Scroll fluid machine

Abstract: A scroll fluid machine is disclosed, which comprises a stationary scroll with an embedded lap which is spiral in form, extending from a central part of a scroll body toward the outer periphery thereof, and a revolving scroll with an embedded spiral lap engaging with said spiral lap, the said revolving scroll having a scroll body coupled to a drive shaft 11 coupled to a drive at the central portion thereof. The drive shaft 11 is cooled directly by cooing means provided inside it. The scroll body of the revolving scroll has a central part coupled to a drive. Heat generated in a process, in which fluid sucked from the scroll edge is led to the central part while being progressively compressed, can be removed at the central part which is elevated to a highest temperature, thus permitting efficient cooling of bearings and seal members near the revolving scroll central part and the drive shaft.

Description: BACKGROUND OF THE INVENTION 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. 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 laps 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 non-driven part, i.e., the stationary scroll, or driven part, i.e., the revolving scroll. Fig. 12 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 lap 115 engaging with a lap 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 laps 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. 13 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 δ. 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 lap 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 hole 216e formed in a diameter direction of above 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 lap 221b formed on the rear side of the plate 211a and a peripheral wall 221c surrounding the lap 221b. The laps 216b and 221b of the revolving and stationary scrolls 216 and 221 engage with or lap 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. 12, 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. 13, 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. DE-A-3810052 discloses a scroll fluid machine having stationary and revolving scrolls with interengaging scroll laps. The revolving scroll is supported on a bearing fitted to an eccentric portion of a drive shaft. The drive shaft extends from one side of the machine to be driven by a motor. A heat pipe is provided within the drive shaft to transfer heat from the bearing to the outside. It is an object of the invention to provide a scroll fluid machine having an improved cooling efficiency. This object is solved by the machine set forth in claim 1. The subclaims are directed to preferred embodiments of the invention. An embodiment of the invention provides a scroll fluid machine with improved durability. A further embodiment of the invention provides a scroll fluid machine which is reduced in size. In a scroll fluid machine comprising stationary scrolls each having a lap embedded spirally in a scroll body such as to extend from a central part toward the outer periphery of the scroll body, and a revolving scroll having spiral laps embedded in a scroll body and engaging with the spiral laps of the stationary scrolls, said the revolving scroll being coupled to a drive shaft coupled to a drive, cooling means is provided in the drive shaft. With this construction, the drive shaft can be cooled directly. Since the revolving scroll is driven by the drive shaft coupled to the drive, it is possible to cool heat generated in a process, in which fluid sucked from the edge of the scroll is led to a central part thereof while being progressively compressed. It is thus possible to obtain efficient cooling of bearings and seal members provided around the revolving scroll and also those provided around the drive shaft. It is also possible to eliminate the thermal expansion difference between the stationary scrolls and the revolving scroll, provide a uniform temperature distribution, prevent scoring of the laps, extend the grease maintenance cycle and improve the durability. It is further possible to reduce heat generation for reducing the scroll clearance, increasing the operation speed and increasing the attainable pressure. It is further suitable to form the drive shaft to be hollow and provide heat transfer means therein. As shown in Fig. 3, heat pipes 24A and 24B may be provided in an axially formed hollow passage 11Cd in a drive shaft 11C. As shown in Fig. 4, each of the heat pipes 24A and 24B has a sealed pipe-like vessel 25 made of such material as copper, stainless steel, nickel, tungsten, molybdenum, etc., a wick structure 28 disposed in the vessel 25, an inner space 25d defined by the wick structure 28 and operating fluid re-circulated between the wick structure and the inner space while being gasified and liquified by heating and cooling. In an evaporating zone 25a, the operating fluid is gasified by receiving heat from the revolving scroll to be transferred to a