KR20070104332A - Toothed belt drive for use with oil - Google Patents

Abstract

Toothed belt drive (1) for use with oil, comprising at least a pair of toothed pulleys (5, 6) and a toothed belt (10) meshing with the pulleys (5, 6), wherein the toothing (14) of the belt (10) and the toothing (25) of each of the pulleys (5, 6) have respective reference profiles with infinite radius pitch line so that the transverse clearance between a tooth (20) of the reference profile of the belt (10) and a groove (29) of the reference profile of a pulley (5, 6) is between-0.1 mm and +0.15 mm at least in an intermediate portion of the respective sides (22, 31).

Description

Toothed belt drive for use with oil

The present invention relates to a tooth belt drive for use with oil. Preferably, but not necessarily, the invention can be applied to a timing system of an internal combustion engine for a motor vehicle, the timing system of an internal combustion engine will be referred to for clarity, but it is excluded that the invention is generalized and used. no.

In an internal combustion engine, the control of timing, ie the synchronized drive of the camshaft or camshafts by the drive shaft, is carried out entirely by a toothed belt or chain. The tooth belts have the following advantages over the chain drive: The tooth belt is inexpensive, light and can be operated dry, thus making the overall drive simpler and cheaper normally.

Moreover, over time the belt stretches less than the chain, which is subject to pin wear. Finally, the belt drive is normally quieter than the chain drive.

In view of the above advantages of tooth belt drive over chain drive, the use of tooth belt drive may be advantageous in dry applications as well as in environments exposed to lubricating oil. However, the use of tooth belts in applications where oil is present must determine a series of technical problems that are difficult to solve.

First, the shape of the teeth of the pulley and belt normally used in the dry application causes the timing error between the driven member (camshaft) and the driving member (drive shaft) to increase when oil is present.

Another problem with the use of toothed belts with oil concerns the aggressive action of the oil on the belt material, in particular the elastomeric material constituting the body of the belt and the resistance inserts embedded in the material. It is related to the difficulty of maintaining attachment over time between (cords).

It is an object of the present invention to create a tooth belt drive for use with oil, which makes it possible to solve the above problems, in particular to ensure a high level of time accuracy and extended life of the belt between the drive member and the driven member of the drive unit. do.

This object is achieved by a drive as described in claim 1.

BRIEF DESCRIPTION OF THE DRAWINGS In order to better understand the present invention, a preferred embodiment will be described below as one non-limiting example with reference to the accompanying drawings.

1 shows an overview of a belt drive according to the invention.

2 is a partial perspective view of the belt drive according to the present invention.

3 shows the ratio between the reference shape of the drive pulley and the reference shape of the belt according to the invention.

With reference to FIG. 1, a synchronous toothed belt drvie for transmitting movement from the first camshaft 2 of the internal combustion engine to the second camshaft 3 is indicated generally by reference numeral 1. The first camshaft moves from the drive shaft (not shown) through the other synchronization drive 4, which is preferably of the same type and is only schematically and partially shown in FIG. 1.

The drive 1, also known as a "cam-to-cam", comprises a tooth drive pulley 5 with a key coupled to the camshaft 2, and a toothed figure with a key coupled to the cam shaft 3; The pulley 6 and the tooth belt 10 wound on the pulleys 5 and 6 are provided.

The belt 10 comprises a body 12 made of elastomeric material (FIG. 2) in which a plurality of longitudinal thread-shaped resistance inserts 13 are embedded. The body 12 has a first side provided with a tooth 14, covered with a coated fabric 15, and a back side 16 of the second side or belt. Preferably, the back side 16 is covered by the fabric 17.

More preferably, the fabric 15 coating the teeth 14 is the same as the fabric 17 coating the back 16. Preferably, the fuselage 12 is the main elastomer, i.e., the elastomer which appears to be more than 50% by weight relative to the other elastomers used in the mixture, the diene and the nitrile group. It includes a copolymer formed from a monomer comprising a.

More preferably, the copolymer used is hydrogenated acrylonitrile butadiene.

Preferably, the copolymer used is obtained from monomers comprising nitrile groups in percentages between 33% and 49% by weight relative to the final copolymer.

More preferably, the copolymer used is obtained from monomers containing nitrile groups in a weight percentage of 39% relative to the final copolymer, for example 50% THERBAN 3446 (Bayer®) and 50% THERBAN 4307. It is possible to use a mixture consisting of (Bayer registered trademark).

Advantageously, the elastomeric material mixture comprises fibers, preferably comprising fibers in weight percent between 0.5% and 15% relative to the elastomeric material, and the fibers preferably have a length between 0.1 and 10 mm.

The fabric 15 coating the teeth 14 and the fabric 17 coating the back 16 may be constituted by one or more layers and are known, for example, in a weaving technique known as 2 x 2 twill. Can be obtained by

The fabrics 15 and 17 are preferably composed of a polymeric material, preferably of aliphatic aliphatic or aromatic polyamides, more preferably of polyamide 6.6 of high thermal resistance and high tenacity. .

