| 摘要 |
PURPOSE:To reduce driving power for a vane pump by a method wherein negative pressure is introduced to act in grooves for vanes in order to force the vanes to be kept sucked to the retracted positions respectively while no pressurized fluid of pump delivery is necessitated. CONSTITUTION:When no power assist by pressurized fluid discharged out of the pump 5 is necessitated any longer because of reduction in wheel resistance to the ground after a rolling stock starts traveling at accelerated speed, actuation of a speed detector switch 24 switches a solenoid controlled valve 20 to connect the vacuum line 18 to the negative pressure source 19. In this way, since negative pressure acts from the side 14B of the groove for each vane, each vane 13 is sucked to that position so that rotation of the rotor 12 does not function as normal pumping action. Therefore, pump delivery becomes almost none, and the driving load of the pump 5 can remarkably be reduced accordingly. |
