JPH05225540A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To exactly control the position of a movable head provided freely and movably in the axial direction of a rotary drum in a magnetic recording and reproducing device such as a video tape recoder. CONSTITUTION:The position of a fan-shaped member 11 is continuously detected by detecting the position of the fan-shaped member 11 having the origin of a center angle coinciding with the rotational center of the rotary drum 3 by plural position sensors disposed so that a part of the fan-shaped member 11 is opposite to at least one or more than the position sensors 12. Also, by storing the quantity of the inclination of the fan-shaped member 11 to a rotational plane and correcting the position output of the position sensors 12 corresponding to the quantity of the inclination, position sensors with high accuracy are constituted and the position of the magnetic head 1 is controlled with high accuracy.

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 a moving means for moving a magnetic head provided on a rotary drum in a direction perpendicular to a recording track of a magnetic tape.

[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. 5 is a diagram showing the recording tracks on the magnetic tape and the loci of the magnetic head. In this figure, recording tracks 102 are 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. The locus of the 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 traveling speed changes and, for example, the speed vector of the tape becomes four times as shown by 106, a head composed of the speed vector 106 of the magnetic tape 101 and the speed vector of the magnetic head by the rotating drum. Locus 10
It becomes 7. 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. 6 is a sectional view showing a drum device as an example of a magnetic recording / reproducing apparatus 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. The bimorph element 2 is supplied with a driving voltage from the outside through the 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, etc. The applied voltage and the head movement amount do not match. Therefore, an error easily occurs between the target position and the actually moved position, and the movable head 1
However, it was difficult to completely trace on the recording track. 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, there are two fixed magnetic heads and two special reproduction magnetic heads.
It is necessary to provide a total of four on the rotary drum 3, one by one, which has a drawback that the cost of the rotary drum device increases.

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 rotary drum, a magnetic head attached to the rotary drum, and head moving means for moving the magnetic head in a direction orthogonal to a recording track. A fan-shaped member which is moved by the head moving means at the same time as the magnetic head, and has a rotation center of the rotating drum and an origin of a center angle,
A storage unit that stores the amount of inclination of the fan-shaped member with respect to the rotation surface of the rotary drum, and a fixed member fixed on the fixed drum. While the rotary drum is rotating, a part of the fan-shaped member faces at least one position sensor. A plurality of position sensors arranged as described above, a correction unit that corrects the position output of the position sensor according to the tilt amount of the storage unit, a signal combining unit that combines the output signals of the position sensor, and the signal combining unit. Position control means for controlling the position of the magnetic head according to the output of the means.

[0009]

According to the present invention, with the above structure, the fan-shaped member is arranged so that the origin of the central angle of the fan-shaped member and the center of rotation of the rotary drum coincide with each other, and a part of the fan-shaped member serves as at least one position sensor. Since the plurality of position sensors are arranged so as to face each other, it is possible to always detect the position of the fan-shaped member even if the rotary drum rotates. Further, by storing the inclination amount of the fan-shaped member with respect to the rotation surface of the rotating drum and correcting the inclination amount by the correction means,
The output of the position sensor is not affected by the inclination of the fan-shaped member with respect to the rotation surface at all, and a highly accurate position output can be obtained. At this time, since the fan-shaped member is rotating at the same time as the magnetic head, the movement amount of the fan-shaped member is equal to the movement amount of the magnetic head, and the position output can be used to control the position of the magnetic head with high accuracy. Becomes

Therefore, the position of the rotating magnetic head is directly detected by the position sensor fixed to the fixed drum without using a transmission means such as a slip ring, and the disturbance of the sensor output in the transmission path is mixed. It is possible to obtain a highly accurate position output that is highly accurate and reliable, and it is possible to control the position of the magnetic head with high accuracy.

[0011]

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.

