JPS62251204A - Pneumatic tire excellent in tractional and braking performance - Google Patents

Abstract

PURPOSE:To improve tractional and braking performances without causing unusual friction to a tread land part by placing the end of the cut of a sipe provided on said tread land part on each of both side zones of a tread, on a inner part than the ground contact end of said tread. CONSTITUTION:A tread T is partitioned by a center main groove 1, pair main grooves 1' provided on both sides of the main groove 1, and lateral grooves 2, 2' which extend along the width direction of the tread T while intersecting to the main grooves 1, 1', forming longitudinal line block groups B, B' of two lines on the center and one line on each of the sides. On a tread land part, e.g., on each block 3 of the central longitudinal line block groups B, cut-off sipes S which are cut from near a projecting corner P and from a recessed corner Q which are faced to either of the circumferential grooves 1, 1' and a cut-off sipe S1 which divides the block 3 at between other recessed corners Q' are provided, while on each block 3' of the side longitudinal line block groups B', sipes S2-S4 are provided. In this case, the cutting ends Te of the sipes S2, S3 which are cut in each of both side tread land parts are positioned on inner parts than the ground contact end (e) of the tread T.

Description

Detailed Description of the Invention (Industrial Applications ￥f) Performance on snow, especially lateral stability, of a block type or rib-block type tread pattern in a pneumatic tire, more preferably a pneumatic radial tire. In this specification, the results of research and development on improving traction and braking performance without abnormal tread wear will be described.

The tread pattern of this type of tire is often a block type or rib block type, especially in all-weather type tires, and in order to increase traction on snow, each block has a tread pattern that is similar to that of the other under the contact surface during load transfer of the tire. While it is customary to have many notches narrow enough to close together at the top, -a tire blocks or ribs.
The block type tread pattern also has a large number of similar cuts, mainly to increase braking force in wet conditions, and such cuts are usually called sipes.

(Prior art) The trend pattern in which sipes are arranged is well known and there is no need to present any literature, but the normal sipe arrangement is -
The so-called blind type, which is independent from the tread groove consisting of a circumferential groove and a horizontal groove, the detached type, which extends between the tread grooves that cross the tread land area and partition it, and the nine-half type, which opens into the tread groove only at one end. It is broadly divided into blind types.

(Problem to be Solved by the Invention) In general, half-blind type sipes have a gap between them and the blind sipes at undesirable points such as excessively lowering the rigidity of the tread land area compared to detachable type sipes. However, it is not enough to improve the snow performance of all-weather tires or the wet braking ability of general tires, but it also causes abnormal local wear at the edges of the tread grooves where the sipes are open. In particular, the separated sipes placed on the tread land area on both sides of the tread can cause abnormal wear called heel-and-toe wear across the front and back of the sipes at the ground-contacting edge of the tread, resulting in an all-weather type trend pattern. This often impairs the on-snow performance of tires, especially their lateral stability.

Therefore, the present invention overcomes these problems, that is, without causing the abnormal wear on the tread land area,
The purpose is to improve traction and braking performance.

(Means for solving the problem) The purpose of the tread is to create a plurality of circumferential grooves that extend along the tread circumference at least in the central area, excluding both sides of the tread, and a trend width in a direction that intersects with these circumferential grooves. The tread land portion includes a plurality of longitudinal block groups separated by horizontal grooves extending along the direction, and the tread land portion is provided with a large number of horizontal sipes cut from the circumferential groove at a depth equal to or less than that of the circumferential groove. This is advantageously achieved by locating the ends of the cuts of the sipes arranged in the tread land portions in both side regions of the tread of the pneumatic tire inwardly from the ground contact ends of the trends.

The end of the sipe cut should be a circular hole with an inner diameter of at least 2.5 times, more preferably 3 to 5 times, the gap between the cuts of the sipe, or a relief hole of a rectangular, polygonal or other arbitrary shape with an equivalent size. It is desirable to do this, and the gap between the cuts is 0.3 to 1 m + m, especially 0.5 mm.
The depth of the cut can be approximately 0.5 to 1.0 times the depth of the circumferential groove.

Of the sipe arrays in this invention, those specified for the tread land areas on both sides of the tread as described above are of the so-called half-blind type, but the sipe arrays for the remaining tread land areas are separated types and/or
Alternatively, it may be a blind type or a half-blind type.

Now, FIG. 1 shows an example of a trend pattern according to the present invention in the case of a block type.
A center main groove 1, a bare main groove l' sandwiching the center main groove 1, and a lateral groove 2 that extends along the width direction of the tread in a crank shape in the illustrated case in a direction that intersects these main grooves 1.1'.
．． 2', two rows in the center and one row on each side, totaling 4
It has a tread land portion that partitions vertical block groups B and B' of the row. In the figure, 3.3' indicates a block.

Both main leads 1.1' can be of a two-stage zigzag type as shown in the figure, but in any case, the lateral grooves 2.2' are formed as circumferential grooves extending along the tread circumference in the central area of the tread T excluding both side areas. Therefore, in this case, all of the column block groups B and B' form the tread land area, but the so-called ribs, which are not separated by the horizontal grooves 2.2', can be used as the tread land area. Tread patterns that include the above can still benefit from the invention.

