JP5594827B2 - Toothed belt - Google Patents

Description

  The present invention relates to a rubber toothed belt having an indicator function.

  When a rubber toothed belt used for power transmission is used over a long period of time, cracks occur due to deterioration of the rubber or the like. When the belt life is near, this crack progresses, so that there is a possibility that the meshing of the toothed belt is shifted, the belt transmission is lowered, and the belt is broken. For this reason, it has been proposed to provide an indicator function for notifying that the belt life is near to the toothed belt.

  For example, in Patent Document 1, foreign matter is embedded in the contact surface of the toothed belt with the pulley, and when the contact surface of the toothed belt is worn or cracked, the foreign matter is exposed on the surface, and the toothed belt travels. Occasionally, noise is generated when the foreign matter comes into contact with the pulley. Therefore, in this case, the belt life can be predicted by using the generated abnormal noise as a warning sound.

  Further, in Patent Document 2, when a tooth cloth is provided on the surface of the tooth portion of the toothed belt, the tooth cloth is colored in a color different from that of the rubber layer of the tooth portion. In this case, when the tooth cloth is worn, a rubber layer having a color different from that of the tooth cloth is exposed, so that the life of the toothed belt can be determined by visual observation.

JP 2004-138237 A JP 2005-036914 A

  However, in the case of Patent Document 1, when using a toothed belt in an atmosphere with vibration noise such as an automobile engine, the above abnormal noise is difficult to hear due to the influence of the vibration noise, and the abnormal noise is warned. There is a problem in that it cannot be recognized as sound and the belt life may not be predicted.

  Moreover, in the thing of patent document 2, since the tooth cloth covered with a tooth | gear part is provided in the inner peripheral side of the toothed belt. The exposure of this color is difficult to see from the outside of the belt, which has the problem that the life of the toothed belt may be overlooked.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a toothed belt capable of reliably predicting the belt life by visual observation.

  The toothed belt according to the present invention is a belt body in which a plurality of tooth portions 1 arranged at predetermined intervals along the belt longitudinal direction and a belt back portion 3 in which a core wire 2 is embedded are formed using rubber as a base material. 4, and a toothed belt made of rubber in which the surface of the plurality of tooth portions 1 is covered with a tooth cloth 5, and an indicator rubber layer 6 is provided on at least a part of the belt back portion 3 of the belt body 4. The amount of the inorganic filler added to the rubber composition forming the indicator rubber layer 6 is embedded in the rubber composition forming the belt body 4 while being embedded with the surface exposed. Compared with the filler, the amount of the inorganic filler added to 100 parts by mass of the rubber is 10 to 50 parts by mass more.

  Since the indicator rubber layer 6 is formed of a rubber composition having a large amount of inorganic filler added as described above, it has a lower elongation at break than the belt body 4 and is susceptible to thermal aging, which is likely to cause cracks. When the belt life approaches, the indicator rubber layer 6 is cracked prior to the belt body 4, and the belt life is obtained by visually observing the crack even in an atmosphere where no abnormal noise can be heard due to vibration noise. Can be reliably predicted. Moreover, since the indicator rubber layer 6 is provided on the surface of the belt back portion 3 on the outer peripheral side of the toothed belt, a crack can be visually recognized from the outside of the toothed belt. It is possible to reliably predict the belt life without overlooking the occurrence of cracks.

  In the present invention, the indicator rubber layer 6 is disposed on the belt back portion 3 of the belt body 4 at a position corresponding to at least the back side of the tooth bottom portion 7 of the tooth portion 1. To do.

  When the toothed belt meshes with the pulley and travels, the belt back portion 3 of the belt body 4 is such that the portion corresponding to the tooth bottom portion 7 of the tooth portion 1 is more easily extended than the other portions. By arranging the rubber layer 6, cracks are likely to occur in the indicator rubber layer 6, and the belt life can be predicted quickly and reliably.

In the present invention, the rubber at the back of the belt has a breaking elongation measured according to JIS-K-6251 of 450 to 600% and 150 ° C. × 50 days measured according to JIS-K-6257. The retention rate of the elongation at break after thermal aging is 50 to 60%, and the rubber of the rubber layer for the indicator is measured at 150 ° C. for 50 days after thermal aging measured according to JIS-K-6257. The degree of retention is reduced in the range of 5 to 70% with respect to the belt back.

