JP2023074118A - Mold for tire and tire manufacturing method - Google Patents

Abstract

To provide a mold 2 for a tire with excellent uniformity.SOLUTION: A mold 2 for a tire has a segment and a sector shoe 12. The sector shoe 12 has an inner surface 24, an outer surface 26, and a pair of side faces 28. Each side faces 28 is a circumferentially outwardly convex curved surface. The side face 28 has a shape that is radially outward toward circumferential inner side. The preferred side face 28 has an arc shape in a cross-section perpendicular to an axial direction.SELECTED DRAWING: Figure 4

Description

This specification discloses a mold for use in the tire vulcanization process. Specifically, this specification discloses a mold having multiple segments for the tread.

A so-called split mold is used in the tire vulcanization process. The split mold has a plurality of segments and a plurality of sector shoes. These segments can be arranged in a ring. These segments form the tread of the tire. Each segment is fixed to one sector shoe. An example of a split mold is disclosed in Japanese Patent Application Laid-Open No. 62-102607.

JP-A-62-102607

When the mold is opened, the sector shoes move radially outward. The sector shoe moves radially inward when the mold is closed. Repeated opening and closing of the mold causes repeated movement of the sector shoe. A gap is provided between the sector shoe and the adjacent sector shoe. This gap suppresses collisions with adjacent sector shoes when the sector shoes move. With this mold, the sector shoe is less likely to be damaged due to collision.

As the mold closes, the segments are pushed by the sector shoe. The force from the sector shoe to the segment is radially inward. In the vulcanization process, the bladder pushes the raw cover (uncrosslinked tire), and the raw cover pushes the segments. The force from the raw cover to the segment is radially outward. During the vulcanization process, the segments are subjected to a radially inward force and a radially outward force.

No radially inward force is applied to the segments corresponding to the gaps between the sector shoes. Only radially outward forces are applied to this point. Due to this force, the segment elastically deforms radially outward at this point. The inner diameter of the mold at this point is larger than at other points. In other words, the cross-sectional shape of the mold in the vulcanization process is inferior in roundness.

A tire obtained from a mold with poor roundness has poor uniformity. Large tire noise can occur due to running on tires with poor uniformity. Electric vehicles do not produce engine noise. Engine noise does not occur even in a hybrid vehicle running on battery. Tire noise is noted in the absence of engine noise.

The decrease in roundness is due to elastic deformation of the segments, as described above. Therefore, when the mold is open, the segments are restored. Measuring the elastic deformation of a segment is not easy.

The applicant's intention is to provide a mold for a tire with good uniformity.

This specification discloses a mold for a tire having a tread. The mold includes (1) a plurality of segments that can be arranged in a ring to form a cavity for the tread and (2) one inner peripheral surface, one outer peripheral surface and one outer peripheral surface to which one segment can be attached. Each has a pair of side surfaces and has a plurality of sector shoes arranged along the circumferential direction. Each side surface includes a curved surface that is convex outward in the circumferential direction. This curved surface has a shape directed radially outward and circumferentially inward.

In this tire mold, elastic deformation of the segments is less likely to occur during the vulcanization process. A tire with excellent uniformity can be obtained from this mold.

FIG. 1 is a plan view showing a portion of a tire mold according to one embodiment. FIG. 2 is an enlarged cross-sectional view taken along line II--II of FIG. 3 is a perspective view showing a segment of the mold of FIG. 2; FIG. 4 is a perspective view showing a sector shoe of the mold of FIG. 2; FIG. 5 is a cross-sectional view taken along line VV of FIG. 4. FIG. 6 is an enlarged plan view showing segments and sector shoes of the mold of FIG. 1; FIG. FIG. 7 is an enlarged view of the portion indicated by symbol VII in FIG. FIG. 8 is an enlarged cross-sectional view taken along line VIII--VIII of FIG. 9 is an enlarged cross-sectional view taken along line IX-IX of FIG. 5. FIG. FIG. 10 is an enlarged view of the portion indicated by symbol X in FIG. FIG. 11 is an enlarged cross-sectional view along line XI-XI of FIG. FIG. 12 is a plan view showing segments and sector shoes of a conventional tire mold. FIG. 13 is a graph showing evaluation results of molds according to Examples and Comparative Examples.

Hereinafter, preferred embodiments of the tire mold will be described in detail with reference to the drawings as appropriate.

