Power transmission member for head movement mechanism, and disk device equipped with the head movement mechanism

The present invention relates to a power transmission member for a head movement mechanism in a disk device. The present invention also relates to a disk device equipped with the head movement mechanism.

Devices that record on or reproduce from disk-shaped recording media, such as optical disk devices for a CD (compact disk), DVD (digital versatile disk), BD (Blu-ray disk), or the like, or magneto-optical disk devices for an MO (magneto-optical disk), MD (mini-disk), or the like, or recording and reproduction magnetic disk devices for an FD (floppy (registered trademark) disk) or the like, and the various disk media used in these devices have already gained widespread acceptance in the world.

Furthermore, technology aimed at increasing recording density is proceeding at a rapid pace today, and this progress brings with it the need for higher precision in the above-mentioned disk devices. In particular, the highest precision is required of the heads acting directly on recording or reproduction on disks.

Meanwhile, the price of these disk devices continues to drop in the marketplace, and the parts, materials, and methods used to make these devices need to be inexpensive yet highly functional.

Also, from the standpoint of lowering transportation costs at the same time, the ideal packaging used to ship these devices is one that is as simple as possible. Reducing the cushioning material used to protect packaged devices has therefore become a goal. The trend today is also toward limiting the use of foamed resins, which are effective as materials used for cushioning, in the viewpoint of environmental protection.

Because the above-mentioned disk devices are thus becoming increasingly precise while fewer options are available for protecting the finished products, either the product strength needs to be increased, or the product itself needs to be capable of protecting its own weak points.

For instance, with an optical disk device that performs recording or reproduction by directing light beam from an optical head at an optical disk that is rotated by a rotation mechanism, the optical head is made up of many optical parts that need to have high precision. Although increasing the joint strength of parts or increasing the part strength itself is one way in order to maintain the precision even after the device has been subjected to an impact or other excessive external force, this often leads to higher unit part prices or more labor in joining the parts. In view of this, it is effective to employ a method that avoids subjecting the optical head to such impact force.

An example of a conventional optical disk device will now be described through reference to FIGS. 16 to 18 . The structures of the device have been disclosed in Japanese Laid-Open Patent Application H10-74370, for example.

The optical head in an optical disk device is generally guided and moved in a radial direction of the disk. If it is subjected to an impact force in this movement direction, the optical head may be forcibly moved to the inside or outside in the radial direction and hit the base member, or a part integrally supported by the base member, at the stop position at the movement range limit. This subjects the optical head to a tremendous impact force. This can cause damages that directly and adversely affects performance of the device, such as damaging the internal parts that make up the optical head, reducing the positional precision between the constituent parts and the like.

FIG. 16 is an example of the mechanism for recording or reproducing with a conventional disk device. In FIG. 16 , 33 is a spindle motor for rotationally driving a disk 31 . The spindle motor 33 includes a turntable on which the disk 31 is placed and fixed. A chucking member for fixing the disk 31 is not shown in FIG. 16 , 34 is an optical head that emits a light beam, 35 A and 35 B are guide shafts for guiding the optical head 34 in the radial direction of the disk placed on the turntable, 37 A, 37 B, 37 C, and 37 D are bearings that support the guide shafts 35 A and 35 B, 39 is a movement motor that serves as a drive source for moving the optical head 34 in the radial direction of the disk placed on the turntable, 38 is a lead screw comprising a spiral groove provided around the peripheral face of a shaft thereof and which is rotated by the drive force of the movement motor 39 , 41 is a transmission member unit that engages with the lead screw 38 and transmits a propulsion force that moves the optical head 34 in the disk radial direction, and 32 is a chassis that integrally supports the above-mentioned members. 32 A and 32 B are an inner peripheral stopper and outer peripheral stopper, respectively, for limiting the movement of the optical head 34 at the disk innermost peripheral location and outermost peripheral location, respectively. The optical head 34 comes into contact with the inner peripheral stopper 32 A and the outer peripheral stopper 32 B at the innermost peripheral location and outermost peripheral location, respectively.

FIG. 17 is a detail diagram of the portion in which the transmission member unit 41 in FIG. 16 is fixed to the optical head 34 and engages with the lead screw 38 shown in FIG. 18 . In FIG. 17 , 43 is a tooth component that engages with the spiral groove provided around the axial peripheral face of the lead screw 38 , and is supported by an elastic support member 42 . 44 is a compression spring for biasing the tooth component 43 toward the lead screw 38 , and 46 is a tooth component thrust limiting member for limiting the position of the tooth component 43 with respect to the axial direction of the lead screw 38 . The tooth component thrust limiting member 46 is disposed with a specific gap between itself and the tooth component 43 . These members are integrally constituted on an attachment base 45 and fixed and supported by the optical head 34 .

With the configurations in FIGS. 16 and 17 , the optical head 34 is moved in the radial direction of the disk 31 by driving the movement motor 39 , and recording or reproduction is performed at a specific radial position of the disk 31 .

FIG. 18 is a diagram of the detailed structure of the engagement portion between the tooth component 43 and the lead screw 38 as seen in the direction of the arrow PJ 2 in FIG. 17 . As shown in FIG. 18 , when the lead screw 38 turns in the direction of the arrow R 11 , the tooth component 43 is subjected to moment in the direction of the arrows D 11 and D 13 . At this point, the optical head 34 is subjected to force from the tooth component 43 via the attachment base 45 and the elastic support member 42 , and is subjected to force in the D 12 direction. Thus, the optical head 34 obtains a propulsion force in the radial direction of the disk. At the same time, the tooth faces of the tooth component 43 are subjected to force in the direction away from the lead screw 38 , but this is blocked by the biasing force of the compression spring 44 .

