JPH0338406A - Pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE:To improve travelling performance on a freezed road or a wet road by forming a plurality of slits having predetermined depth and interval on tread land portions in a pneumatic tire for heavy load using foaming rubber in the tread. CONSTITUTION:A plurality of slits to satisfy a relation 0.1<=w/d<=20 wherein (d) is the depth thereof and is formed 0.1-2.0mm and (w) is the intervals between the slits are provided on the land portion of tread made of foaming rubber. Due to this construction, particularly when the tire is new, travelling performance on a freezed road and a wet road having small friction coefficient can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to a heavy-duty pneumatic tire, and in particular, it greatly improves running performance on wet and frozen roads with a small coefficient of friction.

(Prior Art) It is known that increasing the surface roughness of a tire is one of the methods of improving running performance on wet and frozen roads with a small coefficient of friction. Previously, JP-A-62-283001 and JP-A-63-
No. 90402, etc., provided pneumatic tires with foam rubber treads.

In this pneumatic tire, the water film is removed based on the intake of the water film into the closed cells that open on the surface of the ridge of the tread, and the gills are caused by the opening edges of the closed cells.

Due to this effect, the road grip force on wet road surfaces and frozen road surfaces can be effectively improved.

(Problem to be Solved by the Invention) By the way, when vulcanizing a tire using foamed rubber for the tread, the foamed rubber does not foam at the air interface, and the roughness of the outer surface of the tread is higher than that of the inner surface of the mold. When the tire is new, it is unable to exhibit the effects unique to foam rubber, and in order to bring about that effect, the surface layer of the tread land area must be removed by puffing or other means. The problem was that it was necessary.

This invention advantageously solves the problems of the prior art, and even tires with treads made of foamed rubber can cover wet and frozen roads with a small coefficient of friction even when new. The present invention provides a heavy-duty pneumatic tire with high performance characteristics.

(Means for Solving the Problems) The heavy-duty pneumatic tire of the present invention is provided with a plurality of cuts in the tread land portion, and the depth d of the cuts is within the range of 0.1 to 2.0 cm. and its depth d
The ratio of the cut interval W to the cut interval W is set in the range of 0.1≦w/d≦20.

(Function) In the tire of the present invention, the plurality of notches formed in the tread land portion are used until the closed cells in the tread are exposed, that is, until the outer surface of the tread of a new tire disappears due to wear. By taking over the role of closed-cell foam and gripping the road surface with the edges of its cuts, the tire can fully demonstrate driving, braking, and maneuverability on wet and icy roads with low coefficients of friction, even when the tire is new. As a result, the drivability on these road surfaces can be significantly improved.

By the way, after the notches provided in the tread land portion are worn out, the exposed closed cells perform their original functions, so that the running performance on each of the above-mentioned road surfaces can be maintained at a high level.

Here, since it is sufficient for the cut to function only for a short period of time until the closed cells in the tread are exposed, the depth d can be made approximately equal to the depth of the outer surface of the tread. According to the results, the running performance on frozen road surfaces increases rapidly when the depth d is 0.05 mm or more, and the running performance on wet roads with a small friction coefficient increases when the depth d is 01 to 2.0 mm. Here, the depth of cut d is set to 0.1 to 2. Oa+
The value is within the range of m.

Further, here, in order to ensure that each notch fully functions, the ratio of the notch interval W to the notch depth d is set to a value in the range of 0.1≦w/d≦20.

In other words, when w/d<Q, l, the depth of the cuts relative to the spacing becomes too large, and especially in heavy-duty tires with high ground contact pressure, the portion of the tread land located between the cuts collapses. In addition to not being able to exert the edge effect, the parts located between the notches are easily susceptible to chipping and other damage to the road surface.
Then, the interval between the cuts is too wide relative to the depth,
The function of the cutting depth will not be fully demonstrated.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a diagram showing an embodiment of the present invention, in which a block is provided as an example of a tread land portion with a notch.

Note that the internal structure of the tire, except for the fact that the tread is made of foamed rubber, can be of a conventional general radial or bias structure, so illustration thereof is omitted here.

In this example, a plurality of notches 2 are provided on the surface of block l at predetermined intervals in the circumferential direction of the tire, each of which is inclined at a predetermined angle with respect to the tire equatorial plane. Both ends of 2 are opened completely to partition block l.

Here, each incision 2, which can be formed simultaneously with vulcanization of the tread or by knife cutting after vulcanization, has a depth d in the range of 0.1 to 2.0 degrees. In other words, for a frozen road surface, the depth d of cut 2 is a parameter, and the interval W of cut 2 is 3f.
When the braking index was measured when flII was set, the second
As shown in the figure, the braking index for a frozen road surface is determined by the depth d
is 0.1-2. This is based on the fact that it has become clear that a peak value is shown between
This is because by specifying the range of 2.0a+n+, it is possible to achieve both the performance on wet tread surfaces with a small coefficient of friction and the performance on frozen road surfaces.

