JP7669775B2 - tire - Google Patents

Description

The present invention relates to a tire.

The following Patent Document 1 proposes a pneumatic tire with multiple middle lateral sipes in the inner middle land portion and the outer middle land portion. The pitch interval of the middle lateral sipes is specified in the pneumatic tire, which is expected to improve the driving stability and noise performance.

JP 2018-158730 A

In recent years, vehicles have become quieter, and there is a demand for improved noise performance in tires as well.

The present invention was devised in light of the above-mentioned circumstances, and its main objective is to provide a tire that maintains good wet performance while improving noise performance.

The present invention is a tire having a tread portion, the tread portion includes three or more circumferential grooves extending continuously in the tire circumferential direction between a first tread edge and a second tread edge, and four or more land portions divided into the circumferential grooves, the circumferential grooves include a first shoulder circumferential groove arranged closest to the first tread edge, each of the four or more land portions is provided with no lateral grooves and only sipes, the land portion includes a first shoulder land portion including the first tread edge and a first middle land portion adjacent to the first shoulder land portion via the first shoulder circumferential groove, the first middle land portion is provided with a plurality of first middle sipes that completely cross the first middle land portion in the tire axial direction, the first shoulder land portion is provided with a plurality of first shoulder sipes that extend from the first shoulder circumferential groove to at least the first tread edge, and the circumferential pitch length of the plurality of first shoulder sipes in the tire circumferential direction is smaller than the circumferential pitch length of the plurality of first middle sipes.

In the tire of the present invention, it is preferable that the depth of the first shoulder sipe decreases from the first shoulder circumferential groove side toward the first tread end side.

In the tire of the present invention, it is preferable that the first shoulder land portion is provided with a plurality of first interrupted sipes that extend from the first shoulder circumferential groove and terminate within the first shoulder land portion without reaching the first tread edge.

In the tire of the present invention, the circumferential groove includes a second shoulder circumferential groove arranged closest to the second tread edge, the land portion includes a second shoulder land portion including the second tread edge and a second middle land portion adjacent to the second shoulder land portion via the second shoulder circumferential groove, the second middle land portion is provided with a plurality of second middle sipes that completely cross the second middle land portion in the tire axial direction, the second shoulder land portion is provided with a plurality of second shoulder sipes that extend from the second shoulder circumferential groove to at least the second tread edge, and it is desirable that the circumferential pitch length of the plurality of second shoulder sipes is smaller than the circumferential pitch length of the plurality of second middle sipes.

In the tire of the present invention, it is preferable that the axially inner ends of the second shoulder sipes are all located at different positions in the tire circumferential direction relative to the axially outer ends of the second middle sipes.

In the tire of the present invention, it is desirable that the maximum depth of the second middle sipe is smaller than the maximum depth of the second shoulder sipe.

In the tire of the present invention, it is preferable that the second shoulder land portion is provided with a plurality of second interrupted sipes that extend from the second shoulder circumferential groove and terminate within the second shoulder land portion without reaching the second tread edge.

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 tread edge is located on the outer side of the vehicle when mounted on the vehicle, as described in any one of claims 1 to 7.

In the tire of the present invention, it is desirable that the sum of the groove widths of the circumferential grooves arranged between the tire equator and the first tread edge is smaller than the sum of the groove widths of the circumferential grooves arranged between the tire equator and the second tread edge.

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

1 is a development view of a tread portion showing one embodiment of the present invention. FIG. 2 is a cross-sectional view of a sipe. FIG. 2 is a cross-sectional view of a sipe. FIG. 2 is an enlarged view of a first shoulder land portion and a first middle land portion of FIG. 1 . 5 is a cross-sectional view taken along line AA in FIG. 4. 5 is a cross-sectional view taken along line BB in FIG. 4. 5 is a cross-sectional view taken along line CC of FIG. 4. FIG. 2 is an enlarged view of a second middle land portion and a second shoulder land portion of FIG. 1 . FIG. 2 is an enlarged view of the crown land portion of FIG.

