JP7363363B2 - Tire vulcanization mold and tire manufacturing method - Google Patents

Description

The present invention relates to a tire vulcanization mold and a tire manufacturing method that can shorten tire vulcanization time.

Generally, for tire vulcanization, a vulcanization device is used that includes a vulcanization mold having a cavity for molding the tire, and a bladder that presses the green tire into the cavity, and the green tire is supplied from the vulcanization mold. The heat heats up the green tire. However, as is well known, the thickness of a tire varies depending on the tread, sidewall, bead, and other parts. Therefore, there is a problem in that a long heating time is required especially in the tread portion where the thickness is large, and the heating time for the entire tire becomes long. This problem occurs more noticeably in tires for heavy loads such as those for trucks and buses.

Therefore, in recent years, in order to reduce the heating time of the tread part a, it has been proposed to make a heat conductive pin element c protrude from the tread molding surface bs of the tread mold b, as schematically shown in FIG. (See Reference 1).

The heat conductive pin element c is inserted into the land portion (block, rib, etc.) of the tread portion a during vulcanization, and transmits heat from the tread mold b into the land portion. That is, the tread part a can be heated from the inside, and the heating time of the tread part a can be reduced, thereby making it possible to shorten the heating time of the tire as a whole.

Special Publication No. 2010-516099

However, in the above proposal, the heat-conducting pin element c is provided in the tread mold b. This tread mold b is divided into a plurality of segments d in the tire circumferential direction by a split surface s, and each segment d moves in and out in the tire radial direction when the mold is opened and closed.

Here, the heat conductive pin element c protrudes in the tire radial direction toward the tire axis i. Therefore, in the heat conduction pin element c disposed on the split surface s side, an angular difference θ occurs between its protrusion direction and the movement direction f of the segment d. When the mold is opened, a bending moment acts on the heat conduction pin element c due to this angular difference θ, causing breakage and bending deformation. If bending or bending deformation occurs, much time and labor will be required to replace the heat conduction pin element c, and production efficiency will be significantly reduced.

The present invention provides a tire vulcanization mold and a tire manufacturing method that can reduce the heating time of the tread portion and the heating time of the entire tire without causing bending or bending deformation of the heat conductive pin elements. This is the issue.

The present invention provides a tire vulcanized mold comprising: an annular tread mold having a tread molding surface for molding the outer surface of the tread portion of the tire; and a side mold having a side molding surface molding the outer surface of the sidewall portion of the tire. It is a type,
The side mold includes a heat transfer protrusion that protrudes from the side molding surface in the tire axial direction and extends into the tread portion.

In the tire vulcanization mold according to the present invention, the position where the tread molding surface and the side molding surface intersect is such that the distance in the tire radial direction from the rim baseline is from the rim baseline to the tread molding surface. It is preferable that the maximum height in the radial direction of the tire is 90% or more.

In the tire vulcanization mold according to the present invention, it is preferable that the dividing position is located at a tread end forming part that forms a tread end of the tire.

In the tire vulcanization mold according to the present invention, the heat transfer projection preferably has a pin shape.

In the tire vulcanization mold according to the present invention, the outer surface of the tread portion includes shoulder ribs extending in the tire circumferential direction, and the tread forming surface includes a shoulder rib forming portion for forming the shoulder ribs. Preferably, the height of the heat transfer protrusion in the tire axial direction from the side molding surface is 15% or more of the tire axial width Ws of the shoulder rib molding part.

In the tire vulcanization mold according to the present invention, the heat transfer projections are preferably arranged at equal intervals in the tire circumferential direction.

The present invention is a tire manufacturing method, and includes a step of vulcanizing a green tire using the tire vulcanization mold.

As described above, the present invention provides the side molding surface of the side mold with heat transfer protrusions that protrude in the tire axial direction and extend into the inside of the tread portion.

The heat transfer projections transfer heat from the side mold to the inside of the tread portion during vulcanization. Therefore, the vulcanization of the tread portion can be accelerated, and the heating time of the tire as a whole can be shortened.

