Pneumatic tires and molds for tire molding.

Abstract

To provide a pneumatic tire which can improve wet performance in addition to dry performance.SOLUTION: A pneumatic tire 10 comprises a tread 20 including a block 30 where sipings 40 are formed. A plurality of cavities 41 are formed on one wall surface of the siping 40 in which capacity of the cavity 41 becomes smaller at least at one portion in a tire axial direction X as going to outer side in the tire axial direction X, or capacity of the cavity 41 becomes smaller at the whole tire width in a tire axial direction X as going to outer side in the tire axial direction X.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a pneumatic tire having a tread including blocks formed with sipes, and a tire molding mold for molding the pneumatic tire.

Background Art

[0002] A pneumatic tire has a tread that is the portion in contact with the road surface. The tread includes a plurality of blocks. Sipes are formed in each of the blocks. A sipe is a narrow groove, and has functions such as adjusting the hardness of the block, and increasing the edges of the block to improve grip force. The sipes of a pneumatic tire are molded using sipe blades provided in a tire molding mold.

[0003] For example, Patent Document 1 discloses a pneumatic tire in which a plurality of fine protrusions are formed on the wall surfaces of sipes to improve the water repellency of the sipe wall surfaces and drain water inside the sipes. In addition, Patent Document 2 discloses a pneumatic tire in which irregularities are formed on the inner wall surfaces of sipes to increase the friction coefficient between the inner wall surfaces, thereby suppressing large deformation of the blocks.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of Invention

Problems to be Solved by the Invention

[0005] However, in the pneumatic tire disclosed in Patent Document 1, although multiple micro-protrusions are formed on the wall surface of the sipes to improve the water-repellent effect of the sipes, the micro-protrusions may obstruct the drainage of water from the sipes, which can reduce wet performance. Here, wet performance refers to the ability of a pneumatic tire to grip the road surface and drive in wet conditions such as during rain.

[0006] Furthermore, while the pneumatic tire disclosed in Patent Document 2 improves the coefficient of friction, it does not take into account improving wet performance. Moreover, Patent Documents 1 and 2 do not take into account improving the dry performance of pneumatic tires.

[0007] Therefore, the present invention aims to provide a pneumatic tire and a tire molding die that can improve both dry and wet performance. [Means for solving the problem]

[0008] The pneumatic tire according to the present invention is a pneumatic tire having a tread including blocks on which sipes are formed, wherein a plurality of depressions are formed on one wall surface of the sipes, and the volume of the depressions decreases as they move outward in the tire axial direction, at least in a portion of the tire axial direction. [Effects of the Invention]

[0009] According to the pneumatic tire and tire molding die of the present invention, it is possible to improve both dry performance and wet performance. [Brief explanation of the drawing]

[0010] [Figure 1] This is a plan view showing the block pattern of a pneumatic tire, which is an example of an embodiment. [Figure 2] This is an enlarged view of section A in Figure 1. [Figure 3] This is a front view of the wall surface of a sipe, which is an example of an embodiment (viewed from the direction of arrow B in Figure 1). [Figure 4] This is a front view of the wall surface of a sipe, which is another example of an embodiment. [Figure 5] This is a front view of the wall surface of a sipe, which is another example of an embodiment. [Figure 6] This is a schematic diagram showing a tire molding die, which is an example of an embodiment. [Figure 7] This is a side view showing a sipe blade, which is an example of an embodiment. [Figure 8] This is a plan view showing the block pattern of a pneumatic tire, which is another example of an embodiment. [Figure 9] This is a plan view showing the block pattern of a pneumatic tire, which is another example of an embodiment. [Figure 10] This is a plan view showing the block pattern of a pneumatic tire, which is another example of an embodiment. [Figure 11] This is a plan view showing the block pattern of a pneumatic tire, which is another example of an embodiment. [Figure 12] This is a plan view showing the block pattern of a pneumatic tire, which is another example of an embodiment. [Figure 13] This is a plan view showing the block pattern of a pneumatic tire, which is another example of an embodiment. [Modes for carrying out the invention]

[0011] An example of an embodiment of the present invention will be described in detail below. In the following description, specific shapes, materials, directions, numerical values, etc., are examples provided to facilitate understanding of the present invention and can be appropriately modified according to the application, purpose, specifications, etc.

