TEZUKA TAKASHI (JP)
PAGANO SALVATORE (FR)
MICHELIN RECH TECH (CH)
XUE BOYONG (JP)
TEZUKA TAKASHI (JP)
PAGANO SALVATORE (FR)
JP2001130222A | 2001-05-15 | |||
JP2001071723A | 2001-03-21 | |||
JPH04368203A | 1992-12-21 | |||
JP2012007068A | 2012-01-12 | |||
US20070238829A1 | 2007-10-11 | |||
JP2012512090A | 2012-05-31 |
CLAIMS 1. A pneumatic tire comprising a summit prolonged by two sidewalls, the sidewalls being ended by two beads, the summit comprising a tread having a rolling surface intended to come into contact with a ground surface during the running of the pneumatic tire, the pneumatic tire having a carcass reinforcement passing into the summit and the sidewalls and being anchored in the beads, the summit being reinforced by a crown reinforcement placed circumferentially between the carcass reinforcement and the tread, the summit further comprising one tube or a plurality of tubes each extending circumferentially at least along one complete turn, each tube being partially or totally filled with a liquid, wherein: - each tube is located radially between the crown reinforcement and the rolling surface; - more than 80% of the sum of the internal volume(s) of the tube(s) is filled with the liquid. 2. The pneumatic tire according to Claim 1 , wherein the liquid is a polymer. 3. The pneumatic tire according to Claim 1 or Claim 2, wherein the molecular weight expressed in number (Mn) of the liquid is between 300 and 50000 g/mol. 4. The pneumatic tire according to any one of Claims 1 to 3, wherein the Brookfield Viscosity of the liquid is from 0.1 to 100 Pa.s within a range from 40 to 60 °C. 5. The pneumatic tire according to any one of Claims 1 to 4, wherein the liquid is chosen from the group consisting of liquid polybutadienes, liquid polyisoprenes, liquid copolymers of butadiene and styrene and mixtures thereof. 6. The pneumatic tire according to any one of Claims 1 to 5, wherein at least 90% of the sum of the internal volume(s) of the tube(s) is filled with the liquid. 7. The pneumatic tire according to any one of Claims 1 to 6, wherein the liquid further comprises particles. 8. The pneumatic tire according to Claim 7, wherein the particles are chosen from the group consisting of inorganic material, organic material and mixtures thereof. 9. The pneumatic tire according to Claim 7 or Claim 8, wherein the median size by weight of the particle is from 1 urn to 1 mm. 10. The pneumatic tire according to any one of Claims 7 to 9, wherein the shape of the particles is in the form of a powder, microbeads, granules, balls or mixtures thereof. 11. The pneumatic tire according to any one of Claims 1 to 10, wherein the density of the liquid is between 0.70 and 2.20 g/cm3. 12. The pneumatic tire according to any one of Claims 1 to 11, wherein each tube is made of a material having a Shore A hardness at least equal to 30. 13. The pneumatic tire according to any one of Claims 1 to 12, wherein each tube is made of at least an elastomer. 14. The pneumatic tire according to Claim 13, wherein the elastomer is chosen from the group consisting of diene elastomers, thermoplastic elastomers and mixture thereof. 15. The pneumatic tire according to Claim 13 or 14, wherein each tube is made of a rubber composition comprising at least an elastomer and an additive. |
Title of Invention: A TIRE IMPROVED IN NOISE
FIELD OF THE INVENTION
[0001] The present invention relates to pneumatic tires for motor vehicles and to technical solutions for reducing the noise, in particular the outside noise, emitted by said tires during the running of the vehicles.
BACKGROUND
[0002] It is known that the noise emitted by a tire during rolling originates, inter alia, from the vibrations of its structure following the contact of the tire with the irregularities of the road, also causing a generation of various acoustic waves. The waves are finally perceived in the form of noise, both inside and outside the vehicle. The amplitude of these various manifestations is dependent on the intrinsic modes of vibration of the tire, but also on the nature of the surface on which the vehicle is travelling. The range of frequencies corresponding to noise generated by tires extends typically from 20 to 4000 Hz approximately.