Thereby, the crack generation time by the heat aging of the rubber | gum of the belt back part 3 is delayed, and the lifetime improvement of a belt life can be anticipated. Moreover, since the difference in the EB retention after heat aging of the rubber of the indicator rubber layer 6 and the belt back 3 is within 5 to 70%, the rubber for the back of the belt 3 and the rubber of the tooth 1 are used for the indicator before cracking. A crack is generated in the rubber layer 6 so that the replacement time can be easily known before the belt life.

  In the present invention, the inorganic filler contains at least silica.

  In addition to the advantage that silica has a high reinforcing effect on silica, the color of the surface of the indicator rubber layer 6 becomes light due to the inclusion of silica, so that the occurrence of cracks is easy to visually recognize and the prediction of the belt life is more reliable. It will be.

  In the present invention, the indicator rubber layer 6 is embedded in the belt back portion 3 so that the surface thereof is flush with the surface of the belt back portion 3 of the belt body 4. It is characterized in that it can be removed from the belt back 3 when a crack occurs.

  When the crack generated in the indicator rubber layer 6 becomes large and a part of the indicator rubber layer 6 falls off from the belt back portion 3, this portion of the belt back portion 3 becomes a recess 11 to form a step, and the belt back surface 3 is idler. An abnormal noise is generated when running in contact with a pulley or the like, and the belt life can be notified by sound.

  According to the present invention, as described above, the indicator rubber layer 6 is formed of a rubber composition in which the addition amount of the inorganic filler is larger in the range of 10 to 50 parts by mass than the belt body 4, The indicator rubber layer 6 has a lower elongation at break than the belt body 4, is easily heat-aged, and easily causes cracks. For this reason, when the belt life approaches, the indicator rubber layer 6 is cracked prior to the belt body 4, and the belt life is reliably predicted by visually observing the crack even in an atmosphere where abnormal noise cannot be heard due to vibration noise. Is something that can be done.

BRIEF DESCRIPTION OF THE DRAWINGS An example of embodiment of this invention is shown, (a) is a partial cross section figure, (b) is the perspective view which fractured | ruptured partially. The crack generation state is shown, and (a) to (c) are each a partially broken perspective view.

  Embodiments of the present invention will be described below.

  FIG. 1 shows an example of a toothed belt A. A belt body 4 is formed by providing a tooth portion 1 on the inner peripheral side of a belt back portion 3 in which a plurality of core wires 2 are embedded along the longitudinal direction of the belt. The toothed belt A is formed by stacking the tooth cloth 5 on the surface of the tooth portion 1 of the belt body 4. A large number of tooth portions 1 are provided at predetermined intervals along the longitudinal direction of the belt, and a tooth bottom portion 7 is formed between adjacent tooth portions 1. The tooth cloth 5 is laminated on the surface of the tooth portion 1 and the surface of the tooth bottom portion 7.

  The belt back part 3 and the tooth part 1 forming the belt body 4 are formed of a rubber composition. The belt back portion 3 is provided with an indicator rubber layer 6. The indicator rubber layer 6 is also formed of a rubber composition, and the indicator rubber layer 6 is embedded in the belt back 3 so that the surface thereof is flush with the surface (outer peripheral surface) of the belt back 3. It is provided.

  The composition of the rubber composition forming the belt back portion 3, the tooth portion 1, and the indicator rubber layer 6 is not particularly limited. In the present invention, hydrogenated nitrile rubber is used as the rubber component. it can.

  Examples of the hydrogenated nitrile rubber (H-NBR) used in the present invention include 10 to 40% by mass of an acrylonitrile conjugate consisting of an unsaturated nitrile such as acrylonitrile and methacrylonitrile, 1,3-butadiene, and 2,3-dimethylbutadiene. , Copolymers of 90 to 60% by weight of conjugated dienes such as isoprene and 1,3-pentadiene, and multi-component copolymers obtained by copolymerizing a copolymerizable ethylenically unsaturated monomer in addition to these monomers Is mentioned. If the amount of unsaturated nitrile in the nitrile rubber is too small, it will be difficult to satisfy the function as a power transmission belt due to a decrease in hardness, modulus and oil resistance. There is a possibility that problems such as inferior general physical properties such as hardness, modulus, and the like may occur.

