JP2016112865A - Mold for tire vulcanization - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire manufacturing method to uniformize contact pressure between a side mold and a segment during vulcanization and to improve the durability of the segment.SOLUTION: Vulcanization molding of a tire is performed in a mold-closed state in which a first abutting portion of the radially outer end of a side mold 2 and a second abutting portion of the radially inner end of a segment 3 are abutted each other. The first abutting portion includes a first abutting face 20 forming a cylindrical face concentric with a tire axis, and the second abutting face includes a second abutting face 22 forming a part of the cylindrical face concentric with the tire axis. A radius R1a at a reference temperature on the first abutting face 20 is larger than a radius R2a at the reference temperature on the second abutting face 22.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a tire vulcanization mold with improved segment durability.

  As shown in FIGS. 5A and 5B, a tire vulcanization mold a includes a pair of side molds b for forming sidewalls arranged on both sides in the tire axial direction, and a plurality of annularly arranged molds. A tread mold c for forming a tread composed of a segment c1. Then, a mold in which the first butting surface sb at the radially outer end of each side mold b and the second butting surfaces sc at both sides in the tire axial direction and the radially inner end of the segment c1 are butted together. In the closed state Y, the tire is vulcanized (see Patent Document 1).

  At this time, as shown in FIG. 6, the conventional first and second butted surfaces sb and sc are formed to have the same diameter at room temperature.

  On the other hand, in the tire vulcanization mold a, since the side mold b is subjected to design processing such as marking, a hard iron-based metal (for example, so as not to be worn out by mold cleaning such as shot blasting) SS400). On the other hand, the segment c1 is formed of a soft aluminum-based metal (for example, AC4) in consideration of workability in a mold manufacturing process such as casting / cutting.

  However, the tire vulcanization mold a is heated to a vulcanization temperature of, for example, 160 to 190 ° C. during vulcanization. Therefore, due to the difference in thermal expansion coefficient between the side mold b (iron-based metal) and the segment c1 (aluminum-based metal), the radii rb and rc of the first and second butted surfaces sb and sc are the same at room temperature. Even at the vulcanization temperature, as exaggeratedly shown in FIG. 7A, the radius rc1 of the second abutting surface sc is larger than the radius rb1 of the first abutting surface sb.

  As a result, as exaggeratedly shown in FIG. 7 (B), in the mold closed state Y at the vulcanization temperature, the first and second butted surfaces sb and sc are caused by the difference in radius. Contact pressure is uneven. And the problem that the durability of the segment c1 falls, such as the segment c1 deform | transforming from the site | part Q with a high contact pressure arises.

JP2013-144414A

  Therefore, the invention is based on the principle that the radius of the first butted surface at room temperature is larger than the radius of the second butted surface at room temperature, and the contact pressure between the butted surfaces during vulcanization is reduced. It is an object to provide a tire vulcanization mold that can alleviate unevenness and improve the durability of a segment.

The present invention relates to a tread for forming a tread comprising a pair of side molds for forming sidewalls made of iron-based metal and disposed on both sides in the tire axial direction, and a plurality of segments made of aluminum-based metal and arranged in an annular shape. With a mold,
In a closed state of the tire, the first butted portion at the radially outer end of each side mold and the second butted portion at both sides in the tire axial direction and radially inner end of the segment are butted against each other. A tire vulcanization mold for performing vulcanization molding,
The first abutting portion includes a first abutting surface that forms a cylindrical surface concentric with the tire axis, and the second abutting portion forms a part of a cylindrical surface concentric with the tire axis. And having a second abutting surface to be abutted against the first abutting surface,
A radius R1a at a reference temperature Ta, which is normal temperature, of the first abutting surface is larger than a radius R2a at a reference temperature Ta of the second abutting surface.

In the tire vulcanization mold according to the present invention, when the thermal expansion coefficient of the side mold is α1, the thermal expansion coefficient of the segment is α2, and the rising temperature from the reference temperature Ta to the vulcanization temperature Tb is ΔT. ,
The radii R1a and R2a preferably satisfy the following formula (1).
0.998 ≦ {R2a × (1 + α2 × ΔT)} / {R1a × (1 + α1 × ΔT)} ≦ 1.002 (1)

  In the present invention, as described above, the radius of the first butting surface is set larger than the radius of the second butting surface at normal temperature. Therefore, at the vulcanization temperature, it is possible to reduce the radial difference between the first butted surface and the second butted surface.

  This increases the contact area between the first butted surface and the second butted surface at the vulcanization temperature. As a result, nonuniform contact pressure between the first and second butted surfaces can be alleviated, and the durability of the segment can be improved.

