JPH03287222A - Tracking mirror actuator device - Google Patents

Abstract

PURPOSE:To make the primary resonance frequency of support spring members low and to reduce variance in the primary resonance frequency due to variance in plate thickness by providing support spring members, which support a movable part, with a torsional spring part which twists around a center line of rotation and a bending part which bends in the direction of the center line of rotation. CONSTITUTION:This device is equipped with the right-left symmetric movable part 1 which has a mirror 2, a mirror support 3, and a driving part 4 and a couple of support spring members 15 which support the movable part 1 freely rotatably. Then the support spring parts 15 are provided with the torsion spring part 20 which can twist to deform around the center axis of rotation of the movable part 1 and the bending part 21 which can bends in the direction of the center axis of rotation, and the torsion spring part 20 is supported by the bending part 21 movably in the direction of the center axis of rotation. Consequently, even when the plate thickness of the torsion spring part 20 is made large, the primary resonance frequency becomes sufficiently low and the variance in primary resonance frequency due to the variance in plate thickness becomes small.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a tracking mirror actuator device installed in an optical pickup such as an optical disk drive device.

[Conventional technology]

In optical information recording and reproducing devices such as optical disk drives and magneto-optical disk drives, the optical pickup has a tracking operation for the optical spot in order to precisely control the position of the optical spot focused on the optical information recording medium. A tracking mirror actuator device is provided for carrying out this operation, and this tracking mirror actuator device will be described with reference to FIGS. 3-9.

In FIGS. 8 and 9, the movable part 1 is composed of a mirror 2, a mirror support 3, and two drive coils 4. The two support springs 5 that support the movable part 1 have one end fixed to the mirror support 3 and the other end fixed to the fixed part support 6 on the base 10 side. Mirror support 3 of movable part 1
One end of the yoke 7 of the magnetic circuit fixed on the base 1o side is inserted into the turbulence coil 4 fixed on both sides of the turbulence coil 4, and the turbulence coil 4 is inserted into the magnetic gap 9 formed by the magnet 8 and the yoke 7. One side of the coil 4 is located there.

Further, the support springs 5 are provided symmetrically on both sides of the movable part 1, and the center lines of the support springs 5 on the movable part IWJ side are on the same straight line C. It is the center of rotation. Further, the center of gravity of the movable part 1 is located near the straight line C.

Now, in the tracking mirror actuator device having the above configuration, the direction of the force generated in the drive coil 4 in the magnetic gap 9 in the mirror normal direction (two directions in the figure) is as follows for each coil: For example, JP-A-62-
The one described in Japanese Patent No. 210418 is known.

In the tracking mirror actuator device described in the above publication, a movable part including a mirror and a mirror support is supported by two thin plate-shaped spring members on the left and right, and the center of gravity of the movable part is located near the torsion center line of the support spring members. The thickness direction of the support spring member is fixed to match the in-plane direction of the mirror so that the direction of low rigidity of the support system is the in-plane direction of the mirror, and the direction of high rigidity is the normal direction of the mirror.

Therefore, in this tracking mirror actuator device, even if the mirror moves by a minute amount within the mirror plane, the position of the light beam is not affected at all.

There is no problem even if the support system has low rigidity, and the support system rigidity in the normal direction of the mirror, which is related to the position of the light beam, can be made high, suppressing vibrations that reduce the positioning accuracy of the light spot. be able to.

Here, regarding a specific example of the above-mentioned conventional tracking mirror actuator device, FIG. 8 and FIG. A couple occurs.

Here, if the center of rotation C of the support spring 5 and the center of gravity of the movable part coincide, and the magnitudes of the positive and negative forces generated in the drive coils 4 at both ends are the same, the movable part 1 will have a straight line. Only rotational motion around C occurs.

