排气制动对配气机构的影响

Influence of exhaust braking on valve train

载货汽车排气制动时,通过关闭发动机排气管内蝶阀,提高排气管内压力来提高排气制动功。但提高排气管内压力会对配气机构产生不利影响,主要表现为排气门在压力的作用下容易受损。通过试验结合动力学仿真方法,对比排气制动系统开启与关闭时配气机构的动力学性能,预测凸轮摇臂飞脱及排气门“打顶”的风险。提出增大排气门作用力,以避免排气制动系统开启时摇臂飞脱及排气门“打顶”。

During the exhaust braking of the truck, the butterfly valve in the engine exhaust pipe is closed, and the exhaust braking power is increased by promoting the exhaust pressure. Increasing the exhaust pressure will have an adverse effect on the valve train, which is mainly manifested in the deterioration of the stress on the exhaust valve. Through the test method and dynamic simulation method, the dynamic performance of the valve train when the exhaust braking system is on and off is compared, and the risk of rocker arm losing contact and exhaust valve topping is predicted. It is proposed to increase the exhaust valve force to avoid the rocker arm losing contact and the exhaust valve topping when the exhaust braking system is opened.