JP2021176739A - Pneumatic tire - Google Patents

Abstract

To improve efficiency of load support in a side wall to improve steering stability.SOLUTION: A pneumatic tire 1 comprises: a tread 10; a pair of side walls 20 extending from both ends in a width direction of the tread to an internal diameter side; and a pair of bead parts 30 which are continuous to the internal diameters respectively of the walls and are arranged with an interval to be wider than a rim width W0 of a corresponding normal rim 50 in a non-rim assembled state. Each of the pair of bead parts 30 includes, at an end part at an internal diameter side, a bead base part 34 extending in a tire width direction, a bead heel part 35 curved to an outer diameter side, from an outer end part in the width direction of the bead base part toward outside in the width direction, and a bead back face part 36 extending from an end part at the outer diameter side of the bead heel part toward the outer diameter side. In the non-rim assembled state, on the bead back face part 36 is formed a recessed part 70 recessed toward inside in the width direction. In the rim assembled state, the bead back face part 36 contacts an approximate whole surface of a portion 53a in a radial direction of a rim flange 53 of the normal rim 50.SELECTED DRAWING: Figure 2

Description

The present invention relates to a pneumatic tire.

It is provided with a tread, a pair of sidewalls extending from both sides in the width direction to the inner diameter side, and a pair of bead portions continuous to each inner diameter side, and the pair of bead portions is wider than the normal rim width in the non-rim assembled state. Widely formed pneumatic tires are known. Further, in the non-rim assembled state, the outer surface of the bead portion on the outer side in the tire width direction is inclined outward in the tire width direction toward the outer side in the tire radial direction and extends.

When assembling this pneumatic tire to the corresponding regular rim, it is necessary to bring the pair of bead portions close to the regular rim width. Further, since the pneumatic tire is inclined outward in the tire width direction from the bead portion toward the sidewall, the bead portion is inclined outward in the tire width direction toward the outer side in the tire radial direction in the rim-assembled state. Cheap.

As a result, as shown in FIG. 8, the bead portion 130 is likely to come into contact with the rim sheet portion 51 of the regular rim 50 and the rim flange 53 at two points, and there is a space between the bead portion 130 and the rim flange 53. Part S occurs. In particular, the bead portion 130 tends to come into strong local contact with the rim flange 53 on the outer surface in the width direction due to the inclination of the outer surface in the width direction.

Further, Patent Document 1 discloses a pneumatic tire in which a recess recessed inward in the tire width direction is formed on the back surface of the bead. In the rim-assembled state, this pneumatic tire is in strong local contact with the rim flange at two points, the concave portion on the outer side in the tire radial direction and the concave portion on the inner side in the tire radial direction. It is intended to strengthen the fixing of the bead portion to the rim flange to improve steering stability.

JP 2015-212112

According to the pneumatic tire, the back surface of the bead locally strongly abuts on the rim flange in the rim-assembled state, so that the abutment portion is strongly compressed. For example, when a load is applied in the tire radial direction and / or the tire width direction during turning, the contact portion is already strongly compressed and is less likely to be compressed. Therefore, the portion of the sidewall close to the bead portion is deformed. It is difficult to do, and the deformation tends to be biased to the part close to the tread. That is, the load support on the sidewall is not efficient, and it is difficult to improve the steering stability.

An object of the present invention is to provide a pneumatic tire capable of improving steering stability by improving the efficiency of load support on a sidewall.

The present invention
A tread, a pair of cywalled portions extending inward in the tire radial direction from both ends of the tread in the tire width direction, and a pair of regular rims that are continuous in the tire radial direction of each of the pair of sidewalls and correspond to each other in a non-rim assembled state. Equipped with a pair of bead parts arranged at intervals wider than the rim width,
Each of the pair of bead portions
A bead base that extends in the tire width direction at the inner end in the tire radial direction,
A bead heel portion that is curved outward in the tire radial direction toward the outside in the tire width direction and further curved inward in the tire width direction toward the outside in the tire radial direction from the outer end portion in the tire width direction of the bead base portion.
The bead back portion extending outward in the tire radial direction from the tire radial outer end portion of the bead heel portion, and the bead heel portion.
Including
In the non-rim assembled state, the bead heel portion is formed with a recess recessed inward in the tire width direction from the outer end portion in the tire width direction of the bead heel portion.
The recess is provided with a straight portion that is arranged inside the tire radial direction from the deepest portion and is inclined inward in the tire width direction toward the outside in the tire radial direction.
The straight portion provides a pneumatic tire in which the back surface portion of the bead is formed so as to be in close contact with substantially the entire radial portion of the rim flange of the regular rim extending in the radial direction of the tire in the rim assembled state. ..

According to the present invention, since a recess is formed in the back surface of the bead, the inner diameter side portion of the back surface of the bead located on the inner diameter side from the deepest portion of the recess faces inward in the tire radial direction in the non-rim assembled state. It is inclined outward in the tire width direction. The inner diameter side portion bends inward in the tire width direction starting from the deepest portion of the recess in a rim assembled state in which the pair of bead portions are close to the rim width of the regular rim, and tends to be generally along the tire radial direction. That is, in the rim-assembled state, the back surface of the bead can be easily brought into close contact with the entire radial portion of the rim flange while eliminating the recesses, and the contact area can be expanded. In particular, the straight portion located on the inner diameter side portion and continuous with the bead heel portion makes it easy to align the back surface portion of the bead along the radial portion of the rim flange.

