JP2002051531A - Movable magnet type actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a movable magnet type actuator for increasing generated thrust composed with that of the conventional actuator, and reducing manufacturing costs. SOLUTION: The movable magnet type actuator is provided with an outer yoke 14, a movable part 16 having a movable magnet 30 and a movable yoke 32, and a coil 22 that is arranged in slots 20a-20d formed along the peripheral direction of the outer yoke 14. By energizing the coil 22, magnetic inclination is generated between the movable part 16 and the outer yoke 14, and the movable part 16 and the outer yoke 14 are relatively displaced by thrust being generated by the magnetic inclination.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a movable magnet type actuator capable of converting electric energy into reciprocating kinetic energy or the like by electromagnetic action in control equipment, electronic equipment, machine tools, and the like.

[0002]

2. Description of the Related Art In recent years, linear actuators have been applied in a wide range of fields. For example, unlike a rotary motor, a linear motor has an advantage that it has a simple structure and can be easily miniaturized, and has been widely used in the past.

Here, a movable magnet type actuator according to the prior art is shown in FIG. 25 (see JP-A-6-38486).

This movable magnet type actuator includes a cylindrical yoke 1 formed of a soft magnetic material, and a bobbin 2 fixed to an inner wall surface of the cylindrical yoke 1 and formed of an insulating member such as an insulating resin. The cylindrical yoke 1
In the annular groove 3 formed between the bobbin 2 and the bobbin 2, three coils 4a to 4c are arranged.

The through hole 5 of the bobbin 2 formed in a substantially cylindrical shape
The magnet movable body 6 is slidably provided along the axial direction of the bobbin 2. The magnet movable body 6 is provided with a pair of permanent magnets 7 a and 7 b having the same polarity and opposed to each other. And a soft magnetic body 8 fixed between the permanent magnets 7a and 7b.

The three coils 4a to 4c are wound around the outer periphery of the movable magnet 6, and the left end of the permanent magnet 7a constituting the movable magnet 6, the permanent magnets 7a, 7c
b and the magnetic pole at the right end of the permanent magnet 7b. These coils 4a to 4c are connected such that currents flow in different directions with the magnetic poles of the permanent magnets 7a and 7b as boundaries.

Next, the operation of the movable magnet type actuator according to the prior art will be schematically described.

The magnet movable body 6 increases the magnetic flux component perpendicular to the longitudinal direction of the magnet movable body 6 which contributes to the Lorentz force based on Fleming's left-hand rule, and has three coils 4.
Since a to 4c effectively interlink with the magnetic fluxes of all the magnetic poles of the permanent magnets 7a and 7b, the current is supplied to the three coils 4a to 4c alternately so as to generate a magnetic field of the opposite polarity, whereby an arrow A is formed.
A directional thrust can be generated. As a result, the magnet movable body 6 slides and displaces in the direction of arrow A along the through hole 5 of the bobbin 2 based on the thrust.

As described above, the movable magnet type actuator according to the prior art employs a configuration for generating a thrust (Lorentz force) based on Fleming's left-hand rule.

[0010]

In the field of office automation (OA) and factory automation (FA), a high thrust linear actuator is required to improve the production efficiency.

The present invention has been made in view of the above-mentioned demands, and uses a thrust generation principle different from Fleming's left-hand rule to further increase the thrust generated as compared with the conventional one. It is an object of the present invention to provide a movable magnet type actuator capable of reducing manufacturing costs.

[0012]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an movable yoke having an outer yoke, a movable magnet and a movable yoke, the movable yoke being provided along the hole of the outer yoke. Part, and a coil disposed in a slot formed along the circumferential direction of the outer yoke, and by energizing the coil, a magnetic gradient is generated between the movable part and the outer yoke, The movable portion and the outer yoke are relatively displaced by a thrust generated by the magnetic gradient.

In this case, the longitudinal sectional shape of the slot is
It is preferable to form a composite shape in which a horizontally long rectangular portion and a triangular portion are combined. Preferably, the triangular portion is provided with an inclined surface which forms a slot angle with the inner peripheral surface of the outer yoke having a linear cross section.

It is preferable that a set of slot teeth which gradually becomes thinner toward the center of the slot is formed between the inner peripheral surface of the outer yoke and the slot.

