JPS6362820B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an improvement in a turntable device such as a record player equipped with a motor whose speed is controlled by a speed proportional-integral control system. In turntable devices such as record players, direct drive (hereinafter referred to as DD) motors whose speed is controlled using a phase lock loop (hereinafter referred to as PLL) are often used as the drive source. Speed is controlled using this PLL
The speed of the DD motor is controlled by both speed-proportional and speed-integral control loops. When the angular velocity of a DD motor whose speed is controlled using this PLL decreases, the angular velocity is temporarily increased above the rated speed to compensate for the decrease in speed, and then the motor returns to its original rated speed. The period of this restoration is determined by the gain G ₁ of the integral control loop of the DD motor and the moment of inertia J _a of the turntable, and the natural frequency f _P with respect to the rotation direction of the DD motor is quantitatively determined.

[Formula]. This sufficiently increases the machining accuracy of the turntable device, and even with an ideal DD motor with zero torque unevenness, it is possible that some external disturbances such as friction between the record sound groove and the stylus tip or loads caused by music signals will be applied. This indicates that angular velocity fluctuations occur, resulting in wow and flutter. This wow and flutter frequency has a peak at the natural frequency _fP , and has the disadvantage of being hazy in the bass range of the reproduced sound and making the sound image localization unclear. The present invention has been made in view of the above, and an object of the present invention is to provide a turntable device which eliminates the above-mentioned drawbacks, and which provides a turntable device that is controlled by a speed integral control loop with at least a gain G ₁ and has a moment of inertia J _a . In a turntable device equipped with a driving motor, the natural frequency in the rotation direction