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 tread portion 2 of the present invention includes three or more circumferential grooves 3 that extend continuously in the tire circumferential direction between the first tread edge T1 and the second tread edge T2, and four or more land portions 4 that are divided into these circumferential grooves 3. The tread portion 2 of this embodiment is composed of four circumferential grooves 3 and five land portions 4 that are divided into these circumferential grooves 3. However, the present invention is not limited to this aspect.

For example, the mounting orientation of the tread portion 2 of this embodiment on a vehicle is specified. As a result, the first tread edge T1 is intended to be located on the outer side of the vehicle when mounted on the vehicle. The second tread edge T2 is intended to be located on the inner side of the vehicle when mounted on the vehicle. The mounting orientation on the vehicle is indicated, for example, by letters or symbols on the sidewall portion (not shown). However, the tire 1 of the present invention is not limited to this aspect, and the mounting orientation on the vehicle may not be specified.

The first tread edge T1 and the second tread edge T2 each correspond to the axially outermost contact position when the tire 1 is in a normal state and is loaded with 70% of the normal load and in contact with 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, 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 circumferential grooves 3 include a first shoulder circumferential groove 5 that is disposed closest to the first tread edge T1 among the multiple circumferential grooves 3. Furthermore, the circumferential grooves 3 of this embodiment include a second shoulder circumferential groove 6, a first crown circumferential groove 7, and a second crown circumferential groove 8. The second shoulder circumferential groove 6 is disposed closest to the second tread edge T2 among the multiple circumferential grooves 3. The first crown circumferential groove 7 is disposed between the first shoulder circumferential groove 5 and the tire equator C. The second crown circumferential groove 8 is disposed between the second shoulder circumferential groove 6 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 6 is preferably, for example, 20% to 30% of the tread width TW. The axial distance L2 from the tire equator C to the groove centerline of the first crown circumferential groove 7 or the second crown circumferential groove 8 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 at least 3 mm. Also, 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 among the multiple circumferential grooves 3. As a result, the total groove width of the circumferential grooves 3 arranged between the tire equator C and the first tread edge T1 is smaller than the total groove width of the circumferential grooves arranged between the tire equator C and the second tread edge T2. However, the present invention is not limited to this aspect. The depth of each circumferential groove 3 is preferably, for example, 5 to 10 mm in the case of a pneumatic tire for a passenger car.

Each of the land portions 4 divided into the tread portion 2 is provided with no lateral grooves and only sipes 9. FIGS. 2 and 3 show cross-sectional views of the sipes 9. As shown in FIGS. 2 and 3, in this specification, a "sipe" refers to a cut element having a small width, in which the width between the two inner walls 10w in the main body portion 10 including two inner walls 10w facing each other substantially parallel is 1.5 mm or less. The width of the sipe is preferably 0.5 to 1.5 mm. As shown in FIG. 2, the sipe 9 may extend with a constant width from the opening on the outer surface of the tread portion 2 to the bottom. Hereinafter, in this specification, a sipe with such a cross section is referred to as a non-chamfered sipe. Also, as shown in FIG. 3, the sipe 9 may have one or both of the sipe edges on both sides that appear on the outer surface of the tread portion 2 formed with a chamfered portion 19. Hereinafter, in this specification, a sipe with such a cross section is referred to as a chamfered sipe. The chamfered portion 19 of the chamfered sipe includes an inclined surface 19s that connects to the outer surface of the tread portion 2 and the inner wall 10w. The opening width of the chamfered sipe may exceed 1.5 mm. The bottom of the sipe 9 may be connected to a flask bottom with a width exceeding 1.5 mm.

The lateral grooves mentioned above mean grooves that do not close and can secure a path for water movement even when a ground contact load is applied to the tread portion 2, and specifically mean grooves in which the distance between the groove walls is greater than 1.5 mm. Note that the distance between the groove walls is measured, for example, at the center position of the groove depth.

