JPS6035748B2 - record player - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a record player in which a tone arm is operated by speed servo control or a drive means such as a motor, and in particular, the present invention relates to a record player in which a tone arm is operated by speed servo control or a drive means such as a motor. To provide a record player with a novel structure that prevents malfunctions due to coupling between the tone arm and the magnetic circuit for stable operation of the tone arm.

Generally, in order to prevent electromagnetic coupling between magnetic circuits, it is necessary to devise the layout position so that each magnetic circuit is located a large distance apart, or to apply a magnetic shield to each magnetic circuit. There is a way.

However, the former method is difficult when arranging each magnetic circuit in a limited space such as in a record player, and the latter method requires expensive permalloy etc. to obtain sufficient effect due to magnetic shielding. Both methods have problems in practical application, as they require several magnetic materials and their structures are extremely complex. The present invention relates to a record player that is subjected to speed servo control or whose tone arm is electronically operated by a drive means such as a motor, and which connects a magnetic circuit for driving and a magnetic circuit for speed detection. It is an object of the present invention to provide a record player that enables stable operation of a tone arm by canceling out false signals caused by coupling.

Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment.

FIG. 1 shows an external front view of an embodiment of a record player constructed according to the present invention.

This embodiment is equipped with a vertical drive motor 2 and a horizontal drive motor 3 for driving the tone arm 1 in the height direction and the horizontal direction, respectively, in place of the arm lifter used in the conventional model, and the operation of the tone arm is controlled. The present invention is applied to an electronically controlled record player that is electrically controlled. As shown in FIG. 1, the tone arm 1 has a cartridge shell 7 on one end, in which a pickup cartridge 6 for tracing the sound groove of a record disc 5 on a turntable 4 is attached.
A center shaft 1 shaft bearing mechanism 11 rotatably supported by an arm base 9 arranged and fixed to the player body 8
It is attached through the turret and supported so that it can pivot freely in the vertical and horizontal directions.

A vertical drive motor 2 for driving the tone arm 1 in the height direction has a magnetic circuit section 1 erected on a mounting board 12 that pivots in the horizontal direction integrally with the center shaft 10.
3, and the magnetic circuit section 13 on the other end side of the tone arm.
It consists of a drive coil 14 fixed like an outer drum and a drive coil 14, and position servo control is performed by a detection signal from a height position detector (not shown). The tone arm 1 is held at each predetermined height position. A horizontal drive motor 3 for horizontally driving the tone arm 1 includes a drive coil 16 provided on a mounting board 15 which is physically pivoted with respect to the center shaft 10, and a drive coil 16 mounted on an outer side. and a magnetic circuit 17 fixed to the arm base 9.
Speed servo control is performed by a detection signal from a speed detection section 18, which will be described later, and the tone arm 1 is moved horizontally at a predetermined speed.

As shown in FIG. 2, the speed detection section 18 includes a speed detection coil 19 provided on the mounting board 15 so as to be pivoted integrally with the drive coil 16 of the horizontal drive motor 3;
The speed detection coil 19 is wrapped around the arm base 9, and is composed of a magnetic circuit 20 fixed to the arm base 9, and a false signal detection coil 21 wound and fixed around the magnetic circuit 20. The speed detection coil 19 and the false signal detection coil 21 have the same number of windings, and are connected in series with the winding directions opposite to each other, as shown in FIG. Each terminal 2 at both ends of the speed detection coil 19 and false signal detection coil 21 connected in series
A detection signal obtained between 2a and 22b is supplied to a speed servo circuit (not shown) to perform speed servo control of the horizontal drive motor 3. In an embodiment having such a configuration, when a drive current is supplied to the drive coil 16 of the horizontal drive motor 3, a drive generated by a moving magnetic field generated in the drive coil 16 and a fixed magnetic field from the magnetic circuit 17 is generated. Since the force is applied to the center shaft 1, the tone arm 1 supported by the center shaft 1
At the same time, the drive coil 16 and the speed detection coil 19 are integrally pivotally driven.

Therefore, an electromotive force is generated in the speed detection coil 19 according to the driving speed of the drive coil 16, and a detection product number e is obtained. Here, due to electromagnetic coupling between the magnetic circuit 17 of the horizontal drive motor 3 from which the drive coil 16 is removed and the magnetic circuit 20 of the speed detection section 18 from which the speed detection coil 19 is removed, , the speed detection coil 19
A false signal 1e2 is generated. However, since the false signal detection coil 21 with the same number of windings is connected in series in the opposite direction to the speed detection coil 19, the false signal detection coil 21 has a polarity opposite to that of the false signal +e2 of the speed detection coil 19, and By obtaining false signals -e2 with equal output levels and canceling each false signal +e2 and -e2,
Only the speed detection signal e is obtained between the output terminals 22a and 22b. Therefore, a speed detection signal e, which is correctly proportional to the driving speed of the tone arm 1, can be obtained between the output terminals 22a and 22b without suffering from the adverse effects of false signals due to electromagnetic coupling between the magnetic circuits 17 and 20. Therefore, the horizontal drive motor 3 is subjected to speed servo control based on the speed detection signal, and can drive the tone arm 1 in the horizontal direction at a stable speed. In this embodiment, since the false signal detection coil 21 is fixed to the magnetic circuit 2 of the speed detection section 18, it cannot generate a speed detection signal according to the drive speed of the horizontal drive motor 3. No, false signal-e
2 is generated.

