JPS59207018A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce the damage of a tape in a still picture reproducing mode by making the quantity of projection of a rotary head from a cylinder at a still picture reproducing time relatively smaller than that in a recording/reproducing operation mode. CONSTITUTION:As a structure which changes the quantity of projection of the head between the still picture reproducing mode and the other operation modes, the oscillation due to voltage application of a piezoelectric element is used electrically. A magnetic head supporting part 23 to which a magnetic head 3 is attached is moved by a piezoelectric element 21 consisting of bimorph to change the quantity of projection of the magnetic hed 3. A lead wire 24 for applying a voltage to the piezoelectric element 21 and a positioning stopper 25 for limiting the extent of movement of the magnetic head supporting part 23 are provided, and the magnetic head 3 is driven for projection in the direction of an arrow D. Not only this structure but also structures using an electromagnetc force, a mechanical force of a cam or the like, etc. may be used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic recording/reproducing device using a rotating head such as an 'l/' TR! (Regarding the improvement of #3m, in particular, it relates to a magnetic recording and reproducing device in which the mounting structure of the rotary head to the cylinder has been improved.

FIG. 1 is a perspective view showing the main parts of a conventional rotary/rad type magnetic recording/reproducing device. The magnetic recording/reproducing apparatus shown in FIG. 1 includes a rotating cylinder 1 and a fixed cylinder 2 that form a pair. A rotary head 3 is attached to the rotary cylinder 1, and the rotary head 1 contacts a magnetic tape 6 passed through a pair of guide pins 5, 5 to receive and transmit signals. In FIG. 1, reference numeral 7 indicates a travel locus of the rotary head 3, which scans the magnetic tape 6 in an oblique direction.

By the way, the second figure, which is a plan view of the rotating cylinder 1 in FIG.
As is clear from the figure, a pair of rotary heads 3, 3 are attached to the rotary head 1, and the rotary head 3 is provided so as to protrude outward from the rotary cylinder 1. The protrusion amount 8 of the rotary head 3 was always fixed to be constant (30 to 50 μl) in any operation mode.

On the other hand, the rotary heads 3, 3 are connected to the magnetic tape 6 as described above.
The tape is scanned diagonally across the tape, but during recording, a specific portion of the tape is scanned only once or twice (two scans means overwriting when a wide head is used). ), and during normal playback, the same part is
While it scans at most two times per minute,
When listening to still images, the tape is stopped and the same area is scanned several dozen times per second. Therefore, the rotating head 3
The magnetic tape 6 wears out due to the friction of the magnetic tape 6, and in particularly severe cases, the magnetic layer of the magnetic tape 6 may peel off and become unplayable, greatly deteriorating the image quality.

In an extreme case, as shown in FIG.
As shown in the front view, the scanning locus of the rotary head 3 during still image reproduction forms a so-called stay inclination angle and draws a stay trajectory 9, and a stay in the same diagonal direction as the stay inclination angle is recorded on the magnetic tape 6. 10 scars were observed.

Due to the above-mentioned problems, conventional magnetic recording and reproducing devices of this type are unable to reproduce still images for long periods of time, and can only reproduce still images for short periods of time, for example, about 30 seconds. could not. Furthermore, while the thickness of the magnetic layer in conventional coated magnetic tapes was approximately 2 to 4 mm, in so-called vapor-deposited tapes, which are formed by depositing metal directly onto the Mylar base surface by vacuum deposition, the magnetic layer The layer thickness is extremely thin, about 0.1 μm. Therefore, the still image playback time when the tape is not running as described above has to be further shortened, and moreover, when the magnetic tape 6 is under tension exceeding the limit value, it can be reduced in seconds. A serious problem has arisen in that the magnetic layer peels off even during still image playback for a very short period of time.

To give a specific example, for example, when using a magnetic tape with a width of 8 mm, there is no problem with a tension of 10 grams, but it is known that peeling of the magnetic layer occurs with a tension of 20 grams.

As a method of solving the above-mentioned problems, it is conceivable to use a solid-state device such as a memory element so that the scanning of the rotary head 3 only needs to be repeated once. However, when a solid-state device is used, there are disadvantages in that the apparatus becomes large-scale and the cost also increases significantly.

It is therefore an object of the invention to overcome the above-mentioned drawbacks and to
An object of the present invention is to provide a magnetic recording and reproducing device that can dramatically improve image quality in still image reproducing mode.

The features of this invention will become clear from the following detailed description with reference to the drawings.

