Tire

Abstract

To provide a tire which can improve uneven wear resistance performance.SOLUTION: A belt 6 of a tire comprises: plural layers of crossing belt layers 6a; and one or plural layers of circumferential belt layers 6b which include circumferential belt codes 6bc respectively extending along a tire circumferential direction. An angle of a crossing belt code 6ac to a tire width direction is 20-45°. A tread part 100 includes: a plurality of major grooves 110 respectively extending along a tire circumferential direction; and a sub groove 130 which is arranged at a shoulder land part 121, and whose groove width is narrower than that of the major groove to extend along the tire circumferential direction. An outer groove wall surface positioned at a tire width direction outer side among a pair of groove wall surfaces in the sub groove is positioned at the same position in the tire width direction as the tire width direction outermost end of one or plural layers of the circumferential direction belt layers, or positioned at the inner side in the tire width direction in comparison with the tire width direction outermost end of one or plural layers of the circumferential direction belt layers.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] BACKGROUND ART There have been conventional tires provided with intersecting belt layers and circumferential belt layers (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-71665 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional tires described above, there is room for improvement in terms of uneven wear resistance.

[0005] An object of the present invention is to provide a tire that can improve uneven wear resistance. [Means for solving the problem]

[0006] The tire of the present invention is Belt and A tread surface; A tire comprising: The belt is a plurality of intersecting belt layers each including an intersecting belt cord extending in a direction intersecting each other between the layers; One or more circumferential belt layers each including a circumferential belt cord extending along the tire circumferential direction; and The intersecting belt cords form an angle of 20° to 45° with respect to the tire width direction, The tread surface has A plurality of main grooves each extending along the tire circumferential direction, and a shoulder land portion defined between the outermost main groove located most outward in the tire width direction among the plurality of main grooves and the ground contact end; a sub-groove provided in the shoulder land portion, having a groove width narrower than that of the main groove, and extending along the tire circumferential direction; is provided; Of the pair of groove wall surfaces in the sub-groove, the outer groove wall surface located outward in the tire width direction is located at the same tire width direction position as the outermost end in the tire width direction of the one or more circumferential belt layers, or is located inward in the tire width direction from the outermost end in the tire width direction of the one or more circumferential belt layers. According to the tire of the present invention, the resistance to uneven wear performance can be improved.

[0007] In the tire of the present invention, It is preferable that the tire width direction distance L from the outer groove wall surface of the sub-groove to the outermost end in the tire width direction of the one or more circumferential belt layers is 5% or less of the width W of the one or more circumferential belt layers. Thereby, the resistance to uneven wear performance can be further improved.

[0008] In the tire of the present invention, The circumferential belt cord has a wave shape, It is preferable that the tire width direction distance L from the outer groove wall surface of the sub-groove to the outermost end in the tire width direction of the one or more circumferential belt layers is 2 times or less of both amplitudes B of the wave shape formed by the circumferential belt cord. Thereby, the resistance to uneven wear performance can be further improved.

[0009] In the tire of the present invention, It is preferable that the tire width direction distance L from the outer groove wall surface of the sub-groove to the outermost end in the tire width direction of the one or more circumferential belt layers is 5 mm or less. Thereby, the resistance to uneven wear performance can be further improved.

[0010] In the tire of the present invention, It is preferable that the groove depth D of the secondary groove is 10 to 30% of the groove depth E of the outermost main groove. Thereby, a decrease in rigidity can be suppressed, and after the secondary groove exhibits the expected uneven wear suppressing effect, the secondary groove can be made to disappear.

[0011] In the tire of the present invention, The outer groove wall surface of the secondary groove may be located on the inner side in the tire width direction from the outer ends in the tire width direction of each of the one or more circumferential belt layers.

[0012] In the tire of the present invention, It is preferable that the one or more circumferential belt layers are located on the inner side in the tire radial direction than the plurality of cross belt layers. Thereby, it becomes easier to maintain the shape of the tire when the tire is filled with internal pressure.

Advantages of the Invention

[0013] According to this invention, a tire can be provided that can improve uneven wear resistance performance.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0015] The tire according to the present invention can be used for any type of pneumatic tire, but is preferably used for pneumatic tires for heavy loads, and more preferably for pneumatic tires for trucks and buses. Hereinafter, embodiments of the tire according to the present invention will be exemplified and described with reference to the drawings.

[0016] Hereinafter, embodiments of the tire according to the present invention will be exemplified and described with reference to the drawings. The same reference numerals are given to the members and parts common to each figure. In each figure, the tire width direction, the outer side in the tire width direction, and the inner side in the tire width direction are indicated by the symbols "WD", "WDO", and "WDI", respectively, the tire radial direction, the outer side in the tire radial direction, and the inner side in the tire radial direction are indicated by the symbols "RD", "RDO", and "RDI", respectively, and the tire circumferential direction is indicated by the symbol "CD".

