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1、杭州电子科技大学毕业设计（论文）外文文献翻译毕业设计（论文）题目翻译（1）题目液压制动器基础翻译（2）题目有用的产品学 院机械学院专 业车辆工程姓 名班 级学 号指导教师 液压制动基础空气制动系统得到更多的关注，但更多的车辆上安装液压制动器。了解它们是如何工作的，是安全，具成本效益的诊断和修复的第一步。有没有想过为什么不能只是其中的一种制动？这是由于空气和液压制动器，使一个或某些应用程序的其他抱负的经营特色。重型组合的车辆，空气是明确的选择，由于将需要大量的液体阿卡迪亚所有分泵。此外，充满液压油与制动分泵和软管的将是混乱的。但对于轻型和中型卡车直应用，液压制动器提供的优势涉及：制动感觉- 那就
2、是，踏板越往下压，努力增长;高线压力，允许使用更轻，更紧凑的制动组件;更少的初始费用，由于用更小和更少的元件;卫生，液压制动器是封闭的系统;易于定位泄漏，由于液体是可见的。液压制动系统有更多的排列，比在空气系统中发现，但都基本相似。液压系统所有的液压制动系统包含流体水库，主缸，液压，液压管路，对制动器进行加压流体的软管和一个或多个轮缸（S）对每个车轮产生。分泵扩大流体压力下，迫使制动蹄对鼓的内侧。假如使用盘式制动器，卡钳与不可分割的气瓶打击转子时施加压力。由于车辆必须可以更迅速，它可以加速到停止，需要大量的刹车力。因此，必须减速刹车产生的马力的发动机作用多次。为了发展须持有对鼓或盘制动器衬片的
3、力量，实现受控减速，这是要乘原始的力量施加在刹车踏板。当使用液压系统，机械杠杆是在脚踏板联动。然而，不同分泵或卡尺直径的直径，关系到主缸内径，提供了一个额外增长的比率。液压系统中，各分泵交付的压力，直接影响由活塞地区。例如，假如一个轮缸活塞面积2平方英寸，另一个活塞面积1平方英寸，系统压力为400磅，2平方英寸的活塞将针对制动器推一个迫使800磅。1平方英寸的活塞施加一个400磅的力量。总泵和分泵的地区之间的比例拟定在轮缸活塞的力量倍增。为保持在头脑，直径较大的轮缸的，更流畅，必须提供由主缸行程较长的硕士转化。请记住，直径较大的轮缸的，更流畅，必须由主缸提供，以填补它。这意味着进入一个较长的主
4、缸行程。假如主缸孔直径增长和相同的申请仍然有效，更少的压力将在系统的开发，但一个更大的轮缸活塞可以用来实现在轮缸所需的压力。显然，必须更换主缸，轮缸或卡尺相同的设计，并作为原单位承担。液压系统中，各分泵交付的压力，直接影响由活塞地区。例如，假如一个轮缸活塞面积2平方英寸，另一个活塞面积1平方英寸，系统压力为400磅，2平方英寸的活塞将针对制动鞋推一个迫使800磅。1平方英寸的活塞施加一个400磅的力量。总泵和分泵的地区之间的比例拟定在轮缸活塞的力量倍增。液压制动系统分割的系统，涉及两个谨慎的制动电路。一主缸活塞和水库是一个单独的活塞及伺服制动器上的其他桥（S）的水库，用来驱动一轴刹车。虽然罕见
5、，一些轻型制动系统分裂对角线而非桥桥。分割系统的因素是，假如一个液压回路泄漏的发展，将停止车辆。当然，不应当被驱动的车辆远超过必要的制动系统修复。当液压回路发生故障，压力差开关感官两个电路之间的不平等的压力。互换机包含由弹簧片，并在每年年终电触头位于活塞。从一个液压回路中流体的压力提供压力差开关的一端，并从其他电路的压力提供应另一端。随着压力的一个电路，其他电路的正常压力，迫使活塞的失效一边，关闭的接触，并照亮仪表板警示灯。动力辅助协助电力单位，或助推器，减少运营商的努力，在刹车踏板。真空助力器，轻型汽车的流行，使发动机真空隔阂一侧，对对方的大气压力。一个阀门，使真空作用于刹车踏板的行程中的比
6、例隔阂。这有助于踏板的努力，并增长对制动液的压力，无需过度增长在踏板努力。其他类型的助推器使用液压压力-无论是从车辆的动力转向泵，或从一个单独的电动泵，或两者兼而有之-协助刹车踏板被踩下踏板作用，阀门液压升压室申请增长的压力在增长主缸活塞。有些系统使用真空和液压助力。在其他系统中，从船上压缩机的空气压力产生液压系统的压力。阀杆液压制动系统中常见的阀门涉及：配比，或压力平衡阀门。这些限制液压比例后轮刹车系统压力达成预设的高阻值。提高前轮/后轮在高速制动的制动平衡时，一些车辆的前后重量转移，并有助于防止后轮配料阀高度传感器。也就是说，他们调整后轮制动压力，在车辆荷载的响应。随着车辆的负载增长（减少
7、高度）液压后轮刹车是不允许的; 测光阀门。这些保持了前盘式制动器的压力，让后轮鼓式制动蹄克服返回弹簧的压力，使接触后鼓。这可以防止锁定在湿滑路面上的前刹车灯制动应用。这些阀门不来硬制动过程中发挥作用。泊车停车功能的液压制动系统之间的差别很大。许多轻型车辆使用与后轮鼓式制动器杆和电缆相配合，逐步加大杆或脚踏拉电缆，这反过来，拉杠杆总成，每个后轮结束的客运车类型。杠杆迫使制动蹄外，他们对鼓机械棘轮被释放，直到举起。其他泊车系统涉及弹簧腔，像那些用于空气制动系统。这是弹簧控制，但由液压脱开而不是空气。防抱死许多轻型卡车液压制动，防抱死制动系统上使用的后轮保持轻载时，这些车辆制动稳定性。前面和后轮防抱
8、死通常是一个选项，GVWR超过10,000磅的车辆，这是需要引导和驱动桥防抱死关闭。在当前的液压防抱死系统，转储阀释放压力到一个累加器在即将车轮锁死的情况下液压油。电子控制箱接受来自传感器的传输和/或在车轮速度信号（S）。当施加制动，控制箱检测在后轮的速度，减少和激活转储阀（S），假如减速率超过预定的限制。控制箱通电一系列流血轮液压快速脉冲的单向阀。继续转储阀是脉冲在防抱死模式，以保持车轮转动，同时保持控制的减速。在最后的停止，阀门的激励和累加器中的任何液体返回到主缸，恢复正常的刹车操作。基础刹车在液压系统的基础制动器可以是鼓或光盘。在许多应用中，光盘上使用前轴后方的鼓。鼓式制动器说是自激。这
9、是由于制动蹄扩大和联系一个旋转的滚筒，引导或向前制动蹄被推向对刹车制动箍由移动鼓的力量。这个结果在更高的衬里鼓比将仅由轮缸产生的压力。随着制动器衬片的磨损，必须定期移近鼓，以保证在制动过程中适当的接触。虽然一些旧的鼓式制动器总成，手动调整，大部分都是自动。这些使用一个星轮或棘轮大会，这感官分泵时已超过其正常行程前往，并扩大在另一端的制动蹄的支点。除了摩擦的元素之一，制动鼓或转子也充当散热器。它必须迅速制动过程中吸取的热量，并保持它，直到它可以将空气中消散。鼓或转子较重的是，它可以容纳更多的热量。这是很重要的，由于制动器衬片热，他们更容易受到热衰退。热衰退是诱发反复的硬盘停止和结果的减少鼓形轮子
10、连接的摩擦和增长车辆的制动距离。作为一项规则，高品质的衬里，将显示低于劣质的热褪色。此外碟式刹车比鼓式制动器耐热褪色性能更好。另一个褪色的类型，刹车容易褪色水。鼓式制动器，其表面积大，在安全范围内比盘式制动器每平方英寸之间需要更少的衬力和鼓力。加上鼓的保水的形状，鞋和鼓之间的潮湿条件下促进水面滑行。结果是制动距离大大增长。盘式制动器，具有较小的摩擦表面和高夹紧力，做一个良好的工作从转子擦水，并显示在潮湿时停止能力几乎没有减少。HYDRAULIC BRAKE BASICSAirbrakesget more attention, buthydraulicbrakesare installed on
11、 more vehicles.Understanding how they work is the first step to safe, cost-effective diagnosis and repair.Ever wonder why there cant be just one kind ofbrake?Its because air andhydraulicbrakeseach have operating characteristics that make one or the other ideal for certain applications.In heavy-duty
