V-ribbed belt

Abstract

The present invention relates to a V-ribbed belt having an elastic main body composed of at least one rubber compound, comprising an outer layer as a belt back and a bottom structure with a ribbed force transmission side. In order to improve the friction and to optimize the service life, the V-ribbed belt has a coating made of a knitted fabric on its force transmission side, wherein the average basis weight of the textile before vulcanization is between 140 and 190 g / m 2 .

Description

TECHNICAL FIELD

[0001] The present invention relates to a V-ribbed belt having an elastic main body composed of at least one rubber compound, comprising an outer layer as a belt back and a ribbed bottom structure having a force transmission side. BACKGROUND

[0002] In the functional state, the V-ribbed belt is usually a closed loop and is used in auxiliary equipment of motor vehicles having, for example, an internal combustion engine for driving an electrical generator / alternator. During operation, excessive noise must be avoided. Particularly unpleasant noises are chirp noises that occur when the pulleys in the V-ribbed belt drive are not in the same plane, i.e. are offset or misaligned, for example due to bearing wear.

[0003] Since these misalignments cannot be avoided in many V-ribbed belt drives, most V-ribbed belts are provided with a special surface on the functional side of the ribs. In particular, a textile coating or a textile covering of the functional side has proven to be effective for suppressing chirp noises. However, a textile coating or a textile covering has the disadvantage of reducing friction. Too little friction leads to too much slippage, which leads to a loss of energy transmission, which can lead to the belt heating up and significantly shortening the service life of the belt.

[0004] Textile coverings / textile coatings, in particular for V-ribbed belts, are known.

[0005] Thus, for example, US 3839116 A discloses a method for producing a molded V-ribbed belt, in which an elastic textile is applied to the functional side of the ribs.

[0006] US 3981206 A describes a V-ribbed belt in which a two-sided stretchable textile made of knitted thread is vulcanized into the surface during molding, the textile used being a kind of combined yarn made of elastic polyurethane and polyamide filaments wound around each other. US 4027545 A illustrates the use of such a V-ribbed belt and describes the special provision of these belts.

[0007] DE 102006007509 A1 discloses a V-ribbed belt having a tricot textile as a rib coating, which consists of a polyamide yarn and a polyurethane textile (Charmeuse knit), thereby forming an independent network.

[0008] DE 102007042917 A1 describes a V-ribbed belt having a textile covering made of staple fibers, in particular made of cotton. While cotton coatings are good in their noise properties, they exhibit poor wear resistance for demanding applications.

[0009] DE 112014001531 T5 discloses a V-ribbed belt with a plain knitted fabric as textile covering, wherein the face side ("front side") of the knitted fabric is preferably arranged on the outside of the ribs and the web longitudinal direction is preferably in the belt circumferential direction. The knitted fabric consists of wool reinforced yarns of polyamide, polyester, cotton and nylon fibers or of wrapped yarns with an elastic polyurethane as core yarn. These wrapped yarns are expensive and complex to produce, thus significantly increasing the overall cost of the belt.

[0010] However, the examples listed have the problem that the described textile coatings generally exhibit insufficient friction for use in motor vehicles, i.e. have a coefficient of friction (CoF) that is insufficient. SUMMARY

[0011] It was therefore the object of the present invention to provide a V-ribbed belt with a textile covering / coating that has sufficient friction and is able to ensure the longest possible service life of the belt, in particular in the form of good resistance to bending fatigue. Furthermore, the textile coating / covering must have sufficient wear resistance for use in motor vehicles and provide good protection against chirping noise. The belt should also be able to be produced in a cost-saving manner.

[0012] This object is achieved when the V-ribbed belt has a coating made of a textile on the force transmission side, wherein the average basis weight of the textile before vulcanization is between 140 and 190 g / m 2 .

[0013] The basis weight of the textile is determined according to DIN EN 12127, edition 1997-12.

[0014] It has been surprisingly found that the friction, noise properties and service life, in particular the resistance to bending fatigue, of the belt can be improved when the belt is provided with a textile covering having an average basis weight between 140 and 190 g / m 2 before vulcanization.

[0015] For the sake of simplicity, the terms textile covering and textile coating are used synonymously hereinafter.

[0016] According to the invention, the textile covering is a knitted fabric having an average basis weight between 140 g / m 2 and 190 g / m 2 before vulcanization, preferably between 145 and 170 g / m 2 .

[0017] The knitted fabric is a sheet-like material produced from one or more threads or from one or more thread systems by netting.

[0018] This achieves a good compromise between low material usage (and thus relatively low production costs) and good noise characteristics.