By the way, this running performance, which is related to not only braking performance but also driving performance and maneuverability, is influenced not only by the depth d of the notches 2 but also by the interval between the notches 2. In order to ensure an effective improvement in running performance, the ratio of the distance W to the depth d of the cut 2 is set to 0.1≦w/d≦20.

In other words, when w/d<Q,l, the depth d of the cut 2 with respect to the interval W becomes too large, and the tread ridge portion between the cuts falls down when the tire is transferred, causing the depth d of the cut 2 to become too large. In addition to the edge being unable to produce the edge effect, tread damage becomes severe, and on the contrary, w/d
>2Q, the distance W between the depth (1) of the cut 2 becomes too wide, and the cut 2 cannot fully demonstrate its function.

In addition, in the area shown in the figure, the intersecting angle of the cut 2 with respect to the tire equatorial plane can be appropriately selected as required, and the intersecting angle can be changed for each block row aligned in the circumferential direction of the tire. You can also do it.

According to a tire in which each block l is provided with notches 2 as described above, especially when the tire is new, driving performance and braking performance on frozen roads and wet roads with a small coefficient of friction are improved under the action of the notches 2. It is also possible to sufficiently improve maneuverability and greatly improve drivability on those roads.

After the notches 2 are worn away, the same effect as described above can be produced based on the action of the air bubbles exposed on the block surface.

FIG. 3 is a diagram showing another embodiment of the present invention, and FIG. 3(a) shows a cut 2 having a depth d of 0.5 mm in a - block 1, which is oriented upward to the right in the figure. 2.0+n
The interval W is m, and the one that slopes downward to the right is 1.0 mm.
They are provided at an interval W of .

In addition, in Fig. 3 et al., a cut 2 having a depth d of 1.5 nua is made downward to the right in the right half of the block l, and upward to the right in the left half of the block l, respectively. They are provided at an interval W of 0 mm, and FIG.
Cuts 2 having a depth d of m are formed downward to the right at arbitrary intervals W satisfying the above-mentioned conditions. Here, according to this latter example, by appropriately selecting the interval W between the cuts 2, it is possible to effectively prevent the stiffness of the flock 1, particularly at the corner portions, from decreasing.

In any of these embodiments, the cut 2 can exhibit the same effect as described above when the tire is new, and can greatly improve running performance on frozen roads and wet roads with a small coefficient of friction.

Further, FIG. 4 shows a tire in which a cutout 2 is formed in each of the shoulder block row 11 and the two center block rows 21 located between these block rows, and the cutout 2 is formed at the left end of the figure. A notch 2 is made in the block l of the shoulder block row 11 located upward to the right, and a notch 2 in the block 1 of the shoulder block row 11 located at the right end is made downward to the right, the depth d is 1.2 mm, and the interval W is made. 2
．． 0 nun, and each block l of each center block row 21 has 2
, 0nun interval W, 2mm depth d cut 2
They are arranged to intersect with each other as described with reference to FIG. 3(a).

It goes without saying that such a tire can also provide sufficient running performance based on the effect of each cut 2.

Although the present invention has been described above based on the illustrated examples, the present invention can be applied not only to block-shaped ridges but also to rib-shaped and lug-shaped tread land parts.

[Comparative example]

A comparative test regarding braking performance between the invention tire and the comparative tire will be described below.

・Inventive tire tread is made of foamed rubber, and the block has a depth of 1. O
mm, and the cuts with a spacing of 1.5 mm are made in the circumferential direction.
Comparison Tire I - Comparison tire with foam rubber tread and no cuts on the block surface - Comparison Tire - Comparison tire with a tread made of general rubber and no cuts on the block surface - Test Method: Tires with the same block pattern of size 100OR20, size 7. Attached to the rim of OOT The braking performance was evaluated by measuring the braking distance from when the brakes were locked until the truck came to a stop.

・Test results The test results of each tire, the results of the comparative tire ■ are indexed to 10
0 and expressed as an index in the table below.

Note that the larger the index value, the better the result.

Table According to this table, it is clear that the braking performance of the invention tire when new is far superior to both comparative tires.

Here, for comparison tire ■, approximately 100 km
It has been confirmed that the braking performance improves to 130 after the tread surface wears down and air bubbles are exposed during driving.

(Effects of the Invention) Thus, according to the present invention, by providing a plurality of specific notches on the surface of the ridge of the tread using foamed rubber, it is possible to improve the road surface on frozen roads and wet roads with a small coefficient of friction, especially when the tire is new. The running performance on the road surface can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a diagram showing one embodiment of the present invention, FIG. 2 is a graph showing the relationship between cutting depth and braking index, and FIG. 3.4 is a diagram showing another embodiment. l...Block 2...Depth d...Depth W...Spacing Fig. 1 (a) (b) W-Spacing Fig. 2 + n foot vs. cleanness C clearing)

Claims (1)

[Claims] 1. A pneumatic tire using foamed rubber for the tread, in which a plurality of cuts are provided in the tread land area, and the depth d of the cuts is 0.1 to 2.0 mm. A pneumatic tire for heavy loads, in which the ratio of the cut interval w to the depth d is in the range of 0.1≦w/d≦20.