JPH07186624A - Pneumatic tire excellent in offset abrasion resistance - Google Patents

Abstract

PURPOSE:To prevent offset abrasion from being generated in the range on the ground contact surface of a rib by forming zigzags having many irregularities as deep as or deeper than the pitch on the end side wall of the rib on the ground contact surface of a pneumatic tire, and providing thin width slits to be connected to valley parts in ground-contact and to be closed. CONSTITUTION:Ribs 2 between longitudinal grooves 1 extended in the tire circumferential direction and ribs 3 sandwiched by the longitudinal groove 1 and shoulder ground contact surfaces 4 are provided, notches 7 whose width is increased toward a grove bottom 6 in inclined section are provided on a groove wall 5 of the longitudinal grooves 1, and zigzag part 10 is formed on the groove part 5 in the tire circumferential direction so that mountain parts and valley parts may be positioned on the longitudinal groove 1 side, and the ratio P/H of the pitch P to the longitudinal groove depth H may be within the range of 0.3 to 1.0. Slits 11 are formed in respective ground contact surface side end range of the ribs near the shoulder ground contact end and linearly and continuously extended along the longitudinal groove 1 in the circumferential direction, and the width is so thin as to be easily closed in ground-contacting and the lateral sipe opening to a zigzag valley part is formed.

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 prevention of uneven wear occurring in the end area of the rib on the ground contact surface side.

[0002]

BACKGROUND ART Uneven wear of a pneumatic tire having a rib pattern is mainly categorized as step wear having a shoulder ground contact end as a starting point and river wear occurring at both end areas of a ground surface of a rib adjacent to both sides of a vertical groove. Is. Of these, it is effective to provide the shoulder step wear with a thin groove at the shoulder ground contact end. With respect to river wear, a straight groove from which zigzags and irregularities have been removed has come to be used as a countermeasure, since it originates from the point where the rib end has a particularly low or high rigidity.

[0003]

However, the straight vertical groove has a problem in braking performance when traveling on a wet road, and as a countermeasure against this, a large number of sipes extending in the tire width direction are provided in the rib end area at small intervals in the circumferential direction. The means to install is adopted. Although this is effective as a measure against riverwear, it leads to an increase in die cost, and cracks and chipping due to sipes are likely to occur, so it cannot be said to be perfect.

An object of the present invention is to provide a pneumatic tire capable of effectively preventing uneven wear occurring at the rib end, that is, the end area of the rib on the ground contact surface side.

[0005]

The cause and mechanism of the step wear generated at the shoulder end and the river wear generated at both banks of the longitudinal groove are basically the same.

That is, since the shoulder end and the rib end have more slips in the circumferential direction than other parts, that part is worn in a step shape, and once the step is formed, the step expands including the width due to the circumferential difference.

[0007] As described above, the wear at the rib ends is large.
The deflection of the rib due to the vertical load on the tire is such that the rubber surface movement amount V and the shear stress τ in the tire width direction due to the vertical load of the rib at the rib end or shoulder end are the maximum in the rib, and their product e This is because = τ · V becomes maximum. This corresponds exactly to the amount of energy of the load applied to the rib end, and represents the amount of movement of the rib in the width direction. The rapid movement of the tire in the rib width direction due to rolling of the tire at each contact causes a rapid decrease in the friction coefficient of the resistance force (friction force) to the force trying to slide in the circumferential direction. Therefore, the resistance in the circumferential direction is reduced at the rib end, and the wear from the rib end begins.

Based on the above knowledge, the present invention has a plurality of vertical grooves continuously connected in the tire circumferential direction in order to improve the followability to the circumferential sliding (friction) force, the vertical grooves, the vertical grooves, and the vertical grooves. In a pneumatic tire having continuous or interrupted ribs formed between shoulder ground contact ends, a ratio P / H of adjacent ribs on the end groove wall of the ribs in the tire circumferential direction is set. Forming a zigzag in which a large number of peaks and valleys are alternately repeated at a pitch P of 0.3 to 1.0, and further forming a straight line in the tire circumferential direction along the vertical groove in the ground contact surface side end region of the rib. To form a thin slit having a width that is easily closed at the time of grounding, and the slit is formed by connecting the lateral sipe opening to the valley portion of the zigzag portion in a seamless and continuous state, Individually independent small booth The click and employs a configuration provided on the side edge region of the closest ribs at least in the shoulder ground end of said rib.

