JPH05234188A - Tape speed controller - Google Patents

Abstract

PURPOSE:To miniaturize a device and to prevent the damage of a thin tape by controlling the running speed of a magnetic tape without using a capstan shaft and a pinch roller. CONSTITUTION:A reel motor 13 is engaged with a tape reel 12 and the magnetic tape 1 is driven to be wound to the tape reel 12 by rotating integrally with the reel motor. A speed control signal from a recording amplifier circuit 18 is received and recorded by a recording head 14. The speed control signal recorded by the recording head 14 is reproduced by a reproducing head 15 and the reproducing head 15 is provided on a position separated by a distance (1) of 1/2 of a recording wavelength decided by a required tape speed and the frequency of the speed control signal backward the tape running of the recording head 14. The outputs of a crystal oscillation circuit 17 generating the tape speed control signal based on the oscillation frequency of a crystal 16 and a waveform shaping circuit 20 are inputted respectively to a phase comparator 21 and the phase difference of the outputs is comparated by the comparator 21 and the speed error signal of the tape is outputted from the error and the signal is smoothed by an integrator 22.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to tape speed control of a recording / reproducing apparatus such as a VTR.

[0002]

2. Description of the Related Art FIG. 9 is a block diagram of a conventional tape speed control device described in, for example, Japanese Patent Laid-Open No. 63-71963. Reference numeral 1 is a magnetic tape as a recording medium, 2 is a capstan shaft, 3 is a capstan motor that rotates integrally with the capstan shaft 2, and a magnetic pole (hereinafter referred to as FG) is provided on the outer peripheral surface 3a of the rotor over the entire circumference. Is magnetized. Reference numeral 4 denotes a pinch roller, and the magnetic tape 1 is conveyed by being pinched by the pinch roller 4 and the capstan shaft 2 and pressure-bonded thereto.
Reference numeral 5 denotes a rotation sensor arranged at a small distance from the rotor outer peripheral surface 3a of the capstan motor 3, which detects the FG of the rotor outer peripheral surface 3a and outputs a sinusoidal signal (hereinafter, F
Output as a G signal). Reference numeral 6 is an amplifier circuit for amplifying the FG signal, 7 is a waveform shaping circuit for making the output of the amplifier circuit 5 a rectangular wave, and 8 is a speed control circuit for comparing the FG signal with a reference signal and outputting the error as an error signal. , 9 are motor drive circuits for rotationally driving the capstan motor 3.

Next, the operation will be described. The magnetic tape 1 sandwiched between the capstan shaft 2 and the pinch roller 4 is
When the capstan motor 3 rotates, the capstan shaft 2 that rotates integrally with the capstan motor 3 is driven to travel. At this time, an FG signal corresponding to the rotation speed of the capstan motor 3 is output from the rotation sensor 5, and the signal is input to the speed control circuit 8 via the amplification circuit 6 and the waveform shaping circuit 7. The speed control circuit 8 compares the frequencies of the reference signal and the FG signal, outputs an error signal to the motor drive circuit 9, and causes the motor to rotate at a predetermined rotation speed. That is, the magnetic tape 1 held between the capstan shaft 2 and the pinch roller 4 is
The vehicle is driven and driven at a constant speed.

[0004]

Since the conventional tape speed control device is constructed as described above, the magnetic tape 1
Of the outer peripheral surface 3a of the rotor of the capstan motor 3
The tape was driven at a constant speed by detecting using the FG magnetized on the tape and making the rotation speed of the capstan motor constant. Generally, in order to accurately detect the running speed of the magnetic tape 1, an FG of several 100 Hz to several kHz is used.
In order to magnetize the rotor outer peripheral surface 3a of the capstan motor 3 which requires a signal and has a corresponding FG, the diameter of the rotor is inevitably large, which is not suitable for downsizing the entire apparatus. Had a point. Further, since the magnetic tape 1 is sandwiched and pressure-bonded between the capstan shaft 2 and the pinch roller 4, there is a problem that a part of the magnetic tape 1 may be stretched or damaged, especially when a thin magnetic tape is used. There was a point.

The present invention has been made in order to solve the above problems, and accurately detects the running speed of a magnetic tape without using a capstan shaft or a pinch roller when the magnetic tape is running, The object is to obtain a tape speed control device suitable for miniaturization.

