JP2015077891A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire that shows a favorable side-cut resistance.SOLUTION: In a pneumatic tire, which comprises a pair of sidewall portions, a pair of bead portions, and a carcass consisting of at least a sheet of carcass ply extending in a toroidal shape between bead cores in each bead portion, the sidewall portion includes side wall rubber and a low modulus elastomer having a lower modulus than the side wall rubber. When the distance in a tire radial direction from the innermost end of the carcass in the tire radial direction to the outermost end of the carcass in the tire radial direction is a carcass height CH, a low modulus portion consisting of a low modulus elastomer is positioned within a range of a 0.3 CH distance inside the sidewall portion in the tire radial direction from the outermost end of the carcass in the tire radial direction, and at least a part of the surface of the low modulus portion forms a part of the external surface of the sidewall portion.

Description

  The present invention relates to a pneumatic tire.

  When the vehicle travels, the pneumatic tire may cause a so-called side cut in which the sidewall portion is cut by colliding with an obstacle such as a curb. If this side cut reaches the carcass of the tire, there is a possibility of causing a failure such as a tire puncture.

  Thus, as one countermeasure against such a side cut, a technique of providing a thick portion on the sidewall portion surface of the pneumatic tire has been proposed (see, for example, Patent Document 1). In the pneumatic tire shown in Patent Document 1, at least one concave groove having a specific shape is provided along the tire circumferential direction on the outer side in the tire radial direction of the thick portion, and the thick portion and the specific shape are provided. The side wall portion of the tire is protected from damage due to contact with an obstacle.

JP 2007-22367 A

  However, in the side cut, as shown in FIG. 5, when the pneumatic tire slides in the tire width direction from an obstacle such as a curbstone, the side wall portion is caused by the difference in rigidity between the tread rubber and the side wall rubber. Also included is a side cut that occurs when the tire is pulled by the tread portion and moves inward in the tire width direction and comes into contact with the corner portion of the obstacle. In the above prior art, the side cut caused by the slipping off from the obstacle is not taken into consideration, and sufficient side cut resistance has not been obtained yet.

  Then, the objective of this invention is providing the pneumatic tire which shows favorable side-cut-proof property with respect to the side cut resulting from slipping off from an obstruction.

  That is, the pneumatic tire of the present invention includes a sidewall portion including a sidewall rubber and a low modulus elastic body having a modulus lower than that of the sidewall rubber. When the distance in the tire radial direction from the innermost end to the outermost end in the tire radial direction of the carcass is the carcass height CH, 0.3 CH of the sidewall portion from the outermost end in the tire radial direction of the carcass to the inner side in the tire radial direction. A low modulus portion made of the low modulus elastic body is located within a distance range, and at least a part of a surface of the low modulus portion forms a part of an outer surface of the sidewall portion. . When this pneumatic tire slides down from the obstacle in the tire width direction, the tread portion is deformed toward the sidewall portion and enters between the sidewall portion and the corner portion of the obstacle, Good side-cut resistance is exhibited to reduce contact with the corners of the obstacle.

  Here, “the low modulus portion is located within the distance of aCH (a is less than 1) from the outermost end in the tire radial direction of the carcass in the tire radial direction of the sidewall portion” means the low modulus portion. Is located within the tire radial range between the outermost end in the tire radial direction of the carcass and the tire radial direction position a distance of aCH from the outermost end in the tire radial direction of the carcass to the inner side in the tire radial direction. Means.

Here, in the pneumatic tire of the present invention, it is preferable that a 100% modulus of the low modulus elastic body is 0.68 times or more and 0.84 times or less of a 100% modulus of the sidewall rubber. When the value of the 100% modulus of the low modulus elastic body is within the above range, the tread portion is deformed more toward the sidewall portion and promotes entering between the sidewall portion and the corner of the obstacle. This is because the contact between the sidewall portion and the corner portion of the obstacle can be further reduced, and better side cut resistance can be obtained.
Here, the 100% modulus of the sidewall rubber and the low modulus elastic body is the 100% modulus at 25 ° C. measured according to JIS K6251.

