JPH11139112A - Pneumatic tire for motorcycle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a pattern noise level dB (A) while keeping rectilinear steering stability and abrasion resistance comparable with a conventional tire. SOLUTION: A central block line comprising plural block astride a tread width center circumferential line E, and at least two side block lines separated to a tread width direction each other in both sides of the center circumferential line E are provided in a tread part, and the respective blocks 2 of the central block line have plural fine grooves 2g extended to the tread circumferential direction in their respective surfaces, and longitudinal slender ribs 2r formed by the fine grooves 2g. Respective blocks 3-4 of all the side block lines have smooth surfaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for a two-wheeled vehicle, and more particularly, to an all-around two-wheeled vehicle running on a soft road surface such as a muddy or sandy ground, an uneven road surface such as an irregular surface, and a pavement road surface. More particularly, the present invention relates to a pneumatic tire for a two-wheeled vehicle in which both the abrasion resistance and the handling stability of tread rubber are maintained at an excellent level and the pattern noise is improved.

[0002]

2. Description of the Related Art As described above, a pneumatic tire used for a two-wheeled vehicle that travels all round uses a pneumatic tire having a block pattern in order to ensure good running performance on a soft road surface or uneven road surface. It is common to do.

Since the two-wheeled vehicle is disadvantageous in terms of steering stability as compared with a passenger vehicle, it is necessary to place more emphasis on this performance. For this purpose, the main running of the two-wheeled vehicle is straight running, so that straight running is performed. It is necessary to use a tire having excellent steering stability in the tire, and an optimal tire for realizing this performance is a tire having a block pattern in which a number of central block rows are arranged in a tread width center region.

On the other hand, in order to improve the running performance on a soft road surface, the size of each block of the block pattern of the tire to be used is made as small as possible to reduce the negative ratio (the ratio of the total surface area of the groove to the total surface area of the tread). The arrangement of the central block row plays an important role in compensating for a decrease in the wear resistance of the tread rubber on pavement roads which promotes the wear of the tread rubber, as a result.

However, in the above block pattern, each block in the central block row arranged in the tread width center area has a higher ground pressure than each block in the other block row, so that the impact force at the time of stepping on the ground is large, and especially the rear wheel In addition, since the driving force acts on each block, the impact force is further increased. In addition, there is also a disadvantage that a pattern noise level generated particularly when traveling straight ahead is high. A tire having a block pattern in which two block rows having a predetermined interval, for example, an interval of 8 mm or more, are arranged on both sides of the tread width center peripheral line (tire equatorial plane), excluding the arrangement, is used. There is also.

[0006]

The latter block pattern in which two rows of blocks are arranged on both sides of the equatorial plane of the tire has, of course, insufficient steering stability and abrasion resistance. Each of the two types of typical block patterns has advantages and disadvantages. In other words, it is inevitable that the two types are classified into a type that emphasizes driving stability and wear resistance and a type that emphasizes low noise. Have a problem that cannot satisfy the elderly.

Therefore, according to the inventions described in claims 1 to 3 of the present invention, the pattern noise level dB (A) is ensured while ensuring excellent steering stability during straight running and sufficient abrasion resistance of the tread rubber. It is an object of the present invention to provide a pneumatic tire for a two-wheeled vehicle, which can significantly reduce the above.

[0008]

In order to achieve the above object, the invention described in claim 1 of the present invention is directed to a center block row comprising a plurality of blocks straddling a tread width center circumferential line on a tread side of a tread rubber. And a pneumatic tire for a two-wheeled vehicle including, on a tread portion, at least two side block rows that are separated from each other in the tread width direction on both sides of the center circumferential line. It has a plurality of narrow grooves extending in the circumferential direction of the tread on the surface of the surface, and a plurality of vertically elongated ribs formed by the narrow grooves, and each block of all side block rows has a smooth surface. Is a pneumatic tire for a two-wheeled vehicle.

In a preferred embodiment of the invention described in claim 1, the depth of the plurality of narrow grooves is equal to the depth of the tread surface circumferential groove that defines the central block row. In a preferred embodiment, the plurality of narrow grooves and the plurality of narrow ribs are different from each other in a preferred embodiment. ,
This is a tire that forms a wavy shape in the tread width direction.

The tire described in claims 1 to 3 has a pair of bead portions and a pair of sidewall portions, and a tread portion connected to both sidewall portions in a toroidal shape.
It is customary to provide one or more plies of a carcass for reinforcing layers between bead cores in which each part is embedded in a bead part, and the carcass is composed of two plies or more in the case of a radial ply that becomes a rubber coating of a radial array organic fiber cord. Bias arrangement This includes both the case of the bias ply which becomes the rubber coating of the organic fiber cord.

In the case of a radial ply carcass, a belt made of rubber coating of two or more organic fiber cord layers is provided on the outer periphery of the carcass. In the case of a bias ply carcass, one or more organic fiber cord layers are provided on the outer periphery of the carcass. There is an example with a breaker made of rubber coating and an example without a breaker.

