Information processing apparatus

Abstract: An information processing apparatus includes an optical disk (l0) and a drive mechanism (l2) for rotat­ ing the disk. The disk has a disk-shaped body (l6) and an attractable portion (22) at the central portion of the body. The attractable portion has an attractable member (24) projecting from the body. A center hole (26a), defining the center of rotation of the body, is bored in the attractable member. The drive mechanism includes a turntable (54) which is rotated by a motor (50). A depression (58) is formed in a support surface (54a) of the turntable. A magnetic attraction unit (60) is arranged in the depression so as to magnetically at­ tract the attractable portion, whereby the attractable member is housed in the depression and the surface of the body is in contact with the support surface.

Description: The present invention relates to an information processing apparatus, and more specifically, to an information processing apparatus in which an information memory medium, such as an optical disk, is rotated so that information is recorded. reproduced, or erased by means of laser beams. The present invention also relates to an apparatus for rotatably supporting an information memory medium and to an information memory medium for use in such apparatus. Recently, information processing apparatuses have started to be used frequently which employ an optical disk as a memory medium. As compared with those information processing apparatuses using conventional magnetic memory media, the apparatuses of this type have the following advantages. They have a larger information memory capacity, and can better perform extremely stable reproduction of information with less noises. Moreover, the improved apparatuses are less susceptible to external influences, thus enjoying very stable memory conditions. Also, they can perform information processing with the memory media not in contact with an information processing head, so that the media and head are less liable to be damaged. As the information recording/reproducing apparatuses have come into general use, the demand for thinner, lighter and less expensive apparatuses have increased. However, the conventional apparatuses cannot meet this demand for the following reason. In order to hold the information memory medium or optical disk on a turntable, the disk is pressed against a turntable from the opposite side thereof, by means of a clamper. The clamper receives a clamping force from urging means, such as springs, or by magnetic attraction produced between the clamper and turntable. In the latter case, the clamper has a magnet, and the turntable is formed of magnetic material. The conventional apparatuses require a space for accommodating the clamper. Further, they need a drive mechanism for moving the clamper toward or away from the optical disk. As a result. the apparatus is bulky and complicated in construction, thus inevitably thick, heavy and expensive. Also, the use of the clamp mechanism makes it difficult to assemble the apparatus and to keep it in good condition. If the clamp mechanism is of a spring type, the turntable is always subjected to an urging force. Therefore, the turntable, along with a rotating shaft integral therewith, must be made strong enough to resist the force. If the clamp mechanism is of a magnet type, the clamping force varies, depending on the thickness of the optical disk. When using relatively thick memory media, such as those including two bases stuck together, the clamping force may sometimes be reduced too much to hold the media securely. Prior art document FR-A-2 535 504 discloses an apparatus for magnetical recording, namely a video disc recorder, exhibiting a disk-shaped memory medium being rotably mounted on a motor-driven turntable. The turntable has a center hole defining the center of rotation of the information recording disk and three pivot members equidistantly arranged in a circular fashion on the upper surface of said turntable supporting an annular-shaped yoke. The upper surface of the turntable is equipped with magnetic means attracting said yoke and thereby fixing the disk-spaped memory medium on the turntable. Further, prior art document JP-A-59/14153 discloses an information storage medium which is designed to prevent the excentricity due to a malformation of a rotary center part of a substrate and to ensure the stable information processing by providing an internal reinforcement member having an inner diameter smaller than that of the substrate and high mechanical strength and excellent wear resistance at the rotary center of the substrate. In detail, an information producing film is provided on a single side of a substrate. A further substrate is adhered on the surface of