Pneumatic tire

Abstract

A pneumatic tire is provided, including: an annular-shaped tread portion extending in a tire circumferential direction; a pair of sidewall portions disposed on both sides of the tread portion; and a pair of bead portions disposed on an inner side in a tire radial direction of the sidewall portions; wherein a band-like sound absorbing member is adhered on an inner surface of the tread portion in the tire circumferential direction; and the band-like sound absorbing member has a plurality of cuts extending in two mutually intersecting directions, and of the cuts, a cut extending in one direction is a cut extending parallel with regard to a tire lateral direction or tire circumferential direction.

Claims

1. A pneumatic tire, comprising: an annular-shaped tread portion extending in a tire circumferential direction; a pair of sidewall portions disposed on both sides of the tread portion; and a pair of bead portions disposed on an inner side in a tire radial direction of the sidewall portions; wherein a band shaped sound absorbing member is adhered on an inner surface of the tread portion in the tire circumferential direction; the band shaped sound absorbing member has a plurality of cuts extending in two mutually intersecting directions, and of the cuts, a cut extending in one direction is a cut extending parallel with regard to a tire lateral direction or tire circumferential direction, an absolute value of a difference in angles of the cuts extending in the two mutually intersecting directions being from 15° to 90°; the plurality of cuts have a closed state which transitions to an open state when the pneumatic tire deflects during a rolling motion; the cut extending in one direction extends parallel with regard to the tire circumferential direction; and a depth d of the cuts is from 55% to 80% with regard to a thickness D of the band shaped sound absorbing member.

2. The pneumatic tire according to claim 1, wherein an interval t of the cuts is from 5% to 90% with regard to a width Ws of the band shaped sound absorbing member.

3. The pneumatic tire according to claim 1, wherein a volume of the band shaped sound absorbing member is from 10% to 30% with regard to luminal volume of the tire.

4. The pneumatic tire according to claim 1, wherein the band shaped sound absorbing member has a missing portion in at least one section in the tire circumferential direction.

5. The pneumatic tire according to claim 2, wherein a volume of the band shaped sound absorbing member is from 10% to 30% with regard to luminal volume of the tire.

6. The pneumatic tire according to claim 5, wherein the band shaped sound absorbing member has a missing portion in at least one section in the tire circumferential direction.

7. The pneumatic tire according to claim 1, wherein a volume of the band shaped sound absorbing member is from 22% to 30% with regard to luminal volume of the tire.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is a perspective cross-sectional view of a pneumatic tire according to an embodiment of the present technology.

(2) FIG. 2 is a cross-sectional view of an equator line illustrating a pneumatic tire according to an embodiment of the present technology.

(3) FIG. 3 is a developed view illustrating a portion of a band-like sound absorbing member adhered to an inner surface of a pneumatic tire of the present technology.

(4) FIG. 4 is a cross-sectional view in a tire circumferential direction of the sound absorbing member in FIG. 3.

(5) FIG. 5A to 5D illustrate modified examples of cuts of a band-like sound absorbing member adhered to an inner surface of a pneumatic tire of the present technology, and FIGS. 5A to 5D are developed views of the modified examples.

(6) FIGS. 6A and 6B are schematic views illustrating a portion of a band-like sound absorbing member adhered to an inner surface of a pneumatic tire.

DETAILED DESCRIPTION

(7) A configuration of the present technology will be described in detail below while referring to the attached drawings. FIG. 1 and FIG. 2 illustrate a pneumatic tire according to an embodiment of the present technology. As illustrated in FIG. 1, the pneumatic tire according to the present embodiment includes an annular-shaped tread portion 1 extending in a tire circumferential direction, a pair of sidewall portions 2 disposed on both sides of the tread portion 1, and a pair of bead portions 3 disposed on an inner side in a tire radial direction of the sidewall portions 2.

(8) In the aforementioned pneumatic tire, a band-like sound absorbing member 6 is adhered via an adhesive layer 5 along the tire circumferential direction to a region of a tire inner surface 4 corresponding to the tread portion 1. The band-like sound absorbing member 6 is made of open-cell porous material and has predetermined noise absorbing properties based on the porous structure. Polyurethane foam may be used as the porous material of the band-like sound absorbing member 6. On the other hand, a double-sided adhesive tape is preferable as the adhesive layer 5.

