Pump shaft support structure

A pump shaft support structure comprising:

• a crankcase body which rotatably supports a crankshaft of an engine;
• a pump shaft which interlockingly rotates with the crankshaft, the pump shaft including a supported section that is rotatably supported and an insertion section adjoining one side of the supported section in an axial direction of the pump shaft;
• a crankcase cover which covers the crankcase body;
• a pump cover which is coupled to the crankcase cover to define a pump chamber between the pump cover and the crankcase cover and which rotatably supports the supported section of the pump shaft on the other side of the pump chamber from the crankcase cover, the pump cover having a through bore that passes the insertion section of the pump shaft therethrough;
• and
• a pump rotor which is disposed in the pump chamber and engages with the insertion section of the pump shaft, wherein:
• the insertion section of the pump shaft has a diameter smaller than a diameter of the supported section;
• the through bore has a first area, and a second area which is positioned proximal to the pump chamber such that the first area is positioned distal from the pump chamber;
• the first area has a diameter corresponding to the supported section of the pump shaft;
• and
• the second area has a diameter smaller than the diameter of the first area and greater than the diameter of the insertion section.

A pump shaft support structure comprising:

• a crankcase body which rotatably supports a crankshaft of an engine;
• a pump shaft which interlockingly rotates with the crankshaft, the pump shaft including a supported section that is rotatably supported and an insertion section adjoining one side of the supported section in an axial direction of the pump shaft;
• a crankcase cover which covers the crankcase body;
• a pump cover which is coupled to the crankcase cover to define a pump chamber between the pump cover and the crankcase cover and rotatably supports the supported section of the pump shaft on the other side of the pump chamber from the crankcase cover, the pump cover having a through bore configured to pass the insertion section of the pump shaft therethrough;
• and
• a pump rotor which is disposed in the pump chamber and engages with the insertion section of the pump shaft, wherein
• the pump shaft includes a flange section which comes into abutment with an end face of the pump cover,
• the insertion section of the pump shaft includes an extension protruding from one side of the pump rotor in the axial direction of the pump shaft,
• the crankcase cover has an accommodation space which accommodates the extension of the insertion section in a non-contact manner,
• the pump cover has an oil supply passage defined in said end face of the pump cover, with which the flange section comes into abutment, so as to guide oil pumped from the pump chamber, and
• the pump cover has an oil passage defined in an inner peripheral surface of a bearing section of the pump cover, wherein the oil passage is in the form of a channel defined in the inner peripheral surface of the bearing section so as to extend in the axial direction and communicates with the oil supply passage.