U.S. patent application number 15/307925 was filed with the patent office on 2017-03-23 for transmission belt and associated transmission system.
The applicant listed for this patent is DAYCO EUROPE S.R.L.. Invention is credited to Fabrizio BREGGIA, Marco DI MECO, Domenico PARZIALE, Marino PETACCIA.
Application Number | 20170082174 15/307925 |
Document ID | / |
Family ID | 51176415 |
Filed Date | 2017-03-23 |
United States Patent
Application |
20170082174 |
Kind Code |
A1 |
PARZIALE; Domenico ; et
al. |
March 23, 2017 |
TRANSMISSION BELT AND ASSOCIATED TRANSMISSION SYSTEM
Abstract
A transmission belt his provided which has a first elastomeric
material, a plurality of longitudinal inserts comprising a first
material, a working surface covered by a covering including a
second material, and an opposite surface to said working surface.
At least one of the first material and the second material is a
fibrous metallic material. Advantageously, the transmission belt is
a toothed belt.
Inventors: |
PARZIALE; Domenico; (Chieti,
IT) ; PETACCIA; Marino; (Chieti, IT) ;
BREGGIA; Fabrizio; (Chieti, IT) ; DI MECO; Marco;
(Chieti, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DAYCO EUROPE S.R.L. |
Chieti |
|
IT |
|
|
Family ID: |
51176415 |
Appl. No.: |
15/307925 |
Filed: |
May 2, 2014 |
PCT Filed: |
May 2, 2014 |
PCT NO: |
PCT/IB2014/061164 |
371 Date: |
October 31, 2016 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F16G 1/10 20130101; F16H
57/0489 20130101; F16G 1/12 20130101; F16H 7/023 20130101; F16G
1/28 20130101 |
International
Class: |
F16G 1/28 20060101
F16G001/28; F16H 7/02 20060101 F16H007/02; F16H 57/04 20060101
F16H057/04; F16G 1/12 20060101 F16G001/12 |
Claims
1. A transmission belt comprising a body including a first
elastomeric material, a plurality of longitudinal inserts
comprising a first material, a working surface covered by a
covering comprising a second material, and an opposite surface to
said working surface, wherein at least one of said first material
and said second material is a fibrous metallic material comprising
fibres with a diameter of between 2 and 40 .mu.m.
2. A transmission belt according to claim 1, wherein said fibrous
metallic material comprises fibres with a diameter of between 5 and
15 .mu.m.
3. A transmission belt according to claim 1, wherein said fibrous
metallic material is steel.
4. A transmission belt according to claim 1, wherein the second
material is chosen from the group constituted by woven fabric,
knitted fabric and non-woven fabric.
5. A transmission belt according to claim 4, wherein said second
material is a fabric.
6. A transmission belt according to claim 4, wherein said fibrous
metallic material has a weight of between 500 and 1500
g/m.sup.2.
7. A transmission belt according to claim 4, wherein said fabric
comprises yarns that extend in the longitudinal direction and
include said fibrous metallic material.
8. A transmission belt according to claim 7, wherein said yarns
comprise at least one elastic yarn around which at least one yarn
comprising said second material is wound.
9. A transmission belt according to claim 7, wherein said fabric
comprises both longitudinal yarns and transverse yarns including
said fibrous metallic material.
10. A transmission belt according to claim 1, wherein said first
material is a fibrous metallic material based on fibres having a
diameter of between 2 and 40 .mu.m.
11. A transmission belt according to claim 1, wherein said inserts
are formed by a plurality of yarns and each yarn is formed by a
plurality of filaments.
12. A transmission belt according to claim 1, wherein each one of
said inserts comprises between 3 and 20 yarns.
13. A transmission belt according to claim 11, wherein each one of
said yarns comprises between 50 and 500 filaments.
14. A transmission belt according to claim 11, wherein said inserts
also comprise a second fibrous material.
15. A transmission belt according to claim 1, wherein it is a
toothed belt.
16. (canceled)
17. A transmission system comprising: a transmission belt according
to claim 1.
18. A transmission system for a motor vehicle comprising; at least
one drive pulley, a driven pulley, a transmission belt and means
for maintaining said belt in direct contact with oil or partially
immersed in oil, wherein said transmission belt comprises: a body
including a first elastomeric material, a plurality of longitudinal
inserts including a first material, a working surface covered by a
covering including a second material, and an opposite surface to
said working surface, wherein at least one of said first material
and said second material is a fibrous metallic material comprising
fibres with a diameter of between 2 and 40 .mu.m.
