JP2013061062A - Polyurethane driving belt and method for making the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyurethane driving belt which decreases the coefficient of friction on a belt surface, improves the sliding performance of the belt with respect to a pulley, and suppresses sounding, over a long period of time, and to provide a method for making the belt.SOLUTION: This belt body 2 comprises a polyurethane elastomer which is added with a lubricant (grease) 5. In the belt body, the belt surface 3, as a contact surface with the pulley, comprises a tiny concave-convex portion 6 which repeatedly rises and falls in the length and width directions of the belt surface 3, with the arithmetic mean roughness of the belt surface 3 ranging from 4 to 25 microns.

Description

  The present invention relates to a polyurethane transmission belt and a method for producing the same.

  A polyurethane elastomer is widely used as a material for a transmission belt that is stretched between a plurality of pulleys from the viewpoint of excellent appearance and no wear debris. However, since the polyurethane elastomer has a high coefficient of friction, when it is used as it is as a transmission belt, there is a problem that the slidability of the belt with respect to the pulley is poor and a large sound is generated. In order to solve this problem, various techniques have been conventionally proposed. For example, there are techniques described in Patent Documents 1 to 3 below.

  In the techniques described in Patent Documents 1 to 3, a lubricant such as fats and oils is added to the polyurethane elastomer. The lubricant in the polyurethane elastomer comes out on the belt surface which is a contact surface with the pulley by bleed. By lowering the friction coefficient of the belt surface by the action of this lubricant, the slidability of the belt with respect to the pulley is improved and the sound generation is suppressed.

JP-A-3-346 Japanese Patent Laid-Open No. 5-133440 JP-A-11-264447

  However, in the techniques described in Patent Documents 1 to 3, when the belt is used, the lubricant that has migrated (bleeded) to the belt surface and oozed out immediately upon contact with the pulley or scattered, so that the lubricant is used. The effect of reducing the friction coefficient of the belt surface could not be sufficiently obtained, and there was room for improvement in terms of sliding performance of the belt with respect to the pulley and suppression of sound generation.

  Therefore, the present invention has been made to solve the above-mentioned problems, and the object of the present invention is to prevent the lubricant (oil) from separating from the belt surface and scattering due to contact with the pulley. It is an object of the present invention to provide a polyurethane transmission belt that can reduce the friction coefficient of the belt surface over time and improve the slidability of the belt with respect to the pulley and the suppression of sound generation, and a method for manufacturing the same.

  In order to solve the above problems, a polyurethane transmission belt of the present invention is a polyurethane transmission belt having a belt body made of a polyurethane elastomer to which a lubricant is added, and spanned between a plurality of pulleys, wherein the belt The belt surface that is a contact surface with the pulley in the main body is a rough surface having a large number of fine irregularities that repeatedly undulate along the longitudinal direction and the width direction of the belt surface, and the arithmetic average roughness of the belt surface. Is 4 to 25 μm.

  According to the above-described configuration, the lubricant that has migrated (bleeded) to the belt surface and oozed out always enters the concave portion of the concave and convex portion on the belt surface, which is a contact surface with the pulley, and is accommodated. As a result, when the belt is used, it is possible to prevent the lubricant from coming off and scattering from the belt surface due to contact with the pulley, so even if the belt is used for a long time, the friction coefficient of the belt surface is lowered by the action of the lubricant. As a result, the slidability of the belt with respect to the pulley and the suppression of sound generation can be improved over a long period of time.

  In the polyurethane transmission belt of the present invention, it is preferable that the lubricant transferred to the belt surface is accommodated in the concave portion of the uneven portion of the belt surface.

  In the polyurethane transmission belt of the present invention, the lubricant is preferably oil or fat.

  Moreover, in the polyurethane transmission belt of the present invention, it is preferable that the average molecular weight of the fat is in the range of 500 or more and 2000 or less. According to the above configuration, since the average molecular weight of the oil and fat is in the range of 500 to 2000, the oil and fat in the polyurethane elastomer moves toward the belt surface at an appropriate speed in the polyurethane elastomer and comes out on the belt surface. Therefore, the friction coefficient of the belt surface can be kept low by the action of oils and fats for a long period of time, and as a result, the sliding property of the belt with respect to the pulley can be maintained. And the suppression of pronunciation can be further improved.

  In the polyurethane transmission belt of the present invention, it is preferable that the oil or fat is lard.

  In the polyurethane transmission belt of the present invention, it is preferable that the oil or fat is a hardened oil having a melting point of 50 ° C. or higher and 80 ° C. or lower. According to said structure, when the temperature of a belt main body rises to about 50 degreeC at the time of use, fats and oils will flow partially and will transfer to the surface of a belt easily.

