WO2020144376A1

WO2020144376A1 - Power transmission belt having an aramid tension member

Info

Publication number: WO2020144376A1
Application number: PCT/EP2020/050679
Authority: WO
Inventors: Marcel SCHAPER; Willi Ollenborger; Michael Giessmann
Original assignee: Arntz Beteiligungs Gmbh & Co. Kg
Priority date: 2019-01-11
Filing date: 2020-01-13
Publication date: 2020-07-16
Also published as: CN113474576A; DE102019100654A1; CN113474576B

Abstract

The invention relates to a power transmission belt, in particular a V-belt, which may be toothed, a V-ribbed belt or synchronous belt, comprising at least one tension member which is made of a double-twined base yarn and is embedded in a body made of resilient material. The untwined base yarn is a multifilament yarn which contains a plurality of aramid filaments. In a first twining stage the untwined base yarn is twined to produce an initial twine and in a second twining stage it is twined in the opposite direction of rotation to the first twining stage to produce a final twine, in order to form the tension member. The base yarn according to the invention has a denier of less than 1000 dtex. In the first twining stage two or three threads of the base yarn are twined to form the initial twine and in the second twining stage three to six threads of the initial twine are twined to form the final twine, the ratio of the twine factor for the initial twine (F1) to the twine factor for the final twine (F2) is 0.8 to less than 1 and the ratio of the twine rotation (D1 [m-1]) of the initial twine to the twine rotation (D2 [m-1]) of the final twine is 1 to 1.5. The tear resistance of the belts provided in particular for BSG motors can be significantly increased by the special design of the tension member.

Description

Power transmission belt with aramid tension cord

The invention relates to a power transmission belt, which is embedded in a body by an elastomer at least one tension cord from a two-stage twisted base yarn, the base yarn is an aramid yarn, which is in a first twist stage to a pre-twist and in a second twist stage to the first Twist stage opposite direction of rotation is twisted into a twist that forms the tension cord.

The invention particularly relates to high-performance drive belts that have to withstand high tensile force, bending and wear stresses. V-belts, V-ribbed belts and synchronous belts are used for this purpose.

Such drive belts are usually equipped with tensile cords made of so-called high-modulus cords, which are characterized by a high modulus of elasticity and low extensibility. These cords are strand-like tension strands made of twisted synthetic fibers or yarns. For the synthetic yarns, who mainly uses polyester, aramids and carbon fibers as well as mixed fibers and mixed yarns with the fiber types mentioned. The aramid yarns are characterized by high tensile and tear strength combined with good compressive strength and impact resistance. The cords usually consist of twisted aramid multifilament yarns, monofilaments also being known, as in DE

69108264 T2.

Since the tension cords of drive belts have a significant influence on their usage properties, numerous attempts have already been To improve tensile cords in terms of properties such as tear resistance, fatigue behavior, behavior under alternating loads and service life. These properties are reflected in regularly improved properties of the reinforced belts.

EP 2601333 B2 relates to the use of a cellulosic multifilament yarn with increased single filament titer to improve the fatigue behavior of a tension member or tension strand. It has been found that the increased single filament titer, at least in the case of cellulose fibers, is advantageous compared to smaller single filament titers with a corresponding yarn titer. The tensile cord tested consisted of two twisted simple multifilament yarns with a total titer of 1840 dtex. The two multifilament yarns each had 375 twists (Z-twist of the twist or yarn twist) per meter, the cord twist was 375 twists per meter (S-twist of the twist twist). The construction of the tensile cord tested was: 1840 dtex x 1 x 2 Z / S 375 (symmetrical).

In addition to the yarn titer and filament titer, the twisting of the tensile cord has a decisive influence on the tensile cord properties and thus the belt properties of the drive belt reinforced in this way.