12、combination vehicles, air is the clear choice because of the large volume of liquid that would be needed to acadia all the wheel cylinders.Plus, dealing with gladhands and hoses filled withhydraulicfluid would be messy.But for light and medium-duty straight-truck applications,hydraulicbrakesoffer ad
13、vantages including: Brakefeel that is, as the pedal is pressed farther down, effort increases; High line pressures, which permit the use of lighter, more compact braking components; Less initial expense, due to smaller and fewer components; Cleanliness hydraulicbrakesare closed systems; Ease of loca
14、ting leaks, since fluid is visible.There are many more permutations ofhydraulicbrakesystems than found in air systems, but all have basic similarities.THE HYDRAULIC SYSTEMAll hydraulic brake systems contain a fluid reservoir, a master cylinder, which produceshydraulicpressure,hydrauliclines and hose
15、s to carry pressurized fluid to the brakes, and one or more wheel cylinder(s) on each wheel.The wheel cylinders expand under fluid pressure, and force thebrakeshoes against the insides of the drums.If discbrakesare used, calipers, with integral cylinders, clamp down on the rotors when pressure is ap
16、plied.Because a vehicle must be able to stop much more quickly than it can accelerate, a tremendous amount of braking force is needed.Therefore, the retarding horsepower generated by thebrakesmust be several times that of the engine.In order to develop the forces required to hold thebrakelinings aga
17、inst the drums or discs, and to achieve controlled deceleration, it is necessary to multiply the original force applied at thebrakepedal.When ahydraulicsystem is used, the only mechanical leverage is in the foot pedal linkage.However, varying the diameter of the wheel cylinders or caliper diameters,
18、 in relation to the master cylinder bore diameter, provides an additional increase in ratio.In ahydraulicsystem, the pressure delivered by the various wheel cylinders is directly affected by the areas of their pistons.For example, if one wheel-cylinder piston has an area of 2 square inches, and anot
19、her piston has an area of 1 square inch, and the system pressure is 400 psi, the 2-square-inch piston will push against the brakeshoes with a force of 800 pounds. The 1-square-inch piston will exert a force of 400 pounds.The ratio between the areas of the master cylinder and the wheel cylinders dete
20、rmine the multiplication of force at the wheel cylinder pistons.Keep in mind that the larger a wheel cylinders diameter, the more fluid must be supplied by the master cylinder to fill it.This translates into a longer master-cylinder stroke.If the master cylinder bore diameter is increased and the ap
21、plying force remains the same, less pressure will be developed in the system, but a larger wheel-cylinder piston can be used to achieve the desired pressure at the wheel cylinder.Obviously, a replacement master cylinder, wheel cylinder or caliper must be of the same design and bore as the original u