[0003] As regards the noise perceived inside the vehicle, two modes of sound propagation coexist:
- the vibrations are transmitted by the wheel center, the suspension system and the transmission to finally generate noise in the passenger compartment; this is referred to as solid-route transmission, which is generally dominant for the low frequencies of the spectrum (up to about 400 Hz);
the acoustic waves emitted by the tire are directly propagated via the aerial route into the vehicle, the vehicle acting as a filter; this is referred to as aerial- route transmission, which is generally dominant in the high frequencies (about 600 Hz and above).
[0004] The noise known as "road noise" rather makes reference to the overall level perceived in the vehicle and over a frequency range of up to 2000 HZ. The noise known as "cavity noise" refers to the nuisance caused by the resonance of the inflation cavity of the tire casing.
[0005] As regards the noise emitted outside the vehicle, various interactions between the tire and the road surfacing and between the tire and the air are pertinent, and will be a nuisance to people in the vicinity of the vehicle when it is rolling on a road. In this case, several sources of noise are also distinguished, such as the "indentation" noise due to the impact of the unevenness of the road in the area of contact, the "friction" noise essentially generated on leaving the area of contact, the "profile" noise due to the arrangement of the profile elements and to the resonance in the various grooves. The specific range of frequencies concerned by these outside noises corresponds herein typically to a range of from 300 to 3000 HZ approximately.
[0006] During their research studies, the applicants have discovered a new solution, which makes it possible to reduce the noise emitted outside the vehicles during the running of the tires (called coast-by noise in the present document).
SUMMARY OF THE INVENTION
[0007] Thus, a first subject matter of the present invention is (1) a pneumatic tire comprising a summit prolonged by two sidewalls, the sidewalls being ended by two beads, the summit comprising a tread having a rolling surface intended to come into contact with a ground surface during the running of the pneumatic tire, the pneumatic tire having a carcass reinforcement passing into the summit and the sidewalls and being anchored in the beads, the summit being reinforced by a crown reinforcement placed circumferentially between the carcass reinforcement and the tread, the summit further comprising one tube or a plurality of tubes each extending circumferentially at least along one complete turn, each tube being partially or totally filled with a liquid, wherein each tube is located radially between the crown reinforcement and the rolling surface, and more than 80% of the sum of an internal volume(s) of the tube(s) is filled with the liquid.
[0008] Moreover, aspects of the present invention can be as follows.
(2) The pneumatic tire according to (1), wherein the liquid is a polymer.
(3) The pneumatic tire according to (1) or (2), wherein the molecular weight expressed in number (Mn) of the liquid is between 300 and 50000 g/mol.
(4) The pneumatic tire according to any one of (1) to (3), wherein the Brookfield Viscosity of the liquid is from 0.1 to 100 Pa.s within a range from 40 to 60 °C.
(5) The pneumatic tire according to any one of (1) to (4), wherein the liquid is chosen from the group consisting of liquid polybutadienes, liquid polyisoprenes, liquid copolymers of butadiene and styrene and mixtures thereof.
(6) The pneumatic tire according to any one of (1) to (5), wherein at least 90% of the sum of the internal volume(s) of the tube(s) is filled with the liquid.
(7) The pneumatic tire according to any one of (1) to (6), wherein the liquid further comprises particles.
(8) The pneumatic tire according to (7), wherein the particles are chosen from the group consisting of inorganic material, organic material and mixtures thereof.
(9) The pneumatic tire according to (7) or (8), wherein the median size by weight of the particle is from 1 μηι to 1 mm. (10) The pneumatic tire according to any one of (7) to (9), wherein the shape of the particles is in the form of a powder, microbeads, granules, balls or mixtures thereof.
(11) The pneumatic tire according to any one of (1) to (10), wherein the density of the liquid is between 0.70 and 2.20 g/cm .
(12) The pneumatic tire according to any one of (1) to (11), wherein each tube is made of a material having a Shore A hardness at least 30.
(13) The pneumatic tire according to any one of (1) to (12), wherein each tube is made of at least an elastomer.
(14) The pneumatic tire according to (13), wherein the elastomer is chosen from the group consisting of diene elastomers, thermoplastic elastomers and mixture thereof.