In figures 1 and 2 a tire mold 2 is shown. In FIG. 2 , the horizontal direction is the radial direction of the mold 2 and the vertical direction is the axial direction of the mold 2 . The mold 2 has a lower plate 4 , an upper plate 6 , a pair of sidewall plates 8 , a plurality of segments 10 , a plurality of sector shoes 12 and a container ring 14 . In FIG. 1, illustration of the upper plate 6 is omitted for the sake of convenience. The lower plate 4 has a ring-like shape. The upper plate 6 has a disk-like shape. Each sidewall plate 8 has a substantially ring-like shape. This mold 2 is a so-called "split mold".

One segment 10 is shown in FIG. The planar shape of this segment 10 is substantially fan-shaped (see also FIG. 1). Segment 10 has a cavity surface 16 and a back surface 18 . The cavity face 16 has a plurality of ridges 20 . This ridge 20 corresponds to the groove of the tread of the tire. The ridges 20 form a tread pattern on the tire. In FIG. 2, illustration of the ridge 20 is omitted. Back surface 18 has protrusions 21 . In FIG. 1, a plurality of segments 10 are arranged in a ring. These segments 10 form a cavity. The number of segments 10 is usually 3 or more and 20 or less. In this embodiment, the number of segments 10 is nine.

One sector shoe 12 is shown in FIGS. The sector shoe 12 has a top surface 22 , a bottom surface 23 , an inner peripheral surface 24 , an outer peripheral surface 26 and a pair of side surfaces 28 . In FIG. 1, a plurality of sector shoes 12 are arranged along the circumferential direction. The number of sector shoes 12 matches the number of segments 10 . Therefore, the number of sector shoes 12 is usually 3 or more and 20 or less. In this embodiment, the number of sector shoes 12 is nine.

The inner peripheral surface 24 has a recess 30 . The outer peripheral surface 26 is inclined with respect to the axial direction. The outer peripheral surface 26 has a shape that extends radially outward toward the bottom. As shown in FIGS. 2 and 4, outer peripheral surface 26 has grooves 32 . As is clear from FIG. 4, this groove 32 has an undercut shape.

As is clear from FIG. 2, the rear surface 18 of the segment 10 abuts against the inner peripheral surface 24 of the sector shoe 12 . The recess 30 of the sector shoe 12 is fitted with the protrusion 21 of the segment 10 . Segment 10 is fixed to sector shoe 12 . Fixation is achieved by means not shown, such as bolts.

6 is an enlarged plan view showing the segment 10 and the sector shoe 12 of the mold 2 of FIG. 1. FIG. FIG. 7 is an enlarged view of the portion indicated by symbol VII in FIG. As shown in these figures, each side surface 28 is curved. This side surface 28 has a shape that protrudes outward in the circumferential direction. A two-dot chain line S1 in FIGS. 6 and 7 represents the radial direction. The distance between the two-dot chain line S1 and the side surface 28 gradually increases radially outward. In other words, the side surface 28 has a shape that faces radially outward and circumferentially inward. Therefore, as shown in FIG. 7, a portion of the segment 10 (the portion indicated by symbol A) can be visually recognized in plan view.

In this embodiment, the side surface 28 has an arcuate shape in a cross section perpendicular to the axial direction. Sides 28 may have shapes other than arcs. In this embodiment, as described above, the entire side surface 28 is a curved surface. Therefore, this curved surface extends from the inner peripheral surface 24 to the outer peripheral surface 26 . This curved surface has a boundary with the inner peripheral surface 24 .

A portion of the side surface 28 may be curved. In this case, the portion of the side surface 28 other than the curved surface is flat or otherwise curved.

FIG. 8 is an enlarged cross-sectional view taken along line VIII--VIII of FIG. FIG. 8 shows a sector shoe 12a and another adjacent sector shoe 12b. The side surface 28 of the sector shoe 12a and the side surface 28 of the sector shoe 12b are in contact with each other. The contact point P1 coincides with the position of the inner peripheral surface 24 . In other words, the distance between the side surfaces 28 is approximately zero at the inner peripheral surface 24 . No gap exists between the sector shoes 12 on the inner peripheral surface 24 . The distance between the side surfaces 28 gradually increases radially outward.

Also shown in FIG. 8 is a sector shoe 12c. This sector shoe 12c is adjacent to the sector shoe 12a. The side surface 28 of the sector shoe 12a and the side surface 28 of the sector shoe 12c are in contact with each other. The contact point P2 coincides with the position of the inner peripheral surface 24 . In other words, the distance between the side surfaces 28 is approximately zero at the inner peripheral surface 24 . No gap exists between the sector shoes 12 on the inner peripheral surface 24 . The distance between the side surfaces 28 gradually increases radially outward.

