HK1082095B - Optical disk apparatus - Google Patents

Description

Optical disk device

The present application is a divisional application of an invention patent application having an application date of 2001, 9/20, an application number of 01141857.5, and an invention name of "optical disc apparatus".

Technical Field

The present invention relates to an optical disc apparatus. In particular, the present invention relates to an optical disc apparatus including a mechanism for moving an optical head.

Background

A recording and reproducing apparatus (optical disc apparatus) that records data onto or reproduces data from a disc (recording medium) with an optical head needs to employ a mechanism to move the optical head from the inner periphery to the outer periphery of a disc recording area. A mechanism is widely used in which an optical head is moved along a pair of parallel guides.

A conventional technique using such a mechanism is disclosed in japanese patent No. 2902876. In the technique disclosed in japanese patent No.2902876, a driving force for moving the pickup is transmitted from a pinion to a rack mounted on the pickup. The optical head slides along a cylindrical guide shaft (guide). The rack is provided on the head so as to be rotatable about the guide shaft.

Fig. 15A is a side view of the head moving mechanism described in japanese patent No. 2902876.

Fig. 15B is a plan view of the head moving mechanism in fig. 15A as viewed from the direction indicated by the arrow B.

The head moving mechanism described in japanese patent No.2902876 is described below with reference to fig. 15A. An optical head 102 is moved in and out with respect to the drawing along guide shafts 101R and 101L.

A rack 103 is urged by an urging spring 106 against a pinion 105S in a direction away from the optical head 102. The rack 103 is supported by a guide shaft 101R serving as a support shaft in such a manner as to be freely rotatable in the direction indicated by the arrow 201.

Referring to fig. 15A and 15B, the optical head 102 is guided by guide shafts 101R and 101L arranged in parallel. The optical head 102 is configured to move in the direction indicated by arrow 202. The rack 103 holds the bearing 1001 by holding opposite ends of the bearing 1001 on the guide shaft 101R of the optical head 102, and is rotatably supported by the guide shaft 101R.

The driving force for driving the optical head 102 is transmitted from a driving gear 104 driven by a motor to a large gear 105L. The large gear 105L and the small gear 105S (pinion) are combined to constitute a stepped gear 105 to decelerate and transmit the driving force from the small gear 105S to the rack 103.

As the rack gear 103 is moved in the direction indicated by the arrow 202 (fig. 15B) by the driving force of the motor, the optical head 102, which is held by the rack gear 103 with its bearing 1001, is also moved.

Fig. 16 shows a state in which the rack 103 and the pinion 105S are engaged with each other. When the rack gear 103 and the pinion gear 105S are too close to each other, the gear teeth on the rack gear 103 and the pinion gear 105S may interfere with each other, thereby hindering the transmission of the driving force. In order to avoid such a negative situation, it is necessary to provide a certain amount of backlash between the teeth of the rack 103 and the pinion 105S, which is a well-known technique. The position of the teeth of the rack 103 when the backlash is provided is indicated by reference numeral 103A in fig. 16. Backlash is also inevitably present due to pitch errors in the gear mesh.

In an optical disc device, providing such a backlash is responsible for a large level of hysteresis of the optical head 102 in the moving direction. This lag may be tens to hundreds of times the data track pitch of the optical disc. Since the optical disc apparatus needs to move the optical head with a relatively high accuracy, it is necessary to eliminate such backlash.

In the conventional technique disclosed in japanese patent No.2902876, the rack 103 is urged in the direction indicated by an arrow 203 (fig. 16) by an urging spring 106 (fig. 15A) to eliminate backlash. Reference numeral 103B denotes a position of the gear teeth when the rack 103 is urged by the urging spring 106. In this case, the gear teeth of the pinion 105S are pressed by the gear teeth of the rack 103.

Optical disc devices require very high precision and speed movement of the optical head. Therefore, stability is required for the movement of the optical head. For this reason, it is important to reduce the moving load of the optical head 102 generated between the pair of parallel guide shafts 101R and 101L and the optical head 102 as much as possible. Therefore, it is necessary to reduce the friction between the pair of parallel guide shafts 101R and 101L and the sliding optical head 102 as much as possible.

In the conventional technique described above, as shown in fig. 15A, the urging spring 106 is attached to one point 102A of the optical head 102. The urging spring 106 is compressed to urge the rack 103 against the pinion 105S. Thus, a moment 204 about the guide shaft 101R is exerted on the optical head 102 by the spring 106. A reaction force 1901 for canceling the moment 204 is generated on the guide shaft 101L and applied to the optical head 102. The larger the reaction force 1901, the larger the friction force between the guide shaft 101L and a sliding portion on the optical head 102, and the large friction force may significantly reduce the stability of the movement of the optical head 102.

The number of movements of the optical head 101 may reach several million or more before the end of the lifetime of the optical disc apparatus. Multiple movements of the head 102 will cause the teeth of the rack 103 to wear too much, so that the head 102 may accidentally reach an immovable position. In this case, the rack needs to be replaced. Further, in the manufacturing process of the optical disc apparatus, the defective rack 103 may be found and need to be replaced after having been assembled into the body. Therefore, it is desirable that the rack 103 be easily replaced.

In the conventional optical disc device in fig. 15B, when the rack 103 needs to be replaced, the guide shaft 101R needs to be temporarily detached because the guide shaft 101R passes through the rack 103. After the guide shaft 101R is reinstalled, the tilt of the guide shaft 101R needs to be adjusted to set the tilt of the optical head 102. Such adjustment usually requires much time and effort. Therefore, in the conventional art, the rack 103 cannot be easily attached to or detached from the optical head 102.

