Patent Publication Number: US-2006013706-A1

Title: Compressor

Description:
TECHNICAL FIELD  
      The present invention relates to an improvement of a viscous pump for supplying oil to sliding areas of a compressor.  
     BACKGROUND ART  
      Recently, household refrigerators and air-conditioners have been increasingly and rapidly shifting to energy-saving types to meet demands for protection of the global environment. In this situation, increasing numbers of refrigerant compressors are inverter-controlled, and the number of driving revolution is decreased to reduce the rotational speed. Accordingly, it is difficult to obtain sufficient lubrication by using conventional centrifugal pumps.  
      A conventional compressor, which is disclosed in JP-T-2002-519589, for example, includes a viscous pump which has stable pumping capability even at the time of low-speed revolution in lieu of a centrifugal pump.  
      The related-art compressor mentioned above is herein described with reference to the drawings. In this description, the positional correlations in the vertical direction are shown based on the condition in which a closed type electrically-powered compressor is installed in a normal position.  
       FIG. 34  is a cross-sectional view illustrating a main part of a conventional compressor. In  FIG. 34 , oil  7102  is stored in the bottom area of closed container  7101 . Electrically-powered element  7105  includes stator  7106  and rotor  7107  which contains permanent magnet. Rotor  7107  engages with hollow shaft  7111  of compressing element  7110 , and sleeve  7112  which is soaked with oil  7102  at least at its lower end and rotates integrally with shaft  7111  is fixed to shaft  7111 .  
      Substantially U-shaped bracket  7115  made from elastic material has a concave center portion and its both ends are fixed to shroud  7116  secured to stator  7106 . Insertion member  7120  made from plastic material and inserted into sleeve  7112  has a spiral groove on its outer surface to provide oil passage between insertion member  7120  and sleeve  7112 . The lower end of insertion member  7120  is fixed to the center portion of bracket  7115 .  
      The operation of the conventional compressor having the above structure is now described.  
      When electrically-powered element  7105  is energized, rotor  7107  rotates. Shaft  7111  revolves with the rotation of rotor  7107 , and compressing element  7110  carries out predetermined compressing operations. Oil  7102  rises through the oil passage formed between the spiral groove formed on the outer surface of insertion member  7120  and sleeve  7112  in accordance with the revolution of sleeve  7112  while rotating and being pulled by the inner surface of the sleeve due to viscosity, thereby drawing up oil  7102  toward the upper hollow region of shaft  7111 .  
     DISCLOSURE OF THE INVENTION  
      A compressor has a closed container which stores oil and accommodates a compressing element for compressing refrigerant and an electrically-powered element for driving the compressing element, wherein: the electrically-powered element includes a stator and a rotor; and the compressing element includes a shaft which extends in a vertical direction and rotates, and a viscous pump which is formed inside the shaft and communicates with the oil, the viscous pump having a cylindrical hollow portion formed in the shaft, an insertion member coaxially and rotatably inserted into the cylindrical hollow portion, a spiral groove formed between the inner surface of the cylindrical hollow portion and the outer surface of the insertion member along a direction where the oil rises, and prevention means for preventing rotation of the insertion member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a cross-sectional view illustrating a main part of a compressor in a first embodiment of the present invention.  
       FIG. 2  is a perspective view of a lower part of a shaft in the first embodiment of the invention.  
       FIG. 3  is a cross-sectional view illustrating the main part of the compressor in a driving condition immediately after start-up in the first embodiment of the invention.  
       FIG. 4  is a cross-sectional view illustrating a main part of a compressor in a second embodiment of the invention.  
       FIG. 5  is a perspective view of a lower part of a shaft in the second embodiment of the invention.  
       FIG. 6  is a cross-sectional enlarged view illustrating a sleeve in the second embodiment of the invention.  
       FIG. 7  is a cross-sectional view illustrating a main part of a compressor in a third embodiment of the invention.  
       FIG. 8  is a perspective view of a lower part of a shaft in the third embodiment of the invention.  
       FIG. 9  is a cross-sectional enlarged view illustrating a sleeve in the third embodiment of the invention.  
       FIG. 10  is a cross-sectional view illustrating a compressor in a fourth embodiment of the invention.  
       FIG. 11  is a cross-sectional view illustrating a main part of the compressor in the fourth embodiment of the invention.  
       FIG. 12  is a perspective view illustrating the main part of the compressor in the fourth embodiment of the invention.  
       FIG. 13  is a cross-sectional view illustrating a main part of a compressor in a fifth embodiment of the invention.  
       FIG. 14  is a cross-sectional view illustrating a main part of a compressor in a sixth embodiment of the invention.  
       FIG. 15  is a cross-sectional view of a compressor in a seventh embodiment of the invention.  
       FIG. 16  is a cross-sectional view illustrating a main part of the compressor in the seventh embodiment of the invention.  
       FIG. 17  is a cross-sectional view illustrating a main part of a compressor in an eighth embodiment of the invention.  
       FIG. 18  is a main part assembly view of the compressor in the eighth embodiment of the invention.  
       FIG. 19  is a cross-sectional view illustrating a compressor in a ninth embodiment of the invention.  
       FIG. 20  is a cross-sectional view illustrating a main part of the compressor in the ninth embodiment of the invention.  
       FIG. 21  is a cross-sectional view illustrating a compressor in a tenth embodiment of the invention.  
       FIG. 22  is a cross-sectional view illustrating a main part of the compressor in the tenth embodiment of the invention.  
       FIG. 23  is a cross-sectional view illustrating a compressor in an eleventh embodiment of the invention.  
       FIG. 24  is a cross-sectional view illustrating a main part of the compressor in the eleventh embodiment of the invention.  
       FIG. 25  is an enlarged view illustrating a main part of an insertion member in the eleventh embodiment of the invention.  
       FIG. 26  is a cross-sectional view illustrating a compressor in a twelfth embodiment of the invention.  
       FIG. 27  is a cross-sectional view illustrating a main part of the compressor in the twelfth embodiment of the invention.  
       FIG. 28  is a cross-sectional view illustrating a compressor in a thirteenth embodiment of the invention.  
       FIG. 29  is a cross-sectional view illustrating a main part of the compressor in the thirteenth embodiment of the invention.  
       FIG. 30  is a cross-sectional view illustrating a compressor in a fourteenth embodiment of the invention.  
       FIG. 31  is a cross-sectional view illustrating a main part of the compressor in the fourteenth embodiment of the invention.  
       FIG. 32  is a cross-sectional view illustrating a main part of a viscous pump in the fourteenth embodiment of the invention.  
       FIG. 33  is a cross-sectional view illustrating a main part of a compressor in a fifteenth embodiment of the invention.  
       FIG. 34  is a cross-sectional view illustrating a main part of a conventional compressor. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      According to the description of the structure of the above-described conventional compressor, a hollow opening is provided in an upper area of the viscous pump, and there is a large space for storing transferred oil. Especially, the process for further raising oil drawn by the viscous pump immediately after the start-up requires sufficient time for storing oil until the hollow opening is substantially filled with oil.  
      As a result, oil is transferred upward at lower speed and thus oil supply to sliding areas becomes unstable. This causes sliding components to contact each other while sliding, forming scratches and abrasion therebetween. These damages lead to a locked condition of the compressing element.  
      In order to solve the above problem, an object of the present invention is to provide a highly reliable compressor which transfers oil to each sliding area at high speed and has reliable and stable oil transfer capability even at the time of low-speed driving.  
      For achieving the above object, a compressor of the present invention includes a viscous pump which opens to oil stored in a lower region of a closed container and a second viscous pump connected to an upper region of the former viscous pump, both the viscous pumps being attached to a main shaft portion of a shaft. Since most area of an oil passage in the main shaft portion is occupied by the pumps, the space for storing oil and refrigerant is reduced. Consequently, the oil transfer speed increases. Additionally, oil receives not only centrifugal force which decreases at the time of low-speed revolution but also upward pressure while being pulled due to viscosity within the passage.  
      The compressor provided according to the present invention, which includes a viscous pump and a second viscous pump disposed above the viscous pump, is a highly reliable compressor which transfers oil at high speed and has stable oil transfer capability even at the time of low-speed driving.  
      First through third embodiments of the present invention is hereinafter described with reference to the drawings. The present invention is not limited to those embodiments.  
     Embodiment 1  
       FIG. 1  is a cross-sectional view illustrating a main part of a compressor in the first embodiment of the invention,  FIG. 2  is a perspective view of a lower part of a shaft in the first embodiment, and  FIG. 3  is a cross-sectional view illustrating the main part of the compressor in a driving condition immediately after start-up in the first embodiment.  
      In  FIGS. 1, 2  and  3 , oil  3102  is stored in closed container  3101  which is charged with refrigerant  3103 .  
      Compressing element  3110  includes: block  3109  which forms cylinder  3108 ; piston  3113  reciprocatively inserted into cylinder  3108 ; shaft  3111  having main shaft portion  3116  supported by main bearing  3114  of block  3109  and eccentric portion  3117 ; and connecting rod  3118  for connecting eccentric portion  3117  and piston  3113 . Compressing element  3110  forms a reciprocating compressing mechanism.  
      Electrically-powered element  105  is fixed below block  3109 . Electrically-powered element  105  includes stator  3106  connected to an inverter driving circuit (not shown) and rotor  3107  which contains permanent magnet (not shown) and is fixed to main shaft portion  3116 . Electrically-powered element  105  is an electrically-powered element  105  for driving the inverter, and is driven at a plurality of driving frequencies including those at least in a range from 600 to 1,200 r/min. by the inverter driving circuit.  
      Springs  3104  elastically support compressing element  3110  via stator  3106  so that compressing element  3110  is elastically held on closed container  3101 .  
      Main shaft portion  3116  of shaft  3111  has viscous pump  3130  soaked with oil  3102  and second viscous pump  3150  connected with viscous pump  3130  through communicating hole  3140 . Second viscous pump  3150  is disposed above viscous pump  3130 .  
      Next, the structures of viscous pump  3130  and second viscous pump  3150  connected with each other are described in detail.  
      Viscous pump  3130  includes: cylindrical hollow portion  3135  formed in main shaft portion  3116 ; sleeve  3131  secured to the lower region of cylindrical hollow portion  3135 ; insertion member  3133  coaxially inserted into cylindrical hollow portion  3135  and sleeve  3131 ; and supporting member  3132 . Supporting member  3132  has restricting means  3139  for restricting floating of insertion member  3133  in the rotational and vertical directions.  
      The upper end of cylindrical hollow portion  3135  reaches the lower region of main bearing  3114 .  
      Sleeve  3131  is substantially cylindrical and cap-shaped, whose top and bottom are open. Sleeve  3131  is made from iron plate press material which offers comparatively high accuracy, but may be formed from leaf spring steel.  
      Thread-shaped spiral groove  3134  is formed on the outer surface of insertion member  3133  to provide a spiral oil passage between spiral groove  3134  and sleeve  3131 , through which passage oil  3102  is allowed to flow. Insertion member  3133  has refrigerant-resistance and oil-resistance properties, and is made from plastic material having lower thermal conductivity than the metal material which forms shaft  3111 , such as PPS, PBT, and PEEK.  
      Supporting member  3132  is substantially U-shaped and made from elastic material such as iron spring wire. Both ends of supporting member  3132  are fixed to the lower position of stator  3106 . The center portion of supporting member  3132  engages with engagement holes  3137  through notches  3136  provided at the lower end of insertion member  3133 . Notches  3136  are disposed before engagement holes  3137  in the advancing direction of main bearing  3114  and joined with engagement holes  3137 . The length of joining portions  3138  of engagement holes  3137 , i.e., the length of the openings in contact with notches  3136  is smaller than the outside diameter of supporting member  3132 .  
      Second viscous pump  3150  includes main shaft portion  3116 , lead groove  3151  engraved on the outer surface of main shaft portion  3116 , and main bearing  3114 .  
      Main bearing  3114  is secured to block  3109 , or formed integrally with block  3109  to be secured thereto. Lead groove  3151  having a trapezoidal or substantially semicircular cross section is formed on the outer surface of main shaft portion  3116 , whereby a spiral oil passage through which oil flows is provided between main bearing  3114  and lead groove  3151 .  
      The upper end of lead groove  3151  communicates with eccentric communicating portion  3160  positioned within eccentric portion  3117 .  
      The operation and action of the compressor having the above structure are now described.  
      When stator  3106  is energized by the inverter driving circuit, rotor  3107  rotates with shaft  3111 . The eccentric motion of eccentric portion  3117  thus caused reciprocates piston  3113  within cylinder  3108  via connecting rod  3118 , thereby carrying out predetermined compressing actions for taking in and compressing refrigerant  3103 .  
      In accordance with the rotation of main shaft portion  3116  of shaft  3111 , oil  3102  rises through the oil passage formed between the outer surface of insertion member  3133  and the inner surface of sleeve  3131  included in viscous pump  3130  while being pulled by the rotation of sleeve  3131 . Oil  3102  then passes through communicating hole  3140  and reaches the starting point of lead groove  3151 . Subsequently, oil  7302  further rises through the oil passage formed between lead groove  3151  provided on the outer surface of main shaft portion  3116  of second viscous pump  3150  and the inner surface of main bearing  3114  while being pulled by the rotation of main shaft portion  3116 . Finally, oil  3102  is transferred to eccentric portion  3117 , connecting rod  3118  and other components through eccentric communicating portion  3160 .  
      In this embodiment as described above, most area of the oil passage of main shaft portion  3116  is occupied by viscous pump  3130  and second viscous pump  3150  and the space for storing refrigerant  3103  and oil  3102  is small. Therefore, oil  7302  is transferred to each sliding area at high speed without decreasing the speed. Moreover, oil  3102  receives not only centrifugal force which decreases at the time of low-speed revolution but also upward pressure while oil  3102  is being pulled within the oil passage due to viscosity, thereby drawing up oil  3102  in a reliable and stable manner even at the time of low-speed revolution.  
      Additionally, when oil  3102  in which refrigerant  3103  dissolves is heated by compressing element  3110 , electrically-powered element  3105  and other components and refrigerant  3103  is thus vaporized within the oil passage, the refrigerant gas is transferred together with oil  3102  owing to the high oil-transfer performance of viscous pump  3130  and second viscous pump  3150  connected with each other without hindering transfer of oil  3102 . As a result, oil  3102  can be transferred to each sliding area at high speed immediately after start-up even at the time of low-speed revolution such as 600 r/min., thereby realizing stable oil transfer capability.  