9 is an enlarged cross-sectional view taken along line IX-IX of FIG. 5. FIG. FIG. 10 is an enlarged view of the portion indicated by symbol X in FIG. Figures 9 and 10 show a sector shoe 12a and another adjacent sector shoe 12b. In this cross section, the side surface 28 of the sector shoe 12a and the side surface 28 of the sector shoe 12b are separated. In other words, the distance between sides 28 is greater than zero. A gap 34 exists between the sector shoes 12 on the inner peripheral surface 24 . In this gap 34 part of the rear surface 18 of the segment 10 is not covered by the sector shoe 12 . In other words, the segment 10 is exposed in this gap 34 . The distance between the side surfaces 28 gradually increases radially outward.

Sector shoe 12c is also shown in FIG. This sector shoe 12c is adjacent to the sector shoe 12a. Side 28 of sector shoe 12a and side 28 of sector shoe 12c are spaced apart. In other words, the distance between sides 28 is greater than zero. A gap 34 exists between the sector shoes 12 on the inner peripheral surface 24 . A portion of the rear surface 18 of the segment 10 is exposed in this gap 34 . The distance between the side surfaces 28 gradually increases radially outward.

FIG. 11 is an enlarged cross-sectional view along line XI-XI of FIG. Figure 11 shows a sector shoe 12a and another adjacent sector shoe 12b. The side surface 28 of the sector shoe 12a and the side surface 28 of the sector shoe 12b are in contact with each other. This abutment point P3 coincides with the position of the inner peripheral surface 24 . In other words, the distance between the side surfaces 28 is zero at the inner peripheral surface 24 . No gap exists between the sector shoes 12 on the inner peripheral surface 24 . The distance between the side surfaces 28 gradually increases radially outward.

Also shown in FIG. 11 is a sector shoe 12c. This sector shoe 12c is adjacent to the sector shoe 12a. The side surface 28 of the sector shoe 12a and the side surface 28 of the sector shoe 12c are in contact with each other. The contact point P4 coincides with the position of the inner peripheral surface 24 . In other words, the distance between the side surfaces 28 is zero at the inner peripheral surface 24 . No gap exists between the sector shoes 12 on the inner peripheral surface 24 . The distance between the side surfaces 28 gradually increases radially outward.

As shown in FIG. 1, container ring 14 is cylindrical. As shown in FIG. 2, container ring 14 has an inner surface 36 . This inner surface 36 is inclined with respect to the axial direction. The inner surface 36 has a shape that extends radially outward toward the bottom. The inner surface 36 abuts the outer peripheral surface 26 of the sector shoe 12 . The inner surface 36 has a plurality of ribs 38 . Each rib 38 fits into the groove 32 of the sector shoe 12 . As mentioned above, groove 32 has an undercut shape. The catch between the groove 32 and the rib 38 prevents the sector shoe 12 from coming off the container ring 14 . Rib 38 can rub against groove 32 . The container ring 14 can therefore rub against the sector shoe 12 .

With the mold 2 open, the sector shoe 12 is radially outward from the position shown in FIG. 2 and the container ring 14 is above the position shown in FIG. This container ring 14 is gradually lowered. The sector shoe 12 whose outer peripheral surface 26 is pushed against the inner surface 36 of the container ring 14 gradually moves radially inward. The movement gradually reduces the distance between the sector shoe 12 and the adjacent sector shoe 12 . As the sector shoe 12 moves, the segment 10 gradually moves radially inward. The movement progressively reduces the distance between the segment 10 and the segment 10 adjacent thereto. When the descent of the container ring 14 is completed, the segments 10 abut adjacent segments 10 to form cavities. Mold 2 is closed when segment 10 abuts adjacent segment 10 .

When the closed mold 2 is opened, the container ring 14 rises gradually. Although the groove 32 and the rib 38 are caught, the sector shoe 12 does not rise because gravity is applied to the sector shoe 12. - 特許庁The sector shoe 12 gradually moves radially outward while rubbing against the container ring 14 . The movement gradually increases the distance between the sector shoe 12 and the adjacent sector shoe 12 . As the sector shoe 12 moves, the segment 10 gradually moves radially outward. Due to the movement, the distance between the segment 10 and the segment 10 adjacent thereto gradually increases.

