JPS6158908B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a disc player that uses a direct drive turntable and is capable of properly rotating both an audio disc and a video disc.

Audio disks are used at rotation speeds of 331/3 rpm and 45 rpm, but some types of video disks require rotation speeds of 450 rpm (NTSC system) and 500 rpm (European system), making audio disks and video disks the same. In order to enable use on a turntable that is directly connected to a motor, the rotation speed of the motor must be changed by a factor of ten.

By the way, when the rotational speed of the turntable is changed, the energy accumulated due to its inertia is proportional to the square of the rotational speed, and becomes less susceptible to external forces. This makes it easier to absorb short rotation irregularities. However, on the other hand, it takes a long time to rise from a stopped state to the required rotational speed.

In order to shorten the start-up time, it is necessary to make the turntable smaller, but audio LP disks and video disks are very similar in size and shape, and considering the required strength of the turntable, it is necessary to make the turntable smaller. It is appropriate to use a turntable with low inertia (130 to 140 gcmS2 ⁾ that is used in players.

In addition, if a direct drive DC motor for audio players is used as the drive motor for this turntable, the drive control circuit of the motor can be selected depending on the type of disc, and the turntable can be directly connected to the same DC motor. Both can be played on the top.

By the way, as mentioned above, some video disks are very similar in external dimensions to current audio disks, but the surface of the video disk is coated with metal, and the external dimensions are also similar to those of current audio disks. The center hole is different from a 12-inch LP disk (the center hole is the same as a 7-inch EP disk), and because it rotates at a higher speed than an audio disk, a clamper for holding the disk (current audio disks at 45 rpm) is required. adapter (external dimensions are the same).

Therefore, by paying attention to such differences, it is possible to distinguish between audio discs and video discs.

This invention focuses on the points mentioned above.
The present invention attempts to provide a disc player that detects the type of disc placed on a turntable by an appropriate method and uses this detection signal to switch the rotational speed of a directly connected DC motor.

Hereinafter, one embodiment will be described with reference to the drawings. First, the method for identifying disks is to compare the capacitance of disks (Japanese Unexamined Patent Publication No. 52-119)
150502-3), a method of determining by comparing conductivity (Japanese Patent Application Laid-Open No. 150604, 1983), and a method of determining by comparing the outer diameter and inner diameter of the disk (Japanese Patent Application Laid-Open No. 53-1989).
-3304) was proposed by the present applicant, but in the present invention, one of these will be used, and in this embodiment, a method of discrimination based on comparison of capacitance will be used.

FIG. 1 shows an example of this, in which a detection electrode 5 is fixed to the turntable surface facing the metal coating 1a surface of the video disk 1 placed on the rubber sheet 3 of the turntable 2, and further, while the turntable is rotating. By fixing the detection sensor 6 facing this outside the turntable, the presence or absence of a video disc can be detected without the need to move the detection sensor 6. The detection electrode 5 has flat electrode plates 5a and 5b (area S ₅ ≈10 cm ² ) on both sides, and the distance between the two sides is about 10 mm. The detection sensor 6 has an electrode 6a on a concentric circle of the turntable. Now, the thickness of the disk is 1.5 mm, the distance a between the bottom surface of the disk and the electrode plate 5a of the detection electrode 5 is 0.5 mm, and the flat electrode plate 5
If the distance b between b and the detection electrode 6a is 1 mm, the capacitance between each is as follows.

However, the audio disk 1 is assumed to have metal coating on only one side, and its base is made of vinyl chloride with a dielectric constant of 4 (if both sides are coated, the capacitance change will be large and detection will be easier).

If there is no video disk or if there is an audio disk, C _5a-GND ≈0, so C _6a-GND is only a stray capacitance.

Therefore, if the stray capacitance is 1PF, the difference between when there is a video disk and when there is no video disk is 4.7PF.The ratio of change to the maximum capacity is 4.7/5.7=0.8, which is easy to detect.

Next, motor control will be explained. FIG. 2 shows a block diagram of the control, and the turntable 2 is equipped with a disk discrimination device 7 according to the method described above, and the turntable 2 is equipped with a direct current Motor 1
It is directly connected to 0. And this DC motor 1
0 is rotationally controlled by a motor drive circuit 13 that receives signals from a frequency control circuit 11 and a phase control circuit 12. 14 is a reversal control circuit that applies braking to the DC motor 10. Further, 16 is an audio rotation speed command selector 15 which receives an audio or video signal from the disk discrimination circuit 17.
Alternatively, it is a rotation speed indicator circuit that selects the signal from the video rotation speed command selector 18.

First, in the case of audio, the audio rotation speed command selector 15 instructs the rotation speed command circuit 16 to specify the specified rotation speed, and the rotation speed command circuit 16 receives the signal obtained by the disk discrimination device 7. At step 17, it is appropriately processed and supplied.

