JP4578819B2 - Linear motor - Google Patents

Description

The present invention relates to a linear motor, and particularly suitable for use in a refrigerator compressor, an air compressor, or a hydrogen gas (H ₂ ) compressor at a cryogenic temperature, for example, a cryogenic temperature of about −200 ° C. About.

A linear motor related to the present invention is disclosed in, for example, Japanese Patent Laid-Open No. 2000-23441 (Patent Document 1). The linear motor will be described with reference to FIG.
In FIG. 4, the linear motor includes a fixed portion 300 composed of a yoke 100 made of SS400, pure iron or the like and a permanent magnet 200 described later, and a movable portion 400 reciprocating in the axial direction with respect to the fixed portion 300. I have.
The yoke 100 includes a cylindrical outer yoke 100a, an inner yoke 100b disposed on the inner side of the outer yoke 100a, and a side yoke 100c connecting the outer yoke 100a and the inner yoke 100b on one end side thereof. The permanent magnet 200 is fixed to the inner peripheral surface of the outer yoke 100a.
The permanent magnet 200 and the yoke 300 form a magnetic circuit as indicated by a dotted line. This magnetic circuit generates a magnetic flux in the gap between the permanent magnet 200 and the inner yoke 100b.

  The movable part 400 includes a cylindrical body 400a whose one end is closed, and an output shaft that reciprocates in the axial direction through the through hole 100d of the internal yoke 100b through the central part of the closed part 400b of the cylindrical body 400a. 400c and a coil 400d wound around the outer periphery of the cylindrical body 400a.

When an alternating current is applied to the coil 400d of the linear motor having such a configuration via the lead wire 500, a thrust proportional to the magnetic flux density is generated, whereby the movable portion 400 reciprocates in the axial direction.
JP 2000-23441 A

  However, in the linear motor having such a configuration, there is a possibility that the lead wire is disconnected due to fatigue due to the reciprocating motion of the movable portion. As a result, the life cycle may be shortened. Furthermore, there is a disadvantage that the burden for maintenance of the linear motor becomes large.

  Also, in this linear motor, eddy current loss occurs in the yoke due to the dynamic magnetic flux from the coil, and the efficiency of the linear motor may be reduced. For example, the efficiency may be less than 60%.

On the other hand, so-called other types of linear motors are also known in which the direction of the magnetic flux generated by energizing the coil and the direction of the magnetic flux by the permanent magnet coincide with the moving direction of the movable part.
Examples of such other types of linear motors include, for example, an electromagnet type linear motor, and a plurality of (for example, eight) silicon steel plates laminated on the outer periphery of a cylinder portion disposed in the center portion. A “cylinder type linear motor” that is equally distributed along the circumferential direction is known.

  However, in the electromagnet type linear motor, the axial dimension of the yoke facing the permanent magnet is much smaller than the axial dimension of the external yoke, so that the magnetic flux generated by the coil is not used effectively. is doing.

  Further, in the “cylinder type linear motor”, the space efficiency (rated thrust / volume) between the laminated silicon steel plates is low, and the disadvantage is that the assembling property is also inferior.

It is an object of the present invention to provide a linear motor that overcomes the above disadvantages.
That is, an object of the present invention is to provide a linear motor that can improve space efficiency, has excellent assemblability, and can improve motor efficiency.

According to the present invention, the shape of the cross section in the plane orthogonal to the axial direction is four corners and these corners
A frame formed of a non-magnetic material having a rectangular frame shape defining a hollow at the corner and the side wall, and having a cylindrical shape in the axial direction. And four yokes made of a magnetic material and fixed to the inner walls of two side walls that are continuous and orthogonal to the four corners of the frame, respectively, along the axial direction of the frame. And a movable part that reciprocates the hollow of the frame in the axial direction,
Each yoke includes a first side, a second side that is long in parallel with the first side, a length of the first side, and the second side in a plane orthogonal to the axial direction. It has a trapezoidal shape composed of first and second hypotenuses connected to both ends,
The second side portion faces the corresponding corner of the frame, the first side portion faces the opposite direction to the corner portion, and the connection portions of the first and second oblique sides and the second side portion Is fixed along the axial direction of the frame to the inner walls of the two side walls that continue to the corner,
The opposite hypotenuses of adjacent yokes, fixed inside two side walls that continue to each corner of the frame, are parallel with a peripheral gap between them,
In the axial direction, a coil is disposed on the outer periphery of the first side and the second side of each yoke,
A central gap that is continuous with the four peripheral gaps is defined between the plurality of coils arranged in the yokes at diagonal positions facing the adjacent yokes and the opposite corners,
The movable portion is located in the center gap in the hollow of the cylindrical frame, and is disposed on the surface orthogonal to the axial direction, with an output shaft disposed in the center gap so as to be able to reciprocate in the axial direction. Four plate-shaped magnet mounting portions that protrude in the radial direction from the output shaft and extend to the peripheral gaps at the four locations and are shorter than the length of the frame in the axial direction, and the plate-shaped magnet mounting portions. Having permanent magnets of different magnetic poles fixed on opposite sides to the hypotenuse of the adjacent trapezoidal yoke,
An alternating current is applied to the coils disposed in the yokes.
A linear motor is provided.

