JP2002279782A - Disk unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reliable disk unit by efficiently radiating heat from a laser driver integrated circuit. SOLUTION: The disk unit is provided with a rotating mechanism to rotate a disk being a recording medium, an optical pickup for recording or reproducing information on or from the disk, a driving mechanism for moving the optical pickup in the radial direction of the disk, a laser diode provided on the optical pickup to emit a laser beam, and a laser driver integrated circuit to adjust the drive of the laser diode. The laser driver integrated circuit attached to a flexible printed wiring board to which the laser driver integrated circuit is connected, is connected to a member constituting the easing of the optical pickup.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a disk device for reproducing or recording information by rotating a disk as a recording medium, and more particularly to an optical disk device.

[0002]

2. Description of the Related Art In recent years, high-speed recording has also been attempted in recording disk devices such as CD-R / RW. Such a CD-R / RW is of a thermal recording type. In order to realize high-speed recording, the temperature on a predetermined recording film must be increased in a short time, and it is essential to increase the output of a laser diode as a light source.

[0003] Further, in a laser driver IC (electronic component, element) for driving a laser diode, the driving power also increases, and accordingly, the amount of heat generated also increases. Further, since the laser driver IC section is driven at a high frequency by current, it is sealed by a shield case or the like so that electromagnetic wave noise does not leak to the surroundings. For this reason, since the amount of heat generated by the increase in the output increases, the heat is trapped, and the temperature may exceed the operation guarantee temperature of the laser driver IC.

If the temperature of the laser driver IC element exceeds the operation guarantee temperature, a malfunction of the laser circuit is caused to deteriorate the performance of the device. Further, when a local temperature rise is caused and heat is transmitted to the laser diode portion, the life of the laser element is also deteriorated.

[0005] In order to solve such problems, various techniques have been proposed for dissipating heat generated in the circuit and cooling the circuit. An example of a heat dissipation structure of a laser driver IC for driving a laser diode in a conventional disk drive is disclosed in Japanese Patent Application Laid-Open No.
As described in (Prior Art), a laser driver IC and a shield case are connected by a heat conductive member, heat generated by the laser driver IC is radiated to the shield case, and a part of the heat transmitted to the shield case is shielded. From the outside of the case. Further, part of the heat transmitted to the shield case is transmitted to the mounting base on which the laser diode is mounted, and further transmitted from the mounting base to the slide base on which the laser diode is mounted.

[0006]

However, in this prior art, a laser diode serving as a heat source is transferred to a shield case and transmitted to a slide base via a mounting base provided with the laser diode to dissipate the heat. For this reason, when the amount of heat generated from the shield case becomes large, heat cannot be sufficiently dissipated due to large thermal resistance. Regarding this point, the heat dissipation path and the heat transfer cross-sectional area in consideration of the calorific value have not been considered in the above-described conventional technology.

The object to which the laser driver IC (electronic parts, elements) transmits heat is the mounting base on which the laser diode is mounted, and the heat from the laser diode affects the heat radiation and driving of the laser driver IC. The performance of the laser driver IC, the laser driver IC must be moved far away or the drive performance must be reduced, and the performance and reliability of the device decrease. That was not taken into account.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a highly reliable disk drive by efficiently radiating heat from a laser driver IC.

[0009]

An object of the present invention is to provide a rotating mechanism for rotating a disk as a recording medium, an optical pickup for recording or reproducing information on or from the disk,
A disk device comprising: a drive mechanism for moving the optical pickup in a radial direction of a disk; a laser diode for emitting laser light provided in the optical pickup; and a laser driver IC for adjusting the drive of the laser diode. This is achieved by connecting the laser driver IC attached to the flexible printed circuit board to a member constituting a housing of the optical pickup.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are directed to a rotating mechanism for rotating a disk as a recording medium and an optical pickup for recording or reproducing information on or from the disk in order to improve the reliability of the apparatus. A drive mechanism for moving the optical pickup in the radial direction of the disk, a laser diode for emitting laser light provided in the optical pickup, and a laser driver IC for adjusting the drive of the laser diode. Then, the laser driver IC attached to the flexible printed circuit board was connected to a member constituting a housing of the optical pickup.

