Patent Publication Number: US-2004052661-A1

Title: Joint structure for refrigerant discharge tubes used in hermetic compressors

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] The present invention generally relates to a hermetic reciprocal compressor, and more particularly to a joint structure for a refrigerant discharge tube that serves as a passageway for compressed refrigerant.  
       [0003] 2. Description of the Prior Art  
       [0004] As shown in FIG. 1, a conventional hermetic reciprocal compressor includes an electronic device unit  20  and a compression device unit  30  in a casing  10  which is formed of an upper shell  11  and a lower shell  12 . The compression device unit  30  is driven by the power transmitted from the electronic device unit  20  used to compress the refrigerant.  
       [0005] The electronic device unit  20  includes in the casing  10   a  stator  21  which is fixed, a rotor rotatably disposed relative to the stator  21  and a rotary shaft  23  press-fit in the rotor  22  and having an eccentric portion  23   a  formed at an end thereof.  
       [0006] The compression device unit  30  includes a cylinder block  31  having a compression chamber  31   a , a cylinder head  40  mounted on the cylinder block  31  and having a refrigerant suction chamber  41  and a discharge chamber  42 , a piston  50  disposed in the compression chamber  31   a  of the cylinder block  31  disposed to be movable in a reciprocal fashion, a connecting rod  60 , with one end being connected to the piston  50  and the other end connected to the eccentric portion  23   a  of the rotary shaft  23 , for converting and transmitting the rotary motion of the rotary shaft  23  into the linear reciprocal movement of the piston  50 , and a valve device  70  disposed between the cylinder block  31  and the cylinder head  40  for controlling the flow of the refrigerant.  
       [0007] Further, the hermetic reciprocal compressor includes a suction muffler  80  at one side of the interior of the casing  10  for drawing in the refrigerant into the refrigerant suction chamber  41 , and a refrigerant discharge tube assembly  90  (FIG. 2) disposed adjacent a refrigerant path hole (not shown) formed in the cylinder block  31  to provide fluid communication with the refrigerant discharge chamber  42  of the cylinder head  40 . The refrigerant discharge tube assembly  90  serves as a discharge passageway of the compressed refrigerant.  
       [0008] As shown in FIG. 2, the refrigerant discharge tube assembly  90  includes a refrigerant discharge tube  91  and a discharge muffler  92 . The discharge muffler  92  defines a predetermined space to reduce the noise produced from the pulsation of the refrigerant discharge, and is secured to the cylinder block  31  by a bolt  93 . One end of the refrigerant discharge tube  91  is connected to the discharge muffler  92 , while the other end is connected to a discharge tube (not shown) provided in the casing  10 .  
       [0009] In the refrigerant discharge tube assembly  90  as described above, the refrigerant discharge tube  91  and the discharge muffler  92  are joined with each other by copper-brazing, and the discharge muffler  92  is coupled with the cylinder block  31  using the bolt  93 .  
       [0010] According to the conventional joint structure for the refrigerant discharge tube, the refrigerant discharge tube  91  and the discharge muffler  92  are joined [with] to each other by copper-brazing, and then the discharge muffler  92  is coupled to the cylinder block  31  by the bolt  93 . Accordingly, the number of assembly steps increases, causing the manufacturing efficiency to be reduced and manufacturing costs to increase.  
       [0011] Also, as the refrigerant discharge tube  91  and the discharge muffler  92  are joined with each other by copper-brazing, the refrigerant discharge tube  91  becomes deformed and phase-variation occurs in the structure in the brazing furnace. As a result, durability of the product deteriorates. Even after the brazing, the neck portion of the refrigerant discharge tube  91  is subject to stress during one or more bending processes, and thus, the refrigerant discharge tube  91  becomes less cylindrical, and stress concentration occurs. As a result, often times, the refrigerant discharge tube  91  is broken, and the refrigerant leaks out of the compressor.  
       SUMMARY OF THE INVENTION  
       [0012] Accordingly, it is an object of the present invention to provide a joint structure for a refrigerant discharge tube used in a hermetic reciprocal compressor, which requires fewer operational steps for joining the refrigerant discharge tube relative to the cylinder block, thereby contributing to the improvement of the manufacturing efficiency and to a reduction in manufacturing costs.  
       [0013] It is another object of the present invention to provide a joint structure for a refrigerant discharge tube used in a hermetic reciprocal compressor, intended to overcome problems of durability deterioration and refrigerant discharge tube breakage which may occur due to copper-brazing, by press-fitting the refrigerant discharge tube to the cylinder block.  
       [0014] The above objects are accomplished by a joint structure for a refrigerant discharge tube used in a hermetic reciprocal compressor according to the present invention, in which the refrigerant discharge tube is directly connected to a cylinder block by press-caulking a connecting member connected with the refrigerant discharge tube into a connecting hole formed in the cylinder block. The connecting member is formed to correspond to the shape of the connecting hole.  
       [0015] The connecting hole is formed in a multi-layer or stepped structure, which has at least two layers. For assembly, the connecting member is pre-assembled in the connecting hole by transition-fitting, and then is securely press-fit in the connecting hole by being expanded therein under the pressure of a caulking jig.  
       [0016] According to the preferred embodiment of the present invention, the connecting hole has a thread portion having a pitch in the range of 2 to 5 threads, and thus, the connecting member is more securely fit in the connecting hole because the connecting member is expanded by the pressure provided by the caulking jig.  