However, when excessive drive force is produced by the lead screw 38 due, for example, to a loss of control of the movement motor 39 , and excessive propulsion force is generated in the direction of the arrow D 11 , the moment in the direction of the arrow D 13 also increases, resulting in a state in which the meshing of the tooth component 43 and the lead screw 38 is irregular.

This irregular state is suppressed by limiting displacement with the tooth component thrust limiting member 46 when the tooth component 43 comes into contact with a limiting face 46 A or limiting face 46 B. This keeps the meshing in a regular state.

However, when the optical head 34 is subjected to an excessive external force, such as impact force, in its movement direction, the tooth component 43 may come out of the groove of the lead screw 38 , so that the engagement cannot be maintained, even though the tooth component 43 is restricted in its displacement in the movement direction by the tooth component thrust limiting member 46 . Consequently, the optical head 34 may move in an unrestricted state to the limit of its movable range in this direction, and collide with the inner peripheral stopper 32 A or the outer peripheral stopper 32 B at the innermost peripheral location or outermost peripheral location, respectively. A problem at this point is that the constituent members of the optical head 34 or the places where it is joined are susceptible to being damaged.

To solve this problem, the structure aimed at preventing the tooth component 43 from coming out of the groove of the lead screw 38 has been disclosed in Japanese Laid-Open Patent Application 2000-339882, for example. This structure will now be described through reference to FIGS. 19 and 20 .

In FIG. 19 , 12 is a turntable on which a disk (not shown) is placed and fixed. The turntable 12 is rotationally driven by a spindle motor 11 . The chucking member for fixing the disk is not shown in FIG. 19. 16 is an optical head for recording on or reproducing from a disk by emitting a light beam, 13 and 14 are guide shafts for guiding the optical head 16 in the radial direction of the disk placed on the turntable 12 . 22 A, 22 B, 22 C, and 22 D are bearings that support the guide shafts 13 and 14 . 17 is a movement motor that serves as a drive source for moving the optical head 16 in the radial direction of the disk placed on the turntable 12 , 15 is a lead screw comprising a spiral groove provided around the axial peripheral face of a shaft thereof and which is rotated by the drive force of the movement motor 17 , 18 is a power transmission member that engages with the lead screw 15 and transmits a propulsion force that moves the optical head 16 in the disk radial direction, and 19 is a chassis that integrally supports the above-mentioned members.

With the structure shown in FIG. 19 , when the movement motor 17 is driven, it moves the head 16 in the disk radial direction, and recording or reproduction is performed at a specific radial position of the disk.

FIG. 20 is a diagram of a state in which the power transmission member 18 and the lead screw 15 have been engaged. The power transmission member 18 is made up of an engagement component 20 provided with a tooth component 20 A that fits into a spiral groove 15 A of the lead screw 15 , and a limiting component 21 for preventing the tooth component 20 A from coming out of the spiral groove 15 A.

Providing the limiting component 21 avoids the problem in which the engagement component 20 is displaced perpendicularly to the movement direction and the tooth component 20 A comes out of the spiral groove 15 A when the head 16 is subjected to an excessive movement force caused by impact or the like in the movement direction. This makes it possible to prevent the power transmission member 18 from being in an unrestricted state in the movement direction. This also prevents a situation in which, if the head 16 should be subjected to an impact force in its movement direction, the head 16 moves in an unrestricted state up to the limit of its movable range in the movement direction, collide with the base member 10 itself or one of the parts that are constituted integrally with the base member 10 , and the constituent members of the head 16 , or places where it is joined, are subjected to damage.

Patent Document 1: Japanese Laid-Open Patent Application H10-74370

Patent Document 2: Japanese Laid-Open Patent Application 2000-339882

Problems Which the Invention is Intended to Solve

However, although the structure shown in FIGS. 19 and 20 does avoid the problem of the engagement component 20 coming out of the spiral groove 15 A, it does not solve the problems arising from the collision of the optical head 16 . Specifically, if the spiral advance angle A 11 of the spiral groove 15 A shown in FIG. 20 is large, then when an impact force F 11 is applied, there will be little vertical resistance N 11 as a reaction force from a component force F 12 of the impact force F 11 , and this will result in a smaller frictional force R 11 , so there is the possibility that the tangential force F 13 , which is a component force of the impact force F 11 in the groove face direction of the lead screw 15 , may exceed this frictional force R 11 . If this happens, the lead screw 15 will be subjected to a force in the peripheral direction, that is, it will turn. Therefore, the optical head 16 cannot be stopped from moving in the direction of the impact force F 11 , and ends up moving all the way to the limit of its movable range, so in the end it is inevitable that it will collide with the base member 10 itself or one of the parts that are constituted integrally with the base member 10 . The collision force produced during the collision here propagates directly to the optical head 16 , so a problem is that it results in damage that directly affects performance, such as damage to the constituent parts inside the optical head 16 , reduced positional precision between the constituent parts, etc.

It is an object of the present invention to solve the above problems encountered in the past and provide a power transmission member for a head movement mechanism, as well as a disk device equipped with the head movement mechanism, with which the collision force produced when an optical head is subjected to an impact force in its movement direction and collides with part of a base member, or part of a member fixed to the base member, is attenuated rather than directly propagating to the optical head, which makes it possible to lessen the damage to constituent parts.

Means Used to Solve the Above-Mentioned Problems

To achieve the stated object, the power transmission member of the present invention is a power transmission member of a mechanism for moving a head, used for recording on or reproducing from a disk, relative to a base member in a disk device, comprising a fixed component, a power transmission component, a linking component, and a contacting component. The fixed component is configured to be attached to the head. The power transmission component receives drive from a motor serving as a drive source. The linking component links the fixed component and the power transmission component. The contacting component is fixed to the power transmission component, and comes into contact with a contacted component that is part of the base member, or part of a member fixed to the base member, at least one end of the movement range of the head. This contacting component is linked to the fixed component in an elastic manner, and has a relative position being variable with respect to the fixed component in the movement direction of the head.

