JPS6027274B2 - Control method of DC motor in magnetic recording/reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for a DC motor in a magnetic recording and reproducing device, and includes detecting a back electromotive force generated in the windings of the motor;
It is an object of the present invention to provide a control system for a DC motor that performs stable phase control and speed control using the back electromotive force, has a small number of parts, and does not require highly accurate adjustment.

FIG. 1 is a block system diagram of an example of a conventional control system for a DC motor used as a drum motor of a VTR.

In the figure, 1 is a drum motor, and a disk 2 is fixed above the shaft of the drum motor, and a flywheel 3 is fixed below the shaft.

Two magnets 4 are fixed to the upper surface of the disk 2, and two video heads 5 are fixed to the circumferential surface thereof. A plurality of magnets 6 are provided at equal intervals on the circumferential surface of the flywheel 3. A pickup head 7 is provided at a position corresponding to the magnet 6, and the signal detected by the pickup head 7 is sent to a pulse amplifier 8.
, are supplied to the delay circuit 10 and the sawtooth wave generation circuit 11.

The signal output from the delay circuit 101 is supplied via the gate pulse circuit 12 to the sampling circuit 13 together with the signal output from the sawtooth generation circuit 11. The signal output from the sampling circuit 13 is sent to a holding circuit or an integrating circuit 14, a matching circuit 15, and a motor drive amplifier 16.
V is again supplied to the drum motor via the V to perform speed control. On the other hand, a drum pulse head 18 is provided at a position corresponding to the magnet 4.
The signal detected by 8 is supplied to a phase comparison circuit 19. The input video signal input to the video input terminal 20' is supplied to the phase comparison circuit 19 via the vertical synchronization separation circuit 21 and switch 25, and is controlled via the control pulse recording amplifier duplexer 22 and switch 24. The signal is supplied to the head 23 and recorded on the tape. Here, a phase comparison circuit 19 compares the phase of the signal detected by the drum pulse head 18 with the phase of the input video signal to perform phase control. Note that 26 is a control pulse regenerative amplifier. However, in this conventional example, a large number of magnets 6 and a pickup head 7 provided around the flywheel 3 are required as means for detecting the rotational speed of the motor 1, and a magnet and a drum pulse head 18 are required as a phase detector. Because of this, the number of parts increases,
The cost is high, a large number of magnets 6 must be installed at regular intervals around the flywheel 3, and adjustment is troublesome, and furthermore, there is a possibility that the flywheel 3 and the pickup head 7 may malfunction. If this occurs, you will not be able to obtain an output pulse train that corresponds to the rotation speed.
There were drawbacks such as inability to perform stable control.

The present invention eliminates the above-mentioned drawbacks, and each embodiment thereof will be described with reference to FIG. 2 and subsequent figures.

FIG. 2 is a circuit diagram of an example of a Hall motor used in a drum motor in a DC motor control system in a magnetic recording/reproducing apparatus according to the present invention. To explain the operating principle of this Hall motor, HG, HG2 are Hall elements,
The relative positions of the rotor 27 and the stator windings W, -W4 are detected by the Hall elements HG, , HG2, and a voltage is generated at the voltage terminals thereof. Here, the switching transistors X, .about.X4 are placed in a conductive state according to their relative positions, and current is sequentially switched to flow through the stator windings W, .about.W4, thereby rotating the rotor 27 in a fixed direction. Note that the circuit of this DC motor is designated as 28. FIG. 3 is a block system diagram of first and second embodiments of a DC motor control system in a magnetic recording/reproducing apparatus according to the present invention.

In the figure, the same components as in FIGS. 1 and 2 are given the same reference numerals. In the figure, the back electromotive force generated in the windings of the motor 28 is taken out to the back electromotive force detection terminal 29. The signal passed through the back electromotive force detection terminal 29 is supplied to a speed control means 30 and a phase control means 31, and controls the speed and phase of the DC motor 28 via the motor drive amplifier 16. FIG. 4 is a block system diagram of the first embodiment of the present invention for explaining in more detail the operations of the speed control means 30 and phase control means 31 in FIG.

In the figure, the same components as in FIGS. 1 to 3 are given the same reference numerals. First, the speed control method will be explained.

