RECIPROCATING COMPRESSOR

Abstract

A reciprocating compressor according to the present invention includes a stator disposed in an inner space of a shell, and having a stator core with at least one air gap, and a coil fixed to the stator core, a piston mechanically connected with a magnet, and reciprocating by magnetic energy generated in the stator and interaction with the magnet, a cylinder having the piston inserted therein and forming a compression space, a suction valve opening/closing a suction side of the compression space, a discharge valve opening/closing a discharge side of the compression space, and an electromagnetic resonance spring formed between the stator and the magnet by a restoring force generated by the magnetic energy.

Claims

1. A reciprocating compressor comprising: a shell having an inner space; at least one stator disposed in the inner space of the shell, and provided with a stator core having at least one air gap, and a coil fixed to the stator core and generating magnetic energy in response to power applied; a mover provided with a magnet and reciprocating with respect to the stator; a piston mechanically connected with the mover, and reciprocating by the magnetic energy generated in the stator and interaction with the magnet; a cylinder having the piston inserted therein and forming a compression space; a suction valve opening and closing a suction side of the compression space; a discharge valve opening and closing a discharge side of the compression space; and an electromagnetic resonance spring formed between the stator core and the magnet by a restoring force generated by the magnetic energy.

2. The reciprocating compressor of claim 1, wherein the electromagnetic resonance spring generates a difference of a magnetic level generated between the stator core and the magnet while the magnet moves according to a current supplied to the coil, such that the magnet resonates, in response to a force generated toward a side with a low magnetic level.

3. The reciprocating compressor of claim 2, wherein the stator comprises an outer core disposed at an outer side and an inner core disposed at an inner side based on an air gap therebetween, and wherein the magnet is disposed to be movable between the outer core and the inner core.

4. The reciprocating compressor of claim 2, wherein the stator comprises an outer core disposed at an outer side and an inner core disposed at an inner side based on an air gap therebetween, and wherein the magnet is coupled to the outer core or the inner core so as to be movable along with the coupled outer core or inner core.

5. The reciprocating compressor of claim 1, wherein an electromagnetic center of the magnet is located more eccentric toward the compression space than an electromagnetic center of the stator.

6. The reciprocating compressor of claim 5, wherein the magnet is configured such that N-pole and S-pole are arranged by at least one, respectively, along a reciprocating direction of the piston, and wherein the magnet is located such that a contact point between different poles is more eccentric toward the compression space than the electromagnetic center of the stator.

7. The reciprocating compressor of claim 1, wherein the stator has air gaps at both sides of the coil, and wherein a center of the magnet is located more eccentric toward the compression space than a center of the coil.

8. The reciprocating compressor of claim 1, wherein the stator has one air gap at one side of the coil and another side of the coil forms a magnetic path, and wherein a center of the magnet is located more eccentric toward the compression space than a center of a pole portion forming the air gap.

9. The reciprocating compressor of claim 1, wherein a maximum stroke range of the piston is within a displacement at which the restoring force has an inflection point.

10. The reciprocating compressor of claim 1, wherein the electromagnetic resonance spring is provided in plurality, the plurality of electromagnetic resonance springs being arranged along the reciprocating direction of the piston.

11. The reciprocating compressor of claim 1, wherein magnets having the same pole are provided in a facing manner at one side surface of the piston in the reciprocating direction of the piston and a member corresponding to the piston, respectively.

12. A reciprocating compressor comprising: a stator provided with a stator core having at least one air gap and a coil generating magnetic energy; a mover provided with a magnet and reciprocating with respect to the stator; a cylinder having an accommodation space therein; and a piston coupled to the mover, forming a compression space along with the cylinder, and performing a resonant motion as the magnet receives a restoring force generated due to a difference of a magnetic level generated in the air gap of the stator core.

13. The reciprocating compressor of claim 12, wherein a maximum stroke range of the piston is within a displacement at which the restoring force has an inflection point.

