Magnetic disc apparatus

Abstract: A magnetic disc apparatus in which a rocking type actuator (2) is driven in a rocking motion by a driving force of a VCM (voice coil motor) (2-4), and in this case, two flexible bending members (1-2, 1-4, 1-5) fixed to the rotor move in synchronization with the driving of the rocking type actuator. The respective flexible bending members (1-2, 1-4, 1-5) are attached to two FPC (Flexible printed circuit sheet) fixing portions (2-3b) provided on the outer wall of the rotor (2-3) and radially arranged with respect to the driving center of the rocking type actuator, so as to have the bending portions bent in directions opposite to each other, so that reaction forces of the flexible printed circuit sheets are opposed and cancel one another out at all times and hardly affect driving of the actuator. Therefore, less power is required to be given to the VCM (voice coil motor), while an actuator having a favorable follow-up characteristic with respect to data tracks can be obtained.

Description: The present invention generally relates to a magnetic disc apparatus and more particularly, to a flexible printed circuit sheet employed for transmission of electrical signals between a rocking type actuator of the magnetic disc apparatus and external electrical circuits. Conventionally, in a magnetic disc apparatus as referred to above, since flexibility is required for effecting electrical wirings to a magnetic head 3' subjected to rocking driving together with a rocking type actuator 2-1' and a voice coil motor (referred to as VCM hereinafter) 2-4', etc., a flexible printed circuit sheet (referred to as FPC hereinafter) 1-1' has been employed as shown, for example, in a known magnetic disc apparatus of Fig. 4. In the known arrangement of Fig. 4, a flexible bending portion 1-2' subjected to the bending motion as the rocking type actuator 2-1' is driven, is branched from an apparatus fixing portion 1-3' folded back at right angles and is fixed, in the bent state, to an FPC fixing portion 2-3b' provided on the outer wall of a rotor 2-3a', and thus, repeatedly bent and extended following driving of the rocking type actuator 2-1' as shown in Fig. 5, in which acting directions of reaction forces are represented by Numeral 5' and driving forces, by Numeral 6'. In the above case, the FPC fixing portion 2-3b, has a shape making a certain degree of an angle so that it may not contact other members during driving of the flexible bending portion 1-2', while the flexible bending portion 1-2' is also limited to a length which will not contact other members. In the conventional construction as described above, however, a reaction force in one direction due to a restoring force of the flexible bending portion 1-2' is applied at all times, to the FPC fixing portion 2-3b' and the rotor 2-3a', i.e., to the rocking type actuator 2-1'. Such a reaction force not only results in a loss of torque in the VCM 2-4', but adversly affects as an offset or the like during tracing of the data track. Therefore, the conventional practices for eliminating such disadvantages have been such that the length of the flexible bending portion 1-2' is increased as far as possible, and its width is reduced in order to minimize the reaction force, while the bending radius thereof is set to be large as far as possible, and moreover, the flexible bending portion 1-2' is attached so that the reaction force is directed in a direction perpendicular to the driving direction of the rocking type actuator 2-1'. However, the practices as described above do not necessarily provide solutions to the problem due to limitation in the reduction of size and configuration of the apparatus, and accordingly, it becomes necessary to provide a method generally applicable to any type of apparatuses. Meanwhile, in order to realize a thin type of the drive, it becomes necessary to reduce the width of the flexible bending portion 1-2', thus requiring narrowing of the pattern intervals, but at the present stage, it is difficult to narrow the intervals more than a certain level in order to satisfy the strength, performance and manufacturing limit, etc. Furthermore, there is another defect that, for reducing intervals between patterns, noises between the head line and the VCM line are undesirably carried by the signals from the magnetic head. US-A-4 476 404 discloses another attempt to reduce the reaction force of a flexible printed circuit sheet on a rocking type actuator by providing a flexible member having an arcuate segment curved into a generally U-shaped configuration. Accordingly, an object of the present invention is provide a magnetic disc apparatus which is capable of suppressing the reaction force of a flexible printed circuit sheet on a rocking type a tuator to the minimum. A magnetic disc apparatus, according to this invention which comprises a magnetic head for reading or writing data from or into a magnetic disc, a rocking type actuator including an arm for supporting said magnetic head, a rotor for rocking and driving said arm and a voice coil motor for applying a driving force to said rotor, and a flexible printed circuit sheet having a flexible bending portion and an apparatus fixing portion for transmission of electrical signals between said magnetic head subjected to the rocking driving and said