Magneto-optical recording apparatus

Abstract: In magneto-optical disc recording apparatus a magneto-optical disc (D) is recorded by irradiating it with a recording light beam from an optical pickup head device (5) while an external magnetic field is applied by external magnetic field generating means (8). To ensure close proximity of the magnetic field generating means (8) to the disc (D) and uniform spacing therefrom, a spacer sheet (4) is located over the face of the magneto-optical disc (D) on which the magnetic field generating means (8) acts.

Description: Recently, in the technical field of disc recording apparatus, magneto-optical recording apparatus has been proposed for recording magneto-optical discs. In magneto-optical recording apparatus, a disc in which a perpendicular magnetic recording medium is utilized as a record medium is subjected to an external magnetic field by external magnetic field generating means such as a magnetic field coil. While so subjected, a laser beam irradiates the disc locally to raise its temperature, whereby a coercive force in the portion irradiated by the laser beam is decreased to invert a magnetization by the external magnetic field. By these means a signal can be recorded on or erased from the disc. A permanent magnet or a magnetic field coil may be utilized as external magnetic field generating means for applying an external magnetic field to the perpendicular magnetic recording medium of the disc. When a permanent magnet is employed as the external magnetic field generating means, an inverting mechanism for inverting the permanent magnet must be provided. There is the limit that the magnetic field of the permanent magnet is rapidly inverted by the inverting mechanism. Therefore, a laser beam is modulated on the basis of data to be recorded and the recording is made (this system is referred to as an optical modulation system). When a magnetic field coil is employed as the external magnetic field generating means however, inversion of the magnetic field can be rapidly effected by changing-over a current supplied to the magnetic field coil. Therefore, a current supplied to the magnetic field coil is modulated on the basis of data to be recorded and then the recording is carried out (this system is referred to as a magnetic field modulation system). In a magnetic field modulation system, a so-called overwrite is possible so that a time necessary for erasing unnecessary data on the disc is not required. Thus, a magneto-optical disc can be treated as a standard magnetic disc. Further, the above-mentioned inverting mechanism becomes unnecessary and there is then the advantage that the magneto-optical recording apparatus can be made compact in size. Accordingly, in magneto-optical disc recording apparatus utilizing a magnetic field coil as the external magnetic field generating means, in order to apply sufficient external magnetic field to the disc so that a signal can be positively recorded or erased, the magnetic field coil provided as the external magnetic field generating means must be located close to the disc, and also a distance between the magnetic field coil and the disc must be controlled to become constant. For position control means for controlling the position of the magnetic field coil in magneto-optical recording apparatus, the following methods have been proposed: (a) A stationary method wherein a magnetic field coil is fixedly located in advance relative to the disc with a spacing larger than a tolerance of its surface wobbling; (b) A method utilizing a tyre wherein a tyre is provided rotatably to contact a surface of the disc and a block including a magnetic field coil is provided on a rotation centre axis of the tyre (see Japanese Laid-Open Patent Gazette No. 63-206936); and (c) A method for controlling the position of a magnetic field coil by a combination of a photo sensor and an actuator. A distance from a disc to a magnetic field coil is measured by a photo sensor, and an actuator is driven on the basis of information of the measured distance, whereby the position of the magnetic field coil is controlled. However, previously proposed position control means to control the position of a magnetic field coil have the following unavoidable defects: In the stationary method (a), the distance between the magnetic field coil and the disc must be increased in order to prevent the magnetic field coil from being brought into contact with the disc when the disc wobbles due to warping of the disc. Consequently, a powerful magnetic field is required in order to record (or erase) a signal, and this unavoidably causes the magnetic field coil to consume a large amount of electric power. Therefore, this method (a) is not suitable for miniaturizing magneto-optical disc recording apparatus or even making it portable. In the method (b) utilizing the tyre, when the surface of the disc is irregular or has roughness, the tyre