Tire

Abstract

To provide a tire which can exert excellent dart performance and mud performance.SOLUTION: A tire includes a tread portion 2. The tread portion 2 includes: a shoulder block row 5; a crown block row 6; and an inclined groove 10. Each of the plurality of crown blocks 8 is arranged to overlap the plurality of shoulder blocks 7 in a tire axial direction. Each of the inclined grooves 10 includes: a first groove portion 11; a second groove portion 12; and a third groove portion 13. A recess 16 is formed at a portion of the crown block 8 contacting with the first groove portion 11. The deepest portion of the recess 16 is positioned at an outer side in a tire radial direction relative to a groove bottom of the first groove portion 11. Each of the plurality of inclined grooves 10 includes an average groove width W1 of the first groove portion 11 other than the recess 16, an average groove width W2 of the second groove portion 12 and an average groove width W3 of the third groove portion 13 and satisfies the relation: W1<W2<W3.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Patent Document 1 below proposes a pneumatic tire suitable for an all-season tire for four-wheel drive vehicles. This pneumatic tire is expected to have improved mud and wet performance by specifying the shape of the center block, etc. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-128272 A Summary of the Invention [Problem to be solved by the invention]

[0004] Tires for running on rough terrain are required to not only perform well on relatively hard, packed dirt surfaces (hereafter referred to as "dirt performance"), but also to perform well on soft mud surfaces that contain soft soil or mud (hereafter referred to as "mud performance").

[0005] The present invention has been devised in view of the above circumstances, and has as its main object to provide a tire that can exhibit excellent performance on dirt and muddy roads. [Means for solving the problem]

[0006] The present invention relates to a tire having a tread portion, wherein the tread portion includes a shoulder block row in which a plurality of shoulder blocks are arranged along a tread edge, a crown block row in which a plurality of crown blocks are arranged in the tire axial direction inside the shoulder block row, and a plurality of inclined grooves extending from the crown block row to the tread edge. Each of the plurality of crown blocks is arranged to overlap with the plurality of shoulder blocks in the tire axial direction. Each of the inclined grooves includes a first groove portion and a second groove portion disposed between one of the crown blocks and one of the shoulder blocks, and a third groove portion that is continuous with the outside in the tire axial direction of the second groove portion and is disposed between two of the shoulder blocks. In the crown block, a recess is formed in a portion in contact with the first groove portion, where the block tread surface and the side wall are recessed, and the deepest part of the recess is located outside the tire radial direction with respect to the groove bottom of the first groove portion. Each of the plurality of inclined grooves includes an average groove width W1 of the first groove portion excluding the recess, an average groove width W2 of the second groove portion, and an average groove width W3 of the third groove portion, and satisfies the relationship of W1 < W2 < W3.

Advantages of the Invention

[0007] By adopting the above configuration, the tire of the present invention can exhibit excellent dirt performance and mud performance.

Brief Description of the Drawings

[0008] [Figure 1] It is a developed view of the tread portion of the tire according to an embodiment of the present invention. [Diagram 2] It is an enlarged view of the inclined groove in FIG. 1. [Diagram 3] It is an end view taken along line A-A in FIG. 2. [Figure 4] It is an enlarged view of the crown block in FIG. 1. [Diagram 5] It is an enlarged view of the shoulder block in FIG. 1. [Figure 6] It is a developed view of the tread portion of the tire of the comparative example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The drawings are described to include the features of the present invention, but may include exaggerated expressions and expressions different from the dimensional ratios of the actual structure in order to facilitate understanding of the present invention. In addition, the same reference numerals are used to refer to the same or common elements throughout the embodiments, and duplicated explanations will be omitted.

[0010] Fig. 1 is a development view of a tread portion 2 of a tire 1 according to the present embodiment (hereinafter, may be simply referred to as "tire"). As shown in Fig. 1, the tire 1 according to the present embodiment is suitably used, for example, as a pneumatic tire for an SUV that is also expected to be used off-road. However, the tire 1 of the present invention is not limited to such an embodiment.

[0011] The tread portion 2 of the tire 1 of this embodiment includes a plurality of grooves 3 arranged between two tread edges Te, and a block row in which blocks 4 separated by these grooves 3 are arranged in the tire circumferential direction. As a desirable aspect, the tread portion 2 of this embodiment has a pattern that is point-symmetric with respect to a point on the tire equator C. However, the present invention is not limited to this aspect.

