JPH05330315A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To prevent liver wear until the last stage of abrasion without offset abrasion or cracks, etc., by providing thin grooves, opened in a groove wall of a peripheral direction main groove and having parallel parts extending in parallel along tread configuration lines, and tilted parts, extending to inner sides in a tire radius direction. CONSTITUTION:A thin groove 18, opened in a groove wall of a peripheral direction main groove 14 and is continued in the peripheral direction, has a parallel part 18A, extending along a tread configuration line 12A, a tilted part 18B, extending to the inner side in a tire radius direction, and forms a different-level region 20 on between the thin groove 18 and the peripheral direction main groove 14. The groove width delta of the thin groove 18 is made 1mm<=delta<=4mm, the angle theta between the tilted part 18B and a tread perpendicular 22 is made 0 deg.<=theta<=8 deg., a distance (d) of a thin groove bottom 18C from the tread surface to a peripheral direction main depth D is made 0.8D<=d<=1.2D, the width (a) of a tire radius direction inner side surface 18D in a tire width direction to a tread effective grounding width T is made 0.01T<=a<=0.05T, and the radius direction thickness (t) of the horizontal part 18A is made 0.2D<=t<=0.45D. Consequently liver wear can be surely prevented until the 1st stage of abrasion.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire suitable for heavy-duty vehicles such as trucks and buses and having excellent uneven wear characteristics.

[0002]

2. Description of the Related Art A pneumatic tire having a tread having a circumferential main groove extending in the tire circumferential direction, which is used in heavy-duty vehicles such as trucks and buses, has a rib end on the circumferential main groove side while running. Alternatively, there is a problem that uneven wear called so-called river wear occurs from the block end. Generally, in a pneumatic tire, the ground contact pressure P on the ground contact surface of the rib or block is substantially equal in the tire width direction when no lateral force (so-called side force) acts. However, when cornering is performed and lateral force is input to the rib or block, the ground pressure at the end of each rib or block on the lateral force input side rises, which causes a local wear step, that is, The core of uneven wear is generated. This core greatly spreads during tire rolling and becomes river wear.

In order to prevent this river wear, it is effective to reduce the force applied to the rib end or the block end on the tire width direction side, and as shown in FIG. 14, it is divided by the circumferential main groove 100. In the pneumatic tire 104 having the rib 102, the circumferential main groove 1 is formed at the rib end.
A plurality of sipes 106 having open ends on the 00 side are provided along the circumferential direction to reduce the rigidity of the rib ends and reduce the ground contact force applied to the rib ends. As shown in FIG. 15A, ribs or blocks are provided. Outside the rib end or block end of the tire 110 on the tire width direction side (arrow W direction side) is the tread outer contour 1
A method is known in which a void region is provided by a narrow groove 114 that is parallel to the groove 12 to reduce the ground contact pressure at the rib end or block end on the tire width direction side.

[0004]

However, in the method of using sipes, due to the heavy use of sipes, cracks may occur from the open ends of sipes, and when the sipes have a long length, the area between sipes is a circumferential saw blade. The so-called heel and
Toe wear may occur, and this may serve as a core to develop even larger uneven wear. If the sipe length is shortened in order to avoid the occurrence of cracks and heel-and-toe wear, the effect of lowering the rigidity is not sufficient, and the effect of preventing river wear is poor, and river wear may occur.

On the other hand, in the method of forming the void region by the fine groove 114 which is parallel to the outer contour 112 of the tread, there is a problem that the effect is lost when the void portion is worn and the state becomes a river wear (see FIG. 15B). ). Since this river wear has a small distance from the tire rotation axis with respect to the tread surface, it is dragged when the tire rolls, and spreads greatly as uneven wear travels.

Further, as shown in FIG. 16 (A), a method of providing a large engraved portion 116 instead of a narrow groove may be considered, but as shown in FIG. 16 (B), a small stone 118 during traveling.
If you bite it, it will not come off and may cause damage to the tread.

In view of the above facts, the present invention has an object to provide a pneumatic tire capable of surely preventing river wear until the end of wear without causing other uneven wear and cracks. Is.

