PNEUMATIC TYRE

Abstract

It is provided a pneumatic tyre (1) comprising: an inner surface (2), a tread portion (3), a pair of sidewall portions (4) radially inwardly extending from both edges of the tread portion (3), and bead portions (5) disposed at radially inner edges of the sidewall portions (4), and a sound absorbing device (6) made of a spongy material which is adhered to the inner surface (2) of the pneumatic tyre (1) at a tread region and extends in the tyre circumferential direction, wherein the sound absorbing device (6) comprises at least first and second sound absorbing members (7), wherein the at least first and second sound absorbing members (7) are separated from each other by a distance (S) in the axial tyre direction and are adhered to the inner surface (2) of the pneumatic tyre (1) by an adhesive component (8), wherein the adhesive component (8) comprises at least two annular- shaped adhesive beads (9) provided between each first and second sound absorbing member (7) and the inner surface (2) of the tyre (1), wherein the at least two adhesive beads (9) are arranged spaced apart from each other in the axial direction and extend in the circumferential direction of the tyre (1).

Claims

1. A pneumatic tyre comprising: an inner surface, a tread portion, a pair of sidewall portions radially inwardly extending from both edges of the tread portion, and bead portions disposed at radially inner edges of the sidewall portions, and a sound absorbing device made of a spongy material which is adhered to the inner surface of the pneumatic tyre at a tread region and extends in the tyre circumferential direction, wherein the sound absorbing device comprises at least first and second sound absorbing members, wherein the at least first and second sound absorbing members are separated from each other by a distance in the axial tyre direction and are adhered to the inner surface of the pneumatic tyre by an adhesive component, characterized in that the adhesive component comprises at least two annular shaped adhesive beads provided between each first and second sound absorbing member and the inner surface of the tyre, wherein the at least two adhesive beads are arranged spaced apart from each other in the axial direction and extend in the circumferential direction of the tyre.

2. The tyre according to claim 1, wherein each adhesive bead has a width (Wa) in the axial direction in a range of from 4 mm to 15 mm, and a height (Ha) in the radial direction in a range of from 0.5 mm to 4 mm.

3. The tyre according to claim 1, wherein the spongy material of the sound absorbing members comprises a polyurethane foam material having: a specific gravity in a range of from 0.022 to 0.032, or of from 10 to 25 pores per cm, or a permanent compression set of <10% (measured according to NF EN ISO 1856).

4. The tyre according to claim 1, wherein the first and second sound absorbing members are axially spaced by a distance (S) of from 10 mm to 20 mm.

5. The tyre according to claim 1, wherein the first and second sound absorbing members have a rectangular cross section having a height (Hs) in the radial direction from the inner surface, a width (Ws) in the axial direction and a length in the circumferential direction thereby defining for each member circumferential outer ends, wherein the height (Hs) of the sound absorbing members is in a range of 20 mm < Hs < 40 mm.

6. The tyre according to claim 1, wherein the width (Ws) of the sound absorbing members is of from 30 mm < Ws < 70 mm.

7. The tyre according to claim 1, wherein the circumferential outer ends of the first and second sound absorbing members provide a gap (G) of from 1 % to 5 % of the circumference of the tyre, based on 100% total circumference.

8. The tyre according to claim 1, wherein the circumferential outer ends of the first and second sound absorbing members are substantially devoid of a taper.

9. The tyre according to claim 1, wherein the sound absorbing device has a volume (Vs) in a range of from 6% to 18% of the total volume (Vc) of the tyre cavity.

10. The tyre according to claim 1, wherein the inner surface of the tyre is substantially devoid of silicone-based release agents and polytetrafluoroethylene (PTFE)-based release agents.

11. A wheel assembly comprising a pneumatic tyre assembled onto a wheel, characterized in that the tyre is a tyre according to claim 1.

