tire

Abstract

The present invention provides a tire. The tire has a tread portion (2). The tread portion (2) includes three or four circumferential grooves (3) and a plurality of land portions (4). The plurality of land portions (4) include a shoulder land portion (8) and an intermediate land portion (7). The circumferential grooves (3) include a shoulder circumferential groove (5). An intermediate longitudinal sipe pattern (11) and a plurality of intermediate transverse sipe patterns (12) are provided in the intermediate land portion (7). The shoulder land portion (8) is provided with: a plurality of shoulder transverse grooves (16) extending from the shoulder circumferential groove (5) to at least the first tread end (T1); and a plurality of shoulder transverse sipe patterns (18) extending from the shoulder circumferential groove (5) and interrupted within the shoulder land portion (8) without crossing the first tread end (T1). The present invention can provide a tire having improved handling stability and noise performance.

Description

Technical Field

[0001] The present invention relates to tires. Background Art

[0002] Patent Document 1 below proposes a pneumatic tire having only sipes provided in the inner and outer middle land portions. The pneumatic tire is expected to improve steering stability and ride comfort in a well-balanced manner by further providing the sipes.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2014-184828 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] In recent years, electric and hybrid vehicles have become increasingly popular. These vehicles tend to increase in weight due to the batteries they carry. This trend is particularly pronounced in large SUVs. Generally, the cornering stiffness generated by a tire is positively correlated with the load. Therefore, when a heavy vehicle is equipped with the pneumatic tire described in Patent Document 1, the cornering stiffness and cornering force become excessive. As a result, the vehicle's handling stability, particularly its linearity of operation and behavior near the slip limit, tends to be impaired.

[0008] On the other hand, when grooves are added to the tread portion in order to suppress the cornering stiffness of the tire, there is a tendency for noise during running to increase.

[0009] The present invention has been made in view of the above circumstances, and a main object of the present invention is to provide a tire having improved steering stability and noise performance.

[0010] Means for solving problems

[0011] The tire of the present invention has a tread portion, wherein the tread portion includes: 3 or 4 circumferential grooves extending continuously along the circumferential direction of the tire; and a plurality of land portions divided by the circumferential grooves, the plurality of land portions including: a shoulder land portion including a first tread end; and an intermediate land portion adjacent to the shoulder land portion, the circumferential grooves including a shoulder circumferential groove, the shoulder circumferential groove being arranged between the shoulder land portion and the intermediate land portion, the intermediate land portion being provided with: an intermediate longitudinal sipe extending continuously along the circumferential direction of the tire; and a plurality of intermediate transverse sipes completely cutting off the intermediate land portion in the axial direction of the tire, the shoulder land portion being provided with: a plurality of shoulder transverse grooves extending from the shoulder circumferential groove at least to the first tread end; and a plurality of shoulder transverse sipes extending from the shoulder circumferential groove and interrupted within the shoulder land portion without crossing the first tread end.

[0012] In the tire of the present invention, it is preferable that the groove width of the shoulder lateral groove is constant from the shoulder circumferential groove to the first tread end.

[0013] In the tire of the present invention, the shoulder lateral groove preferably includes a groove bottom raised portion formed by partially raising the groove bottom.

[0014] In the tire of the present invention, it is preferable that the groove bottom raised portion is provided at an inner end portion of the shoulder lateral groove in the tire axial direction.

[0015] In the tire of the present invention, it is preferable that the groove bottom raised portion is provided with a groove bottom sipe extending along the longitudinal direction of the shoulder lateral groove.

[0016] In the tire of the present invention, it is preferred that the maximum depth of the middle longitudinal sipes is smaller than the maximum depth of the shoulder transverse sipes.

[0017] In the tire of the present invention, the plurality of land portions preferably include a crown land portion adjacent to the middle land portion, and the crown land portion is provided with a plurality of crown lateral sipes that completely divide the crown land portion in the tire axial direction.

[0018] In the tire of the present invention, the middle transverse sipes are preferably inclined in a first direction relative to the tire axial direction, and the crown transverse sipes are preferably inclined in a second direction relative to the tire axial direction, wherein the second direction is opposite to the first direction.

