Abstract:
Scroll type fluid machinery, in which two stationary scrolls ( 2 A,  2 B) are fixed onto a housing ( 1 ), and form volume changing mechanisms ( 50 A,  50 B) with matching orbiting scrolls ( 3 A,  3 B). Three orbiting units ( 40 ) are located between the two volume changing mechanisms. Each orbiting unit comprises a rotating member ( 10 ) and a thrust-cancelling shaft ( 20 ). Assembly sets of the thrust-canceling shaft consist of turning elements and a connector, which in turn connects with orbiting scrolls through threads. There exists only circumferential constraint but no axial constraint between the connector and the turning element. Rotating turning element will rotate the connector, and thus move the two orbiting scrolls closer or farther through the threads on the connector. The rotating member of this invention further provides a larger space to the supporting bearings ( 14 A,  14 B) of the thrust-canceling shaft, and also eases component manufacturing, machinery&#39;s assembly and adjustment, and bearings&#39; cooling.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to scroll type fluid machinery, which can be used as compressors, vacuum pumps, expander machines, etc. 
         [0002]    Double-scroll fluid machinery has got people&#39;s attentions due to its many advantages such as thrust force canceling. The technology of Double-Scroll linked by a Plurality of Orbiting units (DSPO) revealed in US patent U.S. Pat. No. 6,988,876 has two volume changing mechanisms, each of which comprises its respective orbiting scroll and stationary scroll. The two stationary scrolls are connected with a housing. Orbiting units are located between the two volume changing mechanisms. Each orbiting unit comprises a rotating member that is rotatably supported on the housing, and a thrust-canceling shaft that is eccentrically and rotatably supported in the rotating member. The thrust-canceling shaft connects the two orbiting scrolls with its two ends to form a frame structure. The orbiting scrolls orbit with respect to the matching stationary scrolls when the rotating members are driven, and thus the continuous changes of the volumes are realized. 
         [0003]    It has been revealed in Chinese Patent Publication CN1963205A that DSPO can easily realize internal fluid injection cooling (especially water injection), because the volume changing mechanisms and the orbiting units are separated by the decompression chambers, and the bearings are not installed directly on the orbiting scrolls. 
         [0004]    Due to the engagement between DSPO&#39;s orbiting scrolls and the respective stationary scrolls, the two orbiting scrolls are required to connect with the thrust-canceling shaft accurately in both radial and axial directions. However, it is not practical to have through holes on the end plates of the orbiting scrolls for installing and tightening the thrust-canceling shaft, since one side of the end plate is a working surface of the compressing chamber. Therefore, the installation and adjustment of the thrust-canceling shaft into the orbiting scrolls are pretty tough. 
         [0005]    DSPO&#39;s orbiting units have two bearing groups, the thrust-canceling shaft supporting bearing group, and the rotating member supporting group. The former is installed inside with a very small space, though it withstands a larger load. The current DSPO technology still has issues in resolving the heat dissipating, and the adjustment of the axial clearance and the pre-load of the bearing group supporting the rotating member. These issues limit the utilization of DSPO technology for the fluid machinery with a large capacity. 
       SUMMARY OF THE INVENTION 
       [0006]    An object of the present invention is, by improving the structure design of DSPO orbiting units, to improve the assembly and the adjustment processes of the scroll type fluid machinery with orbiting units, and thus to improve the reliability and durability of the machine, reduce the manufacturing cost, and improve the cooling of the bearings, which make it possible for DSPO technology to be utilized for the fluid machinery with a larger capacity. 
         [0007]    These improvements include the utilization of the assembled rotating members, the assembly sets of the thrust-canceling shaft, the bearing cooling structure, the load balancing device and method of rotating members, and the bearing pre-tightening and adjusting device. 
         [0008]    According to one aspect of the present invention, the thrust-canceling shaft contains the assembly sets for the installation of orbiting scrolls. The assembly set has a connector connecting directly or indirectly with the orbiting scrolls through threads, and a turning element that directly or indirectly constrains the connector circumferentially but allows the connector to move axially. When the turning element is rotated during the assembly, the connector is turned accordingly, and thus the two orbiting scrolls can be pulled closer and tight through the threads. Therefore, the outer portion of the thrust-canceling shaft is compressed but the connector is stretched, which can result in adequate assembly stress for sound connections. To prevent from loosening, the tightening direction should be opposite to the rotation direction of the rotating members for the fluid energizing machinery, such as compressors, vacuum pumps, etc. The locking device can also be used for this purpose. Meanwhile, the turning element can be rotated in the opposite direction to disassemble the orbiting scrolls. 
