CN117984697A - Tyre for motorcycle - Google Patents

Abstract

The present invention provides a motorcycle tire which improves the drivability and uneven wear resistance on a road while maintaining the straight running stability in off-road. A tire for a motorcycle includes a tread portion (2). The tread portion (2) includes a plurality of grooves (8). The plurality of grooves (8) includes a plurality of crown grooves (10), a plurality of intermediate grooves (20), and a plurality of tires shoulder ditch (30) arranged on the tire equator (C). The plurality of crown grooves (10) each have a V-shape curved in a direction protruding toward one side in the tire circumferential direction. The grooves (8) are arranged so that the shortest distance between each groove (8) and the adjacent other groove (8) is 5 to 30% of the tread development half width TWh.

Description

Tyre for motorcycle

Technical Field

The present invention relates to a tire for a motorcycle.

Background

Patent document 1 proposes a tire for a motorcycle in which a tread portion is provided with a first inclined main groove and a second inclined main groove inclined in opposite directions to each other. The tread portion includes a first region surrounded by a first tread end and the first inclined main groove and the second inclined main groove. The first region has a plurality of blocks. The angle of each vertex of each of the plurality of blocks is set to 45 DEG or more.

Patent document 1: japanese patent laid-open No. 2019-111973

In recent years, various motorcycles have been developed which mainly travel on a road and are also capable of traveling off-road to some extent. For example, a tire used for such a motorcycle is required to have straight running stability in an off-road state so as to pass through the tire without falling down in the off-road state. Further, the tire is required to have uneven wear resistance, on the premise of use in both on-road and off-road conditions.

Disclosure of Invention

The present invention has been made in view of such a practical situation, and a main object thereof is to provide a motorcycle tire that improves drivability and uneven wear resistance on a road while maintaining straight running stability in an off-road.

The motorcycle tire of the present invention includes a tread portion including: the tire includes a first tread end and a second tread end, a ground contact surface between the first tread end and the second tread end, a plurality of grooves disposed on the ground contact surface, and a tread development half width, the tread development half width being a distance along the ground contact surface from a tire equator to the first tread end, the plurality of grooves including: a plurality of crown grooves arranged on the tire equator, a plurality of intermediate grooves arranged on the first tread end side of the plurality of crown grooves, and a plurality of tires shoulder ditch arranged on the first tread end side of the plurality of intermediate grooves, wherein each of the plurality of crown grooves has a V-shape curved in a direction protruding toward one side in the tire circumferential direction, and the shortest distance between each of the grooves and the adjacent other groove is 5% to 30% of the half width of the tread.

By adopting the structure, the motorcycle tire can improve the steering performance and the uneven wear resistance on a road while maintaining the straight running stability in off-road.

Drawings

Fig. 1 is a cross-sectional view showing an embodiment of a motorcycle tire according to the present invention.

Fig. 2 is an expanded view of the tread portion of fig. 1.

Fig. 3 is an enlarged view of the plurality of crown grooves of fig. 2.

Fig. 4 is a sectional view taken along line B-B of fig. 2.

Fig. 5 is an enlarged view of a plurality of intermediate grooves.

Fig. 6 is an enlarged view of a plurality of tires shoulder ditch.

Fig. 7 is an expanded view of a tread portion of a tire for a motorcycle of a comparative example.

Description of the reference numerals

Tread portion; ground plane; furrows; crown groove; intermediate furrows; tire shoulder ditch; t1. a first tread end; t2. a second tread end; twh.

Detailed Description

One embodiment of the present invention will be described below with reference to the drawings.

Fig. 1 is a tire meridian cross-sectional view showing a normal state of a motorcycle tire 1 (hereinafter, simply referred to as "tire") according to the present embodiment. Fig. 2 is an expanded view showing a tread pattern of the tread portion 2 of the tire 1. Fig. 1 corresponds to the sectional view taken along line A-A of fig. 2. As shown in fig. 1 and 2, the tire 1 of the present embodiment is a tire for a motorcycle (hereinafter, sometimes referred to as a "two-purpose vehicle") which is mainly used for running on a road and is capable of running off-road to some extent, and is a tire for a rear wheel. However, the tire 1 of the present invention is not limited to such a configuration.

The "normal state" refers to a state in which the tire is assembled to a normal rim and filled with normal internal pressure and no load is applied when the tire for motorcycles is specified in various specifications. When tires of various specifications are not specified, the normal state means a standard use state and a no-load state corresponding to the purpose of use of the tire. In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the above-described normal state. In particular, the dimensions of the grooves are measured in a tread development view in which the ground contact surface of the tread portion 2 in a normal state is developed into a flat surface.

The "regular Rim" is a Rim in which the standard is defined for each tire in a standard system including the standard according to which the tire is based, and is, for example, "standard Rim" in the case of JATMA, "DESIGN RIM" in the case of TRA, and "Measuring Rim" in the case of ETRTO.

The "normal internal pressure" is the air pressure of each specification defined for each tire in the specification system including the specification according to which the tire is based, and is "highest air pressure" in the case of JATMA, the maximum value described in table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and "INFLATION PRESSURE" in the case of ETRTO.

As shown in fig. 1, a tire 1 of the present embodiment includes a tread portion 2, a pair of sidewall portions 3, and a pair of bead portions 4. The sidewall portion 3 is connected to both sides of the tread portion 2 in the tire axial direction. The bead portion 4 is connected to the inner side of the sidewall portion 3 in the tire radial direction. The tread portion 2 includes: a first tread end T1 and a second tread end T2, and a ground contact surface 2s between the first tread end T1 and the second tread end T2.

