| 摘要 |
PURPOSE:To reduce driving energy for the pump by a method wherein a pressure, applied on one of side plates, is controlled to the same value as a discharging pressure while the revolving number of the pump is low, and the same is controlled to a value lower than the discharging pressure of the pump during while the revolving number of the pump is high. CONSTITUTION:When the revolving number of the pump is increased, a land 28b communicates a communicating port 24 with a chamber 31 so as to increase the degree of communication gradually while decrease the degree of communication between the communicating port 25 and a chamber 32. The chamber 31 is being communicated with a pump suction port 6, therefore, a pressure in chambers 20, 21 is reduced gradually to an extremely low pressure same as the pressure in the pump suction chamber. Accordingly, the pressing forces of the side plates 16, 17 against the opposing side surfaces of gears 3, 4 are reduced gradually, leakage of operating fluid from both sides of the gears is increased gradually and, therefore, the volumetric efficiency of the pump is prevented from being kept in too high beyond necessity and the driving energy for the pump may be reduced. |