[0017] FIG. 1 is a drawing for explaining a tire 1 according to an embodiment of the present invention. FIG. 1 is a cross-sectional view in the tire width direction schematically showing the tire 1 according to an embodiment of the present invention. The tire 1 of the embodiment of FIG. 1 is configured as a pneumatic tire for heavy loads, more specifically, a pneumatic tire for trucks and buses. However, the tire 1 of any embodiment of the present invention may be configured as any type of tire.

[0018] As shown in FIG. 1, the tire 1 includes a tread portion 1a, a pair of sidewall portions 1b extending radially inward in the tire diameter direction from both end portions in the tire width direction of the tread portion 1a, and a pair of bead portions 1c provided at the radially inner end portions of the respective sidewall portions 1b. The bead portion 1c is configured to contact the rim on the radially inner side and the outer side in the tire width direction of the tire 1 when the tire 1 is mounted on the rim. Further, the tire 1 includes a pair of bead cores 4a, a pair of bead fillers 4b, a carcass 5, a belt 6, a tread rubber 7, a side rubber 8, and an inner liner 9.

[0019] Each bead core 4a is embedded in the corresponding bead portion 1c. The bead core 4a includes a plurality of bead wires covered with rubber around the periphery. The bead wire is preferably made of metal (for example, steel). The bead wire can be, for example, a monofilament or a stranded wire.

[0020] Each bead filler 4b is located radially outside the corresponding bead core 4a. The bead filler 4b extends in a tapered shape toward the radially outer side of the tire. The bead filler 4b is made of, for example, rubber. Generally, the bead filler may be called a "stiffener".

[0021] The carcass 5 straddles between the pair of bead cores 4a and extends in a toroidal shape. The carcass 5 is composed of one or more (one in the example of FIG. 1) carcass plies 5a. Each carcass ply 5a includes one or a plurality of carcass cords and a covering rubber covering the carcass cords. The carcass cord can be formed of a monofilament or a stranded wire. It is preferable that the carcass cord 5c is made of metal (for example, steel). The carcass 5 preferably has a radial structure, but may also have a bias structure.

[0022] The side rubber 8 is located in the sidewall portion 1b. The side rubber 8 constitutes the outer surface of the sidewall portion 1b on the outer side in the tire width direction. The side rubber 8 is located on the outer side in the tire width direction than the carcass 5. The side rubber 8 is located on the outer side in the tire width direction than the bead filler 4b. The side rubber 8 is integrally formed with the tread rubber 7.

[0023] The inner liner 9 is disposed inside the tire of the carcass 5 and may be laminated, for example, on the inner side of the tire of the carcass 5. The inner liner 9 is made of, for example, a butyl rubber having low air permeability. The butyl rubber includes, for example, butyl rubber and halogenated butyl rubber which is a derivative thereof. The inner liner 9 is not limited to butyl rubber and can be composed of other rubber compositions, resins, or elastomers.

[0024] As shown in FIG. 1, the belt 6 is disposed on the outer side in the tire radial direction with respect to the crown portion of the carcass 5. The belt 6 has a plurality of layers (five layers in the embodiment of FIG. 1) of belt layers 6a to 6c. The belt 6 has at least a plurality of cross belt layers 6a and one or more circumferential belt layers 6b.

[0025] The plurality of layers (two layers in the embodiment of FIG. 1) of cross belt layers 6a each include a cross belt cord 6ac extending in a direction intersecting with each other between the layers and a cross belt covering rubber 6ar covering the cross belt cord 6ac. The cross belt cord 6ac is a so-called low angle belt cord having a small angle with respect to the tire width direction. Specifically, the cross belt cord 6ac has an angle of 20° to 45° with respect to the tire width direction. The cross belt cord 6ac can be formed of a monofilament or a stranded wire. The cross belt cord 6ac is preferably composed of a metal (for example, steel), but may be composed of an organic fiber made of polyester, nylon, rayon, aramid, or the like.

[0026] One or more circumferential belt layers 6b (two layers in the embodiment of FIG. 1) each include a circumferential belt cord 6bc extending along the tire circumferential direction and a circumferential belt covering rubber 6br covering the circumferential belt cord 6bc. Regarding the circumferential belt cord 6bc, "extending along the tire circumferential direction" includes not only the case of extending parallel to the tire circumferential direction but also the case of extending in a direction forming an angle greater than 0° and equal to or less than 5° with respect to the tire circumferential direction. In addition, when the circumferential belt cord 6bc has a wave shape as described later (FIG. 4), the extending direction of the circumferential belt cord 6bc refers to the extending direction of the amplitude center line of the wave shape formed by the circumferential belt cord 6bc. The circumferential belt cord 6bc can be formed of a monofilament or a twisted wire. The circumferential belt cord 6bc is preferably composed of a metal (for example, steel), but may also be composed of an organic fiber made of polyester, nylon, rayon, aramid, or the like.

