JP6690487B2 - Pneumatic tire - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of reducing weight and reducing rolling resistance without deteriorating a tire yield rate by devising a profile of a sidewall portion.

  In order to reduce the weight of a pneumatic tire and reduce rolling resistance, the thickness of a tire member has been reduced (thin gauge). However, when the thickness of the tire member is reduced, the contact with the mold is weakened during vulcanization, and air is likely to be accumulated at that location, which may cause a poor appearance after vulcanization.

  In order to prevent such a poor appearance, it is common to provide a groove (vent groove) or a hole (vent hole) for letting air escape in the mold (see, for example, Patent Document 1). However, there may be a case where it is not possible to form a groove or a hole in a portion corresponding to a character formed on the sidewall portion of the pneumatic tire, and in such a case, there is a problem that the appearance defect cannot be improved. .

JP, 2011-168178, A

  An object of the present invention is to provide a pneumatic tire that can reduce the weight and the rolling resistance without deteriorating the tire yield rate by devising the profile of the sidewall portion.

The pneumatic tire of the present invention for achieving the above object is a pneumatic tire including a pair of left and right bead portions and a sidewall portion, and a tread portion that is continuous between both sidewall portions, and the most gauge in the sidewall portion. Has a thickness of less than 3.0 mm, and the side surface shape of the tire in a tire meridian cross-sectional view has a first arc having a curvature that is convex outward in the tire width direction, and a tire diameter of the first arc. A second arc having a curvature that extends inward in the tire width direction and is convex toward the inner side in the tire width direction, and a third arc that has a curvature that extends inward in the tire radial direction of the second arc and is convex toward the outer side in the tire width direction And a point P12 that is an inflection point between the first arc and the second arc and a point P23 that is an inflection point between the second arc and the third arc are as follows. ), And it is characterized in satisfying 2), respectively.
(1) The height of the point P12 in the tire radial direction is 110% or more and 130% or less of the height BFh of the bead filler with the root of the bead filler as a base point.
(2) The height of the point P23 in the tire radial direction is 70% or more and 90% or less of the height BFh of the bead filler with the root of the bead filler as a base point.

  In the pneumatic tire of the present invention, since the thickness of the thinnest portion of the sidewall portion is less than 3.0 mm, the sidewall portion can be thinned, and the weight and rolling resistance can be reduced. It will be possible. Further, in the tire meridian cross-sectional view, the side surface shape of the tire has a first arc having a curvature that is convex toward the tire width direction outer side, and is continuous to the tire radial direction inner side of the first arc and is convex toward the tire width direction inner side. A second arc having a curvature of, and a third arc having a curvature that is continuous to the tire radial direction inner side of the second arc and convex toward the tire width direction outer side, of the first arc and the second arc. Since the point P12 which is an inflection point and the point P23 which is an inflection point between the second arc and the third arc satisfy the above conditions (1) and (2), respectively, The contact pressure between the portion corresponding to the second arc and the mold can be increased, and the air between the tire and the mold can be released. As a result, it is possible to suppress the occurrence of a defective appearance due to the thin gauge of the sidewall portion, and it is possible to prevent deterioration of the tire yield rate.

  In the present invention, it is preferable that the radius of curvature R1 of the first arc and the radius of curvature R2 of the second arc satisfy the relationship of R1-45 mm ≦ R2 ≦ R1 + 45 mm. This makes it possible to effectively suppress the appearance defect without lowering the load durability.

  In the present invention, an arc obtained by extending the first arc from the point P12 to the point P23 is a virtual arc, the midpoint between the points P12 and P23 on the virtual arc is a point P123, and the tangent line of the virtual arc is drawn from the point P123. When the point of intersection of the perpendicular and the second arc is point P'123, the distance between point P123 and point P'123 is preferably 1.0 mm or more. As a result, the appearance defect can be effectively suppressed.

  In the present invention, it is preferable to have a protruding portion that is convex on the tire outward in the tire width direction at a position corresponding to the points P12 and P23. As a result, the appearance defect can be effectively suppressed.

  In the present invention, it is preferable that columnar protrusions protruding from the protrusions are arranged at least at two locations on the tire circumference. As a result, the appearance defect can be effectively suppressed.

It is a meridian sectional view showing an example of a pneumatic tire which consists of an embodiment of the present invention. It is explanatory drawing which expands and shows a part of pneumatic tire of FIG. It is a side view which shows the modification of the pneumatic tire which consists of embodiment of this invention. It is a side view which expands and shows a part of pneumatic tire of FIG. It is a perspective view which expands and shows the protrusion part and protrusion formed in the sidewall part of the pneumatic tire of FIG.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. In addition, in FIG. 1, CL is a tire center line.

