V-ribbed belt

Description

[0001] The invention relates to a multi-ribbed belt with an elastic base body made of at least one rubber compound, comprising a top layer as the belt back and a ribbed substructure with a power transmission side.

[0002] V-ribbed belts are typically continuous in their operating state and are used in auxiliary systems of internal combustion engine vehicles, for example, to drive the alternator. Excessive noise during operation must be avoided. A particularly unpleasant noise is the chirping sound that occurs when the pulleys in the V-ribbed belt drive are not in the same plane, i.e., when they are misaligned or, for example, tilted due to bearing wear.

[0003] Since these misalignments are unavoidable in many multi-ribbed belt drives, most multi-ribbed belts are provided with a special surface on the ribbed functional side. In particular, textile coatings or overlays on the functional side have proven effective in suppressing chirping noises. However, a disadvantage of these textile coatings or overlays is that they reduce friction. Insufficient friction leads to excessive slippage and thus to energy transmission losses, which can heat up the belt and significantly reduce its service life.

[0004] Textile coverings or textile coatings, especially for V-ribbed belts, are widely known.

[0005] For example, US3839116 A discloses a method for manufacturing shaped V-ribbed belts (V-ribbed belts) in which an elastic fabric is applied to the ribbed functional side.

[0006] US 3981206 A describes a multi-ribbed V-belt in which a bidirectional stretchable textile made of knitted threads is vulcanized into the surface using a molding process. The textile used consists of a combination yarn of intertwined filaments of elastic polyurethane and polyamide. US 4027545 A specifies the application of such multi-ribbed V-belts and describes specific settings for these belts. DE102006007509 A1 discloses multi-ribbed V-belts with a warp-knitted fabric as a rib coating, consisting of polyamide yarn and polyurethane, interwoven (chameuse pattern) to form independent networks. DE102007042917 A1 describes multi-ribbed V-belts with a textile covering made of staple fibers, in particular cotton. While cotton coatings are good with regard to noise performance, they exhibit poor abrasion resistance for demanding applications.

[0007] DE112014001531 T5 discloses a V-ribbed belt with a jersey knit fabric as a textile covering, in which the right side of the knit ("front") is preferably located on the outside of the ribs, and the stitch direction is preferably in the circumferential direction of the belt. The knit fabric consists of yarns made of polyamide, polyester, cotton, and nylon fibers finished with wool, or of yarns wrapped with elastic polyurethane as the core yarn. These wrapped yarns require complex manufacturing processes, which significantly increases the overall cost of the belt. EP2 981 735 B1 discloses a V-ribbed belt of this type.

[0008] However, in the examples mentioned, the problem is that the described textile coatings usually have too low a friction coefficient (CoF) for use in motor vehicles.

[0009] It is therefore the object of the present invention to provide a multi-ribbed V-belt that has a textile covering or coating which possesses sufficient friction to ensure the longest possible service life, particularly in the form of good resistance to flexural fatigue. In addition, the textile covering or coating must be sufficiently abrasion-resistant for use in motor vehicles and offer good protection against squealing noises. Furthermore, the belt should be cost-effective to manufacture.

[0010] This problem is solved by the fact that the multi-ribbed belt has a coating of a textile on its power transmission side, the knitted fabric being a combination of a multifilament yarn made of polyamide and an elastic thread, being a single jersey and having an average basis weight of the textile before vulcanization between 145 and 170 g / m².

[0011] The determination of the basis weight of the textile is carried out according to DIN EN 12127, edition 1997-12.

[0012] Surprisingly, it has been shown that the friction, noise behavior and service life of the belt, especially its resistance to flexural fatigue, can be improved if it is provided with a textile covering whose average basis weight before vulcanization is between 140 and 190 g / m².

[0013] For the sake of simplicity, the terms textile overlay and textile coatings will be used synonymously in the following.

[0014] According to the invention, the textile covering is a knitted fabric with a medium thickness.

[0015] Basis weight before vulcanization between 145 and 170 g / m².

[0016] A knitted fabric is a flat structure made from one or more threads or from one or more thread systems by forming stitches.

[0017] This surprisingly achieves a good compromise between low material usage, thus lower manufacturing costs, and good noise performance.

[0018] With the average basis weights according to the invention, an open-pored knitted fabric can thus be used as a textile covering, which can positively influence friction and service life at the same time.