Regarding the zigzag formed on the groove wall of the end portion of the rib, usually, a peak portion and a valley portion extend from the opening end of the vertical groove to the groove bottom, and the peak portion and the valley portion are alternately arranged in the tire circumferential direction, A configuration in which the zigzag is repeatedly formed can be adopted, but it is more preferable that the zigzag is formed as a notch whose width and depth increase from the opening end of the vertical groove or the middle of the groove wall toward the groove bottom. This is based on the following reasons.

That is, since the straight vertical groove generally has a V-shaped cross section to prevent stone trapping, the base of the rib is narrower than the ground contact surface. This means that when the rib touches the ground, the rib flexes by the vertical force at the time of loading, and the groove wall swells outward, the rib easily swells on the side of the ground surface where the rib width is narrower than the groove bottom,
The movement of the rib rubber is likely to occur on the ground contact surface side. Also, since the rubber movement inside the rib itself is accumulated at the rib end, the movement of the rubber becomes the largest in the plane of the rib, and as a result, the rib end is moved more than the other portion in the tire width direction on the rib surface. Become. It is well known that this movement in the width direction lowers the friction coefficient of the frictional force against slip in the tire circumferential direction, and as a result, the rib ends become slippery in the tire circumferential direction, which causes river wear. It is thought that Therefore, the rigidity of the rib base side is weakened, and the bulge of the groove wall generated at the time of loading is moved to the groove bottom side as much as possible to reduce the movement of rubber on the rib ground contact surface,
Moreover, in order to secure braking performance on the wet road, the zigzag of the rib end groove wall should be formed as a notch that widens in width and depth from the open end of the vertical groove or the middle of the groove wall toward the groove bottom. Is more preferable.

As described above, the zigzag pitch P is preferably 0.3 to 1.0 in the ratio P / H with the vertical groove depth H. When it exceeds 1.0, the size of the general rib pattern type tire is in the same range as that of the conventional pattern tire having the zigzag at the open end of the tread surface. Then, like the conventional tire, river wear is likely to occur in the zigzag peak portion. That is, the zigzag rib crests have a greater degree of freedom in deformation (smaller deformation resistance) than the troughs, and the rubber is more likely to move toward the crests. This means that the movement of the rib crest portion in the tire width direction is large, and for the reasons described above, the circumferential slippage is large, and therefore wear is likely to occur, which is the starting point of riverwear. Once the starting point of river wear occurs, the diameter of the wear part becomes small, so there is a difference in circumferential length in the tire circumferential direction, especially in front tires where the difference in circumferential length is small, the sliding speed is relatively high with the road surface Will be expanded. On the other hand, if the pitch interval P of the zigzag is less than 0.3 in the ratio P / H with the depth H of the vertical groove, the effect on the riverwear is not affected, but from the dimension of the peak portion of the zigzag cut. The rigidity and strength become too small, so that chipping, cracking, etc., tend to occur at that portion, especially with respect to the load applied as a truck / bus tire, and no improvement in the traction braking effect can be seen.

Slit depth h and sipe depth h
_s is 0.5 to 1.0 the ratio of the longitudinal groove depth H, and preferably optimally to be 0.7 to 1.0. When it is less than 0.5, the rigidity of the small block region in the circumferential direction is reduced only until the middle period of wear, and when it exceeds 1.0, the distance from the slit bottom or the sipe bottom to the belt surface becomes small, and the running condition is reduced. A crack may occur due to deformation or load stress, water may enter, and the belt strength may be deteriorated, resulting in a large accident such as a tire burst. The slit cutting direction is
There is no particular limitation, and the vertical direction may be acceptable, but it is desirable that the depth direction be inclined toward the rib center side.

The width of the slit is 0.3 to 2.5 mm.
The degree is good, and 0.5 to 1.5 mm is most effective.

On the other hand, the surface movement of the rubber in the tire width direction due to the bending of the rib is proportional to the product of the bending amount and the rib width, that is, the bending volume. Therefore, it is necessary for the shape of the rib to reduce the deflection as much as possible under the same load, and to reduce the rib width, which is a trade-off. As a result of earnest studies, when the rib height was H and the distance from the rib center to the slit center was a, the following phenomenon could be found and theoretically confirmed. That is, the load energy becomes maximum in the range of a / H = 1.05 to 1.15. That is, it has an extreme value. Therefore, the ratio a /
H should be smaller than 1.05 to 1.15 or larger than H.

