JPS61255569A - Swing arm device for optical head - Google Patents

Abstract

PURPOSE:To make the overall constitution of an arm symmetrical and thereby to accomplish an excellent dynamic characteristic by inserting an arc-shaped yoke into a hollow coil provided to a swing arm and disposing magnets at the upper and lower side of the yoke and coil. CONSTITUTION:The swing arm 1 on both ends of which are an optical head 16 and a balance weight 17, is freely pivotably supported by a spindle 18. In the arm 1, a pair of coils 2 and 3 that respectively has hollow parts are formed, and the arc-shaped yoke 4 is inserted into the hollow part. And a pair of yokes 8 and 9 are provided at the upper and lower side of the yoke 4 and the coils 2 and 3, on which the magnets 21-24 are fixed. A propulsion force F is generated by a current through the coils 2 and 3 and the electro-magnetic force of the magnetic circuit, and the head pursuing is executed. Accordingly, the structure of the arm is made symmetrical both in the longitudinal direction of an axial line and in the perpendicular direction. Therefore, no unnecessary propulsion force is generated. In result, an excellent dynamic characteristic is accomplished.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a swing arm device for tracking an optical head for recording and reproduction of optical video discs, optical audio discs, and other optical data storage discs.

(Prior Art) A swing for an optical head in which the optical head for recording and reproducing an optical data storage disk is attached to a swing arm device in order to move it in the tracking direction, and the optical head is moved along an arc. Arm devices are known. The one described in Japanese Patent Application Laid-Open No. 58-53035 is one of them.

What is described in the above publication is that the center of mass of the rotating assembly that attaches the swing arm to which the optical head is attached is located on the rotating axis, and the coil device is located on both sides of the rotating axis. The first and second coils are disposed diametrically opposite each other at positions equidistant from the rotation axis and apply equal rotational force to the swing arm, and the first and second rotational forces are arranged perpendicularly to the rotation wheel. It is characterized by operating within a plane.

(Problems to be Solved by the Invention) According to the above-mentioned conventional swing arm device for an optical head, since thrust is generated only on one side of the coil, the thrust generating portion in the drive magnetic circuit is small and efficient. is low, and in order to increase efficiency it is necessary to use a high-energy magnet, which is disadvantageous in terms of cost. In addition, in order to stabilize the dynamic characteristics of the swing arm to which the optical head is attached, it is necessary to generate rotational force in a well-balanced direction in the direction of the rotation wheel. In order to generate rotational force in a well-balanced manner in the direction of the rotation axis in a device that generates rotational force within a single plane, it is necessary to balance the mass of the swing arm so that the plane where rotational force is generated is located at the center of the pair of bearings. It needs to be well distributed. Therefore, there is a problem that the height of the swing arm in the axial direction becomes high, creating a dead space and making it impossible to downsize the swing arm.

The purpose of the present invention is to stabilize the dynamic characteristics by ensuring that the rotational force of the swing arm is generated in perfect balance with respect to the axial direction of the swing arm, and to improve the utilization efficiency of the coil. An object of the present invention is to provide a highly efficient swing arm device for an optical head using an inexpensive and compact magnetic circuit.

(Means for Solving the Problems) The swing arm device for an optical head of the present invention includes an optical head at one end, a balance weight at the other end, a swing arm having a shaft in the center, and a pair of bearings. a frame that rotatably supports the shaft of the swing arm through the frame, and a pair of coils having a hollow portion and disposed at positions equidistant from the shaft of the swing arm; an arcuate yoke inserted into the hollow part of each coil and fixed to the frame; a pair of yokes disposed at opposing positions on both sides in the axial direction, sandwiching the yoke and the pair of coils; and a magnet fixed to each yoke.

(Function) The swing arm rotates about its axis with a pair of coils disposed on the swing arm surrounding an arcuate yoke fixed to the frame. a pair of yokes arranged at opposing positions on both sides in the axial direction with the coil in between, and magnets fixed to each of these yokes;
Two axially symmetrical magnetic circuits are formed between the arcuate yoke and the coils in the magnetic gap included in these magnetic circuits are energized to generate thrust on both sides of the coil in the axial direction. arise.

(Example) In FIGS. 1 to 4, the swing arm 1 consists of two plates 11 and 12 that face each other vertically, and these two plates 1.
1.12 with a predetermined gap between them, spacers 13 and 14 are interposed at both ends, and a spacer 15 is interposed at the center.One end of this swing arm 1 An optical head 16 is provided at one end, and a balance weight 17 is provided at the other end.Furthermore, a shaft 18 is integrally provided passing vertically through the center of the swing arm 1.

The swing arm 1 is controlled by the balance weight 17.
The left and right weights are balanced with respect to the center line XX of the shaft 18. The swing arm 1 is also formed with a pair of holes passing through the opposing plates 11.12 at symmetrical positions with respect to the axis 18, and a pair of coils 2.3 having hollow portions are inserted into these holes. It is arranged so that it is embedded. Therefore, the pair of coils 2.3 are arranged equidistantly apart from the shaft 18. Also,
The hollow part of the pair of coils 2.3 is the swing arm 1.
It is open on both sides.

