JP2017047599A - Tire mold - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold improving the shape precision of a tire.SOLUTION: The segment cavity face 54 of a segment 52 has an arc shape with a curvature radius Rt. A segment abutment face 56 has an arc shape with a curvature radius Rg. The outer circumferential abutment face 50 of a side plate 32 has a circular shape with a curvature radius Rp. The linear expansion coefficient αg of the segment 52 and the linear expansion coefficent αp of the side plate 32 are different. In a room temperature Tn, the center of the curvature radius Rt is defined as a point Ptn and the center of the curvature radius Rp is defined as a point Ppn. In a vulcanization temperature Tv, the center of the curvature radius Rt is defined as a point tv, and the center of the curvature radius Rp is defined as a point Ppv. At this time, the central point Ptn and the central point Ppn are deviated. The correction value C of the deviation amount is 0.5 to 1.5 times the deviation amount β calculated by the following numerical equation:β=Rpn*Td*(αg-αp).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a mold used for vulcanization molding of a tire.

  Japanese Patent Laid-Open No. 2005-533685 discloses a mold for vulcanizing and molding a tire. The mold includes a plurality of segments and a pair of side plates. This segment has a segment cavity surface with which the outer peripheral surface of the raw cover abuts. The side plate includes a side cavity surface that abuts against the axially outer side surface of the raw cover.

  In the tire vulcanization process, a preformed raw cover (raw tire) is put into the mold. The raw cover is heated while being pressurized in the cavity of the mold. By this pressurization and heating, the raw cover is vulcanized. By this vulcanization, a tire having a shape that follows the shape of the cavity surface is obtained. In this mold, the cavity surface of the segment forms a tread surface. The cavity surface of the side plate forms the outer side surface in the axial direction of the tire.

JP 2005-533585 A

  In the vulcanization step, the mold is brought to a preset vulcanization temperature. This segment and the side plate are brought to the vulcanization temperature. This segment and the side plate are thermally expanded. The material of this segment may be different from the material of the side plate. For example, a mold is used in which the material of the segment is an aluminum alloy and the material of the side plate is steel. In such a mold, the linear expansion coefficient of the segment and the linear expansion coefficient of the side plate are different. In this mold, a deviation may occur between the segment and the side plate. This deviation of the mold impairs the shape accuracy of the molded tire.

  An object of the present invention is to provide a mold for improving the shape accuracy of a molded tire.

A tire vulcanization molding die according to the present invention includes a plurality of segments arranged in a ring shape in the circumferential direction, and a side plate positioned radially inward of the plurality of segments.
The inner peripheral surface of each segment includes a segment cavity surface that forms a tread surface of the tire, and a segment contact surface that contacts the side plate. In the cross section perpendicular to the axial direction, the shape of the segment cavity surface is an arc shape with a radius of curvature Rt, and the shape of the segment contact surface is an arc shape with a radius of curvature Rg.
The side plate includes a side cavity surface that forms a side surface on the outer side in the axial direction of the tire, and an outer peripheral contact surface that contacts the segment contact surface. In the cross section perpendicular to the axial direction, the shape of the outer peripheral contact surface is a circle having a curvature radius Rp.
The linear expansion coefficient αg of the segment is different from the linear expansion coefficient αp of the side plate. At room temperature Tn, when the radius of curvature Rt is Rtn, the center point of the radius of curvature Rtn is Ptn, the radius of curvature Rp is Rpn, and the center point of the radius of curvature Rpn is Ppn, The amount of positional deviation from the center point Ppn is a correction value C. The correction value C is not less than 0.5 times and not more than 1.5 times the deviation amount β calculated by the following equation, where Td is the rising temperature from the room temperature Tn to the vulcanization temperature Tv.
β = Rpn · Td · (αg−αp)

  Preferably, the correction value C is not less than 0.7 times and not more than 1.3 times the deviation amount β.

  Preferably, the segment is made of an aluminum alloy. The side plate is made of steel.

  The curvature radius Rg is defined as Rgn at room temperature Tn. At the vulcanization temperature Tv, the curvature radius Rg is Rgv, and the curvature radius Rp is Rpv. At this time, preferably, the absolute value of the difference between the curvature radius Rgv and the curvature radius Rpv at the vulcanization temperature Tv is equal to or less than the absolute value of the difference between the curvature radius Rgn and the curvature radius Rpn at room temperature Tn. .