is directly affected by the uneven surface of the disc and thereby wobbles considerably so that the position of the magnetic field coil becomes unstable. Further, the method (b) is easily affected by external disturbances due to the irregular surface of the disc. Furthermore, a rotary supporting mechanism for the tyre needs a large number of assembly parts, which provides a complicated arrangement. Therefore, the method (b) is not suitable for making portable magneto-optical disc recording apparatus. Further, in the method (c) for controlling the position of the magnetic field coil by the combination of a photo sensor and an actuator, while this method is not affected by external disturbances due to the irregular surface of the disc, many assembly parts such as the photo sensor, the actuator and so on are required, and also the necessary electrical circuit becomes complicated in arrangement. The method (c) is also not suitable for making portable magneto-optical recording apparatus. Patent Specification GB-A-2 192 750 discloses a construction in which during a loading operation of a magneto-optical recording disc onto a recording and reproducing unit, an external magnetic field generating apparatus is moved up and down and rotary holding means are provided to rotate the disc while held by the rotary holding means. According to the invention there is provided magneto-optical disc recording apparatus in which a magneto-optical disc can be recorded by irradiating it with a recording light beam from an optical pickup head device while the magneto-optical disc is subjected to an external magnetic field by external magnetic field generating means and including rotary holding means to rotate the magneto-optical disc with the magneto-optical disc held by the rotary holding means, characterised by a spacer opposed to the magneto-optical disc over its surface opposite to its surface on which the recording light beam from the optical pickup head device is incident, and unitarily rotated together with the magneto-optical disc when the magneto-optical disc is held by the rotary holding means; the spacer being formed of a material which has a smooth surface and the external magnetic field generating means being brought into contact with the spacer. Thus in magneto-optical disc recording apparatus according to the invention the position of a magnetic field coil provided as external magnetic field generating means can be positively controlled by a simplified arrangement. Such a magnetic coil can be located close to the magneto-optical disc without damaging the magneto-optical disc. The apparatus can be fully protected from being affected by concave or convex portions formed on the magneto-optical disc. Power consumption of the magnetic field coil can be reduced. A chucking apparatus for use with a magneto-optical disc recording apparatus can be provided in which upon releasing the chucking, the magneto-optical disc will not be recklessly ejected from the apparatus. Rather the magneto-optical disc can be ejected from a turntable and/or loaded thereto with ease by a disc tray attached to the lid. The invention is diagrammatically illustrated by way of example in the accompanying drawings, in which: Figure 1 is a side view of a portion of a first embodiment of magneto-optical disc recording apparatus according to the invention; Figure 2 is a side view illustrating an overall arrangement of the magneto-optical disc recording apparatus of Figure 1; Figure 3 is a schematic perspective view of the magneto-optical disc recording apparatus of Figures 1 and 2; Figure 4 is a diagrammatic sectional view illustrating an overall arrangement of a second embodiment of magneto-optical disc recording apparatus according to the invention; Figure 5 is a diagrammatic sectional view of the second embodiment of magneto-optical disc recording apparatus, and to which reference will be made in explaining the condition that a disc chucking apparatus is not actuated; Figure 6 is a diagrammatic sectional view of the second embodiment of magneto-optical disc recording apparatus, and to which reference will be made in explaining an action of a disc pushing mechanism; Figure 7 is a diagrammatic sectional view of the second embodiment magneto-optical disc recording apparatus, and to which reference will be made in explaining the condition that the disc chucking operation is finished; Figure 8 is a diagrammatic sectional view illustrating an overall arrangement of a third embodiment of magneto-optical disc recording apparatus according to the invention, and illustrating the condition that an upper lid of the recording apparatus is opened; Figure 9 is a diagrammatic sectional view illustrating an overall arrangement of the third embodiment and illustrating the condition that the upper lid of the recording apparatus is closed; and Figure 10 is a bottom planar view illustrating the upper lid and a disc tray of the