19. The transmission system of claim 17, wherein said transmission
belt is at least partially in an oil bath or continuously in
contact with oil.
Description
TECHNICAL FIELD
[0001] The present invention relates to a transmission belt
comprising a fibrous material covering the working surface that
includes metallic fibres. In a preferred embodiment, the
transmission belt is a toothed belt.
PRIOR ART
[0002] Transmission belts, and especially toothed belts, generally
comprise a body made of an elastomeric material, in which a
plurality of longitudinal thread-like durable inserts, also known
hereinafter as cords or simply inserts, is buried and a working
surface that, in use, transmits the driving force.
[0003] Each component of the belt contributes to increase the
performance in terms of mechanical resistance, in order to decrease
the risk of the belt breaking and to increase the specific
transmissible power.
[0004] In particular, the cords contribute to ensure the required
mechanical characteristics of the belt and make an-essential
contribution to determine the modulus of the belt and, in
particular, to ensure stable performance over time. The cords are
generally obtained by twisting high-modulus fibres several
times.
[0005] The cords or inserts are normally treated with suitable
compounds to increase the compatibility of the fibres with the body
compound surrounding the cords.
[0006] It is known that cords are manufactured in many materials
based on different fibres, such as, purely by way of example,
carbon, aramid, PBO and glass.
[0007] The body compound enables connecting the various elements
and ensures that they contribute to the final performance of the
belt in a synergetic manner.
[0008] Body compounds are based on one or more elastomeric
materials, possibly enriched with fibres to increase hardness.
[0009] Lastly, the transmission belts have a working surface
generally covered by a fibrous material, for example a covering
fabric on the belts, which has the task of increasing abrasion
resistance and thus protects the working surface of the belt from
wear due to rubbing between the sides and the slopes of the teeth
of the belt and the sides and the throats of the grooves of the
pulley with which the belt interacts.
[0010] In addition, the fibrous covering material reduces the
coefficient of friction of the working surface, reduces the
deformability of the teeth and, most of all, reinforces the root of
the tooth, thereby avoiding its breakage.
[0011] However, in recent engines where performance has increased
significantly, toothed belts are subjected to high temperatures and
these temperatures result in quicker deterioration of the materials
forming the various components of the belts.
[0012] Furthermore, the belts are often used "in oil", or rather in
systems in which the belt is inside the crankcase and therefore in
direct contact with oil spray, or even works partially immersed in
an oil bath. In particular, the materials of transmission belts
used "dry", designed to resist oil only for a short time and at low
temperatures, are unable to prevent deterioration of the mechanical
characteristics at high temperatures and can therefore give rise to
teeth breaking and consequently shorten the mean life of the
belt.
[0013] To avoid these problems, it is currently known to use
covering fabrics, especially for toothed belts, for example with a
structure constituted by woven yarns, or rather yarns that extend,
in use, in a longitudinal direction of the belt, including fibres
of polyamide or with a composite structure, each formed by an
elastic yarn as the core and a pair of composite yarns wound around
the elastic yarn. Each composite yarn comprises a yarn of high
thermal and mechanical resistance and at least one covering yarn
wound around the yarn of high thermal and mechanical resistance.
The elastic yarn could be made, for example, of polyurethane. The
yarn of high thermal and mechanical resistance could be made, for
example, of para-aromatic polyamide. The covering yarn is made of
an aliphatic polyamide, in particular nylon 66.
[0014] However, this solution is disadvantageous as it easily
deteriorates and causes quite a few belt breakages, in particular
in high-temperature conditions and in systems where the belt works
continuously in contact with oil.
[0015] Alternative materials are therefore being sought for the
production of a covering for transmission belts, in particular
toothed belts, which enables improving the mechanical and wear
resistance characteristics of known fabrics.
[0016] In addition, in the last few years, more stringent emission
regulations have resulted in designing engines that reach
increasingly higher temperatures in the engine compartment when
running.
[0017] The materials currently used for making the coverings
comprise simple yarns in nylon 66. However, the behaviour of these
yarns is not optimal at high temperatures, whether the belts are
used dry or in air, and even more so when used in systems in oil
and therefore inside the engine crankcase.
[0018] Covering fabrics are therefore sought that are resistant to
the high temperatures of current-day engines, whether dry or in
oil.
[0019] In the end, whether used dry or in oil or inside the engine
crankcase, belts are subjected to attack by numerous chemical
agents. In systems where the belt is used in direct contact or
partially immersed in oil, the engine oil often contains pollutants
such as ethanol, petrol and diesel fuel, and combustion residues.