DE 1808118 A1 discloses a cord thread made from rayon threads with improved strength and fatigue properties for rubber articles to be reinforced, in particular in the tire sector. The rayon cords consist of rayon threads, which were twisted to a pre-twist with a first direction of rotation and then in a second, opposite direction of rotation to an twist. It was found that rayon cord made of rayon thread, which is constructed in a negative asymmetrical thread construction, had improved strength and fatigue properties.

By definition, an “asymmetrical twist” is one in which the twist, also called twist or degree of twist, of the pre-twist differs from the twist of the twist. The degree of twist is below always referred to as twisted thread D, measured in turns (turns) per meter. A “symmetrical twist”, on the other hand, means one in which the pre-twist and the twist were twisted or twisted with the same number of twists, usually in the opposite direction. A positive asymmetrical twist construction is understood to mean one in which the number of turns per meter is greater when pre-twisting than when twisting. A negative asymmetrical twist construction is understood to mean one in which the number of turns per meter in the pre-twisting is smaller than in the twisting.

To characterize a thread and the properties associated with it, the so-called thread factor (F) is often used, which is also referred to as the twist coefficient (a or K) or twist factor (TF) and in the English, non-metric system, based on inch and denier Multiplier (TM) is called. In the following, reference is always made to the "twisting factor F" for the metric system, whereby the following applies:

F = D x VT with D = twists per meter,

T = twiter (yarn count) in tex

The thread factor is regarded as an indicator of the strength and fluff of the thread.

The ratio of the associated twist factors is often used to characterize multi-stage twisted yarns, i.e. in the case of a two-stage twist from pre-twist and twist Fi (twist factor of the first twist stage) to F2 (twist factor of the second twist stage). Single-ply threads are often included in this nomenclature by specifying a first "thread factor" for a twisted basic thread, this concerns thread designs of the "titer x 1 x n" type (n = number of threads of the second thread level).

EP 1861632 B1 discloses an endless belt with an elastomer belt body and a load-bearing cord embedded therein. The cord thread can, too at least partially, consist of aramid fibers. The cord comprises a plurality of yarns which are twisted in a first direction of rotation by a first twist multiplier or twist coefficient, the cord comprising a plurality of these yarns being twisted in the opposite direction of rotation by a second twist coefficient. The cord is characterized by a strong positive asymmetry in that a ratio of the first to the second twist coefficient of greater than 1.5 is prescribed. In the examples examined, Fi is: F2 = 2.5 and D1O2 = 5. Because of the large asymmetry, the tensile cord and thus the one with it

Endless belts reinforced in the tensile cord obtain greater fatigue resistance under changing loads (flexural fatigue, flexural fatigue resistance).

Due to newer engine and auxiliary unit developments, there is a need for high-performance drive belts that can withstand high tensile forces, bending cycles and wear.

The object of the invention is to provide a high-performance drive belt which has a high resistance to bending and a good vibration behavior with high tensile stress and has a longer service life, in particular at low speeds with the decrease of high moments.

This object is achieved by the power transmission belt according to the invention according to claim 1, which, at least embedded in a body made of elastic material, has a tensile cord made of a two-stage twisted base yarn, the base yarn being an aramid yarn, which in a first twist stage becomes a pre-twist and in a second Thread stage is twisted in the opposite direction to the first twist stage to form a twist which forms the tension cord. The power transmission belt is characterized according to the invention in that i) the base yarn has a titer less than 1000 dtex, ii) in the first twist stage two or three threads of the base yarn are twisted to the pre-twist and iii) in the second twist stage three to six threads of the pre-twist are twisted to the twist, the ratio of the twist factor for the pre-twist (Fi) to the twist factor for the twist (F2) being 0.8 to less than 1 and the ratio of Twist twist (Di) of the pre-twist to twist twist (D2) of the twist is 1 to 1, 7 with

Fn = Dn X VT,

F = twist factor, D = twist twist in turns per meter,

T = yarn titer as a measure of the fineness of the yarn in tex,

n = 1 or 2 for the first and second twist stages.