(9) A plurality of cuts 7 extending in two mutually intersecting directions are formed on the band-like sound absorbing member 6. Of the cuts 7, the cut 7 extending parallel with a tire lateral direction or the tire circumferential direction is set as a first cut 7a, and the cut 7 extending in a different direction than the first cut 7a is set as a second cut 7b. Furthermore, as illustrated in FIG. 3, an angle with regard to the tire lateral direction of the first cut 7a is set as angle θ1, an angle with regard to the tire lateral direction of the second cut 7b is set as angle θ2, and an angle formed by the first cut 7a and second cut 7b is set as angle θ3. At this time, the angle θ3 formed by the first cut 7a and second cut 7b is expressed as an angle on an acute angle side. Note that in FIG. 3, Tc represents the tire circumferential direction, and the Tw represents the tire width direction.

(10) In other words, the first cut 7a with a 0° or 90° angle θ1 and the second cut 7b having the angle θ2 are disposed on the band-like sound absorbing member 6. FIG. 3 illustrates a case where the first cut 7a with a 90° angle θ1 and the second cut 7b with a 30° angle θ2 are disposed, and at this time, angle θ3 is 60°.

(11) In the aforementioned pneumatic tire, the angle θ2 is not particularly limited, but in a case where the angle θ1 of the first cut 7a is 0°, the absolute value of the angle θ2 of the second cut 7b is preferably within a range of 15° to 90°, and more preferably within a range of 60° to 90°. On the other hand, in a case where the angle θ1 of the first cut 7a is 90°, the absolute value of the angle θ2 of the second cut 7b is preferably within a range of 0° to 75°. Furthermore, the absolute value of the angle θ3 is preferably within a range of 15° to 90°, and more preferably within a range of 30° to 60°. The plurality of the first cut 7a and second cut 7b extending in two mutually intersecting directions is provided on the band-like sound absorbing member 6, and therefore, the first cut 7a and second cut 7b of the band-like sound absorbing member 6 can open and follow the deformation of a tire when the tire deflects during a rolling motion, relieve stress generated on the band-like sound absorbing member 6, and suppress damaging of the band-like sound absorbing member 6. As a result, the durability of the band-like sound absorbing member 6 can be improved. Furthermore, during repeated deformation, the first cut 7a and second cut 7b of the band-like sound absorbing member 6 open, and thus and an apparent gauge of the band-like sound absorbing member 6 is reduced in thickness, and therefore, heat dissipation from the band-like sound absorbing member 6 can be promoted, and high-speed durability of the pneumatic tire can be improved.

(12) FIG. 6A illustrates a block 61 of a portion of the band-like sound absorbing member 6 demarcated by the first cut 7a with a 90° angle θ1 and second cut 7b with a 30° angle θ2, and FIG. 6B illustrates the block 61 of a portion of the band-like sound absorbing member 6 demarcated by the first cut 7a and second cut 7b with a 45° angle for angle θ1 and angle θ2 as a comparative example of the present technology.

(13) Herein, a force with regard to the tire circumferential direction acts during a rolling motion on the blocks 61 of the band-like sound absorbing member 6 demarcated by the first cut 7a and second cut 7b, and thus collapsing of the blocks 61 occurs. The collapsing of the blocks 61 repeatedly occurs during a rolling motion, and therefore, the blocks 61 rub against each other, which is a factor leading to damaging of the band-like sound absorbing member 6. As illustrated in FIG. 6A, of the first cut 7a and second cut 7b extending in two directions, the first cut 7a is configured so as to extend parallel with the tire circumferential direction or tire lateral direction, such that stress with regard to the tire circumferential direction subjected to the blocks 61 is limited to one block 61 (one diagonally shaded block 61) positioned forward in the rotation direction R, and therefore, collapsing of the block 61 can be suppressed. Thereby, rubbing of the blocks 61 is relieved, and thus damage of the band-like sound absorbing member 6 can be even further suppressed. On the other hand, as illustrated in FIG. 6B, in a case where a first cut 7a and second cut 7b where both are not cuts extending parallel with the tire lateral direction or tire circumferential direction are provided, the blocks 61 are subject to stress with regard to the tire circumferential direction due to collapsing of two blocks 61 (two diagonally shaded blocks 61) positioned forward in the rotation direction R, and therefore, collapsing of the block 61 subject to the stress increases, and thus the band-like sound absorbing member 6 is prone to further damage.