In particular, pollution from petrol that mixes with the oil, even
in quite high percentages, diluting the oil and attacking the
materials constituting the belt, is harmful.
[0020] For example, in some applications, the oil can contain up to
30% fuel. The percentage of fuel is variable, depending on the
running conditions of the engine, and increases with high load and
low engine temperature.
[0021] In addition, the modern, so-called green fuels are
particularly aggressive as they contain numerous additives that
attack the polyamide yarns of the fabric.
[0022] Covering fabrics are therefore sought that are resistant to
chemical agents, especially at the high running temperatures of the
engines in use today with peaks of roughly 150.degree. C. and up to
around 170.degree. C.
[0023] Producing coverings for conveyor belts comprising metal is
already known.
[0024] However, the known coverings in steel are made with single
steel wires of a diameter well above 50 micron, in both weft and
warp, and are extremely rigid. These thick wires are therefore
suitable for being used as sheathing for products that must not
flex or only flex very slightly.
[0025] These fabrics are therefore not used in transmission belts,
especially in toothed transmission belts.
[0026] Using durable inserts made of aramid fibres, for example
those marketed with the Kevlar.RTM. or Twaron.RTM. trademarks, in
belts for high performance in terms of transmissible power is also
known.
[0027] However, as has long been known, aramid fibres have the
drawback of very low dimensional stability over time, and so a belt
with durable inserts in aramid fibres undergoes a shortening of its
length during storage, with consequent alteration (reduction) of
the initial pitch; it is therefore subjected to higher loads and
stress during use, which normally result in premature wear
triggered by the meshing error created between belt and pulley.
Moreover, durable inserts made of aramid fibres require a
particularly complex and expensive adhesion enhancement treatment
to improve the long-term dimensional stability of the durable
insert, which if not carried out accurately can also entail
problems in the step of cutting the belts.
[0028] Alternatively, producing inserts in glass is also known,
although this is a fragile material and therefore not particularly
resistant to bending.
[0029] In the past, durable steel inserts have been produced by
twisting several wires, each having a diameter of more than 50
micron and with high long-term dimensional stability, but having a
high specific weight and, in addition, because the depositing of
the reinforcement element takes place in a helical manner, these
durable elements partially stick out from the side edges of the
belts during the belt cutting step, with the risk of injury to
operators when fitting the belt.
[0030] To avoid this risk it is therefore necessary to proceed with
a further finishing step, which contemplates the removal of the
cord strands that stick out due to the cut and the manual sealing
of all the edges of the belt with adhesive in the areas where the
strands partially stuck out. This extra finishing step entails
significant additional costs, as it is carried out by hand and must
be carried out of every single belt.
[0031] Finally, the flexural strength, i.e. the capacity to support
the bending of these steel wires, is particularly modest, for
example, with respect to glass. For this reason, they are no longer
used nowadays.
SUBJECT OF THE INVENTION
[0032] A first object of the present invention is to obtain a
transmission belt comprising a fibrous covering material that
covers the working surface and which has a simple structure and is
resistant to high temperatures, whether dry or in oil.
[0033] A second object of the present invention is also to obtain a
transmission belt that comprises a fibrous covering material that
is resistant to chemical agents, especially the impurities present
in engine oil.
[0034] A third object of the present invention is to obtain a
toothed transmission belt having an extremely high modulus and very
high long-term stability and that, at the same time, avoids the
above-described problems regarding known durable inserts.
[0035] A further object of the present invention is to obtain a
transmission belt that has a long service life, and which therefore
has excellent mechanical and meshing precision characteristics.
[0036] In accordance with the present invention, these objects are
achieved by a transmission belt according to claim 1.
[0037] In accordance with the present invention, a use according to
claim 16 is also provided.
[0038] In accordance with the present invention, a transmission
system according to claim 17 is also provided.
BRIEF DESCRIPTION OF DRAWINGS
[0039] For a better understanding of the present invention, it will
now be described with reference to the attached figures, in
which:
[0040] FIG. 1 is a partial perspective view of a toothed belt
according to the present invention;
[0041] FIG. 2 is a diagram of a first timing control system using a
first toothed belt according to the present invention;
[0042] FIG. 3 is a diagram of second timing control system using a
second toothed belt according to the present invention; and
[0043] FIG. 4 is a diagram of a third timing control system using a
third toothed belt according to the present invention.
