JP2018024322A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that can suppress occurrence of projection failure and coming-off failure of a down ply.SOLUTION: A carcass 4 includes at least one layer of turn-up ply 41 and at least one layer of down ply 42. The turn-up ply 41 extends from a tread part through a side wall part to a bead part 1, and is wound up, from inside to outside in a tire width direction, around a bead core 1a buried in the bead part 1. The down ply 42 covers the outside in the tire width direction of a wound-up part of the turn-up ply 41, and terminates beside the bead core 1a. Between a rubber chafer 5 forming an outer wall surface of the bead part 1 and the down ply 42 is provided a rubber pad 8.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire provided with a carcass having an up-down structure.

  Patent Document 1 describes a pneumatic tire provided with a carcass having an up-down structure (2-up, 1-down structure) including two layers of turn-up plies and one layer of down plies. The down ply is provided so as to terminate in the vicinity of the bead core without being wound around the bead core embedded in the bead portion. In the pneumatic tire provided with such an up-down structure carcass, the rigidity difference is relatively small, so that the rigidity balance is relatively excellent.

  In the process of forming the green tire, when the bead lock segment strongly presses the bead portion from both sides, the end portion of the down ply may protrude from the bottom surface of the bead, so-called protruding failure may occur. On the other hand, it is conceivable to arrange the end portion of the down ply away from the bottom surface of the bead. In this case, at the stage of vulcanizing the green tire, the down ply is pulled outward in the tire radial direction by the action of tension. The so-called omission failure may occur.

  Patent Document 2 describes a pneumatic tire in which a chacher pad that can improve low heat buildup and workability is arranged on the outer side in the tire width direction of a chacher provided so as to wrap a carcass. Patent Document 3 describes a pneumatic tire in which a chacher pad that can improve scorch and productivity is arranged on the outer side in the tire width direction of the portion where the turn-up ply is wound. However, these do not suggest a solution for the above-described defect problem in the up-down structure.

JP 7-137506 A JP 2009-292309 A JP 2009-292310 A

  This invention is made | formed in view of the said situation, The objective is to provide the pneumatic tire which can suppress generation | occurrence | production of the protrusion failure of a down ply, and omission defect.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention includes a pair of bead portions, a sidewall portion that extends outward in the tire radial direction from each of the bead portions, and a tread portion that is continuous with the tire radial outer end of each of the sidewall portions. And a pneumatic tire comprising a carcass provided so as to be bridged between the pair of bead portions, the carcass includes at least one turn-up ply and at least one layer down-ply, The turn-up ply reaches the bead portion from the tread portion through the sidewall portion, and is wound up from the inside in the tire width direction around the bead core embedded in the bead portion, and the down ply is Covers the outer side in the tire width direction of the portion where the turn-up ply is rolled up, and the bead core side In has been terminated, in which rubber pads are provided between Gomucheha and the down ply forming the outer wall surface of the bead portion.

  In this tire, the end portion of the down ply ends at the side of the bead core, and a rubber pad is provided on the outer side of the down ply in the tire width direction. Is suppressed. In addition, since the down ply is sandwiched between the rubber pad and the rolled up portion of the turn-up ply, the down ply pulled during vulcanization of the green tire does not move greatly, and the occurrence of a failure of the down ply is suppressed. .

  It is preferable that the end portion of the down ply is disposed within a height range from the maximum width position of the bead core to the bottom of the bead core. According to such a configuration, it is possible to more effectively suppress the occurrence of defective down ply.

  It is preferable that the end portion of the rubber pad on the inner side in the tire radial direction is the same height as the maximum width position of the bead core or on the outer side in the tire radial direction than that. According to such a configuration, it is possible to prevent an excessive amount of rubber around the bead core (particularly in the vicinity of the bead bottom surface), and to suppress the occurrence of defects (called bead pinch) in the bead portion with a rubber defect or crack. .