Further, the number of the slots is always set to be smaller by one than the number of the movable magnets, and the axes of a pair of end-side movable magnets disposed at both ends in the axial direction of the movable portion. By setting the thickness along the direction to be smaller than the thickness of the movable magnet disposed between the pair of end side movable magnets, a large thrust is obtained in the stroke direction, and the thrust is substantially orthogonal to the thrust. The vertical force acting in the direction of the movement is suppressed.

According to the present invention, a magnetic gradient is generated between the movable portion and the outer yoke under the action of energizing the coil, and the movable portion and the outer yoke are relatively displaced by a thrust generated by the magnetic gradient. Therefore, by using a thrust generation principle different from Fleming's left-hand rule, the generated thrust is further increased as compared with the related art.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a movable magnet type actuator according to the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1 and FIG.
1 shows a movable magnet type actuator according to an embodiment of the present invention.

The movable magnet type actuator 10 includes a substantially cylindrical outer yoke 14 having a through hole 12 formed therein,
A movable portion 16 that slides and displaces along the through hole 12 of the outer yoke 14. The outer yoke 14
A gap 18 is formed between the inner peripheral surface of the through hole 12 and the outer peripheral surface of the movable portion 16 so as to be separated by a predetermined distance.

A plurality of slots 20a to 20d are formed inside the outer yoke 14 so as to rotate along the circumferential direction of the outer yoke 14.
20d are arranged at predetermined intervals along the axial direction of the outer yoke 14. Each of the slots 20a to 20d has a coil length (L) corresponding to the slot width, and a coil 22 formed by winding a plurality of turns.
Is provided.

Each of the slots 20a to 20d is formed in a composite shape in which a rectangular section having a horizontally long longitudinal section and a triangular section are combined, and a vertex of the triangular section is formed in a through hole 12 of an outer yoke 14. Communicating small holes 24
Is provided. The slots 20a to 20d are a pair of acute angle slots each having an inclined surface 26 inclined upward or downward (downward or downward) with respect to the substantially horizontal inner peripheral surface of the outer yoke 14. It has teeth 28, said set of slot teeth 28 facing each other and formed symmetrically (see FIG. 3). In addition, the inclination angle (slot angle θ) of the inclined surface 26 may be set to a predetermined angle as described later in order to affect the thrust. The small holes 24 are closed, and the slots 20a to 20a are closed.
20d and the through-hole 12 may be formed so as to be in a non-communication state.

The movable portion 16 is integrally formed by alternately laminating a plurality of thin disk-shaped movable magnets 30 and a plurality of thick disk-shaped movable yokes 32, and has a shaft 34 at the center thereof. It is provided so as to penetrate. The movable magnet 3
0 is formed by a permanent magnet, and the movable yoke 32
It is formed of a metal material such as iron.

In FIG. 1, reference numeral 36 is
The back yoke formed between the outer peripheral surface of the outer yoke 14 and the slots 20a to 20d is shown.

The movable magnet type actuator 10 according to the present embodiment is basically constructed as described above. Next, the operation and effect of the actuator will be described.

First, the principle of generating a thrust will be described below based on the basic structure of the movable magnet type actuator 10 shown in FIG. 4A.

As shown in FIG. 4A, the magnetic flux generated from the two movable magnets 30 moves along the arrow P along the movable yoke 32, the gap 18, the slot teeth 28, and the gap 18.
Then, it flows to the movable yoke 32 and returns to the movable magnet 30 again. In this case, when no current is supplied to the coil 22, as shown in FIG. 4B, the magnetic flux density distributions of the right and left portions of the slot 20c are balanced and substantially the same. FIG. 4C
As shown in, collapsed balance of the magnetic flux density B ₂ of the magnetic flux density B ₁ and the right part of the left portion of the slot 20c are magnetic flux density distribution in the gap 18, constructive right (left) side portions of the slot 20c , The left (right) side parts weaken each other, so that a magnetic energy gradient is generated and thrust is generated.

The movable magnet type actuator 10 according to the present embodiment does not generate a thrust based on Fleming's left-hand rule, but uses the gap 18 as described above.
The thrust is generated by the magnetic gradient.

[0028] Incidentally, the magnetic energy W _m in the generated gap 18 is given by the following equation (1).

[0029]

(Equation 1)

However, the magnetic flux density B is given by the following equation (2).

[0031]

(Equation 2)

The proportional constant k depends on the shape of the slots 20a to 20d.

The generated thrust F is represented by a magnetic gradient, and the thrust F in the displacement direction (x direction) is given by the following equation (3).

