Patent Publication Number: US-2007104597-A1

Title: Linear compressor

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a linear compressor, and more particularly, to a linear compressor in which a piston and a cylinder are arranged to extend vertically and oil suction paths are perforated through a wall of the cylinder to supply oil into the cylinder, whereby the oil supply structure of the compressor is simplified, and thus, manufacturing costs and assembling time of the compressor can be reduced.  
      2. Description of the Related Art  
      Generally, a linear compressor is an apparatus configured in such a fashion that a piston reciprocally moves in a cylinder upon receiving a linear drive force of a linear motor to perform suction, compression, and discharge operations of fluid, such as gaseous refrigerant, (hereinafter, referred to as “fluid”).  
       FIG. 1  is a sectional view illustrating a conventional linear compressor.  
      As shown in  FIG. 1 , the conventional linear compressor comprises a shell  2  in which oil O is received, a linear compression unit  10  vibratably arranged in the shell  2  by use of a damper  8  to perform suction, compression, and discharge operations of fluid, and an oil supply device arranged below the linear compression unit  10  to pump the oil O, received in the bottom of the shell  2 , into the linear compression unit  10  when the linear compression unit  10  vibrates.  
      A fluid suction pipe  3  and a fluid discharge pipe  4  are penetrated through the shell  2 , and the fluid discharge pipe  4  is directly connected to the linear compression unit  10 , such that the fluid is sucked into the shell  2  through the suction pipe  3 , and then, is again discharged through the discharge pipe  4  after being compressed in the linear compression unit  10 .  
      The linear compression unit  10  includes a frame  16  having a cylinder  12 , a back cover  24  having a fluid suction pipe  22 , a piston  30  arranged to perform linear reciprocating movements in the cylinder  12 , the piston  30  being internally formed with a fluid suction path  20  to allow the fluid to be sucked into the cylinder  12 , a suction valve  32  mounted in the piston  30  to open or close the fluid suction path  28 , a linear motor  34  to linearly reciprocate the piston  30 , and a discharge valve assembly  35  mounted to open or close a leading end of the cylinder  12 , the discharge valve assembly  35  being connected to the discharge pipe  4 .  
      For the sake of lubricating/cooling both the cylinder  12  and the piston  30 , an oil pocket  36  is formed on at least one of the inner circumference of the cylinder  12  and the outer circumference of the piston  30 .  
      An oil supply path  37  is formed through both the cylinder  12  and the frame  16  such that the oil O is supplied into the oil pocket  36  by the oil supply device. Also, an oil discharge path  38  is formed through both the cylinder  12  and the frame  16  such that the oil O in the oil pocket  36  is discharged out of the linear compression unit  10 .  
      The oil supply device includes an oil pipe  39  which is partially immersed in she oil O, an oil cover  41  coupled to the frame  16  to define an oil passage  40  therebetween, an oil cylinder  44  arranged below the linear compression unit  10  to communicate with the oil passage  40 , an oil piston  45  disposed in the oil cylinder  44  to perform linear reciprocating movements in the cylinder  44 , front and rear oil springs  46  and  47  disposed in the oil cylinder  44  to elastically support the oil piston  45 , an oil suction valve  48  adapted to operate based on a pressure difference between the oil pipe  39  and the oil passage  40  for opening and closing an entrance of the oil passage  40 , and an oil discharge valve  49  adapted to operate based on a pressure difference between the oil passage  40  and the oil supply path  37  for opening and closing an exit of the oil passage  40 .  
      In the linear compressor having the above-described configuration, if the linear compression unit  10  vibrates, the oil piston  45  reciprocally moves simultaneously.  
      Specifically, when the oil piston  45  retracts, the oil passage  40  is in a low-pressure state, causing the oil suction valve  48  to be opened. Thereby, the oil O is sucked through the oil pipe  39  to fill the oil passage  40 .  
      Conversely, when the oil piston  45  advances, the oil passage  40  is in a high-pressure state, causing the oil discharge valve  49  to be opened. Thereby, the oil O in the oil passage  40  is supplied into a space between the cylinder  12  and the piston  30  by passing through the oil supply path  37 .  
      After being used to lubricate/cool both the cylinder  12  and the piston  30 , the oil is discharged out of the linear compression unit  10  by passing through the oil discharge path  38 , to drain into the bottom of the shell  2 .  
