JPS61175104A - Radial-ply tire for heavy duty - Google Patents

Abstract

PURPOSE:To make one-sided wear prevention and long time high-speed running both attainable, by forming a zigzag pitch and a deflection range of each ridgeline, facing a main groove consisting of a shoulder rib and a second rib, in a small extent toward the outside in a tread width direction. CONSTITUTION:Each of zigzag pitches P53, P52 and P42 and deflection ranges W53, W52 and W42 of a ridgeline 42 facing a main groove 2 at an inside end of a shoulder rib 4 in a tread width direction, a ridgeline 52 facing the main groove 2 at an outside end of a second rib 5 in the same direction and a ridgeline 53 facing a main groove 3 at an inside end of the rib 5 is made smaller by degrees toward the outer side of tread width. With this constitution, wavy wear in the shoulder rib 4 is prevented from occurring and, what is more, rail way wear in and around the ridgeline 52 is preventable. In addition, improvements in wet capacity is well promotable.

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a heavy-duty pneumatic radial tire,
In particular, the aim is to improve the tread to prevent uneven wear without impairing the tire's wet performance, and to propose a tire of this type that is suitable for long-term high-speed driving.

(Prior Art) The tread pattern of heavy-duty radial tires used for high-speed driving on good roads is a so-called lip type tread pattern, in other words, the tread is formed by zigzag-shaped main grooves extending in the circumferential direction of the tire. Tread patterns in which a plurality of ribs are formed by dividing the tread in the width direction have been widely used in the past.

(Problems to be Solved by the Invention) However, in such conventional general tires, there has been a problem in that various types of uneven wear occur on each of the plurality of ribs. These uneven wear exhibit various complex aspects, but it is caused by uneven wear in the circumferential direction of the shoulder ribs located at both outermost sides in the tread width direction among the ribs that are divided by the lead. When the tire is viewed from the axial direction, the shoulder rib becomes wavy, and the second rib adjacent to the inner side of the shoulder rib in the tread width direction through the main axis is damaged at its widthwise end portion. A typical example of this is so-called railway wear of the second lip, which occurs continuously and prematurely in the circumferential direction along the ridgeline.

Therefore, in order to solve these problems, especially the problem of railway wear, the applicant first proposed in Utility Model Publication No. 56-54091 that the zigzag pinch and swing width of the lead extending in a zigzag shape on the tread circumference were changed from the conventional one. We proposed a tire that was much smaller than what was conventionally used.

However, although this tire can certainly have a significant effect on railway wear, it has the separate problem of reducing wet performance, in other words, deteriorating traction performance and braking performance on wet road surfaces. It turned out that

The present invention overcomes the problems of these conventional techniques and provides a heavy-duty radial tire that provides a good balance between uneven wear resistance and wet performance.

(Means for Solving the Problems) The heavy-duty radial tire of the present invention divides the tread in the width direction by at least three leads extending in a zigzag shape in the circumferential direction of the tire. , a shoulder rib located at both outermost sides in the tread width direction, and a second rib adjacent to the inner side of the shoulder rib across the main groove, and of these two ribs,
The zigzag pitch and swing width of each ridge line facing the main groove are made smaller toward the outside in the tread width direction.

More preferably, the width of the leading edge adjacent to the inner side of the shoulder rib is narrower than the width of the leading edge adjacent to the inner side of the second lip in the tread width direction.

(Function) In this heavy-duty radial tire, each part on the tread is functionally separated according to the degree of contribution to the required performance of the tire. Although reducing the zigzag pitch and swing width is effective in suppressing uneven wear, it tends to reduce wet performance.On the other hand, increasing the zigzag pitch and swing width contributes to improving wet performance, but We focused on the fact that uneven tread wear is more likely to occur, and while uneven tread wear is severe at the ends of the tread width where the mechanical input is large and in the vicinity thereof, the degree of contribution to wet performance is less at the center of the tread width. Focusing on the large width of the tread, the zigzag pitch and swing width of the rib ridgeline are made smaller toward the edges in the tread width direction, and increased at the center of the tread to improve uneven wear resistance and wet performance. Achieve improvements in both.

Here, wet performance can also be improved by widening the width of the lead, so in addition to the above-mentioned configuration, wet performance can be improved by widening the width of the lead located near the center in the tread width direction. Further improvements will result.

(Example) FIG. 1 is a developed view showing an example of a tread pattern according to the present invention.

Note that the internal reinforcing structure of the tire is a general structure in which the crown portion of the radial carcass extending between the left and right bead cores is reinforced with a rigid belt, so illustration thereof is omitted here.

The tread 1 of this tire has four main grooves 2.2.3.3 extending in a zigzag shape in the circumferential direction of the tire, and shoulder ribs 4.4 located at both outermost sides in the tread width direction, and main grooves 2. It is divided into five ribs 4.5.6 including second ribs 5, 5 which are adjacent to the inner side of the shoulder rib 4 with a distance between them and are substantially symmetrical with respect to the equator line C--C of the tire.

Here, a ridgeline 42. which faces the main groove 2 at the inner end of the shoulder rib 4 in the tread width direction. Regarding each of the ridgeline 52 facing the main groove 2 at the outer end of the second rib 5 in the same direction and the ridgeline 53 facing the main groove 3 at the inner end of the rib 5 in the same direction, the zigzag pitch P 53+ P S2. P
4N and swing width W5. ．． WS2. Each W4° is gradually decreased toward the outside in the tread width direction. That is, it is assumed that Pat<Pst<Ps+ and W4□×Wsm×WS3.

