Tire vulcanizing mold

Abstract

To provide a tire molding mold which prevents a gap from occurring between a mounting part and an etching plate after mounting the etching plate in a tire vulcanizing mold having the etching plate, thereby preventing defects in a tire appearance.SOLUTION: A tire vulcanizing mold includes a mold body 30 having a molding surface for forming a sidewall part, and an etching plate 32 that is detachably attached to the mold body 30. The etching plate 32 is curved in an arc shape along a tire circumferential direction and has a pair of through holes 32t at both ends in a longitudinal direction for attaching fixing screws 33, the mold body 30 has a mounting part 31 to which the etching plate 32 is attached, the mounting part 31 has a pair of screw holes 31t at positions corresponding to the pair of through holes 32t, a center-to-center distance ET of the through holes 32t is larger than the center-to-center distance MT of the screw holes 31t, and a difference between these distances ET and MT is 0.25% to 1.4% of the distance MT.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a tire vulcanization mold for forming a tire having a marking on the outer surface of the sidewall portion, in which the marking is transferred and formed using an etching plate. [Background technology]

[0002] Indications depicting letters, figures, or symbols may be provided on the outer surface of the sidewall of a tire to display various information such as the type, size, load index, ply rating, date of manufacture, and product number of the tire. These indications may be changed as appropriate depending on the tire to be manufactured, and a method of forming such indications using a thin metal plate (called an etching plate, a serial plate, a stencil plate, or the like) having an inscribed portion with a shape that is the inverse of the indication is known (see, for example, Patent Document 1). As described above, the etching plate is provided with an inscribed portion with a shape that is the inverse of the indication, and this transfers and forms the indication on the outer surface of the tire. In addition, the etching plate is detachably attached to a mounting portion provided on the tire molding surface (a surface for molding the outer surface of the sidewall of the tire) of a tire vulcanization mold by a method such as screwing, so that it can be replaced as appropriate. However, since the tire molding surface is a curved surface corresponding to the toroidal shape of the tire, when a thin plate-like etching plate is attached, a gap tends to easily occur between the mounting portion and the etching plate after attachment, and when such a gap occurs, there is a problem that the tire appearance is deteriorated due to overflow. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-055897 A Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to provide a tire molding mold having an etching plate, which makes it possible to prevent a gap from occurring between an attachment portion and the etching plate after the etching plate is attached, thereby preventing defects in the appearance of the tire. [Means for solving the problem]

[0005] In order to achieve the above object, the tire molding mold of the present invention is a tire vulcanization mold for forming a tire having a marking depicting a letter, a figure, or a symbol on the outer surface of a sidewall portion, the tire vulcanization mold comprising: a mold body having a molding surface for forming the sidewall portion; an etching plate that is detachably attached to the mold body for transferring and forming the marking; and a fixing screw for attaching the etching plate to the mold body, the etching plate having a longitudinal shape curved in an arc along the tire circumferential direction, and a pair of through holes for attaching the fixing screws are formed at both ends in the longitudinal direction, the mold body having an attachment portion to which the etching plate is attached, and a pair of screw holes are formed in the attachment portion at positions corresponding to the pair of through holes, the center-to-center distance ET of the through holes of the etching plate when not attached to the attachment portion is greater than the center-to-center distance MT of the screw holes, and the difference between the center-to-center distance ET of the through holes and the center-to-center distance MT of the screw holes is 0.25% to 1.4% of the center-to-center distance MT of the screw holes. Effect of the Invention

[0006] The inventors of the present invention have studied intensively a mounting method for preventing a gap between an etching plate and a mounting portion when mounting an etching plate in a tire molding die equipped with the etching plate, and have found that the aforementioned gap can be suppressed by making the distance ET between the through holes of the etching plate larger than the distance MT between the screw holes of the mounting portion. Based on this finding, the present invention sets the distances ET and MT as described above, so that the dimension of the etching plate (distance ET) becomes an appropriate dimension that takes into account the curvature of the tire molding surface with respect to the distance MT between the screw holes, and it is possible to suppress the gap that occurs between the mounting portion and the etching plate after the etching plate is mounted. As a result, overflow caused by the gap between the mounting portion and the etching plate does not occur, and it is possible to prevent poor tire appearance.

