JPS5833612B2 - magnetic tape scanning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic tape scanning device having a magnetic tape guide drum made of At-8i alloy with good surface condition and excellent wear resistance.

Generally, the guide drum of a magnetic tape scanning device is made of cast At or At alloy.

If necessary, the surface is treated with ceramic coating, alumite coating, or various coatings to reduce the coefficient of sliding friction and to prevent the tape from being scratched or statically charged when contact is broken. There is.

However, such surface treatment is not sufficient in terms of wear resistance and sliding friction coefficient, and has the problem of requiring troublesome post-processing such as polishing and lapping.

Therefore, dimensional accuracy is difficult to obtain, and the finishing step requires many man-hours, making it unsuitable for mass production.

SUMMARY OF THE INVENTION An object of the present invention is to provide a magnetic tape scanning device equipped with a magnetic tape guide drum that can provide high-quality playback images over a long period of time.

The structure of a magnetic tape scanning device in a magnetic head type magnetic recording/reproducing device of a VTR is shown in FIGS. 1 and 2.

A rotary disk 3 is inserted between a cylindrical stationary upper tram 1 and a stationary lower drum 20 with a clearance (gap) 4 maintained therebetween.

The rotary disk 3 and the drums 1 and 2 are coaxially fixed by a shaft 5, and the upper drum 1 and lower drum 2 are connected by a connector 6 and a bolt 6'.

The rotary disk 3 is fixed to the shaft 5 and can be rotated by a ball bearing 11 and a rotating sliding portion.

On the other hand, the drums 1 and 2 are fixed to a base plate 18 with bolts 10 and an auxiliary base plate 17, as shown in FIG.

The rotary disk 3 is composed of one or more magnetic heads 7, and the magnetic head 7 is arranged between the drum 1 and the tape guide 8 of the drum 2 and the rotary disk 3 in a radial direction of 0.05 to 0.3.
It is protruded in the range of mm.

A diagonal or helical tape guide 8 is cut into the drums 1 and 2 to properly guide the magnetic tape.

The lower drum 2 has a sleeve 9 as shown in FIGS. 1 and 2.
A bushing 13 is attached to this sleeve 9 for grounding purposes.

The pulley 14 is fixed to the shaft 5 with bolts 16, and as the pulley 14 is rotated by a belt 15, the shaft 5 and the rotary disk 3 are rotated.

Another type of magnetic head type recording/reproducing device has an upper drum 20 that rotates and a lower drum 21 that is stationary, as shown in FIG.

Therefore, this type does not require a rotary disk 3 as shown in FIG.

In this type, a pair of magnetic heads 22 which protrude slightly from the tape guide are attached to the drum 20, and the upper drum 20 is fixed to the shaft 5.

The upper drum 20 is rotatable by a rotating sliding portion 12 and a ball bearing 11, and is rotated by means similar to those shown in FIGS. 1 and 2.

The present invention provides the above-mentioned apparatus in which the upper drum 1. It is characterized in that a special A, ff-8i alloy is used for the lower drum 2, the rotary disk 3, and the upper drum 20 and lower drum 21 in FIG.

The composition of this At-8i alloy is 8 to 15% Si by weight.
-0.5~4 weight φ Cu-0.05~1.0 weight φ
It is an alloy containing Mg, and the remainder substantially consisting of At.

This alloy is rapidly solidified from stored hot water, and fine Si crystals can be crystallized and filtered.

The faster this cooling rate is, the better, but desirably 30
The 11 Si crystals in the ~b ingot are acicular or flaky, and in this state they are not suitable for use as a magnetic tape guide drum.

This ingot is warm-forged to a working degree of 30φ or more in a temperature range of 200°C to below the melting point, and then shaped again in the above temperature range, or the ingot is heated to a diameter of 200°C to below the melting point. The Si crystal is mechanically finely divided and uniformly dispersed by external force during molding with a processing degree of 30% or more.

In this case, if the temperature after processing is above the recrystallization temperature and below the melting point, the Si crystals separated by external force will be spheroidized.

The average particle diameter of the spheroidized Si crystals is 1.7 μm.
The following is true.

Molded products made by warm forging are subjected to T4 treatment (450 to 520°C for 1 hour → rapid cooling → left for about one week or more) and T6 color treatment (450 to 520°C) to improve the properties of the alloy.
A heat treatment such as X1h→quenching→artificial aging (for example, 150-b→air cooling) or T5 treatment (quenching immediately after warm forming→artificial aging) is performed.

The molded article made as described above is finished by machining and applied to the magnetic tape guide drum of FIGS. 1, 2, and 3.

Example After fermenting the composition of AC→5A and AC-8B shown in Table 1,
Sliding friction test pieces and actual magnetic tape guide drums were manufactured using the casting method.