      A problem of the conventional linear compressor is that it requires many oil pumping parts, such as for example, the oil cylinder  44 , oil piston  45 , front and rear oil springs  46  and  47 , and therefore, suffers from a complicated structure, difficult assembling work, and increased manufacturing costs.  
     SUMMARY OF THE INVENTION  
      Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a linear compressor which can achieve a simplified oil pumping structure, and thus, inexpensive manufacturing costs.  
      In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a linear compressor comprising: a shell; an elongated cylinder extending vertically in the shell; a piston disposed to perform linear reciprocating movements in the cylinder; a linear motor to linearly reciprocate the piston in a vertical direction; and an oil supply device provided in the cylinder to supply oil into a space between the cylinder and the piston.  
      Preferably, the shell may store the oil therein: and the oil supply device may include a plurality of oil suction paths formed in the cylinder for introducing the oil stored in the shell into the space between the cylinder and the piston.  
      Preferably, the oil suction paths may be perforated through a wall of the cylinder.  
      Preferably, the linear compressor may further comprise a motor holder radially spaced apart from an outer circumference of the cylinder and used to secure the linear motor.  
      Preferably, the oil supply device may include: a storage portion formed between the cylinder and the motor holder to store the oil therein; and a plurality of oil suction paths formed in the cylinder for introducing the oil stored in the storage portion into the space between the cylinder and the piston.  
      Preferably, the storage portion may be provided with an oil cap to prevent oil leakage.  
      Preferably, the storage portion may be provided with a casket inserted between the cylinder and the motor holder.  
      Preferably, the oil supply device may include: a storage portion formed in a wall of the cylinder to store the oil therein; and a plurality of oil suction paths formed in the cylinder for introducing the oil stored in the storage portion into the space between the cylinder and the piston.  
      Preferably, the plurality of oil suction paths may be spaced apart from one another by a predetermined distance along a circumferential direction of the cylinder.  
      Preferably, the plurality of oil suction paths may be spaced apart from one another by a predetermined distance along a vertical direction of the cylinder.  
      Preferably, an oil pocket may be formed on at least one of an inner wall surface of the cylinder and an outer wall surface of the piston.  
      Preferably, the oil may be filled to a height higher than the oil suction paths.  
      In the linear compressor of the present invention having the above-described configuration, the piston and the cylinder are arranged to extend vertically in the shell, and the plurality of oil suction paths are perforated through the cylinder for introducing oil, stored in the shell, into a space between the cylinder and the piston without requiring separate pumping means, whereby the oil supply structure can be simplified with a reduced number of oil supply parts, and therefore, the manufacturing costs and assembling time of the linear compressor can be reduced.  
      Further, when the oil storage portion is defined in a space between the cylinder and the motor holder, it is possible to prevent the oil from being introduced into the linear motor or piston, resulting in an improvement in reliability.  
      Furthermore, by providing the storage portion with the oil cap, there is no risk of oil leakage.  
      The plurality of oil suction paths are vertically spaced apart from one another by a predetermined distance, and the oil is filled to a height higher than uppermost ones of the oil suction paths, whereby the oil can be evenly introduced into a space between the cylinder and the piston, and therefore, more effective lubrication and cooling of the piston and the cylinder can be accomplished. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which:  
       FIG. 1  is a sectional view illustrating a conventional linear compressor;  
       FIG. 2  is a sectional view illustrating a linear compressor according to a first embodiment of the present invention; and  
       FIG. 3  is a sectional view illustrating a linear compressor according to a second embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Now, preferred embodiments of the present invention will be explained with reference to the accompanying drawings.  
       FIG. 2  is a sectional view illustrating a linear compressor according to a first embodiment of the present invention.  
      As shown in  FIG. 2 , the linear compressor according to the first embodiment of the present invention comprises a shell  50  formed with a suction port  51  and a discharge port, an elongated cylinder  52  extending vertically in the shell  50 , a piston  53  disposed in the cylinder  52  to perform linear reciprocating movements in the cylinder  52 , a linear motor  60  to linearly reciprocate the piston  53 , a discharge unit assembly  54  mounted to the discharge port at the outside of the shell  50  to allow the fluid, compressed in the cylinder  52 , to be discharged through the discharge unit assembly  54 , and an oil supply device formed in the cylinder  52  to supply oil into a space between the cylinder  52  and the piston  53 .  
      The shell  50  has a cylindrical structure, and is provided at the top thereof with the suction port  51  and at the bottom thereof with the discharge port.  