[0008]

The invention according to claim 1 is
In a pneumatic tire including a tread having a circumferential main groove extending in the tire circumferential direction, a fine groove is provided on a groove wall of the circumferential main groove, and the fine groove is opened in the circumferential main groove and extends along a tread contour line. A horizontal portion extending substantially in parallel with each other and an inclined portion that is continuous with the horizontal portion and extends inward in the tire radial direction.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the width a of the horizontal portion is 0.01T ≦ a ≦ 0.05T with respect to the tread width T, and the horizontal portion The thickness t of the outer portion in the tire radial direction is 0.2D ≦ t ≦ 0.45D with respect to the circumferential main groove depth D, and the distance d from the tread surface of the narrow groove bottom is equal to the circumferential main groove depth D. On the other hand, 0.8 ≦ d ≦ 1.2, and the narrow groove width δ is 1 mm ≦ δ ≦ 4.
The angle θ of the inclined portion with respect to the tread perpendicular is 0 ° ≦ θ ≦ 8 °. In addition, as long as the groove width δ is 1 mm ≦ δ ≦ 4 mm, the groove width δ may be different between the horizontal portion and the inclined portion, or the groove width δ may be changed.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, the end of the horizontal portion on the circumferential main groove side of the outer surface of the horizontal portion in the tire radial direction and the tire radius of the horizontal portion. It is characterized in that the tire axial deviation amount b with respect to the circumferential main groove side end portion of the inner surface in the direction is b ≦ 0.8a.

According to a fourth aspect of the present invention, in the pneumatic tire according to the first aspect, the second aspect or the third aspect, an extension portion is provided which is continuous with the inclined portion and extends in a direction away from the circumferential main groove. , The tire axial length c of the extension is 1
The feature is that mm ≦ c ≦ 3 mm.

According to a fifth aspect of the present invention, in the pneumatic tire according to the first aspect, the second aspect, or the third aspect, an enlarged portion is provided at the bottom of the narrow groove, and the radius of curvature R of the enlarged portion is 1.
The feature is that 5δ / 2 ≦ R ≦ 2.5δ / 2.

[0013]

In the rib or block of the pneumatic tire according to the present invention, a fine groove is provided in the groove wall of the circumferential main groove, and the fine groove is opened in the circumferential main groove and extends along the tread contour line. A horizontal portion extending substantially in parallel with each other, and an inclined portion continuous with the horizontal portion and extending inward in the tire radial direction.

Therefore, the rigidity of the rib end or the block end on the tire width direction side is lowered by the horizontal portion until the wear of the rib or block reaches the horizontal portion of the narrow groove, that is, in the initial stage of wear to the middle stage of wear. Therefore, even if a lateral force is input to the rib or block, the ground pressure increase at the end portion on the lateral force input side is suppressed. This prevents the occurrence of river wear due to the rise in ground pressure at the ends of the ribs or blocks.

When the tire rolls in the vehicle advancing direction under load, the ground contact area of the tread portion is sheared and deformed in the tire tangential direction due to the relative movement with the road surface. When wear progresses and the wear surface reaches the horizontal portion of the narrow groove, the inner surface of the rib or block in the tire radial direction of the horizontal portion appears. On the other hand, the groove width dimension of the horizontal portion is lowered inward in the radial direction of the tire, and a stepped region having a small land portion is formed between the inclined portion of the narrow groove and the circumferential main groove. Since the distance from the tire axis of rotation to the wear surface is small, the top of this step region (wall surface on the inner side in the tire radial direction of the horizontal part) is dragged when the tire rolls, and the shearing force directed in the braking direction is applied. Is large in this step region.

Since the sum of the shearing forces in the driving and braking directions acting per unit area of the ground contact area is considered to be substantially constant, if the shearing force acting in the stepped area increases in the braking direction, it will be adjacent to the stepped area. This is substantially equivalent to the reduction of the shearing force acting on the land portion that acts in the braking direction, and the deviation of the rib end or block end due to the shearing force acting in the tire circumferential direction of the rib or block adjacent to the step area is caused. Wear is suppressed.

Here, after the wear progresses and the outer portion of the horizontal portion in the radial direction of the tire is worn away, the step region serves as a buffer region for the lateral force, and the lateral force is prevented from being directly concentrated on the rib end of the rib. However, the occurrence of river wear in the rib body is prevented, and even if lateral force is input and a core of uneven wear occurs, the step region is mainly worn during tire rolling, and the rib or block is Since it is not dragged, it can be prevented from developing into riverwear.

Moreover, since the step region is separated from the adjacent rib or block body portion by the slanted portion of the narrow groove,
Wear in the step region does not affect the adjacent ribs or blocks.

Further, after wear progresses and the outer portion of the horizontal portion in the radial direction of the tire is worn away, the slanted portion of the narrow groove appears on the tread surface, so that the wet performance after the middle stage of wear is also improved.

According to the invention of claim 2, in the pneumatic tire of claim 1, the width a of the horizontal portion is 0.01T ≦ a ≦ 0.05T with respect to the tread width T.
The ground pressure at the rib end or the block end can be optimally reduced.

