Abstract:
Disclosed is a vacuum preventing device of a scroll compressor comprising: a discharge cover installed at a body of a fixed scroll for dividing inside of a case into a discharge region and a suction region; a vacuum cylinder installed in the discharge cover thus to be connected to a compression chamber formed between the fixed scroll and an orbiting scroll and having a pressure space therein so that the discharge region can be connected to the suction region; a piston movably installed in the pressure space for selectively connecting the discharge region with the suction region by a pressure difference between the compression chamber and the suction region; and an elastic member installed in the pressure space for providing an elastic force to the piston.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to a vacuum preventing device of a scroll compressor, and more particularly, to a vacuum preventing device of a scroll compressor capable of preventing vacuum in a compressor by flowing backward discharge gas of a discharge region into a suction region at the time of abnormal driving such as pump down or expansion valve blocking.  
           [0003]    2. Description of the Conventional Art  
           [0004]    Generally, a compressor is a device for converting mechanical energy into latent energy of a compression fluid, and is largely classified into a reciprocation compressor, a scroll compressor, a centrifugal compressor, and a vane compressor by compression methods.  
           [0005]    The scroll compressor has a structure that gas is sucked, compressed, and discharged by using a rotation member like the centrifugal type and the vane type differently from the reciprocating type which uses a linear reciprocation of an piston.  
           [0006]    [0006]FIG. 1 is a longitudinal section view showing an inner part of a scroll compressor in accordance with the conventional art.  
           [0007]    As shown, the conventional scroll compressor comprises: a case  1  having a gas suction pipe SP and a gas discharge pipe DP; a main frame  2  and a sub frame (not shown) respectively installed at upper and lower portions of an inner circumference surface of the case  1 ; a driving motor  3  installed between the main frame  2  and the sub frame; a rotation shaft  4  engaged to a center portion of the driving motor  3  for transmitting a rotation force of the driving motor  3 ; an orbiting scroll  5  installed to have an eccentric rotation at an upper portion of the rotation shaft  4  and having a wrap  5   a  of an involute curve shape at the upper portion thereof; and a fixed scroll  6  fixed to an upper portion of the main frame  2 , engaged to the orbiting scroll  5 , and having a wrap  6   a  of an involute curve shape so as to form a plurality of compression spaces P therein.  
           [0008]    The case  1  is divided into a suction region S 1  and a discharge region S 2  by a high and low pressure separation plate  7 .  
           [0009]    A gas inlet  6   b  and a gas outlet  6   c  are respectively formed at a lateral surface and a center portion of the fixed scroll  6 , and a non-return valve  8  for preventing discharged gas from flowing backward is installed at an upper surface of the fixed scroll  6 .  
           [0010]    The main frame  2  and the sub frame are fixed to the inner circumference surface of the case  1  by a fixation means such as welding, and the fixed scroll  6  is also fixed to a lower surface of the high and low pressure separation plate  7  by a fixation means such as a bolt.  
           [0011]    Meantime, in case of a pump down and an expansion valve blocking, the suction region S 1  of the compressor becomes a high vacuum state. At this time, components of the compressor may be damaged and destroyed.  
           [0012]    To prevent this, in the conventional art, a vacuum preventing device  20  is provided in the body  6 A of the fixed scroll  6 .  
           [0013]    [0013]FIG. 2 is a longitudinal section view showing an operation of the conventional vacuum preventing device at the time of a normal driving, and FIG. 3 is a longitudinal section view showing an operation of the conventional vacuum preventing device at the time of an abnormal driving.  
           [0014]    Referring to FIGS. 2 and 3, the conventional vacuum preventing device  20  comprises a pressure space  10  formed in the fixed scroll  6 , and a discharge flow path  11  connected to the discharge region S 2  at an upper surface of the pressure space  10 .  
