刘 涛，祝传亮，高玉贵   

    摘要:发动机的爆压及升功率达到一定数值时，考虑到热负荷对活塞的影响，需增加喷油冷却，提高活塞使用寿命，增强发动机可靠性。为了避免活塞与喷油嘴的干涉，需在活塞裙部增加喷油嘴避让缺口，增加缺口后，如果设计结构强度不足，活塞裙部椭圆度设计不合理，缺口处容易出现应力集中导致产生裂纹。本文通过典型实例对活塞喷油嘴避让缺口的裂纹失效进行了全面的分析，并提出设计改进的思路。改进设计后的活塞经发动机台架试验验证后，避让缺口部位没有出现开裂，试验通过，改进效果明显。

    关键词: 爆压；升功率；可靠性；避让缺口；结构强度

    Abstract: When the maximum cylinder pressure and  the power per litre of a engine reach a certain value. Oil injection is used to cool the pistons so as to overcome heat load, prolonging the piston service life and enhance engine reliability. In order to avoid the interference of the nozzle with the piston, a cut for the oil injector is machined in the piston skirt. When the structure strength in the piston skirt is insufficient and if the skirt is not designed reasonably, stress may concentrate on the cut area, causing cracks. This paper analyzes comprehensively failure basing on typical examples and proposes ideas to improve design. The bench test shows that there are no cracks in the cut area of the piston after piston design is improved. 

    Key words: Peak Pressure；Power Per Litre；Reliability；Cut； Structure Strength