Recording or reproducing apparatus

Abstract: A recording or reproducing apparatus for recording or reproducing information by relatively moving a head and a sheet recording medium, the recording or reproducing apparatus comprising: a stabilizing member disposed around the head and arranged to generate pressure which brings the recording medium into contact with the head in accordance with the rotation of the recording medium, wherein the stabilizing member includes a first projection portion having a projection surface projecting toward the recording medium, a second projection portion disposed outside of the first projection portion via a groove portion formed outside the first projection portion, the second projection portion having a projection surface projecting toward the recording medium, and a cut portion formed in a portion of the second projection portion in a lower stream than the head in a direction of rotation of the recording medium, the cut portion being formed by cutting the second projection portion from its surface which confronts the recording medium, and the depth of the groove portion with respect to the recording medium is reduced from the outer portion of the stabilizing member to the inner portion of the same.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a recording or reproducing apparatus of the kind defined by the precharacterizing features of claim 1 and known from the EP-A-0 333 431, and, more particularly, to a stabilizing member (pad) serving as an interface acting to stabilize a condition of contact between a head and a recording medium. Description of the Prior Art Hitherto, there has been a recording or reproducing apparatus capable of recording or reproducing information from a sheet recording medium such as a flexible magnetic disk. In an apparatus of the type described above, the running magnetic sheet has been able to stably come in contact with the magnetic head by hydrodynamical pressure generated by a stabilizing plate (pad) which generates the pressure in association with the rotational action of the magnetic sheet. There has been disclosed a pad of the type described above as shown in Fig. 1. That is, a pad 101 is fastened to surround a magnetic head 100, the pad 101 having a space (recessed groove) 101a capable of generating hydrodynamical negative pressure on its surface confronting the magnetic sheet, the hydrodynamical negative pressure attracting the magnetic sheet to the magnetic head 100 due to the rotation of the magnetic sheet. Furthermore, the pad 101 further comprises a projection portion 101b on the periphery thereof, the projection portion 101b forming the above-described space (recessed groove). In addition, a cut portion 101d is formed at a position in the edge of the pad 101 in the lower stream of the direction of rotation of the magnetic sheet, the cut portion 101d enables air to flow out. The magnetic head 100 is disposed so as to project upwards through a central opening 101c formed in the pad 101. A negative pressure pad of the type described above is arranged to act in such a manner that, when the magnetic sheet is rotated, air in the above-described space and confronting the magnetic sheet flows out through a gap formed between the projection portion and the magnetic sheet and through the cut portion formed in the surface of the projection portion. In addition, since substantially no air flow into the gap between the projection portion and the magnetic sheet, negative pressure is generated in the above-described space and the gap between the projection portion and the magnetic sheet. As a result, the magnetic sheet is attracted by the negative pressure thus generated so as to closely contact with the magnetic head. The above-described conventional negative pressure pad has been usually arranged in such a manner the depth of the groove portion 101a has an uniform depth. The hydrodynamical analysis of the distribution of the negative pressure generated between the negative pressure pad and the magnetic sheet results as designated by curve l 2 shown in Fig. 5. Referring to that Fig. 5, positions denoted by symbols P1 to P8 correspond to the positions P1 to P8 of the surface of the pad 101 shown in Fig. 1 which confronts the magnetic sheet. As is shown, the level of the negative pressure at the inner portion is lower than that at the outer portion. As described above, the conventional negative pressure pad has a problem in that the levels of the negative pressure generated in the inner portion of the disk (magnetic sheet) and the outer portion of the same become considerably different from each other due to the difference in the peripheral velocity between the two portions. That is, since the inner portion of the disk rotates more slowly than the outer portion, the force for attracting the disk becomes too weak. Furthermore, since the inner portion has larger rigidity than the outer portion of the disc because of the structure of the disk having a center core in the center portion thereof. Therefore, the inner portion of the disk cannot be easily deformed in comparison to the outer portion of the same. As a result, in a case where, for example, a frame recording head in which an excellent head touch is desired over a wide area, a problem arises in that desired head touch cannot be obtained due to the insufficient level of the negative pressure in the inner portion. If negative pressure of an excessive level is applied, a problem arises in that the spindle motor suffers from an excessively large load. What is even worse, the disk will be vibrated due to the attractive force and the restoring force of the disk, causing jitter to be generated. Furthermore, if the rotational speed of the spindle motor is changed, recording or reproducing cannot be correctly performed. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to stabilize the relative movement between a head and a sheet recording medium in a recording or reproducing apparatus of the kind defined by the precharacterizing features of claim 1. This object is attained by the characterizing features of claim 1. In accordance with the present invention there is provided a recording or reproducing apparatus capable of equalizing the negative pressure between the inner portion of the stabilizing member and the outer portion of the same and deterioration in the head touch due to the unbalance of the negative pressure is thereby prevented whereby stable and excellent head touch can be obtained. Further, in accordance with the present invention there is provided a recording or reproducing apparatus capable of overcoming the unbalance between the negative pressure at the inner portion of the magnetic sheet and the outer portion of the same by the feature that the depth of the groove formed in a negative pressure pad is reduced in the portion corresponding to the inner portion of the magnetic sheet. This may be realized in an extremely simple manner. Therefore, excellent head touch can be obtained regardless of the position of the head so that the image quality can be improved in a recording or reproducing operation. Furthermore, the vibrations of the disk can be prevented and jitter can thereby be prevented since the magnetic sheet can be stably attracted to the pad. Other and further objects, features and advantages of the invention will be appear more fully from the following description. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 illustrates the shape of a conventional negative pressure pad; Fig. 2 illustrates the deformation of a magnetic sheet on the magnetic head; Fig. 3 is a perspective view which illustrates a disk drive according to the present invention; Fig. 4 illustrates the shape of a negative pressure pad according to the present invention; Fig. 5 illustrates the pressure acting between the negative pressure pad and the magnetic sheet; and Fig. 6 illustrates another embodiment of the negative pressure pad according to the present invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a recording or reproducing apparatus according to the present invention will now be described with reference to the drawings. Fig. 3 is a perspective view which illustrates an embodiment of a recording or reproducing apparatus according to the present invention. Referring to the drawing, reference numeral 1 represents a disk jacket which rotatably accommodates a recording magnetic sheet 3. The magnetic sheet 3 has, at the central portion thereof, a center core 2 which can be reliably aligned and held by a spindle fastened to the rotational shaft of a spindle motor 10 to be described later. Reference numeral 13 represents a disk drive device for rotating a disk accommodated in the disk jacket 1. Reference numeral 4 represents a recording or reproducing magnetic head and 5 represents a negative pressure generating pad disposed around the magnetic head 4 and arranged to generate attractive force (negative pressure) due to the rotation of the disk, the details of the negative pressure being described later. The head 4 and the negative pressure pad 5 are respectively bonded to a head carriage 6 which acts to move the head 4. The head carriage 6 is engaged with a head feeding mechanism, that is, a step motor 9 and a lead screw 8 via a recessed portion 7a of an elastic member 7 made of, for example, a leaf spring. Another end of the head carriage 6 is held by a guide rod 12 in such a manner that it can be slid in the axial direction of the guide rod 12 so that the head carriage 6 is moved in a unit of a predetermined distance in the radial direction of the magnetic sheet 3 designated by arrow A by the rotation of the motor 9. Reference numeral 10 represents a spindle motor for rotating the magnetic sheet 3, the spindle motor 10 having a chucking portion 11 which holds the center core 2 of the disk. The chucking portion 11 and the magnetic sheet arranged to be detached/attached from each other by a known means when the disk jacket is attached/detached. When the spindle motor 10 is rotated, the magnetic sheet 3 is rotated, causing the sheet 3 to be attracted to the pad due to the hydrodynamical action acting between the sheet 3 and the negative pressure pad 5. As a result, the sheet 3 can satisfactorily be brought into contact with the magnetic head 4 so that an excellent head touch can be realized. Fig. 4 is an enlarged view of a negative pressure pad according to the present invention. A negative pressure pad 20 comprises a first block portion 23 disposed around the magnetic head 4 and arranged to have a projection portion having a surface projecting toward the magnetic sheet. The negative pressure pad 20 further comprises a second block portion 21 disposed to surround the first block portion 23 and arranged to have a projection portion having a surface projecting toward the magnetic sheet. Furthermore, the negative pressure pad 20 comprises a recessed groove 22 formed in such a manner that it divides the first block portion 23 and the second block portion 21 from