Power transmission belt and related transmission system

Abstract

A power transmission belt comprising a body (102) made of a sizing material having a main elastomer, a tooth portion (104), and a belt back (107) and a plurality of longitudinal cords (103) embedded in the belt body wherein: the main elastomer constitutes at least 70% by weight of all elastomer materials of the body; the main elastomer is an ethylene-alpha-olefin copolymer; the body comprises at least 12% by weight of fibers; the fiber is selected from the group consisting of glass, aramid fiber, polyester, carbon fiber, polybenzobisoxazole (PBO), polyamide, polyketone (POK), polyether-ether-ketone (PEEK), polyvinyl alcohol (PVA), liquid crystal fiber (LPC), polyethylene naphthalate (PEN) and aliphatic polyamide; the size of the fibers is between 1mm and 6mm; the teeth are coated with a coating material selected from the group consisting of woven fabrics, knitted fabrics and non-woven fabrics; the coating material is treated by adopting a polymer containing nitrile groups; the cladding material is coated with a second treatment layer (109) comprising an elastomer and an antifriction material.

Description

[0001] Cross-references to related applications

[0002] This patent application claims priority to Italian patent application No. 102023000015384, filed on July 21, 2023, the entire disclosure of which is incorporated herein by reference. Technical Field

[0003] This invention relates to power transmission belts, and more particularly to toothed belts and related transmission systems. Background Technology

[0004] The present invention is preferably used for power transmission in a transmission assembly including an electric motor.

[0005] Power transmission is preferably achieved by using a synchronous power transmission belt (also known as a toothed belt).

[0006] This belt can be used for power transmission in motor vehicles as well as in industrial applications.

[0007] A transmission belt typically comprises: a body made of an elastomeric material, preferably HNBR for toothed belts, a plurality of linear tensile inserts embedded longitudinally in the body, and a coupling portion integrally connected to the body and comprising a plurality of teeth, which, in the case of toothed belts, are transverse to the sliding direction of the belt in use.

[0008] A typical problem with toothed belts is that they must be oil-resistant.

[0009] Recently, automotive engines have been developed that include timing transmission systems, in which the chain is replaced by a power transmission belt under the same working conditions, thus maintaining continuous contact with oil or oil mist.

[0010] Such systems have been described in the applicant's patents (e.g., WO2005 / 080820). In these drive systems, the drive belt is referred to as an "oil-in-line belt" or "wet belt" and must meet the same life requirements as an equivalent chain drive system. In the context of this invention, "oil-in-line belt" or "wet belt" refers to a drive belt used in a drivetrain system in which the belt is at least partially immersed in oil during rest and / or operation, or in a drivetrain system where the drive belt is continuously in contact with oil or oil mist, for example, through a specially designed nozzle in the form of a spray, or through a system that supplies oil to the drive belt due to the agitation of the drive belt and pulleys.

[0011] In particular, in these transmission systems, there is no separation between the engine lubricant and the transmission system.

[0012] Therefore, the oil drive belt must be able to withstand continuous contact with high-temperature oil during engine operation and must not be damaged at high operating temperatures or extremely low temperatures.

[0013] Specifically, the key is that the base compound must still be oil-resistant at high temperatures, avoid or at least reduce oil absorption, and maintain good abrasion resistance.

[0014] Therefore, the transmission belt needs to have a combination of oil swelling resistance and low-temperature resistance that is superior to currently available products.

[0015] Drive systems with power transmission belts that are immersed in oil and / or continuously run in oil are generally very similar to systems that use chains for power transmission.

[0016] Materials suitable for drive belt housings (such as hydrogenated nitrile butadiene rubber (HNBR) or HNBR terpolymers) are known.

[0017] Another known drawback of drive belts is that their excellent flexibility and oil swelling resistance cannot be adjusted independently. Typically, there is a correlation between the acrylonitrile monomer (ACN) content, glass transition temperature, and oil swelling properties in HNBR. This means that higher ACN content, i.e., stronger polarity, results in lower oil swelling properties, but simultaneously, a higher glass transition temperature. However, HNBR polymers are known to be expensive, and they do not always ensure ideal belt operation in contact with oil, especially at low temperatures.

[0018] Due to supply difficulties, the use of nitrile rubber is becoming increasingly difficult, and it is currently an obstacle to the application of nitrile rubber-based products.

[0019] Therefore, the currently used tape does not fully solve the problems mentioned.

