JP4815673B2 - Pneumatic radial tire and its mold - Google Patents

Description

【００３４】
【発明の効果】
以上記載の通り、タイヤ回転軸を含むタイヤラジアル方向断面上でタイヤトレッド部の外輪郭を形成する踏面のクラウン形状が、２本以上の直線の繋ぎあわせによって踏面接地幅の８０％以上を構成し、しかも直線のタイヤ径方向の繋ぎあわせ部にタイヤ周方向のストレート溝を配して本発明のタイヤクラウン断面形状を直線で構成したので、耐偏摩耗性や氷上性能の良好なタイヤを提供できしかも、金型製作時間、金型コストを削減できる
【図面の簡単な説明】
【図１】本発明の実施例による空気入りラジアルタイヤのトレッド部のラジアル方向部分断面図。
【図２】本発明他の実施例を示す金型の部分斜視図。
【図３】 本発明に該当しない参考例を示す空気入りラジアルタイヤのトレッド部のラジアル方向部分断面図。
【図４】本発明のさらに他の実施例を示す空気入りラジアル方向タイヤのトレッド部のラジアル方向部分断面図。
【図５】従来の空気入りラジアルタイヤのトレッド部のラジアル方向部分断面図。
【図６】空気入りラジアルタイヤを接地させたラジアル方向断面説明図である。
【符号の説明】
１ キャップトレッド
２ 周方向ストレート溝
３ 周方向リブまたはブロック列
３ａ 周方向リブまたはブロック列の中央部
３ｂ 周方向リブまたはブロック列の接地端部
４ リム
１１ 下型モールド
１２ 背面ブロック
１３ 分割部品
１３ａ第一鋳造分割部品
１３ｂ第二鋳造分割部品
１４ 間隙
１５ 排気孔
１６ 分割部品のタイヤトレッド側表面
Ｓ 直線部分
Ｔ 平面部分
Ｗ 踏面接地幅[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic radial tire and a mold, and more particularly, to a pneumatic radial tire and a mold thereof that have excellent uneven wear resistance and on-ice performance, and that can reduce the manufacturing cost and manufacturing period of the mold. Is.
[0002]
[Prior art]
As shown in FIG. 5 as a typical example, the conventional pneumatic radial tire and mold are formed by a tread radius whose outer contour is a single tread radius or a relatively small tread radius T2 inscribed in a large tread radius T1. Yes. By the way, when a load is applied to the pneumatic radial tire and the outer contour of the tire tread portion is pressed against a road surface that is substantially flat, the groove 2 in which the bending rigidity of the tread portion is relatively small in the tire ground contact portion as shown in FIG. The deformation that bends at the fulcrum is added to the tire tread grounding part.
[0003]
In addition, since many tire circumferential straight grooves with good drainage performance have recently been employed for the purpose of improving wet road running performance, the tendency of the tread portion to bend around the straight grooves has become even stronger. The straight groove as used in the present invention is a so-called `` see-through part '' in which the groove is not completely shielded by the groove wall when viewed from the tire circumferential view from the meaning of increasing the deformation tendency of the tread portion to bend with the groove as a fulcrum. It is assumed that it includes a bent groove portion to the extent that exists.
[0004]
As a result, the outer contour of the tire tread portion is directly pressed against the road surface shape (flat surface), and the tire ground pressure at the center portion of the relatively convex circumferential rib or block row is high. Or, since the ground pressure at the ground end of the block row is low, there is a large difference in the ground pressure at the center of the circumferential rib or block row and the ground end of the circumferential rib or block row, resulting in uneven wear. It is the cause.
[0005]
Further unfortunately, further improvements were required because a decrease in ground contact pressure on the surface convex circumferential ribs or block rows directly leads to a decrease in grip on the tire ice.
[0006]
In addition, when creating a mold for vulcanizing a pneumatic radial tire, the mold tread has a double curvature (tire circumferential direction and radial direction), making it impossible to produce a mold that is uniform for each tire size. Therefore, the increase in mold production cost and production period is inevitable.
[0007]
[Problems to be solved by the invention]
The object of the present invention is to improve the uneven wear resistance and on-ice performance by specifying the outer contour of the tire tread portion, and further reduce the manufacturing cost of the mold and shorten the manufacturing period. And providing the mold.
[0008]
[Means for Solving the Problems]
According to the present invention, the crown shape of the tread that forms the outer contour of the tire tread portion on the tire radial cross section including the tire rotation axis is more than 80% of the tread ground contact width by connecting two or more straight lines. configured, and the connecting together of the tire radial direction of a straight line with each other, is arranged, the tire circumferential direction of the straight groove, and, at least on the tire equator, two straight lines each other among the two or more straight lines Provided is a pneumatic radial tire in which tire radial joining portions joined so as to form a peak facing the tire outer peripheral side and straight grooves in the tire circumferential direction are arranged.
