IT202300002019A1 - POWER TRANSMISSION BELT AND RELATED TRANSMISSION SYSTEM - Google Patents

Description

DESCRIPTION

of the patent for industrial invention entitled:

?POWER DRIVE BELT AND RELATED DRIVE SYSTEM?

TECHNICAL SECTOR

The present invention relates to a power transmission belt and, in particular, to a toothed belt and the related transmission system.

STATE OF THE ART PRIORITY

The present invention is preferably used for the transmission of motion in a transmission unit comprising a motor.

The transmission of motion occurs preferably using synchronous power transmission belts, also called toothed belts.

The belt can be used both for the transmission of motion in motor vehicles and for industrial applications.

Transmission belts generally comprise a body made of elastomeric material, preferably HNBR for toothed belts, a plurality of resistant thread-like inserts embedded longitudinally in the body, and a coupling portion integrally connected to the body and comprising a plurality of teeth transverse to the direction of sliding of the belts in use in the case of toothed belts.

A typical problem with timing belts is high noise, especially at low engine speeds which make the belt ?audible? while driving.

Numerous studies have been conducted to solve this problem and numerous solutions have been proposed, such as covering the work surface with fabrics or materials that would dampen the noise generated, for example, by the meshing of the belt on the pulley.

However, the belts currently used do not completely solve the problem mentioned above.

We are therefore continually looking for less noisy drive belts that can meet the increasingly stringent specifications imposed by car manufacturers and that, in particular, still allow for a long life.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a transmission belt that solves the above-mentioned problems and is achieved by a belt according to claim 1.

BRIEF DESCRIPTION OF THE FIGURES

- Figure 1 is a schematic and partial view of a portion of a toothed belt

- figure 2 is a diagram of a longitudinal section of a toothed belt which allows the quantities used in the definitions of the present invention to be represented;

- figure 3 is a table showing a series of examples of the belt according to the invention and comparisons - figure 4 is a graph schematically representing a noise test;

- Figure 5 is a transmission system used for the noise test in Fig. 4;

- Figure 6 is a graph representing the comparative results of a noise test on a known belt and a belt according to the present invention.

DESCRIPTION OF THE INVENTION

By ?main elastomer? it is meant that it is present in the mixture that constitutes the body of the belt for at least more than 60% by weight calculated on the total weight of all the components in the mixture including therefore any type of additive or fillers or elastomers.

By "first elastomeric material is essentially constituted" it is meant that in addition to additives, it is possible to add small percentages of other polymers or copolymers to the mixture without negatively influencing the functionality and chemical compatibility between the body mixture and the other elements constituting the toothed belt and therefore without departing from the scope of the present invention.

In the following, although they are widely known to those skilled in the art, the various definitions of belt sizes have generally been made in accordance with ISO9010:1997 and more specifically with the sizes illustrated in Figure 2.

More specifically, the connection radius (R) refers to the radius of the circle that joins the flange with the tooth flank, as illustrated in figure 2.

By tooth root we mean the section generated by the intersection of the two tangent lines symmetrical to the tooth axis with the slope line.

In the context of this invention, pressure angle (theta) means the angle formed between the centre line of the tooth perpendicular to the flange and the tangent at the point of connection between the flange connection radius and the side of the tooth.

By ?non-metallic? it is meant that the belt component does not comprise metallic material or comprises metallic material in an amount by weight less than 50% of its own weight.

In one embodiment of the invention, a toothed belt is generally indicated with 101 in Figure 1.

The toothing may be helical, preferably with a helix angle between 1? and 15?.

The belt 101 comprises a body 102 comprising a first main elastomeric material. Embedded in the body 102 are a plurality of resistant longitudinal thread-like inserts 103 also alternatively called ?cords? not made of metallic material.

Non-metallic cords mean that the cords either do not contain any metallic material or the metallic material represents less than 50% by weight of the cord itself, preferably less than 30% by weight, even more preferably less than 10% by weight and therefore have a minimal influence on the Q factor.

