JPS6127803B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tone arm drive device used in a record player system.

As is well known, the natural resonant frequency f ₀ of the tone arm
The so-called MFB is used as a means to prevent unnecessary vibrations during record playing.
Braking based on motional feedback (motional feedback) is known.

FIG. 1 shows an example of a conventional tone arm driving device, in which a tone arm 3 provided with a cartridge 2 having a regeneration needle 1 is horizontally rotatable by an arm shaft 4, and is rotated by a shaft 5 in the direction of arrow a. , vertically rotatable in the direction b, are attached to the player board 6. The output signal of the cartridge 2 is taken out from the lower end of the arm shaft 4 and sent to a speaker (both not shown) through a muting circuit and an amplifier.
It is designed to be supplied to Note that 7 indicates a record disc, which is placed on a turntable (not shown).

At the rear of the tone arm 3, a magnetized magnet 10 is provided via a support rod 11 as shown. Further, a support rod 12 is provided on the arm shaft 4 and is fixed in a free relationship with respect to rotation of the arm shaft 4, and a motor coil L ₁ and a detection coil L ₂ are attached to this support rod 12. , are provided in association with the magnet 10 as shown.
The detection coil _L2 and magnet 10 constitute a speed detector, and the motor coil _L1 and magnet 10 constitute a motor for driving the tone arm 3 in the direction of arrow a or b.

By the way, the amplifier circuit 14 is for supplying a control signal to the motor coil _L1 , and the amplifier circuit 15 configured as a voltage follower is
It is for MFB and is configured to supply an arm speed detection signal to the amplification circuit 14. Resistors R ₁ and R ₂ are for determining the amplification degree of the amplification circuit 15, and resistors R ₃ and R ₄ are input resistances. Note that a vertical balance signal E (DC voltage) for applying an appropriate stylus pressure is supplied to the input terminal 16, but the voltage level of this signal E can be adjusted to any value by a variable resistor (not shown). is set to

Now, when the vertical balance signal E is supplied to the input terminal 16, the input voltage of the amplifier circuit 14 becomes 1/2E due to the action of the input resistors R ₂ and R ₃ . The voltage level of the output signal of the amplifier circuit 14 also becomes 1/2E,
This voltage is supplied to motor coil _L1 . Here, if the resistance of motor coil _L1 is _R1 , the current I flowing through this motor coil _L1 is I=E/
Determined by 2R _L1 .

However, the resistance R _L1 is the motor coil L ₁
It changes depending on the temperature change. Therefore, R
_L1 and I are functions of temperature t, and motor coil
The force F of the motor constituted by L ₁ and the magnet 10 varies depending on the temperature t. Note that since a current I is constantly flowing through the motor coil L ₁ in order to balance the tone arm 3, the temperature rise in the motor coil L ₁ is extremely large. If the motor is driven with a constant voltage in this way, the balance of the tone arm will change depending on the temperature, and if the stylus pressure of cartridge 2 is adjusted based on this, the stylus pressure will change and the stylus pressure will be correct. The drawback is that it is no longer possible to obtain

On the other hand, if the tone arm 3 is driven in the direction of arrow a or b or unnecessary vibration occurs, the magnet 1
A detection signal e is induced in the detection coil _L2 as the sensor 0 moves up and down. Then, the amplified detection signal Ae is obtained from the amplifying circuit 15, and the amplifying circuit 1
4. However, due to the action of the input resistors R ₃ and R ₄ , the output signal of the amplifier circuit 14 becomes 1/2Ae, and this signal is sent to the motor coil L ₁ as an MFB component.
supplied to Therefore, a current iMFB based on the current I and the MFB component flows through the motor coil _L1 . Since the temperature of motor coil _L1 has already increased due to the current I, the temperature of motor coil L1 has already increased by this amount.
iMFB decreases. As a result, the loop gain of the MFB decreases, making it impossible to perform accurate braking of the tone arm 3.

Next, in order to solve the above-mentioned defects, problems when the conventional motor described above is driven at a constant current will be considered.

In FIG. 2, 20 is an input terminal to which a vertical balance signal E is supplied. R ₁₀ and R ₁₁ are input resistances, 21 and 22 are amplification circuits composed of OP amplifiers, L ₁₁ is a motor coil, L ₁₂ is a detection coil, and R ₁₃ determines the amplification degree of the amplification circuit 22. It is a resistance to Further, Rs is a detection resistor, which is connected in series to the motor coil _L11 connected to the output end of the amplifier circuit 21 and grounded. This detection resistor
Since the non-grounded side of Rs is connected to the input terminal of the amplifier circuit 22, the current flowing through the motor coil _L11 is made constant. Note that the motor coil L ₁₁ and the detection coil L ₁₂ are arranged in the same manner as in the conventional example shown in FIG.

