WO2006120592A2

WO2006120592A2 - Disk drive unit having a tilt adjusting mechanism

Info

Publication number: WO2006120592A2
Application number: PCT/IB2006/051325
Authority: WO
Inventors: Godfrey F. W. Ting
Original assignee: Arima Devices Corporation
Priority date: 2005-05-10
Filing date: 2006-04-28
Publication date: 2006-11-16
Also published as: WO2006120592A3; TW200643934A

Abstract

The invention relates to a disk drive unit for use in a device for reading and/or writing data on the disk (9). It comprises a turntable (1) having an axis of rotation (3) and a guide (21) extending in substantially radial direction of the turntable (1). The sledge is connected to and supported by the guide (21). A tilt adjusting mechanism (43, 45, 47, 49, 51, 53, 55) is mounted on the sledge (19). The tilt adjusting mechanism (43, 45, 47, 49, 51, 53, 55) has two adjusting screws (43, 45) at different locations so as to tilt the sledge (19) about an axis parallel to the guide (21) (α direction) and about an axis, which is perpendicular thereto and also perpendicular to the axis of rotation (3)(β direction). The adjusting screws co-operate with a bearing member on the guide. This bearing member also guides adjusting movements of the sledge. The tilt adjustment mechanism is simple and effective.

Description

Disk drive unit having a tilt adjusting mechanism

The present invention relates to a disk drive unit for use in a device for reading and/or writing data on a disk, comprising a turntable having an axis of rotation, a guide extending in substantially radial direction of the turntable, a pickup unit mounted to a sledge, the sledge being connected to and supported by the guide in such a way that it can be moved in a direction parallel to the guide by a driving assembly, and a tilt adjusting mechanism.

A common method to optimise the playability performance of an optical disk drive is to adjust the tilt angle of the sledge of the optical pickup unit with respect to the turntable. The laser beam emitted from and re-entering to the optical pickup unit should be perpendicular to the disk to achieve the best performance. As a consequence of mechanical and optical tolerances after assembling the disk drive unit a tilt adjusting mechanism is required.

Prior art disk drive units comprise tilt adjusting mechanisms which adjust the tilt angle of the guide shafts along which the sledge is guided or a tilt adjusting mechanism on the sledge which tilts about only one axis.

US 5,995,479 discloses a tilt adjusting mechanism which adjusting members are provided above one end of the guide shafts; in order to achieve a tilt movement of the sledge the shaft ends are displaced in a direction parallel to the axis of rotation of the turntable. Changing the position of the guide shafts in this way, however, results in a non parallel relationship between guide shafts and disk and hence a variation of the distance between the optical pickup unit and the disk when moving the sledge along the guide shafts.

Patent application JP2001/101673 discloses a tilt adjusting mechanism comprising adjusting members which are mounted to the sledge. The tilt movement, however, is only possible about one axis by one adjusting screw.

It is an object of the present invention to improve the tilt adjustment of a disk drive unit. In order to achieve this object, the disk drive unit according to the invention is characterised by the features of claim 1.

In the disk drive unit of claim 1 the tilt adjusting mechanism is mounted on the sledge. It has at least two adjusting members at different locations. The axes about which the sledge can be tilted are defined as an axis parallel to the guide of the sledge for a tilt movement in α direction and an axis which is perpendicular thereto and also perpendicular to the axis of rotation of the turntable for a tilt movement in β direction. The present invention has the advantage of enabling a sledge tilt in both α and β directions, without the disadvantage of a varying distance between the optical pickup unit and the disk when moving the sledge along the guide shafts.

According to claim 2, each of the adjusting members comprises at least an adjusting element. The adjusting elements are spaced along the guide. They are mounted such, that moving an adjusting element leads to a local displacement of the sledge in a direction parallel to the axis of rotation of the turntable. This results in a simple tilt adjustment of the optical pickup unit.

In a preferred embodiment according to claim 3, the adjusting element comprises a screw in a threaded hole of the sledge. Turning the screw creates a local displacement of the sledge as the screw moves with respect to the guide and the sledge. Applying a screw as adjusting element facilitates the adjustment operation. A favourable embodiment according to claim 4 comprises a transmission element, which converts the axial movement of the screw into a local displacement of the sledge perpendicular thereto. The advantage of this embodiment is that the center line of the screw is substantially perpendicular to the axis of rotation of the turntable which minimizes the height of the disk drive unit viewed in a direction parallel to the axis of rotation. According to claim 5 the transmission element can be formed by a tapered end portion of an adjusting screw which is a very simple structure.