In other words, as is known, it is possible to produce hybrid cords in two or more materials. In the case of using this type of cord in belts according to the present invention, the metal threads that form part of the hybrid cord must have a weight of less than 50% by weight, preferably less than 30% by weight, even more preferably less than 10% by weight.

The belt also comprises a toothing 104 composed of a plurality of teeth 106 which in use constitute the working surface 105 or the surface which engages with a corresponding pulley of the transmission system.

The toothed belt further comprises a back 107 opposite the working surface 105.

Both the teeth 104 and the back 107 can be covered by a covering material which is generally used to modify the mechanical properties of the surface. The covering material can for example be a fabric, a polymer film, a treatment, an anti-friction coating, etc. Alternatively, it is also possible to use more than one covering material such as, for example, a fabric on which a layer of a mixture of elastomeric material and PTFE is calendered.

According to a preferred form of the present invention the coating material preferably contains less than 50 weight percent metals, more preferably less than 30 weight percent, even more preferably less than 10 weight percent and most preferably contains no metals.

In the context of the present invention, with reference to the power transmission belt, the following is defined:

Wg = Weight (gr)

P = Step (cm)

N = Number of teeth

Wi = Width (cm)

T = Skirt (cm)

H = Tooth height (cm)

E = tooth root (cm)

Theta = angle ? (rad)

A = tooth area = E*H-Ae (cm<2>)

Q = Wg/((E*H-(H)*H*Tan(teta))*Wi*N+N*P*Wi*T)) According to a preferred form of the present invention, it has been found that the belt has a lower noise level when Q is greater than 1.45. Preferably Q is between 1.45 and 2. Alternatively Q is greater than 1.50.

It has been verified that when the Q parameter assumes a value greater than 1.45 the belt has a reduced noise, especially in combination with a number of engine revolutions and torque when the belt noise is particularly felt by the user.

In a preferred embodiment the pitch P of the belt is between 0.1 and 2 cm, more preferably the pitch P is between 0.15 and 1.6 cm.

Preferably, to obtain the Q parameter with a value greater than 1.45, the belt body is made of a mixture comprising a material with a density greater than 1.3 g/cm<3>. More preferably, the material with a density greater than 1.3 g/cm<3 >is added to the mixture in the form of raw fibres or powders or liquids. Even more preferably, the material with a density greater than 1.3 g/cm<3 >makes up more than 35% by weight with respect to the total weight of the belt body, more preferably more than 40% by weight, even more preferably more than 50% by weight.

The upper limit is given by the fact of continuing to maintain the performance of the elastomeric material to hold the remaining components of the belt together.

Even more preferably, material with a density greater than 1.3 g/cm<3> constitutes 50 to 60% of the body weight.

Preferably the material with density greater than 1.3 g/cm<3>? chosen from the group consisting of metals and minerals or mixtures thereof.

More preferably in the case of metal, the material with a density greater than 1.3 g/cm<3> is added in an amount greater than 35% by weight.

More preferably, in the case of mineral material with a density greater than 1.3 g/cm<3>, it is added in a quantity greater than 45% by weight.

Preferably the material with density greater than 1.3 g/cm<3 >? steel or barite.

Preferably the material with a density greater than 1.3 g/cm<3 >? in powder form, but it can also be added in liquid or fibre form or in another form that allows compatibility with the compound that makes up the body.

More preferably in case it is steel or barite it is added in powder form.

Alternatively, it is possible to vary the Q parameter by acting on other elements of the belt in order to still obtain a reduction in noise.