In this way, in the no-load state where the rim is assembled, the surface pressure acts on substantially the entire surface of the bead back surface that is in close contact with the radial portion of the rim flange, so that the surface pressure acts only on a part of the bead back surface. In comparison with, the load carried by the entire back surface of the bead is distributed. That is, a margin can be provided for the compression allowance for elastically deforming the back surface of the bead as compared with the case where a high surface pressure locally acts on the back surface of the bead.

Therefore, the back surface of the bead can be further compressed by the margin compression allowance at the time of load input and lateral force input. In this case, since the sidewall can also be deformed in a portion close to the bead portion with further compression of the bead back portion, the sidewall can be deformed so as to be totally bent from the bead portion side to the tread side. Therefore, the load support on the sidewall is made more efficient, and the maneuverability is improved.

The recess may have a depth of less than 1.0 mm in the tire width direction.

According to this configuration, the inner diameter side portion is appropriately inclined outward in the tire width direction in the non-rim assembled state, so that the inner diameter side portion is bent inward in the tire width direction in the rim assembled state and is inclined outward in the tire width direction. It is easy to eliminate and it is easy to follow the radial part of the rim flange. If the depth of the recess is 1.0 mm or more, the inner diameter side portion tends to be excessively inclined outward in the tire width direction in the non-rim assembled state, so that the tire is bent inward in the tire width direction in the rim assembled state. It is difficult to eliminate the outward inclination in the width direction. In this case, in the rim-assembled state, the concave portion is unlikely to disappear, and the back surface of the bead is difficult to be brought into close contact with substantially the entire radial portion of the rim flange.

The back surface portion of the bead has a center of curvature outward in the tire width direction, and at least a part thereof has a recess R portion constituting the deepest portion of the recess.
The straight line portion may be formed by a tangent line connecting the bead heel portion and the concave portion R portion.

According to this configuration, since the bead heel portion and the concave portion R portion are continuously connected, the bead heel portion and the concave portion R portion are connected discontinuously (for example, the straight portion and the bead heel portion or the concave portion R portion). It is easier to bring the back surface of the bead and the radial portion of the rim flange into close contact with each other while avoiding local contact, as compared with the case where a step or the like is provided between the two.

According to the present invention, steering stability can be improved by improving the efficiency of load support on the sidewall.

A meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. A cross-sectional view of the meridian around the bead of a pneumatic tire before rim assembly. A cross-sectional view of the meridian around the bead of a pneumatic tire with the rim assembled. The graph which shows the fitting pressure on the outer surface of the bead portion 30 at the time of inflating. The graph which shows the fitting pressure on the outer surface of the bead portion 30 at the time of a radial load load. FIG. 5 is a cross-sectional view taken along the meridian showing the deformation of the pneumatic tire of FIG. A meridian cross-sectional view showing deformation of a pneumatic tire under lateral load. A cross-sectional view of the meridian around the bead portion of the pneumatic tire according to the conventional example in which the rim is assembled.

Hereinafter, embodiments according to 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 application, or its use. In addition, the drawings are schematic, and the ratio of each dimension is different from the actual one.

FIG. 1 is a cross-sectional view of the pneumatic tire 1 according to the embodiment of the present invention in the meridian direction, and is shown only on one side with respect to the tire equatorial line CL. The pneumatic tire 1 includes a tread 10, a pair of sidewalls 20 extending inward in the tire radial direction from both ends of the tread 10 in the tire width direction, and a pair of bead portions continuous inward in the tire radial direction of each of the pair of sidewalls 20. It has 30 and.

A bead core 31 and a bead filler 32 connected to the outer side in the tire radial direction are embedded in the bead portion 30. The bead core 31 is formed by coating an annular focusing body formed by winding a bead wire made of a steel wire in a plurality of turns with rubber. The cross-sectional shape of the bead core 31 is formed in a polygonal shape so as to have a bead core outer end surface 31a extending in the tire width direction at the outer end portion in the tire radial direction. The height Hb in the tire radial direction based on the nominal rim diameter (specified by JIS4102) NR (also referred to as the reference rim diameter) of the bead core outer end surface 31a is 6.7 mm in the present embodiment.

The bead filler 32 is made of hard rubber extending in an annular shape along the outer end surface 31a of the bead core, and is formed in a triangular shape having a cross-sectional shape in the meridian direction narrowing in the tire width direction toward the outside in the tire radial direction. There is.

A carcass ply 2 is hung between the pair of bead cores 31 over the tread 10 and the sidewall 20. The carcass ply 2 is folded around the bead core 31 from the inner surface side of the tire to the outer surface side of the tire. An inner liner 3 for maintaining air pressure is provided on the inner surface side of the tire of the carcass ply 2.

In the tread 10, the belt layer 11 and the belt reinforcing layer 12 are laminated in this order on the outer side of the carcass ply 2 in the tire radial direction. In the present embodiment, the belt layer 11 is composed of two layers. A tread rubber 13 is laminated on the outer side of the belt reinforcing layer 12 in the tire radial direction. The tread rubber 13 constitutes the outer surface of the pneumatic tire 1 in the tire radial direction.

