JPH05229315A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To prevent river wear produced on rib both side end parts nipped with longitudinal grooves during travel by providing protruded region parts, protruding from a rib standard surface on a circumference of ribs on main grooves both sides nearest to shoulder ends and having sipes of a degree of closing when a tire is grounded, at intervals. CONSTITUTION:Narrow-width protruded region parts 8, protruding from a rib standard surface 6, crossing in nearly parallel to a tire width direction on circumference in both side parts in a circumferential direction, and having sipes 7 of a degree of closing when a tire is grounded are arranged on a circumference of a at rib 4 intervals. Moreover, sipes 10, each one end part of which is opened in main grooves 3, are formed on a standard region part 9, positioned in the protruded region parts 8 and composing the rib standard surface 6. Consequently, river wear can be prevented with sipes 10, and toe and heel abrasion can be checked with the protruded region parts 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having a rib pattern, and more particularly to an improvement in uneven wear prevention which occurs at both ends of the rib sandwiched by main grooves.

[0002]

2. Description of the Related Art In the case of a pneumatic tire having a rib pattern, at the end portions on both sides of the rib sandwiched by the main grooves during running,
Step-shaped abnormal wear may occur. This is usually
Although it is called riverware, various technical measures have been taken and proposed in order to prevent this riverwear.

As the most commonly used means, there is a technique in which a large number of sipes, one end of which is open to the main groove, are formed in the rib end portion at small intervals in the tire width direction. It also discloses a technique of forming a continuous or intermittent sipe substantially parallel to the main groove at a position slightly apart from the rib end along the rib end. Further, a technique of reducing the zigzag of the vertical groove to form a substantially linear shape is also an effective means.

[0004]

However, when a large number of sipes, one end of which is open to the main groove, are formed in the rib end in the tire width direction, the circumferential rigidity of the rib end is weakened by the large number of sipes. Although it is effective in that it can be done, since many sipes must be formed at the rib end,
There is a problem that many blades for sipes have to be installed in the mold, which is not preferable in terms of mold production and cost. In addition, if you form sipes at small intervals,
During driving, this sipe may cause cracks and chipping.

Further, in the prior art in which the sipes are formed at a position slightly apart from the rib ends, the movement of the rib ends in the tire width direction is controlled, thereby suppressing circumferential slip and preventing uneven wear. However, with such means, the effect of preventing uneven wear is different on both sides of the sipe,
Due to the difference in the amount of wear, another form of uneven wear is likely to be induced, and this configuration also has a drawback in that a tear is likely to occur at the rib end.

On the other hand, the conventional technique in which the vertical groove has a linear shape has less problems as compared with the above technique, but is not always sufficient in terms of preventing uneven wear.

An object of the present invention is to provide a pneumatic tire capable of effectively preventing river wear that occurs at both end portions of ribs sandwiched by vertical grooves during running.

[0008]

Means for Solving the Problems By the way, uneven wear of a rib pattern is caused by river wear, cupping in which the river wear locally progresses, and one rib as a whole wears faster than other ribs in one step. There are also rib rib punches, but in any case, tire wiping action or movement in the tire width direction based on the shearing force of the tire surface generated by vertical load reduces the circumferential frictional force, and the rib end with a large degree The slip in the circumferential direction of the tire becomes large at the portion, which causes wear. Therefore, in order to prevent this, it is effective to weaken the rigidity in the circumferential direction of the ribs so that even if the frictional force becomes weak, the weakened frictional force can be sufficiently followed. As a specific means, it can be achieved by dividing the rib by a lateral groove and forming the rib into a block.

However, when the ribs are formed into blocks, the circumferential front end and the rear end, which are divided by the lateral groove, are in a circumferential direction based on a circumferential force and a vertical load that cause a slip, in view of the relationship with the rotation direction of the tire. Since the resultant distribution of shearing force is greatly different, unsightly uneven wear called so-called toe and hill, which has different wear states, occurs due to the difference in slip state. It can be prevented by setting the width of the lateral groove to zero,
Even if the lateral groove is formed by replacing it with a sipe,
It is technically difficult to set it to 0.3 mm or less. If the tire is post-processed and knife-cut, the width can be made very close to zero, but there are problems in terms of cost and flexibility in design.