As shown in the figure, for ease of explanation, a DC motor 2
8 is a Hall element HG. , transistor X, and winding W will be taken out and explained. The signal entering the motor input terminal 17 is supplied to the motor winding W, via the transistor X, which is rendered conductive by the Hall element HG. Here, a back electromotive force having a frequency corresponding to the number of rotations of the DC motor 28 is generated in the winding W, and this is taken out to the back electromotive force detection terminal 29. The output taken out to the back electromotive force detection terminal 29 is supplied to an amplitude limiter 32 to respond only to changes in frequency, and becomes a rectangular wave. Here, the signal whose phase (time) passing through the zero point has been clarified is supplied to a delay circuit 10, a sawtooth wave generation circuit 11, and a phase comparison circuit 19. Delay circuit 10' The signal delayed for a certain period of time is supplied as a gate pulse (sampling pulse) to a sampling circuit 13 via a gate pulse circuit 12 that generates a sampling pulse. Further, the voltage of the sawtooth wave obtained by the sawtooth wave generation circuit 11 is also supplied to the sampling circuit 13, and a part of the slope waveform is sampled to obtain an output according to the rotation speed of the motor.
The signal is supplied to a holding circuit or an integrating circuit 14 and a mixing circuit 15. Here, the speed control signal is synthesized with a phase control signal, which will be described later, to the motor drive amplifier 16 and the motor input terminal 1.
7 to the motor 28. Here, if there is some variation in the rotation speed of the DC motor 28 and the frequency of the back electromotive force coupled to the motor input terminal 17 decreases,
Connect motor input terminal 1 to keep the frequency of back electromotive force constant.
The current supplied to 7 is increased to control the speed of DC motor 28.

Next, a phase control method will be explained.

First, when a green image is displayed, the switches 24 and 25 are respectively closed to the R side. A vertical synchronization signal is separated from the input video signal input from the video input terminal 20 in a vertical synchronization separation circuit 21, and the vertical synchronization signal is supplied to a phase comparison circuit 19. Further, the vertical synchronization separation signal synchronously separated by the vertical synchronization separation circuit 21 is recorded as a control signal on the tape by the control head 23 via the recording amplifier 22. Here, the phase comparison circuit 19 compares the phase of the synchronization signal with the phase of the back electromotive force signal from the amplitude limiter 32 to generate a phase error signal. This error signal is
It is combined with the signal from 4 in a mixing circuit 15, and is supplied to a DC motor 28 via a motor drive amplifier 16 and a motor input terminal 17. Also, when playing, switch 2
4 and 23 are respectively closed on the P side, and a control pulse regenerated by the control head 23 is supplied to the phase comparator circuit 19 via the regenerative amplifier 26.

The following operation is the same as that for silver painting, so the explanation will be omitted. In addition, in the figure, the same effect can be obtained even if the chain tooth wave generating circuit 11 and the gate pulse circuit 12 are replaced. Fifth
The figure shows a block system diagram of a second embodiment of the system of the present invention.

In this figure, the same components as in FIGS. 1 to 4 are designated by the same reference numerals, and their explanations will be omitted. In the figure, the back electromotive force of the DC motor 28 taken out to the back electromotive force detection terminal 29 is supplied to a rectifier circuit 33, which rectifies the voltage peak value of the back electromotive force according to the rotational speed, and detects the DC peak value potential. be done. On the other hand, a comparison circuit 35 compares the reference potential outputted from the reference voltage generation circuit 34 and the DC high value potential to detect a rotational speed error voltage. The discussion difference voltage is amplified by the DC amplifier 36 and then sent to the motor drive amplifier 1 via the mixer 15 as a speed control signal via the speed control signal forming circuit 37.
6. Here, since the peak value potential of the motor back electromotive force obtained at the back electromotive force detection terminal 29 is directly proportional to the rotation speed of the DC motor 28, when this potential decreases, it enters the motor input terminal. The current is increased to control the speed of the DC motor 28.

Note that the reference potential of the reference voltage generation circuit 34 is the DC motor 2.
It is set by the rated rotation speed of 8. Furthermore, since the phase control is the same as in the first embodiment, its explanation will be omitted. In the method of this embodiment, the circuit of the speed control means can be easily constructed, and therefore can be constructed at a lower cost than the first embodiment.

