JP6920183B2 - Unvulcanized tires and tires - Google Patents

Description

The present invention relates to an unvulcanized tire (green tire) and a tire provided with a carcass member and an inner liner.

Unvulcanized tires are an inner liner that is placed in the innermost layer of the tire to prevent the permeation of air and the like filled inside the tire, and a carcass member that is placed on the outer surface side of the inner liner and serves as a skeleton member of the tire. , A belt member arranged on the outer surface side of the tire of the vulcanization member and a tread rubber constituting the outer peripheral surface of the tire are provided.
In the process of molding an unvulcanized tire, an inner liner is attached to the outer circumference of the tire molding drum, and then a carcass member is attached. Next, the inner liner and the carcass member are expanded outward in the radial direction of the tire, and the belt member and the tread rubber are attached to the outer surface side of the tire of the carcass member. As a result, an unvulcanized tire can be obtained. Further, conventionally, a method for manufacturing a pneumatic tire in which end portions of carcass sheets (carcass members) are overlapped with each other to form a joint portion (joint portion) is known (see Patent Document 1).

FIG. 7 is a cross-sectional view showing an example of a joint portion of a conventional carcass member.
Conventionally, when molding an unvulcanized tire, as shown in the figure, the carcass member 52 (here, having only the carcass ply) is attached to the outer surface side of the tire of the inner liner 51, and one end in the tire circumferential direction. The other end 52b is overlapped on the upper side of the portion 52a. The carcass member 52 has a plurality of cords 53 that are arranged in parallel at intervals in the tire circumferential direction. The place where the carcass members 52 overlap is called a joint portion 55. Further, a place adjacent to the joint portion 55 of the carcass member 52 to be overlapped on the upper side is referred to as a boundary portion 56, and a gap is formed between the carcass member 52 and the inner liner 51 at the boundary portion 56. In FIG. 7, the left-right direction is the length direction of the carcass member 52. The length direction of the carcass member 52 corresponds to the tire circumferential direction.

Further, in molding an unvulcanized tire, the inner liner 51 and the carcass member 52 attached to the outer periphery of the tire molding drum are expanded outward in the radial direction of the tire. At that time, the inner liner 51 and the carcass member 52 are stretched to reduce their thickness.

On the other hand, tires are being reduced in weight in order to reduce fuel consumption by reducing tire rolling resistance. In order to reduce the weight of the tire, it is required to reduce the thickness of the inner liner 51.

In the joint portion 55 of the carcass member 52, since the other end portion 52b is overlapped on the one end portion 52a in the tire circumferential direction, a step is generated there. When molding an unvulcanized tire, the inner liner 51 is stretched by expanding outward in the radial direction of the tire in the inner liner 51. At the same time, the inner liner 51 is stretched by the step generated at the boundary portion 56 of the carcass member 52. That is, the inner liner 51 at the boundary portion 56 of the carcass member 52 is greatly stretched as compared with other places. Therefore, when the thickness of the inner liner 51 is reduced, the inner liner 51 may be cracked at the boundary portion 56 of the carcass member 52, and it is difficult to reduce the gauge of the inner liner 51.

JP-A-2017-121748

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to prevent cracks in the inner liner during molding of an unvulcanized tire even when the thickness of the inner liner is reduced. It is to realize a thin gauge of the inner liner.

In order to solve the problem that cracks occur in the inner liner when molding an unvulcanized tire, the present inventors have made an inner liner and a carcass member up to the occurrence of cracks around the cracks generated in the inner liner. The cause of the cracking of the inner liner was identified by observing the change in detail, and the unvulcanized tire and the tire of the present invention were completed.
That is, the present invention is an unvulcanized tire including a carcass member having a plurality of cords arranged side by side at intervals in the tire circumferential direction and an inner liner arranged on the inner surface side of the tire of the carcass member. It has a joint portion where one end portion and the other end portion overlap in the tire circumferential direction, a main body portion that is in close contact with the inner liner other than the joint portion, and a boundary portion between the joint portion and the main body portion. When the thickness of the joint portion of the member is t and the thickness of the inner liner is T, 0.85 <(t / 2) / T <2.0, and the cord spacing in the main body of the carcass member is set. D, where 1.0 ≦ d / D <1.8, where d is the maximum value of the code spacing at the boundary of the carcass member, ( (t / 2) / T) ² + (d / D) ) 1.25 <L <1.75 when ² = L ^2.
Further, the present invention is a tire composed of a vulcanized unvulcanized tire.

