JPH0581629A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To accurately control the position of a movable head equipped freely movably in the axis direction of a rotary dram. CONSTITUTION:Since high frequency current supplied from an oscillator 21 is supplied to only a single detection coil among plural detection coils 12, even if plural detection coils are used, no interference of high frequency is generated and only the amount of change in accordance with the change of the inductance of the detection coil depending on the distance between an electrically conductive member and the detection coils 12 is detected by detectors 23. By holding the detected position signal in a sample holding circuit 24, highly accurate position sensor is constituted and the positions of the respective electrically conductive members are continuously detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus having moving means for moving a magnetic head in the axial direction of a rotary drum.

[0002]

2. Description of the Related Art In a helical scanning type magnetic recording / reproducing apparatus such as a video tape recorder or a digital audio tape recorder, a magnetic tape is wound around a cylindrical drum with the rotating direction of a rotating drum and the scanning direction of the magnetic tape being inclined. The magnetic head fixed to the rotating drum is rotated to form a recording track inclined with respect to the traveling direction of the tape, and a video signal or the like is recorded on the magnetic tape. In such a conventional magnetic recording / reproducing apparatus, when special reproduction such as slow motion reproduction or quick motion reproduction is performed, a signal recorded at a tape running speed different from that at the time of recording is reproduced. Therefore, the trajectory of the magnetic head with respect to the recording track on the magnetic tape changes, and it becomes difficult to completely trace the recording track.

FIG. 4 is a diagram showing the recording tracks on the magnetic tape and the loci of the magnetic head. In this figure, a recording track 102 is formed on a magnetic tape 101.
During normal recording or reproduction, the magnetic head is traced in the direction indicated by arrow 103 parallel to the recording track 102 as shown in the figure. Locus 103 of this magnetic head
Is a composite of the tape velocity vector 104 and the velocity vector 105 of the magnetic head formed by the rotating drum. When the tape running speed changes and, for example, the tape speed becomes four times as shown by 106, the head locus 1 composed of the speed vector 106 of the magnetic tape 101 and the speed vector of the magnetic head by the rotating drum.
It will be 07. Since the head locus 107 passes through several recording tracks 102 at a time, noise occurs on the reproduction screen. In order to eliminate such noise and completely trace the recording track, it is necessary to move the magnetic head in the direction of arrow 108. Therefore, in order to move the magnetic head, a head moving means using, for example, a bimorph element has been proposed.

FIG. 5 is a sectional view showing a drum device as an example of a magnetic recording / reproducing device having a conventional head moving means.
In the figure, the movable head 1 is fixed to the tip of a bimorph element 2 which is a head moving means. Bimorph element 2
Is fixed to a rotary drum 3 which is rotationally driven at a predetermined rotational speed, and is provided so as to face a fixed drum 4 having the same cylindrical surface as the rotary drum. A drive voltage is supplied to the bimorph element 2 from the outside via a slip ring 5 as shown in the figure. The fixed drum 4 is fixed to the main body of the magnetic recording / reproducing apparatus, and the magnetic tape 6 is wound around the rotary drum 3 and the fixed drum 4 with a predetermined inclination.

The operation of the magnetic recording / reproducing apparatus having the above structure will be described below. When performing special playback such as slow motion or quick motion in a video tape recorder, the tape running speed differs from that during recording. Therefore, the moving amount of the movable head 1 is set so that the moving head 1 traces the recording track completely, and a control voltage corresponding to the moving amount is supplied to the bimorph element 2 via the slip ring 5. The bimorph element 2 is deformed in the direction of arrow 7 by the control voltage, and the movable head 1 also moves. In this way, during special playback, the amount of movement of the movable head 1 is preset according to the mode,
By moving the movable head 1, it is possible to accurately trace on the recording track.

