Tire

Abstract

To provide a 5 rib tire that can improve steering stability and noise performance.SOLUTION: A tread part 2 includes four circumferential grooves 3 and five land parts 4. In each of the five land parts 4 is nor formed a groove whose groove width is more than 2.0 mm but is formed only a sipe 9. The four circumferential grooves 3 include shoulder circumferential grooves 5. The five land parts 4 include shoulder land parts 11 and middle land parts 13. The middle land parts 13 are provided with a plurality of middle sipes 30. The shoulder land parts 11 are provided with a plurality of shoulder sipes 20 extending from the shoulder circumferential grooves 5 up to a position beyond a tread end. At least one of the shoulder sipes 20 includes an inclined part 21. A maximum angle of the inclined part 21 with respect to a tire axial direction is equal to or less than a maximum angle of the middle sipe 30 with respect to the tire shaft direction. A difference between the maximum angle of the inclined part 21 and the maximum angle of the middle sipe 30 is 5° or less.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a tire.

Background Art

[0002] Conventionally, various tires have been proposed in which the tread portion is composed of five land portions in the tire axial direction (hereinafter sometimes referred to as "five-rib tires"). Further, the pneumatic tire of Patent Document 1 below is a five-rib tire, which defines lug grooves and sipes provided in the shoulder land portion, and expects to improve wet performance and handling stability.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] With the recent improvement in performance and quietness of vehicles, there is a greater demand for further improvement in handling stability and noise performance of tires. In particular, in Europe, vehicle exterior noise regulations have been tightened, and tires that can meet these regulations are required.

[0005] The present disclosure has been devised in view of the above actual situation, and the main problem is to provide a five-rib tire capable of improving handling stability and noise performance.

Means for Solving the Problems

[0006] The present disclosure relates to a tire having a tread portion, wherein the tread portion includes four circumferential grooves continuously extending in the tire circumferential direction between two tread ends, and five land portions divided by the four circumferential grooves. Each of the five land portions is provided with no groove having a groove width exceeding 2.0 mm and only sipes are provided. The four circumferential grooves include a shoulder circumferential groove arranged closest to the tread end side. The five land portions include a shoulder land portion including the tread end and a middle land portion adjacent to the shoulder land portion via the shoulder circumferential groove. The middle land portion is provided with a plurality of middle sipes that are inclined with respect to the tire axial direction and completely cross the middle land portion in the tire axial direction. The shoulder land portion is provided with a plurality of shoulder sipes extending from the shoulder circumferential groove to a position beyond the tread end. At least one of the shoulder sipes includes an inclined portion that extends inclined with respect to the tire axial direction from the shoulder circumferential groove. The middle sipes are inclined in a direction opposite to the inclined portion with respect to the tire axial direction. The maximum angle of the inclined portion with respect to the tire axial direction is less than or equal to the maximum angle of the middle sipes with respect to the tire axial direction, and the difference between the maximum angle of the inclined portion and the maximum angle of the middle sipes is 5° or less.

Advantages of the Invention

[0007] By adopting the above configuration, the tire of the present invention can improve the handling stability and noise performance.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. FIG. 1 is a developed view of a tread portion 2 of a tire 1 showing an embodiment of the present disclosure. The tire 1 of the present embodiment is suitably used as, for example, a pneumatic tire for a passenger car. However, the present disclosure is not limited to such a mode, and may be applied to a pneumatic tire for heavy loads or a non-pneumatic tire in which the inside of the tire is not filled with pressurized air.

[0010] As shown in FIG. 1, the tread portion 2 of the present disclosure includes four circumferential grooves 3 that continuously extend in the tire circumferential direction between two tread ends, and five land portions 4 that are divided by these circumferential grooves 3. That is, the tire 1 of the present disclosure is configured as a so-called five-rib tire in which the tread portion 2 is composed of four circumferential grooves 3 and five land portions 4. Hereinafter, in this specification, one of the two tread ends may be referred to as the first tread end T1, and the other may be referred to as the second tread end T2.

[0011] The tread portion 2 of the present embodiment is designated, for example, with respect to the direction of mounting on a vehicle. Accordingly, the first tread end T1 is intended to be located on the outside of the vehicle when the tire is mounted on the vehicle. The second tread end T2 is intended to be located on the inside of the vehicle when the tire is mounted on the vehicle. The direction of mounting on the vehicle is indicated, for example, by letters or symbols on a sidewall portion (not shown). However, the tire 1 of the present disclosure is not limited to such a mode, and may be one in which the direction of mounting on the vehicle is not specified.

[0012] The first tread end T1 and the second tread end T2 respectively correspond to the ends of the 50% load contact surface when 50% of the normal load is applied to the tire 1 in the normal state and the tread portion 2 is grounded on a plane at a camber angle of 0°.

[0013] The "normal state" means that, in the case of a pneumatic tire for which various standards are defined, the tire is rim-mounted on a normal rim and filled with a normal internal pressure, and moreover, it is in a non-loaded state. In the case of a tire for which various standards are not defined or a non-pneumatic tire, the "normal state" means a standard use state according to the purpose of use of the tire, and it means a state in which the tire is not mounted on a vehicle and is non-loaded. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the normal state.

[0014] The "normal rim" is a rim defined for each tire in a standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the "standard rim", in the case of TRA, it is the "Design Rim", and in the case of ETRTO, it is the "Measuring Rim".

[0015] The "normal internal pressure" is the air pressure defined for each tire in a standard system including the standards 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 described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0016] For pneumatic tires with various standards defined, the "normal load" is the load defined for each tire in the standard system including the standards on which the tire is based. In the case of JATMA, it is the "maximum load capacity"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "LOAD CAPACITY". In the case of tires for which no various standards are defined, the "normal load" refers to the maximum applicable load in using the tire, in accordance with the above-mentioned standards.