As shown in FIG. 1, the land portion 4 of the present invention includes a first shoulder land portion 11 including a first tread edge T1, and a first middle land portion 13 adjacent to the first shoulder land portion 11 via a first shoulder circumferential groove 5. The land portion 4 of this embodiment also includes a second shoulder land portion 12, a second middle land portion 14, and a crown land portion 15. The second shoulder land portion 12 includes a second tread edge T2. The second middle land portion 14 is adjacent to the second shoulder land portion 12 via a second shoulder circumferential groove 6. The crown land portion 15 is divided between the first crown circumferential groove 7 and the second crown circumferential groove 8.

FIG. 4 shows an enlarged view of the first shoulder land portion 11 and the first middle land portion 13. As shown in FIG. 4, the first middle land portion 13 is provided with a plurality of first middle sipes 16 that completely cross the first middle land portion 13 in the tire axial direction. The first shoulder land portion 11 is also provided with a plurality of first shoulder sipes 17 that extend from the first shoulder circumferential groove 5 to at least the first tread edge T1. In the present invention, the circumferential pitch length P2 of the plurality of first shoulder sipes 17 is smaller than the circumferential pitch length P1 of the plurality of first middle sipes 16. In the present invention, by adopting the above configuration, it is possible to improve noise performance while maintaining good wet performance. The following mechanism is presumed to be the reason for this.

The tire 1 of the present invention has three or more circumferential grooves 3, which allows it to maintain good wet performance. On the other hand, since none of the four or more land portions 4 have lateral grooves, pumping noises from the lateral grooves are not generated, improving noise performance. In addition, since none of the land portions 4 have lateral grooves, the tire 1 of the present invention is expected to reduce rolling resistance.

In addition, because the pitch length P2 of the first shoulder sipes 17 is smaller than the pitch length P1 of the first middle sipes 16, the circumferential rigidity of the first shoulder land portion 11 is reduced, and impact noise during contact with the ground is reduced. In particular, since the first shoulder land portion 11 does not have lateral grooves and is not configured with blocks, the first shoulder land portion 11 hardly vibrates when the contact surface of the first shoulder land portion 11 leaves the road surface. This makes it possible to reliably reduce the noise generated by the first shoulder land portion 11. It is believed that the above-mentioned mechanism in the present invention makes it possible to improve noise performance while maintaining good wet performance.

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.

In this embodiment, at least the pitch length P2 of two adjacent first shoulder sipes 17 selected arbitrarily from among the multiple first shoulder sipes 17 is smaller than the pitch length P1 formed by the two first shoulder sipes 17 and the two adjacent first middle sipes 16. In a desirable embodiment, the average value of the pitch lengths P2 of the multiple first shoulder sipes 17 over one circumference of the tire is smaller than the average value of the pitch lengths P1 of the multiple first middle sipes 16 over one circumference of the tire. Such an arrangement of sipes can more reliably improve noise performance.

From the viewpoint of achieving a good balance between wet performance and noise performance, the pitch length P2 is, for example, 60% to 90% of the pitch length P1, and preferably 70% to 85%. The first pitch P1 is, for example, 100% to 130% of the width W2 of the ground contact surface of the first middle land portion 13.

The first middle sipes 16 are inclined, for example, in a first direction (slanting downward to the right in each figure in this specification) relative to the tire axial direction. In a desirable embodiment, the angle of the first middle sipes 16 relative to the tire axial direction is, for example, 20 to 40 degrees. Such first middle sipes 16 can also provide friction in the tire axial direction when driving on wet roads.

The first middle sipe 16 is configured as, for example, a chamfered sipe (shown in FIG. 3). The chamfered portion 25 of the first middle sipe 16 includes, for example, a constant width portion 25a, an inner widening portion 25b, and an outer widening portion 25c. The constant width portion 41a extends in the sipe length direction with a constant chamfer width. The inner widening portion 25b is connected, for example, to the first crown circumferential groove 7 side of the constant width portion 25a, and the chamfer width increases from the constant width portion 25a to the first crown circumferential groove 7. The outer widening portion 25c is connected, for example, to the first shoulder circumferential groove 5 side of the constant width portion 25a, and the chamfer width increases from the constant width portion 35a to the first shoulder circumferential groove 5. The first middle sipe 16 having such a chamfered portion 25 can reduce the impact sound when the first middle land portion 13 touches the ground, and can further improve noise performance.

