Abstract:
A pulse tube refrigerator includes a compressor, an after-cooler, a regenerating unit, a pulse tube, an inertance tube, a reservoir, and a vibration absorbing unit which are structured such that vibrations during motor operation are minimized. The vibration absorbing unit is attached with the compressor and is positioned within the reservoir, and has a fixed shaft having one end attached with a housing of the compressor, a plurality of spring plates attached to another end of the fixed shaft, and a mass body attached with the spring plates.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a pulse tube refrigerator, and in particular, to a pulse tube refrigerator which is capable of minimizing vibration occurring during the operation, and having a simple overall structure. 
     2. Description of the Prior Art 
     In general, a pulse tube refrigerator is one type of cryogenic refrigerator having a low-vibration and high-reliability which is used for cooling small size electronic parts or super-conductors. A Stirling refrigerator and a GM refrigerator are widely used as the cryogenic refrigerator. 
     As depicted in FIG. 1, the conventional pulse tube refrigerator comprises a compressor  10  for compressing operating gas by generating a linear reciprocation operating force, a pulse tube  20  for releasing heat on the compressing part  21  and absorbing external heat on an expanding part  22  while the operating gas is compressed and expanded at both ends of the tube by the operation of the compressor  10 , an inertance tube  30  for generating phase difference between mass flow and pressure pulsation of the operating gas fluctuated by connecting to the pulse tube  20  and at the same time achieving the heat balance, a reservoir  40  connected to the end of the inertance tube  30 , a regenerating unit  50  connected between the pulse tube  20  and after-cooler  60  in order to store and release sensible heat of the operating gas passing the pulse tube  20  by being sucked and compressed at the compressor  10 , and an after-cooler  60  placed between the regenerating unit  50  and compressor  10  for cooling the operating gas pushed by the compressor  10  before it reaches the regenerating unit  50 . 
     The compressor  10  for compressing and sucking the operating gas while generating the linear reciprocation operating force comprises a sealed casing  11  having the inner area covering housings  11   b ,  11   c , an upper housing  11   a  closely combined to the upper outer circumference of the sealed casing  11  having a cylinder unit on the center portion, a middle housing  11   b  which is placed inside of the sealed casing  11  and its upper surface is closely combined to the lower surface of the upper housing  11   a , an elastic supporting member  15  is combined inside of it, an operating motor  12  having a piston  14  inserted into the cylinder unit  13  is fixedly installed on it, and a lower housing  11   c  which is placed inside of the sealed casing  11  and its upper surface is closely combined to the lower surface of the middle housing  11   b , the elastic supporting member  15  is combined to it. 
     The operation of the conventional pulse tube refrigerator will now be described. 
     First, when the compressor  10  compresses and sucks the operating gas by being applied power, the operating gas flows into the pulse tube  20  after passing the after-cooler  60  and regenerating unit  50 , is discharged into the inertance tube  30 , repeats the reverse operation, while repeating the above operation, the phase difference is generated between the mass flow and pressure pulsation, according to this the compressing and expanding occur at the compressing part  21  and expanding part  22  of the pulse tube  20 , temperature on the expanding part  22  of the pulse tube  20  lowers drastically. 
     The inertance tube  30  and reservoir  40  accelerate the compressing and expanding of the operating gas at the pulse tube  20 , the after-cooler pre-cools the operating gas pushed from the compressor  10 , and the regenerating unit  50  stores/releases the sensible heat of the operating gas reciprocating between the compressor  10  and pulse tube  20 . 
     While repeating the above-mentioned process, the expanding part  22  of the pulse tube  20  is cooled continually, and accordingly the cryogenic refrigeration is obtained. 
     However, in the conventional pulse tube refrigerator, vibration occurs while the operating gas is compressed by the piston receiving the linear reciprocating motion of the operating motor installed in the compressor, and it causes the vibration noise. 
     In addition, because the reservoir constructed as the additional part is connected to the inertance tube having a certain length, the overall size of the pulse tube refrigerator is big, lots of manufacturing costs are required, it is difficult to transfer, and it requires lots of installation area. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is to provide a pulse tube refrigerator which has a simple overall structure. 
     Another object of the present invention is to provide the pulse tube refrigerator having a vibration absorbing unit which efficiently reduces vibration occurring while compressing operating gas. 
     Another object of the present invention is to provide the pulse tube refrigerator having a combining structure of a sealing member which improves the efficiency of the vibration absorbing unit. 
