JP2009179147A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability by suppressing partial wear or groove cracking. <P>SOLUTION: The pneumatic tire 1 comprises a carcass 6 that is extended from a tread part 2 through a shoulder part 3 and a side wall part 4 to a bead part 5. As it is installed on an authorized rim, with 10% of maximum air pressure charged, the carcass 6 at the shoulder part 3 has a radius of curvature R within a range of 0.74×compression ratio≤R/Xc≤0.80×compression ratio to size Xc of 1/2 of the tire width direction maximum width of the carcass 6. In the pneumatic tire 1, growth of outer diameter of the shoulder part 3 is promoted, while quantity of growth of outer diameter in the tire width direction is equalized. As a result, uneven abrasion or groove cracking of the tread part 2 around the shoulder part 3 can be restricted, thus improving durability. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire that can suppress uneven wear and improve durability.

  For example, in a pneumatic tire having a flatness ratio of 60% to 70%, that is, a so-called flat tire, outer diameter growth is remarkably generated in the vicinity of shoulder portions on both sides in the tire width direction of the tread portion where the tagging effect of the belt layer is weakened. Thereby, the distribution of the outer diameter growth amount in the tire width direction becomes non-uniform. In particular, the outer diameter growth amount increases most in the vicinity of the outermost main groove in the tire width direction. As a result, uneven wear tends to occur in the shoulder rib formed by the outermost main groove in the tire width direction. Further, when the outer diameter growth amount increases in the vicinity of the outermost main groove in the tire width direction, the outer diameter growth amount of the inner edge increases at the inner and outer edges of the shoulder rib made of the main groove in the tire width direction. For this reason, the outermost main groove in the tire width direction is opened due to the difference in the outer diameter growth amount between the edges, and a crack (groove crack) is likely to occur at the groove bottom. As a result, the durability of the pneumatic tire is reduced.

  As a pneumatic tire that suppresses uneven wear in the vicinity of the shoulder portion of the tread portion and improves durability, the belt ply having the largest tire width direction in the belt layer is virtually divided into four equal parts in the tire width direction. In some cases, the inner surface in the tire radial direction at the outer portion in the tire width direction is formed by an arc having a radius of curvature of 2.0 to 2.8 times the maximum width of the pneumatic tire. In this pneumatic tire, a belt ply in the vicinity of the shoulder portion is formed by an arc, and by increasing the rigidity of the portion, the outer diameter growth is suppressed and uneven wear in the vicinity of the shoulder portion is prevented (see, for example, Patent Document 1). .

JP-A-5-131806

  In the pneumatic tire shown in Patent Document 1, the outer diameter growth is suppressed by increasing the rigidity in the vicinity of the shoulder portion of the tread portion having a large outer diameter growth amount. However, as a result of increasing the rigidity and suppressing the outer diameter growth, there is a possibility of affecting the outer diameter growth in other parts, which is not preferable. As described above, the pneumatic tire shown in the cited document 1 does not eliminate the cause of uneven distribution of the outer diameter growth amount in the tire width direction.

  The present invention has been made in view of the above, and provides a pneumatic tire capable of improving durability by uniformizing outer diameter growth in the tire width direction to suppress uneven wear and groove cracks. For the purpose.

  In order to achieve the above object, in the pneumatic tire according to the present invention, in the pneumatic tire having a carcass extending from the tread portion to the bead portion through the shoulder portion and the sidewall portion, the pneumatic tire is attached to a regular rim, In a state where 10% of the maximum air pressure is filled, the radius of curvature R of the carcass of the shoulder portion is 0.74 × the aspect ratio ≦ R / Xc with respect to the dimension Xc which is ½ of the maximum width in the tire width direction of the carcass. ≦ 0.80 × flattening ratio is set.

  According to this pneumatic tire, the outer diameter growth of the shoulder portion can be promoted, and the outer diameter growth amount in the tire width direction can be made uniform. As a result, uneven wear and groove cracks in the vicinity of the shoulder portion of the tread portion can be suppressed, and durability can be improved.

