Patent ID: 7455507

Claim:
A structure for preventing cavitation erosion of an oil pump, comprising: pump gears engaging each other and driven by a pump drive gear, the pump gears being accommodated in a pump case such that small side gaps are defined between both side faces of the pump gears and a side wall face of a gear room of the pump case and a pump gear side end face of a pump cover and such that oil is discharged from the pump by rotation of the engaged pump gears, wherein a side face of the pump gear is formed into a stepped face such that an annular region extending radially from a diameter of a shoulder at the stepped face, the diameter of the shoulder at the stepped face being smaller than a dedendum circle diameter of the pump gear and larger than an outer diameter of a pump gear bearing, to an addendum circle diameter of the pump gear is recessed by a certain depth to increase a size of a side gap in the recessed annular region so that the size of the side gap in the recessed annular region is larger than a size of a side gap in a region between the diameter of the shoulder at the stepped face to the outer diameter of the pump gear bearing.