1. Field of the Invention
This invention relates to scroll fluid machine, in which sucked fluid is compressed with stationary and revolving scrolls and discharged to the outside.
2. Description of the Related Art
A scroll fluid machine compresses fluid sucked from its peripheral part in a sealed space formed by its stationary and revolving scrolls progressively as the fluid is fed toward its central part, and discharges the compressed fluid from the central part. As the fluid is compressed, the temperature in the sealed space formed by the wraps is elevated. This poses a problem that bearings, seal members, etc. provided in drive parts are soon deteriorated. Heretofore, the scrolls are cooled to hold the temperature within a predetermined temperature.
Well-known cooling systems cool either a non-driven part, i.e., the stationary scroll, or a driven part, i.e., the revolving scroll.
FIG. 16 shows a technique concerning a non-driven part cooling system. As shown, a revolving scroll 116 which is mounted on a frame 109 provided in a sealed housing 105, comprises a disc-like body 114 having a shaft 113 depending therefrom. The frame 109 has a central hole, in which a drive shaft 104 coupled to a drive (not shown) is fitted for rotation, and the shaft 113 is eccentrically coupled to the drive shaft 104. The revolving scroll 116 has a wrap 115 engaging with a wrap 111 of a stationary scroll 112.
The stationary scroll 112 has a peripheral wall having a suction hole 118. When the revolving scroll 116 is revolved relative to the stationary scroll 112 with the rotation of the drive shaft 104, a sealed space formed by the wraps 111 and 115 is progressively reduced in volume, thus compressing gas entering the sealed space. The compressed gas is discharged from a discharge hole 121 formed in a central part of the stationary scroll 112 through a discharge pipe 120 to the outside.
A plurality of radially spaced-apart heat pipes 122 are provided in the body 110 of the stationary scroll 112 to remove heat generated in a compression stroke as described above.
FIG. 17 shows a well-known cooling system for cooling driven part, i.e., the revolving scroll.
A housing 211 as shown comprises a rear and a front housing part 212 and 213, and a drive shaft 214 is supported for rotation by bearings 215 in a bearing portion of the rear housing part 212. The drive shaft 214 has an extension projecting outward from the bearing portion and coupled to a motor (not shown). The drive shaft 214 also has an eccentric portion 214b, which has an eccentric axis 02--02 with respect to the axis 01--01 of the drive shaft 214 by a distance .delta..
A revolving scroll 216 which is coupled to the eccentric portion 214b of the drive shaft 214, has a disc-like plate 216a having a mirror finished front surface, a spiral wrap 216b formed on the front side of the mirror finished plate 216a, a boss 216c formed as the driving center with an axial line 02--02 on the rear side of the plate 216a and having smaller diameter than the inner peripheral surface edge of above portion 213b, a ring-like ridge 216d formed on the rear side of the above 216a and on the periphery thereof, and a plurality of radial vent holes 216e formed in a diameter direction above the ridge 216d.
A stationary scroll 221, which is secured to the front housing part 213, has a disc-like plate 211a having a mirror finished rear surface, a spiral wrap 221b formed on the rear side of the plate 211a and a peripheral wall 221c surrounding the wrap 221b.
The wraps 216b and 221b of the revolving and stationary scrolls 216 and 221 engage with or wrap each other at a predetermined deviation angle, and they form a plurality of compression chambers or spaces when the revolving scroll 216 is revolved.
The drive shaft 214 has a counterweight 225 mounted on its portion extending in the rear housing part 212, and a centrifugal fan 226 is mounted on the counterweight 225 to generate cooling air flow with the rotation of the drive shaft 214.
In the prior art non-driven part cooling system shown in FIG. 16, in which the heat pipes 122 are provided in the stationary scroll body, the heat absorbing portions of the heat pipes 122 are more remote from the revolving scroll which is driven than from the stationary scroll. Therefore, the neighborhood of the bearings, seal members and other parts which are driven in contact with the revolving scroll 116 in the driving thereof, is cooled less efficiently compared to the cooling of the stationary scroll. This means that uniform temperature distribution cannot be obtained.
The heat radiating portions of the heat pipes 122 are cooled by their heat radiation to the sealed housing inner space 105a, which is filled with gas-sucked through a suction pipe 119.
In communication with the space 105a is the suction hole 118, through which gas enters the compression space which is formed by the stationary and revolving scrolls. This means that gas having been elevated in temperature by the heat radiation from the heat pipes 122 again enters the compression space through the suction hole 118, thus reducing the cooling efficiency.
In order to prevent the cooling efficiency reduction, it is necessary to provide special cooling means on an external part to which the suction pipe 119 is connected, thus complicating the construction and increasing the size of the apparatus.
In the well-known driven part cooling system shown in FIG. 17, with the rotation of the drive shaft 214 external gas is sucked through a suction passage 227 by the centrifugal fan 226 and led through a ring-like space B and a cooling air passage 220 to be discharged through a discharge passage 228.
Since in this system the gas having cooled down a central part of the revolving scroll 216 is discharged along the rear side of the revolving scroll 216 and through the discharge passage 228, the provision of the discharge passage is necessary. In addition, in order to increase the cooling efficiency, a cooling fan for cooling the rear side of the stationary scroll 221 has to be provided, thus increasing the size of the apparatus.