Oil-lubricated toothed power transmission belt

Abstract

We provide toothed transmission belts suitable for use in contact with oil. [Solution] The device comprises an elastomer belt body, a spirally wound tensile member embedded therein, and a jacket having teeth on the pulley contact surface and covering those teeth. The jacket is a woven fabric having a smooth, continuous outer rubber layer formed from a nitrile-containing elastomer that does not contain fluoropolymers and is compounded with at least one auxiliary agent, an RFS adhesion promoter. The fabric contains para-aramid fibers in the weft and meta-aramid fibers in the warp, but does not contain nylon fibers.

Description

Technical Field

[0001] The present invention relates generally to toothed or synchronous belts, and more specifically to a toothed belt having a special rubber coating on the contact surface for improved use in oil.

Background Art

[0002] Endless toothed belts, also called timing belts or synchronous belts, are often used in internal combustion engines to synchronize or time the movement of valves with the movement of cranks and pistons. They are also used to drive auxiliary equipment such as oil pumps, water pumps, fuel injection pumps and balance shafts. Dry toothed belts for dry belt drives are mounted outside the engine block and protected from contact with oil. Dry belt drives generally require additional seals, covers and space because the crankshaft and camshaft need to pass through the engine wall. Wet belts, or "belts in oil" (BIO) belts and transmissions, are located within the engine block or in similar environments exposed to oil, eliminating the need for additional seals or covers and potentially providing space savings. The width of the timing belt, the width of the pulleys and the width of the tensioner define space requirements. To minimize belt width, the belt must have very high durability, including resistance to bending fatigue under load conditions and resistance to bending radius in the transmission, resistance to abrasion and wear, and resistance to environmental conditions of constant exposure to heat and oil. Wear resistance is particularly important because wear debris remains in the oil, and in severe cases can prematurely clog the oil filter and cause engine damage.

[0003] U.S. Patent Application Publication No. 2020 / 0141283A1, which is incorporated herein by reference, discloses a BIO system. The disclosed belt discloses various conventional oil-resistant materials including treated fabric covering the teeth.

[0004] U.S. Patent Application Publication No. 2014 / 0080647A1 discloses fabric treatments including cured epoxy or epoxy rubber treatments with selective RFL (resorcinol-formaldehyde-latex) treatment. Such treatments are intended to improve the abrasion resistance, oil resistance, and water resistance of the toothed jacket, and to provide a toothed belt that exhibits sufficient durability even when used under high temperature and high load conditions, or in oily or watery environments.

[0005] Japanese Patent Publication No. 06-101741A discloses a toothed belt in which the surface of the cover cloth is covered with a rubber layer formed from rubber paste. Because this rubber layer is more susceptible to thermal degradation than the belt body, it hardens quickly in the initial period of use, reducing the coefficient of friction and minimizing wear.

[0006] U.S. Patent No. 9,927,001B2 describes a toothed belt having a cover cloth with four fabric treatments that are said to withstand high temperatures when dry, especially in oil, and to work very advantageously over the long service life of belts that are in continuous contact with oil at high temperatures. The fourth treatment and outer layer include an anti-friction material, preferably a fluorinated polymer such as PTFE (polytetrafluoroethylene). Similarly, U.S. Patent No. 8,568,260B2 discloses a toothed belt having an outer layer based on a fluorinated plastomer that is used with oil and is present in greater quantities than other elastomer materials. U.S. Patent Application Publication 2011 / 0111902A1 also discloses a toothed belt having an oil-resistant fluorinated protective layer made from PTFE, PVF (polyvinyl fluoride), or PVDF (polyvinylidene fluoride). [Overview of the project]

[0007] The present invention relates to a system and method for providing a smooth, continuous rubber tooth surface coating that has the same or a similar composition as the belt body and possesses heat resistance equal to or better than that of the belt body, without containing fluoropolymers or lubricants such as graphite or molybdenum, or to a system and method for providing a durable toothed belt for BIO applications and power transmission equipment.

[0008] The present invention relates to a toothed transmission belt comprising an elastomer belt body in which a spirally wound tensile member is embedded, and teeth provided on a pulley contact surface having a jacket covering the teeth. The jacket is generally a woven fabric coated on the outside with an oil-resistant and heat-resistant rubber composition that forms a smooth and continuous outer rubber layer.

[0009] The oil- and heat-resistant rubber composition may be based on a nitrile-containing elastomer containing additives and adhesion promoters, but will not contain fluoropolymer additives. The outer rubber layer may have heat resistance equal to or greater than that of the belt body, and may be softer when measured in a rubber hardness test. The oil- and heat-resistant rubber composition will not contain graphite, molybdenum lubricant components, or fluoropolymers. The composition may contain one or more crosslinking aids and a resorcinol-methylene donor-silica ("RFS") adhesion promoter system.

