tire

Abstract

To provide a tire that can maintain balance between dry performance and wet performance even if a tread part is abraded.SOLUTION: The tire has a tread part 2. The tread part 2 includes a first shoulder land part 11. The first shoulder land part 11 is provided with shoulder lateral grooves 16 and shoulder sipes 17. The shoulder lateral groove 16 includes a minimum part 20 at which a groove width of the shoulder lateral groove 16 is minimum, in the middle between a grounding surface 11s and a groove bottom of the shoulder lateral groove 16. Widths of the shoulder sipes 17 are 1.5 mm or less. An inner groove 22 having a groove width larger than the width of the shoulder sipe 17 communicates with an inside in a tire radial direction of the shoulder sipe 17. The inner groove 22 is arranged closer to inside in the tire radial direction than the minimum part 20 and closer to outside in the tire radial direction than the groove bottom of the shoulder lateral groove 16.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a tire. [Background technology]

[0002] Patent Document 1 below proposes a tire having grooves on the tread surface that extend in the tire axial direction. The grooves in Patent Document 1 include a minimum portion where the groove width is locally the smallest on the radially inner side of the openings formed on the tread surface. The tire in Patent Document 1 is expected to improve uneven wear resistance and grip performance in a well-balanced manner by the grooves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-188850 A Summary of the Invention [Problem to be solved by the invention]

[0004] In general, when the tread portion wears, the volume of the grooves provided in the tread portion and the groove width appearing on the ground contact surface tend to decrease, and as a result, the balance between the dry performance and the wet performance of the tire tends to deteriorate compared to when the tire was new. Therefore, it has been conventionally required to maintain the balance even when the tread portion is worn.

[0005] The grooves in Patent Document 1 are shaped such that after the minimum portion is exposed due to wear of the tread portion, the groove width at the contact surface expands with the wear, so that some degree of improvement in maintaining the balance can be expected. However, in recent years, the required standards for various tire performances have been increasing, and further improvement in maintaining the balance is also required.

[0006] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire which is capable of maintaining a balance between dry performance and wet performance even when the tread portion is worn. [Means for solving the problem]

[0007] The present invention is a tire having a tread portion, the tread portion including a first tread edge and a first shoulder land portion which is a land portion including the first tread edge, the first shoulder land portion being provided with a shoulder lateral groove and a shoulder sipe extending in the tire axial direction on the ground contact surface of the first shoulder land portion, the shoulder lateral groove including a minimum portion where the groove width of the shoulder lateral groove is minimum midway between the ground contact surface and a groove bottom of the shoulder lateral groove, the width of the shoulder lateral groove being 1.5 mm or less, the shoulder sipe being connected radially inward to an internal groove having a groove width larger than the width of the shoulder sipe, and the internal groove being arranged radially inward of the minimum portion and radially outward of the groove bottom of the shoulder lateral groove.

[0008] In the tire of the present invention, it is preferable that the shoulder lateral groove crosses the first tread edge.

[0009] In the tire of the present invention, it is preferable that the shoulder sipe crosses the first tread edge.

[0010] In the tire of the present invention, it is preferable that the shoulder lateral groove includes a main body portion located radially inward of the minimum portion, and the maximum groove width of the main body portion is smaller than the groove width of the shoulder lateral groove at the contact patch.

[0011] In the tire of the present invention, in the contact surface of the first shoulder land portion, the distance in the tire circumferential direction from an edge of the shoulder lateral groove to an edge of the shoulder sipe is preferably 1.3 to 2.7 times the groove width of the shoulder lateral groove.