Further, to achieve the stated object, the disk device of the present invention comprises a disk rotation mechanism for rotating a disk capable of recording or reproduction, a head for recording on or reproducing from the disk, a head movement mechanism for moving the head in a radial direction of the disk, and a base member for integrally supporting the disk rotation mechanism, the head, and the head movement mechanism. The head movement mechanism has a power transmission mechanism that includes a power transmission member and transmits power to the head, and a motor that serves as a drive source of the power transmission mechanism. The power transmission member has a fixed component that is configured to be attached to the head, a power transmission component for receiving drive from the power transmission mechanism, a linking component for linking the fixed component and the power transmission component, and a contacting component that is fixed to the power transmission component, for coming into contact with part of the base member, or part of a member fixed to the base member, at least one end of the movement range of the head. This contacting component is linked to the fixed component via the linking component in an elastic manner, and has a relative position being variable with respect to the fixed component in the movement direction of the head.

As described above, the power transmission member and disk device of the present invention offer the following advantageous effects. The head is forcibly moved upon being subjected to an impact force in the disk radial direction, and collides with part of the base member or the like, etc. at least one end of the movement range of the head. At this point, the kinetic energy produced by this movement is attenuated by the elastic deformation of the linking component between the fixed component and the contacting component, and this prevents the collision force from propagating directly to the head itself. As a result, this design avoids damage to the parts that make up the head and to the joints between the respective parts. This prevents deterioration in performance due, for example, to damage to the constituent parts inside the head, or reduced positional precision between the constituent parts, and therefore prevents a situation in which the disk device is unable to perform recording or reproduction. An additional effect of the power transmission member of the present invention is that the head is easier to position, and movement of the head produces less noise and vibration.

Also, with the power transmission member of the present invention, since the relative position of the contacting component is variable with respect to the fixed component in at least the movement direction of the head, even if the contacting component should collide with part of the base member, etc., within the movement range of the head, and subjected to the resulting reaction force, the reaction force will be attenuated before being transmitted to the power transmission component. Therefore, the reaction force to which the power transmission component is subjected is reduced, making it possible to avoid problems in the transmission configuration of the power transmission component.

Also, with the disk device of the present invention, the power transmission mechanism has a lead screw comprising a continuous spiral groove provided around the outer periphery of its cylindrical shaft. The power transmission component has a nut component at least part of which is provided with a rib capable of engaging with the continuous groove. This nut component is constituted integrally with the contacting component, and has a relative position being variable with respect to the head in at least the movement direction of the head. This makes the power transmission mechanism simpler and also increases transmission efficiency.

In this case, even if the contacting component should collide with part of the disk within the movement range of the head, and the resulting reaction force should be applied to the power transmission component, this force will be attenuated. Therefore, the engagement part of the rib can be prevented from coming out of the spiral continuous groove.

FIG. 1 is an oblique perspective view of the overall configuration of a head movement mechanism in a disk device of an embodiment of the present invention;

FIG. 2 is an oblique perspective view of details of the portion in which a power transmission member is driven by a lead screw in the disk device of the embodiment of the present invention;

FIG. 3 is a cross section of a state in which the lead screw and a nut component are engaged in the disk device of the embodiment of the present invention;

FIG. 4 is a diagram of the relationship of engagement between the lead screw and the nut component in the disk device of the embodiment of the present invention;

FIG. 5 is a diagram of the detailed configuration of the power transmission member in the disk device of the embodiment of the present invention;

FIG. 6 is a diagram of the detailed configuration of the power transmission member in the disk device of the embodiment of the present invention;

FIG. 7 is a diagram of the detailed configuration of the power transmission member in the disk device of the embodiment of the present invention;

FIG. 8 is a diagram of the detailed configuration of the power transmission member in the disk device of the embodiment of the present invention;

FIG. 9 is a schematic representation of the operation of the power transmission member of the present invention during the collision of the head;

FIG. 10 is a schematic representation of the operation of the power transmission member of the present invention during the collision of the head;

FIG. 11 is a schematic representation of the operation of the power transmission member of the present invention during the collision of the head;

FIG. 12 is a schematic representation of the operation of a conventional power transmission member during the collision of the head;

FIG. 13 is a schematic representation of the operation of the conventional power transmission member during the collision of the head;

FIG. 14 is a schematic representation of the operation of the conventional power transmission member during the collision of the head;

FIG. 15 is a schematic representation of the operation of another conventional power transmission member during the collision of the head;

FIG. 16 is an oblique perspective view of the overall configuration of a head movement mechanism in a conventional disk device;

FIG. 17 is a detail view of the configuration of the power transmission member unit in the conventional disk device of FIG. 16 ;

FIG. 18 is a detail view of a state in which the lead screw is engaged with the tooth component, out of the transmission unit in the conventional disk device of FIG. 16 ;

FIG. 19 is an oblique perspective view of the overall configuration of a head movement mechanism in another conventional disk device; and

FIG. 20 is a detail view of a state in which the lead screw is engaged with the power transmission member in the conventional disk device of FIG. 19 .

1 turntable

2 spindle motor

3 chassis

5 optical head

6 main guide shaft

7 secondary guide shaft

8 movement motor

9 lead screw

9 A continuous groove

10 power transmission member

10 A nut component

10 B limiting component

10 C nut support component

10 D support column

10 E support column

10 F, 10 G nut support component contact column

10 H fixed side

10 J, 10 K fixed component contact column

The concept behind the disk device in an embodiment of the present invention will now be described. The disk device in this embodiment is an optical disk device that records or reproduces information by emitting a light beam from an optical head onto an optical disk that is rotated by a rotation mechanism, and is generally constituted such that the optical head is guided and moved in a radial direction of the disk.

