JP2012095445A - Magnetic field shield mechanism and actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic field shield mechanism capable of reducing or preventing (limiting) the influence of a magnetic field of a magnet part on a stationary part, and an actuator using the same.SOLUTION: A magnetic field shield mechanism 5 comprises: a first magnet 33 magnetized in a first direction; a yoke 31 disposed on the side of one magnetic pole S of the first magnet 33; and an annular second magnet 36 disposed on the side of one magnetic pole S of the first magnet 33 with the yoke 31 sandwiched and magnetized in a direction crossing the first direction.

Description

  The present invention relates to a magnetic field shielding mechanism for preventing magnetization of a magnetic member close to a magnet and an actuator using the same.

  The linear motor is configured such that the stator side and the rotor (movable element) side of the rotary motor are linearly extended, and converts electric energy into thrust for linear motion. A linear motor capable of obtaining a linear thrust is used as a uniaxial actuator that linearly moves a moving body.

As an example of a linear motor, it has a magnet part (fixed part) in which a plurality of plate-shaped magnets are arranged in a straight line and a coil part (movable part) having a plurality of coils arranged to face this magnet part. Is known (see Patent Document 1).
For example, the coil is supported by the movable part main body in a state where three phases of U, V, and W phases are sequentially and repeatedly arranged. When a three-phase current having a phase difference of 120 degrees is passed through these coils, a moving magnetic field that moves in the axial direction of the coils is generated.
And the movable part which has a coil acquires the thrust which generate | occur | produces between magnet parts with a moving magnetic field, and performs a linear motion with respect to a magnet part synchronizing with the speed of a moving magnetic field.

JP 2008-245474 A

In the linear motor described above, the magnet portion is configured by arranging a plurality of plate-shaped magnets linearly on the back yoke. And this back yoke is fixed to fixing parts, such as a base of a linear motor.
However, when the fixed part in which the magnet part is disposed is a magnetic material such as steel, the fixed part is magnetized. In particular, the region in contact with the magnet part is strongly magnetized. For this reason, there exists a problem that iron powder etc. adhere to the guide rail attached to a fixed part, for example, and the smooth sliding of a movable part is impaired.
Therefore, it is conceivable to form the back yoke thicker than necessary mechanical strength, but the magnet part becomes larger and heavier, which hinders downsizing and thinning of the apparatus.

  Further, even when the fixed portion is formed of a nonmagnetic material such as aluminum, there is a problem that a magnetic scale or the like used for detecting the position of the movable portion cannot be attached in the vicinity of the back yoke. For this reason, it is necessary to select and arrange a magnetic scale or the like in a region that is not affected by magnetism, which hinders downsizing of the apparatus.

  This invention is made in view of such a situation, Comprising: The magnetic field shielding mechanism which can reduce or prevent (suppress) the influence of the magnetic field from a magnet part to the stationary part side, and an actuator using the same are provided. With the goal.

The present invention employs the following means in order to solve the above problems.
A magnetic field shielding mechanism according to the present invention includes a first magnet magnetized in a first direction, a yoke disposed on one magnetic pole side of the first magnet, and one of the first magnets sandwiching the yoke. And an annular second magnet that is arranged on the magnetic pole side and is magnetized in a direction intersecting the first direction.

  An actuator according to the present invention includes a magnet portion in which a plurality of magnets are arranged, and a coil portion in which a plurality of coils are arranged to face the magnet portions, and flows through the magnetic fields of the plurality of magnets and the plurality of coils. 10. The magnetic field shielding mechanism according to claim 1, wherein the magnet unit is configured to relatively move the magnet unit and the coil unit along an arrangement direction of the plurality of magnets by an electric current. It is characterized by having.

  According to the magnetic field shielding mechanism according to the present invention, it is possible to reduce or prevent (suppress) the influence of the magnetic field from the magnet portion to the fixed portion side with a simple configuration. In addition, the magnet portion can be made thinner and lighter.

According to the actuator of the present invention, since the guide member that moves the magnet portion and the coil portion relative to each other is not magnetized, iron powder or the like is attracted to the guide member to inhibit the relative movement of the magnet portion and the coil portion. You can prevent problems. Therefore, it is possible to avoid a decrease in the function of the actuator.
Moreover, since another magnetic member can be arrange | positioned in the vicinity of a magnet part, the reliability improvement of an apparatus, the space-saving of an apparatus, and cost reduction can also be achieved.

It is a perspective view showing a schematic structure of an actuator (linear motor) concerning an embodiment of the present invention. It is an expansion perspective view (partial sectional view) showing a base and a table. It is sectional drawing which shows schematic structure of an actuator. It is a figure which shows a magnet part. It is a perspective view which shows a coil part. It is sectional drawing which shows a linear guide. It is a figure which shows the magnetic field shielding mechanism which concerns on 1st embodiment. It is a figure which shows the effect (analysis result of magnetic flux density) of the magnetic field shielding mechanism which concerns on 1st embodiment. It is a figure which shows the effect (analysis result of magnetic flux density) of the magnetic field shielding mechanism which concerns on 1st embodiment (when a support member is removed). It is a figure which shows the analysis result of the magnetic flux density in a prior art example. It is a figure which shows the magnetic flux density to the coil part side of a magnet part. It is a figure which shows the magnetic field shielding mechanism which concerns on 2nd embodiment. It is a figure which shows the effect (analysis result of magnetic flux density) of the magnetic field shielding mechanism which concerns on 2nd embodiment. It is a figure which shows the magnetic field shielding mechanism which concerns on 3rd embodiment. It is a figure which shows the effect (analysis result of magnetic flux density) of the magnetic field shielding mechanism which concerns on 3rd embodiment. It is a figure which shows the magnetic field shielding mechanism which concerns on 4th embodiment. It is a figure which shows the effect (analysis result of magnetic flux density) of the magnetic field shielding mechanism which concerns on 4th embodiment. It is sectional drawing which shows schematic structure of the actuator (rotary motor) which concerns on embodiment of this invention.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a perspective view showing a schematic configuration of an actuator A (linear motor 1) according to an embodiment of the present invention.
FIG. 2 is an enlarged perspective view (partially sectional view) showing the base 10 and the table 20.
FIG. 3 is a cross-sectional view showing a schematic configuration of the actuator A.