[0017] The circumferential groove 3 includes two shoulder circumferential grooves 5 and 6, and two crown circumferential grooves 7 and 8 provided therebetween. Hereinafter, in this specification, the shoulder circumferential groove arranged on the first tread end T1 side may be referred to as the first shoulder circumferential groove 5, and the shoulder circumferential groove arranged on the second tread end T2 side may be referred to as the second shoulder circumferential groove 6. Also, the two crown circumferential grooves 7 and 8 are arranged so as to sandwich the tire equator C. Hereinafter, in this specification, the crown circumferential groove arranged between the first shoulder circumferential groove 5 and the tire equator C may be referred to as the first crown circumferential groove 7, and the crown circumferential groove arranged between the second shoulder circumferential groove 6 and the tire equator C may be referred to as the second crown circumferential groove 8.

[0018] The distance L1 in the tire axial direction from the tire equator C to the groove center line 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 distance L2 in the tire axial direction from the tire equator C to the groove center line 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. Note that the tread width TW is the distance in the tire axial direction from the first tread end T1 to the second tread end T2 in the normal state.

[0019] Each circumferential groove 3 of the present embodiment extends linearly, for example, parallel to the tire circumferential direction. Each circumferential groove 3 may extend in a wavy shape, for example.

[0020] The groove width W1 of each circumferential groove 3 is desirably at least 3 mm or more. Also, the groove width W1 of each circumferential groove 3 is desirably, for example, 3.0% to 8.5% of the tread width TW. In the present embodiment, the first shoulder circumferential groove 5 has the smallest groove width among the plurality of circumferential grooves 3.

[0021] FIG. 2 is a meridian cross-sectional view of the rotation axis of the tire 1 of the present embodiment. As shown in FIG. 2, the depth of each circumferential groove 3 is, for example, 5 to 10 mm in the case of a pneumatic tire for passenger cars. In a desirable aspect, among the four circumferential grooves 3, the first shoulder circumferential groove 5 has the smallest depth. In a more desirable aspect, the first crown circumferential groove 7, the second crown circumferential groove 8, and the second shoulder circumferential groove 6 are each configured as flat grooves having a depth smaller than the groove width. However, the present disclosure is not limited to such an aspect.

[0022] As shown in FIG. 1, in each of the land portions 4 divided in the tread portion 2, no groove having a groove width exceeding 2.0 mm is provided in the ground contact surface, and only the sipe 9 is provided. The groove means that in its cross section, the region where the distance between the two groove walls exceeds 2.0 mm exceeds 50% of the total depth of the groove. On the other hand, in the present specification, a "sipe" is a small-width cut having two inner walls extending in the tire radial direction, and in its cross section, the region where the distance between the two inner walls is 2.0 mm or less is 50% or more of the total depth of the cut.

[0023] FIG. 3 shows a cross-sectional view of a typical sipe 9 in the present embodiment. As shown in FIG. 3, in the sipe 9, the width W2 between the two sipe walls 9w extending substantially parallel to each other and facing each other is desirably 1.5 mm or less, and in a more desirable aspect, it is 0.4 to 1.0 mm. Also, the total depth of the sipe 9 is, for example, 3.0 to 5.5 mm.

[0024] The side groove 9 may be formed such that at least one of the side edges on both sides is formed by the chamfered portion 16. In the side groove 9 of the present embodiment, each of the side edges on both sides is formed by the chamfered portion 16. Hereinafter, such a side groove 9 may be referred to as a chamfered side groove. The chamfered portion 16 includes an inclined surface 17 that is continuous with the ground surface and the side groove wall 9w. The angle of the inclined surface 17 with respect to the depth direction of the side groove 9 is, for example, 30 to 60°.

[0025] The depth of the chamfered portion 16 is, for example, less than 30% of the total depth of the side groove 9, specifically 2.0 mm or less, more desirably 1.0 mm or less. As long as it includes the chamfered portion 16 with such a depth, the opening width of the chamfered side groove may exceed 2.0 mm. Also, in the present disclosure, the side groove 9 is not limited to the above-described aspect. Therefore, the side groove 9 may extend with a constant width from the opening to the bottom of the ground surface. Further, a flask bottom having a width exceeding 2.0 mm may be connected to the bottom of the side groove 9.

[0026] As shown in FIG. 1, the five land portions 4 of the present disclosure include at least one shoulder land portion including a tread edge and a middle land portion adjacent to the shoulder land portion. The five land portions 4 of the present embodiment include two shoulder land portions (the first shoulder land portion 11 and the second shoulder land portion 12) and two middle land portions (the first middle land portion 13 and the second middle land portion 14).

[0027] The first shoulder land portion 11 includes the first tread edge T1 and is demarcated on the outer side in the tire axial direction of the first shoulder circumferential groove 5. Also, the second shoulder land portion 12 includes the second tread edge T2 and is demarcated on the outer side in the tire axial direction of the second shoulder circumferential groove 6. The first middle land portion 13 is adjacent to the first shoulder land portion 11 and is demarcated between the first shoulder circumferential groove 5 and the first crown circumferential groove 7. The second middle land portion 14 is adjacent to the second shoulder land portion 12 and is demarcated between the second shoulder circumferential groove 6 and the second crown circumferential groove 8. Further, in the present embodiment, the five land portions 4 include the crown land portion 15. The crown land portion 15 is demarcated between the first crown circumferential groove 7 and the second crown circumferential groove 8.

[0028] 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, in the middle land portion, a plurality of middle sipes are provided which are inclined with respect to the tire axial direction and completely traverse the middle land portion in the tire axial direction. In the shoulder land portion, a plurality of shoulder sipes are provided which extend from the shoulder circumferential groove to a position beyond the tread edge. As a more specific aspect, in the first middle land portion 13 of the present embodiment, a plurality of first middle sipes 30 are provided which are inclined with respect to the tire axial direction and completely traverse the first middle land portion 13 in the tire axial direction. In the first shoulder land portion 11, a plurality of first shoulder sipes 20 are provided which extend from the first shoulder circumferential groove 5 to a position beyond the first tread edge T1.

