JP2006281615A - Method for designing tire mold, tire mold, and method for molding tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To mold a pneumatic tire which can control noise. <P>SOLUTION: In a tire mold molding the pneumatic tire having grooves and blocks alternately in the tire circumference direction, the boundary line T between a block molding part molding the blocks and the tire mold is formed by L3 which is a part of a profile line in the tire circumference direction of an arc Q<SB>n-1</SB>P<SB>n</SB>Q<SB>n+1</SB>, a line L1 connecting a point Q<SB>n-1</SB>and a point H<SB>n-1</SB>, and a line L2 connecting a point Q<SB>n+1</SB>and a point H<SB>n+1</SB>. The point Q<SB>n-1</SB>is a position satisfying 0<arc P<SB>n</SB>Q<SB>n-1</SB>≤0.8×arc P<SB>n</SB>O<SB>n-1</SB>, the point Q<SB>n+1</SB>is a position satisfying 0<arc P<SB>n</SB>Q<SB>n+1</SB>≤0.8×arc P<SB>n</SB>O<SB>n+1</SB>, and the point H<SB>n-1</SB>and the point H<SB>n+1</SB>are positions satisfying 0.1×M/(2π)(1-cos(arc P<SB>n</SB>P<SB>n+1</SB>×π/M))≤straight line O<SB>n-1</SB>H<SB>n-1</SB>and straight line O<SB>n+1</SB>H<SB>n+1</SB>≤M/(2π)(1-cos(arc P<SB>n</SB>P<SB>n+1</SB>×π/M)). <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tire mold design method, a tire mold, and a tire molding method.

  In general, a pneumatic tire having a groove and a block partitioned by the groove is molded by a tire mold, and the shapes of the block molding part and the groove molding part of the tire mold are transferred. That is, the shape of the tread portion of the pneumatic tire at the time of deflation is obtained by transferring the shapes of the block molding portion and the groove molding portion of the tire mold. The boundary line between the block molding portion of the tire mold and the tire mold is the surface of the block when the molded pneumatic tire is deflated. This boundary line is formed such that the surface of the tread portion when the molded pneumatic tire is deflated is a circle in the tire circumferential direction. That is, the boundary line in the tire mold axial direction sectional view of the tire mold is formed so as to be positioned on the tire circumferential profile line. As a result, in the molded pneumatic tire, the surface of the block continuous in the tire circumferential direction in the tire axial direction sectional view is positioned on the tire circumferential profile line.

  Here, the pneumatic tire is normally used in a state of being filled with air, that is, in an inflated state, and the inflated pneumatic tire changes in the shape of the tread portion due to internal pressure. Therefore, even if the surface of the block constituting the tread portion of the pneumatic tire is on the tire circumferential profile line when viewed in the tire axial direction during deflation, the surface changes in the tire circumferential profile line. It will no longer be on top.

  In particular, the end of the block in the tire circumferential direction is deformed outward in the tire radial direction in the inflated state as compared with that during deflation. That is, the end of the block in the tire circumferential direction rises above the tire circumferential profile line when inflated. Accordingly, the surface of the tread portion in the inflated state of the molded pneumatic tire has a polygonal shape with the end of the raised block in the tire circumferential direction as a vertex.

  Therefore, conventionally, as shown in Patent Documents 1 to 3, a pneumatic tire that suppresses the rising of the end of the block in the tire circumferential direction in the inflated state, a tire mold for molding such a pneumatic tire, and the like Has been proposed.

JP-A 63-59504 JP-A-8-197910 Japanese Patent Laid-Open No. 7-101209

  By the way, when the surface of the tread portion is polygonal in the tire circumferential direction, hitting sound and vibration are generated when the end of the block that is the apex in the tire circumferential direction comes into contact with the road surface or leaves. Road noise due to the hitting sound and vibration is generated, which may cause noise.