[0006]

However, according to such a conventional magnetic recording / reproducing apparatus, since the position of the movable head 1 is not detected, the bimorph element 2 is subject to hysteresis, external vibration, temperature change, or the like. The applied voltage and the head movement amount do not match. Therefore, an error is likely to occur between the target position and the actually moved position, and it is difficult for the movable head 1 to trace the recording track completely. Further, when a signal recorded by using such a movable head is normally reproduced, the error during recording and the error during reproduction are added, and the error becomes double. Therefore, there is a problem that the quality of the reproduced image is significantly deteriorated. Therefore, it is necessary to separately provide a fixed magnetic head instead of a movable type for recording and normal reproduction. Therefore, it is necessary to provide two fixed magnetic heads and two special reproduction magnetic heads on the rotary drum 3, thus increasing the cost of the rotary drum device.

The present invention has been made in view of the problems of the magnetic recording / reproducing apparatus having such a conventional movable head, and the position of the movable head is detected to control the position with high accuracy. A technical problem is to enable normal recording and reproduction without using a fixed head.

[0008]

In order to solve the above problems, a magnetic recording / reproducing apparatus of the present invention comprises a plurality of movable heads mounted on a rotary drum so as to be movable in the axial direction thereof,
A plurality of head moving means for moving the movable head in the axial direction of the rotary drum, and a plurality of conductive members moved by the head moving means at the same time as the movable head,
A plurality of detection coils arranged at a position facing the conductive member, an oscillator for supplying a high frequency current, and a switching means for supplying a high frequency current supplied from the oscillator to one of the detection coils. A plurality of detectors for detecting a change amount due to a change in the inductance of the detection coil depending on a distance between the conductive member and the detection coil; and a plurality of signal holding means for holding an output signal of the detector. Position control means for controlling the position of the movable head by the output of the signal holding means.

Further, according to the present invention, a plurality of movable heads mounted on a rotary drum so as to be movable in the axial direction thereof, a plurality of head moving means for moving the movable heads in the axial direction of the rotary drum, and the heads. A plurality of conductive members that are moved simultaneously with the movable head by a moving unit, a plurality of detection coils arranged at a position facing the conductive members, and a plurality of high-frequency currents of different frequencies to the detection coils. An oscillator, a plurality of detecting a change amount due to a change in inductance of the detection coil depending on a distance between the conductive member and the detection coil, and removing a frequency component of beat generated by interference of high frequency current of the oscillator. A detector and position control means for controlling the position of the movable head by the output of the detector are provided.

[0010]

According to the present invention having the above structure, the high frequency current supplied from the oscillator is supplied to only one detection coil among the plurality of detection coils. Therefore, even if a plurality of detection coils are used, interference of the high frequency current does not occur. A detector can detect only the amount of change that accompanies the change in the inductance of the detection coil that depends on the distance between the conductive member and the detection coil, and a highly accurate position sensor can be configured. By doing so, it becomes possible to continuously detect the position of each conductive member.

Further, according to the present invention, the frequency of the high frequency current supplied to the detection coil is made different for each oscillator, and the beat component generated by the interference of the high frequency current is removed by a filter provided in the detector, so that a plurality of components are obtained. Even if the detection coil is used, it is not affected by the interference of high-frequency current, and the detector detects only the amount of change due to the change in the inductance of the detection coil that depends on the distance between the conductive member and the detection coil. And the position of the conductive member can be continuously detected.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A magnetic recording / reproducing apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a sectional view of a drum of a magnetic recording / reproducing apparatus according to a first embodiment of the present invention. In the present embodiment, the same parts as those in the above-mentioned conventional example are designated by the same reference numerals, and detailed description thereof will be omitted. In the figure, the movable heads 1a,
1b is fixed to two head moving means, for example, tips of bimorph elements 2a and 2b. Bimorph element 2
The a and 2b are fixed to the rotary drum 3 which is rotationally driven at a constant rotational speed, and hold the movable heads 1a and 1b so as to slightly project from the outer peripheral surface of the cylinder of the rotary drum 3. The bimorph elements 2a and 2b are supplied with a driving voltage from the outside through the slip ring 5, and move the movable heads 1a and 1b in the arrow directions. Now, the movable head 1a,
Disc-shaped conductive members 11a and 11b are attached in parallel above 1b. The conductive members 11a and 11b are moving position detection objects made of aluminum having a diameter of 8 mm and a thickness of 1 mm, and are fixed to the tips of the bimorph elements 2a and 2b. Below the rotary drum 3, a fixed drum 4 having the same cylindrical outer peripheral surface as the cylindrical outer peripheral surface of the rotary head 3 is fixed similarly to the conventional example described above. Detection coils 12a and 12b are fixed to the rotary drum 3 at positions facing the conductive members 11a and 11b. Detection coils 12a, 12
b is an inner diameter of 3 m obtained by winding a wire having a diameter of 0.1 mm 16 times.
m, outer diameter 4 mm, and thickness 0.5 mm. During recording and reproduction, the magnetic tape 6 is wound in an oblique direction along the rotary drum 3 and the fixed drum 4, and is driven by a capstan motor and a pinch roller (not shown).

