JP3717988B2 - Pneumatic radial tire - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire suitable for use on icy and snowy road surfaces, and in particular, while maintaining superior performance on icy and snowy road surfaces, it occurs in a straight main groove formed on the tread rubber tread when used on non-icy and snowy road surfaces. TECHNICAL FIELD The present invention relates to a long-life pneumatic radial tire that advantageously improves preferential wear.
[0002]
[Prior art]
The so-called winter pneumatic radial tire, which has excellent braking / driving performance on icy and snowy road surfaces, as well as excellent slip resistance performance on wet road surfaces, is a tread to ensure the above performance, especially when it is a truck / bus tire. Of the various grooves in the pattern, it is effective to make several circumferential main grooves straight, and the straight main grooves are not simple straight but are slightly in and out while holding the straight on the edge of the tread. Add. This entry / exit is based on the intention to increase the above-mentioned performance to some extent by slightly increasing the edge component with respect to the front-rear direction (rolling direction) of the bent rib or block formed mainly by the straight main groove.
[0003]
[Problems to be solved by the invention]
The edge component formed by the straight main groove is slightly protruded from the straight main groove, so the circumferential rigidity is low, but the circumferential rigidity is much smaller at the initial stage of wear of the tread rubber. Step uneven wear called heel and toe (H & T) occurs in advance in the rib or block portion. However, after the middle period of wear, the rigidity of the rib or block is increased, and there is a difference in rigidity between the protruding part of the straight main groove and the central part of the rib or the central part of the block. This causes uneven wear.
[0004]
Edge wear is local step wear that occurs mainly along the groove edge of the circumferential main groove, and this local step wear is a form of wear that falls one step from the other tread rubber parts, so once edge wear occurs, so-called The wear of the edge wear part is further accelerated due to the drag phenomenon, and finally the edge wear region is expanded without stopping at the enlargement of the edge wear step, so that the wear life of the tread rubber is significantly impaired.
[0005]
Accordingly, an object of the present invention is to provide a tread pattern with a plurality of straight main grooves having a few entrances and exits that exhibit excellent performance on the above-mentioned icy and snowy road surface or wet road surface. An object of the present invention is to provide a long-lasting pneumatic radial tire that effectively suppresses the occurrence of edge wear after the middle stage of wear and effectively uses tread rubber.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a pneumatic radial tire according to the present invention has one straight main groove in each of the tread areas on both sides sandwiching the width center of the tread portion tread, and the straight main grooves are formed at both groove edges. And the opposite groove edges have the same perspective relationship with respect to the width center, and the circumferential closest line passing through both groove edges has a predetermined interval. In a pneumatic radial tire having a tread pattern having,
As the straight main groove moves from the tread surface to the groove bottom, both side wall surfaces gradually become twisted, and the groove portion formed by both side wall surfaces from the bottom of the straight main groove to the groove depth of 50% is zigzag-shaped. Consists of a circumferential groove,
Branch grooves extending from the straight main grooves toward the center of the width are provided, bent ribs are formed by the straight main grooves and the branch grooves, and outer main grooves are respectively formed on the tread edge edges of the straight main grooves. And arranged between the straight main groove and the outer main groove to form a transverse groove that communicates with each other to form a block row that is circumferentially arranged on the tread surface by the main groove and the transverse groove. ,
Each of the transverse grooves communicates with only one of the straight main groove and the outer main groove at the time of 55% wear of the tread rubber, and the main grooves with which the circumferential grooves adjacent to each other communicate with each other are It is characterized by being different from each other .
[0007]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment tire according to the present invention will be described in detail below with reference to FIGS.
FIG. 1 is a developed view of a tread pattern formed on the tread portion tread surface 1 side, and is a diagram in which the circumferential length passing through the edge Te is combined with the circumferential length of the tread surface 1 passing through the tire equator plane E according to the custom. FIG. 2 is a partially enlarged view of the pattern development view shown in FIG. 1, and FIG. 3 is an explanatory view of the occurrence of uneven wear in the block shown in FIG.
