| The high pressure common rail injection system possesses the excellent ability to improve the emission and economic performance of diesel engines, it presents the developing direction of fuel injection system for diesel engine and is the necessary way to make diesel engine reach more rigorous emission laws. The electro-hydraulic injector is one of the most important components of high pressure common rail injection system, the latter must rely on it to realize its excellent functions.Based on consulting and researching extensive related literatures issued by international and domestic organizations, this paper summarizes the history of electronic controlled fuel injection system of diesel engine, the principle and advantages of high pressure common rail injection system and its representative products of foreign countries, then introduces the structure and principle of representative electro-hydraulic injector made by west developed countries in details.In this paper, an electro-hydraulic injector designed by the author is introduced detailedly. This injector can realize the perfect fuel injection rate that is called ⊿-shaped which means beginning injection with a slow-acting rate and then ending the injection suddenly. This kind of injector can reduce the harmful emission quantity from diesel engines.The author has made a study of how to calculate the impact stress of the needle seat by adopting the stress wave theory and methods. Moreover, the author analyzed and researched dynamic load of the needle valve spring by adopting the method of characteristic line and proposed to design the needle valve spring using its dynamic load.At last, in order to resolve the problem of required high degree of accuracy and very difficult to manufacture, the statistical tolerance law was adopted to design the key constructer's size chain, which may enhance the product's economic and technical performance. |
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