  The method for producing a polyurethane transmission belt according to the present invention is a method for producing a polyurethane transmission belt having a belt body made of a polyurethane elastomer to which a lubricant is added and spanned between a plurality of pulleys. A first step of blending a polymer with a lubricant and a curing agent to produce a belt material; an inner mold and an outer mold; and an outer peripheral surface of the inner mold extending in a circumferential direction and a width direction of the outer peripheral surface. A second step of casting the belt material into a mold having a rough surface having a number of fine irregularities that repeat undulations, and an arithmetic average roughness of the outer peripheral surface of 4 to 25 μm; and the belt material And a third step of releasing the mold after solidifying and transferring the shape of the uneven portion of the outer peripheral surface of the inner mold to the belt surface.

  According to the above configuration, the belt main body is made of a polyurethane elastomer to which a lubricant is added, and the belt surface that is a contact surface with the pulley has a large number of minute portions that repeatedly undulate in the longitudinal direction and the width direction of the belt surface. A polyurethane transmission belt having a rough surface with irregularities and an arithmetic average roughness of the belt surface of 4 to 25 μm can be produced.

  Moreover, in the manufacturing method of the polyurethane transmission belt of this invention, it is preferable that the said lubricant is fats and oils.

  The friction coefficient of the belt surface can be reduced over a long period of time, and the slidability of the belt with respect to the pulley and the suppression of sound generation can be improved.

1 is a partial perspective view of a polyurethane transmission belt according to a first embodiment of the present invention. It is a perspective view of a metal mold | die. (A) is sectional drawing in the X surface of the metal mold | die shown in FIG. 2, (b) is a cross-sectional view of the metal mold | die shown in FIG. It is a fragmentary perspective view of the polyurethane transmission belt which concerns on 2nd Embodiment of this invention. It is a graph which shows the relationship between the arithmetic mean roughness of Examples 1-5 and Comparative Examples 3 and 5, and a friction coefficient.

<First Embodiment>
Next, a first embodiment of the present invention will be described with reference to the drawings.
The polyurethane transmission belt according to the present invention is a transmission belt that is stretched between a plurality of pulleys and transmits power to and from these pulleys. Here, although an example in which the polyurethane transmission belt according to the present invention is applied to a toothed belt will be described, the polyurethane transmission belt according to the present invention is a friction transmission belt such as a flat belt or a V-ribbed belt, It can also be applied to other transmission belts.

(Configuration of belt)
As shown in FIG. 1, the toothed belt 1 of the present embodiment includes a belt main body 2 and a plurality of core wires 7 embedded in the belt main body 2 along the belt longitudinal direction. The material of the core wire 7 is not particularly limited, and a low elongation and high elastic modulus rope made of carbon fiber, aramid fiber, glass fiber, steel cord or the like can be used. Further, on the belt surface 3 in contact with the pulley in the belt main body 2, a plurality of tooth portions 4 engaged with the tooth portions of the pulley are arranged at predetermined intervals along the belt longitudinal direction.

(Belt body 2)
The belt body 2 is composed of a polyurethane elastomer (polyurethane elastic body) to which an oil (fat) 5 is added. This fat (lubricant) 5 is added to the polyurethane elastomer in order to move to the belt surface 3 and reduce the friction coefficient of the belt surface 3. In the present embodiment, an aspect in which fats and oils are used as a lubricant will be described. However, the lubricant is not limited to fats and oils, and a commonly used lubricant (for example, fatty acid amide) is used within a range not impairing the effects of the present invention. It can be appropriately selected and used.

  Moreover, the polyurethane elastomer in this embodiment can be obtained from a material in which a curing agent, a plasticizer, or the like is blended with an isocyanate group-terminated urethane prepolymer. The kind of the curing agent is not particularly limited, and examples thereof include polyol compounds such as ethylene glycol, 1,3-propanediol, and 1,4-butanediol, primary amines, secondary amines, and amine compounds of tertiary amines. . Examples of the plasticizer used include phthalic acid diesters such as di-2-ethylhexyl phthalate, dioctyl phthalate, dibutyl phthalate, diethyl phthalate and diisodecyl phthalate, adipic acid diesters such as dioctyl adipate and diisodecyl adipate, and such adipic acid diesters. Other examples include dibasic acid esters such as aliphatic dibasic acid esters, phosphoric acid esters, aromatic carboxylic acid esters, epoxy plasticizers, and polyester plasticizers. These curing agents and plasticizers can be used alone or in combination of two or more.