           [0015]    A compression flow path  12  connected to a compression chamber is formed at a lower surface of the pressure space  10 , a plug  14  having a suction flow path  13  is fixed to an opening portion of the pressure space  10  by a fixation pin  15 , and the suction flow path  13  is connected to the discharge flow path  11 .  
           [0016]    A piston  17  for selectively connecting the discharge flow path  11  and the suction flow path  13  is movably installed in the pressure space  10 .  
           [0017]    A spring  16  for limiting a movement of the piston  17  and providing an elasticity force thereto is installed at the opening portion of the pressure space  10 .  
           [0018]    Hereinafter, operations of the conventional scroll compressor will be explained.  
           [0019]    First, when a power source is applied to the driving motor  3 , the driving motor  3  rotates the rotation shaft  4 , and the orbiting scroll  5  engaged to the rotation shaft  4  is rotated to an extent of its eccentric distance.  
           [0020]    At this time, the plurality of compression spaces P formed between the wrap  5   a  of the orbiting scroll  5  and the wrap  6   a  of the fixed scroll  6  gradually move towards a center portion of the fixed scroll  6  as the orbiting scroll  5  continuously performs an orbiting movement, thereby having a decreased volume.  
           [0021]    By the decreased volume of the compression spaces P, gas of the suction region S 1  is sucked into the compression spaces P through the inlet  6   b , and the sucked gas is discharged to the discharge region S 2  through the gas outlet  6   c.    
           [0022]    When the compressor is normally driven, a pressure of the compression chamber is larger than an elasticity force of the spring  16 , so that the piston  17  overcomes the elasticity force of the spring  16  and blocks the discharge flow path  11 .  
           [0023]    However, when the compressor is abnormally driven due to a pump down or an expansion valve blocking, inside of the compression chamber becomes vacuum and a pressure of the compression chamber P becomes smaller than the elasticity force of the spring  16 , so that the piston  17  is shoved by the elasticity force of the spring  16  and opens the discharge flow path  11 . At this time, the discharge flow path  11  is connected to the suction flow path  13 .  
           [0024]    As the discharge flow path  11  and the suction flow path  13  are connected to each other, gas of the discharge region S 2  flows backward into the suction region S 1  through the discharge flow path  11  and the suction flow path  13 , thereby releasing the vacuum in the compressor.  
           [0025]    However, in the conventional art, since the vacuum preventing device is formed in the fixed scroll, a fabrication cost of the vacuum preventing device is too expensive and an intensity of the fixed scroll is degraded. According to this, the fixed scroll is easily damaged during operation.  
           [0026]    Also, since the pressure space is formed at the lateral surface of the fixed scroll and the plug has to be inserted to an end of the opening portion of the pressure space in order to prevent the spring and the piston installed in the pressure space from being separated, an entire construction becomes complicated and a fabrication cost is increased.  
         SUMMARY OF THE INVENTION  
         [0027]    Therefore, an object of the present invention is to provide a vacuum preventing device of a scroll compressor which can prevent damage of a fixed scroll by enhancing an intensity of the fixed scroll and reduce a fabrication cost of the fixed scroll by installing the vacuum preventing device outside the fixed scroll.  
           [0028]    Another object of the present invention is to provide a vacuum preventing device of a scroll compressor in which a pressure space is formed at a lower portion of a vacuum cylinder adjacent to the fixed scroll, and a plug for preventing a spring and a piston installed in the pressure space from being separated is not required, thus the fixed scroll plays a role of the plug, thereby reducing the number of construction components and reducing a fabrication cost.  
           [0029]    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 vacuum preventing device of a scroll compressor comprising: a discharge cover installed at a body of a fixed scroll for dividing inside of a case into a discharge region and a suction region; a vacuum cylinder installed in the discharge cover thus to be connected to a compression chamber formed between the fixed scroll and an orbiting scroll and having a pressure space therein so that the discharge region can be connected to the suction region; a piston movably installed in the pressure space for selectively connecting the discharge region with the suction region by a pressure difference between the compression chamber and the suction region; and an elastic member installed in the pressure space for providing an elastic force to the piston.  