The present invention is characterized in that a stabilizer having a moment of inertia J _b is installed on the turntable in order to set [Equation] below the flutter frequency at which the detection limit is the lowest.The present invention will be explained below with reference to examples. . FIG. 1 is a partial sectional view showing the configuration of a turntable device according to an embodiment of the present invention. In FIG. 1, 1 is a turntable with a moment of inertia J _a , and 2 is a record sheet. . A record 3 is placed on the turntable 1 via the record sheet 2, and a moment of inertia is created around the outer periphery of the record 3.
A stabilizer 4 having J _b is installed. The stabilizer 4 is preferably made of a material with high rigidity and specific gravity, such as stainless steel or BSBM material. Further, 5 is a DD motor. The DD motor 5, for example, as shown in the configuration diagram in FIG. The speed is controlled by a servo system consisting of a speed integral control loop consisting of a mixer 11 and a mixer 12. Note that S _P is a reference signal and S _V is a reference voltage. The block diagram of the servo system shown in FIG. 2 is as shown in FIG. In Figure 3, S = jω ΔT = Load torque of DD motor V = Angular velocity of DD motor K _V = Speed - voltage conversion gain Kφ = Speed - phase conversion gain Kτ = Phase difference - voltage conversion gain Kt = Drive of DD motor Torque constant A = amplifier gain J = sum of moments of inertia of turntable and stabilizer (J _a +J _b ) ω _O = reference angular frequency of reference signal. The transfer function from load torque fluctuation to angular velocity fluctuation in this servo system is V/ΔT= -1/J・S/S ² +Kv・Kt・A/JS+Kτ・K・Kt・
A/J...(1) It is expressed as: The angular frequency ω _P that makes |V/ΔT| the maximum value is becomes. This angular frequency ω _P is a resonant angular frequency. Also, the Q value, which represents the sharpness of resonance, is It is. Furthermore, instead of the speed integral control loop consisting of the phase difference detection circuit 11 shown in FIG. 2, a servo system using a frequency difference detection circuit 13 and an integrator 14 in the speed integral control loop as shown in FIG. 4 may also be used. The block diagram of the servo system shown in FIG. 4 is as shown in FIG. In Fig. 5, K _f = speed-frequency conversion gain K _D = frequency difference-voltage conversion gain τ = time constant of the integrating circuit, and S, J, K _t , K _V and A are the third
Same as figure. In the block diagram shown in Figure 5, the transfer function from load torque fluctuation to angular velocity fluctuation in this servo system is V/ΔT= -1/J・S/S ² +Kv・Kt・A/JS+Kτ・K・Kt・
A/J...(4) It is expressed as. The angular frequency ω _P that makes |V/ΔT| the maximum value is becomes. This angular frequency ω _P is a resonant angular frequency. Also, the Q value, which represents the sharpness of resonance, is It is. Generally, in a DD motor whose angular velocity is controlled by two types of closed loops, a velocity proportional control loop and a velocity integral control loop, between the load torque input and the angular velocity output, the angular velocity fluctuation V from the load torque ΔT
The transfer function to is expressed as V/ΔT=-X・S/S ² +Y・S+Z (7). Therefore, the angular frequency ω _P and the Q value representing the sharpness of resonance are as follows: ω _P =√...(8) Q=√/Y...(9). Here, X, Y and Z are expressed by algebraic expressions including electrical and mechanical constants of the servo system, and X>
0, Y>0, Z>0. Therefore, if the transfer function V/ΔT and the angular frequency ω _P are expressed by the gain G ₁ of the speed integral control loop of the servo system and the gain G ₂ of the speed proportional control loop, then in the servo system shown in Figure 3, G ₁ = K〓・K 〓・K _t・A ……(10) G ₂ =K _V・K _t・A ……(11), and in the servo system shown in Fig. 5, G ₁ =K _f・K _D・K _t・A/ τ ...(12) G ₂ =K _V・K _f・A ...(13). Therefore, in equation (7) of the transfer function V/ΔT, Y=G ₂ /Y...(14) Z=G ₂ /J...(15) V/ΔT=-X・S/S ² +G ₂ /JS+G ₁ /J……(16
), so the angular frequency ω _P shown in equation (8) is becomes. Since ω _P is the resonant angular frequency, the resonant frequency _P is becomes. On the other hand, if α and β are set as α=1/2(Y+√ ² −4) ……(19) β=1/2(Y−√ ² −4) ……(20), the transfer function becomes (7 ) From formula V/ΔT=-X・S/(S+α)(S+β)……(21
), and the absolute value of V/ΔT is becomes. Therefore, if V/ΔT is called the variation in angular velocity with respect to load, its angular frequency characteristic will be as shown in FIG. 6, which shows equation (22) as a curve. As is clear from equation (22) and Figure 6, the maximum amount of variation in speed with respect to load occurs when ω = √, and its value is X/Y, and the value when ω = α and ω = β is α =X/√2( ² + ² ). The condition that α and β are real numbers is Y ² −4Z≧0 (23), and this condition is set as the control loop gain G ₁ and
If expressed in G ₂ , (G ₂ /J) ² −4G ₁ /J≧0 ... (24), and between the control loop gains G ₁ and G ₂ , 4G ₁ ≦G ₂ ² /J ... (25 ). Therefore, if the gains G ₁ and G ₂ of the control loop are set to 4G ₁ ≦G ₂ ² /J, Q≦0.5 and the turntable will not be under-braked, and the turntable will not be affected by the transient response of the step load. Never overshoot. Here, the value on the left side of equation (25) may be smaller than or approximately equal to the value on the right side. The above points indicate that the coordinates rotating at the rated speed can be regarded as an inertial frame with respect to rotation, but the angular frequency characteristics shown in Figure 6 above are for a turntable driven by a DD motor whose angular velocity is controlled by a velocity proportional-integral control loop. This shows that even if there is no insufficient damping, there is a natural frequency caused by the restoring force in vibration theory. Furthermore, since the fluctuation of the load torque excites minute vibrations of rotation about the DD motor shaft in this inertial frame, the equation (22), that is, the characteristic shown in Figure 6, represents the angular velocity of this minute vibration. Now, if the energy of vibration is W, then W = 1/2 J (angular velocity) ² + (positional energy) ... (26) The angular velocity is maximum when the positional energy is zero, Since the maximum angular velocity is expressed by equation (22), the vibration energy is W=1/2J{M(ω)} ² ∝ω ² /(αβ−ω ² ) ² +ω ² (α+β) ² ……(27
), and the vibration energy W becomes as shown in FIG. Therefore, we adopted a speed proportional integral control loop.
In a turntable device driven by a DD motor, even if mechanical processing accuracy and other technical matters are ideally processed, there is a resonance frequency in the servo system, and the load torque has various frequency components. When the vibration is added, the frequency component of this frequency that matches the resonant frequency resonates, and the angular velocity fluctuation is concentrated at this resonant frequency, and the vibration energy is also concentrated, making it impossible to completely eliminate the angular velocity fluctuation. be. By the way, the signal frequency that is reproduced as sound when playing a record is proportional to the angular velocity of the DD motor, so in a turntable using a DD motor whose speed is controlled by an angular velocity proportional-integral control loop, Angular velocity fluctuations result in wow and flutter. Therefore, the amount of wow and flutter is expressed by equations (22) and (27), that is, the angular frequency characteristics are the same as or similar to those in FIGS. 6 and 7. On the other hand, according to conventional measurement results, the detection limit for wow and flutter, that is, the amount of variation in sound frequency that humans can detect, is as follows: The horizontal axis represents the flutter frequency.
If the detection limit % (Δ/) is shown on the vertical axis, the 8th
The result will be as shown in the figure. (Journal of the Acoustical Society of Japan, Vol. 29, No. 12)
(Page 766) In Figure 8, curves A, B, and C show the measurement results by different measurers, and the measurements were made with a 1000Hz pure tone as the reference signal and a sine wave variation as the variation, and the trends are almost the same. We are doing so. Regarding the detection limit, (a) the wow and flutter detection limit has frequency characteristics; (b) when the wow and flutter frequency is 1 to 5 Hz, it is detected with the smallest amount of variation. The values of (c) and (b) are changes of 0.1%, or 1000Hz.
Even if the signal changes by 1Hz, it can be detected. (d) When the wow and flutter frequency approaches the signal frequency, the detection limit decreases rapidly. The matters listed in (a), (b), (c), and (d) regarding this detection limit are generally accepted. Therefore, in the present invention, the natural frequency of the turntable device is

