Abstract Continuously variable transmission (CVT) is commonly used in automobile to reduce fuel consumption and emission. Apart from wider gear ratio, reduction of friction loss in a radial direction of the pulley surface is an effective method of improving CVT efficiency. On the other hand, to improve torque transmission efficiency, high frictional force on circumferential direction of the pulley is necessary. Therefore, required frictional characteristics differ depending on sliding directions. To create friction anisotropy on belt-pulley contacts, laser surface texturing was proposed to improve friction characteristic and generates friction anisotropy on the surface. In this study, the relationship between surface texture and friction anisotropy was investigated under boundary lubrication by cylinder-on-disk type sliding test. The sliding test was conducted in four different directions, parallel, thirty degrees, sixty degrees, and perpendicular to the direction of the surface texture. Analysis of real contact area was conducted repeatedly in the sliding directions to evaluate change in interaction of asperities in sliding directions over time. The experimental results were then compared with result of the continuous analysis of real contact area. When a groove-type texture was created by a processing laser, texture pattern changes the sliding distance on the plateaus of the texture, which affects the level of metal contact on the surface, generating friction anisotropy. This hypothesis was supplemented by the continuous analysis of the real contact area, which confirmed that the sliding distance on the plateaus of the texture decreased as the sliding angle increased. Furthermore, clear correlation between sliding distance and friction force was observed, which suggests the possibility that friction anisotropy by surface texturing under boundary lubrication will be predicted by a friction force function.

中文翻译：

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边界润滑下表面织构摩擦各向异性的产生机制

摘要 无级变速器（CVT）常用于汽车以降低油耗和排放。除了更宽的传动比外，减少带轮表面径向摩擦损失是提高CVT效率的有效方法。另一方面，为了提高扭矩传递效率，需要在皮带轮圆周方向上施加高摩擦力。因此，所需的摩擦特性因滑动方向而异。为了在皮带轮接触上产生摩擦各向异性，提出了激光表面纹理化以改善摩擦特性并在表面上产生摩擦各向异性。在这项研究中，通过圆柱-盘式滑动试验研究了边界润滑下表面纹理与摩擦各向异性之间的关系。滑动测试在平行、三十度、六十度和垂直于表面纹理方向的四个不同方向上进行。在滑动方向上反复进行实际接触面积的分析，以评估滑动方向上的凹凸相互作用随时间的变化。然后将实验结果与实际接触面积的连续分析结果进行比较。当加工激光创建凹槽型纹理时，纹理图案会改变纹理平台上的滑动距离，从而影响表面金属接触的水平，产生摩擦各向异性。这一假设得到了对真实接触面积的连续分析的补充，证实了纹理平台上的滑动距离随着滑动角度的增加而减小。