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1、外文原文Suspension (vehicle)When people think of automobile performance, they normally think of horsepower, torque and zero-to-60 acceleration. But all of the power generated by a piston engine is useless if the driver cant control the car. Thats why automobile engineers turned their attention to the su
2、spension system almost as soon as they had mastered the four-stroke internal combustion 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 comfortof the passengers. In this article,
3、 well explore how car suspensions work, how theyve 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 wouldnt be necessary. But roads are far from flat. Even freshly paved highways hav
4、e subtle imperfections that can interact with the wheels of a car. Its these imperfections that apply forces to the wheels. According to Newtons laws of motion, all forces have both magnitude and direction. A bump in the road causes the wheel to move up and down perpendicular to the road surface. Th
5、e magnitude, of course, depends on whether the wheel is striking a giant bump or a tiny speck. Either way, the car wheel experiences a vertical acceleration as it passes over an imperfection. Without an intervening structure, all of wheels vertical energy is transferred to the frame, which moves in
6、the same direction. In such a situation, the wheels can lose contact with the road completely. 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
7、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 conside
8、r the dynamics of a moving car from two perspectives: Ride - a cars ability to smooth out a bumpy road Handling - a cars ability to safely accelerate, brake and corner A cars suspension, with its various components, provides all of the solutions described. Lets look at the parts of a typical suspens
9、ion, working from the bigger picture of the chassis down to the individual components that make up the suspension proper. The ChassisThe suspension of a car is actually part of the chassis, which comprises all of the important systems located beneath the cars body. These systems include: The frame -
10、 structural, load-carrying component that supports the cars engine and body, which are in turn supported by the suspension The suspension system - setup that supports weight, absorbs and dampens shock and helps maintain tire contact The steering system - mechanism that enables Chassis the driver to
11、guide and direct the vehicle The tires and wheels - components that make vehicle motion possible by way of grip and/or friction with the road So the suspension is just one of the major systems in any vehicle. With this big-picture overview in mind, its time to look at the three fundamental component
12、s of any suspension: springs, dampers and anti-sway bars. SpringsTodays springing systems are based on one of four basic designs: Coil springs - This is the most common type of spring and is, in essence, a heavy-duty torsion bar coiled around an axis. Coil springs compress and expand to absorb the m
13、otion 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 horse-drawn carriages and were found on most American automobiles until 1985. They are still used today on most trucks an
14、d heavy-duty vehicles. Torsion bars - Torsion bars use the twisting properties of a steel bar to provide coil-spring-like 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 t
15、o 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 Chrysle
16、r 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 cars body, use the compressive qualities of air to absorb wheel vibrations. The concept is actually more than a century old and could be found on horse-drawn buggies. Air springs from this era were made from air-filled,
