Patent Publication Number: US-7909592-B2

Title: Scroll compressor

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. application Ser. No. 10/594,434, filed Sep. 26, 2006, which is a national stage of PCT/JP2004/019237, filed Dec. 22, 2004, the contents of which are hereby incorporated by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a scroll compressor, and more particularly to a scroll compressor having volute teeth on both surfaces of a base plate of an orbiting scroll. 
     BACKGROUND ART 
     In a conventional scroll compressor, for example in a case of a vertical type scroll compressor, a compression section is disposed in an upper space in a container, a motor for driving is placed in a lower space, and a lubricating oil storage chamber is formed below the motor. The compression section is formed by combination of an orbiting scroll having an volute tooth formed on only an upper surface of an orbiting scroll base plate, and a fixed scroll opposed to the above volute tooth. A compression chamber is formed by driving the motor via an eccentric shaft connected to a lower surface of the orbiting scroll (for example, refer to Patent Document 1). 
     There is another type in which volute teeth are formed on both surfaces of an orbiting scroll base plate, compression chambers are formed on an upper and a lower surfaces of the orbiting scroll by opposing fixed scrolls to the respective volute teeth, and the orbiting scroll is driven by a shaft penetrating through each of the scrolls. In this case, the heights of the volute teeth, which are formed on the upper and the lower surfaces of the orbiting scroll, are made different, and an upper compression chamber and a lower compression chamber are connected in series relationship to perform two-stage compression (for example, refer to Patent Document 2). 
     Patent Document 1: Japanese Patent No. 2743568 
     Patent Document 2: Japanese Patent Laid-Open No. 08-170592 
     DISCLOSURE OF THE INVENTION 
     Problems to be Solved by the Invention 
     The conventional scroll compressors are constructed as described above. In particular, in Patent Document 1, the compression section is placed in the upper space while the motor is placed in the lower space, so that it is necessary to pass a lead wire connected to the motor through the compression section to lead it to the upper space and connect it to a terminal in the case where the terminal is provided above, and therefore, there is the problem of unfavorable operability. 
     In the case where the terminal is provided between the compression section and the motor, it is necessary to connect the lead wire to the terminal after the motor is previously fixed to the container by shrink fitting or the like at the time of assembly, and thereafter to fix the compression section to the container. Thus, there is the problem that the assembling operation is complicated. 
     Further, bearing structure is provided only at the lower position of the compression section, so that there are the problems of one-side abutment of the bearing due to tilt of the shaft, and an increase in associated bearing loss and burning. Further in case the orbiting scroll has the volute tooth only on one side, thrust load occurs due to compression of the operating gas, and therefore, there is the problem of needing a thrust bearing. 
     In Patent Document 2, the compression chambers are formed on both sides of the orbiting scroll, thrust loads by the compression of the operation gas are cancelled out, and as a result, the load of the thrust bearing is reduced. However, there are some problems of complicating the construction of the scroll, because it is necessary to control the ratio of the height of the volute tooth on the upper surface of the orbiting scroll and the height of the volute tooth on the lower surface so that the minimum closed volume of one compression chamber and the maximum closed volume of the other compression chamber are substantially equal, or to be substantially equal to the ratio of the maximum closed volume and the minimum closed volume of one compression chamber. 
     The present invention is made to overcome the above described problems, and has an object to provide a scroll compressor that has favorable assembling property, does not require a thrust bearing, has a compression section supported by bearing structure on both sides and is simple in a structure of a scroll. 
     Means for Solving the Problems 
     A scroll compressor according to the present invention comprises a compression section provided in a closed container, said compression section including an orbiting scroll having volute teeth formed substantially symmetrically on both surfaces of an orbiting base plate, and a main shaft being penetrated through and fixed at a center portion of said orbiting scroll and a pair of fixed scrolls opposed to said both surfaces of said orbiting scroll, each of said fixed scroll having volute tooth corresponding to each of said volute teeth of said orbiting scroll to respectively form compression chambers; a motor provided in said closed container for driving said main shaft; a suction pipe provided to said closed container for introducing a suction gas into said closed container and for causing said suction gas to be sucked into said compression section after cooling said motor; and a discharge pipe provided to said closed container for discharging said suction gas compressed by said compression section. 