[0029] At least one of the shoulder sipes (first shoulder sipes 20) includes an inclined portion 21 that extends obliquely from the first shoulder circumferential groove 5 in the tire axial direction. The middle sipes (first middle sipes 30) are inclined in the opposite direction to the inclined portion 21 with respect to the tire axial direction. The maximum angle θ1 of the inclined portion 21 with respect to the tire axial direction is equal to or less than the maximum angle θ2 of the middle sipes (first middle sipes 30) with respect to the tire axial direction. Further, the difference between the maximum angle θ1 of the inclined portion 21 and the maximum angle θ2 of the first middle sipes 30 is 5° or less. The angle θ1 and the angle θ2 are the absolute values of the acute angles formed by a virtual line extending parallel to the tire axial direction and the sipes, and the difference means the value obtained by subtracting the absolute value of the angle θ1 from the absolute value of the angle θ2.

[0030] In the present disclosure, by adopting the above configuration, the handling stability and noise performance can be improved. The reason is speculated as the following mechanism.

[0031] In the present disclosure, in each land portion 4, since there is no groove with a groove width exceeding 2.0 mm and only the sipes 9 are provided, the pattern noise is small and excellent noise performance is exhibited. Further, such a land portion 4 has high pattern rigidity and also helps to enhance the handling stability.

[0032] Further, since the shoulder sipes (first shoulder sipes 20) include the inclined portion 21, the entire edge of the first shoulder sipes 20 can contact the ground with a time difference, and the sound when these edges contact the ground can be reduced.

[0033] In addition, in the present disclosure, the angle θ1 of the inclined portion 21 is equal to or less than the angle θ2 of the middle side (first middle side 30), and the difference between the angle θ1 and the angle θ2 is 5° or less. When the angle between the inclined portion 21 of the first shoulder side 20 and the first middle side 30 has such a relationship, with respect to the rigidity in the tire axial direction of each land portion, the first shoulder land portion 11 becomes equal to or slightly larger than the first middle land portion 13. Such a rigidity distribution enhances the responsiveness and linearity during steering, and thus excellent handling stability is exhibited. In the present disclosure, it is presumed that the noise performance and the handling stability can be improved by the above mechanism.

[0034] Hereinafter, a more detailed configuration of the present embodiment will be described. Each configuration described below shows a specific aspect of the present embodiment. Therefore, it goes without saying that the present disclosure 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 disclosure 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.

[0035] The tire circumferential direction one pitch length P1 of the plurality of first shoulder sides 20 is, for example, 80% to 120% of the ground contact width W3 of the first shoulder land portion 11. Such an arrangement of the first shoulder side 20 helps to enhance the handling stability and the noise performance in a well-balanced manner.

[0036] In the present embodiment, the inclined portion 21 is inclined downward to the right with respect to the tire axial direction. Hereinafter, such an inclination direction may be referred to as "inclined in the first direction with respect to the tire axial direction". The maximum angle θ1 of the inclined portion 21 with respect to the tire axial direction is, for example, 16.5 to 57.9°, preferably 27.2 to 47.2°. Such an inclined portion 21 can enhance the responsiveness during steering while maintaining the noise performance.

[0037] The first shoulder rib 20 of the present embodiment includes an axial portion 22 and a curved portion 23 in addition to the inclined portion 21. The angle of the axial portion 22 with respect to the tire axial direction is smaller than that of the inclined portion 21 and is 10° or less. Further, the axial portion 22 of the present embodiment crosses the first tread end T1 which is the end of the ground contact surface at 50% load. Thereby, in the vicinity of the first tread end T1, the rigidity of the land portion in the tire axial direction is not reduced by the first shoulder rib 20, and the handling stability can be further improved.

[0038] The axial portion 22 extends linearly, for example. The axial portion 22 is preferably arranged at an angle of 5° or less with respect to the tire axial direction, and in a more preferable aspect, is arranged parallel to the tire axial direction. Such an axial portion 22 can provide a large frictional force during braking by its edge.

[0039] The distance L3 in the tire axial direction from the outer end 20a of the first shoulder rib 20 to the first tread end T1 is, for example, 25% to 55% of the width W3 in the tire axial direction of the ground contact surface of the first shoulder land portion 11, and preferably 30% to 50%. Such an axial portion 22 can improve the wandering performance in addition to the improvement of the handling stability and the noise performance.

[0040] The curved portion 23 extends curvedly between the inclined portion 21 and the axial portion 22. The curved portion 23 of the present embodiment is, for example, in an arc shape with a radius of curvature of 10 to 40 mm. Such a curved portion 23 can suppress the uneven wear of the first shoulder land portion 11.

[0041] The first shoulder sip 20 is configured as the chamfered sip described above, and the entire sip edge on both sides is configured as a chamfered portion. Also, in a plan view of the tread, the width of the chamfered portion 24 of the first shoulder sip 20 increases toward the outer side in the tire axial direction. Specifically, the chamfered portions of the inclined portion 21 and the axial portion 22 extend with a constant width, and the chamfered portion of the curved portion 23 has a width that increases toward the outer side in the tire axial direction. As a result, in a plan view of the tread, the width of the chamfered portion of the axial portion 22 is larger than the width of the chamfered portion of the inclined portion 21. Specifically, the width of the chamfered portion of the axial portion 22 is 1.5 to 2.5 times the width of the chamfered portion of the inclined portion 21. The first shoulder sip 20 having such a chamfered portion can effectively suppress uneven wear near the first tread end T1. Needless to say, the width of the chamfered portion described above means the width in a direction perpendicular to the length direction of the sip in a plan view of the tread.

[0042] FIG. 5 shows a cross-sectional view taken along line A-A of FIG. 4. As shown in FIG. 5, the depth of the first shoulder sip 20 increases from the inclined portion 21 toward the axial portion 22. Also, the depth d2 of the inclined portion 21 is 40% to 60% of the maximum depth d1 of the axial portion 22. As a result, the rigidity of the first shoulder land portion 11 on the inner side in the tire axial direction is improved, and excellent handling stability is exhibited.

[0043] As shown in FIG. 4, a plurality of shoulder break sips 25 are provided in the first shoulder land portion 11 of the present embodiment. In the present embodiment, the first shoulder sip 20 and the shoulder break sip 25 are alternately provided in the tire circumferential direction.

