JP2018099805A - Mold for manufacturing tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mold for a tire having a sipe, in which a breakage of a blade is suppressed and a tire with reduced RFV can be manufactured.SOLUTION: The present invention relates to a mold 16 for manufacturing a tire 2 in which a sipe 14 is engraved. A segment 18 of this mold 16 comprises a main body 30 and a plurality of blades 32 for forming a sipe 14. Each blade 32 is located on an inner surface of the main body 30. The plurality of blades 32 have an end blade 32a extending to a circumferential end of the main body 30. On the inner surface of the main body 30, a projection 46 extending to an end in the circumferential direction of the main body 30 is provided. The circumferential end portion of the end blades 32a or the entire end blades 32a is positioned above the projection 46.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a mold for manufacturing a tire. More specifically, the present invention relates to a mold for manufacturing a tire having a sipe engraved on a tread surface.

  A mold for manufacturing a tire includes a plurality of segments whose inner surface is in contact with a tread of a raw cover (an unvulcanized tire). The planar shape of the segment is substantially an arc. A plurality of segments are connected in the circumferential direction to form a ring-shaped cavity surface.

  In tires for running on snowy and snowy roads, a large number of elongated grooves (sipes) may be carved on the tread surface in order to improve grip on ice. In a mold for manufacturing a tire with a sipe carved therein, the segment includes a main body and a plurality of blades for forming the sipe. The blade is located on the inner surface of the main body. The shape of the blade corresponds to the shape of the sipe. The examination about the mold provided with a blade is disclosed by Unexamined-Japanese-Patent No. 2009-113291.

JP 2009-113291 A

  If the blade is provided up to the circumferential end of the segment (that is, the boundary position with the adjacent segment), the blade may be damaged. For this reason, in the conventional segment, the braid | blade was not provided in the vicinity of the edge of the circumferential direction. In the tire formed by this mold, no sipe is formed in the vicinity of the position corresponding to the segment boundary in the tread. For this reason, in the tread, the rigidity in the vicinity of the position corresponding to the segment boundary is larger than the surrounding area. If this difference in rigidity can be reduced, radial force variation (RFV) can be further reduced.

  It is an object of the present invention to provide a mold for a tire having a sipe, in which a tire with reduced RFV can be manufactured while blade breakage is suppressed.

  The present invention relates to a mold for manufacturing a tire having a plurality of sipes engraved on its tread surface. The mold includes a plurality of segments whose inner surfaces are in contact with the tread of the raw cover. Each segment includes a main body and a plurality of blades for forming the sipe. Each blade is located on the inner surface of the body. The plurality of blades have end blades extending to the circumferential ends of the main body. On the inner surface of the main body, a ridge extending to the end in the circumferential direction of the main body is provided. The part of the end blade in the circumferential direction of the end blade or the entire end blade is located on the ridge.

  Preferably, the thickness T of the protrusion is 0.5 mm or more and 1.5 mm or less.

  Preferably, the length L of the protrusion is 3 mm or more and 6 mm or less.

  In this mold, there is an end blade that extends to the circumferential end of the segment body. A sipe is also formed in the vicinity of the position corresponding to the boundary between adjacent segments in the tread. In the tire manufactured with this mold, the difference in rigidity between the position corresponding to the boundary of the segment and the periphery thereof is suppressed. In this tire, a small RFV is realized. In this mold, a protrusion that extends to the end in the circumferential direction of the main body is provided on the inner surface of the main body. The part of the end blade in the circumferential direction or the entire end blade is located on the protrusion. With this structure, the end blade is also prevented from being damaged. In this mold, blade breakage is suppressed.

FIG. 1 is a development view showing a part of a tread surface of a tire in which a sipe is carved. FIG. 2 is a plan view illustrating a mold according to an embodiment of the present invention. FIG. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a cross-sectional view showing the segment of FIG. FIG. 5 is a perspective view showing the blade of FIG. FIG. 6 is a side view showing the blade of FIG. FIG. 7 is a front view showing an end of the blade 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 part of a tire 2 manufactured by a mold according to the present invention. This figure is a part of a development view of the tread surface 4 of the tire 2. In FIG. 1, the direction indicated by the double arrow A is the circumferential direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the radial direction of the tire 2. The tire 2 is for running on icy and snowy roads.