  In the pneumatic tire according to the present invention, a belt layer is provided on the outer side in the tire radial direction of the carcass of the tread portion, and a mutual cord interval h between the carcass and the belt on the inner side in the tire radial direction of the belt layer is set. A rubber portion is provided between the cords in such a manner that 1.0 (mm) ≦ h ≦ 1.5 (mm).

  According to this pneumatic tire, in addition to the effect of adjusting the curvature radius R of the carcass of the shoulder portion, the rigidity of the tread portion can be further increased and the durability can be improved.

  In the pneumatic tire according to the present invention, a belt layer is provided on the outer side in the tire radial direction of the carcass of the tread portion, and the cord of each belt forming the belt layer has an angle of 15 ° or more with respect to the tire equator line. It is characterized by having.

  According to this pneumatic tire, durability can be improved without providing a so-called circumferential reinforcing belt having a cord with an angle of 0 ° to 5 ° with respect to the tire equator line. As well as the manufacturing cost for the circumferential reinforcing belt can be reduced.

  In the pneumatic tire according to the present invention, the flatness ratio is 70% or less.

  According to this pneumatic tire, particularly when the flatness ratio is 70% or less, uneven wear and groove cracks in the vicinity of the shoulder portion of the tread portion can be suppressed, and durability can be improved.

  The pneumatic tire according to the present invention can suppress uneven wear and groove cracks by adjusting the curvature of the carcass at the shoulder portion and uniformizing the outer diameter growth amount in the tire width direction, and is durable. Can be improved.

  Embodiments of a pneumatic tire according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same.

  FIG. 1 is a meridional sectional view showing a pneumatic tire according to an embodiment of the present invention, and FIG. 2 is an enlarged view showing a shoulder portion of the pneumatic tire of FIG.

  As shown in FIG. 1, the pneumatic tire 1 according to the present embodiment is configured to be substantially symmetric with respect to the equator plane C. The equator plane C is a plane that passes through the center of the tire width of the pneumatic tire 1 while being orthogonal to the axis (not shown) of the rotational axis of rotation of the pneumatic tire 1. The tire equator line is a line that is on the equator plane C and extends along the circumferential direction of the pneumatic tire 1. And since the pneumatic tire 1 described below is configured to be substantially symmetric with respect to the equator plane C, FIG. 1 shows only one side centered on the equator plane C. Only one side will be described, and the description on the other side will be omitted.

  In the following description, the tire width direction refers to a direction parallel to the axis of the rotation axis of the pneumatic tire 1, and the inner side in the tire width direction refers to the side toward the equatorial plane C in the tire width direction, the tire width direction. The outside refers to the side away from the equator plane C in the tire width direction. Further, the tire radial direction means a direction orthogonal to the axis of the rotation shaft, the tire radial inner side means the side toward the rotation axis in the tire radial direction, and the tire radial direction outer side means the rotation axis in the tire radial direction. The side away from. The tire circumferential direction is a circumferential direction centered on the axis of the rotating shaft.

  As shown in FIG. 1, the pneumatic tire 1 according to the present embodiment includes a tread portion 2, shoulder portions 3 on both sides of the tread portion 2, and sidewall portions 4 and bead portions 5 that are sequentially continuous from the shoulder portions 3. It is configured to include. Further, the pneumatic tire 1 has a carcass 6 and a belt layer 7.

  The tread portion 2 is exposed to the outside of the pneumatic tire 1, and the surface thereof is the contour of the pneumatic tire 1. A tread surface 21 is formed on the outer peripheral surface of the tread portion 2, that is, on the tread surface that contacts the road surface during traveling. The tread surface 21 includes a plurality of main grooves 22 extending in the tire circumferential direction, and a plurality of ribs 23 forming a plurality of land portions defined by the main grooves 22. For example, in the present embodiment, four main grooves 22 are formed, and five ribs 23 are formed by these main grooves 22. The outermost ribs 23 in the tire width direction form shoulder ribs 23a.