Preferably the elastomeric material forming the body 101 of the belt is selected from the group consisting of natural rubber (NR), polychloroprene (CR), acrylonitrile butadiene (NBR) and related hydrogenated elastomers known as hydrogenated acrylonitrile butadiene (HNBR) or zinc salts of hydrogenated acrylonitrile butadiene grafted with unsaturated carboxylic acid esters, polyisoprene, styrene-butadiene rubbers, ethylene alpha-olefin elastomers, EPM, EPDM, polyurethane, fluoroelastomers, ethylene acrylic elastomers (AEM), bromobutyl, chlorosulfonated polythene (CSM) or alkyl chlorosulfonated polythene, chlorinated natural rubber, SBR, carboxylated NBRs, carboxylated HNBRs, ACM and mixtures of these compounds.

More preferably it is a mixture of one or more copolymers, obtained from a diene monomer and a monomer containing nitrile groups, optionally at least partly modified with a salt of an unsaturated carboxylic acid.

Although the embodiment in which the body mix comprises only one elastomer is preferable, it is also possible to add further elastomers such as nitrile rubbers, advantageously acrylonitrile butadiene rubbers, known by the acronym NBR. Alternatively hydrogenated acrylonitrile butadiene or HNBR or also XHNBR, i.e. hydrogenated and carboxylated acrylonitrile butadiene.

Alternatively, the elastomeric material of the body 102 comprises as a further elastomeric material at least one polyolefin copolymer or a rubber containing acrylonitrile units modified with a salt of an unsaturated carboxylic acid.

More advantageously the unsaturated carboxylic acid is methacrylic or acrylic acid and the said salt is a zinc salt of methacrylic or acrylic acid. Even more advantageously a zinc salt of methacrylic acid is used.

For example, elastomers sold by Zeon under the names: ZSC 1295, ZSC 2095, ZSC 2195, ZSC 2295, ZSC 2295L, ZSC 2295R and ZSC 2395, ZSC2195CX are used to advantage.

The body mix, in addition to elastomeric materials, may include conventional additives such as, for example, reinforcing agents, fillers, pigments, stearic acid, accelerators, vulcanization agents, antioxidants, activators, initiators, plasticizers, waxes, prevulcanization inhibitors, antidegradants, process oils and the like.

Advantageously the body mix also comprises reinforcing fibres, more advantageously the mix comprises between 1 and 20% by weight of fibres, more preferably between 5 and 15% by weight.

The reinforcing fibres have a length between 0.1 and 10 mm, preferably between 1 and 6 mm, even more preferably between 1 and 3 mm.

The use of fibres allows to further increase the mechanical characteristics of the mixture that makes up the body.

The fibers are therefore present throughout the body, including the region surrounding the cords, and this allows for greater rigidity.

Preferably, the fibers are chopped fibers.

The reinforcing fibres preferably comprise at least one substance selected from the group consisting of polyamide, aromatic polyamide, polyester, glass, PBO, carbon fibres, more advantageously aromatic polyamides or aramids, for example Technora? fibres, which can be made to adhere to the mixture by a treatment, preferably based on RFL.

The treatment used can also have a VP-SBR base, that is, a copolymer of vinylpyridine and styrenebutadiene.

Aramid fibres, such as Teijn's 3 mm long Technora? fibres, have proven to be particularly effective.

Cords 103 are formed by a plurality of threads or filaments or yarns and each thread is formed by a plurality of filaments.

The cords preferably comprise high modulus fibres, more preferably of at least one material selected from the group consisting of carbon fibres, PBO, aramid, polyamide, glass or polyester.

Cords can advantageously be of the "hybrid" type, that is, composed of at least a first fibrous material and a second fibrous material.

The use of cord 103 made of two materials in the form of different fibres or filaments allows for better adhesion of cord 3 to the mixture that makes up the body of the belt.

Cords 103 are preferably treated with a water-based treatment known as reactive impregnation, but can also be treated similarly or with RFL, i.e. a composition based on latex, resorcinol and formaldehyde.

In case the cords 103 comprise two fibrous materials, both the first and the second material are preferably chosen from the group consisting of glass fibres, aramid fibres, polyester fibres, carbon fibres, PBO fibres, polyamide fibres, polyketone (POK) fibres, PEEK fibres, polyvinyl acetate (PVA) fibres, liquid crystal fibres (LPC) and PEN fibres.

