JPH06111261A - Magnetic recording/reproduction device - Google Patents

Abstract

PURPOSE:To retain a magnetic head at a specific position on recording by obtaining the position of the magnetic head accurately. CONSTITUTION:In a VTR where magnetic heads 4a and 4b can be displaced in the direction of a rotary axis 8 of a rotary drum 1 by mounting the magnetic heads 4a and 4b to the rotary drum 1 via electro-mechanical converters 6a and 6b, an electrostatic capacity sensor 7 for detecting the height position in the direction of the rotary shaft 8 of the magnetic heads 4a and 4b and an electrode plate 5 with a specific step in the direction of the rotary shaft 8 are provided and the gain of an electrostatic capacitor sensor 7 is obtained by obtaining the step of an electrode plate 5 by the electrostatic capacity sensor 7. Then, a control circuit for compensating the height position in the direction of the rotary shaft 8 of the magnetic heads 4a and 4b based on the gain is provided.

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 such as a VTR (video tape recorder) having a displaceable magnetic head.

[0002]

2. Description of the Related Art In a VTR in which a magnetic head is mounted on an electro-mechanical converter such as a piezoelectric element and the position of the magnetic head can be controlled during recording, an electro-mechanical converter 91 as shown in FIG.
A strain gauge 92 is attached to the.

The electrical resistance of strain gauge 92 changes with strain. When the tip of the electro-mechanical converter 91 is displaced upward by a from the reference position as shown in FIG. 7A, the indicated value of the resistance meter 93 is R ₁ , and as shown in FIG. When the indicator value of the resistance meter 93 is R _{2 when} it is displaced downward by a from the reference position, the electromechanical converter is adjusted so that the indicator value of the resistance meter 93 becomes (R ₁ + R ₂ ) / 2. If 91 is controlled, the displacement of the electromechanical converter 91 becomes zero as shown in FIG. That is, a magnetic head (not shown) mounted on the electro-mechanical converter 91.
Can be kept at the reference position.

[0004]

However, in the above-mentioned conventional configuration, when the strain-resistance characteristic of the strain gauge 92 changes due to temperature rise or the like, the indicated value of the resistance meter 93 becomes (R ₁ + R ₂ ) / 2. However, even if the control is performed so that the position becomes, the position of the magnetic head deviates from the reference position.

[0005]

In order to solve the above problems, a magnetic recording / reproducing apparatus according to the present invention rotates a magnetic head by mounting the magnetic head on a rotary drum via an electromechanical converter. In a magnetic recording / reproducing apparatus capable of being displaced in the rotation axis direction of a drum, position detection means for detecting the height position of the magnetic head in the rotation axis direction, a reference plate having a predetermined step in the rotation axis direction, and position detection It is characterized in that a correction means is provided for obtaining the detection sensitivity of the position detection means by obtaining the step of the reference plate by means, and correcting the height position of the magnetic head in the rotation axis direction based on the detection sensitivity.

[0006]

According to the above-mentioned structure, the detection sensitivity of the position detection means is obtained by obtaining the step of the reference plate by the position detection means, and the height position of the magnetic head in the rotation axis direction is corrected based on the detection sensitivity. The position of the magnetic head can be accurately obtained even if the detection sensitivity of the position detecting means changes due to temperature rise or the like. This makes it possible to hold the magnetic head at a predetermined position during recording.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The following will describe one embodiment of the present invention with reference to FIGS.

VTR (magnetic recording / reproducing apparatus) of the present embodiment
As shown in FIGS. 1A and 1B, includes a rotary head drum 3 including an upper rotary drum 1 and a lower fixed drum 2. The rotary drum 1 has a magnetic head 4a.
And 4b are arranged 180 degrees, and the magnetic heads 4a and 4b
The electrode plate 5 (reference plate) is arranged at a position of 90 degrees in the middle of b.

The above magnetic heads 4a and 4b are provided with a rotary drum 1 via electro-mechanical converters 6a and 6b such as piezoelectric elements.
Is attached to. Thereby, if a voltage is applied to the electro-mechanical converters 6a and 6b, the magnetic heads 4a and 4b will be
Can be moved in the direction of the rotary shaft 8 of the rotary drum 1.

On the other hand, an electrostatic capacitance sensor 7 (position detecting means) having a fixed electrode (not shown) is attached to the fixed drum 2, and the fixed electrode of the electrostatic capacitance sensor 7 and the above electrode plate. 5 forms one capacitor, and the fixed electrode and the electromechanical converter 6a or 6b described above form another capacitor.

In the present embodiment, as shown in FIG. 2, the upper surface of the fixed electrode of the electrostatic capacity sensor 7 is Ref (reference position) in the direction of the rotating shaft 8 (upward direction in the drawing), and Ref On the other hand, the height of the magnetic heads 4a and 4b can be set to a predetermined value.