The constant width portion 25a is, for example, offset toward the first tread edge T1 side from the axial center position of the first middle land portion 13. As a result, the axial length L3 of the inner widened portion 25b is greater than the axial length L4 of the outer widened portion 25c. Specifically, the length L3 of the inner widened portion 25b is 40% to 60% of the width W2 of the ground contact surface of the first middle land portion 13. The length L4 of the outer widened portion 25c is 25% to 35% of the width W2 of the ground contact surface of the first middle land portion 13. As a result, a large chamfer is formed on the tire equator C side of the first middle land portion 13, further improving noise performance.

From the same viewpoint, it is desirable that the maximum chamfer width W3 of the inner widening portion 25b is larger than the maximum chamfer width W4 of the outer widening portion 25c. Specifically, the chamfer width W3 of the inner widening portion 25b is 1.3 to 2.0 times the chamfer width W4 of the outer widening portion 25c.

Figure 5 shows a cross-sectional view taken along line A-A in Figure 4. As shown in Figure 5, the maximum depth d1 of the inner widening portion 25b is greater than the maximum depth d2 of the outer widening portion 25c. Specifically, the depth d1 of the inner widening portion 25b is 1.5 to 2.5 times the depth d2 of the outer widening portion 25c.

The first middle sipe 16 includes, for example, a first middle tie bar 26 with a locally raised groove bottom. The first middle tie bar 26 is arranged, for example, in the central region when the first middle sipe 16 is divided into three equal parts in the axial direction of the tire. The axial length L5 of the first middle tie bar 26 is 30% to 50% of the axial width W2 (shown in FIG. 4) of the ground contact surface of the first middle land portion 13. Note that, when the axial length of the first middle tie bar varies in the radial direction of the tire, the length is measured at the center position in the radial direction of the tire. The depth d4 from the ground contact surface of the first middle land portion 13 to the outer surface of the first middle tie bar 26 is 50% to 70% of the maximum depth d3 of the first middle sipe 16. Such a first middle tie bar 26 is also useful for reducing rolling resistance while improving noise performance.

As shown in FIG. 4, the first shoulder sipes 17 are configured, for example, as non-chamfered sipes (shown in FIG. 2). The first shoulder sipes 17 are arranged, for example, at a smaller angle with respect to the tire axial direction than the first middle sipes 16. The angle of the first shoulder sipes 17 with respect to the tire axial direction is, for example, 10° or less. The first shoulder sipes 17 of this embodiment are inclined, for example, in the first direction.

Figure 6 shows a cross-sectional view of line B-B in Figure 4. As shown in Figure 6, the first shoulder sipe 17 has a smaller depth from the first shoulder circumferential groove 5 side toward the first tread edge T1 side. In this embodiment, the depth of the first shoulder sipe 17 continuously decreases toward the first tread edge T1 side. The depth d6 of the first shoulder sipe 17 at the first tread edge T1 is, for example, 10% to 70% of the maximum depth d5 of the first shoulder sipe 17, and preferably 20% to 65%. Such a first shoulder sipe 17 can increase the rigidity near the first tread edge T1 to improve steering stability and reduce the impact sound when the first shoulder land portion 11 touches the ground.

As shown in FIG. 4, the first shoulder land portion 11 is provided with a plurality of first interrupted sipes 18. The first interrupted sipes 18 extend from the first shoulder circumferential groove 5 and terminate within the first shoulder land portion 11 without reaching the first tread edge T1. In this embodiment, the first shoulder sipes 17 and the first interrupted sipes 18 are provided alternately in the tire circumferential direction. Such first interrupted sipes 18 are useful for improving wet performance and noise performance in a well-balanced manner.