The first material preferably has a lower modulus than the second material and is preferably wrapped around the second material.

Preferably, in the cross-section the second material occupies a surface area of between 15 and 75% of the total surface area of the section itself. Even more preferably, the second material occupies a surface area of between 45 and 55% of the total surface area.

Even more advantageously, in cross-section the fibres of the two materials occupy similar surfaces, so as to balance as much as possible the positive characteristics of both to obtain the best performance on the tape.

The first material is preferably glass fiber and the second material is preferably carbon fiber.

Preferably, the fibres of the first material are wrapped around the fibres of the second material so as to externally coat the fibres of the first material at least in part, and even more preferably to entirely coat the fibres of the second material.

Preferably, 103 strings feature a Lang's Twist, meaning two twists in the same direction.

The number of filaments that form the cord, as well as the number of base filaments or the count or the entire construction of the insert, can be varied.

In order to obtain the best performance, the number of threads formed by the fibres of the first material is preferably between 3 and 18, preferably between 8 and 15.

Advantageously, the working surface of the drive belt 101 is covered by a covering material 108. The covering material 108 is most advantageously chosen from the group consisting of woven fabric, knitted fabric, non-woven fabric.

The covering material 108 covering the teeth 105 or the optional covering material of the back 110 are preferably made of a fabric formed by one or more layers and can be obtained through different weaving techniques, for example, through the weaving technique known as 2x2 twill.

Covering fabrics preferably have a structure consisting of a warp and a weft.

More advantageously, where a woven fabric is used, the covering material 108, 110 comprises threads which extend substantially in the longitudinal direction of the toothed belt. Generally, such longitudinal threads are the weft threads.

Advantageously, the weft threads comprise at least one elastic thread and at least one thread with high thermal and mechanical resistance, such as aliphatic polyamide, aromatic polyamide or aramid, PET, polyesters, but also natural-based fabrics such as cotton, possibly even in complex or mixed structures with several chemical threads wrapped around each other.

Even more advantageously the weft threads comprise an elastic thread and at least a first and a second thread, more preferably the first and second threads are polyamides, even more preferably they are made of an aliphatic polyamide such as polyamide 6, 6 and an aromatic polyamide, such as for example a poly-para-aramid, as for example illustrated in the patent EP0965271.

In a preferred embodiment both the yarn wrapping threads or the elastic threads are made of polyaramid.

In a particularly preferred form of the invention the work surface is covered with a fabric in which a first thread of polyaramid fibres is wrapped around an elastic thread in a first direction S and a second thread of polyaramid fibres is wrapped in the opposite direction Z around the first thread.

Advantageously the weft threads comprise para-polyaramid fibres.

For example, weft threads can be formed by wrapping a pair of para-polyaramid threads, such as Technora threads, around a polyurethane thread.

Advantageously the warp threads comprise meta-polyaramid fibres.

Advantageously the fabric does not include metallic threads. Alternatively the metallic threads are in a smaller quantity by weight than the non-metallic threads, more advantageously they are less than 30% by weight, even more advantageously they are less than 10 & by weight.

Fabric 108, 110 is generally subjected to a plurality of treatments.

These treatments have proven to be very advantageous in order for the belt to be able to have a long life in continuous contact with high temperature oil.

Advantageously, a first treatment can be based on polyisocyanates which are useful for making the polyaramid fibres and therefore the entire fabric adhere to the body elastomers.

Advantageously, the fabric 108, 110 is subsequently subjected to a second treatment with RFL.

Even in this case, latex is preferably an elastomeric material formed by a mixture of one or more copolymers, obtained from a diene monomer and a monomer containing nitrile groups, modified with a salt of an unsaturated carboxylic acid.

Advantageously, the fabric 108, 110 is also subjected to a third treatment based on a rubber, also called cement, preferably comprising an elastomeric material, more preferably a hydrogenated nitrile rubber, even more preferably an elastomeric material formed from a mixture of one or more copolymers, obtained starting from a diene monomer and a monomer containing nitrile groups, modified with a salt of an unsaturated carboxylic acid and even more preferably the same elastomeric material constituting the body.