14. A reciprocating compressor comprising a stator provided with a stator core having at least one air gap, and a coil generating magnetic energy along with the stator core, a mover provided with a magnet and reciprocating with respect to the stator, and a piston coupled to the mover, wherein the magnet generates a magnetic level along with the stator core and performs a resonant motion along with the piston by a restoring force generated toward a side with a low magnetic level, wherein a second position of the piston is located more eccentric toward the compression space than a first position of the piston, under assumption that a point where an electromagnetic center of the magnet and an electromagnetic center of the stator match each other is referred to as the first position and a position of the piston in an assembled or stopped state is referred to as the second position.

15. The reciprocating compressor of claim 14, wherein a maximum stroke range of the piston is within a displacement at which the restoring force has an inflection point.

16. The reciprocating compressor of claim 14, wherein the stator comprises an outer core disposed at an outer side and an inner core disposed at an inner side based on an air gap therebetween, and wherein the magnet is disposed to be movable between the outer core and the inner core.

17. The reciprocating compressor of claim 14, wherein the stator comprises an outer core disposed at an outer side and an inner core disposed at an inner side based on an air gap therebetween, and wherein the magnet is coupled to the outer core or the inner core so as to be movable along with the coupled outer core or inner core.

18. The reciprocating compressor of claim 14, wherein magnets having the same pole are provided in a facing manner at one side surface of the piston in the reciprocating direction of the piston and a member corresponding to the piston, respectively.

19. The reciprocating compressor of claim 12, wherein magnets having the same pole are provided in a facing manner at one side surface of the piston in the reciprocating direction of the piston and a member corresponding to the piston, respectively.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG. 1 is a sectional view of a reciprocating compressor according to the related art.

[0040] FIG. 2 is a longitudinal sectional view of a reciprocating compressor in accordance with the present invention.

[0041] FIG. 3 is a longitudinal sectional view of a reciprocating motor in the compressor according to FIG. 2.

[0042] FIGS. 4 to 9 are conceptual views illustrating effects of an electromagnetic resonance spring according to a flowing direction of a flux in the compressor according to FIG. 2.

[0043] FIG. 10 is a graph illustrating strength of a magnetic spring force for a position of a magnet.

[0044] FIGS. 11 to 15 are conceptual views illustrating effects of an electromagnetic resonance spring with respect to a 2 pole-1 gap structure in a reciprocating compressor in accordance with the present invention.

[0045] FIG. 16 is a longitudinal sectional view illustrating an apparatus of assembling a magnet in a manner of being eccentric toward a compression space by using a magnetic force in a reciprocating compressor in accordance with the present invention.

[0046] FIG. 17 is a longitudinal sectional view illustrating an assembled state that a magnet is eccentric toward a compression space by using a magnetic force when there are a plurality of stators, in a reciprocating compressor in accordance with the present invention.

MODES FOR CARRYING OUT THE PREFERRED EMBODIMENTS

[0047] Hereinafter, description will be given in detail of a reciprocating compressor in accordance with one embodiment of the present invention illustrated in the accompanying drawings.

[0048] FIG. 2 is a longitudinal sectional view of a reciprocating compressor in accordance with the present invention, and FIG. 3 is a longitudinal sectional view of a reciprocating motor in the compressor according to FIG. 2.

[0049] As illustrated in FIGS. 2 and 3, in a reciprocating compressor according to the present invention, a suction pipe 112 may be connected to an inner space 111 of a hermetic shell 110, and a discharge pipe 123 through which a refrigerant compressed in a compression space 141 of a cylinder 140 to be explained later is guided into a refrigeration cycle may be disposed at one side of the suction pipe 112. Accordingly, the inner space 111 of the shell 110 may generate suction pressure by being filled with a refrigerant of suction pressure, and a refrigerant discharged from the compression space 141 may be discharged directly out of the shell 110 toward a condenser.

[0050] A frame 120 may be installed in the inner space 111 of the shell 110 by being elastically supported by a plurality of supporting springs 171 and 172. A reciprocating motor 130 may be fixed to one side surface of the frame 120. The reciprocating motor 130 may generate a reciprocating force and simultaneously induce a resonant motion of a piston 150 to be explained later.

[0051] The cylinder 140 which has the compression space 141 therein and is inserted into a front frame 121 of the frame 120 may be coupled at an inner side of the reciprocating motor 130. The piston 150 which compresses a refrigerant by varying a volume of the compression space 141 of the cylinder 140 may be inserted into the cylinder 140 to reciprocate in the cylinder 140.