      The cylinder  52  is directly fixed to the inner circumference of the shell  50  at a position facing the discharge port of the shell  50 .  
      The linear motor  60  is basically divided into a stator and a mover. The stator includes an outer stator  61 , an inner stator  62  spaced apart inward from the outer stator  61  to have a constant gap therebetween, and a coil  63  mounted in the outer stator  61  to produce a magnetic field. The outer and inner stators  61  and  62  take the form of stacks.  
      The mover includes a magnet  64  located between the outer stator  61  and the inner stator  62  to linearly move by a magnetic force that is produced around the coil  63 , and a magnet frame  65  fixed to both the magnet  64  and the piston  53  to transmit a linear movement force of the magnet  64  to the piston  53 .  
      One side of the outer stator  61  is fixed to a motor base  66  mounted to the shell  50 , and the other side of the outer stator  61  is fixed to a stator cover  67 , which is provided to cover the outer stator  61 .  
      The motor base  66  is made of a non-magnetic material.  
      The stator cover  67  is fastened to a back cover  69 , and in turn, a suction pipe  68  is penetrated through the back cover  69  to be aligned with the suction port  51 .  
      The inner stator  62  is directly fixed to the outer circumference of the cylinder  52 .  
      The piston  53  is provided at a trailing end thereof with a flange  53   a  to be fixed to the magnet frame  65 .  
      To provide the piston  53  with an elastic force when the piston  53  performs linear reciprocating movements, a main spring assembly is mounted to a spring support  70  that is seated onto the flange  53   a.    
      The main spring assembly includes a first main spring  71  located between the spring support  70  and the stator cover  67 , and a second main spring  72  located between the spring support  70  and the back cover  69 .  
      The discharge unit assembly  54  includes a discharge cover  73  fixed to the cuter surface of the shell  50  for the damping of fluid discharged through the discharge port, a discharge valve  74  located inside the discharge cover  73  to open or close the discharge port, and a discharge spring  75  attached to the discharge cover  73  to provide the discharge valve  74  with an elastic force.  
      The shell  50  is configured to store oil O therein. The oil supply device includes a plurality of oil suction paths  76  for introducing the oil O stored in the shell  50  into a space between the cylinder  52  and the piston  53 .  
      The oil suction paths  76  are perforated through the wall of the cylinder  52 . The description of the present embodiment is limited such that the oil suction paths  76  extend horizontally, but it can be understood that the oil suction paths may be tilted upward or downward.  
      Also, in the description of the present embodiment, the plurality of oil suction paths  76  are explained such that they are circumferentially spaced apart from one another by a predetermined distance, but the plurality of oil suction paths may be vertically spaced apart from one another.  
      Preferably, the oil O is filled in the shell  50  to a height higher than a height of the oil suction paths  76 .  
      An oil pocket  77  is formed on at least one of an inner wall surface of the cylinder  52  and an outer wall surface of the piston  53  such that the oil, introduced through the oil suction paths  76 , remains in the oil pocket  77 . The present embodiment is limited such that the inner wall surface of the cylinder  52  has a stepped structure to form the oil pocket  77 .  
      Hereinafter, the operation of the linear compressor according to the first embodiment of the present invention having the above-described configuration will be explained.  
      If a voltage is applied to the coil  63 , the coil  63  produces a magnetic field therearound, such that the magnet  64  performs linear reciprocating movements while interacting with the magnetic field. The linear reciprocating movements of the magnet  64  transmitted to the piston  53  via the magnet frame  65 , such that the piston  53  performs linear reciprocating movements in the cylinder  52 .  
      As the piston  53  linearly reciprocates up and down, the fluid, sucked into the cylinder  52 , is compressed by the piston  53 , and then, is discharged through the discharge valve assembly  54 .  
      During the linear reciprocating movements of the piston  53 , the oil O is sucked into a space between the cylinder  52  and the piston  53  through the oil suction paths  76 .  
      The oil O, sucked through the oil suction paths  76 , is introduced into the oil pocket  77 , thereby being used to lubricate/cool contact areas of both the piston  53  and the cylinder  52  when the piston  53  performs the linear reciprocating movements.  
      In the linear compressor having the above-described configuration, both the cylinder  52  and the piston  53  are arranged to extend vertically in the shell  50 , such that a part of the cylinder  52  and the oil O suction paths  76  are immersed in the oil O. This ensures the oil O to be smoothly supplied into a space between the cylinder  52  and the piston  53  without requiring separate pumping means.  
