JP6530184B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire.

  In general, the profile of the outer peripheral surface of the tread portion of the pneumatic tire in an inflated state is an arc shape (round shape) in which the center of curvature is positioned on the inner side in the tire radial direction with respect to the pneumatic tire. On the other hand, the profile of the outer peripheral surface of the tread portion of the pneumatic tire disclosed in Patent Document 1 has an arc shape (reverse curve shape) in which the center of curvature is located on the outer side in the tire radial direction with respect to the pneumatic tire. In the pneumatic tire disclosed in Patent Document 2, a groove extending along the circumferential direction of the tire is formed in a buttress portion extending from an end portion in the tire width direction of the tread portion toward the side portion.

  When the profile of the outer peripheral surface of the tread portion in the inflated state is a rounded shape, the tire outer diameter is maximum at the central portion of the tread portion, so the contact pressure becomes high at the central portion of the tread portion when the vehicle is traveling. Uneven wear is likely to occur at the center of the part.

  If the profile of the outer peripheral surface of the tread portion is a reverse radius shape, the contact pressure at the central portion of the tread portion can be reduced, but the contact pressure at the end portion in the tire width direction of the tread portion becomes high. In other words, even if the profile of the outer peripheral surface of the tread portion is simply the reverse radius shape as disclosed in Patent Document 1, the contact pressure distribution can not be made uniform. Moreover, in patent document 2, it does not consider in particular about equalization | homogenization of ground pressure distribution.

Japanese Patent Application Laid-Open No. 10-329511 JP, 2002-29217, A

  An object of the present invention is to make contact pressure distribution uniform in a pneumatic tire.

  In the present specification, the "badless portion" refers to the region from the tire width direction end of the tread portion of the pneumatic tire to the tire maximum width portion. Moreover, a "shoulder part" means the area | region where the tread part is connected with respect to the side part, and the tire width direction edge part of a tread part is included. Furthermore, the shoulder portion includes the area of the end portion in the tire width direction of the tread portion in the padless portion.

In the present invention, in the non-inflated state, the outer peripheral surface of the tread portion has a reverse radius shape in which the outer diameter at the end portion is larger than the outer diameter at the central portion, and the tire maximum width portion from the end portion of the tread portion And a main groove formed in the tread portion, the groove being the end portion of the tread portion in the tire width direction It is a pneumatic tire which extends to an overlapping position and is formed on the tire inner diameter side with respect to the bottom wall of the main groove .

  By forming the outer peripheral surface of the tread portion in a reverse radius shape, the outer peripheral surface of the tread portion can be made nearly flat when inflated. Therefore, it is possible to suppress an increase in contact pressure at the central portion of the tread portion and to prevent uneven wear of this portion. By providing the groove extending in the tire radial direction in the padless portion, it is possible to suppress an excessive rise in the contact pressure at the end portion of the tread portion due to the outer circumferential surface of the tread portion being in the reverse radius shape. That is, by forming the outer peripheral surface of the tread portion in a reverse radius shape and providing the groove extending in the tire radial direction in the padless portion, the contact pressure distribution can be made uniform and partial wear at the central portion of the tread portion can be suppressed.

In order to effectively suppress the contact pressure increase at the central portion of the tread portion at the time of inflation, the distance from the tire central axis to the central portion in the tire radial direction and the tire diameter from the tire central axis to the end portion It is preferable that the difference with the distance of the direction is 0.05 times or more and 0.2 times or less of the rubber thickness of the said tread part in the said center part.

  The groove may be provided continuously in the tire circumferential direction or may be provided intermittently in the tire circumferential direction.

  In order to effectively suppress the contact pressure increase at the end portion of the tread portion, the cross-sectional area of the groove in the tire radial direction cross section of the groove is the tire width direction outer side from the central portion of the tread portion in the tire radial direction cross section of the tread portion It is preferable that the cross-sectional area of the area on the end side is 0.8 or more times and 1.2 or less times the virtual line extending in

  By forming the tread portion in a reverse radius shape and providing a groove extending in the circumferential direction of the tire in the padless portion, the contact pressure distribution can be made uniform and uneven wear in the central portion of the tread portion can be suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS The fragmentary sectional view of the meridian direction of the pneumatic tire concerning 1st Embodiment of this invention. The fragmentary sectional view of the meridian direction of the pneumatic tire concerning a 2nd embodiment of the present invention.

  Hereinafter, an embodiment according to the present invention will be described according to the attached drawings. The following description is merely exemplary in nature and is not intended to limit the present invention, its applications, or its applications. The drawings are schematic, and proportions of dimensions may be different from actual ones.