It is difficult to set a / H to a value larger than 1.05 to 1.15 for tire specifications including groove depth, width, and other structural aspects of the tire, which have been known from a long history and experience. This is especially true for a tire having four or more vertical grooves whose rib pattern is the mainstream or four or more vertical grooves similar thereto.

When a / H does not reach 0.6, the rib is impractical because it tends to buckle due to vertical load and lateral force.

When the value of a / H exceeds 0.9, the new tire is already near the extreme value.
As the tire wears, a increases from the same level to slightly increases, and H definitely decreases, so that a / H always passes the extreme value. However, at the time of passing the extreme value, a / H is 1.05 for new tires.
The closer it is to the range of 1.1, the faster it becomes, but at the early time a
Since / H is in a state where both a and H are larger than a / H in the later period, the flexure against the same load on the tire, that is, the moving rubber volume V increases, and e = τ · V increases. That is, even if the extreme value is the same as (1.05 to 1.15), the total load energy e applied to the rib end during the same traveling time becomes large, so that the slip in the circumferential direction in the width direction occurs. It becomes large and easily wears, which further reduces the frictional force in the circumferential direction to increase the circumferential slippage and induce uneven wear. This is the same even before a / H reaches the extreme value, and if the groove depth H is the same, "e" becomes larger and disadvantageous in the initial place where a / H is larger. On the other hand, if a / H is taken from a point where the extremum exceeds 1.05 to 1.15 from the beginning, a / H deviates from the extremum along with wear and moves only in a good direction. It means that the depth is small, which is an important property as a tire, such as poor drainage performance, poor steering stability, insufficient braking performance, drivability, decrease in heat generation durability due to increase in rubber volume of tread, or groove depth. When the depth is shallow, there are many disadvantages such as low wear durability, which is not practical.

[0018]

According to the pneumatic tire of the present invention, a vertical groove is formed in the end area of the rib on the ground contact surface side where the load energy e is the largest among the rib portions, and the friction coefficient in the circumferential direction is most likely to decrease due to the lateral slip. Along the tire circumferential direction linearly continuously, forming a thin slit of a width that is easily closed at the time of grounding, in the slit, a lateral sipe opening to the valley of the zigzag, a continuous seamless Since they are connected in a state to form a small block having independent zigzag peaks, only the bottom surface of the small block is directly connected to the belt portion, and as a result, the rib end portion is connected. Even if slippage occurs due to shear force in the tire width direction and the friction coefficient in the circumferential direction decreases, the followability to the circumferential slip (friction) force is improved, and the relative slippage with the road surface is virtually eliminated, Effectively to prevent the occurrence of Wea.

Further, since the slit formed in the end area of the rib on the grounding surface side is a thin slit having a width that can be easily closed together at the time of grounding, it is closed at the time of grounding and acts as an integral rib against a load. There is no difference in wear between the inside and outside of the slit. In this respect, when a wide slit is installed, the rigidity difference between the outer area of the slit, that is, the area of the small block between the slit and the vertical groove, is different from the inner area of the slit (slit-slit area). Not only does this cause excessive wear and a different wear state, uniform wear is not achieved, but the area outside the slit lacks load-bearing capacity and reduces the effective wear area, which adversely affects wear resistance.

Further, the slit is inclined toward the center of the rib as it goes from the opening end to the rib tread surface toward the bottom of the slit, so that the rib surrounded by the slit, the vertical groove, the shoulder grounding end, the sub groove, etc. In the area of, the rigidity against vertical load on the base side is weaker than that on the tread side of the rib, so the bulge on the groove wall surface under load is biased to the base side, that is, the amount of movement of the rubber on the rib surface for the same load is conventional. Since the load energy e is smaller than that of the tire, the frictional force in the circumferential direction is not weakened, and the slippage in the circumferential direction is not increased at the rib end, so that uneven wear, so-called river wear can be prevented. Of.

In the case where a zigzag is formed by providing a number of notches that become wider toward the groove bottom side on the groove wall of the rib to form a zigzag shape, a strong zigzag shape will appear due to wear during running, and therefore, in a wet road. Braking performance can also be secured.

