JP2003199312A - Inner yoke magnet type linear motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To increase driving force without the need for size change and attain precise operation, because magnetic saturation can be prevented in a slender and rod-like inner yoke 3. <P>SOLUTION: A pair of stator coils 2-1, 2-2 are brought into a close contact with the inside of a cylindrical outer yoke 1. The rod-like inner yoke 3 is coaxially disposed inside the outer yoke 1. A pair of annular field magnets 4-1, 4-2 are fixed on the outer periphery of the inner yoke and arranged side by side with a void formed in the traveling direction of the inner yoke. An auxiliary magnet 6 is disposed so as to be sandwiched inside the void. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inner yoke magnet type linear motor used for an automatic focus tracking device in optical equipment.

[0002]

2. Description of the Related Art Conventionally, inner yoke magnet type linear motors have been
The following configuration was adopted. FIG. 7 is a structural diagram of a conventional inner yoke magnet type linear motor. (a) is a longitudinal sectional view of the inner yoke magnet type linear motor, and (b) is a transverse sectional view of the inner yoke magnet type linear motor. From the figure, the conventional inner yoke magnet type linear motor is
Stator coils 102-1 and 102-2, an inner yoke 103, field magnets 104-1 and 104-2, and an insulating cylinder 105 are provided.

As shown in FIG. 1B, an outer yoke 101, a stator coil 102, an inner yoke 103 and a field magnet 104 are coaxially arranged. The field magnet 104 and the inner yoke 103 are integrally fixed and constitute a mover that moves in the moving direction 106. The mover follows the Fleming's left-hand rule due to the interlinkage of the field magnetic flux generated by the field magnet 104-1 and the field magnet 104-2 and the current flowing through the stator coils 102-1 and 102-2. Get the driving force. The state of the field magnetic field at this time is represented by an electrical equivalent circuit as follows.

FIG. 8 is an equivalent circuit diagram of a conventional inner yoke magnet type linear motor. It is the figure which represented the magnetic circuit which a field magnetic flux passes by the electrical equivalent circuit. In the figure, V1 and V2 are obtained by replacing the magnetomotive forces U of the field magnets 104-1 and 104-2 with voltage sources. I1 and i2 are the magnetic flux Φ flowing in the magnetic circuit.
Is expressed in electric current. Similarly, the magnetic resistance Q in the magnetic circuit is represented by the electric resistance R. Where Rout is the magnetic resistance of the outer yoke 101, and Rg1 is the field magnet 104-1 and the outer yoke 1.
Air resistance between 01 and coil, Rg2 is field magnet 1
Magnetic resistance of air and coil between 04-2 and outer yoke 101, Ra is magnetic resistance of air between field magnet 104-1 and field magnet 104-2, and Rin is magnetic resistance of inner yoke 103. , R1 corresponds to the magnetic resistance in the field magnet 104-1, and r2 corresponds to the magnetic resistance in the field magnet 104-2. The driving force obtained by the mover is that the current flowing through the stator coils 102-1 and 102-2 is the field magnets 104-1 and 1
The field magnetic flux generated by 04-2 is proportional to the number of interlinking magnetic fluxes that interlink, and the number of interlinking magnetic fluxes is proportional to the current i1 on the equivalent circuit.

[0005]

By the way, the above conventional techniques have the following problems to be solved. In the conventional inner yoke magnet type linear motor, it is difficult to increase the number of interlinkage magnetic fluxes between the current flowing through the stator coil and the field magnetic flux generated by the field magnet, and the driving force cannot be increased.

