JP2518836Y2 - Oscillating actuator - Google Patents

Description

[Detailed description of the device]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillating actuator such as an actuator for a magnetic disk, and in particular, an oscillating actuator in which a functional member such as a magnetic head oscillates so as to draw an arc locus. Type) actuator.

[0002]

2. Description of the Related Art Conventionally, an oscillating or rotating actuator as shown in FIGS. 7 and 8 has been used to position a magnetic head on a recording track of a magnetic disk or the like. In both figures, reference numeral 1 designates a yoke, which is arranged to face each other and is assembled by a column 3, and a permanent magnet 2 is fixed to one yoke 1 (lower side), and a magnetic circuit is formed via a gap 4. Reference numeral 5 is an arm, and a flat movable coil 6 is provided at one end.
A magnetic head (not shown) is fixed to the other end, and the movable coil 6 is rotatably and swingably disposed via the shaft 7 so that the movable coil 6 is located in the gap 4.

When a signal current is passed through the movable coil 6, a driving force around the shaft 7 acts on the movable coil 6 according to Fleming's left-hand rule, causing the arm 5 to rotate and swing,
The magnetic head fixed to the arm 5 is positioned on a predetermined recording track on the magnetic disk. The switching of the rotation direction is performed by reversing the direction of the current flowing through the movable coil 6.

In the above conventional magnetic disk actuator, an adhesive is generally used when the movable coil 6 is fixed to the arm 5. However, fixing work with an adhesive is not only complicated and low in workability,
The positioning accuracy of the movable coil 6 is also insufficient,
There is a problem of low reliability. Further, the processing of the terminal of the movable coil 6 also requires complicated work, and there is a problem that the workability of the entire assembling work is deteriorated. Further, in recent fields of magnetic disk devices, demands for miniaturization, thinning, high functionality, etc. of the device have become more severe, and the positioning accuracy of the moving coil and workability and reliability in bonding work are improved. Must be,
The conventional structure has a problem that the above requirements cannot be satisfied.

In order to solve the above problems, it has been proposed to integrate the movable coil 6 with the arm 5 by resin molding (for example, US Pat. No. 4,855,853, Japanese Utility Model Laid-Open No. 60-159566). reference). With such a configuration, the structure for holding the movable coil 6 can be simplified and can be made considerably thin, which is advantageous for downsizing the entire actuator. Further, the magnetic circuit portion can be made thin by having the permanent magnet 2 fixed to only one of the pair of yokes 1.

However, in the case of the resin mold-molded structure as described above, the mechanical strength, particularly the pull-out resistance and the bending strength, are insufficient, and the joint between the arm 5 and the movable coil 6 is insufficient. There is a problem.
Further, since the movable coil 6 is cast around by molding, a considerable amount of resin is deposited on the upper and lower surfaces of the movable coil 6, and the thickness of the movable coil 6 and its vicinity becomes large.
There is no choice but to increase the length of the void portion 4. Therefore, the magnetic performance of the permanent magnet 2 cannot be fully exhibited, and the performance as an actuator deteriorates.

Therefore, as an improvement of an actuator having a coil member formed by such resin molding, the present applicant has already fixed a yoke to one side of permanent magnets having different polarities, and attached these two yokes. A housing formed by facing each other through a magnetic gap between the permanent magnets, and an arm formed by a movable coil at one end and a functional member fixed at the other end to be swingable. In an oscillating actuator in which a movable coil is movably arranged, the arm and the movable coil are integrally fixed by a holding member made of a thermoplastic resin having a specific elastic modulus, and the peripheral portion of the movable coil is fixed. An application is filed for a device that adopts a technical means of forming the holding member to be held in a thickness dimension substantially the same as the thickness of the movable coil. That (Jitsugantaira 1 No. 72492).

FIG. 5 and FIG. 6 are a plan view and a longitudinal sectional view of an essential part showing an embodiment of the invention, respectively, and the same parts are designated by the same reference numerals as those in FIG. In FIGS. 5 and 6, the arm 5 is formed by, for example, aluminum alloy die casting, a mounting hole 8a is bored in the middle portion, and a hole 8b for mounting a functional member (not shown) such as a magnetic head is provided at one end. A retaining claw 5a is provided at the other end. Then 9
Is a holding member made of a thermoplastic resin, and is formed so that the arm 5 and the movable coil 6 are integrally fixed.
That is, the claw 5a and the movable coil 6 protruding from the arm 5
Form to embrace the surroundings.

