JP6965686B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire in which the cap layer of the tread rubber is a strip winding body in which a rubber strip is wound in a spiral shape.

The tread rubber is usually composed of a cap layer forming a tread contact patch and a base layer adjacent to the inside of the cap layer in the radial direction. Generally, rubber having excellent wear resistance and grip is used for the cap layer. In addition, rubber having a hardness higher than that of the cap layer is generally used for the base layer to increase the tread rigidity and ensure steering stability.

In recent years, it has been proposed to use a rubber containing silica as a rubber reinforcing agent (silica-blended rubber) for the cap layer in order to improve the wet grip while suppressing the rolling resistance of the tire to a low level.

On the other hand, a strip wind method is known as a method for forming the cap layer and the base layer (see, for example, Patent Document 1). In this strip wind method, a tape-shaped unvulcanized rubber strip is spirally wound to form a rubber member having a predetermined cross-sectional shape.

However, when the tread rubber using the silica-blended rubber for the cap layer is formed by the strip wind method, the following problems occur.

As shown in FIG. 4A, when forming a raw tire, the tire axial outer end portion a1 of the tread rubber a formed in advance is unwound using, for example, a stitch roller (not shown) and expanded into a toroid shape. A so-called stitch-down is performed in which the tire is pressed against the 1st cover b to be joined. However, silica-blended rubber is inferior in adhesiveness. Therefore, as shown in an exaggerated manner in FIG. 4 (B), at the time of stitching down, peeling K1 or deviation occurs between the wound portions g1 and g1 of the rubber strip g at the outer end portion of the cap layer c, which is desired. There is a problem that the tire shape of is not obtained. Further, an air pool is generated in the portion where the peeling K1 is generated, which causes a defect in the tire after vulcanization. Further, at the time of stitching down, the cap layer c and the base layer d are not adhered to each other, and peeling K2 occurs, which tends to cause a process trouble.

Japanese Unexamined Patent Publication No. 2006-007661

According to the present invention, even when silica-blended rubber is used for the rubber strip of the cap layer, process troubles due to peeling or misalignment between the wound portions of the rubber strip during stitching down and peeling between the cap layer and the base layer can be caused. The challenge is to provide pneumatic tires that can be suppressed.

The present invention is a pneumatic tire including a tread rubber including a cap layer forming a tread contact patch and a base layer adjacent to the inside in the radial direction of the cap layer.
The cap layer is composed of a strip winder obtained by spirally winding a first rubber strip made of the first rubber.
The cap layer is formed by spirally winding a second rubber strip made of a second rubber together with the first rubber strip on the outer side in the tire axial direction until the outer end of the cap layer in the tire axial direction. (1) A cap wing portion in which a winding portion of a rubber strip and a winding portion of a second rubber strip are alternately arranged is provided.

In the pneumatic tire according to the present invention, on the outer surface of the tread portion, the winding portion of the second rubber strip is preferably located outside the tire axial direction from the outer end of the tread ground contact surface in the tire axial direction.

In the pneumatic tire according to the present invention, the base layer has a base wing portion made of the second rubber on the outer side in the tire axial direction, and the base wing portion is in the radial direction of the winding portion of the second rubber strip. It is preferable to join with the inner end portion.

In the pneumatic tire according to the present invention, the first rubber is preferably a high-silica compounded rubber in which the ratio of silica to the rubber reinforcing agent is 75% by mass or more.

In the pneumatic tire according to the present invention, the rubber hardness Hs2 of the second rubber is preferably smaller than the rubber hardness Hs1 of the first rubber, and the difference (Hs1-Hs2) is preferably 10 degrees or more.

In the pneumatic tire according to the present invention, the adhesive strength of the second rubber before vulcanization is preferably 1.3 times or more the adhesive strength of the first rubber before vulcanization.

The "tread ground contact surface" is defined as a surface of the outer surface (tread surface) of the tread portion that can be grounded when a normal load is applied to a tire in a reference state that is rim-assembled on a regular rim and filled with a regular internal pressure. ..

The "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, JATTA is a standard rim, TRA is "Design Rim", or If it is ETRTO, it means "Measuring Rim". The "regular internal pressure" is the air pressure defined for each tire by the standard. If it is JATMA, it is the maximum air pressure. If it is TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", ETRTO. If so, it means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The "regular load" is the load defined by the standard for each tire, and is the maximum load capacity for JATMA and the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. If it is ETRTO, it is "LOAD CAPACITY".

The "rubber hardness Hs" is the durometer A hardness measured in an environment of 23 ° C. by a durometer type A based on JIS-K6253.

The "adhesive strength" is measured under the following conditions using a PIMACA tack tester manufactured by Toyo Seiki Co., Ltd.
--Crimping load: 4.9N
--Peeling speed: 15mm / min
--Crimping time: 30 seconds
--Temperature: 20 ℃
--Humidity: 55%

In the present invention, as described above, the cap layer includes a cap wing portion on the outer side in the tire axial direction. In this cap wing portion, the winding portion of the first rubber strip and the winding portion of the second rubber strip are alternately arranged.

Therefore, even when silica-blended rubber is used for the first rubber strip, the adhesiveness of the second rubber strip causes peeling or misalignment between the wound portions of the rubber strip during stitch down, and the cap layer and the base layer. It is possible to suppress process troubles due to peeling.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is sectional drawing which shows the tread rubber conceptually. It is sectional drawing which conceptually shows the state of the tread rubber at the time of stitching down. (A) is a cross-sectional view for explaining stitch down, and (B) is a cross-sectional view conceptually showing a conventional problem when stitch down is performed.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the pneumatic tire 1 of the present embodiment has a carcass 6 from a tread portion 2 having a tread contact patch S to a bead core 5 of a bead portion 4 through a sidewall portion 3 and a carcass 6 of the carcass 6. It includes a tread reinforcing cord layer 7 arranged on the outer side in the radial direction and inside the tread portion 2.

The carcass 6 is formed of one or more carcass cords arranged at an angle of, for example, 75 to 90 ° with respect to the tire circumferential direction, or one carcass ply 6A in this example. The carcass ply 6A has, for example, ply folded portions 6b folded around the bead core 5 on both sides of a toroid-shaped ply main body portion 6a straddling between the bead cores 5 and 5. A bead apex rubber 8 for reinforcing the bead extending radially outward from the bead core 5 is arranged between the ply main body portion 6a and the ply folded portion 6b.

The tread reinforcing cord layer 7 includes two or more belt cords arranged at an angle of, for example, 15 to 40 ° with respect to the tire circumferential direction, and in this example, two belt plies 7A and 7B. The belt cords intersect each other between the plies, thereby increasing the belt rigidity and reinforcing the tread portion 2. The tread reinforcing cord layer 7 can include a band ply 9 arranged on the outer side in the radial direction of the belt plies 7A and 7B. The band ply 9 is provided with a band cord that spirally winds in the tire circumferential direction to enhance the tag effect and improve high-speed running performance and the like.

Then, the tread rubber 10 is arranged on the outer side in the radial direction of the tread reinforcing cord layer 7. The tread rubber 10 includes a cap layer 10A forming a tread ground contact surface S and a base layer 10B adjacent to the inside of the cap layer 10A in the radial direction. As described above, the tread ground contact surface S is a surface of the outer surface (tread surface) of the tread portion 2 that can be grounded when a normal load is applied to a tire in a reference state that is rim-assembled on a regular rim and filled with a regular internal pressure. Is defined as.

FIG. 2 conceptually shows the tread rubber 10 before stitching down. As shown in the figure, the cap layer 10A is formed of a strip winding body 20 in which a first rubber strip 11 made of the first rubber G1 is spirally wound from one side to the other in the tire axial direction. NS.

Further, the cap layer 10A includes a cap wing portion 21 on the outer side in the tire axial direction. In the cap wing portion 21, the second rubber strip 12 made of the second rubber G2 is spirally wound together with the first rubber strip 11 until the outer end 10e of the cap layer 10A in the tire axial direction. Thus, the cap wing portions 21, and the winding section _{T 11} of the first rubber strip 11, and the wound portion _{T 12} of the second rubber strip 12 is arranged alternately.

Winding portion T ₁₂ of the second rubber strip 12 is located axially outside than the ground end Te. That is, the exposed surface of the winding portion T _{12 on} the tread surface is not in contact with the road surface during traveling. The ground contact end Te is defined as the outer end of the tread ground contact surface S in the tire axial direction.

As the first rubber G1, a silica-blended rubber containing silica is preferably used as a rubber reinforcing agent from the viewpoint of exhibiting high wet grip while suppressing the rolling resistance of the tire to be low. In particular, a high silica-blended rubber having a ratio of silica in the rubber reinforcing agent of 75% by mass or more is more preferably adopted. While this silica-blended rubber has the above advantages, it has a drawback of being inferior in adhesiveness.

Then, in order to overcome this drawback, as the second rubber G2, a rubber showing high adhesiveness before vulcanization is preferably adopted. In particular, it is preferable that the adhesive force f2 of the second rubber G2 before vulcanization is 1.3 times or more, more preferably 1.6 times or more, the adhesive force f1 of the first rubber G1 before vulcanization.

As described above, "adhesive strength" uses a PIMACA tack tester manufactured by Toyo Seiki Co., Ltd., crimping load: 4.9 N, peeling speed: 15 mm / min, crimping time: 30 seconds, temperature: 20 ° C, humidity. : Measured under 55% condition.

In the cap layer 10A having such a structure, the winding portions T ₁₁ of the first rubber strip 11 do not come into contact with each other in the cap wing portion 21. Therefore, even when a high-silica compound rubber is used for the first rubber strip 11, the adhesive force between the wound portions adjacent to each other can be enhanced by the adhesiveness of the second rubber strip 12. As a result, as shown in an exaggerated manner in FIG. 3, peeling and misalignment between the _{wound portions T 11} and T _{12 can be suppressed during stitch down.} The radial inner end of the second rubber strip 12 is in contact with the base layer 10B. Therefore, it is possible to prevent the cap wing portion 21 from peeling off from the base layer 10B and causing process troubles or the like at the time of stitching down.

The above effect is more remarkable when the adhesive force f1 of the first rubber G1 is 3.1 N or less.

Rubber with high adhesiveness has a relatively low rubber hardness after vulcanization. Therefore, in the already vulcanized pneumatic tire 1, it is preferable that the rubber hardness Hs2 of the second rubber G2 is smaller than the rubber hardness Hs1 of the first rubber. In particular, the difference in rubber hardness (Hs1-Hs2) is preferably 10 degrees or more, more preferably 15 degrees or more. As the second rubber G2, a rubber having the same rubber composition as the sidewall rubber 30 forming the outer surface of the sidewall portion 3 can be adopted.

As shown in FIG. 2, in this example, the base layer 10B includes a base wing portion 22 made of a second rubber G2 on the outer side in the tire axial direction. The base wing portion 22 is joined to at least the inner end portion in the radial direction _{of the winding portion T 12 of the second rubber strip 12.}

As a result, the adhesive strength between the cap wing portion 21 and the base wing portion 22 can be increased. Therefore, it is possible to further prevent the cap wing portion 21 from peeling off from the base layer 10B and inducing a process trouble or the like at the time of stitching down.

In this example, the base layer 10B is also formed by the strip wind method. That is, of the base layer 10B, the base main portion 23 arranged between the base wing portions 22 and 22 is formed by spirally winding a third rubber strip 13 made of the third rubber G3. The base wing portion 22 is formed by spirally winding the second rubber strip 12. However, for example, the base layer 10B may be formed by winding a wide sheet-like body obtained by integrally extruding the base main portion 23 and the base wing portions 22 and 22 around.

The cross-sectional shape, size, and the like of the first rubber strips 11 to 3 can be appropriately set according to the strip wind method.

Although the particularly preferable embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments and can be modified into various embodiments.

A pneumatic tire (225 / 50R18) having a tread rubber structure shown in FIGS. 1 to 3 was prototyped based on the specifications shown in Table 1. Then, after stitching down at the time of forming the raw tire, the state of occurrence of peeling between the wound parts of the rubber strip in the shoulder part and the state of occurrence of peeling between the cap layer and the base layer in the shoulder part are evaluated by the following score 1. It was evaluated by 2, 3.