[0034]

(Equation 3)

As shown in FIG. 5, in the present embodiment, a magnetic flux is generated along the arrow C based on the above-described thrust generation principle by energizing a power supply (not shown) and causing a current to flow through each coil 22. Then, on the inner peripheral surface of the outer yoke 14,
A magnetic pole consisting of an S pole and an N pole is generated. When the S and N poles of these magnetic poles and the N and S poles on the surface of the movable yoke 14 attract or repel each other, a thrust is generated in the direction of arrow D, and the movable portion 16 5 is slid along the through hole 12 of the outer yoke 14 toward the right side in FIG.

In other words, a thrust is generated in the direction of arrow D due to the magnetic flux gradient in the gap 18 due to the magnetic flux, and the generated thrust is formed with slots 20a to 20d as shown in FIG. It will be appreciated that the number is even greater than that of the prior art movable magnet type actuator.

For example, the dotted line in FIG. 6 indicates that the displacement x is 0 m
The dotted line in FIG. 7 indicates the magnetic flux when the displacement x is −1.
8 shows the magnetic flux at the time of mm, and the dotted line in FIG.
The magnetic flux at 2 mm is shown. As shown in FIGS. 7 and 8, it can be understood that, when the coil 22 is energized, the magnetic fluxes in the left portions of the slots 20 a to 20 d reinforce each other to generate a magnetic flux gradient.

As described above, in this embodiment, a magnetic flux gradient is generated by providing the slots 20a to 20d,
Even greater thrust can be obtained compared to the prior art.

In the present embodiment, it is not necessary to provide a non-magnetic material such as a bobbin made of a resin material, and the coil 22 and the like are formed by using a material having a good heat radiation effect, such as iron. Heat can be appropriately radiated to the outside to improve heat radiation.

Further, in the present embodiment, the movable magnet 30
Since a thin permanent magnet is used, the amount of permanent magnet used can be reduced and the manufacturing cost can be reduced as compared with the prior art.

Next, a procedure for designing a movable magnet type actuator 10a according to another embodiment using two-dimensional magnetic field analysis (2D-FEM) by the finite element method will be described with reference to the flowchart shown in FIG. explain. In addition,
The same components as those of the movable magnet type actuator 10 shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The design goal is that the outer diameter is φ22 × 4
A movable magnet type actuator 10a that can set 4.4 mm ³ , the length of the movable portion 16 is 35.4 mm, the displacement (stroke) x ± 2 mm, the copper loss is 5 W, and the generated thrust is 8 N or more. (Step S1).

Subsequently, a magnetic circuit is examined with the determined material, and design variables and dimensional parameters are set (step S2). In this design, since there are many dimensions to be considered, only dimensions that have a large effect on thrust are set as parameters. For example, the material of the outer yoke 14 is SS400 (according to JIS standard) and the movable magnet 3
NEOMAX46 (registered trademark) was used as 0.

After setting the number of the movable magnets 30 and the number of the coils 22, respectively, the dimensions of the movable magnet 30 are determined (steps S3 and S4). At this time, as the displacement x of the movable portion 16 increases, the back yoke 3 shown in FIG.
6 easily becomes magnetically saturated, so that the thrust fluctuation increases.
Therefore, the thickness t _by of the back yoke 36 is determined so as not to cause magnetic saturation. The thickness t of the back yoke 36
_by is given _by the following equation (4).

[0045]

(Equation 4)

Since the dimensions of the movable magnet 30 are set based on the conditions of the number of movable magnets and the number of coils determined in step S3, consideration is given to prevent the back yoke 36 from being magnetically saturated.

Since the shape and dimensions of the slot greatly affect the thrust characteristics, the relationship between the slot angle θ of the slot tooth portion 28 and the length L of the coil with the determined dimensions of the movable magnet 30 is examined (step). S5).

Further, since the thrust change is large depending on the displacement x of the movable portion 16, the slot angle θ is determined in consideration of the thrust characteristics when the displacement x is ± 2 mm. The thrust is calculated using a two-dimensional magnetic field analysis (2D-FEM) by the finite element method, and the steps from step S3 to step S6 are repeated until the thrust fluctuation is small and the thrust is maximized (step S7).

Finally, in order to set the model shape of the two-dimensional magnetic field analysis, parameters which cannot be calculated by the two-dimensional magnetic field analysis, such as the number of movable magnets 30 and the number of coils 22, are appropriately changed. , So that the thrust is maximized (step S8).

