JPH0242230A - Toothed belt - Google Patents

Abstract

PURPOSE:To greatly prolong the fatigue-proof life of a toothed belt and to enhance the performance thereof by setting the upper twist coefficient and the catenary to specific values excellent in bending fatigue resistance, and by setting the ratio between the upper twist coefficient and the lower twist coefficient to a value within a specified numeric value range. CONSTITUTION:A core cord has more than 3,000 denier. The core cord 3 has an upper twist coefficient of 3.7 to 5.7, and a catenary of less than 0.8%. Further, the ratio K between the upper and lower twist coefficients is set to as 0.7<=K<=1.2. Thus, during high load transmission, the bending fatigue resistance may be enhanced so as to greatly prolong the fatigue-proof life of the belt. Further, the meandering motion may be reduced, thereby it is possible to exhibit an excellent toothed belt performance.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a toothed belt for high-load transmission, in particular, to a toothed belt for high-load transmission, in particular, after first twisting aramid fiber yarn, a plurality of the first twisted yarns are pulled. It has a core cord of twin-twisted yarn which is aligned and twisted in a direction opposite to the above-mentioned first twist direction, and the core cord is 3,000 yen.
The present invention relates to a toothed belt having a denier or more.

(Conventional technology) There are various types of toothed belts with different tooth shapes, material compositions, etc. depending on the function and application, but due to the diversification of required functions in recent years, bending fatigue resistance and high load transmission performance are required. things are increasing. For example, in automobiles, in the case of a serpentine layout in which a single belt drives many boobies such as an alternator, power steering device, air conditioner, and water pump, the serpentine layout has higher bending fatigue and high load transmission than normal cases. sexuality is required.

Therefore, as described in Japanese Patent Publication No. 57-31018, for example, in order to improve the bending fatigue resistance, the twist index of a core cord formed by twisting a plurality of yarns is TM-tJT/K ( 1) TM: twist index t: number of twists of the cord expressed in turns per inch of length d: denier of the cord: constant of the particular material used to construct the cord (e.g. nylon, polyester, ... 73, Aramid... 68. Glass... 90) Using the following formula, it is proposed to set the value in the range of 4 to 8.

In addition, for high load transmission, cords made of aramid fibers are used and the twist coefficient is set within a specific range to improve bending fatigue resistance, as disclosed in JP-A-4-135954 and JP-A-56- It is described in Publication No. 105135 and the like.

(Problem to be Solved by the Invention) Therefore, the inventor conducted repeated research on improving bending fatigue resistance, and found that bending fatigue resistance is affected by the ply twist coefficient. In terms of modulus, sufficient bending fatigue resistance cannot be obtained with core cords made of aramid fibers that have a high tensile modulus.In other words, such core cords have a high tensile modulus,
Since the torsional rigidity is high, the catenary (pulling alignment ratio) is poor, and due to the deterioration of the catenary, sufficient improvement in bending fatigue resistance cannot be expected.

By the way, when the thickness of the mind-body cord changes, as shown in Figure 8, it changes up to 3000 denier, although not so much.
When it exceeds 3000 denier, the strong variation coefficient R1 (R=o/xc number of samples r-100) σ: standard deviation or: average value increases rapidly. This causes not only variation in strength but also variation in bending fatigue resistance.

In FIG. 8, the strong coefficient of variation is expressed as an index, with the case of 1500 denier being set to 1. in this case,
The ratio of the final twist coefficient to the final twist coefficient is 1.

In order to transmit high loads, a certain degree of cord thickness is required, and for this reason cords of 3000 denier or more are generally used as toothed belts for high loads. As a result, there is a large tendency for the strength variation coefficient to increase, and bending fatigue resistance becomes a particular problem. The object of the present invention is to improve the bending fatigue properties of a toothed belt for high-load transmission in which the core body cord is 3000 deniers or more.

Another object of the invention as claimed in claim (2) is to provide a toothed belt which not only has improved bending fatigue resistance but also has reduced meandering.

(Means for Solving the Problem) The invention of claim (1) provides a method of first twisting aramid fiber yarn, and then pulling a plurality of the first twisted yarns together in a direction opposite to the first twisting direction. Assuming that the toothed belt has a core cord that is ply-twisted and that the core cord is 3000 deniers or more, in order to achieve the above object, the core cord has a ply twist coefficient of 3. .5 to 5.7 and a catenary of 0°8% or less.

Although the core-body cord has a denier of 3,000 or more, it is practically used up to about 40,000 denier.

In the invention of claim '2J, the ratio of the final twist coefficient to the final twist coefficient is 0.7≦K≦1.2.

(Function) In the invention of claim (1), not only the ply twist coefficient but also the catenary is set within a specific numerical range so as to improve the bending fatigue resistance. Flexural fatigue resistance is improved in high-load transmission.

In the invention of claim 2, since the ratio between the final twist coefficient and the final twist coefficient is further specified, not only the bending fatigue property is improved but also the meandering momentum is reduced.

(Example) Embodiments of the present invention will be described in detail below with reference to the drawings.

