Patent ID: 7458369

Claim:
A supercharger comprising: a drive shaft configured to be driven by the rotation of an engine, the drive shaft extending in a first housing; a supercharging mechanism including a turbine; a rotary shaft connected to the turbine; a speed increasing mechanism accommodated in a second housing located between the engine and the supercharging mechanism, the speed increasing mechanism being configured to increase the rotation speed of the drive shaft and to transmit the increased rotation speed to the rotary shaft; an oil sump configured to hold lubricant oil for lubricating the speed increasing mechanism; and a pump mechanism driven by the rotation of the drive shaft and configured to supply the lubricant oil held in the oil sump to the speed increasing mechanism; wherein the pump mechanism comprises a screw pump including a screw spirally provided concentrically on the drive shaft over the outside round surface of the drive shaft in the first housing, a cylindrical member rotatably supporting the drive shaft with a support device and accommodating the screw, and an oil introduction passage configured to connect the oil sump and the interior of the cylindrical member, and wherein a gap is provided between the peripheral edge portion of the screw and the inside round surface of the cylindrical member.