JPH0688252B2 - Tire vulcanization mold - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a tire having a belt layer made of a steel cord, which prevents uneven wear occurring at a rib edge or a block end of a tread portion of a tire for trucks and buses. Regarding the vulcanization mold.

[Conventional technology]

Radial tires with a belt layer made of steel cord in the tread portion are frequently used as tires for trucks and buses due to their excellent wear resistance and puncture resistance.The tread pattern of them is heat generation, especially for good roads. In addition to the rib pattern shown in Fig. 3 in consideration of the above, the block pattern shown in Fig. 4 for so-called all weather, which can withstand various climate changes during the day of operation, is adopted. In many tires having different patterns, a bent groove is used to form a protruding portion B protruding in the tire axial direction, for example, marked with a circle in FIGS. 3 and 4.

[Problems to be solved by the invention]

However, when such a tire is filled with a specified internal pressure, the protrusion B is widened due to the gating phenomenon that the groove width becomes wider.
In, the tire tread surface does not become a single curve,
As exaggeratedly shown in FIG. 5, a protruding portion C protruding outward from the reference tread surface K is formed, and as a result, the protruding portion B is formed.
Uneven wear occurs where the wear in the vicinity progresses early.

It is an object of the present invention to provide a tire vulcanizing mold capable of reducing the uneven wear by making the radius of curvature of the tread surface of an internal pressure filled tire after vulcanization in truck and bus tires uniform.

[Means for solving problems]

The present invention provides a land portion having a protrusion that bulges in the tire axial direction by providing a bending groove having a carcass and a belt layer and having a bending portion that bends in the tire axial direction on the tread surface in the tire circumferential direction. The formed tire is a tire vulcanizing mold for vulcanizing the tire for trucks and buses, and the tread molding surface of the tire vulcanizing mold for forming the tread surface has a radius of curvature of 300 mm or more and 400 mm in a cross section including the tire shaft. It has a reference portion consisting of the following reference arc surface and a protrusion forming portion forming the protrusion, and the upper edge of the protrusion end of the protrusion forming portion is 0.3 to 0.8 mm radially from the reference arc surface. And the protruding portion forming portion connects the reference arc surface and the upper edge and has a radius of curvature R of 80 to 130 m.
It is a tire vulcanization mold consisting of a circular arc surface of m.

[Action]

The protruding portion forming surface of the mold forming the protruding portion in the tire axial direction of the land portion of the tire is previously formed by an arcuate surface continuous with the upper edge located on the inner side in the radial direction. Therefore, even when the groove spreads due to the internal pressure filling, that is, when the gaping occurs, the tire to be molded absorbs the rising because the projecting portion of the tire is preliminarily sunk inward by the projecting portion forming surface. The tread surface of can be formed in an arc shape over the whole. This can prevent uneven wear.

〔Example〕

 An embodiment of the present invention will be described below with reference to the drawings.

The tire T includes a carcass 2 and a belt layer 3, and the belt layer 3 uses a plurality of belt plies using steel cords. Further, as shown in FIGS. 3 and 4, the tread portion has a protruding portion B formed of a rib or a block and protruding in the tire axial direction by providing a bending groove A that bends in a zigzag manner on the tread surface. The land portion L is formed. Further, as shown in FIG. 1 before filling with internal pressure, the projecting portion B is formed as an arcuate surface 7 having a projecting end located downward by an arc curved inward before filling with internal pressure.

The tire vulcanizing mold 1 is for vulcanizing and molding the tire T, and a tread forming surface 11 forming the tread surface is provided with a ridge 10 for forming the bending groove A inwardly expanded. A reference portion 12 formed by a reference arc surface K formed by an arc having a reference curvature radius Rs and a protrusion forming portion forming the protrusion B in a cross section including the tire shaft.
13 and. The reference portion 12 is an arc along the tread surface in a region exceeding at least 50% of the tread surface, and both side portions may be formed by an arc having a radius of curvature different from the radius of curvature Rs.

Further, the reference curvature radius Rs is set to 300 to 400 mm.
The protruding portion forming portion 13 is formed by an arc surface having a radius of curvature R of 80 to 130 mm, which is smaller than the reference radius of curvature Rs.
Further, one end of the arcuate surface is smoothly connected to the reference arcuate surface K, and the other end is continuous with the upper edge 14 forming the protruding end upper edge point a of the protruding portion B. The upper edge 14 is located radially inward from the reference arc surface K and the distance between the upper edge 14 and the reference arc surface K, that is, the camper height CH is 0.3 to 0.8 mm.

Here, the reference radius of curvature Rs is 300 to 400 mm, the radius of curvature R of the arc surface is 80 to 130 mm, and the camber height CH is 0.3 to 0.8 mm. The raised portion C due to the rising of B is absorbed in advance.

The larger the zigzag angle β of the bending groove A and the smaller the inclination angle α of the groove wall, the larger the amount of rising. Therefore, at this time, the camper height CH is increased to approach 0.8 mm, and the radius of curvature is increased. It is good to make R large and to approach 130mm.

The tire T molded by such a mold does not have a bulge associated with the internal pressure filling in the protruding portion B of the land portion L, reduces uneven wear and improves tire durability.

〔Concrete example〕

First, the tires (Examples 1 and 2) having the rib pattern shown in FIG. 2 and having a tire size of 10.00R20 were prepared together with Comparative Examples -1 and -2.
A prototype was produced according to the specifications shown in the table. In addition, JIS standard maximum air pressure was filled and the amount of uneven wear after running 50,000 km in actual vehicle test was measured.
It is also shown in the same table by indexing with the value of Example-1 as 100. The larger the number, the better. In the example, the tread surface is a single curved surface due to the internal pressure filling,
Excellent resistance to uneven wear.

〔The invention's effect〕

As described above, after the internal pressure filling, a tread surface that is almost a single curved surface is formed, and uneven wear can be effectively reduced.

[Brief description of drawings]

FIG. 1 is a sectional view showing an example of a tire, FIG. 2 is a sectional view of a mold showing an embodiment of the present invention, FIGS. 3 and 4 are plan views illustrating tread patterns, and FIG. 5 is a raised portion. FIG. 2 ... Carcass, 3 ... Belt layer, 12 ... Reference part, 13 ... Projection forming part, 14 ... Top edge, A ... Bending groove, B ... Projection, L ... Land.

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Claims (1)

[Claims] 1. A land portion having a carcass and a belt layer, and a tread surface having a bent groove having a bent portion bent in the tire axial direction in the tire circumferential direction, the land portion having a protruding portion bulging in the tire axial direction. A tire vulcanizing mold for vulcanizing a truck or bus tire that has formed a tread forming surface of the tire vulcanizing mold that forms the tread surface has a radius of curvature of 300 mm or more in a cross section including a tire shaft. It has a reference portion consisting of a reference arc surface of 400 mm or less and a protrusion forming portion that forms the protrusion, and the upper edge of the protrusion end of the protrusion forming portion is 0.3 to 0.8 mm from the reference arc surface in the radial direction. While being located inward, the protrusion forming portion connects the reference arc surface and the upper edge and has a radius of curvature R of 80 to 13
Tire vulcanization mold with 0 mm arc surface.