First Embodiment
A rubber pneumatic tire (hereinafter simply referred to as a tire) 1 according to a first embodiment of the present invention shown in FIG. 1 comprises a tread portion 2, a pair of side portions 3 and a pair of bead portions (not shown). Prepare. Each bead portion is provided at the tire radial inner end (the end opposite to the tread portion 2) of the side portion 3. A carcass 4 is provided between the pair of bead portions. In the present embodiment, the carcass 4 includes one carcass ply 5. An inner liner 6 is provided on the innermost circumferential surface of the tire 1. Further, in the tread portion 2, a belt 7 is provided on the tire radial direction outer side of the carcass 4. In the present embodiment, the belt 7 comprises three belt plies 11, 12, 13. A reinforcing ply 14 is further disposed outside the outermost belt ply 13.

  In the following description, a region from the end portion 2 a in the tire width direction of the tread portion 2 to the tire maximum width portion of the side portion 3 is referred to as a baddless portion 15. Further, a region in which the tread portion 2 is connected to the side portion 3 is referred to as a shoulder portion 16. The shoulder portion 16 includes an end 2 a of the tread portion 2. Further, the shoulder portion 16 includes a region on the end portion 2 a side of the tread portion 2 in the padless portion 15.

The cross section in the tire radial direction of the outer peripheral surface 2 b of the tread portion 2 has a reverse radius shape in which the outer diameter R _e at the end portion 2 a is larger than the outer diameter R _{c at} the central portion 2 c in the tire width direction. In other words, the cross-sectional shape of the outer peripheral surface 2 b of the tread portion 2 in the tire radial direction cross section is an arc shape in which the center of curvature is located outside the tire 1 in the tire radial direction. In the present embodiment, the curvature of the outer peripheral surface 2b of the tread portion 2 is substantially uniform from the central portion 2c to the end portion 2a. However, the curvature of the outer peripheral surface 2b of the tread portion 2 may have a distribution in the tire width direction.

  A groove 17 extending along the circumferential direction of the tire is provided in a portion corresponding to the shoulder portion 16 in the padless portion 15. Specifically, in the groove 17, the tire height direction H (the tread portion 2 and the bead portion) between the bottom wall 18 a of the main groove 18 formed in the tread portion 2 and the belt 7 (the reinforcing ply 14) Direction) is provided. The grooves 17 in the present embodiment are continuously provided in the tire circumferential direction and have an endless annular shape when viewed from the tire width direction. However, the grooves 17 may be provided intermittently in the tire circumferential direction. Further, the direction in which the heat dissipation grooves 17 extend as seen from the tire width direction does not have to completely coincide with the tire circumferential direction, and may be substantially along the tire circumferential direction.

  The groove wall 17a of the groove 17 in the present embodiment includes side walls 17c and 17d extending inward in the tire radial direction from the opening 17b side of the groove 17, and a back wall 17e opposed to the opening 17b. In the present embodiment, the side walls 17 c and 17 d are arc-shaped, and the distance between the side walls 17 c and 17 d is substantially constant in the depth direction of the groove 17. Further, the back wall 17 e is a curved surface having a circular cross section in the tire radial direction. Therefore, the cross-sectional shape in the tire radial direction cross section of the groove 17 in the present embodiment is substantially U-shaped. The cross-sectional shape of the groove 17 may be, for example, a circular shape, an oval shape, or a polygonal shape such as a triangle, but does not have sharp edges in order to prevent concentration of stress and strain and generation of cracks resulting therefrom. It is preferable that it is a shape.

  It is assumed that the cross section in the tire radial direction of the outer peripheral surface 2b of the tread portion 2 is not a reverse radius shape, but an arc shape (a radius shape) or a flat shape whose center of curvature is located inside the tire 1 in the tire radial direction. Under this assumption, the cross section in the tire radial direction of the outer peripheral surface 2b of the tread portion 2 at the time of inflation becomes a rounded shape, and the outer diameter of the tire 1 becomes maximum at the central portion 2c. The pressure is high and uneven wear is likely to occur in this part.

  On the other hand, in the present embodiment, by forming the cross section in the tire radial direction of the outer peripheral surface 2b of the tread portion 2 in a reverse radius shape, the outer peripheral surface of the tread portion 2 can be made nearly flat. Therefore, the contact pressure increase at the central portion 2c of the tread portion 2 can be suppressed, and partial wear of this portion can be prevented.