The fabrics 15, 17 may advantageously be of a type in which each weft thread consists of an elastic thread as a core and at least one synthetic thread wound on the elastic thread, wherein the synthetic thread is a high heat And mechanically resistant yarns and at least one coated yarn wound around said high thermal and mechanically resistant yarns.

According to one feature of the invention, the tooth belt 10 comprises a resistive layer 18 disposed outside of the fabric 15.

The resistive layer 18 is constituted by a fluorinated plastomer added with an elastomeric material, the amount of the fluorinated plastomer being higher by weight relative to the elastomeric material.

Examples of useful resistive layers are disclosed in the applicant's European patent EP1157813.

Fluorinated plastomers are preferably polytetrafluoroethylene based mixtures.

Preferably, the fluorinated plastomer is mixed with an elastomeric material to form a resistive layer 18, the elastomeric material being HNBR, more preferably HNBR modified with zinc salt of polymethacrylic acid. , For example ZEOFORTE ZSC (Nippon Zeon registered trademark).

Preferably, the resistive layer 18 is 150-400 g / m ² to ensure the required resistivity. Having a weight between which is equivalent to an average thickness between 0.050 and 1 mm.

Preferably, the fluorinated plastomer is present in an amount of between 101 and 150 weight per 100 parts of elastomeric material.

The resistive layer 18 contains a peroxide as a hardener. Peroxide is normally added in an amount of 1 to 15 parts by weight relative to 100 parts of the elastomeric material.

Preferably, an adhesive material is disposed between the coating fabric 15 and the resistive layer 18.

The resistive insert 13 is made of one or more materials selected from the group consisting of glass fibers, aramid fibers, polyester fibers, carbon fibers and PBO fibers.

Preferably, the resistance inserts 13 are of the type of "hybrid", ie they are made of at least two different materials.

The first material is preferably glass fiber and the second material is preferably carbon fibers. More preferably, the glass fibers are high modulus fibers.

The glass fibers are wound at least partially around the carbon fibers to cover the carbon fibers on the outside and preferably completely cover the carbon fibers.

The resistive insert 13 is treated with a composition of resorcinol-formaldehyde latex based, preferably known as RFL, in particular with an RFL composition suitable for preventing the absorption of oil. Preferably, the RFL so used comprises latex formed from dienes, such as, for example, HNBR or hydrogenated butadiene acrylonitrile, and from monomers comprising nitrile groups. More preferably, latex is obtained from monomers comprising nitrile groups in weight percentage relative to the final copolymer similar to the preferred elastomeric material used to form the body 12 of the tooth belt 10 described previously. .

The teeth 14 of the belt 10 have a conventional type of geometry in a series of teeth 20 and grooves 21. 3 shows the shape of the tooth 14 as a straight configuration of the belt 10 (ie in a configuration taken by the belt in parts between the pulleys, geometrically similar to a rack). Such a shape will hereinafter be referred to in the description and in the claims as a "reference shape with an infinite radius radius pitch line" or more simply as a "reference shape".

For example, the shape of the teeth 20 of the belt 14 may have been released by the applicant under the trade name ISORAN® RHP (registered trademark), which has parabolic sides 22 formed on the circumference 24. Connected to the bottom surface 23 of the adjacent groove 21 by an arc of; The teeth 20 have an upper surface 26 formed by two convex protrusions 27, for example shaped like a circular arc, each of which is a circular arc 28, for example a circular arc. By means of the individual sides 22 and relative to each other.

The pulleys 5, 6 are provided with individual identical teeth, each tooth engaging a groove 29 suitable for receiving the teeth 20 of the belt 10 and a groove 21 of the belt 10. It is formed by the continuation of the teeth 30 suitable for.

With regard to the pulleys 5, 6, the shape of the tooth is shown and described in FIG. 3, which depends on a reference shape with an infinite curvature radius pitch line, ie for cutting the pulleys 5, 6. It depends on the shape of the hop-shaped "negative" or equivalent rack tooth.

Using belts and pulleys in equivalent shapes allows direct comparisons between shapes, despite the number of teeth of the pulleys and thus the pitch line radius of the belt 10 in the portions engaged with the pulleys 5, 6. (FIG. 3).

The shape of each of the grooves 28 is symmetrical with respect to the center line M; Thus, only one of the sides 31 of the groove 29 is described.

The side 31 is formed by a concave arc of parabola connected to the base line 33 and the upper line 34 in a known manner. In particular, the parabolic arc has the following equation.

y = kx ²

This is the coordinate where x is parallel to the baseline 33, y is the coordinate parallel to the height of the groove 29, and constitutes the connection point between the arc of the parabola 32 and the baseline 33 and the vertex of the parabola Is a system of coordinate axes (x, y) originating at point O on base line 33 (FIG. 3). The arc of the parabola 32 is connected to the upper line 34 by an arc of the circumference 35 having a center C and a radius r, and has a distance equal to r from the upper line 34. The tangent point between the arc of the parabola 32 and the arc of the circumference 35 is marked T. The distance of the point C from the center line M of the groove is also denoted by a, the width of the groove 29 measured at the height of the points T on the two sides of the groove is denoted by b, The height, ie the distance between the base line 33 and the upper line 34 is indicated by h.