According to the present invention, it is possible to prevent the inner liner from cracking during molding of an unvulcanized tire, and it is possible to realize a thin gauge of the inner liner.

It is sectional drawing of the unvulcanized tire at the time of molding. A schematic cross-sectional view of a carcass member of an unvulcanized tire is shown. It is a schematic cross-sectional view of the state where the inner liner and the carcass member are attached to the tire molding drum. It is the schematic cross-sectional view of the state which removed the inner liner and the carcass member from the tire molding drum. It is the schematic cross-sectional view of the state in which the inner liner and the carcass member are inflated. It is the schematic sectional drawing of the inner liner and the carcass member of Example 2. FIG. It is sectional drawing which shows the example of the joint part of the conventional carcass member.

An unvulcanized tire and an embodiment of the tire of the present invention will be described with reference to the drawings.
The tire of the present embodiment is an air-filled tire. However, the tire is not limited to the pneumatic tire, and may be a tire filled with nitrogen, helium, or the like.
As shown in FIG. 1, in the step of molding the unvulcanized tire 10, the inner liner 1 is attached to the outer circumference of the rotating cylindrical tire molding drum (not shown), and then the carcass member 2 is attached. wear. A pair of bead cores 3 are arranged, and the carcass member 2 is folded around the bead core 3 to form a pair of bead portions 4. Next, the sidewall rubber 5 is attached to obtain a tubular green case 6.

Next, a device (not shown) for clamping the pair of bead portions 4 is approached toward the center C of the cross section shown in the drawing to narrow the mutual distance between the pair of bead portions 4. At the same time, the inside of the green case 6 is filled with air to expand the green case 6 outward in the radial direction of the tire. Further, the belt member 7 and the tread rubber 8 are attached to the tire outer surface side of the expanded carcass member 2. Then, if necessary, the side portion of the tread rubber 8 is attached to the green case 6. As a result, the unvulcanized tire 10 is obtained.

The unvulcanized tire 10 obtained by the above steps is arranged on the inner liner 1 arranged on the inner surface of the tire, the carcass member 2 arranged on the tire outer surface side of the inner liner 1, and the tire outer surface side of the carcass member 2. The belt member 7 and the tread rubber 8 constituting the outer peripheral surface of the tire are provided.
The inner liner 1 has a function of preventing the permeation of gas such as air filled inside the tire. The thickness of the inner liner 1 is preferably 0.7 mm or more and 1.0 mm or less, and more preferably 0.7 mm or more and 0.9 mm or less. As a result, it is possible to more reliably prevent the inner liner 1 from cracking while realizing a thinner gauge of the inner liner 1. For the inner liner 1, a rubber composition containing butyl rubber, halogenated butyl rubber, or the like as a main raw material is used. However, the present invention is not limited to this, and the inner liner 1 may be a resin film or the like.

The carcass member 2 is a skeleton member of a tire and has at least a carcass ply 20 as shown in FIG. Here, the carcass member 2 is formed in a four-layer structure, and the squeegee rubber 21, the carcass ply 20, the squeegee rubber 22, and the belt are arranged in order from the lower layer side (tire inner surface side) to the upper layer side (tire outer surface side). It has an undercoat rubber 23. However, the present invention is not limited to this, and the carcass member 2 may have, for example, a three-layer structure of the squeegee rubber 21, the carcass ply 20, and the belt underlaying rubber 23, or a one-layer structure of only the carcass ply 20. The carcass ply 20 has a plurality of cords 24 arranged in parallel at intervals in the tire circumferential direction, and the cords 24 are arranged along a direction orthogonal to the tire circumferential direction. The cord 24 is, for example, an organic fiber cord or a steel wire.

The carcass member 2 is attached to the outer surface side of the tire of the inner liner 1 attached to the outer periphery of the tire molding drum at the time of molding the unvulcanized tire 10. At this time, as shown in FIG. 3, one end 2a of the carcass member 2 in the tire circumferential direction is arranged on the lower side (tire inner surface side), and the tire circumference of the carcass member 2 is placed on the upper side (tire outer surface side). The other end 2b in the direction is placed on top of each other. The portion where the one end portion 2a and the other end portion 2b overlap is the joint portion 31. In FIG. 3, the left-right direction is the length direction of the carcass member 2. The length direction of the carcass member 2 corresponds to the tire circumferential direction.
Further, in the carcass member 2, the portion other than the joint portion 31 that is in close contact with the inner liner 1 is the main body portion 32. The main body portion 32 exists on the entire circumference of the carcass member 2 except for the joint portion 31 and the boundary portion 33 described later.
Further, the boundary portion between the joint portion 31 and the main body portion 32 is the boundary portion 33. At the boundary portion 33, a gap is formed between the carcass member 2 and the inner liner 1. Further, the boundary portion 33 is located between the joint portion 31 and the main body portion 32, and is, for example, a portion having the same width as the width of the joint portion 31.