      Accordingly, damages such as flaws and abrasion which may lead to excessive wear or a locked condition of compressing element  3110  are not caused when the sliding components contact each other.  
      In this embodiment, rotor  3107  is fitted to main shaft portion  3116  by shrinkage fitting or press fitting. However, since the inside diameter of cylindrical hollow portion  3135  alters at the time of attachment of rotor  3107 , the dimension of the space between cylindrical hollow portion  3135  and insertion member  3133  in the radial direction is difficult to control. Thus, viscous pump  3130  is not provided in the region where rotor  3107  is fitted to main shaft portion  3116 . The length of that region, i.e., the length from the top surface of insertion member  3133  to communicating hole  3140  is in a range from about 10 mm to about 20 mm, which is substantially equivalent to the fitting length of rotor  3107 .  
      However, according to our finding from experiments in this embodiment, a known parabolic free surface is produced on the upper surface of oil  3102  within the cylindrical hollow portion due to centrifugal force immediately after start-up, and oil  3102  having reached the upper end surface of insertion member  3133  instantly comes to communicating hole  3140  as illustrated in  FIG. 3 . Thus, the oil transfer speed is scarcely affected if the length of the region where the pump is not provided is from about 10 mm to about 20 mm.  
      Since the oil transfer speed is considerably high, oil  3102  within cylindrical hollow portion  3135  rapidly flows into lead groove  3151  immediately after start-up, causing negative pressure inside cylindrical hollow portion  3135 . As a result, such a phenomenon that insertion member  3133  is sucked toward the upper region of cylindrical hollow portion  3135  is caused in very few cases. Additionally, reaction force against the force for moving oil upward caused by viscosity is always applied to insertion member  3133  in the downward direction during continuous operation.  
      However, floating of insertion member  3133  in the vertical direction is restricted by the engagement between the center portion of supporting member  3132  and engagement holes  3137  of insertion member  3133 . Thus, the structure of viscous pump  3130  in which oil  3102  is drawn up through the space between cylindrical hollow portion  3135  and insertion member  3133  due to viscosity can be maintained both at the start-up and during continuous driving.  
      Since the clearance between sleeve  3131  and insertion member  3133  is maintained by the oil pressure generated within spiral groove  3134 , the possibility of sliding abrasion and fixation between sleeve  3131  and insertion member  3133  is extremely low. Additionally, by determining the difference between the inside diameter of engagement holes  3137  and the outside diameter of supporting member  3132  in a range from several hundred μm to 1 mm instead of completely fixing supporting member  3132  to engagement holes  3137 , the clearance between sleeve  3131  and insertion member  3133  can be similarly maintained.  
      Joining portions  3138  of engagement holes  3137  are open in the advancing direction of main shaft portion  3116 , and a force in the rotational direction is applied on the side on which engagement holes  3137  are closed even at the time of high-speed revolution at a driving frequency in a range from 4,200 to 4,800 r/min., for example. However, this force is scarcely applied on the side on which joining portions  3138  are open. In this structure, insertion member  3133 , which does not rotate by the restriction of supporting member  3132 , is prevented from coming off from the predetermined position even at the time of high-speed driving.  
      The length of the regions of joining portions  3138  which are open to notches  3136  is smaller than the outside diameter of supporting member  3132 . Thus, supporting member  3132  does not easily come off from engagement holes  3137  once it is inserted into engagement holes  3137 , even if uncertain events such as vibrations occur during assembly at the line or transportation.  
      The compressor in this embodiment is inexpensive, as it does not require additional components for restricting rotation and vertically floating of insertion member  3133 .  
      Since a reliable and sufficient amount of oil  3102  is transferred even at the time of low-speed revolution, it is possible to reduce heat generated from main shaft portion  3116 , electrically-powered element  3105  and other components and thus prevent temperature increase of oil  3102 . Accordingly, while R600a as isobutane is more soluble in oil  3102  than R134a, vaporization of R600a and resultant accumulation of the gas do not occur within the oil passage, thereby preventing generation of obstruction for the transfer of oil  3102  such as a gas choke phenomenon.  
      Viscous pump  3130  and second viscous pump  3150  are assembled integrally with electrically-powered element  3105  and compressing element  3110 , inserted into closed container  3101 , and finally supported with elasticity by springs  3104  inside closed container  3101 . Thus, constituting components for viscous pump  3130  and second viscous pump  3150  are not required to be provided in closed container  3101 . Accordingly, the compressor in this embodiment is easily assembled and has high productivity, and requires only the minimum number of components and thus realizes cost reduction in manufacture.  
      In this embodiment, sleeve  3131  is fastened within cylindrical hollow portion  3135 . However, insertion member  3133  may be directly inserted into cylindrical hollow portion  3135  formed by the processed main shaft portion to provide a viscous pump instead of using sleeve  3131 , if the accuracy within 500 μm can be secured for the clearance between the outermost surface of insertion member  3133  and the inside surface of cylindrical hollow portion  3135 . While the number of components in this structure is different from that of the above-described embodiment, both cases are basically identical in the aspects of operation, action and advantages.  
     Embodiment 2  
       FIG. 4  is a cross-sectional view illustrating a main part of a compressor in a second embodiment of the invention,  FIG. 5  is a perspective view of a lower part of a shaft in the second embodiment, and  FIG. 6  is a cross-sectional enlarged view illustrating a sleeve in the second embodiment.  
      The second embodiment is herein described with reference to  FIGS. 4, 5  and  6 . Similar numbers are given to the structures similar to those of the first embodiment, and detailed description of those is omitted.  
      Main shaft portion  3216  of shaft  3211  included in compressing element  3210  has viscous pump  3230  soaked with oil  3102  and second viscous pump  3150  connected with viscous pump  3230  through communicating hole  3140 . Second viscous pump  3150  is disposed above viscous pump  3230 .  
      Next, the structures of viscous pump  3230  and second viscous pump  3150  connected with each other are described in detail.  
      Viscous pump  3230  is coaxially inserted into cylindrical hollow portion  3235  formed in main shaft portion  3216  and sleeve  3231  secured to the lower region of cylindrical hollow portion  3235 . Viscous pump  3230  includes insertion member  3233  having two supporting members  3232  which extend from the lower end of insertion member  3233  in the almost horizontal direction, and restricting means  339  having free joints  3261  which is combined with supporting members  3232  such that free joints  3261  and supporting members  3232  can freely rotate so as to restrict floating of insertion member  3233 .  
      The upper end of cylindrical hollow portion  3235  reaches the lower part of main bearing  3114 .  
      Thread-shaped spiral groove  3234  is formed on the inner surface of sleeve  3231  to provide a spiral oil passage between spiral groove  3234  and insertion member  3233 , through which passage oil  3102  is allowed to flow.  
      Insertion member  3233  has refrigerant-resistance and oil-resistance properties, and is made from plastic material or other material having lower thermal conductivity than metal material. Supporting members  3232  made from metal wire penetrate through the lower end of insertion member  3233  to be fixed thereto.  
      Substantially L-shaped free joint  3261  is fixed to the lower part of stator  3106  at one end, and has notch  3236  and engagement hole  3237  at the other end. The end of supporting member  3232  which is formed at the lower end of insertion member  3233  is inserted through notche  3236  into engagement hole  3237 , thereby combining supporting member  3232  and free joint  3261  such that both can freely rotate. This structure restricts floating of insertion member  3233  in the rotational and vertical directions.  
      Notches  3236  are disposed before engagement holes  3237  in the advancing direction of main shaft portion  3216  and joined with engagement holes  3237 . The length of joining portions  3238  of engagement holes  3237 , i.e., the length of the openings in contact with notches  3236  is smaller than the outside diameter of supporting members  3232 .  
      Second viscous pump  3250  include main shaft portion  3216 , lead groove  3251  engraved on the outer surface of main shaft portion  3216 , and main bearing  3114 .  
      Lead groove  3251  having a trapezoidal or substantially semicircular cross section is formed on the outer surface of main shaft portion  3216 , whereby a spiral oil passage through which oil  3102  flows is provided between main bearing  3114  and lead groove  3251 .  
      The operation and action of the compressor having the above structure are now described.  
      When stator  3106  is energized by the inverter driving circuit, main shaft portion  3216  of shaft  3211  rotates. In accordance with this rotation, oil  3102  rises through the oil passage formed between the inner surface of sleeve  3231  and the outer surface of insertion member  3233  included in viscous pump  3230  while being pulled by the rotation of sleeve  3231 . Oil  3102  then passes through communicating hole  3140  and reaches the starting point of lead groove  3251 .  
      Subsequently, oil  3102  further rises through the oil passage formed between lead groove  3251  provided on the outer surface of main shaft portion  3216  and the inner surface of main bearing  3114  included in second viscous pump  3250  while being pulled by the rotation of main shaft portion  3216 .  
      In the embodiment as described above, oil  3102  is transferred to each sliding area at high speed by the similar mechanism as in the first embodiment. Moreover, the stable oil transfer capability can be maintained even at the time of low-speed revolution such as 600 r/min. Accordingly, damages such as flaws and abrasion which may lead to excessive wear or a locked condition of compressing element  3210  are not caused when the sliding components contact each other, and thus a highly reliable compressor can be provided.  
      Moment generated through the rotation applies load, and the load applied to a certain position decreases as the distance from that position to the rotational shaft center of shaft  3211  increases. Since the distance between the rotational shaft center and combining portion  3263  for combining supporting member  3232  and free joint  3261  included in restricting means  3239  is large in this embodiment, the load applied to combining portions  3263  is decreased, thereby considerably reducing the possibility of breaking of combining portions  3263 .  
      In this embodiment, spiral groove  3234  is formed on the inner surface of sleeve  3231  to enlarge the area of inner surface of the rotational body in contact with oil  3102  by adding the surface area of the concaves of spiral groove  3234 . This structure causes large viscous resistance, thereby enhancing oil transfer capability.  
      Furthermore, centrifugal force generated through the rotation of main shaft portion  3216  is applied to oil  3102  existing within the oil passage formed between the inner surface of sleeve  3231  and the outside surface of insertion member  3233  and oil  3102  rises while rotating and inclining toward the farthermost surface from the rotational shaft center in the oil passage. Since there is no clearance in the oil passage to which the centrifugal force is most applied in this embodiment, oil  3102  does not fall to flow out and thus the amount of oil  3102  which falls to flow out can be controlled. Accordingly, the compressor in this embodiment has considerably higher transfer capability of oil  3102  than the example in which the spiral groove is formed on insertion member  3233 .  
     Embodiment 3  
       FIG. 7  is a cross-sectional view illustrating a main part of a compressor in a third embodiment of the invention,  FIG. 8  is a perspective view of a lower part of a shaft in the third embodiment, and  FIG. 9  is a cross-sectional enlarged view illustrating a sleeve in the third embodiment.  
      The third embodiment is herein described with reference to  FIGS. 7, 8  and  9 . Similar numbers are given to the structures similar to those of the first embodiment, and detailed description of those is omitted.  
      Main shaft portion  3316  of shaft  3311  included in compressing element  3310  has viscous pump  3330  soaked with oil  3102  and second viscous pump  3350  connected with viscous pump  3330  through communicating hole  3140 . Second viscous pump  3150  is disposed above viscous pump  3330 .  
      Next, the structures of viscous pump  3330  and second viscous pump  3350  connected with each other are described in detail.  
      Viscous pump  3330  includes: cylindrical hollow portion  3335  formed in main shaft portion  3316 ; sleeve  3331  secured to cylindrical hollow portion  3335 ; spiral member  3373  as a coil spring fixed to the inner surface of sleeve  3331 ; insertion member  3333  coaxially inserted into cylindrical hollow portion  3335  and sleeve  3331 ; and restricting means  3339  having supporting member  3332  for restricting floating of insertion member  3333 .  
      Supporting member  3332  is substantially U-shaped and made from elastic material such as iron spring wire. Both ends of supporting member  3332  are fixed to the lower region of stator  3106 . The center portion of supporting member  3332  engages with engagement grooves  3336  provided at the lower end of insertion member  3333  to restrict floating of insertion member  3333  in the rotational and vertical directions.  
      Eccentric passage  3372  formed above cylindrical hollow portion  3335  has a smaller inside surface diameter than the inside diameter of sleeve  3331 , and is off-centered from the rotational shaft center toward the side where communicating hole  3140  is provided. The floating of insertion member  3333  in the upward direction is restricted by contacting with upper bottom  3380  of cylindrical hollow portion  3335 . The clearance between the upper surface of insertion member  3333  and upper bottom  3380  of cylindrical hollow portion  3335  is so determined as to be smaller than a height (B) of engagement groove  3336  in the longitudinal direction so as to prevent separation of insertion member  3333  from supporting member  3332  when insertion member  3333  rises.  
      The upper end of eccentric passage  3372  reaches the lower part of main bearing  3114 , where eccentric passage  3372  communicates with communicating hole  3140 .  
      An oil passage is formed between spiral member  3373  as the coil spring fixed to the inner surface of sleeve  3331  and insertion member  3333 , through which passage oil  3102  is allowed to flow.  
      Substantially cylindrical sleeve  3331  has a shape of a cap whose top and bottom are open. Sleeve  3331  has substantially L-shaped spring holder  3374  at its lower region. Sleeve  3331  is made from iron plate press material which can be processed with relatively high accuracy in this embodiment, but may be made from leaf spring steel.  
      The length of the coil spring of spiral member  3373  is larger than the total length of the inner surface of sleeve  3331  from which the length of the spring holder  3374  in the axial direction is subtracted. As a result, spiral member  3373  is compressed between upper bottom  3380  of cylindrical hollow portion  3335  and spring holder  3374  and fixed to the inner surface of sleeve  3331 .  
      Spiral member  3373  is made from oil temper wire for springs (SWOV) in this embodiment, but may be made from other material including iron steel such as piano wire (SWP) and spring steel (SUP), non-iron metal such as aluminum, plastic material (PC, PA) whose thermal deformation temperature is 100° C. or higher and which has high formability, and other material having oil transfer capability of the spiral groove.  