Preferably, the ground contact surface 2s of the tread portion 2 is convexly curved in an arc shape outward in the tire radial direction so that a sufficient ground contact area can be obtained even in cornering where the camber angle is large. The first tread end T1 and the second tread end T2 are each the ends of a curved ground contact surface 2s, which can be grounded at least when cornering at maximum camber angle.

The tire 1 of the present embodiment includes a carcass 6 extending from one bead portion 4 to the other bead portion 4 through one sidewall portion 3, the tread portion 2, and the other sidewall portion 3. In the tread portion 2, a tread reinforcing layer 7 is provided on the outer side of the carcass 6 in the tire radial direction. The carcass 6 and the tread reinforcing layer 7 may have a known structure.

As shown in fig. 2, the tread portion 2 has a directional pattern, for example, to which a rotation direction R is assigned. The rotation direction R is displayed on the side wall portion 3 (as shown in fig. 1) in characters or symbols, for example. However, the present invention is not limited to such a configuration. In addition, in some drawings of the present specification, the rotation direction R is indicated by an arrow.

The tread portion 2 includes a plurality of grooves 8 arranged on the ground contact surface 2 s. The plurality of grooves 8 includes a plurality of crown grooves 10, a plurality of intermediate grooves 20, and a plurality of tires shoulder ditch. The plurality of crown grooves 10 are arranged on the tire equator C. The plurality of intermediate grooves 20 are arranged closer to the first tread end T1 than the plurality of crown grooves 10. The plurality of tires shoulder ditch are arranged closer to the first tread end T1 than the plurality of intermediate grooves 20.

An enlarged view of a plurality of crown grooves 10 is shown in fig. 3. In fig. 3, the intermediate groove 20 and the shoulder groove 30 are omitted. As shown in fig. 3, each of the plurality of crown grooves 10 has a V-shape curved in a direction protruding toward one side in the tire circumferential direction. Wherein, this structure includes: the crown groove 10 includes a first inclined groove portion 13 and a second inclined groove portion 14 inclined in opposite directions to each other with respect to the tire axial direction, and their lengths (so-called circumferential lengths (PERIPHERY LENGTH) along the groove) are respectively 30% or more of the entire length of the crown groove 10. In a preferred embodiment, the length of each of the first inclined groove portion 13 and the second inclined groove portion 14 is 40% or more of the entire length of the crown groove 10.

As shown in fig. 2, in the present invention, the grooves 8 are arranged such that the shortest distance L1 (shortest distance along the ground contact surface 2 s) between each groove 8 and the adjacent other groove 8 is 5% to 30% of the tread development half width TWh. The tread development half width TWh corresponds to the distance along the ground contact surface 2s from the tire equator C to the first tread end T1.

By adopting the above-described structure, the tire 1 of the present invention can improve the drivability and uneven wear resistance on a road while maintaining the straight running stability in off-road. The reason for this is as follows.

The tread portion 2 of the tire 1 of the present invention is provided with a plurality of crown grooves 10, a plurality of intermediate grooves 20, and a plurality of tires shoulder ditch. These grooves on the one hand improve the off-road performance and on the other hand also make the tread portion 2 uniform in rigidity, contributing to improved handling on roads. In the present invention, since the plurality of crown grooves 10 each have a V-shape curved in a direction protruding toward one side in the tire circumferential direction, the straight running stability in the off-road can be improved.

In the present invention, since the shortest distance L1 is defined to be 5% or more of the tread width TWh, the grooves are not too close to each other, and the drivability and uneven wear resistance on a road are improved. In the present invention, since the shortest distance L1 is set to 30% or less of the tread width TWh, the grooves are not excessively separated from each other, and thus the sufficient off-road performance is exhibited.

Hereinafter, a more detailed configuration of the present embodiment will be described. Each structure described below represents a specific embodiment of the present embodiment. Therefore, it is needless to say that the present invention can exhibit the above-described effects without having the structure described below. Further, even if any of the structures described below is applied to the tire of the present invention having the above-described features, improvement in performance corresponding to each structure can be expected. Further, when several of the structures described below are applied in combination, improvement of the combination performance corresponding to each structure can be expected.

As shown in fig. 2, in a preferred embodiment, the grooves 8 are arranged such that the shortest distance L1 between each groove 8 and the adjacent other grooves 8 is 10% to 25% of the tread development half width TWh. Thus, the straight running stability and the uneven wear resistance of the off-road performance are improved in a balanced manner.

The grooves 8 are each formed with a chamfer 55 at least in part. In the present specification, in the drawing showing the plan view of the groove 8, dots are applied to the chamfer portion 55. In the present embodiment, by forming the chamfer portion 55 in at least a part of each groove 8, uneven wear resistance can be further improved.

Fig. 4 shows a cross-sectional view taken along line B-B of fig. 2 as an example of the chamfer 55. As shown in fig. 4, the groove wall 8w of the groove 8 includes a groove wall body 54 extending outward in the groove depth direction from the groove bottom surface 8d and a chamfer portion 55 extending from the groove wall body 54 to the ground plane 2s in the region where the chamfer portion 55 is formed. In the region where the chamfer 55 is not formed, the groove wall 8w of the groove 8 is formed by a groove wall body 54 extending from the groove bottom surface 8d to the ground plane 2. Hereinafter, the region where the chamfer portion 55 is not formed may be referred to as "non-chamfer portion 56".

The chamfer portion 55 is formed by an inclined surface 55s connected to the ground contact surface 2s of the tread portion 2. The inclined surface 55s of the present embodiment is planar. In another embodiment, the inclined surface 55s may be curved in an arc shape protruding outward in the groove depth direction or curved in an arc shape recessed inward in the groove depth direction. The angle θ1 of the inclined surface 55s with respect to the tread normal is, for example, 40 to 60 ° from the viewpoint of sufficiently improving uneven wear resistance.