[0027] As shown in FIG. 4, the circumferential belt cord 6bc is preferably a so-called wavy cord having a wave shape. In this case, the circumferential belt cord 6bc extends along the tire circumferential direction while oscillating in the tire width direction along the wave shape. Here, in this specification, the "wave shape" is not limited to the wave shape composed of a smooth curve as shown in FIG. 4, but is a concept including the wave shape composed of a folded line. The circumferential belt cord 6bc is shaped into a wave shape. Generally, the crown portion of the tire is always subjected to a tensile input in the tire circumferential direction by the internal pressure during use, and the circumferential length tends to increase due to creep during use, resulting in distortion. Therefore, by forming the circumferential belt cord 6bc into a wave shape, separation can be effectively prevented without increasing the weight of the tire 1. This is particularly true when the tire 1 is a pneumatic tire for heavy loads (for example, a pneumatic tire for trucks and buses). Both amplitudes B of the wave shape formed by the circumferential belt cord 6bc are preferably, for example, 1.5 to 2.5 mm. Here, "both amplitudes B of the wave shape formed by the circumferential belt cord 6bc" are twice the single amplitude (amplitude) A of the wave shape (FIG. 4). However, the circumferential belt cord 6bc may extend linearly along the tire circumferential direction instead of forming a wave shape.

[0028] As shown in FIG. 1, it is preferable that the one or more circumferential belt layers 6b are located closer to the inner side in the tire radial direction than the plurality of cross belt layers 6a. This makes it easier to maintain the shape of the tire when the tire is filled with internal pressure. However, the positional relationship between the circumferential belt layer 6b and the cross belt layer 6a is arbitrary. For example, the one or more circumferential belt layers 6b may be located closer to the outer side in the tire radial direction than the plurality of cross belt layers 6a.

[0029] As shown in FIG. 1, it is preferable that at least one layer (one layer in the embodiment of FIG. 1) of the plurality of cross belt layers 6a has a wider width (length in the tire width direction) than each circumferential belt layer 6b. This can suppress uneven wear.

[0030] In addition to the one or more circumferential belt layers 6b and the plurality of cross belt layers 6a, the belt 6 may have one or more (one layer in the embodiment of FIG. 1) other belt layers 6c. As shown in FIG. 1, the other belt layer 6c may be located closer to the inner side in the tire radial direction than the one or more circumferential belt layers 6b and the plurality of cross belt layers 6a, may be located between the circumferential belt layer 6b and the cross belt layer 6a, and / or may be located closer to the outer side in the tire radial direction than the one or more circumferential belt layers 6b and the plurality of cross belt layers 6a. In the embodiment of FIG. 1, no other belt layer 6c is interposed between the one or more circumferential belt layers 6b and the plurality of cross belt layers 6a. The other belt layer 6c may be, for example, an inclined belt layer 6c. The inclined belt layer 6c includes an inclined belt cord 6cc extending in a direction inclined with respect to the tire circumferential direction, and an inclined belt covering rubber 6cr covering the inclined belt cord 6cc. The inclined belt cord 6cc can be formed of a monofilament or a stranded wire. The inclined belt cord 6cc is preferably composed of a metal (e.g., steel), but may be composed of organic fibers such as polyester, nylon, rayon, and aramid.

[0031] The tread rubber 7 is located on the outer side in the tire radial direction of the belt 6 in the tread portion 1a. The tread rubber 7 constitutes a tread surface 100 which is the outer surface in the tire radial direction of the tread portion 1a. A tread pattern is formed on the tread surface 100.

[0032] In this specification, the "tread surface (100)" means the outer peripheral surface extending over the entire circumference of the tire that comes into contact with the road surface when a tire assembled to a rim and filled with a predetermined internal pressure is rolled while being loaded with a maximum load. In this specification, the "grounding end (TE)" means the end in the tire width direction of the tread surface (100). In this specification, the "grounding width" means the distance in the tire width direction between a pair of grounding ends of the tread surface (100). Here, the "rim" refers to the industrial standard effective in the region where the tire is produced and used. In Japan, it is the JATMA YEAR BOOK of JATMA (Japan Automobile Tire Manufacturers Association); in Europe, it is the STANDARDS MANUAL of ETRTO (The European Tyre and Rim Technical Organisation); in the United States, it is the YEAR BOOK of TRA (The Tire and Rim Association, Inc.), etc. It refers to the standard rim (Measuring Rim in the STANDARDS MANUAL of ETRTO, Design Rim in the YEAR BOOK of TRA) for the applicable size described therein or to be described in the future (that is, the above "rim" includes sizes that may be included in the above industrial standard in the future in addition to the current sizes. Examples of "sizes to be described in the future" include the sizes described as "FUTURE DEVELOPMENTS" in the 2013 edition of the STANDARDS MANUAL of ETRTO).) In the case of a size not described in the above industrial standard, it refers to a rim with a width corresponding to the bead width of the tire. Also, the "predetermined internal pressure" refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity of a single wheel for the applicable size and ply rating described in the above JATMA YEAR BOOK, etc. In the case of a size not described in the above industrial standard, it refers to the air pressure (maximum air pressure) corresponding to the maximum load capacity defined for each vehicle on which the tire is mounted. The "maximum load" refers to the load corresponding to the above maximum load capacity. Note that the air referred to here can also be replaced with an inert gas such as nitrogen gas or others.