The first interrupted sipes 18 extend, for example, along the first shoulder sipes 17. The angle difference between the first interrupted sipes 18 and the first shoulder sipes 17 is, for example, 5° or less, and in a preferred embodiment, they are arranged parallel to each other. The axial length L6 of the first interrupted sipes 18 is, for example, 30% to 50% of the width W5 of the ground contact surface of the first shoulder land portion 11. Such first interrupted sipes 18 improve wet performance and noise performance in a well-balanced manner.

The first interrupted sipe 18 is configured, for example, as a chamfered sipe (shown in FIG. 3). In a preferred embodiment, the chamfer width of the chamfered portion 28 of the first interrupted sipe 18 increases continuously, for example, from the side of the interrupted end 18a toward the side of the first shoulder circumferential groove 5. The angle θ1 between one edge and the other edge of the first shoulder sipe 17 appearing on the contact surface of the first shoulder land portion 11 is, for example, 5 to 15°. This further improves noise performance.

Figure 7 shows a cross-sectional view of line CC in Figure 4. As shown in Figure 7, the first interrupted sipe 18 includes a first portion 33 arranged on the first shoulder circumferential groove 5 side, and a second portion 34 arranged on the interrupted end 18a side and having a smaller depth than the first portion 33. The depth d8 of the second portion 34 is, for example, 60% to 75% of the depth d7 of the first portion 33. This suppresses rolling resistance while providing excellent noise performance.

Figure 8 shows an enlarged view of the second middle land portion 14 and the second shoulder land portion 12. As shown in Figure 8, the second middle land portion 14 is provided with a plurality of second middle sipes 21 that completely cross the second middle land portion 14 in the tire axial direction. In addition, the second shoulder land portion 12 is provided with a plurality of second shoulder sipes 22 that extend from the second shoulder circumferential groove 6 to at least the second tread edge T2.

In this embodiment, it is desirable that the circumferential pitch length P4 of the second shoulder sipes 22 is smaller than the circumferential pitch length P3 of the second middle sipes 21. Such a sipe arrangement can further improve wet performance and noise performance through the above-mentioned mechanism.

In this embodiment, at least the pitch length P4 of two adjacent second shoulder sipes 22 selected from among the multiple second shoulder sipes 22 is smaller than the pitch length P3 formed by the two second shoulder sipes 22 and the two adjacent second middle sipes 21. In a desirable embodiment, the average value of the pitch lengths P4 of the multiple second shoulder sipes 22 around one circumference of the tire is smaller than the average value of the pitch lengths P3 of the multiple first middle sipes 16 around one circumference of the tire. Such an arrangement of sipes can more reliably improve noise performance.

From the viewpoint of achieving a good balance between wet performance and noise performance, the pitch length P4 is, for example, 70% to 95% of the pitch length P3, and preferably 80% to 90%.

It is preferable that the axially inner ends 22i of the second shoulder sipes 22 are all located at different positions in the tire circumferential direction relative to the axially outer ends 21o of the second middle sipes 21. In addition, when the second middle sipes 21 and the second shoulder sipes 22 are adjacent to each other in the tire axial direction, the distance in the tire circumferential direction between the inner ends 22i of the second shoulder sipes 22 and the outer ends 21o of the second middle sipes 21 is, for example, 1.0 to 3.0 mm, and preferably 1.5 to 2.5 mm. This makes it possible to prevent the pitch sounds of each sipe from overlapping.

The second middle sipes 21 are oriented in a second direction (upward and to the right in each of the figures in this specification) that is opposite to the first direction with respect to the tire axial direction. The angle of the second middle sipes 21 with respect to the tire axial direction is, for example, 20 to 40 degrees. Such second middle sipes 21 can also provide friction in the tire axial direction when driving in wet conditions.

