Pneumatic tire and tread vulcanization molds

Abstract

We provide pneumatic tires that maintain ice performance while suppressing rubber chipping of the tread blocks during tire manufacturing. [Solution] The tire 1 includes a block row 5R in the tread portion 2. The block row 5R consists of multiple blocks 5 arranged in the circumferential direction of the tire. Each block 5 is divided into a small block portion 16 formed between adjacent sipes 11 in the circumferential direction of the tire, and a large block portion 17 which is longer in the circumferential direction of the tire than the small block portion 16. Multiple dividing lines 50 of the tread vulcanization mold 101, consisting of multiple segments 105, are formed in the circumferential direction of the tire in the block row 5R. Each dividing line 50 extends over the contact surface 16s of the small block portion 16 without intersecting the sipes 11.

Description

Technical Field

[0001] The present invention relates to a pneumatic tire and a tread vulcanization mold.

Background Art

[0002] Patent Document 1 below describes a tire vulcanization mold used when vulcanizing and manufacturing a tire in which sipping exists in a tire pattern. The tire vulcanization mold is composed of a plurality of divided split molds. And the divided boundary of the split mold is taken as the splitting position.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Tires having such sipping are said to exhibit high ice performance. However, tires manufactured with a vulcanization mold composed of such split molds have a problem that rubber chipping of the tread portion (blocks) is likely to occur during tire manufacturing in the vicinity of the splitting position.

[0005] The present invention has been devised in view of the above actual situation, and the main object is to provide a pneumatic tire capable of suppressing rubber chipping of blocks during tire manufacturing while maintaining ice performance.

Means for Solving the Problems

[0006] The present invention relates to a pneumatic tire having a tread portion, wherein the tread portion includes at least one row of blocks, the at least one row of blocks having a plurality of blocks arranged in the circumferential direction of the tire by a plurality of transverse grooves, each block having a plurality of sipes that traverse the block in the axial direction of the tire, each block being divided into a small block portion formed between adjacent sipes in the circumferential direction of the tire and at least two large block portions that are longer in the circumferential direction of the tire than the small block, and the at least one row of blocks has a plurality of dividing lines of a tread vulcanization mold consisting of a plurality of segments formed in the circumferential direction of the tire, each dividing line extending over the contact surface of the small block portion of any of the plurality of blocks without intersecting the sipes. [Effects of the Invention]

[0007] By adopting the above configuration, the pneumatic tire of the present invention can maintain ice performance while suppressing rubber chipping of the blocks during tire manufacturing. [Brief explanation of the drawing]

[0008] [Figure 1] This is an enlarged view of the tire tread section, showing one embodiment of the present invention. [Figure 2] This is a partial cross-sectional view of a vulcanizing machine 100 for vulcanizing the tire shown in Figure 1. [Figure 3] This is a cross-sectional view along line AA in Figure 2. [Figure 4] This is a cross-sectional view of the segments forming the dividing line and the tire. [Figure 5] This is a schematic perspective view of block row 5R. [Figure 6] Figure 1 is an unfolded view of the tread section, including the block rows. [Figure 7] Figure 1 is an unfolded view of the tread section, including the block rows. [Figure 8] Figure 6 is a partial perspective view of the segment for vulcanization molding of the tread section shown. [Figure 9]This is an exploded view of the tread section 2. [Figure 10] This is an enlarged view of Figure 8. [Figure 11] This is a cross-sectional view of a sipe in another embodiment. [Figure 12] (a) to (c) are exploded views of the tread portion of another embodiment. [Figure 13] (a) and (b) are exploded views of the tread portion of another embodiment. [Modes for carrying out the invention]

[0009] Hereinafter, one embodiment of the present invention will be described with reference to the drawings. The drawings are described in a manner that encompasses the features of the present invention. Furthermore, the drawings may contain exaggerations or representations that differ from the actual structural dimensional ratios in order to aid in understanding the present invention. In addition, the same reference numerals are used for elements that are the same or common throughout each embodiment, and redundant explanations may be omitted. Furthermore, well-known configurations may be appropriately adopted for configurations not described herein.

[0010] Figure 1 is an enlarged unfolded view of the tread portion 2 of a pneumatic tire (hereinafter sometimes simply referred to as "tire") 1, which is one embodiment of the present invention. The present invention is applicable, for example, to tires for trucks and buses (heavy loads). However, the present invention may also be applied to tires for passenger cars and light trucks.

[0011] In this specification, unless otherwise specified, the dimensions of each part of tire 1 are values ​​measured under normal conditions. "Normal conditions" refer to, in the case of pneumatic tires for which various standards are defined, tire 1 mounted on a normal rim (not shown), filled to the normal internal pressure, and under no load. For tires for which various standards are not defined, the normal conditions refer to the standard usage conditions according to the intended use of the tire, meaning the tire is not mounted on a vehicle and is under no load.

[0012] The "normal rim" is the rim defined for each tire in a standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the "standard rim"; in the case of TRA, it is the "Design Rim"; and in the case of ETRTO, it is the "Measuring Rim".

[0013] The "normal internal pressure" is the air pressure defined for each tire in a standard system including the standards on which the tire is based. In the case of JATMA, it is the "maximum air pressure"; in the case of TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it is the "INFLATION PRESSURE".

[0014] As shown in FIG. 1, the tread portion 2 includes at least one block row 5R. At least one block row 5R has a plurality of lateral grooves 6, and a plurality of blocks 5 are arranged in the tire circumferential direction. Each block 5 is defined by a pair of lateral grooves 6 adjacent in the tire circumferential direction.