  As shown in FIG. 1, a pneumatic tire according to an embodiment of the present invention includes a tread portion 1 extending in a tire circumferential direction and forming an annular shape, and a pair of sidewall portions arranged on both sides of the tread portion 1. 2 and 2 and a pair of bead portions 3 and 3 arranged inside the sidewall portions 2 in the tire radial direction.

  A carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back from the inside of the tire to the outside of a bead core 5 arranged in each bead portion 3. A bead filler 6 made of a rubber composition having a triangular cross section is arranged on the outer periphery of the bead core 5. Further, a chafer 7 is arranged in each bead portion 3 so as to wrap the bead core 5.

  On the other hand, a plurality of layers (two layers in FIG. 1) of belt layers 8 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 8 include a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and the reinforcing cords are arranged so as to intersect each other between the layers. In the belt layer 8, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in the range of, for example, 10 ° to 40 °. A steel cord is preferably used as the reinforcing cord of the belt layer 8. On the outer peripheral side of the belt layer 8, for the purpose of improving high-speed durability, there is arranged at least one belt cover layer 9 in which reinforcing cords are arranged at an angle of, for example, 5 ° or less with respect to the tire circumferential direction. There is. As the reinforcing cord of the belt cover layer 9, an organic fiber cord such as nylon or aramid is preferably used.

  The tire internal structure described above shows a typical example of a pneumatic tire, but is not limited to this.

  In the pneumatic tire, the thickness of the portion of the sidewall portion 2 having the smallest gauge is configured to be less than 3.0 mm. Further, in the tire meridian cross-sectional view, the side surface shape of the tire has a first arc C1 having a curvature that is convex outward in the tire width direction and a tire arc inward in the tire width direction that extends inward in the tire radial direction of the first arc C1. The second arc C2 has a convex curvature, and the third arc C3 has a curvature that is continuous inside the second arc C2 in the tire radial direction and convex toward the outer side in the tire width direction. That is, the shape of the second circular arc C2 is different from the shapes of the first circular arc C1 and the third circular arc C3, and is configured to be convex inward in the tire width direction. In the pneumatic tire of the present invention, characters and the like are formed in the range of the second arc C2. In the side wall portion 2, particularly, a large rubber volume is required near the tip of the bead filler 6, and a defective appearance is likely to occur. Therefore, the shape of the second arc C2 located near the tip of the bead filler 6 is devised. That is effective in suppressing the appearance defect.

An inflection point between the first arc C1 and the second arc C2 is defined as a point P12, and an inflection point between the second arc C2 and the third arc C3 is defined as a point P23. Further, with the root of the bead filler 6 as a base point, the height of the point P12 in the tire radial direction is defined as the height h12, and the height of the point P23 in the tire radial direction is defined as the height h23. At this time, the points P12 and 23 are configured to satisfy the following conditions (1) and (2), respectively. Further, the points P12 and 23 are located on the inner side in the tire width direction with respect to the tire maximum width position.
(1) The height h12 of the point P12 in the tire radial direction is 110% or more and 130% or less of the height BFh of the bead filler 6.
(2) The height h23 of the point P23 in the tire radial direction is 70% or more and 90% or less of the height BFh of the bead filler 6.

  In the pneumatic tire described above, since the thickness of the thinnest portion of the sidewall portion 2 is less than 3.0 mm, the sidewall portion 2 can be thinned to reduce the weight and the rolling resistance. Is possible. In the tire meridian cross-sectional view, the side surface shape of the tire has a first arc C1 having a curvature that is convex outward in the tire width direction, and a first arc C1 that is continuous inward in the tire radial direction and inward in the tire width direction. The first arc C1 includes a second arc C2 having a convex curvature and a third arc C3 having a curvature that is continuous inside the second arc C2 in the tire radial direction and convex toward the outer side in the tire width direction. Since the point P12 which is an inflection point between the second arc C2 and the second arc C2 and the point P23 which is an inflection point between the second arc C2 and the third arc C3 satisfy the above conditions (1) and (2), respectively. The contact pressure between the mold and the portion corresponding to the second arc C2 of the pneumatic tire during vulcanization can be increased, and the air between the tire and the mold can be released. As a result, it is possible to suppress the occurrence of appearance defects due to the thinning of the sidewall portion 2, and it is possible to prevent deterioration of the tire yield rate.

  In particular, it is preferable that the radius of curvature R1 of the first arc C1 and the radius of curvature R2 of the second arc C2 satisfy the relationship of R1-45 mm ≦ R2 ≦ R1 + 45 mm. Thus, by appropriately setting the radius of curvature R2 of the second arc C2 with respect to the radius of curvature R1 of the first arc C1, it is possible to effectively suppress the appearance defect without lowering the load durability. . Here, when the radius of curvature R2 of the second arc C2 is larger than R1 + 45 mm, the contact between the tire and the mold is weakened and the appearance defect cannot be sufficiently suppressed, while the radius of curvature R2 of the second arc C2 is small. Is less than R1-45 mm, the strain is locally concentrated at the portion of the second arc C2, and the load durability deteriorates.

