Internal gear pump

1. An internal gear pump comprising:

a rotor member comprising:

an outer rotor provided with inner teeth to which a torque supplied from a driving device is transmittable; and

an inner rotor provided with outer teeth engageable with the inner teeth of the outer rotor such that the inner rotor is driven by a rotation of the outer rotor;

a pair of housings provided on opposite sides of the rotor member for supporting the rotor member; and

at least one rolling bearing provided between at least one of the pair of housings and the rotor member,

wherein a through hole is formed in the inner rotor such that the through hole coincides with the rotation axis of the inner rotor,

wherein a shaft is rotatably inserted into the through hole such that the shaft protrudes from opposite surfaces of the inner rotor,

wherein opposite ends of the shaft are fixed to the pair of housings such that the shaft rotatably supports the inner rotor,

wherein the shaft comprises a pair of sidewalls for contacting the pair of housings such that a distance is defined between the pair of housings,

wherein said at least one rolling bearing forms around an outer peripheral surface of a cylindrical supporting part of at least one of said pair of housings, said cylindrical supporting part supporting said rotor member,

wherein said outer rotor comprises a rotor part, said rotor part comprising a pair of cylindrical parts extending from opposite edges of said rotor part in an axial direction,

wherein said at least one rolling bearing is provided between inner peripheral surfaces of said pair of cylindrical parts and at least one of said pair of housings, and

wherein at least one seal member is formed on an outside of said at least one rolling bearing in the axial direction and seals clearances between said cylindrical parts and said outer peripheral surface of said cylindrical supporting part.

2. The internal gear pump according to claim 1 , wherein the driving device includes a motor rotor disposed on an outer peripheral side of the outer rotor for driving the rotor member by electric power.

3. The internal gear pump according to claim 2 , wherein an outer peripheral surface of the outer rotor comprises a magnetic member.

4. The internal gear pump according to claim 1 , wherein the rolling bearing is provided between only one of the pair of housings and the rotor member.

5. The internal gear pump according to claim 1 , wherein said at least one rolling bearing comprises:

an outer ring for fitting on said inner peripheral surfaces of said pair of cylindrical parts; and

an inner ring for fitting around said outer peripheral surface of said cylindrical supporting part, and

wherein said rotor member is rotatably supported about an axis of said cylindrical supporting part.

6. The internal gear pump according to claim 1 , wherein said shaft has a diameter that is smaller than a diameter of said through hole.

7. The internal gear pump according to claim 1 , wherein an outer portion of at least one of said pair of housings comprises a flange portion that extends radially outwardly in the axial direction from an outer edge of said cylindrical supporting part, and

wherein said flange portion includes an outer edge that is disposed further from said shaft than an outer edge of said outer rotor.