Scroll fluid machine

Abstract: A scroll fluid machine is disclosed, which comprises a stationary scroll 4, 5 with an embedded lap 6, 7 which is spiral in form and extends from a central part of a scroll body toward the outer periphery thereof, and a revolving scroll 3 with an embedded spiral lap 26, 27 engaging said spiral lap 6, 7, said revolving scroll having a scroll body coupled to a drive shaft 11A coupled to a drive at the central portion thereof. The drive shaft 11A is cooled directly by cooling means 11Ad provided inside. 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 the 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. 13 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. 14 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 O2-O2 with respect to the axis O1-O1 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. 13, 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. 14, 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. JP-A-61-200391 from which the pre-characterising part of claim 1 starts out discloses a scroll fluid machine having a drive shaft for driving a revolving scroll in meshing engagement with a stationary scroll. To cool the bearings and a motor coupled to the drive shaft, the drive shaft has a longitudinal cooling passage open at only one end, and a narrow feeding pipe is introduced from the open end into the cooling passage to inject a fluid into the same and let it return in the space between the walls of the feeding pipe and of the cooling passage to be discharged again from the open end of the cooling passage. This prior art has the disadvantage that the forward and backward flow of the fluid results in a relatively high flow resistance, the diameter of the cooling passage must be large and the fluid must be forced through the cooling passage. JP-A-59-155593 discloses a motor having a shaft provided with a cooling passage. US 5,417,554 relates to a scroll compressor having a cooling fan and cooling fins on the stationary and orbiting scroll bodies. Summary of the invention 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 rediced 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. Suitably, the drive shaft is formed with a hollow cooling passage for introducing cooling gas from one end and discharging the same from the other end in it. Suitably, turbulent flow forming means is provided in the cooling passage to stir the introduced cooling gas. It is thus possible to provide gas cooling means with a simple construction. Besides, by providing the turbulent flow forming means the gas temperature difference between an edge part of the cooling passage adjacent the surface thereof and a central part thereof can be quickly reduced, thus obtaining an improved cooling efficiency. More suitably, a fan is provided at one end of the drive shaft while providing at the other end of the cooling passage with radial communication holes toward the outer periphery of the above drive shaft, thus causing gas having contributed to the cooling by the fun to be compulsively exhausted through the communication holes to cool the drive shaft. Specifically, the revolving scroll 3 (Fig. 3) is cooled by cooling gas 32 passing through the cooling passage 11Ad (Fig. 1) or 11Bd (Fig. 2), and the gas that has contributed to the cooling is exhausted by the fan 13 through the communication holes 11Ac (Fig. 1) or 11Bc (Fig. 2). It is further suitable to form the drive shaft to be hollow and provide heat transfer means therein. 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, 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. It is further effective to provide a fan at one end of the drive shaft, and to form the drive shaft with a hollow cooling passage for introducing cooling gas from one end and discharging the same from the other end of the drive shaft toward the periphery through radial communication holes in the other end of the cooling passage, thereby causing gas having contributed to the cooling by the fan to be compulsively exhausted through the communication holes to cool the central part of the revolving scroll, while cooling the other part thereof except above central part with gas not having passed through said communication hole. With this construction, the central part of the revolving scroll 3 (Fig., 3) is cooled by cooling gas 32 passing through the cooling passage 11Ad (Fig. 1) or 11Bd (Fig. 2), and the gas having contributed to the cooling is compulsively exhausted by the fan 13 through the communication holes 11Ac (Fig. 1) or 11Bc (Fig. 2). The fan 13 further exhausts gas that has cooled the rear side of the housing part 4 (Fig. 3), i.e., the stationary scroll, with the lap 7 embedded therein, in the directions of arrows 40 in Fig. 6. Thus, 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, 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. 6) 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. The invention is further applicable to scroll fluid machine comprising a single-lap revolving scroll with a single lap embedded in one side surface of the scroll body and a single stationary scroll. In this case, either the stationary scroll or the revolving scroll may be located near a fan for exhausting gas having cooled the heat pipes and the stationary or revolving scroll on the side thereof opposite the lap. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view showing the shaft/fan assembly in a first embodiment of the scroll fluid machine according to the invention; Fig. 2 is a view showing the shaft/fan assembly in a second embodiment of the scroll fluid machine according to the invention; 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. 