[0007] In the present invention, when the radius of curvature of the contour of the etching plate on the tire inner diameter side when not attached to the mounting part is ER and the radius from the tire axial center of the lower end position of the mounting part where the end of the etching plate on the tire inner diameter side abuts when the etching plate is attached to the mounting part is MR, it is preferable that the radius of curvature ER is larger than the radius MR and the difference between the radius of curvature ER and the radius MR is 1.5% to 22% of the radius MR. This makes the dimension of the etching plate (distance ET) a more suitable dimension taking into account the curvature of the tire molding surface with respect to the distance MT between the screw holes, which is advantageous in preventing poor tire appearance.

[0008] In the present invention, it is preferable that the angle C of the molding surface at the position where the screw hole is formed with respect to the tire radial direction is 10° or more. That is, since the above-mentioned gap becomes particularly noticeable when the angle C in the mold is large, applying the above-mentioned present invention to such a mold can more effectively prevent defective appearance of the tire.

[0009] In the present invention, it is preferable that the center distance MT of the screw holes is 120 mm or more. That is, when the center distance MT of the screw holes in the mold is large, the above-mentioned gap becomes particularly noticeable, so by applying the above-mentioned present invention to such a mold, it is possible to more effectively prevent defects in the appearance of the tire.

[0010] In the present invention, the plate height EH measured in a direction perpendicular to the longitudinal direction of the etching plate is preferably 20 mm or less. That is, when the plate height EH of the etching plate is small, the above-mentioned gap becomes particularly noticeable, so that by applying the above-mentioned present invention to such a mold, it is possible to more effectively prevent defects in the appearance of the tire. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is an explanatory diagram showing an example of a tire vulcanizing apparatus. [Diagram 2] FIG. 2 is an explanatory view showing a main part of the tire vulcanization mold of the present invention (with an etching plate attached). [Diagram 3] FIG. 2 is a front view showing a state in which the etching plate of the present invention is not attached to the mounting portion. [Figure 4] FIG. 2 is an explanatory view showing the mold body (near the mounting portion) in the tire vulcanization mold of the present invention. [Diagram 5] FIG. 4 is a schematic diagram illustrating an angle of a molding surface at an attachment portion (a position where a screw hole is formed) with respect to the tire radial direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The configuration of the present invention will be described in detail below with reference to the accompanying drawings.

[0013] FIG. 1 shows an example of a tire vulcanizing apparatus including a tire vulcanizing mold (hereinafter, sometimes simply referred to as a "mold") of the present invention. The tire vulcanizing apparatus includes a mold 10 for molding the outer surface of a tire T, and a cylindrical bladder 20 inserted inside the tire T. The tire vulcanizing apparatus also includes a heating and pressurizing medium supplying means (not shown) for supplying a heating and pressurizing medium such as steam into the bladder 20, and a heating means (not shown) for heating the mold 10. Note that the present invention relates to a tire molding mold for molding a tire having a display depicting characters, figures, or symbols on the outer surface of the tire sidewall portion, so the tire vulcanizing apparatus is not limited to the example shown in the figure as long as it has a molding surface or an etching plate (described later) for molding the tire sidewall portion and the display.

[0014] The mold 10 is composed of a pair of side plates 11 (lower side plate 11A and upper side plate 11B) for molding the sidewall portion of the tire T, a pair of bead rings 12 (lower bead ring 12A and upper bead ring 12B) for molding the bead portion of the tire T, and a plurality of sectors 13 for molding the tread portion of the tire T, and the tire T is vulcanized and molded inside the mold 10.