[0019] In the tire of the present invention, preferably, the multiple land portions include a crown land portion adjacent to the middle land portion, and under a normal load load state in which the tire is assembled on a normal rim with a normal internal pressure rim, a normal load is applied, and the tire contacts a flat surface at a camber angle of 0°, the maximum length of the ground contact surface of the shoulder land portion in the tire circumferential direction is 0.80 to 0.85 times the maximum length of the ground contact surface of the crown land portion in the tire circumferential direction.

[0020] Effects of the Invention

[0021] The tire of the present invention can improve steering stability and noise performance by adopting the above-mentioned configuration. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a development view showing a tread portion according to one embodiment of the present invention.

[0023] Figure 2 yes Figure 1 Enlarged view of the middle land area and shoulder land area.

[0024] Figure 3 yes Figure 2 AA line section view.

[0025] Figure 4 yes Figure 2 BB line cross-sectional view.

[0026] Figure 5 yes Figure 2 CC line cross-sectional view.

[0027] Figure 6 yes Figure 2 DD line cross-sectional view.

[0028] Figure 7 yes Figure 1 An enlarged view of the land portion of the tire crown.

[0029] Figure 8 yes Figure 2 EE line cross-sectional view.

[0030] Figure 9 It is an enlarged view showing the shape of the ground contact surface when the tread portion contacts the ground.

[0031] Figure 10 It is an enlarged view of the middle land portion and the shoulder land portion of the comparative example.

[0032] Description of Reference Numerals

[0033] 2 Tread

[0034] 3 Circumferential groove

[0035] 4 Land Department

[0036] 5 Shoulder circumferential groove

[0037] 7 Middle Land

[0038] 8. Shoulder land area

[0039] 11 Middle longitudinal sipe pattern

[0040] 12 Middle horizontal sipe pattern

[0041] 16 shoulder grooves

[0042] 18 shoulder sipes

[0043] T1 1st tread end DETAILED DESCRIPTION

[0044] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. Figure 1This is a developed view showing the tread portion 2 of a tire 1 according to one embodiment of the present invention. The tire 1 of this embodiment is preferably used as a pneumatic tire for passenger cars, for example. It should be noted that the present invention is not limited to the above embodiment and can also be applied to heavy-duty pneumatic tires and non-pneumatic tires that are not filled with pressurized air.

[0045] like Figure 1 As shown, the tread portion 2 includes three or four circumferential grooves 3 extending continuously in the tire circumferential direction between the first tread end T1 and the second tread end T2, and a plurality of land portions 4 defined by these circumferential grooves 3. The tire 1 of this embodiment is configured as a so-called five-rib tire, in which the tread portion 2 includes five land portions 4 defined by the four circumferential grooves 3. In other embodiments of the present invention, the tire 1 may also be configured as a so-called four-rib tire, in which the tread portion 2 includes four land portions 4 defined by the three circumferential grooves 3.

[0046] The first tread end T1 and the second tread end T2 each correspond to the outermost ground contact position in the tire axial direction when the tire 1 is in a normal state and a normal load is applied thereto and the tire 1 contacts a flat surface at a camber angle of 0°.

[0047] For pneumatic tires with established specifications, the "normal condition" refers to the tire being assembled on a standard rim, inflated to the specified internal pressure, and unloaded. For tires with unspecified specifications or non-pneumatic tires, the "normal condition" refers to the standard operating condition corresponding to the tire's intended use, meaning it is not mounted on a vehicle and is unloaded. Unless otherwise specified in this manual, dimensions of various tire components are values ​​measured under the "normal condition."

[0048] A "regular rim" is a rim that is determined for each tire in a standard system that includes the standards that the tire is based on, such as a "standard rim" in JATMA, a "design rim" in TRA, and a "measuring rim" in ETRTO.

[0049] "Normal internal pressure" is the air pressure determined for each tire in the specification system that includes the specifications on which the tire is based. If it is JATMA, it is the "maximum air pressure", if it is TRA, it is the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLDINFLATION PRESSURES", and if it is ETRTO, it is "INFLATION PRESSURE".