[0012] In the tire of the present invention, it is preferable that the tread portion has a specified orientation when mounted on a vehicle, and the first shoulder land portion is disposed on the inner side of the tire equator when mounted on the vehicle. Effect of the Invention

[0013] By adopting the above-mentioned configuration, the tire of the present invention can maintain a balance between dry performance and wet performance even when the tread portion is worn. [Brief description of the drawings]

[0014] [Figure 1] 1 is a development view of a tread portion of a tire according to one embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged view of a first shoulder land portion of FIG. [Diagram 3] 3 is a cross-sectional view taken along line AA in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view taken along line BB in FIG. [Diagram 5] FIG. 4 is a cross-sectional view of a shoulder lateral groove of a comparative example. [Figure 6] FIG. 4 is a cross-sectional view of a shoulder sipe of a comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, an 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 of this embodiment. As shown in Fig. 1, the tire 1 of this embodiment is used, for example, as an all-season pneumatic tire for passenger cars. However, the tire 1 of the present invention is not limited to such an embodiment.

[0016] The tire 1 of this embodiment has a tread portion 2 in which the mounting direction on a vehicle is specified, for example. The mounting direction on a vehicle is indicated, for example, by characters or marks on the sidewall portion (not shown). In addition, the tread portion 2 is configured, for example, in an asymmetric pattern (meaning that the tread pattern is not line-symmetric with respect to the tire equator C).

[0017] The tread portion 2 includes a first tread edge T1 that is located on the inside of the vehicle when mounted on the vehicle, and a second tread edge T2 that is located on the outside of the vehicle when mounted on the vehicle. The first tread edge T1 and the second tread edge T2 each correspond to the axially outermost contact positions when the tire 1 in a normal state is loaded with a normal load and contacts a flat surface with a camber angle of 0°.

[0018] "Normal condition" means, in the case of a pneumatic tire for which various standards are established, that the tire is mounted on a normal rim, inflated to the normal internal pressure, and no load is applied. In the case of a tire for which various standards are not established or a non-pneumatic tire, the normal condition means a standard use condition according to the intended use of the tire, and a state in which no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured in the normal condition.

[0019] A "genuine rim" is a rim that is defined 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."

[0020] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. In the case of JATMA, it is the "maximum air pressure." In the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." In the case of ETRTO, it is the "INFLATION PRESSURE."

[0021] In the case of a pneumatic tire for which various standards are established, the "normal load" is the load that each standard specifies for each tire in the standard system including the standard on which the tire is based. For JATMA, it is the "maximum load capacity", for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is the "LOAD CAPACITY". In addition, in the case of a tire for which various standards are not established or a non-pneumatic tire, the "normal load" refers to the load acting on one tire in the standard mounting state of the tire. The "standard mounting state" refers to a state in which the tire is mounted on a standard vehicle according to the intended use of the tire, and the vehicle is stationary on a flat road surface in a drivable state.

[0022] The tread portion 2 includes a plurality of circumferential grooves 3 extending continuously in the tire circumferential direction between the first tread edge T1 and the second tread edge T2, and a plurality of land portions divided by the circumferential grooves 3. 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 divided by four circumferential grooves 3. However, the present invention is not limited to this embodiment, and for example, the tire may be a so-called four-rib tire in which the tread portion 2 is configured by three circumferential grooves 3 and four land portions.

[0023] The circumferential grooves 3 include, for example, a first crown circumferential groove 4, a second crown circumferential groove 5, a first shoulder circumferential groove 6, and a second shoulder circumferential groove 7. The first crown circumferential groove 4 is provided between the tire equator C and the first tread edge T1. The second crown circumferential groove 5 is provided between the tire equator C and the second tread edge T2. The first shoulder circumferential groove 6 is provided between the first crown circumferential groove 4 and the first tread edge T1. The second shoulder circumferential groove 7 is provided between the second crown circumferential groove 5 and the second tread edge T2.

[0024] The circumferential grooves 3 may have various configurations, such as extending linearly in the tire circumferential direction or extending in a zigzag pattern.

[0025] The axial distance L1 from the groove centerline of the first crown circumferential groove 4 or the second crown circumferential groove 5 to the tire equator C is, for example, 5% to 15% of the tread width TW. The axial distance L2 from the groove centerline of the first shoulder circumferential groove 6 or the second shoulder circumferential groove 7 to the tire equator C is, for example, 25% to 35% of the tread width TW. However, the present invention is not limited to such dimensions. The tread width TW is the axial distance from the first tread edge T1 to the second tread edge T2 in the normal state.