22、nit.Hydraulicbrakesystems are split systems, comprising two discreet braking circuits.One master-cylinder piston and reservoir is used to actuate thebrakeson one axle, with a separate piston and reservoir actuating thebrakeson the other axle(s).Although rare, some light-duty brake systems are split
23、diagonally rather than axle by axle.The reason for the split system is that if a leak develops in onehydrauliccircuit, the other will stop the vehicle.Of course, the vehicle shouldnt be driven any farther than necessary to have thebrakesystem repaired. When one of thehydrauliccircuits fails, a press
24、ure-differential switch senses unequal pressure between the two circuits.The switch contains a piston located by a centering spring and electrical contacts at each end.Fluid pressure from onehydrauliccircuit is supplied to one end of the pressure-differential switch, and pressure from the other circ
25、uit is supplied to the other end.As pressure falls in one circuit, the other circuits normal pressure forces the piston to the inoperative side, closing the contacts and illuminating a dashboard warning light.POWER ASSISTPower assist units, or boosters, reduce operator effort at thebrakepedal.Vacuum
26、 boosters, popular on light-duty vehicles, make use of an engine vacuum on one side of a diaphragm, and atmospheric pressure on the other side.A valve allows the vacuum to act on the diaphragm in proportion tobrakepedal travel.This assists the pedal effort, and allows increased pressure on thebrakef
27、luid, without an undue increase in pedal effort.Other types of boosters usehydraulicpressure either from the vehicles power steering pump or from a separate electric pump, or both to assist pedal effort. As thebrakepedal is depressed, a valve increaseshydraulicpressure in a boost chamber to apply in
28、creased pressure to the master cylinder pistons.Some systems use both vacuum andhydraulicassist.In other systems, air pressure from an onboard compressor is used to generatehydraulicsystem pressure.VALVINGValves commonly found inhydraulicbrakesystems include: Proportioning, or pressure-balance valve
29、s.These restrict a percentage ofhydraulicpressure to the rearbrakeswhen system pressure reaches a preset high value. This improves front/rearbrakebalance during high-speed braking, when some of a vehicles rear weight is transferred forward, and helps prevent rear-wheel lockup. Some proportioning val
30、ves are height-sensing.That is, they adjust rear-brakepressure in response to vehicle load.As a vehicles load increases (decreasing height) morehydraulicpressure to the rearbrakesis allowed; Metering valves.These hold off pressure to front discbrakesto allow rear drumbrakeshoes to overcome return-sp
31、ring pressure and make contact with the rear drums.This prevents locking the frontbrakeson slippery surfaces under light braking applications.These valves do not come into play during hard braking.PARKINGThe parking function varies greatly amonghydraulicbrakesystems.Many light-duty vehicles with rea
32、r drumbrakesuse a passenger-car type lever-and-cable setup. A ratcheted lever or foot pedal pulls a cable, which, in turn, pulls a lever assembly at each rear wheel end.The lever forces thebrakeshoes apart, and they are mechanically held against the drums until the ratchet is released.Other parking