[0019] The average basis weight according to the application thus makes it possible to employ an open-knit textile as a textile covering, which simultaneously has a positive effect on friction and service life.

[0020] The knit is preferably a single-jersey fabric. It is further preferred for the reverse side of the textile to face outwards. This results in a more uniform surface and better long-term durability. The "face" and "reverse" of the mesh construction are shown, for example, in the following textile technology book: Klaus Peter Weber and Marcus Weber, "Wirkerei und Strickerei [Knitting and Knitting]", Melliand [International Textile Bulletin], 4th edition, 2004, pages 14, 15.

[0021] For better manufacturability, the mesh longitudinal direction of the textile can largely be parallel to the circumferential direction of the belt.

[0022] Due to the open-knit nature of the textile covering, the surface area of the force transmission region is preferably covered by the threads or thread system of the textile covering to an extent of less than 40% based on the total surface area of the force transmission region.

[0023] Thus, more than 60% of the surface area of the force transmission region based on the total surface area of the force transmission region consists of the material of the base structure.

[0024] The textile covering according to the application can in principle be made of any natural or synthetic material, either individually or in combination. It is preferred, however, that the textile is formed from a combination of multifilament and elastomeric threads made of polyamide, preferably PA 6 or PA 6.6, particularly preferably PA 6. The elastomeric threads are characterized in that they have an elongation at break of more than 100% according to DIN EN ISO 2062:1995.

[0025] A typical example of such an elastomeric thread is a thread consisting of at least 85% by weight of polyurethane and is referred to as "elastane" or, in English-speaking countries, as "spandex".

[0026] The textile covering is preferably knitted by means of plating knitting, which represents a particularly efficient and cost-saving way of knitting. It is preferred when the elastomeric threads are arranged on the reverse side, as this achieves greater adhesion between the textile and the elastomeric body.

[0027] The multifilament can be a textured yarn to optimize the stretchiness.

[0028] The weight fraction of the elastic threads in the textile covering is advantageously between 8 and 16% by weight. This ensures sufficient extensibility and good processability.

[0029] Furthermore, for good long-term durability and simplicity of production, the V-ribbed belt can have an open textile flap which is perpendicular to the belt circumferential direction and which consists only of the elastomer material of the bottom structure and preferably has a width of 0.5 to 6 mm.

[0030] The belt preferably has a PK profile according to ISO 9981 with a profile depth of 2.2 to 2.6 mm. Belts with a lower profile depth tend to exhibit excessive slippage and poorer wear resistance. A profile depth which is too great makes the overall thickness of the belt too great, thus reducing its resistance to flex fatigue.

[0031] The elastic main body is preferably based on at least one rubber mixture. The rubber mixture of the main body contains at least one rubber component.

[0032] The rubber components employed include, inter alia, ethylene-propylene rubber (EPM), ethylene-propylene-diene rubber (EPDM), (partially) hydrogenated nitrile rubber (HNBR), fluoro rubber (FKM), natural rubber (NR), styrene-butadiene rubber (SBR) or butadiene rubber (BR), either unblended or in a blend with at least one further rubber component, in particular with one of the above-mentioned rubber types, for example in the form of an EPM / EPDM or SBR / BR blend. According to the application, the bottom structure with the force transmission side employs in particular EPM or EPDM or an EPM / EPDM blend. In a preferred embodiment, the EPM, EPDM or blend of EPM with EPDM is peroxically crosslinked.

[0033] The rubber mixture of the main body also contains at least one filler. This is advantageously at least one carbon black or at least one silica. A combination of carbon black and silica has proved to be particularly suitable. The silicas which can be used include all silicas known in the rubber industry, with preference being given to precipitated silicas. All known types of carbon black can likewise be employed, in particular furnace and thermal carbon blacks, such as SAF, SCF, HAF, FF, FEF, XCF, HMF, GPF, SRF, MPF, FT or MT, with FEF carbon black being particularly preferred.

[0034] The mixture constituents of the rubber mixture additionally comprise at least one crosslinking agent or crosslinking agent system (crosslinking agent and accelerator). Other mixture constituents usually also include processing aids and / or plasticizers and / or ageing stabilizers and, optionally, further additives, such as reinforcing fibers and colouring pigments. However, fiber-free mixtures are preferred. In this regard, reference is made to the general prior art in rubber mixing technology.

[0035] In order to achieve a good balance between the flexural fatigue resistance and abrasion resistance of the belt, in an advantageous embodiment, the main rubber compound has a vulcanized Shore A hardness between 70 and 90, preferably between 75 and 87, according to DIN ISO 7619-1 (February 2012). Detailed Implementation

[0036] The invention will now be explained in detail with reference to the comparative examples and working examples summarized in Table 1.

