JP2014156192A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which achieves weight saving and secures excellent durability.SOLUTION: The pneumatic tire comprises a carcass (6) formed of at least ply formed of a ply body part (6a) and a ply folding part (6b). On a tire outside surface from a rim alienation point (F) to a tire maximum width position (P) of a side wall part, a recess (7) being dented in an inside of a tire axial direction, is provided. On a tire axial direction cross section in a non-rim assembled state, the tire outside surface of a bead back surface from a bead heel part (8) to a nodal point (P) of a straight line parallel to the tire axial direction and passing a tire radial direction outermost end of a bead core (5) and the tire outside surface, has a curvature center Cpositioned on the inside of the tire axial direction than the tire outside surface, and is defined by one or more arcs having curvature radius R of 10-80 mm.

Description

  The present invention relates to a pneumatic tire.

  As a way to reduce the weight of a tire, it is effective to reduce the amount of rubber used. In Patent Document 1, the tire maximum width position and the tire outer surface are rim flanges for side rubber in the vicinity of the bead portion where the amount of rubber used is large. It has been proposed to reduce the amount of rubber by the volume of the recess and thereby reduce the tire weight by providing a recess with the outer surface of the tire between the rim separation point away from the inner side in the tire axial direction. Yes.

JP 2000-158919 A

However, as in Patent Document 1, if a recess is provided on the outer surface of the tire near the bead portion, the thickness of the side rubber is reduced and the rigidity of the bead portion is reduced. Therefore, when the tire is pressed against the rim and mounted. In addition, the bead portion is deformed in response to the reaction force from the rim flange, and the end portion of the carcass ply is distorted by the influence of the deformation of the bead portion. As a result, there is a possibility that ply end separation occurs.
Therefore, as described above, it has been demanded to ensure the durability performance of the tire at a high level without enjoying the weight reduction of the tire and at the same time without causing ply end separation.

  Accordingly, an object of the present invention is to provide a pneumatic tire capable of ensuring excellent durability while realizing weight reduction of the tire.

  As a result of the inventor's earnest research to achieve the above object, even when a recess is provided in the side rubber near the bead portion, the bead heel portion It has been found that the influence on the end portion of the carcass ply due to the deformation of the portion can be reduced, and the present invention has been completed.

That is, the gist of the present invention is as follows.
(1) The pneumatic tire according to the present invention includes a tread portion, a pair of sidewall portions, and a pair of bead portions, and extends in a toroid shape between a pair of bead cores embedded in the bead portion. A carcass comprising at least one ply that includes a ply main body portion and a ply turn-back portion extending from the ply main body portion and turning around each bead core from the inner side to the outer side in the tire width direction; A pneumatic tire having a recess that is recessed inward in the tire axial direction on the outer surface of the tire up to the tire maximum width position,
The tire passes through the outermost end in the tire radial direction of the bead core from the bead heel portion in a cross-section in the tire width direction in a non-rim assembled state in which the width between the pair of bead portions is a specified rim width that is not assembled to the rim. The tire outer surface of the bead back surface up to the intersection of the straight line parallel to the axial direction and the tire outer surface has a center of curvature located on the inner side in the tire axial direction from the tire outer surface, and a radius of curvature R of 10 to 80 mm. It is defined by one or more arcs.
The bead heel portion refers to the tire from the intersection of the tire radial direction line passing through the bead core center and the tire outer surface to the intersection of a line passing through the bead core center and parallel to the outer contour line of the bead base portion and the tire outer surface. The outer surface part.

  Here, the rim separation point means that the outer surface of the tire is the rim flange when the tire is assembled to the specified rim, the normal maximum internal pressure specified according to the tire size is filled, and no load is applied. The point that leaves the state of contact. The specified rim is an industrial standard that is effective in the region where tires are produced and used. It is a standard rim specified according to the tire size. The normal maximum internal pressure is the air pressure corresponding to the maximum load capacity of a single wheel in the applicable size / ply rating described in JATMA and the like. The width between the pair of bead portions is defined as the specified rim width. The distance between the bead heel portions of the pair of bead portions in the tire axial direction is the rim width defined in the above-mentioned JATMA or the like (extracting the tire performance). Rim width suitable for).

  According to the configuration of the present invention, the end portion of the carcass ply folding portion can be separated from the region receiving the reaction force from the rim flange, and the load on the end portion can be suppressed. Further, since the tire outer surface in the vicinity of the bead heel portion is in sufficient contact with the rim flange in the entire contact region, the contact pressure is dispersed in the contact region, and a local load is not applied to the end portion. As a result, it is possible to ensure the excellent tire durability while enjoying the effect of reducing the weight of the tire by forming the recesses in the side rubber.

