JPS6069855A - Production of guiding drum for magnetic tape scanner - Google Patents

Abstract

PURPOSE:To improve surface condition and wear resistance by cooling quickly and solidifying a molten Al-Si alloy to produce a casting ingot, forging the above-mentioned casting ingot to a drum shape and forming worked lines on the outside circumference of the drum by machining. CONSTITUTION:An Al-Si alloy is used as an alloy for forming a drum and the compsn. thereof consists of 8-15wt% Si, 0.5-4wt% Cu, 0.05-1.0wt% Mg and the balance Al. The alloy is quickly cooled and solidified from a molten metal to crystallize finely an Si crystal. The cooling is accomplished at >=(30-60 deg.C/ sec) cooling rate. The casting ingot is subjected to warm forging at 200 deg.C- the m.p. or below and >=30% reduction ratio and is again molded in the above- mentioned temp. range to part mechanically the Si crystal to <=5mum average grain size and to disperse uniformly said crystal. Such molded alloy is subjected to a heat treatment such as a T4 treatment (450-520 deg.CX1h quick cooling resting for about >=1 week), etc. and is finished to a drum by machining. Parallel and roughly continuous machined lines having 1-6mum surface roughness are formed to a passage for guiding a tape in the advancing direction of the tape.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a magnetic tape guide drum with good surface condition and excellent wear resistance using an AQ-8i alloy.

Generally, the guide drum of a magnetic tape scanning device is made of a casting of AQ or an AQ alloy.

If necessary, the surface is treated with ceramic coating, alumite coating, or various types of plating to reduce the coefficient of sliding friction and prevent scratches on the tape or static electricity from forming on the contact surface. There is. However, this type of surface treatment is not sufficient in terms of wear resistance and sliding friction coefficient, and
There is a problem that requires troublesome post-processing such as polishing and lapping. Therefore, it has drawbacks such as difficulty in achieving dimensional accuracy, and the number of man-hours required for finishing, making it unsuitable for mass production.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a magnetic tape guide drum that provides a high-quality playback screen for a long period of time.

The present invention involves rapid solidification of molten AQ-3i alloy, forging the obtained ingot into a drum shape, and then machining to create a magnetic tape guide path on the outer periphery of the drum with surface roughness along the magnetic tape traveling direction. The purpose is to form parallel, substantially continuous processing lines of 1 to 6 μm.

A magnetic tape scanning device in a magnetic head type magnetic recording/reproducing device of a VTR has the following configurations (1) to (4).

(1) a guide means for slidingly guiding a magnetic tape along the smooth surface of a guide path formed on the outer periphery of the drum, including a cylindrical stationary drum; stands out,
(3) a rotating magnetic head device including at least one magnetic head provided at a position where it can make full 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 thereof; and (4) means for driving the support means.

- Examples are shown in FIGS. 1 and 2. A rotary disk 3 is inserted between a cylindrical stationary upper drum 1 and a stationary lower drum 2 with a clearance (gap) 4 maintained therebetween. The rotating disk 3 and the drums 1 and 2 are coaxially fixed by a shaft 5, and the upper drum 1 and the lower drum 2 are connected by a connector 6 and a bolt 6'. The rotary disk 3 is fixed to the shaft 5,
It can be rotated by a ball bearing 11 and a rotating sliding part. On the other hand, the drums 1 and 2 are fixed to a base plate 18 by poles 1-10 and an auxiliary base plate 17, as shown in FIG. The rotary disk 3 is composed of 16 or more magnetic heads 7, and the magnetic heads 7 are connected to the tape guides 8 of the drums 1 and 2 and the rotary disk 3.
It protrudes in the radial direction in the range of 0.05 to 0.3 mm. A diagonal or spiral tape guide 8 is cut into the drums 1 and 2 to properly guide the magnetic tape. As shown in FIGS. 1 and 2, the lower drum 2 is integral with a sleeve 9, to which a bush 13 is attached for grounding purposes. The pulley 14 is fixed to the shaft 5 with a bolt 16, and is driven by a belt 15 to rotate the pulley 14, thereby rotating the shaft 5 and the rotary disk 3.