[0050] For pneumatic tires with defined specifications, the "normal load" is the load specified for each tire within the specification system that includes the tire's specifications. For JATMA, this is the "maximum load capacity," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is "LOAD CAPACITY." For tires with undefined specifications or non-pneumatic tires, the "normal load" refers to the load acting on a single tire in its standard mounted state. This "standard mounted state" refers to the tire being mounted on a standard vehicle corresponding to the tire's intended use, with the vehicle stationary on a flat road surface in a drivable state.

[0051] The circumferential grooves 3 include, for example, two shoulder circumferential grooves 5 and two crown circumferential grooves 6. The two crown circumferential grooves 6 are arranged so as to sandwich the tire equator C. The two shoulder circumferential grooves 5 are arranged so as to sandwich the two crown circumferential grooves 6. In the present embodiment, these circumferential grooves 3 are arranged line-symmetrically with respect to the tire equator C.

[0052] The axial distance L1 from the tire equator C to the groove centerline of the shoulder circumferential groove 5 is preferably, for example, 20% to 35% of the tread width TW. The axial distance L2 from the tire equator C to the groove centerline of the crown circumferential groove 6 is preferably, for example, 5% to 15% of the tread width TW. It should be noted that the tread width TW is the axial distance from the first tread end T1 to the second tread end T2 in the normal state.

[0053] 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.

[0054] The groove width W1 of each circumferential groove 3 is preferably, for example, 2.0% to 6.0% of the tread width TW. In the case of a pneumatic tire for a passenger car, the depth of each circumferential groove 3 is preferably, for example, 5 to 10 mm.

[0055] The plurality of land portions 4 include at least a shoulder land portion 8 including a first tread end T1 and a middle land portion 7 adjacent to the shoulder land portion 8. The land portion 4 of this embodiment includes the same shoulder land portion 8 and middle land portion 7 on the second tread end T2 side relative to the tire equator C. Therefore, the configuration of the shoulder land portion 8 and middle land portion 7 on the first tread end T1 side described below can also be applied to the shoulder land portion 8 and middle land portion 7 on the second tread end T2 side.

[0056] Figure 2 7 and 8 are enlarged views of the middle land portion 7 and the shoulder land portion 8. Figure 2As shown, the middle land portion 7 is provided with a middle longitudinal sipe 11 extending continuously in the tire circumferential direction, and a plurality of middle transverse sipes 12 that completely interrupt the middle land portion 7 in the tire axial direction. The shoulder land portion 8 is provided with a plurality of shoulder transverse grooves 16 extending from the shoulder circumferential groove 5 to at least the first tread end T1, and a plurality of shoulder transverse sipes 18 extending from the shoulder circumferential groove 5 and interrupting within the shoulder land portion 8 without crossing the first tread end T1.

[0057] In this specification, "sipe" is a cutout element with a small width, and refers to a pattern in which the width between two sipe walls in the main body of the sipe is 1.5 mm or less. Preferably, the width of the sipe is 0.2 to 1.2 mm, more preferably 0.5 to 1.0 mm. The width of the sipe of this embodiment is 1.5 mm or less throughout its entire depth. It should be noted that the width of the sipe may also exceed 1.5 mm at the opening, etc. In this specification, in the cross section of a certain cutout element, if more than 50% of its entire depth contains an area with a width of less than 1.5 mm, then even if it partially contains an area with a width exceeding 1.5 mm (for example, a chamfered portion), it is also treated as a sipe (a sipe containing a groove element). In addition, if 50% or more of the entire depth of a cutout element in its cross section includes an area with a width greater than 1.5 mm, it is treated as a groove (including a groove of a sipe element) even if it partially includes an area with a width of less than 1.5 mm.

[0058] In the present invention, the above-mentioned configuration is adopted to improve steering stability and noise performance. The reason for this is presumably the following mechanism.

[0059] The middle longitudinal sipes 11 and middle transverse sipes 12 moderate the rigidity of the middle land portion 7, appropriately reducing cornering forces. This improves handling linearity and, consequently, steering stability. Furthermore, these sipes generate virtually no pumping noise during contact, contributing to improved noise performance.