  The shoulder portion 3 is a portion that falls inward in the tire radial direction from the tread surface 21 on both outer sides in the tire width direction of the tread portion 2 and is exposed on both outer sides in the tire width direction of the pneumatic tire 1. In this shoulder portion 3, the outer edge of the shoulder rib 23 a in the tire width direction, the tread portion 2 when the pneumatic tire 1 is mounted on a regular rim defined by JATMA and a maximum load and maximum air pressure prescribed by JATMA are applied. The edge that is the outermost installation end in the tire width direction is defined as a shoulder point Sh.

  The sidewall portion 4 is continuous with the shoulder portion 3 and is exposed on both outer sides in the tire width direction of the pneumatic tire 1. The side wall portion 4 prevents trauma generated in the side wall portion 4 from reaching the carcass 6.

  The bead unit 5 includes a bead core 51 and a bead filler 52. The bead core 51 is formed by winding a bead wire 51a, which is a steel wire, in a ring shape. The bead core 51 supports the tension of the carcass 6 generated by the internal pressure of the pneumatic tire 1. The bead filler 52 is disposed in a space formed by folding the carcass 6 outward in the tire width direction at the position of the bead core 51. The bead filler 52 fixes the carcass 6 at the position of the bead core 51 and adjusts the shape of the bead portion 5. Further, the bead filler 52 increases the rigidity of the bead portion 5.

  The carcass 6 includes a cord layer formed of rubber-coated organic fiber or steel, and the cord is perpendicular to the tire equator line of the pneumatic tire 1 along the tire circumferential direction of the pneumatic tire 1. Arranged to form the skeleton of the pneumatic tire 1. The carcass 6 is suspended from the tread portion 2 to the bead core 51 of the bead portion 5 via the shoulder portions 3 and the sidewall portions 4 on both sides thereof in the tire width direction. The carcass 6 serves as a pressure vessel when the pneumatic tire 1 is filled with air and supports a load applied to the pneumatic tire 1 by the internal pressure.

  The belt layer 7 is provided on the outer side in the tire radial direction than the carcass 6 in the tread portion 2. The belt layer 7 is formed by laminating a plurality of belts formed of rubber-coated organic fibers or steel-made cord layers, and covers the carcass 6 along the tire circumferential direction. The belt layer 7 in the present embodiment is laminated in the order of the first belt 71, the second belt 72, the third belt 73, and the fourth belt 74 from the outer side in the tire radial direction of the carcass 6 toward the outer side in the tire radial direction. It has a four-layer structure. The first belt 71 disposed on the innermost radial direction of the belt layer 7 has a rubber-coated cord disposed at an angle of 48 ° with respect to the tire circumferential direction, that is, the tire equator line. ing. Further, the second belt 72, the third belt 73, and the fourth belt 74 laminated on the outer side in the tire radial direction of the first belt 71 have cords covered with rubber in the tire circumferential direction, that is, the tire equator line. , Arranged at an angle of 17 °. The second belt 72 and the third belt 73 are arranged such that the cords are inclined in opposite directions, and the third belt 73 and the fourth belt 74 are arranged so that the cords are inclined in the same direction. ing. Such a belt layer 7 enhances the rigidity by applying a tightening force to the carcass 6, and also reduces the impact during the traveling of the vehicle on which the pneumatic tire 1 is mounted, so that the trauma generated in the tread portion 2 can be reduced. 6 is prevented.

  The pneumatic tire 1 in the present embodiment having the above-described configuration is mounted on a regular rim stipulated by JATMA and filled with 10% of the maximum air pressure stipulated by JATMA (pneumatic tire 1 in a mold) The radius of curvature R of the inner surface in the tire radial direction of the carcass 6 of the shoulder portion 3 is [0.74 with respect to the dimension Xc that is ½ of the maximum width in the tire width direction of the carcass 6. X flatness ratio ≦ R / Xc ≦ 0.80 × flattening ratio].

  Here, as shown in FIG. 2, the carcass 6 of the shoulder portion 3 is an intersection A obtained by drawing a perpendicular line from the shoulder point Sh to the tangent to the outer surface in the tire radial direction of the carcass 6, and a side wall from the intersection A. It is set as the range (alpha) between the point B which is a 30-mm position along the carcass 6 in the part 4 side.