  It is preferable that an end portion of the rubber pad in the tire radial direction is disposed at a distance of 5 mm or more in the tire radial direction from an end portion of the rubber chacher in the tire radial direction. According to such a configuration, since the end of the rubber pad is disposed at an appropriate distance from the end of the rubber chacher, the step between the members is reduced, the formation of an air reservoir around the member is suppressed, and the rubber flow is good. become. As a result, the generation of air and the occurrence of rubber defects called bears are suppressed.

  It is preferable that the thickness of the rubber chacher is larger than the thickness of the rubber pad in the height of the exposed position of the interface between the side rubber forming the outer wall surface of the side wall portion and the rubber chacher. According to such a configuration, since the thickness of the rubber pad does not become too large, it is effective in suppressing the occurrence of bead pinch.

  It is preferable that the modulus difference between the rubber chacher and the rubber pad is 3 MPa or less, and the tear strength of the rubber pad is 22 MPa or more. Since the rubber pad is disposed at a place where a load is applied during traveling, it is preferable that the rubber pad has a modulus equivalent to that of the rubber chacher. Further, since the rubber pad constitutes a portion that twists and stretches, it is desirable that the rubber pad has such a high tear strength.

The tire meridian half sectional view showing an example of a pneumatic tire according to the present invention Sectional drawing which expands and shows the bead part of the tire of FIG. Sectional drawing which shows the bead part in other embodiment of this invention. Sectional drawing which shows the principal part of the bead part in other embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  A pneumatic tire T shown in FIGS. 1 and 2 includes a pair of bead portions 1, a sidewall portion 2 extending from each of the bead portions 1 to the outer side in the tire radial direction, and a tread continuous to the outer end in the tire radial direction of the sidewall portion 2. And a carcass 4 provided so as to be bridged between the pair of beads 1. Further, the tire T includes a rubber chacher 5 that forms the outer wall surface of the bead portion 1, a side rubber 6 that forms the outer wall surface of the sidewall portion 2, and an inner liner rubber 7 that forms the inner wall surface of the tire T.

  The inner liner rubber 7 faces the internal space of the tire T that is filled with air, and is formed of rubber having low air permeability in order to maintain air pressure. In the sidewall portion 2, the inner liner rubber 7 is directly attached to the inner peripheral side of the carcass 4 (the inner peripheral side of a turn-up ply 41 described later), and other members are interposed therebetween. Absent.

  A bead core 1 a and a bead filler 1 b are embedded in the bead portion 1. The bead core 1a is composed of a converging body obtained by laminating and winding wires covered with rubber, and is formed in an annular shape along the tire circumferential direction. In the present embodiment, the bead core 1a has a hexagonal cross-sectional shape. The bead filler 1b is tapered toward the outer side in the tire radial direction, and is disposed on the outer side in the tire radial direction of the bead core 1a. The tip of the bead filler 1b is disposed on the outer side in the tire radial direction than the winding end 41E of the carcass 4.

  The carcass 4 has a so-called up-down structure, and includes at least one layer of turn-up ply 41 and at least one layer of down ply 42. In the present embodiment, a 1-up 1-down structure including one turn-up ply 41 and one down-ply 42 is provided. Each ply constituting the carcass 4 is formed by rubber coating a plurality of cords arranged in a direction substantially orthogonal to the tire circumferential direction. As the material of the cord, metals such as steel and organic fibers such as polyester, rayon, nylon, and aramid are preferably used.

  The turn-up ply 41 reaches the bead part 1 from the tread part 3 through the sidewall part 2, and is wound up from the inner side in the tire width direction around the bead core 1a. In other words, the turn-up ply 41 is a series of winding portions disposed on the outer side in the tire width direction of the bead core 1a and the bead filler 1b on the main body portion from the tread portion 3 through the sidewall portion 2 to the bead portion 1. Is provided.