  Examples of the ethylenically unsaturated monomer include vinyl aromatic compounds such as styrene, chloromethyl styrene, and α-methyl styrene, (meth) acrylic acid, methyl (meth) acrylate, ethyl (meth) acrylate, ethoxyethyl acrylate, malee Examples thereof include unsaturated dicarboxylic acids such as acid, itaconic acid, monomethylmaleic acid ester and dimethylmaleic acid ester, and monoesters and diesters of these unsaturated dicarboxylic acids.

  The degree of hydrogenation of the hydrogenated nitrile rubber can be indicated by the iodine value, but the iodine value of the hydrogenated nitrile rubber of the rubber composition forming the belt back 3 is preferably 11 mg / 100 mg or less, more preferably 10 mg / 100 mg or less. On the other hand, the iodine value of the hydrogenated nitrile rubber of the rubber composition forming the indicator rubber layer 6 is preferably 11 mg / 100 mg or less.

  Hydrogenated nitrile rubber can be used alone. For example, (i) a composite polymer containing hydrogenated nitrile rubber and unsaturated carboxylic acid metal salt and (b) hydrogenated nitrile rubber are used. It is preferable to use it for improving various physical properties such as tensile elastic modulus, hardness, elongation at break and tear strength. By adopting the blending structure of (a) and (b), the unsaturated carboxylic acid metal salt has a higher polymer structure, and the unsaturated carboxylic acid metal salt is finely dispersed in the polymer. Therefore, it is possible to give a higher tensile strength than when an unsaturated carboxylic acid metal salt is added to the entire amount of hydrogenated nitrile rubber from the beginning.

  More desirably, the rubber component comprises (a) a composite polymer body in which a hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt are blended in a mass ratio of 30:70 to 70:30, and (b) a hydrogenated nitrile rubber. Is preferably blended at a mass ratio of 10:90 to 40:60 in order to ensure tensile modulus, elongation at break, higher tear strength, hardness, and the like.

  The above unsaturated carboxylic acid metal salt is an ionic bond of an unsaturated carboxylic acid having a carboxyl group and a metal. Examples of the unsaturated carboxylic acid include monocarboxylic acids such as acrylic acid and methacrylic acid, maleic acid and fumaric acid. Dicarboxylic acids such as acid and itaconic acid are preferred, and the metals are beryllium, magnesium, calcium, strontium, barium, titanium, chromium, molybdenum, manganese, iron, cobalt, nickel, copper, silver, zinc, cadmium, aluminum, tin, Lead, antimony and the like can be preferably used.

The rubber composition includes silica, carbon black, clay, alumina, aluminum hydroxide, magnesium oxide, magnesium hydroxide, calcium oxide, calcium hydroxide, aluminum oxide magnesium, titanium oxide, kaolin, pyrophyllite, bentonite, talc. Inorganic fillers such as attapulgite, magnesium calcium silicate, aluminum silicate, magnesium silicate, calcium silicate, and crystalline aluminosilicate are blended. Among these, silica and carbon black are preferably used. In particular, silica is most preferable in terms of lightening the rubber layer 6 for an indicator and the reinforcing effect.
Specific examples of the silica include dry silica generally obtained by burning silicon tetrachloride in an oxyhydrogen flame, wet silica obtained by neutralizing an alkali silicate with an acid, tetramethoxysilane, and tetraethoxysilane. Examples thereof include sol-gel silica obtained by hydrolyzing silicon alkoxides in an acidic or alkaline water-containing organic solvent, colloidal silica obtained by dealkalizing an alkali silicate aqueous solution by electrodialysis, and the like.
Here, in the present invention, the inorganic filler means what is blended in the rubber composition in order to mechanically reinforce the rubber, and such an inorganic filler increases the amount of rubber when added. The degree decreases. Therefore, what is mix | blended with a rubber composition as a vulcanization auxiliary like zinc oxide is not contained in an inorganic filler in this invention. Although the compounding quantity of the inorganic filler in a rubber composition is not specifically limited, The range of 10-80 mass parts is preferable with respect to 100 mass parts of rubber components. If the blending amount of the inorganic filler is less than 10 parts by mass, the effect of improving the wear resistance and the effect of improving the adhesiveness will be poor, and conversely if it exceeds 80 parts by mass, the rigidity of the rubber will increase. There is a risk of problems in the flexibility of the belt.

