Linear motor and compressor equipped with linear motor

A linear motor includes an armature with two magnetic poles arranged in the Z direction, and winding wires wound around the two magnetic poles, respectively, and a mover with a permanent magnet, which moves relative to the armature in the Z direction. A first auxiliary magnetic pole is disposed between the two magnetic poles, and a bridge is disposed between the first auxiliary magnetic pole and the magnetic pole. The two winding wires are electrically coupled.

BACKGROUND

The present invention relates to a linear motor, and a compressor equipped with the linear motor.

The linear motor known to be relevant to the invention is disclosed in WO2004/093301.

Specifically, WO2004/093301 discloses an armature 3a constituted by teeth formed by punching the magnetic steel plate into a serrated shape, and an armature core for forming a yoke, and armature winding wires 5u, 5v, 5w formed by winding coils around a plurality of teeth 4u, 4v, 4w of the armature core, respectively. Teeth 6a wound with no coil are disposed between the teeth 4u and 4v, and teeth 4v and 4w, which are wound with coils, respectively. The teeth 4u, 4v, 4w wound with coils and the teeth 6a wound with no coil are arranged alternately (abstract). This makes it possible to improve interphase insulation (page 5, lines 1 to 6).

SUMMARY

According to the above-described structure, the currents flowing through the coils wound around the three teeth 4u, 4v, and 4w have different phases (U-phase, V-phase, W-phase). As there is the time period at which voltage values of the adjacent coils are significantly different, contact between those coils may cause the risk of short-circuit. Provision of the teeth 6a wound with no coil for the purpose of suppressing short-circuit, that is, improving the interphase insulation will narrow the space for accommodating the coil, resulting in difficulty in downsizing of the motor.

The present invention provides a linear motor which includes an armature with two magnetic poles arranged in a Z direction, and winding wires wound around the two magnetic poles, respectively, and a mover with a permanent magnet, which moves relative to the armature in the Z direction. A first auxiliary magnetic pole is disposed between the two magnetic poles, and a bridge is disposed between the first auxiliary magnetic pole and the magnetic pole. The two winding wires are electrically coupled.

The present invention is capable of providing the compact linear motor with improved controllability, and a compressor equipped with the linear motor. Any other structures, tasks and advantages of the present invention will be clarified by the following explanations of the embodiments for carrying out the invention.

DETAILED DESCRIPTION

Embodiments of the present invention will be described referring to the drawings. The same components will be designated with the same signs, and explanations thereof, thus will be omitted. For convenience of explanation, directions of X, Y and Z are orthogonal to one another. However, the gravity direction may be in parallel with any one of the X, Y and Z directions, or any other direction.

The respective components of the present invention are not necessarily independent from one another, which may be configured that a single component is constituted by a plurality of members, the single member is used for constituting a plurality of components, a certain component is a part of another component, the certain component is partially overlapped with another component, and the like.

First Embodiment

<Mover and Permanent Magnet3a>

FIG. 1is a perspective view of a linear motor1according to the embodiment.FIG. 2is a front view (seen from Z direction) of the linear motor1according to the embodiment.

The linear motor1includes an armature2, and a mover (not shown) having a flat plate-like permanent magnet3a. Since the mover may be appropriately designed to have an arbitrary shape in accordance with the device to which the present invention is applied, the mover is not shown in the embodiment. The shape of the mover is not specifically limited so long as it is disposed in the air gap between two magnetic pole teeth part4ato be described below, and movable in the Z direction. For example, the mover may be formed into the flat plate-like shape. The mover according to the embodiment has the single permanent magnet3awith flat plate shape, which is magnetized in the Y direction. It is possible to arrange a plurality of permanent magnets3ain the Z direction. In the case where a plurality of permanent magnets3aare arranged, the respective polarities of the magnets in the Y direction may be alternately inverted.

The mover is movable relative to the armature2in the Z direction.

The length of the permanent magnet3ain the Z direction is equal to or shorter than the distance between centers of the magnetic poles4, that is, the total of dimensions of a first auxiliary magnetic pole5, two bridges7, and the single magnetic pole4in the Z direction.

The armature2includes two magnetic poles4, two first auxiliary magnetic poles5, four end bridges6, four winding wires60, four bridges7, and four armature fixing bolts8. Each of the magnetic poles4includes two opposite magnetic pole teeth parts4a(magnetic pole teeth group) via an air gap in the Y direction. Each of the magnetic pole teeth parts4ais wound with the winding wire60. The winding wire60may be wound around at least one of those two magnetic pole teeth parts4aarranged in the Y direction. Preferably, the winding wires are wound around both magnetic pole teeth parts so as to supply more magnetic flux.