[0006]

SUMMARY OF THE INVENTION A tape speed control device according to the present invention comprises a recording head for recording a speed control signal on a magnetic tape, and a position at which the signal is separated backward by a predetermined distance in the tape running direction. It is provided with a reproducing head for reproducing, a phase comparing circuit for detecting a phase difference between the recording side speed control signal and the reproducing side speed control signal of both heads, and a reel motor for driving and driving the magnetic tape.

The recording head and the reproducing head are composed of one block.

Further, the recording head and the reproducing head are arranged at positions separated by a distance of 1/2 of the recording wavelength determined by the desired tape speed and the frequency of the speed control signal.

Further, a delay circuit for delaying the speed control signal is provided both before or after the recording head for recording the speed control signal and after the reproducing head for reproducing the speed control signal.

[0010]

In the tape speed control device according to the present invention, the speed control signal recorded by the recording head and the speed control signal reproduced by the reproducing head are compared by the phase comparison circuit so that the phase difference is always constant. Control the rotation of the reel motor.

In the tape speed control device of the present invention, the speed control signal recorded by the recording head is delayed by the delay circuit, or the speed control signal reproduced by the reproducing head is delayed by the delay circuit. As a result, the tape speed is variable-controlled with respect to the desired speed.

[0012]

【Example】

Example 1. An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a tape speed control device according to the present invention. In the figure, 1 is a magnetic tape as a recording medium, 1
Reference numeral 2 is a tape reel that houses the magnetic tape 1 wound around it, and 13 is a reel motor that fits into this tape reel 12 and rotates integrally therewith. By rotating the reel motor 13, the magnetic tape 1 is transferred to the tape reel 12. It is driven by winding. Reference numeral 14 is a recording head for recording a speed control signal of a single frequency, and 15 is a reproducing head for reproducing the speed control signal recorded by the recording head 14, which is a desired tape speed and speed behind the tape running of the recording head 14. They are provided at positions separated by a distance that is ½ of the recording wavelength determined by the frequency of the control signal. Reference numeral 16 is a crystal, and 17 is a crystal oscillation circuit, which generates a tape speed control signal recorded by the recording head 14 based on the oscillation frequency of the crystal 16.
Reference numeral 18 is a recording amplifier circuit for recording the speed control signal by the recording head 14, 19 is a reproduction amplifier circuit for amplifying a minute signal reproduced by the reproduction head 15, and 20.
Is a waveform shaping circuit for making the output of the reproduction amplifier circuit 19 into a rectangular wave. Reference numeral 21 is a phase comparison circuit that receives the outputs of the crystal oscillation circuit 17 and the waveform shaping circuit 20 and compares the phase differences, and outputs a tape speed error signal from the comparison error. Reference numeral 22 is an integrator that smoothes this speed error signal, and 23 is a motor drive circuit.

Next, the operation will be described. Magnetic tape 1
A speed control signal having a frequency set by the crystal 16 and the crystal oscillating circuit 17 is recorded on this, and when this frequency reproduces the signal on the magnetic tape 1 to obtain an image, the image shakes due to the tape speed error. 720 (Hz), which is an integral multiple of the field frequency of the TV signal, is selected so that it is hard to see, and this signal is transmitted via the recording amplifier 18 to the magnetic tape 1.
Recorded above. On the other hand, the speed control signal recorded on the magnetic tape 1 is immediately reproduced by the reproducing head 15, amplified by the reproducing amplifier circuit 19 and the waveform shaping circuit 20, and subjected to rectangular wave processing and input to the phase comparison circuit 21. It A speed control signal on the recording side generated by the crystal oscillator circuit 17 is simultaneously input to the phase comparison circuit 21, and a speed error signal is generated by comparing the phase difference between these two signals. This velocity error signal is smoothed by the integrator 22,
The reel motor 13 is driven via the motor drive circuit 23 so that the traveling speed of the magnetic tape 1 becomes constant.