  Furthermore, in the pneumatic tire of the present invention, the low modulus elastic body preferably has a 100% modulus of 1.30 MPa or more and less than 1.44 MPa. This is because when the value of the 100% modulus of the low modulus elastic body is within the above range, better side cut resistance can be obtained.

  In the pneumatic tire of the present invention, the low modulus elastic body is preferably rubber. This is because when the low modulus elastic body is rubber, the rubber and the side wall rubber can be bonded well. Moreover, since an anti-aging agent can be mix | blended with rubber | gum, it is because deterioration of a low modulus part can be prevented.

  Furthermore, in the pneumatic tire of the present invention, it is preferable that the low modulus portion and the carcass are separated from each other in a cross section in the tire width direction. This is because if the low modulus portion and the carcass are separated from each other, it is possible to prevent a tire failure due to poor adhesion between the sidewall rubber and the carcass.

  The pneumatic tire of the present invention includes a low modulus portion center line extending in the depth direction of the low modulus portion and passing through the center of the bottom surface of the low modulus portion in the tire width direction cross section, and the low modulus portion. It is preferable that the tangent line of the carcass passing through the intersection of the center line and the carcass forms an angle of 70 to 90 °. When the center line of the low modulus part and the tangent line of the carcass form an angle within the above range, the tread part 2 is promoted to enter between the sidewall part and the obstacle when the tire slides from the obstacle. This is because the side cut resistance can be improved efficiently. More specifically, the “low modulus portion center line” extends in the depth direction of the low modulus portion from the center of the surface of the low modulus portion 8 forming a part of the outer surface of the sidewall portion, and It shall pass through the center of the bottom surface of the low modulus part. In addition, when the carcass is composed of a plurality of carcass plies, “the tangent line of the carcass passing through the intersection of the low modulus part center line and the carcass” means the tangent line of the carcass passing through the intersection of the center line of the low modulus part and the outer surface of the carcass. Say. The “angle” refers to the smaller one of the angles formed by the low modulus portion center line and the tangent line of the carcass.

  In the pneumatic tire of the present invention, it is preferable that the dimension of the low modulus portion gradually decreases from the outer surface of the sidewall portion in the depth direction of the low modulus portion in the cross section in the tire width direction. By gradually reducing the size of the low modulus portion in this manner, the tread portion can be promoted to enter between the sidewall portion and the obstacle, and the contact between the sidewall portion and the corner portion of the obstacle is further increased. It is because it can reduce and can improve side-cut-proof property efficiently.

  In the pneumatic tire of the present invention, the distance, size, and angle are measured in a no-load state in which the tire is mounted on an applied rim and a predetermined internal pressure is applied. Here, “applied rim” is an industrial standard that is effective in the area where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK is used. In Europe, ETRTO (European Tire and Rim Technical Organization) is used. STANDARD MANUAL, in the US, refers to a standard rim (or “AppliedRim” or “Recommended Rim”) defined in TRA (THE TIRE and RIMASSOCIATION INC.) YEAR BOOK, etc. In addition, the “no load state where a predetermined internal pressure is applied” refers to a no load (no load applied) state where an internal pressure (maximum air pressure) corresponding to the tire maximum load capacity of a standard such as JATMA is applied to a tire of an applicable size. Point to.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which has favorable side cut-proof property with respect to the side cut resulting from the slipping down from an obstacle can be provided.