[0052] A suction valve 152 opening and closing a suction passage 151 of the piston 150 may be coupled to a front end surface of the piston 150, and a discharge valve 142 opening and closing the compression space 141 of the cylinder 140 may be detachably coupled to a front end surface of the cylinder 140 in a manner of being covered with a discharge cover 160.

[0053] The discharge cover 160 may be provided with a discharge space 161 and fixed to the cylinder 140. The discharge valve 142 and a valve spring 143 supporting the discharge valve 142 may be accommodated in the discharge space 161. The discharge cover 160 may be coupled with the discharge pipe 113 such that the discharge space 161 and a condenser can be directly connected to each other through the discharge pipe 113.

[0054] The reciprocating motor 130 may include an outer stator 131, an inner stator 132, and a mover 133 performing a reciprocating motion in an air gap between the outer stator 131 and the inner stator 132.

[0055] The outer stator 131 may be coupled between the front frame 121 and a rear frame 122 to configure a part of a stator core. An annular coil 135 may be coupled to the outer stator 131. The coil 135 may alternatively be coupled to the inner stator 132.

[0056] The inner stator 132 may be disposed within the outer stator 131 with a predetermined gap 134 from the outer stator 131. The inner stator 132 may be coupled between both of the frames 121 and 122 to configure another part of the stator core.

[0057] The mover 133 may be disposed in the air gap 134 between the outer stator 131 and the inner stator 132. A magnet 136 corresponding to the coil 135 may be provided such that the mover 133 can perform a reciprocating motion in a flowing direction of a magnetic flux induced by the magnet 136 and the coil 135.

[0058] Here, a structure of the reciprocating motor 130 may be implicitly defined according to a number of the magnet and a number of air gaps between the outer stator and the inner stator. For example, a 3 pole-2 gap structure refers to a structure in which three magnets 136a, 136b and 136c are arranged between two air gaps to alternately have opposite poles in a reciprocating direction, and 2 pole-1 gap structure refers to a structure in which two magnets are arranged in one air gap to have opposite polarities in a reciprocating direction.

[0059] As illustrated in FIG. 3, for the 3 pole-2 gap structure, the outer stator 131 may have a cross section like having a first pole portion 131a and a second pole portion 131b at both ends thereof. The inner stator 132 may have a cross section like | having a length corresponding to a length between outer ends of the both pole portions 131a and 131b in a radial direction. Both ends of the inner stator 132 may also form a first pole portion 132a and a second pole portion 132b. Accordingly, the outer stator 131 and the inner stator 132 may form gaps 134a and 134b (hereinafter, a front side close to the compression space may be referred to as a first gap, and a rear side may be referred to as second gap), respectively, at both sides in a reciprocating direction (front and rear directions) based on the coil 135.

[0060] It may be preferable that inner ends P1 and P2 of the pole portions 131a and 131b of the outer stator 131 are arranged close to each other in the aspects of minimizing a length of the magnet 136 and maximizing a gap length of the outer stator 131. Therefore, the pole portions 131a and 131b of the outer stator 131 may extend in an inclined manner such that the inner ends P1 and P2 extends toward the coil 135. In this instance, since the coil 135 is formed in the annular shape, the outer stator 131 may be formed in the shape of by combining a shape of with a shape of a reverse or by combining a shape of with a shape of .

[0061] The magnet 136 may be formed in a shape of a rectangular plate which has predetermined length and width and also has an arcuate cross section upon projected from a front side, thus to be coupled to an outer circumferential surface or an inner circumferential surface of a magnet holder 137, or have a cylindrical section to be inserted to the outer circumferential surface or the inner circumferential surface of the magnet holder 137.

[0062] The length of the magnet 136 in the reciprocating direction may be longer than the length of the outer stator 131 in the reciprocating direction. The magnet 136 may be configured to have one pole along the reciprocating direction. However, to increase a resonance spring effect by using the magnet, a plurality of poles may preferably be arranged in an alternating manner along the reciprocating direction so as to increase magnetic energy.