(A), (B) is sectional drawing which shows the operating state of the metal mold | die for tire vulcanization | cure of this invention. It is a perspective view which shows the part. It is a fragmentary perspective view which shows a side mold and a segment notionally. (A) is sectional drawing which shows the butt | matching state of the 1st, 2nd butt | matching surface in reference temperature (normal temperature), (B) is the butt | matching state of the 1st, 2nd butt | matching surface in vulcanization temperature. It is sectional drawing shown. (A), (B) is sectional drawing which shows the conventional metal mold | die for tire vulcanization. It is sectional drawing which shows the conventional butt surface. (A), (B) is sectional drawing which shows the problem by the conventional butt | matching surface.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, a tire vulcanization mold 1 according to this embodiment includes a pair of side molds 2 for forming sidewalls disposed on both sides in the tire axial direction, and a plurality (n) of annularly disposed side molds. And a tread mold 4 for forming a tread composed of the segments 3.

  In the tire vulcanizing mold 1, the first butted portions 5 at the radially outer ends of the side molds 2, and the second butted portions at both sides in the tire axial direction and radially inner ends of the segments 3. The tire T is vulcanized and molded in the mold closed state Y where the tires 6 and 6 are butted together.

  The side mold 2 includes a sidewall molding surface 2S that molds the sidewall of the tire T, and the tread mold 4 includes a tread molding surface 4S that molds the tread of the tire T. As in the prior art, the side mold 2 is formed from an iron-based metal, and the tread mold 4 is formed from an aluminum-based metal. Examples of the iron-based metal include pure iron, steel, and stainless steel. Examples of the aluminum-based metal include pure aluminum and aluminum alloys (for example, Al—Cu alloy, Al—Mn alloy, Al—Mg alloy, Al—Zn alloy, etc.).

  In the figure, reference numeral 10U denotes an upper plate that can be moved up and down to which the upper side mold 2 is mounted. For example, an upper platen plate 11U with a built-in heater, or a lifting platform 12 of a press machine that fixes the upper platen plate 11U. For example, it is supported so as to be movable up and down via known lifting means (not shown) such as a cylinder.

  Reference numeral 10L denotes a lower plate that supports the lower side mold 2, and is attached to the lower platen plate 11L fixed to, for example, a press stand (not shown). Reference numeral 13 denotes a tread sector in which each one segment 3 is exchangeably attached. The tread sector 13 moves inward in the radial direction together with the segment 3 as the annular actuator 14 descends, and the first and second abutting portions 5 and 6 abut against each other to close the mold. Y.

  FIG. 3 is a perspective view showing a part of the side mold 2 and a part of the segment 3, so that the first and second butting portions 5 and 6 are clearly shown. 3 is illustrated with a different viewpoint position. As shown in the figure, the first abutting portion 5 includes a first abutting surface 20 that forms a cylindrical surface concentric with the tire axis. The first butting surface 20 is connected to the sidewall molding surface 2S at the tire axial direction inner edge 20e.

  The second abutting portion 6 includes a second abutting surface 22 that forms a part of a cylindrical surface concentric with the tire axis, and the second abutting surfaces 22 cooperate to form the cylindrical surface. To do. The second butting surface 22 is butted against the first butting surface 20 in the mold closed state Y. The second butting surface 22 is connected to the tread molding surface 4S at the tire axial direction inner edge 22e.

  4A, the radius R1a of the first abutting surface 20 is set to be larger than the radius R2a of the second abutting surface 22 at a reference temperature Ta that is normal temperature. Has been. In addition, 25 degreeC is employ | adopted as reference temperature Ta.

  At the reference temperature Ta (at room temperature), when the first and second butting surfaces 20 and 22 are butted (that is, when the mold is in the closed state Y), as shown in FIG. Since> R2a, the contact pressure on both ends in the circumferential direction of the second butting surface 22 is larger than the contact pressure on the center in the circumferential direction. That is, the contact pressure becomes non-uniform. However, at this stage, since the mold temperature is low and not thermally expanded, the clamping force between the side mold 2 and the segment 3 is small. That is, since the difference in contact pressure itself is small, the durability of the segment 3 is maintained. In the mold closed state Y at the reference temperature Ta, a gap G1 that assumes thermal expansion is formed in advance between the circumferential end surfaces of the segments 3 adjacent in the circumferential direction.

  On the other hand, as exaggeratedly shown in FIG. 4B, at the vulcanization temperature Tb, the side mold 2 and the segment 3 greatly expand. At this time, due to the difference in coefficient of thermal expansion between the side mold 2 (iron-based metal) and the segment 3 (aluminum-based metal), the increase rate Δr2 of the radius of the second butting surface 22 is the first butting surface It becomes larger than the increase rate amount Δr1 of the radius of 20. Therefore, as described above, by setting R1a> R2a, the difference | R2b−R1b | between the radius R2b of the second butted surface 22 and the radius R1b of the first butted surface 20 at the vulcanization temperature Tb is set. It becomes possible to reduce.

