Oil pump including gap between flange portion of tubular core and flange-opposing portion of resin housing

A method for assembling an oil pump, the oil pump comprising:

• an inner rotor having external teeth;
• an outer rotor having an inner rotor housing portion in which the inner rotor is rotatably housed in an eccentric state, and internal teeth that mesh with the external teeth;
• a tubular first core having a rotor housing portion in which the inner rotor and the outer rotor are housed, and a flange portion that projects radially outward from a tubular wall forming the rotor housing portion;
• a housing made of a resin and having a recess in which the first core is held and a flange-opposing portion that opposes the flange portion of the first core;
• and
• a board-shaped second core disposed in contact with the first core in an axial direction and closing an opening of the rotor housing portion, wherein
• the first core has a first contact portion that is in contact with the second core and a first engagement portion that is engaged with the second core in a state where the first contact portion is in contact with the second core,
• the second core has a second contact portion that is in contact with the first core and a second engagement portion that is engaged with the first core in a state where the second contact portion is in contact with the first core, and
• the oil pump has a gap formed between the flange portion of the first core and the flange-opposing portion of the housing in a state where the first contact portion and the second contact portion are in contact with each other, the method comprising:
• a first step of assembling the first core to the second core placed with a contact side thereof with the first core located at an upper side, from above, such that the first contact portion and the second contact portion are brought into contact with each other and the first engagement portion and the second engagement portion are brought into engagement with each other;
• and
• a second step of assembling the housing to the first core that has been assembled to the second core, from above, such that the first core is held in the recess and the flange portion of the first core opposes the flange-opposing portion.