The actuator A includes the linear motor 1, a motor driver 80 (control device) that controls the linear motor 1, and a user terminal 90 (information processing device) connected to the motor driver 80.
The linear motor 1 includes a base 10 that is elongated in one axial direction (X direction) and a table 20 that is slidable with respect to the base 10.
A pair of linear guides 50 is provided between the base 10 and the table 20 so that the table 20 can slide smoothly with respect to the base 10.

The base 10 is formed of an elongated rectangular bottom wall portion 11 and a pair of side wall portions 12 provided perpendicular to both ends in the width direction (Y direction) of the bottom wall portion 11. The base 10 is made of, for example, a magnetic material such as steel or a nonmagnetic material such as aluminum.
A magnet portion 30 in which a plurality of magnets are arranged is attached to the upper surface of the bottom wall portion 11 of the base 10.
Further, the track rails 51 of the linear guide 50 are arranged along the uniaxial direction on the upper surfaces of the side wall portions 12 of the base 10. The two track rails 51 are arranged in parallel, and two moving blocks 52 are attached to each.

The table 20 is made of a nonmagnetic material such as aluminum and is formed in a rectangular plate shape.
The moving blocks 52 of the linear guide 50 are attached to the four corners of the lower surface 20b of the table 20. The moving block 52 is attached to the two track rails 51 described above. In other words, the table 20 is supported on the base 10 by the pair of linear guides 50 so as to be linearly movable.

In addition, a coil unit 40 including three coils 41 and the like is suspended between the four moving blocks 52 on the lower surface of the table 20. The three coils 41 function as a three-phase coil (armature).
A gap g is set between the magnet portion 30 attached to the base 10 and the coil portion 40 attached to the table 20. The gap g is kept constant even when the table 20 moves linearly with respect to the base 10 by the pair of linear guides 50.

FIG. 4 is a diagram illustrating the magnet unit 30. 4A is a top view, FIG. 4B is a side view, and FIG. 4C is a bottom view (when the support member is removed).
The magnet unit 30 generates a magnetic field toward the coil unit 40. Specifically, the magnet portion 30 includes a back yoke 31 formed in an elongated rectangular plate shape, a magnet group 32 arranged in close contact with the upper surface 31 a of the back yoke 31 at a constant pitch, and a lower surface 31 b of the back yoke 31. A magnet group 35 closely arranged at the same pitch as the magnet group 32 and a support member 38 having substantially the same shape as the back yoke 31 and sandwiching the magnet group 35 between the back yoke 31 and the magnet group 35. .

The back yoke (yoke) 31 is made of a magnetic material such as steel and functions as a yoke that concentrates the magnetic lines of force from the magnet group 32. Further, the back yoke 31 is formed with a width (Y direction) smaller than the bottom wall portion 11 of the base 10.
The support member 38 is a member for fixing the magnet portion 30 to the base 10, and is formed of the same material as the back yoke 31, that is, a magnetic material such as steel. The shape of the support member 38 is formed in substantially the same shape as the back yoke 31.

In the magnet group 32, a plurality of magnets 33 whose upper surfaces (33a, 34a) are N-poles and S-pole magnets 34 are alternately arranged at a constant pitch along the longitudinal direction (X direction) of the back yoke 31. It is a thing.
Each of the magnets 33 and 34 of the magnet group 32 is composed of an elongated plate-like permanent magnet. The longitudinal direction of the magnets 33 and 34 is formed shorter than the width (Y direction) of the back yoke 31. The short direction (X direction) of the magnets 33 and 34 is formed corresponding to the length (X direction) of each coil 41 of the coil unit 40 described later. The magnets 33 and 34 are formed to be thicker than the back yoke 31 (Z direction).
The magnets 33 and 34 are fixed to the center in the width direction of the back yoke 31 with an adhesive or the like so that the longitudinal direction thereof is parallel to the width direction (Y direction) of the back yoke 31.

The magnet group 35 includes an N-pole magnet 36 and an S-pole magnet 37 alternately arranged on the outer circumferential surface (outer ring surface) along the longitudinal direction (X direction) of the back yoke 31 at the same pitch as the magnet group 32. A plurality are arranged in a straight line.
The magnets 36 and 37 of the magnet group 35 are made of permanent magnets having substantially the same outer shape as the magnets 33 and 34. That is, the longitudinal direction and the short direction of the magnets 36 and 37 are formed the same as the magnets 33 and 34. The magnets 36 and 37 are thinner than the magnets 33 and 34 and are formed to be approximately the same as the back yoke 31.

The magnets 36 and 37 are fixed to the center of the back yoke 31 in the width direction with an adhesive or the like so that the longitudinal direction thereof is parallel to the width direction (Y direction) of the back yoke 31. Is done.
Further, the magnets 36 and 37 have their lower surfaces 36b and 37b fixed to the center in the width direction of the support member 38 with an adhesive or the like so that the longitudinal direction thereof is parallel to the width direction (Y direction) of the support member 38. Is done.
Furthermore, the magnets 36 and 37 have a one-to-one correspondence with the magnets 33 and 34 arranged on the upper surface 31a of the back yoke 31 when viewed in plan (viewed from a direction perpendicular to the back yoke 31 (Z direction)). Arranged at the (overlapping) position.

As described above, the magnet unit 30 is arranged such that the magnet group 32 (magnets 33 and 34) and the magnet group 35 (magnets 36 and 37) correspond to each other (overlapping) with the back yoke 31 interposed therebetween.
A support member 38 that supports the magnet groups 32 and 35 and the back yoke 31 is fixed in close contact with the bottom wall portion 11 of the base 10.

The magnet unit 30 generates a magnetic field from the magnet group 32 toward the coil unit 40 side, and suppresses the influence of the magnetic field on the base 10 side by the magnet group 35 and the support member 38. That is, it also functions as the magnetic field shielding mechanism 5 that reduces or prevents (suppresses) the influence of the magnetic field on the base 10 side.
The detailed configuration of the magnetic field shielding mechanism 5 will be described later.