      Second viscous pump  3350  includes main shaft portion  3316 , lead groove  3351  engraved on the outer surface of main shaft portion  3316 , and main bearing  3114 .  
      Lead groove  3351  having a trapezoidal or substantially semicircular cross section is formed on the outer surface of main shaft portion  3316 , whereby a spiral oil passage through which oil  3102  flows is provided between main bearing  3114  and lead groove  3351 .  
      The operation and action of the compressor having the above structure are now described.  
      When stator  3106  is energized by the inverter driving circuit, main shaft portion  3316  of shaft  3311  rotates. In accordance with this rotation, oil  3102  rises through the oil passage formed between spiral member  3373  and the outer surface of insertion member  3333  included in viscous pump  3330  while being pulled by the rotation of sleeve  3331 . Oil  3102  then passes through communicating hole  3140  and reaches the starting point of lead groove  3351 .  
      Subsequently, oil  3102  further rises through the oil passage formed between lead groove  3351  and the inner surface of main bearing  3114  included in second viscous pump  3350  while being pulled by the rotation of main shaft portion  3116 .  
      In the embodiment as described above, oil is transferred to each sliding area at high speed by the similar mechanism as in the first embodiment. Moreover, the stable oil transfer capability can be maintained even at the time of low-speed revolution such as 600 r/min. Accordingly, damages such as flaws and abrasion which may lead to excessive wear or a locked condition of compressing element  3310  are not caused when the sliding components contact each other, and thus a highly reliable compressor can be provided.  
      In assembly, the position of insertion member  3333  within cylindrical hollow portion  3335  in the vertical direction can be determined by aligning the upper surface of insertion member  3333  with upper bottom  3380  of cylindrical hollow portion  3335 . Supporting member  3332  can be attached to insertion member  3333  by bringing supporting member  3332  into engagement with engagement grooves  3336  provided at the lower end of insertion member  3333 . Thus, the assembly is facilitated.  
      In this embodiment, viscous pump  3330  which uses the shape of the coil spring itself as spiral member  3373  provided on the inner surface of sleeve  3331  can be far more easily formed than the structure in which a spiral groove is directly engraved on the inner surface of sleeve  3331 .  
      From the viewpoint of energy saving, the amount of oil transfer can be appropriately controlled by replacing the coil spring with the one having a different wire diameter, wire cross-sectional shape, number of winding etc., in accordance with the driving frequency required by the system side such as household refrigerators and air conditioners. Thus, the compressor of this embodiment is highly flexible and capable of meeting a wide variety of demands.  
      Attachment of sleeve  3331  to the lower end of main shaft portion  3316  is completed by forcedly inserting sleeve  3331 , which has the coil spring of spiral member  3373  around its inner surface in advance, into cylindrical hollow portion  3335  formed coaxially with main shaft portion  3316 . Also, formation of the spiral groove necessary for the upward transfer of oil  3102  is completed by compressing spiral member  3373  between upper bottom  3380  of cylindrical hollow portion  3335  and spring holder  3374  and securing spiral member  3373  to the inner surface of sleeve  3331 .  
      Thus, the assembly is extremely practical and easy, thereby enhancing productivity.  
      In the invention as described above, since most area of the oil passage of the main shaft portion is occupied by the pumps, the space for storing oil and refrigerant is small and oil is transferred at high speed. Also, not only centrifugal force which decreases at the time of low-speed revolution but also upward pressure is given to oil while oil is being pulled within the passage due to viscosity, thereby drawing up oil in a reliable and stable manner even at the time of low-speed revolution. Therefore, a highly reliable compressor having positive and stable oil transfer capability can be provided.  
      In addition to the above advantage, the highly reliable compressor provided according to the invention has high productivity and is manufactured at low cost.  
      Another advantage of the highly reliable compressor provided according to the invention is that the rotation, rising and falling of the insertion member can be securely prevented even at the start-up and during continuous driving, thereby realizing reliable and stable oil transfer capability.  
      Another advantage of the highly reliable compressor provided according to the invention is that rising and resultant separation of the insertion member from the restricting means and also abrasion and chipping of the insertion member due to the contact and collision between the inner surface of the cylindrical hollow portion and the outer surface of the insertion member are prevented, thereby realizing reliable and stable oil transfer capability.  
      Another advantage of the highly reliable compressor provided according to the invention is that the possibility of breaking of the restricting means is extremely low.  
      Another advantage of the highly reliable compressor provided according to the invention is that assembly of the compressor is facilitated.  
      Another advantage of the highly reliable compressor provided according to the invention is that multiplicatively large oil transfer capability can be obtained.  
      Another advantage of the highly reliable compressor provided according to the invention is that the compressor is highly flexible and has enhanced productivity.  
      Another advantage of the highly reliable compressor provided according to the invention is that power consumption is reduced since input to the compressor is decreased and oil supply is stabilized.  
      Another advantage of the highly reliable compressor provided according to the invention is that the compressor is easily assembled to achieve enhanced productivity and includes the viscous pumps.  
      Another advantage of the highly reliable compressor provided according to the invention is that generation of obstructions to the oil transfer such as gas choke phenomenon is prevented.  
      Another advantage of the highly reliable compressor provided according to the invention is that the compressor gives extremely little adverse effect on the global environment since the greenhouse effect coefficient of R600a employed is substantially zero and low-speed revolution reduces power consumption.  
      In the above-described conventional structure in which bracket  7115  supports insertion member  7120 , insertion member  7120  comes to be fixed within sleeve  7112  if the dimensional precision is insufficient. This fixation is absorbed by the elasticity of the material of bracket  7115 . However, if the fixation is extremely large, abrasion is generated between sleeve  7112  and insertion member  7120 . The abrasion thus caused may decrease the pumping ability and generate abrasion powder which is circulated with oil toward the sliding area and caught between the sliding components and thus brings about a locked condition of the compressing element.  
      Additionally, as insertion member  7120  passes through rotor  7107  to be indirectly fixed to stator  7106 , additional long components for insertion member  7120  with stator  7106  and suitable means and processes for fixing those components are required. Thus, the cost of the compressor is inevitably raised. It is thus an object of the invention to provide a highly reliable and inexpensive compressor.  
      Compressors in Fourth and fifth embodiments of the present invention are herein described with reference to the drawings.  
     Embodiment 4  
       FIG. 10  is a cross-sectional view illustrating a compressor in the fourth embodiment of the invention,  FIG. 11  is a cross-sectional view illustrating a main part of the compressor in the fourth embodiment, and  FIG. 12  is a perspective view illustrating the main part of the compressor in the fourth embodiment.  
      In FIGS.  10  to  12 , oil  1102  is stored in closed container  1101  which is filled with refrigerant gas  1103 .  
      Compressing element  1110  includes: block  1115  which forms cylinder  1113 ; piston  1117  reciprocatively inserted into cylinder  1113 ; shaft  1125  having main shaft portion  1120  supported by main bearing  1116  of block  1115  and eccentric portion  1122 ; and connecting rod  1119  for connecting eccentric portion  1122  and piston  1117 . Compressing element  1110  forms a reciprocating compressing mechanism.  
      Electrically-powered element  1135  is fixed below block  1115 . Electrically-powered element  1135  includes stator  1136  connected to an inverter driving circuit (not shown) and rotor  1137  which contains permanent magnet and is fixed to main shaft portion  1120 . Electrically-powered element  1135  thus forms an electrically-powered element for driving the inverter.  
      Springs  1139  elastically support compressing element  1110  via stator  1136  so that compressing element  1110  can be elastically supported on closed container  1101 .  
      Main shaft portion  1120  of shaft  1125  has viscous pump  1140  soaked with oil  1102  at its lower end. Viscous pump  1140  includes: cylindrical hollow portion  1142  formed in the lower region of main shaft portion  1120 ; insertion member  1145  coaxially and rotatably inserted into cylindrical hollow portion  1142 ; and impellers  147  having a plurality of vanes which are formed integrally with insertion member  1145 . A thread-shaped spiral projection  1149  is provided on the outer surface of insertion member  1145 , thereby forming a spiral groove  1150  through which oil  1102  flows between spiral projection  1149  and cylindrical hollow portion  1142 .  
      Insertion member  1145  and impellers  1147  have component  1151  formed by a shaped plastic component having refrigerant-resistance and oil-resistance properties. Component  1151  is hollow and has upper region  1152  where penetration  1153  is opened. Screw  1157  inserted into penetration  1153  rotatably connects component  1151  to the ceiling of cylindrical hollow portion  1142 .  
      Communicating hole  1160  extends upward from the ceiling of cylindrical hollow portion  1142  to connect cylindrical hollow portion  1142  with lateral hole  1162  which is open to a sliding area formed by the inner surface of bearing  1116  and the outer surface of main shaft portion  1120 .  
      The operation of the compressor having the above structure is now described. When stator  1136  is energized by the inverter driving circuit, rotor  1137  rotates with shaft  1125 . In accordance with this rotation, the eccentric motion of eccentric portion  1122  reciprocates piston  1117  within cylinder  1113  via connecting rod  1119 , thereby carrying out predetermined actions for compressing gas which is taken in.  
      Cylindrical hollow portion  1142  rotates with the rotation of main shaft portion  1120  of shaft  1125 . Insertion member  1145  then tries to rotate with the rotation of cylindrical hollow portion  1142 , but in reality insertion member  1145  rotates at a number of revolution far smaller than that of cylindrical hollow portion  1142  since impellers  1147  receive strong viscous resistance in the rotational direction within oil  1102 . Thus, there is a difference in the number of revolution between cylindrical hollow portion  1142  and insertion member  1145 , which difference is near the number of revolution of shaft  1125 . Consequently, oil  1102  rises within spiral groove  1150  while being pulled by the rotation of cylindrical hollow portion  1142 . Then, oil  1102  further rises through communicating hole  1160  by the oil pressure thus generated, passes through lateral hole  1162 , and reaches the sliding area formed by the inner surface of bearing  1116  and the outer surface of main shaft portion  1120  to lubricate that area.  
      At this stage, oil  1102  rises while rotating not only by the centrifugal force which decreases at low-speed revolution but by a pulling force generated by viscosity. Thus, oil can be drawn up in a stable manner even at the time of low-speed revolution such as 600 rpm.  
      According to this embodiment, since component  1151  is rotatably connected to the ceiling of cylindrical hollow portion  1142  only by screw  157  inserted into penetration  1153 , lateral pressure due to fixation is scarcely applied between cylindrical hollow portion  1142  and insertion member  1145 , and there is very few possibility of occurrence of sliding abrasion between cylindrical hollow portion  1142  and insertion member  1145 . It is thus possible to prevent generation of abrasion powder which is circulated with oil toward the sliding area and caught between the sliding components and thus brings about a locked condition of the compressing element. Accordingly, the compressor provided according to this embodiment is highly reliable.  
      Furthermore, the rotation of insertion member  1145  is prevented while impellers  1147  are receiving strong viscous resistance in the rotational direction within oil  1102 . Thus, indirect fixing of insertion member  1145  to stator  1136  as in the conventional example is not needed. Also, since the structure is extremely simple in which insertion member  1145  is rotatably connected to the ceiling of cylindrical hollow portion  1142  only by screw  1157  inserted into penetration  1153  of upper region  1152 , only a small number of components and processes are required and cost-reduction of the compressor is attained.  
     Embodiment 5  
       FIG. 13  is a cross-sectional view illustrating a main part of a compressor in a fifth embodiment according to the invention. The fifth embodiment is herein described with reference to  FIG. 13 . Similar numbers are given to the structures similar to those of the fourth embodiment, and detailed description of those is omitted.  
      Viscous pump  1240  soaked with oil  1102  is provided at the lower end of main shaft portion  1220  of shaft  1225 .  
      Communicating hole  1241  is coaxially formed within main shaft portion  1220 . Viscous pump  1240  includes: sleeve  1243  forcedly inserted into communicating hole  1241  and fixed thereto to form cylindrical hollow portion  1242 ; insertion member  1246  coaxially and rotatably inserted into sleeve  1243 ; and impellers  1247  having a plurality of vanes which are formed integrally with insertion member  1246 .  
      Sleeve  1243  is substantially cylindrical and cap-shaped, and has upper surface  1245  where screw hole  1244  is provided. Upper surface  1245  has path hole  1248  through which oil  1102  flows.  
      Sleeve  1243  is made from iron plate press material which offers comparatively high accuracy and is an appropriate material through which insertion member  1246  slides, but may be formed from other suitable materials through which insertion member  1246  slides such as plastics and leaf spring steel.  
      A thread-shaped spiral projection  1249  is provided on the outer surface of insertion member  1246 , thereby forming spiral groove  1250  through which oil  1102  flows between spiral projection  1249  and sleeve  1243 .  
      Insertion member  1246  and impellers  1247  have component  1251  formed by a shaped plastic component having refrigerant-resistance and oil-resistance properties. Component  1251  is hollow and has upper region  1252  where penetration  1253  is provided. Screw  1257  inserted through penetration  1253  is screwed into screw hole  1244  via washer  1257   a  to rotatably connect component  1251  to upper surface  1245 .  
      Washer  1257   a  is made from 4-fluorinated ethylene and controls the sliding with component  1251  in the thrust direction.  
      Communicating hole  1241  opens to a sliding area formed by the inner surface of bearing  1116  and the outer surface of main shaft portion  1220  to communicate with the sliding area through lateral hole  1262 .  
      The operation of the compressor having the above structure is now described.  
      When stator  1136  is energized by the inverter driving circuit, rotor  1137  rotates with shaft  1225 .  
      In accordance with the rotation of main shaft portion  1220  of shaft  1225 , cylindrical hollow portion  1242  formed by sleeve  1243  rotates. Insertion member  1246  then tries to rotate with the rotation of cylindrical hollow portion  1242 , but in reality insertion member  1246  rotates at a number of revolution far smaller than that of cylindrical hollow portion  1242  since impellers  1247  receive strong viscous resistance in the rotational direction within oil  1102 . Thus, there is a difference in the number of revolution between cylindrical hollow portion  1242  and insertion member  1246 , which difference is near the number of revolution of shaft  1225 . Consequently, oil rises through spiral groove  1250  while being pulled by the rotation of cylindrical hollow portion  1242 . Then, oil  1102  further rises through path hole  1248  in communicating hole  1241  by the oil pressure thus caused, passes through lateral hole  1262 , and reaches the sliding area formed by the inner surface of bearing  1116  and the outer surface of main shaft portion  1220  to lubricate that area.  