  The contact pressure at the end portion 2a of the tread portion 2 becomes excessively high if the outer circumferential surface 2b of the tread portion 2 is merely formed in the reverse radius shape. However, in the present embodiment, by providing the groove 17 extending in the tire radial direction in the shoulder portion 16, the contact pressure at the end portion 2 a of the tread portion 2 by making the outer circumferential surface 2 b of the tread portion 2 into a reverse radius shape. Can prevent excessive rise in Specifically, at the portion where the groove 17 of the shoulder portion 16 is provided, the rubber volume is reduced as compared with the other portions, so that the rigidity can be reduced. By appropriately adjusting the rigidity of the shoulder portion 16 by the cross-sectional area and the arrangement of the groove 17, it is possible to suppress an excessive rise in the contact pressure at the end portion 2 a of the tread portion 2.

  As described above, in the pneumatic tire 1 of the present embodiment, the contact pressure distribution is obtained by forming the outer circumferential surface 2 b of the tread portion 2 in a reverse radius shape and providing the groove 17 extending in the tire radial direction in the shoulder portion 16. Can be made uniform and uneven wear at the central portion 2c of the tread portion 2 can be suppressed.

  In order to effectively suppress an increase in the contact pressure of the central portion 2c of the tread portion 2 at the time of inflation, it is preferable that the curvature of the reverse curve has a certain value. For example, the distance P between the central portion 2c of the tread portion 2 and the end portion 2a in the tire height direction H is the rubber thickness h of the tread portion 2 at the central portion 2c (from the reinforcing ply 14 to the outer peripheral surface 2b of the tread portion 2 It is preferable that the distance in the tire radial direction be 0.05 times or more and 0.2 times or less. That is, in order to effectively suppress the contact pressure increase of the central portion 2c, it is preferable that the relationship of the following equation (1) be established between the distance P and the rubber thickness h.

[Equation 1]
0.05 h ≦ P ≦ 0.2 h (1)

  If the cross-sectional area S in the tire radial direction cross section of the groove 17 is excessively small, an excessive rise in the contact pressure at the end portion 2 a of the tread portion 2 can not be suppressed. On the other hand, if the cross-sectional area S of the groove 17 is excessively large, the strength of the shoulder portion 16 is reduced, and for example, the shoulder portion 16 is chipped at a portion on the tread portion 2 side in the tire height direction H than the groove 17 . Assuming that in the tire radial direction cross section of the tread portion 2 a cross sectional area T of a region closer to the end 2 a than a virtual line L extending from the central portion 2 c of the tread 2 to the outer side in the tire width direction The area T is preferably 0.8 times or more and 1.2 times or less. That is, in order to suppress an excessive rise in the contact pressure at the end portion 2a of the tread portion 2 while securing the necessary rigidity of the shoulder portion 16, the relationship of the following formula (2) is satisfied between the cross sectional areas S and T: It is preferable to hold.

[Equation 2]
0.8T ≦ S ≦ 1.2T (2)

  Next, the specific arrangement of the grooves 17 will be described.

  The position of the opening 17b of the groove 17 on the outermost side in the tire radial direction (most tread 2 side in the tire height direction H), in other words, the position where the side wall 17c of the groove wall 17a is connected to the outer peripheral surface of the shoulder portion 16, is The upper end 17 f of the groove 17 is called. Further, the innermost position (the most bead side in the tire height direction H) of the opening 17b of the groove 17 in the tire radial direction, in other words, the position where the side wall 17d of the groove wall 17a is connected to the outer peripheral surface of the shoulder portion 16 , And the lower end 17g of the groove 17. The distances A and B in the tire height direction H from the end 2a of the tread portion 2 to the upper end 17f and the lower end 17g are as follows with respect to the maximum depth g of the main groove 18 formed in the tread portion 2: It is set to.

  First, the distance A is set to at least 1.0 times and not more than 1.5 times the depth g. That is, there is the following relationship between the distance A and the depth g.

[Equation 3]
g ≦ A ≦ 1.5 g (3)

  Next, the distance B is set to 1.3 times or more and 2.5 times or less of the depth g. That is, the following relationship exists between the distance B and the depth g.

[Equation 4]
1.3 g ≦ B ≦ 2.5 g (4)

  The depth C of the groove 17 which is the maximum distance in the tire width direction between the opening 17b of the groove 17 and the back wall 17e is the distance W in the tire width direction between the central portion 2c and the end portion 2a of the tread portion 2. On the other hand, it is set in the range of 0.08 times or more and 0.2 times or less. That is, there is the following relationship between the depth C and the distance W:

[Equation 5]
0.08 W ≦ C ≦ 0.2 W (5)

  The inclination angle θ of the groove 17 which is an angle formed by the direction in which the groove 17 extends with the tire width direction is set in the range of 0 ° to 60 °. In other words, the following relationship exists for the inclination angle θ.