As shown in fig. 3, the crown groove 10 includes a plurality of first crown grooves 11 and a plurality of second crown grooves 12. The first crown groove 11 is disposed on the tire equator C so as to be offset toward the first tread end T1 side. The second crown groove 12 is disposed on the tire equator C so as to be offset toward the second tread end T2 side. The first crown groove 11 and the second crown groove 12 have substantially the same structure except for the above points.

The length L2 of the crown groove 10 in the tire axial direction is, for example, 40% to 70% of the tread development half width TWh (as shown in fig. 2, the same applies hereinafter). The length L3 of the crown groove 10 in the tire circumferential direction is smaller than the length L2 of the crown groove 10 in the tire axial direction, for example. Specifically, the length L3 is 60% to 75% of the length L2.

The crown groove 10 includes: a first inclined groove portion 13 disposed on the first tread end T1 side, and a second inclined groove portion 14 disposed on the second tread end T2 side. The first inclined groove portion 13 and the second inclined groove portion 14 are inclined in opposite directions with respect to the tire axial direction. In the present embodiment, the second inclined groove portion 14 of the first crown groove 11 is disposed on the tire equator C, and the first inclined groove portion 13 of the second crown groove 12 is disposed on the tire equator C.

The crown groove 10 of the present embodiment is curved in a direction protruding toward the forward land side in the rotation direction R. Thus, the crown groove 10 includes the apex 10t of the leading side in the rotation direction R. The distance L4 in the tire axial direction from the tire equator C to the apex 10t is, for example, 5% to 20% of the length L2 in the tire axial direction of the crown groove 10. This facilitates a large ground contact pressure to the crown groove 10, thereby further improving off-road performance.

The angle θ2 of the crown groove 10 with respect to the tire circumferential direction is, for example, 40 to 60 °, preferably 45 to 55 °. The angle θ3 between the first inclined groove portion 13 and the second inclined groove portion 14 of the crown groove 10 is set to 90 ° to 110 °. Such a crown groove 10 can maintain straight running stability in an off-road condition while suppressing uneven wear of its edges. When the crown groove 10 includes a zigzag edge, the angle θ2 corresponds to an angle of an imaginary straight line 13v connecting both ends of the first inclined groove portion 13 or an imaginary straight line 14v connecting both ends of the second inclined groove portion 14 with respect to the tire circumferential direction. Similarly, the angle θ3 corresponds to an angle between the virtual straight line 13v and the virtual straight line 14 v.

The first inclined groove portion 13 includes a leading land side groove edge 13a and a trailing land side groove edge 13b. The first landing side groove edge 13a is disposed on the first landing side in the rotation direction R with respect to the groove center line of the first inclined groove portion 13. The trailing edge 13b is disposed on the trailing side in the rotation direction R with respect to the groove center line. The leading edge 13a includes, for example, a linear edge 15 and a serration edge 16. The linear edge 15 extends in a straight line on the tire equator C side. The serration edge 16 extends in a zigzag manner on the first tread end T1 side of the linear edge 15. More specifically, the serration edge 16 includes alternating portions extending at an angle similar to the straight edge 15 and portions extending at a smaller angle than the portions with respect to the tire circumferential direction. The crown groove 10 having such a first inclined groove portion 13 contributes to an even improvement in the straight running stability and uneven wear resistance in off-road.

In a preferred embodiment, when the first inclined groove portion 13 is disposed on the tire equator C, the straight edge 15 crosses the tire equator C. This further improves the uneven wear resistance.

The rear landing side groove edge 13b of the first inclined groove portion 13 extends, for example, linearly. Thus, the rear land side rim 13b can provide a large grip in the tire circumferential direction at the time of off-road running. However, the present invention is not limited to such a configuration.

The first inclined groove portion 13 becomes smaller in groove width from the tire equator C toward the first tread end T1 side. The groove width corresponds to the distance between the two edges formed on the ground plane 2s, and the same applies to the region where the chamfer 55 is disposed. In a preferred embodiment, the groove width of the first inclined groove portion 13 decreases stepwise toward the first tread end T1 side. The first inclined groove portion 13 is easy to discharge mud entering the inside during off-road running, and can continuously exhibit excellent straight running stability.

The second inclined groove portion 14 has substantially the same structure as the first inclined groove portion 13. Therefore, the structure of the first inclined groove portion 13 described above can be applied to the second inclined groove portion 14.

The crown groove 10 includes a first groove wall 10A on the forward landing side in the rotation direction R and a second groove wall 10B on the rearward landing side in the rotation direction R. Preferably, a chamfer 55 is formed on at least a portion of the first trench wall 10A. The chamfer portion 55 of the present embodiment is connected to the linear edge 15 of the first inclined groove portion 13 and the second inclined groove portion 14, for example. This can reliably suppress uneven wear around the crown groove 10.

On the other hand, the serration edge 16 of the leading edge 13a is preferably formed as a non-chamfered portion 56. Thus, a high edge effect can be expected at the serration edge 16, and the straight running stability in the off-road can be further improved.

The second trench wall 10B includes: two inclined portions 26 inclined in opposite directions to each other with respect to the tire axial direction, and a top portion 27 between the two inclined portions 26. In the present embodiment, a chamfer 55 is formed on the top 27. On the other hand, the second groove wall 10B is not formed with the chamfer portion 55 except for the top portion 27, but is formed as a non-chamfer portion 56. Thereby, off-road performance can be improved while suppressing uneven wear at the top periphery.

