JP7211120B2 - Motorcycle tires for rough terrain - Google Patents

Description

TECHNICAL FIELD The present invention relates to a motorcycle tire for running on rough terrain.

Patent Literature 1 below proposes a motorcycle tire for running on rough terrain, in which a plurality of blocks are provided in the tread portion. In the tire of Patent Document 1, the inner edges of the shoulder blocks protrude from the imaginary tread surface.

JP 2017-013727 A

In general, motorcycle tires for running on rough terrain tend to be used under a lower internal pressure than tires for running on paved roads. In particular, tires for trials on rough terrain are used with extremely low internal pressures of, for example, about 30 to 40 KPa. Therefore, the tread portion of a motorcycle tire for running on rough terrain easily deforms according to the unevenness of the road surface, and a large ground contact pressure acts on each of the shoulder blocks and middle blocks, which in turn exerts sufficient grip. can.

When the tires are used under low internal pressure and a large camber angle is applied, the inner edges of the shoulder blocks are subject to a large contact pressure, while the edges of the middle blocks tend to lift off the road surface. There was a tendency not to exhibit a strong grip.

As a result of various experiments, the inventors obtained the knowledge that not only the shoulder blocks but also the middle blocks can exert a sufficient grip by specifying the relationship between the dimensions of the shoulder blocks and the rubber hardness. I came to complete it.

The present invention has been devised in view of the actual situation as described above, and a main object of the present invention is to provide a motorcycle tire for running on rough terrain that can exhibit excellent grip performance.

The present invention is an off-road motorcycle tire having a tread portion, the tread portion comprising a plurality of shoulder blocks forming tread edges and a plurality of shoulder blocks adjacent to and axially inside of the shoulder blocks. In a meridional cross-section including the tire rotation axis in a normal state in which the middle block is mounted on a normal rim under normal internal pressure and no load is applied, the axially inner edge of the tread surface of the plurality of shoulder blocks is aligned with the middle block. The profile of the tread surface of the block protrudes outward in the tire radial direction from the imaginary profile extending to the shoulder block, and in each of the plurality of shoulder blocks, the protrusion amount P of the inner edge from the imaginary profile is: 2. 0 mm or more, and without parameters consisting of the protrusion amount P (mm), the length L (mm) of the tread surface of the shoulder block in the tire circumferential direction, and the rubber hardness Hs (°) of the shoulder block. The product of dimensional quantities P×L×Hs is 1900-3600.

In the off-road motorcycle tire of the present invention, it is preferable that the inner edge extends parallel to the tire circumferential direction.

In the off-road motorcycle tire of the present invention, the rubber hardness Hs is desirably 47 to 58°.

In the off-road motorcycle tire of the present invention, it is desirable that the middle block has a rubber hardness Hm of 47 to 58°.

In the motorcycle tire for running on rough terrain according to the present invention, the protrusion amount P is preferably 2.5 to 4.0 mm.

In the motorcycle tire for running on rough terrain according to the present invention, the length L is preferably 14 to 18 mm.

In the off-road motorcycle tire of the present invention, the rubber thickness at the bottom surface of the groove between the shoulder block and the middle block is 0.15 of the rubber thickness at the tread portion including the middle block. ~0.25 times is desirable.

In the motorcycle tire for running on rough terrain according to the present invention, it is preferable that the profile of the tread surface of the middle block has an arcuate shape convex outward in the tire radial direction.

In the off-road motorcycle tire of the present invention, it is preferable that the axial width of the tread surface of the shoulder block is smaller than the axial width of the tread surface of the middle block.

In the off-road motorcycle tire of the present invention, the angle between the tread surface of the shoulder block and the axially inner side wall of the shoulder block is the angle between the tread surface of the middle block and the axially outer side wall of the tire. is preferably smaller than the angle of

A tread portion of a motorcycle tire for running on rough terrain according to the present invention includes a plurality of shoulder blocks forming tread edges, and a plurality of middle blocks adjacent to the inner side of the shoulder blocks in the axial direction of the tire. In a meridian cross section including the tire rotation axis in a normal state where the tire is mounted on a normal rim under normal internal pressure and no load, the inner edge in the tire axial direction of the tread surface of the plurality of shoulder blocks corresponds to the profile of the tread surface of the middle block. It protrudes radially outward of the imaginary profile extending to the shoulder block. In each of the plurality of shoulder blocks, the protrusion amount P of the inner edge from the imaginary profile is 2.0 mm or more. This allows the inner edge of each shoulder block to provide greater grip.

