JPH02248741A - Toothed belt - Google Patents

Abstract

PURPOSE:To further improve the durability of a belt by constituting each core body with a core section made of a no-twist fiber bundle and a shell section made of a twisted fiber bundle covering the outer periphery of the core section and having a twist angle larger than that of the core section. CONSTITUTION:Many tooth sections 2 are formed on the bottom section of a rubber structure body 1. Multiple endless core bodies 4 are buried in parallel in the belt width direction in the rubber structure body 1. Each core body 4 is constituted with a double structure of a core section 5 made of a no-twist fiber bundle and a shell section 6 made of a twisted fiber bundle covering the outer periphery of the core section 5 and having a twist angle larger than that of the core section 5. The apparent distortion of the core bodies 4 is decreased when a belt A is bent, thus its stress concentration is eliminated. The durability of the belt A can be improved accordingly.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a toothed belt having a large number of teeth for meshing on the bottom, and particularly relates to a toothed belt having a core (tensile member) embedded in the length direction of the toothed belt. ) regarding the structure of

(Prior Art) Conventionally, this type of toothed belt has been widely used, for example, as a synchro belt (timing belt) in automobile OHC engines, and is basically a rubber compound having a large number of teeth on the bottom. The belt comprises a rubber structure consisting of a rubber structure, and an endless core embedded in the rubber structure in parallel in the belt width direction, and the surface of the teeth of the rubber structure is covered with canvas.

The above-mentioned core body uses a fiber bundle made of high modulus and high tensile strength fibers such as polyester fibers, aromatic polyamide fibers, and glass fibers (carbon fibers), and is made by aligning many fiber bundles. (code) is commonly used.

By the way, it is preferable to use a non-twisted fiber bundle that has not been heated at all as it can obtain high modulus and tensile strength and can exhibit the physical properties of the fibers well. However, on the other hand, it is difficult to handle the fiber bundle. In addition, due to bending and running of the belt, especially the surface layer portion of the fiber bundle is more prone to bending fatigue and filament breakage than the inside.

For this reason, it is usually used with twists such as rung twist, single twist, and plied twist. Therefore, the problem arises that the heated fiber bundle has a low modulus when the belt runs, and the strength per cross-sectional area of the fiber bundle is also low, resulting in low durability.

Therefore, in order to solve the contradictory problems caused by both untwisted m fiber bundles and heated fiber bundles, conventionally,
The one disclosed in Japanese Patent No.-8453 has been proposed.

As shown in Fig. 6, this belt core uses a cord in which a bonded fiber bundle such as polyamide synthetic fiber is spirally wound around a non-twisted fiber bundle a. .

(Problems to be Solved by the Invention) However, in this proposal, the amount of fiber in the fiber bundle around which the cord is wound is extremely small, with a ratio of 1/10 to 1/15 to the fiber bundle a on the inside. Since the surrounding fiber bundles are spirally wound, the fiber bundle a in the center is partially exposed to the outside. For this reason, the cord diameter of the core differs between the portion around which the fiber bundle is wound and the portion without the fiber bundle, and the cord diameter is not uniform in the length direction. As a result, when the belt is used as a synchronized belt that is bent at multiple angles, there will be areas where stress is concentrated on the center body corresponding to the bent parts of the belt, which may lead to early breakage of the belt and reduce durability. In this respect, it is still insufficient.

The present invention has been made in view of these points, and its purpose is to suppress stress concentration during bending of the belt by improving the structure of the fiber bundles constituting the belt core. The aim is to further increase the durability of the

(Means for Solving the Problem) In order to achieve the above object, the solving means of the invention described in claim (1) includes a rubber structure having a large number of teeth at the bottom, and a belt width inside the rubber structure. In a toothed belt comprising endless core bodies embedded in parallel in the direction, each core body is covered with a core part made of a non-twisted fiber bundle such as aramid fiber, and the outer periphery of the core part, It consists of a double-layered cord with a shell part made of heated fiber bundles with a larger twist angle than the core part. Here, the above-mentioned untwisted fiber bundle refers to raw yarn that is not heated after spinning, and usually has a very small amount (1 to 1 per meter).
This refers to something that has been twisted naturally (approximately 10 times).

Further, the solving means of the invention as set forth in claim (2) is such that the cross-sectional area ratio of the core portion to the cord diameter of the core body in the above configuration is 6.
0 to 90%.