An enlarged view of the plurality of intermediate grooves 20 is shown in fig. 5. In fig. 5, the crown groove 10 and the shoulder groove 30 are omitted. As shown in fig. 5, the intermediate groove 20 is inclined toward the first tread end T1 from one end toward the other end in the tire circumferential direction. The intermediate groove 20 of the present embodiment is inclined toward the first tread edge T1 side from the forward landing side toward the rearward landing side in the rotation direction R, for example. Thereby, the intermediate groove 20 is inclined in the same direction as the first inclined groove portion 13 (shown in fig. 3) of the crown groove 10.

The intermediate groove 20 is inclined at a relatively small angle with respect to the tire circumferential direction. The maximum angle θ4 of the intermediate groove 20 with respect to the tire circumferential direction is, for example, 5 to 25 °, preferably 10 to 20 °. Such an intermediate groove 20 moderately eases the rigidity of the tread portion 2 in the tire axial direction, and contributes to improvement of the steering performance (in particular, the lightness at the time of tilting). The angle θ4 is measured at the groove center line of the intermediate groove 20. However, when the groove width suddenly changes and the groove center line is bent into a crank shape, the angle θ4 is measured excluding the bent portion. Hereinafter, the same applies to other grooves.

The intermediate groove 20 includes a first intermediate groove 21 and a second intermediate groove 22 arranged in the tire circumferential direction. The tread portion 2 of the present embodiment is provided with a plurality of groove pairs including a first intermediate groove 21 and a second intermediate groove 22 along the tire circumferential direction. In fig. 5, two of the above-described groove pairs are shown. The first intermediate groove 21 is disposed on the leading side in the rotation direction R and on the tire equator C side with respect to the second intermediate groove 22.

In the groove pair, an end 21a on the forward land side (hereinafter, sometimes simply referred to as "forward land side") in the rotation direction R of the first intermediate groove 21 is disposed at a position closest to the tire equator C. The shortest distance L5 in the tire axial direction from the tire equator C to the intermediate groove 20 is 3% to 18% of the tread development half width TWh. Such an arrangement of the intermediate groove 20 contributes to improvement of the drivability on the road. The shortest distance L5 is measured at the end of the center line of the intermediate groove 20.

As shown in fig. 2, in a preferred embodiment, the end 21a of the first intermediate groove 21 on the forward landing side is located on the rearward landing side in the rotation direction R of the first crown groove 11. In a more preferred embodiment, the distance between the apex 10t of the first crown groove 11 and the end 21a of the first intermediate groove 21 on the leading side in the tire axial direction is set to 10% or less of the tread development half width TWh. Thus, the above-described drivability can be further improved.

The first intermediate groove 21 is inclined toward the first tread end T1 from the end portion 21a toward the rear land side in the rotation direction R (hereinafter, may be simply referred to as "rear land side"). Accordingly, it is preferable that the region 21A on the rearmost ground side in the case where the first intermediate groove 21 is three-divided in the longitudinal direction thereof overlap with the virtual region obtained by extending the second crown groove 12 in parallel with the tire axial direction. Thus, the first intermediate groove 21 can compensate for the grip in the tire axial direction during off-road running, and thus the straight running stability in off-road can be improved.

As shown in fig. 5, the distance L6 in the tire axial direction from the tire equator C to the end 21b on the rear land side of the first intermediate groove 21 is 30% to 40% of the tread development half width TWh.

Preferably, the end portion on the first land side of the second intermediate groove 22 overlaps with the virtual area obtained by extending the end portion on the second land side of the first intermediate groove 21 in parallel with the tire circumferential direction. The distance L7 in the tire axial direction from the tire equator C to the end 22a on the land side of the second intermediate groove 22 is 30% to 40% of the tread development half width TWh. This makes it possible to improve the handleability on roads by making the change in the feel at the time of pouring linear.

The second intermediate groove 22 is inclined toward the first tread end T1 from the end 22a toward the rear tread side in the rotation direction R. As a result, as shown in fig. 2, it is preferable that the region 22A at the center of the second intermediate groove 22 in three equal parts in the longitudinal direction thereof overlap with a virtual region obtained by extending the first crown groove 11 in parallel with the tire axial direction. By disposing such grooves, the above-described operability can be further improved.

As shown in fig. 5, the distance L8 in the tire axial direction from the tire equator C to the end 22b on the rear land side of the second intermediate groove 22 is 50% to 70% of the tread development half width TWh. In a preferred embodiment, the rear land side end 22b of the second intermediate groove 22 is preferably located on the rear land side in the rotation direction R than the front land side end 21a of the first intermediate groove 21 adjacent to the rear land side of the second intermediate groove 22. Thereby, the intermediate grooves 20 can provide grip in the tire axial direction by cooperating.

The length L9 of the first intermediate groove 21 in the tire circumferential direction and the length L10 of the second intermediate groove 22 in the tire circumferential direction are, for example, 80% to 120% of the tread development half width TWh. The length L9 of the first intermediate groove 21 is 90% to 120% of the length L10 of the second intermediate groove 22. The first intermediate groove 21 and the second intermediate groove 22 are combined with the V-shaped crown groove 10, whereby the off-road performance and the on-road performance can be improved in a balanced manner.

In the first intermediate groove 21, for example, the groove width becomes larger as it goes toward the rear land side. The first intermediate groove 21 of the present embodiment has a groove width that increases stepwise toward the rear ground side. Thus, the first intermediate groove 21 includes the first groove 41, the second groove 42, and the third groove 43 having different groove widths. The first groove 41 has a constant groove width W1 in the longitudinal direction thereof. The second groove 42 has a constant groove width W2 in the longitudinal direction thereof. The third groove 43 has a constant groove width W3 in the longitudinal direction thereof.

