Motorcycle tire

Abstract

The present invention provides a motorcycle tire capable of improving uneven wear resistance while maintaining wet performance. A motorcycle tire (1) has a tread portion (2). A tread portion (2) is provided with a plurality of first inclined grooves (3) that open from a crown region (Cr) toward a first tread edge (T1). The first inclined groove (3) includes a first portion (7) in which the groove width (W1) decreases from the crown region (Cr) toward the first tread edge (T1), and a second portion (8) in which the groove width (W1) increases toward the first tread edge (T1) to the first tread edge (T1).

Description

Technical Field

[0001] The invention relates to a tire for motorcycles. Background Art

[0002] The following Patent Document 1 describes a pneumatic tire for motorcycles having a first groove and a second groove whose length in the tire circumferential direction is smaller than that of the first groove in the tread portion. The first groove includes a first inclined portion and a second inclined portion. The first inclined portion has a first end on the tread end side and extends obliquely in the first tire circumferential direction, and the second inclined portion is connected to the first inclined portion and extends obliquely in the first tire circumferential direction to a closed second end. The second groove extends obliquely relative to the tire circumferential direction and has an inner end in the tire axial direction. The inner end of the second groove is located at a position closer to the inner side in the tire axial direction than the first end and the second end of the first groove. With respect to this pneumatic tire for motorcycles, it is expected that the drainage performance and wear resistance performance will be improved.

[0003] [Prior art literature]

[0004] [Patent Document]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2022-161695 Summary of the invention

[0006] [Problems to be solved by the invention]

[0007] In recent years, it is known that the groove width is increased in order to improve wet performance. However, if the groove width is simply increased, there is a problem that the amount of sliding in each tread surface including a pair of groove edges extending in the longitudinal direction of the groove is different, and the wear amount of the two tread surfaces is greatly different (that is, uneven wear occurs).

[0008] The present invention has been developed in view of the above-mentioned problems, and an object of the present invention is to provide a motorcycle tire capable of improving uneven wear resistance while maintaining wet performance.

[0009] [Technical means to solve the problem]

[0010] The present invention is a motorcycle tire having a tread portion, wherein the motorcycle tire is provided with a plurality of first inclined grooves opening from a crown region including a tire equator to a first tread end. The plurality of first inclined grooves respectively include a first portion whose groove width decreases from the crown region toward the first tread end, and a second portion whose groove width increases toward the first tread end and reaches the first tread end.

[0011] [Effects of the Invention]

[0012] The motorcycle tire of the present invention can improve uneven wear resistance while maintaining wet performance by adopting the above-mentioned structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a development view of a tread portion showing an embodiment of a motorcycle tire of the present invention.

[0014] Figure 2 is a plan view of the first inclined trough.

[0015] Figure 3 is a plan view of the first inclined trough.

[0016] Figure 4 yes Figure 2 AA line cross-section diagram.

[0017] Figure 5 It is a development view of the tread portion of the present embodiment.

[0018] Figure 6 is a plan view of the circumferential groove.

[0019] Figure 7 (A) is Figure 6 BB line profile, Figure 7 (B) is Figure 6 CC line profile.

[0020] Figure 8 (A) is Figure 6 DD line profile, Figure 8 (B) is Figure 8 A cross-sectional view of another embodiment of (A).

[0021] Fig. 9 (A) is Figure 6 EE line profile, Fig. 9 (B) is Figure 6 FF line cross-section diagram.

[0022] Fig.10 (A) is Figure 6 GG line profile, Fig.10 (B) is Figure 6 HH line profile.

[0023] Fig.11 is a plan view of the first small inclined trough.

[0024] [Explanation of Symbols]

[0025] 1: Motorcycle tires / tires

[0026] 2: Tread

[0027] 3: First inclined groove

[0028] 7: Part I

[0029] 8: Part 2

[0030] Cr: crown area

[0031] T1: First tread end

[0032] W1: Slot width DETAILED DESCRIPTION

[0033] Hereinafter, one embodiment of the present invention will be described based on the accompanying drawings. The accompanying drawings contain exaggerated representations or representations with different dimensional ratios from the actual structure to help understand the present invention. In addition, when there are multiple embodiments, the same or common components are annotated with the same symbols throughout the specification, and repeated descriptions are omitted.

[0034] Figure 1 The present invention is a plan view of a tread portion 2 of a motorcycle tire (hereinafter sometimes referred to as a "tire") 1 according to an embodiment of the present invention. The present invention can be used for tires of so-called commuter bicycles (bikes) that are intended to be used on the street (comfort / safety is more important than speed). Such tires are more likely to be driven mainly at a small camber angle. In addition, the present invention can be suitably used for bias tires in which the carcass cords (not shown) of the carcass extend at an angle of 20 to 60 degrees relative to the tire circumferential direction.

[0035] like Figure 1 As shown in the figure, the tread portion 2 is provided with a crown region Cr including the tire equator C, and a plurality of first inclined grooves 3 opening from the crown region Cr to the first tread end T1. In addition, the tread portion 2 of the present embodiment is provided with a plurality of second inclined grooves 4 opening from the crown region Cr to the second tread end T2. The second inclined grooves 4 of the present embodiment become a shape that is line-symmetrical with the first inclined grooves 3 when the first inclined grooves 3 are moved an arbitrary distance in the tire circumferential direction and the tire equator C is set as an axis of symmetry. Therefore, in this specification, the first inclined grooves 3 are described as a representative, and the second inclined grooves 4 are described as having a structure different from the first inclined grooves 3.

[0036] The first tread end T1 and the second tread end T2 are the ends forming the maximum width of the tread. In the case of a tire 1 whose maximum tread width is consistent with the total width (maximum width) of the tire, the first tread end T1 and the second tread end T2 are the outer ends of the tire 1 in the tire axial direction. In the case of a tire 1 whose maximum tread width is smaller than the total width of the tire, the first tread end T1 and the second tread end T2 are the two ends of the tire axial direction that are in contact with the plane when a normal load is applied to the tire 1 in a normal state and the camber angle is 30 degrees so that it is inclined to both sides of the tire axial direction and contacts the plane. The length along the tread surface 2a of the tread portion 2 between the first tread end T1 and the second tread end T2 is the tread development width TWe. In addition, 50% of the tread development width TWe is the tread development half width TW. The center of the tire axial direction between the first tread end T1 and the second tread end T2 is the tire equator C. In addition, in this specification, unless otherwise specified, the dimensions of each part of the tire 1 are values ​​measured in a normal state.