A tire side rubber 21 is arranged over the sidewall 20 and the bead portion 30 on the outer side of the carcass ply 2 in the tire width direction. The tire side rubber 21 includes a sidewall rubber 21a extending inward in the tire radial direction from the end portion of the tread rubber 13 in the tire width direction, and a rim strip rubber 21b connected to the inner diameter side end portion and further extending inward in the tire radial direction. Have. The tire side rubber 21 constitutes the outer surface of the pneumatic tire 1 in the tire width direction.

The sidewall rubber 21a constitutes most of the sidewall 20. The rim strip rubber 21b is provided at least corresponding to the portion of the tire side rubber 21 that abuts on the rim flange 53 in a state of being incorporated into the corresponding regular rim 50 (see FIG. 2) (referred to as a rim assembled state). There is. As the rim strip rubber 21b, a rubber having excellent wear resistance as compared with the sidewall rubber 21a is adopted.

The tire side rubber 21 is formed with a rim protector 4 that projects outward in the tire width direction. The rim protector 4 is located inside the tire maximum width position Z in the tire radial direction. The maximum width position Z is the position where the profile line on the outer surface of the sidewall 20 is farthest from the tire equatorial line CL in the tire width direction. That is, the thickness of the tire side rubber 21 gradually increases from the maximum width position Z toward the rim protector 4, and gradually decreases from the rim protector 4 toward the inside in the tire radial direction.

The rim protector 4 is bent inward in the tire width direction from an end extending inward in the tire radial direction from the maximum width position Z, and has the thickest top portion 4a. The top portion 4a is located at a height of H6 outward in the tire radial direction from the nominal rim diameter NR. The height H6 of the top portion 4a is located outside the tire radial direction with respect to the rim flange 53 of the corresponding regular rim 50 in the rim assembled state.

In the present specification, a portion located on the outer diameter side of the tip portion 32a of the bead filler 32 in the tire radial direction is referred to as a sidewall 20, and a portion located on the inner diameter side is referred to as a bead portion 30. The rim protector 4 is located at the bead portion 30. Further, in the present specification, the thickness of the tire side rubber 21 is defined as a direction perpendicular to the outer surface of the carcass ply 2.

FIG. 2 shows an enlarged view of the periphery of the bead portion 30 in a state where it is not incorporated in the regular rim 50 (referred to as a non-rim assembled state), and the periphery of the rim flange 53 of the corresponding regular rim 50 is also shown. It is shown. The regular rim 50 includes a rim seat portion 51 extending outward in the tire width direction, a rim heel portion 52 curved outward in the tire radial direction from the outer end portion in the tire width direction, and a tire radial direction from the outer end portion in the tire radial direction. It has a rim flange 53 extending outward.

The rim seat portion 51 is inclined inward in the tire radial direction toward the inside in the tire width direction, and the inclination angle with respect to a straight line parallel to the tire axis is A0. The rim flange 53 has a flange radial portion 53a extending outward in the tire radial direction parallel to the tire radial direction from the rim heel portion 52, and a circular arc shape outward in the tire width direction continuous with the tire radial outer end portion. It has a curved flange portion 53b.

The outer surface of the rim heel portion 52 located on the side where the pneumatic tire 1 is fitted has an arc shape having a radius of curvature R11 centered on the center of curvature O11 located closer to the pneumatic tire 1 than the outer surface. It is extending. The pair of flange radial portions 53a in the tire width direction are arranged with a rim width W0 apart. The flange radial portion 53a extends from the nominal rim diameter NR outward in the tire radial direction to the height of H11. The flange curved portion 53b extends in an arc shape having a radius of curvature of R12 about the center of curvature O12 located on the outer surface side of the tire.

The regular rim 50 is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, JATMA is a "standard rim", and TRA and ETRTO are "Measuring Rim". ".

The regular rim 50 according to the present embodiment conforms to the flange symbol J of the 5 ° deep bottom rim specified in JATTA, the inclination angle A0 of the rim seat portion 51 is 5 °, and the radius of curvature R11 of the rim heel portion 52 is 6. The height H11 of the flange radial portion 53a is 8.5 mm, the radius of curvature R12 of the flange curved portion 53b is 9.5 mm. Further, the angle between the rim sheet portion 51 and the radial portion 53a of the regular rim 50 according to the present embodiment is 95 °.

The bead portion 30 is curved outward in the tire radial direction from the bead base portion 34 extending in the tire width direction at the inner end portion in the tire radial direction and the outer end portion in the tire width direction of the bead base portion 34 toward the outer side in the tire width direction. It has a bead heel portion 35 and a bead back surface portion 36 extending outward in the tire radial direction from the tire radial outer end portion of the bead heel portion 35 and continuous with the rim protector 4.

The bead base portion 34 is linearly inclined inward in the tire radial direction toward the inside in the tire width direction in the non-rim assembled state, and the inclination angle with respect to the straight line parallel to the tire axis is A1. That is, the bead base portion 34 is composed of a single straight portion. Specifically, the inclination angle A1 is larger than the inclination angle A0 of the rim sheet portion 51. Preferably, the difference between the tilt angle A1 and the tilt angle A0 is 8 ° or less. In the present embodiment, the inclination angle A1 is 12 °, which is 7 ° larger than the inclination angle A0. The bead base portion 34 may have a plurality of base surfaces that gradually incline inward in the tire width direction toward the inside in the tire width direction. In this case, the bead base portion 34 may have a plurality of base surfaces that are most outward in the tire width direction among the plurality of base surfaces. The inclination angle of the base surface (that is, continuous with the bead heel portion 35) parallel to the tire axis is defined as the inclination angle A1 according to the present embodiment.

