JPH0456385B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a recording/reproducing device for recording or reproducing information using a disk-shaped recording medium (hereinafter referred to as a disk). The system detects the diameter of the disk and automatically changes the constants of the control system that are affected by the diameter of the disk, so that it always operates in an optimal state.

Configuration of Conventional Example and Its Problems An example of a disk diameter detection method conventionally used for audio records will be briefly explained with reference to FIG.

1 is a turntable, with one to several holes 1 in a part smaller than the diameter of the EP disc and in a part larger.
A and 1b are open. 2 is a record, which is placed on the turntable 1 and rotated by the motor 3. 4 is a rotation detector that detects the rotation speed of the motor. Reference numerals 5 and 6 are reflection type photocouplers placed under the holes 1a and 1b provided in the turntable, and their outputs are shaped by level detectors 7 and 8, and the outputs are shaped by level detectors 7 and 8. Only the photocoupler without one outputs a pulse, which is converted to DC voltage by the retriggerable monomulti, and then sent to the record detection circuit 11.
Here, the presence or absence of a record and its size are detected, and signals for changing the performance start position and rotation speed are output. 12 is a crystal oscillation circuit which outputs a rotational phase reference, which is divided into necessary frequencies by a frequency divider 13. This frequency divider 13
The frequency division ratio can be changed by the output of the record detection circuit 11 according to the record size, and the EP
The rotation speed of the disc and LP disc can be changed automatically.

14 is a waveform shaping circuit, and the rotation detector 4
By converting the output into pulses and inputting it to the phase comparator 15, the phase difference with the reference frequency, which is the output of the frequency divider 13, is detected, which then passes through the drive circuit 16 and rotates the motor 3. There is.

In this way, in conventional record playback, the presence of a turntable is significant, and the only two factors that are affected by the size of the record are a change in the rotational speed according to the standard and a change in the starting point of the playback. Ta.

However, recently proposed optical video discs are played by shining light from the bottom of the disc, so there is no turntable like in conventional audio record players, and a small turntable with a diameter of about 90 mm is used. It is used as a turntable 1 for installation. Therefore, the moment of inertia of the rotating system is mostly determined by the disk, and the difference in moment of inertia depending on the size of the disk becomes very large.

Generally, the moment of inertia J of a disk-shaped object is given by the following formula.

J=1/2・m・r ² ―(1) J...Moment of inertia m...Mass r...Radius Furthermore, the mass m of the disk is m=σ・π・r ²・d －(2) σ... ... Density of disk material d ... Disc thickness and substituting into equation (1), J=K・r ₄ - (3) (K=1/2・σ・π・d) In this way, the moment of inertia is the radius For example, the ratio of the moment of inertia of a disk with a diameter of 20 cm to that of a disk with a diameter of 30 cm is five times or more.

Therefore, in such an apparatus, in order to ensure the stability of the rotation control system, it is necessary to detect the size of the mounted disk and change the phase compensation or gain of the control system.

Also, the time required for the rotating disk to stop t _S
is given by the following equation.

t _S Jω _o /Flog (ω _o −ω ₁ /ω _o ) -(4) F... Starting torque ω _o ... No-load angular speed of the motor ω ₁ ... Rated angular speed In this way, the amount required to stop the rotation of the disk is The time is also determined by the moment of inertia involving the disk. Conventionally used detection of rotation stop detects when the integrated level of the output of the rotation speed detector mentioned above falls below a certain level, and creates a timing to stop the driving force in the braking direction. are doing. Therefore, if the rotational moment of inertia changes significantly, unless the integral constant is changed, the rotation may run out of control, resulting in an extremely dangerous situation.

Purpose of the Invention In order to improve the above-mentioned problems, the present invention detects the presence or absence of a disk at the time the disk is mounted, and at the same time provides information on the expected moment of inertia to the control system, thereby optimizing the control state. and a time constant for determining the timing of stopping.

Structure of the Invention According to the above-mentioned object, the gain of the rotation control system is changed according to the output of a disk size detection means for detecting the size of the disk, and the integral constant of the stop circuit system is changed according to the output of the disk size detection means. Thus, the structure is such that an optimal stopping operation can be performed.

DESCRIPTION OF EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.