[0010] The fabric may be treated with an epoxy or epoxy rubber-based coating. The jacket may also be coated on the inside with an adhesive rubber composition having the same composition as the oil- and heat-resistant rubber composition. All of these rubber compositions can be based on an oil-resistant nitrile elastomer, such as hydrogenated nitrile rubber ("HNBR").

[0011] The fabric may contain heat-resistant and oil-resistant fibers such as aramid fibers, but does not contain nylon fibers. The fabric may contain para-aramid in the weft and meta-aramid in the warp. The weft may also contain elastic yarn to improve stretchability.

[0012] The present invention also relates to a method for manufacturing a toothed belt for use in contact with oil. This method includes preparing a woven fabric as described above, applying one or more treatments as described above, and finally applying an outer rubber layer as described above to create a jacket. The jacket is then formed together with the belt body material and tensile cord to produce an endless toothed belt having a substantially smooth and continuous outer rubber layer on the toothed surface intended for contact with a pulley.

[0013] The present invention also relates to the above-mentioned jacket for use on the tooth surface of a belt used in oil.

[0014] The outer rubber layer or coating improves the belt's durability in oil, allows for a reduction in belt width, and reduces the generation of wear debris that contaminates the oil.

[0015] To this point, the features and technical advantages of the present invention have been outlined fairly broadly so that the detailed description of the present invention below may be better understood. Additional features and advantages of the present invention that form the subject matter of the claims of the present invention are described below. Those skilled in the art should understand that the disclosed concepts and particular embodiments can be readily used as a basis for modifying or designing other structures to accomplish the same objectives of the present invention. It should also be recognized by those skilled in the art that such equivalent structures do not depart from the spirit and scope of the present invention as set out in the appended claims. Novel features that are considered to be features of the present invention will be better understood from the following description in conjunction with the appended figures, along with further objectives and advantages, with respect to both their configuration and method of operation. However, it should be clearly understood that each figure is presented for illustrative and explanatory purposes only and is not intended to define the limitations of the present invention. [Brief explanation of the drawing]

[0016] The accompanying drawings, which are incorporated herein and constitute part thereof, and in which the same numbers refer to similar parts, and which illustrate embodiments of the present invention together with a detailed description, are used to explain the principles of the present invention.

[0017] [Figure 1] Fig. 1 is a partially broken perspective view of a toothed belt according to an embodiment of the present invention.

[0018] [Figure 2] Fig. 2 is a schematic diagram of an HOL test used for testing the performance of the embodiment of the present invention in oil.

[0019] [Figure 3] Fig. 3 is a schematic diagram of a motor engine BIO drive used for testing belt performance.

[0020] [Figure 4] Fig. 4 is a schematic diagram of a drilling machine wear test.

[0021] [Figure 5] Fig. 5 is a photograph of a part of a novel belt according to an embodiment of the present invention.

[0022] [Figure 6] Fig. 6 is a photograph of a part of the belt of Fig. 5 after being tested for a period of time.

[0023] [Figure 7] Fig. 7 is a photograph of the belt of Fig. 6 after further testing for additional time.

[0024] [Figure 8] Fig. 8 is a photograph of a part of a prior art belt after being tested for a period of time. DETAILED DESCRIPTION OF EMBODIMENTS

[0025] The structure of the synchronous belt 200 of the present invention is shown in Figure 1. Only a portion of the endless belt is shown in Figure 1. The belt 200 includes teeth 214 on one side and engages with a grooved sprocket or grooved pulley. The teeth 214 alternate with lands 215. The curved transition from the flank to the land 215 of the teeth 214 is called the root or tooth root. The belt 200 does not have teeth on the back 220, but in an alternative embodiment, it may have similar teeth on both sides. The body rubber or elastomer comprises tooth rubber 212 and back rubber 222. The toothed side is covered with a tooth jacket 216, and the back 220 is selectively covered with a back jacket 224. The repeating length of the teeth is called the pitch "P". A tensile member 218 is embedded in the rubber of the belt body and gives the belt high tensile elasticity.

[0026] The tooth jacket 216 includes one or more additional fabric treatments, such as a fabric 217, a surface rubber layer 219, and an adhesive layer 213. The jacket 216 is designed to enhance one or more belt properties, such as adhesion, oil resistance, and abrasion resistance, along with the system's performance characteristics, such as timing error and durability. The fabric treatment may be any suitable treatment known in the art. Similarly, the back jacket 224 may include one or more treatments similar to or different from those of the tooth jacket, along with the fabric. Thus, the term “jacket” is used to describe a fabric that includes one or more treatments, which is usually pre-formed in preparation for assembly into a belt. “Fabric” generally refers to raw woven, nonwoven, or knitted material before treatment, but which may include some treatments.