third embodiment. Referring to the drawings and initially to Figures 1 to 3, a first embodiment of magneto-optical disc recording apparatus has a turntable 1 attached to a drive shaft 2A of a spindle motor 2, and a chucking plate 3 is located above the turntable 1 in opposing relation thereto. The chucking plate 3 is rotatably supported on a stationary portion (not shown) and incorporates therein a magnet (not shown) so that, when an magneto-optical disc (hereinafter simply referred to as a disc) D is inserted into the magneto-optical disc recording apparatus, the chucking plate 3 is magnetically attracted to the turntable 1, whereby the disc D is chucked therebetween and hence the disc D can be rotated by the spindle motor 2. In the above-described chucking mechanism, a disc-shaped spacer sheet 4 of a size bigger than the disc D is adhered to the lower surface of the chucking plate 3 so that, when the disc D is chucked by the chucking mechanism, the spacer sheet 4 is applied to the upper surface of the disc D and thereby the disc D and the spacer sheet 4 are rotated together. The spacer sheet 4 is made of a material which is light in weight, flexible and has a smooth surface so as closely to contact the disc D. Referring to Figure 2, an optical pickup head device 5 is provided to emit a laser beam which is then focused on the perpendicular magnetic record medium surface of the disc D by an objective lens (not shown). A magnetic field coil 6 is located above the disc D is opposing relation to the optical pickup head device 5 through the spacer sheet 4 as external magnetic field generating means. When the magnetic field coil 6 is conducted and driven, the magnetic field coil 6 supplies an external magnetic field to the perpendicular record medium surface of the disc D, whereby a magnetization is inverted in the perpendicular magnetic record medium surface at its portion irradiated by the laser beam, and a signal is recorded. The magnetic field coil 6 is brought into mechanical contact with the spacer sheet 4 in the condition that the disc D is chucked and that the spacer sheet 4 is mounted on the top surface of the disc D. More specifically, the magnetic field coil 6 is resiliently supported by a stationary side link mechanism 7 via a leaf plate spring 8, whereby the magnetic field coil 6 is urged against the upper surface of the spacer sheet 4 with a predetermined pressure by the resilient pushing force of the leaf plate spring 8. In that case, it is preferable that the lower surface of the magnetic field coil 6, i.e. , the contact surface thereof by which the magnetic field coil 6 contacts the spacer sheet 4 is treated by a so-called smoothing coating-process. As is clear from the above-described arrangement, in the magneto-optical disc recording apparatus of this embodiment, when the disc D is chucked, the spacer sheet 4 closely contacts the upper surface of the disc D so that, regardless of the bending, distortion or the like of the disc D, the spacer sheet 4 can bend together with the disc D. In this state, the magnetic field coil 6 is pressed against the top surface of the spacer sheet 4 by the spring-biasing force of the leaf plate spring 8, whereby the spacing between the disc D and the magnetic field coil 6 is determined by the thickness of the spacer sheet 4. Therefore, the magnetic field coil 6 can smoothly follow a disc surface which wobbles due to rotation of the disc D. Accordingly, the position of the magnetic field coil 6 relative to the disc D is always kept constant so that the magnetic field coil 6 applies a stable external magnetic field to the perpendicular record medium surface of the disc D, and magneto-optical recording can be positively effected. Although the magnetic field coil 6 is constantly urged against the spacer sheet 4 unitarily rotated with the disc D so that there is friction, flatness of the surface of the spacer sheet 4 can be excellent and if the contact surface of the magnetic field coil 6 is treated by the smoothing coating-process, the sliding contact between the contact surface of the magnetic field coil 6 and the spacer sheet 4 can be excellent. Therefore, the magnetic field coil 6 will not be unduly worn. Magneto-optical disc recording apparatus of the first embodiment can have various advantages which will be explained below. In this embodiment of magneto-optical disc recording apparatus, the spacer sheet 4 is interposed between the magnetic field coil 6 and the disc D, that is, the magnetic field coil 6 is opposed to the disc D through the spacer sheet 4 so that the disc D will not be damaged by the magnetic field coil 6. Further, even when the top surface of the disc D is irregular or rough, the magnetic field coil 6 will not directly be affected by concave or convex portions or roughness of the disc D, and can smoothly follow the disc D along the spacer sheet 4. Therefore, the position of the magnetic field coil 6 is