[0006]

The present invention adopts the following constitution in order to solve the above points. <Structure 1> A cylindrical outer yoke, a pair of annular stator coils that are closely attached to the inside of the outer yoke, are arranged in the moving direction of the inner yoke, and are arranged coaxially with the outer yoke, A rod-shaped inner yoke coaxially arranged inside the outer yoke, and a pair fixed to the outer circumference of the inner yoke, arranged side by side with a gap in the moving direction of the inner yoke, and arranged coaxially with the inner yoke. And an annular auxiliary magnet arranged so as to be sandwiched in the gap between the pair of field magnets, the pair of stator coils having opposite polarities. When the stator magnetic field is excited, the direction of magnetization of the pair of field magnets is parallel to the direction from the axis of the magnet to the outer peripheral surface, and the direction of magnetization of one field magnet is The direction of magnetization of the field magnet is opposite to that of the auxiliary The direction of magnetization of the stone is parallel to the axis of the inner yoke, and the polarity of the magnetic pole of the auxiliary magnet matches the polarity of the outer peripheral surface of the field magnet with which the magnetic pole of the auxiliary magnet is in contact. Inner-yoke magnet type linear motor.

<Structure 2> A cylindrical outer yoke and three or more annular stators which are closely attached to the inner side of the outer yoke and are arranged in the moving direction of the inner yoke and arranged coaxially with the outer yoke. A coil, a rod-shaped inner yoke coaxially arranged inside the outer yoke, and an outer yoke fixed to the inner yoke and arranged side by side with a gap in the moving direction of the inner yoke, coaxial with the inner yoke. An annular field magnet of a number equal to or less than the number of the stator coils arranged, and an annular auxiliary magnet arranged so as to be sandwiched in the gap between all the field magnets, the adjacent In the stator coil, stator magnetic fields having mutually opposite polarities are excited, and the magnetization directions of all the field magnets are parallel to the direction from the magnet axis to the outer peripheral surface, and are adjacent to each other. Make sure that the magnetization directions of the magnets are opposite to each other. The direction of magnetization of the auxiliary magnet is
The inner yoke is parallel to the axis of the inner yoke, and the direction of magnetization of the auxiliary magnet coincides with the polarity of the outer peripheral surface of the field magnet with which the magnetic pole of the auxiliary magnet is in contact. Magnet type linear motor.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to specific examples. <Specific Example 1> In the inner-yoke magnet linear motor of the first specific example, the auxiliary magnet is arranged so as to be sandwiched between the two field magnets of the conventional inner-yoke magnet linear motor. The magnetization direction of this auxiliary magnet is oriented in the moving direction of the mover. The polarity is matched with the polarity of the outer peripheral surface of the field magnet with which this auxiliary magnet is in contact. As a result, it is possible to increase the number of interlinkage magnetic fluxes between the current flowing through the stator coil and the field magnetic flux generated by the field magnet, and the driving force is increased. The details will be described below with reference to the drawings.

FIG. 1 is a structural diagram of an inner yoke magnet type linear motor of the first embodiment. (a) is a longitudinal sectional view of the inner yoke magnet type linear motor, and (b) is a transverse sectional view of the inner yoke magnet type linear motor. As shown in the figure, the inner yoke magnet type linear motor of the first specific example has an outer yoke 1 and a stator coil 2-.
1, 2-2, inner yoke 3, field magnets 4-1, 4-2, and insulating cylinder 5
And an auxiliary magnet 6.

The outer yoke 1 includes a field magnet 4-1, which will be described later.
4-2 is a part that guides the movement of the mover including the auxiliary magnet 6 and the inner yoke 3, and is also a part that supports the stator coils 2-1 and 2-2 described later. It is composed of a cylindrical magnetic material. The outer diameter and the length are set according to the application of the motor. For example, in the case of being used for an automatic focus tracking device in an optical device, the outer diameter and the length are often small and have a size of several cm or less.

The stator coils 2-1 and 2-2 are the outer yoke 1
And a pair of annular coils which are closely supported inside and are arranged side by side in the moving direction of the moving element. Stator magnetic fields having polarities opposite to each other are excited in the two stator coils 2-1 and 2-2. That is, voltages having positive and negative inversions are applied. The current flowing at this time and the field magnet described later
The field magnetic flux generated by 4-1 and 4-2 and the auxiliary magnet 6 interlinks. This interlinkage generates a driving force according to Fleming's left-hand rule. The magnetic circuit through which the field magnetic flux passes at this time will be described later in detail using an electrical equivalent circuit.