(2) In the pneumatic tire of the present invention, in the non-rim assembled state, the bead base width of the bead portion is preferably 135 to 250% of the maximum width in the tire axial direction of the bead core.
The bead base width refers to the length from the bead toe of the bead portion to the intersection of the tangent line of the bead base portion and the outer surface straight line of the bead back surface portion. The bead seat portion refers to a portion of the bead seat in the tire axial direction from the intersection of the tangent line of the back surface of the bead and the extension line of the bead seat portion to the hump at the rim separation point.
According to such a configuration, when the tire is mounted on the rim, the bead base portion can be brought into contact with the bead seat portion with a sufficient area, and the reaction force from the rim flange is caused by the rubber near the bead base portion. Can absorb enough. As a result, the influence on the end portion of the ply turn-back portion is reduced, and the occurrence of ply end separation can be further suppressed.

(3) In the pneumatic tire of the present invention, the rubber thickness in the tire axial direction on the straight line drawn in parallel to the tire axial direction through the center of gravity of the bead core passes through the center of gravity of the bead core in the non-rim assembled state. It is preferably 100 to 150% of the rubber thickness in the tire radial direction on a straight line drawn parallel to the tire radial direction.
According to such a configuration, when the tire is mounted on the rim, the reaction force from the rim flange can be uniformly received by the entire rubber near the bead heel portion. As a result, the influence on the end portion of the ply turn-back portion is reduced, and the occurrence of ply end separation can be further suppressed.

(4) In the pneumatic tire of the present invention, in the non-rim assembled state, a first intersection point that is an intersection point of a straight line passing through the center of gravity of the bead core and parallel to the tire axial direction and the tire outer surface, and the tire diameter of the bead core Two points of intersection, the second intersection point, which is the intersection point of the straight line parallel to the tire axial direction and the tire outer surface, passes through 50% of the tire radial direction maximum width of the bead core from the outermost end in the tire direction. The angle α formed between the outer surface straight line of the bead back surface portion and the tire axial direction is preferably 70 to 100 °.
According to such a configuration, the end portion of the carcass ply folding portion can be separated from the region receiving the reaction force from the rim flange, and the load on the end portion of the folding portion can be suppressed. It becomes possible to ensure the sex.

(5) The pneumatic tire according to the present invention includes a third intersection which is an intersection of a straight line passing through the center of gravity of the bead core and parallel to the tire axial direction and the ply turn-up portion in the non-rim assembled state, and the bead core tire. Two intersections of the fourth intersection that is the intersection of the straight line parallel to the tire axial direction passing through a point 50% outside the tire radial direction maximum width of the bead core in the tire radial direction from the radially outermost end and the ply turn-up portion It is preferable that the angle β formed by the ply turn-up portion inclination line passing through the tire and the tire axial direction is 70 to 100 °.
As described above, by adjusting the angle of the ply turn-up portion, the end portion of the ply turn-up portion can be separated from the deformation region by the rim flange, and the occurrence of distortion at the end portion can be suppressed. it can. In addition, since the end of the carcass ply turn-up portion can be separated from the region that receives the reaction force from the rim flange and the load on the end of the turn-up portion can be suppressed, the tire is formed by forming a recess in the side rubber. While enjoying the effect of reducing the weight, excellent tire durability can be ensured at the same time.

(6) In the pneumatic tire of the present invention, the tire is mounted on a specified rim, filled with the normal maximum internal pressure, and in the rim assembly state in which there is no load, the tire outer surface and the rim flange are separated in the tire axial direction. The distance gradually increases toward the outer side in the tire radial direction, and the maximum separation distance is preferably 10 to 30% of the maximum width in the tire axial direction of the bead core.
The maximum separation distance refers to the distance in the tire axial direction between the flange end and a contact point between the straight line passing through the flange end and parallel to the tire axial direction and the tire outer surface.
According to such a configuration, since the contact area between the tire and the rim flange is closer to the inner side in the tire radial direction than in the past, the influence of the rubber deformation of the bead portion on the end portion of the ply folded portion is reduced, and the ply end separation is achieved. Can be further suppressed.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which can ensure the outstanding durability simultaneously with implement | achieving weight reduction of a tire can be provided.

It is a figure which shows the tire axial direction cross section of the pneumatic tire of this invention in the non-rim assembly state based on one Embodiment of this invention. FIG. 2 is an enlarged view of a bead portion and a sidewall portion on one side in FIG. 1. (A) is the figure which showed the contact state of the bead part and a rim flange in the state which mounted | wore the pneumatic tire according to this invention to the prescription | regulation rim, filled the regular maximum internal pressure, and was set as the prescription | regulation load. (B) is the figure which showed the contact state of the bead part and a rim flange in the state which mounted | worn the conventional pneumatic tire on the prescription | regulation rim, filled the regular maximum internal pressure, and was set as the prescription | regulation load. FIG. 2 is an enlarged view of a bead portion and a sidewall portion on one side in FIG. 1. FIG. 2 is an enlarged view of a bead portion and a sidewall portion on one side in FIG. 1. FIG. 2 is an enlarged view of a bead portion and a sidewall portion on one side in FIG. 1. It is a figure which shows the tire axial direction cross section of the pneumatic tire of this invention in the state which is mounted | worn to a prescription | regulation rim, is filled with normal maximum internal pressure, and is no load.