The tire manufacturing method according to the present invention includes:
A preforming step in which a raw cover is obtained by combining members constituting each part of the tire, and a vulcanizing step in which the raw cover is put into a mold and vulcanized to obtain the tire.
The mold for the vulcanization step includes a plurality of segments arranged in a ring shape in the circumferential direction, and a side plate positioned on the radially inner side of the plurality of segments.
The inner peripheral surface of each segment includes a segment cavity surface that forms a tread surface of the tire, and a segment contact surface that contacts the side plate. In the cross section perpendicular to the axial direction, the shape of the segment cavity surface is an arc shape with a radius of curvature Rt, and the shape of the segment contact surface is an arc shape with a radius of curvature Rg.
The side plate includes a side cavity surface that forms a side surface on the outer side in the axial direction of the tire, and an outer peripheral contact surface that contacts the segment contact surface. In the cross section perpendicular to the axial direction, the shape of the outer peripheral contact surface is a circle having a curvature radius Rp.
The linear expansion coefficient αg of the segment is different from the linear expansion coefficient αp of the side plate. At room temperature Tn, when the radius of curvature Rt is Rtn, the center point of the radius of curvature Rtn is Ptn, the radius of curvature Rp is Rpn, and the center point of the radius of curvature Rpn is Ppn, The amount of positional deviation from the center point Ppn is a correction value C.
The correction value C is not less than 0.5 times and not more than 1.5 times the deviation amount β calculated by the following equation, where Td is the rising temperature from the room temperature Tn to the vulcanization temperature Tv.
β = Rpn · Td · (αg−αp)

Another tire vulcanization molding die according to the present invention includes a plurality of segments arranged in a ring shape in a circumferential direction, and a side plate positioned radially inward of the plurality of segments. .
The inner peripheral surface of each segment includes a segment cavity surface that forms a tread surface of the tire, and a segment contact surface that contacts the side plate. In the cross section perpendicular to the axial direction, the shape of the segment cavity surface is an arc shape with a radius of curvature Rt, and the shape of the segment contact surface is an arc shape with a radius of curvature Rg.
The side plate includes a side cavity surface that forms a side surface on the outer side in the axial direction of the tire, and an outer peripheral contact surface that contacts the segment contact surface. In the cross section perpendicular to the axial direction, the shape of the outer peripheral contact surface is a circle having a curvature radius Rp.
The linear expansion coefficient αg of the segment is different from the linear expansion coefficient αp of the side plate. At room temperature Tn, the radius of curvature Rt is Rtn, the center point of the radius of curvature Rtn is Ptn, the radius of curvature Rp is Rpn, and the center point of the radius of curvature Rpn is Ppn. At the vulcanization temperature Tv, the curvature radius Rt is Rtv, the center point of the curvature radius Rtv is Ptv, the curvature radius Rp is Rpv, and the center point of the curvature radius Rpv is Ppv. At this time, the positional deviation amount between the central point Ptv and the central point Ppv at the vulcanization temperature Tv is equal to or smaller than the positional deviation amount between the central point Ptn and the central point Ppn at room temperature Tn.

  At the vulcanization temperature, this segment cavity surface has excellent shape accuracy. The tire vulcanized with this mold has excellent shape accuracy. The tread surface of this tire is excellent in roundness, and the tread surface is restrained from running out. In this tire, the generation of noise when rolling on the road surface is suppressed.

FIG. 1 is a sectional view showing a part of a vulcanizing apparatus using a mold according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing the mold and bladder of FIG. FIG. 3 is a side view of the mold of FIG. 4A is an explanatory view showing a segment of the mold of FIG. 1, and FIG. 4B is an explanatory view showing a part of the side plate of the mold of FIG. FIG. 5 is a partially enlarged view of the mold shown in FIG. FIG. 6 is an explanatory diagram of correction values of the mold shown in FIG. FIG. 7 is another explanatory diagram of the correction value of the mold of FIG.

  Hereinafter, the present invention will be described in detail based on preferred embodiments with appropriate reference to the drawings.

  FIG. 1 shows a vulcanization molding apparatus 14 including a mold 12 according to the present invention. FIG. 1 shows a raw cover 15 together with a vulcanization molding device 14. The vertical direction in FIG. 1 is the axial direction of the mold 12, the horizontal direction is the radial direction, and the direction perpendicular to the paper surface is the circumferential direction. The vulcanization molding apparatus 14 includes an actuator 16, a sector shoe 18, an upper container plate 20, a lower container plate 22, an upper clamp ring 24, a lower clamp ring 26, a mold ring 28, a molding ring 30, a pair of side plates 32, and an upper part. A bead ring 36, a lower bead ring 38, and a bladder 40 are provided.

  2 includes a forming ring 30, a pair of side plates 32, and an upper bead ring 36 and a lower bead ring 38 as a pair of bead rings. The mold 12 is in contact with the raw cover 15 to form the outer shape of the tire.

  FIG. 3 shows a side view of the molding ring 30 and one side plate 32 of the pair of side plates 32 as viewed from the outside in the axial direction. The molding ring 30 has a ring shape. As shown in FIG. 2, the molding ring 30 includes a tread cavity surface 42 and a pair of inner peripheral contact surfaces 44.

  As shown in FIG. 3, the forming ring 30 includes a plurality of segments 52. In this mold 12, the molding ring 30 is divided into nine equal parts in the circumferential direction. The molding ring 30 is formed by arranging nine segments 52 in the circumferential direction. The number of segments 52 constituting the molding ring 30 is usually 3 or more and 20 or less.

