JPS5956879A - Speed setting circuit for motor - Google Patents

Abstract

PURPOSE:To accelerate the shift of the specified speeds at starting and stopping time by forming to include a counter in a pulse generator for varying the speed of a motor and enabling to set the output pulse width in response a load amount. CONSTITUTION:An acceleration pulse generator 7 is operated by a signal from a terminal 8, a capstan motor 4 for a VTR is rotated by the output, and a pulse signal proportional ro the speed of a rotation detector 5 is supplied to the generator 7. A counter is contained in the generator 7 to count whenever the pulses of a speed signal is counted, and when the counter counts the preset number, the output of the generator 7 is stopped. Accordingly, the counter can be always counted to the prescribed initial set value. Thus, the output pulse width is shortened when the load is small, the lengthened when large, thereby accelerating the shift to the specified speed to largely shorten the time for reaching the stabilized value.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a motor speed setting circuit suitable for a cab tan motor of a home video tape recorder.

Home video tape recorders are configured to allow special playback such as slow and still playback. Such special playback is an operation in which the same recording track is repeatedly scanned for playback multiple times. In particular, when the capstan motor is driven intermittently during noiseless slow playback, when the magnetic tape starts running or stops running, Irregular l-ranking deviations cause noise.

In order to reduce such noise, it is necessary to quickly change the pressure at the transfer speed when the magnetic tape starts and stops running, and to shorten the period during which the transfer speed changes as much as possible. (hereinafter referred to as the motor)
It is necessary to quickly shift the motor from a zero stopped state to a certain specified speed state, and from the specified speed state to a stopped state.

The conventional technique for setting the speed of the motor to such a zero speed state or a specified speed state is a method in which a pulse with a constant pulse width is applied to the speed control system of the motor to forcibly change the speed of the motor. It had been taken. However, the running load applied to the motor fluctuates at the beginning and end of winding the magnetic tape, for example.

As mentioned above, when the pulse width of the pulses applied to the motor is constant, the speed of the motor after being changed by the pulses will vary significantly depending on the running load.

This problem will be explained in more detail by taking as an example the case where the motor is started and transferred from a stopped state to a specified speed state.

FIG. 1 is an acceleration characteristic diagram showing speed changes caused by the conventional motor starting circuit at time t.

Change in motor speed with respect to running load when an acceleration pulse is applied during period T1 from time t1 to time t1 In the same figure, if the specified speed is υ1, 5 When the optimum running load is applied to the motor, the motor speed is As shown in characteristic curve 1, the speed changes so that the specified speed becomes V at time t1, and then the speed control system immediately operates and the speed changes to V at time t1.
From 1, the motor rotates at the specified speed υ1.7 However, when the running load is small, the motor speed change is large, and at time t1, the speed v2 (where v, (v2)) is significantly different from the specified speed v1. Further, when the running load is heavy, the speed change of the motor is small, and at time t1, the speed vs (however, υs <Ul) is 15, which is also significantly different from the specified speed v1.

Since the speed control system operates at time t1, the speed ν2. The speed v3 eventually changes to the specified speed v1, but this requires an additional period T2. Therefore, when the motor is started, undesirable noise will appear on the playback screen for a long time depending on the running load.

The same applies to the case where the motor is stopped by applying a deceleration pulse with a constant pulse width.

The object of the present invention is to eliminate the drawbacks of the above-mentioned prior art.

To provide a speed setting circuit for a motor that can always quickly shift the motor to a predetermined speed state even when the running load changes.

To achieve this objective, the invention proposes that the pulse width of the pulses applied to the motor and changing the speed of the motor be
The present invention is characterized in that the running load is set to L5 so that the speed state of the motor due to the pulse is approximately the predetermined speed state.

Embodiments of the present invention will be described below with reference to the drawings. .

FIG. 2 is a block diagram showing an embodiment of a motor speed setting circuit according to the present invention, in which 4 is a motor, 5 is a rotation detector, 6 is an amplifier, 7 is an acceleration pulse generator, 8 is an input terminal, 9 is a motor drive amplifier. .

Next, the operation of this embodiment will be explained.

In FIG. 2, when a start signal is supplied from the input terminal 8, the acceleration pulse generator 7 starts operating and generates an output voltage. This output voltage is amplified by the motor drive amplifier 9 and supplied to the motor 4, and the motor 4 starts rotating. When the motor 4 rotates, the rotation detection 65 detects that the motor 4
A Norculus signal (hereinafter referred to as speed signal) with a repetition frequency proportional to the speed of the motor is generated. The speed signal is amplified by an amplifier 6 and supplied to an acceleration/curse generator 7.

The acceleration pulse generator 7 is equipped with a counter (not shown) which is activated by a start signal from the input terminal 8 and counts each pulse of the applied speed signal. Then, when the count is counted by a predetermined number (hereinafter referred to as the initial setting value),
The acceleration pulse generator 7 stops generating the output voltage.

