JP4159279B2 - Disk drive device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a disk drive device that suppresses surface vibration, deformation, and tilt that occur when a disk rotates, and in particular, a CD-ROM, CD-R, CD-RW, DVD, DVD-ROM, DVD-RW, and the like. The present invention relates to a high-speed rotating disk drive device that uses laser light for reading and writing data.
[0002]
[Prior art]
In recent years, demands for speeding up CD-ROMs, DVD drives and the like have become stricter, and high-speed driving reaching a critical rotational speed has been performed. The critical rotational speed is a rotational speed in which one of the natural frequencies of the backward vibration that proceeds in the direction opposite to the rotational direction of the disk becomes 0, and the disk drifts slowly when viewed from the housing side. Looks like. The disk is generally unstable at this rotational speed, and is easily deformed and vibrated easily by the influence of disturbance. In order to avoid defects, it is desirable to avoid the use at critical rotational speeds.
[0003]
However, in a CD-ROM drive that pursues high speed, it is generally necessary to vary the rotational speed in accordance with the access position, so that it is difficult to use it with the critical rotational speed removed. For this reason, it is necessary to take measures against deformation and vibration accompanying rotation around the critical rotation speed. In addition, the medium itself has been changed from a CD-ROM, which has a relatively low recording density, to a DVD-ROM, etc., which requires a higher density and higher reading accuracy. Requests are becoming more demanding. In addition, in recent years, the speed of disk devices capable of writing data, such as CD-R and DVD-RW, has been increased. In writing operations, countermeasures are indispensable because adverse effects such as deformation and vibration are far more serious than reading.
[0004]
Japanese Patent Application Laid-Open No. 2000-57666 discloses a technique that pays attention to the fact that the air flow generated by the rotation of the disk causes vibration. In other words, the top and bottom surfaces of the disc are sandwiched between windage reduction walls with a narrow gap of several mm or less, and a wall is also provided at the end of the disc, so that Reduce the noise and vibration by minimizing the air vortex generated. However, with this method, the structure is slightly complicated, and a notch for the spindle motor and pickup is required on the lower surface side of the disk. Therefore, turbulent flow and pressure nonuniformity occur in this notch. Was the cause of vibration.
[0005]
[Problems to be solved by the invention]
Stable data reading and writing are realized by devising the internal structure of a CD-ROM, DVD drive, or the like. In particular, an effective technique is provided even under conditions of high-speed rotation around the critical rotation speed, at which it is most difficult to read and write stable signals.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, according to the first aspect of the present invention, at least a polycarbonate resin disk having a radius of 6 (cm) is held and rotated in the housing, and a signal is read from or written to the disk. It has a pickup portion for reading of the signal from the disk, or a disk drive device comprising at least 6000 (rpm) between the upper and lower limits of the rotational speed range for signal writing to the disk, pickups 12 (cm)>a> 6√2 (cm) with respect to the width a of the disk in the circumferential direction of the disk.
[0009]
According to the second aspect of the present invention, at least a polycarbonate resin disk having a radius of 6 (cm) is held and rotated in the housing, a pickup unit for reading or writing signals on the disk, and the disk It has a surface with an adjacent pickup section, and has a notch or groove provided on the surface for moving the pickup section in the radial direction, and reads out signals from the disk or signals to the disk a disk drive device comprising at least 6000 (rpm) between the upper and lower limit engine speed range for writing, the width L of the lack Ri switching, for 12 (cm)>L> 6√2 (cm) ·· ... A disk drive device characterized by satisfying Formula 2 is provided.
[0010]
According to a third aspect of the present invention, there is provided the disk drive device according to the first or second aspect, wherein the pickup section comprises a pickup main body and a pickup cover.
[0011]
According to a fourth aspect of the present invention, there is provided the disk drive device according to any one of the first to third aspects, wherein at least the disk-facing surface of the pickup section is a streamlined curved surface.
[0012]
In the invention of claim 5 , the disk drive device according to claim 1 , 3 or 4 satisfies the following expression 3 when a radial width of the pickup portion is b: a> b A disk drive device is provided.
[0013]
Hereinafter, the reason why the problem is solved by these means will be described.