  Preferably, the magnet mounting portion and / or yoke of the linear motor of the present invention is configured by laminating a large number of silicon steel plates.

  More preferably, permanent magnets having different polarities along the axial direction of the output shaft are respectively arranged and fixed on both surfaces of each magnet mounting portion in the linear motor of the present invention.

  Preferably, in the linear motor of the present invention, a separator is inserted between the yoke and the movable part.

  According to the linear motor having the above-described configuration, the magnetic flux generated by the permanent magnet flows in the circumferential direction along the yoke as the fixed portion. Therefore, even if the permanent magnet as the movable portion reciprocates in the axial direction, iron loss is significantly reduced. Can be small.

  Furthermore, since the magnetic flux generated by the coil flows in the circumferential direction along the yoke as the fixed portion, the iron loss can be remarkably reduced.

  Further, since each coil is wound around the outer periphery of the yoke of the fixed portion, the magnetic flux generated from each coil effectively flows in the yoke, and thereby the axial dimension is reduced compared to the conventional linear motor. As a result, the linear motor can be miniaturized.

A preferred embodiment of a linear motor of the present invention will be described in detail with reference to the accompanying drawings.
1 is a front view of a linear motor according to an embodiment of the present invention, FIG. 2 is a perspective view of a movable part of the linear motor illustrated in FIG. 1, and FIG. 3 is a movable part illustrated in FIGS. FIG.
A linear motor according to an embodiment of the present invention includes a frame 1 that has a rectangular shape (square) in FIG. 1 illustrating the front, a movable portion 2 that is housed in the frame 1 and has a substantially cross shape, 1 and 4 are arranged in a part 3 separated by a movable part 2 and fixed in the frame 1 and have four substantially trapezoidal yokes 4 and coils 5 wound around the outer periphery of each yoke 4. ing.

  The frame 1 is made of a nonmagnetic material, and two engaging portions 6a and 6b are provided on the opposing inner surfaces so as to protrude from each other.

As shown in FIG. 2, the movable portion is provided so as to project radially in the outer periphery of the output shaft 7 and the output shaft 7 supported between a pair of bearings (not shown) so as to reciprocate in the direction of the axis A. Four flat plate magnet mounting portions 8a, 8b, 8c, 8d (represented as 8 representative of 8a, 8b, 8c, 8d) and shafts on both sides of each of the magnet mounting portions 8a, 8b, 8c, 8d A first permanent magnet 9a and a second permanent magnet 9b are arranged and fixed along the direction.
Each of the magnet attachment portions 8 is preferably formed by laminating a number of silicon steel plates having the same shape and the same dimensions. This is because the generation of eddy currents can be reduced according to the laminated structure of silicon steel plates.

The first permanent magnet 9a and the second permanent magnet 9b are made of permanent magnets having different polarities along the direction of the axis A, for example, an S-pole permanent magnet and an N-pole on one side of the first magnet mounting portion 8a. The permanent magnets are arranged and fixed downward in the figure, and the N-pole permanent magnet and the S-pole permanent magnet are arranged and fixed downward in the figure on the other surface of the first magnet mounting portion 8a.
An N-pole permanent magnet and an S-pole permanent magnet are arranged and fixed downward in the figure on the other surface of the second magnet mounting portion 8b, and an S-pole permanent magnet is provided on one surface of the second magnet mounting portion 8b. A magnet and an N-pole permanent magnet are arranged and fixed downward in the figure.
Similarly, on both surfaces of the third and fourth magnet mounting portions 8c and 8d, downward in the figure, an S-pole permanent magnet and an N-pole permanent magnet (or an N-pole permanent magnet and an S-pole permanent magnet). ) Is fixed.

  In this way, permanent magnets having different polarities are arranged between the opposing magnet mounting portions 8a, 8b, 8c, 8d, for example, between the first magnet mounting portion 8a and the second magnet mounting portion 8b. become. As a result, a magnetic flux φ1 is generated between the permanent magnets along the circumferential direction.

Each yoke 4 is formed by laminating a large number of silicon steel plates having the same shape and the same dimensions. These yokes 4 have their upper bottom portions 4a directed toward the center in the frame 1 and lower bottom portions thereof. Both sides of 4b are disposed so as to abut against the side walls of a pair of locking portions 6b, 6c facing each other at the corner 3 of the frame 1.
If each yoke 4 is formed by laminating silicon steel plates, the generation of eddy currents can be reduced.