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 that protrude slightly from the tape guide are combined with 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 is directed to the above-mentioned apparatus, as shown in FIGS. 1 and 2.
Upper drum 1 in the diagram. At least one of the lower drum 2 and the rotary disk 3
At least one of the upper drum 20 and the lower drum 2J shown in FIG. 3 is manufactured by the method described above. The preferred composition of the AQ-Si alloy is 8 to 15
wt% 5i-0,5-4wt% Cu-0,05-1
．． The alloy contains 0% by weight of Mg, and the remainder consists essentially of AQ. This alloy is rapidly solidified from a molten metal to finely crystallize Si crystals. The faster the cooling rate, the better, but it is preferable to carry out continuous casting at a cooling rate of 30 to 30 b. The Si crystal in the form of an ingot is acicular or flaky, and in this state is not suitable for use as a magnetic tape guide drum. This ingot is warm forged in a temperature range of 200°C to below the melting point with a working degree of 30% or more, and then shaped again in the above temperature range, or the ingot has a diameter of 200°C to below the melting point. Using an external force during molding at a temperature range of 30% or more, the Si product is mechanically finely divided and uniformly dispersed. 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 divided spheroidized Si
The average particle size of the crystals is 1.7 μm or less. It is desirable that the forging process divides the eutectic Si into particles having an average grain size of 5 μm or less. This facilitates the formation of nearly continuous machining lines.

In order to improve the properties of the alloy, molded products made by warm forging are subjected to T4 treatment (450 to 1h → quenching → leaving for about 1 week or more), T6 treatment (450 to 520℃Xlh → quenching → artificial aging; e.g. 150 ~200°C x 8 hours → air cooling) It is desirable to perform heat treatment such as T5 treatment (quenching immediately after warm forming → artificial aging).

The molded product produced as described above is finished by machining, and parallel, almost continuous machining lines with a surface roughness of 1 to 6 μm are formed along the tape traveling direction in the magnetic tape guide path on the outer periphery of the drum. Ru.

In the present invention, the ingot is forged and the eutectic Si is finely divided before being machined, so that the machining lines can be formed to be substantially continuous. The magnetic tape guide drum shown in FIGS. 1, 2, and 3 is used.

Example After melting the compositions of AC-5A and AC-8B shown in Table 1, sliding friction test pieces and actual magnetic tape guide drums were manufactured by a casting method. On the other hand, the AQ of the composition shown in Table 1
After melting the -3i alloy, a 30-b billet was prepared and subjected to 40-90% plastic working at 450°C. After that, various heat treatments such as 450℃~520℃
The specimens were subjected to solution treatment at 170°C x 8h, left for one week or more, and then subjected to aging treatment at 170'x8h→slow cooling. Further, the size of the 84 crystals after 6 plastic working, which was also heat treated by quenching immediately after warm forging, is 1.6 μm to 2.8 μm. From the above samples, a sliding friction test piece 3o and an actual magnetic tape guide drum were fabricated by machining.

FIG. 4 shows a method for measuring the coefficient of friction, in which a VTR magnetic tape (Cry2 tape) 31 is placed between a load 32 and a spring gauge 33. The angle θ of the magnetic tape at this time is 9o6. magnetic tape 31
It is pulled by the force FW for adjusting the sliding friction coefficient and the spring gauge 33, and a sliding friction force F-1 is obtained. However, the load in this case is within the range of 10 to 100 g.

Based on test results conducted using such equipment and conditions.

The sliding friction coefficient μ can be determined by the following formula.

FIG. 5 shows the measurement results obtained using the above formula. Curve A is A
Q-Si is the sliding friction coefficient of the i-based alloy, and is a value of 0.3 or less.

Normally, when a VTR performs recording and playback under normal operating conditions, the present AQ-8i alloy has a low sliding friction coefficient of 0.24 to 0.25 within this range, making it suitable 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 AQ-8i alloy is much superior to the ceramic coating.

We also tested a rod with hard chrome plating, and found that the coefficient of sliding friction was greater than that of a ceramic rod. Curve B is the sliding friction coefficient when A-8B material is machined to a surface roughness of 3 to 4 μm.