(14) As illustrated in FIG. 3, an interval between the cuts 7 is set as interval t. At this time, the interval t of the cuts 7 is preferably from 5% to 90%, and more preferably from 15% to 30% with regard to a width Ws of the band-like sound absorbing member 6. “Interval t” as referred to herein is an interval between cuts 7 extending in the same direction. Furthermore, the interval of the cuts 7 on the band-like sound absorbing member 6 may be randomly disposed, but the cuts 7 are more preferably disposed at equal intervals with constant intervals t of the cuts 7 on the band-like sound absorbing member 6, from the perspective of being able to uniformly correspond tensile strain in each direction. Thereby, the cuts 7 of the band-like sound absorbing member 6 can open and follow deformation of the tire during a ground-contacting rolling motion in a condition with high tire deflection, relieve stress generated on the band-like sound absorbing member 6, and suppress damaging of the band-like sound absorbing member 6. As a result, the durability of the band-like sound absorbing member 6 can be improved.

(15) FIG. 4 is a cross-sectional view in the tire circumferential direction of the band-like sound absorbing member 6. A depth of the cuts 7 is set as a depth d, and a thickness of the band-like sound absorbing member 6 is set as a thickness D. At this time, a depth d of the cuts 7 is preferably from 20% to 80%, and more preferably from 30% to 60% with regard to a thickness D of the band-like sound absorbing member 6. Thereby, the cuts 7 of the band-like sound absorbing member 6 can open during ground contact, promote heat dissipation from the band-like sound absorbing member 6, and improve the high-speed durability of the pneumatic tire. Furthermore, damaging of the band-like sound absorbing member 6 caused by a ground-contacting rolling motion in a condition with a high tire deflection can be effectively suppressed. Herein, when the depth d of the cuts 7 is too shallow, heat dissipation from the band-like sound absorbing member 6 is reduced, and thus high-speed durability of the tire deteriorates. On the other hand, when the depth d of the cuts 7 is too deep, the band-like sound absorbing member 6 tends to become prone to damage during a rolling motion at a low temperature.

(16) In the aforementioned pneumatic tire, a volume of the band-like sound absorbing member 6 is preferably from 10% to 30% with regard to the luminal volume of a tire. Furthermore, the width Ws of the band-like sound absorbing member 6 is more preferably from 30% to 90% with regard to a tire ground contact width. Thereby, a sound absorbing effect based on the band-like sound absorbing member 6 can be even further achieved. Herein, when the volume of the band-like sound absorbing member 6 is less than 10% with regard to the luminal volume of the tire, a sound absorbing effect cannot be appropriately achieved. Furthermore, when the volume of the band-like sound absorbing member 6 exceeds 30% with regard to the luminal volume of the tire, the reducing effect against noise due to the cavernous resonance phenomenon will be constant, and a further reducing effect cannot be expected.

(17) Furthermore, as illustrated in FIG. 2, the band-like sound absorbing member 6 preferably has a missing portion 9 in at least one section in the tire circumferential direction. The missing portion 9 is a portion where the band-like sound absorbing member 6 is not present on a tire circumference. By providing the missing portion 9 on the band-like sound absorbing member 6, long-term resistance is possible against expansion due to tire inflation and shear strain of an adhering surface caused by a ground-containing rolling motion, and shear strain generated on the adhering surface of the band-like sound absorbing member 6 can be effectively relieved. The missing portion 9 is preferably provided at one or three to five sections on the tire circumference. In other words, when the missing portion 9 is provided on two sections on the tire circumference, tire uniformity significantly deteriorates due to mass unbalance, and when the missing portion 9 is provided on 6 sections or more, manufacturing cost significantly increases.