[0012] <Air-filled tires> An example of an embodiment, a pneumatic tire 10, will be described using Figures 1 and 2.

[0013] As shown in Figure 1, the pneumatic tire 10 has a tread 20 including a block 30 in which sipes 40 are formed. According to the pneumatic tire 10, although details will be described later, it is possible to improve dry performance as well as wet performance.

[0014] Hereinafter, each member will be described according to the tire axial direction X, the tire circumferential direction Y, and the tire radial direction Z. Further, in the tire axial direction X, description may be made using the equator side and the shoulder side in the tire width. Specifically, for a tire in which the mounting orientation to a vehicle is specified, the side located on the vehicle outer side when mounted on the vehicle is defined as the outer side (OUT side), and the side located on the vehicle inner side when mounted on the vehicle is defined as the inner side (IN side). In the drawings, the equator CL, the shoulder side SH, the inner side IN, and the outer side OUT are indicated in each direction.

[0015] The tread 20 is a portion of the pneumatic tire 10 that comes into contact with the road surface. The tread 20 has a plurality of blocks 30 partitioned by main grooves 21 and sub-grooves 22. Each of the blocks 30 is formed in the same rectangular shape in a plan view, and is formed in alignment on the tread 20. However, without being limited to the shape of the blocks 30 of the present embodiment, the blocks 30 may be rhombic or parallelogram-shaped as long as they are partitioned by the main grooves 21 and the sub-grooves 22, and the shape is not particularly limited.

[0016] The main grooves 21 are grooves formed in a linear shape so as to extend along the tire circumferential direction Y. The sub-grooves 22 are grooves formed in a linear shape so as to extend along the tire axial direction X. However, without being limited to the main grooves 21 or the sub-grooves 22 of the present embodiment, the main grooves 21 may be formed to be inclined with respect to the tire circumferential direction Y, and the sub-grooves 22 may be formed to be inclined with respect to the tire axial direction X.

[0017] <Sipes> As shown in Figures 1 and 2, three sipes 40 are formed on the block 30. The sipes 40 are grooves that are at least narrower in width than the main grooves 21 and the secondary grooves 22, and are formed so that the depth of the grooves is in the radial direction Z of the tire. However, the number of sipes 40 is not limited to that of this embodiment; it is sufficient for 3 to 5 sipes 40 to be formed on the block 30.

[0018] The sipe 40 is formed in a straight line along the tire axis X. However, the shape of the sipe 40 is not limited to that of this embodiment; for example, the sipe 40 may be formed at an angle with respect to the tire axis X, may be formed in a corrugated shape, or may be formed in a zigzag shape. A plurality of recesses 41, which will be described in detail later, are formed on one wall surface of the sipe 40.

[0019] With the sipes 40, the hardness of the blocks 30 on the tread 20 can be adjusted by changing the shape or number of the sipes 40. In addition, the sipes 40 increase the edge of the blocks 30, which can improve the grip of the pneumatic tire 10. Furthermore, the sipes 40 absorb water from the water film on wet or icy road surfaces, causing the blocks 30 to adhere more closely to the road or ice, thus improving the grip of the pneumatic tire 10.

[0020] <Indentation> Using Figure 3, we will describe a recess 41, which is an example of an embodiment.

[0021] In the following, blocks 30 will be described as blocks 30A, 30B, 30C, 30D, and 30E, in order from the inside to the outside in the tire axis direction X. When describing all blocks 30, they will simply be referred to as block 30. Similarly, sipes 40 will be described as sipes 40A, 40B, 40C, 40D, and 40E, which are formed on blocks 30A, 30B, 30C, 30D, and 30E, respectively. When describing all sipes 40, they will simply be referred to as sipes 40.

[0022] Multiple depressions 41 are formed on one wall surface of the sipe 40. The depressions 41 allow water from the block surface of the tread 20 to be absorbed, thereby improving the water absorption effect of the sipe 40. In addition, the depressions 41A, 41B, 41C, 41D, and 41E formed on the respective sipes 40A, 40B, 40C, 40D, and 40E formed on each block 30 are smaller in areas other than where the depressions 41 are formed on the flat surface.

[0023] In this embodiment, a depression 41 of the same depression volume is formed in the sipe 40 of one of the multiple blocks 30. In addition, in this embodiment, the number of depressions 41 formed in each of the sipes 40A, 40B, 40C, 40D, and 40E is the same.