The slip 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 AQ-Si 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. did. According to experiments, the coefficient of friction of the magnetic tape guide drum is 0.
, 3 or less, preferably 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 to 6c are cross-sections of the surfaces of magnetic tape guide drums made of H-3i alloy, AC-5A, and AC-8B materials, taken with a microscope at 400x magnification. It is machined to a surface roughness of 3 to 4 μm. Figure 6a shows the present AQ-5i alloy,
The figure shows AC-5A material, and FIG. 6C shows AC-8B material. This AQ-8i series alloy is a small Si product, but AC-5A
.

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

In addition, looking at the surface condition, AQ-8i alloy only has unevenness due to machined lines, but AC-5A and AC-8B
The material shows traces of relatively large Si crystals being removed, or unevenness caused by casting cavities.

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 surface condition of the AΩ-Si alloy of the present invention, Figure 7A shows the surface condition of AC-5A, and Figure 7C shows the surface condition of AC-8b material, all of which are machined to a surface roughness of 3 to 4μm. This is what is being done. As can be seen from this figure, the machining lines on the surface of the present AQ-S i alloy are almost continuous in the direction of movement of the magnetic tape and are smooth. However, AC-5A and AC-8
Material B has dents on its surface, and material A C-813 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 a relatively large Si product was removed during machining. Stiff dents can also cause damage to magnetic tape.

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

Figures 8a to 8c show the results of an Ir wear test conducted continuously for 600 to 700 hours using an actual magnetic tape guide drum. Furthermore, the magnetic tape used in this test was the same as that used in the sliding friction test. Figure 8 a shows the AQ-Si alloy of the present invention, Figure 8 shows A C-5A,
FIG. 8C shows the test results for the AC-8B drum, and the amount of wear is shown by the decrease in wear. For comparison, the roughness before test 1 is shown on the left side of Figures 8a to 81fflc, but these curves are records of roughness N1, and the actual surfaces are shown in Figures 7a to 7th. It should be noted that there is a depression as shown in Figure C.

! ; The amount of wear of the AQ-Sim drum of the invention is 0.5 μm, while the amount of wear of the drums made of A, C-5A, and AC-8B is 0.7 μm.
It can be seen that the AQ-S i drum of the present invention can maintain a desired surface condition even after long-term use, and has excellent wear resistance. Furthermore, the inventors determined the composition of the AM-8i alloy as shown in Table 1,
As a result of conducting the above tests on drums with different Si product sizes and heat treatments, it was found that if the Si crystals were larger than 5 μm, it was difficult to machine the tape guide surface to the desired surface condition; It was found that the size should be 5 μm or less.

Table 1 Processing conditions T4: 500°C x 1 hr → Rapid cooling → Releasing at room temperature for 1 week or more T5: 470°C warm forming → Rapid cooling → l 70°C
8 hr aging treatment '176: 500℃×1hr-*Rapid cooling → 170℃×8hr aging treatment as caSL: :
If the Si content is 8% by weight or less, the amount of drum wear will increase, while if the Si content is 15% by weight or more, a large amount of primary Si crystals will crystallize, which cannot be separated and dispersed by plastic working. , 8C-5A, and AC-8B materials, dents are formed during machining, which can cause damage to the magnetic tape.

Desirably, a 12-fold close-up view around the AQ-Si co-component component is preferable.

Furthermore, Mg combines with Si to form an intermetallic compound, which acts to strengthen the matrix by precipitation. However, when Mg is added in an amount of 0.05% by weight or less, the effect is small, and when added in an amount of 1.0% by weight or more, the toughness and impact value tend to decrease, resulting in poor warm castability. It should preferably be between 0.3 and 0.6% by weight. In addition, Cu is dissolved in the base of AQ and Cu-
1/IQ, strengthens through heat treatment, and improves machinability or wear resistance. but,
If Cu is less than 0.5% by weight, the heat treatment effect will be small, and if it is more than 3% by weight, the improvement in mechanical properties will be saturated. Therefore, from an economical point of view, the content should be less than 4% by weight, and preferably 1 to 3% by weight. It is preferable to add 3% by weight. Other Fe.