Here, if the signal from the audio disk device is supplied to the rotation speed command circuit 16, the signal from the rotation speed command circuit 16 is sent to the audio rotation speed command selector 1.
A signal corresponding to the rotational speed commanded by 5 is supplied to the frequency control circuit 11 and the motor drive circuit 13.

For example, if the command rotation speed from the audio rotation speed command selector 15 is 331/3 rpm, the internal frequency comparison circuit and phase compensation circuit in the frequency control circuit 11 are switched to constants corresponding to the command rotation speed. . At this time, in the motor drive circuit 13, the signal from the phase control circuit 12 is cut off by the signal from the rotation speed command circuit 16, and as a result, only frequency control is performed. And this frequency control circuit 1
The signal from 1 is fed to the motor drive circuit 13 and cooperates with the signal from the rotor position detector 8 to
The rotation speed of the DC motor 10 is set to a selected appropriate rotation speed,
For example, the frequency is controlled to be 331/3 rpm.

The above is the audio rotation speed command selector 15.
Similarly, if a command rotation speed of 45 rpm is given, it will be 45 rpm.
Frequency control is performed to ensure proper rotation.

Next, in the case of a video disc, rotation speed command circuit 1
6 outputs a command signal from the video rotation speed command selector 18 as an output, for example, a rotation speed of 450 rpm, regardless of the signal from the audio rotation speed command selector 15. As a result, the frequency control circuit 11
Switched for 450rpm, and phase control circuit 12
A signal from the motor enters the motor drive circuit 13. Therefore, in the motor drive circuit 13, the signal from the phase control circuit 12 is mixed with the signal from the frequency control circuit 11.

On the other hand, a stable frequency signal (for example, 3.58 MHz) from the crystal oscillator of the built-in video color signal processing circuit 19 in the device is transmitted to the frequency divider 20.
The frequency corresponding to 450 rpm is divided, and using this signal as a reference signal, it is compared with the rotation speed detector 9 and phase-locked. Therefore, when playing a video,
It is possible to maintain rotational performance that satisfies the conditions necessary for its reproduction.

The above is from the video rotation speed command selector 18.
When a command rotation speed of 500 rpm is given, the frequency divider 20 is similarly switched to 500 rpm, and the frequency control circuit 11 is also switched to 500 rpm.

The reverse rotation control circuit 14 is activated when a signal from the stop button 21 is applied. In the case of an audio disc, this is not necessarily necessary as the rotation speed is low, but in the case of a video disc, since it rotates at high speed, it takes time to stop, so braking is forcibly applied to stop the disc. In this case, the rotation speed of the DC motor 10 is detected by the rotation speed detector 9, a braking signal proportional to the rotation speed is applied to the motor drive circuit 13, and the reverse braking ends when the DC motor 10 stops.

In the above description, it goes without saying that the DC motor 10 and the motor drive circuit 13 must have sufficient individual characteristics to cover the maximum rotational speed of the turntable.

As described above, the present invention automatically distinguishes between an audio disk with a low rotational speed and a video disk with a high rotational speed by a disk discrimination means, and drives one motor at a rotational speed that matches the respective rotational speeds. At the same time, when rotating at high speed in the case of a video disk, phase error information based on the reference signal for video signal processing recorded on the video disk and frequency error information based on the output signal of the rotation speed detection means are used. Therefore, since the motor is driven, high-speed rotation for video disc playback, which is difficult to control the rotation speed, can be achieved with high precision.
This has advantages such as being able to accurately reproduce an audio disc and a video disc with a single DC motor, and having a simple configuration and manufacturing at low cost.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the disk discrimination device, and FIG. 2 is a block diagram of the motor control circuit. 7... Disc discrimination device, 10... DC motor, 11... Frequency control circuit, 12... Phase control circuit, 13... Motor drive circuit, 16... Rotation speed command circuit.

Claims (1)

[Claims] 1. A disc player for reproducing signals from a disc on which signals are recorded concentrically or spirally, and a turntable for rotationally driving an optionally mounted audio disc or video disc; a disk determining means for detecting whether the disk mounted on the turntable is for audio or video;
A rotation speed detection means for generating a signal corresponding to the rotation speed of the turntable, a rotor position detection means for generating a signal according to the phase of the turntable, and a disk mounted on the turntable by the disk discrimination means. is detected to be the audio disk, the turntable is rotated at a predetermined low speed based on the output signals of the rotation speed detection means and the rotor position detection means, and the disk is mounted on the turntable by the disk discrimination means. When it is detected that the disc is the video disc, it is determined based on the phase error information based on the reference signal for video signal processing recorded on the video disc and the output signal of the rotation speed detection means. A disc player comprising: means for controlling the drive of rotating the turntable at a predetermined high speed based on frequency error information.