[0033] Figure 2 is a plan view schematically showing a developed view of the tread surface 100 of the tire 1 in Figure 1. In Figure 2, the interior of each groove, which is recessed radially inward of the tire diameter from the tread surface 100, is shown by dot hatching. Here, in this specification, the "developed view of the tread surface 100" refers to viewing the tread surface in a plan view with the tread surface 100 developed on a plane.

[0034] In this specification, unless otherwise specified, the positional relationship and dimensions of each element of the tire 1 are measured in the "reference state". The "reference state" refers to a state in which the tire 1 is assembled on the rim, filled with the above-mentioned predetermined internal pressure, and is in a non-loaded state. Here, regarding the dimensions of each element such as the grooves and sipes on the tread surface 100, they are measured in the developed view of the tread surface 100.

[0035] As shown in FIGS. 1 to 2, in this embodiment, a plurality of main grooves 110 are provided in the tread surface 100. Each main groove 110 continuously extends along the tire circumferential direction. These plurality of main grooves 110 include a pair of outermost main grooves 111 located on the outermost side in the tire width direction. These pair of outermost main grooves 111 are located on both sides of the tire equatorial plane CL. As in the embodiment of FIGS. 1 to 2, in addition to the pair of outermost main grooves 111, these plurality of main grooves 110 may include one or a plurality (three in the embodiment of FIGS. 1 to 2) of center main grooves 112 between the pair of outermost main grooves 111, or may include only the pair of outermost main grooves 111. The groove width of the main groove 110 is preferably 6 mm or more, more preferably 7 mm or more, and even more preferably 8 mm or more. The groove width of the main groove 110 is preferably 12 mm or less, and more preferably 10 mm or less. The groove depth of the main groove 110 is preferably 6 mm or more, more preferably 7 mm or more, and even more preferably 8 mm or more. The groove depth of the main groove 110 is preferably 12 mm or less, and more preferably 10 mm or less.

[0036] In this specification, a "groove" is one in which the groove width on the tread surface 100 is 1.3 mm or more in the above reference state. In this embodiment, there are a main groove 110 and sub-grooves 130 as grooves. It is preferable that the groove width of the groove is 1.5 mm or more. The "groove width" is the distance between a pair of groove wall surfaces facing each other when measured perpendicular to the extending direction of the groove, and may be constant or variable in the tire radial direction. The "groove" is preferably configured such that when the tire is assembled to the rim, filled with a predetermined internal pressure, and loaded with the maximum load, a pair of groove wall surfaces facing each other do not contact each other when under the load. In this specification, a "sipe" is one in which the sipe width on the tread surface 100 is less than 1.3 mm in the above reference state. In this embodiment, there are one-end open sipes 121t, 122t and both-ends open sipe 122k as sipes. It is preferable that the sipe width is 1.0 mm or less, and more preferably 0.8 mm or less. The "sipe width" is the distance between a pair of sipe wall surfaces facing each other when measured perpendicular to the extending direction of the sipe. The "sipe" is preferably configured such that when the tire 1 is assembled to the rim, filled with a predetermined internal pressure, and loaded with the maximum load, a pair of sipe wall surfaces facing each other contact at least partially when under the load.

[0037] As shown in FIGS. 1 to 2, the tread surface 100 is provided with a plurality (five in this embodiment) of main grooves 110 and a plurality (six in this embodiment) of land portions 120 partitioned by a pair of grounding ends TE. These plurality of land portions 120 include a pair of shoulder land portions 121 partitioned between a pair of outermost main grooves 111 and a pair of grounding ends TE. Further, these plurality of land portions 120 further include one or a plurality (four in this embodiment) of center land portions 122 partitioned between the plurality of main grooves 110. The shoulder land portion 121 is provided with a sub-groove 130. As shown in FIGS. 1 to 2, it is preferable that the sub-groove 130 is provided in each shoulder land portion 121, but it may be provided only in one of the shoulder land portions 121. The sub-groove 130 has a groove width narrower than that of the main groove 110 and extends along the tire circumferential direction. As shown in FIG. 2, it is preferable that the sub-groove 130 extends linearly.

[0038] Hereinafter, when explaining the sub-groove 130, the outermost end 6bg in the tire width direction of the circumferential belt layer 6b of one layer or a plurality of layers, the shoulder land portion 121, etc., unless otherwise specified, it is assumed that the structure is being described when looking at one half of the tire 1 with respect to the tire equatorial plane CL. It is preferable that the tire 1 has a similar structure also in the structure when looking at the other half of the tire 1 with respect to the tire equatorial plane CL.

