Tyre for motorcycle and pair of tyres for motorcycle

Abstract

Improvement of cornering performance and grip performance. A motorcycle tire (1) is of bias-ply construction. A plurality of main grooves (8) and a plurality of sipes (9) are provided in a tread portion (2). The main grooves (8) have a first main groove (11) extending from a crown region (Cr) to one side of a pair of shoulder regions (Sh) and a second main groove (12) extending from the crown region (Cr) to the other side of the pair of shoulder regions (Sh). The sipes (9) are formed only in the pair of shoulder regions (Sh).

Description

Technical Field

[0001] This invention relates to motorcycle tires and motorcycle tire pairs. Background Technology

[0002] Patent Document 1 describes a motorcycle tire with a tread pattern. The tread pattern includes main grooves with a width exceeding 2 mm and smaller grooves with a width of less than 2 mm. Both the main grooves and the smaller grooves are inclined relative to the tire's circumference.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-104329

[0004] Generally, motorcycle tires with a bias-ply construction do not have a belt layer in the tread area to provide a rim effect. In such motorcycle tires, because the rubber thickness in the shoulder area of ​​the tread is increased, its rigidity is higher, which can easily lead to a deterioration in steering performance. Furthermore, steering performance refers to the ease of steering maneuvers that involve tilting the motorcycle body and applying a camber angle to the tires when turning.

[0005] On the other hand, if multiple grooves or sipes are made on the tread, there is a problem of deteriorated grip performance. Summary of the Invention

[0006] The present invention was made in view of the actual situation described above, and its main purpose is to provide motorcycle tires, etc., that can improve steering performance and grip performance.

[0007] The present invention relates to a motorcycle tire, comprising a tread portion having a pair of tread ends and a carcass with a bias-ply structure. The tread portion includes: a pair of shoulder regions having a width in the tire axial direction equal to 30% of the tread width in the tread development view, extending axially inward from the pair of tread ends; and a crown region between the pair of shoulder regions. The tread portion is provided with a plurality of main grooves and a plurality of sipes. The main grooves include: a first main groove extending from the crown region to one side of the pair of shoulder regions; and a second main groove extending from the crown region to the other side of the pair of shoulder regions. The sipes are formed only in the pair of shoulder regions.

[0008] The preferred embodiment of the motorcycle tire of the present invention is that the maximum depth of the sipe is the same as the maximum depth of the main groove.

[0009] The preferred motorcycle tire of the present invention has one of the aforementioned sipes and one of the aforementioned main grooves configured to be adjacent in the tire circumferential direction and having an overlapping portion that overlaps in the tire axial direction, wherein the aforementioned sipe and the aforementioned main groove have the same depth on a first tire circumferential line passing through the aforementioned overlapping portion.

[0010] The preferred embodiment of the motorcycle tire of the present invention is that the first main groove, the second main groove, and the sipe are configured not to be interconnected.

[0011] The preferred embodiment of the motorcycle tire of the present invention is that each of the above-mentioned main grooves is not connected to the above-mentioned tread end but forms an end.

[0012] The preferred motorcycle tire according to the present invention is one in which the main groove includes a widened portion in the shoulder region where the groove width increases from the inner side of the tire axial direction toward the outer side.

[0013] The preferred embodiment of the present invention is that the widened portion extends to the outer end of the tire axial direction of the main groove.

[0014] The preferred motorcycle tire according to the present invention has a sipes groove having at least one raised portion that partially raises the bottom of the sipes groove.

[0015] The preferred motorcycle tire according to the present invention is one in which the raised portion is an arc shape protruding radially outward in the cross section along the sipe.

[0016] The preferred motorcycle tire of the present invention has the sipes offset at a position further outward from the center of the tire axial direction than the center of the tire shoulder region.

[0017] The present invention is a motorcycle tire pair, which uses the above-mentioned motorcycle tires as a front wheel tire and a rear wheel tire, wherein the rear wheel tire has more sipes than the front wheel tire.

[0018] In the motorcycle tire pair involved in this invention, it is preferable that the land area ratio of the tread portion of the rear wheel tire is 80% or more.

[0019] In the motorcycle tire pair involved in the present invention, it is preferable that, for the tread portion of the rear wheel tire, the land ratio of the crown region is greater than or equal to the land ratio of the shoulder region.

[0020] In the motorcycle tire pair according to the present invention, it is preferable that the land ratio of the tread portion of the front wheel tire is smaller than that of the rear wheel tire.