[0037] In the present embodiment, the crown region Cr is a region that contacts the plane when the tire 1 in the normal state is loaded with the normal load and the camber angle is 0 degrees, and the region that contacts the plane is mainly when the tire is running straight. The "normal state" is a state where the tire 1 is clamped to a normal rim (not shown), adjusted to a normal internal pressure, and unloaded. The "normal load" refers to the load specified for each tire in each specification in the specification system including the specifications based on the tire. If it is the Japan Automobile Tire Manufacturers Association (JATMA), it is set to the maximum load capacity, if it is the Tire and Rim Association (TRA), it is set to the maximum value recorded in the table "Tire Load Limits at Various Cold Inflation Pressures", and if it is the European Tire and Rim Technical Organization (ETRTO), it is set to "Load Capacity". “Regular rim” is a rim specified for each tire in a specification system including the specification to which the tire 1 is based, for example, “standard rim” in JATMA, “design rim” in TRA, and “measuring rim” in ETRTO. “Regular internal pressure” is the air pressure specified for each tire in each specification in a specification system including the specification to which the tire 1 is based, for example, “maximum air pressure” in JATMA, the maximum value listed in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in TRA, and “inflation pressure” in ETRTO.

[0038] Figure 2 is a plan view of the first inclined groove 3. Figure 2As shown, the plurality of first inclined grooves 3 respectively include a first portion 7 where the groove width W1 decreases from the crown region Cr toward the first tread end T1 side, and a second portion 8 where the groove width W1 increases toward the first tread end T1 and reaches the first tread end T1. Generally speaking, the contour of the tread portion 2 (not shown) is curved in an arc shape convex to the outside in the radial direction of the tire (not shown). Therefore, in the motorcycle tire 1, in the tread 2a, the amount of slip during driving is more likely to increase on the first tread end T1 side than in the crown region Cr. In addition, on wet roads that are prone to sliding, there is a tendency that turning driving at a large camber angle is restricted. As a result, the first portion 7 where the groove width W1 decreases toward the first tread end T1 side reduces the amount of slip on the outside of the tire axial direction where the amount of slip is more likely to increase, and reduces the difference in the amount of wear generated in the tread 2a on both sides of the groove width direction of the first portion 7, thereby improving the uneven wear resistance. In addition, during wet driving with a reduced camber angle, the reduction in the groove width W1 of the first inclined groove 3 in the area in contact with the road surface is suppressed, so that wet performance can be maintained. Furthermore, the second portion 8 makes drainage from the first tread end T1 smooth, so that wet performance can be maintained. Therefore, the tire 1 of the present invention can improve uneven wear resistance while maintaining wet performance.

[0039] The groove width W1 is the length of the first inclined groove 3 in the direction perpendicular to the groove center line 3c. In addition, when the first inclined groove 3 is connected to a groove or notch having a groove depth smaller than that of the first inclined groove 3, the groove width W1 is measured by using the virtual groove edge 3v obtained by filling the small groove or notch at the location where the small groove or notch is formed. Figure 2 In the figure, for convenience, the first portion 7 and the second portion 8 are indicated by hatching lines in different directions. In addition, the imaginary groove edge 3v is indicated by a double-dot chain line.

[0040] The length L1 of the first portion 7 in the tire axial direction is preferably 50% or more, more preferably 55% or more, of the tread half width TW, and is preferably 75% or less, more preferably 70% or less. Since the length L1 of the first portion 7 is 50% or more of the tread half width TW, the uneven wear resistance can be improved. Since the length L1 of the first portion 7 is 75% or less of the tread half width TW, the flow of water in the first inclined groove 3 can be suppressed from being excessively reduced.

[0041] The length L2 of the second portion 8 in the tire axial direction is preferably 5% or more, more preferably 7% or more, and is preferably 15% or less, more preferably 13% or less. Since the length L2 of the second portion 8 is 5% or more of the tread half width TW, water can be drained smoothly. Since the length L2 of the second portion 8 is 15% or less of the tread half width TW, the rigidity near the first tread end T1 is suppressed from being excessively reduced, and the amount of slip can be suppressed from becoming excessively large.

[0042] In order to improve the uneven wear resistance while maintaining the wet performance, the maximum value W1a of the groove width W1 of the first portion 7 is preferably 5% or more, more preferably 7% or more, and is preferably 15% or less, more preferably 13% or less of the tread half width TW. In addition, the maximum value W1b of the groove width W1 of the second portion 8 is preferably 80% or more, more preferably 90% or more, and is preferably 120% or less, more preferably 110% or less of the maximum value W1a of the groove width W1 of the first portion 7.

[0043] like Figure 1 and Figure 2 As shown, the tread portion 2 of the present embodiment is specified in the tire rotation direction R. The tread portion 2 contacts the road surface from the bottom to the top of the figure.

[0044] The plurality of first inclined grooves 3 extend toward the first tread end T1 side toward the rear ground contact side in the tire rotation direction R. Each first inclined groove 3 extends continuously to the first tread end T1 toward the rear ground contact side in the tire rotation direction R. The first inclined groove 3 is formed, for example, in a curved shape convex toward the rear ground contact side in the tire rotation direction R.

[0045] The plurality of first inclined grooves 3 respectively include a pair of groove edges 3e extending along the length direction of the first inclined groove 3, and an inner end 3i in the tire axial direction. Each first inclined groove 3 includes a tapered portion 9, in which a pair of groove edges 3e of the first inclined groove 3 extend in a tapered shape toward the inner end 3i. Such tapered portion 9 can smoothly guide the water film on the tread 2a into the first inclined groove 3. The length L3 of each tapered portion 9 in the tire circumferential direction is ideally 5% or more of the length La of the first inclined groove 3 in the tire circumferential direction, more ideally 7% or more, and ideally 13% or less, more ideally 11% or less. The tapered portion 9 of this embodiment is connected to the first portion 7.