  Each segment 52 has a substantially arc shape when viewed in the axial direction. The segment 52 includes a segment cavity surface 54, a pair of segment contact surfaces 56, and a pair of end surfaces 58. The end surface 58 is formed at the circumferential end of the segment 52 so as to face the circumferential direction. The segments 52 are arranged in the circumferential direction. The end surfaces 58 of adjacent segments 52 abut. A plurality of segments 52 are arranged to form the forming ring 30.

  As shown in FIG. 2, the segment cavity surface 54 is formed on the inner peripheral surface 46 of the segment 52. The segment cavity surface 54 is located at the center of the segment 52 in the axial direction. The segment cavity surface 54 constitutes a part of the tread cavity surface 42 of the molding ring 30. In the cross section perpendicular to the axial direction, the shape of the segment cavity surface 54 is an arc shape (see FIG. 3). This segment cavity surface 54 forms part of the tread surface of the tire. Although not shown, the segment cavity surface 42 may be uneven. A groove may be formed on the tread surface of the tire due to the unevenness.

  The segment abutment surface 56 is formed on the inner peripheral surface 46 of the segment 52. The segment abutment surface 56 is located outside the segment cavity surface 54 in the axial direction. The segment contact surface 56 constitutes a part of the inner peripheral contact surface 44 of the molding ring 30. In the cross section perpendicular to the axial direction, the shape of the segment contact surface 56 is an arc shape (see FIG. 3). The segment contact surface 56 contacts the outer peripheral contact surface 50 of the side plate 32.

  The segment 52 is made of, for example, an aluminum alloy. The segment 52 includes a segment cavity surface 54 that forms a tread surface. The segment 52 made of an aluminum alloy is easy to cast. This segment 52 is also excellent in workability such as cutting. The segment 52 can easily form a segment cavity surface 54 having a complicated uneven shape. This segment 52 facilitates the manufacture of the mold 12.

  As shown in FIG. 3, the shape of the side plate 32 is a ring shape. As shown in FIG. 2, the side plate 32 includes a side cavity surface 48 and an outer peripheral contact surface 50. The side cavity surface 48 is formed on the axially inward surface of the side plate 32. The side cavity surface 48 mainly forms a side surface on the outer side in the axial direction of the tire. Although not shown, irregularities are formed on the side cavity surface 48. Due to the unevenness, a design such as a marking is formed on the side surface of the tire.

  The outer peripheral contact surface 50 is formed on the outer peripheral surface in the radial direction of the side plate 32. In the cross section perpendicular to the axial direction, the outer peripheral contact surface 50 has a circular shape. The outer peripheral contact surface 50 contacts the inner peripheral contact surface 44 of the molding ring 30. The outer peripheral contact surface 50 and the inner peripheral contact surface 44 have complementary shapes. The outer peripheral contact surface 50 of one side plate 32 is in contact with one inner peripheral contact surface 44 of the molding ring 30. The outer peripheral contact surface 50 of the other side plate 32 contacts the other inner peripheral contact surface 44 of the molding ring 30.

  The side plate 32 is made of, for example, a steel material. As this steel material, a general structural rolled steel material (SS400) is exemplified. The side plate 32 is cleaned after the tire is vulcanized. In this cleaning, dirt on the side cavity surface 48 is removed. The side cavity surface 48 is cleaned by shot blasting or the like. Since the side plate 32 is made of steel, the unevenness of the side cavity surface 48 is suppressed. By using the steel material, the service life of the side plate 32 is improved.

  A point P1 in FIG. 2 represents the midpoint of the segment cavity surface 54 in the axial direction. A one-dot chain line CL represents a straight line extending in the radial direction through the point P1. The straight line CL is a straight line corresponding to the equator plane of the tire. This point P1 is a point corresponding to the intersection of the tire tread surface and the equator plane. In the segment cavity surface 54 having a concavo-convex shape formed on the surface, the position of this point P1 is determined by the virtual cavity surface that is assumed that this concavo-convex shape is not formed.

  The arrow Rg in FIG. 4A represents the radius of curvature of the segment contact surface 56. An arrow Rt represents the radius of curvature of the segment cavity surface 54. This curvature radius Rt is measured at the position of point P1 in FIG. 2 in the axial direction. An arrow Rp in FIG. 4B represents the radius of curvature of the outer peripheral contact surface 50 of the side plate 32. In this specification, the unit of the curvature radius including the curvature radius Rg, the curvature radius Rt, and the curvature radius Rp is all (mm), but the description of the unit is omitted.

  An alternate long and short dash line Lg in FIG. 4A represents a tangent line of the contour of the segment contact surface 56 in a cross section perpendicular to the axial direction. Reference symbol P2 represents a contact point between the contour of the segment contact surface 56 and the tangent line Lg. An alternate long and short dash line Lp in FIG. 4B represents a tangent to the outer peripheral contact surface 50 in a cross section perpendicular to the axial direction. Reference P3 represents a contact point between the outer peripheral contact surface 50 and the tangent line Lp.