  When the pneumatic tire 1 is filled with air, an internal pressure is generated in the carcass 6 toward the outer side in the tire radial direction, and the internal pressure generates a tension toward the inner side in the tire radial direction against the internal pressure. The carcass 6 of the shoulder portion 3 has a smaller radius of curvature R than the carcass 6 of the tread portion 2. For this reason, the tension is large at the carcass 6 of the shoulder portion 3 and is small at the carcass 6 of the tread portion 2. As a result, the outer diameter growth amount is small in the carcass 6 of the shoulder portion 3, the outer diameter growth amount is large in the carcass 6 of the tread portion 2, and the outer diameter growth amount of the carcass 6 in the tire width direction becomes uneven.

  Therefore, the outer diameter growth amount of the carcass 6 in the tire width direction is adjusted by adjusting the outer diameter growth amount of the carcass 6 of the shoulder portion 3 so as to be closer to the outer diameter growth amount of the carcass 6 of the tread portion 2. Becomes uniform. That is, the radius of curvature R of the carcass 6 of the shoulder portion 3 is increased so as to be close to the radius of curvature of the carcass 6 of the tread portion 2.

  The tension applied to the point of interest in the carcass 6 of the shoulder portion 3 is defined by the integral sum in the tire width direction in the range from the crown center of the tread portion 2 that is the position of the equator plane C to the point of interest. That is, even if the radius of curvature R of the carcass 6 of the shoulder portion 3 is the same, if the distance from the crown center, which is a substantially flat curvature, to the point of interest is large, the curvature displacement of the carcass 6 of the shoulder portion 3 increases. Conceivable. Therefore, the relationship between the radius of curvature R of the inner surface in the tire radial direction of the carcass 6 of the shoulder portion 3 and the dimension Xc of 1/2 of the maximum width in the tire width direction of the carcass 6 from the crown center to the shoulder point Sh [R / Xc ] Is considered.

  Further, the range of the radius of curvature R of the carcass 6 [0.74 × flat ratio ≦ R / Xc ≦ 0.80 × flat ratio] applies to the pneumatic tire 1 having a flat ratio of 60%, 65%, and 70%. It is preferable that The range of numerical values to be multiplied by the aspect ratio is derived from the ideal value of R / Xc in which the carcass 6 in the tire width direction has a uniform outer diameter growth amount in the pneumatic tire 1 having the aspect ratio. Specifically, the ideal value of the pneumatic tire 1 with a flatness ratio of 60% is [0.44 ≦ R / Xc ≦ 0.46], and the ideal value of the pneumatic tire 1 with a flatness ratio of 70% is [ 0.52 ≦ R / Xc ≦ 0.54]. Then, [0.74 × flat ratio ≦ R / Xc ≦ 0.80 × flat ratio] is derived as an ideal range for the pneumatic tire 1 with a flat ratio of 60% and 70%.

  In this way, the inventor of the present application has a smaller radius of curvature R of the carcass 6 at the shoulder portion 3 than at the tread portion 2, so that the growth amount of the outer diameter of the shoulder portion 3 is smaller than that of the tread portion 2, thereby reducing the tire width. We focused on the non-uniform distribution of the outer diameter growth in the direction. Then, by increasing the radius of curvature R of the carcass 6 of the shoulder portion 3 close to the radius of curvature of the carcass 6 of the tread portion 2, the outer diameter growth in the tire width direction is promoted by promoting the outer diameter growth of the shoulder portion 3. Can be made uniform. As a result, uneven wear and groove cracks in the vicinity of the shoulder portion 3 of the tread portion 2 can be suppressed, and the durability of the pneumatic tire 1 can be improved.

