JP4711373B2 - Pneumatic tire - Google Patents

Description

表１の結果が示すように、実施例では、脱型時の切断により凸部の形成が好適に行え、サイプの閉塞やブロックの倒れ込みを抑制することで、氷雪路性能、ウエット制動性能、耐偏摩耗性などが従来品より良好であった。また、ベントスピューの数が従来品より少ないため、ノイズ性能やタイヤ外観も従来品より良好となった。
【００５１】
これに対して、開口部のテーパ角が小さすぎる比較例２では、所望の位置に凸部が十分形成されず、各性能の改善効果が小さかった。また、開口部のテーパ角が大きすぎる比較例３では、凸部の側壁面同士の係合作用が小さく、倒れ込み抑制効果が低下するため、各性能の改善効果が小さかった。これは、凸部側壁面の間隔が大きすぎる比較例４についても同様であった。
【図面の簡単な説明】
【図１】本発明の空気入りタイヤの一例のトレッド面を示す平面図
【図２】本発明のおけるサイプの一例の縦断面を示す要部断面図
【図３】サイプ形成用のブレードの一例を示す図
【図４】本発明におけるサイプの他の例を示す要部断面図
【図５】従来のサイプの縦断面を示す要部断面図
【符号の説明】
１ ブロック
１０ サイプ
１１ａ 内壁面
１１ｂ 内壁面
１２ 凸部
１２ａ 上面
１２ｂ 側壁面
１３ 凸部
１３ａ 上面
１３ｂ 側壁面
θ テーパ角
Ｄ 側壁面同士の間隔[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire including a tread pattern having a plurality of blocks each having a plurality of sipes, and is particularly useful as a studless tire.
[0002]
[Prior art]
Conventionally, in order to improve the ice performance of a studless tire, a tire pattern in which a plurality of sipes are arranged in each part (center part, mediate part, shoulder part) is known. Conventionally, the shape of such a sipe is generally a plane or corrugated sipe whose shape does not change in the depth direction of the sipe. By forming such sipes in blocks, the edge effect, the water removal effect, and the adhesion effect are improved, so the number of sipes has tended to increase in recent years.
[0003]
However, increasing the number of sipe and increasing the sipe density will increase the number of edges, but the rigidity of the whole block will decrease and the sipe will collapse, so the edge effect will be reduced and the ice performance will also decrease Problems arise. For this reason, attention has recently been paid to so-called three-dimensional sipe, in which the shape of the sipe is changed in the depth direction to suppress the sipe collapse.
[0004]
For example, in JP 2000-177330 A, in a studless tire in which at least one sipe 35 is provided in a block 34 as shown in FIG. A plurality of small blocks 36a and 36b are formed on the inner wall surfaces 35a and 35b for the sipe 35 having 30% or more of the total number of sipes, and the small blocks 36a and 36b of the inner wall surfaces 35a and 35b facing each other are combined with each other. The one arranged like this is proposed. Further, examples of the shape of the small block include a hemispherical shape, a cylindrical shape, a quadrangular prism shape, and a shape in which a tapered portion is formed by partially cutting out the quadrangular prism.
[0005]
[Problems to be solved by the invention]
However, in the studless tire described in the above publication, since the blade disposed in the mold to form a sipe having a small block has a shape having no opening, each block section partitioned by the blade It was necessary to provide a vent spew for venting air. When the number of bent spews increases in this way, the tire appearance, ice / snow road performance, noise performance, etc. when new are easily deteriorated.
[0006]
On the other hand, Japanese Patent Application Laid-Open No. 11-105512 discloses a pneumatic tire in which a cylindrical or tapered protrusion is formed inside a sipe by a blade having an opening. However, in this tire, since the engaging action between the protrusions does not occur, the sipe collapse cannot be sufficiently suppressed. Further, if the taper angle of the tapered protrusion is not appropriate, there is a problem that the protrusion cannot be formed as planned by cutting at the time of demolding.