The first groove 41 is located at the position closest to the ground side, and includes the end 21a of the first intermediate groove 21 on the ground side. The second groove 42 is connected to the rear ground side of the first groove 41. The second groove 42 has a groove width W2 larger than the groove width W1 of the first groove 41. Specifically, the groove width W2 of the second groove 42 is 1.50 to 2.50 times the groove width W1 of the first groove 41. In a more preferred embodiment, the maximum depth of the second groove 42 is greater than the maximum depth of the first groove 41. Such first groove 41 and second groove 42 contribute to the improvement of the drainage of the first intermediate groove 21 while maintaining the uneven wear resistance.

The third groove portion 43 is connected to the rear landing side of the second groove portion 42, and includes an end portion 21b of the rear landing side of the first intermediate groove 21. The third groove 43 has a groove width W3 greater than the groove width W1 of the first groove 41 and greater than the groove width W2 of the second groove 42. The groove width W3 of the third groove 43 is 2.0 to 3.0 times the groove width W1 of the first groove 41. In addition, the length of the third groove 43 in the tire circumferential direction is longer than the length of the first groove 41 in the tire circumferential direction and longer than the length of the second groove 42 in the tire circumferential direction. In a preferred embodiment, the maximum depth of the third groove 43 is greater than the maximum depth of the first groove 41. In the present embodiment, the second groove 42 and the third groove 43 have the same depth. Such a third groove 43 contributes to improvement of the wet performance.

In the second intermediate groove 22, for example, the groove width becomes smaller toward the rear land side. The second intermediate groove 22 of the present embodiment has a groove width that decreases stepwise toward the rear ground side. Thus, the second intermediate groove 22 includes the first groove 46 and the second groove 47 having different groove widths. The first groove 46 has a constant groove width W4 in the longitudinal direction thereof. The second groove 47 has a constant groove width W5 in the longitudinal direction thereof.

The first groove portion 46 of the second intermediate groove 22 includes the end portion 22a of the second intermediate groove 22 on the leading ground side. The second groove 47 of the second intermediate groove 22 is connected to the rear ground side of the first groove 46. The second groove 47 has a groove width W5 smaller than the groove width W4 of the first groove 46. Specifically, the groove width W5 of the second groove 47 is 50% to 70% of the groove width W4 of the first groove 46. The length of the second groove 47 (so-called circumferential length in the longitudinal direction) is smaller than the length of the first groove 46. The length of the second groove 47 is 30% to 40% of the length of the first groove 46. In a more preferred form, the maximum depth of the second groove 47 is less than the maximum depth of the first groove 46. The second intermediate groove 22 including such a first groove portion 46 and a second groove portion 47 contributes to a balanced improvement in off-road performance and uneven wear resistance.

The intermediate groove 20 includes an inner groove wall 20A on the tire equator C side and an outer groove wall 20B on the first tread end T1 side. In the present embodiment, a chamfer 55 is formed in at least a part of the outer groove wall 20B. On the other hand, the inner groove wall 20A is entirely formed as the non-chamfered portion 56. Such an intermediate groove 20 contributes to a balanced improvement in uneven wear resistance and off-road performance.

From the viewpoint of further improving the above-described effect, it is preferable that the first intermediate groove 21 has a chamfered portion 55 formed on the entire outer groove wall 20B of the third groove portion 43, and the other regions are configured as non-chamfered portions 56.

From the same point of view, it is preferable that the entire outer groove wall 20B of the second intermediate groove 22 is formed as the chamfer 55.

An enlarged view of a plurality of tires shoulder ditch is shown in fig. 6. In fig. 6, the crown groove 10 and the intermediate groove 20 are omitted. As shown in fig. 6, the shoulder groove 30 is inclined toward the first tread end T1 from one end toward the other end in the tire circumferential direction. The shoulder groove 30 of the present embodiment is inclined toward the first tread end T1 side from the first land side toward the second land side in the rotation direction R, for example. Thus, the shoulder groove 30 is inclined with respect to the tire circumferential direction in the same direction as the intermediate groove 20 (shown in fig. 5). Such shoulder grooves 30 contribute to improvement in uneven wear resistance.

It is preferable that the maximum angle θ5 of the shoulder groove 30 with respect to the tire circumferential direction is larger than the angle θ4 of the intermediate groove 20 with respect to the tire circumferential direction (as shown in fig. 5). The angle θ5 of the shoulder groove 30 is similar to the angle θ2 of the crown groove 10 with respect to the tire circumferential direction (as shown in fig. 3), and the difference between the angles is preferably 10 ° or less. Specifically, the angle θ5 of the shoulder groove 30 is, for example, 35 to 55 °, preferably 40 to 50 °. Such a shoulder groove 30 is likely to converge and fall down during cornering, and improves drivability.

The tire shoulder ditch includes a first tire shoulder ditch, a second tire shoulder ditch, and a third tire shoulder ditch, which are arranged in the tire circumferential direction. The tread portion 2 of the present embodiment is provided with a plurality of groove groups each including a first tire shoulder ditch, a second tire shoulder ditch, and a third tire shoulder ditch 33 along the tire circumferential direction. In fig. 6, two of the above-described groove groups are shown. In one groove group, the first tire shoulder ditch is disposed at a position closest to the ground contact side in the rotation direction R. The third tire shoulder ditch is disposed at a position closest to the rear ground in the rotation direction R. The second tire shoulder ditch is disposed between the first tire shoulder ditch 31 and the third tire shoulder ditch.

As shown in fig. 2, the first tire shoulder ditch is adjacent to the first tread end T1 side of the first intermediate groove 21. Specifically, the first tire shoulder ditch overlaps with a virtual region obtained by extending the third groove portion 43 of the first intermediate groove 21 in parallel toward the first tread end T1. Thus, the uneven wear resistance can be further improved.

