Device for controlling the pressure in the bearings of a roots blower supercharger

Claim 1

A pressure controlling device for controlling pressure acting on bearings provided in a Roots blower type supercharger mounted on an internal combustion engine, said supercharger having a housing formed with an inner wall to define a chamber therein, said bearings being provided in said housing and outside of said inner wall, two rotary shafts extending through said inner wall and provided with impellers which are housed in said chamber and mated with each other, said shafts being rotatably supported by said bearings, an annular sealing member being provided on an end face of at least one of said bearings to form an annular space between said at least one of said bearings and said inner wall, said annular space being communicated with the atmosphere through an air passage formed in said housing, said pressure controlling device comprising; a control valve connected to said air passage, means for sensing an increase in load of said internal combustion engine, and means for controlling said control valve to vary a flow passage area of said air passage according to said engine load, said controlling means closing said valve to reduce said flow passage area for a predetermined period after said sensing means senses an engine load which is higher than a predetermined value.