       [0017] The connecting member can be formed of a soft iron metal or a soft non-iron metal. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0018] The above-mentioned objects and the feature of the present invention will be more apparent by describing the preferred embodiment of the present invention in detail referring to the appended drawings, in which:  
     [0019]FIG. 1 is a cross-sectional view schematically showing the structure of a conventional hermetic reciprocal compressor;  
     [0020]FIG. 2 is a perspective detail view showing a joint structure for a refrigerant discharge tube used in the compressor shown in FIG. 1;  
     [0021]FIG. 3 is a cross-sectional view showing the joint structure for a refrigerant discharge tube used in a hermetic reciprocal compressor according to the preferred embodiment of the present invention;  
     [0022]FIG. 4 is a cross-sectional view showing the refrigerant discharge tube being connected to the cylinder block by the joint structure according to the present invention; and  
     [0023]FIG. 5 is a perspective view showing the hermetic reciprocal compressor according to the present invention. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT  
     [0024] The objects and other characteristics of the present invention will be made more apparent by describing the preferred embodiments with reference to the accompanying drawings. Elements that are similarly constructed and have similar functions as those like elements of FIGS. 1 and 2 will be identified by identical reference numerals in FIGS.  3 - 5 .  
     [0025] Referring to FIGS. 3 and 4, the joint structure for the refrigerant discharge tube of the hermetic reciprocal compressor according to the preferred embodiment of the present invention includes a connecting hole  101  penetrated through a side of the cylinder block  100 , a refrigerant discharge tube  110  fit in the connecting hole  101  and a connecting member  120  for securing the refrigerant discharge tube  110  relative to the connecting hole  101 .  
     [0026] The connecting hole  101  is formed to be in fluid communication with a refrigerant path hole (not shown) formed inside of the cylinder block  100 . The refrigerant path hole is in fluid communication with the refrigerant discharge chamber  42  of the cylinder head  40  (see FIG. 1). The connecting hole  101  is formed having a multi-layer structure in which two or more layers are formed, and may be provided with a thread portion  101   a  formed in an inner circumference of the hole  101  having a pitch in a range of from 2 to 5 threads.  
     [0027] The refrigerant discharge tube  110  is inserted in an insertion hole  120   a  formed in the center of the connecting member  120 , and accordingly, the refrigerant discharge tube  110  is connected to the cylinder block  100  as the connecting member  120  is secured to the connecting hole  101 .  
     [0028] The connecting member  120  is also formed having a multi-layer structure corresponding to the shape of the connecting hole  101 , and is force-caulked in the connecting hole  101  by a pressing member, such as the caulking jig  130  shown in FIG. 3.  
     [0029] Preferably, the connecting member  120  is formed of materials having rigidity, but that allow inward or outward expansion by the pressure of the caulking jig  130 . Soft iron metal, or soft non-iron metal, can be used as the connecting member  120 .  
     [0030] Hereinbelow, the method of using the joint structure for the refrigerant discharge tube of the hermetic reciprocal compressor according to the preferred embodiment of the present invention will be described.  
     [0031] First, as shown in FIG. 3, the connecting member  120  is fit in the refrigerant discharge tube  110 , and pre-assembled in the connecting hole  101  of the cylinder block  100  by transition-fitting.  
     [0032] Next, the connecting member  120  is pressed from the rear side by the caulking jig  130 , press-fitting the connecting member  120  into the connecting hole  101 . At this time, the connecting member  120  expands inwardly and outwardly, coming into close contact with the refrigerant discharge tube  110  relative to the refrigerant discharge tube  110  inserted in the insertion hole  120   a  of the connecting member  120 , with the connecting hole  101  and the connecting member  120  contacting each other very tightly. Due to the presence of the thread portion  101   a  on the inner circumference of the connecting hole  101 , the connecting member  120  penetrates into the threaded portion  101   a  during expansion, thereby being press-fit in the connecting hole  101  tightly.  
     [0033]FIG. 4 is a view showing the connecting member  120  being press-caulked in the connecting hole  101 . As shown in FIG. 4, the refrigerant discharge tube  110  is secured in the cylinder block  100  due to the expansion of connecting member  120  into the connecting hole  101 . As described above, the connecting member  120  is secured in the connecting hole  101  by being expanded under the external pressure of the caulking jig  130  (FIG. 3), and is further tightly secured due to the connecting member  120  being partially and fixedly penetrated into the thread portion  101   a  formed on the inner circumference of the connecting hole  101 . As a result, a strong binding force is acquired, and the connecting member  120  is not separated from the connecting hole  101 .  
     [0034]FIG. 5 shows the hermetic reciprocal compressor having the joint structure for a refrigerant discharge tube as described above. As shown in FIG. 5, the refrigerant discharge tube  110  is directly secured to the cylinder block  100  by the connecting member  120 .  
     [0035] As described above, according to the present invention, since the refrigerant discharge tube  110  is directly connected to the cylinder block  100 , the structure becomes simplified, while the number of assembly steps required for assembling the compressor is reduced. As a result, manufacturing efficiency improves and manufacturing costs are reduced.  
     [0036] Further, since the connecting member is secured by press-caulking, instead of brazing, durability is increased, and thus, breakage of the refrigerant discharge tube  110  can be prevented.  
     [0037] Although a preferred embodiment of the present invention has been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiment, but various changes and modifications can be made to remain within the spirit and scope of the present invention as defined by the appended claims and their equivalents.