JP2019112040A - Pneumatic tire - Google Patents

Abstract

To improve operation stability and uniformity in a pneumatic tire.SOLUTION: A side wall part 3 includes a rim protector 5 having an apex part 6 protruding nearer outward in a tire width direction than a bead part 4. On a bead base surface 14 to be an external surface of the bead part 4, a protrusion part 15 which protrudes to a reference surface 13 of a rim 12 and is composed of a member different from the bead base surface 14 is formed. When a distance in a tire radial direction from an internal end in the tire radial direction of the bead base surface 14 to the apex part 6 is Hp, distance H1 in the tire radial direction from an inner end in the tire radial direction of the bead base surface 14 to an outer end in the tire radial direction of the projection satisfies Hp×0.55≤H1≤Hp×0.95.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire.

  Conventionally, a pneumatic tire is known that is assembled to a rim such that the bottom surface of a fitting portion (bead portion) is in pressure contact with the seat surface of the rim (see, for example, Patent Document 1).

  However, in the conventional pneumatic tire, the pressure-contacting portion with the rim is the bottom of the bead core, and the rim restraining force is insufficient. For this reason, it can not be said that the desired steering stability performance and uniformity can be obtained.

JP, 2015-101228, A

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

The present invention, as means for solving the above problems,
A tread portion that constitutes a tread surface,
A pair of sidewall portions that extend inward in the tire radial direction from both sides in the tire width direction of the tread portion;
A pair of bead portions that are continuous to the tire radial direction inner side of the side wall portion and are assembled to the rim;
Equipped with
The sidewall portion includes a rim protector having a top protruding outward in the tire width direction relative to the bead portion.
A bead base surface, which is an outer surface of the bead portion, is formed with a protrusion which protrudes with respect to the reference surface of the rim and which is a separate member from the bead base surface.
The tire diameter from the tire radial direction inner end of the bead base surface to the tire radial direction outer end of the protrusion when the distance in the tire radial direction from the tire radial direction inner end of the bead base surface to the top is Hp The distance H1 in the direction is
Hp × 0.55 ≦ H1 ≦ Hp × 0.95
To provide a pneumatic tire that satisfies the

  According to this configuration, the protrusion of the bead portion comes in pressure contact with the rim, and the contact pressure between both members can be increased. This position is a position defined by the distance H1 away from the tire radial direction inner end of the bead base surface. As a result, the rigidity in the tire radial direction outer portion of the bead portion which tends to be unstable can be enhanced, and the rim restraint force can be improved. And, by improving the rim restraining force, it becomes possible to suppress the fall at the time of cornering and to improve the steering stability performance. Further, by enhancing the rigidity of the bead portion in the tire radial direction outer portion, the overall rigidity balance can be improved, and the uniformity can also be improved.

The 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 × 0.41 ≦ H2 ≦ Hp × 0.75
H2 ≦ H1
It is preferable to satisfy

  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 make the overall rigidity balance even more appropriate. Is possible.

  It is preferable that the protrusion has a hardness higher than that of the other portion constituting the bead base surface.

  According to this configuration, the rigidity of the protrusion that increases the contact pressure with the rim can be enhanced, the deformation of the protrusion can be suppressed at the time of cornering or high load, and the steering stability can be improved.

The bead base surface is
A first curved recess that is continuous to the outer side in the tire radial direction of the protrusion;
A second curved recess that is continuous to the inside in the tire radial direction of the protrusion;
Have
The radius of curvature R2 of the first curved recess and the radius of curvature R3 of the second curved recess are:
5 mm ≦ R2, R3
It is preferable to satisfy

  It is preferable that the tire meridional section has a circular arc shape, and a plurality of the protruding portions are formed.

  According to this configuration, it is possible to disperse the pressure contact points and to increase the rigidity of the contact surface in a wide range. This makes it possible to improve the uniformity.

  The bead base surface may be configured by a combination of a protrusion having an arc shape in a tire meridional section and a flat portion having a linear shape.

  According to the present invention, since the protrusion provided at a position apart from the tire radial direction inner end of the bead base surface is pressed against the rim, the rim restraining force can be enhanced to improve the steering stability and the uniformity. . Since the projection is made of a separate member, the characteristics can be freely changed only by this part.

