Abstract: A gear•rear shaft containing main body of a bottomed type is penetrated with a bearing hole and a rear face of the gear•rear shaft containing main body is coupled with a closing plate to form an airtight seal from an outside environment. Shafts extended from two gears to a side of the rear face are set to be shorter than a length of the bearing hole in an axis core direction. Bushes are also set to a length that is the same as that of the shafts. The gear•rear shaft containing main body is formed with a recess portion at the rear face and the bearing hole is penetrated to open to the recess portion. The gear•rear shaft containing main body is bored to penetrate with a low pressure port communicating with a low pressure region in an axis core direction.

Abstract: A gear.rear shaft containing main body of a bottomed type is penetrated with a bearing hole and a rear face of the gear.rear shaft containing main body is coupled with a closing plate to seal in airtight from outside. Shafts extended from two gears to a side of the rear face are set to be more less shorter than a length of the bearing hole in an axis core direction. Bushes are also set to a length the same as that of the shafts. The gear.rear shaft containing main body is formed with a recess portion at the rear face and the bearing hole is penetrated to open to the recess portion. The gear.rear shaft containing main body is bored to penetrate with a low pressure port communicating with a low pressure region in an axis core direction.