Patent Description:
In general, the reciprocating compressor is a type of compressor of sucking, compressing and discharging a refrigerant by linearly reciprocating a piston in a cylinder. The reciprocating compressors may be classified into a connection type and a vibration type according to a driving method of the piston.

In the connection type reciprocating compressor, a piston is connected to a rotation shaft of a driving motor via a connecting rod to compress a refrigerant while reciprocating in a cylinder. In the vibration type reciprocating compressor, the piston reciprocates in the cylinder and vibrates while connected with a mover of a reciprocating motor, thereby compressing a refrigerant. The present invention relates to the vibration type reciprocating compressor, and hereinafter, the vibration type reciprocating compressor is abbreviated as a reciprocating compressor.

<FIG> is a sectional view of a reciprocating compressor according to the related art.

As illustrated in <FIG>, the related art reciprocating compressor includes a frame <NUM> elastically installed in an inner space of a shell <NUM>, a reciprocating motor <NUM> and a cylinder <NUM> both fixed to the frame <NUM>, and a piston <NUM> coupled to a mover <NUM> of the reciprocating motor <NUM> and performing a reciprocating motion in the cylinder <NUM>.

The cylinder <NUM> is provided with a compression space <NUM>, and the piston <NUM> is provided with a suction passage <NUM>. A suction valve <NUM> for opening and closing the suction passage <NUM> is installed at an end of the suction passage <NUM>. A discharge valve <NUM> for opening and closing the compression space <NUM> of the cylinder <NUM> is installed at a front end surface of the cylinder <NUM>. A discharge cover <NUM> having a discharge space <NUM> therein is coupled to the front end surface of the cylinder <NUM>, and the discharge valve <NUM> is accommodated in the discharge space <NUM> of the discharge cover <NUM>.

The inner space <NUM> of the shell <NUM> communicates with a suction pipe <NUM>, and the discharge space <NUM> of the discharge cover <NUM> communicates with a discharge pipe <NUM> which is connected with an inlet of a condenser (not illustrated) of a refrigeration cycle device. Accordingly, suction pressure is generated in the inner space <NUM> of the shell <NUM>. The suction passage <NUM> of the piston <NUM> communicates with the inner space <NUM> of the shell <NUM> so as to guide a refrigerant of suction pressure to be introduced into the compression space <NUM>.

Meanwhile, one resonance spring <NUM>, <NUM> which induces the piston <NUM> to resonate along with the mover <NUM> may be installed at one side in a motion direction of the piston <NUM>, or one resonance spring or a plurality of resonance springs <NUM> and <NUM> may be installed at each of both sides in the motion direction of the piston <NUM>. The resonance springs <NUM> and <NUM> may be implemented as a compression coil spring. When the resonance springs are installed at the both sides of the piston <NUM>, one end of each of the resonance springs <NUM> and <NUM> may be supported, respectively, at front and rear side surfaces of a spring supporter <NUM> coupled to the piston <NUM>, and another end of each of the both resonance springs <NUM> and <NUM> may be supported at a rear frame <NUM> supporting the stator <NUM>, <NUM> of the reciprocating motor <NUM>, and a back cover <NUM> coupled to the rear frame <NUM> and disposed at a rear side of the piston <NUM>.

An unexplained reference numeral <NUM> denotes a front frame, <NUM> denotes a coil, <NUM> denotes a magnet, and <NUM> denotes a valve spring.

In the reciprocating compressor according to the related art, when power is supplied to the coil <NUM> of the reciprocating motor <NUM>, the mover <NUM> of the reciprocating motor <NUM> performs a reciprocating motion. The piston <NUM> coupled to the mover <NUM> then fast reciprocates within the cylinder <NUM>. Accordingly, a refrigerant is sucked into the inner space <NUM> of the shell <NUM> through the suction pipe <NUM>. The refrigerant sucked into the inner space <NUM> of the shell <NUM> is introduced into the compression space <NUM> of the cylinder <NUM> through the suction passage <NUM> of the piston <NUM>. The introduced refrigerant is then discharged from the compression space <NUM> into the discharge space <NUM> by pushing the discharge valve <NUM> during a forward motion of the piston <NUM>, thereby flowing into a condenser of the refrigeration cycle through the discharge pipe <NUM>. Such series of processes are repeated.

