Variable displacement oil pump including swing member

A variable displacement oil pump for an internal combustion engine, comprising:

• a pump housing including a pump accommodation chamber;
• a swing member accommodated in the pump accommodation chamber, and structured to swing about a swing fulcrum, wherein the swing fulcrum is set at an inner periphery of the pump housing defining the pump accommodation chamber;
• a pump forming member accommodated inside the swing member, including a rotational center eccentric from a center of an inside diameter of the swing member, defining a plurality of pump chambers between the pump forming member and the swing member radially outside the rotational center, and configured to suck working oil via a suction part formed in a suction region in which each of the plurality of pump chambers increases in volumetric capacity along with rotation of the pump forming member, and discharge working oil via a discharge part formed in a discharge region in which each of the plurality of pump chambers decreases in volumetric capacity along with rotation of the pump forming member;
• a biasing member mounted with application of a setting load so as to bias the swing member in a direction to increase a quantity of eccentricity between the center of the inside diameter of the swing member and the rotational center of pump forming member, the biasing member including a single spring;
• a first seal member defined at an outer peripheral surface of the swing member, and being in contact with the inner periphery of the pump housing;
• a second seal member defined at an outer peripheral surface of the swing member farther from the swing fulcrum than the outer peripheral surface where the first seal member is defined, wherein the second seal member is in contact with the inner periphery of the pump housing;
• a first control oil chamber formed between the inner periphery of the pump housing and the swing member and between the swing fulcrum disposed in the discharge region and the first seal member, wherein movement of the swing member in a direction to reduce the quantity of eccentricity by supply of working oil to the first control oil chamber causes an increase in volumetric capacity of the first control oil chamber;
• and
• a second control oil chamber formed between the inner periphery of the pump housing and the swing member and between the swing fulcrum and the second seal member, wherein movement of the swing member in a direction to increase the quantity of eccentricity by supply of working oil to the second control oil chamber causes an increase in volumetric capacity of the second control oil chamber;
• wherein the swing member includes a first pressure-receiving surface facing the first control oil chamber, and a second pressure-receiving surface facing the second control oil chamber, wherein the second pressure-receiving surface has a larger area than the first pressure-receiving surface.