JP6809839B2 - Pneumatic tires - Google Patents

Description

The present invention relates to a pneumatic tire having 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-one-down structure) including a two-layer turn-up ply and a one-layer down ply. 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. A pneumatic tire equipped with a carcass having such an up-down structure has a relatively excellent rigidity balance because the rigidity step is small.

In the process of molding a green tire, when the beadlock segment strongly crimps the bead portion from both sides, the end portion of the down ply may protrude from the bottom surface of the bead, which is a so-called protrusion failure. On the other hand, it is conceivable to arrange the end of the down ply away from the bottom surface of the bead, but in that case, at the stage of vulcanizing the green tire, the down ply pulls outward in the radial direction of the tire due to the action of tension. It sometimes caused so-called pull-out failure, which caused it to move.

Patent Document 2 describes a pneumatic tire in which a checker pad capable of improving low heat generation and workability is arranged on the outer side in the tire width direction of the checker provided so as to wrap the carcass. Further, Patent Document 3 describes a pneumatic tire in which a checker pad capable of improving scorchability and productivity is arranged on the outside in the tire width direction of the wound portion of the turn-up ply. However, these do not suggest a solution to the above-mentioned problem of defects in the up-down structure.

Japanese Unexamined Patent Publication No. 7-13756 JP-A-2009-292309 JP-A-2009-292310

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire capable of suppressing the occurrence of poor protrusion and poor removal of down ply.

The above object can be achieved by the present invention as described below. That is, the pneumatic tire according to the present invention has a pair of bead portions, a sidewall portion extending outward in the tire radial direction from each of the bead portions, and a tread portion connected to each tire radial outer end of the sidewall portion. In a pneumatic tire comprising a carcass provided to bridge between the bead portion and the bead portion, the carcass includes at least one layer of turn-up ply and at least one layer of down ply. The turn-up ply reaches the bead portion from the tread portion via the sidewall portion, and is wound around the bead core embedded in the bead portion from the inside to the outside in the tire width direction. A rubber pad is provided between the rubber chafer that covers the outside of the wound portion of the turn-up ply in the tire width direction and is terminated on the side of the bead core and forms the outer wall surface of the bead portion. It is what has been done.

In this tire, the end of the down ply is terminated on the side of the bead core, and a rubber pad is provided on the outside in the tire width direction of the down ply, so that the down ply is poorly projected due to crimping of the bead. Is suppressed. Moreover, since the down ply is sandwiched between the rubber pad and the wound part of the turn-up ply, the down ply pulled during vulcanization of the green tire does not move significantly, and the occurrence of poor pulling out of the down ply is suppressed. ..

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

It is preferable that the inner end portion of the rubber pad in the tire radial direction is arranged at the same height as the maximum width position of the bead core or on the outer side in the tire radial direction. According to this configuration, it is possible to prevent the amount of rubber around the bead core (particularly near the bottom surface of the bead) from becoming excessive, and to suppress the occurrence of defects (called bead pinch) in the bead portion accompanied by rubber defects and cracks. ..

It is preferable that the end portion of the rubber pad on the outer side in the tire radial direction is arranged at a distance of 5 mm or more in the tire radial direction from the end portion on the outer side in the tire radial direction of the rubber cheer. According to this configuration, since the end portion of the rubber pad is appropriately separated from the end portion of the rubber chain, the step between the members is reduced, the formation of air pools around the member is suppressed, and the rubber flow is good. become. As a result, the occurrence of air entry and the occurrence of rubber defects called bears are suppressed.

It is preferable that the thickness of the rubber chain is larger than the thickness of the rubber pad at the height of the exposed position of the interface between the side rubber forming the outer wall surface of the sidewall portion and the rubber chain. According to this configuration, the thickness of the rubber pad does not become too large, which is effective in suppressing the occurrence of bead pinch.