  FIG. 2 is an enlarged view showing the vicinity of the tip portion of the bead filler 6 in the pneumatic tire of FIG. As shown in FIG. 2, an arc formed by extending the first arc C1 from the point P12 to the point P23 is referred to as a virtual arc CR. In addition, an intermediate point between the points P12 and P23 on the virtual arc CR is a point P123, and an intersection of a perpendicular line L2 drawn from the point P123 to the tangent line L1 of the virtual arc CR and the second arc C2 is a point P′123. . At this time, it is preferable that the distance d between the point P123 and the point P′123 is 1.0 mm or more. By properly setting the distance d in this manner, it is possible to effectively suppress the appearance defect. The first arc C1 and the third arc C3 exist on the same arc.

  3 to 5 show a modified example of the pneumatic tire according to the embodiment of the present invention, which has a tire structure similar to that of the above-described embodiment and further projects to the sidewall portion 2. The part 10 and the protrusion 11 are formed. As shown in FIGS. 3 and 4, on the tire, projecting portions 10 that project outward in the tire width direction are formed at positions corresponding to points P12 and P23. The protrusion 10 extends in the tire circumferential direction and has an annular shape. In the pneumatic tire having the protrusions 10 formed in this way, air can escape from the grooves (grooves corresponding to the protrusions 10) formed in the circumferential direction of the mold during vulcanization. It can be effectively suppressed.

  As shown in FIGS. 3 and 4, columnar protrusions 11, so-called spew pieces, are formed at least at two locations on the tire circumference. That is, on the tire circumference, two protrusions 11 are formed respectively on the protrusion 10 at the position corresponding to the point P12 and on the protrusion 10 at the position corresponding to the point P23. Further, the columnar projection 11 projects from the projecting portion 10 toward the outer side in the tire width direction, as shown in FIG. In the pneumatic tire having the projections 11 thus formed, air is exhausted from holes (holes corresponding to the projections 11) formed on the circumferential groove of the mold at the time of vulcanization, resulting in poor appearance. Can be effectively suppressed. Although the projections 11 are present on the tire immediately after vulcanization, they may be cut because they are generally cut from the root during the tire manufacturing process.

  In the pneumatic tire described above, the protrusion 10 is provided with a vent groove extending in the tire circumferential direction in a mold (side plate) for molding the sidewall portion 2 of the tire, and the tire is vulcanized and molded using the mold. It is formed by Further, by connecting the vent hole to the vent groove provided in the mold, a columnar protrusion 11 protruding from the protrusion 10 is formed. The protrusions 10 and the protrusions 11 formed in this manner contribute to the escape of air remaining between the tire and the mold during vulcanization, and are suitable for suppressing appearance defects.

  In a pneumatic tire having a tire size of 175 / 65R15, a pair of left and right bead portions and a sidewall portion, and a tread portion that is continuous between both sidewall portions, the thickness of the portion of the sidewall portion having the smallest gauge (mm) , The shape of the first arc (convex inward or outward), the shape of the second arc (inward or outward convex), the shape of the third arc (inward or outward convex), bead filler height Ratio of height h12 of P12 to BFh (h12 / BFh × 100%), ratio of height h23 of P23 to bead filler height BFh (h23 / BFh × 100%), radius of curvature R1 (mm) of first arc , Radius of curvature R2 (mm) of second arc, radius of curvature R3 (mm) of third arc, presence / absence of protrusion on tire at position corresponding to P12, position at position corresponding to P23 Producing tires of Conventional Examples 1 and 2, Comparative Examples 1 and 2 and Examples 1 to 12 in which the presence or absence of a protrusion on the tire and the number of columnar protrusions on the tire circumference are set as shown in Tables 1 and 2. did.

  In each test tire, a bead filler having a bead filler height BFh of 25 mm was used. Further, in the shape of the first arc, the shape of the second arc and the shape of the third arc in Tables 1 and 2, "convex inward" means having a curvature that is convex inward in the tire width direction, The “convex outward” means that it has a curvature that is convex outward in the tire width direction.

  With respect to these test tires, the tire weight, rolling resistance, vulcanization yield rate and load durability were evaluated by the following test methods, and the results are also shown in Tables 1 and 2.

Tire weight:
The weight of each test tire was measured. The evaluation result is shown by an index with the value of Conventional Example 1 being 100, using the reciprocal of the measured value. The larger the index value, the lighter the tire weight.