condensing zone 25c as shown by arrow 37. In the condensing zone 25c, it releases heat and is liquified again to return to the wick structure 28. The heat pipes 24A and 24B can transfer heat a great deal, specifically several hundred times compared to such metals as copper and aluminum which are good heat conductors, thus it is possible to get a efficient cooling of revolving scroll. It is further suitable to provide a fan at an end of the drive shaft for cooling the heat radiating part of the heat transfer means. The heat transfer means may be provided in the hollow drive shaft such that its heat absorbing zone and heat radiating zone are inclined with respect to the axis of rotation of the drive shaft. Particularly, it may be provided such that the heat absorbing zone is located in an eccentric portion of the shaft and the heat radiating portion is located in a portion other than the eccentric portion. With this arrangement, a centrifugal force generated by the rotation of the drive shaft has an effect of forcing the operating fluid having been liquified in the condensing zone 25c (Fig. 4) to the heating zone, thus promoting the re-circulation of the operating fluid and improving the cooling efficiency. In a scroll fluid machine comprising stationary scrolls having a lap embedded spirally in a scroll body such as to extend from a central part toward the outer periphery of the scroll body, and a revolving scroll having spiral laps embedded in a scroll body and engaging the spiral laps of the stationary scrolls, said the revolving scroll being coupled to a drive shaft (coupled to a drive) at the central portion of the scroll body, to drive the eccentric portion of the drive shaft being cooled. The revolving scroll thus has a central part of its body driven by the drive shaft coupled to the drive, and heat generated in the process, in which fluid sucked from the edge of the scroll is led to a central part thereof while being progressively compressed, can be removed in the central part which is at the highest temperature. Thus, parts provided in the neighborhood of the central part of the revolving scroll can be cooled efficiently. Not only the central part of revolving scroll but also other parts can be cooled, that is, efficient cooling can be obtained. It is further effective to provide a fan on an end of said drive shaft, said heat transfer means being able to cool a central part of said revolving scroll, said fan being able to cool said revolving scroll inclusive of the heat radiating zones of the heat transfer means or said stationary scrolls on the side thereof opposite the laps side. In this case, the fans (Fig. 3) produce cooling air flows in the directions of arrows 35 and 36 to cool the heat radiating zones (i.e., condensing zones). Where the double-lap revolving scroll with laps embedded in opposite side surfaces of the scroll body is combined with the stationary scrolls, the fans 12 and 13 produce cooling air flows in the directions of arrows 39 and 40 (Fig. 8) to cool the heat pipes, while exhausting gas having cooled the stationary scrolls constituted by the housing parts 4 and 5 on the side thereof opposite the laps. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing a shaft/fan assembly in an embodiment of the scroll fluid machine according to the invention; Fig. 2 is a view showing a heat pipe; Fig. 3 is a view showing a scroll fluid machine embodying the invention; Fig. 4 is a view taken along line C-C in Fig. 5; Fig. 5 is a view taken along line D-D in Fig. 5; Fig. 6 is an enlarged-scale view showing a portion shown in Fig. 1; Figs. 7(a) and 7(b) are schematic views showing a scroll state at the commencement of gas ballast gas introduction; Figs. 8(a) and 8(b) are schematic views showing a scroll state during the gas ballast gas introduction; Figs. 9(a) and 9(b) are schematic views showing a scroll state immediately before the end of the gas ballast gas introduction; Figs. 10(a) and 10(b) are schematic views showing a scroll state when a gas ballast gas suction hole is closed; Fig. 11 is a view showing a modification of the shaft/fan assembly in the embodiment of the scroll fluid machine according to the invention; Fig. 12 is a view showing a prior art non-driven part cooling system; and Fig. 13 is a view showing a prior art driven part cooling system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the invention will now be described. It is to be construed that unless particularly noted the sizes, materials, shapes and relative dispositions shown in the embodiments have no sense of limiting the scope of the invention but are merely exemplary. The basic scroll fluid machine construction adopting a shaft cooling system embodying the invention will now be described. Fig. 3 shows a pump 1 having a shaft 11, which is coupled at its right end to a drive shaft of a motor 2 for being rotated by the torque thereof. The shaft 11 has a central eccentric portion 11a having some swelling part to