However, in general, the center of rotation C and the center of gravity of the movable part 1 are misaligned, and the forces generated by the two drive coils 4 are not of the same magnitude. In addition, the support springs 5 on both sides of the movable part 1 are also
Discrepancies in shape and material properties are inevitable. Therefore, due to these influences, in addition to the rotation about the straight line 0, the movable part 1 undergoes linear movement in the x, y, and z directions and rotational movement about the x and z axes.

Therefore, in the above conventional technology, the thickness direction of the support spring 5 is
It is fixed so as to be in the in-plane direction of the mirror 2. In other words, the support spring 5 has sufficiently large rigidity in the longitudinal direction (y direction) and the width direction (two directions), so that the displacement in the two directions, the linear movement in the y direction, and the rotational movement around the X axis is sufficiently small. Become.

In addition, since the rigidity of the support spring 5 in the thickness direction (X direction) is small, the displacement in the linear movement in the However, since the position and angle of the light beam reflected by the mirror 2 do not change, it can be ignored.

[Problem to be solved by the invention]

By the way, in the above-mentioned conventional tracking mirror actuator device, the primary resonance frequency of the movable part l is usually 5.
Since it is necessary to set the frequency around 0 Hz, for example, if stainless steel is used as the material for the support spring 5, the plate thickness should be set to 20 μm.
It is necessary to make it very thin, around m. This is support spring 5
When twisted due to the rotation of the movable part 1, it contracts slightly in the longitudinal direction (y direction in the figure), whereas the support spring 5 has one end fixed to the mirror support 3 and the other end fixed to the fixed part support 6. This is because it has a structure that is very difficult to shrink. Therefore, if a general cantilever = 7- can be achieved, the influence of variations in plate thickness will be reduced,
Although it is possible to reduce the variation in the -order resonance frequency,
If the thickness of the support spring member 5 is increased while maintaining the configuration of the conventional device shown in FIGS. 8 and 9, the -th resonance frequency will be increased to 50H.
In order to make it around z, the longitudinal direction of the support spring member 5 (y
Either the length of the support spring member 5 in the width direction (X direction) must be made extremely long, or the length of the support spring member 5 in the width direction (X direction) must be made extremely short.

However, if the length of the support spring member 5 in the longitudinal direction (y direction) is made extremely long, a problem arises in that the device becomes larger. When is made extremely short, the shear stress (kgf/a?) that acts on the support spring member 5 due to the rotation of the movable part l
There is a problem in that the stress becomes excessive and exceeds the allowable stress of the support spring member.

The present invention has been made in view of the above circumstances, and has a spring constant that is significantly lower than that of a torsion spring that can reduce the -order resonance frequency well and also reduce the variation in the primary resonance frequency. It gets expensive.

By the way, stainless steel plates inevitably have an error of about ±2 μm in their thickness due to manufacturing reasons, so when stainless steel plates are used as support springs, the thickness of the support springs 5 will vary by about ○% of the diameter of the earthworks. It turns out.

In the case of the tracking mirror actuator device having the configuration shown in FIG. 8, the torsional spring constant of the support spring 5 is proportional to the cube of the plate thickness, and the -th order resonance frequency is proportional to the 1/2 power of the spring constant. For example, if the plate thickness has a variation of ±10%, the -th order resonance frequency will have a variation of about ±15%.

Generally, considering the specifications of the control system of the tracking mirror actuator device, the primary resonance frequency of the movable part 1 is ±
Therefore, in the configuration of the conventional device described above, the variation in the primary resonance frequency becomes too large and the specification of the control system cannot be satisfied.

By the way, it is an object of the present invention to provide a tracking mirror actuator device in which the plate thickness of the support spring member 5 is increased.

[Means to solve the problem]

In order to achieve the above object, a first configuration of the present invention includes a substantially bilaterally symmetrical movable part having a mirror, a mirror support, and a drive part, and a movable part that is parallel to the center of rotation of the movable part from both left and right sides of the movable part. and a pair of support spring members extending from and rotatably supporting the movable part, and tracking the light spot on the optical information recording medium by rotating the movable part by the drive part. In a tracking mirror actuator device configured to perform an operation,
The support spring member has a torsion spring part that can be torsionally deformed around the rotation center axis of the movable part and a bending part that can be bent in the direction of the rotation center axis, and one end of the torsion spring part is bent by the bending part. It is characterized in that it is supported so as to be movable in the direction of the rotational center axis, and that the thickness direction of the torsion spring portion is aligned with the inward direction of the reflective surface of the mirror.