      At this stage, oil  1102  rises while rotating not only by the centrifugal force which decreases at low-speed revolution but by a pulling force generated by viscosity. Thus, oil can be drawn up in a stable manner even at the time of low-speed revolution such as 600 rpm.  
      According to this embodiment, component  1251  is rotatably connected to upper surface  1245  via washer  1257   a  only by screw  1257  inserted through penetration  1253 . Thus, lateral pressure due to fixation is scarcely applied between sleeve  1243  and insertion member  1246 , and there is very few possibility of occurrence of sliding abrasion between sleeve  1243  and insertion member  1246 . It is thus possible to prevent generation of abrasion powder which is circulated with oil and caught between the sliding components and thus brings about a locked condition of the compressing element. Accordingly, the compressor provided according to this embodiment is highly reliable.  
      A force in the downward direction as a reaction to a force for pushing up oil  1102  is applied to sleeve  1243 . The downward force is given to the sliding surface as a load in the thrust direction. The sliding area exists at the position between upper surface  1245  of sleeve  1243  and washer  1257   a  in this embodiment, but extreme abrasion at that position is prevented by the self-lubrication ability of washer  1257   a  which is made from 4-fluorinated ethylene.  
      The rotation of insertion member  1246  is prevented while impellers  1247  are receiving strong viscous resistance in the rotational direction within oil  1102 . Thus, indirect fixing of insertion member  1246  to stator  1136  as in the conventional example is not needed. Also, since the structure is extremely simple in which insertion member  1246  is rotatably connected to upper surface  1245  via washer  1257   a  only by screw  1257  inserted through penetration  1253  of upper region  1252 , only a small number of components and processes are required and thus cost-reduction of the compressor can be attained.  
      In this embodiment, viscous pump  1240  is assembled in advance as an independent component by joining sleeve  1243  and component  1251  by screw  1257  inserted via washer  1257   a . After rotor  1137  is forcedly fitted to shaft  1225 , viscous pump  1240  as the independent component is forcedly fitted to communicating hole  1241  to complete the assembly. Thus, drastically practical and enhanced productivity can be attained.  
     Embodiment 6  
       FIG. 14  is a cross-sectional view illustrating a main part of a compressor in a sixth embodiment according to the present invention. The sixth embodiment is herein described with reference to  FIG. 14 . Similar numbers are given to the structures similar to those of the fourth embodiment, and detailed description of those is omitted.  
      Viscous pump  1340  soaked with oil  1102  is provided at the lower end of main shaft portion  1320  of shaft  1325 .  
      Communicating hole  1341  is coaxially formed within main shaft portion  1320 . Viscous pump  1340  includes: sleeve  1343  forcedly inserted into communicating hole  1341  and fixed thereto to form cylindrical hollow portion  1342 ; insertion member  1346  coaxially and rotatably inserted into sleeve  1343 ; and impellers  1347  having a plurality of vanes which are formed separately from insertion member  1346 .  
      Sleeve  1343  is substantially cylindrical and cap-shaped, and has bottom surface  1345  where rod hole  1344  is formed at its center. Bottom surface  1345  has path hole  1348  through which oil  1102  flows. Sleeve  1343  is made from iron plate press material which offers comparatively high accuracy and is an appropriate material through which insertion member  1336  slides, but may be formed from other suitable materials through which insertion member  1336  slides such as plastics and leaf spring steel.  
      Insertion member  1346  is formed by a shaped plastic component having refrigerant-resistance and oil-resistance properties and has thread-shaped spiral projection  1349  on its outer surface, thereby forming spiral groove  1350  through which oil  1102  flows between spiral projection  1349  and sleeve  1343 . Bottom region  1352  has a small-diameter hole  1353 .  
      In this embodiment, impellers  1347  are stamped out from thin iron plate, and rod  1349  made from steel wire which is resistance-welded to impellers  1347  is forcedly inserted through rod hole  1344  into small-diameter hole  1353  formed on bottom region  1352  to be fixed thereto. Communicating hole  1341  opens to a sliding area formed by the inner surface of bearing  1116  and the outer surface of main shaft portion  1320  through lateral hole  1362  to communicate with the sliding area.  
      The operation of the compressor having the above structure is now described. When stator  1136  is energized by the inverter driving circuit, rotor  1137  rotates with shaft  1325 . In accordance with the rotation of main shaft portion  1320  of shaft  1325 , cylindrical hollow portion  1342  formed by sleeve  1343  rotates. Insertion member  1346  tries to rotate with the rotation of cylindrical hollow portion  1342 , but in reality insertion member  1346  rotates at a number of revolution far smaller than that of cylindrical hollow portion  1342  since impellers  1347  receive strong viscous resistance in the rotational direction within oil  1102 . Thus, there is a difference in the number of revolution between cylindrical hollow portion  1342  and insertion member  1346 , which difference is near the number of revolution of shaft  1325 . Consequently, the oil having entered through path hole  1348  rises through spiral groove  1350  while being pulled by the rotation of cylindrical hollow portion  1342 . Then, the oil further rises through communicating hole  1341  by the oil pressure thus generated, passes through lateral hole  1362 , and reaches the sliding area formed by the inner surface of bearing  1116  and the outer surface of main shaft portion  1320  to lubricate that area.  
      At this stage, oil  1102  rises while rotating not only by the centrifugal force which decreases at low-speed revolution but by a pulling force generated by viscosity. Thus, oil can be drawn up in a stable manner even at the time of low-speed revolution such as 600 rpm.  
      According to this embodiment, insertion member  1346  and sleeve  1343  provide a thrust sliding area formed by bottom region  1352  and bottom surface  1345  which rotatably contact with each other. Thus, lateral pressure due to fixation is scarcely applied between sleeve  1343  and insertion member  1346 , and there is very few possibility of occurrence of sliding abrasion between sleeve  1343  and insertion member  1346 . It is thus possible to prevent generation of abrasion powder which is circulated with oil toward the sliding area and caught between the sliding components and thus brings about a locked condition of the compressing element. Accordingly, the compressor provided according to this embodiment is highly reliable.  
      A force in the downward direction as a reaction to a force for pushing up oil  1102  is applied to sleeve  1343 . The downward force is given to the thrust sliding area forming by above mentioned bottom region  1352  and bottom surface  1345  as a load in the thrust direction. In this embodiment, the surface pressure applied to the thrust sliding area can be reduced by widening bottom surface  1345  of sleeve  1343 , thereby improving abrasion resistance.  
      While not shown in the above respective embodiments, a spacer having abrasion resistance such as 4-fluorinated ethylene and valve steel may be interposed between bottom region  1352  and bottom surface  1345  to further enhance abrasion resistance.  
      The rotation of insertion member  1346  is prevented while impellers  1347  are receiving strong viscous resistance in the rotational direction within oil  1102 . Thus, indirect fixing of insertion member  1346  to stator  1136  by a component for preventing the rotation of insertion member  1346  as in the conventional example is not needed. Also, since the structure is extremely simple, only a small number of components and processes are required and thus cost-reduction of the compressor can be attained.  
      According to the above respective embodiments, viscous pump  1340  is assembled in advance as an independent component by inserting insertion member  1346  into sleeve  1343  and forcedly inserting rod  1349  to which impellers  1347  are fixed through rod hole  1344  into small-diameter hole  1353  formed on bottom region  1352 . After rotor  1137  is forcedly inserted into shaft  1325 , viscous pump  1340  as the independent component is forcedly inserted into communicating hole  1341  to complete the assembly. Thus, drastically practical and enhanced productivity can be attained.  
      While the spiral projection is provided on the insertion member in the fourth through sixth embodiments, the spiral projection may be disposed on the cylindrical hollow portion to similarly form the spiral groove through which oil flows.  
      While description is made based on the reciprocating internal suspended-type compressor in the fourth through sixth embodiments, the present invention is applicable to internal fixed-type compressors such as vertical rotary-type compressors and scroll-type compressors as long as the lower end of their shafts extends to reach oil.  
      Types of gas and oil are not specifically limited. Needless to say, the advantages of the invention can be generally offered in any combination of all types of refrigerant involving environment-protective refrigerant such as HFC, HC and CO2 and all types of oil involving oil compatible with those refrigerant by employing the above materials having gas-resistance and oil-resistance properties for the components included in the viscous pump.  
      According to the invention as described above, a component for fixing the insertion member to the stator is not required, and thus a highly reliable and inexpensive compressor can be provided.  
      Another advantage offered according to the invention is that a material having high abrasion resistance can be used to further enhance reliability.  
      Another advantage offered according to the invention is that the viscous pump is assembled into one piece in advance, and thus a further inexpensive compressor can be provided.  
      Another advantage offered according to the invention is that the viscous pump assembled into one piece in advance, and thus a further inexpensive compressor can be provided.  
      Another advantage offered according to the invention is that the viscous pump is incorporated in the compressor which is elastically supported, and thus a highly reliable and inexpensive compressor can be provided.  
      Another advantage offered according to the invention is that the compressor is driven at a low-speed revolution, and thus a highly reliable and inexpensive compressor can be provided.  
      The force for pulling oil due to viscosity increases as the contact area between the inner surface of the rotational body and oil increases. However, the contact surface is chiefly formed by the flat smooth surface of sleeve  7112  and only insufficient force is applied to oil in the structure of the conventional example.  
      Additionally, there is a clearance between the end surface of spiral projection  7121  and the inner surface of sleeve  7112 , which clearance is positioned at the outermost surface of insertion member  7120  in the conventional structure. The centrifugal force generated through the rotation of shaft  7111  is applied to oil within the oil passage formed by the spiral groove and the inner surface of sleeve  7112 , and oil rises while rotating and inclining toward the inside surface. Thus, oil falls to flow out through the clearance between spiral projection  7121  and inner surface of sleeve  7112  and the oil supply amount to the upper area decreases.  
      Accordingly, especially in an extremely low driving frequency range such as 600 to 1,200 r/min., the force for pulling oil due to viscosity decreases and also the amount of oil which falls to flow out through the clearance between sleeve  7112  and insertion member  7120  increases. In this case, a sufficient oil amount cannot be transferred to the sliding area positioned above.  
      It is therefore an object of the present invention to provide a compressor capable of drawing up a sufficient amount of oil with efficiency even at the time of low-speed revolution.  
      Compressors in seventh and eighth embodiments are herein described with reference to the drawings.  
     Embodiment 7  
       FIG. 15  is a cross-sectional view of a compressor in the seventh embodiment of the invention;  FIG. 16  is across-sectional view illustrating a main part of the compressor in the seventh embodiment.  
      In  FIGS. 15 and 16 , oil  2102  is stored in closed container  2101  which is filled with refrigerant gas  2103 .  
      Compressing element  2110  includes: block  2115  which forms cylinder  2113 ; piston  2117  reciprocatively inserted into cylinder  2113 ; shaft  2125  having main shaft portion  2120  supported by bearing  2116  of block  2115  and eccentric portion  2122 ; and connecting rod  2119  for connecting eccentric portion  2122  and piston  2117 . Compressing element  2110  forms a reciprocating compressing mechanism.  
      Electrically-powered element  2135  is fixed below block  2115 . Electrically-powered element  2135  includes stator  2136  connected to an inverter driving circuit (not shown) and rotor  2137  which contains permanent magnet and is fixed to main shaft portion  2120 , thus providing an electrically-powered element for driving the inverter.  
      Springs  2139  elastically support compressing element  2110  via stator  2136  such that compressing element  2110  can be elastically held on closed container  2101 .  
      Viscous pump  2140  soaked with oil  2102  is provided at the lower end of main shaft portion  2120  of shaft  2125 . Viscous pump  2140  includes: cylindrical hollow portion  2142  formed in the lower region of main shaft portion  2120 ; insertion member  2145  coaxially inserted into cylindrical hollow portion  2142 ; and substantially-U-shaped bracket  2143  both ends of which are fixed to the lower region of stator  2136 . Bracket  2143  engages with the lower end of insertion member  2145  to support insertion member  2145  such that insertion member  2145  cannot rotate.  
      Thread-shaped spiral projection  2149  is formed on the inner surface of cylindrical hollow portion  2142  to provide a spiral groove through which oil  2102  is allowed to flow between spiral projection  2149  and insertion member  2145 .  
      Insertion member  2145  is hollow and a shaped component made from resin having refrigerant-resistance and oil-resistance properties. Insertion member  2145  has bracket insertion portion  2146  and rise prevention member  2147 . Insertion member  2145  floats inside the cylindrical hollow portion, but is prevented from rising too high and rotating therein.  
      The operation of the compressor having the above structure is now described. When stator  2136  is energized by the inverter driving circuit, rotor  2137  rotates with shaft  2125 . The eccentric motion of eccentric portion  2122  thus caused reciprocates piston  2117  within cylinder  2113  via connecting rod  2119 , thereby carrying out predetermined actions for compressing gas which is taken in.  
      In accordance with the rotation of main shaft portion  2120  of shaft  2125 , cylindrical hollow portion  2142  rotates. Insertion member  2145  engages with the center portion of substantially U-shaped bracket  2143  both ends of which are fixed to the lower region of stator  2136  to be supported by bracket  2143  in such a manner as not to rotate. In this structure, oil rises through the spiral groove while being pulled by the rotation of cylindrical hollow portion  2142 . Then, oil further rises through communicating hole  2160  by the oil pressure thus caused, passes through lateral hole  2162 , and finally reaches a sliding area formed by the inner surface of bearing  2116  and the outer surface of main shaft portion  2120  to lubricate that area.  
      At this stage, oil  2102  rises while rotating not only by the centrifugal force which decreases at low-speed revolution but by a pulling force generated by viscosity. In addition, spiral projection  2149  is formed on the cylindrical hollow portion to enlarge the area of the inner surface of the rotational body in contact with oil by adding the surface area of spiral projection  2149  in this embodiment. This structure causes large viscous resistance, thereby enhancing oil transfer capability.  