         [0009]    The thrust-canceling shaft can have multiple assembly sets, and the connector can have a thread on one end, two threads with opposite directions on the two ends, or two threads with the same direction but different pitches on the two ends. The number of the assembly sets, the different options of the connector threads and the turning elements make up different forms of thrust-canceling shafts. The connector and the turning element not only form the assembly set and realize the pre-load and the assembly of orbiting scrolls and the thrust-canceling shaft, but also have other functions. For example, the turning element can be used to adjust the axial position of the orbiting scrolls, and serves as the sealing washer of the bearing. The connector can also directly fit into the inner ring of the bearing group supporting the thrust-canceling shaft to take the radial load from the bearing group. 
         [0010]    The assembled rotating member provided in the present invention comprises 1) a rotator with an eccentric hole to hold the bearing group supporting the thrust-canceling shaft, and 2) two rotating hubs on which the supporting bearings of the rotating member are installed. The two rotating hubs are assembled together with the rotator to ensure a co-axle for the two bearings on the rotating hubs. The supporting bearing group of the thrust-canceling shaft can take a larger space, because of the fact that the bearings are located at different axial positions, which also benefits the manufacturing of the components, and the assembling and the adjustment of the bearings. There are air cooling holes and ducts on the rotator and the rotating hubs. The centrifugal force makes the air to flow around to cool the rotating members and the bearings when the machinery operates. The rotator can be an assembly of separate pieces and comprises: a) an eccentric ring, which is assembled with the two rotating hubs, and b) an outer driving ring, which can have the form of gear, sprocket, or synchronizing pulley, etc., the driving ring is fitted onto the eccentric ring, and can have elastic connections with the rotating hubs in the circumferential direction. This can make the load more evenly distributed among the orbiting units. Considering the relatively long length of the thrust-canceling shaft, a bearing support can be installed between the thrust-canceling shaft and the rotating hubs. Furthermore, the rotator and a rotating hub can be integrated into one component. 
         [0011]    The present invention also provides cooling water ducts, cooling blades on rotating members, isolating plates for cooling air disturbance prevention, and the axial clearance adjustment device for the supporting bearings of the rotating members. 
         [0012]    The present invention further provides the method to adjust the wrapping angles of the flexible driving element on the rotating members, in order to minimize the difference of the loads among rotating members. 
         [0013]    The advantages of the present invention include the increased space for the supporting bearings of the thrust-canceling shaft due to the improvement of the DSPO orbiting unit structures, and the improvement of assembly and adjustment processes of the DSPO machinery. Thus the reliability and the durability of the machinery are improved, the manufacturing cost is reduced, the load difference on different bearings is minimized, and the bearings are cooled more efficiently. Thus the manufacturing of the DSPO machine models of larger capacities becomes possible. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic sectional view of a water-injection oil-free scroll air compressor according to embodiment  1  of the present invention. 
           [0015]      FIG. 2  is an enlarged schematic view of an orbiting unit of the machinery shown in  FIG. 1 . 
           [0016]      FIG. 3  is a schematic view of a rotating hub of the machinery shown in  FIG. 1 . 
           [0017]      FIG. 4  is the layout view of the cooling water ducts of the machinery shown in  FIG. 1 . 
           [0018]      FIG. 5  is a schematic sectional view of an orbiting unit of the machinery according to embodiment 2 of the present invention. 
           [0019]      FIG. 6  is a schematic sectional view of an orbiting unit of the machinery according to embodiment 3 of the present invention. 
           [0020]      FIG. 7  is a schematic sectional view of an orbiting unit of the machinery according to embodiment 4 of the present invention. 
           [0021]      FIG. 8  is a schematic sectional view of an orbiting unit of the machinery according to embodiment  5  of the present invention. 