[0009]
By doing so, even if deformation that bends with the circumferential straight groove 2 being a fulcrum as a fulcrum is applied to the tire tread grounding portion at the tire grounding portion, the bending rigidity of the tread portion is relatively small. It is difficult to make a difference between the contact pressure and the contact pressure at the contact end portion of the tire circumferential rib or block row, and good uneven wear resistance can be enjoyed.
[0010]
In addition, as a result, the contact pressure at the contact end of the tire circumferential rib or the block row is increased, and the grip force on ice is improved and good on-ice performance is achieved.
[0011]
Here, the tread contact width is the maximum radial direction on a flat plate when a tire is mounted on a standard rim described in the 2000 edition JATMA and a load corresponding to 88% of the maximum load capacity is applied to the tire at an air pressure of 180 kPa. The value of the ground contact width.
[0012]
Further, according to the present invention, a pneumatic radial tire is provided in which the number of straight grooves provided in the straight joining portion is 1 to 6. By doing so, the drainage effect on the wet road surface is enhanced and better tire performance can be enjoyed.
[0013]
Further, according to the present invention, there is provided a pneumatic radial tire in which the shape of the tread surface that forms the outer contour of the tire tread portion is composed of a plurality of divided planes. This makes it possible to give a certain degree of curvature to the belt layer inside the tire, increase the flexibility of the belt layer, enjoy better tire ride performance, and substantially improve the curvature in the tire circumferential direction. Therefore, it is difficult to make a difference between the contact pressure at the center of the tire circumferential block row and the contact pressure at the contact end portion of the tire circumferential block row, and good uneven wear resistance can be enjoyed.
[0014]
Further, according to the present invention, the crown shape of the tread that forms the outer contour of the tire tread portion on the tire radial cross section including the tire rotation axis is 80% or more of the tread ground contact width by connecting two or more straight lines. In addition, there is provided a mold for vulcanizing a pneumatic tire in which straight grooves in the tire circumferential direction are arranged at joint portions in the tire radial direction between straight lines. By doing this, the mold tread shape does not have double curvature (the tire circumferential direction and radial direction), but only the circumferential curvature, that is, the truncated cone shape is continuous, so the mold production period is shortened. it can.
[0015]
According to the present invention, there is also provided a pneumatic tire vulcanization mold in which an outer contour portion of the mold is composed of a plurality of aluminum cast divided parts in a tire radial direction and a circumferential direction. By doing so, it is possible to configure the mold from aluminum cast divided parts obtained by dividing the frustoconical shape, which can significantly shorten the mold production period and reduce the mold production cost.
[0016]
Moreover, according to this invention, the tire tread side surface of the said division | segmentation components provides the mold for pneumatic tire vulcanization | cure. In this way, it is possible to form a flat aluminum cast divided part when manufacturing the mold, further reducing the manufacturing cost of the mold and significantly shortening the manufacturing period. In addition, there is an advantage that molds having different tire sizes and different outer shapes can be shared by changing the number of the divided parts.
[0017]
According to the present invention, a pneumatic radial tire vulcanizing mold formed by providing a gap of 0.001 mm to 0.1 mm in the cast seaming portion of the divided parts is provided. By doing so, it is possible to discharge air remaining on the surface of the unvulcanized tire during vulcanization of the tire, and it is not necessary to process a vent hole called a vent hole. It can be remarkably reduced and the production period can be remarkably shortened.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings, but the scope of the present invention is of course not limited to these embodiments. FIG. 1 is a partial cross-sectional view showing a crown shape of a tread that forms an outer contour of a tire tread portion on a tire radial cross-section according to an embodiment of the present invention, where 1 is a cap tread, 2 is a tire circumferential straight groove, 3 Is a circumferential rib or block row, 3a is a central portion of the circumferential rib or block row, 3b is a grounding end of the circumferential rib or block row, D is a tire outer diameter, W is a tread grounding width, and S is a straight portion. is there.
[0019]
Further, the tread land portion is composed of six straight lines, and five tire circumferential straight grooves 2 are provided at the connecting portion of the straight lines, and the tread surface circumferential direction forms the outer contour of the tire tread portion. The cross section (tire surface) of the ground contact portion of the rib or block row 3 is a straight line. That is, in the pneumatic radial tire of the present invention, the outer contour of the tire tread portion is formed by a straight joint, and a circumferential straight groove is disposed at the joint. The tire diameter is such that at least two of the two or more straight lines described above are connected at least to the tire equator so as to form a peak facing the tire outer peripheral side (that is, the mold outer peripheral side). The connecting portion in the direction and the straight groove in the tire circumferential direction are arranged (FIGS. 1, 4 and 5) .