[0063] FIG. 3 illustrates an example in which the three magnets 136a, 136b and 136c are arranged to have different poles along the reciprocating direction. In this instance, one of an N-pole magnet and an S-pole magnet may be configured such that a length thereof in the reciprocating direction is longer than or equal to a stroke length of the piston 150 on the basis of an outer circumferential surface of the magnet 136. This may extend a range that the magnetic energy is applied to the magnet 136, thereby increasing a resonance-allowable range.

[0064] For example, as illustrated in FIG. 4, in case of arranging the magnets in an alternating order of S-N-S pole based on their outer circumferential surfaces, a sum of cross sections of both side magnets 136a and 136c (hereinafter, a left magnet is referred to as a first magnet, and a right magnet is referred to as a third magnet) may be the same as a cross section of a middle magnet 136b (hereinafter, referred to as a second magnet). A total length of the first and third magnets 136a and 136c or a length of the second magnet 136b may be longer than or equal to the stroke length of the piston 150. If the length of the magnet is shorter than the stroke length, the magnet may easily be deviated out of a range of an attractive magnetic force of the reciprocating motor. This may drastically lower a centering force of the coil and the core in the reciprocating direction, which is generated by the attractive magnetic force, which may interfere with a smooth reciprocating motion. Of course, in case where a total length of the magnets is shorter than an interval between both gaps, the magnets may not be deviated from the range of the attractive magnetic force even though the length of the magnets is shorter than the length of the stroke, but the magnetic fluxes may offset each other. This may cause an increase in an amount of unavailable magnetic flux, thereby lowering the centering force in the reciprocating direction.

[0065] The magnet 136 may preferably be configured such that a number of poles thereof can be the same as or at least one more than a number of the gap 134 of the stator core. If the number of poles of the magnet 136 is smaller than the number of the gap 134 of the stator core, it may be difficult to transfer the flux to the magnet 136 from at least one gap 134. Accordingly, an amount of invalid flux may increase, thereby lowering efficiency of the compressor.

[0066] And, the magnet 136 may preferably be configured such that contact points P3 and P4 between different poles belong to a range of the first gap 134a and the second gap 134b. More preferably, the contact point P3, P4 may be located to match a center of the air gap 134a, 134b, namely, a center of the stator pole portion so as to increase efficiency of the motor.

[0067] However, it may be more preferable that the contact point between the different poles of the magnet 136 is located to be slightly eccentric from the center of the pole portion 131a, 131b toward the compression space 141. This may compensate for a pushed amount of the piston 150 in advance, considering that the piston is pushed away from the compression space 141 by gas force, which is generated in the compression space during an operation. This may allow the piston 150 to always perform a stroke up to a top dead point.

[0068] To this end, the reciprocating motor 130 may be asymmetrically controlled such that an electromagnetic center of the magnet 136 is eccentric more toward the compression space 141 than the electromagnetic center of the stator 131, 132, or the cylinder 140 may be configured to be eccentric in a direction getting away from the compression space 141, considering the gas force. In case where the cylinder 140 is located eccentric, if a state that a stroke of the piston is symmetric in left and right directions based on the electromagnetic center of the stator is a first state and a left/right asymmetric state is a second state, the cylinder 140 may be located such that an end surface of the cylinder 140 is located closer to the stator than the position illustrated in FIG. 2 in the second state.

[0069] Here, the electromagnetic center of the magnet 136 may be a center of the middle second magnet, and the electromagnetic center of the stator may be a center of the coil. This may also be applied to the piston 150. If a matching point between the electromagnetic center of the magnet 136 and the electromagnetic center of the stator is referred to as a first position of the piston 150 and a position of the piston 150 in an assembled or stopped state is referred to as a second position of the piston 150, the second position of the piston 150 may be located more eccentric toward the compression space 141 than the first position of the piston 150.

[0070] For example, as illustrated in FIG. 3, the contact point P3 (also, P4) between the first magnet 136a and the second magnet 136b may be controlled to be located eccentric more toward the compression space 141 by a predetermined interval t1 than a center O of the first pole portion 131a corresponding to the contact point P3, or a center O of the second magnet 136b may be controlled to be located more eccentric toward the compression space 141 by a predetermined interval t2 than a center O of the stator core.