There are two first auxiliary magnetic poles5each as the magnetic substance disposed in the Y direction between the two magnetic poles4arranged in the Z direction. Each of the bridges7is disposed between the magnetic pole4and the first auxiliary magnetic pole5so that the distance therebetween is defined. The first auxiliary magnetic pole5includes a first auxiliary magnetic pole teeth part5a. The two opposite first auxiliary magnetic teeth parts5a(auxiliary magnetic teeth group) in the Y direction are located at both sides of the permanent magnet3avia the air gap in the Y direction. The material for forming the first auxiliary magnetic pole5is not limited so long as it is formed as the magnetic substance, which may be a metallic plate such as iron, the magnetic steel plates laminated in the Z direction, and the soft magnetic material such as a soft ferrite.

The mover and the permanent magnet3aare located in the air gap between the magnetic pole teeth groups, which move in the Z direction relative to the armature2. The armature2has substantially a rectangular parallelepiped shape, which allows effective arrangement of a plurality of linear motors1or a plurality of armatures2in the X or Y direction.

In the embodiment, two magnetic poles4are arranged in the Z direction. However, the number of the magnetic poles to be arranged is arbitrarily set so long as the number is two or larger. For example, if three magnetic poles4are arranged, four first auxiliary magnetic poles5will be disposed between the respective magnetic poles4.

The armature2is configured to have the magnetic flux distribution part with higher conductivity and higher permeability orthogonally directed to the relative moving direction (Z direction) of the armature2and the mover. In other words, the conductivity and the permeability of the magnetic pole4in the X and Y directions are higher than those in the Z direction so as to exhibit anisotropy. In the embodiment, the magnetic pole4is produced by the laminated steel plate derived from laminating a plurality of magnetic steel plates as the magnetic substance in the Z direction. The magnetic flux generated by the current applied to the winding wire60allows the magnetic pole4to have a loop substantially in parallel with the XY plane.

Referring toFIG. 2, the magnetic pole4is structured to be separable into two half-magnetic poles each having a single magnetic pole teeth part4a(upper and lower half sections of the magnetic pole4shown inFIG. 2). This makes it possible to improve assembling efficiency of the winding wire60to the magnetic pole teeth part4a, and assembly workability of the armature2.

FIG. 3is a perspective view of the first auxiliary magnetic pole5of the embodiment. The bridges7are disposed at both sides of a base end5dof the first auxiliary magnetic pole5in the Z direction. The base end5dhas insertion holes92.

The first auxiliary magnetic pole5extending along the Y direction includes connecting portions5bfor connecting the base end5dand the auxiliary magnetic pole teeth part5a. The first auxiliary magnetic pole5has a space defined by the base end5d, the connecting portions5b, and the auxiliary magnetic pole teeth part5a. The space allows the first auxiliary magnetic pole5to be communicated in the Z direction, which is larger than the XY dimension where the winding wire60is disposed when seen from the Z direction. This makes it possible to partially provide the winding wire60in the space, thus increasing the space for accommodating the winding wire60. In other words, the number of turns of the winding wire60may be increased.

Alternatively, the space may be replaced with a recess thinner than each of the base end5d, the connection portions5b, and the auxiliary magnetic pole teeth part5ain the Z direction.

The magnetic pole4, the first auxiliary magnetic pole5, and an end bridge6have insertion holes91,92,93, respectively (seeFIGS. 2 to 4). The bridge7also has an insertion hole94(not shown). The armature2allows insertion of the armature fixing bolts8into the insertion holes91to94, which makes it possible to efficiently fix the laminated steel plate of the magnetic pole4, the first auxiliary magnetic pole5, the end bridge6, and the bridge7, which have been laminated in the Z direction. In the embodiment, four armature fixing bolts8penetrate through the armature2in the Z direction so as to be fastened with nuts from both sides in the Z direction for fixing the armature2. In this way, the armatures2may be assembled one by one, improving assembly workability. The member for fixing the armature2is not limited to the bolt, which is allowed to use caulking pins. It is preferable to fix the armature2with the member extending in the Z direction through the insertion hole so that the armature2is assembled into a compact structure.

In the embodiment, each number of the insertion holes92and93is four corresponding to the number of the armature fixing bolts8. Referring to the insertion holes93(shown inFIG. 2), upon use of a plurality of armatures2for manufacturing the linear motor1, the insertion holes91to94more than the armature fixing bolts8allow the individually assembled armatures2to be collectively fixed using another fixing member such as bolts. Like the case as described above, upon use of the linear motor1for manufacturing the device such as the compressor, the linear motor1and the cylinder block or the like may be fixed collectively. In the embodiment, the end bridge6has many insertion holes93. It is possible to lessen each number of the insertion holes91,92,94by using members which can be screwed with the insertion holes93.