  In this mold 12, at the room temperature Tn, the radius of curvature Rg of the segment contact surface 56 is represented by the radius of curvature Rgn. The curvature radius Rt of the segment cavity surface 54 is represented by the curvature radius Rtn. The curvature radius Rp of the outer peripheral contact surface 50 of the side plate 32 is represented by the curvature radius Rpn. The curvature radii Rgn and Rtn are finishing dimensions (working dimensions) of the segment 52. The radius of curvature Rpn is the finished dimension (working dimension) of the side plate 32. The room temperature Tn is a temperature at which the finishing dimension of the curvature radii Rg and Rt of the segment 52 and the curvature radius Rp of the side plate 32 is measured. In this specification, the unit of the room temperature Tn, the vulcanization temperature Tv and the rising temperature Td described later is (K), but the description of the unit is omitted.

  FIG. 5 shows a part of the mold 12 in a closed state at room temperature Tn. In the mold 12, the segment contact surface 56 and the outer peripheral contact surface 50 of the side plate 32 are in contact. In this mold 12, at the room temperature Tn, the radius of curvature Rgn of the segment abutment surface 56 and the radius of curvature Rpn of the outer circumferential abutment surface 50 of the side plate 32 are substantially the same.

  The symbol Pgn in FIG. 5 represents the center point of the curvature radius Rgn. The symbol Ptn represents the center point of the curvature radius Rtn. The symbol Ppn represents the center point of the radius of curvature Rpn. In this mold 12, the center point Pgn and the center point Ppn are at the same position. The center point Ptn is displaced with respect to the center point Pgn and the center point Ppn. A double arrow C in FIG. 5 represents the amount of displacement. In the present invention, this misalignment amount is referred to as a correction value C. In this specification, the unit of misalignment is (mm), but the description of the unit is omitted.

  In FIG. 5, the contact P2 of the segment 52 and the contact P3 of the side plate 32 are overlapped at the same position. The tangent line Lg of the segment 52 and the tangent line Lp of the side plate 32 are overlapped. The dashed-dotted line Lc of FIG. 5 represents the straight line extended in the radial direction which passes the contact P2 and the contact P3 in the state of FIG. The positional deviation amount of the present invention is measured along this straight line Lc. Even when the curvature radius Rgn of the segment contact surface 56 and the curvature radius Rpn of the outer peripheral contact surface 50 of the side plate 32 are different, the positional deviation amount is measured in the same manner.

The mold 12 is heated to a preset vulcanization temperature Tv in the tire vulcanization process. The temperature of the mold 12 rises from the room temperature Tn to the vulcanization temperature Tv. This elevated temperature is represented as Td. The rising temperature Td is a value obtained by subtracting the room temperature Tn from the vulcanization temperature Tv. In this mold 12, the linear expansion coefficient of the segment 52 is expressed as αg, and the linear expansion coefficient of the side plate 32 is expressed as αp. In this specification, the unit of linear expansion coefficient is (10 ⁻⁶ / K), but the description of the unit is omitted.

  In the vulcanization process, the segment 52 and the side plate 32 are thermally expanded. At the vulcanization temperature Tv, the curvature radius Rg of the segment 52 is expressed as a curvature radius Rgv, and the curvature radius Rt is expressed as a curvature radius Rtv. Similarly, the curvature radius Rp of the side plate 32 is expressed as a curvature radius Rpv.

  The correction value C of the mold 12 will be described with reference to FIGS. 6 and 7. 6 and 7, a virtual mold 62 is shown. In this mold 62, the curvature radius Rgx of the segment contact surface 56 and the curvature radius Rpx of the outer peripheral contact surface 50 of the side plate 32 are equal at room temperature Tn. In this mold 62, the center point Pgx of the curvature radius Rgx of the segment contact surface 56, the center point Ptx of the curvature radius Rtx of the segment cavity surface 54, and the center point Ppx of the curvature radius Rpx of the side plate 32 are the same position. It is in. The other configuration of the mold 62 is the same as that of the mold 12.

FIG. 7 shows a state in which the mold 62 is set to the vulcanization temperature Tv. Due to the thermal expansion of the segment 52, the curvature radius Rgx becomes the curvature radius Rgy. The curvature radius Rtx is the curvature radius Rty. The curvature radius Rpx becomes the curvature radius Rpy due to the thermal expansion of the side plate. At this time, the curvature radius Rgy, the curvature radius Rty, and the curvature radius Rpy are expressed by the following equations (1) to (3) because the curvature radius Rgx and the curvature radius Rpx are equal.
Rgy = Rpx · (1 + αg · Td) (1)
Rty = Rtx · (1 + αg · Td) (2)
Rpy = Rpx · (1 + αp · Td) (3)

  In this mold 62, the linear expansion coefficient αg and the linear expansion coefficient αp are different. Therefore, the curvature radius Rgy and the curvature radius Rpy are different. There is a positional shift between the center point Pgy of the curvature radius Rgy and the center point Pty of the curvature radius Rty and the center point Ppy of the curvature radius Rpy. A double arrow β in FIG. 7 represents the misalignment amount between the center point Pgy and the center point Pty and the center point Ppy. In the present invention, this β is referred to as a deviation amount. In FIG. 7, the shift amount β is exaggerated for convenience of explanation.