[0024] The recess 41 in this embodiment is formed in a hemispherical shape, but is not limited thereto. For example, it may be semi-ellipsoidal. In this embodiment, the recess 41 is preferably formed in a portion from the block surface side to a length of 50 or more when the length of the sipe 40 in the tire radial direction Z (sipe depth) is set to 100. In this embodiment, the recess 41 is preferably formed in a length of 50 or more when the length of the sipe 40 in the tire axial direction X is set to 100.

[0025] It should be noted that the configuration is not limited to the recess 41 being formed on one wall surface of the sipe 40, as in the recess 41 of this embodiment; the recess 41 may also be formed on the other wall surface of the sipe 40. It is preferable that the opposing surfaces of the recess 41 be flat surfaces, and that the recess 41 be formed only on one wall surface of the sipe 40.

[0026] <Effects> The above configuration improves both wet performance and dry performance during cornering. Details are explained below.

[0027] In the case of pneumatic tires 10, they are often mounted in a tilted position (negative camber) when viewed from the front of the vehicle. In the pneumatic tire 10 of this embodiment, the volume of the inner recess 41 in the tire axial direction X of the sipe 40 is larger than the volume of the outer recess 41. As a result, the contact area on the inner side in the tire axial direction X is increased, which improves braking performance on wet surfaces and thus improves wet performance.

[0028] Furthermore, in the pneumatic tire 10 of this embodiment, the volume of the inner recess 41 in the tire axial direction X among the multiple recesses 41 is larger than the volume of the outer recess 41. By moderately reducing the rigidity, the contact length of the pneumatic tire 10 (the length in the tire circumferential direction Y that the pneumatic tire 10 is in contact with) can be increased, thereby increasing the contact area and improving wet performance.

[0029] On the other hand, in the pneumatic tire 10 of this embodiment, the volume of the outer recess 41 in the tire axial direction X is smaller than the volume of the inner recess 41. As a result, the stiffness per unit area on the outer side in the tire axial direction X is higher than the stiffness per unit area on the inner side, which improves cornering performance on dry roads and thus improves dry performance.

[0030] <Another embodiment (recess)> Using Figures 4 and 5, we will describe another example of the embodiment, the recess 41.

[0031] In the following, only the parts that differ from the embodiment illustrated in Figure 3 will be described, and the parts that are the same as the embodiment illustrated in Figure 3 will not be explained.

[0032] As shown in Figure 4, each sipe 40A, 40B, 40C, 40D, and 40E has recesses 41A, 41B, 41C, 41D, and 41E with different recess volumes. The recess volume of the recess 41 decreases as you move outward in the tire axial direction X across the entire tire width in the tire axial direction X. In other words, the recess volumes of the recesses 41A, 41B, 41C, 41D, and 41E formed in each sipe 40A, 40B, 40C, 40D, and 40E formed in each block 30 decrease as you move outward in the tire axial direction X.

[0033] In this embodiment, the sipe 40 of one of the multiple blocks 30 has a depression 41 of the same depression volume. Also in this embodiment, the number of depressions 41 formed in each sipe 40A, 40B, 40C, 40D, and 40E decreases as you move outward in the tire axis direction X.

[0034] As shown in Figure 5, each sipe 40A, 40B, 40C, 40D, and 40E has recesses 41A, 41B, 41C, 41D, and 41E with different recess volumes. The recess volume of the recess 41 decreases as you move from the equator CL in the tire axis direction X towards the shoulder side along the entire tire width in the tire axis direction X. In other words, the recess volumes of the recesses 41C, 41D, and 41E formed in each sipe 40C, 40D, and 40E formed in each block 30 decrease as you move from the equator CL in the tire axis direction X towards the shoulder side SH. Also, the recess volumes of the recesses 41C, 41B, and 41A formed in each sipe 40C, 40B, and 40A formed in each block 30 decrease as you move from the equator CL in the tire axis direction X towards the shoulder side SH.

[0035] In this embodiment, a recess 41 of the same recess volume is formed in the sipe 40 of one of the multiple blocks 30. Furthermore, in this embodiment, the recess volumes of recesses 41A and 41E are the same, and the recess volumes of recesses 41B and 41D are the same.

[0036] <Tire mold> Using Figure 6, we will describe a mold 50, which is an example of an embodiment.