Furthermore, preferably the fabric of the working surface 105 of the timing belts 101 of the present invention is covered with a fourth treatment, even more preferably such treatment forms a layer 109 which is for example calendered over the fabric to form a distinct layer.

Such layer 109 preferably comprises a fluorinated polymer, e.g. PTFE, and a treating elastomer, e.g. a material similar to that used for the body compound or a fluoroelastomer.

Advantageously, one or more copolymers formed from a monomer containing nitrile groups and a diene can be used as elastomers for the fourth treatment, and more preferably an elastomeric material formed from a mixture of one or more copolymers, obtained from a diene monomer and a monomer containing nitrile groups, modified with a salt of an unsaturated carboxylic acid, and even more preferably the same elastomeric material used as the main elastomer in the mixture constituting the body.

By appropriately choosing the quantities of the materials that make up the fourth treatment, a distinct covering layer is conveniently formed, separate from the fabric itself, also referred to below as the resistant layer 109.

Advantageously, the elastomeric material is present in the resistant layer 109 in a quantity greater in phr than the sum of the fluorinated elastomer and the second elastomeric material.

The thickness of the resistant layer 109 is advantageously between 0.03 mm and 0.3 mm.

The resistant layer 109 can be arranged above the fabric 108 in different ways. Preferably it is arranged by means of a calendering step.

An adhesive material may be placed between the fabric 109 and the resistant layer 108 to improve the adhesion of the resistant layer 109 to the fabric 108.

Preferably, the resistant layer 108 has a weight between 200 and 400 g/m<2> to ensure the necessary resistance.

Preferably the back 107 of the belt is also covered with a fabric, even more preferably the fabric on the working surface 105 and on the back 107 are the same and are treated with the same treatments and with the same materials.

Preferably, the back covering fabric 107 is also treated with different treatments. It has been found to be particularly advantageous to treat the back 107 with a treatment similar to the fourth treatment of the fabric 108 covering the work surface 105 described above. More advantageously, this fourth treatment forms a resistant layer above the fabric. Even more preferably, the resistant layer covering the back covering fabric 110 ? is the same as that covering the tooth covering fabric 108.

From an examination of the characteristics of the belt made according to the present invention, the advantages that it allows to obtain are evident.

By using a toothed transmission belt, according to the present invention, significant improvements have been achieved and, in particular, the problems mentioned above have been overcome. In particular, it is possible to obtain lower noise and have a comparable belt life.

The invention will be described below by means of examples, but is not intended to be limited to them.

Examples according to the invention and comparisons 1-13

The table in Figure 3 shows a series of belts according to the invention (designated Inv) and comparative ones (designated comp) for which the different quantities that lead to the calculation of the Q parameter have been calculated.

The belts according to the invention are identical in composition and shape to some comparative belts except for the addition of a high density material.

The high density material added in the belts according to the invention is steel powder and is added in an amount of 50 % by weight.

The comparative belt in example 1 includes a body made from the compound in table 1.

Table 1

In the belt of the invention of example 2, 50% by weight of steel powder is added to the composition of table 1.

The strap covering fabric is made of polyamide 66 with a raw weight of 275 g/m2 and is treated with an HNBR mixture.

The teeth are helical. The cord is type E glass with a water-based treatment known as reactive impregnation.

The strap also includes a back fabric in nylon polyamide 66 with a raw weight of 200 gr/m2.

This belt is marketed by Dayco under the number 998009.

The belts are subjected to a noise test shown in figure 4.

The test to which the three belts are subjected is a constant torque test which is carried out by mounting the belts in the transmission system illustrated in figure 4.

The driving pulley rotates with a speed ramp from 0 to 1200 revolutions per minute (RPM). The driven pulley applies a constant resisting torque in a first speed ramp equal to 3Nm and in a second speed ramp equal to 8Nm.