[0007]
Therefore, the object of the present invention is to suitably form the convex portion by cutting at the time of demolding, and by suppressing the blockage of the sipe or the collapse of the block, it is possible to improve the snow and snow road performance, wet braking performance, uneven wear resistance, etc. The object is to provide an improved pneumatic tire.
[0008]
[Means for Solving the Problems]
The above object can be achieved by the present invention as described below.
That is, the pneumatic tire of the present invention is a pneumatic tire having a tread pattern having a plurality of blocks each having a plurality of sipes, and the sipes are alternately formed in the depth direction from both opposing inner wall surfaces, A convex portion whose upper surface is substantially in contact with the opposing inner wall surface, the taper angle in the longitudinal section of the side wall surface of the convex portion is 10 to 30 °, and the convex portion is formed by cutting, and is formed vertically The interval between the side wall surfaces in the longitudinal section of the projected portion is 0.5 to 2.0 mm.
[0009]
In the present invention, the taper angle is the average of the shape of the side wall surface appearing in the vertical section of the convex portion when the shape of the side wall surface is not a straight line, or when the taper angle of the upper and lower side wall surfaces is different (vertical asymmetry). Calculate with values. Moreover, about the space | interval of side wall surfaces, when the shape of the side wall surface which appears in the vertical cross section of a convex part is not a straight line, it calculates with the position where the space | interval of the direction parallel to an inner wall surface becomes the shortest.
[0010]
In the above, it is preferable that the area of the upper surface of the said convex part is 2-20 mm < ² >. Here, the upper surface of a convex part refers to the surface cut | disconnected at the time of demolding, and the area is calculated as a plane enclosed by the peripheral part.
[0011]
[Function and effect]
According to the present invention, the upper surface of the convex portion formed on the inner wall surface of the sipe is substantially in contact with the opposite inner wall surface, and the taper angle in the longitudinal section of the side wall surface is 10 to 30 °. As the result of the example shows, the projection can be suitably formed at a desired site by cutting at the time of demolding. In addition, since the blade of the mold for forming the sipe opens at the portion where the convex portion is formed, it is possible to reduce the vent spew for air bleeding. Moreover, since the space | interval of the side wall surfaces in the longitudinal cross-section of a convex part is 0.5-2.0 mm while having said taper angle, it suppresses the fall of a block suitably by the engagement effect | action of side wall surfaces. Can do. As a result, it is possible to suitably form the convex part by cutting at the time of demolding, and by suppressing the blockage of the sipe and the collapse of the block, the air and snow road performance, wet braking performance, uneven wear resistance, etc. are improved. Tires can be provided.
[0012]
Also, the area of the upper surface of the convex portion, when a 2 to 20 mm ^2, the number of side wall surfaces which mutually engage can reasonably secure, yet more reliably collapsing of the closure and block sipes by reduced-rigidity of the projecting portion Can be suppressed. Further, the projection can be more reliably formed by cutting at the time of demolding.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the pneumatic tire of the present invention includes a tread pattern T having a plurality of blocks 1 each having a plurality of sipes 10. In the present embodiment, an example is shown in which a plurality of quadrangular blocks 1 divided by circumferential grooves 2, zigzag grooves 3 and oblique grooves 4 are formed, and eight rows of blocks 1 are arranged in the tire width direction.
[0014]
Each block 1 is formed with a plurality of rows of sipes 10 in the tire width direction or in a direction slightly inclined from the tire width direction. Both ends of each sipe 10 are opened in a groove adjacent to the block 1, but the present invention is not limited to this. The sipe 10 is not limited to the side wall of the block 1, and is not exposed from the side wall of the block 1. It can be properly used depending on the pattern configuration.
[0015]
The sipe 10 in the present embodiment extends in the depth direction from a linear opening on the surface of the block 1 as shown in FIGS. 1 and 2, but may be a wave sipe as described later. .
[0016]
As shown in FIG. 2, the sipe 10 according to the present invention has opposed inner wall surfaces 11a and 11b, and has convex portions 12 and 13 that are alternately formed in the depth direction from both of them. The convex portions 12 and 13 have the upper surfaces 12a and 13a substantially in contact with the opposed inner wall surfaces 11b and 11a. The inner wall surfaces 11b and 11a and the upper surfaces 12a and 13a may be completely in contact with each other or may have a slight gap. In either case, it can be formed by a blade having an opening.