FIG. 1A is a cross-sectional view in the tire width direction of a tire half portion shown in an unloaded state in which an example of a pneumatic tire according to the present invention is assembled to an application rim and a predetermined internal pressure is applied. FIG. 2 is an enlarged view around the low modulus portion of FIG. FIG. 2 (a) is a cross-sectional view in the tire width direction of a tire half portion shown in an unloaded state in which another example of a pneumatic tire according to the present invention is assembled to an applied rim and a predetermined internal pressure is applied. ) Is an enlarged view around the low modulus portion of FIG. It is a figure which shows the state before the obstacle riding of the vehicle with which the pneumatic tire was mounted | worn. It is a tire width direction sectional view of the tire when a vehicle equipped with an example of a pneumatic tire according to the present invention slides down from the obstacle in the tire width direction. It is sectional drawing of the tire width direction of this tire when the vehicle equipped with the conventional tire slides down in the tire width direction from the obstacle. It is a figure which shows the modification of the shape of a low modulus part.

Hereinafter, the pneumatic tire of the present invention will be described in detail with reference to the drawings.
As shown in FIG. 1, the pneumatic tire 1 according to an embodiment of the present invention includes a tread portion 2, a pair of bead portions 3, a pair of sidewall portions 4, and a carcass 5. Here, the carcass 5 extends in a toroidal shape between the bead cores 6 in each bead part from the tread part 2 via the pair of sidewall parts 4, and in this example, two carcass plies 50a and 50b. Consists of. A belt 7 composed of three belt layers 70a, 70b, and 70c is disposed on the outer side in the tire radial direction of the crown portion of the carcass 5, and a tread rubber 11 is disposed further on the outer side in the tire radial direction of the belt 7. Yes. The structure of the bead portion, the carcass, the belt layer, and the like is an example, and the present invention is not limited to this.

In the pneumatic tire 1, the sidewall portion 4 includes a sidewall rubber 9 and a low modulus elastic body 10 having a modulus lower than that of the sidewall rubber 9.
Here, the pneumatic tire 1 is assembled to an applied rim, and the carcass tire radial direction outermost end A is extended from the tire radial direction innermost end B of the carcass within a cross section in the tire width direction in which a predetermined internal pressure is applied. The distance in the tire radial direction up to is the carcass height CH. At this time, the low modulus portion 8 made of the low modulus elastic body 10 is positioned within a distance of 0.3 CH from the outermost end A in the tire radial direction of the carcass of the sidewall portion 4 to the inner side in the tire radial direction.

  At least a part of the surface of the low modulus part 8 forms a part of the outer surface of the sidewall part 4. In this example, the low modulus portion 8 is provided continuously in the tire circumferential direction of the pneumatic tire 1.

As shown in FIG. 5, in the conventional pneumatic tire 1 ″, due to the difference in rigidity between the tread portion 2 ″ and the sidewall portion 4 ″ when sliding in the tire width direction from the obstacle 12 such as a curbstone, The sidewall portion 4 ″ is pulled inward in the tire width direction. Specifically, the more rigid tread portion 2 ″ moves inward in the tire width direction with almost no deformation due to the pressure load by the corner portion of the obstacle 12, while the rigidity is lower than the tread portion 2 ″. The easily deformable sidewall portion 4 ″ is pulled by the end portion on the inner side in the tire radial direction of the tread portion 2 ″ moved inward in the tire width direction. As a result, when the vehicle 12 slides in the tire width direction from the obstacle 12 such as a curbstone, the sidewall portion 4 ″ that is pulled by the tread portion 2 ″ and moved inward in the tire width direction is likely to come into contact with the corner portion of the obstacle 12. The side wall 4 ″ was likely to be cut.
On the other hand, in the pneumatic tire 1 of the present invention, low modulus elasticity having a modulus lower than that of the sidewall rubber 9 within a distance of 0.3 CH from the outermost end A in the tire radial direction of the carcass to the inner side in the tire radial direction. By positioning the low modulus portion 8 made of the body 10, as shown in FIG. 4, the tread portion 2 can be easily deformed (deformed toward the sidewall portion 4) by the pressure load from the corner portion of the obstacle 12. Yes. Therefore, compared with the case where the low modulus portion 8 is not provided, the tread portion 2 is greatly deformed toward the sidewall portion 4 and enters between the sidewall portion 4 and the corner portion of the obstacle 12. Contact between the portion 4 and the corner of the obstacle 12 is reduced. Therefore, the side wall portion 4 is less likely to be cut, and good side cut resistance can be obtained with respect to the side cut caused by the sliding off from the obstacle 12.
Moreover, in the pneumatic tire 1 of this invention, compared with the case where a thick layer is provided in the surface of the sidewall part 4, for example, a weight is not increased. Furthermore, since the low modulus elastic body 10 is located in the side wall rubber 9, for example, the side wall constituting the wall surface of the concave portion compared to a pneumatic tire in which only the concave portion is provided in the side wall portion 4. Ozone cracks can be prevented from occurring in the rubber 9.