The graph in figure 6 is obtained, where the noise is reported as the engine speed increases with a torque of 3 and 8 Nm.

It is evident to note how the belt line of the invention presents a lower noise progression in particular at low and medium speeds and therefore has a lower noise precisely at the number of engine revolutions in the area where it is most perceived by the user.

Claims (15)

CLAIM S 1. Power transmission belt comprising a body (102) comprising a first elastomeric material, a plurality of non-metallic cords (103) embedded in the body of the belt, a back (107) and a toothing (106) covered by at least a first non-metallic covering material (108), wherein: Wg = Weight (gr) P = Step (cm) N = Number of teeth Wi = Width (cm) T = Skirt (cm) H = Tooth height (cm) E = tooth root (cm) Theta = angle ? (rad) A = tooth area = E*H-Ae (cm<2>) Q = Wg/((E*H-(H)*H*Tan(theta))*Wi*N+N*P*Wi*T)) characterized by the fact that: Q > 1.45. 2. Transmission belt (101) according to claim 1, characterised in that Q is between 1.45 and 2. 3. Transmission belt (101) according to claims 1 or 2, characterised in that Q>1.50. 4. Transmission belt (101) according to any of the preceding claims, characterised in that P is between 0.1 and 2 cm. 5. Transmission belt (101) according to any of the preceding claims, characterised in that P is between 0.15 and 1.6 cm. 6. Transmission belt (101) according to any of the preceding claims, characterised in that said body comprises a material with a density greater than 1.3 g/cm<3>. 7. Transmission belt (101) according to claim 6, characterised in that said material with density greater than 1.3 g/cm<3 >is added to the mix in the form of first fibres or powders or liquids. 8. Transmission belt (101) according to claims 6 or 7, characterised in that said material with a density greater than 1.3 g/cm<3 > constitutes more than 35% by weight with respect to the total weight of the belt body. 9. Transmission belt (101) according to claims 6 or 7, characterised in that said material with a density greater than 1.3 g/cm<3 > constitutes from 40 to 60% by weight of said body. 10. Transmission belt (101) according to claims 6 to 9, characterised in that said material with density greater than 1.3 g/cm<3 >? selected from the group consisting of metals or minerals, 11. Transmission belt (101) according to claims 6 to 9, characterised in that said material with density greater than 1.3 g/cm<3 >? steel or barite. 12. Transmission belt (101) according to any of the preceding claims, characterised in that said body comprises second fibres in a material selected from the group consisting of glass, aramid, polyester, carbon, poly(p-phenylene-2,6-benzobisoxazole) PBO, polyamide, polyketone (POK), polyether ether ketone (PEEK), polyvinyl acetate (PVA), liquid crystals (LPC), polyethylene naphthalate (PEN). 13. Transmission belt (101) according to any of the preceding claims, characterised in that said elastomeric material is? selected from the group consisting of natural rubber (NR), polychloroprene (CR), acrylonitrile butadiene (NBR) and related hydrogenated elastomers known as hydrogenated acrylonitrile butadiene (HNBR) or zinc salts of hydrogenated acrylonitrile butadiene grafted with unsaturated carboxylic acid esters, polyisoprene, styrene-butadiene rubbers, ethylene alpha-olefin elastomers, EPM (ethylene propylene monomer), EPDM (ethylene propylene diene monomer), polyurethane, fluoroelastomers, ethylene acrylic elastomers (AEM), bromobutyl, chlorosulfonated polythene (CSM) or alkyl chlorosulfonated polythene, chlorinated polythene, epoxidized natural rubber, SBR, carboxylated NBRs, carboxylated HNBRs, ACM and mixtures of these compounds. 14. Transmission belt (101) according to any of the preceding claims, characterised in that the toothing (106) is helical with a helix angle between 1° and 15°. 15. Power transmission system comprising a belt according to any of claims 1 to 14.