One of your inventions! For example, the protrusion opening of the rotary head from the cylinder during still image playback when the tape running speed is zero is shown in each recording/playback operation mode of the tape running state, that is, recording mode, standard playback mode, slow playback mode, and high speed playback mode.・By making the protruding layer from the rotating land cylinder relatively small in double speed playback mode, etc., damage to the magnetic tape in still image playback mode can be prevented.
It also provides good image quality. The basis for this will be explained in detail below.

Let us consider the mechanism by which the tape wears out in the still image playback mode. As mentioned above, tape tension is one parameter of magnetic tape wear, and when the tension is high, tape wear becomes significant. @Figure 4 shows the vertical force generated on the tape by the tape tension king and the rotating head, that is, the tape reaction force F.
FIG. As is clear from Figure 4,
The tape reaction force F is the Dave tension 'T to the power of α (α to i
, /' 2). On the other hand, the tape reaction force F and the frictional force P between the tape and the head have a friction coefficient of μ
As, there is a relationship of P=μF. Therefore, k,.

If k2 is a proportionality constant, P−μ(k+T”)− is 2T
″...(However, α→1/2<1).

Therefore, it can be seen that reducing the tape tension will reduce the frictional force, and increasing the tape tension will increase the frictional force. It is thought that this repeated increase in frictional force accelerates the wear of the magnetic tape.

As is clear from the above discussion, it can be seen that reducing the tape tension can improve the image quality in the still image playback mode. However, as mentioned above, I
I! The friction is the α power of the change in tape tension (α → 1,
' 2 < 1).

Therefore, for example, if the allowable range of tape tension at the cylinder inlet is 10 to 15 gr, it is not possible to significantly reduce the frictional force.

Next, we will consider three alternative methods for reducing the tape tensicon. Figure 5 is a diagram showing the relationship between the output side (1 and 1 tape reaction force) of the rotary head from the cylinder. Introducing the relationship P-μF between the frictional force P between the rotating head and the magnetic arp and the tape reaction force, and expressing the relationship between 1] and d using the proportionality constant 1(., P = 3d From this, it can be seen that the rotation and protrusion H of the throat are proportional to 1311 of the frictional force.

Therefore, it is understood that it is more effective to reduce the amount of protrusion of the rotary head from the cylinder than to reduce the amount of rotation.

As shown in the above (2), it can be seen that if the amount of protrusion of the rotating head is reduced, the friction force will be reduced.Therefore, the 17 gap, or spacing, between the head mechanism and the rotating head and the magnetic arc. Let's consider the relationship. Figure 6 is a diagram showing this relationship. As is clear from Figure 6, 10
It can be seen that within the range of the head protrusion amount of ~40 .mu.Ill, the spacing is constant, and no spacing loss occurs due to the change in the protrusion amount after 7 inches. Therefore, no image quality degradation occurs due to spacing loss. It is also understood that since the Iff force is small, the vertical movement of the magnetic arp is also reduced, making it possible to cope with the narrowing of the track.

As is clear from the above considerations, it has been found that by setting the protruding foot of the rotary head from the cylinder small, various effects such as prevention of damage to the magnetic tape can be produced. Taking a more concrete example with numerical values, for example, if the protrusion amount of the rotary head is approximately 30 μm in the current recording/reproduction mode 1~, the rotation head protrusion amount will be approximately 30 μm during still image reproduction (still reproduction). The protrusion opening may be approximately 10 AIll. It was found that this resulted in good image quality in all operating modes.

By the way, as a structure for changing the l\\ sonode radiation in the still image reproduction mode and in other operation modes, it is possible to electrically use vibrations caused by voltage application to a piezoelectric element. For example, vibrations in the transgressive direction of a disc or cylindrical piezoelectric element, longitudinal vibrations of a bar-shaped piezoelectric element, bending vibrations of a plate-shaped piezoelectric element, etc. are utilized. Fig. 7 (j) is a schematic side view showing the case of using this type of piezoelectric element.
A piezoelectric element 21 made of a bimorph with a width of 1 x 1 and a thickness of 0.5 cp+ moves the magnetic head support part 23 to which the magnetic nod 22 is attached to change the magnetic Δ and the protruding opening of the nod 22. :Ru. In addition, in FIG. 7, 24 is a lead wire for applying pressure to the piezoelectric element 21,
Reference numeral 25 denotes a magnetic X j: a positioning stopper for restricting the movement opening of the support portion 23, and D indicates the driving direction for the protrusion of the throat 22 toward the magnet.