From the same point of view, the second tire shoulder ditch and the third tire shoulder ditch are adjacent to the first tread end T1 side of the second intermediate groove 22, respectively. Specifically, the second tire shoulder ditch overlaps with a virtual region obtained by extending the first groove portion 46 of the second intermediate groove 22 in parallel toward the first tread end T1. The third tire shoulder ditch overlaps with a virtual region in which the second groove portion 47 of the second intermediate groove 22 extends parallel to the first tread end T1.

As shown in fig. 6, the length of each shoulder groove 30 included in one groove group in the tire axial direction is smaller as the shoulder groove is located on the rear ground side. That is, the length L11 of the first tire shoulder ditch in the tire axial direction is largest in one groove group. The length L13 of the third tire shoulder ditch in the tire axial direction is smallest in one groove group. The length L12 of the second tire shoulder ditch in the tire axial direction is smaller than the length L11 of the first tire shoulder ditch 31 and larger than the length L13 of the third tire shoulder ditch 33. Such groove sets help to improve uneven wear resistance and road performance in a balanced manner.

The length L11 of the first tire shoulder ditch in the tire axial direction is, for example, 40% to 60% of the tread development half width TWh. The distance L14 in the tire axial direction from the tire equator C to the end 31a of the first tire shoulder ditch on the tire equator C side is, for example, 40% to 60% of the tread development half width TWh. Thus, the shortest distance in the tire axial direction from the tire equator C to the shoulder groove 30 is 40% to 60% of the tread development half width TWh. Such a first tire shoulder ditch can improve the wet performance and handling performance.

From the same point of view, the length L12 of the second tire shoulder ditch in the tire axial direction is, for example, 40% to 50% of the tread development half width TWh. The distance L15 in the tire axial direction from the tire equator C to the end 32a of the second tire shoulder ditch on the tire equator C side is, for example, 50% to 60% of the tread development half width TWh. Similarly, the length L13 of the third tire shoulder ditch in the tire axial direction is, for example, 20% to 30% of the tread development half width TWh. The distance L16 in the tire axial direction from the tire equator C to the end 33a of the third tire shoulder ditch on the tire equator C side is, for example, 70% to 80% of the tread development half width TWh.

As shown in fig. 2, the distance L17 in the tire axial direction from the first tread end T1 to the first tread end T1-side end of each shoulder groove 30 is, for example, 10% or less, preferably 5% or less of the tread development half width TWh. Thus, the yaw performance is improved.

As shown in fig. 6, each shoulder groove 30 includes an inner groove portion 36 on the tire equator C side and an outer groove portion 37 on the first tread end T1 side. The length L18 of the inner groove 36 in the tire axial direction is 40% to 60% of the length of the shoulder groove 30 in the tire axial direction. The inner groove 36 and the outer groove 37 each have a constant groove width. The groove width W7 of the outer groove 37 is smaller than the groove width W6 of the inner groove 36. The groove width W7 of the outer groove 37 is 70% to 80% of the groove width W6 of the inner groove 36. This improves stability during cornering with a large camber angle.

The tire shoulder ditch includes a first groove wall 30A on the forward landing side in the rotation direction R and a second groove wall 30B on the rearward landing side in the rotation direction R. The shoulder groove 30 of the present embodiment has a chamfer 55 formed in at least a part of the first groove wall 30A. In a preferred embodiment, the first groove wall 30A forms a chamfer 55 in the entire portion constituting the inner groove 36. On the other hand, the other regions are configured as non-chamfered portions 56. Such shoulder grooves 30 improve road performance while maintaining uneven wear resistance.

As shown in fig. 2, the land ratio of the tread portion 2 is, for example, 80% to 90%. Thus, both on-road and off-road performance are improved in balance. The "land ratio" refers to the ratio Sb/Sa of the actual total ground contact area Sb to the total area Sa of the virtual ground contact areas obtained by filling all the grooves of the ground contact surface 2s disposed on the tread portion 2.

The same intermediate groove 20 and shoulder groove 30 as those provided between the tire equator C and the first tread end T1 are provided between the tire equator C and the second tread end T2. The intermediate groove 20 and the shoulder groove 30 provided between the tire equator C and the second tread end T2 also have the above-described features.

The tire 1 of the present embodiment is for a rear wheel, and the rotation direction R is upward in fig. 2. On the other hand, the tread pattern shown in fig. 2 may also be used for a tire for a front wheel. In this case, the structure of each groove 8 remains unchanged in fig. 2, and the designated rotation direction R is opposite (downward) to that of fig. 2. Thus, the wet performance on the road is improved.

In the case of a front wheel tire, there is a tendency that a large load acts on each groove during braking. Therefore, in the case of the front wheel tire, it is preferable that the crown groove 10 includes a first groove wall on the forward landing side in the rotation direction R and a second groove wall on the rearward landing side in the rotation direction R, and a chamfer (reference numeral or the like is omitted) is formed in at least a part of the second groove wall. This can suppress uneven wear around the crown groove 10 of the front wheel tire.

While the motorcycle tire according to the embodiment of the present invention has been described in detail above, the present invention is not limited to the above-described specific embodiment, and may be implemented in various forms.

Examples (example)

As a tire for a rear wheel of the example, a tire having a tread pattern shown in fig. 2 was produced. In addition, as a tire for a front wheel of the example, a tire having a tread pattern shown in fig. 2 and having a specified rotation direction R opposite to that of fig. 2 was produced.

As a tire for a rear wheel of the comparative example, a tire having a tread pattern shown in fig. 7 was produced. As a tire for a front wheel of the comparative example, a tire having a tread pattern shown in fig. 7 and having a specified rotation direction R opposite to that of fig. 7 was produced.