[0014]
The pressure that the disk receives from the atmosphere is constant and uniform everywhere on the disk when stationary, but a complex force is applied during rotation. This is because the air flow caused by the rotation of the disk becomes a turbulent flow and interacts with the components inside the housing to create a non-uniform pressure. The deformation and vibration of the disk due to this pressure non-uniformity appear particularly strongly at the critical rotational speed, causing serious adverse effects such as frequent write errors.
[0015]
In order to reduce the adverse effects of pressure non-uniformity, the air flow on the disk surface may be adjusted to smooth the pressure distribution on the disk surface. The method disclosed in Japanese Patent Laid-Open No. 2000-57666 is an invention based on this technical idea. However, the effect is limited because a notch must be provided in the windage reduction wall on the lower surface side of the disk. In particular, when applied to high-speed rotation conditions near the critical rotation speed at which deformation and displacement easily expand, the adverse effect of this defect appears strongly and is not necessarily practical.
[0016]
On the other hand, the present invention does not intend to make the pressure distribution simple. Large deformation that becomes a problem in the critical rotational speed can be suppressed without making the pressure distribution completely uniform. The present invention was made by finding the conditions.
[0017]
In order to understand the conditions that the pressure distribution should satisfy, it is necessary to understand the cause of the large deformation at the critical rotational speed. The wave of deformation that travels in the circumferential direction of the disk must connect smoothly with itself at one round, so there is a limit to the wavelengths that can exist stably. This is called a mode, and there is something like FIG. In this figure, + is a portion displaced upward with respect to the paper surface,-is a portion displaced downward, and a straight line passing through the center of the disk is a collection of points where the displacement is zero. The frequency corresponding to each vibration mode is referred to as a natural frequency.
[0018]
In FIG. 1, for example, (0, 3) mode is displayed indicating that three lines of zero displacement cross. 0 in the (0, 3) mode represents a vibration mode in the radial direction. At a frequency much higher than the driving speed of a normal CD-ROM, a circle with zero displacement appears due to radial vibration. Depending on the number of circles with zero displacement, (1,3) mode or (2,3) mode appears. However, in a normal CD or DVD drive, such an ultra-high speed rotation has not been put to practical use so far.
[0019]
Normally, a zero displacement line is called a nodal diameter when it is a diameter line, and a nodal circle when it is a circumferential line. In this specification, it is described following the notation. However, a node is a term for an antinode of a standing wave, and therefore, it is an error to use it in the description of the present invention. This is because the vibration excited on the disk at the critical rotational speed is not a standing wave but a traveling wave, as will be described below. However, this term is used because the word verse is common.
[0020]
The disk deformation wave traveling in the circumferential direction on the disk is generated even if the rotation speed is not critical. If an external force is repeatedly applied to the disk at a timing corresponding to the natural frequency, the amplitude of the deformed wave will increase. However, it goes without saying that it is usually impossible for an external force to act on the deformation wave generated on the disk rotating at high speed from the housing in time.
[0021]
However, at the critical rotation speed, the speed of the deformation wave that travels in the direction opposite to the rotation direction on the disk coincides with the rotation speed of the disk, so that the deformation wave of the disk appears to be stationary from the housing side. . In this state, it is not necessary to match the timing. If there is a ledge or dent fixed in the housing, the decrease or increase in pressure that occurs will automatically apply a time-matched force to the disk and excite large deformations. The deformation wave excited in this way is a traveling wave and not a standing wave. If it is a standing wave, it vibrates in the vertical direction of the disk at its antinode, so it cannot be excited by a fixed ledge.
[0022]
The large deformation wave that becomes a problem at the critical rotation speed is not a standing wave, so if you apply a force that moves upward at a part of the disk, it will move downward in the adjacent antiphase region across the node. And Therefore, if there is a structure in the drive that applies an upward force to the disk, if an element that applies an upward force is placed next to it, the generation of large deformation waves at the critical rotational speed will occur. Can be prevented.
[0023]
With a general CD-ROM drive device or DVD drive device in mind, a fixed bulge or dent that affects the generation of the deformation wave of the disc causes the pickup portion and the pickup portion to move in the radial direction. It is a groove provided for this purpose.