[0027] The belt of the present invention exhibits excellent wear resistance and abrasion resistance when used in oil-immersed or partially oil-immersed transmission systems. The key features contributing to this performance are the fibrous material used in the surface rubber layer 219 and the tooth fabric 217. The effect is synergistic and greater than the sum of the individual parts. By reducing wear particles generated by abrasion and wear, the system is protected from the adverse effects of such particles. In conventional BIO systems, failures occur in real-world use due to clogging of the oil filter by belt wear particles. By reducing wear and increasing durability, belt life can be extended, and a narrower belt width can be used to save space within the engine.

[0028] The tooth fabric 217 may be any suitable woven, knitted, or nonwoven fabric having appropriate elasticity, strength, abrasion resistance, heat resistance, and environmental resistance as required by the application. When used in a flow-through belt manufacturing process (defined later), it is preferable to have longitudinal stretch of more than 80% or more than 100%. In a pre-forming process, lower stretch may be suitable, or no significant stretch may be suitable. The fabric is preferably made only of high-strength, oil-resistant, abrasion-resistant, and heat-resistant fibers such as aramid, PPS, PEEK, polyester, and combinations thereof. The fabric is preferably made only of aramid fibers and selectively contains elastic yarn components for stretchability. Aramid fibers or aramid yarns may be paraaramid fibers or paraaramid yarns, metaaramid fibers or metaaramid yarns, or combinations thereof.

[0029] Typical examples of fabric weaving patterns include 2x2 twill and 3x1 twill. However, many other weaving patterns are also possible.

[0030] A typical example of a woven fabric has a warp of meta-aramid yarn and a weft of para-aramid yarn. The para-aramid yarn may include copolymer para-aramid yarn. The para-aramid yarn may also contain an elastic yarn component that provides stretch in the weft direction. The elastic yarn may be rubber elastic yarn or polyurethane elastic yarn. Elastic means highly stretchable, for example, meaning that it can be stretched by 100-500% or more in a highly contracted state. The weft direction is preferably the longitudinal direction when it becomes a belt. These directions and materials may be reversed, in which case the stretch direction becomes the warp direction and is oriented in the longitudinal direction of the belt. Yarns with sufficient stretch are obtained by known methods suitable for selected fibers, including texture processing, winding of an elastic core, bias orientation, and combinations thereof. Winding of aramid onto an elastic core is preferred in the weft yarn or in the stretch direction. Nylon and polyamide fibers are not suitable for use in the present invention, either as weft or warp. Therefore, nylon 6-6, the main fiber of conventional automotive timing belt jackets, is not suitable for use in the present invention.

[0031] Suitable para-aramid fibers include those sold by DuPont under the trademark Kevlar, those sold by Teijin Aramid under the trademarks Twaron and Technora (polymer), and those sold by Kolon Industries under the trademark Heracron. Suitable meta-aramid fibers include those sold by DuPont under the trademark Nomex, and those sold by Teijin under the trademark Conex.

[0032] The surface rubber layer 219 is formed from a rubber composition having oil resistance and heat resistance. The surface rubber composition consists of any suitable highly oil-resistant elastomer, such as nitrile group-containing copolymer elastomers such as nitrile butadiene rubber (NBR), hydrogenated nitrile butadiene rubber (HNBR), or carboxylated nitrile (XNBR or HXNBR). The nitrile group-containing elastomer may contain a third monomer that reduces the glass transition of the rubber. A mixture of different grades of nitrile group-containing elastomers may be used. Typical examples of elastomers include various grades sold by Zeon under the trademark Zetpol, which includes materials known as ZSC, and various grades sold by Alantheo under the trademark Terban. Fluoroelastomers and fluoropolymers are not used in this invention.

[0033] The surface rubber composition may contain, in addition to the base elastomer, any of a wide variety of compounding components, including reinforcing fillers, plasticizers, degradation inhibitors, adhesion promoters, auxiliary agents, and curing agents. Typical examples of reinforcing fillers include carbon black, silica, and short fibers. It is preferable to include one or more auxiliary agents, such as zinc diacrylate or zinc dimethacrylate, which may be added during the mixing of the composition or included in one grade of HNBR used in the composition (e.g., Zeon's ZSC). Other acrylate or methacrylate auxiliary agents can be used alone or in combination. It is also preferable to include an adhesion promoter in the composition. Preferred adhesion promoters are resorcinol and / or formaldehyde-based resins, such as the Cohedr product sold by Lanxess. The rubber composition may favorably contain a reactive resin system or equivalent to resorcinol, such as resorcinol, formaldehyde, or methylene donor, and silica, commonly referred to as an "RFS" bonding system, as disclosed by reference herein in The. Kempermann et al., "Manual for the Rubber Industry," 2nd edition, Bayer AG, Leverkusen, Germany, pp. 372 & 512-535 (1991). The main purpose of this "RFS" system is to enhance adhesion between the fabric and the outer rubber layer. Silica also serves as a reinforcing filler. Silica with a high surface area is preferred. Peroxide curing systems are preferred from the viewpoint of heat resistance.

