Patent ID: 7500837

Claim:
A small size gear pump comprising: a disc-shaped case having a motor rotor chamber, a bearing chamber and a gear chamber piled sequentially and being communicated with each other, a suction port connected to the rotor chamber communicating with outside, a discharge port connected to the gear chamber communicating with outside, a rotation shaft having an end positioned in the motor rotor chamber and the other end extending to the gear chamber, a motor rotor fixed around the rotation shaft in the motor rotor chamber, a first bearing provided in the motor rotor chamber for supporting the end of the rotation shaft in radial and thrust directions, a second bearing provided in the bearing chamber for supporting an intermediate portion of the rotation shaft in the radial direction, a stator on the outer surface of a bottom of the motor rotor chamber, wherein the stator and the motor rotor are part of a motor; an outer rotor provided in rotary fashion in the gear chamber, and an inner rotor connected with the other end of the rotation shaft, wherein the inner and outer rotors are part of a trochoid gear, a vertical communicating hole provided in the bearing chamber for connecting the rotor chamber with the gear chamber, an outside communicating hole provided in the bearing chamber for connecting the gear chamber with the discharge port, first and second arc-shaped concave portions provided on upper ends of the vertical communicating hole and the outside communication hole, wherein a fluid is introduced through the suction port, vertical communicating hole and a first one of the arc-shaped concave portions into the gear chamber and is discharged from the discharge port through the outside communication hole and a second one of the arc-shaped concave portions by rotation of the trochoid gear.