the film via inside and outside spacers made of a circular plate and functioning as reinforcement members, so that a space part is formed. The inner diameter of the inside spacer is smaller than those of both substrates, and only the inner diameter part of the inside spacer has a contact with the shaft of a rotary motor. This prevents the excentricity due to a malformation of the rotary center part of the substrate and therefore ensures stable information processing. There is, furthermore, known from EP 0 118 146 A1 an information processing apparatus according to the preamble of claim 1. When in this apparatus the attractable member is attracted by the magnet the information memory medium (disk) is received by an elastic ring which becomes deformed due to the attraction force of the magnet, resulting in the lower surface of the disk coming into contact with the upper end surface of the positioning portion in form of a spindle such that the disk is rigidly supported only in its center by the upper end surface of the spindle which has a small surface area. When vibrations are externally applied to the apparatus under the above condition, the peripheral portion of the disk easily vibrates upwards and downwards due to the elasticity of the ring. Since the ring is elastic, the disk cannot easily stop vibrating. As a result the distance between the surface of the disk and the reading head fluctuates as the disk vibrates, which is considerably disadvantageous in this type of apparatus. JP-A- 57/130237 discloses at the peripheral part of a drive spindle hole of a magnetic disc inserted into a jacket, a reinforcing pad made of synthetic resin which has a coefficient of thermal expansion close to that of the disc. It is an object of the present invention to provide an information processing apparatus, which can perform stable information processing, and in which an information memory medium can be mounted securely on a turntable with ease, irrespective of the thickness of the medium, and without the use of any clamper that prevents reduction in thickness, weight. and costs of the apparatus. This object is solved by an information processing apparatus as defined in claim 1. Particularly, due to the fact that the disk-shaped body and the centering member fixed thereto are approximate in coefficient of thermal expansion, even if the memory medium is heated, distortion or damage of the memory medium due to a difference of these members in coefficient of thermal expansion can be prevented. EP-B-0 052 454 discloses an information storing medium comprising two base plates which hold spacers therebetween. The information storing medium does not have a centering member as disclosed in the present invention, and thus, this prior art does not disclose that the centering member and the base plate an formed of materials whose coefficients of thermal expansion approximate to each other. Furthermore, this prior art does not disclose holding the information recording medium on the turntable by use of magnetic attraction. This invention can be more fully understood from the following detailed description when taken in conjunction with the accompanying drawings, in which: Figs. 1 to 7 show an information processing apparatus according to a first embodiment of the present invention, in which Fig. 1 is a side view, partially in section, of the apparatus with an information memory medium off its drive mechanism, Fig. 2 is a side view, partially in section, of the apparatus with the information memory medium on the drive mechanism, Fig. 3 is an enlarged sectional view showing an essential part of the information memory medium, Fig. 4 is a sectional view of a die, for illustrating a process of forming a base plate of the information memory medium, Fig. 5 is an enlarged sectional view showing a bore portion of the base plate, Fig. 6 is an enlarged plan view showing an attractable portion of the information memory medium, and Fig. 7 is an exploded perspective view of the attractable portion. Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings. As shown in Fig. 1, an information processing apparatus comprises optical disk 10 as an information memory medium, and drive mechanism 12 arranged in a processing apparatus housing (not shown) and used to rotate the disk. Disk 10, along with cartridge 14 (indicated by two-dot and dash line) in which it is contained, is adapted to be inserted into the apparatus housing through a medium slot in the housing. Thereupon, disk 10 is automatically introduced horizontally into a predetermined position by a medium guiding/loading mechanism. During this process, part of cartridge 14 is open so that the center portion of disk 10 is exposed. Thereafter, cartridge 14 moves along the plane of disk 10, so that the