The bead heel portion 35 is located on the inner side in the tire radial direction and the outer side in the tire width direction with respect to the bead core 31. The outer surface of the bead heel portion 35 is composed of a first curved portion 61 (heel R portion). The first curved portion 61 curves and extends outward in the tire radial direction toward the outside in the tire width direction from the first point P1 located at the outer end in the tire width direction of the bead base portion 34, and the bead extends in the non-rim assembled state. Along with reaching the second point P2 located on the outermost side in the tire width direction of the inner part in the tire radial direction of the portion 30, the portion 30 is curved inward in the tire width direction from the second point P2 toward the outer side in the tire radial direction and further extends. It has reached the third point P3.

The first curved portion 61 is formed of an arc-shaped portion having a radius of curvature R1 centered on the center of curvature O1 located on the inner surface side of the tire with respect to the outer surface of the bead portion 30. The center of curvature O1 and the radius of curvature R1 are set to be substantially the same as the center of curvature O11 and the radius of curvature R11 of the rim heel portion 52, respectively. In the present embodiment, the radius of curvature R11 of the rim heel portion 52 is 6.5 mm, so the radius of curvature R1 of the first curved portion 61 is set to 5.5 mm or more and 7.5 mm or less.

The bead back surface 36 is located on the outer surface inside in the tire radial direction and forms at least a part of the recess 70 described later. It has at least a third curved portion 64 (outer R portion) that is located at the top of the rim protector 4 and reaches the top 4a.

The second curved portion 62 extends in a direction inclined inward in the tire width direction toward the outside in the tire radial direction and extends from the fourth point P4 located outside the tire radial direction and inside in the tire width direction with respect to the third point P3. It has reached 5 points P5. The fifth point P5 is located outside the second point P2 in the tire width direction. The second curved portion 62 is formed of an arc-shaped portion having a radius of curvature R2 centered on the center of curvature O2 located on the outer surface side of the tire with respect to the outer surface of the bead portion 30.

The height H2 of the center of curvature O2 in the tire radial direction with respect to the nominal rim diameter NR is equal to or higher than the height H11 of the flange radial portion 53a of the corresponding regular rim 50. Further, preferably, the height H2 of the center of curvature O2 is 1.5 times or less the height H11 of the flange radial portion 53a. In the present embodiment, since the height H11 of the flange radial portion 53a is 8 mm, the height H2 of the center of curvature O2 is set to 8 mm or more and 12 mm or less. Further, preferably, the height H2 of the center of curvature O2 based on the nominal rim diameter NR in the tire radial direction is 0 of the height H6 of the top 4a of the rim protector 4 based on the nominal rim diameter NR in the tire radial direction. . 2 times or more and 0.6 times or less.

Further, the center of curvature O3 is located in the radial range W between the radial position X1 of 2 mm inward in the tire radial direction and the radial position X2 of 9 mm in the tire radial direction with reference to the bead core outer end surface 31a in the tire radial direction. doing.

Furthermore, the height H3 of the center of curvature O3 is set to be less than 0.25 times the tire cross-sectional height H0 (see FIG. 1). The tire cross-sectional height H0 is calculated as the outer diameter of the pneumatic tire 1 minus the nominal rim diameter divided by 2.

The radius of curvature R2 is larger than the radius of curvature R12 of the flange curved portion 53b of the corresponding regular rim 50. Preferably, the radius of curvature R2 is 1.4 times or more the radius of curvature R12, and more preferably 1.6 times or more and 2.4 times or less the radius of curvature R12. In the present embodiment, the radius of curvature R12 of the flange curved portion 53b is 9.5 mm, so the radius of curvature R2 is set to 14 mm or more, more preferably 16 mm or more and 22 mm or less.

Further, the radius of curvature R2 is set to be 1.0 times or more and 4.5 times or less of the radius of curvature R1 of the first curved portion 61.

The third curved portion 63 curves inward in the tire radial direction toward the inside in the tire width direction from the sixth point P6 located at the top 4a of the rim protector 4, and reaches the seventh point P7. The third curved portion 63 is formed of an arc-shaped portion having a radius of curvature R3 centered on the center of curvature O3 located on the outer surface side of the tire with respect to the outer surface of the bead portion 30. The radius of curvature R3 is set to a size equal to or greater than the radius of curvature R2 of the second curved portion 62. Preferably, the radius of curvature R3 is 1.2 times or more the radius of curvature R2.

As shown in the enlarged view of FIG. 2, the virtual curve 62a in which the second curved portion 62 is extended outward in the tire radial direction and the virtual curve 63a in which the third curved portion 63 is extended inward in the tire width direction are the tires at the virtual intersection P8. It intersects so as to be convex on the inner surface side.

The height H8 of the virtual intersection P8 based on the nominal rim diameter NR in the tire radial direction is larger than 1.5 times the height H2 of the center of curvature O2 of the second curved portion 62 and less than 3.0 times. More preferably, the height H8 of the virtual intersection P8 is greater than twice the height H2 of the center of curvature O2 and less than 2.5 times. Further, the height H8 of the virtual intersection P8 is 0.7 times or more the height H6 of the top 4a of the rim protector 4. The height H8 of the virtual intersection P8 is, for example, 15 mm or more and 25 mm or less, preferably 20 mm or more and 24 mm or less.