           [0022]      FIG. 9  is a schematic sectional view of an orbiting unit of the machinery according to embodiment  6  of the present invention. 
           [0023]      FIG. 10  is a schematic sectional view of a water-injection oil-free scroll air compressor according to embodiment  7  of the present invention. 
           [0024]      FIG. 11  is an enlarged schematic view of an orbiting unit of the machinery shown in  FIG. 10 . 
           [0025]      FIG. 12  is a further enlarged schematic view of the right portion of  FIG. 11 . 
           [0026]      FIG. 13  is a layout view of cooling air ducts of the machinery shown in  FIG. 10 . 
           [0027]      FIG. 14  is a view of a thread anti-loosening device of the machinery shown in  FIG. 10 . 
           [0028]      FIG. 15  is a schematic sectional view of an orbiting unit formed with a multi-piece assembled rotating member according to embodiment  8  of the present invention. 
           [0029]      FIG. 16  is a schematic sectional view of the machinery shown in  FIG. 10  with a bearing on a rotating hub. 
           [0030]      FIG. 17  is a schematic sectional view of an orbiting unit of a water-injection oil-free scroll air compressor according to embodiment  9  of the present invention. 
           [0031]      FIG. 18  is a schematic sectional view of an orbiting unit with rotating member and rotating hub integrated as one entity according to the present invention. 
           [0032]      FIGS. 19A-19C  are the schematic views of flexible DSPO driving mechanisms. 
       
    
    
     DETAILED DESCRIPTION OF INVENTION 
     Embodiment 1 
     Water-Injection Oil-Free Scroll Air Compressors 
       [0033]    As shown in  FIGS. 1-4 , according to the present invention, this embodiment comprises volume changing mechanisms  50 A and  50 B consisting of orbiting scrolls  3 A and  3 B and respective stationary scrolls  2 A and  2 B. Stationary scrolls  2 A and  2 B are connected with a housing  1 , and three orbiting units  40  are arranged between volume changing mechanisms  50 A and  50 B. Each orbiting unit comprises an assembled rotating member  10 , which is supported on housing  1  through bearings  11 A and  11 B, a thrust-canceling shaft  20 , which is supported eccentrically in rotating member  10  through bearings  14 A and  14 B. The two ends of thrust-canceling shaft  20  connect with orbiting scrolls  3 A and  3 B. The outer rings of the three rotating members are pulleys. When rotating member  10  is driven, orbiting scrolls  3 A and  3 B make orbiting motion while engaging with stationary scrolls  2 A and  2 B to continuously change the volumes formed between orbiting scrolls  3 A,  3 B and stationary scrolls  2 A,  2 B. Air enters volume changing mechanisms  50 A and  50 B through inlets  4 A and  4 B, and is discharged from outlets  5 A and  5 B after the air is compressed. Water is injected into volume changing mechanisms  50 A and  50 B through-hole sets  27 A and  27 B or inlets  4 A and  4 B to provide functions of sealing, lubricating, and cooling. 
         [0034]    The assembled rotating member  10  comprises a rotating ring  47  and rotating hubs  41 A and  41 B. Rotating ring  47  and rotating hubs  41 A,  41 B are fastened together by screw set  42 . The inner rings of bearings  11 A and  11 B are located on rotating hubs  41 A and  41 B, and the outer rings of bearing  14 A and  14 B are located in the eccentric hole of rotating ring  47 . There are also centrifugally cooling air ducts  44 A,  44 B,  45 A, and  45 B in rotating hubs  41 A and  41 B, as shown in  FIG. 3 . End covers  86 A,  84 A,  86 B, and  84 B of bearings  11 A and  11 B are fixed on housing  1  through screw sets  89 A,  82 A,  89 B, and  82 B. Compensating shims  94 A and  94 B are used to adjust the axial gaps of bearings  11 A and  11 B. Cooling water ducts  93 A and  93 B wind around bearings  11 A and  11 B on housing  1  with heat conducting materials filling in the gaps between housing  1  and ducts  93 A and  93 B.  FIG. 4  is the layout plan of cooling water duct  93 A. 
