Abstract This paper examines the effect of tappet insert clearance on the tribological and tribochemical performance of the camlobe/follower tribopair when lubricated in a fully-formulated oil containing 1 wt% of Molybdenum Dialkyl Dithiocarbamate (MoDTC). Tests were performed on a Single Cam Rig (SCR), taken from 1.25 l FORD Zetec (SE) engine. White Light Interferometry and Talysurf contact profilometry were used to characterise the wear scar on the tappet inserts and camlobes respectively. In addition, Scanning Electron Microscopy (SEM) was used on both (i.e. camlobes and tappet inserts) for wear mechanisms assessment as well as to access the durability of coatings used on tappet inserts. Energy-Dispersive X-ray (EDX) and Raman spectroscopy analyses were also used to understand the tribochemical interactions between oil additives and the cam/follower interface. Results show that the chemistry of the tribofilm derived on camlobes and tappet inserts vary as a function of tappet insert clearance and cam profile. Also, regardless of the type of coating, the smaller clearance of tappet inserts exhibited higher friction and wear. Therefore, based on this work, the use of the thicker tappet insert would be inadvisable as this possibly can cause higher fuel consumption and inefficient performance of the intake/exhaust valves of the engine.

中文翻译：

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挺杆嵌件和凸轮凸角之间的间隙对凸轮/从动件表面的摩擦学和摩擦化学性能的影响

摘要 本文研究了在含有 1 wt% 二烷基二硫代氨基甲酸钼 (MoDTC) 的全配方油中润滑时挺杆刀片间隙对凸轮凸角/从动摩擦副摩擦学和摩擦化学性能的影响。测试是在取自 1.25 l FORD Zetec (SE) 发动机的单凸轮钻机 (SCR) 上进行的。白光干涉测量法和 Talysurf 接触轮廓测量法分别用于表征挺杆嵌件和凸轮凸角上的磨痕。此外，扫描电子显微镜 (SEM) 被用于两者（即凸轮凸角和挺杆插入件）的磨损机制评估以及用于评估挺杆插入件上使用的涂层的耐用性。能量色散 X 射线 (EDX) 和拉曼光谱分析也用于了解油添加剂与凸轮/从动件界面之间的摩擦化学相互作用。结果表明，凸轮凸角和挺杆嵌件上产生的摩擦膜的化学性质随挺杆嵌件间隙和凸轮轮廓的函数而变化。此外，无论采用何种涂层，挺杆嵌件间隙越小，摩擦和磨损越大。因此，基于这项工作，使用较厚的挺杆嵌件是不可取的，因为这可能会导致更高的燃料消耗和发动机进气/排气门的低效性能。无论采用何种涂层，挺杆嵌件间隙越小，摩擦和磨损越大。因此，基于这项工作，使用较厚的挺杆嵌件是不可取的，因为这可能会导致更高的燃料消耗和发动机进气/排气门的低效性能。无论采用何种涂层，挺杆嵌件间隙越小，摩擦和磨损越大。因此，基于这项工作，使用较厚的挺杆嵌件是不可取的，因为这可能会导致更高的燃料消耗和发动机进气/排气门的低效性能。