JPH07123683A - Swing type actuator - Google Patents

Abstract

PURPOSE:To provide a swing actuator in which the change of thrust in swing direction is small and whose constituent member can be manufactured at low cost and besides with high accuracy. CONSTITUTION:In a swing actuator, where a permanent magnet 5 is fixed to a yoke 1 being made roughly in the shape of E out of a cylindrical center yoke 2, an outer yoke, and an inner yoke, and an arm provided with a mobile coil is constituted shiftably along the center yoke 2, the thickness dimension of the vicinity of the stroke end of the mobile coil of the center yoke 2 is made larger than the thickness dimension of the middle section, and also the permanent magnet 5 fixed to the outer yoke is formed being magnetized in the direction going to the center axis of curvature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillating actuator used for positioning means of a magnetic head in a magnetic disk device, that is, a functional member such as a magnetic head oscillates so as to draw an arc locus. In particular, the present invention relates to an oscillating actuator that can reduce the change in thrust in the oscillating direction, improve so-called linearity, and manufacture components at low cost and with high accuracy.

[0002]

2. Description of the Related Art FIG. 7 is a plan view of an essential part showing an example of a conventional rocking type actuator. In FIG. 7, reference numeral 1 denotes a yoke, which is made of a ferromagnetic material such as soft iron to have a substantially E-shaped projection on a plane. Reference numeral 2 is a center yoke, and 3 is a side yoke, each of which forms a projection shape on a plane into an arc shape. Reference numeral 4 denotes a counter yoke, which is formed of a material similar to that of the yoke 1 into a flat plate shape and fixed to the open end of the yoke 1 by, for example, a screw.

Next, 5 is a permanent magnet, which has a circular arc-shaped cross section, is magnetized in the thickness direction, and is fixed, for example, with an adhesive so that the same pole faces the inside of the side yoke 3. Then, a magnetic gap 6 is formed between the center yoke 2 and the center yoke 2. An arm 7 has a movable coil 8 formed in the shape of a hollow prism at one end and a functional member (not shown) such as a magnetic head fixed to the other end. The movable coil 8 and the permanent magnet 5 are fixed to each other. It is rotatably or swingably disposed via a shaft 9 so as to be positioned in a magnetic gap 6 formed by the center yoke 2.

When a signal current is applied to the movable coil 8 with the above-described structure, a driving force around the shaft 9 acts on the movable coil 8 according to Fleming's left-hand rule, causing the arm 7 to rotate or swing to move. For example, a magnetic head provided at the other end of 7 can be positioned on a predetermined recording track on the magnetic disk. The rotation or swinging direction is switched by reversing the direction of the current flowing through the movable coil 8.

FIG. 8 is a horizontal cross-sectional plan view of an essential part showing an example of the molding means of the permanent magnet 5 in FIG. In FIG. 8, 10 is a molding die, and a core 11 made of a ferromagnetic material.
And the outer die 12 and the member 13 made of a non-magnetic material. 14 is a molding cavity.
The molding die 10 is placed between a pair of electromagnets 15, 15 and compression-molded in a radial magnetic field as shown by the broken line, and the resulting molded body is sintered and heat-treated to obtain the permanent magnet shown in FIG. The magnet 5 can be obtained. The magnetization of the permanent magnet 5 is
It may be performed by a magnetizing device (not shown) having the same configuration as that in FIG.

However, since the structure of the molding die 10 in the case of compression molding in the radial magnetic field as described above becomes extremely complicated, not only the manufacturing cost becomes high, but also the orientation of the magnetic powder in the molded body is difficult. Or the orientation is disturbed. Further, if the permanent magnet 5 has a large radius of curvature, the molding die 10 is necessarily large, whereas if the permanent magnet 5 has a small radius of curvature, it may be difficult to form an accurate radial magnetic field. .

FIG. 9 is a horizontal cross-sectional plan view of an essential part showing another example of the molding means for the permanent magnet 5 in FIG. 7, and the same parts are designated by the same reference numerals as in FIG. In FIG. 9, the molding cavity 14 is formed in a substantially arc shape corresponding to the cross-sectional contour of the permanent magnet 5 shown in FIG. 7, and is arranged in the parallel magnetic field shown by the broken line. According to such a molding die 10, the permanent magnet 5 can be obtained more easily than that shown in FIG.