[0046] The pair of groove edges 3e includes a leading land-contact-side inclined groove edge 11A located on the leading land-contact-side in the tire rotation direction R, and a rear land-contact-side inclined groove edge 11B located on the rear land-contact-side in the tire rotation direction R. In this specification, the leading land-contact-side inclined groove edge 11A and the rear land-contact-side inclined groove edge 11B refer to a form that includes the virtual groove edge 3v and extends continuously between the inner end 3i and the first tread end T1.

[0047] The tread portion 2 includes at least one shallow groove 12 connected to the first inclined groove 3. Such shallow groove 12 removes the water film on the tread surface 2a to improve the ground contact with the road surface, and suppresses the reduction of the rigidity of the tread portion 2, thereby improving the wet performance while maintaining high uneven wear resistance. The shallow groove 12 has a groove depth d2 ( Figure 4 shown) is formed.

[0048] Figure 3 is a plan view of the first inclined groove 3. Figure 3 As shown, the shallow groove 12 includes an opening 14 connected to the first inclined groove 3. Water in the shallow groove 12 flows to the first inclined groove 3 through the opening 14 and is discharged to the outside of the tread 2a during running. The position of the opening 14 overlaps with the virtual groove edge 3v.

[0049] The shallow groove 12 includes a pair of groove edges 12e connected to the groove edge 3e of the first inclined groove 3. In the present embodiment, at least one of the pair of groove edges 12e is formed in a curved shape convex toward the rear ground contact side in the tire rotation direction R.

[0050] The pair of groove edges 12e of the shallow groove 12 are connected to the groove edge 3e of the first inclined groove 3, for example, by means of arcs 18. Thus, the load on the portion where the first inclined groove 3 and the shallow groove 12 are connected is dispersed, thereby improving the uneven wear resistance. In this embodiment, an opening 14 is formed between each arc 18.

[0051] The tread surface 2a of the tread portion 2 includes an acute angle portion 20 sandwiched by one of the groove edges 3e of the first inclined groove 3 and one of the pair of groove edges 12e of the shallow groove 12. In addition, the tread surface 2a of the tread portion 2 includes an obtuse angle portion 21 sandwiched by one of the groove edges 3e of the first inclined groove 3 and one of the pair of groove edges 12e of the shallow groove 12. Moreover, in the acute angle portion 20, the radius of curvature r1 of the arc 18 is preferably 0.5 mm or more, and more preferably 0.7 mm or more. Since the radius of curvature r1 is 0.5 mm or more, the uneven wear resistance can be improved. There is no particular limitation on the upper limit of the radius of curvature r1 of the arc 18, but if the aesthetic design of the pattern is considered, it is preferably 1.5 mm or less, and more preferably 1.3 mm or less. In addition, in the obtuse angle portion 21, the radius of curvature r2 of the arc 18 is preferably 20 mm or more, and more preferably 30 mm or more, and is preferably 100 mm or less, and more preferably 90 mm or less.

[0052] The shallow groove 12 extends from the opening 14 toward the rear ground contact side in the tire rotation direction R and toward the first tread end T1 side. In other words, a pair of groove edges 12e extend from the arc 18 toward the rear ground contact side in the tire rotation direction R and toward the first tread end T1 side. Such shallow grooves 12 relatively reduce the amount of sliding during driving, thereby improving the uneven wear resistance. In addition, such shallow grooves 12 disperse and reduce the load generated near the first inclined groove 3, thereby improving the uneven wear resistance. In this embodiment, the shallow groove 12 has an end 12t that terminates at a position on the rear ground contact side in the tire rotation direction R.

[0053] In the present embodiment, the pair of groove edges 12e includes a first groove edge 12a located on the rear ground contact side in the tire rotation direction R, and a second groove edge 12b located on the front ground contact side in the tire rotation direction R. Moreover, in the present embodiment, the first groove edge 12a defines an acute angle portion 20. In other words, the acute angle portion 20 is arranged on the rear ground contact side in the tire rotation direction R relative to the shallow groove 12. In addition, the second groove edge 12b defines an obtuse angle portion 21. In other words, the obtuse angle portion 21 is arranged on the front ground contact side in the tire rotation direction R relative to the shallow groove 12. Thus, the effect of relatively reducing the amount of slip during the driving can be effectively exerted.

[0054] The shallow groove 12 has a groove width W2 parallel to the opening width Wa of the opening portion 14. Moreover, the groove width W2 of the shallow groove 12 decreases, for example, as it moves away from the first inclined groove 3. As a result, it is possible to suppress an excessive decrease in the rigidity of the tread portion 2 (tread surface 2a). In this specification, the so-called "moving away from the first inclined groove 3" is a direction orthogonal to the opening width Wa.

[0055] Figure 4 yes Figure 2 AA line cross-section diagram. Figure 4 As shown, the groove depth d2 of the shallow groove 12 decreases as it moves away from the first inclined groove 3. This can suppress an excessive decrease in the rigidity of the tread 2a. The groove depth d2 of the shallow groove 12 is the largest at the opening and the smallest at the one end 12t.

[0056] The maximum groove depth d2a of the shallow groove 12 is ideally 0.3 times or more, more ideally 0.4 times or more, and ideally 0.7 times or less, more ideally 0.6 times or less. Since the maximum groove depth d2a of the shallow groove 12 is at least 0.3 times the groove depth d1 of the first inclined groove 3, the effect of improving wet performance can be achieved. Since the maximum groove depth d2a of the shallow groove 12 is less than 0.7 times the groove depth d1 of the first inclined groove 3, an excessive reduction in the rigidity of the tread portion 2 can be suppressed. In the present specification, the first inclined groove 3 at the opening 14 is an area A3 where the first inclined groove 3 intersects with a line segment that is orthogonal to the opening width Wa between a pair of groove edges 12e, 12e of the shallow groove 12. Figure 3 In FIG. 1 , for convenience, area A3 is indicated by hatching.

[0057] like Figure 3 As shown, the opening width Wa is preferably 1.0 times or more, more preferably 1.5 times or more, and is preferably 4.0 times or less, more preferably 3.5 times or less, of the groove width W1d of the first inclined groove 3 at the position of the opening 14 (area A3). Since the opening width Wa is 1.0 times or more of the groove width W1d of the first inclined groove 3, the effect of improving wet performance can be achieved. Since the opening width Wa is 4.0 times or less of the groove width W1d of the first inclined groove 3, excessive reduction in the rigidity of the tread portion 2 can be suppressed.

