JP5829632B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  In recent years, it has been demanded to improve the fuel efficiency of automobiles from the viewpoint of environmental consideration and economy. Under such circumstances, there is a demand for reducing rolling resistance in tires, and for that purpose, reducing the weight of the constituent members of the tire and the respective members has been performed.

  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 the side rubber near the bead portion is provided with a recess, the bead portion is deformed by devising the shape of the tire outer surface of the bead portion. It has been found that the influence on the end portion of the carcass ply by 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 including a ply main body part, a bead core extending from the ply main body part and turning around each bead core from the inner side in the tire axial direction to the outer side in the tire radial direction; and A pneumatic tire having a recess that is recessed inward in the tire axial direction on a tire outer surface from a rim separation point to a tire maximum width position of the sidewall portion,
A straight line that passes through the center of gravity of the bead core and is parallel to the tire axial direction in a cross-section in the tire axial 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 and the outside of the tire A first intersection that is an intersection with the surface, a straight line parallel to the tire axial direction passing through a point on the outer side in the tire radial direction of the bead core 50% of the maximum width in the tire radial direction from the outermost end in the tire radial direction of the bead core and the outside of the tire The angle α formed by the outer surface straight line of the back surface of the bead passing through the two intersections of the second intersection that is the intersection with the surface and the tire axial 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 angle β formed by the direction is 70 ° to 100 °,
In the non-rim assembled state, the rubber thickness gradually decreases toward the outer side in the tire radial direction in at least a part of the tire radial direction region including the recess, and then the tire cross-section height increases toward the outer side in the tire radial direction. over the tire radial direction area of up to 1/2, Ri constant thickness der,
In the non-rim assembled state, the tire radial distance from the intersection of the outer surface straight line of the bead back surface portion and the tangent of the bead base portion of the bead portion to the end portion of the ply turn-up portion is the tire axis of the bead core. It is characterized by being 100 to 225% of the maximum width in the direction .

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 area where tires are produced and used. In Japan, JATMA Y of the Japan Automobile Tire Association
EAR BOOK, ETRO (European Tire and Rim Technical Organization) STANDARD MANUAL in Europe, TRA (The Tire and Rim Association Inc.) YEAR BOOK, etc. 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).
The rubber thickness is the shortest distance of rubber from the cord surface of the member in the tire to the tire outer surface. The cord surface of the member means a cord surface closest to the outer surface of the tire among the members existing in each region such as a carcass and a chafer. In addition, the constant thickness means that the maximum rubber thickness and the minimum rubber thickness in the region are within a range of ± 10% of the average rubber thickness.

According to the configuration of the present invention, the end portion of the carcass ply folded portion can be separated from the region that receives the reaction force from the rim flange, and the load on the end portion of the folded portion can be suppressed. It is possible to ensure the excellent durability of the tire while simultaneously enjoying the effect of reducing the weight of the tire by forming the tire.
Further, according to such a configuration, by reducing the rubber thickness outside the bead portion in the tire radial direction while securing the rubber thickness in the vicinity of the bead portion and avoiding the concentration of strain on the end portion of the carcass ply folded portion. Further, the weight of the tire can be more sufficiently reduced.

(2) In the pneumatic tire according to the present invention, in the non-rim assembled state, the outer surface of the tire has a center of curvature in the order from the bead heel portion to the tire maximum width position in the tire radial direction in order. One or more arcs located on the inner side in the tire axial direction from the surface, one or more arcs having a center of curvature located on the outer side in the tire axial direction from the outer surface of the tire, and a center of curvature located on the inner side in the tire axial direction from the outer surface of the tire And one or more arcs.

  According to this configuration, the weight of the tire can be reduced by reducing the amount of side rubber. Moreover, the reaction force of a rim flange can be disperse | distributed to the whole bead part by making the bead part near a bead heel part, and a rim flange fully contact. As a result, load concentration on the end of the carcass ply turn-up portion is suppressed, and it is possible to ensure better tire durability.

(4) The pneumatic tire according to the present invention includes, in the non-rim assembled state, a third 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 ply folded portion, 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. Further, the end portion of the carcass ply turn-up portion can be further separated from the region receiving the reaction force from the rim flange, and the load on the end portion of the turn-up portion can be further suppressed, so a recess is formed in the side rubber. While enjoying the effect of reducing the weight of the tire, it is possible to sufficiently ensure excellent tire durability.