[0021] In the motorcycle tire pair according to the present invention, it is preferable that, for the tread portion of the front wheel tire, the land ratio of the shoulder region is greater than or equal to the land ratio of the crown region.

[0022] The motorcycle tire of the present invention can improve steering performance and grip performance by adopting the above structure. Attached Figure Description

[0023] Figure 1 This is a unfolded view of the tread portion of an embodiment of the present invention.

[0024] Figure 2 yes Figure 1 A-A line sectional view.

[0025] Figure 3 yes Figure 1 Enlarged image.

[0026] Figure 4 yes Figure 1 Enlarged image.

[0027] Figure 5 yes Figure 1 Enlarged image.

[0028] Figure 6 This is a longitudinal sectional view of the tool groove.

[0029] Figure 7 This is a unfolded view of the tread area in other embodiments.

[0030] Explanation of reference numerals in the attached figures:

[0031] 1…Motorcycle tire; 2…Tread; 8…Main groove; 9…Sipe; 11…First main groove; 12…Second main groove; Cr…Crown area; Sh…Shoulder area. Detailed Implementation

[0032] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0033] Figure 1 This is a developed view of the tread portion 2 of the motorcycle tire 1 (hereinafter simply referred to as "tire") of the present invention. The tire 1 of this embodiment is suitable for use on roads such as dry asphalt surfaces. However, the tire 1 of the present invention is not limited to this use.

[0034] Figure 2 yes Figure 1 A sectional view along line A-A. For example... Figure 2 As shown, the tread surface 2a of the tire 1 is curved into an arc shape that bulges outward in the radial direction of the tire so that sufficient contact area can be obtained even when turning with a large camber angle.

[0035] The tire 1 includes, for example, a tire carcass 6 mounted between the bead portions 4 and 4, and a belt layer 7 disposed on the radial outer side of the tire carcass 6 and inside the tread portion 2.

[0036] The tire carcass 6 is, for example, composed of two carcass plies 6A and 6B arranged radially inside and outside the tire. Each carcass ply 6A and 6B is, for example, a diagonal structure in which the carcass cords (not shown) are arranged at an angle of 30 to 45 degrees relative to the tire circumference. Each carcass ply 6A and 6B is made of a known material.

[0037] The belt layer 7 is composed of one or more crown belt cords 7A formed by spirally winding the crown belt cords (not shown) at an angle of less than 5 degrees relative to the tire circumference. In this embodiment, it is composed of one crown belt cord 7A. The crown belt cord 7A is made of a known material.

[0038] like Figure 1 As shown, the tread portion 2 includes a pair of shoulder regions Sh, each having a tire axial width Ws that is 30% of the tread spread width TWe, extending axially inward from a pair of tread ends Te, Te. The crown region Cr is located between the pair of shoulder regions Sh. The shoulder regions Sh are areas that experience high contact pressure primarily during cornering. The crown region Cr is an area that experiences high contact pressure primarily during straight-line driving. In this specification, the tread spread width TWe is the tire axial distance between the tread ends Te, Te when the tread portion 2 is unfolded into a flat surface.

[0039] In this embodiment, the tread portion 2 is provided with a plurality of main grooves 8 and a plurality of sipes 9. The tread portion 2 also includes, for example, circumferential grooves 10 extending along the tire circumference. In this specification, the main grooves 8 and circumferential grooves 10 are grooves with a maximum width exceeding 1.5 mm. In this specification, the sipes 9 are grooves with a maximum width of 1.5 mm or less. In this specification, unless otherwise specified, the dimensions of various parts of the tire are values ​​measured in a tire 1 in its normal state.

[0040] The aforementioned "normal condition" refers to the unloaded state in which tire 1 is assembled with a normal rim (illustration omitted) and filled with normal internal pressure.

[0041] The aforementioned "standard rim" refers to a rim whose specifications are determined for each tire within a specification system that includes the specifications on which the tire is based. For example, if it is JATMA, it is a "standard rim"; if it is TRA, it is a "Design Rim"; and if it is ETRTO, it is a "Measuring Rim".

[0042] The aforementioned "standard internal pressure" refers to the air pressure determined for each tire within the specification system, including 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 ATVARIOUS COLD INFLATION PRESSURES"; and if it is ETRTO, it is the "INFLATION PRESSURE".

