JPS5942391B2 - Pickup control device for rotating recording media - Google Patents

Description

[Detailed description of the invention] When an audio signal is converted to a PCM signal and recorded and played back, the S/
Since N is extremely good, the dynamic range becomes wide, and good recording and reproduction can be performed.

Conventionally, such a PCM signal recording/reproducing device is as follows.
Although a VTR (magnetic recording and reproducing device) was used, it was proposed to use a disc-shaped magnetic disk from the viewpoint of ease of handling and simplification of the device configuration.

In such devices, it has been considered to provide a guide groove on the surface of the magnetic disk, similar to conventional record discs, and to guide the position of the pickup by dropping the tip of the pickup, for example a magnetic head, into the guide groove. .

In this case, the head gap of the magnetic head must always be oriented in a direction that coincides with the radius of the disk.

Otherwise, the signal will deteriorate due to so-called azimuth loss. Therefore, it is necessary to transport the pickup linearly according to the position of the guide groove.

By the way, when recording and reproducing using a magnetic disk, if the signal has periodicity like a video signal, by rotating the disk at a constant speed in synchronization with the period,
Special playback such as slow, still, and quick playback can be performed, which is good.

However, in the case of audio signals, there is no such need;
On the other hand, in the case of constant speed rotation, the recording density changes between the outer and inner circumferences, so if you record according to the innermost circumference, the recording density will be lower on the outer circumference, which is uneconomical. If recording is performed in accordance with the recording density, the recording density will be high in the inner circumferential portion, making it impossible to perform good recording and reproduction. Therefore, it has been considered to detect the position of the pickup and perform equal linear speed control so that the speed of the recording medium in contact with the pickup is always constant.

Conventionally, this type of device detects the swing angle of the pickup, supplies this detection signal to the transport motor, and drives the motor so that the angle becomes a predetermined value. .

That is, in FIG. 1, 1 is a magnetic disk,
This disk 1 is rotated by a motor 2, and
A pickup (e.g. magnetic head) on this disk 1
3 is opposed.

Then, the position of this pickup 3 (distance from the center of the disk 1) is detected by a potentiometer 4, and a voltage VR proportional to the distance is formed.This voltage VR is supplied to a control circuit 5. A signal from the control circuit 5 drives the motor 2 at a constant linear speed. Further, 6 is a motor for linearly transporting the pickup 3.

Furthermore, 7 is a detector for detecting the angle of the pickup 3, and a detection signal (voltage VA) from this detector 7 is supplied to a comparator circuit 8.

On the other hand, a voltage VO equal to the detection signal when the direction of the head gap coincides with the radius is supplied from the voltage source 9 to this comparison circuit, and this comparison output Vx is supplied to the motor 6 through the amplifier 10. In this way, the pick-up is transferred so that the direction of the head gap coincides with the radius of the disk.

However, in this device, when the disk is subjected to uniform speed control, the rotation speed of the disk changes depending on whether the pick-up is on the outer circumference or on the inner circumference.For example, the guide groove changes from a position with a radius of 15 cTrL to a radius of 5CTIL
, the rotation speed at the innermost circumference is three times the rotation speed at the outermost circumference.

Therefore, the speed of the pit-up transfer also changes three times, and the dynamic range is too wide for normal control systems to perform good control. Furthermore, when the disk is eccentric, the detection signal due to this eccentricity has small repetitions.

The frequency is equal to the rotational speed or an integral multiple thereof, and a normal motor cannot follow such high frequency control. In view of these points, the present invention is designed to provide good pickup control with a simple configuration.

By the way, let the radius of the outermost circumference of disk 1 be b1 be the distance from the center of the disk to the position that pick-up 3 reaches after time t after starting from the outermost circumference be r1 be the pitch of the guide groove P1 be the relative speed between the pick-up and the disk. The formula , holds true, and from this formula, the relationship is obtained.

Also, the rotation speed F8 of disk 1 is From, substituting equation (1), becomes.

Therefore, the transfer speed Vh of the pickup 3 is as follows.
The speed Vh is inversely proportional to r.