     In order to achieve the objects, the pulse tube refrigerator according to the present invention comprises a compressor having a sealed casing with a cylinder and an opening at one end thereof, a motor mounted in the sealed casing, and a piston operatively attached with the motor to compress and expand an operating gas via the opening, an after-cooler connected with the compressor in order to cool the operating gas discharged from the compressor, a regenerating unit connected with the after-cooler in order to store and release latent heat of the operating gas reciprocating between the compressor and reservoir formed at an outer surface of the sealed casing and a cover integrally attached to the sealed casing, a pulse tube connected with the regenerating unit, the pulse tube having a cryogenic portion formed thereon, an inertance tube connected with the pulse tube in order to accelerate a formation of the cryogenic portion and connected with the cover, and a vibration absorbing unit which is placed inside of the reservoir and is fixedly attached to the sealed casing in order to reduce the vibration occurring due to the operation of the motor. 
     In addition, in order to achieve the above-mentioned objects, the pulse tube refrigerator according to the present invention comprises a compressor having a sealed casing with a cylinder and an opening at one end thereof, a motor mounted in the sealed casing, and a piston operatively attached with the motor to compress and expand an operating gas via the opening, an after-cooler connected with the compressor in order to cool the operating gas discharged from the compressor, a regenerating unit connected with the after-cooler in order to store and release latent heat of the operating gas reciprocating between the compressor and a reservoir formed at an outer surface of the sealed casing a a cover attached to the sealed casing, a pulse tube connected with the regenerating unit, the pulse tube having a cryogenic portion formed thereon, an inertance tube connected with the pulse tube in order to accelerate a formation of the cryogenic portion and connected with the cover, a sealing member which is placed between the cover and casing in order to prevent leakage of the operating gas, and a vibration absorbing unit placed inside of the reservoir and fixedly attached to the sealing member in order to reduce the vibration occurring due to the operation of the motor. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic sectional view illustrating the conventional pulse tube refrigerator. 
     FIG. 2 is a schematic sectional view illustrating a pulse tube refrigerator in accordance with the first embodiment of the present invention. 
     FIG. 3 is a partial sectional view illustrating the operation state of the pulse tube refrigerator in accordance with the first embodiment of the present invention. 
     FIG. 4 is a schematic front view illustrating a pulse tube refrigerator in accordance with the second embodiment of the present invention. 
     FIG. 5 is a sectional view illustrating a compressor of the pulse tube refrigerator of FIG. 4 in accordance with the second embodiment of the present invention. 
     FIG. 6 is a partial sectional view illustrating a sealing member combination according to the embodiment of the present invention for constructing the compressor in accordance with the second embodiment of the present invention. 
     FIG. 7 is a partial sectional view illustrating the sealing member combination according to the other embodiment of the present invention for constructing the compressor in accordance with the second embodiment of the present invention. 
     FIG. 8 is a partial sectional view illustrating the sealing member combination according to the another embodiment of the present invention for constructing the compressor in accordance with the second embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Hereinafter, the embodiments of a pulse tube refrigerator according to the present invention will now be described with reference to the accompanying drawings. 
     As depicted in FIG. 2, the pulse tube refrigerator according to the first embodiment of the present invention comprises a compressor  100  for compressing and sucking operating gas by generating a linear reciprocation operating force, a pulse tube  20  for releasing heat on the compressing part  21  by the mass flow of the compressed and sucked operating gas on the compressor  200  and absorbing external heat on an expanding part  22  while the operating gas is separately compressed and expanded at both ends of the pulse tube  20  by the operation of the compressor  100 , an inertance tube  300  for generating phase difference between mass flow and pressure pulsation of the operating gas fluctuated by connecting to the pulse tube  20  and at the same time achieving the heat balance, a reservoir  400  connected to the end of the inertance tube  300 , and a regenerating unit  50  connected between the pulse tube  20  and an after-cooler  60  in order to release sensible heat of the operating gas passing the pulse tube  20  by being sucked and compressed at the compressor  100 , the after-cooler  60  being utilized for cooling the operating gas pushed by the compressor  100  before it reaches the regenerating unit  50 . 
     The compressor  100  comprises a sealed casing  110  having a cylinder shape including inner area covering housings  110   b ,  110   c , an upper housing  110   a  closely combined to the upper outer circumference of the sealed casing  110  having a cylinder unit on the center portion, the middle housing  110   b  which is placed inside of the sealed casing  110  and its upper surface is closely combined to the lower surface of the upper housing  110   a , an elastic supporting member  150  is combined inside of it, an operating motor  120  having an operating shaft  160  combined to a piston  140  inserted into the cylinder unit  130  is fixedly installed on it, and the lower housing  110   c  which is placed inside of the sealed casing  110  and its upper surface is closely combined to the lower surface of the middle housing  110   b , the elastic supporting member  150  is combined to it. 