[0043] The main groove 8 has a first main groove 11 extending from the tread region Cr to one of the pair of shoulder regions Sh (left in the figure), and a second main groove 12 extending from the tread region Cr to the other of the pair of shoulder regions Sh (right in the figure). These first and second main grooves 11 and 12 mitigate the rigidity of the shoulder regions Sh, even when the rubber thickness on both sides of the tread 2 is thick. Therefore, the tire 1 of this embodiment improves the contact patch of the shoulder regions Sh with the road surface during cornering, thereby improving steering performance.

[0044] The sipes 9 are formed only in a pair of shoulder areas Sh. Therefore, excessive reduction in rigidity in both the crown area Cr and the shoulder area Sh is suppressed, resulting in excellent grip performance. The sipes 9 include a first sipe 9A disposed on one side of the shoulder area Sh and a second sipe 9B disposed on the other side of the shoulder area Sh.

[0045] The tread portion 2 of this embodiment is suitable for use as the tread portion 2 of a front wheel tire for a motorcycle (not shown). Furthermore, Figure 1 The tread pattern 2 shown can also be applied to the tread pattern 2 of rear wheel tires.

[0046] The first main groove 11, the second main groove 12, and the sipe 9 are configured, for example, not to be interconnected. This suppresses a significant reduction in the rigidity of the tread portion 2.

[0047] In this embodiment, the main groove 8 further includes a third main groove 13, a fourth main groove 14, a fifth main groove 15, and a sixth main groove 16. In this embodiment, the third main groove 13 is formed to be adjacent to the first main groove 11 in the tire circumferential direction, and its axial length is smaller than that of the first main groove 11. The third main groove 13 extends, for example, from the crown region Cr to the shoulder region Sh. The fourth main groove 14 is formed to be adjacent to the second main groove 12 in the tire circumferential direction, and its axial length is smaller than that of the second main groove 12. The fourth main groove 14 extends from the crown region Cr to the other side of the shoulder region Sh. In this embodiment, the fifth main groove 15 is formed only on one side of the shoulder region Sh. In this embodiment, the sixth main groove 16 is formed only on the other side of the shoulder region Sh.

[0048] In this embodiment, the first main groove 11 and the second main groove 12, which are offset circumferentially from the tire, are linearly symmetrical across the tire equator C. In this embodiment, the third main groove 13 and the fourth main groove 14, which are offset circumferentially from the tire, are linearly symmetrical across the tire equator C. In this embodiment, the fifth main groove 15 and the sixth main groove 16, which are offset circumferentially from the tire, are linearly symmetrical across the tire equator C. Therefore, in this specification, unless otherwise specified, the descriptions of the first main groove 11, the third main groove 13, and the fifth main groove 15 also serve as descriptions of the second main groove 12, the fourth main groove 14, and the sixth main groove 16.

[0049] Figure 3 yes Figure 1 An enlarged image. For example... Figure 3 As shown, each main groove 8 is inclined to one side (upper left in the figure) relative to the tire circumferential direction, for example, from the inner side of the tire axial direction towards the outer side. In this embodiment, the first main groove 11, the third main groove 13, and the fifth main groove 15 are inclined to the upper left. These main grooves 8 exhibit high drainage performance due to the smooth flow of water within them. In this embodiment, the second main groove 12, the fourth main groove 14, and the sixth main groove 16 are inclined to the upper right (e.g., Figure 1 (As shown).

[0050] The main groove 8 includes, for example, a widening portion 18 in the shoulder region Sh whose width increases from the inside to the outside of the tire axial direction. This widening portion 18 further improves the contact patch of the shoulder region Sh with the road surface during cornering. The widening portion 18 is formed, for example, in the first main groove 11. In this embodiment, the widening portion 18 extends from the crown region Cr to the shoulder region Sh. The widening portion 18 refers to a portion where the ratio (wb-wa) of the difference between the minimum groove width wa and the maximum groove width wb of each main groove 8 to its axial length La ((wb-wa) / La) is 3% or more, distinguishing it from the uniform width portion where the ratio ((wb-wa) / La) is less than 3%.

[0051] Each main groove 8 is not connected to the tread end Te but forms an end. Therefore, the rigidity of the shoulder region Sh is maintained at a high level. The distance Li between the outer end 8e of the main groove 8 in the tire axial direction and the tread end Te is preferably 1 mm or more, more preferably 2 mm or more. Furthermore, the distance Li is preferably 30% or less of the width Ws of the shoulder region Sh in the tire axial direction, more preferably 25% or less. In this embodiment, the main groove 8 and the sipe 9 are not connected to the tread end Te but form ends.