[0039] FIG. 3 is an enlarged view of a part of FIG. 1. As shown in FIGS. 1 and 3, the outer end 6be in the tire width direction of at least one layer (one layer in the embodiments of FIGS. 1 and 3) of the circumferential belt layer 6b among the one layer or a plurality of layers of circumferential belt layers 6b is located within the tire width direction region corresponding to the shoulder land portion 121 (that is, outside the outermost main groove 111 in the tire width direction and inside the grounding end TE in the tire width direction). As in the embodiments of FIGS. 1 and 3, it is preferable that the outer end 6be in the tire width direction of each circumferential belt layer 6b is located within the tire width direction region corresponding to the shoulder land portion 121 (that is, outside the outermost main groove 111 in the tire width direction and inside the grounding end TE in the tire width direction). As in the embodiments of FIGS. 1 and 3, it is preferable that the outer end in the tire width direction of at least one layer (one layer in the embodiments of FIGS. 1 and 3) of the plurality of cross belt layers 6a is located within the tire width direction region corresponding to the shoulder land portion 121 (that is, outside the outermost main groove 111 in the tire width direction and inside the grounding end TE in the tire width direction).

[0040] As shown in FIG. 3, in the present embodiment, among a pair of groove wall surfaces 130a and 130b facing each other in the sub-groove 130, the groove wall surface 130a located on the outer side in the tire width direction (hereinafter referred to as the "outer groove wall surface 130a") is located on the inner side in the tire width direction from the outermost end 6bg in the tire width direction of one or a plurality of circumferential belt layers 6b included in the belt 6. Here, the "outermost end 6bg in the tire width direction of one or a plurality of circumferential belt layers 6b" refers to the outermost end 6be in the tire width direction among the respective outer ends 6be in the tire width direction of each circumferential belt layer 6b that is located most on the outer side in the tire width direction.

[0041] Here, the operation and effect of the present embodiment will be described. First, in the present embodiment, as described above, the belt 6 has a plurality of layers of intersecting belt layers 6a and one or more layers of circumferential belt layers 6b, and the intersecting belt cords 6ac of the intersecting belt layer 6a are belt cords at a low angle (the angle formed with respect to the tire width direction is 20° to 45°) (FIG. 1). Due to such a configuration of the belt 6 in which the crossing angles between the belt cords of the plurality of belt layers are large (specifically, the crossing angle between the circumferential belt cord 6bc of the circumferential belt layer 6b and the intersecting belt cord 6ac of the intersecting belt layer 6a is large), as shown by the solid line graph in FIG. 8, a large tension step occurs in the belt 6 in the vicinity of the outermost end 6bg in the tire width direction of one or more layers of circumferential belt layers 6b. In FIG. 8, the solid line graph schematically shows the tension acting on the belt 6 of the tire 1 of the present embodiment. In FIG. 8, the broken line graph schematically shows the tension acting on the belt of a tire according to a conventional general reference example provided with a belt in which the crossing angles between the belt cords of the plurality of belt layers are small. As can be seen from the broken line graph in FIG. 8, in such a belt of a conventional general tire, almost no or no tension step is observed, and the tension smoothly decreases from the tire equatorial plane CL toward the outer side in the tire width direction. As shown in FIG. 5, when a load is applied to the tire 1 of the present embodiment, due to the above-mentioned tension step, the tread rubber 7 between the outermost end 6bg in the tire width direction of one or more layers of circumferential belt layers 6b and the road surface G bulges and deforms outward (hereinafter referred to as "outward crushing") H1 due to being compressed by the load. This outward crushing H1 may lead to uneven wear at the shoulder land portion 121. This outward crushing H1 becomes particularly prominent when the tire 1 is a pneumatic tire for heavy loads (for example, a pneumatic tire for trucks and buses). Therefore, in the present embodiment, as described above, in the tread surface 100, the shoulder land portion 121 is provided with the secondary groove 130. By providing the secondary groove 130, as shown in FIG. 5, when a load is applied to the tire 1, the tread rubber 7 in the vicinity of the outer groove wall surface 130a of the secondary groove 130 is compressed by the load, and a phenomenon (hereinafter referred to as "inward crushing") H2 of bulging and deforming toward the inner side in the tire width direction occurs. And, as described above, since the outer groove wall surface 130a of the secondary groove 130 is located on the inner side in the tire width direction with respect to the outermost end 6bg in the tire width direction of the one or more circumferential belt layers 6b of the belt 6, the outward crushing H1 caused by the outermost end 6bg in the tire width direction of the one or more circumferential belt layers 6b can be offset by the inward crushing H2 caused by the outer groove wall surface 130a of the secondary groove 130. Therefore, uneven wear at the shoulder land portion 121 can be suppressed, and thus, the uneven wear resistance performance can be improved.

[0042] Not limited to the above-described embodiment, as in another embodiment shown in FIG. 6, the outer groove wall surface 130a of the secondary groove 130 may be located at the same position in the tire width direction as the outermost end 6bg in the tire width direction of the one or more circumferential belt layers 6b of the belt 6. In this case, as shown in FIG. 7, when a load is applied to the tire 1, the position of the inward crushing H2 caused by the outer groove wall surface 130a of the secondary groove 130 more firmly overlaps with the position of the outward crushing H1 caused by the outermost end 6bg in the tire width direction of the one or more circumferential belt layers 6b, so that the outward crushing H1 can be more effectively offset. Therefore, the uneven wear resistance performance can be further improved.