On the other hand, after melting the At-8i alloy with the composition shown in Table 1,
0 to b sheets were prepared and subjected to 40 to 90% plastic working at 450°C.

After that, various heat treatments such as 450°C to 520°C
An aging treatment of slow cooling at ℃×8 hours was performed.

In addition, a heat treatment was also performed in which the material was rapidly cooled immediately after warm forging.

The size of Si crystal after plastic working is 1.6 μm to 2.8 μm
It is.

From the above samples, sliding friction test pieces and actual magnetic tape guide drums were fabricated by machining.

FIG. 4 shows a method for measuring the coefficient of sliding friction, in which a magnetic tape (CrO2 tape) 31 for VTR is set on a load 32 and a spring gauge 33.

The angle θ of the magnetic tape at this time is 90°.

The magnetic tape 31 has a force F1 for determining the sliding friction coefficient.
and the spring gauge 33 to obtain a sliding friction force F2.

However, the load in this case is within the range of 10 to 100 g.

From the test results conducted using such equipment and conditions, the sliding friction coefficient μ can be determined by the following formula.

μ・θ F2-Fl・e FIG. 5 shows the measurement results obtained using the above formula.

Curve A is the sliding friction coefficient of At-8i alloy, and is 0
．． 1 shift of 3 or less.

Normally, when a VTR is recording and playing back under normal operating conditions, this At-8i alloy has a small Bezi friction coefficient of 0.24 to 0.25, making it suitable for use as a guide drum.

The curve is the sliding friction coefficient when a ceramic coating is applied to the surface, and it can be seen that the present At-8i alloy is much better than the ceramic coating.

We also tested the case of hard chrome plating, and found that the ceramic rod also had a high coefficient of friction.

Curve B//'1AC-5A and Curve C are the overall friction coefficients of AC-8B material when the surface roughness is machined to 3 to 4 μm.

The sliding friction coefficient of AC-5A and AC-8B is 0.27
~0.31.0.26~0.0 even under a load of 30~40g.
27, indicating that the present A, /, -8i series alloy is superior.

If the sliding friction coefficient is large, it tends to cause screen flickering, and we confirmed that the sliding friction coefficient measured in this way reproduces the sliding friction of the actual magnetic tape guide drum.

According to experiments, the coefficient of friction of the magnetic tape guide drum is 0.3.
Below, it should preferably be 0.28 or less.

Further, in order to obtain a sliding friction coefficient of 0.3 or less, the surface roughness should be 1 to 6 μm, preferably 2 to 5 μm.

Figures 6a and 6c are cross-sectional images of the surfaces of magnetic tape guide drums made of KL-8i alloy, AC-5A, and AC-8B materials, taken with a microscope at a magnification of 400 times. It is machined to a roughness of 3 to 4 μm.

Figure 6a shows this At-8i alloy, Figure 6 shows AC-5A.
, FIG. 6C is AC-8B material.

This At-8i alloy is a small Si crystal, but AC-5
A.

The AC-8B material is a large Si crystal, and cavities are also observed.

In addition, looking at the surface condition, At-8i alloys only have unevenness due to machined lines, but AC-5A and AC-8B
The material shows marks where relatively large Si crystals were removed or unevenness caused by casting holes.

Figures 7a to 7c are the results of observing the tape guide surface of the magnetic tape guide drum using an electron microscope, and the magnification is 2.
000 times.

Figure 7a shows the Al-8i alloy of the present invention, Figure 7 shows AC
-5A.

FIG. 7C shows the surface condition of AC-8b material, all of which have been machined to a surface roughness of 3 to 4 μm.

As can be seen from this figure, the machined lines on the surface of the A,/-8i series alloy are continuous in the direction of movement of the magnetic tape and are smooth.

However, the AC-5A and AC-8B materials have dents on the surface, and the AC-8B material in particular has dents on the surface, and the AC-8B material in particular has large dents.

This depression is a plan view of the unevenness shown in FIG. 6, and is a hole or a hole where relatively large Si crystals were removed during machining.

These depressions can also cause damage to the magnetic tape.

Another important feature of the present invention is that it has good abrasion resistance.

Figures 8a to 8c show the results of wear tests conducted continuously for 600 to 700 hours using an actual magnetic tape guide drum.

The magnetic tape used in this test was the same as that used in the sliding wear test.

Figure 8 a shows the At-8i alloy of the present invention, Figure 8 shows AC
-5A and FIG. 8C are the test results for drums made of AC-8B, and the amount of wear is shown by the decrease in wear.

For comparison, the roughness before the test is shown on the left side of Figures 8a to 8C, but these curves are records of the roughness meter, and the actual surfaces are shown in Figures 7a to 7. It should be noted that there is a depression as shown in C.

