Abstract:
Disclosed is an exhaust valve capable of correctly opening/shutting an exhaust port of a cylinder based upon variation of the flux density of an electromagnet. The inventive exhaust valve may comprise a guide connected in parallel to an exhaust port of a cylinder, a needle valve provided inside the guide for opening/shutting the exhaust port while moving in cooperation with the guide. The needle valve may be controlled with an electromagnet. The invention enables complete opening of the exhaust port of the cylinder in exhaustion thereby preventing degradation of compression efficiency due to valve damage while reducing generation of vibration and noise.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    The present invention relates to an exhaust valve, in particular, capable of correctly opening an outlet port of a cylinder while maximizing compression efficiency.  
           [0003]    2. Description of the Related Art  
           [0004]    Generally in a cooling cycle, fluid having a large amount of heat is sucked and then exhausted after loosing heat through compressing, condensing, expanding and evaporating processes.  
           [0005]    A cooling apparatus for performing the above processes may comprise a compressor, a condenser, expansion valves and an evaporator. The compressor sucks and compresses coolant evaporated in the evaporator to raise the pressure thereof so that coolant may be converted into a state liquefiable at a relatively high temperature.  
           [0006]    In general, the compressor is divided into a reciprocating compressor, a revolving compressor, a scrolling compressor and the like according to application policies thereof. The reciprocating compressor can compress coolant through processes of sucking, compressing and exhausting coolant gas as a piston reciprocates inside a cylinder. The reciprocating compressor has a suction valve for sucking coolant, a cylinder for compressing coolant introduced through the suction valve and an exhaust valve for exhausting coolant compressed in the cylinder.  
           [0007]    [0007]FIG. 1 is a schematic perspective view illustrating a conventional reciprocating compressor.  
           [0008]    Referring to FIG. 1, the reciprocating compressor comprises a column-shaped cylinder  11 , a piston  12  for being inserted into one side of the cylinder  11  and performing a linear reciprocating motion inside the cylinder  11  to compress fluid, suction and exhaust valves  14  and  15  arranged in opposition to the front of the piston  12  for sucking and exhausting fluid, a valve plate  13  arranged between the suction valve  14  and the exhaust valve  15  for supporting the suction and exhaust valves  14  and  15  and a head cover  16  having channels for fluid which is introduced into the cylinder  11  and exhausted from the same.  
           [0009]    The reciprocating compressor further comprises a connecting rod  17  connected to the rear of the piston  12  and a crank shaft  18  connected to the rod  17  and rotated by a motor (not shown).  
           [0010]    Briefly describing the operation of the reciprocating compressor, the motor (not shown) is driven to rotate the crank shaft  18  so that the connecting rod  17  connected to the crank shaft  18  may move in a circle in cooperation with the connecting rod  17 . The movement of the connecting rod  17  causes the piston  12  connected thereto to perform a linear reciprocating motion so that fluid is sucked into the cylinder  11 , compressed therein, and then exhausted therefrom.  
           [0011]    In the above operation, the suction and exhaust valves  14  and  15  perform sucking and exhausting procedures as follows and have the following structures.  
           [0012]    [0012]FIGS. 2A to  2 D are schematic plan views illustrating a head cover (FIG. 2A), an exhaust valve (FIG. 2B), a valve plate (FIG. 2C) and a suction valve (FIG. 2D), respectively, in a conventional reciprocating compressor. Seen from the front of the piston in FIG. 1, the cylinder may be sequentially coupled with the inlet valve, the valve plate, the outlet valve and the head cover in the order of description, i.e. from the inlet valve to the head cover.  
           [0013]    Referring to FIGS. 2A to  2 D, the valve plate  13  includes a suction port  13   a  for sucking fluid and an exhaust port  13   b  for exhausting fluid as a member for supporting the suction valve  14  and the exhaust valve  15 .  
           [0014]    The suction valve  14  is a member arranged between the valve plate  13  and the cylinder  11 , and has a suction plate  14   a  at a position corresponding to the suction port  13   a  of the valve plate  13  and an exhaust port  14   b  at a position corresponding to the exhaust port  13   b  of the valve plate  13 .  
