JPS6321249B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contact force measuring device for a rotating magnetic head, for example, for measuring the contact pressure between a video head and a video tape in a video tape recorder.

For example, in a magnetic recording/reproducing device such as a video tape recorder, when a magnetic head and a magnetic tape are run in contact with each other, there are problems with the contact (contact pressure) of the head against the tape, friction, wear, etc. This may adversely affect the life of the tape, head, rotating drum, etc., and may adversely affect the life of the tape, head, rotating drum, etc. For this reason, it is necessary to measure in advance the acting forces associated with contact, such as the contact pressure and frictional force, during design or product assembly, and adjust them to appropriate values.

Conventionally, strain gauges and other devices have been used to detect and measure the force acting upon contact, but the structure has become complicated, and sensing elements such as strain gauges have low response speeds and are not reversible, resulting in poor detection accuracy. It is difficult to increase the performance, and when used for control, there is a disadvantage that the number of component parts increases.

The present invention has been made in view of these circumstances, and provides a rotating magnetic head with a simple structure, high precision, and a fast response speed by supporting the magnetic head with a piezoelectric element that has a quick response and is reversible. The purpose of the present invention is to provide a contact force measuring device.

That is, in order to achieve the above object, the contact force measuring device for a rotating magnetic head according to the present invention brings a magnetic head supported on a rotating drum via a piezoelectric element into rotational contact with a magnetic recording medium, and also uses the piezoelectric The element is mounted so that the mechanical-electrical deflection direction is tangential, normal, or rotating axial to the rotating drum, and the acting force from the magnetic recording medium to the magnetic head due to the rotating contact is transferred to the piezoelectric element. It is characterized by detection by electrical output according to the deformation.

Preferred embodiments of the present invention will be described below with reference to the drawings.

1 and 2 show a first embodiment of a contact force measuring device 1 for a magnetic head according to the present invention. In FIGS. 1 and 2, a head chip 2 is used to record and reproduce video signals on a magnetic tape, for example, and a head chip mounting member 3 made of an insulating material
It is attached and fixed to the tip of the bimorph element 4, which is a piezoelectric element, via a . The base end of this bimorph element 4 is supported and fixed to a head base 6 via a bimorph support member 5 made of an insulating material such as glass ceramic.

Here, the bimorph element 4 is constructed by, for example, bonding two piezoelectric plates 7 and 8 via an intermediate electrode 9 such that their polarization directions are opposite to each other, and placing surface electrodes 10 on both sides of these piezoelectric plates 7 and 8. , 11, and these surface electrodes 10, 11
When a voltage is applied between them, the bimorph element 4 undergoes a curved deformation, and the amount and direction of the curved deformation change depending on the magnitude and direction (positive or negative polarity) of the applied voltage. Conversely, a voltage is generated between the two surface electrodes according to the deformation of the bimorph element 4, and since this voltage has a constant relationship with the deformation, the amount and direction of the deformation can be detected by detecting this voltage. can do.

Since the base end of the bimorph element 4 has a cantilever structure in which it is supported and fixed to the head base 6 via the bimorph support member 5, the displacement of the tip of the bimorph element 4 (in the direction of arrow X) This corresponds to the above-mentioned curved deformation of 4 itself. The head chip 2 is erected perpendicularly to the plate surface of the bimorph element 4 by means of a mounting member 3, and the displacement direction (direction of arrow X) coincides with the head protrusion (or retreat direction). The recording medium M such as magnetic tape is
Since the bimorph element 4 is disposed at the position indicated by the broken line in FIG.
can be detected by the output voltage from the surface electrode.

Next, each electrode 9, 10, 11 of such a bimorph element 4 is connected to a lead wire 12, 1, respectively.
3 and 14, electrical connection is made by soldering or the like to conductive patterns 15, 16, and 17 formed on the back surface of the head base 6 as shown in FIG. 1, for example. Similarly, the end of the coil of the head chip 2 of the video head is also connected to the head base 6.
Conductive patterns 18 and 19 formed on the back surface of
An electrical connection is made by soldering or the like.
Further, the bimorph element 4 of the head base 6
A damper member 20 made of rubber or the like that elastically supports the displacement of the bimorph element 4 is disposed at a position facing the tip of the bimorph element 4 .

The magnetic head contact force measuring device 1 shown in FIGS. 1 and 2 has a structure capable of detecting a force acting in a direction perpendicular to the surface of the magnetic recording medium M (in the direction of the arrow X). However, the acting force accompanying the contact between the head chip 2 and the recording medium M is:
It is preferable to also detect acting forces in the Y and Z directions that are parallel to the surface of the recording medium M and perpendicular to each other.

