Relief valve structure

Abstract

To provide a relief valve structure for an oil pump, which is capable of appropriately controlling/switching the discharge pressure and flow rate of oil to an optimum condition in low, middle and high speed regions of an engine. The relief valve structure has: a relief valve having formed therein a valve flow path for communicating between a valve head part and an outer circumferential side part; a valve housing in which a valve passage accommodating the relief valve is formed; a relief flow-in part formed on an axial direction one end side of the valve passage and communicating with the valve passage; a first discharge part formed in the valve housing and communicating with the valve flow path by the movement of the relief valve; and a second discharge part that is opened by allowing the valve head part to pass therethrough. The second discharge part is positioned nearer to the relief flow-in part than the first discharge part. The shortest gap between an outer circumferential side part opening of the valve flow path and the first discharge part is the same as or shorter than the shortest gap between the valve head part and the second discharge part during an initial state of the relief valve.