FIG. 1 is a simplified view of the configuration of the disk device in this embodiment. In FIG. 1 , 1 is a turntable on which a disk (not shown) is placed and fixed, and is rotationally driven by a spindle motor 2 . The spindle motor 2 is fixed and supported by a chassis 3 . The disk and the chucking member for fixing the disk are not shown in FIG. 1. 5 refers to an optical head that emits a light beam. 6 and 7 refer to a main guide shaft and a secondary guide shaft, respectively, that guide the optical head 5 in the radial direction of the disk placed on the turntable 1 . The main guide shaft 6 and secondary guide shaft 7 are each supported by bearings 3 A, 3 B, 3 C, and 3 D provided to a base face 3 E of the chassis 3 . 8 refers to a movement motor that serves as a drive source for moving the optical head 5 in the radial direction of the disk placed on the turntable 1 , and 9 refers to a lead screw comprising a spiral continuous groove provided around the peripheral face of a shaft thereof, and which is rotated by a drive force obtained on the same axis as that of the movement motor 8 . 10 refers to a power transmission member that engages with the lead screw 9 and transmits a propulsion force that moves the optical head 5 in the disk radial direction.

FIG. 2 is a detail view of a state in which the power transmission member 10 is engaged with the lead screw 9 . In FIG. 2 , 8 A refers to a motor bracket provided to the movement motor 8 , for fixing and supporting the movement motor 8 to the chassis 3 . 9 A refers to a spiral continuous groove provided to the lead screw 9 . 10 A refers to a nut component provided to the power transmission member 10 , and is part of a spiral rib that fits into and engages with the continuous groove 9 A. In this embodiment, the spiral direction of the continuous groove 9 A is that of a right-hand thread.

10 B refers to a limiting component that prevents the nut component 10 A from coming out of the spiral continuous groove 9 A. The function of this limiting component 10 B will now be described.

FIG. 3 is a cross section along the plane P 1 in FIG. 2 . This plane P 1 is an imaginary plane that includes the axis of the movement motor 8 and the lead screw 9 , and is parallel to the side of the turntable 1 where the disk is placed in FIG. 1 .

As shown in FIG. 3 , the continuous groove 9 A and the nut component 10 A each have a trapezoidal cross section whose sloped sides form an angle A 1 , and the sloped sides of the trapezoids are in contact with each other. Also, the nut component 10 A is pushed by a pushing force F 1 into the continuous groove 9 A. When the lead screw 9 turns in the direction of the arrow R 1 in FIG. 2 , because the continuous groove 9 A is a right-hand thread, a propulsion force F 2 is generated in the continuous groove 9 A. If we use the lead screw 9 as a reference, the propulsion force F 2 is broken down into a horizontal force F 3 and a vertical force F 4 that act on the nut component 10 A. If we let M 1 be the coefficient of friction at the interface between the continuous groove 9 A and the nut component 10 A here, then the frictional force R 11 in the direction parallel to the horizontal force F 3 is expressed by Equation 1 below.

R 11 =M 1 ·F 4  (Equation 1)

Here, F 4 is expressed by the following Equation 2.

F 4= F 2 cos( A 1)  (Equation 2)

Therefore, Equation 1 is expressed by the following Equation 3.

R 11 =M 1 ·F 2 cos( A 1)  (Equation 3)

F 3 is expressed by the following Equation 4.

F 3 =F 2 sin( A 1)  (Equation 4)

The force F 5 acting in the direction in which the nut component 10 A comes out of the continuous groove 9 A here is expressed by the following Equation 5 from Equations 3 and 4, as the combined force of the component force F 31 (Equation 1) from the horizontal force F 3 in FIG. 3 and the component force R 1 from the frictional force R 11 .

M 1 is a value less than 1, and A 1 is 90 degrees or less, so the right side in Equation 5 is always a positive number.

Therefore, to keep the nut component 10 A from coming out of the continuous groove 9 A, the relation expressed by the following Equation 6 must be satisfied.

F 1 >F 5 =F 2{sin( A 1)− M 1 cos( A 1)} cos( A 1)  (Equation 6)

Because of Equation 6, to keep the nut component from coming out, either the pushing force F 1 must be increased, or the frictional force M 1 must be increased.

However, when either of these is increased, there is greater frictional force at the interface between the nut component 10 A and the continuous groove 9 A. In this case, the sliding load between the two increases, so this leads to adverse effects such as an increase in the rotational load of the movement motor 8 , or accelerated wear at the interface.

In view of this, if the limiting component 10 B is provided, then even if the nut component 10 A should be subjected to a force in the direction in which it would come out of the continuous groove 9 A, the side of the continuous groove 9 A opposite the nut component 10 A will be limited, preventing the nut component 10 A from coming out.

This holds true not only when the propulsion force F 2 from the continuous groove 9 A is applied to the nut component 10 A, but also when a force is applied from the nut component 10 A to the continuous groove 9 A. For example, this corresponds to a situation in which an excessive external force is applied in the movement direction of the optical head 5 in a state in which no drive force is being generated in the lead screw 9 .

A situation in which an external force is applied in the movement direction of the optical head 5 in a state in which no drive force is being generated in the lead screw 9 will now be described through reference to FIG. 4 .

FIG. 4 is a schematic transparent view of the limiting state of the nut component 10 A and the continuous groove 9 A, as seen in the direction of the arrow PJ in FIG. 2 . The nut component 10 A and the continuous groove 9 A both have an advance angle A 2 . The coefficient of friction at the interface between the two is M 2 .

