JP2011235791A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of eliminating a conventional problem while the thinning of a sidewall progresses and having such satisfactory appearance that a streak-shaped projecting parts caused by a lap splice of an inner liner are not generated.SOLUTION: In the pneumatic tire in which an inner liner comprising a butyl rubber layer and a tie rubber layer is provided at an inner peripheral side of a carcass layer, the butyl rubber layer is longer than the tie rubber layer by 5 to 25 mm in a tire peripheral direction at one edge A of the inner liner and the tie rubber layer is longer than the butyl rubber layer by 5 to 25 mm in the tire peripheral direction at the other edge B, and the splice of the inner liner is formed by joining the edges A and B to each other.

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire having a good appearance in which a streak-like convex portion due to a splice portion of an inner liner is not generated on the surface of a sidewall portion.

  The innermost layer of the pneumatic tire is provided with a rubber inner liner excellent in non-air permeability. This inner liner generally has a two-layer laminated structure of a butyl rubber layer on the tire inner peripheral side and a tie rubber layer on the tire outer peripheral side (carcass layer side).

  Conventionally, when manufacturing a pneumatic tire, at least one lap splice portion is formed by winding an inner liner around an outer peripheral surface of a tire molding drum and overlapping a winding start end and a winding end end ( Patent Document 1).

  The thickness of this splice part of the inner liner is thicker than the thickness of other parts. Generally, the thickness of the inner liner layer is 1.0 to 2.0 mm. It becomes a convex shape with steps corresponding to the thickness, and appears in a streak shape.

  Particularly in recent years, pneumatic tires have a tendency to reduce the rubber thickness of the sidewall portion in order to reduce the weight of the tire, and the minimum rubber thickness portion is 2 mm or more and 5 mm or less. For this reason, when the vulcanized tire is filled with high-pressure air and inflated, the lap splice portion in the form of a convex portion having a step of the inner liner described above pushes up the rubber of the thinned sidewall portion and becomes remarkable. A streak-like convex part appears on the side wall part. The appearance of such a streak-like convex portion form in the sidewall portion is generally called “bumpy side failure” and is a factor that impairs the appearance of the tire.

  Incidentally, such a bumpy side failure may occur at a portion where the ends of the carcass layer in the tire circumferential direction are lap spliced. However, in the case of the lap splice portion of the carcass layer, the lap splice portion of the carcass layer is significantly stiffer than the lap splice portion of the inner liner, so that the lap splice portion is generally not a streaky convex portion but a streaky concave portion. Bumpy side failure appears. Conventionally, for a bumpy side failure caused by such a lap splice portion of the carcass layer, a butt splice in which both ends of the carcass layer are abutted and joined together, and the lap splice portion of the inner liner is overlaid on the butt splice portion. It has been proposed to improve it (Patent Document 2).

  However, the proposal of Patent Document 2 is intended to prevent the occurrence of a streak-like concave portion caused by the lap splice portion of the carcass layer. The object to be improved is different, and the butt splice that is a butt joint is used. There is a tendency for stress to concentrate on the joints and easily cause opening failures, so it cannot be a measure to eliminate the streaky protrusions caused by the lap splice part of the inner liner described above It is.

  Further, as a proposal to improve the lap splice portion of the inner liner, a butyl rubber layer is formed in a layer continuous in the tire circumferential direction by connecting one end in the tire circumferential direction to the other end side, and the tie rubber layer is also formed in the tire circumferential direction. There has been proposed a pneumatic tire formed in a continuous layer by connecting the other end of the direction to the one end side (Patent Document 3).

  However, the pneumatic tire proposed in Patent Document 3 is intended to suppress the occurrence of cracks in the splice portion of the inner liner, and the streak resulting from the above-described lap splice portion of the inner liner. The convex part of was not solved.

JP-A-6-55661 Japanese Patent Laid-Open No. 5-221204 JP-A-10-129208

The purpose of the present invention is to solve the above-mentioned conventional problems while the thinning of the sidewall portion proceeds,
An object of the present invention is to provide a pneumatic tire having a good appearance in which a streak-like convex portion due to a lap splice portion of an inner liner does not occur.

The pneumatic tire of the present invention that achieves the above-described object has the following configuration (1).
(1) In a pneumatic tire in which an inner liner made of a butyl rubber layer and a tie rubber layer is provided on the inner peripheral side of the carcass layer, the butyl rubber layer is closer to the tire circumferential direction than the tie rubber layer at one edge portion A of the inner liner. The tie rubber layer is formed 5 to 25 mm longer in the tire circumferential direction than the butyl rubber layer at the other edge portion B, and the splice portion of the inner liner is formed by bonding the edge portions A and B together. A pneumatic tire characterized in that is formed.

