Use of helical gear in gear pump is an effective measure, which can reduce the mechanical voice and flow pulse.

According to the volume oil formula of the straight gear pump, the volume oil formula of the helical gear pump is got and the helix Angle no trapping is found.

Analyze the Helical Gear Pump for the instant displacement, single gear displacement, theinstant change ratio and change value of trapping volume and the influnce of screw angle in detail.