         [0035]    Thrust-canceling shaft  20  has an assembly set comprising a screw rod  22  (as connector) and retaining rings  28 A and  28 B (as turning elements). Screw rod  22  has threads with opposite direction on its two ends, which engage with the thread holes on orbiting scrolls  3 A and  3 B, respectively. Screw rod  22  has two flat surfaces, and fits into the hole in shaft  23  with the similar shape, as shown in view A-A of  FIG. 2 . Retaining rings  28 A and  28 B (or turning elements) constrains screw rod  22  (or connector) circumferentially while allowing it to move freely in the axial direction. Retaining rings  28 A and  28 B can rotate shaft  23  through keys  74 A and  74 B, and so rotate screw rod  22 . The two ends of the screw rod  22  screw into and pulls tightly orbiting scrolls  3 A and  3 B. With the pulling effect of screw rod  22 , the outer portion of thrust-canceling shaft  20 , sleeves  73 A and  73 B, retaining rings  28 A and  28 B, and the middle shoulder of shaft  23  are compressed, and thus appropriate assembly stress is obtained. When disassembling the machine, retaining rings  28 A and  28 B are turned in the other direction, which results in pushing the orbiting scrolls  3 A and  3 B apart through the threads at the two ends of screw rod  22 . 
         [0036]    Five different thrust-canceling shaft structures are provided in the following embodiments 2-6. The same constituent elements as those in the embodiment 1 are denoted by the same reference numerals in  FIGS. 5-9 , and a description thereof is omitted. 
       Embodiment 2 
       [0037]    As shown in  FIG. 5 , retaining rings  28 A and  28 B (turning elements) replace portions of shaft  23  and connect orbiting scrolls  3 A and  3 B. Only the two ends of screw rod  22  (connector) are made to have two flat surfaces, fitting into the similar shape holes in retaining rings  28 A and  28 B. Thus there exists circumferential constraint between the retaining rings  28 A,  28 B and screw rod  22 , but no axial constraint between them, as shown in view A-A of  FIG. 5 . Retaining rings  28 A and  28 B can then rotate screw rod  22  to assemble or disassemble orbiting scrolls  3 A and  3 B. 
         [0038]    In the above embodiments 1 and 2, only one retaining ring,  28 A or  28 B, is needed to assemble or disassemble orbiting scrolls  3 A and  3 B. In these cases, the constituent elements forming the circumferential constraint, such as the key or the flat surfaces, can be eliminated at one end. 
       Embodiment 3 
       [0039]    As shown in  FIG. 6 , the right end of screw rod  22  (connector) is connected with orbiting scroll  3 B through thread, but its left end is made to a form of round head. The left retaining ring  28 A is fixed onto orbiting scroll  3 A by screw set  29 A. There is a slot hole in retaining ring  28 B (turning element) to form only circumferential constraint to screw rod  22 , as shown in view A-A of  FIG. 6 . Retaining ring  28 B can directly rotate screw rod  22  to assemble or disassemble orbiting scrolls  3 A and  3 B. 
       Embodiment 4 
       [0040]    As shown in  FIG. 7 , comparing with embodiment 2, the differences of this embodiment include that thrust-canceling shaft  20  has two independent assembly sets. Screw rods  22 A and  22 B (connectors) are made to have two flat surfaces and opposite direction threads at their two ends on each rod, and they are connected with orbiting scrolls  3 A and  3 B and shaft  23  accordingly. Retaining rings  28 A and  28 B (turning elements) can then rotate the screw rods  22 A and  22 B to assemble or disassemble orbiting scrolls  3 A and  3 B separately. 
       Embodiment 5 
       [0041]    As shown in  FIG. 8 , comparing with embodiment 4, the differences of this embodiment include that shaft  23  connects with orbiting scroll  3 A through a regular screw rod  22 A. Retaining ring  28 A can rotate shaft  23  and screw rod  22 A through key  74 A to realize the assembling and disassembling of orbiting scroll  3 A (Orbiting scroll  3 A should be assembled first but disassembled last). Shaft  23  can be directly turned, and so key  74 A and other constituent elements can be eliminated. Screw rod  22 B (connector) is made to have two flat surfaces and opposite direction threads at its two ends. Turn retaining ring  28 B (turning elements), which has a slot hole, can rotate the screw rod  22 B to assemble or disassemble orbiting scroll  3 B. 