[0022]

1 is a schematic development view of a tread portion showing an embodiment of a pneumatic tire according to the present invention, in which 1 is a vertical groove continuous in the tire circumferential direction, and 2 is a vertical groove 1 and a vertical groove. The ribs 3 sandwiched between the grooves 1 are ribs sandwiched between the vertical groove 1 and the shoulder ground contact end 4. Reference numeral 5 denotes a side wall of the ribs 2 and 3, that is, a groove wall of the vertical groove 1, which has an inclined cross section, and the groove wall 5 is provided with a notch 7 whose width increases toward the groove bottom 6. Accordingly, the groove wall 5 is formed with a zigzag portion 10 in which a mountain portion 8 and a valley portion 9 are repeated in a zigzag cross-sectional shape on the vertical groove 1 side in the tire circumferential direction.

Reference numeral 11 is a slit formed in the end area of each of the ribs 2 and 3 closest to the shoulder ground contact end on the ground contact surface side.
It extends linearly continuously in the tire circumferential direction along the vertical groove 1, and has a width that is thin enough to be easily closed at the time of contact with the ground. The slit 11 of this embodiment has a depth direction inclined toward the center of the ribs 2 and 3, as shown in FIG. Reference numeral 12 is a lateral sipe having one end opened to the valley portion 9 of the zigzag portion 10 and the other end connected to the slit 11 in a seamless and continuous state, whereby a small block 13 having the mountain portion 8 of the independent zigzag portion 10 is formed. But rib 2,
3 is formed continuously in the tire circumferential direction along the vertical groove 1 in the end area on the ground contact surface side. Reference numeral 14 is a narrow groove on the shoulder side.

Next, the above-mentioned tire having a tire size of 11R24.5 was prototyped, mounted on the front wheels (steering wheels) of a truck and actually run, and the uneven wear resistance at the rib end was evaluated. In FIG. 4, the groove depth H of the vertical groove was 15.2 mm, and the depth h of the slit, the depth h _S of the lateral sipe, and the distance a from the rib center to the slit center were as shown in Table 1. The pitch P of the zigzag portion 10 shown in FIG. 3 is also as shown in Table 1.

The uneven wear resistance is evaluated by the uneven wear index (step wear index) K on the outside of the slit and the uneven wear index (step wear index) K _s on the inside of the slit measured after running for 150,000 km. The uneven wear index (step wear index) K is the uneven wear amount S on the outside of the slit, and the uneven wear index (step wear index) K _{s on the} inside of the slit is the wear cross-sectional area as shown in FIG. After grasping and calculating with 1/2 of the product of the length α in the width direction and the length β in the depth direction, 100 is obtained in Comparative Example 1.
It is evaluated as an index. The reference numerals in FIG. 5 are the same as those in the above-mentioned embodiment.

Table 1 shows the results. Note that Table 1 also shows occurrence of toe and heel wear.

[0027]

[Table 1]

As is clear from Table 1, in the tires of Examples, uneven wear did not occur in any of the areas outside and inside the slit. In addition, the toe and heel wear due to the formation of the lateral sipe did not occur. On the other hand, in the conventional tire (Comparative Example 6) in which the small blocks according to the present invention are not formed at the rib ends, large uneven wear occurs. Further, it is recognized from Table 1 that the pitch P of the zigzag portion is preferably in the range of 0.3 to 1.0 in terms of the ratio P / H with the depth H of the vertical groove. Further, from the table, the depth h of the slit and the depth h _{s of the} sipe are ratio h / H and h _s with the depth H of the vertical groove.
/ H 0.5-1.0, preferably 0.7-1.
The optimum value is 0.

FIG. 6 is a diagram showing the relationship between the uneven wear index K and a / H when h / H = 0.85. From the figure a /
When H is in the range of 0.6 to 0.9, the uneven wear index K = 0, and it is recognized that uneven wear does not occur. Also, it can be seen that the uneven wear amount sharply increases at a portion exceeding 0.9.

The present invention is not limited to the above embodiment. For example, independent small blocks can be formed in the end areas on the ground plane side of all the ribs.

