JPS60127436A - Contact-force measuring device of magnetic head - Google Patents

Abstract

PURPOSE:To measure the contact force of a magnetic head highly accurately by minutely displacing the rotary magnetic head in correspondence with the contact force, and optically measuring the amount of displacement. CONSTITUTION:A rotary magnetic head 1 is supported by a head supporting means 5 and can be displaced minutely in the direction of A in correspondence with the contact force with a magnetic tape 3. As the supporting means 5, a head assembly 4, which has, e.g., an L shaped cut-in part 7 and is formed so that the assembly is displaced in the direction A in correspondence with the contact force with the tape 3, is used. The amount of displacement of the head 1 is measured by a photoelectric-conversion measuring means 6. The measuring means 6 is provided in a rotary cylinder 2 so that the means 6 is rotated as a unitary body with the head 1. In this constitution, the contact force of the magnetic head can be measured highly accurately.

Description

Detailed Description of the Invention (Field of the Invention) The present invention relates to a video tape recording and reproducing machine (hereinafter referred to as 1'-VT
This invention relates to a device for measuring the total contact force between a magnetic rotary head (referred to as RJ) and a running magnetic tape.

(Technical Background of the Invention) A magnetic rotary head with a VTI% of about 5
It slides at a speed of m/s. In order to make this sliding smooth, it is necessary to fully understand the friction and wear conditions during sliding, and to do so, it is necessary to understand the contact force that the sliding head receives from the tape, especially the normal to the contact surface between the two. It is important to measure directional forces with high precision.

However, the rotating head of the current 1/2" VTR is very small (surface area: 2 mm x 0.15 mm), and the head itself is fixed to a rotating cylinder and rotates at a high speed of 1800 rpm. It is not easy to measure the total contact force.

For example, the inventor attempted to measure the contact force described above using a commercially available pressure/strain sensor, but since the head is minute in shape, the j15! The contact force in the normal direction, which is a constant target, is minute, and the electromagnetic method using the above-mentioned sensor has a high impedance and therefore generates a lot of noise. Ta.

On the other hand, devices using conventional piezoelectric elements have been proposed as contact force measuring devices for magnetic heads, but these devices require the preparation of expensive piezoelectric elements specially manufactured to match the tiny dimensions of the head, and are not commonly used. It has the disadvantage of not being accurate.

(Objective of the Invention) In view of the above circumstances, the object of the present invention is to provide a system that can be manufactured at low cost and compactly, enables highly accurate measurement, and further allows the head to rotate and slide under normal V']"R operating conditions. An object of the present invention is to provide an overall contact force measuring device for a magnetic head that can measure contact force while moving the magnetic head.

(Structure of the Invention) In order to achieve all of the above objects, the measuring device according to the present invention displaces the magnetic rotary head in accordance with the contact force in the normal direction on the contact surface between the head and the magnetic tape. 9 (Effects of the invention) comprising means for supporting the head, photoelectric conversion measuring means for measuring the entire displacement needle of the head, and installed on a rotating cylinder to which the measuring means is fully attached. As mentioned above, the measuring device according to the present invention is configured to make a small displacement according to the total contact force of the head and measure the amount of displacement, so there is no need to use all the expensive piezoelectric elements as in the past, and the overall Can be made cheaply. Best of all, we have adopted photoelectric conversion measurement means with a low impedance electrical conversion system as the displacement measurement means, making it possible to perform highly accurate measurements with little noise. Furthermore, since this measuring means can be incorporated into the rotating cylinder, the apparatus can be manufactured compactly. Furthermore, the above measurement method? By installing the measuring means in a rotating cylinder and rotating the measuring means integrally with the rotating head, it is possible to measure the normal Vi
(Under operating conditions, 1 IcI can be added continuously while the head is fully rotated.Using this measurement result, we can solve the problem of friction and wear between the tape and the head, which until now was largely unknown. It is possible to completely improve the accuracy of quality evaluation.

(Examples) Hereinafter, the present invention will be described in detail with reference to examples shown in the drawings.