[0008]

However, in the rocking type actuator using the permanent magnet 5 molded by the molding means as shown in FIG. 9, the rocking motion acting on the movable coil 8 or the arm 7 shown in FIG. There is a problem that the change in thrust in the direction is large and the linearity is low.

FIG. 6 is a diagram showing the relationship between the magnetic flux density in the magnetic gap 6 shown in FIG. 7 and the rotation angle of the arm. Curves a and b in FIG. 6 correspond to the outer and inner magnetic gaps 6 and 6a in FIG. 7, respectively. As is clear from FIG. 6, the magnetic flux densities at the arm rotation angles near 0 ° and 50 ° are lower than the magnetic flux densities at the intermediate portion, and in particular the curve a (corresponding to the outer magnetic gap) ) Is extremely severe. Now, change the magnetic flux change rate (maximum value −
When expressed by (minimum value) / maximum value, it is 40 in curve a.
%, Which is a factor that reduces the performance of the swing actuator.

In the conventional structure shown in FIG. 7, the center yoke 2 and the permanent magnet 5 have the same thickness in the swinging direction of the movable coil 8. On the other hand, since there is a leakage magnetic flux at both end edges of the permanent magnet 5, the effective magnetic flux in the magnetic gap 6 naturally decreases. Therefore, as shown in FIG. This is one of the causes of the decrease.

Further, the yoke 1 shown in FIG. 7 is made of the iron-based ferromagnetic material as described above.
These materials are formed by forming means such as cold forging, powder metallurgy and precision casting. In order to secure the mounting accuracy of the permanent magnet 5 and the air gap dimensional accuracy of the magnetic air gap 6 at a high level, the concave and convex cylindrical surfaces of the center yoke 2 and the side yoke 3 which constitute the yoke 1 are machined to have a dimensional accuracy of 0.05, for example. Must be less than mm.

However, the work of machining the concave-convex cylindrical surface of the yoke 1 with high accuracy is extremely complicated, and the working man-hour and the working time are usually large. Therefore, the machining cost will increase, which will result in a high manufacturing cost of the swing actuator.

When a means such as precision casting is used, the magnetic characteristics of the material are equivalent to S10C, and the saturation magnetic flux density Bs is 1.6 to 1.7 (T). On the other hand, steel plates used in flat plate type voice coil type motors (SS41, SP
(Such as C) has a saturation magnetic flux density Bs of about 1.8 (T),
The magnetic characteristics will deteriorate.

Further, as shown in FIG. 7, since the yoke 1 has a complicated overall shape, the work for molding this material is also complicated and there is a problem that the productivity is lowered. It should be noted that any of the material forming means as described above requires a mold for forming, and a mold for forming a material having a complicated shape inevitably requires a high manufacturing cost. This is one of the reasons for increasing the manufacturing cost of the die actuator.

On the other hand, in recent years, the demands for downsizing and cost reduction of this type of oscillating actuator have become particularly strict, and the above-mentioned conventional structure satisfies the above requirements because the manufacturing cost increases. There is a problem that you cannot do it.

The present invention solves the above-mentioned problems existing in the prior art, reduces the change in thrust in the swing direction, and
An object of the present invention is to provide an oscillating actuator capable of manufacturing the constituent members at low cost and with high accuracy.

[0017]

In order to achieve the above object, in the first aspect of the invention, first of all, an arc-shaped outer yoke and an inner yoke which are coaxial with the arc-shaped center yoke are provided on both sides of the center yoke. A yoke having a substantially E-shaped projected shape, an arc-shaped permanent magnet that is fixed to the inner surfaces of the outer yoke and the inner yoke and has the same poles on the opposite surfaces, and the open end of the yoke. The counter yoke is fixed, and the movable coil is fixed to one end and the functional member is fixed to the other end. The arm is swingably formed. The movable coil is formed in a hollow cylindrical shape and extends along the center yoke. In the swingable actuator configured to be movable, the thickness of the moving coil of the center yoke near the stroke end is formed to be larger than the thickness of the intermediate portion, and Formed by magnetizing in a direction toward the permanent magnet which is fixed to the outer yoke to the center of curvature axis even without adopts the technical means of.