[0034] The outer rubber composition can be applied to a toothed fabric or treated toothed fabric (see below) by any suitable method, resulting in a nearly smooth, continuous coating that seals in any porosity present within the fabric. The outer rubber layer of the finished belt will be glossy or shiny, especially when wet with oil, but will typically have a smooth, matte finish when dry. The outer rubber composition can be applied by preparing a liquid rubber cement and applying the cement to the fabric by brushing, spraying, coating, or dipping. Alternatively, the rubber composition may be laminated as solid rubber using calendering or lamination processes such as friction or skimming. Alternatively, the outer rubber layer may be laminated during the belt forming process. A rubber thickness of 1 mil (25 μm) to 10 mil (0.25 mm) is sufficient for lamination.

[0035] The outer rubber layer is expected to provide superior chemical resistance and abrasion resistance compared to conventional belt structures. Filling the fabric's texture and pores with rubber prevents the incorporation of particles and liquids and the penetration of oil, and the absence of nylon is expected to enhance chemical resistance. The outer rubber layer is also expected to improve the integrity and robustness of the composite, helping to suppress the occurrence of tooth root cracks at the rubber-jacket interface, suppressing delamination and extending the service life. The tooth jacket of the present invention is expected to exhibit minimal dimensional changes over its service life, which is beneficial for tooth meshing and the noise it generates.

[0036] The backing fabric may be any suitable woven, knitted, or nonwoven fabric with appropriate elasticity, strength, abrasion resistance, heat resistance (high or low temperatures), and environmental resistance for the application. Generally, since the backing fabric is simply laid flat on the back of the belt, there are no specific requirements regarding the degree of elasticity needed. Some degree of elasticity would be preferable to maintain the flexibility of the belt. The backing fabric has been shown to improve cold resistance and reduce the occurrence of cracks on the back due to repeated cold starts. The backing fabric may be RFL coated. The backing fabric does not need to be as smooth as a toothed fabric or coated with a smooth continuous rubber layer, but it may be coated in the same way.

[0037] Preferred fabric treatments for either or both of the tooth fabric 213 and / or back fabric 224 include epoxy or epoxy rubber treatment, as described in Yamada et al., U.S. Patent Application Publication No. 2014 / 0080647A1, incorporated herein by reference, with RFL treatment being selectively applied first. Such treatment improves the abrasion resistance, oil and water resistance of the tooth jacket, resulting in a toothed belt that exhibits sufficient durability even when used under high temperature and high load conditions, or in oily or watery environments. This treatment will also improve the adhesion of the fabric to the belt body and / or outer rubber layer. Epoxy rubber treatment would be the first treatment on the fabric. The rubber component may be an oil-resistant latex such as NBR, HNBR, or XHNBR latex. Fabric treatment is performed by dipping, spraying, brushing, roll coating, knife coating, or other suitable process.

[0038] Therefore, the treated tooth fabric, i.e., the jacket covering the teeth of the belt of the present invention, is preferably an aramid stretch fabric free of nylon fibers, which is first treated by immersion in epoxy rubber, followed by the application of a smooth, continuous outer rubber layer 219. Other layers, such as the aforementioned RFL, may be interposed, or other layers may be included on the inner surface for adhesion to the belt body material or tooth rubber.

[0039] Any suitable rubber composition can be used for the tooth rubber 212 or the back rubber 222. Furthermore, if necessary, there may be other rubber layers, such as an adhesive rubber layer or other layers, in contact with the tensile cord 218. If necessary, the same or different compounds can be used for the teeth, the tensile cord layer, the back side, or other parts of the belt. Whitfield's U.S. Patent No. 6,358,171B1, incorporated herein by reference, describes typical rubber formulations for tooth rubber or belt body rubber. As described therein, the belt body rubber composition may include a nitrile group-containing copolymer elastomer such as HNBR, and the elastomer may include a third monomer that reduces the glass transition of the elastomer. The rubber composition may also contain about 0.5 to about 50 parts by weight ("PHR") of fiber reinforcement per 100 parts by weight of elastomer. U.S. Patent No. 9,140,329B2, incorporated herein by reference, describes other typical rubber formulations for tooth rubber or belt body rubber. As described therein, the belt body rubber composition may include HNBR or HXNBR rubber, resorcinol, and melamine compounds.

[0040] The rubber composition of the belt body and the outer rubber layer may further contain additional components known in the art, such as fillers, plasticizers, degradation inhibitors, processing aids, curing agents, additives, and compatibilizers.

