JPH0460406B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a mold for vulcanization molding of tires, and more specifically, it is a mold for vulcanization molding of tires. This invention relates to a tire molding mold for molding tires. [Conventional technology] In recent years, the driving performance of passenger cars has improved, and in response to this, the tread pattern of tires has linear grooves arranged at wide intervals, and tires with excellent maneuverability such as traction, braking, and steering response are used. I started to be able to do it. on the other hand,
Along with the running performance of a tire, the design of the tire is also a major factor that influences its commercial value. In recent years, the body design of passenger cars has adopted an angular shape based on flat surfaces, which harmonizes with the angular tread pattern of tires with grooves based on straight lines, and the shape of the tire sidewall has also changed. In order to harmonize with the tread pattern of a passenger car's body and tires, a design with a strong, angular shape is required rather than a shape with rounded curves. For example, Utility Model Application Publication No. 60-28503 discloses a flat conical annular surface on the side of a tire for the purpose of making it easier to stamp a concave-convex pattern on a vulcanization mold to form letters, etc. to be displayed on the tire. A tire is disclosed. In this way, when a part of the side part of the tire is made up of a conical surface, and at the same time the conical surface is a smooth surface with no letters or patterns, the reflection of light from the conical surface is caused by the reflection of light from the curved surface adjacent to the conical surface. There is a clear difference between reflection and
The sides of the tire give a powerful feel that blends in with the angular design of the treaded pattern. [Problems to be Solved by the Invention] As described above, when a part of the side portion of the tire is formed of a conical surface, so-called bare spots are likely to occur on the conical surface during vulcanization molding of the tire, as will be described later. When bears occur on the conical surface, the bears become more noticeable and unsightly due to differences in the reflection state of light rays. Typical methods for manufacturing tires include laminating tread rubber and sidewall rubber on a carcass on a green tire molding machine to form a green tire, loading this into a vulcanization mold, heating and pressurizing it, and molding it into a tire. used. In the state of a green tire, the thickness of the sidewall is fairly uniform in each part, and in a tire that does not have a conical surface on the tire side part shown in Figure 2, the thickness of the sidewall of the tire after vulcanization molding is also uniform. However, in a tire having a conical surface 2 on the tire side portion 1 as shown in FIG. The sidewalls are thicker at both end regions 4 and 5 of the surface. In order to vulcanize and mold a tire having such a conical side surface, when the green tire is loaded into the mold and the mold is closed, the sidewall of the green tire is first formed in the middle area of the conical surface 2 on the inner surface of the mold. 3 and when the mold is further closed, the conical surface intermediate region 3 cannot accommodate any more rubber, so the excess rubber is pushed out toward the end regions 4 and 5, and rubber is replenished in that region. Therefore, the sidewall 6 becomes thicker than when using a green tire. The air that existed between the mold and the green tire gathers from the part where the rubber came into contact with the mold into the space that remains without contact. When the mold is sufficiently closed and internal pressure is applied, the air remaining between the mold and the green tire collects in the recesses on the inside of the mold, and some of it diffuses into the rubber, but most of it is compressed. It remains in this state until vulcanization is completed. The traces of this air buildup appear as depressions on the tire surface. In order to prevent the occurrence of bare air, a vent hole for air release is provided through the mold, but rubber flows into the vent hole during tire molding, causing whiskers on the surface of the tire after vulcanization. There is a forest of spews made of shaped rubber. This is cut to finish the tire, but in the case of tires with conventional curved side parts, the radius of curvature of the sidewall surface in the radial cross section of the tire is 50 to 100 mm, and the spew stands at the top of the curved surface. Because of this, it can be cut and removed without leaving any traces from the root, and it is not noticeable after cutting. On the other hand, the conical surface of the tire side part, which is composed of a conical surface, has a small radius of curvature and is close to a flat surface, so when cutting the spewer, only the thickness of the blade remains, making cutting marks more noticeable and spoiling the appearance. , reducing the commercial value of tires. Therefore, the present invention prevents the occurrence of bare tires in the manufacture of tires that give a strong visual appearance