Patent Application
20140202604
1. Field
Disclosed herein are tires and, more particularly, tires designed to be fitted to light vehicles with low energy consumption.
2. Description of Related Art
Most tires for passenger vehicles comprise a textile carcass reinforcement the reinforcing elements of which are oriented radially, as well as two crown reinforcements. Each of the crown reinforcements comprises reinforcing elements (metal cords) oriented at an angle of about 22° with respect to the circumferential direction.
Sometimes, the crown reinforcements are surmounted by a hooping reinforcement formed of reinforcing elements that are oriented substantially circumferentially.
For fitting to low energy consumption vehicles such as, for example, the so-called “Urban Concept” vehicles taking part in the Shell Eco-Marathon or the solar-powered vehicles taking part in the World Solar Challenge organized in Australia, tire designers have generally opted for simplified and lighter-weight designs. They have notably used tires comprising a single radial carcass reinforcement, surmounted by a crown reinforcement made up of two crossed plies. Each of these plies is reinforced with threadlike metal reinforcing elements which are parallel within each ply and crossed from one ply to the other, making an angle of ±22° with the circumferential direction.
While these tires have actually made it possible to obtain very low rolling resistance, their cornering stiffness is unsatisfactory under certain driving conditions, and their resistance to damage (puncturing, knocks, also known as road hazards) is sometimes insufficient.
One of the objectives of embodiments of the present invention is to obtain tires designed to be fitted to low energy consumption vehicles that have excellent rolling resistance while at the same time making it possible to obtain a cornering stiffness suited to these vehicles.
This objective is achieved using a tire designed to be fitted to a light vehicle, comprising:
two beads designed to come into contact with a mounting rim, each bead comprising at least one annular reinforcing structure;
two side walls extending the beads radially outwards, the two side walls meeting in a crown;
at least one carcass reinforcement anchored in the beads and extending from the beads, through the side walls as far as the crown, the carcass reinforcement comprising a plurality of carcass reinforcing elements, these carcass reinforcing elements being textile and oriented radially;
a crown reinforcement consisting of a fabric of textile reinforcing elements, wherein the fabric is obtained by interlacing, in the same plane, reinforcing elements, that are laid in a first direction and reinforcing elements, that are laid in a second direction perpendicular to the first direction, the fabric being arranged in the tire in such a way that the first direction makes an angle greater than or equal to 40° and less than or equal to 50° with the circumferential direction and that the second direction makes an angle greater than or equal to −50° and less than or equal to −40° with the circumferential direction, which reinforcement is surmounted by a tread;
the crown further comprising a textile hooping reinforcement, the hooping reinforcement being formed of reinforcing elements that are oriented circumferentially.
According to a first preferred embodiment, a tire according to an embodiment of the invention comprises a single carcass reinforcement, in order to reduce its weight.
According to a second preferred embodiment, the fabric of textile reinforcing elements is made of nylon, because such a fabric, which can undergo a great deal of elongation before breaking, is more resistant to road hazards.
According to a third preferred embodiment, the hooping reinforcement is made of aramid. This is because this textile is stiff enough for well withstanding tension in the crown region.
According to a fourth preferred embodiment, the tire has no “inner liner”, i.e. a butyl-based rubber layer, impermeable to the inflating gas, coating the interior surface of the tire, as this makes the tire lighter. As a matter of fact, the usual rubber compounds used in the manufacture of the tires are sufficiently impermeable to the inflation gases to allow the tire to be used in trials of the Shell Eco-Marathon or World Solar Challenge type without the need for very frequent re-inflation.
According to a fifth preferred embodiment, the tread comprises a tread pattern and the radial height of the tread pattern in the new condition is less than or equal to 5 mm, and preferably less than or equal to 2 mm. Such heights of tread pattern contribute to reducing the rolling resistance.
Of course, it may be advantageous to combine several or even all of the preferred embodiments.
In the use of the word “radial” it is appropriate to make a distinction between the various different uses that the person skilled in the art makes of that word. First, the expression refers to a radius of the tire. It is in this sense of the word that a point P1 is said to be “radially inside” a point P2 (or “radially on the inside of” point P2) if it is closer to the axis of rotation of the tire than is point P2. Conversely, a point P3 is said to be “radially outside” a point P4 (or “radially on the outside of” point P4) if it is further away from the axis of rotation of the tire than is point P4. Progress is said to be being made “radially inwards (or outwards)” when it is being made in the direction of smaller (or larger) radii. Where radial distances are concerned, it is this sense of the word that also applies.
By contrast, a thread or reinforcement is said to be “radial” when the thread or the reinforcement elements of the reinforcement make an angle greater than or equal to 80° and less than or equal to 90° with the circumferential direction. Let us specify that, in this document, the term “thread” is to be understood in a very general sense and comprises threads in the form of monofilaments, multifilaments, cords, yarns or an equivalent assembly, and irrespective of the material of which the thread is made or of the surface treatment which it has undergone in order to enhance its bonding to the rubber.
Finally, a “radial section” or “radial cross section” here means a section or cross section on a plane containing the axis of rotation of the tire.
