Vehicle anti-lock brake system

In a wheeled vehicle having means for supplying pressurized brake fluid to actuate the associated wheel brakes of the vehicle, a brake control system for controlling the application of pressurized brake fluid to at least one selected wheel brake to control the braking of the associated wheel, said control system comprising:

• a normally open isolation valve means connected between the supply means and the selected wheel brake;
• a normally closed dump valve means connected between the selected wheel brake and a fluid reservoir;
• and
• control means connected to operate said isolation valve means and said dump valve means, said control means including means for detecting an impending wheel lock-up condition of the associated wheel and means for sensing the deceleration of the associated wheel, said control means operable to close said isolation valve means to hold the fluid pressure to the selected wheel brake at a relatively constant first predetermined pressure after said impending wheel lock-up condition of the associated wheel is detected, said control means operable to selectively open said dump valve means for a first dumping cycle after said isolation valve means is closed and the deceleration of the selected wheel exceeds a first predetermined amount of enable fluid to flow into said fluid reservoir to selectively reduce fluid pressure to the selected wheel brake until the deceleration of the associated wheel is less than said first predetermined amount, said control means further operable to selectively reopen said dump valve means for a second renewed dumping cycle to further reduce fluid pressure to the selected wheel brake when the deceleration of the associated wheel is greater than a second predetermined amount less than said first predetermined amount and said impending lock-up condition of the associated wheel has continued for a predetermined time period after said first dumping cycle is terminated.

In a wheeled vehicle having means for supplying pressurized brake fluid to actuate the associated wheel brakes of the vehicle, a brake control system for controlling the application of pressurized brake fluid to at least one selected wheel brake to control the braking of the associated wheel, said control system comprising:

• a normally open isolation valve means connected between the supply means and the selected wheel brake;
• a normally closed dump valve means connected between the selected wheel brake and a fluid reservoir;
• and
• control means connected to operate said isolation valve means and said dump valve means, said control means including means for detecting wheel speed departures of the associated wheel and means for sensing the acceleration of the associated wheel during spin-up portions of said wheel speed departures, said control means operable to close said isolation valve means to hold the fluid pressure to the selected wheel brake at a relatively constant level after a first wheel speed departure of the associated wheel is detected, said control means operable to selectively open said dump valve means after said isolation valve means has been closed to enable fluid to flow into said fluid reservoir to selectively reduce pressure to the selected wheel brake and correct said first wheel speed departure of the associated wheel, said control means further operable to selectively open said isolation valve means to selectively increase pressure to the selected wheel brake to cause a second wheel speed departure after said wheel first wheel speed departure has been corrected and the acceleration of the associated wheel during a spin-up portion of said first wheel speed departure exceeds a predetermined rate.

In a wheeled vehicle having means for supplying pressurized brake fluid to actuate the associated wheel brakes of the vehicle, a brake control system for controlling the application of pressurized brake fluid to at least one selected wheel brake to control the braking of the associated wheel, said control system comprising:

• a normally open isolation valve means connected between the supply means and the selected wheel brake;
• a normally closed dump valve means connected between the selected wheel brake and a fluid reservoir;
• and
• control means connected to operate said isolation valve means and said dump valve means, said control means including means for detecting a wheel lock-up condition of the associated wheel, said control means including means for detecting a wheel lock-up condition of the associated wheel, said control means operable to close said isolation valve means to hold the fluid pressure to the selected wheel brake at a relatively constant level after said wheel lock-up condition of the associated wheel is detected, said control means operable to selectively open said dump valve means during a dump cycle after said wheel lock-up condition has been detected to enable fluid to flow into said fluid reservoir to selectively reduce pressure to the selected wheel brake and correct the lock-up condition of the associated wheel, said control means including means for monitoring the time said dump valve means has been open during said dump cycle, said control means further operable to selectively open said isolation valve means to increase pressure to the selected wheel brake to cause a wheel speed departure of the associated wheel after said dump cycle when the total time said dump valve has been open during said dump cycle exceeds a predetermined amount, said control means further operable to selectively open said dump valve means after said increase in pressure to enable fluid to flow into said fluid reservoir to selectively reduce pressure to the selected wheel brake and correct said wheel speed departure.

In a wheeled vehicle having means for supplying pressurized brake fluid to actuate the associated wheel brakes of the vehicle, a brake control system for controlling the application of pressurized brake fluid to at least one selected wheel brake to control the braking of the associated wheel, said control system comprising:

• a normally open isolation valve means connected between the supply means and the selected wheel brake;
• a normally closed dump valve means connected between the selected wheel brake and a fluid reservoir;
• and
• control means connected to operate said isolation valve means and said dump valve means, said control means including means for detecting wheel speed departures of the associated wheel and means for sensing the deceleration of the associated wheel, said control means operable to close said isolation valve means to hold the fluid pressure to the selected wheel brake at a relatively constant level after a first wheel speed departure of the associated wheel is detected, said control means operable to selectively open said dump valve means after said isolation valve means has been closed to enable fluid to flow into said fluid reservoir to selectively reduce pressure to the selected wheel brake to a first predetermined pressure and correct said first wheel speed departure, said control means further operable to selectively open said isolation valve means to increase pressure to the selected wheel brake when the deceleration of the vehicle increases by a predetermined amount to cause a second wheel speed departure after said first wheel speed departure has been corrected, said control means operable to selectively open said dump valve means after said second wheel speed departure has been detected to selectively reduce pressure to the selected wheel brake to a second predetermined pressure greater than said first predetermined pressure.