3; Fig. 5 is a view taken along line D-D in Fig. 3; 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 first embodiment of the scroll fluid machine according to the invention; Fig. 12 is a view showing a modification of the shaft/fan assembly in the second embodiment of the scroll fluid machine according to the invention; Fig. 13 is a view showing a prior art non-driven part cooling system; and Fig. 14 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. 8) 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 shows cooling means, i.e., a shaft/fan assembly, in a first embodiment of the scroll fluid machine according to the invention. Referring to the figure, a drive shaft 11A has a cooling passage 11Ad formed in it along its axis of rotation for introducing outer gas from a left open end 11Ag. The right end of the cooling passage 11Ad is shielded by a shield 23. The drive shaft 11A has a plurality of radially spaced-apart holes 11Ac formed adjacent its right end 11Ab and communicating the cooling passage 11Ad and its outside. A fan 13 is provided on the drive shaft 11A, that is, its boss 20A is fitted on and secured to the right end 11Ab of the drive shaft 11A. The boss 20A has holes 13a in communication with the holes 11Ac. The fan 13 thus can exhaust cooling gas having cooled the cooling passage 11Ad through the holes 13a to the outside as shown by arrows 34. Another fan 12 is provided on the left end llAe of the drive shaft 11A with its boss 20B secured thereto by a nut 22 screwed on a threaded end portion 11Af of the drive shaft 11A. The fan 12 can exhaust cooling gas, which has been led through holes 29Ba in a shield 29B (Fig. 5) and cooled the housing part 5 (Fig. 3) on the side thereof opposite the lap, to the outside as shown by arrows 39. With this construction, a central part of the revolving scroll 3 is cooled by cooling gas 32 passing through the cooling passage 11Ad, and the gas having contributed to the cooling is exhausted by the fan 13 through the communication holes 11Ac and the holes 29Ab in the shield 29A (Fig. 4). Fig. 2 is a view showing a shaft/fan assembly in a second embodiment of the scroll fluid machine according to the invention. Referring to the figure, a drive shaft 11B has a cooling passage 11Bd formed in it along its axis of rotation for introducing external gas from a left open end 11Bg. A helical groove 11Bb is formed in the inner surface of the passage 11Bd. The right end of the passage 11Bd is shielded by a shielded 23. The drive shaft 11B has a plurality of radially spaced-apart holes 11Bc formed adjacent its right end 11Bb and communicating the cooling passage 11Bd and its outside. A fan 13 is provided on the drive shaft 11 on the drive shaft 11B with its boss 20A fitted on and secured to the right end 11Bb of the drive shaft 11B, the boss 20A having a plurality of radially spaced-apart holes 13a. Coolant having cooled the cooling passage 11Bd is by the fan 13 through the holes 13a exhausted to the outside as shown by arrows 34. Another fan 12 is provided on the left end 11Be of the drive shaft 11B with its boss 20B secured thereto by a nut 22 screwed on a threaded end portion 11Bf of the drive shaft 11B. The fan 12 exhausts cooling gas having cooled the housing part (Fig. 3) on the side thereof opposite the lap through holes 29Ba formed in a shield 29B (Fig. 5) to the outside as shown by arrows 39. With this construction, a central part of the revolving scroll 3 is cooled by cooling gas 32 passing through the cooling passage 11Bd. At this time, the helical groove 11Bh functions as turbulent flow forming means to stir the introduced cooling gas, thus quickly reducing the gas temperature difference between an edge part of the cooling passage adjacent the surface thereof and a central part of the passage. Thus, efficient cooling can be obtained. It is possible to form the turbulent flow forming means by inserting a helical coil spring in the cooling passage 11Bd as well. It is further possible to insert a mixing pipe, which has an outer diameter equal to the inner diameter of the cooling passage 11Bd and mixes together two fluids, in the cooling passage 11Bd. 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). Fig. 11 is a view showing a modification of the shaft/fan assembly in the first embodiment of the scroll fluid machine of Fig. 1 according to the invention. In this case, a drive shaft 11D into which cooling gas is introduced, comprises a small diameter cylindrical part 11Dk, a large diameter eccentric cylindrical part 11Da, and a medium diameter cylindrical part 11Db. The small and medium diameter parts 11Dk and 11Db each have a cooling passage 11Dd of an equal diameter, and the large diameter eccentric part 11Da has a cooling passage 11Dj of a greater diameter and is provided between two cooling passages 11Dd of left and right side. These parts 11Dk, left side 11Dd, 11Dj and right side 11Dd being interconnected to one another in the mentioned order along line M-M on the inner peripheral surface of 11Da and 11Dj by solders 4 cones having 40a, 40b, 40c and 40d provided between adjacent ends of them. With this construction, when the drive shaft 11D, i.e., the passage 11Dj in the eccentric part 11Da, is rotated, cooling gas introduced into the cooling passage 11Dd is spread in the passage 11Dj in the eccentric part 11Da and is pushed by the inner peripheral surface of the passage 11Dj, thus generating a turbulent flow. Thus, efficient heat exchange can be obtained. Fig. 12 is a view showing a modification of the shaft/fan assembly in the second embodiment of the scroll fluid