JPH0538444Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a head feeding device in an optical information reproducing device such as a CD (compact disc) player or a CD/ROM.

[Conventional technology]

Usually, in this type of optical information reproducing device,
When reading information recorded on a disk-shaped recording medium, the recording medium is driven to rotate, and a reading head equipped with an optical pickup is controlled to be fed in the track direction of the recording medium, that is, in the radial direction.

In this case, the general method for feeding the head is to use electromagnetic driving force generated by a driving coil provided in the head.

For example, FIG. 6 shows a conventional head feeding device of this type, in which 1 is a reading head with a head section 2 on the right side consisting of an optical pickup, an objective lens drive device, etc., and 3 is a head section. A slide bearing 5 is provided on the left side of the head 1 and penetrated by the shaft 4 in the head feeding direction (back and forth direction), and a ball 5 is supported on the right end surface of the head 1 and runs on a guide rail (not shown) parallel to the shaft 4. The head 1 is supported so as to be movable along the shaft 4 via a bearing 3 and a ball bearing 5.

Reference numeral 6 denotes a square cylindrical driving coil provided in the center of the head 1, 7 a plate made of a magnetic material loosely inserted in the hollow portion of the driving coil 6 and parallel to the shaft 4, and 8
A pair of yokes are provided on both sides of the plate 7 with a gap between them, and are parallel to each other. The ends of the pair of yokes are integrally connected to the plate 7. A pair of driving permanent magnets 9 are attached to the surfaces of the yokes 8 facing the plate 7, and generate magnetic flux perpendicular to the driving coil 6 almost uniformly in a direction parallel to the shaft 4.
A magnetic circuit is formed by this and a permanent magnet 9. Reference numeral 10 denotes a balance adjustment section provided integrally with the left side of the head 1.

Therefore, when a current is passed through the drive coil 6, an electromagnetic driving force is generated in the drive coil 6 by the action of the magnetic flux of the permanent magnet 9, and the head 1 is moved by this electromagnetic driving force.

By the way, in the above-mentioned head feeding device, in order to move the head 1 smoothly, it is necessary to make the point of action of the electromagnetic driving force generated by the drive coil 6 approximately coincide with the center of gravity of the head 1. In the conventional device, the head 1 is particularly provided with a balance adjusting section 10, and the center of gravity of the head 1 is aligned with the point of action of the electromagnetic driving force by adjusting the adjusting section 10.

However, in the above-mentioned configuration, since the balance adjusting section 10 is particularly required, the mass of the entire head 1 becomes larger than necessary, and not only the drive coil 6 which is the drive force generating section but also the plate 7, yoke 8,
The magnetic flux generating section consisting of the permanent magnet 9 must also be made large, which has the disadvantage of increasing the size of the device.

Furthermore, since a slide bearing 3 such as an oil-impregnated bearing or a Rulon bearing is used in the bearing portion of the head 1, a large frictional force is generated between the bearing 3 and the shaft 4.
This has the disadvantage that it is difficult to move the head 1 smoothly and with high precision.

For this reason, originally, when the reading head 1 is moved by the electromagnetic driving force of the drive coil 6, the objective lens driving device of the head 1 only needs to be capable of driving and controlling the drive in the focus direction, but as described above, When the mass of the head 1 is large and the frictional force of the bearing 3 becomes large, it is extremely difficult to achieve high resolution sufficient to read information on the recording medium by controlling the movement of the head 1 alone. The objective lens drive device must be capable of driving control in the track direction as well, that is, be a two-dimensional drive actuator, resulting in a complicated configuration of the objective lens drive device.

In addition, another type of head feeding device of this type is disclosed in Japanese Patent Application Laid-open No. 114133/1983.

However, in the case of this publication, the reading head is movably supported by a pair of shafts via bearings provided on both sides, and the head is equipped with an optical pick-up, an automatic focus control device, etc. in the center of the head. Because of the structure in which the head and the drive coil for generating the drive force are arranged, the electromagnetic drive force of the drive coil does not act on the center of gravity of the head, making it difficult to move the head smoothly. Frictional forces are generated and have the same disadvantages as described above.

[Problem that the invention attempts to solve]

Therefore, in this invention, taking into consideration the above-mentioned conventional drawbacks, the electromagnetic driving force from the drive coil provided in the reading head is applied to the center of gravity of the head without increasing the mass of the reading head unnecessarily, and the shaft of the head is It is an object of the present invention to provide a means for reducing the frictional force of the bearing against the bearing.

[Means for solving problems]

This invention provides a head feeding device for an optical information reproducing device, which includes: a reading head equipped with a pick-up for optically reading information recorded on a recording medium; a shaft made of a magnetic material that guides the head in a movable manner; A drive coil is provided integrally on both sides of the head, and a drive coil is provided parallel to the shaft to form vertical magnetic flux to each of the drive coils, and applies an electromagnetic drive force to the head when the drive coils are energized. Generate 1
comprising a pair of magnetic flux generating sections and a permanent magnet fixed directly below the shaft of the head to attract the shaft, and aligning the point of action of the electromagnetic driving force generated by the magnetic flux generating section with the center of gravity of the head; The magnetic head is configured to cancel the attraction force (fm) generated between the permanent magnet and the shaft and the gravitational force (f1) acting on the center of gravity of the head, thereby reducing the frictional force between the bearing portion of the head and the shaft. This is how it was done.