The inner yoke 3 is a magnetic rod (column) coaxially arranged on the center line of the outer yoke 1. However, the figure
As shown in 1, it may be a cylindrical rod in which the center of the cylinder is hollow. As described above, the field magnets 4-1 and 4-will be described later.
This is a part that constitutes a moving element composed of 2 and the auxiliary magnet 6. A field magnet 4 described later with the inner yoke 3 as an axis
-1, 4-2 and the auxiliary magnet 6 are fixed. When used in an automatic focus tracking device in optical equipment, a lens support mechanism is attached to the tip of the inner yoke 3.

The field magnets 4-1 and 4-2 are fixed to the inner yoke 3 and arranged side by side in the moving direction of the mover to form the stator coil 2-.
It is an annular permanent magnet that is placed inside the 1 and 2-2. The direction of magnetization of the pair of field magnets is parallel to the direction from the magnet axis to the outer peripheral surface, and the direction of magnetization of one field magnet is the same as the direction of magnetization of the other field magnet. It is supposed to be in the opposite direction. The details will be described later with reference to other drawings.

The auxiliary magnet 6 is a ring-shaped permanent magnet arranged so as to be sandwiched between the two field magnets 4-1 and 4-2. The direction of this magnetization is parallel to the axis of the inner yoke 3, and the polarities of the magnetic poles are matched with the polarities of the outer peripheral surface of the field magnet with which the auxiliary magnet is in contact. The dotted line is shown in the figure and the auxiliary magnet is shown as if it was divided into two parts. The reason for this will be clarified later in the explanation of the equivalent circuit. Next, the field magnet
The configurations of 4-1 and 4-2 and the auxiliary magnet 6 will be described in detail with reference to other drawings.

FIG. 2 is an explanatory diagram of a field magnet and an auxiliary magnet. (a) is a figure showing a field magnet, (b) is a figure showing an auxiliary magnet. The annular field magnets 4-1 and 4-2 are (a)
It is manufactured by molding a magnetic material into a fan shape as shown in, and then magnetizing it in the direction from the axis of the magnet to the outer peripheral surface. Here, the opening angle of the fan shape is represented as 90 degrees, but the present invention is not limited to this example. That is,
It is manufactured by dividing it into multiple pieces to make 360 degrees. The reason for this is to facilitate the magnetizing process in the direction from the axis of the magnet to the outer peripheral surface. Further, from (b), the auxiliary magnet is manufactured by molding a magnetic material into a ring shape and then magnetizing it in the direction of the inner yoke as shown in the figure.

Returning to FIG. 1 again, the insulating cylinder 5 is a cylinder for holding the stator coils 2-1 and 2-2. As described above, the stator coils 2-1 and 2-2 are held in close contact with the outer yoke 1, but a strong force acts between them and the field magnets 4-1 and 4-2. Used to complete. Therefore, sometimes it is not necessary to use it. Usually, a material that is a non-magnetic material and has a high degree of insulation is used in consideration of the influence on the magnetic circuit. Next, the magnetic circuit of the inner yoke magnet type linear motor of the present invention will be described.

FIG. 3 is an equivalent circuit diagram of the inner yoke magnet type linear motor of the present invention. (a) is an enlarged view of a portion necessary for explanation, and (b) is an equivalent circuit thereof. As shown in (a), the auxiliary magnet 6 has an N pole on the left side in the length direction of the inner yoke 3,
It is arranged so that the south pole faces the right side. Therefore, the N pole on the radially outer side of the auxiliary magnet 6 is in contact with the N pole of the field magnet 4-1, and the S pole on the radially outer side of the auxiliary magnet 6 is the field magnet 4-2.
It is in contact with the south pole.

Similarly, the N pole on the radially inner side of the auxiliary magnet 6 is
It is in contact with the S pole of the field magnet 4-1 and the S pole on the radially inner side of the auxiliary magnet 6 is in contact with the N pole of the field magnet 4-1. Therefore, as shown by the dotted line in FIG. 6A, the auxiliary magnet 6 is divided into two, namely, a radially outer magnet and a radially inner magnet.