  Hereinafter, an embodiment of a pneumatic tire according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a pneumatic tire 1 according to the present invention (hereinafter referred to as “non-rim assembled state”) in a state (hereinafter referred to as “non-rim assembled state”) in which the width between a pair of bead portions is a specified rim width before being assembled to a rim. FIG. 2 is a view showing a cross section in the tire axial direction.

The tire 1 includes a tread portion 2, a pair of sidewall portions 3 and 3, and a pair of bead portions 4 and 4. Further, a ply body 6a extending in a toroidal shape between a pair of bead cores 5 and 5 embedded in the bead parts 4 and 4, and a tire axial direction around each bead core 5 and 5 extending from the ply body 6a. A carcass 6 made of at least one ply, including a ply folding portion 6b folded from the inside to the outside, is provided.
The ply folded portion 6b is not folded along the outer surface of the bead core 5 around the bead core 5, but after being folded along the bead core 5, in this embodiment, substantially parallel to the ply main body portion 6a. It extends outward in the tire radial direction.

  The tire 1 further has a recess 7 that is recessed inward in the tire axial direction on the tire outer surface in the tire radial direction region from the rim separation point F to the tire maximum width position E of the sidewall portion 3.

In FIG. 1, the tire axial direction is a direction indicated by an arrow X, and the tire radial direction is a direction indicated by an arrow Y. Moreover, the tire maximum width position E of the sidewall portion 3 refers to the outermost end of the sidewall portion 3 in the tire axial direction.
The concave portion 7 is formed on at least a part of the region so that the entire region is included in the outer surface of the tire in the tire radial direction region between the rim separation point F and the tire maximum width position E. In the form, it is provided in the vicinity of the bead portion 4 and is formed by being thinned so as to be concave toward the inner side in the tire axial direction.
Thus, by providing the recess 7, the weight of the tire is reduced, and as a result, the rolling resistance of the tire can be reduced.

  FIG. 2 shown next is an enlarged view of a part of the bead part 4 and the side wall part 3 on one side in FIG.

In the present invention, in addition to the above-described configuration, when the width between the pair of bead portions 4 and 4 in the tire axial cross section of FIG. tire outer surface of the bead rear portion to an intersection P ₂ of a straight line parallel with the tire outer surface as the tire axial direction X of the tire radial direction outermost end P ₁ is, than the center of curvature C ₁ is the outer surface of the tire It is important to be defined by one or more arcs located on the inner side in the axial direction and having a radius of curvature R of 10 to 80 mm.
Here, the width between the bead portions is defined as the specified rim width. The distance in the width direction between the bead heels 8 and 8 of the bead portions 4 and 4 of the tire 1 is set to the rim width (tire Rim width suitable for drawing out the performance of the above), and the above dimensions are values measured in this state. Further, the heel portion 8, from the intersection point A ₁ of the tire radial direction line and the outer surface of the tire passing through the bead core center C _5, a line parallel to the tire outer surface to the outer contour line of the street bead base portion of the bead core center C ₅ to an intersection a ₂ and refers to the tire outer surface portion.

  FIG. 3 (a) shows a pneumatic tire 1 according to the present invention having a radius of curvature R defining the outer surface of the bead back surface of 15 mm, mounted on a specified rim, and having a normal maximum internal pressure and a specified load. It is the figure which showed the contact state of the bead part 4 and the rim flange 20 in the case. On the other hand, FIG. 3 (b) shows a case where a conventional pneumatic tire 101 having a radius of curvature R of an arc defining the outer surface of the tire on the back surface of the bead is 140 mm is mounted on a specified rim, and a normal maximum internal pressure is set. It is the figure which showed the contact state of the bead part 40 and the rim flange 200 at the time of doing.

  As described above, when the concave portion is provided in the side rubber in the tire radial direction region from the rim separation point to the tire maximum width position, the weight of the tire can be reduced, but the thickness of the side rubber is reduced and the rigidity of the bead portion is reduced. Therefore, when the tire is attached to the rim, the tire is pressed against the rim and receives a reaction force from the rim flange, so that the rubber of the bead portion is easily deformed.

First, in the conventional pneumatic tire 101, as shown in FIG. 3B, when the tire is mounted on the rim, the contact area S ₂ (hatched portion) between the bead portion 40 and the rim flange 200 is The region extends from the bead toe 120 to the vicinity of the rim flange end 200a. And since the radius of curvature of the tire outer surface of the bead back surface is relatively large, when the tire is mounted on the rim, the tire outer surface around the rim separation point F and the tire outer surface around the bead toe 120 in the bead portion 40. The surface makes strong contact with the rim flange 200. That is, the contact pressure of the tire outer surface and the rim flange 200 of the bead portion 40 in the contact area S ₂ includes a peripheral rim separation point F, bead toe 120 particularly high around the contact pressure at the periphery bead heel portion 80 and the low state Become.
Thus, since the end 90 of the ply turn-up portion 60b is close to the rim separation point F where the contact pressure increases, the end 90 is easily affected by the reaction force of the rim flange 200, and the bead portion In some cases, distortion occurs with the deformation of 40 and ply end separation occurs.