[0020] Therefore, the industry continues to seek drive belts that meet the increasingly stringent requirements of automakers, and in particular, still achieve a long service life. Summary of the Invention

[0021] The object of the present invention is to provide a transmission belt that solves the above-mentioned problems, and to achieve this by means of the belt according to claim 1 and the transmission system according to claim 10. Attached Figure Description

[0022] Figure 1 This is a schematic diagram and a partial view of the toothed band.

[0023] Figure 2 Curves showing the oil swelling characteristics of belts with different fiber percentages;

[0024] Figure 3 A table is shown for different comparison bands and for durability testing according to the present invention; and

[0025] Figure 4 A graph representing the noise test under constant torque; and

[0026] Figure 5 Representative for Figure 4 A schematic diagram of the transmission system used for noise testing. Detailed Implementation

[0027] "Main elastomer" is defined as the elastomer constituting the main body of the rubber compound, which accounts for more than 70% by weight of the total elastomer in the main body of the rubber compound. Other components such as additives or fillers may also be added to the elastomer.

[0028] The term "the first elastomer material is basically composed of..." means that the elastomer material is the only elastomer that determines the physical and chemical properties and performance of the main rubber compound. Even if other elastomer polymers or copolymers are added in small amounts to the rubber compound in addition to conventional additives, as long as they do not negatively affect the functionality and chemical compatibility between the main rubber compound and other components used to manufacture the toothed belt, they do not depart from the protection scope of this invention.

[0029] In the following text, "elastomer material additives" refers to a class of materials added to elastomer materials to change their chemical and physical properties.

[0030] The terms "in oil" or "in oil mist" refer to a drivetrain belt that is partially immersed in an oil bath or in continuous direct contact with oil or oil mist. Typically, oil-immersed drivetrain belts in use are located inside the engine block, such as in replacement chains or gear systems.

[0031] In the following text, polymer abbreviations follow the ISO 1043-1:2011 standard.

[0032] exist Figure 1 In an embodiment of the invention, 101 represents the toothed strip as a whole.

[0033] The teeth may optionally be helical, and the helix angle is preferably between 1° and 15°.

[0034] The band 101 includes a body 102 made of a primary elastomer. A plurality of longitudinal linear tensile inserts 103 (also referred to as “cords”) are embedded in the body 102.

[0035] The belt also includes a toothed portion 104, which is composed of a plurality of teeth 106. When in use, the teeth 106 form a working surface 105, which meshes with the corresponding pulley of the transmission system.

[0036] The toothed belt also includes a belt back 107 opposite to the working surface 105.

[0037] The main body 102 includes an ethylene-α-olefin copolymer as the main elastomer.

[0038] Preferably, the main elastomer accounts for more than 90% of the total weight of the elastomer in the rubber compound by weight percentage.

[0039] More preferably, the main elastomer accounts for more than 95% by weight of the total weight of the elastomer in the rubber compound.

[0040] The main elastomer accounts for more than 30% by weight of the total weight of the rubber compound, more preferably more than 40%, and even more preferably between 40% and 50%.

[0041] The sum of the weight of the main elastomer and the fiber accounts for more than 50% by weight of the total weight of the rubber compound, more preferably more than 60% by weight.

[0042] Preferably, the ethylene-α-olefin copolymer is EPDM (ethylene propylene diene monomer) or EPM (ethylene propylene diene monomer).

[0043] In addition to elastomer materials, the main rubber compound may include conventional additives such as reinforcing agents, fillers, pigments, stearic acid, accelerators, vulcanizing agents, antioxidants, activators, initiators, plasticizers, waxes, scorch inhibitors, antioxidants, processing oils, etc.

[0044] Advantageously, the main rubber compound also includes reinforcing fibers; more advantageously, the rubber compound includes 12% to 30% fibers by weight, and more preferably 12% to 18% by weight.

[0045] The reinforcing fibers include those with a length between 0.1 mm and 10 mm, preferably between 1 mm and 6 mm, and more preferably between 1 mm and 3 mm.

[0046] The use of fibers allows for further enhancement of the mechanical properties of the mixture that constitutes the main body.

[0047] Therefore, the fibers are distributed throughout the entire body, including the area around the cord, which achieves higher stiffness.

[0048] Preferably, the fiber is a fiber cut to a specific length or a "short fiber". "Short fiber" is defined as a textile fiber of discrete length.

[0049] The reinforcing fiber preferably comprises at least one substance selected from polyamide, aromatic polyamide, polyester, glass, PBO carbon fiber, more preferably aliphatic polyamide, and even more preferably at least one substance comprising the group consisting of polyamide 6 or polyamide 66, which can be bonded to the mixture by preferably RFL-based treatment.

[0050] The treatment used can also be based on VP-SBR, which is a copolymer of vinylpyridine and styrene-butadiene rubber.

