JPH0760575B2 - Swing arm device for optical head - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a swing arm device for tracking an optical head for recording / reproduction of an optical video disc, an optical audio disc and other optical data storage discs.

(Prior Art) A swing arm for an optical head, which is attached to a swing arm device to move the recording / reproducing optical head of an optical data storage disk in a tracking direction, and moves the optical head along an arc. The device is known. The one described in JP-A-58-53035 is one of them.

According to the above-mentioned publication, the center of mass of a rotating assembly having a swing arm equipped with an optical head is located on the rotation axis, and the coil device is arranged on both sides of the rotation axis. Firstly arranged diametrically opposed to each other at a position equidistant from the axis and exerting equal turning power on the swing arms
And a second coil, and the first and second powers are operated in a plane perpendicular to the rotation axis.

(Problem to be Solved by the Invention) According to the above-described conventional swing arm device for an optical head, since the thrust is generated only on one side of the coil, the thrust generating portion in the drive magnetic circuit is small and the efficiency is high. If it is low and efficiency is increased, it is necessary to use a high energy magnet, which is a cost disadvantage.
Further, in order to stabilize the dynamic characteristics of the swing arm equipped with the optical head, it is necessary to generate the turning force in a well-balanced manner in the turning axis direction. When trying to generate a turning force in a well-balanced manner in the direction of the turning axis in a device that generates turning force in a vertical plane, the mass of the swing arm should be adjusted so that the turning force generation plane is located at the center of the pair of bearings. It needs to be distributed in a good balance. Therefore, there is a problem that the axial height of the swing arm becomes high, dead space occurs, and the size cannot be reduced.

It is an object of the present invention to have a swing arm in which weight distribution and generated torque are balanced in all directions, and a swing arm for an optical head having stable dynamic characteristics without exerting an unnatural force on its bearing. To provide a device.

(Means for Solving the Problem) The present invention relates to a swing arm device for an optical head, which has an optical head at one end, a balance weight at the other end, and a swinging part at the center, and In a swing arm device for an optical head having a frame that rotatably supports a rotating portion via a pair of rotation supporting portions, the swing arm is provided at a position equidistant from the rotating portion, And a pair of hollow coils opened in the rotating direction, a ring-shaped intermediate yoke fixed to the frame and having the hollow portions of the pair of hollow coils inserted thereinto, and the intermediate yoke and the pair of hollow coils sandwiched therebetween. A pair of annular outer yokes respectively disposed at opposite positions on both sides in the axial direction, and on the surfaces of the pair of outer yokes facing each other, A swing arm including a magnet fixed to a position facing the movable range of the empty coil, the swing arm including the optical head and the balance weight has a center of gravity of the swing arm on the axis of the rotating portion, Further, the pair of hollow coils are arranged so as to substantially coincide with the center between the pair of rotation supporting portions, and the pair of hollow coils are arranged symmetrically with respect to a line passing through the center of gravity and perpendicular to the axis of the rotation portion. It is characterized by being

(Operation) The swing arm rotates about the rotating portion in a state in which the pair of coils arranged on the swing arm surrounds the annular yoke fixed to the frame. Two magnetic circuits that are symmetrical in the axial direction between a pair of yokes arranged at opposite positions on both sides in the axial direction across the coil, magnets fixed to these yokes, and the annular yoke. Are formed, and by energizing the coil in the magnetic gap included in these magnetic circuits, thrust is generated on both sides in the axial direction of the coil.

The pair of coils and the swing arm are arranged symmetrically with respect to a line that passes through the center of gravity of the swing arm and is perpendicular to the axis of the rotating portion, and the optical head and the balance weight pass through the center of gravity and with respect to the axis of the rotating portion. Since it is provided on a vertical line, the weight distribution of the swing arm is perfectly balanced in all directions with respect to the center of gravity, and stable dynamic characteristics are obtained.