The amount of wear of the A,/, -8i drum of the present invention is 0.5 μm
However, AC-5A and AC-8B drums are 0.7
~0.9 μm, indicating that the At-8i drum of the present invention can maintain a desired surface condition even during long-term use and has excellent wear resistance.

Furthermore, as shown in Table 1, the inventors conducted the above tests on drums with different At-8i alloy compositions, Sl crystal sizes, and heat treatments, and found that when the Sl crystals were larger than 5 μm, It was found that it was difficult to obtain the desired surface condition by machining the surface of the tape (Gf), and that the size of the Sl crystal should be 5 μm or less.

When the amount of Si is 8 weight, the amount of wear on the drum increases, and when the amount of Si is 15 weight φ or more, a large amount of primary Si crystals, which cannot be divided and dispersed by plastic working, crystallizes out. Like the -5A and AC-8B materials, dents are formed during machining, which can cause damage to the magnetic tape.

Preferably, it is about 12 weight φ near the At-8i eutectic component.

Furthermore, Mg combines with Sl to form an intermetallic compound, which acts to strengthen the matrix by precipitation.

However, when Mg is added in an amount less than 0.05 weight φ, the effect is small, and when added in an amount more than 1.0 weight φ, the toughness and impact strength tend to decrease, and warm forgeability deteriorates.

Preferably, the weight φ should be 0.3 to 0.6.

In addition, Cu is hardened to the At base to form Cu2At, which strengthens the material through heat treatment and improves machinability or wear resistance.

However, Cu requires less heat treatment when the weight is less than 0.5 φ.
If the weight is 3 or more, the improvement in mechanical properties will be saturated, so from the economic point of view, the weight should be 4 or less, and it is preferable to add 1 to 3 parts by weight.

Other Fe. Impurities such as Cry Niy Zry 'ri are present in the alloy, but the total amount of them is 5 weight φ
It should be:

As described in detail above, the magnetic tape scanning device of the present invention uses a special KL-8i alloy for the magnetic tape guide drum, which improves the surface condition and wear resistance of the drum compared to conventional ceramic coatings and AC-8i alloys. It has excellent characteristics that are not found in 5A, AC-8B, etc.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing the external appearance of the magnetic tape scanning device, FIG. 2 is a sectional view thereof, and FIG. 3 is a sectional view of the magnetic tape scanning device having a different structure from FIGS. 1 and 2. , Figure 4 is a schematic diagram of the sliding friction coefficient testing device, Figure 5 is a graph showing the results of the Pesci friction coefficient test, Figure 6 is a microscopic photograph of the cross section of the surface of the magnetic tape guide drum, and Figure 7 is the magnetic tape guide. An electron microscope photograph of the surface condition of the tape guide drum and FIG. 8 are graphs showing the results of measuring the surface condition of the magnetic tape guide drum before and after use with an aging meter. 1... Stationary upper drum, 2... Stationary lower drum, 3... Rotating disk, 4... Gap, 5
...Shaft, 6...Connector, 6
'...Bolt, 7...Magnetic head, 8
...Tape guide, 9...Sleeve,
10... Bolt, 11... Ball bearing, 12... Excitation coil, 13...
・Butshu 14...7', -Lee, 15...
・01. Magnetic tape, 20, songs, rotating drum, 22...
...Magnetic head, 21...Stationary drum, 3
0...rod, sample), 31°°°...magnetic tape, 32...weight, 33...spring.

Claims (1)

[Scope of Claims] 1. A magnetic tape scanning device characterized by including the following configuration. (1) a guide means including a circular stationary drum for slidingly guiding the magnetic tape along the smooth surface of a guide path formed on the outer periphery of the drum; (2) a guide means radially extending from the circumference of the drum; slightly protruding,
(3) a rotating magnetic head device including at least one magnetic head disposed at a position where it can make sliding contact with a magnetic tape; (3) a rotating magnetic head device that supports the magnetic head device and the guide drum concentrically; (4) means for supporting the guide drum for rotation independently of the guide drum by forming a small gap between the upper ends of the guide drum; and (4) means for driving the support means, wherein at least the guide passageway comprises: , silicon 8~15 layers #φ, copper 1~
4% by weight, magnesium 0.05 to 0.6% by weight, and the remainder substantially aluminum, and the average grain size of the spherical eutectic silicon in this alloy is 5%.
.mu.m or less, and parallel fine continuous processed lines with a surface roughness of 1 to 6 .mu.m are formed along the traveling direction of the magnetic tape on the surface of the passage. 2. Magnetic tape scanning according to claim 1, characterized in that the guide path has surface characteristics such that the Veggie friction coefficient is 0.28 or less in the magnetic tape load range of 10 to 100 grams. Device.