[0015] The heating and pressurizing medium supplying means (not shown) is adapted to supply steam adjusted to a predetermined temperature and pressure and nitrogen gas adjusted to a predetermined pressure as the heating and pressurizing medium at appropriate times. When such a heating and pressurizing medium is introduced into the bladder 20, the tire T is pressed from the inside toward the inner surface of the mold 10 based on the pressure. It is also possible to use only steam as the heating and pressurizing medium.

[0016] Heating means (not shown) is attached to the lower side plate 11A, the upper side plate 11B and the sector 13 that constitute the mold 10, and the tire T is vulcanized by heating the mold 10 with the heating means.

[0017] In the tire vulcanizing apparatus thus configured, the tire molding mold (mold 10) of the present invention, for example, at least one of a pair of side plates 11 (lower side plate 11A and upper side plate 11B) for molding a sidewall portion, includes a mold body 30 constituting a main portion of the side plate 11, and an etching plate 32 attached to a mounting portion 31 provided on the mold body 30, as shown in FIG. 2. The etching plate 32 is detachably screwed to the mounting portion 31 by, for example, a fixing screw 33, as described later. Hereinafter, a case will be described in which the object (mold body 30) to which the etching plate 32 is attached is the side plate 11, but at least one of a pair of bead rings 12 (lower bead ring 12A and upper bead ring 12B) for molding a bead portion of the tire T may be the mold body 30 depending on the arrangement of the display object.

[0018] The etching plate 32 is a member for transferring and forming a marking on the sidewall of the tire, and is made of a metal plate having a longitudinal shape in which the length in the tire circumferential direction is longer than the length in the tire radial direction, as shown in FIG. 3. The etching plate 32 has a shape curved in an arc shape along the tire circumferential direction. One surface of the etching plate 32 is provided with unevenness (not shown) corresponding to the marking, and this unevenness is transferred to the tire surface after vulcanization molding, thereby forming the marking on the sidewall of the tire. The other surface of the etching plate 32 is a surface that contacts the mounting part 31 described later when the etching plate 32 is attached to the mold main body 30 (molding surface). A pair of through holes 32t for screw fastening is formed at both ends of the longitudinal direction of the etching plate 32. Since the through holes 32t are used for screw fastening as described later, it is preferable that they are round holes. The material of the etching plate 32 is not particularly limited, but stainless steel (SUS304, etc.) can be used, for example.

[0019] The thickness of the etching plate 32 is not particularly limited, but can be set to, for example, 0.8 mm to 1.5 mm. The length L of the etching plate 32 along the longitudinal direction is appropriately set according to the length of the display (for example, a character string) to be formed with the etching plate 32, but can be set to, for example, 60 mm to 300 mm. The length of the etching plate 32 along the lateral direction (plate height H measured along the direction perpendicular to the longitudinal direction) is preferably set to 20 mm or less.

[0020] The mold body 30 has a molding surface that forms the outer surface of the tire (the surface of the sidewall portion and the bead portion), and constitutes the main part of the side plate 11 (the lower side plate 11A and / or the upper side plate 11B). As shown in FIG. 4, the mold body 30 is provided with a mounting portion 31 to which the etching plate 32 is attached, and this mounting portion 31 has a pair of screw holes 31t formed at positions corresponding to a pair of through holes 32t of the etching plate 32. The mounting portion 31 can be formed as a recess (drilled) having a shape corresponding to the etching plate 32, so that the etching plate 32 can be fitted when attached (for example, a racing tire, etc.). However, since it is difficult to precisely fit the etching plate 32 into the recessed mounting portion 31, it is preferable that the mounting portion 31 is flat with respect to the molding surface of the mold body 30, as in the illustrated example. In other words, the attachment portion 31 is a virtual area (that is, the attachment position of the etching plate 32) estimated from the position of the screw hole 31t and the shape of the etching plate 32 to be attached (see the dashed line in the figure).

