Abstract:
A reciprocating compressor is provided, a size of which may be reduced by closely attaching and securing a reciprocating motor and a cylinder of a compression device to a sealed receptacle to reduce a gap between a main body of the compressor and the sealed receptacle. In addition, an assembling process for the compressor may be simplified by separating a mover of the reciprocating motor and a piston of the compression device from each other. In addition, vibration of the sealed receptacle may be minimized by properly adjusting a mass of components in the reciprocating motor and the compression device, and elasticity of a spring that supports the reciprocating motor and the compression device to offset a force applied to the sealed receptacle. In addition, efficiency of the reciprocating motor may be enhanced by increasing a relative velocity of the reciprocating motor in comparison with a relative velocity of the compression device.

Description:
BACKGROUND 
     1. Field 
     The present invention relates to a reciprocating compressor and, more particularly, to a reciprocating compressor using vibration. 
     2. Background 
     In general, a reciprocating compressor is a compressor in which a piston linearly reciprocates within a cylinder to suck, compress, and discharge a refrigerant. The reciprocating compressor may be classified into a connection type reciprocating compressor and a vibration type reciprocating compressor according to a piston driving method. 
     In the connection type reciprocating compressor, a piston is connected to a rotational shaft of a rotary motor by a connecting rod and reciprocates within a cylinder to compress a refrigerant. Meanwhile, in the vibration type reciprocating compressor, a piston is connected to a mover of a reciprocating motor which reciprocates, so as to vibrate together and reciprocate to compress a refrigerant. The present invention relates to a vibration type reciprocating compressor, and hereinafter, the vibration type reciprocating compressor will be referred to as a reciprocating compressor. 
     In the reciprocating compressor, the piston and the cylinder relatively reciprocate in a magnetic flux direction of the reciprocating motor to repeatedly perform a sequential process of sucking, compressing, and discharging a refrigerant. 
     However, in the related art reciprocating compressor, a compressor main body comprised of a reciprocating motor and a compression unit is installed to vibrate in a horizontal direction in an internal of an airtight container and supported by a support spring as a coil spring. Namely, a predetermined space is required for the compressor main body to be supported by the support spring between the airtight container and the compressor main body, increasing a size of the compressor. 
     Also, in the related art reciprocating compressor, since the mover of the reciprocating motor and the piston of the compression unit are combined to be assembled, concentricity of the mover and the piston should be consistent, making an assembly process of the compressor complicated as much. 
     In addition, in the related art reciprocating compressor, since the support spring is connected to a stator of a reciprocating motor and a cylinder of a compression unit and fixed in the airtight container, vibration of the reciprocating motor and that of the compression unit are transmitted to the airtight container as is to increase compressor vibration. 
     Also, in the related art reciprocating compressor, a stator of the reciprocating motor is integrally coupled to the cylinder of the compression unit or connected by a resonance spring, and a mover of the reciprocating motor is integrally connected to the piston of the compression unit, and thus, a velocity of the reciprocating motor and a relative velocity of the compression unit are equal. As a result, there is a limitation in increasing a velocity of the reciprocating motor, degrading compressor efficiency. 
     Therefore, an object of the present invention is to provide a reciprocating compressor reduced in size by reducing a space between a compressor main body and an airtight container. 
     Another object of the present invention is to provide a reciprocating compressor in which a mover and a piston of a compression unit are easily assembled to thus simplify an assembly process of the compressor. 
     Another object of the present invention is to provide a reciprocating compressor in which compressor vibration is attenuated by offsetting vibration of a reciprocating motor and vibration of a compression unit. 
     Another object of the present invention is to provide a reciprocating compressor in which a velocity of a reciprocating motor is increased by differently controlling a relative velocity of a reciprocating motor and a relative velocity of a compression unit, thus enhancing compressor efficiency. 