[0015] In this embodiment, the block 5 has a plurality of sipes 11 formed across the block 5 in the tire axial direction. The plurality of sipes 11 exhibit basic ice performance. In this specification, the "sipe" includes the sipe 11 and the longitudinal sipe 30 described later, and refers to a cut-like portion with a width Wa at the ground contact surface 2s of the tread portion 2 less than 1.5 mm. Also, the "groove" including the lateral groove 6 and the circumferential groove 7 (shown in FIG. 6) described later is a recessed portion with a width Wb at the ground contact surface 2s of 1.5 mm or more, and is clearly distinguished from the sipe.

[0016] In this specification, the "contact surface" refers to the portion of the tire 1 in its normal state that contacts the plane when a normal load is applied and the camber angle is set to 0°. The "normal load" refers to the load specified for each tire in the standard system, including the standard on which the tire is based, in the case of pneumatic tires for which various standards are defined. For JATMA, this is the "maximum load capacity," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "LOAD CAPACITY." The contact surface 2s of the tread portion 2 includes the contact surface 5s of the block 5 and the contact surface 16s of the small block portion 16, which will be described later.

[0017] Furthermore, each block 5 is divided into a small block portion 16 formed between adjacent sipes 11 in the circumferential direction of the tire, and at least two large block portions 17. The large block portions 17 are formed to have a greater length La in the circumferential direction of the tire than the small block portions 16. In this embodiment, each block 5 has two small block portions 16 and three large block portions 17. The large block portions 17 include, for example, a pair of first large block portions 17A adjacent to the lateral groove 6, and a second large block portion 17B sandwiched between two small block portions 16. The first large block portions 17A are formed between the lateral groove 6 and the sipes 11 adjacent to the lateral groove 6. The second large block portions 17B are formed between adjacent sipes 11 in the circumferential direction of the tire.

[0018] Furthermore, at least one block row 5R has multiple dividing lines 50 formed in the circumferential direction of the tread vulcanization mold 101 (shown in Figure 2). The dividing lines 50 are visible lines formed by the seams of the tread vulcanization mold 101 on the block 5, and are also referred to as parting lines.

[0019] Figure 2 is a partial cross-sectional view of a vulcanizing machine 100 for vulcanizing the tire 1 shown in Figure 1. Figure 2 shows the vulcanizing machine 100 and the tire 1 in a horizontal position placed inside the vulcanizing machine 100. As shown in Figure 2, the vulcanizing machine 100 includes a tread vulcanizing mold 101 for forming the tread portion 2 of the tire 1, a side vulcanizing mold 102 for forming the sidewall portion 3 of the tire 1, and a bead vulcanizing mold 103 for forming the bead portion 4 of the tire 1. The side vulcanizing mold 102 and the bead vulcanizing mold 103 have well-known configurations, so their explanation is omitted.

[0020] In this specification, when the tire 1 is positioned in the vulcanizing machine 100, the direction in which the tire axis direction is the same as the mold axis direction, the direction in which the tire radial direction is the mold radial direction, and the direction in which the tire circumferential direction is the mold circumferential direction. In the vulcanizing machine 100 of this embodiment, since the tire 1 is positioned horizontally, the mold axis direction coincides with the vertical direction. In the drawings including the tread vulcanizing mold 101, the mold axis direction is indicated by arrow j, the mold radial direction is indicated by arrow r, and the mold circumferential direction is indicated by arrow s.

[0021] The tread vulcanization mold 101 is formed, for example, in an annular shape. The tread vulcanization mold 101 has an inner circumferential surface 104 for forming the tread portion 2. The inner circumferential surface 104 faces inward in the radial direction of the tread vulcanization mold 101. The inner circumferential surface 104 forms the outer circumferential surface including the contact surface 2s of the tread portion 2.

[0022] Figure 3 is a cross-sectional view taken along line AA in Figure 2. Figure 3 is a partial cross-sectional view of the tread vulcanization mold 101 cut along the circumferential direction of the mold. As shown in Figures 2 and 3, the inner circumferential surface 104 of the tread vulcanization mold 101 is provided with a reference surface 110 that forms the contact surface 5s of the block 5 (shown in Figure 1), and a plurality of axial protrusions 111 that form a plurality of transverse grooves 6. The inner circumferential surface 104 is also provided with a plurality of knife blades 112 that form a plurality of sipes 11. The knife blades 112 are provided, for example, between adjacent axial protrusions 111 in the circumferential direction of the mold. In this embodiment, the axial protrusions 111 and the knife blades 112 each protrude from the reference surface 110 and extend in the direction of the mold axis. The axial protrusions 111 and the knife blades 112 also extend, for example, in the direction normal to the inner circumferential surface 104 on which they are arranged.

[0023] Block 5 (shown in Figure 4) is defined between adjacent axial protrusions 111 in the circumferential direction of the mold. The reference surface 110 also includes a small length portion 116 formed between adjacent axial protrusions 111 and adjacent knife blades 112 in the circumferential direction of the mold, and at least two large length portions 117 having a length Lt in the circumferential direction of the mold greater than that of the small length portion 116. In this embodiment, the small length portion 116 forms the contact surface 16s (shown in Figure 4) of the small block portion 16. The large length portions 117 form, for example, the contact surface 17s (shown in Figure 4) of the large block portion 17.

[0024] In this embodiment, the tread vulcanization mold 101 is composed of a plurality of segments 105. Each segment 105 includes a pair of side surfaces 105a located at both ends in the circumferential direction of the mold, and an inner surface 105b connecting the inner ends of the pair of side surfaces 105a in the radial direction of the mold. Each side surface 105a constitutes a dividing surface 106 in which adjacent segments 105 in the circumferential direction of the mold are in close contact. Each inner surface 105b constitutes the inner circumferential surface 104 of the tread vulcanization mold 101.

[0025] The dividing surface 106 includes a dividing edge 105e that forms the inner end in the radial direction of the mold. This dividing edge 105e constitutes the dividing line 50. The dividing edge 105e extends in the axial direction of the mold without intersecting the short length portion 116 with the knife blade 112.