In addition, in order to achieve the above object, the second configuration of the present invention includes a substantially bilaterally symmetrical movable part having a mirror, a mirror support, and a drive part, and a rotation center axis of the movable part from both left and right sides of the movable part. and a pair of support spring members extending along the movable section and rotatably supporting the movable section, the light spot on the optical information recording medium being rotated by the movable section by the driving section. In the tracking mirror actuator device, each of the pair of support spring members is a thin plate-like spring member having a center line colinear with the rotational center axis of the movable portion. The pair of support spring members on the left and right sides of the mirror are fixed at both ends in a state where they are twisted in the same direction by a small angle around the central axis of rotation, and the thickness direction of the pair of support spring members is the same as that of the mirror. It is characterized by being provided in accordance with the direction within the reflective surface.

[For production]

In the tracking mirror actuator device according to the first configuration of the present invention, it is possible to excellently control the 11-turn device that twists the support spring member supporting the movable portion around the center line of one rotation.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective configuration diagram of a tracking mirror actuator device showing an embodiment of the first configuration of the present invention, and FIG.
, ) is a plan view schematically showing the support spring member of the tracking mirror actuator device as seen from two directions in the figure, and FIG. 2(b) is a sectional view taken along the line ■-■ in FIG. 2(a). be.

In FIGS. 1 and 2, a movable part 1 of this tracking mirror actuator device is composed of a mirror 2, a mirror support 3, and two turbulence coils 4. The two support spring members 15 that respectively support the left and right sides of the movable part 1 have one end on the mirror support 3 and the other end on the base.
It is fixed to the fixed part support body 6 on the side. One end of a U-shaped yoke 7 of a magnetic circuit fixed to the base 10 is inserted into a rectangular turbulence coil 4 fixed to both sides of the mirror support 3 of the movable part l. By providing a torsion spring portion and a bending portion that bends in the direction of the rotation center line, one end side of the torsion spring portion can be moved in the rotation center line direction by the action of the bend portion, and the support spring member Even if the plate thickness of the torsion spring portion is increased, the primary resonance frequency can be lowered, and variations in the primary resonance frequency due to variations in plate thickness can also be reduced, making it possible to better control the tracking mirror actuator device.

Further, in the tracking mirror actuator device according to the second configuration of the present invention, the pair of support spring members on the left and right sides of the movable part are twisted in the same direction by a small angle around the rotation center axis, and both ends of the support spring members are twisted in the same direction by a small angle around the rotation center axis. and the fixed part, so even when torsion occurs due to rotation of the movable part, the length of each support spring member in the direction of the rotation center axis will be reduced, with one support spring member contracting and the other supporting spring member contracting. Since the spring member acts to extend, the primary resonance frequency can be lowered even if the plate thickness of the support spring member is increased, and variations in the primary resonance frequency due to variations in plate thickness can also be reduced.
Tracking mirror actuator 12 - A magnet 8 fixed to this yoke end and the other end of the yoke 7
One side of the turbulent coil 4 is located in the magnetic gap 9 formed by the above.

The support spring members 15 are provided symmetrically on both sides of the movable part 1, and the support spring members 15 on both sides of the movable part 1
are torsion spring parts 20 that twist around the same straight line C, respectively.
and a bent portion 21 bent in the direction of the vertical vAC.

Here, the torsion spring part 20 is made of a thin plate-shaped spring having a center line directly on tlc, and has one end connected to the mirror support member 3 of the movable part 1 and the other end connected to the bent part 21 of the support spring member 15.
Fixed on the side. The bent portion 21 has a surface perpendicular to the straight line C and a surface parallel to the straight line IsC, and is formed so as to be bendable in the direction of the straight line C. It supports the body 6 so as to be movable in the direction of a straight line C.