Therefore, when a load is applied to the tire as shown in FIG. 6 and the outer contour of the tire tread portion is pressed against a substantially flat road surface, the circumferential straight is relatively small in bending rigidity of the tread portion at the tire ground contact portion. Although deformation that bends about the groove 2 as a fulcrum is applied to the tire tread grounding portion, there is a difference between the ground pressure at the center portion 3a of the tire circumferential rib or block row and the ground pressure at the ground end portion 3b of the tire circumferential rib or block row. Difficult and good uneven wear resistance can be enjoyed.
[0020]
In addition, it is necessary to comprise 80% or more of the tread ground contact width with a straight line, and preferably 85% or more and 100% or less is excellent in uneven wear resistance. If it is less than 80%, uneven wear tends to occur at the curved portion, which is not preferable.
[0021]
In addition, by arranging the circumferential straight groove in the joining portion, a bending point (line) does not occur in the same tire circumferential rib or block row, so that the difference in ground pressure between the inside and outside of the bending point (line) can be reduced. The possibility of occurrence is small and the occurrence of uneven wear can be further suppressed. Further, the number of straight grooves is preferably 6 or less, and if it is 7 or more, the width of each land portion becomes too small, which is not preferable from the viewpoint of steering stability.
[0022]
FIG. 2 is a partial perspective view of a lower mold showing an embodiment of the present invention, wherein 11 is a lower mold, 12 is a back block, 13 is a divided part, 13a is a first cast divided part, and 13b is a second cast. A divided part, 14 is a gap, 15 is an exhaust hole, and 16 is a tire tread side surface of the divided part. Since the mold includes tire circumferential ribs or block rows 3 constituted by a plurality of plane portions T, the outer diameter increases or decreases the number of divided parts as long as the tire radial dimension (tread ground contact width) matches. In this way, commonality is achieved.
[0023]
In addition, when the mold divided part 13 is manufactured, the first cast divided part 13a is first cast with aluminum, and then the second cast divided part 13b is cast. The hole becomes useless. The exhaust hole 15 is a through hole for releasing gas from the tire surface or the like. When the width of the gap 14 is 0.001 mm or less, the effect of removing air is small, and when the width is 0.1 mm or more, rubber penetrates into the gap during vulcanization, which is not preferable.
[0024]
FIG. 3 is a reference example not corresponding to the present invention, and is an example in which the tread land portion 3 is constituted by three straight lines and the two tire circumferential direction straight grooves 2 are provided at the connecting portion of the straight lines. The tire circumferential ribs or block rows 3 on the tread that form the outer contour of the tire tread portion are straight lines. The straight line of the tire circumferential rib or block row 3 intersects only at the two second straight grooves from the center. In the reference example, the connecting portion in the tire radial direction between straight lines is not formed in the tire equator.
[0025]
FIG. 4 shows another embodiment of the present invention, in which one straight groove 2 is provided in the tire circumferential direction, but the tire circumferential ribs or block rows on the tread that form the outer contour of the tire tread portion. The straight line 3 intersects only at one central straight groove.
[0026]
【Example】
A pneumatic radial tire having a tire size of 205 / 65R15 and comprising two steel belt layers and two polyester carcass layers, and the tread land portion is composed of six straight portions S as shown in FIG. A tire having five tire circumferential direction straight grooves 2 in the straight joining portion and 72 divisional planes in the tire circumferential direction was defined as Example 1. Further, as shown in FIG. 3, a tire in which a tread land portion is configured by 85% by three straight lines and two tire circumferential straight grooves 2 are provided at a connecting portion of the straight lines is referred to as a reference example 1 . Further, as shown in FIG. 4, a tire in which the tread land portion is configured by 80% with two straight lines and one tire circumferential direction straight groove 2 is provided at the connecting portion of the straight lines is referred to as Example 2 . . Further, as shown in FIG. 5 , conventional tires each made of a tread having five straight grooves 2 in the tire circumferential direction and having a crown radius of 530/150 mm were manufactured and subjected to the following evaluation.
[0027]
For each tire, the results of Table 1 were obtained in which the contact surface pressure, uneven wear resistance, performance on ice, mold production time, and mold cost were measured under the following conditions. The value is an index, and the larger the value, the better.