12. A method of preparing a pneumatic tyre according to claim 1, comprising the steps of: - providing a tyre assembly comprising a mold for defining a shape of an outer wall of the tyre after vulcanizing-molding and a bladder for pressing an inner wall of a green tyre towards the mold during vulcanizing-molding, and providing in the mold a green tyre comprising an inner surface; - vulcanizing the green tyre in the tyre assembly by pressing the bladder against the inner surface; - providing an adhesive for adhering the sound absorbing device to the inner surface; - applying at least two annular- shaped adhesive beads onto the inner surface ; - providing a sound absorbing device comprising at least first and second sound absorbing members made of a spongy material to be adhered onto the inner surface ; and - placing the at least first and second sound absorbing members onto the adhesive beads and pressing so as to contact the sound absorbing device with the inner surface.

13. The method according to claim 12, wherein the green tyre is vulcanized using a permanently coated bladder or a bladder coated with a non-silicone or non polytetrafluoroethylene (PTFE) based release agent.

14. The method according to claim 12, wherein the green tyre is vulcanized using a permanently coated bladder and a bladder coated with a non-silicone or non polytetrafluoroethylene (PTFE) based release agent.

Description

[0045] In the drawings:

[0046] FIG. 1 schematically shows a wheel assembly comprising a pneumatic tyre according to one embodiment of the invention assembled onto a wheel.

[0047] FIG. 2 schematically shows an equator cross-sectional view of the pneumatic tyre according to the embodiment of FIG. 1.

[0048] As shown in FIG. 1, a wheel assembly comprises a pneumatic tyre 1 assembled onto a wheel 20. The pneumatic tyre 1 comprises an inner surface 2, a tread portion 3, and a pair of sidewall portions 4 radially inwardly extending from both edges of the tread portion 3. Bead portions 5 are disposed at radially inner edges of the sidewall portions 4. A sound absorbing device 6 made of a spongy material is adhered to the inner surface 2 of the pneumatic tyre 1 at a tread region and extends in the tyre circumferential direction. The sound absorbing device 6 comprises first and second sound absorbing members 7, wherein the sound absorbing members 7 are separated from each other by a distance S in the axial tyre direction. The distance S may be of from 10 mm to 20 mm, such as 15 mm in a passenger tyre. The sound absorbing members 7 have a rectangular cross section having a height Hs in the radial direction from the inner surface 2, a width Ws in the axial direction and a length Ls in the circumferential direction. The height Hs may be 30 mm < Hs < 33 mm. The width Ws may be 30 mm ≤ Ws ≤ 70 mm, such as 40 mm, 45 mm, 50 mm, 55 mm, 60 mm, 65 mm, or 70 mm.

[0049] The sound absorbing members 7 are adhered to the inner surface 2 of the pneumatic tyre 1 by an adhesive component 8. The adhesive component 8 comprises two annular-shaped adhesive beads 9 which are provided between each of the sound absorbing members 7 and the inner surface 2 of the tyre 1. The two adhesive beads 9 are arranged spaced apart from each other in the axial direction and extend in the circumferential direction of the tyre 1.

[0050] FIG. 2 illustrates an equator cross-sectional view of the pneumatic tyre according to the embodiment of FIG. 1. The sound absorbing members further have a length Ls in the circumferential direction thereby defining circumferential outer ends 7a, 7b. The circumferential outer ends 7a, 7b of the first and second sound absorbing members 7 provide a gap G of from 1% to 2% of the circumference of the tyre, based on 100% total circumference. Preferably, the circumferential outer ends 7a, 7b of the first and second sound absorbing members 7 are substantially devoid of a taper. When a plurality of sound absorbing members is provided, each gap G between the ends of the corresponding sound absorbing member may be displaced by a circumferential distance D between the gaps of preferably at least 10% of the circumferential extent of the tyre. The displacement D may be used in compensating a possible reduction of uniformity of the vulcanized tyre after vulcanization. The displacement may support maintaining endurance performance and high speed performance.

[0051] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

EXAMPLE 1: INTERIOR NOISE TESTS

[0052] Prototypes of tyres equipped with a sound absorbing device component were compared to a reference tyre. A set of inventive example E1 tyres were built having two sound absorbing members applied to the inner-liner of a 245/45R18 UHP summer tyre. The reference Ref 1 tyres were built having a sound absorbing component with one single sound absorbing member applied to the inner liner of a 245/45R18 UHP summer tyre.