FIG. 5 is a perspective view showing the coil unit 40.
A coil portion 40 as an armature composed of three coils 41 functioning as a three-phase coil and a core 42 is attached to the central portion of the lower surface of the table 20. The material of the core 42 is a magnetic material such as silicon steel. The core 42 has three comb teeth 42a, 42b, and 42c that strengthen the magnetic field generated in the three-phase coil (coil 41).
The three coils 41 are respectively wound around the three comb teeth 42a, 42b, and 42c of the core 42 to form a U-phase coil 41a, a V-phase coil 41b, and a W-phase coil 41c. The three coils 41 are arranged along the moving direction of the table 20.

The three coils 41 are supplied with three-phase alternating currents having different phases by 120 degrees. As a result, a traveling magnetic field is generated from the coil unit 40. Thereby, a thrust is generated in the coil unit 40 (table 20) by the action of the magnetic field generated in the magnet unit 30.
The current flowing through the three coils 41 of the coil unit 40 is controlled by the motor driver 80.

FIG. 6 shows a perspective view of the linear guide 50.
The linear guide 50 has a track rail 51 attached to the upper surface of the side wall portion 12 of the base 10.
A plurality of mounting holes 51b are formed in the track rail 51 at a predetermined pitch in the longitudinal direction. The track rail 51 is fixed to the side wall portion 12 by passing a bolt through the mounting hole 51 b and screwing the bolt into the screw hole of the side wall portion 12 of the base 10.
A plurality of ball rolling grooves 51a in which the balls 55 roll along the longitudinal direction are formed on the track rail 51. The cross-sectional shape of the ball rolling groove 51a is a circular arc groove shape made of a single arc slightly larger than the radius of the ball 55, or a Gothic arch groove shape made of two arcs.
The ball rolling groove 51 a is formed not only on the side surface of the track rail 51 but also on the upper surface of the track rail 51. By forming the ball rolling groove 51 a on the upper surface of the track rail 51, the vertical rigidity of the linear guide 50 can be increased.

The moving block 52 is formed in a bowl shape straddling the track rail 51. In the moving block 52, a load ball rolling groove 52a facing the ball rolling groove 51a of the track rail 51 is formed, and a ball circulation path including the load ball rolling groove 52a is formed.
An end plate 53 is attached to each end face of the moving block 52 in the uniaxial direction. The ball circulation path includes a load ball rolling groove 52a, a ball return path 52b extending in parallel with the load ball rolling groove 52a, an end plate 53 and an end of the load ball rolling groove 52a and the ball return path 52b. And a U-shaped direction change path 52c connecting the end portions of the two, and the whole is formed in a circuit shape.
A plurality of balls 55 are arranged and accommodated in the ball circulation path.
A mounting screw 52d for mounting the table 20 is processed on the moving block 52. The moving block 52 is screwed to the lower surface 20 b of the table 20.

  When the moving block 52 is moved relative to the track rail 51, the ball 55 interposed between the ball rolling groove 51a of the track rail 51 and the loaded ball rolling groove 52a of the moving block 52 rolls. . The ball 55 rolled to one end of the load ball rolling groove 52a is guided to the direction changing path 52c, passes through the ball return path 52b and the opposite direction changing path 52c, and then to the other end of the load ball rolling groove 52a. Returned. By interposing the ball 55 between the track rail 51 and the moving block 52, the resistance when the moving block 52 moves with respect to the track rail 51 can be reduced.

The position / velocity / acceleration of the table 20 with respect to the base 10 is detected by the magnetic encoder 60. The magnetic encoder 60 has a resolution of about 1 μm, for example.
The magnetic encoder 60 includes a magnetic scale 61 attached to the base 10 and a magnetic sensor 62 attached to the table 20.
The magnetic scale 61 is made of an elongated rectangular magnetic body, and its upper surface is magnetized so that N poles and S poles alternately have a constant pitch (for example, 2 mm). The magnetic scale 61 is disposed in close contact with the end of the bottom wall 11 of the base 10 (in the vicinity of the side wall 12) along the longitudinal direction (X direction) of the base 10.

The magnetic sensor 62 detects the magnetism of the magnetic scale 61 with an MR element, and outputs a sine wave signal by relatively moving along the magnetic scale 61.
The signal detected by the magnetic sensor 62 is sent to the motor driver 80 via a signal processing unit (not shown). And the motor driver 80 controls the electric current supplied to the coil part 40 so that the table 20 moves to a command position based on the position command from the user terminal 90. In this way, the linear motor 1 is controlled.

  As a control method of the linear motor 1, feedback control or the like is performed. That is, the position information, speed information, and acceleration information of the table 20 detected by the table 20 are sent to the motor driver 80, and the difference from the target value (command value) is calculated. The three-phase alternating current with respect to the three coils 41 of the coil part 40 is controlled so that it may approach.

FIG. 7 is a diagram showing the magnetic field shielding mechanism 5 according to the first embodiment. FIG. 7A is a cross-sectional view, and FIG. 7B is a bottom view (when the support member is removed).
FIG. 7 shows the magnetic field shielding mechanism 5 according to the combination of the magnet 33 and the magnet 36. The magnetic field shielding mechanism 5 which is a combination of the magnet 34 and the magnet 37 has the same configuration and has the same effect.
Therefore, hereinafter, the magnetic field shielding mechanism 5 mainly relating to the combination of the magnet 33 and the magnet 36 will be described as an example.

In the magnetic field shielding mechanism 5, ring-shaped (ring-shaped) magnets 36 and 37 are arranged on the lower surfaces 33 b and 34 b of the magnets 33 and 34 arranged on the upper surface of the magnet unit 30 with the back yoke 31 interposed therebetween. Further, a support member 38 is disposed in close contact with the lower surfaces 36b, 37b of the magnets 36, 37. And the influence of the magnetic field from the magnets 33 and 34 to the base 10 side is suppressed by the action of the magnets 36 and 37 and the support member 38.
The magnetic field shielding includes not only the case where the influence (magnetization) of the magnetic field from the magnet group 32 to the base 10 is completely blocked (shielded) but also the case where the influence of the magnetic field is weakened (decreased). That is, magnetic leakage from the magnet group 32 to the base 10 side is prevented or reduced.

The magnets (first magnets) 33 and 34 of the magnet group 32 are sintered magnets such as ferrite magnets, alnico magnets, neodymium magnets, and samarium cobalt magnets, and are formed in a rectangle such as a rectangle. The magnets 33 and 34 are each magnetized in the thickness direction (Z direction: first direction).
The thickness of the magnets 33 and 34 is 2 mm, for example.