     Advantages of the Invention 
     The scroll compressor according to this invention is constructed as described above. Accordingly in case of assembling a vertical type, for example, the compression section is placed in a lower space of the container, the motor is placed in an upper space, and a glass terminal can be provided at an upper end portion above the motor. Therefore, after the compression section and the motor are all fixed inside the container, a lead wire can be finally connected to the terminal, and therefore, assembling property is improved. 
     Further, the substantially symmetrical volute teeth are formed on both surfaces of the orbiting scroll and the thrust loads caused by compression of an operating gas are cancelled by each other so that a thrust bearing does not have to be provided. 
     Accordingly, it can be prevented that an increase in abrasion loss and burning due to a broken oil film occurs due to its low circumferential speed and difficulty in forming oil film, that is caused in case of thrust bearing using a gas such as CO 2  gas at high pressure with a high load. 
     Further, since the compression section is supported by bearing structure on both sides thereof, a moment does not occur to the shaft, and therefore, one-side abutment on the bearing due to tilt of the shaft may be prevented, and an associated increase in bearing loss and burning may be prevented. 
     Further, as described above, the volute teeth on both surfaces of the orbiting scroll are formed to be substantially symmetrical and have substantially the same heights, and therefore, they are simple in structure and can be formed easily. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic sectional view showing one example of an entire construction in the case of using a vertical container according to a first embodiment; 
         FIG. 2  shows a construction of an orbiting scroll in the first embodiment, (a) is a sectional view, (b) is a plane view showing a construction of the upper, and (c) is a plane view showing a construction of the lower surface; 
         FIG. 3  shows a construction of a core part located in a center portion of the orbiting scroll shown in  FIG. 2 , (a) is a perspective view, (b) is a perspective view showing a construction of a seal ring each provided at an upper surface and a lower surface; 
         FIG. 4  is an explanatory sectional view for explaining an operational effect of the seal ring in the core part; 
         FIG. 5  shows the construction of a fixed scroll at the lower side in  FIG. 1  of the fixed scroll s in the first embodiment, (a) is a plane view, and (b) is a sectional view taken along the line A-A in (a); 
         FIG. 6  is an enlarged view of the penetration structure of the main shaft and the compression section and the structure of the lower end portion of the main shaft; 
         FIG. 7  is an explanatory view to show relation of the orbiting movement of the orbiting scroll and compression chambers. 
     
    
    
     EXPLANATION OF THE REFERENCE NUMERALS 
       1  closed container,  2  motor,  3  compression section,  4  lubricating oil storage chamber,  5  suction pipe,  6  glass terminal,  7  main shaft,  8  discharge pipe,  31  orbiting scroll,  32  compression chamber,  33  upper fixed scroll,  34  lower fixed scroll,  35  Oldham joint,  76  oil feed pump,  77  lubricating oil. 
     BEST MODE FOR CARRYING OUT THE INVENTION 
     First Embodiment 
     A first embodiment of this invention will be first described with reference to the drawings.  FIG. 1  is a schematic sectional view showing one example of an entire construction using a vertical container according to the first embodiment,  FIG. 2  shows a construction of an orbiting scroll in the first embodiment, (a) is a sectional view taken along the line A-A in (c) that will be described later, and the left side shows an upper surface while the right side shows a lower surface. (b) is a plane view showing a construction of the upper surface of the orbiting scroll, and (c) is a plane view showing a construction of the lower surface of the same. 
       FIG. 3  shows a construction of a core part located in a center portion of the orbiting scroll shown in  FIG. 2 , (a) is a perspective view showing the shape of the core part, (b) is a perspective view showing a construction of a seal ring each provided at an upper surface and a lower surface of the core part,  FIG. 4  is an explanatory sectional view for explaining an operational effect of the seal ring in the core part,  FIG. 5  shows the construction of a lower side fixed scroll in  FIG. 1  in the first embodiment, (a) is a plane view, and (b) is a sectional view taken along the line A-A in (a). 
     In a scroll compressor of  FIG. 1 , a motor  2  is placed at an upper portion in a vertical closed container  1 , a compression section  3  is placed in a lower portion, and a lubricating oil storage chamber  4  is formed under the compression section  3 . 