It is preferable that the modulus difference between the rubber cheer and the rubber pad is within 3 MPa, and the tear strength of the rubber pad is 22 MPa or more. Since the rubber pad is arranged at a place where a load is applied during traveling, it is preferable to have a modulus equivalent to that of the rubber cheer. Further, since the rubber pad constitutes a portion to be twisted or stretched, it is desirable to have such a high tear strength.

A tire meridian half cross section showing an example of a pneumatic tire according to the present invention. A cross-sectional view showing an enlarged view of the bead portion of the tire of FIG. Sectional drawing which shows the bead part in another embodiment of this invention Sectional drawing which shows the main part of the bead part in another embodiment of this invention.

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

The pneumatic tire T shown in FIGS. 1 and 2 has a pair of bead portions 1, a sidewall portion 2 extending outward in the tire radial direction from each of the bead portions 1, and a tread connected to the outer end in the tire radial direction of the sidewall portion 2. The portion 3 and the carcass 4 provided so as to be bridged between the pair of bead portions 1 are provided. Further, the tire T includes a rubber chafer 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 filled with air, and is made of rubber having low air permeability in order to maintain the 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 the turn-up ply 41 described later), and other members are interposed between them. Absent.

A bead core 1a and a bead filler 1b are embedded in the bead portion 1. The bead core 1a is formed of a convergent body in which rubber-coated wires are laminated and wound, and is formed in an annular shape along the tire circumferential direction. In this embodiment, the bead core 1a has a hexagonal cross-sectional shape. The bead filler 1b is formed so as to taper toward the outer side in the tire radial direction, and is arranged on the outer side in the tire radial direction of the bead core 1a. The tip of the bead filler 1b is arranged outside the winding end 41E of the carcass 4 in the tire radial direction.

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, it is a 1-up / 1-down structure including one layer each of the turn-up ply 41 and the down ply 42. 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, a metal such as steel and an organic fiber such as polyester, rayon, nylon and aramid are preferably used.

The turn-up ply 41 reaches the bead portion 1 from the tread portion 3 through the sidewall portion 2, and is wound around the bead core 1a from the inside to the outside in the tire width direction. In other words, the turn-up ply 41 has a series of winding portions arranged outside 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 to the bead portion 1 via the sidewall portion 2. It is provided in.

The down ply 42 covers the outside of the wound portion of the turn-up ply 41 (that is, the above-mentioned winding portion) in the tire width direction, and terminates on the side of the bead core 1a without being wound around the bead core 1a. There is. 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 down ply 42 is divided in the tire width direction by the tread portion 3.

The end portion 42E of the down ply 42 is arranged within the height range R from the top to the bottom of the bead core 1a. In the present embodiment, the end portion 42E is arranged at the height of the bottom portion of the bead core 1a, and is not arranged inside the tire radial direction from this. According to such a configuration, since the 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 crimping of the bead portion 1 during green tire molding is suppressed. On the other hand, since the down ply 42 becomes easy to move due to the action of tension, there is a concern that poor removal may occur.

As described above, the end portion 42E is arranged at the same height as the top of the bead core 1a or inside the tire radial direction. If it is arranged outside in the radial direction of the tire, tension is less likely to be generated in the down ply 42 during traveling, and the performance of the up / down structure is not sufficiently exhibited. Further, the end portion 42E is arranged at the same height as the bottom portion of the bead core 1a or outside the tire radial direction. If the tire is placed inside in the radial direction of the tire, protrusion defects are likely to occur during molding of the green tire, and the end portion 42E bends during vulcanization, causing deterioration of rubber flow, which causes bares. Become.

From the viewpoint of more effectively suppressing the occurrence of poor pulling out of the down ply 42, the end portion 42E of the down ply 42 is arranged within the range R'of the height from the maximum width position of the bead core 1a to the bottom of the bead core 1a. Is preferable.

In this tire T, a rubber pad 8 is provided between the rubber cheer 5 and the down ply 42 in order to suppress the occurrence of the down ply 42 from sticking out and coming off. The rubber pad 8 is located on the side of the bead filler 1b and is attached to the outside of the down ply 42 in the tire width direction. Since the down ply 42 is sandwiched between the rubber pad 8 and the wound portion of the turn-up ply 41, the down ply pulled during vulcanization of the green tire does not move significantly, and the occurrence of poor pulling out of the down ply 42 is suppressed. Will be done.