Next, FIG. 4 shows a schematic cross-sectional view of essential parts of another embodiment of the present invention. In this embodiment, the only difference is the structure of the horizontal drive motor 3 and the speed detection section 18' from the above-described embodiment, so only the structure of this portion will be explained.

That is, in this embodiment, the horizontal drive motor 3' has a drive coil 16' attached to the center shaft 10' that supports the tone arm, and surfaces facing each other with the drive coil 16' in between have the same polarity. It consists of magnetic circuits 17a and 17b magnetized to each other, and a motor.

The speed detection section 18' also includes first and second speed detection coils 19a, 19b which are provided to pivot integrally with the center shaft 10', and each coil 19a, 19b.
The coils 19a and 19b are configured to cross magnetic fields of opposite polarity from the magnetic circuit 20'. The first and second detection coils 19a and 19b are wound in opposite directions and have the same number of windings, and are connected in series. Therefore, in this embodiment, each speed detection coil 19a, 19b of the speed detection section 18' crosses the magnetic field of opposite polarity from the magnetic circuit 20', so that the tone generated by the horizontal drive motor 3' is With respect to the movement of the arm, each speed detection signal +e, , -e, having a signal level corresponding to the speed and having opposite polarity is output, and the magnetic circuits 17a, 17b of the horizontal drive motor 3' and the Due to the electromagnetic coupling of the speed detection section 18' with the magnetic circuit 20', false signals e2 having the same signal level and the same polarity are generated.

That is, the first speed detection coil 19a has V=e.
・10e2...The detection signal VL expressed by the first equation is obtained, and the second speed detection coil 19b has VL2=-e・10e2
...A detection signal VL expressed by the second equation is obtained.

Since the detection coils 19a and 19b are connected in series in opposite winding directions, VL:VL, -VL2
= (e, 10 e2) - (1 el + e2) = 21 ... A speed detection signal VL expressed by the third equation is obtained, and the speed servo control of the horizontal drive motor 3' is performed by this speed detection signal VL. It will be rubbed.

The speed detection signal VL is transmitted to each magnetic circuit 17a, 17b,
The false signal e, due to the electromagnetic coupling between the 20' and Since it has a level, it is possible to improve the response characteristics of the speed servo control of the horizontal drive motor 3'.

As is clear from the description of each embodiment described above, according to the present invention, the first magnetic means for driving the tone arm, the second magnetic means for detecting the driving speed of the tone arm, and the first magnetic means for detecting the driving speed of the tone arm are provided. and a third magnetic means for detecting leakage magnetic flux from the magnetic means to the second magnetic means, and the second magnetic means and the third magnetic means are combined to cancel out false signals due to the leakage magnetic flux. By obtaining a detection signal proportional to the drive speed of the tone arm and performing speed servo control on the drive of the tone arm using the detection signal, the magnetic circuit for drive is provided. Since false signals caused by coupling between the magnetic circuit and the magnetic circuit for speed detection are canceled out, stable speed servo control can be achieved without having to separate the magnetic circuits or apply magnetic seals. It is possible to provide a record player in which the tone arm can be driven under control, and the intended purpose can be fully achieved.

[Brief explanation of drawings]

FIG. 1 is an external front view of an embodiment of a record player according to the present invention. FIG. 2 is a schematic plan view of the main parts in the above embodiment. FIG. 3 is a wiring diagram showing the connection state between the speed detection coil and the false signal detection coil. FIG. 4 is a longitudinal sectional side view schematically showing the main parts of another embodiment of the present invention. 1...
...Tone arm, 10... Center shaft, 3, 3'...
...Horizontal drive motor, 16, 16'...Horizontal drive motor drive coil, 17, 17a, 17b...
...Magnetic circuit of horizontal drive motor, 18, 18'...
...speed detection section, 19, 19a, 19b, 21. ．．・
...Detection coil of speed detection section, 20, 20'...
Magnetic circuit of speed detection section. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A first magnetic means for driving the tone arm, a second magnetic means for detecting the driving speed of the tone arm, and leakage magnetic flux from the first magnetic means to the second magnetic means. and a third magnetic means for detecting the second magnetic means and the third magnetic means.
is combined with magnetic means to cancel the false signal caused by the leakage magnetic flux, obtain a detection signal proportional to the drive speed of the tone arm, and perform speed servo control on the drive of the tone arm using the detection signal. A record player characterized by: 2. The second magnetic means and the third magnetic means are fixedly wound around a magnetic circuit to which a detection coil driven integrally with the tone arm is fitted, and a detection coil having the same number of windings as the detection coil is wound and fixed. The record player according to claim 1, characterized in that the detection coils are connected in series with winding directions opposite to each other. 3. The second magnetic means and the third magnetic means integrally integrate two detection coils connected in series with each other with the same number of windings and with opposite winding directions to the tone arm. A magnetic circuit is provided between each detection coil to be driven, and each detection coil is configured to cross magnetic fields in mutually opposite directions from the magnetic circuit. The record player described in scope 1.