Next, the effects of the coil length L and slot angle θ (see FIG. 11) examined in step S5 on the thrust characteristics will be described below.

FIGS. 12 to 14 show the thrust characteristics when the length L of the coil is changed. Slot angle θ is 20
In the case of degrees, as shown in FIG. 13, the thrust tends to be saturated as the displacement x becomes negative. When the slot angle θ is 10 degrees, as shown in FIG.
It is understood that the thrust caused by the displacement x fluctuates greatly. This is presumed that magnetic saturation occurs in the slots 20a and 20b and the detent force increases, so that the thrust varies greatly.

FIGS. 15 to 17 show the thrust characteristics when the slot angle θ is changed. Coil length L is 6m
At m, the thrust characteristic shows a tendency to be saturated by changing the slot angle θ (see FIG. 15). It was also confirmed that the smaller the slot angle θ, the larger the thrust.

When the length L of the coil is 8 mm and the slot angle θ is 20 degrees and 30 degrees, the thrust tends to be saturated, but when the slot angle θ is 10 degrees, the thrust shows a maximum value ( See FIG. 16). Also, if the coil length L is 10
When the slot angle θ is 20 degrees or less, the change in thrust is large (see FIG. 17).

By setting the coil length L and the slot angle θ to appropriate values in this manner, the magnetic flux density distribution in the gap 18 becomes symmetrical, and the magnetic flux density distribution in the gap 18 is balanced. It is good to set as follows.

Next, FIG. 18 shows thrust characteristics when the displacement x of the movable portion 16 is 0 mm and the length L of the coil and the slot angle θ are used as parameters.

As can be understood from FIG. 16, when the length L of the coil is set to 8 mm, the thrust at the positive and negative displacement x becomes substantially symmetric, and the thrust at the time when the displacement x is 0 becomes maximum in the slot. This is when the angle θ is 10 degrees. Therefore, the slot angle θ is 10 degrees, and the coil length L is 10 m.
When set to m, the thrust at the time when the displacement x is 0 is maximized, but as shown in FIG. 17, the thrust characteristics at the positive and negative displacement x are unbalanced. It was found that the best mode was obtained when the length L of the coil was 8 mm. FIG. 19 shows the dimensions (unit: mm) of the movable magnet type actuator 10a according to another embodiment designed by such a design procedure.

Next, FIG. 20 shows comparison characteristics between the movable magnet type actuator 10a according to another embodiment designed in this way and Comparative Examples 1 to 3.

In the designed movable magnet type actuator 10a, the thrust constant is 39 N / A and the tangential stress is 22.
It was 8 kN / m ² , and the thrust could be further improved as compared with the other comparative examples 1 to 3.

In FIG. 20, the electric time constant refers to the value of the voltage applied to the coil 22 when the voltage is applied to the coil 22.
Means the time required for the current flowing through to reach 63.2% of the maximum value. This electrical time constant is determined by the impedance of the coil 22. Similarly, the mechanical time constant refers to the time required for the displacement speed of the movable portion 16 to reach 63.2% of the maximum value when a constant current is applied to the coil 22. In order to improve the responsiveness of the movable magnet type actuator 10a, the electric time constant and the mechanical time constant may be reduced. Note that the electrical time constant and the mechanical time constant are obtained by the following equation (5).

[0060]

(Equation 5)

In FIG. 20, the motor constant is obtained by dividing the thrust by the square root of the copper loss. Increasing the motor constant, as required by small motors, is equivalent to increasing the thrust / input ratio. Note that the motor constant is obtained by the following equation (6).

[0062]

(Equation 6)

Further, in FIG. 20, the tangential stress refers to a thrust generated per unit area (thrust / area ratio). Using the tangential stress, it is possible to theoretically confirm the limit value of the generated thrust of the linear electromagnetic actuator. The tangential stress is obtained by the following equation (7).

[0064]

(Equation 7)

Next, the thrust generated in the stroke direction and the force (vertical force) generated in the direction substantially perpendicular to the axis of the movable part when the movable part is displaced in the direction substantially perpendicular to the axis thereof. Will be described below.