[0071] Meanwhile, the foregoing embodiment has exemplarily illustrated that the pole portions are formed only at both ends of the outer stator 131. However, a multi gap structure in which at least three pole portions are formed along a reciprocating direction and coils are disposed between adjacent pole portions may also be employed. Even in this instance, the center of the magnet may preferably be located more eccentric toward the compression space than the center of the pole portion.

[0072] Hereinafter, an operation of the reciprocating compressor according to this exemplary embodiment will be described.

[0073] That is, when an alternating current (AC) is applied to the coil 135 of the reciprocating motor 130, an alternating magnetic flux is generated between the outer stator 131 and the inner stator 132. The magnet 136 of the mover 133 which is placed in the gap between the outer stator 131 and the inner stator 132 then continuously reciprocates while moving along a flowing direction of the magnetic flux. Accordingly, the piston 140 coupled to the mover 133 sucks and compresses a refrigerant while reciprocating within the cylinder 140. The compressed refrigerant then opens the discharge valve in a pushing manner so as to be discharged into the discharge space 161. Such series of processes are repeatedly performed.

[0074] In this instance, while the magnet 136 reciprocates within the reciprocating motor 130, an electromagnetic resonance spring may be generated between the magnet 136 and the stator core, thereby inducing a resonant motion of the mover 133 and the piston 150. This may allow the piston 150 to compress the refrigerant by resisting the gas force generated in the compression space 141.

[0075] FIGS. 4 to 9 are conceptual views illustrating effects of an electromagnetic resonance spring based on a flowing direction of a flux in the compressor according to FIG. 2. FIGS. 4 and 5 are conceptual views illustrating a resonant motion of the magnet (piston) when a current flows in a clockwise direction, FIGS. 6 to 8 are conceptual views illustrating a resonant motion of the magnet (piston) when the current flows in a counterclockwise direction, and FIG. 9 is a conceptual view illustrating a resonant motion of the magnet (piston) when the current flows back in the clockwise direction. For reference, FIG. 3 illustrates an example in which the magnet is eccentric toward the compression space, but FIGS. 4 to 9 illustrate an example in which the center of the magnet matches the center of the stator without being eccentric, for the sake of explanation.

[0076] As illustrated in FIG. 4, when a flux which is generated in the outer stator 131 and the inner stator 132 in a direction of a current flowing along the coil 135 flows in a clockwise direction, namely, a direction A, the left first pole portion 132a of the inner stator 132 forms an N-pole and the right second pole portion 132b forms an S-pole, whereas the left first pole portion 131a of the outer stator 131 forms the S-pole and the right second pole portion 131b forms the N-pole. Accordingly, the first magnet 136a which has an inner circumferential surface with the N-pole and an outer circumferential surface with the S-pole and is located at a left end generates a repulsive force against the left pole portions 131a and 132a of the outer stator 131 and the inner stator 132. On the other hand, the second magnet 136b which has an inner circumferential surface with the S-pole and an outer circumferential surface with the N-pole and is located at the middle portion generates an attractive force with the left pole portions 131a and 132a of the stator 131, 132 and a repulsive force against the right pole portions 131b and 132b. Also, the third magnet 136c which has an inner circumferential surface with the N-pole and an outer circumferential surface with the S-pole and is located at the right end generates an attractive force with the right pole portions 131b and 132b of the stator 131, 132. Accordingly, the magnet 136 which has been located at the center of the stator 131, 132 may be moved to left in the drawing of FIG. 5, due by a force F1, which is applied in a direction (a) (a direction toward a top dead point or a forward direction), as illustrated in FIG. 5, by the flowing direction of the flux and the magnetic flux generated by the magnet 136 as the mover 133.