     SUMMARY 
     According to an aspect of the present invention, there is provided a reciprocating compressor including: an airtight container; a reciprocating motor including a stator fixed within the airtight container and a mover reciprocating in an air gap of the stator; a piston separated from the mover, elastically supported in the airtight container and making a reciprocal motion (or reciprocates); and a cylinder coupled within the airtight container such that it is spaced apart from the reciprocating motor and allowing the piston to be inserted therein to form a compression space. 
     According to another aspect of the present invention, there is provided a reciprocating compressor including: an airtight container communicating with a suction pipe and a discharge pipe; a reciprocating motor including stators fixed to the airtight container and a mover making a reciprocal movement with respect to the stator; a cylinder fixedly coupled within the airtight container; a piston slidably inserted into the cylinder to compress a refrigerant sucked into an internal space of the airtight container; a first resonance spring elastically supporting the mover with respect to the airtight container to induce a resonant motion of the mover; and a second resonance spring elastically supporting the piston with respect to the airtight container to induce a resonant motion of the piston. 
     In the case of the reciprocating compressor according to embodiments of the present invention, since the stators of the reciprocating motor and the cylinder of the compression unit are tightly attached and fixed to the airtight container, a space between the compressor main body and the airtight container is reduced to reduce a size of the compressor. In addition, since the cylinder of the compression unit is tightly attached to the airtight container, a pipe such as a loop pipe is not required, reducing fabrication cost. 
     Also, since the mover of the reciprocating motor and the piston of the compression unit are separated, there is no need to make concentricity of the mover and the piston consistent, simplifying an assembly process of the compressor. Besides, since vibration of the reciprocating motor is transmitted to the compression unit through the airtight container, vibration of the airtight container can be attenuated. 
     Also, force applied to the airtight container can be offset by appropriately adjusting a mass of the stator of the reciprocating motor, and stiffness of the supporting spring, and a mass of the mover of the reciprocating motor, a mass of the piston of the compression unit, and stiffness of the resonance spring, whereby vibration of the airtight container can be minimized. 
     Also, a relative velocity of the reciprocating motor can be adjusted to be faster than that of the compression unit, thereby increasing motor efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a vertical sectional view illustrating an example of a reciprocating compressor according to an embodiment of the present invention; 
         FIG. 2  is a vertical sectional view illustrating a portion of the reciprocating motor in the reciprocating compressor of  FIG. 1 ; 
         FIG. 3  is a schematic view illustrating a structure of the reciprocating compressor of  FIG. 1 ; 
         FIG. 4  is a graph showing a mechanical loss and motor efficiency of the reciprocating motor of  FIG. 1 ; and 
         FIG. 5  is a vertical sectional view illustrating an example of a reciprocating compressor according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a reciprocating compressor will be described in detail with reference to a reciprocating compressor illustrated in the accompanying drawings. 
       FIG. 1  is a vertical sectional view illustrating an example of a reciprocating compressor according to an embodiment of the present invention.  FIG. 2  is a vertical sectional view illustrating a portion of the reciprocating motor in the reciprocating compressor of  FIG. 1 .  FIG. 3  is a schematic view illustrating a structure of the reciprocating compressor of  FIG. 1 ; 
     Referring to  FIG. 1 , in the reciprocating compressor according to an embodiment of the present invention, a gas suction pipe  110  and a gas discharge pipe  120  are formed to be connected to both ends of an airtight container  100 , a reciprocating motor  200 , which linearly reciprocates, is installed within the airtight container  100 , and a compression unit  300 , in which a piston  320  separated from a mover  230  of the reciprocating motor  200  independently reciprocates with respect to the mover  230  to compress a refrigerant, is installed to be spaced apart from the reciprocating motor  200  within the airtight container  100 . 
     The airtight container  100  is elastically supported by an installation surface on which the airtight container  100  is mounted, such that it may be able to vibrate in a motion direction of the mover  230 , and the gas suction pipe  110  and the gas discharge pipe  120  are connected to both sides of the airtight container such that the gas suction pipe  110  and the gas discharge pipe  120  communicate therewith. An end of the gas suction pipe  110  is connected to communicate with an internal space  130  of the airtight container  100 , and an end of the gas discharge pipe  120  is directly connected to a discharge cover  360  (to be described). 