Here, the 100% modulus of the low modulus elastic body 10 is preferably 0.68 to 0.84 times the 100% modulus of the sidewall rubber 9. When the value of the 100% modulus of the low modulus elastic body 10 is within such a range, the rigidity of the sidewall portion 4 is further reduced in the low modulus portion 8, and the pneumatic tire 1 is moved from the obstacle 12 to the tire width direction. The deformation of the tread portion 2 when sliding down is promoted, the tread portion 2 can easily enter between the sidewall portion 4 and the corner of the obstacle 12, and the corner portion of the sidewall portion 4 and the obstacle 12 is facilitated. Can be further reduced, and the side cut resistance can be further improved. When the difference between the 100% modulus of the low modulus elastic body 10 and the 100% modulus of the sidewall rubber 9 is too small, that is, the difference between the 100% modulus of the low modulus elastic body 10 and the 100% modulus of the sidewall rubber 9 is too large. If there is not, a portion having low local rigidity cannot be formed in the sidewall portion 4, and the deformation of the tread portion 2 toward the sidewall portion 4 may not be sufficiently promoted. On the other hand, when the difference between the 100% modulus of the low modulus elastic body 10 and the 100% modulus of the sidewall rubber 9 is too large, that is, when the 100% modulus of the low modulus elastic body 10 is too low with respect to the sidewall rubber 9. Further, the rigidity of the sidewall portion 4 becomes too low at the low modulus portion 8, and the tire performance may be lowered, for example, the rolling resistance during normal running increases. Furthermore, the difference in 100% modulus between the low modulus elastic body 10 and the sidewall rubber 9 is preferably 0.3 MPa or more and 0.7 MPa or less, for example.
The 100% modulus of the low modulus elastic body 10 is, for example, 1.30 MPa or more and less than 1.44 MPa. When the value of the 100% modulus of the low modulus elastic body 10 is within the above range, better side cut resistance can be obtained in the same manner as described above.

  Examples of the low modulus elastic body 10 include rubber and urethane. The low modulus elastic body 10 is preferably rubber. When the low modulus elastic body 10 is rubber, the rubber and the sidewall rubber 9 can be favorably bonded, and the adhesion between the members can be improved. When the low modulus elastic body 10 is rubber, an anti-aging agent can be blended in the rubber to prevent the deterioration of the low modulus portion 8. In addition, the tire can be easily manufactured as compared with the case where other materials are used.

  As shown in FIG. 2, the low modulus portion 8 made of the low modulus elastic body 10 is provided within a distance range of 0.1 to 0.2 CH from the outermost end A in the tire radial direction of the carcass to the inner side in the tire radial direction. Is preferred. By providing the low modulus portion 8 in such a range, the region of the sidewall portion 4 that may come into contact with the corner portion of the obstacle 12 is further reduced, and the side cut resistance can be further improved. .