For the movable coil 6, for example, a self-fusing electric wire (an electric wire having a fusion coating formed on the outermost layer of the core wire) is wound in a predetermined shape by a predetermined number to form a multi-layer air-core coil, and the air-core coil is energized. , Can be manufactured by integrating the whole with a fusion coating.

As a means for integrally fixing the arm 5 and the movable coil 6 as described above, for example, injection molding means is effective. That is, after the arm 5 and the movable coil 6 which have been die-cast molded in advance are inserted into the injection molding die and positioned,
For example, a heated melt of a thermoplastic resin such as glass-filled polyphenylene sulfide resin may be injected, cooled and solidified, and then taken out from the mold. Arm 5 by the above injection molding
And the movable coil 6 are integrally fixed. In this case, since the claw 5a provided on the arm 5 is embedded in the holding member 9,
Effectively acts as a retainer in the direction.

[0011]

In the structure described above, the work of adhering the movable coil 6 is unnecessary as compared with the structure of the related art, so that the assembly work is extremely easy and the workability is greatly improved. Besides, there is an effect that the positioning accuracy and the fixing reliability of the movable coil 6 and the arm 5 are significantly improved, but there are some points to be improved as described below.

That is, the outer circumference of the hollow movable coil 6 is crimped by the holding member 9. However, in order to avoid interference with other constituent members of the actuator, a holding member to be provided on the outer circumference of the movable coil 6. In many cases, it is not possible to sufficiently secure the layer thickness of 9, and the rigidity of the movable coil 6 in the direction along the surface of the permanent magnet may be insufficient. Therefore, there is a problem that the movable coil 6 is deformed or the resonance frequency is lowered, causing a resonance phenomenon in a high frequency region.

The present invention solves the above-mentioned problems, and provides a swing type actuator capable of increasing the rigidity of the peripheral portion of the moving coil in addition to improving the workability and reliability in addition to downsizing and thinning. The purpose is to do.

[0014]

In order to achieve the above object, in the present invention, a permanent magnet is fixed to at least one of a pair of opposed yokes, and a magnetic gap is formed on the surface of the permanent magnet. And a movable coil at one end and a functional member at the other end, respectively, and an arm swingably formed, and the movable coil is movably disposed in the magnetic gap. In the actuator,
The arm and the moving coil are integrally fixed by a holding member made of a thermoplastic resin, and the thickness of the holding member that holds the peripheral edge of the moving coil is formed to be substantially the same as the thickness of the moving coil. At the same time, a technical means of fixing a thin plate made of a non-magnetic material to a part or all of the surface of the movable coil facing the permanent magnet was adopted.

In the present invention, it is preferable that the thickness of the thin plate is formed to be ⅓ or less of the length of the magnetic gap.

[0016]

With the above structure, the rigidity of the movable coil in the direction along the surface of the permanent magnet can be improved.

[0017]

1 is a plan view of an essential part showing an embodiment of the present invention, FIG. 2 is a view in the direction of arrow B in FIG. 1, and the same portions are designated by the same reference numerals as those in FIGS. In FIGS. 1 and 2, reference numeral 10 denotes a thin plate, which is made of, for example, stainless steel having a thickness of 50 μm and has a substantially U shape.
Is fixed to the surface of the movable coil 6 including, for example, with an adhesive.

With the above configuration, the direction along the surface of the permanent magnet of the movable coil 6 (the direction along the plane of FIG. 1, FIG. 2).
Rigidity in the direction perpendicular to the plane of the drawing) can be increased.

FIG. 3 is a diagram showing the relationship between the pressure applied and the amount of deformation of the movable coil. That is, in the embodiment shown in FIG. 1, the arm 5 and the holding member 9 are fixed and the movable coil 6 is fixed.
Movable coil 6 when a pressurizing pressure in the direction of arrow C is applied to
The amount of deformation is expressed by the displacement at the portion 6a. Note that the components shown in FIG. 5 are also represented in the same manner.

As is apparent from FIG. 3, in the curve b of the improved device shown in FIG. 5, the amount of deformation of the moving coil rapidly increases as the pressurizing pressure increases, and the pressurizing pressure 1.0 kg. Indicates 0.13 mm. On the other hand, in the curve a of the present invention shown in FIG. 1, the rigidity is increased by fixing the thin plate 10 to the surface of the movable coil 6, and the deformation amount of the movable coil due to the increase of the pressurizing pressure is increased. Even at a pressurizing pressure of 1.0 kg, it remains at 0.07 mm, which is about half that shown by the curve b.

