JPS59229762A - Tension controllr for magnetic tape device - Google Patents

Abstract

PURPOSE:To perform the adequate control of tension with a magnetic tape without receiving the effect of a reel winding diameter of the tape and with no secular change, by applying the braking force to the supply side of the tape with an electromagnetic brake. CONSTITUTION:A piezoelectric ceramic 26 serving as a pressure detecting means is provided between head cores 18 and 19 via a slight gap 24. A bounded guide part 16 applies the braking force corresponding to the output signal value fed from a power amplifier 48 to a rotary cylinder 70. As a result, the tension of a magnetic tape 10 is always controlled by servo to the set value at the part of a magnetic head 12. Thus the head 12 can record and reproduce an accurate signal to the tape 10. Thus no effect is exerted from the winding diameter and the disturbance winding state of the tape 10. In such a way, the mechanical wear and the secular change of the tape tension is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a tension control device for a magnetic tape device, which is used in a recording/reproducing device using a magnetic tape, such as a tape recorder, and is used to control the tension of the magnetic tape.

[Background Art] Magnetic tape tension control in conventional tape recorders, etc. detects the tension in the middle part of the magnetic tape between the supply side reel and the magnetic head, and then adjusts the supply side reel based on this detected tension value. The band brake provides frictional resistance to control tape tension.

(See, for example, Japanese Patent Publication No. 58-5464).

As described above, in the conventional tension control device, since the tension is controlled at a location away from the magnetic head, there is a large time lag between tension control at the magnetic head, which is the recording/reproducing location of the magnetic tape. In addition, when the brake force is applied to the supply reel, the magnetic tape tension changes depending on the winding diameter of the magnetic tape on the reel and the influence of irregular winding.Furthermore, in the case of a band brake, the tape tension changes over time due to wear of the drum, which is the friction surface.

[Object of the Invention] Taking the above facts into consideration, the present invention provides a magnetic tape that is not affected by the winding diameter of the magnetic tape, does not change over time, and can accurately control the tension in the magnetic head portion of the magnetic tape. The purpose is to obtain a tension control device for equipment.

[Structure of the Invention] In the tension control device for a magnetic tape device according to the present invention, a pinch roller is pressed against a rotating sill around which the supply side of the magnetic tape is wound to pinch the magnetic tape, and an electromagnetic brake is applied according to a detected tension value. Said.

Accurate tension control is achieved by applying braking force to the rotating cylinder.

[Embodiments of the Invention] FIG. 1 shows a tape recorder to which the present invention is applied. The middle part of the magnetic tape IO is wound around the magnetic head 12, one end is wound onto a pick-up reel (not shown) via a capstan drive unit 14, and the other end is wound through a restraining guide unit 16 (not shown). It is wound onto the supply reel. - As shown in FIG. 2, the magnetic head 12 includes a pair of helad cores 18 and 19 fixed at appropriate intervals to a head base 20 by screws 22, and the head base 20 is fixed to a chassis (not shown). As a result, the head cores 18 and 19 form a magnetic loop including the magnetic tape 10 when energized, and record and reproduce information between them and the magnetic tape IO.

A piezoelectric ceramic 26 serving as pressure detection means is provided between the head cores 18 and 19 with a slight gap 24 interposed therebetween. The tip of this piezoelectric ceramic 26 is the head core 1.
Together with 8 and 19, it forms a smooth arc shape and becomes the contact surface of the magnetic tape 10. Moreover, the base of this piezoelectric ceramic 26 protrudes from between the helad cores 18 and 19, and
It is fixed to one side of the metal fitting 28. This L u metal fitting 28
The other side is fixed to the head base 20 with screws 30.

The piezoelectric ceramic 26 is grounded on one side by a lead wire 32, and the other side is connected via a lead wire 34 to an amplifier 36 shown in FIG.

The piezoelectric ceramic 26 is therefore subjected to pressure parallel to the surface to which the leads 32, 34 are connected and a charge Q is generated. This charge Q is Q=d(sentence/1) ・F ・1 (1)
Here, d [C/N] is the piezoelectric constant of the piezoelectric ceramic, E is the length and thickness of the piezoelectric ceramic 26, and F is the applied pressure. Also piezoelectric ceramic 2
Capacitance C [F] when no pressure is applied to 6
is C=εT(W sentence/1) (2), where ε[F/m] is the stress-free dielectric constant and W is the piezoelectric ceramic 2
The width dimension is 6.

