Dynamic information storage or retrieval – Dynamic mechanism subsystem – Specified detail of transducer assembly support structure
Reexamination Certificate
2001-09-11
2004-11-02
Huber, Paul W. (Department: 2653)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Specified detail of transducer assembly support structure
C369S253000
Reexamination Certificate
active
06813236
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk apparatus. More specifically, the present invention relates to an optical disk apparatus including a mechanism for moving an optical head.
2. Description of the Related Art
A recording and reproduction apparatus (optical disk apparatus) for recording data to and reproducing data from a disk (recording medium) using an optical head requires a mechanism for moving an optical head from an inner circumference to an outer circumference of a recording region of the disk. A mechanism in which an optical head is moved along a pair of parallel guide members is widely used.
Japanese Patent No. 2902876 discloses a conventional technique adopting such a mechanism in the technique disclosed in Japanese Patent No. 2902876, a driving force for moving an optical head is transferred from a pinion to a rack which are mounted on the optical head. The optical head is slid along a column-shaped guide shaft (guide member). The rack is provided in the optical head in such a manner as to be rotated about the guide shaft.
FIG. 15A
is a side view showing a moving mechanism of an optical head described in Japanese Patent No. 2902876.
FIG. 15B
is a plan view of the moving mechanism of the optical head of
FIG. 15A
, viewed in a direction indicated by an arrow B.
The moving mechanism of the optical head described in Japanese Patent No. 2902876 will be described below with reference to FIG.
15
A. An optical head
102
is moved along guide shafts
101
R and
101
L in and out with respect to the plane of the figure.
A rack
103
is pressed by a pressing spring
106
in a direction from the optical head
102
to a small gear
105
S. The rack
103
is supported by the guide shaft
101
R as a supporting shaft in such a manner as to be freely rotated in a direction indicated by an arrow
201
.
Referring to
FIGS. 15A and 15B
, the optical head
102
is guided by the guide shafts
101
R and
101
L which are arranged in parallel. The optical head
102
is configured to be moved in a direction indicated by an arrow
202
. The rack
103
seizes a shaft bearing
1001
of the guide shaft
101
R of the optical head
102
by holding the opposite ends of the shaft bearing
1001
, and is supported by the guide shaft
101
R in such a manner as to be freely rotated.
A driving force for the optical head
102
is transferred from a driving gear
104
driven by a motor to a large gear
105
L. The large gear
105
L and the small gear
105
S (pinion) are integrated to constitute a stepped gear
105
so that the driving force is decelerated and transferred from the small gear
105
S to the rack
103
.
As the driving force of the motor causes the rack
103
to be moved in the direction indicated by the arrow
202
(FIG.
15
B), the optical head
102
whose shaft bearing
1001
is seized by the rack
103
is moved.
FIG. 16
shows states of the rack
103
and the small gear
105
S which are engaged with each other. When the rack
103
and the small gear
105
S are too close to each other, the gear teeth of the rack
103
and the small gear
105
S interfere with each other, obstructing the transference of a driving force. To avoid such an adverse situation, a certain amount of backlash is provided between the gear teeth of the rack
103
and the small gear
1055
, which is a known technique.
FIG. 16
shows, by reference numeral
103
A, the positions of gear teeth of the rack
103
when backlash is provided. Backlash is also inevitably present due to pitch error in the engagement of gears.
In optical disk apparatuses. the provision of such backlash is responsible for a large level of lag in a direction of the movement of the optical head
102
. This lag may be several tens to several hundreds times as large as the pitch of data tracks on the optical disk. Since optical disk apparatuses need to move an optical head with considerably high precision, the removal of such backlash is required.
In the conventional technique disclosed in Japanese Patent No. 2902876, the rack
103
is pressed by the pressing spring
106
(
FIG. 15A
) in a direction indicated by an arrow
203
(
FIG. 16
) so as to remove backlash. Reference numeral
103
B indicates the position of the gear teeth of the rack
103
pressed by the pressing spring
106
. In this case, the gear teeth of the small gear
105
S are pressed by the gear teeth of the rack
103
.
Optical disk apparatuses require very highly-precise and high-speed movement of an optical head. Thus, the stability is required for the movement of an optical head. To this end, it is important to reduce a load on the movement of the optical head
102
generated between the pair of parallel guide shafts
101
R and
101
L and the optical head
102
as much as possible. Therefore, friction between the pair of parallel guide shafts
101
R and
101
L and the sliding optical head
102
needs to be reduced as much as possible.
In the above-described conventional technique, as shown in
FIG. 15A
, the pressing spring
106
is attached to a point
102
A of the optical head
102
. The pressing spring
106
is compressed so as to press the rack
103
against the small gear
105
S. Therefore, a moment
204
around the guide shaft
101
R is exerted on the optical head
102
by the pressing spring
106
. A reaction
1901
canceling the moment
204
is generated at the guide shaft
101
L, and exerted on the optical head
102
. The greater the reaction
1901
, the greater the friction between the guide shaft
101
L and a sliding portion of the optical head
102
. The large friction significantly reduces the movement stability of the optical head
102
.
The number of movements of the optical head
102
may reach several millions or more before the life of the optical disk apparatuses is expired. A large number of movements of the optical head
102
lead to much abrasion of the gear teeth of the rack
103
, such that the optical head
102
may be eventually brought to a state where it cannot be moved. In such a case, the rack
103
needs to be replaced. Also in the production process of optical disk apparatuses, a defective rack
103
may be found after it is already integrated into the body and therefore needs to be replaced. Therefore, it is desirable to easily replace the rack
103
.
In the conventional optical disk apparatus of FIG.
15
B. when the rack
103
needs to be replaced, the guide shaft
101
R needs to be temporarily removed since the guide shaft
101
R goes through the rack
103
. When the guide shaft
101
R is reattached, the tilt of the guide shaft
101
R needs to be adjusted to set the tilt of the optical head
102
. This adjustment typically requires considerable time and effort. As such, in the conventional technique, the rack
103
cannot be easily attached to and detached from the optical head
102
.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, an optical disk apparatus includes an optical head for recording data to or reproducing data from a disk having a recording region ranging from an outer circumference portion to an inner circumference portion, a first guide member having a first axis substantially parallel to the disk, for supporting the optical head in such a manner that the optical head can be moved along the first axis from an end of the outer circumference portion to an end of the inner circumference portion, a second guide member for limiting rotation of the optical head about the first axis, a rack provided on the optical head, having a reference pitch line substantially parallel to the first axis, a pinion for moving the optical head by the pinion being engaged with the rack and being rotated, and a pressing member for pressing the rack toward the pinion. The vector of a force exerted by the pinion on the rack in response to the pressing member pressing the rack toward the pinion substantially intersects the first axis.
In one embodiment of this invention, the rack is mounted on the head in such a manner that the rack can be rotated about a second axis subst
Ezawa Kozo
Okazawa Hironori
Tatsumi Terumi
Teramae Kazuo
Wakikawa Masanao
Huber Paul W.
Renner , Otto, Boisselle & Sklar, LLP
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