JP4989753B2 - Motorcycle tires - Google Patents

Description

  The present invention relates to a motorcycle tire having improved rolling resistance performance without deteriorating uneven wear resistance performance, steering stability performance, and wet performance by improving the groove shape of a crown inclined groove.

  In recent years, motorcycle tires with reduced rolling resistance have been demanded in order to improve fuel efficiency in relation to global environmental problems.

  For example, in order to reduce the rolling resistance of a tire, it has been proposed to reduce the amount of rubber heat generated by reducing the amount of rubber in the tread portion. However, such tires tend to have low tread rigidity and tend to deteriorate uneven wear resistance and steering stability.

  On the other hand, a tire provided with a straight groove extending in the tire circumferential direction in the tread portion is also effective in reducing rolling resistance. However, such a tire has a problem that, when the groove width is increased in order to improve the wet performance, the tread rigidity is lowered, and the uneven wear resistance performance and the steering stability performance are deteriorated. Related technologies include the following.

JP 2007-131112 A

  The present invention has been devised in view of the above problems, and the groove shape of the crown inclined groove extending over the tire equator and extending at an angle of 20 degrees or less with respect to the tire circumferential direction and the land ratio of the center region The main object is to provide a tire for a motorcycle that improves rolling resistance performance without impairing uneven wear resistance performance, steering stability performance, and wet performance.

  The invention according to claim 1 of the present invention is a motorcycle tire comprising a tread portion having a crown inclined groove extending over the tire equator and extending at an angle of 20 degrees or less with respect to the tire circumferential direction. The land ratio of the center region, which is a region of 30% of the tread width centering on the center, is 75 to 95%, and the groove wall surface of the crown inclined groove has a main wall portion extending from the groove bottom portion to the outside in the tire radial direction, A chamfered portion that is chamfered with an arc or a straight line between the main wall portion and the tread surface of the tread portion, is assembled to a normal rim and filled with a normal internal pressure, and is loaded with a normal load at a camber angle of 0 degrees. The ground contact surface of the tread portion has a ground contact width in the tire axial direction of 30 to 65% of the ground contact length in the tire circumferential direction in a normal load application state in which the ground contact is made on a flat surface.

  The invention according to claim 2 is the pneumatic tire according to claim 1, wherein a width of the chamfered portion is 0.3 to 0.5 times a groove width of the crown inclined groove.

  The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the crown inclined groove has a tire axial direction component of 20 to 60% of the contact width.

  According to a fourth aspect of the present invention, the crown inclined groove extends in a zigzag shape continuously in the tire circumferential direction, and is folded at the outer end in the tire axial direction of the crown inclined groove and spaced apart in the tire circumferential direction. 2. A bent portion and an inclined portion that connects between the bent portions adjacent to each other in the tire circumferential direction, and a groove depth of the bent portion is smaller than a groove depth at an intermediate position in the length direction of the inclined portion. The motorcycle tire according to any one of 1 to 3.

  The invention according to claim 5 is the motorcycle according to any one of claims 1 to 4, wherein the groove depth of the bent portion is 1.5 to 5.0 times the chamfer depth of the chamfered portion. Tire.

  The invention according to claim 6 is the motorcycle tire according to claim 4 or 5, wherein the depth of the crown inclined groove gradually increases from the bent portion toward the intermediate position of the inclined portion.

  According to a seventh aspect of the present invention, the width and / or chamfering depth of the chamfered portion at the bent portion is larger than the width and / or chamfered depth of the chamfered portion at the intermediate position of the inclined portion. The motorcycle tire according to any one of the above.

  The motorcycle tire according to the present invention includes a crown inclined groove extending over the tire equator and extending at an angle of 20 degrees or less with respect to the tire circumferential direction, and is an area of 30% of the tread width centering on the tire equator. The land ratio of the center region is 75 to 95%. Such motorcycle tires expand the ground contact area and disperse stress within a range that does not impair driving stability, and reduce distortion of the tread rubber, thereby suppressing heat generation in the center region and improving rolling resistance performance. . Furthermore, this type of crown inclined groove can collect a water film on the road surface in a wider range than a straight groove, and therefore has good wet performance.