[0052] The main groove 8 has a pair of groove edges 8s and 8t extending along its length. In this embodiment, one groove edge 8s is positioned axially inside the tire than the other groove edge 8t.

[0053] The main groove 8 includes: a first width-reducing portion 19, whose groove width decreases towards the inner end 8i of the tire axial direction; a second width-reducing portion 20, whose groove width decreases towards the outer end 8e of the tire axial direction; and a base 21 connecting the first width-reducing portion 19 and the second width-reducing portion 20. In this embodiment, the first width-reducing portion 19 includes the inner end 8i. In this embodiment, the second width-reducing portion 20 includes the outer end 8e. The base 21 includes a maximum width portion 21a that becomes the maximum groove width wb of the main groove 8. The first width-reducing portion 19 and the second width-reducing portion 20 maintain a large rubber volume in the tread portion 2, suppressing excessive reduction in the rigidity of the tread portion 2.

[0054] The first width reduction portion 19 is formed, for example, by a portion of one of the pair of groove edges 8s and 8t of the main groove 8 extending at an angle relative to the tire circumference smaller than the angle of the other groove edge 8s and 8t relative to the tire circumference. In this embodiment, the groove edge 8s disposed on the inner side of the tire axial direction is formed such that its angle relative to the tire circumference is smaller than that of the groove edge 8t disposed on the outer side of the tire axial direction. The first width reduction portion 19 is, for example, a portion where the groove width continuously decreases from the base 21.

[0055] Although not specifically limited, when the tire 1 is designated to rotate in the direction N, in order to improve grip and drainage performance, it is preferable that one groove edge 8s becomes the rear contact side in the direction N, and the other groove edge 8t becomes the first contact side in the direction N.

[0056] Preferably, the length Lc of the first width reduction portion 19 of the first main groove 11 and the length Lc of the first width reduction portion 19 of the third main groove 13 are equal to the axial width Wc of the tread region Cr (e.g., Figure 1 The percentage of the tire shoulder region Sh is 5% or more, more preferably 10% or more, more preferably 30% or less, and more preferably 25% or less. Furthermore, the length Lc of the first width reduction portion 19 of the fifth main groove 15 is preferably equal to the width Ws of the tire shoulder region Sh (as shown). Figure 1 The percentage of the width reduction portion (as shown) is 3% or more, more preferably 5% or more, more preferably 17% or less, and more preferably 15% or less. This improves steering performance and grip. Furthermore, the first width reduction portion 19 suppresses the formation of trench bottom cracks. The length Lc of the first width reduction portion 19 is its length along its width centerline.

[0057] Each of the second width reduction portions 20 is formed, for example, such that one of the pair of groove edges 8s and 8t includes an arc-shaped portion 22 that connects the base 21 to the second width reduction portion 20 with a smooth arc, and the other groove edge 8t has a crank-shaped portion 23 that is bent into a crank shape in the direction of reducing the groove width. Each of the second width reduction portions 20 is, for example, a portion whose groove width is sharply reduced compared to the base 21.

[0058] Although not particularly limited, it is preferable that the maximum groove width wc of each second width reduction portion 20 is 15% or more of the maximum groove width wb of each main groove 8, more preferably 20% or more, more preferably 50% or less, and more preferably 40% or less. Furthermore, it is preferable that the tire axial length Ld of each second width reduction portion 20 is equal to the width Ws of the shoulder region Sh (e.g., ...). Figure 1 The percentage of the second width reduction portion 20 is 15% or more, more preferably 20% or more, more preferably 30% or less, and more preferably 25% or less. Furthermore, the maximum depth da of each second width reduction portion 20 is preferably the maximum depth D1 of each main groove 8 (as shown). Figure 2 The second width reduction portion 20 is 15% or more (as shown), more preferably 20% or more, more preferably 50% or less, and more preferably 40% or less. This second width reduction portion 20 improves grip and steering performance, and suppresses the formation of cracks at the bottom of the trench. For example, the maximum depth D1 of each main trench 8 is preferably 3.8 mm or more, more preferably 4.0 mm or more, more preferably 8.0 mm or less, and more preferably 7.2 mm or less.