       Embodiment 6 
       [0042]    As shown in  FIG. 9 , comparing with embodiment 5, the differences of this embodiment include that screw rod  22 B (connector) has two flat surfaces and threads at its two ends with the same direction but different pitches. Thread  221  at the left end of screw rod  22 B has smaller pitch than thread  222  at the right end. When assembling orbiting scroll  3 B, screw rod  22 B is put into shaft  23  first. Retaining ring  28 B (turning element), which has a slot hole, can rotate screw rod  22 B to assemble and disassemble orbiting scrolls  3 B. 
       Embodiment 7 
     Water-Injection Oil-Free Scroll Air Compressors 
       [0043]    In this embodiment, the same constituent elements as those in embodiment 1 are denoted by the same reference numerals, and a description thereof is omitted, except specific instructions. 
         [0044]    As shown in  FIGS. 10-14 , comparing with embodiment 1, the current embodiment differs in that sleeve  71  replaces the shaft shoulder in middle of shaft  23  in embodiment 1. Shaft  23  functions as a connector, and fits in the inner rings of bearings  14 A and  14 B. It also can have small axial adjustment during assembly. The two ends of shaft  23  have internal threads with opposite directions, and connect with orbiting scrolls  3 A,  3 B through screw rods  22 A and  22 B separately. Retaining rings  28 A and  28 B (turning elements) constrain shaft  23  circumferentially through keys  74 A and  74 B, but not axially, and rotate shaft  23  directly to assemble and disassemble orbiting scrolls  3 A and  3 B through screw rods  22   a  and  22 B. Shaft  23  and screw rods  22 A and rod  22 B can be integrated into a single connector with the two ends having opposite direction threads. 
         [0045]    As shown in  FIGS. 10 ,  11  and  13 , rotating hubs  41 A and  41 B have blades  43 A,  43 B attached on their outer edges for ventilation and cooling purposes. Isolation plates  431  shown in  FIG. 13  prevent the disturbance between the air flows generated by blades  43 A (not shown in  FIGS. 13) and 43B  of three rotating members  10  (only one shown in  FIG. 13 ). 
         [0046]    As shown in  FIGS. 11 and 12 , the axial clearance adjustment and preloading devices for bearings  11 A and  11 B differs from embodiment 1. Pressing rings  98 A and  98 B are located between housing  1  and bearings  11 A and  11 B; covers  83 A and  83 B are fixed onto pressing rings  98 A and  98 B through screw sets  85 A and  85 B. Screw sets  99 A and  99 B on housing  1  are, respectively, on the sides of pressing rings  98 A and  98 B to adjust the axial positions of the outer rings of bearings  11 A and  11 B, and achieve the desirable axial gaps between the bearings. Compensating shims  97 A and  97 B with appropriate thickness are put between housing  1  and pressing rings  98 A and  98 B, respectively, to fill the axial gaps and replace the screw sets  99 A and  99 B to withstand the thrust forces to housing  1  from bearings  11 A and  11 B. After the adjustment is completed, bolts  82 A and  82 B are tightened to maintain the preload. The axial clearance adjustment and preloading can also be achieved using only one side of the two devices described above, but using both makes it easier to adjust the axial position of rotating member  10 . 
         [0047]    As shown in  FIGS. 12 and 14 , an anti-thread-loosing device comprises locking blocks  281  and  282 , and pin  284 . On locking block  281  there are pins  283  fitting into the wrench holes  285  in retaining ring  28 B. The holes in locking block  282  align with notches  287  on the outer edge of orbiting scroll  3 B. Holes  286  are drilled to align with the holes in locking block  282  after retaining rings  28 B is tightened, and then pins  284  are inserted into the holes. 
       Embodiment 8 
       [0048]    When the outer edge of the rotating member have the form of gears, sprockets, or synchronic pulleys, rotating ring  47  can be made of separate pieces.  FIG. 15  is a schematic sectional view of an orbiting unit with a rotating ring made of separate pieces. Rotating ring  47  comprises an eccentric ring  471 , which is assembled with rotating hubs  41 A and  41 B, a driving ring  472 , which can be made to the form of gears, sprockets, synchronic pulleys, etc. Driving ring  472  is fitted on eccentric ring  471 , and connects with rotating hubs  41 A and  41 B through elastic elements  473  and pins  474 . 
