U.S. patent application number 10/659382 was filed with the patent office on 2004-03-11 for device for supporting an optical disc driving device.
This patent application is currently assigned to Pioneer Electronic Corporation. Invention is credited to Hoshinaka, Eiji, Ishii, Katsumi, Kiyomiya, Masaaki, Takagi, Keiichi.
Application Number | 20040047277 10/659382 |
Document ID | / |
Family ID | 15375817 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040047277 |
Kind Code |
A1 |
Kiyomiya, Masaaki ; et
al. |
March 11, 2004 |
Device for supporting an optical disc driving device
Abstract
A main frame is supported in a box, by first elastic members. An
optical disc driving device is mounted on the main frame. A
sub-frame is supported on the main frame by second elastic
members.
Inventors: |
Kiyomiya, Masaaki;
(Saitama-ken, JP) ; Takagi, Keiichi; (Saitama-ken,
JP) ; Hoshinaka, Eiji; (Saitama-ken, JP) ;
Ishii, Katsumi; (Saitama-ken, JP) |
Correspondence
Address: |
ARENT FOX KINTNER PLOTKIN & KAHN, PLLC
SUITE 400
1050 CONNECTICUT AVENUE, N.W.
WASHINGTON
DC
20036-5339
US
|
Assignee: |
Pioneer Electronic
Corporation
|
Family ID: |
15375817 |
Appl. No.: |
10/659382 |
Filed: |
September 11, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10659382 |
Sep 11, 2003 |
|
|
|
09306572 |
May 6, 1999 |
|
|
|
Current U.S.
Class: |
720/651 ;
369/254; G9B/33.024; G9B/7.056 |
Current CPC
Class: |
G11B 33/08 20130101;
F16F 7/104 20130101; G11B 7/08582 20130101; G11B 7/0946
20130101 |
Class at
Publication: |
369/247 ;
369/254 |
International
Class: |
G11B 007/00 |
Foreign Application Data
Date |
Code |
Application Number |
May 11, 1998 |
JP |
10-145031 |
Claims
What is claimed is
1. A supporting mechanism for an optical disc driving device,
comprising: a box; a main frame provided in the box; first elastic
members elastically connecting the main frame to the box; an
optical disc driving device mounted on the main frame, the optical
disc driving device including a spindle motor and a turntable
securely mounted on a rotating shaft of the spindle motor; a
sub-frame; and second elastic members elastically connecting the
sub-frame to the main frame.
2. The mechanism according to claim 1 wherein the mass of the
sub-frame is 1/10-1/3 of the mass of the main frame.
3. The mechanism according to claim 1 wherein the sub-frame has a
shape of a flat plate.
4. The mechanism according to claim 1 wherein the sub-frame is made
of metal.
5. The mechanism according to claim 1 wherein the second elastic
member is made of either of rubber and plastic.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a supporting mechanism for
an optical disc driving device.
[0002] In an optical disc player, there is a limit to ability to
accurately control the trucking servo and focusing servo against
the external vibration applied from the outside and the internal
vibration. In particular, in the case of the computer disc player,
the vibration generated inside the player at high speed reading
becomes problem.
[0003] FIG. 9 shows a device for damping the external vibration. As
shown in the drawing, a main frame 4 is mounted on a box 1 by three
elastic members 2 at corners. On the main frame 4, a turntable 6
and a spindle motor (not shown) for rotating the turntable are
provided.
[0004] A pickup 5 for reading information recorded in a disc is
slidably mounted on a pair of guide rails 11a and 11b. The pickup
engages with a driving screw 8 so as to be moved in a radial
direction of a disc loaded on the turntable 6. The driving screw 8
is connected to a rotating shaft of a stepping motor 9 so that the
pickup 5 is moved along the guide rails 11a and 11b by the rotation
of the driving screw 8.
[0005] In operation, the main frame 4 including various members
mounted therein are vibrated by imbalance of the disc and others
when the disc is rotated by the spindle motor. In particular, at
high speed reading of information, the rotating speed of the disc
is increased, and hence the vibration is accordingly increased.
[0006] Since the main frame 4 is mounted in the box 1 through the
elastic members 2, the vibration transmitted from the main frame 4
to the box 1 is reduced. The external vibration transmitted to the
box 1 is damped by the elastic members 2. Therefore, the quantity
of vibration transmitted to the main frame 4 is reduced.
[0007] FIG. 10 shows a vibration model of the structure shown in
FIG. 9, where the elastic member 2 has a stiffness of k and a
coefficient of loss (viscosity) of .mu., and a main frame device 20
has a mass of m.