If the width a of the horizontal portion is less than 0.01T, the rigidity in the tire circumferential direction of the step region becomes too small after the wear reaches the horizontal portion, resulting in a shearing force acting in the braking direction. Cannot be applied to the step area, and the shearing force acting on the rib or block in the braking direction is relatively increased, and the effect of lowering the ground contact pressure at the adjacent rib end or block end is small. It becomes impossible to effectively prevent uneven wear of the rib end or the block end.

On the other hand, when the width a of the horizontal portion exceeds 0.05T, the ground contact pressure of the outer portion in the tire radial direction of the horizontal portion is decreased more than necessary, and the decrease in the ground contact pressure causes a narrow groove inward in the radial direction. The burden is increased by concentrating on the non-existing parts, and the wear resistance of the tread is reduced. In addition, before the wear reaches the horizontal portion, the rigidity of the outer portion of the horizontal portion in the radial direction of the tire is greatly reduced, and there is a possibility that baldness may occur even when a lateral force is input.

Further, the thickness t of the outer portion of the horizontal portion in the radial direction of the tire is set to 0.2D≤t≤0 with respect to the circumferential main groove depth D.
Since it is set to 45D, the rigidity of the outer portion of the horizontal portion of the rib or block in the tire radial direction can be optimally maintained, and the ground pressure at the rib end or block end can be optimally reduced. The thickness t of the outer portion of the horizontal portion in the radial direction of the tire is set to 0.2 or more because the time of occurrence of river wear is about 20% of the normal wear rate (wear amount / groove depth), and less than 0.2D. However, the rigidity of the outer portion of the horizontal portion in the radial direction of the tire may be insufficient, and baldness may occur when a lateral force is input. If it exceeds 0.45D, the contact pressure lowering effect is less and wear is reduced in the horizontal portion. Before
It becomes impossible to effectively prevent liverware.

Further, the distance d of the bottom of the narrow groove from the tread surface is 0.8D ≦ d ≦ 1.2D with respect to the circumferential main groove depth D.
Therefore, uneven wear can be effectively prevented until the end of wear.

Further, since the groove width δ of the narrow groove is set to 1 mm ≦ δ ≦ 4 mm, the deformation of the rib or block is allowed, the rigidity of the rib end or the block end can be optimally reduced, and the tire radius of the horizontal portion can be reduced. The amount of deformation of the outer side portion in the direction can be kept optimal, and further, it is prevented that the inclined portion of the narrow groove bites a small stone or the like after abrasion progresses and the outer portion of the horizontal portion in the radial direction of the tire is worn away. ..

When the groove width δ of the fine groove is less than 1 mm,
After the wear progresses and the outer portion of the horizontal portion in the radial direction of the tire is worn away, the step region sufficiently bears the ground contact pressure even when a relatively small load is applied to the normal load. The shearing force in the braking direction cannot be substantially concentrated on the region, and the effect of reducing the ground pressure of the rib or block becomes insufficient. Further, the blade for forming the narrow groove has a problem in strength.

On the other hand, when the groove width δ of the narrow groove exceeds 4 mm, the rigidity of the rib or block is remarkably decreased, and further, after the wear progresses and the outer portion of the horizontal portion in the radial direction of the tire is worn away, the regular load is applied. Even if the above load is applied, the step region does not come into contact with the road surface, the effect of the step region cannot be expected, and pebbles and the like are caught in the inclined portion, which causes a tire failure.

Further, since the angle θ of the inclined portion with respect to the tread perpendicular is set to 0 ° ≦ θ ≦ 8 °, the inclined portion and the circumferential main portion are kept even after the wear progresses and the outer portion in the radial direction of the tire is worn away. The rigidity of the step region between the groove and the groove is sufficiently secured, and the strength is not insufficient. When the angle θ of the inclined portion with respect to the tread perpendicular exceeds 8 °, there is a problem in that the blade forming the narrow groove is not easily removed.

The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the end of the horizontal part on the circumferential main groove side of the outer surface of the horizontal part in the radial direction of the tire and the tire radius of the horizontal part. By setting the amount of axial deviation b of the inner side surface in the circumferential direction of the main groove in the tire axial direction to b ≦ 0.8a, it is possible to prevent the blade forming the narrow groove from coming off and to prevent rubber breakage or blade breakage. At the same time, the effect of reducing the grounding pressure at the rib end or the block end can be kept good.

The tire axial deviation amount b between the end of the horizontal portion on the circumferential main groove side of the outer surface in the radial direction of the tire and the end of the inner portion of the horizontal portion on the inner side of the tire radial direction in the circumferential direction on the circumferential main groove is 0. If it exceeds 8a, the effect of reducing the ground pressure at the rib end or the block end cannot be expected. Here, when the width a of the horizontal portion is large, it is preferable to increase the deviation amount b within the previous period range in consideration of the omission of the blade forming the narrow groove.