Disclosure of Invention

According to an aspect of the present invention, an optical disc apparatus includes an optical head for recording data onto or reproducing data from a disc having a recording area ranging from an outer peripheral portion to an inner peripheral portion; a first guide having a first axis substantially parallel to the disk and for supporting the optical head in such a manner that the optical head can move along the first axis from one end of the outer peripheral portion to one end of the inner peripheral portion; a second guide for limiting the rotation of the optical head about the first axis; a rack provided on the optical head and 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 rotated; and a pushing member for pushing the rack toward the pinion. A vector of a force applied to the rack by the pinion resulting from the urging member urging the rack toward the pinion substantially intersects the first axis.

In one embodiment of the invention, the rack is mounted on the optical head in such a way that the rack can rotate about a second axis substantially parallel to the reference pitch line.

In one embodiment of the invention, the rack is mounted on the head in such a way that the rack can be mounted on or removed from the head.

In one embodiment of the invention, a male portion is provided on one of the rack and the head, a female portion is provided on the other of the rack and the head, and the rack is mounted on the head by engagement of the male portion with the female portion.

In one embodiment of the invention, the shape of the protruding portion is obtained by cutting away a portion of the cylinder along a plane parallel to the axis of the cylinder, the recessed portion being provided with a slot having a width smaller than the diameter of the cylinder, the protruding portion passing through the slot when the rack is mounted on or removed from the optical head.

In one embodiment of the present invention, the optical disc apparatus further comprises an elastic member for urging the rack gear in a direction along the second axis, thereby substantially eliminating a gap between the rack gear and the optical head along the second axis.

In one embodiment of the invention, the biasing element and the resilient element are combined.

In one embodiment of the invention, the rack is mounted on the optical head in such a way that a portion of the rack which engages with the pinion is rotatable about a second axis substantially parallel to the reference pitch line. The rack is made of a flexible material and a portion of the rack along the second axis is shaped to allow the rack to rotate about the second axis.

In one embodiment of the present invention, when the optical head is placed at the first position on one of the end of the inner peripheral portion and the end of the outer peripheral portion, the shift of the rack is limited to such an extent that the engagement of the rack with the pinion is not released, and when the optical head is placed at the second position on the other of the end of the inner peripheral portion and the end of the outer peripheral portion and when a rotational force greater than or equal to a predetermined value is applied to the pinion, the shift of the rack is allowed to such an extent that the engagement of the rack with the pinion is released.

In one embodiment of the invention, a first portion of the rack is engaged with the pinion when the optical head is disposed in the first position, and a second portion of the rack is engaged with the pinion when the optical head is disposed in the second position. The optical head includes a first contact for limiting the displacement of the first contact point of the rack from the pinion, and a second contact for limiting the displacement of the second contact point of the rack from the pinion. The first location is in a range between the first and second contact points of the rack. The second location is outside the range between the first and second contact points of the rack.

In one embodiment of the present invention, the rack is mounted on the optical head in such a manner that the rack is rotatable about a second axis parallel to the reference pitch line, and the rack is deformable in such a manner that the reference pitch line has a staggered relationship with the second axis without intersecting when the optical head is placed at the second position and when a rotational force greater than or equal to a predetermined value is applied to the pinion.

In one embodiment of the present invention, the optical disc apparatus further comprises a driving section for rotating the pinion gear in the presence of an applied excitation current. The predetermined value is set such that the magnitude of the energizing current required to drive the pinion gear to obtain a rotational force having the predetermined value is less than or equal to a permissible limit value, above which the disk device is harmed by thermal influence.

According to another aspect of the present invention, an optical disc apparatus includes an optical head for recording data onto or reproducing data from a disc having a recording area ranging from an outer peripheral portion to an inner peripheral portion; a first guide having a first axis substantially parallel to the disk and for supporting the optical head in such a manner that the optical head can move along the first axis from one end of the outer peripheral portion to one end of the inner peripheral portion; a second guide for limiting the rotation of the optical head about the first axis; a rack provided on the optical head and having a reference pitch line substantially parallel to the first axis; a pinion for moving the optical head by meshing the pinion with the rack and rotating about a third axis substantially perpendicular to the reference pitch line; and a pushing member for pushing the rack toward the pinion. A line perpendicular to both the third axis and the reference pitch line substantially intersects the first axis.

According to another aspect of the present invention, an optical disc apparatus includes an optical head for recording data onto or reproducing data from a disc having a recording area ranging from an outer peripheral portion to an inner peripheral portion; a first guide having a first axis substantially parallel to the disk and for supporting the optical head in such a manner that the optical head can move along the first axis from one end of the outer peripheral portion to one end of the inner peripheral portion; a second guide for limiting the rotation of the optical head about the first axis; a rack provided on the optical head and 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 rotated; and a pushing member for pushing the rack toward the pinion. A vector of a force applied to the rack by the pinion resulting from the urging member urging the rack toward the pinion substantially intersects the first axis. When the optical head is placed at a first position on one of the end of the inner peripheral portion and the end of the outer peripheral portion, the offset of the rack is limited to such an extent that the engagement of the rack with the pinion is not released, and when the optical head is placed at a second position on the other of the end of the inner peripheral portion and the end of the outer peripheral portion and when a rotational force greater than or equal to a predetermined value is applied to the pinion, the offset of the rack is allowed to such an extent that the engagement of the rack with the pinion is released.