In FIG. 1 showing the cross-sectional structure of the belt, 1 is a toothed belt for high-load transmission, 2 is a rubber structure as an elastic body forming the back portion 1a and toothed portion 1b of the toothed belt 1, and 3 is rubber. An 8-body cord is embedded in the structure 2 in a spiral shape at an angle with respect to the belt length direction. Reference numeral 4 denotes a tooth canvas coated on the surface of the tooth portion 1b, and constitutes a tooth surface.

The comb structure 2 is made of a well-known rubber compound suitable for the intended use of the belt, such as chloroprene rubber, styrene-butadiene rubber, shrimp chlorohydrin rubber, polyurethane rubber, or hydrogenated acrylonitributadiene rubber. be done.

The above-mentioned 8-piece cord 3 is made of aramid fiber twisted yarn cord, and its cord configuration is 1500 d e / 2 × 3,
That is, two 1500 denier strands were collected and first twisted, and three strands were collected and final twisted in the opposite direction to the first twisting direction.

The tooth canvas 4 is made of yarns or blended yarns made of materials such as nylon 6, nylon 66, aromatic polyester, Tetron, cotton, rayon, Teflon, etc., singly or in combination, and has the abrasion resistance required as a belt tooth canvas. , and is configured to satisfy the friction coefficient. Note that it is desirable to use a woolly canvas that uses curled yarn for the weft.

To manufacture the toothed belt 1, first, a toothed canvas 4 (Woolley canvas) having a desired winding angle is prepared, and a well-known adhesive such as RFL, epoxy, isocyanate, etc. is applied to this toothed canvas 4. Then, if necessary, rubber glue or the like is further applied, and the material is bonded to a vulcanization mold having an uneven shape corresponding to the toothed portion 1b on the circumferential surface.

At this time, the toothed canvas 4 made of woolly canvas is joined into a cylindrical shape by a well-known method, with the width direction of the canvas being the length direction of the belt, and is adhered to a vulcanization mold. Note that when the woolly canvas is not used as the tooth canvas, the tooth canvas 4 that has been subjected to adhesive treatment is attached along the uneven shape of the mold.

Then, on the tooth canvas 4 attached to the vulcanization mold,
Wrap the body cord 3 in a spiral shape.

This 8-piece cord 3 has been subjected to adhesive treatment in advance by a well-known method.

Subsequently, an unvulcanized rubber sheet having a predetermined rubber composition constituting the rubber structure 2 of the back portion 1a and tooth portion 1b is wrapped thereon.

The unvulcanized belt material thus formed is charged into a vulcanizer together with a mold, and pressure vulcanized at a predetermined temperature for a predetermined time (e.g., 160°C, 30 to 60 minutes). . When the vulcanization is completed, the vulcanized product is removed from the vulcanization device, removed from the vulcanization mold, and cut into a predetermined belt width to obtain the toothed belt 1.

Next, a test conducted on the toothed belt 1 will be explained.

The sample belt dimensions are: belt width 1.9mm, tooth pitch 8.
0mm, cord pitch 1.5mm, and belt length 40 inches. As the 8-piece cord, a twisted yarn cord made of aramid fiber (manufactured by DuPont, trade name: Kevlar) was used.

Its code structure is 1500 d e / 2 x 3
It is.

Test method: The bending fatigue test was carried out using four toothed pulleys 21, 22, 23, 23, 23, 23, 22, 23, 22, 23, 23, 23, 23, 23, 23, 23, 23, 23, 22, 23, 23, 23, 22, 23, 23, 22, 23, 22, 23, 23, 23, 23, 23 , 23 . . . . 24 (24 teeth in each case)
and four tension pulleys 25, 26, 27.28
One sample belt 29 is wound around (32 mm in diameter),
It was run for 2 x 107 cycles under a tension of 2To-40Kg f. Note that one toothed pulley 21 was a drive pulley (rotation speed: 5570 rpm).

After the running was completed, the eight cords were taken out from the sample belt 29, the residual tensile strength was measured, and the strength retention rate was calculated as a ratio to the initial strength.

The tensile test was conducted using Tensilon manufactured by Toyo Baldwin, with a sample (gauge length) of 500 mm, at an elongation rate of 60%/min, and an initial load of 1/20 g/de.

Furthermore, the elongation rate caused by bending fatigue was calculated from the belt length before and after running.

In addition, untwist the twisted yarn cord (8-piece cord), break it down into the lower twisted yarn, measure the length of each, set the longest one as A, and the shortest one as C, and use them to calculate the following formula: The catenary W (alignment rate) was calculated.

W (C-A) ÷Ax100 (%) The meandering index is an index that expresses the degree of rolling of the core cord when it is wound around a cylindrical mold. The wire is spirally wound 50 times at a pitch of 1, the gaps between each of the 50 wires are measured, and the variation in pitch is displayed. The calculations were made based on the ratio K of the upper and lower twist coefficients being 1.

Test results (1) Relationship between ply twist coefficient, strength retention rate after bending fatigue, generated elongation rate, and original strength 1500 de/'2x
3 aramid cord with 20 twists/10 c
Figures 3 and 4 show the results of testing with m fixed and only the ply twist coefficient varied. Note that the final twist coefficient and the final twist coefficient are calculated using the above-mentioned formula (1). In this test, the lower twist coefficient was 4.2 (fixed) and the catenary was 1%.
(fixed). The original strength index of the cord was expressed as an index with the ply-twist coefficient of 3.5 set as 100.