Set [Formula] below the flutter frequency where the detection limit is the lowest. Therefore, even when a load torque having a frequency component that resonates with the natural frequency of the turntable is applied, the frequency fluctuation of the reproduced sound due to the speed fluctuation with respect to the load will not be detected. Therefore, hazyness in the low frequency range and unclear sound image localization are improved. For example, even if the variation in wow and flutter in audio equipment is suppressed to 0.03%, in the case of record playback, during recording, cutting (twice),
When playing, I am affected by wow and flutter at least 4 times. Therefore, the overall wow and flutter characteristic is at the peak value.
The value is 0.12% (calculated from 1.0003 ⁴ ). This value is on the order of enough to be detected in terms of the detection limit characteristics shown in FIG. In addition, if the mixing process is repeated before cutting during record production, the amount of fluctuation will be added to the amount of fluctuation equal to the number of times the peak value has passed through the recording/playback machine.

[Formula] is preferably set to a small value. In addition, in the measurement shown in Figure 8, the reference signal was set to 1000
Hz, a pure tone, and a sine wave fluctuation as the fluctuation. However, from the paragraph (d) regarding the detection limit, for example, 100
If a sound with a frequency of Hz is selected as a reference signal and the detection limit is measured, the frequency characteristics shown in FIG. 8 may not necessarily be obtained. When the reference signal is 100Hz and receives a fluctuation of 0.05% at a flutter frequency of 10Hz,
Since the position is at point P indicated by X in FIG. 8, it should not be detected because it is below the detection limit, but there is a possibility that it will be detected because of the item (d) regarding the detection limit. However, human perception generally has the property that the slower the change, the less it can be detected, and the natural frequency of the turntable device

