Supercharger with heat insulated gear case

Abstract

A positive displacement supercharger includes a housing having a rotor cavity. A pair of positive displacement rotors are oppositely rotatable in the rotor cavity and have interleaved helical lobes forming rotor chambers operative to carry air axially from an inlet end to an outlet end of the cavity. A gear case adjacent the rotor cavity is drivably connected with and supports the rotors, the gear case including a bearing housing having an end surface facing the rotor cavity and the outlet ends of the rotors. A heat insulating material is applied to the end surface of the bearing housing and is effective to reduce heat flow between the rotor cavity and the end surface of the bearing housing to effectively reduce lubricating oil temperatures in the gear case. The insulating material may be a ceramic plate fixed to the bearing housing end surface.

Description

TECHNICAL FIELD[0001]This invention relates to positive displacement compressors or superchargers, such as roots type or screw compressors utilized for automotive engine superchargers and other purposes.BACKGROUND OF THE INVENTION[0002]It is known in the art to utilize positive displacement compressors having lobed rotors for supercharging internal combustion engines and for providing compressed air for other purposes. Such a compressor used as an automotive supercharger may include a housing having a rotor cavity in which a pair of parallel rotors having interleaved lobes rotate to compress air drawn into one end of the housing and discharged through an opening in the cavity wall near an opposite end of the housing. The rotors may be belt driven by the engine through a pulley connected directly, or through a gear train, to the pair of rotors.[0003]Roots type and screw type compressors used on original equipment automotive engines are made with a bearing housing between the rotors a...

AI Technical Summary

Benefits of technology

[0007]Since high temperature of the compressed air at the discharge end of the compressor rotor cavity appears to be a main source of heat flow to the gear case oil, the present invention is designed to reduce the rate of heat flow between the rotor cavity and the gear case oil of a supercharger.

[0008]The heat flow may be reduced by applying a suitable insulating material between the rotor cavity and the associated bearing housing of the supercharger.

[0011]If desired, other forms of heat insulation may be applied in any suitable manner to the cavity facing face of the bearing housing. Alternatively, or in addition, other forms of insulation or insulators may be applied between the rotors and extensions thereof into the gear case to further reduce heat transmission to the gear case oil.

Problems solved by technology

The boosted air heats the gear case oil by forced convection / conduction through the aluminum bearing plate At high boost levels, this can lead to unacceptable gear case temperatures at continued high speeds and loads.

This in turn may require speed limits or boost trim to prevent gear case oil damage or seal damage that can lead to catastrophic supercharger damage.

This problem is limited in some vehicle installations because continuous maximum speed operation is not possible for most vehicle installations.

However, with less under hood air flow and / or higher continuous speeds, the gear case temperatures could exceed design limits.

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