stabilized and is not affected by an external disturbance due to the concave and convex surface or the like of the disc D. The magnetic field coil 6 is constantly located close to the disc D so that, even though the magnetic field coil 6 does not generate a powerful magnetic field or consume large quantities of electric power, it can apply a sufficient external magnetic field to the perpendicular record medium surface of the disc D. Therefore, the power consumption of the magnetic field coil 6 can be quite small. The magneto-optical disc recording apparatus of this embodiment is provided with the position control mechanism for controlling the position of the magnetic field coil 6 as described above. This position control mechanism has a very simplified construction wherein the spacer sheet 4 is mounted on the disc D and the magnetic field coil 6 contacts the upper surface of the spacer sheet 4. Therefore, the position control mechanism can be constructed with a smaller number of assembly parts and the overall arrangement thereof can be made compact in size. In addition, only a pushing force by which the magnetic field coil 6 is pushed toward the spacer sheet 4, that is, the resiliency of the leaf plate spring 8 need be adjusted, which reduces the items to be adjusted and also which removes a cumbersome adjusting process. Owing to the aforementioned various advantages of this embodiment, conditions necessary for miniaturizing the magneto-optical disc recording apparatus can be satisfied. In the disc chucking device of the first embodiment in which the spacer sheet 4 is unitarily attached to the chucking plate 3, there is presented the substantial possibility that, when the chucking plate 3 is lifted in a chucking releasing operation, the disc D will also be lifted together with the spacer sheet 4 and the disc D will be ejected from the turntable 1. Because, upon chucking, the spacer sheet 4 is pressed so as closely to contact the top surface of the disc D, the spacer sheet 4 and the disc D may be caused to be stuck to each other by a so-called atmospheric pressure. The second embodiment can remove the aforementioned shortcoming, and is described with reference to Figures 4 to 7. In Figure 4, it will be seen that an openable and/or closable upper lid 211 is attached to an apparatus body 102 in which a turntable 22 is mounted. A chucking plate 24 for chucking the disc D is secured to the upper lid 211, and a spacer sheet 25 is attached to the chucking plate 24 to control the position of a magnetic field coil. Thus, when the upper lid 211 is opened to load the disc D onto the turntable 22 and the upper lid 211 is then closed, the disc D is chucked (attached by means of chucking) on the turntable 22 by the chucking plate 24, and the spacer sheet 25 attached to the chucking plate 24 comes into close contact with the upper surface of the disc D. In this condition, a magnetic field coil 213 contacts the surface of the spacer sheet 25 and the spacing between the magnetic field coil 213 and the disc D is maintained constant. Figures 5, 6 and 7 show a disc chucking device 21 located above the turntable 22 and comprising the chucking plate 24 and the spacer sheet 25. The chucking plate 24 can chuck the disc D set on the turntable 22 or release the disc D from being chucked by moving itself closer to or by moving itself apart from the turntable 22. The spacer sheet 25 is attached to the chucking plate 24 and is brought in close contact with the top surface of the disc D upon chucking. The chucking plate 24 is provided with a disc pushing mechanism 26 which will be described more fully later. The turntable 22 is made of a magnetic material such as a metal, and is rotated by a spindle motor (not shown). The chucking plate 24 comprises a small-diameter hollow cylinder portion 27 whose upper end is closed, a middle-diameter cylindrical portion 28 coaxially communicating with the hollow cylinder portion 27 at its lower opening portion and a large-diameter flange portion 29 coaxially communicating with the middle-diameter cylinder portion 28 at its lower opening portion. An annular groove 210 is formed on the outer peripheral surface of the upper end portion of the small-diameter hollow cylindrical portion 27. Thus, when a portion of the upper lid 211 of the magneto-optical disc recording apparatus is engaged with the annular groove 210 with clearance, the chucking plate 24 is rotatably attached to the upper lid 211. When the upper lid 211 is closed from the opened state, the large-diameter flange portion 29 approaches the turntable 22 and an attraction surface 29 a of the large-diameter flange portion 29 is attracted to the turntable 22 by the magnetic force of a magnet 212 attached to the flange portion 29. Therefore, the disc D is chucked to the turntable D at an inner peripheral portion thereof between the attraction surface 29 a of the flange portion 29 and the turntable 22. The