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Since the working surface of the cylinders is a subject to wear in the course of operation due to the side pressure of the pistons the cylinder block is enlarged. In order to avoid the subsequent replacement of the cylinder block, liners are pressed into the cylinders to be worked in the same way as the original cylinder.
Modern constructions are designed for cylinder liners from the beginning. There are either dry cylinder liners surrounded by a grey-cast iron or light-metal jacket, or wet liners, the centre of which is surrounded by the cooling water.
A copper-asbestos or iron-asbestos gasket is placed between the surfaceground cylinder block and cylinder head. The gasket is required to seal all the holes such as an overflow opening for the cooling water, attachment bolts and the compression spaces from each other.
If a defective gasket is used, the combustion gases will enter adjacent cylinders. Instead of the fuel-air mixture produced in the carburetor, gases from the adjacent cylinders are sucked in during the intake stroke and the mixture ratio becomes, unfavorable. The service life of the engine becomes shorter.
In the gasket is leaky and the cooling water enters the cylinder space there may be serious damages or total destruction of the engine.
Engine control comprises all the parts of an internal-combustion engine controlling the cycle of the strokes. Depending on the type of the control members, a difference is made between valve timing gear and port control (for the two-stroke cycle system only).
Tasks
1. Translate the terms:
working surface, pistons, liner, dry liners, wet liners, cooling water, gasket, to seal, hole, overflow opening, combustion gases, mixture ratio, the service life, leaky, valve timing gear, port control.
2.Write out the terms unknown to you.
3.Find out the attributes to the following nouns:
surface, pressure, cylinder, constructions, liners, iron, jacket, water, opening, water, bolts, spaces, gases, mixture, stroke, ratio, engine.
4.Make a list of words unknown to you.
5.Write out all the verbs in the text in Present Simple Active.
6.Write out all the verbs in Present Simple Passive.
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7.Find out the Infinitive in Passive Voice.
8.Find out the Modal Verb in the text. Define its form.
9.Find out the Participle II and write out them.
10.Find out the verb in Future Simple Active.
11.Make these sentences negative:
1.Modern constructions are designed for cylinder liners from the very beginning.
2.The working surface of the cylinders is subject to wear.
3.The center of liners is surrounded by the cooling water.
4.A copper-asbestos gasket is placed between the surface-ground cylinder block and cylinder head.
5.The gasket is required to seal all the holes in overflow opening, attachment bolts, and compression spaces.
6.The mixture ratio becomes unfavorable.
7.There may be serious damages or total destruction of the engine.
8.Engine comprises all the parts of an internal-combustion engine.
9.A difference is made between valve timing gear and port control.
12. Answer the questions:
1.What can be worn?
2.What can be enlarged?
3.What can be wet and dry?
4.Why is the working surface of the cylinder the subject to wear?
5.What are the liners pressed into the cylinders for?
6.What are cylinder liners are?
7.What are cylinder liners made of?
8.In what case will the combustion gases enter the adjacent cylinders?
9.What may happen if the gasket is leaky?
10.What parts of an internal-combustion engine does engine control comprise?
13. Reproduce the sentences from these prompts.
1. Since ... surface ... is ... to wear in the course of operation due to the ... of the pistons, the cylinder ... is enlarged.
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2.There are either ... cylinder ... surrounded by a ... iron, or wet ... , the center of which is ... by the ... water.
3.The gasket is ... to seal all the holes such as ... for the ... water, ... bolts and the ... spaces from ... .
4.If a ... gasket is ... , ... gases will ... cylinders.
5.The ... life of the ... becomes ... .
6.A difference is ... between ... timing ... and ... control.
14. Fill gaps with correct verb tense.
1.The cylinder block (to enlarge).
2.Liners (to press) into the cylinders.
3.Modern constructions (to design) for cylinder liners from the very beginning.
4.The combustion gases (to enter) the adjacent cylinders.
5.Gases from the adjacement cylinders (to suck in) during the intake stroke.