  As described above, the back yoke 31 is made of a magnetic material such as SS400 and functions as a yoke that concentrates the magnetic lines of force from the magnet group 32. The thickness of the back yoke 31 is 1 mm, for example.

Magnets (second magnets) 36 and 37 of the magnet group 35 are sintered magnets such as ferrite magnets, alnico magnets, neodymium magnets, and samarium cobalt magnets, and have the same outer shape as the magnets 33 and 34, and have a central portion. Is a square ring-shaped magnet having a space (hollow part).
The thickness of the magnets 36 and 37 is 1 mm, for example.
Further, the thickness of the magnets 36 and 37 in the square ring shape is, for example, 1 mm.

The magnets 36 and 37 are two-layer (laminated) magnets magnetized in a direction (XY plane) intersecting with the Z direction (magnetization direction of the first magnet: first direction). That is, the magnetization direction (Z direction: first direction) of the magnets 33 and 34 and the magnetization direction (XY plane) of the magnets 36 and 37 are orthogonal (intersect).
Note that the direction intersecting the Z direction is a direction of thickness in a square ring shape (a direction perpendicular to the inner peripheral surfaces 36d and 37d and the outer peripheral surfaces 36c and 37c). Specifically, in FIG. 7B, a portion extending in the X direction of the magnet (second magnet) 36 is magnetized in the Y direction, and a portion extending in the Y direction is magnetized in the X direction. . That is, the direction intersecting the Z direction means all directions in the XY plane.

The magnets 36 are arranged along a direction intersecting the Z direction so that the two magnets 36p and 36q face each other with the same polarity. In the present embodiment, two quadrangular ring-shaped magnets 36p and 36q having similar shapes are joined so as to fit each other. The inner magnet 36p is magnetized with an S-pole on the inner peripheral surface and an N-pole on the outer peripheral surface. On the other hand, the outer magnet 36q is magnetized with an N-pole on the inner peripheral surface and an S-pole on the outer peripheral surface. Therefore, the outer peripheral surface (outer ring surface) 36c and the inner peripheral surface (inner ring surface) 36d of the magnet 36 are both magnetized to the S pole.
Similarly, the outer peripheral surface (outer ring surface) 37c and the inner peripheral surface (inner ring surface) 37d of the magnet 37 are both magnetized to the N pole.

The magnet 36 is arranged such that its upper surface 36 a faces the lower surface 33 b of the magnet 33 through the back yoke 31, and the lower surface 36 b is in close contact with the bottom wall portion 11 of the base 10. That is, the magnetic pole (S pole) of the lower surface 33b of the magnet 33 and the magnetic pole (S pole) of the outer peripheral surface 36c and the inner peripheral surface 36d of the magnet 36 are the same (same pole).
Similarly, the magnet 37 is disposed such that its upper surface 37 a faces the lower surface 34 b of the magnet 34 through the back yoke 31, and the lower surface 37 b is in close contact with the bottom wall portion 11 of the base 10. That is, the magnetic pole (N pole) on the lower surface 34b of the magnet 34 and the magnetic pole (N pole) on the outer peripheral surface 37c and the inner peripheral surface 37d of the magnet 37 are the same (same pole).

The magnetic force (magnetic flux density) of the magnets 36 and 37 (magnet group 35) is smaller (weaker) than the magnetic force of the magnets 33 and 34 (magnet group 32).
For example, when the magnets 33 and 34 are, for example, about 45 MG (45 KT), the magnets 36 and 37 are, for example, about 23 MG (23 KT) or less. That is, the magnetic force of the magnets 36 and 37 is about ½ or less of the magnetic force of the magnets 33 and 34. In the present embodiment, the magnetic force of the magnets 36 and 37 is about ¼ of the magnetic force of the magnets 33 and 34 (about 12 MG (12 KT)).
Therefore, relatively inexpensive magnets can be used as the magnets 36 and 37 (magnet group 35).

As described above, the support member 38 is made of a magnetic material such as SS400, and supports the magnet groups 32 and 35 and the back yoke 31. Moreover, the influence of the magnetic field from the magnet groups 32 and 35 to the base 10 side is reduced.
The thickness of the support member 38 is 2 mm, for example.

FIG. 8 is a diagram showing the effect (magnetic flux density analysis result) of the magnetic field shielding mechanism 5 according to the first embodiment. 8A and 8B are cross-sectional views of the magnetic field shielding mechanism 5, and FIG. 8C is a bottom view of the magnetic field shielding mechanism 5 (a view showing the lower surface 38b of the support member 38).
FIG. 9 is a diagram illustrating the effect (analysis result of the magnetic flux density) of the magnetic field shielding mechanism 5 according to the first embodiment, in which the support member 38 is removed. 9A and 9B are cross-sectional views of the magnetic field shielding mechanism 5, and FIG. 9C is a bottom view of the magnetic field shielding mechanism 5 (a view showing the lower surface 36b of the magnet 36).
FIG. 10 is a diagram illustrating the analysis result of the magnetic flux density in the conventional example. That is, the case where the magnet 33 is directly arranged on the base 10 (the magnetic field shielding mechanism 5 is not arranged) is shown. 10A and 10B are cross-sectional views, and FIG. 10C is a bottom view (a view showing a lower surface 931b of the back yoke 931).

  8, 9, and 10, the dark (dark) portion of the color tone has a high magnetic flux density, and the thin (bright) portion has a low magnetic flux density.

As shown in FIGS. 8A and 8B, it can be confirmed that the upper surface 38a of the support member 38 is hardly magnetized, and the portion in contact with the magnet 36 is slightly magnetized. Moreover, as shown in FIG.8 (c), it can confirm that the lower surface 38b of the supporting member 38 is hardly magnetized.
Further, as shown in FIG. 9C, since the magnetic flux density on the lower surface 36b of the magnet 36 is low, it can be confirmed that the degree of magnetization of the support member 38 is low.
Therefore, it can be understood that the influence of the magnetic field from the magnet unit 30 to the base 10 side is blocked or suppressed (relieved).