spacer sheet 25 is formed as a disc-shaped sheet of a diameter larger than that of the disc D and having a predetermined thickness by moulding a light-weight, smooth non-magnetic plastics material having a low friction coefficient. Further, the spacer sheet 25 has a sufficient flexibility for it closely to contact the top surface of the disc D so that the spacer sheet 25 is unitarily stuck to the attraction surface 29 a of the flange portion 29. When the attraction surface 29 a of the flange portion 29 is stuck to the turntable 22, as shown in Figure 7, the spacer sheet 25 closely contacts the upper surface of the disc D chucked to the turntable 22. Accordingly, if the magnetic field coil 213 contacts the upper surface of the spacer sheet 25, then the spacing between the magnetic field coil 213 and the disc D is naturally controlled to be determined as the thickness of the spacer sheet 25. The disc pushing mechanism 26 comprises a movable member pushing coil spring 214 secured within the small-diameter hollow cylindrical portion 27 of the chucking plate 24 and a movable member 216 having one end spring-biased by the coil spring 214 and the other end, which is formed as an annular-shaped disc pushing portion 215, projecting from the lower opening portion of the middle-diameter cylindrical portion 28 to push the innermost peripheral portion of the disc D. The spring-biasing force of the coil spring 214 is determined to be slightly weaker than the attracting force of the magnet 212 in the chucking operation, whereby upon non-chucking the annular-shaped disc pushing portion 215 of the movable member 216 is projected from the attraction surface 29 a of the flange portion 29 by a predetermined length by the spring-biasing force of the coil spring 214 as shown in Figure 5. When the chucking plate 24 is moved downward together with the upper lid 211 in order to effect chucking, the chucking plate 24 is attracted to the turntable 22 by the magnetic force of the magnet 212. At that time, as shown in Figure 6, the tip end of the annular-shaped disc pushing portion 215 comes into contact with the top surface of the disc D, and the disc pushing portion 215 is pushed into the middle-diameter cylindrical portion 28 against the spring-biasing force of the coil spring 214. When the chucking operation is finished, as shown in Figure 7, the disc D is pushed at the innermost peripheral portion of the upper surface thereof by the disc pushing portion 215 and the outer peripheral portion of the disc D adjacent to its innermost peripheral portion is pushed by the flange portion 29. In addition, the spacer sheet 25 attached to the flange portion 29 is brought into close contact with the top surface of the disc D so that, when the magnetic field coil 213 contacts the top surface of the spacer sheet 25, recording is effected under the condition that the clearance between the magnetic field coil 213 and the disc D is maintained the same as the thickness of the spacer sheet 25. When chucking is released after completion of the recording operation, conversely, the chucking plate 24 and the spacer sheet 25 are moved together upwards in the condition that the disc pushing portion 215 of the movable member 216 is pushed to the disc D by the spring-biasing force of the coil spring 214 as shown in Figure 6. In other words, the disc pushing portion 215 projects from the attraction surface 29 a of the flange portion 29 to cause the turntable 22 to be moved downward relatively and the spacer sheet 25 to be detached from the surface of the disc D. When the chucking plate 24 is further moved upwards (i.e. more than the maximum projected length of the disc pushing portion 215), as shown in Figure 5, the disc D is released from being pushed by the disc pushing portion 215. A concave portion 217 and a convex portion 218 are respectively formed on the upper surface of the turntable 22 and on the lower surface of the movable member 216 to centre the turntable 22 and the movable member 216. In Figure 7, reference numeral 219 designates an optical pickup head device. While a disc chucking device of magnet type is described in the second embodiment shown in Figures 4 to 7, the invention is not restricted to a disc chucking device of magnet type. In the first and second embodiments as described above, the spacer sheet 4, 25 is thin so that, when the magneto-optical disc is exchanged, the spacer sheet can easily be damaged by external forces, such as via the disc. Further, the magnetic field coil provided through the spacer sheet can also easily be damaged. In a third embodiment described with reference to Figures 8 to 10, magneto-optical recording apparatus 31 has an apparatus body 33 in which a turntable 32 is provided, an openable and/or closable upper lid 34 attached to the apparatus body 33, a chucking plate 35 mounted on the upper lid 34 and a spacer sheet 36 attached to the chucking plate 35 to control the