Furthermore, the side mold moves in the tire axial direction when the mold is opened and closed. Therefore, the protruding direction of the heat transfer protrusions is the same as the moving direction of the side mold, and it is possible to suppress bending or bending deformation of the heat transfer protrusions when opening the mold.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial perspective view showing an embodiment of a tire formed using a tire vulcanization mold of the present invention. FIG. 2 is a cross-sectional view showing a tire vulcanization mold. FIG. 3 is a partial cross-sectional view showing the main parts of the vulcanization mold. (a) to (c) are conceptual diagrams illustrating a tread end portion and a tread end forming portion of a tire. (a) and (b) are a partial perspective view of a tire showing another example of a vulcanization mold, and a partial sectional view of the vulcanization mold. It is a partial sectional view showing an example of a vulcanization mold explaining background art.

Embodiments of the present invention will be described in detail below. FIG. 1 is a partial perspective view showing an embodiment of a tire T formed using a tire vulcanization mold 1 of the present invention.

As shown in FIG. 1, the tire T of this embodiment is a tire for heavy loads such as trucks and buses, and includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of a bead portion 4. , and a belt layer 7 arranged inside the tread portion 2 and outside the carcass 6 in the tire radial direction.

The carcass 6 is formed from one or more carcass plies 6A, in this example one carcass ply 6A, in which carcass cords are arranged at an angle of, for example, 70° to 90° with respect to the tire circumferential direction. This carcass 6 includes folded parts 6b that are folded back from the inside to the outside in the tire axial direction around the bead cores 5 at both ends of a toroidal main body part 6a spanning between the bead cores 5.

Further, bead apex rubber 8 extending outward in the tire radial direction from the bead core 5 is disposed between the main body portion 6a and the folded portion 6b, thereby reinforcing the bead portion 4.

The belt layer 7 is formed from a plurality of belt plies using belt cords. In this example, a case is shown in which the belt layer 7 is formed from first to fourth belt plies 7A to 7D arranged in order from the carcass 6 side toward the outside in the tire radial direction. The second belt ply 7B is the widest among the belt plies.

Although not limited to this, the angle α1 (not shown) of the belt cord of the first belt ply 7A with respect to the tire circumferential direction is, for example, 45 to 75 degrees. Further, the angle α2 (not shown) of the belt cord of the second to fourth belt plies 7B to 7D with respect to the tire circumferential direction is, for example, 10 to 35°. The second belt ply 7B and the third belt ply 7C have different inclination directions of the belt cords. As a result, the belt cords cross each other between the belt plies 7B and 7C, and the belt rigidity is increased.

A belt cushion rubber 10 having a triangular cross section is arranged between the outer end of the belt layer 7 in the tire axial direction and the carcass 6. The belt cushion rubber 10 is made of low elasticity rubber and relieves stress concentration at the outer end of the belt layer 7.

Various tread patterns consisting of tread grooves 11 are formed in the tread portion 2 . In this example, a plurality of (for example, three) circumferential grooves 11A extending in the tire circumferential direction are formed as the tread grooves 11, and thereby ribs made of a plurality of (for example, four) ribs 12 extending in the tire circumferential direction are formed. A pattern is formed. In this example, the circumferential groove 11A includes a shoulder circumferential groove 11As disposed on the outermost side in the axial direction of the tire, and the rib 12 includes a shoulder rib 12s disposed on the outermost side in the axial direction of the tire. . Further, small holes 27 are formed in the outer surface of the tread portion 2, which are the remains of heat transfer projections 25, which will be described later.

As shown in FIG. 2, the vulcanization mold 1 includes an annular tread mold 20 and side molds 21 arranged on both sides in the tire axial direction.

The tread mold 20 has a tread forming surface 20S that forms the outer surface 2S of the tread portion 2 of the tire T. The outer surface 2S of the tread portion 2 includes a tread surface 2Sa having a convex arc shape extending between the tread ends Te. Groove forming convex portions 22 for forming tread grooves 11 are provided in a protruding manner on this tread forming surface 20S. The groove forming convex portion 22 includes a shoulder groove forming convex portion 22s for forming the shoulder circumferential groove 11As, and a shoulder rib 12s is provided between the shoulder groove forming convex portion 22s and the tread end molding portion 26. A shoulder rib molding portion 13 for molding is formed.

The tread mold 20 is divided into a plurality of segments 23 in the tire circumferential direction. Each segment 23 is supported so as to be movable in and out of the tire radial direction Fx between a mold closed state Y1 and a mold open state (not shown).

The side mold 21 has a side molding surface 21S that molds the outer surface 3S of the sidewall portion 3 of the tire T. This side mold 21 is supported so as to be movable in and out in the tire axial direction Fy between a mold closed state Y1 and a mold open state (not shown).