voice coil motor and external fixed electrical circuit means, is characterised in that said flexible bending portion is composed of two flexible bending members respectively attached to, two projecting portions which are provided on an outer wall of said rotor and radially arranged with respect to driving center of said rotor, so as to be bent in opposite directions to one another whereby they provide torques of opposite sense to said rotor. More specifically, according to one preferred embodiment of the present invention, there is provided a magnetic disc apparatus which includes, a magnetic head for reading or writing data from or into a magnetic disc, a rocking type actuator including an arm for supporting said magnetic head, a rotor for rocking and driving said arm and a VCM (voice coil motor) for applying a driving force to said rotor, and an FPC (flexible printed circuit sheet) having a flexible bending portion and an apparatus fixing portion for transmission of electrical signals between said magnetic head subjected to the rocking driving and said VCM, and external fixed electrical circuit means. The flexible bending portion is composed of two flexible bending members respectively attached to two projecting portions which are provided on an outer wall of said rotor and radially arranged with respect to a driving center of said rotor and the two flexible bending members are, so as to be bent in directions opposite to each other. Furthermore, said two flexible bending members are arranged to be separated by a magnetic head signal line and a VCM signal line. By the construction according to the present invention as described above, owing to the arrangement to divide the flexible bending portion into two directions, although the projecting portions on the rotor outer wall are subjected to reaction forces from respective flexible bending members, since the bending portions are directed to opposite directions, the respective reaction forces are to be cancelled to each other after all. Accordingly, the loss torque applied in one direction with respect to the rocking type actuator becomes small. Moreover, the width of the FPC (flexible printed circuit sheet) may be made narrower than in the conventional arrangements since it only has to carry half of the wiring, and the height of the drive may be reduced. Furthermore, by the separation of the magnetic head line and the VCM line, the defect that noises are contained in the signals from the magnetic head may be advantageously prevented. Preferred embodiments of a magnetic disc apparatus in accordance with this invention will now be described and contrasted with the prior art with reference to the accompany drawings, in which:- Fig. 1 is a perspective view of a magnetic disc apparatus according to one preferred embodiment of the present invention; Fig. 2 is a fragmentary top plan view for explaining functioning state of an FPC (flexible printed circuit sheet) employed in the arrangement of Fig. 1; Fig. 3 is a fragmentary top plan view of an essential portion of a magnetic disc apparatus according to a second embodiment of the present invention; Fig. 4 is a view similar to Fig. 1, which particularly shows a conventional magnetic disc apparatus; and Fig. 5 is a view similar to Fig. 2, which particularly relates to the conventional arrangement of Fig. 4. Before the description of the present invention proceeds, it is to be noted that like parts are designated by like reference numerals throughout the accompanying drawings. Referring now to the drawings, there is shown in Fig. 1, a magnetic disc apparatus according to one preferred embodiment of the present invention which includes a magnetic head 3 for reading or writing data from or into a magnetic disc 4, a rocking type actuator 2-1 including an arm 2-2 for supporting the magnetic head 3, a rotor 2-3a for rocking and driving the arm 2-2 and a VCM (voice coil motor) 2-4 for applying a driving force to the rotor 2-3a, and an FPC (flexible printed circuit sheet) 1-1 having a flexible bending portion 1-2 and an apparatus fixing portion 1-3 for transmission of electrical signals between said magnetic head 3 subjected to the rocking driving and said VCM 2-4, and external fixed electrical circuit means. The flexible bending portion 1-2 is composed of two flexible bending members which are respectively attached to two projecting portions 2-3b being provided on an outer wall of said rotor 2-3a and radially arranged with respect to a driving center of said rotor, so as to be bent in directions opposite to each other. More specifically, as shown in Fig. 1, the rocking type actuator 2-1 has the magnetic head 3 at its forward end, and the VCM 2-4 at its rear end, and the respective signals thereof are transmitted to external electrical circuits, etc. (not shown) through the flexible bending portion 1-2 of the FPC 1-1 fixed to the FPC fixing portion 2-3b on the outer wall of the driving portion for the rotor 2-3a. The FPC 1-1 includes the flexible bending portion 1-2 subjected to bending motion as the rocking type actuator 2-1 is driven, and the apparatus fixing portion 1-3 fixed to the magnetic disc apparatus and having a connector portion for connecting the external electrical circuits. Meanwhile, the flexible bending portion 1-2 consists of two flexible bending members which are