JPS6023414B2 - Rotational phase detection method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotational phase detection method for detecting the rotational phase of a head cylinder in a magnetic green image reproduction device using one phase detection head.

The rotational phase detection system and phase control system of the subordinate Head Schilling are constructed as shown in the block diagram of FIG.

FIG. 2 shows waveforms at various parts of the block diagram of FIG. 1. 1st
In the figure, 1 is a motor whose head cylinder is directly connected to its rotating shaft. The rotation of the head shilling is detected by the two phase detection heads 3, 3' as signals S, , S2 as shown in Fig. 2, and the respective signals S, , S2 are outputted to the pulse amplifiers 4, 5 to output the signals S3, S3, and S2. Obtain S4. signal S3,
The voltage is applied to the monostable multipipe layers 6 and 7 (hereinafter referred to as monomulti) operating in the green light before each pulse of S4, and the time constant determination constant (R,,C,) of each monomultiply 6 and 7 is applied. , (R2, C2) to determine the delay time. The waveforms of the control terminals of the monomultis 6 and 7 are signal M and signal S6 as shown in FIG. The outputs of the monomultis 6 and 7 are as shown in Fig. 2, and the signals S7 and S8 are obtained.
is applied to the flip-flop circuit 8 which continuously performs set and reset at the trailing edge of the signal S8, thereby obtaining a signal S9 as shown in FIG. Signal S9 is used as a switching signal for the video head reproduction amplifier. On the other hand, the phase of the signal S9 is compared with the reference signal from the reference signal circuit 9 by the phase comparison circuit 10, and the phase comparison signal is applied to the drive circuit 11 to control the head cylinder motor. Conventionally, when the relative speed was high, the diameter of the head cylinder was large, so the space inside the cylinder was large and it was possible to install two phase detection heads, but when the relative speed was low, the cylinder The diameter is also small, making it difficult to secure space within the cylinder to install two phase detection heads.

Therefore, a method is required in which one phase detection head detects two signals having different phases. SUMMARY OF THE INVENTION An object of the present invention is to provide a rotational phase detection method that can accurately detect the rotational phase of a head cylinder by separating two signals detected by one phase detection head.

In order to achieve the above object, the present invention provides two magnetic bodies on different circumferences on a rotating cylinder surface with a phase difference of 180 degrees, and on a fixed cylinder surface at positions on both sides of the coil in the radial direction. a phase detection head made of a magnet of opposite polarity, which detects the magnetic body and alternately generates a sinusoidal differential pulse signal of opposite phase, and a Schmitt circuit that operates at a zero-crossing point of the differential pulse signal; The output of the Schmitt circuit and its inverted output are applied to a monostable multipipulator and delayed, and each delayed signal operates a flip-flop circuit, and the phase detection head is activated by rotation of the head cylinder. detects sinusoidal differential pulse signals of opposite phases alternately,
In order to operate the Schmitt circuit at the zero-crossing point of this differential pulse signal, the leading and trailing edges of the output signal of the Schmitt circuit are approximately It can be made to coincide with the zero cross point, and the phase of the head cylinder can be detected with high accuracy using one phase detection head.

Hereinafter, a head cylinder rotational phase control method using the rotational phase detection method of the present invention will be explained with reference to FIGS. 3 to 5.

FIG. 3 shows this block diagram, and FIG. 4 shows waveforms of each part. In FIG. 3, reference numeral 1 denotes a motor to which a head cylinder 2 is directly connected to its rotational drive shaft. 12 is a phase detection head 12, which detects the fourth phase by rotation of the head cylinder 2.
A signal S as shown in the figure is obtained.

FIG. 5 shows the structure of the rotational phase detection section within the head cylinder 2. In FIG. 5, reference numeral 21 denotes an upper cylinder to which a video head is attached, which rotates at the same time as the motor 1. 16 and 17 are iron pieces attached to the upper cylinder 21, and are arranged with a phase difference of about 18 degrees.

Reference numeral 22 denotes a non-rotating lower cylinder, on which a phase detection head 20 is attached, and magnets 18 and 19 are attached on both sides of the cylinder with opposite polarities. The outer iron pieces 17 pass above the middle between the phase detection head 20 and the magnet 18 or above the middle between the phase detection head 20 and the magnet 19, respectively.

