JP3329622B2 - Friction disc - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a friction disk in a friction false twist device for applying false twist to a synthetic fiber filament / microfilament yarn running while being drawn, and particularly to obtaining a high quality processed yarn. The present invention relates to a friction disk for a friction false twisting device, which is capable of forming a work piece and is excellent in stability at work, dimensional accuracy, durability and running cost.

[0002]

2. Description of the Related Art The structure of a triaxial circumscribed friction false twist device is shown in FIG.
As shown in FIG. 3, three rotating shafts 20 each having a plurality of friction disks 10 are arranged so that the friction disks 10 partially overlap each other. When the yarn 30 is spirally provided so as to be in contact with each friction disk 10 and the yarn 30 is run in the direction of the arrow while rotating each friction disk 10, false twist is applied to the yarn 30. I can do it.

[0003] The friction disk system is widely used because it has an excellent action of uniformizing the yarn tension and can increase the processing speed as compared with a false twist system such as a pin system or a nip belt system. . Therefore, various proposals have been made regarding the material, shape, combination, and the like of the friction disk 10.

For example, in Japanese Patent Application Laid-Open No. 49-13457, a friction disk made of resin is disclosed in Japanese Patent Application Laid-Open No. 49-699.
Japanese Patent Application Laid-Open No. 52-15652 discloses a ceramic friction disk having a groove formed on a contact surface with a yarn.
In the publication, friction disks with ceramic coating or chromium plating are introduced.

[0005] Here, when a characteristic comparison was performed for each of the above materials, as shown in Table 1, the friction disk 10
Yarn quality, durability and cost are different depending on the material. In other words, the yarn made of resin has a good yarn quality, but causes a fluctuation in tension due to a change in frictional conditions due to a rise in the temperature of the disk at the beginning of operation of the apparatus, which adversely affects the quality of the next process such as a loom, or Since the outer diameter swells as much as 0.2 mm in six months depending on the use atmosphere and the oil agent, the durability is low and the cost of the apparatus due to the provision of a tension monitor is problematic.

On the other hand, those coated with ceramics have a problem that the yarn quality such as the number of twists and the strength of the yarn is insufficient and the cost is high.

[0007] Ceramic friction disks are excellent in work stability, dimensional accuracy, durability, and running cost, but are liable to generate fluff and snow and have a problem in yarn quality.

[0008]

[Table 1]

Therefore, there has been proposed a method of improving the twisting force by variously controlling the surface roughness and the crystal particle diameter of a ceramic friction disk to reduce snow (fiber abrasion powder, oil). For example, Japanese Patent Publication No. 53-10185 discloses a crystal particle size of alumina ceramics of 10 to 40 μm.
m, a method of realizing a high twisting force by making the crystal grains and single filaments mesh with each other with a surface roughness of 1 to 3 s has been proposed. Japanese Patent Application Laid-Open No. 51-92335 proposes a method of forming scratches simultaneously with false twisting by setting the average crystal particle diameter of alumina ceramics to 30 μm or more and the surface roughness to 3 s or more. Japanese Patent Application Laid-Open No. 52-18948 proposes a method of obtaining a high twisting force with a surface roughness of 4 to 12 s using ceramics and metal. JP-A-52-63461
In Japanese Patent Laid-Open No. H11-264, there is proposed a method of improving twisting force and reducing snow with a ceramic crystal particle diameter of 2 to 30 μm and a surface roughness of 1 to 6 s.

Japanese Patent Application Laid-Open No. 52-132146 discloses an alumina ceramic having a purity of 89% or more and a surface roughness R.
A method of improving twisting power and reducing snow has been proposed with z = 2 to 3.5 μm and Rmax = 3 to 4.5 μm. Japanese Patent Application Laid-Open No. 53-111148 discloses that a ceramic or ceramic coating has a crystal particle size of 2 or less.
Methods of improving twisting power and reducing snow have been proposed with a thickness of up to 30 μm and a surface roughness of 1 to 3 s. JP-A-55-
No. 76127 discloses alumina ceramics having a purity of 97% or more and having an average crystal particle diameter of 3 to 10 μm and a surface roughness Rz =
1.6 to 2.7 μm, disk thickness = 6 to 6.2 mm,
There has been proposed a method for improving the twisting force by setting the fiber contact surface R = 3.2 to 3.4 mm and the connection r between the fiber contact surface and the disk side r = 0.4 to 0.6 mm.

[0011]

Although a number of proposals have been made as described above, a friction disk made of ceramics having a sufficient yarn quality for microfilament processing has not been obtained.

When the friction disk 10 is formed of ceramics, the ceramic raw material is formed into a predetermined shape, fired, and then the surface is ground and polished with a diamond grindstone or the like to improve the dimensional accuracy and to obtain a predetermined surface roughness. For this reason, the crystal grains on the surface have sharp edges, and it is inevitable to cut the yarn 30 to generate snow.