  The isocyanate group-terminated urethane prepolymer can be obtained by carrying out the reaction so that the isocyanate group of the polyisocyanate compound is excessive in molar ratio with respect to the hydroxyl group of the polyol. The isocyanate group-terminated urethane prepolymer of the present embodiment bear is not particularly limited as long as it has at least two isocyanate groups in the urethane prepolymer molecular chain. The position of the isocyanate group in the urethane prepolymer molecular chain is not particularly limited, and may be at the end of the main chain of the urethane prepolymer molecular chain or at the end of the side chain.

  Specific examples of the polyol compound include polyether polyols such as polyethylene glycol, polypropylene glycol, and polytetramethylene ether glycol, adipic acid, sebacic acid, itaconic acid, maleic anhydride, terephthalic acid, isophthalic acid, and fumaric acid. , Succinic acid, succinic acid, malonic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid and the like and ethylene glycol, diethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, neopentyl glycol 1,2-propanediol, 1,3-propanediol, 1,9-nonanediol, 3-methyl-1,5-pentanediol, tripropylene glycol, trimethylolpropane, glycerin and other polyols Polyester polyols obtained by the compound is reacted, polycaprolactone polyols, polylactone polyester polyols such as poly-β- methyl-δ- valerolactone.

  Examples of the isocyanate include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5′-naphthene diisocyanate, tolidine diisocyanate, diphenylmethylmethane diisocyanate, and tetraalkyldiphenylmethane. Diisocyanate, 4,4′-dibenzyl diisocyanate, 1,3-phenylene diisocyanate and the like can be mentioned.

(Uneven portion 6)
The belt surface 3 of the belt body 2 is a rough surface (so-called satin surface) having a large number of fine irregularities 6 that repeatedly undulate along the longitudinal direction and the width direction of the belt surface 3. The oil / fat 5 added to the polyurethane elastomer passes through the soft segment of the polyurethane elastomer, moves to the belt surface 3, and is accommodated in the recess 6 a of the uneven portion 6. Thus, since the oil / fat 5 transferred to the belt surface 3 is accommodated in the recess 6a of the concavo-convex portion 6, the oil / fat 5 from the belt surface 3 due to contact with the pulley during use of the belt is suppressed. Even if it is used for a long time, the friction coefficient of the belt surface 3 can be kept low by the action of oils and fats. As a result, the sliding property of the belt with respect to the pulley for a long time is improved. And the pronunciation can be suppressed.

  The friction coefficient of the belt surface 3 is, for example, preferably in the range of 0.21 to 0.32, more preferably 0.21 to 0.3, when measured with a sheet of the same material as the toothed belt 1 by the following method. Range. If the coefficient of friction is less than 0.21, sound generation during belt running is reduced, but the mold release property of the belt molded body from the mold may be deteriorated. On the other hand, if the friction coefficient exceeds 0.32, the sound during belt running may increase.

  The method for measuring the friction coefficient is performed in accordance with JIS K7125-1999 “Plastic Film and Sheet Friction Coefficient Test Method”. A test body (sheet body) is placed on a mating material (fixed) made of the same material as the test body, and a hard chrome-plated cylinder with a diameter of 38 mm and a mass of 200 g (vertical drag N) is placed on the test body. After placing the weight, the specimen is pulled at a speed of 10 mm / min. Then, the load (friction force F) at the start of sliding is measured with a load cell, and the friction coefficient μ (μ = F / N) is calculated from the friction force F.

  Further, the sound generation during belt running is preferably 80 to 90 dB when the following sound generation test is performed on the toothed belt 1.

  In the sound generation test, a toothed belt as a test body is stretched between a driving pulley (number of teeth: 24 teeth) and a driven pulley (number of teeth: 24 teeth) to give a predetermined tension to the belt, and the driving pulley is connected to a DC motor. To rotate the driven pulley at a load of 25.0 N · m. Then, a microphone is arranged near the center of both pulleys at a position 20 mm away from the belt tension side, and the sound generation is measured.

  When the toothed belt 1 is mounted on a drive device of a large-sized mechanical device and travels under a high load condition, the pitch of the tooth portion 4 is shifted and the deformation of the tooth portion 4 becomes large, and the surface of the tooth portion 4 ( The wear of the belt surface 3) is promoted. However, if a high elastic modulus represented by carbon fiber or aramid fiber is used as the core 7, such a problem is solved and the uneven portion 6 is formed over a long period of time. Thus, the slidability of the belt with respect to the pulley and the suppression of sound generation are further improved.