[0024]
Under the technical background as described above, the width of the pickups parts per (0,2) deformation wave modes, there is a concept of limited constant so as to have a desired width. As shown in FIG. 1, in the (0, 2) mode, the disk is divided into four equal parts by the node diameter, and the width of one area is set as the lower limit a of the width of the pickup section. In FIG. 5, a is a chord of the arc D. Based on elementary geometry knowledge about the length of the chord, it can be seen that the lower limit of the pickup section at this time is twice the root (= 1.41421356) of the radius R of the disk, and the formula (i) is obtained. For other higher order vibrations, the width of the individual regions divided by the node diameter is smaller than in the (0,2) mode. Therefore, for all higher-order natural vibrations in (0, 2) mode and higher, force is also applied to the adjacent antiphase region across the node, and deformation and vibration at the critical rotational speed are suppressed. The
[0025]
In the first aspect of the present invention, the natural vibration in question is identified, and the force of the pickup unit is applied so that a force is applied to the adjacent antiphase region across the nodes for the minimum frequency among the natural vibrations. The width is determined. As already described, since the minimum value a of the width is the length of the chord of the arc D in FIG. 5, it can be calculated by elementary geometry knowledge, and Equation 1 is obtained. Thereby, an antiphase force is applied to a specific range of natural vibration, and deformation and vibration at the critical rotational speed are suppressed.
[0026]
Further, there is a concept of the pickup unit width of the groove to move in the radial direction, to limit the constant so as to be large enough. As a result, antiphase forces are applied to higher-order natural vibrations in the (0, 2) mode or higher, and deformation and vibration at the critical rotational speed are suppressed. As shown in FIG. 1, in the (0, 2) mode, the disk is divided into four equal parts by the node diameter, and the width L of one region is set as the lower limit of the groove width. In FIG. 5, L is a chord of the arc D. From elementary geometry knowledge about the chord length, it can be seen that the lower limit of the groove at this time is twice the root of the radius R of the disk (= 1.41421356), and the formula (ii) is obtained. For other higher order vibrations, the width of the individual regions divided by the node diameter is smaller than in the (0,2) mode. Therefore, for all higher-order natural vibrations in (0, 2) mode and higher, a force that cancels the generation of waves is applied to the adjacent antiphase region across the node, and deformation at the critical rotational speed And vibration is suppressed.
[0027]
In the second aspect of the invention, the natural vibration in question is specified, and the width of the groove is determined so that an antiphase force is applied to the natural vibration of the minimum frequency. The minimum value L of the width can be calculated based on elementary geometry knowledge, and conditional expression 2 is obtained. Thereby, an antiphase force is applied to a specific range of natural vibration, and deformation and vibration at the critical rotational speed are suppressed.
[0028]
In the invention described in claim 3 , it is defined that the pickup section is composed of a pickup body and a pickup cover. As a result, the external dimensions of the pickup can be freely selected, and it becomes easy to configure a pickup unit having a large size or a pickup unit having a different shape as required.
[0029]
In the invention described in claim 4 , since the upper surface of the pickup portion is a streamlined type having a low air resistance, the generated air resistance itself is reduced, and the deformation and vibration of the disk are suppressed.
[0030]
In the invention described in claim 5 , by making the radial direction b size of the pickup portion less than or equal to the circumferential size a, the generated pressure and loss can be reduced, and the deformation and vibration of the disc are suppressed.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
(First Embodiment) A first embodiment of the present invention will be described below with reference to FIGS. FIG. 2 schematically shows the positional relationship between a groove and deformation excited by a disk at a critical rotational speed in a conventional drive. The display of the components of the disk drive that are not directly related to the present invention, such as the power supply device, is omitted. Since the air pressure is relatively increased above the groove, the disk receives an upward force F1. The disc receiving the force induces a deformation wave in which the region A immediately above the groove is a mountain, and is displaced upward by d1. On the other hand, in the regions B and C adjacent to A, the phase of the deformation wave is the opposite region, so that it is displaced downward by d2 and d3. The size of d2 and d3 is equal to d1 if there is no disturbance factor. On the other hand, FIG. 3 shows a case where the method of the present invention is used. Although the air pressure rises above the groove and the deformation wave is induced such that the region A directly above the groove becomes a mountain, in this example, the upward force also extends to the regions B and C. If no upward force is applied, it should try to be displaced by B and C as in FIG. 2, but because the groove is wide, a part of it is erased, resulting in d5, The displacement amounts of d6 and d7 are smaller than those of the conventional example in FIG. 2 even if other conditions are the same.