[0060] Furthermore, the shoulder lateral grooves 16 mitigate the rigidity of the shoulder land portion 8 and, by reducing the contact patch of the shoulder land portion 8, reduce the cornering force generated by the shoulder land portion 8. As a result, the behavior is particularly stable near the slip limit, enabling excellent steering stability. Furthermore, since the shoulder land portion 8 of the present invention is provided with the shoulder lateral sipes 18 extending from the shoulder circumferential groove 5, it is estimated that the shoulder lateral grooves 16 are easily closed near their inner ends, effectively preventing the generation of pumping noise and, in turn, suppressing pattern noise resonance in the middle land portion 7 and the shoulder land portion 8.

[0061] As described above, the present invention is believed to achieve both improved handling linearity and stabilized behavior near the slip limit by mitigating the rigidity of the middle land portion 7 and shoulder land portion 8 in different ways, significantly enhancing handling stability. Furthermore, this configuration disperses the frequency band of the impact sound produced when the middle land portion 7 and shoulder land portion 8 make contact, further improving noise performance. It is speculated that the present invention improves handling stability and noise performance through this mechanism.

[0062] The following describes the detailed configuration of this embodiment. It should be noted that each configuration described below represents a specific aspect of this embodiment. Therefore, it goes without saying that the present invention can achieve the aforementioned effects even without the configurations described below. Furthermore, even with the aforementioned features, even with the application of any one of the configurations described below, the tire of the present invention can be expected to exhibit improved performance corresponding to each configuration. Furthermore, when several of the configurations described below are combined, it can be expected to exhibit improved performance corresponding to the combined configurations.

[0063] The middle longitudinal sipes 11 extend linearly, for example, parallel to the tire circumferential direction. Note that the middle longitudinal sipes 11 are not limited to the above-described embodiment, and may extend in a wavy manner, for example.

[0064] Middle longitudinal sipes 11 are, for example, arranged in the central region of the tread of middle land portion 7, dividing the tire into three equal parts in the axial direction. The axial distance from the axial center of middle land portion 7 to middle longitudinal sipes 11 is, for example, no greater than 15% of the axial width W2 of middle land portion 7 (i.e., the tread width, hereinafter referred to as "width of the tread"), preferably no greater than 10%, and more preferably no greater than 5%. Such middle longitudinal sipes 11 can achieve the aforementioned effects while suppressing uneven wear of middle land portion 7.

[0065] The circumferential pitch length P1 of the plurality of middle transverse sipes 12 is, for example, greater than the axial width W2 of the middle land portion 7. Specifically, the pitch length P1 of the middle transverse sipes 12 is 120% to 140% of the width W2. Such middle transverse sipes 12 contribute to a well-balanced improvement in wet performance and handling stability. It should be noted that, in this specification, the pitch length of a sipe refers to the circumferential distance from the sipe centerline of one sipe to the sipe centerline of the adjacent sipe. The same applies to the pitch length of the lateral grooves.

[0066] The middle transverse sipe 12 of the present embodiment has a constant depth in its longitudinal direction. The depth of the middle transverse sipe 12 is, for example, 2.0 to 4.0 mm.

[0067] The middle transverse sipes 12 are inclined, for example, in a first direction (downward and right in the various figures of this specification) relative to the tire axial direction. The maximum angle of the middle transverse sipes 12 relative to the tire axial direction is, for example, 18 to 25 degrees. The middle transverse sipes 12 of this embodiment are smoothly curved. Such middle transverse sipes 12 can also provide friction in the tire axial direction.

[0068] Figure 3 Shown in Figure 2 AA line section view. Figure 3 As shown, the maximum depth d2 of the middle transverse sipe 12 is greater than the depth d1 of the middle longitudinal sipe 11. The depth d2 of the middle transverse sipe 12 is, for example, 60% to 80% of the depth of the shoulder circumferential groove 5. Such middle transverse sipes 12 improve steering stability and noise performance in a well-balanced manner.

[0069] The middle transverse sipe 12 includes, for example, a shallow bottom portion formed by a raised bottom portion. In this embodiment, the shallow bottom portion includes a first shallow bottom portion 12a located at the end portion on the first tread end T1 side; a second shallow bottom portion 12b located at the end portion on the tire equator C side; and a third shallow bottom portion 12c located between the first and second shallow bottom portions 12a and 12b. This middle transverse sipe 12 having multiple shallow bottom portions can prevent an excessive reduction in the rigidity of the middle land portion 7.