Thus, the invention described herein may obtain the advantage of providing: (1) an optical disk device capable of stably moving an optical head; and (2) an optical disk apparatus in which the rack is easily attached to or detached from the optical head.

The above and other advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the following detailed description with reference to the accompanying drawings.

Drawings

Fig. 1A is a diagram for showing a structure of an optical disc apparatus 1000 according to the present invention.

Fig. 1B is a plan view of the optical disc apparatus 1000 in fig. 1A of the present invention as viewed from the direction indicated by the arrow B.

Fig. 2 is a diagram for showing how the urging spring 6 is incorporated into the rack 3 detached from the optical head 2 in fig. 1A.

Fig. 3 is a diagram for showing when the rack 3 is mounted on the optical head 2 in fig. 1A.

Fig. 4 is a schematic view for showing when the rack 3 is pushed toward the pinion 5S in fig. 1A.

Fig. 5 is a diagram for showing how the rack 3 is detached from the optical head 2 in fig. 1A.

Fig. 6A is a diagram for showing the relationship between the rotating support shaft 3E in fig. 2 and the rotating hole 2A for mounting the rack 3 to the optical head 2 shown in fig. 1A.

Fig. 6B is a diagram for showing the relationship between the rotating support shaft 3E and the rotating hole 2A in fig. 2 after the rack 3 is rotated by 90 ° in the direction indicated by the arrow 309 in fig. 5.

Fig. 7 is a diagram for showing how the rack 3 is detached from the optical head 2 in fig. 1A.

Fig. 8 is a diagram for showing a state where the optical head 2 is disposed at one end (first position) of an inner peripheral portion of a recording area of the disc 8 in fig. 1A.

Fig. 9 is a diagram for showing when the optical head 2 is disposed at one end (second position) of the outer peripheral portion of the recording area of the disc 8 in fig. 1A.

Fig. 10 is a diagram for showing how the engagement between the rack 3 and the pinion 5S is released when the optical head 2 is placed at the end (second position) of the outer peripheral portion of the recording area of the disk 8 in fig. 1A.

Fig. 11 is a diagram for illustrating the principle of the pinion 5S applying the radial force 2010 to the rack 3 in fig. 1A.

Fig. 12 is a diagram for showing the principle that the engagement between the rack 3 and the pinion 5S is not released when the optical head 2 is placed at the end (first position) of the inner peripheral portion of the recording region of the disk 8 in fig. 1A.

Fig. 13 is a diagram for showing the principle of the release of the engagement between the rack 3 and the pinion 5S when the optical head 2 is placed at the end (second position) of the outer peripheral portion of the recording area of the disk 8 in fig. 1A.

Fig. 14 is a diagram for showing a moving mechanism of the optical head 2 in the optical disc apparatus 1000a, which is a modification of the preferred embodiment of the present invention described above.

Fig. 15A is a side view of the head moving mechanism described in japanese patent No. 2902876.

Fig. 15B is a plan view of the head moving mechanism in fig. 15A as viewed from the direction indicated by the arrow B.

Fig. 16 is a diagram for showing a state in which the rack 103 and the pinion 105S in fig. 15A are meshed with each other.

Detailed Description

The invention is described below by way of illustrative example with reference to the accompanying drawings. The same components are denoted by the same reference characters in all the drawings, and the description is not repeated.

The structure of an optical disc apparatus 1000 according to the present invention is shown in fig. 1A. The optical disc apparatus 1000 includes an optical head 2, a disc driving section 1011, a recording/reproducing section 1012, an optical head driving section 1013, a control section 1010, and a motor 1014.

In fig. 1A, the disc drive section 1011, the recording/reproducing section 1012, the head drive section 1013, and the control section 1010 may have a well-known structure and are thus represented as functional blocks.

The disk drive section 1011 drives a motor (not shown) for rotating a turntable 9 on which a disk 8 (recording medium) is placed. The disc 8 may be any optical disc such as a DVD, CD-R, CD-ROM or the like.

An optical head 2 is used for recording data onto the disc 8 and/or reproducing data stored on the disc 8. The recording/reproducing section 1012 is used to process data reproduced from the disc 8. The recording/reproducing section 1012 is also used to generate data to be recorded onto the disc 8 and output such data to the optical head 2.

The disc 8 has a recording area ranging from an outer peripheral portion to an inner peripheral portion. The optical head 2 moves between the outer peripheral portion and the inner peripheral portion to record and/or reproduce data onto and/or from a desired portion of the recording area. The optical head 2 is moved in and out with respect to the drawing plane in fig. 1A.

The head driving section 1013 drives the motor 1014 by applying an excitation current thereto to move the head 2.

The control section 1010 controls the disc drive section 1011, the recording/reproducing section 1012, and the head drive section 1013.

Fig. 1B is a plan view of the optical disc apparatus 1000 in fig. 1A of the present invention as viewed from the direction indicated by the arrow B. Note that in fig. 1B, the control section 1010, the disc drive section 1011, the recording/reproducing section 1012, the head drive section 1013, and the disc 8 are not shown for clarity. The arrow 301 indicates the direction of movement of the optical head 2.

Referring again to fig. 1A, the moving mechanism of the optical head 2 used in the optical disc apparatus 1000 of the present invention will be described.

