JPH0135343Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a pickup device for a video disc player, and particularly relates to an improvement of a stylus pressure coil in the pickup device.

A video disc is a system that reproduces video and audio on a television receiver or the like using the same principle as a record disc, and various systems are currently being developed.

One of them is the so-called grooveless capacitance variable type.
In other words, a dimple (bit) is formed on the surface of the conductive band that forms the disk, an extremely thin insulator is coated on top of the dimple, and information is recorded as changes in capacitance, which are then passed through a needle with an electrode ( For example, Safaya needle)
This is a VHD (Video High Density
Disc) method. FIG. 1 is a schematic bottom plan view of a video disc player according to the above-described system, and FIG. 2 is a side sectional view taken along the line - in FIG.

Referring to FIGS. 1 and 2, a pickup device 10 includes an outer frame 1 fixed to a pickup device moving device (not shown). A needle pressure coil 12, an arm stretcher coil 4, and tracking coils 3a, 3b, 3c, and 3d are attached to the upper inner surface and three inner surfaces of the outer frame 1, respectively. The arm 7 is attached so that its rear end coincides with a portion surrounded by the end faces of the needle pressure coil 12, arm stretcher coil 4, and tracking coils 3a, 3b, 3c, and 3d. The arm 7 is tapered and becomes thinner toward the tip. A stylus holder 8 made of an insulating material is attached to the tip of the arm 7, and a needle 9 is held by the stylus holder 8.

The rear end of the arm 7 is inserted into a suspension cylindrical portion 6B provided at the center of the suspension 6, so that the entire arm 7 is held by the suspension 6. As described above, the suspension 6 has a cylindrical portion 6B in the center thereof, and has arm portions 6A extending from the cylindrical portion 6B to both ends, and each end of the arm portion 6A is attached to the inner frame 5. It is being This inner frame 5 is fixed to the outer frame 1.

The suspension 6 is made of a flexible material such as silicone rubber, and in its natural state keeps the arm 7 horizontal (Fig. 2), but when an external force is applied to the arm 7, the direction of the applied external force changes. The holding state of the arm 7 can be changed by.

Further, a permanent magnet 11 is embedded inside the rear end of the arm 7 as shown by the dotted line, and the suspension 6 has a central axis of the arm portion 6A that is connected to the permanent magnet 11.
It is arranged so as to be located between the north pole and the south pole of 1.

The operation of the video disk player pickup device 10 having the above configuration is as follows.

First, as the turntable (not shown) rotates, the disk 2 placed on the turntable
rotates. Subsequently, when a DC voltage is applied to the needle pressure coil 12, a magnetic force acts between the needle pressure coil 12 and the permanent magnet 11, and the arm 7 tilts around the suspension 6 to the position shown by the dashed line 16.
The needle 9 comes into contact with the surface of the disc 2.

On the surface of the disk 2, tracks on which video signals and the like are recorded are formed in a spiral shape, and the needle 9 moves sequentially from the outer track to the inner track each time the disk 2 rotates once. A pick-up cartridge moving device (not shown) is used to move the contacts. The needle 9 then electrically detects the video signal from the track as a change in capacitance.

The above is the general configuration and operation of the pickup device for a video disc player.

By the way, the above-mentioned conventional pickup device 1
0, the stylus pressure coil 12 (FIG. 2) had to have a large shape. This is because, as already explained, the needle force coil 12 tilts the arm 7 to the position shown by the dashed line 16. In order for the arm 7 to tilt to such a large extent, a considerably large magnetic force must act between the needle pressure coil 12 and the permanent magnet 11. Therefore, it was necessary to increase the diameter of the end face of the needle pressure coil 12 and increase the length of the coil to generate strong magnetic force. As a result, the stylus force coil 12 has a relatively large shape compared to the other parts constituting the pick-up device 10, which has been an obstacle in reducing the overall thickness of the pick-up device 10.

Therefore, the purpose of this invention is to
The present invention is intended to reduce the size of the pickup device 2 and to make the entire pickup device 10 thinner.

Simply put, this invention is a pickup device for a video disc player in which the stylus pressure coil is a thin rod-like coil and is arranged parallel to the rear end of the arm.