According to the invention, the transverse gap between the groove of the reference shape of the pulley in the middle of the individual sides in the range of 1/5 to 4/5 of the tooth height and the teeth of the reference shape of the belt is between -0.1 mm and + 0.15 mm. Is between; The negative value of the gap identifies the condition of the interference.

Preferably, the gap is between -0.05 mm and 0.1 mm. More preferably, the gap is equal to zero.

As one pure example, the latter of the above conditions is obtained with the following values of the parameters of the groove for a belt having a conventional ISORAN® RHP® trademark.

k = 1.49633

h = 2.92 mm

a = 3.264 mm

b = 5.30 mm

In FIG. 3, it can be seen that there is a substantial correspondence between the reference shape of the pulley and the reference shape of the belt in the described example, except for the portion corresponding to the upper portion of the tooth.

Although in the above example there is a substantially zero gap in the entire middle portion of the side, which ranges from 1/5 to 4/5 of the tooth height, this condition is not essential according to the invention, and at least of the above intermediate portion In some parts, the transverse gap is sufficient to be in the above-mentioned range, preferably substantially zero.

According to the present invention, the use of a coated fabric provided with a cured fluorine-plated plastomer-based resistive layer added with elastomeric material combines with the dimensions of the tooth to determine a substantially low or zero clearance between the teeth of the belt and the grooves of the pulley. When used with oil, it is possible to significantly reduce the timing error between the drive member and the driven member without shortening the duration of the belt.

For example, the drive according to the invention was used to connect the camshafts of the `` Common Rail '' engine of the IVECO UNIJET HPI 2.3 liter. The test performed produced a maximum timing error between the two shafts, such as 0.5 ° at 3000 rpm. The same conditions but tests performed using conventional belts and pulleys (RHP standard shape) resulted in a maximum error such as 0.95 °.

The increase in timing error found in applications where oil is present using a conventional type of profile is due to a substantially reduced belt / pulley friction coefficient due to the presence of an oil gap at the engagement site.

The use of a fluorine-plated plastomer-based resistive layer, even though it has contributed to further reducing the friction coefficient, allows for a very precise engagement between the teeth of the belt and the pulley, i.e. as the gap is reduced or zero, Engagement is achieved without shortening the life of the belt.

Thus, combining the use of the layer and the coupling precision between teeth can surprisingly solve the problems of the known art.

Moreover, this layer protects the belt from oil penetration and thereby limits its aggressive effect, in particular the negative effect on the attachment between the elastomeric material and the resistance inserts.

Finally, it is apparent that the above-described drive unit can be modified and modified without departing from the scope defined in the claims.

In particular, the shape of the material constituting the body of the belt, the resistance insert, the coated fabric and the teeth can be varied.

The present invention is used in the belt drive field, in particular in the belt drive of an internal combustion engine.

Claims (10)

A tooth belt drive for use with oil, having at least one pair of pulleys 5, 6 with individual teeth and tooth belts 10 engaged with the pulleys, the belts 10 being a body 12 made of elastomeric material. ), A plurality of fibrous resistance inserts 13 embedded in the fuselage, and teeth 14 provided with a coated fabric 15, Individual sides 22, 31 with a transverse clearance between the teeth 20 of the belt's reference profile and the groove 29 of the pulley's reference shape ranging from 1/5 to 4/5 of the height of the teeth 20. The teeth of the belt 14 and the teeth 25 of each pulley 5, 6 have a separate reference shape with an infinite curvature radius pitch line, so that at least in the middle part of-between 0.1 mm and + 0.15 mm, The coated fabric (15) is characterized in that it is covered with a resistive layer (18) comprising a fluorine-added plastomer added with elastomeric material. The method of claim 1, And the gap is between -0.05 mm and +0.10 mm. The method of claim 1, Tooth gap drive, characterized in that the gap is substantially zero (O). The method of claim 1, wherein In the resistive layer (18), the amount of the fluorine-added plastomer is characterized in that the weight is large compared to the elastomeric material in terms of weight. The method of claim 1, wherein The fluorine-added plastomer is a tooth belt drive unit, characterized in that the polytetrafluoroethylene-based compound. The method of claim 1, wherein And the elastomeric material into which the fluorinated plastomer is mixed to form a resistive layer comprises HNBR. The method of claim 6, And the elastomeric material is HNBR modified with zinc salt of polymethacrylic acid. The method of claim 1, wherein The resistance insert 13 of the belt 10 is characterized in that the tooth belt is composed of at least one material selected from the group consisting of glass fibers, aramid fibers, polyester fibers, carbon fibers and PBO fibers. Drive part. The method of claim 8, The resistance insert (13) is characterized in that it comprises a glass fiber and carbon fiber, tooth belt drive. The method of claim 1, wherein The resistance insert (13) is characterized in that the tooth belt drive, characterized in that treated with RFL comprising a latex formed from a monomer comprising a diene and a nitrile group.

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