           [0015]    Further, the exhaust valve  15  is a member arranged between the valve plate  13  and the head cover  16 , and has an exhaust plate  15   a  at a position corresponding to the exhaust port  13   b  of the valve plate  13  and a suction port  15   b  at a position corresponding to the suction port  13   a  of the valve plate  13 .  
           [0016]    The head cover  16  is a member for defining the channels of fluid sucked and exhausted into/from the cylinder, and has a suction tube  16   a  at a position corresponding to the suction port  13   a  of the valve plate and an exhaust tube  16   b  at a position corresponding to the exhaust port  13   b.    
           [0017]    Description will be made about the operation of the conventional reciprocating compressor including the suction valve  14 , the valve plate and the exhaust valve  15  having the above configuration. When the piston  12  moves backward inside the cylinder  11  due to the circular motion of the crank shaft, the pressure within the cylinder  11  is lowered to fold the suction plate of the suction valve. Therefore, fluid is sucked into the cylinder via the folded suction plate  14   a  after passing through the suction tube  16   a , the suction port  15   b  and the suction port  13   a  of the valve plate.  
           [0018]    Fluid sucked as above is compressed as the piston  12  moves forward due to the circular motion of the crank shaft. Fluid compressed like this passes through the exhaust port  14   b  of the suction valve and the exhaust port  13   b  of the valve plate, and then flows out via the exhaust tube  16   b  of the head cover pushing out the exhaust plate  15   a  of the exhaust valve which is supported by a spring and the like.  
           [0019]    [0019]FIGS. 3A and 3B schematically illustrate the operation of the exhaust valve in the conventional reciprocating compressor, in which the suction valve is not shown for the convenience&#39;s sake of description.  
           [0020]    Describing a process of exhausting fluid from the cylinder in reference to FIGS. 3A and 3B, fluid compressed via forward movement of the piston is exhausted via the exhaust port  13   b  of the valve plate, i.e. out of the cylinder pushing out the exhaust plate  15   a  of the exhaust valve. Preferably, the exhaust plate of the exhaust valve is made of a material capable of resisting a certain amount of pressure.  
           [0021]    After fluid is exhausted, the piston moves backward due to the circular motion of the crank shaft accordingly lowering the pressure within the cylinder so that the exhaust pate  15   a  is shut due to its own elasticity to prevent further exhaustion of fluid.  
           [0022]    The above process continuously takes place as the crank shaft continuously performs the circular motion while the piston connected thereto repeatedly performs the reciprocating motion.  
           [0023]    However, according to the operation of the exhaust valve in the above reciprocating compressor, it can be seen that the exhaust plate  15   a  of the exhaust valve is folded for a certain degree instead of being completely folded in an exhausting process. Since the exhaust plate  15   a  is not completely folded as above, fluid is obstructed in exhaustion along a proceeding direction thereby preventing smooth exhaustion.  
           [0024]    Further, the above valve is opened according to the fluid pressure inside the cylinder so that the exhaust valve is opened later than a desired time point thereby resulting in overshooting as a problem.  
           [0025]    Further, when the exhaust valve  15   a  is shut in a sucking process, the entire portion of the exhausting valve  15   a  contacting to the valve plate  13  hits the valve plate  13  to produce noise. Heavy noise also takes place from vibration of the valve and fluid leakage through a gap which is produced by the valve folded in exhaustion.  
           [0026]    The above phenomena not only degrade the entire efficiency of the reciprocating compressor but also provide users with displeasure due to heavy noise.  
         SUMMARY OF THE INVENTION  
         [0027]    The present invention has been made in conjunction with the above problems and it is therefore an object of the invention to provide an exhaust valve capable of elevating compression efficiency by correctly opening an exhaust port.  
           [0028]    It is another object of the invention to provide a reciprocating compressor having the above exhaust valve.  