An experiment was performed using a movable magnet type actuator 50 having a structure as shown in FIG. The movable magnet type actuator 50 includes a first slot 20a and a second slot 2 around which the coil 22 is wound, respectively.
0b, a pair of end-side movable magnets 52a, 52b provided at both ends along the axial direction of the movable portion 16 and each having a thickness W of the magnet along the axial direction, and the pair of end portions. The movable magnet 30 is provided between the side movable magnets 52a and 52b, and has a thickness set to be larger than the thickness W of the end movable magnets 52a and 52b.

In this case, in FIG. 21, a single movable magnet 30 is shown between a pair of end-side movable magnets 52a and 52b, but the present invention is not limited to this. A plurality of movable magnets 30 may be arranged between them. The thicknesses W of the magnets along the axial direction of the one end side movable magnet 52a and the other end side movable magnet 52b are set to be the same.

FIG. 22 shows the magnetic flux generated when a current of 0.3 mA is applied to each of the coils 22 of the movable magnet type actuator 50 configured as described above. FIG. 23 shows the relationship between the thrust and the normal force.

As will be understood from FIG.
The thickness W along the axial direction of the end-side movable magnets 52a (52b) is formed to be smaller than the thickness along the axial direction of the movable magnet 30 disposed substantially at the center of the movable magnet 30. It is preferable that the thickness W along the axial direction of the side movable magnet 52a (52b) is set to 1 (mm). because,
This is because a large thrust can be obtained in the stroke direction and the vertical force can be suppressed. The thickness W
Is 1 (mm), the thrust generated is approximately three times as large as when the end-side movable magnets 52a (52b) are not provided (W = 0).

As shown in FIG. 24, the material of the end side movable magnets 52a and 52b is, for example, a samarium cobalt magnet (SmCo) so that the coercive force is about 800 (kA / m) or less. The use of a neodymium magnet (Nd magnet) having a coercive force of about 1000 (kA / m) has a problem that the normal force is larger than the thrust.

From the above experimental results, a large thrust can be obtained in the stroke direction and the conditions for suppressing the vertical force are as follows. First, the number of the slots 20 formed in the outer yoke 14 Side movable magnets 52a, 5
Second, the number of movable magnets 30 including 2b is always set to be smaller by one. Second, the axes of a pair of end-side movable magnets 52a, 52b disposed at both ends of the movable portion 16 The thickness W along the direction corresponds to the set of the end-side movable magnets 5.
It has been found that the thickness may be set to be smaller than the thickness of the movable magnet 30 or the plurality of movable magnets 30 disposed between 2a and 52b along the axial direction.

[0072]

According to the present invention, the following effects can be obtained.

That is, by providing a slot in the outer yoke, a magnetic flux gradient is generated, and a greater thrust can be obtained as compared with the prior art.

Further, in the present invention, it is not necessary to provide a nonmagnetic material such as a bobbin made of a resin material, and the heat generated by the coil or the like is preferably formed by using a material having a good heat radiation effect such as iron. To the outside to improve heat dissipation.

Further, in the present invention, by using a thin permanent magnet as the movable magnet, the amount of the permanent magnet used can be reduced as compared with the prior art, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view along an axial direction of a movable magnet type actuator according to an embodiment of the present invention.

FIG. 2 is a view as seen from the direction of arrow B in FIG.

FIG. 3 is a partially enlarged longitudinal sectional view of FIG. 1;

FIG. 4A is a basic structural diagram for explaining the principle of thrust generation, FIG. 4B is an explanatory diagram showing a magnetic flux density distribution when no current flows through the coil, and FIG. It is explanatory drawing which shows the magnetic flux density distribution at the time of flowing.

FIG. 5 is an operation explanatory view of the movable magnet type actuator shown in FIG. 1;

FIG. 6 is an explanatory diagram showing a magnetic flux when the displacement amount is 0 mm.

FIG. 7 is an explanatory diagram showing a magnetic flux when the displacement amount is −1 mm.

FIG. 8 is an explanatory diagram showing a magnetic flux when the displacement amount is −2 mm.

FIG. 9 is an explanatory diagram showing a relationship between a displacement amount and a thrust.

FIG. 10 is a flowchart showing a procedure for designing a movable magnet type actuator.

FIG. 11 is an explanatory diagram showing parameters used in the design procedure.

FIG. 12 is an explanatory diagram showing thrust characteristics when the slot angle is 30 degrees.

FIG. 13 is an explanatory diagram showing thrust characteristics when the slot angle is 20 degrees.

FIG. 14 is an explanatory diagram showing thrust characteristics when the slot angle is 10 degrees.