(Embodiment) In FIGS. 1 to 4, a swing arm 1 has two plates 11 and 12 vertically opposed to each other, and these two plates 11 and 12 are integrally connected with a predetermined gap. Spacers 13 and 14 provided at both ends and a spacer 1 provided at the center for
5, an optical head 16 is provided at one end of the swing arm 1, and a balance weight 17 is provided at the other end thereof. A shaft 18 forming a moving part is integrally provided. Swing arm 1 has a balance weight of 17
Thus, the left and right weights are balanced with respect to the center line XX of the shaft 18. The swinging arm 1 also has a shaft
A pair of holes penetrating the opposite plates 11 and 12 are formed at symmetrical positions with respect to the center 18, and a pair of coils 2 and 3 having a hollow portion are arranged so as to be embedded in these holes. ing. Therefore, the pair of coils 2 and 3 are arranged at positions equidistant from the shaft 18. The hollow portions of the pair of coils 2 and 3 are open to both sides of the swing arm 1.

One common annular yoke 4 is inserted into the hollow portions of the pair of coils 2 and 3. Four sector-shaped spacers 7 are fixed to the yoke 4 so as to face each other with the central axis line XX interposed therebetween, and also to sandwich the yoke 4 from above and below.

Inner rings of ball bearings 5 and 6 that constitute a rotation support portion are fitted and fixed to the upper and lower ends of the shaft 18, respectively.
The outer rings of these ball bearings 5 and 6 are fitted and fixed in the central holes of the frames 30 and 31, respectively.

An annular yoke 8 is fitted and fixed to the outer peripheral upper edge portion of the frame 30, and an annular yoke 9 which is paired with the yoke 8 is fitted and fixed to the outer peripheral lower edge portion of the frame 31. . These yokes 8 and 9 are fixed to spacers 7 fixed above and below the yoke 4 by means such as screwing. On the lower surface of the yoke 8, fan-shaped magnets 21 and 22 are fixed at opposite positions with a shaft 18 interposed between a pair of spacers 7 on the upper surface side of the yoke 4. On the other hand, on the upper surface of the yoke 9, a pair of spacers 7 on the lower surface side of the yoke 4,
The fan-shaped magnets 23 and 24 are fixed at positions facing each other with the shaft 18 interposed therebetween. The magnet 21 and the magnet 23 face the upper and lower surfaces of the coil 3 with a proper gap therebetween, and the magnet 22 and the magnet 24 face the upper and lower surfaces of the coil 2 with a proper gap therebetween. .

The yoke 4, the pair of frames 30 and 31, the pair of yokes 8 and 9, the magnets 21, 22, 23 and 24, and the spacer 7 form a fixed portion, and the swing arm 1 has a ball bearing 5 against the fixed portion. , 6 are rotatably supported via.
The swing arm 1 is arranged along the circular ring of an annular yoke 4 which is inserted into the hollow portions of the pair of coils 2 and 3, and has a constant space between the hollow portion and the yoke 4. It is designed to rotate in the open state.

The outer ring of one ball bearing 6 of the pair of ball bearings 5, 6 is a leaf spring interposed between the frame 31 and the frame 31.
A preload is applied to each of the ball bearings 5 and 6 by urging them in the direction of the central axis X-X by 25.

Each of the magnets 21, 22, 23, 24 is magnetized in a direction parallel to the axis 18, and as shown by the broken line in FIG.
1, the upper magnetic path passing through the yoke 4, the magnet 22, and the yoke 8 and the lower magnetic path passing through the magnet 23, the yoke 4, the magnet 24, and the yoke 9 are formed symmetrically, and the upper magnetic path is The upper side of the pair of coils 2 and 3 is crossed, and the lower magnetic path crosses the lower side of the pair of coils 2 and 3.

Therefore, when a current is made to flow through the pair of coils 2 and 3, the portion of the coils 2 and 3 sandwiched by the yoke 4, the magnet 21 and the magnet 22 is caused by the electromagnetic force of the current of this coil and the magnetic flux of the magnetic circuit. And yoke 4 and magnet
Thrust F is generated in the portion sandwiched between 23 and magnet 24. Since this thrust F is generated symmetrically about the central axis XX in the paired coils 2 and 3, it does not apply a thrust to the shaft 18 but a turning torque to the swing arm 1. Based on this rotation torque, the swing arm 1 rotates about 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 coils 2 and 3.