  Further, in the motorcycle tire of the present invention, the groove wall surface of the crown inclined groove has an arc or straight line between the main wall portion extending from the groove bottom portion to the outer side in the tire radial direction and the tread surface of the main wall portion. And a chamfered portion to be chamfered. Since the crown inclined groove provided with such a chamfered portion can secure a large groove volume, the wet performance is improved. In addition, since the rigidity of the groove edge portion of the crown inclined groove is increased, the deformation amount (travel deformation amount of the tread rubber) during travel of the groove edge portion is suppressed. Therefore, the rolling resistance performance of the motorcycle tire of the present invention is further improved.

  In the normal load application state, the contact surface of the tread portion has a contact width in the tire axial direction limited to 30 to 65% of the contact length in the tire circumferential direction. In such a tire for a motorcycle, the contact width is ensured with an optimum size, so that the rigidity of the tread is maintained. Therefore, uneven wear resistance and steering stability are maintained in a well-balanced manner.

FIG. 3 is a cross-sectional view showing the motorcycle tire of the present embodiment (showing the AA portion in FIG. 2). FIG. 2 is a development view of the tread portion of FIG. 1. (A) is a top view which shows the contact surface which the tire for motorcycles of this embodiment grounded to the road surface, (b) is sectional drawing parallel to the tire equator surface which shows the state of (a). It is sectional drawing which shows the groove wall surface of the crown inclination groove | channel where a chamfer part is a straight line. FIG. 3 is a partially enlarged view of FIG. 2. 2A is a sectional view taken along line BB in FIG. 2, FIG. 2B is a sectional view taken along line CC in FIG. 2, and FIG. 3C is a sectional view taken along line DD in FIG. It is sectional drawing which shows the groove | channel wall surface of the crown inclination groove | channel where a chamfering part is a circular arc. (A)-(c) is an expanded view of the tread part of other embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a motorcycle tire (hereinafter, simply referred to as “tire”) 1 according to the present embodiment is assembled to a regular rim (not shown) and filled with a regular internal pressure, and is unloaded. It is sectional drawing of a normal state. Further, the motorcycle tire 1 of the present embodiment is a motorcycle tire in which the rotation direction is specified. The tire rotation direction N is displayed by characters and / or symbols on, for example, a sidewall portion (not shown). Unless otherwise specified, the dimensions and the like of each part of the tire are values measured in this normal state.

  Here, the “regular rim” is a rim defined for each tire in the standard system including the standard on which the tire is based, and is “standard rim” for JATMA, and “for TRA” “Design Rim” or “Measuring Rim” for ETRTO. In addition, the “regular internal pressure” is an air pressure determined by each standard for each tire in the standard system including the standard on which the tire is based. TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES "Maximum value", ETRTO, "INFLATION PRESSURE".

  As shown in FIG. 1, the motorcycle tire 1 of the present embodiment includes a carcass 6 that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and the outer side in the radial direction of the carcass 6. And a tread reinforcing layer 7 disposed inside the tread portion 2.

  The carcass 6 is constituted by, for example, one carcass ply 6A. The carcass ply 6A includes a main body portion 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 embedded in the bead portion 4, and a folded portion 6b connected to the main body portion 6a and folded around the bead core 5. including.

  Further, the carcass ply 6A has a carcass cord that is arranged to be inclined with respect to the tire equator C at an angle of, for example, 75 to 90 degrees, more preferably 80 to 90 degrees. As the carcass cord, for example, an organic fiber cord such as nylon, polyester, or rayon is suitably employed. A bead apex 8 made of hard rubber is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A.

  The tread reinforcing layer 7 includes, for example, at least one or more belt cords arranged at a small angle of, for example, 5 to 40 degrees with respect to the tire equator C. The belt plies 7A and 7B are configured to overlap each other so that the belt cords cross each other. For the belt cord, for example, a steel cord, aramid, or rayon is suitably employed.

  Further, in the tire 1, the tread outer surface 2S between the tread ends 2t and 2t of the tread portion 2 is convex outward in the tire radial direction so that a sufficient contact area can be obtained even when turning with a camber angle. While extending in a circular arc shape, the tread width TW, which is the distance in the tire axial direction between the tread ends 2t and 2t, forms the maximum tire width.

  As shown in FIGS. 1 and 2, the tread portion 2 of the present embodiment includes a center region Cr that is a region of 30% of the tread width TW around the tire equator C, and the center region Cr in the tire axial direction. Virtually divided into a shoulder region Sh which is an outer region.

  Further, as shown in FIG. 2, the tread portion 2 of the present embodiment is formed in the crown inclined groove 11 extending over the tire equator C and the shoulder region Sh and on the rear arrival side of the tire rotation direction N. And a shoulder groove 19 extending toward the tread end 2t. Note that “straddling the tire equator C” means that at least a part of the crown inclined groove 11 intersects the tire equator C.

  The crown inclined groove 11 needs to be limited to an angle of 20 degrees or less with respect to the tire circumferential direction. When the angle θ1 exceeds 20 degrees, the rigidity of the tread portion 2 cannot be secured, the steering stability performance and the uneven wear resistance performance are deteriorated, and the distortion of the tread rubber cannot be suppressed, and the rolling resistance performance is deteriorated. Conversely, if the angle θ1 is close to 0 degrees, the water film on the road surface cannot be accumulated, so that the wet performance deteriorates. From such a viewpoint, the angle θ1 is preferably 15 degrees or less, more preferably 10 degrees or less, and preferably 2 degrees or more, more preferably 4 degrees or more.

  Further, the crown inclined groove 11 of the present embodiment is provided only in the center region Cr. Thereby, it is easy to ensure the steering stability performance when traveling straight ahead.

  The land ratio of the center region Cr is set to 75 to 95%. That is, when the land ratio is less than 75%, the rigidity of the center region Cr to which the greatest ground pressure acts during straight traveling decreases, and the steering stability performance and uneven wear resistance performance deteriorate. On the other hand, if the land ratio exceeds 95%, the amount of rubber in the center region Cr cannot be reduced, and the heat generation amount increases, so that the rolling resistance performance deteriorates. From such a viewpoint, the land ratio is preferably 80% or more, and preferably 90% or less.

  As shown in FIG. 3A, the contact surface 10 of the tread portion 2 of the present embodiment is formed such that the contact width W1 in the tire axial direction is 30 to 65% of the contact length L1 in the tire circumferential direction. Is done. That is, if the ratio W1 / L1 between the ground contact width W1 and the ground contact length L1 is less than 30%, the lateral rigidity of the tread portion 2 becomes too small, and steering stability performance and uneven wear resistance performance during straight traveling are reduced. It deteriorates and the distortion of the tread rubber cannot be sufficiently suppressed. On the other hand, if the ratio W1 / L1 exceeds 65%, the contact width W1 becomes excessively large and the camber angle cannot be easily given, and as a result, the steering stability during turning is deteriorated. From such a viewpoint, the ratio W1 / L1 is preferably 35% or more, more preferably 40% or more, and preferably 60% or less, more preferably 55% or less.

    Here, the ground contact surface 10 has a tread outer surface 2S and a plane S (FIG. 3 (b)) in a normal load applied state in which the normal load is applied to the tire 1 in the normal state and is grounded to a plane with a camber angle of 0 degrees. The surface is in contact with

  The “regular load” is a load determined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum value described in “LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES”, or “LOAD CAPACITY” in the case of ETRTO. In addition, when neither standard exists, a tire manufacturer's recommendation value is applied.

  In order to obtain such a contact surface 10 of the tread portion 2, for example, the radius of curvature TR (shown in FIG. 1) of the center region Cr of the tread portion 2 is made larger than that of a conventional motorcycle tire. Can be achieved. Specifically, the radius of curvature TR of the center region Cr is preferably 0.6 times or more, more preferably 0.65 times or more of the tread width TW. Note that when the radius of curvature TR is excessively large, it is difficult to turn and the steering stability tends to deteriorate. From such a viewpoint, the radius of curvature TR is preferably 0.75 times or less, more preferably 0.7 times or less.

  4, the groove wall surface 11n of the crown inclined groove 11 includes a groove bottom portion 12, a main wall portion 13 extending outward in the tire radial direction from the groove bottom portion 12, and the main wall portion 13 and the tread. The chamfered portion 14 is formed by chamfering between the tread surface 2n of the portion 2 and extending. Since the motorcycle tire 1 provided with such a chamfered portion 14 can secure a large groove volume, wet performance is improved. Moreover, since the groove edge part used as the stepping-in end and kicking-out end during running becomes a highly rigid chamfered part 14, the amount of deformation of the tread rubber at the time of ground contact is suppressed, and as a result, rolling resistance performance is improved. In addition, although the groove wall surface 11n of the crown inclination groove | channel 11 of this embodiment is formed in line symmetry across the center line G1 of the crown inclination groove | channel 11, it is not limited to such an aspect.

  In the present embodiment, the main wall portion 13 is formed as a flat surface (that is, the curvature radius is ∞). However, the main wall portion 13 is not limited to such a form, and has a curvature radius of about 50 to 100 mm and the center line G1. It may be formed by an arc that is convex in the opposite direction.

  Further, the normal 2b of the virtual tread 2a that smoothly joins the chamfered edges 14a, 14a, which are the intersections of the chamfer 14 standing on the outer end 13a in the tire radial direction of the main wall 13 and the tread 2n, and the main wall The main wall angle α1 that is an angle formed by the portion 13 is preferably formed in a range of 0 to 10 degrees. Such a main wall portion 13 can prevent a decrease in land portion rigidity on both sides thereof, and can ensure high steering stability performance and uneven wear resistance performance.

  In addition, when the chamfering angle α2, which is an angle formed between the normal 2c of the tread surface standing on the chamfered edge 14a and the chamfered portion 14, increases, the contact area tends to be significantly reduced and the steering stability tends to deteriorate. On the contrary, if the chamfer angle α2 is reduced, the groove edge portion of the crown inclined groove 11 may be greatly deformed during travel, and the rolling resistance performance may not be improved. From such a viewpoint, the chamfer angle α2 is preferably 20 degrees or more, more preferably 30 degrees or more, and preferably 60 degrees or less, more preferably 50 degrees or less.

  Further, from the viewpoint of exerting the above-described effects, the angle difference α2-α1 between the chamfering angle α2 and the main wall angle α1 is preferably 10 degrees or more, more preferably 20 degrees or more, and preferably 60 degrees or less. More preferably, 50 degrees or less is desirable.

  The groove width W2 of the crown inclined groove 11 is not particularly limited, but if it is too small, the ground contact area cannot be sufficiently reduced, and there is a possibility that the rolling resistance performance cannot be exhibited. On the other hand, if it is too large, the land ratio may be excessively decreased, and the steering stability performance may be deteriorated. From such a viewpoint, the groove width W2 of the crown inclined groove 11 is preferably 5 mm or more, more preferably 6 mm or more, and preferably 10 mm or less, more preferably 9 mm or less.

  As shown in FIG. 4, in this specification, the groove width W2 of the crown inclined groove 11 (the groove width perpendicular to the longitudinal direction of the groove) is expressed by the length between the chamfered edges 14a and 14a. Is done.

  The groove depth D1 of the crown inclined groove 11 is not particularly limited, but is preferably 4 to 8 mm from the viewpoint of ensuring a good balance between tread rigidity and wet performance.

  Further, it is desirable that the crown inclined groove 11 is disposed such that the intermediate position 17a of the inclined portion 17 intersects the tire equator C. As a result, the rigidity of the tread portion 2 is arranged in a balanced manner in the left-right direction in the tire axial direction, which is useful for improving steering stability performance and uneven wear resistance performance.

  Further, from the same point of view, the width W3 of the chamfered portion 14 (the width perpendicular to the longitudinal direction of the groove) is preferably 0.3 times or more, more preferably 0.00 times the groove width W2 of the crown inclined groove 11. 35 times or more is desirable, preferably 0.5 times or less, more preferably 0.45 times or less.

  2 and 5, the crown inclined groove 11 is folded back at the outer end 11t in the tire axial direction of the crown inclined groove 11 by continuously extending in a zigzag shape in the tire circumferential direction. A bent portion 16 is provided, and an inclined portion 17 is provided between the bent portions 16 and 16 adjacent to each other in the tire circumferential direction. Such a zigzag-shaped crown inclined groove 11 can increase the lateral rigidity of the tread portion 2 and can improve the steering stability performance during turning. Moreover, since such a crown inclined groove 11 can reduce the amount of rubber in the vicinity of the tire equator C of the tread rubber 2G and reduce the heat generation of the tread rubber 2G, the rolling resistance performance can be improved.

  The bent portion 16 of the present embodiment is an end portion and is formed at the position of the outer end 11t. The bent portion 16 of the present embodiment is not disposed on the tire equator C.

  Further, the inclined portion 17 of the present embodiment is formed in a straight line shape. Therefore, the rigidity of the tread portion 2 is maintained relatively high in the vicinity of the inclined portion 17. Moreover, in this embodiment, since the inclined part 17 is arrange | positioned on the tire equator C where the largest contact pressure acts, the rigidity of the tread part 2 can be maintained high. Therefore, the motorcycle tire 1 having the crown inclined groove 11 of the present embodiment does not impair the steering stability performance and the uneven wear resistance performance.

  In addition, as for the said inclination part 17, the length L2 of a tire circumferential direction is set to the range of 50-150 mm, for example, and it is desirable to arrange | position 7-20 pieces at a tire circumferential direction. Further, the inclined portion 17 of the present embodiment is formed with substantially the same length L2.

  Further, as shown in FIG. 2, the crown inclined groove 11 of the present embodiment has a tire axial direction component SW, which is a distance between the outer ends 11 t and 11 t of the crown inclined groove 11, in the tire axial direction. It is formed in 20 to 60% of W1 (shown in FIG. 3A). That is, if the tire axial direction component SW is too small as compared with the contact width W1, it is difficult to collect the water film on the road surface and there is a possibility that the wet performance cannot be exhibited. On the other hand, if the tire axial direction component SW is too large compared to the contact width W1, the tread rigidity cannot be sufficiently secured, so that the distortion of the tread rubber cannot be suppressed, and the rolling resistance performance may be deteriorated. In addition, the steering stability performance and uneven wear resistance performance may not be maintained. From such a viewpoint, the tire axial direction component SW of the crown inclined groove 11 is preferably 25% or more, more preferably 30% or more, and preferably 55% or less, more preferably 50% of the contact width W1. % Or less is desirable.

  Further, the groove depth D1a (shown in FIG. 6A) of the bent portion 16 of the present embodiment is the groove depth D1b (shown in FIG. 6) at the intermediate position 17a (shown in FIG. 5) in the length direction of the inclined portion 17. It is formed smaller than (shown in (b)). That is, the groove depth D1b is small at the bent portion 16 where the rigidity of the tread portion 2 is relatively small, and the groove depth D1b is large at the intermediate position 17a where the rigidity of the tread portion 2 is relatively large. The Such a motorcycle tire 1 ensures the rigidity of the tread portion 2 in a well-balanced manner in the tire circumferential direction while maintaining a ground contact area.

  Specifically, the ratio D1a / D1b between the groove depth D1a of the bent portion 16 and the groove depth D1b at the intermediate position 17a of the inclined portion 17 is preferably 0.7 or more, more preferably 0.8. 75 or more is desirable, preferably 0.9 or less, more preferably 0.85 or less.

  Further, from the viewpoint of further exerting the above-described effects, the groove depth D1 of the crown inclined groove 11 gradually increases from the bent portion 16 toward the intermediate position 17a of the inclined portion 17, as shown in FIG. It is desirable to do.

  Further, as shown in FIG. 6 (a), the groove depth D1a of the bent portion 16 is preferably 1.5 times or more, more preferably, the chamfer depth D2a of the chamfered portion 14 at the bent portion 16. 2.0 times or more is desirable, preferably 5.0 times or less, and more preferably 4.0 times or less. In such a bent portion 16, the rigidity in the vicinity of the bent portion 16, where the rigidity of the tread portion 2 is relatively small, is secured, and steering stability performance and uneven wear resistance performance are maintained.