In this instance, the front resonance spring <NUM> and the rear resonance spring <NUM> which have the same spring constant are provided in plurality, respectively, at front and rear sides of the piston <NUM>, so as to elastically support the piston <NUM>. This may allow a power supply frequency (operating frequency) of the compressor to match a resonance frequency of the resonance spring at a specific cooling capacity, resulting in improvement of compressor efficiency.

<CIT> relates to a linear compressor with a small size and a light weight comprising a fixed member including a cylinder having a compression space defined therein, an inner stator installed on the outside of the cylinder, and an outer stator forming a pole in an air gap from the inner stator; and a moving member including a piston performing reciprocal linear motion into the compression space of the cylinder and compressing an operating fluid introduced into the compression space and a permanent magnet performing reciprocal linear motion with the piston due to a mutual electromagnetic force in the air gap between the inner stator and the outer stator.

<CIT> relates to a spring-less buried magnet linear-resonant motor including a buried magnet system and a stator operable to produce an alternating magnetic field exerting alternating axial forces on the buried magnet system that has a self-centering force and a required stiffness to reciprocate at a frequency near an alternating current (AC) supply frequency.

<CIT> relates to a bi-directional operating compressor using a transverse flux linear motor, the compressor comprising: a pair of stators including a plurality of U-shape upper stator iron cores and a plurality of U-shape lower stator iron cores, and a pair of neighboring circular winding coils; a rotor placed between the pair of stators including a plurality of permanent magnets connected to iron cores, a rotor center installed between a pair of structures facing each other, a pair of supports connected to both sides of the center, and a pair of pistons connected to one side of the support respectively; and a pair of cylinders provided facing the pistons at both side ends of the rotor, for compressing air in response to the reciprocating motion of the pistons.

As such, in the related art reciprocating compressor, a vibrating body including the piston <NUM> is supported by a mechanical resonance spring which is a compression coil spring. However, the resonance frequency of the resonance spring is not allowed to be used within an operating frequency of a predetermined section (period) due to self-resonance which occurs in the coil spring in view of a characteristic of the coil spring.

In addition, the compression coil spring as the related art mechanical resonance spring <NUM>, <NUM> has limits on mechanical stress, vibration distance and the like, which requires for predetermined wire diameter and length of the coil spring. This causes a limit in reducing a horizontal length of the compressor.

Furthermore, to install the compression coil spring as the related art mechanical resonance spring, the spring supporter <NUM> is disposed at the piston <NUM> and the back cover <NUM> is provided at the rear frame <NUM> supporting the stator <NUM>, <NUM>, so as to fix both ends of the resonance spring <NUM>, <NUM> as the compression coil spring. This makes a device structure of the compressor complicated. Also, the plurality of resonance springs <NUM> and <NUM> should be installed at each of the front and rear sides of the piston <NUM> in a pressing manner with predetermined pressure. This causes a difficult assembly process.

Therefore, an aspect of the detailed description is to provide a reciprocating compressor capable of overcoming a limit on a frequency to be usable within an operating frequency of a predetermined period.

Another aspect of the detailed description is to provide a reciprocating compressor capable of reducing a size of the compressor by reducing a length of a resonance spring in a reciprocating direction thereof.

Another aspect of the detailed description is to provide a reciprocating compressor, capable of reducing fabricating costs by simplifying a structure and an assembly process of resonance springs which enable a resonant motion of a piston with respect to a cylinder. The invention is specified by the independent claim. In the following description, although numerous features may be designated as optional, it is nevertheless acknowledged that all features comprised in the independent claim are not to be read as optional.

To achieve these and other advantages and in accordance with an example, there is provided a recip-
rocating compressor including a stator provided with a stator core with at least one air gap, and a coil generating magnetic energy, 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 resonates by a restoring force generated toward a side with a low magnetic level, and the piston is arranged such that a center of a stroke thereof is eccentric with respect to a center of the stator core in a reciprocating direction in an initially assembled state or a stopped state.

Here, the piston may be arranged to be eccentric toward a compression space in an assembled or stopped state.

The magnet may be arranged such that N-pole and S-pole are arranged by at least one, respectively, along a reciprocating direction of the magnet. A middle point between different poles of the magnet may be located more eccentric toward the compression space than a center of the air gap.

