JP2002059711A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain uneven wear on a shoulder block due to turning driving. SOLUTION: A chamfer 17 chamfering width W between a lower ridge edge KL crossing a groove wall 16 and an upper ridge edge KU crossing a tread surface 2S of which increases toward the later grounding side from the tire first grounding side is formed on the groove wall 16 of the tire equatorial side of the shoulder block 12. Chamfering width Wo on a block end on the later grounding side is more than two times of chamfering width Wi on a block end on the first grounding side and less than 8.0 mm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of suitably preventing uneven wear on a shoulder block during cornering.

[0002]

2. Description of the Related Art In a pneumatic tire, a lateral force acts strongly on a tread shoulder during turning. Therefore, in the case of a tire having a block pattern or a rib block pattern in which a block is formed on the tread shoulder portion, the shoulder block may be set to a horizontal position when the vehicle travels severely with a sharp steering operation such as running on a winding road at high speed. Deform in the direction.

As a result, as shown schematically in FIG. 6, uneven wear b occurs in the shoulder block a starting from the inward edge a1 in the tire axial direction, and the steering block has relatively early steering stability. There is a problem of lowering. In particular, the uneven wear b tends to increase from the ground first arrival side to the rear arrival side.

For this reason, conventionally, the lateral rigidity of the block is increased by increasing the inclination angle α of the wall surface of the shoulder block a, or by increasing the size of the shoulder block a, thereby suppressing the deformation itself. However, the effect has not yet been sufficiently obtained.

[0005] Therefore, the present invention is based on the above-mentioned uneven wear based on forming a chamfered portion in which a chamfering width W increases in a predetermined range from a first arrival side to a rear arrival side in a groove wall on the tire equator side of the shoulder block. It is an object of the present invention to provide a pneumatic tire capable of effectively suppressing the occurrence of a tire and maintaining the steering stability and appearance over a long period of time.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, a plurality of vertical main grooves extending in the tire circumferential direction on both sides of a tire equator on a tread surface and intersecting the same are provided. By providing a horizontal main groove in the direction, a shoulder block surrounded by a tread edge, a horizontal main groove, and a vertical main groove closest to the tread edge forms an outer block row in which a tire circumferential direction is arranged, while the shoulder block is formed. Notch the groove wall on the tire equator side facing the vertical main groove of the block in a chamfered shape,
The chamfer width W, which is the length in the tire axial direction, between the lower ridge where the radially inner end of the notch intersects the groove wall and the upper ridge formed by the notch and the tread surface, While forming a chamfer that increases from the first arrival side to the second arrival side,
The chamfer width Wo at the rear end block end is at least twice the chamfer width Wi at the first arrival block end,
And is 8.0 mm or less.

[0007] In the invention of claim 2, the chamfered portion sets the chamfering depth H, which is the length in the tire radial direction, between the lower edge and the upper edge, from the tire first arrival side to the rear. The chamfering depth Ho at the block end on the rear arrival side is greater than or equal to twice the chamfering depth Hi at the block end on the first arrival side, and 6.0 mm or less, while increasing toward the receiving side. I have.

According to the third aspect of the present invention, the chamfer width W
Is characterized in that it gradually increases in a curved shape from the tire first arrival side to the rear arrival side.

In the invention according to claim 4, the shoulder block has a sipe-shaped lateral narrow groove having a groove width Wy of 2.0 mm or less inclined between the adjacent horizontal main grooves in the same direction as the horizontal main groove. Is formed.

In the invention of claim 5, the tread surface is smoothly connected from the tire equator side to the tread edge side in a tire meridional section in a standard state where the tire is assembled to a regular rim and filled with a normal internal pressure. It is characterized by comprising at least five arc portions having different radii of curvature, and each of the arc portions has a gradually decreasing radius of curvature from the tire equator side to the tread edge side.