[0021] As shown in Fig. 2, the etching plate 32 is detachably attached to the mounting portion 31 via a fixing screw 33. More specifically, the fixing screw 33 is screwed into a screw hole 31t formed in the mounting portion 31 via a through hole 32t of the etching plate 32. As the fixing screw 33, any fastening element (screw, bolt, screw, etc.) having a shaft portion with a helical groove and a head portion provided at one end of the shaft portion can be used. In the present invention, the fixing screw 33 is preferably a countersunk screw having a tapered bottom surface of the head portion, and when fastened, the top surface of the head portion is preferably substantially flush with the molding surface of the die.

[0022] In the present invention, the center-to-center distance ET of the through holes 32t of the etching plate 32 before being attached to the attachment portion 31 is configured to be larger than the center-to-center distance MT of the screw holes 31t provided in the mold body 30 (attachment portion 31). Specifically, the difference between the center-to-center distance ET of the through holes 32t and the center-to-center distance MT of the screw holes 31t is set to 0.25% to 1.4% of the center-to-center distance MT of the screw holes 31t. By setting such dimensions, the dimension (distance ET) of the etching plate 32 becomes an appropriate dimension with the curvature of the tire molding surface taken into account with respect to the center-to-center distance MT of the screw holes 31t, and it is possible to suppress a gap occurring between the attachment portion 31 and the etching plate 32 after the etching plate 32 is attached. As a result, overflow caused by the gap between the attachment portion 31 and the etching plate 32 does not occur, and it is possible to prevent poor tire appearance.

[0023] In this case, if the difference between the center distance ET of the through holes 32t and the center distance MT of the screw holes 31t is less than 0.25% of the center distance MT of the screw holes 31t, there is no substantial difference between the distances ET and MT, and the above-mentioned effect cannot be sufficiently obtained. If the difference between the center distance ET of the through holes 32t and the center distance MT of the screw holes 31t exceeds 1.4% of the center distance MT of the screw holes 31t, the difference between the distances ET and MT becomes too large, making it difficult to properly attach the etching plate 32 to the attachment portion 31.

[0024] Furthermore, when the radius of curvature of the contour of the etching plate 32 on the tire inner diameter side when not attached to the attachment portion 31 is ER, and the radius from the tire axial center of the lower end position of the attachment portion 31 where the end of the etching plate 32 on the tire inner diameter side abuts when the etching plate 32 is attached to the attachment portion 31 is MR, it is preferable to make the radius of curvature ER larger than the radius MR. Specifically, the difference between the radius of curvature ER and the radius MR is preferably 1.5% to 22% of the radius MR. This makes the dimension of the etching plate (distance ET) more suitable for the distance MT between the screw holes 31t, taking into account the curvature of the tire molding surface, which is advantageous for preventing poor tire appearance. In particular, when grooves or protrusions extending around the entire tire circumference are present near the tire inner diameter side or outer diameter side of the attachment portion 31, it is possible to suppress the deviation between these grooves or protrusions and the contour of the etching plate 32 on the tire inner diameter side or outer diameter side, and to improve the tire appearance near the etching plate 32 (near the display formed by the etching plate 32).

[0025] In this case, if the difference between the radius of curvature ER and the radius of curvature MR is less than 1.5% of the radius of curvature MR, there is no substantial difference between the radius of curvature ER and the radius of curvature MR, and therefore the effect added by setting the radius of curvature as described above cannot be expected to be sufficient. If the difference between the radius of curvature ER and the radius of curvature MR exceeds 22% of the radius of curvature MR, the difference between the radius of curvature ER and the radius of curvature MR becomes too large, making it difficult to properly attach the etching plate 32 to the attachment portion 31.