  In the tire 2, the tread 6 has a plurality of main grooves 8. Each of these main grooves 8 extends substantially in the circumferential direction. The tread 6 further includes a plurality of lateral grooves 10. These lateral grooves 10 extend substantially in the axial direction. In the tread 6, a region divided by the main groove 8 and the lateral groove 10 is referred to as a block 12. A plurality of blocks 12 are formed on the tread 6. The surface of each block 12 forms part of the tread surface 4.

  A plurality of zigzag elongated grooves (sipes 14) are formed on the surface of each block 12. The sipe 14 is provided over almost the entire surface of the block 12. As shown in the figure, the length of the sipe 14 is not constant. There are sipe 14 of various lengths. The sipe 14 contributes to an improvement in grip force on ice.

  As will be described later, the mold for manufacturing the tire 2 includes a plurality of segments for forming the tread surface 4. In FIG. 1, a dotted line BL is a position that was a boundary between two adjacent segments when the tire 2 was vulcanized. As shown in the figure, in the tire 2, the sipe 14 is also carved in the vicinity of the segment boundary position BL. There is a sipe 14 extending to the boundary position BL. As shown in FIG. 1, in this sipe 14, the width of the portion in contact with the boundary position BL is wider than the width of other portions. This portion is referred to as a boundary portion 14a of the sipe 14. For example, the width of the boundary portion 14a of the sipe 14 is 1.0 mm, and the width of the other portion of the sipe 14 is 0.5 mm.

  FIG. 2 is a plan view showing a mold 16 according to an embodiment of the present invention. In FIG. 2, the direction indicated by the double arrow A is the circumferential direction of the tire 2 manufactured by the mold 16, and the direction perpendicular to the paper surface is the axial direction of the tire 2. FIG. 3 is a cross-sectional view taken along line III-III in FIG. In FIG. 3, the vertical direction is the axial direction of the tire 2, the horizontal direction is the radial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. FIG. 3 also shows a raw cover R (unvulcanized tire).

  The mold 16 includes a plurality of segments 18, a pair of upper and lower side plates 20, and a pair of upper and lower bead rings 22. In FIG. 3, the mold 16 is closed. In this state, the inner surface 24 of the segment 18, the inner surface 26 of the side plate 20, and the inner surface 28 of the bead ring 22 are combined to form a cavity surface. The cavity surface is in contact with the raw cover R and forms the outer surface of the tire 2.

  As shown in FIG. 3, the inner surface 24 of each segment 18 abuts on the tread 6 of the raw cover R. The inner surface 24 of the segment 18 forms the tread surface 4 of the tire 2. In this figure, a protrusion for forming a groove in the tread 6, which will be described later, is omitted. As shown in FIG. 2, the planar shape of the segment 18 is substantially arcuate. A plurality of segments 18 are connected in the circumferential direction. A plurality of segments 18 are arranged in a ring shape. The circumferential end of the segment 18 is in contact with the circumferential end of the segment 18 adjacent thereto. The end of the segment 18 in the circumferential direction is the boundary position BL. In this embodiment, nine segments 18 are arranged. In this embodiment, there are nine boundary positions BL of the segment 18. The number of segments 18 need not be nine. The number of segments 18 may be more or less than nine.

  As shown in FIG. 3, the inner surface 26 of each side plate 20 comes into contact with the side portion of the raw cover R. The inner surface 26 of the side plate 20 forms the outer surface of the side portion of the tire 2.

  As shown in FIG. 3, the inner surface 28 of each bead ring 22 contacts the bead portion of the raw cover R. The inner surface 28 of the bead ring 22 forms the outer surface of the bead portion of the tire 2. The bead ring 22 is fixed to the side plate 20.

  In FIG. 4, a cross section of the segment 18 is shown. The segment 18 includes a main body 30 and a plurality of blades 32. The inner surface of the main body 30 includes a protrusion 34 for forming the main groove 8 and the lateral groove 10 and a bottom 36 for forming the block 12. The blade 32 is located on the bottom 36. The sipe 14 is formed by the blade 32. As shown in FIG. 1, a plurality of sipes 14 are formed on the block 12. Correspondingly, a plurality of blades 32 are provided on the bottom 36.

  FIG. 5 shows the blade 32 in an enlarged manner. In this figure, a part of the main body 30 is also shown. As described above, a plurality of blades 32 are located on the bottom portion 36, but only one of the blades 32 is shown in the figure. The blade 32 has a zigzag shape in a top view corresponding to the zigzag sipe 14. The blade 32 has a plate shape bent in a zigzag manner. The tip of this bend is called the top 38. The blade 32 of FIG. 5 has six tops 38. The thickness of the blade 32 is typically 0.3 mm to 1.3 mm. A typical blade 32 material is steel.