[0032]
(Second Embodiment) Next, a second embodiment will be described with reference to FIG. In FIG. 4, the groove 18 for moving the pickup portion has a width L that exceeds 1.4142 times the disk radius R by the method of the present invention. In addition, the circumferential length a of the pickup section 14 is set to a size exceeding 1.4142 times the disk radius R, and the pickup section is composed of a pickup and a pickup cover. Is made smaller than the circumferential length a.
[0033]
In addition to making the groove width L large, by attaching a pickup cover to the pickup to form a wide pickup part, the force for eliminating the deformation of the disc described in FIG. Deformation is more effectively suppressed. Further, by suppressing the radial length b of the pickup portion to be smaller than the circumferential length, unnecessary air resistance is reduced and vibration is further reduced.
[0034]
(Third Embodiment) Next, a third embodiment will be described with reference to FIG. In the figure, the method according to claims 5 and 6 of the present invention is applied, and the pickup section 24 includes a pickup 25 and a pickup cover 26. The surface of the pickup cover 26 that faces the disk has a substantially streamlined cross section. Thereby, in the pickup unit, the flow of air is adjusted, and unnecessary noise and vibration are suppressed.
[0035]
Next, matters common to the first and second embodiments will be described. In order to obtain a favorable effect by widening, there are conditions on the size of the groove and the pickup part. This limitation is illustrated in FIG. FIG. 5 is a plan view of the disk drive as viewed from directly above (clamper side in the case of a CD-ROM), and shows a state in which (0, 3) mode vibration is induced in the disk. In order for the groove to act to suppress this vibration, in FIG. 5, the groove must extend beyond the region A and extend to the regions B and C. Therefore, the lower limit of the groove width is the horizontal width of the region A, that is, the length of the chord of the arc D, and can be calculated by elementary knowledge of geometry. This condition does not change even if the groove changes to the pickup cover.
[0036]
Since there are a plurality of critical rotational speeds depending on the vibration mode, the length of the chord of the arc D also differs depending on the rotational speed of interest. For this reason, depending on the rotational speed range used in the operation of the disk drive, the critical rotational speed that is a problem is determined in advance, and if there are a plurality of them, the critical rotational speed that requires the largest groove width is used. Must design the drive. For example, in the case of a disk made of polycarbonate resin having a diameter of 12 cm and a thickness of the current standard, the critical rotational speed corresponding to the natural vibration of (0,2) mode is about 6000 rpm, and about 7400 rpm in (0,3) mode. , (0,4) mode is about 9400 rpm.
[0037]
In general, the higher the critical rotational speed, the larger the number of corresponding node diameters and the shorter the chord of the arc D. Therefore, check the minimum critical rotational speed within the operating rotational speed range and set the corresponding string length. The width of the pick-up part and the groove must be decided so as to exceed.
[0038]
In the case where the critical rotational speed is not included in the rotational speed range to be used, the consideration as in the present invention is not necessarily required. However, CDs and DVDs are basically removable disks, and if the material is changed due to changes in standards, the critical rotational speed on the disk side will change, even if the drive itself does not change, It may be necessary to operate at a critical speed.
[0039]
In order to avoid such a situation, it is desirable to follow the technical idea of the present invention in the design of the drive even if it deviates from the critical rotational speed for the time being. In other words, considering that the critical speed may change if the disc material and design are different, even if the rotational speed is out of the rotational speed range used for drive operation, Measures should be taken by the method of claim 1 or claim 2 of the invention. Alternatively, if the method described in paragraphs 0024 and 0026 is adopted, an effect can be expected for all critical rotational speeds having a frequency of (0, 2) mode or higher. However, since this method is severely limited in the size of the pickup portion and the groove portion, it is necessary to appropriately use the method of claims 1 and 2 in consideration of ease of design.