(18) Note that if the missing portion 9 is provided on two or more sections on the tire circumference, the band-like sound absorbing member 6 is interrupted in the tire circumferential direction. However, even in this case, for example, in a case where a plurality of the band-like sound absorbing members 6 are mutually connected by another laminate such as an adhesive layer 5 formed from a double-side adhesive tape, the band-like sound absorbing members 6 can be handled as an integral member, and therefore, the work of applying to the tire inner surface 4 can be easily performed.

(19) In addition to FIG. 1, the cuts 7 can be such that the first cut 7a extending parallel with the tire lateral direction and second cut 7b extending parallel with the tire circumferential direction are disposed as illustrated in FIG. 5A, or such that the first cut 7a extending in the tire circumferential direction and the second cut 7b with an absolute value of the angle θ2 of 30° are disposed as illustrated in FIG. 5B. Furthermore, the cuts 7 can also be such that the first cut 7a extending in the tire lateral direction and the second cut 7b with an absolute value of the angle θ2 of 60° are disposed as illustrated in FIG. 5C and FIG. 5D.

(20) The present technology is further described below by examples, but the scope of the present technology is not limited to these examples.

EXAMPLES

(21) Tires of Examples 1 to 20 having a plurality of cuts extending in two mutually intersecting directions on a band-like sound absorbing member were prepared for a pneumatic tire provided with an annular-shaped tread portion extending in a tire circumferential direction, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on an inner side in a tire radial direction of the sidewall portions, at a tire size of 275/35ZR20, where a band-like sound absorbing member is adhered on an inner surface of the tread portion in the tire circumferential direction, and the band-like sound absorbing member has a plurality of cuts extending in two mutually intersecting directions.

(22) In Examples 1 to 20, the presence/absence of a cut, angle θ1 with regard to the tire lateral direction of the first cut, angle θ2 with regard to the tire later direction of the second cut, interval of the cuts (interval t/width Ws×100%), and depth of the cuts (depth d/thickness D×100%) were set as shown in Table 1-1 and Table 1-2.

(23) For comparison, tires of conventional examples were prepared without providing any cuts in the band-like sound absorbing member. Furthermore, a tire of Comparative Example 1 having the same structure as Example 1 was prepared except that the shape of the cuts was a rectangular groove extending in the tire lateral direction, and a tire of Comparative Example 2 having the same structure as Example 1 was prepared except that only a plurality of cuts extending in the tire lateral direction were provided. Furthermore, a tire of Comparative Example 3 having the same structure as Example 1 was prepared except that only a plurality of cuts extending in the tire circumferential direction, and a tire of Comparative Example 4 having the same structure as Example 1 was prepared except that the cuts were disposed to mutually intersect at an angle of 45° with regard to the tire lateral direction.

(24) For these test tires, the high-speed durability, durability of the band-like sound absorbing member during high strain, durability of the band-like sound absorbing member at a low temperature (−20° C.), and collapsing of a block of the band-like sound absorbing member were evaluated, and the results thereof are collectively shown in Table 1-1 and Table 1-2.

(25) High-Speed Durability:

(26) The test tires were assembled on wheels having a rim size of 20×9½J, and then subjected to a traveling test on a drum testing machine under testing conditions where the air pressure was 360 kPa and the load was 5 kN. Specifically, an initial speed was 250 km/h, the speed was increased by 10 km/h every 20 minutes, and the tire was run until failure occurred, and the reached step (speed) was measured. The results are shown in Table 1-1 and Table 1-2.

(27) Durability of Band-Like Sound Absorbing Member During High Strain:

(28) The test tires were assembled on wheels having a rim size of 20×9½J, and subjected traveling test on a drum testing machine under testing conditions where the traveling speed was 80 km/h, the air pressure was 160 kPa, the load was 8.5 kN, and the traveling distance was 6000 km, and then peeling of the adhering surface on the band-like sound absorbing member or presence/absence of damage on the band-like sound absorbing member was visually observed. The results are shown in Table 1-1 and Table 1-2. For the aforementioned items, cases where no dropout or damage occurred were denoted as “Excellent”; cases where peeling of the adhering surface or damaging of the band-like sound absorbing member occurred in a portion but was not problem were denoted as “Good”; cases where peeling of the adhering surface or damaging of the band-like sound absorbing member occurred on ¼ or less of the entire band-like sound absorbing member were denoted with “Fair”; and cases where peeling of the adhering surface or damaging of the band-like sound absorbing member occurred on ¼ or more of the entire band-like sound absorbing member were denoted as “Poor”.