[0026] Furthermore, the vulcanizing machine 100 includes sector shoes 107 positioned outside the segment 105 in the radial direction of the mold. The number of divisions in segment 105 is, for example, the same as the number of sector shoes 107.

[0027] The sector shoe 107 includes a conical outer surface 107S that tapers upward. The outer surface 107S is guided vertically along the conical inner surface portion of a ring-shaped actuator (not shown). After vulcanization, the segment 105 is made removable from the tire 1 together with the sector shoe 107 by the upward movement of the ring-shaped actuator.

[0028] Figure 4 is a cross-sectional view of the tire 1 and the segments 105 that form the dividing line 50. As shown in Figures 1 and 4, each dividing line 50 extends over the contact surface 16s of any of the small block portions 16 of the multiple blocks 5 without intersecting the sipes 11. In other words, during tire vulcanization molding, two segments 105, the first segment 105A and the second segment 105B, are arranged on the contact surface 16s of the small block portion 16. The first segment 105A is positioned on the first tire circumferential direction s1 side from the dividing line 50. The second segment 105B is positioned on the second tire circumferential direction s2 side from the dividing line 50. When separating the tire 1 from the segments 105A and 105B after tire vulcanization molding, the first segment 105A is removed outward in the radial direction of the mold (normal direction shown by arrow a1) at the intermediate position C1 in the circumferential direction of the mold of the first segment 105A. Furthermore, after tire vulcanization molding, the second segment 105B is removed outward in the radial direction of the mold (normal direction shown by arrow a2) at the intermediate position C2 in the circumferential direction of the mold for the second segment 105B. As a result, a pulling force acts on the knife blade 112a, which is located on the side of the first segment 105A closest to the second segment 105B, in the direction of arrow b1. Similarly, a pulling force acts on the knife blade 112b, which is located on the side of the second segment 105B closest to the first segment 105A, in the direction of arrow b2. On the other hand, the pulling force from these knife blades 112a and 112b is either not generated or extremely small in the small block portion 16 between the knife blades 112a and 112b, thus suppressing rubber chipping of the block 5 during tire manufacturing in this portion. Therefore, the pneumatic tire 1 of this embodiment can suppress rubber chipping of the block 5 during tire manufacturing while maintaining ice performance. Note that the second tire circumferential direction s2 is opposite to the first tire circumferential direction s1 in terms of tire circumferential direction.

[0029] Figure 6 is an unfolded view of the tread portion 2 of this embodiment. Figure 6 includes the block row 5R shown in Figure 1. As shown in Figure 6, the tread portion 2 of this embodiment includes multiple block rows 5R. In each of the multiple block rows 5R, each dividing line 50 extends over the contact surface 16s of any of the multiple block 5's small block portions 16 without intersecting the sipes 11. This effectively brings about the above-mentioned effect. In this embodiment, each dividing line 50 extends over the contact surfaces 16s of two small block portions 16. Note that in each of the block rows 5R, the dividing line 50 may extend over the contact surface 16s of any of the multiple block 5's small block portions 16 without intersecting the sipes 11 (not shown).

[0030] The tread portion 2 includes a plurality of circumferential grooves 7 that extend continuously in the circumferential direction of the tire, and a plurality of longitudinal grooves 8 that extend in the circumferential direction of the tire. The circumferential grooves 7 are formed with a groove width W1 that is larger than that of the longitudinal grooves 8. The groove width W1 of the circumferential grooves 7 is, for example, 5 to 20 mm. The groove width W2 of the longitudinal grooves 8 is, for example, 1.5 mm or more and less than 5 mm. The longitudinal grooves 8 may also be formed as longitudinal sipes (not shown) with a width of less than 1.5 mm.

[0031] The circumferential grooves 7 include, for example, a crown circumferential groove 7A located on the tire equator Co, and a pair of shoulder circumferential grooves 7B located on both sides of the crown circumferential groove 7A in the tire axial direction. The longitudinal grooves 8 include, for example, a crown longitudinal groove 8A located between the crown circumferential groove 7A and the shoulder circumferential groove 7B, and a shoulder longitudinal groove 8B located between the shoulder circumferential groove 7B and the tread edge Te. The crown longitudinal grooves 8A and the shoulder longitudinal grooves 8B are arranged in the circumferential direction of the tire. The groove width of the crown circumferential groove 7A may be the same as or different from the groove width of the shoulder circumferential groove 7B. The groove width of the crown longitudinal groove 8A may be the same as or different from the groove width of the shoulder longitudinal groove 8B.

[0032] In this embodiment, each circumferential groove 7 and crown longitudinal groove 8A extends in a zigzag pattern. The shoulder longitudinal groove 8B extends, for example, in a straight line. The circumferential groove 7 and longitudinal groove 8 are not limited to this configuration; each circumferential groove 7 and crown longitudinal groove 8A may extend in a straight line, or the shoulder longitudinal groove 8B may extend in a zigzag pattern.

[0033] Block 5 includes a crown block 21 positioned between the crown circumferential groove 7A and the shoulder circumferential groove 7B, and a shoulder block 22 positioned between the shoulder circumferential groove 7B and the tread edge Te. The crown block 21 is divided into a first crown block 21A positioned between the crown circumferential groove 7A and the crown longitudinal narrow groove 8A, and a second crown block 21B positioned between the crown longitudinal narrow groove 8A and the shoulder circumferential groove 7B. The shoulder block 22 is divided into a first shoulder block 22A positioned between the shoulder circumferential groove 7B and the shoulder longitudinal narrow groove 8B, and a second shoulder block 22B positioned between the shoulder longitudinal narrow groove 8B and the tread edge Te.

[0034] In this specification, the tread edge Te is defined as the outermost contact point in the tire axial direction that makes contact with the plane in the tire 1 under normal load conditions. The distance in the tire axial direction between the two tread edges Te is defined as the tread width TW.