Note that the DC motor controlled by the method of the present invention can achieve the same effect even if a motor other than the Hall motor is used, and the greater the number of magnetic poles of the rotor, the higher the control sensitivity can be achieved.

As described above, according to the control method of the DC motor in the magnetic recording/reproducing device according to the present invention, the back electromotive force generated in the motor windings corresponding to the rotation of the motor is detected, and the rectangular wave of the back electromotive force is detected. The phase of the signal is compared with the phase of an external reference signal generated during green video and playback of the VTR to perform phase control, and the speed is controlled by keeping the frequency of the signal due to the rectangular wave of the back electromotive force constant. control, or perform speed control by comparing the DC peak value potential obtained by rectifying the voltage peak value of the back electromotive force with a reference potential set according to the rated rotation speed of the motor, or perform speed control on the back electromotive force. Since speed control is performed using a sampling pulse generated from a delayed detection signal or a back electromotive force detection signal, and a ramp wave generated from a delayed signal or a back electromotive force detection signal, the conventional method For example, it is possible to detect the phase of a VTR motor without attaching a phase detector, and it is also necessary to provide a means to extract pulses corresponding to the rotational speed of the motor by installing a flywheel, many magnets, a pickup head, etc. outside the motor. Because there are no components, the number of parts can be significantly reduced, resulting in a low-cost configuration.Furthermore, since high-precision adjustment of these parts is not required, manufacturing man-hours can be reduced, and stable motor control can be achieved. It has the following.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an example of a conventional DC motor control system, Fig. 2 is a circuit diagram of an example of a Hall motor controlled by the method of the present invention, and Fig. 3 is a basic diagram of the control method of the present invention. Block System Diagrams FIGS. 4 and 5 are block system diagrams of the first and second embodiments of the system of the present invention, respectively. 1...Drum motor, 2...Disk, 3...Flywheel, 4, 6...Magnet, 5...Video head, 7...
Pickup head, 8...Pulse amplifier, 10...
- Delay circuit, 11... Sawtooth wave generation circuit, 12... Gate pulse circuit, 13... Sampling circuit, 14... Holding circuit or integrating circuit, 15... Mixer, 16. ．．
．． Motor drive amplifier, 18... drum pulse head, 19... phase comparison circuit, 20... video input terminal, 2
DESCRIPTION OF SYMBOLS 1... Vertical synchronization separation circuit, 23... Control head, 27... Rotor, 28... DC motor, 29... Back electromotive force detection terminal, 30... Speed control means, 31...
Phase control means, 32... amplitude limiter, 33... rectifier circuit, 34... reference voltage generation circuit, 35... comparator circuit,
36...DC amplifier, HG,,HG2...Hall element,
X,, ~X4...Transistor, W, ~W4...Winding. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1. Means for detecting a back electromotive force generated in the windings of a motor, means for obtaining a speed control signal according to the rotation speed of the motor from the back electromotive force, means for obtaining a signal corresponding to the rotational phase and comparing the phase of the signal with the phase of an external reference signal generated during recording and reproduction to obtain a phase control signal; and the speed control signal and the phase control signal. 1. A method for controlling a DC motor in a magnetic recording/reproducing device, characterized in that speed control and phase control of the motor are performed by means for mixing the mixture and means for driving the motor according to the output of the mixing means. 2. The means for obtaining a speed control signal according to the rotation speed of the motor from the back electromotive force includes means for rectifying the voltage peak value of the back electromotive force to detect the DC peak value potential, and and means for generating a rotational speed error by comparing the reference potential and the DC peak value potential. A speed control method for a DC motor in a magnetic recording/reproducing device. 3. The means for obtaining a speed control signal according to the rotation speed of the motor from the back electromotive force includes a delay means for delaying the output of the means for detecting the back electromotive force, and an output signal from the delay means or the back electromotive force. means for generating a sampling pulse from the output signal from the means for detecting electric power; means for generating a ramp wave from the output signal from the delay means or the output signal from the means for detecting back electromotive force; and the sampling pulse. 2. A control signal system for a DC motor in a magnetic recording/reproducing apparatus according to claim 1, further comprising means for generating a rotational speed error voltage from said gradient wave.