[0012] The tread edge Te is the axially outermost contact position when the tire 1 in a normal state is loaded with 60% of the normal load and contacts a flat surface with a camber angle of 0°.

[0013] "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.

[0014] 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."

[0015] "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."

[0016] For pneumatic tires with various standards, the "normal load" is the load that each standard specifies for each tire in the standard system that includes 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". For tires without various standards, the "normal load" refers to the maximum load that can be applied when using the tire according to the above standards.

[0017] The tread portion 2 includes a shoulder block row 5 and a crown block row 6. The shoulder block row 5 includes a plurality of shoulder blocks 7 aligned along the tread edge Te. In other words, the shoulder blocks 7 form the tread edge Te. The crown block row 6 includes a plurality of crown blocks 8 aligned in the tire circumferential direction. The tread portion 2 of this embodiment is composed of four block rows, including two crown block rows 6 on the tire equator C side and two shoulder block rows 5 arranged so as to sandwich these two crown block rows 6. However, the tire 1 of the present invention is not limited to this embodiment.

[0018] Each of the multiple crown blocks 8 is arranged to axially overlap with the shoulder block 7. This configuration means that in a plan view of the tread, a virtual area 34 (dotted in FIG. 1 for ease of understanding) obtained by extending one crown block 8 in parallel to the tire circumferential direction overlaps with the adjacent shoulder block 7.

[0019] The tread portion 2 includes a plurality of inclined grooves 10 extending from the crown block row 6 to the tread edge Te due to the arrangement of the blocks described above.

[0020] FIG. 2 shows an enlarged view of one of the inclined grooves 10. As shown in FIG. 2, each of the inclined grooves 10 includes a first groove portion 11, a second groove portion 12, and a third groove portion 13. The first groove portion 11 and the second groove portion 12 are disposed between one crown block 8 and one shoulder block 7 (these blocks are shown in FIG. 1). The third groove portion 13 is disposed between two shoulder blocks 7. For ease of understanding of the invention, the elongated recess 23 disposed at the bottom of the third groove portion 13 shown in FIG. 1 is omitted in FIG. 2.

[0021] Fig. 3 shows an end view of line AA in Fig. 2. As shown in Figs. 1 and 3, the crown block 8 has a recess 16 in which the block tread surface 8s and the side wall 8w are recessed at a portion in contact with the first groove portion 11. In Fig. 2, dots are applied to the recess 16 to make this configuration easy to understand. Also, as shown in Fig. 3, the deepest portion of the recess 16 is located radially outward of the groove bottom of the first groove portion 11.

[0022] As shown in Fig. 2, each of the plurality of inclined grooves 10 includes the average groove width W1 of the first groove portion 11 excluding the recess 16, the average groove width W2 of the second groove portion 12, and the average groove width W3 of the third groove portion 13, and satisfies the relationship of W1 < W2 < W3. In this specification, the groove width means the distance between two groove edges in a direction orthogonal to the groove length direction. The average groove width means a value calculated by a weighted average of the groove widths of the corresponding grooves weighted by the groove length. Further, as shown in Fig. 3, the average groove width W1 of the first groove portion 11 excluding the recess 16 means the average of the groove widths measured with the intersection of the extension line of the block tread surface 8s of the crown block 8 and the extension line of the side wall 8w of the crown block 8 as the virtual groove edge 11e in the cross section of the first groove portion 11.

[0023] By having the above-described configuration, the tire 1 of the present invention can exhibit excellent dirt performance and mud performance. The reasons are as follows.

[0024] As shown in Fig. 1, the inclined groove 10 of the present invention is formed to include the above-described first groove portion 11, second groove portion 12, and third groove portion 13 by arranging the crown block 8 and the shoulder block 7 so as to overlap in the tire axial direction. Such an inclined groove 10 can provide a well-balanced frictional force in the tire circumferential direction and the tire axial direction when traveling on a dirt road surface and a mud road surface.

[0025] Further, as shown in Figs. 2 and 3, the above-described recess 16 formed in the crown block 8 of the present invention can maintain the dirt performance without excessively reducing the rigidity of the crown block 8. Further, the above-described recess 16 can shear mud together with the first groove portion 11 during traveling on a mud road surface to provide a large reaction force, and can enhance the mud performance.

