Abstract:
A system for cooling a turbo compressor includes two compressing parts on opposite ends of a rotational shaft driven by a motor. Fluid from a fluid chamber within the casing of the device is supplied to a bearing chamber when the temperature of the bearing chamber increases. A supply passage is formed in a first support where the radial bearing for supporting a load in the axial direction is formed. The open-and-shut valve supplies fluid when the temperature of the bearing chamber increases.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a turbo compressor, and more particularly, to a turbo compressor that is capable of effectively cooling a bearing which supports a rotational shaft. 
     2. Description of the Background Art 
     FIG. 1 is a sectional view of a turbo compressor in accordance with a conventional art. 
     As shown in FIG. 1, the conventional turbo compressor includes a casing  106  having a suction hole  102  for sucking a fluid from an outside and a discharge hole  104  for discharging the sucked fluid, and having a certain space; a driving unit  108  installed inside the casing  106  and generating a rotational force; a first compressing part  112  connected to the driving unit  108  by a rotational shaft  110  and first compressing fluid; and a second compressing part  114  for secondly compressing the fluid compressed by the first compressing part  112 . 
     In the casing  106 , a fluid chamber  120  for sucking a fluid through the suction hole is formed, a first support member  116  for rotatably supporting one end portion of the rotational shaft  110  is fixed at one side of the casing  106 , and a second support member  118  for rotatably supporting the other end portion of the rotational shaft  110  is fixed at the other side of the casing  106 . 
     The driving unit  108  includes a stator  122  fixed at an outer circumferential face of the casing  106  and receiving a power from an external source, and a rotor  124  fixed at a circumferential face of the rotational shaft  110  and being rotated by an interaction with the stator  122 . 
     The first compressing part  112  includes a first impeller  126  connected to one end portion of the rotational shaft  110  and compressing the fluid by being rotated along with the rotational shaft  110 ; and a first cover member  132  in which the first impleller  126  is rotatably inserted, a first compression chamber  128  is connected to the discharge hole  104  of the main body, into which the fluid of the fluid chamber  120  is introduced and first compressed, and a transfer passage  130  is formed to discharge the compressed fluid. 
     The second compressing part  114  includes a second impeller  134  connected to the other end portion of the rotational shaft  110  and compressing the fluid by being rotated along with the rotational shaft  110 ; and a second cover member  140  in which the second impeller  134  is rotatably inserted, a second compression chamber  136  is formed connected to the transfer passage  130  into which the first compressed fluid is introduced and secondly compressed, and a discharge hole  138  is formed to externally discharge the compressed coolant. 
     A radial bearing  142  is inserted between the first support member  116  and the outer circumferential face of the rotational shaft  110  and between the second support member  118  and the outer circumferential face of the rotational shaft  110 , to support a load working in a radial direction of the rotational shaft  110 . 
     A bearing bush  144  is connected in a vertical direction to the rotational shaft at one side thereof. The bearing bush  144  is supplied by a thrust bearing  146  which supports a load working in an axial direction of the rotational shaft  110 . 
     The thrust bearing  146  is installed between the first cover member  132  and the first support member  116 , and a bearing chamber  148  is formed where the bearing bush  144  is rotatably positioned. 
     A sealing member  150  is inserted between the outer circumferential face of both end portions of the rotational shaft  110  and the first cover member  132 , to prevent leakage of the fluid compressed in the first and the second compression chambers  128  and  136 . 
     The operation of the turbo compressor in accordance with the conventional art constructed as described above will now be explained. 
     When the driving unit  108  is driven, the rotational shaft  110  is rotated. Then the first impeller  126  and the second impeller  134  connected to the rotational shaft  110  are rotated to perform a compressing operation of the fluid. 
     That is, the fluid is introduced into the fluid chamber  120  through the suction hole  102 , and the fluid introduced into the fluid chamber  120  is introduced into the first compression chamber  128  through the discharge hole  104 , first compressed according to the rotation of the first impeller  126  and then supplied to the transfer passage  130 . 
     The fluid supplied to the transfer passage  130  is introduced into the second compression chamber  136 , secondly compressed by the rotation of the second impeller  134  and then externally discharged through the discharge hole  138 . 
     At this time, when the rotational shaft  110  is being rotation, a load working in a radial direction of the rotational shaft  110  is supported by the radial bearing  142 . 
