【正文】 forced back to the master cylinder and braking ceases. The primary purpose of the parking brake is to hold the vehicle stationary while it is unattended. The parking brake is mechanically operated by the driver when a separate parking braking hand lever is set. The hand brake is normally used when the car has already stopped. A lever is pulled and the rear brakes are approached and locked in the “on” position. The car may now be left without fear of its rolling away. When the driver wants to move the car again, he must press a button before the lever can be released. The hand brake must also be able to stop the car in the event of the foot brake failing. For this reason, it is separate from the foot brake uses cable or rods instead of the hydraulic system. A speed sensor is fitted at each wheel sends signals about wheel rotation to control unit. Each speed sensor consists of a sensor unit and a gear wheel. The front sensor mounts to the steering knuckle and its gear wheel is pressed onto the stub axle that rotates with the wheel. The rear sensor mounts the rear suspension member and its gear wheel is pressed onto the axle. The sensor itself is a winding with a magnetic core. The core creates a magnetic field around the winding, and as the teeth of the gear wheel move through this field, an alternating current is induced in the winding. The control unit monitors the rate o change in this frequency to determine impending brake lockup. Most cars today have a transparent r reservoir so that you can see the level without opening the cover. The brake fluid level will drop slightly as the brake pads wear. This is a normal condition and no cause for concern. If the level drops noticeably over a short period of time or goes down to about two thirds full, have your brakes checked as soon as possible. Keep the reservoir covered except for the amount of time you need to fill it and never leave a cam of brake fluid uncovered. Brake fluid must maintain a very high boiling point. Exposure to air will cause the fluid to absorb moisture which will lower that boiling point.The brake fluid travels from the master cylinder to the wheels through a series of steel tubes and reinforced rubber hoses. Rubber hoses are only used in places that require flexibility, such as at the front wheels, which move up and down as well as steer. The rest of the system uses noncorrosive seamless steel tubing with special fittings at all attachment points. If a steel line requires a repair, the best procedure is to replace the pete line. If this is not practical, a line can be repaired using special splice fittings that are made for brake system repair. You must never use copper tubing to repair a brake system. They are dangerous and illegal. The control unit’s function can be divided into three parts: signal processing, logic and safety circuitry. The signal processing section is the converter that receives the alternating current signals form the speed sensors and converts them into digital form for the logic section. The logic section then analyzes the digitized signals to calculate any brake pressure changes needed. If impending lockup is sensed, the