Further, the upper surface of the mold portion of the laser driver IC and the housing of the optical pickup are directly or firstly connected.
And the ratio of the contact area or an arbitrary cross-sectional area parallel to the mold surface of the heat conductive member to the area of the upper surface of the mold portion of the laser driver IC is 0.5 or more. It is also characterized by. Further, a laser driver IC is provided on the lower surface side of the optical pickup housing.
A groove or a step having a depth equal to or greater than the thickness of the laser driver IC is provided, and the laser driver IC is mounted such that the upper surface of the mold portion of the laser driver IC faces the bottom of the groove or the step of the optical pickup housing. It is also characterized.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is an exploded perspective view schematically showing the structure of an optical disk device 1 according to the present invention. The disk device 1 mainly includes an apparatus main body 12, a top cover 2 covering the upper surface of the apparatus main body 12, a disk tray 4 for carrying a disk (not shown) into or out of the apparatus, and a disk tray 4. 4 and a front cover 3 attached to the front front. The device main body 12 includes a lock mechanism (not shown) for holding the disc tray 4, a loading mechanism (not shown) for carrying the disc tray 4 from the device main body 12 along the guide rail 10, and electronic devices. A circuit board 11 for performing drive control and signal processing of components is mounted.

A mechanical chassis 6 is attached to the disk tray 4, and a bottom cover 8 covers a lower surface thereof. The mechanical chassis 6 includes a spindle motor 5 for holding and rotating the disk, and a recording / reproducing device for recording or reproducing information on or from the disk.
A read-only optical pickup 7 and an optical pickup feed mechanism for moving the optical pickup 7 in the radial direction of the disk along a guide bar, not shown, are mounted. The optical pickup 7 that reads information from a disk has a laser diode 74 or an electronic component as a heat-generating component provided in the optical pickup 7.

In the structure of the device according to the prior art, due to the heat generated by these components, there is a local heat distribution in the housing of the optical pickup 71. For example, thermal problems such as deterioration of the life of the laser element and malfunction due to circuit components are caused. Had occurred.

The configuration of the conventional optical pickup 7 is as follows.
This will be described with reference to FIG. FIG. 8A is a perspective view of an optical pickup in a conventional disk device.
FIG. 9B is an enlarged cross-sectional view of the portion B (the mounting portion of the laser diode and the laser driver IC) in FIG. The arrows drawn with solid and dotted lines in the figure are:
Laser driver IC 76 and laser diode 7 respectively
4 shows the flow of heat from FIG.

As shown in FIG. 8A, an optical pickup housing 71 has a laser diode 7 for emitting laser light.
4, a laser diode fixing member 75 for fixing the laser diode 74, a photodetector (not shown) for detecting information on the disk with the laser light and detecting the return light from the disk, and an illustration for guiding the laser light to the photodetector Not shown and a laser driver IC for driving and controlling the laser diode 74
76, a flexible printed circuit board 9, and the like. The objective lens 73 is mounted on the actuator 72 and driven in the focus and tracking directions.

A wiring pattern made of copper foil is provided on the flexible printed wiring board 9, and a focus coil for driving an actuator 72 on which the objective lens 73 is mounted in a focus direction and a focus coil for driving an actuator 72 in a tracking direction. The power is supplied to the tracking coil and the laser driver IC 76 and the like, and is electrically connected to the circuit board 11 which performs drive control of the spindle motor 5 and the actuator 72 and processes signals obtained from the optical pickup 7. As described above, since a large number of components must be arranged in the optical pickup 7, the volume becomes large. Meanwhile, the optical pickup 7
The optical pickup 7 moves at a high speed in the radial direction of the disk and quickly reads out information from the disk. Therefore, the mass of the optical pickup 7 including the above-mentioned components serving as a movable portion must be reduced. That is, miniaturization of the optical pickup 7 is required.

The size of the optical pickup 7 in the height direction is, for example, in the case of a notebook-type personal computer disk device having a height of 12.7 mm, the distance from the bottom surface of the disk to the bottom surface of the optical pickup 7 is 7 mm. There are dimensional restrictions such as that the size must be kept within 3 mm. Further, from the laser driver IC 76 to the laser diode 74
In order to efficiently transmit a high-frequency drive signal, both parts must be arranged close to each other. Therefore, the distance between the laser diode 74 and the laser driver IC 76 can be reduced by disposing the laser diode 74 and the laser driver IC 76 on the same substrate provided separately from the flexible printed circuit board 9 or by directly connecting the laser driver IC 76 to the flexible printed circuit board 9. It was arranged in a separate place while keeping it close.

In the disk device 1 having a function of writing to a disk, it is possible to stably write information to the disk in an environment where the ambient temperature of the device is 5 ° C. to 45 ° C. Is required. In particular, a device such as a CD-R / RW writes information to a disk by increasing the temperature of the recording layer of the disk to several hundred degrees Celsius by the thermal energy of a laser beam and changing the physical properties to record information. This is a thermal recording type.