[0058] In the present embodiment, the shallow groove 12 includes a first shallow groove 12A connected to the inclined groove edge 11A on the first ground contact side, and a second shallow groove 12B connected to the inclined groove edge 11B on the rear ground contact side. In the present embodiment, the first shallow groove 12A is located at a position closer to the inner end 3i side (the first ground contact side in the tire rotation direction R) than the second shallow groove 12B. In the present embodiment, the second shallow groove 12B includes: an inner second shallow groove 23, which is arranged at a position overlapping with the first shallow groove 12A in the tire axial direction; and an outer second shallow groove 24, which is located at a position closer to the first tread end T1 than the inner second shallow groove 23. In the present embodiment, the outer second shallow groove 24 is located at a position spanning the first portion 7 and the second portion 8. In the present embodiment, each shallow groove 12 is located at a position closer to the first tread end T1 than the crown region Cr.

[0059] One end 24e of the outer second shallow groove 24 on the rear ground contact side in the tire rotation direction R is located closer to the rear ground contact side in the tire rotation direction R than one end 3b of the first inclined groove 3 on the rear ground contact side in the tire rotation direction R. Such an outer second shallow groove 24 helps to collect a larger amount of water film on the tread 2a into the first inclined groove 3.

[0060] Figure 5 2 is a development diagram of the tread portion 2. Figure 5As shown, the tread portion 2 of the present embodiment is further provided with a circumferential groove 26 extending continuously in the tire circumferential direction and a small inclined groove 40 having a smaller length than the first inclined groove 3 .

[0061] Figure 6 is a plan view of the circumferential groove 26. Figure 6 As shown, the circumferential groove 26 extends in a wave shape, for example. Such a circumferential groove 26 has a larger groove volume than, for example, a circumferential groove extending in a straight line along the circumference of the tire (not shown), and therefore reduces the amount of water splashing. In addition, in the present embodiment, the circumferential groove 26 extends in a sinusoidal wave shape. Such a circumferential groove 26, for example, compared with a circumferential groove extending in a sawtooth shape or a pseudo-sinusoidal wave shape, makes the flow of water in the circumferential groove 26 smoother, and reduces the amount of water splashing when contacting with a wet road surface without damaging the drainage of the tread surface 2a. As a result, the driving performance on a wet road surface is improved. The sinusoidal wave shape is of course a sine wave, which includes a form formed by multiple waves with different wavelengths and / or multiple waves with different amplitudes.

[0062] The amplitude λ of the circumferential groove 26 is related to the half wavelength A ( Figure 5 The ratio (λ / A) of the circumferential groove 26 is preferably not less than 0.04, more preferably not less than 0.06, and is preferably not more than 0.12, more preferably not more than 0.10. Since the ratio (λ / A) is not more than 0.12, the splashing water when contacting with the wet road surface can be made to form a large angle to the left and right relative to the direction of travel. Since the ratio (λ / A) is not less than 0.04, the flow of water in the circumferential groove 26 becomes smooth, and the splashing water can be suppressed. The amplitude λ and the half-wavelength A are specifically specified by the groove centerline 26c of the circumferential groove 26. The groove centerline 26c is specifically specified by the position on the tread 2a in the radial direction of the tire.

[0063] The circumferential groove 26 is disposed, for example, in the crown region Cr. The circumferential groove 26 is preferably located on the tire equator C. In the present embodiment, the center line 26K of the amplitude of the circumferential groove 26 is located on the tire equator C. This can suppress the splashing of water during straight travel, which is relatively high-speed travel.

[0064] The circumferential groove 26 includes a plurality of first inclined portions 28 inclined in a first direction relative to the tire circumferential direction and a plurality of second inclined portions 29 inclined in a direction opposite to the first direction. The first inclined portion 28 and the second inclined portion 29 make the splashing water when contacting with the wet road surface form an angle to the left and right relative to the traveling direction, thereby reducing the splashing water forward. In this way, the circumferential groove 26 has the basic performance of suppressing the splashing water forward. In the present embodiment, the first inclined portion 28 is inclined to the upper right side. In the present embodiment, the second inclined portion 29 is inclined to the upper left side. In addition, the first inclined portion 28 may be inclined to the upper left side and the second inclined portion 29 may be inclined to the upper right side.

[0065] The circumferential groove 26 further includes a connecting portion 30 connecting the first inclined portion 28 and the second inclined portion 29 adjacent in the tire circumferential direction. The connecting portion 30 includes a first connecting portion 30A located on the first tread end T1 side, and a second connecting portion 30B located on the second tread end T2 side. The first connecting portion 30A is located, for example, at a position closer to the first tread end T1 than the tire equator C. In addition, the second connecting portion 30B is located, for example, at a position closer to the second tread end T2 than the tire equator C.

[0066] The circumferential groove 26 includes a pair of groove walls 31 extending from the tread surface 2a toward the inner side in the tire radial direction. Figure 7 (A) is Figure 6 BB line cross-section diagram. Figure 7 (A) is a groove cross section of each of the plurality of first inclined portions 28 in the tire meridian direction. Figure 7 As shown in (A), in each of the plurality of first inclined portions 28, the pair of groove walls 31 are inclined toward the first tread end T1 side toward the inner side in the tire radial direction relative to the tread normal line n standing at the groove edge 26e. Figure 7 (B) is Figure 6 CC line profile. Figure 7 (B) is a groove cross section of each of the plurality of second inclined portions 29 in the tire meridian direction. Figure 7 As shown in (B), in each of the plurality of second inclined portions 29, a pair of groove walls 31 are respectively inclined toward the second tread end T2 side inwardly in the radial direction of the tire relative to the tread normal line n standing upright at the groove edge 26e. By utilizing the inclination, splashing water during driving on a wet road can be further dispersed to the left and right. In addition, when the wear of the tread portion 2 intensifies, the first inclined portion 28 and the second inclined portion 29 have a portion where the inclination angle relative to the tire circumferential direction becomes larger. As a result, at the end of wear when the groove volume becomes smaller, splashing water can be generated at a larger angle relative to the traveling direction, so splashing water to the front can be suppressed for a long time.