[0041] The tensile cord 218 of the belt may be any known in the art, but preferably it contains glass fiber, PBO (i.e., polyp-phenylene-2,6-benzobisoxazole), aramid, carbon fiber, or a hybrid of two or more of these. The tensile cord preferably includes an oil-resistant adhesive treatment for use in oil-soaked environments. For example, the adhesive treatment may be based on nitrile-containing latex or rubber, or other oil-resistant material. Preferred tensile cords may include carbon fiber, as disclosed in Knutson's U.S. Patent No. 6,945,891, or glass / carbon hybrid cords, as described in Akiyama et al.'s U.S. Patent No. 7,682,274. Preferred glass fibers for the tensile cord include high-strength glass fibers such as K-glass, U-glass, M-glass, or S-glass.

[0042] The toothed belt of the present invention can be manufactured according to known belt manufacturing methods. The most common approach involves winding various materials onto a grooved mandrel. Starting with the tooth cover jacket, then a spirally wound tensile cord or core wire, then body rubber or multiple rubbers, and finally the back jacket. Next, the mandrel with the belt slab wound onto it is inserted into a pressurized shell that can compress and integrate the materials by heating and pressurizing, the rubber is poured into the tooth grooves, and the tooth jacket is pressed into the shape of the grooves (known as the "flow-through" method). Alternatively, the tooth jacket can be roughly pre-formed into a groove shape before or while it is being placed on the mandrel ("pre-forming method"), and the tooth rubber can be selectively filled into the teeth. Other variations of these methods are also possible. A key additional feature for manufacturing belts with a cloth backing is that, as is often done with belts with a rubber backing, the back of the belt cannot be polished to a predetermined dimension, so the rubber layer must be carefully measured to obtain the required final belt thickness. While the pre-forming method may be preferred depending on the aramid fabric, both methods are available.

[0043] The rubber compound of the belt body generally has a modulus level optimized for the stiffness of the teeth and the allowable load of the teeth and timing belt. The back rubber compound, if it is different from the tooth rubber, does not directly bear the load like the tooth rubber, so its modulus is set somewhat lower, i.e., softer, to increase the flexibility of the belt. The tooth cover jacket reinforces the teeth and also contributes to the stiffness of the teeth and the load-bearing capacity of the belt. Generally, the tensile cord determines the tensile properties of the timing belt, such as modulus (or span stiffness) and strength. By selecting these materials, it has been found that optimizing the combination of belt span stiffness and tooth stiffness reduces the system load and allows the same timing error in the system to be achieved even with narrow belts, while minimizing the strength required for the belt. For example, see U.S. Patent Application Publication 2020 / 0141283A1, the contents of which are incorporated herein by reference.

[0044] The outer rubber layer compound would be advantageous if it had a lower modulus of elasticity than the tooth or back rubber. The outer rubber layer is thought to enhance the cushioning of the fabric and prevent oil penetration. A formulation that is somewhat softer than the tooth rubber (for example, as measured by a rubber hardness tester such as Shore A or IRHD) and that maintains that softness over the belt's lifespan in the presence of high-temperature oil is preferred.

[0045] Examples

[0046] The story of how this invention was discovered is significant. It was found that narrowing the belt width to save space resulted in excessive wear in BIO tests in a controlled structure. The control belt performed exceptionally well under the BIO conditions for which it was designed. The control belt features a state-of-the-art fabric with a blend of high-performance nylon and p-aramid in the weft and a blend of nylon in the warp, and several special coatings applied to the fabric, as described in Yamada et al., U.S. Patent Publication No. 2014 / 0080647. Because the special coatings are highly oil-resistant, it was expected that they would perform similarly even under more severe BIO conditions. However, the belt life in the initial experiments, where the severity of the BIO tests was increased, was very disappointing, with excessive jacket wear observed in both the tooth flanks and root regions. Interestingly, it was further observed that the rubber layer used to bond the jacket to the belt body material did not wear down. This rubber layer was designed for bonding and had excellent heat and oil resistance, but it did not have any special features to enhance abrasion or wear resistance. This rubber layer did not contain PTFE, graphite lubricants, molybdenum disulfide, or other well-known friction modifiers.

[0047] This observation regarding the rubber layer quickly led to the idea of ​​applying the same rubber layer to the outside of the belt. Unfortunately, when this second experiment was performed, the BIO test did not show any positive effect on improving the belt's lifespan or wear resistance.

[0048] After some time, it became clear that the presence of nylon in the fabric could negatively impact the belt's lifespan in oil under harsh conditions. In the third experiment, it was found that replacing the nylon with more para-aramid or meta-aramid fibers approximately doubled the belt's lifespan. Although it had previously been found that the rubber layer had no positive effect, it was decided to try it again on the outside of the nylon-free fabric. Surprisingly, in the fourth experiment, the outer rubber layer more than doubled the belt's lifespan again, representing an improvement of more than six times compared to the first two unsuccessful experiments. Thus, removing the nylon and adding the rubber layer yielded a synergistic effect that could not have been predicted from the individual effects of the first three experiments.