(15) The pneumatic tire according to (13) or (14), wherein each tube is made of a rubber composition comprising at least an elastomer and an additive.
[0009] In any case and irrespective of the above aspects of the invention, the tube(s) placed on an inside of the summit of the pneumatic tire of the invention, which is not visible from the outside of the pneumatic tire.
[0010] The pneumatic tires of the present invention are particularly intended to equip passenger motor vehicles, including 4x4 (four-wheel drive or all- wheel drive) vehicles and SUV (Sport Utility Vehicles) vehicles, two-wheel vehicles (in particular motorcycles), and also industrial vehicles in particular chosen from vans and heavy-duty vehicles (i.e., underground vehicles, bus vehicles or heavy road transport vehicles (lorries, tractors, trailers)), or off-road vehicles, such as agricultural vehicles or earthmoving equipment.
[0011] The invention relates to the above tires both in the uncured state (i.e. before curing) and in the cured state (i.e.after crosslinking or vulcanization). [0012] The invention and its advantages will be readily understood in light of the description and exemplary embodiments that follow, and also figures 1-2 relating to these embodiments which schematically show tire cross sectional views of different embodiments of pneumatic tires according to the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 shows a schematic view of a tire cross sectional view of an embodiment of this invention.
[0014] FIG. 2 shows a schematic view of a tire cross sectional view of another embodiment of this invention.
DEFINITIONS
[0015] In the present application, the following definitions are understood:
[0016] "axial": It is a direction parallel to the axis of rotation of the pneumatic tire; this direction may be "axially interior" when it is oriented towards the inside of the pneumatic tire and "axially exterior" when it is oriented towards the outside of the pneumatic tire;
[0017] "radial": It is a direction that passes through the axis of rotation of the pneumatic tire and normal to the latter; this direction may be "radially internal (or inner)" or "radially external (or outer)" depending on whether it is oriented towards the axis of rotation of the pneumatic tire or towards the outside of the pneumatic tire;
[0018] "bead": It may be an essentially inextensible portion of the pneumatic tire internally radially adjacent to the sidewall and the base of which is intended to be mounted on a rim seat of a vehicle wheel; [0019] "sidewall": It is a portion of the pneumatic tire, usually of low flexural stiffness, prolonging the summit of the pneumatic tire and being ended by two beads, that is, being located between the summit and the bead;
[0020] "carcass reinforcement": It composes the pneumatic tire and passes into the summit and the sidewalls and is anchored in the beads. The carcass reinforcement is formed from at least one ply reinforced by radial textile and/or metallic cords, that is to say these cords are placed practically parallel to one another and extend from one bead to the other so as to form an angle of between 80 and 90 degrees with the median circumferential plane (plane perpendicular to the axis of rotation of the pneumatic tire which is located half way between the two beads and passes through the middle of the crown reinforcement mentioned below.
[0021] "crown reinforcement": It reinforces the summit of the pneumatic tire and is placed circumferentially between the carcass reinforcement and the tread of the pneumatic tire, and the crown reinforcement comprises a belt which generally consists of at least two superposed belt plies, occasionally referred to as "working" plies or "crossed" plies, whose elements are arranged virtually parallel to each other inside a ply, but crossed from one ply to another, i.e., inclined, symmetrically or non-symmetrically, relative to the median circumferential plane, by an angle that is generally between 10° and 45° depending on the type of tire under consideration. Each of these two crossed plies consists of a rubber matrix sometimes called "calendering rubber" coating textile and/or metallic reinforcements. In the belt, the crossed plies may be completed by various other auxiliary plies comprising reinforcements; mention will be made, in particular, of "protective" plies responsible for protecting the rest of the belt against external attack, perforations, or alternatively "hooping" plies comprising reinforcements oriented substantially to parallel to the circumferential direction of the pneumatic tire ("zero-degree" plies), that is to say making, with this direction, an angle that does not deviate by more than five degrees from the circumferential direction, whether they are radially outer or inner relative to the crossed plies.
[0022] "cut-out": the cut-out means either a groove or an incision or sipe. Incision or sipe is to be distinguished over groove by the fact that in the contact with the road incision is closing at least partially (its opposite walls contact each other).
