JPH02241806A - Pneumatic tire having sipes with gap difference and sipe forming blade of tire mold - Google Patents

Abstract

PURPOSE:To achieve an increased tire edge component and improved braking and driving performance by forming a sipe formed in the land-portion of the tread surface from a narrow-gap portion having a minute gap and a wide-gap portion with a wider gap that encompasses the narrow-gap portion. CONSTITUTION:The surface of the tread of a tire is provided with groove portions 1, and land portions 2 separated by the groove portions 1 to form an uneven tread pattern consisting of blocks 3. On each of the blocks 3 is formed a sipe S by cutting through the surface of the tread. The sipe S has a minute gap C1, but substantially it is formed by joining together a knife-cut portion S1, or a narrow-gap portion, and a wide-gap portion S2 which partially encompasses the periphery of the knife-cut portion S1 and which is wider than the above-mentioned gap C1 but also separates a minute gap C2. This arrangement achieves an increased tire edge component and improved braking performance particularly on icy roads.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) Tires used for running on snowy and/or icy roads, such as studless tires, are required to have high trough stability and braking performance.

The present invention aims to advantageously improve the running performance on snow and ice of pneumatic tires mounted on vehicles that run on such snowy and icy roads.

(Prior Art) As a means of improving the performance of tires used for driving on snowy and/or icy roads, land areas (blocks) forming part of the tire tread pattern are used to increase the edge component of the tire. It has been well known that it is effective to provide a large number of sipes (corresponding to blocks in the pattern).

By the way, when a large number of sizes are provided on the land area on the tread surface of a tire, the rigidity of the land area decreases, which not only has a negative effect on traction on snowy road surfaces, but also increases the deformation of the tread land area, causing the tread to deteriorate. Due to the reduced contact area of the tread and the local pressure increase on the tread surface, a large amount of melted water is generated between the tire and the road surface, which affects the braking performance of the tire and turning, especially on icy roads. Performance was significantly degraded.

For example, if you make the sipe gap as small as possible,
Even if it is used extensively, the contact pressure of the gap wall on the tire tread can be increased, so the adhesion force between the sipe walls increases and a decrease in the rigidity of the land portion can be avoided. However, in order to process such sipes, it is necessary to make the blade for forming sipes arranged inside the tire mold extremely thin, and it is difficult to guarantee the strength of thin blades, and it is difficult to ensure the strength of the blades when the tire is vulcanized. There was a disadvantage that the process was extremely complicated.

(Problem to be solved by the invention) Braking performance on road surfaces where formation of a water film is unavoidable, such as on ice, is achieved by increasing the edge component of the tire without adversely affecting the rigidity of the land portion on the tread surface. SUMMARY OF THE INVENTION It is an object of the present invention to propose a pneumatic tire that can advantageously improve and improve turning performance and a blade for forming sipes in a mold used in manufacturing this tire.

(Means for Solving the Problems) The present invention includes an uneven tread pattern in which grooves and land portions separated by the grooves are arranged on the entire surface of the tread, and the land portions are separated from the surface of the tread. In a pneumatic tire having a large number of sipes formed with cuts,
The sipe has a narrow gap or a knife-cut portion which are virtually connected to each other through an extremely fine gap C, and a gap which surrounds the narrow gap or knife-cut portion at least partially and is wider than the above-mentioned gap. This is a pneumatic tire having sipes with a gap difference characterized by a wide gap portion separated by a minute interval C2.

Further, the present invention is arranged in a mold having a cavity corresponding to an uneven tread pattern consisting of grooves on the entire surface of the tread and land portions separated by the grooves, and creates a gap difference between the land portions of the tread. A blade for cutting and forming a large number of sipes with a relatively thick frame-like part of the sipe, a window hole part partitioned by the frame-like part, and a window hole part farthest from the mold cavity. A tire mold sipe forming blade characterized by having a cutting blade portion provided at the edge thereof, a relatively thick frame portion, and a wall thinner than the frame portion partitioned by the frame portion. This is a tire mold sipe forming blade characterized by having a thick and thin part.

Now, FIG. 1 shows a tread portion of a pneumatic tire according to the present invention, 1 in the figure is a groove on the tread surface, 2 is a land portion separated by the groove 1, and the groove 1 and land portion 2 are the tread portion. The tread pattern is placed over the entire surface of the tread and forms an uneven tread pattern.

Further, 3 is a block, for example, in which the land portion 2 is divided by the groove portion 1, and the size S shown in the example shown in the block 3 is the main part (A-Δ arrow position and B-B cross section). As shown in FIGS. 2(a) and 2(b) on an enlarged scale, there is a narrow gap or knife-cut portion St that is virtually joined to each other through an extremely fine gap C+, and a layer of this narrow gap or knife-cut portion. at least partially surrounding the surrounding area, with a gap C
It consists of a wide gap portion S2 separating a gap C8 which is wider than 0 but still minute.

In addition, FIGS. 3(a) and 3(b) schematically show an example of a sipe forming blade used for processing the sipe S with the above-mentioned gap difference, in which 4 is the mold body and 5 is the tire mold manufacturing stage. It is a blade whose base part is buried and fixed in the mold main body 4 and exposed in the cavity, and this blade 5 has a frame-shaped part 5a having a jI corresponding to the fine interval Cz of the sipes S, and a frame-shaped part 5a. It has a partitioned window portion 5b and a cutout portion 5c provided at its edge facing the window portion 5b furthest from the mold cavity.

Further, FIGS. 4(a) and 4(b) show another example of the sipe forming blade used for processing the sipe S having a large gap difference, in which the blade 5 is embedded and fixed in the mold body 4.
may have a structure including a frame-shaped portion 5a and a thin-walled portion 5d that is partitioned by the frame-shaped portion 5a and has a thickness thinner than that of the frame-shaped portion 5a.