In the tire manufacturing method using this mold 2, first, a raw cover is obtained through a preforming step. Next, the raw cover is introduced into mold 2 while mold 2 is open and the bladder (not shown) is contracted. A bladder is located inside the low cover. At this stage, the raw cover rubber composition is in an uncrosslinked state. The mold 2 is then tightened and the segment 10 forms a cavity. The bladder is then inflated. The raw cover is pressed against the cavity surface 16 of the mold 2 by the bladder and pressurized. The low cover Rc in this state is shown in FIG. The raw cover Rc is heated simultaneously with the pressurization. The pressure and heat cause the rubber composition to flow. Heating causes the rubber to undergo a cross-linking reaction, and a tire is obtained (vulcanization step). This tire has a tread and sidewalls. This tread is shaped by cavities formed by a plurality of segments 10 . The sidewalls are shaped by sidewall plates 8 .

As mentioned above, in the cross-sections shown in FIGS. 9 and 10, there are gaps 34 between sector shoes 12 . Near this gap 34, the rear surface 18 of the segment 10 is partially exposed. In the vulcanization process, no force from the sector shoe 12 is applied to the exposed portion. Force from the bladder is applied to this point. However, as is apparent from FIGS. 9 and 10, the size of this gap 34 is small. Moreover, no gap exists in the cross section of FIG. 8, and no gap exists in the cross section of FIG. Therefore, in this mold 2, elastic deformation of the segments 10 is suppressed. The cross-sectional shape of the mold 2 in the vulcanization process is close to a perfect circle. A tire obtained from this mold 2 has excellent uniformity.

In the cross section of FIG. 8, the distance between adjacent inner peripheral surfaces 24 is zero. Also in the cross section of FIG. 11, the distance between adjacent inner peripheral surfaces 24 is zero. In other words, in this mold 2, the minimum distance L1 between the inner peripheral surface 24 of the sector shoe 12 and the inner peripheral surface 24 of another sector shoe 12 adjacent to this sector shoe 12 is zero. This minimum distance L1 may be greater than zero. From the viewpoint of suppressing elastic deformation of the segment 10, the minimum distance L1 is preferably 3.0 mm or less, more preferably 2.0 mm or less, and particularly preferably 1.0 mm or less. An ideal minimum distance L1 is 0.0 mm.

When the mold 2 opens, the sector shoe 12 may tilt unintentionally. Since the side surface 28 has a curved surface that extends radially outward and circumferentially inward, even if the minimum distance L1 is small, the collision between the sector shoes 12 caused by the inclination of the sector shoes 12 is suppressed. . Furthermore, the curved surface facilitates the sliding of the sector shoes 12 and suppresses damage to the sector shoes 12 when the sector shoes 12 collide with each other. This mold 2 is excellent in durability.

Arrow L2 in FIG. 1 indicates the maximum distance between the bottom surface 23 of the sector shoe 12 and the bottom surface 23 adjacent thereto. From the viewpoint of durability of the mold 2, the maximum distance L2 is preferably 6 mm or longer, more preferably 10 mm or longer, and particularly preferably 16 mm or longer. The maximum distance L2 is preferably 100 mm or less.

Arrow Ts in FIG. 3 represents the thickness of segment 10 . This thickness Ts is measured along the radial direction. Thickness Ts is the distance between cavity surface 16 and back surface 18 . This thickness Ts measurement assumes that there are no ridges 20 on the cavity face 16 and no protrusions 21 on the back face 18 . A segment 10 having a small thickness Ts is likely to be elastically deformed. In the mold 2 having the segment 10 with a small thickness Ts, the sector shoe 12 including a curved surface that protrudes outward in the circumferential direction exhibits a great effect. This sector shoe 12 is suitable for a mold 2 having a thickness Ts of 73.0 mm or less, further 66.5 mm or less, particularly 54.5 mm or less.

Although the effects of the tire molds according to the examples will be clarified below, the scope disclosed in the present specification should not be construed to be limited based on the description of the examples.

[Example 1]
A mold as shown in FIGS. 1-11 was provided. This mold was for a tire having a size of "225/55R17". The side surface of the sector shoe of this mold was curved. The cross-sectional shape of this curved surface was an arc. The minimum distance L1 of this sector shoe was 0.0 mm. The segment thickness Ts of this mold was 43.0 mm.

[Example 2-7]
Molds of Examples 2-7 were obtained in the same manner as in Example 1, except that the mold specifications were as shown in Tables 1 and 2 below.

[Comparative Example 1]
A mold as shown in FIG. 12 was prepared. This mold was for a tire having a size of "225/55R17". The side of the sector shoe of this mold was flat. A gap existed between the sector shoe and the adjacent sector shoe. The minimum distance L1 of the sector shoe was 18.0 mm. The segment thickness Ts of this mold was 43.0 mm.