Furthermore, the solving means of the invention described in claim (2) is such that the twist angle in the direction perpendicular to the fiber axis of the fiber bundle in the shell portion is 2
The twist angle is 5 to 50''. The twist angle is zero in the direction perpendicular to the fiber axis, and is 90'' for non-twisted fibers.

(Function) According to the above structure, in the invention described in claim (1), the core part of the core is a non-twisted fiber bundle, and the periphery thereof is covered with the shell part made of the heated vaM1 bundle, so that the fibers have a high The physical properties of modulus and high tensile strength are exhibited as well as the original untwisted fiber bundle. Moreover, the apparent distortion (elongation, compression) of the core body (extension, compression) when the core body (belt) is bent is reduced, and stress concentration can be avoided, thus improving the fatigue resistance of the core body as a whole when the belt is running. This can increase the durability of the belt.

Further, since the outer circumferential shell portion of the core body is a heated fiber bundle, unlike the case of non-twisted fibers, high-order processing is facilitated in the same way as with only a heated fiber bundle. Moreover, due to the double structure of the core, the cord diameter can be set to a predetermined value, and good engagement with the boob of the m section of the belt can be ensured.

Further, in the invention described in claim (2), since the cross-sectional area ratio of the core portion to the cord diameter of the core body is 60% or more, the core portion can satisfactorily exhibit high modulus and high tensile strength of the fiber. I can do it. In addition, since the same ratio is less than 90%, the fiber bundle of the shell part covers the core part uniformly, and even from a microscopic perspective, the cord diameter of the core body can be made uniform in the belt length direction, and when the belt is bent, the core part can be uniformly covered. This prevents stress concentration and maintains the strength of the cord even after the body and mind become fatigued due to belt running.

Furthermore, in the invention described in claim (3), the twist angle of the fiber bundle in the shell portion in the direction perpendicular to the fiber axis is 25 to 5.
Since it is 0@, the strength of the above-mentioned core body after fatigue can be kept large.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 2 shows a toothed belt A according to an embodiment of the present invention, 1
is a rubber structure as an elastic body, and the bottom thereof has a large number of teeth 2, 2 . ... are formed in line in the length direction,
This part 1 2, 2. By meshing with the outer circumferential teeth of a toothed pulley (not shown), the rotation is synchronized with the pulley and power is transmitted. The above rubber structure 1
is composed of chloroprene rubber (neobrene), styrene-butadiene rubber, shrimp chlorohydrin rubber, polyurethane rubber, hydrogenated acrylonitrile-butadiene rubber, etc., and is formed from a known rubber compound suitable for the intended use of belt A. Ru.

Tooth portions 2, 2 of the rubber structure 1. ... surface (tooth surface)
is covered with a tooth canvas 3. This tooth canvas 3 uses threads or blended yarns made of 6 nylon, 66 nylon, 46 nylon, aromatic polyester, Tetron, cotton, rayon, Teflon, etc., singly or in combination, and is required as a belt tooth canvas. It is woven to meet the wear resistance and friction coefficient.

Further, inside the rubber structure 1, an endless plurality of core bodies 4, 4. ... are embedded in parallel in the belt width direction at a constant pitch and in a spiral shape, each inclined to the belt length direction. As shown in enlarged detail in FIG. 1, each core body 4 includes a core portion 5 made of a non-twisted fiber bundle such as aromatic polyamide (aramid) fiber, and a core portion 5 that covers the outer periphery of the core portion 5. It has a double structure with a shell part 6 made of a heated fiber bundle with a larger twist angle than the shell part 6. That is, for example, 300 aramid fiber filaments with a diameter of 13 μm
0 denier (approximately 2,000 fibers) are bundled without twisting to form a core portion 5, and a 3,000 denier (approximately 2,000 fibers) untwisted fiber bundle is wound around the core portion 5 in a coil shape to form a heating fiber bundle. A code is formed.

Further, the cross-sectional area ratio of the core portion 5 to the cord diameter of each core body 4 is in the range of 60 to 90%, and - the shell portion 6
The twist angle θ perpendicular to the fiber axis of the fiber bundle is 25
~50''.