           [0030]    A suction flow path for connecting the suction region with the pressure space is formed at an upper portion of the vacuum cylinder, a discharge flow path for connecting the discharge region with the pressure space is formed at a lateral surface of the vacuum cylinder, and a compression flow path for connecting the compression chamber with the pressure space is formed at the body of the fixed scroll.  
           [0031]    Diameters of the suction flow path, the discharge flow path, and the compression flow path are formed to be shorter than a diameter of the pressure space.  
           [0032]    The vacuum cylinder is extended from an inner upper surface of the discharge cover to an upper surface of the body of the fixed scroll as a unit with the discharge cover.  
           [0033]    One end of the elastic member is fixed to an upper portion of the pressure space, and another end thereof is fixed to a spring fixing protrusion formed at an upper portion of the piston.  
           [0034]    The pressure space is formed with a predetermined depth from a lower surface of the vacuum cylinder to an upper surface thereof, and an inner diameter of the pressure space is formed equally from the upper portion thereof to the lower portion thereof.  
           [0035]    A sealing member is installed at contact surfaces between the body of the fixed scroll and the discharge cover, and between the body of the fixed scroll and the vacuum cylinder.  
           [0036]    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  
       [0037]    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.  
         [0038]    In the drawings:  
         [0039]    [0039]FIG. 1 is a longitudinal section view showing a scroll compressor in accordance with the conventional art;  
         [0040]    [0040]FIG. 2 is a longitudinal section view showing an operation of a vacuum preventing device when the conventional scroll compressor is normally driven;  
         [0041]    [0041]FIG. 3 is a longitudinal section view showing an operation of the vacuum preventing device when the conventional scroll compressor is abnormally driven;  
         [0042]    [0042]FIG. 4 is a longitudinal section view showing a scroll compressor according to the present invention;  
         [0043]    [0043]FIG. 5 is a disassembled longitudinal section view showing a vacuum preventing device according to the present invention;  
         [0044]    [0044]FIG. 6 is a longitudinal section view showing an operation of the vacuum preventing device when the scroll compressor of the present invention is normally driven; and  
         [0045]    [0045]FIG. 7 is a longitudinal section view showing an operation of the vacuum preventing device when the scroll compressor of the present invention is abnormally driven 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0046]    Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.  
         [0047]    [0047]FIG. 4 is a longitudinal section view showing a scroll compressor according to the present invention, FIG. 5 is a disassembled longitudinal section view showing a vacuum preventing device according to the present invention, FIG. 6 is a longitudinal section view showing an operation of the vacuum preventing device when the scroll compressor of the present invention is normally driven, and FIG. 7 is a longitudinal section view showing an operation of the vacuum preventing device when the scroll compressor of the present invention is abnormally driven.  
         [0048]    In a vacuum preventing device according to the present invention, a discharge cover  120  is installed at a body  111  of a fixed scroll  110 , a vacuum cylinder  130  having a pressure space  131  is installed at the discharge cover  120 , and a piston  140  which moves by an elastic force of a spring  141  according to a pressure difference between the compression chamber and the suction region is installed in the pressure space  131 .  
         [0049]    The fixed scroll  110  is composed of the body  111  and a wrap  110   a  formed at the lower portion of the body  111  with an involute shape. A discharge hole  112  connected to a compression chamber P and a discharge region S 2  of the discharge cover  120  is formed at a center of the body  111 .  
         [0050]    A compression flow path  113  connected to the compression chamber P is formed at one side of the body  111  of the fixed scroll, and refrigerant gas inlet  114  is formed at anther side of the body  111 .  
         [0051]    As aforementioned, the discharge cover  120  connected to a gas discharge pipe DP is installed at the upper surface of the body  111  of the fixed scroll  110  to cover the body  111 . Also, the discharge cover  120  divides its inside and outside into a suction region S 1  and a discharge region S 2 , respectively.  