The invention according to claim 4 is the same as claim 1,
The pneumatic tire according to claim 2 or 3, wherein an extension portion is provided continuously with the inclined portion and extends in a direction away from the circumferential main groove, and a tire axial length c of the extension portion is 1
Since mm ≦ c ≦ 3 mm, the stress at the bottom of the narrow groove can be dispersed, which prevents the occurrence of cracks at the bottom of the narrow groove. In addition, the tire axial length c of the extension is 1 mm
If it is less than 3, there is no effect on the stress dispersion, and if it exceeds 3 mm, the rigidity of the rib or block is significantly reduced.

The invention according to claim 5 is the same as claim 1,
The pneumatic tire according to claim 2 or 3, wherein an enlarged portion is provided at the bottom of the inclined portion, and the radius of curvature R of the enlarged portion is set to 1.5δ / 2 ≤ R ≤ 2.5δ / 2. It is possible to disperse the stress at the bottom, which prevents cracking from the bottom of the narrow groove. It should be noted that if the radius of curvature R of the enlarged portion is less than 1.5δ / 2, there is no effect on stress dispersion, and if it exceeds 2.5δ / 2, the rigidity of the rib or block is significantly reduced. The radius of the enlarged portion may be provided on one side of the narrow groove or may be continuously provided on both sides.

[0033]

【Example】

[First Embodiment] A first embodiment of the present invention will be described with reference to FIGS.

The pneumatic tire 10 of this embodiment is TBR1.
Since it is 1R22.5 14PR and the internal structure is a normal radial structure, description and illustration of the internal structure are omitted.

As shown in FIGS. 2 and 3, in the tread 12 of the pneumatic tire 10 of this embodiment, the tire width is defined by four circumferential main grooves 14 extending in the tire circumferential direction (arrow S direction). It is provided with five ribs 16A, 16B, and 16C divided in the direction (arrow W direction).

In this embodiment, the circumferential main groove 14 has a groove width GW of 10 mm at the opening and a groove depth D of 1 mm.
It is 3 mm.

As shown in FIG. 2, the tread center CL
The width R1 of the rib 16A arranged in the
The width R2 of the ribs 16B adjacent to both sides of the rib is 28.5 mm, and the width R3 of the ribs 16C on both ends of the tread is 37.5.
mm, and the effective ground contact width T of the tread 12 is 200 mm.

As shown in FIGS. 2 and 3, the rib 16B has a circumferential main groove 14 on the outer side in the tire width direction (arrow W direction).
Has a narrow groove 18 which is opened in the groove wall and is formed substantially continuously in the tire circumferential direction (arrow S direction).

As shown in detail in FIG.
Has a horizontal portion 18A extending substantially in parallel along the tread contour line 12A, and an inclined portion 18B which is continuous with the horizontal portion 18A and extends inward in the tire radial direction (direction of arrow R in FIG. 1). A small rib-shaped step region 20 is formed between the narrow groove 18 and the circumferential main groove 14.

The groove width δ of the narrow groove 18 is within the range of 1 mm ≦ δ ≦ 4 mm, and in this embodiment, the horizontal portion 18A and the inclined portion 18B.
Both are 2 mm. The groove width δ of the narrow groove 18 is equal to the horizontal portion 18
A and the inclined portion 18B may be different. Further, by forming the narrow groove 18 in a tapered shape, it is possible to improve the releasing property of the mold forming the narrow groove 18. Also,
In the present embodiment, the narrow groove bottom 18C of the narrow groove 18 has an arc shape,
The radius of curvature R is set to 1 mm.

Here, the inclined portion 18B and the tread contour line 1
The angle θ formed by the tread perpendicular 22 vertically lowered from 2A is 0 ° ≦ θ ≦ 8 °, and in the present embodiment, θ is 4 °.
Is.

Further, the distance d of the narrow groove bottom 18C of the narrow groove 18 from the tread surface is 0.8 with respect to the circumferential main groove depth D.
D ≦ d ≦ 1.2D, and d is 13 mm (D
= D).

On the other hand, in the horizontal portion 18A, the width a of the tire radial inner surface 18D in the tire width direction is within the range of 0.01T≤a≤0.05T with respect to the tread effective ground contact width T (see FIG. 2). In this embodiment, the inner surface 18 of the tire radial direction is
The width a of D in the tire width direction is 2 mm.

In this embodiment, the tire axial shift amount b is 0.
mm (in FIG. 1, the circumferential main groove side end portion 18F and the circumferential direction main groove side end portion 18G are illustrated as being shifted in the tire width direction for easy understanding, but in the present embodiment, Are matched.).

Further, the thickness t of the outer portion of the horizontal portion 18A in the radial direction of the tire is 0.2D ≦ the depth D of the circumferential main groove.
t ≦ 0.45D, and in this embodiment, t is 4 mm (t /
D = 0.13).