           [0029]    According to an aspect of the invention to obtain the above objects, it is provided an exhaust apparatus comprising: a guide connected in parallel to an exhaust port of a cylinder; a needle valve provided inside the guide for opening/shutting the exhaust port while moving in cooperation with the guide; and an electromagnet provided in the rear of the guide for controlling the needle valve.  
           [0030]    In the exhaust apparatus, the needle valve is preferably a permanent magnet.  
           [0031]    Preferably, the exhaust apparatus further comprises metallic materials having magnetism at both sides of the exhaust port for opening the exhaust port of the cylinder for a predetermined range, in which the predetermined range means a range where the electromagnet has a flux density larger than a critical flux density, and the critical flux density is determined from the attraction between the metallic materials and the needle valve.  
           [0032]    In the exhaust apparatus, the guide is connected in perpendicular to the exhaust port of the cylinder, and the electromagnet is provided in the rear of the guide when the guide is provided perpendicular to the exhaust port of the cylinder.  
           [0033]    According to another aspect of the invention to obtain the above objects, it is provided a reciprocating compressor comprising: a cylinder having a predetermined internal space; a piston for linearly reciprocating inside the cylinder; and exhaust means for exhausting fluid which is compressed due to linear reciprocation of the piston according to opening/shutting means moving corresponding to the flux density of an electromagnet.  
           [0034]    In the reciprocating compressor, the exhaust means may comprise: a guide connected in parallel or perpendicular to an exhaust port of the cylinder; and the electromagnet provided in the rear of the guide for controlling the opening/shutting means.  
           [0035]    In the reciprocating compressor, the opening/shutting means is preferably a permanent magnet.  
           [0036]    Preferably, the reciprocating compressor may further comprise an exhaust tube on one side of the guide for exhausting fluid and metallic materials having magnetism at both sides of the exhaust port of the cylinder for maintaining the attraction with the opening/shutting means when the guide is parallel to the exhaust port of the cylinder.  
           [0037]    Preferably, the reciprocating compressor may further comprise an exhaust tube parallel to the exhaust port of the cylinder and a metallic material having magnetism at one end of the guide for maintaining the attraction with the opening/shutting means when the guide is perpendicular to the exhaust port of the cylinder.  
           [0038]    In the reciprocating compressor, the intensity of the flux density of the electromagnet is varied proportionally to the displacement of the piston, and the flux density of the electromagnet takes place according to a current applied to the electromagnet.  
           [0039]    According to still another aspect of the invention to obtain the above objects, it is provided an exhaust apparatus comprising: a guide penetrating in parallel an exhaust port connected in parallel to an exhaust port of a cylinder; a needle valve provided inside the guide for opening/shutting the exhaust port while moving in cooperation with the guide; and an electromagnet provided in the rear of the guide for controlling the needle valve. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]    [0040]FIG. 1 is a schematic perspective view illustrating a conventional reciprocating compressor;  
         [0041]    [0041]FIGS. 2A to  2 D are schematic plan views illustrating a head cover, an exhaust valve, a valve plate and a suction valve, respectively, in a conventional reciprocating compressor;  
         [0042]    [0042]FIGS. 3A and 3B schematically illustrate the operation of an exhaust valve in a conventional reciprocating compressor;  
         [0043]    [0043]FIGS. 4A to  4 C illustrate a reciprocating compressor according to the first embodiment of the invention;  
         [0044]    [0044]FIG. 5 illustrates an opening range of an exhaust port of a cylinder according to the flux density of an electromagnet in a reciprocating compressor according to the first embodiment of the invention; and  
         [0045]    [0045]FIGS. 6A and 6B illustrate a reciprocating compressor according to the second embodiment of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0046]    The following detailed description will present preferred embodiments of the invention in reference to the accompanying drawings.  
         [0047]    [0047]FIGS. 4A to  4 C illustrate a reciprocating compressor according to the first embodiment of the invention, in which FIG. 4A shows a position where an exhaust port is shut, FIG. 4B shows a position where the exhaust port is shut, and FIG. 4C shows the relation between a permanent magnet and an electromagnet.  