On the other hand, in the conventional example shown in FIG. 10, it can be confirmed that the lower surface 931b of the back yoke 931 is magnetized even if the thickness (Z direction) of the back yoke 931 is about 4 mm.
Therefore, in the conventional example, it can be understood that when the magnet portion is fixed to the base 10, the influence of the magnetic field on the base 10 side occurs.

Thus, by providing the magnetic field shielding mechanism 5 in the magnet part 30, the influence of the magnetic field on the base 10 side can be prevented (suppressed).
Moreover, in the magnetic field shielding mechanism 5, the combined thickness (4 mm) of the back yoke 31, the magnet 36, and the support member 38 is the same as the thickness (4 mm) of the back yoke 931 of the conventional example. Therefore, the magnet part 30 is not increased in size and weight.
Furthermore, as shown in FIG. 9, even when the support member 38 is not provided, the influence of the magnetic field on the base 10 side can be reduced or prevented (suppressed). For this reason, it is possible to fix the magnet part 30 from which the support member 38 is removed to the base 10. Therefore, it is possible to make the magnet portion 30 thinner and lighter than in the past.

FIG. 11 is a diagram illustrating the magnetic flux density of the magnet 33 (magnet unit 30) toward the coil unit 40.
FIG. 11A shows a conventional example when the magnetic field shielding mechanism 5 is arranged between the magnet 33 and the base 10.
In FIG. 11, the vertical axis represents the magnetic flux density, and the horizontal axis represents the position of the magnet 33 in the longitudinal direction (Y direction). Each graph line indicates the result of the magnetic flux density at a position (offset amount) away from the upper surface 33a of the magnet 33 toward the coil portion 40 side.

As shown in FIG. 11, even when the magnetic field shielding mechanism 5 is arranged (FIG. 11 (a)), the same magnetic flux density as in the conventional example (FIG. 11 (b)) is directed toward the coil part 40 side. Can be confirmed.
That is, it can be confirmed that the magnetic field shielding mechanism 5 does not adversely affect the magnetic flux density of the magnet unit 30 that contributes to the performance of the linear motor 1.

Thus, by arranging the magnet 36 (magnet group 35) between the magnet 33 (magnet group 32) and the base 10, magnetization of the base 10 can be prevented (suppressed).
Since the magnetic lines of force from the magnetic poles (S poles) of the outer peripheral surface 36 c and the inner peripheral surface 36 d of the magnet 36 are opposed to the magnetic lines of force from the magnetic poles (S pole) of the lower surface 33 b of the magnet 33, It is estimated that the magnetic field lines from the magnetic pole (S pole) on the lower surface 33b do not reach the base 10 (the influence of the magnetic field is reduced).
Similarly, by arranging the magnet 37 (magnet group 35) between the magnet 34 (magnet group 32) and the base 10, the magnetization of the base 10 can be prevented (suppressed).

The magnetic force (magnetic flux density) of the magnet 36 (magnet group 35) is weaker (smaller) than the magnet group 32 because it is sufficient to face the magnetic field lines from the magnetic poles on the lower surface 33b of the magnet 33 (magnet group 32). May be.
As described above, in the present embodiment, the magnetic force of the magnet 36 is about ½ or less of the magnetic force of the magnet 33 (about 45 MG (45 KT)). Specifically, the magnetic force of the magnet 36 is about ¼ (about 12 MG (12 KT)).

Further, since the magnetic force of the magnet 36 (magnet group 35) is about ½ or less of the magnetic force of the magnet group 32, the influence of the magnetic field on the base 10 of the magnet 36 is also smaller than that of the magnet group 32. In addition, since the N pole and the S pole are magnetized on the lower surface 36 b where the magnet 36 (magnet group 35) is in contact with the base 10, the lines of magnetic force from the lower surface 36 b of the magnet 36 (magnet group 35) are generated inside the base 10. It does not spread greatly.
For this reason, the influence of the magnetic field on the base 10 of the magnet 36 (magnet group 35) is kept very small.

Further, as described above, in the magnetic field shielding mechanism 5, the combined thickness (4 mm) of the back yoke 31, the magnet 36 and the support member 38 is the same as the thickness (4 mm) of the conventional back yoke 931. Therefore, the magnet part 30 is not increased in size and weight.
Furthermore, even when the support member 38 is not provided, the influence of the magnetic field on the base 10 side can be reduced or prevented (suppressed). Therefore, the magnet part 30 can be made thinner and lighter.

Thus, according to the magnetic field shielding mechanism 5 of the present embodiment, the influence of the magnetic field on the base 10 side can be reduced or prevented (suppressed) with a simple configuration.
Therefore, for example, the track rail 51 of the linear guide 50 arranged on the side wall portion 12 of the base 10 is not magnetized. Therefore, it is possible to prevent a problem that iron powder or the like is adsorbed on the upper surface of the track rail 51 and hinders the linear movement of the moving block 52. Therefore, the movement of the table 20, that is, the function deterioration of the actuator A (linear motor 1) can be avoided.

Further, the magnetic scale 61 of the magnetic encoder 60 that detects the position of the table 20 and the like can be disposed in the vicinity of the magnet unit 30.
In the conventional example, since the base 10 is magnetized by the magnet portion, it is necessary to keep the magnetic scale 61 away from the magnet portion in order to avoid the influence of this magnetism. For this reason, the magnetic scale 61 is attached to one outer wall of the side wall portion 12 of the base 10, for example.
On the other hand, in the present embodiment, since the magnetic field shielding mechanism 5 is provided, the magnetic scale 61 can be attached to an arbitrary position of the base 10. As described above, the magnetic scale 61 can be attached to the end of the bottom wall 11 of the base 10 (in the vicinity of the side wall 12).
As described above, since the magnetic scale 61 can be arranged inside the base 10, it is possible to avoid magnetic influences from the outside and to prevent damage due to contact with obstacles and the like, thereby improving the reliability of the apparatus. To do. In addition, since the magnetic scale 61 can be arranged at an arbitrary position of the base 10, it is possible to reduce the space and cost of the apparatus.