A disk 21 is mounted on a small-diameter turntable 22 and rotated by a motor 23. 24 is its rotation detector. A pickup device 25 includes a detector for reading information from the disk 21 and a servo actuator for following the information track, and is driven in the radial direction by a feed screw 26 and a feed motor 27. be done. Reference numeral 28 denotes a potentiometer as a pickup position detector, which is used to detect the inner and outer circumferential limit positions of the disk and to control the position of the pickup device. 2
9 and 31 are light emitting elements, and 30 and 32 are light receiving elements. With each of these combinations, a photocoupler for detecting the size of the disk is placed between the disks, but it may also be a reflective photocoupler like the conventional example. 33,3
4 is a level detector that converts information about the presence or absence of a disk and its size into a stable DC level.
is input to the disk size detection circuit. This size detection circuit 35 is composed of a simple logic circuit,
For example, when the output of the inner light receiving element 30 is high,
This means that there is no disc, and is input to a command device such as a microcomputer as information that does not cause the player to enter the playback state. Alternatively, when the outputs of both the light receiving elements 30 and 32 are low, it means that the disk size is large, so it serves to provide that information to the rotation control system and the feed control system.

6 is a crystal oscillator that generates a reference frequency for disk rotation, and a demodulation circuit 31 that demodulates the information signal output of the pickup device 25 and separates the synchronization signal.
The phase is compared with the output of the phase comparator 38 to obtain a control signal for the rotational phase of the disk. The output of this phase comparator 38 is given to a phase compensation circuit 39. At this time, the switch 40 operates according to the disk size and changes its phase compensation characteristics to prevent deterioration of the control characteristics due to the disk size. 41 is a drive amplifier circuit, and the output of this circuit drives and controls the motor 23 via a switch circuit 42. Reference numeral 43 denotes a command device for instructing the start and end of regeneration, which operates the brake voltage generation circuit 44 when stopped, and applies an inversion signal to the amplifier 41 so as to cause the motor 23 to generate brake torque.

45 is a waveform shaping circuit, and the rotation detector 2
The output of No. 4 is pulsed and input to an integrating circuit No. 46. The integral constant at this time is also changed according to the disk size by a switch circuit 47. A level detector 48 detects that the output of the integrating circuit 46 has fallen below a set level, opens the switch circuit 42, and operates so that no brake signal is applied to the motor. The level detector 48 is configured not to operate until the disk starts rotating from a stopped state and reaches a predetermined number of rotations.

49 is an outer circumference limit detection circuit, and when the output of the position detector 28 of the above-mentioned pickup device exceeds a certain level, that is, when the pickup device 25 is out of a predetermined movement range, the feed control circuit 50 is activated. The signal given from the circuit to the feed motor 27 is
The switch circuit No. 1 serves to open the circuit. At this time, information on the disk size is also input to the outer circumference limiting circuit 49, so that the pickup device 25 is configured not to be fed beyond the diameter of the disk.

Effects of the Invention According to the present invention, stable control characteristics can always be obtained by detecting the size of the disk and feeding back information regarding the disk diameter to the disk rotation control system and stop circuit system.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of a conventional recording/reproducing apparatus, and FIG. 2 is a block diagram showing an embodiment of the recording/reproducing apparatus of the present invention. 21...disc, 22...turntable,
23...Motor, 24...Rotation speed detector, 2
5...Pickup device, 26...Feed screw, 2
7...Feed motor, 28...Position detector, 2
9, 31... Light emitting element, 30, 32... Light receiving element, 33, 34... Level detector, 35... Size detection circuit, 36... Crystal oscillator, 37... Synchronization separation circuit, 38... Phase comparison 39...Phase compensation circuit, 40...Switch circuit, 41...Amplifier, 42...Switch circuit, 43...Command device,
44...brake circuit, 45...waveform shaping circuit,
46...Integrator circuit, 47...Switch circuit, 48
... Level detector, 49 ... Outer circumference limit detection circuit,
50...Feed control circuit, 51...Switch circuit.

Claims (1)

[Claims] 1. A disk size detection means that generates an output according to the diameter of a disk placed on a turntable that is rotationally driven by a drive motor, a signal that corresponds to the rotational phase of the disk, and a reference signal. and a rotation control system for controlling the rotation of the drive motor by a signal corresponding to the phase difference, and the control gain of the rotation control system is varied according to the output of the disk size detection means. A recording/reproducing device characterized by: 2. Rotation detection means that generates a detection signal with a frequency corresponding to the rotational speed of the turntable, an integrating circuit that integrates the detection signal to create a signal with a level corresponding to the frequency of the detection signal, and the integrating circuit. a level detector for detecting that the output of the drive motor reaches a predetermined level; and means for releasing the braking force of the drive motor based on the output of the level detector;
2. The recording/reproducing apparatus according to claim 1, wherein the time constant of said integrating circuit is changed in accordance with the output of the disk size detecting means.