On the other hand, in the pneumatic tire 1 of the present invention shown in FIG. 3A, the bead portion 4 and the rim are reduced by making the radius of curvature R of the outer surface of the bead back surface smaller than that of the conventional pneumatic tire 101. The contact region S ₁ (hatch portion) with the flange 20 is located on the inner side in the tire radial direction than the conventional contact region S ₂ , that is, closer to the bead heel portion 8. In other words, the rim separation point F is closer to the inner side in the tire radial direction than the conventional pneumatic tire. Further, since the radius of curvature R is relatively small, when the tire is mounted on the rim, the fit with the rim flange is improved by adapting to the shape of the bent bead seat end of the rim flange 20. Then, the contact pressure of the bead portion 4 of the outer surface of the tire and the rim flange 20 in the contact area S ₁ becomes substantially uniform in the contact area S within _1. Therefore, the end portion 9 of the ply turnup portion 6b, it is possible away from the contact region S _1, the contact pressure is distributed within the contact region S _1, as in the prior art, the closest rim separation to the end portion 9 There is no particular increase in contact pressure at point F. As a result, the influence of the reaction force of the rim flange 20 on the end portion 9 is remarkably suppressed as compared with the prior art, and it is possible to realize a highly durable pneumatic tire that does not cause ply end separation. It is.

  Here, the reason why the radius of curvature R is set in the range of 10 to 80 mm is that if the radius is less than 10 mm, the radius is extremely small, the contact pressure is locally increased, and the contact pressure is not uniformly distributed. . On the other hand, when the radius of curvature R exceeds 80 mm, the rising angle of the outer surface of the bead back surface from the bead heel portion 8 to the outer side in the tire radial direction becomes small, and the end portion 9 of the folded portion 6b is sufficiently separated from the rim separation point F. This is because it is difficult to separate. The curvature radius R is more preferably 15 to 70 mm.

In the pneumatic tire of the present invention, as shown in FIG. 4, in the non-rim assembled state, the outer surface of the tire is between the bead heel portion 8 and the tire maximum width position E and outward in the tire radial direction. toward the order, and one or more arcs center of curvature C ₂ is in the tire axial direction inner side than the outer surface of the tire, and one or more arcs of curvature centered C ₃ located in the tire axial direction outer side than the outer surface of the tire, preferably the center of curvature C ₄ is defined by the one or more arcs are in axially inward from the outer surface of the tire.

Thus, by the convex shape of the outer surface of the tire of the bead heel portion 8 on the tire outer, and a bead heel portion 8 near the bead portion 4 and the rim flange 20, it is sufficiently contacted with the whole of the contact region S ₁ since it is, the reaction force of the rim flange 20 are distributed throughout of the region S _1. As a result, the load on the end portion 9 of the carcass ply turn-up portion 6b is reduced, and the occurrence of ply end separation can be suppressed.
Moreover, according to this structure, the amount of rubber | gum can be reduced and the weight reduction of a tire can be aimed at by making the shape of the one part tire outer surface of a side rubber convex in the tire inner side.

In FIG. 4, only three arcs whose centers of curvature are C ₂ , C ₃ , and C ₄ are shown, but the tire outer surface between the arc of the center of curvature C _{2 and} the arc of the center of curvature C ₃ is A plurality of arcs having other centers of curvature are drawn so as to be smoothly continuous.
Further, for example, the recess 7 is not drawn by only one arc as shown in FIG. 4, but may be defined by a plurality of arcs. Further, the center of curvature and the radius of curvature that define the shape of the outer surface of the tire are not limited to the example shown in FIG.

  In the non-rim assembled state, the bead base width W is preferably 200 to 260% of the maximum width b of the bead core 5 in the tire axial direction.

Here, as shown in FIG. 5, the bead base width W is the intersection P between the bead toe 12 of the bead part 4 and the tangent L ₁ of the outer surface of the bead base part 11 and the outer surface straight line L ₂ of the bead back part. Say the length up to ₃ . Note that the outer surface straight line L ₂ of the bead rear portion, the center of gravity C _{5 (invention} of the bead core 5, and the centroid C ₅ of the bead core 5, instead of the actual center of gravity in consideration of the weight, the gravity center of the cross section itself The first intersection point Q ₁ , which is the intersection of the straight line parallel to the tire axial direction and the outer surface of the tire, and the outermost end P _{1 of the} bead core 5 in the tire radial direction of the bead core 5. Passing through two points of intersection Q ₁ and Q ₂ of a second intersection point Q ₂ that is an intersection point of a straight line parallel to the tire axial direction and an arbitrary point P ₄ on the outer side in the tire radial direction of 50% of the large a. It is a straight line.
Further, as shown in FIG. 7, the bead seat portion is the tire axial direction of the bead seat from the intersection of the tangent line of the back surface of the bead and the extended line of the bead seat portion to the hump 21 at the rim separation point. Say that part.