As the ply twist coefficient increases, the bending fatigue resistance improves, but the core cord stretches during bending. Their relationship is correlated with bending fatigue properties.

Generally, if a belt stretches by 0.25% during running, it will cause poor meshing and break during actual running under load. Therefore, the ply twist coefficient must be at least 3.5.

Further, as the ply twist coefficient increases, the original strength decreases, and when it exceeds a certain value, the decrease becomes significant. Therefore, the ply twist coefficient needs to be 5.7 or less.

(2) Relationship between catenary and strength retention after bending fatigue The experimental results are shown in Figure 5. In addition, in this test, the top twist coefficient was 3.5 (fixed) and the bottom twist coefficient was 4.
．． 2 (fixed).

From the above results, it can be seen that when the catenary exceeds 0.8, the strength retention rate decreases rapidly.Therefore, the catenary must be 0.8 or less.

(3) The relationship test results between the first twist coefficient and the catenary are the 6th
As shown in the figure. In addition, in this test, the ply twist coefficient was 3.5 (fixed).

From the above results, it can be seen that when the pre-twist coefficient exceeds 2.1, the catenary becomes smaller.

Note that the catenary is the pulling rate, and to improve this it is necessary to drastically change the mechanism of the twisting machine, but the above test results show that the catenary can be improved by varying the pre-twist coefficient. .

(4) Relationship between the ratio of upper and lower twist coefficients of twisted cord and meandering The test results are shown in FIG.

From the above results, the ratio between the final twist coefficient and the final twist coefficient is 0,
It can be seen that meandering is less in the range of 7 to 1.2.

Therefore, in order to reduce the meandering momentum, the above ratio should be set to 0.
It needs to be in the range of 7 to 1.2.

(Effect of the invention) As configured as above, the invention of claim (1) has a specific numerical range in which the ply twist coefficient and the catenary are excellent in bending fatigue resistance, so that the bending fatigue resistance is improved in high load transmission. The fatigue life of the belt is greatly extended.

In the invention of claim (2), since the ratio of the upper twist coefficient and the lower twist coefficient is set within a specific numerical range, not only the bending fatigue resistance is improved, but also the meandering momentum is further reduced, resulting in excellent toothing. Demonstrates belt performance.

[Brief explanation of the drawing]

The drawings show embodiments of the present invention; FIG. 1 is a sectional view showing the structure of a toothed belt, FIG. 2 is a schematic diagram of a test device, and FIGS. 3 to 8 are diagrams showing test results. DESCRIPTION OF SYMBOLS 1... Toothed belt, 1a... Back, 1b... Teeth, 2... Rubber structure, 3... Heart body cord, 4...
Tooth Canvas Figure 1 77 shows 'l - ('/,) Figure 5 Lower T teri 1 1 Bo Figure 6 21 Terrification coefficient Figure 3 79th Code of ↑Bi↑'Neil also 8 Procedural Amendments September 1988 r Date 1, Indication of the case 1986 Patent Application No. 193080 2, Title of invention Toothed Belt 3, Person making the amendment Relationship to the case Patent applicant address: 3-2-15 Meiwa-dori, Hyogo-ku, Kobe, Hyogo Prefecture Name (506) Band-Kagaku Co., Ltd. Representative: Shogo Susube 4, Agent 6, Subject of amendment (1) Specification Column for detailed description of the invention (2) Drawings (3) Document certifying power of attorney 76 Contents of amendment (1) "Indicator" on page 2, line 18 of the specification is corrected to "coefficient." (2) rKJ on page 2, line 19 and page 3, line 4 of the specification
is corrected to "k". (3) Correct "Number of turns" in the first line of page 3 of the specification to "Number of twists." (4) Page 3 of the specification, lines 13 to 14
135954 Publication" is corrected to "Japanese Unexamined Patent Publication No. 54-135954." (5) "R-..." on page 4, lines 12 to 14 of the specification.
....average value" should be corrected as follows. r R-σ/nu σ: Standard deviation E: Average value (number of samples r-100) (6) "A, the shortest one is C" in the second line of page 11 of the specification
” should be corrected to “C5, the shortest one is A.” (7) Correct Figures 1, 3, and 4 as shown in the attached sheet. (8) Supplement the power of attorney. 8. List of attached documents (1) Amended drawings (1 copy) (2) Power of attorney (1 copy) Akira 1 drawing

Claims (1)

[Scope of Claims] (1) A core body formed by first twisting the aramid fiber yarn, then pulling a plurality of the first twisted yarns together and applying final twist in the opposite direction to the first twisting direction. In a toothed belt having a core cord of 3000 denier or more, the core cord has a twist coefficient of 3.5 to 5.7 and a catenary of 0.8% or less. A toothed belt featuring (2) The toothed belt according to claim (1), wherein the ratio of the first twist coefficient to the second twist coefficient of the core cord is 0.7≦K≦1.2.