         [0048]    Referring to FIGS. 4A and 4B, the reciprocating compressor has a cylinder  110  with a space therein, a piston  120  performing a linear reciprocating motion inside the cylinder  110  and an exhaust valve for exhausting fluid according to the linear reciprocating motion of the piston  120 . The exhaust valve connected in the direction of the linear reciprocating motion of the piston  120  has a guide  210  connected to an exhaust port  225  of the cylinder  110 , a needle valve  220  moving in cooperation with the guide  210  for opening/shutting the exhaust port  225  and an electromagnet  230  for controlling movement of the needle valve  220 . Preferably, the needle valve  220  is a permanent magnet.  
         [0049]    Describing the above in more detail, the cylinder  110  is a member having a column-shaped internal space in general with a suction port (not shown) and the exhaust port  225  provided at the closed end of the internal space for suction/exhaustion of fluid.  
         [0050]    The piston  120  is a member for linearly reciprocating in the internal space of the cylinder to compress fluid introduced into the cylinder  110 . Therefore, it is preferred that the piston  120  is cylindrically shaped so as to conform to the internal space of the cylinder  110 .  
         [0051]    Further, the piston  120  is provided at one end with a connecting rod  170  for linearly reciprocating the piston  120  and a crank shaft  180  connected to the connecting rod  170 .  
         [0052]    The exhaust valve has the needle valve  220  and the electromagnet  230  for moving the needle valve  220  as set forth above. The needle valve  220  may be made of a permanent magnet. The electromagnet  230  has an iron core  234  having a certain length and a coil  232  wound around the iron core  234  with a certain interval. Further, the exhaust valve is provided with the guide  210  which is so connected to the exhaust port  225  that the needle valve  220  may move.  
         [0053]    The guide  210  defines a non-magnetic linear space having a certain length connected to the exhaust port  225  and parallel to the cylinder  110 , in which the length is preferably longer than the length of the needle valve  220 . To a specific side region of the guide  210 , in particular, to a specific region of the internal space of the guide  210  which is defined when the needle valve  220  moves backward, is connected an exhaust tube  190 .  
         [0054]    The needle valve  220  is a member for opening/shutting the exhaust port  225  while moving in cooperation with the guide  210 , and preferably made of a permanent magnet having a certain degree of magnetism. The needle valve  220  has a diameter which is so large to cover the exhaust port  225  and a length which is determined considering the relation with the exhaust tube  190 . In other words, the needle valve  220  has such a length that the exhaust valve  225  may be opened when the needle valve  220  moves backwards in cooperation with the guide  210 .  
         [0055]    The electromagnet  230  is a member for having magnetism due to application of electricity, and positioned in the rear of the guide  210  (i.e. in the right of the guide  210  in the drawings) for reciprocating the needle valve  220  in the guide  210 . Positive (+) and negative (−) currents are alternatingly applied to the electromagnet  230  to change the polarity of the electromagnet.  
         [0056]    In this embodiment, the needle valve  220  has fixed poles such as S pole on the side of the electromagnet and N pole on the opposite side (i.e. on the side of the cylinder). Therefore, when the positive (+) current is applied to the left coil wound around the electromagnet  230 , a front portion of the electromagnet has N polarity. On the contrary, when the negative (−) current is applied to the left coil, the front portion of the electromagnet has S polarity.  
         [0057]    Therefore, if the front portion of the electromagnet has N polarity, the needle valve  220  is attracted toward the electromagnet  230 . If the front portion of the electromagnet has S polarity, the needle valve moves farther apart from the electromagnet.  
         [0058]    The operation of the reciprocating compressor according to the first embodiment of the invention will be described as follows: When AC power drives a motor, the crank shaft  180  accordingly performs a circular motion. The piston  120  moves forward in cooperation with the connecting rod  170  connected to the crank shaft  180  to compress fluid existing inside the cylinder  110 . When the piston  120  moves forward, positive (+) current is applied to the left coil of the electromagnet  230  to increase the flux density of the electromagnet. In this case, the flux density of the electromagnet increases in proportion of the degree of forward movement of the piston  120 .  