FIG. 4is a view of an XY plane section of the linear motor1.FIG. 5is a perspective view of a YZ plan section of the linear motor1. Solid arrows shown in the drawing represent an example of the magnetic flux flow upon motor driving.

The magnetic pole4includes cores4bextending in the Y direction at both ends of the magnetic pole teeth parts4ain the X direction. The cores4bserve to connect two half magnetic poles (upper half and lower half sections of the magnetic pole4shown inFIG. 2), which constitute a magnetic circuit including the permanent magnet3a, the two opposite magnetic pole teeth parts4ain the Y direction, and the cores4b. Application of current to the winding wire60(upper wiring wire61and/or lower wiring wire62) generates the magnetic flux flowing through the magnetic pole teeth part4aaround which the wiring wire60is wound. As described above, the magnetic pole4generates the magnetic flux loop along the XY plane. The direction of the magnetic flux loop may be varied by controlling direction of the current applied to the wiring wire60. In the embodiment, the linear motor1is driven while controlling directions of the magnetic flux loops flowing through the two magnetic poles4to be reversed (reverse phases).

The magnetic pole4may be formed into an arbitrary shape so long as the magnetic flux loop may be formed. The magnetic pole4according to the embodiment has a shape having the cores4bat both sides of the magnetic flux teeth parts4a, that is, two half magnetic poles are connected to form the “E”-like shape. It is also possible to form the “C”-like shape.

[Suppression of Magnetization of First Auxiliary Magnetic Pole5]

The first auxiliary magnetic pole5suppresses detent caused by the armature2to improve controllability and noise reduction of the linear motor1. The detailed explanation will be described later. The structure for suppressing magnetization of the first auxiliary magnetic pole5, and the resultant effect will be described hereinafter.

The magnetic pole4exhibits the above-described anisotropic property in the conductivity and permeability resulting from laminated magnetic steel plate. Then the linear motor1forms the magnetic flux loop in parallel with the XY plane on the magnetic pole4. The bridge7allows the magnetic pole4and the first auxiliary magnetic pole5to be apart from each other in the direction (Z direction) orthogonal to the plane (XY plane) where the loop is generated. This makes it possible to suppress magnetic flux leakage from the magnetic pole4to the first auxiliary magnetic pole5. That is, the bridge7allows suppression of magnetization of the first auxiliary magnetic pole5. Excessive leakage of the magnetic flux to the first auxiliary magnetic pole5necessitates the design in consideration of the effect resulting from magnetizing the first auxiliary magnetic pole5, and saturation of the magnetic flux. The first auxiliary magnetic pole5perpendicularly directed to the plane where the magnetic flux loop is generated allows suppression of magnetizing the first auxiliary magnetic pole5, resulting in improved flexibility in design and the compact linear motor1.

It is preferable to lower the conductivity and permeability of the bridge7in the Z direction for the purpose of further suppressing the magnetic flux leakage in the Z direction. It is preferable to use non-magnetic material, for example, aluminum alloy, a certain type of stainless-steel based metal, the resin material, or the steel plates laminated in the Z direction for forming the bridge7. Most preferably, the non-magnetic material is used to form the bridge7so as to effectively suppress the magnetic flux leakage to the first auxiliary magnetic pole5.

[Connection Relationship of Wiring Wire60]

Four wiring wires60and four magnetic pole teeth parts4ashown inFIG. 5will be designated individually using the respective signs.

Referring toFIG. 5, the armature2includes a magnetic pole teeth part4a1dopposite a magnetic pole teeth part4a1uin the Y direction, a magnetic pole teeth part4a2uadjacent to the magnetic pole teeth part4a1uin the Z direction, and a magnetic pole teeth part4a2ddiagonally opposite the magnetic pole teeth part4a1u. Connection relationship among wiring wires61,62,63,64respectively wound around the magnetic pole teeth parts4a1u,4a1d,4a2u,4a2dwill be described.

The wiring wires61and63arranged in the Z direction are electrically coupled, and the wiring wires62and64arranged in the Z direction are electrically coupled. In other words, the in-phase current is applied to the wiring wires61and63arranged in the Z direction, and the in-phase current is applied to the wiring wires62and64. As the wiring wires61and63, and62and64are electrically coupled, respectively, the voltage between those wires exhibits the small value in accordance with the lead length. Accordingly, in the case where the two wiring wires60adjacent in the Z direction are brought into contact with each other, insulation deterioration owing to partial discharge and the like hardly occurs, which makes the short-circuit unlikely to occur. As described above, it is possible to form the recess portion by reducing the thickness of the first auxiliary magnetic pole5in the Z direction, and the space in the first auxiliary magnetic pole5for accommodating the wiring wire60. As the process of insulating coating of the wiring wire60and the like may be easily executed, it is possible to increase the number of turns of the wiring wire60, thus realizing high outputs of the linear motor1.