rotating central axial line of outer peripheral, which the both edge side of a eccentric portion 11a are driven to be supported for rotation in bearings and packing sections in housing parts 4 and 5. The housing parts 4 and 5 are cap-like in shape and constitute respective stationary scrolls. Their peripheral walls are sealed together via an intervening seal member to define a sealed inner space. The housing part 4 has a lap sliding surface 4b perpendicular to its axis and also has a hole 4i (see Fig. 6), which is formed in a central portion of the lap sliding surface 4b, and in which the end portion of the shaft 11, adjacent the eccentric portion 11a and not eccentric, is fitted for rotation. The housing part 4 has a lap 7 embedded in it. The lap 7 (see Figs 7(a) and 7(b)) is spiral clockwise when viewed in the direction of arrow 30 and has an end 7a located in the neighborhood of the hole 4i. The lap 7 has a tip groove formed in its tip or outer edge. A tip seal 14 is fitted in the tip groove. The tip seal 14 is made of a fluorine type resin or the like and is self-lubricating to provide perfect seal with the associated rubbing surface in contact with it ( see Fig. 6). The housing part 4 further has a discharge hole 4c (see Figs. 6, 7), which is open in the lap rubbing surface 4b in the neighborhood of the end 7a of the lap 7. Compressed gas is discharged through the discharge hole 4c through a discharge passage 4d from a discharge port 9 formed in the peripheral wall 4a of the housing part 4 to the outside. The side of the housing part 4 opposite the lap 7 constitutes a scroll body 4f which is provided with a suction pipe 10 for gas ballast gas introduction. Gas is sucked from the suction pipe 10 through a suction passage 4g (see Fig. 6) and suction hole 4e into a sealed space R. Three revolving mechanism sets 17 are mounted on the peripheral wall 4a of the housing part 4 on 3 spots by 120° in the peripheral direction. These revolving mechanism sets 17 are coupled to a revolving scroll to be described later. A peripheral port 4a of housing 4 has a absorbing port 8 which are coupled to a vessel to be evacuated (not shown), at where the gas is sucked through the hole 8a from above vessel. The other housing part 5 likewise has a lap sliding surface 5b perpendicular to its axis, as well as a hole formed in a central portion of the lap sliding surface 5b, the end portion of the shaft 11 adjacent the eccentric portion 11a and not eccentric being fitted for rotation in the hole. A lap 6 which is spiral counterclockwise when viewed in the direction of arrow 31, is also embedded in the housing part 5, and has an end located in the neighborhood of the hole. The lap 6 has a tip groove formed on its tip, and a tip seal 14 (Fig. 6) is fitted in the tip groove and provides perfect seal with the associated rubbing surface in contact with it. A revolving scroll 3 is disposed for revolving in the inner space defined in the housing parts 4 and 5. The revolving scroll 3 is disc-like in shape and has opposite side lap rubbing surfaces 3d and 3f with laps 26 and 27 embedded thereon for engaging with the stationary scroll laps. The lap 26 is spiral clockwise when viewed in the direction of arrow 30, and the opposite side lap 27 is spiral counterclockwise when viewed in the direction of arrow 31. The revolving scroll 3 has a central hole 3a, in which the eccentric portion 11a of the shaft 11 is fitted for rotation. The central hole 3a is surrounded by ring-like lap ends 26a and 27a of the laps 26 and 27 over the entire length of the eccentric portion 11a. The lap ends 26a and 26b communicate with a passage 3b leading to the discharge hole 4c, and a final compression space defined by the laps 26 and 6 is communicated by a hole 3g with the passage 3b. A sealed space R which is defined by the stationary scroll lap 7 and the revolving scroll lap 27 for introducing gas ballast gas, and a sealed space L defined by the stationary scroll lap 6 and the revolving scroll lap 26, are communicated with each other by a communicating hole 3e. Gas entering from the suction pipe 10 is led from the sealed space R through the communicating hole 3e so as to fill the sealed space L. Fan 12 and 13 are provided outside of housing 5 and housing 4 on the shaft 11 to cool the vacuum pump and a cover 18 and 19 having a hole 18a in the central portion are mounted in housing 5 and 4 in order to protect those fans. Between the housing part 5 and a cover 18 is mounted a shield 29B (see Fig. 5) having numbers of holes 29Ba and 29Bb, and between the housing part 4 and a cover 19 is mounted a shield 29A (see Fig. 4) having numbers of holes 29Aa and 29Ab. The three revolving mechanism sets 17 on 3 spots by 120° in the peripheral direction are supported at one end by housing 4 and at the other end by outer periphery of the revolving scroll, and the revolving scrolls are revolved through above revolving mechanism 17 by an axis eccentric rotating centers with