Note that the center of gravity of the movable part 1 is located near the straight line C, and this straight line C becomes the center of rotation of the movable part 1.

Now, in the tracking mirror actuator device having the configuration shown in FIGS. 1 and 2, the direction of the force generated in the drive coil 4 in the magnetic gap 9 in the mirror normal direction (two directions in the figure) is different from that of each coil. By determining the direction of the current flowing through each drive coil 4 so as to be opposite to each other, a magnetic force couple is generated in the movable part 1, and the movable part 1 is rotated about the straight line C. Therefore, a predetermined tracking operation is performed by controlling the direction of rotation on the movable part according to the tracking error signal.

By the way, during this racking operation, torsional deformation occurs in the torsion spring part 20 of the support spring member work 5, and the torsion spring part 20 contracts slightly in the longitudinal direction (y direction in the figure).
As described above, one end of the torsion spring portion 20 is supported movably in the direction of the straight line C (rotation center axis) by the bent portion 21, so the spring constant at this time is equal to that of a typical cantilevered torsion spring. It is almost equivalent to . Therefore, the plate thickness of the torsion spring part 20 of the support spring member 15 can be made sufficiently thicker than in the conventional case where both ends are fixed, and the bending part 21 of the spring member 15 has a rigidity in the y direction of 15 - Because of its small size, the movable part 1 tends to undergo linear movement in the y direction and rotational movement around the Z axis, but since both movements occur within the reflective surface of the mirror 2, the light flux reflected by the mirror 2 There is no effect on the equipment or angle.

Next, FIG. 5 is a perspective configuration diagram of a tracking mirror actuator device showing an embodiment of the second configuration of the present invention.

In FIG. 5, a movable part 1 of this tracking mirror actuator device is composed of a mirror 2, a mirror support 3, and two drive coils 4, and the structure on this movable part is shown in FIGS. 1 to 4. This is the same as the first configuration described in .

The two support spring members 25 that respectively support the left and right sides of the movable part 1 are made of thin plates whose center lines lie on the same straight line C, and are twisted at a slight angle about the straight line C, with one end movable. The other end is fixed to the mirror support 3 of the part 1, and the other end is fixed to the fixed part support 6 on the base 10 side. Here, in FIG. 6, the variation in the primary resonance frequency due to the variation in the support spring member is sufficiently small.

Next, FIGS. 3 and 4 show a second embodiment of the tracking mirror actuator device having the first configuration of the present invention. Here, FIG. 3 is a perspective configuration diagram of the tracking mirror actuator device, and FIG. 4(a) is a plan view schematically showing the support spring member of the tracking mirror actuator device as seen from two directions in the figure. 4(b) is a cross-sectional view taken along the mV-IV line of FIG. 4(a).

3 and 4, the structure of the tracking mirror actuator device in this embodiment is approximately the same as that in the first embodiment, but in this embodiment, an L-shaped thin plate is used as the support spring member 5. The torsion spring part 20 and the bending part 21
This is an example in which both are formed by a single leaf spring. When the torsion spring portion 20 and the bent portion 21 are formed by a single leaf spring in this manner, the number of parts can be reduced and the assembly work can be simplified.

In addition, in the above-mentioned Embodiments I and 2, FIG. 7 is a diagram schematically showing the state before the support 16-25 is fixed, and FIG. 7 is a diagram schematically showing the state after the support spring member 25 is fixed. The support spring members 25 on both sides of the movable part 1 are fixed in a twisted state in the same direction.

The center of gravity of the movable part 1 is located near the straight line gAC, and this straight line C becomes the center of rotation on the movable part.