  Of the above-mentioned inorganic fillers, silica is preferably used. Silica has a high effect of reinforcing rubber, and it is easy to visually recognize the occurrence of cracks by including silica in the rubber composition, and the life of the belt is predicted by cracks in the rubber layer 6 for indicator as described later. Is easier.

Carbon black is blended in order to maintain high properties such as belt hardness and modulus, and examples thereof include HAF, MAF, EPC, SAF, and ISAF. Among them, those having a nitrogen adsorption specific surface area of 40 to 120 m ² / g and a 24M4DBP oil absorption of 80 to 130 ml / 100 g are preferably used.

  Furthermore, in addition to the above components, various additives can be blended in the rubber composition as necessary. For example, plasticizer, short fiber, crosslinking agent, anti-aging agent, heat resistance agent, tackifier, scorch prevention agent, crosslinking accelerator, acceleration aid, crosslinking retarder, colorant, UV absorber, flame retardant, oil resistance An improving agent etc. are mentioned.

  Among these, it is desirable to mix an organic peroxide as a crosslinking agent. Examples of the organic peroxide include dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, benzoyl peroxide, 1,3-bis (t-butylperoxyisopropyl) benzene, 2,5 -Dimethyl-2,5-di (t-butylperoxy) hexyne-3,2,5-dimethyl-2,5- (benzoylperoxy) hexane, 2,5-dimethyl-2,5-mono (t- Butyl peroxy) hexane and the like. This organic peroxide is desirably added alone or as a mixture in an amount of 1 to 8 parts by weight, more preferably 1.5 to 4 parts by weight, per 100 parts by weight of the rubber (polymer) component. In addition, it is also possible to use well-known crosslinking agents other than an organic peroxide.

  Moreover, as a short fiber, the short fiber about 1-10 mm in length which consists of fibers, such as cotton, polyester, polyamide, an aramid, and PBO, can be used. When a very short fiber of a special size having a diameter of 0.1 to 2.0 μm and a length of 10 μm to 1.0 mm is used as the short fiber, the dispersibility and homogeneity are further increased. can do. The amount of short fibers mixed is preferably in the range of 1 to 30 parts by mass with respect to 100 parts by mass of rubber. If the amount is less than 1 part by mass, the effect of improving the modulus of the short fiber cannot be sufficiently obtained, and if it exceeds 30 parts by mass, the hardness becomes too high, which is not preferable.

  Here, in the present invention, the rubber composition forming the indicator rubber layer 6 has a larger amount of the inorganic filler such as silica than the rubber composition forming the belt body 4 (particularly, the belt back portion 3). It is set and adjusted so that the breaking elongation (EB) after heat aging of the rubber layer for indicator 6 is lower than that of the belt body 4. That is, the amount of the inorganic filler added to the rubber composition forming the indicator rubber layer 6 is 100 parts by mass of rubber compared to the inorganic filler added to the rubber composition forming the belt body 4. The added amount of the inorganic filler is set to be 10 to 50 parts by mass. By setting the addition amount of the inorganic filler in the rubber composition of the indicator rubber layer 6 in this manner, the breaking elongation of the indicator rubber layer 6 can be set lower than that of the belt body 4. Thus, the indicator rubber layer 6 is adjusted so that cracks are more likely to occur than the belt body 4, and the belt life can be predicted as will be described later. If the difference in the amount of the inorganic filler added between the indicator rubber layer 6 and the belt main body 4 is less than 10 parts by mass, the time difference during which cracks occur in the indicator rubber layer 6 and the belt main body 4 is eliminated, and the belt life is predicted. Cannot serve as an indicator. Conversely, if the amount of the inorganic filler added to the rubber layer for indicator 6 exceeds 50 parts by mass than the belt body 4, the elongation at break of the rubber layer 6 for indicator becomes too low, and the indicator rubber layer is used in a short period of time. Cracks occur in the rubber layer 6, and in this case as well, it cannot serve as an indicator for predicting the belt life.