Now, the mechanism of generating the velocity error signal will be described in detail. First, the principle of detecting the tape running speed will be described. To detect the running speed of the magnetic tape 1 using the recording head 14 and the reproducing head 15,
The speed control signal passes through the recording head 14 and the reproducing head 1
It suffices to measure the time until it is reproduced in step 5. Although various methods such as using a timer can be considered as a method for realizing this, a method that is equivalent to this method and can be realized with a simpler configuration will be described with reference to FIG. In the figure, (a) is a speed control signal recorded by the recording head 14, and (b), (c), and (d) are speed control signals reproduced by the reproducing head 15, respectively. The distance between the recording head 14 and the reproducing head 15 in the present invention is set to 1/2 of the recording wavelength determined by the desired tape speed and the frequency of the recording side speed control signal. If it is traveling at, the phase relationship between the recording side speed control signal and the reproducing side speed control signal is
As shown in (a) and (b), it takes a time t ₀ from the recording of the speed control signal to the reproduction thereof, and the phase is just inverted. When the tape is traveling at a speed higher than the desired speed, the relationship between (a) and (c) is satisfied, and a time of t ₁ (t ₁ <t ₀ ) is required from recording to reproduction. On the contrary, when the tape is running at a speed lower than the desired speed, the relationship of (a) and (d) is established, and a time of t ₂ (t ₂ > t ₀ ) is required from recording to reproduction. From the above, the speed error signal of the magnetic tape 1 can be obtained by comparing the phases of the recording side speed control signal and the reproducing side speed control signal. That is, by controlling the reel motor so that the phases of the recording side speed control signal and the reproducing side speed control signal are inverted, the magnetic tape 1 can be run at a desired speed and at a constant speed.

Next, how the velocity error signal is generated will be described with reference to FIG. (A) is a speed control signal recorded by the recording head 14, (b) is a speed control signal reproduced by the reproducing head 15, and (c) is a speed control signal on the recording side and a speed on the reproducing side. The PWM wave-shaped speed error signal obtained by the phase comparison circuit 21 comparing the phase difference of the control signal, and (d) is a signal obtained by smoothing the PWM wave-shaped speed error signal by the integrator 22. Now, the speed error signal generation when the tape speed changes from a state faster than a desired value to a state slower than the desired value will be described. In the figure, section A shows a state where the tape speed is faster than a desired value, section B shows a state where the tape speed is slower than the desired value, and section A shows a speed error of the PWM wave depending on the speed error below the neutral level. The signal is obtained. On the other hand, in the section B, a PWM wave speed error signal corresponding to the speed error is obtained above the neutral level, and the speed error signal (c) is smoothed by the integrator 22 and the direct current component (d) of the speed error signal is obtained. To get That is, the output of the integrator 22 that smoothes the speed error signal outputs a low voltage when the tape speed is higher than a desired value, and outputs a high voltage when the tape speed is lower than the desired value.

Example 2. Next, as a second embodiment, FIG. 4 shows that the recording head 14 and the reproducing head 15 for recording / reproducing the speed control signal are configured as one block. Other configurations and operations are the same as those of the first embodiment. With this configuration, the recording head 14 and the reproducing head 1 are
5 can be arranged very close to each other, which is advantageous for downsizing the device. As a practical problem, the recording frequency of the speed control signal is 720 Hz, and the running speed of the magnetic tape 1 is 9
Assuming 9.9 mm / s, the recording wavelength λ becomes λ = 99.9 / 720 = 0.139 mm, and the distance L between the recording head 14 and the reproducing head 15 is ½ of this λ. It is necessary to dispose at a very small distance of /2=0.695 mm = 69.5 μm, but the recording head 14 and the reproducing head 15 can be adjacent to each other at a very small distance by using a thin film head or the like.

Embodiment 3. Next, a third embodiment will be described with reference to FIG. 5, in which two recording heads 14 and two reproducing heads 15 for recording / reproducing a speed control signal are provided. Basically, the configuration of Example 1 is duplicated,
Explaining the difference, it has two fixed heads 14 and 34 for recording / reproducing the speed control signal and two reproducing heads 15 and 35, and speed control signals of different single frequencies are supplied to these fixed heads 14 and 34. Is recorded on the magnetic tape 1. Further, the fixed head 14 and the reproducing head 15 and the fixed head 34 and the reproducing head 35 are arranged at positions separated by different distances L ₁ and L ₂ , respectively, and these distances correspond to desired tape speeds. Each of them is set to 1/2 of the recording wavelength determined by the speed control signal.
The speed control signals recorded by the fixed heads 14 and 34 having this configuration are immediately reproduced by the reproducing heads 15 and 35, and the recording side speed control signal and the reproducing side speed control signal are separately separated. 41 is input. The phase comparison circuits 21 and 41 generate speed error signals according to the principle described in the first embodiment. The speed error signals are smoothed by the integrators 22 and 42 and further added by the adder 50 before driving the motor. The reel motor 13 is controlled via the circuit 23 so that the traveling speed of the magnetic tape 1 becomes constant.