[0028]
[Ground pressure]
The measurement condition is that a tire is mounted on a standard rim described in the 2000 edition JATMA, and a mass corresponding to 88% of the maximum load capacity at an air pressure of 180 kPa is applied to the tire, and the center of the tire circumferential rib or block row and the tire circumferential rib or The ground pressure at the ground end of the block row was compared.
[0029]
[Uneven wear resistance]
Measurement conditions were as follows: tires were mounted on a standard rim described in the 2000 edition JATMA, mounted on a 2500 cc ordinary passenger car with an air pressure of 210 kPa, traveled for 5000 kilometers on a general road including an expressway, and the level of step wear was compared.
[0030]
[Ice performance]
Measurement conditions were as follows: tires were mounted on standard rims described in the 2000 edition of JATMA, mounted on 2500 cc ordinary passenger cars with air pressure of 210 kPa, and braking distances on ice were compared. The temperature was measured at -5 degrees and the road surface temperature was -2 degrees with no wind.
[0031]
[Mold making time]
The actual time required for production was compared.
[0032]
[Mold cost]
We compared the actual costs.
[0033]
[Table 1]

[0034]
【Effect of the invention】
As described above, the crown shape of the tread that forms the outer contour of the tire tread portion on the cross section in the tire radial direction including the tire rotation axis constitutes 80% or more of the tread ground contact width by connecting two or more straight lines Moreover, since the tire crown cross-sectional shape of the present invention is configured by straight lines by arranging straight grooves in the tire circumferential direction at the connecting portions in the straight tire radial direction, a tire with good uneven wear resistance and on-ice performance is provided. Moreover, mold production time and mold cost can be reduced [Brief description of drawings]
FIG. 1 is a partial sectional view in a radial direction of a tread portion of a pneumatic radial tire according to an embodiment of the present invention.
FIG. 2 is a partial perspective view of a mold showing another embodiment of the present invention.
FIG. 3 is a radial partial cross-sectional view of a tread portion of a pneumatic radial tire showing a reference example not corresponding to the present invention .
FIG. 4 is a partial radial sectional view of a tread portion of a pneumatic radial tire showing still another embodiment of the present invention.
FIG. 5 is a partial sectional view in the radial direction of a tread portion of a conventional pneumatic radial tire.
FIG. 6 is a cross-sectional explanatory view in the radial direction in which a pneumatic radial tire is grounded.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Cap tread 2 Circumferential straight groove | channel 3 Circumferential rib or block row | line | column 3a Circumferential rib or center part 3b of a block row | line | column 4 Grounding edge part 4 of a circumferential rib or block row | line | column Rim 11 Lower mold 12 One cast divided part 13b Second cast divided part 14 Gap 15 Exhaust hole 16 Tire tread side surface S of the divided part Straight line part T Flat part W Tread surface ground contact width

Claims (7)

The crown shape of the tread that forms the outer contour of the tire tread portion on the tire radial cross section including the tire rotation axis constitutes 80% or more of the tread ground contact width by connecting two or more straight lines, and a straight line A straight groove in the tire circumferential direction is arranged at the connecting portion in the tire radial direction, and at least two of the two or more straight lines are directed toward the tire outer peripheral side at least in the tire equator portion . A pneumatic radial tire comprising a tire radial joining portion joined so as to form a peak and a straight groove in the tire circumferential direction.   2. The pneumatic radial tire according to claim 1, wherein the number of straight grooves in the tire circumferential direction of the straight joining portion is 1 to 6. 3.   The pneumatic radial tire according to claim 1 or 2, wherein a shape of a tread that forms an outer contour of the tire tread portion includes a plurality of divided planes. The crown shape of the tread that forms the outer contour of the tire tread on the tire radial cross section including the tire rotation axis constitutes more than 80% of the tread ground contact width by connecting two or more straight lines, and the straight lines Of the two tires in the tire radial direction are provided with convex portions for forming straight grooves in the tire circumferential direction, and at least two of the two straight lines at a position where the tire equator portion is formed. Pneumatic, characterized in that a tire radial connecting portion and a convex portion for forming a straight groove in the tire circumferential direction are arranged so as to form a peak facing the tire outer periphery side. Mold for radial tire vulcanization.   5. The mold for vulcanizing a pneumatic radial tire according to claim 4, wherein an outer contour portion of the tire tread portion of the mold is composed of a plurality of aluminum cast divided parts in a tire radial direction and a circumferential direction.   6. The mold for vulcanizing a pneumatic radial tire according to claim 4, wherein the tire tread side surface of the divided parts is a flat surface.   The pneumatic radial tire vulcanization mold according to any one of claims 4 to 6, wherein a gap of 0.001 mm to 0.1 mm is provided in a cast joint portion of the divided parts.

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