[0026] Also, as shown in FIG. 2, in the present invention, each of the plurality of inclined grooves 10 satisfies the relationship of W1 < W2 < W3 with respect to the groove width. Thereby, the rigidity of the crown block row 6 (shown in FIG. 1) becomes relatively large, and excellent dirt performance can be exhibited. Further, such inclined grooves 10 can quickly discharge the mud and soil inside toward the third groove portion 13 side from the first groove portion 11 side when driving on a muddy road surface, so that clogging is less likely to occur and excellent mud performance can be continuously exhibited. For such reasons, the tire 1 of the present invention can exhibit excellent dirt performance and mud performance.

[0027] Hereinafter, a more detailed configuration of the present embodiment will be described. Note that each configuration described below shows a specific aspect of the present embodiment. Therefore, it goes without saying that the present invention can exhibit the above-described effects even if it does not have the configurations described below. Further, even if any one of the configurations described below is applied alone to the tire of the present invention having the above-described features, an improvement in performance corresponding to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a combined improvement in performance corresponding to each configuration can be expected.

[0028] As shown in FIG. 1, one crown circumferential groove 20 extending in a zigzag shape is provided in the tread portion 2 of the present embodiment on the tire equator C side. This crown circumferential groove 20 includes a first crown inclined portion 21 and a second crown inclined portion 22 that are inclined in opposite directions with respect to the tire circumferential direction. The angle θ6 of the first crown inclined portion 21 and the second crown inclined portion 22 with respect to the tire circumferential direction is, for example, 25 to 35°. Also, the first crown inclined portion 21 and the second crown inclined portion 22 extend linearly. Such a crown circumferential groove 20 can provide a reaction force in the tire circumferential direction during rough terrain driving.

[0029] The inclined groove 10 of this embodiment is connected to the crown circumferential groove 20. In a preferred embodiment, the inclined groove 10 is connected to a portion of the crown circumferential groove 20 where the first crown inclined portion 21 and the second crown inclined portion 22 are connected. More specifically, the second crown inclined portion 22 and the innermost portion 14 of the inclined groove 10 are connected to form a linear groove portion, and the first crown inclined portion 21 is connected to this groove portion in a T-shape. As a result, a T-shaped three-way intersection is formed by the first crown inclined portion 21, the second crown inclined portion 22, and the innermost portion 14 of the inclined groove 10. As a result, a large reaction force is obtained at this three-way intersection when traveling on a muddy road surface, and excellent mud performance is demonstrated.

[0030] As shown in FIG. 2, in this embodiment, the recess 16 is provided in the entire area of ​​the crown block 8 where the first groove portion 11 is in contact. The recess 16 preferably extends along the first groove portion 11 with a constant width. As shown in FIG. 3, the recess 16 includes a bottom surface 16a extending parallel to the block tread surface 8s and a side surface 16b extending parallel to the side wall 8w of the crown block 8. The maximum depth d2 of the recess 16 is 40% to 60% of the maximum depth d1 of the first groove portion 11. The opening width W7 of the recess 16 is 35% to 50% of the groove width W1 of the first groove portion 11. Such a recess 16 is useful for improving the dirt performance and the mud performance in a well-balanced manner.

[0031] As shown in Fig. 2, the first groove portion 11 and the second groove portion 12 are connected to each other so as to bend. Similarly, the second groove portion 12 and the third groove portion 13 are connected to each other so as to bend. Here, "groove portions connected to each other so as to bend" refers to a mode in which two groove portions extending linearly at different angles are connected to each other, so that the angle of the inclined groove 10 changes suddenly within a specific range, and more specifically, refers to a mode in which the specific range is 5% or less of the total length of the inclined groove 10. However, the inclined groove 10 of the present invention is not limited to such a mode.

[0032] The length of the first groove portion 11 (so-called periphery length along the groove length direction, the same applies below) is 15% to 25% of the total length of the inclined groove 10. The length of the second groove portion 12 is 20% to 30% of the total length of the inclined groove 10. The length of the third groove portion 13 is 20% to 30% of the total length of the inclined groove 10.

