JPH07272359A - Magnetic recording/reproducing device - Google Patents

Abstract

PURPOSE:To reduce a head impact sound by suppressing tape vibration of a tape out side with simple constitution in a rotary head magnetic recording/ reproducing device. CONSTITUTION:A first minute protrusion 10 is arranged in the vicinity of the outside where a tape like recording medium 4 is detached from a fixed cylinder 3 and on the position close to the rotary head so as to slide contact to the tape like recording medium 4, and a second minute protrusion 11 is arranged on the position closed to a lead than the first minute protrusion 10 on the fixed cylinder, and the second minute protrusion 11 is formed at least two kinds of lead curves. Thus, a tape distortion causing a snap through phenomenon immediately before a magnetic head passes through the first minute protrusion is suppressed, and the tape vibration occurring due to the impact at the time is suppressed also, and the noise is reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a helical scan type magnetic recording / reproducing apparatus, that is, a video tape recorder or an R-type.
The present invention relates to a rotary head recording / reproducing device in DAT or the like.

[0002]

2. Description of the Related Art In a helical scan type video tape recorder, a rotary cylinder having a plurality of magnetic heads on its outer peripheral surface and a fixed cylinder having a lead for helically winding a magnetic tape are coaxially arranged. Recording and reproduction are performed by rotating the.

By the way, it has been observed that tape vibration occurs on the entry side and the removal side of the magnetic head with respect to the magnetic tape of the magnetic recording / reproducing apparatus. Especially, in the case of a VTR with a built-in camera, four magnetic heads are arranged on the outer circumference of a rotating cylinder by shifting them by 90 degrees and the magnetic tape is wound around the cylinder by 270 degrees or more. As a result, problems such as image quality deterioration and tape vibration noise occur.

The principle of occurrence and countermeasures against the above problems are described in detail in the monthly magazine "TV Technology", May 1987. Further, for example, concrete measures are disclosed in Japanese Patent Laid-Open No. 1-213856. That is, the surface pressure is high at the contact portion of the magnetic tape with the head, and the head rapidly separates from the magnetic tape, so that the magnetic tape from which the magnetic head has been removed vibrates violently. 5 to prevent this vibration
By providing a protrusion of about 0 μm to reduce the surface pressure applied to the magnetic head at the magnetic tape separation surface, unnecessary winding of the magnetic tape around the magnetic head is prevented, and tape vibration due to smooth separation of the magnetic head and magnetic tape. I try to prevent it.

Further, in the conventional rotary head recording / reproducing apparatus, the magnetic tape is pressed down by the upper flange portion of the tape guide near the cylinder so that the magnetic tape travels downward along the cylinder travel restriction portion called a lead. Magnetic tape is regulated. In addition, when the magnetic tape is fast-forwarded or rewound, if the magnetic tape is regulated upward or downward, uneven winding occurs, which causes inconvenience. In general, the magnetic tape is made to generate an upward traveling vector, and the upper regulation is generally strengthened.

FIG. 6 shows a schematic diagram of a general rotary head recording / reproducing apparatus. The rotating cylinder 2 to which the magnetic head 1 for recording and reproducing is attached is arranged coaxially with the lower fixed cylinder 3 and rotates. The magnetic tape 4 is regulated by an entrance side tape guide 5 provided on the entrance side of the cylinder unit and a tape guide 6 provided on the tape exit side, and is wound around the cylinder unit and run in the direction of the arrow. The lower fixed cylinder 3 is provided with a lead portion 7 for downwardly regulating the tape running, and the magnetic tape 4 which is upwardly regulated by the entrance side tape guide 5 and the ejection side tape guide 6 is pressed against the lead portion 7. Is common.

There is also seen an example in which the lower fixed cylinder 3 is formed with minute projections 8 for reducing tape vibration on the cylinder exit side, which will be described later.

Next, FIG. 7 shows an explanatory view of the principle of tape vibration caused by head impact. In the helical scan type video tape recorder, as shown in FIG. 6, a plurality of magnetic heads 1 are arranged on the outer circumferential surface of the rotary cylinder 2 which is divided into four portions in the circumferential direction. The magnetic tape 4 is wound around the rotary cylinder 2 to run, and at this time, the rotary cylinder 2 is rotated in the direction of the arrow, and each magnetic head 1 is recorded and reproduced in an angle range of 270 degrees running from P to Q. I shall. Further, the magnetic tape 4 is additionally wound by α degrees on both the entry side and the removal side of the magnetic head 1. The so-called overlap range is an extra scanning range that is reserved for performing so-called head switching in switching the magnetic head for recording / reproducing and is for scanning and reproducing the video signal itself.

The entrance tape guide 5 and the exit tape guide 6 are guide members for helically supplying and winding the magnetic tape 4 to the rotary cylinder 2.

