JP2008094147A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic radial tire having good fittability and concentricity when assembled with a rim. <P>SOLUTION: In a pneumatic radial tire, a plurality of cords is arranged along a rotating shaft, and at least one layer of carcass plys folded by bead cores at both ends to be supported is provided. A rubber layer forming a tread portion, a side wall portion, and a bead portion is attached to the outside of the carcass plys. At at least one place from a base surface 1b to a rising surface 1a of the rubber layer 1 forming the bead portion 2, a recessed portion 3 oriented to the axis 0 of the bead core is provided with a bottom wall 3a as a leading end. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  Of course, depending on the state of fitting with the rim, the air sealability of the tire may be impaired. The response at the time of a small rudder angle, the performance at the limit, the relatively low order (1-2) It is known that the ride comfort associated with the occurrence of the vibration mode is also affected, and how well and uniformly the tire is fitted to the rim is an important position.

  The present invention relates to a pneumatic radial tire, and is intended to improve the fitting property and concentricity when assembling a tire rim by reducing as much as possible the dimensional variation caused in the tire manufacturing process, particularly the dimensional variation in the bead portion. Is.

  When a pneumatic tire is assembled with a rim, the fitting to the rim is performed by tightening the rim by a bead portion of the tire.

  The ideal fit of the tire to the rim is that the rubber layer under the bead wire is sufficiently deformed and that the tire and the rim are concentric.

  Normally, tires are made with the inner circumference of the bead portion set smaller than the outer circumference of the rim, and when assembling the tire rim, the tire swells along with the air filling and slides up along the slope of the rim bottom (this When the bead portion is gradually crushed, a reliable seal is achieved and the tire is positioned relative to the rim.

  Therefore, the slipperiness of the bead part, the shape that affects the degree of tightening, and the rigidity are recognized as important factors for ensuring the fitting property of the tire.

  Considering the phenomenon that the tire tightens the rim, the rubber layer is the main cause of deformation, and then the treat, but the most influential part is the bead (wire), between the rim and the bead. Then, the rubber layer and the treat are crushed and tightening is established.

The rim is a metal part, and the dimensions such as the inclination angle of the outer periphery and the bottom of the rim are controlled in the standards (JIS, JATMA), and the bead is made of a material having a tensile strength (1400-3500 N / mm ² ). The wire or plate is bundled in a circular shape, and its inner periphery has a great influence on the fitting performance, so this is also strictly controlled.

  By the way, in the manufacturing process of a tire, the arrangement | positioning state of a bead may vary by the connection part (joint part), thickness, etc. of a structural member (refer FIG. 2 (a) (b)), This has been a cause of degradation of tire fitting and concentricity.

For tire rim assembly, conventionally, there is known a technique for ensuring airtightness and fit by interposing a lubricant between the bead portion and the rim, and the rim slip caused by the use of the lubricant is known. In order to avoid this, a technique in which a concave portion that captures and holds the lubricant at the bead portion of the tire has been proposed (see, for example, Patent Document 1), but the effect of the bead misalignment that occurs in the tire manufacturing process is proposed. However, the present situation is that there is a limit to further improving the fitting property and concentricity by stably deforming the bead portion.
JP 2005-81997

  An object of the present invention is to provide a novel pneumatic radial tire capable of ensuring concentricity with a rim when assembling the rim of a tire by reducing the influence of variations in components generated in the manufacturing process of the tire, and vulcanization molding used in the production thereof There is a place to propose a mold.

The present invention has at least one carcass ply in which a plurality of cords are arranged along the rotation axis of a tire and both ends thereof are folded back and supported by a bead core, and a tread portion and a sidewall portion are provided outside the carcass ply. And in a pneumatic radial tire formed by attaching a rubber layer that forms a bead part,
A pneumatic radial, characterized in that a recess is provided at least at one location from the base surface to the rising surface of the rubber layer forming the bead portion, with the bottom wall being directed to the axis of the bead core. Tire.

  In the pneumatic radial tire configured as described above, it is preferable that the recess has a depth of 1 to 4 mm and is present at least at three locations along the periphery of the tire.

  Further, the present invention is a tire vulcanization mold, and the mold is directed to an axis of a bead core incorporated in a vulcanized green tire at a corresponding portion of an inner wall that forms a bead portion of the tire. A mold for vulcanization molding of a tire, characterized by having protrusions that form recesses by pressing rubber layers existing between them.