     A suction pipe  5  is provided for sucking a suction gas in the closed container  1  at an intermediate portion between the motor  2  and the compression section  3 , and a glass terminal  6  is provided at an upper end of the closed container  1  at the upper side of the motor  2 . 
     The motor  2  is constructed by a known stator  21  formed into a ring shape, and a rotor  22  supported to be rotatable in the inside of the stator  21 . A main shaft  7  is fixed to the rotor  22 , and the main shaft  7  penetrates through the compression section  3  to extend to the lubricating oil storage chamber  4 . The relationship between the compression section  3  and the main shaft will be described later. 
     The compression section  3  includes an orbiting scroll  31  having volute teeth formed on an upper surface and a lower surface of an orbiting base plate in substantially symmetrical shape with substantially same heights, an upper fixed scroll  33  which is disposed to be opposed to the upper surface of the orbiting scroll  31  and has an volute tooth which corresponds to the upper surface volute tooth of the orbiting scroll  31  to form a compression chamber  32 , a lower fixed scroll  34  which is disposed to be opposed to the lower surface of the orbiting scroll  31  and has a volute tooth which corresponds to the lower surface volute tooth of the orbiting scroll  31  to form the compression chamber  32 , and a known Oldham joint  35  which is placed between the lower fixed scroll  34  and the orbiting scroll  31 . 
     The detailed construction of the orbiting scroll  31  will be described with reference to  FIG. 2 . As shown in this drawing, the orbiting scroll  31  has a core part  31 A which forms a center portion and is constituted of a curved line such as an arc, and a disk-shaped orbiting base plate  31 B which extends on the outer periphery of the core part  31 A. 
     As shown in the enlarged view of  FIG. 3(   a ), in the core part  31 A, a hole  31 C, through which a main shaft  7  penetrates, is formed in a center portion, and an orbiting bearing  31 D is provided on its inner peripheral wall. A seal ring groove  31 E is respectively formed on both surfaces of the core part at an outer side of the orbiting bearing  31 D, and a seal ring  31 G having an abutment joint  31 F as shown in  FIG. 3(   b ) is inserted in a respective groove. The details of the seal ring  31 G will be described later. 
     In the core part  31 A, a volute tooth is usually formed in an involute curve or an arc outward from its center, and the number of turns of the volute tooth is proportional to the compression ratio of the compressor. In the case of using an HFC gas in air-conditioning for example, the compressor is operated at the compression ratio of 3, so that the number of turns of the volute tooth needs to be three or more. But in the case of using a CO 2  gas with a low compression ratio, the compressor is operated at the compression ratio of 2, so that the number of turns of volute tooth becomes two or more, and thus it is possible to reduce the number of turns of the volute tooth by one turn as compared with the case of the HFC gas. 
     Accordingly, by decreasing the turns of the volute tooth by the amount of one turn or more at the center portion, it becomes possible to form the hole  31 C in the center portion of the core part  31 A for penetrating the main shaft and to provide the orbiting bearing  31 D. 
     This can be applied for any other case where the low compression ratio is a rated condition as well as the case of CO 2  gas. 
     Two or more turns of a volute tooth are formed respectively on the upper surface and the lower surface of the orbiting base plate  31 B in volute curves or arcs substantially symmetrically and substantially in the same height as the core part. 
     “Substantially symmetrical” means that the thickness t, height h, pitch p and the numbers of turns n of the volute tooth shown in  FIG. 2(   a ) are substantially equal, and thereby, the reaction force in the thrust direction which occurs at the time of gas compression is made completely or substantially equal. 
     Therefore, the thrust forces, which act on the orbiting scroll  31  to upward and downward direction at the time of compression, are cancelled out, and the load in the thrust direction becomes substantially zero, so that the thrust bearing can be eliminated. 
     Since the thrust forces can be cancelled out by each other, the tooth height of the scroll can be made low, and the volute may be enlarged in the diameter direction into a so-called thin pancake shape, whereby the radial direction force can be made relatively small, and reliability of the journal bearing can be enhanced. 
     The volute teeth on the upper surface and the lower surface are made substantially symmetrical, but in actual a slight difference is made to occur in the gas pressures of the upper and lower compression chambers for example in order to give rise a slight thrust force downwardly. 