FIG. 1 is a sectional view of a drum of a magnetic recording / reproducing apparatus according to an 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 magnetic head 1 is fixed to a head moving means, for example, the tip of a bimorph element 2.
The bimorph element 2 is fixed to a rotary drum 3 which is rotationally driven at a constant rotation speed, and holds the magnetic head 1 so as to slightly project from the outer peripheral surface of the cylinder of the rotary drum 3. The bimorph element 2 is provided with a drive voltage from the outside through the slip ring 5, and moves the magnetic head 1 in the arrow direction. Below the magnetic head 1, as shown in the bottom view of the movable portion in FIG. 2, a pair of fan-shaped fan-shaped members 11a,
11b is attached in parallel to the upper surface of the fixed drum 4.
The fan-shaped member 11 has a central angle of 90 °, a width of 6 mm, and a thickness of 1 m.
m moving position detectors made of aluminum, each fixed to the tip of the bimorph element 2. Below the rotary drum 3, similar to the above-mentioned conventional example, the rotary drum 3 is provided.
Fixed drum 4 having the same cylindrical outer peripheral surface as that of
Is fixed. At a position facing the fan-shaped member 11 of the fixed drum 4, a plurality of, for example, six position sensors 12a to 12a.
12f is provided. The position sensor 12 is an eddy current sensor that detects a change in magnetism, and has a wire diameter of 0.1 mm, for example.
The wire is wound 16 times and has an inner diameter of 3 mm, an outer diameter of 4 mm, and a thickness of 0.5 mm. These position sensors 12a to 12f are arranged at equal intervals along the loci of the fan-shaped members 11a and 11b as illustrated. 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). Further, as shown in FIG. 2, a fixed detected body 13 is provided at a position having the same distance from the center as the fan-shaped member 11 of the rotary drum 3. The detected object 13 is the fan-shaped member 1
It is made of the same material as 1a and 11b and is fixed to the rotary drum 3.

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 given to six position sensors 12a to 12f in parallel via resistors. The hot end sides of the position sensors 12a to 12f are the detection circuits 22 respectively.
It is connected to, and envelope-detects the signal. The output of the detection circuit 22 is given to the synthesis circuit 23, and is output as a continuous position output. The output of the synthesis circuit 23 is given to the A / D conversion circuit 24 and converted into a digital signal. The digital output of the A / D conversion circuit 24 is given to the microprocessor 25 as a position signal. The inclination amount of the fan-shaped member with respect to the rotation surface of the rotary drum 3 is stored in advance in the memory circuit 26 inside the microprocessor 25, and after the inclination amount is corrected by the microprocessor 25, the vertical position of the bimorph element 2 is stored. Is converted into a position signal for controlling. This position signal is the D / A conversion circuit 2
It is converted into an analog signal by 7 and given to the bimorph element drive circuit 28, and the position of the bimorph element 2 is controlled through the slip ring 5 based on this position signal.

The operation of the magnetic recording / reproducing apparatus having the above structure will be described below.

When special reproduction such as slow motion reproduction or quick motion reproduction is performed, a control voltage corresponding to the movement amount of the magnetic head 1 which is predetermined for each mode is set so that the recording track is completely traced. It is supplied to the bimorph element 2 from the bimorph element drive circuit 28 via the slip ring 5. Then, the magnetic head 1 is moved by the deformation of the bimorph element 2. A high-frequency current is applied to the position sensor 12, and the fan-shaped member 1
Since 1 is conductive, an eddy current is generated, and the eddy current changes the inductance of the position sensor 12. Since the amount of change in inductance corresponds to the position of the fan-shaped member 11, the amount of change in inductance is detected by the detection circuit 22 and a voltage output is obtained. Although the rotary drum 3 is rotating, the fan-shaped member 11 faces at least one of the six position sensors 12, so
The output of each position sensor 12 is combined with the position output by the combining circuit 23 every time the movement is performed by 0 °, and the fan-shaped member 1 is combined in the entire range.
One position signal can be obtained. The inclination amount of the fan-shaped member with respect to the rotation surface of the rotary drum 3 is stored in advance in the storage circuit 26 inside the microprocessor 25,
By correcting this tilt amount by the microprocessor 25, the position output of the position sensor 12 is not affected by the tilt of the fan-shaped member 11 with respect to the rotation surface at all, and highly accurate position output can be obtained, and the fan-shaped position with respect to the rotation surface is obtained. The allowable value at the time of attaching the member 11 can be increased, and the assembly can be performed by a simple work.

Further, in order to improve the accuracy of the position output, the position output value of the detected object 13 is stored in the memory circuit 26 of the microprocessor 25 for each position sensor 12, and this output value is used as the reference position output value. It is also possible to correct the detection sensitivity of the position output of each position sensor 12 or the absolute position output so as to eliminate the influence of the output change due to disturbance such as temperature change. In this case, as shown in FIG. 4, the position output of one position sensor 12 during one rotation is detected in the order of the fan-shaped member 11a, the detected body 13, and the fan-shaped member 11b. When the position output is combined with, the position output of the detected object 13 is combined so as to be output, the output level of the detected object 13 is stored in the memory circuit 26 of the microprocessor 25, and this output value is used as the reference position output value. Then, the position output of each position sensor 12 can be corrected.

