JPH03215155A - voice coil motor - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention mainly relates to a voice coil motor used in an information recording/reproducing device.

(Prior Art) Magneto-optical or optical information recording and reproducing devices employ a voice coil motor as a drive device for the tracking direction of an optical head. As shown in FIGS. 3 and 4, an objective lens 1 for condensing a laser beam onto the surface of a disk-shaped recording medium is disposed on a carriage 3, and an actuator 2 is used to control focus and tracking directions. It is designed to be subject to minute movement control.
Furthermore, the large movement in the tracking direction is achieved by moving the carriage 3 in the rail direction by the voice coil motor 5 while being supported by a rail (not shown) via a bearing 4 provided thereon. It has been realized. The voice coil motor 5 includes an upper yoke 6, a lower yoke 7, a middle yoke 8, and a relay yoke 9. A magnet IO is arranged on the opposing surface of the upper yoke 6i3 and the lower yoke 7, and surrounds the middle yoke 8. For 1 liter of hollow pobbin, 1 coil
3 is wrapped around it. Above hollow pobin 1
1 has a frame structure with a rectangular or trapezoidal cross section with ribs l2 at both ends, and a coil 13 is wound around the frame.
The gap between the magnet 10 and the magnet 10 is made as small as possible.

(Problem to be Solved by the Invention) Usually, the coils in the voice coil motor described above are simply wound around the bobbin, that is, the coils are fixed only by the winding contact pressure between each other and the bobbin. In this case, the frequency characteristics of the carriage in the tracking direction by the voice coil motor exhibit characteristics as shown by the dotted line in the graph of FIG. Here f+. f
i is the secondary resonance of the voice coil motor, the latter (f2)
is the sub-resonance of the voice coil motor popin, and the former (f1) is the sub-resonance of the voice coil itself. When such sub-resonance occurs, the motor servo becomes unstable, making it difficult to move the carriage to a predetermined position. Therefore, as a means to suppress such resonance of the coils, the coils l3 are hardened to each other or to the bobbin using an adhesive l4 (see Fig. 6).6 However, when using porous ceramic materials, When used on a bobbin, there is a problem that the adhesive penetrates into the bobbin and the original adhesive effect cannot be fully demonstrated.In addition, when using this adhesive, it is not only necessary to adhere the turns of the coil to each other. , it is necessary to supply adhesive to the bobbin for each winding layer, which requires a great deal of time and effort to wind the coil. (Objective of the Invention) The present invention has been made based on the above circumstances, and by improving the bobbin shape and increasing the winding contact pressure of the coil against the bobbin, the gain swing of the sub-resonant frequency in the resonance of the coil itself is reduced. The aim is to provide a voice coil motor that achieves this. (Means for Solving the Problems) Therefore, in the present invention, a bobbin wound with a coil is arranged so that the coil cuts the magnetic flux between the magnets provided on the yoke, and the current supplied to the coil is applied to the yoke. In a voice coil motor configured to move a bobbin relative to the other, the coil winding surface of the bobbin is configured to have a convex shape in the winding direction.

(Function) For this reason, the winding contact pressure at each part of the coil turn can be greatly improved compared to when the coil is wound along a flat surface. It is possible to sufficiently damp the resonance of the coil and improve the frequency characteristics without increasing the fixing strength. (Example) An example of the present invention will be specifically described below with reference to FIG. In addition, here, the same reference numerals are given to the same parts as those shown in the conventional example, and the explanation thereof will be omitted. The pobbin l1 adopted here has a generally rectangular frame shape as a whole, as in the conventional case, but in particular, the upper and lower long flat surfaces have a chevron-shaped or crown-like shape with respect to the winding direction of the coil 13. Convex shape protruding from a. It is formed in b. Having such a convex shape increases the winding contact pressure between the coil l3 and the pobbin 11, thereby damping the resonance of the coil as described above. This state is shown by the solid line at the corresponding location in Figure 5, where the conventional example is shown by the dotted line. In other words, the gain peak at the sub-resonant frequency in the frequency characteristics of the voice coil motor in the tracking direction is reduced, and a large margin for oscillation at the sub-resonant frequency can be secured. In addition, in this way, the shape of the bobbin is changed to a convex shape a. b, as shown in Figure 2, by matching the shape of the middle yoke 8 to this, the actual gap between the magnet and the coil can be minimized, increasing the magnetic flux density between the gaps. It also improves the thrust of the voice coil motor. (Effects of the Invention) The present invention has been described in detail above, and since the surface on which the coil is wound by the bobbin is configured to have a convex shape in the winding direction, sufficient winding contact pressure of the coil against the bobbin can be ensured. As a result, the resonance of the coil can be sufficiently damped and the frequency characteristics can be improved without using adhesives.
Therefore, effects such as stably realizing tracking control used in optical or magneto-optical information recording and reproducing devices can be obtained.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a voice coil motor showing one embodiment of the present invention, Fig. 2 is a sectional view of a voice coil motor showing another embodiment, Fig. 3 is a perspective view of a conventional example, and Fig. 4 is a sectional view of a voice coil motor showing an embodiment of the present invention. 5 is a frequency characteristic diagram of the voice coil motor, and FIG. 6 is a sectional view of another conventional voice coil motor.

Claims (1)

[Claims] A voice coil in which a bobbin wound with a coil is arranged so that the coil cuts the magnetic flux between magnets provided on a yoke, and the bobbin is moved relative to the yoke by the current supplied to the coil. A voice coil motor, characterized in that the coil winding surface of the bobbin is configured to have a convex shape in the winding direction.