[0067] Figure 8 (A) is Figure 6 DD line profile. Figure 8 (A) is a groove cross section of each of the plurality of connection portions 30 in the tire meridian direction. Figure 8 (A) shows the groove cross section of the first connecting portion 30A in the tire meridian direction. Figure 8 As shown in (A), in the connection portion 30, a pair of groove walls 31 extend at an angle θ of 0 degrees relative to the tread normal line n standing upright at the groove edge 26e. In addition, in the connection portion 30, the pair of groove walls 31 may also extend inward in the radial direction of the tire in a tapered shape ( Figure 8 Such a connection portion 30 allows the water in the first inclined portion 28 and the second inclined portion 29 to flow smoothly, thereby reducing the amount of water splashing.

[0068] Fig. 9 (A) is Figure 6 EE line profile. Fig. 9 (B) is Figure 6 FF line cross-section diagram. Fig. 9 (A) Fig. 9 (B) is a groove cross section of each of the plurality of first inclined portions 28 in the tire meridian direction. Fig. 9 (A) Fig. 9 The cross-section shown in each figure of (B) is the middle portion 28c ( Figure 6 28 (shown) is a cross section closer to the two ends 28e (connecting portion 30) of the first inclined portion 28. Fig.10 (A) is Figure 6 GG line profile. Fig.10 (B) is Figure 6 HH line profile. Fig.10 (A) Fig.10 (B) is a groove cross section of each of the plurality of second inclined portions 29 in the tire meridian direction. Fig.10 (A) Fig.10 The cross-section shown in each figure of (B) is the middle portion 29c ( Figure 6 29 (shown) is a cross section closer to the two ends 29e (connecting portion 30) of the second inclined portion 29.

[0069] In each of the plurality of first inclined portions 28, the angle θ1 ( Figure 7 (A) Fig. 9 (A) Fig. 9 (B) For example, the angle θ2 ( Figure 7 (B) Fig.10 (A) Fig.10(B) For example, the first inclined portion 28 and the second inclined portion 29 are the same from one end 29e (connecting portion 30) side through the middle portion 29c to the other end 29e (connecting portion 30) side. Such first inclined portion 28 and second inclined portion 29 can reduce the change in the inclination angle of the first inclined portion 28 and the second inclined portion 29 relative to the tire circumferential direction at the end of wear, thereby introducing a large amount of water into the circumferential groove 26, thereby suppressing splashing. In this specification, the middle portion 28c of the first inclined portion 28 refers to an area within 1 / 4 of the length Lx of the first inclined portion 28 in the tire circumferential direction, centered at the midpoint of the length direction of the first inclined portion 28. The middle portion 29c of the second inclined portion 29 is also defined in the same manner.

[0070] The angle θ1 of each of the pair of groove walls 31 relative to the tread normal n is at least the largest at the middle portion 28c in the length direction of each of the plurality of first inclined portions 28. In addition, the angle θ2 of each of the pair of groove walls 31 relative to the tread normal n is at least the largest at the middle portion 29c in the length direction of each of the plurality of second inclined portions 29. Such middle portions 28c and middle portions 29c effectively play the role described above. In the present embodiment, the angle θ of each of the pair of groove walls 31 relative to the tread normal n changes between the GG line section and the FF line section adjacent in the tire circumferential direction across the first connecting portion 30A. In addition, in the present embodiment, the angle θ of each of the pair of groove walls 31 relative to the tread normal n changes between the EE line section and the HH line section adjacent in the tire circumferential direction across the second connecting portion 30B.

[0071] The maximum values ​​of the angles θ1 and θ2 of the pair of groove walls 31 relative to the tread normal line n are preferably 5 degrees or more, more preferably 7 degrees or more, and are preferably 15 degrees or less, more preferably 13 degrees or less. Since the maximum values ​​of the angles θ1 and θ2 are 5 degrees or more, splashing water can be generated at a larger angle relative to the traveling direction at the end of wear. Since the maximum values ​​of the angles θ1 and θ2 are 15 degrees or less, the rigidity change of the tread portion 2 near the circumferential groove 26 can be maintained small. In addition, since the maximum values ​​of the angles θ1 and θ2 are 15 degrees or less, damage caused when pulling from a mold (not shown) used to manufacture the tire 1 can be suppressed.

[0072] like Figure 5As shown, each first connection portion 30A is, for example, located at a position closer to the tire equator C side than the inner end 3i of the first inclined groove 3. In other words, in the present embodiment, the inner end 3i of each of the plurality of first inclined grooves 3 is located at a position closer to the first tread end T1 side than the plurality of first connection portions 30A. In addition, each second connection portion 30B is, for example, located at a position closer to the tire equator C side than the inner end 4i of the second inclined groove 4. In other words, in the present embodiment, the inner end 4i of each of the plurality of second inclined grooves 4 is located at a position closer to the second tread end T2 side than the plurality of second connection portions 30B. Thus, an excessive reduction in the rigidity of the tread portion 2 can be suppressed, and thus, the occurrence of uneven wear can be suppressed. In addition, the split position of the mold (not shown) for manufacturing the tire 1 can be arranged between the circumferential groove 26 and the first inclined groove 3 or the second inclined groove 4, and thus, groove bottom cracks (not shown) generated by the intersection of the split position and the groove can be suppressed. Although not particularly limited, the length Ls between the inner end 3i and the first connecting portion 30A (groove edge 26e) in the tire axial direction is preferably 5% or more of the tread half width TW, more preferably 7% or more, and is ideally 15% or less, more preferably 13% or less. In addition, the length Lt between the inner end 4i and the second connecting portion 30B (groove edge 3e) in the tire axial direction is ideally 5% or more of the tread half width TW, more preferably 7% or more, and is ideally 15% or less, more preferably 13% or less.

