Principle of Operation of the Four-Stroke Petrol Engine
Емтихан (25 минут)
1 нұсқа
Тапсырма: Мәтіні оқып шығу және аудару
TEXT
Automobile Production
I study at the college, at the automobile-construction department. When I graduate from the college I shall become a technician. All specialists in automobile industry dealing with manufacturing automobiles (cars or trucks) must know that the production of the automobile comprises the following phases:
-designing;
-working out the technology of manufacturing processes;
-laboratory tests;
-road tests;
-mass manufacturing (production).
Why is it necessary to know all these facts? It is important to know them, as before the automobile is put into mass production it should be properly designed and the car must meet up-to-date requirements. What are these requirements?
The automobile must have high efficiency, long service life, driving safety, ease of handling and maintenance, pleasant apperance. Also it must be comfortable and ecological. In order to obtain these qualities the specialists should develop up-to-date methods of designing cars using new types of resistant to corrosion light materials. Also it is important to know computer sciences because computers offer quick and optimal solutions of the problems. Besides they are used for better operation of mechanisms in cars.
Before the car is put into mass production the units of the car are subjected to tests in the Works laboratory and then the car undergoes a rigid quality control in road tests. Why are these tests required? What qualities are required of the automobile? They are needed because the modern automobile must be rapid in acceleration, have smooth acting clutch, silent gearbox, dependable braking and steering systems, dependable ignition system, low fuel consumption and be stable on the road.
Емтихан (25 минут)
2 нұсқа
Тапсырма: Мәтіні оқып шығу және аудару
TEXT
Components of the Automobile
The automobile is made up of three basic parts: the power plant, or the engine, the chassis and the body.
The engine is the source of power that makes the wheels rotate and the car move. It includes fuel, cooling, lubricating and electric systems. Most automobile engines have six or eight cylinders
|
|
|
The chassis includes a power train (power transmission), a running gear, steering and braking systems as well.
The power train carries the power from the engine to the car wheels.
The power transmission, in turn, contains the clutch, gearbox, propeller or cardan shaft, final drive, differential, rear axle and axle shafts. The running gear consists of a frame with axles, wheels and springs.
The body has a hood, fenders and accessories: the heater, stereo tape recorder, windshield wipers, conditioner, speedometer and so on.
Емтихан (25 минут)
3 нұсқа
Тапсырма: Мәтіні оқып шығу және аудару
TEXT
Chassis
The main units of the chassis are: the power transmission, the running gear and the steering mechanism. The power transmission includes the whole mechanism between the engine and the rear wheels. This entire mechanism consists of the clutch, gearbox, propeller (cardan) shaft, rear axle, final drive, differential and axle shafts.
At the front end of the car is the engine. On the back of it is the flywheel. Behind the flywheel is the clutch. The clutch is a friction device connecting the engine with the gears of the gearbox. The main function of the gearbox is to change the speed of the car.
The power is always transmitted by the cardan shaft to the live back axle. The final drive reduces the high speed of the engine to the low speed of the driving wheels. The differential enables the driving wheels to turn at different speeds which is necessary when turning the car. The foundation of the automobile is the frame to which different chassis units are attached.
The rear axle is capable of moving up and down about the frame. The rear axle is an important part of the transmission. It carries the greater portion of the weight of the car.
The steering mechanism is designed for changing the direction of the car.
The brakes are used for stopping the car, for decreasing its speed and for holding the car position.
Емтихан (25 минут)
|
|
|
4 нұсқа
Тапсырма: Мәтіні оқып шығу және аудару
TEXT
Frame
The foundation of the automobile chassis is the frame which provides support for the engine, body and power-train members. Cross members reinforce the frame. The frame is rigid and strong so that it can withstand the shocks, vibrations, twists and other strains to which it is put on the road.
The frame provides a firm structure for the body, as well as a good point for the suspension system. There are two types of frames, namely: conventional frames and integral (unibody) frames (frameless constructions).
Conventional frames are usually made of heavy steel channel sections welded or riveted together. All other parts of the car are attached to the frame.
In order to prevent noise and vibrations from passing to the frame and from there to the passengers of the car, the frame is insulated from these parts by rubber pads.
It is also important to insulate the frame in order to prevent metal- to-metal contacts.
Frameless (unibody) constructions are called so because they are made integral with the body. The body parts are used to structurally strengthen the entire car. Some unibody frames have partial front and rear frames for attaching the engine and suspension members.
Емтихан (25 минут)
5 нұсқа
Тапсырма: Мәтіні оқып шығу және аудару
TEXT
Clutch
The clutch is a friction device. It connects the engine to the gears in the gearbox. It is used for disconnecting the engine from the gearbox, for starting the car and for releasing the engine from the car wheels.
The clutch is fixed between the flywheel of the engine and the gearbox und consists of two plates (discs): the friction disc and the pressure disc. The friction disc is situated between the flywheel and the pressure plate and has a hard-wearing material on each side.
The basic principal operation of the clutch is a frictional force acting between two discs. The clutch is controlled by the clutch pedal. When the pedal is at rest the clutch is engaged and the running engine is connected to the gearbox. When the pedal is pressed down the clutch is disengaged and the engine runs idly.
|
|
|
Емтихан (25 минут)
6 нұсқа
Тапсырма: Мәтіні оқып шығу және аудару
TEXT
Gearbox
The gearbox is placed between the clutch and the propeller shaft. I lie principal function of the gearbox is to vary the speed of the car movement to meet the road conditions. The gearbox provides four forward speeds and one reverse, as follows:
1. First or low gear;
2.Second gear;
3.Third gear;
4.Fourth or top gear;
5.Reverse gear.