[0077] In this instance, when the flux flows in a counterclockwise direction, namely, a direction B as illustrated in FIG. 6, the magnet 136 generates a force attracting the stator 131, 132. However, since the stator 131, 132 is fixed to the frame 120, a force F2 trying to pull the magnet 136 toward the stator 131, 132 is applied to the magnet 136 by the attractive force. However, the force F2 proportionally increases as the magnet 136 is getting away from the stator 131, 132, and thus serves as a type of spring force. This is referred to as a magnetic spring force. The magnetic spring force is generated toward a side, to which the magnetic flux can well flow due to low magnetic resistance, namely, a side with a low magnetic level. Accordingly, magnetic energy is accumulated between the magnet 136 and the stator 131, 132. The accumulated magnetic energy generates a restoring force along with the flux generated between the outer stator 131 and the inner stator 132. The restoring force allows the magnet 136 to resonate in a right direction (a direction toward a bottom dead point or a backward direction) which is an opposite direction to that illustrated in FIG. 5.

[0078] Accordingly, the magnet 136 which is located at the left side based on the outer stator 131 and the inner stator 132 due to the flowing direction of the flux and the magnetic flux generated by the magnet 136 is moved by a force F1 applied in the right direction in the drawing, as illustrated in FIGS. 7 and 8.

[0079] Even in this instance, when the flux flows back in the clockwise direction, namely, the direction A as illustrated in FIG. 9, a magnetic spring force F2 is generated toward a side with a low magnetic level in proportion to the magnet 136 getting away from the stator 131, 132. Accordingly, magnetic energy is accumulated between the magnet 136 and the stator 131, 132. The accumulated magnetic energy generates a restoring force along with the flux, which is generated between the outer stator and the inner stator 132 when a current supplied to the coil 135 flows in an opposite direction. Accordingly, the magnet 136 may perform a resonant motion in an opposite direction, namely, a direction (a).

[0080] Here, the magnetic spring force may not continuously increase as the magnet is getting away from the stator, but increase in a range belonging to the influence range of the magnetic flux and then may be drastically lowered when exceeding the range. That is, in the electromagnetic resonance spring, the restoring force which is generated by the magnetic energy between the stator and the magnet has an inflection point according to a displacement of the piston 150. It may be preferable to limit a maximum stroke range of the piston 150 within the displacement at which the inflection point of the restoring force is located. This may thusly increase efficiency of the electromagnetic resonance spring.

[0081] FIG. 10 is a graph illustrating strength of a magnetic spring force for a position of a magnet. As illustrated in FIG. 10, it can be noticed that the magnetic spring force is continuously increasing from zero (0) in an X-axial direction to a point of about 7 mm in a back-and-forth direction in a 3 pole-2 gap structure with a ferrite magnet. However, it can also be noticed that the magnetic spring force is drastically lowered when the magnetic spring force of the magnet exceeds a predetermined range, namely, the range of 7 mm. This may indicate that the magnetic spring force is generated only when the magnet is located within a range of the magnetic flux. Therefore, the piston may preferably be controlled to perform the stroke within a range that the magnet has a maximum magnetic spring force. This can be equally generated in a 2 pole-1 gap structure with an Nd magnet to be explained later.

[0082] Hereinafter, description will be given of another exemplary embodiment of a reciprocating motor in a reciprocating compressor according to the present invention.

[0083] That is, the foregoing embodiment has illustrated the 3 pole-2 gap structure that the outer stator and the inner stator have the gaps at both sides in the axial direction, respectively, and the magnet has the three poles. This exemplary embodiment, however, illustrates a 2 pole-1 gap structure that an outer stator 231 and an inner stator 232 are connected at one of both sides in an axial direction thereof and form a gap 234 at the other side and a magnet 236 has two poles. Here, considering the magnet 236, a left magnet in the drawing is referred to as a first magnet 236a and a right magnet is referred to as a second magnet 236b. The first magnet 236a may be magnetized such that an outer side surface thereof has an N-pole and an inner side surface has an S-pole. Opposite to the first magnet 236a, the second magnet 236b may be magnetized such that an outer side surface thereof has the S-pole and an inner side surface has the N-pole. In this instance, a contact point P5 of the magnet 236 may preferably be located more eccentric toward a compression space (a left side in the drawing) than a center (O) of a pole portion, taking into account gas force. Here, an electromagnetic center of the magnet may be a contact point between the two magnets and an electromagnetic center of the stator may be the center of the pole portion.