Next, the operation of this embodiment will be described. By running, the wear of the tread 12 reaches the horizontal portion 18A of the narrow groove 18, that is, the rigidity of the outer end of the rib 16B in the tire width direction is reduced by the horizontal portion 18A during the initial stage of wear to the middle stage of wear. When lateral force is input,
In the rib 16B on the side to which the lateral force is input, an increase in the ground contact pressure at the tire width direction outer end portion is suppressed, and river wear is prevented.

As shown in FIG. 4, when the worn surface 12B of the tread 12 reaches the horizontal portion 18A of the narrow groove 18 as the wear progresses, the step region 20 serves as a lateral force buffer region, and the direct rib 06B is covered. Lateral force is prevented from concentrating on the rib end 12C, and river wear of the rib 16B main body is prevented. Moreover, the rib 16B main body has the slanted portion 18
Since it is separated from the step region 20 by B, the abrasion of the step region 20 does not affect the adjacent rib 16B.

Further, when the wear progresses and the wear surface 12B of the tread 12 reaches the horizontal portion 18A of the narrow groove 18,
The top of the step region 20 (the inner surface 18D of the horizontal portion 18A in the radial direction of the tire) is lowered inward in the radial direction of the tire with respect to the wear surface 12B of the rib 16B. That is, since the distance (radius) from the tire rotation axis (not shown) to the wear surface 12B of the tread 12 is small, the top of the step region 20 is dragged when the tire rolls, and the braking direction is changed. The directed shearing force is large in this step region 20. Therefore, the shearing force acting on the rib 16B forming the step region 20 in the braking direction is relatively small, and the bias due to the shearing force acting on the rib 16B forming the step region 20 in the tire circumferential direction is caused. Wear is suppressed. That is, as the wear progresses, the narrow groove 18
Even after the horizontal portion 18A disappears, even if the core of uneven wear occurs due to the side force, the generation of the river wear of the rib 16B is suppressed by the drag applied to the step region 20 when the tire rolls.

In the present embodiment, the distance d of the narrow groove bottom 18C from the tread surface is the same as the circumferential main groove depth D (13 mm). Therefore, the uneven wear suppressing effect by the step region 20 is reached until the end of wear. It is possible to suppress uneven wear due to the shearing force that is sustained and acts in the tire circumferential direction until the end of wear.

Further, in this embodiment, the relationship between the width a of the horizontal portion and the tread width T is a = 0.01T (a: 2 mm, T: 2).
Since it is set to 00 mm), the ground contact pressure at the tire width direction outer end of the rib 16B can be optimally reduced.

After the middle stage of wear, the horizontal portion 1
Since the outer portion of 8A in the radial direction of the tire is worn away and the inclined portion 18B of the narrow groove 18 is opened on the tread surface, drainage of the circumferential main groove 14 is supplemented. Here, since the groove width δ of the inclined portion 18B is set to 2 mm in this embodiment, the inclined portion 18B is
B bite stones are prevented from being caught.

Further, in this embodiment, the inclined portion 18B,
When the pneumatic tire 10 of this embodiment is released from the mold (not shown), the angle θ formed by the tread perpendicular line 22 vertically lowered from the tread contour line 12A is 4 ° and θ is not excessively large. It does not hinder the operation.

The thickness t of the outer portion of the horizontal portion 18A in the radial direction of the tire is t = 0.31 with respect to the depth D of the circumferential main groove.
Since it is D, the rigidity of the outer portion of the horizontal portion 18A in the radial direction of the tire can be optimally maintained and the rib 16
It is possible to optimally reduce the ground contact pressure at the tire width direction outer end portion of B.

Further, since the groove width δ of the narrow groove 18 is set to δ1 = 2 mm, the rib 16B is allowed to be deformed and the rib 16B is allowed.
Can optimally reduce the rigidity of the tire width direction outer end portion of the tire and can keep the deformation amount of the tire radial direction outer portion of the horizontal portion 18A optimal, and further, the angle θ of the inclined portion 18B with respect to the tread perpendicular 22. Is set to θ = 4 °, the rigidity of the step region 20 is sufficiently ensured even after the wear progresses and the outer portion of the horizontal portion 18A in the radial direction of the tire is worn away.

Here, in FIG. 5, the ground contact pressure (index) and t / T (t: tire radius of the horizontal portion 18A) at the rib end on the side to which the lateral force is input are clarified by the inventor's experiment. Direction outside thickness, T: effective tread width (T: effective contact width),
FIG. 6 shows the ground contact pressure (index) at the rib end and a / T (a: the width in the tire width direction of the tire radial inner surface 18D of the horizontal portion, T: the tread effectiveness, which are clarified by the inventors' experiments. FIG. 7 shows the relationship with the ground contact width) and the lateral force burden rate at each portion of the rib 16 when the lateral force is input, which is clarified by the inventor's experiment.