Now, assuming that the magnetic head 1 is performing a reproducing operation, when the magnetic tape is scanned from point Q by α, the magnetic head 1a separates from the magnetic tape 4. At this time, the magnetic tape 4 vibrates at the time of separation, and this appears as jitter on the reproduction screen or becomes a noise source as head impact sound. Therefore, in order to prevent the above vibration, a minute protrusion 8 of about 50 μm is provided to reduce the surface pressure applied to the magnetic head at the magnetic tape detachment surface, thereby preventing unnecessary winding of the magnetic tape around the magnetic head. In some cases, tape vibration is prevented by smoothly separating the magnetic head and the magnetic tape. However, as shown in FIG. 6, in order to regulate the top of the magnetic tape 4, the mounting state of the entrance side tape guide 5 and the exit side tape guide 6 is slightly deviated from the ideal tape running condition and tilted in the directions of arrows A and B and forced. Since the magnetic tape 4 has an upward running vector, the tape vibration 9 is likely to occur because the upper end of the magnetic tape 4 is slack, especially on the output side of the magnetic tape 4. It has been confirmed that this tape vibration causes a large low-frequency component in the audible frequency band due to a decrease in tape tension, resulting in a head-impact sound that is harsh to the ear.

[0011]

However, in the above-mentioned structure, there are the following problems.

Under the above guide roller mounting conditions, although the magnetic tape is regulated upward, there is a drawback that the upper end of the magnetic tape is loosened and the magnetic tape easily vibrates.
Therefore, even if the minute protrusions are provided, the sufficient effect of reducing the vibration is small.

Further, there has been a demand for recent improvement in image quality of video equipment, that is, reduction in jitter and reduction in equipment noise. This is generally called "head impact sound" and is in the audible frequency range from several KHz to 16K.
The noise is about Hz. Such head impact sound not only causes ambient noise to be recorded from the recording microphone as the video device becomes smaller, but also causes a problem as a portable video device. In addition, it is natural that even stationary video equipment becomes a problem when used in a quiet environment such as at night.

[0014]

The present invention has been made in view of the above problems and is based on the following means.

On the fixed cylinder corresponding to the magnetic tape exit side where the magnetic tape and the magnetic head are detached, the first minute protrusions are arranged at positions corresponding to the upper end of the magnetic tape,
The second minute protrusions are substantially arranged below the first minute protrusions. In the present embodiment, the method of forming the minute protrusions is a cutting method, and the second minute protrusions are formed by two types of lead processing curves.

Thus, as in the conventional case, a part of the back side facing the outer peripheral surface on which the magnetic tape of the fixed cylinder is slidably contacted is thinned, and the thin part is pressed from the back side of the fixed cylinder and pressed to form a member by plastic deformation. The feature is that they are all formed by cutting. For this reason, not only the problems such as the processing strain in the plastic processing and the cost increase due to the separate processing, which have been conventionally problems, are solved, but also the tape vibration when the magnetic tape is detached by the first and second minute protrusions is eliminated. Since it is suppressed, it greatly contributes to the reduction of the head impact sound.

[0017]

[Function] By arranging the second minute protrusion below the first minute protrusion arranged for improving the jitter due to the head impact, a lifting force is generated at the lower edge of the tape from above the fixed cylinder, By the lever principle with the first minute protrusion as a fulcrum, a pressing force in the cylinder surface direction is generated at the upper end of the magnetic tape near the detachment point, and the upper end of the tape is regulated in the cylinder surface direction. As a result, the tape distortion that causes the snap-through phenomenon immediately before the magnetic head passes through the first minute protrusion is suppressed,
The tape vibration generated by the impact at that time is also suppressed, and the noise can be reduced.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a perspective view of a rotary cylinder according to an embodiment of the present invention. Although description of the common elements described in FIG. 6 is omitted, in the present embodiment, the first minute protrusions 10 are arranged at the positions corresponding to the upper end of the magnetic tape, and the second minute protrusions 11 are the first minute protrusions. Substantially arranged below 10. The present embodiment is characterized in that the method of forming these minute protrusions is a cutting method, and that the second minute protrusions 11 are formed by two types of lead processing curves.

FIG. 2 shows an explanatory view of the method of forming minute projections in this embodiment. FIG. 2A is a front view of the lower fixed cylinder 3 near the tape exit side. In the present embodiment, both the first minute protrusion 10 and the second minute protrusion 11 are formed by the cutting residual when the tape running surface 12 and the lead portion 7 are formed. First
The formation of the minute projections 10 is performed by the first lead curve 13 as in the conventional case, in which the cutting tool in the radial direction and the feed direction is synchronized with the rotation of the lower fixed cylinder to form an uncut portion. The formation of the second minute protrusions 11 is performed by cutting the first lead curve 13 to a desired position, and then using the second lead curve 14. In this case, the uncut portion, that is, the lead curve other than the second minute protrusion 11 may have the same curve as the first and second lead curves. Further, feed control is performed, and finally the lead portion 7
Will be formed.