(A) In the figure, Rout is the magnetic resistance of the outer yoke 1 and R
g1 is the magnetic resistance of the air and the coil between the field magnet 4-1 and the outer yoke 1, Rg2 is the magnetic resistance of the air and the coil between the field magnet 4-2 and the outer yoke 1, Rg3 is the magnetic reluctance of the air between the field magnets 4-1 and 4-2, and Rin is the inner yoke.
3 to the magnetic resistance, r1 to the magnetic resistance inside the field magnet 4-1
r2 corresponds to the magnetic resistance inside the field magnet 4-2, r3 corresponds to the magnetic resistance inside the auxiliary magnet 6 inside in the radial direction, and r4 corresponds to the magnetic resistance inside the auxiliary magnet 6 outside in the radial direction.

FIG. 2B is an electrical equivalent circuit described according to the definition in FIG. In the figure, V1 is a field magnet
The magnetomotive force of 4-1 is represented by a voltage source. V2 represents the magnetomotive force of the field magnet 4-2 by a voltage source. V3 is
The magnetomotive force of the auxiliary magnet 6 on the radially inner side is represented by a voltage source. V4 represents the magnetomotive force of the auxiliary magnet 6 on the radially outer side by a voltage source. The current of each part when the voltage sources V1 and V2 on this electrical equivalent circuit are valid and the voltage sources V3 and V4 are set to 0 and the voltage sources V3 and V4 are valid
The current of each part when V1 and V2 are set to 0 is calculated and analyzed using the theory of superposition.

FIG. 4 shows that the voltage sources V1 and V2 are valid, the voltage sources V3 and
It is a circuit diagram where V4 is set to 0. (a) is an enlarged view of a portion necessary for explanation, and (b) is an equivalent circuit thereof. As shown in (a), magnetic resistances R1, R2, R3, and R4 are generated between the field magnets 4-1 and 4-2 and the auxiliary magnet 6. The meaning of this will be described.

The field magnets 4-1 and 4-2 are usually manufactured by radially magnetizing an anisotropic (radial anisotropy) magnetic material. Therefore, the magnetic resistance in the direction from the magnet axis to the outer peripheral surface is
(Equivalent to r1 here) is extremely small. On the other hand, the magnetic resistance (corresponding to R1 here) in the direction of the inner yoke becomes extremely large. On the other hand, the auxiliary magnet 6 is manufactured by magnetizing an anisotropic (axial anisotropy) magnetic material in the direction of the inner yoke 3. Therefore, the magnetic resistance in the direction of the inner yoke 3 (here, r3 or r4
Is very small. On the other hand, the magnetic resistance (not shown) in the direction from the axis of the magnet to the outer peripheral surface becomes extremely large.

From (b), at this time, loops V1, Rg1, Rou
The current (magnetic flux) flowing through t, Rg2, r2, V2, Rin, r1 and V1 is i
1, the current through the loop V1, Rg3, r2, V2, Rin, r1, V1
(Magnetic flux) is defined as i2. As mentioned above, the magnetic resistances R1 and R
2, R3, R4 are very large, so loops V1, R1, r4, R
Current flowing through 3, r2, V2, R4, r3, R2, r1, V1 (magnetic flux)
Is ignored. Next, enable the voltage sources V3 and V4 and
Calculate the current of each part when V1 and V2 are set to 0.

FIG. 5 shows that the voltage sources V3 and V4 are enabled and the voltage sources V1 and V4 are
It is a circuit diagram in which V2 is set to 0. (a) is an enlarged view of a portion necessary for explanation, and (b) is an equivalent circuit thereof. As shown in (a), magnetic resistances R1, R2, R3, and R4 are generated between the field magnets 4-1 and 4-2 and the auxiliary magnet 6, and this position is shown in the above figure on the equivalent circuit. A little different from 5. It means that the magnetic flux generated by the auxiliary magnet 6 does not easily enter the inside of the field magnets 4-1 and 4-2, and travels to the outer yoke 1 and the inner yoke 3.

From (b), V4, Rg1, Rout, Rg2, r4, V4
Is defined as i3, the current (magnetic flux) flowing through the loops V4, Rg3, r4, and V4 is i4, and the current (magnetic flux) flowing through the loops V3, Rin, r3, and V3 is defined as i5. As described above, the magnetic resistances R1, R2, R3, and R4 are extremely large, so loops V4, R1, and
The current (magnetic flux) flowing through r1, R2, V3, r3, R4, r2, R3, r4, V4 is ignored.