[0026] The groove width W1 of the circumferential groove 3 is desirably at least 3 mm or more. In a desirable embodiment, the groove width W1 of the circumferential groove 3 is 3.0% to 7.0% of the tread width TW.

[0027] The land portion includes at least a first shoulder land portion 11. The first shoulder land portion 11 is sectioned on the axially outer side of the first shoulder circumferential groove 6, and includes a first tread edge T1.

[0028] The land portion of this embodiment includes, in addition to the first shoulder land portion 11, a second shoulder land portion 12, a first middle land portion 13, a second middle land portion 14, and a crown land portion 15. The second shoulder land portion 12 is located axially outward of the second shoulder circumferential groove 7 and includes the second tread edge T2. The first middle land portion 13 is located between the first shoulder circumferential groove 6 and the first crown circumferential groove 4. The second middle land portion 14 is located between the second shoulder circumferential groove 7 and the second crown circumferential groove 5. The crown land portion 15 is located between the first crown circumferential groove 4 and the second crown circumferential groove 5.

[0029] Fig. 2 shows an enlarged view of the first shoulder land portion 11. As shown in Fig. 2, the first shoulder land portion 11 is provided with shoulder lateral grooves 16 and shoulder sipes 17 that extend along the contact surface 11s of the first shoulder land portion 11 in the tire axial direction.

[0030] In this specification, the term "sipe" refers to a cut element having a small width, and the width between two inner walls facing each other is 1.5 mm or less. The width of the sipe is preferably 0.3 to 1.0 mm. The opening of the sipe may be connected to a chamfered portion having a width exceeding 1.5 mm.

[0031] In this embodiment, the shoulder lateral grooves 16 and the shoulder sipes 17 each communicate with the first shoulder circumferential groove 6 and cross the first tread edge T1. However, the present invention is not limited to this embodiment, and the shoulder lateral grooves 16 and the shoulder sipes 17 may have discontinuous ends within the contact patch of the first shoulder land portion 11.

[0032] In this embodiment, the angle of the shoulder lateral groove 16 with respect to the tire axial direction and the angle of the shoulder sipe 17 with respect to the tire axial direction are, for example, 45° or less, preferably 25° or less, and more preferably 15° or less. The angle difference between the shoulder lateral groove 16 and the shoulder sipe 17 is preferably 5° or less, and in this embodiment, they are arranged parallel to each other.

[0033] Fig. 3 shows a cross section taken along line AA in Fig. 2. As shown in Fig. 3, the shoulder lateral groove 16 includes a minimum portion 20 where the groove width of the shoulder lateral groove 16 is minimum, between the ground contact surface 11s of the first shoulder land portion 11 and the groove bottom of the shoulder lateral groove 16.

[0034] Fig. 4 shows a cross-sectional view of line BB in Fig. 2. As shown in Fig. 4, the width W2 of the shoulder sipe 17 is 1.5 mm or less. Further, the shoulder sipe 17 communicates with an internal groove 22 having a groove width larger than the width W2 of the shoulder sipe 17 on the inner side in the tire radial direction.

[0035] The internal groove 22 is disposed radially inward of the minimum portion 20 and radially outward of the groove bottom 16d (shown in FIG. 3) of the shoulder lateral groove 16. By adopting the above-mentioned configuration, the tire 1 of the present invention can maintain a balance between dry performance and wet performance even when the tread portion 2 is worn. The following mechanism is presumed to be the reason for this.

[0036] In the tire 1 of the present invention, after the tread portion 2 wears and the minimum portion 20 is exposed, the groove width of the shoulder lateral groove 16 in the contact surface 11s increases with the wear, so that wet performance can be ensured for a long period of time. Also, while the shoulder sipes 17 are exposed to the contact surface 11s, the rigidity of the first shoulder land portion 11 is maintained, and the deterioration of dry performance can be suppressed.