The tread land portion, in this example, each block 3 of the vertical block row B in the central region has a cut-off sipe S cut from the protruding corner P facing the circumferential groove 1.1' and from the inlet corner Q. , each block 3 is divided into two parts between its other entrance corners Q' and Q', and in addition to the separation sipes s1 extending in a crank shape, the same extends to each block 3' of the vertical block group B' in both side areas. It has sipes St+S3 and s4 cut from the corners and inside corners.

Among the sipes arranged on the land area of the tread on both sides, S
The end of the cut 2+33 is located inward from the ground contact end e of the tread T.

In the figure, an escape hole is bored at the end of the cut of sipe St+53, both of which are larger in size than the width and depth of the cut.

The depth of the escape hole includes each sipe St*3:l,
Under the custom of sipe arrangement, which is equal to or less than the depth of the main grooves 1 and 1', it is approximately equal to or less than the leading depth, numerically about 0.5 to 1.0 times. .

(Function) When the ground contact edge e of the tread T forms a so-called square shoulder, the ground contact pressure on both sides of the trend is high. Because the degree of wear differs between the front and rear, so-called heel-and-toe wear occurs, and as a result, the tire's traction, braking performance, and snow performance deteriorate as the tire is used. In contrast, the low edge rigidity on the circumference of the ground contact edge, combined with the heel-and-toe wear described above, reduces the edge effect in the lateral direction, making skidding more likely to occur, especially on snow. By positioning the cut ends of the sipes arranged on the tread land portions in both side regions inward from the ground contact edge e of the trend T by 3-b, in other words, about 2.5-5% apart from the tread width, This advantageously prevents not only a decrease in rigidity but also heel and toe wear.

Here, a plurality of grooves defined by a plurality of circumferential grooves extending along the tread circumferential line and a large number of lateral grooves extending along the width direction of the tread in a direction intersecting the circumferential grooves in the central area of the tread T excluding both side areas. It is necessary for the tread to have a tread land section that includes vertical block rows of 1 to 10 cm for on-snow performance, and these tread land sections must also be provided with a large number of horizontal sipes cut from the circumferential groove to a depth equal to or less than that of the circumferential groove. This contributes to enhanced traction and braking performance.

Here, the cutting width of the slits is 0.3 to 1.0 mm, which increases the edge effect caused by the sipe while reducing heel-and-toe wear that causes a step difference between the front and rear sides of the sipe, so that the slits close together under the contact surface. Approximately omm is suitable.

In this way, heel-and-toe wear is eliminated, and at the same time, the tread land portion at the ground contact edge is made rigid, preventing lateral slippage, and significantly improving on-snow performance.

(Example) As the tread T according to the present invention is shown in FIG.
Position it further inward.

Tire size 165SR13, Sipe S, 31-3a
are all 0.7 times the depth of the circumferential grooves 1 and 1', and the widths are 0 and 5.
ms+ closed.

A circular hole with an inner diameter of 2111111 was bored to the same depth as the sipe, with the distance of the cutting end Te of the sipes 511S and 1 from the grounding end e being 4.5 mm.

Although the sipes s and s of the column block group 3 are shown as an example of a detachable type, they can also be combined with circular holes similar to the sipes St+s= in the tread land portions of both side regions.

Compared to the tire according to the present invention, a conventional tire with separated sipes extending several +wm beyond the ground contact edge e of the tread on the tread land area on both sides of the l/red area was used as a control, and its performance was set as 100. We compared the braking and skidding performance on snow using the index and obtained the results shown in the table below. Of course, the larger the value of the index, the better.

Here, the test tires were tested and evaluated after being used in 13+w on an actual vehicle.

Table 1 Performance on snow was evaluated by braking performance (brake stopping distance) and lateral slip (lateral acceleration during turning), and heel-and-toe wear was measured by comparing the step size before and after the sipe was sandwiched.

(Effects of the Invention) According to the present invention, remarkable improvements in snow traction performance and wet braking performance are advantageously realized without causing the uneven wear that has often occurred in the past with all-weather type tires, especially with sphere shoulders. be done.

[Brief explanation of drawings]

FIG. 1 is a developed view of the tread pattern. l, 1'... Circumferential groove 2, 2'... Lateral groove B, B
'...Column block group T...Tread Sl+ 34...Separated sipe S2+ s,...Hemi-blind sipe h...Escape hole Figure 1

Claims (1)

[Claims] 1. The central region of the tread, excluding both side regions, is divided by a plurality of circumferential grooves extending along the tread circumference and a number of lateral grooves extending along the width direction of the tread in a direction intersecting the circumferential grooves. , the pneumatic tire has a tread land section including a plurality of vertical block groups, and the tread land section has a large number of horizontal sipes cut from the circumferential groove to a depth equal to or less than that of the circumferential groove, and the tread area on both sides of the tread is A pneumatic tire with excellent traction and braking performance, characterized in that the end of the cut of the sipe arranged on the land portion is located inward from the ground contact end of the tread.