When the vertical balance signal E is supplied to the input terminal 20, a current flows through the motor coil L ₁₁ and the detection resistor Rs. Therefore the motor is driven and the sensing resistor
The voltage across Rs is supplied to the amplification circuit 22. Then, due to the feedback via the amplification circuit 21, the DC current I of the coil becomes I=kH/Rs (k is a constant). That is, a constant current I proportional to the vertical balance signal E, which is independent of the resistance R _L1 of the coil, flows regardless of temperature changes. Further, when vertical vibration is applied to the tone arm, a detection signal voltage corresponding to the vertical movement speed of the tone arm is induced in the detection coil L ₁₂ , and the amplification circuit 22 receives the vertical balance signal E and the detection signal. A voltage across the detection resistor Rs based on the voltage is supplied, and an output signal in which these are superimposed and amplified is obtained from the output terminal.
This output signal is sent to the amplifier circuit 2 via the input resistor _R11 .
1.

Therefore, MFB is performed in a vertically balanced state.

Therefore, with motor coil L ₁ , balance drive and
Since braking is performed based on the MFB component,
Depending on the set voltage level of the vertical balance signal E,
The operating point of MFB changes. That is, as shown in FIG. 3, when the vertical balance signal E is set approximately at the center of the MFB operating range determined by the power supply voltages +DC and -DC, the MFB operation will be as shown by line A. It will be done. However, if the cartridge 2 is heavy, for example, it is necessary to set the voltage level of the vertical balance signal E high as shown in FIG. 4, and the MFB operation is saturated in the range shown by diagonal lines. Also, if cartridge 2 is light, the 5th cartridge
As shown in the figure, it is necessary to set the voltage level of the vertical balance signal E low, and the MFB operation is saturated in the range shown by diagonal lines. Therefore, in the saturation range,
Even if unnecessary vibration occurs in the tone arm, it cannot be damped.

In order to prevent such inconveniences, it is necessary to widen the +DC and -DC power supply voltage bands or to increase the motor drive torque, which not only increases costs but also increases the motor speed. There was a defect that the etc. were large.

The present invention was invented to correct the above-mentioned defects, and it is an object of the present invention to provide a tone arm drive device that can accurately drive and brake a tone arm.

The configuration of the present invention will be described below based on examples.

FIG. 6 shows an example of a balance drive dedicated circuit. Note that the same components as in FIG. 2 are given the same reference numerals. The configuration of this embodiment is as follows:
A detection resistor Rs is connected to the output end of the amplifier circuit 21, and a motor coil is connected between this detection resistor Rs and the ground.
L ₁₁ is provided, the middle point of these connections is connected to the input end of the amplification circuit 22, and the output end of the amplification circuit 22 is connected to the other input end of the amplification circuit 21. As a result, the voltage across the detection resistor Rs becomes constant, and the current I ₁ flowing through the motor coil L ₁₁
becomes constant corresponding to the set voltage E. Therefore, the current I ₁ flowing through the motor coil L ₁₁ becomes irrelevant to the MFB drive detection signal corresponding to the moving speed of the tone arm.

FIG. 7 shows an example of an MFB dedicated circuit, in which a detection coil _L12 is connected to one input terminal of the amplifying circuit 25, and the other input terminal is grounded via a resistor _R15 . Note that the resistor R ₁₆ is the amplifier circuit 25
This determines the degree of amplification. A newly provided motor coil _L13 is connected to the output end of the amplifying circuit 25, and this motor coil _L13 performs braking corresponding to the moving speed of the tone arm.

Next, we will describe the circuit operations of the balance drive dedicated circuit and the MFB dedicated circuit in relation to each other.

When the vertical balance signal E is supplied to the input terminal 20 shown in FIG. 7, a current _I1 flows from the output end of the amplification circuit 21 to the motor coil _L11 via the detection resistor Rs. As a result, the tone arm moves downward and acts to apply stylus pressure to the cartridge in accordance with the vertical balance signal E. Further, when vertical vibration is applied to the tone arm, a voltage proportional to the speed of the vibration is detected by the detection coil _L12 shown in FIG. And the detection signal is amplified by the amplification circuit 2.
5 and the amplified output signal is supplied to one end of motor coil _L13 .

