JP2012244678A - Linear motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear motor in which a leakage of a magnetic flux is suppressed.SOLUTION: A linear motor 1 comprises: a first main magnet 25A having a magnetization direction directed in a direction (z direction) perpendicular to a movable direction (x direction); a first coil 19A having a length in an axial direction which is smaller than a length in the x direction of the first main magnet 25A, having the axial direction directed in the x direction, and having an outer peripheral surface directed to the first main magnet 25A; an outer yoke 7 for covering a side of the first main magnet 25A opposite to the first coil 19A; a leakage prevention magnet 31 adjacent to one end in the x direction of the first main magnet 25A and having a magnetic pole directed to the first main magnet 25A, the magnetic pole being the same as a magnetic pole of the first main magnet 25A directed to the first coil 19A; and a leakage prevention yoke 12 for covering a side of the leakage prevention magnet 31 opposite to the first coil 19A and a side of the leakage prevention magnet 31 opposite to the first main magnet 25A.

Description

  The present invention relates to a linear motor such as a voice coil motor.

  Linear motors such as voice coil motors are widely known. In Patent Document 1, a linear magnet that does not require a yoke is provided by providing an auxiliary magnet having a magnetization direction in a direction orthogonal to the magnetization direction of the main magnet adjacent to the main magnet that generates a magnetic flux interlinking with the coil. A motor is disclosed.

JP 2010-158140 A

  In recent years, downsizing of devices including linear motors has been attempted. As a result, the linear motor and the magnetic driven member driven by the linear motor come close to each other. Then, the driven member is attracted to the linear motor by the magnetic flux leaking from the linear motor. Such suction causes a reduction in high-speed control performance and constant thrust performance. Therefore, it is preferable that leakage of magnetic flux from the linear motor is suppressed.

  The linear motor according to one aspect of the present invention has a first main magnet having a magnetization direction oriented in a direction orthogonal to the movable direction, and an axial length smaller than a length of the first main magnet in the movable direction. A first coil having an axial direction directed to the movable direction and an outer peripheral surface directed to the first main magnet; an outer yoke covering an opposite side of the first main magnet from the first coil; and the first main A leakage preventing magnet adjacent to one end of the moving direction of the magnet and having the same magnetic pole as the first main magnet directed to the first coil directed to the first main magnet; and A leakage preventing yoke that covers a side opposite to the first coil and a side opposite to the first main magnet;

  Preferably, the linear motor is adjacent to a side of the first main magnet opposite to the leakage prevention magnet, and the first main magnet has the same magnetic pole as the magnetic pole facing the first coil. A first auxiliary magnet facing the main magnet is further provided, and the leakage preventing magnet has a length in the movable direction smaller than a length in the movable direction of the first auxiliary magnet.

  Preferably, the linear motor is adjacent to a side of the first auxiliary magnet opposite to the first main magnet, and a second main magnet having a magnetic pole direction opposite to the first main magnet; A second coil having an axial length smaller than a length of the second main magnet in the movable direction, coaxially arranged with the first coil and having an outer peripheral surface facing the second main magnet; A second auxiliary magnet that is adjacent to the opposite side of the two main magnets to the first auxiliary magnet and that has the same magnetic pole as the magnetic pole that the second main magnet is directed to the second coil directed to the second main magnet. The outer yoke includes the first auxiliary magnet, the second main magnet, and the first coil and the second auxiliary magnet of the second auxiliary magnet. Opposite side covering the coil, and the second main magnet of the second auxiliary magnet to cover the opposite side, the end yoke extending seen in the moving direction to a position overlapping the second coil is provided.

  Preferably, the linear motor has the same magnetic pole as the magnetic pole that the second main magnet faces the second coil in a direction orthogonal to the movable direction and the magnetization direction of the second main magnet. A sub-magnet facing the outer peripheral surface of the sub-magnet, a side of the sub-magnet opposite to the second coil, a sub-yoke continuous with the end yoke, and inserted into the second coil and continuous with the end yoke And a center yoke.

  Preferably, a magnet and a yoke that are opposed to the outer peripheral surface of the first coil in a direction orthogonal to the movable direction and the magnetization direction of the first main magnet are not provided.

  According to said structure, the leakage of the magnetic flux from a linear motor is suppressed. As a result, for example, the attraction of the magnetic material by the linear motor is suppressed.