According to the above-described embodiment, as shown in FIG. 5, the thrust F generated in the coils 2 and 3 is generated in the plane perpendicular to the central axis line XX, and each of the coils 2 and 3 has a thrust. Both top and bottom
It occurs on the A and B sides. Therefore, the utilization efficiency of the coil is improved, and the swing arm device having high efficiency can be obtained by the inexpensive and small magnetic circuit.

Further, as shown in FIG. 6, the central axis line XX
In the above, it is assumed that the center point of the distance between the pair of bearings 5 and 6 is Z, and a plane perpendicular to the rotation axis of the swing arm 1 passing through this center point Z is assumed. Swing arm 1 has optical heads 16 and balance weights arranged at both ends thereof.
Since 17 can be regarded as substantially the same in terms of mass, they are symmetrical in terms of mass with respect to the rotation axis, and the center of torque and the center of mass coincide. Further, it is also symmetrical with respect to a plane perpendicular to the rotation axis including the center point Z. Therefore, the weight distribution of the swing arm 1 and the swing arm 1
Since the torque generated in the bearing is perfectly balanced in all directions with respect to the center of gravity of the swing arm, no unnatural force acts on the bearing, and a swing arm device for an optical head with stable dynamic characteristics is obtained. be able to.

(Effect of the invention) According to the present invention, the structure of the swing arm is symmetrical both in the axial direction and in the direction perpendicular to the axial line, so that the weight distribution is balanced and the swing arm is generated in the coil. The torque is symmetrical both in the axial direction and in the direction perpendicular to the axial line, so that these two configurations work together to balance statically and dynamically. Therefore, it is possible to provide a swing arm device for an optical head having excellent dynamic characteristics without generating unnecessary thrust on the bearing. Further, since the magnetic circuit is formed symmetrically in the axial direction, and the magnetic circuit acts on both sides of the coil to generate torque, a swing arm device for an optical head having a high coil utilization efficiency and a high torque constant is provided. It is possible to provide a swing arm device for an optical head which has a small number of parts and a simple structure. Further, since the frame structure is symmetrical in the axial direction, the disk device or the like can be mounted on the chassis either on the upper surface or the lower surface, and there is an advantage that the degree of freedom in layout is high.

[Brief description 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 as above, FIG. 3 is a sectional view taken along line III-III in FIG. 2, and FIG. 5 is a cross-sectional view taken along line IV-IV, FIG. 5 is a schematic side view of a swing arm portion showing a thrust generation position in the above embodiment, and FIG. 6 is a schematic side view showing the positional relationship of each part of the above embodiment. Is. 1 ... Swing arm, 2,3 ... coil, 4 ... annular yoke, 5,6 ... bearing, 8,9 ... pair of yokes, 16 ...
… Optical head, 17 …… Balance weight, 18 …… Axis, 2
1,22,23,24 …… Magnet, 30,31 …… Frame.

Claims (1)

[Claims] 1. A swing arm having an optical head at one end, a balance weight at the other end, and a rotating portion at the center, and the rotating portion is rotatable through a pair of rotating support portions. A swing arm device for an optical head having a frame supported on
A pair of hollow coils provided at positions equidistant from the rotating portion and opened in the rotating direction, and an annular intermediate member fixed to the frame and having the hollow portions of the pair of hollow coils inserted therethrough. On the surfaces of the yoke, the intermediate yoke and the pair of hollow coils sandwiching the intermediate coil and the pair of hollow coils, the pair of annular outer yokes, which are respectively disposed at opposing positions on both sides in the axial direction, and the pair of outer yokes, which are opposed to each other. And a magnet fixed to a position facing the movable range of the hollow coil, the swing arm including the optical head and the balance weight has a center of gravity of the swing arm on the axis of the rotating portion. The pair of hollow coils are arranged so as to substantially coincide with the center between the pair of rotation support portions, and the pair of hollow coils pass through the center of gravity and are perpendicular to the axis of the rotation portion. A swing arm device for an optical head, which is arranged symmetrically with respect to a line.