Therefore, assuming that the electromechanical coupling coefficient of the voltage V [v] between the lead wires 32 and 34 is extremely small, V=Q/C= (
d/C)-(1/w) ・F-g(1/W)@F
1.(3), where g [V 9m/N] is the voltage output coefficient of the piezoelectric ceramic element.

This voltage is amplified by an amplifier 36,
The amplifier 36 includes a tension signal calibrator 40 and a low-pass filter 4.
2 is connected, and the output side of the low-pass filter 42 is connected to one input side of the differential amplifier 44, and the output side of the low-pass filter 42 is connected to one input side of the differential amplifier 44.
4 is connected to one end of a comparison reference voltage 46 whose other end is grounded. The output side of this differential amplifier 44 is connected to the input side of a power amplifier 48, and the output side of the power amplifier 48 is connected to an electromagnetic brake coil 50 whose other end is grounded.

In the capstan drive unit 14, the magnetic tape 10 is wound around a capstan 54 driven by a capstan motor 52, and the magnetic tape 10 is moved at a constant speed in the direction of arrow A.
It is designed to be driven in the direction. This capstan 5
A take-up side pinch roller 56 is disposed on the opposite side of the Bi-air tape 10 wrapped around the 4. This take-up side pinch roller 56 is pivotally supported via a pin 58 to an arm 60, and this arm 60 is pivotally supported to a chassis 64 via a pin 62. A tension coil spring 66 is interposed between the arm 60 and the chassis 64.
As a result, the take-up side pinch roller 56 presses the magnetic tape 10 onto the capstan 54 and presses the 1 m tape 10 onto the capstan 54.
A tensile force is applied in the direction of arrow A.

The restraining guide part 16 has a chassis 6 as shown in FIG.
Rotating cylinder 707 to fixed shaft 68 fixed to 4
5 (＠ll supported. This rotating cylinder 70 has a cylindrical shape, and both ends in the axial direction abut against a striker 72 attached to the fixed shaft 68, so that movement in the axial direction is restrained. This rotation An intermediate portion of the magnetic tape IO is wound around the cylinder 70, and a supply-side pinch roller 74 is disposed via the magnetic tape IO in the same manner as on the pick-up side.

This supply side pinch roller 74 is connected to the arm 7 by a pin 76.
8, and the arm 78 is attached to the chassis by a bin 80.
It is pivoted at 64. Furthermore, the arm 78 is connected to the chassis 6.
A tension coil spring 82 is interposed between the supply-side pinch roller 74 and the supply-side pinch roller 74 to press the magnetic tape IO to the rotating cylinder 70. As a result, the supply side pinch low shift 4 is rotated by the tape driving force, and the supply side pinch roller 74 is pressed against the rotating cylinder 70, thereby generating a tape driving force.

As shown in FIG. 4, a large diameter portion 84 with an enlarged outer shape is fixed to one axial end of the rotating cylinder 70, and the front and back surfaces of this large diameter portion 84 correspond to the tip of the yoke B6. There is. An electromagnetic brake coil 50 is wound around this yoke 86. Therefore, the yoke 86 and the electromagnetic brake coil 50 constitute an electromagnetic brake, and the braking force applied to the rotary cylinder 70 changes according to the current value applied to the electromagnetic brake coil 50.

Next, the operation of this embodiment will be explained.

The capstan motor 52 rotates the capstan 54, so the magnetic tape 10 moves in the direction of arrow A while being held between the capstan 54 and the take-up side pinch roller 56.
Receives driving force in the direction. In the magnetic head 12 part, the magnetic tape lO moves while being in contact with the winding angle 2β.
A compressive force (F=2Tsi
nβ) acts. A corresponding compressive force acts on the piezoelectric ceramic 26 as a gap spacer sandwiched between the head cores 18 and 19, and a charge Q proportional to this compressive force is generated. Therefore, a corresponding voltage is generated between the lead wires 32 and 34, this voltage is amplified by the amplifier 36, and the tension signal calibrator 40 performs voltage calibration proportional to the tape tension.

A low-pass filter 42 blocks high frequency components.

