JP7613101B2 - tire - Google Patents

Description

The present invention relates to a tire.

The following Patent Document 1 proposes a pneumatic tire with inner lug grooves, outer lug grooves, and intermediate slots in the shoulder land area. These lug grooves and slots allow the pneumatic tire to suppress heel-and-toe wear in the shoulder land area while maintaining drainage performance, thereby improving noise performance.

JP 2010-132181 A

In recent years, as vehicles have become more powerful, there has been a demand for tires to have better wet and noise performance. However, the pneumatic tire of Patent Document 1 has a relatively loud pumping noise, and there is room for improvement in noise performance.

The present invention was devised in light of the above-mentioned circumstances, and its main objective is to provide a tire with improved wet performance and noise performance.

The present invention is a tire having a tread portion with a specified orientation for mounting on a vehicle, the tread portion including a first tread edge that is on the outer side of the vehicle when mounted on the vehicle, a second tread edge that is on the inner side of the vehicle when mounted on the vehicle, a plurality of circumferential grooves that extend continuously in the tire circumferential direction between the first tread edge and the second tread edge, and a plurality of land portions divided into the circumferential grooves, the plurality of land portions including a first shoulder land portion including the first tread edge and a second shoulder land portion including the second tread edge, the first shoulder land portion is provided with a plurality of first shoulder sipes extending in the tire axial direction, the second shoulder land portion is provided with a plurality of second shoulder sipes extending in the tire axial direction, and the total number of the second shoulder sipes is greater than the total number of the first shoulder sipes.

In the tire of the present invention, it is desirable that the total number of the second shoulder sipes is 1.5 to 2.5 times the total number of the first shoulder sipes.

In the tire of the present invention, it is preferable that only sipes are provided in the first shoulder land portion and the second shoulder land portion.

In the tire of the present invention, it is preferable that the first shoulder sipe and the second shoulder sipe are inclined in the same direction relative to the tire axial direction.

In the tire of the present invention, it is desirable that the maximum angle of the first shoulder sipe relative to the tire axial direction is greater than the maximum angle of the second shoulder sipe relative to the tire axial direction.

In the tire of the present invention, it is preferable that the first shoulder sipe completely crosses the first shoulder land portion in the tire axial direction.

In the tire of the present invention, it is preferable that the first shoulder sipe includes a portion where the angle with respect to the tire axial direction increases toward the tire equator.

In the tire of the present invention, it is preferable that the second shoulder sipe extends in a straight line.

In the tire of the present invention, it is preferable that the second shoulder sipes include a transverse second shoulder sipe that completely crosses the second shoulder land portion in the tire axial direction, and an interrupted second shoulder sipe that extends at least from the second tread edge in the tire axial direction and has an interrupted end within the second shoulder land portion.

In the tire of the present invention, it is desirable that the axial length of the interrupted second shoulder sipe is 50% to 90% of the axial width of the second shoulder land portion.

In the tire of the present invention, the circumferential groove includes a first groove wall and a second groove wall facing each other, the first groove wall is provided with a plurality of first recesses recessed outward in the groove width direction from the groove edge of the circumferential groove where the tread surface of the tread portion appears, the second groove wall is provided with a plurality of second recesses recessed outward in the groove width direction from the groove edge of the circumferential groove where the tread surface of the tread portion appears, the first recesses and the second recesses each have a gradually decreasing recession amount from the groove edge from the deepest part recessed furthest outward in the groove width direction toward both sides in the tire circumferential direction, the land portion adjacent to the circumferential groove is provided with a plurality of sipes in the tire circumferential direction that communicate with the circumferential groove, and it is preferable that one each of the first recesses and the second recesses is provided within a length 1.0 to 3.0 times the pitch length of the sipe.

By adopting the above-mentioned configuration, the tire of the present invention can improve wet performance and noise performance.

1 is a development view of a tread portion showing one embodiment of the present invention. FIG. 2 is an enlarged view showing the shape of the contact surface of the tread portion when the tread portion contacts the ground. FIG. 2 is an enlarged view of a first shoulder land portion and a first middle land portion of FIG. 1 . 4 is a cross-sectional view taken along line AA in FIG. 3. 4 is a cross-sectional view taken along line CC of FIG. 3. 4 is a cross-sectional view taken along line BB in FIG. 3. 4 is a cross-sectional view taken along line D-D of FIG. 3. 2 is an enlarged view of a first middle land portion, a crown land portion, and a second middle land portion of FIG. 1 . FIG. 2 is an enlarged view of a second shoulder land portion of FIG. 1 . 10 is a cross-sectional view taken along line E-E of FIG. 9. 2 is a cross-sectional view taken along line FF in FIG. 1. 2 is a cross-sectional view taken along line GG in FIG. 1. FIG. 4 is a development view of the tread portion 2 of another embodiment. FIG. 11 is an enlarged view of a first middle land portion according to another embodiment. FIG. 11 is an enlarged view of a first middle land portion according to another embodiment.

Below, one embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a development view of a tread portion 2 of a tire 1 showing one embodiment of the present invention. The tire 1 of this embodiment is preferably used, for example, as a pneumatic tire for passenger cars. However, the present invention is not limited to such an embodiment, and may also be applied to pneumatic tires for heavy loads and non-pneumatic tires that do not have pressurized air filled inside the tire.

As shown in FIG. 1, the tire 1 of this embodiment has a tread portion 2 for which the orientation for mounting on a vehicle is specified. The tread portion 2 has a first tread edge T1 intended to be located on the outer side of the vehicle when the tire 1 is mounted on the vehicle, and a second tread edge T2 intended to be located on the inner side of the vehicle when the tire is mounted on the vehicle. The orientation for mounting on the vehicle is indicated, for example, by letters or symbols on the sidewall portion (not shown).

The first tread edge T1 and the second tread edge T2 each correspond to the axially outermost contact position when the tire 1 in a normal state is loaded with 50% of the normal load and contacts the ground on a flat surface with a camber angle of 0°.