[0013]

Accordingly, the present invention provides a ceramic friction disk having a maximum crystal grain diameter of 20 μm or less, an average crystal grain diameter of 2 to 7 μm, and a maximum aspect ratio of a crystal grain at a contact surface with a yarn. Is 3 or less, and the edges of the crystal grains are rounded.

That is, the friction disk of the present invention
After grinding and polishing the surface of ceramics, heat treatment such as re-baking, chemical etching, physical etching, etc. are performed to round the edges of the crystal grains, thereby preventing the occurrence of snow without damaging the yarn. It is like that.

Further, it has been found that the maximum particle diameter and the maximum aspect ratio are important for the crystal particle diameter of ceramics. That is, when coarse particles having abnormal grain growth are present on the surface of the ceramic, the yarn is liable to slip at these particle portions, the friction coefficient is reduced, and the number of twists is reduced. Therefore, the maximum particle diameter of the crystal particles is 20 μm or less,
If the maximum aspect ratio is 3 or less, a sufficient number of twists can be given to the yarn.

The aspect ratio is the ratio of the major axis to the minor axis of the crystal grains. In the present invention, the maximum aspect ratio is 3 or less.

[0017]

Embodiments of the present invention will be described below.

As shown in FIGS. 1 and 2, the friction disc 10 is a disc-shaped body made of ceramics, has a through hole 11 for attachment to a rotating shaft at the center, and has a thread-like shape.
The contact surface 12 is curved.

When this friction disk 10 is used in a triaxial circumscribed friction false twist device, it is mounted on a rotating shaft 20 as shown in FIG. 3, and the friction disks 10 are arranged so as to partially overlap with each other. When the yarn 30 is run in the direction of the arrow while rotating each friction disk 10, the yarn 30 can be false-twisted.

At this time, since the thread 30 is twisted by the contact surface 12 of the friction disk 10, the state of the contact surface 12 is important.

In the present invention, the edge of the crystal grain is rounded on the contact surface 12 so that the maximum crystal grain diameter is 20 mm.
By setting the maximum aspect ratio to 3 μm or less, the damage to the thread 30 is reduced to prevent the occurrence of snow and to impart a large amount of twist.

Here, a round edge of a crystal particle means that each crystal has no sharp edge and a round shape when the crystal particle is observed by a micrograph of the surface or the like. Then, in order to round the edges of the crystal grains, re-firing, chemical / physical etching, or the like may be performed. For example, when refiring is performed, the ceramic friction disk 1 obtained by a predetermined manufacturing method is used.
After grinding and polishing to 0, firing may be performed again at a temperature equal to or higher than the firing temperature. By re-baking in this manner, the crystal edge is heated and softened to have a round shape without sharp edges. In addition, if chemical and physical etching is performed, the edges of the crystal grains are removed by etching, resulting in a rounded shape.

The reason why the maximum particle size is set to 20 μm or less is that if coarse particles having a particle size exceeding 20 μm are present, the filament 30 slips in the coarse particles, the frictional force is weakened, and twist is hardly imparted. It is because it becomes. On the other hand, if the maximum crystal particle diameter is 20 μm or less, the overall crystal particle diameter is small and uniform. By the way, the average particle size is 2-7μ
m is preferably within the range.

Furthermore, the aspect ratio of a crystal grain is the ratio of the major axis to the minor axis of the particle. The reason why the maximum aspect ratio is set to 3 or less is that if there is a columnar particle having an aspect ratio exceeding 3, Thread-like 30
This is because the frictional force with the above becomes weak and it becomes difficult to impart twist. In other words, when the aspect ratio of the crystal particles is small and the shape is a polygonal shape close to a sphere, the R shape of the crystal particles that comes into contact with the yarn increases on average, and the amount of generated snow decreases.

The maximum crystal grain size and the maximum aspect ratio can be measured based on a micrograph of the surface. In order to keep the maximum crystal particle diameter and the maximum aspect ratio within the above ranges, the composition and particle size of the ceramic raw material, the conditions for main firing and re-firing, and the like may be adjusted.

The surface roughness (Ra) of the contact surface 12 of the friction disk 10 is preferably in the range of 0.6 to 0.9 μm.

Furthermore, various materials such as alumina and zirconia can be used as ceramics forming the friction disk 10.

Experimental Example 1 A friction disk 10 shown in FIGS.
99.5% or more of Al ₂ O ₃ ,
A mixed raw material comprising MgO, SiO ₂ as a sintering aid, and unavoidable impurities was pulverized to obtain a fine powder raw material having a particle size of less than 3 μm, preferably less than 1 μm. A binder component necessary for molding was added to the raw material powder, and the mixture was granulated and formed into a disk shape, and calcined at a relatively low temperature so as to suppress the growth of crystal grains and obtain a dense body. Next, a predetermined size and shape were obtained by grinding, and the surface was finished by barrel processing.

FIG. 4 shows a micrograph of the contact surface 12 of the friction disk 10 of the embodiment of the present invention obtained by the above-mentioned method at 400 times magnification and a schematic view of the crystal grains. As shown in FIG. , Average crystal particle size 1
At 0 μm or less, the maximum aspect ratio was 2-3, and the crystal grains were round and small.

