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我厂生产的发动机,采用预置气阀结构,凸轮与挺杆端面间的接触应力及滑动速度都比侧置气阀发动机大得多。挺杆体如仍采用渗碳钢,尽管有较高的硬度及强度,但由于渗碳钢附油性能差,在高接触应力及滑动速度下很易出现擦伤,引起凸轮与挺杆这一对摩擦副的强烈磨损。根据试验结果以及参考国外有关资料,我厂生产的EQ240发动机采用渗碳钢气阀挺杆不能满足使用要求。因此,我们设计和试制了冷激铸铁气阀挺杆,经过多次工艺试验和二万五千公里行车试验,证明冷激铸铁气阀挺杆和中碳钢高频淬火凸轮之间的磨损都较小,工作性能良好,工艺简单,成本较低,是这类发动机气阀挺杆的一种较好材料。挺杆使用失效一般有下述几种情况:
I plant the engine, the use of pre-configured valve structure, the contact surface between the cam and tappet stress and sliding speed are much larger than the side valve engine. Rod body still use carburized steel, despite higher hardness and strength, but due to carburizing steel poor oil performance, high contact stress and sliding speed is prone to bruising, causing the cam and tappet of the pair Friction pair strong wear and tear. According to the test results and reference to relevant foreign information, I plant EQ240 engine carburizing steel valve tappet can not meet the requirements. Therefore, we designed and trialled the cold-shock cast iron valve lifter. After several process tests and 25,000 km driving test, we proved that all the wear and tear between the chilled cast iron valve lifter and the medium carbon steel quench cam Smaller, good work performance, simple process, low cost, is a good material for such engine valve lifter. Tappet failure generally have the following conditions: