JP2012183884A - Pneumatic tire and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that improves both productivity and ice performance and a method for manufacturing the same.SOLUTION: In the pneumatic tire, a plurality of sipes extending across a tread circumference are formed in a land part that has tread rubber and side rubber adjacent to both sides in a tread width direction of the tread rubber, wherein a border on a tire surface between the tread rubber and the side rubber is located more outside in the tread width direction than the plurality of sipes.

Description

  The present invention relates to a pneumatic tire with improved productivity and ice performance and a method for manufacturing the same.

A conventional pneumatic tire has a configuration in which a tread rubber is disposed in a tread portion, and side rubbers are disposed on both outer sides in the tire width direction of the tread rubber. Regarding the tread rubber, side rubber, and arrangement method, there were the following two types.
1st is the structure where the boundary P of the tread rubber 6 and the side rubber 8 exists in a shoulder part as shown to the tire width direction cross section which expanded the vicinity of the tread end TE in Fig.1 (a). However, since the shoulder portion is greatly bent and deformed when the tire rolls, there is a possibility that the boundary P existing in the shoulder portion becomes a starting point of failure. Further, in particular, when the tread rubber 6 is made of foamed rubber in order to ensure the ice performance, the user may visually recognize the foamed rubber at the shoulder portion and consider it as a poor appearance.
Therefore, secondly, as shown in FIG. 1B, the side rubber 8 is disposed from the shoulder portion to the sidewall portion, the tread rubber 6 is disposed between the both side rubbers 8, and the tread rubber 6 is disposed on the shoulder portion. It is the structure which is not exposed (for example, patent document 1).

JP 2007-911167 A

However, in the pneumatic tire having the second configuration shown in FIG. 1B described above, as shown in FIG. 1C, the rubber in the tread portion in the vicinity of the tread end TE is slightly chipped (width 1.0 mm). And a depth of about 1.0 mm). Such a lack of rubber does not cause a problem in tire performance, but it is handled as a defective product in an appearance inspection before shipment, and there is a problem that productivity is lowered.
The inventor has examined this problem in detail and found that the lack of rubber occurs when the vulcanized tire is removed from the mold after the raw tire is vulcanized. Furthermore, it was found that the rubber chipping did not occur in the center of the tread but occurred only in the vicinity of the sipe near the tread end TE. Based on the above knowledge, the present inventor diligently studied the relationship between a blade for shaping a sipe, a tread rubber and a side rubber, and completed the present invention.

  And the objective of this invention is providing the pneumatic tire which improved productivity and ice performance, and its manufacturing method.

The gist of the present invention is as follows.
(1) Pneumatic having a tread rubber and side rubbers adjacent to both sides in the tread width direction of the tread rubber, and a plurality of sipes extending in a direction crossing the tread circumferential direction are formed in a land portion including a tread end. In the tire,
The pneumatic tire according to claim 1, wherein a boundary between the tread rubber and the side rubber on a tire surface is outside the plurality of sipes in a tread width direction.

(2) When viewed in a tire width direction cross section, a boundary line passing through the tire surface between the tread rubber and the side rubber is located on the inner side in the tire width direction from a line segment passing through the tread edge and parallel to the tire equatorial plane. The pneumatic tire according to (1) above.

(3) When viewed in a tire width direction cross section, a boundary point on the tire surface between the tread rubber and the side rubber exists in a shoulder portion, and a boundary line passing through the boundary point between the tread rubber and the side rubber is The pneumatic tire according to (1) above, which passes through a tread end and intersects a line segment parallel to the tire equator plane.

(4) The tread rubber is foam rubber,
The side rubber is non-foamed rubber,
The pneumatic tire according to any one of the above (1) to (3), wherein

(5) A pneumatic tire having a tread rubber and side rubbers adjacent to both sides in the tread width direction of the tread rubber, wherein a plurality of sipes extending in a direction crossing the tread circumferential direction are formed in a land portion including a tread end. In the manufacturing method of
A pneumatic tire manufacturing method comprising performing vulcanization molding by placing a blade for shaping the sipe on the inner side in the tread width direction from a boundary between the tread rubber and the side rubber on the tire surface.

  The present invention can provide a pneumatic tire with improved productivity and ice performance and a method for manufacturing the same.

It is a partial expanded width direction sectional view of the conventional pneumatic tire. It is a width direction sectional view of the pneumatic tire of the present invention. It is a partial expanded width direction sectional view of the pneumatic tire of the present invention. It is a partial expanded width direction sectional view of the conventional pneumatic tire. 1 is a partially enlarged width direction sectional view of a pneumatic tire according to a preferred embodiment of the present invention.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
FIG. 2 is a cross-sectional view in the width direction of the pneumatic tire of the present invention. A pneumatic tire 10 according to the present invention has a carcass 2 straddling a toroidal shape between a pair of bead portions in which a bead core 1 is embedded, and the outer side in the tire radial direction of the crown portion of the carcass 2 with respect to the tire equatorial plane CL. A plurality of cords arranged obliquely are covered with rubber, and a belt 3 composed of inclined belt layers 3a and 3b where the cords cross each other between the laminated layers is arranged. In addition, the structure of these bead parts, a carcass, and a belt is an example, and this invention is not limited to this.
Further, the tread portion in the illustrated example is provided with circumferential grooves 4a and 4b extending in the tire circumferential direction, and rib-shaped land portions 5a, 5b and 5c are formed by these circumferential grooves 4a and 4b. The shape and number of these grooves are also an example, and when the circumferential groove is not provided, the land portion can be formed in a block shape by further providing a lug groove.

Moreover, the tread rubber 6 is arrange | positioned at the tread part, and the side rubber 8 is arrange | positioned from the shoulder part to the sidewall part. That is, the side rubber 8 is disposed adjacent to both outer sides in the tire width direction of the tread rubber 6.
The tread rubber 6 and the side rubber 8 are different types of rubber. The tread rubber 6 is a rubber having a good grip for contacting the road surface and transmitting braking / driving, and the side rubber 8 is a rubber having a good deformability and strong against deterioration due to aging and the environment.
The tread rubber 6 needs to determine its physical properties so as to transmit various forces applied to the tire such as a driving force, a braking force, and a turning force to the road surface, and to protect an internal skeleton member (belt or the like) from an external force. . Therefore, performance such as grip properties and wear resistance is required, and in particular, in the case of winter tires, it is necessary to select a material that retains flexible elasticity in order to enhance adhesion to the road surface even in a low temperature environment. .
The tread rubber 6 can also be composed of two layers of a base rubber on the inner side in the tire radial direction and a cap rubber on the outer side in the tire radial direction. In this case, the cap rubber has the physical properties of the tread rubber 6 described above.
On the other hand, since the side rubber 8 protects the internal skeleton member from an external force, it is necessary to determine its physical properties so as to maintain its durability even when subjected to repeated bending deformation and suppress the expansion of the trauma as much as possible.

FIG. 3A is a cross-sectional view in the width direction in which the vicinity of the tread end TE of the pneumatic tire in FIG. 2 is enlarged, and FIG. 3B is a modification thereof.
As shown to Fig.3 (a), the sipe 7 extended in the direction which crosses the tread circumferential direction is formed in the land part 5a containing the tread end TE. The sipe 7 is formed at a position where the distance d from the tread end TE to the outer end in the tread width direction of the sipe 7 is about 1.0 mm to 2.0 mm in order to adjust the rigidity of the land portion 5a.
Here, it is important that the boundary between the tread rubber 6 and the side rubber 8 on the tire surface (in the illustrated example, this boundary coincides with the tread end TE) is located outside the sipe 7 in the tread width direction.
Further, as shown in FIG. 3B, the boundary P on the tire surface between the tread rubber 6 and the side rubber 8 may be on the inner side in the tread width direction from the tread end TE.
The sipe 7 in the illustrated example extends in the tread width direction (that is, the direction orthogonal to the tread circumferential direction), and the sipe wall of the sipe 7 is planar, but the present invention is not limited to this. The sipe 7 may be a so-called 3D sipe that is inclined with respect to the tread width direction or zigzag-shaped toward the tread width direction and the depth direction of the sipe 7.

A pneumatic tire is manufactured by placing a raw tire in a mold, performing vulcanization molding, and taking out the vulcanized tire from the mold. Here, in order to manufacture a tire having a sipe, it is necessary to use a mold having a blade for shaping the sipe. As shown in FIG. 4A, in order to manufacture a tire in which the boundary P on the tire surface between the tread rubber 6 and the side rubber 8 is on the inner side in the tread width direction than the sipe 7, a gold having a blade at the position of the sipe 7 is used. It is necessary to remove this blade from the vulcanized tire after vulcanizing and molding the raw tire using a mold. The problem of the rubber chipping described above is that the side rubber 8 in the vicinity of the boundary P is in close contact with the blade and does not come off from the blade when the blade is removed after vulcanization molding. As shown in FIG. It turned out to be due to that. A tire with such a rubber chip is treated as a defective product in an appearance inspection before shipment, and thus a reduction in productivity has been a problem.
As a result of further diligent research on this phenomenon, the present inventor has found that this rubber chipping is caused by the fact that the side rubber 8 has higher adhesion to the blade than the tread rubber 6. Therefore, in the present invention, the boundary between the tread rubber 6 and the side rubber 8 on the tire surface is set outside the sipe 7 in the tread width direction.

  Furthermore, in order to achieve the desired ice performance, it is preferable to place a tread rubber 6 on the tread surface that contacts the road surface as shown in FIG. On the other hand, in order to ensure the rigidity in the vicinity of the tread end TE, as shown in FIG. 3B, it is preferable to dispose a highly rigid side rubber 8 in the vicinity of the tread end TE. In order to make these two performances compatible, the present inventor has found that it is preferable to arrange the tread rubber 6 on the tread surface and arrange the side rubber 8 inside the tread portion other than the tread surface.

Therefore, as shown in FIG. 5A, a boundary line B1 passing through the tire surface between the tread rubber 6 and the side rubber 8 passes through the tread end TE and is a line segment L (two points in the figure) parallel to the tire equatorial plane CL. The tread rubber 6 and the side rubber 8 are arranged so as to be on the inner side in the tire width direction from the chain line). By carrying out like this, while achieving desired ice performance, the rigidity near tread end TE can be secured and uneven wear near tread end TE can be controlled.
The angle θ formed by the boundary line B1 and the tread surface is preferably 10 ° or more and 120 ° or less.
This is because when the angle exceeds 120 °, the amount of the side rubber 8 in the vicinity of the tread end TE is small, so that there is a possibility that sufficient rigidity of the tread end TE cannot be secured.
On the other hand, when the angle is less than 10 °, the amount of the tread rubber 6 in the vicinity of the tread edge TE is small, so that sufficient grip performance may not be ensured.
The boundary line B2 between the tread rubber 6 and the side rubber 8 that does not pass through the tire surface is not particularly defined.
Further, as shown in FIG. 5B, the boundary P on the tire surface between the tread rubber 6 and the side rubber 8 is between the tread end TE and the sipe 7, and the side rubber 8 is sipe 7 inside the tread portion. It may be possible to overlap the area.
Furthermore, as shown in FIG. 5C, the boundary P between the tread rubber 6 and the side rubber 8 is in the shoulder portion on the outer side in the tread width direction from the tread end TE, and the boundary line B1 passing through P is a line segment L. You may cross. However, if the shoulder P has the boundary P in this way, when the tread rubber 6 is made of foamed rubber, the foamed rubber is visually recognized by the user and may be regarded as a poor appearance.
Therefore, from the viewpoint of tire performance, productivity and appearance, the case of FIG.

  The tread rubber 6 is preferably composed of foamed rubber (foaming rate: 5% to 45% (temperature: 26 ° C.)), and the side rubber 8 is preferably composed of non-foamed rubber (foaming rate 0%).

Examples of the present invention will be described below, but the present invention is not limited thereto.
Invention tires and conventional tires were prototyped and evaluated for productivity, ice braking performance, and uneven wear rate.
Each test tire (tire size: 195R / 65R15, rim: 6JJ) has the same configuration except for the arrangement of the tread rubber 6 and the side rubber 8. A block-shaped land portion is formed by four circumferential grooves extending in the tire circumferential direction and lug grooves extending in the tire width direction. In the block including the tread end TE, so-called 3D sipes are formed at intervals of 5 mm in the circumferential direction.
As shown in FIG. 3 (a), the tire 1 of the invention is such that the boundary point between the tread rubber 6 and the side rubber 8 on the tire surface coincides with the tread end TE, and the boundary line between the tread rubber 6 and the side rubber 8 is the tire. It extends toward the outside in the width direction.
As shown in FIG. 5 (a), the tire 2 of the invention example passes through the tire surface of the tread rubber 6 and the side rubber 8 with the boundary point on the tire surface of the tread rubber 6 and the side rubber 8 coinciding with the tread end TE. The boundary line B1 extends inward in the tire width direction from a line segment L passing through the tread end TE and parallel to the tire equatorial plane CL. The angle θ formed by the boundary line B1 and the tread surface is 45 °.
In the conventional tire, as shown in FIG. 4A, a boundary point P on the tire surface between the tread rubber 6 and the side rubber 8 exists in a region where the sipe 7 is formed.

(1) Evaluation of productivity 100 test tires were produced one by one, and it was visually confirmed whether or not the block sipe portion of each test tire after vulcanization molding had a rubber chip. If the rubber chip was less than 2 places, it was a non-defective product.

(2) Evaluation of ice braking performance Each test tire was run on an ice road surface under the conditions shown in Table 1, and the braking distance was measured when the ABS was operated by applying braking force at a speed of 40 km / h. The results are shown as an index with the braking distance of the conventional tire as 100. In addition, it shows that it is excellent in ice braking performance, so that an index | exponent is large.

(3) Evaluation of Uneven Wear Rate After running each test tire on a general road for 5000 km under the conditions shown in Table 2, the ratio of wear amount between the tread center portion and the tread end portion was measured as the uneven wear rate. In addition, it shows that it is excellent in performance, so that an index | exponent is large.

  As shown in Table 3, it can be seen that in the inventive tires 1 and 2, the productivity and ice braking performance are improved compared to the conventional example. Furthermore, it can be seen that the invention example tire 2 has improved uneven wear rate compared to the invention example tire 1.

1 Bead core 2 Carcass 3 Belt 4 Circumferential groove 5 Land 6 Tread rubber 7 Sipe 8 Side rubber 10 Pneumatic tire

Claims (5)

In a pneumatic tire having a tread rubber and side rubbers adjacent to both sides in the tread width direction of the tread rubber, a plurality of sipes extending in a direction crossing the tread circumferential direction are formed on a land portion including a tread end.
The pneumatic tire according to claim 1, wherein a boundary between the tread rubber and the side rubber on a tire surface is outside the plurality of sipes in a tread width direction.   When viewed in a cross section in the tire width direction, a boundary line passing through the tire surface between the tread rubber and the side rubber is located on the inner side in the tire width direction from a line segment passing through the tread end and parallel to the tire equatorial plane. Item 2. The pneumatic tire according to Item 1.   When viewed in a cross section in the tire width direction, a boundary point on the tire surface between the tread rubber and the side rubber exists in a shoulder portion, and a boundary line passing through the boundary point between the tread rubber and the side rubber is a tread edge. The pneumatic tire according to claim 1, wherein the pneumatic tire intersects with a line segment parallel to the equatorial plane of the street tire. The tread rubber is foam rubber,
The side rubber is non-foamed rubber,
The pneumatic tire according to any one of claims 1 to 3. A pneumatic tire manufacturing method comprising a tread rubber and side rubbers adjacent to both sides in the tread width direction of the tread rubber, wherein a plurality of sipes extending in a direction crossing the tread circumferential direction are formed in a land portion including a tread end. In
A pneumatic tire manufacturing method comprising performing vulcanization molding by placing a blade for shaping the sipe on the inner side in the tread width direction from a boundary between the tread rubber and the side rubber on the tire surface.

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