More specifically, the graph shown in FIG. 5 shows that in the pneumatic tire having the same structure as this embodiment, the effective ground contact width T (200 mm) of the tread 12 and the groove depth D (1
3 mm), the groove width GW (10 mm) of the circumferential main groove 14 and the width R1 (28 m) of the rib 16A arranged on the tread center CL.
m), width R2 of rib 16B (28.5 mm), rib 16C
Width R3 (37.5 mm), groove width δ (2 mm) of the narrow groove 18,
The angle θ (4 between the inclined portion 18B and the tread perpendicular 22)
°), the distance d (13 mm) from the tread surface of the narrow groove bottom 18C of the narrow groove 18, the circumferential main groove side end portion 18F of the tire radial outer side surface 18E of the horizontal portion 18A, and the tire radial direction of the horizontal portion 18A. A tire width direction deviation amount b (0 mm) from the circumferential main groove side end portion 18G of the inner side surface 18D and a tire width direction width a width of the tire radial direction inner side surface 18D of the horizontal portion 18A are fixed to fix the horizontal portion. When the thickness t of the tire radial direction outer portion of 18A is changed, t / D and the ground contact pressure (t
Is zero, that is, 100 when the thin groove 18 is not present).

Further, the graph shown in FIG. 6 shows in detail the tread 12 in the pneumatic tire having the same construction as this embodiment.
Effective ground contact width T (200 mm), the groove depth D of the circumferential main groove 14 (13 mm), the groove width GW (10 mm) of the circumferential main groove 14, and the width R1 of the rib 16A arranged on the tread center CL.
(28 mm), the width R2 (28.5 mm) of the rib 16B, the width R3 (37.5 mm) of the rib 16C, and the groove width δ (2
mm), the angle θ between the inclined portion 18B and the tread perpendicular 22
(4 °), the distance d (13 mm) from the tread surface of the narrow groove bottom 18C of the narrow groove 18, the circumferential main groove side end portion 18F of the tire radial outer side surface 18E of the horizontal portion 18A, and the horizontal portion 18A.
End portion 18 of the inner side surface 18D of the tire in the circumferential direction on the main groove side
The amount of deviation b (0 mm) in the tire width direction from G and the horizontal portion 18A
A / T and the tire width of the rib 16B when the thickness t (4 mm) of the tire radial outside portion is fixed and the width a of the tire radial inner surface 18D in the tire width direction is changed. Pressure at the outer end in the direction (a is zero, that is, the narrow groove 18
Is assumed to be 100).

Further, the graph 3 shown in FIG. 7 is, in detail, a pneumatic tire of which the fine grooves 18 are removed from the pneumatic tire of this embodiment is trial-produced, and the rib when the lateral force is applied to this trial tire is shown. The lateral force load ratio in each part of 16B is shown.

As is clear from the graph of FIG. 7, the lateral force load factor is highest at the end on the side where the lateral force is input,
When this is set to 100, the burden ratio is about 50 near the opposite end. Here, in order to keep the lateral force load constant, the lateral force load ratio in the vicinity of the end on the side where the lateral force is input is about 70, that is, in the sense of equalizing the lateral force load, the lateral force at the rib end is equalized. It can be seen that the burden reduction rate of 30% is necessary. Further, it can be seen that the region where the lateral force load ratio should be 70 or less is from the end portion on the side where the lateral force is input to the position of 30%.

Further, as is clear from the graph of FIG.
The ground pressure at the end of the rib 16B on the side where the lateral force is input is 30%.
It can be seen that the value of t / D is 0.45 or less in order to decrease the degree.

Further, as is clear from the graph of FIG.
It can be seen that the value of a / T is 0.01 or more in order to reduce the lateral force load ratio near the end on the side where the lateral force is input by 30%.

[Second Embodiment] Next, a second embodiment of the present invention will be described with reference to FIG. The same components as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

The rib 16B of this embodiment is provided with an extension portion 30 continuously extending in the direction away from the circumferential main groove 14 at the tip of the inclined portion 18B of the narrow groove 18.

As a result, the stress easily concentrated on the narrow groove bottom 18C is widely dispersed, so that the generation of cracks from the narrow groove bottom 18C is prevented. In this embodiment, the length c of the extension portion 30 in the tire axial direction is 2 mm. Here, the axial length c of the extension portion 30 in the tire axial direction is preferably set to 1 mm ≦ c ≦ 3 mm. When c is less than 1 mm, the effect of dispersing stress is not exerted, and when c exceeds 3 mm, the rigidity of the rib 16B is reduced. It is not preferable because Other configurations and operations are similar to those of the first embodiment.