To achieve these and other advantages and in accordance with an embodiment of the present invention, as embodied and broadly described herein, there is provided a reciprocating compressor including a shell having an inner space, at least one stator provided with a stator core having at least one air gap, and a coil fixed to the stator core to generate magnetic energy in response to power supply, 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 and the magnet by a restoring force generated by the magnetic energy.

The electromagnetic resonance spring may allow the magnet to perform a resonant motion, in response to a force generated toward a side with a low magnetic level according to a difference of the magnetic level generated between the stator core and the magnet while the magnet moves according to a current supplied to the coil.

The stator may include an outer core disposed at an outer side and an inner core disposed at an inner side based on an air gap therebetween, and the magnet may be disposed to be movable between the outer core and the inner core.

The stator may include an outer core disposed at an outer side and an inner core disposed at an inner side based on an air gap therebetween, and the magnet may be coupled to the outer core or the inner core so as to be movable along with the coupled outer core or inner core.

An electromagnetic center of the magnet is located more eccentric toward the compression space than an electromagnetic center of the stator.

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

The stator may have air gaps at both sides of the coil, respectively, and a center of the magnet may be located more eccentric toward the compression space than a center of the coil.

A maximum stroke range of the piston may be within a displacement at which the restoring force has an inflection point.

The electromagnetic resonance spring may be provided in plurality, arranged along a reciprocating direction of the piston.

Magnets having the same pole may be 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.

To achieve these and other advantages and in accordance with an example,
there is provided a reciprocating compressor including 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.

Here, a maximum stroke range of the piston may be within a displacement at which the restoring force has an inflection point.

To achieve these and other advantages and in accordance with an example,
there is provided a reciprocating compressor including 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.

In a reciprocating compressor according to the detailed description, a limit on a frequency to be usable within an operating frequency of a predetermined period can be prevented in advance by resonating a vibrating body using an electromagnetic resonance spring.

Also, a stress limit can be overcome by applying the electromagnetic resonant spring, and a vibration distance of the electromagnetic resonance spring and a vibration distance of a vibrating body including a piston can be the same as each other, which may result in a remarkable reduction of a horizontal length of the compressor.

In addition, a number of components for constructing a resonance spring can remarkably be reduced by utilizing a reciprocating motor as an electromagnetic coil spring, which may result in greatly simplifying a device structure and an assembly process of the compressor.

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.

<FIG> is a longitudinal sectional view of a reciprocating compressor in accordance with the present invention, and <FIG> is a longitudinal sectional view of a reciprocating motor in the compressor according to <FIG>.

As illustrated in <FIG> and <FIG>, in a reciprocating compressor according to the present invention, a suction pipe <NUM> may be connected to an inner space <NUM> of a hermetic shell <NUM>, and a discharge pipe <NUM> through which a refrigerant compressed in a compression space <NUM> of a cylinder <NUM> to be explained later is guided into a refrigeration cycle may be disposed at one side of the suction pipe <NUM>. Accordingly, the inner space <NUM> of the shell <NUM> may generate suction pressure by being filled with a refrigerant of suction pressure, and a refrigerant discharged from the compression space <NUM> may be discharged directly out of the shell <NUM> toward a condenser.

A frame <NUM> may be installed in the inner space <NUM> of the shell <NUM> by being elastically supported by a plurality of supporting springs <NUM> and <NUM>. A reciprocating motor <NUM> may be fixed to one side surface of the frame <NUM>. The reciprocating motor <NUM> may generate a reciprocating force and simultaneously induce a resonant motion of a piston <NUM> to be explained later.

The cylinder <NUM> which has the compression space <NUM> therein and is inserted into a front frame <NUM> of the frame <NUM> may be coupled at an inner side of the reciprocating motor <NUM>. The piston <NUM> which compresses a refrigerant by varying a volume of the compression space <NUM> of the cylinder <NUM> may be inserted into the cylinder <NUM> to reciprocate in the cylinder <NUM>.

A suction valve <NUM> opening and closing a suction passage <NUM> of the piston <NUM> may be coupled to a front end surface of the piston <NUM>, and a discharge valve <NUM> opening and closing the compression space <NUM> of the cylinder <NUM> may be detachably coupled to a front end surface of the cylinder <NUM> in a manner of being covered with a discharge cover <NUM>.