At this point, if an external force F 6 is applied in the direction D 1 in FIG. 2 to the nut component 10 A in a state in which no drive force is being generated in the lead screw 9 , a vertical force F 7 and a horizontal force F 8 are generated at the interface as component forces of F 6 . At the same time, the frictional force R 2 shown in Equation 7, below is generated at this interface.

R 2= M 2 ·F 7  (Equation 7)

F 7 here is expressed by the following Equation 8.

F 7 =F 6 cos( A 2)  (Equation 8)

Therefore, R 2 is expressed by the following Equation 9.

R 2= M 2 ·F 6 cos( A 2)  (Equation 9)

Also, F 8 is expressed by the following Equation 10.

F 8 =F 6 sin( A 2)  (Equation 10)

At this point, if the horizontal force F 8 is greater than the frictional force R 2 , slippage will occur at this interface, that is, the lead screw 9 will be forcibly rotated. This condition is expressed by the following Equation 11.

F8>R2  (Equation 11)

Based on Equations 9 to 11, we obtain the following Equation 12.

F 6 sin( A 2)> M 2 ·F 6 cos( A 2)  (Equation 12)

This can be rewritten as in the following Equation 13.

M 2<Tan( A 2)  (Equation 13)

Whether or not this condition is met is determined by the value of the coefficient of friction M 2 and the advance angle A 2 . That is, the result will vary with the combination of materials of the lead screw 9 and the nut component 10 A, and the setting of the advance angle A 2 . For example, when the coefficient of friction M 2 is 0.2 and the advance angle A 2 is 15 degrees, the right side of Equation 13 is 0.27, and the condition is met.

“No drive force is generated in the lead screw 9 ” is a state in which it is assumed, for example, that there is no cogging or other static holding force present in the movement motor 8 .

Under this condition, when, for example, the disk device of this embodiment has been dropped in the direction of the arrow D 1 in FIG. 1 and hit the ground, most of the momentum attributable to the velocity just prior to the collision propagates to the head 5 , and the head 5 is forcibly moved with this momentum in the direction of the arrow D 1 . Here, the position of at least the head 5 prior to being dropped is separated by a gap from the chassis 3 or some other member held integrally with the chassis 3 . The only thing limiting the head 5 from going in the movement direction at this point is the frictional force at the interface between the nut component 10 A and the continuous groove 9 A.

With the momentum generated at the highest velocity attained by acceleration produced in this forcible movement, the head 5 collides with the chassis 3 itself, or with some other member held integrally with the chassis 3 , at the limit to the movement range of the head 5 . This collision causes most of the momentum had by the head 5 to work as an impact force against the head 5 , the chassis 3 or another member thereof, and mainly results in deformation of the member, damage to connected portions, or the like.

In view of this, if the above-mentioned momentum could be reduced, it would be possible to avoid the deformation of members, damage to connected portions, and so forth. To this end, it is effective to stop the head 5 that has been forcibly moved, while lessening the impact at the movement range limit.

A configuration for stopping the head 5 that has been forcibly moved while lessening the impact at the movement range limit, when, as a result of the disk device of this embodiment being dropped and colliding with the ground, most of the momentum attributable to the velocity just prior to the collision is transmitted to the head 5 , will now be described through reference to FIGS. 2 and 5 .

FIG. 5 is a detail view of the structure of the power transmission member 10 . In FIG. 5 , 10 C refers to a nut support component for integrally supporting the nut component 10 A and the limiting component 10 B. The nut support component 10 C is supported by support columns 10 D and 10 E, and is able, through the bending of the support columns 10 D and 10 E, to pivot in the arrow D 5 direction or the arrow D 6 direction. A nut support component contact column 10 F and a nut support component contact column 10 G are integrally provided to the nut support component 10 C. A fixed component contact column 10 J and a fixed component contact column 10 K are integrally provided to the side 10 H of the power transmission member 10 which is fixed to the head 5 . The nut support component contact column 10 F and the nut support component contact column 10 G have a nut-side contact face 10 FA and a nut-side contact face 10 GA, respectively, and the fixed component contact column 10 J and the fixed component contact column 10 K have a fixed-side contact face 10 JA and a fixed-side contact face 10 KA, respectively. The nut-side contact face 10 FA and the nut-side contact face 10 GA, and the fixed-side contact face 10 JA and the fixed-side contact face 10 KA are respectively across from each other with a gap P in between.

With the structure described above, when the head 5 is forcibly moved in the arrow D 1 direction or the arrow D 2 direction in FIG. 1 , first a nut-side contact face 10 FB or a nut-side contact face 10 GB, which is a back side of the nut-side contact face 10 FA or the nut-side contact face 10 GA of the nut support component contact column 10 F or the nut support component contact column 10 G, comes into contact with a contact face 8 AF or 8 AG of the motor bracket 8 A in FIG. 2 , and the movement range limit is reached.

Since at this point the kinetic energy produced by the movement of the head 5 has still not been attenuated, the head 5 is subjected to an inertial force that carries it in its direction of movement. This inertial force causes the nut support component 10 C to pivot backward away from the movement with respect to the fixed side 10 H. At this point, the kinetic energy here is attenuated by being converted into the elastic energy required to bend the support column 10 D and the support column 10 E.

After further movement by remaining kinetic energy that has not been converted into elastic energy, the nut-side contact face 10 FA or the nut-side contact face 10 GA hits the fixed-side contact face 10 JA or the fixed-side contact face 10 KA, and the movement of the head 5 comes to a halt.