         [0059]    When the piston  120  moves for a certain degree, the flux density of the electromagnet exceeds the critical flux density, where the flux density of the electromagnet moves the needle valve  220  toward the electromagnet so as to open the exhaust port of the cylinder  110 . In order that the needle valve  220  may not move toward the electromagnet until the flux density of the electromagnet reaches the critical flux density, the exhaust port  225  of the cylinder  110  is preferably provided at both sides with metallic materials  215  having magnetism. Therefore, magnetic attraction acts between the metallic materials  215  and the needle valve  220  so that the needle valve may not move toward the electromagnet until the flux density of the electromagnet exceeds the critical flux density.  
         [0060]    In this case, the critical flux density is proportional to the attraction between the needle valve and the metallic materials. Therefore, the attraction between the needle valve and the metallic materials are adjusted so that a valve opening range where the flux density of the electromagnet is larger than the critical flux density may continue for a certain area.  
         [0061]    As the exhaust port  225  of the cylinder  110  is opened, fluid compressed in the cylinder  110  is exhausted to the outside via the exhaust tube  190  formed in the side of the guide  210 .  
         [0062]    In the meantime, as the crank shaft  180  performs the circular motion beyond the top dead point, the piston  120  accordingly moves backward. Further, as the positive (+) current applied to the electromagnet decreases, the flux density of the electromagnet also decreases. At the moment that the flux density of the electromagnet decreases to or under the critical flux density, the needle valve  220  moved toward the electromagnet moves backward to the cylinder  110  due to attraction to the metallic materials installed in the opposite direction so as to shut the exhaust port  225 .  
         [0063]    [0063]FIGS. 6A and 6B illustrate a reciprocating compressor according to the second embodiment of the invention, in which FIG. 6A shows a position where an exhaust port is shut, and FIG. 6B shows a position where the exhaust port is opened. In the second embodiment of the invention, description of those portions same or similar to the first embodiment shown in FIG. 4 will be omitted in order to avoid repetition.  
         [0064]    Referring to FIGS. 6A and 6B, it can be seen that a guide  240  is installed with an angle different from that of the guide shown in FIGS. 4A and 4B. In other words, the guide  210  is installed parallel to the cylinder  110  in FIGS. 4A and 4B, whereas the guide  240  is installed perpendicular to the cylinder  110  in FIGS. 6A and 6B. Preferably, an exhaust tube  190  is installed parallel to the cylinder  110 . The guide  240  is installed perpendicular to the exhaust tube  190  at a certain distance from the exhaust tube  190  connected in parallel to the exhaust port  252  of the cylinder, and has a project  242  in the opposite of an electromagnet  260  for assisting the exhaust tube  190  to be completely shut. The guide project  242  is preferably attached with a metallic material  245  having magnetism for inducing attraction between the guide project  242  and the needle valve  250 .  
         [0065]    Further, in the opposite of the guide project  242 , is provided an electromagnet  260  and a needle valve  250  which is moved into the guide  240  by the electromagnet  260 .  
         [0066]    According to the above configuration, the pressure due to fluid existing inside the cylinder and applied to the needle valve in FIGS. 4A and 4B does not interfere movement of the needle valve as the needle valve  250  is installed perpendicular to the cylinder  110 .  
         [0067]    As set forth above, the exhaust valve of the invention has the needle valve together with the guide and the electromagnet for assisting the needle valve to open/shut the exhaust port of the cylinder so that the exhaust port of the cylinder can be completely opened in exhaustion, thereby reducing degradation of compression efficiency due to valve damage and generation of vibration noise.  
         [0068]    Further, the movement of the piston and the flux density of the electromagnet are adjusted so that the exhaust port of the cylinder can be opened thereby complementing damage due to overshooting.  
         [0069]    The exhaust valve described in the invention is simple with configuration and operation so as to be applied to all devices requiring suction and exhaust procedures thereby maximizing the range of application thereof.