The optical disc device 1000 includes a guide shaft 1R (first guide), a guide shaft 1L (second guide), a rack 3 mounted on the optical head 2, a step gear 5, and a pressing spring 6 (pressing means) which constitute a moving mechanism of the optical head 2.

A drive gear 4 is attached to the shaft of the motor 1040. The stepped gear 5 includes a pinion gear 5S (pinion) engaged with the rack 3 and a large gear 5L engaged with the drive gear 4, which are combined with each other.

An excitation current is applied to the motor 1040 to rotate the motor. The drive gear 4 rotates with the rotation of the motor 1040. The rotational force of the drive gear 4 is transmitted to the large gear 5L of the stepped gear 5 to rotate the large gear. Finally, the pinion 5S engaged with the rack 3 rotates. In this way, the motor 1014, the drive gear 4 and the large gear 5L as a whole function as a drive section for rotating the small gear 5S in the presence of an applied excitation current.

The pinion 5S is engaged with the rack 3 and rotates about the rotation axis 1021 to move the optical head 2. The axis of rotation 1021 is substantially perpendicular to the reference pitch line 1018 of the rack 3.

The guide shaft 1R has a central axis 1017 (first axis) substantially parallel to the disk 8. The guide shaft 1R supports the optical head 2 in such a manner that the optical head 2 can move along the central axis 1017 from one end of the outer peripheral portion to one end of the inner peripheral portion of the disc 8. As used herein, "substantially parallel" and "substantially perpendicular" refer to parallel and perpendicular within ordinary design tolerances.

The guide shaft 1L restricts (or restrains) the rotation of the optical head 2 about the central axis 1017.

The rack 3 is mounted on the optical head 2, and the urging spring 6 is combined with the rack 3. The rack 3 can rotate about an axis 1019 (second axis) in the direction indicated by arrow 302.

Fig. 2 shows how the urging spring 6 is combined with the rack 3 detached from the optical head 2 in fig. 1A. In the example shown in fig. 2, the urging spring 6 is a torsion coil spring.

The coil center of the bias spring 6 slides onto a bearing boss 3B provided on the rack 3 (arrow 57). One spring end 6A of the urging spring 6 is hooked on a stopper boss 3C, and the other spring end 6B of the urging spring 6 is hooked on a hook 3D. The hook 3D is provided to temporarily hold the spring end 6B when the rack 3 is removed from the head 2.

The rack 3 with the thus combined urging spring 6 is mounted on the optical head 2 in such a manner that the rack 3 can rotate about an axis 1019 (second axis) passing through the centers of both the rotation support shafts 3E and 3F.

Fig. 3 shows a rack 3 mounted on the optical head 2 as viewed in the direction indicated by the arrow a in fig. 1A. When the rack 3 is mounted on the optical head 2, the central axis 1017 of the guide shaft 1R is substantially parallel to the reference pitch line 1018 of the rack 3. As shown in fig. 3, the rack 3 grips the optical head 2 with arms 3J and 3K. Therefore, as the rack 3 is moved by rotating the pinion 5S, the optical head 2 is also moved back.

In fig. 3, the spring end 6B contacts and presses against one corner 2G of the head 2 and is released from the head 2. Therefore, by pressing the corner 2G of the optical head 2, the pressing spring 6 presses the support boss 3B in the direction indicated by the arrow 304.

As described above, with this simple structure, the rack 3 can be moved reliably and smoothly toward the pinion 5S.

Since the rack 3 is pushed toward the pinion 5S, backlash between the teeth of the rack 3 and the pinion 5S can be substantially eliminated.

Fig. 4 shows a situation in which the rack 3 is pushed toward the pinion 5S.

The shapes of the rack 3 and the pinion 5S are designed in such a manner that the rack 3 moves at a constant linear velocity when the pinion 5S rotates at a constant angular velocity. For this, as an example, the gear teeth of the rack 3 may take a trapezoidal shape, and the pinion 5S may have involute gear teeth. When the rack 3 and the pinion 5S are designed in this manner, the meshing between the rack 3 and the pinion 5S can be represented by the contact between the reference pitch line 1018 of the rack 3 and the reference pitch circle 1020 of the pinion 5S.

The reference pitch line 1018 of the rack 3 passes through the center of the meshing width between the rack 3 and the pinion 5S.

Reference is made again to fig. 1A to describe the principle of the optical head 2 that can be moved stably in the optical disc apparatus 1.

As described above, the urging spring 6 urges the rack 3 toward the pinion 5S (arrow 304: this urging force is referred to as an urging force 304). In response to this urging force, the pinion 5S applies a reaction force 304a to the rack 3. The optical disc apparatus 1 is designed such that the vector of the reaction force 304a substantially intersects the central axis 1017.

When the vector of the reaction force 304a intersects the central axis 1017, the moment on the rack 3 about the central axis 1017 due to the reaction force 304a is zero. Therefore, there is no moment about the central axis 1017 on the head 2 carrying the rack 3. As a result, a reaction force for canceling (or resisting) the moment applied to the optical head 2 about the central axis 1017 is not generated on the guide shaft 1L. Thus, the friction between the guide shaft 1L and the sliding portion of the optical head 2 is not increased by such a reaction force, and the optical head 2 can be moved in a stable manner.

It should be noted that "the vector of the reaction force 304a substantially intersects the central axis 1017" includes the meaning: even if the vector of the reaction force 304a does not precisely intersect the central axis 1017, the resultant reaction force (resisting moment) generated on the guide shaft 1L is smaller than the load normally exerted on the guide shaft 1L due to the weight of the optical head 2.