Therefore, in the above embodiment, each core 4 of the belt A is composed of a core part 5 made of a non-twisted fiber bundle and a shell part 6 made of a heated fiber bundle surrounding the core part 5. Physical properties such as modulus and high tensile strength can be obtained. Also, when the core body 4 (belt A) is bent,
Since the apparent distortion (elongation, compression) of the core body 4 is reduced, there is no stress concentration, and the fatigue resistance of the core body 4 can be maintained as a whole while the belt is running, thus improving the durability of the belt A. can be increased.

Further, since the outer peripheral shell portion 6 of the core body 4 is a heated fiber bundle, unlike the case of a non-twisted fiber bundle, high-order processing is facilitated as in the case of only a heated fiber bundle. Moreover, when the core body 4 is composed of only non-twisted fiber bundles, the diameter of the core body 4 becomes thinner,
Although the meshing of the toothed pulley with the toothed portion is poor (although in this embodiment, the cord diameter of the core body 4 can be adjusted to the set value by the shell portion 6 on the outer periphery of the core portion 5, the toothed portion 2 of the belt A .2. Good meshing with the pulley can be ensured.

Furthermore, since the cross-sectional area ratio of the core portion 5 to the cord diameter of each core body 4 is 60% or more, the fiber can exhibit high modulus and high tensile strength due to the core portion 5. Moreover, since the upper limit of the above ratio is 90%, the core part 5 can be uniformly covered by the fiber bundle of the shell part 6, and from a microscopic point of view, the cord diameter of the core body 4 can be made uniform in the belt length direction. Stress concentration at the time of belt bending can be prevented, and the cord strength can therefore be kept high after the core body 4 is fatigued by belt running.

In addition, since the twist angle θ of the fiber bundle in the shell portion 6 of each core body 4 in the direction perpendicular to the fiber axis is 25 to 50'', the strength of the cord after fatigue of the core body 4 is maintained high as in the above case. be able to.

In addition, since the shell portion 6 is composed of a heating fiber bundle,
Good adhesion between the core body 4 and the rubber structure 1 can be maintained.

Here, the results of a test in which the toothed belt A having the configuration of the above embodiment was manufactured and the strength of its core body was evaluated will be specifically described. The manufactured toothed belt A had a width of 19 fins, a tooth pitch of 860 mm, a center-to-center pitch of 1.5 inches, and a circumferential length of 40 inches.

The rubber structure was a rubber compound using chloroprene rubber, and the tooth canvas was a woolly canvas made of 66 nylon. The core body was made of aramid fiber and had the same structure as in the above embodiment. In addition, as shown in Fig. 5, the test machine for bending and running the toothed belt A produced in this way was equipped with four toothed pulleys 10 to 13 (each having a number of teeth) each having a rotation center in the horizontal direction. 24) and four tension booths 14-17. The above four toothed pulleys 10
- 13 are arranged in pairs to face each other vertically and horizontally, and the sample belt A to be tested is hung on these toothed pulleys 10 - 13. Further, the tension pulleys 14 to 17 are arranged between the toothed pulleys 10 to 13, and apply a predetermined tension to the belt A by pressing the back surface of the belt A in a reverse bend state.

Then, by rotating the lowermost toothed pulley 10 as a drive wheel at a predetermined rotational speed, the belt A is caused to travel while being bent.

The core bodies were taken out from belt A before and after this running test, and their cord strength was measured. For comparison, the measured value was divided by the cord strength of a single-stranded structure, that is, a twisted structure without a core part. We calculated the code strength index based on the structure. Then, the cross-sectional area ratio of the core part to each core body was changed from 0% (no core part at all) to 10%.
When the above-mentioned cord strength index was determined by changing the value to 0% (for the core portion only), the test results shown in FIG. 3 were obtained. In Figure 383, the solid line indicates the cord strength index before fatigue (before the test), and the broken line indicates the same index after fatigue (after the test). Further, the twist angle θ of the fiber bundle in the shell portion in the direction perpendicular to the fiber axis was fixed at 45°. In addition, when determining the cross-sectional area ratio of the core part, the filament corresponding to the core part is dyed in advance, the core part and the shell part form a core body, the cross section is photographed, and the core part is formed based on the image. The cross-sectional area ratio of the section was calculated.