[0035] Each crown block 21 and the first shoulder block 22A is composed of, for example, two small block sections 16 and three large block sections 17. In other words, each crown block 21 and the first shoulder block 22A is provided with four sipes 11. The second shoulder block 22B is composed of, for example, two small block sections 16 and four large block sections 17. The large block sections 17 of the second shoulder block 22B include, for example, two first large block sections 17A and two second large block sections 17B. In other words, the second shoulder block 22B is provided with five sipes 11.

[0036] Figure 7 is an unfolded view of the tread portion 2 of this embodiment. As shown in Figure 7, the lateral groove 6 includes a crown lateral groove 25 defining the crown block 21 and a shoulder lateral groove 26 defining the shoulder block 22. The crown lateral groove 25 is divided into a first crown lateral groove 25A extending from the crown circumferential groove 7A to the second crown block 21B, and a second crown lateral groove 25B extending from the shoulder circumferential groove 7B to the first crown block 21A. The shoulder lateral groove 26 is divided into a first shoulder lateral groove 26A extending from the shoulder circumferential groove 7B to the second shoulder block 22B, and a second shoulder lateral groove 26B extending from the tread edge Te to the first shoulder block 22A. Furthermore, the first crown lateral groove 25A and the second crown lateral groove 25B, which are adjacent in the circumferential direction of the tire, are connected to the crown longitudinal narrow groove 8A (shown in Figure 6). The first shoulder lateral groove 26A and the second shoulder lateral groove 26B, which are adjacent in the circumferential direction of the tire, are connected to the shoulder longitudinal narrow groove 8B (shown in Figure 6).

[0037] Each lateral groove 6 extends in a straight line, for example. Such lateral grooves 6 increase the rigidity of each block 5 and exhibit a high edge component, thereby improving ice performance. The angle α1b of the second shoulder lateral groove 26B with respect to the tire axis is formed to be smaller than the angle α1a of the first crown lateral groove 25A, the second crown lateral groove 25B, and the first shoulder lateral groove 26A with respect to the tire axis.

[0038] In this embodiment, the lateral groove 6 includes a shallow groove portion 28 and a deep groove portion 29 having a greater groove depth than the shallow groove portion 28. The shallow groove portion 28 and the deep groove portion 29 are provided in the first crown lateral groove 25A, the second crown lateral groove 25B, the first shoulder lateral groove 26A, and the second shoulder lateral groove 26B. In the first crown lateral groove 25A, the second crown lateral groove 25B, and the first shoulder lateral groove 26A, the deep groove portion 29 is provided on the side of the circumferential groove 7 that connects each of the lateral grooves 25A, 25B, and 26A, respectively, more so than the shallow groove portion 28. In the second shoulder lateral groove 26B, the deep groove portion 29 is provided on the tread edge Te side more than the shallow groove portion 28.

[0039] The lateral grooves 6 are, for example, offset in the circumferential direction from adjacent lateral grooves 6 in the tire axial direction. In this embodiment, the lateral grooves 6 do not overlap in the circumferential direction with adjacent lateral grooves 6 in the tire axial direction. The first crown lateral groove 25A does not overlap in the circumferential direction with adjacent first crown lateral grooves 25A and second crown lateral grooves 25B in the tire axial direction. The second crown lateral groove 25B does not overlap in the circumferential direction with adjacent first crown lateral grooves 25A and first shoulder lateral groove 26A in the tire axial direction. The first shoulder lateral groove 26A does not overlap in the circumferential direction with adjacent second crown lateral grooves 25B and second shoulder lateral grooves 26B in the tire axial direction. This arrangement of lateral grooves 6 suppresses deformation of each block 5 in the tire axial direction, thereby maintaining high ice performance.

[0040] The circumferential groove width W3 of the lateral groove 6 is preferably less than or equal to the axial groove width W1 of the circumferential groove 7, and preferably smaller than the groove width W1. The angle α1 of the lateral groove 6 with respect to the axial direction of the tire is, for example, set to 0 to 45 degrees. From the viewpoint of maintaining high ice performance due to the edge component of the lateral groove 6, the angle α1 is preferably 30 degrees or less, and more preferably 15 degrees or less.

[0041] In this embodiment, the sipe 11 is provided on each of the crown blocks 21 and each of the shoulder blocks 22. The sipe 11 includes, for example, a first crown sipe 31A, a second crown sipe 31B, a first shoulder sipe 32A, and a second shoulder sipe 32B. The first crown sipe 31A is located on the first crown block 21A. The second crown sipe 31B is located on the second crown block 21B. The first shoulder sipe 32A is located on the first shoulder block 22A. The second shoulder sipe 32B is located on the second shoulder block 22B. The number of first crown sipes 31A located on one first crown block 21A is the same as the number of second crown sipes 31B located on one second crown block 21B. Furthermore, the number of first crown sipes 31A in one first crown block 21A is the same as the number of first shoulder sipes 32A in one first shoulder block 22A. The number of second shoulder sipes 32B in one second shoulder block 22B is greater than the number of first crown sipes 31A in one first crown block 21A. For example, one first crown block 21A has four first crown sipes 31A. One second shoulder block 22B has five second shoulder sipes 32B.

[0042] The angle α2 of the sipe 11 with respect to the tire axis is, for example, set to 0 to 70 degrees. From the viewpoint of maintaining higher ice performance, an angle α2 of 30 degrees or less is desirable, and an angle of 15 degrees or less is more desirable. Furthermore, the absolute value of the difference between the angle α2 of the sipe 11 and the angle α1 of the lateral groove 6 that separates the block 5 in which the sipe 11 is located, |α2-α1|, is preferably 30 degrees or less, more preferably 15 degrees or less, and most preferably 0 degrees. In this embodiment, the angle α2 of the zigzag-extending sipe 11 is defined by the angle of a virtual straight line n1 connecting both ends of the width centerline of the sipe 11.