[0033] The first groove portion 11 includes a portion where the groove width is constant in the groove length direction. As a more preferable embodiment, the first groove portion 11 of this embodiment extends with a constant groove width over its entirety. That is, the first groove portion 11 extends while maintaining the above-mentioned average groove width W1. The groove width W1 of the first groove portion 11 is, for example, 4.5% to 6.5% of the tread width TW (shown in FIG. 1). Such a first groove portion 11 can improve the dirt performance and mud performance while maintaining the running performance on paved roads (hereinafter referred to as "road performance"). The tread width TW corresponds to the axial distance from one tread edge Te to the other tread edge Te in the normal state.

[0034] The first groove portion 11 extends linearly. The maximum angle θ1 (the angle of the groove center line, the same applies below) of the first groove portion 11 with respect to the tire axial direction is preferably 45° or less, specifically 25° to 35°. Such a first groove portion 11 improves traction performance and cornering performance on rough terrain.

[0035] The second groove portion 12 includes a portion in which the groove width increases continuously toward the third groove portion 13. In a preferred embodiment, the groove width increases continuously toward the third groove portion 13 throughout the entire second groove portion 12. The second groove portion 12 includes an inner groove edge 12a on the tire equator C side and an outer groove edge 12b on the tread edge Te side. The inner groove edge 12a and the outer groove edge 12b extend linearly so as to be spaced apart from each other toward the third groove portion 13 side. Such a second groove portion 12 can quickly discharge mud from inside when traveling on a muddy road surface, and can continuously exhibit excellent mud performance.

[0036] The angle θ2a of the inner groove edge 12a relative to the tire axial direction is 65 to 75°. The angle θ2b of the outer groove edge 12b relative to the tire axial direction is 55 to 65°. As a result, the angle θ2 of the second groove portion 12 relative to the tire axial direction is greater than the angle of the first groove portion 11 relative to the tire axial direction. Specifically, the angle θ2 of the second groove portion 12 is 60 to 70°. Such a second groove portion 12 makes it easier to actively discharge mud by utilizing the rotation of the tire, and can reliably achieve the above-mentioned effects.

[0037] The minimum groove width of the second groove portions 12 is desirably 1.1 to 1.4 times the groove width W1 of the first groove portions 11. The maximum groove width of the second groove portions 12 is 1.4 to 1.7 times the groove width W1 of the first groove portions 11. As a result, the average groove width W2 of the second groove portions 12 is 1.3 to 1.5 times the average groove width W1 of the first groove portions 11. This provides a balanced improvement in dirt and mud performance while maintaining road performance.

[0038] The third groove portion 13 includes an inner portion 13a and an outer portion 13b. The inner portion 13a is disposed on the second groove portion 12 side, and more specifically, is connected to the second groove portion 12. The groove width of the inner portion 13a increases continuously toward the outer portion 13b side. The outer portion 13b is connected to the axially outer side of the inner portion 13a. The groove width of the outer portion 13b is constant in the groove length direction of the third groove portion 13. Such a third groove portion 13 is useful for suppressing uneven wear near the tread edge Te of the shoulder block 7 (shown in FIG. 1).

[0039] The maximum angle θ3a of the groove edge of the inner portion 13a relative to the tire axial direction is 35 to 45°. The maximum angle θ3b of the groove edge of the outer portion 13b relative to the tire axial direction is 10° or less, and is set to 0° in this embodiment. As a result, the maximum angle θ3 of the third groove portion 13 relative to the tire axial direction is smaller than the angle θ2 of the second groove portion 12 relative to the tire axial direction. Such a third groove portion 13 can effectively discharge mud inside the inclined groove 10 outward in the axial direction of the tire when traveling on muddy roads.

[0040] The minimum value of the groove width of the third groove portion 13 is 1.6 to 1.9 times the groove width W1 of the first groove portion 11. Moreover, the maximum value of the groove width of the third groove portion 13 is 2.4 to 2.8 times the groove width W1 of the first groove portion 11. As a result, the average groove width W3 of the third groove portion 13 is 2.0 to 2.4 times the average groove width W1 of the first groove portion 11. Such a third groove portion 13 is useful for improving the dirt performance and the mud performance in a well-balanced manner.

[0041] As shown in Fig. 1, it is preferable that an elongated recess 23 extending in the axial direction of the tire is provided at the bottom of the outer side 13b of the third groove portion 13. The elongated recess 23 is a recess having an opening width of 1 to 3 mm at the bottom of the outer side 13b of the third groove portion 13 and a depth of 1 to 2 mm. Such an elongated recess 23 helps to further improve mud performance.