As a modification of the magnetic field shielding mechanism 5, both the outer peripheral surface 36c and the inner peripheral surface 36d of the magnet 36 may be magnetized to the N pole. That is, the magnetic pole is different from the magnetic pole (S pole) on the lower surface 33 b of the magnet 33. Even in this case, the same effect can be obtained although being slightly inferior to the above (see the relationship between the magnet 34 and the magnet 336 in FIGS. 16 and 17).
The magnetic lines of force from the magnetic pole (S pole) on the lower surface 33b of the magnet 33 are attracted to the magnetic lines of force from the magnetic poles (N pole) of the outer peripheral surface 36c and the inner peripheral surface 36d of the magnet 36, so ) Will not reach the base 10 (the influence of the magnetic field is reduced).

FIG. 12 is a schematic diagram showing a schematic configuration of the magnetic field shielding mechanism 105 according to the second embodiment. FIG. 12A is a cross-sectional view, and FIG. 12B is a bottom view (when the support member is removed).
In the following description, the same components as the magnetic field shielding mechanism 5 are denoted by the same reference numerals, and the description thereof is simplified or omitted.

In the magnetic field shielding mechanism 105 according to the second embodiment, two (plural) ring-shaped (square ring) magnets 136 are arranged on the lower surface 31 b of the back yoke 31.
The magnet 136 is a two-layered (laminated) magnet that is magnetized in a direction that intersects the Z direction. That is, the magnet (second magnet) 136 has an outer peripheral surface (outer ring surface) 136 c and an inner peripheral surface (inner ring surface) 136 d that are both magnetized to the S pole, and is disposed on the upper surface 31 a of the back yoke 31. Is the same polarity as the magnetic pole (S pole) of the lower surface 33b.
The magnet 136 has a longitudinal direction (Y direction) that is less than or equal to half the longitudinal direction (Y direction) of the magnet 36 (for example, about 1/3 to 1/4). The short side direction (X direction) and thickness are the same as those of the magnet 36.

The two magnets 136 are arranged at positions corresponding to (overlapping) both ends of the magnet 33 in the longitudinal direction. That is, two magnets 136 are arranged via the back yoke 31 for one magnet 33.
The magnetic force (magnetic flux density) of the magnet 136 is weaker (smaller) than the magnetic force of the magnet 33. It is about ½ or less of the magnetic force of the magnet 33.
For example, when the magnet 33 is about 45 MG (45 KT), for example, the magnet 136 is about 23 MG (23 KT) or less. That is, the magnetic force of the magnet 136 is about ½ or less of the magnetic force of the magnet 33. Further, the magnetic force of the magnet 136 may be about 1/4 of the magnetic force of the magnet 33 (about 12 MG (12 KT)).

  Note that both the outer peripheral surface 136c and the inner peripheral surface 136d of the magnet 136 may be magnetized to the N pole. That is, it is different from the magnetic pole (S pole) on the lower surface 33 b of the magnet 33.

Further, as the two magnets 136, a magnet in which both the outer peripheral surface 136c and the inner peripheral surface 136d are magnetized to the N pole and a magnet in which both the outer peripheral surface 136c and the inner peripheral surface 136d are magnetized to the S pole may be combined.
Further, the number of magnets 136 is not limited to two, and may be three or more.

FIG. 13 is a diagram illustrating an effect (magnetic flux density analysis result) of the magnetic field shielding mechanism 105 according to the second embodiment. 13A and 13B are cross-sectional views of the magnetic field shielding mechanism 105, and FIG. 13C is a bottom view of the magnetic field shielding mechanism 105 (a view showing the lower surface 38b of the support member 38).
In FIG. 13, the dark (dark) color portion has a high magnetic flux density, and the thin (light) portion has a low magnetic flux density.

As shown in FIG. 13, it can be understood that the same effect as the magnetic field shielding mechanism 5 can be obtained in the magnetic field shielding mechanism 105 according to the second embodiment.
That is, as shown in FIGS. 13A and 13B, it can be confirmed that the upper surface 38a of the support member 38 is hardly magnetized, and the portion in contact with the magnet 36 is slightly magnetized. Moreover, as shown in FIG.13 (c), it can confirm that the lower surface 38b of the supporting member 38 is hardly magnetized.
Therefore, it can be understood that by using the magnetic field shielding mechanism 105, the influence of the magnetic field from the magnet unit 30 to the base 10 side is blocked or suppressed (relieved). For this reason, the functional fall of actuator A (linear motor 1) can be avoided.

FIG. 14 is a schematic diagram showing a schematic configuration of the magnetic field shielding mechanism 205 according to the third embodiment. 14A and 14B are sectional views, and FIG. 14C is a bottom view (when the support member is removed).
In the following description, the same components as the magnetic field shielding mechanisms 5 and 105 are denoted by the same reference numerals, and the description thereof is simplified or omitted.

In the magnetic field shielding mechanism 205 according to the third embodiment, one ring shape is formed on the lower surface 31b of the back yoke 31 with respect to the two (plural) magnets 33 and 34 disposed adjacent to the upper surface 31a of the back yoke 31. A (square ring-shaped) magnet 236 is disposed.
The magnet 236 is a two-layer (stacked) magnet that is magnetized in a direction that intersects the Z direction. That is, in the magnet (second magnet) 236, the outer peripheral surface (outer ring surface) 236c and the inner peripheral surface (inner ring surface) 236d are both magnetized to the S pole. That is, it is the same polarity as the magnetic pole (S pole) of the lower surface 33 b of the magnet 33 and is different from the magnetic pole (N pole) of the lower surface 34 b of the magnet 34.
The length of the magnet 236 (X direction) is approximately twice the short direction (X direction) of the magnets 36 and 136. That is, the length is the sum of the short directions of the two magnets 33 and 34.
The width (Y direction) and thickness of the magnet 236 are the same as those of the magnet 36.

The magnetic force (magnetic flux density) of the magnet 236 is weaker (smaller) than the magnetic force of the magnet 33. It is about ½ or less of the magnetic force of the magnet 33.
For example, when the magnet 33 is about 45 MG (45 KT), for example, the magnet 236 is about 23 MG (23 KT) or less. That is, the magnetic force of the magnet 236 is about ½ or less of the magnetic force of the magnet 33. Furthermore, the magnetic force of the magnet 236 may be about 1/4 of the magnetic force of the magnet 33 (about 12 MG (12 KT)).

  Note that both the outer peripheral surface 236c and the inner peripheral surface 236d of the magnet 236 may be magnetized to the N pole. That is, the magnetic pole is different from the magnetic pole (S pole) on the lower surface 33 b of the magnet 33 and is the same polarity as the magnetic pole (N pole) on the lower surface 34 b of the magnet 34.