The wiring wires61and62arranged in the Y direction are electrically coupled, and the wiring wires63and64are further electrically coupled. It is therefore possible to align current phases for generating the respective magnetic flux loops in the XY plane.

The wiring wires60may be electrically coupled either in series or in parallel. The current applied to the winding wires60may be formed into a sine wave AC or a rectangular wave AC. The waveform may be shaped using the inverter. The DC current may be applied either continuously or discretely.

[Magnetization Relationship of Magnetic Pole Teeth Part4a]

As described above, the embodiment is configured to oppositely direct the two magnetic flux loops induced by the current to the wiring wire60in the XY plane. When the magnetic pole teeth part4a1uis magnetized to N pole, the opposite magnetic pole teeth part4a1dand the adjacent magnetic pole teeth part4a2uare magnetized to S pole as unlike pole, and the diagonally opposite magnetic pole teeth part4a2dis magnetized to N pole as a like-pole. The magnetization may be carried out by adjusting the winding direction of the winding wires61to64, and direction of the current to be applied.

Even if the magnetic flux leakage occurs via the bridge7, the magnetic fluxes each with the opposite phase pass through the first auxiliary magnetic pole5. As a result, magnetization of the first auxiliary magnetic pole5may be suppressed.

The force received by the mover corresponds to a sum of the force exerted to the permanent magnet3a. Each of one or more permanent magnets3aof the mover receives the magnetic force derived from magnetization of the magnetic pole teeth part4a, and the detent force (magnetic attraction force) from the magnetic substance part of the armature2.

The detent is determined by the relative positional relationship between the permanent magnet3aand the magnetic substance part of the armature2. As the mover moves in the Z direction, large fluctuation in the detent at the position of the permanent magnet3ain the Z direction causes the thrust ripple upon driving of the mover. This may deteriorate controllability of the linear motor1. In the case of a plurality of armatures2, the design for setting off the detent may be employed by forming the multilayer driving structure, and optimizing the pitch of the armature2. However, the design on the assumption of a plurality of armatures2and phases will make it difficult to downsize the linear motor1.

In the embodiment, since the detent caused by the armature2is suppressed by the first auxiliary magnetic pole5provided for the armature2, it is possible to improve controllability of the linear motor1which is driven through multiphase with the plural armatures2and phases as well as the single-phase, which will be described in detail hereinafter.

Detent Force of Comparative Example

The detent force F in a comparative example will be described.FIG. 6is a perspective sectional view of a linear motor10as the comparative example, which has the similar structure to that of the linear motor1according to the embodiment except that the armature does not include the first auxiliary magnetic pole5.FIG. 7is a view representing the relationship between the detent force F (y-axis) received by the permanent magnet3aand the position of the permanent magnet3a(x-axis) at the center in the Z direction of the embodiment in comparison with the comparative example. The forward direction of the detent force F is defined as the +Z axial direction. In this case, each forward direction of the X, Y, and Z axes will be referred to as +X, +Y, and +Z directions. The reverse directions will be referred to as −X, −Y, and −Z directions, respectively.

A point A represents Z coordinates of the magnetic pole teeth group4a1including the magnetic pole teeth parts4a1uand4a1d. A point C represents the Z coordinates of the magnetic pole teeth group4a2including the magnetic pole teeth parts4a2uand4a2d. A point B as a midpoint between the points A and C represents the Z coordinates of the auxiliary magnetic pole teeth group including the first auxiliary magnetic pole teeth parts5auand5ad. A point D is a midpoint between the points A and B, and a point E is a midpoint between the points B and C.

The permanent magnet3aat the point A receives the magnetic attraction force mainly from the magnetic pole teeth group4a1. Directions of the respective forces are in the +Y and −Y directions, which are canceled to provide the resultant force of zero. The detent force F caused by the magnetic pole teeth group4a1becomes zero. As the magnetic attraction force is proportional to the inverse square of the distance, the detent force F added in the +Z direction, which is caused by the magnetic pole teeth group4a2exhibits a small value which will be ignored for explanation convenience.

