JP3195419B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in prevention of uneven wear occurring at ends of ribs adjacent to both sides of a vertical groove in a pneumatic tire having a rib pattern.

[0002]

2. Description of the Related Art In the case of a pneumatic tire having a rib pattern, abnormal running like a step may occur at the end of a rib adjacent to both sides of a vertical groove during running. This is usually called riverware, but conventionally, various technical measures have been taken and proposed to prevent this riverware.

As the most commonly used means, there is a technique for forming a large number of sipes at one end of a rib at one end in a longitudinal groove at small intervals in the tire width direction. Also disclosed is a technique of forming a continuous or discontinuous sipe substantially parallel to the longitudinal groove at a position slightly away from the rib end along the rib end. In addition, a technique for reducing the zigzag of the vertical groove and making it substantially linear is also an effective means.

[0004]

However, when a large number of sipes having one end opening in a vertical groove are formed in the rib end portion in the tire width direction, the circumferential rigidity of the rib end portion 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 end of the rib,
There is a problem that a large number of sipe blades must be installed in the mold, which is not preferable in terms of mold production and cost. When sipe is formed at small intervals,
During running, the sipe may cause cracks and chipping.

Further, the prior art in which a sipe is formed at a position slightly away from the end of the rib is intended to control the movement of the end of the rib in the width direction of the tire, thereby suppressing the slip in the circumferential direction and preventing uneven wear. However, in such means, the effect of preventing uneven wear is different on both sides of the sipe,
The difference in the amount of wear easily induces another form of uneven wear, and this configuration also has the disadvantage that the rib ends are liable to tear.

[0006] On the other hand, the prior art in which the vertical grooves are formed in a linear shape has few problems as compared with the above-mentioned technology, but it is not always sufficient in terms of preventing uneven wear.

An object of the present invention is to provide a pneumatic tire which can effectively prevent riverware generated at a rib end portion during running.

[0008]

Means for Solving the Problems In the uneven wear of the rib pattern, river wear, cupping in which the river wear progresses locally, and one rib as a whole wears faster than the other ribs in one step. There are also rib punches that can be attached, but in any case, the movement in the tire width direction based on the tire wiping action and the shear force on the tire surface generated by the vertical load reduces the circumferential friction force, and the rib end with a large degree The slip in the circumferential direction of the tire increases, causing wear. Therefore, in order to prevent this, it is necessary to minimize the lateral slip per se in the tire width direction on the rib surface at the time of load.

It is considered that the cause of the lateral slip on the rib surface is that, under a vertical load, the deformation of the tire surface pushes the rib surface from the inside to the outside, which appears as a lateral slip. Also, comparing the deformation of the tire surface with the deformation of the base of the rib, it is considered that the deformation of the surface of the tire is larger than the deformation of the base of the rib, and this is the cause of increasing the shear strain on the surface of the tire. It is. Therefore, the present invention can cause a deformation in the opposite direction to cancel and cancel the deformation of the ribs from the inside to the outside at the time of the vertical load on the tire surface, and as much as possible the bending deformation of the tire surface and the deformation of the base of the rib. And a rib structure capable of reducing distortion in the width direction due to a normal force on the tire surface is provided on the tire tread portion.

That is, the present invention has a rib sandwiched on both sides by a plurality of longitudinal grooves continuously extending in the tire circumferential direction, a rib at one end at the tire shoulder end, and a rib at the other end sandwiched by the longitudinal groove. In the pneumatic tire, at least one of the ribs is formed with a narrow circumferential groove having a width substantially extending in a circumferential direction of the tire substantially in a substantially central region thereof substantially in parallel with the longitudinal groove, The rib is divided into rib elements, and each groove wall of the circumferential groove is formed to be a wall surface substantially parallel to a groove wall surface of a vertical groove adjacent to the rib element.

Preferably, the circumferential groove has a structure in which the groove width increases in the depth direction. This is because, in the case of the rib, the cross section is usually a substantially trapezoidal or a cross-sectional shape close to the trapezoidal shape. It is easy to fall down, and the deformation of the base of the rib can be facilitated to be approximately equal to the bending deformation of the tire surface. Even in the case of a tire in which the wall surface of the vertical groove rises vertically and the cross section of the rib approaches a square or rectangular shape, the circumferential groove is a wall surface substantially parallel to the groove wall of the vertical groove, but in this case, It is not necessary to widen the bottom of the circumferential groove.