[0043] The spacing Lc of the sipes 11 that divide the small block sections 16 is preferably 7.0 mm or less, and more preferably 6.0 mm or less. Such spacing Lc helps to increase the number of sipes 11 provided in each block 5. If the spacing Lc is excessively small, the rigidity of the small block sections 16 will decrease, and there is a risk of rubber chipping during tire manufacturing. For this reason, the spacing Lc is preferably 3.0 mm or more, and more preferably 5.0 mm or more. The length Lf of the large block sections 17 in the tire circumferential direction is preferably greater than 7.0 mm, and more preferably 9.0 mm or more. The spacing Lc is the shortest distance between virtual straight lines n1.

[0044] As shown in Figures 7 and 4, the sipe 11 is a three-dimensional sipe 11S that extends in a zigzag pattern from the contact surface 5s of the block 5 in the radial direction of the tire, and also extends in a zigzag pattern on the contact surface 5s of the block 5. When the three-dimensional sipe 11S makes contact with the road surface, the walls of the sipes restrain each other, increasing the apparent rigidity of the block 5, thereby maintaining higher ice performance.

[0045] As shown in Figure 5, although not particularly limited, the amplitude C on the contact surface 5s of the 3D sipe 11S is preferably 0.5 mm or more, more preferably 1.0 mm or more, preferably 3.5 mm or less, and even more preferably 3.0 mm or less. Also, the number E of wavelengths λ1 on the contact surface 5s of the 3D sipe 11S is preferably 1.0 or more, more preferably 1.5 or more, preferably 5 or less, and even more preferably 3 or less. Furthermore, the number F of wavelengths λ2 in the tire radial direction of the 3D sipe 11S is preferably 1.0 or more, more preferably 1.5 or more, preferably 5 or less, and even more preferably 3 or less. In the 3D sipe 11S shown in Figure 5, the amplitude C is 2.5 mm, the number E is 1.5, and the number F is 1.0.

[0046] The sipe 11 is not limited to these configurations. For example, it may extend in a zigzag pattern on the contact surface 5s of the block 5 and linearly inward from the contact surface 5s of the block 5 in the radial direction of the tire (not shown). Alternatively, the sipe 11 may extend linearly on the contact surface 5s of the block 5 and linearly inward from the contact surface 5s of the block 5 in the radial direction of the tire (not shown).

[0047] If each sipe 11 is a three-dimensional sipe 11S, it is desirable that it satisfies the following equation (1). 5≦A 3 ×(1.29-0.036×G)÷(2×B 3 ) + C × E × F ÷ 2 ≤ 35 … (1) Here, A is the depth D (mm) of the 3D sipe 11S (shown in Figure 4), B is the spacing Lc (mm) of the 3D sipe 11S that divide the small block section 16 (shown in Figure 7), and C is the amplitude (mm) of the 3D sipe 11S on the contact surface 5s (shown in Figure 5). Also, E is the number of wavelengths λ1 (shown in Figure 5) on the contact surface 5s of the 3D sipe 11S, F is the number of wavelengths λ2 (shown in Figure 5) in the tire radial direction of the 3D sipe 11S, and G is the number of segments 105.

[0048] The meaning of equation (1) is explained. First, the depth D of the three-dimensional sipe 11S and the spacing Lc between the three-dimensional sipe 11S are inversely related parameters for ice performance and suppressing block chipping. For this reason, A / B is adopted as the basic configuration. Next, as the number of segments 105 G increases continuously, the stress generated in block 5 decreases continuously. For this reason, (1.29 - 0.036 × G) is adopted. The constants 1.29 and 0.036 were derived from various experiments. Also, as the number of segments 105 G increases continuously, the difference between the exit angle of the knife blade 112 and the pull-out angle of the segments decreases, which is favorable for preventing block chipping. For this reason, (1.29 - 0.036 × G) is placed on the numerator side of the basic equation A / B. Furthermore, as the amplitude C, the number of wavelengths λ1, and the number of wavelengths λ2 increase, these parameters become unfavorable to rubber chipping; therefore, these parameters are elements added to the basic configuration. The cubed values ​​of A and B were derived from the results of various experiments.

[0049] Furthermore, if each sipe 11 is a three-dimensional sipe 11S, it is even more desirable that it satisfies equation (2) below. 20≦A 3 ×(1.29-0.036×G)÷(2×B 3 ) + C × E × F ÷ 2 ≤ 35 … (2)

[0050] As shown in Figure 7, the tread portion 2 of this embodiment is provided with longitudinal sipes 30 extending in the circumferential direction of the tire. In this embodiment, the longitudinal sipes 30 are provided on the first crown block 21A, the second crown block 21B, and the first shoulder block 22A. The longitudinal sipes 30 are provided, for example, on the large block portion 17. In this embodiment, the longitudinal sipes 30 are provided on each of the pair of first large block portions 17A adjacent to the transverse groove 6.

[0051] Figure 8 is a partial perspective view of a segment 105 of a tread vulcanization mold 101 for vulcanizing the tread portion 2 shown in Figure 6. As shown in Figure 8, the inner surface 105b of this embodiment further includes a plurality of circumferential protrusions 113 that form circumferential grooves 7, a plurality of circumferential small protrusions 114 that form a plurality of longitudinal narrow grooves 8, and a plurality of circumferential knife blades 115 that form a plurality of longitudinal sipes 30.

[0052] The number of segments 105 is preferably 17 or more, more preferably 19 or more, preferably 29 or less, and more preferably 23 or less. With this number of segments 105, after vulcanization molding, the pull-out force between the tire 1 and the segments 105 is reduced, suppressing rubber chipping of the block 5 and ensuring ease of pull-out between the tire 1 and the segments 105. Furthermore, from the viewpoint of suppressing noise and vibration of the tire 1, a prime number of segments 105 is preferable. Moreover, from the viewpoint of ensuring the roundness of the tire 1, it is even more preferable that the number of segments 105 be 19.