In the case of pneumatic tires for which various standards are established, the "normal state" refers to a state in which the tire is mounted on a normal rim, inflated to the normal internal pressure, and unloaded. In the case of tires for which various standards are not established or non-pneumatic tires, the normal state refers to a standard usage state according to the intended use of the tire, in which the tire is not mounted on a vehicle and is unloaded. In this specification, unless otherwise specified, the dimensions of each part of the tire are values measured in the normal state.

A "genuine rim" is a rim that is specified for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "design rim," and in the case of ETRTO, it is called a "measuring rim."

"Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. For JATMA, it is the "maximum air pressure." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "INFLATION PRESSURE."

In the case of pneumatic tires for which various standards are established, the "normal load" is the load that is established for each tire in the standard system including the standards on which the tire is based, and is the "maximum load capacity" for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. In addition, in the case of tires for which various standards are not established or non-pneumatic tires, the "normal load" refers to the load acting on a single tire in the standard mounting state of the tire. The "standard mounting state" refers to the state in which the tire is mounted on a standard vehicle corresponding to the intended use of the tire, and the vehicle is stationary on a flat road surface in a drivable state.

The tread portion 2 has a plurality of circumferential grooves 3 that extend continuously in the tire circumferential direction between the first tread edge T1 and the second tread edge T2, and a plurality of land portions 4 that are divided into the circumferential grooves. The tire 1 of this embodiment is configured as a so-called five-rib tire in which the tread portion 2 includes five land portions 4 that are divided into four circumferential grooves 3.

The circumferential grooves 3 include, for example, a first shoulder circumferential groove 5, a second shoulder circumferential groove 8, a first crown circumferential groove 6, and a second crown circumferential groove 7. The first shoulder circumferential groove 5 is provided between the first tread edge T1 and the tire equator C. The second shoulder circumferential groove 8 is provided between the second tread edge T2 and the tire equator C. The first crown circumferential groove 6 is provided between the first shoulder circumferential groove 5 and the tire equator C. The second crown circumferential groove 7 is provided between the second shoulder circumferential groove 8 and the tire equator C.

The axial distance L1 from the tire equator C to the groove centerline of the first shoulder circumferential groove 5 or the second shoulder circumferential groove 8 is preferably, for example, 25% to 35% of the tread width TW. The axial distance L2 from the tire equator C to the groove centerline of the first crown circumferential groove 6 or the second crown circumferential groove 7 is preferably, for example, 5% to 15% of the tread width TW. The tread width TW is the axial distance from the first tread edge T1 to the second tread edge T2 in the normal state.

In this embodiment, each circumferential groove 3 extends, for example, linearly in parallel to the tire circumferential direction. Each circumferential groove 3 may extend, for example, in a wavy manner.

The groove width W1 of each circumferential groove 3 is preferably, for example, 2.0% to 8.0% of the tread width TW. In this embodiment, the first shoulder circumferential groove 5 has the smallest groove width of the four circumferential grooves 3. However, the present invention is not limited to this aspect. In the case of a pneumatic tire for a passenger car, the depth of each circumferential groove 3 is preferably, for example, 5 to 10 mm.

The land portion 4 of the present invention includes at least a first shoulder land portion 11 and a second shoulder land portion 15. The first shoulder land portion 11 includes a first tread edge T1. The second shoulder land portion 15 includes a second tread edge T2.

In this embodiment, the land portion 4 includes a first middle land portion 12, a crown land portion 13, and a second middle land portion 14. The first middle land portion 12 is divided into a first shoulder circumferential groove 5 and a first crown circumferential groove 6, and is adjacent to the second tread edge T2 side of the first shoulder land portion 11. The second middle land portion 14 is divided into a second shoulder circumferential groove 8 and a second crown circumferential groove 7, and is adjacent to the first tread edge T1 side of the second shoulder land portion 15.

The crown land portion 13 is divided between the first crown circumferential groove 6 and the second crown circumferential groove 7. As a result, the crown land portion 13 is provided between the first middle land portion 12 and the second middle land portion 14. In this embodiment, the crown land portion 13 is provided on the tire equator C.

In this embodiment, each land portion 4 is provided with a sipe 16. In this specification, a "sipe" refers to a cut element having a small width, and the width between two sipe walls in the main body of the sipe 16 is 1.5 mm or less. The width of the sipe 16 is preferably 0.2 to 1.2 mm, and more preferably 0.5 to 1.0 mm. The sipe 16 may include a widened portion that opens with a width larger than the width, or a flask bottom that is larger than the width.

The first shoulder land portion 11 is provided with a plurality of first shoulder sipes 21 extending in the tire axial direction. The second shoulder land portion 15 is provided with a plurality of second shoulder sipes 50 extending in the tire axial direction. The total number of second shoulder sipes 50 is greater than the total number of first shoulder sipes 21. As a result, the number of sipes arranged in the first shoulder land portion 11 on the vehicle outer side is reduced, so that the impact sound (especially the impact sound when the edge of the sipes touches the ground) of the first shoulder land portion 11, which has a large impact on noise performance, is reduced, and noise performance is improved. On the other hand, the second shoulder land portion 15 on the vehicle inner side has many sipes arranged, so a large friction force can be expected on wet road surfaces. In the present invention, it is presumed that this mechanism can improve wet performance and noise performance.

To improve noise performance and wet performance while maintaining driving stability, the total number of second shoulder sipes 50 is preferably 1.3 times or more, more preferably 1.5 times or more, and even more preferably 1.8 times or more, and preferably 2.8 times or less, more preferably 2.5 times or less, and even more preferably 2.2 times or less, the total number of first shoulder sipes 21.

The following describes the configuration of this embodiment in more detail. Each of the configurations described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the above-mentioned effects even if it does not have the configurations described below. Furthermore, even if any one of the configurations described below is applied alone to a tire of the present invention having the above-mentioned characteristics, an improvement in performance corresponding to each configuration can be expected. Furthermore, when several of the configurations described below are applied in combination, a composite improvement in performance corresponding to each configuration can be expected.