[0017]
The taper angle θ in the longitudinal section of the side wall surfaces 12b, 13b of the convex portions 12, 13 is 10 to 30 °, preferably 12 to 20 °. When the taper angle θ is less than 10 °, it becomes difficult to form the convex portions 12 and 13 at a desired position by cutting during demolding. When the taper angle θ exceeds 30 °, the effect of suppressing the collapse of the block due to the engaging action of the convex portions 12 formed on the upper and lower sides and the side wall surfaces 12b of the convex portions 13 becomes insufficient.
[0018]
Moreover, the space | interval D of the side wall surfaces 12b and 13b in the vertical cross section of the convex parts 12 and 13 formed up and down is 0.5-2.0 mm, Preferably it is 0.8-1.7 mm. If the distance D is less than 0.5 mm, problems such as breakage due to a decrease in the strength of the mold blade are likely to occur, and if it exceeds 2.0 mm, the engagement between the side wall surfaces 12b and 13b becomes insufficient and the block collapses. The suppression effect is reduced.
[0019]
The protrusions 12 and 13 are most preferably formed on the entire inner wall surfaces 11a and 11b, but are preferably formed at least in a region having a depth of 50% from the surface of the block 1. Moreover, about the convex part 13 located in the part nearest to the block 1 surface, it is preferable that the position of the upper end of the upper surface is located in 0.3-0.8 mm from the block 1 surface. Thus, when the convex part 13 approaches the block 1 surface, air bleeding can be more reliably performed at the time of the vulcanization molding by a metal mold | die.
[0020]
The groove width of the sipe 10, that is, the distance between the opposing inner wall surfaces 11 a and 11 b is preferably 0.3 to 1.0 mm, and more preferably 0.3 to 0.8 mm. Further, the depth of the sipe 10 is preferably 6.0 to 10.0 mm.
[0021]
In the present invention, since the fall-in suppressing effect of the block 1 is large, the edge effect can be further enhanced by increasing the number of edges by increasing the number of sipes 10 and increasing the sipe density.
[0022]
The sipe 10 having the convex portions 12 and 13 as described above can be manufactured as follows. In the present embodiment, the convex portions 12 and 13 are alternately formed in the depth direction from both of the opposed inner wall surfaces 11a and 11b, and the convex portions 12 and 13 are also formed in the lateral direction (sipe opening direction). An example of alternately forming is shown. By alternately forming the convex portions 12 and 13 in the lateral direction, even when a lateral shearing force is generated in the block pieces on both sides divided by the sipe 10, the engaging action between the side wall surfaces 12b and 13b is performed. Thus, deformation of the block piece can be effectively suppressed.
[0023]
The sipe 10 having the convex portions 12 and 13 can be formed by vertically arranging a blade 20 as shown in FIG. 3 on the tread forming surface of the vulcanization mold. 3 (a) is a front view of the blade 20, FIG. 3 (b) is a cross-sectional view taken along the line bb in FIG. 3 (a), and FIG. 3 (c) is a cross-sectional view taken along line cc in FIG. It is an arrow cross section.
[0024]
When the green tire is sealed in the vulcanization mold in which the blade 20 is erected, the tread rubber enters the openings 21, 22, 25, and 26 of the blade 20, and the convex portion 12 is cut after cutting. , 13 are formed. At that time, the tread rubber spreads over the entire tread forming surface of the mold to form the tread T, but air passes through the openings 21, 22, 25, and 26 of the blade 20, so that the blade 20 partitions the tread rubber. It is not necessary to provide a vent spew for venting air in each block 1 block.
[0025]
When the tire is demolded after vulcanization molding and the blade 20 is pulled out, the communication portion is cut by the peripheral portions 23 and 27 of the openings 21 to 26 of the blade 20 so that the convex portions 12 and 13 are in desired positions. It is formed. When the shape is maintained until the tire is used, the inner wall surfaces 11b and 11a and the upper surfaces 12a and 13a of the convex portions 12 and 13 are in contact with each other, but a slight gap is generated due to deformation during use. There is a case.