[0059] The first main groove 11, for example, has a circumferential overlap portion 25 that overlaps with the first main groove 11 adjacent to it in the tire circumferential direction. This first main groove 11 further reduces the rigidity of the tread portion 2, improves contact with the road surface, and thus improves steering performance. Preferably, the tire circumferential length Le of the circumferential overlap portion 25 is 5% or more of the tire circumferential length L1 of the first main groove 11, more preferably 8% or more, more preferably 15% or less, and more preferably 12% or less.

[0060] Figure 4 yes Figure 1 An enlarged image. For example... Figure 4 As shown, the third main groove 13 includes, for example, a neck 26 whose width is reduced at the center side of its tire axial direction. The base 21 of the third main groove 13 includes, for example, the neck 26, a first equal width portion 27 that connects the first width reduction portion 19 to the neck 26 and is of equal width, and a second equal width portion 28 that connects the second width reduction portion 20 to the neck 26 and is of equal width.

[0061] The neck 26 is formed, for example, by an arc-shaped portion 31 extending in an arc shape from one side of the groove edge 8s toward the center line of the groove, and a crank-shaped portion 32 extending in a crank shape from the other side of the groove edge 8t toward the direction of narrowing the groove width.

[0062] Figure 2 This indicates the constriction 26 of the fourth main groove 14. (Example) Figure 2As shown, the minimum depth dc of the neck 26 is preferably 10% or more of the maximum depth D1 of the fourth main groove 14, more preferably 20% or more, more preferably 50% or less, and more preferably 40% or less. The depth of the neck 26 smoothly increases outwards from both ends in its length direction. Furthermore, as... Figure 4 As shown, the minimum width wf of the neck 26 is preferably 10% or more of the maximum width wb of the third main groove 13, more preferably 20% or more, more preferably 50% or less, and more preferably 40% or less. This neck 26 suppresses the generation of groove bottom cracks.

[0063] The fifth main channel 15 is, for example, formed to include a third equal-width portion 35 disposed between the first width reduction portion 19 and the second width reduction portion 20.

[0064] Figure 5 yes Figure 1 An enlarged image. For example... Figure 5 As shown, preferably, the axial length LA of the first main groove 11 is 30% or more of the tread width TWe, more preferably 35% or more, more preferably 50% or less, and more preferably 45% or less. Preferably, the axial length LB of the third main groove 13 is 25% or more of the tread width TWe, more preferably 30% or more, more preferably 45% or less, and more preferably 40% or less. Preferably, the axial length LC of the fifth main groove 15 is 25% or more of the tread width TWe, more preferably 30% or more, more preferably 45% or less, and more preferably 40% or less.

[0065] The sipe 9 is inclined, for example, from the inner side of the tire axial direction towards the outer side relative to the tire circumferential direction to one side (upper left in the figure). The first sipe 9A is inclined in the same direction as the first main groove 11. The second sipe 9B is inclined in the same direction as the second main groove 12 (e.g., Figure 1 (As shown).

[0066] Figure 6 This is a longitudinal sectional view of the tool groove 9. (Example) Figure 6 As shown, the maximum depth de of the preferred groove 9 is the same as that of the main groove 8, and in this embodiment, it is the same as the maximum depth D1 of the first main groove 11. This reduces the rigidity of the tire shoulder area Sh, increases the contact patch of the tire shoulder area Sh with the road surface during cornering, and thus significantly improves steering performance.

[0067] The sipe 9 has at least one raised portion 38 that locally elevates the sipe bottom 9s. This raised portion 38 moderately increases the rigidity of the sipe bottom 9s and suppresses the formation of cracks in the sipe bottom. In addition, the raised portion 38 can improve steering performance without compromising grip.

[0068] In this embodiment, the raised portion 38 is formed in an arc shape protruding radially outward from the tire. The raised height h of the raised portion 38 gradually increases smoothly from both ends in the length direction toward the middle position 38c. This raised portion 38 suppresses excessive reduction in the rigidity of the tire shoulder region Sh.

[0069] like Figure 5 As shown, in this embodiment, a single raised portion 38 is provided. At this time, the raised portion 38 is positioned at the middle position 9c in the length direction of the cutter groove 9 (e.g., ...). Figure 5 (As shown). When there are n raised portions 38, it is preferable to divide the cutting groove 9 into n equal parts along its length direction, and to provide a raised portion 38 at the middle position along the length direction of each part (illustration omitted).