         [0049]    When thrust-canceling shaft is long, a supporting bearing can be put between the thrust-canceling shaft and the rotating hub, as shown in  FIG. 16 . Rotating hubs  41 A and  41 B support sleeves  73 A and  73 B through bearings  141 A and  141 B, thus the bending stress in shaft  23  of thrust-canceling shaft  20  is reduced significantly. Bearings  141 A and  141 B can be pin bearings or sliding bearings, and the radial clearance should be slightly larger. 
       Embodiment 9 
     Water-Injection Oil-Free Scroll Air Compressors 
       [0050]    In this embodiment, the same constituent elements as those in embodiment 7 are denoted by the same reference numerals, and a description thereof is omitted, except specific instructions. As shown in  FIG. 17 , wherein:
       1. Rotating member  47  comprises eccentric ring  471  and driving ring  472 , which can be made to the form of a synchronic pulley. When the rubber teeth of the synchronic belt has proper elasticity, rotating hubs  41 A,  41 B and driving ring  472  are connected rigidly with bolts  474 A and  474 B. Driving ring  472  can make angular adjustment to certain degree (as shown in View K of  FIG. 18 )   2. The supporting bearing group for thrust-canceling shaft  20  comprises a single bearing  14  which can be a spherical rotor bearing, self-aligning ball bearing or spherical bearing, and is assembled on sleeve  143  with certain pre-load through sleeve  141 , locknut  142 , and lock-washer  144 .   3. Ducts  411 A and  411 B exist on the rotating hubs  41 A and  41 B to remove the water accumulated in cavities  412 A and  412 B.   4. Threaded adjusting ring  980 A and  980 B are used to adjust the axial clearance of bearings  11 A and  11 B and to apply appropriate pre-load, while locking screws  981 A and  981 B are used to lock adjusting rings  980 A and  980 B.       
 
         [0055]    Although the assembled rotating member described in the above embodiments comprises a rotating member and two rotating hubs, the rotating member can be integrated with a rotating hub. As shown in  FIG. 18 , the integrated rotating member  47 ′ and rotating hub  41 A are assembled together by screw set  42  to form an assembled rotating member. 
         [0056]    When the DSPO machinery described in the aforementioned embodiments is driven by a flexible element (such as a chain or a belt), it is very important for the loads on rotating members are balanced.  FIGS. 19A ,  19 B, and  19 C show DSPO machinery using flexible driving systems. Driving element  31  transmits the power to rotating members  10   a ,  10   b , and  10   c  through flexible element  33  (as belt or chain). Tensioning device  32  is to tighten the flexible element  33 . In general, when the wrapping angles of flexible element  33  on the rotating members are close enough, the load transmitted to rotating member  10   a  is the largest among the three rotating members, with rotating member  10   b  the next and rotating member  10   c  the smallest. The wrapping angles of flexible element  33  on rotating members  10   a  and  10   b  can be adjusted accordingly to even the load distribution. As shown in  FIG. 19B , the position of driving element  31  is changed to reduce the wrapping angle, θa, of the flexible element  33  on rotating element  10   a . An idler  321  can also be used to reduce the wrapping angles, θa, θb, of flexible element  33  on rotating element  10   a  and  10   b , as shown in  FIG. 19C . The method described above to balance the loads on the rotating members can be applied to other DSPO machinery. 
         [0057]    Although in the foregoing embodiments, the present invention has been described using air scroll compressors as examples, the present invention is not limited to air scroll compressors, and it can be applied to other scroll type fluid machinery, such as vacuum pumps, refrigerant compressors and expanders, etc. 
         [0058]    Although in the foregoing embodiments, the scroll type fluid machinery comprises two volume changing mechanisms having the same functions, the present invention is not limited to the described usages. For example, one of the two volume changing mechanisms can be used as a compression mechanism while the other used as an expansion mechanism. 
         [0059]    Although a description for some common mechanical devices, such as balancer, tip seal, shaft seal, alignment pin, etc, is omitted in the foregoing embodiments, the present invention is not limited from their utilizations.