[0019] According to the invention, the knitted fabric is a single jersey. Preferably, the

[0020] The wrong side of the fabric faces outwards. This results in a more uniform surface and better durability. The stitch patterns "right side" and "wrong side" are shown, for example, in the textile technology book "Hatching and Knitting" by Klaus Peter Weber and Marcus Weber, Melliand, 4th edition, 2004, pages 14, 15.

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

[0022] It is preferred that, due to the open porosity of the textile covering, the surface of the force transmission zone is covered by the threads or thread systems of the textile covering to less than 40% of the total surface area of ​​the force transmission zone.

[0023] More than 60% of the surface area of ​​the power transmission zone, relative to its total surface area, therefore consists of the material of the substructure.

[0024] In principle, any natural or synthetic material can be used for the textile covering, alone or in combination. According to the invention, the textile is formed from a combination of a multifilament yarn made of polyamide, preferably PA6 or PA6.6, particularly preferably PA6, and an elastic thread.

[0025] Elastic thread is characterized by having an elongation at break of more than 100% according to DIN EN ISO 2062:1995. A typical example of such elastic threads are those consisting of at least 85% polyurethane by weight, known as "elastane" or, in English-speaking countries, "spandex".

[0026] The textile overlay is preferably knitted using a plated method, which is a particularly efficient and cost-effective knitting technique. It is preferred that the elastic yarn is located on the reverse side of the fabric, as this results in greater adhesion between the textile and the elastomeric base.

[0027] To optimize elasticity, the multifilament yarn can be textured.

[0028] The weight percentage of the elastic thread in the textile overlay is advantageously between 8 and 16% by weight. This ensures sufficient elasticity and good processability.

[0029] Additionally, for good durability and ease of manufacture, the multi-ribbed belt can have an open textile joint that is transverse to the belt circumferential direction and consists only of the elastomeric material of the substructure and preferably has a width of 0.5 to 6 mm.

[0030] Preferably, the belt has a PK profile according to ISO 9981 with a profile depth of 2.2 to 2.6 mm. Belts with a shallower profile depth tend to exhibit excessive slippage and poorer wear resistance. An excessively deep profile results in an overall belt thickness that reduces its bending fatigue resistance.

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

[0032] The rubber component used is, in particular, ethylene propylene rubber (EPM), ethylene propylene diene monomer rubber (EPDM), (partially) hydrogenated nitrile rubber (HNBR), fluorocarbon rubber (FKM), natural rubber (NR), styrene-butadiene rubber (SBR), or butadiene rubber (BR), either unblended or blended with at least one other rubber component, especially one of the aforementioned rubber types, for example, in the form of an EPM / EPDM or SBR / BR blend. According to the present invention, EPM or EPDM, or an EPM / EPDM blend, is used, in particular, for the substructure with the power transmission side. In a preferred embodiment, the EPM, EPDM, or the blend of EPM and EPDM is peroxide-cured.

[0033] The rubber compound of the base material further contains at least one filler. Advantageously, this filler is at least one carbon black or at least one silica. The combination of carbon black and silica has proven particularly suitable. All silicas known in the rubber industry can be used, preferably precipitated silicas. Likewise, all known types of carbon black can be used, 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 blacks being particularly preferred.

[0034] The rubber compound's ingredients additionally comprise at least one crosslinking agent or crosslinking system (crosslinking agent and accelerator). Further compound ingredients are typically processing aids and / or plasticizers and / or antioxidants, as well as optionally other additives, such as fibers for reinforcement and color pigments. However, a fiber-free compound is preferred. In this regard, reference is made to the general state of the art in rubber compound technology.

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

[0036] The invention will now be explained in more detail with reference to comparative and exemplary embodiments, which are summarized in Table 1.

[0037] For each example, a multi-ribbed V-belt was manufactured with a core made of a peroxide-crosslinked, fiber-free rubber compound containing 100 phr EPDM for both the cover layer and the substructure. The Shore A hardness of the vulcanized compound, according to DIN ISO 7619-1 (February 2012), was 79.

[0038] The examined multi-ribbed belts are 6PK belts with a length of 1330 mm and have a PK profile with a profile depth of 2.3 mm.

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

[0040] A coefficient of friction (CoF) between 1.45 and 1.85 is considered good. Belts with lower values ​​often cannot transmit enough power for many applications. CoF values ​​greater than 1.85 tend to be noisy, especially during engine start-up.