As the permanent magnet3amoves in the +Z direction to reach the point D, the magnetic attraction force received by the permanent magnet3afrom the magnetic pole teeth group4a1generates the component in the −Z direction. Simultaneously, since the permanent magnet3aapproaches the magnetic pole teeth group4a2, the influence of the magnetic attraction force caused by the magnetic pole teeth group4a2in the +Z direction becomes relatively large. The magnetic attraction force received from the magnetic pole teeth group4a1is larger than the one received from the magnetic pole teeth group4a2. The detent force F, thus exhibits a negative value.

As the permanent magnet3amoves in the +Z direction to reach the midpoint B between the two magnetic poles4, the detent force F becomes zero again. The sum of the force becomes zero because the respective magnetic attraction forces received from the magnetic pole teeth groups4a1and4a2exhibit equal values and are oppositely directed.

As the permanent magnet3amoves in the +Z direction to reach the point E, the magnetic attraction force of the magnetic pole teeth group4a2becomes dominant, thus bringing the detent force F into the positive value.

As the permanent magnet3areaches the point C, the detent force F caused by the magnetic pole teeth group4a2becomes zero because the detent force F applied in the −Z direction owing to the magnetic pole teeth group4a1exhibits the small value.

The relationship between the detent force F and the position Z of the permanent magnet3aof the linear motor10according to the comparative example is indicated by the dashed line inFIG. 7. The graph clearly shows that the permanent magnet3areceives large detent force F from the armature2at the points D and E at the inner side of the armature2in the Z direction.

Detent Force of the Embodiment

The detent force F of the linear motor1according to the embodiment, in the case where the first auxiliary magnetic pole5is located at the point B will be described. The detent force F generated in the linear motor1according to the embodiment is derived from the sum of the magnetic attraction force generated in the permanent magnet3aof the linear motor10according to the comparative example, and the magnetic attraction force received by the permanent magnet3afrom the first auxiliary magnetic pole5.

For example, existence of the magnetic attraction force at the point A in the +Z direction, which is received by the permanent magnet3afrom the first auxiliary magnetic pole5allows the detent force F to have the positive value while having the absolute value larger than that of the comparative example.

Similarly, existence of the magnetic attraction force at the point C in the −Z direction, which is received by the permanent magnet3afrom the first auxiliary magnetic pole5, allows the detent force F to have the negative value while having the absolute value larger than that of the comparative example.

At the midpoint B, the component of the magnetic attraction force in the Z direction received by the permanent magnet3afrom the first auxiliary magnetic pole5becomes zero. Accordingly, like the comparative example, the detent force F takes the value of zero. It is also possible to provide the single unit of the first auxiliary magnetic pole5in the Y direction without forming the auxiliary magnetic pole teeth group having two opposite auxiliary magnetic poles disposed in the Y direction. The auxiliary magnetic pole teeth group of the embodiment allows setting of the component of the detent force in the Y direction to zero. This makes it possible to reduce the force applied to the mechanism (not shown) for holding the mover in the Y direction, thus allowing suppression of the friction loss in the holding mechanism.

At the point D, the magnetic attraction force received by the permanent magnet3afrom the first auxiliary magnetic pole5acts in the +Z axial forward direction. Then the detent force F exhibits the negative value while having the absolute value smaller than that of the comparative example. Similarly, the detent force F at the point E exhibits the positive value while having the absolute value smaller than that of the comparative example.

The resultant relationship between the detent force F and the position Z of the permanent magnet3aof the embodiment is indicated by the solid line inFIG. 7. The maximum amplitude value of the detent force F may be reduced to be less than the comparative example so that controllability is improved. It is also possible to suppress the detent force at the points D and E at the inner side of the armature2in the Z direction to allow further improvement of controllability by driving to remove the regions around the points A and C from the motion range of the permanent magnet3a.

The aforementioned structure may suppress magnetization of the first auxiliary magnetic pole5, which makes it possible to downsize the linear motor1while improving the controllability.

[Lamination Direction of Magnetic Pole4]

The electromagnetic steel plates laminated in the X direction may be used for producing the magnetic pole4. In this case, the linear motor1is driven by the magnetic flux for forming the loop in parallel with the YZ plane. Therefore, it is preferable to allow passage of the magnetic flux by using the magnetic substance for forming the bridge7. In the aforementioned case, leakage of the magnetic flux to the first auxiliary magnetic pole5is likely to occur. It is therefore necessary to design in consideration of effect of magnetizing the first auxiliary magnetic pole5, and saturation of the magnetic flux. It is preferable to use the magnetic steel plates laminated in the Z direction for producing the magnetic pole4from downsizing aspect.