  According to the pneumatic tire of the present invention, in the pneumatic tire in which the inner liner made of the butyl rubber layer and the tie rubber layer is provided on the inner peripheral side of the carcass layer, the butyl rubber layer is more than the tie rubber layer at one edge portion A of the inner liner. Is 5 to 25 mm longer in the tire circumferential direction, and the tie rubber layer is formed 5 to 25 mm longer in the tire circumferential direction than the butyl rubber layer in the other edge portion B, and both edge portions A and B are bonded together to form an inner liner. Therefore, the splice portion has a flat shape and does not form a streak-like convex portion. Therefore, a bumpy side failure due to the formation of the line-shaped convex portions does not occur, and a pneumatic tire having a good appearance can be configured.

  Furthermore, since the thickness of the splice part and other parts is uniform, it is superior to both static balance and dynamic balance of pneumatic tires compared to the case where convex parts exist in the form of streaks. Yes.

  Further, the pneumatic tire of the present invention is formed by meshing the meshing three-dimensional structure formed in the tire radial direction on the edge end surface of the butyl rubber layer and / or the tie rubber layer to bond the edge portion A and the edge portion B together. When configured to be joined, especially in the case of a meshing three-dimensional structure formed in the tire radial direction on the edge end surface of the butyl rubber layer, the edge portion of the butyl rubber layer can be joined so as to overlap without any gap, and therefore vulcanization is performed. It is possible to satisfactorily prevent the occurrence of air leakage when the subsequent tire is filled with air.

  In addition, in the case of a meshing three-dimensional structure formed in the tire radial direction on the edge end surface of the tie rubber layer, the edge portion of the tie rubber layer can be joined so as to overlap without any gap, so that the butyl rubber layer and the carcass layer are in contact with each other. It is possible to prevent peeling between the two layers.

  Further, in the case of the meshing three-dimensional structure formed in the tire radial direction on the edge end surface of the butyl rubber layer and the meshing three-dimensional structure formed in the tire radial direction on the edge end surface of the tie rubber layer, the above-described 2 It can be set as the pneumatic tire which has the effect of two cases.

  Furthermore, in the pneumatic tire of the present invention described above, when the thickness of the butyl rubber layer is set to 0.3 mm or more and 1.0 mm or less, the air holding ability is excellent and the cost is not excessively high. A pneumatic tire can be realized.

  Furthermore, in the pneumatic tire of the present invention described above, when the thickness of the tie rubber layer is 0.2 mm or more and 1.0 mm or less, there is a problem that the adhesion between the inner liner and the carcass layer is good and the appearance is poor. Fewer pneumatic tires can be realized.

  Furthermore, in the pneumatic tire of the present invention described above, when the minimum tread rubber thickness in the sidewall portion is 1.2 mm or more and 5.0 mm or less, the amount of tread rubber used in the sidewall portion is smaller. A pneumatic tire that is lightweight as a whole and has a good appearance with no bumpy side failure.

1 is a partially cutaway perspective view of a half cross section of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is a cross-sectional view of an essential part showing a portion where both end portions of an inner liner layer of the pneumatic tire of FIG. 1 are spliced together. It is principal part sectional drawing which shows the other embodiment of a splice part. It is principal part sectional drawing of the splice part which showed the example of the meshing three-dimensional structure formed in the tire radial direction on the edge end surface of a butyl rubber layer and a tie rubber layer.

  Hereinafter, the pneumatic tire of the present invention will be described in more detail.

  1 and 2 show an embodiment of the present invention. The pneumatic tire T is provided so that the sidewall portion 2 and the bead portion 3 are connected to the left and right of the tread portion 1. Inside the tire, a carcass layer 4 as a skeleton of the tire is provided so as to straddle between the left and right beads 3 and 3 in the tire width direction.

  An inner liner 6 made of butyl rubber 8 and tie rubber 9 excellent in air permeability is provided inside the carcass layer 4. Two belt layers 5 made of steel cord are provided on the outer peripheral side of the carcass layer 4 corresponding to the tread portion 1. An arrow D indicates the tire circumferential direction. The carcass layer 4 is provided with at least one ply. The sidewall portion 2 is provided so that the thickness changes in the tire radial direction, but preferably the minimum thickness t is between 1.2 and 5.0 mm in order to reduce the weight of the tire. ing. The portion with the minimum thickness t is generally the portion with the maximum tire width. The inner liner 6 has a splice portion 7 to which both ends are joined.

  In the pneumatic tire of the present invention, the butyl rubber layer 8 is 5 to 25 mm longer in the tire circumferential direction than the tie rubber layer 9 at one edge portion A of the inner liner 6, and the tie rubber layer 9 is longer than the butyl rubber layer 8 at the other edge portion B. The edge portion A, B is bonded to each other to form the splice portion 7 of the inner liner 6.

  That is, as shown in FIG. 2, the edge portion 8A on the A side of the butyl rubber layer 8 is longer than the edge portion 9A on the A side of the tie rubber layer 9 by a length L, and L is 5 mm or more and 25 mm or less. Further, the edge portion 9B on the B side of the tie rubber layer 9 is longer than the edge portion 8B on the B side of the butyl rubber layer 8 by a length L, and L is not less than 5 mm and not more than 25 mm. Both edge portions 8A and 8B of the butyl rubber layer 8 and both edge portions 9A and 9B of the tie rubber layer 9 are butt spliced (butt splice), and the butyl rubber layer 8 and the tie rubber layer 9 overlap in the tire circumferential direction D. But they are joined.

  Thus, since both edge parts A and B are comprised and the splice part 7 of an inner liner is formed, the splice part 7 is a flat form and does not form a stripe-like convex part. Therefore, it is possible to configure a pneumatic tire having a good appearance without causing bumpy side failure due to the formation of the line-shaped convex portions. Further, since the thicknesses of the splice part and the other part are uniform, the pneumatic tire is excellent in both static balance and dynamic balance of the pneumatic tire. If the length L between the two edges is shorter than 5 mm, it is not preferable because the area where the splice part is bonded becomes smaller and the adhesive force becomes smaller. Further, when it is larger than 25 mm, the productivity is lowered. The length L is preferably 10 to 20 mm from the viewpoint of adhesive strength between the two edges and productivity.

  Further, according to the knowledge of the present inventors, as shown in FIG. 3, the edge portion 8A of the butyl rubber layer 8 may overlap the edge portion 8B as long as it has a slight circumferential length. According to the study by the present inventors, if the overlapping length WI is about 3 mm or less, the overlapping portion is thicker than the other portion, but the tire is filled with air. Even in some cases, the appearance performance is hardly affected.

  The same applies to the case of the tie rubber layer 9, and the edge portion 9A of the tie rubber layer 9 may overlap the edge portion 9B if it has a slight circumferential length. According to the study by the present inventors, as in the case of the butyl rubber layer, if the overlapping length WB is about 3 mm or less, the overlapping part is thicker than the other part, Even when the tire is filled with air, the appearance performance is hardly affected.

  Thus, the presence of overlapping portions of the butyl rubber layers or the tie rubber layers is preferable because their adhesive force (bonding force) increases. In the embodiment shown in FIG. 3, the shift length LA on the edge A side and the shift length LB on the edge B side are not necessarily the same, and may be different.

  Further, it is preferable that the edge portions A and B are bonded to each other by engaging and engaging meshing three-dimensional structures formed in the tire radial direction on the edge end surfaces of the butyl rubber layer and / or the tie rubber layer. In particular, in the case of a meshing three-dimensional structure formed in the tire radial direction on the edge end surface of the butyl rubber layer, the edge portion of the butyl rubber layer can be joined so as to overlap without any gaps, so that the vulcanized tire is filled with air. It is preferable because sometimes air leakage can be well prevented. In addition, in the case of a meshing three-dimensional structure formed in the tire radial direction on the edge end surface of the tie rubber layer, the edge portion of the tie rubber layer can be joined so as to overlap without any gap, so that the butyl rubber layer and the carcass layer are in contact with each other. This is preferable because it is possible to prevent the occurrence of peeling between the two layers. Further, in the case of the meshing three-dimensional structure formed in the tire radial direction on the edge end surface of the butyl rubber layer and the meshing three-dimensional structure formed in the tire radial direction on the edge end surface of the tie rubber layer, the above-described 2 Since it can be set as the pneumatic tire which has the effect of two cases, it is preferable.

  An example of the meshing three-dimensional structure formed in the tire radial direction on the edge end face of the butyl rubber layer and / or tie rubber layer is schematically shown in FIGS. The length L of the difference between the edges of the butyl rubber layer and the tie rubber layer is shown as L (LA) on the edge A side in these drawings. The distance between the bases indicating the shortest of the layers. Further, as shown in FIG. 4 (d), when a three-dimensional structure is formed by meshing in the tire radial direction on the edge end surfaces of the butyl rubber layer and the tie rubber layer, the form is not necessarily the same in both layers. There is no difference.

  In the present invention, the butyl rubber layer is a generic term for both a layer made of butyl rubber or a layer made of a butyl rubber-based composition. The thickness of the butyl rubber layer is preferably 0.3 mm or more and 1.0 mm or less, and if the range is satisfied, an excellent pneumatic tire that has excellent air retention capability and does not become too expensive can be realized. . A more preferable thickness of the butyl rubber layer is 0.4 mm or more and 0.8 mm or less.

