JPH0455086B2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The technical content described in this specification in connection with the advantageous production of pneumatic tires, especially extra-large heavy-duty tires as a representative example of so-called OR tires, is as follows:
The object of the present invention is to propose the development results of advantageously and easily obtaining different pattern treads using the same mold by adding ingenuity to the application of the mold in the vulcanization molding process of the tire.

(Problem) Among the heavy-duty tires mentioned above, ultra-large tires that are used as self-propelled wheels for civil engineering and construction machinery, in other words, OR tires, are also used for heavy-duty buses and trucks. Since the production volume is much smaller than the TB tires used, it is economically difficult to provide detailed support to meet the various requirements for performance and uses, and it is difficult to provide uniformity. Needless to say, they were produced with a small variety of tread patterns, which often resulted in unsatisfactory performance requirements.

(Prior Art and Disadvantages) Conventionally, tire molds generally correspond to one type of tire size and tread pattern to be made, and at most only a trivial selection such as the necessity or change of the size can be made. However, the molds for ultra-large tires such as OR tires can cost tens of millions of yen per unit, so in order to meet the different performance requirements for such tires in a wide variety of uses, a wide variety of products are being manufactured. Preparing a tread pattern requires a very large amount of expense.

(Objective of the invention) To adapt a mold used for vulcanization molding of pneumatic tires with a highly versatile tread pattern to various uses by making it possible to effectively and appropriately change the tread pattern. It is an object of the present invention to provide a method for vulcanization and molding of a pneumatic tire, which satisfies the required performance without requiring excessive investment.

(Structure of the Invention) According to the present invention, the above object is advantageously achieved by a procedure mainly based on the matters described below.

That is, in the vulcanization molding of a pneumatic tire, this invention uses a pair of molds that are separated by a dividing surface that joins in a plane perpendicular to the center of rotation of the tire, and that form a pair of molds. By making it possible to perform vulcanization molding by shifting one mold in the circumferential direction from one mold-matching joint position to another mold-matching joint position, it is possible to create different tread patterns with one set of molds. A method for vulcanization and molding of a pneumatic tire, characterized in that it is applied to a pneumatic tire.

In this embodiment, one of the bonding positions participates in the formation of a tread pattern having horizontal grooves in a direction that intersects a plane including the dividing plane of the mold and a land portion divided by the horizontal grooves. The lateral groove and the land portion shall have widths corresponding to 3 to 20% and 15 to 35% of the tread width, respectively, on the central circumference of the tread, and the mutual separation of the joint positions shall be greater than the width of the lateral groove. The width of the land portion shall be larger than the width of the land portion, and the land portion shall have an arcuate profile that smoothly connects the groove wall with the plane near the intersection area of the groove wall of the lateral groove with the plane including the dividing surface. The radius of curvature of the arc-shaped profile is equivalent to 10% or more of the width of the lateral groove. A minute ridge with an arcuate profile that smoothly connects the groove bottom with the flat surface is provided in the vicinity, the radius of curvature of the arcuate profile is equal to or more than 10% of the groove depth, and a tread pattern. Preferably, the tread has a lug-type pattern separated by transverse grooves extending connecting both ends of the tread.

Now, regarding vulcanization molding of pneumatic tires, a pair of molds that are separated by a splitting surface that joins on a plane perpendicular to the rotational axis of the tire and form a pair is generally called a full mold. It is distinguished from a split mold, which uses a combination of multiple segments divided at intervals along the outer periphery.

As shown in Fig. 1, an example of a full mold is a mold half that uses the central circumferential surface P of a normal tire as a dividing surface S, and forms a molding cavity C in the internal cavity by joining at this surface S. A pair of U and L,
Consisting of a bead-shaped ring M and a bladder B that fit on their respective inner peripheries, the cavity C in this example has a deep recess R for forming lugs cut into the mold inner surface F forming the bottom of the transverse groove. In the figure, H and H' are positioning holes, and T is a positioning tenon.

The projection of the inner surface F of the mold at one joining position shown in FIG. 1 is shown in FIG. A similar projection at the joint location is shown.