(5) 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.

(6) 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 70 to 300% 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.

(7) In the pneumatic tire of the present invention, in the non-rim assembled state, the bead base width of the bead portion is preferably 200 to 260% 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.

  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. Here, the bead seat portion refers to a portion in the tire axial direction of the bead seat from the intersection of the tangent line of the bead back surface portion at the rim separation point and the extended line of the bead seat portion to the hump.

(8) In the non-rim assembled state, the pneumatic tire of the present invention extends from the intersection of the outer surface straight line of the bead back surface portion and the tangent of the bead base portion of the bead portion to the end portion of the ply turn-up portion. The distance in the tire radial direction is preferably 100 to 225% of the maximum width in the tire axial direction of the bead core.

  According to this configuration, the carcass ply can be shortened to reduce the weight of the tire.

(9) In the non-rim assembled state, the pneumatic tire of the present invention extends from the intersection of the outer surface straight line of the bead back surface portion and the tangent of the bead base portion of the bead portion to the end portion of the ply turn-up portion. The distance in the tire radial direction is 135 to 200% of the maximum width in the tire axial direction of the bead core.

  According to this configuration, the carcass ply can be shortened to reduce the weight of the tire.

  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. 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. FIG. 2 is an enlarged view of a bead portion and a sidewall portion on one side in FIG. 1.

  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.

Tire 1 further to the tire outer surface in the tire radial direction in the region from the rim separation point F to the tire maximum width position P ₃ of the side wall portion 3 has a recess 7 which is concave on the inner side in the tire axial direction .

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. Further, the tire maximum width position P ₃ of the side wall portion 3, the sidewall portion 3 refers to the outermost end in the tire axial direction.
Recess 7, the outer surface of the tire in the tire radial direction area between the rim separation point F and the tire maximum width position P _3, so as to be included in its entirety in the area is at least part of the region, the In the embodiment, 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 in the side rubber region from the rim separation point F to the tire maximum width position P ₃ , the rubber material corresponding to the volume of the recess 7 can be omitted, so that the tire weight is reduced. 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 structure, as in the tire axial direction cross-section of FIG. 2, when the width defined rim width between the pair of bead portions 4, the center of gravity C ₅ of the bead core 5 a first intersection point P ₁ is an intersection of the axially parallel straight line and a tire outer surface, 50% tire diameter of the tire radial direction maximum width a of the bead core 5 from the tire radial direction outermost end P ₅ of the bead core 5 The outer surface straight line of the back surface of the bead passing through _two intersection points P ₁ and P ₂ of the second intersection point P ₂ which is an intersection point of the straight line parallel to the tire axial direction and passing through an arbitrary point P ₆ outside the direction and the tire outer surface. and L _1, an angle α formed by the tire axial direction X, it is important that a 70 to 100 °.
In the present invention, the center of gravity C ₅ of the bead core 5, instead of the actual center of gravity in consideration of the weight, is intended to refer to the center of gravity of the cross-sectional shape itself. The width between the bead portions is defined as the specified rim width. The distance between the bead heel portions 8 and 8 of the bead portions 4 and 4 of the tire 1 is set to the rim width (tire of the tire) defined in the above-mentioned JATMA or the like. The angle α is a value measured in this state. The angle α and, among the outer surface straight line L ₁ and the tire axial direction X and forms an angle of the bead rear portion, a tire axial direction outer side than the outer surface lines L ₁ of the bead rear portion, and the first intersection point It refers to the angle which is located outside the tire radial direction from a line parallel to P ₁ as the tire axial direction.