[0008]
In FIG. 1, the tread surface 1 includes one or more (two in the illustrated example) straight grooves 2 in both side regions sandwiching the center (E) of the tread width that coincides with the tire equator plane E. The straight groove 2 has a groove edge that is straight and repeats the distance with respect to the width center E at both groove edges. Further, as is apparent from FIG. 1, the opposing groove edges have different perspective relations with respect to the width center E. That is, when the straight main groove 2 is viewed along the circumference, when the groove edge on the width center E side is located far from (overhangs) the width center E, the groove edge on the end edge Te side facing this groove edge is also There is a mutual relationship located far from the width center E. Similarly, when the groove edge on the side of the width center E is located close to the width center E, the groove edge on the side of the edge Te facing the groove edge also has an interrelationship located close (overhanging) about the width center E. This is repeated along the circumference of the tread 1.
[0009]
Further, it is assumed that the circumferential lines having the closest relationship among the circumferences on the tread surface 1 passing through both groove edges of the straight main groove 2 are separated from each other by a predetermined interval. In other words, it is a so-called see-through state in which the groove space formed by the circumferential main groove 2 along the circumference of the tread surface 1 can be seen over the entire circumference.
[0010]
Here, it is assumed that the straight main groove 2 has a structure in which both side wall surfaces of the groove are gradually twisted in the circumferential direction from the tread surface 1 toward the groove bottom, and the degree of twist is gradually increased toward the groove bottom. By gradually increasing the torsion of both wall surfaces, the both-side groove wall surfaces extending from the groove bottom of the straight main groove 2 to the groove depth of 50% no longer form a straight main groove but a zigzag bent circumferential groove. The state of the zigzag circumferential groove is shown by a two-dot chain line in FIG. At this time, the remaining groove depth of the zigzag groove 2 is about 45% of that in a new article.
[0011]
The tread pattern shown in FIG. 1 has a branch groove 3 extending from the two straight main grooves 2 toward the width center E, respectively, in the central region of the tread surface 1 in order to suitably adapt to safe and reliable running on an icy and snowy road surface. 4 is formed, thereby forming a bent rib 6. Between the straight main groove 2 in the outer region of the rib 6 and the straight main groove adjacent to the tread surface edge Te side, these main grooves are mutually connected. Crossing grooves 5 that communicate with each other are provided, thereby forming a row of blocks 7 arranged in the circumferential direction on the tread surface 1. Excellent driving / braking performance and wet performance can be exhibited by the bent rib 6 and the row of blocks 7.
[0012]
FIG. 3 (a) is a plan view of the block 7 taken out from FIG. 1 for the sake of convenience, and unlike the embodiment, the straight main groove 2 holds a straight shape close to the groove bottom, which is shown in FIG. FIG. 3B is a cross-sectional view taken along line A-A in FIG. 3A, and FIG. 3A shows the edge wear portion generated in the initial to middle period of the tire by hatching. As can be seen, the edge wear is local step wear (see FIG. 3 (b)) of the projecting portion toward the straight main groove 2, and the height (depth) of the step D is an amount and a region as the travel proceeds. As mentioned earlier, the increase and expansion of
[0013]
However, since the zigzag groove 2 shown by the two-dot chain line in FIG. 2 appears from the middle stage of wear when the step wear is most likely to occur, the external force concentrated on the shaded portion (protruding portion) in FIG. It becomes possible to suppress the occurrence of edge wear by dispersing the external force with the chevron shown in FIG. Since the angle of the angle of the mountain is relatively gentle, a remarkable deterrent effect is exhibited against edge wear. As a secondary effect, the lower half of the straight main groove 2 having a chevron shape has a large rigidity, so that it has an advantageous deterrent against edge wear that occurs from the new article to the middle stage of wear.
[0014]
The pneumatic radial tire provided with the tread pattern described above is not shown as being in accordance with the conventional practice, but is composed of a pair of bead portions, a pair of sidewall portions and a tread portion, and each of these bead cores embedded in the bead portion. It includes a radial carcass of 1 ply or more that reinforces the belt and a belt that reinforces the tread portion. The tire according to the present invention is effective for use in a vehicle traveling on a paved road surface, but is particularly suitable for a heavy-duty pneumatic radial tire for trucks and buses. In addition, the code | symbol 8 of FIG. 1 is a sipe (slit), and it is desirable to provide in the range which does not produce a remarkable bad influence on uneven wear.