As shown in FIGS. 2 and 3, the side mold 21 is provided with a heat transfer protrusion 25 that protrudes from the side molding surface 21S in the tire axial direction and extends into the inside of the tread portion 2.

The heat transfer projections 25 transfer heat from the side mold 21 to the inside of the tread portion 2 during vulcanization. This makes it possible to speed up the vulcanization of the tread portion 2 and shorten the heating time of the tire as a whole.

It is preferable that the heat transfer protrusions 25 are formed on the outer side of the tire radial direction than the second belt ply 7B in the belt layer 7, but on the inner side of the tire radial direction than the second belt ply 7B. It may be arranged.

Various metal materials, such as aluminum alloy, steel, and SUS, can be used for the heat transfer protrusion 25 from the viewpoint of excellent heat conduction. Further, as the heat transfer projection 25, a pin-shaped body 25A parallel to the tire axis or a plate-shaped body is suitable. In particular, the pin-shaped body 25A is more suitable from the viewpoint of strength.

If the protrusion height L of the heat transfer protrusion 25 from the side molding surface 21S in the tire axial direction is too small, the effect of promoting vulcanization of the tread portion 2 will be insufficient. On the other hand, if the protrusion height L is too large, the strength of the heat transfer protrusion 25 itself and the strength of the vulcanized tire T will tend to be reduced. Therefore, the lower limit of the protrusion height L is preferably 15% or more, more preferably 30% or more of the tire axial width Ws (shown in FIG. 2) of the shoulder rib molded portion 13. Further, the upper limit is preferably 40% or less.

When the heat transfer protrusion 25 is a pin-shaped body 25A, its thickness is preferably φ2 to 5 mm from the viewpoint of the strength of the heat transfer protrusion 25 itself and the strength of the vulcanized tire T.

It is preferable for such heat transfer projections 25 to be arranged at equal intervals in the tire circumferential direction in order to uniformly perform vulcanization. The interval between the heat transfer protrusions 25 is preferably 15 to 20 degrees in terms of the central angle around the tire axis i.

Here, in order to insert the heat transfer protrusion 25 into the tread portion 2, the split position P where the tread molding surface 20S and the side molding surface 21S intersect must be set at the tire radius compared to the conventional vulcanization mold. It is preferable to move it to the outside of the direction. Specifically, the distance Hp of the split position P from the rim baseline BL in the tire radial direction is 90% or more of the maximum height H0 in the tire radial direction from the rim baseline BL to the tread forming surface 20S. preferable. When the distance Hp is less than 90% of the maximum height H0, the position of the heat transfer protrusion 25 also becomes lower, making it difficult to supply heat to the portion where vulcanization is slowest.

In particular, it is preferable that the split position P be located at the tread end forming part 26 that forms the tread end Te of the tire T.

The tread end Te is defined as follows. As shown in FIG. 4A, in the case of a square shoulder where the tread surface 2Sa and the outer surface 3S of the sidewall portion 3 directly intersect, the intersection Q is defined as the tread end Te. As shown in FIG. 4(b), in the case of a tapered shoulder in which the tread surface 2Sa and the outer surface 3S of the sidewall portion 3 are connected via a slope 30, the slope 30 (including both ends of the slope 30). is defined as the tread end Te. As shown in FIG. 4(c), in the case of a so-called round shoulder in which the tread surface 2Sa and the outer surface 3S of the sidewall portion 3 are smoothly connected via the circular arc surface 31, the circular arc surface 31 (the circular arc surface 31 ) is defined as the tread end Te.

In the case of a square shoulder, the tread end forming part 26 is a part that forms the intersection Q, in the case of a tapered shoulder, a part that forms a slope 30, and in the case of a round shoulder, a part that forms an arcuate surface 31. defined.

As shown in FIGS. 2 and 3, when the split position P is located at the tread end molding part 26, when the vulcanization mold 1 is closed, the rubber of the green tire is bitten between the side mold 21 and the segment 23. A new effect can be achieved in that it is possible to suppress the intrusion. In this example, a case is shown in which the dividing surface Ps of the side mold 21 and the segment 23 is inclined outward in the tire radial direction toward the outer side in the tire axial direction. However, the split surface Ps may be parallel to the tire axial direction.