FIG. 2 shows an enlarged view of the shape of the ground contact surface of the tread portion 2 when the tire is grounded. As shown in FIG. 2, when the tire is assembled to a regular rim with a regular internal pressure, and is placed on a flat surface with a camber angle of 0° under a 50% load condition in which the tire is loaded with 50% of the regular load, the widths of the ground contact surfaces in the tire axial direction of the first shoulder land portion 11, the first middle land portion 12, the crown land portion 13, the second middle land portion 14, and the second shoulder land portion 15 are W1s, W1m, Wc, W2m, and W2s, respectively, and it is preferable that the following formula (1) is satisfied. In a more preferable aspect, the tire 1 of this embodiment also satisfies the following formula (2). In such a tire 1, the land portion close to the first tread end T1 has a greater rigidity. Therefore, even when the center of the ground contact surface moves toward the first tread end T1 due to steering, the steering response is stable, and a cornering force is generated linearly with respect to an increase in the steering angle. Therefore, excellent steering stability and ride comfort are obtained.
W1m>Wc>W2m...(1)
W1s>W1m>Wc>W2m≧W2s…(2)

Under a 50% load condition, it is desirable that the axial width W1s of the ground contact surface of the first shoulder land portion 11 is 115% to 125% of the axial width Wc of the ground contact surface of the crown land portion 13. This optimizes the rigidity of the first shoulder land portion 11, and in addition to the above-mentioned effects, noise performance can also be improved.

From a similar perspective, it is desirable that, under a 50% load condition, the axial width W1m of the ground contact surface of the first middle land portion 12 be 101% to 107% of the axial width Wc of the ground contact surface of the crown land portion 13.

Under a 50% load condition, it is desirable that the axial width W2m of the ground contact surface of the second middle land portion 14 is 90% to 99% of the axial width Wc of the ground contact surface of the crown land portion 13. This improves noise performance when traveling straight. In addition, tire vibrations when traveling straight are less likely to be transmitted to the vehicle body, improving ride comfort.

From a similar perspective, it is desirable that, under a 50% load condition, the axial width W2s of the ground contact surface of the second shoulder land portion 15 is 90% to 99% of the axial width Wc of the ground contact surface of the crown land portion 13.

As a more desirable aspect, in this embodiment, under a 50% load condition, the width W2m of the second middle land portion 14 is set to be the same as the width W2s of the second shoulder land portion 15. This makes the wear progression of the second middle land portion 14 and the second shoulder land portion 15 uniform, improving uneven wear resistance.

Figure 3 shows an enlarged view of the first shoulder land portion 11 and the first middle land portion 12. As shown in Figure 3, the first shoulder land portion 11 is provided with only sipes. This increases the rigidity of the first shoulder land portion 11. In this embodiment, the first shoulder land portion 11 is provided with a plurality of first shoulder sipes 21 extending in the tire axial direction.

The circumferential pitch length P1 of the first shoulder sipe 21 is, for example, 100% to 130% of the axial tread width W3 of the first shoulder land portion 11. The circumferential pitch length of two sipes is the distance parallel to the circumferential direction of the tire from the center position in the width direction of the cross section of one sipe to the center position of the other sipe. If the distance changes in the axial direction of the tire, the intermediate distance corresponds to the circumferential length of one sipe.

It is desirable that the first shoulder sipe 21 is at least connected to the first shoulder circumferential groove 5. In this embodiment, the first shoulder sipe 21 extends, for example, from the first shoulder circumferential groove 5 to the first tread edge T1, completely across the tread surface of the first shoulder land portion 11. However, the first shoulder sipe 21 is not limited to this form, and may have an interrupted end within the first shoulder land portion 11.

The first shoulder sipes 21 are, for example, inclined in a first direction (upward and to the right in each figure of this specification) with respect to the tire axial direction. The angle of the first shoulder sipes 21 with respect to the tire axial direction is, for example, 5 to 35 degrees. In a more desirable embodiment, the first shoulder sipes 21 include a portion where the angle with respect to the tire axial direction increases toward the second tread edge T2 side. Such first shoulder sipes 21 also exert frictional force in the tire axial direction, improving wet performance.

The opening width W4 at the tread surface of the first shoulder sipe 21 is, for example, larger than the opening width W5 at the tread surface of the first middle sipe 30. Specifically, the opening width W4 of the first shoulder sipe 21 is, for example, 4.0 to 8.0 mm. The opening width W5 of the first middle sipe 30 is, for example, 2.0 to 6.0 mm. The opening width W5 of the first middle sipe 30 is 50% to 90% of the opening width W4 of the first shoulder sipe 21. Such first shoulder sipes 21 and first middle sipes 30 are useful for improving wet performance and noise performance in a well-balanced manner.

Figure 4 shows a cross-section of the first shoulder sipe 21, taken along line A-A in Figure 3. As shown in Figure 4, the first shoulder sipe 21 includes a main body portion 21a extending in the tire radial direction, and a widened portion 21b that opens at the tread of the land portion and has a width greater than that of the main body portion 21a. In this embodiment, the width of the main body portion is, for example, 0.5 to 1.5 mm.

The widened portion 21b of the first shoulder sipe 21 includes an inclined surface 22 that extends from the main body portion 21a to the tread surface. In this embodiment, the inclined surface 22 is flat and inclined at an angle θ1 of 50 to 70° relative to the tire radial direction. Such widened portion 21b allows the entire inclined surface 22 to come into contact with the ground when a large ground contact pressure acts on the land portion, thereby reliably expanding the effective contact area of the tread portion. Therefore, wet performance can be improved while also improving steering stability and ride comfort.

The depth d1 of the widened portion 21b of the first shoulder sipe 21 is 10% to 30% of the maximum depth d3 of the first shoulder sipe 21, and in a preferred embodiment, is 0.5 to 2.0 mm. The maximum depth d3 of the first shoulder sipe 21 is, for example, 70% to 100% of the depth of the circumferential groove 3.

The width W6 of the widened portion 21b of the first shoulder sipe 21 (the width along the tread surface in the cross section of the sipe) is, for example, 2.0 to 4.0 mm.