This selection is different from tires with lug-type patterns in which the lateral grooves run in a series across both tread ends of the tire to separate the lugs, and the lateral grooves end at the center circumference of the tire. It is clear that other types of tires with different lug type patterns may be obtained.

These lateral grooves and the lugs, or land areas in this example, that are divided by them have a width of 3 to 20% and 15 to 15 _% , respectively, of the tread width Wt of the tire to be manufactured.
At 35%, the former is smaller than the latter in width W _g ,
It is preferable to set the width to W _l , and the widths W _g and W _l are both based on the value on the center circumferential surface of the tire.

In the staggered arrangement of the lateral grooves on the left and right sides of the tire as shown in FIG. It intersects with the center end wall at an angle close to 90°, which may result in stress concentration at the inner corner of the lateral groove of the product tire.

Regarding these points, first, in the vicinity of the intersection area of the land portion of the product tire with the plane containing the dividing plane S of the groove wall of the lateral groove, a bulge having an arcuate profile that smoothly connects the groove wall with the plane. Chamfers ch ₁ and ch ₂ forming protrusions are provided in the cavity C. Radius of curvature of the arcuate contour of Qianhua ch ₁ , ch ₂ r ₁ , r ₂
is preferably about 10% or more of the standard width W _g of the lateral groove on the tire center circumferential surface. On the other hand, in the vicinity of the intersection area of the groove bottom of the lateral groove with the plane containing the dividing surface S, a channel ch ₃ is formed in the cavity C so as to form a minute bulge having an arcuate profile that smoothly connects the groove bottom with the plane. Provided for. Radius of curvature of the arcuate profile of Qianhua ch ₃ r ₃
(See Figure 1) should be about 10% or more of the standard groove depth D planned on the tire center circumferential surface, but as shown in Figure 1, if the bottom is raised in this area,
It is even better if a shallow recess h forming a so-called platform is formed on the inner surface of the cavity C.

That is, in this way, the lateral groove of the product tire formed at the joining position of the mold halves U and L shown in FIG. Since they are connected through rounded corners, stress concentration, which is a concern with sharp corners, is eliminated, and in the molded product at the joining position shown in Figure 2 a, minute knife edges are formed on the groove bottom and groove wall. It does not cause any particular trouble.

The above has mainly described the application of the present invention to a lug type pattern, but for a block type pattern tire as shown in FIG. At the setting position of the mold that separates the circumferential interval of
In other settings of the mold, such as in the alternating herringbone arrangement of seeds B'', B, and also in other positions of the mold separated by 1/4 circumferential intervals, such as the center rib J, as shown in Fig. 3c. In the last-mentioned center rib side block composite pattern, the end of the horizontal groove cut into the center rib J has a similar bulge as shown in FIGS. 1 and 2. It is desirable to apply protrusions and protrusions.

The present invention is applicable not only to the lug or block type pattern described above, but also to the rib-lug type as shown in FIG. 4 or the rib-type tread pattern as shown in FIG. It can also be used to change the zigzag arrangement of ribs J′, J″. In this case, changing the arrangement will affect uneven wear, so the appearance suitability judgment at the examination stage to determine the commercial pattern should be used to reduce uneven wear. The application of the present invention is also advantageous when it is carried out in accordance with the schedule.

In this invention, the distance between the set positions of the mold is defined as x mm, depending on the value of x.
Different patterns as mentioned earlier can be easily obtained using the same mold, but where p is the pitch length of the array lag or block, and n is an integer, the above mutual spacing becomes X + np (mm). , it is natural that the same pattern appears again, and this invention is not limited to production tires, but is useful for grasping the degree of reduction in uneven wear caused by changing the setting position at the stage of consideration. It also provides significant benefits when applied to the production of test tires.

Now, according to Figures 1 and 2, size 14.00R25
An example of applying this invention to an OR tire will be explained.