DESCRIPTION OF INVENTION
[0044] FIG. 1 shows a toothed belt, indicated as a whole by
reference numeral 1. The belt 1 comprises a body 2, including a
first elastomeric material in which a plurality of longitudinal
thread-like durable inserts 3 is buried, and toothing 4 composed of
a plurality of teeth that, in use, constitute the working surface
5, or rather the surface that meshes with a corresponding pulley of
the transmission system.
[0045] The toothed belt also comprises a back 7 opposite to the
working surface 5.
[0046] Preferably, the body 2 is made of a compound comprising one
or more elastomeric materials and numerous additives. For
convenience, the elastomeric material(s) is/are hereinafter
indicated altogether as the "first elastomeric material".
[0047] The body of the belt advantageously comprises an elastomer
as the main elastomer in the first elastomeric material that is
chosen from the group constituted by natural rubber (NR),
polychloroprene (CR), acrylonitrile butadiene (NBR) and associated
hydrogenated elastomers known as hydrogenated acrylonitrile
butadiene (HNBR) or zinc salts of hydrogenated acrylonitrile
butadiene seamed with esters of unsaturated carboxylic acid,
polyisoprene, styrene-butadiene rubbers, ethylene-alpha-olefin
elastomers, EPDM, polyurethane, fluoroelastomers, ethylene-acrylic
elastomers (AEM), bromobutyls, chlorosulphonated polythene (CSM) or
chlorosulphonated alkyl, chlorinated polythene, epoxidized natural
rubber, SBR, NBR carboxylates, HNBR carboxylates, ACM and mixtures
of these compounds.
[0048] The "main elastomer" is intended as being present in the
compound that constitutes the body for more than 50% by weight,
calculated on the total weight of all the elastomers in the
compound and therefore excluding all other non-elastomeric
components of the belt.
[0049] The body preferably comprises at least one copolymer of
polyolefin or a rubber containing acrylonitrile units as the first
or a further elastomeric material.
[0050] More advantageously, the copolymer(s) used as body compounds
are nitrile rubbers, advantageously acrylonitrile butadiene
rubbers, known as NBR. Even more advantageously, they are
hydrogenated acrylonitrile butadiene, or HNBR, or even XHNBR, i.e.
hydrogenated and carboxylated acrylonitrile butadiene.
[0051] Advantageously, the HNBR used for making the transmission
systems in which the belt is partially in an oil bath or in direct
contact with oil and impurities has a high level of hydrogenation,
for example so-called completely saturated HNBRs can be used, these
having a percentage of residual double bonds of 0.9% at most, but
HNBRs with a lower level of unsaturation can also be used in
alternative, such as, for example, so-called partially saturated
HNBRs having a saturation level of 4% or 5.5%.
[0052] Some examples of HNBR copolymers that can be used in the
body compound, but also in the different treatments of the various
elements forming the toothed belt, include copolymers belonging to
the THERBAN family made by Lanxess, such as THERBAN 3407 with 34%
nitrile groups and a hydrogenation level of 0.9% at most, THERBAN
3406 with 34% nitrile groups and an unsaturation level of 0.9% at
most, THERBAN 3607 with 36% nitrile groups and an unsaturation
level of 0.9% at most, THERBAN 3446 with 34% nitrile groups and an
unsaturation level of 4% at most, THERBAN 3447 with 34% nitrile
groups and an unsaturation level of 5.5% at most, THERBAN 3627 with
36% nitrile groups and an unsaturation level of 2% at most, THERBAN
3629 with 36% nitrile groups and an unsaturation level of 2% at
most, and THERBAN 3907 with 39% nitrile groups and an unsaturation
level of 0.9% at most.
[0053] Alternatively, it is also possible to use HNBRs made by
Nippon Zeon with the name ZETPOL. In particular, ZETPOL 2000 with
36% nitrile groups and an unsaturation level of 0.9% at most,
ZETPOL 2000L with 36% nitrile groups and an unsaturation level of
0.9% at most, ZETPOL 2010 with 36% nitrile groups and an
unsaturation level of 4% at most, ZETPOL 2010L with 36% nitrile
groups and an unsaturation level of 4% at most, ZETPOL 2010H with
36% nitrile groups and an unsaturation level of 4% at most, ZETPOL
2020 with 36% nitrile groups and an unsaturation level of 5.5% at
most, and ZETPOL 2020L with 36% nitrile groups and an unsaturation
level of 5.5% at most.
[0054] More advantageously, the acrylonitrile units in the
elastomer for applications in oil are between 33% and 51%, for
example 50% by weight, while for dry applications they are between
15% and 25% by weight, for example 21% by weight.
