The present invention relates to a liquid-cooled rotor assembly for a compressor or supercharger assembly.
Roots-type and screw-type positive displacement compressors are employed in industrial and automotive applications. The compressor or supercharger may be operatively connected to an internal combustion engine to increase the volume of intake air communicated to the internal combustion engine thereby increasing the volumetric efficiency thereof. The supercharger typically includes two interleaved and counter-rotating rotors each of which may be formed with a plurality of lobes to convey intake air for subsequent introduction to the internal combustion engine. The efficiency of the supercharger is dependent on the running clearances between each of the two rotors and a housing within which the two rotors are rotatably supported.
A rotor assembly for a supercharger assembly is provided. The rotor assembly includes at least one lobe defining at least one cavity. The at least one cavity is configured to contain a fluid, such as oil or coolant, operable to cool the at least one lobe.
In one embodiment, the rotor assembly includes a rotatable shaft member and the at least one lobe is operatively connected to the shaft member. The shaft member defines a feed passage operable to communicate the fluid to the at least one cavity. The shaft member further defines a return passage operable to exhaust the fluid from the at least one cavity. The feed passage is positioned generally along an axis of rotation of the shaft member, while the return passage is positioned generally adjacent to the outer periphery of the shaft member. A supercharger incorporating the rotor assembly is also disclosed.
The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings.
Referring to the drawings wherein like reference numbers correspond to like or similar components throughout the several figures, there is shown in
A rotor cavity 20 is defined by the housing 12 and is configured to contain a first and second rotor assembly 22 and 24, respectively, rotatably disposed therein. The first and second rotor assemblies 22 and 24 are interleaved and counter-rotating with respect to each other. The first rotor assembly 22 includes a plurality of lobes 26 extending radially outward in a clockwise twisting helical shape, as viewed from the inlet passage 14, while the second rotor assembly 24 includes a plurality of lobes 28 extending radially outward in a counter-clockwise twisting helical shape, as viewed from the inlet passage 14. The first and second rotor assemblies 22 and 24 cooperate to convey intake air 16 from the inlet passage 14 to the outlet passage 18. The first and second rotor assemblies 22 and 24 are rotatably supported within the rotor cavity 20 by respective first and second shaft member 30 and 32.
During operation of the supercharger assembly 10, the first and second rotor assemblies 22 and 24 cooperate to convey intake air 16 from the inlet passage 14 to the outlet passage 18. The temperature of the intake air 16 tends to increase as the intake air 16 is transferred from the inlet passage 14 to the outlet passage 18, thereby forming a thermal gradient along the longitudinal axis of the first and second rotors 22 and 24. As a result, the degree of thermal expansion of the first and second rotor assemblies 22 and 24 will increase during operation of the supercharger assembly 10, thereby increasing the likelihood of “scuff”. Scuff is defined as metal transfer as a result of the first and second rotor assemblies 22 and 24 contacting one another or the housing 12. Scuff occurs when the running clearances, i.e. the clearance dimension between the lobes 26 and 28 and the housing 12 when the supercharger assembly 10 is operating, reaches zero causing an interference condition and material transfer between the first and second rotor assemblies 22 and 24 and the housing 12.
A cooling system 34, such as a loop or a simple tank, is schematically depicted in
Referring to
The structure and operation of the first and second rotor assemblies 22 and 24 will be discussed in greater detail with reference to
During operation of the supercharger assembly 10 of
By cooling the lobes 26 and 28, the running clearances between the lobes 26 and 28 and the housing 12 may be minimized while reducing the likelihood of scuff. Therefore, the operating efficiency of the supercharger assembly 10 may be increased by maintaining the temperature of lobes 26 and 28 within predetermined limits. It should be understood that with certain configurations of the first rotor assembly 22 and operating speeds of the supercharger assembly 10, the pump 38 may not be necessary since the feed passage 40 is centrally located along the axis of rotation A of the first shaft member 30, while the return passage 48 is provided on the outer periphery of the first shaft member 30. As such, the centrifugal forces exerted on the fluid 36 by the rotation of the first shaft member 30 may be sufficient to enable the pumping of the fluid 36 through the first rotor assembly 22 in lieu of the pump 38. The first and second rotor assemblies 22 and 24 may have helical-type, screw-type, or straight-type configurations for lobes 26 and 28 while remaining within the scope of that which is claimed. As stated hereinabove, the lobes 26 and 28 of the first and second rotor assemblies 22 and 24 have a generally helical shape; as such, the fluid 36 is pumped through the cavities 44 during rotation of the first and second rotor assemblies 22 and 24.
Referring to
In operation of the first rotor assembly 22A, the fluid 36 is communicated to the feed passage 40 and is subsequently communicated to the cavities 44 via the radially extending passages 42. As with the first rotor assembly 22 of
Although the discussion has focused on the application of the supercharger assembly 10 to an internal combustion engine, those skilled in the art will recognize other applications of the supercharger 10 such as a compressor for industrial application, compressor for fuel cell applications, etc. While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.
Number | Name | Date | Kind |
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3299862 | Peras | Jan 1967 | A |
4005955 | Pamlin | Feb 1977 | A |
6045343 | Liou | Apr 2000 | A |
6758660 | Kriehn et al. | Jul 2004 | B2 |
6884050 | Prior | Apr 2005 | B2 |
20080170958 | Prior | Jul 2008 | A1 |
Number | Date | Country | |
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20090004038 A1 | Jan 2009 | US |