position of a magnetic field coil which will be described later. A disc tray 38 is attached to the upper lid 34 so as to cover the underside of the spacer sheet 36. Accordingly, when the upper lid 34 is opened and/or closed, the disc tray 38 is operated to eject the disc D from and to load the disc D onto the turntable 32. The apparatus body 33 is formed as a rectangular-shaped upwardly open box formed by erecting front, rear, left and right side plates 33 b , 33 c , 33 d and 33 e from the four edges of a bottom plate 33 a . The turntable 32 is provided at the middle portion of the apparatus body 33. The upper lid 34 is formed as a downwardly open rectangular-shaped box formed by extending downwardly front, rear, left and right side plates 34 b , 34 c , 34 d and 34 e from the four edges of an upper plate 34a. The upper lid 34 and the apparatus body 33 form a pair. The lower edge of the rear side plate 34 c (opposite side to the side to and/or from which the disc D is loaded and/or ejected) is pivotally coupled to the upper edge of the rear side plate 33 c of the apparatus body 33 by a shaft 39 so that, when the upper lid 34 is rotated around the shaft 39, the opening portion of the apparatus body 33 is opened and/or closed. A rotation centre shaft 310 is provided at the middle portion of the chucking plate 35. The rotation centre shaft 310 is engaged with a bearing aperture 312 of a clamp support base 311 provided on the lower surface of the upper plate 34 a of the upper lid 34 and secured thereto by a stop member 313 whereby the shaft 310 and hence the chucking plate 35 are rotatably supported on the upper lid 34. When the upper lid 34 is closed, the chucking plate 35 is attracted to the turntable 32 by the magnetic force of a magnet 314, whereby the disc D loaded on the turntable 32 is pressed to the turntable 32 side, thereby being chucked thereto. The spacer sheet 36 is formed as a disc-shaped sheet having a thickness of a few microns by utilizing a non-magnetic high polymer material. The spacer sheet 36 is attached to the attracting surface (under surface) of the chucking plate 35 so that, when the disc D is chucked by the chucking plate 35, the spacer sheet 36 is closely stuck to the upper surface of the disc D. The disc tray 38 is composed of a bottom plate 38 a and left and right side plates 38 b and 38 c erected from the left and right sides of the bottom plate 38 a , as shown in Figure 10. The disc tray 38 is formed substantially as an unfolded fan wherein one corner portion of the bottom plate 38 a is cut-away as an arc surface 38 d which has a curvature diameter slightly smaller than the outer diameter of the disc D. Further, the bottom plate 38 a has formed therethrough at the central portion thereof a chucking cut-out-window 315 having a diameter larger than that of the turntable 32, and also has formed therethrough and lying on a radius thereof a cut-out-window 316 through which a laser beam can irradiate the disc D. On the respective side portions of the rear upper surface of the bottom plate 38 a of the disc tray 38, there are provided a pair of left and right inclined surface portions 317 and 318 which are used to determine the position of the disc D. By means of these inclined surface portions 317 and 318, the position of the disc D loaded on the bottom plate 38 a is determined, and one side of the outer peripheral portion of the disc D projects beyond the arc surface 38 d of the bottom plate 38 a , thereby making it possible to eject the disc D from the disc tray 38 with ease. In the disc tray 38, one side plate 38 b is short and the other side plate 38 c is long. Under the condition that these side plates 38 b and 38 c are overlapped on the inside surfaces of the side plates 34 d and 34 e , these side plates 38 b and 38 c are pivotally attached at their rear end portions thereof to the upper lid 34 by shafts 319 and 319. Also, one side plate 38 b has formed therethrough at substantially the central portion thereof in the lengthwise direction a cut-away window 320 which permits the disc tray 38 to be opened by a predetermined angle ϑ relative to the upper lid 34 to enable the disc D to be inserted into the disc tray 38 as shown in Figure 8. Thus a boss 321 provided on the side plate 34 d of the upper lid 34 projects into the cut-away window 320 and permits the disc tray 38 to rotate. When the upper lid 34 is opened around the shaft 39 by the predetermined angle ϑ relative to the disc tray 38, the boss 321 contacts with the upper edge of the cut-away window 320 formed through the side plate 38 b of the disc tray 38, thereafter causing the disc tray 38 to rotate together with the upper lid 34. Then, under the condition that the upper lid 34 is opened and the disc tray 38 is opened by the predetermined angle ϑ relative to the upper lid 34, if the disc D is inserted into the disc tray 38 and then the upper lid 34 is closed, the disc tray 38 is moved