[0026]
The pneumatic tire of the present invention is the same as a normal pneumatic tire except that it includes the tread pattern T as described above, and any conventionally known material, shape, structure, manufacturing method, and the like can be employed in the present invention.
[0027]
The pneumatic tire of the present invention is particularly useful as a studless tire because it exhibits the effects as described above and is excellent in ice performance and snow performance.
[0028]
[Other Embodiments]
Hereinafter, other embodiments of the present invention will be described.
[0029]
(1) In the above-described embodiment, an example is shown in which the sipe 10 having the convex portions 12 and 13 shown in FIG. 2 is formed. However, the shape of the convex portion of the sipe in the present invention is that the upper surface is circular. Any shape such as a rectangle such as an ellipse, a triangle, a rhombus, a parallelogram, and other polygons may be used. Further, the shape of the vertical section of the convex portion may be a shape as shown in FIGS. 4 (a) to 4 (b), for example.
[0030]
FIG. 4A shows an example in which the taper angles of the upper and lower wall surfaces of the convex portions 12 and 13 are different (asymmetric). In that case, it is preferable that the taper angle of the lower side wall surface is larger than the upper side from the viewpoint of cutting property at the time of demolding.
[0031]
FIG. 4B shows an example in which the side wall surface of the portion adjacent to the upper surfaces 12a and 13a has a round shape (the taper angle is locally large) in order to further improve the cutting property at the time of demolding. .
[0032]
(2) In the above-described embodiment, an example of the block pattern as shown in FIG. 1 has been shown. However, the block pattern is not limited to this shape, and may be a parallelogram, V-shaped, pentagonal, or curved block. . In addition, a grooved block or a part of land portion may be continuous in the circumferential direction near the center or near the end.
[0033]
(3) In the above-described embodiment, the sipe 10 has a linear shape as shown in FIG. 1, but a sipe of a wave shape or a zigzag shape may be used. In this case, the wavy line is not limited to a wave close to a sine wave, and may be any shape such as a wave line obtained by alternately combining a straight line and a curve or a wave close to a rectangular wave.
[0034]
(4) In the above-described embodiment, as shown in FIG. 1, an example in which a plurality of rows of sipes are formed in the tire width direction or the like has been described. It is not limited to being parallel to the width direction. However, the angle formed by the direction of the center line and the tire width direction is preferably 0 to 45 °.
[0035]
(5) In the above-described embodiment, as shown in FIG. 2, an example is shown in which the sipe is formed so as to be perpendicular to the block surface. (15 ° or less) may be inclined.
[0036]
【Example】
Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.
[0037]
(1) Ice braking performance tires (P235 / 75R15, used rim 15 x 6.5 JJ, air pressure 240 kPa) mounted on a real vehicle (domestic 3000cc class Krokan 4WD vehicle), frozen road surface under load conditions of 4 passengers The braking distance when the vehicle was fully locked by applying braking force at a speed of 40 km / h was evaluated as an index. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.
[0038]
(2) Snow traction performance Based on SAE-J1466, using a snow traction tester on a snowy road, the vehicle traveled at a speed of 8 km / h, and the average value of the slip rate to the wear factor of 20 to 300% was taken in ( n = 10).
[0039]
(3) Wet braking performance As in (1) above, tires are mounted on an actual vehicle, and a wet road surface with a water depth of 1 mm is run under the load condition of four passengers. A braking force of 20 km / h is applied at an initial speed of 90 km / h. The distance required to decelerate to h was evaluated by an index. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.
[0040]
(4) Wear resistance performance The amount of step wear (step difference between sipe and sipe due to wear) when traveling 9600 km on a paved road was measured and evaluated by an index. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.
[0041]
(5) Sensory evaluation by two noise performance test drivers and an index evaluation. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.
[0042]
(6) Tire appearance Sensory evaluation by 10 general consumers was performed and evaluated by an index. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is set to 100, and a larger value indicates a better result.