The width of the circumferential groove itself may be widened in relation to the regulation of the rib deformation. However, the width of the circumferential groove should be as small as possible on the tire surface, and should be close to a normal non-split type rib. Is preferable from the viewpoint of securing the ground contact area. Therefore, the width of the circumferential groove is the width a on the rib surface.
In this case, it is preferable that the width is about 1 to 5% of the rib width. The width b at the bottom of the circumferential groove is naturally determined to be a certain range when the width a on the rib surface is determined.
It is desirable to set it to about 10%.

On the other hand, the depth of the circumferential groove also greatly contributes to these deformations, but in this regard, it is desirable that the depth be at least half the depth of the vertical groove adjacent to the rib element. In particular, when the depth of the circumferential groove is made the same as the depth of the vertical groove, for example, the slip on the rib surface can be suppressed optimally. However, as the wear progresses on the tire surface along with the running, the groove becomes shallow, and the bending, that is, the shear deformation in the width direction decreases sharply, so considering the after running, the occurrence of new uneven wear is in the direction of decreasing, The depth of the circumferential groove does not necessarily have to match the depth of the vertical groove.

[0014]

According to the present invention, a narrow circumferential groove extending continuously in the tire circumferential direction substantially parallel to the longitudinal groove in a substantially central region of the rib is formed, and the rib is divided into rib elements. Since the pneumatic tire is configured such that each groove wall of the circumferential groove is formed substantially parallel to the groove wall surface of the adjacent vertical groove with the rib element interposed therebetween, the shear deformation from the inside to the outside on the tire surface at the time of vertical load. Is divided into the deformation and the deformation in the opposite direction from the outside to the inside in each rib element, which is approximately の of the deformation before dividing into the elements. In addition, when the circumferential groove is formed, bending caused by a load, particularly when the bottom of the circumferential groove is widened, is largely shared by the base of the rib, so that bending deformation on the tire surface can be reduced.

Therefore, the movement in the tire width direction based on the shearing force of the tire surface generated by the vertical load is restricted, and the lateral slip of the rib surface is well prevented, so that the frictional force in the circumferential direction does not decrease and the conventional frictional force is reduced. As described above, the slip in the tire circumferential direction does not increase at the end of the rib. Therefore, generation of riverware can be effectively prevented.

[0016]

FIG. 1 is a schematic view of a rib pattern showing an embodiment of the pneumatic tire of the present invention, and FIG. 2 is a sectional view taken along the line II-II of FIG.
It is a line sectional view.

In FIG. 1, reference numeral 1 denotes a tire tread portion, 2 denotes a shoulder portion, and a longitudinal groove 3 is formed in the tire tread portion 1 so as to be continuous in the circumferential direction. 4 is a rib sandwiched between the vertical grooves 3 and 3, 5 is a tire shoulder end 2a at one end,
The other end is a rib on the tire shoulder side sandwiched between the vertical grooves 3.

Reference numeral 6 denotes a narrow circumferential groove formed in a substantially central region of the rib 4, and reference numeral 7 denotes a narrow circumferential groove formed in a substantially central region of the rib 5 on the tire shoulder side. These circumferential grooves 6 and 7 are formed substantially in parallel with the longitudinal groove 3 and continuously in the tire circumferential direction. 4a, 4
Reference symbol b denotes a rib element formed by dividing the rib 4 by the circumferential groove 6, and reference numerals 5a and 5b denote respective shoulder-side rib elements formed by dividing the rib by the circumferential groove 7.

Each of the circumferential grooves 6 and 7 has a wall surface 8 in which each groove wall 8 is substantially parallel to the groove wall surface 9 of the vertical groove 3 adjacent to the rib element 4a, 4b, 5a or 5b. The groove width is configured to gradually increase from the opening end 10 toward the bottom 11 of the groove.

Therefore, when the tire is further contacted with a road surface G as shown in FIG. 3 and a vertical load L is further applied thereto, as shown in FIG. The deformation occurs, and the deformation toward the outside of the rib without the circumferential groove (f _{3 in} FIG. 6) is divided into _two deformations f ₁ and f ₂ , and the size is reduced to approximately １ ／ of f _3. Therefore, a reduction in circumferential frictional force at the rib ends is prevented. Also as shown
The deflection of the ribs 4 due to the vertical load is also largely shared by the rib base 12 because the difference between the surface of the rib element and the width of the base divided by the groove is smaller than when the groove width is not widened or when there is no groove. That is, the amount of slip on the surface of the rib 4 is reduced. In FIG. 4, reference numeral 13 denotes a displacement curve indicating a slip amount at each point on the surface of each of the rib elements 4a and 4b.

