汽车制动系统英文文献及中英文翻译.doc

Brake systems We all know that pushing down on the brake pedal slows a car to a stop. But how does this happen? How does your car transmit the force from your leg to its wheels? How does it multiply the force so that it is enough to stop something as big as a car? Brake Image Gallery Layout of typical brake system.? See more brake images. When you depress your brake pedal, your car transmits the force from your foot to its brakes through a fluid. Since the actual brakes require a much greater force than you could apply with your leg, your car must also multiply the force of your foot. It does this in two ways: Mechanical advantage (leverage) Hydraulic force multiplication The brakes transmit the force to the tires using friction, and the tires transmit that force to the road using friction also. Before we begin our discussion on the components of the brake system, well cover these three principles: Leverage Hydraulics Friction Leverage and Hydraulics In the figure below, a force F is being applied to the left end of the lever. The left end of the lever is twice as long (2X) as the right end (X). Therefore, on the right end of the lever a force of 2F is available, but it acts through half of the distance (Y) that the left end moves (2Y). Changing the relative lengths of the left and right ends of the lever changes the multipliers.  The pedal is designed in such a way that it can multiply the force from your leg several times before any force is even transmitted to the brake fluid. The basic idea behind any hydraulic system is very simple: Force applied at one point is transmitted to another point using an incompressible fluid, almost always an oil of some sort. Most brake systems also multiply the force in the process. Here you can see the simplest possible hydraulic system: Your browser does not support JavaScript or it is disabled. Simple hydraulic system In the figure above, two pistons (shown in red) are fit into two glass cylinders filled with oi