      Furthermore, centrifugal force generated by the rotation of shaft  2120  is applied to oil existing in the space between the spiral groove formed on the inner surface of cylindrical hollow portion  2142  and insertion member  2145 . Thus, oil rises while rotating and inclining toward the roots of the spiral groove, i.e., the farthermost surface from the rotational shaft center of shaft  2120 . Structurally there is no clearance in the vicinity of the roots of the spiral groove to which the centrifugal force is applied. Accordingly, oil does not fall to flow out, thereby preventing fall and outflow of oil.  
      As described above, enhanced oil transfer capability can be realized, allowing drawing up oil in a stable manner even at the time of low-speed revolution such as 600 r/min.  
      According to this embodiment, the compressing element is elastically supported, and insertion member  2145  engages with the center of bracket  2143  made from an elastic body to float within cylindrical hollow portion  2142  without rotating. Thus, lateral pressure due to fixation is scarcely applied between cylindrical hollow portion  2142  and insertion member  2145 , and there is very few possibility of occurrence of sliding abrasion between cylindrical hollow portion  2142  and insertion member  2145 . It is thus possible to prevent generation of abrasion powder which is circulated with oil toward the sliding area and caught between the sliding components and thus brings about a locked condition of the compressing element. Accordingly, the compressor provided according to this embodiment is highly reliable.  
     Embodiment 8  
       FIG. 17  is a cross-sectional view illustrating a main part of a compressor in an eighth embodiment of the invention; and  FIG. 18  is an assembly view of the main part in the eighth embodiment. The eighth embodiment is herein described with reference to  FIGS. 17 and 18 . Similar numbers are given to the structures similar to those of the seventh embodiment, and detailed description of those is omitted.  
      Viscous pump  2240  soaked with oil  2102  is provided at the lower end of main shaft portion  2220  of shaft  2225 .  
      Communicating hole  2260  and sleeve attachment hole  2254  are coaxially formed within main shaft portion  2220 . Viscous pump  2240  includes: sleeve  2251  which is forcedly inserted into sleeve attachment hole  2254  to be fixed thereto and forms cylindrical hollow portion  2242 ; coil spring  2253  secured to the inner surface of sleeve  2251  as a spiral member; insertion member  2145  coaxially and rotatably inserted into sleeve  2251 ; and bracket  2143 . Bracket  2143  which is made from an elastic body is substantially U-shaped, both ends of which are fixed to the lower region of stator  2136 . The center of bracket  2143  engages with the lower end of insertion member  2145  to support insertion member  2145  in such a manner that insertion member cannot rotate.  
      Sleeve  2251  is substantially cylindrical and cap-shaped, whose top and bottom are open. Sleeve  2251  has spring holder  2252  at its lower end. Sleeve  2251  is made from iron plate press material which offers comparatively high accuracy, but may be formed from other materials such as leaf spring steel.  
      The length of coil spring  2253  is larger than the total length of the inner surface of sleeve  2251  from which the height of the spring holder  2252  is subtracted. Coil spring  2253  is made from oil temper wire for springs (JIS:SWOV) in this embodiment, but may be made from other material including iron steel such as piano wire (JIS:SWP) and spring steel (JIS:SUP), non-iron metal such as aluminum, and resins whose thermal deformation temperature is 100° C. or higher and which has high formability such as polycarbonate (PC) and polyamide (PA).  
      Cylindrical hole  2255  formed by the lowermost end surface of main shaft portion  2220  has one step to provide a smaller-diameter hole. Sleeve attachment hole  2254  in to which a predetermined length of sleeve  2251  is forcedly inserted is formed in a hole on the first step, while communicating hole  2260  is formed in a hole on the second step. The inner surface diameter of communicating hole  2260  is slightly smaller than the inner surface diameter of sleeve  225   i . Coil spring  2253  is compressed between spring holder  2252  at the lower end of the sleeve and the step formed by the difference in the inner surface diameter between sleeve  2251  and communicating hole  2260  to be fixed to the inner surface of sleeve  2251 .  
      Insertion member  2145  is formed by a shaped resin component having refrigerant-resistance and oil-resistance properties in this embodiment, but may be comparatively light metal such as aluminum. Insertion member  2145  is a hollow component, and has bracket insertion portion  2146  and rise prevention member  2147 . Insertion member  2145  floats inside the cylindrical hollow portion, but is prevented from rising too high and rotating therein.  
      The operation of the compressor having the above structure is now described.  
      When stator  2136  is energized by the inverter driving circuit, rotor  2137  rotates with shaft  2125 . Then, operations similar to those in the seventh embodiment are performed to supply oil.  
      According to this embodiment, the structure which uses the shape of the coil spring itself as the spiral groove provided on the inner surface of the lower end of the shaft can be far more easily formed than the structure in which a spiral groove is directly engraved on the inner surface of the lower end of the shaft. From the viewpoint of energy saving, the amount of oil transfer can be appropriately controlled by replacing the coil spring with the one having a different wire diameter, wire cross-sectional shape, number of winding etc., in accordance with the driving frequency required by the system side such as household refrigerators and air conditioners. Thus, the compressor of this embodiment is highly flexible and capable of meeting a wide variety of demands. Moreover, by forcedly inserting sleeve  2251  provided with coil spring  2253  on its inner surface in advance into sleeve attachment hole  2254  formed coaxially with main shaft portion  2220 , sleeve  2251  is attached to the lower end region of main shaft portion  2220  and simultaneously coil spring  2253  is compressed between spring holder  2252  at the lower end of the sleeve and the step formed by the difference in the inner surface diameter between sleeve  2251  and communicating hole  2260  to be fixed to the inner surface of sleeve  2251 . Accordingly, the formation of the spiral groove necessary for transferring oil upward is easily completed, and thus considerably practical and high productivity can be achieved.  
      According to the present invention as described above, it is possible to secure a wide area in contact with oil which causes viscous resistance needed for the rotational rising movement of oil. Accordingly, the force for pulling oil due to viscosity increases and thus an enhanced oil transfer capability can be obtained.  
      Another advantage of the invention is that the assembly in this embodiment which uses the shape of the coil spring itself as the spiral groove is more facilitated than in an example in which a groove is engraved. Also, the amount of oil transfer can be appropriately controlled by replacing the coil spring with the one having a different wire diameter, wire cross-sectional shape, number of winding etc., which enhances the flexibility. Further, the spiral groove formed by the coil spring is simultaneously provided when the sleeve is forcedly inserted, which increases the productivity.  
      Another advantage of the invention is that power consumption of household refrigerators and air-conditioners is reduced since input to the compressor is decreased during low-speed driving and oil supply is stabilized.  
      Another advantage of the invention is that the insertion member floats but not rotates inside the cylindrical hollow portion during the operation of the compressing element. This provides a structure in which oil is pulled by viscosity and also prevents abrasion and chipping due to the contact and collision between the inner surface of the cylindrical hollow portion and the outer surface of the insertion member which damages may lead to deterioration of the pumping ability and bring about excessive abrasion and a locked condition of the compressing element. Accordingly, long-term reliability can be secured.  
      Another advantage of the invention is that the components included are not required to be fixed on the closed container. Since the insertion member only floats inside the cylindrical hollow portion, lateral pressure due to fixation is scarcely applied between the cylindrical hollow portion and the insertion member and there is very few possibility of occurrence of sliding abrasion between the cylindrical hollow portion and the insertion member. Thus, a highly reliable compressor which includes the viscous pump and is elastically supported can be provided.  
      In the above-described conventional structure, bracket  7115  and insertion member  7120  engage with each other through longitudinal groove  7521 . Thus, the wall surface of the longitudinal groove of insertion member  7120  collides with engagement portion  7523  of bracket  7115  at every start-up, and the wall surface of the longitudinal groove is kept pressed thereon during continuous driving. As a result, abrasion occurs due to rubbing of the engagement portion, or bracket  7115  is twisted and the stress is concentrated on the bended portion or other position of bracket  7115 , which causes fatigue to develop for a period of time.  
      When abrasion and fatigue thus caused further develop, thin film projections (extrusion) and depression of cracks (intrusion) occur at the engagement portion and the bended portion. Especially, the depression develops into visual minute cracks, which gradually spread to finally cause corruption of bracket  7115 . In this case, the rotation of insertion member  7120  inside sleeve  7112  may not be restricted.  
      Thus, it is difficult to maintain the structure of viscous pump  7113  in a stable condition for a long period of time.  
      For solving the above problem, an object of the present invention is to provide a highly reliable compressor capable of maintaining the structure of viscous pump  7113  for a long-term period without causing abrasion and fatigue by the contact between components at the time of restriction of the rotation of insertion member  7120 .  
      Ninth and tenth embodiments according to the present invention are now described with reference to the drawings. However, the invention is not limited to those embodiments.  
     Embodiment 9  
       FIG. 19  is a cross-sectional view illustrating a compressor in the ninth embodiment of the invention, and  FIG. 20  is a cross-sectional view illustrating a main part of the compressor in the ninth embodiment.  
      In  FIGS. 19 and 20 , oil  4102  is stored in closed container  4101  which is filled with refrigerant gas  4103 .  
      Compressing element  4110  includes: block  4115  which forms cylinder  4113 ; piston  4117  reciprocatively inserted into cylinder  4113 ; shaft  4125  having main shaft portion  4120  supported by bearing  4116  of block  4115  and eccentric portion  4122 ; and connecting rod  4119  for connecting eccentric portion  4122  and piston  4117 . Compressing element  4110  forms a reciprocating compressing mechanism.  
      Electrically-powered element  4135  is fixed below block  4115 , and includes stator  4136  connected to an inverter driving circuit (not shown) and rotor  4137  which contains permanent magnet and is fixed to main shaft portion  4120 . Electrically-powered element  4135  provides an electric motor for driving the inverter, and is driven at a plurality of driving frequencies including those below 20 Hz, for example, by the inverter driving circuit (not shown).  
      Springs  4139  elastically support compressing element  4110  via stator  4136  such that compressing element  4110  is elastically held on closed container  4101 .  
      Viscous pump  4140  soaked with oil  4102  is provided at the lower end of main shaft portion  4120  of shaft  4125 .  
      Next, the structure of viscous pump  4140  is described in detail.  
      Cylindrical hollow portion  4141  is formed in main shaft portion  4120 . Hollow sleeve  4142  is fixed to the lower region of cylindrical hollow portion  4141 . Sleeve  4142  is substantially cylindrical and cap-shaped, whose top and bottom are open. Sleeve  4142  is made from iron plate press material which offers comparatively high accuracy in this embodiment, but may be formed from leaf spring steel.  
      Insertion member  4143  coaxially inserted into cylindrical hollow portion  4141  and sleeve  4142  is made from a plastic material which has lower thermal conductivity than the metal material which forms shaft  4125  and possesses refrigerant-resistance and oil-resistance properties such as PPS, PBT, and PEEK. Spiral groove  4144  is engraved on the outer surface of insertion member  4143 , whereby oil passage  4145  through which oil flows is provided between spiral groove  4144  and the inner surface of sleeve  4142 . The difference between the outermost diameter of insertion member  4143  and the inside diameter of sleeve  4142 , i.e., the matching clearance is established in a range from 100 μm to 500 μm. Insertion member  4143  has bolt hole  4146  at its upper end surface, and a plurality of arms  4147  at its lower sides which extend substantially in the horizontal direction.  
      Bolt  4150  is employed as supporting member  4152  for slidingly connecting insertion member  4143  with sleeve  4142 . Bolt  4150  inserted through washer  4151  penetrates bolt hole  4146  and reaches the upper surface of cylindrical hollow portion  4141  to be attached thereto, thereby rotatably connecting insertion member  4143  to main shaft portion  4120  of shaft  4125  and closing the lower end of bolt hole  4146 . Washer  4151  is made from a plastic material having high abrasion-resistance property such as self-lubrication characteristic (PPS, PEE and PEEK etc.). Alternatively, bolt  4150  may be formed from a similar self-lubrication material to eliminate washer  4151 .  
      First permanent magnet  4148  is fixed to each arm  4147  which is disposed on the lower sides of insertion member  4143  to extend substantially in the horizontal direction. Also, each second permanent magnet  4149  is provided on the inner surface of the bottom of closed container  4101  via joint  4153  such that the S-pole of second permanent magnet  4149  is opposed to the S-pole of first permanent magnet  4148  in the rotational direction with a predetermined space therebetween sufficiently within the reach of magnetic force. Alternatively, the N-poles of both permanent magnets  4148  and  4149  may be opposed to each other.  
      The operation of the compressor having the above structure is herein described.  
      Main shaft portion  4120  rotates with the rotation of shaft  4125 . Sleeve  4142  fixed to main shaft portion  4120  rotates in synchronization with the rotation of main shaft portion  4120 . Insertion member  4143  is pulled by the rotation of sleeve  4142 , but the rotation of insertion member  4143  is prevented by the repulsion between the same poles of first permanent magnet  4148  provided on the insertion member and second permanent magnet  4149 . As a result, oil rises through oil spiral passage  4145  while rotating and being pulled by the inner surface of sleeve  4142  due to viscosity.  
      At this stage, oil  4102  rises while rotating not only by the centrifugal force which decreases at low-speed revolution but by a pulling force generated by viscosity. Thus, oil  4102  can be drawn up in a stable manner even at the time of low-speed revolution such as 600 rpm.  
      According to this embodiment as described above, the rotation of insertion member  4143  is prevented by a non-contact method utilizing the repulsion between first permanent magnet  4148  and second permanent magnet  4149 , causing no abrasion and fatigue by the contact between the components in relation to the restriction of insertion member  4143 . Accordingly, the structure of viscous pump  4140  is maintained in a stable condition for a long period of time, and thus a highly reliable compressor can be provided.  
      According to this embodiment, second permanent magnet  4149  is disposed in the vicinity of the inner surface of the bottom of closed container  4101  for the structural reason of the compressor. Thus, joints  4153  require not a complicated but an extremely simple structure so as to secure second permanent magnet  4149  to closed container  4101 .  
      Second permanent magnet  4149  is directly or indirectly fixed on closed container  4101 , but is kept prevented from contacting with first permanent magnet  4148  since the same poles are opposed. Consequently, sound and vibration generated from compressing element  4110  and electrically-powered element  4135  are not transmitted though first permanent magnet  4148  and second permanent magnet  4149  to closed container  4101 .  