Further, the height H8 of the virtual intersection P8 is smaller than the height H9 of the tip portion 32a of the bead filler 32 based on the nominal rim diameter NR. Specifically, the height H9 of the tip portion 32a of the bead filler 32 is preferably 1.1 times or more, more preferably 1.3 times or more, with respect to the height H8 of the virtual intersection P8.

The intersection angle A3 between the virtual curve 62a and the virtual curve 63a, that is, the tangent line 62b to the second curved portion 62 (virtual curve 62a) extending from the virtual intersection P8 and the third curved portion 63 (virtual curve 63a) extending from the virtual intersection P8. ) Is greater than 0 ° and less than or equal to 45 °. When the intersection angle A3 exceeds 45 °, strain tends to concentrate between the second curved portion 62 and the third curved portion 63, and the bead durability tends to deteriorate. Preferably, the crossing angle A3 is 30 ° or less. The intersection angle A3 is defined as an angle between the tangent line 62b and the tangent line 63b extending outward in the tire width direction from the virtual intersection P8.

Further, the bead back surface portion 36 has a linear portion 69 that linearly connects the third point P3 and the fourth point P4 and a fifth point P5 and the seventh point P7 that are connected in an arc shape to the outer surface. It further has 4 curved portions 64 (connection R portions).

The straight portion 69 connects the first curved portion 61 and the second curved portion 62 in a tangential continuous manner. In other words, the third point P3 constitutes a contact point with respect to the straight line portion 69 in the first curved portion 61, and the fourth point P4 constitutes a contact point with respect to the straight line portion 69 in the second curved portion 62. The straight line portion 69 is inclined inward in the tire width direction toward the outside in the tire radial direction, and the inclination angle with respect to the straight line parallel to the tire radial direction is A2. The inclination angle A2 is set to be smaller than the inclination angle A1 of the bead base portion 34. In the present embodiment, the inclination angle A2 is 10 ° or less. Further, the inclination angle A2 is set so that the angle A4 between the straight line portion 69 and the bead base portion 34 is 95 ° or more and 105 ° or less. Further, the inclination angle A2 is set to be smaller than the value obtained by subtracting the inclination angle A0 of the seat portion 51 of the rim from the inclination angle A1 of the bead base portion 34 (A2 <A1-A0).

The fourth curved portion 64 connects the second curved portion 62 and the third curved portion 63 in a tangential continuous manner, and has a radius of curvature of R4 centered on the curvature center O4 located on the tire outer surface side of the bead portion 30. It is composed of a certain arcuate part. In other words, the fifth point P5 constitutes a contact point with respect to the fourth curved portion 64 in the second curved portion 62, and the seventh point P7 constitutes a contact point with respect to the fourth curved portion 64 in the third curved portion 63.

The radius of curvature R4 of the fourth curved portion 64 is smaller than the radius of curvature R2 and R3 of the second curved portion 62 and the third curved portion 63.

Here, in the non-rim assembled state, a recess 70 recessed inward in the tire width direction is formed inside the bead portion 30 in the tire radial direction over the bead heel portion 35 and the bead back surface portion 36. The recess 70 means a portion of the bead heel portion 35 and the bead back surface portion 36 located inside in the tire width direction with respect to the radial straight line L1 that passes through the second point P2 and extends parallel to the tire radial direction. That is, the recess 70 is a portion of the first curved portion 61 located between the second point P2 and the third point P3, a straight portion 69, and a portion of the second curved portion 62 located inside in the tire radial direction. It is composed of and.

The recess 70 has the deepest portion 71 that is most recessed inward in the tire width direction. The deepest portion 71 is located on the second curved portion 62. The deepest portion 71 is located radially outside the straight portion 69. In other words, the straight portion 69 is provided inside the tire radial direction with respect to the deepest portion 71. The depth D of the deepest portion 71 is set to less than 1.0 mm, preferably 0.8 mm or less, more preferably 0.3 mm or more and 0.5 mm or less with respect to the radial straight line L1.

The height H10 of the deepest portion 71 based on the nominal rim diameter NR is equal to or higher than the height H11 of the flange radial portion 53a of the corresponding regular rim 50. Further, preferably, the height H10 of the deepest portion 71 is 1.5 times or less the height H11 of the flange radial direction portion 53a. In the present embodiment, since the height H11 of the flange radial portion 53a is 8 mm, the height H11 of the deepest portion 71 is set to 8 mm or more and 12 mm or less.

In the present embodiment, since the deepest portion 71 is located on the width direction straight line L2 extending parallel to the tire width direction from the curvature center O2 of the second curved portion 62 extending in an arc shape, the deepest portion 71 of the deepest portion 71. The height H10 is equal to the height H2 of the center of curvature O2 of the second curved portion 62.

Here, in the pneumatic tire 1, the pair of bead portions 30 are arranged at intervals wider than the rim width W0 in the non-rim assembled state. Specifically, the outer width W1 (that is, the distance between the second points P2) between the pair of bead heel portions 35 in the tire width direction is larger than the rim width W0. For example, the difference between the outer width W1 and the rim width W0 is 1.5 inches or less, preferably 1 inch or less.