1 is a partial perspective view including a cross section in a tire meridian direction of a pneumatic tire according to a first embodiment. It is tire meridional sectional drawing in the bead part which shows the state before assembling the pneumatic tire shown in FIG. 1 to a rim | limb. It is an enlarged view of the protrusion part shown in FIG. 2, a 1st curved recessed part, and a 2nd curved recessed part. It is tire meridian sectional drawing which shows the state assembled | attached to the rim from FIG. It is an enlarged view of the protrusion part of a pneumatic tire concerning a 2nd embodiment, the 1st curving recess, and the 2nd curving recess.

  Hereinafter, an embodiment according to the present invention will be described according to the attached drawings. The following description is merely illustrative in nature, and is not intended to limit the present invention, its applications, or its applications. In addition, the drawings are schematic, and ratios of respective dimensions and the like are different from actual ones.

First Embodiment
FIG. 1 shows a partial perspective view of a pneumatic tire 1 (hereinafter referred to as a tire 1) according to a first embodiment. The tire 1 includes a tread portion 2 constituting a tread surface, a pair of sidewall portions 3 extending from both sides in the tire width direction TW of the tread portion 2 in the tire radial direction TR, and a tire radial direction TR of the sidewall portion 3 It has a pair of bead parts 4 which continue inside and are assembled to the rim 12. The sidewall portion 3 and the bead portion 4 are formed 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 rim strip rubber is harder than the sidewall rubber.

  The side wall portion 3 is provided with a rim protector 5 for protecting the rim 12 from trauma. The rim protector 5 is annularly connected in the tire circumferential direction TC, and has a top 6 that protrudes outside the bead portion 4 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 continuously extending annularly in the tire circumferential direction TC. The bead core 7 and the bead filler 8 are stiffer than other parts of the bead portion 4, i.e., the rim strip rubber, so that the bead portion 4 can be properly assembled to the rim 12.

  The bead core 7 is formed by bundling a plurality of wires in a rectangular shape in cross section, and is disposed on both sides in the tire width direction TW. The bead filler 8 is gradually curved to the outside in the tire width direction TW as it goes from the upper surface of the bead core 7 to the outer side of the tire radial direction TR, and the width dimension gradually narrows as it goes to the tip.

  A carcass ply 9 is stretched around the bead core 7. Both sides of the carcass ply 9 are folded from the inside to the outside of the bead core 7 and extend beyond the bead filler 8 to the outside of the tire radial direction TR. The bead core 7 is surrounded by chafers 10 disposed on the outer surface of the carcass ply 9. The inner portion of the carcass ply 9 in the tire radial direction TR is the inner liner 11.

The outer surface of the bead portion 4 is a bead base surface 14 that abuts on the reference surface 13 of the rim 12. The bead base surface 14 is provided with a protrusion 15. The protruding portion 15 is made of a separate member from the rim strip rubber constituting the bead portion 4 and has a substantially trapezoidal cross section. Specifically, as shown in FIG. 3, the protrusion 15 includes a flat surface 15 a and a circular arc surface 15 b continuing to the outer side and the inner side in the tire radial direction. The flat surface 15a is parallel to a plane connecting boundary positions BL1 and BL2 described later.
The protrusion 15 protrudes from the virtual reference surface IRF along the reference surface 13 of the rim 12 toward the rim 12. The maximum protrusion dimension PD of the protrusion 15 from the virtual reference plane IRF is set to satisfy 0.3 mm ≦ PD ≦ 2.5 mm. Thus, by setting the projecting dimension of the projecting portion 15, the magnitude of the pressing force acting on the rim 12 can be made appropriate, and the overall rigidity can be made well balanced.
Further, the protruding portion 15 has a hardness higher than that of the rim strip rubber of the bead portion 4. Here, the rubber hardness of the protrusion 15 is 55 or more and 100 or less (durometer hardness defined in JIS K6253-1-2012). As a result, even when the pressing force of the protrusion 15 against the rim 12 is increased at the time of cornering or under heavy load, the steering stability can be improved by suppressing the deformation of the protrusion 15.

  Further, on the bead base surface 14, a first curved recess 16 and a second curved recess 17 are formed on both sides of the protrusion 15.

