JPS63863B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for correcting the placement position of a record so that the center of the record coincides with the center of rotation of a turntable.

When playing a record, if the center of the record and the center of rotation of the turntable that rotates the record do not coincide, wow occurs due to eccentricity, which deteriorates the playback characteristics.

For this reason, generally, a turntable is provided with a record-fitting shaft (commonly known as a spindle), and a record center hole is fitted into this to position the record relative to the turntable's center of rotation. Dimensions etc. are specified in the standards.

However, for example, in the Japanese Industrial Standards, the outer diameter
In the case of a 30cm LP disc, the eccentricity of the record itself
Up to 0.2mm is allowed, and the diameter dimensions of the center hole and fitting shaft are 7.24~7.33mm and 7.05~7.15mm, respectively.
A gap is always created between the two when they are inserted, and this gap can be quite large depending on the combination of record and player used.

Therefore, it is difficult to align the center of the record with the center of rotation of the turntable using only the positioning of the center hole and the fitting shaft, and conventionally, the record is played by being placed eccentrically on the turntable. is normal, and
The amount of eccentricity was largely influenced by how the record was placed.

In view of this, the present invention provides a method for correcting the placement position of a record by which the center of the record placed on the turntable can be aligned with the center of rotation of the turntable. This will be explained in detail. In Figure 1,
Reference numeral 1 denotes a record in which required grooves such as sound grooves are formed, and this record 1 is placed on a turntable 3 with its center hole 1a fitted into a shaft portion 2. An arm 5 rotatably supported by a support shaft 4 has a tracing needle (not shown) at its tip for tracing the grooves on the record 1, and a light emitting element 6a such as a lamp at the other end. A shutter plate 8 is provided interposed between the photodetector 7a and a photodetector 7a that receives light from the element 6a. The photodetector 7a outputs a required electrical signal V whose level changes in response to a change in the amount of light received due to the angular displacement of the arm 5, and this output is input to the control circuit 9. Furthermore, optical sensor means consisting of a light emitting element 6b and a photodetector 7b is provided to detect rotational position information of the turntable 3. As shown in FIG. 2, this optical sensor means is arranged, for example, corresponding to the perforation positions of a plurality of through holes 3 ₁ , 3 _{2 .} . . of the same shape formed at equal intervals on the circumferential surface of the turntable 3. , the light from the light emitting element 6b is reflected and non-reflected by the photodetector 7b in accordance with the rotation of the turntable 3, and a pulse position signal _P1 is extracted from the photodetector 7b. P ₁ is input to the control circuit 9. In this embodiment, in order to simplify the explanation, 12 through holes 3 ₁ , 3 ₂ , . . . 3 are provided on the circumferential surface of the turntable 3.
₁₂ shall be perforated. The control motor 10, which is controlled in forward and reverse directions by the control circuit 9, drives a correction lever 11 that corrects the placement position of the record 1. For example, when the motor rotates in the forward direction, it moves in the direction of the arrow A in the figure, and when it rotates in the reverse direction, it moves in the direction of the arrow A. The correction levers 11 are respectively moved in opposite directions. Correction lever 11
is normally located at a distance from the turntable 3, and when moved in the direction of arrow A by normal rotation of the control motor 10, it directly collides with the circumferential surface of the record 1 and causes the record 1 to slide in the radial direction. . As shown in FIG. 3, the detection switch 12 is attached to the correction lever 11 and moves together with the correction lever 11.
The normally open contacts 12a and 12b are closed by colliding with the circumferential surface of the record 1 prior to the correction lever 11, thereby outputting a detection signal _P2 .
This detection signal P ₂ is input to the control circuit 9. Further, the control circuit 9 controls a mechanical brake means 13 arranged to stop the rotation of the turntable 3 and a drive motor 14 of the turntable 3.

In such a configuration, first, the deviation between the center of the record placed on the turntable and the center of rotation of the turntable is measured, and the peak eccentricity position and amount of eccentricity are detected, and the mounting position of the record is corrected. However, in this embodiment, among the various grooves formed on the record 1, the final groove 1, which is a concentric circle, is
An example is shown in which such detection and correction are carried out by tracing b. are arranged so that their operating positions, where they abut against the circumferential surface of the record 1, are located on this straight line at a rotational angle of 180 degrees from the detection position of the optical sensor means.