FIG. 15 is a diagram showing an effect (magnetic flux density analysis result) of the magnetic field shielding mechanism 205 according to the third embodiment. 15A and 15B are cross-sectional views of the magnetic field shielding mechanism 205, and FIG. 15C is a bottom view of the magnetic field shielding mechanism 205 (a view showing the lower surface 38b of the support member 38).
In FIG. 15, a dark (dark) portion of the color tone has a high magnetic flux density, and a thin (light) portion has a low magnetic flux density.

As shown in FIG. 15, the magnetic field shielding mechanism 205 according to the third embodiment can achieve the same effects as the magnetic field shielding mechanisms 5 and 105.
That is, as shown in FIGS. 15A and 15B, it can be confirmed that the upper surface 38a of the support member 38 is hardly magnetized and the portion in contact with the magnet 36 is slightly magnetized. Moreover, as shown in FIG.15 (c), it can confirm that the lower surface 38b of the supporting member 38 is hardly magnetized.
Therefore, it can be understood that by using the magnetic field shielding mechanism 205, the influence of the magnetic field from the magnet unit 30 to the base 10 side is blocked or suppressed (relieved). For this reason, the functional fall of actuator A (linear motor 1) can be avoided.

FIG. 16 is a schematic diagram illustrating a schematic configuration of the magnetic field shielding mechanism 305 according to the fourth embodiment.
16A and 16B are cross-sectional views, and FIG. 16C is a bottom view (when the support member is removed).
In the following description, the same components as the magnetic field shielding mechanisms 5, 105, 205 are denoted by the same reference numerals, and the description thereof is simplified or omitted.

In the magnetic field shielding mechanism 305 according to the fourth embodiment, a ring shape (square) is formed on the lower surface 31 b of the back yoke 31 with respect to the two (plural) magnets 33 and 34 disposed adjacent to the upper surface 31 a of the back yoke 31. Two (plural) magnets 336 having a ring shape are arranged.
The magnet 336 is a two-layer (stacked) magnet that is magnetized in a direction that intersects the Z direction. That is, in the magnet (second magnet) 336, the outer peripheral surface (outer ring surface) 336c and the inner peripheral surface (inner ring surface) 336d are both magnetized in the S pole, and the magnetic pole (S pole) on the lower surface 33b of the magnet 33. It has the same polarity and is different from the magnetic pole (N pole) on the lower surface 34 b of the magnet 34.

The magnet 336 has the same width (Y direction) as the longitudinal direction (Y direction) of the magnet 136. That is, the magnet 336 is not more than half of the longitudinal direction (Y direction) of the magnet 36 (for example, about 1/3 to 1/4).
The magnet 336 has the same length (X direction) as the length of the magnet 236 (X direction). That is, it is about twice as long as the short direction (X direction) of the magnets 36 and 136, and is the combined length of the two magnets 33 and 34 in the short direction (X direction).
The magnet 336 has the same thickness as the magnets 36, 136, and 236.

The two magnets 336 are disposed at positions corresponding to (overlapping) both ends in the longitudinal direction (Y direction) of the two magnets 33 and 34, respectively. That is, two magnets 336 are arranged in a cross-beam shape with respect to the two magnets 33 and 34 via the back yoke 31.
The magnetic force (magnetic flux density) of the magnet 336 is weaker (smaller) than the magnetic force of the magnet 33. It is about ½ or less of the magnetic force of the magnet 33.
For example, when the magnet 33 is about 45 MG (45 KT), for example, the magnet 336 is about 23 MG (23 KT) or less. That is, the magnetic force of the magnet 336 is about ½ or less of the magnetic force of the magnet 33. Further, the magnetic force of the magnet 336 may be about 1/4 of the magnetic force of the magnet 33 (about 12 MG (12 KT)).

  Note that both the outer peripheral surface 336c and the inner peripheral surface 336d of the magnet 336 may be magnetized to the N pole. That is, the magnetic pole is different from the magnetic pole (S pole) on the lower surface 33 b of the magnet 33 and is the same polarity as the magnetic pole (N pole) on the lower surface 34 b of the magnet 34.

The two magnets 336 may be a combination of a magnet having both the outer peripheral surface 336c and the inner peripheral surface 336d magnetized to the N pole and a magnet having both the outer peripheral surface 336c and the inner peripheral surface 336d magnetized to the S pole.
Further, the number of magnets 336 is not limited to two, and may be three or more.

FIG. 17 is a diagram illustrating the effect (magnetic flux density analysis result) of the magnetic field shielding mechanism 305 according to the fourth embodiment. 17A and 17B are cross-sectional views of the magnetic field shielding mechanism 305, and FIG. 17C is a bottom view of the magnetic field shielding mechanism 305 (a view showing the lower surface 38b of the support member 38).
In FIG. 17, the dark (dark) color tone portion has a high magnetic flux density, and the thin (light) portion has a low magnetic flux density.

As shown in FIG. 17, the magnetic field shielding mechanism 305 according to the fourth embodiment can obtain the same effects as the magnetic field shielding mechanisms 5, 105, and 205.
That is, as shown in FIGS. 17A and 17B, it can be confirmed that the upper surface 38a of the support member 38 is hardly magnetized, and the portion in contact with the magnet 36 is slightly magnetized. Moreover, as shown in FIG.17 (c), it can confirm that the lower surface 38b of the supporting member 38 is hardly magnetized.
Therefore, it can be understood that by using the magnetic field shielding mechanism 305, the influence of the magnetic field from the magnet unit 30 to the base 10 side is blocked or suppressed (relieved). For this reason, the functional fall of actuator A (linear motor 1) can be avoided.

FIG. 18 is a cross-sectional view showing a schematic configuration of the actuator A (rotary motor 2) according to the embodiment of the present invention.
The magnetic field shielding mechanisms 5, 105, 205, and 305 described above are all applied to the magnet unit 30 of the linear motor 1, but may be applied to the magnet unit 430 of the rotary motor 2.