In this embodiment, the tape speed control device of the present invention can be operated more stably. This is shown in FIG.
This will be described with reference to FIG. In FIG. 6, (a) is a recording side speed control signal, (b), (c) and (d) are reproducing side speed control signals, (b) is a normal operation, and (c) and (d) are timings at the time of malfunction. .. As described in the first embodiment, when the magnetic tape 1 is running at a desired speed, the phases of the recording side speed control signal and the reproducing side speed control signal are just in the inverted state. Therefore, for the recording side speed control signal (a), (b) (c)
All of (d) are judged to be normal operations. However, in reality, the relationship between (a) and (b) is normal, but (a)
And (c) have a relationship of 1/3 of the desired speed, and (a) and (d) have a relationship of 1/5 of the desired speed. This malfunction is caused by the fact that when the speed control signal recorded by the recording head 14 is immediately reproduced by the reproducing head 15, the servo should be locked at a position half of the recording wavelength, and this part can be detected. Instead, it occurs when the servo locks at the next edge or at the next edge.

However, since the third embodiment records / reproduces speed control signals of two different frequencies as shown in FIG. 7, the recording side speed control signal 1 (a) and the reproduction side speed control signal 1 ( b) The respective phases of the recording side speed control signal 2 (c) and the reproducing side speed control signal 2 (d) must be in the inverted state, and when these are satisfied, the magnetic tape 1 can run at a desired speed. ..

Example 4. Next, as a fourth embodiment, description will be made with reference to FIG. 8 in which a delay circuit for delaying the speed control signal is provided at both the front stage of the recording head for recording the speed control signal and the rear stage of the reproducing head for reproducing the speed control signal. To do. In this embodiment, two delay circuits are added to the configuration of the first embodiment. Specifically, the delay circuit is provided at a position where the recording side speed control signal and the reproducing side speed control signal are input to the phase comparison circuit 21. 1 (24) and the delay circuit 2 (25) are inserted.

The operation of this configuration will be described below.
As described in the first embodiment, the recording side speed control signal and the reproduction for the three cases of the tape running at the desired speed, the tape faster than the desired speed, and the tape slower than the desired speed. The phase relationship of the side speed control signal is shown in Fig. 2.
As shown in. Explaining again here, when the tape is running at a desired speed, the phase relationship between the recording side speed control signal and the reproducing side speed control signal becomes the relationship of (a) and (b) in the figure, and the recorded speed control is performed. T until the signal is reproduced
_It takes ₀ time, and the phase is just reversed. If the tape is running faster than you want,
Due to the relationship between (a) and (c), it takes a time t ₁ from recording to reproduction. On the contrary, when the tape is traveling at a speed lower than the desired speed, the relationship of (a) and (d) is established, and a time of t ₂ is required from recording to reproduction. That is, it is understood that the tape speed can be arbitrarily set by operating the time from the recording of the speed control signal to the reproduction thereof.
For example, when the tape is traveling at a speed higher than the desired tape speed shown in FIG. 2, the relationship between (a) and (c) is controlled by the servo so that the relationship between (a) and (b) is maintained. It Therefore, the recording side speed control signal 2 is set to (t ₀ −t ₁ ).
If the servo is locked after delaying for a time, the relationship between (a) and (c), that is, the tape can be run at a constant speed higher than a desired speed. On the contrary, when it is desired to travel at a speed lower than the desired speed, the relationship between (a) and (d) in the figure may be maintained, and the reproduction side speed control signal may be changed to (t
It may be delayed by ₂ −t ₀ ) time.

As described above, by delaying the recording side speed control signal or the reproducing side speed control signal by the delay circuit 1 (24) or the delay circuit 2 (25), a variable speed can be obtained with respect to a desired speed. This enables constant tape speed control. This means that when the distance between the recording head and the reproducing head causes a slight speed error in the actual tape speed with respect to the desired tape speed due to an error such as mounting accuracy, the error can be corrected, and the tape fast-forward / forward You can also control the speed of the tape during rewinding and searching.

