JPS58201041A - Device for detecting tension of tape - Google Patents

Abstract

PURPOSE:To expand a detectable range by providing the titled device with permanent magnet fitted to a tension arm moving part, plural magnetic flux sensing elements spaced in the moving direction and a detecting circuit to detect the tension of a tape from the output of said element. CONSTITUTION:The permanent magnets 8, 9 are fitted to the moving part 1' of the tension arm 1 mounted on the surface of a travelling base freely rotating around the revolving shaft 7 and engaged with a magnetic tape 2. H 1 elements 15, 16 as the magnetic flux sensing elements are connected in parallel and with a spacing on the travelling base surface opposed to the surface on which the permanent magnets 8, 9 are moved in accordance with the movement of the arm 1 in the moving direction of the magnets 8, 9, and the output terminals of the elements 15, 16 are connected to amplifiers 17, 18 respectively. The outputs of the amplifiers 17, 18 are added by an adder 19.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tape tension detection device, and more particularly to a tape tension detection mydriasis in a magnetic tape running device that controls the tension of a magnetic tape to be constant during running of the magnetic tape.

FIG. 1 is an example of a conventional tape tension detection device. 1st
The outline of the tape tension detection device will be explained with reference to the drawings.

One end of the tension arm 1 is rotatably attached to the running base surface by a rotating shaft 7. A tension post 3 is provided on the upper surface of the other end of the tension arm 1, and a magnetic tape 2 is hung on the tension post 3.

A force is applied to the tension post on which the magnetic tape 2 is hung in one direction due to the tension of the magnetic tape 2, and as a result, the tension arm 1 rotates about the rotating shaft 7. Tension arm movable part 1 near the center of tension arm 1
' is engaged with one end of a spring 4, and the other end of the spring 4 is engaged with a shaft protruding from the running base surface, and the tension of this spring 4 is applied to the magnetic field applied to the tension post 3. The tension of the tape 2 prevents the tension arm 1 from freely rotating. That is, the tension arm 1 stands still at a position where the force of the tension of the magnetic tape 2 acting on the tension post 3 to rotate the tension arm 1 and the tension of the spring 4 are balanced.

A permanent magnet 5 is attached to the lower surface of the movable part 1' of the tension arm 1.
Further, a magnetic flux sensing element 6 is fixed to the running base surface facing the permanent magnet 5. When the tension of the magnetic tape 2 changes and the position of the tension arm 1 changes, the permanent magnet 5 disposed in the movable part 1' and the magnetic flux sensing element 6 fixed to the running base surface facing the permanent magnet 5
As the distance from the tension arm 1 changes, the magnetic flux density that the permanent magnet 5 gives to the magnetic flux sensing element 6 changes. It can be detected.

FIG. 4 is an example of a tape tension detection device W1 (7) using a Hall element as the magnetic flux sensing element 6 shown in FIG. The principle of the conventional tape tension detection device will be explained in detail with reference mainly to FIG.

In FIG. 4, two permanent magnets 8 and 9 are attached to the lower surface of the tension arm movable part 1' in the same direction as the rotation direction in which the movable part 1' rotates around a rotation axis (not shown in FIG. 4). is located.

The permanent magnets 8 and 9 are arranged so that their magnetization direction is perpendicular to the plane created by the movement of the movable part 1' of the tension arm, and the polarity of the permanent magnets 8 and 9 is It's reversed. Permanent magnet 8.9
A Hall element 10 is fixed on the running base surface facing the terminal 1 from the terminal 11 of the Hall element 10.
2 is supplied with a supply current l. In this way, if a supply current is passed through the Hall element 10, it will receive magnetic flux from the permanent magnets 8 and 9, as is clear from the properties of the Hall element, and a voltage will be generated between the output terminals 13 and 14 of the Hall element 10. A potential difference E is generated depending on the magnetic flux density.

By the way, as mentioned above, the tension arm movable section 1' rotates around the rotation axis (not shown) in response to changes in the tape tension, so the positions of the permanent magnets 8 and 9 provided in the tension arm movable section 1' vary. also changes. As a result, the magnetic flux that the Hall element 10 receives from the permanent magnets 8 and 9 changes. Now, we will first examine how the magnetic flux given to the Hall element 10 by the permanent magnets 8 and 9 changes.

For simplicity, the movement 5- of the tension arm movable part 1' is assumed to be a straight line, the direction of movement is taken as the x-axis, and the direction perpendicularly intersecting the plane created by the movement of the movable part 1' of the tension arm 1 is taken as the y-axis. In this orthogonal coordinate, the origin is set as the center of the Hall element 10.

