JPH0417024B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a linear actuator, and more particularly to a linear actuator for driving a recording/reproducing head of a disk medium that is small and has good vibration characteristics.

Conventionally, voice coil type linear actuators have been widely used as linear actuators for driving recording/reproducing heads of magnetic disks or optical disk devices. This type is often used as a high-speed, high-precision positioning actuator.As shown in Figure 1, its structure is such that the coil 1 is located behind the frame 4 on which the recording/reproducing head is mounted, and Since the magnetic member 2 such as the magnet 21 into which the coil is inserted is provided first, there is a drawback that the longitudinal dimension becomes large. coil 1
The frame 4 with the guide wheels 51, 52, 5
3, 54, 55, 56 guide surfaces 25a, 25b,
The coil 1 moves on the coils 26a and 26b, but as the amount of movement increases, that is, the stroke becomes larger, it becomes necessary to increase the strength of the coil 1 itself, which increases the weight of the movable part. That is, the strength of the coil 1 must be increased approximately in proportion to the square of the stroke length, and the weight of the movable portion increases in accordance with the stroke. Furthermore, as the weight increases, the volume of the magnet 21 and the yoke increases;
The external size of the device becomes significantly larger.

Generally, guide wheels 51, 52, 53, 54, 5
Highly rigid parts such as ball bearings are used as the guide wheels 51, 52, 53, 54 as seen from the front, as shown in FIG.
The shaft is obliquely attached to the frame 4 and slides on rails 26a and 26b on an inclined surface. Further, the guide wheels 55 and 56 are connected to the U-shaped rail 25.
a, 25b, and is pushed upward by a spring. These guide wheels 5
The arrangement of 1, 52, 53, 54, 55, and 56 is also a factor in increasing the size of the device.

In addition, these guide wheels 51, 52, 53, 5
4, 55, and 56 can be equivalently considered to be the same as spring support, and as the longitudinal dimension of the movable length increases, the inertia in pitching and yawing directions increases as the weight increases. In other words, as shown in Fig. 3, if the x-axis and y-axis are taken horizontally with respect to the frame 4, and the z-axis is taken vertically, the vertical axis on the x-axis will be Pitching 9, which is a directional oscillation, and yawing 15, which is a lateral oscillation with respect to the x-axis, occur. Furthermore, regarding the ease of rotation around the x-axis, y-axis, and z-axis, as inertia increases, the rotation period becomes longer and the rigid body mode vibration frequency decreases. In this case, if the rigid body mode vibration frequency around each axis is _fo , the inertia is I, and the spring constant is K, then the following equation holds true.

In addition, in the voice coil type linear actuator, as shown in FIG. vibration modes are more likely to be induced. In FIG. 4a, with respect to the position of the recording/reproducing head 41, in addition to vibrations 9 in the pitching direction appearing as vibrations in the vertical direction 18 and tracking direction 17 of the head, in the side direction in FIG. The vibration 15 appears as a vibration in the jitter direction 19.

In addition, these vibrations have a small damping coefficient, so
Once induced, it takes time to stabilize,
In particular, if this vibration occurs within the head positioning servo system band, it will increase the settling time for positioning or reduce positioning stability, and if it occurs within the recording/reproduction band, it will reduce the device performance as it increases signal jitter and noise. I will let you do it.

Note that a recording/reproducing device that uses a voice coil type linear actuator to drive the recording/reproducing head is
It is disclosed in JP-A-54-144912 and JP-A-56-11662.

In order to eliminate these conventional drawbacks, the present invention aims to provide a linear motor which reduces the induction of rigid body and elastic vibration modes in the movable part and shortens the longitudinal dimension, thereby making it possible to miniaturize the device. The purpose of this invention is to provide an actuator.

