A Noise Reducing Tread

Abstract

The tread has a contact face intended to come into contact with ground during rolling and comprising at least one primary groove having depth D and being delimited by groove sidewalls. The groove sidewalls are axially connected by a groove bottom. The primary groove is provided with a closing device including at least two flexible fences. A first flexible fence has a thickness t1 extending from the groove bottom, and a second flexible fence has a thickness t2 extending from one of groove sidewalls toward the other. The flexible fences are distant each other in an orientation the primary groove extends with a gap g and overlap partly in sectional view of the primary groove. The gap g is at most equal to 1.0 mm. This tread provides further satisfactory reduction on groove resonance and productivity for manufacturing such tread.

Claims

1. A tread for a tire having a contact face intended to come into contact with ground during rolling and comprising at least one primary groove having depth D and being delimited by two opposite groove sidewalls, these groove sidewalls being axially connected by a groove bottom, the primary groove being provided with a plurality of closing device including at least two flexible fences, the closing device covering at least equal to 70% of sectional area of the primary groove, the at least two flexible fences of the closing device being at least one first flexible fence having thickness t1 and extending from the groove bottom in a radially outward orientation of the tire, and at least one second flexible fence having thickness t2 and extending from one of groove sidewall toward the other groove sidewall, the at least two flexible fences of the closing device being distant from each other in an orientation along which the primary groove extends with a gap g, the first flexible fence and the second flexible fence overlapping partly in a sectional view of the primary groove, and the gap g is at most equal to 1.0 mm, and the closing device including one first flexible fence and two second flexible fences and each of the second flexible fences extending from each of opposite groove sidewalls.

2. The tread according to claim 1, wherein the gap g is at least equal to 0.05 mm and at most equal to 0.5 mm.

3. (canceled)

4. The tread according to claim 2, wherein the two second flexible fences overlap partly in the sectional view of the primary groove.

5. The tread claim 1, wherein the thickness t1 of the first flexible fence is different from the thickness t2 of the second flexible fence.

6. (canceled)

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Other characteristics and advantages of the disclosure arise from the description made hereafter in reference to the annexed drawings which show, as nonrestrictive examples, the embodiments of the disclosure.

[0038] In these drawings:

[0039] FIG. 1 is a schematic view of a portion of a tread for a tire according to a first embodiment of the present disclosure;

[0040] FIG. 2 is an enlarged schematic view showing a portion indicated as II in FIG. 1;

[0041] FIG. 3 is a schematic cross sectional view taken along line in FIG. 1;

[0042] FIG. 4 is an enlarged schematic view of a portion according to a second embodiment of the present disclosure;

[0043] FIG. 5 is a schematic cross sectional view according to the second embodiment of the present disclosure;

[0044] FIG. 6 is an enlarged schematic view of a portion according to a third embodiment of the present disclosure; and

[0045] FIG. 7 is a schematic cross sectional view according to the third embodiment of the present disclosure.

DETAILED DESCRIPTION OF THE ENABLING EMBODIMENTS

[0046] Preferred embodiments of the present disclosure will be described below referring to the drawings.

[0047] A tread 1 for a tire according to a first embodiment of the present disclosure will be described referring to FIGS. 1, 2 and 3. FIG. 1 is a schematic view of a portion of a tread 1 according to the first embodiment of the present disclosure. FIG. 2 is an enlarged schematic view showing a portion indicated as II in FIG. 1. FIG. 3 is a schematic cross sectional view taken along line in FIG. 1.

[0048] The tread 1 is a tread for a tire having dimension 225/45R17 and comprises a contact face 2 intended to come into contact with the ground during rolling, a plurality of primary groove 3 extending in a tire circumferential orientation indicated as XX. The primary grooves 3 are delimited by two groove sidewalls 31, 32 facing each other and being connected by a groove bottom 33. The primary groove 3 has a width W at a level of the contact face 2 and a depth D (as shown in FIG. 3).