As can be seen from fig. 1A and 3, the urging force 304 for urging the rack 3 against the pinion 5S is perpendicular to the reference pitch line 1018 of the rack 3 and the rotation axis 1021 of the pinion 5S. Since the reaction force 304a (fig. 1A) is equal to and opposite to the force pushing the rack 3 against the pinion 5S, the vector of the reaction force 304a is located on a straight line perpendicular to both the reference pitch line 1018 of the rack 3 and the rotation axis 1021 of the pinion 5S. Therefore, "the vector of the reaction force 304a substantially intersecting the center axis 1017" is equivalent to "a straight line that is perpendicular to both the reference pitch line 1018 of the rack 3 and the rotation axis 1021 of the pinion 5S and substantially intersects the center axis 1017". Such a perpendicular is to be understood as a straight line that includes a line segment between the reference pitch line 1018 and the axis of rotation 1021, but not the line segment itself.

In addition to the above-described advantage that the optical head 2 can be stably moved, the optical disc apparatus 1000 of the present invention has various advantages. The advantages of the optical disc apparatus 1000 of the present invention are described below.

1. Attaching or detaching heads to or from racks

The way in which the rack 3 is removed from the head 2 is shown in fig. 5. After the step gear 5 and the motor 1014 are detached from the optical disc apparatus 1000, the rack 3 is detached. In this case, the rack 3 can be rotated by 90 ° about the axis 1019 in the direction indicated by the arrow 309.

The rack 3 is mounted to the optical head 2 by engaging the rotation support shafts 3E and 3F (convex portions) with the respective rotation holes 2A and 2B (concave portions).

Fig. 6A shows the relationship between the rotary support shaft 3E and the rotary hole 2A for mounting the rack 3 to the optical head 2. The shape of the rotary support shaft 3E (projecting portion) is obtained by cutting out a part of a cylinder along a plane parallel to the axis of the cylinder. In the example in fig. 6A, the shape of the rotating support shaft 3E is obtained by cutting out a portion of a cylinder along two parallel planes equidistant from the cylinder axis. Further, the rotation hole 2A (concave portion) is provided with a groove 1601 through which the rotation support shaft 3E passes when the rack 3 is attached to or detached from the optical head 2. The width of the groove 1601 is less than the diameter of the cylinder.

The width of the groove 1601 is smaller than the diameter of the rotary support shaft 3E. Therefore, when the rotary support shaft 3E is located at the position shown in fig. 6A, the center of the rotary support shaft 3E coincides with the center of the rotary hole 2A, and the rotary support shaft 3E cannot be detached from the rotary hole 2A.

Fig. 6B shows the relationship between the rotating support shaft 3E and the rotating hole 2A after the rack 3 is rotated by 90 ° in the direction indicated by the arrow 309 (fig. 5). In the case of fig. 6B, the rotary support shaft 3E can pass through the groove 1601.

The relationship between the rotating support shaft 3F and the rotating hole 2B is similar to the above-described relationship between the rotating support shaft 3E and the rotating hole 2A shown in fig. 6A and 6B.

The way in which the rack 3 is removed from the head 2 is shown in fig. 7. As shown in fig. 7, the rack 3 rotated by 90 ° in the direction of the arrow 309 (fig. 5) is pulled in the direction of the arrow 310, thereby making it easy to detach the rack 3 from the optical head 2.

The rack 3 can be easily mounted to the optical head 2 according to the reverse order of the above-described removal procedure. Since the guide shaft 1R does not need to be removed from the optical head 2 when the rack 3 is attached to or detached from the optical head 2, the rack 3 can be easily attached to or detached from the optical head 2.

In the optical disc apparatus 1000, a rotation support shaft (convex portion) and a rotation hole (concave portion) are provided on the rack 3 and the optical head 2, respectively, which are engaged with each other to mount the rack 3 on the optical head 2. Therefore, it is not necessary to increase the number of parts for mounting the rack 3 to the optical head 2.

In the above-described example, the rack 3 is provided with the rotation support shafts 3E and 3F (convex portions), and the optical head 2 is provided with the rotation holes 2A and 2B (concave portions). Conversely, the rack 3 may be provided with a concave portion, and the optical head 2 may be provided with a convex portion for engagement with the concave portion.

In the above described example, the rack 3 is rotated by 90 ° to be detached from the optical head 2. Such a rotation angle is not limited to 90 °. The rack 3 and the head 2 may be designed such that the rack 3 can be detached from the head 2 at any position other than the orthogonal position.

2. Along the firstTwo-axis pushing rack

As described above with reference to fig. 3, the rack 3 grips the optical head 2 with the arms 3J and 3K. In order to enable the rack 3 to rotate about the axis 1019 (second axis), the distance between the arms 3J and 3K is set such that a predetermined amount of clearance (gap) can be created between the arms 3J and 3K and the optical head 2. Such a gap between the rack 3 and the head 2 in the direction of the axis 1019 is disadvantageous in that the rack 3 is followed by the head 2.

In the optical disc apparatus 1000 of the present invention, when the optical head 2 is normally moved, the rack 3 is pushed along the axis 1019 in such a manner that such a gap can be eliminated. The urging of the rack 3 is achieved by the spring 6 urging the corner 2G of the optical head 2, as shown in fig. 3. Specifically, as a result of the spring 6 pushing the corner 2G of the optical head 2, the pushing force 304 pushing the rack 3 toward the pinion 5S and the pushing force 305 pushing the rack 3 along the axis 1019 are simultaneously generated.

