汽车系统构造英文版-Lesson14SuspensionSystem资料

• Most automotive vehicles have independent front suspension, usually using coil springs as part of either a short-arm long-arm or a MacPherson-strut suspension system. A MacPherson-strut suspension (see illustration) combines a coil spring and shock absorber into a strut assembly that requires only a beam-type lower control arm.
• Some vehicles with short-arm long-arm front suspension use either longitudinal or transverse torsion bars for the front springs. One end of the torsion bar is attached to the lower control arm, and the other end is anchored to the vehicle body or frame. As the tire and wheel move up and down, the torsion bar provides springing action by twisting about its long axis.
Lesson 14 Suspension System
• Suspension is the term given to the system of springs, shock absorbers and linkages that connects a vehicle to its wheels. Suspension systems serve a dual purpose – contributing to the car's roadholding/handling and braking for good active safety and driving pleasure, and keeping vehicle occupants comfortable and reasonably well isolated from road noise, bumps, and vibratinsion systems of most vehicles in current production make use of coil springs. Two lower control arms, which are connected to the frame and rear axle housing, keep the housing from shifting too far toward the front or rear. A pair of upper control arms (torque arms) also connect the frame and rear axle housing. The upper and lower control arms prevent the differential and rear axle housing from rotating.
Rear suspension system parts
• The differential housing and rear axle housings move up and down as the wheels strike obstacles in the road. A flat base for the U-bolt plate is welded to the bottom of the rear axle housing near each end.
• Whenever power is transmitted to the rear wheels of a vehicle equipped with a Hotchkiss drive system, the wheels attempt to force the differential and rear axle housing to turn in the direction opposite from wheel rotation. Leaf springs control this torque and prevent damage to the drive line and rear suspension system.
• In a typical suspension system for a vehicle with front-engine and front-wheel drive (see illustration), the weight of the vehicle applies an initial compression to the coil springs. When the tires and wheels encounter irregularities in the road, the springs further compress or expand to absorb most of the shock. The suspension at the rear wheels is usually simpler than for the front wheels, which require multiple-point attachments so the wheels can move up and down while swinging from side to side for steering.
• The secondary leaves are placed underneath the main leaf, and the assembly is held together near the ends by alignment clips and, in the center, by two U-bolts and a plate. The U-bolt and plate assembly also fastens the differential and rear axle housing to, and aligns it with, the spring. Thin interliners are installed between the spring leaves to eliminate noise and to enable the leaves to move freely against each other.
• Spring-loaded valves open to permit quicker flow of the fluid if fluid pressure rises high enough, as it may when rapid wheel movements take place. Most automotive vehicles use gas-filled shock absorbers in which the air space above the fluid is filled with a pressurized gas such as nitrogen. The gas pressure on the fluid reduces the creation of air bubbles and foaming.
• Rear Suspension Systems
• Semi-elliptical leaf springs or coil springs are used in the rear suspension systems of all automobiles built in the United States. A leaf spring may consist of a single leaf of flat spring steel, or it may have a series of leaves. A multileaf spring includes a main leaf and three, four, or five secondary leaves that are progressively shorter and have progressively smaller radii.
• These goals are generally at odds, so the tuning of suspensions involves finding the right compromise. It is important for the suspension to keep the road wheel in contact with the road surface as much as possible, because all the forces acting on the vehicle do so through the contact patches of the tyres. The suspension also protects the vehicle itself and any cargo or luggage from damage and wear. The design of front and rear suspension of a car may be different.
Front-wheel-drive car with MacPherson-strut front suspension and strut-type independent rear suspension. (Saturn Corp.)