[0049] As shown in FIG. 1, a contact patch 5 has a contact patch length L in a tire circumferential orientation when the tire with the tread 1 is mounted onto its standard rim and inflated at its nominal pressure and its nominal load is applied. According to ETRTO Standard Manual 2015 the standard rim for this size is 7.5 J, the nominal pressure is 250 kPa and the nominal load is 615 kg.

[0050] As shown in FIG. 1, in the primary groove 3, a plurality of closing device 4 is provided. The closing device 4 comprises one first flexible fence 41 and two second flexible fences 42 for dividing an air column created between the ground and the primary groove 3 in the contact patch 5 during rolling. Each closing device 4 is spaced from each other by distance P in the tire circumferential orientation in the primary groove 3. The distance P is preferably shorter than the contact patch length L so that at least one closing device 4 is always located in the contact patch 5 during rolling in each primary groove 3.

[0051] The first flexible fence 41 has a thickness of t1 and extends from the groove bottom 33 of the primary groove 3 and two second flexible fences 42 have a thickness of t2 and extend from each of the opposite groove sidewalls 31, 32. Two second flexible fences 42 are offset each other in a circumferential orientation in the primary groove 3. The first flexible fence 41 is placed at a circumferential position between two second flexible fences 42, 42 and distant in circumferential orientation (an orientation the primary groove 3 extends) with a gap g which is at most equal to 1.0 mm, from both of the second flexible fences 42 in the primary groove 3, as shown in FIG. 2.

[0052] The thickness t1 of the first flexible fence 41 is thinner than the thickness t2 of the second flexible fence 42, as shown in FIG. 2. The first and the second flexiblea fences 41, 42 partly overlap in a circumferential orientation (in sectional view of the primary groove 3), and the two second flexible fences 42, 42 also overlap partly in a circumferential orientation (in sectional view of the primary groove 3). The first and the second flexible fences 41, 42 cover at least equal to 70% of the cross sectional area of the primary groove 3, as shown in FIG. 3.

[0053] As shown in FIG. 3, the first flexible fence 41 has a pentagon shape as to extend in radially outward orientation of the tread 1 from the groove bottom 33. The width of the first flexible fence 41 is less than the width W of the primary groove 3 and the height of the first flexible fence 41 is less than the depth D of the primary groove 3

[0054] Further, a radially inner edge of the second flexible fence 42 extends obliquely upwardly from the groove sidewall 31, 32 so as to form a triangular space defined by the radially inner edges of the two second flexible fences 42 and the groove bottom 33. A radially outer edge of the second flexible fence 42 extends substantially parallel to the contact face 2. The axial width of the second flexible fence 42 is less than the width W of the primary groove 3.

[0055] The tread 1 has the same structure as the conventional tread except for an arrangement regarding the closing device 4 and is intended to be applied to a conventional pneumatic radial tire and other non-pneumatic tire. Thus, description of the internal construction of the tread 1 will be omitted.

[0056] The primary groove 3 is provided with the plurality of closing device 4 each covering at least equal to 70% of the radial cross sectional area of the primary groove 3. Therefore, the length of the air column formed by the primary groove 3 in the contact patch 5 is shifted to a length whose groove resonance peak is outside of the frequency audible range for the human ear. Thus, groove resonance due to air column resonance of the primary groove 3 can be harmless.

[0057] The flexible fences of the closing device 4 are provided so as to be distant each other with the gap g which is at most equal to 1.0 mm in an orientation along which the primary groove 3 extends. Therefore, it is possible to effectively improve groove resonance due to air column as a sound wave generated by groove resonance has difficulty in propagating between each the flexible fences of the closing device 4. This effect of improving groove resonance due to air column is further emphasized by setting this gap g at least equal to 0.05 mm and at most equal to 0.5 mm while ensuring enough gap between flexible fences to bend. Preferably this gap g is at least equal to 0.1 mm and at most equal to 0.3 mm, and more preferably at least equal to 0.1 mm and at most equal to 0.2 mm.