As described above, the urging spring 6 serves as an urging means for urging the rack 3 toward the pinion 5S and an elastic means for urging the rack 3 along the axis 1019. That is, in this example, the urging means and the elastic means are combined together. Therefore, the number of parts is small, resulting in advantages in terms of apparatus cost and assembly cost. Alternatively, the pressing means and the elastic means may be separated.

In normal movement of the optical head 2, the gap in the direction of the reference pitch line 1018 can thus be eliminated. However, when a large force is applied to the rack 3, a required amount of clearance can be secured by the bending of the urging spring 6.

3. Safety mechanism

Fig. 8 shows the optical head 2 disposed at one end (first position) of the inner peripheral portion of the recording area of the disc 8. After the optical disc apparatus 1000 starts, the optical head 2 is switched to the first position.

The switching of the head 2 to the first position is effected by rotation of the motor 1014 in the direction indicated by arrow 51. The rotational force of the motor 1014 is transmitted to the rack 3 through the driving gear 4 and the step motor 5. As a result, the optical head 2 moves in the direction indicated by the arrow 52. When the optical head 2 reaches the first position, an inner peripheral projection 2004A provided on the rack 3 collides with an innermost peripheral position stopper 11 to stop the optical head 2.

In the optical disc apparatus 1000, the position of the stopped optical head 2 is detected as a reference point for causing the optical head 2 to switch positions. Therefore, the optical head 2 needs to be stopped at the end (first position) of the inner peripheral portion of the recording area of the disc 8 as accurately as possible.

The optical head 2 is shown in fig. 9 as being disposed at one end (second position) of the outer peripheral portion of the recording area of the disc 8.

The switching of the head 2 to the second position is effected by rotation of the motor 1014 in the direction indicated by arrow 53. The rotational force of the motor 1014 is transmitted to the rack 3 through the driving gear 4 and the step motor 5. As a result, the optical head 2 moves in the direction indicated by the arrow 54. When the optical head 2 reaches the second position, an outer peripheral projection 2004B provided on the rack 3 collides with an outermost peripheral position stopper 12 to stop the optical head 2.

In normal operation of the optical disc apparatus 1000, the optical head 2 is not switched to the second position in fig. 9. This is because in the normal operation of the optical disc apparatus 1000, the optical head 2 disposed on the outer peripheral portion of the recording area of the disc 8 can be detected by reading data recorded in the outer peripheral portion of the recording area of the disc 8. Therefore, the optical head 2 moving until the outer peripheral projection 2004B provided on the rack 3 collides with the outermost peripheral position stopper 12 means that the optical disc apparatus 1000 is in an abnormal state (runaway). Such an abnormal state is caused, for example, because scratches or dust attached to the surface of the disc 8 cause a failure in reading data recorded in the outer peripheral portion of the recording area of the disc 8.

Specifically, the CAV method (a control method using a constant angular velocity) is adopted in the optical disc apparatus 1000, and the linear velocity of the disc 8 is larger at the outer peripheral portion than at the inner peripheral portion of the recording area. Therefore, scratches or dust are more easily attached on the outer peripheral portion than on the inner peripheral portion.

In such an abnormal state, a rotational force (torque) larger than a normal rotational force is liable to occur in the motor 104. When the optical head 2 reaches and collides with the outermost peripheral position stopper 12 with such a large rotational force, it is desirable that the rack 3 is released from its engagement with the pinion 5S. This is because if the engagement of the rack 3 with the pinion 5S cannot be released, the motor 1014 may be stopped (locked) while maintaining a large rotational force, resulting in generation of excessive heat in the motor 104. Such an abnormal heat quantity has a negative influence on the function of the optical disc apparatus 1000, and may cause a worse case, such as a fire in the optical disc apparatus 1000.

In view of this, it is desirable to provide a safety mechanism in the optical disc apparatus 1000 so that the engagement of the rack 3 with the pinion 5S is released when the optical head 2 is located at the second position (fig. 9) to cause a large force to be generated in the motor 1014 (i.e., a rotational force greater than or equal to a predetermined value is applied to the pinion 5S). In contrast, when the optical head 2 is located at the first position in fig. 8, it is desirable that the engagement of the rack 3 with the pinion 5S is not released, thereby improving the accuracy of the stop position of the optical head 2.

In fig. 10, it is shown how the engagement between the rack 3 and the pinion 5S is released when the optical head 2 is placed at the end portion (second position) of the outer peripheral portion of the recording area of the disk 8. In fig. 10, the pinion 5S applies a radial force 2010 to the rack 3. Rack 3 will move in the direction indicated by arrow 64 due to the action of radial force 2010.

The principle of the pinion 5S applying a radial force 2010 to the rack 3 of fig. 1A is shown in fig. 11. As shown in fig. 11, the rack gear 3 and the pinion gear 5S have involute gear teeth with a pressure angle θ (the rack gear 3 having trapezoidal gear teeth can be regarded as an involute gear having a pitch circle with an infinite radius). In the case shown in fig. 9, when a rotational force in the direction indicated by the arrow 60 is applied to the pinion 5S, one tooth surface of the pinion 5S is pushed against one tooth surface of the rack 3 in the direction indicated by the arrow 61. The pressing force 61 includes a component force 62 in the direction along the reference pitch line of the rack 3 and a component force 2010 (radial force) perpendicular to the component force 62. Thus, the rack 3 will move in the direction shown by the head 64. The magnitude of the radial force 2010 depends on the rotational force exerted on the pinion 5S.