     The reservoir  400  having a predetermined sealed area is combined as one body to the outer bottom surface of the sealed casing  110  of the compressor  100 . 
     The reservoir  400  is formed by combining the cover  410  having a cup shape to the lower side surface of the sealed casing  110  so as to be formed on the lower side surface of the sealed casing  110  of the compressor  100 . 
     In addition, in the other embodiment of the reservoir  400 , the sealed casing  110  is formed longer, and a predetermined sealed area can be formed by blocking the inner side of the sealed casing  110 . 
     The sealed casing  110  and reservoir  400  can be combined by welding, or using bolts, nuts, pins and rivets, etc. 
     The inertance tube  300  is formed so as to coil around the outer circumference of the compressor  100  and reservoir  400  formed as one-body in order to minimize installation area of the pulse tube refrigerator. Herein, the inertance tube  300  coils around them as a spiral shape. 
     The vibration absorbing unit  170  for reducing the vibration occurring by the operation of the operating motor  120  is combined to the center lower side surface of the sealed casing  110  so as to be placed inside of the reservoir  400 . 
     The vibration absorbing unit  170  comprises a fixed shaft  171  fixedly attached to the sealed casing  110  so as to be placed on the same line of the vibration direction of the operating motor  120 , a plurality of plate springs  172  attached to the end of the fixed shaft  171 , and a mass body  173  fixedly secured between the plate springs  172 . 
     Hereinafter, the operation effect of the pulse tube refrigerator according to the first embodiment of the present invention will now be described. 
     When the power is applied to the operating motor  120  installed inside of the compressor  100 , the operating motor  120  performs the linear reciprocating motion. The operating force is transmitted to the piston  140 , and the piston  140  performs the linear reciprocating motion inside of the cylinder unit  130  in order to compress and sucks the operating gas. The vibration occurs during the motion and is transmitted to the sealed casing  110 . 
     Herein, as depicted in FIG. 3, the vibration transmitted to the sealed casing  110  is transmitted to the vibration absorbing unit  170  installed inside of the sealed casing  110 . The vibration of the vibration absorbing unit  170  has a second mode opposing the vibration mode occurring from the sealed casing  110 , and the vibration of the sealed casing  110  is reduced. The vibration occurring during the operating can be reduced, and the vibration noise due to the vibration can be reduced also, and quietness in the operation can be improved. 
     In addition, in the pulse tube refrigerator according to the first embodiment of the present invention, the reservoir  400  provided with the vibration absorbing unit  170  performs the same function as the conventional reservoir  40 , and is combined to the lower side surface of the sealed casing  110 . The inertance tube  300  is formed so as to coil around the outer circumference of the sealed casing and reservoir formed as one body. Accordingly the overall size of the pulse tube refrigerator can be reduced, the transferring of the pulse tube refrigerator is easy, and the required installation area can be reduced. 
     Hereinafter, the pulse tube refrigerator according to the second embodiment of the present invention will now be described in detail. 
     The construction of the pulse tube refrigerator according to the second embodiment of the present invention will now be described with reference to accompanying FIGS. 4 and 5. The pulse tube refrigerator according to the second embodiment of the present invention comprises a compressor  200  for compressing and sucking the operating gas by generating the linear reciprocation operating force, a pulse tube  20  for releasing the heat on the compressing part  21  by the mass flow of the compressed/sucked operating gas on the compressor  200  and phase difference of the pressure pulsation and absorbing the heat on the expanding part  22 , an inertance tube  300  for accelerating the mass flow and pressure pulsation on the pulse tube  20  and at the same time achieving the heat balance, a reservoir  500  formed on the lower end of the compressor  200  as one body, a regenerating unit  50  connected between the pulse tube  20  and compressor  200  in order to release sensible heat of the operating gas passing the pulse tube  20  by being sucked and compressed at the compressor  200 , and an after-cooler  60  for cooling the operating gas pushed by the compressor  200 . 
     The compressor  200  comprises a cylinder unit  230  on the side, an upper housing  210   a  having a fixedly installed elastic supporting member  250 , and the middle housing  210   b  having various construction parts. 