     Since the pressure in the first compression chamber  128  which compresses the fluid first is smaller than that of the second compression chamber  136 , an axial-directional load works on the rotational shaft  110  due to the pressure difference between the first compression chamber  128  and the second compression chamber  136 . Such axial-directional load is supported by the thrust bearing  146 . 
     In this respect, since the rotational shaft  110  is rotated at a high speed, a temperature of the bearing chamber  148  with the thrust bearing  146  is inserted is increased and the thrust bearing  146  is degraded. Thus, in view of the performance of the whole system and in order to lengthen the life of the bearing, it is requisite to cool the thrust bearing  146  and maintain its temperature to below a certain level. 
     The conventional bearing cooling method is that, in designing a structure of the sealing member  150  inserted between the first cover member  132  and the rotational shaft  110 , a certain leakage of fluid is allowed to occur, so that when the fluid which is first compressed after being introduced into the first compression chamber  128  is introduced into the bearing chamber  148  through the sealing member  150 , thereby performing a cooling operation of the thrust bearing  146 . 
     However, the conventional turbo compressor has a problem that the leakage amount of fluid supplied from the first compression chamber to the bearing chamber differs depending on a structure designing of the sealing member. 
     That is, if a small amount of fluid is leaked to the bearing chamber, the cooling operation of the thrust bearing is not smoothly performed, and thus, the temperature is increased according to the friction of the bearing. Then, a coating layer of the bearing is damaged, resulting in that the performance of the whole system is degraded, the durability of the bearing is shortened, and a reliability is degraded. 
     On the other hand, if a large amount of fluid is leaked to the bearing chamber, when the fluid is compressed, a large amount of fluid is leaked, resulting in that a compression efficiency of the compressor is degraded. 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide a turbo compressor that is capable of smoothly performing a cooling operation of a bearing without degrading a compression performance of a compressor in such a manner that when a temperature of a bearing chamber with a thrust bearing inserted therein increases, a fluid is supplied to perform a cooing operation, and when the temperature of the bearing chamber reaches a suitable level, the fluid supply to the bearing chamber is cut off. 
     To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a turbo compressor including: a casing having a fluid chamber for receiving a fluid from an external source; a driving unit disposed in the casing and generating a rotational force; a first compressing part installed at one side of a rotational shaft rotated according to the driving of the driving unit and first compressing the fluid; a second compressing part installed at the other side of the rotational shaft and secondly compressing the fluid compressed in the first compressing part; and a bearing cooling unit for supplying a fluid of the fluid chamber to a bearing chamber to perform a cooling operation when a temperature of the bearing chamber where the thrust bearing for supporting a load working in an axial direction of the rotational shaft is mounted is increased, and cutting off the fluid from being introduced into the bearing chamber when the temperature of the bearing chamber is maintained at a proper level. 
     In the turbo compressor of the present invention, the bearing cooling unit includes a supply passage formed inside the casing to allow the bearing chamber and the fluid chamber to communicate with each other; and an open-and-shut valve installed at the supply passage and opening and closing the supply passage according to an internal temperature of the bearing chamber. 
     In the turbo compressor of the present invention, the supply passage is penetratingly formed at a first support member which is fixed at the inner side of the casing and rotatably supports one side of the rotational shaft. 
     In the turbo compressor of the present invention, the open-and-shut valve includes a valve body part formed having a certain space at the supply passage, a fixed plate fixed at one side of the valve body part and having a through hole communicating with the supply passage at a center thereof; and a bi-metal positioned adhesive to one face of the fixed plate, having a plurality of through holes at its marginal portion, and being deformed according to a temperature inside the bearing chamber. 
     The foregoing and other objects, features, aspects and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
     In the drawings: 
     FIG. 1 is a sectional view of a turbo compressor in accordance with a conventional art; 
     FIG. 2 is a sectional view of a turbo compressor in accordance with a preferred embodiment of the present invention; 
     FIG. 3 is an enlarged sectional view showing a structure of a first compressing part of the turbo compressor in accordance with the preferred embodiment of the present invention; 
     FIG. 4 is an enlarged view of portion ‘A’ of FIG. 3 showing a bearing cooling unit of the turbo compressor in accordance with the preferred embodiment of the present invention; and 
     FIG. 5 is a view showing an operation state of the bearing cooling unit of the turbo compressor in accordance with the preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. 