The height from Ref to the lower surface of the magnetic head 4a is x ₁ , and the height from the electromechanical transducer 6a to the lower surface is s.
_1, height x ₂ up to the lower surface of the magnetic head 4b, electrical - a height to the lower surface of the transducer 6b and s _2, up to the lower surface of the lower of the electrode plate 5 having a step height s ₃ , S ₄ is the height up to the lower surface. Electro - mechanical converter d ₁ the thickness of 6a, electro - mechanical converter d ₂ the thickness of 6b, when the step of the electrode plate 5 and d _3, the following equation holds.

X ₁ = s ₁ + d ₁ x ₂ = s ₂ + d ₂ s ₄ = s ₃ + d ₃ where d ₁ , d ₂ and d ₃ have been previously measured at the time of manufacture and are known.

Therefore, if s ₁ and s ₂ are measured by the capacitance sensor 7, x ₁ and x ₂ can be obtained.
Further, if s ₃ and s ₄ are measured, the gain of the electrostatic capacity sensor 7 can be obtained as described later. If x ₁ and x ₂ are corrected by this gain, the magnetic head 4a
The position of 4b can be accurately obtained.

The above s ₁ can be obtained by measuring the capacitance of the capacitor formed by the fixed electrode and the electro-mechanical converter 6a by the capacitance sensor 7. Similarly, s ₂ can be obtained by measuring the capacitance of the capacitor formed by the fixed electrode and the electro-mechanical converter 6b with the capacitance sensor 7. Also, s ₃ and s
₄ is formed by the fixed electrode and the electrode plate 5 having a step 2
It can be obtained by measuring the electrostatic capacities of various types of capacitors with the electrostatic capacity sensor 7. The four condensers described above are sequentially switched as the rotary drum 1 rotates.

As shown in FIG. 3, the capacitance sensor 7 includes an AC bridge composed of a high frequency generating circuit E, capacitors C _{1 to} C ₄ and diodes D _{1 to} D ₁ , an operational amplifier 11 and resistors R _{1 to} R _{1. It is} composed of an amplifier composed of ₄ and an LPF (low pass filter) 12. At the output of the operational amplifier 11, the unbalanced component of the AC bridge appears after full-wave rectification. By integrating this with the LPF 12 and amplifying it with the external amplifier 13, the degree of imbalance of the AC bridge can be obtained as the value of the DC voltage. That is, the electrostatic capacity of the capacitor C ₃ can be converted into a DC voltage.

If a capacitor formed by the fixed electrode 7 and the electromechanical converter 6a is used as the capacitor C ₃ , s ₁ can be known from the value of the DC voltage. The same applies to s _{2 to} s ₄ . Therefore,
The heights x ₁ and x ₂ of the magnetic heads 4a and 4b can be known.

FIG. 4 shows a block configuration of a control circuit (correction means) for setting the heights x ₁ and x ₂ of the magnetic heads 4a and 4b to a predetermined value x by using the capacitance sensor 7 described above. Although the capacitance sensor 7 is built in the fixed drum 2 as described above, it is shown as a separate block in the figure for convenience.

[0019] First, the x of d ₁ to d ₃ and the target position from the terminal d is input, d ₁ to d ₃ is calculator 20a, 20b,
17 are respectively stored in memory, and x is an arithmetic unit 21a and 21
It is stored in b.

The output from the capacitance sensor 7 is the amplifier 1
Amplified by 3 and converted into a digital value by an A / D (analog-digital) converter 14. When the rotary drum 1 rotates and the electrode plate 5 comes on the fixed electrode of the electrostatic capacitance sensor 7, the digital values (v ₃ , v ₄ ) are s ₃ , s _4.
And stores them in the registers 15b and 15c, respectively.

The values of the registers 15b and 15c are the arithmetic unit 1
6 and the difference between v ₃ and v ₄ is calculated. This result is given to the calculator 17 and is divided by the value d ₃ stored therein. In other _{words, | v 3 -v 4 | /} d 3 is required. This is the gain (g) of the capacitance sensor 7.
Is shown. That is, the detected voltage per unit distance is shown, and more specifically, the voltage change of 1 μm position change is detected.

When the rotary drum 1 rotates and the magnetic head 4a comes on the fixed electrode of the electrostatic capacity sensor 7, the digital value (denoted as v ₁ ) from the A / D converter 14 corresponds to s _1. It is stored in the register 15a. v ₁
Is given to the arithmetic unit 18, divided by the above-mentioned g, and stored in the register 19a. That is, v ₁ / g = v _{1
· D 3 / | v 3 -v} 4 | is stored. This value (denoted by h) is equal to the height of the electromechanical converter 6a corrected according to the gain (g).

H stored in the register 19a is
D given to the arithmetic unit 20a and stored in the memory
Added to ₁ . That is, this value is x ₁ corrected according to the gain (g).