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

  The second curved recess 17 is continuous to the inside of the protruding portion 15 in the tire radial direction TR, and the tire meridional section is formed in an arc shape having a radius of curvature R3. The curvature radius R3 is set to satisfy 5 mm ≦ R3, and is preferably 10 mm.

As shown in FIG. 2, the boundary position BL1 between the protrusion 15 and the first curved recess 16 is the distance in the tire radial direction TR from the inner end of the bead base surface 14 in the tire radial direction TR to the top 6 of the rim protector 5. When Hp, the distance H1 in the tire radial direction TR from the tire radial direction inner end of the bead base surface 14 to the boundary position BL1 is set to satisfy the following equation.
Hp × 0.55 ≦ H1 ≦ Hp × 0.95
Here, the tire radial direction inner end of the bead base surface 14 means the tire radial direction inner end of the chafer 10 in a state where the tire 1 is assembled to the rim 12 as shown in FIG. 4.

The boundary position BL2 between the projecting portion 15 and the second curved recess 17 is set such that the 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 satisfies the following equation There is.
Hp × 0.41 ≦ H2 ≦ Hp × 0.75
H2 <H1

  According to the pneumatic tire 1 of the first embodiment, the position of the protrusion 15 in pressure contact with the rim 12 is on the outer side of the tire radial direction TR of the bead portion 4. It can be enlarged outside of the TR. Thereby, the rigidity of the bead part 4 in the state which assembled | attached the tire 1 to the rim 12 can be made uniform uniformly in the whole. As a result, it is possible to prevent the bead filler 8 from falling when cornering or under high load, and to improve the steering stability and the uniformity at the tire side portion. In particular, since the protruding portion 15 is configured as a separate member from the strip rubber of the bead portion 4 and the hardness is set high, in the protruding portion 12 the contact pressure with the rim 12 becomes high at cornering or under high load. It is possible to suppress deformation and improve steering stability performance.

Second Embodiment
FIG. 5 is an enlarged view showing the vicinity of the protrusion 15 of the pneumatic tire according to the second embodiment. Here, the protrusion 15 does not have a flat portion, and is formed in an arc shape as a whole. That is, the outer surface of the projecting portion 15 is configured by an arc surface connecting the boundary position BL1 and the boundary position BL2. The curvature radius R1 of the surface of the protrusion 15 in the tire meridian cross section is set to satisfy 20 mm ≦ R1 ≦ 70 mm, and preferably R1 = 50 mm. Further, the maximum protrusion dimension PD of the protrusion 15 from the virtual reference plane IRF is set to satisfy 0.3 mm ≦ PD ≦ 2.5 mm.

The steering stability and the uniformity were compared for the tires 1 of the comparative example and the examples 1 to 5. Here, the tire size used is 225 / 50R17.
In the steering stability test, each tire should be mounted on a passenger car as the specified air pressure of the vehicle, and run with acceleration, braking, turning, and lane change on a dry asphalt-paved road surface with a load equivalent to two passengers. Went by. The steering stability was relatively evaluated from the viewpoint of the limit performance, response performance, and straight running performance by a specialized driver, and the index of the other tire was determined with the tire of the comparative example as an index of 100. The larger the index is, the better the steering stability is.
The uniformity test is based on JASO C-607, and each tire with an air pressure of 220 kPa is assembled to the rim 12 of 15X6-JJ, and it runs on a drum with a diameter of 854 mm at one rotation per second with a load of 4609 N applied. It was carried out by measuring the fluctuation of the force acting in the radial direction. The smaller the variation, the better the uniformity. The indexes of the other tires were determined using the tire of Comparative Example 1 as the index 100. The larger the index, the better the uniformity.

In the comparative example, a projecting portion that protrudes in an arc shape toward the rim side is provided inside the tire radial direction TR of the bead portion 4.
In Example 1, the protrusion part 15 which the tire meridian cross section becomes from the other member of a trapezoidal shape is provided in the outer side of the tire radial direction TR of the bead part 4 (1st Embodiment).
The second embodiment differs in that the position where the protrusion 15 is provided is further on the outer side in the tire radial direction TR than the first embodiment.
The third embodiment has substantially the same configuration as the first embodiment, but differs in that the rubber hardness of the protruding portion 15 is higher than the strip rubber of the bead portion 4.
The fourth embodiment is different from the first embodiment in that the tire meridional cross-sectional shape of the protrusion 15 is arc-shaped (second embodiment).
The fifth embodiment has substantially the same configuration as the second embodiment, but differs in that the trapezoidal leg portion is concavely curved.
The detailed positions of the protrusions 15 and the rubber hardness are as shown in Table 1.