In order to achieve the above object, the linear actuator of the present invention has (a) twin-barrel type coils 1a and 1b that generate thrust, and a double-barrel type coil that is arranged in a penetrating portion of the twin-barrel type coil and that crosses the twin-barrel type coil. It is equipped with magnetic members 2a and 2b that generate magnetic flux, and a movable part consisting of a frame 4 on which a recording/reproducing head is mounted and on which the axes of a plurality of guide wheels 50 to 56 are fixed, and the thrust of the twin body type coil is The center of gravity of the movable part and the composite point of the reaction force that the plurality of guide wheels receive from the guide surface are made to almost match, and the guide surface provided on the magnetic member is movable via the plurality of guide wheels. It is characterized by supporting the parts. Thereby, it is possible to reduce the vibration vibration induced in the movable part due to thrust generation, and to reduce the external size of the device. Also,
(b) The magnetic member is constructed by arranging a pair of magnets and a yoke with a gap parallel to the movable direction of the movable part, and a guide surface is arranged on one side of the yoke itself facing the gap, and Another feature is that the type coils are connected by a plate, the plate is connected to the frame, and a plurality of guide wheels are arranged between the frame and the guide surface for transition. Thereby, it is possible to improve the dimensional accuracy between the guide surfaces. Another feature of the (c) plate is that it is connected to a double-barrel type coil at the gap portion of the magnetic member, and the thrust force generated by the coil is generated on and inside the flat plate-like surface. Thereby, the vibration amplitude of the torsional mode of the coil and plate can be reduced. (d) The magnetic member is constructed by arranging a pair of magnets and a yoke with a gap parallel to the movable direction of the movable part, and has a total of four guide surfaces on the magnetic member. Of the guide surfaces, two guide wheels are placed on each pair of facing guide surfaces, and one guide ring is placed on one of the other two guide surfaces, and the axes of the five guide wheels are Another feature is that it is fixed to the frame, and the shafts of one or two guide wheels and the frame are connected to the remaining one guide surface using an elastic body to apply preload to the guide surface. This makes it possible to provide highly rigid support regardless of the orientation of the device. Furthermore, (e) the double-barrel type coil is also characterized in that the parts other than the connection with the plate are supported by a fork-shaped rim from the frame. Thereby, folding mode vibration of the coil in the movable direction can be suppressed.

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 5 is a partially sectional perspective view of a linear actuator showing an embodiment of the present invention, and FIG. 6 is an exploded view of the magnetic member in FIG. 5.

In addition, the subscripts a and b added to the numbers in the figure are
A symmetrical arrangement is shown.

Cylindrical coils 1a and 1b that generate thrust are arranged parallel to each other, and these coils 1a and 1b
Magnetic members 2a and 2b are arranged in parallel, penetrating through the insides of the two. When the magnetic members 2a, 2b are disassembled, as shown in FIG. 6, the magnets 21a, 21b and the yokes 23a, 23b, 24a, 24b face each other with gaps 22a, 22b interposed therebetween. In FIG. 5, guide surfaces 25a, 25b, 2
6a and 26b each have an inclination of approximately 45° with respect to the horizontal plane on one of the yokes 23a and 23b. Coils 1a and 1b are connected to plate 3
The frame 4 is also connected to the plate 3. Rims 8a and 8b connect the sides of coils 1a and 1b to frame 4. A recording/reproducing head 41 is mounted on the frame 4.

7 is a vector diagram of the force generated by the coil in FIG. 5, and FIGS. 8a and 8b are exploded perspective views of the guide ring and the coil in FIG. 5.

Seven guide wheels (bearings) are attached, among which bearings 50 to 54 have their shafts fixed to the frame 4, and movable bearings 55 and 56 are elastically supported by the frame 4 via bearings 6 and leaf springs 7. . The arrow 10 in FIG. 8a is the direction of movement of the movable part.

In FIG. 6, now magnets 21a, 21b,
Gap 2 of magnetic members 2a and 2b composed of yokes 23a, 23b, 24a and 24b
When magnetic fields 220a and 220b are generated in coils 2a and 22b in the direction of the arrows, as shown in FIG. Forces 100a and 100b are generated in the directions of the arrows in areas 1'a and 1'b, respectively, where 1'a and 1'b intersect with the magnetic field. If the direction of the current is reversed, the directions of 100a and 100b will also be reversed, and the direction of thrust will be reversed. 10 of these powers
0a and 100b are proportional to the magnitude of the currents 101a and 101b, and are generated in a direction perpendicular to the direction of the currents 101a and 101b. Magnetic fields 220a and 2
Strength H of 20b, number of turns n of coils 1a and 1b, and currents 101a and 101b flowing through the coils.
If the product (Hni) of (i) is made approximately equal, the thrust forces generated in both coils 1a and 1b will be approximately equal,
The combined thrust acts as shown in section 11 of FIG.