         [0052]    A structure of the discharge cover  120  will be explained in detail.  
         [0053]    The discharge cover  120  is hermetically engaged to the upper surface of the fixed scroll  110 , and the vacuum cylinder  130  of a pillar shape is protruded towards a longitudinal direction in the discharge cover  120  and thus extended to the upper surface of the body  111 .  
         [0054]    It is preferable that the vacuum cylinder  130  is formed of the same material with the discharge cover  120  for intensity.  
         [0055]    The vacuum cylinder  130  can be formed with a tube shape so that the inner circumference surface and the outer circumference surface can have the pressure space of a circle shape or a polygon shape.  
         [0056]    In the present invention, the pressure space  131  is formed with a predetermined depth from the lower surface of the vacuum cylinder  130  to the upper surface thereof, and an inner diameter of the pressure space  131  is formed equally from the upper portion thereof to the lower portion thereof.  
         [0057]    Although not shown, if the pressure space  131  is formed with a predetermined depth from the upper surface of the vacuum cylinder  130  to the lower surface, the spring  141  and the piston  140  have to be assembled in the pressure space  131  and the plug  14  (Referring to FIG. 2) has to be installed at the end of the opening portion of the pressure space  131  in order to prevent the spring  141  and the piston  140  from being separated from the pressure space  131 . However, in the present invention, if the pressure space  131  is formed with a predetermined depth from the lower surface of the vacuum cylinder  130  to the upper surface thereof, the discharge cover  120  is assembled to the body  111  and the body  111  plays a role of the plug. According to this, the conventional plug  14  is not required in the present invention.  
         [0058]    The lower portion of the pressure space  131  is positioned to cover the compression flow path  113  formed at the body  111  of the fixed scroll  110 .  
         [0059]    A discharge flow path  132  connected to the discharge region S 2  in the discharge cover  110  is formed at a middle portion of the vacuum cylinder  130 , and a suction flow path  133  connected to the suction region in the case  1  is formed at the upper portion of the vacuum cylinder  130 .  
         [0060]    In order to make the piston  140  be slid smoothly in the pressure space  131 , the inner diameter of the pressure space  131  and an outer diameter of the piston  140  have to be properly set.  
         [0061]    That is, if the inner diameter of the pressure space  131  is too longer than the outer diameter of the piston  140  and thus a clearance (not shown) generated between the pressure space  131  and the inner circumference surface of the vacuum cylinder  130  becomes to large, compression gas can be leaked from the clearance. On the contrary, if the clearance is too small, the piston  140  is not operated smoothly. Therefore, the clearance has to be properly set.  
         [0062]    When the compressor is abnormally operated, the discharge flow path  132  has to be formed slantingly so that discharge gas of the discharge region S 2  can be fast exhausted to the suction region S 1 . Also, the inside of the discharge flow path  132  is preferably located more high than the outside thereof.  
         [0063]    It is preferable that a diameter of the suction flow path  133  is formed to be shorter than that of the pressure space  131 .  
         [0064]    The compression spring  141  installed in the pressure space  131  has an upper end fixed to the upper portion of the pressure space  131  and a lower end fixed to a spring fixing protrusion  140   a  formed at the upper surface of the piston  140 .  
         [0065]    A sealing member  150  such as O-ring is preferably installed at a contact surface between the lower end surface of the vacuum cylinder  130  and the body  111  of the fixed scroll  110 .  
         [0066]    The piston  140  is preferably formed of light-weight material such as engineering plastic so that the piston  140  can be smoothly moved up and down in the pressure space  131  and noise generated when the piston collides with the body  111  can be reduced.  
         [0067]    The piston  140  can be formed as a circle shape or a polygon shape in accordance with a shape of the pressure space  131 , and the spring fixing protrusion  140   a  for fixing the spring  141  is preferably formed at the upper surface of the piston  140 .  