FIG. 5 shows another example of the vulcanization mold 1. In the tread portion 2 of the tire T of this example, a shoulder lateral groove 11B is arranged as the tread groove 11, and extends in the tire axial direction across the tread end Te. In this case, a groove forming convex portion 32 is formed in the vulcanization mold 1 in order to form the shoulder lateral groove 11B. The groove forming convex portion 32 is divided into a main portion 32A on the inner side in the tire axial direction and a sub portion 32B on the outer side in the tire axial direction by a dividing line J extending inward in the tire radial direction from the dividing position P. The main portion 32A is formed on the tread molding surface 20S, and the sub portion 32B is provided on the side molding surface 21S. The heat transfer protrusion 25 is arranged between the groove forming convex portions 32, 32 adjacent to each other in the tire circumferential direction.

Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments, and can be modified and implemented in various ways.

In order to confirm the effects of the present invention, a vulcanization mold having the structure shown in FIGS. 2 and 3 was prototyped based on the specifications shown in Table 1. Heavy-duty tires for trucks and buses (297/75r22.5) having the structure shown in FIG. 1 were molded through a vulcanization process using a prototype vulcanization mold. Then, when the vulcanization process was performed, the presence or absence of bending or bending deformation in the heat transfer projections and the vulcanization time were measured.

In both the comparative example and the example, a pin-shaped body was used as the heat transfer protrusion. The comparative example and the example have substantially the same specifications except for the presence or absence of heat transfer protrusions or the formation position of the heat transfer protrusions. In the example,
Projection height L of heat transfer protrusion: 10 mm (29.5% of Ws)
Thickness of heat transfer protrusion: φ3mm
Spacing (center angle) of the heat transfer protrusions in the tire circumferential direction: 20 degrees.

In the vulcanization time test, we measured the internal temperature of the tread shoulder, where vulcanization takes the slowest time, and conducted a thermotest to evaluate the evolution of the internal temperature over time. The amount of heat supplied (ECU) was determined from the graph of "internal temperature - elapsed time", and the time when the amount of heat supplied (ECU) reached the reference value required for vulcanization was defined as the vulcanization time.

In the example, it can be confirmed that the heating time can be shortened to the same level as Comparative Example 1 while suppressing bending and bending deformation of the heat transfer protrusions.

1 Vulcanization mold 2 Tread portion 2S Outer surface 3 Sidewall portion 3S Outer surface 20 Tread mold 20S Tread molding surface 21 Side mold 21S Side molding surface 25 Heat transfer protrusion 26 Tread end molding portion BL Rim baseline P Split position T Tire Te tread end

Claims (7)

A tire vulcanization mold comprising: an annular tread mold having a tread forming surface for forming an outer surface of a tread portion of the tire; and a side mold having a side forming surface for forming an outer surface of a sidewall portion of the tire. ,
The side mold includes a heat transfer protrusion that protrudes from the side molding surface in the tire axial direction and extends into the tread portion ,
The tire includes a carcass extending from the tread portion through the sidewall portion to a bead core of the bead portion, and a belt layer disposed inside the tread portion and outside the carcass in the tire radial direction,
The belt layer is formed from a plurality of belt plies using belt cords,
The heat transfer protrusion is located inside the widest belt ply in the belt layer in the tire radial direction during tire vulcanization.
Tire vulcanization mold. The position where the tread forming surface and the side forming surface intersect is such that the distance in the tire radial direction from the rim baseline is 90% or more of the maximum height in the tire radial direction from the rim baseline to the tread forming surface. The tire vulcanization mold according to claim 1. 3. The tire vulcanization mold according to claim 2, wherein the dividing position is located at a tread end forming part for forming a tread end of the tire. The tire vulcanization mold according to any one of claims 1 to 3, wherein the heat transfer projection is pin-shaped. The outer surface of the tread portion includes shoulder ribs extending in the tire circumferential direction,
The tread forming surface includes a shoulder rib forming part for forming the shoulder rib,
According to any one of claims 1 to 4, the heat transfer protrusion has a protrusion height in the tire axial direction from the side molding surface that is 15% or more of the tire axial width Ws of the shoulder rib molded part. vulcanization mold for tires. The tire vulcanization mold according to any one of claims 1 to 5, wherein the heat transfer projections are arranged at equal intervals in the tire circumferential direction. A method for manufacturing a tire, comprising the step of vulcanizing a green tire using the vulcanization mold according to any one of claims 1 to 6.

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