[0073] In this embodiment, the first inclined portion 28 is adjacent to the inner end 3i of the first inclined groove 3. In other words, the inner end 3i of each of the plurality of first inclined grooves 3 is located adjacent to the plurality of first inclined portions 28 in the tire axial direction. In this embodiment, the inner end 3i is closer to the first inclined portion 28 than to the second inclined portion 29. Figure 7 (A) and Fig. 9 (A) Fig. 9 As shown in (B), the pair of groove walls 31 of the first inclined portion 28 is inclined toward the first tread end T1 side. As a result, the tread 2a of the tread portion 2 between the first inclined portion 28 and the inner end 3i is easy to move, and the load generated in the inner end 3i can be dispersed and reduced, thereby suppressing the occurrence of local wear. In addition, the tread 2a adjacent to the second groove wall 31B on the second tread end T2 side of the first inclined portion 28 is accelerated to wear due to load concentration. Therefore, the difference in the amount of wear at both sides of the first inclined portion 28 in the tire axial direction becomes smaller, and the uneven wear resistance performance can be improved.

[0074] In addition, in the present embodiment, the second inclined portion 29 is adjacent to the inner end 4i of the second inclined groove 4. In other words, the inner end 4i of each of the plurality of second inclined grooves 4 is located adjacent to the plurality of second inclined portions 29 in the tire axial direction. In the present embodiment, the inner end 4i is closer to the second inclined portion 29 than to the first inclined portion 28. Figure 7 (B) Fig.10 (A) Fig.10 As shown in (B), the pair of groove walls 31 of the second inclined portion 29 are inclined toward the second tread end T2 side toward the inner side in the tire radial direction. As described above, the difference in the amount of wear of the tread surfaces 2a on both sides of the second inclined portion 29 is reduced.

[0075] The pair of groove walls 31 of the circumferential groove 26 includes a first groove wall 31A on the first tread end T1 side and a second groove wall 31B on the second tread end T2 side. Figure 7 (A) and Fig. 9 (A) Fig. 9 As shown in (B), in each cross section of the tire meridian of the first inclined portion 28, the angle θ1a of the first groove wall 31A relative to the tread normal line n is preferably the same as the angle θ1b of the second groove wall 31B relative to the tread normal line n (the same absolute value). Figure 7 (B) and Fig.10 (A) Fig.10 As shown in (B), in each cross section of the tire meridian of the second inclined portion 29, the angle θ2a of the first groove wall 31A relative to the tread normal n is preferably the same as the angle θ2b of the second groove wall 31B relative to the tread normal n (the same absolute value). In the cross section of the first inclined portion 28, the same angle means that the absolute value of the difference |θ1a-θ1b| between the angle θ1a of the first groove wall 31A and the angle θ1b of the second groove wall 31B is 0 degrees, including the case where it is 3 degrees or less. In addition, in the cross section of the second inclined portion 29, the absolute value of the difference |θ2a-θ2b| between the angle θ2a of the first groove wall 31A and the angle θ2b of the second groove wall 31B is 0 degrees, including the case where it is 3 degrees or less. In each cross section of the tire meridian of the first inclined portion 28, the first groove wall 31A forms an acute angle with the tread 2a, and the second groove wall 31B forms an obtuse angle with the tread 2a. In each transverse section of the second inclined portion 29 along the tire meridian, the first groove wall 31A forms an obtuse angle with the tread surface 2a, and the second groove wall 31B forms an acute angle with the tread surface 2a.

[0076] like Figure 8As shown in (B), the circumferential groove 26 also includes a groove bottom 33 connected to a pair of groove walls 31. The pair of groove walls 31 extend in a straight line, for example. The straight line is of course extending in a straight line in the groove section in the meridian direction of the tire, including the case where it extends in an arc with a curvature radius of more than 100 mm. The groove bottom 33 includes a groove bottom with the maximum groove depth, and is formed in an arc shape in the present embodiment. Such a groove bottom 33 allows the water in the circumferential groove 26 to flow smoothly, and disperses the stress generated in the groove bottom, thereby suppressing the occurrence of cracks in the groove bottom. The arc shape of course includes an arc with a single curvature radius, and also includes a form formed by an arc forming the groove bottom, and a pair of arcs connected to both ends of the arc and having a smaller curvature radius than the arc of the groove bottom (omitted in the figure). In addition, the arc forming the groove bottom may also be a straight line.

[0077] The groove width W3 of the circumferential groove 26 is, for example, preferably 2% or more of the tread half width TW, more preferably 3% or more, and preferably 7% or less, more preferably 6% or less. The groove depth d3 of the circumferential groove 26 is, for example, preferably 1.1 times or more of the groove width W3, more preferably 1.5 times or more, and preferably 3.5 times or less, more preferably 3.0 times or less.

[0078] like Figure 5 As shown, the small inclined grooves 40 include a plurality of first small inclined grooves 40A extending from the crown region Cr toward the first tread end T1 side, and a plurality of second small inclined grooves 40B extending from the crown region Cr toward the second tread end T2 side. In the present embodiment, the second small inclined grooves 40B have the same shape (line symmetric shape) as the shape of the first small inclined grooves 40A inverted with respect to the tire equator C. Therefore, in this specification, the first small inclined grooves 40A are described as a representative, and the second small inclined grooves 40B are described as having a structure different from the first small inclined grooves 40A.

[0079] The first small inclined groove 40A has an inner end 40i located closer to the first tread end T1 than the inner end 3i of the first inclined groove 3 and opens to the first tread end T1. The first small inclined groove 40A extends toward the rear ground contact side in the tire rotation direction R and toward the first tread end T1.

[0080] Fig.11 40A is a plan view of the first small inclined groove. Fig.11 As shown, the first small inclined groove 40A has a pair of groove edges 40e extending from the inner end 40i to the first tread end T1. The pair of groove edges 40e includes a leading ground contact side small groove edge 43 located on the leading ground contact side in the tire rotation direction R, and a trailing ground contact side small groove edge 44 located on the trailing ground contact side in the tire rotation direction R.

[0081] In the present embodiment, the first small inclined groove 40A includes a first portion 48 whose groove width W4 decreases toward the first tread end T1 side, and a second portion 49 whose groove width W4 increases toward the first tread end T1 until reaching the first tread end T1. The first portion 48 reduces the amount of slippage on the outer side of the tire axial direction where the amount of slippage tends to increase, and reduces the difference in the amount of wear generated on both sides of the groove width direction of the first portion 48, thereby improving the uneven wear resistance. The second portion 49 makes drainage from the first tread end T1 smooth, thereby maintaining wet performance.