by forming a part of the side part of the tire with a conical surface. An object of the present invention is to provide a tire vulcanization molding mold capable of molding an inconspicuous tire. [Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a mold for tire vulcanization molding, which covers a range from the shoulder part of the tire to the maximum cross-sectional width position of the mold inner surface. The outer side part is made of a conical surface coaxial with the tire center axis, and the inner side part corresponding to the range from the maximum cross-sectional width position of the tire to the bead part is made of a straight line or concave curve that runs along the tire center axis. It consists of a curved surface obtained by rotating around the center, and an annular groove with a triangular cross section is provided on the inner surface of the mold along the maximum cross-sectional width position of the tire, and a through hole that communicates with the outside of the mold from the bottom of the annular groove. An exhaust hole such as a vent hole or a hole in which a vent plug having a large number of minute holes is embedded is provided. Next, the contents of the present invention will be explained in detail with reference to the drawings. FIG. 1 is a sectional view of a left part of the upper half of the tire vulcanization mold of the present invention. In the drawings, reference numeral 7 denotes a mold, into which a green tire is loaded and a tire 8 is molded as shown by an imaginary chain line. The side portion 1 of the tire 8 is composed of a carcass 9 and a sidewall 6 covering the outside thereof. One end of the sidewall 6 is connected to a shoulder portion 10, and the other end is connected to a bead portion 11. The maximum cross-sectional width position 12 of the tire is located in the middle of the sidewall 6. Of the inner surface of the mold 7, the outer side portion 13 corresponding to the range from the shoulder portion 10 of the tire 8 to the maximum cross-sectional width position 12 is constituted by a conical surface coaxial with the rotational axis of the tire. On the inner surface of the mold, the inner side portion 14 corresponding to the tire's maximum cross-sectional width position 12 to the bead portion 11 is constituted by a concave curved surface obtained by rotating a straight line or a concave curve about the tire center axis. An annular groove 15 having a triangular cross-section is provided along the maximum cross-sectional width position 12 at an inner surface position of the mold corresponding to the maximum cross-sectional width position 12 of the tire. As shown in the enlarged sectional view of FIG. 4, this annular groove 15 has a width w of the annular groove.
2 to 20 mm, preferably 5 to 15 mm, depth d is 0.1
-2 mm, preferably 0.3-1 mm. The side surface 16 on one side of the annular groove 15 may be formed by extending the side outer portion 13 as shown in FIG. 4. In this case, the depth d of the annular groove 15
is the depth from the virtual extension surface 17 of the side inner part 14 to the groove bottom 18, and the width w is the length until the extension surface intersects with the conical surface. Preferably, a vent hole 19 is provided, which is a through hole communicating from the groove bottom 18 of the annular groove 15 to the outside of the mold. In this case vent hole 1
A plurality of grooves 9 are provided along the annular groove bottom 18 at appropriate intervals. Appropriate characters, symbols, etc. may be engraved on the conical surface of the side outer portion 13 of the mold of the present invention. Passenger car tires are usually not limited to the mounting direction on the rim, and both sides of the tire are molded in the same shape, but in the case of asymmetric tires that specify the mounting direction on the rim, they are mounted facing outward. Only the inner surface of the mold corresponding to the sidewall can be configured in the above shape, and the portion corresponding to the other sidewall can be configured in any known shape. [Function] When a green tire is loaded into the tire vulcanization mold 7 of the present invention, the thickness of the rubber on the side part of the green tire is initially uniform, but as shown in FIG. During vulcanization, the rubber was From middle area 3 to edge area 4,
5, the thickness of each part is adjusted. As shown in FIG. 5, when the conical surface of the side outer part 13 and the concave curved surface of the side inner part 14 are smoothly continuous, the rubber is moved from the intermediate region 3 and the side inner part 14 toward the end region 5. It flows and the rubber from both sides join together. The air remaining between the inner surface of the mold and the green tire also flows in the direction of the rubber flow, and the air is trapped at the joints of the rubber, which tends to cause bare spots. According to the present invention, when an annular groove 15 having a triangular cross section is provided along the maximum cross-sectional width position 12 as shown in FIG. The rubber flows, and finally the annular groove is filled with rubber. The air that moves as the rubber moves moves to the groove bottom 1 of the annular groove 15.