Therefore, in order to realize high-speed recording, for example, 80 mW at 4 × writing speed and 1 m at 8 × speed are used.
A higher output laser diode is required, such as 00 mW and 130 mW at 12 × speed. Accordingly, the driving power of the laser driver IC 76 for driving the laser diode 74 increases, and the amount of heat generated accordingly increases. On the other hand, the laser driver IC 76
Is guaranteed to be around 70 ° C.

However, in the conventional disk drive, the temperature of the laser driver IC 76 rises sharply when the writing operation is started due to the above-mentioned increase in the output of the laser diode 74 and the accompanying increase in the driving power of the laser driver IC 76. Assuming that the ambient temperature is 45 ° C., the operation assurance temperature of the laser driver IC 76 is significantly higher. As a result, there arises a problem that the performance of the laser circuit is deteriorated due to the temperature rise and the life of the laser element is deteriorated. In addition, due to such a problem caused by the above components, accurate information cannot be reproduced or recorded on a disk, and the reliability of the apparatus itself may be reduced. Therefore, it is required to lower the temperature of the laser driver IC 76 to improve the performance and reliability of the device.

As shown in FIG. 8B, the laser diode fixing member 75 has a laser diode 74 mounted thereon, and is positioned and fixed to the optical pickup housing 71 by a surface. A pickup circuit board 78 is attached to the laser diode fixing member 75. A laser driver IC 76 is fixed to the pickup circuit board 78 by soldering. When driving the laser diode 74, the laser driver IC 76 is covered with a shield case 79 so that electromagnetic noise of several hundred MHz emitted from the laser driver IC 76 does not leak to the surroundings.

Further, the laser driver IC 76 and the shield case 79 are connected via a heat conductive member 792 to dissipate the heat generated by the laser driver IC 76 to the shield case 79. In this case, the heat generated by the laser driver IC 76 is transmitted to the shield case 79 through the heat transfer member, but the shield case 79 cannot secure a sufficient size for heat radiation due to the size limitation of the optical pickup 7. . Therefore, it is necessary to further transfer the heat transmitted to the shield case 79 to the optical pickup housing 71.

However, as described above, the laser diode 74 is connected and fixed to the laser diode fixing member 75 interposed between the shield case 79 and the optical pickup housing 71. The laser diode 74 is also a heat generating component, and the heat transmitted from the laser driver IC 76 and the heat transmitted from the laser diode 74 interfere in the laser diode fixing member 75. Also, for adjusting the optical axis of the laser diode 74, the laser diode fixing member 7 to which the laser diode 74 is attached is attached.
5 is attached to the optical pickup housing 71 with its position adjusted during assembly. For this reason, an adhesive layer or an air layer having a low thermal conductivity is interposed at the joint between the laser diode fixing member 75 and the optical pickup housing 71. Due to these factors, in the conventional disk device 1, the heat generated by the laser driver IC 76 cannot be efficiently radiated to the optical pickup housing, and the temperature of the laser driver IC 76 locally increases.

The present invention is to improve the heat radiation of the optical pickup 7 provided with the heat-generating component in such a disk device, and to transfer the heat from the driver IC to the housing or the housing mounted in contact with the driver IC. The heat is conducted to the housing via a heat conductive member attached to the housing.

In the embodiment of the present invention, the heat generated by the laser driver IC 76 can be transferred efficiently to the optical pickup housing 71 having a high heat capacity and high thermal conductivity. The configuration will be described with reference to FIGS.

FIG. 2 is a perspective view showing an optical pickup section of the disk device according to the embodiment of the present invention. FIG. 2 (a)
2 is a perspective view of an optical pickup 7 having a heat dissipation structure according to an embodiment of the present invention, and FIG. 2B is an enlarged perspective view of a portion A in FIG. . FIG. 3 is a cross-sectional view schematically showing the structure of the optical pickup unit having the heat radiation structure shown in FIG. FIG. 4 is a graph showing the relationship between the heat transfer cross-sectional area ratio from the laser driver IC to the optical pickup housing and the temperature of the laser driver IC mold during operation. FIG. 5 is a sectional view schematically showing the structure of an optical pickup section according to a modification of the embodiment shown in FIG. FIG.
FIG. 13 is a cross-sectional view of a laser driver IC mounting portion of an optical pickup unit according to still another modification of the embodiment shown in FIG. 1. FIG.
FIG. 7 is a cross-sectional view of a laser driver IC mounting portion of an optical pickup unit according to still another modification of the embodiment shown in FIG.
In the figure, arrows indicate the flow of heat from the laser driver IC 76.