[0084] Even in this instance, when a flux which is generated in the outer stator 231 and the inner stator 232 along a direction of a current flowing on the coil 235 flows in a direction A, the magnet 236 which has been located at a center of the outer stator 231 is moved by a force F1 applied in a direction (a), as illustrated in FIG. 12, by the flowing direction of the flux and the magnetic flux generated by the magnet 236.

[0085] In this instance, when the flux flows in a counterclockwise direction as illustrated in FIG. 13, the magnet 236 is affected by a force F2 trying to pull the magnet 236 toward the stator. Accordingly, as described in the foregoing embodiment, as the magnet 236 is getting away from the stator 231, 232, the magnetic spring force is generated toward a side with a low magnetic level up to a predetermined range, and accordingly magnetic energy is accumulated between the magnet and the stator. The accumulated magnetic energy generates a restoring force along with the flux generated between the outer stator 231 and the inner stator 231 when the current supplied to a coil 235 flows in an opposite direction. The restoring force may allow the magnet to resonate in a direction (b) (a direction toward a bottom dead point or a backward direction), which is opposite to the direction in FIG. 12. That is, when the flux generated in the outer stator 231 and the inner stator 232 flows in a counterclockwise direction, namely, a direction B, the magnet 236 which has been moved to left in the drawing based on the outer stator 231 due to the flowing direction of the flux and the magnetic flux generated by the magnet 236 may be moved in a direction (b) while performing a resonant motion, as illustrated in FIG. 14, by a centering force generated by an attractive magnetic force between the coil and the core and a force F2 generated by the flux.

[0086] When the flux flows in the clockwise direction, namely, the direction A as illustrated in FIG. 15, a magnetic spring force F2 is generated between the magnet 236 and the stator 231, 232 toward a side with a low magnetic level, and accordingly, magnetic energy is accumulated between the magnet 236 and the stator 231, 232. The accumulated magnetic energy generates a restoring force along with the flux generated between the outer stator 231 and the inner stator 232, such that the magnet 236 can strongly resonate in a direction (a) as an opposite direction to that illustrated in FIG. 14.

[0087] Even in this instance, the magnetic spring force may not continuously increase as the magnet is getting away from the stator, but increase within an influence range of the magnetic flux and then be drastically lowered when exceeding the range. This has been described in relation to FIG. 10.

[0088] As such, in a reciprocating compressor in which a piston compresses a refrigerant while reciprocating in a cylinder, in order for a vibrating body including the piston to efficiently compress a refrigerant by resisting gas force, a resonance spring is required for resonating the vibrating body. However, upon applying the mechanical resonance spring as applied in the related art, a specific frequency cannot be used at an operating frequency of a predetermined period, in view of the characteristic of the coil spring. However, when allowing the vibrating body to perform a resonant motion by using an electromagnetic resonance spring as illustrated in the embodiment according to the present invention, every frequency can be used at an operating frequency of a predetermined period. This may result in increasing an operation band of the compressor, improving compressor efficiency and enabling an efficient operation of a product employing such compressor.

[0089] Also, upon applying the electromagnetic resonance spring, compared with employing the mechanical resonance spring such as a compression coil spring, there may not be any limit on mechanical stress and a vibrating distance of the electromagnetic resonance spring can match a vibrating distance of the vibrating body including the piston, which may result in reducing a horizontal length of the compressor.

[0090] In addition, as the reciprocating motor is used as the electromagnetic resonance spring, a remarkable reduction of a number of components can be achieved, as compared with employing the compression coil spring as a resonance spring, which may allow for a remarkable simplification of a device structure and an assembly process of the compressor.

[0091] Meanwhile, FIG. 16 is a longitudinal sectional view illustrating an apparatus of assembling a magnet in a manner of being eccentric toward a compression space by a magnetic force in a reciprocating compressor in accordance with the present invention.