Next, the guide surfaces 25a and 26a are connected to the yoke 23a.
Further, the guide surfaces 25b and 26b are provided on the yoke 23b, respectively, and an eighth guide surface is provided on the yoke 23b.
Guide wheels 50-56 are arranged as shown in Figure b.

Figures 9a, b, and c are more detailed layout views of the guide wheels and guide surfaces, with Figure 9a being a front view, Figure 9b being a longitudinal side view, and Figure 9c being a top view. It is.

The guide wheels 50 and 51 are attached to the guide surface 25b, the guide wheels 52 and 53 are attached to the guide surface 25a, and the guide wheel 54 is attached to the guide surface 25b.
are in contact with the guide surface 26a, and the shafts of these guide wheels are fixed to the frame 4. Further, the guide wheels 55 and 56 are in contact with the guide surface 26b,
These guide wheels are elastically supported by the frame 4 and apply preload in a direction perpendicular to the guide surface 26b. In FIG. 8b, preloads 141 and 142 are indicated by arrows. In this way, in the bearing arrangement of the present invention, the guide wheels 50, 51, 52, 53
By supporting the frame 4 at four points, the position and attitude of the frame 4 in the direction 131 shown in FIG.
The frame 4 is supported in the direction 1 by the three-point support of 3 and 54.
32 positions and postures are defined.

Next, the guide wheels 50 to 56 are connected to the guide surfaces 25a, 2
The resultant force of the reaction forces received from 5b, 26a and 26b acts equivalently at position 13 in FIG. 8b.
Note that, as described above, the guide surfaces 25a, 26a and 25b, 26b are connected to the yokes 23a, 26b, respectively.
Since it is on the integral member of 3b, processing is easy and dimensional accuracy can be increased. That is, it is easy to set the static position of the head 41 within a predetermined accuracy, and each guide surface 25a, 2
5b, 26a, and 26b each have an inclination of approximately 45° with respect to the horizontal plane.
It has a function of automatically statically fixing positional deviations of 54 to 54.

Furthermore, in the embodiments shown in FIGS. 5 to 9, the magnetic members 2a and 2b are arranged on a horizontal plane, but
Even when placed on a surface other than horizontal, the frame 4 is stably supported. For example, for a recording/reproducing head of a vertically arranged disk, the magnetic members 2a, 2b can be arranged on a vertical plane.

Next, the center of gravity G of the movable part is at position 12 in Figure 8a.
The rigid body vibration mode of the movable part is determined by the relative positional relationship between the center of gravity 12 and the reaction point 13 (position 13 in Figure 8b) received by the guide wheel, and its amplitude is determined by the applied force and moment. Depends on size.

In the present invention, the thrust force 11 (11 in FIG. 7)
, the center of gravity point 12 (12 in Figure 8a), and the point of reaction force application 1
3 (13 in Fig. 8b), the vibration mode is simplified and the amplitude of each mode is prevented from increasing due to thrust, and the head 4
This has the effect of increasing the dynamic position accuracy of item 1. In addition to the above-mentioned rigid body vibration mode, the influence of the elastic vibration mode is considered, but in the present invention, the parts 1'a and 1'b where thrust is generated in the coils 1a and 1b are aligned with the joint with the plate 3. By doing so, the torsional vibration mode of the plate 3 is suppressed. That is, since the thrust forces 100a and 100b are transmitted to the frame 4 by stress in the shear direction of the plate 3, torsional vibration of the plate 3 is suppressed. Further, the coils 1a and 1b are connected to the rim 8a.
By reinforcing the coils 1a and 8b from the sides, the folding vibration mode of the coils 1a and 1b is suppressed.
This prevents a decrease in the dynamic position accuracy of the head 41 due to elastic vibration within the movable part.

Figure 10 shows the present invention and the voice coil type linear
FIG. 3 is a diagram comparing the external shape with an actuator.