[0015]
【Example】
This is a pneumatic radial tire for trucks and buses, the size is 11R22.5 (tubeless), the carcass is made of a one-ply radial array steel cord, and the belt is made of four steel cord cross layers. The tread pattern is in accordance with FIG. 1, and the straight main groove 2 is a groove in which a zigzag bent groove indicated by a two-dot chain line in FIG. 2 appears at a groove depth of 50%.
[0016]
The conventional example prepared for verifying the uneven wear resistance performance of the example includes the tread pattern shown in FIG. 1, but the straight main groove maintains a straight shape from the time of new article to the point of complete wear. Are tires adapted to the examples. The comparative evaluation test of an Example and a prior art example was implemented in the following way.
[0017]
The evaluation test is based on an actual vehicle test. The test vehicle is a 2D4 vehicle (a vehicle with a single tire on the front axle, a double tire on each rear axle, and a drive shaft in front of the rear two axles). 10 tires and 10 conventional tires were attached to each tire, and the tire load was 100% load, and the vehicle was allowed to travel 60000 km. The road surface is 100% paved and there is no snow.
[0018]
The amount of the step D of the edge wear shown in FIG. 3 was measured for all the tires when the running was completed, and the amount of the step D obtained by averaging the measured values was given by an index with the conventional tire as 100. It was about 70, and it was found that the edge wear was improved by about 30%. In addition, when these two types of tires were actually run on snowy and snowy road surfaces in winter, no difference was found in braking / driving performance and slip resistance performance, and the tires of the examples had excellent snowy and snowy road performance and wet performance. It was confirmed that it was retained.
[0019]
【The invention's effect】
According to the present invention, the straight main groove is provided with a projecting portion useful for ensuring excellent icy and snowy road surface running performance and wet performance, and it is possible to exhibit excellent performance on icy and snowy road surfaces or wet road surfaces. In addition, it is possible to provide a long-lasting pneumatic radial tire that can remarkably suppress the occurrence of edge wear due to uneven wear that has occurred in the protruding portion, and that can sufficiently utilize the tread rubber.
[Brief description of the drawings]
FIG. 1 is a development view of a tread pattern of an embodiment of a tire according to the present invention.
FIG. 2 is an enlarged view showing a part of the developed view shown in FIG. 1 and the form of the straight main groove according to the present invention.
3 is a plan view of the block shown in FIG. 1 and a cross-sectional view taken along line AA. FIG.
4 is a pattern development view when the tread rubber having the pattern shown in FIG. 1 is worn at 55%. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Tread part tread 2 Straight main groove 3, 4 Branch groove 5 Crossing groove 6 Bending rib 7 Block 8 Sipe E Tire equatorial surface Te Tread edge

Claims (1)

Each comprise a single straight main grooves on both sides tread areas which sandwich the width center of the tread surface, the straight-shaped main groove has a groove edges repeating perspective in straight relates to the aforementioned width center at its both groove edges In the pneumatic radial tire, the opposite groove edges have the same perspective with respect to the width center, and the circumferential closest line passing through both groove edges has a tread pattern having a predetermined interval.
As the straight main groove moves from the tread surface to the groove bottom, both side wall surfaces gradually increase in twist, and the groove portion formed by both side wall surfaces from the bottom of the straight main groove to the groove depth of 50% is zigzag-shaped. Consists of a circumferential groove,
Branch grooves extending from the straight main grooves toward the center of the width are provided, bent ribs are formed by the straight main grooves and the branch grooves, and outer main grooves are respectively formed on the tread edge edges of the straight main grooves. And arranged between the straight main groove and the outer main groove to form a transverse groove that communicates with each other to form a block row that is circumferentially arranged on the tread surface by the main groove and the transverse groove. ,
Each of the transverse grooves communicates with only one of the straight main groove and the outer main groove at the time of 55% wear of the tread rubber, and the main grooves with which the circumferential grooves adjacent to each other communicate with each other are A pneumatic radial tire characterized by being configured to be different from each other .

Images