First, prior to explaining the present invention, the relationship between a magnetic rotary head and a magnetic tape of a general VTR will be explained based on FIGS. 1 to 3. Figure 1 is a conceptual plan view showing the relationship between the two.
FIG. 2 is a conceptual front view. As shown in the figure, two spades 1 are installed on a rotating cylinder 2, and both spades 1 alternately slide over a magnetic tape 3 to perform magnetic recording and reproduction. The rotating cylinder 2 is arranged at a predetermined angle with respect to the tape 3,
The head l slides on the tape 3 in a diagonal direction. Arrows in the figure indicate the rotation direction of the cylinder 2 and the running direction of the tape 30. FIG. 3 is an enlarged view of a portion of the head 1, and as shown in FIG. 1, the head 1 is fixed to a head assembly 4, and the assembly 4 is fixed to the cylinder 2.

During recording and playback, the surface of the head 1 slides on the magnetic surface of the tape 3 at a speed of approximately 5 m/sec, and the contact force that the head 1 receives from the tape 3 depends on the mutual physical properties of the head and tape, such as surface roughness, Affected by lubricity, hardness, etc.

Next, the present invention will be explained based on FIG. 4 showing one embodiment of the present invention. FIG. 4 is a conceptual plan view showing the rotary cylinder/cylinder section of a VTR incorporating an embodiment of the measuring device according to the present invention. As shown in the figure, the measuring device of the present invention includes a magnetic rotating disk 1
means 5 for supporting the head J so as to displace the head J in accordance with the contact force in the normal direction (in the direction of the arrow) on the contact surface between the disk 1 and the magnetic tape, and measuring the amount of displacement of the head 1. The measuring means 6 is installed in the rotary cylinder 2 to which the helad is attached.

In this embodiment, as the support means 5, the support means 5 shown in FIGS.
A head assembly 4 is used in which the head 1 portion is formed to be movable in the above-mentioned normal direction A by providing L-shaped notches 7 or 8 wedge-shaped notches as shown in the figure. , as other embodiments, for example, the head built-in body 4 is made entirely of rubber,
It is also possible to employ an entire configuration in which the head 1 can be displaced in the above-mentioned normal direction by attaching all of the valves to the rotating cylinder 2 using an elastic material such as a nystomer. In other words, the support means 5 may be of any type as long as it can be supported so as to be deformed in response to the contact force in the normal direction from the head LK tape 3.
"According to the contact force" means that the contact force and the amount of deformation do not necessarily have to be proportional, but it is sufficient that the two correspond to each other. It is conceivable that the head built-in body 4 generates natural vibration when the spatula 1 and the tape 3 come into contact, making accurate measurement difficult. Tip fulcrum part 7
A + 8 The natural vibration inhibitor can be completely fixed to a. In addition, since the built-in body 4 formed in this way has exactly the same performance as a normal standard type built-in body for recording and playing back video signals, it is possible to measure contact force at the same time as recording and playing back. Next, the photoelectric conversion measuring means 6 will be explained.

The photoelectric conversion measurement means 6 of the embodiment shown in FIG.
, a photosensor 11 that receives light from the light source 10 and performs an electrical output, and a light amount changing device 12 that changes the amount of light received by the photosensor 11 in accordance with the displacement of the helad 1. As shown in FIG. 7, the device 12 includes a needle member 13 fixed to a portion of the head assembly 4 that is displaced together with the head 1, and a cam member 14 that engages with the needle member 13.
a rotating shaft 15 fixed to the cam member 14;
It consists of a mirror 16 fixedly attached to the photo sensor 11, and a light amount control slit 17 placed in front of the photo sensor 11. It is transmitted as rotational motion, and mirror 1
The rotation of 6 cooperates with the slit 17 to generate a photo sensor.
The amount of light received at step 11 is changed, and this change in the amount of received light is taken out as a change in total electrical output, and the total contact force is measured. Note that 18 is a condensing system.