[0043]
(7) Formability of convex portion The ratio of the convex portion formed at a desired position on the inner wall surface after vulcanization is shown as a percentage (%).
[0044]
Example 1
In the tread pattern as shown in FIG. 1, an opening (taper angle is 15 °, the area of the circular upper surface is 9 mm ² , and the interval between the convex side walls is 1) in the region 50% deep from the block surface of the blade shown in FIG. .2 mm) was used to produce a prototype radial tire. For other sizes of sipe, the sipe depth was 8 mm and the groove width was 0.5 mm. In addition, the number of vent spewes for venting air was set to 1/4 of the conventional molding die. Table 1 shows the results of each performance evaluation described above using this tire.
[0045]
Example 2
In Example 1, except that a blade having an opening formed on the entire surface was used, a prototype radial tire was manufactured in the same manner as in Example 1, and the above performance evaluations were performed. The results are shown in Table 1.
[0046]
Comparative example 1 (conventional product)
In Example 1, a trial radial tire was manufactured in the same manner as in Example 1 except that a blade having no opening was used, and each performance evaluation was performed. The results are shown in Table 1. The number of bent spews was the same as before.
[0047]
Comparative Example 2
In Example 1, a prototype radial tire was manufactured in the same manner as in Example 1 except that a blade whose opening taper angle was changed to 5 ° was used, and each performance evaluation was performed. The results are shown in Table 1.
[0048]
Comparative Example 3
In Example 1, a trial radial tire was manufactured in the same manner as in Example 1 except that a blade with the opening taper angle changed to 40 ° was used, and each performance evaluation was performed. The results are shown in Table 1.
[0049]
Comparative Example 4
In Example 1, a trial radial tire was manufactured in the same manner as in Example 1 except that a blade in which the interval between the convex side wall surfaces was changed to 3 mm was used, and each performance evaluation was performed. The results are shown in Table 1.
[0050]
[Table 1]

As shown in the results of Table 1, in the examples, the convex portions can be suitably formed by cutting at the time of demolding, and by suppressing the sipe blockage and the block collapse, the snowy road performance, wet braking performance, Uneven wear was better than the conventional product. In addition, since the number of vent spews is smaller than the conventional products, the noise performance and the tire appearance are also better than the conventional products.
[0051]
On the other hand, in Comparative Example 2 in which the taper angle of the opening is too small, the convex portion is not sufficiently formed at a desired position, and the improvement effect of each performance is small. Further, in Comparative Example 3 in which the taper angle of the opening is too large, the engagement effect between the side wall surfaces of the convex portions is small, and the effect of suppressing the collapse is lowered, so the effect of improving each performance is small. This was the same for Comparative Example 4 in which the interval between the convex portion side wall surfaces was too large.
[Brief description of the drawings]
FIG. 1 is a plan view showing a tread surface of an example of a pneumatic tire of the present invention. FIG. 2 is a cross-sectional view of a main part showing a longitudinal section of an example of a sipe according to the present invention. FIG. 4 is a cross-sectional view of a main part showing another example of a sipe according to the present invention. FIG. 5 is a cross-sectional view of a main part showing a longitudinal section of a conventional sipe.
1 block 10 sipe 11a inner wall surface 11b inner wall surface 12 convex portion 12a upper surface 12b side wall surface 13 convex portion 13a upper surface 13b side wall surface θ taper angle D spacing between side wall surfaces

Claims (2)

In a pneumatic tire provided with a tread pattern having a plurality of blocks formed with a plurality of sipes,
The sipe is formed alternately in the depth direction from both of the opposing inner wall surfaces, and has a convex portion whose upper surface abuts on the opposing inner wall surface, and the taper angle in the longitudinal section of the side wall surface of the convex portion is 10 to 10. The pneumatic tire is 30 °, the convex portions are formed by cutting, and the interval between the side wall surfaces in the longitudinal section of the convex portions formed vertically is 0.5 to 2.0 mm. . The pneumatic tire according to claim 1, wherein an area of an upper surface of the convex portion is ² to 20 mm ² .

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