FIG. 3 shows the periphery of the bead portion 30 when the pneumatic tire 1 is rim-assembled to the corresponding regular rim 50 and the specified internal pressure is applied to inflate the tire 1, and the area before rim assembly is shown by a virtual line. The pneumatic tire 1 and the pneumatic tire 1 at the time of load input are also shown by the broken line. In the pneumatic tire 1, the outer width W1 between the pair of bead portions 30 is formed wider than the rim width W0 of the corresponding regular rim 50. Therefore, when the pneumatic tire 1 is rim-assembled, the pair of beads It is necessary to bring the portions 30 close to each other inward in the tire width direction. At this time, the pneumatic tire 1 is deformed so as to be inclined inward in the tire width direction toward the inside in the tire radial direction over the sidewall 20 and the bead portion 30 (arrow Y1 in the figure).

Further, since the inclination angle A1 of the bead base portion 34 is larger than the inclination angle A0 of the rim seat portion 51, when the bead base portion 34 is fitted to the rim seat portion 51 in the tire radial direction, the inclination angles A0 and A1 The bead base portion 34 rotates clockwise in FIG. 3 by an angle excluding the amount by which the bead base portion 34 is compressed from the angle difference (arrow Y2 in the figure). The bead base portion 34 rotates so that the inclination angle A1 becomes smaller, and is fitted in the radial direction with respect to the rim seat portion 51.

As a result, in the bead portion 30, the portion located inside the deepest portion 71 in the tire radial direction from the periphery of the deepest portion 71 of the recess 70 is shown inward in the tire width direction as compared with the non-rim assembled state. It is tilted so as to rotate in the clockwise direction in No. 3 (arrow Y3 in the figure). With the rotation of the bead base portion 34, the bead back portion 36 starts from the periphery of the deepest portion 71 so that the inclination angle A2 becomes zero, that is, the straight portion 69 extends along the tire radial direction. It rotates inward in the tire width direction. In the present embodiment, the inclination angle A1 is 7 ° larger than the inclination angle A0, so that the portion located inside the deepest portion 71 in the tire radial direction rotates at an angle of 7 ° or less.

As a result, in the pneumatic tire 1 in the rim-assembled state, the recess 70 disappears so that the portion of the bead back surface 36 located inside the deepest portion 71 in the tire radial direction is substantially along the tire radial direction. It deforms to extend. Therefore, in the bead portion 30, the portion of the bead base portion 34, the bead heel portion 35, and the bead back surface portion 36 located on the inner diameter side of the deepest portion 71 is in the radial direction of the rim seat portion 51, the rim heel portion 52, and the rim flange 53. It is in close contact with the portion 53a over substantially the entire surface.

From this non-rim assembled state to the inflated state, the bead core 31 rotates clockwise in FIG. 3 like the bead base portion 34 (arrow Y2 in the figure). The rotation angle A6 of the bead core 31 substantially coincides with the inclination angle A2 with respect to a straight line parallel to the tire radial direction. In the present embodiment, the rotation angle A6 of the bead core 31 is the angle formed by the extension line L7 of the outer end surface 31a of the bead core 31 in the non-rim assembled state and the extension line L8 of the outer end surface 31a of the bead core 31 in the inflated state. It is defined.

In this rim assembled state, the bead back surface portion 36 is formed so as to be sufficiently separated from the flange curved portion 53b in the tire radial direction. Specifically, the apex P10 located on the outermost side in the tire radial direction of the flange curved portion 53b, the intersection P11 of the radial straight line L3 extending in the tire radial direction through the apex P10 and the bead back surface portion 36 The bead back surface portion 36 is formed so that the distance between them in the tire radial direction is 4 mm or more.

As shown by the broken line in FIG. 3, the bead back surface 36 is sufficiently separated from the flange curved portion 53b in the tire radial direction even in the load input state corresponding to the load index set on the pneumatic tire 1. It is formed like this. Specifically, the bead back surface 36 is formed so that the distance in the tire radial direction between the apex P10 and the intersection P12 between the radial straight line L3 and the bead back surface 36 in the load input state is 3 mm or more. ing.

FIG. 4 is a graph showing the fitting pressure at the fitting portion between the bead portion 30 and the regular rim 50 in a state where the pneumatic tire 1 is rim-assembled on the regular rim 50 and inflated. The fitting pressure was measured by a sheet type pressure sensor sandwiched between the bead portion 30 and the specified rim 50. In this graph, the horizontal axis is the position from the inner end of the bead base 34 along the outer surface of the bead 30 in the tire width direction to the bead back surface 36, and the vertical axis is the fitting pressure. .. Further, FIG. 4 also shows the fitting pressure of the bead portion 130 in the pneumatic tire 100 according to the conventional example of FIG. The fitting pressure in the case of the pneumatic tire 1 is shown by a solid line, and the fitting pressure in the case of the pneumatic tire 100 is shown by a broken line.

As shown in FIG. 4, in the pneumatic tire 100 according to the conventional example, the bead base portion 134 and the abutting portion 136a of the bead back surface portion 136 located on the outer side in the tire radial direction are locally fitted at two points. Combined pressure is occurring. The peak at the bead base portion 134 is generally the fitting pressure A, and the peak at the contact portion 136a is lower than the fitting pressure A and slightly exceeds the fitting pressure B, which is smaller than the fitting pressure A. That is, with reference to FIG. 8, the fitting pressure is not generated in the non-contact portion 136b located between the bead base portion 134 and the bead back surface portion 136 and not in contact with the regular rim 50. ..