The perspective view which shows the external appearance of the linear motor which concerns on embodiment of this invention. The perspective view which shows the external appearance from the other direction of the linear motor of FIG. The perspective view which shows the external appearance of the needle | mover of the linear motor of FIG. The figure which looked at the linear motor of FIG. 1 in the movable direction. The figure which looked at the linear motor of FIG. 1 from the side of the movable direction. The figure explaining the effect | action of the linear motor of FIG.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, about the same or similar structure, the same code | symbol may be attached | subjected. Further, in this case, “coil 19” is “first coil 19A” and “second coil 19B”, and the names are prefixed with numerals and capital letters are added to the reference numerals, and the same or similar configuration. May be distinguished.

  FIG. 1 is a perspective view showing an appearance of a linear motor 1 according to an embodiment of the present invention. FIG. 2 is a perspective view of the linear motor 1 as viewed from the back side in FIG.

  The linear motor 1 is a linear motor that exhibits a driving force in the x direction. That is, the linear motor 1 includes a stator 3 and a movable element 5 that can move in the x direction with respect to the stator 3. In FIG. 1, only a part of the mover 5 is shown.

  The linear motor 1 is configured as a so-called moving coil type linear motor. That is, the stator 3 has magnets (25, 27, 29, and 31) and yokes (7, 9, 11, 12, and 13), and the mover 5 has a coil 19.

  The yoke not only constitutes the magnetic path of the magnet but also serves as a member for holding the magnet, and constitutes a substantially rectangular parallelepiped outer shape (box) of the linear motor 1. Specifically, the stator 3 includes a pair of outer yokes 7 constituting a rectangular parallelepiped z-direction surface, a pair of sub yokes 9 constituting a y-direction surface, and an end yoke 11 constituting an x-direction surface. (FIG. 2) and a leakage preventing yoke 12 provided at the end of the outer yoke 7 in the x direction. In addition, the stator 3 has a center yoke portion 13 disposed so as to extend in the x direction at the center of the yoke constituting these outer shapes.

  The pair of outer yokes 7 are each formed in a substantially rectangular flat plate shape, and face each other in the z direction with the mover 5 interposed therebetween. The pair of sub yokes 9 are each formed in a substantially rectangular flat plate shape, and face each other in the y direction with the mover 5 interposed therebetween. The sub yoke 9 is approximately half the length in the x direction of the outer yoke 7 and closes about half of the gap in the y direction formed by the pair of outer yokes 7. The end yoke 11 is formed in a substantially rectangular flat plate shape, and closes the opening formed on the positive side in the x direction formed by the pair of outer yokes 7 and the pair of sub yokes 9.

  The leakage prevention yoke 12 has an outer portion 12a having the same cross-sectional shape as the cross-sectional shape orthogonal to the x direction of the outer yoke 7, and an end surface portion 12b protruding from the outer portion 12a to the coil 19 side. The end surface portion 12b is formed to be thinner in the x direction than the outer portion 12a, and smaller in the y direction than the outer portion 12a.

  The center yoke portion 13 has a center yoke 15 (FIG. 1) as a main body and a tubular member 17 surrounding the center yoke 15.

  The center yoke 15 is made of a magnetic material such as iron, and has a rectangular cross section, for example. The center yoke 15 has substantially the same length as the pair of outer yokes 7 in the x direction.

  The tubular member 17 is formed in a cylindrical shape similar to the outer shape of the center yoke 15 (in this embodiment, a cylindrical shape having a rectangular cross section), and covers substantially the entire center yoke 15. The tubular member 17 is made of a nonmagnetic and conductive material. Examples of such a material include copper, aluminum, and stainless steel. The tubular member 17 contributes to suppression of the mutual inductance of the pair of coils 19.

  The yokes (7, 9, 11 and 12) constituting the outer shape are made of a magnetic material such as iron, for example. The yokes (7, 9, 11, 12, and 13) described above may be fixed to each other by an appropriate method such as a screw or an adhesive. Further, some yokes may be formed integrally with each other, or one yoke may be composed of a plurality of members. For example, the outer portion 12a may be formed integrally with the outer yoke 7 and the end surface portion 12b may be formed by a separate member from the outer portion 12a.

  FIG. 3 is a perspective view showing the appearance of the mover 5.

  The mover 5 includes two coils 19, a holding member 21 that holds the two coils 19, and a connecting member 23 that is fixed to the holding member 21. 1 and 2, the holding member 21 and the connecting member 23 are not shown.