[0070] The depth d3 of the first shallow bottom portion 12a and the depth d4 of the second shallow bottom portion 12b are, for example, 30% to 45% of the maximum depth d2 of the middle transverse sipe 12. The axial length L3 of the first shallow bottom portion 12a and the axial length L4 of the second shallow bottom portion 12b are, for example, the axial width W2 of the middle land portion 7 (e.g., Figure 2 (as shown). It should be noted that in this specification, the axial length of the shallow bottom, etc., is measured at the center of the height of the shallow bottom, etc. The middle transverse sipe 12 having such a first shallow bottom 12a and second shallow bottom 12b improves steering stability and noise performance in a well-balanced manner.

[0071] The depth d5 ​​of the third shallow bottom portion 12c is preferably greater than the depths of the first shallow bottom portion 12a and the second shallow bottom portion 12b. The depth d5 ​​of the third shallow bottom portion 12c is 55% to 75% of the maximum depth d2 of the middle transverse sipe 12. Furthermore, the axial length L5 of the third shallow bottom portion 12c is preferably smaller than the lengths of the first shallow bottom portion 12a and the second shallow bottom portion 12b. The length L5 of the third shallow bottom portion 12c is 3% to 15% of the axial width W2 of the middle land portion 7. This third shallow bottom portion 12c can suppress uneven wear of the middle land portion 7 and facilitates proper expansion of the center portion of the middle transverse sipe 12, thereby improving wet performance.

[0072] In this embodiment, the middle longitudinal sipe 11 communicates with the third shallow bottom portion 12c. Furthermore, the depth of the middle longitudinal sipe 11 is smaller than the depth of the third shallow bottom portion 12c. This further reduces uneven wear of the middle land portion 7.

[0073] like Figure 2 As shown, the shoulder lateral grooves 16 and the shoulder transverse sipes 18 are arranged alternately in the tire circumferential direction. Furthermore, the shoulder lateral grooves 16 have a circumferential pitch length P2 that is, for example, smaller than the axial width W3 of the shoulder land portion 8. Specifically, the shoulder lateral grooves 16 have a pitch length P2 that is 80% to 95% of the width W3 of the shoulder land portion 8. In this embodiment, the shoulder lateral grooves 16 have a pitch length P2 that is substantially the same as the pitch length P1 of the middle transverse sipes 12. Furthermore, the shoulder transverse sipes 18 are also arranged with the same pitch length as the shoulder lateral grooves 16.

[0074] The shoulder lateral grooves 16 are inclined, for example, in a first direction relative to the tire axial direction. The maximum angle of the shoulder lateral grooves 16 relative to the tire axial direction is, for example, 5 to 15 degrees.

[0075] It is preferred that the groove width W4 of the shoulder lateral groove 16 is constant from the shoulder circumferential groove 5 to the first tread end T1. The groove width W4 of the shoulder lateral groove 16 is the groove width W1 of the circumferential groove 3 (e.g. Figure 1 Such shoulder lateral grooves 16 contribute to improving wet performance and handling stability in a well-balanced manner.

[0076] Figure 4 Shown in Figure 2 BB line cross-sectional view. Figure 4 As shown, the shoulder lateral groove 16 includes a groove bottom ridge 16a formed by partially raising the groove bottom. In this embodiment, the groove bottom ridge 16a connects the tread blocks on both sides of the shoulder lateral groove 16 in the tire circumferential direction. Such groove bottom ridge 16a helps reduce pumping noise in the shoulder lateral groove 16.

[0077] The groove bottom raised portion 16a is provided at the inner end portion in the tire axial direction of the shoulder lateral groove 16. The tire axial length L6 of the groove bottom raised portion 16a is, for example, the tire axial width W3 of the shoulder land portion 8 (e.g., Figure 2 Such groove bottom raised portion 16a contributes to improving the steering stability and noise performance in a well-balanced manner.