  Here, the rubber of the belt back portion 3 has a breaking elongation measured in accordance with JIS-K-6251 of 450 to 600% and after heat aging (150 ° C. measured in accordance with JIS-K-6257). It is desirable that the retention of elongation at break after 50 days) is 50 to 60%. Further, the rubber of the indicator rubber layer 6 has a retention rate of breaking elongation of 5 to 70% with respect to the belt back 3 after heat aging (after 150 ° C. × 50 days) measured according to JIS-K-6257. It is desirable that the heat aging resistance is adjusted to be inferior to that of the belt back portion 3 so as to be smaller in the range, preferably in the range of 30 to 40%. If the retention rate of the breaking elongation of the rubber of the indicator rubber layer 6 is small within this range, the indicator rubber layer 6 cracks immediately before the belt life when the belt back 3 cracks, and the expected accuracy of the belt life is improved. It will be expensive.

  In order to satisfy such a breaking elongation condition, the rubber composition of the belt back portion 3 is a rubber component containing a hydrogenated nitrile rubber, and the rubber component has (i) an iodine value of 11 mg / 100 mg or less. A composite polymer obtained by blending a hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt in a mass ratio of 30:70 to 70:30, and (b) a hydrogenated nitrile rubber having an iodine value of 11 mg / 100 mg or less, It is desirable that the mass ratio is 0: 100 to 40:60, and that 35 parts by weight or less of silica and 5 parts by weight or less of carbon black are blended with respect to 100 parts by weight of the blend (b). The rubber composition of the indicator rubber layer 6 is a rubber component containing hydrogenated nitrile rubber, and the rubber component is (i) a hydrogenated nitrile rubber having an iodine value of 11 mg / 100 mg or more, an unsaturated carboxylic acid metal salt, Compounded with a mass ratio of 30:70 to 70:30 and (b) a hydrogenated nitrile rubber having an iodine value of 11 mg / 100 mg or more in a mass ratio of 0: 100 to 80:20 However, it is desirable that the inorganic filler is blended more than the belt back portion 3 within the above range.

  Further, the hardness difference between the belt back portion 3 and the indicator rubber layer 6 is preferably within 3 ° in terms of JIS-A hardness. If the difference in hardness between the belt back portion 3 and the indicator rubber layer 6 is large, a difference in wear occurs between the belt back portion 3 and the surface of the indicator rubber layer 6 in the back polishing process when the toothed belt is manufactured. There may be a step between the back portion 3 and the indicator rubber layer 6.

  Next, as the core wire 2 used for the toothed belt A of the present invention, for example, a cord such as an aramid fiber, a glass fiber, or a carbon fiber can be used. The composition of the glass fiber may be either E glass or S glass (high-strength glass), and is not limited to the thickness of the filament, the number of converging filaments, and the number of strands.

  Further, as the tooth cloth 5 that covers the surface of the tooth portion 1 of the toothed belt A, a canvas made of a plain woven fabric, a twill woven fabric, a satin woven fabric, or the like is used.

  As the wefts arranged in the belt longitudinal direction of these woven fabrics, for example, multifilament yarns obtained by converging filament base yarns of para-aramid fibers of 0.3 to 1.2 deniers are 20 to 80 of the total amount of wefts in the belt longitudinal direction. What contains the mass% is preferable. That is, the weft is a yarn including a multi-filament yarn of para-aramid fiber, and the multi-filament yarn of the para-aramid fiber can include a yarn made of a meta-aramid fiber. The specific configuration of the weft is a combination of three types of yarns, a multi-filament yarn of para-aramid fiber, a spun yarn made of meta-aramid fiber, and a urethane elastic yarn. Other specific wefts are composed of three types of yarn: para-aramid multifilament yarn, aliphatic fiber yarn (6 nylon, 66 nylon, polyester, polyvinyl alcohol, etc.) and urethane elastic yarn. It may be what you did.

