Measurement And Analysis Of Slip Characteristics In Cam-roller Units Of Internal Combustion Engines Based On Giant Magnetoresistance Sensors

The Cam-roller valve train is widely used in internal combustion engines.Compared with the sliding friction caused by the cam-tappet valve train,it greatly reduces the energy loss caused by friction.Cam-roller valve train has two important friction pairs: Cam-roller pair and roller-pin pair.Theoretically,the motion between the cam and roller is expected to be pure rolling.However,research has shown that the motion between the cam and roller is not purely rolling;there exists a sliding component between them.Studying the cam-roller unit involves considering multiple moving pairs,varying curvature radii,linear velocities of the cam and roller,as well as contact loads.If simulation techniques are employed for this research,it can be challenging due to the complexity of these factors.A Cam-roller slip measurement system is designed for a certain type of internal combustion engine valve train components of Weichai Power CO.,LTD.By changing the working conditions in the experiment,the causes of roller slip and the change of slip value are studied,the law of slip formation is summarized,and suggestions for suppressing slip are put forward.At the same time,the effect of the textured pin on the slip of the roller is explored.The following is the main work done:Investigate the types of valve trains for internal combustion engines,and understand the advantages and specific operation methods of Cam-roller valve trains.Design,check,and build a Cam-roller slip measurement system based on an internal combustion engine component.Through experiments,it is verified that the system can accurately measure the average rotational speed of the roller over a period of time,so as to carry out the rest of the experiments.Under the condition of full oil supply,the effect of 10W-30 on roller slippage was studied.The effects of different cam speeds,different ambient temperatures,and different initial pressures between the cam and the roller on the slippage of the roller were studied experimentally.With the increase of the cam speed,the roller slipping goes through three stages in turn: slight slipping,sharp increase of slipping,and gentle slipping.Raising a certain initial pressure and ambient temperature can suppress slippage.The occurrence of oil passage blockage can result in insufficient lubrication to the cam-roller unit,leading to delays in oil supply.Therefore,studying the patterns of roller slippage under non-sufficient oil supply conditions holds practical significance.Research has found that as the operating time of the cam increases,the slippage rate of the roller also increases.Higher loads can effectively suppress roller slippage.However,excessively high environmental temperatures can accelerate the loss of lubricating oil,leading to severe slippage.In both oil-rich and oil-deficient conditions,the occurrence of roller slippage has been observed.This paper proposes the preparation of different surface textures on the pin shaft to mitigate roller slippage.Research has revealed that depending on the specific texture applied,roller slippage can either be suppressed or aggravated.For textures that effectively suppress roller slippage,they act as micro-bearings in the contact area,improving lubrication and inhibiting slippage under sufficient oil supply conditions.Under non-sufficient oil supply conditions,these textures serve as reservoirs,reducing lubricant loss and delaying the growth of slippage.