[0078] The depth d7 of the groove bottom raised portion 16a is, for example, 30% to 50% of the maximum depth d6 of the shoulder lateral groove 16. In this embodiment, the depth d7 of the groove bottom raised portion 16a is 80% to 120% of the depth of the first shallow bottom portion 12a and the second shallow bottom portion 12b of the middle lateral sipe 12. In addition to the aforementioned effects, such groove bottom raised portion 16a can also suppress uneven wear of the middle land portion 7 and the shoulder land portion 8.

[0079] Figure 5 Shown in Figure 2 The CC line cross-sectional view. Figure 5 As shown, the groove bottom ridge 16a is provided with a groove bottom sipe 20 that opens on its outer surface and extends along the longitudinal direction of the shoulder lateral groove 16. Such a groove bottom ridge 16a can suppress the pumping sound of the shoulder lateral groove 16, and can also relax the rigidity of the shoulder land portion 8, thereby improving the steering stability.

[0080] The depth d8 of the bottom sipe 20 from the outer surface of the bottom raised portion 16a is 80% to 120% of the depth d7 of the bottom raised portion 16a (the depth from the outer surface of the shoulder land portion 8 to the outer surface of the bottom raised portion 16a). In a further preferred embodiment, the depth d8 of the bottom sipe 20 is greater than the maximum depth of the middle longitudinal sipe 11 and greater than the depths of the first shallow bottom portion 12a and the second shallow bottom portion 12b of the middle transverse sipe 12. Such bottom sipes 20 can reliably achieve the aforementioned effects.

[0081] The shoulder lateral groove 16 preferably includes a chamfered portion 16b inclined at an angle of 30 to 60 degrees relative to the tire normal line passing through its groove edge. Such a chamfered portion 16b can reduce the sound of the shoulder lateral groove 16's edge hitting the ground. Furthermore, such a chamfered portion 16b helps suppress the angular cornering force and prevent the vehicle from sliding.

[0082] like Figure 2 As shown, the shoulder lateral sipes 18 are inclined in the first direction. The angle of the shoulder lateral sipes 18 relative to the tire axial direction is, for example, 5 to 15 degrees. The angle difference between the shoulder lateral sipes 18 and the shoulder lateral grooves 16 is preferably 5 degrees or less. In this embodiment, the shoulder lateral sipes 18 extend parallel to the shoulder lateral grooves 16. Such shoulder lateral sipes 18 help suppress uneven wear on the shoulder land portion 8.

[0083] The shoulder sipes 18 are at least 40% of the axial width W3 of the shoulder land portion 8's tread. In this embodiment, they extend across the axial center of the shoulder land portion 8's tread. This allows the contact patch of the shoulder land portion 8 to be appropriately reduced, improving handling stability. The axial length L6 of the shoulder sipes 18 is greater than the axial width W2 of the middle land portion 7's tread. The length L6 of the shoulder sipes 18 is, for example, 60% to 75% of the axial width W3 of the shoulder land portion 8's tread. This shoulder sipe 18 achieves the aforementioned effects and can also reduce the impact sound of the shoulder land portion 8 and the middle land portion 7 contacting the tire to white noise.

[0084] It is preferred that the distance between the shoulder lateral sipes 18 and the middle lateral sipes 12 in the tire circumferential direction be small. Specifically, it is preferred that the middle lateral sipes 12 and the shoulder lateral sipes 18 be provided in a virtual belt layer 25 extending with a smaller width (for ease of understanding, Figure 2 (a virtual belt layer is colored). The width of the virtual belt layer 25 is, for example, 8.0 mm or less, preferably 5.0 mm or less, and more preferably 3.0 mm or less. As a result, the middle transverse sipes 12 and the shoulder transverse sipes 18 work together to provide high friction in the tire circumferential direction, improving wet performance.

[0085] Figure 6 Shown in Figure 2 DD line cross-sectional view. Figure 6 As shown, the maximum depth d9 of the shoulder transverse sipes 18 is, for example, 55% to 70% of the depth of the shoulder circumferential groove 5. In this embodiment, the maximum depth of the middle longitudinal sipes 11 is smaller than the maximum depth d9 of the shoulder transverse sipes 18. This facilitates the conversion of the impact sound of the middle land portion 7 and the impact sound of the shoulder land portion 8 into white noise, thereby improving noise performance.