[0058] The closing device 4 includes one first flexible fence 41 and two second flexible fences 42 and each of the second flexible fences 42 extends from each of opposite groove sidewalls 31, 32. Therefore, it is possible to cover as broader cross sectional area of the primary groove 3 as effectively as possible by the closing device 4, while maintaining good productivity of the tread 1 with the flexible fences as closing device 4, as the sectional area covered by each flexible fence can be reduced using simple tool for manufacturing the tread 1 with the flexible fences as the closing device 4, and to have higher flexibility of an arrangement of the first and the second flexible fences.

[0059] The first flexible fence 41 and the second flexible fence 42 of the closing device 4 overlap partly in a circumferential orientation (in sectional view of the primary groove 3). Also, two second flexible fences 42 of the closing device 4 overlap partly in a circumferential orientation (in sectional view of the primary groove 3). Therefore, it is possible to further effectively attenuate groove resonance due to air column resonance of the primary groove 3, as the sound wave generated by groove resonance has more difficulty in propagating between each the flexible fences of the closing device 4.

[0060] The thickness t1 of the first flexible fence 41 is thinner than the thickness t2 of the second flexible fence 42. It is possible to achieve easier bending of the first flexible fence 41 even when the groove depth decreases, which results further improvement on drainage capability. Both the thickness t1 of the first flexible fence 41 and the thickness t2 of the second flexible fence 42 is preferably less than or equal to 1.5 mm, more preferably between 1.0 mm and 0.2 mm, and a difference between two thicknesses t1 and t2 is preferably less than or equal to 1.0 mm, more preferably less than or equal to 0.5 mm.

[0061] The gap g between the flexible fences 41, 42 of the closing device 4 may have different value position by position, and the thickness t2 of the second flexible fence 42 may have different thickness one another.

[0062] A tread 21 according to a second embodiment of the present disclosure will be described referring to FIGS. 4 and 5. FIG. 4 is an enlarged schematic view of a portion according to the second embodiment of the present disclosure. FIG. 5 is a schematic cross sectional view according to the second embodiment of the present disclosure. The constitution of this second embodiment is similar to that of the first embodiment other than the arrangement shown in FIGS. 4 and 5, thus description will be made referring to FIGS. 4 and 5.

[0063] In the second embodiment, a closing device 24 comprises one first flexible fence 241 having a thickness of t1 and extending from a groove bottom 233 of a primary groove 23 and two second flexible fences 242 having a thickness of t2 and extending from each of opposite groove sidewalls 231, 232. Two second flexible fences 242 are substantially in line each other in an axial orientation in the primary groove 23. The first flexible fence 241 is placed as to be distant in circumferential orientation (an orientation along which the primary groove 23 extends) from the second flexible fences 242 with a gap g which is at most equal to 1.0 mm, in the primary groove 23.

[0064] The thickness t1 of the first flexible fence 241 is thicker than the thickness t2 of the second flexible fence 242, as shown in FIG. 4. The first and the second flexible fences 241, 242 partly overlap in a circumferential orientation (in sectional view of the primary groove 23). The first and the second flexible fences 241, 242 cover at least equal to 70% of the cross sectional area of the primary groove 23, as shown in FIG. 5. The width of the first flexible fence 241 is less than the width W of the primary groove 23. Side portions of the second flexible fences 242 facing to the primary groove 23 overlap the each side of the first flexible fence 241.

[0065] As shown in FIG. 5, the first flexible fence 241 has a rectangular shape as to extend in radially outward orientation of the tread 21 from the groove bottom 233 to substantially same level as a contact face 22, and covers major part of the primary groove 23.

[0066] Further, a radially inner edge of the second flexible fence 242 extends obliquely upwardly from the groove sidewall 231, 232 so as to form a triangular space thereunder with the groove bottom 233. A radially outer edge of the second flexible fence 242 extends substantially parallel to the contact face 22 at radially inward level from the contact face 22 and covers relatively minor part of the primary groove 23 without overlapping each other in circumferential orientation (in sectional view of the primary groove 23).