[0055] Even more advantageously, a polymer formed by a mixture of
one or more copolymers, obtained starting from a diene monomer and
a monomer containing nitrile groups where an acid or salt of an
unsaturated carboxylic acid is added to one or more of these
copolymers, is used in combination with a first polymer. More
advantageously, the unsaturated carboxylic acid is methacrylic or
acrylic acid and said salt is a zinc salt of methacrylic or acrylic
acid. Even more advantageously, a zinc salt of methacrylic acid is
used. Even more advantageously, the zinc salt of methacrylic acid
is added in a quantity in the range between 10 and 60 phr.
[0056] For example, the elastomers sold by Zeon under the following
names can be used advantageously: ZSC 1295, ZSC 2095, ZSC 2195, ZSC
2295, ZSC 2295L, ZSC 2295R and ZSC 2395.
[0057] In particular, it is possible to partially or entirely
replace the previously mentioned HNBRs, namely ZETPOL and/or
THERBAN with a ZSC that comprises an unsaturated carboxylic acid
and zinc oxide and/or with THERBAN ART that comprises an
unsaturated carboxylic acid salt.
[0058] Mixed compounds of polyolefin and rubber containing
acrylonitrile units are also preferred, more preferably compounds
containing a copolymer of ethylene with NBRs or HNBRs or the
above-mentioned modified HNBRs. For example, rubbers containing
EPDM (ethylene-propylene diene monomer) or EPM (ethylene-propylene
monomer) can be added to polymers containing acrylonitrile units in
quantities preferably in the range between 1% and 30%.
[0059] In addition to the elastomeric materials, the body compound
can comprise conventional additives such as, for example,
reinforcement agents, extenders, pigments, stearic acid,
accelerators, vulcanization agents, antioxidants, activators,
initiators, plasticizers, waxes, prevulcanization inhibitors,
antidegradants, process oils and similar.
[0060] Advantageously, carbon black can be employed as an extender,
being advantageously added in quantities in the range between 0 and
80 phr, more advantageously about 40 phr. Advantageously,
light-coloured reinforcing extenders such as talc, calcium
carbonate, silica and silicates are added in quantities
advantageously in the range between 0 and 80 phr, advantageously
about 40 phr. It is also possible to advantageously use silanes in
quantities in the range between 0 and 5 phr.
[0061] Advantageously, zinc and magnesium oxides are added in a
quantity ranging between 0 and 15 phr.
[0062] Advantageously, ester plasticizers such as trimellitates or
ethyl esters are added in a quantity advantageously ranging between
0 and 20 phr.
[0063] Advantageously, vulcanization coagents such as triallyl
cyanurates and organic or inorganic methacrylates such as metal
salts are advantageously added in a quantity ranging between 0 and
20 phr, or organic peroxides, such as isopropyl benzene peroxide
for example, in a quantity advantageously ranging between 0 and 15
phr.
[0064] It is understood that use "in-oil" means that the belt is
used partially immersed in an oil bath or in direct contact with
oil. In general, in use, the belt can be inside the engine
crankcase, for example, as an alternative to chain or gear
systems.
[0065] It is understood that "dry" use means that the belts are
outside the engine crankcase and are only accidentally in contact
with engine oil and not generally in contact with oil mixed with
petrol.
[0066] It is understood that use "in oil mixed with petrol" means
that the toothed belt is used in a mixture of oil with percentages
of petrol even exceeding 30%.
[0067] In the following, reference will be made to an example of
producing the transmission belt of the present invention with
reference to a toothed belt, but it is obvious that the
transmission belt could also be a multi-groove belt or so-called
poly-V belt.
[0068] In one aspect of the present invention, the transmission
belt comprises inserts 3, also known as cords or durable inserts,
arranged in a longitudinal direction and including a fibrous
metallic material.
[0069] It is understood that fibrous metallic material means a
material including metallic fibres.
[0070] It is understood that metallic fibres means composite fibres
not only just of metal, but also metal covered by polymeric
material or fibres of a polymeric material covered by metal.
[0071] In another aspect of the present invention, the working
surface 5 of the transmission belt is covered with a covering 8
including a fibrous metallic material.
[0072] It is understood that working surface means the face of the
belt that, in use, meshes with the pulley and via which the drive
is transmitted. Clearly, the working surface can comprise one or
more coverings and subsequent treatments that all contribute to the
belt's performance and only one of them will be effectively on the
outside and in contact with the pulley.
[0073] Advantageously, the transmission belt comprises both inserts
3 and the covering 8 including a fibrous metallic material.