respect to the stationary scrolls. The operation of the above basic construction will now be described with reference to Figs. 7 to 10. Figs. 7(a) to 10(a) are taken along line A-A in Fig. 6, and Figs. 7(b) to 10(b) are taken along line B-B. Referring to Fig. 3, when the shaft 11 is rotated, the revolving scroll 3 is revolved to suck gas from a vessel (not shown). The sucked gas is led from the outer peripheries of the stationary scroll laps by the revolving scroll laps 26 and 27 into a sealed space defined by these stationary and revolving scroll laps for compression in the space. While the gas is compressed in three or more sealed spaces, the sealed space is changed from one shown at R0 in Fig. 10(a) to one shown at R1 in Fig. 7(a), whereupon the suction hole 4e of the gas ballast suction pipe 10 is opened. When the pressure in the vessel to be evacuated is close to the atmospheric pressure, the pressure in the sealed space R1, into which gas is introduced form the suction hole 4e, is already higher than the atmospheric pressure. When the pressure of gas introduced from the suction pipe 10 is lower than the pressure in the sealed space R1, no gas is introduced through the suction hole 4e. With the revolving of the revolving scroll 3 the sealed spaces R and L are changed from the states R1 and L1 (Figs. 7) to states R2 and L2 (Figs. 8), then states R3 and L3 (Figs. 9) and then states R4 and L4 ( Figs. 10), whereby the compressed gas is discharged through the discharge hole 4c. When the gas in the vessel contains steam at the instant of the states R1 and L1, the saturated vapor pressure is exceeded in the final seal space states R4 and L4. The steam is thus condensed and liquified into water drops, which are attached to and accumulated on the lap surfaces defining the final sealed spaces. When steam is liquified before the states R1 and L1 are reached, slight water drops are caused to flow reversely through the suction hole 4e in the stationary scroll 4 into the suction pipe 10. However, since the suction hole 4e is narrow and gas ballast gas is present therein, only very slight water drops are introduced into the suction pipe 10. As the pressure in the vessel to be evacuated is reduced, liquefaction of steam in the vessel proceeds, but even with compression of the sucked gas before the reaching of the sealed spaces R1 and L1, into which gas is introduced from the gas ballast suction hole 4e, the pressure in the sealed spaces R1 and L1 becomes lower than the pressure of the gas to be introduced through the suction hole 4e. The gas is thus introduced through the suction hole 4e. At this time, the steam content in the introduced gas or fluid is reduced. The fluid containing the steam is compressed through the states R2 and L2 (Figs. 8) up to the states R3 and L3 (Figs. 9). The pressure of the compressed fluid in the sealed spaces R3 and L3 at this moment is higher than the gas ballast gas pressure. However, since the stationary scroll suction hole 4e is small in diameter while the revolving scroll is driven at a high speed and gas ballast gas is present in the suction hole, only slight compressed gas flows reversely through the suction hole 4e. Besides, the suction hole 4e is closed by the lap end 27a of the revolving scroll 3 right before the sealed spaces R4 and L4 (Figs. 10) are communicated with the discharge hole 4c. When the sealed spaces R4 and L4 are communicated to the discharge hole 4c (Figs. 10), the partial pressure of steam is reduced and becomes lower than the saturation vapor pressure in the scroll fluid machine. The steam thus is not liquified while liquefying water drops having been attached to the lap surfaces after the condensation and liquefaction of steam noted above, and the overall steam is discharged through the discharge hole 4c. With rotation of the shaft 11 by 90° spaces S0(a) and T0(b) shown in Figs. 10(a) and 10(b) are compressed to states S1(a) and T1(b) as shown in Figs. 7(a) and 7(b). The spaces S1(a) and T1(b) are not communicated with the gas ballast suction hole. These spaces are changed to states S2 and T2 as shown in Figs. 8(a) and 8(b) and then to states S3 and T3 as shown in Figs. 9(a) and 9(b), which are communicated with the discharge hole 4c, whereupon the compressed gas is discharged to the outside. In this stroke, the saturation vapor pressure may be exceeded, resulting in condensation and liquefaction of steam, and water drops produced are attached to and accumulated on the lap inner surfaces defining the final sealed spaces. In this case, subsequent to the discharging of the compressed fluid from the sealed spaces S3 and T3 through the discharge hole 4c, the spaces R4 and L4 (as shown Fig. 10) which are in communication with the gas ballast suction pipe are communicated with the discharge hole 4c. Thus, compressed gas containing steam under a low partial pressure, lower than the saturation vapor pressure in the scroll fluid machine, is discharged through the discharge