Advantageous developments of the invention are characterized in the subclaims.

The term power transmission belt encompasses all current types of belts known to the person skilled in the art as suitable, such as V-belts, V-ribbed belts, synchronous belts or toothed belts and special belt shapes for special drive purposes. V-belts, V-ribbed belts and synchronous belts are preferably used for the application purposes specified by the task, wherein the V-belts can be toothed.

All of these straps have a strap body made of elastic material, in which at least one tension cord, also referred to as a cord, is embedded. In the production of endless belts which is customary today, the body is generally built up in layers on a drum, the tensile cord being wound spirally between two layers of the elastic material. The elastic material of the belt body is formed by at least one elastomer customary for belt production. The same or different elastomers can be used for different belt layers, such as belt back or cover plate, cord embedding level, core, teeth or substructure or compression zone, cover layers on the power transmission side, etc. Additional materials (fibers, tie layers, etc.) can be incorporated into the body.

Standard elastomers for belt production, which can be used here for the various areas of the belt body, include, among others, R- Elastomers, M-elastomers and S-elastomers. Elastomers from the group EPM, EPDM, ACSM, HNBR, CR, SBR, BR and blends of these elastomers are preferred, but also, but not preferred, PU and PU-containing elastomers.

According to the invention, the tension cord consists of a two-ply twisted base yarn, the base yarn being an aramid yarn. The tension cord can be impregnated, treated, e.g. Plasma treated or coated. Its thickness, the titer of the individual yarns and the twisting depend on the intended use within the framework specified by the invention and can be adapted in a case-by-case manner by the person skilled in the art.

Aramid fibers, yarns and cords are used to reinforce a wide variety of technical rubber products and are commercially available in a wide variety of designs. The fibers or filaments consist of aromatic or essentially aromatic polyamides, which are obtained, for example, from aromatic diamines and aromatic dicarboxylic acids. In addition to amide groups, other functional groups, in particular imide groups, can also be present. Aramid yarns also include blended yarns that are predominantly, i.e. containing more than 50% by weight of aramid fibers or filaments in addition to other fibers or filaments, for example made of polyester or carbon.

According to the invention, the base yarn of the tensile cord or cord consists of aramide yarn. Aramid blended yarns are included in the term aramid yarn here, as described above. A “basic yarn” is understood to mean the starting yarn of a single or multiple, one or two-stage thread.

The following applies:

A "yarn" is a structure made of textile fibers, such as staple fibers, filaments or ribbons. The yarn can contain single or few filaments - this includes very thin synthetic fibers - or numerous filaments; it is then also referred to as multifilament yarn. The filaments of a yarn can lie untwisted, essentially parallel to one another; they can be equipped with adhesive to hold the yarn together. The yarn can also be twisted in itself, it then has a spinning twist or a protective twist, which also holds the yarn together with the aid of a small number of twists per meter. A yarn twist is not a twist twist, but can be labeled with a twist factor according to the twist factor.

A “twine” is a textile structure that is made by twisting at least two yarns together.

A "pre-twist" is a twist made from untwisted yarn, i.e. from base yarns as described above. The twisting of a base yarn into a pre-twist, which is then twisted even further, is referred to as the first twist stage.

A "twisting" is a twisting of single-stage or multi-stage twisted yarns to an end product, like here the cord or tension cord. The thread is therefore the cord thread. In the invention, the twisting in the second twisting stage he will keep

The relative direction of rotation of the twists to each other is very important for the properties of a two-stage twine. Pre-twisting and untwisting can be twisted in the same direction or in opposite directions. In the invention, pre-twisting and twisting are opposed, i.e. twisted in the opposite direction.

The "titer" (yarn titer) is the measure of the fineness of the yarn and is specified in the metric system in tex or dtex (decitex).

