JPH0235946B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotation detection device, which extracts rotation pulses having at least two types of periods during a level change determination period, and prevents the level detection timing and the pulses from synchronizing with each other during the determination period. configured,
When detecting the level change of the rotation pulse at a certain timing, it is possible to detect both the H level and the L level of the rotation pulse within a predetermined time at any rotation speed, and it is possible to reliably detect whether or not the rotating body is rotating. An object of the present invention is to provide a rotation detection device.

For example, a video tape recorder is provided with a circuit for detecting whether or not a reel disk is rotating, separate from a circuit for detecting the rotational speed of a capstan in a capstan servo system. This is different from capstan servo systems, and simply determines whether or not the reel disk is rotating.For example, if the magnetic tape becomes entangled for some reason and stops moving, the reel disk If the disc motor is left as it is, there is a risk of burning it out, so to prevent this, this circuit is used to detect when the reel disc motor stops rotating and cut off the power supply to the motor.

For example, as shown in FIG. 1, a light-shielding disc 2 having notches provided on the circumference at predetermined intervals is attached to the rotating shaft of a reel disc motor 1 that drives a reel disc, and the notches of the disc 2 are A disk 2 that rotates light from a light emitting diode 3 provided on one side of the disk 2.
The phototransistor 4 is supplied to the phototransistor 4 provided on the opposite side of the cutout.
A waveform shaping circuit 5 shapes the electric signal obtained by passing and blocking the light into an alternating pulse signal,
For example, the pulse signal is supplied to a detection unit 6 composed of a microcomputer, and changes in the level of the pulse signal are detected. The detection unit 6 is provided with a level judgment time of, for example, 3 seconds, and when the motor 1 is rotating, the pulse signal from the waveform shaping circuit 5 is a repetition of H level and L level, so this repetition is It is determined within 3 seconds that the current is being maintained, and a signal is supplied to the motor 1 to cause the motor 1 to continue to rotate.
On the other hand, if the motor 1 stops rotating for some reason even though power is being supplied to the motor 1, the pulse signal from the waveform shaping circuit 5 disappears and becomes a signal at the same level, and the detection unit 6 The motor 1 determines that the same level signal continues for 3 seconds and sends a signal to cut off the power supply to the motor 1.
supply to.

By the way, for example, the rotational speed of the take-up reel in the playback mode is fast at the beginning of tape winding and slows down as it approaches the end of the tape.
As shown in FIG. 2, the frequency of the pulse signal taken out from the waveform shaping circuit 5 gradually becomes lower. in this case,
As shown in FIG. 3, in the conventional disc 2, the notches 2a are provided at equal intervals on the circumference, so although the frequency of the pulse signal changes gradually, it remains constant during the 3 seconds of judgment time in the detection section 6. be. On the other hand, the timing at which the detection unit 6 detects the level of the pulse signal from the waveform shaping circuit 5 differs depending on each mode such as fast forward, rewind, and playback, but is constant within a certain mode. , in the reproduction mode, as shown by arrows (↓) in FIGS. 2A to 2D.

In this way, in this conventional device, since the notches 2a of the disk 2 are provided at equal intervals on the circumference, for example, as is clear from FIG. The timing of the H level of the signal is the judgment time 3 in the detection unit 6.
There are periods of agreement that last for seconds or more. Therefore, the detection unit 6 receives the H from the waveform shaping circuit 5.
Even though a pulse signal in which the level and L level repeatedly occur is extracted, only the H level is detected for 3 seconds or more, and even though the reel is rotating normally, the motor 1 A signal was supplied to motor 1 to cut off the power supply to motor 1.
It had drawbacks such as low operational reliability.

The present invention eliminates the above drawbacks, and the fourth
An example will be described below with reference to the drawings.

FIG. 4 shows a plan view of an embodiment of the light-shielding disk 7 used in the rotation detecting device according to the present invention. In the same figure, 7
a is a notch having the same spacing as the notch 2a shown in the third figure; 7b is a notch having a width that is, for example, three times the width of the notch 7a; a notch group constituted by a plurality of notches 7a; 7a ₁ and 7a ₂ are located at one location each on the circumference, and notch groups 7b ₁ and 7b ₂ each constituted by a plurality of notches 7b are located at one location _each on the circumference _. , 7a ₂ , and 7b ₂ are successively provided on the circumference in this order. Specifically, the notches of the notch groups 7a ₁ and 7a ₂ are formed when the disk 7 is rotated at a speed at which a pulse signal having a frequency as shown in FIG. 2B is extracted from the waveform shaping circuit 5. As shown in Figure B, the second
They are provided at equal intervals so that the duration of the H-level pulse P _a , which is the same as the H-level pulse shown in FIG. B, is less than the determination time (3 seconds) in the detection unit 6.