[0037] The mold 50, used as a mold for molding tires, is a mold for molding the pneumatic tire 10 described above. The pneumatic tire 10 has a tread 20 including blocks 30 on which sipes 40 are formed, as described above, and a sidewall (not shown) that forms the side. The mold 50 makes it possible to mold a pneumatic tire 10 that can improve both dry and wet performance.

[0038] In the following, each component will be described according to the tire axial direction X, tire circumferential direction Y, and tire radial direction Z of the pneumatic tire 10 molded by the mold 50.

[0039] Furthermore, in the following, the sipe blades 60 will be described as sipe blades 60A, 60B, 60C, 60D, and 60E, in order from the inside to the outside along the tire axis X. When describing all of the sipe blades 60, they will simply be referred to as sipe blades 60.

[0040] The mold 50 includes a tread mold 51 for molding the surface of the tread 20 of the pneumatic tire 10, and a pair of side molds 52 for molding the surface of the sidewall.

[0041] The tread mold 51 includes a main body 54 having a tread molding surface 53, protrusions 55 protruding from the tread molding surface 53, and sipe blades 60 protruding from the tread molding surface 53 and provided between the protrusions 55.

[0042] The main body 54 is made of a metal material, for example, an aluminum alloy. Suitable aluminum alloys include, for example, AC4 series and AC7 series. The projection 55 is the part that forms the main groove 21 in the pneumatic tire 10. The projection 55 is made of the same metal material as the main body 54.

[0043] <Siped Blade> An example of an embodiment, the sipe blade 60, will be described using Figure 7.

[0044] The sipe blade 60 forms the sipes 40 of the pneumatic tire 10. The sipe blade 60 protrudes from the tread forming surface 53 in the radial direction Z of the tire between the projections 55. The sipe blade 60 is flat and made of a metal material, which may be stainless steel, for example. Suitable stainless steels include SUS303, SUS304, SUS630, SUS631, etc. When using a 3D molding machine, SUS304L, SUS630 equivalent material 17-4PH, etc., are suitable.

[0045] The general method for processing the sipe blade 60 involves using a press molding machine to form its shape. For sipe blades like the one in this embodiment, where the shape changes in the thickness direction, machining is used to form the shape through cutting. Furthermore, by using a 3D modeling machine, complex shapes that are difficult to form with machining can be created.

[0046] The sipe blade 60 includes sipe blades 60A, 60B, 60C, 60D, and 61E, each having protrusions 61A, 61B, 61C, 61D, and 61E with different volumes of the protruding portion (hereinafter referred to as protrusion volume), as will be described in detail later.

[0047] <Protrusion> Multiple protrusions 61 are formed on one side of the sipe blade 60. The protrusions 61 are the parts that form the depressions 41 of the sipes 40 of the pneumatic tire 10 described above. The protrusions 61 in this embodiment are formed in a hemispherical shape, but are not limited to this. For example, they may be semi-ellipsoidal. In this embodiment, it is preferable that the protrusions 61 are formed from the block surface side to a portion of 50 or more when the length of the sipe 40 in the tire radial direction Z (sipe depth) is set to 100. In this embodiment, it is preferable that the protrusions 61 are formed in a length of 50 or more when the length of the sipe 40 in the tire axial direction X is set to 100.

[0048] Each of the sipe blades 60A, 60B, 60C, 60D, and 60E has protrusions 61A, 61B, 61C, 61D, and 61E with different volume characteristics.

[0049] In this embodiment, the projection 61 has a reduced recess volume as it extends outward in the tire axial direction X across the entire tire width in the tire axial direction X. In other words, the projection volume of the projections 61A, 61B, 61C, 61D, and 61E formed on each sipe blade 60A, 60B, 60C, 60D, and 60E decreases as it extends outward in the tire axial direction X.

[0050] In this embodiment, one of the multiple sipe blades 60 has a projection 61 with the same projection volume. Also, in this embodiment, the number of projections 61 formed on each sipe blade 60 is the same.

[0051] <Another embodiment (block)> Figures 8 to 13 illustrate another example of the embodiment, a pneumatic tire 10.

[0052] The following describes a configuration in which the arrangement of the blocks 30 of the pneumatic tire 10 described above differs. In the pneumatic tire 10 described below, the sipes 40 and recesses 41 are formed in the same way as in the pneumatic tire 10 described above. Furthermore, in the following, the blocks 30 will be described as blocks 30A, 30B, 30C, 30D, and 30E in order from the inside to the outside in the tire axis direction X.