disk is mounted automatically on drive mechanism 12. Body 16 of optical disk 10 includes two disk-shaped base plates 18 each having bore 19. Information record layer 20 is formed on one side of each base plate 18. Base plates 18 are bonded concentrically to each other, with inside ring-shaped spacer 21 and an outside ring-shaped spacer (not shown) between them. The base plates are formed from glass or optically transparent plastic material, such as acrylic resin, polycarbonate, etc., by injection molding. Inside and outside spacers are bonded to plates 18 by means of ultraviolet-curing resin. As shown in Figs. 1, 2 and 3, optical disk 10 is provided with attractable portion 22 at the central portion of body 16. Portion 22 includes a pair of attractable members 24 fixed to the central portions of their corresponding base plates 18. Members 24 each include centering member 26 and magnetic member 28 attached thereto. Centering member 26 is a discoid of thickness t, which is formed of synthetic resin and has center hole 26a. Further, member 26 has ring-shaped projection 30 coaxial with hole 26a. While projection 30 is fitted in bore 19 of its corresponding base plate 18, it is fixedly bonded to the outer surface of the base plate, or the opposite surface thereof to that surface on which information record layer 20 is formed. Thus, centering member 26 is coaxially positioned relatively to base plate 18. Also, member 26 is bonded to base plate 18 by means of a bonding agent having no bad influences on the base plate, such as epoxy resin. In order to shorten the working time for base plates 18, bore 19 of each plate 18 is formed during the process of injection molding. As shown Fig. 4, the die assembly for forming plates 18 includes fixed die 32, movable die 33, spool bush 34 guided by bush guide 35, and punch 36 guided by punch guide 37. In the state shown in Fig. 4, molten plastic material 38 is injected into cavity 40, defined between fixed and movable dies 32 and 33, through spool 39 of spool bush 34 and gates 41, as indicated by arrow a. Thereafter, punch 36 is moved in the direction of arrow b to cut the resin at gate 41. Thus, base plate 18 with bore 19 is completed. Bore 19, formed in this manner, is stepped, including large- and small-diameter portions 19a and 19b. Portion 19a is defined by the end portion of spool bush 34, and portion 19b is formed by ripping off the resin at the gate portion by means of punch 36. Moreover, the diameter of portion 19a is high in accuracy, while the inner peripheral surface of portion 19b is not smooth, and its diameter is low in accuracy. Information record layer 20 is formed on that surface of each base plate 18 on the side of small-diameter portion 19b. As described above, large-diameter portion 19a of bore 19 is formed with higher dimensional accuracy than small-diameter portion 19b. Therefore, height h1 of projection 30 of each centering member 26 is shorter than axial length h2 of portion 19a so that projection 30 can engage only portion 19a of higher accuracy. Thus, members 26 are fixed with high positional accuracy, without being substantially eccentric to base plates 18. Bore 19 of each base plate 18 is worked with high accuracy, so as to be coaxial with a spiral pre-groove (not shown) for recording and reproduction, formed on the base plate. Likewise, the outer peripheral surface of projection 30 and center hole 26a of each centering member 26 are worked with high accuracy, so as to be coaxial with each other. Thus, when member 26 is fixed to base plate 18, the center of the pre-groove is accurately in alignment with that of hole 26a or the center of rotation of base plate 18. It is therefore possible to prevent lowering of recording/reproducing accuracy or increase of access time, which will be caused if the pregroove is eccentric to the rotational center of base plate 18. From an idealistic viewpoint, disk base plates 18 and centering members 26 should be formed of the same material. The reason is that if base plates 18 and members 26 are more or less different in coefficient of thermal expansion, bonded or fitted regions between the base plates and centering members will be distorted in case of a temperature change. As shown in Figs. 3, 6 and 7, magnetic member 28 of each attractable member 24 is formed from a metal plate into a disk-shaped member, having aperture 28a in the center. Member 28 is located in annular depression 42 which is formed in the outer surface of each corresponding centering member 26. Depression 42 is a little larger than member 28. Further, member 28 is attached to member 26 by mounting mechanism 44, so that the magnetic member is immovable in the direction perpendicular to the surface of base plate 18 and, is slightly movable in the