[0070] In this embodiment, the tread portion 2 has a shoulder region Sh with a sipe 9 and a main groove 8 (in this embodiment, a first main groove 11) adjacent to each other in the tire circumferential direction, and an overlap portion 39 that overlaps them in the tire axial direction. Preferably, the sipe 9 and the main groove 8 have the same depth along the first tire circumferential line n passing through the overlap portion 39. This moderately reduces the rigidity of the shoulder region Sh, improving steering performance and grip. In this embodiment, the overlap portion 39 forms the sipe 9 and the first main groove 11 at the same depth throughout its tire axial direction. The overlap portion 39, for example, has the same tire axial length Lg as the sipe 9.

[0071] The sipe 9 is offset to the outer side of the tire axial direction, from the center position Si of the shoulder region Sh. This reduces stiffness and improves steering performance in the outer side of the tire axial direction of the shoulder region Sh, where the rubber thickness is greater. In this embodiment, the inner end 9i of the sipe 9 is located to the outer side of the tire axial direction, from the center position Si of the shoulder region Sh.

[0072] In this embodiment, the circumferential groove 10 extends continuously along the tire circumference on the tire equator C. This circumferential groove 10 improves drainage performance. The circumferential groove 10 is formed in a serrated pattern, with a first portion 10A that is inclined to one side relative to the tire circumference (lower left in the figure) and a second portion 10B connected to the first portion 10A and inclined in the opposite direction relative to the tire circumference. Thus, the pair of groove edges 10e, 10e extending along the length direction of the circumferential groove 10 are respectively formed in an alternating pattern of an outer portion 10s on the outer side of the tire axial direction and an inner portion 10t on the inner side of the tire axial direction than the outer portion 10s.

[0073] The circumferential groove 10, for example, includes a cutout portion 40 at the intersection 10k of the first portion 10A and the second portion 10B, extending from the tread surface 2a toward the first portion 10A and the second portion 10B. This cutout portion 40 improves drainage performance and resistance to eccentric wear.

[0074] The cut-out portion 40 is configured, for example, to connect with the outer portion 10s. In this embodiment, the cut-out portion 40 is formed to include: a first edge portion 40a smoothly connected to the outer portion 10s, and a second edge portion 40b inclined at an angle larger than the first edge portion 40a relative to the tire circumferential direction. The first edge portion 40a suppresses excessive reduction in the rigidity of the tread 2 near the tire equator C. When the second edge portion 40b is positioned on the rear contact side in the rotational direction N, more so than the first edge portion 40a, the second edge portion 40b helps to capture the water film between the road surface and the tread 2a and drain it outwards into the circumferential groove 10.

[0075] Figure 7 This is a developed view of the tread portion 2 according to another embodiment. For structures identical to this embodiment, the same reference numerals may be used, and their descriptions may be omitted. The tread portion 2 of this embodiment is suitable for use as a rear wheel tire for motorcycles. Furthermore, this tread portion 2 can also be used as a front wheel tire.

[0076] like Figure 7 As shown, in this embodiment, the tread surface 2 is formed by a main groove 8 and a sipe 9, but no circumferential grooves are formed. The main groove 8 in this embodiment is composed of a first main groove 11 to a sixth main groove 16. In this specification, unless otherwise specified, the descriptions of the first main groove 11, the third main groove 13, and the fifth main groove 15, for this embodiment, also serve as descriptions of the second main groove 12, the fourth main groove 14, and the sixth main groove 16, respectively.

[0077] The first main groove 11, for example, does not cross the tire equator C but extends axially within any shoulder region Sh. The first main groove 11 in this embodiment is compared to... Figure 1 The first main groove 11 has its inner end 11i in the tire axial direction close to the tire equator C. In this embodiment, it is preferable that the distance Lh between the inner end 11i and the tire equator C in the tire axial direction is within 3% of the tread width TWe.

[0078] In this embodiment, the widened portion 18 of the first main groove 11 extends to the outer end 11e of the first main groove 11 in the tire axial direction. In other words, the first main groove 11 does not have a second width reduction portion 20. This first main groove 11 improves drainage performance.

[0079] In this embodiment, the fifth main groove 15 extends from the crown region Cr to one of the shoulder regions Sh. This fifth main groove 15 not only moderately reduces the rigidity of the shoulder region Sh, but also moderately reduces the rigidity of the crown region Cr.