The discharge cover <NUM> may be provided with a discharge space <NUM> and fixed to the cylinder <NUM>. The discharge valve <NUM> and a valve spring <NUM> supporting the discharge valve <NUM> may be accommodated in the discharge space <NUM>. The discharge cover <NUM> may be coupled with the discharge pipe <NUM> such that the discharge space <NUM> and a condenser can be directly connected to each other through the discharge pipe <NUM>.

The reciprocating motor <NUM> may include an outer stator <NUM>, an inner stator <NUM>, and a mover <NUM> performing a reciprocating motion in an air gap between the outer stator <NUM> and the inner stator <NUM>.

The outer stator <NUM> may be coupled between the front frame <NUM> and a rear frame <NUM> to configure a part of a stator core. An annular coil <NUM> may be coupled to the outer stator <NUM>. The coil <NUM> may alternatively be coupled to the inner stator <NUM>.

The inner stator <NUM> may be disposed within the outer stator <NUM> with a predetermined gap <NUM> from the outer stator <NUM>. The inner stator <NUM> may be coupled between both of the frames <NUM> and <NUM> to configure another part of the stator core.

The mover <NUM> may be disposed in the air gap <NUM> between the outer stator <NUM> and the inner stator <NUM>. A magnet <NUM> corresponding to the coil <NUM> may be provided such that the mover <NUM> can perform a reciprocating motion in a flowing direction of a magnetic flux induced by the magnet <NUM> and the coil <NUM>.

Here, a structure of the reciprocating motor <NUM> 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 <NUM> pole-<NUM> 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 <NUM> pole-<NUM> gap structure refers to a structure in which two magnets are arranged in one air gap to have opposite polarities in a reciprocating direction.

As illustrated in <FIG>, for the <NUM> pole-<NUM> gap structure, the outer stator <NUM> 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 <NUM> 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 <NUM> may also form a first pole portion 132a and a second pole portion 132b. Accordingly, the outer stator <NUM> and the inner stator <NUM> 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 <NUM>.

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

The magnet <NUM> 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 <NUM>, or have a cylindrical section to be inserted to the outer circumferential surface or the inner circumferential surface of the magnet holder <NUM>.

The length of the magnet <NUM> in the reciprocating direction may be longer than the length of the outer stator <NUM> in the reciprocating direction. The magnet <NUM> 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.

<FIG> 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 <NUM> on the basis of an outer circumferential surface of the magnet <NUM>. This may extend a range that the magnetic energy is applied to the magnet <NUM>, thereby increasing a resonance-allowable range.

For example, as illustrated in <FIG>, 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 <NUM>. 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.

The magnet <NUM> 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 <NUM> of the stator core. If the number of poles of the magnet <NUM> is smaller than the number of the gap <NUM> of the stator core, it may be difficult to transfer the flux to the magnet <NUM> from at least one gap <NUM>. Accordingly, an amount of invalid flux may increase, thereby lowering efficiency of the compressor.

And, the magnet <NUM> 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.

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

To this end, the reciprocating motor <NUM> may be asymmetrically controlled such that an electromagnetic center of the magnet <NUM> is eccentric more toward the compression space <NUM> than the electromagnetic center of the stator <NUM>, <NUM>, or the cylinder <NUM> may be configured to be eccentric in a direction getting away from the compression space <NUM>, considering the gas force. In case where the cylinder <NUM> 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 <NUM> may be located such that an end surface of the cylinder <NUM> is located closer to the stator than the position illustrated in <FIG> in the second state.

Here, the electromagnetic center of the magnet <NUM> 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 <NUM>. If a matching point between the electromagnetic center of the magnet <NUM> and the electromagnetic center of the stator is referred to as a first position of the piston <NUM> and a position of the piston <NUM> in an assembled or stopped state is referred to as a second position of the piston <NUM>, the second position of the piston <NUM> may be located more eccentric toward the compression space <NUM> than the first position of the piston <NUM>.

For example, as illustrated in <FIG>, 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 <NUM> 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 <NUM> by a predetermined interval t2 than a center O" of the stator core.

Meanwhile, the foregoing embodiment has exemplarily illustrated that the pole portions are formed only at both ends of the outer stator <NUM>. 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.