The basic structure of the optical pickup 7 of this embodiment is the same as that shown in FIG. 8A, but has the following two features.

(1) A groove, a notch or a step is provided on the lower surface of the housing 71 near the mounting portion of the laser diode 74 of the optical pickup 7, and the laser driver IC 76
Is installed. Although the attachment is not explicitly indicated by a reference numeral, it is connected and fixed on the flexible substrate 9. In this embodiment, the side of the surface of the IC on which the laser driver IC 76 is mounted, and the side opposite to the surface of the substrate on which the IC is mounted, are covered with the shield plate 77 serving also as the elastic member. At this time, the laser driver IC 76 was directly connected to the flexible printed wiring board 9 by soldering, so that the laser driver IC 76 had flexibility in the installation direction. Also, the lower surface of the attached member does not protrude from the lower surface of the optical pickup housing 71.

(2) The surface side of the mold portion of the laser driver IC 76 is connected and fixed to the housing 71 of the optical pickup directly or via a heat conducting member 792. That is, the heat generated from the driver IC is transferred from the molded portion to the housing 71.
Alternatively, the heat is transmitted to the heat conductive member 792 having elasticity, and further transmitted to the side of the housing having a larger volume and a larger area for conducting heat to be dissipated.

By adopting the configuration shown in (1), the height of the optical pickup 7 can be reduced. When the optical pickup housing 71 is made of, for example, a conductive member, the optical pickup housing 71 itself functions as a shield case. By doing so, the laser driver IC 7
Shield plate 7 for blocking electromagnetic noise radiated from 6
7 can be only the lower surface, and the shape of the shield plate 77 can be simplified.

In this embodiment, the position of the groove or the step is provided on the lower surface side of the optical pickup housing 71, but the direction is not particularly limited.
1 may be provided on the top and side surfaces.

In the configuration (2), the heat transfer area can be increased, and the number of members interposed between the laser driver IC 76 as a heat source and the optical pickup housing 71 is small. Becomes smaller. Further, the flow of heat from another heat source such as the laser diode 74 between the heat radiation paths is reduced. Therefore, efficient heat radiation from the laser driver IC 74 to the optical pickup housing 71 can be achieved, and the temperature of the laser driver IC 76 can be reduced.

Regarding the following (2), a laser driver IC
A specific connection method between the optical pickup 76 and the optical pickup housing 71 will be described.

FIG. 4 shows the relationship between the heat transfer cross-sectional area ratio from the laser driver IC 76 to the optical pickup housing and the temperature of the mold surface of the laser driver IC 76 during operation. Here, the heat transfer cross-sectional area ratio is defined as the ratio of the contact area to the area of the upper surface of the mold portion of the laser driver IC 76 or the ratio of an arbitrary cross-sectional area parallel to the mold surface of the heat conducting member.

As shown in the figure, the above-mentioned relationship means that as the heat transfer cross-sectional area ratio increases (closes to 1), the heat radiation efficiency to the optical pickup housing 71 is improved, and the temperature of the mold portion of the laser driver IC 76 is reduced. Is possible. As the output of the laser increases, the amount of heat generated by the laser driver IC increases. Therefore, in order to keep the temperature of the laser driver IC 76 below the operation guarantee temperature set in order to prevent the malfunction of the circuit system, it is necessary to increase the temperature above the intersection of the mold temperature curve shown in FIG. It is necessary to set the thermal cross section ratio. From the figure, it can be seen that in the case of a general disk device, it is preferable to set the value to about 0.5 or more.

On the other hand, as the number of members interposed in the heat radiation path increases, the heat radiation efficiency from the laser driver IC 76 decreases due to contact thermal resistance between the members. In particular, considering variations in actual parts and variations in mounting conditions in the mounting process, the laser driver IC 76
It is better that the number of heat radiation members interposed between the optical pickup housing 71 and the optical pickup housing 71 is small.

Therefore, as an embodiment of the present invention, a conductive elastic member is used instead of the shield plate 77 attached to the lower surface side of the laser driver IC 76 as shown in FIG. In this case, the laser driver IC 76 can tightly fix the upper surface of the molded portion of the laser driver IC 76 to the optical pickup housing 71 by the elastic member by the elastic member. Further, since a conductive material is used for the elastic member, it is not necessary to newly provide a shield plate. That is, the shield plate 77 can be shared.