[0023] "diene elastomer (or rubber)": It is an elastomer resulting at least in part (i.e. a homopolymer or a copolymer) from diene monomer(s) (i.e. monomer(s) bearing two carbon-carbon double bonds which may or may not be conjugated);
[0024] "thermoplastic elastomers (abbreviated to TPE)": the elastomers have a structure intermediate between thermoplastic polymers and elastomers. They are block copolymers composed of rigid thermoplastic sequences connected via flexible elastomer sequences, for example polybutadiene, polyisoprene, poly (ethylene/butylene) or else polyisobutylene. A softening point of the thermoplastic is measured in accordance with ISO-4625 (ring and ball method).
[0025] "number average molecular weight" (denoted by Mn): It may be determined by vapor phase osmometry (VPO) (in accordance with ASTM D 3592).
[0026] "Brookfield Viscosity": It characterizes, in a known way, liquid substances. The apparent viscosity according to the Brookfield method is measured at a given temperature (for example at 45° C) in accordance with European and International Standard EN ISO-2555 (1999) or JIS K7117-1. Use is made, for example, of a BH-type rotary viscometer.
[0027] "median size by weight of particles": Various known methods are applicable for the analysis of the particle size and the calculation of the median size of the particles (or median diameter for the particles assumed to be substantially spherical). Use is preferably made of an analysis of the particle size by mechanical sieving; the operation consists of sieving a defined amount of sample (for example 200 g) on a vibrating table for 30 min with different sieve diameters (for example, according to a progressive ratio equal to 1.26, with meshes of 1000, 800, 630, 500, 400, ... 100, 80, and 63 μηι); the oversize collected in each sieve is weighed on a precision balance; the % of oversize for each mesh diameter with respect to the total weight of product is deduced therefrom; the median size (or median diameter) or mean size (or mean diameter) is finally calculated in a known way from the histogram of the particle size distribution.
[0028] "shore A hardness": The Shore A hardness of the compositions after curing is assessed in accordance with Standard ASTM D 2240-86.
[0029] "density (or specific gravity)": The density (or the specific gravity) of liquid may be determined by liquid pycnometer method in accordance with JIS Z 8804.
[0030] Moreover, in the present description and unless expressly indicated otherwise, all the percentages (%) indicated are % by weight; similarly, any interval of values denoted by the expression "between a and b" represents the range of values of greater than "a" and of less than "b" (i.e. the limits a and b excluded) Whereas any interval of values denoted by the expression "from a to b" means the range of values going from "a" to "b" (i.e. including the strict limits a and b). DETAILED DESCRIPTION OF THE INVENTION
[0031] The pneumatic tire of the invention therefore has the essential feature of being provided with at least one tube or a plurality of tubes which is or are filled (partially to totally filled) with a liquid, wherein the total volume of liquid is more than 80% of the sum of the internal volume(s) of the tube(s), and wherein the tube(s) extends or extend circumferentially at least along one complete turn in the summit of the pneumatic tire, which is described in detail below.
- TUBE(S) - [0032] Each tube may be made of metal, polymer as for example plastic and/or rubber composition. It is preferably made of at least an elastomer, this elastomer being more preferably chosen from the group consisting of diene elastomers, thermoplastic elastomers and mixture thereof; still more preferably; each tube is made of a rubber composition comprising at least an elastomer and an additive.
[0033] According to a preferable embodiment of the invention, each tube is made of a diene elastomer rubber composition, with or without any reinforcing filler. Mention may in particular be made, by way of example, of tubes made of cured natural rubber (without filler) provided by Fuso rubber industry Co., Ltd.
[0034] According to another preferable embodiment of the invention, each tube is made of at least a thermoplastic elastomer having a softening point which is higher than the usual curing temperatures used for the pneumatic tires.
[0035] According to another preferable embodiment of the invention, each tube is made of a material having a Shore A hardness which is at least equal to 30 in order to prevent from worsening the steering stability of the pneumatic tire and/or decreasing the initial internal volume of each tube. The Shore A is preferably from 30 to 70, more preferably from 30 to 60, more still preferably from 30 to 50.