Figure 5 shows a cross-sectional view of line CC in Figure 3. As shown in Figure 6, the first shoulder sipe 21 includes a shallow bottom portion 23 whose bottom portion is locally raised. The shallow bottom portion 23 in this embodiment is provided, for example, at a communicating portion with the first shoulder circumferential groove 5. The minimum depth d4 of the shallow bottom portion 23 of the first shoulder sipe 21 is 40% to 60% of the maximum depth d3 of the first shoulder sipe 21. The axial length L3 of the shallow bottom portion 23 is 10% to 30% of the axial width W3 (shown in Figure 3) of the first shoulder land portion 11. The length L3 of the shallow bottom portion 23 is measured, for example, at the center position in the height direction of the shallow bottom portion 23. The first shoulder sipe 21 having such a shallow bottom portion 23 maintains the rigidity of the first shoulder land portion 11 and improves steering stability.

As shown in FIG. 3, the first middle land portion 12 includes a first vertical edge 12a on the first tread edge T1 side, a second vertical edge 12b on the second tread edge T2 side, and a tread surface between the first vertical edge 12a and the second vertical edge 12b. The first middle land portion 12 is provided with only sipes. This increases the rigidity of the first middle land portion 12. In this embodiment, the first middle land portion 12 is provided with a plurality of first middle sipes 30 extending in the tire axial direction.

Figure 6 shows a cross-sectional view of the first middle sipe 30 taken along line B-B in Figure 3. As shown in Figure 6, the first middle sipe 30 includes a main body portion 30a extending in the tire radial direction and a widened portion 30b that opens at the tread of the land portion and has a width greater than that of the main body portion 30a. In this embodiment, the width of the main body portion is, for example, 0.5 to 1.5 mm.

The widened portion 30b of the first middle sipe 30 includes an inclined surface 25 that extends from the main body portion 30a to the tread surface. In this embodiment, the inclined surface 25 is flat and inclined at an angle θ2 of 30 to 60° relative to the tire radial direction.

The depth d2 of the widened portion 30b of the first middle sipe 30 is 15% to 30% of the maximum depth d5 of the first middle sipe 30. The depth d2 of the widened portion 30b of the first middle sipe 30 is, for example, 1.0 to 3.0 mm. In a more desirable embodiment, the depth d1 of the widened portion 21b of the first shoulder sipe 21 is smaller than the depth d2 of the widened portion 30b of the first middle sipe 30. The depth d1 of the widened portion 21b of the first shoulder sipe 21 is 50% to 90% of the depth d2 of the widened portion 30b of the first middle sipe 30, and preferably 60% to 80%.

The width W8 of the widened portion 30b of the first middle sipe 30 (the width along the tread surface in the cross section of the sipe) is, for example, 1.0 to 3.0 mm.

The first middle sipes 30 include an outer first middle sipe 31 that extends from the first vertical edge 12a and has an interrupted end 31a within the first middle land portion 12, and an inner first middle sipe 32 that extends from the second vertical edge 12b and has an interrupted end 32a within the first middle land portion 12.

The first middle sipes 30 extend linearly in a plan view of the tread. The first middle sipes 30 are inclined in a first direction relative to the tire axial direction. More specifically, the outer first middle sipes 31 and the inner first middle sipes 32 each extend linearly in a plan view of the tread and are inclined in a first direction relative to the tire axial direction.

The angle of the outer first middle sipe 31 relative to the tire axial direction and the angle of the inner first middle sipe 32 relative to the tire axial direction are each preferably 20° or more, more preferably 25° or more, and preferably 45° or less, more preferably 40° or less. Such outer first middle sipe 31 and inner first middle sipe 32 provide a well-balanced friction force in the tire axial direction and the tire circumferential direction.

The angle difference between the outer first middle sipe 31 and the inner first middle sipe 32 is preferably 10° or less, more preferably 5° or less, and in this embodiment, they are arranged parallel to each other. Such outer first middle sipe 31 and inner first middle sipe 32 can suppress uneven wear of the first middle land portion 12.

The outer first middle sipe 31 and the inner first middle sipe 32 are each terminated without crossing the axial center position of the first middle land portion 12. The axial length La of the outer first middle sipe 31 is 20% or more, more preferably 25% or more, and preferably 45% or less, and more preferably 40% or less of the axial width W7 of the first middle land portion 12. Similarly, the axial length Lc of the inner first middle sipe 32 is 20% or more, more preferably 25% or more, and preferably 45% or less, and more preferably 40% or less of the axial width W7 of the first middle land portion 12. Such outer first middle sipe 31 and inner first middle sipe 32 can improve ride comfort and noise performance while maintaining steering stability.

The end 31a of the outer first middle sipe 31 and the end 32a of the inner first middle sipe 32 are misaligned in the tire circumferential direction. The distance Lb in the tire circumferential direction between the end 31a of the outer first middle sipe 31 and the end 32a of the inner first middle sipe 32 is, for example, 50% or less of one pitch length P2 of the first middle sipe 30 in the tire circumferential direction, and is preferably 25% to 40%. In a more desirable embodiment, the distance Lb is in the range of the following formula (3). This makes it easier for the pitch sound of each sipe to become white noise, improving noise performance.
Lb=2La±1(mm)...(3)

The pitch length P2 of the first middle sipe 30 is, for example, 80% to 120% of the pitch length P1 of the first shoulder sipe 21, and more preferably, they are the same.

In this embodiment, the outer first middle sipe 31 communicates with the first shoulder circumferential groove 5. In addition, in a plan view of the tread, the widened portion of the outer first middle sipe 31 overlaps with an area obtained by extending the widened portion 21b of the first shoulder sipe 21 along its length direction. This allows the outer first middle sipe 31 and the first shoulder sipe 21 to cooperate to further improve wet performance.

The first middle sipe 30 has a constant depth in its length direction. More specifically, the outer first middle sipe 31 and the inner first middle sipe 32 each have a constant depth in their length direction. The depth of the inner first middle sipe 32 is, for example, 70% to 100% of the depth of the circumferential groove 3. The maximum depth of the outer first middle sipe 31 is smaller than the maximum depth of the inner first middle sipe 32. The maximum depth of the outer first middle sipe 31 is 30% to 70% of the maximum depth of the inner first middle sipe 32, and in a desirable embodiment, is 1.0 to 2.5 mm.

The cross-sectional shape of the sipes shown in FIG. 6 can be applied to the outer first middle sipes 31 and the inner first middle sipes 32. Such outer first middle sipes 31 and inner first middle sipes 32 improve noise performance by converting the pitch sound of each sipe into white noise, and also improve ride comfort and handling stability in a well-balanced manner.