[0080] For example, by having Figure 1 The front wheel tire shown in the diagram 2 has a tread area and a tread area of ​​2. Figure 7 The rear wheel tire of the tread section 2 shown constitutes a motorcycle tire pair T.

[0081] Preferably, the rear tire has more sipes 9 than the front tire. Because the rear tire has a larger tread width TWe than the front tire, the shoulder area Sh has greater rigidity. Therefore, by adopting the above structure, the contact patch of the rear tire is improved, thereby improving steering performance. In the rear tire, two sipes 9 are provided within one pitch P1 of the first main groove 11 (e.g., Figure 7 As shown), in the front wheel tire, a sipe 9 is provided within one pitch P1 of the first main groove 11 (as shown). Figure 1 (As shown). Preferably, the pitch P1 of the first main groove 11 of the rear tire is the same as the pitch P1 of the first main groove 11 of the front tire.

[0082] The land ratio of the tread portion 2 of the rear tire is preferably 80% or more. This prevents excessive reduction in the rigidity of the tread portion 2 of the rear tire and maintains grip performance. In this specification, the land ratio refers to the ratio of the surface area SA of the tread surface of the imaginary tread portion (not shown) obtained by filling the main groove 8 or the circumferential groove 10 to the surface area SB of the tread surface 2a of the tread portion 2 (SB / SA).

[0083] Rear wheel tires are those that have little impact on the rider's steering. For these tires, grip is more important than steering performance. Therefore, it is preferable that the land ratio of the crown region Cr in the tread area 2 of the rear wheel tire is greater than or equal to the land ratio of the shoulder region Sh, and even more preferably, the land ratio of the crown region Cr is greater than the land ratio of the shoulder region Sh.

[0084] Front tires significantly impact steering performance. For these tires, steering performance is more important than grip. Therefore, it is preferable that the land ratio of the shoulder area Sh in the tread portion 2 of the front tire is greater than or equal to the land ratio of the crown area Cr, and more preferably, the land ratio of the shoulder area Sh is greater than the land ratio of the crown area Cr.

[0085] In order to effectively perform the above functions, it is preferable that the land area ratio of the tread portion 2 of the front wheel tire is smaller than that of the tread portion 2 of the rear wheel tire.

[0086] Such a tire 1 is formed, for example, from a vulcanizing mold (not shown) comprising a pair of molds. Each pair of molds has a dividing position that bisects the tread portion 2 in the tire axial direction, and the tread portion 2 is vulcanized and formed separately. These dividing positions extend circumferentially along the tire. The pair of molds forming the front tire has a dividing position located away from the circumferential groove in the tire axial direction. The pair of molds forming the rear tire has a dividing position on the tire equator C.

[0087] The above describes a particularly preferred embodiment of the present invention, but the present invention is not limited to the embodiments shown in the figures and can be implemented in various ways.

[0088]

Example

[0089] Trial production with Figure 1 or Figure 7 Motorcycle tires with basic tread patterns were tested. Then, the steering performance, grip, water drainage, resistance to uneven wear, and high-speed durability of each tire were tested. The common specifications and testing methods for each tire are described below.

[0090] <Steering performance, grip performance, resistance to uneven wear, durability>

[0091] Each test tire was mounted on the motorcycle (1500cc displacement) under the following conditions. Additionally, it has... Figure 1 The tire tread is used on the front wheels and has Figure 7 The tires used on the rear wheels were employed in this configuration. Test riders then used the vehicle on a dry asphalt test track, evaluating steering and grip performance using their senses. Additionally, they evaluated the degree of uneven wear, groove bottom cracks, and sipe bottom cracks after riding using their senses. Results were expressed using a scoring system of 100 points, similar to Comparative Example 1. Higher scores indicate better performance. A score of 95 or higher is considered passing.

[0092] Front tire specifications (size, rim, internal pressure): 110 / 70-13M / C, 13×3.00MT, 200kPa

[0093] Rear wheel tire specifications (size, rim, internal pressure): 130 / 70-13M / C, 13×3.50MT, 220kPa

[0094] <Drainage performance>

[0095] Using the aforementioned vehicle, test riders rode it on a test track with a wet asphalt surface. The difficulty of riding was evaluated by the riders' senses. The results were represented using a score of 100 points, as in Comparative Example 1. Higher scores indicate better drainage performance. A score of 95 or higher is considered passing.

[0096] The test results are shown in Table 1.

[0097] The symbols in Table 1 have the following meanings.

[0098] "A": The first and second major grooves extend from the crown area to the shoulder area.