[0074] Advantageously, the fibrous metallic material is based on
fibres having a diameter of between 2 and 40 .lamda.m.
[0075] More advantageously, the fibrous metallic material is based
on fibres having a diameter of between 5 and 15 .mu.m.
[0076] More advantageously, the fibrous metallic material is steel,
even more advantageously stainless steel.
[0077] For example, the fibrous metallic material could be a
material chosen from those sold under the Naslon registered
trademark.
[0078] Advantageously, the fibrous metallic material comprises
filaments including fibres, more advantageously it comprises yarns
including filaments including metallic fibres.
[0079] Advantageously, the fibrous metallic material comprises
complex or hybrid yarns composed of several fibrous materials.
[0080] Advantageously, the covering 8 of the working surface 5 is
chosen from the group constituted by woven fabric, knitted fabric
and non-woven fabric.
[0081] In the case where a woven fabric or a knitted fabric is
used, the fabric yarns include the fibrous metallic material.
[0082] More advantageously, the fibrous metallic material is a
fabric.
[0083] Advantageously, the fibrous metallic material has a weight
of between 500 and 1500 g/m2.
[0084] More advantageously, the fabric comprises yarns that extend
substantially in the longitudinal direction of the toothed belt. As
a rule, these longitudinal yarns are weft yarns.
[0085] In the case where the transmission belt is a toothed belt,
the longitudinal yarns including the fibrous metallic material are
substantially parallel to the inserts 3.
[0086] Advantageously, the fabric comprises longitudinal yarns and
transverse yarns both including the fibrous metallic material.
[0087] Alternatively, the transverse yarns include a material
chosen from the group constituted by polyamides and polyesters.
More advantageously, the transverse yarns include polyamides, even
more advantageously aromatic polyamides such as para-aramids or
meta-aramids for example, e.g. materials sold under the Conex
registered trademark.
[0088] Advantageously, the longitudinal yarns comprise composite
yarns formed by at least two yarns.
[0089] More advantageously, the yarns comprise at least one elastic
yarn around which at least one yarn including metallic fibres is
wound.
[0090] The covering fabric 8 of the toothing 4 can be formed by one
or more layers and can be obtained via different weaving
techniques, for example, preferably twill weaving, even more
preferably 2.times.2 twill weaving.
[0091] For example, in a first embodiment of the present invention,
the covering fabric 8 has a structure constituted by longitudinal
yarns forming the weft and transverse yarns forming the warp, in
which at least the weft is constituted by yarns including metallic
fibres.
[0092] Advantageously, the yarns include metallic fibres for at
least 25% by weight and, even more preferably, could be made
entirely of metallic fibres.
[0093] Optionally, the warp is also constituted by warp yarns
including metallic fibres.
[0094] In a second embodiment of the present invention, the
covering fabric 8 has a structure constituted by longitudinal yarns
forming the weft and transverse yarns forming the warp, in which at
least the weft has a composite structure, i.e. constituted by weft
yarns each formed from an elastic yarn as the core and a pair of
composite yarns wound around the elastic yarn; each composite yarn
comprises a yarn of high thermal and mechanical resistance and at
least one covering yarn wound around the yarn of high thermal and
mechanical resistance. The elastic yarn is made, for example, of
polyurethane. The yarn of high thermal and mechanical resistance is
made, for example, of para-aromatic polyamide. The covering yarn is
made of metallic fibres.
[0095] In a third embodiment of the present invention, the covering
fabric 8 has a structure constituted by longitudinal yarns forming
the weft and transverse yarns forming the warp, in which at least
the weft has a composite structure, i.e. constituted by weft yarns
each formed from an elastic yarn as the core around which a yarn of
high thermal and mechanical resistance is wound. A covering yarn is
subsequently wound on the yarn of high thermal and mechanical
resistance. The elastic yarn is made, for example, of polyurethane.
The yarn of high thermal and mechanical resistance is made, for
example, of para-aromatic polyamide. The covering yarn is made of
metallic fibres.
[0096] According to a preferred embodiment of the present
invention, the woven, knitted, or non-woven covering fabric of the
working surface 8 of the transmission belt 1 is treated with at
least a first and/or second protection or adhesion enhancement
treatment.
[0097] Advantageously, it is subjected to a first protection or
adhesion treatment, for example, with RFL.
[0098] More advantageously, it is also subjected to a second
protection treatment comprising a second elastomeric material
different from or the same as that forming the body of the
belt.