Next, displacement and suppression of displacement of the inner liner 1 and the carcass member 2 at the joint portion 31 and the boundary portion 33 of the carcass member 2 that occur during molding of the unvulcanized tire 10 will be described.
When the inner liner 1 and the carcass member 2 are removed from the state where the inner liner 1 and the carcass member 2 are attached to the tire molding drum (not shown) (see FIG. 3), the carcass member 2 is as shown in FIG. Is displaced inward in the tire radial direction at the joint portion 31 (arrow A shown in the figure). The minimum amount of displacement of the carcass member 2 is the thickness of the carcass ply 20 in one carcass member 2, and the maximum is the thickness of one carcass member 2. Here, the displacement amount of the carcass member 2 is about half the thickness of one carcass member 2 (squeegee rubber 21, carcass ply 20, squeegee rubber 22, belt underlay rubber 23).
As a result, the inner liner 1 arranged on the inner surface side of the tire of the carcass member 2 is also displaced inward in the radial direction of the tire.

Next, when the inner liner 1 and the carcass member 2 are expanded outward in the radial direction of the tire in order to attach the belt member 7 and the tread rubber 8, the inner liner 1 and the carcass member 2 are stretched as shown in FIG. At that time, the elongation of the inner liner 1 and the carcass member 2 at the boundary portion 33 becomes larger than the elongation at the main body portion 32 and the joint portion 31. The direction of elongation here is the length direction of the inner liner 1 and the carcass member 2 (corresponding to the tire circumferential direction).
That is, at the boundary portion 33 of the carcass member 2, the inner liner 1 and the carcass member 2 extend due to the expansion of the inner liner 1 and the carcass member 2 outward in the tire radial direction. At this time, by overlapping the carcass members 2 at the joint portion 31, the elongation at the joint portion 31 is restricted, and the elongation at the boundary portion 33 is increased by that amount. At the same time, the inner liner 1 and the carcass member 2 are extended by the displacement of the inner liner 1 and the carcass member 2 inward in the radial direction of the tire. Due to these two factors, at the boundary portion 33 of the carcass member 2, the inner liner 1 and the carcass member 2 are greatly elongated as compared with the elongation at the main body portion 32 and the joint portion 31 (arrow B shown in FIG. 5). As a result, the inner liner 1 may be cracked at the boundary portion 33 of the carcass member 2.

Therefore, by making the inner liner 1 and the carcass member 2 satisfy the following three conditions, the elongation of the inner liner 1 at the boundary portion 33 does not exceed the elongation limit of the material of the inner liner 1. , Prevents the inner liner 1 from cracking during molding of the unvulcanized tire 10.

(First condition)
In the thickness of the carcass member 2 and the inner liner 1, when the thickness of the joint portion 31 of the carcass member 2 is t and the thickness of the inner liner 1 is T (see FIG. 3), (t / 2) / T. Is set to 0.85 <(t / 2) / T <2.0.
The thickness t of the joint portion 31 of the carcass member 2 is the thickness of the portion where one end 2a and the other end 2b of the carcass member 2 are overlapped with each other, and is 2 of the thickness of one carcass member 2. It is double.
When (t / 2) / T is 0.85 or less, the ratio of the thickness of the inner liner 1 to the thickness of the carcass member 2 becomes high, so that it becomes difficult to reduce the gauge of the inner liner 1.
Further, when (t / 2) / T is 2.0 or more, the thickness of the carcass member 2 at the joint portion 31 becomes thick. From this, the amount of displacement of the inner liner 1 and the carcass member 2 inward in the tire radial direction when the inner liner 1 and the carcass member 2 are removed from the tire molding drum, and the elongation of the inner liner 1 at the boundary portion 33 are increased. It may grow larger.
On the other hand, when (t / 2) / T satisfies the condition of 0.85 <(t / 2) / T <2.0, the ratio of the thickness of the inner liner 1 to the thickness of the carcass member 2 is high. It is possible to prevent the inner liner 1 from becoming thinner, and it is possible to realize a thinner gauge of the inner liner 1. Further, the amount of displacement of the inner liner 1 and the carcass member 2 inward in the tire radial direction when the inner liner 1 and the carcass member 2 are removed from the tire molding drum can also be reduced. As a result, it is possible to prevent the inner liner 1 from being stretched significantly at the boundary portion 33.