[Equation 6]
0 ° ≦ θ ≦ 60 ° (6)

  The shortest distance D from the end portions 11a, 12a, 13a of the belt plies 11, 12, 13 to the groove 17 (represented conceptually by a broken circle in FIG. 1) is the maximum value of the rubber thickness at the shoulder portion 16 (maximum rubber Thickness is set to 30% or more of E. That is, the following relationship exists between the shortest distance D and the maximum rubber thickness E.

[Equation 7]
D 0.3 0.3 E (7)

  With respect to the groove 17, the distance B of the lower end 17g, the depth C, and the inclination angle θ are set as in equations (4), (5) and (6), respectively, and the step area S is further By setting as in the above, it is possible to more reliably suppress an excessive rise in the contact pressure at the end 2 a of the tread portion 2 while securing the necessary rigidity of the shoulder portion 16. Further, by setting the distance A of the upper end 17f of the groove 17 as in the equation (3), the amount of rubber necessary for securing the rigidity exists between the outer peripheral surface 2b of the tread portion 2 and the groove 17. Chipping of the shoulder portion 16 at a portion on the tread portion 2 side in the tire height direction H relative to the groove 17 can be prevented. Furthermore, by setting the shortest distance D from the end portions 11a to 13a of the belt plies 11 to 13 to the groove 17 as in equation (7), the end portions 11a to 11 of the belt plies 11 to 13 due to manufacturing tolerances The protrusion of the groove 13 a into the groove 17 can be prevented.

Second Embodiment
In the tire 1 according to the second embodiment of the present invention shown in FIG. 2, the recess 21 and the protrusion 22 are provided in the entire groove wall 17a of the groove 17, that is, in the entire side walls 17c and 17d and the back wall 17e.

  Since the amount of rubber is large in the shoulder portion 16, particularly near the end portions 11 a to 13 a of the belt plies 11 to 13, the amount of heat generation during traveling is large compared to the other portions of the tire 1. In addition, around the end portions 11a to 13a of the belt plies 11 to 13, distortion is likely to occur repeatedly as the tire rolls. However, since the generated heat is dissipated through the grooves 17, it is possible to prevent the occurrence of a thermal deterioration near the end portions 11a to 13a of the belt plies 11 to 13 and a failure such as separation caused thereby. By providing the recess 21 and the protrusion 22, the surface area of the groove wall 17 a of the groove 17, that is, the heat radiation area is expanded, so that the heat generation in the shoulder portion 16 can be suppressed more effectively.

  Other configurations and operations of the second embodiment are the same as those of the first embodiment.

1 tire
Reference Signs List 2 tread portion 2a end portion 2b outer peripheral surface 2c central portion 3 side portion 4 carcass 5 carcass ply 6 inner liner 7 belt 11, 12, 13 belt ply 14 reinforcement ply 15 baddless portion 16 shoulder portion 17 groove 17 a groove wall 17 b opening 17 c, 17d side wall 17e back wall 17f upper end 17g lower end 18 main groove 18a bottom wall 21 recessed portion 22 convex portion A, B, W distance C depth D shortest distance g depth h rubber thickness P distance S, T sectional area θ inclination angle

Claims (5)

In the non-inflated state, the outer peripheral surface of the tread portion has a reverse radius shape in which the outer diameter at the end portion is larger than the outer diameter at the central portion;
A groove which is a region from the end of the tread portion to the tire maximum width portion includes a groove provided along a tire circumferential direction and a main groove formed in the tread portion .
The pneumatic tire extends to a position overlapping the end of the tread portion in the tire width direction , and is formed on the tire inner diameter side with respect to a bottom wall of the main groove .   The difference between the distance in the tire radial direction from the tire central axis to the central portion and the distance in the tire radial direction from the tire central axis to the end portion is 0. 0 of the rubber thickness of the tread portion at the central portion. The pneumatic tire according to claim 1, which is at least 05 times and at most 0.2 times.   The pneumatic tire according to claim 1, wherein the groove is provided continuously in the tire circumferential direction.   The pneumatic tire according to claim 1, wherein the groove is provided intermittently in the tire circumferential direction.   The cross-sectional area of the tire radial direction cross section of the groove is 0. 0 of the cross-sectional area of the end side region of the imaginary line extending outward from the central portion of the tread portion in the tire radial direction cross section of the tread portion. The pneumatic tire according to any one of claims 1 to 4, which is 8 times or more and 1.2 times or less.

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