[0099] More advantageously, the second protection treatment also
comprises an anti-friction material, for example, chosen from the
group constituted by copper powder, molybdenum sulphide, graphite
and a fluorinated homopolymer or copolymer or mixture thereof.
[0100] Even more advantageously, the anti-friction material is
PTFE.
[0101] Advantageously, one or more copolymers formed from a monomer
containing nitrile groups and a diene are used as the second
elastomeric material.
[0102] Advantageously, the monomers containing nitrile-groups are
in a percentage in the range between 15% and 60% with respect to
the entirety of end copolymers.
[0103] More advantageously, they are between 15% and 25% by weight
for cold applications with temperatures down to -40.degree. C.,
between 33% and 39% by weight for belts with dry applications and
between 39% and 51% by weight for in-oil applications.
[0104] Even more advantageously, for in-oil applications they are
between 34% and 49% by weight, while for dry applications also
suitable for low-temperature starting they are between 19% and 23%
by weight, for example 21% by weight.
[0105] More advantageously, the copolymer(s) used are nitrile
rubbers, advantageously acrylonitrile butadiene rubbers, known by
the acronym NBR. Even more advantageously, they are hydrogenated
acrylonitrile butadiene or HNBR, or even XHNBR, i.e. carboxylated
hydrogenated acrylonitrile butadiene.
[0106] By opportunely choosing the quantities of the materials of
which it is composed, the protection treatment can form a covering
coating 9, distinct and separate from the fibrous material, also
referred to hereinafter as the wear-resistant coating 9. The
wear-resistant coating 9 constitutes the working surface of the
belt and therefore further increases wear resistance and avoids oil
absorption.
[0107] Advantageously, PTFE is present in the wear-resistant
coating in a larger phr quantity than the second elastomeric
material.
[0108] The gauge of the wear-resistant coating 9 is advantageously
between 0.03 mm and 0.2 mm.
[0109] The wear-resistant coating 9 can be placed over the covering
fabric 8 in different ways. Preferably, it is placed by means of a
calendering step.
[0110] Preferably, to ensure the necessary resistance, the
wear-resistant coating 9 weighs between 50 and 400 gr/m.sup.2.
[0111] Preferably, the back 7 of the belt is also covered by a
fibrous covering material, preferably the same as that previously
described.
[0112] In one aspect of the present invention, the inserts 3 are
formed by a plurality of filaments or yarns and each yarn is formed
by a plurality of filaments.
[0113] Advantageously, each insert 3 comprises between 3 and 20
yarns.
[0114] Even more advantageously, each insert 3 comprises between 5
and 15 yarns twisted together. For example, the embodiment in which
there are 11 yarns proved to be particularly preferred.
[0115] More advantageously, each yarn comprises between 50 and 500
filaments. Even more advantageously, between 100 and 300 filaments,
for example 200.
[0116] Even more preferable, each filament is made from metallic
fibres having a diameter of between 10 and 15 micron. For example,
the embodiment in which the diameter of the single fibres forming
the filaments is 12 micron proved to be particularly preferred.
[0117] In an alternative preferred embodiment of the invention, the
inserts 3 also comprise a second fibrous material.
[0118] The second fibrous material used for producing the inserts 3
is preferably chosen from a group composed of glass fibres, aramid
fibres, polyester fibres, carbon fibres and PBO fibres.
[0119] The fibrous metallic material preferably has a higher
modulus than the second material and the second material is
preferably wound around the fibrous metallic material.
[0120] The second material is preferably chosen so as to solve
problems of compatibility with the compound of the surrounding
body.
[0121] In section, the second material preferably occupies an area
of between 15% and 75% with respect to the overall surface of the
section. Even more preferably, the second material occupies an area
of between 45% and 55% with respect to the overall surface.
[0122] Preferably, the inserts according to the present invention
have a twist of the Lang's twist type, namely they have two twists
in the same direction, as this this construction has been found to
be particularly effective.
[0123] It is possible to vary the number of filaments or yarns that
form a durable insert, as well as the number of base filaments or
the count or the entire construction of the insert without
departing from the present invention.
[0124] Preferably, the fibres forming the cord are treated with
HNBR latex vulcanized with water-soluble peroxides by means of the
procedure illustrated in patent WO2004057099 in the name of Nippon
Glass.
[0125] Preferably, the treatment therefore comprises a treatment
liquid, preferably an aqueous adhesive and consequently including
more than 50% water, comprising elastomeric latex material and a
vulcanization accelerator.
[0126] As a rule, the water portion evaporates during vulcanization
and only the latex remains on the finished belt.