  The down ply 42 covers the outer side in the tire width direction of the portion of the turn-up ply 41 that has been rolled up (that is, the above-described winding portion), and ends on the side of the bead core 1a without being rolled up around the bead core 1a. Yes. In the present embodiment, the down ply 42 extends from the tread portion 3 through the sidewall portion 2 to the bead portion 1, and the tread portion 3 continuously extends in the tire width direction. However, the present invention is not limited to this, and the down ply 42 may have a so-called hollow structure in which the tread portion 3 is divided in the tire width direction.

  The end portion 42E of the down ply 42 is disposed within the range R of the height from the top to the bottom of the bead core 1a. In the present embodiment, the end portion 42E is disposed at the height of the bottom portion of the bead core 1a, and is not disposed on the inner side in the tire radial direction than this. According to such a configuration, since the terminal end portion 42E of the down ply 42 is appropriately separated from the bead bottom surface 1c, the occurrence of poor protrusion of the down ply 42 due to the pressure bonding of the bead portion 1 at the time of green tire molding is suppressed. On the other hand, since the down ply 42 is easy to move due to the action of tension, there is a concern about the occurrence of omission.

  As described above, the end portion 42E is disposed at the same height as the top of the bead core 1a or on the inner side in the tire radial direction than that. If it is arranged on the outer side in the tire radial direction than this, tension is unlikely to be generated in the traveling down ply 42, and the performance of the up-down structure is not sufficiently exhibited. Further, the end portion 42E is disposed at the same height as the bottom of the bead core 1a or on the outer side in the tire radial direction than that. If it is arranged on the inner side in the tire radial direction than this, it becomes easy to cause a protrusion failure at the time of molding a green tire, and the end portion 42E is bent at the time of vulcanization to cause deterioration of the rubber flow, Become.

  From the viewpoint of more effectively suppressing the occurrence of a failure of the down ply 42, the end portion 42E of the down ply 42 is disposed within a range R ′ of the height from the maximum width position of the bead core 1a to the bottom of the bead core 1a. It is preferable.

  In this tire T, a rubber pad 8 is provided between the rubber chafer 5 and the down ply 42 in order to suppress the occurrence of poor protrusion and disconnection failure of the down ply 42. The rubber pad 8 is located on the side of the bead filler 1b and is attached to the outer side of the down ply 42 in the tire width direction. Since the down ply 42 is sandwiched between the rubber pad 8 and the rolled up ply 41, the down ply pulled during the vulcanization of the green tire does not move greatly, and the occurrence of a failure of the down ply 42 is suppressed. Is done.

  The rubber pad 8 has a crescent-shaped cross-sectional shape having a relatively large thickness at the center and a relatively small thickness at both ends. The maximum thickness of the rubber pad 8 is preferably 1.5 mm or more in order to suppress the occurrence of poor protrusion of the down ply 42. The maximum thickness of the rubber pad 8 is preferably 5.0 mm or less in order to suppress the occurrence of bead pinch. The thickness of the rubber pad 8 or the like is measured along a perpendicular to the down ply 42.

  Further, from the viewpoint of suppressing the occurrence of bead pinch, it is preferable that the thickness T5 of the rubber chacher 5 is larger than the thickness T8 of the rubber pad 8 at the height of the exposed position P at the interface between the side rubber 6 and the rubber chacher 5. The thicknesses T8 and T5 are thicknesses measured along the perpendicular to the downply 42 as described above, and the perpendicular passes through the exposure position P.

  The length L8 of the rubber pad 8 is set, for example, in a range of 20 to 40% of the tire cross-section height TH. This length L8 is calculated | required as a tire radial direction distance from the one edge part 8a of the rubber pad 8 to the other edge part 8b. In the present embodiment, the end portion 8a on the inner side in the tire radial direction of the rubber pad 8 is located on the inner side in the tire radial direction with respect to the exposed position P, and is located on the outer side in the tire radial direction with respect to the terminal portion 42E. Further, the end 8b of the rubber pad 8 on the outer side in the tire radial direction is located on the outer side in the tire radial direction with respect to the exposed position P, and is located on the inner side in the tire radial direction with respect to the tip of the bead filler 1b and the winding end 41E of the turn-up ply 41. To do.

