【正文】 e of luxury cars. The Cadillac division of General Motors was going to offer power steering as optional equipment on some models in the early 1930s, but the depression interfered with development. During World War Ⅱ power steering was fitted to military vehicles。當(dāng)功率需要減小時，就用較高的變速比，此變速比使曲軸以較少的轉(zhuǎn)數(shù)帶動后輪軸。低檔位置可防止變速機(jī)構(gòu)變速超出較低的變速比范圍。 為使汽車容易轉(zhuǎn)向，改變了轉(zhuǎn)向柱末端轉(zhuǎn)向箱的傳動比，結(jié)果只需較小的扭矩轉(zhuǎn)動方向盤。而這是能安全駕駛的一個重要因素。這樣如果液壓系統(tǒng)一旦失靈，盡管司機(jī)要費些力氣，汽車任然可以開 動。為了降低壓力，加寬了輪胎，也加大了輪胎間距，并給輪胎充了氣。發(fā)動機(jī)以空擋起動，操縱桿移至“行駛”擋為正常向前運行。為此，低速比可使曲軸傳動數(shù)周而后輪軸只轉(zhuǎn)一周。Automobile Transmissions and Power Steering Automobiles, trucks, buses, and tractors all depend on transmissions to deliver power from the engine to the wheels, The gasoline and diesel engines that power these vehicles cannot be connected directly to the wheels, because the engines must keep turning at a certain seed to keep from stalling. Also, different amount of torque (turning force) must be delivered to the wheels at different times. A large amount of force is needed to get a car moving from a standstill. Less force is needed to keep the car moving once it is rolling. Going up a hill of driving at high speed requires still other amount of force. It is the job of the transmission to deliver the particular amount of force that is needed. The transmission also allows a motor vehicle to back up gasoline and diesel engines can run in only one direction, but the transmission can reverse the direction of the force. And when a car stops, the transmission lets the engine keep running without moving the wheels. The heart of any transmission—— even an automatic one— is a set of gears. Gears do not change the power of an engine, but they can increase the torque by decreasing the speed. They can also increase the speed by decreasing the torque. The automobile transmission uses a series of gears which enables the engine to continue to operate at maximum efficiency when the vehicle’s speed is altered. Setting an automobile in motion requires a large amount of power to overe the inertia of the vehicle’s weight. This process requires high engine speed, needed for high power, and a gradual increase in a vehicle’s speed to avoid a jerky start. To do this, a low gear ratio is allows the crankshaft to revolve several times in order to turn the real axle once. The low gear