[0042] As shown in FIG. 2, the inclined groove 10 includes an innermost portion 14 and a longitudinal groove portion 15 in addition to the above-mentioned first groove portion 11, second groove portion 12, and third groove portion 13. The innermost portion 14 communicates with the crown circumferential groove 20 (shown in FIG. 1) and is inclined in the same direction as the first groove portion 11. The innermost portion 14 extends linearly with a constant groove width. The length of the innermost portion 14 is 10% to 20% of the length of the inclined groove 10. The angle θ4 of the innermost portion 14 with respect to the tire axial direction is, for example, 45 to 55°. In a desirable embodiment, the angle difference between the first groove portion 11 and the innermost portion 14 is 10° or less.

[0043] The longitudinal groove portion 15 is disposed between the innermost portion 14 and the first groove portion 11. The longitudinal groove portion 15 extends linearly with a constant groove width. The length of the longitudinal groove portion 15 is 5% to 20% of the length of the inclined groove 10. The longitudinal groove portion 15 of this embodiment is continuous with the first groove portion 11 and extends along the tire circumferential direction. When traveling on a muddy road surface, such a longitudinal groove portion 15 guides mud inside to the first groove portion 11 side and strongly compacts the mud in the recessed portion 16. As a result, the compacted mud provides a large reaction force, and further improvement in mud performance can be expected.

[0044] The angle θ5 of the longitudinal groove portion 15 with respect to the tire circumferential direction is 10° or less, and in a more desirable embodiment, the longitudinal groove portion 15 extends parallel to the tire circumferential direction. Thereby, the above-described effects can be surely obtained.

[0045] As a more desirable embodiment, in the present embodiment, with respect to the average groove width W1 of the first groove portion 11, the average groove width W4 of the innermost portion 14, and the average groove width W5 of the longitudinal groove portion 15, the relationship of W4 < W5 < W1 is satisfied. Thereby, while maintaining the load performance and the dirt performance, when driving on a muddy road surface, the mud in the inclined groove 10 is more easily discharged.

[0046] As shown in FIG. 1, a connecting transverse groove 25 for connecting two adjacent inclined grooves 10 in the tire circumferential direction is provided in the tread portion 2 of the present embodiment. The connecting transverse groove 25 extends linearly, for example, with a constant groove width. Further, the connecting transverse groove 25 extends from the communication portion between the second groove portion 12 and the third groove portion 13 of one inclined groove 10 to the communication portion between the innermost portion 14 and the longitudinal groove portion 15 of the other inclined groove 10. Thereby, the connecting transverse groove 25 extends at an angle of 10° or less with respect to the tire axial direction. As a more desirable embodiment, the connecting transverse groove 25 of the present embodiment extends parallel to the tire axial direction. Such a connecting transverse groove 25 improves the traction performance on a dirt road surface and a muddy road surface.

[0047] It is desirable that the average groove width W6 of the connecting transverse groove 25 is smaller than the average groove width W4 (shown in FIG. 2) of the innermost portion 14 of the inclined groove 10. Thereby, the load performance can be maintained.

[0048] FIG. 4 shows an enlarged view of two crown blocks 8. As shown in FIG. 4, no grooves or sipes are provided on the block tread 8s of the crown block 8. Such a crown block 8 has high rigidity and can enhance the load performance and the dirt performance.

[0049] The width W8 in the tire axial direction of the block tread surface 8s of the crown block 8 is 25% to 35% of the tread width TW (shown in FIG. 1). Moreover, the length L1 in the tire circumferential direction of the block tread surface 8s of the crown block 8 is 100% to 110% of the width W8 of the crown block 8. Moreover, one pitch length P1 of the multiple crown blocks 8 is, for example, 25% to 40% of the tread width TW. Such an arrangement of the crown blocks 8 helps to improve traction performance and cornering performance in a well-balanced manner when traveling on rough terrain.