Next, in the second aspect of the present invention, an arc-shaped center yoke is provided on both sides with an arc-shaped outer yoke and an inner yoke, which are coaxial with the arc-shaped center yoke. An arc-shaped permanent magnet that is fixed to the inner surfaces of the yoke and the inner yoke and has the same poles on the opposite surfaces, a counter yoke fixed to the open end of the yoke, and a movable coil at one end. An oscillating actuator having a movable coil formed in a hollow cylindrical shape and movable along the center yoke, the oscillating actuator having at least an outer member and an arm formed by oscillating with functional members fixed to each end. The permanent magnet fixed to the yoke is magnetized in the direction toward the center of curvature, and the thickness of the circumferential edge is larger than that of the middle part. Formed is adopted technical means of.

In the above invention, the thickness of the movable coil of the center yoke in the vicinity of the stroke end of the movable coil is made larger than that of the middle portion, and / or a plurality of thin plates having the same cross-sectional shape as the yoke are laminated. To form the yoke,
A coating made of a thermoplastic resin material may be provided on the outer surfaces of the yoke and the permanent magnet.

In the above invention, since the permanent magnet as a constituent member cannot have a high operating point because its thickness is limited, it is preferable to use a rare earth magnet having a large coercive force. Further, in recent years, further thinning and higher performance are required, so in order to secure a high magnetic flux density in the magnetic gap, the R-Fe-B system (R: Y, N
It is more preferable to use a permanent magnet of one or more rare earth elements such as d).

Next, the thin plate forming the yoke in the above invention is preferably stamped and formed by a punch / die set, and in this case, it is also possible to continuously laminate in the punching die. Further, the thin plates can be tightly integrated with each other by engaging dowels and dowel holes, but an adhesive may be interposed between the layers. Further, a through hole may be provided in the laminated body, and after the lamination, they may be integrated with each other via a rivet or other fastening means.

Since the above-mentioned yoke is usually made of an iron-based material, a coating made of a corrosion-resistant material is provided on the outer surface for rust prevention, but a known resin material should be used as such a material. You can As the coating forming means, in addition to coating, spraying, etc., molding (injection molding) in which the laminated body is inserted into a mold and filled with a resin material
Can be used.

Further, a thermoplastic resin material can be used as the above resin material. For example, known resins such as polyphenylene sulfide resin, polybutylene terephthalate resin, polyamide resin, polyimide resin, polyamideimide resin, polyester resin (preferably heat resistant) can be used. Resin having a property) can be used.

[0024]

With the above structure, the magnetic flux density of the magnetic gap at the stroke end of the moving coil can be secured,
Linearity can be improved by reducing the change in thrust in the swing direction.

Further, the outer contour dimensions of the thin plates constituting the yoke are ensured in accuracy during the molding of the thin plates, and the thin plates can be accurately positioned by the engagement of the integrally formed dowels and dowel holes, for example. Therefore, machining after lamination can be omitted. As a result, highly accurate and low cost manufacturing is realized.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view of essential parts showing a magnetic circuit according to an embodiment of the present invention, and the same parts are designated by the same reference numerals as those in FIG. In FIG. 1, 21 is a wall thickness increasing portion,
The center yoke 2 is provided near the tip and the root, that is, near the stroke end of the movable coil (not shown, see reference numeral 8 in FIG. 7), and the thickness t ₁ thereof is larger than the thickness t of the intermediate portion. To form.

Next, reference numeral 51 is a split magnet, which is provided on the outer side yoke 3 (outer yoke), and is, for example, approximately 1/3 of the circumferential length of the permanent magnet 5 shown in FIG. Then, the divided magnets 51 are connected in the circumferential direction to form the permanent magnet 5. These split magnets 5
Numeral 1 is formed in the thickness direction and is oriented in a magnetic field parallel to a plane including the center axis of curvature and the intermediate portion in the circumferential direction. The broken line is the orientation direction of the magnetic field. Such a split magnet 51 can be easily formed by a parallel magnetic field forming means as shown in FIG.