Therefore, according to the present invention, a rib sandwiched on both sides by a plurality of continuously connected main grooves in the circumferential direction of the tread, and a rib sandwiched at one end by the tire shoulder end and at the other end by the main groove. In a pneumatic tire having, at least on the circumference of the ribs on both sides of the main groove closest to the shoulder end, project from the rib reference surface, and are substantially parallel to the tire width direction on both sides in the circumferential direction. A large number of narrow convex regions having a sipe that closes when the tire touches the ground are arranged at intervals. That is, the ribs are made into blocks with thin sipes to reduce the rigidity of the ribs, while two or more sipes are arranged in parallel within a narrow range, and the ribs between sipes slightly project from the rib reference surface, and the projecting part at the time of ground contact. By utilizing the fact that the narrow convex area part that is the lower rigidity than the reference area part located between the convex area parts, the bending is caused at the tip of the protruding rubber capacity according to the ground pressure. As a result, the sipe is closed, and the block is integrated with the rib by further pressing them together. Incidentally, in the rib end portion in the tire width direction of the reference region portion located between the convex region portions adjacent to each other in the circumferential direction, in order to increase the followability to the circumferential frictional force of the end portion and to reduce slip, It is also possible to form a sipe whose one end opens into the main groove.

The amount of protrusion of the convex region varies depending on the tire to which it is applied, but is preferably about 0.5 to 3.0 mm. This is because if it is less than 0.5 mm, the rubber deformation at the time of contact with the ground does not reach the point where the sipes are blocked and it becomes difficult to integrate the block with the rib.
This is because if the thickness is equal to or larger than mm, the rib rigidity becomes too high, and the flexibility in the circumferential direction is lost.

Regarding the depths H of the sipes located on both sides of the convex region, the depth of the longitudinal grooves on both sides of the rib is defined as (sipe area / length of sipes on rib surface) as the average depth of the sipes. It is desirable to be about 50 to 120% of H _G. If it is less than 50%, sufficient reduction of the rigidity in the circumferential direction cannot be obtained, and if it exceeds 120%, the amount of rubber increases because the thickness of the non-skid base needs to be secured, resulting in tire durability, that is, heat resistance. However, there is a problem in terms of increase in weight and cost.

The narrow sipes located on both sides of the convex region may be formed by cutting in the vertical direction, but they may be gradually separated from the opening end of the tire tread surface in the depth direction. It is preferable that the taper is formed so as to be inclined, because the vicinity of the open end of the sipe is particularly well closed and the block can be integrated as a rib. Width B of convex area portion 8
Based on, the distance B ′ between the bottoms of the sipes 7, 7
Is preferably 1.0 to 1.5 in the ratio B '/ B.
The narrow sipes located on both sides of the convex area are
It is preferable that it is closed at the position near the opening end at the time of contact with the ground, but rather not closed inside because sufficient flexibility in the circumferential direction can be secured and followability to the circumferential force trying to slip can be exhibited. Therefore, the width of the sipe, that is, the gap between the convex region and the reference region adjacent to the convex region may not be uniform, but may be increased from the beginning in the vicinity of the bottom. In this case, specifically, it is desirable that the distance from the bottom of the sipe to about 1/3 of the average depth of the sipe is about 2 to 4 times the thickness of the open end of the sipe.

A sipe may be formed in the convex area portion in order to reduce the rigidity of the convex area portion. In this case, a sipe whose both ends do not open to the main groove is particularly provided at a large portion where it is necessary to reduce the rigidity. It is desirable to form.

Further, the convex area portion can be applied to all or some of the ribs as long as at least one end is a rib sandwiched by the main grooves. Particularly, the river wear is the main groove adjacent to the shoulder rib and the main groove adjacent thereto. Since it often causes a problem in the rib between the ribs, it is desirable to form the rib at least near the shoulder rib.