By setting the bead base width W to the above length, when the tire is mounted on the rim, the bead base portion 11 can be brought into contact with the bead seat portion of the rim with a sufficient area, and from the rim flange. The reaction force can be reliably absorbed by the rubber near the bead base. As a result, the influence on the end portion of the ply turn-up portion is reduced, the occurrence of ply end separation can be suppressed, and the durability of the tire can be further ensured.
If the bead base width W is less than 200% of the maximum width b in the tire axial direction of the bead core 5, the load on the rear surface of the bead increases and the reaction force from the rim flange increases. Therefore, the influence on the end portion 9 is increased, and the distortion at the end portion 9 is increased. On the other hand, if it exceeds 260%, the rubber weight of the bead portion increases, which is contrary to weight reduction, and the volume of the bead portion increases, which may increase heat generation.

Further, as shown in FIG. 5, in the non-rim assembled state, the rubber thickness m in the tire axial direction on a straight line passing through the center of gravity C ₅ of the bead core 5 and parallel to the tire axial direction is the center of gravity C _{5 of the} bead core _5. It is preferable that it is 70 to 300% of the rubber thickness n in the tire radial direction on a straight line passing through and parallel to the tire radial direction.

  In this way, by making the rubber thickness around the bead core 5 in the bead heel portion 8 substantially uniform, the reaction force from the rim flange 20 is uniform throughout the rubber in the vicinity of the bead heel portion 8 when the tire is mounted on the rim. Can receive. As a result, no load is locally applied to the end portion 9 of the ply turn-up portion 6b, the load on the end portion 9 is reduced, and the occurrence of ply end separation can be further suppressed.

Further, as shown in FIG. 6, in the non-rim assembled state, the first intersection Q ₁ that is an intersection of a straight line passing through the center of gravity C ₅ of the bead core 5 and parallel to the tire axial direction and the tire outer surface, and the tire of the bead core 5 the more radial outermost end P ₁ is an intersection of the tire radial direction maximum width a of 50% the tire radial direction outside an arbitrary point P ₄ of the parallel to the street tire axial direction line and the tire outer surface of the bead core 5 of the two intersection points _{Q 2,} and two intersections _Q 1, _{Q 2} outer surface straight line _{L 2} of the bead rear portion through the angle α formed by the tire axial direction X, is preferably 70 to 100 °.
Here, the angle α, of the outer surface straight line L ₂ and the tire axial direction X and the angle formed of the bead rear portion, a tire axial direction outer side than the outer surface straight line L ₂ of the bead rear portion, and the intersection point Q An angle that passes through ₁ and is located on the outer side in the tire radial direction from a straight line parallel to the tire axial direction.
Note that the angle α is set in the range of 70 to 100 °. If the angle α is set to 70 ° or more, the end portion 9 of the folded portion 6b is sufficiently separated from the rim flange 20 to cause distortion at the end portion 9. Can be suppressed. On the other hand, if the angle is 100 ° or less, the end portion 9 is further separated from the ply main body portion 6a, and distortion generated by the deformation of the ply main body portion 6a can be further suppressed. In addition, since the end of the carcass ply turn-up portion can be separated from the region that receives the reaction force from the rim flange and the load on the end of the turn-up portion can be suppressed, the tire is formed by forming a recess in the side rubber. While enjoying the effect of reducing the weight, excellent tire durability can be ensured at the same time.

Furthermore, as shown in FIG. 6, the third intersection Q ₃ is an intersection of the straight line parallel to the ply turnup portion 6b of the center of gravity C ₅ of the bead core 5 as axially, the tire radial direction outermost end of the bead core 5 fourth intersection point than P ₁ is an intersection of the tire radial direction maximum width straight line parallel to 50% the tire radial direction arbitrary point P ₄ of the outer as the tire axial direction of a and the ply turnup portion 6b of the bead core 5 Q ₄ The angle β formed by the ply turn-up portion inclination line L ₃ passing through the two intersections Q ₃ and Q ₄ and the tire axial direction is preferably 70 to 100 °.
Incidentally, the angle β, of the angle formed by the ply turnup portion inclined line L ₃ and the tire axial direction, a tire axial direction outer side than the ply turnup portion inclined line L _3, and, as the tire axial direction an intersection Q ₃ This is the angle located on the outer side in the tire radial direction than the straight line parallel to the.
Note that the angle β is set to 70 ° or more because the end 9 is sufficiently separated from the rim flange 20 when the angle β is set to be equal to or greater than this angle, and the occurrence of distortion at the end 9 can be suppressed. is there. On the other hand, if the angle β is set to 100 ° or less, if it exceeds 100 °, there is a risk of contact with the bead core 5, and if the folded portion 6b is wound around the bead core 5, the manufacturing cost increases. Because there is. If the angle exceeds 110 °, the ply body portion 6a becomes too close to the ply body portion 6a, and the distortion of the ply folded portion 6b due to the deformation of the ply body portion 6a becomes large.