[0036] The external diameter (Li) of the tube(s) may be from 1 to 6 mm and the internal diameter (Mi) of the tube(s) may be from 0.5 to 5 mm although each diameter is dependent on size of the pneumatic tire. [0037] The tubes may be filled with a liquid by any equipment for inserting the liquid, for instance an injection system, and then one end of each tube may be jointed with the other end of said tube so that the liquid is hermetically closed inside the tube by the material forming the tube.
[0038] Each tube circumferentially extends at least along one complete turn (or revolution) and is radially located between the crown reinforcement (for instance, a steel and/or textile belt) and the rolling surface. Number of tubes may vary for example from 1 to 15. Number of turns for each tube may vary for example from 1 to 15 although each number is dependent on sizes of the pneumatic tire and the tube(s). A winding method of the tube(s) inside the pneumatic tires may be hoop winding and/or helical one.
- LIQUID FILLING IN THE TUBE(S) -
[0039] Preferably, at least 90%, more preferably at least 95% of the sum of the internal volume(s) of the tube(s) is filled with the liquid. Still more preferably, each tube is totally filled with the liquid because the liquid may absorb the indentation noise, which is one of causes of the coast-by noise, rather than that having each tube partially filled with an air because the impact between the road and the tread may be damped by the former rather than by the latter, and the former may keep the initial volume of each tube rather than the latter.
[0040] According to a preferable embodiment of the invention, the liquid is a liquid polymer. Liquid polymers resulting from the polymerization of dienes, such as, for example, those selected from the group consisting of polybutadienes (BR), polyisoprenes (IR), copolymers of butadiene and styrene (SBR), and the mixtures of these liquid diene polymers, are also suitable. The liquid polymer is preferably liquid BR.
[0041] The number-average molar mass of such liquid is preferably within a range extending between 300 and 50000 g/mol, more preferably between 500 and to 20 0000 g/mol and still more preferably between 700 and 10000 g/mol.
[0042] The Brookfield Viscosity of the liquid is preferably from 0.1 to 100 Pa.s within a range from 40 to 60 °C. Such liquids are well known and are commercially available, for example known as "B-1000" and "B-2000" (Liquid 1 ,2-Polybutadiene) provided by Nippon Soda Co., Ltd.
[0043] According to a more preferable embodiment of the invention, the liquid further comprises particles that are solid particles. These particles are preferably chosen from the group consisting of inorganic material (e.g. silicon carbide), organic material and mixtures thereof.
[0044] The median size by weight of the particle is preferably from 1 um to 1 mm. A shape of the particles is preferably in the form of a powder, microbeads, granules, balls or mixtures thereof.
[0045] Before the tube(s) are hermetically closed, the particles may be directly filled into the tube(s) by manual or the liquid comprising the particles may be filled into the tube(s) by any equipment for inserting the liquid.
[0046] According to a still more preferable embodiment of the invention, the density (or specific gravity) of the liquid (with or without the particles) is between 0.70 and 2.20 g/cm 3 , more preferably between 0.75 and 2.00g/cm 3 and still more preferably between 0.80 and 1.80 g/cm 3 . - TIRE OF THE INVENTION -
[0047] Each tube filled with the liquid, as described previously, is placed radially between the rolling surface and the crown reinforcement of the pneumatic tire of the invention. During the running of the pneumatic tire, the impact from the ground may travel to each filled tube through the rolling surface and the tread, and the impact may deform each filled tube. Then the liquid may circulate in each filled tube due to this deformation, and the impact may be damped without going to the crown reinforcement below each filled tube, which may prevent the impact from propagating the crown reinforcement to other tire parts (for instance sidewalls) and finally avoid the other tire parts from generating the coast-by noise. Also, it is therefore immediately understood that each tube filled with the liquid constitute an internal part of the tire, located on the very inside of its structure and not intended to come into contact with the road; in other words, the tubes(s) do not give onto the outside of the pneumatic tire, i.e. they are not visible from the outside of said tire in the new state.
[0048] The appended FIG. 1 very schematically (in particular not to a specific scale) represents, in radial cross section, a pneumatic tire (1) of dimension 205/55R16, width of a tread 164mm, and thickness of center of tread 8.4mm, the pneumatic tire (1) having radial carcass reinforcement, according to the invention.