[0023]

As described above, according to the present invention, since the running speed of the magnetic tape can be controlled without using the capstan shaft and the pinch roller, it is suitable for downsizing, and when a thin tape is used. This has the effect of providing a tape speed control device that can prevent tape damage.

Further, by constituting the recording head and the reproducing head for recording / reproducing the speed control signal on the magnetic tape by one member, the recording head and the reproducing head can be arranged very close to each other, and the device There is an effect that the size can be reduced.

Further, the distance between the recording head for recording / reproducing the speed control signal on the magnetic tape and the reproducing head is set to 1/2 of the recording wavelength determined by the desired tape speed and the frequency of the speed control signal. There is an effect that the running speed of the magnetic tape 1 can be detected with a simple circuit configuration.

Further, by setting the frequency of the speed control signal recorded on the magnetic tape to be an integral multiple of the field frequency of the TV signal, it is possible to make the fluctuation of the image due to the tape speed error less noticeable.

Further, two recording heads for recording the speed control signal and two reproducing heads for reproducing this signal are provided on the magnetic tape so that the frequency of the speed control signal recorded by each recording head is different. By doing so, it is possible to prevent a malfunction during tape speed control.

Further, by providing a delay circuit for delaying the speed control signal in both the stage before the recording head for recording the speed control signal and the stage after the reproducing head for reproducing the speed control signal, the running speed of the magnetic tape. Can be varied, and the desired tape speed can be obtained with high accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram showing a tape speed control device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a speed control signal according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating generation of a speed error signal according to an embodiment of the present invention.

FIG. 4 is a diagram in which a recording head and a reproducing head according to an embodiment of the present invention are configured by one member.

FIG. 5 is a block diagram of a tape speed control device according to another embodiment of the present invention.

FIG. 6 is a diagram illustrating a malfunction in the configuration of FIG.

7 is a diagram showing a speed control signal on the recording side and a speed control signal on the reproducing side in the configuration of FIG.

FIG. 8 is a block diagram showing a tape speed control device according to another embodiment of the present invention.

FIG. 9 is a block diagram of a conventional tape speed control device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 magnetic tape 12 tape reel 13 reel motor 14 recording head 15 reproducing head 17 crystal oscillation circuit 18 recording amplifier circuit 19 reproducing amplifier circuit 20 waveform shaping circuit 21 phase comparison circuit 22 integrator 23 motor drive circuit

Claims (6)

[Claims] 1. A magnetic recording / reproducing apparatus for recording / reproducing signals such as audio and video using a magnetic tape as a recording medium,
A recording head for recording a speed control signal for controlling the traveling speed of the magnetic tape on the magnetic tape, a reproducing head for reproducing this signal at a position separated by a predetermined distance behind the tape traveling direction, and this reproducing head A phase comparison circuit for detecting a phase difference between the speed control signal reproduced by the recording head and the speed control signal recorded by the recording head, and a reel motor for driving the magnetic tape to travel, and a recording head detected by the phase comparison circuit. A tape speed control device for controlling the rotation of the reel motor so that the phase difference of the speed control signal of the reproducing head is always constant. 2. The tape speed control device according to claim 1, wherein the recording head for recording the speed control signal on the magnetic tape and the reproducing head for reproducing the signal are constituted by one block. .. 3. The distance between the recording head for recording the speed control signal on the magnetic tape and the reproducing head for reproducing this signal is 1/2 the recording wavelength determined by the desired tape speed and the frequency of the speed control signal. The tape speed control device according to claim 1, wherein: 4. The tape speed control device according to claim 1, wherein the frequency of the speed control signal recorded on the magnetic tape is an integral multiple of the field frequency of the TV signal. 5. A magnetic tape is provided with two recording heads for recording a speed control signal and two reproducing heads for reproducing this signal, and the frequency of the speed control signal recorded by each recording head is different. Claim 1 characterized by
A tape speed control device as described in the paragraph. 6. Both a front stage of a recording head for recording a speed control signal and a rear stage of a reproducing head for reproducing a speed control signal,
2. The tape speed control device according to claim 1, further comprising a delay circuit for delaying the speed control signal.