However, the acceleration pulse generator 7 generates an output voltage for a period from the time when the start signal is supplied from the input terminal 8 until the time when the counter counts up to the initial setting value, and this output voltage is used as an acceleration pulse to drive the motor 4. accelerate.

Incidentally, the speed of the motor 4 increases as the running load decreases, and decreases as the running load increases, so the repetition frequency of the speed signal increases as the running load decreases and decreases as the running load increases.

Since the non-counter of the acceleration pulse generator 7 always counts up to a certain initial setting value, the pulse width of the acceleration pulse is shorter as the running load is smaller, and longer as the running load is larger.

On the other hand, the frequency of pulse generation of the speed signal is proportional to the speed of the motor, and the movement of the magnetic tape (not shown) is proportional to the speed of the motor. However.

The counter of the acceleration pulse generator 7 measures the amount of movement of the magnetic hoop by counting the speed signal.
Since the counted value is up to a certain initial setting value, the counter detects that the magnetic tape has moved by a certain amount. Therefore, the pulse width of the acceleration pulse is equal to the time width required for the magnetic tape to move a certain amount, regardless of the running load, ie, the speed of the motor.

By the way, the running load has a fluctuation range.

Therefore, the running load that is at the center of the fluctuation range is set as the optimum running load, and the acceleration pulse is applied to the motor 4 at the optimum running load.
When the motor 4 is accelerated, the pulse width of the acceleration pulse is
The above-mentioned initial setting value of the counter of the acceleration pulse generator 7 is determined so that the width becomes such that the speed becomes the specified speed v1.

FIG. 5 is an acceleration characteristic diagram showing the speed change with respect to the running load in FIG.
12 shows the speed change when the running load is large.

Now, in Fig. 6, the speed v2 is motor 4 (Fig. 2)
Assuming that the specified speed is , from the above, in the case of the optimum running load, an acceleration pulse equal to the time width from time to to 12 is applied to the motor 4, and the speed of the motor 4 becomes the specified speed υ. Become.

At this time, the magnetic tape has been transferred by a length S, and a speed control system (not shown) is activated from time t2.

When the running load is small, as mentioned earlier, the time t corresponds to the running load. An acceleration pulse equal to the time width from tl to tl is applied to the motor 4, and the speed of the motor 4 follows the characteristic line 1.
1 and reaches the speed v1 at time t1.

At this time, the magnetic tape is also being transported by a length S. If an acceleration pulse with a pulse width equal to the acceleration pulse at the optimum running load is applied to the motor 4, at time t2, the speed of the motor 4 becomes v1', which is much different than the specified speed υ2. However, as mentioned above, the speed v1 of the motor 4 approaches the specified speed υ due to the acceleration pulse with a pulse width (11-to) corresponding to the running load, and therefore, the speed control system starts changing from time t. Even if the motor 4 is activated, the speed of the motor 4 is immediately pulled to the specified speed v2 by 1°.Also, when the running load is heavy, the time t corresponds to the running load. An acceleration pulse equal to the time width up to 3 is applied to the motor 4, and the speed of the motor 4 is determined by the characteristic line 12.
The speed changes as follows, and at time t6 the speed v! , becomes. At this time, the magnetic tape is also being transported by a length S. If an acceleration pulse with a pulse width equal to the acceleration pulse at the optimum running load is applied to the motor 4, 1
At time t2, the speed of the motor 4 becomes v5', which is significantly different from the specified speed v2, but as described above, the speed of the motor 4 is changed to υ5 due to the acceleration pulse with the pulse width (t3-to) according to the running load. is very close to the specified speed 112, so even if the speed control system is activated from time t, the speed of the motor 4 is immediately pulled to the specified speed v2.

As described above, at any running load, the speed of the motor obtained by acceleration approaches the specified speed, so the speed control system quickly pulls the motor to the specified speed.

The time required for stabilizing the speed at the time of starting the motor is significantly shortened, and the influence of fluctuations in running load is reduced.

Next, an example in which the present invention is applied to noise reduction/slow playback by intermittent driving of a capstan motor in a VTR will be described.

FIG. 4 is a block diagram showing such an example, where 13 is a frequency-voltage converter, 14 is a DC amplifier, 15 is a reference voltage source, 16 is an intermittent drive signal generator, 17 is a diode, 1
8 is a resistor, 19 is a switch, and parts corresponding to those in FIG. 2 are given the same reference numerals.

FIG. 5 is a signal waveform diagram showing the signals of each part in FIG. 4, and the same symbols are given to the signals corresponding to the signals in each part of FIG. 6.

Next, the operation of this application example will be explained.

In FIGS. 4 and 5, time t. -tl, the output signal a of the intermittent drive signal generator 16 is at a low level (hereinafter referred to as L), the switch 19 is in the on state, the input of the motor drive amplifier 90 is L, and the motor 4 has a drive current. Intermittent 1 drive signal generator 1 at stop time t1 without being supplied
Suppose that the output signal α of No. 6 changes to a high level (hereinafter referred to as H) and remains H'' until time t4 of No. 5.
The period switch 19 is turned off, the acceleration pulse generator 7 is activated, and the output voltage, that is, the acceleration pulse C, is supplied to the motor 1 drive circuit 9 via the diode 1-17. Therefore, a starting current flows from the motor 1 drive circuit 9 to the motor 4 in response to the acceleration pulse C, and the motor 4
is activated and begins accelerated rotation.