[0008] There is a following relationship if external force is F and
displacement of the main frame device is x,
md2x/dt2=F-.mu.dx/dt-kx
[0009] If the equation of motion is solved under a condition, the
relationship between the resonance frequency f.sub.0 and the mass m
can be obtained. The resonance frequency can be expressed as
follows.
f.sub.0=1/(2.pi.)*(k/m)1/2
[0010] The ratio of the resonance frequency f.sub.1 for the box 1
of mass m.sub.1 to the resonance frequency f.sub.0 for the main
frame device 20 of mass m.sub.0 is follows.
f.sub.0/f.sub.1=(m.sub.1/m.sub.0)1/2
[0011] If the mass m.sub.0 is multiplied by 2, the resonance
frequency f.sub.1 becomes about 0.7 f.sub.1.
[0012] Thus, the transmissibility can be expressed by the mass and
the stiffness and the coefficient of loss of the elastic member. It
is possible to obtain a desired transmissibility by selecting the
mass, stiffness and coefficient of loss.
[0013] From the foregoing, it will be understood that in order to
interrupt the transmittance of the external vibration to the main
frame device 20, it is effective to reduce the stiffness of the
elastic member 2 and to increase the mass of the main frame device
supported by the elastic member 2.
[0014] However, it is desirable to reduce the size of the device.
Since it is difficult to increase the mass of the main frame device
20, the stiffness of the elastic member 2 is reduced
heretofore.
[0015] Thus, the external vibration can be damped.
[0016] However, the own vibration of the main frame 4 caused by the
imbalance of the disc and others can not be damped since the
stiffness of elastic member is reduced.
[0017] If the main frame vibrates, the pickup 5 mounted in the main
frame 4 through guide rails 11a and 11b is vibrated. If the pickup
vibrates, the servo operation for controlling the information
reading operation may be disturbed. As a result, the information
can not be accurately read out.
SUMMARY OF THE INVENTION
[0018] An object of the present invention is to provide a device
which may damp an internal vibration caused by operation of driving
mechanisms in the device.
[0019] According to the present invention, there is provided a
supporting mechanism for an optical disc driving device,
comprising, a box, a main frame provided in the box, first elastic
members elastically connecting the main frame to the box, an
optical disc driving device mounted on the main frame, the optical
disc driving device including a spindle motor and a turntable
securely mounted on a rotating shaft of the spindle motor, a
sub-frame, and second elastic members elastically connecting the
sub-frame to the main frame.
[0020] These and other objects and features of the present
invention will become more apparent from the following detailed
description with reference to the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS
[0021] FIG. 1 is a plan view showing an optical disc reproducing
device according to the present invention;
[0022] FIG. 2 is a sectional view of the device;
[0023] FIG. 3 is an illustration of a vibration model of the
device;
[0024] FIGS. 4 to 8 are graphs showing a vibration characteristic
of the device;
[0025] FIG. 9 is a plan view showing a conventional disc
reproducing device; and
[0026] FIG. 10 is an illustration of a vibration model of the
conventional device.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] Referring to FIGS. 1 and 2, the same parts as FIG. 9 are
identified with the same reference numerals as FIG. 9 and the
explanation for the parts will be omitted.
[0028] In the box 1, the main frame 4 is elastically supported by
the first elastic members 2. A sub-frame 32 is mounted on the main
frame 4 through second elastic members 31.
[0029] The turntable 6 for rotating an optical disc 10 is securely
mounted on a rotating shaft of a spindle motor 7 which is mounted
on the main frame 4.
[0030] The pickup 5 is slidably mounted on the guide rails 11a and
11b mounted on the main frame and engaged with the driving screw 8.
The driving screw 8 is connected to the stepping motor 9.
[0031] The rotation of the rotating shaft of the stepping motor 9
causes the screw 8 to rotate, which in turn moves the pickup in the
radial direction of the disc 10. The moving direction of the pickup
is determined by the rotating direction of the rotating shaft of
the stepping motor 9.
[0032] When the external vibration is applied to the box 1, the
external vibration is not transmitted to the main frame 4 by the
interruption of the first elastic members 2.
[0033] When the optical disc 10 is rotated, the main frame 4 is
vibrated by the imbalance of the disc 10. The vibration is
transmitted to the sub-frame 32 through the second elastic members
31.
[0034] Therefore, the sub-frame 32 is vibrated in accordance with
the transmitting characteristic of the sub-frame 32 and the second
elastic member 31.
[0035] At a frequency sufficiently lower than the resonance
frequency of both vibration systems, the sub-frame 32 vibrates
together with the main frame 4. At a frequency sufficiently higher
than the resonance frequency, the vibration is hardly transmitted
from the main frame 4 to the sub-frame 32.
