Rotary compressor housing

A rotary compressor housing is outwardly formed with reinforcing grids in the form of square, diaper or honeycomb. The reinforcing grids allow the intermediate wall portions between the bolted wall portions to thermally expand as much as the bolted wall portions, resulting in that the inner periphery of the center housing always keep its circularity when the inner temperature rises due to an unavoidable compression of air.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to a rotary compressor housing for use in a 
movable-vane compressor that is utilizable as a supercharger for an 
internal combustion engine. 
2. Description of the Prior Art 
It is unavoidable that the compressor housing is heated and caused to 
thermally expand by adiabatic compression of air while the compressor 
runs. In general, the center housing is axially secured to the opposite 
side housings or the like by four or more bolts which are circularly 
equidistantly disposed to pass through the center and the side housings 
and fasten them as one body. The bolts prevent the bolted portions of the 
center housing from radially thermally expanding but permit the radial 
thermal expansion of the four intermediate portions between the adjacent 
bolted portions, so that the inner periphery of the center housing 
thermally expands in the form of a somewhat square. Therefore, there is 
the possiblity of a trouble that the inner periphery of the center housing 
is thermally deformed to reduce the performance of compressor. 
In Japanese Published Unexamined Patent Application No. 58-65988 published 
on Apr. 19, 1983, we have shown a rotary compressor provided with a rotary 
sleeve interposed between a center housing and a rotor and floatingly 
supported by compressible fluid. The compressor is particularly suitable 
for a supercharger with use for an automobile engine required to operate 
over a wide range of speeds. The rotary sleeve rotates together with the 
vanes to prevent frictional heat and wear at the apex of each vane. 
However, if the inner periphery of the center housing is thermally 
deformed the bearing capacity of the air-bearing room defined between the 
inner periphery of the center housing and the outer periphery of the 
rotary sleeve may lower to the extent that the rotary sleeve scuffs the 
inner periphery of the center housing. 
SUMMARY OF THE INVENTION 
The primary object of the invention is to provide a rotary compressor 
housing of which the inner periphery always keeps its roundness 
irrespective of a temperatur-rise in the compressor due to an unavoidable 
adiabatic compression. 
To accomplish the object as described, the compressor housing of the 
invention comprises a center housing having the outer periphery thereof 
integrally formed with reinforcing grids. The grid may be either of 
square, diaper, and honeycomb. The reinforcing grids decentralize thermal 
stress in the intermediate portions between the adjacent bolted portions 
and prevent the inner periphery of the center housing from becoming out of 
roundness. The reinforcing grids radiate heat efficiently from the center 
housing to the open air. In particular, the honeycomb or diapered grids is 
more effective to cool the center housing because of producing 
discontinuous air-flowing about the outer periphery of the center housing. 
The advantages offered by the invention are mainly that the compressor 
performance is not lowered by a temperature-rise due to an unavoidable 
adiabatic air-compression. And further there hardly occurs a scuffing or 
seizing trouble in the compressor of the type having a rotary sleeve 
mounted in a center housing for rotation with a plurality of vanes. 