  The arithmetic average roughness (Ra) of the belt surface 3 is set in the range of 4 to 25 μm. The reason why the lower limit of the arithmetic average roughness (Ra) of the belt surface 3 is set to 4 μm is that when the thickness is less than 4 μm, the size of the concavo-convex portion 6 becomes too small to sufficiently store oil and fat in the concave portion 6a. As a result, when the belt is used, it becomes impossible to sufficiently suppress the separation or scattering of the oil 5 from the belt surface 3 due to contact with the pulley. The reason why the upper limit of the arithmetic average roughness (Ra) of the belt surface 3 is set to 25 μm is that when it exceeds 25 μm, the size of the concavo-convex portion 6 becomes too large and the demolding property is deteriorated.

  The arithmetic average roughness (Ra) is a value obtained by measurement in accordance with JIS B0601-2001 “one definition and indication of surface roughness”. The surface of the belt is measured with a surface roughness measuring instrument Serve Test 500 (manufactured by Mitutoyo), a surface roughness chart is drawn with a cut-off value of 2.5 mm and a feed rate of 2.0 mm / second, and an evaluation length L ( L = 12.5 m) is extracted, and when the center line (average line) of the extracted portion is the X axis and the vertical direction is the Y axis, the roughness curve is expressed by Y = f (X), The value obtained in step (value converted to μm) is used as the arithmetic average roughness (Ra).

(Formula 1)

(Oil 5)
As described above, the oil 5 moves to the belt surface 3 and reduces the friction coefficient of the belt surface 3. Here, fats and oils refer to esters of fatty acids having higher carbon numbers (higher fatty acids) and glycerin. Examples of the fats and oils 5 include lard (pig fat) and beef tallow for animal solid fats, and palm oil and the like for vegetable solid fats. Moreover, you may use together fatty acid amide generally used as a lubricant with fats and oils.

  As the fat 5, for example, it is preferable to use a fat having an average molecular weight in the range of 500 to 2000. The reason why the lower limit of the average molecular weight of the oil / fat 5 is 500 is that when the oil / fat is less than 500, the oil / fat tends to move through the soft segment of the polyurethane elastomer at a high speed. It is because fats and oils may be consumed. Also, the reason why the upper limit of the average molecular weight of the oil 5 is 2000 is that if the average molecular weight is greater than 2000, the oil moves at a slow speed through the soft segment of the polyurethane elastomer. This is because it is difficult to appear and as a result, pronunciation may occur. Lard (triglyceride rich in saturated fatty acids) has an average molecular weight of about 800, passes through the soft segment of the polyurethane elastomer at an appropriate speed, and migrates to the belt surface. It is preferable from the viewpoint of blending cost and workability.

  Further, as another example of the oil 5, an oil (hardened oil) having a melting point of 50 ° C. or higher and 80 ° C. or lower may be used. By using oils and fats having such a melting point, when the temperature of the belt body rises to about 50 ° C. during use, the oils and fats partially flow and easily migrate to the belt surface. Examples of the fats and oils (cured oil) having a melting point of 50 to 80 ° C. include hardened oils derived from vegetable oils such as soybean hardened oil, soybean extremely hardened oil, rapeseed hardened oil, rapeseed hardened oil, beef fat hardened oil, and beef fat hard Hardened oil derived from animal oils such as hardened oil, hardened tallow oil, hardened tallow oil, hardened tallow oil, hardened tallow oil, hardened tallow oil, hardened whale oil, extremely hardened oil of whale oil, etc. Among these hardened oils, beef tallow hardened oil or beef tallow extremely hardened oil, soybean hardened oil or soybean hardened hardened oil, rapeseed hardened oil or rapeseed hardened oil is widely used.

  As a method of adding the oil / fat 5 to the isocyanate group-terminated urethane prepolymer, for example, after heating the oil / fat at a temperature equal to or higher than the melting point of the oil / fat 5 (for example, 30 to 38 ° C. in the case of lard), There is a method in which a hardener is further mixed and stirred after being added to the base end urethane prepolymer and stirred, and then cast into a mold 30 described later.

  As the addition amount of the fats and oils 5, it is preferable to add 0.5 to 10 parts by mass of the fats and oils 5 with respect to 100 parts by mass of the polyurethane in the toothed belt as in this embodiment. The reason for this is that if the addition amount of the oil / fat 5 is less than 0.5 parts by mass, the effect of the oil / fat 5 is small and the sound generation may not be sufficiently suppressed, and the addition amount of the oil / fat 5 is 10% by mass. This is because the physical properties of the polyurethane elastomer are deteriorated when the amount exceeds the range, and the life of the toothed belt may be shortened.

  When the polyurethane transmission belt is a friction transmission belt such as a flat belt or a V-ribbed belt, it is preferable to add 0.5 to 7 parts by mass of the oil / fat 5 with respect to 100 parts by mass of the polyurethane. The reason for this is that if the addition amount of the fat 5 is less than 0.5 parts by mass, the effect of the fat 5 may be small and the sound generation may not be sufficiently suppressed, and the addition amount of the fat 5 is 7 masses. This is because, in a friction transmission belt that requires a high transmission force beyond the range, there is a possibility that slip may occur and predetermined power cannot be transmitted.