Therefore, the pneumatic tire 100 is locally strongly fitted at the bead base portion 134 and the contact portion 136a, and the bead portion 130 is strongly compressed at these two locations.

On the other hand, in the pneumatic tire 1 according to the present embodiment, a fitting pressure is generated between the bead base portion 34, the bead heel portion 35, and the bead back surface portion 36 with the regular rim 50. That is, unlike the pneumatic tire 100, the bead heel portion 35 and the inner diameter side portion of the bead back surface portion 36 are also in contact with the regular rim 50.

Specifically, in the pneumatic tire 1, the fitting pressure of the portion of the pneumatic tire 100 corresponding to the locally strongly fitted portion is lower than that of the pneumatic tire 100. That is, the peak at the bead base portion 34 is approximately the fitting pressure B, and the peak at the bead back surface portion 36 is slightly lower than the fitting pressure C, which is smaller than the fitting pressure B. On the other hand, in the pneumatic tire 1, a fitting pressure is generated in a portion of the pneumatic tire 100 corresponding to the unfitted portion. That is, the pneumatic tire 1 has a fitting pressure from the bead base portion 34 to the bead back surface portion 36 and is in close contact with the regular rim 50, and local compression is suppressed.

FIG. 5 shows the fitting pressure on the outer surface of the bead portion 30 in a state where a load is applied in the tire radial direction from the state of FIG. Similar to FIG. 4, the fitting pressure in the case of the pneumatic tire 1 is shown by a solid line, and the fitting pressure in the case of the pneumatic tire 100 is shown by a broken line. As shown in FIG. 5, in the conventional pneumatic tire 100, since the bead base portion 134 and the bead back portion 136 are already strongly fitted at the contact portion 136a in the inflated state, the load is applied in the tire radial direction. Even in the state of being applied, it is more difficult to be compressed in these parts, and the increase margin of the fitting pressure is small.

On the other hand, in the pneumatic tire 1 according to the present embodiment, the fitting pressure in the inflated state is lower than that in the pneumatic tire 100 of the conventional example, so that the fitting pressure increases in the state where a further load is applied. There is a charge. Therefore, as compared with the state of FIG. 4, the fitting pressure rises as a whole, and in the bead base portion 34, the fitting pressure B rises to a level exceeding the fitting pressure A, and the bead back surface portion 36 In, the fitting pressure C increases to the fitting pressure B.

FIG. 6 is a cross-sectional view in the meridian direction showing the deformation of the pneumatic tires 1,100 in the state of FIG. As shown in FIG. 6, in the pneumatic tire 100 according to the conventional example, the bead portion 130 side is more difficult to be compressed with respect to the further load in the bead portion 130 in the inflated state, so that the tread 110 of the sidewall 120 It is deformed so that it bends at a position that is biased to the side.

On the other hand, in the pneumatic tire 1 according to the present embodiment, since the margin for the further load in the bead portion 30 is larger than that of the pneumatic tire 100 in the inflated state, the bead can be subjected to the further load. Since there is room for deformation in the portion 30, the sidewall 120 can be deformed so as to be totally bent from the tread 10 side to the bead portion 30 side.

FIG. 7 is a cross-sectional view in the meridian direction showing a state in which a load is applied to the inflated pneumatic tires 1,100 in the tire width direction. As shown in FIG. 7, similarly to FIG. 6, in the pneumatic tire 1, the sidewall 20 is deformed so as to be totally bent from the bead portion 30 to the tread 10, while the pneumatic tire 100 is deformed. The sidewall 120 is deformed so as to bend at a position biased toward the tread 110 side. Since the pneumatic tire 1 deforms the sidewall 20 so as to bend as a whole, it is easy to increase the amount of load absorption as compared with the pneumatic tire 100, and as a result, the steering stability is improved.

According to the pneumatic tire 1 according to the present embodiment, the following effects are obtained.

(1) Since the recess 70 is formed in the bead back surface 36, the inner diameter side portion of the bead back surface 36 located on the inner diameter side from the deepest portion 71 of the recess 70 is inside in the tire radial direction in the non-rim assembled state. It is inclined outward in the tire width direction toward. The inner diameter side portion bends inward in the tire width direction starting from the deepest portion 71 of the recess 70 in a rim assembled state in which the pair of bead portions 30 are close to the rim width W0 of the regular rim 50, and tends to generally follow the tire radial direction. .. That is, in the rim-assembled state, the bead back surface portion 36 can be easily brought into close contact with the substantially entire surface of the radial portion 53a of the rim flange 53 while eliminating the recess 70, and the contact area can be expanded. In particular, the straight portion 69 located on the inner diameter side portion and continuous with the bead heel portion 35 makes it easy to align the bead back surface portion 36 with the radial portion 53a of the rim flange 53.

In this way, in the no-load state where the rim is assembled, the surface pressure acts on substantially the entire surface of the bead back surface portion 36 which is in close contact with the radial portion 53a of the rim flange 53, so that the surface pressure acts only on a part of the bead back surface portion 36. The load of the bead back surface 36 as a whole is distributed as compared with the case where the bead back surface 36 acts. That is, a margin for compression allowance for elastic deformation of the bead back surface 36 can be provided as compared with the case where a high surface pressure locally acts on the bead back surface 36.