[0082] In addition, the tread portion 2 includes at least one small shallow groove 45 connected to the first small inclined groove 40A. The small shallow groove 45 is formed with a groove depth smaller than the groove depth (not shown) of the first small inclined groove 40A. In the present embodiment, the small shallow groove 45 has an opening 46 connected to the first small inclined groove 40A and an end 47 located on the rear ground contact side in the tire rotation direction R. The small shallow groove 45 extends, for example, from the opening 46 toward the rear ground contact side in the tire rotation direction R and toward the first tread end T1 side.

[0083] The tread surface 2a of the tread portion 2 includes an acute angle portion 50 sandwiched by one of the groove edges 40e of the first small inclined groove 40A and one of the pair of groove edges 45e of the small shallow groove 45. In addition, the tread surface 2a of the tread portion 2 includes an obtuse angle portion 51 sandwiched by one of the groove edges 40e of the first small inclined groove 40A and one of the pair of groove edges 45e of the small shallow groove 45. In the present embodiment, the acute angle portion 50 is defined by the groove edge 45e on the rear ground contact side in the tire rotation direction R. In the present embodiment, the obtuse angle portion 51 is defined by the groove edge 45e on the front ground contact side in the tire rotation direction R.

[0084] The small shallow groove 45 includes a first small shallow groove 45A connected to the small groove edge 43 on the front ground contact side, and a second small shallow groove 45B connected to the small groove edge 44 on the rear ground contact side. The first small shallow groove 45A is located closer to the inner end 40i (front ground contact side in the tire rotation direction R) than the second small shallow groove 45B. One end 47t on the rear ground contact side in the tire rotation direction R of the second small shallow groove 45B is located closer to the rear ground contact side in the tire rotation direction R than one end 40b on the rear ground contact side in the tire rotation direction R of the first small inclined groove 40A. Such a second small shallow groove 45B helps to collect a larger amount of water film on the tread portion 2 into the first small inclined groove 40A.

[0085] The land ratio of the tread portion 2 is preferably 75% or more, more preferably 80% or more, and is preferably 95% or less, more preferably 90% or less. Since the land ratio is 75% or more and 95% or less, in this specification, the land ratio is represented by the ratio (A2 / A1) of the area A1 of the virtual tread surface obtained by filling all the grooves of the tread portion 2 to the area A2 of the tread surface 2a.

[0086] As mentioned above, although the particularly preferred embodiment of the present invention has been described in detail, the present invention is not limited to the illustrated embodiment, and can be implemented in various modified forms.

[0087] [Example]

[0088] Based on the specifications in Table 1, we have produced Figure 1 The basic pattern of motorcycle tires. In addition, the wet performance, dry performance, uneven wear resistance and life performance of the test tires were tested. The test method and the general specifications of each test tire are as follows.

[0089] Tire size: 100 / 90-10

[0090] <Wet performance / Dry performance>

[0091] Each test tire was mounted on the front and rear wheels of a motorcycle. The test rider drove the motorcycle on a test course on a wet road surface and a dry asphalt road surface. Both properties were evaluated based on the senses of the test rider and represented by a score with Comparative Example 1 being 100. With respect to both properties, the larger the numerical value, the more excellent it is considered to be.

[0092] Internal pressure: 170kPa (front), 225kPa (rear)

[0093] Motorcycle: A small motorcycle with a displacement of 100cc (scooter)

[0094] <Uneven wear resistance / life performance>

[0095] The test rider drove the motorcycle on a test course of dry asphalt. With regard to the uneven wear resistance performance, after the running, the occurrence of uneven wear was evaluated by the tester's visual inspection. The evaluation was expressed by a score with the occurrence of uneven wear in Comparative Example 1 as 100. In addition, with regard to the life performance, the estimated life of the tire was indexed according to the groove depth of the circumferential groove after the running. With regard to both performances, the larger the numerical value, the better it is considered to be.

[0096] The results are shown in Table 1.

[0097] In Table 1, "A" means that the first inclined groove is inclined toward the rear ground contact side in the tire rotation direction and toward the first tread end, and "B" means that the first inclined groove is inclined toward the rear ground contact side in the tire rotation direction and toward the tire equator.

[0098] In addition, "C" in Table 1 means that the shallow groove is Figure 3 The shape of "D" means that the portion of the shallow groove including one end 12t is an arc.

[0099] Furthermore, "E" in Table 1 means that the shallow groove is Figure 4 The shape of "F" means that the groove depth d2 of the shallow groove is the same from the opening 14 to the one end 12t.

[0100] In addition, the acute angle portion of Example 7 has an arc with a curvature radius of 0.5 mm, and the acute angle portion of Example 8 has an arc with a curvature radius of 1.5 mm.

[0101] [Table 1]

[0102]

[0103] The test results show that the tires of the embodiment have excellent uneven wear resistance while maintaining wet performance compared to the tires of the comparative example. In addition, it is confirmed that the tires of the embodiment have high dry performance and life performance.

[0104] [Note]

[0105] The present invention includes the following aspects.

[0106] [Present invention 1]

[0107] A motorcycle tire comprises a tread portion.

[0108] In the motorcycle tire,

[0109] The tread portion is provided with: a plurality of first inclined grooves opening from a crown region including the tire equator to a first tread end;

[0110] Each of the plurality of first inclined grooves includes a first portion where the groove width decreases from the crown region toward the first tread end, and a second portion where the groove width increases toward the first tread end and reaches the first tread end.

[0111] [Present invention 2]

[0112] According to the motorcycle tire of the first invention, the length of the second portion in the tire axial direction is 5% to 15% of the half width of the tread.

[0113] [Present invention 3]

[0114] According to the motorcycle tire of Invention 1 or 2, the length of the first portion in the tire axial direction is 50% to 75% of the half width of the tread.

[0115] [Present invention 4]

[0116] According to any one of the first to third aspects of the present invention, the tread portion is assigned a tire rotation direction.

[0117] The plurality of first inclined grooves extend toward the first tread end toward the rear ground contact side in the tire rotation direction.