  As the warp of the tooth cloth 5, a filament yarn made of para-aramid fiber or meta-aramid fiber, polyamide yarn such as 6 nylon, 66 nylon or 12 nylon, filament yarn such as polyvinyl alcohol or polyester is used. be able to. Preferably, the filament yarn of the aramid fiber is a multifilament yarn in which the filament base yarn of the para-aramid fiber is converged on the weft 5, and if this yarn is used, the rigidity of the tooth cloth 5 having a uniform thickness can be obtained. Can be formed.

  Of course, the materials of the warp and weft are not limited to these, and other forms include cords, non-woven fabrics, knitted fabrics, etc., and are not particularly limited. Further, it is desirable to adhere adhesive rubber to the tooth cloth 5 by soaking, spreading, coaching or the like.

  In the toothed belt A of the present invention formed as described above, when the belt life is reached after long-term use, cracks occur in the rubber of the belt body 4 composed of the tooth portion 1 and the belt back portion 3. Since the rubber layer for indicator 6 provided on the back portion 3 is set to have a low elongation at break by increasing the content of the inorganic filler, before the crack is formed in the belt body 4 (particularly the belt back portion 3), the indicator rubber layer 6 is used. Cracks occur in the rubber layer 6.

  At this time, as shown in FIG. 2 (a), when the crack 10 starts to occur in the indicator rubber layer 6, it is difficult to visually distinguish the crack 10 because it is small, but immediately before the belt body 4 starts to crack. 2, the crack 10 of the indicator rubber layer 6 grows and becomes large as shown in FIG. 2B, and it is easily determined by visual observation that the crack 10 is generated in the indicator rubber layer 6. Can do. If it is determined by visual observation that the crack 10 has occurred in the indicator rubber layer 6 as described above, it is possible to predict that the toothed belt A is near the belt life. If the belt A is exchanged for a new one, it is possible to prevent the meshing of the toothed belt A, the belt transmission performance from lowering, and further the belt breakage. At this time, since the indicator rubber layer 6 is provided on the belt back portion 3 forming the outer peripheral surface of the toothed belt A, the crack 10 of the indicator rubber layer 6 can be easily seen from the outside of the toothed belt A. It is easy to predict the belt life by visually observing the occurrence of the crack 10.

  Further, when the crack 10 of the indicator rubber layer 6 grows and becomes larger, the indicator rubber layer 6 is divided by the crack 10 and is cut into pieces. Then, the small pieces of the indicator rubber layer 6 divided by the crack 10 fall off from the belt back 3 as shown in FIG. When the small piece of the indicator rubber layer 6 is detached from the belt back portion 3 in this way, the indicator rubber layer 6 is embedded flush with the surface of the belt back portion 3, so that the small piece of the indicator rubber layer 6 is removed. In addition, the recess 11 is formed in the belt back portion 3, and a step is generated on the surface of the belt back portion 3. Accordingly, when the toothed belt A is suspended from the pulley and travels, an abnormal noise is generated at this step when the belt back surface 3 comes into contact with an idler pulley, a tension pulley or the like, and the life of the belt is also notified by sound. It is something that can be done. In particular, the indicator rubber layer 6 falls off and a step formed by the dent 11 is formed on the belt back portion 3 when the belt life is almost exhausted. It can be alarmed.

Here, the thickness _{T 2} of the indicator for the rubber layer 6 is preferably equal to 0.1mm or more. When the thickness T ₂ of the indicator for the rubber layer 6 is 0.1mm or less, even flake off indicator rubber layer 6, since step formed on the belt back 3 is small, the belt back 3 idler pulley and tension pulley Therefore, it is difficult to determine the life by hearing. The width of the indicator rubber layer 6 is not particularly limited in terms of length and the like, but it is preferably 1/1000 or more and 1/10 or less of the area of the belt back 3.

  A mechanism for automatically detecting cracks in the indicator rubber layer 6 may be provided. For example, a mechanism for detecting unevenness of the belt back portion 3 caused by a crack in the indicator rubber layer 6 with a high-precision laser displacement meter is conceivable. Further, by making the hues of the indicator rubber layer 6 and the belt back 3 different, the occurrence of cracks can be easily distinguished by color.