The tread width of the tread portion preferably has the maximum width of the tire when the tire is mounted on an applicable rim and air pressure corresponding to the maximum load capacity is applied thereto. The applicable rim and the air pressure corresponding to the maximum load capacity follow the contents described in JATMA YEAR BOOK (1997 version).

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a partially developed view of a tread of a pneumatic tire for a two-wheeled vehicle, and FIG.
FIG. 3 is a sectional view of the central block taken along line II-II of FIG.
FIG. 4 is a central block sectional view of a modification of the block shown in FIG. 2, and FIG. 4 is a plan view of the block shown in FIG.

In FIG. 1, a tread portion (not shown) of a pneumatic tire for a two-wheeled vehicle (hereinafter referred to as a tire) has
The tread 1 side of the tread rubber (reference numeral T _R in Fig. 2), the central circumferential line E of width between both side edges of the tread surface 1 Te (developed width W)
A central block row composed of a plurality of blocks 2 arranged on the tire equatorial plane and at least two rows separated from each other in the width direction of the tread 1 on both sides of the central peripheral line E; In the illustrated example, the rows of the side blocks 3 (two rows on both sides), the rows of the side blocks 4 (two rows on both sides), and the rows of the side blocks 5 (two rows on both sides) are aligned in order from the center peripheral line E. And six rows of side blocks, each block 2,
The portions other than 3, 4, and 5 are the grooves for partitioning these blocks. In particular, the tread circumferential groove 7 and the tread width direction groove 8 for forming each block 2 are shown.

Referring to FIG. 1 and FIG. 2, each block 2 of the central block row has a plurality of, in the illustrated example, five narrow grooves 2g extending in the circumferential direction of the tread 1 cut into the respective surfaces 2S. While the illustrated example has six vertically elongated ribs 2r formed by the narrow grooves 2g, each of the blocks 3, 4, and
5 has a smooth surface.

In the tire having the above-described block configuration in the tread portion, first, each block 2 of the central block row is located in the central area distributed to both sides in the width direction of the tread from the center peripheral line E of the tread 1 so that the tire travels straight. properties of both the wear resistance of the steering stability and tread rubber T _R can be satisfactorily ensured in. In this regard, it is desirable that the arrangement pitch of the blocks 2 is smaller than the contact length on the equatorial plane E of the tire and that at least one block 2 exists in the contact surface under rolling of the tire under load.

Next, a narrow groove 2g is provided only on the surface of each block 2 in the central block row, and the surface of each block in all the other side block rows is made smooth so that the two-wheeled vehicle travels straight. Excellent maneuvering stability is promised not only at the time of turning with camber, but also when the narrow grooves are provided on the surface of each block of the side block row, the steering stability is significantly impaired. Shall be excluded.

Finally, by providing a plurality of narrow grooves 2g extending in the circumferential direction of the tread surface 1 on the surface of each block 2 of the central block array, the central block array which is responsible for a high contact pressure under the rolling load of the tire. The impact force acting upon each of the blocks 2 when stepping on the ground is applied to the plurality of, and in the illustrated example, the six vertically elongated ribs 2s formed by the five narrow grooves 2g provided in the block 2, so that the impact force is greatly reduced. As a result, the level (dB) of the pattern noise proportional to the magnitude of the impact force
(A)) is greatly reduced.

Here, the groove depth d of the narrow groove 2g, in other words, the height d of the vertically elongated rib 2s is determined by each block 2 in the central block row.
Depth D of the tread circumferential groove 7 that partitions the tread in the width direction of the tread 1
Is in the range of 5 to 30%. If the groove depth d to the height d is less than 5% of the groove depth D, the effect of alleviating the impact force is small, and the pattern noise level does not decrease to the extent that practically low noise can be sensed, while exceeding 30%. And both steering stability and abrasion resistance are reduced, so both should be avoided.

FIGS. 3 and 4 show a modification of the narrow groove 2g provided on the surface of the block 2 shown in FIGS. FIG.
The narrow grooves 2g shown in FIG. 4 are continuous in a waveform in the tread width direction.
The thin ribs 2r form a series of chevron at a pitch w. The feature of this example is that the effect of alleviating the impact force is larger than that of the block 2 shown in FIG. 2 and the pattern noise is effective for further reducing the pattern noise, but the wear resistance is slightly lower than that of the block 2 shown in FIG. . Therefore, it is better to use them properly according to the required characteristics.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Two-wheeled vehicle tires are also used on uneven terrain, the front wheel size is 3.00-21, and the rear wheel size is 4.60-18.
For both size tires, the carcass has a 2-ply 18
A 90D / 2 nylon cord rubber coating is provided, and the breaker is a two-layer 1260D / 2 nylon cord rubber coating. The tread portion has a block pattern having the blocks 2 in the central block row shown in FIGS. 1, 3 and 4, and the developed width W of the tread 1 is 110 mm for the front tire and 150 mm for the rear tire.