On the other hand, as a comparative example, the maximum crystal grain diameter was increased to 40 to 60 μm by increasing the particle diameter of the raw material powder to 3 μm and increasing both the firing temperature and the refiring temperature by the same production method as described above. Thus, a friction disk 10 having a large crystal grain and a rounded edge was produced (Comparative Example 1). As shown in FIG. 5 which is a micrograph and a schematic diagram of the contact surface 12 magnified 400 times, the crystal grains were round and large.

Further, as another comparative example, the contact surface 12 remains the barrel finished surface without the re-firing after the grinding / barrel processing, with the particle diameter of the raw material powder being 1 to 3 μm by the same manufacturing method as described above. Was manufactured (Comparative Example 2). As shown in FIG. 6, a schematic diagram of a micrograph of the contact surface 12 magnified 400 times is shown in FIG.
Approximately 15 μm, elongated crystal grains having a maximum aspect ratio of 2-3 were formed, and the crystal grains had sharp and small edges.

Further, as another comparative example, one coated with ceramics and one made of resin (polyurethane) were prepared, and each was mounted on an actual machine and subjected to a use test. As the yarn 30, polyester 150d / 48f and polyester 75d / 36f were used.

Each of the number of twists, strength,
Tables 2 and 3 show the results obtained by measuring the elongation and the amount of generated snow.
In addition, each numerical value is represented by ○, in order of excellent characteristic value,
Table 4 shows the results evaluated by Δ and ×.

Comparing the yarn qualities of the three ceramic materials, the comparative example 2 in which re-firing was not performed produced a large amount of snow, whereas the comparative examples 1 and 2 in which the crystal was rounded by re-firing. Has less snow. That is, since the sharp edges present in the crystal grains on the thread contact surface act as cutting edges and generate soft snow by shaving the soft thread material, it is necessary to round the edges of the crystal grains to reduce the amount of snow generated. Understand.

On the other hand, from the viewpoint of the number of twists, in Comparative Example 1 having a large crystal particle diameter, the slip phenomenon occurs and the number of twists is reduced. It can be seen that a sufficient number of twists can be obtained.

Therefore, the examples of the present invention are excellent in the overall characteristics of the yarn quality such as the amount of generated snow, strength, elongation, and number of twists, and have excellent characteristics even when compared with the conventional product coated with ceramics. You can see that it is doing.

[0037]

[Table 2]

[0038]

[Table 3]

[0039]

[Table 4]

Next, the relationship between the amount of generated snow and the number of twists in the three types of friction disks made of ceramics was summarized using the above experimental results, as shown in FIG.

As is clear from this graph, Comparative Example 2
Since the crystal grains were small and sharp, the number of twists was large, but the amount of snow generated was large. In Comparative Example 1, the crystal grains were large and round, and the number of twists was small, but the number of twists was small. On the other hand, in the examples of the present invention, since the crystal grains are small and round, the amount of generated snow is small and the number of twists can be increased.

In the above-mentioned experimental example, the edges of the crystal grains were rounded by re-baking. However, the same applies to the case where the edges were rounded by a method such as chemical etching or physical etching. The material of the ceramics constituting the friction disk is not limited to the above-mentioned alumina ceramics, and various ceramics can be used.

[0043]

As described above, according to the present invention, the maximum crystal grain size at least at the contact surface of the ceramic friction disk with the yarn is 20 μm or less, the maximum aspect ratio of the crystal grains is 3 or less, and By rounding the edges of the particles, it is possible to reduce the occurrence of snow and increase the number of twists while maintaining the work stability, dimensional accuracy, durability, and low running costs, which are the characteristics of ceramic friction discs. And a high twisting force can be realized.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a friction disk of the present invention.

FIG. 2 is a sectional view taken along line XX in FIG.

FIG. 3 is a side view showing a friction type false twisting machine using a friction disk.

FIG. 4 is a view showing crystal grains on a contact surface of the friction disk according to the embodiment of the present invention.

FIG. 5 is a view showing crystal grains on a contact surface of a friction disk according to a comparative example.

FIG. 6 is a view showing crystal grains on a contact surface of a friction disk according to a comparative example.

FIG. 7 is a graph showing the relationship between the amount of generated snow and the number of twists when various types of friction disks are used.

[Explanation of symbols]

 10: Friction disk 11: Through hole 12: Contact surface 20: Rotating shaft 30: Yarn

────────────────────────────────────────────────── ─── Continuing from the front page Examiner Kenji Sano (56) Reference Literature 4-123272 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) D02G 1/08

Claims (1)

(57) [Claims] 1. A friction disk made of ceramics, wherein a maximum crystal particle diameter at a contact surface with a yarn is 20 μm or less , an average crystal particle diameter is 2 to 7 μm , and a maximum aspect ratio of crystal particles is 3 or less, A friction disk characterized in that the edges of the crystal grains are rounded.