     There may exist a plurality of embodiment of a turbo compressor in accordance with the present invention, of which the most preferred one will now be described. 
     FIG. 1 is a sectional view of a turbo compressor in accordance with a conventional art, and FIG. 2 is a sectional view of a turbo compressor in accordance with a preferred embodiment of the present invention. 
     A turbo compressor of the present invention includes: a a casing  6  having a suction hole  2  for sucking a fluid from an outside and a discharge hole  4  for discharging the sucked fluid, and having a certain space; a driving unit  8  installed inside the casing  6  and generating a rotational force; a first compressing part  12  connected to the driving unit  8  by a rotational shaft  10  and first compressing fluid which is discharged from the discharge hole  4  of the casing  6 ; and a second compressing part  14  for secondly compressing the fluid compressed by the first compressing part  12 . 
     The casing  6  has a cylindrical form, and a first support member  16  rotatably supporting one side of the rotational shaft  10  is hermetically fixed at one side of the casing  6 , and a second support member  18  rotatably supporting the other side of the rotational shaft  10  is hermetically fixed at the other side of the casing  6 . 
     A fluid chamber  20  is formed inside the casing  6 . The fluid chamber  20  is hermetically sealed by the first and the second support members  16  and  18  and a fluid is sucked into the fluid chamber  20  through a suction hole  2 . 
     The driving unit  8  includes a stator  22  fixed at an outer circumferential face of the casing and receiving a power supply from an external source, and a rotor  24  fixed at a circumferrential face of the rotational shaft  10  and is rotated according to an interaction with the stator  22 . 
     The first compressing part  12  includes a first cover member  30  provided with a first compression chamber  26  fixed at a side face of the first support member  16  and connected to the discharge hole  4  of the main body and a transfer passage  28  for moving the fluid compressed in the first compression chamber  26  to a second compression chamber; and a first impeller  32  rotatably disposed at the first compression chamber  26  of the first cover member, connected to the rotational shaft  10 , and compressing first the fluid introduced into the first compression chamber  26 . 
     The second compressing part  14  includes a second cover member  36  having a second compression chamber  39  fixed at side face of the second support member  18  and connected to the transfer passage  28  and a discharge hole  34  for externally discharging the fluid which has been secondly compressed in the second compression chamber  39 ; and a second impeller  38  rotatably disposed at the second compression chamber  39  and secondly compressing the fluid introduced into the second compression chamber  39 . 
     Sealing members  40  and  42  are respectively inserted between the rotational shaft  10  and the first cover member  30  and between the rotational shaft  10  and the second cover member  36 , in order to prevent leakage of the fluid compressed in the first compression chamber  26  and the second compression chamber  39 . 
     A radial bearing  44  is inserted between the rotational shaft  10  and the first support member  16  and between the rotational shaft  10  and the second support member  18 , in order to support a load working in a radial direction of the rotational shaft  10 . 
     A bearing bush  46  is fixed at one side of the rotational shaft  10  in a vertical direction to the rotational shaft  10 . The bearing bush  46  is rotatably supported by a thrust bearing  48  which supports a load working in an axial direction of the rotational shaft  10 . 
     The thrust bearing  48  is mounted between the first cover member  30  and the first support member  16 , and a bearing chamber  50  is formed where the bearing bush  46  is rotatably positioned. 
     A bearing cooling unit is formed at one side of the first support member, to supply the fluid introduced into the fluid chamber  20  to the bearing chamber  50  to perform a cooling operation when a temperature of the bearing chamber  50  increases, and cut off the fluid from being introduced into the bearing chamber  50  when the temperature of the bearing chamber  50  is maintained at a suitable level. 
     The bearing cooling unit includes a supply passage formed at one side of the first support member  16  and allows the bearing chamber  50  and the fluid chamber  20  to communicate with each other and supplying the fluid inside the fluid chamber to the bearing chamber  50 , and an open-and-shut valve  54  installed at the supply passage  52  and opening and closing the supply passage  52  according to an internal temperature of the bearing chamber  50 . 
     The supply passage  52  is penetratingly formed at the first support member  16  and serves to supply the fluid introduced into the fluid chamber  20  to the bearing chamber  50 . 