The second middle sipe 21 is configured, for example, as a chamfered sipe (shown in FIG. 3). The chamfered portion 35 of the second middle sipe 21 includes, for example, a constant width portion 35a, an inner widened portion 35b closer to the second crown circumferential groove 8 than the constant width portion 35a, and an outer widened portion 35c closer to the second shoulder circumferential groove 6 than the constant width portion 35a. The configurations of the constant width portion 25a, inner widened portion 25b, and outer widened portion 25c (shown in FIG. 4) of the chamfered portion 25 of the first middle sipe 16 described above can be applied to these, and the description here will be omitted.

In addition, the second middle sipe 21 can have the same configuration as the first middle sipe 16 (shown in Figure 5) in a cross section along its longitudinal direction.

In a preferred embodiment, the maximum depth of the second middle sipes 21 is smaller than the maximum depth of the second shoulder sipes 22. This maintains the rigidity of the second middle land portion 14, improving steering stability and reducing rolling resistance.

The configuration of the first shoulder sipe 17 described above can be applied to the second shoulder sipe 22, and the explanation will be omitted here.

In this embodiment, the second shoulder land portion 12 is provided with a plurality of second interrupted sipes 23. The second interrupted sipes 23 are configured, for example, as non-chamfered sipes (as shown in FIG. 2). The second interrupted sipes 23 extend from the second shoulder circumferential groove 6 and are interrupted within the second shoulder land portion 12 without reaching the second tread edge T2. In this embodiment, the second shoulder sipes 22 and the second interrupted sipes 23 are alternately arranged in the tire circumferential direction. Such second interrupted sipes 23 are useful for improving wet performance and noise performance.

The second interrupted sipes 23 are, for example, inclined in the second direction with respect to the tire axial direction. The angle difference between the second interrupted sipes 23 and the second shoulder sipes 22 is, for example, 5° or less. The axial length L7 of the second interrupted sipes 23 is, for example, 80% to 95% of the axial width W6 of the contact surface of the second shoulder land portion 12. Such second interrupted sipes 23 can improve wet performance while suppressing uneven wear near the second tread edge T2.

9 shows an enlarged view of the crown land portion 15. As shown in FIG. 9, the crown land portion 15 is provided with a plurality of first crown sipes 31 and a plurality of second crown sipes 32. The first crown sipes 31 and the second crown sipes 32 are configured, for example, as non-chamfered sipes (shown in FIG. 2). The first crown sipes 31 extend, for example, from the first crown circumferential groove 7 and are interrupted within the crown land portion 15. The second crown sipes 32 extend, for example, from the second crown circumferential groove 8 and are interrupted within the crown land portion 15. Such first crown sipes 31 and second crown sipes 32 can reduce rolling resistance and improve noise performance.

To ensure the above-mentioned effects, the first crown sipe 31 and the second crown sipe 32 do not cross the axial center position of the crown land portion 15, and do not cross the tire equator C. The axial length L8 of the first crown sipe 51 or the second crown sipe 52 is, for example, 15% to 30% of the axial width W7 of the contact surface of the crown land portion 15.

The first crown sipes 31 and the second crown sipes 32 are inclined, for example, in the first direction with respect to the tire axial direction. The angle of the first crown sipes 31 or the second crown sipes 32 with respect to the tire axial direction is, for example, 20 to 40 degrees. This suppresses uneven wear of the crown land portion 15.

In this embodiment, no sipes are provided in each land portion other than the sipes described above. This allows the various performance characteristics described above to be exhibited in a well-balanced manner. However, the present invention is not limited to this embodiment.

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 Table 1. Note that the pitch length P1 of the first middle sipe is common between the tires of each example. Similarly, the pitch length P3 of the second middle sipe is common between the tires of each example.

As a comparative example, a tire was produced in which the pitch length P2 of the first shoulder sipes is the same as the pitch length P1 of the first middle sipes, and the pitch length P4 of the second shoulder sipes is the same as the pitch length P3 of the second middle sipes. The comparative tire has substantially the same pattern as that shown in FIG. 1, except for the above-mentioned points. The pitch length P1 of the first middle sipes and the pitch length P2 of the second middle sipes of the comparative example are the same as those of each of the examples.