A common arc-shaped yoke 4 is inserted into the hollow portion of the pair of coils 2.3. Four fan-shaped spacers 7 are fixed to the yoke 4 at positions facing each other across the central axis line XX, and sandwich the yoke 4 from above and below.

Inner rings of ball bearings 5.6 are fitted and fixed to both upper and lower ends of the shaft 18, respectively. The outer rings of these ball bearings 5.6 are respectively fitted and fixed into holes in the center of the frame 30.31.

A disk-shaped yaw 8 is fitted and fixed to the upper outer edge of the frame 30, and a disk-shaped yoke 9, which is paired with the yoke 8, is fitted and fixed to the lower outer edge of the frame 31. has been done. These yokes 8, 9 are fixed to spacers 7 fixed above and below the arcuate yoke 4 by means such as screws. On the lower surface of the yoke 8, fan-shaped magnets 21.7 are positioned opposite to each other with the shaft 18 in between a pair of spacers 7.7 on the upper surface of the arcuate yoke 4.
22 is fixed. On the other hand, on the upper surface of the yoke 9, a fan-shaped magnet 2 is placed opposite to each other with the shaft 18 between the pair of spacers 7.7 on the lower surface of the arc-shaped yoke 4.
3.24 is fixed. The magnet 21 and the magnet 23 are opposed to the upper and lower surfaces of the coil 3 with a suitable gap in between, and the magnet 22 and the magnet 24
are opposed to the upper and lower surfaces of the coil 2 with appropriate gaps in between.

The arc-shaped yoke 4, the pair of frames 30.31, the pair of yokes 8.9, the magnets 21.22.23.24, and the spacer 7 form a fixed part, and the swing arm is connected to this fixed part. It is rotatably supported via ball bearings 5.6. The swing arm is
The pair of coils 2.3 are arranged along the arc of the arc-shaped yoke 4 inserted through the hollow part of the coil 2.3, and with a certain gap between the hollow part and the arc-shaped yoke 4. It is designed to rotate.

The outer ring of one of the pair of ball bearings 5.6, 6, is biased in the central axis XX direction by a leaf spring 25 interposed between the ball bearings 5.6 and the frame 31. 6 is given a preload.

Each magnet 21, 22, 23, 24 is magnetized in a direction parallel to axis 18, as shown by dashed lines in FIG.
magnet 21, arc-shaped yoke 4, magnet 22,
An upper magnetic path passing through the yoke 8 and a lower magnetic path passing through the magnet 23, arc-shaped yoke 4, magnet 24, and yoke 9 are vertically symmetrical, and the upper magnetic path is formed by a pair of coils. 2.3, and the lower magnetic path crosses the lower sides of the pair of coils 2.3.

Now, when a current is passed through the pair of coils 2.3, the portion of the coil 2.3 sandwiched between the yoke 4 and the magnets 21 and 22 is affected by the electromagnetic force caused by the current of this coil and the magnetic flux of the magnetic circuit. In addition, a thrust force F is generated in the portions sandwiched between the yoke 4 and the magnets 23 and 24, respectively.

This thrust F is applied to the central axis X in the pair of coils 2.3.
Since it occurs symmetrically about -X, no thrust is applied to the shaft 18, but rotational torque is applied to the swing arm 1. Based on this rotation torque, the swing arm 1 rotates around the shaft 18, and the optical head 16 moves in an arc. Therefore, if the optical head 16 is installed so as to move in the radial direction of the optical data storage disk, tracking can be performed by controlling the current flowing through the coil 2.3.

According to the above embodiment, as shown in FIG. 5, the thrust force F generated in the coils 2.3 is generated in a plane perpendicular to the central axis Occurs on both sides ASB side.

Therefore, the utilization efficiency of the coil is improved, and a highly efficient swing arm device can be obtained with an inexpensive and compact magnetic circuit.

Moreover, as shown in FIG. 6, the central axis X-X
In the above, the center point of the distance between the pair of bearings 5.6 is assumed to be Z, and a plane passing through this center point Z and perpendicular to the rotating wheel of the swing arm 1 is assumed.

Since the optical head 16 and the balance weight 17 disposed at both ends of the swing arm 1 can be considered to be substantially the same in terms of mass, the swing arm 1 is substantially symmetrical with respect to the rotation axis. It is also symmetrical with respect to a plane that includes the center point Z and is perpendicular to the rotation axis. Therefore, the weight distribution of the swing arm 1 is perfectly balanced both horizontally and vertically, and the generated torque is also perfectly balanced both horizontally and vertically with respect to the support. Therefore, no unnatural force acts on the bearing, and a swing arm device for an optical head with stable dynamic characteristics can be obtained.