[0049] The above observations are reflected in the data in Tables 1 and 2 below. Table 1 shows data from a high-temperature oil test machine ("HOL") operated at 140°C, 18kW, and 6200rpm. The driven pulley was partially immersed in a tank 235 of Castrol motor oil. The drive layout 230 of the HOL test machine is shown in Figure 2. Pulley 231 is a driving pulley with 20 grooves, and pulley 232 is a driven sprocket with 40 grooves. Both have RPX profile grooves. The outer diameter of the idler 233 is 61mm. The tested belt 200 was always 10mm wide and had 85 teeth with a 9.525mm pitch and an RPP tooth profile. The mounting tension was 160N. Comparative examples of belts are shown as "Comparative Examples," and examples of belts of the present invention are shown as "Examples."

[0050] Table 1 compares four belts tested at 18kW on a HOL test machine. Belt life, expressed in time, is normalized using the average of control belts tested multiple times on multiple test machines to account for variability between test machines. Comparing Comparative Example 1 and Comparative Example 2, it is shown that when nylon is present in the fabric, adding the outer rubber layer of the present invention does not improve belt life. Comparing Comparative Example 3 with Comparative Examples 1 and 2, it is shown that removing nylon from the fabric and using only aramid more than doubles the belt life. However, in Example 4, which combines both aramid-only fabric and the outer rubber layer, the belt life is 7 to 8 times longer than in Comparative Examples 1 and 2, and approximately three times longer than that of Comparative Example 3. In other words, the outer rubber layer appears to have a positive effect only when the fabric consists of aramid, i.e., nylon-free fabric.

[0051] It is also important to note that the failure modes of the belts of the present invention are improved. All of the comparison belts fail due to excessive flank and root wear, and delamination at some point, ultimately leading to tooth breakage. The belts of the present invention tend to fail in a more generally acceptable way, with root cracking occurring before significant wear is seen. While root cracking in the belts of the present invention can also lead to tooth breakage, the longer lifespan should give the user an opportunity to spot the crack and replace the belt before a fatal failure occurs, and the absence of root and flank wear significantly improves the wear debris problem, even if wear debris is not completely eliminated. [Table 1]

[0052] Table 2 shows data from the above-mentioned high-temperature oil test machine ("HOL"), but operated at a higher load of 22 kW. It should be noted that at such high loads, belt life may be shortened to less than 100 hours, and unreliable numerical comparisons and estimates may be made due to the over-accelerated failure modes. Nevertheless, the trends seen in Table 2 are consistent with Table 1 and thus illustrate the advantages of the present invention. Comparative Examples 1 and 6 have the same belt structure. Examples 4 and 11 have the same belt structure as the present invention. Comparative Examples 5-8 show that nylon in the fabric shortens the belt life to an unacceptable degree. Example 9 shows that replacing nylon with aramid improves life somewhat. Examples 10 and 11 show that the outer rubber layer of two different aramid fabrics significantly extends belt life (up to 9 times). These two belts of the present invention differ in the type of aramid used in the warp threads of the fabric. As mentioned above, the belt failure modes change from severe wear and abrasion debris in the comparative example belts to cracking at the tooth roots in the present invention belts. A comparison of Comparative Examples 7 and 8 shows that the use of fluoroelastomers is equivalent to using non-fluorinated polymers for the outer coating. The fluoroelastomer in Comparative Example 7, which also contained PTFE powder additives, still exhibited significant wear. [Table 2]

[0053] Table 3 shows four different belts that have the same structure as Examples 4 and 11 above, but with different outer rubber layer compositions. These belts were run in a motor-driven engine test as described in U.S. Patent Application Publication No. 2020 / 0141283A1. The belts were run for 465 hours and then removed for inspection. In each comparative example and example in Table 3, the test layout was a dual overhead cam drive on a three-cylinder engine driven by an electric motor connected to the crankshaft, as shown in Figure 3. This three-cylinder engine is known as the 1.0L Fox engine manufactured by Ford Motor Company. The standard oil-wet timing drive system was modified to accommodate various test drives. In this comparison, all belts were 10 mm wide, 116 teeth, and run in an oil-wet condition using Castrol Magnetec 5W-20 oil at an oil temperature of 140°C. Test layout 240 included an idler pulley 244 and a driving pulley, namely crank pulley 243, with 19 grooves having an RPX groove cross-section and a 9.525 mm pitch to fit belt 200 with an RPP tooth profile, and driven cam pulleys 242 and 245 with 38 grooves. The speed of the driving pulley was 4750 rpm.