     The open-and-shut valve  54  includes a valve body part  60  formed having a space in a certain shape at one side of the supply passage  52 , a fixed plate  62  hermetically fixed at the supply passage  52  of the valve body part  60  and having a through hole  66  communicating with the supply passage  52  at its central portion; and a bi-metal  64  positioned contacting one side of the fixed plate  62 , having a plurality of through holes  68  at its marginal portion, and being deformed according to a temperature inside the bearing chamber  50 . 
     That is, in the open-and-shut valve  54 , when a temperature of the bearing chamber  50  is increased to a certain degree, the bi-metal  64  is deformed and separated from the fixed plate  62 . Then, the supply passage  52  is opened so that the fluid inside the fluid chamber  20  is introduced into the bearing chamber  50  through the supply passage  52  to the bearing chamber  50 , to perform a cooling operation. 
     When the temperature of the bearing chamber  50  is cooled to a proper level, the bi-metal  64  is restored to its original state and adhered to the fixed plate  62 , thereby shutting the supply passage  52 . 
     The operation of the turbo compressor constructed as described above will now be described. 
     When the driving unit  8  is driven, the rotor  24  is rotated. Then, the rotational shaft  10  is rotated and the first and the second impellers  32  and  38  connected to the rotational shaft are rotated, thereby performing a compression operation of the fluid. 
     That is, the fluid is sucked into the fluid chamber  20  through the suction hole  2  of the main body, supplied to the first compression chamber  26  through the discharge hole  4 , first compressed according to rotation of the first impeller  32  and then moved to the transfer passage  28 . 
     After being discharged into the transfer passage  28 , the fluid is supplied to the second compression chamber  39 , secondly compressed according to rotation of the second impeller  38 , and then externally discharged through the discharge hole  34 . 
     At this time, the radial directional load of the rotational shaft  10  is supplied by the radial bearing  44  mounted between the rotational shaft  10  and the first and the second support member  16  and  18 . 
     A load is generated in an axial direction at the rotational shaft  10  due to the pressure difference between the first compression chamber  26  which compresses the fluid first and the second compression chamber  39  which compresses the fluid secondly, the load working in the axial direction of the rotational shaft  10  is supported by the thrust bearing  48  mounted in the bearing chamber  50 . 
     During the compression operation, when a temperature of the bearing chamber  50  is increased due to the friction of the thrust bearing  48 , the open-and-shut valve  54  is operated to open the supply passage  52  allowing the fluid chamber  20  and the bearing chamber  50  to communication with each other. 
     Then, the fluid introduced into the fluid chamber  20  is supplied to the bearing chamber  50  through the supply passage  52 , to thereby perform a cooling operation of the thrust bearing  48 . 
     As for the open-and-shut valve  54 , when a temperature of the bearing chamber  50  is increased, the bi-metal  64  is deformed and separated from the fixed plate  62 , and accordingly, the through hole  66  formed at the fixed plate  62  and the through hole  68  formed at the bi-metal  64  are communicated with each other, to open the supply passage  52 . 
     And then, as the fluid is introduced into the bearing chamber  50  and cools the thrust bearing  48 , when the temperature of the bearing chamber drops to a proper level, the bi-metal  64  is returned to its original state and adhered to the fixed plate  62 , to thereby shut the supply passage  52 . 
     The turbo compressor constructed and operated as described above is preferably used as a compressor of a freezing cycle. 
     As so far described, the turbo compressor of the present invention has many advantages. 
     That is, for example, the supply passage for allowing the bearing chamber and the fluid chamber receiving the fluid to communicate each other is formed at the first support member where the radial bearing supporting a load working in an axial direction of the rotational direction is formed and the open-and-shut valve is formed to open and shut the supply passage according to a temperature of the bearing chamber, in order to supply fluid to the bearing chamber according to the temperature of the bearing chamber and perform a cooling operation of the radial bearing. 
     Thus, the temperature of the radial bearing can be constantly maintained at a proper level, so that a degradation due to a friction of the bearing can be prevented, and the lifespan and a reliability of the bearing can be improved. 
     In addition, since the fluid is supplied to the bearing chamber only when the temperature of the bearing chamber is increased, a performance degradation of the compressor according to a leakage of the fluid can be prevented. 
     As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalence of such meets and bounds are therefore intended to be embraced by the appended claims.