513 20馬力輪式拖拉機的半軸與制動器設計（有cad圖等）
513 20馬力輪式拖拉機的半軸與制動器設計（有cad圖等）,513,20馬力輪式拖拉機的半軸與制動器設計（有cad圖等）,20,馬力,輪式拖拉機,制動器,設計,cad
汽車工程英語
Brake system
Automobile brake is the most important system in cars.Brake are actually energy conversion ,which convert the kinetic energy of the vehicle into thermal energy .When stepping on the brakes,the drive commands a stopping force ten times as powerful as the force that puts the cars in motin .The brakeing system can exert thousands of pounds of pressure on each of the four brakes.
Each vehicle must have two indenpent brake systems for safety.The main brake system which is locate under the hood and is directly connect to the brake pedal is hydraulically operated and is called the service brake system.The secondary or parking brake system is mechanically operated.To increase safety ,most modern car brake system are broken into two circuits,with two wheels on each circuit.There is a fluid-filled cylinder,called the master cylinder .It supplies pressure to hoth circuits of the car ,and if a fluid leak occurs in one circuit ,only two of the wheels will lose their brakes and the car will be stopped.
Why that pushig down on the brake pedal can slow a car to stop? How dose the car transmits the force from the driver’leg to its wheel? It is the work that brakes did.
Layout of Typical Brake system When depressing the breke pedal ,the car transmits the force the drive’s foot to its brakes through a fluid.Since the actual brakes require a much greater force than the drive could apply with his leg ,the car must also multipy the force of the driver’s foot.It dose this in two ways: mechanical advantage and hydraulic force multiplication .
Leverge The pedal is designed in such a way that it can multiply the force from the driver’s leg several times before any force is even transmitted to the brake fluid.
In the figure above ,a force F is being applied to the left end of the lever.The left end of the lever is twice as long 2X) as the right end (x).Therefore ,on the right end of the lever a force of 2F is available,but it acts through half of the distans (Y) that the left end moves (2Y) .Changing the relative lengths of the left and right ends of the lever changes the mulitipliers.
Hydraulic Brake Systems The hydraulic system is that force applied at one point is thansmitted to another point using an incompressible fluid , almost alwaays an oil of some sort .Most brake systems also muitiply the force in the process .The great thing about hydraulic systems is that the pipe connecting the two cylinders can be any length and shape , allowing it to snake through all sorts of things separating the two pistons .The pipe can also fork ,so that one master cylinder can drive more than one salve cylinder if desired .The other neat thing about a hydraulic system is that it makes force multiplication fairly easy . In a hydralic system , all you have to do change the size of one piston and cylinder to the other .
The automobile brake systems are divided into three types of service brake combinations:drum brake , disc brakes and disc-drum combinations.
Drum Brake It uses an internal expanding brake shoe with the lining attactet , working within the confines of a rotating brake surface called a brake drum .The brake shoe diameter is expanded to contact the brake surface by a hydraulic cylinder that is referred to as a wheel cylinder . With drum brake , the fluid is forced into the wheel cylinde which pushed the brake shoes out so that the friction lining are pressed againtst the drum , and cause the wheel to stop .
Power brakes back in the day , when most cars had drum brakes ,power brakes were not really necessary ---- drum brakes naturally provide some of their own power assist .Since most cars today have disc brakes ,at least on the front wheels , they need power brakes,Without this device ,a lot of drivers would have very tired legs .
The brake booster use Vacuum from the engine to multipiy the force that your foot applies to the master cylinder .
Disc Brakes Most modern cars have disc brake on the front wheels , and some have disc brakes on all four wheels ,Disc brakes employ a brake disc that rotates with the wheel ,so it is usually referred to as a brake rotor . On a disc brake , the fluid from the master cylinder is forced into a caliper where it presses against a piston ,in—turn , squeezes two brake pads against the disk which is attached to the wheel ,forcing it to slow down or stop .This process is similar to a bicycle brake where two rubber pads rub against the wheel rim creating friction.
The most common type of disc brake on modern cars is the single-piston floating caliper.
Self-Adjusting brakes The single-piston floating-caliper disc brake is self-centering and self-adjusting .The caliper is able to slide from side to side so it will move to the center each time the brakes are applied .Also,since there is no spring to pull the pads away from the disc ,the pads always stay in light contact with the rotor .This is important because the pistons in the brakes are much larger in diameter than the ones in the master cylinder .If the brake pistons retracted into their cylinders ,it might take several applications of the brake pedal to pump enough fluid into the brake cylinder to engage the brake pads.
Self-Adjusting disc brake Older cars had dual or four-pistin fixed-caliper desiger .A piston on each side of the rotor pushed the pad on that side .This design has been largely eliminated because single-piston designs are cheaper and more reliable .
Emergence Brakes In cars with disc brakes on all four wheels ,an emergency brake has to be actuated by a separate mechanism than the primary brakes in case of a total primary brake failure .Most cars use a cable to actuate the emergency brake .Some cars with four-wheel disc brakes have a separate drum brake integrated into the hub of the rear wheels .This drum brake is only for the emergency brake sysem ,and it is actuated only by the cable;it has no hydraulics .