In the mold 62, the shift amount β is measured in the same manner as the correction value C described above. This deviation amount β is expressed by the following equation (4).
β = Rgy−Rpy (4)
Here, Formula (4) is represented by the following Formula (5) from Formula (1) and Formula (3).
β = Rpx · Td · (αg−αp) (5)

  In this mold 62, the center point Pgy of the segment 52 and the center of the side plate 32 are brought into contact with the segment contact surface 56 and the outer peripheral contact surface 50 of the side plate 32 at the vulcanization temperature Tv. The position is shifted from the point Ppy by a shift amount β. This misalignment promotes the deflection of the segment cavity surface 54. In the tire molded by this mold 62, radial treads are likely to occur on the tread surface.

In the mold 12 of FIG. 5, the radius of curvature Rtv (mm) of the segment cavity surface 54 at the vulcanization temperature Tv is corrected by the shift amount β. This curvature radius Rtv is expressed by the following equation (6).
Rtv = Rty-β (6)

Here, the radius of curvature Rtn of the segment 52 at room temperature Tn is expressed by the following equation (7).
Rtn = Rtv / (1 + αg · Td) (7)
Further, from the equations (2) and (6), the curvature radius Rtn is expressed by the following equation (8).
Rtn = (Rtx · (1 + αg · Td) −β) / (1 + αg · Td) (8)
Further, the radius of curvature Rtn is expressed by the following formula (8 ′).
Rtn = Rtx− (β / (1 + αg · Td)) (8 ′)

The linear expansion coefficient αg of the segment 52 is, for example, 23 (10 ⁻⁶ / K) when made of an aluminum alloy. The vulcanization temperature of a tire is generally 160 (° C.) to 190 (° C.). This rising temperature Td is generally about 170 (K) at most. This “αg · Td” is extremely smaller than “1”. Therefore, “1 + αg · Td” can substitute “1”. At this time, the curvature radius Rtn of the equation (8 ′) represents that the curvature radius Rtx is corrected by the approximate deviation amount β.

  This radius of curvature Rtx is the radius of curvature of the segment cavity surface 54 at room temperature Tn in the mold 62. In the mold 62, the center point Ptx of the curvature radius Rtx of the segment cavity surface 54 and the center point Ppx of the curvature radius Rpx of the outer peripheral contact surface 50 of the side plate 32 are set at the same position. The radius of curvature Rtn of the mold 12 is relative to the radius of curvature Rtx of the mold 62 where the center point Ptx of the radius of curvature Rtx and the center point Ppx of the radius of curvature Rpx of the outer peripheral contact surface 50 of the side plate 32 are at the same position. Therefore, the shift amount β is reduced.

  In this mold 12, the center point Ptn of the curvature radius Rtn of the segment cavity surface 54 is shifted with respect to the center point Ppn of the side plate 32. This amount of displacement is the correction value C. The correction value C is set to a shift amount β.

  In this mold 12, the radius of curvature Rtn is corrected with the correction value C at room temperature Tn. With this correction value C, the amount of positional deviation between the center point Ptv of the curvature radius Rtv of the segment 52 and the center point Ppv of the curvature radius Rpv of the side plate 32 is reduced at the vulcanization temperature Tv. In the mold 12, the radial runout of the tread surface of the tire is suppressed. In this mold 12, the amount of displacement between the center point Ptn of the radius of curvature Rtn and the center point Ppn of the radius of curvature Rpn is increased by the correction value C at room temperature Tn.

  A tire manufacturing method using the vulcanization molding apparatus 14 will be described. The tire manufacturing method includes a member preparation step, a preforming step, and a vulcanization step.

  In the member preparation step, members constituting each part of the tire such as a tread, a sidewall, a clinch, and a carcass are prepared. The member which comprises each part of this tire contains the unvulcanized rubber composition.

  In the pre-molding step, members constituting each part of the tire are combined to obtain a raw cover (raw tire).

  In the vulcanization process, the raw cover is vulcanized to obtain a tire. This vulcanization process includes a raw cover charging process, a pressure heating process, and a tire removing process.

  In the raw cover loading process, although not shown, the mold 12 is in an open state. FIG. 1 shows a state where the mold of the vulcanization molding apparatus 14 is closed. In a state where the mold 12 is opened, the upper container plate 20 and one side plate 32 of FIG. 1 are in the standby position on the outer side in the axial direction (upward in FIG. 1). The actuator 16 is in a standby position on the outer side in the axial direction (upward in FIG. 1). The sector shoe 18 and the segment 52 are in a standby position radially outward (leftward in FIG. 1). The bladder 40 is in a contracted standby posture.