[0011] In the invention according to claim 6, the tread surface is an inner block row in which an inner block surrounded by the vertical main groove and the horizontal main groove is arranged in the tire circumferential direction inside the shoulder block in the tire axial direction. And a groove wall on the outer side in the tire axial direction of the inner block is cut out in a chamfered shape, and a chamfered portion in which a chamfer width W decreases from a tire first arrival side to a rear arrival side is formed.

In the present application, the “regular rim” is a standard rim defined by JATMA and defined by TRA.
"Design Rim" or "Measur" specified by ETRTO
ing Rim ", and the" regular internal pressure "is the maximum air pressure specified by JATMA and the table" TIRE LOAD "specified by TRA.
Maximum value described in "LIMITS AT VARIOUS COLD INFLATION PRESSURES" or "INFLATION PR specified by ETRTO"
ESSURE ", especially for passenger car tires.
0 KPa.

[0013] The "tread edge" means both edges of a tread surface area where the tread surface can contact the ground when a normal load is applied to the tire in the standard state, and the "normal load" is defined by JATMA. If there is, the maximum load capacity, if TRA, the table
"TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESS
URES ", the maximum value for ETRTO," LOAD CAP
ACITY ".

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment of the present invention will be described.
This will be described together with the illustrated example. 1 is a meridional section in a standard state in which the pneumatic tire of the present invention is assembled to a regular rim and filled with a regular internal pressure, FIG. 2 is a developed view of a tread pattern thereof, and FIGS. It is a top view and a perspective view.

In FIG. 1, a pneumatic tire 1 has a carcass 6 which is folded back around a bead core 5 of a bead portion 4 from a tread portion 2 to a sidewall portion 3 and is locked.
And a belt layer 7 disposed radially outside of the carcass 6 and inside the tread portion 2.

The carcass 6 comprises at least one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 75 to 90 degrees with respect to the tire circumferential direction. In this embodiment, one carcass ply 6A is used. Organic fiber cords such as polyester, rayon, and aromatic polyamide can be suitably used.

The belt layer 7 is composed of two or more steel cords or aromatic polyamide cords arranged at an angle of 10 to 35 degrees with respect to the tire circumferential direction. Belt plies 7A and 7B. By laying the belt cords with the inclination directions of the cords different from each other so that the belt cords intersect between the plies, the substantially entire width of the tread portion 2 is reinforced with a hammer effect and the tread rigidity is increased. .

Next, in the pneumatic tire 1 of the present embodiment, as shown in FIG. 2, a plurality of vertical main grooves 10 extending in the tire circumferential direction on both sides of the tire equator C on the tread surface 2S.
And a horizontal main groove 11 that intersects with the tread edge TE, the horizontal main groove 11, and the tread edge T
A shoulder block 12 surrounded by the vertical main groove 10 closest to E forms an outer block row 13 arranged in the tire circumferential direction.

More specifically, in the present embodiment, the vertical main groove 10
The figure shows an example in which each of the vertical main grooves 10 extends substantially linearly, which is composed of four vertical main grooves 10A on the tire equator side and outer vertical main grooves 10B on the tread edge TE side.

In the present embodiment, the horizontal main groove 11 is formed by connecting the inner and outer vertical main grooves 10A and 10B to form an inner block row 15 in which the inner blocks 14 are arranged in the tire circumferential direction. 11A and an outer horizontal main groove 11B which forms an outer block row 13 in which the shoulder blocks 12 are arranged by joining between the outer vertical main groove 10B and the tread edge TE.

In this embodiment, as shown in FIG. 3 in an enlarged manner, the groove wall 16 on the tire equator C side facing the outer vertical main groove 10B of the shoulder block 12 is provided.
A chamfered portion 17 is formed by notching 6 in a chamfered shape.

As shown conceptually in FIG. 4, the chamfered portion 17 has a lower ridge KL where the notch intersects the groove wall 16 and an upper ridge KU where the notch forms the tread surface 2S. The width of the chamfer W, which is the length in the tire axial direction, increases from the tire first arrival side to the rear arrival side. At this time,
7. The chamfer width Wo at the block end on the rear arrival side is at least twice the chamfer width Wi at the block end on the first arrival side, and
0 mm or less.