(Manufacturing method of toothed belt 1)
Next, the manufacturing method of the toothed belt 1 is demonstrated, referring FIG.2 and FIG.3. In the present embodiment, a belt material is poured into the mold 30 and then cured (solidified) to produce a belt molded body, and the belt molded body is cut to produce a plurality of toothed belts 1. . This will be specifically described below.

(Mold 30)
First, the structure of the metal mold | die 30 used for manufacture of a toothed belt is demonstrated. As shown in FIGS. 3 and 4, the mold 30 includes a bottomed cylindrical outer mold 31 and a columnar inner mold 32 that is fitted into the outer mold 31. The outer mold 31 and the inner mold A space 33 is formed between the belt 32 and the belt material.

  On the outer peripheral surface 32a of the inner mold 32, a plurality of tooth portion forming portions 32b that form the tooth portions 4 of the belt body 2 are recessed at predetermined intervals along the circumferential direction. The outer peripheral surface 32a of the inner mold 32 is a rough surface (so-called satin surface) having a large number of fine irregularities 35 that repeatedly undulate along the circumferential direction and the width direction of the outer peripheral surface 32a, and its arithmetic average roughness (Ra ) Is in the range of 4 to 25 μm. The uneven portion 6 on the belt surface 3 is formed by being transferred from the uneven portion 35 on the outer peripheral surface 32a of the inner mold 32 during molding.

  Examples of the mold surface treatment (rough surface treatment) on the outer peripheral surface 32a of the inner die 32 include methods such as shot blasting and chemical etching. The conditions when the rough surface treatment of the outer peripheral surface 32a of the inner mold 32 is performed by shot blasting are shown below.

(Conditions for shot blasting)
Injection method: Direct pressure air type Injection pressure: 5-10 kg / cm ²
Injection distance: 10-20cm
Injection time: 60 to 120 seconds Injection material: Polygonal steel grid Injection material hardness: Hv 790 to 950
Injection material dimensions: (1) 0.177 to 0.710 mm (G-50 described in JIS Z0311 (2004)) 5 to 12 μm (blast surface roughness)
(2) 1.00-1.68 mm (G-140 described in JIS Z0311 (2004)) ... 12-20 μm (blast surface roughness)

  Then, the manufacturing method of the toothed belt 1 using the metal mold | die 30 demonstrated above is demonstrated.

  First, the inner mold 32 in which the core wire 7 is spirally wound in advance is inserted into the outer mold 31.

  Next, a fat and oil (lubricant) and a curing agent are blended with the urethane prepolymer to adjust the belt material (first step). Preferably, after adding melted fats and oils to a liquid isocyanate group-terminated urethane prepolymer and stirring, a liquid belt material is prepared by further mixing and blending a curing agent.

  This liquid belt material is cast into a space 33 formed between the outer mold 31 and the inner mold 32 (second step). A liquid belt material may be cast, or a softened belt material may be cast.

  Then, the belt material is solidified, and the shape of the concavo-convex portion 35 of the outer peripheral surface 32a of the inner mold 32 is transferred to the belt surface, followed by demolding (third step). Preferably, the belt material is cross-linked over a predetermined time under a temperature condition of about 100 ° C. to 120 ° C., and when cured, the outer mold 31 and the inner mold 32 are separated, and the belt molded body is removed from the mold 30. Type. Thereafter, the belt molded body is cut into a predetermined width and divided into a plurality of toothed belts 1.

  The toothed belt 1 can be manufactured through the above steps.

  According to the polyurethane transmission belt of the present embodiment described above, the oil 5 transferred to the belt surface 3 enters and is accommodated in the recess 6a of the uneven portion 6 of the belt surface 3 which is a contact surface with the pulley. . Therefore, when the belt is used, it is possible to suppress the separation and scattering of the oil / fat 5 from the belt surface 3 due to contact with the pulley. As a result, even if the belt is used for a long time, the action of the oil / fat 5 causes the belt surface. The friction coefficient of 3 can be kept low, and as a result, the slidability of the belt with respect to the pulley and the suppression of sound generation can be improved over a long period of time.

  Further, according to the present embodiment, when the oil / fat 5 having an average molecular weight in the range of 500 to 2000 is added to the polyurethane elastomer, the oil / fat 5 in the polyurethane elastomer is transferred to the belt surface 3 at an appropriate speed in the polyurethane elastomer. The belt surface 3 and the belt surface 3 to enter the concave portion 6a of the concave-convex portion 6 of the belt surface 3 to be accommodated. As a result, the slidability of the belt with respect to the pulley and the suppression of sound generation can be further improved.