(Second condition)
In the plurality of cords 24 of the carcass member 2 (carcass ply 20), when the cord spacing at the main body 32 of the carcass member 2 is D and the maximum value of the cord spacing at the boundary 33 of the carcass member 2 is d ( (See FIG. 5), d / D is set to 1.0 ≦ d / D <1.8.
The code interval is an interval between adjacent codes 24 in a plurality of parallel codes 24. The maximum value of the cord spacing at the boundary portion 33 of the carcass member 2 is the cord spacing where the carcass member 2 is stretched most at the boundary portion 33 when the carcass member 2 is stretched at the time of molding.
In the molding of the unvulcanized tire 10, the d / D is always 1 or more, and it is difficult to make the d / D smaller than 1.0 in the general molding process of the unvulcanized tire 10.
Further, when the d / D is 1.8 or more, the cord spacing at the boundary portion 33 becomes wider than the cord spacing at the main body portion 32, which has the effect of suppressing cracking of the inner liner 1 at the boundary portion 33. There is a risk of impact.
On the other hand, when the d / D satisfies the condition of 1.0 ≦ d / D <1.8, the unvulcanized tire 10 can be easily molded by a general molding step. Further, the effect of suppressing the cracking of the inner liner 1 at the boundary portion 33 can be enhanced.

(Third condition)
In the relationship between the thickness and cord spacing of the carcass member 2 of the inner liner 1 and the carcass member 2, when the ^{((t / 2) / T} ) 2 + (d / D) 2 = L 2, the L 1. Set 25 <L <1.75.
It is difficult to reduce L to 1.25 or less in the molding process of a general unvulcanized tire 10.
Further, when L is 1.75 or more, the elongation of the inner liner 1 at the boundary portion 33 may increase.
On the other hand, when L satisfies the condition of 1.25 <L <1.75, the unvulcanized tire 10 can be easily molded by a general molding step. Further, it is possible to suppress the elongation of the inner liner 1 at the boundary portion 33 from becoming large.

As described above, in the unvulcanized tire 10 of the present embodiment, the thickness of the inner liner 1 is reduced by satisfying the three conditions regarding (t / 2) / T, d / D, and L. Even in this case, the elongation of the inner liner 1 can be prevented from exceeding the elongation limit of the material. Therefore, it is possible to prevent the inner liner 1 from cracking during molding of the unvulcanized tire 10, and it is possible to realize a thin gauge of the inner liner 1.

After molding the unvulcanized tire 10 so as to satisfy the above three conditions, the unvulcanized tire 10 is vulcanized under known vulcanization conditions in the vulcanization treatment step of the next step in tire production. As the vulcanization condition, for example, the vulcanization treatment is performed at a temperature of 100 ° C. or higher and 200 ° C. or lower. Further, the unvulcanized tire 10 is molded while being vulcanized by the tire mold. As a result, a pneumatic tire (tire) having a predetermined shape can be obtained. As described above, the present invention can be implemented as a tire manufacturing method for manufacturing a tire by vulcanizing the unvulcanized tire 10.

(Molding test of unvulcanized tire 10)
In order to confirm the effect of the unvulcanized tire 10 of the present invention, tests were conducted using Examples 1 and 2 and Comparative Examples 1, 2 and 3 satisfying the above three conditions.
The unvulcanized tire 10 to be tested is for a passenger car radial tire (195 / 70R14). The material of the inner liner 1 is brombutyl rubber, and the thickness thereof is 1.0 mm and 0.9 mm. The carcass member 2 has a three-layer structure of a squeegee rubber 21, a carcass ply 20, and a belt underlay rubber 23. The thickness of the squeegee rubber 21 is 0.3 mm, the thickness of the carcass ply 20 is 0.8 mm, and the thickness of the belt underlay rubber 23 is 1.5 mm. Therefore, the thickness of the carcass member 2 is 2.6 mm.

In Example 1, an inner liner 1 having a thickness of 1.0 mm was used. Further, in the joint portion 31 of the carcass member 2, one end portion 2a and the other end portion 2b were overlapped with each other to firmly press the joint portion 31. As a result, the joint portion 31 is made elastic, the joint portion 31 is easily stretched, and the stretch at the boundary portion 33 adjacent to the joint portion 31 is suppressed. As a result, (t / 2) / T was 1.30, d / D was 1.00, and L was 1.64. (T / 2) / T, d / D, and L satisfy the above three conditions.