The rubber pad 8 has a crescent-shaped cross-sectional shape in which the thickness is relatively large at the central portion thereof and the thickness is relatively small at both ends thereof. 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. Further, 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 and the like shall be measured along a vertical line with respect 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 cheer 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 cheer 5. The thicknesses T8 and T5 are thicknesses measured along a perpendicular line to the down ply 42 as described above, and the perpendicular line passes through the exposed position P.

The length L8 of the rubber pad 8 is set, for example, in the range of 20 to 40% of the tire cross-sectional height TH. This length L8 is obtained as the tire radial distance from one end 8a of the rubber pad 8 to the other end 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 portion 8b on the outer side in the tire radial direction of the rubber pad 8 is located on the outer side in the tire radial direction from 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.

It is preferable that the end portion 8a of the rubber pad 8 is arranged at the same height as the maximum width position of the bead core 1a or on the outer side in the tire radial direction. As a result, it is possible to prevent the amount of rubber from becoming excessive around the bead core 1a (particularly in the vicinity of the bead bottom surface 1c) and suppress the occurrence of bead pinch. It is preferable that the end portion 8a is appropriately separated from the terminal portion 42E of the down ply 42, for example, 5.0 mm or more in the tire radial direction. As a result, the step between the members can be reduced, and the occurrence of air entry and deterioration of the rubber flow can be suppressed.

It is preferable that the end portion 8b of the rubber pad 8 is appropriately separated from the end portion 5E on the outer side of the rubber chain 5 in the tire radial direction, for example, 5 mm or more in the tire radial direction. As a result, the step between the members can be reduced, and the occurrence of air entry and deterioration of the rubber flow can be suppressed. In the present embodiment, an example in which the end portion 8b is located outside the end portion 5E of the rubber chain 5 in the tire radial direction is shown, but the end portion 8b is located outside the end portion 5E as in another embodiment (see FIG. 3) described later. It may be located inside the tire radial direction.

It is preferable that the end portion 8b of the rubber pad 8 is appropriately separated from the tip of the bead filler 1b, for example, 5 mm or more in the tire radial direction. When they are close to each other, dents are formed around their ends and air collects, which makes it easy for air to enter. Further, when such a dent is formed, it causes deterioration of the rubber flow and may cause the occurrence of bears.

In the present embodiment, the interface between the rubber chain 5 and the side rubber 6 is inclined inward in the tire width direction toward the outside in the tire radial direction, and the end portion 5E of the rubber chain 5 is in contact with the rubber pad 8. Therefore, the rubber flow during vulcanization of the green tire is relatively good, and the rubber cheer 5 and the side rubber 6 can be appropriately brought into close contact with the down ply 42. On the other hand, when the interface is inclined outward in the tire width direction toward the outside in the tire radial direction, the side rubber 6 is arranged between the rubber pad 8 and the rubber cheer 5, and the rubber flow is deteriorated. There is a risk of doing.

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

Since the rubber pad 8 is arranged at a place where a load is applied during traveling, it is preferable to have a modulus equivalent to that of the rubber cheer 5. Specifically, it is preferable that the modulus difference between the rubber cheer 5 and the rubber pad 8 is within 3 MPa. The value of the modulus is the value of the tensile stress (300% tensile modulus) at 300% elongation when the tensile test is performed at 23 ± 2 ° C. according to JIS K6251.

Further, it is preferable that the rubber pad 8 has the same rubber hardness as the rubber cheer 5. Specifically, it is preferable that the rubber hardness difference between the rubber cheer 5 and the rubber pad 8 is 3 or less. The value of the rubber hardness shall be the value of the rubber hardness measured at 23 ± 2 ° C. according to the durometer hardness test (type A) of JIS K6253.