The amount of kinetic energy that is converted at this time depends on the spring constant of the support column 10 D or the support column 10 E, and the larger is the spring constant, the greater is this amount of energy, but there is also greater impact force produced by the reaction from the spring force caused by backward bending. Accordingly, the spring constant is preferably optimized by taking into account the magnitude of impact, the weight of the head 5 , the value of the gap P, and so forth.

Thus optimizing the support column 10 D and support column 10 E and attenuating the forcible movement of the head 5 causes the kinetic energy had by the head 5 to work on the head 5 , the chassis 3 , or another member, which prevents the deformation of members, damage to connected portions, or the like.

The condition for converting all of the kinetic energy produced by the movement of the head 5 into elastic energy for bending the support column 10 D and support column 10 E is expressed by the following Equation 14, where Mh is a mass of the head 5 , Vh is the velocity of the head 5 just before the nut-side contact face 10 FA or the nut-side contact face 10 GA comes into contact with the fixed-side contact face 10 JA or the fixed-side contact face 10 KA, respectively, and Ks is the combined spring constant of the support column 10 D and support column 10 E.

(½)· Mh·Vh 2<(½)· Ks·P 2  (Equation 14)

However, if the condition of Equation 14 is not met, such as when the gap P cannot be made large enough, or when the relationship of the constituent materials imposes a limit to the combined spring constant Ks, it may be impossible to completely eliminate the above-mentioned kinetic energy when the nut-side contact face 10 FA or the nut-side contact face 10 GA comes into contact with the fixed-side contact face 10 JA or the fixed-side contact face 10 KA, respectively.

Therefore, after the two have come into contact, just the fixed side 10 H and the portion constituted integrally therewith (including the head 5 ) rebound and begin forcible movement in the opposite direction from that of the initial movement, corresponding to the remaining kinetic energy. The nut support component 10 C is stationary at this time until the bending of the support column 10 D and support column 10 E has been released.

In the forcible movement of the head 5 , as already described above, if the condition of Equation 13 has been met, the lead screw 9 is also forcibly rotated, but if the head 5 is forcibly moved in the opposite direction from its initial movement, then the lead screw 9 also rotates in the opposite direction. This imparts rotational inertia to the lead screw 9 , and the nut component 10 A is subjected to a force in the direction in which it comes out of the continuous groove 9 A.

As described above, when the limiting component 10 B subjects the nut component 10 A to a force in the direction in which it would come out of the continuous groove 9 A as shown in FIG. 3 , the movement is limited on the side of the continuous groove 9 A across from the nut component 10 A, but when the force F 5 acting in the direction in which the nut component 10 A comes out of the continuous groove 9 A is larger than the limiting force of the limiting component 10 B, the nut component 10 A is again displaced in the direction in which it would come out of the continuous groove 9 A.

Situations in which the limiting force of the limiting component 10 B is less than the force F 5 acting in the direction in which the nut component 10 A comes out of the continuous groove 9 A include when the limiting component 10 B is damaged because its breaking strength cannot withstand F 5 , so no limiting force at all is generated, and when the elastic strength of the limiting component 10 B is less than F 5 . In the former case, since there is no limiting force after the damage, the nut component 10 A cannot be prevented from coming out of the continuous groove 9 A. In the latter case, the nut component 10 A again cannot be prevented from coming out of the continuous groove 9 A unless the elastic strength of the limiting component 10 B is greater than F 5 in the region of displacement required for the nut component 10 A to come out of the continuous groove 9 A.

Thus, when an impact force causes the head 5 to move backward from its initial movement, and the lead screw 9 is forcibly rotated, the impact imparts excessive rotational inertia, so the elastic strength and breaking strength of the limiting component 10 B must be increased in order to avoid this, but if F 5 is large enough to exceed this strength, then it will be impossible to avoid a situation in which the nut component 10 A comes out of the continuous groove 9 A. Depending on how the force is received during the impact, the nut component 10 A or the lead screw 9 may deform or break, causing the nut component 10 A to come out of the continuous groove 9 A. Furthermore, if the nut component 10 A does come out of the continuous groove 9 A, the lead screw 9 will be unable to impart a movement propulsion force to the power transmission member 10 . Specifically, it will be impossible to move the head 5 , and the device will not function as an optical disk device.

To avoid this problem, it is effective to provide a structure in which the force of forcible movement exerted on the nut support component 10 C is attenuated even when at least the head 5 has been subjected to an impact and then rebounded and forcibly moved in the opposite direction from its initial movement.

With the disk device of this embodiment, as described above, after the head 5 has been subjected to an impact and the nut-side contact face 10 FA or the nut-side contact face 10 GA has come into contact with the fixed-side contact face 10 JA or the fixed-side contact face 10 KA, respectively, the nut support component 10 C is stationary with no force propagating to the nut support component, until the bending of the support column 10 D and support column 10 E is released. Specifically, there is a delay from the time when the head 5 is subjected to an impact until the nut support component 10 C is subjected to movement force in the opposite direction from its initial movement. The movement force that propagates to the nut support component 10 C in the opposite direction from the initial movement can be attenuated by the time until the bending of the support column 10 D and support column 10 E is released during this period.

Next, the characteristic structure of the power transmission member 10 in this embodiment, and the action thereof, will be described while comparing them to those of a power transmission member in a typical, conventional configuration.

FIGS. 9 to 11 are embodiments having a configuration that allows an impact to be lessened as the head 5 is stopped when the head 5 has been forcibly moved in the arrow D 1 direction, reaches its movement range limit, and collides with the chassis 3 itself or some member that is supported integrally with the chassis 3 . These drawings schematically illustrate the relationship between the contact face 8 AG and the head 5 , the power transmission member 10 , and the lead screw 9 . FIGS. 12 to 15 illustrate conventional configurations for the sake of comparison with this embodiment.