In the pneumatic tire 1, as shown in FIG. 1, it is preferable that the low modulus portion 8 and the carcass 5 are separated from each other in the tire width direction cross section. If the low modulus portion 8 and the carcass 5 are separated from each other, it is possible to prevent a failure of the tire due to poor adhesion between the sidewall rubber 9 and the carcass 5 (in this example, the carcass ply 50b). Specifically, for example, the sidewall rubber 9 is interposed between the low modulus portion 8 and the carcass 5, and separation occurs between the carcass 5 and the low modulus portion 8 due to pressure load at the time of tire rolling. This can prevent this and ensure the durability of the pneumatic tire 1.
The separation distance d between the low modulus portion 8 and the carcass 5 is, for example, 0.5 to 2.5 mm. Here, the separation distance d between the low modulus portion 8 and the carcass 5 refers to the distance to the low modulus portion 8 measured along the direction orthogonal to the carcass 5. When the separation distance d between the low modulus portion 8 and the carcass 5 is too large, the depth of the low modulus portion 8 becomes shallow and the deformation of the tread portion 2 toward the sidewall portion 4 is efficiently promoted. When the separation distance d is too small, adhesion failure may occur between the sidewall portion 4 and the carcass 5.

  The depth of the low modulus portion 8 is, for example, 1.5 to 8.0 times the separation distance d. When the depth of the low modulus portion 8 is significantly larger than the separation distance d between the low modulus portion 8 and the carcass 5, the separation distance d between the low modulus portion 8 and the carcass 5 becomes too short, and the sidewall There is a risk of poor adhesion between the portion 4 and the carcass 5. When the depth of the low modulus portion 8 is significantly smaller than the separation distance d, it is difficult to efficiently promote the deformation of the tread portion 2 toward the sidewall portion 4. The depth of the low modulus portion 8 is, for example, 3.5 to 4.0 mm. Here, the depth of the low modulus portion 8 is the distance from the surface of the low modulus portion 8 to the farthest position in the low modulus portion 8.

  From the viewpoint of promoting the deformation of the tread portion 2 toward the sidewall portion 4 by locally reducing the rigidity of the sidewall portion 4 in the dimension w of the opening of the low modulus portion 8 in the tire width direction cross section. For example, it is 3.0-5.0 mm. Here, the dimension w of the opening of the low modulus part 8 refers to the dimension of the low modulus part 8 along the direction orthogonal to the center line CL of the low modulus part. If the dimension w of the low modulus portion 8 is too small, it is difficult to efficiently promote the deformation of the tread portion 2 toward the sidewall portion 4, and if the dimension w of the low modulus portion 8 is too large, the sidewall portion There is a possibility that the rigidity of 4 falls in a wider range than necessary.

Further, the pneumatic tire 1 has an angle α formed between the low modulus portion center line CL and the carcass tangent line TL passing through the intersection D of the low modulus portion center line CL and the carcass 5 in the tire width direction cross section. 70 to 90 ° is preferable. 1 and 2, the tangent line TL of the carcass passing through the intersection D between the low modulus portion center line CL and the carcass 5 is the low modulus portion center line CL and the carcass 5 (in this example, the carcass ply 50b). A tangent line of the carcass 5 passing through the intersection point D. When the low modulus portion center line CL and the tangent line TL of the carcass form an angle α in the above range, the pressure applied to the tread portion 2 when the pneumatic tire 1 slides from the obstacle 12 in the tire width direction is reduced. Since the modulus elastic body 10 can be efficiently deformed and the deformation of the tread portion 2 toward the sidewall portion 4 can be efficiently promoted, the side cut resistance can be efficiently improved. If the angle α formed by the low modulus portion center line CL and the tangent line TL is too small, the low modulus elastic body 10 cannot be efficiently deformed when the pneumatic tire 1 slides from the obstacle 12 in the tire width direction. There is a possibility that the deformation of the tread portion 2 toward the sidewall portion 4 is efficiently promoted and the side cut resistance cannot be improved efficiently.
The angle α formed by the low modulus portion center line CL and the tangent TL is more preferably 80 to 90 °, and most preferably 90 °.