The guide may comprise parallel shafts according to claim 6. The sledge can be displaced along these shafts. This is a simple and accurate configuration for a guide.

The driving assembly for moving the sledge may comprise a drive shaft being configured as a screw spindle according to claim 7. The follower mounted to the sledge is in engagement with the groove of the screw spindle resulting in a translation of the sledge when rotating the screw spindle. The advantage of this embodiment is its simplicity of driving the sledge. According to claim 8 one of the guide shafts can also be the drive shaft. The integration of both functions, guiding and driving, reduces the number of components. In a favourable embodiment according to claim 9, a bearing member is slidably mounted on the shaft, whereas the sledge is slidably mounted on the bearing member in order to provide freedom of movement of the sledge with respect to the bearing member in the direction of adjustment. The adjusting screw acts between the sledge and the bearing member. The bearing member acts as an accurate guide member to guide the sledge with respect to the drive shaft. Furthermore, it provides the contact surface for the adjustment element, e.g. the adjustment screw, thereby preventing direct sliding contact between the adjustment element and the drive shaft. In the case of a screw having a tapered end portion, it may prevent the tapered end portion from penetrating into the groove of the screw spindle, if present. If the shaft would be smooth the bearing member prevents a sliding contact between the tapered end or other transmission element and the shaft.

In a particular embodiment according to claim 10, the bearing member is substantially U-shaped. This configuration of the bearing member has two functions. The web portion provides the contact surface for the adjusting screw, and the legs of the U-shaped bearing member guide the sledge in the direction of adjustment, and prevent a sledge movement parallel to the center line of the adjusting screw.

According to claim 11 the sledge, in particular a follower thereof, is clamped to the guide by means of the spring member. This spring member also allows the sledge to move with respect to the guide against the spring force of the spring, and keeps the adjusting member in contact with the guide or drive shaft. Using a spring for these functions keeps the construction simple.

In a preferred embodiment according to claim 12 the spring member can be combined with the follower, which engages the sledge to a screw spindle to convert the shaft rotation into a sledge translation. The integration of follower and spring member reduces the number of components to be used.

According to claim 13, the spring member may be a simple leaf spring on which the follower is mounted. In a preferred embodiment according to claim 14 the follower is positioned between the adjusting members in order to use the available space of the sledge efficiently and enables the use of only one spring. When the adjusting members are positioned on the sledge at the side of the drive shaft, another portion of the sledge can be connected and supported by at least a supporting element to a guide shaft, according to claim 15.

The invention also relates to a device for reading and/or writing data on a disk, provided with the disk drive unit according to the invention.

These and other aspects and advantages of the invention will be apparent from the following description with reference to the drawings. In the drawings: Fig. 1 is a very schematic drawing of an optical player including a disk drive unit according to the invention.

Fig. 2 is a schematic perspective view of a disk drive unit according to the invention.

Fig. 3 is a top view of a disk drive unit according to the invention. Fig. 4 is a cross sectional view of the disk drive unit according to the line IV-

IV in Fig. 3.

Fig. 5 is an enlarged cross sectional view of detail V in Fig. 4. Fig. 6 is a perspective bottom view of the sledge in non-assembled condition according to the invention.

Fig. 1 diagrammatically shows an optical player in accordance with the invention, which comprises a turntable 1, which can be rotated about an axis of rotation 3 and driven by an electric motor 5, which is secured on a frame 7. An optically scannable information carrier or disk 9, such as a CD, DVD or Blue ray disk or the like, can be placed on the turntable 1, which disk is provided with a disk-shaped substrate 11 on which an information layer 13 having a spiral- shaped information track is present. The information layer 13 is covered with a transparent protective layer 14.