3 (a) is the angle α formed between the outer surface straight line L ₁ and the tire axial direction X of the bead rear portion was 80 °, the pneumatic tire 1 according to the present invention mounted on a specified rim, and a normal maximum pressure FIG. 5 is a view showing a contact state between a bead portion 4 and a rim flange 20 when a specified load is set. On the other hand, FIG. 3 (b), the angle α formed between the outer surface straight line L ₁ and the tire axial direction X of the bead rear portion was 60 °, the conventional pneumatic tire 101 mounted on a prescribed rim, normal maximum pressure It is the figure which showed the contact state of the bead part 40 and the rim flange 200 at the time of setting it as prescription | regulation load.
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, as shown in FIG. 3B, in the conventional pneumatic tire 101, when the tire is mounted on the rim, the normal maximum internal pressure, and the specified load, the bead portion 40 and the rim flange 200 The contact region S ₂ (hatched portion) is a region extending from the bead heel portion 80 to the vicinity of the rim flange end 200a. Thus, since the end 90 of the ply turnup portion 60b is positioned closer to the contact region S _2, the end 90 is susceptible to influence of the reaction force of the rim flange 200, with the deformation of the bead portion 40 In some cases, distortion occurred and ply end separation occurred.

On the other hand, in the pneumatic tire 1 of the present invention shown in FIG. 3A, the rising angle α of the outer surface of the tire on the outer side in the tire radial direction from the bead heel portion 8, that is, the outer surface of the back surface of the bead is set to the conventional pneumatic tire. By making it larger than 101, the contact region S ₁ (hatched portion) between the bead portion 4 and the rim 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. It becomes. As a result, the end portion 9 of the ply turnup portion 6b is made to be spaced apart from the contact region S _1, the influence of the end 9 due to the reaction force of the rim flange 20 is significantly suppressed than conventional ply end It becomes possible to realize a highly durable pneumatic tire that does not cause separation.

  Thus, according to the configuration of the present invention characterized in that the tire outer surface of the bead back portion is set so that the angle α is 70 to 100 °, the tire is attached to the rim, and the normal maximum internal pressure is set. Even in the case of a specified load, it is possible to reduce the influence of the rim flange 20 on the end portion 9 of the ply turn-up portion 6b as much as possible, and as a result, to provide a pneumatic tire with sufficient durability. Is possible.

  Here, the angle α is set in the range of 70 to 100 ° when the end portion 9 of the folded portion 6b is sufficiently separated from the rim flange 20 when the angle α is set to 70 ° or more. It is because generation | occurrence | production can be suppressed. On the other hand, the reason why the angle is set to 100 ° or less is that the end portion 9 is separated from the ply main body portion 6a and distortion generated by the deformation of the ply main body portion 6a can be suppressed.

The angle α formed between the outer surface straight line L ₁ and the tire axial direction X of the bead rear portion is more preferably set to 80-90 °. This is because the end portion 9 of the folded portion 6b can be sufficiently separated from the rim flange 20 by setting the angle to 80 ° or more, and the generation of distortion at the end portion 9 can be further suppressed. This is because the end portion 9 is 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 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 P _3, and the outer side in the tire radial direction. sequentially towards, and one or more circular arc center of curvature C ₁ is at the axially inner side than the outer surface of the tire, and one or more arcs center of curvature C ₂ is in the tire axial direction outer side than the outer surface of the tire it is preferable that the center of curvature C ₃ is defined by the one or more arcs are in axially inward from the outer surface of the tire.

In this way, by making the shape of the outer surface of the tire of the bead heel portion 8 convex toward the tire outer side, the bead portion 4 and the rim flange 20 in the vicinity of the bead heel portion 8 can be sufficiently brought into contact with the entire contact region S1. As a result, the reaction force of the rim flange 20 is dispersed throughout the region S1. 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.
Further, by making the shape of the tire outer surface of a part of the side rubber convex toward the inside of the tire, the amount of rubber can be reduced and the weight of the tire can be reduced.

In FIG. 4, only three arcs whose centers of curvature are C ₁ , C ₂ , and C ₃ are shown, but the tire outer surface between the arc of the center of curvature C _{1 and} the arc of the center of curvature C ₂ 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.

  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.

Further, as shown in FIG. 5, a third intersection P ₇ 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 ply turn-up portion 6 b and the outermost end in the tire radial direction of the bead core 5. A fourth intersection P ₈ which is an intersection of a straight line passing through an arbitrary point P ₆ on the outer side in the tire radial direction 50% of the maximum tire radial width a of the bead core ₅ from P ₅ and parallel to the tire axial direction, and the ply turn-up portion 6b. The angle β formed by the ply turn-up portion inclination line L ₂ passing through the two intersections P ₇ and P ₈ and the tire axial direction is preferably 70 to 100 °.
Note that the angle β is an outer side in the tire axial direction from the ply turn-up portion inclination line L ₂ among angles formed by the ply turn-up portion inclination line L ₂ and the tire axial direction X, and passes through the third intersection P ₇ . It means the angle located on the outer side in the tire radial direction than the straight line parallel to the tire axial direction.