It accumulates at 8. During vulcanization, a pressure of 15 to 30 kg/cm ² is applied, so the air accumulated in the groove bottom 18 is compressed, and some of it diffuses into the rubber, so its volume becomes smaller and the air accumulates in the groove bottom 18. Since the air caused by the air accumulated in the annular groove 15 resembles a state in which the corners corresponding to the groove bottom 18 are chamfered, the appearance will not be significantly impaired. However, if there is a large amount of air accumulated in the groove bottom 18, it is discharged from the groove bottom 18 through the vent hole 19 to the outside of the mold. Unvulcanized rubber has a high viscosity, so it moves in a laminar flow within the mold, and the closer it is to the inner surface of the mold, the slower the flow rate is, making it difficult to flow into narrow parts. Therefore, the groove bottom 18 of the annular groove 15 is filled with rubber only after the rubber has been heated and its viscosity has decreased. For this reason, there is a time lag between the closing of the mold and the filling of the rubber into the groove bottom 18. During this time, the groove bottom 18 is connected in an annular manner, so by providing a small number of vent holes 19 at appropriate intervals, air can be completely removed. can be discharged. By making the cross-sectional shape of the annular groove 15 triangular, residual air can be easily collected uniformly at the bottom of the groove over the entire circumference, and can be completely discharged from the vent hole if necessary. In particular, if the side wall 20 on the inner side side of the annular groove 15 is formed into a convex curved surface, the exhaust effect will be increased. If the depth of the annular groove 15 is less than 0.1 mm, its function as a communication groove for storing and discharging air will be small.
If the depth exceeds 2 mm, it will be necessary to vary the amount of rubber in the sidewall near the annular groove, which will actually cause an increase in bareness. Therefore, as mentioned above, the preferred depth of the annular groove is 0.1 to 2 mm. If the width of the annular groove is less than 2 mm, it will quickly lose its function as a communication groove after the mold is closed, and the occurrence of bare air will not be reduced. If it is wider than 20 mm, the triangular cross section of the annular groove will become too flat, and There is a risk that residual air will not collect at the bottom of the groove, resulting in bare air. [Example] In a vulcanization mold for a tire with a tire size of 185/70R 14, an annular mold having the cross-sectional shape shown in FIG. 4 and the groove depth and groove width shown in Table 1 along the maximum cross-sectional width position was used. A tire was vulcanized using a mold of the present invention having a groove and vent holes provided at four locations at the bottom of the annular groove. Table 1 shows the bare occurrence rate when molding was repeated using each mold. Further, as a comparative example, Table 1 shows the bare occurrence rate when tires of the same size were molded using a mold shown in FIG. 5 without an annular groove.

[Table] [Effects of the Invention] According to the mold for tire vulcanization molding of the present invention, there is less bare formation in the side portion of the tire during vulcanization molding, and
In addition, the cut marks of the whisker-like spills caused by the vent holes are not noticeable, and the side part is composed of different surfaces, a conical surface and a rotating convex curved surface, with the annular protrusion formed on the side wall as a boundary, resulting in an excellent design effect. Tires can be manufactured.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of the upper half of the tire vulcanization mold of the present invention. Fig. 2 is a sectional view of the right half of a tire manufactured using a conventional mold, Fig. 3 is a sectional view of the right half of a tire having a conical surface on the tire side, and Fig. 4 is a vulcanized tire of the present invention. FIG. 5 is a partially enlarged sectional view of an example of a molding die. FIG. 5 is a partially enlarged sectional view of a conventional tire vulcanization mold. 1... Tire side part, 2... Conical surface, 3...
Middle region, 4, 5...End region, 6...Side wall, 7...Mold, 8...Tire, 9...Carcass, 10...Shoulder part 11...Bead part, 1
2...Maximum section width position, 13...Side outer part,
14... Side inner part, 15... Annular groove, 16...
...Side surface, 17... Extension surface, 18... Groove bottom, 19...
...Vent hole, 20...Side wall.

Claims (1)

[Scope of Claims] 1. Of the inner surface of the tire vulcanization mold, the outer side portion corresponding to the range from the shoulder portion of the tire to the maximum cross-sectional width position of the tire is a conical surface coaxial with the tire center axis. The side inner part corresponding to the range from the maximum cross-sectional width position of the adjacent tire to the bead part is composed of a curved surface obtained by rotating a straight line or a concave curve about the tire center axis, and A tire vulcanization mold characterized in that an annular groove having a triangular cross section is provided along a boundary line between an outer side portion and an inner side portion corresponding to the maximum cross-sectional width position of the tire. 2 The width of the annular groove is 2 to 20 mm, and the depth is 0.1 to 2 mm.
A tire molding mold according to claim 1. 3 The width of the annular groove is 5 to 15 mm, and the depth is 0.3 to 1 mm.
A tire vulcanization mold according to claim 2. 4. The tire vulcanization mold according to claim 1, wherein the inner side portion is constituted by a concave curved rotating surface. 5. The tire vulcanization mold according to claim 1, wherein one side surface of the annular groove is formed by an extension of a conical surface constituting the outer part of the tire. 6. The tire vulcanization mold according to claim 1, wherein an appropriate number of exhaust holes are provided that communicate from the bottom of the annular groove to the outside of the mold.