Rolling resistance:
Each test tire was mounted on a wheel having a rim size of 15 × 5 J, filled with air pressure of 210 kPa, and rolling resistance was measured using a drum tester having a drum diameter of 2000 mm in accordance with ISO regulations. The evaluation result is shown by an index with the value of Conventional Example 1 being 100, using the reciprocal of the measured value. The larger the index value, the smaller the rolling resistance.

Vulcanization yield:
Each of the 1000 test tires was manufactured, and the presence or absence of a defective appearance after being extracted from the mold was visually inspected, and the number of tires having a defective appearance was counted. The evaluation result is shown by an index with the value of Conventional Example 1 being 100, using the reciprocal of the measured value. The larger this index value is, the smaller the number of tires with poor appearance and the better the vulcanization yield rate are.

Load durability:
Each test tire was mounted on a wheel with a rim size of 15 × 5J, filled with air pressure of 240 kPa, and using a drum tester with a drum diameter of 1707 mm, the running speed was 81 km / h, and the load was 88% of the maximum load specified by JATMA. The total running distance until the tire was broken was measured while increasing it by 13% every 4 hours, and the result was evaluated. The evaluation results are shown by an index with Conventional Example 1 set to 100. The larger the index value, the better the load durability.

  As can be seen from Tables 1 and 2, the thickness of the thinnest portion of the sidewall portion is less than 3.0 mm, and the side surface shape of the tire in the tire meridian cross-sectional view is devised to give Examples 1 to 8 The tire of No. 1 had a vulcanization yield rate and load durability equivalent to those of Conventional Example 1, while the tire weight was reduced and the rolling resistance was improved.

  In the tire of Example 9, the radius of curvature R2 of the second arc was set large, but the load durability equivalent to that of Conventional Example 1 was maintained. In the tire of Example 10, the radius of curvature R2 of the second arc was set small, but the vulcanization yield rate equivalent to that of Conventional Example 1 was maintained.

  The tire of Example 11 was provided with no protrusions at the positions corresponding to P12 and P23, but the vulcanization yield rate equivalent to that of Conventional Example 1 was maintained. In the tire of Example 12, the number of columnar protrusions in the protruding portion was set to be small, but the load durability equivalent to that of Conventional Example 1 was maintained.

  On the other hand, in Comparative Example 1, the ratio of the height h12 of P12 to the bead filler height BFh was made small, while the ratio of the height h23 of P23 to the bead filler height BFh was set large, so that the vulcanization yield rate was It got worse. Further, in Comparative Example 2, the ratio of the height h12 of P12 to the bead filler height BFh was increased, while the ratio of the height h23 of P23 to the bead filler height BFh was set small, so the load durability deteriorated. .

1 tread part 2 sidewall part 3 bead part 4 carcass layer 5 bead core 6 bead filler 7 chafer 8 belt layer 9 belt cover layer C1 first arc C2 second arc C3 third arc CR virtual arc P12 first arc and second arc Inflection point with arc P23 Inflection point with second arc and third arc

Claims (5)

In a pneumatic tire comprising a pair of left and right bead portions and sidewall portions, and a tread portion that is continuous between both sidewall portions,
The thickness of the thinnest portion of the sidewall portion is less than 3.0 mm, the side surface shape of the tire in a tire meridian cross-sectional view, the first arc having a curvature that is convex outward in the tire width direction, A second arc having a curvature that connects to the tire radial direction inner side of the first arc and has a curvature that becomes convex toward the tire width direction inside, and a second arc that connects to the tire radial direction inner side of the second arc and becomes convex toward the tire width direction outside. A point P12 which is an inflection point between the first arc and the second arc and a point P23 which is an inflection point between the second arc and the third arc, including a third arc having a curvature. And P satisfy the following conditions (1) and (2), respectively.
(1) The height of the point P12 in the tire radial direction is 110% or more and 130% or less of the height BFh of the bead filler with the root of the bead filler as a base point.
(2) The height of the point P23 in the tire radial direction is 70% or more and 90% or less of the height BFh of the bead filler with the root of the bead filler as a base point.   The pneumatic tire according to claim 1, wherein the radius of curvature R1 of the first arc and the radius of curvature R2 of the second arc satisfy the relationship of R1-45 mm ≤ R2 ≤ R1 + 45 mm.   An arc obtained by extending the first arc from the point P12 to the point P23 is a virtual arc, and an intermediate point between the points P12 and P23 is a point P123 on the virtual arc, and the point P123 is a virtual arc. The distance between the point P123 and the point P'123 is 1.0 mm or more when the point of intersection of the perpendicular drawn to the tangent line and the second arc is the point P'123. Pneumatic tire described.   The pneumatic tire according to any one of claims 1 to 3, further comprising a protrusion that is convex on the tire outward in the tire width direction at a position corresponding to the points P12 and P23. The pneumatic tire according to claim 4 , wherein columnar protrusions protruding from the protrusion are arranged at least at two positions on the tire circumference.

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