The optical player further comprises an optical pickup unit 15 in accordance with the invention for optically scanning the information track present on the information layer 13 of the disk 9. The optical pickup unit 15 can be displaced with respect to the axis of rotation 3 mainly in two opposite radial directions X and X' by means of a sledge mechanism 17 of the optical player. For this purpose, the optical pickup unit 15 is secured to a sledge 19 of the sledge mechanism 17, and the sledge mechanism 17 is further provided with a straight guide 21 provided on the frame 7 and extending parallel to the X direction, over which guide 21 the sledge 19 is displaceably guided, and with an electric motor 23 by means of which the sledge 19 can be displaced over the guide 21. In operation, an electrical control unit of the optical player, which is not shown in Fig. 1, controls the motors 5 and 23 so as to cause the disk 9 to rotate about the axis of rotation 3 and, simultaneously, the optical pickup unit 15 to be displaced parallel to the X-direction, in such a manner that the spiral- shaped information track present on the information layer 13 of the disk 9 is scanned by the optical pickup unit 15. During scanning, the information present on the information track can be read by the optical pickup unit 15, or information can be written on the information track by the optical pickup unit 15.

The disk 9 is read by detection of light reflected in the disk 9. For example, a light beam is reflected in the direction of the disk 9 by means of a mirror, which is part of the optical pickup unit 15. If the optical pickup unit 15 is also suited for writing information on the disk, the light beam will have a different power level and/or wavelength during writing, but must also be focussed onto a point in the disk 9, as is the case when the disk 9 is being read. Light reflected by the mirror is focussed onto the disk 9 by means of an objective lens 25 or other optical element, situated in a lens holder 27 (see Fig. 2). The lens holder 27 can make small movements with respect to the sledge 19 by means of an actuator which is not further described here. With reference to Fig. 2, the guide 21 comprises two guide shafts 29, 31 extending parallel at a distance from each other. The guide shaft 29 is smooth and straight and has a circular cross section. It is precisely manufactured and positioned on the frame 7. The sledge 19 of the sledge mechanism 17 is positioned between the guide shafts 29 and 31. The sledge 19 is guided with respect to the guide shaft 29 by means of a supporting element or slider 33. This slider 33 guides sliding movements of the sledge 19 and also allows small tilting movements of the sledge 19.

The other guide shaft 31 also has the iunction of drive shaft which is driven by the electric motor 23 in order to be rotated about its longitudinal axis. At the position of the drive shaft 31, the sledge 19 is provided with a separate part, i.e. a follower 35. This follower 35 is connected to the sledge 19 in a manner to be described and is in engagement with the drive shaft 31. The follower 35 and drive shaft 31 are provided with a transmission, here consisting of a lead screw transmission, i.e. the drive shaft 31 is constructed as a screw spindle having a helical groove, whereas the follower 35 is provided with at least one tooth (here two teeth 39) which is in engagement with the helical groove of the drive shaft 31. The teeth may be angled to engage the helical groove. By means of this transmission, a rotation of the drive shaft 31 is converted into a translation of the sledge 19 along the guide shafts 29 and 31.

As mentioned, the follower 35 is secured to the sledge 19. In the embodiment of Fig. 2, the follower 35 is integrated with a spring member 41 in order to clamp the sledge 19 to the guide 29, 31 as well as holding the follower 35 in the groove of the drive shaft 31. The spring member 41 here has the form of a leaf spring fixed to the sledge 19 and carrying the teeth 39 of the follower 35, the teeth being preferably angled to engage the helical groove and formed as projections embossed from the leaf spring 41. With reference to Fig. 2 - 6, there is shown an embodiment of an adjusting mechanism for adjusting the angle of the sledge 19 and therefore the optical pickup unit, in this case the angle about the X and Y directions, i.e. the α and β tilt. The adjusting mechanism comprises adjusting members 43, 45 at different locations on the sledge 19, here at a distance along the drive shaft 31 on both sides of the follower 35. Preferably, the follower 35 is positioned centrally between the adjusting members 43, 45 so that the spring member 41 of the follower 35 acts equally on both adjusting members 43, 45. Each of the adjusting members 43, 45 comprises an adjusting element. Fig. 2 shows an embodiment in which each adjusting element 43, 45 is formed by an adjusting screw. With reference to Fig. 5, a favourable embodiment is to mount the adjusting screws 43, 45 in threaded holes 47, 49 of the sledge 19 with their center line extending substantially perpendicularly to the axis of rotation 3 of the turntable 1 (and preferably substantially perpendicularly to the drive shaft 31). The advantage of this position is that the height of the disk drive unit in Z direction can be minimized.