[0051] The cord 103 is formed of multiple threads, bundles or yarns, and each thread is formed of multiple filaments.

[0052] The cord 103 preferably comprises high-modulus fibers, and more preferably is selected from at least one of the following materials: carbon fiber, PBO, aramid, polyamide, glass or polyester fiber.

[0053] The cord can advantageously be of a "hybrid" type, that is, composed of at least a first fiber material and a second fiber material.

[0054] By using a cord 103 formed from two different fibers or filaments, the adhesion between the cord 103 and the mixture constituting the belt body can be improved.

[0055] The cord 103 is preferably treated with a known reactive impregnation aqueous treatment agent, but can also be treated in a similar manner or with RFL (i.e., a composition based on latex, resorcinol and formaldehyde).

[0056] In the case of a cord 103 comprising two fiber materials, the first material and the second material are preferably selected from the group consisting of glass fiber, aramid fiber, polyester fiber, carbon fiber, PBO fiber, polyamide fiber, polyketone (POK) fiber, PEEK fiber, polyvinyl alcohol (PVA) fiber, liquid crystal fiber (LPC) and PEN fiber.

[0057] The modulus of the first material is preferably lower than that of the second material, and it is preferably wrapped around the outer periphery of the second material.

[0058] Preferably, in cross-section, the second material accounts for between 15% and 75% of the total cross-sectional area, more preferably between 45% and 55% of the total cross-sectional area.

[0059] More advantageously, the fibers of the two materials occupy similar surface areas in cross-section, thereby balancing their excellent properties as much as possible and achieving optimal performance on the belt.

[0060] The first material is preferably glass fiber, and the second material is preferably carbon fiber.

[0061] Preferably, the fibers of the first material are wound around the outer periphery of the fibers of the second material, in which case the fibers of the first material are at least partially coated with the outer surface of the second material, and more preferably the fibers of the second material are completely coated.

[0062] Preferably, the cord 103 is a Ranswick twist, that is, two twists in the same direction.

[0063] The number of filaments forming the cord, as well as the number of base filaments, fineness, or overall implementation of inserts can all vary.

[0064] To achieve optimal performance, the number of strands formed from the fibers of the first material is preferably between 3 and 18, more preferably between 8 and 15.

[0065] Both the toothed portion 104 and the backing 107 may be covered with a coating material 108, which is typically used to modify the mechanical properties of the surface. The coating material may be, for example, fabric, polymer film, treatment layer, friction-reducing coating, etc.

[0066] Alternatively, various coating materials may be used, such as a calendered layer of elastomer material and PTFE on a fabric.

[0067] Advantageously, the working surface of the transmission belt 101 is covered with a covering material 108, which is selected from the group consisting of woven fabrics, knitted fabrics or nonwoven fabrics.

[0068] The covering material 108 covering the teeth 105 or the optional fabric covering the backing 107 is preferably composed of one or more layers of fabric and can be obtained by different weaving processes, such as the known 2×2 twill weaving process.

[0069] The covering fabric preferably has a structure consisting of warp and weft yarns.

[0070] More advantageously, when using woven fabrics, the covering materials 108 and 110 comprise yarns that extend substantially longitudinally along the toothed band, typically as weft yarns.

[0071] Advantageously, the weft yarn includes at least one elastic yarn and at least one yarn with high heat resistance and high mechanical resistance, such as aliphatic polyamide, aramid or aramid, PET, polyester, or natural fabrics like cotton, or a composite or blended structure in which multiple chemically-based yarns are wound around one another.

[0072] More advantageously, the weft yarn includes an elastic filament and at least a first filament and a second filament, more preferably the first filament and the second filament are polyamides, and even more preferably they are made of aliphatic polyamides (such as polyamide 6, 66) and aromatic polyamides (such as para-aramid), as shown in, for example, patent EP0965271.

[0073] In a preferred embodiment, both of the two threads wound around one (or more) elastic threads are made of aramid.

[0074] In a particularly preferred embodiment of the present invention, the working surface is covered with a fabric, wherein a first aramid fiber strand is wound around the outer periphery of the elastic yarn in a first direction S, and a second aramid fiber strand is wound around the outer periphery of the first strand in the opposite direction Z.

[0075] Advantageously, the weft yarn includes para-aramid fibers.

[0076] For example, weft yarns can be formed around polyurethane yarns by winding pairs of para-aramid yarns (such as Technora yarns).

[0077] Advantageously, the warp yarns include meta-aramid fibers.

[0078] Fabrics 108 and 110 typically undergo multiple treatments.

[0079] This type of treatment has been proven to be highly beneficial for achieving long service life when belts are in continuous contact with oil at high temperatures.