Next, the circuit configuration for detecting the position of this embodiment will be described with reference to the block diagram of FIG. In the figure, an oscillator 21 is an oscillator that oscillates a high frequency of 10 MHz, for example, and its output is the switching circuit 2.
2 to the detection coils 12a and 12b via a resistor. The hot ends of the detection coils 12a and 12b are connected to the detection circuits 23a and 23b, respectively, and the signals thereof are subjected to envelope detection. Detection circuit 23a, 23b
Is held by the sample and hold circuits 24a and 24b, given to the A / D conversion circuits 25a and 25b, and converted into digital signals. A / D conversion circuits 25a and 25
The digital output of b is given to the microprocessor 26 as a position signal and converted into a position signal for controlling the vertical position of the bimorph elements 2a and 2b. This position signal is converted into an analog signal by the D / A conversion circuits 27a and 27b and given to the bimorph drive circuits 28a and 28b. Based on this position signal, the positions of the bimorph elements 2a and 2b are determined via the slip ring 5. To control. In addition, the microprocessor 26 uses the switching circuit 2
2 switching timing and sample hold circuit 24
By controlling the sample and hold timings of a and 24b, the high frequency output of the oscillator 21 is detected by the detection coil 12 for a certain period
a and 12b, and the detection circuit 2 at that time
The outputs of 3a and 23b are sampled and held.

The operation of the magnetic recording / reproducing apparatus having the above structure will be described below. When performing special reproduction such as slow-motion reproduction or quick-motion reproduction, the slip ring 5 is supplied with a control voltage corresponding to the moving amount of the movable heads 1a and 1b which is predetermined for each mode via the bimorph drive circuits 28a and 28b. Is supplied to each bimorph element 2a, 2b. Then, the movable head 1 is deformed by the deformation of the bimorph elements 2a and 2b.
a and 1b will move. At this time, the detection coil 1
High-frequency current is alternately applied to 2a and 12b,
The eddy current changes the inductance of the detection coils 12a and 12b. Since the amount of change in inductance corresponds to the positions of the conductive members 11a and 11b, the detection circuit 2
The positions of the conductive members 11a and 11b, that is, the positions of the movable heads 1a and 1b can be detected by detecting the amount of change in the inductance with 3a and 23b.
At this time, since the high frequency current supplied from the oscillator 21 is supplied to only one of the two detection coils 12a and 12b, interference of the high frequency current does not occur even if a plurality of detection coils are used, and the conductivity is high. It is possible to configure a highly accurate position sensor by detecting only the amount of change due to the change in the inductance of the detection coil, which depends on the distance between the member and the detection coil, by the detection circuits 23a and 23b. Further, by holding the detected position signal by the sample hold circuits 24a and 24b, it becomes possible to continuously detect the positions of the conductive members 11a and 11b, that is, the positions of the movable heads 1a and 1b. The drive amount of each bimorph element 2a, 2b can be corrected based on this position signal, and the bimorph element 2a, 2b corresponding to the drive voltage due to hysteresis of the bimorph element 2a, 2b, external vibration, temperature change, or the like.
By removing the movement error of b, it becomes possible to control the position of each movable head 1a, 1b with respect to the magnetic tape with high accuracy.