     As a result, the volute tooth at the lower side of the orbiting scroll  31  is brought into pressure contact with the lower fixed scroll  34 , and the volute tooth at the upper side has a gap from the upper fixed scroll  33 . Therefore, in the volute tooth of the upper side, a tip seal groove  31 H is formed at the upper end surface of the volute tooth as shown in  FIGS. 2(   a ) and ( b ), and a tip seal  36  ( FIG. 6)  is fitted inside of it. On the lower side of the orbiting scroll  31 , an Oldham groove  31 J corresponding to the Oldham joint  35  is formed at an outermost peripheral portion. 
     The seal ring  31 G provided at the core part  31 A is formed as a ring which is rectangular in section as shown in  FIG. 3(   b ) and has the abutment joint  31 F, and is fitted in the seal ring groove  31 E shown in  FIG. 3(   a ). This seal ring  31 G is placed in the core part  31 A to separate the main shaft  7  and the orbiting bearing  31 D from the center side of the volute tooth in order to prevent leakage therebetween, since at the time of a compressing operation, the main shaft  7  and the orbiting bearing  31 D are at a low pressure, while the center side of the volute tooth is at a high pressure. 
     The separating action is performed by contact sealing of the seal ring  31 G by pressure difference. The seal ring  31 G is pressed against the right side wall and to the upper side fixed scroll  33  in the seal ring groove  31 E being pressed from the high pressure left side and the lower side as shown by the arrow in  FIG. 4 . 
     In this case, sliding contact occurs at the surface of the fixed scroll, but the sliding is at a low circumferential speed of a grinding motion in a small radius as the tip seal, and therefore, friction and sliding loss are small. 
     In the core part  31 A, a communication port  31 K is formed at the outer side of the seal ring groove  31 E. The communication port  31 K penetrates through the orbiting base plate  31 B in the vertical direction and combines the gases, which are compressed in the compression chambers on both surfaces of the orbiting scroll  31  as will be described later, to flow to a discharge port of the fixed scroll. 
     The communication port  31 K is formed as a long hole along the seal ring groove  31 E, or is formed as a plurality of holes disposed adjacently each other to perform substantially equivalent action as the long hole, and is provided at the position which is not across the compression chambers, and always communicates with the discharge port of the fixed scroll, that will be described later. 
     Next, the detailed construction of the fixed scroll will be described with reference to  FIG. 5 .  FIG. 5  shows one example of the lower fixed scroll  34 . 
     As shown in  FIGS. 5(   a ) and ( b ), a hole  34 B is formed in a center portion of a fixed base plate  34 A through which the main shaft  7  penetrates, and a main shaft bearing  34 C is provided on an inner peripheral surface of this hole. 
     A recessed portion  34 D is formed in the peripheral portion of the main shaft bearing  34 C, i.e. the center portion of the fixed base plate  34 A, and accommodates the core part  31 A of the orbiting scroll  31  and allows the orbiting movement of the orbiting scroll  31 . At the outer periphery of the recessed portion  34 D, an volute tooth  34 E is formed in two or more turns in the same size as the volute tooth of the orbiting scroll  31  in the volute curve or the arc but is rotated 180 degrees in phase. 
     A discharge port  34 F is provided in the recessed portion  34 D for discharging the compressed gas without crossing the seal ring  31 G of the orbiting scroll. 
     The discharge port  34 F is formed as a long hole along an inner side of the innermost volute tooth of the fixed scroll, or is formed as a plurality of holes disposed adjacently each other to perform substantially the equivalent action with the long hole, and is provided at the position which always communicates with the communication port  31 K of the orbiting scroll. 
     Further, a discharge passage  34 G is formed which communicates with the discharge port  34 F and flows the compressed gas out of the compressor via a discharge pipe  8  ( FIG. 1 ). A discharge valve  34 H is placed at a position opposed to the discharge port  34 F in the discharge passage  34 G as shown in  FIG. 1 , and prevents a backflow of the discharge gas. 