The shape of the low modulus portion 8 can be changed as appropriate.
For example, as in a pneumatic tire 1 according to another embodiment of the present invention shown in FIG. 2, in the cross section in the tire width direction, the dimension of the low modulus portion is from the outer surface of the sidewall portion to the low modulus portion. It is preferable to gradually decrease in the depth direction. When the low modulus portion 8 has such a shape, the outer side in the tire width direction is more greatly deformed than the inner side in the tire width direction of the low modulus portion 8, and the deformation of the tread portion 2 toward the sidewall portion 4 is efficiently performed. The side cut resistance can be improved efficiently.

In the tire width direction cross section, it is preferable that angles β and β ′ formed by the side walls 80a and 80b of the low modulus portion and the low modulus portion center line CL are 0 to 50 °, respectively. When the angles β and β ′ formed by the side walls 80a and 80b of the low modulus part and the low modulus part center line CL are too small, the deformation of the tread part 2 toward the side wall part 4 cannot be increased, and It may be difficult to improve the side cut efficiency efficiently. On the other hand, when the angles β and β ′ are too large, the deformation of the tread portion 2 toward the sidewall portion 4 becomes too large, and the region of the sidewall portion 4 located on the inner side in the tire radial direction than the low modulus portion 8 is formed. On the other hand, it may be easy to contact an obstacle and it may be difficult to improve the side cut resistance. Furthermore, the rigidity of the sidewall portion 4 of the pneumatic tire 1 may be lowered in a wider range than necessary. From the viewpoint of efficiently accelerating the deformation of the tread portion 2 toward the sidewall portion 4, the side wall surfaces 80 a and 80 b of the low modulus portion 8 have a low modulus portion center line CL within the tire width direction cross section. It is preferable that both sides have the same angle as the center, that is, the angle β and the angle β ′ are equal. In the tire width direction cross-sectional view, when the low modulus portion side wall surfaces 80a and 80b are bent, the angle formed between the amplitude center line of the side wall surfaces 80a and 80b and the low modulus portion center line CL is β , Β ′.
In the cross section in the tire width direction, the angles β and β ′ formed by the side walls 80a and 80b of the low modulus portion and the low modulus portion center line CL are more preferably 0 to 45 °, and most preferably 0 to 30 °. is there.

  The shape of the low modulus part 8 is not limited to what was mentioned above, A change can be added suitably. For example, as shown in FIG. 6, either or both of the side wall surface and the bottom surface of the low modulus portion 8 in the tire width direction cross section may be curved or linear.

  In this example, the low modulus portion 8 is provided continuously in the tire circumferential direction, but the low modulus portion 8 may be provided intermittently in the tire circumferential direction. In the case where the low modulus portion 8 is intermittently provided in the circumferential direction, for example, it is preferably provided in 60 to 80% of the tire circumferential direction. A plurality of low modulus portions 8 may be provided along the tire radial direction.

  When the rotation direction of the tire is specified, the low modulus portion 8 only needs to be provided at least on the outer side of the vehicle when attached to the vehicle. As shown in FIG. 3, the boarding of the obstacle 12 on the curb or the like usually occurs on the outside of the vehicle. Therefore, if the low modulus portion 8 is provided at least on the outer side of the vehicle, the obstacle 12 The cut of the side wall part 4 at the time of sliding down can be reduced.

  As mentioned above, although the example of the pneumatic tire of this invention was demonstrated with reference to drawings, the pneumatic tire of this invention is not limited to the said example, A change is suitably added to the pneumatic tire of this invention. be able to.