[0050] FIG. 5 shows an enlarged view of two shoulder blocks 7. As shown in FIG. 5, the block tread surface 7s of the shoulder block 7 is provided with a shoulder lateral groove 31 and a shoulder sipe 32. The shoulder lateral groove 31 extends from the tread edge Te along the third groove portion 13 (shown in FIG. 2) of the inclined groove 10 and ends in the block tread surface 7s without communicating with the inclined groove 10. The shoulder sipe 32 extends from the end of the shoulder lateral groove 31 on the inner side in the tire axial direction along the second groove portion 12 (shown in FIG. 2) of the inclined groove 10 and ends in the block tread surface 7s. Such shoulder lateral grooves 31 and shoulder sipes 32 can effectively improve the dirt performance and mud performance. In this specification, the term "sipe" means a cut having a width of less than 1.5 mm.

[0051] The width W9 of the block tread surface 7s of the shoulder block 7 in the tire axial direction is 25% to 35% of the tread width TW (shown in FIG. 1). The length L2 of the block tread surface 7s of the shoulder block 7 in the tire circumferential direction is 75% to 85% of the width W9 of the shoulder block 7. In a preferred embodiment, the length L2 of the shoulder block 7 in the tire circumferential direction is smaller than the length L1 of the crown block 8 in the tire circumferential direction (shown in FIG. 4). In addition, in the present embodiment, as shown in FIG. 1, the entire block tread surface 7s of the shoulder block 7 is included within a virtual area 35 (dotted in FIG. 1) in which the crown block 8 is extended in parallel to the tire axial direction toward the tread edge Te side in a plan view of the tread. As a result, when the shoulder block 7 falls axially inward during running on a muddy road surface, the mud is reliably compacted between the shoulder block 7 and the crown block 8, and the reaction force when the mud is sheared is large. Therefore, the mud performance is further improved.

[0052] 5, one pitch length P2 of the multiple shoulder blocks 7 is, for example, 25% to 40% of the tread width TW. Such an arrangement of the shoulder blocks 7 helps to improve traction performance and cornering performance in a well-balanced manner when traveling on rough terrain.

[0053] As shown in Fig. 1, the tread portion 2 includes a crown region Cr on the tire equator C side and two shoulder regions Sh arranged on both sides of the crown region Cr. The width Wc in the tire axial direction of the crown region Cr is 60% of the tread width TW. Also, the center position in the tire axial direction of the crown region Cr coincides with the tire equator C. The width Ws in the tire axial direction of one shoulder region Sh is 20% of the tread width TW. In this embodiment, the land ratio Rc of the crown region Cr is 60% - 75%. The land ratio Rs of the shoulder region Sh is smaller than the land ratio Rc of the crown region Cr. Specifically, the land ratio Rs of the shoulder region Sh is 45% - 55%. Thereby, the crown region Cr can contribute to the improvement of dirt performance, and the shoulder region Sh can contribute to the improvement of mud performance. Therefore, the dirt performance and the mud performance can be improved in a well-balanced manner. Note that the land ratio of each region means the ratio of the actual tread surface to the virtual tread surface obtained by filling all the grooves and sipes arranged in the region.

[0054] As described above, one embodiment of the tire of the present invention has been described in detail. However, the present invention is not limited to the above specific embodiments and can be implemented in various forms.

Example

[0055] A pneumatic tire of size 235 / 80R17 having the tread pattern shown in Fig. 1 was prototyped. As a comparative example, a pneumatic tire having the tread pattern shown in Fig. 6 was prototyped. In the tire of the comparative example, no recess as in the present invention is formed in the crown block B, and the groove width of the second groove portion b of the inclined groove A becomes smaller toward the third groove portion c side. Thereby, in the comparative example, regarding the average groove width Wa of the first groove portion a, the average groove width Wb of the second groove portion b, and the average groove width Wc of the third groove portion c (in Fig. 6, the symbols of each groove width are omitted), Wa > Wb < Wc, which is different from the present invention. The tire of the comparative example is substantially the same as the tire shown in Fig. 1 except for the above-described configuration. For each test tire, the dirt performance and the mud performance were tested. The common specifications and test methods of each test tire are as follows. Test vehicle: 3000cc, 4-wheel drive Test tire mounting position: All wheels Rim: 17×6.5 Tire pressure: 230kPa for all wheels

[0056] <Dirt performance> The performance of the test vehicle when it was driven on a dirt road surface was evaluated by the driver. The results were a rating of the performance, with a higher value indicating better dirt performance.

[0057] <Mud performance> The performance of the test vehicle when it was driven on a muddy road surface was evaluated by the driver. The results were a rating of the performance, with a higher value indicating better muddy road performance. The test results are shown in Table 1.