As described above, each of the magnetic fluxes passing through the two adjacent magnetic pole teeth parts4aat both sides of the first auxiliary magnetic pole5in the Z direction is oppositely directed (reverse phase). It is possible to offset some of or all the magnetic fluxes flowing through the first auxiliary magnetic pole5. Accordingly, the magnetic pole4constituted by the magnetic steel plates laminated in the X direction allows suppression of magnetizing the first auxiliary magnetic pole5. The linear motor1may be designed to be downsized on the assumption that the first auxiliary magnetic pole5is not magnetized. While the permanent magnet3adeviates from the exact front of the auxiliary magnetic pole teeth part5a(point B), the magnetic flux leakage to the first auxiliary magnetic pole5is likely to occur. As a result, there may be the risk of deterioration in controllability of the linear motor1under the influence of leaked magnetic flux. It is therefore preferable to use the magnetic steel plates laminated in the Z direction for producing the magnetic pole4, from the aspect of controllability and downsizing.

The armature disclosed in the above-described WO2004/093301 is produced by punching the magnetic steel plate into a serrated shape (see page 4, line 32). In other words, the respective magnetic steel plates extend in the direction in parallel with the drawing ofFIG. 1. The linear motor described in WO2004/093301 exhibits large values of conductivity and permeability in the relative moving direction between the mover and the armature than those in the direction orthogonal to the aforementioned direction. The large magnetic flux flows not only to the teeth wound with coil but also to the teeth wound with no coil (see page 7, lines 19 to 36). It is therefore difficult to establish downsizing and/or controllability of the motor.

[Relationship Between the Numbers of Permanent Magnets3aand Magnetic Poles4]

It is preferable to set the total of the number of the permanent magnets3aof the mover, and the number of the magnetic poles4of the armature2to the odd number from downsizing aspect. Most preferably, the number of the magnetic poles4is set to two, and the number of the permanent magnets3ais set to one from the aspect of downsizing the linear motor1.

[Motion Range of Mover]

In the region around the points A and C shown inFIG. 5at the ends of the armature2, there may be the case where the detent is intensified depending on the shape and material for forming the first auxiliary magnetic pole5. It is possible to drive the linear motor1only in the region at which the detent force F is small by controlling to remove the ends of the armature2from the motion range of the permanent magnet3a. In other words, controllability of the linear motor1may be improved by controlling the permanent magnet3ato move at inner sides between the two magnetic pole teeth groups4a1,4a2in the Z direction. The center of the permanent magnet3ain the Z direction, and each center of the magnetic pole teeth groups4a1,4a2in the Z direction may be set to the corresponding reference positions, respectively. All the permanent magnets3amay be controlled to be positioned at the side inner than the innermost sides between the magnetic pole teeth groups4a1and4a2in the Z direction from aspect of suppressing the detent most effectively.

The linear motor1of the embodiment is of moving magnet type having the mover driven and the armature2fixed. It is also possible to use the motor of moving coil type having the mover fixed, and the armature2movable.

A plurality of armatures2according to the embodiment may be arranged in the Z direction so as to constitute the linear motor1with multiphase drive.

Two opposite first auxiliary magnetic poles5in the Y direction may be connected with each other via the core.

According to the embodiment, the first auxiliary magnetic pole5disposed between the two magnetic poles4of the armature2allows suppression of the detent caused by the armature2, thus improving controllability.

The embodiment is configured that the direction in which the magnetic pole4exhibits high conductivity and high permeability is orthogonal to the relative moving direction (Z direction) between the armature2and the mover. This makes it possible to suppress magnetization of the first auxiliary magnetic pole5, and achieve downsizing and/or improved controllability.

Furthermore, the first auxiliary magnetic pole5has the space or recess portion to increase the number of turns of the winding wire60to achieve both downsizing and high output. The current flowing to the adjacent winding wire in the Z direction may have either the coordinate phase or reverse phase so long as it is in-phase.

The embodiment is configured to allow suppression of the detent caused by the armature2. The use of a few armatures2or the compact armature2(that is, a few magnetic pole teeth parts4a) allows improved controllability. It is therefore possible to achieve both improved controllability and downsizing.

The embodiment is configured to have the opposite magnetic pole teeth groups4a1,4a2in the Y direction, and the auxiliary magnetic pole teeth group5a, thus offsetting the detent in the Y direction.

The use of the insertion hole and the fixing member such as the armature fixing bolt8achieves improved assembly workability and downsizing.

Second Embodiment

A second embodiment according to the present invention will be described referring toFIGS. 8 and 9. The structure of the embodiment which is different from that of the first embodiment will be described hereinafter.

FIG. 8is a perspective view of the linear motor1of the embodiment.FIG. 9is a perspective sectional view of the linear motor1of the embodiment.