As a result of various experiments, the inventors have found that, in order to exert sufficient grip not only on the shoulder blocks but also on the middle blocks, it is necessary to appropriately deform the shoulder blocks so that the middle blocks also have a large ground contact. We have found that it is important to apply pressure. In addition, the inventors found that the factors related to the deformation of the shoulder blocks are the amount of protrusion P (mm), the length L (mm) of the tread surface of the shoulder block in the tire circumferential direction, and the rubber of the shoulder block. Focusing attention on the hardness Hs (°), the present invention was completed.

According to the present invention, in each of the plurality of shoulder blocks, the protrusion amount P (mm), the tire circumferential length L (mm) of the tread surface of the shoulder block, and the rubber hardness Hs (°) of the shoulder block The product P×L×Hs of dimensionless quantities of each parameter is 1900 to 3600. This allows the inner edge of the shoulder block to provide a high grip while allowing the shoulder block to deform moderately. Therefore, a large ground contact pressure acts on the outer edge of the tread surface of the middle block in the tire axial direction, and the middle block also exerts a sufficient grip. As described above, the off-road motorcycle tire of the present invention can exhibit excellent grip performance by both the shoulder blocks and the middle blocks.

1 is a cross-sectional view showing a motorcycle tire for running on rough terrain according to the present embodiment; FIG. FIG. 2 is an exploded view of the tread portion of FIG. 1; FIG. 2 is an enlarged cross-sectional view of the middle block and shoulder blocks of FIG. 1; 1 is a cross-sectional view of a tire of the present invention when running; FIG. FIG. 10 is a cross-sectional view of a conventional tire when running;

An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 exemplifies a tire for a rear wheel for a trial competition as a motorcycle tire (hereinafter sometimes simply referred to as "tire") 1 for traveling on rough terrain according to the present embodiment. Therefore, the tire 1 of this embodiment is used in a state filled with a low internal pressure of 30 to 40 kPa, for example. FIG. 1 is a tire meridian cross-sectional view including a tire rotation axis in a normal state of the tire 1. FIG. FIG. 2 is a developed view of the tread portion 2 of the tire 1 of FIG. A cross-sectional view taken along line AA of FIG. 2 is shown in FIG.

The "normal state" is a no-load state in which the tire is mounted on a normal rim and filled with a normal internal pressure. Hereinafter, unless otherwise specified, the dimensions of each part of the tire are values measured in this normal state.

A "regular rim" is a rim defined for each tire in a standard system including standards on which tires are based. For example, JATMA standard rims, TRA "Design Rims", or ETRTO If there is, it means "Measuring Rim".

"Regular internal pressure" is the air pressure specified for each tire by the above-mentioned standards, the maximum air pressure for JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and ETRTO If there is, it means "INFLATION PRESSURE".

As shown in FIG. 1 , the tire 1 of this embodiment includes, for example, a carcass 6 and belt layers 7 . The carcass 6 is, for example, formed in a toroidal shape extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 embedded in the bead portion 4 . The belt layer 7 is arranged, for example, outside the carcass 6 in the tire radial direction and inside the tread portion 2 to reinforce the tread portion 2 . The carcass 6 and the belt layer 7 preferably employ known structures.

The outer surface between two tread edges Te of the tread portion 2 is convex outward in the tire radial direction and curved in an arc shape, and provided with a plurality of blocks 10 protruding from the groove bottom surface 9 . The tread edge Te means, for example, the outermost edge in the tire axial direction of the block positioned furthest in the tire axial direction among the blocks 10 arranged in the tread portion 2 .

As shown in FIG. 2 , the tread portion 2 includes, for example, first regions 14 , second regions 15 and third regions 16 . The first region 14 is 25% of the developed tread half width TWh from the tread edge Te. The second region 15 has a width of 50% of the developed tread half width TWh, and is centered on the tire equator C. As shown in FIG. A third region 16 is a region between the first region 14 and the second region 15 . The tread developed half width TWh is the distance from the tire equator C to the tread edge Te when the tread portion 2 is developed.

Blocks 10 include, for example, shoulder blocks 11 , middle blocks 12 and crown blocks 13 . The shoulder block 11 has its centroid located in the first region 14 and forms a tread edge Te. The middle block 12 has its centroid located in the third area 16 . The crown block 13 has its centroid located in the second region 15 . The crown block 13 of this embodiment is arranged on the tire equator C, for example.