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

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

In this instance, while the magnet <NUM> reciprocates within the reciprocating motor <NUM>, an electromagnetic resonance spring may be generated between the magnet <NUM> and the stator core, thereby inducing a resonant motion of the mover <NUM> and the piston <NUM>. This may allow the piston <NUM> to compress the refrigerant by resisting the gas force generated in the compression space <NUM>.

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

As illustrated in <FIG>, when a flux which is generated in the outer stator <NUM> and the inner stator <NUM> in a direction of a current flowing along the coil <NUM> flows in a clockwise direction, namely, a direction A, the left first pole portion 132a of the inner stator <NUM> 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 <NUM> 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 <NUM> and the inner stator <NUM>. 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 <NUM>, <NUM> 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 <NUM>, <NUM>. Accordingly, the magnet <NUM> which has been located at the center of the stator <NUM>, <NUM> may be moved to left in the drawing of <FIG>, due by a force F<NUM>, which is applied in a direction (a) (a direction toward a top dead point or a forward direction), as illustrated in <FIG>, by the flowing direction of the flux and the magnetic flux generated by the magnet <NUM> as the mover <NUM>.

In this instance, when the flux flows in a counterclockwise direction, namely, a direction B as illustrated in <FIG>, the magnet <NUM> generates a force attracting the stator <NUM>, <NUM>. However, since the stator <NUM>, <NUM> is fixed to the frame <NUM>, a force F<NUM> trying to pull the magnet <NUM> toward the stator <NUM>, <NUM> is applied to the magnet <NUM> by the attractive force. However, the force F<NUM> proportionally increases as the magnet <NUM> is getting away from the stator <NUM>, <NUM>, 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 <NUM> and the stator <NUM>, <NUM>. The accumulated magnetic energy generates a restoring force along with the flux generated between the outer stator <NUM> and the inner stator <NUM>. The restoring force allows the magnet <NUM> 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>.

Accordingly, the magnet <NUM> which is located at the left side based on the outer stator <NUM> and the inner stator <NUM> due to the flowing direction of the flux and the magnetic flux generated by the magnet <NUM> is moved by a force F<NUM>' applied in the right direction in the drawing, as illustrated in <FIG> and <FIG>.

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

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 <NUM>. It may be preferable to limit a maximum stroke range of the piston <NUM> within the displacement at which the inflection point of the restoring force is located. This may thusly increase efficiency of the electromagnetic resonance spring.

<FIG> is a graph illustrating strength of a magnetic spring force for a position of a magnet. As illustrated in <FIG>, it can be noticed that the magnetic spring force is continuously increasing from zero (<NUM>) in an X-axial direction to a point of about ±<NUM> in a back-and-forth direction in a <NUM> pole-<NUM> 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 ±<NUM>. 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 <NUM> pole-<NUM> gap structure with an Nd magnet to be explained later.

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

That is, the foregoing embodiment has illustrated the <NUM> pole-<NUM> 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 <NUM> pole-<NUM> gap structure that an outer stator <NUM> and an inner stator <NUM> are connected at one of both sides in an axial direction thereof and form a gap <NUM> at the other side and a magnet <NUM> has two poles. Here, considering the magnet <NUM>, 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 <NUM> 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.

Even in this instance, when a flux which is generated in the outer stator <NUM> and the inner stator <NUM> along a direction of a current flowing on the coil <NUM> flows in a direction A, the magnet <NUM> which has been located at a center of the outer stator <NUM> is moved by a force F<NUM> applied in a direction (a), as illustrated in <FIG>, by the flowing direction of the flux and the magnetic flux generated by the magnet <NUM>.

In this instance, when the flux flows in a counterclockwise direction as illustrated in <FIG>, the magnet <NUM> is affected by a force F<NUM> trying to pull the magnet <NUM> toward the stator. Accordingly, as described in the foregoing embodiment, as the magnet <NUM> is getting away from the stator <NUM>, <NUM>, 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 <NUM> and the inner stator <NUM> when the current supplied to a coil <NUM> 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>. That is, when the flux generated in the outer stator <NUM> and the inner stator <NUM> flows in a counterclockwise direction, namely, a direction B, the magnet <NUM> which has been moved to left in the drawing based on the outer stator <NUM> due to the flowing direction of the flux and the magnetic flux generated by the magnet <NUM> may be moved in a direction (b) while performing a resonant motion, as illustrated in <FIG>, by a centering force generated by an attractive magnetic force between the coil and the core and a force F<NUM> generated by the flux.