[0054] The results in Table 3 show that while the rubber layer can be varied, not all compositions are the same. Comparative Example 12 shows that a rubber outer layer containing PTFE-added HNBR has adhesion problems and problematic abrasion resistance. Even with the use of a compatible primer, the adhesion problems become apparent at the end of the BIO test. Example 13 shows that a typical HNBR rubber composition without fluoropolymer additives can solve the abrasion problem and may have some utility in BIO applications, although it may also have some adhesion problems. Example 14 is another HNBR composition with a higher ACN level and is expected to provide higher oil resistance than Comparative Example 12 or Example 13. Example 14 also does not contain fluoropolymer additives. Example 14 largely avoids the abrasion problems of Comparative Example 12, but there is still room for improvement in adhesion strength and the use of a primer. As mentioned above, Example 14 demonstrates the potential utility of an adhesive primer. Example 15, which has the same outer rubber composition as Examples 14 and 11 above, does not show adhesion problems thanks to the RFS adhesion promoting component. Abrasion resistance is also not a problem. The outer rubber bonding agent (cement) used in Examples 8, 10, 11, and 15 is the same as the adhesive rubber bonding agent (cement) used in all examples.

[0055] The materials in Table 3 were also tested in a dry abrasion test called the drill press test. Fig. Figure 4 shows the drill press test 400 used here. In this test, the jacket is cut into a 1.1-inch (outer diameter 28 mm) circle with a 0.75-inch (inner diameter 19 mm) hole. The resulting jacket ring 410 is vulcanized onto a rubber substrate 415. The jacket contact surface 420 is abraded by the opposing surface 430 of a rotating aluminum disc 425 at approximately 200 rpm for 72 hours under a contact force of 7 kg. The weight lost indicates the abrasion resistance of the jacket and the amount of abrasion debris generated by the sample.

[0056] Unsurprisingly, the PTFE of Comparative Example 12 is the smoothest in this dry test. Surprisingly, however, Examples 13 and 15 have almost equivalent performance, with only a slight weight reduction compared to Comparative Example 12. Therefore, the jackets and belts of the present invention may be useful not only in oil-wet applications but also in dry belt applications. [Table 3]

[0057] The useful and preferred composition range for the outer rubber layer can be summarized as follows. This description is not intended to be limiting, as many components may be substituted, other components may be included, or some may be omitted depending on the requirements of the specific application. The base elastomer is HNBR having, for example, an ACN content in the range of 35-45% by weight, an unsaturation level in the range of 0-10%, or preferably in the range of 0-4%. Acrylate and methacrylate additives are present, for example, in the range of 0 or 5-40 PHR, preferably 10-30 PHR. The reinforcing filler may be carbon black and / or silica in the range of 20 to 80 PHR, preferably 30 to 70 PHR, and preferably containing 30 to 50 PHR of silica. Depending on the handling and physical properties requirements, antioxidants, processing aids, peroxide curing agents, and compatible plasticizers may be added. The adhesion promoting system may contain resorcinol and methylene donor components in the range of 0.5, 1 or 2 to 10 PHR, an equal amount of maleic anhydride-based material, or other adhesion promoting materials or systems.

[0058] Regarding physical properties, the outer rubber layer is similar in many ways to the typical HNBR rubber compound used in the timing belt body, but there are some notable differences. Both the belt body and the outer layer need to have excellent oil and heat resistance. It is considered advantageous for the outer layer to be somewhat softer than the main rubber to promote a cushioning effect when the jacket contacts the pulley. Table 4 compares the hardness of the tooth rubber, back rubber, and outer rubber layer used in belts of Examples 4, 11, and 15. The outer rubber layer starts softer than the other belt rubber components and remains soft even after 168 hours of hot air aging at 150°C. If the tooth rubber or back rubber is filled with fibers and the outer layer does not, the stiffness or modulus of the outer layer is generally lower. Table 3 supports the idea that a softer outer rubber layer is superior to a harder layer, although many other factors also differ in the table. [Table 4]

[0059] While no explanation is intended to be restrictive or limiting, nylon has lower heat and oil resistance than aramid, and therefore, as long as nylon is present in the fabric, the benefits of a rubber layer in BIO applications are not realized. Furthermore, in oily environments, lubrication is already provided, so the presence of PTFE or other lubricating additives is considered unnecessary. Thus, although such lubricating additives are known to have excellent heat resistance and promote wear resistance, they are not as useful in BIO applications as one might imagine, and may actually cause adhesion problems and reduce wear resistance. Finally, conventional treatments of fabrics, such as coating the fibers or following the weave contours, leave pores into which oil can penetrate and pockets into which oil can remain, whereas the rubber layer of the present invention completely seals the fabric, providing a smooth, oil-resistant finish to the teeth and bases of belt teeth.

[0060] Figure 5 shows photographs of portions of belts from Examples 4, 11, and 15 before testing or exposure to oil. Figure 6 shows a photograph of the same belt showing the glossy, smooth surface provided by the outer rubber layer after 107 hours in the MER test. The glossy surface is very evident due to the oil used during the test. Unused new belt surfaces, or belts that have been used slightly in this manner, may show traces of the weave of the underlying fabric (such as slight waviness), but are usually very smooth and continuous. Figure 7 shows a portion of the test belt from Example 15 after 465 hours in the MER test. Here again, the pulley contact surface, including the teeth and tooth roots, is very smooth and glossy, with no signs of fabric exposure. In contrast, Figure 8 shows a portion of a conventional belt (e.g., Comparative Example 9) without an outer rubber coating on the pulley contact surface after approximately 152 hours of MER testing. This fabric is not glossy despite being tested in oil, the fiber coating does not fill the fabric, and the surface is not continuous and smooth like the belt of the present invention.