The middle block 12 is adjacent to the axially inner side of the shoulder block 11 . The middle block 12 overlaps at least an area extending axially inward of the shoulder block 11 . The centroid of the middle block 12 of this embodiment is displaced from the centroid of the shoulder block 11 in the tire circumferential direction. However, the present invention is not limited to such an aspect.

FIG. 3 shows an enlarged sectional view of the middle block 12 and the shoulder blocks 11. As shown in FIG. As shown in FIG. 3 , in a meridional cross section including the tire rotation axis in the normal state, the axially inner edge 20 of the tread surface of the shoulder block 11 extends the profile of the tread surface of the middle block 12 to the shoulder block 11 . It protrudes outward in the tire radial direction from the imaginary profile 18 . Also, the protrusion amount P of the inner edge 20 from the imaginary profile 18 is 2.0 mm or more. This allows the inner edge 20 of each shoulder block 11 to provide greater grip.

As a result of various experiments, the inventors have found that in order to make not only the shoulder blocks 11 but also the middle blocks 12 exhibit sufficient grip, the shoulder blocks 11 should be appropriately deformed so that the middle blocks 12 also have a large ground contact. We have found that it is important to apply pressure. In addition, the inventors found that factors related to the deformation of the shoulder block 11 are the protrusion amount P (mm), the tire circumferential length L (mm) of the tread surface of the shoulder block 11, and the rubber of the shoulder block 11. Focusing on the hardness (°), the present invention was completed.

In the present invention, the product P× L×Hs is 1900-3600. The rubber hardness Hs corresponds to the rubber hardness indicated by JIS-A hardness conforming to JIS-K6253.

FIG. 4 shows a cross-sectional view of the tire of the present invention during running. As shown in FIG. 4, in the tire of the present invention, grip is exhibited by the inner edge 20 of the shoulder block 11, while the shoulder block 11 can be moderately deformed. Therefore, a large ground contact pressure acts on the outer edge 21 of the middle block 12 in the tire axial direction, and the middle block 12 also exerts a sufficient grip. On the other hand, for example, as shown in FIG. 5, when the product P×L×Hs exceeds 3600, moderate deformation of the shoulder block a cannot be expected, and the outer edge c of the middle block b tends to float. Further, when the product P×L×Hs is smaller than 1900, the grip exerted by the shoulder blocks a tends to be small.

As described above, the off-road motorcycle tire of the present invention can exhibit excellent grip performance by both the shoulder blocks 11 and the middle blocks 12 .

As shown in FIG. 3, the protrusion amount P is preferably 2.5 mm or more, more preferably 3.0 mm or more, and preferably 4.5 mm or less, more preferably 4.0 mm or less. Thereby, the shoulder block 11 and the middle block 12 exhibit well-balanced grip.

The rubber hardness Hs is preferably 47° or higher, more preferably 50° or higher, and preferably 58° or lower, more preferably 56° or lower. The shoulder block 11 having such a rubber hardness Hs exhibits excellent grip performance under both low load and high load conditions.

The rubber hardness Hm of the middle block 12 is, for example, 47-58°. In this embodiment, the middle block 12 and the shoulder block 11 are made of the same rubber hardness.

As shown in FIG. 2, the inner edge 20 of the shoulder block 11 preferably extends parallel to the tire circumferential direction. As a result, the inner edge 20 exerts a large grip in the axial direction of the tire.

The length L of the tread surface of the shoulder block 11 in the tire circumferential direction is preferably specified by, for example, a value obtained by dividing the area of the tread surface of the shoulder block 11 by the maximum axial width of the tire. In another aspect, the length L may be specified by, for example, the maximum length of the shoulder block 11 in the tire circumferential direction.

The length L is preferably 12 mm or more, more preferably 14 mm or more, and preferably 20 mm or less, more preferably 18 mm or less.

In this embodiment, the length of the shoulder block 11 in the tire circumferential direction gradually increases inward in the tire axial direction. Thereby, the shoulder block 11 of this embodiment has a trapezoidal tread surface.

The axial width W1 of the tread surface of the shoulder block 11 is preferably smaller than the axial width W2 of the tread surface of the middle block. The width W1 is, for example, 0.70 to 0.85 times the width W2. Such a shoulder block 11 is moderately easy to deform and helps to increase the ground pressure acting on the middle block 12 .

The middle block 12 has, for example, a rectangular tread. Such a middle block 12 has high rigidity, and excellent grip performance can be obtained especially in trial running.

As shown in FIG. 3, the profile of the tread surface of the middle block 12 is desirably arcuate, convex outward in the tire radial direction.