[0036] At a frequency approximately equal to the resonance
frequency, vibration is enhanced when braking is small, and the
influence of secondary resonance does not occur when the braking is
large.
[0037] On the other hand, the phase of the vibration of the
sub-frame is the same as that of the transmitted vibration at a
frequency lower than the resonance frequency, is a reverse phase at
a frequency higher than the resonance frequency, and 90 degrees
phase at the resonance frequency.
[0038] Therefore, the sub-frame 32 has vibration suppressing effect
at a frequency lower than the resonance frequency by selecting the
resonance frequency and the coefficient of loss.
[0039] FIG. 3 shows a vibration model of the disc reproducing
device of the present invention.
[0040] An equation of motion similar to the equation of motion of
FIG. 10 can be obtained from FIG. 3.
[0041] FIGS. 4-7 show results of simulations based on the model of
FIG. 3.
[0042] FIGS. 4 and 5 are results of simulations where the mass m of
the sub-frame 32 is changed at the resonance frequency of constant
120 Hz. In addition, FIGS. 4 and 5 show vibration acceleration of
the main frame device 20 and the box 1 to the rotative velocity of
the disc as the result of calculation in the conditions where the
imbalance of the disc is 0.5 g-cm and the mass of the sub-frame 32
is 10 g, 20 g and 40 g.
[0043] It will be understood from FIGS. 4 and 5 that the vibration
suppression effect is high in the range between about 4,000 and
7,000 rpm as the mass of the sub-frame increases, and that a large
mass of the main frame device 20 is effective to reduce the
acceleration of the box 1 and the main frame 4.
[0044] FIGS. 6 and 7 are results of simulations where the mass m of
the sub-frame 32 is 30 g, and the resonance frequency of the
sub-frame 32 is changed. In addition, FIGS. 4 and 5 show vibration
acceleration of the main frame device 20 and the box 1 to the
rotative velocity of the disc as the result of calculation in the
conditions where the imbalance of the disc is 0.5 g-cm and the
resonance frequency of the sub-frame 32 is 100 Hz, 110 Hz and 130
Hz.
[0045] It will be understood from FIGS. 6 and 7 that the vibration
suppression effect is high, in the condition when the rotative
velocity is set 6,000 rpm, the resonance frequency f.sub.0 is 110
Hz, and when the rotative velocity is set 7,000 rpm, fo is 130 Hz
in the range between about 4,000 and 7,000 rpm as the mass of the
sub-frame increases, and that a large mass of the main frame device
20 is effective to reduce the acceleration of the box 1 and the
main frame 4.
[0046] FIG. 8 shows measured values of the characteristic of the
vibration damping device according to the present invention, namely
FIG. 8 shows vibration acceleration of the box to the rotative
velocity of the disc when the imbalance of the disc is 0.5 g-cm. In
the graph, the mark indicates results of the present invention, and
the mark b shows results of the conventional device in which the
vibration damping device by the sub-frame is not provided.
[0047] It will be seen that the box acceleration is 0.07G at 6,000
rpm when provided with the damping device, and the box acceleration
is 0.27G when not provided with the damping device, and that
present invention has a damping effect.
[0048] Here, if the rotative velocity is R rpm, the resonance
frequency f is R/60, and hence if the rotative velocity is 6,000
rpm, the resonance frequency f is 100 Hz.
[0049] It is preferable that the weight of the sub-frame including
mounted members is 1/10-1/3 of the whole weight of the main frame
including mounted members so as to suppress the main frame at a
high speed rotation of the disc, from a point of view of the
positional limitation of respective component members.
[0050] Furthermore, it is necessary that the sub-frame is thin in
order to mount the optical reproducing device in the computer. To
this end, it is preferable that the sub-frame has a shape of a flat
plate, and that the sub-frame is made of metal from a point of view
of weight.
[0051] By disposing the surface of the sub-frame so as to be
orthogonal with the shaft of the spindle motor, the vibration
suppression effect of the sub-frame is increased.
[0052] The elastic member 2 (31) is made of rubber or plastic in
order to decrease the thickness of the device and enhance the
braking effect.
[0053] In accordance with the present invention, the external
vibration is damped by the first elastic member, thereby preventing
external vibration from transmitting to the main 5 frame, the
vibration of the sub-frame which is caused by the imbalance of the
disc and others is suppressed by the damping effect of the
composition of the sub-frame and the second elastic member. Thus,
it is possible to accurately read information recorded on the
optical disc at a high speed rotation of the disc.
[0054] While the invention has been described in conjunction with
preferred specific embodiment thereof, it will be understood that
this description is intended to illustrate and not limit the scope
of the invention, which is defined by the following claims.
* * * * *