  In the vulcanization mold having the above-described configuration, the projection can be provided with a moving mechanism that can slide back and forth along its axis, and the projection gradually decreases in cross-sectional area toward the tip. Those having a tapered shape are particularly advantageously adapted.

  The tip of the protrusion is preferably substantially flat and has a pressing area that exceeds the diameter of the filament of the bead core.

  If a concave portion with the bottom wall as the tip and directed to the axis of the bead core (bead wire) is provided in at least one place from the base surface to the rising surface of the rubber layer forming the bead portion, the position of the bead core in the bead portion As a result, the concentricity with the rim is secured and the fitting property is improved.

  Providing protrusions that form the above-mentioned recesses on the tire vulcanization mold, the bead core is supported by the protrusions when vulcanizing the green tire, and the positional relationship between the mold and the bead (core) is stable. Turn into.

Hereinafter, the present invention will be described more specifically with reference to the drawings.
FIG. 1 is a view showing an embodiment of a pneumatic radial tire according to the present invention along with a rim adapted to the cross section of a bead portion.

  In the figure, 1 is a rubber layer forming the bead portion of the tire, and 2 is a bead core embedded and fixed in the rubber layer 1. Although not shown in the figure, this tire has at least one carcass ply in which a plurality of cords are arranged along the rotation axis of the tire and both ends thereof are folded back and supported by the bead core 2, and outside the carcass ply. It has a general tire structure with a rubber layer that forms a tread portion and a sidewall portion.

  Reference numeral 3 denotes a recess formed in the rising surface 1a of the rubber layer 1. The concave portion 3 has an arrangement configuration in which the bottom wall 3a is pointed toward the axis O of the bead core 2.

  An inclination suitable for the rim 4 is provided on the base surface 1b of the bead portion of the tire, and the diameter (inner diameter) is set smaller than the diameter of the rim 4 which is a mating partner. During molding, the position of the bead core with respect to the mold may change as shown in FIGS.

  Normally, the fluidity of the rubber member increases during vulcanization, so the rubber member flows out in the high pressure part and flows in the low pressure part. Tension is generated, and the bead core 2 is relatively lifted in the thickness direction by the amount of joint at the joint portion of the member, which causes the positional deviation of the bead core 2.

  The concave portion 3 formed on the rising surface 1a of the rubber layer 1 can be formed by a projection 5 such as a pin as shown in FIG. 3 provided on the wall surface corresponding to that portion of the vulcanization mold. If the protrusion 5 is provided, the protrusion 5 will support the bead core 2 even if the vulcanization tire is pressed against the mold more than necessary due to the internal pressure of the vulcanization molding or the clamping force of the mold. The arrangement position of the bead core 2 is not easily shifted.

In order to support the bead core 2, it is important for the protrusion 5 to have its tip directed toward the axis O of the bead core 2, and the tip surface is substantially flat and ensures a pressing area of about 1 to 25 mm ² . Further, the protrusion 5 secures a protrusion margin that can make the depth of the recess 3 about 1 to 4 mm. Since there are at least three recesses 3 along the periphery of the tire, the same number of protrusions 5 are provided at corresponding portions of the inner wall of the mold.

  When the protrusion margin of the protrusion 5 is large, there is a concern that the bead portion may be torn or damaged when taking out from the mold only by deformation of the rubber. Therefore, the sectional area is gradually reduced toward the tip in consideration of die cutting. In some cases, a hole 6 is provided in the wall surface of the mold as shown in FIG. 4, and the projection 5 is slid back and forth along the hole 6. As the moving mechanism for sliding the protrusion 5, specifically, hydraulic pressure, pneumatic pressure, electromagnetic valve, or the like is applied.

  Pneumatic radial tires of the size 120 / 70ZR17M / C (tyre example 1) and 180 / 55ZR17M / C (tyre example 2) having the cross section shown in FIGS. 5 to 8 (the internal structure of the tire is the same as that of a conventional tire) ), And the tires are assembled into 17XMT3.50 and 17XMT5.50 rims and filled with internal pressure (both 260 kPa), then the tire runout (peak to peak) evaluation, uniformity evaluation, and sensory evaluation by professional riders (1000cc) Actual vehicle performance (riding comfort, maneuverability) by mounting on a road motorcycle was performed. The results are shown in Table 1.