[0053] Figure 9 is an unfolded view of the tread portion 2 of this embodiment. As shown in Figure 9, in the tread unfolded view, each dividing line 50 includes at least one straight portion 51 and at least one curved portion 52. The dividing line 50 having such a curved portion 52 can extend without intersecting the sipes 11. Specifically, the dividing line 50 does not come into contact with the sipes 11 between the tread ends Te on both sides. For this reason, as shown in Figure 8, the knife blade 112 that forms the sipes 11 can be provided within a single segment 105 without being divided by adjacent segments 105 in the circumferential direction of the mold. This suppresses a decrease in the rigidity of the knife blade 112 and allows for the formation of the sipes 11 with high precision, thereby maintaining higher ice performance. The straight portion 51 includes an embodiment formed by an arc with a radius of curvature Ra of 500 mm or more, and the curved portion 52 includes an embodiment with a radius of curvature Ra of less than 500 mm.

[0054] Each dividing line 50 in this embodiment includes a plurality of straight sections 51 and a plurality of curved sections 52. For example, a dividing line 50 includes 11 straight sections 51 and 10 curved sections 52. In this embodiment, the straight sections 51 and curved sections 52 are arranged alternately in the direction of the tire axis. The number of straight sections 51 is not particularly limited, but it is preferable to have 2 to 13.

[0055] The straight section 51 includes, for example, a pair of outer straight sections 51a extending over the tread edges Te on both sides, and an inner straight section 51b positioned inward in the tire axial direction from the pair of outer straight sections 51a. The outer straight sections 51a extend substantially parallel to the tire axial direction. "Substantially parallel to the tire axial direction" means that the angle α3 of the straight section 51 with respect to the tire axial direction is not only 0 degrees, but also includes configurations where the angle is 5 degrees or less. The inner straight section 51b may extend substantially parallel to the tire axial direction, or it may be inclined with respect to the tire axial direction. If the angle α4 of the inner straight section 51b with respect to the tire axial direction is excessively large, the length of the portion where the side surfaces 105a rub against each other will increase when the segment 105 closes (the side surfaces 105a (shown in Figure 3) of adjacent segments 105 in the circumferential direction of the mold come into close contact with each other). This may accelerate wear of the side surfaces 105a and increase the width of the dividing line 50. Therefore, the angle α4 is preferably 45 degrees or less, and even more preferably 30 degrees or less.

[0056] The curved portion 52 includes, for example, a first curved portion 52a formed in a convex arc shape in the first tire circumferential direction s1, and a second curved portion 52b formed in a convex arc shape in the second tire circumferential direction s2. In this embodiment, the first curved portion 52a and the second curved portion 52b may be arranged alternately in the tire axial direction, or they may be arranged non-alternately in the tire axial direction.

[0057] The radius of curvature Rb of the curved section 52 is preferably 10 mm or more, and more preferably 20 mm or more. Such a curved section 52 can suppress damage to the side surface 105a (shown in Figure 3) of the segment 105 by preventing the force acting on the curved section 52 from concentrating on the curved section 52 during vulcanization molding. From this viewpoint, the upper limit of the radius of curvature Rb should be smaller than the radius of curvature Ra of the straight section 51.

[0058] Figure 10 is an enlarged view of Figure 9. As shown in Figure 10, the angle α5 between the straight sections 51 located on both sides of the curved section 52 in the tire axis direction is preferably 90 degrees or more, and more preferably 110 degrees or more. Such an angle α5 prevents the amount of rubber that enters between the side surfaces 105a when the side surfaces 105a of the segment 105 are in close contact, thereby preventing damage to the appearance of the tire 1. From this viewpoint, the angle α5 should be less than 180 degrees.

[0059] As shown in Figure 4, during vulcanization molding, a greater force acts on the axial protrusions 111 that form the lateral grooves 6 than on the reference surface 110. For this reason, although not shown, in segments that form a tread portion where the dividing line extends over the lateral grooves, there is a risk that a large amount of rubber will be caught on the side surface forming the divided axial protrusions during vulcanization molding when these segments are in close contact with each other. For this reason, as shown in Figure 10, it is desirable that the dividing line 50 does not extend over the lateral grooves 6. Also, in this embodiment, the dividing line 50 does not intersect with the lateral grooves 6. The dividing line 50 in this embodiment does not come into contact with any of the lateral grooves 6 that are aligned in the axial direction of the tire.

[0060] The dividing line 50 intersects, for example, the longitudinal groove 8. In this embodiment, the dividing line 50 intersects the crown longitudinal groove 8A and / or the shoulder longitudinal groove 8B.

[0061] The longitudinal groove 8 intersecting the dividing line 50 is divided into a first longitudinal groove 8a located on the first tire circumferential direction s1 side and a second longitudinal groove 8b located on the second tire circumferential direction s2 side. In other words, the circumferential small protrusion 114 includes a first circumferential small protrusion 114a (shown in Figure 8) that forms the first longitudinal groove 8a and a second circumferential small protrusion 114b that forms the second longitudinal groove 8b. The smaller of the lengths Le of the first longitudinal groove 8a or the second longitudinal groove 8b in the tire circumferential direction is preferably 3.0 mm or more, and more preferably 10 mm or more. This suppresses excessive reduction in rigidity of the first circumferential small protrusion 114a or the second circumferential small protrusion 114b, which have a smaller length in the mold circumferential direction, thereby suppressing rubber chipping of the block 5. In the crown longitudinal groove 8A shown in Figure 10, the first longitudinal groove 8a has a shorter length in the tire circumferential direction than the second longitudinal groove 8b.