FIGS. 4 (a) and 4 (b) are views showing the relationship between the frequency and the sensitivity with respect to the moving coil in the present invention and the improved device, respectively. The moving coil 6 shown in FIGS. 1 and 5 is placed on the vibration source. The sensitivity is measured by placing the acceleration sensor on the movable coil 6 and placing it on the movable coil 6. in this case,
The movable coil 6 was formed by a copper wire (300 turns) having an outer diameter of 1 mm, and was measured at an input current of 0.2 A. The sensitivity was calculated by the following formula.

[0022]

[Equation 1]

However, g: sensitivity (dB) f: frequency V: voltage

First, in the improved device shown in FIG. 4 (b), the sensitivity sharply increases when the frequency of the vibration source exceeds 1 kHz, and the maximum sensitivity, that is, resonance occurs near 1.5 kHz. On the other hand, in the device of the present invention shown in FIG. 4 (a), the sensitivity remains unchanged even when the frequency of the vibration source exceeds 2 kHz, and the resonance frequency is in the vicinity of 3 kHz. That is, it is extremely stable even when used as a high-speed actuator.

In this embodiment, an example in which the thin plate is made of stainless steel has been described, but it may be made of other non-magnetic material. However, a material having a large mass (a metal material having a specific gravity of 7 or more is preferable) is suitable. Further, the thin plate does not necessarily need to be fixed to both surfaces of the movable coil, and may be provided on one surface or a part thereof as needed.

The thickness of the thin plate is not particularly limited,
If the thickness is too thin, the effect of improving the rigidity of the moving coil cannot be expected, so the thickness is preferably 20 μm or more. On the other hand, the upper limit of the thickness dimension is determined by the gap formed between the movable coil and the permanent magnet, but if the thickness is too thick, the inertia of the movable portion becomes large, which is not preferable. (More preferably 1/5 or less) is preferable.

The magnetic circuit section may of course have a structure in which permanent magnets are fixed to both surfaces of a pair of opposed yokes and opposite poles are opposed to each other.

[0028]

Since the present invention has the structure and operation as described above, the rigidity in the direction along the surface of the permanent magnet is increased even if the thickness of the holding member surrounding the outer periphery of the movable coil is small. can do. Therefore, the resonance frequency becomes large, and there is an effect that stable driving can be performed without causing a resonance phenomenon even in a high frequency region.

[Brief description of drawings]

FIG. 1 is a plan view of an essential part showing an embodiment of the present invention.

FIG. 2 is a view on arrow B in FIG.

FIG. 3 is a diagram showing a relationship between a pressurizing pressure and a deformation amount of a movable coil.

4A and 4B are diagrams showing a relationship between frequency and sensitivity with respect to a movable coil, wherein FIG. 4A is of the present invention and FIG. 4B is of an improved device.

FIG. 5 is a plan view of an essential part showing an embodiment of the improved device.

FIG. 6 is a longitudinal sectional view of an essential part showing an embodiment of the improved device.

FIG. 7 is a plan view of a partially crushed and partially cross-sectional view showing an example of a conventional swing-type actuator.

FIG. 8 is a view on arrow A in FIG.

[Explanation of symbols]

 1 yoke 2 permanent magnet 5 arm 6 moving coil 9 holding member 10 thin plate

Claims (2)

(57) [Scope of utility model registration request] 1. A housing in which a permanent magnet is fixed to at least one of a pair of opposed yokes and a magnetic gap is formed on the surface of the permanent magnet, and a movable coil is fixed to one end and a functional member is fixed to the other end. In the swing-type actuator configured by movably disposing a movable coil in the magnetic gap, the arm and the movable coil are held by a holding member made of a thermoplastic resin. The holding member that is integrally fixed and holds the peripheral edge of the moving coil has a thickness dimension substantially the same as the thickness of the moving coil, and a part of the facing surface of the moving coil that faces the permanent magnet. Alternatively, an oscillating actuator characterized in that a thin plate made of a non-magnetic material is fixed to the whole. 2. The thickness dimension of the thin plate is 1 / the length of the magnetic gap.
The oscillating actuator according to claim 1, wherein the oscillating actuator is formed in three or less.