The invention is now characterized in that, compared to the examples in the prior art, relatively more threads with a relatively low titer are twisted in two stages, the ratio of the twisting factors from pre-twisting to twisting (Fi: F2) being less than 1, and indeed little , namely 10 - 20% - less than 1, while the twist ratio of the pre-twist and the twist to each other is 1 to 1.7, which means that the 2-stage cord twist is symmetrically or slightly positively asymmetrically twisted.

It was found that this twist construction or cord twist has a very positive influence on the belt properties of aramid cord-reinforced high-performance belts manufactured in this way, for which a significantly increased service life under high load, in particular also bending load, is found at low speeds with the decrease of high moments could.

The titer of the aramid base yarn of the drawstring is 200 to 1000 dtex, more preferably 250 to 800 dtex and particularly preferably 450 to 650 dtex.

The base yarn is preferably a multifilament yarn that contains a large number of aramid filaments.

The base yarn of the twisted cord and thus the tension cord is preferably not twisted in itself or provided with a protective twist. The protective rotation can be up to approx. 50 turns per meter.

In a further development of the invention, the ratio of the twisting factors Fi: F2 is 0.8 to 0.9.

In the currently particularly preferred embodiments, the two-stage twist of the tension cord is a positive asymmetrical twist (Di> D2).

It is also considered to be advantageous if the twist twist Di of the front twist is 150 to 400 twists per meter (TPM, 1 / rrr ¹ ). The twist of the twist then results from the twist of the pre-twist being 1 to 1.7 times or preferably (> 1) to 1.7 times the twist of the twist. According to one aspect of the invention, the power transmission belt is a V-belt which can be toothed, a V-ribbed belt or a synchronous belt. The performance tests described below were carried out on V-ribbed belts as example belts. However, since and insofar as they are based on the properties of the integrated tension cord, these results can be transferred to other types of belts.

The invention is explained in more detail below on the basis of exemplary embodiments and with reference to drawings and diagrams. The examples are intended to be illustrative and not restrictive. They are only intended to facilitate the understanding of the invention as generally described above.

The drawing shows:

Fig. 1 shows a first embodiment for a V-ribbed belt, in

schematic perspective sectional view;

Fig. 2 shows a second embodiment of a tooth

ten V-belt, in a schematic perspective sectional view;

Fig. 3 is a sketchy representation of a two-stage twisted

Pull cord;

characters

4 to 7 diagrams for performance tests of the invention

Example belt (1) compared to example belt

from the prior art ((2), (3)), namely

Fig. 4 is a bar graph for the results of a performance test on the example belt; Fig. 5 is a bar graph for the results of a rotational nonuniformity test;

6 shows a bar diagram for the results of a first RSG test with a load acceptance torque of 50 Nm;

Fig. 7 is a bar graph for the results of a second RSG test with load torque 70 Nm.

FIG. 1 shows a first exemplary embodiment of a power transmission belt according to the invention, namely a V-ribbed belt designated as a whole with 10 with a cover plate 11 and a belt body 12, in which tensile cords 14 are embedded in the usual manner, here from the aramid cord 550 according to the invention dtex x 2 x 3 (340/230). The cord strands form a flat tension member layer parallel below the belt back or the cover plate 11.

This tension member layer may lie within a coring bed layer, not shown separately here. The figure shows a cross-section of an endless V-ribbed belt with here four ribs 16. The number of ribs can of course also be selected differently, for example six ribs. For this type of belt, 2 to 20 ribs, preferably 2 to 16 ribs, in particular 2 to 6 ribs, are generally preferred.

Figure 2 shows a second embodiment of a power transmission belt according to the invention, namely a cross-section of a wedge belt 20 with a cover fabric 21 and a body 22 on which one

Form toothing 23 is formed. In the body 22 tensile cords 24 from the aramid cord according to the invention, in the example 550 dtex x 2 x 3 (340/230), are embedded.