On the other hand, the rotation speed of the motor 6 for transporting the pitta up 3 is
Then, it becomes.

Further, if the voltage supplied to the motor 6 is E, then from equations (4) and (5), the following can be obtained.

Furthermore, from FIG. 1, if the gain of the amplifier 10 is A,
becomes.

Here, since VO is an arbitrary constant, it may be set as VO - O. Therefore, from equations (3), (6), and (7), the following is a necessary condition. That is, in the device shown in FIG.
If the gain of 0 is controlled in inverse proportion to the distance r of the pickup 3 from the center of the disk 1, extremely good control can be achieved.

The present invention focuses on this point.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

In FIG. 2, a signal from a detector 7 is supplied to a comparison circuit 8 through a low-pass filter 11.

In addition, the comparison output Vx from the comparison circuit 8 is converted into analog depressurization VR.
is supplied to the divider 12, and in this divider 12 VX/VR
The output signal is supplied to the amplifier 10f. Furthermore, the pickup 3 is configured as shown in FIG.

That is, a worm gear 21 for transfer is connected to the motor 6, and this gear 21 is inserted into a screw hole 23 provided in the pick-up support 22.

Note that 24 is a support rod having both ends fixed. By rotating the motor 6 in this way, the gear 21 is rotated,
Support 22 is moved. Further, a potentiometer 4 is connected to the end of the gear 21, and the rotation amount of the gear 21 and the support body 2 are controlled by a potentiometer 4.
Since the amount of movement of the pick-up 2 is proportional, the position of the pick-up 3 is detected by the potentiometer 4. Furthermore, a sufficiently long head support rod 27 is provided from the support 22 through a first pivot 25 that swings in the left-right direction and a second pivot 26 that swings in the vertical direction, and a magnetic head 28 is attached to the tip of this head support rod 27. .

Further, a shielding plate 29 is provided extending from the first pivot 25, and this shielding plate 29 is inserted into a photocoupler serving as a detector 7 provided at an extension of the support 22.

The head 28 is then dropped into the groove of the disk 1.

Therefore, in this device, the signal supplied to the amplifier 10 is divided in advance by a signal proportional to the distance r, so that the output signal of the amplifier 10 is obtained by dividing the signal Vx from the comparator circuit 8 by a gain inversely proportional to the distance r. It becomes an amplified signal and satisfies equation (8).

Further, fluctuations in the vertical direction due to surface runout of the disk 1 are absorbed by the second pivot 26, and changes in the horizontal direction are detected by the detector 7.
is detected and supplied to the control system. At this time, by making the length of the head support rod 27 sufficiently long, the change in the angle ratio between the direction of the head gap and the radius of the disk 1 due to the eccentricity of the disk 1 can be made extremely small. There is no need to control high frequency fluctuations due to eccentricity of the low-pass filter 11.
The rotation of the motor 6 can be controlled by extracting only the low frequency component. In this way, the pick-up is transferred in a straight line.According to the present invention, the gain of the control system is controlled in inverse proportion to the distance of the pick-up from the center of the disk, making it possible to perform extremely good control. I can do it.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a conventional device, FIG. 2 is a system diagram of an example of the present invention, and FIG. 3 is a configuration diagram of an example of a pickup. 1 is a disk, 3 is a pick-up, 4 is a potentiometer, 6 is a pick-up transfer motor, 7 is a detector, 11
is a low-pass filter, and 12 is an analog divider.

Claims (1)

[Claims] 1. A part of the pickup is dropped into the guide groove of a rotating recording medium having a spiral guide groove, the relative position of the guide groove and the pickup is detected, and this detection signal is sent to the pickup through a predetermined transmission system. In a pickup control device for a rotating recording medium, the pickup is supplied to a transfer motor to linearly transfer the pickup, the distance from the pickup to the center of rotation of the rotating recording medium is detected, and the gain of the transmission system is controlled by the gain of the transfer system. A pickup control device for a rotating recording medium that is controlled to be inversely proportional to the distance.