       FIG. 3  is a sectional view illustrating a linear compressor according to a second embodiment of the present invention.  
      As shown in  FIG. 3 , the linear compressor according to the second embodiment of the present invention comprises a shell  80  formed with a suction port  81  and a discharge port, an elongated cylinder  82  extending vertically in the shell  80 , a piston  83  disposed in the cylinder  82  to perform linear reciprocating movements, a linear motor  84  to linearly reciprocate the piston  83  up and down, a discharge unit assembly  85  mounted to the discharge port at the outside of the shell  80  to allow the fluid, compressed in the cylinder  82 , to be discharged through the discharge unit assembly  35 , and an oil supply device formed in the cylinder  82  to supply oil into a space between the cylinder  82  and the piston  83 .  
      In the present embodiment, a motor holder  90  is provided around the cylinder  82  to secure the linear motor  84 .  
      The motor holder  90  has a cylindrical shape, and is radially spaced apart from the outer circumference of the cylinder  82 . An inner stator of the linear motor  34  is fixedly mounted to the motor holder  90 .  
      The oil supply device includes a storage portion  91  defined between the cylinder  82  and the motor holder  90  to store the oil O therein, and a plurality of oil suction paths  92  perforated through a wall of the cylinder  82  for introducing the oil O stored in the storage portion  91  into a space between the cylinder  92  and the piston  83 . No detailed explanation of other configurations and operations of the oil supply device will be given.  
      The cylinder  82 , having a cylindrical shape, is formed with a radially protruding flange  82   a , such that the cylinder  82  is fixed to the inner circumference of the shell  80  at a position facing the discharge port of the shell  80 .  
      The storage portion  91  is a space defined between the cylinder  82  and the motor holder  90 . The bottom of the storage portion  91  is defined by the flange  82   a , and an oil cap  93  is provided to cover the top of the storage portion  91  to prevent leakage of the oil stored in the storage portion  91 .  
      A gasket  94  is inserted between the flange  82   a  of the cylinder  82  and the motor holder  90 .  
      The plurality of oil suction paths  92  are perforated through the wall of the cylinder  82  such that they are vertically and circumferentially spaced apart from one another by predetermined distances.  
      Preferably, the oil is stored in the storage portion  91  to a height higher than uppermost ones of the oil suction paths  92 .  
      An oil pocket  95  is formed on at least one of an inner wall surface of the cylinder  82  and an outer wall surface of the piston  83  such that the oil, introduced through the oil suction paths  92 , remains in the oil pocket  95 . The description of the present embodiment is limited such that the inner wall surface of the cylinder  82  has a stepped structure to form the oil pocket  95 .  
      In the linear compressor having the above-described configuration, the oil O stored in the storage portion  91  is introduced into a space between the cylinder  92  and the piston  83  through the oil suction paths  92  in accordance with vibrations of the compression unit, thereby serving to lubricate/cool both the cylinder  82  and the piston  83 .  
      With the present embodiment due to the fact that the oil O is stored in the storage portion  91 , it is possible to prevent the oil O from being introduced into the linear motor  84  or the piston  83 .  
      Meanwhile, the second embodiment of the present invent on explains that the storage portion  91  is defined between the cylinder  82  and the motor holder  90 , but is not limited thereto. Alternatively, the oil storage portion may be formed in the wall of the cylinder.  
      As is apparent from the above description, the present invention provides a linear compressor having the following several advantages.  
      Firstly, the linear compressor is configured such that a piston and a cylinder are arranged to extend vertically in a shell, and oil suction paths are perforated through the cylinder for introducing oil, stored in the shell, into a space between the cylinder and the piston without requiring separate pumping means, whereby the oil supply structure can be simplified with a reduced number of oil supply parts, and therefore, the manufacturing costs and assembling time of the linear compressor can be reduced.  
      Secondly, when an oil storage portion is defined in a space between the cylinder and a motor holder, it is possible to prevent the oil from being introduced into a linear motor or piston, resulting in an improvement in reliability.  
      Thirdly, by providing the storage portion with an oil cap, there is no risk of oil leakage.  
      Fourthly, the plurality of oil suction paths are vertically spaced apart from one another by a predetermined distance, and the oil is filled to a height higher than uppermost ones of the oil suction paths, whereby the oil can be evenly introduced into a space between the cylinder and the piston, and therefore, more effective lubrication and cooling of the piston and the cylinder can be accomplished.  
      Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.