According to Fig. 3, as the cross-sectional area of the core increases, the strength of the cord after fatigue (after the test) increases, but when the cross-sectional area ratio of the core exceeds 90%, the strength of the cord after fatigue increases. Code strength decreases. This is because it becomes difficult for the fibers of the shell portion to uniformly cover the core portion, and when viewed microscopically, there are portions with different cord diameters in the belt length direction, and stress is concentrated in those portions. From this, it can be seen that the optimum cross-sectional area ratio of the core portion is within the range of 60 to 90% as defined by the present invention.

In addition, the cross-sectional area ratio of the core part in the belt center body is 75%.
When the same test was carried out by fixing the fiber bundle to 1 and instead changing the twisting angle θ perpendicular to the fiber axis of the fiber bundle in the shell portion, the results shown in FIG. 4 were obtained. The twist angle θ was determined by photographing the side surface of the core body and determining the deviation from the fiber axis of the shell portion. Moreover, in FIG. 4, the solid line shows the chord strength index before fatigue, and the broken line shows the same index after fatigue.

According to FIG. 4, the original cord strength of the core decreases as the twist angle θ of the shell portion increases. On the other hand, the cord strength after fatigue (after the test) increases as the twist angle θ increases. This is because fatigue due to compression is alleviated,
This is because the residual strength increases. However, since the original strength of the cord is low, if the twist angle θ becomes too large, the strength of the cord after fatigue will also decrease. Therefore, it can be seen that when the twist angle θ of the shell portion is set in the range of 25 to 50@ as defined in the present invention, a large cord strength index after fatigue can be ensured.

(Effects of the Invention) As described above, according to the invention described in claim (1), the core body of the toothed belt includes a core portion made of a non-twisted fiber bundle, and the outer periphery of the core portion is covered, and By adopting a double structure with the shell part made of heated fiber bundles with a large twist angle, the non-twisted fiber bundles in the core part can exhibit excellent physical properties of high modulus and high tensile strength, while also providing excellent physical properties such as high modulus and high tensile strength when the belt is bent. It is possible to reduce the apparent distortion of the core body and avoid stress concentration thereof, thereby increasing the durability of the belt. In addition, the core can be easily processed to a higher degree in the same way as when only heating fiber bundles are used, and the cord diameter of the core can be adjusted to the set value to ensure good engagement with the pulleys on the teeth of the belt. Practical use 1: Has excellent effects.

Further, according to the invention described in claim 2, the cross-sectional area ratio of the core portion to the cord diameter of the core body in the above configuration is 60.
By setting the ratio to ~90%, it is possible to satisfactorily exhibit high modulus and high tensile strength of the fiber in the core part, and the core part is uniformly covered by the fiber bundle in the shell part to reduce stress concentration when the belt is bent. It is possible to prevent this and maintain the strength of the cord after mental and physical fatigue due to belt running.

Furthermore, according to the invention described in claim (3), the twist angle in the direction perpendicular to the fiber axis of the fiber bundle in the shell portion is set to 25.
By setting the angle to ~50°, the strength of the cord after the core body is fatigued can be maintained at a high level. Therefore, according to these inventions, the durability of the belt can be further improved.

[Brief explanation of drawings]

1 to 5 show embodiments of the present invention, FIG. 1 is an enlarged perspective view of the belt core, FIG. 2 is a cross-sectional view in the longitudinal direction of the belt, and FIG. 3 is a core portion of the belt core. Figure 4 is a characteristic diagram showing the cord strength before and after mind-body fatigue as a result of changes in the cross-sectional area ratio of the core body. The figure is a schematic diagram of a testing machine that performs a belt bending test. FIG. 6 is a perspective view of a conventional belt core. A...Toothed belt...Rubber structure 2...Tooth section 4...Center body 5...Core section 6...Shell section θ...Twisting angle of shell section

Claims (3)

[Claims] (1) In a toothed belt comprising a rubber structure having a large number of teeth at the bottom and endless core bodies embedded in the rubber structure in parallel in the belt width direction, each of the core bodies is free. A toothed device characterized by having a double structure consisting of a core part made of twisted fiber bundles and a shell part which covers the outer periphery of the core part and consists of heated fiber bundles with a larger twist angle than the core part. belt. (2) The cross-sectional area ratio of the core to the cord diameter of the core is 6
The toothed belt according to claim 1, characterized in that the ratio is 0 to 90%. (3) A claim characterized in that the twist angle of the fiber bundle in the shell portion in the direction perpendicular to the fiber axis is 25 to 50 degrees (
The toothed belt described in 1) or (2).