畢業(yè)設(shè)計---汽車轉(zhuǎn)向機構(gòu)英文翻譯資料-汽車設(shè)計-在線瀏覽
2025-03-24 04:38本頁面
【正文】 urther apart and inflated to lower pressures .In addition, the trend of development has been to place more than half the weight on the front wheels, especially the weight of the engine , which itself is larger and heavier than in the early days. To make cars easier to steer, the gear ratio in the steering box at the end of the steering column was changed to that turning the wheel required less torque, but this increased the number of turns of the steering wheel required on modern cars without power steering pared to or 3 turns for cars built before 1940. Modern cars with power steering only require about three turns. Power assisted steering was first developed in the 1920s。 in 1952 Chrysler began offering it , and it is now standard equipment on many of the biggest American cars . Electric devices were tried , but power steering today is always hydraulic , with oil pressure of perhaps 1000 psi (70kg/cm2) maintained by a pump driven by the engineer of the car . The system is a servomechanism, or servo loop, which makes a correction to pensate for the torque applied to the steering wheel by the driver. It consists of an actuator and a control valve. The actuator is a hydraulic cylinder with a piston, or ram, which is free to travel in either direction from the center. The function of the control valve is to respond to the torque from the steering wheel by actuating smaller valves at each end of the cylinder. The system is designed to assist the steering linkage, rather than to replace it, and it does not do all of the work of steering , but leaves some of it for the driver. Thus if the hydraulics fail the car can still be steered , though with greater effort, and at all times the feel of the road is mechanically transmitted from the front wheels to the hands of the hands of the driver on the steering wheel, an essential element of safe driving. The power steering makes a positive contribution to safe driving in that if the driver hits a small obstacle in the road or has a flat tyre at speed, the power unit makes it easier to keep the car under control. Many large cars fitted with wide, stiff radial ply tyres would be nearly impossible to steer at parking speeds without power steering. Hydrostatic systems, designed for offtheroad vehicles, are exception to
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