A proportioning valve is a valve that relies on the laws of fluid pressure to distribute input

force In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...

s to one or more output lines. A proportioning valve can increase or decrease forces for each output, depending on the cross-sectional

surface area The surface area of a solid object is a measure of the total area that the surface of the object occupies. The mathematical definition of surface area in the presence of curved surfaces is considerably more involved than the definition of arc ...

s of those output lines. A simple example is an input tube with cross-sectional area ''A'' entering a chamber. Leading out of the chamber are two more tubes, one with cross-sectional area 3''A'' and the other with area ''A''/2. If a force ''F'' is applied to the fluid in the input tube, the pressure in that tube will be ''F''/''A''. Utilizing pressure laws, we find that each output tube will see the same pressure. This means the output tube with area 3''A'' will yield a force of 3''F'', and the output tube with area ''A''/2 will yield a force of ''F''/2. Thus, if you apply a 10- pound force to the input, you will get forces of 30 lbf and 5 lbf, respectively, from the outputs. If you apply a 10-

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force to the input, you will get forces of 30 N and 5 N, respectively, from the outputs Proportioning valves are frequently used in cars to reduce the brake fluid pressure to the rear brakes. In cars with

disc brakes A disc brake is a type of brake that uses the calipers to squeeze pairs of pads against a disc or a "rotor" to create friction. This action slows the rotation of a shaft, such as a vehicle axle, either to reduce its rotational speed or to hol ...

on the front and drum brakes on the back, more pressure is needed for the disc brakes in the front. The proportioning valve prevents the rear brakes from engaging before the front brakes during panic stops.

References

*''Fundamentals of Automotive Technology: Principles and Practice.'' Jones & Bartlett Publishers, Aug 1, 2013 pg. 1013 {{DEFAULTSORT:Proportioning Valve Valves Vehicle braking technologies

See also

References