[0053] The tyres were tested in an indoor test facility on a test machine with a rotating drum. One drum is used simultaneously driving both rear tyres. Only the rear-left tyre is changed between the tests. The rear right tyre is devoid of a sound absorbing device and is used as control tyre. A relative smooth surface of the drum was used. Both a coast-down of 145 - 20 km/h and three constant speed measurements (120, 80 and 60 km/h) were carried out. Resulting vibrations were measured with an accelerometer at the hub.

[0054] Noise levels inside the car were measured with a microphone. Also microphones were placed at outside locations to measure exterior noise. Measurement values are for the vibrations of the hub in x-, y- and z- direction, and the sound pressure levels.

[0055] The Close Proximity (CPX) method, standardized in ISO/DIS 11819-2, is used as the measurement method for tyre/road noise. The CPX method includes the measurement of the A-weighted sound pressure level generated by the tyre/road interaction over a specified road distance using at least two microphones in the vicinity of the reference tire. A-weighting is a standard method for altering the sound pressure levels recorded by a microphone to closely match the perception of the human ear.

[0056] The CPX setup is as follows. Two microphones are located on the side of the vehicle at a height of 10 cm above the road and a distance of 20 cm measured in the axial direction from the plane of the undeflected sidewall. A first front microphone is placed at a distance of 20 cm in a vehicle front direction from a target plane (CPX-Front). A rear microphone is placed at a distance of 20 cm measured in a vehicle rear direction from the target plane (CPX-Rear). The target plane is the plane containing the tyre axis and the tyre-road contact center-point.

[0057] The results and configuration details of the “Ref 1” as well as the inventive example “E1” are given in the Table 1 below. The peak reduction is the cavity noise peak reduction in the frequency range between 180 and 250 Hz at driver’s left ear position at 80 km/h.

TABLE-US-00001 Indoor measurements Ref 1 E1 # sound absorbing members 1 2 # of glue beads 4 4 Hs (mm) 30 30 Ws (mm) 120 50 S (mm) - 20 G (mm) 50 30 Foam density (+/- 2 kg/m3) 23 23 Peak reduction ( dB(A) ) 9.4 12.7

[0058] The two sound absorbing members in inventive example “E1” effectively reduce the tyre cavity noise, even more efficient than a concept with 20% higher volume of foam.

EXAMPLE 2: HIGH SPEED TESTS

[0059] All high speed tests were performed on prototype 245/45R18 UHP summer tyres. A set of inventive example E2 tyres were built having two sound absorbing members applied to the inner-liner of a 245/45R18 UHP summer tyre. Two reference tyres were built and used in the high speed tests. A first set Ref 2 of reference tyres were built having no sound absorbing component. A second set Ref 3 of reference tyres were built having one single sound absorbing member applied to the inner liner of a 245/45R18 UHP summer tyre.

[0060] The high speed test is a destructive test procedure measuring the total running time before failure of a tyre rotating against a drum. A Y rated tyre must pass the legal lower limit of 60 minutes running time according to the speed ramp up shown in Table 2. Table 2 displays the speed ramp used during a high speed test for a Y rated tyre. In Table 2, the running time is the time interval at the given speed, while total time is the accumulated duration of the test at the end of each interval. Table 3 shows the configuration of the prototype tyres and the results of the high speed test.

TABLE-US-00002 Speed ramp for a Y rated tyre Speed Running Time (minutes) Total test time (minutes) 260 10 10 270 20 30 280 10 40 290 10 50 300 10 60 310 10 70 320 10 80 330 10 90 340 10 100

TABLE-US-00003 Total running time at high speed Ref 2 Ref 3 E2 # sound absorbing members - 1 2 # of glue beads - 4 4 Hs (mm) - 30 30 Ws (mm) - 120 50 G (mm) - 12 30 S (mm) - - 20 Foam density (+/- 2 kg/m3) 23 23 23 Test duration (minutes) 87 58 83

[0061] The tests results reported in Table 3 show that a sound absorbing component comprising a single sound absorbing member according to the “Ref 3” tyres significantly deteriorates the high speed performance due to more heat buildup, especially in the tread portion around the tyre equatorial plane. Results in Table 3 show a similar high speed performance of “Ref 2” tyres without a sound absorbing component and the inventive example “E2” tyres.