[0043] Incidentally, if, as in another reference example shown in FIG. 9, the outer groove wall surface 130a of the secondary groove 130 is located outside the tire width direction of the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b of the belt 6, when a load is applied to the tire 1, an outward crushing H3 also occurs in the tread rubber 7 in the vicinity of the inner groove wall surface 130b of the secondary groove 130 in the vicinity of the outward crushing H1 by the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b. Therefore, the outward crushings H1 and H3 will increase, and there is a risk of deterioration of uneven wear on the shoulder land portion 121. This is particularly true when the inner groove wall surface 130b of the secondary groove 130 is located at the same position in the tire width direction as the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b of the belt 6.

[0044] Incidentally, at the time of designing the tire 1, as shown in FIG. 3, it is preferable to set the outer groove wall surface 130a of the secondary groove 130 at a predetermined position inside the tire width direction of the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b. Since there may be some variations in the actually manufactured tire 1, the positional relationship between the outer groove wall surface 130a of the secondary groove 130 and the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b of the belt 6 may deviate slightly from the expected one. By presetting the outer groove wall surface 130a of the secondary groove 130 at a predetermined position inside the tire width direction of the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b, even if such a slight deviation occurs during manufacturing, in the manufactured tire 1, the outer groove wall surface 130a of the secondary groove 130 is located outside the tire width direction of the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b of the belt 6 (FIG. 9), which can be more reliably avoided.

[0045] In each of the embodiments described in this specification, the tire width direction distance L (FIG. 3) from the outer groove wall surface 130a of the secondary groove 130 to the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b is preferably 5% or less of the width W (FIG. 1) of one or more circumferential belt layers 6b. The tire width direction distance L may be 0% of the width W as in the embodiment of FIG. 6, or may be more than 0% of the width W as in the embodiment of FIG. 3. Thereby, the position of the inward crushing H2 by the outer groove wall surface 130a of the secondary groove 130 can be made closer to the outward crushing H1 by the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b, and the outward crushing H1 can be more effectively offset. Therefore, the uneven wear resistance performance can be further improved (FIGS. 5 and 7). Here, the "width W of one or more circumferential belt layers 6b" (FIG. 1) refers to the tire width direction distance between the outermost ends 6bg (FIG. 3) in the tire width direction on both sides of one or more circumferential belt layers 6b.

[0046] In each of the embodiments described in this specification, when the circumferential belt cord 6bc has a wave shape as described above (FIG. 4), the tire width direction distance L (FIG. 3) from the outer groove wall surface 130a of the secondary groove 130 to the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b is preferably 2 times or less the both amplitudes B (FIG. 4) of the wave shape formed by the circumferential belt cord 6bc. The tire width direction distance L may be 0 times the both amplitudes B as in the embodiment of FIG. 6, or may be more than 0 times the both amplitudes B as in the embodiment of FIG. 3. Thereby, the position of the inward crushing H2 by the outer groove wall surface 130a of the secondary groove 130 can be made closer to the outward crushing H1 by the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b, and the outward crushing H1 can be more effectively offset. Therefore, the uneven wear resistance performance can be further improved (FIGS. 5 and 7).

[0047] In each embodiment described in this specification, it is preferable that the tire width direction distance L (FIG. 3) from the outer groove wall surface 130a of the sub-groove 130 to the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b is 5 mm or less. The tire width direction distance L may be 0 mm as in the embodiment of FIG. 6, or may be more than 0 mm as in the embodiment of FIG. 3. Thereby, the position of the inward crushing H2 by the outer groove wall surface 130a of the sub-groove 130 can be made closer to the outward crushing H1 by the outermost end 6bg in the tire width direction of one or more circumferential belt layers 6b, and the outward crushing H1 can be more effectively offset. Therefore, the uneven wear resistance performance can be further improved (FIGS. 5 and 7). This configuration is particularly suitable when the tire 1 is a pneumatic tire for heavy loads (for example, a pneumatic tire for trucks and buses).

[0048] As shown in FIG. 3, the outer groove wall surface 130a of the sub-groove 130 may be located on the inner side in the tire width direction than the outer end 6be in the tire width direction of each of the one or more circumferential belt layers 6b.

[0049] In each embodiment described in this specification, it is preferable that the groove depth D (FIG. 3) of the sub-groove 130 is 10% or more of the groove depth E (FIG. 3) of the outermost main groove 111. Thereby, the effect of the inward crushing H2 by the outer groove wall surface 130a of the sub-groove 130 can be obtained more firmly, and the uneven wear resistance performance can be further improved. Also, it is preferable that the groove depth D of the sub-groove 130 is smaller than the groove depth E of the outermost main groove 111, for example, it is preferable that it is 30% or less of the groove depth E of the outermost main groove 111. Thereby, a decrease in rigidity can be suppressed. Further, when the groove depth D of the sub-groove 130 is 10 to 30% of the groove depth E of the outermost main groove 111, the sub-groove 130 can be made to disappear after the sub-groove 130 exhibits a desired uneven wear suppression effect (for example, a wear rate of about 20%).