each other. In addition, the negative pressure pad 20 has a cut portion 25 formed by cutting the projection portion of the second block 21 in the lower stream of the direction of the rotation of the magnetic sheet, the cut portion 25 acting to cause the air to flow out. The bottom surface of the recessed groove 22 is slanted from the inside to the outside of the magnetic sheet in such a manner that the depth of the recessed groove 23 is reduced in the inner portion in comparison to the depth of the outer portion. The first block portion 23 has an opening 24 at the central portion thereof so as to fasten the magnetic head. When the magnetic sheet is rotated while disposing the negative pressure pad 20 around the head, an air flow is generated between the negative pressure pad and the magnetic sheet due to the rotation of the magnetic sheet so that negative pressure which attracts the magnetic sheet to the head is generated. The hydrodynamical analysis of the distribution of the negative pressure generated between the negative pressure pad and the magnetic sheet results as designated by curve l 1 shown in Fig. 5. As shown in Fig. 5, the unbalance of the distribution of the negative pressure between the inner portion of the magnetic sheet and that at the outer portion of the same can be overcome in comparison to the pressure distribution l 2 obtainable from the structure in which the depth of the recessed groove 22 is arranged to be equal. Positions P1 to P8 correspond to the positions P1 to P8 shown in Fig. 2. Therefore, the inner portion of the sheet and the outer portion of the same causes uniform attractive force. As a result, satisfactory excellent head touch can be realized between the magnetic sheet and the magnetic head regardless of the position of the magnetic head. Furthermore, undesirable vibrations of the magnetic sheet due to the unbalance of the attractive force can be prevented. Although the bottom surface of the groove portion is slanted according to this embodiment in terms of easily manufacture the structure, another structure can, of course, be employed in which the bottom surface of the recessed groove 22' is, as shown in Fig. 6, arranged to be substantially in parallel to the magnetic sheet. If the depth of the same at the inner portion and that at the outer portion are different from each other with respect to the magnetic sheet, the similar effect can be obtained. As described above, according to the recording or reproducing apparatus according to the present invention, the undesired unbalance in the pressure distribution taken place between the inner portion of the magnetic sheet and the outer portion of the same can be overcome by an extremely simple structure in which the depth of the groove formed in the negative pressure pad is arranged to be different between the inner portion and the outer portion. Therefore, a desired head touch can be obtained regardless of the position of the head, causing the image quality to be improved. Furthermore, since the magnetic sheet can stably be attracted to the pad, vibrations of the disk can be prevented, causing jitter to be prevented.

Claims: A recording or reproducing apparatus for recording or reproducing information by relatively moving a head (4) and a rotatable sheet recording medium (3), said recording or reproducing apparatus comprising: a stabilizing member (20) disposed around said head (4) and arranged to generate pressure which brings said sheet recording medium (3) into contact with said head (4) in response to a rotation of the former, wherein said stabilizing member (20) includes a first projection portion (23) having a projection surface projecting toward said sheet recording medium (3), a second projection portion (21) disposed outside of said first projection portion (23) via a groove portion (22) formed outside said first projection portion (23), said second projection portion (21) having a projection surface projecting toward said sheet recording medium (3), and a cut portion (25) formed in a portion of said second projection portion (21) downstream from said head (4) with respect to the direction of rotation of said sheet recording medium (3), said cut portion (25) being formed by cutting said second projection portion (21) from its surface which confronts said rotating sheet recording medium (3), characterized in that the depth of said groove portion (22) with respect to said sheet recording medium (3) decreases from an outer portion (22, 22') of said stabilizing member (20) being remote from the rotation center of said sheet recording medium (3) to an inner portion thereof facing the center of rotation of said sheet recording medium (3). A recording or reproducing apparatus according to Claim 1, wherein the bottom surface of said groove portion (22) is slanted from said inner portion of said stabilizing member (20) toward said outer portion of the same. A recording or reproducing apparatus according to Claim 1 or 2, wherein said stabilizing member (20) is a circular negative pressure generating member disposed around said head (4). A recording or reproducing apparatus according to Claim 3, wherein said first and second projection portions (24, 21) are concentrically formed around said head (4).

Inventors: FUKUYAMA SHIGERU, NANBA ATSUSHI, UEHARA TSUKASA, WATANABE YOSHITAKA, FUKUYAMA, SHIGERU, NANBA, ATSUSHI, UEHARA, TSUKASA, WATANABE, YOSHITAKA
Applicants: CANON KK, CANON KABUSHIKI KAISHA
Application year: 1990
Main classification: G11B17
IPC codes: G11B17