The internal structure of the tire illustrated in FIG. 1 above is the same as that of a general radial tire, and is not shown here.

(Function) In this invention, the narrow gap or knife cant portion Sl is widened by the large cut portion 5c or thin portion 5d of the blade 5 when taking out the tire from the mold after molding and curing in the tire mold. It is formed together with the gap S2. The ultra-fine gap C9 that virtually joins each other in the narrow gap or knife cut part S is smaller than the interval C2 of the wide gap SA that at least partially surrounds the narrow gap or knife cut part S. Since the land portions 2 are narrow, the narrow gap portion or knife cut portion S in the contact area of the tire tread strongly adheres to fix the land portions 2 to each other. Therefore, even if a large number of sipes are provided on the land portion 2 of the tread surface, the decrease in the rigidity of the land portion is small, and there is no risk that the braking performance or turning performance of the tire will deteriorate.

Regarding the tire mold sipe forming blade 5, the window hole portion 5a and the cut portion 5C or the thin portion 5b are provided at the edge of the window hole portion 5a farthest from the mold cavity. There is no lack of strength, which is a concern due to the thinning of the blade.

Window hole portion 5a or thin wall portion 5d provided in blade 5
for the cross-sectional area of at least 1 of the total area of the blade 5
It is preferable to set it to 0%. This is because if the area of the window hole portion or the thin wall portion is small, the area of the narrow gap portion of the sipe or the knife cut portion Sl will be small, and sufficient fixation against land portion deformation cannot be obtained.

In addition, Figure 3 (a) (b) and Figure 4 (a) shown above
The blade shown in (b) is an example according to this invention,
In addition to this, the present invention can also use configurations as shown in FIGS. 5(a), 5(b), and 5(e).

In addition, in Fig. 1 above, the example is shown in which the sipes S with a gap difference are provided in the blocks of the tread part, but the sipes S are not limited to this, and the sipes S are provided in all the lugs, ribs, rib lugs, etc. Applicable to tread patterns.

(Example) Size 175/70R1 with tread shown in Figure 6
Icy road with a surface temperature of -5°C using tires with a temperature of 3.
A driving test was conducted using a front-wheel drive 1800cc class passenger car on a compacted snow road that had been compacted by driving a passenger car on fresh snow, with two people on board, and the braking performance and turning performance of the tire on icy roads were evaluated. We also investigated the driving performance on compacted snow roads.

In this test, a tire of the same size and having a tread as shown in FIG. 7 was used as a reference.

The results are shown in the table below, and the tire according to the present invention exhibited higher performance than a tire with a similar tread (simply with an increased number of sipes) as shown in FIG. 6, which was used as a comparison tire. It was confirmed that

(Effects of the Invention) According to the present invention, the edge component on the land portion of the tread surface is increased without reducing its rigidity, thereby improving the running performance of the tire on snowy and icy roads, especially braking performance and turning performance on icy roads. By improving this, stable driving can be realized.

Further, according to the present invention, even when thinning the blade, which poses a problem of insufficient strength, sipes having extremely fine gaps can be processed without adding complicated steps.

[Brief explanation of drawings]

Figure 1 is an enlarged view of the main parts of the pneumatic tire according to the present invention, Figures 2 (a) and (b) are enlarged views of the main parts of Sipe S, Figures 3 (a) and (b), and Figure 4. (a) (b) are schematic diagrams of a blade for forming sipes according to the present invention; Figures 5(a), (b), and (c) are diagrams showing other examples of blades for forming sipes according to the present invention; FIG. 7 is a diagram showing a tread portion of a pneumatic tire according to the present invention, and FIG. 7 is a diagram showing a tread portion of a standard tire. 1...Groove portion 2...Land portion 3...Block 4...Mold body 5...Blade 5a...Frame-shaped portion 5b...Window hole portion
5c...Cutting blade part S...Sipe
C1...extremely minute gap C2...gap part
Sl...Knife cut part Fig. 2 (a) Fig. 1 (b) Fig. 3 Ca) ←-C (b) Fig. 4 (b) Fig. 6

Claims (1)

[Claims] 1. The tread has an uneven tread pattern in which grooves and land portions separated by the grooves are arranged on the entire surface of the tread, and the land portions have a large number of incisions formed from the surface of the tread. In a pneumatic tire having sipes, the sipes include a narrow gap or a knife cut portion which are virtually joined to each other through an extremely fine gap C_1, and at least partially surround this narrow gap or knife cut portion. A pneumatic tire having sipes with a gap difference characterized by a wide gap part separating a gap C_2 which is wider than the above gap but still minute. 2. Disposed in a mold having a cavity corresponding to an uneven tread pattern consisting of grooves on the entire surface of the tread and land areas separated by the grooves,
A blade that cuts and forms a large number of sipes with a gap difference in the land part of the tread, the blade having a relatively thick frame-like part of the sipe, and a window hole part divided by the frame-like part and the most from the mold cavity. A blade for forming sipes in a tire mold, characterized in that it has a cutting edge portion facing a remote window hole portion and provided at an edge thereof. 3. Disposed in a mold having a cavity corresponding to an uneven tread pattern consisting of grooves on the entire surface of the tread and land areas separated by the grooves,
A blade that cuts and forms a large number of sipes with a gap difference in the land portion of the tread, the sipe having a relatively thick frame-shaped portion and a wall partitioned by the frame-shaped portion and having a thinner wall thickness than that. A tire mold sipe forming blade characterized by having a thin wall portion.