Parking Brakes Cars also have the parking brake system .It is used to hold one or more of the vehicle brakes in an applied position for an extended period of time .This brake system must be capable of holding the vehicle on a grade and bringing the vehicie to a stop if the service brakes fail .The parking brake system used on most current model passenger vehicles operates by applying two rear-wheel brakes through a mechanical system of cable and levers.
There are air brakes ,anti-lock brakes ,too .The forme used in heavy trucks and utilizes compressed air as a source of force to stop the truck .The latter used for solving the lockup problem: it can rapidly pump the brakes whenever the system detects a wheel that is locked up .This pumping of the brakes occurs at ten or more times a second ,far fasrer than a human can pump the brake manually.
Post-Sale Service and Callback
The automobile post-sale service means the sale branch provides all the technical service to the customer before or after they buy the car .It may carry on in pre-sale ,or when selling carries on .What but are more is sells after the vehicles ,cerris on the quality guarantee ,the routine maintenance ,the repair ,the technical consultation and the spare parts supply according to the deadline and so on a series of work .
In recent years ,the products performances ,product qualities and product prices are almost convergence the same among those famous international automobile companies .As a result ,the focus of competition in the market focus and transfer to post-sale .Post-sale functions should be enable to use good car products and to create the best returns ,and thus can prove the successful post-sale work .
A perfect post-sale service should have two function : to serve both customers and companies themselves .For customers ,the post-sale service could satisfy them and help them solve problems ;for the companies themselves ,it could accurately reflect product utility information ,quality information ,and important social information ,so that the company can make right decisions based on them .
Automobile is the most typical product which highly unifies the sale and the post-sale service .In the intermation market ,one important criterion for automobile sale agent is whethe they have and fulfill post-sale service .When a customer wants to purchase a car ,the first thing he asks is where to repaire the car and whether there are spare-parts .
Only getting postive replies ,will he think of other things .Big automobile companies from Eupope ,the US and Japan all recognize that the first car is sold by sales personnel ,but the second car mainly relies on good post-sale service .
The automobile is a big product ,so it is very difficult to fulfill all kinds of post-sale service only depending upon manufaturers .Usually ,a service network undertakes all technical service for manufacturers.In foreign countries ,the post-sale service network is usually linked with sales network .So it can provide technical service while selling automobile .And the post-sale service network is composed by distributors ,agents and repairing shops .
Post-sale service itself belongs to the technical service category.
Automobile is hightly technology-intensive ,so the post-sale service includes technical guidance ,technical consultation ,and technical demonstration and so on .Main points which need to be introduced to the society ,dealers ,post-sale service network and customers are completely done by post-sale department .
On the other hand ,as a post-sale service man ,one should make sure that you have satisfied your customers when doing your work ,and should make it clear that you want to know if there are any problems with you work ,no matter when they develop .
Since you made the project ,you are naturally the best person to service it ,if and when the need arises .Make this clear to your client .Nobody likes callbacks ,and if you’ve done your job well ,you should have few ,if any ,for months or years after the installation or delivery.But let the client know that for repairs that result from ordinary use ,you’ll be glad to keep your work looking and working like new---for a modest fee ,of course .
If ,however ,problems arise that are clearly due to shoddy workmanship ,it is incumbent on you to correct them free of charge .This is ,of course ,perhaps the best reason to get it right the first time .
There’s no trick to determine whether you are being called back because of a problem due to you workmanship or the client’t use of the unit .Like everything else we’ve covered in this series ,doing right by your customers is just a matter of honesty .Put honesty into practice as part of your selling system and you’ll find that it is the best way to do what is right for your business ,too .
A checklist for maintaining good customer relations:
Do anything you can to help the client visualize in advance how the finished project will look .
Don’t give ballpark prices unless you already have a well established relationship with the client .
Use customers as references ,but only when you are sure they are totally satisfied.
Tell customers you want to know if there are problems with your work and that you can provide any routine service .
In everything you do ,be honest with your client .
Automobile callback system originated from the U.S in 1960s .Now it is not new in the U.S.,European countries ,Japan and South Korea .The U.S.has the longest history of automobile callback and the most strict regulations .Until now ,the American grand has totally recalled more than 200 million vehicles since 1966 ,and more than 24 million tires ,including passenger vehicle ,trucks ,buses ,motorcycles and so on ,And nearly all auto manufactures in the world have recalled cases in the U.S.
China’s Flaw Automobile Prosuct Management Stipulation was implemented since October1 ,2004 .Automobile is the machine which is assembled by tens of thousands of components and it is not strang to have this kind of flaw or that kind in materials or designs .But most flaws are recessive ,so they will be gradually exposed after using a period of time and people can then realize the flaw’s existence .Sometimes some batch of vehicle components processing ,assembly or material formula change ,and they possibly bring the flaws .The scope of callback system is extremely explicit ,that is the flaw has to be associated with safety and should appear in the batch .Recall system mainly aims at the systematic and unified flaws which are related with safety and existing in one batch of vehicles .The goal of the automobile recall is to eliminate the flaw and hidden danger ,ensure the public security ,the public benefit and the social economic order .
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