Therefore, the one-rotation detector 5 generates a speed signal with a repetition frequency corresponding to the speed of the motor 4, and the speed signal has a frequency -
Together with the voltage converter 13, it is supplied to the acceleration pulse generator 7. As explained in FIG. 2, the acceleration pulse generator 7 sets the pulse width of the acceleration pulse C to a value corresponding to the running load of the motor 4. Let the pulse width of acceleration pulse C be (i
2-61), at time t2, the output of the accelerating pulse generator 7 becomes L'', and the speed of the motor 4 is near the standard speed, which is the specified speed.

On the other hand, (rotation detector 5 →) amplifier 6 → frequency-voltage converter 13 → DC amplifier 14 → motor drive circuit 9
It operates so that the output voltage d of the frequency-to-voltage converter 15 and the voltage of the reference voltage source 15 are equal, and when both are equal, the speed of the motor 4 becomes the standard speed.

At time t2 after acceleration by acceleration pulse C.

Since the speed of the motor 4 is near the standard speed, the difference between the output voltage of the 1-frequency-voltage converter 13 and the voltage of the reference voltage source 15 is small, and when the speed control system operates at time t2, the speed of the motor 4 immediately changes. will shift to standard speed. Therefore, the period during which the motor 4 shifts from the stopped state to the standard speed state is short, the motor 4 is quickly shifted to the standard state, and the generation of noise on the playback screen is reduced.

Next, at time t5, a control signal is supplied from the intermittent drive signal generator 16 to the motor drive amplifier 9, the direction of the motor drive current is reversed, and the brake is applied to the motor 4, causing the motor 4 to rapidly decelerate. be done. At time t4, the intermittent drive signal generator 6 turns on and the motor 4 is stopped without being supplied with drive current.

As described above, by using an acceleration pulse generator, it is possible to set an appropriate acceleration period, which reduces the effects of the running load on the motor, such as accelerating the motor too much during the acceleration period or not reaching the motor's standard speed. 3. Since the motor can quickly shift from a stopped state to a standard speed state, it is possible to avoid noise on the playback screen when the motor is started.

In the above embodiment, the acceleration of the motor has been explained, but the explanation also applies to the case where the motor is decelerated and stopped, and the case where the speed is changed so that the motor rotating at a certain speed is rotated at another speed. It is clear that the present invention can be applied to the same manner. .

Furthermore, the present invention can be applied not only to slow playback but also to other playback modes such as normal playback, and the generation of noise on the playback screen when the motor is started or stopped is reduced.

As explained above, according to the present invention, by varying the width of the pulse that changes the speed of the motor depending on the running load of the motor, the speed state of the motor changed by the pulse can be adjusted to Since the speed can always be set near the predetermined speed regardless of changes in load,
The motor can be quickly shifted to a predetermined speed state, and the influence of fluctuations in running load on the transition period of the motor to the predetermined speed state can be reduced, and the drawbacks of the above-mentioned conventional technology can be eliminated. We can provide motor speed setting circuits with excellent functionality.

[Brief explanation of the drawing]

Fig. 1 is an acceleration characteristic diagram showing speed changes due to a conventional motor starting circuit, Fig. 2 is a block diagram showing an embodiment of a motor speed setting circuit according to the present invention, and Fig. 5 is a running load of Fig. 2. Figure 4 is an acceleration characteristic diagram showing the speed change for
FIG. 5 is a block diagram showing an example in which the embodiment shown in the figure is applied to noiseless slow playback by intermittent driving of a capstan motor in a video tape recorder. FIG. 5 is a signal waveform diagram showing signals of each part in FIG. 4. 4... Motor, 5... Rotation detector, 6... Amplifier, 7... Acceleration pulse generator, 8... Input terminal, 9...
...Motor drive amplifier. Representative Patent Attorney Susuki 1) Li 7' Yuki・2 O 1 Figure '1-2 Figure 6 f 3 Figure

Claims (1)

[Claims] (1) In a motor speed setting circuit that quickly shifts the motor to a predetermined speed state, a pulse generator is provided that generates pulses that are supplied to the motor to change the speed of the motor, and the pulse generator The speed of the motor is characterized in that a speed signal corresponding to the speed of the motor is supplied, and the pulse width of the pulse can be set to a width corresponding to a change in the speed of the motor. Setting circuit 1, (2. In claim (1), the pulse generator includes a counter, the speed signal is a pulse signal having a repetition frequency that differs depending on the speed of the motor, and the counter A speed setting circuit for a motor, characterized in that the circuit is configured to count pulses of the speed signal by a preset constant number, and to set the pulse width equal to the counting period of the counter. .