At this time, the magnetic flux given to the Hall element 10 by the permanent magnet 8.9 has a magnetic charge Qm l-Qm whose magnetization direction is parallel to the y-axis and whose magnetization directions are opposite to each other, as shown in FIG. It can be expressed as the y-axis component HV of the magnetic field created at the origin O by a pair of magnetic dipoles M1 and M2.

Let the y-coordinates of both ends of the pair of magnetic dipoles M and M2 be Ω and g +t, respectively, and let the x-coordinates of the magnetic dipoles M and M2 be X-XQ and X+XQ, respectively, so that this pair of magnetic dipoles is Assume that it moves in parallel in the axial direction. Assuming that the y-axis component of the magnetic field created by the magnetic dipole M at the origin O is H+V+the y-axis component of the magnetic field created at the magnetic dipole origin 2O is HzV, Hly and H2V are expressed by the following equations.

H+V-(Qm-g)/(x-XO)2+<12)+Q
Il (0+t)/((x-XQ)26- →-(o+t)2)... (1
)H2V-(Qllll-(1)/((X+XO)2+
! ;I 2 )+ (, -Qn+ (o +t
) ) /((X +X o ) 2
+ (0+t) 2)... (2) Therefore, if Hy is the y-axis component of the magnetic field created at the origin of the pair of magnetic dipoles Ml and M2, then Hy -H+ V +H
2V...(3).

Figure 3 is a graph when the value of x in equations (1), (2>, and (3) is sequentially changed from minus to plus.In other words, the pair of magnetic dipoles M1 and M2 is It is a graph showing a change in the composite magnetic field HV due to a pair of magnetic dipoles M, M2 at the origin 0 when moving in parallel in the axial direction.

From the graph shown in FIG. 3, changes in the magnetic flux applied to the Hall element 10 of the permanent magnets 8 and 9 shown in FIG. 4 could be determined.

By the way, we have seen how the magnetic flux received by the Hall element 10 changes with the movement of the permanent magnets 8 and 9 arranged in the tension arm movable part 1-, in other words, with the movement of the tension arm 1. The Hall element 10 changes in response to changes in magnetic flux due to the properties of 10.
Unless the change in the potential difference E between the output terminals 13 and 14 corresponds one-to-one to the change in the magnetic flux, the amount of movement of the tension arm cannot be measured. That is, in the tape tension detection device, the position of the tension arm and the output of the detector need to correspond one-to-one. Then, in the characteristic diagram shown in Figure 3, if you use the areas outside each of the two peaks on the left and right, or if you use the area between the two peaks, the change in magnetic flux and the position of the tension arm can be matched in a single pair. This corresponds to 1. In general, the region between the two peaks is used for the purpose of making the device compact and because it allows a wide dynamic range of the detection output.

However, using the region between the two peaks has the disadvantage that the range of movement of the tension arm 1 is limited. That is, as is clearer from FIG. 5, which is an actual measurement example, when the rotation angle of the movable part 1' of the tension arm is θ in FIG. 4, and the potential difference between the output terminals 13 and 14 of the Hall element 10 is E. The area between the two output peaks is only 20' when expressed as the rotation angle of the movable part 1' of the tension arm, and it can only be used as a tape tension detection device within this 20° range.

Specifically, since the movable range of the rotation angle of the tension arm movable section 1' is limited to within 20 degrees, when feedback control of the tape tension is performed using the output of the tape tension detection device of this example, the tension arm 1 If the tension arm rotates more than 10 degrees from the center position,
The situation is now out of control.

By the way, in Fig. 2, Qm, Q, and t are fixed, and xo is expressed as Xo = O, Xo -5/4Q, Xo
-2g, a pair of magnetic dipoles IVl+
The magnitude of the y-axis component of the strength of the magnetic field that the origin 0 receives due to the movement of +M2 in the X-axis direction is calculated and graphed as shown in FIG. 6. As shown in FIG. 6, by increasing the distance between the pair of magnetic dipoles M+ and Mz, the region between the two peaks can be expanded without impairing the dynamic range of the output.

In addition, in tape tension control, it is sufficient that the y-axis component of the magnetic field strength has linearity near the normal operating point (near the origin O in Fig. 6), and it is sufficient for any of the characteristic curves in Fig. 6 to have linearity. There is no problem even if there is.