respectively fixed to the two FPC fixing portions 2-3b provided on the outer wall of the rotor 2-3a and radially disposed with respect to the driving center in such a manner that the bending portions thereof are directed in opposite directions to each other. Referring also to Fig. 2, the state of functioning of the flexible bending portion in the magnetic disc apparatus as described so far will be explained hereinafter. In Fig. 2, acting directions of reaction forces are represented by Numeral 5, while the driving directions, by Numeral 6. In Fig. 2, there is shown the functioning state of the flexible bending portion 1-2 when the rocking type actuator 2-1, i.e., rotor 2-3a is subjected to the maximum displacement, and as is seen from Fig. 2, the reaction forces are applied in two directions, and are cancelled to each other with respect to the driving direction. Upon comparison of the above state with that explained earlier with reference to the conventional arrangement of Fig. 5, it is seen that in the conventional arrangement, reduction of the reaction force is not easy, and moreover, in order to obtain the driving portion of the flexible bending portion, disposition of members other than the driving section and reduction of size of the apparatus are also limited. On the contrary, according to the present invention, since the angle of the projecting portions which serve as the FPC fixing portion can be varied as desired, contact of the flexible bending portion with other members may be readily prevented without deterioration by the influence of the reaction force. Moreover, by dividing the flexible bending portion into two flexible bending members, the width of the flexible bending portion may be made narrower than in the conventional arrangement, thus making it possible to form the drive to be thinner in structure. Referring further to Fig. 3, there is shown a magnetic disc apparatus according to a second embodiment of the present invention, in which a head line side FPC is shown by Numeral 1-4, a VCM line side FPC is denoted by Numeral 1-5, a head signal line is indicated by Numeral 7-1, and a VCM signal line, by Numeral 7-2, with like parts in the first embodiment of Fig. 1 being designated in Fig. 3 by like reference numerals for brevity of explanation. Although the construction of the magnetic disc apparatus for the second embodiment in Fig. 3 is generally similar to that for the first embodiment in Fig. 1, in the second embodiment, the two flexible bending members 1-2 are separated by the head line side 7-1 and a VCM line side 7-2 which are of patterns entirely different in the signals to be transmitted. In connection with the above, in the conventional one flexible bending portion, there are such disadvantages that two kinds of patterns are to be disposed side by side, and noises are generated in the signal from the magnetic head 3. According to the second embodiment in Fig. 3, the respective patterns are completely separated, and the problem as referred to above may be solved. As is clear from the foregoing description, according to the magnetic disc apparatus of the present invention, by separating the flexible bending portion in two directions, the reaction force of the flexible bending portion acting on the rocking type actuator may be reduced to provide a reserve power to the VCM, with simultaneous improvement of the follow-up performance for the data track. Moreover, the width of the FPC can be still more reduced, thus making it possible to form the drive to be thinner. Furthermore, by separating the patterns at the head line side and the VCM line side with entirely different signals, into two directions, it becomes possible to prevent noises from being carried on the signal from the magnetic head.

Claims: A magnetic disc apparatus which comprises a magnetic head (3) for reading or writing data from or into a magnetic disc (4), a rocking type actuator (2) including an arm (2-2) for supporting said magnetic head (3), a rotor (2-3) for rocking and driving said arm (2-2) and a voice coil motor (2-4) for applying a driving force to said rotor, and a flexible printed circuit sheet (1) having a flexible bending portion (1-2) and an apparatus fixing portion (1-3) for transmission of electrical signals between said magnetic head (3) subjected to the rocking driving and said voice coil motor (2-4) and external fixed electrical circuit means, characterised in that said flexible bending portion (1-3) is composed of two flexible bending members (1-2, 1-4,1-5) respectively attached to two projecting portions which are provided on an outer wall of said rotor (2-3), and radially arranged with respect to a driving center (2-3a) of said rotor, so as to be bent in opposite directions to one another whereby they provide torques of opposite sense to said rotor (2). A magnetic disc apparatus as claimed in Claim 1, wherein said two flexible bending members (1-4, 1-5) separately carry a magnetic head signal line (7-1) and a voice coil motor signal line (7-2).

Inventors: KOHSO HIROSHI, KUWAMOTO MAKOTO, TANAKA MICHIRO, YAGI YUJI, KOHSO, HIROSHI, KUWAMOTO, MAKOTO, TANAKA, MICHIRO, YAGI, YUJI
Applicants: MATSUSHITA ELECTRIC IND CO LTD, MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD.
Application year: 1992
Main classification: G11B5
IPC codes: G11B21, G11B33, G11B5