Adaptive control for fluid pressure braking systems

Claim 2

In an adaptive braking system for fluid pressure operated brakes, means for reducing the pressure in a fluid pressure brake actuator in response to an impending skid comprising an exhaust port connected to the actuator, an exhaust valve for controlling the flow of fluid from said actuator through said exhaust port, means responsive to an impending skid for opening said exhaust valve, means for controlling the rate of fluid flow from said actuator upon opening of said exhaust valve, and means responsive to the fluid pressure in the actuator and operatively connected to said flow rate controlling means for establishing a flow rate in accordance with the pressure in the actuator, said flow rate controlling means including means for varying the effective exhaust area in the path of fluid flow from said actuator through said port upon opening of said exhaust valve, aid last-named means being operatively connected to said means responsive to the pressure in the actuator whereby the exhaust area is established in accordance with the pressure in the actuator.

Claim 3

The adaptive braking system of claim 1 wherein the means responsive to the pressure in the actuator and the exhaust area varying means are operatively connected so as to provide a small effective exhaust area in response to high pressure in the actuator and provide a large effective exhaust area in response to a low pressure in the actuator.

Claim 4

In the adaptive braking system of claim 1 wherein the means responsive to the pressure in the actuator and the exhaust area varying means are operatively connected to provide a substantially constant mass rate of flow from said actuator for any pressure existing in the actuator at the time said exhaust valve is open.

Claim 5

In the adaptive system of claim 1 including means responsive to acceleration of said wheel following the opening of said exhaust valve for closing said exhaust valve and restoring fluid pressure in said actuator.

Claim 6

The system of claim 1 including delivery port means for connecting said actuator with a source of fluid pressure, delivery valve means for controlling the flow of fluid pressure from said source to said actuator through said delivery port means, and means responsive to deceleration of said wheel to an impending skid for closing said delivery valve means to cut off all delivery of fluid pressure to said actuator at the same time as said exhaust valve is opened in response to deceleration of the wheel to an impending skid.

Claim 7

The system of claim 5 wherein said delivery port means includes a main delivery port and a choke port, said delivery valve means including a main delivery valve controlling said main port and a second valve for controlling said choke port, the means responsive to deceleration of said wheel to an impending skid for opening said exhaust valve including other means responsive to said impending skid for closing said main and choke valve at the same time as said exhaust valve is opened, means for retaining said main valve closed until the source of fluid pressure is disconnected from said actuator, and means responsive to the acceleration of said wheel following the opening of said exhaust valve for closing said exhaust valve and opening the valve controlling said choke port whereby said fluid pressure is restored to said actuator at a controlled rate solely through said choke port.

Claim 8

In the adaptive system of claim 1 wherein the means for varying the effective exhaust area comprises a cylinder intersecting the path of fluid flow from said actuator through said exhaust port, a variable area piston reciprocal in said cylinder and constructed and arranged that in one extreme position it offers maximum restriction to flow through said cylinder to said exhaust port and in a second extreme position it offers minimum restriction to flow through said cylinder, the restriction offered by said piston varying in accordance with its position between said extremes, a pressure responsive member exposed at all times to pressure in said actuator and operatively connected to said piston, and resilient means acting on said piston to urge it towards the extreme position wherein it offers minimum resistance to fluid flow through said cylinder, said resilient means resisting movement of said piston towards its other extreme position in response to increased pressure in said actuator whereby said piston is positioned in the cylinder relative to its extreme position in accordance with the pressure in said actuator.

Claim 9

In the adaptive system of claim 7 wherein the variable area portion of said piston is so constructed and arranged that the mass flow rate from said actuator is substantially constant for any position taken by said piston in response to the pressure in said actuator.

Claim 10

The modulator valve of claim 8 wherein a variable area restrictor is provided in the path of fluid flow from said actuator upon opening of said exhaust valve, and means responsive to fluid pressure in the actuator for positioning the restrictor in the path of fluid flow such that for a high pressure in the actuator a large restriction is offered to fluid flow from the actuator and for a low pressure in the actuator a small restriction is offered to fluid flow from the actuator.

Claim 11

In the adaptive system of claim 1 including a tare check valve for controlling said exhaust port, said tare check valve including a valve element arranged to close said exhaust port in opposition to fluid flow therethrough, a spring operating on said valve to urge it towards its closed position, the rate of said spring being selected to close said valve and trap residual pressure in said actuator at a level just sufficient to prevent retraction of the brake shoes from the drum following the opening of said exhaust valve in response to an impending skid.