In this embodiment, the chamfered portion 17 further sets a chamfering depth H, which is the length in the tire radial direction between the lower ridge KL and the upper ridge KU, from the tire first arrival side. The chamfering depth Ho at the block end on the rear arrival side is set to be at least twice the chamfering depth Hi at the block end on the first arrival side and at most 6.0 mm. .

In the shoulder block 12 having the chamfered portion 17 formed therein, the groove wall 16 serving as a starting point of uneven wear is provided.
Since the side block edge is cut off in advance, the occurrence and progress of the uneven wear can be suppressed. In particular, since the external force acting at the time of turning increases from the first arrival side to the second arrival side, by changing the size of the chamfered portion 17 accordingly, uneven wear can be more effectively suppressed.

The rate of increase of the external force acting during turning tends to gradually increase from the first arrival side to the second arrival side. Therefore, the chamfering width W increases in a curved shape from the first arrival side to the rear arrival side. In other words, it is preferable to form the upper edge KU by curving the upper edge KU in an arc shape protruding inward in the tire axial direction with a minimum amount of chamfer to obtain a higher uneven wear suppressing effect. In this example, the lower edge KL is formed in a substantially straight line in order to facilitate the manufacture of the mold.

Here, the chamfer width Wo on the rear arrival side is 8.
If it exceeds 0 mm, the contact area of the shoulder block 12 becomes too small, and the running performance with new tires is hindered. Conversely, if the chamfer width Wo is less than twice the chamfer width Wi on the first-arrival side, the effect of preventing uneven wear is insufficient, and uneven wear tends to occur from the block edge on the rear-wear side. Therefore, it is desirable that the chamfer width Wo be 2 × Wi to 6.0 mm.

Similarly, the chamfering depth Ho on the rear arrival side is
If it exceeds 6.0 mm, the running performance with a new tire tends to be impaired. Conversely, if it is less than twice the chamfering depth Hi on the first arrival side, the effect of suppressing uneven wear cannot be sufficiently exhibited. Therefore, the chamfering depth Ho is more preferably set to 2 × Hi to 4.0 mm.

In this embodiment, the shoulder block 12
A lateral narrow groove 19 inclined in the same direction as the horizontal main groove 11B is formed between the adjacent horizontal main grooves 11B, 11B, and the shoulder block 12 is provided with a block portion 12i on a first arrival side and a rear arrival side. A case where the image is divided into 12o is illustrated. The lateral narrow groove 19 has a sipe shape with a groove width Wy of 2.0 mm or less,
At the time of turning, the groove walls contact each other, and the apparent block lateral rigidity can be maintained high. Therefore, a large cornering force can be secured while improving the wet performance. Further, since the occurrence of uneven wear can be limited to the block portion 12o on the rear wear side, the chamfer width W can be reduced, and the decrease in the ground contact area of a new tire can be suppressed.

Here, as shown in FIG. 1, the chamfered portion 17 has an angle .theta.
0 to 90 °, the groove width Wg of the outer vertical main groove 10B is 4 to 12 mm, and the distance L from the tire equator C to the center of the outer vertical main groove 10B is from the tire equator C of the tread edge TE. A tire having a distance TW of 0.40 to 0.80 times, particularly the angle θ is 40 to 70 °, and a distance L is 0.45 × TW to 0.75.
X It can be more preferably adopted for TW tires.

This is because the angle θ is less than 30 ° and the groove width W
If g is larger than 12 mm and the distance L is larger than 0.80 × TW, the block deformation during turning becomes too large, for example, the block rigidity becomes too small, and the chamfer 17 alone sufficiently suppresses uneven wear. It becomes difficult. If the groove width Wg is less than 4 mm, the rigidity of the block is high and uneven wear is less likely to occur, so that the necessity of the chamfer 17 is reduced. If the distance L is less than 0.4 × TW, the external force received during turning is not so large, uneven wear is unlikely to occur, and the necessity of the chamfer 17 is reduced. This is because the position is on the equator side where the ground pressure is high, and the noise performance deteriorates.