FIG. 9 shows the state when the head 5 has been forcibly moved in the arrow D 1 direction, and the nut-side contact face 10 GB is in contact with the contact face 8 AG. The nut component 10 A, which is part of the power transmission member 10 , stops its displacement with respect to the contact face 8 AG at this stage.

Meanwhile, when the lead screw 9 rotates in the direction of the arrow R 2 , it generates a movement force in the arrow D 1 direction of the head 5 . Therefore, when the head 5 is forcibly moved in the arrow D 1 direction by another external force, the lead screw 9 is forcibly rotated in the arrow R 2 direction, and the inertia from this rotation remains even at the stage shown in FIG. 9 , so the rotational force itself continues.

Also, since the nut component 10 A and the fixed side 10 H in the power transmission member 10 are configured so as to be able to be forcibly displaced by the support columns 10 D and 10 E, the head 5 itself is also capable of being displaced with respect to the nut component 10 A in an elastic manner. Accordingly, even if the nut-side contact face 10 GB comes into contact with the contact face 8 AG, the movement of the head 5 itself will continue under the inertia of the force remaining in the arrow D 1 direction. A force F 10 is acting on the head 5 and the power transmission member 10 at this time.

FIG. 10 illustrates the state immediately after the state shown in FIG. 9 , in which the head 5 has elastically deformed the support columns 10 D and 10 E by its inertia. At this stage, the elastic deformation of the support columns 10 D and 10 E disperses the force F 10 by splitting in by weight ratio between the head 5 and the nut component 10 A, with the force F 11 acting on the head 5 and F 12 , which is smaller than F 11 , acting on the nut component 10 A. Also, the rotational force in the arrow R 2 direction acting on the lead screw 9 continues.

FIG. 11 illustrates the state immediately after the state shown in FIG. 10 , in which the head 5 has returned in the arrow D 2 direction by rebound produced by the elastic strength of the support columns 10 D and 10 E. The nut-side contact face 10 GB remains in contact with the contact face 8 AG at this time. At this stage, the head 5 and the nut component 10 A are subject to forces F 13 and F 14 , which are rebound of F 11 and F 12 , and whose severity is substantially equivalent to the result of F 11 and F 12 being attenuated somewhat, work in the arrow D 2 direction.

The rotational force in the arrow R 2 direction acting on the lead screw 9 continues at this time as well. This rotational force acts as a force to move the head 5 in the arrow D 11 direction, while the nut component 10 A is subject to a force in the direction in which it is forcibly moved by the force F 14 in the arrow D 2 direction, which is the opposite direction, so these forces act as mutually opposing forces. Accordingly, the nut component 10 A is subject to a force that would make it come out of the continuous groove 9 A, but as shown in FIG. 11 , the force F 14 is sufficiently smaller than the force F 13 , so the nut component 10 A does not end up coming out.

Meanwhile, with the conventional configuration shown in FIGS. 12 to 14 , the basic structure of the head 5 , the power transmission member 10 , the lead screw 9 , and the contact face 8 A is substantially the same as that in the case of FIGS. 9 to 11 , but the structure of the power transmission member 10 is different.

The difference between the structure of this embodiment shown in FIGS. 9 to 11 and the structure shown in FIGS. 12 to 14 is that the power transmission member 10 in the former has the function of lessening the impact of collision when the head 5 is forcibly moved. With the structure in this embodiment, the impact is absorbed by the support columns 10 D and 10 E, but with the structure shown in FIGS. 12 to 14 , it is absorbed by the elasticity of the cushioning spring component 110 E. This action will now be described.

In FIGS. 12 to 14 , the power transmission member 10 is constituted such that the nut component 10 A and the fixed side 10 H are in a rigid state. Also, the cushioning spring component 110 E is provided to the face of the power transmission member 10 that is across from the contact face 88 AG on the arrow D 1 side.

FIG. 12 illustrates a state in which the head 5 has been forcibly moved in the arrow D 1 direction, and the cushioning spring component 1110 E is in contact with the contact face 88 AG. Displacement of the power transmission member 10 with respect to the contact face 8 AG stops at this stage. Meanwhile, the lead screw 9 rotates in the arrow R 2 direction and generates a force that moves the head 5 in the arrow D 11 direction, so when the head 5 is forcibly moved by another external force in the arrow D 1 direction, the lead screw 9 is forcibly rotated in the arrow R 2 direction, and the inertia from this rotation remains even at the stage shown in FIG. 12 , so the rotational force itself continues. Also, since the power transmission member 10 is configured so as to be able to be displaced by the cushioning spring component 110 E in an elastic manner, the head 5 itself is also capable of being elastically displaced with respect to the contact face 88 AG. Accordingly, even if the cushioning spring component 110 E comes into contact with the contact face 88 AG, the movement of the head 5 itself will continue under the inertia of the force remaining in the arrow D 1 direction. A force F 10 is acting on the head 5 and the power transmission member 10 at this time. This force is the same as F 10 in FIG. 9 .

FIG. 13 illustrates the state immediately after the state shown in FIG. 12 , in which the head 5 has elastically deformed the cushioning spring component 110 E by its inertia. The force F 10 at this stage is split so that F 15 acts on the head 5 and F 16 on the nut component 10 A, but because the nut component 10 A is rigid with respect to the fixed side 10 H, the result is that the force F 15 acting on the head 5 is equivalent to the force F 16 acting on the nut component 10 A. Also, the rotational force in the arrow R 2 direction acting on the lead screw 9 continues.

