The principle of operation of the engine DOHC

About 100 years ago in the automobile factory Peugeot employed four engineers, who at the same time, there were riders: Paul Zukkarelli, Jules Gu, Georges Buallay, Erno Henry - in that time called "Gang of Four". This quartet has a nickname for the rapid want any ways to get what they want done. Together they wanted to, engaged in design, construction and test of the new racing Motor racing: Double overhead cam-shafts - DOHC, with established two camshafts in the cylinder head for each cylinder it had four valves (4 valves). At that time there were almost no high-speed engine (maximum speed was about 2000 per minute) - massive and heavy rocker, long radius arms hardly moved the valve springs. In this article we would like to tell you about the principle of the engine DOHC. Time passed and the "gang of four" its still made. Racing cars of Peugeot started to win competitions more often. Similar design were copied brands such as "Ballo", "Sunbeam", "Vauxhall", "Salmson" and many other smaller companies. Experience proved that this decision despite the technical complexity, it is very profitable. While it was common opinion - than the more complicated mechanism, so it is safer. There were a lot of simple designs, which because of its simplicity, the calculation of the imperfect loads, insufficient lubrication, or errors in the selection of materials for manufacturing - quickly fell into disrepair. For such a new idea immediately took hold and builders of aircraft engines. Very reliable and fairly complex aircraft engines were quickly scale production. (As an example, like to quote a famous motor A. Mikulina which production started in the early 30's.) Many automobile manufacturers also produce engines of this type, but the number of registration had not been a large scale. The first domestic car was released by the Minsk factory MAZ-525 with diesel engine D-12A, it had two camshafts with four valves installed. It is not excluded that the force DOHC engine would remain the lot of sports and racing cars, but the desire to raise the capacity of small car and the oil crisis combined with the struggle to reduce emissions were the impetus to seek alternatives. When the car-sewed the latest technology, the fear disappeared complex structures. In the early nineties in a row started and carried chetyrehklapannye twin-shaft engines. To date, about fifty firms produce these motors. However, mass production makes their challenges. In order to ensure the drive in the cylinder head of the two camshafts can use a chain timing belt or a set of gears. Strap cheaper in the issue, does not require lubrication, has almost no noise, but if it terminates, it will be a catastrophe for the entire engine: valve that does not controlled, will face on the piston, and both will be destroyed, causing harm to the cylinder liner and block. Chain, despite its noise is much more reliable. A disadvantage may be only a gradual stretching. Device for automatic tension easily solve this problem, but for the chain, which should always be in the oil, as needed, and sealed the oil sump. A set of gears, in turn, is very reliable, but noisy and complicated. By constructivizable currently rating looks like this: above all - a belt, then - the circuit and completes the list of gear. If the execution of any of the mechanisms will not be good enough, then its owner will be very disappointed at failure on the road. In the case of correct execution of the driver, it is likely at all forget to ask how his device works drive in the system DOHC. On why four valves per cylinder, it's a good idea, it already was. But do not forget: the greater the degree of compression - the higher the efficiency of the engine. It is not surprising that now manufactured engines are produced with high compression ratio. In such cases the most convenient form of the combustion chamber is hemispherical, which turns into a segment of the population. But not for all this construction is acceptable. Therefore we must seek a compromise. On one side of the combustion chamber needs to be done in the form of a ball, on the other side "tent" should be rounded and sloping. This can be achieved only through a decrease in the angle between the exhaust and intake valves. In general, the producers gave themselves setting: the degree of compression above - the angle between the valves is less. If the cylinder will be installed on the four-valve, the only place where you can put a candle - it is a combustion chamber cavity in the center. These gas channels to increase the height of the cylinder head so that the candle will be located at the bottom of a deep well. Screw and unscrew it from there can only be a special key. You can of course to silence the cavity over a candle something useful, for example, individual ignition coils, above all cover the top lid. In such a situation in rainy weather, all arrangements will remain dry. Time-consuming adjustment could not please the racers and their mechanics. Designers had invented a considerable number of different smart devices to adjust, but they were only able to weight the valve actuator, with all the advantages of DOHC went awry. Decision came just in time. In the gap between the tappet and stakanchikovym "neck" valve apply pressure from the lubrication system - oil. This gap should always be present, regardless of whether hot or cold engine, valve seat is worn or not. In other words, the basic principle of the DOHC engine has a hydraulic drive, which is still used on most engines mounted with a valve mechanism - from the "Opel Corsa" to "the Cadillac Northstar."