In addition, a prototype tire was produced as a reference tire for comparing noise performance, in which the width of each land portion of the tread was the same as that shown in Figure 1, and no grooves or sipes were provided on each land portion.

Each test tire was tested for wet performance and noise performance. The common specifications and test methods for each test tire are as follows:
Rim: 19 x 7.5J
Tire pressure: front wheel 230kPa, rear wheel 210kPa
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 expressed as a score based on the wet performance of the comparative example being 100, with a higher value indicating better wet performance.

<Noise performance>
The maximum sound pressure of the external noise was measured when the test vehicle was driven on a dry road at a speed of 70 km/h. The results are shown as an index in which the reduction in sound pressure, which is the difference from the sound pressure of the reference tire, is set to the reduction in sound pressure of the comparative example as 100. The larger the index, the smaller the maximum sound pressure of the noise, indicating excellent noise performance.
The results of the tests are shown in Table 1.

The test results confirmed that the tire of the embodiment has improved noise performance while maintaining good wet performance.

2 tread portion 3 circumferential groove 4 land portion 5 first shoulder circumferential groove 11 first shoulder land portion 13 first middle land portion 16 first middle sipe 17 first shoulder sipe P1 one pitch length of first middle sipe P2 one pitch length of first shoulder sipe T1 first tread edge T2 second tread edge

Claims (7)

A tire having a tread portion with a specified mounting direction on a vehicle ,
The tread portion includes three or more circumferential grooves extending continuously in the tire circumferential direction between a first tread end located on the vehicle outer side when mounted on a vehicle and a second tread end located on the vehicle inner side when mounted on the vehicle , and four or more land portions divided by the circumferential grooves,
the circumferential grooves include a first shoulder circumferential groove disposed closest to the first tread end and a second shoulder circumferential groove disposed closest to the second tread end ,
Each of the four or more land portions is not provided with a lateral groove and is provided with only a sipe,
the land portion includes a first shoulder land portion including the first tread edge, a first middle land portion adjacent to the first shoulder land portion via the first shoulder circumferential groove , a second shoulder land portion including the second tread edge, and a second middle land portion adjacent to the second shoulder land portion via the second shoulder circumferential groove ,
The first middle land portion is provided with a plurality of first middle sipes that completely cross the first middle land portion in the tire axial direction,
The first shoulder land portion is provided with a plurality of first shoulder sipes extending from the first shoulder circumferential groove to at least the first tread edge,
A pitch length of the first shoulder sipes in the tire circumferential direction is shorter than a pitch length of the first middle sipes in the tire circumferential direction,
The second middle land portion is provided with a plurality of second middle sipes that completely cross the second middle land portion in the tire axial direction,
The second shoulder land portion is provided with a plurality of second shoulder sipes extending from the second shoulder circumferential groove to at least the second tread edge,
a pitch length of the second shoulder sipes in the tire circumferential direction is shorter than a pitch length of the second middle sipes in the tire circumferential direction;
tire. The tire according to claim 1, wherein the first shoulder sipe has a depth that decreases from the first shoulder circumferential groove side toward the first tread end side. The tire according to claim 1 or 2, wherein the first shoulder land portion is provided with a plurality of first interrupted sipes that extend from the first shoulder circumferential groove and terminate within the first shoulder land portion without reaching the first tread edge. 4. The tire according to claim 1 , wherein axially inner ends of the plurality of second shoulder sipes are all provided at different positions in the tire circumferential direction relative to axially outer ends of the second middle sipes. The tire according to claim 1 , wherein a maximum depth of the second middle sipe is smaller than a maximum depth of the second shoulder sipe. 6. The tire according to claim 1, wherein the second shoulder land portion is provided with a plurality of second interrupted sipes extending from the second shoulder circumferential groove and interrupted within the second shoulder land portion without reaching the second tread end. 7. The tire according to claim 1, wherein a sum of groove widths of the circumferential grooves arranged between the tire equator and the first tread edge is smaller than a sum of groove widths of the circumferential grooves arranged between the tire equator and the second tread edge.

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