  As described above, the sipe 14 extending to the boundary position BL of the segment 18 exists in the tire 2 manufactured by the mold 16. Correspondingly, the bottom 36 has a blade 32 extending to the circumferential end 44 of the segment 18 (ie, the boundary position BL). This blade 32 is referred to as an end blade 32a. The end of the end blade 32a on the boundary position BL side is referred to as an outer end 40. The other end of the end blade 32 a is referred to as an inner end 42. The blade 32 of FIG. 5 extends to the circumferential end 44 of the segment 18. The blade 32 in FIG. 5 extends to the boundary position BL. This blade 32 is an end blade 32a.

  FIG. 6 is a side view of the end blade 32a of FIG. This is a view of the end blade 32a as viewed from a direction perpendicular to a straight line (straight line M in FIG. 5) connecting the even-numbered apexes 38 counted from the outer end 40 of the blade 32a. FIG. 7 is a view of the outer end 40 of the end blade 32 a as viewed from the front of the outer end 40. This is a view of the outer end 40 of the end blade 32 a as viewed from the direction of a straight line connecting the outer end 40 and the next top portion 38 of the outer end 40. A part of the main body 30 is also shown in FIGS.

  As shown in FIG. 5-7, a protrusion 46 extending to the circumferential end 44 (boundary position BL) of the main body 30 is provided on the inner surface of the main body 30. As shown in FIGS. 5 and 6, the circumferential end portion of the end blade 32 a is located on the upper side of the protrusion 46 (on the opposite side to the bottom 36 side). A portion of the end blade 32a located on the protrusion 46 is referred to as an outer portion 48 of the end blade 32a. In the example of FIGS. 5 and 6, the portion from the outer end 40 of the end blade 32 a to the first top 38 is located on the ridge 46. In the end blade 32 a, a portion from the outer end 40 to the first top portion 38 is an outer portion 48. The ridge 46 extends along the outer portion 48 located thereon. In the example of FIGS. 5-6, the ridge 46 extends from the lower side (the bottom 36 side) of the outer end 40 to the lower side of the first top 38. As shown in FIG. 7, the thickness of the protrusion 46 is larger than the thickness of the end blade 32a.

  In FIG. 6, the double arrow Hb is the height of the blade 32 measured from the bottom 36. The height Hb is a distance between the bottom portion 36 and the upper end of the blade 32. The height Hb corresponds to the depth of the sipe 14 formed by the blade 32 and the protrusion 46. As shown in the figure, the height Hb does not change between the outer portion 48 and portions other than the outer portion 48.

  The outer portion 48 may have a bend. For example, the outer portion 48 may be a portion from the outer end 40 to the second top portion 38. At this time, the ridge 46 positioned below the outer portion 48 also has a bend. The outer portion 48 may be zigzag shaped. At this time, the protrusion 46 located under the outer portion 48 also has a zigzag shape. The entire end blade 32 a may be located on the protrusion 46. At this time, the entire end blade 32 a is the outer portion 48.

  The boundary portion 14 a of the sipe 14 described above is a portion formed by the outer portion 48 of the end blade 32 a and the protrusion 46 below it. The width of the boundary portion 14 a of the sipe 14 on the tread surface 4 is determined by the thickness of the protrusion 46. As described above, since the thickness of the protrusion 46 is larger than the thickness of the end blade 32a, the width of the boundary portion 14a of the sipe 14 is larger than the width of other portions on the tread surface 4. The width of the boundary portion is larger than the width of the other portion by the height of the protrusion 46 from the tread surface 4 in the depth direction.

  Below, the effect of this invention is demonstrated.

  If the blade is provided up to the end of the segment in the circumferential direction (boundary position BL), the blade may be damaged. For this reason, in the conventional segment, the braid | blade was not provided in the vicinity of the edge of the circumferential direction. In the tire formed of this mold, no sipe is formed in the vicinity of the position corresponding to the boundary position BL in the tread. For this reason, in the tread, the rigidity in the vicinity of the position corresponding to the segment boundary is larger than the surrounding area. If this difference in rigidity can be reduced, radial force variation (RFV) can be further reduced. For example, as shown in FIG. 2, when nine boundary positions BL exist, nine portions having higher rigidity than the surroundings exist in the tread. These rigidity differences particularly affect the 9th-order component of RFV (the 9th-order harmonic component when the RFV waveform is Fourier-expanded, expressed as RFV9H). RFV9H can be reduced by reducing the difference between these stiffnesses.