hole 4e while liquefying water drops produced as a result of condensation and liquefaction in the spaces S3 and T3. The scroll fluid machine operating as described above, continuously compresses fluid sucked from its periphery as the fluid is led toward its central part. That is, the fluid is compressed utmost in the central part, which is thus elevated to the highest temperature. Cooling means for cooling the central part of the apparatus will now be described. Fig. 1 is a view showing a shaft/fan assembly in a third embodiment of the scroll fluid machine according to the invention. Referring to the figure, a drive shaft 11C has a passage formed in it along its axis of rotation, and heat pipes 24A and 24B are disposed in the passage 11Cd. A fan 13 is provided on the drive shaft 11C with its boss 21A fitted on and secured to the right end 11Cb of the drive shaft 11C. The fan 13 can exhaust cooling gas having cooled heat radiating zones 25c of the heat pipes 24A and 24B to the outside as shown by arrows 36. Another fan 12 is provided on the left end 11Ce of the drive shaft 11e with its boss 21B secured thereto by a nut 22 screwed on a threaded end portion 11Cb of the drive shaft 11C. The fan 12 exhausts cooling gas having cooled heat radiating zone 25c of the heat pipe 24B to the outside as shown by arrows 36. Fig. 2 shows either heat pipe 24A or 24B in detail. As shown, the heat pipe has a sealed pipe-like vessel 25 made of copper, stainless steel, nickel, tungsten, molybdenum or like material, a wick structure 28 disposed in the vessel 25, an inner space 25d defined in the wick structure 28 and operating fluid re-circulated between the wick structure 28 and the inner space 25d while being gasified and liquified by being heated and cooled. In an evaporating zone 25a, the operating fluid is gasified by receiving heat from a central part of the revolving scroll 3. The gasified operating fluid moves to a condensing zone (or heat radiating zone) 25c as shown by arrows 37, and in the condensing zone 25c it is liquified again by radiating heat to return to the wick structure 28. Referring back to Fig. 1, with the above construction of the drive shaft 11C in the third embodiment having the heat pipes 24A and 24B disposed in the passage 11Cd, the heating zones (or evaporating zones) 25a in the vessels 25 of the heat pipes 24A and 24B absorb heat generated in the revolving scroll 3 to cause evaporation and liquefaction of the operating fluid in the heat pipes, and the gasified fluid is cooled and liquified in the condensing zones 25c by external gas sucked by the fans 12 and 13 as shown by arrows 35, 35. The gas having contributed to the cooling is exhausted through the holes 29Ab and 29Bb in the shields 29A and 29B (Figs. 4 and 5) to the outside as shown by arrows 36, 36. The gas having cooled the housing parts 4 and 5 on the side thereof opposite the stationary scroll laps is exhausted through the holes 29Aa and 29Ba in the shields 29A and 29B (Figs. 4 and 5) and together with gas having cooled the central part of the revolving scroll 3 to the outside as shown by arrows 39 and 40 (Fig. 6). The heat pipes 24A and 24B can transfer heat a great deal, specifically several hundred times compared to such good heat conductor metals as copper and aluminum. It is thus possible to cool the central part of the revolving scroll efficiently. Besides, the heat pipes are light in weight because they each are hollow only have the wick structure defining the inner space filled with the operating fluid, while permitting very quick transfer of heat from locality remote from the source of heat and even with a small temperature difference. Efficient cooling of revolving scroll central part thus can be obtained. It is further possible to easily set the heat transfer capacity by adequately designing the heat insulating zone 25b and appropriately designing the size and shape of the evaporating and condensing zones 25a and 25c. Fig. 11 shows a modification of the shaft/fan assembly in the embodiment of the scroll fluid machine according to the invention. In this case, a drive shaft 11F has passages 11Fr and 11Fl formed in it at an angle a inclination with respect to its axis P of rotation from its opposite ends toward its eccentric portion 11Fa. Heat pipes 24A and 24B are disposed in the passages 11Fr and 11Fl. A fan 13 is provided on the drive shaft 11F with its boss 21A fitted on and secured to the right end 11Fb of the drive shaft 11F. The fan 13 can exhaust cooling gas having cooled a heat radiating zone 25c of the heat pipe 24A to the outside as shown by arrows 36. Another fan 12 is provided on the left end 11Fe of the drive shaft 11F with its boss 21B secured in position by screwing a nut 22 on a threaded end portion 11Ff of the drive shaft 11F. The fan 12 can exhaust cooling gas having cooled a heat radiating zone 25c of the heat pipe 24B as shown by arrows 36. With this modified construction, heat exchange is obtained by the