[0041] Additionally, a heat bending cycle test (HBW) was performed. In the HBW test, the multi-ribbed V-belts are tested for durability (bending cycles) and heat aging, with daily visual inspection of the belt.

[0042] Typically, multi-ribbed V-belts undergoing HBW testing first exhibit cracks and then breakages after a certain operating time. A target value of more than 250 hours is specified. The test was terminated whenever three or more cracks or one or more breakages were observed on the belt's base during the daily inspection. The test was a 5-pulley test (drive pulley diameter = 60 mm, other pulleys = 50 mm), based on the VDA heat bending cycle test (dated September 27, 2005), which uses 9 pulleys. The test was conducted at a constant ambient temperature of 130°C.

[0043] Additionally, a noise test was conducted to examine the noise behavior under pulley misalignment. The noise test rig has a ribbed drive pulley with a diameter of 130 mm. On the load side, this is followed by an unprofiled idler pulley with a diameter of 65 mm, a ribbed pulley with a diameter of 60 mm, and a driven pulley with a diameter of 50 mm. The belts were pre-tensioned with a pulley force of 330 N and driven by the drive pulley at 1000 revolutions per minute. The drive pulley itself is driven by an electric motor via a universal joint, which ensures non-uniform movement of the drive pulley. During the noise test, the ribbed pulley is deflected forward from its neutral position, perpendicular to the multi-ribbed belt drive, resulting in an offset between the profiled pulleys in the multi-ribbed belt drive.This causes the belt run between the idler pulley and the profiled roller to be deflected by an angle α from the plane enclosed by the belt, which can cause some belts to produce a chirping noise. Belts that were silent even at misalignments of up to 2° were rated as good "+". Belts that were silent up to 1.5° but noisy at 2° were rated as satisfactory "o". Belts that also produced noise at misalignments of less than 1.5° were rated as noisily poor "-".

[0044] Table 1 shows that the best results are achieved with fabric 4, a jersey knit fabric plated with PA6 and PU (elastane) (with the wrong side of the fabric facing outwards and the PU on the wrong side) with a basis weight of 156 g / m². The differences in the HBW (high-yield weight) running times are particularly surprising, demonstrating the advantage of PA6 compared to a knit fabric made of cotton and elastane. Table 1 Textile structure material wt% filament yarn to elastane Length weight main yarn Weight per unit area [g / m²< ] CoF HBW duration Noise behavior 1 Charmeuse warp knit fabric PA6 / PU 80:20 44 dtex 155 1,73 240 h + 2 Jersey knit PA6 / PU 87:13 110 dtex 128 2,02 312 h - 3 Jersey knit PA6 / PU 87:13 110 dtex 142 1,88 288 h o 4 Jersey knit PA6 / PU 87:13 110 dtex 156 1,70 344 h + 5 Jersey knit BW / PU 91:9 147 dtex 196 1,52 186 h + 6 Jersey knit BW / PU 91:9 147 dtex 103 1,65 206 h + 7 Jersey knit BW / PU 91:9 147 dtex 133 1,81 160 h + 8 Jersey knit BW / PU 91:9 147 dtex 195 1,75 179 h +

Claims

1. V-ribbed belts with an elastic base body consisting of at least one rubber compound, comprising a top layer as the back of the belt and a substructure with a ribbed power transmission side, the ribbed power transmission side having a coating of a knitted fabric, the knitted fabric consisting of a combination of a polyamide multifilament yarn and an elastic thread, characterised in that the knitted fabric is a single jersey and the average basis weight of the textile before vulcanisation is 145 g / m2 to 170 g / m2, whereby the basis weight of the textile was determined in accordance with DIN EN 12127, edition 1997-12.

2. V-ribbed belts according to claim 1, wherein the polyamide is PA 6 or PA 6.6.

3. V-ribbed belt according to claim 1 or 2, wherein the elastic thread is made of polyurethane.

4. A V-ribbed belt according to any one of claims 1 to 3, wherein ethylene-propylene rubber (EPM) or ethylene-propylene-diene rubber (EPDM) or a combination of EPM and EPDM is used as rubber for the rubber compound of the substructure.

5. V-ribbed belt according to any one of claims 1-4, wherein the rib depth is between 2.2 and 2.6 mm.