Based on the thermal balance principle, an optimal clearance formula of piston friction pair for water hydraulic pump was proposed. Simulation and experimental research were put forward on its influence factors, such as the structure size, couple material and environmental parameters. The results are as follows：a minimum thermal clearance exists in each piston friction pair, which must be smaller than its initial clearance, otherwise it will happen to death; there are some effective measures to reduce the minimum thermal balance clearance, such as decreasing the plunger diameter or swash-plate tilt angle, choosing the appropriate couple material, reducing friction coefficient and fully running-in, etc.

water hydraulic pump, friction pair, thermal balance, clearance, couple material

基于热平衡原理提出了水压泵柱塞摩擦副的间隙优化公式，对结构尺寸、对偶材料配对以及环境参数等影响因素进行了仿真和试验研究。研究结果表明:每对柱塞摩擦副都存在一个最小的热平衡间隙，水压泵柱塞摩擦副的初始间隙必须大于这一间隙，否则就容易发生卡死现象;减小柱塞直径或斜盘倾角、选择合适的对偶材料、减小摩擦因数和充分跑合都是减小最小热平衡间隙的十分有效的措施。

水压泵, 摩擦副, 热平衡, 间隙, 对偶材料