In this way, by setting the zigzag pitch P4□ and swing width W4□ of the ridge line 42 of the shoulder rib 4 to the smallest values, wavy wear of the shoulder rib 4 can be effectively prevented, and the second rib By selecting a small zigzag pitch psz of the ridge line 52 of No. 5, railway wear that tends to occur near the ridge line 52 can be effectively prevented, and wet performance can be improved by the action of the main groove 2. Furthermore, by setting the zigzag pitch P53 and swing width Ws3 of the ridgeline 53 of the second lip 5 to the thickest (setting), the function of the main groove 3, which contributes the highest degree to wet performance, can be sufficiently enhanced.

Therefore, the wave-like wear of the shoulder rib 4, the second lip 5
In addition to effectively preventing railway wear, the main grooves 2 and 3 bring about a sufficient improvement in wet performance, and the various performances required of the tire are exhibited in a well-balanced manner.

In addition, each zigzag pitch and swing width here are the zigzag pitch Ps of the ridge line 52 of the second lip 5.
t and swing width W0 are respectively set to 7 to 16% and 1 to 7% with respect to tread width T, and zigzag pinch P4. , P 53, zigzag pitch Ps! are set to 40 to 63% and 125 to 150%, respectively, and further, the swing width W4tW is set to the swing width WS, respectively.
! In order to achieve the above-mentioned effects, it is particularly preferable to set the ratio to 40 to 63% and 125 to 150%.

Here, main a2 and a3 are relatively wide widths to the extent that the groove walls do not come into contact with each other in the ground contact area during load transfer of the tire, preferably 4 to 9% of the tread width T.
However, as mentioned above, in order to achieve both uneven wear resistance and wet performance, in addition to the above, grooves adjacent to the inside of the shoulder rib 4 in the tread width direction are The width W2 of the main groove 2 is the width W of the main groove 3 adjacent to the inner side of the second lip 5.

It is preferable to make the width narrower, and specifically, it is appropriate that the width Wt is 60 to 90% of the width W3. Here, the width W, , W3 of the leading edge 2.3 is 42° 52 .
It shall be expressed as the distance in the tread width direction from the center position of the swing of 53.63.

Furthermore, from the viewpoint of suppressing uneven wear, it is preferable that the width W4 of the shoulder rib 4 is 13 to 25% of the tread width T.

In addition, in the illustrated example, regarding the rib 6 located at the center in the tread width direction, the zigzag pitch pia and swing width W63 of the ridge lines 63 and 63 on both sides of the rib 6 are compared to the adjacent ridge line 53.
Although it is possible to make the main grooves even larger than those of the ridge line 53, as shown in the figure, the desired effect can be achieved even if the main grooves are made the same as those of the ridge line 53. The same applies even if there are many.

[Comparative example]

Comparative test results for confirming the effects brought about by this invention are shown below.

As shown in Table 1, the tires tested were two types of tires A and B according to the present invention and two types of tires C and D according to the prior art (all units in the table are n).
), tire size is 10.00R2014PR.
The tread had a basic pattern with four main grooves as shown in Figure 1, and the internal structure of the tire was standardized to that of a typical heavy-duty radial tire.

These tires were subjected to actual vehicle tests under JIS standard internal pressure and standard load, and the results shown in Table 2 were obtained. The test method and evaluation method are as follows.

First, regarding wet performance, the braking distance from a speed of 80 kn+8 on a wet road surface was measured, and the measurement results for conventional tire C were converted into an index of 100.

Next, regarding uneven wear resistance, shoulder rib 4 and second rib were measured when a vehicle equipped with these tires was driven for 50,000 km on a test road that included highways and ordinary roads at a ratio of 7 = 3. The degree of uneven wear that occurred between the tires was visually compared and checked.

Regarding the railway wear of the second rib 5, the tires A and B of the present invention cannot achieve any reduction effect than the conventional tire D, but the absolute amount of railway wear of the second rib 5 is the same as that of the shoulder rib 4. In addition to the fact that the wave-like wear is not very large, we take into consideration the fact that ensuring wet performance, which directly affects safety, is a more important issue.

Also, as is clear from comparing the results of Tire A and Tire B, by narrowing the width of the main groove 2, the second rib 5
It is also worth noting that the railway wear is much improved.

(Effects of the Invention) As described above, according to the present invention, it is possible to achieve both uneven wear resistance and wet performance in a well-balanced manner.

[Brief explanation of the drawing]

FIG. 1 is a developed view of a tread pattern showing an embodiment of the present invention. 1--Tread 2.3--Leading 4--Shoulder rib 5--Second lip 42.52.5
3.63-・Ridge line T-・Tread width P4□,
Pst, Pss, Pbs・-zigzag pitch W
,,W, -Main groove width W4-...Shoulder rib width W, -Second rib width

Claims (1)

[Claims] 1. By dividing the tread in the width direction by at least three main grooves extending in a zigzag shape in the circumferential direction of the tire, the tread is located at least on both outermost sides in the width direction of the tread. In a pneumatic tire formed by forming a shoulder rib and a second rib adjacent to the inside of the shoulder rib across a main groove, the zigzag pitch and swing width of each ridgeline facing the main axis of both ribs are as follows: A heavy-duty radial tire that is characterized by a tread that is smaller toward the outside in the width direction. 2. The tire according to item 1, wherein the width of the main groove adjacent to the inside of the shoulder rib is narrower than the width of the main groove adjacent to the inside of the second rib in the tread width direction.