Further, in the present invention, as shown in FIG. 7, the tire outer surface and the rim flange 20 are mounted in a rim assembly state in which the tire is mounted on a specified rim, filled with a normal maximum internal pressure, and in a no-load state. The distance t in the tire axial direction increases gradually toward the outer side in the tire radial direction, and the maximum distance t _max of the distance t is 10-30% of the maximum width b of the bead core 5 in the tire axial direction. It is preferable.

Here, the separation distance t refers to the shortest distance in the tire axial direction from the outer surface of the tire to the innermost end in the tire axial direction of the rim flange 20, and as described above, the maximum separation distance _tmax refers to the flange. It means the distance in the tire axial direction between the end and the contact point between the straight line passing through the flange end and parallel to the tire axial direction and the tire outer surface. In addition, the maximum tire axial width b of the bead core 5 is a line parallel to the tire radial direction passing through the innermost end of the bead core 5 and parallel to the tire radial direction passing through the outermost end of the bead core 5 in the tire axial direction. This is the distance between the two lines.

According to the configuration of the present invention, the contact area between the tire and the rim flange is closer to the inner side in the tire radial direction than in the prior art, so even if the bead portion is deformed by the reaction force of the rim flange, the ply The influence on the end portion 9 of the folded portion 6b is reduced, and the occurrence of ply end separation can be further suppressed.
The maximum separation distance _{tmax is set} to 10-30% of the maximum width b in the tire axial direction of the bead core 5 by 10% or more, so that the rubber deformation of the bead portion is caused by the reaction force of the rim flange. Even if it occurs, the influence on the end portion 9 of the ply turn-up portion 6b is reduced. On the other hand, by setting it to 30% or less, a steep rigidity step is eliminated and the end portion 9 is not ply. This is because it is possible to prevent the end portion 9 from being too close to the main body portion 6a and to suppress distortion of the end portion 9.

  Further, as shown in FIG. 4, in the non-rim assembled state, the rubber thickness d gradually decreases toward the outer side in the tire radial direction in at least a part of the tire radial direction region including the concave portion 7, and thereafter the tire radial direction. It is preferable that the thickness is constant over the tire radial direction region up to ½ of the tire cross-section height H toward the outside.

  Here, the rubber thickness d refers to the shortest distance of rubber from the cord surface closest to the tire outer surface to the tire outer surface among members existing in the region such as carcass and chafer in the tire. The tire cross-sectional height H is a distance in the tire radial direction from the bead heel portion 8 to the outermost end in the tire radial direction. In addition, the constant thickness means that the maximum rubber thickness and the minimum rubber thickness are within ± 10% of the average rubber thickness in the region from the end of the gradually decreasing portion to 1/2 of the tire cross-section height H. Means that

  As described above, in the vicinity of the bead portion 4, it is possible to avoid the concentration of strain on the end portion 9 of the carcass folded portion 6 b due to the reaction force from the rim flange 20 by ensuring a relatively thick rubber thickness. Can do. In addition, by gradually reducing the rubber thickness and suppressing the difference in rubber thickness in this region, local deformation of the bead portion can be prevented, and further, when the tire is filled with air. The area with the prescribed rubber thickness required to ensure performance such as rigidity, durability, and steering stability can receive the force on the outer side in the tire axial direction evenly, ensuring good steering stability It becomes possible to do.

Furthermore, as shown in FIG. 5, in the non-rim assembly state, from the intersection P ₃ between the tangent line L ₁ of the outer surface of the outer surface straight line L ₂ and the bead base portion 11 of the bead rear portion, the end portion of the ply turnup portion 6b The tire radial distance h up to 9 is preferably 100 to 225% of the maximum width b of the bead core 5 in the tire axial direction. More preferably, it is 135 to 195% of the maximum width b in the tire axial direction of the bead core 5.

  Thus, by adopting a structure that keeps the folding height of the ply folding portion 6b relatively low, the amount of use of the carcass ply 6 can be reduced and the tire weight can be further reduced. Further, in reducing the amount of the carcass ply 6 used, the folded portion is not wound around the bead core 5, and thus the folded height of the ply folded portion 6b is kept relatively low, thereby reducing the manufacturing cost. Increase can be suppressed.

  Next, in order to confirm the effect of the present invention, an example tire according to the present invention and a comparative example tire are prepared, and by comparing the durability of the bead portion of these tires, the end portion of the carcass ply folded portion The separation resistance was evaluated.

  Invention Example Tire 1 has a tire size of 275 / 80R22.5, and, as shown in FIG. 1, the radius of curvature R of the outer surface of the tire on the bead back surface is 15 mm. This is a pneumatic tire. Invention Example Tires 2 to 16 are in accordance with the structure of Invention Example Tire 1 except that each specification is changed to the values shown in Table 1. The tire 1 of the comparative example conforms to the structure of the tire 1 of the invention except that the radius of curvature R of the outer surface of the bead back surface portion is 140 mm. Further, the comparative example tire 2 conforms to the structure of the inventive example tire 1 except that the radius of curvature R of the outer surface of the bead back surface portion is 5 mm.