In the first embodiment, the narrow groove 18 is provided outside the rib 16B in the tire width direction, but the present invention is not limited to this, and as shown in FIG.
6C may be provided on the inner side in the tire width direction, and as shown in FIG. 10, it may be further provided on the inner side in the tire width direction of the rib 16B and both ends of the rib 16A. In any case, the rigidity of the rib end portion where the narrow groove 18 is provided is reduced and the rise of the ground contact pressure is suppressed, so uneven wear can be prevented.

Further, the end portion 18F on the circumferential main groove side of the outer side surface 18E in the tire radial direction of the horizontal portion 18A and the horizontal portion 18A.
End portion 18 of the inner side surface 18D of the tire in the circumferential direction on the main groove side
The amount of deviation b from G in the tire width direction is b ≦ 0.8a (b = 2 m
m, b = 0.4a, a = 5 mm), and the horizontal part 1
8A of the tire radial direction outer side surface 18E of the circumferential direction main groove side end portion 18F, and the horizontal portion 18A of the tire radial direction inner side surface 18D.
Since the tire axial deviation amount b from the circumferential main groove side end portion 18G is b ≦ 0.8a, it is possible to maintain a good ground pressure reducing effect at the tire width direction outer end portion of the rib 16B. ..

Further, in the first embodiment, the shape of the narrow groove bottom 18C of the narrow groove 18 is an arc shape, but the present invention is not limited to this, and as shown in FIG. 11, the narrow groove bottom 18C has a circular cross section. The arc-shaped enlarged portion 28 may be provided.

As a result, the stress acting on the narrow groove bottom 18C is widely dispersed, so that the generation of cracks from the narrow groove bottom 18C is prevented. The radius of curvature R of the enlarged portion 28 is preferably set to 1.5δ / 2 ≦ R ≦ 2.5δ / 2. If R is less than 1.5δ / 2, the effect of dispersing stress is not obtained.
When R exceeds 2.5δ / 2, the rigidity of the rib 16B decreases, which is not preferable.

Further, in the above-mentioned embodiment, the fine groove 18 is provided in the rib of the pneumatic tire having the rib pattern, but the present invention is not limited to this, and as shown in FIGS. 12 (A) and 12 (B). In addition, the narrow groove 18 may be provided in the block 36 of the pneumatic tire 38 having a so-called block pattern having a plurality of blocks 36 divided into the plurality of circumferential main grooves 14 and the plurality of lateral grooves 34. As shown, of course, the fine groove 18 may be provided in the rib 16 of the pneumatic tire 42 having a so-called rib / lug pattern having the rib 16 and the lug groove 40 defined by the plurality of circumferential main grooves 14. Is. Even in these cases, the ribber wear generated at the end of the rib 16 or the block 36 on the side where the lateral force is input is used as the narrow groove 18
Can be prevented by.

[Test Example] Eight pneumatic tires to which the present invention was applied and seven pneumatic tires of Comparative Examples were respectively used for each two kinds.
2.5 * 7.50 fitted to the rim, the internal pressure and 8.0 kg / cm ^2, 7 million km by mounting them to the front shaft of the 2D-4 vehicle
After running, the occurrence of uneven wear at the rib ends and the wear resistance were measured.

Uneven wear is visually inspected for occurrence,
The wear resistance is an index display in which the wear rate of the pneumatic tire of Comparative Tire 1 after running 70,000 km is 100, and the larger the value, the better. The wear rate of the pneumatic tire of comparative tire 1 at this time was 46%.

The invention tire 1 in Table 1 is the pneumatic tire 10 of the first embodiment of the present invention, and the invention tire 4 is the pneumatic tire 10 of the second embodiment of the present invention. Invention tires 2, 3 and 5 to 8 are pneumatic tires having the same structure as the pneumatic tire 10 of the first embodiment, but different in size as shown in Table 1. Further, the comparative tire 1 is the pneumatic tire 10 of the first embodiment with the fine grooves 18 removed, and the comparative tire 4 is the pneumatic tire 10 of the first embodiment with the fine grooves 18 removed to form the rib end. It is the conventional pneumatic tire (pneumatic tire shown in FIG. 14) provided with a large number of sipes, and the comparative tires 2, 3, 5-7 are the first.
It has the same structure as the pneumatic tire 10 of the example, but has different dimensions.

[0073]

[Table 1]

From the test results shown in Table 1 above, the pneumatic tire 10 according to the example of the present invention has a higher effect of preventing uneven wear as compared with the conventional pneumatic tire, and exhibits good wear resistance. It became clear to have.