  Although not specifically illustrated, the coil 19 is configured, for example, by aligning and winding wires. The wire may be a round wire or a flat wire. In addition, from the viewpoint of improving the space factor, the wire is preferably a rectangular wire. The wire may be formed of an appropriate conductive material such as copper. In addition, from the viewpoint of reducing the weight (speeding up) of the mover 5, the wire is preferably formed of aluminum.

  For example, the coil 19 is formed in a rectangular shape when viewed in the axial direction (opening direction). For example, the two coils 19 have the same configuration, are arranged coaxially with each other, and are held by a holding member 21. Note that the two coils 19 may or may not be connected to each other.

  The holding member 21 may be formed of an insulating material such as resin, or may be formed of a conductive material such as metal. When formed of an insulating material, generation of eddy current can be suppressed, and when formed of a conductive material (metal), the holding member 21 can be downsized while ensuring strength. When the holding member 21 is made of metal, a plurality of holes may be formed in order to suppress the generation of eddy current. The coil 19 and the holding member 21 are fixed to each other by an adhesive, for example.

  The connecting member 23 is a member connected to the driving target of the linear motor 1 and is schematically illustrated in a rectangular parallelepiped shape in FIG. The connecting member 23 is formed of a resin such as a glass epoxy resin, for example. The connecting member 23 is fixed to the holding member 21 by an appropriate method such as a screw, an adhesive, or embedding.

  In the stator 3 shown in FIGS. 1 and 2, the sub yoke 9 and the end yoke 11 are provided only on the negative side in the x direction, and the positive side in the x direction is open. This is to secure a large space.

  4 is a diagram of the linear motor 1 viewed in the x direction, and FIG. 5 is a diagram of the linear motor viewed in the y direction. 4 and 5, the mover 5 is shown with a part thereof omitted.

  The stator 3 includes a main magnet 25 (FIGS. 1, 2 and 5), a sub magnet 27 (FIGS. 1 and 4), an auxiliary magnet 29 (FIGS. 1 and 5), and a leakage prevention magnet 31 (FIG. 1, 2 and 5).

  Specifically, the main magnet 25 is disposed on the negative side in the x direction with respect to the pair of first main magnets 25A opposed to the pair of first main magnets 25A in the z direction. A pair of second main magnets 25B is provided.

  For example, the first main magnet 25A and the second main magnet 25B have the same configuration. The main magnet 25 is formed, for example, in a rectangular flat plate shape, and the thickness direction is formed as the magnetization direction. The main magnet 25 is provided on the inner surface of the outer yoke 7 so that the magnetic poles are directed toward the outer peripheral surface of the coil 19 in the z direction. The main magnet 25 is formed to have a length in the x direction larger than that of the coil 19.

  Therefore, the magnetic flux emitted from the main magnet 25 is linked in the z direction to the portion of the coil 19 extending in the y direction. Accordingly, when a current is passed through the coil 19, a force in the x direction is applied to the coil 19 in accordance with Fleming's left-hand rule.

  The effective stroke of the mover 5 is defined by, for example, a length (L3 + L4) obtained by subtracting the length L2 of the coil 19 in the x direction from the length L1 of the main magnet 25 in the x direction, as shown in FIG. The The interval between the first coil 19A and the second coil 19B is set so that the relative position of the first coil 19A with respect to the first main magnet 25A and the relative position of the second coil 19B with respect to the second main magnet 25B are the same. Yes.

  In the first main magnet 25A and the second main magnet 25B, the directions of the magnetic poles with respect to the first coil 19A and the second coil 19B are opposite to each other. Therefore, between the first main magnet 25 </ b> A and the second main magnet 25 </ b> B, the magnetic path connecting the inner magnetic poles is formed by the center yoke portion 13, and the magnetic path connecting the outer magnetic poles is formed by the outer yoke 7. As a result, the magnetic flux efficiently links to the coil 19.

  The pair of coils 19 are supplied with current so that the current directions are opposite to each other. Thereby, the magnetic flux generated by supplying a current to the pair of coils 19 is canceled out and iron loss is suppressed.

