Abstract:
A drive section is disposed on only one side of a moving member. In the drive section, a coil is disposed sideways of a support portion so as to be in a vertically long state, and a guide portion is provided on an upper surface of the coil so as to extend from the coil onto a U-shaped yoke disposed on the side opposed to the coil. One side of the yoke is inserted into the coil. On an upper surface of the yoke is disposed a guide receiving portion which supports the tip end of the guide portion slidably. The yoke can be utilized to prevent rotation of the moving member, whereby it is possible to attain the simplification of structure.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a head moving device for moving a head with respect to a disk. Particularly, the invention is concerned with a head moving device having a reduced size of a drive section for driving a head. 
     2. Description of the Related Art 
     FIG. 5 is a plan view showing a conventional head moving device  30  and FIG. 6 is a sectional view taken on line  6 — 6  in FIG.  5 . 
     In the head moving device  30  shown in FIG. 5, a guide shaft  28  is fixed to a chassis (not shown), and a fitting hole (a bearing portion)  26   d  of a moving member  26  is fitted on the guide shaft  28 . The guide shaft  28  is disposed in the radial direction of a disk D and is movable in the same direction. 
     On the moving member  26  are mounted a head body  27   a  on a 0 side opposed to the lower surface of the disk D and a head body  27   b  on a 1 side opposed to the upper surface of the disk, the head body  27   b  being fixed to the tip of an arm such as a plate spring extending from a support portion  26   a  of on the moving member  26  toward the disk D. 
     An extending portion  26   b  is integral with the moving member  26 , the extending portion  26  projecting in an L shape sideways from the moving member, as shown in FIG.  6 . 
     A drive section  31  is disposed sideways of the moving member  26 . Although in FIGS. 5 and 6 the drive section  31  is disposed on only one side of the moving member  26 , a drive section similar to the drive section  31  is sometimes disposed also on the opposite side of the moving member  26 . 
     In the drive section  31 , a coil  22  is fixed into a recess  26   c  with use of an adhesive or the like. The recess is formed by both support portion  26   a  and extending portion  26   b.  A generally turned square U-shaped guide portion  24  is provided at the distal end of the extending portion  26   b,  and a recess  24   a  of the guide portion  24  is supported by a sub-guide shaft  29  so as to be slidable with respect to the sub-guide shaft, the sub-guide shaft  29  being provided on the chassis side in parallel with the guide shaft  28 . 
     A yoke  21   b  is inserted into a coil center hole  22   a  formed inside the coil  22 . Also above the coil  22  is disposed a yoke  21   a.  Both yokes  21   a  and  21   b  are fixed at both ends thereof with screws. A plate-like magnet  23  having approximately the same shape as the yoke  21   a  is attached to the yoke  21   a.    
     In the head moving device  30  constructed as above, when the coil  22  is energized, a drive force acting in the radial direction of the disk D is generated in the moving member  26 . The moving member  26  is prevented from rotating about the guide shaft  28  by sliding contact of the sub-guide shaft  29  with the recess  24   a  of the guide portion  24 . As the moving member  26  moves, the head bodies  27   a  and  27   b  slide in the radial direction of the disk D while holding the disk therebetween. 
     However, the following problems have been encountered in the above conventional head moving device  30 . 
     In the head moving device  30 , if driving sections  31  are disposed on both sides of the moving member  26 , the whole of the device becomes larger in size, but if a driving section  31  is disposed on only one side of the moving member  26 , the entire device can be somewhat reduced in size, as shown in FIGS. 5 and 6. However, for stabilizing the balance of the moving member  26 , it is required to use such an expensive component as the sub-guide shaft  29  and thus it is impossible to attain a further reduction of cost. 
     Besides, as shown in FIG. 6, the plate-like shape of the yokes  21   a  and  21   b  is wider in the same planar direction as the disk D, and the coil  22  is also wide planarly. Consequently, as shown in FIG. 5, the distance L 2  between a work line of a driving force F generated in the coil  22  (a center line S 1  in the width direction of the coil) and a center line S 2  of the guide shaft  28  becomes very long, so that a planar moment M acting on the center of the moving member  26  during operation becomes very large. As a result, a sliding friction force between the fitting hole (bearing portion)  26   d  of the moving member  26  and the guide shaft  28  becomes large and the motion of the moving member  26  becomes stiff, or the guide shaft  28  and the fitting hole (bearing portion)  26   c  is apt to wear. 