[0037] When the wear of the tread portion 2 progresses and the distance between the internal groove 22 and the ground contact surface becomes smaller, the internal groove 22 compensates for drainage and can suppress excessive deterioration of wet performance. In addition, in the present invention, the internal groove 22 is arranged radially inward of the minimum part 20 and radially outward of the groove bottom 16d of the shoulder lateral groove 16, so that after the minimum part 20 is exposed, the internal groove 22 is exposed to the ground contact surface before the shoulder lateral groove 16 disappears due to wear, and therefore deterioration of wet performance can be reliably suppressed. It is presumed that this mechanism allows the present invention to maintain a balance between dry performance and wet performance even when the tread portion 2 is worn.

[0038] A more detailed configuration of this embodiment will be described below. Each configuration described below shows 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 configuration described below. In addition, even if any one of the configurations described below is applied alone to the tire of the present invention having the above-mentioned characteristics, an improvement in performance according to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a composite improvement in performance according to each configuration can be expected.

[0039] 2, the shoulder lateral grooves 16 and the shoulder sipes 17 are alternately provided in the tire circumferential direction. A one-pitch length P1 of the shoulder lateral grooves 16 in the tire circumferential direction and a one-pitch length P2 of the shoulder sipes 17 in the tire circumferential direction are each, for example, 70% to 100% of a width W3 of the first shoulder land portion 11 in the tire axial direction.

[0040] On the contact surface 11s of the first shoulder land portion 11, the distance L3 in the tire circumferential direction from the edge of the shoulder lateral groove 16 to the edge of the shoulder sipe 17 is preferably 1.3 times or more, more preferably 1.5 times or more, even more preferably 1.7 times or more, and preferably 2.7 times or less, more preferably 2.5 times or less, and even more preferably 2.3 times or less, of the groove width W5 on the contact surface 11s of the shoulder lateral groove 16. Such an arrangement of the shoulder lateral groove 16 and the shoulder sipe 17 helps to improve dry performance and wet performance in a well-balanced manner.

[0041] As shown in FIG. 3, in the ground contact surface of the first shoulder land portion 11, the groove width W5 of the shoulder lateral groove 16 is, for example, 50% to 70% of the groove width W4 of the first shoulder circumferential groove 6 (shown in FIG. 2).

[0042] The maximum depth d1 of the shoulder lateral groove 16 is, for example, 70% to 90% of the maximum depth of the first shoulder circumferential groove 6. However, the shoulder lateral groove 16 is not limited to this embodiment.

[0043] The depth d2 from the ground contact surface 11s to the minimum portion 20 is, for example, less than 50% of the maximum depth d1 of the shoulder lateral groove 16. The depth d2 of the minimum portion 20 is preferably 40% or less of the depth d1, more preferably 30% or less, and preferably 5% or more, and more preferably 10% or more. This allows the minimum portion 20 to be exposed to the ground contact surface 11s at a stage when the wear of the tread portion 2 has progressed moderately, and the deterioration of wet performance due to the subsequent wear of the tread portion can be suppressed.

[0044] The groove width W6 of the minimum portion 20 is, for example, 30% to 60%, and preferably 40% to 50%, of the groove width W5 at the contact surface 11s of the shoulder lateral groove 16. Such a minimum portion 20 helps to maintain a balance between dry performance and wet performance.

[0045] In the region from the contact surface 11s to the minimum portion 20, the angle θ1 of the groove wall of the shoulder lateral groove 16 with respect to the tire normal is, for example, 40 to 60°. As a result, when the tire starts to be used, the groove wall on the outer side in the tire radial direction than the minimum portion 20 comes into contact with the ground moderately in response to an increase in ground pressure. In other words, the groove wall on the outer side in the tire radial direction than the minimum portion 20 can play the role of a chamfered portion, which is expected to improve traction performance and braking performance. In addition, the first shoulder land portion 11 in which such shoulder lateral grooves 16 are arranged can make the ground pressure during braking more uniform, so that it is expected to improve uneven wear resistance and reduce pattern noise when worn.