In Example 2, an inner liner 1 having a thickness of 0.9 mm was used. Further, as shown in FIG. 6, the upper portion of one end portion 2a of the carcass member 2 is diagonally cut to form the first slope portion 25, and the end surface is also diagonally cut to form the second slope portion 26. Then, the thickness t of the joint portion 31 of the carcass member 2 was reduced. Here, since the first slope portion 25 and the second slope portion 26 are formed on one end portion 2a of the carcass member 2, the thickness changes depending on the position of the joint portion 31. Therefore, the thickness t is an average value of the thicknesses of the joint portions 31. By forming the first slope portion 25 and the second slope portion 26, the inner liner 1 and the carcass member 2 are connected at the boundary portion 33 from the joint portion 31 toward the main body portion 32 with a gentle inclination, and the boundary portion is formed. I tried to suppress the growth at 33. As a result, (t / 2) / T became 1.39, d / D became 1.00, and L became 1.71. (T / 2) / T, d / D, and L satisfy the above three conditions.

In Comparative Example 1, an inner liner 1 having a thickness of 1.0 mm was used. Further, in the joint portion 31 of the carcass member 2, one end portion 2a and the other end portion 2b are simply overlapped without being pressed. As a result, (t / 2) / T became 1.30, d / D became 1.20, and L became 1.77. The value of L does not satisfy the above condition of L.

In Comparative Example 2, an inner liner 1 having a thickness of 0.9 mm was used. Further, in order to see the influence of the temperature of the inner liner 1 and the carcass member 2, the joint portion 31 of the carcass member 2 is heated to a temperature higher than 15 ° C. by a heating means (infrared heater, warm air, embedded electric heater, etc.) at the time of molding. Heated. As a result, (t / 2) / T became 1.44, d / D became 1.00, and L became 1.75. The value of L does not satisfy the above condition of L.

In Comparative Example 3, an inner liner 1 having a thickness of 0.9 mm was used. Further, in order to see the influence of the temperature of the inner liner 1 and the carcass member 2, the joint portion 31 of the carcass member 2 was cooled to a temperature lower than 15 ° C. at the time of molding. As a result, (t / 2) / T was 1.44, d / D was 1.05, and L was 1.78. The value of L does not satisfy the above condition of L.

The test results are shown in Table 1 below.

In Examples 1 and 2, the occurrence of cracks in the inner liner 1 was 0%. In Comparative Examples 1, 2 and 3, the occurrence of cracks in the inner liner 1 was 12%, 8% and 15%. That is, the unvulcanized tire 10 shown in Examples 1 and 2 was able to prevent the inner liner 1 from cracking during molding.

1 ... Inner liner, 2 ... Carcass member, 3 ... Bead core, 4 ... Bead part, 5 ... Sidewall rubber, 6 ... Green case, 7 ... Belt member, 8 ... tread rubber, 10 ... unvulcanized tires, 20 ... carcass ply, 21 ... squeegee rubber, 22 ... squeegee rubber, 23 ... belt underlay rubber, 24 ... cord, 25 ... 1st slope part, 26 ... 2nd slope part, 31 ... Joint part, 32 ... Main body part, 33 ... Boundary part.

Claims (3)

An unvulcanized tire having a carcass member having a plurality of cords arranged in parallel at intervals in the tire circumferential direction and an inner liner arranged on the inner surface side of the tire of the carcass member.
The carcass member has a joint portion in which one end portion and the other end portion overlap in the tire circumferential direction, a main body portion that is in close contact with the inner liner other than the joint portion, and a boundary portion between the joint portion and the main body portion. death,
When the thickness of the joint part of the carcass member is t and the thickness of the inner liner is T,
0.85 <(t / 2) / T <2.0,
When the cord spacing at the main body of the carcass member is D and the maximum value of the cord spacing at the boundary of the carcass member is d,
1.0 ≦ d / D <1.8,
( (T / 2) / T) ² + (d / D) ² = L ²
An unvulcanized tire, characterized in that 1.25 <L <1.75. In the unvulcanized tire according to claim 1,
An unvulcanized tire characterized in that the thickness of the inner liner is 0.7 mm or more and 0.9 mm or less. A tire comprising a vulcanized unvulcanized tire according to claim 1 or 2.

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