[Comparative Example 2-7]
Molds of Comparative Examples 2 to 7 were obtained in the same manner as in Comparative Example 1 except that the mold specifications were as shown in Tables 2 and 3 below.

[Evaluation of Uniformity]
A tire was manufactured using a mold. The 9th order RFV of this tire was measured. The results are shown in Tables 1-3 below and in FIG.

As shown in Tables 1-3 and FIG. 13, the tires obtained from the example molds are superior in uniformity to the tires obtained from the comparative example molds having the same size as this mold size. . The reason for this is that the elastic deformation of the segments is suppressed in the molds of the examples. From this evaluation result, the superiority of the tire molds of the examples is clear.

[Disclosure items]
The following items are disclosures of preferred embodiments.

[Item 1]
A mold for a tire having a tread, comprising:
(1) a plurality of segments that can be arranged in a ring to form a cavity for the tread; and (2) an inner peripheral surface, an outer peripheral surface, and a pair of a plurality of sector shoes each having a side surface and arranged along the circumferential direction,
each side surface includes a circumferentially outwardly convex curved surface,
A mold for a tire, wherein the curved surface has a shape that extends radially outward and circumferentially inward.

[Item 2]
The mold according to item 1, wherein the curved surface has an arcuate shape in a cross section perpendicular to the axial direction.

[Item 3]
3. The mold according to item 1 or 2, wherein the curved surface has a boundary with the inner peripheral surface.

[Item 4]
4. The mold according to item 3, wherein the curved surface extends from the inner peripheral surface to the outer peripheral surface.

[Item 5]
5. The mold according to any one of items 1 to 4, wherein the minimum distance between the inner peripheral surface of the sector shoe and the inner peripheral surface of another sector shoe adjacent to this sector shoe is 3.0 mm or less.

[Item 6]
6. The mold according to any one of items 1 to 5, wherein the segment has a thickness of 73.0 mm or less.

[Item 7]
A method of manufacturing a tire having a tread, comprising:
(A) a step of inserting a raw cover into the mold;
and (B) pressurizing and heating the raw cover in the mold,
The mold of the above step A is
(1) a plurality of segments that can be arranged in a ring to form a cavity for the tread; each having a side surface of and having a plurality of sector shoes arranged along the circumferential direction,
A method for manufacturing a tire, wherein each side surface includes a curved surface that protrudes outward in the circumferential direction, and the curved surface has a shape that extends radially outward and circumferentially inward.

Tires for various vehicles can be obtained with the aforementioned tire molds.

2... Tire mold 4... Lower plate 6... Upper plate 8... Side wall plate 10... Segment 12... Sector shoe 14... Container ring 16... Cavity surface 18 Back surface 20 Ridge 21 Protrusion 24 Inner peripheral surface 26 Outer peripheral surface 28 Side surface 30 Recess 32 Groove 34 Gap 36・Inner surface 38 Ribs

Claims (7)

A mold for a tire having a tread, comprising:
(1) a plurality of segments that can be arranged in a ring to form a cavity for the tread; and (2) an inner peripheral surface, an outer peripheral surface, and a pair of a plurality of sector shoes each having a side surface and arranged along the circumferential direction,
each side surface includes a circumferentially outwardly convex curved surface,
A mold for a tire, wherein the curved surface has a shape that extends radially outward and circumferentially inward. 2. The mold of claim 1, wherein the curved surface has an arcuate shape in a cross section perpendicular to the axial direction. 3. The mold according to claim 1, wherein the curved surface has a boundary with the inner peripheral surface. 4. The mold according to claim 3, wherein the curved surface extends from the inner peripheral surface to the outer peripheral surface. The mold according to any one of claims 1 to 4, wherein the minimum distance between the inner peripheral surface of the sector shoe and the inner peripheral surface of another sector shoe adjacent to this sector shoe is 3.0 mm or less. . 6. A mold according to any preceding claim, wherein the segment thickness is 73.0 mm or less. A method of manufacturing a tire having a tread, comprising:
(A) a step of inserting a raw cover into the mold;
and (B) pressurizing and heating the raw cover in the mold,
The mold of the above step A is
(1) a plurality of segments that can be arranged in a ring to form a cavity for the tread; each having a side surface of and having a plurality of sector shoes arranged along the circumferential direction,
A method for manufacturing a tire, wherein each side surface includes a curved surface that protrudes outward in the circumferential direction, and the curved surface has a shape that extends radially outward and circumferentially inward.

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