[0058] [Table 1]

[0059] As shown in Table 1, the comparative tire had dirt performance and mud performance of 5.0 points each, whereas the example tire had dirt performance of 6.0 points and mud performance of 8.0 points, which are significantly improved. In other words, it was confirmed that the example tire exhibited excellent dirt performance and mud performance.

[0060] [Note] The present invention includes the following aspects.

[0061] [Invention 1] A tire having a tread portion, The tread portion is A shoulder block row in which a plurality of shoulder blocks are arranged along a tread edge; a crown block row in which a plurality of crown blocks are arranged in a circumferential direction of the tire on an axially inner side of the shoulder block row; a plurality of inclined grooves extending from the crown block row to the tread edge; each of the plurality of crown blocks is arranged to overlap with the plurality of shoulder blocks in the tire axial direction; each of the inclined grooves includes a first groove portion and a second groove portion disposed between one of the crown blocks and one of the shoulder blocks, and a third groove portion that is continuous with the outside in the tire axial direction of the second groove portion and is disposed between the two shoulder blocks; in the crown block, a recess is formed in a portion in contact with the first groove portion, where the block tread surface and the side wall are recessed; the deepest part of the recess is located outside the tire radial direction with respect to the groove bottom of the first groove portion; each of the plurality of inclined grooves includes an average groove width W1 of the first groove portion excluding the recess, an average groove width W2 of the second groove portion, and an average groove width W3 of the third groove portion, and satisfies the relationship of W1 < W2 < W3; a tire. [Invention 2] The tire according to Invention 1, wherein the first groove portion includes a portion having a constant groove width in the groove length direction. [Invention 3] The tire according to Invention 1 or 2, wherein the second groove portion includes a portion in which the groove width continuously increases toward the third groove portion side. [Invention 4] The third groove portion includes an inner portion on the second groove portion side and an outer portion continuous with the outside in the tire axial direction of the inner portion, the groove width of the inner portion continuously increases toward the outer portion side, The tire according to any one of Inventions 1 to 3, wherein the groove width of the outer portion is constant in the groove length direction. [Invention 5] The tire according to Invention 4, wherein the maximum angle of the groove edge of the inner portion with respect to the tire axial direction is 35 to 45°. [Invention 6] The tire according to any one of claims 1 to 5, wherein each of the plurality of inclined grooves includes a longitudinal groove portion that is continuous with the first groove portion on an axially inner side of the tire and extends along the tire circumferential direction. [Invention 7] The first groove portion has a constant groove width in a groove length direction, The minimum value of the groove width of the second groove portion is 1.1 to 1.4 times the groove width of the first groove portion, The tire according to any one of claims 1 to 6, wherein the maximum value of the groove width of the second groove portions is 1.4 to 1.7 times the groove width of the first groove portions. [Invention 8] The first groove portion has a constant groove width in a groove length direction, The minimum value of the groove width of the third groove portion is 1.6 to 1.9 times the groove width of the first groove portion, The tire according to any one of claims 1 to 7, wherein the maximum groove width of the third groove portions is 2.4 to 2.8 times the groove width of the first groove portions. [The present invention 9] The first groove portion and the second groove portion are connected to each other in a bent manner, The tire according to any one of claims 1 to 8, wherein an angle of the second groove portion with respect to the tire axial direction is larger than an angle of the first groove portion with respect to the tire axial direction. [The present invention 10] The second groove portion and the third groove portion are connected to each other in a bent manner, The tire according to any one of claims 1 to 9, wherein an angle of the third groove portion with respect to the tire axial direction is smaller than an angle of the second groove portion with respect to the tire axial direction. [The present invention 11] The tire according to any one of claims 1 to 10, wherein the maximum angle of the first groove portion with respect to the tire axial direction is 25 to 35°. [The present invention 12] The second groove portion includes an inner groove edge on a tire equator side and an outer groove edge on a tread edge side, The angle of the inner groove edge with respect to the tire axial direction is 65 to 75 degrees, 12. The tire according to any one of claims 1 to 11, wherein the angle of the outer groove edge with respect to the tire axial direction is 55 to 65°. [The present invention 13] The tread portion includes a crown region on the tire equator side and two shoulder regions disposed on both sides of the crown region, The axial width of the crown region is 60% of the tread width, The land ratio of the crown region is 60% to 75%; 13. The tire according to any one of claims 1 to 12, wherein the land ratio of the shoulder region is 45% to 55%. [Explanation of symbols]