This embodiment is configured to dispose second auxiliary magnetic poles50at both sides of the armature2(outside the magnetic pole4in Z direction) via the end bridges6. The end bridge6serves to separate the magnetic pole4and the second auxiliary magnetic pole50from each other in the Z direction so that the magnetic flux leakage to the second auxiliary magnetic pole50is suppressed. The second auxiliary magnetic pole50has the same structure as that of the first auxiliary magnetic pole5, and the end bridge6may be structured similar to the bridge7. The second auxiliary magnetic pole50has an insertion hole (not shown) which allows insertion of the fixing member.

The first auxiliary magnetic pole5and the second auxiliary magnetic pole50will be collectively referred to as “auxiliary magnetic poles5,50” hereinafter.

The auxiliary magnetic poles5,50are disposed at both sides of the magnetic poles4in the Z direction. That is, the first auxiliary magnetic pole5is positioned at inner sides of the magnetic poles4in the Z direction, and the second auxiliary magnetic poles50are disposed at outer sides of the magnetic poles4in the Z direction. Specifically, since the auxiliary magnetic poles5,50are disposed in +Z and −Z directions when seen from the points A and C as positions of the magnetic pole teeth groups4a1,4a2, respectively, the respective detent forces F at the points A and C may be reduced.

The embodiment is capable of providing similar effects to those derived from the first embodiment. Suppression of the detent forces at the points A and C around the ends of the armature2allows retention of controllability even if the movable range of the mover in the Z direction is expanded. This makes it possible to establish both improved controllability and high output of the linear motor1.

Third Embodiment

[Magnetic Pole Structure at One Side]

A third embodiment according to the present invention will be described referring toFIGS. 10 to 12. The structure of the embodiment, which is different from those of the first and the second embodiment will be described hereinafter.

FIG. 10is a perspective view of the linear motor11according to the embodiment.FIG. 11is a perspective view of a YZ plane section of the linear motor11according to the embodiment.FIG. 12is a perspective view of the mover according to the embodiment.

The armature20includes the magnetic poles4and the first auxiliary magnetic poles5arranged alternately having the bridges7interposed therebetween. The linear motor11according to the embodiment includes six magnetic poles4, and five first auxiliary magnetic poles5. However, the structure is not limited to the one as described above so long as two or more magnetic poles4and one or more first auxiliary magnetic poles5are provided. The armature20includes the end bridge6at the end in the Z direction.

The mover includes the permanent magnets3aand a back yoke30, and concave sections30aextending along the Z direction, which is formed around the permanent magnet3aat the outer side in the X direction. The length of the permanent magnet3ain the X direction is shorter than the distance between the concave sections30ain the X direction. As a result, the magnetic flux looping in the XY plane is allowed to easily pass through the permanent magnet3aand the magnetic pole teeth parts4a,4bso as to reduce the leaked magnetic flux. The concave section30aserves to suppress the magnetic flux from avoiding the permanent magnet3a, thus providing the highly efficient linear motor11.

The embodiment is capable of providing similar effects to those derived from the first or the second embodiment. The resultant linear motor has the dimension further reduced in the Y direction.

Fourth Embodiment

<Device Equipped with Linear Motor>

This embodiment is formed as the device equipped with the linear motor1or11. The device equipped with the linear motor1will be described hereinafter.

FIG. 13is a perspective view of a compressor100as an exemplary device equipped with the linear motor1.

The compressor100is a reciprocating compressor including a compression element110and a motor element120. The motor element120includes the armature2and the mover.

A flat plate-like mover3includes the flat plate-like permanent magnet3a, and a piston112at one end in the Z direction. Application of current to the winding wire60of the motor element120imparts the reciprocating force in the Z direction to the mover3so that the piston112attached to the mover3reciprocates in a cylinder111a.

The compression element110includes a cylinder block111that constitutes the cylinder111a, and a cylinder head (not shown) that is assembled with the end surface of the cylinder block111. The work fluid supplied into the cylinder111ais compressed through reciprocating motion of the piston112.

The mover3is connected to a resonant spring114. In the case where the motor element120is driven to allow reciprocation of the mover3at the specific frequency, the restoring force of the resonant spring114causes resonance phenomena. In the resonant state, the mover3is allowed to reciprocate with less exciting force. If the motor element120is driven around the resonant frequency, the work fluid may be compressed by the reciprocating motion of the piston112with less power consumption.

The compressor100according to the embodiment includes the second auxiliary magnetic pole50with a plurality of insertion holes94. The cylinder block111includes insertion holes95. Those holes allow insertion of a cylinder fixing bolt80(second fixing member) for fixing the cylinder block111to the armature2in addition to the armature fixing bolt8(first fixing member) for fixing and fastening the magnetic poles4, the first auxiliary magnetic poles5, the end bridges6, and the bridges7of the armature2.

