JP7105064B2 - pneumatic tire - Google Patents

Description

The present invention relates to pneumatic tires.

2. Description of the Related Art Conventionally, a pneumatic tire is known that is assembled to a rim such that the bottom surface of a fitting portion (bead portion) is pressed against the seat surface of the rim (see, for example, Patent Document 1).

However, in the conventional pneumatic tire described above, the bottom surface of the bead core is in pressure contact with the rim, and the rim restraining force is insufficient. For this reason, it cannot be said that desired steering stability performance and uniformity are obtained.

JP 2015-101228 A

An object of the present invention is to provide a pneumatic tire capable of improving steering stability performance and uniformity.

As a means for solving the above-mentioned problems, the present invention provides a tread portion that forms a tread surface, a pair of sidewall portions that continue from both sides of the tread portion in the tire width direction to the inner side in the tire radial direction, and a tire of the sidewall portions. a pair of bead portions connected radially inward and assembled to the rim, wherein the sidewall portion includes a rim protector having a top portion projecting outward in the tire width direction from the bead portion; and an outer surface of the bead portion. The bead base surface is formed with a protruding portion that protrudes with respect to the reference surface of the rim. A distance H1 in the tire radial direction from the tire radial direction inner end of the bead base surface to the tire radial direction outer end of the protrusion satisfies Hp× 0.86 ≦H1≦Hp×0.95, and The protruding portion is a curved protruding portion that protrudes in an arcuate cross-section and is entirely pressed against the rim when attached to the rim, and the radius of curvature R1 of the curved protruding portion satisfies 20 mm≦R1≦70 mm. Provide inboard tires.

With this configuration, the protruding portion of the bead portion is pressed against the rim, and the contact pressure between the two members can be increased. This position is a position away from the tire radial direction inner end of the bead base surface defined by the distance H1. As a result, it is possible to increase the rigidity of the tire radially outer portion of the bead portion, which tends to be unstable, and improve the rim restraining force. By improving the rim restraining force, it is possible to suppress tilting during cornering and improve steering stability. In addition, by increasing the rigidity of the bead portion at the radially outer portion of the tire, the overall rigidity balance is improved, and the uniformity can also be improved.

In addition, the protruding portion is formed of a curved protruding portion which protrudes in an arcuate cross-section and is wholly press-contacted to the rim when it is attached to the rim, and the radius of curvature R1 of the surface of the curved protruding portion satisfies 20 mm ≤ R ≤ 70 mm. , the contact pressure of the protrusions against the rim can be made appropriate to sufficiently increase the rim restraining force.

A distance H2 in the tire radial direction from the tire radial direction inner end of the bead base surface to the tire radial direction inner end of the protrusion satisfies Hp× 0.65 ≦H2≦Hp×0.75 and H2<H1. Satisfied is preferred.

With this configuration, it is possible to suppress an increase in the contact pressure between the bead base surface and the rim in the vicinity of the tire radial direction inner end of the bead base surface, and to further optimize the overall rigidity balance. becomes possible.

The bead base surface is
a first curved concave portion continuous to the tire radial direction outer side of the projecting portion;
a second curved recess that continues to the inner side of the protrusion in the tire radial direction;
has
The curvature radius R2 of the first curved recess and the curvature radius R3 of the second curved recess are
5mm≤R2, R3
is preferably satisfied.

It is preferable that the hardness of the rim strip rubber from at least the tire radial direction inner end of the bead portion to the second curved recess is equal to or higher than the hardness of the strip rubber of other portions.

With this configuration, it is possible to suppress tilting during cornering or when a heavy load is applied, thereby improving steering stability.

According to the present invention, since the projecting portion provided at a position away from the tire radial direction inner end of the bead base surface is brought into pressure contact with the rim, it is possible to increase the rim restraining force and improve steering stability performance and uniformity. .

1 is a partial perspective view of a pneumatic tire according to an embodiment including a cross section in the tire meridian direction; FIG. FIG. 2 is a tire meridional cross-sectional view at a bead portion showing a state before the pneumatic tire shown in FIG. 1 is attached to a rim; 3 is an enlarged view of a curved convex portion, a first curved concave portion, and a second curved concave portion shown in FIG. 2; FIG. FIG. 3 is a cross-sectional view taken along the meridian line of the tire shown in FIG. 2 when attached to the rim;

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that the following description is essentially merely an example, and is not intended to limit the present invention, its applications, or its uses. Moreover, the drawings are schematic, and the ratio of each dimension is different from the actual one.