  As apparent from Table 1, the steering stability and the uniformity were able to be improved by arranging the protrusion 15 outside the tire radial direction TR (Example 1). In particular, steering stability performance and uniformity were able to be most improved by further disposing the protrusion 15 outside the tire radial direction TR (Example 2). In addition, the steering stability and the uniformity were able to be improved by increasing the rubber hardness of the rim strip rubber constituting the bead portion 4 as compared with the example 1 (example 3). In addition, the steering stability and the uniformity were able to be improved as compared with the comparative example by making the protrusion 15 as a whole in an arc shape (Example 4). In addition, even in the case where the projecting portion 15 has a trapezoidal shape and the leg portion is curved in a concave shape, the steering stability and the uniformity can be improved as compared with the comparative example (Example 5).

  In addition, this invention is not limited to the structure described in the said embodiment, A various change is possible.

  In the embodiment described above, the protruding portion 15 is configured to be expanded at one point in the central portion, but may be configured to have two or more expanded portions. Also, the plurality of bulges can be constituted by a plurality of protrusions 15. As described above, by providing the bead base surface 14 with two or more bulged portions, it is possible to disperse the press-contacting portion with the rim 12 and to increase the rigidity of the contact surface in a wide range. This makes it possible to improve the uniformity.

  In the embodiment described above, the first curved concave portion 16 and the second curved concave portion 17 are formed on both sides of the projecting portion 15, but the both sides of the projecting portion 15 do not necessarily have to be recessed and may be configured by flat surfaces. Is also possible.

Reference Signs List 1 tire 2 tread portion 3 sidewall portion 4 bead portion 5 rim protector 6 top 7 bead core 8 bead filler 9 carcass ply 10 chafer 11 inner liner 12 rim 13 reference surface 14 ... Bead base surface 15 ... Protrusion 16 ... First curved recess 17 ... Second curved recess

Claims (6)

A tread portion that constitutes a tread surface,
A pair of sidewall portions that extend inward in the tire radial direction from both sides in the tire width direction of the tread portion;
A pair of bead portions that are continuous to the tire radial direction inner side of the side wall portion and are assembled to the rim;
Equipped with
The sidewall portion includes a rim protector having a top protruding outward in the tire width direction relative to the bead portion.
A bead base surface, which is an outer surface of the bead portion, is formed with a protrusion which protrudes with respect to the reference surface of the rim and which is a separate member from the bead base surface.
The tire diameter from the tire radial direction inner end of the bead base surface to the tire radial direction outer end of the protrusion when the distance in the tire radial direction from the tire radial direction inner end of the bead base surface to the top is Hp The distance H1 in the direction is
Hp × 0.55 ≦ H1 ≦ Hp × 0.95
Satisfy, pneumatic tire. The 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 × 0.41 ≦ H2 ≦ Hp × 0.75
H2 <H1
The pneumatic tire according to claim 1, satisfying the following conditions.   The pneumatic tire according to claim 1, wherein the protrusion has a hardness higher than that of the other portion forming the bead base surface. The bead base surface is
A first curved recess that is continuous to the outer side in the tire radial direction of the protrusion;
A second curved recess that is continuous to the inside in the tire radial direction of the protrusion;
Have
The radius of curvature R2 of the first curved recess and the radius of curvature R3 of the second curved recess are:
5 mm ≦ R2, R3
The pneumatic tire according to claim 3, wherein   The pneumatic tire according to any one of claims 1 to 4, wherein a tire meridional section has a circular arc shape, and a plurality of the projecting portions are formed.   The pneumatic tire according to any one of claims 1 to 4, wherein the bead base surface is formed of a combination of a projecting portion having an arc shape in a tire meridional section and a flat portion having a linear shape.

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