If [Formula] is set to, for example, 1 Hz or less, even if the amount of wow and flutter fluctuation is around 0.1%, it will be sufficiently below the detection limit and will not be detected. Furthermore, split vibrations of the record occur during record tracing by the cartridge, as shown in FIGS. It also has the effect of damping split vibrations having an open end at the center or outer circumference of the record shown in FIGS. 9a to 9d. Further, by using the stabilizer 4, it is not necessary to make the record sheet 2 of a vibration absorbing type, and a material with high rigidity can be used for the record sheet 2. Therefore, a damping effect is produced even for split vibrations of the record as shown in FIGS. 9e and 9f. Note that the shape of the stabilizer 4 is not limited to that shown in FIG. 1, and may be of any shape. Further, in the embodiment shown in FIG. 1, an outer periphery stabilizer provided on the outer periphery of the record has been described, but as another embodiment of the present invention, an inner periphery stabilizer that is inserted into the center spindle of a player and presses down the inner periphery of the record is used. It's okay. When this inner periphery stabilizer is used, it also has the effect of damping the split vibration of the record as shown in FIGS. 9b and 9c. As explained above, according to the present invention, there is provided a turntable device that is controlled by a speed integral control loop with a gain of G ₁ and a speed proportional control loop with a gain of G ₂ and includes a motor that drives a turntable having a moment of inertia J _a . , natural frequency in rotational direction

In order to set [Formula] below the flutter frequency at which the detection limit is the lowest, a stabilizer with a moment of inertia J _b was installed on the turntable, resulting in hazy bass frequencies and unclear sound image localization. is improved. Also the natural frequency

[Formula] is related to the gain G ₁ of the speed integral control loop, and setting the natural frequency below the frequency at which the detection limit is the lowest means that the gain of the speed integral control loop, that is, the phase-locked loop, is small enough to suppress drift. This means that the gain may be used, which also has the effect of making it easier to provide and manufacture the phase-locked loop. Furthermore, by setting 4G ₁ ≦G ₂ ² /J _a +J _b , the turntable will not be under-braked, and the turntable will not overshoot. Further, by installing a stabilizer with a moment of inertia J _b on the record, there is an effect of damping the vibration of the record, and it is also possible to correct the warping of the record itself.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing the configuration of a turntable device of the present invention. FIG. 2 is a configuration diagram showing an example of a speed control system of a DD motor. FIG. 3 is a block diagram of the speed control system shown in FIG. 2. FIG. 4 is a configuration diagram showing another example of the speed control system of the DD motor. FIG. 5 is a block diagram of the speed control system shown in FIG. 4. FIG. 6 is an angular frequency characteristic curve of load speed angular variation of a turntable device driven by a DD motor having the speed control system shown in FIGS. 2 and 4. Figure 7 is similar to Figures 2 and 4.
Angular frequency characteristic curve of vibration energy of a turntable device driven by a DD motor having the speed control system shown in the figure. Figure 8 shows the characteristic curve of flutter frequency versus detection limit. FIGS. 9a to 9f are diagrams showing split vibrations of a record. 1... Turntable, 2... Record sheet, 3
…Record, 4…Stabilizer, 5…DD motor, 6…Speed detector, 7…Speed voltage conversion circuit, 8
...Comparator, 9...Amplifier, 10...Motor drive circuit,
11... Phase difference detection circuit, 12... Mixer, 13... Frequency difference detection circuit, 14... Integrator.

Claims (1)

[Claims] 1. A motor that is controlled by a speed proportional integral control system consisting of a speed integral control loop with a gain of _G1 and a speed proportional control loop with a gain of _G2 , and that drives a turntable having a moment of inertia J _a . In turntable devices, the moment of inertia is
A turntable device characterized in that a stabilizer having J _b is installed on the turntable. 2. In a turntable device that is controlled by a speed proportional integral control system consisting of a speed integral control loop with a gain G ₁ and a speed proportional control loop with a gain G ₂ , and includes a motor that drives a turntable having a moment of inertia J _a , In order to set the natural frequency [formula] below the flutter frequency where the detection limit is the lowest, the moment of inertia is
A turntable device characterized in that a stabilizer having J _b is installed on the turntable, and 4G ₁ ≦G ₂ ² /J _a +J _b is satisfied.