With the above structure, the outer side yoke 3
The orientation directions of the split magnets 51 provided in the respective magnets are parallel, but the orientation direction of the permanent magnet 5 as a whole is the central axis of curvature of the side yoke 3 (not shown, axis of axis 9 in FIG. 7).
Since the so-called radial orientation is directed toward, the effective magnetic flux in the magnetic gap 6 can be secured, and the performance of the magnetic circuit can be improved.

Further, by providing the thickness increasing portion 21 at the tip and the root of the center yoke 2, the magnetic flux from the permanent magnet 5 can be directed to the thickness increasing portion 21, and the movable coil 8 shown in FIG. It is possible to reduce the leakage magnetic flux at the stroke end portion and secure the effective magnetic flux in the magnetic gap 6 at this portion.

In the above-mentioned embodiment, the example in which the split magnets 51 are connected as the permanent magnets 5 is shown, but the present invention is not limited to this, and the integrally formed permanent magnets (however, the direction toward the center axis of curvature, that is, A magnetized in the radial direction) can also be used.

2A and 2B are plan views of a main part of a magnetic circuit according to another embodiment of the present invention. FIG. 2A is an example in which the thickness dimension of the split magnet is continuously changed, and FIG. 2B is a split magnet. Fig. 1 shows an example in which the thickness dimension is intermittently changed.
The same reference numerals are used. Note that, in FIG. 2, the split magnets 5 provided on the outer side yokes 3 are illustrated for convenience of description.
Although the NS pole display for 1 is omitted, it is the same as that shown in FIG.

In FIG. 2A, the thickness dimension of the free end edge of the divided magnet 51 at the edge in the circumferential direction is T ₁ , T ₂ ,
The thickness dimension of the intermediate portion of the intermediate magnet 51 is T, and the thickness of the permanent magnet 5 as a whole is formed so as to continuously change from T to T ₁ and T ₂ . The thickness T,
T ₁ and T ₂ are formed so that T ₁ and T ₂ > T. Therefore, if the thickness dimension of the connection edge between the split magnets 51, 51 is T _C , then T ₁ , T ₂ > T _C > T. In addition, the split magnet 51 is subjected to the same magnetic field orientation as that shown in FIG.

With the above structure, the magnetic flux density at the free end edge of the permanent magnet 5 formed by connecting the split magnets 51 can be made larger than that at the intermediate portion, and even if the leakage magnetic flux is subtracted, the permanent magnet 5 It is possible to secure the effective magnetic flux in the magnetic air gap 6 at the free end edge of No. 5, that is, at the stroke end of the movable coil 8 shown in FIG. Although T ₁ = T ₂ in FIG. 2A, T ₁ ≠ T ₂ may be set.

Next, in the one shown in FIG. 2B, the thickness dimension of the split magnet 51 at the center is T, and the thickness dimensions of the split magnet 51 at the circumferential edge portion are T ₃ and T ₄ . When T ₃ , T ₄
> T. The magnetic field orientation direction of the split magnet 51 is the same as that shown in FIGS. 1 and 2A. With such a configuration, as in the case shown in FIG. 2A, the effective magnetic flux in the magnetic gap 6 at the stroke end of the movable coil 8 shown in FIG. 7 can be secured. In FIG. 2B, T ₃ = T ₄ , but
It may be T ₃ ≠ T ₄ .

FIG. 5 is a diagram showing the relationship between the magnetic flux density in the magnetic gap of the magnetic circuit and the arm rotation angle in the embodiment of the present invention, and is a diagram corresponding to FIG. That is, FIG.
2 shows the magnetic flux density distribution in the magnetic gaps 6 and 6a formed by the permanent magnet 5 fixed to the outer side yoke 3 (outer yoke) shown in FIG.