[0016]

As described above, according to the present invention, the rib is sandwiched on both sides by a plurality of continuous main grooves in the circumferential direction of the tread, and one end is sandwiched by the tire shoulder end and the other end is sandwiched by the main groove. In a pneumatic tire having ribs, at least on the circumference of the ribs on both sides of the main groove closest to the shoulder end, projecting from the rib reference plane, and on both sides in the circumferential direction, the circumference of the tire in the tire width direction. Since it is a pneumatic tire in which a large number of narrow convex regions having a sipe that closes when the tire touches the ground are arrayed at intervals, the sipe blocks the ribs and lowers the rib rigidity. Therefore, even if the frictional force in the circumferential direction becomes weak, a state in which the weakened frictional force can be followed can appear at both ends of the rib, and the occurrence of riverwear can be prevented. In addition, the narrow convex area section separated by this sipe bends early at the time of grounding and closes this sipe,
Since the block is integrated as a rib, it is possible to prevent the toe-and-heel wear due to the block.

Therefore, it is possible to prevent the river wear which occurs at both side ends of the rib sandwiched by the vertical grooves during traveling, and to effectively prevent the toe-and-heel wear from occurring simultaneously.

[0018]

1 is a schematic view of a rib pattern showing an embodiment of a pneumatic tire according to the present invention, and FIG.
A sectional view taken along line A, FIG. 3 is a sectional view taken along line BB, and FIG. 4 is a sectional view taken along line CC.

In the figure, reference numeral 1 is a tread portion, 2 is a shoulder portion, and the tread portion 1 has a main groove 3 continuous in the circumferential direction.
Are formed. Reference numeral 4 is a rib sandwiched between the main grooves 3 and 3, and 5 is a shoulder rib.

As shown in the drawing, on the circumference of the rib 4, the rib 4 projects from the rib reference surface 6 and crosses the circumference on both sides in the circumferential direction substantially parallel to the tire width direction and closes when the tire touches the ground. Narrow convex region 8 having sipe 7, 7
Are arranged at intervals. Reference numeral 9 is a reference area portion that forms the rib reference surface 6 and is located between the convex area portions 8 and 8. One end portion of the reference area portion 9 is opened to the main groove 3 as shown in FIG. A sipe 10 is formed.
Reference numeral 11 is a narrow groove formed at the shoulder end. In FIG. 3, H is the depth of the sipe 10 located on both sides of the convex region 8, and H _G is the depth of the vertical groove on both sides of the rib 10.

When this tire is used, when it comes into contact with the road surface G, as shown in FIG. 5, in addition to the bending of the rubber of the tread portion 1 due to the load, the convex area portion 8 is strongly compressed and has a constant volume V. As a result of being pushed back by the amount, the pushed back rubber fills the narrow groove of the sipe 7 with a strong compressive force CF.
When a braking force DF is applied to the tire from the road surface, the rigidity in the circumferential direction is reduced due to the presence of the sipe 7, as shown in FIG. It is possible to improve slippage, prevent slippage due to reduced frictional force, and prevent the occurrence of riverwear. Further, since the compressive force CF by the convex area portion 8 acts strongly even under load, the block is integrated as a rib, the opening of the sipe 7 is prevented, and toe-and-heel wear can be prevented at the same time.

By the way, a tire according to the example having a tire size of 11R22.5 was actually manufactured as a trial and the effect of preventing uneven wear of river wear and toe and heel was tested. Table 1 shows the results.

[0023]

[Table 1]

In the table, h is the protrusion amount (mm) of the convex area 8 from the rib reference surface 6, H is the average depth of the sipes 7 (mm), and H _G is the depth of the main groove 3 (mm). , B is the width (mm) of the convex region portion 8.
Note that B is the width of the convex region portion 8 and B'is the distance between the bottom portions of the sipes 7, 7 (see FIG. 2). The width of each sipe is the same.

Toe and heel wear index K _T is K _T = K
It is shown as ₁ / K ₂ . K ₁ is the value of this embodiment and is shown in FIG.
As shown in, K ₁ = (t / p) × 100. K
₂ is the value of Comparative Example 1, similarly K ₂ = (t / p) × 100
It is represented by. Here, t is the convex region 8 due to uneven wear.
Is a step (mm) formed between the reference region 9 and the reference region 9, and p is a pitch length (mm) of the convex region 8 and the reference region 9 in units of one pitch. The smaller K _T indicates the better.