The above-mentioned objects and features of this device will become clearer from the following description of embodiments with reference to the drawings.

FIG. 3 is a side sectional view of one embodiment of this invention. In the figure, a permanent magnet 11 is embedded in the rear end of the arm 7 in parallel with the arm 7. Further, the needle pressure coil 12 is a thin rod-shaped coil, and its central axis extends in the longitudinal direction of the arm 7. That is, the needle pressure coil 12 has one end disposed near the upper part of the rear end of the arm 7, and the other end fixed to the rear inner surface of the outer frame 1. In this way, the central axis of the thin bar-shaped needle pressure coil 12 is arranged parallel to the longitudinal direction of the arm 7, and the magnetic pole at the front end of the needle pressure coil 12 is configured to be close to the rear magnetic pole of the permanent magnet 11. This is one of the features of this embodiment.

If the number of turns and current value of the thin rod-shaped coil are constant,
It is known that the strength of the magnetic field inside a coil is approximately inversely proportional to the coil diameter. Therefore, the attractive force generated between the tip 12A of the thin bar-shaped stylus pressure coil 12 and the magnetic pole at the rear end of the permanent magnet 11 is as follows: If the number of turns and the current value are the same,
Placing the central axis close to the permanent magnet will make the coil stronger than increasing the diameter of the coil. Therefore, with the configuration of this embodiment, there is no need to increase the thickness of the pickup device 10. Furthermore, since the needle pressure coil 12 can be made long, a large number of turns can be secured.

In FIG. 3, the tip 12 of the needle pressure coil 12
A current is passed through the needle pressure coil 12 so that a north pole is generated at A. Then, an attractive force acts between the N pole of the needle pressure coil 12 and the S pole of the permanent magnet 11, and the arm 7
is rotated to the position shown by the dashed line 16, and the video signal is detected. The degree of inclination of the arm 7, in other words, the magnitude of the needle pressure of the needle 9 at the tip of the arm 7 can be adjusted by controlling the current flowing through the needle pressure coil 12. By adjusting the current flowing through the needle pressure coil 12,
This is because the attractive force between the needle pressure coil 12 and the permanent magnet 11 increases or decreases.

In FIG. 3, parts that are the same as or correspond to those of the conventional example shown in FIG. 2 are given the same numbers.

FIG. 4 is a side sectional view of another embodiment of the invention, with only the characteristic parts being partially depicted.

The feature of FIG. 4 is that the length of the thin bar-shaped stylus pressure coil 12 is a little more than twice the length of the permanent magnet 11. In this way, if the needle pressure coil 12 is made long, the tip 12A of the needle pressure coil 12 is located on the north pole of the permanent magnet 11. Furthermore, the permanent magnet 11
The central part of the needle pressure coil 12 near the N pole is located above the S pole. Therefore, the north pole of the tip 12A of the needle force coil 12 and the north pole of the permanent magnet 11 repel each other. Furthermore, since the position of the S pole of the permanent magnet 11 is closer to the N pole than the S pole of the needle pressure coil 12,
The attractive force of the north pole is stronger than the repulsive force of the pole. Therefore, a moment of force is efficiently applied to the arm 7 around the central axis of the arm portion 6a of the suspension 6, causing the arm 7 to rotate.

Also, since the length of the needle pressure coil 12 is increased,
This has the advantage that the generated magnetic force is also stronger.

In the case of the embodiment shown in FIG. 4, it is preferable that the length of the needle pressure coil 12 be at least twice the length of the permanent magnet 11, but conversely, it is better not to make it less than twice the length of the permanent magnet 11. good. This is because the tip 12A of the needle pressure coil 12 and the N pole of the permanent magnet 11 repel each other.
This is because while the arm 7 is being pushed downward, the center S pole of the stylus force coil 12 and the S pole of the permanent magnet 11 repel each other, creating a force that tries to keep the arm 7 horizontal. Then, rotate arm 7,
This is because the efficiency of applying needle pressure to the needle 9 decreases.