As shown in FIG. 3, the first middle land portion 12 is provided with a first longitudinal sipe 33 that extends in the tire circumferential direction. In this embodiment, the first longitudinal sipe 33 extends continuously in the tire circumferential direction. Such a first longitudinal sipe 33 provides a frictional force in the tire axial direction during wet driving. Further embodiments of the first longitudinal sipe 33 will be described later.

The first vertical sipes 33 are provided, for example, in the central region when the first middle land portion 12 is divided into thirds in the axial direction. The axial distance from the first vertical sipes 33 to the axial center position of the first middle land portion 12 is preferably 10% or less of the axial width W7 of the first middle land portion 12, and more preferably 5% or less. Such an arrangement of the first vertical sipes 33 can suppress uneven wear of the first middle land portion 12.

Figure 7 shows a cross-sectional view taken along line D-D in Figure 3. As shown in Figure 7, the first vertical sipe 33 has, for example, a constant width from the opening end to the bottom.

Figure 8 shows an enlarged view of the first middle land portion 12, the crown land portion 13, and the second middle land portion 14. As shown in Figure 8, the crown land portion 13 includes a first vertical edge 13a on the first tread edge T1 side, a second vertical edge 13b on the second tread edge T2 side, and a tread surface between the first vertical edge 13a and the second vertical edge 13b. Similarly, the second middle land portion 14 includes a first vertical edge 14a on the first tread edge T1 side, a second vertical edge 14b on the second tread edge T2 side, and a tread surface between the first vertical edge 14a and the second vertical edge 14b.

The crown land portion 13 includes an outer ground contact surface 36 located on the first tread edge T1 side of the tire equator C, and an inner ground contact surface 37 located on the second tread edge T2 side of the tire equator C. In this embodiment, when the axial widths of the outer ground contact surface 36 and the inner ground contact surface 37 are Wco and Wci, respectively, the following formula (4) is satisfied. Such a crown land portion 13 is useful for improving steering stability.
Wco>Wci…(4)

The axial width Wco of the outer ground contact surface 36 is, for example, 51% to 60% of the axial width W9 of the ground contact surface of the crown land portion 13, and preferably 51% to 55%. This improves steering stability while suppressing uneven wear of the crown land portion 13.

Only sipes are provided in the crown land portion 13. This increases the rigidity of the crown land portion 13.

The crown land portion 13 is provided with a plurality of crown sipes 40 that are inclined in a second direction (downward to the right in each figure of this specification) that is opposite to the first direction with respect to the tire axial direction. The crown sipes 40 in this embodiment extend linearly and inclined in the second direction. Such crown sipes 40 cooperate with the first middle sipes 30 to provide frictional forces in multiple directions, improving wet performance.

The circumferential pitch length P3 of the crown sipes 40 is, for example, 80% to 120% of the circumferential pitch length P2 (shown in FIG. 3) of the first middle sipes 30, and in this embodiment, these are the same. Such a sipe arrangement improves uneven wear resistance.

The angle of the crown sipes 40 with respect to the tire axial direction is preferably 20° or more, more preferably 25° or more, and preferably 45° or less, more preferably 40° or less. The crown sipes 40 provide a balanced friction force in the tire circumferential and axial directions.

The crown sipes 40 include outer crown sipes 41 that extend from the first longitudinal edge 40a and have an interrupted end 41a within the crown land portion 13, and inner crown sipes 42 that extend from the second longitudinal edge 40b and have an interrupted end 42a within the crown land portion 13.

The angle difference between the outer crown sipes 41 and the inner crown sipes 42 is preferably 10° or less, more preferably 5° or less, and in this embodiment, they are arranged parallel to each other. Such outer crown sipes 41 and inner crown sipes 42 suppress uneven wear of the crown land portion 13.

The outer crown sipes 41 and the inner crown sipes 42 are each interrupted without crossing the axial center position of the crown land portion 13. The axial length L4 of the outer crown sipes 41 and the axial length L5 of the inner crown sipes 42 are, for example, 20% to 35% of the axial width W9 of the crown land portion 13. Such outer crown sipes 41 and inner crown sipes 42 improve steering stability and ride comfort in a well-balanced manner.

The end 41a of the outer crown sipe 41 and the end 42a of the inner crown sipe 42 are misaligned in the tire circumferential direction. The distance L6 in the tire circumferential direction between the end 41a of the outer crown sipe 41 and the end 42a of the inner crown sipe 42 is preferably smaller than the distance Lb in the tire circumferential direction between the end 31a of the outer first middle sipe 31 and the end 32a of the inner first middle sipe 32. Specifically, the distance L6 is preferably 70% or less, more preferably 60% or less, and preferably 30% or more, more preferably 40% or more of the distance Lb. Such an arrangement of sipes turns the pitch sound of each sipe into white noise, improving noise performance.

The outer crown sipes 41 and the inner crown sipes 42 each have a constant depth in the length direction. The depth of the inner crown sipes 42 is, for example, 70% to 100% of the depth of the circumferential groove 3. The maximum depth of the outer crown sipes 41 is smaller than the maximum depth of the inner crown sipes 42. The maximum depth of the outer crown sipes 41 is 30% to 70% of the maximum depth of the inner crown sipes 42, and in a desirable embodiment, is 1.0 to 2.5 mm.

The cross-sectional shape configuration of the first middle sipe 30 described in FIG. 6 can be applied to the outer crown sipe 41 and the inner crown sipe 42. Therefore, the description here is omitted.

Only sipes are provided in the second middle land area 14. This increases the rigidity of the second middle land area 14.

The second middle land portion 14 is provided with a plurality of second middle sipes 45 that are inclined in the second direction with respect to the tire axial direction. In this embodiment, the second middle sipes 45 extend linearly and inclined in the second direction.

The circumferential pitch length P4 of the second middle sipes 45 is, for example, 80% to 120% of the circumferential pitch length P3 of the crown sipes 40, and in this embodiment, these are the same. Such a sipe arrangement improves uneven wear resistance.