  The present invention has been made in view of the above, and an object of the present invention is to provide a tire mold design method, a tire mold, and a tire molding method for molding a pneumatic tire that can suppress the generation of noise. And

In order to solve the above-described problems and achieve the object, the present invention provides a tire mold design method for a tire mold for forming a pneumatic tire having grooves and blocks alternately in the tire circumferential direction, In a cross-sectional view in the mold axial direction, a procedure in which a midpoint between adjacent groove forming portions that are located on the tire circumferential profile line and mold the groove is defined as _Pn, and from the midpoint _Pn to the adjacent point A procedure in which intersection points of the tire circumferential profile line extending toward the matching groove forming portion and the adjacent groove forming portion are set to On _-1 and On _{+ 1} , respectively, and located on the tire circumferential profile line and, and a step of a point between the middle point P _n and the intersection O _n-1 and Q _n-1, located in the tire circumferential direction profile line on, and the intersection with the middle point P _n a step of a point between the O n _{+ 1} and Q _{n + 1} A step of a point located on a line connecting the center of the intersection O _n-1 and the tire circumferential direction profile line and H _n-1, the center of the intersection O _{n + 1} and the tire circumferential direction profile line A procedure for setting a point located on the connecting line as H _{n + 1} , an arc Q _n-1 P _n Q _{n + 1} , a line L1 connecting the point Q _n-1 and the point H _n-1, and the point Q by a line L2 _{(n + 1)} and connecting the said point H _{n + 1,} comprises, a step of forming a boundary line T between the block forming portion and the tire mold for molding the block, arc P _n Q _n-1 , Arc P _n Q _{n + 1} , straight line O _n-1 H _n-1 , and straight line O _{n + 1} H _{n + 1} are within the ranges of the following formulas (1) to (3), respectively. . Here, M is the length of the tire circumferential profile line.

0 <arc P _n Q _n−1 ≦ 0.8 × arc P _n O _n−1 (1)
0 <arc P _n Q _{n + 1} ≦ 0.8 × arc P _n O _{n + 1} (2)
0.1 × M / (2π) (1-cos (arc P _n P _{n + 1} × π / M) ≦ straight line O _n−1 H _n−1 , straight line O _{n + 1} H _{n + 1} ≦ M / ( 2π) (1-cos (arc P _n P _{n + 1} × π / M) (3)

According to the present invention, in a tire mold for forming a pneumatic tire having grooves and blocks alternately in the tire circumferential direction, the groove is located on a tire circumferential profile line in a sectional view in the axial direction of the tire mold, and the groove A midpoint between adjacent groove forming portions that form a tire is defined as P _n , a tire circumferential profile line extending from the midpoint P _n toward the adjacent groove forming portion, and the adjacent groove forming portion, The intersection points are O _n-1 and O _{n + 1} , respectively, are located on the tire circumferential profile line, and satisfy 0 <arc P _n Q _n-1 ≦ 0.8 × arc P _n O _n-1 A point between the middle point P _n and the intersection point O _n-1 is defined as Q _n-1 , located on the tire circumferential profile line, and 0 <arc P _n Q _{n + 1} ≦ 0.8 × arc and Q _{n + 1} points between the middle point P _n satisfying P _n O n _{+ 1} and the intersection O _{n + 1} The length of the tire circumferential profile line is M, located on a line connecting the intersection On _-1 and the center of the tire circumferential profile line, and 0.1 × M / (2π) (1 −cos (arc P _n P _{n + 1} × π / M) ≦ straight line O _n−1 H _n−1 ≦ M / (2π) (1−cos (arc P _n P _{n + 1} × π / M) is satisfied The point is H _n−1 , located on a line connecting the intersection O _{n + 1} and the center of the tire circumferential profile line, and 0.1 × M / (2π) (1-cos (arc P _n P _{n + 1} × π / M) ≦ O _{n + 1} H _{n + 1} ≦ M / (2π) (1-cos (arc P _n P _{n + 1} × π / M) is defined as H _{n + 1} . In this case, the boundary line T between the block molding portion for molding the block and the tire mold is defined by an arc Q _n-1 P _n Q _{n + 1} , the point Q _n-1 and the point H _n-1 . line connecting line L1, and the point Q _{n + 1} connecting the said point H _{n + 1} Characterized in that it is formed by 2.

  Further, according to the present invention, there is provided a tire molding method, a procedure for molding a green tire, a procedure for loading a green tire into the tire mold (the tire mold according to claim 2), and a diameter of the green tire. The method includes a procedure of expanding outward in the direction and contacting the tire mold, and a procedure of heating and vulcanizing the green tire.

According to these inventions, the tire mold, the block molding portion, and the boundary line T are a curve L3 (arc Q _n-1 P _n Q _{n + 1} ) that is a part of the tire circumferential profile line, and this tire circumferential direction. Connect L1 (point Q _n-1 and point H _n-1) which is a line connecting one end of a part of the profile line and the groove forming portion located on one side in the tire circumferential direction of the block forming portion. Line), L2 (point Q _{n + 1} and point), which is a line connecting the other end of a part of the tire circumferential profile line and the groove forming portion located on the other side in the tire circumferential direction of the block forming portion H _{n + 1} ). Therefore, in the pneumatic tire molded in the tire mold, the tire circumferential direction on the surface of the block continuous in the tire circumferential direction is L3, which is a part of the tire circumferential profile line, and a part of the tire circumferential profile line. A line L1 that connects one end of the tire and a groove located on one side in the tire circumferential direction of the block and that is on the inner side in the tire radial direction from the tire circumferential profile line, and the other of a part of the tire circumferential profile line And a groove L located on the other side of the block in the tire circumferential direction is connected to a line L2 that is on the inner side in the tire radial direction of the tire tire circumferential profile line. As a result, in the inflated state of the pneumatic tire, the surface of the tread portion (the surface of the block continuous in the tire circumferential direction) in a cross-sectional view in the tire axial direction can be formed into a substantially circular shape. Generation | occurrence | production can be suppressed, generation | occurrence | production of the road noise resulting from this hit sound and vibration can be suppressed, and noise can be suppressed.

  The tire mold designing method, the tire mold, and the tire molding method according to the present invention provide an air that allows the surface of a block continuous in the tire circumferential direction in an inflated state to be substantially circular in a cross-sectional view in the tire axial direction. Since the entering tire can be molded, there is an effect that noise can be suppressed.

  Hereinafter, the present invention will be described in detail with reference to the drawings. The present invention is not limited to the following examples. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art or those that are substantially the same. Here, the pneumatic tire includes not only a pneumatic tire mounted on a passenger car or the like but also a heavy-duty pneumatic tire mounted on a truck, a bus or the like. Further, deflate refers to a state where no internal pressure is applied to the pneumatic tire. Inflation refers to a state in which a pneumatic tire is filled with a specified air pressure (air pressure specified in JATMA or the like) and an internal pressure is applied.

  First, a tire mold design method according to the present invention will be described. FIG. 1 is a view showing a configuration example of a tire mold according to the present invention. As shown in the figure, when designing the tire mold 1, first, the tire is the center of the mold, and the tire 10 (two-dot chain line in the figure) formed by the tire mold 1. A circle 2 serving as a circumferential profile line is determined (in the figure, a one-dot chain line). Next, based on the tread pattern of the tire 10 formed by the tire mold 1, the groove region portion 3 that forms a groove (lateral groove, lug groove, etc.) continuous in the tire circumferential direction in the tire axial direction sectional view is determined. . That is, the groove region portion 3 that is continuous in the tire mold circumferential direction in the tire mold axial section is determined. The groove region portion 3 projects from the circle 2 that is the tire circumferential profile line toward the inside in the radial direction of the tire mold, that is, toward the inside in the radial direction of the pneumatic tire 10 formed by the tire mold 1. It is formed. In addition, the groove | channel 11 continuous in the tire circumferential direction in the tread pattern of the tire 10 shape | molded with this tire metal mold | die 1 may be either equally spaced or unequal spaced.

Next, a midpoint between the adjacent groove region portions 3 and 3 located on the circle 2 serving as the tire circumferential profile line and adjacent to each other in the formed groove region portion 3 is determined as P _n . That is, in the tire mold 1, the groove region portions 3 and the midpoints P _n are alternately arranged in the tire mold circumferential direction.

Next, the intersection points of the circle 2 serving as a tire circumferential profile line extending from the midpoint P _n toward the adjacent groove forming portions 3 and 3 and the adjacent groove forming portions 3 and 3 are respectively O _{n−. 1} and determined as On _{+ 1} . That is, since the middle point P _n is located on the circle 2 that is the tire circumferential profile line and the groove forming portion 3 is formed from the circle 2 that is the tire circumferential profile line, the intersection points O _n-1 and O _{n + 1} is an intersection of the circle 2 and both ends of the groove forming portion 3 in the tire mold circumferential direction.

Next, positioned on the circle 2 of the tire circumferential direction profile line, and determines that Q _n-1 points between the middle point P _n and the intersection point O _n-1. That is, the point Q _n-1 is located on the arc P _n O _{n-1 in the} circle 2 serving as the tire circumferential profile line. Here, the position of this point Q _n-1 is determined so that the arc P _n Q _n-1 falls within the range of the following equation (4).

0 <arc P _n Q _n−1 ≦ 0.8 × arc P _n O _n−1 (4)

Next, positioned on the circle 2 of the tire circumferential direction profile line, and determines that Q _{n + 1} points between the middle point P _n and the intersection point O _{n + 1.} That is, the point Q _{n + 1} is located on the arc P _n O _{n + 1 in the} circle 2 that becomes the tire circumferential direction profile line. Here, the position of this point Q _{n + 1} is determined so that the arc P _n Q _{n + 1} falls within the range of the following equation (5).

0 <arc P _n Q _{n + 1} ≦ 0.8 × arc P _n O _{n + 1} (5)

Next, the intersection point O _n-1 and the line connecting the center (not shown) of the circle 2 which becomes the tire circumferential direction profile line to L _n-1 above decision, a point located on the line L _n-1 H Determine _n-1 . Here, the line L _n-1 forms one of both end portions in the tire mold circumferential direction of the groove forming portion 3. That is, the point H _n-1 is located on the end of the groove forming portion 3 in the tire mold circumferential direction.

Next, a line connecting the intersection O _{n + 1} and the center (not shown) of the circle 2 serving as the tire circumferential profile line is determined on L _{n + 1} , and a point located on this line L _n-1 is determined as H. Determine _{n + 1} . Here, the line L _{n + 1} forms the other of the end portions in the circumferential direction of the tire mold of the groove forming portion 3. That is, the point H _{n + 1} is located on the tire mold circumferential end of the groove forming portion 3.

Here, the positions of H _n-1 and H _{n + 1} are set so that the straight line O _n-1 H _n-1 and the straight line O _{n + 1} H _{n + 1} are within the range of the following equation (6). decide.

0.1 × M / (2π) (1-cos (arc P _n P _{n + 1} × π / M) ≦ straight line O _n−1 H _n−1 , straight line O _{n + 1} H _{n + 1} ≦ M / ( 2π) (1-cos (arc P _n P _{n + 1} × π / M) (6)

Next, an arc Q _n-1 P _n Q _{n + 1} , that is, a curve L3 that is a part of the circle 2 that is the tire circumferential profile line, a line L1 that connects the point Q _n-1 and the point H _n-1 , A boundary between the block molding portion 4 for molding the block 12 of the pneumatic tire 10 molded by the tire mold 10 and the tire mold 10 by a line L2 connecting the point Q _{n + 1} and the point H _{n + 1.} A line T is formed. Here, the lines L1 and L2 may be composed of one straight line or a plurality of straight lines. Further, the lines L1 and L2 may be configured with a curve having one radius of curvature, or may be configured with a curve having a plurality of curvature radii. The lines L1 and L2 may be configured by the straight line and the curve.

  Next, a method for manufacturing the tire 10 using the tire mold 1 will be described. First, green tires (green tires) are produced by a molding machine (not shown) using each member constituting the pneumatic tire 10 such as a belt, carcass, tread (cap tread, undertread, side tread), bead wire, etc. manufactured in the previous process. Tire). Next, this green tire is loaded into the tire mold 1. Next, the tire mold 1 loaded with the green tire is heated, and the green tire is expanded radially outward by a pressure device such as a bladder (not shown) to form the inner surface of the tire mold 1, that is, groove forming. It is made to contact | abut to the surface in which the part 3 and the block formation part 4 are formed.

Next, the green tire is heated and vulcanized by combining rubber molecules and sulfur molecules constituting the tread of the green tire. At this time, the shapes of the groove forming portion 3 and the block forming portion 4 of the tire mold 1 are transferred to the tread of the green tire. That is, the molded tire 10 is formed such that the shape of the surface 12a of the block 12 in the tire circumferential direction is the same as the boundary line T in the tire axial direction sectional view. That is, the surface of the block 12 of the molded pneumatic tire 10 has a curved line L3 that is a part of a circle 2 whose tire circumferential direction is an arc Q _n-1 P _n Q _{n + 1} , that is, a tire circumferential profile line. , A line L1 connecting the point Q _n-1 and the point H _n-1 and a line L2 connecting the point Q _{n + 1} and the point H _{n + 1} .

  As described above, the surface of the block 12 of the molded pneumatic tire 10 has L3 which is a part of the circle 2 whose tire circumferential direction is a tire circumferential profile line, one end of this L3, and the block 12 Connected to the groove 11 located on one side in the tire circumferential direction is a line L1 that is on the inner side in the tire radial direction from the tire circumferential profile line, the other end of this L3, and the other direction side in the tire circumferential direction of the block 12 It is comprised by the line | wire L2 which connects the groove | channel 11 located in this, and is a tire radial inside from this tire tire circumferential direction profile line. Thereby, in the inflated state, the pneumatic tire 10 can have a substantially circular surface of the tread portion (a surface of the block 10 continuous in the tire circumferential direction) in the tire axial direction sectional view. Generation of vibration can be suppressed, generation of road noise due to the hitting sound and vibration can be suppressed, and noise can be suppressed.

  Below, the noise of the conventional example, the comparative example, and the pneumatic tire 10 molded by the tire mold according to the present invention was compared. FIG. 2 is a diagram showing the shape of an inflated state between the comparative example and the present invention. In the figure, the vertical axis represents the distance from the tire center, and the horizontal axis represents the tire circumferential direction. Each pneumatic tire used in this comparison has a tire size of 205 / 65R15, is mounted on a rim of 15 × 6JJ, and the noise is compared in a state where the internal pressure (air pressure) is 200 kPa and the load is 4 kPa. . This noise comparison was performed by using the stand-alone bench test of JASO C 606 “Tire Noise Test Method” and the median value indicated by the sound level meter at a speed of 50 km / h.

In addition, each pneumatic tire used in the above comparison has a length of the outer circumference circle, that is, a tire circumferential profile line length M of 2016 mm, a block interval of equal intervals, a pitch number of 72, and a block height of 8 mm, the arc O _n-1 O _{n +} 1 to 24 mm, the width of the groove is intended to be 4 mm. Accordingly, arc P _n P _{n + 1} = 28 mm. When the pneumatic tire 10 having the above conditions is molded by the tire mold 1 of the present invention, the positions of the points Q _n-1 and Q _{n + 1} are the arc P _n Q _n-1 and the arc P _n Q _{n + 1.} Is within the range of more than 0 mm and not more than 9.6 mm, and the positions of the points H _n-1 and H _{n + 1} are straight line O _n-1 H _n-1 and straight line O _{n + 1} H _{n + 1} are 0. The position is within a range of 0.03 mm to 0.3 mm.

Here, as the “conventional example”, the point Q _n−1 and the point Q _{n + 1} are positions where the circular arc P _n Q _n−1 and the circular arc P _n Q _{n + 1} = 12 mm, the point H _n−1 , the point H n _{+ 1} is linear _{O n-1 H n-1} , the straight line _{O n + 1 H n + 1} = use a pneumatic tire is molded by a tire mold which becomes 0mm a position. In this “conventional example”, the central portion in the tire circumferential direction of each block is 8 mm, and both end portions in the tire circumferential direction of each block are also 8 mm. That is, the “conventional example” is formed by a tire mold in which the straight line O _n−1 H _n−1 and the straight line O _{n + 1} H _{n + 1} are zero. Note that the noise of this “conventional example” is +0.4 dB.

Here, as “Comparative Example 1”, the point Q _n−1 and the point Q _{n + 1} become positions where the arc P _n Q _n−1 and the arc P _n Q _{n + 1} = 5 mm, and the points H _n−1 , A pneumatic tire formed by a tire mold in which the point H _{n + 1} is a position where the straight line O _n-1 H _n-1 and the straight line O _{n + 1} H _{n + 1} = 0.02 mm is used. In “Comparative Example 1”, the central portion of each block in the tire circumferential direction is 8 mm, and both end portions of each block in the tire circumferential direction are 7.98 mm. That is, “Comparative Example 1” is formed by using a tire mold in which the straight line O _n-1 H _n-1 and the straight line O _{n + 1} H _{n + 1} are different (short) from the tire mold _{1 according} to the present invention. It is. The noise of “Comparative Example 1” is 0 dB.

Here, as “Comparative Example 2”, the point Q _n−1 and the point Q _{n + 1} are positions where the arc P _n Q _n−1 and the arc P _n Q _{n + 1} = 5 mm, and the points H _n−1 , A pneumatic tire formed by a tire mold in which the point H _{n + 1} is a position where the straight line O _n-1 H _n-1 and the straight line O _{n + 1} H _{n + 1} = 0.35 mm are used. In “Comparative Example 2”, the central portion of each block in the tire circumferential direction is 8 mm, and both end portions of each block in the tire circumferential direction are 7.65 mm. That is, in “Comparative Example 2”, the straight line O _n-1 H _n-1 and the straight line O _{n + 1} H _{n + 1} are molded by a tire mold different from (long) the tire mold _{1 according} to the present invention. It is.

Here, as an “Example”, the point Q _n−1 and the point Q _{n + 1} are positions where the arc P _n Q _n−1 and the arc P _n Q _{n + 1} = 5 mm, the point H _n−1 , the point A pneumatic tire formed by a tire mold in which H _{n + 1} is a straight line O _n-1 H _n-1 and a straight line O _{n + 1} H _{n + 1} = 0.10 mm is used. In this “Example”, the center portion in the tire circumferential direction of each block is 8 mm, and both end portions in the tire circumferential direction of each block are 7.90 mm.

  As is clear from FIG. 2 and this table, “Comparative Example 1” is a tire in which the positions of both ends in the tire circumferential direction of each block are the positions of both ends in the tire circumferential direction of each block of “Conventional Example”. Since it is close to the circumferential profile line, both ends rise in the inflation state as in the “conventional example”. Therefore, in this “Comparative Example 1”, in the inflated state, the surface of the tread portion in the tire axial cross-sectional view is substantially polygonal with both ends in the tire circumferential direction of each block as vertices, and the impact sound and vibration are Generation cannot be suppressed, generation of road noise due to the hitting sound and vibration cannot be suppressed, and noise is generated.

  In addition, in “Comparative Example 2”, the positions of both ends in the tire circumferential direction of each block are far from the tire circumferential profile line that is the positions of both ends in the tire circumferential direction of each block of “Conventional Example”. The block has an arc shape with the center at the top in the tire circumferential direction. Therefore, this “Comparative Example 2” is in an inflated state, and the surface of the tread portion in the tire axial direction sectional view is substantially polygonal with the central portion in the tire circumferential direction of each block as the apex, and the sound of impact and vibration Generation cannot be suppressed, generation of road noise due to the hitting sound and vibration cannot be suppressed, and noise is generated. Further, as shown in Table 1, the noise of “Comparative Example 2” is +0.2 dB, and noise is generated more than “Comparative Example 1”.

  As apparent from FIG. 2 and this table, since the “Example” is formed by the tire mold 1 according to the present invention, the distance between the surface 12a of the block 12 and the tire center in the inflated state is approximately It becomes constant. Therefore, as shown in Table 1, the noise of this “Example” is −0.8 dB, and the noise is suppressed more than “Conventional Example”, “Comparative Example 1”, and “Comparative Example 2”. This is because, in the “Example”, the surface of the tread portion in the tire axial direction sectional view is substantially circular in the inflated state, and it is possible to suppress the occurrence of hitting sound and vibration, and road noise caused by this hitting sound and vibration. It is because generation | occurrence | production of can be suppressed.

  As described above, the tire mold design method, tire mold, and tire molding method according to the present invention are suitable for suppressing noise.

It is a figure which shows the structural example of the tire metal mold | die concerning this invention. It is a figure which shows the shape of the inflation state of a comparative example and this invention.

Explanation of symbols

1 Tire mold 2 yen (tire circumferential profile line)
3 Groove forming part 4 Block forming part 10 Pneumatic tire 11 Groove 12 Block

Claims (3)

A tire mold design method for a tire mold for forming a pneumatic tire having grooves and blocks alternately in a tire circumferential direction,
In the tire mold axial cross-sectional view, a procedure of setting P _n as a midpoint between adjacent groove forming portions that are located on the tire circumferential profile line and that form the groove;
A procedure in which intersection points of the tire circumferential profile line extending from the midpoint P _n toward the adjacent groove forming portion and the adjacent groove forming portion are respectively On _-1 and On _{+ 1} ,
A procedure that is located on the tire circumferential profile line and that a point between the midpoint _Pn and the intersection On _-1 is _Qn-1 .
A procedure that is located on the tire circumferential profile line and that a point between the midpoint _Pn and the intersection On _{+ 1} is _{Qn + 1} ;
A procedure of setting a point located on a line connecting the intersection On _-1 and the center of the tire circumferential profile line as _Hn-1 .
A procedure of setting a point located on a line connecting the intersection O _{n + 1} and the center of the tire circumferential profile line as H _{n + 1} ;
An arc Q _n-1 P _n Q _{n + 1} , a line L1 connecting the point Q _n-1 and the point H _n-1 , and a line L2 connecting the point Q _{n + 1} and the point H _{n + 1} , A procedure for forming a boundary line T between the block molding portion for molding the block and the tire mold,
, Arc P _n Q _n-1 , arc P _n Q _{n + 1} , straight line O _n-1 H _n-1 , straight line O _{n + 1} H _{n + 1} are respectively represented by the following formulas (1) to (3) A tire mold design method characterized by being within the range of. Here, M is the length of the tire circumferential profile line.

0 <arc P _n Q _n−1 ≦ 0.8 × arc P _n O _n−1 (1)
0 <arc P _n Q _{n + 1} ≦ 0.8 × arc P _n O _{n + 1} (2)
0.1 × M / (2π) (1-cos (arc P _n P _{n + 1} × π / M) ≦ straight line O _n−1 H _n−1 , straight line O _{n + 1} H _{n + 1} ≦ M / ( 2π) (1-cos (arc P _n P _{n + 1} × π / M) (3)
In a tire mold for forming a pneumatic tire having grooves and blocks alternately in the tire circumferential direction,
P _n is a midpoint between adjacent groove forming portions that are located on the tire circumferential profile line in the tire mold axial sectional view and that form the groove,
The intersections of the tire circumferential profile line extending from the middle point P _n toward the adjacent groove forming portion and the adjacent groove forming portion are respectively On _-1 and On _{+ 1} ,
Between located in the tire circumferential direction profile line on, and 0 <and the middle point P _n satisfying arc _{P n Q n-1 ≦ 0.8} × arc P _n O _n-1 and the intersection O _{n-1 Let} Q _n-1 be the point of
Between it located in the tire circumferential direction profile line on, and 0 <a circular arc P _n Q n _{+ 1} ≦ 0.8 × arc P _n O n the middle point P _n satisfying _{+ 1} and the intersection O _{n + 1 Let} Q _{n + 1} be the point of
The length of the tire circumferential profile line is M,
It is located on a line connecting the intersection O _n-1 and the center of the tire circumferential profile line, and 0.1 × M / (2π) (1-cos (arc P _n P _{n + 1} × π / M) ≤Line O _n-1 H _n-1 ≤M / (2π) (1−cos (arc P _n P _{n + 1} × π / M) is defined as H _n-1 ,
It is located on a line connecting the intersection O _{n + 1} and the center of the tire circumferential profile line, and 0.1 × M / (2π) (1-cos (arc P _n P _{n + 1} × π / M) When a point satisfying ≦ O _{n + 1} H _{n + 1} ≦ M / (2π) (1-cos (arc P _n P _{n + 1} × π / M) is defined as H _{n + 1} ,
The boundary line T between the block molding portion for molding the block and the tire mold is an arc Q _n-1 P _n Q _{n + 1} , a line L1 connecting the point Q _n-1 and the point H _n-1. The tire mold is formed by a line L2 connecting the point Q _{n + 1} and the point H _{n + 1} . The procedure for molding green tires,
A procedure for loading a green tire into the tire mold according to claim 2;
Expanding the green tire radially outward and contacting the tire mold;
A procedure for heating and vulcanizing the green tire;
A tire molding method comprising:

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