FIG. 5 is an enlarged cross-sectional view of a main part of the conventional tire in a contact state, and FIG. 6 is an enlarged cross-sectional view of the main part in the same load state. In conventional tires, as shown in these figures,
When acting vertical load L, the ribs 14 flex, deformation respectively is skid with a constant force f ₃ at both ends direction of the ribs 14 from the center area of the surface of the rib due to the deflection. Accordingly, the amount of slip also gradually increases toward both ends of the rib 14 from the center area of the rib 13 as shown in the displacement curve indicated by reference numeral 15, and induces slip in the tire circumferential direction at both ends of the rib 14. Making it easy to do. On the other hand, in this embodiment, as shown in FIG. 4, the slip in the different direction on the surface of each rib element 4a, 4b is の of f ₃ .
At the end of the rib, which is approximately ₃ of f ₃ , so that the slip at the end of the rib 4 is substantially prevented.

The present invention is not limited to the above embodiment.

By the way, a tire of this embodiment having a tire size of 11R24.5 was actually produced as a trial, and a test was conducted on the effect of preventing the occurrence of riverware. Table 1 shows the results. For comparison, a conventional tire was also evaluated. Riverware was evaluated by the amount of uneven wear occurring after the tire was mounted on a long-distance truck and traveled 80,000 km on a completely paved road. The number of test tires is 20 for each condition (conventional tire, example tire). As shown in FIG. 7, the uneven wear generation amount is the width m (m
The product mn of m) and the depth n (mm) of shoulder drop at the end of the rib is represented by an index with the conventional tire being 100. For the number of uneven wear, the number of riverware in 20 tires was represented by%.

[0024]

[Table 1]

From Table 1, it is recognized that the uneven wear amount of the tire of the embodiment in which the circumferential groove having a smaller width is formed in the rib than the conventional tire decreases as the groove depth h increases. Can be In particular, the groove depth h of the circumferential groove is set to the groove depth H of the vertical groove.
In the second embodiment, which is the same as the first embodiment, no riverware is generated.

[0026]

According to the present invention, a narrow circumferential groove is formed on a rib of a tire tread portion so as to extend continuously in the tire circumferential direction substantially parallel to the longitudinal groove in a substantially central region thereof, and the rib is formed. Is divided into rib elements, and each groove wall of the circumferential groove is constituted by a wall surface substantially parallel to a groove wall surface of a vertical groove adjacent to the rib element. It is possible to suppress the lateral slip in the direction, and thereby it is possible to effectively prevent the riverware generated at both ends of the rib during traveling.

[Brief description of the drawings]

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

FIG. 2 is a sectional view of the tire taken along the line II-II in FIG.

FIG. 3 is an enlarged sectional view of a main part showing a contact state of the tire.

FIG. 4 is an enlarged sectional view of a main part showing a ground contact state when a load is applied to the tire.

FIG. 5 is an enlarged sectional view of a main part showing a contact state of a conventional tire.

FIG. 6 is an enlarged sectional view of a main part showing a ground contact state when a load is applied to a conventional tire.

FIG. 7 is an enlarged view of a main part showing a state after uneven wear.

[Explanation of symbols]

 2a tire shoulder end 3 vertical groove 4 rib 4a rib element 4b rib element 5 rib 5a rib element 5b rib element 6 circumferential groove 7 circumferential groove 8 groove wall 9 groove wall surface

Claims (2)

(57) [Claims] 1. A pneumatic tire having a rib sandwiched on both sides by a plurality of longitudinal grooves continuously extending in a tire circumferential direction, a tire shoulder at one end and a rib sandwiched at the other end by the longitudinal groove. in, at least one rib of the rib to form a narrow circumferential groove width extending continuously the substantially central region in the longitudinal groove and relatively substantially parallel to the tire circumferential direction, the circumferential the ribs The ribs are divided into rib elements separated by directional grooves, and the width of the circumferential grooves is set in the depth direction.
A pneumatic tire characterized by being increased toward . 2. The circumferential groove has a depth of at least 1/2 of a vertical groove adjacent to the rib element.
1 Symbol placement pneumatic tire of.