In FIG. 2B, CC ′ of FIG. 2A is shown.
A cross-sectional view is shown. The tape running surface 12 has a first and a second
The minute projections 10 and 11 and the lead portion 7 for regulating the lower end of the magnetic tape 4 are formed. It should be noted that the position where the second minute protrusion 11 is arranged is substantially the center of the tape running surface 12 in FIG. 2, but it goes without saying that it can be arranged at a position close to the lead portion 7 depending on the situation.

In order to show the effect of the presence or absence of the second minute protrusions 11 in FIG. 3, the tape deformation state in the tape running state in the vicinity of the first minute protrusions 10 on the tape ejection side is observed.

It can be confirmed from FIG. 3 that the upper end 15 of the magnetic tape is pressed when the second minute projections 11 are arranged. That is, by arranging the second minute protrusions 11 below the first minute protrusions 10, a lifting force is generated at the lower edge of the tape from above the fixed cylinder, and the first minute protrusions 1 are generated.
By the lever principle with 0 as a fulcrum, a pressure force in the cylinder surface direction is generated at the upper end portion of the magnetic tape near the separation point to regulate the tape upper end portion 15 in the cylinder surface direction. As a result, the tape distortion that causes the snap-through phenomenon immediately before the magnetic head 1 passes through the first minute protrusions 10 is suppressed, and the tape vibration that is generated due to the impact at that time is also suppressed, resulting in noise reduction. It is possible to reduce.

FIG. 4 shows a head impact sound waveform when the second minute protrusion 11 is not provided, and FIG. 5 shows the second minute protrusion 11.
It shows the head impact sound waveform when there is.

In FIGS. 4 and 5, (a) shows the time-based change of sound pressure, (b) shows the frequency characteristics of the head impact sound, the horizontal axis is the measurement frequency, and the vertical axis is the sound pressure level. The head impact sound has a frequency of 15
It is confirmed that the sound pressure level is low in the region below KHz.

[0026]

As described above in detail, the first minute protrusion and the second minute protrusion are arranged on the fixed cylinder corresponding to the magnetic tape exit side where the magnetic tape and the magnetic head are separated. As a result, the tape vibration when the magnetic tape is detached is suppressed, which greatly contributes to the reduction of the head impact sound. Further, in the present embodiment, the method of forming the minute protrusions is performed by the cutting method, and the second minute protrusions are formed by two kinds of lead processing curves, so that the magnetic tape of the fixed cylinder is slid as in the conventional case. A part of the back side facing the contacting outer peripheral surface is made thin, and the thin part is pressed against the back side of the fixed cylinder to form a plastic deformation by press-contacting a member, and there is a problem of processing strain in plastic working and cost increase due to separate processing. It has been solved and has the effect of being excellent in mass productivity.

[Brief description of drawings]

FIG. 1 is a perspective view of a rotary cylinder according to an embodiment of the present invention.

FIG. 2A is a front view of a main part for explaining formation of minute protrusions in the embodiment. FIG. 2B is a sectional view taken along the line CC ′ of FIG.

FIG. 3 is an explanatory view showing a tape deformation state according to the presence or absence of a second minute protrusion in the embodiment.

FIG. 4 (a) is a head impact sound waveform when the second micro-projection is not provided in the same embodiment, and FIG. 4 (b) is also a frequency characteristic diagram.

FIG. 5 (a) is a head impact sound waveform when the second minute protrusion is provided in the same embodiment, and FIG. 5 (b) is also a frequency characteristic diagram.

FIG. 6 is a perspective view showing a configuration of a cylinder and a tape guide of a conventional rotary head recording / reproducing apparatus.

FIG. 7 is a plan view illustrating conventional head impact and tape vibration.

[Explanation of symbols]

 1 Magnetic Head 2 Rotating Cylinder 3 Lower Fixed Cylinder 4 Magnetic Tape 7 Lead Part 10 First Micro Protrusion 11 Second Micro Protrusion 12 Tape Running Surface 13 First Lead Curve 14 Second Lead Curve 15 Magnetic Tape

Claims (3)

[Claims] 1. A rotary cylinder having a plurality of rotary heads on its outer peripheral surface, a fixed cylinder arranged coaxially with the rotary cylinder and having leads for winding and guiding a tape-shaped recording medium at an angle, and the fixed cylinder. A first arrangement is provided on the cylinder so as to be in sliding contact with the tape-shaped recording medium at a position near the exit side where the tape-shaped recording medium is separated from the fixed cylinder and close to the rotary head.
And a second microprojection on the fixed cylinder at a position closer to the lead than the first microprojection, and the second microprojection has at least two types of lead curves. A magnetic recording / reproducing apparatus characterized by being formed by. 2. The magnetic recording / reproducing apparatus according to claim 1, wherein the first and second minute protrusions are formed by a cutting method. 3. The machining radius of the second minute protrusions is set such that the lead curve is set such that the radius R2 of the first minute protrusion side R1 and the radius R2 of the lead side machining have a relation of R1> R2. The magnetic recording / reproducing apparatus according to claim 1.