Now, in the tracking mirror actuator device having the configuration shown in FIG. 5, the direction of the force generated in the drive coil 4 in the magnetic gap 9 in the mirror normal direction (two directions in the figure) is opposite for each coil. By determining the direction of the current flowing through the drive coil 4, a magnetic force couple is generated on the movable part, and the movable part 1 is rotated about the straight line C. Therefore, a predetermined tracking operation is performed by controlling the direction and magnitude of the current flowing through the drive coil 4 according to the tracking error signal and controlling the rotation of the movable part 1.

By the way, during this tracking operation, the support spring member 25 is twisted in accordance with the rotation of the movable part 1, and one support spring member 25 is twisted in a direction that increases the predetermined twist, and the support spring member 25 on the other side The member 25 twists in a direction that reduces the pre-given twist. Therefore, one support spring member 25 is slightly compressed in the longitudinal direction (y direction in the figure), and the other support spring member 25 is slightly extended in the longitudinal direction (y direction). Therefore, the spring constant of the support spring members 25 is the same as when one end of each support spring member 25 is in a movable state. Therefore, the support spring member 2
The thickness of the plate No. 5 can be made sufficiently thicker than that of the conventional device, and the variation in the primary resonance frequency due to the variation in the plate thickness can be made sufficiently small.

By the way, the problem with the above configuration is that the support spring member 25 goes from a pre-twisted state to a state where it is further twisted by an angle necessary for tracking, so the shear stress acting on the support spring member 25 ( kgf/af) becomes larger.

Therefore, if there is a risk that the shear stress (kgf/d) of the support spring member 25 exceeds the allowable stress, the support spring member 25
is a state in which a flat thin plate is torsioned 19- Since the spring part is configured with a bent part that supports one end of the spring part so as to be movable in the direction of the rotation center axis, primary resonance will not occur even if the plate thickness of the torsion spring part is increased. The frequency can be lowered sufficiently,
In addition, variations in the primary resonance frequency due to variations in plate thickness can also be reduced.

Further, in the tracking mirror actuator device having the first configuration, when the torsion spring portion and the bending portion of the support spring member are formed by a single leaf spring, the number of parts can be reduced and the assembly work can be simplified.

Next, in the tracking mirror actuator device having the second configuration according to the present invention, the support spring members that support both sides of the movable part are twisted by a small angle in the same direction around the central axis of rotation of the movable part. Since the spring constant of the support spring member is fixed in the fixed state, the spring constant of the support spring member is the same as when one end of the support spring member is movable in the direction of the rotation center axis, and even if the plate thickness of the support spring member is increased, the primary resonance frequency is sufficiently low. In addition, instead of being fixed at the primary resonance frequency due to variations in plate thickness, it is sufficient to form the plate in a slightly twisted state in advance. That is, in a state where no torsional force is applied, a thin plate with a minute amount of twist may be manufactured and used as the support spring member 25. In this case, the shear stress acting on the support spring member 25 due to the tracking operation is This is approximately the same as in the case of the support spring member of the conventional device shown in the figure.

In the embodiments described above, the effect of the present invention can be obtained as long as the torsion angle given to the support spring member 25 is equal to or larger than the rotation angle required for tracking, and this angle is a very small angle. Therefore, also in the case of this embodiment, the rigidity of the support spring member 25 in the Z direction and the y direction is considered to be equivalent to that of the conventional device, and unnecessary vibrations in the two directions and the y direction can be prevented.

〔Effect of the invention〕

As described above based on the embodiments, in the tracking mirror actuator device of the first configuration according to the present invention, the pair of support spring members that support both sides of the movable part are arranged around the central rotation axis of the movable part. It is also possible to reduce the variation in the number of torsion springs and the number of twists.

Further, in the tracking mirror actuator device having the second configuration, thin plates shaped in advance so as to be twisted at a slight angle in the same direction around the rotation center axis of the movable part are used as support spring members that support both sides of the movable part. When using , the spring constant is the same as when one end of the support spring member is movable in the direction of the rotation center axis, and even if the plate thickness of the support spring member is increased, the primary resonance frequency cannot be made sufficiently low. Moreover, it is possible to reduce the variation in the primary resonance frequency due to the variation in plate thickness without increasing the shear stress acting on the support spring.