Specifically, the separation resistance was evaluated by assembling each tire on a specified rim, adjusting the internal pressure to 875 kPa, and then applying a load load (3395 kgf) corresponding to the maximum load capacity (specified load) specified by JATMA as the initial load. The drum test was performed under the condition of a speed of 60 km / h, and the drum travel distance was measured until separation occurred in the carcass ply, the vibration increased, and the test was forced to be interrupted. The measurement distance thus obtained is used as an index when the traveling distance of the comparative example tire 1 is 100, and the results are shown in Table 1. In addition, it represents that it is excellent in the separation resistance, so that a value is large.
Further, the tire weight reduction amount (kg) in Table 1 represents a reduction amount (rubber weight (kg)) from the tire based on a tire having no recess.

  From the results shown in Table 1, it was found that the inventive tire achieved weight reduction due to the recesses, and the separation resistance of the tire was improved as compared with the comparative tire 1 and durability could be ensured at a high level. In addition, it was confirmed that the inventive tire had a locally increased contact pressure compared to the comparative tire 2 and could not uniformly disperse the contact pressure, and also caused separation on the rear surface of the tire.

  According to the present invention, it is possible to provide a pneumatic tire that realizes sufficient weight reduction and at the same time ensures excellent durability.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire, 2 tread part, 3 side wall part, 4 bead part, 5 bead core, 6 carcass, 6a ply main-body part, 6b ply folding | turning part, 7 recessed part, 8 bead heel part, end part of 9 ply folding part 6b, 11 bead base, 12 bead toe, 20 rim flange, intersection of tire radial direction line passing through center of A ₁ bead core and tire outer surface, line passing through center of A ₂ bead core and parallel to outer contour of bead base , Intersection with tire outer surface, E tire maximum width position, F rim separation point, center _of curvature of tire outer surface of C ₁ bead back _, C ₂ , C ₃ , C ₄ center of curvature, center of gravity of C ₅ bead core 5, H tire cross section height, tangent line of outer surface of L ₁ bead base portion 11, outer surface straight line of L ₂ bead back surface portion, L ₃ ply folded portion inclined line, P ₁ bead core 5 Tire radial direction outermost end _of, P ₂ intersections of the bead core in the tire radial direction outermost end P ₁ parallel to the street tire axial direction line and the outer surface of the _tire, P ₃ the bead base portion of the tangent line L ₁ and the bead back portion Intersection point with outer surface straight line L _{2 ,} P ₄ bead core outermost end P _{1 in the} radial direction of tire, 50% of tire core radial direction maximum width a point in the tire radial direction _, W bead base width, W ′ bead sheet tire width, X axially, Y tire radial direction, tire radial direction maximum width of a bead core 5, b bead core 5 axially maximum width, the rubber thickness of d tire from h intersection P _3, to the end portion 9 Radial distance, m Tire diameter on a straight line passing through the center of gravity of the bead core and parallel to the tire axial direction, Rubber thickness in the tire axial direction, n Straight line drawn through the center of gravity of the bead core and parallel to the tire radial direction Direction of the rubber thickness, t distance, t _max maximum distance, alpha outer surface straight line L ₂ and the tire axial direction X and the angle formed of the bead rear portion, and a β ply turnup portion inclined line L ₃ and the tire axial direction X Angle

That is, the gist of the present invention is as follows.
(1) The pneumatic tire according to the present invention includes a tread portion, a pair of sidewall portions, and a pair of bead portions, and extends in a toroid shape between a pair of bead cores embedded in the bead portion. A carcass comprising at least one ply that includes a ply main body portion and a ply turn-back portion extending from the ply main body portion and turning around each bead core from the inner side to the outer side in the tire width direction; A pneumatic tire having a recess that is recessed inward in the tire axial direction on the outer surface of the tire up to the tire maximum width position,
The tire outer surface of the bead heel portion has a center of curvature in the tire width direction cross section in a non-rim assembled state in which the width between the pair of bead portions is an ISO 15 ° DC rim width and is not assembled to the rim. It is located on the inner side in the tire axial direction from the outer surface, and is defined by one or more arcs having a curvature radius R of 10 to 80 mm.
The bead heel portion refers to the tire from the intersection of the tire radial direction line passing through the bead core center and the tire outer surface to the intersection of a line passing through the bead core center and parallel to the outer contour line of the bead base portion and the tire outer surface. The outer surface part.

Here, the rim separation point means that the outer surface of the tire is the rim flange when the tire is assembled to the specified rim, the normal maximum internal pressure specified according to the tire size is filled, and no load is applied. The point that leaves the state of contact. The specified rim is an industrial standard that is effective in the region where tires are produced and used. It is a standard rim specified according to the tire size. The normal maximum internal pressure is the air pressure corresponding to the maximum load capacity of a single wheel in the applicable size / ply rating described in JATMA and the like. The width between the pair of bead portions is defined as the specified rim width. The distance between the bead heel portions of the pair of bead portions in the tire axial direction is the rim width defined in the above-mentioned JATMA or the like (extracting the tire performance). Rim width suitable for).
In particular, the pneumatic tire of the present invention is used by being assembled on an ISO 15 ° DC rim.