[0026] In the mold 10 to which the above-mentioned configuration is applied, as shown in Fig. 5, when the angle C of the molding surface forming the outer surface of the sidewall portion at the position where the screw hole 31t is formed with respect to the tire radial direction is set, this angle C is preferably 10° or more, more preferably 10° to 35°. That is, since the above-mentioned gap becomes particularly noticeable when the angle C in the mold 10 is large, by applying the above-mentioned present invention to such a mold 10, it is possible to more effectively prevent defective appearance of the tire. The position where the screw hole 31t is formed is specifically the center position of the screw hole 31t, and the angle that the tangent to the inner surface of the mold at this position (the tangent to the mold cross section in Fig. 5) forms with the tire radial direction is "angle C".

[0027] Even if the angle C is smaller than the above-mentioned range, a gap may occur between the mounting portion 31 and the etching plate 32 after the etching plate 32 is attached, and the application of the present invention described above is effective in this case. On the other hand, in the case where the angle C is smaller than the above-mentioned range, it is possible to suppress the above-mentioned gap by making the center-to-center distance ET of the through holes 32t of the etching plate 32 in a state where the etching plate 32 is not attached to the mounting portion 31 smaller than the center-to-center distance MT of the screw holes 31t provided in the mold body 30 (mounting portion 31) (for example, by making it smaller by about 0.1%), contrary to the present invention described above.

[0028] The above-mentioned distances ET and MT are appropriately set according to the length of the display (e.g., character string) to be formed by the etching plate 32, but the center-to-center distance MT of the screw holes 31t formed in the mounting portion 31 is preferably 120 mm or more, and more preferably 150 mm to 300 mm. That is, since the above-mentioned gap becomes particularly noticeable when the center-to-center distance MT of the screw holes 31t in the mold body 30 (mounting portion 31) is large, applying the above-mentioned present invention to such a mold 10 can more effectively prevent defects in the appearance of the tire.

[0029] The present invention will be further described below with reference to examples, but the scope of the present invention is not limited to these examples. EXAMPLES

[0030] In a tire vulcanization mold equipped with an etching plate, the center-to-center distance ET of the through holes in the etching plate, the center-to-center distance MT of the screw holes formed in the mold body, the ratio of the difference between these distances to the distance MT ((ET-MT) / MT x 100%), the radius of curvature ER of the contour of the etching plate on the tire inner diameter side, the radius MR from the tire axial center at the lower end position of the mounting part where the end of the etching plate on the tire inner diameter side abuts when the etching plate is attached to the mounting part, the ratio of the difference between these radii of curvature to the radius MR ((ER-MR) / MR x 100%), the angle C of the molding surface at the position where the screw holes are formed with respect to the tire radial direction, and the plate height H measured in a direction perpendicular to the longitudinal direction of the etching plate were each varied as shown in Table 1 (Comparative Examples 1 to 3, Examples 1 to 3).

[0031] The size of the gap when the etching plate was attached to the mounting part of each of these tire curing molds was measured. The gap was measured at the longitudinal end and center of the etching plate at both the tire inner diameter side contour and the tire outer diameter side contour of the etching plate. In addition, three etching plates were prepared for each example, and the average of the measurements of these three plates was calculated. Table 1 shows the size of the gap at each part (average value, unit: mm).

[0032] [Table 1]

[0033] As is clear from Table 1, the molds of Examples 1 to 3 were able to prevent excessive gaps at the end and center of the tire inner diameter side and outer diameter side during installation, compared to Comparative Examples 1 to 3. On the other hand, the mold of Comparative Example 1 did not generate any gaps on the inner diameter side, but a significant gap occurred at the center of the outer diameter side. The mold of Comparative Example 2 generated significant gaps at the centers of both the inner diameter side and the outer diameter side (especially the center of the outer diameter side). The mold of Comparative Example 3 did not generate any gaps on the inner diameter side, but a significant gap occurred at the center of the outer diameter side.