[0062] In the tread development diagram, the amplitude P1 of the dividing line 50 in the tire circumferential direction is preferably 30 mm or less, and more preferably 20 mm or less. The amplitude P1 is the length in the tire circumferential direction between the outer end 50e on the first tire circumferential direction s1 side of the dividing line 50 and the outer end 50i on the second tire circumferential direction s2 side of the dividing line 50. Such dividing lines 50 reduce the stress acting on the knife blades 112, for example, 112a, 112b (shown in Figure 4), located on the outside of the mold circumferential direction of the segment 105 when the tire 1 is pulled out from the segment 105, thereby suppressing bending deformation and breakage. This reduces the possibility of defects occurring in the block 5. In the tire 1 of this embodiment, the amplitude P1 of each dividing line 50 is set to 20 mm or less. From the viewpoint of suppressing defects occurring in the block 5, a smaller amplitude P1 is preferable.

[0063] The shortest distance Ln between the dividing line 50 on the contact surface 16s of the small block section 16 and the sipe 11 separating the small block section 16 is preferably 2.0 mm or more, more preferably 2.5 mm or more, preferably 5.0 mm or less, and more preferably 4.5 mm or less. If the shortest distance Ln is less than 2.0 mm, there is a risk that the knife blade cannot be firmly fixed. If the shortest distance Ln exceeds 5.0 mm, it will be too close to the other sipe 11, and similarly, there is a risk that the knife blade cannot be firmly fixed.

[0064] Figure 11 is a cross-sectional view of a sipe 11 in another embodiment. As shown in Figure 11, in this embodiment, the sipe 11 includes a sipe body 35 extending radially inward from the contact surface 5s of the block 5, and a widening portion 36 connected to the radial inner end of the sipe body 35 and having a wider width than the sipe body 35. Such a sipe 11 can increase the discharge of melted water on an icy road surface, thereby maintaining higher ice performance. The cross-sectional shape of the widening portion 36 may be circular, elliptical, or track-shaped.

[0065] While not particularly limited, the maximum width Wm of the widened section 36 is preferably 5 times or more the width Ws of the sipe body section 35 at the contact surface 5s, more preferably 7 times or more, preferably 13 times or less, and even more preferably 11 times or less. Furthermore, the width Ws of the sipe body section 35 is preferably 0.2 mm or more, more preferably 0.3 mm or more, preferably 1.0 mm or less, and even more preferably 0.6 mm or less.

[0066] The knife blades 112 (shown in Figure 8) that form the sipes 11 shown in Figures 1 and 4, and the knife blade (not shown) that form the sipes 11 shown in Figure 11, are subjected to relatively large forces when the tire 1 is pulled out of the tread vulcanization mold 101. For this reason, as in the present invention, extending the dividing line 50 over the contact surface 16s of the small block portion 16 without intersecting the sipes 11 helps to suppress rubber chipping even in the block 5 where such sipes 11 are arranged.

[0067] Figures 12(a) to 12(c), 13(a), and 13(b) are unfolded views of the tread portion 2 of other embodiments. Figures 12(a) to 12(c), 13(a), and 13(b) show dividing lines 50 with a different shape from the dividing line 50 of this embodiment. The dividing lines 50 shown in each figure also satisfy the constituent requirements of each dividing line 50 of this embodiment.

[0068] The dividing line 50 shown in Figure 12(a) extends over the contact surfaces 16s of the three small block sections 16. The dividing lines 50 shown in Figures 12(b), 12(c), 13(a), and 13(b) each extend over the contact surfaces 16s of the four small block sections 16.

[0069] Although particularly preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments and can be implemented in various modified forms.

[0070] [Note] The present invention includes the following embodiments.

[0071] [Invention 1] A tire having a tread portion, The tread portion includes at least one row of blocks, The aforementioned at least one row of blocks is arranged in the circumferential direction of the tire by multiple lateral grooves, Each block has multiple sipes formed across it in the direction of the tire axis, Each of the aforementioned blocks is divided into a small block portion formed between adjacent sipes in the circumferential direction of the tire, and at least two large block portions that are longer in the circumferential direction of the tire than the small block. In at least one of the aforementioned block rows, multiple dividing lines of a tread vulcanization mold consisting of multiple segments are formed in the circumferential direction of the tire. Each dividing line extends on the contact surface of the subblock portion of any of the plurality of blocks without intersecting the sipe. Pneumatic tires. [Invention 2] The aforementioned block sequence includes multiple block sequences, The pneumatic tire according to the present invention 1, wherein in at least two of the plurality of block rows, each dividing line extends over the contact surface of the small block portion of any of the plurality of blocks without intersecting the sipe. [Invention 3] The aforementioned block sequence includes multiple block sequences, The pneumatic tire according to the present invention, wherein in each of the plurality of block rows, each dividing line extends over the contact surface of the small block portion of any of the plurality of blocks without intersecting the sipe. [4th Invention] In the tread development diagram, each dividing line includes at least one straight section and at least one curved section, according to any one of inventions 1 to 3. [5th ​​Invention] In the tread development diagram, the amplitude of each dividing line in the tire circumferential direction is 30 mm or less, as described in any one of invention 1 to 4. [Invention 6] The shortest distance between the dividing line on the contact surface of the small block portion and the sipe separating the small block portion is 2.0 to 5.0 mm, as described in any one of invention 1 to 5. [7th Invention] The pneumatic tire according to any one of invention 1 to 6, wherein the spacing between the sipes that divide the small block portion is 7.0 mm or less. [8th Invention] The pneumatic tire according to any one of invention 1 to 7, wherein each sipe includes a sipe body portion extending radially inward from the contact surface of the block, and a widened portion connected to the inner end of the sipe body portion in the radial direction of the tire, and having a wider width than the sipe body portion. [Invention 9] The pneumatic tire according to any one of invention 1 to 7, wherein each of the sipes extends in a zigzag pattern inward in the radial direction of the tire from the contact surface of the block, and is a three-dimensional sipe that extends in a zigzag pattern on the contact surface of the block. [Invention 10] The pneumatic tire according to the present invention, wherein each of the sipes is the three-dimensional sipe, and the following formula (1) is satisfied. 5≦A 3 ×(1.29-0.036×G)÷(2×B 3 ) + C × E × F ÷ 2 ≤ 35 … (1) Here, A is the depth of the three-dimensional sipe (mm), B is the spacing between the sipes that divide the small block section (mm), C is the amplitude of the three-dimensional sipe on the contact surface (mm), E is the number of wavelengths of the three-dimensional sipe on the contact surface, F is the number of wavelengths of the three-dimensional sipe in the tire radial direction, and G is the number of segments. [Invention 11] A tread vulcanization mold for vulcanizing a tire in which a plurality of blocks are arranged in the circumferential direction of the tire by a plurality of lateral grooves in the tread portion, and a plurality of sipes are formed in each block that cross the block in the axial direction of the tire, The inner circumferential surface of the tread vulcanizing mold is provided with a reference surface that forms the contact surface of the block, a plurality of axial protrusions that form the plurality of transverse grooves, and a plurality of knife blades that form the plurality of sipes. The plurality of axial protrusions protrude from the reference surface and extend in the direction of the mold axis, The plurality of knife blades protrude from the reference surface and extend in the direction of the mold axis, The reference surface includes a short length portion formed between adjacent axial protrusions in the circumferential direction of the mold and between adjacent knife blades in the circumferential direction of the mold, and at least two long lengths portion that are longer in the circumferential direction of the mold than the short length portion. The tread vulcanization mold consists of multiple segments, The dividing edges between adjacent segments in the circumferential direction of the mold extend without intersecting the knife blade with the shorter portion. Tread vulcanization mold. [Explanation of symbols]