As for the variable protrusion amount structure of the rotating head from the cylinder,
In addition to those using piezoelectric elements as shown above, various known structures can be used, such as those using electromagnetic force and those using mechanical structures such as cams. It is preferable to change the amount of protrusion of the throat (1L.--O), since the friction coefficient varies depending on the type of magnetic arp, it is preferable to change the amount of protrusion of the rotary head from the cylinder depending on the type of magnetic arp.

Furthermore, in the above embodiment, only the amount of head protrusion was changed, but by combining varying the amount of head protrusion with changing the tape tension, it is also possible to obtain an even better still image. .

Although the above-mentioned embodiment describes a VTR having a rotary cylinder to which two rotary heads are attached, and in which the two rotary heads are movable, the present invention is not limited to this. do not have.

In other words, it is a so-called multi-head type VTR with four or six heads fixed to a rotating cylinder.
In this case, only the head protrusion amount of one pair of magnetic heads may be made smaller than the protrusion amount of the other magnetic heads, and the pair of magnetic heads with the smaller protrusion amount may be used exclusively for the still image reproduction mode. Furthermore, in the above example, 811111
I explained a VTR using a 1-width magnetic tape, but
VH8 system VTR using 1/2 inch wide magnetic tape
It should be pointed out that the present invention can be similarly applied to a β-type VTR in which the upper and lower cylinders are fixed and the central head is rotated.

As described above, according to the present invention, the amount of protrusion of the rotary head from the cylinder during still image playback when the tape running speed is zero is calculated from the rotation l\rad cylinder in each recording/playback operation mode in the tape running state. Since the amount of protrusion is relatively smaller than the amount of protrusion, damage to the tape in the still image playback mode can be significantly reduced, making it possible to obtain good image quality. Furthermore, since the frictional force between the rotary head and the tape is reduced, the torque of the cylinder drive motor can be reduced, which also contributes to reducing power consumption. Furthermore, due to the reduction in frictional force, disturbances in the vertical direction of the tape are reduced, and the vertical movement of the tape can be reduced, thus making it possible to realize high-density recording. In general, reducing the frictional force between the head and the tape has various useful effects, such as extending the life of the magnetic head.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the main parts of a conventional magnetic recording/reproducing apparatus using a rotary head. FIG. 2 is a plan view of the rotary head and cylinder of the magnetic recording/reproducing apparatus shown in FIG. FIG. 3 is a front view showing a scanning pattern on a magnetic t\rad magnetic tape in a conventional magnetic recording/reproducing apparatus. FIG. 4 is a characteristic diagram showing the relationship between tape tension and tape reaction force. FIG. 5 is a diagram showing the relationship between the amount of protrusion of the rotary head and the tape reaction force. FIG. 6 is a diagram showing the relationship between the amount of protrusion of the rotary head and the spacing between the head and the magnetic tape. FIG. 7 is a schematic side view showing an example of a structure for changing the amount of protrusion of the rotary head. In the figure, 1 is a cylinder, 3, 3, 22 is a rotary head, 6 is a magnetic tape, and d and 8 are protrusion amounts. Agent Masuo Oiwa 1st figure 2nd figure 7 Diagram 1, Showa year, month, day 1, Indication of the case, Japanese Patent Application No. 58-82936 2, Name of the invention to representative Hitoshi Katayama Part 4, Column for detailed explanation of the invention and drawings in the memorandum to be amended by the agent Contents of correction in the brief explanation column and drawings in Figure 7 (1) The text r (01 rotating head 1) in the first line of page 2 of the specification is corrected to read ``rotary head 3''. (2) “Vertical effect” in page 1, item 16 of the specification and item 5,
Correct to "normal force". :3) Correct the symbol ◇ between "magnetic head 22" and "magnetic head 3" on page 9, line 6, line 7, and lines 411 to 12 of page 9 of the specification. (4) The phrase "may be modified" on page 11, line 16 of the specification is amended to "apply/may be". 5) Correct r3.3°j on page 12, line 13 of the specification to "3." 6) Correct Figure 7 of the drawings as shown in the attached sheet. that's all

Claims (1)

[Claims] In a magnetic recording and reproducing device using a rotating head that receives and transfers signals from a magnetic tape, the amount of protrusion from the rotary l\rad cylinder at the time of Dave's running mode or zero static image is calculated for each tape running state. A thermal recording/reproducing device characterized in that the rotation t in the recording/reproducing operation mode is relatively smaller by 1,7 than the amount of protrusion from the rad cylinder.