A coil for every plug

An ignition system featuring an individual coil for each sparking plug is being introduced by Scania's car manufacturing sister, Saab, next month. It does away with the distributor and ignition cables.

A much stronger spark is claimed as a result of working on the high-tension side at 40, 000 volts instead of the more usual 25, 000 volts. As a result the sparking plugs points can be gapped at up to 1.5mm. The generation time for the ignition voltage, one micro second, is 20 times faster than is provided by ordinary systems, says Saab.

The 400 volts supplied to the igni­tion coils on the plugs is described as " relatively low" and is not stepped up to the ignition voltage until the moment of firing.

There is a useful booster system for cold starting in which about 50 sparks are delivered to each plug whenever the engine is started. According to Saab tests, this high intensity spark­ing burns away moisture or deposits on the electrodes and insulators of the plugs. As soon as the engine speed exceeds 600 r.p.m. the Saab ignition system switches automatically to its normal mode. Then, when the engine is switched off; the Saab ignition system supplies something like 1.000 sparks to all the cylinders simultaneously in a purging operation designed to ease subsequent restart.

Another refinement is monitoring of the combustion behaviour in each cylinder. If misfiring or pre-ignition should be detected the microprocessor can modify the ignition timing for the misbehaving cylinder, or through the link with the fuel injection control, increasing the fuel supply. This affords the ability to run on a wide range of fuels without knock - 92 to 98 octane.

Задание 2. Передайте содержание текста на английском языке.

При ответе используйте следующие слова и словосочетания:

an ignition system, a coil, a sparkling plug, a booster system, cold starting, a refinement, an ignition timing.

Текст 21

Задание 1. Слушайте и повторяйте:

Задание 2. Найдите соответствующий вариант перевода каждого английского словосочетания:

A. Traction electric motor; high speed engine; racing car; driving wheels; to propel the car; road wheel; tractive effort; road speed; carriage unit; power train; gear box; live axle; dead axle.

B. Ведущая ось; тяговое усилие; гоночный автомобиль; ведущие колеса; неподвижная ось; коробка передач; силовая передача; тяговый электродвигатель; приводить в движение автомобиль; ходовое колесо; транспортная установка; скорость движения; высокоскоростной двигатель.

Задание 3. Прочтите текст " Functions of the Power Train" и ответьте на следующие вопросы:

1. Какие функции выполняет силовая передача?

2. Какие три основные категории механической силовой передачи Вы знаете?

FUNCTIONS OF THE POWER TRAIN

It is known that the internal combustion engine, as used in motor - cars and lorries, has the following characteristics.

1. It has to be started by the application of external energy.

2. Its maximum torque is small compared with that of a steam engine or traction electric motor of the same maximum horse power.

3. It is a comparatively high - speed engine, its maximum power being developed at speeds ranging from about 1, 000 r.p.m. in lorries up to 6, 000 r.p.m. in racing cars.

These characteristics have their effect on the nature of the transmission, causing to bе very different in many respects from that of a steam-engined vehicle.

The engine is arranged to be disconnected from the driving wheels when being started.

Once started the engine has then to be connected to the driving wheels so as to propel the car along. This connection must be accomplished smoothly and without shock so that the passengers are not incommoded or the mechanism of the car damaged.

The torque developed by the engine is then transmitted to the road wheels where it gives rise to a propulsive force, or, " tractive effort", between those wheels and the road. When the vehicle is starting from the rest a large tractive effort is required in order to accelerate rapidly. This necessitates the introduction of considerable " leverage" between the engine and the driving wheels so that small torque will produce a large tractive effort. This large leverage is also required when climbing hills or traversing very rough.

It is necessary, however, to be able to vary this leverage, because if the same leverage was used when travelling on the level or when climbing steep, hills maximum speed possible would be unduly low.

A large leverage implies a large reduction in speed bet­ween the engine and the driving wheels and at quite moderate road speeds the engine. Speed would be very high. But at high speeds the engine torque falls off so that the tractive effort would be reduced and the road speed limited.

The engine is universally carried on the frame of the carriage unit while the driving wheels are carried on axles attached to the frame by springs.

The power train must therefore:

1. Enable the engine to be disconnected from the driving wheels.

2. Enable the engine, when running, to be connected smoothly and without shock to the driving wheels.

3. Enable the leverage between the engine and the driving wheels to be varied.

4. Reduce the speed of the engine in the ratio of about 4 to 1 in passenger cars and in a greater ratio in lorries.

5. Turn the drive round through 90'.

6. Enable the driving wheels to be driven at different speeds.

7. Provide for the relative movement between the engine and the driving wheels due to flexing of the road springs.

These requirements can be met in a number of constructions working on different principles.

Thus power train systems may be classified under three heads:

1. Mechanical.

2. Hydraulic.

3. Electrical and electromagnetic.

Of these the first is the commonest, but hydraulic power trains are now being used to a considerable extent in lorries and coaches.

Electric power trains have been used for road vehicles but they are no longer made; they are, however, extensively used in diesel-electric locomotives and have been used in tanks. Both hydraulic and electric power trains nearly always incorporate mechanical components; with the former, in fact, the hydraulic portion merely replaces the clutch and gear- box of a mechanical power train.

Mechanical power trains are very numerous, but the majority falls within the following categories;

1. Clutch, gear -box and " live" axle power trains.

2. Clutch, gear -box and " dead" axle power trains.

3. Clutch, gear -box, axeless power trains.

A very large percentage of the passenger cars and lorri­es in use today are provided with power trains of the first type, but since all the types have in common the clutch and gear box the constructions of those components may be considered without reference to the power - train systems in which they are to be used.

Задание 4. Закончите следующие предложения, используя текст.

1. The engine is arranged...

2. The torque developed by the engine is transmitted to...

3. This necessitates the introduction of considerable “leverage”...

4. A large leverage is also required...

5. A large leverage implies...

6. The power train must...

7. The power train systems may be classified...

8. Electric power trains have been used for...

9. Mechanical power trains are...

Задание 5. Найдите отвeт, соответствующий содержанию текста.

1. What is the function of the power train?

2. What can a power train provide?

3. Of what parts does the standard train consist?

4. What function does the transmission fulfil?

5. What kinds of transmissions are mostly used in modern vehicles?

6. What do the mechanical transmission comprise?

7. How are the components of transmission arranged?

Задание 6. Используя текст " Functions of the Power Train", перечислите функции силовой передачи.

При ответе используйте следующие выражения:

the subject of the discussion is...; I know that...; it should bе noted, that...; the text deals with...; as for the problem of...; it should be noted, that....