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2025-07-19 12:02 本頁面
【文章內(nèi)容簡(jiǎn)介】 In ahydraulicsystem, the pressure delivered by the various wheel cylinders is directly affected by the areas of their pistons.For example, if one wheelcylinder piston has an area of 2 square inches, and another piston has an area of 1 square inch, and the system pressure is 400 psi, the 2squareinch piston will push against the brakeshoes with a force of 800 pounds. The 1squareinch piston will exert a force of 400 pounds.The ratio between the areas of the master cylinder and the wheel cylinders determine the multiplication of force at the wheel cylinder pistons.Keep in mind that the larger a wheel cylinder39。s diameter, the more fluid must be supplied by the master cylinder to fill it.This translates into a longer mastercylinder stroke.If the master cylinder bore diameter is increased and the applying force remains the same, less pressure will be developed in the system, but a larger wheelcylinder piston can be used to achieve the desired pressure at the wheel cylinder.Obviously, a replacement master cylinder, wheel cylinder or caliper must be of the same design and bore as the original unit.Hydraulicbrakesystems are split systems, prising two discreet braking circuits.One mastercylinder piston and reservoir is used to actuate thebrakeson one axle, with a separate piston and reservoir actuating thebrakeson the other axle(s).Although rare, some lightduty brake systems are split diagonally rather than axle by axle.The reason for the split system is that if a leak develops in onehydrauliccircuit, the other will stop the vehicle.Of course, the vehicle shouldn39。t be driven any farther than necessary to have thebrakesystem repaired. When one of thehydrauliccircuits fails, a pressuredifferential switch senses unequal pressure between the two circuits.The switch contains a piston located by a centering spring and electrical contacts at each end.Fluid pressure from onehydrauliccircuit is supplied to one end of the pressuredifferential switch, and pressure from the other circuit is supplied to the other end.As pressure falls in one circuit, the other circuit39。s normal pressure forces the piston to the inoperative side, closing the contacts and illuminating a dashboard warning light.POWER ASSISTPower assist units, or boosters, reduce operator effort at thebrakepedal.Vacuum boosters, popular on lightduty vehicles, make use of an engine vacuum on one side of a diaphragm, and atmospheric pressure on the other side.A valve allows the vacuum to act on the diaphragm in proportion tobrakepedal travel.This assists the pedal effort, and allows increased pressure on thebrakefluid, without
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