[0040]
The embodiment of the present invention is not limited to the contents described here. The disc tray is not an essential component, and the width of the pickup portion may be larger than the groove portion. Further, the spindle motor, the clamper, and the like omitted in the drawing may be arbitrarily selected as long as they do not affect the essence of the present invention.
[0041]
Furthermore, the technical idea of the present invention is not necessarily exhausted by the methods recited in the claims. In order to suppress the deformation of the disk, it is not impossible to adjust the shape of the space in the housing so that an antiphase force is applied to the deformation if a more advanced mathematical method is used. However, in practical terms, an effect can be obtained if the size is limited to the most basic elements such as the pickup portion and the groove notch without taking such trouble. For actual production, such a concise and essential limitation is preferable, and the engineering value is also high. The present invention has been made based on such an idea.
[0042]
【The invention's effect】
According to the present invention, deformation, tilt, and vibration generated in the disc main body are suppressed by a relatively simple design device such as a change in the size of the pickup unit and the groove in which the pickup unit moves. In particular, deformation, inclination, vibration, and the like can be effectively suppressed under high-speed rotation conditions including a critical rotation speed.
[Brief description of the drawings]
FIG. 1 is an explanatory view of a vibration mode of a disk. FIG. 2 is an explanatory view explaining deformation of a disk in a conventional disk drive. FIG. 3 is an explanatory view explaining deformation of a disk in a disk drive according to the present invention. 4 is a perspective view for explaining the structure of a disk drive according to the present invention. FIG. 5 is an explanatory diagram for explaining the basis of the limiting conditions of the present invention. FIG.
1,13,23 Disc 2 Wide groove or notch 3 in the present invention 3 Wide pickup section 4 in the present invention Groove or notch A in the prior art A Adjacent to areas B and CA that are deformed upward on the disc, Area on the disk that deforms downward
F1 Upward force applied to the disk near the groove in the prior art
F5, F6, F7 In the present invention, upward force applied to the disk near the groove
d1 Displacement of A due to upward force in conventional technology
d2, d3 Downward displacement in B and C, which occurs according to the displacement of A in the prior art
d5 A displacement amount in the present invention
d6, d7 In the present invention, the downward displacement at the B and C portions that occurs in accordance with the displacement of A R The radius of the disk a The circumferential length of the pickup portion b The radial length L of the pickup portion The width of the notch D The arc length of the area delimited by the nodal diameter θ The central angle of the area delimited by the nodal diameter 11, 21 Drive housing 14, 24 Pickup unit 15, 25 Pickup 16, 26 Pickup cover 17, 27 Guide 18 Wide groove or notch 22 disc tray in the present invention

Claims (5)

The housing has a turntable for holding and rotating at least a polycarbonate resin disk having a radius of 6 (cm), and a pickup unit for reading or writing signals on the disk, and reading signals from the disk, or, a disk drive device comprising at least 6000 (rpm) between the upper and lower limits of the rotational speed range for signal writing to the disk, pickups unit disk circumferential width a of about 12 (cm) >A> 6√2 (cm) ... A disk drive device satisfying Formula 1. A turntable that holds and rotates at least a polycarbonate resin disc having a radius of 6 (cm) in the housing, a pickup unit for reading or writing signals on the disc, and a surface provided with a pickup unit adjacent to the disc On the surface of which the pick-up part has a notch or groove provided to move in the radial direction, and reads the signal from the disk or writes the signal to the disk. a disk drive device comprising at least 6000 (rpm) between the upper and lower limits of the width L of the lack Ri switching, for 12 (cm)>L> 6√2 (cm) satisfies ..... equation 2 A disk drive device characterized in that: 3. The disk drive device according to claim 1, wherein the pickup unit includes a pickup body and a pickup cover. The disk drive device according to claim 1, wherein at least a disk-facing surface of the pickup unit is formed of a streamlined curved surface. 5. The disk drive device according to claim 1, wherein when the radial width of the pickup portion is b, a> b... Formula 3 is satisfied. .

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