  The sub-magnet 27 is formed in, for example, a rectangular flat plate shape, and the thickness direction is formed as the magnetization direction. Further, the sub magnet 27 has the same magnetic pole (N pole in the present embodiment) as the magnetic pole that the second main magnet 25B faces the second coil 19B so as to face the outer peripheral surface of the second coil 19B in the y direction. The inner surface of the sub yoke 9 is provided. The sub magnet 27 has a length equivalent to that of the second main magnet 25B in the x direction.

  Therefore, the magnetic flux emitted from the submagnet 27 is linked in the y direction with respect to the portion of the second coil 19B extending in the z direction. Therefore, when a current is passed through the second coil 19B, an x-direction force is applied to the second coil 19B in accordance with Fleming's left-hand rule.

  The center yoke portion 13 and the sub yoke 9 facing the two magnetic poles (N pole and S pole) of the sub magnet 27 are connected by the end yoke 11. Accordingly, the center yoke portion 13, the end yoke 11, and the sub yoke 9 constitute a magnetic path through which the magnetic flux emitted from the N pole of the sub magnet 27 enters the S pole of the sub magnet 27. As a result, the magnetic flux efficiently links to the coil 19.

  Specifically, the auxiliary magnet 29 is disposed between the first main magnet 25A and the second main magnet 25B, and a pair of first auxiliary magnets 29A adjacent to the main magnet 25 and the second main magnet 25B. A pair of second auxiliary magnets 29B are provided on the opposite side to the first auxiliary magnet 29A.

  For example, the first auxiliary magnet 29A and the second auxiliary magnet 29B have the same configuration. The auxiliary magnet 29 is formed in, for example, an elongated rectangular parallelepiped shape, and the width direction perpendicular to the longitudinal direction is formed as the magnetization direction. Further, the auxiliary magnet 29 is provided on the inner surface of the outer yoke 7 so that the same magnetic pole as that of the adjacent main magnet 25 is directed to the coil 19 is directed to the adjacent main magnet 25. That is, in the present embodiment, the first auxiliary magnet 29A directs the S pole to the first main magnet 25A, the N pole to the second main magnet 25B, and the second auxiliary magnet 29B sets the N pole to the second main magnet 25B. Is aimed at.

  Therefore, the first auxiliary magnet 29A suppresses the magnetic flux emitted from the north pole of the second main magnet 25B from flowing to the south pole of the first main magnet 25A without passing through the center yoke portion 13, and is efficient. The magnetic flux can be linked to the coil 19.

  Further, the second auxiliary magnet 29B suppresses the magnetic flux emitted from the N pole of the second main magnet 25B from flowing to the S pole of the second main magnet 25B without passing through the center yoke portion 13, and is efficient. The magnetic flux can be linked to the coil 19.

  The leakage prevention magnet 31 is formed in, for example, an elongated flat plate shape, and the thickness direction is formed as the magnetization direction. The leakage prevention magnet 31 is provided on the inner side (coil 19 side) of the leakage prevention yoke 12 and between the end surface portion 12b and the first main magnet 25A. In other words, the leakage prevention magnet 31 is covered with the leakage prevention yoke 12 on the side opposite to the first coil 19A and the side opposite to the first main magnet 25A. Further, the leakage prevention magnet 31 has the same magnetic pole (S pole in this embodiment) as the first main magnet 25A facing the coil 19 facing the first main magnet 25A.

  Therefore, the magnetic flux toward the south pole of the first main magnet 25A is prevented from leaking to the open end side (negative side in the x direction) of the linear motor 1. Further, the leakage of the magnetic flux from the N pole of the leakage preventing magnet 31 to the open end side is suppressed by the magnetic flux flowing through the leakage preventing yoke 12.

  Since the leakage prevention magnet 31 is mainly intended for leakage of magnetic flux, the leakage prevention magnet 31 is larger in size (and consequently stronger in magnetic field) than the auxiliary magnet 29 for efficiently linking the magnetic flux to the coil 19. A) may be small. Further, by reducing the leakage prevention magnet 31, the leakage prevention yoke 12 that prevents the leakage of magnetic flux from the leakage prevention magnet 31 can be reduced, and the size reduction can be achieved synergistically. The leakage preventing magnet 31 is, for example, less than half the size of the auxiliary magnet 29 in the x direction.

  FIG. 6 is a diagram for explaining the operation of the linear motor 1.