The dashed line in fig. 11 indicates the offset of the rack 3.

The offset of the rack 3 is caused by the rack 3 being deformed in such a manner that the reference pitch line 1018 (fig. 3) of the rack 3 has a staggered relationship with the axis 1019 (second axis) without intersecting. When the rack 3 is undeformed (the optical disc apparatus 1000 operates normally), the reference pitch line 1018 of the rack 3 is parallel to the axis 1019. However, when the rack 3 is deformed, the reference pitch line 1018 of the rack 3 is no longer parallel to the axis 1019.

The principle that the engagement between the rack 3 and the pinion 5S is not released when the optical head 2 is placed at the end (first position) of the inner peripheral portion of the recording area of the disk 8 is shown in fig. 12. As shown in fig. 12, when the optical head 2 is disposed at the end of the inner peripheral portion of the recording region of the disk 8, the rack 3 is meshed with the pinion 5S at one portion 2301 (first portion). In this case, when a rotational force is applied to the pinion 5S, a radial force 2010 is applied to the rack 3.

The optical head 2 is provided with contacts 2121 and 2122. The contact 2121 contacts and pushes the rack 3 so that one point 2221 (first contact point) on the rack 3 is restricted from deviating from the pinion 5S. Also, the contact 2122 contacts and pushes the rack 3 so that one point 2222 (second contact point) on the rack 3 is restricted from deviating from the pinion 5S.

As shown in fig. 12, a portion 2301 of the rack 3 that meshes with the pinion 5S is located between points 2221 and 2222 on the rack 3. Thus, when a radial force 2010 is applied to rack 3 at location 2301, rack 3 will simultaneously contact and push against contacts 2121 and 2122. Thus, the rack 3 is not displaced to such an extent that the engagement of the rack 3 with the pinion 5S is released.

The principle that the engagement between the rack 3 and the pinion 5S will be released when the optical head 2 is placed at the end of the outer peripheral portion of the recording area of the disk 8 (second position) is shown in fig. 13. As shown in fig. 13, when the optical head 2 is disposed at the end of the outer peripheral portion of the recording area of the disk 8, the rack 3 is meshed with the pinion 5S at one portion 2302 (second portion). In this case, when a rotational force is applied to the pinion 5S, a radial force 2010 is applied to the rack 3.

As shown in fig. 13, a portion 2302 of the rack 3 that meshes with the pinion 5S is located outside the range between points 2221 and 2222 on the rack 3. Thus, when a radial force 2010 is applied to the rack 3 at location 2302, the rack 3 contacts and pushes against only one of the contactors 2121 and 2122 (contactor 2121 in the example of fig. 13). Thus, the rack 3 will be offset in the direction shown by arrow 64 about the point 2221 at which the rack 3 contacts the contact 2121.

When the rack 3 is shifted in the direction indicated by the arrow 64, the outer peripheral projection 2004B will slide on one surface of the outermost peripheral position stopper 12 in the direction indicated by the arrow 65. Therefore, it is desirable that the outer peripheral projection 2004B and the outer peripheral position stopper 12 have smooth surfaces to reduce the frictional force in such sliding. The surface of the peripheral position stop 12 may be tapered to further facilitate sliding of the peripheral tabs 2004B in the direction indicated by arrow 65.

As mentioned above, this offset is produced by deformation of the toothed rack 3. The rigidity of the rack 3 may be appropriately adjusted so as to release the engagement between the rack 3 and the pinion 5S when the radial force 2010 is greater than or equal to a predetermined value. Due to this. The magnitude of the radial force 2010 depends on the rotational force exerted on the pinion gear 5S, and therefore the optical disc apparatus 1000 may be designed such that the meshing between the rack 3 and the pinion gear 5S can be released when the rotational force on the pinion gear 5S is greater than or equal to a predetermined value.

By changing the shape and/or material of the rack 3, the stiffness of the rack 3 can be adjusted.

The predetermined value of the rotational force on the pinion gear 5S may be set such that the magnitude of the energizing current required to be supplied to the motor 1014 for applying the rotational force to the pinion gear 5S is less than or equal to an allowable limit value beyond which thermal influence may be detrimental to the disc device 1000.

Needless to say, the rigidity of the rack 3 needs to be adjusted such that the engagement between the rack 3 and the pinion 5S is not accidentally released in the normal movement of the optical head 2.

As described above, in the optical disc apparatus 1000 of the present invention, the shift of the rack 3 is restricted so that the engagement between the rack 3 and the pinion 5S is not released when the optical head 2 is placed at the end (first position) of the inner peripheral portion of the recording area of the disc 8. Further, the rack 3 is allowed to be displaced to such an extent that the engagement between the rack 3 and the pinion 5S is released when the optical head 2 is placed at the end (second position) of the outer peripheral portion of the recording area of the disk 8. In this manner, a security mechanism is provided in the optical disc device 1000.

The safety mechanism is achieved by torsional (deflection) deformation of the rack 3. The invention is not limited thereto. For example, the rack 3 may be designed such that the first portion 2301 in fig. 12 and the second portion 2302 in fig. 13 are included in separate parts, and the separate parts may be coupled with an elastic member so as to be biased with respect to each other.