[0049] In this FIG. 1, the pneumatic tire (1) shown schematically comprises a summit (2) prolonged by two sidewalls (5), the sidewalls (5) being ended by two beads (4), a carcass reinforcement (6) passing into the summit (2) and the sidewalls (5) and being anchored in the beads (4).
[0050] The summit (2) is, in a manner known per se, reinforced by a crown reinforcement (7) which is at least partly metallic and radially external with respect to the carcass reinforcement (6) passing into the summit (2), the crown reinforcement (7) being formed for example from at least two superposed crossed plies reinforced by metal cords.
[0051] The carcass reinforcement (6) is here anchored into each bead (4) by winding around the two bead wires (4a, 4b), the turn-up (6a, 6b) of this reinforcement (6) being for example positioned towards the axially outside of the pneumatic tire (1), which is shown here mounted on its rim (9).
[0052] Of course, this pneumatic tire (1) additionally comprises, in a known manner, an inner elastomer or rubber layer (commonly referred to as inner liner") that defines the radially inner face of the pneumatic tire and that is intended to protect the carcass ply from the diffusion of air coming from the space inside the pneumatic tire.
[0053] This FIG. 1 illustrates a possible embodiment of the invention, wherein six tubes (11) filled with the liquid extend circumferentially along one complete turn in the summit (2) and are located radially between a crown reinforcement (7) and surfaces of a tread (3) which the summit (2) comprises. The surfaces are intended to come into contact with a ground during the running of the pneumatic tire (1). The six tubes have an external diameter (Lj, L 2 , L 3 , L 4 , L 5 , L 6 : 5.8 mm) and an internal diameter (M 1; M 2 , M 3 , M 4 , M 5 , M 6 : 4.0mm). The four of the tubes (1 1) are located below the bottom of transverse cut-outs (10a, 10b) and above the crown reinforcement. The transverse cutouts (10a, 10b) have a bottom distance from the rolling surface by a distance (di : 2 mm).
[0054] In FIG. 1 , the width (Wl , W2) of each axial portion (3b, 3c) of the tread (2) provided with transverse cut-outs (10a, 10b) is 25mm.
[0055] In FIG. 1, a distance (d 2 ) from the radially outermost part of the tubes (11) to the bottom of the transverse cut-outs (10a, 10b) is 0.4 mm. [0056] In FIG. 1, the tubes (1 1) are made of cured natural rubber (without filler) provided by Fuso rubber industry Co., Ltd. The cured natural rubber has Shore A hardness equal to 35.
[0057] In FIG. 1, the tread (3) comprises three circumferential cut-outs (8a, 8b, 8c) extending, each circumferential (8a, 8b, 8c) cut-out having a bottom distant from the rolling surface by 5mm.
[0058] In the FIG. 1, the width (CW) of each circumferential cut-out (8a, 8b, 8c) is 5mm.
[0059] The pneumatic tire (1) according to the invention is characterized in that more than 80% of the sum of an internal volume(s) of the all tubes (11) is filled with the liquid and the tubes (11) are located radially between the crown reinforcement and the rolling surface as described in detailed above.
[0060] FIG. 2 illustrates another possible embodiment of the invention, six tubes (11) filled with a liquid extend in a summit (2) and are located circumferentially between a crown reinforcement (7) and surfaces of a tread (3) which the summit (2) comprises, the surfaces are intended to come into contact with a ground during the running of the pneumatic tire (1) and the all tubes (11) are located under transverse cutouts (10a, 10b). Each of the six tubes (11) has different distance to the rolling surface with others. That arrangement may make transverse rigidity of the summit of the pneumatic tire equivalent in parallel to maintain sound/vibration absorbability of the tubes. RUNNING TESTS
[0061] The goal of these tests is to compare a performance of anti-coast-by noise of three pneumatic tires according (denoted T-2, T-3 and T-4) to the present invention with a reference tire (denoted T-l) devoid of tubes.
[0062] T-2, T-3 and T-4 have a tire cross section shown in FIG. 1. In these examples, each tube is totally filled, by injection, with liquid 1,2-Polybutadiene (containing also particles of silicone carbide in case of tire T-4) as mentioned in Tables 1, 2 and as follows.