[0031]

As described above, according to the present invention, the ratio P / H with the depth H of the adjacent vertical grooves is 0.3 to 1.0 on the end groove wall of the rib in the tire circumferential direction. Forming a zigzag portion in which the peaks and valleys are repeated in a zigzag shape in a sectional shape on the vertical groove side at a pitch P of
Along the vertical groove, it continuously extends linearly in the tire circumferential direction, forming a thin slit that easily closes at the time of ground contact,
The slit is a pneumatic tire having a small block of an independent zigzag portion formed by connecting a lateral sipe opening to the valley portion of the zigzag portion in a seamless and continuous state. Even if slippage occurs due to shearing force in the width direction and the friction coefficient in the circumferential direction decreases,
It is possible to improve the followability to the circumferential sliding (friction) force, substantially eliminate the relative slip with the road surface, and effectively prevent the uneven wear generated in the end area of the rib on the ground contact surface side.

Further, since the slit formed in the end area of the rib on the grounding surface side is a thin slit having a width that can be easily closed at the time of grounding, since it is closed at the time of grounding, it acts on the load as an integral rib. There is no difference in wear between the inside and outside of the slit.

In particular, the vertical groove depth is H, the distance from the rib center to the slit center is a, and a / H is 0.6 to
When the tire is set to 0.9, uneven wear can be significantly prevented.

Further, since the slit is inclined toward the center of the rib as it goes from the opening end to the rib tread surface toward the bottom of the slit, the rib surrounded by the slit, the vertical groove, the shoulder grounding end, the sub groove, etc. In the area of, the rigidity against vertical load on the base side is weaker than that on the tread side of the rib, so the bulge on the groove wall surface under load is biased to the base side, that is, the amount of movement of the rubber on the rib surface for the same load is conventional. Since the load energy e is smaller than that of the tire, the frictional force in the circumferential direction is not weakened, and the slippage in the circumferential direction is not increased at the rib end, so that uneven wear, so-called river wear can be prevented. Of.

When a zigzag is formed by providing a number of notches that become wider toward the bottom of the groove on the groove wall of the rib, a strong zigzag shape appears due to wear during running, so that the zigzag shape appears on a wet road. Braking performance can also be secured.

[Brief description of drawings]

FIG. 1 is a schematic pattern diagram of a tread portion showing an embodiment of a pneumatic tire according to the present invention.

FIG. 2 is an enlarged plan view of the relevant part.

3 is a cross-sectional view taken along the line AA in FIG.

FIG. 4 is an enlarged sectional view of the main part.

FIG. 5 is a schematic explanatory view showing a rib cross section in an uneven wear resistance test.

FIG. 6 is a diagram showing a relationship between an uneven wear index K and a / H.

[Explanation of symbols]

 1 Vertical Groove 2 Rib 3 Rib 4 Shoulder Grounding End 5 Groove Wall 6 Groove Bottom 7 Notch 8 Crest 9 Valley 10 Zigzag 11 Slit 12 Horizontal Sipe 13 Small Block

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location 8408-3D B60C 11/06 A

Claims (3)

[Claims] 1. A pneumatic tire having a plurality of vertical grooves continuously extending in the tire circumferential direction, and continuous or intermittent ribs formed between the vertical grooves and the vertical grooves, and the vertical groove and the shoulder ground contact end, The ratio P / H with the vertical groove depth H adjacent to the end groove wall of the rib in the tire circumferential direction is 0.3.
Zigzag portions are formed by alternately repeating peaks and troughs on the vertical groove side at a pitch P of ˜1.0, and further, in the end area of the rib on the grounding surface side, linear in the tire circumferential direction along the vertical groove. To form a thin slit having a width that is easily closed at the time of grounding, and the slit is formed by connecting the lateral sipe opening to the valley portion of the zigzag portion in a seamless and continuous state, A pneumatic tire having good uneven wear resistance, characterized in that individual small blocks are provided at least in the side end regions of the ribs closest to the shoulder ground contact ends. 2. An air with good uneven wear resistance according to claim 1, wherein a / H is 0.6 to 0.9, where H is the depth of the flutes and a is the distance from the center of the rib to the center of the slit. Included tires. 3. The slit has a direction inclining toward the rib center from the opening end to the tread surface toward the bottom of the slit, and the depth h of the slit and the depth h _{s of the} sipe are the vertical groove depth. 0.5 at the ratios h / H and h _s / H with H, respectively.
It is -1.0, The pneumatic tire with good uneven wear resistance according to claim 1 or 2.