Impurities such as Cr y N l p Z r + Ti may be present in the alloy, but their total amount should be less than 5% by weight.

As detailed above, by manufacturing a magnetic tape guide drum by the method of the present invention, the surface condition and abrasion resistance of the drum are improved compared to conventional ceramic coating, AC-5.
It has superior characteristics that are not found in A, 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. , Fig. 4 is a schematic diagram of the testing device for the sliding friction coefficient, and Fig. 5 is the sliding friction coefficient test device. Graph showing the friction coefficient test results, Figure 6 is a microscopic photograph of the cross section of the surface of the magnetic tape guide drum, Figure 7 is an electron microscope photograph of the state of the tape guide surface of the magnetic tape guiding drum, and Figure 8 is before and after use. It is a graph showing the results of measuring the surface condition of the magnetic tape guide drum after that using an aging meter. 1... Stationary upper drum, 2... Stationary lower drum, 3...
・Rotary disk, 4... Gap, 5... Shaft, 6...
Connector, 6'...Bolt, 7...Magnetic head,
8...Tape guide, 9...Sleeve, 10...
Pol 1-111... Ball bearing, 12... Excitation coil, 13... Bush, 14... Pulley,
15... Magnetic tape, 20... Rotating drum, 21.
...Stationary drum, 22...Magnetic head, 30...Test piece, 31...Magnetic tape, 32...Weight, Figure 7 (C) Continued from page 10 Invention Person Temple 1) Meiyu 29 Uchida-cho, Kikyusho, Totsuka-ku, Yokohama Hitachi, Ltd. Home Appliances Research Procedures Amendment (
Methoden Showa 5 resistance +1i 2+14 1'+1i'+'I-; Nagasaki Shiga Gakudono/I-f'l
No. 77405 special frlRfi No. 77405 of 1984. The merit of the invention. Manufacturing method of guide drum for magnetic tape scanning device 1], then the relationship with 1"・1'1 1 'r 111' + Ix
r1 person, 1'1 West ml, It-style kake 1, made
Agent 1, Agent 2, amend the brief description of the drawings in the specification as follows. (1) Add "indicates metallographic structure" before "micrograph" on page 17, line 16. (2) On page 17, line 17, "state" is corrected to "scanning type that shows the macroscopic metal structure of". I”d

Claims (1)

[Scope of Claims] 1. In a magnetic tape scanning device that includes a circular stationary drum and a rotating drum and slides and guides a magnetic tape along a guide path formed on the outer periphery of these drums, at least one of the drums is configured as follows. A method for manufacturing a guide drum for a magnetic tape scanning device, characterized in that it is manufactured by the steps of: (1) A step of rapidly cooling and solidifying a molten aluminum-silicon alloy to produce an ingot; (2) A step of forging the ingot to produce a drum-shaped molded product; and (:l) machining. forming parallel, substantially continuous processing lines with a surface roughness of ~6 μm along the traveling direction of the magnetic tape on the outer periphery of the molded product. 2. A method for manufacturing a guide drum for a magnetic tape scanning device according to claim 1, characterized in that the forging step divides the eutectic silicon of the ingot into particles having an average grain size of 5 μm or less. 3. In a magnetic tape scanning device that includes a circular stationary drum and a rotating drum and slides and guides a magnetic tape along a guide path formed on the outer periphery of these drums, at least one of the drums is manufactured by the following process. A method for manufacturing a guide drum for a magnetic tape scanning device, characterized by: (1) a step of rapidly cooling and solidifying a molten aluminum-silicon alloy to produce an ingot; (2) a step of forging the ingot to produce a drum-shaped molded product; (3) a step of manufacturing the molded product. A heat treatment process including solution treatment and subsequent aging treatment, and (4) machining are performed to form a substantially parallel surface roughness of 1 to 6 μm along the traveling direction of the magnetic tape on the outer periphery of the molded product. The process of forming a continuous processing line. 4. The method of manufacturing a guide drum for a magnetic tape scanning device according to claim 3, wherein the forging step divides the eutectic silicon of the ingot into particles having an average grain size of 5 μm or less.