[0075]

As described above, since the pneumatic tire of the present invention has the above-mentioned constitution, it prevents river wear surely until the end of wear without causing other uneven wear and crack generation. It has an excellent effect of being able to.

[Brief description of drawings]

FIG. 1 is a tire width direction sectional view showing ribs of a pneumatic tire according to a first embodiment of the present invention.

FIG. 2 is a plan view showing a tread of a pneumatic tire according to a first embodiment of the present invention.

FIG. 3 is a sectional view taken along the axis of the pneumatic tire according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view in the tire width direction showing ribs in the middle stage of wear of the pneumatic tire according to the first embodiment of the present invention.

FIG. 5 is a ground contact pressure (index) at a rib end and t (thickness of a tire radial outer side portion of a horizontal portion) / T (tread effective ground contact width)
It is a graph which shows the relationship of tread.

FIG. 6 is a graph showing the relationship between the ground contact pressure (index) at the rib end and a (width in the tire width direction of the inner surface in the tire radial direction) / T (effective tread contact width).

FIG. 7 is a graph showing a lateral force load ratio in the rib 16.

FIG. 8 is a tire width direction sectional view showing ribs of a pneumatic tire according to a second embodiment of the present invention.

FIG. 9 is a tire width direction sectional view showing a tread of a pneumatic tire according to another embodiment of the present invention.

FIG. 10 is a tire width direction sectional view showing a tread of a pneumatic tire according to still another embodiment of the present invention.

FIG. 11 is a tire width direction sectional view showing ribs of a pneumatic tire according to still another embodiment of the present invention.

12 (A) is a plan view showing a tread of a pneumatic tire according to still another embodiment of the present invention, and FIG. 12 (B) is 12 (B) -12 (B) of FIG. 12 (A). It is a line sectional view.

13 (A) is a plan view showing a tread of a pneumatic tire according to still another embodiment of the present invention, and FIG. 13 (B) is 13 (B) -13 (B) of FIG. 13 (A). It is a line sectional view.

FIG. 14 is a plan view showing a tread of a pneumatic tire according to a conventional example.

FIG. 15 (A) is a sectional view in the tire width direction showing ribs of a pneumatic tire according to another conventional example when it is new.
FIG. 15B is a cross-sectional view in the tire width direction showing ribs of the pneumatic tire shown in FIG.

FIG. 16 (A) is a tire width direction cross-sectional view showing a rib of a pneumatic tire according to still another conventional example, and FIG. 16 (B) is a tire width direction cross-sectional view showing a state in which pebbles are bitten. is there.

[Explanation of symbols]

 10 Pneumatic tire 12 Tread 12A Tread contour line 14 Circumferential main groove 18 Narrow groove 18A Horizontal part 18B Sloping part 18C Narrow groove bottom 22 Tread perpendicular 30 Extended part 32 Enlarged part

Claims (5)

[Claims] 1. A pneumatic tire including a tread having a circumferential main groove extending in the tire circumferential direction, wherein a groove is provided on a groove wall of the circumferential main groove, and the thin groove is opened to the circumferential main groove. A pneumatic tire comprising: a horizontal portion extending substantially parallel to the contour line of the tread; and an inclined portion continuous with the horizontal portion and extending inward in the tire radial direction. 2. The width a of the horizontal portion is 0.01T ≦ a ≦ 0.05T with respect to the tread width T, and the thickness t of the outer portion in the tire radial direction of the horizontal portion is the circumferential main groove depth D. Is 0.2D ≦ t ≦ 0.45D, and the distance d of the bottom of the narrow groove from the tread surface is 0.8 with respect to the depth D of the circumferential main groove.
≦ d ≦ 1.2, the narrow groove width δ is 1 mm ≦ δ ≦ 4 mm, and the angle θ of the inclined portion with respect to the tread perpendicular is 0 ° ≦
The pneumatic tire according to claim 1, wherein θ ≦ 8 °. 3. A tire axial deviation amount b between a circumferential main groove side end portion of a tire radial outer side surface of the horizontal portion and a circumferential main groove side end portion of a tire radial inner surface of the horizontal portion. b ≦
The pneumatic tire according to claim 1 or 2, wherein the pneumatic tire has a diameter of 0.8a. 4. An extension portion, which is continuous with the inclined portion and extends in a direction away from the circumferential main groove, is provided, and a tire axial length c of the extension portion is 1 mm ≦ c ≦ 3 mm. The pneumatic tire according to claim 1, claim 2, or claim 3. 5. An enlarged portion is provided on the bottom of the narrow groove, and a radius of curvature R of the enlarged portion is set to 1.5δ / 2 ≦ R ≦ 2.5δ / 2. Alternatively, the pneumatic tire according to claim 3.