     Hereinafter, the construction of the middle housing  210   b  will now be described in detail. 
     The middle housing  210   b  comprises the operating motor  220  connected between the operator  280  of the operating motor  220  and piston  240  with the operating shaft  260  in order to transmit the linear reciprocation operating force of the operating motor  220  to the piston  240  inserted into the cylinder unit  230 , and the elastic supporting member  250  connected to the operating shaft  220  in order to guide the linear motion of the piston  240 . 
     A flange portion having the through hole is formed on the lower circumference of the middle housing  210   b , a through hole corresponding to the through hole formed on the flange portion is formed on the outer circumference of each of a cup-shaped cover  510  and a circular plate-type sealing member  70 . The middle housing  210   b , sealing member  70 , and cover  510  are fixedly combined by a predetermined combining member, and the reservoir  500  is formed by the combination. 
     The side of the inertance tube  300  is connected with the side of the cover  510 . 
     In addition, the inertance tube  300  can be formed so as to coil around the outer circumference of the upper housing  210   a  and middle housing  210   b  of the compressor  200  as the spiral shape in order to minimize the installation space, and it connects the pulse tube  20  to the reservoir  500 . 
     The combination of the upper housing  210   a , middle housing  210   b , sealing member  70  and cover are fixedly combined by welding, or using bolts, nuts, pins and rivets, etc. 
     The elastic supporting member  250  stores the linear reciprocating motion of the operating motor  220  as elastic energy, converts the stored elastic energy into the linear motion, induces a resonance motion of the piston  240 , and guides the linear reciprocating motion of the piston  240  combined to the operating shaft  260 . 
     Meanwhile, the motion of the moving mass constructed with the operator  280  of the operating motor  220 , operating shaft  260 , and piston  240  performing the linear reciprocating motion in the operation of the compressor  200  causes the axial direction vibration, and a vibration absorbing unit  600  is formed inside of the reservoir  500  in order to absorb and reduce the axial direction vibration. 
     A fixed shaft  610  is attached to the sealing member  70  in order to coincide with the center line of the operating shaft  260  of the operating motor  220 , a plurality of plate springs  620  are attached to the fixed shaft  610 , and a mass body  630  having a certain weight is attached to the plate springs  620 . 
     When the vibration occurs by the operation of the compressor  200 , the excitation frequency of the vibration absorbing unit  600  coincides with the inherent frequency of the plate springs  620  and mass body  630 , the vibration occurring on the compressor  200  is absorbed by the plate springs  620  and mass body  630 , and the plate springs  620  and mass body  630  vibrate. 
     Herein, it is advisable to coincide the axial direction vibration center of the moving mass with the vibration center of the vibration absorbing unit  600  for absorbing the vibration in order to improve the absorbing efficiency of the vibration absorbing unit  600 . 
     Hereinafter, the method for coinciding the axial direction vibration center of the moving mass with the vibration center of the vibration absorbing unit  600  will now be described in detail with reference to the accompanying drawings. 
     As depicted in FIG. 6, a combining part  81  is protrusively formed on the upper surface of a position setting type sealing plate  80  having the disk shape which is attached to the inner circumference of the middle housing  210   b.    
     The fixed shaft  610  having a predetermined length is attached to the center of the sealing plate  80  on a side opposite to the side surface of the combining part  81 . The position setting type sealing plate  80  is inserted and secured to the lower portion of the middle housing  210   b  in order to locate the combining part  81  at the inner circumference of the middle housing  210   b.    
     Herein, the center of the operating shaft  260  placed inside of the housing  210   b  coincides with the center of the fixed shaft  610 , and the position setting type sealing plate  80  seals the middle housing  210   b.    
     The position setting type sealing plate  80  is fixedly combined to the middle housing  210   b  by a plurality of bolts  1  inserted into a plurality of through holes H formed on the flange portion  700  extended-formed on the end of the middle housing  210   b  and the position setting type sealing plate  80 . 
     The plurality of plate springs  620  are fixedly attached to the end of the fixed shaft  610 , and the mass body  630  having a predetermined weight is fixedly secured to the plate springs  620 . The cover  510  having the cup shape is fixedly formed on the position setting type sealing plate  80  in order to cover the plate springs  620  and the mass body  630 . The reservoir  500  having a predetermined sealed area is constructed by the position setting type sealing plate  80  and cover  510 , and the side of the inertance tube  300  is connected to the side of the cover  510 . 