The angle of the second middle sipe 45 with respect to the tire axial direction is preferably 20° or more, more preferably 25° or more, and preferably 45° or less, more preferably 40° or less. The crown sipe 40 provides a balanced friction force in the tire circumferential and axial directions.

The second middle sipes 45 include an outer second middle sipe 46 that extends from the first longitudinal edge 14a and has an interrupted end 46a within the crown land portion 13, and an inner second middle sipe 47 that extends from the second longitudinal edge 14b and has an interrupted end 47a within the crown land portion 13.

The angle difference between the outer second middle sipe 46 and the inner second middle sipe 47 is preferably 10° or less, more preferably 5° or less, and in this embodiment, they are arranged parallel to each other. Such outer second middle sipe 46 and inner second middle sipe 47 suppress uneven wear of the second middle land portion 14.

The outer second middle sipes 46 and the inner second middle sipes 47 are each terminated without crossing the axial center position of the second middle land portion 14. The axial length L7 of the outer second middle sipes 46 and the axial length L8 of the inner second middle sipes 47 are, for example, greater than the length L4 of the outer crown sipes 41 and the length L5 of the inner crown sipes 42. Specifically, the length L7 of the outer second middle sipes 46 and the length L8 of the inner second middle sipes 47 are 25% to 35% of the axial width W10 of the second middle land portion 14. Such outer second middle sipes 46 and inner second middle sipes 47 are useful for improving wet performance and ride comfort.

The end 46a of the outer second middle sipe 46 and the end 47a of the inner second middle sipe 47 are misaligned in the tire circumferential direction. The distance L9 between the end 46a of the outer second middle sipe 46 and the end 47a of the inner second middle sipe 47 in the tire circumferential direction is, for example, smaller than the distance Lb between the end 31a of the outer first middle sipe 31 and the end 32a of the inner first middle sipe 32 in the tire circumferential direction, and preferably smaller than the distance L6 between the end 41a of the outer crown sipe 41 and the end 42a of the inner crown sipe 42 in the tire circumferential direction. Specifically, the distance L9 is preferably 80% or less, more preferably 70% or less, and preferably 40% or more, more preferably 50% or more of the distance L6. Such an arrangement of sipes optimizes the rigidity balance of each land portion and improves the steering stability of wet performance in a well-balanced manner.

The outer second middle sipes 46 and the inner second middle sipes 47 each have a constant depth in the length direction. The depth of the inner second middle sipes 47 is, for example, 70% to 100% of the depth of the circumferential groove 3. The maximum depth of the outer second middle sipes 46 is smaller than the maximum depth of the inner second middle sipes 47. The maximum depth of the outer second middle sipes 46 is 30% to 70% of the maximum depth of the inner second middle sipes 47, and in a desirable embodiment, is 1.0 to 2.5 mm. Such outer crown sipes 41 and inner crown sipes 42 improve noise performance by converting the pitch sound of each sipe into white noise, and also improve ride comfort and handling stability in a well-balanced manner.

The cross-sectional shape configuration of the first middle sipe 30 described in FIG. 6 can be applied to the outer second middle sipe 46 and the inner second middle sipe 47. Therefore, the description here is omitted.

The second middle land portion 14 is provided with, for example, second longitudinal sipes 48 extending in the tire circumferential direction. In this embodiment, the second longitudinal sipes 48 extend continuously in the tire circumferential direction. The second longitudinal sipes 48 also have a cross-sectional shape similar to that of the first longitudinal sipes 33 described above. Such second longitudinal sipes 48 provide frictional force in the tire axial direction.

The second longitudinal sipe 48 is provided, for example, in the central region when the second middle land portion 14 is divided into thirds in the axial direction. The axial distance from the second longitudinal sipe 48 to the axial center position of the second middle land portion 14 is preferably 10% or less of the axial width W10 of the second middle land portion 14, and more preferably 5% or less.

Figure 9 shows an enlarged view of the second shoulder land portion 15 in Figure 1. As shown in Figure 9, the second shoulder land portion 15 is provided with only sipes. This increases the rigidity of the second middle land portion 14.

The second shoulder land portion 15 is provided with, for example, a plurality of second shoulder sipes 50 extending in the tire axial direction.

The circumferential pitch length P5 of the second shoulder sipe 50 is, for example, 30% to 70% of the circumferential pitch length P4 (shown in FIG. 8) of the second middle sipe 45.

The second shoulder sipes 50 are inclined, for example, in the first direction. That is, the first shoulder sipes 21 and the second shoulder sipes 50 are inclined in the same direction relative to the tire axial direction. In this embodiment, the second shoulder sipes 50 extend linearly, inclined in the first direction.

The angle of the second shoulder sipes 50 relative to the tire axial direction is, for example, 20° or less, preferably 15° or less, and more preferably 10° or less. As a result, in this embodiment, the maximum angle of the first shoulder sipes 21 relative to the tire axial direction is greater than the maximum angle of the second shoulder sipes 50 relative to the tire axial direction. This sipe arrangement further improves noise performance.

The cross-sectional shape of the first shoulder sipe 21 described in FIG. 4 can be applied to the second shoulder sipe 50. Therefore, the description here is omitted.

The second shoulder sipes 50 include, for example, transverse second shoulder sipes 51 that completely cross the second shoulder land portion 15 in the tire axial direction, and interrupted second shoulder sipes 52 that extend in the tire axial direction from at least the second tread edge T2 and have an interrupted end within the second shoulder land portion 15.

The interrupted second shoulder sipes 52 have a greater axial length than any of the first middle sipes 30, the crown sipes 40, and the second middle sipes 45. The axial length L10 of the second shoulder sipes 50 is preferably 50% or more, more preferably 60% or more, and preferably 90% or less, more preferably 80% or less of the axial width W11 of the second shoulder land portion 15. Such interrupted second shoulder sipes 52 improve wet performance and noise performance in a well-balanced manner.

Figure 10 shows a cross-sectional view of line E-E in Figure 9. As shown in Figure 10, the transverse second shoulder sipe 51 includes a shallow bottom portion 53 whose bottom portion is locally raised. The shallow bottom portion 53 in this embodiment is provided, for example, at a portion communicating with the second shoulder circumferential groove 8. The shallow bottom portion 53 of the second shoulder sipe 50 can be configured as the shallow bottom portion 23 of the first shoulder sipe 21 (shown in Figure 5), and a description thereof will be omitted here. The transverse second shoulder sipe 51 including such a shallow bottom portion 53 maintains the rigidity of the second shoulder land portion 15 and improves driving stability.