FIG. 15 is an explanatory diagram showing thrust characteristics when the length of a coil is 6 mm.

FIG. 16 is an explanatory diagram showing thrust characteristics when the length of a coil is 8 mm.

FIG. 17 is an explanatory diagram showing thrust characteristics when the length of a coil is 10 mm.

FIG. 18 is an explanatory diagram showing thrust characteristics using a coil length and a slot angle as parameters.

FIG. 19 is an explanatory diagram showing dimensions of a movable magnet type actuator set according to the design procedure.

20 is a comparative characteristic diagram of the actuator shown in FIG. 19 and Comparative Examples 1 to 3.

FIG. 21 is a partially omitted longitudinal sectional view of a movable magnet type actuator used in an experiment on a relationship between a thrust and a normal force.

FIG. 22 is an explanatory diagram of a magnetic flux generated by energizing a coil of the movable magnet type actuator shown in FIG. 21;

FIG. 23 is an explanatory diagram showing a relationship between a thrust and a normal force when the thickness of the end-side movable magnet is changed in the movable magnet actuator shown in FIG. 21;

FIG. 24 is an explanatory diagram showing the relationship between the thrust and the normal force when the coercive force of the end-side movable magnet is changed in the movable magnet actuator shown in FIG. 21;

FIG. 25 is a longitudinal sectional view of a movable magnet type actuator according to the related art.

[Explanation of symbols]

10, 10a, 50: movable magnet actuator 12: through hole 14: outer yoke 16: movable portion 18: gap 20a to 20d: slot 22: coil 24: small hole 26: inclined surface 28: slot tooth portion 30: movable magnet 32 ... Movable yoke 34. Shaft 36. Back yoke 52a, 52b.

Continued on the front page (72) Kazuya Tamura, Inoui, Tsuwaramura, Tsukuba-gun, Ibaraki Prefecture 4-2-2 Inside Tsukuba Technical Center, SMC Corporation (72) Inventor Hisashi Yajima 4-2, Kinudai, Yawahara-mura, Tsukuba-gun, Ibaraki 2 Within SMC Corporation Tsukuba Technology Center (72) Nobuhiro Fujiwara Nobuhiro Fujiwara, Yawahara-mura, Tsukuba-gun, Ibaraki Prefecture 4-2-2 Within SMC Corporation Tsukuba Technology Center (72) Inventor Hiroyuki Wakiwaka 5 Wakasato, Nagano City, Nagano Prefecture -16-3-5 (72) Inventor Norhisum Mithlon 3-10-37 Wakasato, CANNO 5th Building 302 No. 302, Wakasato, Nagano City, Nagano Prefecture (72) Inventor Akinori Kamiya 1-30-12 Heights, Aokishimacho, Nagano City, Nagano Prefecture 207 Yamazaki 207 F term (reference) 5H002 AA01 AA07 AA09 AE06 AE07 5H641 BB06 BB14 GG02 GG04 GG08 GG12 HH03 HH08 HH16 HH20

Claims (5)

[Claims] A movable portion having an outer yoke, a movable magnet and a movable yoke, the movable portion being displaceable along a hole of the outer yoke, and a slot formed along a circumferential direction of the outer yoke. A coil is disposed, and by energizing the coil, a magnetic gradient is generated between the movable portion and the outer yoke, and the movable portion and the outer yoke relatively move by a thrust generated by the magnetic gradient. A movable magnet type actuator characterized by being displaced. 2. The movable magnet type actuator according to claim 1, wherein the longitudinal section of the slot has a complex shape in which a horizontally long rectangular portion and a triangular portion are combined. 3. The movable magnet type actuator according to claim 2, wherein the triangular portion has an inclined surface that forms a slot angle with the inner peripheral surface of the outer yoke having a linear cross section. Actuator. 4. The set according to claim 1, wherein a portion between the inner peripheral surface of the outer yoke and the slot gradually becomes thinner toward the center of the slot. The movable magnet type actuator characterized by forming the slot tooth portion of (1). 5. The actuator according to claim 1, wherein the number of the slots is always set to be smaller by one than the number of the movable magnets, and the number of the slots in the axial direction of the movable portion is changed. The thickness along the axial direction of a pair of end-side movable magnets disposed at both ends is set to be smaller than the thickness of a movable magnet disposed between the pair of end-side movable magnets. A movable magnet type actuator characterized by the above-mentioned.