[0061] While the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions, and modifications can be made herein without departing from the scope of the invention as defined by the appended claims. Furthermore, the scope of this application is not intended to be limited to specific embodiments of the processes, machines, manufactures, material compositions, means, methods, and steps described herein. Those skilled in the art will readily understand from the disclosure of the present invention that current or future-developed processes, machines, manufactures, material compositions, means, methods, or steps that perform equivalent functions and produce substantially equivalent results to the corresponding embodiments described herein can be used in accordance with the present invention. Accordingly, the appended claims are intended to include such processes, machines, manufactures, material compositions, means, methods, or steps within their scope. The present invention disclosed herein can be adequately implemented without elements not specifically disclosed herein.

Claims

1. An elastomer belt body in which a spirally wound tensile member is embedded, The pulley has teeth on the contact surface having a jacket covering the teeth, A toothed transmission belt characterized in that the jacket includes a woven fabric coated on the outside with an oil-resistant and heat-resistant rubber composition, forming a smooth and continuous outer rubber layer.

2. The toothed transmission belt according to claim 1, characterized in that the oil-resistant and heat-resistant rubber composition contains the same base elastomer as the belt body.

3. The toothed transmission belt according to claim 1, characterized in that the oil-resistant and heat-resistant rubber composition does not contain a fluoropolymer or fluoroelastomer component.

4. The toothed transmission belt according to claim 1, characterized in that the outer rubber layer has heat resistance equal to or greater than that of the elastomer belt body.

5. The toothed transmission belt according to claim 1, characterized in that the oil-resistant and heat-resistant rubber composition does not contain graphite or molybdenum lubricant components.

6. The toothed transmission belt according to claim 1, characterized in that the jacket further comprises a first fabric treatment based on epoxy or epoxy rubber.

7. The toothed transmission belt according to claim 1, characterized in that the inside of the jacket is further coated with an adhesive rubber composition.

8. The toothed transmission belt according to claim 7, characterized in that the adhesive rubber composition has the same composition as the oil-resistant and heat-resistant rubber composition.

9. The toothed transmission belt according to claim 8, characterized in that the belt body, the adhesive rubber composition, and the oil-resistant / heat-resistant rubber composition each contain an oil-resistant nitrile elastomer.

10. The toothed transmission belt according to claim 9, characterized in that the oil-resistant and heat-resistant rubber composition comprises an HNBR elastomer and an RFS adhesion promoter system.

11. The toothed transmission belt according to claim 1, characterized in that the woven fabric contains aramid fibers but does not contain nylon fibers.

12. The toothed transmission belt according to claim 11, characterized in that the woven fabric contains meta-aramid fibers in the warp threads and para-aramid fibers in the weft threads.

13. The toothed transmission belt according to claim 12, characterized in that the woven fabric further includes elastic yarn in the weft.

14. The toothed transmission belt according to claim 1, characterized in that the outer rubber layer exhibits a durometer hardness lower than that of the elastomer belt body.

15. A woven fabric using para-aramid yarn and elastic yarn for the weft and meta-aramid yarn for the warp, An epoxy or epoxy rubber treatment is applied to the fibers of the woven fabric, One side of the epoxy-treated woven fabric is coated with an adhesive rubber coating, and this side is intended to be in contact with the body of the toothed belt. The epoxy-treated woven fabric comprises a smooth, continuous rubber layer on the opposite side, The opposite side is intended to contact the pulley, and the rubber layer comprises a heat-resistant and oil-resistant nitrile rubber composition that does not contain fluoropolymer components. A jacket for a toothed belt used in contact with oil, characterized by the following features.

16. A woven fabric is prepared consisting of para-aramid yarn and elastic yarn for the weft and meta-aramid yarn for the warp. The fibers of the woven fabric are treated with epoxy or epoxy rubber. An adhesive rubber coating is applied to one side of the epoxy-treated woven fabric, and this side is intended to come into contact with the body of the toothed belt. A jacket is formed by applying a heat-resistant, oil-resistant nitrile rubber composition that does not contain fluoropolymer components to the opposite side of the epoxy-treated woven fabric. The belt is formed with the jacket covering the teeth of the toothed belt, and the heat-resistant and oil-resistant nitrile rubber composition forms an outer rubber layer on the tooth surface, which is intended to come into contact with a glossy, smooth, continuous pulley. A method for manufacturing a toothed belt used in contact with oil, characterized by the following features.

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