  Thereby, the contact area of the 1st butt | matching surface 20 and the 2nd butt | matching surface 22 increases at the vulcanization temperature Tb. As a result, nonuniform contact pressure between the first and second butting surfaces 20 and 22 can be alleviated, and the durability of the segment can be improved.

Here, in order to exhibit the effect of improving the durability of the segment 3 highly, it is preferable that the radii R1a and R2a satisfy the following formula (1). In the formula (1), α1 represents the thermal expansion coefficient of the side mold 2, α2 represents the thermal expansion coefficient of the segment 3, and ΔT represents the temperature rise from the reference temperature Ta to the vulcanization temperature Tb.
0.998 ≦ {R2a × (1 + α2 × ΔT)} / {R1a × (1 + α1 × ΔT)} ≦ 1.002 (1)

  {R2a × (1 + α2 × ΔT)} in the equation corresponds to the radius R2b of the second butting surface 22 at the vulcanization temperature Tb. {R1a × (1 + α1 × ΔT)} corresponds to the radius R1b of the first butt surface 10 at the vulcanization temperature Tb. Therefore, according to the equation (1), the difference | R2b−R1b | between the radius R2b of the second butting surface 22 and the radius R1b of the first butting surface 20 at the vulcanization temperature Tb can be made close to zero. it can. When {R2a × (1 + α2 × ΔT)} / {R1a × (1 + α1 × ΔT)} is less than 0.998 or greater than 1.002, the difference | R2b−R1b | It is difficult to achieve a high improvement effect. In addition, 160 degreeC is employ | adopted as raise temperature (DELTA) T.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

A tire vulcanization mold having the structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1 and tested for durability in the segments. The mold is a tire size of a tire for a passenger car having a tire size of 195 / 65R15, and each mold is different only in the radius of the abutting surface, and the other specifications are substantially the same. In Table 1,
F = {R2a × (1 + α2 × ΔT)} / {R1a × (1 + α1 × ΔT)}
The value of F is changed.

The side mold is made of iron-based metal (SS400), its thermal expansion coefficient α1 is 1.15 × 10 ⁻⁵ (unit / K), the segment is made of aluminum-based metal (AC4), and its thermal expansion coefficient α2 is 2. 24 × 10 ⁻⁵ (unit / K). In each mold, the radius R1a at the reference temperature Ta of the first abutting surface is the same at 298 mm, and by changing only the radius R2a of the second abutting surface, the value of F in the following equation (2) Are different. The reference temperature Ta is 25 ° C., and the vulcanization temperature Tb is 185 ° C. (that is, the rising temperature ΔT = 160 ° C.).

  Durability was determined by measuring the shape of the butt surfaces of the segments each time 1000 tires were vulcanized in each mold and comparing with the CAD three-dimensional model. And about each segment, the location where the deformation | transformation (displacement amount) of the butt | matching surface was the largest was measured, and it evaluated by the average value of the deformation | transformation. Smaller numbers result in less deformation and better segment durability.

1 Tire vulcanization mold 2 Side mold 3 Segment 4 Tread mold 5 First butting section 6 Second butting section 20 First butting surface 22 Second butting surface Y Mold closed state

Claims (2)

A pair of side molds for forming sidewalls made of an iron-based metal and disposed on both sides in the tire axial direction, and a tread mold for forming a tread made of an aluminum-based metal and having a plurality of segments arranged in an annular shape. ,
In a closed state of the tire, the first butted portion at the radially outer end of each side mold and the second butted portion at both sides in the tire axial direction and radially inner end of the segment are butted against each other. A tire vulcanization mold for performing vulcanization molding,
The first abutting portion includes a first abutting surface that forms a cylindrical surface concentric with the tire axis, and the second abutting portion forms a part of a cylindrical surface concentric with the tire axis. And having a second abutting surface to be abutted against the first abutting surface,
A tire vulcanization mold, wherein a radius R1a at a reference temperature Ta, which is normal temperature, of the first butted surface is larger than a radius R2a at a reference temperature Ta of the second butted surface. When the thermal expansion coefficient of the side mold is α1, the thermal expansion coefficient of the segment is α2, and the rising temperature from the reference temperature Ta to the vulcanization temperature Tb is ΔT, the radii R1a and R2a are expressed by the following formula (1): The tire vulcanization mold according to claim 1, wherein:
0.998 ≦ {R2a × (1 + α2 × ΔT)} / {R1a × (1 + α1 × ΔT)} ≦ 1.002 (1)

Images