As shown in FIG. 1, in this embodiment, only sipes 16 are provided in each of the five land portions 4, and no lateral drainage grooves are provided. This maintains the rigidity of each land portion, and is expected to improve noise performance because no pumping noise is generated by the lateral grooves.

As a further desirable aspect, in this embodiment, the circumferential groove 3 includes a first groove wall 3a and a second groove wall 3b facing each other, and the first groove wall 3a is provided with a plurality of first recesses 56 recessed outward in the groove width direction from the groove edge of the circumferential groove 3 where the tread surface of the tread portion 2 appears. In addition, the second groove wall 3b is provided with a plurality of second recesses 57 recessed outward in the groove width direction from the groove edge of the circumferential groove 3 where the tread surface of the tread portion 2 appears. Such first recesses 56 and second recesses 57 can improve the drainage of the circumferential groove 3 and effectively suppress the hydroplaning phenomenon. In addition, the first recesses 56 and second recesses 57 can be expected to have the effect of attenuating the sound pressure of the noise generated by the circumferential groove 3, and are also useful for improving noise performance.

It is desirable that the first recess 56 has a gradually decreasing recession amount from the groove edge from the deepest part recessed furthest outward in the groove width direction to both sides in the tire circumferential direction. Similarly, it is desirable that the second recess 57 has a gradually decreasing recession amount from the groove edge from the deepest part recessed furthest outward in the groove width direction to both sides in the tire circumferential direction. Such first recess 56 and second recess 57 can prevent the formation of parts in the land portion with locally reduced rigidity and suppress uneven wear of the land portion.

To further enhance the above-mentioned effect, it is preferable that the first recesses 56 and the second recesses 57 are arranged alternately in the tire circumferential direction.

In this embodiment, the land portion is provided with multiple sipes that communicate with the circumferential grooves 3, and one first recess 56 and one second recess 57 are provided between the circumferential length of the sipes, which is 1.0 to 3.0 times the pitch length of the sipes. In other words, the circumferential length of the pair of first recess 56 and second recess 57 is 1.0 to 3.0 times the pitch length of the sipes. This improves noise performance while maintaining the rigidity of the land portion.

Figure 11 shows a cross-sectional view taken along line F-F in Figure 1. Figure 12 shows a cross-sectional view taken along line G-G in Figure 1. As shown in Figures 11 and 12, the first groove wall 3a and the second groove wall 3b have substantially the same shape. Furthermore, the first recess 56 and the second recess 57 have substantially the same shape. For this reason, the configuration of the first groove wall 3a described below can be applied to the second groove wall 3b. Furthermore, the configuration of the first recess 56 can be applied to the second recess 57.

The first groove wall 3a includes an outer portion 18 that extends from the groove edge of the circumferential groove 3 toward the inside in the tire radial direction at an incline in a direction that reduces the groove width. The first groove wall 3a also includes an inner portion 19 that extends from the outer portion 18 toward the inside in the tire radial direction at an incline in a direction that increases the groove width and is connected to the groove bottom. This inner portion 19 forms the bottom surface of the first recess 56.

The height h1 of the first recess 56 in the tire radial direction is, for example, 30% to 70% of the total depth d6 of the circumferential groove 3, and preferably 40% to 60%. Such a first recess 56 can improve wet performance and noise performance while suppressing uneven wear of the land portion.

From a similar perspective, the depth d7 of the first recess 56 is, for example, 1.0 to 3.0 mm, and preferably 1.5 to 2.5 mm. The depth d7 corresponds to the distance in the groove width direction (the direction parallel to the tread surface) from the first groove wall 3a where the first recess 56 is not provided to the deepest part of the first recess 56. It goes without saying that the height h1 and depth d7 of the first recess 56 described above can also be applied to the second recess 57.

Other embodiments of the present invention are described below. In the figures showing the other embodiments, the elements already described are given the same reference numerals as those described above, and the configurations described above can be applied.

Figure 13 shows an exploded view of the tread portion 2 of another embodiment. As shown in Figure 13, in this embodiment, the first middle land portion 12, the crown land portion 13, and the second middle land portion 14 have the same width in the tire axial direction. The tire axial width W12 is, for example, 10% to 20% of the tread width TW.

In this embodiment, the first shoulder land portion 11 and the second shoulder land portion 15 have the same width in the tire axial direction. The tire axial width W13 is, for example, 15% to 20% of the tread width TW.

In the embodiment of FIG. 13, the land portion described above can further improve the uneven wear resistance of the tread portion 2.

Figure 14 shows an enlarged view of the first middle land portion 12 of another embodiment. As shown in Figure 14, the first longitudinal sipes 33 provided in this first middle land portion 12 extend in a zigzag pattern in the tire circumferential direction. The first longitudinal sipes 33 may extend in a wavy pattern with a smooth curve, for example. The amplitude A1 (peak-to-peak value) of the first longitudinal sipes 33 in the tire axial direction is, for example, 1.0% to 8.0% of the axial width W7 of the first middle land portion 12. The first longitudinal sipes 33 extend in a zigzag pattern so that one period is equal to two pitches of the first middle sipes 30. Such first longitudinal sipes 33 can also provide friction in the tire circumferential direction.

Figure 15 shows an enlarged view of the first middle land portion 12 of yet another embodiment. As shown in Figure 15, the first longitudinal sipes 33 provided in this first middle land portion 12 extend intermittently in the tire circumferential direction. That is, the first longitudinal sipes 33 are composed of a plurality of longitudinal sipe pieces 54 arranged in the tire circumferential direction. The tire circumferential length L11 of one longitudinal sipe piece 54 is, for example, 20% to 60% of one pitch length P2 of the first middle sipe 30 in the tire circumferential direction. Such a first longitudinal sipe 33 can provide frictional force in the tire axial direction while maintaining the rigidity of the first middle land portion 12.