[0080] Advantageously, the initial treatment can be based on polyisocyanates, which help to produce aramid fibers, thereby bonding the entire fabric to the elastomer of the body.

[0081] Advantageously, fabrics 108 and 110 are then subjected to a second treatment via RFL.

[0082] In the same case, the latex is preferably an elastomeric material formed by a mixture of one or more copolymers, which are obtained by reacting diene monomers with nitrile monomers and modified with unsaturated carboxylates.

[0083] Advantageously, fabrics 108 and 110 are further subjected to a third treatment based on rubber (also known as adhesive), preferably including an elastomer material, more preferably hydrogenated nitrile rubber, and even more preferably an elastomer material formed by mixing one or more copolymers, which are obtained by mixing a diene monomer with a nitrile monomer and modified with an unsaturated carboxylate, and even more preferably the same as the elastomer material constituting the main body.

[0084] Furthermore, the fabric of the working surface 105 of the toothed belt 101 of the present invention is preferably subjected to a fourth treatment, more preferably the treatment forming a layer 109, for example, calendered on top of the fabric to form a separate layer.

[0085] The layer 109 preferably includes a friction-reducing material.

[0086] The friction-reducing material is defined as a material that can change the friction between the working surface of the transmission belt and the pulley.

[0087] Examples of friction-reducing materials include fluoropolymers, molybdenum sulfide, and copper powder.

[0088] Preferably, it is a fluoropolymer, such as PTFE.

[0089] Advantageously, layer 109 also includes a processing elastomer, such as a material similar to that used in the main adhesive or a fluorinated elastomer.

[0090] Therefore, one or more copolymers formed from a nitrile monomer and a diene, and more preferably an elastomer material formed from a mixture of one or more copolymers, wherein the copolymer is obtained from a diene monomer and a nitrile monomer and modified with an unsaturated carboxylate, and further preferably the same as the main elastomer in the main adhesive, can be used as an elastomer for the fourth treatment.

[0091] By rationally selecting the amount of materials constituting the fourth treatment, a coating layer that is different from and independent of the fabric itself can be easily formed, hereinafter also referred to as the resistance layer 109.

[0092] Advantageously, the amount of elastomer material used in the resistant layer 109 (in phr) is greater than the sum of the amounts of the fluorinated elastomer and the second elastomer material.

[0093] The thickness of the resistance layer 109 is advantageously between 0.03 mm and 0.3 mm.

[0094] The resistant layer 109 can be arranged on the fabric 108 in different ways, preferably by calendering.

[0095] An adhesive material can be placed between the fabric 109 and the resistance layer 108 to improve the adhesion between the resistance layer 109 and the fabric 108.

[0096] Preferably, the weight of the resistance layer 108 is between 200 g / m² and 400 g / m² to ensure the required resistance.

[0097] Preferably, the backing 107 of the belt is also covered with fabric, and more preferably the working surface 105 is the same as the fabric on the backing 107 and is treated with the same material.

[0098] Preferably, the fabric covering the backing belt 107 is also treated differently. It has been found that treating the backing belt 107 in a manner similar to the fourth treatment of the fabric 108 covering the working surface 105 described above is particularly advantageous. More advantageously, this fourth treatment forms a resistant layer on top of the fabric. More preferably, the resistant layer of the covering fabric 110 (which covers the backing belt 107) is the same as the resistant layer of the covering fabric 108 (which covers the teeth).

[0099] By examining the characteristics of the belt manufactured according to the present invention, its advantages become apparent.

[0100] Significant improvements have been achieved by employing the toothed drive belt of the present invention, particularly overcoming the aforementioned problems. Specifically, it achieves a combination of optimal belt life and low oil absorption.

[0101] The invention is described below by way of example, but is not intended to limit the invention.

[0102] Example 1

[0103] Manufacturing a transmission belt with a different composition from the main rubber material.

[0104] The fabric covering the drive belt is made of polyamide 66, with an original weight of 380 g / m², and is treated with HNBR adhesive.

[0105] The teeth are non-helical. The cord is made of K-type glass and treated with RFL.

[0106] The belt also includes a nylon polyamide 66 backing fabric with an original weight of 380g / m².

[0107] The contrast strip of Example 1 includes a body made of the adhesives in Table 1.

[0108] Table 1

[0109]

[0110] The tape of the invention in Example 1 includes a body made of the adhesives listed in Table 2.

[0111] Table 2

[0112]

[0113] Figure 3 The table in the figure shows the oil stain test results of the belt with high fiber content and the belt with low fiber content according to the present invention.