FIG. 14 illustrates the state immediately after the state shown in FIG. 13 , in which the head 5 has returned in the arrow D 2 direction by rebound produced by the elastic strength of the cushioning spring component 110 E. The cushioning spring component 110 E remains in contact with the contact face 88 AG at this time. At this stage, the head 5 and the nut component 10 A are subject to forces F 17 and F 18 , which are rebound of F 15 and F 16 and whose severity is substantially equivalent to the result of F 15 and F 16 being attenuated somewhat, work in the arrow D 2 direction. However, as described above, since the force F 15 acting on the head 5 is equivalent to the force F 16 acting on the nut component 10 A, the force F 17 generated by rebound and acting on the head 5 is also equivalent to the force F 18 acting on the nut component 10 A.

Here again, the rotational force in the arrow R 2 direction acting on the lead screw 9 continues at this time as well. Just as in the case of the state shown in FIG. 11 , this rotational force acts as a force to move the head 5 in the arrow D 11 direction, while the nut component 10 A is subject to a force in the direction in which it is forcibly moved by the force F 18 in the arrow D 2 direction, which is the opposite direction, so these forces act as mutually opposing forces. Accordingly, just as in the state shown in FIG. 11 , the nut component 10 A is subject to a force that would make it come out of the continuous groove 9 A. However, with the state in the embodiment shown in FIG. 11 , the force F 14 is sufficiently smaller than the force F 13 , so the nut component 10 A does not end up coming out of the continuous groove 9 A, whereas with the state in the conventional configuration shown in FIG. 14 , since the force F 18 is equivalent to the force F 17 , the nut component 10 A more readily comes out of the continuous groove 9 A.

As shown in FIG. 15 , this holds true in a configuration in which the cushioning spring component 110 E is added not to the power transmission member 10 , but to the contact surface 88 A side.

Thus, in the embodiment, the power transmission member 10 is constituted so that the nut component 10 A and the fixed side 10 H are capable of elastic relative displacement, and therefore when the head 5 is forcibly moved, collides, and then rebounds, the nut component 10 A can be prevented from coming out of the continuous groove 9 A. As a result, it is possible to prevent the head 5 from being incapable of moving by the lead screw 9 after a collision.

Furthermore, an additional effect of the power transmission member 10 pertaining to this embodiment is that the head 5 is easier to position, and movement of the head 5 produces less noise and vibration. More specifically, the head 5 can be positioned with respect to the chassis 3 by bringing the nut-side contact face 10 GB into contact with the contact face 8 AG. However, when this contact is achieved by an ordinary movement operation of the head 5 , this is limited to a case in which the rigidity of the support columns 10 D and 10 E is set such that the amount of bending of the support columns 10 D and 10 E will be sufficiently small with respect to the amount required for the movement precision of the head 5 . Any noise and vibration produced by movement of the head 5 will be absorbed by minute movements of the support columns 10 D and 10 E.

Furthermore, with the power transmission member 10 in the above-described embodiment, in order for the nut support component 10 C to have the function of being displaced with respect to the fixed side 10 H, a structure involving the bending of the support columns 10 D and 10 E is used, but another structure that accomplishes the same function may be used instead. In the above embodiment, elasticity is obtained by bending the support columns 10 D and 10 E in their lengthwise direction, but it is also possible, for example, to obtain elasticity by the buckling of a column made of an elastic material.

If kinetic energy cannot be attenuated with just this elastic deformation, then as shown in FIG. 6 , for example, another effective means is to increase the amount of energy that can be absorbed by partial linking, leaving gaps G 5 and G 6 between the nut support component contact column 10 F and nut support component contact column 10 G and the fixed component contact column 10 J and fixed component contact column 10 K, and thereby raising rigidity by having areas of elastic deformation extend entirely over these components.

Also, to further improve the attenuation effect in the above embodiment, it is effective to use an elastomer or other attenuating member to fill the gaps between the nut-side contact face 10 FA and nut-side contact face 10 GA and the fixed-side contact face 10 JA and fixed-side contact face 10 KA. Examples of materials suitable to this application include butyl rubber and silicone rubber.

Also, rather than filling the gaps with these attenuating members, it is possible to improve the attenuation effect by adding them to one of the faces of the nut-side contact face 10 FA and nut-side contact face 10 GA or the fixed-side contact face 10 JA and fixed-side contact face 10 KA.

Furthermore, the attenuation achieved by bending the support columns 10 D and 10 E, or the attenuation achieved by bringing the nut-side contact face 10 FA and nut-side contact face 10 GA into contact with the fixed-side contact face 10 JA and fixed-side contact face 10 KA, can be improved by using an elastomer or other such material with good attenuation properties for the material that makes up the power transmission member 10 .

Also, with the power transmission member 10 in the above embodiment, the nut support component 10 C, the support columns 10 D and 10 E, and the fixed side 10 H had an integral structure, but the nut support component 10 C and the fixed side 10 H may instead be linked by separate elastic members 10 M and 10 N, such as a leaf spring, as shown in FIG. 7 . Or, as shown in FIG. 8 , they may be linked by a separate elastic member such as a coil spring. In this case, the same effect can be obtained by choosing the proper spring constant.

The integral structure shown in FIG. 5 is effective in terms of reducing the number of parts required, but when the relationship with other functions is taken into account, manipulating the spring constant may be difficult. With the separate structures shown in FIGS. 7 and 8 , more parts are required, but an advantage is that this affords greater freedom in setting the spring constant.

Furthermore, in the above embodiment, the head 5 was moved by employing a so-called thread-feed mechanism with the lead screw 9 , but a so-called rack and pinion mechanism may be used instead.

The power transmission member and disk device of the present invention are effective as means for recording or reproducing data, and more specifically as recorders for recording audio or video content, players for reproducing the same, personal computer storage devices, and so forth.