Electric motor-driven compressor having bi-directional liquid coolant passage

Abstract

An electric motor-driven compressor includes a motor having a rotor and a stator in a motor housing, a low-pressure compressor mounted to one end of the motor housing, and a high-pressure compressor mounted to the other end of the motor housing, the compressors forming a two-stage compressor. The motor housing defines a convoluted liquid coolant passage having a plurality of axially spaced-apart, convoluted passageways arranged for serial flow of liquid coolant from the passage inlet, then through each of the convoluted passageways one after another, and finally out from the outlet. The coolant passage further defines at least a first bypass passage that intersects with the convoluted passageways and extends in a non-convoluted fashion so as to interconnect the convoluted passageways and provide an alternative flow path for the coolant.

What is claimed is: 
     
         1 . An electric motor-driven compressor comprising:
 a housing assembly comprising a motor housing and a first compressor housing mounted to one end of the motor housing, the motor housing containing a motor stator and a motor rotor having a shaft, the motor housing defining a bore through which the motor rotor and the shaft pass;   the first compressor housing containing a first centrifugal compressor wheel that is mounted on one end of the shaft for rotation therewith, the first compressor housing also defining a first compressor flow path including a first air inlet that leads air into the first compressor wheel, and a first volute that collects compressed air that has passed through and been compressed by the first compressor wheel; and   the motor housing defining a convoluted liquid coolant passage therein, the coolant passage defining an inlet and an outlet respectively located proximate opposite ends of the motor housing, the coolant passage defining a plurality of axially spaced-apart, convoluted passageways arranged for serial flow of liquid coolant from the inlet, then through each of the convoluted passageways one after another, and finally out from the outlet.   
     
     
         2 . The electric motor-driven compressor of  claim 1 , the coolant passage further defining at least a first bypass passage that intersects with the convoluted passageways and extends in a non-convoluted fashion so as to interconnect the convoluted passageways and provide an alternative flow path for some of the liquid coolant from the inlet to the outlet. 
     
     
         3 . The electric motor-driven compressor of  claim 2 , wherein the coolant passage further defines a second bypass passage that intersects with the convoluted passageways and extends in a non-convoluted fashion so as to interconnect the convoluted passageways, the first and second bypass passages being circumferentially spaced apart from each other. 
     
     
         4 . The electric motor-driven compressor of  claim 1 , further comprising a second compressor housing mounted to an opposite end of the motor housing and a second centrifugal compressor wheel contained in the second compressor housing and affixed to an opposite end of the shaft, the second compressor housing defining a second compressor flow path including a second air inlet that leads air into the second compressor wheel, and a second volute that collects compressed air that has passed through and been compressed by the second compressor wheel, and further comprising an interstage duct that connects the second volute to the first air inlet such that air compressed by the second compressor wheel is led by the interstage duct from the second volute into the first air inlet and is further compressed by the first compressor wheel and delivered into the first volute, the second compressor wheel thus constituting a low-pressure compressor wheel and the first compressor wheel constituting a high-pressure compressor wheel. 
     
     
         5 . The electric motor-driven compressor of  claim 4 , wherein the inlet to the coolant passage is proximate the high-pressure compressor wheel and the outlet from the coolant passage is proximate the low-pressure compressor wheel. 
     
     
         6 . The electric motor-driven compressor of  claim 4 , wherein the convoluted passageway proximate the high-pressure compressor wheel has a larger cross-sectional area than the convoluted passageway proximate the low-pressure compressor wheel. 
     
     
         7 . The electric motor-driven compressor of  claim 4 , further comprising a heat shield disposed between the motor housing and the first compressor housing, wherein the heat shield defines a mounting flange captured between the motor housing and the first compressor housing, the mounting flange being in contact with a portion of the motor housing cooled by the coolant passage so as to facilitate heat transfer from the mounting flange to said portion of the motor housing. 
     
     
         8 . The electric motor-driven compressor of  claim 1 , further comprising a heat-conducting material disposed between the motor stator and the motor housing such that the heat-conducting material is in contact with both the motor stator and the motor housing and serves as a thermally conductive pathway from the motor stator to the motor housing. 
     
     
         9 . The electric motor-driven compressor of  claim 8 , wherein the heat-conducting material is a heat-conducting epoxy.