The other objects and advantages of the invention will become apparent from 
the following detailed description of the invention in conjunction with 
the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The compressor housing of the invention is described in detail below with 
reference to the drawings. Referring initially to FIG. 1, the compressor 
has a rotor 10 integrally provided with a rotary shaft 12, which is 
rotatably supported by bearings 18, 19 in the respective front and rear 
side housings 21, 23 and fixed at the front end to a pulley 14 which is 
rotated by a non-illustrated engine. A plurality of vanes 16 are radially 
slidably fitted in the respective vane grooves 15 in the rotor 10 and have 
their apex in contact with the inner periphery of a rotary sleeve 30. The 
rotary sleeve 30 is mounted within the center housing 22 to define an 
air-bearing room 40 of 0.02-0.15 mm width therebetween. Gasket is 
interposed between the rear side housing 23 and the rear cover 24 in which 
discharge and suction chambers 41, 51 are provided. The discharge chamber 
41 is internally connected through a discharge valve 60 to a discharge 
port 42 and the suction chamber 51 is internally connected to a suction 
port 52. The rear side housing 23 is formed with a high-pressure hole 44 
extending from the discharge valve 60 to high-pressure groove 45 in the 
joining surface between the center housing 22 and the rear side housing 
23. Center housing 22 is formed with a high-pressure passage 46, which 
extends axially from the high-pressure groove 45. The high-pressure 
passage 46 is provided with a plurality of throttles 47 opened to an 
air-bearing room 40 defined by the inner periphery of the center housing 
and the outer periphery of the rotary sleeve 30. Thus, the discharge 
chamber 41 is internally connected to the air-bearing room 40. Bolts 27 
pass through the thickened portions 28 of the center housing 22, the front 
and rear side housings 21, 23, and the rear cover 24 to fasten them 
axially as one body. The front and rear side housings 21, 23 are formed in 
the inner surfaces with annular grooves 26 in which the oilless bearing 
members 25, made of carbon, alumina, silicon nitride or the like, are 
embedded for smooth contact with the respective side surfaces of the 
rotary sleeve 30. 
As seen in FIG. 2, the high-pressure passages 46 are disposed on the 
high-pressure groove 45 which forms a circular arc of subtended angle of 
about 170 degrees in the compression side of the compressor. Four vanes 16 
fitted in the vane grooves 15 confine suction working space 53 in the 
suction side and compression working space 43 in the compression side 
together with the outer periphery of the rotor 10 and the inner periphery 
of the rotary sleeve 30. Four bolts 27 are circularly equidistantly 
disposed in the thickened portions 28 of the center housing 22. The 
thickened portions 28 are peripherally connected to each other by 
reinforcing grids 29. The air-bearing room 40 between the rotary sleeve 30 
and the center housing 22 should keep its circularity to floatingly 
support the rotary sleeve 30. 
As seen in FIGS. 3 and 4, the center housing 22 has its outer periphery 
integrally formed with square reinforcing grids 29 which extend in the 
both axial and peripheral directions. The reinforcing grids are the same 
in radial thickness as the thick wall 28 through which the bolt passes. 
The reinforcing grids 29 are not limited to be square but shaped in either 
form of diaper and honeycome as seen in FIGS. 5 and 6. The reinforcing 
grids 29 axially terminate in the opposite flanges of the center housing 
22 to which the front and rear side housings are secured. 
In operation, the rotation of engine is transmitted to the rotor 10 by the 
pulley 14. As the rotor 10 rotates, air is adiabatically compressed in the 
compression working space 43 thus raising its temperature. This heat is 
transferred to the center housing 22 through the rotary sleeve 30. 
Frictional heat, generated in the bearings, sealings, and other parts, is 
also transferred to the center housing 22. Consequently, the center 
housing 22 has it's temperature rise to about 85 C. and thermally expands. 
The reinforcing grids 29 permit the intermediate portions between the 
bolted portions 28 to expand thermally as much as the vicinity of the 
bolted portions 28 in the both axial and radial directions, resulting in 
that the inner periphery of the center housing 22 expands without 
deforming its circularity. Otherwise, the intermediate portion would 
expand more than the vicinity of the bolted portions 28 to shape the inner 
periphery of the center housing 22 in the form of a somewhat square. The 
air-bearing room 40 between the inner periphery of the center housing 22 
and the outer periphery of the rotary sleeve 30 always keeps its 
circularity and the same bearing capacity to floatingly support the rotary 
sleeve 30 irrespective of the temperature rise in the compressor, so that 
the rotary sleeve 30 can rotate without scuffing nor seizing the inner 
periphery of the center housing 22. The diapered or honeycomb reinforcing 
grids 29 not only radiate heat from the center housing 22 but also produce 
discontinuous air-flowing to cool the center housing 22 with the result 
that the temperature in the center housing 22 does not exceed a tolerable 
limit. 
It will be understood that the rotary compressor housing of the invention 
is not only available for the rotary compressor of the type having a 
rotary sleeve as described above, but also the conventional one in which 
the vanes frictionally slide along the inner periphery of the center 
housing.