When the flux flows in the clockwise direction, namely, the direction A as illustrated in <FIG>, a magnetic spring force F<NUM>' is generated between the magnet <NUM> and the stator <NUM>, <NUM> toward a side with a low magnetic level, and accordingly, magnetic energy is accumulated between the magnet <NUM> and the stator <NUM>, <NUM>. The accumulated magnetic energy generates a restoring force along with the flux generated between the outer stator <NUM> and the inner stator <NUM>, such that the magnet <NUM> can strongly resonate in a direction (a) as an opposite direction to that illustrated in <FIG>.

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>.

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.

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.

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.

Meanwhile, <FIG> 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.

As illustrated in <FIG>, a bracket <NUM> may be coupled to the rear frame <NUM>, and auxiliary magnets 182a and 182b having the same pole may be disposed at an inner side surface (front surface) of the bracket <NUM> and a rear surface of a flange of the piston <NUM> facing the inner side surface, such that the piston <NUM> and the magnet <NUM> as the vibrating bodies can be assembled to be slightly eccentric toward the compression space <NUM> by a repulsive force between the both auxiliary magnets 182a and 182b. An unexplained reference numeral <NUM> denotes an outer stator, <NUM> denotes an inner stator, <NUM> 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.

To this end, during the operation of the compressor, the piston <NUM> can be moved as much as being pushed out due to gas force generated in the compression space <NUM>, 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.

Meanwhile, as illustrated in <FIG>, when the stator is provided in plurality, the same effect as those in the foregoing embodiments can be obtained.

That is, a plurality of outer stators <NUM> and <NUM>' may be arranged alongside in a reciprocating direction of the piston <NUM>, and inner stators <NUM>' corresponding to the outer stators <NUM> and <NUM>', respectively, may be arranged at an inner side of each outer stator <NUM> and <NUM>' in the reciprocating direction of the piston <NUM>.

A plurality of magnets <NUM> and <NUM>' may be arranged in gaps between the outer stators <NUM> and <NUM>' and the inner stator <NUM> and <NUM>', respectively.

Here, the outer stators <NUM> and <NUM>', the inner stators <NUM> and <NUM>' and the magnets <NUM> and <NUM>' are the same as those in the embodiment illustrated in <FIG> and <FIG>, so detailed description thereof will be omitted. Reference numerals <NUM> and <NUM>' denote a coil, and <NUM> denotes a cylinder.

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.

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

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.

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.

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 <NUM>-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 <NUM>-gap shape having only one end with a pole portion and another end connected to the inner stator.

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 <NUM> pole-<NUM> gap structure, or two of such magnet may be alternately arranged to form an electromagnetic resonance spring with a <NUM> pole-<NUM> gap structure.

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.

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.

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.

Claim 1:
A reciprocating compressor comprising:
a shell (<NUM>) having an inner space (<NUM>);
at least one stator (<NUM>,<NUM>) (<NUM>,<NUM>) disposed in the inner space (<NUM>) of the shell (<NUM>), and provided with a stator core having at least one air gap (<NUM>), and a coil (<NUM>) fixed to the stator core and generating magnetic energy in response to power applied;
a mover (<NUM>) provided with a magnet (<NUM>,136a,136b,136c) (<NUM>,236a,236b) and reciprocating with respect to the stator (<NUM>,<NUM>);
a piston (<NUM>) mechanically connected with the mover (<NUM>), and reciprocating by the magnetic energy generated in the stator and interaction with the magnet (<NUM>,136a,136b,136c) (<NUM>,236a,236b);
a cylinder (<NUM>) having the piston (<NUM>) inserted therein and forming a compression space (<NUM>);
a suction valve (<NUM>) opening and closing a suction side of the compression space;
a discharge valve (<NUM>) opening and closing a discharge side of the compression space; and
an electromagnetic resonance spring (<NUM>) formed between the stator core and the magnet by a restoring force generated by the magnetic energy,
characterized in that an electromagnetic center of the magnet is located more eccentric toward the compression space (<NUM>) than an electromagnetic center of the stator.