall operable by a variable differential pressure across the wall for producing power force which acts through hydraulic pressure to apply said wheel brakes, said power unit including a manually actuated control valve connected to two fluid pressure sources for modulating the differential pressure across said power wall by selective connection to said sources, a variable proportioning device including means for controlling said hydraulic pressure to vary the ratio of front to rear braking forces applied to the wheels by the wheel brakes as a predetermined function of vehicle deceleration so as to produce substantially the same tire-road coefficient of friction at both front and rear under any tire-road condition, and achieve maximum vehicle deceleration when said wheel brakes apply braking force which produces slip ratios corresponding to the peak tire-road coefficient of friction concurrently at both front and rear, and deceleration responsive means including a valve for modulating the supply pressure to said power unit control valve from one of said fluid pressure sources as a function of vehicle deceleration, and for controlling said power unit to cyclically reduce and increase the power force produced thereby and the resulting braking force in response to changes in deceleration reflecting slip ratios at both front and rear exceeding that corresponding to the peak tire-road coefficient of friction and return to rolling contact with the road, to maintain maximum vehicle deceleration without wheel lock-up.

Claim 25

In a hydraulic brake system for a vehicle having front and rear wheel brakes, the combination comprising: a power unit having a movable power wall operable by a variable differential pressure across the wall for producing power force which acts through hydraulic pressure to apply said wheel brakes, said power unit including a manually actuated control valve connected to two fluid pressure sources for modulating the differential pressure across said power wall by selective connection to said sources, a variable proportioning device including means for controlling said hydraulic pressure to vary the ratio of front to rear braking forces applied to the wheels by the wheel brakes as a predetermined function of vehicle deceleration so as to produce substantially the same tire-road coefficient of friction at both front and rear under any tire-road condition, and achieve maximum vehicle deceleration when said wheel brakes apply braking force which produces slip ratios corresponding to the peak tire-road coefficient of friction concurrently at both front and rear, and deceleration responsive means including a valve for modulating the supply pressure to said power unit control valve from one of said fluid pressure sources as a function of vehicle deceleration, and for controlling said power unit to cyclically reduce and increase the power force produced thereby and the resulting braking force in response to changes in deceleration reflecting slip ratios at both front and rear exceeding that corresponding to the peak tire-road coefficient of friction and return to rolling contact with the road, to maintain maximum vehicle deceleration without wheel lock-up.

Claim 26

In a hydraulic brake system, the combination according to claim 14 wherein said power unit includes a power chamber on one side of said power wall, said control valve is operable to modulate the pressure in the power chamber by selective connection to said fluid pressure sources, and said deceleration responsive means is operable to maintain the supply pressure from said one source at a substantially constant differential lead pressure relative to the power chamber pressure over an initial range of operation of the power unit up to the point where braking force produces slip ratios substantially at the peak tire-road coefficient of friction concurrently at both front and rear, and is operable to cyclically change said supply pressure and the power chamber pressure to cause the power unit to cyclically reduce and increase the power force and the resulting braking force in response to changes in deceleration reflecting slip ratios past the peak tire-road coefficient of friction and return to rolling contact with the road, to maintain maximum vehicle deceleration without wheel lock-up.

Claim 27

The combination in a hydraulic system as defined in claim 15 for an automotive vehicle wherein said power unit comprises a vacuum suspended power booster, said two fluid pressure sources comprise air and vacuum from the intake manifold of the vehicle engine, respectively, and the air supply pressure is modulated by said deceleration responsive means valve.

Claim 28

In a hydraulic brake system, the combination according to claim 15 wherein said power unit is a vacuum suspended power booster, said two fluid pressure sources comprise a source of air at atmospheric pressure and a source of vacuum, and said deceleration responsive means modulates the air supply pressure to said manually actuated control valve as a function of vehicle deceleration to maintain the air supply pressure at a substantially constant differential lead pressure greater than the power chamber pressure over said initial range of operation of the power unit, and is operable to reduce said air supply pressure below said power chamber pressure and to increase the air supply pressure above the power chamber pressure cyclically in repsonse to change in deceleration reflecting slip ratios past the peak tire-road coefficient of friction and return to rolling contact with the road to cause the power unit to cyclically reduce and increase the power force and the resulting braking force, to maintain maximum vehicle deceleration without lock-up.