[0118] [Present invention 5]

[0119] In the motorcycle tire according to any one of Inventions 1 to 4, the tread portion includes at least one shallow groove connected to the first inclined groove.

[0120] [Present invention 6]

[0121] According to the motorcycle tire of the fifth aspect of the present invention, the shallow groove includes an opening connected to the first inclined groove.

[0122] The groove depth of the shallow groove decreases as it moves away from the first inclined groove.

[0123] [Present invention 7]

[0124] According to the motorcycle tire of the sixth aspect of the present invention, the shallow groove has a groove width parallel to the opening width of the opening portion.

[0125] The groove width of the shallow groove becomes smaller as it is away from the first inclined groove.

[0126] [Present invention 8]

[0127] According to any one of the present inventions 5 to 7, the motorcycle tire, wherein the shallow groove includes a pair of groove edges connected to the groove edge of the first inclined groove,

[0128] The groove edge of the first inclined groove and each of the pair of groove edges of the shallow groove are connected by a circular arc.

[0129] [Present invention 9]

[0130] According to the motorcycle tire of the eighth aspect of the present invention, the tread surface of the tread portion includes an acute angle portion sandwiched between one of the groove edges of the first inclined groove and one of the pair of groove edges of the shallow groove,

[0131] In the acute angle portion, the radius of curvature of the arc is 0.5 mm to 1.5 mm.

[0132] [Present invention 10]

[0133] According to the motorcycle tire of the present invention 9, the tread portion is designated with respect to the tire rotation direction.

[0134] The pair of groove edges of the shallow groove include: a first groove edge located on the rear ground contact side in the tire rotation direction;

[0135] The first groove edge defines the acute angle portion.

[0136] [Present invention 11]

[0137] According to any one of Inventions 6 to 10 of the present invention, the maximum groove depth of the shallow groove is 0.3 to 0.7 times the groove depth of the first inclined groove at the position of the opening.

[0138] [Present invention 12]

[0139] In the motorcycle tire according to the seventh aspect of the present invention, the opening width is 1 to 4 times the groove width of the first inclined groove at the position of the opening.

[0140] [Present invention 13]

[0141] According to any one of the present inventions 5 to 12, in the motorcycle tire, the tread portion is assigned a tire rotation direction.

[0142] The first inclined groove includes: a front-contact-side inclined groove edge located on the front-contact-side of the tire rotation direction, and a rear-contact-side inclined groove edge located on the rear-contact-side of the tire rotation direction.

[0143] The shallow groove includes: a first shallow groove connected to the inclined groove edge on the first ground contact side, and a second shallow groove connected to the inclined groove edge on the rear ground contact side.

[0144] [Present invention 14]

[0145] According to any one of Inventions 1 to 13 of the present invention, the tread portion is further provided with a plurality of second inclined grooves opening from the crown region toward a second tread end.

[0146] [Present invention 15]

[0147] In the motorcycle tire according to any one of Inventions 1 to 14, a land ratio of the tread portion is 75% to 95%.

Claims

1. A motorcycle tire having a tread portion, characterized in that: In the motorcycle tire, The tread portion is provided with: a plurality of first inclined grooves opening from a crown region including the tire equator to a first tread end; Each of the plurality of first inclined grooves includes a first portion where the groove width decreases from the crown region toward the first tread end, and a second portion where the groove width increases toward the first tread end and reaches the first tread end.

2. The motorcycle tire according to claim 1, characterized in that: The length of the second portion in the tire axial direction is 5% to 15% of the half width of the tread.

3. The motorcycle tire according to claim 1, characterized in that: The length of the first portion in the tire axial direction is 50% to 75% of the half width of the tread.

4. The motorcycle tire according to any one of claims 1 to 3, characterized in that: The tread portion is assigned a tire rotation direction, The plurality of first inclined grooves extend toward the first tread end toward the rear ground contact side in the tire rotation direction.

5. The motorcycle tire according to any one of claims 1 to 3, characterized in that: The tread portion includes at least one shallow groove connected to the first inclined groove.

6. The motorcycle tire according to claim 5, characterized in that: The shallow groove includes an opening connected to the first inclined groove, The groove depth of the shallow groove decreases as it moves away from the first inclined groove.

7. The motorcycle tire according to claim 6, characterized in that: The shallow groove has a groove width parallel to the opening width of the opening portion, The groove width of the shallow groove becomes smaller as it is away from the first inclined groove.

8. The motorcycle tire according to claim 5, characterized in that: The shallow groove comprises a pair of groove edges connected to the groove edge of the first inclined groove, The groove edge of the first inclined groove and each of the pair of groove edges of the shallow groove are connected by a circular arc.

9. The motorcycle tire according to claim 8, characterized in that: The tread surface of the tread portion includes an acute angle portion sandwiched between one of the groove edges of the first inclined groove and one of the pair of groove edges of the shallow groove, In the acute angle portion, the radius of curvature of the arc is 0.5 mm to 1.5 mm.

10. The motorcycle tire according to claim 9, characterized in that: The tread portion is assigned a tire rotation direction, The pair of groove edges of the shallow groove include: a first groove edge located on the rear ground contact side in the tire rotation direction; The first groove edge defines the acute angle portion.

11. The motorcycle tire according to claim 6, characterized in that: The maximum groove depth of the shallow groove is 0.3 to 0.7 times the groove depth of the first inclined groove at the position of the opening.

12. The motorcycle tire according to claim 7, characterized in that: The opening width is 1 to 4 times the groove width of the first inclined groove at the position of the opening.

13. The motorcycle tire according to claim 5, characterized in that: The tread portion is assigned a tire rotation direction, The first inclined groove includes: a front-contact-side inclined groove edge located on the front-contact-side of the tire rotation direction, and a rear-contact-side inclined groove edge located on the rear-contact-side of the tire rotation direction. The shallow groove includes: a first shallow groove connected to the inclined groove edge on the first ground contact side, and a second shallow groove connected to the inclined groove edge on the rear ground contact side.

14. The motorcycle tire according to any one of claims 1 to 3, characterized in that: The tread portion is further provided with a plurality of second inclined grooves opening from the crown region toward a second tread end.

15. The motorcycle tire according to any one of claims 1 to 3, characterized in that: The land ratio of the tread portion is 75% to 95%.

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