  In the mold 16, there is an end blade 32 a extending to the end 44 in the circumferential direction of the main body 30 of the segment 18. A sipe 14 is also formed in the vicinity of the position corresponding to the boundary position BL in the tread 6. In the tire 2 manufactured with this mold 16, the difference in rigidity between the position corresponding to the boundary position BL of the segment 18 and its periphery is suppressed. In the tire 2, a small RFV is realized.

  In the mold 16, a protrusion 46 extending to the end in the circumferential direction is provided on the inner surface of the main body 30. A portion of the end blade 32 a on the end side in the circumferential direction or the entire end blade 32 a is located on the protrusion 46. The protrusion 46 effectively prevents the end blade 32a from being damaged. This structure prevents the end blade 32a from being damaged. In the mold 16, damage to the blade 32 is suppressed.

  In this mold 16, since the breakage of the end blade 32a is suppressed, the position of the sipe 14 can be determined without considering the boundary position BL. This mold 16 improves the degree of freedom in designing the sipe 14.

  In FIG. 7, the double arrow T is the thickness of the protrusion 46. The thickness T is preferably 0.5 mm or more. By setting the thickness T to 0.5 mm or more, the end blade 32a is effectively prevented from being damaged by the damage of the protrusion 46. In this respect, the thickness T is more preferably equal to or greater than 0.7 mm. The thickness T is preferably 1.5 mm or less. By setting the thickness T to 1.5 mm or less, the boundary portion 14a of the sipe 14 formed by the protrusion 46 is not easily noticeable. In the tire 2, an excellent appearance is maintained. In this respect, the thickness T is more preferably equal to or less than 1.3 mm. From the viewpoint of preventing damage to the end blade 32a and the appearance of the tire 2, the thickness T is more preferably 1.0 mm.

  5 and 6, the double arrow L is the length of the protrusion 46. This length L is measured along the extending direction of the protrusion 46. That is, when the protrusion 46 has a zigzag shape, the length L is measured along the zigzag. The length L is preferably 3.0 mm or more. By setting the length L to 3.0 mm or more, the protrusion 46 effectively prevents the end blade 32a from being damaged. In this respect, the length L is more preferably 3.5 mm or more. The length L is preferably 6.0 mm or less. By setting the length L to 6.0 mm or less, the boundary portion 14a of the sipe 14 formed by the protrusion 46 is not easily noticeable. In the tire 2, an excellent appearance is maintained. In this respect, the length L is more preferably equal to or less than 5.0 mm. From the viewpoint of preventing damage to the end blade 32a and the appearance of the tire 2, the length L is more preferably 4.5 mm.

  In FIG. 6, the double arrow Hr is the height of the protrusion 46. The height Hr is a distance between the bottom portion 36 and the upper end of the protrusion 46. The height Hr is preferably 1.5 mm or more. By setting the height Hr to 1.5 mm or more, the protrusion 46 effectively prevents the end blade 32a from being damaged. In the mold 16, damage to the blade 32 is suppressed. In this respect, the height Hr is more preferably equal to or greater than 2.0 mm. The height Hr is preferably 5.0 mm or less. Of the boundary portion 14 a of the sipe 14, the portion formed by the protrusion 46 is wider than the other portions. By setting the height Hr to 5.0 mm or less, the depth of the wide portion at the boundary portion 14a of the sipe 14 is suppressed. The sipe 14 effectively contributes to the grip force on ice. In the tire 2, an excellent grip force on ice is realized. From the viewpoint of preventing damage to the end blade 32a and gripping force on ice, the height Hr is more preferably 2.5 mm.

  The ratio of the height Hr to the height Hb (Hr / Hb) is preferably 0.2 or more. By setting the ratio (Hr / Hb) to be 0.2 or more, the protrusion 46 effectively prevents the end blade 32a from being damaged. In the mold 16, damage to the blade 32 is suppressed. In this respect, the ratio (Hr / Hb) is more preferably equal to or greater than 0.3. The ratio (Hr / Hb) is preferably 0.7 or less. By setting the ratio (Hr / Hb) to be 0.7 or less, the depth of the wide portion of the boundary portion 14a of the sipe 14 is suppressed. The sipe 14 effectively contributes to the grip force on ice. In the tire 2, an excellent grip force on ice is realized.