[0086] The shoulder sipe 18 includes an inner shallow bottom 18a formed by a bottom bulge at the inner end portion in the tire axial direction. The depth d10 of the inner shallow bottom 18a is 35% to 50% of the maximum depth d9 of the shoulder sipe 18. The axial length L7 of the inner shallow bottom 18a is the axial length L6 of the shoulder sipe 18 (as shown in FIG. Figure 2 (shown) 5% to 20%.

[0087] Figure 7 FIG shows an enlarged view of the crown land portion 9. Figure 7 As shown, the crown land portion 9 is provided with a plurality of crown transverse sipes 21 that completely divide the crown land portion 9 in the tire axial direction.

[0088] The circumferential pitch length P3 of the plurality of crown transverse sipes 21 is, for example, greater than the axial width W5 of the crown land portion 9. Specifically, the pitch length P3 of the crown transverse sipes 21 is 1.40 to 1.80 times the width W5 of the crown land portion 9. Preferably, the pitch length P3 of the crown transverse sipes 21 is 80% to 120% of the pitch length P1 of the middle transverse sipes 12. More preferably, the pitch length P3 is equal to the pitch length P1 of the middle transverse sipes 12.

[0089] like Figure 1 As shown, the crown transverse sipes 21 do not overlap with the region where the middle transverse sipes 12 are extended parallel to the tire axial direction. Such an arrangement of the crown transverse sipes 21 helps to suppress uneven wear of each land portion.

[0090] like Figure 7 As shown, the crown transverse sipes 21 are inclined, for example, in a second direction (upper right in the figures of this embodiment) relative to the tire axial direction. This second direction is opposite to the first direction. The angle of the crown transverse sipes 21 relative to the tire axial direction is, for example, 5 to 15 degrees. This reduces the tire's taper and helps prevent vehicle skidding.

[0091] Figure 8 Shown in Figure 7 EE line cross-sectional view. Figure 8 As shown, the crown transverse sipe pattern 21 includes a first shallow bottom 21a formed by a bottom bulge at the end on one side of the tire axial direction, and a second shallow bottom 21b formed by a bottom bulge at the end on the other side of the tire axial direction. The depth d12 of the first shallow bottom 21a and the depth d13 of the second shallow bottom 21b are, for example, 30% to 45% of the maximum depth d11 of the crown transverse sipe pattern 21. The axial length L8 of the first shallow bottom 21a and the axial length L9 of the second shallow bottom 21b are the width W5 ( Figure 7 The crown transverse sipe 21 including the first shallow bottom 21a and the second shallow bottom 21b can suppress uneven wear of the crown land portion 9 and improve steering stability.

[0092] Figure 9 FIG. 2 shows an enlarged view of the ground contact surface shape when the tread portion 2 is grounded. Figure 9As shown, it is preferred that, under a normal load condition, with a normal internal pressure rim assembled on a normal wheel rim and a normal load applied, and contacting a flat surface at a camber angle of 0°, the combined contact area S2 of the two middle land portions 7 is 2.0 to 2.5 times the contact area S1 of the crown land portion 9. Furthermore, the combined contact area S3 of the two shoulder land portions 8 is 4.2 to 4.6 times the contact area S1 of the crown land portion 9. This improves handling linearity and behavior near the slip limit, thereby enhancing steering stability.

[0093] To reliably achieve the above-mentioned effects, the maximum circumferential length L11 of the contact patch of the shoulder land portion 8 is preferably 0.80 to 0.85 times the maximum circumferential length L10 of the contact patch of the crown land portion 9. The maximum circumferential length L12 of the contact patch of the middle land portion 7 is preferably 0.90 to 0.98 times the maximum circumferential length L10 of the contact patch of the crown land portion 9. It should be noted that the circumferential length of the contact patch of each land portion is measured at the center position of each land portion in the tire axial direction.

[0094] While the tire according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described specific embodiment and can be implemented in various modified forms.