  The raw cover is put into the mold 12 in the opened state. The upper container plate 20 and the one side plate 32 move inward in the axial direction (downward in FIG. 1) from the standby position. The bladder 40 expands by filling with gas. The actuator 16 moves inward in the axial direction (downward in FIG. 1) from the standby position. The movement of the actuator 16 causes the sector shoe 18 and the segment 52 to move radially inward from the standby position toward the side plate 32. One segment contact surface 56 contacts the outer peripheral contact surface 50 of one side plate 32. The other segment contact surface 56 contacts the outer peripheral contact surface 50 of the other side plate 32. The end surfaces 58 of adjacent segments 52 abut. In this way, the mold 12 is closed. In the vulcanization molding apparatus 14, the mold 12 thus moves from the open state to the closed state.

  In the pressure heating process, the internal pressure of the bladder 30 is increased. The raw cover 2 is pressurized by the cavity surface of the mold 12 and the bladder 30. The raw cover is heated by the mold 12 and the bladder 30. By this pressurization and heating, the mold 12 is brought to a preset vulcanization temperature Tv. The rubber composition of the raw cover flows in the mold 12. The segment cavity surface 54 (tread cavity surface 42) forms the tread surface of the tire. The side cavity surface 48 forms the outer side surface in the axial direction of the tire. In this way, a tire is obtained from the raw cover.

  In the tire removing step, the upper container plate 20 and the one side plate 32 move to the standby position outside in the axial direction. The actuator 16 moves to the standby position outside in the axial direction (upward in FIG. 1). The sector shoe 18 and the segment 52 move to a standby position radially outward. The bladder 40 is in a contracted standby posture. In this way, the mold 12 is changed from the closed state to the opened state. The tire is taken out from the mold 12 in the opened state.

  In the mold 12, the center point Ptn of the radius of curvature Rtn of the segment cavity surface 54 is displaced from the center point Ppn of the side plate 32 at room temperature Tn. The correction value C of the positional deviation amount is a deviation amount β. In this segment 52, the positional deviation between the center point Ptv of the curvature radius Rtv of the segment cavity surface 54 and the center point Ppv of the curvature radius Rpv of the side plate 32 is small at the vulcanization temperature Tv. Thereby, in the tire vulcanized by the mold 12, the radial runout of the tread surface is suppressed.

  In the mold 12, the shift amount β is used as the correction value C, but the present invention is not limited to this. From the viewpoint of suppressing radial deflection of the tread surface, the correction value C is preferably 0.5 times or more, more preferably 0.7 times or more, and particularly preferably 0.9 times or more of the shift amount β. It is. From the same viewpoint, the correction value C is preferably 1.5 times or less, more preferably 1.3 times or less, and particularly preferably 1.1 times or less the deviation amount β.

  Here, the center point Ptn of the curvature radius Rtn is corrected with the correction value C, but the present invention is not limited to this. In the mold 12, the amount of positional deviation between the center point Ptv of the curvature radius Rtv of the segment 52 and the center point Ppv of the curvature radius Rpv of the side plate 32 is the center point Ppn of the curvature radius Rtn and the center point Ppn of the curvature radius Rpn. If the amount of misalignment is less than or equal to this, the effect of suppressing the shake of the tread surface in the radial direction can be exhibited. From this viewpoint, preferably, the positional deviation amount between the center point Ptv and the central point Ppv is made smaller than the positional deviation amount between the center point Ptn and the central point Ppn.

In this mold 12, the radius of curvature Rgn of the segment contact surface 56 of the segment 52 is not corrected, but the radius of curvature Rgn may be corrected. This curvature radius Rgn may be corrected with the correction value C, for example, similarly to the curvature radius Rtn. This correction value C is the aforementioned shift amount β. At this time, the curvature radius Rgv is expressed by the following formula (9).
Rgv = Rgy-β (9)

The radius of curvature Rgn at room temperature Tn (K) is expressed by equation (10) below.
Rgn = Rgv / (1 + αg · Td) (10)
Further, from the equations (1) and (9), the radius of curvature Rgn is expressed by the following equation (11).
Rgn = (Rpx · (1 + αg · Td) −β) / (1 + αg · Td) (11)

In the mold 12, the curvature radius Rgn of the segment 52 is determined based on the curvature radius Rpn of the outer peripheral contact surface 50 of the side plate 32. The curvature radius Rpx is expressed as the curvature radius Rpn, and the curvature radius Rgn is expressed by the following equation (12).
Rgn = (Rpn · (1 + αg · Td) −β) / (1 + αg · Td) (12)

  In this mold 12, the radius of curvature Rgn is corrected by the correction value C (the amount of slip β). In the mold 12, the absolute value of the difference between the curvature radius Rgv and the curvature radius Rpv is small at the vulcanization temperature Tn. The positional deviation amount between the center point Pgv and the center point Ppv is small. The segment contact surface 56 of the segment 52 and the outer peripheral contact surface 50 of the side plate 32 can stably contact. As a result, the tire vulcanized by the mold 12 is further improved in outer shape accuracy. The radial runout of the tread surface of the tire is further suppressed.

