齿轮泵侧隙卸荷的界定标准与验证

为解决当前泵用齿轮副侧隙大、小界定含糊的问题,基于侧隙传动与困油的性能要求,从双齿啮合区内的2困油容积连通和单齿啮合区卸荷的性能完善方面,通过困油循环及困油过程的分析,建立出2类区域内的困油流量及峰值,推导出卸荷用侧隙、连通用侧隙及其均值和峰值;并进行实例运算和验证分析。结果表明:卸荷区与连通区的困油流量峰值比为3,前者的卸荷负担最大;连通区的真正连通,所需侧隙高达2.41 mm,实际上并不存在;卸荷侧隙大于连通侧隙,以连通侧隙作为侧隙大与小的分界点,卸荷侧隙作为上限值的界定可行;计算与试验的侧隙误差为7.5%,比较吻合,且上限值有20%的安全裕度,比较可靠等。泵用侧隙的界定为大、小侧隙的正确区分提供了参考,也可为后续的相关研究提供参考。

Demarcated standard and verification of backlash relief in external gear pumps

The gear pumps are used for pumping the working fluid, and its key component is a pair of gear pairs. In the power transmission, the backlash of the gear pair is used to form the lubricating oil film to avoid sticking due to the friction and heat expansion of the gear teeth, but it also affects the stability of the oil film. The choice of backlash in the gear pump is also limited. The backlash of the gear has an influence on the trapped oil performance and volumetric efficiency of the gear pump, while the definition whether there is a backlash existed and the definition what is large backlash and what is small backlash is vague. Based on the common requirements of different backlash values to transmission performance and trapped oil performance, the special trapped-oil circulation and trapped-oil process were analyzed in this study, and the emphasis was on the double teeth meshing range and the single tooth meshing range. From the connection aspect of two different trapped-oil volumes in double teeth meshed range and the improvement aspect of trapped oil performance in single tooth meshed range, we used to separately calculate dynamic trapped-oil flow rate and its maximum value under the two different ranges of double teeth meshing and single tooth meshing, as well as the different formulas to separately calculate dynamic backlash values, its mean value, its lower limiting value used for the connection in double teeth meshed range, and the relief in single tooth meshed range. From such exercises, we derived the definition what was large backlash and what was small backlash. The backlash therefore was defined as, a small backlash was when the backlash value was less than the maximum peak of the backlash for connection, and when the backlash value was greater than the maximum peak of the backlash for connection and less than the maximum peak of the backlash for trapped oil relief, it was a large backlash, and when the backlash value was greater than the maximum peak of the backlash for trapped oil relief, it belonged to the large backlash. An instance of an external gear pump which backlash was 30, 50, 200μm, was operated and its operation results were analyzed by the theory we developed. The results showed that when the trapped oil flow peak ratio of the unloading area and the connected area was 3, the unloading burden of the former was large. In fact, the really communicating to the communication area required up 2.41 mm backlash, which did not actually exist. So the gear pairs used in gear pumps was the gear pairs with backlash forever. The absolute connection of each other of two different trapped-oil volumes in double teeth meshed range and the absolute trapped-oil relief in single tooth meshed range were nonexistent, but only relatively existed under a certain permission pressure difference. As long as the trapped-oil relief requirement in single tooth meshed range was satisfied by an adopted backlash value, then the connection of two different trapped-oil volumes each other would naturally be met by the adopted backlash value. Backlash for trapped oil relief was larger than the backlash for connection, which can be used in definition what was large backlash and what was small backlash, and the backlash for trapped oil relief can be used as the upper limit. The error in the calculation and experiment was 7.5%, which was reasonable, and the upper limit of the safety margin was 20%, which was reliable. This research provided a reference for distinguishing large backlash between small backlash by Pump backlash defining, and which also provided a theoretical basis for the subsequent studies.