[0044] The shoulder break groove 25 extends from the first shoulder circumferential groove 5 and breaks off without reaching the first tread end T1. The shoulder break groove 25 breaks off, for example, axially inside the tire in relation to the axial portion 22 of the first shoulder groove 20, and in a preferred embodiment, breaks off axially inside the tire in relation to the curved portion 23 of the first shoulder groove 20. In an even more preferred embodiment, the shoulder break groove 25 breaks off without crossing the axial center position of the contact surface of the first shoulder land 11. The axial length L4 of the shoulder break groove 25 is, for example, 25% to 45% of the width W3 of the contact surface of the first shoulder land 11, preferably 30% to 40%. Such a shoulder break groove 25 can further enhance handling stability and noise performance.

[0045] The shoulder break groove 25 is inclined in a first direction with respect to the tire axis. That is, the shoulder break groove 25 is inclined in the same direction as the inclined portion 21 of the first shoulder groove 20. The angle θ3 of the shoulder break groove 25 with respect to the tire axis is, for example, 16.5 to 57.9°, preferably 27.2 to 47.2°. Also, the angle difference between the shoulder break groove 25 and the inclined portion 21 is, for example, 10° or less, preferably 5° or less. In a more preferred embodiment, in the present embodiment, the shoulder break groove 25 and the inclined portion 21 extend parallel to each other. Thereby, uneven wear of the first shoulder land 11 is suppressed.

[0046] The shoulder break sidewall 25 is preferably configured as a chamfered sidewall. The chamfered portion of the shoulder break sidewall 25 is narrower in width from the side of the first shoulder circumferential groove 5 toward the outer side in the tire axial direction. As a result, the width of the chamfered portion at the inner end in the tire axial direction of the chamfered portion of the shoulder break sidewall 25 is larger than the width of the chamfered portion at the outer end in the tire axial direction of the chamfered portion of the shoulder break sidewall 25. In a more preferable aspect, the maximum width of the chamfered portion of the shoulder break sidewall 25 is formed at the end on the side of the first shoulder circumferential groove 5 of the shoulder break sidewall 25 and is the same as the width of the chamfered portion of the inclined portion 21. Further, the width of the chamfered portion of the shoulder break sidewall 25 continuously decreases toward the outer side in the tire axial direction from the position where the maximum width is formed.

[0047] FIG. 6 shows a cross-sectional view taken along line B-B of FIG. 4. As shown in FIG. 6, the shoulder break sidewall 25 includes a first portion 26 communicating with the first shoulder circumferential groove 5 and a second portion 27 connected to the outer side in the tire axial direction of the first portion 26 and having a depth smaller than that of the first portion 26. The depth d4 of the second portion 27 is, for example, 60% to 75% of the depth d3 of the first portion 26. Such a shoulder break sidewall 25 can maintain the rigidity of the first shoulder land portion 11 and improve the handling stability.

[0048] As shown in FIG. 4, the tire circumferential pitch length P2 of the plurality of first middle sidewalls 30 is, for example, 100% to 150% of the width W4 in the tire axial direction of the grounding surface of the first middle land portion 13, and in this embodiment, it is the same as the pitch length P1 of the first shoulder sidewall 20.

[0049] The first middle sip 30 is inclined, for example, upward to the right with respect to the tire axial direction. Hereinafter, such an inclination direction may be referred to as "inclined in a second direction with respect to the tire axial direction". In other words, the first middle sip 30 is inclined in a direction opposite to the inclined portion 21 of the first shoulder sip 20 with respect to the tire axial direction. Thereby, the edges of these sips provide frictional forces in multiple directions, and excellent handling stability can be obtained. However, the present disclosure is not limited to such an aspect. For example, even if the first middle sip 30 and the inclined portion 21 of the first shoulder sip 20 are inclined in the same direction with respect to the tire axial direction, the above-described effects can be expected.

[0050] The maximum angle θ2 of the first middle sip 30 with respect to the tire axial direction is, for example, 15.9 to 65.3, preferably 28.6 to 52.6°. Such a first middle sip 30 can provide frictional forces well-balanced in the tire circumferential direction and the tire axial direction.

[0051] The circumferential distance L5 of the tire from the end 30a on the first shoulder circumferential groove 5 side of the first middle sip 30 to the end 20b on the first shoulder circumferential groove 5 side of the first shoulder sip 20 is, for example, 10% to 50% of the circumferential pitch length P2 of a plurality of first middle sips 30, preferably 30% to 50%. Thereby, the handling stability and the noise performance are improved in a well-balanced manner.

[0052] Also, the circumferential distance of the tire from the end 30a of the first middle sip 30 to the end 25a on the first shoulder circumferential groove 5 side of the shoulder break sip 25 is, for example, 20% or less of the pitch length P2, preferably 10% or less. In the present embodiment, the above-described distance is substantially 0. In other words, the end 30a faces the end 25a.

[0053] The first middle sip 30 is configured as a chamfered sip, for example. Specifically, in the first middle sip 30, the entire side edge on both sides is formed by a chamfered portion. Also, in a plan view of the tread, the width of the chamfered portion of the first middle sip 30 continuously increases toward the tire equator C side. As a result, at the end of the first middle sip 30 on the tire equator C side, the width of the chamfered portion is the largest. Further, in a more desirable aspect, the maximum width of the chamfered portion 31 of the first middle sip 30 is larger than the maximum width of the chamfered portion of the inclined portion 21 of the first shoulder sip 20. Thereby, while suppressing uneven wear of the first middle land portion 13, the handling stability and noise performance can be improved.

[0054] FIG. 7 shows a cross-sectional view taken along line C-C of FIG. 4. As shown in FIG. 7, the first middle sip 30 includes, for example, a first middle rib 32 with a locally raised bottom. The first middle rib 32 is arranged, for example, in the central region when the first middle sip 30 is divided into three equal parts in the tire axial direction. The axial length L7 of the first middle rib 32 is 30% to 50% of the axial width W4 (shown in FIG. 4) of the contact surface of the first middle land portion 13. When the axial length of the first middle rib 32 varies in the tire radial direction, the length shall be measured at the central position in the tire radial direction. The depth d6 from the contact surface of the first middle land portion 13 to the outer surface of the first middle rib 32 is 50% to 70% of the maximum depth d5 of the first middle sip 30. Such a first middle rib 32 can maintain the rigidity of the first middle land portion 13 and further improve the handling stability.