  In this mold 12, the correction value C is set to the shift amount β, but is not limited thereto. From the viewpoint of suppressing radial deflection of the tread surface, the correction value C is preferably 0.5 times or more, more preferably 0.7 times or more, and particularly preferably 0.9 times or more of the shift amount β. It is. From the same viewpoint, the correction value C is preferably 1.5 times or less, more preferably 1.3 times or less, and particularly preferably 1.1 times or less the deviation amount β.

  In the mold 12, due to the correction value C, the absolute value of the difference between the curvature radius Rgv and the curvature radius Rpv is smaller than the absolute value of the difference between the curvature radius Rgy and the curvature radius Rpy of the mold 62. Due to the correction value C, the absolute value of the difference between the curvature radius Rgn and the curvature radius Rpn is larger than the absolute value of the difference between the curvature radius Rgx and the curvature radius Rpx of the mold 62.

  In this mold 12, due to the correction value C, the amount of displacement between the center point Pgv of the curvature radius Rgv and the center point Ppv of the curvature radius Rpv is the center of the center point Pgy of the curvature radius Rgy and the curvature radius Rpy of the mold 62. Smaller than the amount of positional deviation from the point Ppy. Due to the correction value C, the positional deviation amount between the center point Pgn of the curvature radius Rgn and the central point Ppn of the curvature radius Rpn is the positional deviation between the central point Pgx of the curvature radius Rgx of the mold 62 and the central point Ppx of the curvature radius Rpx. Larger than the amount.

  Here, the curvature radius Rgn (mm) is corrected with the correction value C, but is not limited thereto. The absolute value of the difference between the curvature radius Rgv of the segment 52 and the curvature radius Rpn of the side plate 32 is set to be equal to or smaller than the absolute value of the difference between the curvature radius Rgn and the curvature radius Rpn, thereby reducing the radial runout of the tread surface. The suppressing effect can be exhibited. More preferably, the absolute value of the difference between the curvature radius Rgv and the curvature radius Rpv is smaller than the absolute value of the difference between the curvature radius Rgn and the curvature radius Rpn.

  Further, the positional deviation amount between the center point Pgv of the curvature radius Rgv of the segment 52 and the central point Ppv of the curvature radius Rpv of the side plate 32 is the positional deviation between the central point Pgn of the curvature radius Rgn and the central point Ppn of the curvature radius Rpn. By setting the amount to be equal to or less than the amount, an effect of suppressing the shake of the tread surface in the radial direction can be exhibited. Preferably, the positional deviation amount between the central point Pgv and the central point Ppv is set smaller than the positional deviation amount between the central point Pgn and the central point Ppn.

  Hereinafter, the effects of the present invention will be clarified by examples. However, the present invention should not be construed in a limited manner based on the description of the examples.

[Example 1]
The mold shown in FIGS. 2 and 3 was obtained. The mold segment was made of an aluminum alloy AC4. The side plate was made of general structural rolled steel SS400. The center point Ptn of the cavity surface of the segment was displaced from the center point Ppn of the outer peripheral contact surface of the side plate. The correction value C, which is the positional deviation amount, is set to the aforementioned deviation amount β (mm). 1000 tires were manufactured using this mold.

[Comparative Example 1]
A mold was obtained in the same manner as in Example 1 except that the correction value C was set to 0. 1000 tires were manufactured using this mold.

[Example 2-7]
A mold was obtained in the same manner as in Example 1 except that the correction value C was set as shown in Table 1. 1000 tires were manufactured using each mold.

[RRO evaluation]
The tire tread radial runout (diameter variation) was measured. The tire is rotated once at a low speed where the centrifugal force is negligible. The RRO (radial run out) was measured with the sensor facing the tread surface of the rotating tire. This RRO was measured for one round. The measured RRO data was subjected to order analysis, and the 9th, 18th and 27th order components of RRO were calculated. The results are shown in Table 1. This RRO is an average value of each tire. The RRO is closer to a perfect circle as the numerical value is smaller. The smaller the value, the better.

  As shown in Table 1, the tire of the example has a higher evaluation than the tire of the comparative example. From this evaluation result, the superiority of the present invention is clear.

  The metal mold | die demonstrated above can be widely used for the manufacturing method of a tire provided with a tread surface.