[0037] The product manufactured for all examples is a V-ribbed belt with a body based on a fiberless rubber compound that is peroxidized and cross-linked, containing 100 phr of EPDM for the outer and bottom structures. The Shore A hardness of the vulcanized compound is 79 according to DIN ISO 7619-1 (February 2012).

[0038] The V-ribbed belt studied is a 6PK belt with a length of 1330mm and a PK profile with a profile depth of 2.3mm.

[0039] The coefficient of friction (CoF, according to SAE_J_2432) was determined.

[0040] A CoF value between 1.45 and 1.85 is considered good. Bands with lower values ​​often cannot deliver enough power for many applications. CoF values ​​greater than 1.85 tend to be noisy, especially during engine start-up.

[0041] In addition, a thermal bending fatigue test (HBW) was conducted. During the HBW test, the long-term durability (bending fatigue) and thermal aging of the belt were tested by routine visual inspection of the V-ribbed belt.

[0042] During the HBW test, the V-ribbed belt typically cracks first, followed by fracture after a certain running time. Values ​​exceeding 250 hours are designated as target specifications. During daily inspections, the test is terminated in each case when three or more cracks or one or more fractures are observed in the bottom structure. The test is based on the VDA thermal bending fatigue test (version 09.27.2005) with a five-pulley test (drive pulley diameter = 60 mm, auxiliary pulley = 50 mm), which uses nine pulleys. The test is conducted at a constant ambient temperature of 130°C.

[0043] Noise tests were also conducted, investigating the noise characteristics under pulley misalignment conditions. The noise testing apparatus consisted of a 130mm diameter ribbed drive pulley. Under load, this was followed by a 65mm diameter non-rough-shaped deflection pulley, a 60mm diameter ribbed pulley, and a 50mm diameter driven pulley. The belt was tensioned with a running force of 330N and driven by the drive pulley at 1000 rpm. The drive pulley itself was driven by an electric motor via a universal joint, ensuring uneven movement of the drive pulley. During the noise test, the ribbed pulley was deflected forward from its zero position perpendicular to the V-ribbed belt drive, causing misalignment between the rough-shaped pulleys in the V-ribbed belt drive. As a result, the belt running between the deflection pulley and the rough-shaped pulley deviated from the plane surrounded by the belt by an angle α, resulting in some belts exhibiting chirping noise. Belts that did not exhibit noise even with misalignment up to 2° were rated as good "+". A band that exhibits no noise within 1.5° but noise at 2° is rated satisfactory "0". A band that produces noise at a misalignment of less than 1.5° is rated poor "-" in terms of noise.

[0044] As can be clearly seen from Table 1, fabric 4, which is knitted from PA 6 and PU (elastic fiber) through yarn-padded knitting, has a weight of 156 g / m². 2 The best results were achieved with the base weight of plain knit fabrics (where the reverse side is on the outside and PU is on the reverse side). Particularly surprising was the difference in HBW running time, where the advantage of PA 6 over knit fabrics composed of cotton and elastane was evident.

[0045]

Claims

1. A V-ribbed belt, the V-ribbed belt having an elastic body made of at least one rubber compound, comprising an outer layer as the back of the belt and a bottom structure having ribbed force transmission sides, characterized in that, The ribbed force transmission side has a coating made of knitted fabric, wherein the average basis weight of the textile before vulcanization is 140 g / m² to 190 g / m², wherein the basis weight of the textile is determined according to DIN EN 12127, 1997-12, wherein the coating is made of open-knitted fabric.

2. The V-ribbed belt as described in claim 1, characterized in that, The average basis weight of the textiles before vulcanization is 145 g / m² to 170 g / m².

3. The V-ribbed belt as described in claim 1 or 2, characterized in that, The knitted fabric is composed of a combination of polyamide multifilaments and elastic yarns.

4. The V-ribbed belt as described in claim 3, characterized in that, The polyamide is PA 6 or PA 6.

6.

5. The V-ribbed belt as described in claim 3, characterized in that, The elastic line is composed of polyurethane.

6. The V-ribbed belt as described in claim 1, characterized in that, The rubber is a rubber compound that uses ethylene-propylene rubber (EPM) or ethylene-propylene-diene rubber (EPDM) or a combination of EPM and EPDM as the bottom structure.

7. The V-ribbed belt as described in claim 1, characterized in that, The rib depth is between 2.2 and 2.6 mm.

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