downwardly together with the upper lid 34 to load the disc D on the turntable 32. Thereafter, the disc tray 38 is inhibited from being rotated further by a stopper which will be described later. When the upper lid 34 is further moved downwardly, the spacer sheet 36 is closely stuck to the upper surface of the disc D, and the chucking plate 35 is attracted to the turntable 32 side, thereby clamping the disc D. In this condition, the upper lid 34 is fully closed. Referring to Figures 8 and 9, a magnetic field coil 322 is located above the spacer sheet 36 within the upper lid 34. The magnetic field coil 322 is attached to one end (tip end) of a gimbal supporting arm 324 through a gimbal plate spring 323, whereas the other end (base end) of the gimbal supporting arm 324 is pivotally supported on a gimbal support arm base 326 by a pivot shaft 325. The gimbal support arm 324 is spring-biased by a coil spring 327 having one end engaged with the gimbal support arm 324 near the pivot shaft 325 and the other end engaged with the gimbal support arm base 326 in the counter-clockwise direction in Figure 8. Thus, when the upper lid 34 is closed, the magnetic field coil 322 lightly contacts the upper surface of the spacer sheet 36. When the upper lid 34 is opened by an angle more than the predetermined angle ϑ, a boss 328 formed on one side wall of the upper lid 34 comes into contact with an upper edge of a gimbal supporting arm operating cut-away window 329 formed through one side wall of the gimbal support arm 324 thereby to urge the gimbal supporting arm 324 to be rotated in the clockwise direction in Figure 8 against the spring-biasing force of the coil spring 327. Thus, the magnetic field coil 322 is spaced apart from the spacer sheet 36 by a very small amount. Figure 8 shows a stopper 330 provided on the gimbal supporting arm base 326. The stopper 330 comes in contact with the gimbal supporting arm 324 spring-biased by the coil spring 327, thereby inhibiting the gimbal supporting arm 324 from rotating further. A photo pickup head device 331 attached to the gimbal supporting arm base 326 can be moved in the radial direction of the disc D together with the magnetic field coil 322 by a slide operation mechanism (not shown). The third embodiment of the magneto-optical disc recording apparatus is constructed as described above so that, when the upper lid 34 is opened, the disc tray 38 is opened by a predetermined angle (determined by the height of the rotation operating cut-away window 320) relative to the upper lid 34. Then, if a disc D is inserted into the disc tray 38, the disc D is positioned by the disc positioning inclined surface portions 317 and 318. Under this condition, if the upper lid 34 is closed, then the disc tray 38 is closed together with the upper lid 34 and the disc D in the disc tray 38 is loaded onto the turntable 32. Then, after the spacer sheet 36 is closely stuck to the upper surface of the disc D, the disc D is chucked to the turntable 32 by the chucking plate 35, and the magnetic field coil 322 is brought into contact with the top surface of the spacer sheet 36. While the cut-away window 320 is formed on the disc tray 38 side for rotating the disc tray 38 and the boss 321 is formed on the upper lid 34 side in the third embodiment shown in Figures 8 to 10, a variant is also possible wherein the boss 321 is formed on the disc tray 38 side and the cut-away window 320 is formed on the upper lid 34 side. In this case, the opening angle of the disc tray 38 relative to the upper lid 34 may be properly determined by the sizes of the cut-away window 320 and the boss 321. Furthermore, the construction in which the disc tray 38 is attached to the upper lid 34 is not limited to that of the above-described third embodiment and can be varied freely. For example, any construction may be possible so long as it can protect the spacer sheet 36 when the upper lid 34 is opened. While magneto-optical disc recording apparatus utilizing a magnetic field coil as external magnetic field generating means is described above, the invention is equally applicable to magneto-optical disc recording apparatus which utilizes a permanent magnet instead of a magnetic field coil. Since the magnetic field coil is brought into mechanical contact with the spacer sheet located on the disc thereby to control the position of the magnetic field coil relative to the disc, the magnetic field coil can be located close to the disc without damaging the disc, and the magnetic field coil can be protected from being affected by external disturbances caused by concave and convex portions of the disc. Further, the power consumption of the magnetic field coil can be reduced. In addition, the magneto-optical disc recording apparatus of the invention can be simple in construction and have less assembly parts and less portions to be adjusted making it very advantageous for making the apparatus compact in size.