[Brief explanation of the drawing]

FIG. 1 is a perspective configuration diagram of a tracking mirror actuator device showing an embodiment of the first configuration of the present invention, and FIG.
a) is a plan view schematically showing the support spring member of the tracking mirror actuator device as seen from two directions in the figure; FIG. 2(b) is a sectional view taken along the line ■-■ of FIG. 2(a);
FIG. 3 is a perspective configuration diagram of a tracking mirror actuator device showing another embodiment of the first configuration of the present invention, and FIG. 4(a) is a support spring member of the same tracking mirror actuator device as seen from the Z direction in the figure. FIG. 4(b) is a sectional view taken along the line IV--IV of FIG. 4(a), and FIG.
FIG. 6 is a perspective view of the racking mirror actuator device, and FIG. 6 is an explanatory diagram showing the state before the support spring member of the tracking mirror actuator device is fixed, and FIG. Fig. 7 is a view of the support spring member as seen from the X direction in Fig. 5, and Fig. 7 is a view of the support spring member of the racking mirror actuator device shown in Fig. FIG. 5(a) is an explanatory diagram showing the state after the member is fixed, and FIG.
FIG. 5B is a view of the support spring member as seen from the X direction in FIG. 5. FIG. Figure 9(a) shows the support spring member of the conventional tracking mirror actuator device as shown above when viewed from the X direction in the figure.
- A plan view schematically showing the viewed state, and FIG. 9(b) is a sectional view taken along the line IX-IX of FIG. 9(,). ■...Movable part, 2...Mirror, 3...Mirror support, 4...Drive coil, 15.25...
Support spring member, 6... fixed part supporter, 7... yoke, 8... magnet, 9... magnetic gap, 1
0...Base, 20...Torsion spring part, 21...
...Bending part, C...Rotation center line. 24-

Claims (1)

[Claims] 1. A tracking mirror actuator used to perform a tracking operation of the optical spot in an optical information recording and reproducing device that records and reproduces information by forming a minute optical spot on an optical information recording medium. The apparatus includes a substantially bilaterally symmetrical movable part having a mirror, a mirror support, and a drive part, and a movable part extending from both left and right sides of the movable part along a rotation center axis of the movable part. A tracking mirror actuator device comprising: a pair of support spring members rotatably supported; and the movable portion is rotated by the drive portion to perform a tracking operation on the optical spot on the optical information recording medium. In the above, the support spring member has a torsion spring part that is torsionally deformable about the rotation center axis of the movable part and a bending part that is bendable in the direction of the rotation center axis, and one end of the torsion spring part is arranged in the bending part. A tracking mirror actuator device, characterized in that the tracking mirror actuator device is supported movably in the direction of the rotation center axis by the torsion spring portion, and the thickness direction of the torsion spring portion is aligned with the inward direction of the reflective surface of the mirror. 2. A tracking mirror actuator device used to perform a tracking operation of the optical spot in an optical information recording and reproducing device that records and reproduces information by forming a minute optical spot on an optical information recording medium, the mirror a substantially bilaterally symmetrical movable part having a mirror support and a drive part; and a movable part extending from both left and right sides of the movable part along the rotation center axis of the movable part and rotatably supporting the movable part. A tracking mirror actuator device comprising: a pair of support spring members, the tracking mirror actuator device configured to perform a tracking operation on a light spot on the optical information recording medium by rotating the movable section by the drive section; The spring members are thin plate-like spring members each having a center line on the same straight line as the rotation center axis of the movable part, and the pair of supporting spring members on the left and right of the movable part are aligned at a small angle around the rotation center axis. A tracking mirror actuator characterized in that both ends of the actuator are fixed in a twisted state, and the thickness direction of the pair of support spring members is aligned with the inward direction of the reflective surface of the mirror. Device.