     In an outermost peripheral portion of the lower fixed scroll  34 , a suction port  34 J is provided as a suction inlet of the suction gas to the lower compression chamber. A discharge port  34 K ( FIG. 1 ) is provided which communicates from the suction port  34 J to the lubricating oil storage chamber  4  at the lower portion of the closed container. A check valve  34 L is provided for the discharge port  34 K at the side of the lubricating oil storage chamber  4  as shown in  FIG. 1 . 
     The check valve  34 L, is provided to prevent that oil foams with remaining refrigerant and flows out of the compressor when actuating the compressor. The suction path for suctioning gas into the compression chamber is formed as shown by the broken line arrow G in  FIG. 1 . The suction path includes the suction port  33 A formed in the outermost peripheral portion of the upper fixed scroll  33  and the suction port  34 J of the lower fixed scroll  34 , and the suction gas is introduced into the respective compression chambers formed both on the upper surface and the lower surface of the orbiting scroll  31 . 
     As shown in  FIG. 1 , the upper end portion of the main shaft  7  is fitted into the rotor  22  of the motor  2 . The main shaft penetrates the through-hole of the upper fixed scroll  33 , the through-hole  31 C of the orbiting scroll  31  and the through-hole  34 B of the lower fixed scroll  34  and is immersed at its lower end portion in the lubricating oil  77  in the lubricating oil storage chamber  4 . 
       FIG. 6  shows an enlarged view of the penetration structure of the main shaft  7  into the compression section  3  and the structure of the lower end portion of the main shaft  7 . Namely, a main shaft bearing  33 B is provided between the main shaft  7  and the upper fixed scroll  33 . On the surface of the main shaft  7 , a notch part  71 , having flat surface, is formed from the portion in contact with the main shaft bearing  33 B down to the lower end. A slider  72 , having an eccentric hole (not shown) with a partially flat surface corresponding to the notch part  71 , is fitted to the notch part  71  of the main shaft  7 . The outer peripheral surface of the slide  72  is placed to be in contact with the inner peripheral surface of the orbiting bearing  31 D of the orbiting scroll  31  shown in  FIG. 2 . The slider  72 , forming an eccentric shaft in combination with the main shaft, drives the orbiting scroll  31  via the orbiting bearing  31 D. 
     On the upper and the lower surfaces of the slider  72 , recesses  73  are formed for the paths of lubricating oil. On the surface of the outer peripheral portion of the slider  72 , which is in contact with the orbiting bearing  31 D, an oil feed groove  74  is formed in the vertical direction and allows the recess  73  on the upper surface to communicate with the recess  73  on the lower surface. 
     In main shaft  7 , an eccentric oil feed hole  75  is formed and extended from the lower end to reach the main shaft bearing  33 B of the upper fixed scroll  33 . An oil feed pump  76  is provided at the lower end of the main shaft  7  and is immersed in lubricating oil  77  at the lower end of the closed container  1 . 
     Next, an operation of the first embodiment will be explained. 
     The gas, which is sucked into the closed container  1  from the suction pipe  5 , flows into a part of the motor  2 . After cooling the motor  2 , the gas is taken into the compression chambers  32  on the upper and lower surfaces of the orbiting scroll  31  from the suction port  33 A provided in the outer peripheral portion of the upper fixed scroll  33  as shown by the broken line arrow G. 
     Thereafter, the orbiting scroll  31  performs orbiting movement, without rotating around its own axis, with respect to the upper and the lower fixed scroll s  33  and  34 . A pair of crescent compression chambers, which are formed by the known compression principle, reduce their volumes gradually toward the center. The pair of compression chambers finally communicate with each other in the innermost chambers in which the discharge port  34 F is present, and flows are guided outside the compressor through the discharge passage  34 G. 
       FIG. 7  shows the process in which a pair of crescent compression chambers, which are formed by the orbiting movement of the orbiting scroll  31 , gradually reduce their volumes toward the center.  FIG. 7(   a ) shows the state of the orbiting scroll  31  at the orbit angle of 0°. The diagonally slashed portion represents the volute tooth of the orbiting scroll, and the portion painted in black represents the volute tooth of the fixed scroll. 
     In the state of  FIG. 7(   a ), the compression chambers at the outermost periphery complete containing of the gas, and a pair of crescent compression chamber A and B are formed.  FIG. 7(   b ) shows the state in which the orbiting scroll  31  orbits by the orbit angle of 90° in the counterclockwise direction. 