However, the shape of the tension arm is almost determined by the position and model of the magnetic recording/reproducing device in which the tension arm is used, and the arrangement of a pair of permanent magnets with opposite polarities attached to the movable part of the tension arm. It is almost impossible to freely change the shape of the tension arm depending on the location. Furthermore, even if the shape of the tension arm is allowed to change depending on the location of the permanent magnets, the mechanical resonance frequency of the tension arm is
Since it is determined by the constant of the spring system and the magnitude of the inertia of the movable part, there is a drawback that the degree of freedom in designing the shape etc. is greatly restricted.

Therefore, it is an object of the present invention to solve the above-mentioned drawbacks. An object of the present invention is to provide an erased tape tension detection device.

To put it simply, this invention has a permanent magnet provided in the tension arm movable part, instead of arranging a pair of permanent magnets with opposite polarities at a distance in the tension arm movable part as described above. A plurality of magnetic flux sensing elements are disposed at a distance in the direction of movement of the permanent magnet on a traveling base surface opposite to a surface created by movement of a permanent magnet provided in the movable part as the tension arm moves. This is a tape tension detection device characterized by the following.

As a result of this arrangement, the same characteristics as those shown in FIG. 6 described above can be obtained by maintaining an appropriate distance between the magnetic flux sensing elements.

Next, the theoretical basis of this invention will be explained with reference to experimental results. A pair of magnetic dipoles M1. The y-axis component of the magnetic field that M2 gives to the point (-X I, O) is expressed as H(-
), the V-axis component of the magnetic field applied to the point (X I, 0) is H
(+) and calculate l-1(-) +H(+), the result is as shown in FIG. H(-) +H(+
) and the characteristics of xO-2g in FIG. 6 match. Therefore, the point (−×Ito) and the point (x, , O
), and if a current is supplied so that it is sensitive to the y-axis component magnetic field given by a pair of magnetic dipoles M+ and Mz, the same effect as when xo is increased in Fig. 2 can be obtained. You can get it.

Therefore, by arranging multiple magnetic flux sensing elements along the direction in which the movable part 1' of the tension arm moves, and adding together the detection outputs of these multiple magnetic flux sensing elements, the area between the two peaks can be expanded. can do.

In FIG. 4, an embodiment of the tape tension detecting device will be described below when two Hall elements are sequentially arranged in the moving direction of the movable portion 1' of the tension arm.

FIG. 8 shows a connection configuration between a plurality of Hall element output terminals and an amplifier in the tape tension detection device of the present invention. The output terminals of Hall elements 15 and 16 are connected to amplifiers 17 and 18, respectively, and the outputs of amplifiers 17 and 18 are added by adder 19. Now amplifier 17
The output voltage of VHI + the output voltage of amplifier 18 is VHz
*If the output voltage of the adder 19 is Vs + +VH2, V□ with respect to the rotation angle of the movable part of the tension arm.

VH2 and VH+ +VH2 form the graph shown in FIG. The graph shown in FIG. 9 coincides with the theoretical calculation results shown in FIG. 7 described above.

In addition, in the embodiment shown in FIGS. 8 and 9,
Although the outputs of the Hall elements 15 and 16 are amplified and then added together, a series connection configuration may be adopted in which the outputs of the Hall elements 15 and 16 are added together and then amplified. FIG. 10 shows an example in which the output terminals of the Hall elements 15 and 16 are connected in series. In FIG. 10, terminal 20
The current supplied from the resistor R is regulated by the resistor R and applied to the Hall elements 15 and 16. In addition, the Hall element 15
and 16 are connected in series, and a potential difference between the two Hall elements 15 and 16 appears between terminals 21 and 22. As is well known, in a Hall element, a potential difference proportional to the product of the magnitude of the supplied current and the width of the input magnetic flux is generated in a direction perpendicular to the plane formed by the direction of the supplied current and the direction of the input magnetic flux. It is something. The potential at both ends where this potential difference occurs is determined by the charge distribution within the Hall element, which is uniquely determined by the supplied current and input magnetic flux.

Therefore, the connection between the terminals where this potential difference occurs and, for example, an amplifier is usually done with high impedance as shown in the example shown in Figure 8, and the influence of the amplifier on the receiving side is influenced by the terminal where the output potential difference of the Hall element occurs. It is made so that it does not affect the electric potential. By the way, according to the example shown in FIG. 10, by directly connecting the terminals that have the potential that they should have, a current that is originally in an undesirable direction will exist inside the Hall elements 15 and 16. As shown in Figure 11, the electronic difference between terminals 21 and 22 is VH in Figure 9.
It was found that characteristics equivalent to those of 1+VHz could be obtained and there were no problems in practical use. With this configuration, it is possible to obtain tape tension detection @stomach with the same performance with a simpler configuration than the circuit configuration shown in FIG.