      According to this embodiment, insertion member  4143  is rotatably connected to main shaft portion  4120  of shaft  4125  by means of bolt  4150  which is inserted through washer  4151 . Thus, the position of insertion member  4143  relative to sleeve  4142  fixed at the lower end of main shaft portion  4120  is determined by this connecting portion, and an almost constant clearance is maintained between insertion member  4143  and sleeve  4142 . This clearance is maintained by the fact that lateral pressure due to fixation is scarcely caused and also that the oil pressure is generated between insertion member  4143  and sleeve  4142 . Accordingly, there is very few possibility of occurrence of sliding abrasion between insertion member  4143  and sleeve  4142 .  
      Spiral groove  4144  is provided on the outer surface of insertion member  4143  to form spiral oil passage  4145  in this embodiment, but may be disposed on the inner surface of sleeve  4142  to form oil passage  4145 . In this case, the area of the inner surface of the rotational body in contact with oil  4102  is enlarged by adding the surface area of the concaves of the spiral groove. This structure causes large viscous resistance, thereby enhancing oil  4102  transfer capability. Moreover, centrifugal force generated through the rotation of main shaft portion  4120  is applied to oil  4102  existing within the oil passage  4145  formed between the inner surface of sleeve  4142  and the outside surface of insertion member  4143 , and the oil rises while rotating and inclining toward the farthermost surface from the rotational shaft center in oil passage  4145 . Since there is no clearance in the position to which the centrifugal force is most applied, oil does not fall to flow out and thus the amount of oil which falls to flow out can be decreased. Accordingly, the compressor in this embodiment obtains considerably higher oil transfer capability than the example in which spiral groove  4144  is formed on insertion member  4143 .  
     Embodiment 10  
       FIG. 21  is a cross-sectional view illustrating a compressor in a tenth embodiment of the invention, and  FIG. 22  is a cross-sectional view illustrating a main part of the compressor in the tenth embodiment.  
      The tenth embodiment is herein described with reference to  FIGS. 21 and 22 . Similar numbers are given to the structures similar to those of the ninth embodiment, and detailed description of those is omitted.  
      Viscous pump  4240  soaked with oil  4202  is provided at the lower end of main shaft portion  4120  of shaft  4125 .  
      Next, the structure of viscous pump  4240  is described in detail.  
      Cylindrical hollow portion  4241  is formed in main shaft portion  4120 . Hollow sleeve  4242  is fixed to the lower region of cylindrical hollow portion  4241 . Sleeve  4242  is substantially cylindrical and cap-shaped, whose top and bottom are open. Sleeve  4242  is made from iron plate press material which offers comparatively high accuracy in this embodiment, but may be formed from leaf spring steel.  
      Insertion member  4243  coaxially inserted into cylindrical hollow portion  4241  and sleeve  4242  is made from a plastic material which has lower thermal conductivity than the metal material which forms shaft  4125  and possesses refrigerant-resistance and oil-resistance properties such as PPS, PBT, and PEEK. Spiral groove  4244  is engraved on the outer surface of insertion member  4243 , whereby oil passage  4245  through which oil flows is provided between spiral groove  4244  and the inner surface of sleeve  4242 . The difference between the outermost diameter of insertion member  4243  and the inside diameter of sleeve  4242 , i.e., the matching clearance is established in a range from 100 μm to 500 μm. Insertion member  4243  has bolt hole  4246  at its upper end surface, and a plurality of arms  4247  at its lower sides which extend substantially in the horizontal direction.  
      Bolt  4250  is employed as supporting member  4252  for slidingly connecting insertion member  4243  with sleeve  4242 . Bolt  4250  inserted through washer  4251  penetrates bolt hole  4246 , and reaches the upper surface of cylindrical hollow portion  4241  to be attached thereto, thereby rotatably connecting insertion member  4243  to main shaft portion  4120  of shaft  4125  and closing the lower end of bolt hole  4246 . Washer  4251  is made from a plastic material having high abrasion-resistance property such as self-lubrication characteristic (PPS and PEEK etc.). Alternatively, bolt  4250  may be formed from a similar self-lubrication material to eliminate washer  4251 .  
      First permanent magnet  4248  is fixed to each arm  4247  which is disposed on the lower sides of insertion member  4243  to extend substantially in the horizontal direction. Also, each second permanent magnet  4249  is provided such that the S-pole of second permanent magnet  4249  is opposed to the S-pole of first permanent magnet  4248  in the rotational direction with a predetermined space therebetween sufficiently within the reach of magnetic force. Each second permanent magent  4249  is fixed on one end of substantially L-shaped joint  4253  the other end of which is secured to the lower region of stator  4136 . The N-poles of both permanent magnets  4248  and  4249  may be opposed to each other.  
      The operation of the compressor having the above structure is herein described.  
      Main shaft portion  4120  rotates with the rotation of shaft  4125 . Sleeve  4242  fixed to main shaft portion  4120  rotates in synchronization with the rotation of main shaft portion  4120 . Insertion member  4243  is pulled by the rotation of sleeve  4242 , but the rotation of insertion member  4243  is prevented by the repulsion between the same poles of first permanent magnet  4248  provided on the insertion member and second permanent magnet  4249 . As a result, oil rises through oil spiral passage  4245  while rotating and being pulled by the inner surface of sleeve  4242  due to viscosity.  
      At this stage, oil  4202  rises while rotating not only by the centrifugal force which decreases at low-speed revolution but by a pulling force generated by viscosity. Thus, oil can be drawn up in a stable manner even at the time of low-speed revolution such as 600 rpm.  
      According to this embodiment as described above, the rotation of insertion member  4243  is restrained by a non-contact method through the same mechanism as in the ninth embodiment, causing no abrasion and fatigue by the contact between the components in relation to the restriction of insertion member  4243 . Accordingly, the structure of viscous pump  4240  is maintained in a stable condition for a long period of time, and thus a highly reliable compressor can be provided.  
      According to this embodiment, insertion member  4243  having first permanent magnets  4248  is connected to main shaft portion  4120  via bolt  4250 , and second permanent magnets  4249  are secured to the lower region of stator  4136  via joints  4253 . It is thus possible to attach all the components included in viscous pump  4240  to electrically-powered element  4135  or compressing element  4110  in advance, and assembly is facilitated and productivity is enhanced by collectively installing those components in closed container  4101 .  
      Second permanent magnets  4249  are fixed to the lower part of electrically-powered element  4135  having stator  4136  through joints  4253  in this embodiment, but may be secured to any component of compressing element  4110  such as block  4115  through joints  4253 .  
      As described above, no abrasion and fatigue by the contact between the components in relation to the restriction of the insertion member are caused in the invention and the structure of the viscous pump is maintained in a stable condition for a long period of time. Thus, a highly reliable compressor can be provided.  
      In the invention, the structure is considerably simple and the second permanent magnets are kept prevented from contacting with the first permanent magnets since the same poles are opposed. As a result, sound and vibration generated from the compressing element and the electrically-powered element are not transmitted through the first permanent magnets and the second permanent magnets to the outside of the closed container, and thus a highly reliable compressor can be provided.  
      In the invention, it is possible to attach all the components included in the viscous pump to the electrically-powered element or the compressing element in advance and collectively install these components in the closed container. Accordingly, assembly is facilitated and productivity is increased, and thus a highly reliable compressor can be provided.  
      In the invention, generation of abnormal sound caused by vibration is prevented, and thus a highly reliable compressor can be provided.  
      In the invention, input to the compressor which drives at driving frequencies including at least in a range from 600 to 1,200 r/min. is reduced and the structure of the viscous pump is maintained in a stable condition for a long period of time. Accordingly, power consumption is lowered and thus a highly reliable compressor is provided.  
      In the invention, the rotation of the insertion member is prevented by a non-contact method utilizing repulsion between the permanent magnets. Accordingly, no abrasion and fatigue by the contact between the components in relation to the restriction of the insertion member are caused and the structure of the viscous pump is maintained in a stable condition for a long period of time. Thus, a highly reliable compressor can be provided.  
      The structure of the viscous pump can be maintained in a stable condition for a long period of time by preventing the rotation of the insertion member by a non-contact method, and thus a highly reliable compressor can be provided.  
      In the conventional structure in which bracket  7115  supports the weight of insertion member  7120  at two points, insertion member  7120  inserted into sleeve  7112  is inclined and contacts sleeve  7112 . When bracket  7115  does not have high dimensional accuracy or the center of gravity of insertion member  7120  is off the shaft center, the contact between the upper end of longitudinal groove  7621  provided at the lower end of insertion member  7120  and bracket  15  becomes a point contact. In this case, abrasion or fixation between sleeve  7112  and insertion member  7120  may be caused, resulting in deterioration of the pumping ability and generation of abrasion powder which is circulated with oil toward the sliding area and caught between the sliding components and brings about a locked condition of the compressing element.  
      An object of the present invention is to provide a highly reliable compressor.  
      Eleventh through thirteenth embodiments are herein described with reference to the drawings. The invention is not limited to those embodiments.  
     Embodiment 11  
       FIG. 23  is a cross-sectional view illustrating a compressor in the eleventh embodiment of the invention,  FIG. 24  is a cross-sectional view illustrating a main part of the compressor in the eleventh embodiment, and  FIG. 25  is an enlarged view illustrating a main part of an insertion member in the eleventh embodiment.  
      In  FIGS. 23, 24  and  25 , oil  5102  is stored in closed container  5101  which is filled with refrigerant gas  5103 .  
      Compressing element  5110  includes: block  5115  which forms cylinder  5113 ; piston  5117  reciprocatively inserted into cylinder  5113 ; shaft  5125  having main shaft portion  5120  supported by bearing  5116  of block  5115  and eccentric portion  5122 ; and connecting rod  5119  for connecting eccentric portion  5122  and piston  5117 . Compressing element  5110  forms a reciprocating compressing mechanism.  
      Electrically-powered element  5135  is fixed below block  5115 , and includes stator  5136  connected to an inverter driving circuit (not shown) and rotor  5137  which contains permanent magnet and is fixed to main shaft portion  5120 . Electrically-powered element  5135  provides an electric motor for driving an inverter, and is driven at a plurality of driving frequencies including those below 1,200 rpm, for example, by the inverter driving circuit (not shown).  
      Springs  5139  elastically support compressing element  5110  via stator  5136  such that compressing element  5110  is elastically held on closed container  5101 .  
      Viscous pump  5140  soaked with oil  5102  is provided at the lower end of main shaft portion  5120  of shaft  5125 .  
      Next, the structure of viscous pump  5140  is described in detail.  
      Hollow portion  5141  is formed in main shaft portion  5120 . Hollow sleeve  5142  is fixed to the lower region of hollow portion  5141  to form cylindrical hollow portion  5143 . Sleeve  5142  is substantially cylindrical and has a wall thickness in a range from about 0.5 mm to about 11.0 mm. Sleeve  5142  is cap-shaped whose top and bottom are open. Sleeve  5142  is made from iron plate press material which offers comparatively high accuracy in this embodiment, but may be formed from leaf spring steel.  
      Insertion member  5144  coaxially inserted into cylindrical hollow portion  5143  has a plurality of projections  5145  on its upper outside surface, and receiving portion  5146  at the upper end of sleeve  5142  (corresponding to the thin-wall portion of sleeve  5142 ) rotatably receives the thrust surfaces of projections  5145  in a face contact condition. The difference between the inside diameter of cylindrical hollow portion  5143  and the outermost diameter of projections  5145  is determined within a range from 0.1 mm to 0.5 mm. As for the method of installing insertion member  5144 , projections  5145  of insertion member  5144  which has been inserted into sleeve  5142  in advance are disposed in such a position as to be received by receiving portion  5146  at the upper end of sleeve  5142 , and subsequently sleeve  5142  is fixed. By this method, installment of the insertion member can be simultaneously completed. Alternatively, in a structure in which projections  5145  are disposed on free joint  5154  which is elastically deformable in the radial direction, insertion member  5144  may be inserted and positioned after sleeve  5142  is forcedly inserted into cylindrical hollow portion  5141  and fixed thereto.  
      Insertion member  5144  is made from a synthetic resin material which has lower thermal conductivity than the metal material which forms shaft  5125  and possesses refrigerant-resistance and oil-resistance properties such as PPS, PBT, and PEEK. Spiral groove  5147  is engraved on the outer surface of insertion member  5144 , whereby oil passage  5148  through which oil flows is provided between spiral groove  5147  and the inner surface of sleeve  5142 . The difference between the inside diameter of sleeve  5142  and the outermost diameter of insertion member  5144  is almost equivalent to or slightly larger than the difference between the inside diameter of cylindrical hollow portion  5143  and the outermost diameter of projections  5145 .  
      Substantially U-shaped bracket  5149  formed by an elastic body both ends of which are fixed to the lower region of stator  5136  are provided as means  5170  for preventing rotation of insertion member  5144 . The center of bracket  5149  engages with vertical groove  5150  provided at the lower end of insertion member  5144  to support insertion member  5144  while preventing the rotation of insertion member.  
      Main shaft portion  5120  has hollow portion  5141  which includes large-diameter portion  5151  and small-diameter portion  5152 . Insertion member  5144  is supported inside cylindrical hollow portion  5143  while being prevented from rising by disposing projections  5145  in such a position as to be sandwiched between receiving portion  5146  and step  5153  formed by large-diameter portion  5151  and small-diameter portion  5152  with a certain clearance in the vertical direction.  
      The operation of the compressor having the above structure is now described.  
      Main shaft portion  5120  rotates with the rotation of shaft  5125 . Cylindrical hollow portion  5143  rotates in synchronization with the rotation of main shaft portion  5120 . The thrust surfaces of projections  5145  of insertion member  5144  are rotatably received by receiving portion  5146  formed on sleeve  5142 . Insertion member  5144  is pulled by the rotation of cylindrical hollow portion  5143 , but the rotation of insertion member  5144  is prevented by bracket  5149 .  
      As a result, oil rises through spiral oil passage  5148  while rotating and being pulled by the inner surface of cylindrical hollow portion  5143  due to viscosity. At this stage, oil  5102  rises while rotating not only by the centrifugal force which decreases at low-speed revolution but by a pulling force generated by viscosity. Thus, oil  5102  can be drawn up in a stable manner even at the time of low-speed revolution such as 600 rpm.  