  Moreover, in this invention, a tie rubber layer is a rubber layer used in order to join the butyl rubber layer and carcass layer which exhibit the air retention function of an inner liner. The thickness of the tie rubber layer is preferably 0.2 mm or more and 1.0 mm or less, and if the range is satisfied, a pneumatic tire with good adhesion between the inner liner and the carcass layer and with few problems of appearance defects is realized. it can. The thickness of the tie rubber layer is more preferably 0.3 mm or more and 0.8 mm or less.

  Further, the minimum tread rubber thickness in the sidewall portion is preferably 1.2 mm or more and 5.0 mm or less, and when the range is satisfied, the amount of the tread rubber used in the sidewall portion is smaller and the whole is lightweight. In addition, it is possible to realize an excellent pneumatic tire having a good appearance without causing a bumpy side failure.

  The pneumatic tire of the present invention is optimal as a tire for a small truck in which the minimum tread rubber thickness in the sidewall portion is relatively small while a large load is applied.

  Hereinafter, the pneumatic tire of the present invention will be described with reference to examples. In addition, evaluation of the pneumatic tire was evaluated by the following method based on the occurrence state / level of the bumpy side failure in the sidewall portion of each test tire.

  In addition, the number of plies of the carcass layer of each evaluation tire is 1, and the minimum rubber thickness of the sidewall portion is 3.2 mm.

(1) Bumpy side failure resistance (bumpy side index):
Ten test tires, 700R15 8PR (TUBELESS), were prepared for each of the examples and the conventional examples, each of which was attached to a JATMA standard rim 15X5 1 / 2K, and the tire internal pressure was 24 times at normal temperature with JATMA maximum air pressure (450 kPa). After standing for a period of time, the unevenness of the sidewall portion was measured over the entire circumference of the tire, and the average value of 10 tires was obtained.

  Bumpy side failure resistance was evaluated by index evaluation with the unevenness amount of the conventional example as 100. The smaller the index, the better the bumpy side fault resistance.

(2) The thickness of the butyl rubber layer, the thickness of the tie rubber layer, and the minimum tread rubber thickness in the side wall portion All 10 cut samples were created from each test tire (1 point / 1 tire), and each cut With respect to the sample, the thickness of the butyl rubber layer, the thickness of the tie rubber layer, and the minimum tread rubber thickness in the sidewall portion were measured (n number = 10), and the minimum value among them was taken as each value.

Examples 1 to 6 and Conventional Example As shown in Table 1, six types of pneumatic tires according to examples of the present invention by changing the shift length L of each edge, the form of the splice portion, etc., and the air according to the conventional example One type of entering tire was created and evaluated. In the conventional example, the inner liner is wrapped to form a splice portion, and L is 0 mm.

  The results of evaluating the bumpy side failure resistance of each pneumatic tire are as shown in Table 1, and it can be seen that the improvement effect is remarkable according to the present invention.

1: tread portion 2: sidewall portion 3: bead portion 4: carcass layer 5: belt layer 6: inner liner 7: lap splice portion of inner liner 8: butyl rubber layer 8A: edge on the A side of butyl rubber layer 8B: butyl rubber B side edge of layer 8 9: Tie rubber layer 9A: Edge A side of tie rubber layer 9 B: Edge B side of tie rubber layer 9 D: Tire circumferential direction L: Edge misalignment between butyl rubber layer 8 and tie rubber layer 9 Length LA: Length of deviation on the edge A side LB: Length of deviation on the edge B side T: Pneumatic tire

Claims (5)

  In a pneumatic tire in which an inner liner made of a butyl rubber layer and a tie rubber layer is provided on the inner peripheral side of the carcass layer, the butyl rubber layer is 5 to 25 mm in the tire circumferential direction than the tie rubber layer at one edge portion A of the inner liner. In the other edge part B, the tie rubber layer is formed 5 to 25 mm longer than the butyl rubber layer in the tire circumferential direction, and the edge parts A and B are bonded together to form a splice part of the inner liner. A pneumatic tire characterized by   The bonding of the edge portions A and B is formed by meshing and joining meshing three-dimensional structures formed in the tire radial direction on the edge end surfaces of the butyl rubber layer and / or the tie rubber layer. Item 2. The pneumatic tire according to Item 1.   The pneumatic tire according to claim 1 or 2, wherein a thickness of the butyl rubber layer is 0.3 mm or more and 1.0 mm or less.   The pneumatic tire according to any one of claims 1 to 3, wherein a thickness of the tie rubber layer is 0.2 mm or more and 1.0 mm or less.   The pneumatic tire according to any one of claims 1 to 4, wherein a minimum tread rubber thickness in the sidewall portion is 1.2 mm or more and 5.0 mm or less.

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