Examples of the present invention will be described below, but the present invention is not limited thereto.
Example and comparative tires in which a low modulus portion 8 made of rubber having a predetermined 100% modulus value is provided at a predetermined depth at a predetermined position of the sidewall portion 4 shown in Table 1 below, and the sidewall portion 4 A conventional tire without a low modulus portion 8 was prototyped. The test tire size was 275 / 80R22.5. The position of the low modulus portion 8 shown in Table 1 is the center of the surface of the low modulus portion 8 and the center of the bottom portion of the low modulus portion 8 forming a part of the outer surface of the sidewall portion in the tire cross section. It is assumed that the point where the connecting straight line intersects the carcass is located at a predetermined position shown in Table 1. In the test tire, the maximum depth of the low modulus portion 8 at which the low modulus portion 8 does not contact the carcass ply is 4 mm.
1. Side cut resistance test The prototype tire, the comparative tire, and the conventional tire were mounted on a rim having a width of 8.25, applied with an internal pressure of 900 kPa, and mounted on all shafts of the test vehicle 2-D4. The cut depth after sliding off was measured and shown in Table 1. In Table 1, the cut depth of the conventional tire is shown as 10 and is indicated as an index. The smaller the cut depth value, the better the side cut resistance.
2. Rolling Resistance Test Subsequently, a force type rolling resistance measuring tester compliant with ISO 28580 was used with a normal internal pressure of 900 kPa and a normal load of 2750 kgf applied to the example tire, the comparative example tire, and the conventional tire. The vehicle was run at a speed of 80 km / h, and the rolling resistance was measured. The results are shown in Table 1 as an index with the rolling resistance of the tire of Conventional Example 1 being 100, and the smaller the value, the better the rolling resistance.

DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Tread part, 3 ... Bead part, 4 ... Side wall part, 5 ... Carcass, 6 ... Bead core, 7 ... Belt, 8 ... Low modulus part, 9 ... Side wall rubber, 10 ... Low modulus Elastic body, 11 ... tread rubber, 12 ... obstacle, 50a, 50b ... carcass ply, 70a, 70b, 70c ... belt layer, 80a, 80b ... side wall surface of low modulus part in tire width direction cross section, A ... carcass Tire outermost end in radial direction of tire, B ... innermost end of tire in radial direction of carcass, D ... intersection of low modulus center line and carcass, CL ... center line of low modulus, EQ ... tire equatorial plane, TL ... low modulus The tangent line of the carcass passing through the intersection D between the center line and the carcass

Claims (7)

A pneumatic tire comprising a tread portion, a pair of sidewall portions, a pair of bead portions, and a carcass made of at least one carcass ply extending in a toroid shape between bead cores in each bead portion,
The sidewall portion includes a sidewall rubber and a low modulus elastic body having a lower modulus than the sidewall rubber,
In the cross section in the tire width direction, when the tire radial direction distance from the innermost end in the tire radial direction of the carcass to the outermost end in the tire radial direction of the carcass is defined as the carcass height CH, A low modulus portion made of the low modulus elastic body is located within a distance of 0.3 CH from the outermost end in the tire radial direction to the inner side in the tire radial direction,
A pneumatic tire characterized in that at least part of the surface of the low modulus part forms part of the outer surface of the sidewall part.   2. The pneumatic tire according to claim 1, wherein a 100% modulus of the low modulus elastic body is 0.68 times or more and 0.84 times or less of a 100% modulus of the sidewall rubber.   The pneumatic tire according to claim 1 or 2, wherein a 100% modulus of the low modulus elastic body is 1.30 MPa or more and less than 1.44 MPa.   The pneumatic tire according to claim 1, wherein the low modulus elastic body is rubber.   The pneumatic tire according to any one of claims 1 to 4, wherein the low modulus portion and the carcass are spaced apart from each other in a cross section in the tire width direction.   Within the cross section in the tire width direction, it extends in the depth direction of the low modulus portion, passes through the center of the bottom surface of the low modulus portion, and passes through the intersection of the low modulus portion center line and the carcass. The pneumatic tire according to claim 1, wherein the tangent line of the carcass forms an angle of 70 to 90 °.   The dimension of the said low modulus part is gradually reduced toward the depth direction of the said low modulus part from the outer surface of the said side wall part in a tire width direction cross section. The pneumatic tire according to item 1.

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