When using a disc in which some of the notches are provided at irregular intervals in this way, the pulse signal obtained by the rotation of the take-up reel in the playback mode is as shown in Fig. 5 from the beginning of tape winding to the end of tape winding. While the disc 7 rotates once, a pulse signal P _a obtained by the notch 7 a and a pulse signal P _b obtained by the notch 7 b are generated, and the detection unit 6
A portion where the pulse width changes within the judgment time occurs. Therefore, as shown in FIG. 5B, even if the generation timing of the pulse P _a of the pulse signal obtained by the notch 7a during the reproduction mode coincides with the level detection timing (↓) in the detection section 6,
Since the notch group 7a ₁ or 7a ₂ is provided as described above, it takes less than 3 seconds for the detection unit 6 to determine that the signals from the waveform shaping circuit 5 are at the same level (H level in this case), and the notch group 7a1 or 7a2 is provided as described above. When the duration of the pulse P _a by the notch group 7a ₁ ends, the L level due to the pulse P _b by the notch group 7b ₂ is detected.

That is, since there is an H level due to the pulse P _a and an L level due to the pulse P _b at the level detection timing within the determination time in the detection unit 6, the detection unit 6 detects both the H level and the L level. As a result, even if there is a period in which the level detection timing of the detection unit 6 and the H level of the pulse P _a match during the playback mode, this is less than the judgment time in the detection unit 6, so that the judgment time is different from that in the conventional device. There is no possibility that the H level continues longer than this and a signal is supplied to the motor 1 to cut off the power supply to the motor 1.
A signal is supplied to the motor 1 to cause the motor 1 to rotate as it is.

In addition, even in modes other than the playback mode, the frequencies are different, but the frequencies shown in Figure 5 A to D are different depending on the tape winding diameter.
Since a pulse signal as shown in FIG. 5B is extracted and the level detection timing differs depending on the mode, a situation as shown in FIG. 5B may occur in any mode. In this example,
Since the disc 7 is formed as described above, the above-described operation does not cause any inconveniences as in the prior art as long as the reel disc rotates normally in any mode.

Further, the shape of the light-shielding disk is not limited to the shape shown in FIG. 4, and for example, as shown in FIG. 6, the shape of the light-shielding disk is not limited to that shown in FIG. It may be a circular plate in which one notch 8b having a width three times the width of the notch 8a and one light shielding part 8b having a width three times the light shielding part 8c are provided (note that the notch 8c and the light shielding part The relative position with respect to 8d is not limited to the one shown in the figure, but may be set to any positional relationship such as, for example, so that both are in symmetrical positions with respect to the center of the rotation axis), or as shown in FIG. as,
It may be a circular plate provided with a notch 9a in one half of the circumference and a notch 9b having a width three times the width of the notch 9a in the remaining half. In each disc, the duration during which the H level of the pulse obtained by the notch 8a or 9a and the level detection timing in the detector 6 coincide is set to be less than the level determination time in the detector 6.

Further, the means for obtaining the pulse signal is not limited to the light-shielding disk provided with a notch as in the above embodiment, but may also be a disk provided with holes, for example. An apparatus may also be used in which a disc coated with different colors at two different periods is used to irradiate light onto this part and to receive light reflected from the disc.

As described above, the rotation detection device according to the present invention includes a pulse signal generating means that generates a pulse signal having at least two types of cycles during a predetermined level change determination period, and a pulse signal generating means that generates a pulse signal having at least two types of cycles during a level change determination period. and a level change detection means for detecting a level change of the pulse signal so that the period of the same level of one of the pulse signals is not synchronized, so that the timing of detecting the level change is coincident with one period of the pulse. Even if the pulse of the other period does not coincide with this detection timing, it is possible to always detect both the H level and L level of the pulse for one revolution of the rotating body, that is, within a predetermined time, at any rotational speed. As a result, unlike conventional devices, by detecting the same level of pulses at the portion where the detection timing and pulse coincide, the rotating body is incorrectly judged to have stopped rotating even though it is rotating. It has features such as not being stored away, being able to reliably distinguish between rotation and rotation stop, and improving operational reliability.

[Brief explanation of drawings]

FIG. 1 is a block system diagram of an example of a general rotation detection device, FIGS. 2A to D are signal waveform diagrams for explaining the operation of the conventional device, and FIG. 3 is a plan view of an example of a light-shielding disc used in the conventional device. FIG. 4 is a plan view of an embodiment of the light shielding disc used in the device of the present invention, FIGS. 5A to D are signal waveform diagrams for explaining the operation of the device of the present invention, and FIGS. FIG. 7 is a plan view of another example of the light-shielding disc used. 1... Reel motor, 3... Light emitting diode,
4...Phototransistor, 6...Detection section, 7...
...shading disc, 7a, 7b, 8a, 8b, 9a, 9
b... Notch portion, 8c, 8d... Light shielding portion.

Claims (1)

[Claims] 1. Detecting a level change of a pulse signal with a frequency corresponding to the rotational speed of a rotating body at a constant timing,
In a rotation detection device that detects the presence or absence of rotation of the rotating body based on the presence or absence of a level change, a pulse signal generating means generates a pulse signal having at least two types of periods during a predetermined level change presence/absence determination period. and a level change detection means for detecting a level change of the pulse signal in such a manner that the constant timing and the same level period of any of the pulse signals are not synchronized during the level change determination period. A rotation detection device characterized by: