JP2013147231A - Tire for motorcycle for irregular ground running - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire for a motorcycle for irregular ground running which improves earth removing performance in the vicinity of a shoulder part, and gripping force and steering stability when turning.SOLUTION: In a tire for a motorcycle for irregular ground running, a plurality of blocks 9 are provided in a tread section 2, and a rotation direction R is specified. The block 9 includes a crown block 11, a shoulder block 12, and a middle block 13. A land-sea ratio L/S which is a ratio of a summation L of grounded areas of the blocks 9 to a summation S of areas of a groove bottom surfaces 10 is 15 to 25%. Groove bottom projections 14 are provided in a shoulder groove bottom region 15. A height h4 of the groove bottom projection 14 is 1 to 8 mm. A maximum size W4 of a cross section in a groove bottom surface 10 is 0.5 to 5 mm. A ratio Sp/Sb of a summation Sp of areas of the cross sections of the groove bottom projections 14 in the groove bottom surfaces 10, to a total area Sb of the shoulder groove bottom regions is 10 to 40%.

Description

  The present invention relates to a motorcycle tire for traveling on rough terrain, in which the gripping power and steering stability at the time of turning are improved by improving the soil removal property near a shoulder portion.

  For example, in a motorcycle tire for running on rough terrain used in off-road racing, etc., in order to ensure good grip performance on an uneven terrain surface, the sum L of the ground contact area of the block with respect to the total sum S of the groove bottom surface area A block pattern in which the ratio (hereinafter referred to as “land sea ratio L / S”) is significantly smaller than that of a tire for running on a paved road surface is employed.

  Such a motorcycle tire for traveling on rough terrain is easy to bite into the road surface when traveling on rough terrain such as muddy ground, and exhibits an edge effect and good grip. On the other hand, in a soft muddy area, mud adheres to the bottom of the groove near the shoulder block and becomes clogged, and the grip force during turning tends to decrease. In particular, since the grip force varies depending on the degree of mud adhesion, there is a problem in that the steering stability during turning decreases, for example, the controllability of the tire slide changes.

  In response to such problems, motorcycle tires for running on rough terrain have been proposed that improve the soil removal and traction by defining the block spacing in the tire circumferential direction of the shoulder block and middle block ( For example, the following patent document 1). However, even though such motorcycle tires are improved in soil removal properties, the number of blocks in the tire circumferential direction of the shoulder blocks and middle blocks is reduced, and the grip force during turning is still insufficient. There was room for further improvement because it was not yet effective.

JP 2003-72318 A

  The present invention has been devised in view of the actual situation as described above, and a groove bottom projection extending outward in the tire radial direction is provided on the groove bottom surface in the tire axial direction of the middle block, and its height and maximum dimension are provided. The main purpose is to provide motorcycle tires for running on rough terrain, with improved soil removal in the vicinity of the shoulder, and improved grip and steering stability during turning. .

  Of the present invention, the invention according to claim 1 is a motorcycle tire for traveling on rough terrain provided with a plurality of blocks in the tread portion, wherein the block is a meridian cross section including a tire rotation axis. Provided in a region between the crown block and the shoulder block, a crown block that is spaced apart in the tire circumferential direction on the tire equator, a shoulder block that is disposed closest to the tread end and spaced in the tire circumferential direction The land sea ratio L / S, which is the ratio of the total contact area L of the block to the total sum S of the groove bottom areas, is 15 to 25%. In the shoulder groove bottom region, which is the region of the groove bottom on the outer side in the tire axial direction with respect to the tire circumferential direction line passing through the edge in the tire axial direction outer side of the middle block, A groove bottom protrusion extending radially outward is provided, and the groove bottom protrusion has a height of 1 to 8 mm from the groove bottom surface to the outer end in the tire radial direction, and the maximum cross-sectional dimension at the groove bottom surface is 0. And the ratio Sp / Sb between the total area Sb of the shoulder groove bottom region and the total sum Sp of the sectional area of the groove bottom projection at the groove bottom surface is 10 to 40%. Features.

  According to a second aspect of the invention, the number of blocks in the tire circumferential direction of the middle block and the shoulder block is larger than the number of blocks in the tire circumferential direction of the crown block. This is a tire for motorcycles.

  According to a third aspect of the present invention, the groove bottom surface is provided with a recess connected to the outer surface of the groove bottom protrusion, and the recess is provided on one side of the groove bottom protrusion in the tire circumferential direction. The motorcycle tire for traveling on rough terrain according to 1 or 2.

  According to a fourth aspect of the present invention, there is provided a motorcycle for running on uneven terrain according to the third aspect, wherein the tread portion has a designated rotational direction, and the concave portion is provided on the rear landing side in the rotational direction. Tire.

  The invention according to claim 5 is the motorcycle tire for running on rough terrain according to claim 3 or 4, wherein the recess has a maximum depth larger than the maximum dimension of the groove bottom protrusion.

  The invention according to claim 6 is the motorcycle for traveling on rough terrain according to any one of claims 3 to 5, wherein the recess has a tire circumferential length greater than a height of the groove bottom protrusion. Tire.

  A motorcycle tire for traveling on rough terrain according to the present invention has a groove extending outward in the tire radial direction, in which a height and a maximum dimension are defined in a shoulder groove bottom region which is a groove bottom surface in the tire axial direction of the middle block. A bottom protrusion is provided. Such groove bottom protrusions prevent the mud from adhering to the groove bottom between the middle block and the shoulder block, and enhance the effect of discharging the adhering mud. Thereby, the grip force and steering stability at the time of turning improve.

1 is a cross-sectional view showing an embodiment of a motorcycle tire for running on rough terrain according to the present invention. FIG. 2 is a development view of the tread portion of FIG. 1. It is a perspective view of the shoulder block and groove bottom protrusion of FIG. (A) is an enlarged perspective view of the groove bottom projection of the present embodiment, and (B) and (C) are enlarged perspective views of the groove bottom projection of another embodiment. It is an AA expanded sectional view of FIG. It is an expanded view of the tread part which shows other embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a tire meridian cross-sectional view including a tire rotation axis in a normal state of a motorcycle tire 1 for traveling on rough terrain according to the present embodiment.

  Here, the normal state is a no-load state in which the tire is assembled on a normal rim (not shown) and filled with a normal internal pressure. Hereinafter, unless otherwise specified, dimensions and the like of each part of the tire are values measured in the normal state.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, “Standard Rim” for JATMA and “Design Rim” for TRA. "If ETRTO," Measuring Rim ".

  The “regular internal pressure” is the air pressure defined by each standard for each tire in the standard system including the standard on which the tire is based, and is “maximum air pressure” for JATMA and table for TRA. TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES "Maximum value", ETRTO, "INFLATION PRESSURE".

  As shown in FIG. 1, a motorcycle tire (hereinafter simply referred to as a “tire”) 1 for traveling on rough terrain according to this embodiment includes a bead portion 4 from a tread portion 2 through a sidewall portion 3. A carcass 6 reaching the bead core 5, a belt layer 7 disposed on the outer side in the tire radial direction of the carcass 6 and on the inner side of the tread portion 2, and a bead extending from the bead core 5 toward the outer side in the tire radial direction. Apex rubber 8 is provided.

  The carcass 6 includes, for example, two radial carcass plies 6A and 6B. The carcass plies 6A and 6B include 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 connected to the main body portion 6a and folded around the bead core 5. 6b. For the carcass cord, for example, an organic fiber cord such as nylon, polyester, or rayon is suitably employed.

  The belt layer 7 includes two belt plies 7A and 7B in which belt cords are arranged to be inclined with respect to the tire equator C. For example, aramid or rayon is suitably used for the belt cord.

  The bead apex rubber 8 is made of hard rubber, is disposed between the main body portion 6a and the folded portion 6b, and extends in a tapered manner from the bead core 5 outward in the tire radial direction. Thereby, the bead part 4 and the sidewall part 3 are reinforced.

  In the tread portion 2, the outer surface 2S between the tread ends Te and Te of the tread portion 2 is convex outward in the tire radial direction and curved in an arc shape so that a sufficient contact area can be obtained even when turning with a large camber angle. And then extend. Further, the tread width TW, which is the distance in the tire axial direction between the tread ends Te, Te, forms the maximum tire width.

  FIG. 2 shows a development view of the tread portion 2. The tread portion 2 of the present embodiment includes a pattern in which the rotation direction R is designated. The rotation direction R is displayed with, for example, characters or marks on the sidewall portion 3 or the like.

  The tread portion 2 is provided with a groove bottom surface 10 and a plurality of blocks 9 protruding from the groove bottom surface 10. In the motorcycle tire 1 of the present invention, the land sea ratio L / S, which is the ratio of the total sum L of the ground contact area of the ground contact surface 9A of the block 9 to the total sum S of the area of the groove bottom surface 10, is set to 15 to 25%. Is done. When the land sea ratio L / S is smaller than 15%, the contact area is reduced and the steering stability is lowered. On the contrary, when the land sea ratio L / S is larger than 25%, the load acting on each block 9 is reduced, the amount of biting into the road surface of the block 9 is reduced, and the traction in the muddy ground and the grip when turning Performance decreases.

  The block 9 includes a crown block 11, a shoulder block 12, and a middle block 13. Further, a groove bottom protrusion 14 is provided in a region outside the middle block 13 in the tire axial direction.

  The crown block 11 is spaced apart on the tire equator C in the tire circumferential direction. When such a crown block 11 travels straight on rough terrain, it deeply digs into the road surface and exhibits good grip. The crown block 11 is preferably disposed on the tire equator C with the center in the tire axial direction of the ground contact surface 9A. As a result, the driving force can be applied to the road surface throughout the crown block 11 during straight travel, and the traction can be improved.

  If the block width W1 of the ground contact surface 9A in the tire axial direction of the crown block 11 is reduced, the traction performance during straight running may be deteriorated, and block missing may occur. On the contrary, when the block width W1 is increased, the amount of the crown block 11 biting into the road surface is decreased, and the grip force may be reduced. From this point of view, the block width W1 of the crown block 11 is preferably 20% or more, more preferably 22% or more of the tread development width TWe which is the distance between the tread ends Te and Te along the groove bottom surface 10. Desirably, it is preferably 26% or less, more preferably 24% or less.

  If the block length L1 in the tire circumferential direction of the crown block 11 is reduced, the edge effect in the tire axial direction may be reduced and the turning performance may be reduced. If the block length L1 is increased, the amount of biting of the crown block 11 into the road surface is increased. As a result, the traction performance may be reduced. From such a viewpoint, it is desirable that the block length L1 of the crown block 11 is set to 10 to 15 mm.

  Further, when the height h1 of the crown block 11 is increased, the rigidity may be reduced and the steering stability may be decreased. When the height h1 is decreased, the amount of biting into the road surface may be decreased and the grip force may be decreased. From such a viewpoint, the height h1 is preferably set to 13 to 17 mm.

  Further, if the number of blocks n1 in the tire circumferential direction of the crown block 11 is decreased, the number of blocks to be grounded at the same time is decreased, and grip performance may be deteriorated. When the number is increased, mud is easily clogged in the groove bottom surface 10. Therefore, there is a concern that the running performance particularly in soft muddy areas may be deteriorated. From this point of view, the number n1 of the crown blocks 11 is preferably set to 25 to 45.

  The shoulder block 12 is disposed closest to the tread end Te of the blocks 9 and is spaced apart in the tire circumferential direction. In the present embodiment, since the edge 12a on the outer side in the tire axial direction of each shoulder block 12 spaced in the tire circumferential direction is arranged on the same tire circumferential direction line, the end on the outer side in the tire axial direction of the shoulder block 12 The edge 12a becomes the tread end Te. As another embodiment, when the edge 12a of each shoulder block 12 is not on the same tire circumferential direction line, the edge 12a of the shoulder block 12 arranged on the outermost side in the tire axial direction is the tread end Te.

  If the block width W2 in the tire axial direction of the ground contact surface 9A of the shoulder block 12 is reduced, there is a possibility that block chipping may occur, and if it is increased, mud is easily clogged in the groove bottom surface 10 and soil removal performance is reduced. There is a fear. From this point of view, the block width W2 is preferably 10% or more, more preferably 12% or more, and preferably 16% or less, more preferably 14% or less of the tread development width TWe.

  If the block length L2 in the tire circumferential direction of the shoulder block 12 is reduced, the rigidity is reduced, and there is a possibility that block chipping may occur at the time of turning, and if it is increased, the amount of biting into the road surface is reduced, There is a risk that the grip performance will deteriorate. From this point of view, the block length L2 is preferably set to 10 to 15 mm.

  Further, if the height h2 of the shoulder block 12 is reduced, the amount of biting into the road surface may be reduced and the turning performance may be reduced. If the height h2 is increased, the rigidity may be reduced and a block chip may be generated. . From such a viewpoint, the height h2 is desirably set to 13 to 17 mm.

  The middle block 13 is provided in a region between the crown block 11 and the shoulder block 12, and is spaced apart in the tire circumferential direction. Such a middle block 13 can touch the road surface when turning at a relatively small camber angle and exert a gripping force, thereby improving turning performance.

  If the block width W3 in the tire axial direction of the middle block 13 is reduced, the traction performance particularly at the time of starting from turning may be lowered, and the steering stability at the time of falling may be lowered. As a result, mud is easily clogged in the groove bottom surface 10, and there is a possibility that the soil removal performance may be reduced. From this point of view, the block width W3 is preferably 10% or more, more preferably 12% or more, and preferably 16% or less, more preferably 14% or less of the tread development width TWe.

  If the block length L3 in the tire circumferential direction of the middle block 13 is reduced, the rigidity is lowered, and there is a risk that the steering stability at the time of tilting is lowered, and if it is increased, the amount of biting into the road surface is reduced, There is a possibility that the turning performance at a small camber angle is lowered. From this point of view, the block length L3 is preferably set to 10 to 15 mm.

  Further, if the height h3 of the middle block 13 is reduced, the amount of biting into the road surface may be reduced and the turning performance may be reduced. If the height h3 is increased, the soil removal performance may be reduced. From such a viewpoint, the height h3 is preferably set to 13 to 17 mm.

  The number of blocks n2 and n3 in the tire circumferential direction of the shoulder block 12 and the middle block 13 is preferably set to be larger than the number of blocks n1 in the tire circumferential direction of the crown block 11. When the number of blocks n2 and n3 of the shoulder block 12 and the middle block 13 is increased, the grip force and the steering stability during turning can be remarkably improved. In addition, the deterioration of the soil removal property with the increase in the number of blocks can be prevented by the groove bottom protrusion 14 of the present invention.

  FIG. 3 is a perspective view of the shoulder block 12 and the groove bottom protrusion 14. As shown in FIGS. 2 and 3, the shoulder block bottom region 15, which is an outer region in the tire axial direction than the circumferential line E, passes through the edge 13 a on the outer side in the tire axial direction of the middle block 13. A groove bottom protrusion 14 extending outward in the tire radial direction is provided. The groove bottom protrusion 14 of the present embodiment is formed in a conical shape whose diameter decreases toward the outer side in the tire radial direction. When mud tries to enter the shoulder groove bottom region 15, the groove bottom protrusion 14 has a lower rigidity than the block 9, and therefore does not pierce the mud and is bent between the groove bottom surface 10 and the mud. . Thereby, it is suppressed that mud adheres to the groove bottom face 10, and clogging is suppressed. Further, mud is effectively discharged by the reaction force that the groove bottom protrusion 14 returns to the original state and the centrifugal force of the tire rotation.

  The cross-sectional shape of the groove bottom protrusion 14 at the groove bottom surface 10 is not limited to a circle as shown in FIG. 4A, but as shown in FIGS. 4B and 4C. Alternatively, it may be rectangular or elliptical.

  As shown in FIG. 5 which is an AA cross section of FIG. 2, a height h4 from the groove bottom surface 10 of the groove bottom projection 14 to the outer end 14e in the tire radial direction is set to 1 to 8 mm. If the height h4 is less than 1 mm, the groove bottom protrusion 14 does not bend when mud enters the groove bottom surface 10, and the soil removal performance is deteriorated. Conversely, when the height h4 is greater than 8 mm, the groove bottom projection 14 itself traps and traps mud, so that the soil removal performance is lowered and the grip force during turning is lowered. Furthermore, since mud adheres to the groove bottom protrusion 14, the durability of the groove bottom protrusion 14 may be reduced. From this viewpoint, the height h4 is preferably 2 mm or more, more preferably 3 mm or more, preferably 5 mm or less, more preferably 4 mm or less.

  Further, the maximum dimension W4 of the groove bottom protrusion 14 in the cross section at the groove bottom surface 10 is set to 0.5 to 5 mm. The maximum dimension W4 is the maximum dimension of the cross section when the groove bottom protrusion 14 is cut along the groove bottom surface 10, as shown in FIG. If the maximum dimension W4 is smaller than 0.5 mm, the rigidity of the groove bottom protrusion 14 becomes too small, mud cannot be discharged by the restoring force at the time of deformation, and the durability of the groove bottom protrusion 14 is reduced. It becomes easy to break. On the contrary, if the maximum dimension W4 is larger than 5 mm, the rigidity of the groove bottom protrusion 14 becomes too high, and when the mud enters the groove bottom face 10, the groove bottom protrusion 14 bites into the mud and the soil removal performance is lowered. From such a viewpoint, the maximum dimension W4 is preferably 1 mm or more, preferably 3 mm or less, more preferably 2 mm or less.

  The groove bottom protrusion 14 has a ratio Sp / Sb of 10 to 40% between the total area Sb of the shoulder groove bottom region 15 and the total cross section Sp of the groove bottom protrusion 14 at the groove bottom surface 10. If the ratio Sp / Sb is less than 10%, the groove bottom projection 14 is insufficient, and the soil removal effect due to this is not expected. On the contrary, if the ratio Sp / Sb is larger than 40%, the density of the groove bottom protrusions 14 becomes too high, and the groove bottom protrusions 14 themselves trap mud, which causes clogging. From such a viewpoint, the ratio Sp / Sb is preferably 30% or less, more preferably 20% or less.

  The number of the groove bottom protrusions 14 is not particularly limited as long as the maximum dimension W4 is 0.5 to 5 mm and the ratio Sp / Sb is 10 to 40%. Therefore, as in another embodiment shown in FIG. 6, the sectional area per groove bottom protrusion 14 may be reduced and the number of groove bottom protrusions 14 may be increased.

  As shown in FIG. 5, it is desirable that the groove bottom surface 10 is provided with a recess 16 that is continuous with the outer surface of the groove bottom protrusion 14. The recess 16 is desirably provided on one side of the groove bottom protrusion 14 in the tire circumferential direction. Thereby, when mud enters the groove bottom surface 10, a space is easily interposed between the groove bottom surface 10 and the mud, so that adhesion of mud can be suppressed and soil removal performance can be improved. Furthermore, by providing the recess 16 adjacent to one side in the rotational direction of the groove bottom protrusion 14, the groove bottom protrusion 14 can easily fall down effectively in the tire circumferential direction, and the soil removal performance can be further improved.

  The recess 16 is preferably provided on the rearward side of the groove bottom protrusion 14 in the rotational direction. As a result, the groove bottom protrusion 14 is more likely to fall down on the arrival side in the rotational direction.

  If the maximum depth d1 of the concave portion 16 is reduced, the movement of the groove bottom protrusion 14 in the tire circumferential direction may be reduced and the soil removal property may be reduced. If the maximum depth d1 is increased, the groove bottom protrusion 14 may be easily broken. is there. From this point of view, the maximum depth d1 is preferably larger than the maximum dimension W4 of the groove bottom protrusion 14, and is preferably 1.5 times or less of the maximum dimension W4.

  The length L4 of the recess 16 in the tire circumferential direction is preferably larger than the height h4 of the groove bottom protrusion 14. As a result, when the groove bottom protrusion 14 is bent, the groove bottom protrusion 14 enters the recess 16, so that breakage of the groove bottom protrusion 14 is suppressed. On the contrary, if the length L4 of the concave portion 16 is too large, it is difficult to arrange the groove bottom protrusions 14 at a necessary density. From this viewpoint, the length L4 is preferably 1.5 times or less, more preferably 1.3 times or less of the height h4.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

Motorcycle tires for running on rough terrain having the basic structure of FIG. 1 and the tire size 120 / 80-19 having the basic pattern of the tread pattern of FIG. It was installed on the rear wheel of a 450cc motocross racing vehicle and tested for performance. For comparison, a tire with no groove bottom projection was also tested as a conventional example. The common specifications are as follows.
tire size:
Front wheel: 80 / 100-21
Rear wheel: 120 / 80-19
Rim size:
Front wheel: 21 x 1.60
Rear wheel: 19 x 2.15
internal pressure:
Front wheel: 80 kPa
Rear wheel: 80 kPa
The test method is as follows.

<Grip strength and steering stability during turning>
Using the vehicle, “grip force during turning” and “steering stability” when actually running on a motocross course were evaluated by sensory evaluation by a test rider. A result is a score which sets a prior art example to 100, and shows that it is so favorable that a numerical value is large.

<Durability of groove bottom protrusion>
The remaining state of the groove bottom protrusion after the actual running was visually evaluated. A result is a score which made Example 1 100, and shows that it is so favorable that a numerical value is large.
The test results are shown in Table 1.

  As a result of the test, it was confirmed that the motorcycle tire of the example had significantly improved grip strength and steering stability during turning.

6 Carcass 7 Belt layer 8 Bead apex rubber 9 Block 10 Groove bottom 11 Crown block 12 Shoulder block 13 Middle block 14 Groove bottom projection 15 Shoulder groove bottom area 16 Recess

Claims (6)

A motorcycle tire for running on rough terrain provided with a plurality of blocks in the tread portion,
In the meridian cross section including the tire rotation axis, the block is a crown block that is spaced apart in the tire circumferential direction on the tire equator, a shoulder block that is disposed on the most tread end side and spaced in the tire circumferential direction, A middle block provided in a region between the crown block and the shoulder block and spaced in the tire circumferential direction;
The land sea ratio L / S, which is the ratio of the total sum L of the ground contact area of the block to the total sum S of the groove bottom areas, is 15 to 25%
A groove bottom projection extending outward in the tire radial direction is provided in a shoulder groove bottom region, which is a region of the groove bottom on the outer side in the tire axial direction with respect to the tire circumferential direction line passing through the outer edge in the tire axial direction of the middle block. ,
The groove bottom protrusion has a height from the groove bottom surface to the outer end in the tire radial direction of 1 to 8 mm, and a maximum cross-sectional dimension at the groove bottom surface of 0.5 to 5 mm,
Moreover, the ratio Sp / Sb between the total area Sb of the shoulder groove bottom region and the sum Sp of the sectional area of the groove bottom protrusion at the groove bottom surface is 10 to 40%. Motorcycle tires.   The motorcycle tire for rough terrain travel according to claim 1, wherein the number of blocks in the tire circumferential direction of the middle block and shoulder block is larger than the number of blocks in the tire circumferential direction of the crown block. The groove bottom surface is provided with a recess that is continuous with the outer surface of the groove bottom protrusion,
The motorcycle tire for rough terrain travel according to claim 1 or 2, wherein the recess is provided on one side of the groove bottom protrusion in the tire circumferential direction. The tread portion has a designated rotation direction,
The motorcycle tire for traveling on rough terrain according to claim 3, wherein the recess is provided on the rear landing side in the rotational direction.   The motorcycle tire for rough terrain travel according to claim 3 or 4, wherein the concave portion has a maximum depth larger than the maximum dimension of the groove bottom protrusion.   The motorcycle tire for rough terrain travel according to any one of claims 3 to 5, wherein the recess has a length in the tire circumferential direction that is greater than a height of the groove bottom protrusion.

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