[0034] The present disclosure includes the following inventions. Invention [1] A tire vulcanization mold for forming a tire having a marking depicting a letter, figure, or symbol on the outer surface of the sidewall portion, comprising: a mold body having a molding surface for forming the sidewall portion, an etching plate that is detachably attached to the mold body and transfers and forms the display object, and a fixing screw that attaches the etching plate to the mold body, the etching plate has a longitudinal shape curved in an arc shape along the tire circumferential direction, and a pair of through holes for attaching the fixing screws are formed at both ends in the longitudinal direction, the die body includes a mounting portion to which the etching plate is attached, and the mounting portion has a pair of screw holes formed at positions corresponding to the pair of through holes; A tire vulcanization mold, characterized in that the center-to-center distance ET of the through holes in the etching plate when not attached to the mounting portion is larger than the center-to-center distance MT of the screw holes, and the difference between the center-to-center distance ET of the through holes and the center-to-center distance MT of the screw holes is 0.25% to 1.4% of the center-to-center distance MT of the screw holes. Invention [2] A tire vulcanization mold according to invention [1], characterized in that, when a radius of curvature of the contour of the etching plate on the tire inner diameter side when not attached to the mounting portion is ER and a radius from the tire axial center of the lower end position of the mounting portion where the end of the etching plate on the tire inner diameter side abuts when the etching plate is attached to the mounting portion is MR, the radius of curvature ER is larger than the radius MR and a difference between the radius of curvature ER and the radius MR is 1.5% to 22% of the radius MR. Invention [3] A tire vulcanization mold according to invention [1] or [2], characterized in that an angle C of the molding surface at the position where the screw hole is formed with respect to the tire radial direction is 10° or more. Invention [4] The mold for vulcanizing tires according to any one of inventions [1] to [3], characterized in that the center-to-center distance MT of the screw holes is 120 mm or more. Invention [5] A tire vulcanization mold according to any one of inventions [1] to [4], characterized in that a plate height H measured in a direction perpendicular to the longitudinal direction of the etching plate is 20 mm or less. [Explanation of symbols]

[0035] 10. Mold 11 Side plate 12 Bead ring 13 Sectors 20 Bladder 30 Mold body 31 Mounting part 31t screw hole 32 Etching plate 32t through hole 33 Fixing screw

Claims

1. A tire vulcanization mold for forming a tire having a marking depicting a letter, a figure, or a symbol on an outer surface of a sidewall portion, a mold body having a molding surface for forming the sidewall portion, an etching plate that is detachably attached to the mold body and transfers and forms the display object, and a fixing screw that attaches the etching plate to the mold body, the etching plate has a longitudinal shape curved in an arc shape along the tire circumferential direction, and a pair of through holes for attaching the fixing screws are formed at both ends in the longitudinal direction, the die body includes a mounting portion to which the etching plate is attached, and the mounting portion is formed with a pair of screw holes at positions corresponding to the pair of through holes; a center-to-center distance ET of the through holes in the etching plate when the etching plate is not attached to the mounting portions is larger than a center-to-center distance MT of the screw holes, and a difference between the center-to-center distance ET of the through holes and the center-to-center distance MT of the screw holes is 0.25% to 1.4% of the center-to-center distance MT of the screw holes.

2. 2. The tire vulcanization mold according to claim 1, characterized in that, when a radius of curvature of a contour of the etching plate on the tire inner diameter side when the etching plate is not attached to the mounting portion is ER, and a radius from a tire axial center of a lower end position of the mounting portion with which an end of the etching plate on the tire inner diameter side abuts when the etching plate is attached to the mounting portion is MR, the radius of curvature ER is larger than the radius MR, and a difference between the radius of curvature ER and the radius MR is 1.5% to 22% of the radius MR.

3. 3. The tire vulcanization mold according to claim 1, wherein an angle C of said molding surface at a position where said screw hole is formed with respect to the tire radial direction is 10° or more.

4. 3. The mold for vulcanizing a tire according to claim 1, wherein a center-to-center distance MT of the screw holes is 120 mm or more.

5. 3. The tire vulcanization mold according to claim 1, wherein a plate height H measured in a direction perpendicular to the longitudinal direction of the etching plate is 20 mm or less.

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