     SUMMARY OF THE INVENTION 
     The present invention has been accomplished for solving the above-mentioned problems and it is an object of the invention to provide a head moving device capable of keeping the balance of a moving member stable even without using an expensive component such as a sub-guide shaft, also capable of attaining the reduction in size and weight of the mechanism and further capable of diminishing the moment acting on the moving member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view showing a head moving device according to an embodiment of the present invention; 
     FIG. 2 is a sectional view taken on line  2 — 2  in FIG. 1; 
     FIG. 3 is a perspective view showing a yoke with a magnet attached thereto; 
     FIG. 4 is a sectional view showing a head moving device according to another embodiment of the present invention; 
     FIG. 5 is a plan view showing a conventional head moving device; and 
     FIG. 6 is a sectional view taken on line  6 — 6  in FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Head moving devices embodying the present invention will be described hereinunder with reference to the accompanying drawings, in which FIG. 1 is a plan view showing a head moving device according to an embodiment of the present invention, FIG. 2 is a sectional view taken on line  2 — 2  in FIG. 1, FIG. 3 is a perspective view showing a yoke with a magnet attached thereto, and FIG. 4 is a sectional view showing a head moving device according to another embodiment of the present invention. 
     The head moving device  10  shown in FIG.  1  and indicated at  10  comprises a moving member  6 , a guide shaft  8  and a drive section  9 . 
     As shown in FIG. 2, a fitting hole (bearing portion)  6   c  is formed in the moving member  6  and it is fitted on the guide shaft  8  slidably. The guide shaft  8  is disposed in the radial direction of a disk D and is fixed to a chassis (not shown). 
     The moving member  6  has a support portion  6   a,  and a head body  7  is provided on the disk D side of the support portion  6   a.  In the head body  7 , a lower (0 side) head  7   a  for reading and writing data on a lower surface of the disk D is supported on an upper surface of gimbals  7   c  which is located on the moving member  6 , while an upper (1 side) head  7   b  for reading and writing data on an upper surface of the disk D is fixed to a lower surface of a resilient plate spring  7   d  at a position opposed to the head  7   a,  the plate spring  7   d  projecting from the support portion  6   a . Further provided is a retracting mechanism (not shown) for retracting the head  7   b  upward. 
     In the drive section  9 , a coil  2  is disposed sideways of the moving member  6 . As shown in FIG. 2, the coil  2  is centrally formed with a rectangular insertion hole (a coil center hole)  2   a,  and an upper surface of an extending portion  6   b  extending in a lateral direction from the bottom of the support portion  6   a,  a side face of the support portion  6   a,  and the coil  2 , are fixed together using an adhesive or the like. 
     As shown in FIG. 2, the coil  2  is disposed so that in the section in its winding direction, its longitudinal direction corresponds to a vertical direction. 
     A U-shaped yoke  1  is disposed sideways of the moving member  6 . One yoke portion  1   b  is inserted from behind into the insertion hole  2   a  of the coil  2  and is fixed to the chassis side (not shown). A plate-like magnet  3  is attached to the inner surface side of a yoke portion  1   a  located on the side opposed to the coil  2 . The yoke portions  1   a,    1   b  and the magnet  3  are disposed in such a manner that their width direction correspond to the vertical direction. 
     On an upper surface of the yoke portion  1   a  on the side where the magnet  3  is attached to the yoke portion, a guide receiving portion  1   c  having a guide hole  5  is formed integrally with the yoke portion  1   a,  the guide hole  5  being formed in the moving direction of the moving member  6 . Instead of the guide hole  5 , which is a through hole, a guide slot (recess) may be formed in the guide receiving portion  1   c  in such a manner that the guide portion  4  can be held therein slidably. 
     The guide portion  4  is formed, for example, by a resin plate of a relatively high rigidity and a base end portion thereof is fixed to an upper surface of the coil  2  with use of an adhesive or the like, while the opposite end portion thereof is supported slidably within the guide hole  5 . The base end portion of the guide portion  4  may be fixed to the moving member  6 . 