In the present embodiment, the shoulder block 12 further has a sipe-shaped vertical narrow groove 20 extending in the tire circumferential direction, for example, having a groove width of 2.0 mm or less, near the tread edge TE. The ring performance is enhanced, and so-called shoulder uneven wear (shoulder wear) starting from the tread edge TE is prevented from progressing inward in the tire axial direction.

In this embodiment, a chamfered portion 22 is also formed on the groove wall 21 of the inner block 14 facing the groove wall 16. In the chamfered portion 22, contrary to the chamfered portion 17, at least the chamfering width W, in this example, the chamfering width W and the chamfering depth H decrease from the tire first arrival side to the rear arrival side. Thereby, the change in the groove volume of the outer vertical main groove 10B is suppressed, and the drainage performance is made uniform.

The groove 23 on the tire equator side of the inner block 14 is also provided with a chamfer 17 'having the same configuration as the chamfer 17 in order to suppress uneven wear in the inner block 14. However, according to the magnitude of the external force received at the time of turning, the chamfering width W and the chamfering depth H of the chamfered portion 17 ′ are set to be relatively smaller than those of the chamfered portion 17 in order to secure the contact area. preferable. The inner block 14 also has a sipe-shaped lateral narrow groove 24 having a groove width of 2.0 mm or less that is inclined in the same direction as the lateral main groove 11A between the adjacent lateral main grooves 11A. In the present example, the inner block row 15 is displaced in the circumferential direction at substantially a half pitch with respect to the outer block row 13, whereby the lateral narrow groove 24 is formed.
And the outer horizontal main groove 11B, and the horizontal narrow groove 19 and the inner horizontal main groove 11A are configured to be continuous in the tire axial direction.

Next, in this example, as shown in FIG. 5, the tread surface 2S in the tire meridional section in the standard state smoothly continues from the tire equator C side to the tread edge TE side and has a radius of curvature R And at least five arc portions P each having a different tire equator C
A preferred case in which the radius of curvature R is sequentially reduced from the side toward the tread edge TE is illustrated. In particular, in this example, the tread surface 2S includes first to tenth arc portions P1 to P10, and the radii of curvature R1 to R10 are R1>R2>R3>R4>R5>R6>R7>R8> R
9> R10 exemplifies a case where the lines are smoothly connected.

In the tread surface 2S including the plurality of arc portions P, there is little change in the shape of the ground contact surface (so-called footprint) from straight running to turning. That is, the contact pressure is made uniform, and the force acting on the shoulder block 12 during turning is reduced. As a result, due to the synergistic action with the chamfered portion 17, the uneven wear suppressing effect of the present invention can be more effectively exerted.

Although the preferred embodiment of the present invention has been described in detail, the present invention is not limited to the illustrated embodiment, but may be implemented in various forms.

[0037]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire having the structure shown in FIG. 1 and having a tread pattern according to FIG. 2 has a tire size of 225 / 55R1.
The pneumatic tire No. 6 was prototyped based on the specifications shown in Table 1, and the test stability of each test tire when new, the steering stability after abrasion, and the appearance after the abrasion were tested.

(1) Steering stability: The test tire was mounted on a rim (8
J) and the internal pressure (230 kPa).
0cc) is mounted on all the wheels, the tire runs on a dry asphalt tire test course, and characteristics related to steering wheel responsiveness, rigidity, grip, and the like are indicated by an index with the conventional example set to 100 by sensory evaluation of the driver. The larger the index, the better. It should be noted that the steering stability when new is, for example, 30
km after running-in, and the steering stability after abrasion was such that the inner main vertical groove 10A had a groove depth of 60
% Was measured after traveling on a winding road until the wear state reached%.

(2) Appearance after abrasion The appearance state after the abrasion was examined by visual inspection to compare the conventional example with one.
It is indicated by an index of 00. The larger the index, the better.