[0114] The present invention comprises a strip containing 15% nylon fiber by weight, the percentage being given relative to the total weight of the body rubber compound.

[0115] The contrast bands contain 4% and 8% fibers, respectively.

[0116] The bar chart showing duration indicates that the 15% fiber content scheme achieves a minimum performance of over 60 hours, the minimum duration required to pass the test.

[0117] Example 2

[0118] Figure 3 It shows that it includes the use of Figure 2 A graph showing the average and dispersion of the four band types in the so-called drag test.

[0119] The test was conducted on a four-cylinder VW EA189 engine, using a belt with the same dimensions as the commercially available product, part number 160CWC150. The temperature was set at 140°C, the belt tension at 1700N, and the engine speed at 3750rpm.

[0120] An example of the present invention, containing 15% fiber by weight, can achieve performance similar to that of HNBR belts. Belts with low fiber content cannot practically achieve sufficient performance to pass the 60-hour limit.

[0121] Obviously, if the fiber content is below a certain percentage, the belt cannot guarantee the required minimum service life.

[0122] Example 3

[0123] Figure 4The following diagram shows the comparative results of a timed tape durability test performed on a tape (line A) manufactured according to the present invention and a control tape (line B), with the layout as follows: Figure 5 As shown.

[0124] The parameters used for testing are:

[0125] Model 150-pitch 8-150, 150 teeth, 15mm width;

[0126] The temperature is room temperature (20℃);

[0127] The toothed pulley has 22 teeth;

[0128] The motor pulley speed is set to 6000 rpm.

[0129] The system includes a three-toothed pulley layout with a drive pulley, a driven pulley, and an idler pulley. The idler pulley is adjustable and is used to set the appropriate tension on the belt before the test begins.

[0130] The test bench can transmit torque ranging from 7 Nm to 25 Nm. The torque to be transmitted is considered as the test parameter, and a suitable mounting tension is associated with it; this method is chosen to prevent tooth skipping during testing. Each test corresponds to the torque to be transmitted and the branch tension. As the torque to be transmitted increases, the duration decreases significantly (power transmission always occurs under steady-state conditions).

[0131] therefore, Figure 4 The figure shows the duration distribution of the reference structure (line B) and the structure according to the new invention (line A) under the same steady-state loading conditions. The results show that the strip (line A) according to the new invention has performance advantages.

Claims

1. A power transmission belt comprising a main body (102) made of a compound having a main elastomer, a tooth portion (104) and a belt back (107) and a plurality of longitudinal cords (103) embedded in the belt main body, characterized in that, - the main elastomer constitutes at least 70% by weight of all the elastomer material of the main body; - the main elastomer is an ethylene-a-olefin copolymer; - the main body comprises at least 12% by weight of fibers; - the fibers are selected from the group consisting of glass, aramid, polyester, carbon fibers, polybenzoxazole (PBO), polyamide, polyketone (POK), polyether ether ketone (PEEK), polyvinyl alcohol (PVA), liquid crystal fibers (LPC), polyethylene naphthalate (PEN), aliphatic polyamide; - the fibers have a size comprised between 1 mm and 6 mm; - the tooth is covered with a covering material (108) selected from the group consisting of woven fabric, knitted fabric, non-woven fabric; - the covering material is treated with a polymer containing nitrile groups; - the covering material is coated with a second treatment layer (109) comprising an elastomer and an anti-friction material.

2. The drive belt (101) according to claim 1, characterized in that The ethylene-a-olefin copolymer is an ethylene-propylene-diene terpolymer (EPDM) or an ethylene-propylene copolymer (EPM).

3. The drive belt (101) according to claim 1 or 2, characterized in that The main elastomer has a weight percentage of more than 90%.

4. The drive belt (101) according to claim 1 or 2, characterized in that The transmission belt comprises at least 14% by weight of fibers.

5. The drive belt (101) according to any one of the preceding claims, characterized in that, The fibers are nylon.

6. The drive belt (101) according to any one of the preceding claims, characterized in that The fibers have a length comprised between 1 mm and 3 mm.

7. The drive belt (101) according to any one of the preceding claims, characterized in that The fibers are short fibers.

8. The drive belt (101) according to any one of the preceding claims, characterized in that The main elastomer has a weight percentage of more than 30% of the total weight of the compound.

9. The drive belt (101) according to any one of the preceding claims, characterized in that The sum of the weight of the main elastomer and the weight of the fibers has a weight percentage of more than 45% of the total weight of the compound.

10. A power transmission system comprising a transmission belt according to any one of claims 1 to 9, said transmission belt being in continuous contact with oil or oil mist.

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