  The tire run-out for the MCR120 / 70ZR17M / C tire is an internal pressure of 250kPa built into the MT3.50 / 17 rim, and for the MCR180 / 55ZR17M / C tire is an internal pressure built into the MT3.50 / 17 rim. The evaluation was performed at 290 kPa, with the maximum value and the minimum value of the fluctuation width of the dial gauge. Uniformity has a built-in internal pressure of 250 kPa in the MT3.50 / 17 rim for MCR120 / 70ZR17M / C tires, and a built-in internal pressure of 290 kPa in the rim of MT3.50 / 17 for MCR180 / 55ZR17M / C tires. It is evaluated from the peak value to the peak value of the fluctuation value when pressed against the drum with normal load and JATMA standard value.

  Example 1 has a flat bottom wall with 12 recesses having a depth of 1.5 mm and a diameter of 3.8 mm formed around the tire at intervals of about 170 mm. Example 2 is the same as Example 1 Is basically the same, but with the corners rounded while leaving a flat part on the bottom wall in consideration of die cutting, the depth of the recess in Example 3 is 3.5 mm (otherwise as in Example 2) In the same way, Example 4 uses a die with movable pins in consideration of tire laceration. In Example 4, the depth of the recess is 3.5 mm, and the same recess is formed on the bottom surface of the bead core. There are two rows of recesses (9 (40 °) formed at intervals of 8 mm around the tire), and Example 5 has a convex part at the center of the bottom wall to form a bifurcated shape in the radial direction of the bead core. The bead heel portion is provided with a rectangular (2.8 × 2.8 mm) concave portion in order to regulate the position in the width direction.

  As is clear from Table 1, it is confirmed that the pneumatic radial tires according to the present invention have much smaller tire runout and tend to be improved in uniformity, ride comfort and maneuverability. It was done.

  It is possible to provide a pneumatic radial tire with small dimensional variations that occur during the manufacturing process, and improved fitting and concentricity when the rim is assembled.

It is the figure which showed embodiment of the pneumatic radial tire according to this invention with the rim | limb which fits it in the cross section of a bead part. (a) (b) is the figure which showed the position shift situation of the bead core. It is the figure which showed the cross section of the vulcanization molding die. It is the figure which showed the cross section of the vulcanization molding die. It is the figure which showed the cross section of the principal part of the tire of Example 1. FIG. It is the figure which showed the cross section of the principal part of the tire of Example 2, 3. FIG. It is the figure which showed the cross section of the principal part of the tire of Example 4. FIG. FIG. 6 is a view showing a cross section of the main part of a tire of Example 5.

Explanation of symbols

1 Rubber layer forming bead part 2 Bead core 3 Recess
3a Bottom wall 4 Rim 5 Projection

Claims (6)

A plurality of cords are arranged along the rotation axis of the tire, and at least one carcass ply supported by being folded back at both ends by a bead core, and a tread portion, a sidewall portion, and a bead portion are provided outside the carcass ply. In pneumatic radial tires with rubber layers to form each,
A pneumatic radial, characterized in that a recess is provided at least at one location from the base surface to the rising surface of the rubber layer forming the bead portion, with the bottom wall being directed to the axis of the bead core. tire.   2. The pneumatic radial tire according to claim 1, wherein the recess has a depth of 1 to 4 mm and is provided at least at three locations along the periphery of the tire. A mold for tire vulcanization molding,
The mold is directed to the core of the bead core incorporated in the green tire for vulcanization at the corresponding portion of the inner wall forming the bead portion of the tire, and the rubber layer existing between them is pressed to form a recess. A mold for vulcanization molding of a tire, characterized by having protrusions.   The mold for vulcanization molding according to claim 3, wherein the protrusion has a moving mechanism that is slidable back and forth along its axis.   5. The vulcanization mold according to claim 3, wherein the protrusion has a tapered shape that gradually decreases in cross-sectional area toward the tip.   The vulcanization mold according to any one of claims 3 to 5, wherein the protrusion has a substantially flat tip and a pressing area exceeding the diameter of the filament of the bead core.

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