[0046] The shoulder lateral groove 16 includes a main body portion 25 located radially inward of the minimum portion 20. The maximum groove width W7 of the main body portion 25 is equal to or smaller than the groove width W5 of the shoulder lateral groove 16 at the contact surface 11s. The maximum groove width W7 of the main body portion 25 is, for example, 50% to 100%, and preferably 70% to 100%, of the groove width W5 of the shoulder lateral groove 16 at the contact surface 11s. This allows sufficient wet performance to be exhibited when the tread portion 2 is worn to the extent that the vicinity of the maximum groove width W7 is exposed.

[0047] Furthermore, the maximum groove width W7 of the main body portion 25 is, for example, 300% or less, and preferably 150% to 250% of the groove width W6 of the very small portion 20. This makes it possible to suppress molding defects during vulcanization molding and to exhibit sufficient wet performance.

[0048] A depth d3 from the ground contact surface 11s to the position of the maximum groove width W7 of the main body portion 25 is, for example, 80% to 90% of the maximum depth d1 of the shoulder lateral groove 16.

[0049] The main body 25 includes a region in which the groove width increases toward the inside in the tire radial direction. The angle θ2 of the groove wall in this region with respect to the tire normal is smaller than the angle θ1, and is, for example, 15 to 25°.

[0050] As shown in FIG. 4, a depth d4 from the ground contact surface 11s to the bottom of the internal groove 22 is, for example, smaller than the maximum depth d1 of the shoulder lateral groove 16, and is desirably 70% to 90% of the depth d1.

[0051] The shoulder sipe 17 has, for example, a sipe wall that is connected to the ground contact surface and extends parallel to the tire radial direction. The depth d5 ​​of the shoulder sipe 17 is, for example, greater than the depth d2 from the ground contact surface 11s to the minimum part 20 and is 300% or less of the depth d2. Specifically, the depth d5 ​​of the shoulder sipe 17 is preferably 150% or more, more preferably 180% or more, and preferably 250% or less, more preferably 220% or less of the depth d2. As a result, after the minimum part 20 of the shoulder lateral groove 16 is exposed, the inner groove 22 is exposed in a state where wear has progressed to a certain extent, so that the balance between dry performance and wet performance can be maintained even if the tread part is worn.

[0052] The maximum groove width W8 of the internal groove 22 is, for example, 500% or less of the width W2 of the shoulder sipe 17. Specifically, the maximum groove width W8 of the internal groove 22 is desirably 200% or more, more desirably 250% or more, and desirably 400% or less, more desirably 350% or less of the width W2 of the shoulder sipe 17. Such an internal groove 22 can exert the above-mentioned effects while suppressing vulcanization molding defects.

[0053] The cross-sectional area of ​​the internal groove 22 is desirably 10% to 50% of the cross-sectional area of ​​the main body 25 of the shoulder lateral groove 16. This allows the internal groove 22 to sufficiently supplement the drainage performance of the shoulder lateral groove 16.

[0054] 1, in this embodiment, at least the above-mentioned shoulder lateral grooves 16 and shoulder sipes 17 are provided in the first shoulder land portion 11 that is disposed on the vehicle inner side of the tire equator C when mounted on the vehicle. In a more preferable embodiment, the above-mentioned shoulder lateral grooves 16 and shoulder sipes 17 are also provided in the second shoulder land portion 12. This makes it possible to more reliably achieve the above-mentioned effects.

[0055] Although the tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the above specific embodiment and can be modified and carried out in various aspects. EXAMPLES

[0056] A tire having a size of 275 / 40ZR20 and the pattern shown in FIG. 1 was prototyped based on the specifications in Tables 1 and 2. As a comparative example, a tire having shoulder lateral grooves a having a cross-sectional shape shown in FIG. 5 and shoulder sipes b having a cross-sectional shape shown in FIG. 6 was prototyped. The comparative tire has substantially the same configuration as the tire shown in FIG. 1, except for the above-mentioned points. Each test tire was tested for dry performance and wet performance at the beginning of use, wet performance when worn, and the balance between dry performance and wet performance when worn. The common specifications and test methods of each test tire are as follows. Rim: 20×9.5J Tire pressure: 220kPa for all wheels Test vehicle: 3500cc, rear-wheel drive Tire mounting position: All wheels

[0057] <Dry and wet performance at the beginning of use> The above test vehicle was used, and the performance of the tire when it was driven on dry or wet roads at the beginning of its use was evaluated by the driver's senses. The results are given as a score based on the performance of the comparative example being 100, with a higher value indicating better dry or wet performance.