The tread pattern of the tire of the comparative example shown in fig. 7 is configured such that the crown groove a is not V-shaped and the shortest distance L1a between the crown groove a and the intermediate groove b is set to about 2% of the tread development half width TWh. In addition, each groove does not include a chamfer portion. The tires of the comparative examples were substantially the same as those of the examples except for the above matters.

The rear tires were each constructed to have a size of 150/70R17, a mounting rim of MT4.00, and an inner pressure of 280kPa. The tires for front wheels were each constructed so that the tire size was 110/80R19, the mounting rim was MT2.50, and the tire internal pressure was 225kPa.

Each of the test tires was mounted on a dual-purpose vehicle having an exhaust capacity of 650cc, and the straight running stability in off-road, the handling performance on road, and the uneven wear resistance were tested. The test method is as follows.

< Straight-on stability in Cross-country >)

The straight running stability when running off road using the above-described test tire was evaluated by the driver's sense. The results are shown as scores of 100 in comparative examples, and the larger the numerical value is, the more excellent the straight running stability is.

< Drivability on Highway >

The drivability of the test vehicle on road was evaluated by the driver's sense. The results are expressed as scores of 100 for the comparative examples, and the larger the numerical value is, the more excellent the above-mentioned drivability is.

< Uneven wear resistance >

The test vehicle was run for 5000km on a road surface, and the difference in wear was measured by comparing the groove with the largest wear and the groove with the smallest wear for the tire for the rear wheel. The results were evaluated by the reciprocal of the difference between the abrasion amounts, and were expressed as an index of 100 in the comparative example. The larger the value, the smaller the difference between the abrasion amounts, and the more excellent the uneven wear resistance.

The results of the test are shown in table 1.

TABLE 1

Results of the test: the tires of examples 1 to 7 maintained the straight running stability in the off-road at 98 to 108 minutes, and the steering performance on the road at 103 to 115 minutes, and the uneven wear resistance at 103 to 110 minutes. That is, it was confirmed that the tires of examples 1 to 7 improved the drivability and uneven wear resistance on roads while maintaining the straight running stability in off-road.

In addition, tires having the angle θ1 of the inclined surface of the chamfer portion and the land ratio of the tread portion were produced and the straight running stability in the off-road, the handling performance on the road and the uneven wear resistance were tested in the same manner.

The results of the test are shown in table 2.

TABLE 2

Results of the test: the tires of examples 8 to 12 maintained straight running stability in the off road at 97 to 102 minutes, and steering performance on the road at 105 to 115 minutes, and uneven wear resistance at 110 to 115 minutes. That is, it was confirmed that the tires of examples 8 to 12 improved the drivability and uneven wear resistance on roads while maintaining the straight running stability in off-road.

[ Additionally remembered ]

The present invention includes the following aspects.

[ Invention 1]

A tire for a motorcycle, comprising a tread portion, wherein,

The tread portion includes: a first tread end and a second tread end, a ground contact surface between the first tread end and the second tread end, a plurality of grooves arranged on the ground contact surface, and a tread development half width, which is a distance along the ground contact surface from the tire equator to the first tread end,

The plurality of grooves includes: a plurality of crown grooves arranged on the tire equator, a plurality of intermediate grooves arranged on the first tread end side of the plurality of crown grooves, and a plurality of tires shoulder ditch arranged on the first tread end side of the plurality of intermediate grooves,

The plurality of crown grooves are each formed in a V-shape curved in a direction protruding toward one side in the tire circumferential direction,

The grooves are arranged so that the shortest distance between each groove and the adjacent other groove is 5 to 30% of the half width of the tread.

[ Invention 2]

The tire for a motorcycle according to the invention 1, wherein,

In the cross section of the tread portion, the contact surface is curved in an arc shape so as to protrude outward in the tire radial direction.

[ Invention 3]

The tire for a motorcycle according to the present invention 1 or 2, wherein,

The shortest distance in the tire axial direction from the tire equator to the intermediate groove is 3 to 18% of the half width of the tread development.

[ Invention 4]

A tire for a motorcycle according to any one of the present invention 1 to 3, wherein,

The shortest distance in the tire axial direction from the tire equator to the shoulder groove is 40% to 60% of the half width of the tread development.

[ Invention 5]

The tire for a motorcycle according to any one of the present invention 1 to 4, wherein,

The crown groove has an angle of 40 to 60 DEG with respect to the tire circumferential direction.

[ Invention 6]

The tire for a motorcycle according to any one of the present invention 1 to 5, wherein,

The intermediate groove is inclined toward the first tread end side from one end portion toward the other end portion in the tire circumferential direction.

[ Invention 7]

The tire for a motorcycle according to claim 6, wherein,

The maximum angle of the intermediate groove with respect to the tire circumferential direction is 5 to 25 °.

[ Invention 8]

The tire for a motorcycle according to the present invention 6 or 7, wherein,

The shoulder groove is inclined in the same direction as the intermediate groove with respect to the tire circumferential direction.

[ Invention 9]

The tire for a motorcycle according to claim 8, wherein,

The maximum angle of the shoulder groove with respect to the tire circumferential direction is 35 to 55 degrees.

[ Invention 10]

The tire for a motorcycle according to any one of the present invention 1 to 9, wherein,

The grooves are each formed with a chamfer at least in part.

[ Invention 11]

The tire for a motorcycle according to the present invention 10, wherein,

The motorcycle tire is a tire for a front wheel, a rotation direction of the tire is specified,

The crown groove includes a first groove wall on a first landing side in the rotation direction and a second groove wall on a second landing side in the rotation direction,

The chamfer is formed on at least a part of the second groove wall.