EXAMPLE 3: ENDURANCE TESTS

[0062] The endurance test is a destructive indoor test measuring distance to failure. The test speed is 120 km/h. The test is ended at a survival distance of 30,000 km. Measurement is the total kilometers of running on a drum before tyre and/or foam failure.

[0063] Three sets of prototype tyres were built. Namely, a first set Ref 4 having 245/45R18 100Y UHP All Season tyres, a second set Ref 5 of 245/45R18 96W high performance tyres and a third inventive set E3 of 245/45R18 100Y UHP All Season tyres. All tyre sets were configured as shown in Table 4 having a sound absorbing device component.

TABLE-US-00004 Endurance measurements Ref 4 Ref 5 E3 # sound absorbing members 1 1 2 # of glue beads 4 4 4 Hs (mm) 30 30 30 Ws (mm) 120 100 50 S (mm) - - 20 G (mm) 50 0 30 Foam density (kg/m3) 23 +/- 2 20 - 30 23 +/- 2 16.800 km NOK NOK OK 30.000 km - - OK

[0064] “Ref 4” from Table 4 showed mixed results on foam adhesion but major failures after 16,800 km. “Ref 5” from Table 4 showed complete foam detachment after 16,800 km.

[0065] The inventive example “E3” tyre s reached the end of the test (30,000 km) with good result on endurance performance for the tyre and the adhesive interface.

EXAMPLE 4: BENDING TESTS

[0066] Two new sets of prototype tyres were built. Namely, a set of inventive example E4 245/45R18 100Y UHP All Season tyres and a set of inventive example set E5 of 235/55R19 (101Y) UHP summer tyres. Inventive examples “E4” and “E5” were configured having a sound absorbing device component with two sound absorbing members. The length of the sound absorbing member provides for an extent of 98% to 99% of the tyre circumference. The gap between the ends of the corresponding sound absorbing members was displaced by a circumferential distance D of about 10% of the circumferential extent of the tyre, also compensating uniformity values for the tyres. The Ref 1 tyres and the inventive E1 tyres were also included in the subjective bend test.

[0067] The sound absorbing members were made of a spongy material. The spongy material was a foam produced by Metzeler Schaum GmbH. The adhesive component in the inventive examples was configured having two beads of adhesive material per sound absorbing member. The adhesive material was a Loctite SI 5930 FIT provided by Henkel. The width Wb of the adhesive beads was between 8 and 9 mm. Each bead was configured having different circumferential positions for the starting point of each bead application. Tyres were vulcanized in a vulcanizing press having a permanently coated bladder without bladder paint.

[0068] A test of internal bending stress was made by examining the shape of the glue beads for a tyre cross section given a simple bending test. Bending a tyre with one single sound absorbing member adhered with multiple glue beads results in visible stresses inside the foam, resulting in a less durable concept. Bending a tyre with two strips of foam with a small spacing in between did not result in significant stresses inside the foam.

TABLE-US-00005 Subjective bend test example Ref 1 E1 E4 E5 # sound absorbing members 1 2 2 2 # of glue beads 4 4 4 4 Hs (mm) 30 30 31 31 Ws (mm) 120 50 50 50 S (mm) - 20 15 15 G (mm) 50 30 30 30 Foam density (kg/m3) 23 23 28 28 Subjective bending test NOK OK OK OK

[0069] Reference signs:

TABLE-US-00006 1 tyre 2 tyre inner surface 3 tread portion 4 sidewall portion 5 bead portion 6 sound absorbing device 7 sound absorbing member 7a,7b outer ends of sound absorbing members 8 adhesive component 9 adhesive bead 20 wheel Hs height of sound absorbing member Ws width of sound absorbing member Ls length of sound absorbing member G gap between circumferential outer ends Ha height of adhesive bead Wa width of adhesive bead Vc volume of tyre cavity Vs volume of sound absorbing member S axial spacing of sound absorbing members D circumferential distance between the gaps G