(Effects of the Invention) According to the present invention, since the structure of the swing arm is symmetrical both in the axial direction and in the direction perpendicular to the axis, the weight distribution is balanced and the weight distribution is balanced. Since the torque is symmetrical both in the axial direction and in the direction perpendicular to the axis, unnecessary thrust is not generated in the bearing, making it possible to provide a swing arm device for an optical head with excellent dynamic characteristics.

In addition, the magnetic circuit is formed symmetrically in the axial direction, and this magnetic circuit acts on both sides of the coil to generate torque, thereby providing a swing arm device for an optical head that has high coil utilization efficiency and a high torque constant. At the same time, it is possible to provide a swing arm device for an optical head that has a small number of parts and a simple configuration. Furthermore, since the frame structure is symmetrical in the axial direction, disk devices and the like can be attached to the chassis either on the top or the bottom, giving the advantage of a high degree of freedom in layout.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing an embodiment of the present invention, FIG. 2 is a plan view of the same, and FIG. 3 is a sectional view taken along line m-m in FIG.
FIG. 4 is a sectional view taken along line IV-IV in FIG. 2, FIG. 5 is a schematic side view of the swing arm portion showing the thrust generation position in the above embodiment, and FIG. 6 is the arrangement of each part in the above embodiment. FIG. 3 is a schematic side view schematically showing the relationship. 1 - Swing arm, 2.3 - Coil, 4 - Arc-shaped yoke, 5.6 - Bearing, 8.9 - One pair of yokes, 16 - Optical head, 17 - Balance weight, 18 - Axis, 21.22.23.24 - Magnet, 30.31 - Frame. April procedural amendment July 30, 1985 1. Indication of the case 1985 Patent Application No. 096502 2. Name of the invention Swing arm device for optical head 3. Person making the amendment Relationship to the case Patent application Name (223) Sankyo Seiki Seisakusho Co., Ltd. 4, Agent address 4-5-4 Kyodo, Setagaya-ku, Tokyo "
Column 6 of ``Scope of Claims'' and ``Detailed Description of the Invention,'' Contents of Amendment (1) The scope of claims will be revised as shown in the attached sheet. (2) "Axis" in line 8 of page 4 of the specification has been changed to "rotating part." (3) "Bearing" in line 9 of the same page has been changed to "rotation support section." (4) "Axis of the arm" in line 9 of the same page has been changed to "rotating part of the arm." (5) "Axis" in line 12 of the same page has been changed to "rotating part." (6) "Axis direction" in line 15 of the same page has been changed to "axial direction." (7) "Axis" in the second line of page 5 has been changed to "rotating part." (8) "Axis direction" in lines 3, 6, and 9 of the same page has been changed to "axis direction." (9) In the 19th line of the same page, add "constituting a rotating part" before "shaft 1B". (10) Add ``constituting a rotation support section'' before ``ball'' in line 16' of page 6. (II) At the end of page 10, line 19, change the line and add the following sentence. "As is well known, the relationship between the shaft and the bearing may be reversed. For example, in the illustrated embodiment, the swing arm 1 is provided with the shaft 18, which serves as the rotating part, and the frame 3
A pole bearing 5.6 was installed on the 0.31 and used as a rotating support part, but in some cases, a pole bearing was installed on the swing arm and used as a rotating part, and a shaft was provided on the frame to rotate it. It may also be used as a dynamic support part. (12) "Axis" in the first and second lines of page 11 has been changed to "axis line." (13) In the fourth line of the same page, change "also in the axial direction, along the axis" to "also in the axial direction, along the axis." (14) "Bearing J" in line 5 of the same page has been changed to "rotation support part." (15) "Axis direction" in lines 8 and 14 of the same page has been changed to "axis direction." Claims: An optical head at one end, a balance weight at the other end,
In the center is a swing arm with [! A swing arm device for an optical head having a frame rotatably supporting nine plates of the swing arm through a frame, the swing arm device having a hollow portion and located at a position equidistant from the drinking plates of the swing arm. A pair of arranged coils, an arc-shaped yoke that is inserted into the hollow part of each coil and fixed to the frame, and opposing positions on both sides in the axial direction, sandwiching the yoke and the pair of coils. A swing arm device for an optical head, comprising a pair of yokes disposed in the yokes and magnets respectively fixed to the pair of yokes.

Claims (1)

[Claims] Optical head on one end, balance weight on the other end,
A swing arm device for an optical head comprising a swing arm having a shaft in the center and a frame rotatably supporting the shaft of the swing arm via a pair of bearings, the swing arm having a hollow portion; a pair of coils arranged equidistant from the axis of the coil, an arc-shaped yoke inserted into the hollow part of each coil and fixed to the frame, and sandwiching the yoke and the pair of coils. A swing arm device for an optical head, comprising a pair of yokes disposed at opposing positions on both sides in the axial direction, and magnets respectively fixed to the pair of yokes.