The second fixing member is inserted into the insertion holes94and95which are differently positioned from the insertion holes91,92,93,94for insertion of the first fixing member in the X direction. This makes it possible to fix the armature2and the cylinder block111.

Like the armature fixing bolt8, the cylinder fixing bolt80may be configured to penetrate through the armature2. It may be configured to be screwed with the insertion hole94of the second auxiliary magnetic pole50. This makes it possible to fix the armature2and the cylinder block111even if the insertion hole for insertion of the cylinder fixing bolt80is not formed in the member other than the second auxiliary magnetic pole50(magnetic pole4, first auxiliary magnetic pole5, end bridge6, bridge7), which is the member at the end of the armature2in the Z direction. The cylinder fixing bolt80as a magnetic substance allows suppression of the magnetic flux leakage in the Z direction.

Preferably, the non-magnetic substance is used for forming the first fixing member and/or the second fixing member from the aspect of suppressing the magnetic flux leakage.

The use of two types of fixing members of the first and the second fixing members allows assembly of the armature2, and then attachment of the compression element110to the armature2, resulting in improved assembly workability. Various kinds of known members such as bolts and caulking pins may be used for the fixing member.

The armature fixing bolt8is configured to penetrate through the armature2so as to have both ends fastened and fixed, which allows the magnetic pole4, the first auxiliary magnetic pole5, the end bridge6, the bridge7, and the second auxiliary magnetic pole50to be fixed.

It is also possible to provide the armature2with any other members which may be disposed between the second auxiliary magnetic pole50and the cylinder block111, for example. Specifically, an end frame (not shown) having a plurality of insertion holes may be provided at the outer side of the second auxiliary magnetic pole50in the Z direction. In the aforementioned state, the second auxiliary magnetic pole50does not serve as the member positioned at the end of the armature2in the Z direction. Accordingly, the insertion hole94for insertion of the cylinder fixing bolt80does not have to be formed. The similar effects may be obtained by fixing the armature2and the end frame with the armature fixing bolt8, and fixing the cylinder block111and the end frame with the cylinder fixing bolt80.

The compressor100according to the embodiment is formed by fixing the compression element110and the motor element120, more specifically, the armature2and the cylinder block111so as to be assembled into substantially a rectangular parallelepiped shape. It is therefore possible to efficiently arrange plural units of compressors100.

The aforementioned process provides the compressor100equipped with the linear motor1. Similarly, the compressor equipped with the linear motor11may also be provided.

A refrigerator200will be described as an example of the appliance equipped with the linear motor1or the aforementioned compressor100.

FIG. 14is a longitudinal sectional view of the refrigerator200equipped with the linear motor1.

Referring toFIG. 14, the linear motor1is incorporated in a sealed type compressor1000equipped with the compressor100. The refrigerator200includes a heat insulation casing210. The sealed type compressor1000is disposed in the region defined by the heat insulation casing210and a partition211. A refrigeration cycle using such refrigerant as R600a is formed by connecting the sealed type compressor1000, a heat radiation pipe, a capillary tube, and a cooler260.

The refrigerator200includes such storage compartments as a refrigerating compartment220, an upper freezing compartment230, a lower freezing compartment240, and a vegetable compartment250, each inner space of which is cooled through activation of the freezing cycle (not shown) by driving the sealed type compressor1000.

The refrigerator200according to the embodiment includes the heat insulation casing210and the partition211, which form substantially a rectangular parallelepiped shape. The sealed type compressor1000outside the heat insulation casing210is located to the rear of the vegetable compartment250(right side of the figure), which reduces storage capacity of the vegetable compartment250. Preferably, the sealed type compressor1000is structured compact for the purpose of increasing capacity of the refrigerator200. The linear motor according to the embodiment may be downsized so that the machine chamber that stores the sealed type compressor1000is made compact, thus increasing capacity of the vegetable compartment250. The vegetable compartment250may be used as the freezing compartment250or the refrigerating compartment250by varying the set temperature zone.

The location at which the sealed type compressor1000is disposed is not particularly restricted. It is possible to dispose the compressor arbitrarily in the area around the heat insulation casing210. For example, it may be disposed to the rear of or around any one of the above-described storage compartments.

The device to be equipped with the linear motor1or11is not particularly restricted, which is applicable to the device for various uses such as the electric pump, the XY stage in addition to the compressor and the refrigerator. For example, for the use of refrigeration air conditioning, it is applicable to such system as the air conditioning system, and freezing/refrigerating showcase.