machine according to the invention. In this case, a drive shaft 11E into which cooling gas is introduced, comprises a small diameter cylindrical part 11Ek, a large diameter eccentric cylindrical part 11Ea, and a medium diameter cylindrical part 11Eb, these parts 11Ek, 11Ea and 11Eb being interconnected along line N-N by solders 40a to 40d provided between adjacent ends of them. The small and medium diameter parts 11Ek and 11Eb each have a cooling passage 11Ed of an equal diameter, and the large diameter eccentric part 11Ea has a passage 11Ej of a greater diameter. A helical groove 11Eh is formed in the inner surfaces of the passages 11Ed. With this construction, when the drive shaft 11E is rotated, the helical groove 11Ed forms a turbulent flow of cooling gas introduced into the cooling passage 11Ed. Further, with the rotation of the passage 11Ej of the eccentric part 11Ea the cooling gas is spread therein and pushed by the inner peripheral surface of this passage 11Ej, thus promoting the turbulent flow and permitting more efficient heat exchange. As described before in connection with the second embodiment, it is possible to replace this turbulent flow forming means with a helical coil spring inserted in the passages 11Ed and 11Ej. As a further alternative, a mixing pipe having an outer diameter equal to the inner diameter of the cooling passages 11Ed for mixing two different fluids may be inserted in the passages 11Ed. The invention has so far been described in conjunction with embodiments comprising the double-side revolving scroll with laps embedded in the opposite side surfaces of the scroll body and the stationary scrolls as shown in Fig. 3. However, this is by no means limitative, and the invention is also applicable to an embodiment comprising a single lap revolving scroll with a single lap embedded in only one side surface of a scroll body and a single stationary scroll. In this case, either the stationary scroll or the revolving scroll is located near the fan noted above. The fan can of course exhaust gas having cooled the heat pipes and also the stationary or revolving scroll on the side thereof opposite the lap. In the above embodiments of the invention, the fan is provided at one end of the drive shaft, which has the radial communication holes formed adjacent the other end of the cooling passage for communication thereof toward the outer periphery of axis. The fan serves to compulsively exhaust gas having contributed to the cooling of the cooling passage through the communication holes, thus cooling the revolving scroll central part while also cooling other parts of the scroll fluid machine with gas not passing through the cooling passage. Specifically, the central part of the revolving scroll 3 is cooled by cooling gas 32 passing through the cooling passage 11Ad (Fig. 1) or 11Bd (Fig. 2), while the gas having contributed to the cooling is compulsively exhausted by the fan 13 through the communication holes 11Ac (Fig. 1) or 11Bc (Fig. 2). 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, cooing 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 stationary scroll (4, 5) with an embedded spiral lap (6, 7) extending from a central part of a scroll body toward the outer periphery edge thereof, a revolving scroll (3) with an embedded spiral lap (26, 27) engaging said stationary scroll spiral lap, said revolving scroll having a scroll body coupled to a drive shaft (11) coupled to a drive (2), said drive shaft (11) for driving said revolving scroll (3) having a hollow longitudinal cooling passage (11Ad to 11Ed), one end of the cooling passage having an inlet opening (11Ag to 11Eg) for a coolant flowing therethrough, characterised in that the other end of the cooling passage communicates with radial holes (11Ac to 11Ec) in the drive shaft (11) for radially outwardly exhausting the coolant flowing through the cooling passage. A machine according to claim 1, wherein a fan (13) is provided on the drive shaft (11) near said radial holes (11Ac to 11Ec) to let cooling gas compulsively flow through the cooling passage (11Ad to 11Ed) and outwardly through said radial holes. A machine according to claim 1 or 2, wherein turbulent flow forming means (11Bh, 11Eh) is provided in the cooling passage (11Ad to 11Ed) to stir the coolant flowing therethrough. A machine according to any of claims 1 to 3, wherein said revolving scroll (3) is coupled to an eccentric portion (11Aa to 11Ea) of the drive shaft (11) for being driven to revolve when the drive shaft rotates. A machine according to any of claims 1 to 4, comprising another stationary scroll (5, 4) with a spiral lap (7, 6), wherein said revolving scroll (3) has a disk-like body, said spiral lap (26, 27) of the revolving scroll being provided on one side (3d, 3f) of the body, another spiral lap (27, 26) being provided on the other side (3f, 3d) of the body and engaging the spiral lap of the other stationary scroll. A machine according to claim 2, wherein said fan (13) is provided to compulsively exhaust cooling gas not having flown through the cooling passage for cooling a non-central part of the revolving scroll (3) and to compulsively exhaust cooling gas flowing through the cooling passage and the radial holes for cooling a central part of the revolving scroll. A machine according to claim 2, wherein said fan (13) is provided to compulsively exhaust cooling gas not having passed through said cooling passage for cooling said stationary scroll (26, 27) and to compulsively exhaust cooling gas flowing through the cooling passage and the radial holes for cooling 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, F04C18