[0099] "B": The first and second main grooves extend only in the shoulder area.

[0100] "C": The sipes are formed only in the tire shoulder area.

[0101] "D": No tool groove formed.

[0102] "E": The first main groove, the second main groove, and the cutter groove are not connected.

[0103] "F": The first main groove, the second main groove, and the cutter groove are connected respectively.

[0104] "G": The main groove and sipes are not connected to the tread end.

[0105] "H": The main groove is connected to the tread end.

[0106] "I": The number of sipes on the front tires is less than the number of sipes on the rear tires.

[0107] "J": The number of sipes on the front tires is greater than the number of sipes on the rear tires.

[0108] "K": On the tire circumferential line passing through the overlap, the depth of the first main groove is equal to the depth of the sipe.

[0109] "L": On the tire circumferential line passing through the overlap, the depth of the first main groove is greater than the depth of the sipe.

[0110] "M": The widened part of the first main channel is of equal width.

[0111] Table 1

[0112]

[0113] Based on the test results, it can be understood that the tires (motorcycle tire pair) of the embodiment have superior steering and grip performance compared to the tires (motorcycle tire pair) of the comparative example.

Claims

1. A motorcycle tire, wherein, The motorcycle tire has a tread portion having a pair of tread ends and a carcass with a bias-ply structure. The tread portion includes: a pair of shoulder regions, each having a width in the tire axial direction equal to 30% of the tread width in the tire axial direction from each pair of tread ends in the tread development diagram; and a crown region between the pair of shoulder regions. The tread surface is provided with multiple main grooves and multiple sipes. The main groove comprises: a first main groove extending from the crown region toward one of the pair of shoulder regions; a second main groove extending from the crown region toward the other of the pair of shoulder regions; a third main groove adjacent to the first main groove in the tire circumferential direction and having a tire axial length smaller than the first main groove; and a fourth main groove adjacent to the second main groove in the tire circumferential direction and having a tire axial length smaller than the second main groove. The sipes are formed only in the pair of tire shoulder areas. The sipe is offset to the outer side of the tire axial direction, relative to the center of the tire shoulder region. The third and fourth main grooves are respectively contained in a necking pattern where the width of the central side groove is reduced in the axial direction of the tire.

2. The motorcycle tire according to claim 1, wherein, The maximum depth of the cutting groove is the same as the maximum depth of the main groove.

3. The motorcycle tire according to claim 1 or 2, wherein, One of the said sipes and one of the said main grooves are configured to be adjacent in the tire circumferential direction and have overlapping portions that overlap in the tire axial direction. On the first tire circumferential line passing through the overlapping portion, one of the sipes and one of the main grooves have the same depth.

4. The motorcycle tire according to claim 1 or 2, wherein, The first main groove, the second main groove, and the cutter groove are configured not to be interconnected.

5. The motorcycle tire according to claim 1 or 2, wherein, Each of the main grooves is not connected to the tread end but forms a terminal.

6. The motorcycle tire according to claim 1 or 2, wherein, The main groove includes a widened portion in the shoulder region where the groove width increases from the inside to the outside of the tire axial direction.

7. The motorcycle tire according to claim 6, wherein, The widened portion extends to the outer end of the tire axial direction of the main groove.

8. The motorcycle tire according to any one of claims 1, 2, and 7, wherein, The cutting groove has at least one raised portion that locally raises the bottom of the cutting groove.

9. The motorcycle tire according to claim 8, wherein, The raised portion is an arc shape that bulges outward radially from the tire in the cross section along the groove.

10. A motorcycle tire pair, wherein the motorcycle tire according to any one of claims 1 to 9 is used as a front wheel tire and a rear wheel tire, wherein, The rear tire has more sipes than the front tire.

11. The motorcycle tire pair according to claim 10, wherein, The land area ratio of the tread of the rear wheel tire is 80% or more.

12. The motorcycle tire pair according to claim 10 or 11, wherein, For the tread portion of the rear wheel tire, the land area ratio of the crown region is greater than or equal to the land area ratio of the shoulder region.

13. The motorcycle tire pair according to claim 10 or 11, wherein, The land area ratio of the tread of the front tire is smaller than that of the rear tire.

14. The motorcycle tire pair according to claim 10 or 11, wherein, For the tread portion of the front wheel tire, the land ratio of the shoulder region is greater than or equal to the land ratio of the crown region.

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