(29) Durability at a Low Temperature (−20° C.):

(30) The test tires were assembled on wheels having a rim size of 20×9½J, and subjected traveling test on a drum testing machine under testing conditions where the traveling speed was 80 km/h, the air pressure was 160 kPa, the load was 5 kN, and the traveling distance was 6,000 km, and then peeling of the adhering surface on the band-like sound absorbing member or presence/absence of damage on the band-like sound absorbing member was visually observed.

(31) The results are shown in Table 1-1 and Table 1-2. For the aforementioned items, cases where no dropout or damage occurred were denoted as “Excellent”; cases where peeling of the adhering surface or damaging of the band-like sound absorbing member occurred in a portion but was not problem were denoted as “Good”; cases where peeling of the adhering surface or damaging of the band-like sound absorbing member occurred on ¼ or less of the entire band-like sound absorbing member were denoted as “Fair”; and cases where peeling of the adhering surface or damaging of the band-like sound absorbing member occurred on ¼ or more of the entire band-like sound absorbing member were denoted as “Poor”.

(32) Collapsing of Block of Band-Like Sound Absorbing Member:

(33) The test tires were assembled on wheels having a rim size of 20×9½J, and then subjected to a traveling test on a drum testing machine under testing conditions where the air pressure was 360 kPa and the load was 5 kN. Specifically, an initial speed was 250 km/h, the speed was increased by 10 km/h every 20 minutes, and the tire was run until a speed of 310 km/h was achieved, and then the presence/absence of damaging on the band-like sound absorbing member due to collapsing of a block on the band-like sound absorbing member was visually confirmed. The results are shown in Table 1-1 and Table 1-2. For the aforementioned items, cases where no damage of the band-like sound absorbing member occurred were denoted as “Excellent”; cases where damaging of the band-like sound absorbing member occurred in a portion but was not problem were denoted as “Good”; and cases where damaging of the band-like sound absorbing member occurred on ¼ or less of the entire band-like sound absorbing member were denoted as “Fair”.

(34) TABLE-US-00001 TABLE 1-1-1 Conven- tional Comparative Comparative example Example 1 Example 2 Presence/absence of cuts Absence Presence Presence Angle θ1 of first cut with regard — 0° 0° to tire lateral direction Angle θ2 of second cut with — — — regard to tire lateral direction Interval of cuts —  5%  5% (Interval t/width Ws × 100%) Depth of cuts — 20% 20% (Depth d/thickness D × 100%) High-speed durability 310 330 320 (reached speed: km/h) Durability of During high Poor Fair Fair band-like strain sound At low Poor Fair Fair absorbing temperature member (−20° C.) Collapsing of block of band-like Excellent Excellent Excellent sound absorbing member

(35) TABLE-US-00002 TABLE 1-1-2 Comparative Comparative Example 3 Example 4 Presence/absence of cuts Presence Presence Angle θ1 of first cut with 90° 45° regard to tire lateral direction Angle θ2 of second cut with — 45° regard to tire lateral direction Interval of cuts  5%  5% (Interval t/width Ws × 100%) Depth of cuts 20% 20% (Depth d/thickness D × 100%) High-speed durability 320 340 (reached speed: km/h) Durability of During high Poor Good band-like strain sound At low Poor Good absorbing temperature member (−20° C.) Collapsing of block of band- Excellent Fair like sound absorbing member

(36) TABLE-US-00003 TABLE 1-1-3 Example 1 Example 2 Example 3 Example 4 Example 5 Presence/absence of cuts Presence Presence Presence Presence Presence Angle θ1 of first cut with  0°  0°  0°  0° 90° regard to tire lateral direction Angle θ2 of second cut with 90° 60° 30° 15° 75° regard to tire lateral direction Interval of cuts  5%  5%  5%  5%  5% (Interval t/width Ws × 100%) Depth of cuts 20% 20% 20% 20% 20% (Depth d/thickness D × 100%) High-speed durability 340 350 350 340 340 (reached speed: km/h) Durability of During high Good Good Good Good Good band-like strain sound At low Good Good Good Good Good absorbing temperature member (−20° C.) Collapsing of block of band- Good Excellent Excellent Excellent Excellent like sound absorbing member