Even when recording and normal reproduction are performed, the position of the movable head can be detected with high accuracy by the same operation, and the position of the movable head with respect to the magnetic tape can be kept completely constant. Become.

In the above-mentioned embodiment, the bimorph element is used as the moving means, but the same effect can be obtained by other moving means such as moving magnet type and moving coil type. Also, although two detection coils were used,
Even if three or more detection coils are used, the same effect can be obtained by supplying the high frequency current supplied from the oscillator to only one detection coil among the plurality of detection coils.

(Embodiment 2) Next, a magnetic recording / reproducing apparatus according to a second embodiment of the present invention will be described with reference to the drawings.

The drum device according to the present embodiment is the same as the drum device according to the first embodiment. Detailed description will be omitted, and the circuit configuration for detecting the position according to the present embodiment will be described with reference to the block diagram of FIG. While explaining. In the figure, an oscillator 31a is an oscillator that oscillates a high frequency of 10 MHz, for example, and its output is given to the detection coil 12a via a resistor, while an oscillator 31b is an oscillator that oscillates a high frequency of 9 MHz, and its output Is the detection coil 1
2b through a resistor. Detection coil 12a, 1
The hot end side of 2b is connected to each of the detection circuits 33a and 33b, and the signal is envelope-detected. Further, each of the detection circuits 33a and 33b internally has a frequency of 1 MHz generated by the interference between the high frequency current of the oscillator 31a and the high frequency current of the oscillator 31b.
It has a filter for removing the frequency component of No. 1 and does not detect the beat component generated by the interference of the high frequency current. The outputs of the detection circuits 33a and 33b are given to the A / D conversion circuits 25a and 25b and converted into digital signals. The digital outputs of the A / D conversion circuits 25a and 25b are given to the microprocessor 26 as position signals,
It is converted into a position signal for controlling the vertical position of the bimorph elements 2a, 2b. This position signal is converted into an analog signal by the D / A conversion circuits 27a and 27b and given to the bimorph drive circuits 28a and 28b. Based on this position signal, the positions of the bimorph elements 2a and 2b are determined via the slip ring 5. To control.

The operation of the magnetic recording / reproducing apparatus having the above structure will be described below. When performing special reproduction such as slow-motion reproduction or quick-motion reproduction, the slip ring 5 is supplied with a control voltage corresponding to the moving amount of the movable heads 1a and 1b which is predetermined for each mode via the bimorph drive circuits 28a and 28b. Is supplied to each bimorph element 2a, 2b. Then, the movable head 1 is deformed by the deformation of the bimorph elements 2a and 2b.
a and 1b will move. At this time, the detection coil 1
A high frequency current is applied to 2a and 12b, and the inductance of the detection coils 12a and 12b changes due to the eddy current. The amount of change in inductance is determined by the conductive member 11
Since it corresponds to the positions of a and 11b, the detection circuit 33
The positions of the conductive members 11a and 11b, that is, the positions of the movable heads 1a and 1b can be detected by detecting the amount of change in inductance with a and 33b. At this time, the beat component generated by the interference of the high frequency current supplied to the detection coil is removed by the filter provided in the detector, so that even if the plurality of detection coils 12a and 12b are used, the influence of the interference of the high frequency current is exerted. Instead, the detector can detect only the amount of change due to the change in the inductance of the detection coil depending on the distance between the conductive members 11a and 11b and the detection coils 12a and 12b, and a highly accurate position sensor can be configured. The position of the elastic member can be continuously detected. Bimorph element 2 based on this position signal
It is possible to correct the driving amounts of the a and 2b, and the bimorph elements 2a and 2b with respect to the driving voltage due to hysteresis of the bimorph elements 2a and 2b, external vibration, temperature change and the like.
It becomes possible to control the position of each movable head 1 with respect to the magnetic tape with high accuracy by removing the movement error of.

Even when recording and normal reproduction are performed, the position of the movable head can be detected with high accuracy by the same operation, and the position of the movable head with respect to the magnetic tape can be kept completely constant. Become.