  In FIG. 6, the horizontal axis indicates the position in the x direction, and the vertical axis indicates the magnetic field strength at the position of the coil 19. A solid line Ln1 indicates the magnetic field strength of the linear motor 1, and a solid line Ln0 indicates the magnetic field strength of the comparative example. As a comparative example, the linear motor 1 without the auxiliary magnet 29, the leakage prevention magnet 31, and the leakage prevention yoke 12 was assumed.

  In the solid line Ln0 and the solid line Ln1, the regions R1 and R2 that are higher in the positive direction and the negative direction correspond to the magnetic field of the main magnet 25, respectively. Compared with the comparative example, the linear motor 1 has a longer length in the x direction in which the magnetic field strength is constant in the regions R1 and R2. That is, the stroke in which the thrust is maintained constant is long. Further, in the linear motor 1, the strength of the magnetic field is rapidly reduced on the negative side in the positive direction of the region R1, and the leakage of magnetic flux is suppressed.

  The present invention is not limited to the above embodiment, and may be implemented in various aspects.

  Either the magnet or the coil may be a mover or a stator. In addition, both of them may move with respect to a housing or the like of a device provided with a linear motor.

  The second main magnet (25B) and the second coil (19B) may not be provided. In other words, a pair of main magnets may not be provided in the movable direction. For example, the linear motor 1 may be configured with a yoke or the like so that magnetic flux flows from the N pole to the S pole of the first main magnet (see the sub magnet 27 in the embodiment). Further, the sub magnet and the auxiliary magnet are not essential requirements of the present invention.

  The shape of the magnet or coil may be set as appropriate. For example, the coil may be circular, and the magnet may be formed in an annular shape surrounding the outer peripheral surface of the coil, or in this case, may be formed in a circular shape. Further, the magnet such as the main magnet may be composed of a plurality of magnets, or conversely, the main magnet and the sub magnet may be integrally formed.

  DESCRIPTION OF SYMBOLS 1 ... Linear motor, 7 ... Outer yoke, 12 ... Leakage prevention yoke, 19A ... 1st coil, 29A ... 1st main magnet, 31 ... Leakage prevention magnet

Claims (5)

A first main magnet having a magnetization direction in a direction perpendicular to the movable direction;
A first coil having an axial length smaller than a length of the first main magnet in the movable direction, with the axial direction facing the movable direction and an outer peripheral surface facing the first main magnet;
An outer yoke covering the opposite side of the first main magnet from the first coil;
A leakage preventing magnet adjacent to one end of the first main magnet in the movable direction and having the same magnetic pole as the first main magnet directed to the first coil directed to the first main magnet;
A leakage preventing yoke that covers the opposite side of the leakage preventing magnet from the first coil and the opposite side of the first main magnet;
Linear motor having A first auxiliary that is adjacent to the side opposite to the leakage preventing magnet of the first main magnet and that has the same magnetic pole as the magnetic pole that the first main magnet faces toward the first coil faces the first main magnet. A magnet,
The linear motor according to claim 1, wherein the leakage prevention magnet has a length in the movable direction smaller than a length in the movable direction of the first auxiliary magnet. A second main magnet which is adjacent to the first auxiliary magnet on the opposite side of the first main magnet, and whose magnetic pole direction is opposite to the first main magnet;
A second coil having an axial length smaller than a length of the second main magnet in the movable direction, arranged coaxially with the first coil and having an outer peripheral surface facing the second main magnet;
The second main magnet is adjacent to the side opposite to the first auxiliary magnet, and the second main magnet has the same magnetic pole as the second magnetic pole directed to the second coil. An auxiliary magnet,
Further comprising
The outer yoke covers the opposite side of the first auxiliary magnet, the second main magnet, and the second auxiliary magnet from the first coil and the second coil,
The linear motor according to claim 2, wherein an end yoke that covers the opposite side of the second auxiliary magnet from the second main magnet and extends to a position overlapping the second coil when viewed in the movable direction is provided. A sub-magnet in which the same magnetic pole as the second main magnet is directed to the second coil in the direction perpendicular to the movable direction and the magnetization direction of the second main magnet is directed to the outer peripheral surface of the second coil; ,
A sub yoke that covers the side of the sub magnet opposite to the second coil and that is continuous with the end yoke;
A center yoke that is inserted through the second coil and continues to the end yoke;
The linear motor according to claim 3, further comprising: The linear motor according to claim 4, wherein a magnet and a yoke facing the outer peripheral surface of the first coil are not provided in the movable direction and a direction orthogonal to the magnetization direction of the first main magnet.

Images