Claim 12

In an adaptive braking system for a wheeled vehicle having fluid pressure operated brakes: means for controlling braking pressure in response to an impending skidding condition, said means including a housing defining a chamber therewithin having an inlet port communicating said chamber with a fluid pressure source when a brake application is effected, an exhaust port communicating with said chamber, valve means normally preventing communication between said chamber and said exhaust port, but opening to permit communication therebetween in response to said impending skidding condition of a vehicle wheel, and means responsive to the fluid pressure level in said chamber to vary the effective area of said exhaust port for establishing a flow rate through said exhaust port in accordance with the fluid pressure level in said chamber.

Claim 13

In an adaptive braking system for a wheeled vehicle having fluid pressure operated brakes: means for controlling braking pressure in response to an impending skidding condition, said means including a housing defining a chamber therewithin having an inlet port communicating said chamber with a fluid pressure source when a brake application is effected, an exhaust port communicating with said chamber, valve means normally preventing communication between said chamber and said exhaust port, but opening to permit communication therebetween in response to said impending skidding condition of a vehicle wheel, and means responsive to the fluid pressure level in said chamber to vary the effective area of said exhaust port for establishing a flow rate through said exhaust port in accordance with the fluid pressure level in said chamber.

Claim 14

The invention of claim 11: said means responsive to the fluid pressure level in said chamber being constructed and arranged to establish a substantially constant mass rate of fluid flow from said chamber for any pressure existing in the latter at the time said valve means is actuated.

Claim 15

The invention of claim 11: said means responsive to the fluid pressure level in said chamber providing a relatively small effective area of said exhaust port in response to high pressure in said chamber and a larger effective area of said exhaust port in response to low pressure in said chamber.

Claim 16

For use in an adaptive brake system, modulating valve means for controlling the reduction and restoration of fluid pressure in said actuator in response to skidding conditions of a wheel comprising a delivery port for connecting a source of fluid pressure to said actuator, a valve for controlling said delivery port, a choke delivery port in said actuator, a normally open valve for controlling said choke delivery port, an exhaust port in said actuator, a normally closed exhaust valve for controlling said exhaust port, a diaphragm operatively connected to said exhaust valve and to said choke port valve, a second diaphragm connected to said delivery valve, a control chamber having an inlet port and a vent port, a double acting valve element normally closing said inlet port and opening said vent port, said control chamber being connected to pressure spaces above the diaphragm for said delivery valve and the diaphragm connected to said choke port valve and said exhaust valve, a solenoid connected to said double acting valve element and adapted to be energized in response to a wheel deceleration to the level of an impending skid whereby said valve is moved to a position disconnecting said vent port from said control chamber while connecting the latter to delivery pressure from said source through said inlet port, the fluid pressure in said control chamber operating on the diaphragm over said delivery valve to close the same, and operating on the second diaphragm to close said choke port valve and thereafter by continued movement of said diaphragm to open said exhaust valve to reduce pressure in said actuator and permit said wheel to accelerate, check valve means for preventing the escape of fluid pressure from the diaphragm closing said delivery valve until release of delivery pressure, said solenoid being de-energized in response to acceleration of said wheel to move said valve element to its first position closing said inlet port and opening said vent port to relieve pressure from said first diaphragm and enable said choke port valve to open and said exhaust valve to close whereupon pressure is restored to said actuator solely through said choke port.

Claim 17

For use in an adaptive brake system, modulating valve means for controlling the reduction and restoration of fluid pressure in said actuator in response to skidding conditions of a wheel comprising a delivery port for connecting a source of fluid pressure to said actuator, a valve for controlling said delivery port, a choke delivery port in said actuator, a normally open valve for controlling said choke delivery port, an exhaust port in said actuator, a normally closed exhaust valve for controlling said exhaust port, a diaphragm operatively connected to said exhaust valve and to said choke port valve, a second diaphragm connected to said delivery valve, a control chamber having an inlet port and a vent port, a double acting valve element normally closing said inlet port and opening said vent port, said control chamber being connected to pressure spaces above the diaphragm for said delivery valve and the diaphragm connected to said choke port valve and said exhaust valve, a solenoid connected to said double acting valve element and adapted to be energized in response to a wheel deceleration to the level of an impending skid whereby said valve is moved to a position disconnecting said vent port from said control chamber while connecting the latter to delivery pressure from said source through said inlet port, the fluid pressure in said control chamber operating on the diaphragm over said delivery valve to close the same, and operating on the second diaphragm to close said choke port valve and thereafter by continued movement of said diaphragm to open said exhaust valve to reduce pressure in said actuator and permit said wheel to accelerate, check valve means for preventing the escape of fluid pressure from the diaphragm closing said delivery valve until release of delivery pressure, said solenoid being de-energized in response to acceleration of said wheel to move said valve element to its first position closing said inlet port and opening said vent port to relieve pressure from said first diaphragm and enable said choke port valve to open and said exhaust valve to close whereupon pressure is restored to said actuator solely through said choke port.