FIG. 1 shows a partial perspective view of a pneumatic tire 1 (hereinafter referred to as tire 1) according to this embodiment. The tire 1 includes a tread portion 2 forming a tread surface, a pair of sidewall portions 3 continuous from both sides of the tread portion 2 in the tire width direction TW to the inner side in the tire radial direction TR, and a pair of sidewall portions 3 extending in the tire radial direction TR. A pair of bead parts 4 which continue inside and are assembled to the rim 12 are provided. The sidewall portion 3 and the bead portion 4 are made of different rubber materials. The sidewall portion 3 is made of sidewall rubber, and the bead portion 4 is mainly made of rim strip rubber. The hardness of the rim strip rubber is greater than or equal to that of the sidewall rubber.

The sidewall portion 3 is provided with a rim protector 5 that protects the rim 12 from external damage. The rim protector 5 is annularly connected in the tire circumferential direction TC and has a top portion 6 projecting outward in the tire width direction TW.

As shown in FIG. 2, the bead portion 4 is provided with a bead core 7 and a bead filler 8 that continuously extend annularly in the tire circumferential direction TC. The bead core 7 and bead filler 8 are stiffer than the rest of the bead 4, ie the rim strip rubber, so that the bead 4 can be properly assembled to the rim 12.

The bead core 7 is formed by bundling a plurality of wires so as to have a rectangular cross section, and is arranged on both sides in the tire width direction TW. The bead filler 8 is gradually curved outward in the tire width direction TW from the upper surface of the bead core 7 toward the outer side in the tire radial direction TR, and the width dimension is gradually narrowed toward the tip.

A carcass ply 9 is laid over the bead core 7 . Both sides of the carcass ply 9 are folded back from the inner side to the outer side of the bead core 7 and extend outward in the tire radial direction TR beyond the bead filler 8 . Also, the bead core 7 is surrounded by a chafer 10 arranged on the outer surface of the carcass ply 9 . An inner liner 11 is provided inside the carcass ply 9 in the tire radial direction TR.

The outer surface of the bead portion 4 is a bead base surface 14 that contacts the reference surface 13 of the rim 12 . When the tire 1 is mounted on the rim 12, the bead base surface 14 has a curved convex portion 15 projecting in the middle with respect to the virtual reference surface IRF (see FIG. 3) along the reference surface 13 of the rim 12, and It comprises a first curved recess 16 and a second curved recess 17 which are located and recessed. Here, the curved convex portion 15 is the projecting portion of the present invention.

As shown in FIG. 3, the curved convex portion 15 is formed into an arc having a radius of curvature R1 in a tire meridian cross section. The radius of curvature R1 is set to satisfy 20 mm≦R1≦70 mm, preferably R1=50 mm. By setting the radius of curvature R1 in this way, it is possible to secure a sufficient pressure contact area of the curved convex portion 15 against the rim 12 and increase the rigidity over a wide range. Further, the curved convex portion 15 is set so as to satisfy 0.3 mm≦PD≦2.5 mm, where PD is the maximum projecting dimension from the virtual reference plane IRF. By setting the projecting dimension of the curved convex portion 15 in this way, the magnitude of the pressure contact force acting on the rim 12 can be made appropriate, and the overall rigidity can be well-balanced.

The first curved concave portion 16 is continuous with the outer side of the curved convex portion 15 in the tire radial direction TR, and the cross section of the tire meridian is formed in an arc shape with a radius of curvature R2. The radius of curvature R2 is set to satisfy 5 mm≦R2, preferably 10 mm.

The second curved concave portion 17 is continuous to the inner side of the curved convex portion 15 in the tire radial direction TR, and the tire meridian cross section is formed in an arc shape with a radius of curvature R3. The radius of curvature R3 is set to satisfy 5 mm≦R3, preferably 10 mm.

As shown in FIG. 2 , the boundary position BL1 between the curved projection 15 and the first curved recess 16 (the point of inflection in the tire meridional cross section) extends from the inner end of the bead base surface 14 in the tire radial direction TR to the top of the rim protector 5. 6, the distance H1 in the tire radial direction TR from the inner end of the bead base surface 14 in the tire radial direction to the boundary position BL1 is Hp×0.55≦H1≦Hp× It is set to satisfy 0.95. Here, the tire radially inner end of the bead base surface 14 means the tire radially inner end of the chafer 10 when the tire 1 is mounted on the rim 12, as shown in FIG.

A boundary position BL2 (a point of inflection in the tire meridian cross section) between the curved convex portion 15 and the second curved concave portion 17 is such that a distance H2 in the tire radial direction TR from the tire radial direction inner end of the bead base surface 14 to the boundary position BL2 is It is set to satisfy Hp×0.41≦H2≦Hp×0.75 and H2<H1.

The rim strip rubber of the bead portion 4 is configured so that the region from the bead core 7 to the second curved recess 17 has a rigidity equal to or greater than that of other portions.

According to the pneumatic tire 1 according to the above-described embodiment, the position of the curved convex portion 15 that presses against the rim 12 is outside the bead portion 4 in the tire radial direction TR. can be increased outside of . As a result, the rigidity of the bead portion 4 can be made uniform as a whole when the tire 1 is mounted on the rim 12 . As a result, it is possible to prevent the bead filler 8 from collapsing during cornering or when a heavy load is applied, thereby improving steering stability and uniformity at the tire side portion. Also, by increasing the rigidity of the rim strip rubber in the vicinity of the bead core 7, it is possible to improve the steering stability performance.