  In addition, according to the present embodiment, when an oil or fat 5 (cured oil) having a melting point of 50 ° C. or higher and 80 ° C. or lower is added to the polyurethane elastomer, when the temperature of the belt body rises to about 50 ° C. during use, Partly flows and tends to migrate to the surface of the belt.

  In addition, according to the present embodiment, the inner mold 32 and the outer mold 31 are provided, and the outer peripheral surface 32a of the inner mold 32 has a large number of minute irregularities that repeatedly undulate along the circumferential direction and the width direction of the outer peripheral surface 32a. A polyurethane transmission belt is manufactured by casting a belt material into a mold having a rough surface having a portion 35 and an arithmetic average roughness of the outer peripheral surface 32a of 4 to 25 μm. The belt surface 3 which is a surface is a rough surface having a large number of fine irregularities 6 that repeatedly undulate along the longitudinal direction and the width direction of the belt surface 3, and the arithmetic average roughness of the belt surface 3 is 4 to 25 μm. A polyurethane transmission belt can be manufactured.

Second Embodiment
Next, a second embodiment of the present invention will be described. However, about the thing which has the structure similar to 1st Embodiment, the description is abbreviate | omitted suitably using the same code | symbol.

  As shown in FIG. 4, the toothed belt 201 of the present embodiment includes a belt main body 202, a plurality of core wires 7 embedded in the belt main body 202 along the belt longitudinal direction, and a part of the belt main body 202. And an embedded reinforcing fabric 208. Similar to the first embodiment, the belt body 202 is made of a polyurethane elastomer (polyurethane elastic body) to which oils and fats are added. In addition, a plurality of tooth portions 204 that are engaged with the tooth portions of the pulley are arranged on the belt surface 203 of the belt main body 202 at predetermined intervals along the belt longitudinal direction. Further, the belt surface 203 of the belt main body 202 is a rough surface (so-called satin surface) having a large number of fine irregularities, and the oil and fat transferred to the belt surface 203 is accommodated in the recesses.

  The reinforcing cloth 208 has a tooth bottom surface between the tooth portions 204 and a power transmission region of the tooth portion 204 (when the height H from the core wire position to the tip of the tooth portion 204 is 2 / 3H from the core wire position. Within the area). The reinforcing cloth 208 is disposed so as to bend toward the tooth tip side in the power transmission region, and reinforces the power transmission region. Note that the power transmission region is a region that receives a large compressive stress from the pulley and transmits power.

  The reinforcing cloth 208 is a non-woven fabric formed by needle punching or the like using short fibers such as polyethylene, polypropylene, polyamide, polyester, acrylic, and glass having a length of 5 to 60 mm, for example, and is not subjected to binder treatment. preferable. When the binder treatment is not performed, the short fibers are raised on the surface of the reinforcing cloth 208. That is, the short fiber fixed to the surface of the reinforcing cloth 208 has its tip raised away from the surface of the reinforcing cloth 208. A part of the short fibers constituting the reinforcing cloth 208 is separated from the reinforcing cloth 208 and diffused. As a result, the short fibers are randomly arranged in the power transmission region and reinforce the power transmission region.

Next, a method for manufacturing the toothed belt 201 will be described.
The reinforcing cloth 208 is disposed on the outer peripheral surface 32 a of the inner mold 32, and the core wire 7 is wound thereon, and then the inner mold 32 is inserted into the outer mold 31. Then, the belt material described in the first embodiment is filled in the space 33 between the outer mold 31 and the inner mold 32 and cast. Here, a liquid belt material may be cast, or a softened belt material may be cast. Thereafter, the belt material is cross-linked and cured by heating at a predetermined temperature for a predetermined time, and then demolded. The obtained belt molded body is cut into a predetermined width to form a plurality of toothed belts 201.

  According to the toothed belt 201 of the present embodiment, the power transmission region of the tooth portion 204 can be reinforced by the reinforcing cloth 208 and the short fibers separated from the reinforcing cloth 208. As a result, it is possible to prevent a crack from occurring at the root portion of the tooth portion 204. In addition, the same effects as those of the first embodiment can be obtained.

  As mentioned above, although embodiment of this invention was described based on drawing, it should be thought that a specific structure is not limited to these embodiment and an Example. The scope of the present invention is shown not only by the description of the above-described embodiment and examples described later, but also by the scope of claims for patent, and further includes all modifications within the meaning and scope equivalent to the scope of claims for patent.

