【正文】 附錄Ⅰ外文資料及翻譯：Suspension Principle Of WorkWhen people think of automobile performance, they normally think of horsepower, torque and zeroto60 acceleration. But all of the power generated by a piston engine is useless if the driver can39。s why automobile engineers turned their attention to the suspension system almost as soon as they had mastered the fourstroke internal bustion engine. The job of a car suspension is to maximize the friction between the tires and the road surface, to provide steering stability with good handling and to ensure the fort of the passengers. In this article, we39。ve evolved over the years and where the design of suspensions is headed in the future. Vehicle DynamicsIf a road were perfectly flat, with no irregularities, suspensions wouldn39。s these imperfections that apply forces to the wheels. According to Newton39。s vertical energy is transferred to the frame, which moves in the same direction. In such a situation, the wheels can lose contact with the road pletely. Then, under the downward force of gravity, the wheels can slam back into the road surface. What you need is a system that will absorb the energy of the vertically accelerated wheel, allowing the frame and body to ride undisturbed while the wheels follow bumps in the road. The study of the forces at work on a moving car is called vehicle dynamics, and you need to understand some of these concepts in order to appreciate why a suspension is necessary in the first place. Most automobile engineers consider the dynamics of a moving car from two perspectives: Ride a car39。s ability to safely accelerate, brake and corner These two characteristics can be further described in three important principles road isolation, road holding and cornering. The table below describes these principles and how engineers attempt to solve the challenges unique to each. PrincipleDefinitionGoalSolutionRoad IsolationThe vehicle39。s ability to steer, brake and accelerate.Minimize the transfer of vehicle weight from side to side and front to back, as this transfer of weight reduces the tire39。s center of gravity while cornering, raising one side of the vehicle and lowering the opposite side.Transfer the weight of the car during cornering from the high side of the vehicle to the low side.A car39。s look at the parts of a typical suspension, working from the bigger picture of the chassis down to the individual ponents that make up the suspension proper. The ChassisThese systems include: The frame structural, loadcarrying ponent that supports the car39。s springing systems are based on one of four basic designs: Coil springs This is the most mon type of spring and is, in essence, a heavyduty torsion bar coiled around an axis. Coil springs press and expand to absorb the motion of the wheels. Leaf springs This type of spring consists of several layers of metal (called leaves) bound together to act as a single unit. Leaf springs were first used on horsedrawn carriages and were found on most American automobiles until 1985. They are still used today on most trucks and heavyduty vehicles. Torsion bars Torsion bars use the twisting properties of a steel bar to provide coilspringlike performance. This is how they work: One end of a bar is anchored to the vehicle frame. The other end is attached to a wishbone, which acts like a lever that moves perpendicular to the torsion bar. When the wheel hits a bump, vertical motion is transferred to the wishbone and then, through the levering action, to the torsion bar. The torsion bar then twists along its axis to provide the spring force. European carmakers used this system extensively, as did Packard and Chrysler in the United States, through the 1950s and 1960s. Air springs Air springs, which consist of a cylindrical chamber of air positioned between the wheel and the car39。 they were replaced with moldedrubber air springs in the 1930s. Shock AbsorbersUnless a dampening structure is present, a car spring will extend and release the energy it absorbs from a bump at an uncontrolled rate. The spring will continue to bounce at its natural frequency until all of the energy originally put into it is used up. A suspension built on springs alone would make for an extremely bouncy ride and, depending on the terrain, an uncontrollable car. Enter the shock absorber, or snubber, a device that controls unwanted spring motion through a process known as dampening. Shock absorbers slow down and reduce the magnitude of vibratory motions by turning the kinetic energy of suspension movement into heat energy that can be dissipated through hydraulic fluid. To understand how this works, it39。s unsprung weight, while extension controls the heavier, sprung weight. All modern shock absorbers are velocitysensitive the faster the suspension moves, the more resistance the shock absorber provides. This enables shocks to adjust to road conditions and to control all of the unwanted motions that can occur in a moving vehicle, including bounce, sway, brake dive and acceleration squat. Suspension Types: FrontSo far, our discussions have focused on how springs and dampers function on any given wheel. But the four wheels of a car work together in two independent systems the two wheels connected by the front axle and the two wheels connected by the rear axle. That means that a car can and usually does have a different type of suspension on the front and back. Much is determined by whether a rigid axle binds the wheels or if the wheels are permitted to move independently. The former arrangement is known as a dependent system, while the latter arrangement is known as an independent system. In the following sections, we39。t been used in mainstream cars for years. Front Suspension Independent SystemsIn this setup, the front wheels are allowed to move independently. The MacPherson strut, developed by Earle S. MacPherson of General