- T- 1 : A control pneumatic tire without tube;
- T-2: A pneumatic tire with six tubes according to the present invention, each of the six tubes filled with B-1000 (20 ml) having an average molecular weight (1100 g/mol) and a Brookfield viscosity (10 Pa · s);
- T-3: A pneumatic tire with six tubes according to the present invention, each of the six tubes filled with B-2100 (20ml) having higher an average molecular weight (2100 g/mol) and a Brookfield viscosity (62 Pa ■ s);
- T-4: A pneumatic tire with six tubes according to the present invention, each of the six tubes filled with B-1000 (20ml) and particles of Silicon carbide (40 g).
- Table 1
(1) A material of the tubes: Cured natural rubber (Fuso rubber industry Co., Ltd, Shore A: 35)
(2) B-1000: Liquid 1 ,2-Polybutadiene (Nippon Soda Co., Ltd)
(3) B-2000: Liquid 1,2-Polybutadiene (Nippon Soda Co., Ltd)
(4) Silicon carbide: "SICF 900" (Akzo Nobel; median size of particles by weight measured by mechanical sieving: approximately 100 μιη, Specific gravity by liquid pycnometer in accordance with ISO- 1183: 3.22g/cm 3 );
(5) Specific gravity (25°C/4°C) by liquid pycnometer in accordance with JIS Z8804
- Table 2
- (6) Number average molecular weight measured by VPO in accordance with
ASTM D3592
- (7) Brookfield Viscosity (45°C) measured by a BH-type rotary viscometer in
accordance with ISO-2555
[0063] One end of each tube was jointed with the other end of said tube in order to be hermetically closed. Each tube extended circumferentially along one complete turn and was placed radially between a crown reinforcement and the bottom of transverse cut-outs or a rolling surface of each of the pneumatic tires as shown in FIG. l.
[0064] The above pneumatic tires were conventionally manufactured with a size of
205/55 R16 and in all respects identical apart from the tubes. [0065] In order to compare the anti-coast-by noise performance between each invention tire (T-2, T-3 and T-4) and the reference one (T-l), machine rolling tests were performed by placing in contact (each tire under 180 kPa of inflation pressure of the pneumatic tire mounted on 6.5Jxl6 rim and subjected to 4.25 kN of load of the pneumatic tire) on the outer surface of a cylinder provided with a rough surface. The assembly is placed in a soundproof chamber (semi-anechoic). Several microphones are placed around the contact area to record the coast-by noise level during rolling, over a range of frequencies ranging from 500 to 2500 Hz, for a given rolling speed (80 km/hour).
[0066] The result from Table 3 express the differences in the recorded sound level between each of the pneumatic tires (T-2, T-3 and T-4) in accordance with the present invention and the control pneumatic tire (T-l), at a frequency range from 500 to 2500 Hz.
Table 3
(8) Difference between each of the invention tires and the reference tire
[0067] These differences are expressed as sound energy (dB(A)) which corresponds to the integration of the sound pressure as a function of the frequency at the frequency range in question, a negative value indicating a reduction in the noise relative to the control pneumatic tire (T-l). [0068] On reading Table 3, it is unexpectedly observed that, at the effective frequency range (500 to 2500Hz) typical of outside noise (coast-by noise), the pneumatic tires (T-2, T-3 and T-4) of the present invention emit much less noise than the control pneumatic tire (T-1), a reduction of from 1.1 to 2.3 dB(A) for example being considered as very significant for a person skilled in the art.
[0069] Such a result can of course only be attributed to the specific location of the tube(s) between the crown reinforcement and the rolling surface of the tread of the pneumatic tire of the present invention, and to the presence a liquid filling, according to the recommended volume fraction, said tubes.
[0070] In conclusion, the invention makes it possible to strongly reduce the outside noise emission due to the rolling of the pneumatic tires.
[0071] The invention is not limited to the examples described and represented and various modifications, for instance each tube has a cross section having a form chosen from the group consisting of circle, oval, triangle and quadrilateral, can be made there without leaving its framework as fixed by the following claims.
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