That is, the second embodiment shown in FIGS. 3 and 4 has a structure capable of detecting the contact force in the direction of the arrow Y, which is parallel to the surface of the recording medium M and also parallel to the surface of the head base 6'. A signal conversion head contact force measuring device 21 is shown. The head chip 2 is attached to the tip of the bimorph element via the mounting member 3', and the bimorph element 4 is attached to the head base 6' via the bimorph support member 5' so that the Y direction is the displacement direction. Support is fixed. That is, the bimorph element 4 may be arranged so that the plate surface thereof is perpendicular to the direction of the arrow Y.

Next, in the third embodiment shown in FIGS. 5 and 6, a signal converting head contact structure capable of detecting contact force in the direction of arrow Z, which is perpendicular to the surface of the head base 6'', is described. A force measuring device 31 is used.
In this case, the bimorph element 4 may be supported and fixed so that its plate surface is perpendicular to the Z direction.

For other structures in the second and third embodiments, the same reference numbers (or the same reference numbers with a dash ', etc.) are used for parts that have the same functions as in the first embodiment. By this,
The explanation will be omitted.

The state of contact between the head chip 2 of the magnetic head contact force measuring device 1, 21, 31 having the above structure and a magnetic recording medium M such as a video tape will be explained with reference to FIG. In FIG. 7, the head chip 2 is arranged so as to slightly protrude from the outer periphery of a rotating drum R rotating in the direction of arrow A, and a magnetic recording medium M such as a video tape is wound around the outer periphery of the rotating drum R. It has become a new form. Magnetic recording medium M for head chip 2
When the components of the force caused by the contact are a component F _N in the direction perpendicular to the surface of the magnetic recording medium M, a component F _T in the tangential direction, and a component F _Z in the direction of the rotational axis of the rotary drum R, the above X direction , Y direction and Z direction are each component
It matches the orientation of F _N , F _T , and F _Z . Therefore, in order to measure these contact force components F _N , F _T , F _Z , the magnetic head contact force measuring devices 1 and 1 of the first, second, and third embodiments are required, respectively. 21,
31 may be used.

Next, FIGS. 8 to 10 show a fourth embodiment in which the contact force measuring device for a magnetic head according to the present invention is applied to a magnetic card recording/reproducing device (magnetic card recorder).

First, FIG. 8 is a perspective view for explaining the principle of the magnetic card recorder 40, in which the head chip 2 of the magnetic head is provided to protrude from a predetermined position on the outer peripheral surface of a rotating drum 42 rotating in the direction of arrow A. A guide body 45 has a guide groove 44 formed along the locus of rotational movement of the head chip 2.
(referred to as a female guide) is arranged in an angular range of approximately 180° near the outer periphery of the rotating drum 42. A flexible magnetic card 43 is inserted into the gap between the rotating drum 42 and the guide body 45,
The leading end of the magnetic card 43 is stopped by a stopper piece 46 attached and fixed to the end of the guide body 45.
In this state, the magnetic card 43 is movable in the direction of the rotation axis (direction of arrow Z).
A plurality of recording tracks parallel to each other are formed on the magnetic card 43 by being fed stepwise by a predetermined pitch in the direction.

9 and 10 show a specific example of such a magnetic card recorder 40, in which a rotating drum 42
It is formed into a slightly flat, thick-walled cylindrical shape with a bottom. As a contact force measuring device for measuring the acting force when the magnetic head contacts the card, for example, the X shown in the first embodiment and the second embodiment may be used.
A device 1 for measuring the contact force in the direction (the above component F _N ) and a device 21 for measuring the contact force in the Y direction (the component F _T ) are used. These magnetic head contact force measuring devices 1 and 21 are installed on the inner bottom surface of the rotating drum 42 by screwing screws 4 at an angle difference of 180° along the circumference.
8 and 48 are fixed with screws. Also,
An adjustment screw 49 inserted from the outer bottom surface of the rotating drum 42 toward the inner side allows adjustment of the mounting elevation angle of the head base 6 of the contact force measuring device 1, etc. Each head chip 2, 2 protrudes slightly from the outer peripheral surface of the rotary drum 42 through through holes 50, 50 formed in the outer peripheral wall thereof, and comes into sliding contact with the magnetic card 43.

The rotating drum 42 is connected to a rotating shaft 51, which is rotatably supported via a bearing 52 and is also connected to a motor (not shown).
Rotationally driven by. The primary coil 53 provided on the rotating shaft 51 side constitutes a rotating transformer (rotary transformer) 56 together with the secondary coil 55 provided on the bearing housing 54 side, and each rotating magnetic head contact force measuring device 1, It is responsible for transmitting video signals between the head chips 2, 2 of 21 and a circuit section (not shown) on the main body side of the magnetic card recorder. In addition, slip rings 57,... are arranged at the tip of the rotating shaft 51, etc., and mainly through sliders (brushes) 58,... that come into sliding contact with these slip rings 57,... A detection signal of contact force from the bimorph element 4 is transmitted.