  Incidentally, in the pneumatic tire 1 having the above-described configuration, as shown in FIG. 3, the cord 6 a of the carcass 6 and the cord of the first belt 71 on the outer side in the tire radial direction of the carcass 6 (the innermost side in the tire radial direction of the belt layer 7). The code interval h with respect to 71a is set in a range of 1.0 (mm) ≦ h ≦ 1.5 (mm). For example, as shown in FIG. 3, the rubber member 8 is disposed between the carcass 6 and the first belt 71, or the rubber covering the cord 6 a of the carcass 6 and / or the cord 71 a of the first belt 71. The cord interval h can be increased by increasing the thickness of the rubber covering the wire. By comprising in this way, in addition to the effect at the time of adjusting the curvature radius R of the carcass 6 of the said shoulder part 3, the rigidity of the tread part 2 can be increased further and durability of the pneumatic tire 1 can be improved.

  In the pneumatic tire 1 having the above-described configuration, in the belt layer 7, the cords of the belts 71, 72, 73, and 74 have an angle of 15 ° or more, preferably 15 ° or more and 48 ° or less with respect to the tire equator line. is doing. That is, the pneumatic tire 1 does not include a so-called circumferential reinforcing belt having a cord with an angle of 0 ° to 5 ° with respect to the tire equator line. As described above, the pneumatic tire 1 according to the present embodiment can improve the durability without the need for the circumferential reinforcing belt, and can further reduce the weight of the circumferential reinforcing belt. The manufacturing cost for the circumferential reinforcing belt can be reduced.

  Moreover, the pneumatic tire 1 having the above configuration can be suitably used for a tire having an aspect ratio of 70% or less. In particular, in a pneumatic tire having an aspect ratio of 70% or less, in the vicinity of the shoulder portion 3 of the tread portion 2. The uneven wear and groove cracks can be suppressed, and the durability can be improved.

  FIG. 4 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention. An embodiment of the present invention will be described with reference to FIG. Here, the pneumatic tire 1 according to the above-described embodiment is prototyped, and the performance test between the pneumatic tire 1 and the conventional pneumatic tire is performed, and uneven wear resistance, durability, and groove cracking are performed. The occurrence was evaluated.

  In this performance test, the uneven wear resistance was imparted to 10% of the maximum air pressure specified by JATMA (90 kPa against maximum 900 kPa) by attaching a pneumatic tire of tire size 315 / 60R22.5 to a regular rim specified by JATMA. In this case, the difference between the maximum outer diameter growth and the minimum outer diameter growth in the range of the tire width direction from the crown center to the shoulder point Sh is measured and indexed, and the index increases as the difference in outer diameter growth decreases. It shows large uneven wear resistance. In addition, the durability of pneumatic tires with a tire size of 315 / 60R22.5 is attached to regular rims specified by JATMA, and the maximum air pressure and 140% of maximum load specified by JATMA are applied. This is an indexed measurement of the distance traveled until the entering tire breaks. The larger the index, the better the durability. Groove cracks occur when a pneumatic tire with a tire size of 315 / 60R22.5 is mounted on a regular rim specified by JATMA, and the maximum load is applied in a lower pressure state (700 kPa against 900 kPa maximum) than the maximum air pressure specified by JATMA. The sample was attached to an indoor drum tester, and after traveling 10,000 km in ozone irradiation, the occurrence of cracks was examined.

  In this example, as shown in FIG. 4, two types of conventional examples to be compared with the present invention, two types of examples of the present invention, and one type of comparative example are tested by the above method. In the pneumatic tires shown in Examples 1 and 2, R / Xc is 0.44 and 0.46, which are within the ideal value range of a pneumatic tire having a flatness ratio of 60%, and R / (Xc / flattening ratio) is 0.73 and 0.77. In contrast, the pneumatic tires shown in the conventional examples 1 and 2 have R / Xc of 0.30 and 0.39 and R / (Xc · flat ratio) of 0.50 and 0.65. The pneumatic tire shown in Comparative Example 1 has an R / Xc of 0.51 and an R / (Xc / flat ratio) of 0.85.

  As apparent from FIG. 4, the pneumatic tires of Examples 1 and 2 in which R / Xc is within the ideal value range of the pneumatic tire having a flatness ratio of 60% have the curvature radius R of the carcass 6 of the shoulder portion 3. As a result of adjusting as appropriate, uneven wear resistance is improved, groove cracks are not generated, and durability is improved.