Therefore, the bead back surface portion 36 can be further compressed by the margin compression allowance at the time of load input and lateral force input. In this case, since the sidewall 20 can also deform the portion close to the bead portion 30 with the further compression of the bead back portion 36, the sidewall 20 is deformed so as to be totally bent from the bead portion 30 side to the tread 10 side. Can be done. Therefore, the load support on the sidewall 20 is made more efficient, and the maneuverability is improved.

(2) When the depth D of the recess 70 is less than 1.0 mm, the portion located on the inner diameter side of the deepest portion 71 is appropriately inclined outward in the tire width direction in the non-rim assembled state, so that the rim assembled. In this state, it is easily bent inward in the tire width direction to eliminate the inclination outward in the tire width direction, and it is easy to just follow the radial portion 53a of the rim flange 53. When the depth of the recess is 1.0 mm or more, the portion located on the inner diameter side from the deepest portion 71 tends to be excessively inclined outward in the tire width direction in the non-rim assembled state, and therefore is inside in the tire width direction in the rim assembled state. Even if it is bent to the outside, it is difficult to eliminate the inclination to the outside in the tire width direction. In this case, the recess 70 is unlikely to disappear in the rim assembled state, and the bead back surface portion 36 is difficult to be brought into close contact with the rim flange 53 over substantially the entire radial portion 53a. When the depth D of the recess 70 is 0.8 mm or less, the portion located on the inner diameter side from the deepest portion 71 is more appropriately inclined to the outside in the tire width direction in the non-rim assembled state, and is in the rim assembled state. The radial portion 53a of the rim flange 53 makes it easier to follow. Furthermore, when the depth D of the recess 70 is 0.3 mm or more and 0.5 mm or less, the portion located on the inner diameter side of the deepest portion 71 is more appropriately inclined to the outside in the tire width direction in the non-rim assembled state. In the rim assembled state, the radial portion 53a of the rim flange 53 makes it easier to follow.

(3) Since the straight portion 69 is formed by a tangent line connecting the bead heel portion 35 and the third curved portion (recessed portion R portion 63), the bead heel portion and the concave portion R portion are continuously connected. Compared to the case where the bead heel portion and the concave portion R portion are connected discontinuously (for example, a step or the like is provided between the straight portion and the bead heel portion or the concave portion R portion), local contact is avoided. However, it is easier to bring the back surface of the bead and the radial portion of the rim flange into close contact with each other.

The present invention is not limited to the configuration described in the previous embodiment, and various modifications can be made.

In the above embodiment, in the present embodiment, the recess 70 is formed of an arcuate portion, but the present invention is not limited to this. That is, the recess 70 may be formed in a trapezoidal shape or a triangular shape, and various configurations can be adopted. As in the present embodiment, by forming the recess 70 with a continuous tangential and arcuate portion, the bead back surface portion 36 can be easily deformed so as to extend parallel to the tire radial direction when the rim is assembled. Excellent in sex.

1 Pneumatic tire 4 Rim protector 10 Tread 20 Side wall 30 Bead part 31 Bead core 31a Bead core outer end surface 32 Bead filler 32a Bead filler tip part 34 Bead base part 35 Bead heel part 36 Bead back part 50 Regular rim 51 Rim seat part 52 Rim heel part 53 Rim flange 53a Radial part 53b Curved part 61 1st curved part 62 2nd curved part 63 3rd curved part 64 4th curved part 65 5th curved part 69 Straight part 70 Recessed part 71 Deepest part

Claims (3)

A tread, a pair of cywalled portions extending inward in the tire radial direction from both ends of the tread in the tire width direction, and a pair of regular rims that are continuous in the tire radial direction of each of the pair of sidewalls and correspond to each other in a non-rim assembled state. Equipped with a pair of bead parts arranged at intervals wider than the rim width,
Each of the pair of bead portions
A bead base that extends in the tire width direction at the inner end in the tire radial direction,
A bead heel portion that is curved outward in the tire radial direction toward the outside in the tire width direction and further curved inward in the tire width direction toward the outside in the tire radial direction from the outer end portion in the tire width direction of the bead base portion.
The bead back portion extending outward in the tire radial direction from the tire radial outer end portion of the bead heel portion, and the bead heel portion.
Including
In the non-rim assembled state, the bead heel portion is formed with a recess recessed inward in the tire width direction from the outer end portion in the tire width direction of the bead heel portion.
The recess is provided with a straight portion that is arranged inside the tire radial direction from the deepest portion and is inclined inward in the tire width direction toward the outside in the tire radial direction.
The straight portion is a pneumatic tire formed so that the back surface portion of the bead is in close contact with substantially the entire surface of the radial portion extending in the radial direction of the tire in the rim flange of the regular rim in the rim assembled state. The pneumatic tire according to claim 1, wherein the recess is less than 1.0 mm in depth in the tire width direction. The back surface portion of the bead has a center of curvature outward in the tire width direction, and at least a part thereof has a recess R portion constituting the deepest portion of the recess.
The pneumatic tire according to claim 1 or 2, wherein the straight portion is formed by a tangent line connecting the bead heel portion and the concave portion R portion.

Images