[0055] Fig. 8 shows an enlarged view of the second shoulder land portion 12 and the second middle land portion 14. As shown in Fig. 8, a plurality of shoulder sipes (second shoulder sipes 35) are provided in the second shoulder land portion 12. Also, a plurality of middle sipes (second middle sipes 40) are provided in the second middle land portion 14. The configurations of the above-described shoulder sipes (first shoulder sipes 20) and middle sipes (first middle sipes 30) can also be applied to the second shoulder sipes 35 and the second middle sipes 40.

[0056] The tire circumferential direction one pitch length P3 of the plurality of second shoulder sipes 35 is preferably, for example, smaller than the tire axial direction width W5 of the ground contact surface of the second shoulder land portion 12, and specifically, is 60% to 80% of the width W5. Also, the first pitch length P3 is 40% to 60% of the one pitch length P1 (shown in Fig. 4) of the first shoulder sipes 20. Thereby, the number of shoulder sipes (second shoulder sipes 35) arranged in the second shoulder land portion 12 is larger than the number of shoulder sipes (first shoulder sipes 20) arranged in the first shoulder land portion 11. With such a sipe arrangement, the hitting sound when the first shoulder land portion 11 and the second shoulder land portion 12 come into contact with the ground is whitened, and the noise performance is improved.

[0057] The second shoulder sipes 35 extend from the second shoulder circumferential groove 6 to a position beyond the second tread end T2. The second shoulder sipes 35 include, for example, an inclined portion 41, an axial portion 42, and a curved portion 43. The inclined portion 41 extends obliquely from the second shoulder circumferential groove 6. The angle of the axial portion 42 with respect to the tire axial direction is smaller than that of the inclined portion 41 and is 10° or less. Also, the axial portion 42 crosses the second tread end T2. The curved portion 43 extends curving between the axial portion 42 and the axial portion 42. Such second shoulder sipes 35 can improve the handling stability and the noise performance by the same mechanism as the first shoulder sipes 20.

[0058] For the inclined portion 41, axial portion 42, and curved portion 43 of the second shoulder sip 35, the configurations of the inclined portion 21, axial portion 22, and curved portion 23 of the first shoulder sip 20 described above can be applied, except for the matters described below.

[0059] The inclined portion 41 of the second shoulder sip 35 is inclined in a first direction with respect to the tire axial direction. The maximum angle θ4 in the tire axial direction of the inclined portion 41 of the second shoulder sip 35 is, for example, 16.5 to 53.7°, desirably 26.1 to 44.1°. Further, it is desirable that the angle θ4 is equal to or less than the angle θ1 of the inclined portion 21 of the first shoulder sip 20. Also, it is desirable that the difference between the angle θ1 and the angle θ4 is 5° or less. Thereby, when the first shoulder sip 20 and the second shoulder sip 35 come into contact with the ground, the impact sound is likely to be whitened, and the noise performance can be improved.

[0060] The second shoulder sip 35 includes, for example, a standard type second shoulder sip 36 and a small type second shoulder sip 37. For the standard type second shoulder sip 36, it is desirable that the distance L8 in the tire axial direction from the outer end 36a in the tire axial direction to the second tread end T2 is larger than the distance L3 (shown in FIG. 4) in the tire axial direction from the outer end 20a of the first shoulder sip 20 to the first tread end T1, specifically 125% to 140%.

[0061] The small type second shoulder sip 37 has a length in the tire axial direction smaller than that of the standard type second shoulder sip 36. The distance L9 in the tire axial direction from the outer end 37a of the small type second shoulder sip 37 to the second tread end T2 is 15% to 25% of the distance L8 from the outer end 36a of the standard type second shoulder sip 36 to the second tread end T2. In the second shoulder land portion 12 of the present embodiment, the standard type second shoulder sip 36 and the small type second shoulder sip 37 are alternately provided in the tire circumferential direction. Such a sip arrangement helps to enhance the noise performance and the wandering performance.

[0062] FIG. 9 shows a cross-sectional view taken along line D-D of FIG. 8. As shown in FIG. 9, the standard type second shoulder size 36 includes, for example, a second shoulder tie bar 38 with a raised bottom at a position away from the end on the side of the second shoulder circumferential groove 6. The second shoulder tie bar 38 of the present embodiment is provided, for example, at a position including at least a part of the curved portion 43. The depth d8 from the ground surface to the outer surface of the second shoulder tie bar 38 is 40% to 60% of the maximum depth d7 of the standard type second shoulder size 36. Such a second shoulder tie bar 38 helps maintain the rigidity of the second shoulder land portion 12 and improve the handling stability.

[0063] FIG. 10 shows a cross-sectional view taken along line E-E of FIG. 8. As shown in FIG. 10, the small type second shoulder size 37 has a bottom that extends flat in its length direction. That is, the small type second shoulder size 37 does not include a tie bar with a raised bottom. In the present embodiment, by providing such a small type second shoulder size 37 and the above-described standard type second shoulder size 36, the impact sound when these sizes contact the ground is whitened, and the noise performance is improved.

[0064] As shown in FIG. 8, the configuration of the above-described first middle size 30 can be applied to the second middle size 40 except for the matters described below, and the description here is omitted.

[0065] The maximum angle θ5 of the second middle sip 40 with respect to the tire axial direction is preferably smaller than the maximum angle θ2 (shown in FIG. 4) of the first middle sip 30 with respect to the tire axial direction. In a more preferable embodiment, the absolute value |θ5 - θ4| of the difference between the maximum angle θ5 of the second middle sip 40 with respect to the tire axial direction and the maximum angle θ4 of the inclined portion 41 of the second shoulder sip 35 with respect to the tire axial direction is preferably larger than the absolute value |θ2 - θ1| of the difference between the maximum angle θ2 of the first middle sip 30 with respect to the tire axial direction and the maximum angle θ1 of the inclined portion 21 of the first shoulder sip 20 with respect to the tire axial direction. Thereby, while suppressing uneven wear of each land portion, the hitting sound when each sip contacts the ground is likely to be whitened, and the wear resistance performance and noise performance are improved.

