Motor-driven roots pump

A motor-driven Roots pump comprising:

• a housing;
• a drive shaft and a driven shaft that are rotationally supported by the housing in a state arranged parallel to each other in the housing;
• a drive gear that is fixed to the drive shaft;
• a driven gear that is fixed to the driven shaft and meshed with the drive gear;
• a drive rotor that is arranged on the drive shaft;
• a driven rotor that is arranged on the driven shaft and meshed with the drive rotor;
• an electric motor that rotates the drive shaft;
• a motor chamber that is formed in the housing and accommodates the electric motor;
• a gear chamber that is formed in the housing, accommodates the drive gear and the driven gear, and retains oil in a sealed manner;
• and
• a rotor chamber that is formed in the housing and accommodates the drive rotor and the driven rotor, wherein
• the motor chamber, the gear chamber, and the rotor chamber are arranged in this order along a rotational axis of the drive shaft,
• the housing includes
• a first partition wall that separates the gear chamber from the motor chamber in a direction of the rotational axis of the drive shaft,
• a second partition wall that separates the gear chamber from the rotor chamber in the direction of the rotational axis of the drive shaft,
• an outer wall that separates the rotor chamber from the exterior in the direction of the rotational axis of the drive shaft, and
• a rotor-chamber wall that has a shape of a circumferential wall that extends along the rotational axis of the drive shaft and defines the rotor chamber together with the second partition wall and the outer wall, wherein
• the rotor-chamber wall has, at positions opposed to each other with the rotor chamber in between, a suction port and a discharge port through which the rotor chamber communicates with the exterior,
• the first partition wall has a first seal accommodating recess that accommodates an annular first seal member for sealing the gear chamber and the motor chamber from each other, with the drive shaft extending through the first seal member,
• the second partition wall has
• a second seal accommodating recess that accommodates an annular second seal member for sealing the gear chamber and the rotor chamber from each other, with the drive shaft extending through the second seal member, and
• a third seal accommodating recess that accommodates an annular third seal for sealing the gear chamber and the rotor chamber from each other, with the driven shaft extending through the third seal member,
• a side on which the discharge port is located with respect to a plane that includes both the rotational axis of the drive shaft and the rotational axis of the driven shaft is a first side,
• an end surface of the first partition wall that defines the gear chamber has a first recess on the first side,
• an end surface of the second partition wall that defines the gear chamber has a second recess that is opposed to the first recess in the direction of the rotational axis,
• as viewed in the direction of the rotational axis of the drive shaft, the first recess and the second recess at least partially overlap with each other in a range between the drive gear and the driven gear,
• the first partition wall has a first oil supply passage that is configured to supply the oil from the first recess to the first seal accommodating recess, and
• the second partition wall has
• a second oil supply passage that is configured to supply oil from the second recess to the second seal accommodating recess, and
• a third oil supply passage that is configured to supply oil from the second recess to the third seal accommodating recess.