[0072] 1 tire 2 Tread section 5 blocks 5R Block Row 11 sipes 16 Small Block Section 16s ground plane 17. Major Block Section 50 division lines 101 Tread vulcanization mold 105 segments

Claims

1. A tire having a tread portion, The tread portion includes at least one row of blocks, The aforementioned at least one row of blocks is arranged in the circumferential direction of the tire by multiple lateral grooves, Each block has multiple sipes formed across it in the direction of the tire axis, Each of the aforementioned blocks is divided into a small block portion formed between adjacent sipes in the circumferential direction of the tire, and at least two large block portions that are longer in the circumferential direction of the tire than the small block. In at least one of the aforementioned block rows, multiple dividing lines of a tread vulcanization mold consisting of multiple segments are formed in the circumferential direction of the tire. Each dividing line extends on the contact surface of the subblock portion of any of the plurality of blocks without intersecting the sipe. Pneumatic tires.

2. The aforementioned block sequence includes multiple block sequences, The pneumatic tire according to claim 1, wherein in at least two of the plurality of block rows, each dividing line extends over the contact surface of the small block portion of any of the plurality of blocks without intersecting the sipe.

3. The aforementioned block sequence includes multiple block sequences, The pneumatic tire according to claim 1, wherein in each of the plurality of block rows, each dividing line extends over the contact surface of the small block portion of any of the plurality of blocks without intersecting the sipe.

4. The pneumatic tire according to claim 1, wherein in the tread development diagram, each of the division lines includes at least one straight section and at least one curved section.

5. The pneumatic tire according to claim 4, wherein, in the tread development diagram, the amplitude of each dividing line in the tire circumferential direction is 30 mm or less.

6. The pneumatic tire according to claim 4, wherein the shortest distance between the dividing line on the contact surface of the small block portion and the sipe separating the small block portion is 2.0 to 5.0 mm or less.

7. The pneumatic tire according to claim 1, wherein the spacing between the sipes that divide the small block portion is 7.0 mm or less.

8. The pneumatic tire according to any one of claims 1 to 7, wherein each sipe includes a sipe body portion extending radially inward from the contact surface of the block, and a widened portion connected to the inner end of the sipe body portion in the radial direction of the tire, and having a wider width than the sipe body portion.

9. The pneumatic tire according to any one of claims 1 to 7, wherein each of the sipes extends in a zigzag pattern inward in the radial direction of the tire from the contact surface of the block, and is a three-dimensional sipe that extends in a zigzag pattern on the contact surface of the block.

10. The pneumatic tire according to claim 9, wherein each of the sipes is the three-dimensional sipe, and the following formula (1) is satisfied. 5≦A ３ ×(1.29-0.036×G)÷(2×B ３ )+C×E×F÷2≦35…(1) Here, A is the depth of the three-dimensional sipe (mm), B is the spacing between the sipes that divide the small block section (mm), C is the amplitude of the three-dimensional sipe on the contact surface (mm), E is the number of wavelengths of the three-dimensional sipe on the contact surface, F is the number of wavelengths of the three-dimensional sipe in the tire radial direction, and G is the number of segments.

11. A tread vulcanization mold for vulcanizing a tire in which a plurality of blocks are arranged in the circumferential direction of the tire by a plurality of lateral grooves in the tread portion, and a plurality of sipes are formed in each block that cross the block in the axial direction of the tire, The inner circumferential surface of the tread vulcanizing mold is provided with a reference surface that forms the contact surface of the block, a plurality of axial protrusions that form the plurality of transverse grooves, and a plurality of knife blades that form the plurality of sipes. The plurality of axial protrusions protrude from the reference surface and extend in the direction of the mold axis, The plurality of knife blades protrude from the reference surface and extend in the direction of the mold axis, The reference surface includes a short length portion formed between adjacent axial protrusions in the circumferential direction of the mold and between adjacent knife blades in the circumferential direction of the mold, and at least two long lengths portion that are longer in the circumferential direction of the mold than the short length portion. The tread vulcanization mold consists of multiple segments, The dividing edges between adjacent segments in the circumferential direction of the mold extend without intersecting the knife blade with the shorter portion. Tread vulcanization mold.

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