(37) TABLE-US-00004 TABLE 1-1-4 Exam- Exam- Exam- Exam- ple 6 ple 7 ple 8 ple 9 Presence/absence of cuts Pres- Pres- Pres- Pres- ence ence ence ence Angle θ1 of first cut with regard 90° 90° 90° 90° to tire lateral direction Angle θ2 of second cut with 60° 45° 30° 15° regard to tire lateral direction Interval of cuts  5%  5%  5%  5% (Interval t/width Ws × 100%) Depth of cuts 20% 20% 20% 20% (Depth d/thickness D × 100%) High-speed durability 350 350 350 340 (reached speed: km/h) Durability of During high Good Good Good Good band-like strain sound At low Good Good Good Good absorbing temperature member (−20° C.) Collapsing of block of band-like Excel- Excel- Excel- Excel- sound absorbing member lent lent lent lent

(38) TABLE-US-00005 TABLE 1-2-1 Example 10 Example 11 Example 12 Example 13 Example 14 Example 15 Presence/absence of cuts Presence Presence Presence Presence Presence Presence Angle θ1 of first cut with 90° 90° 90° 90° 90° 90° regard to tire lateral direction Angle θ2 of second cut with 45° 45° 45° 45° 45° 45° regard to tire lateral direction Interval of cuts 15% 30% 45% 60% 90% 95% (Interval t/width Ws × 100%) Depth of cuts 20% 20% 20% 20% 20% 20% (Depth d/thickness D × 100%) High-speed durability 350 350 340 340 340 330 (reached speed: km/h) Durability of During high Excellent Excellent Excellent Excellent Excellent Good band-like strain sound At low Excellent Excellent Good Good Good Good absorbing temperature member (−20° C.) Collapsing of block of band- Excellent Excellent Excellent Excellent Excellent Excellent like sound absorbing member

(39) TABLE-US-00006 TABLE 1-2-2 Example 16 Example 17 Example 18 Example 19 Example 20 Presence/absence of cuts Presence Presence Presence Presence Presence Angle θ1 of first cut with 90° 90° 90° 90° 90° regard to tire lateral direction Angle θ2 of second cut with 45° 45° 45° 45° 45° regard to tire lateral direction Interval of cuts 15% 15% 15% 15% 15% (Interval t/width Ws × 100%) Depth of cuts 30% 50% 60% 80% 90% (Depth d/thickness D × 100%) High-speed durability 350 350 350 350 350 (reached speed: km/h) Durability of During high Excellent Excellent Excellent Excellent Good band-like strain sound At low Excellent Excellent Excellent Good Good absorbing temperature member (−20° C.) Collapsing of block of band- Excellent Excellent Excellent Good Good like sound absorbing member

(40) As seen from Table 1-1 and Table 1-2, the pneumatic tires of Examples 1 to 20 all had simultaneously improved high-speed durability, durability of the band-like sound absorbing member during high strain, durability of the band-like sound absorbing member at a low temperature (−20° C.), and collapsing of the band-like sound absorbing member, as compared to the conventional examples.

(41) On the other hand, in Comparative Example 1, the shape of the cuts was a rectangular groove extending in the tire lateral direction, and therefore, the improving effect of high-speed durability was low without a heat dissipating effect. Furthermore, in Comparative Example 2 and Comparative Example 3, only a plurality of cuts extending in the tire lateral direction or tire circumferential direction were provided, and therefore, an effect of increasing the heat dissipation area of the band-like sound absorbing member was not significantly achieved, and thus an improving effect of high-speed durability was low. Furthermore, in Comparative Example 4, the cuts were disposed so as to mutually intersect at an angle of 45° with regard to the tire lateral direction, and therefore, collapsing of a block occurred on the band-like sound absorbing member, and the blocks rubbed against each other, which resulted in damaging of a portion of the band-like sound absorbing member.