[0067] The flexible fences of the closing device 24 are provided so as to be distant from each other with the gap g which is at most equal to 1.0 mm in an orientation the primary groove 23 extends. Therefore, it is possible to effectively improve groove resonance due to air column as a sound wave generated by groove resonance has difficulty in propagating between each the flexible fences of the closing device 24. This effect of improving groove resonance due to air column is further emphasized by setting this gap g at least equal to 0.05 mm and at most equal to 0.5 mm while ensuring enough gap between flexible fences to bend. Preferably this gap g is at least equal to 0.1 mm and at most equal to 0.3 mm, and more preferably at least equal to 0.1 mm and at most equal to 0.2 mm.

[0068] The closing device 24 includes one first flexible fence 241 and two second flexible fences 242 and each of the second flexible fences 242 extends from each of opposite groove sidewalls 231, 232. Therefore, it is possible to effectively cover as broader cross sectional area of the primary groove 23 as possible by the closing device 24, while maintaining good productivity of the tread 21 with the flexible fences as closing device 24, as the sectional area covered by each flexible fence can be reduced using simple tool for manufacturing the tread 21 with the flexible fences as the closing device 24, and to have higher flexibility of an arrangement of the first and the second flexible fences.

[0069] The first flexible fence 241 and the second flexible fence 242 of the closing device 24 overlap partly in a circumferential orientation (in sectional view of the primary groove 23). Therefore, it is possible to further effectively attenuate groove resonance due to air column resonance of the primary groove 23, as the sound wave generated by groove resonance has more difficulty in propagating between each the flexible fences of the closing device 24.

[0070] The thickness t1 of the first flexible fence 241 is thicker than the thickness t2 of the second flexible fence 242. Therefore it is possible to have a regular wear of the first flexible fence 241 with tread wear by increased bending rigidity of the first flexible fence 241 relative to the second flexible fence 242. Both the thickness t1 of the first flexible fence 241 and the thickness t2 of the second flexible fence 242 is preferably less than or equal to 1.5 mm, more preferably between 1.0 mm and 0.2 mm, and a difference between two thicknesses t1 and t2 is preferably less than or equal to 1.0 mm, more preferably less than or equal to 0.5 mm.

[0071] A tread 51 according to a third embodiment of the present disclosure will be described referring to FIGS. 6 and 7. FIG. 6 is an enlarged schematic view of a portion according to the third embodiment of the present disclosure. FIG. 7 is a schematic cross sectional view according to the third embodiment of the present disclosure. The constitution of this third embodiment is similar to that of the first embodiment other than the arrangement shown in FIGS. 6 and 7, thus description will be made referring to FIGS. 6 and 7.

[0072] In the third embodiment, a closing device 54 comprises one first flexible fence 541 having a thickness t1 and extending from a groove bottom 533 of the primary groove 53 and one second flexible fence 542 having a thickness t2 and extending from one groove sidewall 531. The thickness t1 of the first flexible fence 541 is substantially equal to the thickness t2 of the second flexible fence 542, as shown in FIG. 6. The first flexible fence 541 is placed as to be distant in circumferential orientation (an orientation the primary groove 53 extends) from the second flexible fence 542 with a gap g which is at most equal to 1.0 mm, in the primary groove 53.

[0073] As shown in FIG. 7, the first flexible fence 541 has a rectangular shape as to extend in radially outward orientation of the tread 51 from the groove bottom 533, and a radially outer edge of the first flexible fence 541 offsets radially inwardly from the level of the contact face 52, and the first flexible fence 541 covers major part of the primary groove 53.

[0074] Further, a radially inner edge of the second flexible fence 542 extends substantially parallel to the groove bottom 533 and quadrantly notched at connecting part to the groove sidewall 531. A radially outer edge of the second flexible fence 542 extends substantially parallel to the contact face 52 at radially inwardly offset level from the level of the contact face 52 and the second flexible fence 542 covers relatively minor part of the primary groove 53. The first and the second flexible fences 541, 542 cover at least equal to 70% of the cross sectional area of the primary groove 53, as shown in FIG. 7.