  The end 8a of the rubber pad 8 is preferably disposed at the same height as the maximum width position of the bead core 1a or on the outer side in the tire radial direction than that. Thereby, it is possible to prevent the rubber amount from being excessive in the vicinity of the bead core 1a (particularly in the vicinity of the bead bottom surface 1c), and to suppress the occurrence of bead pinch. The end portion 8a is preferably disposed at a distance from the end portion 42E of the down ply 42, for example, 5.0 mm or more in the tire radial direction. Thereby, the level | step difference between members can be made small and generation | occurrence | production of air entry and the deterioration of a rubber flow can be suppressed.

  The end portion 8b of the rubber pad 8 is preferably disposed at a distance from the end portion 5E on the outer side in the tire radial direction of the rubber chacher 5, for example, 5 mm or more in the tire radial direction. Thereby, the level | step difference between members can be made small and generation | occurrence | production of air entry and the deterioration of a rubber flow can be suppressed. In the present embodiment, an example is shown in which the end portion 8b is positioned on the outer side in the tire radial direction from the end portion 5E of the rubber chacher 5, but the end portion 8b is more than the end portion 5E as in another embodiment (see FIG. 3) described later. May also be located on the inner side in the tire radial direction.

  The end portion 8b of the rubber pad 8 is preferably disposed at a distance from the tip of the bead filler 1b, for example, 5 mm or more in the tire radial direction. When these are close to each other, depressions are formed around the end portions, air is collected, and air is easily generated. Moreover, when such a dent is formed, the rubber flow is deteriorated, which may cause generation of bears.

  In the present embodiment, the interface between the rubber chafer 5 and the side rubber 6 is inclined inward in the tire width direction toward the outer side in the tire radial direction, and the end portion 5E of the rubber chacher 5 is in contact with the rubber pad 8. For this reason, the rubber flow at the time of vulcanization of the green tire becomes relatively good, and the rubber chafer 5 and the side rubber 6 can be properly adhered to the down ply 42. On the other hand, when the interface is inclined outward in the tire radial direction toward the outer side in the tire radial direction, the side rubber 6 is arranged between the rubber pad 8 and the rubber chacher 5, and the rubber flow is deteriorated. There is a fear.

  Since the rubber chacher 5 is disposed at a site that rubs against the rim flange, it is made of rubber having excellent wear resistance. The rubber pad 8 is formed of a rubber different from that of the rubber chacher 5, and is preferably formed of a rubber excellent in adhesiveness (adhesion).

  Since the rubber pad 8 is disposed at a place where a load is applied during traveling, it is preferable that the rubber pad 8 has a modulus equivalent to that of the rubber chacher 5. Specifically, the modulus difference between the rubber chafer 5 and the rubber pad 8 is preferably within 3 MPa. The value of the modulus is a value of tensile stress at 300% elongation (300% tensile modulus) when a tensile test is performed at 23 ± 2 ° C. according to JISK6251.

  The rubber pad 8 preferably has a rubber hardness equivalent to that of the rubber chacher 5. Specifically, it is preferable that the rubber hardness difference between the rubber chafer 5 and the rubber pad 8 is 3 or less. The value of rubber hardness is the value of rubber hardness measured at 23 ± 2 ° C. according to JIS K6253 durometer hardness test (type A).

  Since the rubber pad 8 constitutes a portion that twists and stretches, it is desirable that the rubber pad 8 has a high tear strength. Specifically, it is preferable that the tear strength of the rubber pad 8 is 22 MPa or more, thereby enhancing the effect of suppressing the failure of the down ply 42. The tear strength of the rubber pad 8 is preferably higher than the tear strength of the rubber chacher 5, and the difference between them is preferably 6 MPa or more. The tear strength of the rubber chacher 5 is set to 16 MPa or more, for example. The value of tear strength is determined using a crescent test piece in accordance with JIS K6252.