(3) Noise The vehicle used in the test of the steering stability was coasted on a smooth road surface at a speed of 100 km / h to 40 km / h (gears were neutrally coasted), and the noise in the vehicle was reduced by the driver. It is indicated by an index with the conventional example as 100 by sensory evaluation. The larger the index, the better.

[0041]

[Table 1]

As shown in the table, the tires of the examples can greatly suppress uneven wear without substantially impairing steering stability when new, and can maintain high steering stability and appearance for a long period of time. You can check.

[0043]

As described above, according to the present invention, a chamfered portion in which the chamfer width W increases in a predetermined range from the first arrival side to the rear arrival side is formed in the groove wall on the tire equator side of the shoulder block. In addition, uneven wear generated on the shoulder block can be effectively suppressed, and steering stability and appearance can be maintained for a long time.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a developed view showing the tread pattern.

FIG. 3 is an enlarged plan view showing a shoulder block.

FIG. 4 is a schematic perspective view of a shoulder block conceptually showing a chamfer.

FIG. 5 is a diagram showing a contour shape of a tread surface.

FIG. 6 is a diagram illustrating a problem of the related art.

[Explanation of symbols]

 2S Tread surface 10 Vertical main groove 11 Horizontal main groove 12 Shoulder block 13 Outer block row 14 Inner block 15 Inner block row 16 Groove wall 17 Beveled part 19 Horizontal narrow groove 21 Groove wall 22 Beveled part C Tire equator KL Lower edge KU Upper edge P, P1 to P10 Arc R, R1 to R10 Radius of curvature TE Tread edge

Claims (6)

[Claims] A tread surface is provided with a plurality of vertical main grooves extending in the tire circumferential direction on both sides of the tire equator and horizontal main grooves extending in a direction intersecting the vertical main grooves. While the shoulder block surrounded by the vertical main groove closest to the edge forms an outer block row lined up in the tire circumferential direction, the groove wall on the tire equator side facing the vertical main groove of the shoulder block is chamfered. A chamfering width W, which is the length in the tire axial direction between a lower ridge where a radially inner end of the notch intersects the groove wall and an upper ridge formed by the notch with a tread surface, While forming a chamfered portion increasing from the tire first arrival side to the rear arrival side, the chamfer width Wo at the rear end block end is at least twice the chamfer width Wi at the first arrival block end,
And a pneumatic tire having a size of 8.0 mm or less. 2. The chamfered portion has a chamfering depth H that is a length in a tire radial direction between the lower ridge and the upper ridge.
From the tire first arrival side to the rear arrival side, and the chamfering depth Ho at the block end on the rear arrival side.
2. The pneumatic tire according to claim 1, wherein the depth of the pneumatic tire is at least twice the chamfering depth Hi at the end of the first-arrival block and at most 6.0 mm. 3. The pneumatic tire according to claim 1, wherein the chamfer width W gradually increases in a curved manner from the tire first arrival side to the rear arrival side. 4. The shoulder block has a groove width Wy that is inclined in the same direction as the horizontal main groove between the adjacent horizontal main grooves.
4. The pneumatic tire according to claim 1, wherein a sipe-shaped lateral narrow groove of 0 mm or less is formed. 5. The tread surface has a smooth radius from the tire equator side to the tread edge side and has a different radius of curvature in a tire meridional section in a standard state where the tire is assembled to a normal rim and filled with a normal internal pressure. 5. The pneumatic tire according to claim 1, wherein the pneumatic tire comprises at least five arc portions, and each arc portion has a radius of curvature gradually reduced from a tire equator side to a tread edge side. 6. The tread surface has, on the inner side in the tire axial direction of the shoulder block, an inner block row in which inner blocks surrounded by the vertical main groove and the horizontal main groove are arranged in the tire circumferential direction. 5. A chamfered cutout in a groove wall on the outer side in the tire axial direction of the block to form a chamfered portion in which a chamfer width W decreases from a tire first arrival side to a rear arrival side. Or the pneumatic tire according to 5.