[0127] Preferably, the latex comprises a third elastomeric material
including one or more copolymers formed from a monomer containing
nitrile groups and a diene in which the monomers containing nitrile
groups are in a percentage of between 30% and 39% by weight with
respect to entirety of end copolymers. More preferably, the nitrile
groups are in a percentage of between 30% and 32% by weight with
respect to entirety of end copolymers.
[0128] A transmission belt and, in particular, a toothed
transmission belt 1 according to the present invention are produced
using known manufacturing processes.
[0129] The transmission belts according to the present invention
are particularly suitable for being used in systems in direct
contact with or partially immersed in oil, in particular engine oil
at high temperatures, such as those reached in recently developed
engines, for example even higher than 130.degree., and inside the
vehicle's engine crankcase. In particular, excellent results have
been achieved in the case where the belt is used as a replacement
for traditional gear or chain systems, systems in which the belt is
exposed for its entire working life to continuous contact with oil
spray or is possibly partially immersed in an oil bath.
[0130] In this case, when a covering fabric 10 is present on the
back, it is quite advantageous to carry out the adhesive treatment
and/or the protection treatment on the back 7 of the transmission
belt as well. In this case, the treatment enables preventing oil
penetration from the back 7 of the toothed belt 1 as well, and is
particularly advantageous when the toothed belt 1 is used in
control systems in which the back 7 of the belt is in contact with
shoes or tensioners. In fact, in these systems oil remains
interposed between the contact surface of the shoe or tensioner
with the belt and the back of the belt and therefore penetration
inside the mixture that constitutes the body would be favoured.
[0131] Preferably, the toothed belt 1 can be treated on all the
outside surfaces and, in particular, on the sides where the body
mixture is most exposed to attack by oil, with a swelling resistant
rubber, for example ENDURLAST (registered trademark of Lord).
[0132] The belt 1 according to the present invention is
advantageously used, for example, in a timing control system for a
motor vehicle of the type depicted in FIG. 2. The timing control
system is indicated as a whole in the figure by reference numeral
11 and comprises a drive pulley 12 rigidly fastened to the
driveshaft, not shown, a first 13a and a second 13b driven pulley
and a tensioner 14 for tensioning the toothed belt.
[0133] According to a second alternative embodiment, shown in FIG.
3, a toothed belt according to the present invention is indicated
by reference numeral 1, this belt having toothing on both faces and
therefore a covering 8 on one or both of the toothings.
[0134] The timing control system is indicated as a whole in the
figure by reference numeral 21 and comprises a drive pulley 22
rigidly fastened to the driveshaft, not shown, a first 23a, a
second 23b and a third 24 driven pulley.
[0135] According to a third embodiment of the present invention,
shown in FIG. 4, a toothed belt 1 according to the present
invention can advantageously be used in a timing control system
indicated as a whole in the figure by reference numeral 31, which
comprises a drive pulley 32 rigidly fastened to the driveshaft, not
shown, a first 33a and a second 33b driven pulley, a shoe tensioner
34 and a shoe 35.
[0136] In particular, the transmission belt of the present
invention has proved to be particularly effective when used in a
transmission system commonly referred to as balance shafts.
[0137] In use, the toothed belts 1 in the respective control
systems 11, 21 and 31 are in direct contact with oil.
[0138] FIGS. 2 to 4 refer to control systems related to the
movement of balance countershafts, but it is clear that the belt
according to the present invention can also be used in so-called
cam-to-cam systems or for driving the oil pump. In these cases, the
belt becomes partially immersed in an oil bath during
operation.
[0139] Furthermore, it is also possible to use the belt of the
present invention in the main transmission for driving cams and
also for driving the injection pump in diesel engines.
[0140] It has been experimentally verified that the use of the
fabric and inserts according to the present invention enables
achieving effective oil resistance even at high temperatures and
consequently enables passing the endurance tests to which toothed
belts are subjected in order to be used in motor vehicles and
therefore avoids all the belt problems when used in contact with
oil and, in particular, the fall-off in mechanical characteristics,
less adhesion, worse meshing and less wear resistance.
[0141] Alternatively, the belt according to the present invention
can also be used as a dry belt for engine timing.
[0142] From examination of the characteristics of the belt produced
according to the present invention, the advantages that can be
achieved with it are evident.
[0143] Advantageously, the above-described belts can consequently
be used for both dry and in-oil high-temperature applications, even
in the presence of contaminants, for example green fuels, which are
particularly aggressive.
* * * * *