According to the fourth embodiment, one contact force measuring device 1 measures the component F _N in the direction perpendicular to the surface of the magnetic card 43 (normal direction), and the other contact force measuring device 21 measures the component F N of the rotating circle. tangential component of
F _T can be measured respectively. Therefore, by performing calculations on these detection outputs, the static friction coefficient μ _S , the dynamic friction coefficient, μ _D , and the friction angle θ
It is also possible to check automatically. Here the first
FIG. 1 is a time chart showing the detection outputs from the contact force measuring devices 1 and 21 in the magnetic card recorder 40, and the solid line in the figure indicates the contact force measuring device 1.
The broken line in the figure is the output that detected _{the F T component} from the contact force measuring device 21. One cycle T of each detection output corresponds to the rotation cycle of the rotary drum 42, and for example, when rotating at _30HZ , the above T is 1/30 seconds. Each head chip 2, 2 is arranged with an angular difference of 180° from each other, and since the magnetic card 43 is wound around the rotating drum 42 within an angle of about 180°, each head chip 2, 2 It contacts the magnetic card 43 alternately in T/2 cycles. As an acting force accompanying this contact, an impactful contact force acts on the head tips 2, 2 at the start and end of the contact,
If this transient portion is excluded, a substantially constant force is acting, and the averages _N and _T of these acting forces can be taken as the above-mentioned components F _N and F _T , respectively. Regarding the configuration, explanations will be omitted by assigning the same reference numerals to parts that operate in the same way as in the fourth embodiment.

In this fifth embodiment, it is possible to measure each contact force component etc. in a tension-free state when the magnetic tape 61 stops running, and it is also possible to easily measure the contact force etc. when the magnetic tape 61 is driven to run in the direction of arrow B. Can be measured. Therefore, it is possible to obtain the true contact force component without tape tension and the calculated friction coefficients, etc.
In addition to high-precision measurements, it is also possible to detect contact force, including the effects of tape tension during tape running. evaluation can be carried out.

As is clear from the above explanation, according to the contact force measuring device for a rotating magnetic head according to the present invention, magnetic force can be measured with an extremely simple configuration without using a complicated configuration using a strain gauge or the like as in the past. It becomes possible to measure the acting force associated with head contact. In addition, since measurements can be performed without applying tension to magnetic cards, video tapes, etc., the true contact force (the above F _N , F _T , F _Z components, etc.) and the calculated static friction coefficient μ _S and dynamic friction coefficient μ _D , friction angle θ, etc. can be obtained. Furthermore, in magnetic card recorders, video tape recorders, etc. that are actually used,
Because the structure in which the head chip is supported by a bimorph element is used, contact force can be measured in a form that is almost completely equivalent to the form of actual use, making it extremely useful when evaluating products and obtaining experimental data for design. High quality and highly accurate measurement data can be obtained. Furthermore, due to the reversibility of the bimorph element, there is an advantage that the measurement device can be used as is for control purposes. Furthermore, based on the data measured in this way, optimal adjustments can be made during design and assembly, making it possible to solve problems such as head contact, friction, and wear, and effectively prevent deterioration of image quality and shortening of product life. Of course, this can be prevented.

[Brief explanation of the drawing]

1 and 2 show a first embodiment of the present invention, with FIG. 1 being a back view and FIG. 2 being an enlarged perspective view of the main parts. 3 and 4 show a second embodiment of the present invention, with FIG. 3 being a back view and FIG. 4 being an enlarged perspective view of the main parts. Figures 5 and 6 are
A third embodiment of the present invention is shown, and FIG. 5 is a back view;
FIG. 6 is an enlarged perspective view of the main parts. FIG. 7 is a schematic perspective view for explaining the components of contact force when the three basic embodiments described above are applied to a magnetic recording/reproducing apparatus. 8 to 11 show a fourth embodiment in which the first and second embodiments described above are applied to a magnetic card recorder, and FIG. 8 is a schematic perspective view for explaining the principle of the magnetic card recorder. , FIG. 9 is a side view, and FIG. 10 is a cross-sectional view taken along the - line in FIG. 9.
FIG. 11 is a time chart showing the detected voltage waveform. FIG. 12 is a plan view showing a fifth embodiment in which the first and second embodiments described above are applied to a rotary head device of a video tape recorder. 1, 21, 31... Contact force detection device for magnetic head, 2... Head chip, 4... Bimorph plate,
40...Magnetic card recorder, 43...Magnetic card, 60...Rotary head device, 61...Video tape.

Claims (1)

[Claims] 1. A magnetic head supported on a rotating drum via a piezoelectric element is brought into rotational contact with a magnetic recording medium, and the piezoelectric element is rotated so that the mechanical-electrical bias direction is tangential, normal, or rotating axis direction of the rotating drum. A contact force measuring device for a rotating magnetic head, characterized in that the contact force measuring device for a rotating magnetic head is mounted so as to detect the force acting on the magnetic head from the magnetic recording medium due to the rotating contact by an electrical output corresponding to the deformation of the piezoelectric element. .