Figure 3 shows the basic structure of a twisted according to the invention

Drawstring 30, sketchy in part, namely at a twisted end of the section shown Darge, untwisted representation to the individual strands, yarns and to make filaments more recognizable. The base yarn 31 consists of numerous rich aramid filaments 32, which are essentially untwisted here next to each other. Two threads of the base yarn 31, which has a yarn count of 550 dtex in the selected example cord, are each twisted together to form a pre-twist 33, specifically in the example shown here with a Z twist. Three before twists 33 are twisted together to form the twist 34, specifically in the example shown with an S rotation, that is to say in the opposite direction to the twist 33. The illustration shows the structure only in principle and is not to size. The twist of the twist 34 is smaller than that of the pre-twist 33 for this example cord.

Belt tests

The line tests described below, the results of which are shown in FIGS. 4 to 7, were carried out on a belt according to the invention (example belt, code number (1)) and two comparison belts (code numbers (2) and (3)). All these belts were V-ribbed endless belts made of EPDM elastomer for core and back material, without embedding, with the profile PK, namely 6 PK, 2050 mm for the belts with the runtime results in FIGS. 4 and 5 and 6 PK,

1130 mm for the belts with the runtime results in FIGS. 6 and 7. The test belts each had a completely identical structure and differed only in the spiral-wound aramid cord used in the respective test belt.

The aramid cord in the example belt according to the invention (1) had the configuration 550 dtex x 2 x 3 (Z / S) (340/230), ie the aramid base yarn had a fineness of 550 dtex, 2 threads of the base yarn were for pre-twisting and 3 threads of the pre-twist twisted in the opposite direction to the twist, the twist twist of the pre-twist being 340 rrr ¹ and the twist twist of the twist being 230 rrr ¹ . The ratio D1: D2 was therefore 1.48 and the ratio of the twisting factors F1: F2 was 0.85. The aramid cord in the comparison belt (2) had the configuration 1100 x 1 x 3, twisted in opposite directions asymmetrically, the aramid cord in the comparison belt (3) had the configuration 1100 x 1 x 3 twisted in opposite directions symmetrically.

1. Examination for performance breakdown

In the performance disruption test, the belt is subjected to many bending cycles while the performance is decreasing.

It is a performance disruption test at an ambient temperature> 100 ° C. The test part with a reference length of approx. 2000 mm is subjected to repeated bending and counter-bending around smooth and profiled pulleys. A high belt speed and reduced braking power act as additional loads. All loads are kept constant.

The results shown in a bar chart in FIG. 4 show that the example belt (1) passed the three test runs shown here reliably over a sufficient test period of approximately 250 to 300 hours. Comparison belt (2) shows significantly more fluctuating, i.e. less reliable results, while comparison belts (1) already gave worse results in the two test runs shown.

2. Test under rotational irregularity

When testing under rotational nonuniformity, test belts are alternately given acceleration and deceleration. As a result, the belt experiences an uneven or pulsating load.

The results are shown in Figure 5. The test belt (3) with symmetrical twist fails under these conditions. The results of the example belt (1) and those of the comparison belt (2) are similar, namely good.

It is a performance disruption test at an ambient temperature> 100 ° C. The test part with a reference length of approx. 2000 mm is Holter bend and counter-bend exposed to smooth and profiled pulleys. As a further load, a rotational non-uniformity is impressed into the belt drive by means of a cardan shaft which is deflected. This is intended to simulate the rotational irregularity of a real internal combustion engine, which is created there by the staggered ignition of the individual cylinders. As a further tightening, a high braking power is also removed in this test. All loads are kept constant.

3. Check for RSG simulation status

For the suitability of the straps etc. in belt-driven starter generators (RSG). BSG, the belts are subjected to start / stop changes. The belt must transmit high moments at a low speed at the time of starting. In addition, with this type of operation, the train and load sections change in constant succession. This leads to a significant increase in the load on the belt drive, which can be mapped by this performance test.