[0075] The flexible fences of the closing device 54 are provided so as to be distant from each other with the gap g which is at most equal to 1.0 mm in an orientation along which the primary groove 53 extends. Therefore, it is possible to effectively improve groove resonance due to air column as a sound wave generated by groove resonance has difficulty in propagating between each the flexible fences of the closing device 54. This effect of improving groove resonance due to air column is further emphasized by setting this gap g at least equal to 0.05 mm and at most equal to 0.5 mm while ensuring enough gap between flexible fences to bend. Preferably this gap g is at least equal to 0.1 mm and at most equal to 0.3 mm, and more preferably at least equal to 0.1 mm and at most equal to 0.2 mm.

[0076] The closing device 54 includes one first flexible fence 541 and one second flexible fence 542 and the second flexible fence 542 extends from one of the groove sidewall 531. Therefore, it is possible to cover as broader cross sectional area of the primary groove 53 as effectively as possible by the closing device 54, while maintaining good productivity of the tread 51 with the flexible fences as closing device 54, as the sectional area covered by each flexible fence can be reduced using simple tool for manufacturing the tread 51 with the flexible fences as the closing device 54, and to have higher flexibility of an arrangement of the first and the second flexible fences.

[0077] The first flexible fence 541 and the second flexible fence 542 of the closing device 54 overlap partly in a circumferential orientation (in sectional view of the primary groove 53). Therefore, it is possible to further effectively attenuate groove resonance due to air column resonance of the primary groove 53, as the sound wave generated by groove resonance has more difficulty in propagating between each the flexible fences of the closing device 54.

[0078] In order to confirm the effect of the present disclosure, three types of pneumatic tires of Example to which the present disclosure is applied and another type of pneumatic tire of Comparative Example were prepared. An internal construction of these tires was typical radial tire construction for passenger car tire.

[0079] The Examples were pneumatic tires having a tread as shown in FIG. 3 described in the above embodiment with three different gap g between each the flexible fence of the closing device. The Comparative Example was a pneumatic tire having a tread as shown in FIG. 3 with gap g out of the range of the present disclosure, and Reference was a pneumatic tire without having the closing device.

[0080] The tire dimension of the Examples, Comparative Example and Reference were all 205/55R16, mounted onto a rim of 6.5 J16, and inflated to 180 kPa.

Noise Test:

[0081] A sound pressure level of the unused test tires mounted onto abovementioned rim, inflated to abovementioned internal pressure were measured while applying a load of 452 daN, running 90 kph on a drum of 2.7 m in diameter having ISO surface in a semi-anechoic chamber, via a microphone installed axially 1 m outward from a center of tire contact, radially 0.2 m backward from a tire rolling axis and 0.32 m in height. The data acquired through the measurements were processed to calculate an absorption level of a sound at groove resonance frequency. The results are shown in table 1. In this table 1, results are represented by an index of 100 for Reference, higher the number indicates better the noise performance.

TABLE-US-00001 TABLE 1 Com- parative Example 1 Example 2 Example 3 Example Reference Gap g (mm) 1.0 0.5 0.2 2.0 Noise 106 107 108 103 100 performance (index)

[0082] As seen from table 1, the Example tires show improvement on noise performance.

[0083] The disclosure is not limited to the examples described and represented and various modifications can be made there without leaving its framework.

REFERENCE SIGNS LIST

[0084] 1, 21, 51 tread [0085] 2, 22, 52 contact face [0086] 3, 23, 53 primary groove [0087] 31, 231, 531 groove sidewall of the primary groove [0088] 32, 232, 532 groove sidewall of the primary groove [0089] 33, 233, 533 groove bottom of the primary groove [0090] 4, 24, 54 closing device [0091] 41, 241, 541 first flexible fence [0092] 42, 242, 542 second flexible fence [0093] 5 contact patch