Since the rubber pad 8 constitutes a portion to be twisted or stretched, it is desirable that the rubber pad 8 has a high tear strength. Specifically, the tear strength of the rubber pad 8 is preferably 22 MPa or more, and this also enhances the effect of suppressing poor removal of the down ply 42. Further, the tear strength of the rubber pad 8 is preferably higher than the tear strength of the rubber cheer 5, and the difference between them is preferably 6 MPa or more. The tear strength of the rubber chainer 5 is set to, for example, 16 MPa or more. The tear strength value is determined using a crescent-shaped test piece in accordance with JIS K6252.

Each of the above-mentioned dimensional values is measured in a normal state with no load in which the tire T is mounted on the normal rim and the normal internal pressure is charged. A regular rim is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, if it is JATMA, it is a standard rim, if it is TRA, it is "Design Rim", or if it is ETRTO. Let's say "Measuring Rim". The regular internal pressure is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, the maximum air pressure, and for TRA, the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION". The maximum value described in "PRESSURES", or "INFLATION PRESSURE" for ETRTO.

FIG. 3 shows a modified example in which the mode of the rubber pad 8 is changed. In this example, the length of the rubber pad 8 is shorter than that of the above-described embodiment, and the end portion 8b of the rubber pad 8 is located inside the end portion 5E of the rubber chain 5 in the tire radial direction. In this configuration, since the entire length of the rubber pad 8 is covered with the rubber chafer 5, the shape change during vulcanization of the green tire is small and the rubber flow is good.

FIG. 4 shows another modified example in which the mode 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 the 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 crimping of the bead portion 1 during green tire molding can be more effectively suppressed.

The pneumatic tire of the present invention is the same as a normal pneumatic tire except for the above-mentioned configuration regarding the carcass and the rubber pad, and all conventionally known materials, shapes, structures, manufacturing methods and the like 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 load used for heavy vehicles such as trucks, buses, industrial vehicles, and construction vehicles. It is useful as.

1 bead part 1a bead core 1b bead filler 1c bead bottom surface 2 sidewall part 3 tread part 4 carcass 5 rubber chaher 6 side rubber 7 inner liner rubber 8 rubber pad 41 turn-up ply 42 down ply

Claims (5)

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 outer end of the sidewall portion, and a pair of the bead portions. In pneumatic tires with carcass provided to be passed
The carcass comprises at least one layer of turn-up ply and at least one layer of down ply.
The turn-up ply reaches the bead portion from the tread portion via the sidewall portion, and is wound around the bead core embedded in the bead portion from the inside to the outside in the tire width direction.
The down ply covers the outside of the wound portion of the turn-up ply in the tire width direction, and is terminated on the side of the bead core.
A rubber pad is provided between the rubber chafer forming the outer wall surface of the bead portion and the down ply .
A pneumatic tire characterized in that the modulus difference between the rubber chafer and the rubber pad is within 3 MPa, and the tear strength of the rubber pad is 22 MPa or more . The bead core has a hexagonal cross-sectional shape in which two opposing sides are parallel to the tire width direction.
The pneumatic tire according to claim 1, wherein the end portion of the down ply is arranged within a height range from the position of the outermost apex of the hexagon of the bead core in the tire width direction to the bottom of the bead core. .. The bead core has a hexagonal cross-sectional shape in which two opposing sides are parallel to the tire width direction.
Claim 1 or 2 in which the inner end portion of the rubber pad in the tire radial direction is arranged at the same height as the position of the outermost apex of the hexagon in the tire width direction of the bead core, or outside the tire radial direction. Pneumatic tires described in. The inflated portion according to any one of claims 1 to 3, wherein the tire radial outer end of the rubber pad is arranged at a distance of 5 mm or more in the tire radial direction from the tire radial outer end of the rubber cheer. tire. According to any one of claims 1 to 4, the thickness of the rubber chain is larger than the thickness of the rubber pad at the height of the exposed position of the interface between the side rubber forming the outer wall surface of the sidewall portion and the rubber chain. Pneumatic tires listed.

Images