direction parallel to the base plate surface. Mounting mechanism 44 includes three retaining portions 46 formed on centering member 26. Portions 46 are arranged at regular intervals along the circumference of a circle concentric with the centering member. Also, mechanism 44 includes three retaining claws 48 formed on magnetic member 28. Claws 48 are arranged corresponding in position to portions 46, so that they can engage with portions 46. Each retaining claw 48 is formed into an L-shaped piece by cutting and raising part of magnetic member 28 toward centering member 26. Claw 48 includes vertical portion 48a extending vertically from member 28 and horizontal portion 48b extending parallel to member 28, from the extended end of portion 48a. Each retaining portion 46 includes aperture 46a, large enough to allow insertion of its corresponding claw 48 therein, and engaging projection 46b projecting into aperture 46a. Projection 46b defines slit 46c which is continuous with aperture 46a. Detent projection 46d is formed on the lower surface of projection 46b. In mounting magnetic member 28 on centering member 26, retaining claws 48 are first passed through their corresponding apertures 46a of member 26. Then, member 28 is rotated in the clockwise direction of Fig. 6, so that vertical portions 48a of claws 48 are inserted into slits 46c of their corresponding retaining portions 46. As a result, horizontal portions 48b of claws 48 engage the lower surfaces of projections 46b. In doing this, portions 48b are deformed elastically, and then get over detent projections 46d on the lower surfaces of projections 46b. Thus, if claws 48 are urged to move back toward apertures 46a, they cannot do so, hindered by projections 46d. Mounted on centering member 26 in this manner, magnetic member 28 is restrained from moving in a direction perpendicular to the surface of base plate 18, as horizontal portions 48b of retaining claws 48 engage projections 46b of their corresponding retaining portions 46. In a direction parallel to the surface of base plate 18, on the other hand, the magnetic member is allowed to move for the width of a gap formed between vertical portions 48a of claws 48 and their corresponding slits 46c. As shown in Figs. 1 and 2, moreover, drive mechanism 12 for driving optical disk 10, constructed in this manner, includes brushless DC motor 50 of an outer-rotor type, for use as a drive source, and turntable 54 mounted on rotating shaft 52 of motor 50 and adapted to rotate in one with shaft 52. Tip end portion 52a of shaft 52 is inserted into center hole 26a of disk 10, as mentioned later, thus constituting a positioning portion for positioning the disk relatively to turntable 54. Motor 50 is supported by frame 55, which is fitted with control board 56 for controlling the operation of the motor. Turntable 54, which is formed of nonmagnetic metal, has support surface 54a perpendicular to shaft 52 of motor 50. Also, turntable 54 is formed with circular depression 58, which is coaxial with shaft 52, and opens to surface 54a. Diameter D2 of depression 58 is greater than diameter D1 of centering members 26 of optical disk 10. Depression 58 contains magnetic attraction means 60 which magnetically attracts attractable portion 22 of disk 10. Attraction means 60 includes ring-shaped yoke 62 and magnet 64, which are arranged coaxially with shaft 52. Yoke 62 has inner and outer peripheral walls 62a and 62b, coaxial with each other, and magnet 64 is located between the peripheral walls. The top faces of yoke 62 and magnet 64 are located at distance T from support surface 54a of turntable 54. Distance T is greater than height t of projection of centering members 26 of optical disk 10. Thus, housed in depression 58, magnetic attraction means 60 can fully exhibit its force of attraction for mounting disk 10 on turntable 54, and prevent magnetic leakage to the outside. As described above, diameter D1 and height t of centering member 26 are smaller than diameter D2 of depression 58 and distance T, respectively. Therefore, if optical disk 10 is set on turntable 54 so that positioning portion 52a of shaft 52 is inserted in one of center holes 26a of attractable portion 22, as shown in Fig. 2, one of attractable members 24 is housed fully in depression 58. As a result, magnetic member 28 of the attractable member is attracted by magnet 64, so that disk 10 is mounted in direct contact with support surface 54a of turntable 54. Thus, base plate 18, with information record layer 20 thereon, is held securely against turntable 54, so that vibration of base plate 18 perpendicular to its surface can be minimized. Accordingly, information can be recorded or reproduced stably. In the case of an arrangement such that attractable member 24, instead