In this way, by adjusting the angle of the ply turn-up portion 6b, the end portion 9 of the ply turn-up portion 6b can be separated from the rim flange 20, and the occurrence of distortion at the end portion 9 is suppressed. be able to. Further, the end portion of the carcass ply turn-up portion can be further separated from the region receiving the reaction force from the rim flange, and the load on the end portion of the turn-up portion can be further suppressed, so a recess is formed in the side rubber. While enjoying the effect of reducing the weight of the tire, it is possible to sufficiently ensure excellent tire durability.
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 the angle β exceeds 100 °, the end 9 may come into contact with the bead core 5, and if the folded portion 6b is wound around the bead core 5, the manufacturing cost is increased. This is because there is a case where becomes higher. If the angle exceeds 110 °, the end portion 9 becomes too close to the ply body portion 6a, and the distortion of the ply turn-up portion 6b due to the deformation of the ply body portion 6a becomes large.

Further, in the present invention, as shown in FIG. 6, 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 the distortion of the end portion 9.

Further, as shown in FIG. 7, in the non-rim assembled state, the rubber thickness m in the tire axial direction on the straight line drawn in parallel to the tire axial direction through the center of gravity C ₅ of the bead core 5 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.

  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, the bead base width W, from the bead toe 12 of the bead portion 4, that the intersection length to P ₉ of the outer surface straight line L ₁ between the tangent line L ₃ of the outer surface of the bead base portion the bead rear portion Say.

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.

In the non-rim assembly state, from the intersection P ₉ of the outer surface straight line L ₁ and the tangential line L ₃ of the outer surface of the bead base portion 11 of the bead rear portion, the tire radial distance to the end 9 of the ply turnup portion 6b h 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 200% of the maximum width b of the bead core 5 in the tire axial direction.

  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, it is possible to reduce the manufacturing cost by adopting a structure in which the folded height of the ply folded portion 6b is kept relatively low instead of the structure in which the folded portion is wound around the bead core 5. Can be suppressed.

  Next, in order to confirm the effects of the present invention, the tires of the examples according to the present invention and the tires of the comparative examples are prepared, and by comparing the durability of the bead portions of these tires, Separation resistance at the edge was evaluated.

The tire of Example 1 has a tire size of 275 / 80R22.5, and has a recess in the region from the rim separation point to the tire maximum width position as shown in FIG. The surface angle α is 70 °, and each specification is a pneumatic tire as shown in Table 1.
The tires of Examples 2 to 10 and Reference Examples 1 to 4 conform to the tire structure of Example 1 except that the respective specifications are changed to the values shown in Table 1.
The tire of Comparative Example 1 conforms to the structure of the tire of Example 1 except that the angle α of the tire outer surface of the bead back surface portion is 60 °.
Further, the tire of Comparative Example 2 conforms to the structure of the tire 1 of Example 1 except that the angle α of the tire outer surface of the bead back surface portion is 110 °.

Specifically, the separation resistance is evaluated by assembling each tire on a specified rim, adjusting the internal pressure to 875 kPa, and then initializing a load load (3395 kgf) corresponding to the maximum load capacity (specified load) specified by JATMA. The drum test was performed under the condition that the load was set to 60 km / h and the separation was generated in the carcass ply, the vibration was increased, and the drum travel distance until the test was forced to be stopped was measured. . The measurement distance thus obtained is shown as an index in Table 1 with the travel distance of the tire of Comparative Example 1 as 100. 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 of Table 1, it was found that the tires of the examples achieved weight reduction by the recesses, improved the separation resistance of the tires compared to the tires of Comparative Example 1, and ensured durability at a high level. .
In addition, it was confirmed that the tires of the examples were deteriorated and damaged due to the ply ends being too close to the outer surface as compared with the tires of Comparative Example 2.