  In order to confirm the effects of the present invention, a friction coefficient test was performed on the sheet-like test bodies of Examples (Examples 1 to 10) and Comparative Examples (Comparative Examples 1 to 5). In addition, when these specimens were prepared, the demoldability was examined.

  A liquid belt material is poured into a flat mold (100 mm × 100 mm × depth 2 mm) preheated to 100 ° C., and crosslinked for a predetermined time under a temperature condition of about 100 ° C. to 120 ° C. After curing, the mold was removed to prepare a sheet, and a sheet body obtained by cutting the sheet into 20 mm × 20 mm was used as a test body. The thickness of the sheet body is 2 mm.

As liquid belt materials of Examples 1 to 5 and Comparative Examples 3 and 5, 100 parts by mass of a polyether urethane prepolymer (Adiprene-LF950A manufactured by Chemtura) and 3,3′-dichloro-4,4 as a curing agent were used. A liquid polyurethane raw material (temperature adjusted to 60 ° C.) in which 13 parts by mass of '-diaminodiphenylmethane, 10 parts by mass of lard as fats and oils and 10 parts by mass of dioctyl fullerate as a plasticizer was used was used.
Moreover, in the liquid belt material of Examples 6-10, beef fat hardened oil (made by NOF Corporation, melting | fusing point 54 degreeC, iodine value 23.5) is used instead of lard as fats and oils, and implementation is carried out otherwise. The liquid polyurethane raw materials of Examples 1 to 5 and Comparative Examples 3 and 5 were the same.
Further, as the liquid belt materials of Comparative Examples 1, 2, and 4, those obtained by removing lard (oils and fats) from the liquid polyurethane raw materials of Examples 1 to 5 and Comparative Examples 3 and 5 were used.

Further, in Examples 1 to 10 and Comparative Examples 1, 2, and 5, as the mold, the inner surface was roughened by shot blasting to obtain the arithmetic average roughness (Ra) shown in Table 1. used.
Further, in Comparative Examples 3 and 4, as the molds, those whose inner surfaces were not subjected to shot blasting and had the arithmetic average roughness (Ra) shown in Table 1 were used.
The arithmetic average roughness (Ra) of the surface of the sheet body of each example and each comparative example was substantially the same as the arithmetic average roughness of the inner surface of the mold shown in Table 1. The arithmetic average roughness (Ra) is a value obtained by measuring in accordance with JIS B0601-1994 “Definition and Display of Surface Roughness”, and the specific measuring method is described in the above embodiment. The method is the same. Table 1 also shows the presence / absence of fats and oils in each Example and each Comparative Example.

(Demoldability)
The ease of peeling when the above-mentioned sheet was removed from the mold was evaluated, and the results are shown in Table 1. When the sheet could be easily peeled without stretching, it was evaluated as “good”, and when the sheet was peeled while being stretched, it was evaluated as “triangle”.

(Friction coefficient test)
The friction coefficient test was performed in accordance with JIS K7115-1999 “Plastic film and sheet friction coefficient test method”. Specifically, it is the same as the procedure of the friction coefficient test described in the first embodiment. Note that the weight of the test specimen was 1.4 g. The calculated friction coefficient is also shown in Table 1. In addition, regarding Examples 1 to 5 and Comparative Examples 3 and 5, the relationship between the arithmetic average roughness (Ra) of the surface and the friction coefficient μ is shown in the graph of FIG.

  From the results shown in Table 1, it can be seen that when the arithmetic average roughness (Ra) of the surface is 24 μm or less, the releasability from the mold is improved. Further, as shown in Table 1 and FIG. 5, it is understood that the friction coefficient can be lowered to less than 0.32 by adding fats and oils and setting the arithmetic average roughness (Ra) of the surface to 5.4 μm or more.

  Further, in order to confirm the effect of the present invention, a friction coefficient test and a sound generation test were performed on the toothed belts of Examples 11 and 12.

The toothed belts of Examples 11 and 12 have a reinforcing cloth similarly to the second embodiment described above, and were created by the following procedure using the mold 30 shown in FIGS. 2 and 3.
A reinforcing cloth is attached to the outer peripheral surface 32 a of the inner mold 32, and a core wire is wound thereon. Then, the inner mold 32 is inserted into the outer mold 31, and then the liquid belt material is used as the inner mold 32 and the outer mold 31. After filling the space portion 33 between the two and curing by crosslinking, the mold was removed. The obtained sleeve-shaped belt molded body was cut into a width of 15 mm, and the obtained toothed belt (belt size S8M560) was used as a test body.