of base plate 18, is adapted to be in contact with support surface 54a of turntable 54, optical disk 10 will vibrate considerably, unless the surfaces of member 24 and base plate 18 are worked so as to be very accurately parallel to each other. Therefore, member 24 and the bonding agent must be made uniform in thickness. This requires a very difficult work. The length of positioning portion 52a of shaft 52 is set so that portion 52a can engage only center hole 26a of the turntable-side attractable member when optical disk 10 is mounted on turntable 54. There will be no substantial problem even if center holes 26a of attractable members 26a are not aligned with high accuracy. If positioning portion 52a engages center holes 26 of both attractable members 24, the two center holes must be very accurately coaxial with each other. However, it is very difficult to align bores 19 of base plates 18 or center holes 26a of members 24. If positioning portion 52a is unnecessarily long, moreover, it takes optical disk 10 a long time to be set on turntable 54. This helps wear the disk. Thus, magnetic attraction means 60 is housed in depression 58 formed in turntable 54, so that magnetic leakage to the outside is restricted to a low level. Accordingly, iron filings or powder of other magnetic material can be prevented from hindering the engagement of shaft 52 and center hole 26a by sticking to shaft 52. As mentioned before, height t of projection of each centering member 26 is shorter than distance T between the top faces of yoke 62 and magnet 64 and support surface 54a of turntable 54. When optical disk 10 is mounted on turntable 54, therefore, gap G is defined between attractable member 24 and magnetic attraction means 60. Gap G has a size such that the disk can be subjected to a force of attraction which allows the driving force of turntable 54 to be transmitted securely to disk 10, and which allows the disk to be removed easily from turntable 54, by only lifting cartridge 14 with the disk therein. In this embodiment, gap G has a size such that a force of attraction of about 700 g acts on attractable member 24. In Fig. 2, numeral 66 designates a head, which is moved in the radial direction of optical disk 10 by head moving means, such as a linear motor. Head 66 performs information processing, such as recording or reproduction, on information record layer 20 formed on lowerside base plate 18 of disk 10. According to the information processing apparatus constructed in this manner, optical disk 10, including disk base plates 18 and attractable portion 22 in the center of plates 18, is mounted on turntable 54 by magnetic attraction means 60 attached to the turntable. Thus, disk 10 can be mounted stably on turntable 54, irrespectively of the thickness of the disk, and without requiring any clamp mechanism, which has conventionally been used, preventing reduction in thickness, weight, and costs of the apparatus. Moreover, each attractable member 24 is provided with centering member 26 and magnetic member 28, which is attached to member 26 by mounting means 44, so as to be slightly movable in the direction parallel to the surface of disk base 18. Therefore, even if disk 10 is subjected to any thermal effect, such as a change of ambient temperature, the mobility of magnetic member 28 can absorb the difference in the degree of thermal expansion between member 28 and the combination of base plate 18 and centering member 26, attributable to their different coefficients of thermal expansion. Thus, information can be processed stably without causing any distortion in base plates 18. In the embodiment described above, the material of centering members 26 is not limited to synthetic resin. The centering members must only be formed of a material whose coefficient of thermal expansion resembles that of base plates 18. Thus, the material of the centering members depends on that of the base plates. If the base plates are made of glass, for example, the centering members may be formed of glass or ceramic material In the embodiments described above, an optical disk with two disk base plates is used as the information memory medium. Alternatively, however, the disk may be provided with only one plate. Further, magnetic attraction means 60 may be formed only of a magnet. The shape of depression 58 in turntable 54 is not limited to the circular configuration, and may alternatively be a hexagonal or rectangular one. Each attractable member 24 must only have shape and size such that it can be housed in the depression. In the aforementioned embodiments, moreover, the yoke of the magnetic attraction means has inner and outer peripheral walls. Alternatively, however, it may be provided only with an inner peripheral wall, or an outer peripheral wall.