By superimposing i1, i2, i3, i4 and i5 thus obtained, the magnetic flux flowing through each portion of the inner yoke magnet type linear motor according to the present invention is obtained. The magnetic flux interlinking with the current flowing through the stator coils 2-1 and 2-2 is i1 in FIG.
It can be seen that this is equivalent to the value obtained by adding the i3 in FIG. The points to be noted here are as follows.

I1 is the same value as i1 (FIG. 8) found in the conventional inner yoke magnet type linear motor described above. Therefore, in the inner-yoke magnet linear motor according to the present invention, the number of flux-linkage magnetic fluxes corresponding to i3 increases as compared with the conventional inner-yoke magnet linear motor.

Further, in the inner yoke magnet type linear motor according to the present invention, the magnetic flux flowing in the inner yoke 3 (FIG. 1) is a value obtained by subtracting i5 in FIG. 5 from a value obtained by adding i1 and i2 in FIG. I know that it corresponds. Therefore, in the inner yoke magnet type linear motor according to the present invention, the magnetic flux flowing in the inner yoke 3 (FIG. 1) is reduced by the amount corresponding to i5 as compared with the conventional inner yoke magnet type linear motor. It This has important implications. That is, in the thin rod-shaped inner yoke 3, magnetic saturation usually occurs easily, but since the amount of magnetic flux can be reduced by the present invention, magnetic saturation becomes difficult.

<Effect of Concrete Example 1> As described above, 2
By disposing the auxiliary magnet so as to be sandwiched between the field magnets, the driving force can be increased without changing the size. Further, since magnetic saturation in the thin rod-shaped inner yoke 3 can be prevented, precise operation becomes possible.

<Specific Example 2> The inner-yoke magnet linear motor of the specific example 2 is an expansion example of the inner-yoke magnet linear motor of the specific example 1, in which the number of field magnets, auxiliary magnets, and stator coils is changed. Take the configuration to increase arbitrarily. As a result, the driving force is increased. The details will be described below with reference to the drawings.

FIG. 6 is a structural diagram of the inner yoke magnet type linear motor of the second specific example. (a) is a longitudinal sectional view of the inner yoke magnet type linear motor, and (b) is a transverse sectional view of the inner yoke magnet type linear motor. From the figure, the inner yoke magnet type linear motor of the specific example 2 has the outer yoke 21 and the stator coil 2-
1, 2-2, 2-3, 2-4, inner yoke 23, and field magnets 4-1, 4-
2, 4-3, 4-4, an insulating cylinder 25, and auxiliary magnets 6-1, 6-2, 6-3 are provided.

Here, four stator coils and four field magnets are used.
Although three and three auxiliary magnets are arranged, this is an example and the present invention is not limited to this example. The respective configurations and functions are exactly the same as those of the first specific example, and therefore the description thereof will be omitted.

<Effect of Concrete Example 2> As described above,
Specific example 1 by increasing the number of stator coils etc.
In addition to the effect of, without enlarging the outer shape of the motor,
The driving force can be increased and the operation speed can be increased.

[Brief description of drawings]

FIG. 1 is a structural diagram of an inner yoke magnet type linear motor of a first specific example. (a) is a longitudinal sectional view of the inner-yoke magnet type linear motor, and (b) is a transverse sectional view of the inner-yoke magnet type linear motor.

FIG. 2 is an explanatory diagram of a field magnet and an auxiliary magnet. (a)
[Fig. 3] is a diagram showing a field magnet, and (b) is a diagram showing an auxiliary magnet.

FIG. 3 is an equivalent circuit diagram of an inner yoke magnet type linear motor of the present invention. (a) is an enlarged view of a portion necessary for explanation, and (b) is an equivalent circuit thereof.

FIG. 4 is a circuit diagram in which the voltage sources V1 and V2 are valid and the voltage sources V3 and V4 are 0. (a) is an enlarged view of a portion necessary for explanation, and (b) is an equivalent circuit thereof.