14- FIGS. 12 and 13 are examples in which an MR element (magnetoresistive element) whose electrical resistance changes depending on the magnitude of magnetic flux is used as an example of a magnetic flux sensing element.

FIG. 12 shows a diagram of the principle of the MR element. A constant current I is supplied to the MR element 23, and when a magnetic flux H is input, a voltage E is generated between the current input and output terminals shown in the figure, and this voltage E changes depending on the magnitude of the supplied magnetic flux H. The resistance component that is not affected by the magnetic flux of the MR* element is ρ0. If the maximum value of the resistance component that changes due to magnetic flux is Δρ, the following equation holds true.

E-1-(ρ0+Δρ(1-H'/(Hk)2)1, where Hk is a constant...(4) The state of resistance change with respect to the input magnetic flux of the MR element 23 is
Shown in Figure 3. In FIG. 13, for example, if a constant bias magnetic field He is applied to the MR element, the movement of the movable part of the tension arm receives the magnetic flux from the permanent magnet, causing a voltage change according to the above equation (4). Due to the curved portion near the magnetic field Ho in FIG. 13, it can be used as a tape tension detection device. In order for multiple MR elements to obtain detection outputs as in the example of the Hall element described above, ~1R elements are connected in series and a current is supplied, and the sum of the resistance changes of the individual MR elements can be It can be easily detected as a change.

As described above, according to the present invention, it is possible to obtain a tape tension detection device that is simple, compact, does not limit the shape of the tension arm, and has a wide range of applications.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an embodiment of a conventional tape tension detection device, and FIG. 2 shows a pair of magnetic dipoles M1. M2 is the origin 0
FIG. 3 is a model diagram showing the magnitude of the magnetic field created by Figure 3 shows
In FIG. 2, a pair of magnetic dipoles M1. FIG. 3 is a diagram showing a calculated change in the magnitude of the magnetic field component in the y-axis direction at the origin O when M2 is translated in the x-axis direction. FIG. 4 shows the results when the value of xo is changed in the tension arm in the embodiment shown in FIG. This is a graph of life expectancy. FIG. 7 is a model diagram of FIG. 2, in which a pair of magnetic dipoles M1. M2 point (-Xl,
0), a graph drawn by calculating the magnetic field created at the point (-x2, O) and its composite value. FIG. 8 is a Hall element detection output circuit diagram of an embodiment of the present invention in which two Hall elements are arranged in a fixed part. FIG. 9 is a diagram showing actual measured values of the output voltages of each part of the circuit section shown in FIG. 8 when the rotation angle of the movable part of the tension arm is changed. FIG. 1 is a circuit diagram of an embodiment of the present invention when the output terminals of two Hall elements are connected in series. FIG. 11 is a diagram showing the output of the detection circuit 811 (lII) in the embodiment of FIG. 10. FIG. 124 is a diagram of the principle of the MR probe.
The figure is a diagram showing the relationship between the magnitude of the input magnetic flux and the resistance of the MR element. 17- In the figure, 1 is a tension arm, 1' is a tension arm movable part, 2 is a magnetic tape, 3 is a tension post, 4 is a spring, 5, 8.9 are permanent magnets, 6 is a magnetic flux sensing element, 7 is a rotation Axis, 10.15° 16 is a Hall element, and 23 is an MR element. Agent Shin Kuzuno - (1 other person)
18- @I:ll:! Shimoe R-Acupuncture

Claims (1)

[Scope of Claims] (1) A tape tension detection device for detecting the tension of a magnetic tape running in a magnetic tape recording/reproducing device, which comprises: a tension arm provided with a tension post with which the tape engages; a permanent magnet provided in the tension arm movable section; A tape tension detection device comprising: a plurality of magnetic flux sensing elements provided at a distance in a moving direction of the permanent magnet; and a detection circuit that detects the tension of the tape from the output of the magnetic flux sensing element. (2) The tape tension detection device according to claim 1, wherein a plurality of Hall elements are used as the plurality of magnetic flux sensing elements. (3) The tape tension detection device according to claim 2, wherein the output terminals of the plurality of Hall elements are connected in parallel. (4) The tape tension detection device according to claim 2, wherein the output terminals of the plurality of Hall elements are connected in series. (5) The tape tension detection device according to claim 1, wherein magnetoresistive elements are used as the plurality of magnetic flux sensing elements.