33、systems include spring chambers, like those used on air-brakesystems.These are spring-engaged, but are disengaged byhydraulicpressure instead of air.ANTILOCKOn many hydraulically braked light-duty trucks, antilockbrakesare used on the rear wheels to preserve braking stability when these vehicles are
34、 lightly loaded.Front and rear-wheel antilock is usually an option, except for vehicles over 10,000 pounds GVWR, which are required to have steer and drive-axle antilock.In currenthydraulicantilock systems, a dump valve releases pressurizedhydraulicfluid into an accumulator in the event of an impend
35、ing wheel lockup.An electronic control box receives speed signal(s) from sensors in the transmission and/or at the wheels.When thebrakesare applied, the control box senses the decrease in rear wheel speed, and activates the dump valve(s) if the rate of deceleration exceeds a predetermined limit.The
36、control box energizes the dump valve with a series of rapid pulses to bleed-off wheelhydraulicpressure.Continuing in antilock mode, the dump valve is pulsed to keep the wheels rotating, while maintaining controlled deceleration.At the end of such a stop, the valve de-energizes and any fluid in the a
37、ccumulator is returned to the master cylinder.Normalbrakeoperation resumes.FOUNDATION BRAKESFoundationbrakesinhydraulicsystems can be either drum or disc.In many applications, discs are used on the front axle and drums on the rear.Drumbrakesare said to be self-energizing.Thats because when thebrakes
38、hoes expand and contact a rotating drum, the leading, or forward,brakeshoe is pushed against the trailing shoe by the force of the moving drum.This results in higher lining-to-drum pressure than would be produced by the wheel cylinder alone.Asbrakelinings wear, the shoes periodically must be moved c
39、loser to the drums to ensure proper contact during braking.While some older drumbrakeassemblies are manually adjusted, most are automatic.These use a star wheel or ratchet assembly, which senses when the wheel cylinder has traveled beyond its normal stroke, and expands the pivot point at the other e
40、nd of thebrakeshoes.In addition to being one of the friction elements, thebrakedrum or rotor also acts as a heat sink.It must rapidly absorb heat during braking, and hold it until it can be dissipated into the air.The heavier a drum or rotor is, the more heat it can hold.This is important, since the
41、 hotter thebrakelinings get, the more susceptible they are to heat fade.Heat fade is induced by repeated hard stops and results in reduced lining-to-drum/rotor friction and increased vehicle stopping distance.As a rule, high-quality linings will display less heat fade than inferior ones.Also, discbr
42、akesare far more resistant to heat fade than drumbrakes.Another type of fade thatbrakesare susceptible to is water fade.Drumbrakes, with their large surface areas, apply fewer pounds per square inch of force between lining and drum during a stop than discbrakes.This, added to the drums water-retaini
43、ng shape, promotes hydroplaning between shoe and drum under wet conditions.The result is greatly increased stopping distance.Discbrakes, with their smaller friction surfaces and high clamping forces, do a good job of wiping water from rotors, and display little reduction in stopping capability when wet.有用的产品气动钢瓶