As the reinforcing fabrics of Examples 11 and 12, cylindrical nonwoven fabrics made of 6.6 nylon fibers that were formed by needle punching and not subjected to binder treatment were used. The thickness of the nonwoven fabric is 1.3 mm. Further, the nonwoven fabric is composed of a core portion and the surface portion, basis weight 30 g / m ² of the core, the basis weight of the surface portion is 70 g / m ^2.

As the core wire of Example 11, untwisted multifilament yarn made of carbon fiber (manufactured by Toray Industries, Inc., product number “T700GC · 6K · 31E”, fineness 4300 denier) was used.
Moreover, as a core wire of Example 12, an aramid fiber twisted yarn (manufactured by Teijin Limited, trade name “Technola”) was used.
The liquid belt materials of Examples 11 and 12 were the same as those of Examples 6 to 10 described above.

Further, as the molds of Examples 11 and 12, the outer peripheral surface 32a of the inner mold 32 was roughened by a shot blasting process and the arithmetic average roughness (Ra) shown in Table 2 was used. .
The arithmetic average roughness (Ra) of the tooth surface of the toothed belt (test body) was almost the same as the arithmetic average roughness of the outer peripheral surface of the inner mold shown in Table 2.

(Friction coefficient test)
The friction coefficient test was performed after running the running test for 72 hours. In the running test, a specimen (toothed belt) is stretched between a driving pulley (number of teeth: 24 teeth) and a driven pulley (number of teeth: 24 teeth) to give a predetermined tension to the belt, and the driving pulley is driven by a DC motor. The number of revolutions was 3600 rpm, and the driven pulley was rotated at a load of 25.0 N · m.
In the friction coefficient test, the test body (toothed belt, 1.6 g) after the running test is made of the same material as the test body and is installed on a belt body (fixed) having three grooves. After the belt teeth and grooves were fitted together, a hard chromium-plated cylindrical weight with a diameter of 38 mm and a mass of 200 g (vertical drag N) was placed on the test specimen, and then the test specimen was moved at a speed of 10 mm. Pulled at / min. Then, the load (friction force F) at the start of sliding was measured with a load cell, and the friction coefficient μ (μ = F / N) was calculated from the friction force F. The results are also shown in Table 2.

(Pronunciation test)
The pronunciation test is the same as the pronunciation test procedure described in the first embodiment. The measurement results are shown in Table 2.

  From the results shown in Table 2, it can be seen that when carbon fiber is used as the material of the core wire, the friction coefficient can be lowered and sound generation can be suppressed as compared with the case where aramid fiber is used.

1,201 Toothed belt (Polyurethane transmission belt)
2, 202 Belt body 3, 203 Belt surface 4, 204 Tooth part 5 Oil 6 Uneven part 6a Recess 7 Core wire 30 Mold 31 Outer mold 32 Inner mold 32a Inner outer peripheral surface 32b Tooth part forming part 33 Spatial part 35 Uneven part Part 208 Reinforcement cloth

Claims (8)

A polyurethane transmission belt having a belt body made of a polyurethane elastomer to which a lubricant is added and spanned between a plurality of pulleys,
The belt surface, which is a contact surface with the pulley in the belt body, is a rough surface having a large number of fine irregularities that repeatedly undulate along the longitudinal direction and the width direction of the belt surface, and the arithmetic average roughness of the belt surface. A polyurethane transmission belt having a length of 4 to 25 μm.   2. The polyurethane transmission belt according to claim 1, wherein the lubricant transferred to the belt surface is accommodated in a concave portion of the uneven portion of the belt surface.   The polyurethane transmission belt according to claim 1 or 2, wherein the lubricant is oil.   4. The polyurethane transmission belt according to claim 3, wherein an average molecular weight of the oil and fat is in a range of 500 or more and 2000 or less.   The polyurethane transmission belt according to claim 3 or 4, wherein the oil is lard.   The polyurethane transmission belt according to claim 3, wherein the fat is a hardened oil having a melting point of 50 ° C. or higher and 80 ° C. or lower. A method for producing a polyurethane transmission belt having a belt body made of a polyurethane elastomer to which a lubricant is added, and being spanned between a plurality of pulleys,
A first step of blending a urethane prepolymer with a lubricant and a curing agent to produce a belt material;
An inner mold and an outer mold, and the outer peripheral surface of the inner mold is a rough surface having a number of fine irregularities that repeatedly undulate along the circumferential direction and the width direction of the outer peripheral surface. A second step of casting the belt material into a mold having an average roughness of 4 to 25 μm;
And a third step of releasing the mold after solidifying the belt material and transferring the shape of the concavo-convex portion of the outer peripheral surface of the inner mold to the belt surface. Method.   The method for producing a polyurethane transmission belt according to claim 7, wherein the lubricant is oil.