RSG exam:

It is a performance disruption test at room temperature. The test piece with a reference length of approx. 1000 mm is subjected to repeated bending and counter-bending around smooth and profiled pulleys. In contrast to the above tests, the load is not kept constant here. Similar to the real vehicle, a stage cycle with different speeds and load torques is run through. The load in the belt drive also changes, so that the load and empty strands are reversed (power input / power consumption) via belts. With its high dynamics, this test represents the sharpest and most realistic load for the belt. It shows that a belt with the tension member to be patented has a significantly improved performance here.

Two tests were carried out with different outputs, namely at 50 Nm and at 70 Nm. The relevant results are shown in FIGS. 6 and 7. The previously failed comparison belt 3 was here no longer checked. The belt according to the invention shows significantly better performance, which promises great advantages when using the belts according to the invention in RSG units. The cord according to the invention with finer raw yarns has an at least 10% higher tensile strength compared to a conventional two-stage asymmetrically twisted cord with a comparable total thread (as in comparative example (2)): in a tensile test, the force-elongation diagram for the invention according to the invention showed Test belts (550/2 x 1 x 3) determine an average breaking force of 640 N, compared to a breaking force of only 560 N for the comparison belt (1100 x 1 x 3). The belts according to the invention are particularly suitable for RSG drives, since they have particularly good tensile strength values and a long service life even under high loads.

Claims

1. power transmission belt (10, 20), which is embedded in a body (12, 22) made of elastic material and has at least one tension cord (14, 24) made of a two-stage twisted base yarn (31), the base yarn (31) being an aramid yarn, which is twisted in a first twist stage to form a pre-twist (33) and in a second twist stage in the opposite direction to the first twist stage to form a twist (34) which forms the tension cord (14, 24),

characterized in that i) the base yarn (31) has a titer less than 1000 dtex, ii) in the first twist stage two or three threads of the base yarn (31) are twisted to the pre-twist (33) and iii) in the second twist stage three to six threads of the pre-twist (33) to the twist (34) are twisted, the ratio of the twist factor for the pre-twist (Fi) to the twist factor for the twist (F2) being 0.8 to less than 1 and the ratio of the twist ( Di) of the pre-twist to twist the twist (D2) of the twist is 1 to 1, 7 with

Fn = Dn x VT,

F = twist factor, D = twist twist in turns per meter,

T = yarn titer as a measure of the fineness of the yarn in tex,

n = 1 or 2 for the first and second twist stages.

2. Power transmission belt (10, 20) according to claim 1, characterized in that the titer of the base yarn (31) of the tension cord (14, 24) is 200 to 1000 dtex, preferably 250 to 800 dtex and further preferably 450 to 650 dtex.

3. Power transmission belt (10, 20) according to claim 1 or 2, characterized in that the base yarn (31) is a multifilament yarn that contains a large number of aramid filaments (32).

4. Power transmission belt (10, 20) according to claim 3, characterized in that the base yarn (31) of the tension cord (14, 24) is not twisted in itself or is provided with a protective twist.

5. Power transmission belt (10, 20) according to one of claims 1 to 4,

characterized in that the ratio of the twisting factors Fi: F2 is 0.8 to 0.9.

6. Power transmission belt (10, 20) according to one of claims 1 to 5,

characterized in that the two-stage twist of the tensile cord (14, 24) is a positive asymmetrical twist (Di> D2).

7. Power transmission belt (10, 20) according to one of claims 1 to 6,

characterized in that the twist twist Di of the pre-twist is 150 to 400 twists per meter (TPM, 1 / rrr ¹ ).

8. Power transmission belt (10, 20), according to one of claims 1 to 7,

characterized in that the belt is a V-belt (20), a toothed V-belt (20), a V-ribbed belt (10) or a synchronous belt.

9. Power transmission belt (10, 20) according to one of the preceding claims, characterized in that the belt is a high-performance drive belt.