  Each dimension value described above is measured in a normal state with no load in which the tire T is mounted on a normal rim and filled with a normal internal pressure. A regular rim is a rim determined for each tire in the standard system including the standard on which the tire is based. For example, JATMA is a standard rim, TRA is "Design Rim", or ETRTO "Measuring Rim". The normal internal pressure is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based, the maximum air pressure for JATMA, and the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION for TRA" The maximum value described in "PRESSURES". If ETRTO, "INFLATION PRESSURE".

  In FIG. 3, the modification which changed the aspect of the rubber pad 8 is shown. In this example, the length of the rubber pad 8 is shorter than that of the above-described embodiment, and the end 8b of the rubber pad 8 is located on the inner side in the tire radial direction than the end 5E of the rubber chacher 5. In this configuration, since the entire length of the rubber pad 8 is covered with the rubber chacher 5, the shape change during vulcanization of the green tire is small, and the rubber flow is good.

  FIG. 4 shows another modification in which the aspect of the rubber pad 8 is changed. In this example, the rubber pad 8 has a substantially trapezoidal cross-sectional shape, and the rubber pad 8 has a maximum thickness Tm at the height of the top of the bead core 1a. The thickness Tm is a thickness measured along the perpendicular to the down ply 42 as described above, and the perpendicular passes through the outer wall surface at the height of the top of the bead core 1a. According to such a configuration, the occurrence of poor protrusion of the down ply 42 due to the pressure bonding of the bead portion 1 at the time of forming the green tire is more effectively suppressed.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except for the above-described configuration relating to carcass and rubber pads, and any conventionally known material, shape, structure, manufacturing method, etc. can be adopted in the present invention. it can.

  The pneumatic tire according to the present invention is provided with the rubber pad as described above and has excellent durability of the bead portion. Therefore, the pneumatic tire for heavy loads used for heavy vehicles such as trucks, buses, industrial vehicles, and construction vehicles. Useful as.

1 Bead part 1a Bead core 1b Bead filler 1c Bead bottom face 2 Side wall part 3 Tread part 4 Carcass 5 Rubber chacher 6 Side rubber 7 Inner liner rubber 8 Rubber pad 41 Turn-up ply 42 Down ply

Claims (6)

A pair of bead portions, a sidewall portion extending outward in the tire radial direction from each of the bead portions, a tread portion connected to each tire radial direction outer end of the sidewall portion, and a pair of the bead portions. In a pneumatic tire provided with a carcass provided to be passed,
The carcass includes at least one turn-up ply and at least one down-ply;
The turn-up ply reaches the bead portion from the tread portion through the sidewall portion, and is wound up from the inner side in the tire width direction around the bead core embedded in the bead portion,
The down ply covers the outer side in the tire width direction of the rolled up portion of the turn-up ply and terminates at the side of the bead core,
A pneumatic tire, wherein a rubber pad is provided between a rubber chacher forming an outer wall surface of the bead portion and the down ply.   2. The pneumatic tire according to claim 1, wherein an end portion of the down ply is disposed within a height range from a maximum width position of the bead core to a bottom portion of the bead core.   3. The pneumatic tire according to claim 1, wherein an end portion of the rubber pad on the inner side in the tire radial direction is disposed at the same height as the maximum width position of the bead core or on the outer side in the tire radial direction than the same.   The pneumatic tire according to any one of claims 1 to 3, wherein an end portion on the outer side in the tire radial direction of the rubber pad is disposed 5 mm or more away from an end portion on the outer side in the tire radial direction of the rubber chacher in the tire radial direction. tire.   The thickness of the rubber chacher is larger than the thickness of the rubber pad in the height of the exposed position of the interface between the side rubber forming the outer wall surface of the side wall portion and the rubber chacher. The described pneumatic tire.   The pneumatic tire according to any one of claims 1 to 5, wherein a modulus difference between the rubber chafer and the rubber pad is 3 or less, and a tear strength of the rubber pad is 22 MPa or more.

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