The depth D of the circumferential groove 7 is 11.5 mm, and the depth d of the narrow groove 2 g of each block 2 in the central block row is 3 m.
In m, (d / D) × 100 (%) was set to 26%. The arrangement pitch of the blocks 2 in the center block row is 146 mm for the front wheel tires and 137 mm for the rear wheel tires, and at least one of the blocks 2 of the front and rear wheel tires exists in the ground contact surface in actual use. For comparison of the performance of this example tire, a comparative example tire was prepared according to the example except that the block 2 of the central block row was made a smooth surface and the narrow groove 2g was omitted.

The tires of the example and the comparative example were used as test tires and mounted on a two-wheeled vehicle having an engine displacement of 250 cc. The front tires were 1.5 kgf / cm ² , and the rear tires were 1.75 kgf / cm ^2. And the load on the front wheel tires was set to 80 kgf and the load on the rear wheel tires was set to 160 kgf, and actual vehicle tests were performed for the following test items. (1) Noise test: Noise traveling straight ahead at a constant speed of 40 km / h on a flat dry pavement surface of a test course was measured at a noise level dB (A) via a microphone installed at a position 7.5 m away from the test vehicle. ) Is measured. The smaller the value, the better. (2) Maneuvering stability test: The tires of the comparative example were tested on the dry pavement road surface of the test course by using the test driver's feelings on the wandering of the vehicle traveling straight ahead at a speed range from a very low speed near zero to 150 km / h in a speed range of 150 km / h. It is represented by an index of 100. The larger the value, the better. (3) Abrasion resistance test: The test vehicle was run at a ratio of 30% on a general road and 70% on a highway, and the abrasion resistance (running per tread rubber abrasion amount of 1 mm) was calculated from the average value of tread rubber abrasion after traveling 1500 km. Distance) is calculated and expressed as an index with the average value of the comparative tire being 100. The larger the value, the better.

The above test results were as follows. (1) Noise test: The example tire was 73 dB (A), and the comparative example tire was 75 dB (A). (2) Maneuvering stability test: 98 tires were obtained for the comparative example tires compared to 100 tires for the comparative example. This is a natural result of the arrangement of the corrugated narrow grooves 2g on the surface of the block 2 with the aim of significantly reducing the pattern noise. The steering stability level of the tire of the example falls within a range where there is no practical problem. (3) Abrasion resistance test: Comparative tire 100 was 98 in comparison with tire 100, and the abrasion resistance was somewhat reduced due to the formation of corrugated grooves 2g on the surface of block 2. However, there was a problem in practical use. It is not enough.

From the above results, block 2 shown in FIGS.
The tread pattern including the block 2 is suitable for a tire mainly configured to reduce pattern noise, while the tread pattern including the block 2 illustrated in FIGS. 1 and 2 reduces steering noise and abrasion resistance instead of slightly reducing pattern noise. It fits tires that are held at the same level as conventional tires, and can be used properly as needed.

[0026]

According to the first to third aspects of the present invention, it is possible to maintain the steering stability in straight running and the abrasion resistance of the tread rubber at the same excellent level as that of the conventional tire, and to improve the pattern noise. Can be advantageously reduced, and the pneumatic tire for a two-wheeled vehicle can be provided which can control the steering stability and the abrasion resistance according to the pattern noise reduction level.

[Brief description of the drawings]

FIG. 1 is a developed view of a tread pattern according to an embodiment of the present invention.

FIG. 2 is a block cross-sectional view of a central block row taken along line II-II shown in FIG.

FIG. 3 is a block cross-sectional view of a center block row according to another embodiment.

FIG. 4 is a block plan view of a central block row shown in FIG. 3;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Tread surface 2 Block of central block row 2S Block surface of central block row 2g Block narrow groove of central block row 2r Block narrow rib of central block row 3, 4, 5 Block of side block row 7 Blocks of central block row Tread surface circumferential groove 8 Tread width direction groove which divides block of central block row W tread surface development width Te tread surface edge T _R tread rubber w narrow rib arrangement pitch D tread surface circumferential groove depth which divides block of central block row d Depth of the narrow groove in the center block row E Tread width center circumference

Claims (3)

[Claims] 1. A central block row composed of a plurality of blocks straddling a tread width center peripheral line on a tread side of a tread rubber, and at least two lateral sides spaced apart from each other in the tread width direction on both sides sandwiching the central peripheral line. In the pneumatic tire for a two-wheeled vehicle provided with a block row in a tread portion, each block of the central block row has a plurality of narrow grooves extending in a circumferential direction of a tread on each surface, and a plurality of narrow grooves formed by the narrow grooves. Characterized in that each side block row has a smooth surface.
Pneumatic tires for wheeled vehicles. 2. The tire according to claim 1, wherein the depth of the plurality of narrow grooves is in the range of 5 to 30% of the depth of the tread circumferential grooves that define the central block row. 3. The tire according to claim 1, wherein the plurality of narrow grooves and the plurality of narrow ribs form a waveform in a tread width direction.