The photodetector 7b is a turntable 3 that rotates at a constant speed.
In response to the rotation of the turntable 3, a pulse position signal _P1 of 12 pulses is output for one rotation of the turntable 3, as shown in FIG. 4b. On the other hand, the photodetector 7a is
As shown in FIG. 4a, when the center of the record 1 and the rotation center of the turntable 3 are aligned and there is no eccentricity, there is no angular displacement of the arm 5, so an electric signal V of a constant level _V0 is output. , if the two do not match, angular displacement of the arm 5 will occur in response to the eccentricity state, so the electrical signal V will have a peak level depending on the maximum and minimum eccentricity peak positions.
It becomes a sine waveform with V ₁ and V ₂ . In this way, when the eccentric state of record 1 is detected, the control circuit 9
takes the maximum level V ₁ at the detection time t ₁ of the maximum eccentric position
At this time, as shown in FIG. 4c, the drive motor 14 of the turntable 3 is driven in the reverse direction to brake the turntable 3 and slow down its rotation. The control circuit 9 counts the number of pulses of the pulse position signal _P1 from time _t1 , and when the sixth pulse is detected at time _t2 , it energizes the mechanical brake means 13 to initiate a turn, as shown in FIG. 4d. Further braking force is applied to the table 3, and the rotation of the turntable 3 is stopped at a position where the operating position of the correction lever 11 and the maximum eccentric position coincide. At this time, the electrical signal V is at the minimum level
Indicates V ₂ . At time _t3 after the turntable stops rotating, the control circuit 9 drives the control motor 10 in the forward rotation at high speed with a large drive voltage, and moves the correction lever 11 in the direction of the arrow A, as shown in FIG. 4e.
During this movement of the correction lever 11, which is moved at a fast speed, the normally open contacts 12a and 12b of the detection switch 12 are closed by collision with the peripheral surface of the record 1 at time _t4 , and the detection signal _P2 is detected. Then, the control circuit 9 switches the forward rotation drive of the control motor 10 from a large drive voltage to a small drive voltage, and slows down the moving speed of the correction lever 11. Thereafter, at time _t5 , when the correction lever 11 collides with the peripheral surface of the record 1 and starts sliding the record 1, the level of the electric signal V from the photodetector 7a changes according to the amount of sliding of the record 1. It gradually increases from V ₂ . Then, at time t ₆ when the level of the electric signal V reaches the level V ₁ +V ₂ /2, the control circuit 9 drives the control motor 10 to reverse rotation at high speed to return the correction lever 11 to its original position, and also controls the turntable. The braking action of the mechanical brake means 14 for the brake system 3 is released.

As described above, the eccentricity of the record is detected and its placement position is corrected, but such detection and correction are not limited to one time, but may be repeated several times. Furthermore, it goes without saying that by increasing the number of pulses of the pulse position signal formed in one rotation of the turntable, highly accurate control can be achieved, and the operating position of the correction means is limited to the above-mentioned embodiment. It can be arranged in various positions.

Further, in the above-described embodiment, the correction means is configured to act directly on the record, but the present invention is not limited to this, and the correction disk is slidably disposed on the top surface of the turntable, and the record is placed on the correction disk. However, a correction means may be applied to this correction disk. Further, as the arm, tracing needle, etc., the tone arm and reproduction needle normally provided in the player can be used as they are, or an arm and needle exclusively for detection can be used.

According to the present invention, the eccentricity of the center of the record with respect to the center of rotation of the turntable, which occurs due to the gap that inevitably exists between the center hole of the record and the spindle of the turntable, is corrected,
Excellent playback characteristics can be obtained in record playback.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining an embodiment embodying the method of the present invention, FIGS. 2 and 3 are diagrams for explaining the detailed configuration of the embodiment of FIG. 1, and FIG. Time charts are shown for explaining the operation of the embodiment shown in the figures. DESCRIPTION OF SYMBOLS 1... Record, 3... Turntable, 5... Arm, 6a, 6b... Light emitting element, 7a, 7b... Photodetector, 9... Control circuit, 10... Control motor, 11... Correction lever, 14... Drive motor, V... electoronic signals,
P ₁ ...Pulse position signal.

Claims (1)

[Claims] 1. The deviation between the center of a record placed on a turntable and the rotational center of the turntable is measured, and the eccentricity peak position and the amount of eccentricity of the center of the record with respect to the rotational center are determined. a step of detecting, a step of stopping the rotation of the turntable at a position where the eccentricity peak position coincides with an operating position of a correcting means that is biased to slide the record in the radial direction; A method for correcting the placement position of a record, which comprises the step of, after stopping rotation, energizing the correcting means to slide the record by an amount responsive to the amount of eccentricity. 2. The method for correcting the mounting position of a record according to claim 1, wherein the eccentricity peak position is the maximum eccentricity position.