  FIG. 5 is a diagram showing the distribution of the outer diameter growth amount in the tire width direction. Here, it is the analysis result by FEM (finite element method) which compared the said Example 2 (solid line), the prior art example 1 (one-dot chain line), and the prior art example 2 (broken line), Comprising: Tire size 315 / 60R22.5 This pneumatic tire is mounted on a regular rim defined by JATMA. The horizontal axis indicates the distance in the tire width direction from the crown center (0), and the vertical axis indicates the difference in the outer diameter growth amount on the surface of the tread portion between the air pressure of 90 kPa and the air pressure of 900 kPa. Further, the part where the analysis result is interrupted is the position of the main groove 22. As can be seen from FIG. 6, the pneumatic tire of Example 2 has a uniform outer diameter growth amount in the tire width direction.

  FIG. 6 is a diagram showing the outer diameter growth amount of the tread portion and the opening amount of the main groove. Here, the analysis result by FEM (finite element method) which compares the said Example 2 (FIG. 6 (a)) with the prior art example 1 (FIG. 6 (b)) and the prior art example 2 (FIG. 6 (c)). In this case, a pneumatic tire with a tire size of 315 / 60R22.5 is mounted on a regular rim defined by JATMA, and the air pressure is 90 kPa (one-dot chain line) and the air pressure is 900 kPa (solid line). The unit of the numerical value of the outer shape growth in the upper part of FIG. 6 is mm. As is apparent from the upper part of FIG. 6, the pneumatic tire of Example 2 shows that the outer diameter growth amount in the tire width direction from the crown center to the shoulder point is made uniform. Further, as is apparent from the lower part of FIG. 6, it can be seen that the pneumatic tire of Example 2 has little groove opening resistance and groove bottom main strain and has groove crack resistance.

  As described above, the pneumatic tire according to the present invention is suitable for making the outer diameter growth in the tire width direction uniform, suppressing uneven wear and groove cracks, and improving durability.

It is a meridional sectional view showing a pneumatic tire according to an embodiment of the present invention. It is an enlarged view which shows the shoulder part of the pneumatic tire of FIG. It is the schematic which shows the cord space | interval of a carcass and a 1st belt. It is a graph which shows the result of the performance test of the pneumatic tire concerning the Example of this invention. It is a figure which shows distribution of the outer diameter growth amount in a tire width direction. It is a figure which shows the outer diameter growth amount of a tread part, and the opening amount of a main groove.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 21 Tread surface 22 Main groove 23 Rib 23a Shoulder rib 3 Shoulder part 4 Side wall part 5 Bead part 6 Carcass 6a Cord 7 Belt layers 71, 72, 73, 74 Belt 71a Cord 8 Rubber member A Shoulder Intersection point perpendicular to the tangent line of the carcass of the shoulder portion from the point B Point at a position 30 mm along the carcass from the intersection point C Equatorial plane h Cord interval R Curvature radius Sh Shoulder point Xc 1/2 size in the tire width direction α Carcass range of shoulder

Claims (4)

In a pneumatic tire having a carcass extending from a tread portion to a bead portion via a shoulder portion and a sidewall portion,
When mounted on a regular rim and filled with 10% of the maximum air pressure, the radius of curvature R of the carcass of the shoulder portion is 0.74 × with respect to a dimension Xc that is ½ of the maximum width in the tire width direction of the carcass. A pneumatic tire characterized by being set within a range of flat ratio ≦ R / Xc ≦ 0.80 × flat ratio.   A belt layer is provided on the outer side in the tire radial direction of the carcass in the tread portion, and a cord distance h between the carcass and the belt on the inner side in the tire radial direction of the belt layer is 1.0 (mm) ≦ h ≦ 1. The pneumatic tire according to claim 1, wherein a rubber portion is provided between the cords in a mode of 5 (mm).   The belt layer is provided on the outer side in the tire radial direction of the carcass of the tread portion, and the cord of each belt forming the belt layer has an angle of 15 ° or more with respect to the tire equator line. The pneumatic tire according to 1 or 2.   The pneumatic tire according to any one of claims 1 to 3, wherein the flatness ratio is 70% or less.

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