Score 1 --- After stitching down, large peeling occurs either between the winding parts of the rubber strip on the shoulder part or between the cap layer and the base layer: (Raw tire cannot be molded)
Score 2 --- After stitching down, slight peeling occurs either between the winding parts of the rubber strip on the shoulder part or between the cap layer and the base layer: (Raw tire can be molded, but air There is a risk of accumulation.)
Score 3 --- After stitching down, no peeling occurs between the winding parts of the rubber strip at the shoulder part and between the cap layer and the base layer.

In the test, three types of rubbers A, B, and C having different adhesive strengths f1 at a molding temperature of 20 ° C. were prepared as the first rubber. Further, as the second rubber, one kind of rubber D having an adhesive force f2 at a molding temperature of 20 ° C. larger than the adhesive force f2 of the first rubber G1 was prepared. In Example 1, rubber A is used as the first rubber, in Example 2, rubber B is used as the first rubber, and in Example 3, rubber C is used as the first rubber. Rubber D is used as the second rubber in both Examples 1 to 3. For comparison, a conventional example in which the cap wing portion was formed only of the first rubber was prototyped. In Conventional Example 1, rubber A is used as the first rubber, in Conventional Example 2, rubber B is used as the first rubber, and in Conventional Example 3, rubber C is used as the first rubber.

In the conventional example, the peeling becomes worse as the adhesive strength decreases, but in the examples, all are good, and it can be confirmed that a rubber having a low adhesive strength can be adopted as the first rubber.

1 Pneumatic tire 10 Tread rubber 10A Cap layer 10B Base layer 11 1st rubber strip 12 2nd rubber strip 20 Strip winding body 21 Cap wing part 22 Base wing part G1 1st rubber G2 2nd rubber S Tread ground contact surface T ₁₁ wound portion _{T 12} winding portion

Claims (6)

A pneumatic tire provided with tread rubber including a cap layer forming a tread contact patch and a base layer adjacent to the inside of the cap layer in the radial direction.
The cap layer is composed of a strip winder obtained by spirally winding a first rubber strip made of the first rubber.
The cap layer is formed by spirally winding a second rubber strip made of a second rubber together with the first rubber strip on the outer side in the tire axial direction until the outer end of the cap layer in the tire axial direction. ingredients to give a 1 rubber windings of the strip and the cap wing portion and the winding portion of the second rubber strip are alternately disposed,
The cap wing portions are provided outside the ground contact end in the tire axial direction and on both sides in the tire axial direction.
The cap layer is a pneumatic tire formed only by the first rubber strip between the cap wings. A pneumatic tire provided with tread rubber including a cap layer forming a tread contact patch and a base layer adjacent to the inside of the cap layer in the radial direction.
The cap layer is composed of a strip winder obtained by spirally winding a first rubber strip made of the first rubber.
The cap layer is formed by spirally winding a second rubber strip made of a second rubber together with the first rubber strip on the outer side in the tire axial direction until the outer end of the cap layer in the tire axial direction. A cap wing portion in which the winding portion of the 1 rubber strip and the winding portion of the 2nd rubber strip are alternately arranged is provided.
The rubber hardness Hs2 of the second rubber, the less than the rubber hardness Hs1 of the first rubber, and a pneumatic tire Ru der the difference (Hs1-Hs2) is more than 10 degrees. The pneumatic tire according to claim 1 or 2, wherein on the outer surface of the tread portion, the winding portion of the second rubber strip is located outside the tire axial outer end of the tread ground contact surface in the tire axial direction. The base layer has a base wing portion made of the second rubber on the outer side in the tire axial direction, and the base wing portion is joined to the inner end portion in the radial direction of the winding portion of the second rubber strip. Pneumatic tire according to any one of ~ 3. The pneumatic tire according to any one of claims 1 to 4, wherein the first rubber is a high-silica compounded rubber in which the ratio of silica to the rubber reinforcing agent is 75% by mass or more. The pneumatic tire according to any one of claims 1 to 5, wherein the adhesive strength of the second rubber before vulcanization is 1.3 times or more the adhesive strength of the first rubber before vulcanization.

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