[0095] [Example]

[0096] Based on the specifications in Table 1, a prototype with Figure 1 The basic pattern of the tire is 235 / 55R19. As a comparative example, a tire with Figure 10 The tire of the comparative example has a middle land portion a and a shoulder land portion b. The middle transverse sipe c of the tire of the comparative example is interrupted in the middle land portion a, and the shoulder transverse groove d extends from the tread end and is interrupted in the shoulder land portion b. Except for the above matters, the tire of the comparative example is the same as Figure 1 The tires shown in the figure are substantially the same. Each test tire was tested for handling stability and noise performance. The common specifications and testing methods for each test tire are as follows.

[0097] Installed rim: 19×7.0J

[0098] Tire internal pressure: 230kPa

[0099] Test vehicle: 2000cc four-wheel drive vehicle

[0100] Tire installation position: all wheels

[0101] <Handling stability>

[0102] The handling stability of the test vehicle on a dry road was evaluated based on the driver's experience. It should be noted that this handling stability is a comprehensive evaluation of initial responsiveness, linearity, and controllability at the slip limit. The results are scored, with the comparative example's handling stability set to 100. Higher values ​​indicate superior handling stability.

[0103] Noise performance

[0104] The test vehicle was driven on a dry road at 40 to 100 km / h, and the maximum sound pressure of the vehicle interior noise was measured. The results were expressed as an index, with the inverse of the maximum sound pressure set to 100. A higher index indicates lower sound pressure and better noise performance.

[0105] The test results are shown in Table 1.

[0106]

Table 1

[0107]

[0108] As a result of the test, it was confirmed that the tires of the examples had improved steering stability and noise performance.

Claims

1. A tire having a tread portion, wherein: The tread portion includes: 3 or 4 circumferential grooves extending continuously along the circumference of the tire; and a plurality of land portions divided by the circumferential grooves, The plurality of land portions include: a shoulder land portion including a first tread end; a middle land portion adjacent to the shoulder land portion; and a crown land portion adjacent to the middle land portion. The circumferential grooves include shoulder circumferential grooves, which are arranged between the shoulder land portion and the middle land portion. The middle land portion is provided with: a middle longitudinal sipe pattern extending continuously along the tire circumferential direction; and a plurality of middle transverse sipe patterns which completely cut off the middle land portion in the tire axial direction. The shoulder land portion is provided with: a plurality of shoulder lateral grooves extending from the shoulder circumferential groove to at least the first tread end; and a plurality of shoulder lateral sipes extending from the shoulder circumferential groove and interrupted within the shoulder land portion without crossing the first tread end. In the middle land portion and the shoulder land portion adjacent to each other in the axial direction, the middle lateral sipe and the shoulder lateral sipe are provided on a virtual belt layer extending with a width of 8.0 mm or less. A plurality of crown transverse sipes are provided on the crown land portion, wherein the plurality of crown transverse sipes completely cut off the crown land portion in the tire axial direction, and the crown transverse sipes do not overlap with a region where the middle transverse sipes are extended parallel to the tire axial direction. The middle transverse sipe pattern is inclined in a first direction relative to the tire axial direction. The crown lateral sipe is inclined in a second direction relative to the tire axial direction, wherein the second direction is opposite to the first direction.

2. The tire according to claim 1, wherein The groove width of the shoulder lateral groove is constant from the shoulder circumferential groove to the first tread end.

3. The tire according to claim 1 or 2, characterized in that The shoulder lateral groove includes a groove bottom raised portion formed by partially raising the groove bottom.

4. The tire according to claim 3, characterized in that The groove bottom raised portion is provided at an inner end portion of the shoulder lateral groove in the tire axial direction.

5. The tire according to claim 3, characterized in that The groove bottom raised portion is provided with a groove bottom sipe extending along the longitudinal direction of the shoulder lateral groove.

6. The tire according to claim 1 or 2, characterized in that The maximum depth of the middle longitudinal sipe is less than the maximum depth of the shoulder transverse sipe.

7. The tire according to claim 1 or 2, characterized in that The plurality of land portions include a crown land portion adjacent to the middle land portion, When assembled on a regular rim with a regular internal pressure, a regular load is applied, and the tire contacts a flat surface at a camber angle of 0°, the maximum circumferential length of the contact patch of the shoulder land portion is 0.80 to 0.85 times the maximum circumferential length of the contact patch of the crown land portion.

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