As shown in FIG. 1, the conventional boost voice coil type linear actuator has a large longitudinal dimension, so when the head 41 and actuator are attached to the disk 20, the magnetic member 2 has a protruding shape, making it difficult to miniaturize the external size of the device. On the other hand, a linear actuator equipped with a twin-body type drive coil according to the present invention has magnetic members 2a,
2b is included within the area of the disk 20, there is no protruding part, and the external size of the device can be made smaller.

As explained above, according to the present invention, since a twin-body type drive coil is used and the magnetic member serves both as a guide surface, the induction of rigid body and elastic vibration modes of the movable part is reduced, and the position of the recording/reproducing head is Accuracy can be improved, and the longitudinal dimension can be shortened to realize miniaturization of the device.

[Brief explanation of drawings]

Figure 1 is a perspective view of a conventional voice coil type linear actuator, Figure 2 is a front view of Figure 1, Figures 3 and 4 are illustrations of the vibration mode in Figure 1, and Figure 5. 6 is an exploded view of the magnetic member of FIG. 5, FIG. 7 is an explanatory diagram of the thrust generated by the coil of FIG. 5, and FIG. 8 is an exploded perspective view of the guide ring and coil of FIG. 5, FIG. 9 is a layout diagram of the guide ring and guide surface of FIG. 5, and FIG. 10 is a comparison diagram of the external shapes of the actuator of the present invention and the conventional actuator. 1a, 1b: coil, 2a, 2a: magnetic member,
3: Plate, 4: Frame, 6: Bearing, 7: Elastic body, 8a, 8b: Rim, 10: Movement direction, 1
1: Point of application of combined thrust, 12: Center of gravity of moving part, 13:
Guide wheel reaction force application point, 21a, 21b: magnet, 22
a, 22b: gap, 23a, 23b, 24
a, 24b: yoke, 25a, 25b, 26a,
26b: Guide surface, 50-56: Guide wheel.

Claims (1)

[Scope of Claims] 1. A twin-barrel type coil that generates thrust, a magnetic member that is disposed in a penetrating portion of the twin-barrel coil and generates a magnetic flux that crosses the twin-barrel coil, and a recording/reproducing head. and a movable part consisting of a frame on which the axes of a plurality of guide wheels are fixed,
The combination point of the thrust of the twin body type coil, the center of gravity of the movable part, and the combination point of the reaction force received by the plurality of guide wheels from the guide surface are approximately aligned, and the guide surface provided on the magnetic member is A linear actuator characterized in that the movable part is supported via the plurality of guide wheels. 2 A twin-barrel type coil that generates thrust, a magnetic member that is arranged in the penetrating part of the twin-barrel coil and generates a magnetic flux that crosses the twin-barrel coil, and a recording/reproducing head, and a plurality of a movable part consisting of a frame to which the axis of a guide ring is fixed; the magnetic member is constructed by arranging a pair of magnets and a yoke with a gap parallel to the movable direction of the movable part; A guide surface is disposed on one side of the yoke itself facing the gap, and the twin body type coils are connected by a plate, the plate is connected to the frame, and the plurality of above-mentioned coils are connected between the frame and the guide surface. A linear actuator characterized by moving by arranging guide wheels. 3. The plate according to claim 2, wherein the plate is connected to a double-barrel type coil at a gap portion of the magnetic member, and the thrust by the coil is generated on and inside the flat plate-like surface. linear
Actuator. 4 A twin-barrel type coil that generates thrust, a magnetic member that is arranged in the penetrating part of the twin-barrel coil and generates a magnetic flux that crosses the twin-barrel coil, and a recording/reproducing head, and a plurality of a movable part consisting of a frame to which the axis of a guide ring is fixed; the magnetic member is constructed by arranging a pair of magnets and a yoke with a gap parallel to the movable direction of the movable part; There are a total of four guide surfaces on the magnetic member, two guide wheels each for one pair of facing guide surfaces, and two guide wheels for one of the other two guide surfaces. Arrange one guide wheel, fix the shafts of the five guide wheels to the frame, and
A linear actuator characterized in that a preload is applied to a guide surface by connecting the shafts of one or two guide wheels and a frame with an elastic body. 5. The double-barrel type coil according to claim 1 or 2, wherein each of the twin-barrel type coils is supported by a fork-shaped rim from the frame at a portion other than the connection portion with the plate. linear
Actuator.