operation as described above in connection with the third embodiment. Specifically, the heat pipes 24A and 24B evaporate and gasify operating fluid in them by absorbing heat generated in the revolving scroll 3 from their heating zones (or evaporating zones) 25a in the vessels 25, and in their condensing zones 25c the gasified fluid is cooled and liquified by external gas sucked by the fans 12 and 13 as shown by arrows 35, 35. The external gas having contributed to the cooling is exhausted through the holes 29Ab and 29Bb in the shields 29A and 29B (Figs. 4 and 5) to the outside as shown by arrow 36, 36. Gas which has cooled the housing parts 4 and 5 on the side thereof opposite the stationary scroll laps is exhausted through the holes 29Aa and 29Ba of the shields 29A and 29B (Figs. 4 and 5) together with the gas having cooled the central part of the revolving scroll to the outside as shown by arrows 39 and 40 (Fig. 6). Since in this modification the passages 11Fr and 11Fl are inclined with respect to the drive shaft axis P, in the above heat exchange process the heating zones 25a revolve about the axis P to generate centrifugal forces forcing the operating fluid that is liquified in the condensing zones 25c to the heating zones 25a, thus promoting the re-circulation of the operating fluid and improving the cooling effect. It will be seen that according to the invention it is possible to use heat pipes of rotary type utilizing centrifugal forces as well as heat pipes based on the operating fluid re-circulating system having capillary tube action type, thus those using are of a very wide range. The fan 13 further exhausts gas having cooled the rear side of the housing part 4 as the stationary scroll opposite the lap side thereof as shown by arrows 40 (Fig. 6). Thus, not only the revolving scroll central part but other scroll fluid machine parts can be cooled, thus improving the cooling efficiency. As has been described in the foregoing, the scroll fluid machine drive shaft, on which the central part of the revolving scroll is mounted, and which is coupled to the drive, can be cooled directly, that is, heat generated in the process, in which fluid sucked from the edge of the revolving scroll is fed to the central part thereof while being progressively compressed, can be removed at the central part which is elevated to the highest temperature. It is thus possible to efficiently cool bearings and seal members provided near the revolving scroll central part and the drive shaft. In addition, the thermal expansion difference between the stationary and revolving scrolls can be eliminated to provide a uniform temperature distribution, prevent scoring of the laps and extend the grease maintenance cycle, thus improving the durability. Since heat generation can be reduced, the clearance between adjacent scrolls can be reduced. Also, the high speed operation can be increased to increase the attainable pressure. In the above embodiments, the lap sliding surface of the revolving scroll is formed with the gas ballast suction hole, which has a smaller diameter than the thickness of the revolving scroll laps so that it can be opened and closed by driving of above revolving scroll lap, that is, closed above suction hole in synchronism to the instant when the final sealed spaces formed by the stationary and revolving scrolls are communicated with the discharge passage to the outside. More specifically, the gas ballast suction hole is closed while the final sealed spaces are communicated with the discharge passage. Thus, compressed fluid can be discharged through the discharge passage to the outside without possibility of its back flow through the suction hole. Since the back flow of compressed fluid can be eliminated by a simple arrangement of setting the diameter of the suction hole to be smaller than the lap thickness, it is not necessary to provide any particular check valve in the gas ballast suction hole. In the above embodiments, which comprise the double side lap revolving scroll with the laps provided on the opposite sides and the first and second stationary laps with the laps thereof engaging with the respective revolving scroll laps, the gas ballast suction hole is formed in one of the stationary scrolls, the communication hole is formed in the scroll body of the revolving scroll to lead gas to the sealed space formed by the lap of the other stationary scroll and the associated revolving scroll lap, and the discharge hole is formed in the afore-mentioned one stationary scroll, thereby discharging compressed gas from both the sealed spaces through the discharge hole to the outside. That is, the suction hole and the discharge hole are both formed in one of the stationary scrolls. In other words, those above two holes are concentratedly provided on the side of the afore-mentioned one stationary scroll opposite the lap side thereof. This construction is simple and ready to manufacture compared to the case of forming the