FIG. 5 is a partial side sectional view showing another embodiment of the invention. In FIG. 5, two thin bar-shaped needle pressure coils are provided. The needle pressure coil 12 and the needle pressure coil 12' are attached so that their end surfaces face each other. Each needle pressure coil 12 and 1
A north pole is formed on the opposite end surfaces of the ends 2'. These N poles are arranged so that a magnetic force acts between them and the N pole and S pole of the permanent magnet 11. With such a configuration, the arm 7 can be rotated with less current.

Note that the needle pressure coil 12' may be fixed to the inner upper surface of the outer frame 1, for example.

FIGS. 6 and 7 are diagrams showing still other embodiments of this invention. Figure 6 shows needle pressure coil 1.
2, and FIG. 7 is a side sectional view of the pickup device 10 to which the stylus force coil 12 shown in FIG. 6 is attached. FIG. 7 shows a side sectional view of the needle pressure coil 12 of FIG. 6 taken along line -.

As shown in FIG. 6, the needle pressure coil 12 of this embodiment has a structure in which salient pole coils 15 and 16 and an annular coil 17 are combined. The salient pole coils 15 are attached so that their end faces face each other, and the salient pole coils 16 are similarly attached.
They are attached so that their end faces face each other. Each opposing end face of the salient pole coil 15 has an N pole, and each opposing end face of the salient pole coil 16 has an S pole. A salient pole coil 15 having a north pole on its end face is mounted so as to be positioned parallel to the central axis of the arm 7. With such a configuration, the number of coil turns of the needle pressure coil 12 can be significantly increased, and the magnetic field generated in the needle pressure coil can be made stronger. Therefore, it is possible to efficiently control the stylus force.

In addition, in FIG. 6, the south pole generated on the opposing end surfaces of the salient pole coil 16 does not directly affect the rotational control of the arm 7. However, this salient pole coil 1
6, the magnetic resistance between the respective salient ends of the needle force coil 12 is reduced, and a strong magnetic field can be generated more efficiently with less current.

As described above, according to this invention, the needle pressure coil is a thin rod-shaped coil, and the coil is disposed parallel to the rear end of the arm, so that the entire pickup device can be made thinner.

[Brief explanation of drawings]

FIG. 1 is a bottom plan view of a conventional pickup device for a video disc player. FIG. 2 is a side sectional view taken along line - in FIG. 1. FIG. 3 is a side sectional view of a pickup device according to an embodiment of this invention. FIG. 4 is a partial side sectional view of a pickup device according to another embodiment of the invention. FIG. 5 is a partial side sectional view of another embodiment of the invention. FIG. 6 is a plan view of a needle pressure coil according to still another embodiment of this invention. FIG. 7 is a partial side sectional view of the pickup device to which the stylus pressure coil shown in FIG. 6 is attached. In the figure, 1 is an outer frame, 5 is an inner frame, 6 is a suspension, 7 is an arm, 9 is a needle, 10 is a pickup device, 11 is a permanent magnet, and 12 is a needle pressure coil. In addition, the same numbers are attached to the same or corresponding parts in the figures.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) An arm having a signal detection needle attached to its tip, a permanent magnet magnetized in the longitudinal direction of this arm and embedded in the rear end of this arm, and a suspension that supports the arm at a position between the N and S poles of a permanent magnet; and a stylus pressure coil arranged to provide a magnetic field that rotates the permanent magnet around a position supported by the suspension. By applying a control current to the stylus pressure coil, the magnetic force generated by the stylus pressure coil and the permanent magnet in the rear end of the arm are repelled or attracted, and the arm rotates around the suspension. A pick-up device for a video disc player in which the stylus pressure at the tip of the arm is controlled, wherein the center line of the stylus pressure coil extends in the longitudinal direction of the arm. Device. (2) The stylus pressure coil has a thin bar shape having a length that is at least twice as long as the permanent magnet, and the permanent magnet is
A pickup device for a video disc player according to claim 1, wherein the pick-up device for a video disc player is arranged in line with a portion from a position forward of the central portion of the needle pressure coil to the front end thereof. (3) The needle pressure coil consists of two coaxially arranged coils, each end of which is opposite to the other above the center of the permanent magnet, and the opposing ends have: A pickup device for a video disc player according to claim 1, characterized in that magnetic poles of mutually different polarities are generated.