As mentioned above, the current I ₁ flowing through the motor coil L ₁₁
is unrelated to the detection signal detected by the detection coil _L12 , so the voltage level of the vertical balance signal E is free within the range of the power supply voltage +DC and -DC, as shown by the dotted line in FIG. This means that it can be set to . The MFB operation is performed with reference to approximately the center of the power supply voltages +DC and -DC, as shown by line A in FIG. Therefore, depending on the voltage level of the vertical balance signal E and replacing the head shell,
There is no inconvenience such as MFB operation becoming saturated.

Further, the dedicated balance drive circuit may have a simple circuit configuration as shown in FIG. That is, the vertical balance signal E is supplied to one input terminal of the amplifier circuit 21. A motor coil _L11 is connected to the output end of the amplification circuit 21, and is grounded via a detection resistor Rs. The output from the midpoint of the connection between the motor coil L ₁₁ and the detection resistor Rs is applied to the other input terminal of the amplifier circuit 21 . Also in this case, a constant current according to the setting of the vertical balance signal E is applied to the motor coil L ₁₁ ,
Flows through the detection resistor Rs. Therefore, by using this balance drive dedicated circuit together with the MFB dedicated circuit shown in FIG. 7, it is possible to move and brake the tone arm as described above.

Note that since a constant current is always flowing through the motor coil _L11 , the temperature tends to rise, but the amount of current does not change due to this temperature rise, and the driving torque does not change. On the other hand, the MFB drive is not performed all the time, but is performed when the tone arm moves or when unnecessary vibrations occur. Therefore, since the motor coil _L13 generates little heat, the loop gain of the MFB dedicated circuit does not fluctuate, and stable circuit operation is always achieved.

Furthermore, in order to prevent the temperature of the above-mentioned motor coil L ₁₃ from rising due to the motor coil L ₁₁ , motor coils L ₁₁ and L ₁₃ are installed on the left and right sides of the same bobbin.
It is even more effective to wind it.

In the above-described embodiment, the balance drive dedicated circuit and the MFB dedicated circuit are used for driving and braking the tone arm in the vertical direction, but the present invention is not limited thereto and may be used for driving and braking the tone arm in the horizontal direction.

As described above, the present invention provides a tone arm driving device for driving a tone arm with a motor, which includes a driving device including a driving coil and a driving circuit, a braking coil, and a tone arm moving speed detection signal that is connected to the braking coil. A brake drive device consisting of a brake drive circuit for driving the drive circuit is separately provided, a detection resistor is provided in series with the drive coil at the output end of the drive circuit, and the potential difference between both ends of the detection resistor is constant. Since the drive coil is configured to supply a constant current to the driving coil, it is possible to suppress changes in torque due to a rise in temperature of the coil, and it is possible to maintain accurate stylus pressure. Also
There is an advantage that MFB can be obtained stably.

[Brief explanation of the drawing]

FIG. 1 shows an example of a conventional tone arm driving device, and is a side view and a circuit configuration diagram of the tone arm. FIG. 2 is a circuit diagram showing an example of constant current driving of the tone arm driving device. 3 to 5 are waveform diagrams for explaining the circuit operation of FIG. 2. Figure 6~
FIG. 9 shows an embodiment of the present invention,
Figure 6 is a circuit configuration diagram of the circuit dedicated to balance drive, Figure 7 is a circuit diagram of the circuit dedicated to MFB, Figure 8 is a waveform diagram to explain the circuit operation of the circuit dedicated to balance drive, and Figure 9 is dedicated to MFB. A waveform diagram for explaining the circuit operation of the circuit, and FIG. 10 is a circuit configuration diagram showing a modification of the balance drive dedicated circuit. In addition, in the symbols used in the drawings, 2
1, 22, 25...Width increasing circuit, Rs...Detection resistor, _L11 , _L13 ...Motor coil, _L12 ...Detection coil.

Claims (1)

[Claims] 1. In a tone arm drive device that drives a tone arm with a motor, there is a drive device consisting of a drive coil and a drive circuit for driving this coil, a braking coil, and a tone arm movement speed detection signal that connects the braking coil to the tone arm moving speed detection signal. A brake drive device consisting of a brake drive circuit for driving in accordance with the drive circuit is separately provided, a detection resistor is provided in series with the drive coil at the output end of the drive circuit, and the potential difference between both ends of the detection resistor is constant. A tone arm driving device characterized in that the tone arm driving device is configured to supply a constant current to the driving coil as follows.