[0066] FIG. 11 shows an enlarged view of the crown land portion 15 of FIG. 1. As shown in FIG. 11, the center position of the crown land portion 15 in the tire axial direction is located on the side of the first tread end T1 (shown in FIG. 1) rather than the tire equator C. Thereby, in the crown land portion 15, the width W7 of the ground contact surface of the outer region 15a on the side of the first tread end T1 rather than the tire equator C is larger than the width W8 of the ground contact surface of the inner region 15b on the side of the second tread end T2 rather than the tire equator C. Specifically, the width W7 of the outer region 15a is 51% to 55% of the width W6 of the ground contact surface of the crown land portion 15. Such a crown land portion 15 linearizes the change in the cornering force accompanying the change in the steering angle and helps to improve the steering stability and riding comfort.

[0067] A plurality of first crown sips 46 and a plurality of second crown sips 47 are provided in the crown land portion 15. The first crown sip 46 extends from, for example, the first crown circumferential groove 7 and is interrupted within the crown land portion 15. The second crown sip 47 extends from, for example, the second crown circumferential groove 8 and is interrupted within the crown land portion 15.

[0068] The first crown rib 46 and the second crown rib 47 do not cross the tire axial center position of the crown land portion 15, respectively, and do not cross the tire equator C. The tire axial length L10 of the first crown rib 46 or the second crown rib 47 is, for example, 15% to 30% of the tire axial width W6 of the ground contact surface of the crown land portion 15. Thereby, the rigidity of the crown land portion 15 is surely maintained, and excellent handling stability is exhibited.

[0069] The first crown rib 46 and the second crown rib 47 are inclined, for example, in the second direction with respect to the tire axial direction. The maximum angle θ6 of the first crown rib 46 or the second crown rib 47 with respect to the tire axial direction is, for example, 16.5 to 64.7°, desirably 28.6 to 52.6°. In a more desirable aspect, the angle difference between the first crown rib 46 and the second crown rib 47 is 5° or less, and in this embodiment, they are arranged in parallel. Such first crown rib 46 and second crown rib 47 can provide frictional force well-balanced in the tire circumferential direction and the tire axial direction.

[0070] In an even more desirable aspect, the maximum angle θ6 of the first crown rib 46 or the second crown rib 47 with respect to the tire axial direction is desirably equal to or less than the angle θ2 (shown in FIG. 4) of the first middle rib 30 with respect to the tire axial direction, and desirably equal to or greater than the angle θ5 (shown in FIG. 8) of the second middle rib 40 with respect to the tire axial direction. Thereby, while suppressing uneven wear of each land portion, the noise performance is improved.

[0071] The first crown rib 46 and the second crown rib 47 are each configured as a chamfered rib. In a desirable aspect, the widths of the chamfered portions of the first crown rib 46 and the second crown rib 47 become smaller toward the tire equator side. Such first crown rib 46 and second crown rib 47 can suppress uneven wear of the crown land portion 15.

[0072] In this embodiment, on each land portion, in addition to the above-described sipes, no sipes are provided. As a result, the above-described various performances are exhibited in a well-balanced manner. However, the present disclosure is not limited to such an aspect.

[0073] FIG. 12 shows an enlarged view of the ground contact surface shape of the tread portion 2 of this embodiment when it comes into contact with the ground. As shown in FIG. 12, in a state where it is rim-mounted on a regular rim at a regular internal pressure and loaded with 50% of the regular load and grounded on a flat surface at a camber angle of 0° (hereinafter, sometimes referred to as the "50% load state"), the width W1s of the ground contact surface in the tire axial direction of the first shoulder land portion 11 is preferably larger than the width W2s of the ground contact surface in the tire axial direction of the second shoulder land portion 12. Also, the width W1m of the ground contact surface in the tire axial direction of the first middle land portion 13 is preferably larger than the width W2m of the ground contact surface in the tire axial direction of the second middle land portion 14. Due to such a distribution of the widths of the land portions, the handling stability is further improved.

[0074] In a more desirable aspect, in the 50% load state, when the widths of the ground contact surfaces in the tire axial direction of the first shoulder land portion 11, the first middle land portion 13, the crown land portion 15, the second middle land portion 14, and the second shoulder land portion 12 are W1s, W1m, Wc, W2m, and W2s, respectively, it is desirable to satisfy the following formula (1). Further, as a more desirable aspect, the tire 1 of this embodiment also satisfies the following formula (2). Such a tire 1 has a greater rigidity in the land portion closer to the first tread end T1. Therefore, even when the center of the ground contact surface moves toward the first tread end T1 side by steering, the feel of steering is stable, and a cornering force is generated linearly with respect to an increase in the steering angle. Therefore, excellent handling stability and ride comfort are obtained. W1m>Wc>W2m…(1) W1s>W1m>Wc>W2m≧W2s…(2)

[0075] In the 50% load condition, it is desirable that the width W1s in the tire axis direction of the contact surface of the first shoulder land portion 11 is 115% to 125% of the width Wc of the contact surface in the tire axis direction of the crown land portion 15. Thereby, the rigidity of the first shoulder land portion 11 is optimized, and together with the above-described effects, the noise performance can also be improved.

[0076] From the same viewpoint, in the 50% load condition, it is desirable that the width W1m in the tire axis direction of the contact surface of the first middle land portion 13 is 101% to 107% of the width Wc of the contact surface in the tire axis direction of the crown land portion 15.

[0077] In the 50% load condition, it is desirable that the width W2m in the tire axis direction of the contact surface of the second middle land portion 14 is 90% to 99% of the width Wc of the contact surface in the tire axis direction of the crown land portion 15. Thereby, the noise performance during straight running is improved. Also, the vibration of the tire during straight running is less likely to be transmitted to the vehicle body side, and the riding comfort is also improved.