     A first spring supporter  140  and a second spring supporter  150  are integrally formed to be spaced apart by a certain interval on both sides of an inner circumferential surface of the airtight container  100  in order to support ends of resonance springs  251 ,  252 ,  361  and  362  elastically supporting the mover  230  (to be described) and the piston  320 . 
     The reciprocating motor  200  includes an outer stator  210  having a coil  211  and fixed to the airtight container  100 , an inner stator  220  installed at an inner side of the outer stator  210  with an air gap having a certain space present therebetween and fixed to the airtight container  100  together with the outer stator  210 , and a mover  230  linearly reciprocating between the outer stator  210  and the inner stator  220 . 
     The outer stator  210  and the inner stator  220  may have an air gap formed in both sides based on the coil  211 . In this case, however, magnetic flux generated by the coil  211  and the magnet  232  may be leaked to the outside of the stators and the magnet  232  is lengthened to increase fabrication cost. Thus, the outer stator  210  and the inner stator  220  may be formed to have a so-called 1-pole 2-gap configuration in which one sides thereof are connected based on the coil  211  and the other sides thereof have an air gap. 
     For example, the stator includes the outer stator  210  having the coil  211  and having a cylindrical shape and the inner stator  220  disposed at an inner side of the outer such that one side thereof is connected with the outer stator  210  and the other side thereof is disposed with a certain air gap, based on the coil  211 , as shown in  FIG. 2 . 
     Since the annular coil is required to be installed at an inner side of the stator, the outer stator  210  and the inner stator  220  may have a channel-like shape and a straight line shape, separately, rather than being integrally formed, and assembled through welding, or the like. 
     The mover  230  includes a cylindrical magnet holder  231 , and a plurality of magnets  232  are fixedly coupled to an outer circumferential surface of the magnet holder  231 . A mover side supporter  240  is coupled to one end of the magnet holder  231 , and a first motor side resonance spring  251  and a second motor side resonance spring  252  are installed in both sides of the mover side supporter  240 . The other ends of the first motor side resonance spring  251  and the second motor side resonance spring  252  are fixed to one sides of the first spring supporter  140  and the second spring supporter  150  of the airtight container  100 . 
     The motor side resonance springs  251  and  252  may be configured as a single compression coil spring or may be configured as a plurality of compression coil springs in a circumferential direction according to circumstances. 
     The compression unit  300  includes a cylinder  310  fixedly coupled to an inner circumferential surface of the airtight container  100 , a piston  320  coupled to the mover  230  of the reciprocating motor  200  and reciprocating in a compression space  311  of the cylinder  310 , a suction valve  330  installed in a front end of the piston  320  to open and close a suction flow channel  321  of the piston  320  and opening and closing a suction side of the compression space  311 , a discharge valve  340  detachably installed in the cylinder  310  to open and close a discharge side of the compression space  311 , and a valve spring  350  elastically supporting the discharge valve  340 . 
     The cylinder  310  is fixed such that an outer circumferential surface thereof is tightly attached to an inner surface of the airtight container  100 . The compression space  311  having an annular shape is formed in a central portion of the cylinder  310 , and a discharge space  312  accommodating the discharge valve  340  and the valve spring  350  therein is formed in a row at an outer side of the compression space  311 . The as discharge pipe  120  is directly connected to the discharge space  312  in a communicating manner and hermetically sealed. 
     The piston  320  is formed to have a cylindrical shape to form the suction flow channel  321  therein. A plurality of suction through holes  322  may be formed on an outlet of the suction flow channel  321  such that they communicate with the suction flow channel  321 . A piston stopper  323  is coupled to one end of the piston  320 , and a first compression unit side resonance spring  361  and a second compression unit side resonance spring  362  are installed in both sides of the piston stopper  323 , respectively. The other ends of the first compression unit side resonance spring  361  and the second compression unit side resonance spring  362  are fixedly coupled to the other ends of the cylinder  310  and the second spring stopper  150 . 