In FIG. 5, curves A ₁ , A ₂ and A ₃ correspond to magnetic circuits having the following configurations, respectively. (Curve A ₁ ) The center yoke 2 is formed to have the same thickness, and the permanent magnet 5 is formed by connecting three divided magnets 51 shown in FIG. 1 in the circumferential direction. (Curve A ₂ ) A structure in which the center yoke 2 is provided with the wall thickness increasing portion 21 shown in FIG. 1 and the permanent magnet 5 has the conventional structure shown in FIG. 7. (Curve A ₃ ) The magnetic circuit having the configuration shown in FIG. 1.

In FIGS. 5 and 6, the permanent magnet is N
d-Fe-B system sintered magnet (HS42 manufactured by Hitachi Metals, Ltd.)
AH) is used to show the magnetic flux density distribution in the middle of the magnetic gap (the region where R ₁ = 18.15 mm and R ₂ = 26.95 mm in FIG. 2A).

As is clear from FIG. 5, the magnetic flux change rate is 23% in the curve A ₁ , which is improved from the 40% in the curve a in FIG. That is, it is recognized that the permanent magnet 5 as a whole is in the radial orientation. The rate of change of magnetic flux in the curve A ₂ is improved to 18%, and the same improvement as in the curve A ₁ is recognized. This is the thickened portion 21 provided in the center yoke 2 shown in FIG.
It is recognized that this is an effect of magnetic flux convergence due to. Then, in the curve A ₃ , the magnetic flux change rate was improved to 13%, and it is considered that the synergistic effect due to the radial orientation and the magnetic flux convergence appeared.

In the structure shown in FIG. 1, the permanent magnet 5
As a result, by adopting the configuration shown in FIG. 2, it is possible to further reduce the magnetic flux change rate and significantly improve the linearity.

FIG. 3 is a plan view showing a main part of a yoke in still another embodiment of the present invention, FIG. 4 is a partial sectional side view of the yoke in FIG. 3, and FIG. 3A is a stack of dowels and dowel holes. Joining example, (b) shows a laminated joining example by rivets. In FIGS. 3 and 4, reference numeral 20 denotes a thin plate, which is formed of a mild steel plate such as SPCC to have the same plane shape as the cross-sectional shape of the yoke 1 shown in FIG.

In order to form such a thin plate 20, it is preferable to apply punching and forming means by a punch / die set. Reference numerals 16 and 17 are dowels and dowel holes, respectively, which are formed to have the same outer diameter and inner diameter, and to have a height dimension and a depth dimension smaller than the thickness dimension of the thin plate 20, for example. In order to form the dowel 16 and the dowel hole 17 as described above, a punch and a die for forming the dowel 16 and the dowel hole 17 are incorporated in the punch / die set, and a so-called half punch means is applied to punch the thin plate 20. It is preferable to perform molding at the same time as the blanking. After forming the thin plate 20, for example, Araldite AV138 is applied on the surface and a predetermined number of layers are laminated to form the yoke 1 having a predetermined size.

With the above-mentioned structure, the divided magnets (not shown, reference numeral 51 in FIG. 1) magnetized in advance are inserted and fixed in a predetermined position in the yoke 1, and are inserted into the molding die to form each structure. A thermoplastic resin (for example, polyphenylene sulfide, polycarbonate, unsaturated polyester, engineering plastic such as liquid crystal plastic) is injection-molded on the surface of the member to form a coating. This coating prevents rusting of the surface of each component,
Due to the hugging action of the coating, relative movement of each component can be prevented.

Next, in the laminated joining example shown in FIG. 2 (b), the rivet holes 18 are formed at the same time when the thin plate 20 is stamped and formed, and after laminating a predetermined number of sheets, they are fastened via the rivets 19. . In this case, in order to prevent the warp of the yoke 1, it is desirable that the uppermost thin plate 20a and the lowermost thin plate 20b have a larger thickness than the other thin plates 20.
In this case, a bolt or other fastening means may be used instead of the rivet 19.