In the above embodiment, the bimorph element is used as the moving means. However, the same effect can be obtained by using other moving means such as a moving magnet system and a moving coil system. Also, although two detection coils were used,
Even if three or more detection coils are used, if the frequency of the high frequency current supplied to each detection coil is different for each oscillator and the detector is equipped with a filter for removing the beat component generated by the interference of the high frequency currents. The same effect can be obtained.

[0023]

As described above, according to the present invention, since the high frequency current supplied from the oscillator is supplied to only one of the plurality of detection coils, the interference of the high frequency current can be achieved even if the plurality of detection coils are used. Does not occur, the detector can detect only the amount of change due to the change in the inductance of the detection coil that depends on the distance between the conductive member and the detection coil, and a highly accurate position sensor can be configured. It is possible to continuously detect the position of each conductive member by holding the. The drive amount of the bimorph element can be corrected based on this position signal, and the movement error of the bimorph element with respect to the drive voltage due to hysteresis of the bimorph element, external vibration, temperature change, etc. is removed, and each movable head for the magnetic tape is removed. The position of can be controlled with high accuracy.

Further, according to the present invention, the frequency of the high frequency current supplied to the detection coil is different for each oscillator,
By removing the beat component generated by the interference of the high frequency current with the filter equipped in the detector, even if multiple detection coils are used, the influence of the interference of the high frequency current does not affect the distance between the conductive member and the detection coil. The detector can detect only the amount of change that accompanies the change in the inductance of the dependent detection coil, so that a highly accurate position sensor can be configured, and the position of the conductive member can be continuously detected. The drive amount of the bimorph element can be corrected based on this position signal, and the movement error of the bimorph element with respect to the drive voltage due to hysteresis of the bimorph element, external vibration, temperature change, etc. is removed, and each movable head for the magnetic tape is removed. The position of can be controlled with high accuracy. Therefore, the same magnetic head can be used for each mode such as recording, normal reproduction, special reproduction, etc., and the effect of reducing the cost of the device can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view of a rotary drum of a magnetic recording / reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration of a position detection circuit according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of a position detection circuit according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a locus of a magnetic head on a magnetic tape.

FIG. 5 is a sectional view of a rotary drum of a conventional magnetic recording / reproducing apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 movable head 2 bimorph element 3 rotating drum 11 conductive member 12 detection coil 21 oscillator 22 switching circuit 23 detection circuit 24 sample hold circuit

Claims (2)

[Claims] 1. A plurality of movable heads attached to a rotary drum so as to be movable in the axial direction thereof, a plurality of head moving means for moving the movable heads in the axial direction of the rotary drum, and the head moving means A plurality of conductive members that move at the same time as the magnetic head; a plurality of detection coils arranged at positions facing the conductive members; an oscillator that supplies a high frequency current; and a high frequency current that is supplied from the oscillator. A switching unit that supplies one of the detection coils to the detection coil; a plurality of detectors that detect a change amount due to a change in the inductance of the detection coil depending on a distance between the conductive member and the detection coil; A plurality of signal holding means for holding the output signal of the detector, and a position control for controlling the position of the magnetic head by the output of the signal holding means Magnetic recording and reproducing apparatus comprising: a stage, a. 2. A plurality of movable heads mounted on a rotary drum so as to be movable in the axial direction thereof, a plurality of head moving means for moving the movable heads in the axial direction of the rotary drum, and the head moving means for moving the heads. A plurality of conductive members that move at the same time as the magnetic head, a plurality of detection coils arranged at a position facing the conductive members, a plurality of oscillators that supply high-frequency currents of different frequencies to the detection coils, A plurality of detectors that detect a change amount due to a change in the inductance of the detection coil depending on the distance between the conductive member and the detection coil, and remove a frequency component of the beat generated by interference of the high frequency current of the oscillator, A magnetic recording / reproducing apparatus comprising: a position control unit that controls the position of the magnetic head according to the output of the detector.