[0058] <Wet performance when worn> The above test vehicle was used, and the performance when the tire was driven on a wet road surface in a state where the depth of the shoulder lateral grooves had worn down to 50% of that of a new tire was evaluated by the driver's senses. The results were evaluated based on the performance of the comparative example being 100, and the higher the value, the better the wet performance when worn.

[0059] <Balance between dry and wet performance when worn> The above test vehicle was used to run on dry and wet roads with the depth of the shoulder lateral grooves worn down to 50% of that of a new tire, and the balance between dry and wet performance was evaluated. The results are expressed as an index with the balance of the comparative example being 100, and the higher the value, the better the balance. The results of the tests are shown in Tables 1 and 2.

[0060] [Table 1]

[0061] [Table 2]

[0062] As shown in Tables 1 and 2, the tires of the examples show high scores for the "balance between dry performance and wet performance during wear." In other words, it was confirmed that the balance was maintained in the present invention.

[0063] Specifically, the following can be confirmed from Tables 1 and 2. That is, in each Example, the score for "dry performance at the beginning of use" is 97 to 102 points. In addition, in each Example, the score for "wet performance at the beginning of use" is 101 to 107 points. In contrast, in each Example, the score for "wet performance when worn" is 105 to 113 points, and it can be understood that the wet performance when worn is maintained remarkably compared to the comparative example. As described above, in the past, wet performance deteriorates as the tire wears, and the balance between dry performance and wet performance deteriorates, but in the tires of each Example, the deterioration of wet performance is small even with wear, and it was confirmed that the balance between dry performance and wet performance when worn is maintained. [Explanation of symbols]

[0064] 2 Tread section 11 First Shoulder Land Section 11s ground plane 16 Shoulder groove 17 Shoulder sipes 20 Minimal part 22 Internal groove T1 First tread edge

Claims

1. A tire having a tread portion, The tread portion includes a first tread edge and a first shoulder land portion that is a land portion including the first tread edge, The first shoulder land portion is provided with a shoulder lateral groove and a shoulder sipe extending in the tire axial direction on a ground contact surface of the first shoulder land portion, the shoulder lateral groove includes a minimum portion, between the ground contact surface and a groove bottom of the shoulder lateral groove, where the groove width of the shoulder lateral groove is minimum, The width of the shoulder sipe is 1.5 mm or less, An internal groove having a groove width larger than the width of the shoulder sipe is connected to the inside of the shoulder sipe in the tire radial direction, the internal groove is disposed radially inward of the minimum portion and radially outward of the groove bottom of the shoulder lateral groove, The groove width of the minimum portion is 30% to 60% of the groove width of the shoulder lateral groove at the ground contact surface. tire.

2. The tire of claim 1 , wherein the shoulder lateral groove traverses the first tread edge.

3. The tire of claim 1 or 2, wherein the shoulder sipe traverses the first tread edge.

4. the shoulder lateral groove includes a main body portion located radially inward of the minimum portion, The tire according to claim 1 , wherein a maximum groove width of the main body portion is smaller than a groove width of the shoulder lateral groove in the contact patch.

5. 5. The tire according to claim 1, wherein a distance in the tire circumferential direction from an edge of the shoulder lateral groove to an edge of the shoulder sipe in the contact surface of the first shoulder land portion is 1.3 to 2.7 times a groove width of the shoulder lateral groove.

6. The tread portion has a specified orientation for installation on a vehicle, The tire according to claim 1 , wherein the first shoulder land portion is disposed on an inner side of a tire equator when the tire is mounted on a vehicle.

Images