[ Invention 12]

The tire for a motorcycle according to the present invention 10, wherein,

The motorcycle tire is a tire for a rear wheel, a rotation direction of the tire is specified,

The crown groove includes a first groove wall on a first landing side in the rotation direction and a second groove wall on a second landing side in the rotation direction,

The chamfer is formed on at least a part of the first groove wall.

[ Invention 13]

The tire for a motorcycle according to any one of the present invention 10 to 12, wherein,

The chamfer part is formed by an inclined surface connected with the ground plane,

The inclined surface has an angle of 40 to 60 DEG with respect to the normal line of the tread.

[ Invention 14]

The tire for a motorcycle according to the present invention 10, wherein,

The direction of rotation of the tire is specified,

The crown groove is curved in a direction protruding toward the forward landing side in the rotation direction and includes a first groove wall on the forward landing side in the rotation direction and a second groove wall on the rearward landing side in the rotation direction,

The second trench wall includes: two inclined portions inclined in opposite directions relative to the axial direction of the tire, and a top portion between the two inclined portions,

The chamfer is formed on the top.

[ Invention 15]

The tire for a motorcycle according to any one of claims 10 to 14, wherein,

The intermediate groove includes an inner groove wall on the tire equatorial side and an outer groove wall on the first tread end side,

The chamfer is formed on at least a part of the outer groove wall.

[ Invention 16]

The tire for a motorcycle according to any one of the present invention 10 to 15, wherein,

The direction of rotation of the tire is specified,

The shoulder groove includes a first groove wall on a first land side in the rotation direction and a second groove wall on a second land side in the rotation direction,

The chamfer is formed on at least a part of the first groove wall.

Claims (16)

1. A tire for a motorcycle, comprising a tread portion, wherein,

The tread portion includes: a first tread end and a second tread end, a ground contact surface between the first tread end and the second tread end, a plurality of grooves arranged on the ground contact surface, and a tread development half width, which is a distance along the ground contact surface from a tire equator to the first tread end,

The plurality of grooves includes: a plurality of crown grooves arranged on the tire equator, a plurality of intermediate grooves arranged on the first tread end side of the plurality of crown grooves, and a plurality of tires shoulder ditch arranged on the first tread end side of the plurality of intermediate grooves,

The plurality of crown grooves are each in a V-shape curved in a direction protruding toward one side in the tire circumferential direction,

The grooves are respectively configured such that the shortest distance between each groove and the adjacent other grooves is 5% -30% of the half width of the tread.

2. A tire for a motorcycle according to claim 1, wherein,

In the cross section of the tread portion, the contact surface is curved in an arc shape so as to protrude outward in the tire radial direction.

3. A tire for motorcycles according to claim 1 or 2, wherein,

The shortest distance in the tire axial direction from the tire equator to the intermediate groove is 3 to 18% of the half width of the tread development.

4. A tire for motorcycles as claimed in any one of claims 1 to 3, wherein,

The shortest distance in the tire axial direction from the tire equator to the shoulder groove is 40% to 60% of the half width of the tread development.

5. A tire for motorcycles according to any one of claims 1 to 4, wherein,

The crown groove has an angle of 40-60 DEG with respect to the tire circumferential direction.

6. A tire for motorcycles according to any one of claims 1 to 5, wherein,

The intermediate groove is inclined toward the first tread end side from one end toward the other end in the tire circumferential direction.

7. A tire for a motorcycle according to claim 6, wherein,

The maximum angle of the intermediate groove with respect to the tire circumferential direction is 5 to 25 °.

8. A tire for motorcycles as claimed in claim 6 or 7, wherein,

The shoulder groove is inclined in the same direction as the intermediate groove with respect to the tire circumferential direction.

9. A tire for a motorcycle according to claim 8, wherein,

The maximum angle of the shoulder groove relative to the tire circumferential direction is 35-55 degrees.

10. Tyre for motorcycles according to any one of claims 1 to 9, wherein,

The grooves are each formed with a chamfer at least in part.

11. A tire for a motorcycle according to claim 10, wherein,

The tire for a motorcycle is a tire for a front wheel, a rotation direction of the tire is specified,

The crown groove comprises a first groove wall on the first landing side of the rotation direction and a second groove wall on the second landing side of the rotation direction,

The chamfer is formed on at least a portion of the second groove wall.

12. A tire for a motorcycle according to claim 10, wherein,

The tire for a motorcycle is a tire for a rear wheel, a rotation direction of the tire is specified,

The crown groove comprises a first groove wall on the first landing side of the rotation direction and a second groove wall on the second landing side of the rotation direction,

The chamfer is formed on at least a portion of the first groove wall.

13. Tyre for motorcycles according to any one of claims 10 to 12, wherein,

The chamfer portion is formed by an inclined surface connected to the ground plane,

The inclined surface has an angle of 40-60 DEG relative to the normal line of the tread.

14. A tire for a motorcycle according to claim 10, wherein,

The direction of rotation of the tire is specified,

The crown groove is curved in a direction protruding toward the leading side of the rotation direction and includes a first groove wall on the leading side of the rotation direction and a second groove wall on the trailing side of the rotation direction,

The second trench wall includes: two inclined portions inclined in opposite directions to each other with respect to the tire axial direction, and a top portion between the two inclined portions,

The chamfer is formed on the top.

15. Tyre for motorcycles according to any one of claims 10 to 14, wherein,

The intermediate groove includes an inner groove wall on the tire equatorial side and an outer groove wall on the first tread end side,

The chamfer is formed on at least a portion of the outer groove wall.

16. Tyre for motorcycles according to any one of claims 10 to 15, wherein,

The direction of rotation of the tire is specified,

The shoulder groove includes a first groove wall on a first land side of the rotation direction and a second groove wall on a second land side of the rotation direction,

The chamfer is formed on at least a portion of the first groove wall.