      According to this embodiment, the position of insertion member  5144  relative to cylindrical hollow portion  5143  is determined by the surface contact between receiving portion  5146  and the thrust surfaces of projections  5145  provided on insertion member  5144 . Accordingly, an almost constant clearance between insertion member  5144  and cylindrical hollow portion  5143  is maintained and thus excessive lateral pressure which may be produced by fixation is scarcely generated. As fluid film pressure also develops within spiral groove  5147 , there is very few possibility of occurrence of sliding abrasion between insertion member  5144  and cylindrical hollow portion  5143 .  
      Accordingly, it is possible to prevent generation of abrasion powder which is circulated with oil toward the sliding area and caught between the sliding components and brings about a locked condition of the compressing element, and thus a highly reliable compressor can be provided.  
      In this embodiment, sleeve  5142  is fixed to hollow portion  5141  provided in the lower region of shaft  5125 , and receiving portion  5146  is formed by the upper end of sleeve  5142  to effectively utilize the thin-wall region of sleeve  5142  as receiving portion  5146 . Thus, complicated processing is not required to form sleeve  5142  and shaft  5125 , and a compressor which is inexpensive and has high productivity can be provided.  
      In this embodiment, insertion member  5144  including projections  5145 , spiral groove  5147  and vertical groove  5150  is integrally formed from a self-lubricating synthetic resin. Thus, a compressor which is inexpensive and has high accuracy and high abrasion resistance can be provided.  
      Spiral groove  5147  is formed on the outer surface of insertion member  5144  to provide oil passage  5148  in this embodiment, but the spiral groove may be disposed on the inner surface of sleeve  5142  to form oil passage  5148 . In this case, the area of the inner surface of the rotational body in contact with oil is enlarged by adding the surface area of the concaves of the spiral groove. This structure causes large viscous resistance, and thus oil transfer capability is enhanced.  
     Embodiment 12  
       FIG. 26  is a cross-sectional view illustrating a compressor in a twelfth embodiment of the invention, and  FIG. 27  is a cross-sectional view illustrating a main part of the compressor in the twelfth embodiment.  
      The twelfth embodiment is herein described with reference to  FIGS. 26 and 27 . Similar numbers are given to the structures similar to those of the eleventh embodiment, and detailed description of those is omitted.  
      Viscous pump  5240  soaked with oil  5102  is provided at the lower end of main shaft portion  5220  of shaft  5125 .  
      Next, the structure of viscous pump  5240  is described in detail.  
      Hollow portion  5241  is formed in main shaft portion  5220 . Hollow sleeve  5242  is inserted from outside and fixed to the lower region of hollow portion  5241  to form cylindrical hollow portion  5243 . Sleeve  5242  is substantially cylindrical and has large-diameter portion  5251  and small-diameter portion  5252 . The wall thickness of sleeve  5242  is determined in a range from about 0.5 mm to about 1.0 mm. Sleeve  5242  is cap-shaped whose top and bottom are open. Sleeve  5242  is made from iron plate press material which offers comparatively high accuracy, but may be formed from leaf spring steel.  
      Insertion member  5244  coaxially inserted into cylindrical hollow portion  5243  has a plurality of projections  5245  on its upper outside surface, and receiving portion  5246  formed by a step between large-diameter portion  5251  and small-diameter portion  5252  of sleeve  5242  rotatably receives the thrust surfaces of projections  5245  in a face contact condition. The thrust surface of receiving portion  5246  has a tapered shape, and the thrust surfaces of projections  5245  have tapered shapes in correspondence therewith. The difference between the inside diameter of receiving portion  5246  and the outermost diameter of projections  5245  is determined within a range from 0.1 mm to 0.5 mm. As for the method of installing insertion member  5244 , projections  5245  of insertion member  5244  which has been inserted into sleeve  5242  in advance are disposed in such a position as to be received by receiving portion  5246  provided on the upper end of sleeve  5242 , and subsequently insertion member  5244  is inserted from outside and fixed. By this method, installment of insertion member  5244  can be simultaneously completed.  
      Insertion member  5244  is made from a synthetic resin material which has lower thermal conductivity than the metal material which forms shaft  5125  and possesses refrigerant-resistance and oil-resistance properties such as PPS, PBT, and PEEK. Spiral groove  5247  is engraved on the outer surface of insertion member  5244 , whereby oil passage  5248  through which oil flows is provided between spiral groove  5247  and the inner surface of sleeve  5242 . The difference between the inside diameter of sleeve  5242  and the outermost diameter of insertion member  5244  is almost equivalent to or slightly larger than the difference between the inside diameter of receiving portion  5246  and the outermost diameter of projections  5245 .  
      A plurality of impellers  5249  as means  5270  for preventing rotation of insertion member  5244  are disposed at the lower sides of insertion member  5244  to extend toward the periphery.  
      Insertion member  5244  is supported inside cylindrical hollow portion  5243  while being prevented from rising by disposing projections  5245  in such a position as to be sandwiched between the lower end of main shaft portion  5220  and receiving portion  5246  formed by large-diameter portion  5251  and small-diameter portion  5252  with a certain clearance in the vertical direction.  
      The operation of the compressor having the above structure is now described.  
      Main shaft portion  5220  rotates with the rotation of shaft  5125 . Cylindrical hollow portion  5243  rotates in synchronization with the rotation of main shaft portion  5220 . The thrust surfaces of projections  5245  of insertion member  5244  are rotatably received by receiving portion  5246  formed by large-diameter portion  5251  of sleeve  5242  and small-diameter portion  5252 . Insertion member  5244  is pulled by the rotation of cylindrical hollow portion  5243 , but rotates at a rotational frequency far lower than that of cylindrical hollow portion  5243  since impellers  5249  receive large viscous resistance in the rotational direction within oil  5102 . Thus, there is a difference in rotational frequency between cylindrical hollow portion  5243  and insertion member  5244 , which difference is near the rotational frequency of shaft  5125 .  
      As a result, oil rises through spiral oil passage  5248  while rotating and being pulled by the inner surface of cylindrical hollow portion  5243  due to viscosity. At this stage, oil  5102  rises while rotating not only by the centrifugal force which decreases at low-speed revolution but by a pulling force generated by viscosity. Thus, oil can be drawn up in a stable manner even at the time of low-speed revolution such as 600 rpm.  
      According to this embodiment, the position of insertion member  5244  relative to cylindrical hollow portion  5243  is determined by the surface contact between receiving portion  5246  and the thrust surfaces of projections  5245  provided on insertion member  5244 . Accordingly, an almost constant clearance between insertion member  5244  and cylindrical hollow portion  5243  is maintained and thus excessive lateral pressure which may be produced by fixation is scarcely generated. As fluid film pressure is generated within spiral groove  5247  and generation of the fluid film pressure is promoted by providing the tapered thrust surfaces of projections  5245  and receiving portion  5246 , there is very few possibility of occurrence of sliding abrasion between insertion member  5244  and cylindrical hollow portion  5243 .  
      Accordingly, it is possible to prevent generation of abrasion powder which is circulated with oil toward the sliding area and caught between the sliding components and brings about a locked condition of the compressing element, and thus a highly reliable compressor can be provided.  
      In this embodiment, sleeve  5242  is fixed to hollow portion  5241  provided in the lower region of shaft  5125 , and receiving portion  5246  is formed by large-diameter portion  5251  and small-diameter portion  5252  of sleeve  5242  to effectively utilize the step of sleeve  5242  as receiving portion  5246 . Thus, complicated processing is not required to form shaft  5125  and sleeve  5242 , and a compressor which is inexpensive and has high productivity can be provided.  
      Since the rotation of sleeve  5242  is prevented by large viscous resistance applied to impellers  5249  in the rotational direction within oil  5102 , indirect fixing of sleeve  5242  to stator  5136  or other components is not needed and the structure is considerably simplified requiring only a small number of components and processes. Thus, a viscous pump having high productivity can be provided.  
     Embodiment 13  
       FIG. 28  is a cross-sectional view illustrating a compressor in a thirteenth embodiment of the invention, and  FIG. 29  is a cross-sectional view illustrating a main part of the compressor in the thirteenth embodiment.  
      The thirteenth embodiment is herein described with reference to  FIGS. 28 and 29 . Similar numbers are given to the structures similar to those of the eleventh embodiment, and detailed description of those is omitted.  
      Viscous pump  5340  soaked with oil  5102  is provided at the lower end of main shaft portion  5320  of shaft  5125 .  
      Next, the structure of viscous pump  5340  is described in detail.  
      Hollow portion  5341  is formed in main shaft portion  5320 . Hollow sleeve  5342  is inserted from outside and fixed to the lower region of hollow portion  5341  to form cylindrical hollow portion  5343 . Sleeve  5342  is substantially cylindrical and has large-diameter portion  5351  and small-diameter portion  5352 . The wall thickness of sleeve  5342  is determined in a range from about 0.5 mm to about 11.0 mm. Sleeve  5342  is cap-shaped whose top and bottom are open, and is made from iron plate press material which offers comparatively high accuracy, but may be formed from leaf spring steel.  
      Insertion member  5344  coaxially inserted into cylindrical hollow portion  5343  has a plurality of projections  5345  on its upper outside surface, and receiving portion  5346  formed by a step between large-diameter portion  5351  and small-diameter portion  5352  of sleeve  5342  rotatably receives the thrust surfaces of projections  5345  in a face contact condition. The thrust surface of receiving portion  5346  has a tapered shape, and the thrust surfaces of projections  5345  have tapered shapes in correspondence therewith. The difference between the inside diameter of receiving portion  5346  and the outermost diameter of projections  5345  is determined within a range from 0.1 mm to 0.5 mm.  
      Spiral groove  5347  is engraved on the outer surface of insertion member  5344 , whereby oil passage  5348  through which oil flows is provided between spiral groove  5347  and the inner surface of sleeve  5342 . The difference between the inside diameter of sleeve  5342  and the outermost diameter of insertion member  5344  is almost equivalent to or slightly larger than the difference between the inside diameter of receiving portion  5346  and the outermost diameter of projections  5345 . A plurality of arms  5349  radially project from the lower sides of insertion member  5344 .  
      As means  5370  for preventing the rotation of insertion member  5344 , permanent magnet  5350  is fixed on each arm  5349  formed on insertion member  5344 , and each permanent magnet  5360  is fixed to the inner surface of the bottom of closed container  5101  in such a position as to be substantially opposed to each permanent magnet  5350  with a sufficient predetermined clearance within the reach of mutual magnetic force. The opposed surfaces of permanent magnet  5350  and permanent magnet  5360  have different poles from each other.  
      Insertion member  5344  is supported inside cylindrical hollow portion  5343  while being prevented from rising by disposing projections  5345  in such positions as to be sandwiched between the lower end of main shaft portion  5320  and receiving portion  5346  formed by large-diameter portion  5351  and small-diameter portion  5352  with a certain clearance in the vertical direction.  
      The operation of the compressor having the above structure is now described.  
      Main shaft portion  5320  rotates with the rotation of shaft  5125 . Cylindrical hollow portion  5343  rotates in synchronization with the rotation of main shaft portion  5320 . The thrust surfaces of projections  5345  of insertion member  5344  are rotatably received by receiving portion  5346  formed by large-diameter portion  5351  of sleeve  5342  and small-diameter portion  5352 . Insertion member  5344  is pulled by the rotation of cylindrical hollow portion  5343 , but the rotation of insertion member  5344  is prevented since permanent magnets  5350  and permanent magnets  5360  adhere to each other.  
      As a result, oil rises through spiral oil passage  5348  while rotating and being pulled by the inner surface of cylindrical hollow portion  5343  due to viscosity. At this stage, oil  5102  rises while rotating not only by the centrifugal force which decreases at low-speed revolution but by a pulling force generated by viscosity. Thus, oil can be drawn up in a stable manner even at the time of low-speed revolution such as 600 rpm.  
      According to this embodiment, the position of insertion member  5344  relative to cylindrical hollow portion  5343  is determined by the surface contact between receiving portion  5346  and the thrust surfaces of projections  5345  provided on insertion member  5344 . Accordingly, an almost constant clearance between insertion member  5344  and cylindrical hollow portion  5343  is maintained and thus excessive lateral pressure which may be produced by fixation is scarcely generated. As fluid film pressure is generated within spiral groove  5347  and generation of the fluid film pressure is promoted by providing the tapered thrust surfaces of projections  5345  and receiving portion  5346 , there is very few possibility of occurrence of sliding abrasion between insertion member  5344  and cylindrical hollow portion  5343 .  
      Accordingly, it is possible to prevent generation of abrasion powder which is circulated with oil toward the sliding area and caught between the sliding components and brings about a locked condition of the compressing element, and thus a highly reliable compressor can be provided.  
      Additionally, the rotation of insertion member  5344  is prevented by permanent magnet  5350  fixed on each arm  5349  formed on insertion member  5344  and permanent magnet  5360  each fixed to the inner surface of the bottom of closed container  5101  in such a position as to be substantially opposed to each permanent magnet  5360  with a predetermined clearance. As a result, indirect fixing of insertion member  5344  to stator  5136  or other components is not needed and the structure is considerably simplified requiring only a small number of components and processes. Accordingly, a viscous pump having high productivity can be provided.  
      An example which utilizes adhering force of the permanent magnets is shown in this embodiment, but similar operation and advantage can be attained by utilizing repulsion force generated by disposing the same poles of the permanent magnets in such positions as to be opposed to each other in the rotational direction of shaft  5125  to prevent the rotation of insertion member  5344 .  
      In this embodiment, iron dust such as abrasion powder floating in oil  5102  is collected by the permanent magnets which are disposed in oil  5102 . Accordingly, the dust is prevented in advance from being caught between the components in the viscous pump or in the sliding areas during oil circulation, and thus reliability can be enhanced.  
      According to the compressor of the invention, the position of the insertion member relative to the sleeve is restricted and abrasion and fixation between the insertion member and the sleeve are scarcely caused. Thus, a highly reliable compressor can be provided.  
      In the compressor of the invention, the position of the insertion member relative to the sleeve is determined by the surface contact between the thrust surfaces of the projections and the receiving portion. Accordingly, abrasion and fixation between the insertion member and the cylindrical hollow portion are scarcely caused and thus a highly reliable compressor can be provided.  