     As depicted in FIG. 7, a position setting portion A is formed on the outer circumference of the middle housing  210   b , and a sealing plate  90   a  secured to the fixed shaft  610  is secured to the middle housing  210   b  in order to set the position by the position setting portion A. 
     The position setting portion A comprises the flange portion  700  extended-formed on the lower end of the middle housing  210   b  so as to correspond to the outer diameter of the sealing plate  90   a , and a position setting protrusion portion  710 , which is extended-bent downwardly from the end of the flange portion  700 . 
     The sealing plate  90   a  is inserted into a groove formed by the flange portion  700  and the position setting protrusion portion  710 , and accordingly, the center of the operating shaft  260  placed on the middle housing  210   b  coincides with the center of the fixed shaft  610  attached to the sealing plate  90   a , and the middle housing  210   b  is sealed. 
     A plurality of through holes H are formed on the outer circumference of the flange portion  700  of the middle housing  210   b  and outer circumference of the sealing plate  90   a  in order to secure the sealing plate  90   a  to the middle housing  210   b , and the sealing plate  90   a  is attached to the middle housing  210  by inserting and fastening a plurality of bolts  1  into the through holes H and securing them with nuts  2 . 
     The plurality of plate springs  620  are fixedly attached to the end portion of the fixed shaft  610 , and the mass body  630  having a predetermined weight is fixedly attached to the plate springs. The cover  510  having the cup shape is fixedly attached to the sealing plate  90   a  so as to cover the vibration absorbing unit  600 . The reservoir  500  is constructed by the sealing plate  90   a  and cover  510 , and the side of the inertance tube  300  is connected with the side of the cover  510 . 
     As depicted in FIG. 8, a plurality of position setting pins  3  are fixedly secured to the outer circumference of a flange portion  800  of the middle housing  210   b.    
     A plurality of pin holes  91  where the plurality of the position setting pins  3  are inserted are formed on the outer circumference of the sealing plate  90   b , the fixed shaft  610  is attached to the lower center portion of the sealing plate  90   b , and is attached to the flange portion of the middle housing  210   b.    
     The sealing plate  90   b  seals the middle housing  210   b  by coinciding the center of the operating shaft  260  with the center of the fixed shaft  610  by inserting the plurality of the position setting pins  3  into the plurality of the pin holes  91 . 
     The plurality of the position setting pins  3  are fixedly attached to the flange portion  800  extended-formed on the end portion of the middle housing  210   b , and the plurality of the pin holes  91  are formed on the outer circumference of the sealing plate  90   b.    
     The middle housing  210   b  is secured to the sealing plate  90   b  by forming the plurality of through holes H on the edge of the flange portion of the middle housing  210   b  and sealing plate  90   b , and inserting the plurality of bolts  1  inserted into the through holes H and securing them with the nuts  2 . 
     The plurality of plate springs  620  are fixedly formed on the end portion of the fixed shaft  610 , and the mass body  630  having a certain weight is fixedly attached to the plurality of plate springs  620 . The cover  510  having the cup shape is fixedly attached to the sealing plate  90   b  so as to cover the vibration absorbing unit  600 . The reservoir  500  having a predetermined sealed area is constructed by the sealing plate  90   b  and cover  510 , and the side of the cover  510  is connected to the side of the inertance tube  300 . 
     In addition, the plurality of the pin holes are formed on the flange portion  800  of the middle housing  210   b , the plurality of the position setting pins  3  corresponding to the plurality of the pin holes are fixedly attached to the sealing plate  90   b , and according to this, the center of the fixed shaft  610  fixedly combined to the sealing plate  90   b  coincides with the center of the operating shaft  260  placed inside of the middle housing  210   b.    
     Hereinafter, the operation effect of the pulse tube refrigerator in accordance with the second embodiment of the present invention will now be described. 
     The pulse tube refrigerator in accordance with the present invention is capable of preventing an eccentric vibration of the plate springs and mass body about the axial directional vibration of the compressor by performing the axial directional vibration in the operation of the compressor on the same line with the axial direction vibration of the plate springs and mass body of the vibration absorbing unit for absorbing the vibration. 
     Accordingly, the pulse tube refrigerator in accordance with the present invention is capable of improving the quietness in the operation by reducing the vibration noise of the overall system by stabilizing the vibration of the plate springs and mass body. And, the pulse tube refrigerator in accordance with the present invention can be transported easily and requires a smaller installation area by reducing the size of the pulse tube refrigerator by placing the inertance tube at a proper position and forming the reservoir so as to be one-bodied to the housing.