The adjusting screws 43, 45 have a tapered end portion 51 acting as a transmission element. For this purpose, the tapered end portion 51 contacts a contact surface 53, which is associated with the screw spindle 31 and has a fixed position with respect to the screw spindle 31. In this case each contact surface 53 is formed on a bearing member 55. When turning the adjusting screw 43, 45 the screw will move longitudinally with respect to the sledge 19 and bearing member 55. As a result of the engagement of the tapered end portion 51 and the contact surface 53, the screw 43, 45 will be guided along the contact surface 53 thereby moving the sledge 19 in a direction parallel to the axis of rotation 3 of the turntable 1 (Z direction), as the sledge 19 can only move in this direction due to the engagement of the sledge 19 and the bearing member 55. Turning an adjusting screw 43, 45 clockwise results in a local +Z movement of the sledge 19 and turning the screw 43, 45 anti- clockwise results in local -Z movement. The embodiment of Fig. 2 has two adjusting screws 43, 45, whereas the supporting member 33 is located opposite to the second adjusting screw 45 at the same position in X direction, engaging the sledge 19 to the guide shaft 29. Turning the second screw 45 clockwise and keeping the first screw 43 stationary results in a combined -α and -β tilt adjustment. Turning the first screw 43 clockwise and keeping the second screw 45 stationary, leads to a +β and -α tilt in the embodiment of Fig. 2. Turning both screws 43, 45 clockwise or anti-clockwise over an identical angle leads to a -α or +α tilt, respectively. The last two movements create an independent α and β tilt.

The bearing member 55 as mentioned above has several functions. It not only provides a contact surface 53 for the tapered end portion 51 of the adjusting screw 43, 45, it also acts as a slider 33 for the sledge 19 in order to enable an accurate sliding engagement between the sledge 19 and the drive shaft 31. Furthermore it guides the adjusting movements of the sledge 19 with respect to the drive shaft 31.

Fig. 5 shows the bearing member 55 on a larger scale. The bearing member 55 should have a width larger than the width of the groove of the screw spindle 31. A favourable embodiment of the bearing member 55 is a U-shaped slider as shown. It has a semi-circular web portion 57 and two substantially parallel legs 59, the semi-circular portion 57 fitting around the screw spindle 31. Fig. 5 illustrates that the U-shaped slider 55 is slidably mounted in a guide groove 61 of the sledge 19. This allows a movement of the sledge 19 with respect to the bearing member 55 when the adjusting screw 43, 45 is actuated. In that case, the bearing member 55 will stay in contact with the adjusting screw 43, 45 and the screw spindle 31 and the screw 43, 45 and hence the sledge 19 will move with respect to the bearing member 55 when performing a tilt adjustment of the sledge 19. The sledge 19 will locally move in a direction substantially parallel to the axis of rotation 3 of the turntable 1. Preferably, the bearing member 55 is made of a polymer material, particularly a thermoplastic material such as acetal plastic, in particular polyoxymethylene (POM). POM has low friction which provides proper guidance with the sledge 19 and drive shaft 31.

The invention is not restricted to the above-described embodiment as shown in the drawings, which can be varied in several ways without departing from the scope of the invention. For example, the guide may have two guide shafts 29 and a separate drive shaft 31. The adjusting member may use other elements than a screw, while the orientation may be different if desired. The supporting element 33 may for example be located on another location along the guide shaft 29 such that a β tilt will be achieved by turning both adjusting screws 43, 45 in opposite directions. In the presently preferred embodiments, the disk is an optical disk. However, it should be understood that the invention can also be used for all kinds of other disks e.g. ferro-electric, magnetic, magneto-optic, near- field, active charge storage disks or other disks using combinations of these techniques or other reading and/or writing techniques. In these cases the lens and laser will be replaced by another reading/writing member which may require cooling.

In general it is noted that, in this application, the expression "comprising" does not exclude other elements, and "a" or "an" does not exclude a plurality. A single processor or unit may fulfil the functions of several elements in the appended claims. Reference signs in the claims shall not be construed as limiting the scope thereof.