Similarly, when recording and normal reproduction are performed, the position of the magnetic head 1 with respect to the magnetic tape 6 is kept constant by highly accurately detecting the position of the magnetic head 1 and driving the bimorph element 2. You can

In the above embodiment, the bimorph element is used as the moving means for moving the magnetic head. However, the same effect can be obtained by other moving means such as a moving magnet system or a moving coil system. An eddy current type position sensor was used as the position sensor.
Even with an optical position sensor using a laser beam or the like, the same effect can be obtained as long as the position of the fan member can be detected.

Further, although only one detected object is used, a plurality of detected objects having different heights are used to correct the signal level and sensitivity of each position sensor by the position output of each point, thereby further improving the accuracy. Moreover, it becomes possible to detect the position of the magnetic head. Further, by setting the position of the detected object so that the position output of the magnetic head for recording and normal reproduction is the same as the position output of the detected object, the position of the magnetic head can be detected with higher accuracy. It becomes possible to do.
Further, if the material of the rotary drum and the material of the fan-shaped member are the same, the rotary drum and the object to be detected can be integrated, and the height of the object to be detected can be processed with high accuracy. At the same time, cost reduction can be achieved.

[0020]

As described above, according to the present invention, a rotating drum, a magnetic head attached to the rotating drum,
A head moving unit that allows the magnetic head to move in a direction orthogonal to a recording track; and a fan-shaped member that is moved by the head moving unit at the same time as the magnetic head so that the rotation center of the rotating drum coincides with the origin of the central angle. A storage unit that stores the amount of inclination of the fan-shaped member with respect to the rotation surface of the rotary drum, and a fixed member fixed on the fixed drum. While the rotary drum is rotating, a part of the fan-shaped member faces at least one position sensor. A plurality of position sensors arranged as described above, a correction unit that corrects the position output of the position sensor according to the tilt amount of the storage unit, a signal combining unit that combines the output signals of the position sensor, and the signal combining unit. By providing position control means for controlling the position of the magnetic head according to the output of the means, the origin of the central angle of the fan-shaped member and the rotation center of the rotary drum are provided. The fan-shaped members are arranged so that they coincide with each other, and a plurality of position sensors are arranged so that a part of the fan-shaped members faces at least one or more position sensors. It becomes possible to always detect the position of the member. Further, by storing the inclination amount of the fan-shaped member with respect to the rotation surface of the rotary drum and correcting the inclination amount by the correction means, the output of the position sensor is not affected by the inclination of the fan-shaped member with respect to the rotation surface and is high. An accurate position output can be obtained. At this time, since the fan-shaped member is rotating at the same time as the magnetic head,
The moving amount of the fan-shaped member is equal to the moving amount of the magnetic head, and the position output can be used to control the position of the magnetic head with high accuracy.

Therefore, the position of the rotating magnetic head is directly detected by the position sensor fixed to the fixed drum without using a transmission means such as a slip ring, and the disturbance of the sensor output in the transmission path is mixed. It is possible to obtain a highly accurate position output that is highly accurate and reliable, and it is possible to control the position of the magnetic head with high accuracy. Further, 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 plan view showing a positional relationship between a fan-shaped member and a position sensor according to this embodiment.

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

FIG. 4 is an output waveform diagram of the position sensor of this embodiment.

FIG. 5 is an explanatory diagram showing a locus of a magnetic head on a magnetic tape.

FIG. 6 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 4 fixed drum 6 magnetic tape 11 fan-shaped member 12 detection coil 13 detected object 21 oscillator 22 detection circuit 23 synthesis circuit 25 microprocessor 26 memory circuit 28 bimorph drive circuit

Claims (2)

[Claims] 1. A rotary drum, a magnetic head attached to the rotary drum, a head moving means for moving the magnetic head in a direction orthogonal to a recording track, and a head moving means for simultaneously moving the magnetic head. A fan-shaped member whose center of rotation coincides with the origin of the center angle, storage means for storing the amount of inclination of the fan-shaped member with respect to the rotational surface of the rotary drum, and the rotary drum fixed on the fixed drum. During the rotation, a plurality of position sensors are arranged so that a part of the fan-shaped member faces at least one or more position sensors, and the position sensor of the position sensor is stored according to the inclination amount of the fan-shaped member stored in the storage unit. A correction unit that corrects the position output, a signal combining unit that combines the output signals of the position sensor, and an output of the signal combining unit Magnetic recording and reproducing apparatus having a position control means for controlling the position of the head, the. 2. The magnetic recording / reproducing apparatus according to claim 1, further comprising a detected body for correcting the position output of the position sensor, which is provided on the rotary drum.