     The compression unit side resonance springs  361  and  362  may be configured as a single compression coil spring or may be configured as a plurality of compression coil springs in a circumferential direction according to circumstances. 
     The reciprocating compressor according to an embodiment of the present invention operates as follows. 
     Namely, as illustrated in  FIG. 3 , when power is applied to the coil  211  of the reciprocating motor  200 , magnetic flux is formed between the outer stator  210  and the inner stator  220 . Then, the mover  230  placed in the air gap between the outer stator  210  and the inner stator  220  moves in the direction of the magnetic flux and continuously reciprocates by the resonance springs  251  and  252 . 
     Then, primary vibration is generated according to the reciprocating motion of the mover  230 , and the primary vibration is transmitted to the airtight container  100 . 
     Then, upon receiving the primary vibration through the airtight container  100 , the piston  320  generates secondary vibration in a state of being elastically supported by the compression unit side resonance springs  361  and  362  and reciprocates. The piston  320  continuously reciprocates to compress a refrigerant to discharge the compressed refrigerant to a refrigerating cycle system. This sequential operation is repeatedly performed. 
     Here, force applied to the airtight container may be offset by appropriately adjusting a mass of the stator of the reciprocating motor and stiffness of the motor side resonance springs, and a mass of the mover of the reciprocating motor, a mass of the piston of the compression unit, and stiffness of the compression unit side resonance springs, whereby vibration of the airtight container can be minimized. In addition, since reciprocating motor and the compression unit serves as a mutual dynamic damper by the medium of the airtight container, vibration of the reciprocating motor can be attenuated. 
     Also, since the stators of the reciprocating motor has a displacement, a relative displacement of the mover and the stators of the reciprocating motor and a relative displacement of the piston and the cylinder of the compression unit differ. By using such characteristics, a relative velocity of the reciprocating motor may be adjusted to be higher than a relative velocity of the compression unit, and such characteristics increase motor efficiency at a low velocity as shown in  FIG. 4 , and thus, motor efficiency can be increased, while reducing an input loss of the motor, on the whole. 
     Also, by tightly attaching and fixing the stators of the reciprocating motor and the cylinder of the compression unit to the airtight container, a space between the compressor main body and the airtight container may be reduced to reduce the size of the compressor. In addition, since the cylinder of the compression unit is tightly attached to the airtight container, there is no need to install a pipe such as a loop pipe having elasticity for sending a compressed refrigerant to the cycle, and thus, fabrication cost can be reduced. 
     Meanwhile, a reciprocating motor according to another embodiment of the present invention will be described. 
     Namely, in the foregoing embodiment, the mover of the reciprocating motor is supported by the resonance spring, but in the present embodiment, the mover  230  is installed to be able to reciprocate in an air gap between the outer stator  210  and the inner stator  220  such that the mover  230  can reciprocate in a free state. 
     In this case, a basic configuration and operational effect of the reciprocating compressor according to the present embodiment are similar to those of the foregoing embodiment, so a detailed description thereof will be omitted. However, in the present embodiment, the mover  230  is placed in the air gap in a free state and reciprocates according to magnetic flux. Thus, in order for the mover  230  to smoothly reciprocate, preferably, the stator of the reciprocating motor  200  is formed to have a so-called ‘1-pole 2-gap’ configuration as in the foregoing embodiment. 
     In addition, in the present embodiment, motor side resonance springs for elastically supporting the mover  230  and a spring supporter, a spring supporter for supporting the motor side resonance springs, and a mover side supporter are not required, and thus, fabrication cost can be reduced relative to the foregoing embodiment. 
     Also, although not shown, the stator of the reciprocating motor may be formed to have a 2-pole 2-gap configuration in which air gaps are formed in both sides of the motor.