  Further, although not particularly limited, as shown in FIG. 6B, the groove depth D1b of the intermediate position 17a of the inclined portion 17 is equal to the chamfering depth D2b of the chamfered portion 14 at the intermediate position 17a. Is preferably 1.5 times or more, more preferably 2.0 times or more, and preferably 5.0 times or less, more preferably 4.0 times or less.

  Further, as shown in FIGS. 5 and 6A and 6B, the width W3a and / or the chamfering depth D2a of the chamfered portion 14 in the bent portion 16 is set at the intermediate position 17a of the inclined portion 17. It is larger than the width W3b and / or the chamfering depth D2b of the chamfered portion 14. Such a crown inclined groove 11 ensures a more balanced rigidity between the bent portion 16 having a relatively low rigidity and the intermediate position 17a having a relatively higher rigidity.

  From the viewpoint of exhibiting the above-described effects, the chamfering depth D2 of the chamfered portion 14 of the present embodiment gradually decreases from the bent portion 16 toward the intermediate position of the inclined portion 17 as shown in FIG. .

  Further, as shown in FIG. 7, the chamfered portion 14 of the crown inclined groove 11 may be formed in an arc that is convex outward in the tire radial direction (convex upward in the drawing). Such a chamfered portion 14 smoothly contacts the road surface with the stepping-in end and the kicking-out end during running adapted to each camber angle. Therefore, since the deformation amount of the tread rubber can be further suppressed, the rolling resistance performance is improved. If the radius of curvature R of the arc is too small, the groove volume of the crown inclined groove 11 becomes too large, and the rigidity of the tread portion 2 cannot be ensured. From such a viewpoint, the radius of curvature R is preferably 2 mm or more, more preferably 2.5 mm or more, and preferably 4 mm or less, more preferably 3.5 mm or less.

  Further, as shown in FIG. 2, the shoulder groove 19 preferably extends at an angle θ2 of 30 to 60 degrees with respect to the tire circumferential direction. Such a shoulder groove 19 can efficiently guide and drain the water interposed between the tread outer surface 2S and the road surface to the vicinity of the tread end 2t by the pressure accompanying the tire contact, thereby improving the wet performance of the tire. sell.

  Further, the shoulder grooves 19 of the present embodiment are provided at a pitch that is substantially half the zigzag pitch of the crown inclined grooves 11. Further, the inner end 19i of the shoulder groove 19 in the tire axial direction is arranged to face the outer end 11t of the crown inclined groove 11 every other shoulder groove 19 adjacent in the tire circumferential direction. With such an arrangement, the change in rigidity from the center region Cr to the shoulder region Sh becomes smooth, transient characteristics when moving the ground contact region can be improved, and steering stability can be improved.

FIG. 8 shows another embodiment of the crown inclined groove 11.
The crown inclined groove 11 shown in FIG. 8 (a) has a smooth wave shape and extends continuously in the tire circumferential direction. Further, in FIG. 8B, the crown inclined grooves 11 extending at an angle of 20 ° or less with respect to the tire circumferential direction and the auxiliary grooves 20 extending at an angle larger than the angle of the crown inclined grooves are alternately arranged. A lightning bolt is shown. Further, the crown inclined groove 11 shown in FIG. 8 (c) is formed as a non-continuous zigzag extending in the tire circumferential direction, and is inclined in one direction with respect to the tire circumferential direction and extends linearly. The inclined portions 11A and second inclined portions 11B that are inclined in the other direction with respect to the tire circumferential direction and extend linearly are alternately arranged. These crown inclined grooves 11 can also improve the rolling resistance performance in order to reduce the amount of rubber in the center region Cr.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.

Motorcycle tires having the basic structure of FIG. 1 and having a tread portion as specified in Table 1 were manufactured and their performance was tested. The common specifications are as follows.
Tire size: 180 / 55R17
Rim size: MT5.50x17
Tread TW width: 180mm
Tread circumference: 1980mm
Crown circumferential groove length L2 in the tire circumferential direction: 100 mm
Groove width W2 of crown inclined groove: 7mm
Main wall angle α1: 0 degrees The test method is as follows.