An “axial” direction is a direction parallel to the axis of rotation of the tire. A point P5 is said to be “axially inside” a point P6 (or “axially on the inside of” point P6) if it is closer to the mid plane of the tire than is point P6. Conversely, a point P7 is said to be “axially outside” a point P8 (or “axially on the outside of” point P8) if it is further from the mid plane of the tire than is point P8. The “mid plane” of the tire is the plane perpendicular to the axis of rotation of the tire and situated equidistant between the annular reinforcing structures of each bead.
A “circumferential” direction is a direction which is perpendicular both to the radius of the tire and to the axial direction.
Within the context of this document, the expression “rubber composition” denotes a rubber composition containing at least one elastomer and one filler.
A “tire designed to be fitted to a light vehicle” here means a tire capable of bearing a load of the order of 100 kg but not exceeding 200 kg and the mass of which tire is less than or equal to 5 kg and preferably less than or equal to 2 kg.
When it is said of a fabric that its reinforcing elements are “oriented at ±45° with respect to the circumferential direction”, that means that the fabric is obtained by interlacing, in the same plane, threads that are laid in a first direction and threads that are laid in a second direction perpendicular to the first direction, the fabric being arranged in the tire in such a way that the first direction makes an angle greater than or equal to 40° and less than or equal to 50° with the circumferential direction and that the second direction makes an angle greater than or equal to −50° and less than or equal to −40° with the circumferential direction.
As used in this document, “textile” refers to one or more fibers or portions of fibers that are suitable for being arranged relative to other fibers or other parts of the same fiber to form a fabric, and includes natural and synthetic fibers, in particular, polymeric fibers such as nylons, polyesters, and the like, as well as inorganic fibers, such as carbon fiber and the like.
The tire 10 further comprises a carcass reinforcement 60 which extends from the beads 20, through the side walls 30, as far as the crown. This carcass reinforcement 60 here comprises threadlike reinforcing elements oriented substantially radially, that is to say making an angle greater than or equal to 80° and less than or equal to 90° with the circumferential direction.
The carcass reinforcement 60 comprises a plurality of carcass reinforcing elements; it is anchored in the two beads 20 by being wrapped around the bead wire 70, so as to form, in a known way, a main portion and a wrapped-around portion within each bead.
The reference 110 denotes the layers of rubber compound designed to reinforce the shoulders of the tire. The mid plane of the tire is indicated with the reference 130.
While such tires have actually made it possible to obtain a very low rolling resistance, their corner stiffness is unsatisfactory under certain driving conditions.
One of the objectives of the present invention is to obtain tires designed to be fitted to low energy consumption vehicles that have excellent rolling resistance while at the same time making it possible to obtain a cornering stiffness suited to these vehicles.
This objective, as well as others, is achieved by a tire according to an embodiment of the invention, which is depicted in
The crown reinforcement 180 is surmounted by a hooping reinforcement 100, desirably made of aramid and formed of reinforcing elements oriented circumferentially.
This is an individual thread placed at 0° with respect to the circumferential direction. It is not mandatory to use aramid, but it is advisable to use a material that has a ply rupture strength of at least 400 daN/cm, the purpose of this being to avoid the crown bursting if the tire is inflated well beyond its service pressure.
The hooping reinforcement is surmounted by a tread 40. It will be noted that, in the illustrated embodiment, the tire has no butyl-based rubber composition layer covering the interior surface of the tire. It will further be noted that, in this instance, the hooping reinforcement is positioned radially on the outside of the crown reinforcement and that the hooping reinforcement extends axially beyond the crown reinforcement. These are exemplary embodiments, however, and the disclosure herein contemplates other embodiments, such as those where the hooping reinforcement is positioned radially on the inside of the crown reinforcement and/or where the crown reinforcement extends axially beyond the hooping reinforcement.
The tread comprises a tread pattern (not depicted); the radial height of the tread pattern in certain of the embodiments described herein is less than or equal to 5 mm, and preferably less than or equal to 2 mm.
In order to demonstrate the advantages obtained with a tire according to an embodiment of the invention, a reference tire with the design depicted in
The following table shows the rolling resistance (“RR”) values obtained. The rolling resistance is substantially unchanged, with perhaps a small advantage for the tires according to an embodiment of the invention. These values were obtained using a method similar to the ISO 28580 method, using the following special conditions: load 70 daN, pressure 5 bar, speed 30 and 90 km/h.
The behavior of the tires was compared in subjective tests carried out on the high-speed oval circuit at the DRW Test Centre at Lalystad (the Netherlands). The evaluation program included maneuvers in a straight line such as slalom, lane changes or avoidance maneuvers, at speeds of between 80 and 120 km/h. The same make and model of three-wheeled vehicle were used to test each set of tires, which were mounted on the vehicles in sets of three identical new tires, and experienced test drivers were used for each vehicle. The test was conducted in a “blind” fashion, in that the test drivers gave their impressions with regard to linearity, gain, lag, etc., without knowing the design of the tire. The results of these tests revealed that the tire according to an embodiment of the invention (i.e., the tire shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 1156332 | Jul 2011 | FR | national |
This application is a 371 of PCT/EP2012/063531, filed 11 Jul. 2012, which claims benefit of FR1156332, filed 12 Jul. 2011, and U.S. Ser. No. 61/544,089, filed 6 Oct. 2011, the entire contents of each of which is incorporated by reference herein for all purposes.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/063531 | 7/11/2012 | WO | 00 | 3/21/2014 |
| Number | Date | Country | |
|---|---|---|---|
| 61544089 | Oct 2011 | US |