Claims: Magneto-optical disc recording apparatus in which a magneto-optical disc (D) can be recorded by irradiating it with a recording light beam from an optical pickup head device (5, 219, 331) while the magneto-optical disc (D) is subjected to an external magnetic field by external magnetic field generating means (6, 213, 322) and including rotary holding means (1, 3, 22, 24, 32, 35) to rotate the magneto-optical disc (D) with the magneto-optical disc (D) held by the rotary holding means, characterised by a spacer (4, 25, 36) opposed to the magneto-optical disc (D) over its surface opposite to its surface on which the recording light beam from the optical pickup head device (5, 219, 331) is incident, and unitarily rotated together with the magneto-optical disc (D) when the magneto-optical disc (D) is held by the rotary holding means; the spacer (4, 25, 36) being formed of a material which has a smooth surface and the external magnetic field generating means (6, 213, 322) being brought into contact with the spacer (4, 25, 36). Magneto-optical disc recording apparatus according to claim 1, including spring-biasing means (8, 327) whereby the external magnetic field generating means (6, 213, 322) is spring-biased into contact with the spacer (4, 25, 36). Magneto-optical disc recording apparatus according to claim 1 or claim 2, wherein the spacer (4, 25, 36) is made of a flexible material so that it can closely adhere to the magneto-optical disc (D). Magneto-optical disc recording apparatus according to any one of claims 1 to 3, wherein the rotary holding means comprises a chucking plate (3, 24, 35) and a turntable (1, 22, 32), and the spacer (4, 25, 36) is secured to the chucking plate (3, 24, 35). Magneto-optical disc recording apparatus according to any one of claims 1 to 4, wherein the rotary holding means includes releasing means (26) to release the spacer (4, 25, 36) from the magneto-optical disc (D) when the rotary holding means (1, 3, 22, 24, 32, 35) is changed from holding the magneto-optical disc to a non-holding state. Magneto-optical disc recording apparatus according to claim 5, wherein the releasing means (26) includes a movable member (216) to move the magneto-optical disc (D) so that the magneto-optical disc is spaced apart from the spacer (4, 25, 36) when the rotary holding means (1, 3, 22, 24, 32, 35) is changed from holding the magneto-optical disc to a non-holding state. Magneto-optical disc recording apparatus according to any one of claims 1 to 6, further comprising protecting means (38) to protect the spacer (4, 25, 36) when the magneto-optical disc (D) is inserted into and/or ejected from the apparatus. Magneto-optical disc recording apparatus according to claim 7, wherein the protecting means is a disc tray (38) to prevent the magneto-optical disc (D) from contacting the spacer (36) when the magneto-optical disc is loaded onto and/or ejected from the apparatus.

Inventors: ANDO RYO C O PATENTS DIVISION, FUJISAWA HIROTOSHI C O PATENTS, OHMORI TAKASHI C O PATENTS DIV, ANDO, RYO, C/O PATENTS DIVISION, FUJISAWA, HIROTOSHI, C/O PATENTS DIVISION, OHMORI, TAKASHI, C/O PATENTS DIVISION
Applicants: SONY CORP, SONY CORPORATION
Application year: 1990
Main classification: G11B11
IPC codes: G11B17, G11B11