  Next, an example of the manufacturing method of the toothed belt A of the present invention will be described. The manufacturing method of the toothed belt A is not limited to the following. First, a canvas forming the tooth cloth 5 is wound around the outer periphery of a cylindrical mold having a plurality of mold groove parts corresponding to the tooth parts 1 of the toothed belt A. Subsequently, the tensile body constituting the core wire 2 is wound around the outer periphery of the cylindrical mold from above the tooth cloth 5 at a predetermined pitch in the longitudinal direction of the cylindrical mold (direction orthogonal to the circumference). Next, a rubber sheet forming the tooth portion 1 and a rubber sheet forming the belt back portion 3 are wound around the core wire 2 to form an uncrosslinked rubber sleeve on the outer periphery of the cylindrical mold. At this time, the rubber sheet forming the indicator rubber layer 6 is overlapped on a part of the outer surface of the rubber sheet forming the belt back portion 3. Then, the cylindrical mold around which the crosslinked rubber sleeve is wound is transferred into a crosslinking can, and heated and pressurized to press-fit the rubber sheet into the mold groove to form the tooth portion 1, and the rubber sheet is crosslinked. Let Thereafter, each of the toothed belts A can be obtained by cutting the obtained cross-linked sleeve-shaped formed body into a predetermined cut width with a cutter.

  A preforming method will be described as another example of the manufacturing method of the toothed belt A of the present invention. First, a tooth cloth 5 and a rubber sheet forming the tooth part 1 are laminated on the surface of a flat mold having a plurality of mold recesses corresponding to the tooth part 1 of the toothed belt A, and then the tooth cloth is pressed. 5 and a rubber sheet are molded to prepare a pre-formed body in which the tooth portion 1 is formed. Subsequently, after the preform is wound around a cylindrical mold having a plurality of mold grooves corresponding to the tooth portions 1 of the toothed belt A, the tensile body constituting the core wire 2 is cylindrically formed from above the preform. It is wound around the outer periphery of the mold so as to have a predetermined pitch in the longitudinal direction. Next, a rubber sheet for forming the belt back portion 3 is wound around the core wire 2, and a rubber sheet for forming the indicator rubber layer 6 is further stacked on the outer side to form an uncrosslinked sleeve. Thereafter, in the same manner as described above, each toothed belt A can be obtained by crosslinking by heating and pressurizing and then cutting with a cutter.

  Next, the present invention will be specifically described with reference to examples.

  A rubber sheet for forming the tooth portion 1 is prepared by blending “T-0” shown in Table 1, and a rubber sheet for forming the belt back portion 3 is blended by blending “B-1” to “B-6”. The rubber sheet which forms the rubber layer 6 for indicators by the mixing | blending of "I-1"-"I-4" was produced. In Table 1, silica and carbon black correspond to the inorganic filler.

  Further, the tooth cloth 5 is made of a 2/2 twill weave, a tooth cloth made of 66 nylon and a warp is made of 66 nylon and spandex, and the core wire 2 is made of 3/11 and has a thickness of 1.1 mm. The glass core wire was used. And the toothed belt A of Examples 1-8 and Comparative Examples 1-3 was produced with the above-mentioned preforming method using these materials.

  The belt size of the toothed belt A is 105 MY (number of belt teeth: 105 teeth, tooth type: MY, belt width: 19.1 mm), and the rubber layer for indicator 6 is formed on the surface of the belt back 3 at the full width of the belt. And it is provided so that it may become 1/50 of the area of the belt back part 3. FIG. The thickness of the belt back 3 is 0.8 mm, and the thickness of the indicator rubber layer 6 is 0.5 mm.

  For the toothed belts A of Examples 1 to 8 and Comparative Examples 1 to 3 manufactured as described above, a durability test using a triaxial high load running tester was performed. Test conditions are: drive pulley teeth number: 21 teeth, driven pulley teeth number: 42 teeth, tension pulley: flat pulley (φ52 mm), set tension: 147 N, rotation speed: 7200 rpm, load: 3.67 kW with respect to the driven pulley, Atmospheric temperature: 150 ° C.

  And the time until a crack generate | occur | produces in the rubber | gum of the tooth | gear part 1, the time until a crack generate | occur | produces in the belt back part 3, and the time until a crack generate | occur | produces in the rubber layer 6 for indicators were measured. The results are shown in Table 2.