Steering stability performance and uniformity were compared for tires 1 of Comparative Example and Examples 1 to 3. Here, the tire size used is 225/50R17.
In the steering stability performance test, each tire is installed on a passenger car with the specified air pressure for the vehicle, and the vehicle is driven on a dry asphalt-paved road with a load equivalent to two people on board while accelerating, braking, turning, and changing lanes. It was done by Steering stability was relatively evaluated from the viewpoint of marginal performance, response performance, and straight running performance by a professional driver. A larger index indicates better steering stability performance.
The uniformity test conforms to JASO C-607, each tire with an air pressure of 220kPa is mounted on a rim 12 of 15X6-JJ, and run on a drum with a diameter of 854mm at 1 rotation per second with a load of 4609N. This was done by measuring the variation of the force acting in the radial direction when the pressure was applied. The less variation, the better the uniformity. Taking the tire of Comparative Example 1 as an index of 100, the indices of the other tires were determined. A higher index indicates better uniformity.

In the comparative example, a protruding portion is provided inside the bead portion 4 in the tire radial direction TR so as to protrude in an arc shape toward the rim side.
In Example 1, a protruding portion that protrudes in an arc shape toward the rim is provided on the outer side of the bead portion 4 in the tire radial direction TR.
Example 2 has substantially the same configuration as Example 1, but differs in that the rim strip rubber including the protrusions has a higher rubber hardness.
The third embodiment has substantially the same configuration as the first embodiment, but is different in that the projecting portion is further formed outside the bead portion 4 in the tire radial direction TR.
Table 1 shows detailed positions of protrusions, rubber hardness (durometer hardness specified in JIS K6253-1-2012), and the like.

As is clear from Table 1, by arranging the curved convex portion 15 on the outer side in the tire radial direction TR, it was possible to improve steering stability and uniformity. In particular, by increasing the rubber hardness of the rim strip rubber forming the bead portion 4, it was possible to further improve steering stability and uniformity. Further, by arranging the curved convex portion 15 further outside in the tire radial direction TR, it was possible to further improve the steering stability performance.

DESCRIPTION OF SYMBOLS 1... Tire 2... Tread part 3... Side wall part 4... Bead part 5... Rim protector 6... Top part 7... Bead core 8... Bead filler 9... Carcass ply 10... Chafer 11... Inner liner 12... Rim 13... Reference surface 14 ... bead base surface 15 ... curved convex portion 16 ... first curved concave portion 17 ... second curved concave portion

Claims (5)

a tread portion forming a tread;
A pair of sidewall portions continuous from both sides in the tire width direction of the tread portion to the inner side in the tire radial direction;
a pair of bead portions connected to the inner side in the tire radial direction of the sidewall portion and attached to the rim;
with
The sidewall portion includes a rim protector having a top portion projecting outward in the tire width direction from the bead portion,
The bead base surface, which is the outer surface of the bead portion, is formed with a projecting portion projecting from the reference surface of the rim,
The tire diameter from the tire radially inner end of the bead base surface to the tire radially outer end of the protrusion, where Hp is the distance in the tire radial direction from the tire radially inner end of the bead base surface to the top portion. The directional distance H1 is
satisfying Hp× 0.86 ≦H1≦Hp×0.95,
The protruding portion is formed of a curved protruding portion that protrudes in an arcuate cross-section and is entirely press-contacted with the rim when it is attached to the rim,
The curvature radius R1 of the curved convex portion is
A pneumatic tire satisfying 20 mm≦R1≦70 mm. 2. The pneumatic tire according to claim 1, wherein a maximum projection dimension of said curved projection from said virtual reference plane of said rim is 0.3 mm or more and 2.5 mm or less. A distance H2 in the tire radial direction from the tire radial direction inner end of the bead base surface to the tire radial direction inner end of the protrusion is
Hp× 0.65 ≦H2≦Hp×0.75
The pneumatic tire according to claim 1 or 2, satisfying H2<H1. The bead base surface is
a first curved recess that continues to the outside in the tire radial direction of the curved protrusion;
a second curved recess that continues to the inner side of the curved protrusion in the tire radial direction,
The curvature radius R2 of the first curved recess and the curvature radius R3 of the second curved recess are
The pneumatic tire according to any one of claims 1 to 3, which satisfies 5mm≤R2, R3. 5. The rim strip rubber according to any one of claims 1 to 4, wherein the hardness of the rim strip rubber from at least the tire radial direction inner end of the bead portion to the second curved recess is equal to or higher than the hardness of the strip rubber of other portions. Pneumatic tires as described.

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