In this embodiment, the case where the number of the divided magnets 51 is three has been described, but the present invention is not limited to this, and the operation is the same even if an arbitrary number of magnets are used. Further, the split magnet 51 may be provided not only on the outer side yoke 3 (outer yoke) but also on the inner side yoke 3 (inner yoke) if necessary.

[0045]

EFFECTS OF THE INVENTION Since the present invention has the structure and operation as described above, it is possible to secure the magnetic flux density of the magnetic gap at the stroke end of the moving coil, reduce the change in thrust in the swing direction, Linearity can be improved. In addition, the yoke, which is a constituent member, can be formed only by punching and laminating thin plates, and subsequent machining can be omitted.
High accuracy can be secured. Further, by providing a coating made of a corrosion resistant material on the surfaces of the yoke and the permanent magnet, it is possible to prevent rusting and prevent contamination of the inside of the apparatus by foreign matter.

[Brief description of drawings]

FIG. 1 is a plan view of relevant parts showing a magnetic circuit according to an embodiment of the present invention.

FIG. 2 is a plan view of a main part showing a magnetic circuit according to another embodiment of the present invention, in which (a) is an example in which the thickness dimension of the split magnet is continuously changed, and (b) is the thickness of the split magnet. An example of intermittently changing the size is shown below.

FIG. 3 is a plan view showing a main part of a yoke according to still another embodiment of the present invention.

FIG. 4 is a partial cross-sectional side view of the yoke in FIG.
(A) shows an example of laminated joining by means of dowels and dowel holes, and (b) shows an example of laminated joining by means of rivets.

FIG. 5 is a diagram showing a relationship between a magnetic flux density in a magnetic gap of a magnetic circuit and an arm rotation angle in an example of the present invention.

6 is a diagram showing the relationship between the magnetic flux density in the magnetic gap 6 shown in FIG. 7 and the rotation angle of the arm.

FIG. 7 is a plan view of relevant parts showing an example of a conventional rocking type actuator.

8 is a horizontal cross-sectional plan view of an essential part showing an example of a forming unit of the permanent magnet 5 in FIG.

9 is a horizontal cross-sectional plan view of an essential part showing another example of the forming means of the permanent magnet 5 in FIG.

[Explanation of symbols]

 1 yoke 2 center yoke 3 side yoke 5 permanent magnet 21 thickened portion 51 split magnet

Claims (4)

[Claims] 1. A yoke in which an arc-shaped outer yoke and an inner yoke coaxial with the arc-shaped center yoke are provided on both sides of the arc-shaped center yoke, and a projected shape on a plane is formed into a substantially E shape, and inner surfaces of the outer yoke and the inner yoke. And a counter yoke fixed to the open end of the yoke, a movable coil is fixed to one end, and a functional member is fixed to the other end. And a swingable arm, wherein the movable coil is formed in a hollow cylindrical shape and configured to be movable along the center yoke, the stroke end of the movable coil of the center yoke. The thickness of the vicinity is made larger than the thickness of the middle part, and at least the permanent magnet fixed to the outer yoke is directed toward the center axis of curvature. Rocking type actuator, characterized in that formed by magnetization. 2. A yoke in which an arc-shaped outer yoke and an inner yoke which are coaxial with the arc-shaped center yoke are provided on both sides of the arc-shaped center yoke, and which has a substantially E-shaped projection on a plane, and inner surfaces of the outer yoke and the inner yoke. And a counter yoke fixed to the open end of the yoke, a movable coil is fixed to one end, and a functional member is fixed to the other end. A permanent magnet fixed to at least an outer yoke, wherein the movable coil is formed in a hollow cylindrical shape and is movable along the center yoke. Is magnetized in the direction toward the center axis of curvature, and the thickness of the circumferential edge is larger than that of the middle portion. Type actuator. 3. The oscillating actuator according to claim 2, wherein the thickness of the movable coil of the center yoke near the stroke end is larger than that of the intermediate part. 4. A yoke is formed by laminating a plurality of thin plates having the same cross-sectional shape as the yoke, and a coating made of a thermoplastic resin material is provided on the outer surfaces of the yoke and the permanent magnet. An oscillating actuator according to any one of claims 1 to 3.