The configuration of the first vertical sipes 33 shown in Figures 14 and 15 can also be applied to the second vertical sipes 48 provided in the second middle land area 14.

The tire according to one embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment described above and can be modified and implemented in various ways.

A tire of size 235/55R19 having the basic pattern of Figure 1 was prototyped based on the specifications in Tables 1 and 2. In addition, as a standard tire (reference tire) for comparing noise performance, a tire having the pattern shown in Figure 1 and no widened portions in each sipe was prototyped. The reference tire is substantially the same as the pattern in Figure 1, except for the points mentioned above.

As a comparative example, a tire was produced in which the total number of first shoulder sipes was the same as the total number of second shoulder sipes by excluding the interrupted second shoulder sipes from the pattern in Fig. 1. The comparative tire was substantially the same as that shown in Fig. 1 except for the above-mentioned points. The wet performance and noise performance of each test tire were tested. The common specifications and test methods of each test tire are as follows.
Rim: 19 x 7.0J
Tire pressure: 230kPa
Test vehicle: 2000cc displacement, four-wheel drive Tire mounting position: All wheels

<Wet performance>
The wet performance of the test vehicle when it was driven on a wet road surface was evaluated by the driver. The results are rated based on the wet performance of the comparative example being 100, with a higher value indicating better wet performance.

<Noise performance>
The test vehicle was driven on a dry road surface at 40 to 100 km/h, and the maximum sound pressure of noise inside the vehicle was measured. The results are expressed as an index of the reduction in sound pressure, which is the difference from the sound pressure of the reference tire, with the reduction in sound pressure of the comparative example taken as 100. The larger this index, the smaller the maximum sound pressure of the noise, indicating excellent noise performance.
The results of the tests are shown in Tables 1-2.

The test results confirmed that the tires of the embodiment have improved wet performance and noise performance.

2 Tread portion 3 Circumferential groove 4 Land portion 11 First shoulder land portion 15 Second shoulder land portion 21 First shoulder sipe 50 Second shoulder sipe T1 First tread edge T2 Second tread edge

Claims (11)

A tire having a tread portion with a specified mounting direction on a vehicle,
the tread portion includes a first tread edge that is on an outer side of the vehicle when mounted on the vehicle, a second tread edge that is on an inner side of the vehicle when mounted on the vehicle, a plurality of circumferential grooves that extend continuously in the tire circumferential direction between the first tread edge and the second tread edge, and a plurality of land portions that are divided by the circumferential grooves,
the plurality of land portions include a first shoulder land portion including the first tread edge and a second shoulder land portion including the second tread edge,
The first shoulder land portion is provided with a plurality of first shoulder sipes extending in the tire axial direction,
The second shoulder land portion is provided with a plurality of second shoulder sipes extending in the tire axial direction,
The total number of the second shoulder sipes is greater than the total number of the first shoulder sipes,
the plurality of circumferential grooves include a first shoulder circumferential groove provided between the first tread edge and a tire equator, and a first crown circumferential groove provided between the first shoulder circumferential groove and the tire equator,
the plurality of land portions include a first middle land portion divided into the first shoulder circumferential groove and the first crown circumferential groove,
the first middle land portion includes a first vertical edge on the first tread end side,
The first middle land portion is provided with a plurality of first middle sipes extending in the tire axial direction,
The first middle sipe includes a main body portion extending in a tire radial direction and a widened portion that opens at a tread surface of the land portion and has a width larger than that of the main body portion,
The first middle sipe includes an outer first middle sipe extending from the first longitudinal edge and having an interrupted end within the first middle land portion,
The first shoulder sipe communicates with the first shoulder circumferential groove,
The first shoulder sipe includes a main body portion extending in a radial direction of the tire and a widened portion that opens at a tread surface of the land portion and has a width larger than that of the main body portion,
In a tread plan view, the widened portion of the outer first middle sipe overlaps with a region obtained by extending the widened portion of the first shoulder sipe along its length direction.
tire. The tire according to claim 1, wherein the total number of the second shoulder sipes is 1.5 to 2.5 times the total number of the first shoulder sipes. The tire according to claim 1 or 2, wherein only sipes are provided in the first shoulder land portion and the second shoulder land portion. The tire according to any one of claims 1 to 3, wherein the first shoulder sipe and the second shoulder sipe are inclined in the same direction relative to the tire axial direction. The tire according to any one of claims 1 to 4, wherein the maximum angle of the first shoulder sipe relative to the tire axial direction is greater than the maximum angle of the second shoulder sipe relative to the tire axial direction. The tire according to any one of claims 1 to 5, wherein the first shoulder sipe completely crosses the first shoulder land portion in the tire axial direction. The tire according to any one of claims 1 to 6, wherein the first shoulder sipe includes a portion in which the angle with respect to the tire axial direction increases toward the tire equator. The tire according to any one of claims 1 to 7, wherein the second shoulder sipe extends linearly. The tire according to any one of claims 1 to 8, wherein the second shoulder sipes include a transverse second shoulder sipe that completely crosses the second shoulder land portion in the tire axial direction, and an interrupted second shoulder sipe that extends from at least the second tread edge in the tire axial direction and has an interrupted end within the second shoulder land portion. The tire according to claim 9, wherein the axial length of the interrupted second shoulder sipe is 50% to 90% of the axial width of the second shoulder land portion. The circumferential groove includes a first groove wall and a second groove wall facing each other,
The first groove wall is provided with a plurality of first recesses recessed in a groove width direction outward from a groove edge of the circumferential groove where a tread surface of the tread portion appears,
The second groove wall is provided with a plurality of second recesses recessed in a groove width direction outward from a groove edge of the circumferential groove where a tread surface of the tread portion appears,
The first recess and the second recess each have a recess amount from the groove edge that gradually decreases from a deepest portion recessed furthest outward in the groove width direction toward both sides in the tire circumferential direction,
A plurality of sipes communicating with the circumferential groove are provided in the land portion adjacent to the circumferential groove in the tire circumferential direction,
The tire according to any one of claims 1 to 10, wherein the first recessed portion and the second recessed portion are provided one by one within a length that is 1.0 to 3.0 times a pitch length of the sipe.

Images