holes distributedly in the two stationary scrolls. Moreover, since the communication hole formed in the scroll body of the revolving scroll leads gas, which is introduced through the gas ballast suction hole into the sealed space formed by one of the revolving scroll laps and the lap of one stationary scroll, to the sealed space formed by the other revolving scroll lap and the lap of the other stationary scroll, both the stationary scroll each need not be formed with a gas ballast suction hole but only a single stationary scroll may be formed with a suction hole, thus simplifying the construction and manufacture. The above embodiments can further be modified variously. Introducing gas into the spaces R and L through the gas ballast suction hole as shown above is by no means limitative; it is possible to introduce gas ballast gas into the spaces S and T. The suction pipe 10 and the discharge passage 4c, 4d are may be provided on the side of the hosing part 5 instead of providing them on the side of the housing part 4 (Fig. 6). It is possible to provide ballast gas suction holes in both the housing parts 4 and 5 to introduce gas ballast gas into the spaces R and L formed by the revolving and stationary scrolls from both sides. With this case, it is not necessary to arrange a suction hole 3e which are connected the space R with L, thus gas ballast gas can be introduced quickly from both sides, and the cooling efficiency is improved. It is of course possible to provide a discharge passage on the side of the housing part 5 as well as the discharge passage 4c, 4d on the side of the housing 4. As the gas ballast gas, atmospheric gas may be introduced through the suction pipe 10. It is desirable to heat dry gas air, N 2 gas, etc. to be introduced. In this case, it is possible to quicken the drying of vapor or fluid in the scroll lap and prevent it from deterioration. Moreover, in the above embodiments it is possible to introduce N 2 gas or like diluting gas through the suction pipe to dilute any harmful gas sucked from a vessel to be evacuated till safety standards. As has been shown, cooling means having high cooling efficiency is used to prevent scoring of the laps and extend the grease maintenance cycle for providing improved durability. Also, by reducing the heat generation the clearance between adjacent scrolls can be reduced. Furthermore, the high speed operation can be increased to increase the attainable pressure.

Claims: A scroll fluid machine comprising: a first and a second stationary scroll (4, 5), each having an end plate and an embedded scroll lap (6, 7) extending from the central part toward the outer periphery of the end plate (4, 5, 4b, 5b); a revolving scroll (3) having an end plate and scroll laps (26, 27) embedded in each side of the end plate, each scroll lap meshing with a respective scroll lap of the stationary scrolls; and a drive shaft (11) having an eccentric portion (11a), supporting the revolving scroll (3) the revolving scroll being revolved by the rotation thereof, the drive shaft having a hollow passage (lid) in it, characterised by a pain of heat pipes (24A, B) each having a heat absorbing zone (25a) and heat radiating zone (25c) and being installed in the hollow passage as a heat transfer means with each heat absorbing zone positioned at the longitudinal center part (11a) of the hollow passage and each heat radiating zone positioned at a respective end part (11b, e) of the hollow passage of the drive shaft. A scroll fluid machine according to claim 1, wherein the heat absorbing zone is positioned in the eccentric portion (11a) of the drive shaft and the heat radiating zone is positioned at the station-ary scroll side end part (11b, e) of the hollow passage (11d) of the drive shaft. A scroll fluid machine according to claim 1 or 2, wherein the hollow passage (11d, l, r) is inclined with respect to the axis (P) of rotation of the drive shaft (11) so that its center at the longitudinal center part of the passage is offset from the axis of rotation of the drive shaft and its center at each end of the passage intersects the axis of rotation of the drive shaft. A scroll fluid machine according to any of claims 1 to 3 which comprises cooling fans (12, 13) provided at both ends (11b, e) of the drive shaft (11) for cooling the radiating zone (25c) of each heat pipe (24A, B). A scroll fluid machine according to claim 4, wherein each cooling fan introduces air from the outer periphery side of the end plate (4, 5, 4b, 5b) of each stationary scroll (4, 5) toward the center thereof to cool the rear surface of each stationary scroll and the heat radiating zone (25c) of each heat pipe (24A, B), the air is exhausted flowing through each fan, and the heat absorbing zone (25a) of each heat pipe cools the central part of the revolving scroll (3).

Inventors: HAGA SHUJI, HAGA, SHUJI
Applicants: ANEST IWATA CORP, ANEST IWATA CORPORATION
Application year: 1996
Main classification: F04C29
IPC codes: F04C29