Conversely, it can be assumed that the optical disc apparatus 1000 detects the reference position of the optical head 2 at the end of the outer peripheral portion of the recording area of the disc 8. When the optical head 2 is placed at the end of the inner peripheral portion of the recording area of the disk 8, the engagement between the rack 3 and the pinion 5S can be allowed to be released. When the optical head 2 is disposed at the end of the outer peripheral portion of the recording area of the disk 8, the engagement between the rack 3 and the pinion 5S is restricted from being released.

4. Variants of toothed racks

Fig. 14 shows a moving mechanism of the optical head 2 in an optical disc apparatus 1000a, which is a modification of the preferred embodiment of the present invention described above. The optical disc apparatus 1000a includes a rack gear 13 and a pressing spring 16 instead of the rack gear 3 and the pressing spring 6 in the optical disc apparatus 1000 in fig. 1A. The rack 13 includes a gear portion 13G for meshing with the pinion 5S, a support portion 13J, and a hinge portion 13H. The rack 13 is made of a flexible material. The hinge portion 13H (second axis) has a shape that can be bent around the hinge portion 13H (i.e., a shape having sufficiently low rigidity). Therefore, the gear portion 13G can rotate about the hinge portion 13H in the direction indicated by the arrow 311. The hinge portion 13H is arranged parallel to a reference pitch line (not shown) of the rack 13.

The rack 13 is fixed to the optical head 2 by a screw 17 on the support portion 13J. The rack 3 is preferably made of a material suitable for making a hinge, such as polyacetal, polypropylene, polyethylene or nylon.

The urging spring 16 is provided between the optical head 2 and the gear portion 13G. Accordingly, the gear portion is urged toward the pinion gear 5S, specifically, in the direction indicated by the arrow 312. The urging spring 16 is not limited to a specific form. The optical disc apparatus 1000a is also configured such that a vector of a force applied to the gear portion 13G of the rack 13 by the pinion gear 5S due to the gear portion 13G being pushed toward the pinion gear 5S substantially intersects with the central axis 1017 of the guide shaft 1L.

In the optical disc apparatus 1000a, the rack 13 is fixed to the optical head 2 from the rear side thereof by a screw 17. Therefore, the rack 13 is more easily attached to or detached from the optical head 2 than the optical disc apparatus 1000 described with reference to fig. 5, 6A, and 6B. Thus, the number of steps of the replacement operation of the rack 13 due to a defect or the like can be reduced.

In the foregoing explanation, the gear and the rack have involute gear teeth. The invention is not limited thereto. For example, the gears and racks may have cycloidal or other shaped teeth.

Although in the above described example the head 2 is driven by a rotary motor 1014, the head 2 may be driven by a direct drive method, for example by a linear motor or a solenoid, or any other means capable of moving the head 2.

The cross-sectional shape of the guide shafts 1R and 1L may not be circular. The cross-sectional shape of the guide shaft 1R may be any shape as long as the guide shaft 1R can support the optical head 2 along one axis so that the optical head 2 can move. The cross-sectional shape of the guide shaft 1L may be any shape as long as the guide shaft 1L can restrict the rotation of the optical head 2 about the axis.

The urging spring 6 is not limited to the torsion coil spring. The urging spring 6 may be made of any suitable elastic material (e.g., rubber) as long as the urging spring 6 can urge the rack 3 toward the pinion 5S.

In the optical disc device of the present invention, the optical head is supported by the first guide in such a manner that the optical head is movable along the first axis of the first guide. A pushing tool pushes a rack toward a pinion. According to this, the vector of the force exerted by the pinion on the rack intersects the first axis. Thus, no torque about the first axis is applied to the rack. Since the rack is mounted on the optical head, no torque about the first axis is applied to the optical head. As a result, no force for resisting the torque is generated on the second guide for restricting the rotation of the optical head about the first axis. Therefore, the optical head can be moved in a stable manner.

Further, in the optical disc apparatus of the present invention, the rack is mounted on the optical head with a convex portion provided on one of the rack and the optical head and a concave portion provided on the other of the rack and the optical head and engaging with the convex portion. The shape of the projecting portion is obtained by cutting the cylinder along a plane parallel to the axis of the cylinder. The recessed portion is provided with a groove having a width smaller than the diameter of the cylinder, and the protruding portion passes through the groove when the rack is attached to or detached from the optical head. By passing the projection through the groove, the rack is easily attached to or detached from the optical head.

Various other modifications may be understood and readily made by those of ordinary skill in the art without departing from the scope and spirit of the present invention. Accordingly, the scope of the appended claims should not be construed as limited to the description set out herein, but rather construed broadly.

Claims (1)

1. An optical disc apparatus, comprising:

an optical head for recording data onto or reproducing data from a disc having a recording area ranging from an outer peripheral portion to an inner peripheral portion;

a first guide having a first axis substantially parallel to the disk and for supporting the optical head in such a manner that the optical head can move along the first axis from one end of the outer peripheral portion to one end of the inner peripheral portion;

a second guide for limiting the rotation of the optical head about the first axis;

a rack provided on the optical head and having a reference pitch line substantially parallel to the first axis;

a pinion for moving the optical head by meshing the pinion with the rack and rotating about a third axis substantially perpendicular to the reference pitch line; and

a pushing member for pushing the rack toward the pinion;

wherein a line perpendicular to both the third axis and the reference pitch line substantially intersects the first axis.