In this case, the tread width W _t is 320 mm, the groove width W _g of the horizontal groove is the standard value on the center circumferential surface of 40 mm, and the lug width W _l is also 100 mm, so they are approximately 13% and 31% of the tread width, respectively. Similarly, the groove depth D is assumed to be 40 mm, and the height of the platform spread over a width of 40 mm on the central peripheral surface is assumed to be 25 mm, and the radii of curvature r ₁ , r ₂ and further r ₃
Both patterns are 5 mm, and the distance along the circumference at each setting position is 60 mm. Pattern A is a series of horizontal grooves (Fig. 2a), and pattern A is an alternate horizontal groove type in which the horizontal grooves end at the center circumference (Fig. 2a). A pattern B shown in FIG. 2b) was formed.

In comparing both patterns, both patterns are suitable for OR tires, especially for rough roads.Pattern A is a so-called traction pattern with excellent traction performance, and C is suitable for muddy terrain, especially in areas with many ups and downs (slopes). Pattern B is far less slippery than Pattern B. In a so-called rock pattern,
In addition to being excellent in cut resistance and abrasion resistance, a. It was observed that there was less lug chipping and wear, especially uneven wear, which tend to occur with pattern A on hard roads and with lots of stones.

Next, for size 33.25R35R33, a in Figure 3
→ b Also, by selecting each pattern shown in a → c, basically the required performance for rough roads is almost satisfied, and b
It was found that the c-type has stronger traction, and the c-type is more suitable for hard road surfaces that are closer to good roads than the a and b types, and has excellent vibration resistance and wear resistance.

(Effects of the Invention) According to the present invention, when changing or adjusting the basic shape of a tread pattern, it is not necessary to make a new mold, and when joining a set of molds at the dividing plane, two or more molds are simply aligned at a distance from each other. Vulcanization molding can be easily performed in irregular patterns that are different from the basic shape by selecting the joining position, which reduces mold costs and significantly reduces the number of replacement man-hours required for attaching and detaching the mold. Due to the wide use of small molds, storage space costs can also be expected to be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the mold, FIGS. 2 a and b are internal views of the mold at respective joining positions of different cavities, and FIGS. 3 a, b, and c are procedures for changing the tread pattern for another embodiment. Fig. 4 and Fig. 5 are also front views of similar different examples. P...Central peripheral surface, U, V...a set of molds,
S...Dividing surface, H...Selection hole for joining position, T...
Tenon.

Claims (1)

[Scope of Claims] 1. In vulcanization molding of pneumatic tires, a pair of molds is used, which are separated by a dividing surface that joins in a plane orthogonal to the rotation center of the tire, and are paired with each other. By making it possible to carry out vulcanization molding in which one of the two molds is shifted circumferentially from one mold joining position to the other mold and moved to another mold joining position, different training can be performed with one set of molds. A method for vulcanizing and molding a pneumatic tire, characterized by imparting a pneumatic tire with a dot pattern. 2. Claim 1, wherein one of the bonding positions participates in the formation of a tread pattern having horizontal grooves in a direction intersecting a plane including the dividing plane of the mold, and a land portion divided by the horizontal grooves. The method described in section. 3. Claim 2, wherein the lateral groove and the land portion have widths corresponding to 3 to 20% and 15 to 35% of the tread width, respectively, on the central circumference of the tread.
The method described in section. 4. Claims in which the distance measured on the central circumference of the tread between one mold-matching joint position and another mold-matching joint position is greater than the width of the transverse groove and smaller than the width of the land portion. The method according to paragraph 2 or 3. 5. Claim No. 5, wherein the land portion is provided with a minute bulge having an arcuate profile that smoothly connects the groove wall with the plane in the vicinity of the intersection area of the groove wall of the horizontal groove with the plane including the dividing surface. The method described in Section 4. 6 The radius of curvature of the arcuate profile is 10 relative to the width of the horizontal groove.
% or more, the method according to claim 5. 7. Claims 4 to 7, wherein the lateral groove has a minute protuberance with an arcuate profile that smoothly connects the groove bottom with the plane including the dividing plane near the intersection of the groove bottom with the plane including the dividing plane. The method described in any one of Item 6. 8. The method according to claim 7, wherein the radius of curvature of the arcuate profile corresponds to 10% or more of the groove depth. 9. The method according to claim 2, wherein the tread pattern is a lug type pattern separated by transverse grooves extending connecting both ends of the tread.