There are many constructional arrangements of gearboxes, which can be classified as follows:
1.Sliding-mesh type;
2.Constant-mesh type;
3.Epicyclic (planetary) type.
The sliding-mesh type is the simplest one and is the oldest historically. The constant-mesh type is the most widely used type. They are termed "ordinary" gearing, the characteristic feature of which is that I lie axes of the various gears are fixed axes. The gears simply rotate about their own axes.
The characteristic feature of epicyclic (planetary) gearing is that one gear rotates about its own axis and also rotates bodily about some other axis.
To secure the several speeds of the car the clutch shaft is mounted In direct line with the gearbox shaft. The gearbox shaft carries on it the sliding gears which are used for shifting to secure the forward speeds and the reverse drive.
Емтихан (25 минут)
7 нұсқа
Тапсырма: Мәтіні оқып шығу және аудару
TEXT
Brakes
Brakes are used to slow or stop the car where it is necessary. It is one of the most important mechanisms of the car as upon its proper performance the safety of passengers depends. Car brakes can be divided into two types, namely: drum brakes and disc brakes. The drum type may be either a band brake or a shoe brake. Depending on their functions, the automobile has foot brakes and hand brakes (parking brakes). According to their mode of operation, the brakes are classified as: mechanical brakes, hydraulic brakes, airbrakes, electric brakes. Brakes are controlled by the brake pedal.
|
|
|
Most braking systems in use today are hydraulic. This system consists of a master cylinder mounted on the car frame and wheel cylinders. When the driver pushes down on the brake pedal, it forces the piston to move in the master cylinder and brake fluid is delivered from 11 to the wheel cylinders. The piston movement causes brake shoes to move and the brakes are applied (the brake shoes are pressed against the brake drums).
The air brake uses compressed air to apply the braking force to the brake shoes.
Electric brakes use electromagnets to provide the braking effort against the brake shoes.
Formerly brakes were applied only to the two rear wheels, but now all cars are equipped with all-wheels brakes. Today many improvements are being made in brakes.
Емтихан (25 минут)
8 нұсқа
Тапсырма: Мәтіні оқып шығу және аудару
TEXT
Steering System
То guide the car, it is necessary to have some means of turning the front wheels so that the car can be pointed in the direction the driver wants to go. The steering wheel in front of the driver is linked by gears and levers to the front wheels for this purpose. The front wheels are on pivots so they can be swung to the left or right. They are attached by steering knuckle arms to the rods. The tie-rods are, in turn, attached (o (he pitman arm.
When the steering wheel is turned, gearing in the steering gear as- sembly causes the pitman arm to turn to the left or right. This movement is carried by the tie-rods to the steering knucle arms, and wheels, musing them to turn to the left or right.
The steering system incorporates: the steering wheel and column, steering gear, pitman arm, steering knuckle arm, front axle, steering knuckle pivot, tie-rods.
There are several different manual steering gears in current use, such as the rack and pinion type and the recirculating ball type. The rack and pinion steering gear is widely used. Another manual steering gear which is popular in imported cars is the worm and sector type.
The steering wheel and column are the source of injury to the driver, air bags and other devices being developed now to safe the life of a driver.
Energy-absorbing columns must stop the steering wheel and column from being pushed to the rear as the front of the car is crushed in an impact.
Energy-absorbing columns must also provide the driver with a tolerable impact as he moves forward and strikes the wheel with his chest.
Емтихан (25 минут)
9 нұсқа
Тапсырма: Мәтіні оқып шығу және аудару
TEXT
Principle of Operation of the Four-Stroke Petrol Engine
The internal combustion engine is called so because fuel is burned directly inside the engine itself. Most automobile engines work on a 4-stroke cycle. A cycle is one complete sequence of 4 strokes of the piston in the cylinder. The operating cycle of the four-stroke petrol engine includes: inlet stroke (intake valve opens), compression stroke (both valves closed), power stroke (both valves closed), exhaust stroke (exhaust valve is opened).
To describe the complete cycle, let's assume that the piston is at the top of the stroke (top dead center) and the inlet and the exhaust valves are closed. When the piston moves down the inlet valve opens to intake a charge of fuel into the cylinder. This is called the inlet (intake) stroke. On reaching the lowest position (bottom dead center) the piston begins to move upward into the closed upper part on the cylinder, (he inlet valve is closed and the mixture is compressed by the rising piston. This is called the compression stroke. As the piston again reaches the top dead center the spark plugs ignite the mixture, both valves being closed during its combustion. As a result of burning mixtures the both valves being closed during its combustion. As a result of burning mixtures the gases expand and great pressure makes the piston move back down the cylinder. This stroke is called the power stroke. When the piston reaches the bottom of its stroke, the exhaust valve is opened, pressure is released, and the piston again rises. It lets the burnt gas flow through the exhaust valve into the atmosphere. This is called the exhaust stroke which completes the cycle. So the piston moves in the cylinder down (intake stroke), up (compression stroke), down (power stroke), up (exhaust stroke).
The heat released by the fuel is transformed into work so that the reciprocating movement of the pistons is converted into rotary movement of a crankshaft by means of connecting rods.
Дата добавления: 2018-06-01; просмотров: 482; Мы поможем в написании вашей работы! |
Мы поможем в написании ваших работ!