  As can be seen from Table 2, in each of the examples, the time during which cracks occur in the indicator rubber layer 6 is earlier than the time during which cracks occur in the belt back portion 3 and the tooth portion 1, and the indicator rubber layer. 6 is not significantly different from the time at which a crack occurs in the belt back portion 3 and the tooth portion 1, and the life of the belt can be predicted by the occurrence of a crack in the rubber layer 6 for indicator. It is confirmed that it is effective. Since the rubber of the belt back 3 used in each example has an EB of 450 to 600% and an EB retention after heat aging of 50 to 60%, the crack generation time due to the heat aging of the rubber of the belt back 3 Can be expected to increase the belt life. Moreover, since the difference in the EB retention after heat aging of the rubber of the indicator rubber layer 6 and the belt back 3 is within 5 to 70%, the rubber for the back of the belt 3 and the rubber of the tooth 1 are used for the indicator before cracking. A crack is generated in the rubber layer 6 so that the replacement time can be easily known before the belt life.

  On the other hand, in Comparative Example 1, since the addition amount of the inorganic filler in the indicator rubber layer 6 is smaller than the addition amount of the belt back portion 3, after the crack occurs in the belt back portion 3, the indicator rubber layer 6 is cracked. In addition, in Comparative Example 2, the amount of the inorganic filler added to the indicator rubber layer 6 is too much than the amount added to the belt back portion 3, so that the time during which cracks occur in the indicator rubber layer 6 is The difference between the time when the belt back 3 and the tooth 1 are cracked becomes large, and in Comparative Example 3, the added amount of the inorganic filler in the indicator rubber layer 6 is the added amount of the tooth 1 and the belt back 3. Therefore, after the crack is generated in the tooth portion 1 and the belt back portion 3, the indicator rubber layer 6 is cracked. It was those of the not possible to predict the belt life by generation. In particular, in Comparative Example 1, the rubber EB of the belt back 3 is less than 450%, and the EB retention after heat aging is less than 50%. Furthermore, since the cracking time of the indicator rubber layer 6 is longer than the cracking time of the belt back 3, the indicator function cannot be performed. In Comparative Example 2, the difference in the EB retention after heat aging between the rubber of the belt back 3 and the rubber of the indicator rubber layer 6 is greater than 70%, so that the indicator can be displayed much earlier than the time when the belt back 3 cracks. The rubber layer 6 is cracked, and the meaning as an indicator is weakened.

1: Tooth part 2: Core wire 3: Belt back part 4: Belt body 5: Tooth cloth 6: Rubber layer for indicator 7: Tooth bottom part

Claims (5)

  A plurality of tooth portions arranged at predetermined intervals along the belt longitudinal direction and a belt back portion in which a core wire is embedded are provided with a belt body formed of rubber as a base material, and the surfaces of the plurality of tooth portions are teeth. A rubber toothed belt covered with a cloth, wherein an indicator rubber layer is embedded in at least a part of a belt back portion of the belt body with the surface exposed, and the indicator rubber layer is The amount of the inorganic filler added to the rubber composition to be formed is 10% by weight of the inorganic filler relative to 100 parts by mass of the rubber, compared to the inorganic filler compounded in the rubber composition forming the belt body. Toothed belt characterized in that there are more to 50 parts by mass.   2. The toothed belt according to claim 1, wherein the indicator rubber layer is disposed on the back of the belt body at a position corresponding to at least the back side of the tooth bottom of the tooth. . The rubber at the back of the belt has an elongation at break measured in accordance with JIS-K-6251 of 450 to 600% and 150 ° C. × 50 days after heat aging measured in accordance with JIS-K-6257. The retention rate of breaking elongation is 50 to 60%, and the rubber of the rubber layer for indicator has a breaking elongation retention rate after heat aging of 150 ° C. × 50 days measured according to JIS-K-6257. The toothed belt according to claim 1, wherein the toothed belt becomes smaller in a range of 5 to 70% with respect to the belt back portion.   The toothed belt according to any one of claims 1 to 3, wherein the inorganic filler contains at least silica.   The indicator rubber layer is embedded in the belt back so that the surface is flush with the surface of the belt back of the belt body. When the indicator rubber layer cracks, it falls off the belt back. The toothed belt according to any one of claims 1 to 4, wherein the toothed belt is possible.