Electric supercharging device and multi-stage supercharging system

An electric supercharging apparatus which is configured to rotate an electric motor that comprises a rotor shaft rotatably supported in a motor housing to which a motor coil and a stator are fixed, so as to drive and supercharge a compressor connected to one end of the rotor shaft, the electric supercharging apparatus comprising:

• a gas supply port and a gas discharge port which are provided in the motor housing;
• wherein the gas discharge port in the motor housing is connected to an intake passage, and
• wherein the gas supply port opens to another end side of the motor housing opposite to one end side at which the motor housing is connected to the compressor;
• a first cooling passage which connects the gas supply port and the gas discharge port in the motor housing and which is formed in the stator along the motor coil in an outer periphery of the motor coil;
• and
• a second cooling passage which connects the gas supply port to the gas discharge port in the motor housing and which is formed along the rotor shaft between the rotor shaft and the motor coil,
• wherein the second cooling passage joins the first cooling passage in the motor housing and outside air is introduced to the first cooling passage and the second cooling passage from the gas supply port by a negative pressure of an inlet port of the compressor applied to the first cooling passage via the intake passage.