As a modification of the first embodiment, as shown in FIG. 5, the shield plate 77 attached from the lower surface of the laser driver IC 76 and the optical pickup housing 71 may be fixed by fastening means 771 such as screws.

As another modified example, when the optical pickup casing 71 is made of the same material as the molded part of the laser driver IC 76, as shown in FIG. May be press-fitted into the groove provided in the groove and fixed. In this case, the area in close contact with the optical pickup housing 71 can be increased without the interposition of the adhesive layer. Further, a new member is not required for fixing the laser driver IC 76, and the cost can be reduced.

As shown in FIG. 7, a first heat conductive member 792 may be provided between the laser driver IC 74 and the optical pickup housing 71. As a result, the upper surface of the mold portion of the laser driver IC 76 and the optical pickup housing 7
1 can be improved, and the mold portion of the laser driver IC 76 can be prevented from being damaged. Further, apart from this embodiment, a laser driver IC
The upper surface of the mold section 76 and the optical pickup housing 71 may be connected and fixed using an adhesive having good thermal conductivity or a double-sided tape.

Although the present embodiment refers to a laser driver IC, the present invention can be easily applied to all electronic components which are mounted on the optical pickup 7 and generate heat.

As described above, according to the above embodiment, the upper surface of the mold section of the laser driver IC is connected and fixed to the optical pickup housing directly or via a heat conducting member. In addition, a large heat transfer area can be secured without using a member having low thermal conductivity such as a flexible printed circuit board. Further, since no other heat source such as a laser diode is interposed between the heat radiating paths, the heat of the laser driver IC can be smoothly radiated.

Therefore, the temperature of the laser driver IC can be suppressed below the operation guarantee temperature, and the laser circuit can be stabilized.

[0046]

As described above, according to the present invention, it is possible to efficiently dissipate heat from the laser driver IC and to provide a highly reliable disk device.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing the structure of a disk device according to an embodiment of the present invention.

FIG. 2 is an enlarged perspective view showing an optical pickup unit having the heat dissipation structure of the disk device shown in FIG.

FIG. 3 is a cross-sectional view schematically showing the structure of an optical pickup unit having the heat radiation structure shown in FIG.

FIG. 4 is a graph showing a relationship between a heat transfer cross-sectional area ratio from a laser driver IC to an optical pickup housing and a temperature of a laser driver IC mold portion during operation.

FIG. 5 is a cross-sectional view schematically showing the structure of an optical pickup unit according to a modification of the embodiment shown in FIG.

FIG. 6 is a sectional view of a laser driver IC mounting portion of an optical pickup unit according to still another modification of the embodiment shown in FIG.

FIG. 7 is a sectional view of a laser driver IC mounting portion of an optical pickup unit according to still another modification of the embodiment shown in FIG.

FIG. 8 is a perspective view schematically showing a structure of an optical pickup unit mounted on a conventional disk device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Disk device, 2 ... Top cover, 3 ... Front cover, 4 ... Disk tray, 5 ... Spindle motor, 6 ... Unit mechanical chassis, 7 ... Optical pickup,
71: Optical pickup housing, 72: Actuator,
73 ... objective lens, 74 ... laser diode, 75 ...
.Laser diode fixing member 76 laser driver I
C, 77 ... shield plate, 771 ... fastening means, 78 ...
Pickup circuit board, 791 ... shield case,
792: heat transfer sheet, 8: bottom cover, 9: flexible printed wiring board, 10: guide rail, 1
1 ... circuit board, 12 ... device body.

Continuation of the front page (72) Inventor Yoshiaki Yamauchi 502, Kandachicho, Tsuchiura-shi, Ibaraki Pref. Machinery Research Laboratory, Hitachi, Ltd. (72) Inventor Masayoshi Watanabe 1 Kitano, Makino, Mizusawa City, Iwate Prefecture Inside Hitachi Media Electronics Co., Ltd. 5D119 AA33 FA32 FA33 MA01

Claims (1)

[Claims] A rotating mechanism for rotating a disk serving as a recording medium; an optical pickup for recording or reproducing information on or from the disk; a driving mechanism for moving the optical pickup in a radial direction of the disk; In a disk drive comprising: a laser diode for emitting laser light provided in the optical pickup; and a laser driver IC for adjusting driving of the laser diode, the laser driver IC attached to a flexible printed circuit board and the optical pickup A disk device in which members constituting a housing are connected.