  A coil 5 is disposed on the outer periphery of the central portion of each yoke 4, and another coil 5 disposed at another corner 3 is disposed on a line orthogonal to the axis of the coil 5.

  Further, as shown in FIG. 1, each yoke 4 provided with a coil 5 on its outer periphery is disposed at four corners in the frame 1, and then a lid (not shown) is fastened and fixed to the frame 1. , Integrated with the frame 1. As a result, the yoke 4 and the coil 5 fixed to the frame 1 constitute a fixed portion.

  Each coil 5 configured in this manner is supplied with an alternating current as an exciting current having a predetermined frequency, thereby generating a magnetic flux φ2 in the same direction as the aforementioned magnetic flux φ1.

  It is desirable to insert a separator (not shown) between the yoke 4 and the movable part 2. When the separator is provided, the influence of the gas generated from the coil can be prevented.

Modified Embodiment In the above-described embodiment, the case where two first permanent magnets and two second permanent magnets are arranged and fixed along the axial direction has been described, but any one permanent magnet may be provided.

  In the embodiment described above, the case where four magnet mounting portions are used has been described. However, in the linear motor of the present invention, the number of magnet mounting portions is not limited to four, depending on the scale of the linear motor. You can change the number.

  According to the linear motor of the present invention, since the magnetic flux by the permanent magnet flows in the circumferential direction along the yoke as the fixed portion, the iron loss is remarkably reduced even if the permanent magnet as the movable portion reciprocates in the axial direction. Further, since the magnetic flux generated by the coil flows in the circumferential direction along the yoke as the fixed portion, the iron loss can be remarkably reduced.

  Furthermore, according to the linear motor of the present invention, since each coil is wound around the outer periphery of the yoke of the fixed portion, the magnetic flux generated from each coil effectively flows in the yoke, and thus, the conventional linear motor Compared to the above, the axial dimension can be greatly reduced, and the linear motor can be downsized.

FIG. 1 is a front view of a linear motor as an embodiment of the linear motor of the present invention. FIG. 2 is a perspective view of a movable portion in the linear motor illustrated in FIG. FIG. 3 is a perspective view of a fixing portion in the linear motor illustrated in FIGS. 1 and 2. FIG. 4 is a schematic configuration diagram of a conventional linear motor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Frame, 2 ... Moving part, 4 ... Yoke, 5 ... Coil, 7 ... Output shaft 8 (8a, 8b, 8c, 8d) ... Magnet attaching part 9a, 9b ... Permanent magnet

Claims (4)

The cross-sectional shape in the plane orthogonal to the axial direction has four corners and side walls that are continuous with these corners, and has a square frame shape that defines the hollow between the corners and the side walls. A frame formed of a non-magnetic material having a cylindrical shape in the axial direction;
Four yokes made of a magnetic material, respectively, fixed along the axial direction of the frame to the inner walls of two side walls that are continuous and orthogonal to each of the four corners of the frame;
A movable part that reciprocates in the axial direction of the hollow of the frame;
Have
Each yoke includes a first side, a second side that is long in parallel with the first side, a length of the first side, and the second side in a plane orthogonal to the axial direction. It has a trapezoidal shape composed of first and second hypotenuses connected to both ends,
The second side portion faces the corresponding corner of the frame, the first side portion faces the opposite direction to the corner portion, and the connection portions of the first and second oblique sides and the second side portion Is fixed along the axial direction of the frame to the inner walls of the two side walls that continue to the corner,
The opposite hypotenuses of adjacent yokes, fixed inside two side walls that continue to each corner of the frame, are parallel with a peripheral gap between them,
In the axial direction, a coil is disposed on the outer periphery of the first side and the second side of each yoke,
A central gap that is continuous with the four peripheral gaps is defined between the plurality of coils arranged in the yokes at diagonal positions facing the adjacent yoke and the opposite corner,
The movable part is
An output shaft located in the central gap in the hollow of the cylindrical frame, and disposed so as to be capable of reciprocating in the axial direction in the central gap;
Four plate-like magnet mounting portions that protrude in the radial direction from the output shaft in a plane orthogonal to the axial direction and extend to the peripheral gaps at the four locations, and shorter than the length of the frame in the axial direction;
Permanent magnets of different magnetic poles fixed on opposite sides of the adjacent trapezoidal yoke on opposite sides of each plate-shaped magnet mounting portion;
Have
An alternating current is applied to the coils disposed in the yokes.
Linear motor. Each of the plurality of magnet mounting portions and / or each of the plurality of yokes is configured by laminating a plurality of silicon steel plates,
The linear motor according to claim 1. On both surfaces of each magnet mounting portion, permanent magnets having different polarities are arranged and fixed along the axial direction of the output shaft, respectively.
The linear motor according to claim 1 or 2. A separator is inserted between the yoke and the movable part,
The linear motor in any one of Claims 1-3.

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