Single gain skid control valve and skid control system

A vehicle skid control system comprising:

• a skid control circuit including a valve driver for providing a skid control current signal;
• a source of substantially constant pressure hydraulic fluid;
• a pressure metering valve for providing hydraulic fluid at a pressure which is metered by the vehicle operator;
• control pressure generating means having a constant pressure supply port for accepting said constant pressure hydraulic fluid and for providing a control pressure in response to said skid control current, said control pressure being exclusively controlled by said skid control signal and having a level which is inversely proportional to the magnitude of said skid control current signal;
• and
• brake pressure valving means having an input port for accepting said metered pressure fluid, a brake port for providing hydraulic fluid at brake port pressure, a hydraulic return port, and a control pressure port for accepting said control pressure, said brake pressure valving means including a pressure balancing spool valve operative to cause said brake port pressure to be modulated by said metered pressure when said metered pressure is below said control pressure and to cause said brake port pressure to be modulated by said control pressure independently of variations in said metered pressure when said metered pressure is above said control pressure, thereby providing a single gain valving response characteristic when said control pressure is modulating the brake port pressure.

A method of controlling brake pressure for a wheel comprising the steps of:

• generating a variable skid control signal from wheel speed data;
• generating a control pressure which is exclusively controlled by the skid control signal and which has a pressure level which is a predetermined function of the skid control signal;
• comparing a metered pressure with the control pressure generated;
• and
• generating a brake pressure which is equal to the metered pressure if the metered pressure is less than the control pressure and which is equal to the control pressure if the metered pressure exceeds the control pressure.