FIG. 5 is a circuit diagram in which the voltage sources V3 and V4 are valid and the voltage sources V1 and V2 are 0. (a) is an enlarged view of a portion necessary for explanation, and (b) is an equivalent circuit thereof.

FIG. 6 is a structural diagram of an inner yoke magnet type linear motor of a specific example 2. (a) is a longitudinal sectional view of the inner-yoke magnet type linear motor, and (b) is a transverse sectional view of the inner-yoke magnet type linear motor.

FIG. 7 is a structural diagram of a conventional inner yoke magnet type linear motor. (a) is a longitudinal sectional view of the inner-yoke magnet type linear motor, and (b) is a transverse sectional view of the inner-yoke magnet type linear motor.

FIG. 8 is an equivalent circuit diagram of a conventional inner yoke magnet type linear motor.

[Explanation of symbols]

1 outer yoke 2-1 Stator coil 2-2 Stator coil 3 Inner yoke 4-1 Field magnet 4-2 Field magnet 5 Insulation tube 6 auxiliary magnet

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Satoshi Muranishi             2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa             No. Showa Densen Denki Co., Ltd. (72) Inventor Osamu Kokubo             2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa             No. Showa Densen Denki Co., Ltd. (72) Inventor Akama Akahiro             2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa             No. Showa Densen Denki Co., Ltd. (72) Inventor Ikuma Naruyoshi             2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa             No. Showa Densen Denki Co., Ltd. F-term (reference) 2H051 FA01 FA10                 5H633 BB08 BB10 GG02 GG09 GG13                       GG17 HH03 HH07 HH13                 5H641 BB06 BB14 BB19 GG02 GG04                       GG08 HH03 HH11

Claims (2)

[Claims] 1. A cylindrical outer yoke, and a pair of annular stator coils that are closely attached to the inner side of the outer yoke, are arranged in the moving direction of the inner yoke, and are arranged coaxially with the outer yoke. A rod-shaped inner yoke coaxially arranged inside the outer yoke, and an outer yoke fixed to the inner yoke, arranged side by side with a gap in the moving direction of the inner yoke, and arranged coaxially with the inner yoke. A pair of annular field magnets and an annular auxiliary magnet arranged so as to be sandwiched in the gap between the pair of field magnets are provided, and the pair of stator coils have mutually opposite polarities. The stator magnetic field is excited, the directions of magnetization of the pair of field magnets are both parallel to the direction from the axis of the magnet to the outer peripheral surface, and the direction of magnetization of one field magnet is the other. Is set to be in the direction opposite to the magnetization direction of the field magnet of Note that the direction of magnetization of the auxiliary magnet is parallel to the axis of the inner yoke, and the polarity of the magnetic pole of the auxiliary magnet matches the polarity of the outer peripheral surface of the field magnet with which the magnetic pole of the auxiliary magnet is in contact. The inner yoke magnet type linear motor is characterized by having 2. A cylindrical outer yoke, and three or more annular stator coils that are closely attached to the inner side of the outer yoke and are arranged in the moving direction of the inner yoke and are arranged coaxially with the outer yoke. A rod-shaped inner yoke coaxially arranged inside the outer yoke, fixed to the outer periphery of the inner yoke, arranged with a gap in the moving direction of the inner yoke, and arranged coaxially with the inner yoke. And a plurality of annular field magnets, the number of which is equal to or less than the number of the stator coils, and an annular auxiliary magnet arranged so as to be sandwiched in the gap between all the field magnets. Stator magnetic fields with mutually opposite polarities are excited in the coils, and the magnetization directions of all field magnets are parallel to the direction from the magnet axis to the outer peripheral surface. The magnetization directions of are set to be opposite to each other, The direction of magnetization of the auxiliary magnet is parallel to the axis of the inner yoke, and the direction of magnetization of the auxiliary magnet coincides with the polarity of the outer peripheral surface of the field magnet with which the magnetic pole of the auxiliary magnet is in contact. The inner yoke magnet type linear motor is characterized by having