DESCRIPTION OF SYMBOLS 12 ... Mold 14 ... Vulcanization molding apparatus 30 ... Molding ring 32 ... Side plate 42 ... Tread cavity surface 44 ... Inner peripheral contact surface 46 ... Inner peripheral surface 48 ... Side cavity surface 50 ... Outer peripheral contact surface 52 ... Segment 54 ... Segment cavity surface 56 ... Segment contact surface

Claims (6)

A plurality of segments arranged in a ring shape in the circumferential direction, and a side plate positioned radially inward of the plurality of segments;
Each segment has a segment cavity surface that forms the tread surface of the tire, and a segment contact surface that contacts the side plate,
In a cross section perpendicular to the axial direction, the shape of the segment cavity surface is an arc shape with a radius of curvature Rt, and the shape of the segment contact surface is an arc shape with a radius of curvature Rg,
The side plate includes a side cavity surface that molds an axially outer side surface of the tire, and an outer peripheral abutment surface that abuts the segment abutment surface,
In the cross section perpendicular to the axial direction, the shape of the outer peripheral contact surface is a circle having a radius of curvature Rp,
The linear expansion coefficient αg of the segment is different from the linear expansion coefficient αp of the side plate,
At room temperature Tn, when the radius of curvature Rt is Rtn, the center point of the radius of curvature Rtn is Ptn, the radius of curvature Rp is Rpn, and the center point of the radius of curvature Rpn is Ppn, The amount of positional deviation from the center point Ppn is the correction value C,
When the correction value C is Td, which is the temperature rise from the room temperature Tn to the vulcanization temperature Tv, the correction value C is 0.5 to 1.5 times the deviation amount β calculated by the following formula. Mold for sulfur molding.
β = Rpn · Td · (αg−αp)   The mold according to claim 1, wherein the correction value C is not less than 0.7 times and not more than 1.3 times the deviation amount β. The segment is made of an aluminum alloy,
The mold according to claim 1 or 2, wherein the side plate is made of steel. When the radius of curvature Rg is Rgn at room temperature Tn, the radius of curvature Rg is Rgv at the vulcanization temperature Tv, and the radius of curvature Rp is Rpv,
The absolute value of the difference between the curvature radius Rgv and the curvature radius Rpv at the vulcanization temperature Tv is equal to or less than the absolute value of the difference between the curvature radius Rgn and the curvature radius Rpn at room temperature Tn. A mold for vulcanization molding of a tire according to claim 1. A preforming step in which a raw cover is obtained by combining members constituting each part of the tire;
A vulcanization step in which the raw cover is put into a mold and vulcanized to obtain the tire; and
The mold for the vulcanization step includes a plurality of segments arranged in a ring shape in the circumferential direction, and a side plate positioned radially inward of the plurality of segments,
The inner peripheral surface of each segment includes a segment cavity surface that forms the tread surface of the tire, and a segment contact surface that contacts the side plate,
In a cross section perpendicular to the axial direction, the shape of the segment cavity surface is an arc shape with a radius of curvature Rt, and the shape of the segment contact surface is an arc shape with a radius of curvature Rg,
The side plate includes a side cavity surface that molds an axially outer side surface of the tire, and an outer peripheral abutment surface that abuts the segment abutment surface,
In the cross section perpendicular to the axial direction, the shape of the outer peripheral contact surface is a circle having a radius of curvature Rp,
The linear expansion coefficient αg of the segment is different from the linear expansion coefficient αp of the side plate,
At room temperature Tn, when the radius of curvature Rt is Rtn, the center point of the radius of curvature Rtn is Ptn, the radius of curvature Rp is Rpn, and the center point of the radius of curvature Rpn is Ppn, The amount of positional deviation from the center point Ppn is the correction value C,
The correction value C is not less than 0.5 times and not more than 1.5 times the deviation amount β calculated by the following equation, where Td is the rising temperature from the room temperature Tn to the vulcanization temperature Tv.
Tire manufacturing method.
β = Rpn · Td · (αg−αp) A plurality of segments arranged in a ring shape in the circumferential direction, and a side plate positioned radially inward of the plurality of segments;
Each segment has a segment cavity surface that forms the tread surface of the tire, and a segment contact surface that contacts the side plate,
In a cross section perpendicular to the axial direction, the shape of the segment cavity surface is an arc shape with a radius of curvature Rt, and the shape of the segment contact surface is an arc shape with a radius of curvature Rg,
The side plate includes a side cavity surface that molds an axially outer side surface of the tire, and an outer peripheral contact surface that contacts the segment contact surface,
In the cross section perpendicular to the axial direction, the shape of the outer peripheral contact surface is a circle having a radius of curvature Rp,
The linear expansion coefficient αg of the segment is different from the linear expansion coefficient αp of the side plate,
At room temperature Tn, the radius of curvature Rt is Rtn, the center point of the radius of curvature Rtn is Ptn, the radius of curvature Rp is Rpn, the center point of the radius of curvature Rpn is Ppn,
At the vulcanization temperature Tv, when the radius of curvature Rt is Rtv, the center point of the radius of curvature Rtv is Ptv, the radius of curvature is Rp is Rpv, and the center point of the radius of curvature Rpv is Pvv,
A mold for vulcanization molding of a tire, wherein a displacement amount between the center point Ptv and the center point Ppv at a vulcanization temperature Tv is equal to or less than a displacement amount between the center point Ptn and the center point Ppn at room temperature Tn.

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