[0092] As illustrated in FIG. 16, a bracket 181 may be coupled to the rear frame 122, and auxiliary magnets 182a and 182b having the same pole may be disposed at an inner side surface (front surface) of the bracket 181 and a rear surface of a flange of the piston 140 facing the inner side surface, such that the piston 150 and the magnet 136 as the vibrating bodies can be assembled to be slightly eccentric toward the compression space 141 by a repulsive force between the both auxiliary magnets 182a and 182b. An unexplained reference numeral 131 denotes an outer stator, 132 denotes an inner stator, 135 denotes a coil, O denotes a center of a pole portion, O denotes a center of a second magnet, and O denotes a center of the coil.

[0093] To this end, during the operation of the compressor, the piston 150 can be moved as much as being pushed out due to gas force generated in the compression space 141, which may allow a stroke of the piston to be carried out between a top dead point and a bottom dead point, thereby preventing compressor efficiency from being lowered.

[0094] Meanwhile, as illustrated in FIG. 17, when the stator is provided in plurality, the same effect as those in the foregoing embodiments can be obtained.

[0095] That is, a plurality of outer stators 131 and 131 may be arranged alongside in a reciprocating direction of the piston 150, and inner stators 132 corresponding to the outer stators 131 and 131, respectively, may be arranged at an inner side of each outer stator 131 and 131 in the reciprocating direction of the piston 150.

[0096] A plurality of magnets 136 and 136 may be arranged in gaps between the outer stators 131 and 131 and the inner stator 132 and 132, respectively.

[0097] Here, the outer stators 131 and 131, the inner stators 132 and 132 and the magnets 136 and 136 are the same as those in the embodiment illustrated in FIGS. 2 and 3, so detailed description thereof will be omitted. Reference numerals 135 and 135 denote a coil, and 140 denotes a cylinder.

[0098] In this manner, when the plurality of stators and magnets are arranged alongside in the reciprocating direction of the piston, a compressor capacity can increase and an electromagnetic resonant spring force can also increase. This can more improve a performance of the compressor than an embodiment employing one stator, and thus be appropriate for a large-capacity compressor.

[0099] Meanwhile, although not illustrated, a separate electromagnetic resonance spring may additionally be disposed at a rear side of the piston.

[0100] Even in this case, a spring holder in a cylindrical shape may be provided at a rear side of the magnet holder and one or a plurality of magnets for spring may be coupled to an outer circumferential surface of the spring holder.

[0101] A back cover may be coupled to a rear side of a frame supporting the stator, and a stator for spring forming the electromagnetic resonance spring along with the magnets for spring may be coupled to a front side of the back cover.

[0102] The stator for spring may be formed in a shape similar to or the same as those of the outer stator and the inner stator which construct the reciprocating motor. That is, the stator for spring may be implemented in a 2-gap shape in a manner of having a shape with pole portions at both ends thereof, similar to the outer stator of the reciprocating motor, or implemented in a 1-gap shape having only one end with a pole portion and another end connected to the inner stator.

[0103] Three of such magnet may be alternately arranged, similar to the aforementioned magnets of the reciprocating motor, to form the electromagnetic resonance spring with the 3 pole-2 gap structure, or two of such magnet may be alternately arranged to form an electromagnetic resonance spring with a 2 pole-1 gap structure.

[0104] An operation effect of the reciprocating compressor may be the same as or similar to the aforementioned embodiments. However, this embodiment may increase an entire size and fabricating costs of the compressor further including the spring holder and the magnets for spring, but can increase the spring force and enhance compression efficiency accordingly by virtue of the additional electromagnetic resonance spring in addition to the electromagnetic resonance spring of the reciprocating motor.

[0105] Meanwhile, although not illustrated, an electromagnetic resonance spring may be formed even in an embodiment that the magnet is integrally coupled to the inner stator.

[0106] That is, the foregoing embodiments have illustrated that the magnet is located in the gap between the outer stator and the inner stator and reciprocates along with the mover, but this embodiment can illustrate that the magnet is coupled to an outer circumferential surface of the inner stator and accordingly the piston reciprocates along with the inner stator.

[0107] A basic configuration of the reciprocating compressor and an operation effect thereof according to this embodiment are the same as or similar to the foregoing embodiments. However, in this instance, as the magnet is coupled to the inner stator, it may be facilitated to manage a clearance between the inner stator and the mover and to match concentricity among the inner stator, the mover and the piston.