  According to the present invention, it is possible to provide a pneumatic tire that can achieve a sufficient weight reduction and at the same time can ensure 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, 9 edge part of ply folding part 6b, 11 bead base, 12 bead toe, 20 rim flange, F rim separation point, C ₁ , C ₂ , C ₃ center of curvature, center of gravity of C ₅ bead core 5, H tire cross-section height, L ₁ bead back surface straight line , L ₂ ply turn part inclination line, tangent line of outer surface of L ₃ bead base part 11, P ₁ first intersection point _, P ₂ second intersection point _, P ₃ tire maximum width position _, P ₅ bead core 5 tire radial direction outermost side _end point of 50% the tire radial direction outer side in the tire radial direction maximum width a of the bead core 5 from the tire radial direction outermost end _{P 5} of P ₆ bead core, _{P 7} a third intersection _point, P ₈ fourth _Point, the intersection of the outer surface straight line L ₁ of the tangent line L ₃ and the bead back portion of the outer surface of the P ₉ bead base portion, W bead base width, X axially, Y tire radial direction, tire radial direction of a bead core 5 maximum width, b bead core 5 in the tire axial direction maximum width, d rubber thickness, from h intersection P _9, the tire radial distance to the end 9, on a straight line drawn parallel to the centroid as the tire axial direction of the m bead core , Rubber thickness in the tire axial direction, n rubber thickness in the tire radial direction on a straight line passing through the center of gravity of the bead core and parallel to the tire radial direction, t separation distance, t _max maximum separation distance, α outer surface of the bead back portion angle which the straight line L ₁ and the tire axial direction X and the angle formed by the β ply turnup portion sloping line L ₂ and the tire axial direction X forms

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 Each bead core is folded back from the inner side in the tire axial direction to the outer side, and has a carcass made of at least one ply formed of a ply folded portion extending outward in the tire radial 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 a significant position,
A straight line that passes through the center of gravity of the bead core and is parallel to the tire axial direction in a cross-section in the tire axial 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 and the outside of the tire A first intersection that is an intersection with the surface, a straight line parallel to the tire axial direction passing through a point on the outer side in the tire radial direction of the bead core 50% of the maximum width in the tire radial direction from the outermost end in the tire radial direction of the bead core and the outside of the tire The angle α formed by the outer surface straight line of the back surface of the bead passing through the two intersections of the second intersection that is the intersection with the surface and the tire axial 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 angle β formed by the direction is 70 ° to 100 °,
In the non-rim assembled state, the rubber thickness gradually decreases toward the outer side in the tire radial direction in at least a part of the tire radial direction region including the recess, and then the tire cross-section height increases toward the outer side in the tire radial direction. over the tire radial direction area of up to 1/2, Ri constant thickness der,
In the non-rim assembled state, the tire radial distance from the intersection of the outer surface straight line of the bead back surface portion and the tangent of the bead base portion of the bead portion to the end portion of the ply turn-up portion is the tire axis of the bead core. A pneumatic tire characterized by being 100 to 225% of the maximum width in the direction . In the non-rim assembled state, the tire outer surface is one or more whose center of curvature is in the tire axial direction inner side than the tire outer surface in order from the bead heel portion to the tire maximum width position in the tire radial direction outer side. A center of curvature is defined by one or more arcs located outside the tire outer surface in the tire axial direction, and one or more arcs whose curvature centers are located inside the tire outer surface in the tire axial direction. The pneumatic tire according to claim 1. 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. The pneumatic tire according to claim 1 , wherein the maximum separation distance is 10 to 30% of the maximum width in the 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 any one of claims 1 to 3, which is 70 to 300% of a rubber thickness in a tire radial direction. 5. The air according to claim 1, wherein in the non-rim assembled state, a bead base width of the bead portion is 200 to 260% of a maximum width in a tire axial direction of the bead core. Enter tire. In the non-rim assembled state, the tire radial distance from the intersection of the outer surface straight line of the bead back surface portion and the tangent of the bead base portion of the bead portion to the end portion of the ply turn-up portion is the tire axis of the bead core. The pneumatic tire according to any one of claims 1 to 5, wherein the pneumatic tire has a maximum width of 135 to 200%.

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