      In the compressor of the invention, complicated processing is not required for forming the sleeve. Thus, a compressor which is inexpensive and has high productivity and reliability can be provided.  
      In the compressor of the invention, the step formed on the sleeve is utilized as the receiving portion. Accordingly, complicated processing is not required for forming the shaft and thus a compressor which is inexpensive and has high productivity and reliability can be provided.  
      In the compressor of the invention, fluid film pressure is easily generated due to the oil having flowed into the clearance between the projections and the receiving portion. Accordingly, the contact between the projections and the receiving portion is prevented and thus a compressor having high durability and reliability can be provided.  
      In the compressor of the invention, the rotation of the insertion member is prevented by a simple structure and the viscous pump is constructed in a reliable manner. Thus, a highly reliable compressor can be provided.  
      In the compressor of the invention, a process for fixing the insertion member is not required. Accordingly, a compressor which is easily assembled and has high productivity and high reliability can be provided.  
      In the compressor of the invention, the rotation of the insertion member is securely restrained and iron dust such as abrasion powder is collected by the magnets to prevent the dust from being caught between the components in the viscous pump or in the sliding areas in advance. Thus, a highly reliable compressor can be provided.  
      In the compressor of the invention, the insertion member which is inexpensive and has high accuracy and high abrasion resistance is employed. Thus, a highly reliable compressor can be provided.  
      In the compressor of the invention, vibration transmitted from the compressing element including the viscous pump and the electrically-powered element is reduced. Accordingly, generation of abnormal sound caused by vibration is eliminated and thus a highly reliable compressor can be provided.  
      In the compressor of the invention, oil supply is stabilized, and input to the compressor is decreased since the electrically-powered element is driven at driving frequencies including those lower than the power source frequency. Accordingly, power consumption is reduced and thus a highly reliable compressor can be provided.  
      In the above-described conventional structure, both ends of bracket  7115  are fixed to stator  7106 . Additionally, stopper  7623  for preventing rotation of insertion member  7120  is provided at a position extremely close to the rotational shaft center. As a result, moment generated through the rotation applies large load to stopper  7623 , thereby curving bracket  7115  into a twisted condition starting from the position of stopper  7623 . If the twisted condition is continued, fatigue of material develops especially at the position of stopper  7623 , and thin film projections (extrusion) and depression of cracks (intrusion) finally occur. Particularly, the depression develops into visual minute cracks, which gradually spread to finally cause corruption of bracket  7115 . In this case, the rotation of insertion member  7120  inside sleeve  7112  may not be prevented.  
      Moreover, for dispersing the load applied on stopper  7623  or increasing the fatigue resistance strength of stopper  7623 , bracket  7115  is required to have a complicated shape. In this case, the cost of the compressor is inevitably raised.  
      In order to solve these problems, an object of the present invention is to provide a compressor which is inexpensive and highly reliable, and is capable of maintaining the structure of viscous pump  7113  in a stable condition for a long period of time without causing material fatigue to the components in relation to the restriction of insertion member  7120 .  
      Fourteenth and fifteenth embodiments of the invention are hereinafter described with reference to the drawings, and the invention is not limited to those embodiments.  
     Embodiment 14  
       FIG. 30  is a cross-sectional view illustrating a compressor in a fourteenth embodiment of the invention,  FIG. 31  is a cross-sectional view illustrating a main part of the compressor in the fourteenth embodiment, and  FIG. 32  is a cross-sectional view illustrating a main part of a viscous pump in the fourteenth embodiment.  
      In  FIGS. 30, 31  and  32 , oil  6102  is stored in closed container  6101  which is filled with refrigerant gas  6103 .  
      Compressing element  6110  includes: block  6115  which forms cylinder  6113 ; piston  6117  reciprocatively inserted into cylinder  6113 ; shaft  6125  having main shaft portion  6120  supported by bearing  6116  of block  6115  and eccentric portion  6122 ; and connecting rod  6119  for connecting eccentric portion  6122  and piston  6117 . Compressing element  6110  forms a reciprocating compressing mechanism.  
      Electrically-powered element  6135  is fixed below block  6115 , and includes stator  6136  connected to an inverter driving circuit (not shown) and rotor  6137  which contains permanent magnet and is fixed to main shaft portion  6120 . Electrically-powered element  6135  provides an electric motor for driving an inverter, and is driven at a plurality of driving frequencies including those below 1,200 rpm, for example, by the inverter driving circuit (not shown).  
      Springs  139  elastically support compressing element  6110  via stator  6136  such that compressing element  6110  is elastically held on closed container  6101 .  
      Viscous pump  6140  soaked with oil  6102  is provided at the lower end of main shaft portion  6120  of shaft  6125 .  
      Next, the structure of viscous pump  6140  is described in detail.  
      Cylindrical hollow portion  6141  is formed in main shaft portion  6120 . Hollow sleeve  142  is fixed to the lower region of cylindrical hollow portion  6141 . Sleeve  142  is substantially cylindrical and cap-shaped, whose top and bottom are open. Sleeve  142  is made from iron plate press material which offers comparatively high accuracy in this embodiment, but may be formed from leaf spring steel.  
      Insertion member  6143  coaxially inserted into cylindrical hollow portion  6141  and sleeve  142  is made from a plastic material which has lower thermal conductivity than the metal material which forms shaft  6125  and possesses refrigerant-resistance and oil-resistance properties such as PPS, PBT, and PEEK. Spiral groove  6144  is engraved on the outer surface of insertion member  6143 , whereby oil passage  6145  through which oil flows is provided between spiral groove  6144  and the inner surface of sleeve  142 . The difference between the outermost diameter of insertion member  6143  and the inner surface of sleeve  142 , i.e., the matching clearance is established in a range from 100 μm to 500 μm. Insertion member  6143  has bolt hole  6146  at its upper end, and a plurality of first contacting members  6147  at its lower sides off the rotational shaft center of shaft  6125 .  
      Each second contacting member  6148  is fixed to the inner surface of the bottom of closed container  6101  in such a position as to be opposed to each first contacting member  6147  in the rotational direction with a sufficient predetermined clearance from rotating sleeve  142 . Both first contacting members  6147  and second contacting members  6148  are completely soaked with oil  6102  stored in the bottom area of closed container  6101 . First contacting members  6147  are made from plastic and formed integrally with insertion member  6143 , but may be formed by fixing metal wires or fragments, for example, to the lower region of insertion member  6143 . Second contacting members  6148  are substantially L-shaped and made from elastic material such as metal wires and fragments.  
      Bolt  6150  is employed as supporting member  6152  for slidingly connecting insertion member  6143  with sleeve  142 . Bolt  6150  inserted through washer  6151  penetrates bolt hole  6146 , and reaches the upper surface of cylindrical hollow portion  6141  to be attached thereto, thereby rotatably connecting insertion member  6143  to main shaft portion  6120  of shaft  6125  and closing the lower end of bolt hole  6146 . Washer  6151  is made from a plastic material having high abrasion-resistance property such as self-lubrication characteristic (PPS and PEEK etc.). Alternatively, bolt  6150  may be formed from a similar self-lubrication material to eliminate washer  6151 .  
      The operation of the compressor having the above structure is herein described.  
      Main shaft portion  6120  rotates with the rotation of shaft  6125 . Sleeve  142  fixed to main shaft portion  6120  rotates in synchronization with the rotation of main shaft portion  6120 . Insertion member  6143  is pulled by the rotation of sleeve  142 , but the rotation of insertion member  6143  is prevented by the elastic contact between first contacting members  6147  provided on insertion member  6143  and second contacting members  6148  provided on closed container  6101 . As a result, oil rises through spiral oil passage  6145  while rotating and being pulled by the inner surface of sleeve  142  due to viscosity. At this stage, oil  6102  rises while rotating not only by the centrifugal force which decreases at low-speed revolution but by a pulling force generated by viscosity. Thus, oil can be drawn up in a stable manner even at the time of low-speed revolution such as 600 rpm.  
      In the embodiment as described above, first contacting members  6147  and second contacting members  6148  are disposed away from the rotational shaft center of shaft  6125 . This arrangement decreases load applied by the moment which is generated through the rotation while first contacting members  6147  and second contacting members  6148  are contacting each other. Also, as both the contacting members elastically contact with each other, impact received is absorbed and material fatigue of the components in relation to the restriction of insertion member  6143  is scarcely caused. Accordingly, the structure of viscous pump  6140  is maintained in a stable condition for a long period of time, and thus a highly reliable compressor can be provided. Moreover, first contacting members  6147  and second contacting members  6148  are not required to have a complicated shape for reducing the load applied by the moment generated through the rotation at the time of the contact. Thus, a considerably simple and inexpensive compressor can be provided.  
      Since first contacting members  6147  and second contacting members  6148  are soaked with oil  6102 , impact caused at the time of the contact between the contacting members is reduced by the viscosity of oil  6102 . Also, even if rubbing is caused between the contacting members due to vibration from compressing element  6110 , abrasion does not develop owing to the lubricating function of oil  6102 . Thus, reliability can be further increased.  
      Second contacting members  6148  are formed by metal wires or fragments in this embodiment, but may be made from nitrile rubber (NBR) which is comparatively inexpensive and has oil-resistance and refrigerant-resistance properties, if mineral oil or diester synthetic oil is used as oil  6102 . The nitrile rubber may be L-shaped as in the embodiment, or may be disposed on the contact portions of the metal wires or fragments. Additionally, it is possible to reduce sound and vibration transmitted to the outside of closed container  6101  at the time of the contact between the contacting members by utilizing the shock absorbing characteristic of the nitrile rubber.  
      According to this embodiment, insertion member  6143  is rotatably connected to main shaft portion  6120  of shaft  6125  by means of bolt  6150  which is inserted through washer  6151 . Thus, the position of insertion member  6143  relative to sleeve  142  fixed at the lower end of main shaft portion  6120  is restricted by this connecting portion, and an almost constant clearance is maintained between insertion member  6143  and sleeve  142 . This clearance is maintained by the fact that lateral pressure due to fixation is scarcely caused and also by the oil pressure generated between insertion member  6143  and sleeve  142 , and thus there is very few possibility of occurrence of sliding abrasion between insertion member  6143  and sleeve  142 .  
      Spiral groove  6144  is provided on the outer surface of insertion member  6143  to form spiral oil passage  6145  in this embodiment, but may be disposed on the inner surface of sleeve  142  to form oil passage  6145 . In this case, the area of the inner surface of the rotational body in contact with oil  6102  is enlarged by adding the surface area of the concaves of the spiral groove. This structure causes large viscous resistance, thereby enhancing oil transfer capability.  
     Embodiment 15  
       FIG. 33  is a cross-sectional view illustrating a main part of a compressor in a fifteenth embodiment of the invention.  
      The fifteenth embodiment is herein described with reference to  FIG. 33 . Similar numbers are given to the structures similar to those of the fourteenth embodiment, and detailed description of those is omitted.  
      Insertion member  6143  coaxially inserted into sleeve  142  has a plurality of first contacting members  6247  at its lower sides off the rotational shaft center of shaft  6125 .  
      Each second contacting member  6248  is fixed to the inner surface of the bottom of closed container  6101  in such a position as to be opposed to each first contacting member  6247  in the rotational direction with a sufficient predetermined clearance from rotating sleeve  142 . Both first contacting members  6247  and second contacting members  6248  are completely soaked with oil  6102  stored in the bottom area of closed container  6101 . First contacting members  6247  are made from plastic and formed integrally with insertion member  6143 , but may be formed by fixing metal wires or fragments, for example, to the lower region of insertion member  6143 . Second contacting members  6148  are substantially L-shaped and made from elastic material such as metal wires and fragments. Each second contacting member  6248  has metal flat plate  6249  disposed in such a position as to contact with the face of first contact member  6247 .  
      According to this embodiment, since the faces of first contacting members  6247  and second contacting members  6248  contact each other and also receive viscous resistance of oil  6102 , the face pressure is securely and extremely decreased by a simple structure. Accordingly, chipping at the contact portion is prevented and thus reliability can be further increased.  
      In this embodiment, each second contacting member  6148  has metal flat plate  6249  in this embodiment. However, flat plate  6249  may be made from nitrile rubber (NBR) which is comparatively inexpensive and has oil-resistance and refrigerant-resistance properties, or has a coil spring or other means on the contact portion of flat plate  6249  to greatly enhance its shock absorbing characteristic at the time of the contact.  
      In the invention as described above, both the contacting members are disposed away from the rotational shaft center. This arrangement decreases load applied by the moment which is generated through the rotation at the time of the contact. Also, as both the contacting members elastically contact with each other, impact received is absorbed and material fatigue of the components in relation to the restriction of the insertion member is scarcely caused. Accordingly, as the contacting members are not required to have a complicated structure for reducing the load, the structure of the viscous pump is maintained in a stable condition for a long period of time, and thus a compressor which is inexpensive and highly reliable can be provided.  
      In the invention, impact caused at the time of the contact between the contacting members is reduced by the viscosity of oil. Also, even if rubbing is caused between the contacting members due to vibration from the compressing element, abrasion does not develop. Thus, a compressor which is inexpensive and highly reliable can be provided.  
      In the invention, at least either the first contacting members or the second contacting members are made from elastic bodies. Accordingly, the number of the components included is decreased and thus a compressor which is inexpensive and highly reliable can be provided.  
      In the invention, the elastic body is interposed between the first contacting member and the second contacting member. As a result, comparatively large impact caused by the contact during assembly or transportation of the compressor is reduced, and the positions of the second contacting members are not required to be accurately determined. Thus, a compressor which is inexpensive and highly reliable can be provided.  
      According to the invention, since the faces of the first contacting members and the second contacting members contact each other, the face pressure is securely more decreased by a simple structure. Accordingly, chipping at the contact portion is prevented and thus a compressor which is inexpensive and highly reliable can be provided.  
     INDUSTRIAL APPLICABILITY  
      A compressor provided according to the present invention is a highly reliable compressor capable of transferring oil in a stable manner even at the time of low-speed driving. Thus, the compressor is applicable to household refrigerators, and also to refrigerant cycles in dehumidifiers, showcases, vending machines and so forth.