  The height Hb is preferably 4 mm or more. By setting the height Hb to 4 mm or more, the sipe 14 formed by the blade 32 effectively contributes to improvement of the grip force on ice. In the tire 2, an excellent grip force on ice is realized. In this respect, the height Hb is more preferably 5 mm or more. The height Hb is preferably 10 mm or less. By setting the height Hb to 10 mm or less, the influence of the sipe 14 formed by the blade 32 on the wear resistance of the tread 6 is suppressed. In the tire 2, excellent wear resistance is maintained. In this respect, the height Hb is more preferably 8 mm or less.

  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. 2-7 was prepared. This mold has nine segments. The specifications for this segment are shown in Table 1. The segment includes an end blade and a ridge located under the end blade. The height Hr of the ridge was set to 2.5 mm. The height Hb of the blade was 7 mm. The width of the blade was 0.4 mm.

[Comparative Example 1]
The mold of Comparative Example 1 does not include an end blade. Therefore, it does not have a ridge located under the end blade. The mold is the same as the mold of Example 1 except for this. This is a conventional mold.

[Comparative Example 2]
The mold of Comparative Example 2 includes an end blade, but does not include a protrusion located below the end blade. The mold is the same as the mold of Example 1 except for this.

[Example 2-4]
A mold of Example 2-4 was prepared in the same manner as Example 1 except that the thickness T of the protrusions was as shown in Table 1.

[Example 5-7]
A mold of Example 5-7 was prepared in the same manner as in Example 1 except that the length L of the protrusions was as shown in Table 2.

[RFV]
Tires were prototyped using the molds of the examples and comparative examples. Twenty tires were created for each example and comparative example. The tire size was 185 / 65R15. For these tires, radial force variation (RFV) was measured in accordance with the conditions of the uniformity test specified in “JASO C607: 2000”. The average of the 9th-order components was calculated for 20 measured RFVs. The results are shown in the column of “RFV9H” in Table 1 below, using an index with Comparative Example 1 being 100. A smaller numerical value is preferable.

[appearance]
About the tire manufactured by evaluation of said RFV, the external appearance was evaluated in the following four steps by visual observation.
A: Very good with little influence on the appearance of the sipe boundary.
B: Good although there is some influence on the appearance of the boundary part of the sipe.
C: The influence on the appearance of the boundary part of the sipe is conspicuous.
D: The influence on the appearance of the boundary part of the sipe is conspicuous.
The results are shown in Table 1-2. “A”, “B”, “C”, “D” are preferable in this order.

[Blade damage prevention]
About the mold which manufactured the tire by the said RFV evaluation, the presence or absence of damage of a braid | blade was confirmed visually. The results were evaluated in the following four stages.
A: No damage to the blade.
B: Although the blade is slightly damaged, it is not a problem.
C: Although the blade is broken, the standard is satisfied.
D: The blade is broken and does not satisfy the standard.
The results are shown in Table 1-2. “A”, “B”, “C”, “D” are preferable in this order.

  As shown in Table 1-2, the examples have higher evaluations than the comparative examples. From this evaluation result, the superiority of the present invention is clear.

  The technology according to the present invention can be applied to the manufacture of various tires having sipes.

2 ... tyre 4 ... tread surface 6 ... tread 8 ... main groove 10 ... lateral groove 12 ... block 14 ... sipe 14a ... sipe boundary 16 ... mold 18 ... Segment 20 ... Side plate 22 ... Bead ring 24 ... Inner surface of segment 26 ... Inner surface of side plate 28 ... Inner surface of bead ring 30 ... Main body 32 ... Blade 32a ... End blade 34 ... Projection 36 ... Bottom 38 ... Top 40 ... Blade outer end 42 ... Blade inner end 44 ... Segment end 46 ... Projection Article 48 ... Outer part of end blade

Claims (3)

A mold for manufacturing a tire having a plurality of sipes engraved on its tread surface,
The mold includes a plurality of segments whose inner surfaces are in contact with the tread of the raw cover,
Each segment includes a body and a plurality of blades for forming the sipe,
Each blade is located on the inner surface of the body,
In the plurality of blades, there is an end blade extending to an end in the circumferential direction of the main body,
On the inner surface of the main body, a ridge extending to the end in the circumferential direction of the main body is provided,
A tire mold in which a circumferential end portion of the end blade or the entire end blade is located on the ridge.   The mold for tire according to claim 1, wherein a thickness T of the protrusion is 0.5 mm or more and 1.5 mm or less.   The mold for tire according to claim 1 or 2, wherein a length L of the protrusion is 3 mm or more and 6 mm or less.

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