     As shown in FIG. 3, the yoke portion  1   a  extends longer than the yoke portion  1   b  in the operating direction of the drive section  9  to constitute an extending portion  1   d  integrally, with a tapped hole  1   e  being formed in the extending portion  1   d.  This tapped hole  1   e  portion and a portion raised from the chassis and formed with a mounting hole are fixed together with a screw. 
     In the head moving device  10  constructed as above, a flexible substrate (not shown) is connected to the coil  2  and the coil is energized, whereby the coil moves while being guided by the yoke portion  1   b  and at the same time the guide portion  4  moves while sliding within the guide hole  5  of the guide receiving portion  1   c.    
     Since the guide portion  4  slides within the guide hole  5  located on the yoke portion  1   a,  the moving member  6  is prevented from rotating about the guide shaft  8  even without using such a sub-guide shaft  29  as shown in FIGS. 5 and 6, whereby it is possible to reduce the number of components used and also reduce the size of the device. 
     Further, since the coil  2  is disposed in a vertical fashion, the distance L between a center line S 1  of the coil  2  (a work line of a driving force F) and a center line S 2  of the guide shaft  8  becomes shorter than in a horizontal installation of the coil  2 . Consequently, it is possible to diminish a moment M in a plane induced by the driving force F, also possible to diminish a sliding friction between the fitting hole (bearing portion)  6   c  and the guide shaft  8 , further possible to move the moving member smoothly, and still further possible to diminish the wear of the guide shaft  8  and of the fitting hole (bearing portion)  6   c.    
     FIG. 4 is a sectional view showing a head moving device  20  according to another embodiment of the present invention. 
     In the head moving device  20 , drive sections  19  are disposed respectively on both sides of a moving member  16 . 
     The moving member  16  is fitted on a guide shaft  18  and is thereby supported so as to be movable in the radial direction of the disk D. As in the previous embodiment shown in FIG. 1, a head body  17  is supported by the moving member  16 . 
     Extending portions  16   b  are formed integrally with the bottom of a support portion  16   a  so as to extend respectively from both sides of the bottom. Coils  12 , which are disposed in a vertical fashion as in the previous embodiment, are fixed respectively onto upper surfaces of the extending portions  16   b  with use of an adhesive or the like. 
     Guide portions  14  are affixed respectively to upper surfaces of the coils  12  using an adhesive or the like. The guide portions  14  are in the shape of such a plate as shown in FIG.  1  and it suffices for the guide portions to have a length sufficient to extend onto both the coils  12  and yokes  11  which will be described later. 
     The yokes  11  are each formed integrally in U shape. Each yoke portion  11   b  thereof is inserted respectively into the coils  12 , and magnets  13  are attached respectively to the other yoke portions  11   a  on the side opposed to the coils  12 . The yokes  11  and the magnet  12  are also positioned in a vertical fashion. 
     In the head moving device  20 , the guide shaft  18  is fixed to a chassis (not shown), and extending portions of the yokes  11 , which portions are formed in the same way as in FIG. 3, are fixed with screws or the like to portions which have been cut and raised from the chassis. 
     The guide portions  14  disposed on the coils  12  are supported slidably by upper surfaces of the yoke portions  11   a,  whereby the moving member  16  is prevented from rotation. In this embodiment, the rotation of the moving member  16  can be prevented by merely allowing the guide portions  14  to slide on the upper surfaces (or lower surfaces) of the yoke portions  11   a . Thus, the entire structure can be made extremely simple. 
     Consequently, even when drive sections  19  are disposed respectively on both sides of the moving member  16 , each drive section can be formed in a narrow width, so that it is possible to constitute the device smaller in both size and weight than the conventional device. Guide holes or slots, such as that shown in FIG. 3, may be formed respectively in the yokes  11   a  disposed on both sides of the moving member  16  and the guide portions may be allowed to slide therein. 
     The present invention is not limited to the head moving devices of the above embodiments. For example, the portion of the yoke which supports the guide portion may be disposed on the magnet-free side, not the magnet-mounted side, or the guide portion may be disposed on the lower surface side of the coil and be supported slidably on the lower surface of the yoke.