Brake Proportioning/Combination Valve: Description and Operation

OPERATION
1. Operation before the split point
Piston is held by spring so that valve is kept away from valve seat.
Under this condition, fluid pressure "P3" to rear wheel cylinders equals fluid pressure "P2" from master cylinder.





2. Operation near the split point
- Force "f1", applied to piston by spring, is one-half of spring force "F". In other words, "f1" = "F".
- Force "f2" is also applied to piston in the direction opposite to spring force "F" due to fluid pressure "P2" generated by master cylinder according to cross sectional area "A".
- Force "f2" increases respondingly with fluid pressure "P2". When "f2" is greater than, piston moves in direction opposite to spring force "F". This causes valve to come in contact with valve seat, blocking fluid passage.
3. Immediately before fluid passage is closed, fluid pressure "P2" is held equal to pressure "P3". When brake pedal is depressed to increase fluid pressure "P2", piston moves in the same direction as spring force "F", opening fluid passage.
However, since fluid passage is closed again immediately after pressure "P2" equals "P3", pressure "P3" is held at a value of less than pressure "P2".