(2) In the pneumatic tire of the present invention, in the non-rim assembled state, the bead base width of the bead portion is preferably 150 to 300 % of the maximum width in the tire axial direction of the bead core.
The bead base width refers to the length from the bead toe of the bead portion to the intersection of the tangent line of the bead base portion and the outer surface straight line of the bead back surface portion. The bead seat portion refers to a portion of the bead seat in the tire axial direction from the intersection of the tangent line of the back surface of the bead and the extension line of the bead seat portion to the hump at the rim separation point.
According to such a configuration, when the tire is mounted on the rim, the bead base portion can be brought into contact with the bead seat portion with a sufficient area, and the reaction force from the rim flange is caused by the rubber near the bead base portion. Can absorb enough. As a result, the influence on the end portion of the ply turn-back portion is reduced, and the occurrence of ply end separation can be further suppressed.

In the non-rim assembled state, the bead base width W is preferably 150 to 300 % of the maximum width b of the bead core 5 in the tire axial direction.

By setting the bead base width W to the above length, when the tire is mounted on the rim, the bead base portion 11 can be brought into contact with the bead seat portion of the rim with a sufficient area, and from the rim flange. The reaction force can be reliably absorbed by the rubber near the bead base. As a result, the influence on the end portion of the ply turn-up portion is reduced, the occurrence of ply end separation can be suppressed, and the durability of the tire can be further ensured.
If the bead base width W is less than 150 % of the maximum width b in the tire axial direction of the bead core 5, the load on the rear surface of the bead increases and the reaction force from the rim flange increases. Therefore, the influence on the end portion 9 is increased, and the distortion at the end portion 9 is increased. On the other hand, if it exceeds 300 %, the rubber weight of the bead portion increases, which is contrary to weight reduction, and the volume of the bead portion increases, which may increase heat generation.

Claims (6)

A ply body portion that is formed by connecting a tread portion, a pair of sidewall portions, and a pair of bead portions, and extends in a toroid shape between a pair of bead cores embedded in the bead portion, and extends from the ply body portion A carcass made of at least one ply that folds around each bead core from the inner side to the outer side in the tire width direction, and further includes an outer surface of the tire from the rim separation point to the tire maximum width position of the sidewall part. A pneumatic tire having a concave portion which is concave on the inner side in the tire axial direction,
The tire passes through the outermost end in the tire radial direction of the bead core from the bead heel portion in a cross-section in the tire width direction in a non-rim assembled state in which the width between the pair of bead portions is a specified rim width that is not assembled to the rim. The tire outer surface of the bead back surface up to the intersection of the straight line parallel to the axial direction and the tire outer surface has a center of curvature located on the inner side in the tire axial direction from the tire outer surface, and a radius of curvature R of 10 to 80 mm. A pneumatic tire defined by one or more arcs.   2. The pneumatic tire according to claim 1, wherein in the non-rim assembled state, a bead base width of the bead portion is 135 to 250% of a maximum width in a tire axial direction of the bead core. In the non-rim assembly state, the rubber thickness in the tire axial direction on the straight line passing through the center of gravity of the bead core and parallel to the tire axial direction is the straight line drawn through the center of gravity of the bead core and parallel to the tire radial direction. The pneumatic tire according to claim 1 or 2, which is 100 to 150% of a rubber thickness in a tire radial direction. In the non-rim assembly state, a first intersection that is an intersection of a straight line that passes through the center of gravity of the bead core and is parallel to the tire axial direction and the tire outer surface, and a tire radial direction of the bead core from a tire radial outermost end of the bead core The outer surface straight line of the back surface of the bead passing through the two intersections, the second intersection that is the intersection of the straight line parallel to the tire axial direction and passing through a point 50% of the maximum width in the tire radial direction, and the tire axis The pneumatic tire according to any one of claims 1 to 3, wherein an angle α formed by the direction is 70 to 100 °.   In the non-rim assembled state, the tire diameter of the bead core from the outermost end in the tire radial direction of the bead core, and a third intersection that is an intersection of the straight line passing through the center of gravity of the bead core and parallel to the tire axial direction and the ply turn-up portion A ply turn-up portion inclination line passing through two intersections, a fourth intersection that is an intersection of a straight line parallel to the tire axial direction passing through a point 50% of the maximum width in the tire radial direction and the ply turn-up portion, and the tire shaft The pneumatic tire according to any one of claims 1 to 4, wherein an angle β formed with the direction is 70 to 100 °. In the rim assembly state in which the tire is mounted on the specified rim, the normal maximum internal pressure is filled, and no load is applied, the separation distance in the tire axial direction between the tire outer surface and the rim flange gradually increases toward the outer side in the tire radial direction. In addition, the maximum separation distance of the separation distance is 10 to 30% of the maximum width in the tire axial direction of the bead core. The pneumatic according to any one of claims 1 to 5 tire.

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