         [0068]    Modulus of elasticity of the spring  141  has to be properly set by considering a case of a normal driving of the compressor and a case of an abnormal driving. That is, when the compressor is normally driven, the piston  140  has to overcome elasticity of the spring  141  by a pressure applied through the compression flow path  113 , move, and block the suction flow path  133  and the discharge flow path  132 . On the contrary, when the compressor is abnormally driven, the piston  140  has to connect the discharge flow path  132  and the suction flow path  133  by the elasticity of the spring  141 .  
         [0069]    Unexplained reference numeral  1  denotes a case,  2  denotes a main frame,  100  denotes an orbiting scroll, and  100   a  denotes a wrap of the orbiting scroll.  
         [0070]    Operations of the scroll compressor according to the present invention will be explained.  
         [0071]    First, when a power source is applied to the driving motor  3 , the driving motor  3  rotates the rotation shaft  4 , and an orbiting scroll  160  engaged to the rotation shaft  4  is rotated to an extent of its eccentric distance.  
         [0072]    At this time, the plurality of compression spaces P formed between a wrap  160   a  of the orbiting scroll  160  and the wrap  110   a  of the fixed scroll  110  gradually move towards a center portion of the fixed scroll  110  as the orbiting scroll  160  continuously performs an orbiting movement, thereby having a decreased volume.  
         [0073]    By the decreased volume of the compression spaces P, gas of the suction region S 1  is sucked into the compression spaces P through the inlet  114 , and the sucked gas is discharged to the discharge region S 2  through the gas outlet  112 .  
         [0074]    When the compressor is normally driven, as shown in FIG. 6, gas of high pressure is introduced into the pressure space  131  of the vacuum cylinder  130  through the compression flow path  113 , and the gas of high pressure overcomes low pressure of the suction side of the vacuum cylinder  130  and resistance of the spring  141 . The gas of high pressure pushes up the piston  140  towards the suction flow path  133  and blocks the discharge flow path  132 , thereby preventing a part of the discharge gas discharged to the discharge region S 2  of the discharge cover  120  from flowing backward into the suction region S 1  of the case  1  through the discharge flow path  132 .  
         [0075]    On the contrary, when the compressor is abnormally driven due to expansion valve blocking or pump down, as shown in FIG. 7, the spring  141  compressed in a state that a pressure of the suction region S 1  and a pressure of the compression chamber P are almost equal expands and pushes the piston  140  towards the compression flow path  113 . Herein, in a state that the discharge flow path  132  and the suction flow path  133  are connected to each other, a part of the discharge gas of high pressure is introduced to inside of the pressure space  131  of the vacuum cylinder  130  through the discharge flow path  132 , and introduced into the suction region S 1  of the case  1  through the suction flow path  133 , then sucked into the compression chamber P as its pressure is lowered. According to this, over-compression or high-vacuum state of each compression chamber is prevented.  
         [0076]    Then, if the compressor performs a normal driving again, compression gas of the compression chamber P is introduced into the pressure space  131  of the vacuum cylinder  130  through the compression flow path  113 , and pushes up the piston  140 , thereby blocking the discharge flow path  132  and the suction flow path  133 .  
         [0077]    As aforementioned, in the present invention, by constructing the vacuum preventing device at the discharge cover  120  which forms the discharge region S 2 , the fixed scroll  110  is easily processed thus to reduce a fabrication cost and to maintain an intensity of the fixed scroll  110 , thereby enhancing a reliability of the compressor.  
         [0078]    Also, by processing the discharge cover  110  with a simple method such as die casting, a processing cost can be reduced. Besides, the spring  141  and the piston  140  can be assembled in the pressure space  131  easily and conveniently without the plug used in the conventional art.  
         [0079]    Also, by forming the vacuum piston with light-weight material, collision noise can be reduced.  
         [0080]    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 metes and bounds of the claims, or equivalence of such metes and bounds are therefore intended to be embraced by the appended claims.