Claims

CLAIMS:

1. Disk drive unit for use in a device for reading and/or writing data on a disk (9), comprising a turntable (1) having an axis of rotation (3) and a guide (21) extending in substantially radial direction of the turntable (1), and a pickup unit (15) mounted to a sledge (19), the sledge being connected to and supported by the guide (21) in such a way that it can be moved in a direction parallel to the guide (21) by a driving assembly (23, 31), and a tilt adjusting mechanism (43, 45, 47, 49, 51, 53, 55) mounted on the sledge (19), which tilt adjusting mechanism (43, 45, 47, 49, 51, 53, 55) has at least two adjusting members (43, 45) at different locations so as to tilt the sledge (19) about an axis parallel to the guide (21) (α direction) and about an axis, which is perpendicular thereto and also perpendicular to the axis of rotation (3)(β direction).

2. Disk drive unit according to claim 1, wherein each adjusting member (43, 45) comprises at least an adjusting element (43, 45), said adjusting elements of the adjusting members (43, 45) being spaced along the guide (21) and being independently movable with respect to the sledge (19) and the guide (21) such that a movement of these elements (43, 45) results in a local displacement of the sledge (19) with respect to the guide (21) in a direction substantially parallel to the axis of rotation (3) of the turntable (1).

3. Disk drive unit according to claim 2, wherein the adjusting element comprises a screw which is mounted in a threaded hole (47, 49) in the sledge (19), which axial movement is converted to the tilt movement of the sledge (19) when turning the screw (43, 45).

4. Disk drive unit according to claim 3, wherein the screw (43, 45) and the guide (21) are in engagement with each other through a transmission element (51, 53, 55) converting an axial movement of the screw (43, 45) into the local movement of the sledge (19) in a direction substantially perpendicularly thereto, the screw (43, 45) having a center line being preferably positioned substantially perpendicularly to the axis of rotation (3) of the turntable (1).

5. Disk drive unit according to claim 4, wherein the transmission element (51, 53, 55) is formed by a tapered end portion (51) of the screw (43, 45) contacting a supporting surface (53) associated with the guide (21), which has a fixed position with respect to the guide (21) in transverse direction, such that the center line will move in a direction substantially parallel to the axis of rotation (3) of the turntable (1) when turning the screw (43, 45).

6. Disk drive unit according to claim 1, wherein the guide (21) comprises at least two parallel guide shafts (29, 31 ).

7. Disk drive unit according to claim 6, wherein the driving assembly comprises a drive shaft(31) and an electric motor (23) connected to the drive shaft (31) to bring it in rotation, the drive shaft (31) being configured as screw spindle (31) having a helical groove and being in engagement with the sledge (19) by a follower (35) mounted to the sledge (19) so as to move the sledge (19) along the screw spindle (31) when rotating it.

8. Disk drive unit according to claim 7, wherein the drive shaft (31) is one of the guide shafts (29, 31).

9. Disk drive unit according to claim 7 or 8, comprising a bearing member (55) which is slidably mounted on the drive shaft (31), the sledge (19) being mounted on the bearing (33), slidable in the direction of adjustment, the adjusting member (43, 45) acting between the sledge (19) and the bearing member (55).

10. Disk drive unit according to claim 9, wherein the bearing member (55) being substantially U-shaped, having a semi-circular web portion (57) and two substantially parallel legs (55), the semi-circular portion (57) fitting around the screw spindle (31), and the legs (59) fitting into a corresponding guide groove (61) in the sledge (19) so as to slidably guide the sledge (19).

11. Disk drive unit according to claim 1, comprising a spring member (41) clamping the adjusting members (43, 45) to the guide (21) on the one hand and allowing a tilt movement of the sledge (19) with respect to the guide (21) on the other hand.

12. Disk drive unit according to claims 7 and 11, wherein the follower (35) and the spring member (41) are integrated.

13. Disk drive unit according to claim 12, wherein the spring member (41) is a leaf spring (41), on which a following member (39) of the follower (35) is mounted, said following member (35) engaging into the groove of the screw spindle (31).

14. Disk drive unit according to claim 7, wherein the follower (35) is positioned between the adjusting members (43, 45).

15. Disk drive unit according to claim 7, wherein each of the adjusting members (43, 45) contacts a portion of the sledge (19) as well as a surface (53) associated with the screw spindle (31), while another portion of the sledge (19) is slidably engaged to a parallel shaft (29) by at least a supporting element.

16. Device for reading and/or writing data on a disk, provided with the disk drive unit according to any one of the preceding claims.