The angle θ1 between the tread surface of the shoulder block 11 and its axially inner side wall is preferably smaller than the angle θ2 between the tread surface of the middle block 12 and its axially outer side wall. In a desirable aspect, the angle θ1 is an acute angle. Also, the angle θ2 is an obtuse angle. Such a shoulder block 11 easily digs into the road surface even with a low load, and exhibits excellent grip performance.

The rubber thickness t2 at the bottom surface 23 of the groove between the shoulder blocks 11 and the middle blocks 12 is preferably 0.15 to 0.25 times the rubber thickness t1 of the tread portion 2 including the middle blocks 12 . As a result, the groove bottom surface 22 is moderately deformable, and the shoulder block 11 and the middle block 12 work together to improve the grip performance. Incidentally, the rubber thickness is measured from the outer surface of the belt layer 7 .

Although the motorcycle tire for running on rough terrain according to one embodiment of the present invention has been described in detail above, the present invention is not limited to the specific embodiment described above, and can be modified in various ways. can be implemented

A trial competition rear wheel tire having the basic structure shown in FIG. 1 and the tread pattern shown in FIG. As comparative examples, a plurality of trial tires having the product P×L×Hs outside the range of 1900 to 3600 were produced. The tire of the comparative example has the same configuration as that shown in FIGS. 1 and 2 except for the configuration described above. Each test tire was tested for grip performance under low load and high load. Common specifications and test methods for each test tire are as follows.
Vehicle used: 300cc motorcycle for trial competition Tire size: 120/100-18 (rear wheel)
Rim size: 2.15 x 18 (rear wheel)
Internal pressure: 30kPa
The test method is as follows.

<Grip performance at low load and high load>
The grip performance under low load (mainly the grip performance when the rear suspension stroke is less than 60%) and the grip performance under high load when the vehicle equipped with each test tire was driven on the trial course. Grip performance (mainly grip performance in a state where the stroke amount of the rear suspension is 60% or more) was evaluated by the driver's senses. The results are scored with Comparative Example 1 being 100, and the larger the number, the better the grip performance.
The results of the tests are shown in Table 1.

As a result of the test, it was confirmed that the tires of the examples exhibited excellent grip performance under both low load and high load conditions.

2 tread portion 11 shoulder block 12 middle block 18 imaginary profile 20 inside edge Te tread edge

Claims (9)

A motorcycle tire for running on rough terrain having a tread portion,
The tread portion includes a plurality of shoulder blocks forming tread edges and a plurality of middle blocks adjacent to the inner side of the shoulder blocks in the axial direction of the tire,
In a meridian cross section including the tire rotation axis in a normal state where the tire is mounted on a normal rim under normal internal pressure and no load, the inner edge in the tire axial direction of the tread surface of the plurality of shoulder blocks corresponds to the profile of the tread surface of the middle block. protrudes radially outward of the imaginary profile extending to the shoulder block,
In each of the plurality of shoulder blocks,
A protrusion amount P of the inner edge from the virtual profile is 2.0 mm or more, and
Product P×L of dimensionless quantities of parameters consisting of the amount of protrusion P (mm), the length L (mm) of the tread surface of the shoulder block in the tire circumferential direction, and the rubber hardness Hs (°) of the shoulder block × Hs is 1900 to 3600,
Motorcycle tires for rough terrain. The off-road motorcycle tire according to claim 1, wherein the inner edge extends parallel to the tire circumferential direction. The motorcycle tire for running on rough terrain according to claim 1 or 2, wherein said rubber hardness Hs is 47 to 58°. The motorcycle tire for running on rough terrain according to any one of claims 1 to 3, wherein said middle block has a rubber hardness Hm of 47 to 58°. The motorcycle tire for running on rough terrain according to any one of claims 1 to 4, wherein the protrusion amount P is 2.5 to 4.0 mm. The motorcycle tire for running on rough terrain according to any one of claims 1 to 5, wherein said length L is 14 to 18 mm. The motorcycle tire for running on rough terrain according to any one of claims 1 to 6, wherein the profile of the tread surface of the middle block has an arcuate shape projecting outward in the tire radial direction. The off-road motorcycle tire according to any one of claims 1 to 7, wherein the axial width of the tread surface of the shoulder block is smaller than the axial width of the tread surface of the middle block. 9. Any one of claims 1 to 8, wherein the angle between the tread surface of the shoulder block and its axially inner side wall is smaller than the angle between the tread surface of the middle block and its axially outer side wall. A motorcycle tire for running on rough terrain as described.

Images