[Effect]

The operation of the means described above will be explained with reference to FIGS. 3 to 5. First, as shown in FIG. 1
2, and drive coils 13 are integrally provided on both sides of the head 11. When both drive coils 13 are energized, the drive coils 13 are moved by the action of the magnetic flux of each magnetic flux generating section. As a result, an electromagnetic driving force fo is generated, and the resultant force 2fo acts on the center of the head 11, that is, the center of gravity G. Therefore, the point of application of the electromagnetic driving force and the center of gravity G of the head 11 can be adjusted without providing a balance adjustment part. It is possible to match the

Next, as shown in FIG.
The pair is supported by the shaft 12 via slide bearings 14, but at this time, the head 1
1 is a contact point A between both bearings 14 and both shafts 12,
Since it is supported by A', the gravity f ₁ acting on the center of gravity G of het 11 is applied to both contact points A and A', respectively.
A force of f ₁ /2 acts. Here, contact point A,
Assuming that the coefficient of friction at A' is μ, a friction force of μf ₁ /2 is generated at both contact points A and A′, respectively.

As shown in FIG. 5, permanent magnets 1 are placed directly below each shaft 12 on the bottom surface of the head 11.
5 is fixed, an attractive force fm is generated between both permanent magnets 15 and both shafts 12, and a force of f'=f ₁ /2-fm acts on both contact points A and A', respectively. The frictional forces at both contact points A and A' are μf'=μ(f ₁ /2−fm), respectively. Here, fm=
If a permanent magnet 15 capable of generating an attractive force of f ₁ /2 is fixed directly below the shaft 12 of the head 11, it is possible to reduce the frictional force to zero.

〔Example〕

Next, this invention will be explained in detail with reference to FIGS. 1 and 2 showing one embodiment thereof.

As shown in these drawings, a reading head 11 is equipped with a pickup for optically reading information recorded on a recording medium and an objective lens driving device for controlling the focus of the pickup. The head 11 is movably supported by a shaft 12 via a slide bearing 14, and rectangular cylindrical drive coils 13 are integrally provided on both sides of the head 11.
Permanent magnets 15 that attract the shafts 12 are fixed directly below both shafts 12 on the lower surface of the shaft.

Further, drive coils 13 are provided on both sides of the head 11.
A plate 16 loosely inserted into the hollow part, a yoke 17 arranged parallel to the plate 16 at a predetermined distance on the outside of the drive coil 13, and a permanent driving member fixed to the surface of the yoke 17 on the plate 16 side. A magnetic flux generating section including a magnet 18 is provided parallel to the shaft 12, and magnetic flux perpendicular to the drive coil 13 is uniformly formed in a direction parallel to the shaft 12.

Therefore, the drive coils 1 on both sides of the head 11
Since the resultant force of the electromagnetic driving force generated at each of the heads 3 acts on the center of the head 11, that is, the center of gravity,
The head 11 can move smoothly, there is no need to provide a balance adjustment section to match the point of application of the driving force with the center of gravity of the head 11, and the head 11 and the magnetic flux generating section can be made smaller and lighter. Become. Furthermore, since an attractive force acts between the shaft 12 and the permanent magnet 15 fixed directly under the shaft 12 on the lower surface of the head 11, the frictional force in the slide bearing 14 becomes extremely small, allowing the head 11 to move with high resolution. Control becomes possible. As a result, the objective lens drive device provided in the head 11 only needs to be driven in the focus direction, and the configuration of the drive device can be simplified.

[Effect of idea]

As described above, the head feeding device of an optical information reproducing device includes a reading head equipped with a pick-up that optically reads information recorded on a recording medium, and a shaft made of a magnetic material that guides the head in a movable manner. , a drive coil provided integrally on both sides of the head, and a magnetic flux provided perpendicularly to each of the drive coils provided parallel to the shaft, and when both drive coils are energized, an electromagnetic driving force is applied to the head. Since a pair of magnetic flux generating parts that generate a magnetic flux and a permanent magnet that is fixed directly under the shaft of the head and attracts the head are provided, the point of action of the electromagnetic driving force generated by the magnetic flux generating part is fixed to the head. The bearing part of the head is aligned with the center of gravity, and the attraction force (fm) generated between the permanent magnet and the shaft cancels out the gravity (f1) acting on the center of gravity of the head. This reduces the frictional force of the device, making it possible to make the device smaller and lighter, as well as realizing smooth movement of the reading head and high-resolution feed control, which has the effect of enabling high-speed information searches. That's what you get.

[Brief explanation of drawings]

FIGS. 1 and 2 show one embodiment of the head feeding device of the optical information reproducing device of this invention.
The figure is a perspective view, FIG. 2 is a cutaway front view, FIGS. 3 to 5 show a schematic configuration for explaining the operation of this invention, FIG. 3 is a plan view, and FIGS. 4 and 5 are FIG. 6 is a cutaway front view of a conventional head feeding device. 11...reading head, 12...shaft,
13... Drive coil, 15... Permanent magnet, 16...
...Plate, 17...Yoke, 18...Permanent magnet for driving.

Claims (1)

[Scope of utility model registration request] A reading head equipped with a pick-up for optically reading information recorded on a recording medium, a shaft made of a magnetic material that guides the head in a movable manner, and a driving coil provided integrally on both sides of the head. a pair of magnetic flux generating portions that are provided parallel to the shaft and generate magnetic flux in a perpendicular direction to the drive coils, respectively, and generate electromagnetic driving force in the head when the drive coils are energized; and the shaft of the head. a permanent magnet that is fixed directly under the shaft and attracts the head, so that the point of action of the electromagnetic driving force generated by the magnetic flux generation section coincides with the center of gravity of the head, and the attraction generated between the permanent magnet and the shaft is provided. A head of an optical information reproducing device, characterized in that the head is configured to cancel the gravitational force (f1) acting on the center of gravity of the head with a force (fm), thereby reducing the frictional force between the bearing portion of the head and the shaft. Feeding device.