logic section sends mands to the modulator assembly. Modulator assembly The hydraulic modulator assembly regulates pressure to the wheel brakes when it receives mands from the control utuit. The modulator assembly can maintain or reduce pressure over the level it receives from the master cylinder, it also can never apply the brakes by itself. The modulator assembly consists of three highspeed electric solenoid valves, two fluid reservoirs and a turn delivery pump equipped with inlet and outlet check valves. The modulator electrical connector and controlling relays are concealed under a plastic cover of the assembly. Each front wheel is served by electric solenoid valve modulated independently by the control unit. The rear brakes are served by a single solenoid valve and modulated together using the selectlow principle. During antibraking system operation, the control unit cycles the solenoid valves to either hold or release pressure the brake lines. When pressure is released from the brake lines during antibraking operation, it is routed to a fluid reservoir. There is one reservoir for the front brake circuit. The reservoirs are lowpressure accumulators that store fluid under slight spring pressure until the return delivery pump can return the fluid through the brake lines to the master cylinder. 譯 文:汽車制動系統(tǒng)制動系統(tǒng)是汽車中最重要的系統(tǒng)。 如果制動失靈，結(jié)果可能是損失慘重的。制動器實際就是能量轉(zhuǎn)換裝置，它將汽車的動能（動量）轉(zhuǎn)化成熱能（熱量）。當(dāng)駕駛員踩下制動踏板，所產(chǎn)生的制動力是汽車運(yùn)動時動力的10倍。制動系統(tǒng)能對四個剎車系統(tǒng)中的每個施加數(shù)千磅的力。每輛汽車上使用兩個完全獨(dú)立的制動系統(tǒng)，即行車制動器和駐車制動器。行車制動器起到減速、停車、或保持車輛正常行駛。制動器是由司機(jī)用腳踩、松制動器踏板來控制的。駐車制動器的主要作用就是當(dāng)車內(nèi)無人的時候，汽車能夠保持靜止。當(dāng)獨(dú)立的駐車制動器—踏板或手桿，被安裝時，駐車制動器就會被機(jī)械地操作。制動系統(tǒng)是由下列基本的成分組成:位于發(fā)動機(jī)罩下方，而且直接地被連接到制動踏板的“制動主缸”把駕駛員腳的機(jī)械力轉(zhuǎn)變?yōu)橐簤毫?。鋼制的“制動管路”和有柔性的“制動軟管”把制動主缸連接到每個輪子的“制動輪缸”上。 制動液, 特別地設(shè)計為的是工作在極端的情況，填充在系統(tǒng)中?！爸苿颖P”和“襯塊”是被制動輪缸推動接觸“圓盤”和“回轉(zhuǎn)體”如此引起緩慢的拖拉運(yùn)動, (希望)使汽車減慢速度。典型的制動系統(tǒng)布置有前后盤式，前盤后鼓式，各個車輪上的制動器通過一套管路系統(tǒng)連接到制動主缸上?；旧现v，所有的汽車制動器都是摩擦制動器。當(dāng)司機(jī)剎車時，控制裝置會迫使制動蹄，或制動襯片與車輪處的旋轉(zhuǎn)的制動鼓或制動盤接觸。接觸后產(chǎn)生的摩擦使車輪轉(zhuǎn)動減慢或停止，這就是汽車的制動。在最基本的制動系統(tǒng)中，有一個制動主缸，這個主缸內(nèi)部填充制動液，并包含兩個部分，每個部分里都有一個活塞，兩個活塞都連接駕駛室里的制動踏板。當(dāng)制動踏板被踩下時，制動液會從制動主缸流入輪缸。在輪缸中，制動液推動制動蹄或制動襯片與旋轉(zhuǎn)的制動鼓或制動盤接觸。靜止的制動蹄或制動襯片與旋轉(zhuǎn)的制動鼓或制動盤之間產(chǎn)生摩擦力使汽車的運(yùn)動逐漸減緩或停止。制動液的裝置位于主缸的頂部。目前大多數(shù)的車都有一個容易看見的裝制動液的裝置，為的是不用打開蓋子就可以看得見制動液的油面。隨著制動踏板的運(yùn)動制動液就會緩慢的下降，正常情況下是這樣的。如果制動液在很短的時間內(nèi)下降得明顯或者下降了三分之二，那么就要盡快的檢查你的制動系統(tǒng)了。保持制動液裝置充滿制動液除非你需要維修它，制動液必須保持很高的沸點(diǎn)。位于在空氣中的制動液就會吸收空氣中的潮氣引起制動液低于沸點(diǎn)。制動液通過一系列的管路從主缸到達(dá)各車輪。橡膠軟管只用在需要彈力的地方，比如應(yīng)用在前輪。在車的行進(jìn)中上下來回運(yùn)動。系統(tǒng)的其它部分在所有的連接點(diǎn)上都應(yīng)用了無腐蝕性的無縫鋼管。如果鋼線需要修理的話，最好的方法就是代替這條線。如果這不符合實際，那么為了制動系統(tǒng)可以用特殊的裝置修理它。你不可以用銅管來修理制動系。它們是危險也是不正確的。鼓式制動器包括制動鼓，一個輪缸，回拉彈簧，一個制動底版，兩個帶摩擦層的制動蹄。制動底版固定在輪軸外部的法蘭或轉(zhuǎn)向節(jié)。制動鼓固定在輪轂上。制動鼓的內(nèi)部表面與制動蹄的內(nèi)層之間有空隙。要使用制動器時，司機(jī)就要踩下踏板，這時輪缸擴(kuò)大制動片，對其施加壓力，是制動蹄觸碰制動鼓。制動鼓與摩擦片之間產(chǎn)生的摩擦制動了車輪，從而使汽車停止。要釋放制動器時，司機(jī)松開踏板，回拉彈簧拉回制動片，這樣車輪會自由轉(zhuǎn)動。盤式制動器包括制動盤而不是鼓，在它的兩面上各有一個薄的制動片或叫盤式制動器的制動片。制動片是靠擠住旋轉(zhuǎn)的制動盤來停住汽車。制動主缸里流出的制動液迫使活塞向里部的金屬盤移動，這便使摩擦片緊緊地貼住制動盤。這時制動片與制動盤產(chǎn)生的摩擦使汽車減速、停止，出現(xiàn)了制動行為?；钊?