Head 1. The planar positional relationship of the mirror 161, photo sensor 11, etc. is as shown in FIG. 8, which is a conceptual plan view of FIG. It is installed in the rotating cylinder 2 so that it rotates. However, because the light source power source, amplifier, etc. cannot be installed inside the cylinder 2 due to dimensional constraints, these wirings are connected to the slip ring 20, light source power source brush 21, and photosensor power source brush 21 shown in Figure 4. Using a brush 22, it is constructed as shown in FIG. 23 in the figure is a CRT oscillograph.

Is FIG. 10 another embodiment of the light amount changing device 12? The illustrated device 12 includes a displacement slit 24 provided in a portion of the head assembly 4 that is displaced together with the head 1, an immovable slit 25 provided in a portion that is not displaced, and both slits 2.
4.2EJ - Consists of a power source io and a photosensor 11 placed on the opposite side. In this case, the displacement slit 24
The distance between the two slits 24 and 25 changes according to the displacement of the slits 24 and 25, and the amount of light received by the photosensor 11 changes accordingly.

Note that 26 is a condensing system.

The photoelectric conversion measuring means according to the present invention may be of any type as long as it can detect a change in the total light intensity due to the displacement of the head 1 and extract this as a change in electrical output. How is it? It can be taken.

FIG. 11 is a diagram showing the relationship between the contact force and time obtained by the device of the present invention, and T in the figure indicates the time for one rotation. Note that the data shown in this figure is data obtained for only one of the two heads attached to the rotating cylinder.

[Brief explanation of drawings]

Fig. 1 is a conceptual plan view showing the relationship between a general magnetic rotary head and a magnetic tape, Fig. 2 is a conceptual front view thereof, Fig. 3 is an enlarged view of the head portion, and Fig. 4 is a diagram according to the present invention. FIGS. 5 and 6 are a conceptual plan view of a rotating cylinder incorporating an embodiment of the device, respectively. FIGS. Figure 8 is a perspective view showing a part of the photoelectric conversion measurement means, and Figure 8 is the positional relationship of the photoelectric conversion measurement means. Fig. 4 is a conceptual front view of Fig. 4, Fig. 9 is a diagram showing the wiring relationship of the photoelectric conversion measuring means, Fig. 10 is a perspective view showing another embodiment of the photoelectric conversion measuring means, and Fig. 11 is a diagram showing the measurement by this device. FIG. 3 is a diagram showing the relationship between contact force and time. l...... Rad to magnetic rotation 2...
...Rotating cylinder 3...Magnetic tape 5
・・・・・・・・・Head support means 6・・・・・・・・・ Light throat ■ 11 Yodo means No. 1 Figure 1!3 Figure @4 Figure 11!5 Figure 8 Figure 8 (Spontaneous) Procedure... Officially dated March 14, 1981, Commissioner of the Japan Patent Office, 1, Indication of the case, Patent Application No. 58-235261, 2, Name of the invention, Magnetic head contact force measuring device 3, Person making the amendment, Relationship to the case, Patent applicant, Place. 210 Nakanuma, Minamiashigara City, Kanagawa Prefecture Name: Fuji Photo Film Co., Ltd. 4, Agent

Claims (1)

[Claims] (2) Contact force acting on the contact surface between the magnetic rotary head and the magnetic tape of a video tape recording/playback machine? A measuring device comprising means for supporting the magnetic rotary head so as to displace the head in accordance with a contact force in a direction normal to the contact surface, and a photoelectric conversion measuring means for measuring the total amount of displacement of the head. A contact force measuring device for a magnetic head, characterized in that the photoelectric conversion measuring means is installed in a rotating cylinder to which the head is attached. (2) The magnetic rotary head? Supporting means is fixed to one end of the magnetic rotary head and partially fixed to the rotating cylinder, for displacing the head in the normal direction between a part fixed to the cylinder and the head. 2. A contact force measuring device for a magnetic head according to claim 1, wherein the magnetic head contact force measuring device is a head built-in body having a notch.