The output signal value from the low-pass filter n42 is output to the differential amplifier 44.
, it is compared with a comparison reference voltage 46 corresponding to the reference tape tension, the voltage difference is amplified by a power amplifier 48 , and a current proportional to the potential difference is supplied to the electromagnetic brake coil 50 .

As a result, the restraint guide section 16 applies a braking force to the rotary cylinder 70 in accordance with the output signal value from the power increase #A device 48. As a result, the tension of the magnetic tape 10 in the magnetic head 12 portion is always servo-controlled to the set value, and the magnetic head 12 can accurately record and reproduce signals on the AI tape 10.

In this embodiment, since the tape tension is detected particularly at the magnetic part 7112, the magnetic head 12 records and reproduces signals on the magnetic tape 10 at the same place, and there is no time difference. Since the rotating cylinder 70 that applies a binding force to the magnetic tape l has a structure that applies tension at a portion closer to the magnetic head 12 than the supply reel, the rotating cylinder 70 also has an influence up to the supply reel (not shown).
For example, it is not affected by the winding diameter of the magnetic tape on the supply reel and the irregular winding state of the magnetic tape, and there is little time lag in recording and reproducing on the magnetic head 12.
Furthermore, in this embodiment, an electromagnetic brake consisting of an electromagnetic brake coil 50 and a yoke 86 is used as the tension applying means, so there is no mechanical wear and there is no change in tape tension over time.

FIG. 5 shows a magnetic head 1 according to an FF12 embodiment of the present invention.
A two-part tension sensing structure is shown. In this embodiment, the helad core 18, 19 is fixed to the middle part of the piezoelectric ceramic 26, and both ends of the piezoelectric ceramic 26 are abutted against a block 88, 89, and are fixed to this block 88, 89 with screws 9o. Tips of clamps 91,92 press these ends against blocks 88,89.

The piezoelectric ceramic 26 has a two-layer structure, the junction of the two layers is grounded by a lead wire 94, and the front and back surfaces are connected to an amplifier. Therefore, in this embodiment, the piezoelectric ceramic 26 which is subjected to a compressive force due to the tape tension receives this compressive force in the longitudinal direction to generate a bending stress, and a voltage proportional to this bending stress is generated.

Therefore, in this embodiment, as in the previous embodiment, the tape tension force in the magnetic head 12 portion can be detected reliably and accurately.

Although the above embodiment shows a structure in which the tape tension is detected in the magnetic head part, the tension detection according to the present invention is not limited to the magnetic head part, but can be performed in other places, for example, in the magnetic tape on the supply side, at right angles to the longitudinal direction of the MfIB. Detection is also possible by providing a tension arm that biases in the direction.

Further, in the above embodiment, the present invention is applied to magnetic tape tension control of a tape recorder, but the present invention is also applicable to other magnetic tape devices such as a video tape recorder.

[Effects of the Invention] As explained above, in the magnetic tape a-tension control device according to the present invention, since the electromagnetic brake applies braking force to the supply side of the magnetic tape, it is not affected by the reel winding diameter of the magnetic tape. Therefore, it becomes possible to perform appropriate magnetic tape tension control without any deterioration over time.

[Brief explanation of drawings]

FIG. 1 is a plan view showing a cheap record to which the first embodiment of the present invention is applied, FIG. 2 is a partially enlarged view of FIG. 1, and FIG.
4 is a sectional view showing an electromagnetic brake portion, and FIG. 5 is an enlarged view showing a magnetic head portion according to the Mtj2 embodiment of the present invention. lO...Magnetic tape, 12.1 Magnetic head 14...
・Kirpustan drive unit, 26...Piezoelectric ceramic, 50...Brake coil, 70...Rotating cylinder, 74・＠ψ pinch roller, 86・Flash Φ yoke. Applicant: Trio Co., Ltd.

Claims (1)

[Claims] (1) A capstan drive unit that clamps the pick-up side of the magnetic tape and applies a tensile force, a tension detection means that detects the tension due to the tensile force of the magnetic tape, and a rotating cylinder around which the supply side of the magnetic tape is wound. A tension control device for a magnetic tape device, comprising: a pinch roller that presses the magnetic tape against the rotating cylinder; and an electromagnetic brake that applies a braking force to the rotating cylinder in accordance with the detected tension value.