<Rolling resistance performance>
Using a rolling resistance tester, rolling resistance was measured under the following conditions. The evaluation was performed using an index with the reciprocal of Comparative Example 1 as 100. The larger the value, the smaller the rolling resistance and the better.
Internal pressure: 290 kPa
Load: 1.3kN
Speed: 80km / h

<Uneven wear resistance>
Under the same vehicle conditions as above, the difference in wear amount at both groove edges in the tire axial direction of the crown inclined groove after running was measured. Specifically, it is mounted on the rear wheels of each sample tire, runs on a dry asphalt road surface for 10,000 km, the center line of the crown inclined groove is located on the tire equator, and the average value is measured at five points on the tire circumference. Calculated. The results are displayed as an index with the reciprocal of Comparative Example 1 as 100. The larger the value, the smaller the amount of uneven wear and the better.

<Real car running test>
Each test tire is assembled on the rim, filled with an internal pressure of 290 kPa, mounted on the rear wheel of a motorcycle with a displacement of 1300cc, and stable driving on dry and wet roads when running on a racing course. The property was evaluated by sensory evaluation of the driver. A result is displayed by the index | exponent which sets the comparative example 1 to 100, and it is so favorable that a numerical value is large.
Table 1 shows the result of the test in which the chamfered portion is a straight line, and Table 2 shows the result of the test in which the chamfered portion is an arc.

  As a result of the test, it was confirmed that the motorcycle tire of the example can improve rolling resistance performance while maintaining uneven wear resistance performance, steering stability performance, and wet performance.

DESCRIPTION OF SYMBOLS 1 Motorcycle tire 2 Tread part 2n Tread tread part 10 Tread part contact surface 11 Crown inclined groove 12 Groove bottom part 13 Main wall part 14 Chamfer C Tire equator Cr Center region L1 Contact length TW Tread width W1 Contact width

Claims (7)

A motorcycle tire having a crown inclined groove extending over the tire equator and extending at an angle of 20 degrees or less with respect to the tire circumferential direction on the tread portion,
The land ratio of the center region, which is 30% of the tread width centered on the tire equator, is 75 to 95%,
The groove wall surface of the crown inclined groove includes a main wall portion extending radially outward from the groove bottom portion, and a chamfered portion chamfered with an arc or a straight line between the main wall portion and a tread surface of the tread portion,
In the normal load loading state where the rim is assembled to the normal rim and the normal internal pressure is filled, and the normal load is applied and the camber angle is 0 degrees and grounded to the plane,
The tread portion has a ground contact surface in which a ground contact width in a tire axial direction is 30 to 65% of a contact length in a tire circumferential direction.   The pneumatic tire according to claim 1, wherein a width of the chamfered portion is 0.3 to 0.5 times a groove width of the crown inclined groove.   The pneumatic tire according to claim 1 or 2, wherein the crown inclined groove has a tire axial direction component of 20 to 60% of the contact width. The crown slant groove extends continuously in a zigzag shape in the tire circumferential direction, and then is bent at the outer end in the tire axial direction of the crown slant groove and adjacent to the bend portion spaced in the tire circumferential direction. Including an inclined portion that connects between the bent portions that fit,
The tire for a motorcycle according to any one of claims 1 to 3, wherein a groove depth of the bent portion is smaller than a groove depth at an intermediate position in a length direction of the inclined portion.   The motorcycle tire according to any one of claims 1 to 4, wherein a groove depth of the bent portion is 1.5 to 5.0 times a chamfer depth of the chamfered portion.   The motorcycle tire according to claim 4 or 5, wherein a groove depth of the crown inclined groove gradually increases from the bent portion toward the intermediate position of the inclined portion.   The motorcycle tire according to any one of claims 4 to 6, wherein a width and / or a chamfering depth of the chamfered portion at the bent portion is larger than a width and / or a chamfered depth of the chamfered portion at the intermediate position of the inclined portion. .

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