As shown in FIG. 13, a magnetic field shielding mechanism 405 having substantially the same configuration as the magnetic field shielding mechanism 105 is applied to the rotary motor 2.
That is, ring-shaped magnets 436 and 437 that are magnetized in the direction intersecting the Z direction are arranged on the outer peripheral side of the magnet portion 430 that is the stator of the rotary motor 2 via the cylindrical back yoke 431.
The magnet (second magnet) 436 is an annular magnet in which an outer peripheral surface (outer ring surface) 436c and an inner peripheral surface (inner ring surface) 436d are magnetized to N poles. The magnet (second magnet) 437 is an annular magnet in which an outer peripheral surface (outer ring surface) 437c and an inner peripheral surface (inner ring surface) 437d are magnetized to the south pole.

  According to the magnetic field shielding mechanism 405, the magnetization of the housing 410 can be reliably prevented (suppressed) with a simple configuration without impairing the rotational performance of the coil portion 440. For this reason, the functional fall of actuator A (rotary motor 2) can be avoided.

  Various shapes, combinations, and the like of the constituent members shown in the above-described embodiments are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  For example, when the outer shape of the first magnet (magnets 33, 34) that generates a magnetic field toward the coil portion and the outer shape of the corresponding second (overlapping) second magnet (magnets 36, 37, etc.) are mostly matched. However, the present invention is not limited to this. The first magnets (magnets 33, 34) and the second magnets (magnets 36, 37, etc.) need only partially overlap in the Z direction, and the outer shapes do not have to match.

  The first magnet may be formed in a parallelogram in order to make the magnetic field generated in the X direction approach a sine wave. Of course, in this case, the second magnet is also formed in a parallelogram.

Although the case where a magnetic material is used as the support member 38 has been described, it may be formed of a nonmagnetic material such as plastic instead.
Further, a nonmagnetic material may be disposed in the hollow portion of the second magnet. Thereby, the mechanical strength of the second magnet can be increased.

Although the case where a sintered magnet was used as a 1st magnet and a 2nd magnet was demonstrated, it is not restricted to this. So-called bonded magnets (also called rubber magnets, vinyl chloride magnets, plastic magnets, etc.) may be used. That is, a flexible magnet obtained by crushing a ferrite magnet or the like and kneading it into rubber or plastic may be used.
In particular, since the second magnet can sufficiently perform the function of the magnetic field shielding mechanism even with a relatively weak magnetic force, the device cost can be reduced by using an inexpensive bond magnet.
The magnetization of the second magnet is not limited to two layers, and may be multilayer. Further, the second magnet is not limited to a square ring shape, and may be a ring shape or the like.

  Further, instead of the magnetic encoder 60, an optical linear encoder or the like may be provided to detect the position of the table 20 with respect to the base 10.

  Further, the present invention is not limited to the case where a plurality of balls 55 are used as the rolling elements of the linear guide 50, and rolling elements such as rollers may be used. Further, instead of the linear guide 50, a sliding guide mechanism may be used.

The linear motor 1 and the rotary motor 2 have been described as the actuator A, but are not limited to these embodiments. For example, the case where a coil part is fixed and a magnet part moves may be sufficient. That is, it is only necessary that the magnet part and the coil part move relative to each other.
Moreover, the installation direction of the actuator A (linear motor 1, rotary motor 2) is not limited to the embodiment. For example, the linear motor 1 may be installed on a ceiling or a wall.
The actuator A can be used in various industries. For example, it can be used for machine tools, semiconductor manufacturing apparatuses, linear motor cars, shaving machines, camera autofocus mechanisms, and the like.

  A ... Actuator, 1 ... Linear motor, 2 ... Rotation motor, 5 ... Magnetic field shielding mechanism, 30 ... Magnet part, 31 ... Back yoke (yoke), 33, 34 ... Magnet (first magnet), 36 ... Magnet (second) Magnet), 36c ... outer peripheral surface (outer ring surface), 36d ... inner peripheral surface (inner ring surface), 37 ... magnet (second magnet), 37c ... outer peripheral surface (outer ring surface), 37d ... inner peripheral surface (inner Ring surface), 38 ... support member, 40 ... coil part, 105 ... magnetic field shielding mechanism, 136 ... magnet (second magnet), 136c ... outer peripheral surface (outer ring surface), 136d ... inner peripheral surface (inner ring surface), 205 ... Magnetic field shielding mechanism, 236 ... Magnet (second magnet), 236c ... Outer circumferential surface (outer ring surface), 236d ... Inner circumferential surface (inner ring surface), 305 ... Magnetic field shielding mechanism, 336 ... Magnet (second magnet) 336c ... Peripheral surface (outer ring surface), 336d ... Inner peripheral surface (inner ring surface), 405 ... Magnetic field shielding mechanism, 430 ... Magnet part, 440 ... Coil part, 431 ... Back yoke (yoke), 436 ... Magnet (second magnet) ), 436c ... outer peripheral surface (outer ring surface), 436d ... inner peripheral surface, 437 ... magnet (second magnet), 437c ... outer peripheral surface (outer ring surface), 437d ... inner peripheral surface (inner ring surface)

Claims (6)

A first magnet magnetized in a first direction;
A yoke disposed on one magnetic pole side of the first magnet;
An annular second magnet disposed on one magnetic pole side of the first magnet across the yoke and magnetized in a direction intersecting the first direction;
A magnetic field shielding mechanism comprising:   The magnetic field shielding mechanism according to claim 1, wherein the one magnetic pole of the first magnet and the magnetic poles of the outer ring surface and the inner ring surface of the second magnet have the same polarity.   2. The magnetic field shielding mechanism according to claim 1, wherein the one magnetic pole of the first magnet and the magnetic poles of the outer ring surface and the inner ring surface of the second magnet are different polarities.   The magnetic field shielding mechanism according to claim 2 or 3, wherein the second magnet is a laminated magnet magnetized in a plurality of layers.   5. The magnetic field shielding mechanism according to claim 1, wherein the second magnet is arranged at a position overlapping the first magnet in the first direction. 6. A magnet section in which a plurality of magnets are arranged; and
A coil portion in which a plurality of coils are arranged to face the magnet portion;
With
In the actuator that relatively moves the magnet portion and the coil portion along the arrangement direction of the plurality of magnets by the magnetic field of the plurality of magnets and the current flowing through the plurality of coils,
The said magnet part has the magnetic field shielding mechanism as described in any one of Claims 1-5, The actuator characterized by the above-mentioned.