6.The mixture ratio (to become) unfavourable.
7.If the cooling water (to enter) the cylinder space, there (to be) serious damages of the engine.
15.Make a plan of the text.
16.Compose a short summary of the text using the next phrases:
The text informs about ...
From the text we learn that ... .
It should be mentioned ... .
The text runs about ... .
In conclusion it should be summarized that ... .
Unit VI
Valve timing gear
The valve timing gear of the four-stroke cycle engine operating with vertical valves comprises the following components: camshaft, tappets, valves with springs, spring plates and valve cones .
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In case of the valve-in-head engine the following components are additionally required: the valve push rods and the rocker arms with the rocker bearings. If the camshaft is arranged above the valves, the tappets and the valve push rods are not required.
The port control used for two-stroke cycle engines is based on the opening and closing of ports in the cylinder wall by means of the top or bottom edge of the piston. In contrast to the valve timing gear, this type of control is not requiring any parts additionally to be moved.
Main component of the valve timing gear is the valve. It is a plate-like blocking device equipped with a valve face, valve disk and a valve stem. Opening of the valve is forcibly actuated by lifting its stem via the tappet by the cam of the camshaft. The valve is closed by the valve spring.
The filling rate of the cylinders and the engine are subject to the design and mode of operation of the valve mechanism. In order to achieve a leak proof seal of the valve, the entire actuating mechanism of the valve timing gear must have a clearance. For clearance adjustment, either the tappets or the rocker arms are equipped with adjusting screws or eccentrics. The extent of the clearance is a subject to the degree of heating and the length of the valve stem.
The valve mechanism, with vertical valve arrangement is the most simple, because it is operating with a minimum of components. The camshaft is supported in the crankcase actuates the valve tappet guide in a bushing arranged in the crankcase. The tappet movement is transmitted to the valve stem. The valve stem moves in the valve guide forced into the cylinder block with good fit and is held by the valve spring.
Tasks
1.Read and translate the following words and word combinations. Pay attention to their pronunciation:
gear, valve timing gear, four-stroke cycle engine, camshaft, tappets, springs, plates, cones, push rod, rocker arm, bearings, rocker bearings, edge, device, valve face, actuated, forcibly, via, rate, clearance, seal, adjustment, screw.
2.Guess the meaning of the words and word combinations given below: four-stroke cycle engine, vertical, components, cones, valve-in-head engine, push rod, port control, opening, closing, bottom, top, blocking device, valve face, valve disk, lifting, mode, valve mechanism, actuating mechanism, clearance, eccentrics.
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3.Underline all the verbs in the first passage.
4.Make a list of regular verbs and give their 3 forms.
5.Make a list of irregular verbs and give their 3 forms.
6.Underline all the Participles I and Gerund.
7.Make a list of attributes before the noun determined.
Pay attention to the nouns in the function of attribute. Example: the valve mechanism, intake stroke, power stroke.
8.Make sentences negative and interrogative.
1)The tappets and the valve push rods are not required.
2)Camshaft is arranged above the valves.
3)The port control is based on the opening and closing of ports.
4)The main component of the valve timing gear is the valve.
5)A blocking device is equipped with a valve face, a valve disk and a valve
stem.
6)The valve is closed by the valve spring.
7)The actuating mechanism must have a clearance.
8)The valve mechanism is operating with a minimum of components.
9)The camshaft is supported in the crankcase.
9.Make a list of special terms you have already known.
10.Make a list of special terms unknown to you.
11.Give synonyms to the next words:
to operate, to comprise, components, to require, push rod, top, bottom, edge, device, to equip, to lift, rate, design, entire, screw.
12. Read the text for the second time and find the answers to the next questions:
1)What components does the valve timing gear compose of?
2)What components are required in case of the valve-in-head engine?
3)What is not required if the camshaft is arranged above the valves?
4)What is the port control used for two-stroke cycle engines based on?
5)What mechanism is the main component of the valve timing gear?
6)What does a blocking device look like?