[0062] 2 Tread section Te tread edge 7. Shoulder Block 5. Shoulder Block Row 8 Crown Block 6 Crown Block Row 10 Slant groove 11 First groove 12 Second groove 13 Third Groove 16 Recess W1 Average groove width of the first groove W2 Average groove width of the second groove W3 Average groove width of the third groove

Claims

1. A tire having a tread portion, The tread portion is A shoulder block row in which a plurality of shoulder blocks are arranged along a tread edge; a crown block row in which a plurality of crown blocks are arranged in a circumferential direction of the tire on an axially inner side of the shoulder block row; a plurality of oblique grooves extending from the crown block row to the tread edge; The crown blocks are arranged to overlap the shoulder blocks in the tire axial direction, Each of the inclined grooves includes a first groove portion and a second groove portion disposed between one of the crown blocks and one of the shoulder blocks, and a third groove portion connected to an axially outer side of the second groove portion and disposed between two of the shoulder blocks, The crown block has a recess in which a block tread surface and a side wall are recessed at a portion in contact with the first groove portion, a deepest portion of the recess is located radially outward of a groove bottom of the first groove portion, Each of the plurality of inclined grooves includes an average groove width W1 of the first groove portion excluding the recess, an average groove width W2 of the second groove portion, and an average groove width W3 of the third groove portion, and The relationship W1<W2<W3 is satisfied. tire.

2. The tire according to claim 1 , wherein the first groove portion includes a portion in which the groove width is constant in the groove length direction.

3. The tire according to claim 1 or 2, wherein the second groove portion includes a portion in which a groove width continuously increases toward the third groove portion.

4. the third groove portion includes an inner portion on the second groove portion side and an outer portion continuing to an axially outer side of the inner portion, The groove width of the inner portion increases continuously toward the outer portion, The tire according to claim 1 or 2, wherein the groove width of the outer portion is constant in the groove length direction.

5. The tire according to claim 4, wherein a maximum angle of the groove edge of the inner portion with respect to the tire axial direction is 35 to 45 degrees.

6. The tire according to claim 1 , wherein each of the plurality of inclined grooves includes a longitudinal groove portion that is continuous with the first groove portion on an axially inner side of the tire and extends along a circumferential direction of the tire.

7. The first groove portion has a constant groove width in a groove length direction, a minimum value of the groove width of the second groove portion is 1.1 to 1.4 times the groove width of the first groove portion; 3. The tire according to claim 1, wherein a maximum value of the groove width of the second groove portion is 1.4 to 1.7 times the groove width of the first groove portion.

8. The first groove portion has a constant groove width in a groove length direction, a minimum value of the groove width of the third groove portion is 1.6 to 1.9 times the groove width of the first groove portion; 3. The tire according to claim 1, wherein a maximum value of the groove width of the third groove portion is 2.4 to 2.8 times the groove width of the first groove portion.

9. The first groove portion and the second groove portion are connected to each other in a bent manner, The tire according to claim 1 or 2, wherein an angle of the second groove portion with respect to the tire axial direction is larger than an angle of the first groove portion with respect to the tire axial direction.

10. The second groove portion and the third groove portion are connected to each other in a bent manner, The tire according to claim 1 or 2, wherein an angle of the third groove portion with respect to the tire axial direction is smaller than an angle of the second groove portion with respect to the tire axial direction.

11. 3. The tire according to claim 1, wherein a maximum angle of the first groove portion with respect to the tire axial direction is 25 to 35 degrees.

12. The second groove portion includes an inner groove edge on a tire equator side and an outer groove edge on a tread edge side, The angle of the inner groove edge with respect to the tire axial direction is 65 to 75 degrees, The tire according to claim 1 or 2, wherein an angle of the outer groove edge with respect to the tire axial direction is 55 to 65 degrees.

13. The tread portion includes a crown region on a tire equator side and two shoulder regions disposed on both sides of the crown region, The axial width of the crown region is 60% of the tread width, The land ratio of the crown region is 60% to 75%; The tire according to claim 1 or 2, wherein the land ratio of the shoulder region is 45% to 55%.

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