[0050] Note that the groove depths of the grooves (main groove 110 and sub-grooves 130) shall be measured along the direction perpendicular to the tread surface 100. Further, as in the embodiments of FIGS. 1 to 2, when the main groove 110 has the protrusions 111s and 112s described below on its groove bottom surface, the groove depth of the main groove 110 shall refer to the groove depth of the main groove 110 when the protrusions 111s and 112s are considered non-existent. In other words, it shall refer to the distance from the opening surface of the main groove 110 to the inner ends in the tire diameter direction of the protrusions 111s and 112s on the tread surface 100.

[0051] In each of the embodiments described in this specification, it is preferable that the groove width of the sub-groove 130 is 10% or more of the groove width of the outermost main groove 111. Thereby, the effect of the inward crushing H2 by the outer groove wall surface 130a of the sub-groove 130 can be obtained more firmly, and the uneven wear resistance performance can be further improved. From the same viewpoint, it is preferable that the groove width of the sub-groove 130 is 1.5 mm or more, and more preferably 1.8 mm or more. Also, it is preferable that the groove width of the sub-groove 130 is 20% or less of the groove width of the outermost main groove 111. Thereby, a decrease in rigidity can be suppressed. From the same viewpoint, it is preferable that the groove width of the sub-groove 130 is 2.5 mm or less, and more preferably 2.2 mm or less.

[0052] In each of the embodiments described in this specification, when counted along the tire diameter direction, the number of belt layers 6a to 6c of the belt 6 (the number of laminations in the tire diameter direction. In the embodiment of FIG. 1, it is 5 layers) is preferably 4 layers or more, and more preferably 5 layers or more. Also, the number of circumferential belt layers 6b of the belt 6 (in the embodiment of FIG. 1, it is 2 layers) is preferably 2 layers or more. In this case, since the tension step at the vicinity of the outermost end 6bg in the tire width direction of the one or more circumferential belt layers 6b described above becomes particularly large, the uneven wear suppression effect by the sub-groove 130 becomes particularly advantageous. Also, it is preferable that each of the belt layers 6a to 6c of the belt 6 has a thickness of 1.3 mm or more. These configurations are particularly suitable when the tire 1 is a pneumatic tire for heavy loads (for example, a pneumatic tire for trucks and buses).

[0053] In each of the embodiments described in this specification, regarding the tread pattern provided on the tread surface 100, as long as the secondary groove 130 is provided in the shoulder land portion 121 partitioned between the outermost main groove 111 and the ground contact end TE, the effect of suppressing uneven wear by the above-described secondary groove 130 can be obtained. Therefore, the tread pattern provided on the tread surface 100 may be arbitrary as long as the secondary groove 130 is provided in the shoulder land portion 121 partitioned between the outermost main groove 111 and the ground contact end TE.

[0054] In the embodiment of FIG. 2, in each shoulder land portion 121, in addition to the secondary groove 130, a plurality of one-end open sipes 121t are provided. Each of these plurality of one-end open sipes 121t has one end opening to the outermost main groove 111, extending outward in the tire width direction, and terminating inside the shoulder land portion 121 before reaching the secondary groove 130. Further, these plurality of one-end open sipes 121t are arranged at intervals along the tire circumferential direction. No other grooves or sipes are provided in each shoulder land portion 121 other than the secondary groove 130 and the plurality of one-end open sipes 121t. As in the embodiment of FIG. 2, it is preferable that each shoulder land portion 121 is configured as a rib that is not divided in the tire circumferential direction by a groove extending along the tire width direction. In this case, since the outward crushing H1 (FIG. 5) by the outermost end 6bg in the tire width direction of the above-described one or more circumferential belt layers 6b is more likely to occur significantly, the effect of suppressing uneven wear by the secondary groove 130 becomes particularly advantageous. However, each shoulder land portion 121 may be configured as a block row divided in the tire circumferential direction by a groove extending along the tire width direction.

[0055] In the embodiment of FIG. 2, each center land portion 122 is provided with a plurality of one - end - open sipes 122t and a plurality of both - ends - open sipes 122k, respectively. In each center land portion 122, a plurality of one - end - open sipes 122t arranged at intervals along the tire circumferential direction are open to each of a pair of main grooves 110 partitioning the center land portion 122. Each of these plurality of one - end - open sipes 122t opens to one of the pair of main grooves 110 partitioning the center land portion 122, extends in the tire width direction, and the other end terminates inside the center land portion 122. Further, in each center land portion 122, the plurality of both - ends - open sipes 122k each extend along the tire width direction, and both ends open to each of the pair of main grooves 110 partitioning the center land portion 122. The plurality of both - ends - open sipes 122k are arranged at intervals along the tire circumferential direction. In each center land portion 122, no other grooves or sipes are provided other than the plurality of one - end - open sipes 122t and the plurality of both - ends - open sipes 122k. As in the embodiment of FIG. 2, it is preferable that each center land portion 122 is configured as a rib that is not divided in the tire circumferential direction by a groove extending along the tire width direction. In this case, since the outward crushing H1 (FIG. 5) by the outermost circumferential belt layer 6b of the above - described one - layer or multiple - layer circumferential belt layer 6b at the outermost end 6bg in the tire width direction is more likely to occur significantly, the effect of suppressing uneven wear by the sub - grooves 130 is particularly advantageous. However, each center land portion 122 may be configured as a block row divided in the tire circumferential direction by a groove extending along the tire width direction.