The calculator 21a obtains the difference between x ₁ and x. Here, if x ₁ > x, a control voltage is applied from the D / A converter 22a to the electromechanical converter 6a so that the magnetic head 4a is displaced downward. If x ₁ <x, a control voltage is applied from the D / A converter 22a to the electromechanical converter 6a so that the magnetic head 4a is displaced upward.

The same applies to the magnetic head 4b. That is, the register 19b, the arithmetic unit 20b, the arithmetic unit 21
b, the D / A converter 22b is the register 1
9a, arithmetic unit 20a, arithmetic unit 21a, D / A converter 22
A control voltage is applied from the D / A converter 22b to the electro-mechanical converter 6b.

By repeating the above operation, the magnetic heads 4a and 4b can be held at the predetermined position x during recording.

As described above, in the present embodiment, the gain (g) of the capacitance sensor 7 is obtained using the electrode plate 5, and this is used to correct the positions of the magnetic heads 4a and 4b. Therefore, the positions of the magnetic heads 4a and 4b can be accurately obtained even if the characteristics of the capacitance sensor 7 change due to temperature rise or the like. Therefore, the positions of the magnetic heads 4a and 4b can be accurately controlled without being affected by the temperature drift.

Therefore, the magnetic heads 4a and 4 of this embodiment are
According to b, accurate recording can be performed even on a narrow recording track.

In the above embodiments, the magnetic heads 4a and 4b are used.
The electrostatic capacity sensor 7 is used as the position detecting means in order to obtain the heights x ₁ and x ₂ of the sensor. However, the present invention is not limited to this, and a sensor that uses a change in eddy current or light reflection is used. A sensor or the like can be used. When using a sensor that utilizes light reflection, a mirror having a step (reference plate) may be used instead of the electrode plate 5.

The VTR corresponding to the present invention is the magnetic head 4
The magnetic heads 4a and 4b are attached to the rotary drum 1 by attaching the a.
In a VTR that can be displaced in the direction of the rotary shaft 8 of the rotary drum 1, a capacitance sensor 7 that detects the height position of the magnetic heads 4a and 4b in the direction of the rotary shaft 8 The gain of the capacitance sensor 7 is obtained by obtaining the step of the electrode plate 5 having a predetermined step and the electrode plate 5 by the capacitance sensor 7, and the direction of the rotation axis 8 of the magnetic heads 4a and 4b is obtained based on the gain. A control circuit is provided to correct the height position of the.

According to this configuration, even if the gain of the capacitance sensor 7 changes due to temperature rise or the like, the magnetic head 4
The positions of a and 4b can be accurately obtained. This makes it possible to hold the magnetic heads 4a and 4b at a predetermined position during recording.

[0032]

As described above, the magnetic recording / reproducing apparatus according to the present invention includes the position detecting means for detecting the height position of the magnetic head in the rotation axis direction and the reference plate having a predetermined step in the rotation axis direction. The position detecting means obtains the detection sensitivity of the position detecting means by obtaining the step of the reference plate, and the correcting means is provided to correct the height position of the magnetic head in the rotation axis direction based on the detecting sensitivity. The detection sensitivity of the position detection means is obtained by obtaining the step of the reference plate by the detection means, and the height position of the magnetic head in the rotation axis direction is corrected based on the detection sensitivity. The position of the magnetic head can be accurately determined even if the position changes. As a result, the magnetic head can be held at a predetermined position during recording.

[Brief description of drawings]

FIG. 1 shows a schematic structure of a rotary head drum of a VTR of the present invention, FIG. 1 (a) is a front view of the rotary head drum, and FIG. 1 (b) is a plan view of the rotary head drum.

FIG. 2 is an explanatory view showing height positions of a magnetic head and an electrode plate of the rotary head drum of FIG.

FIG. 3 is a circuit diagram of the capacitance sensor of FIG.

FIG. 4 is a block diagram of a control circuit that holds the height of a magnetic head at a predetermined position by using the capacitance sensor of FIG.

FIG. 5 shows a conventional example and is an operation explanatory view of an electro-mechanical converter to which a strain gauge is attached.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 rotary drum 2 fixed drum 3 rotary head drum 4a magnetic head 4b magnetic head 5 electrode plate (reference plate) 6a electric-mechanical converter 6b electric-mechanical converter 7 electrostatic capacity sensor (position detecting means) 21a calculator (correction) Means) 21b Operation unit (correction means) 22a D / A converter 22b D / A converter

Claims (1)

[Claims] 1. A magnetic recording / reproducing apparatus in which a magnetic head is mounted on a rotary drum via an electromechanical converter so that the magnetic head can be displaced in the rotary axis direction of the rotary drum. Position detection means for detecting the height position of the reference plate, a reference plate having a predetermined step in the direction of the rotation axis, and the detection sensitivity of the position detection means by obtaining the step of the reference plate by the position detection means. A magnetic recording / reproducing apparatus comprising: a correction unit that corrects the height position of the magnetic head in the rotation axis direction.