Claims: An optical information processing apparatus comprising: (a) an information memory medium (10) having a disk-shaped body (16) including a disk-shaped base plate (18) having a bore (19) at the central portion thereof and on which said information record layer (20) is formed, an attractable portion (22) provided at the central portion of the body (16) and having an attractable and centering member (24,26) which projects from the body (16), and a center hole (26a) formed in the attractable member (24) and defining the center of rotation of the body (16); (b) a drive mechanism (12) for rotating the information memory medium (10), said mechanism including a turntable (54) having a support surface (54a) for supporting the memory medium (10) and having a depression (58) formed in the support surface (54a), magnetic attraction means (60) housed in the depression (58), for attracting the attractable portion (22), a positioning portion (52) for engaging the center hole of the attractable and centering member (24,26) so as to align the memory medium (10) with the turntable (54), and a drive source (50) for rotating the turntable (54); wherein (c) said support surface (54a) of the turntable (54) is formed of a non-magnetic material; and (d) said attractable and centering member (24,26) is formed such that it is housed in the depression (58) with a predetermined gap with respect to the inner face of the depression (58) and with respect to the attraction means (60) when the memory medium (10) is set on the turntable (54), and such that the disk-shaped body (16) directly contacts the support surface (54a); characterized in that: said attractable and centering member (24,26) includes a centering member fitted to the bore (19) of the base plate (18), and a magnetic member (28) attached to the centering member (26) and adapted to be attracted by the magnetic attraction means (60), said centering member (26) having the center hole (26a) at the central portion of the centering member; said centering member (26) is formed of a material whose coefficient of thermal expansion approximates to that of said base plate (18); and said support surface (54a) of the turntable (54) is formed of a non-magnetic metal. An information processing apparatus according to claim 1, characterized in that said magnetic attraction means (60) has a top surface located at distance T from the support surface (54a) of the turntable (54), and the height of projection of the attractable member (24) from the body (16) is shorter than distance T. An information processing apparatus according to claim 2, characterized in that said depression (58) has a circular cross section and is coaxial with the positioning portion (52a), and said attractable member (24) has a circular cross section and is coaxial with the center hole (26a), said attractable member (24) having a diameter smaller than that of the depression (58). An information processing apparatus according to claim 1, characterized in that said magnetic attaction means (60) includes a magnet (64) and a yoke (62). An information processing apparatus according to claim 4, characterized in that said magnet (64) and yoke (62) are ring-shaped, and are arranged so as to be coaxial with the positioning portion (52a). An information processing apparatus according to claim 1, characterized in that said drive source includes a motor (50) having a rotating shaft (52), and said turntable (54) is fixed coaxially to the shaft, said shaft (52) having a tip end portion constituting the positioning portion (52a). An information processing apparatus according to claim 1, characterized in that said body (16) of the information memory medium (10) includes a disk-shaped base plate (18) having a bore (19), said bore (19) including a first portion (19a) having a predetermined axial length, and a second portion (19b), and said attractable member (24) includes a projection (30) fitted in the first portion (19a) of the bore (19), the height of said projection (30) being shorter than the axial length of the first portion (19a). An information processing apparatus according to claim 1, characterized in that said body (16) of the information memory medium (10) includes a pair of disk-shaped base plates (18) each having a bore (19) and fixed coaxially to each other, and information record layers (20) formed individually on the base plates (18), said attractable portion (22) includes a pair of attractable members (24) attached to the central portions of their correspoding base plates (18) and each having the center hole (26a), and said positioning portion (52a) has a length such that the positioning portion (52a) engages the center hole (26a) of that attractable member (24) fixed to the turntable-side base plate (18) when the information memory medium (10) is mounted on the turntable (54). An information processing apparatus according to claim 1, characterized in that said attractable member (24) includes mounting means (44) for mounting the magnetic member (28) to the centering member (26) so that the magnetic member (28) is immovable in the axial direction of the body (22), and is slightly movable in the radial direction of the body (22). An information processing apparatus according to claim 9, characterized in that said magnetic member (28) is ring-shaped. and is arranged to be coaxial with the center hole (26a), and said mounting means (44) includes a retaining portion (46) formed on the centering member (26), and a retaining claw (48) formed on the magnetic member (28) so as to engage the retaining portion (46). An information processing apparatus according to claim 1, characterized in that said centering member (26) and said disk-shaped base plate (18) are formed of the same material.

Inventors: INAGE NOBUO, ODAWARA KAZUHARU, TAGO YOSHIAKI, INAGE, NOBUO, ODAWARA, KAZUHARU, TAGO, YOSHIAKI, ODAWARA, KAZUHARU C/O PATENT DIVISION, TAGO, YOSHIAKI C/O PATENT DIVISION
Applicants: TOSHIBA INTELLIGENT TECH, TOSHIBA KK, KABUSHIKI KAISHA TOSHIBA, TOSHIBA INTELLIGENT TECHNOLOGY LTD.
Application year: 1987
Main classification: G11B17
IPC codes: G11B17, G11B33, G11B23, G11B19