[0056] In the embodiment of FIG. 2, each outermost main groove 111 and each center main groove 112 each have protrusions 111s, 112s protruding outward in the tire radial direction on their groove bottom surfaces. As shown in FIG. 1, the outer ends in the tire radial direction of these protrusions 111s, 112s are located inside the tread surface 100 in the tire radial direction. However, each outermost main groove 111 may not have the protrusion 111s on its groove bottom surface. Also, each center main groove 112 may not have the protrusion 112s on its groove bottom surface.

Industrial Applicability

[0057] The tire according to the present invention can be used for any type of pneumatic tire, but is preferably used for a pneumatic tire for heavy loads, and more preferably for a pneumatic tire for trucks and buses.

Explanation of Signs

[0058] 1: Tire, 1a: Tread portion, 1b: Sidewall portion, 1c: Bead portion, 4a: Bead core, 4b: Bead filler, 5: Carcass, 5a: Carcass ply, 6: Belt, 6a: Cross belt layer (belt layer), 6ac: Cross belt cord, 6ar: Cross belt covering rubber, 6b: Circumferential belt layer (belt layer), 6bc: Circumferential belt cord, 6br: Circumferential belt covering rubber, 6be: Outer end in the width direction, 6bg: Outermost end in the width direction, 6c: Inclined belt layer (belt layer), 6cc: Inclined belt cord, 6cr: Inclined belt covering rubber, 7: Tread rubber, 8: Side rubber, 9: Inner liner, 100: Tread tread surface, 110: Main groove, 111: Outermost main groove, 111s: Protrusion, 112: Center main groove, 112s: Protrusion, 120: Land portion, 121: Shoulder land portion, 121t: One - end - open sipe, 122: Center land portion, 122t: One - end - open sipe, 122k: Both - ends - open sipe, 130: Sub - groove, 130a: Outer groove wall surface, 130b: Inner groove wall surface, CL: Tire equator plane, TE: Ground contact end, WD: Tire width direction, WDO: Outer side in the tire width direction, WDI: Inner side in the tire width direction, RD: Tire radial direction, RDO: Outer side in the tire radial direction, RDI: Inner side in the tire radial direction, CD: Tire circumferential direction, G: Road surface

Claims

1. A belt, a tread surface, A tire comprising: The belt includes: a plurality of cross-belt layers each including cross-belt cords extending in directions intersecting each other between layers; one or more circumferential belt layers each including circumferential belt cords extending along the circumferential direction of the tire; and has the angle formed by the cross-belt cords with respect to the tire width direction is 20° to 45°; On the tread surface, a plurality of main grooves each extending along the circumferential direction of the tire; a shoulder land portion defined between the outermost main groove located outermost in the tire width direction among the plurality of main grooves and the ground contact end; a sub-groove provided in the shoulder land portion, having a groove width narrower than that of the main groove, and extending along the circumferential direction of the tire; are provided, Of the pair of groove wall surfaces in the sub-groove, the outer groove wall surface located on the outer side in the tire width direction is located at the same position in the tire width direction as the outermost end in the tire width direction of the one or more circumferential belt layers, or is located inside in the tire width direction from the outermost end in the tire width direction of the one or more circumferential belt layers; The groove depth D of the sub-groove is 10% to 30% of the groove depth E of the outermost main groove; The shoulder land portion is configured as a rib that is not divided in the circumferential direction of the tire by a groove extending along the tire width direction. A tire.

2. The tire according to claim 1, wherein the tire width direction distance L from the outer groove wall surface of the sub-groove to the outermost end in the tire width direction of the one or more circumferential belt layers is 5% or less of the width W of the one or more circumferential belt layers.

3. The circumferential belt cords are wavy, The tire according to claim 1 or 2, wherein the tire width direction distance L from the outer groove wall surface of the sub-groove to the outermost end in the tire width direction of the one or more circumferential belt layers is 2 times or less of both amplitudes B of the wave shape formed by the circumferential belt cords.

4. The tire according to any one of claims 1 to 3, wherein the tire width direction distance L from the outer groove wall surface of the sub-groove to the outermost end in the tire width direction of the one or more circumferential belt layers is 5 mm or less.

5. The tire according to any one of claims 1 to 4, wherein the outer groove wall surface of the sub-groove is located inside in the tire width direction from each outermost end in the tire width direction of the one or more circumferential belt layers.

6. The tire according to any one of claims 1 to 5, wherein the circumferential belt layer of the one or more layers is located closer to the inner side in the tire radial direction than the plurality of staggered belt layers.

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