This passing timing is detected by the phase detection head 20', and a signal S as shown in FIG.
, is obtained. Regarding this signal S, zero crossing points A and B must be detected. This signal S is applied to a Schmitt circuit 13 having hysteresis characteristics to obtain a signal S2 as shown in FIG. The input sensitivity of the Schmitt circuit 13 is set so that the sensitivity to positive direction signals and the sensitivity to negative direction signals are approximately equal. The signal S2 is a rectangular wave whose leading edge detects point A and its trailing edge detects point B.
In this case, since the rise and fall of the signal S near the points A and B are steep, the front green and rear green of the output signal S2 of the Schmitt circuit 13 almost coincide with the points A and B of the signal S. Further, even if the waveform of the signal S changes, there is almost no change in the detected phase, so there is little change in the phase due to temperature changes or the like. Then, the signal S2 is inverted to obtain the signal S3, and the signals S2 and S3 are applied to the monomultis 14 and 15, respectively, and the respective time constant determination constants (R3, C3) (R4, C4) are applied.
Determine the delay time. The waveforms of the control terminals become signals S4 and S5 as shown in FIG. The outputs of the monomultis 14 and 15 provide signals S6 and S7 as shown in FIG. Since the input signals S2 and S3 of each mono multi 14 and 15 are rectangular waves with approximately 50% duty, when configuring a mono multi using an integrated circuit, the circuit is simpler than in the case of a general mono multi. can. In this case, the delay time that can be achieved with monomulti is up to T, (or T2), but the delay time L (
or T4) is much shorter than T, so there is no problem. Output signals S6 and S of monomultis 14 and 15, respectively
Signals S6 and S7 are applied to the flip-flop circuit 8, which is continuously set and reset at the front green of 7, to obtain a signal S8 as shown in FIG. In this case, since there is no period in which the signals S6 and S7 are at the /.- level at the same time, it is extremely easy to construct the flip-flop circuit 8 in an integrated circuit. signal S8
is used as a switching signal for the video head playback amplifier. On the other hand, the phase of the signal S8 is compared with the reference signal from the reference signal circuit 9 by the phase comparison circuit 10, and the phase comparison signal is applied to the drive circuit 11 to control the rotation of the head cylinder motor. As explained above, according to the present invention, the phase detection head alternately detects sinusoidal differential pulse signals of opposite phases as the head cylinder rotates, and the Schmitt circuit is operated at the zero-crossing point of the differential pulse signal. ,
The leading and trailing edges of the output signal of the Schmitt circuit can be made to almost coincide with the zero-crossing point of the sinusoidal differential pulse signal, and the output signal of the flip-flop circuit is output by the output signal of the Schmitt circuit and its inverted output signal. The fluctuations in the rise and fall of the signal become very small even when the level of the sinusoidal differential pulse signal changes, so the output signal of the flip-flop circuit can be used as a switching signal for the video head reproduction amplifier, and one The phase detection head can easily detect the phase of the head cylinder, and is suitable for integrated circuits.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional rotational phase control method, Fig. 2 is a diagram showing waveforms of each part in Fig. 1, and Fig. 3 is a block diagram of a rotational phase control method using the rotational phase detection method according to the present invention. 4 is a diagram showing waveforms of each part in FIG. 3, and FIG. 5 is a side view of the rotational phase detecting section in the head cylinder. DESCRIPTION OF SYMBOLS 1...Motor, 2...Head cylinder, 8...Flip-flop circuit, 10...Phase comparison circuit, 11...
...Drive circuit, 13... Schmitt circuit, 14, 15
...Monostable multipipulator, 16, 17...
... Iron piece, 18, 19 ... Magnet, 20 ...
・Phase detection head, 21... Upper cylinder, 22
...lower shilling. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 Two magnetic bodies are provided on different circumferences on the rotating cylinder surface with a phase difference of 180°, and on the fixed cylinder surface, the coil and magnets of opposite polarity are provided on both sides of the coil in the radial direction, A phase detection head is provided which detects a magnetic substance and alternately generates sinusoidal differential pulse signals of opposite phases, a Schmitt circuit is provided which operates at the zero cross point of the differential pulse signal, and an output of the Schmitt circuit and its inverted output are provided. are applied to a monostable multivibrator and delayed, respectively.
A rotational phase detection method characterized by operating a flip-flop circuit using each of the delayed signals.