[0053] As shown in Figure 8, the block 30C formed on the equator CL may be the size of multiple (four in the illustrated example) the other blocks 30A, 30B, 30D, and 30E in the tire circumferential direction Y.

[0054] As shown in Figure 9, block 30C formed on the equator CL and block 30D adjacent to the outside of block 30C may be the size of multiples of the other blocks 30A, 30B, and 30E (four in the illustrated example) in the tire circumferential direction Y. Also, block 30C formed on the equator CL and block 30B adjacent to the inside of block 30C may be the size of multiples of the other blocks 30A, 30C, and 30E (four in the illustrated example) in the tire circumferential direction Y.

[0055] As shown in Figure 10, the block 30C formed on the equator CL may be the size of multiple blocks 30A, 30B, and 30E (three in the illustrated example) in the tire circumferential direction Y. Furthermore, the positions of both ends of block 30C in the tire circumferential direction Y do not have to be the same as the end positions of the other blocks 30A, 30B, and 30E in the tire circumferential direction Y.

[0056] As shown in Figure 11, the block 30C formed on the equator CL may be the size of multiple blocks 30A, 30B, and 30E (four in the illustrated example) in the tire circumferential direction Y. Also, the block 30D adjacent to the outside of block 30C may be the size of multiple blocks 30A, 30B, and 30E (two in the illustrated example) in the tire circumferential direction Y.

[0057] As shown in Figures 12 and 13, the tire is divided along the same axial length from the inner contact point to the outer contact point in the tire axis direction X, and is further divided into the innermost shoulder section SH, the innermost shoulder section SH, and the central section Ce sandwiched between the two shoulder sections.

[0058] Here, the contact edge refers to the end of the tread 20 including the contact surface when a normal load is applied with a camber angle of 0° under normal conditions. "Normal conditions" refers to an unloaded state in which the pneumatic tire 10 is mounted on a normal rim and adjusted to the normal internal pressure.

[0059] As shown in Figure 12, the innermost block 30A may be positioned across the shoulder portion SH and the central portion Ce. Alternatively, the outermost block 30A may be positioned across the shoulder portion SH and the central portion Ce.

[0060] As shown in Figure 13, the innermost block 30A and the block 30B adjacent to the outside of block 30A may be placed on the shoulder portion SH. Alternatively, the outermost block 30E and the block 30D adjacent to the inside of block 30E may be placed on the shoulder portion SH.

[0061] However, the present invention is not limited to the embodiments and their modifications described above, and it goes without saying that various changes and improvements are possible within the scope of the claims of this application. [Explanation of symbols]

[0062] 10 Pneumatic tire, 20 Tread, 21 Main groove, 22 Secondary groove, 30 Block, 40 Sipe, 40A Wall surface, 40B Wall surface, 41 Recess, 41A Recess, 41B Recess, 41C Recess, 41D Recess, 41E Recess, 50 Mold, 51 Tread mold, 52 Side mold, 53 Tread molding surface, 54 Main body, 55 Protrusion, 60 Sipe blade, 61 Protrusion, 61A Protrusion, 61B Protrusion, 61C Protrusion, 61D Protrusion, 61E Protrusion

Claims

1. A pneumatic tire having a tread that includes blocks with sipes formed therein, Multiple indentations are formed on one wall surface of the aforementioned sipe. The aforementioned depression has a volume that decreases as it moves outward in the tire axial direction across the entire tire width in the tire axial direction. Pneumatic tires.

2. The pneumatic tire according to Claim 1, The aforementioned blocks are formed in multiple locations along the tire axis, In one of the multiple blocks, the sipe has multiple depressions of the same volume. Pneumatic tires.

3. A pneumatic tire according to Claim 1, The aforementioned blocks are formed in multiple locations along the tire axis, The number of recesses in the sipes of each of the blocks is the same. Pneumatic tires.

4. A tire molding die equipped with a sipe blade for forming sipes in the tread blocks of a tire, Multiple protrusions are formed on at least one side surface of the sipe blade. The aforementioned protrusions have a volume that decreases as they move outward in the tire axial direction across the entire tire width in the tire axial direction. Mold for tire molding.

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