[0078] From the same viewpoint, in the 50% load condition, it is desirable that the width W2s in the tire axis direction of the contact surface of the second shoulder land portion 12 is 90% to 99% of the width Wc of the contact surface in the tire axis direction of the crown land portion 15.

[0079] As a more desirable aspect, in the present embodiment, in the 50% load condition, the width W2m of the second middle land portion 14 is made the same as the width W2s of the second shoulder land portion 12. Thereby, the progress of wear between the second middle land portion 14 and the second shoulder land portion 12 becomes uniform, and the uneven wear resistance performance is improved.

[0080] As described above, one embodiment of the tire of the present disclosure has been described in detail. However, the present disclosure is not limited to the above specific embodiment and can be implemented in various aspects.

Example

[0081] A tire of size 235 / 45R19 having the basic pattern of FIG. 1 was prototyped based on the specifications in Table 1. Further, as Comparative Example 1, as shown in FIG. 13, a tire was prototyped in which the maximum angle θ1 of the inclined portion of each shoulder size a with respect to the tire axial direction was larger than the maximum angle θ2 of the middle size b with respect to the tire axial direction. As Comparative Example 2, a tire having the basic pattern of FIG. 1 and in which the difference between the angle θ1 and the angle θ2 exceeds 5° was prototyped. In addition, the tires of Comparative Examples 1 and 2 are substantially the same as those shown in FIG. 1 except for the above matters.

[0082] In addition, as a tire (reference tire) serving as a reference for comparing noise performance, a tire was prototyped in which the width of each land portion of the tread portion was the same as that shown in FIG. 1 and no grooves and sipes were provided in each land portion.

[0083] The handling stability and noise performance of each test tire were tested. The common specifications and test methods of each test tire are as follows. Mounting rim: 19×7.5J Tire internal pressure: Front wheel 230 kPa, Rear wheel 210 kPa Test vehicle: Displacement 2000 cc, Front-wheel drive vehicle Tire mounting position: All wheels

[0084] <Handling stability> The handling stability when the test vehicle was driven in a turning motion on a dry road surface was evaluated by the driver's sensory evaluation. The results are shown as scores with the handling stability of the comparative example being 100, and the larger the numerical value, the better the handling stability.

[0085] <Noise performance> The maximum sound pressure of the external noise when the test vehicle was driven on a dry road surface at a speed of 70 km / h was measured. The results are shown as an index of the sound pressure reduction amount, which is the difference from the sound pressure of the reference tire, with the sound pressure reduction amount of the comparative example being 100. The larger this index, the smaller the maximum sound pressure of the noise, indicating that excellent noise performance is exhibited. The test results are shown in Table 1.

[0086]

Table 1

[0087] As a result of the test, it was confirmed that the tires of the examples had improved handling stability and noise performance.

[0088] [Appendix] This disclosure includes the following aspects.

[0089] [This Disclosure 1] A tire having a tread portion, The tread portion includes four circumferential grooves continuously extending in the circumferential direction of the tire between two tread ends, and five land portions divided by the four circumferential grooves, In each of the five land portions, a groove having a groove width exceeding 2.0 mm is not provided, and only sipes are provided, The four circumferential grooves include a shoulder circumferential groove arranged closest to the tread end side, The five land portions include a shoulder land portion including the tread end, and a middle land portion adjacent to the shoulder land portion via the shoulder circumferential groove, In the middle land portion, a plurality of middle sipes are provided which are inclined with respect to the tire axial direction and completely cross the middle land portion in the tire axial direction, In the shoulder land portion, a plurality of shoulder sipes are provided which extend from the shoulder circumferential groove to a position beyond the tread end, At least one of the shoulder sipes includes an inclined portion inclined in the tire axial direction from the shoulder circumferential groove, The middle sipes are inclined in a direction opposite to the inclined portion with respect to the tire axial direction, The maximum angle of the inclined portion with respect to the tire axial direction is equal to or less than the maximum angle of the middle sipes with respect to the tire axial direction, The difference between the maximum angle of the inclined portion and the maximum angle of the middle sipes is 5° or less. Tire. [Disclosure 2] The shoulder side includes an axial direction part whose angle with respect to the tire axial direction is smaller than that of the inclined part and is 10° or less, and a curved part that curves and extends between the inclined part and the axial direction part. The tire according to Disclosure 1. [Disclosure 3] At least one of the side edges on both sides of the middle side is formed by a chamfered part. In a plan view of the tread, the width of the chamfered part of the middle side increases toward the tire equator side. The tire according to Disclosure 1 or 2. [Disclosure 4] At least one of the side edges on both sides of the inclined part is formed by a chamfered part. In a plan view of the tread, the maximum width of the chamfered part of the middle side is larger than the maximum width of the chamfered part of the inclined part. The tire according to Disclosure 3. [Disclosure 5] The direction of mounting on the vehicle is specified. The shoulder land part includes a first shoulder land part that becomes the outside of the vehicle when mounted on the vehicle and a second shoulder land part that becomes the inside of the vehicle when mounted on the vehicle. The middle land part includes a first middle land part that becomes the outside of the vehicle when mounted on the vehicle and a second middle land part that becomes the inside of the vehicle when mounted on the vehicle. The five land parts include a crown land part provided between the first middle land part and the second middle land part. In a 50% load state where the tire is rim - assembled on a standard rim at a standard internal pressure and loaded with 50% of the standard load and grounded on a plane at a camber angle of 0°. The width of the ground - contact surface of the first shoulder land part is larger than the width of the ground - contact surface of the second shoulder land part. The width of the ground - contact surface of the first middle land part is larger than the width of the ground - contact surface of the second middle land part. The tire according to any one of Disclosures 1 to 4. [Disclosure 6] The shoulder side includes a first shoulder side provided on the first shoulder land portion and a second shoulder side provided on the second shoulder land portion. The middle side includes a first middle side provided on the first middle land portion and a second middle side provided on the second middle land portion. The maximum angle of the inclined portion of the first shoulder side with respect to the tire axis direction is larger than the maximum angle of the inclined portion of the second shoulder side with respect to the tire axis direction. The maximum angle of the first middle side with respect to the tire axis direction is larger than the maximum angle of the second middle side with respect to the tire axis direction. The tire according to the fifth aspect of the present disclosure. [The seventh aspect of the present disclosure] The absolute value of the difference between the maximum angle of the second middle side with respect to the tire axis direction and the maximum angle of the inclined portion of the second shoulder side with respect to the tire axis direction is larger than the absolute value of the difference between the maximum angle of the first middle side 30 with respect to the tire axis direction and the maximum angle of the inclined portion of the first shoulder side with respect to the tire axis direction. The tire according to the fifth or sixth aspect of the present disclosure. [The eighth aspect of the present disclosure] A plurality of first crown sides and a plurality of second crown sides inclined with respect to the tire axis direction are provided on the crown land portion. The maximum angle of the first crown side and the second crown side with respect to the tire axis direction is equal to or less than the maximum angle of the first middle side with respect to the tire axis direction, and equal to or more than the maximum angle of the second middle side with respect to the tire axis direction. The tire according to any one of the fifth to seventh aspects of the present disclosure.