The riverwear index K _R is K _R = K ₁ ′ / K
Indicated by ₂ '. K ₁ ′ is the value of this embodiment and is represented by K ₁ ′ = w × (r / W) as shown in FIG. 8, and K ₂ ′ is the value of Comparative Example 1 and K ₂ ′ = w. It is represented by x (r / W). Here, w is the shoulder drop width (mm) at the rib end, r is the rib drop shoulder depth (mm), and W is the rib width (mm). The smaller K _R indicates the better.

From Table 1, it can be seen that in the embodiment, the river wear that occurs at both ends of the rib is prevented, and the toe and heel wear is also effectively prevented. Further, it is recognized that the projecting amount of the convex region portion is particularly excellent when it is in the range of 0.5 to 3.0 mm.

Needless to say, the present invention is not limited to the above embodiment. For example, as shown in FIGS. 9 and 10, a sipe 12 whose both ends are not opened to the main groove can be provided in the convex region 8 at a position where it is necessary to particularly improve the reduction in rigidity of the convex region 8. .. Further, in order to increase the effect of preventing the riverwear, as shown in FIG. 11, it is possible to employ a sipe 13 having a wide portion 14 in the lower portion inside the sipe.

[0029]

As described above, according to the present invention, the ribs sandwiched between the main grooves are projected on the circumference of the rib from the rib reference surface, and the both sides of the rib in the circumferential direction are substantially covered in the tire width direction. Since it is a pneumatic tire formed by forming a narrow convex region portion having a sipe that crosses in parallel and closes when the tire touches the ground,
River ware can be prevented by the above sipe,
Toe and heel wear can also be effectively prevented by the convex area portion.

[Brief description of drawings]

FIG. 1 is a schematic view of a rib pattern showing an embodiment of a pneumatic tire according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along line BB of FIG.

FIG. 4 is a sectional view taken along line C-C of FIG.

FIG. 5 is a grounding state diagram of the same.

FIG. 6 is a grounding state diagram when the same braking force is applied.

FIG. 7 is a schematic cross-sectional view showing a state of toe and heel wear.

FIG. 8 is a schematic cross-sectional view showing a state of riverwear.

FIG. 9 is a schematic view of a rib pattern of another embodiment in which a sipe is formed in a convex area portion.

FIG. 10 is a sectional view taken along line D-D of FIG.

FIG. 11 is a cross-sectional view showing another embodiment in which a wide portion is formed in a sipe.

[Explanation of symbols]

 1 Tread Part 3 Main Groove 4 Rib 6 Rib Reference Surface 7 Sipe 8 Convex Area Part 9 Reference Area Part 10 Sipe 12 Sipe 13 Sipe

Claims (7)

[Claims] 1. A pneumatic tire having a rib sandwiched on both sides by a plurality of continuous main grooves in the circumferential direction of the tread portion, and a rib sandwiched between the tire shoulder end at one end and the main groove at the other end. In the tire, on at least the circumference of the ribs on both sides of the main groove closest to the shoulder end, project from the rib reference surface, and traverse the circumference on both sides in the circumferential direction substantially parallel to the tire width direction, A pneumatic tire characterized in that a large number of narrow convex regions having a sipe that closes when the tire touches the ground are arranged at intervals. 2. The pneumatic tire according to claim 1, wherein a sipe whose one end is open to the main groove is formed at a rib end portion of the reference area portion located between the adjacent convex area portions in the circumferential direction. 3. The pneumatic tire according to claim 1, wherein the amount of protrusion of the convex area portion is 0.5 to 3.0 mm. 4. The pneumatic tire according to claim 1, 2 or 3, wherein the average depth of sipes located on both sides of the convex region is 50 to 120% of the depth of the flutes on both sides of the rib. 5. A sipe located on both sides of the convex area portion,
The tire tread portion is formed so as to be gradually inclined from the opening end of the tire tread portion in a direction away from each other in the depth direction.
The pneumatic tire according to 3 or 4. 6. The pneumatic tire according to claim 1, 2, 3, 4, or 5, wherein the width of the sipe is increased in the vicinity of the bottom thereof. 7. The pneumatic tire according to claim 1, wherein the convex region portion is formed with a sipe whose both ends do not open into the main groove.