The driving torque required for driving a rotary-vane vacuum pump is divided into a mechanical friction torque among the pump elements, a torque which is consumed by generation of oil pressure at the dead space (oil pressure torque) and a torque which opposes the differential air pressure on both faces of the vane (differential air pressure torque). Operating the vacuum pump with the object of keeping at a high vacuum in a steady state, we should design the rotary-vane vacuum pump so that the driving torque approaches the mechanical friction torque as much as postage, because there is little air flow.
In this study, we equipped pressure transducers inside the rotor of pump, and measured continuously the pressure variation in the working chamber. Based on the pressure variation, we investigated the characteristics of oil pressure torque and differential air pressure torque. Besides, we varied the outlet port timing and diameter of delivery tube of the system, and examined a method of reducing the torque due to the oil pressure and differential air pressure, and confirmed its effectiveness experimentally.

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