Explanation of reference numerals

[0090] 2 Tread portion 3 Circumferential groove 4 Land portion 5 Shoulder circumferential groove 9 Side 11 Shoulder land portion 13 Middle land portion 30 Middle side 20 Shoulder side 21 Inclined portion

Claims

1. A tire having a tread portion, wherein the tread portion includes four circumferential grooves continuously extending in the circumferential direction of the tire between two tread ends, and five land portions divided by the four circumferential grooves, each of the five land portions is not provided with a groove having a groove width exceeding 2.0 mm and is provided with only sipes, the four circumferential grooves include a shoulder circumferential groove arranged closest to the tread end side, the five land portions include a shoulder land portion including the tread end and a middle land portion adjacent to the shoulder land portion via the shoulder circumferential groove, the middle land portion is provided with a plurality of middle sipes that are inclined with respect to the tire axial direction and completely cross the middle land portion in the tire axial direction, the shoulder land portion is provided with a plurality of shoulder sipes extending from the shoulder circumferential groove to a position beyond the tread end, at least one of the shoulder sipes includes an inclined portion that extends inclined with respect to the tire axial direction from the shoulder circumferential groove, the middle sipes are inclined in a direction opposite to the inclined portion with respect to the tire axial direction, the maximum angle of the inclined portion with respect to the tire axial direction is equal to or less than the maximum angle of the middle sipes with respect to the tire axial direction, the difference between the maximum angle of the inclined portion and the maximum angle of the middle sipes is 5° or less, a tire.

2. The tire according to claim 1, wherein the shoulder sipes include an axial portion having an angle with respect to the tire axial direction that is smaller than the inclined portion and is 10° or less, and a curved portion that curves and extends between the inclined portion and the axial portion.

3. At least one of the side edges of both sides of the middle sipes is formed as a chamfered portion, in a plan view of the tread, the width of the chamfered portion of the middle sipes increases toward the tire equator side, the tire according to claim 1 or 2.

4. At least one of the side edges of both sides of the inclined portion is formed as a chamfered portion, in a plan view of the tread, the maximum width of the chamfered portion of the middle sipes is larger than the maximum width of the chamfered portion of the inclined portion, the tire according to claim 3.

5. The direction of mounting on a vehicle is specified, the shoulder land portion includes a first shoulder land portion that becomes the outside of the vehicle when mounted on the vehicle and a second shoulder land portion that becomes the inside of the vehicle when mounted on the vehicle, The middle land portion includes a first middle land portion that becomes the outside of the vehicle when the tire is mounted on the vehicle, and a second middle land portion that becomes the inside of the vehicle when the tire is mounted on the vehicle. The five land portions include a crown land portion provided between the first middle land portion and the second middle land portion. In a 50% load state where the tire is rim-mounted on a standard rim at a standard internal pressure and loaded with 50% of the standard load and grounded on a flat surface at a camber angle of 0°. The width of the ground contact surface of the first shoulder land portion is larger than the width of the ground contact surface of the second shoulder land portion. The width of the ground contact surface of the first middle land portion is larger than the width of the ground contact surface of the second middle land portion. The tire according to any one of claims 1 to 4.

6. The shoulder sipe includes a first shoulder sipe provided on the first shoulder land portion and a second shoulder sipe provided on the second shoulder land portion. The middle sipe includes a first middle sipe provided on the first middle land portion and a second middle sipe provided on the second middle land portion. The maximum angle of the inclined portion of the first shoulder sipe with respect to the tire axis direction is larger than the maximum angle of the inclined portion of the second shoulder sipe with respect to the tire axis direction. The maximum angle of the first middle sipe with respect to the tire axis direction is larger than the maximum angle of the second middle sipe with respect to the tire axis direction. The tire according to claim 5.

7. The shoulder sipe includes a first shoulder sipe provided on the first shoulder land portion and a second shoulder sipe provided on the second shoulder land portion. The middle sipe includes a first middle sipe provided on the first middle land portion and a second middle sipe provided on the second middle land portion. The absolute value of the difference between the maximum angle of the second middle sipe with respect to the tire axis direction and the maximum angle of the inclined portion of the second shoulder sipe with respect to the tire axis direction is larger than the absolute value of the difference between the maximum angle of the first middle sipe with respect to the tire axis direction and the maximum angle of the inclined portion of the first shoulder sipe with respect to the tire axis direction. The tire according to claim 5 or 6.

8. The middle sipe includes a first middle sipe provided on the first middle land portion and a second middle sipe provided on the second middle land portion. A plurality of first crown sipes and a plurality of second crown sipes inclined with respect to the tire axis direction are provided on the crown land portion. The maximum angle of the first crown size and the second crown size with respect to the tire axial direction is less than or equal to the maximum angle of the first middle size with respect to the tire axial direction and greater than or equal to the maximum angle of the second middle size with respect to the tire axial direction. The tire according to any one of claims 5 to 7.

Images