     A pair of compression chamber A and B moves toward the center while reducing in volume. 
       FIG. 7(   c ) shows the state of the orbit angle of 180°, and  FIG. 7(   d ) shows the state of the orbit angle of 270°. In this state, the compression chambers A and B communicate with each other in the innermost chamber in which the discharge port  34 F is present, and the gas is discharged from the discharge port  34 F. 
     In  FIG. 7 , the shape of the core part  31 A of the orbiting scroll  31  forms the volute curve up to the portion shown by the broken line, and forms one border of the compression chamber B. The center side from this becomes the curve of the core part and forms the innermost chamber that does not contribute to compression, and forms a border surface in combination with the inner surface of the volute tooth of the fixed scroll  34 . 
     The discharge port  34 F is provided in the innermost chamber which does not contribute to compression, and is positioned not to cross the aforementioned seal ring  31 G during the compression step, so that a sufficient flow passage is ensured. For that purpose, the curve of the core part and the curve of the inner surface of the volute tooth of the fixed scroll are formed to secure a clearance space in order not to block the discharge port  34 F completely with the core part  31 A during the compression step. 
     In a type of compressor in which an integrated volume ratio is fixed as a scroll compressor, compression insufficiency loss occurs in the final discharge step when the operation is performed with a higher compression ratio than a set compression ratio. The compression insufficiency loss means that the pressure in the innermost chamber is higher than the pressure of the compression chambers A and B, when the innermost chamber and the compression chambers A and B communicate each other as in  FIG. 7(   d ) for example. Then, backflow occurs to the compression chambers A and B from the innermost chamber, and causes loss of the compression power. 
     Therefore, the top clearance volume is restrained to a minimum, which is defined as the volume upstream of the discharge valve  34 H, namely the total sum of the innermost chamber, the discharge port  34 F and the communication port  31 K. Further, a little relief portion  34 M is formed in the core part  31 A. The relief portion  34 M is to secure a flow passage by expanding width with reduced radius of the curvature. 
     Next, oil feed will be described. As shown in  FIG. 6 , the lubricating oil  77 , which is sucked as shown by the arrow from the lower end of the main shaft  7  by the oil feed pump  76 , is sucked up through the oil feed hole  75  in the main shaft  7  as shown by the arrow, and is fed into the main shaft bearing  33 B of the upper fixed scroll  33 . 
     Thereafter, the lubricating oil passes the flat portion of the notch part  71  formed on the main shaft to flow down and, via the recess  73  formed on the upper surface of the slider  72 , flows into the oil feed groove  74  which is formed in the vertical direction on the outer peripheral surface of the slider  72  to lubricate the slider  72 . 
     The oil, which flowed down in the oil feed groove  74 , passes via the recess  73  on the lower surface of the slider, and passes through a return hole  34 N formed in the lower fixed scroll  34 , and flows towards the center direction of the main shaft, and flows down in the notch part  71  of the main shaft  7  again while feeding oil to the main shaft bearing  34 C of the lower fixed scroll  34 , and is discharged outside the main shaft from the lower end portion of the main shaft bearing  34 C as shown by the arrow, and returns to the lubricating oil storage chamber  4 . 
     As described above, the oil feed path forms a circulating closed loop from feeding through discharging without directly contacting the flow of the suction gas. 
     Accordingly, it is prevented that the oil is caught by the suction gas and flows out of the compressor. 
     The first embodiment is constructed as above, and therefore the compressor is suitable, for example, in a case where a heat exchanger volume of an air conditioner is made large for energy saving, in a case where the apparatus is tuned to perform a normal operation with a low compression ratio as an ice thermal storage system for peak-cut and load-leveling, and in a case where a refrigerant such as a CO 2  gas is used and normal operation is performed at a low compression ratio for air conditioning operation. A high efficiency of the apparatus can be maintained. 
     INDUSTRIAL APPLICABILITY 
     This invention can be favorably utilized in an air conditioner or an ice heat storage system that are tuned to be normally operated with a low compression ratio, or in an air conditioner using a refrigerant such as a CO 2  gas and having a low compression ratio at normal operation.