JP2016117329A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformize contact pressure distribution in a pneumatic tire.SOLUTION: An outer peripheral surface 2b of a tread part 2 of a pneumatic tire 1 has an inverted round shape in which an outside diameter Rof an end 2a is larger than an outside diameter Rof a central part 2c. A buttress part 15, which is a region from the end 2a of the tread part 2 to a tire-maximum-width part, is provided with a groove 17 that is extended along a circumferential direction of the tire.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  Generally, the profile of the outer peripheral surface of the tread portion of the pneumatic tire in the inflated state is an arc shape (R shape) in which the center of curvature is located 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 radius 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 Literature 2, a groove extending along the tire circumferential direction is formed in a buttress portion extending from an end portion of the tread portion in the tire width direction toward the side portion.

  If the profile of the outer peripheral surface of the tread part in an inflated state is round, the tire outer diameter becomes maximum at the center part of the tread part. Partial wear tends to occur at the center of the part.

  When the profile of the outer peripheral surface of the tread portion is an inverted round shape, the contact pressure at the center portion of the tread portion can be reduced, but the contact pressure at the end portion of the tread portion in the tire width direction is increased. That is, even if the profile of the outer peripheral surface of the tread portion is simply an inverted round shape as disclosed in Patent Document 1, the contact pressure distribution cannot be made uniform. Further, Patent Document 2 does not particularly examine the uniforming of the ground pressure distribution.

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

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

  In this specification, the “padless portion” refers to a region from the tire width direction end portion of the tread portion of the pneumatic tire to the tire maximum width portion. Further, the “shoulder portion” refers to a region where the tread portion is connected to the side portion, and includes an end portion in the tire width direction of the tread portion. Furthermore, a shoulder part contains the area | region of the tire width direction edge part side of a tread part among padless parts.

  In the present invention, the outer peripheral surface of the tread portion has an inverted round shape in which the outer diameter at the end portion is larger than the outer diameter at the center portion, and is a region from the end portion of the tread portion to the maximum tire width portion. It is a pneumatic tire provided with a groove provided in the tire circumferential direction.

  By making the outer peripheral surface of the tread portion have an inverted round shape, the outer peripheral surface of the tread portion can be made nearly flat during inflation. Therefore, it is possible to suppress an increase in contact pressure at the center portion of the tread portion, and to prevent uneven wear at this portion. Providing a groove extending along the tire radial direction in the padless portion can suppress an excessive increase in contact pressure at the end portion of the tread portion due to the outer peripheral surface of the tread portion having an inverted round shape. That is, by making the outer peripheral surface of the tread portion have an inverted round shape and providing a groove extending in the tire radial direction in the padless portion, the contact pressure distribution can be made uniform and uneven wear at the center portion of the tread portion can be suppressed.

  In order to effectively suppress the contact pressure increase at the center of the tread during inflation, the distance in the tire height direction from the center to the end of the tread is determined by the distance between the tread at the center. The thickness is preferably 0.05 times or more and 0.2 times or less of the rubber thickness.

  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 an increase in contact pressure at the end of the tread portion, the cross-sectional area of the tire in the tire radial direction cross section is the outer side in the tire width direction from the central portion of the tread portion in the tire radial cross section of the tread portion. It is preferable that it is 0.8 times or more and 1.2 times or less of the cross-sectional area of the region on the end side with respect to the imaginary line extending to.

  By providing the tread portion with an inverted round shape and providing a groove extending in the tire circumferential direction in the paddle portion, the contact pressure distribution can be made uniform and uneven wear at the center portion of the tread portion can be suppressed.

The fragmentary sectional view of the meridian direction of the pneumatic tire which concerns on 1st Embodiment of this invention. The fragmentary sectional view of the meridian direction of the pneumatic tire which concerns on 2nd Embodiment of this invention.

  Embodiments according to the present invention will be described below with reference to the accompanying drawings. The following description is merely illustrative in nature and is not intended to limit the present invention, its application, or its use. The drawings are schematic, and the ratio of each dimension may be different from the actual one.

(First embodiment)
A rubber pneumatic tire (hereinafter simply referred to as a tire) 1 according to the first embodiment of the present invention shown in FIG. 1 includes 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 an inner end portion of the side portion 3 in the tire radial direction (an end portion opposite to the tread portion 2). 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 peripheral surface of the tire 1. In the tread portion 2, a belt 7 is provided outside the carcass 4 in the tire radial direction. In the present embodiment, the belt 7 includes three belt plies 11, 12, and 13. A reinforcing ply 14 is further arranged outside the outermost belt ply 13.

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

Tire radial cross section of the outer peripheral surface 2b of the tread portion 2 has a reverse radius shape the outer diameter R _e is larger in the end portion 2a than the external diameter R _c in the tire width direction of the central portion 2c. In other words, the cross-sectional shape in the tire radial direction cross section of the outer peripheral surface 2 b of the tread portion 2 is an arc shape in which the center of curvature is located on the outer side in the tire radial direction with respect to the tire 1. 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 tire circumferential direction is provided in a portion corresponding to the shoulder portion 16 of the paddle portion 15. Specifically, the groove 17 has a tire height direction H (the tread portion 2 and the bead portion face each other) between the bottom wall 18a of the main groove 18 formed in the tread portion 2 and the belt 7 (reinforcement ply 14). Direction). The grooves 17 in the present embodiment are continuously provided in the tire circumferential direction and are endless annular when viewed from the tire width direction. However, the groove 17 may be provided intermittently in the tire circumferential direction. Further, the direction in which the heat radiating grooves 17 extend as viewed from the tire width direction does not have to be completely coincident 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 that extend inward in the tire radial direction from the opening 17b side of the groove 17, and a back wall 17e that faces the opening 17b. In the present embodiment, the side walls 17 c and 17 d have a circular arc shape, and the distance between the side walls 17 c and 17 d is substantially constant in the depth direction of the groove 17. The back wall 17e is a curved surface having a circular cross section in the tire radial direction. Therefore, the cross-sectional shape of the cross section in the tire radial direction of the groove 17 in the present embodiment is generally 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 a sharp edge in order to prevent the concentration of stress and strain and the occurrence of cracks resulting therefrom. The shape is preferred.

  Suppose that the tire radial direction cross section of the outer peripheral surface 2b of the tread portion 2 is not an inverted round shape but an arc shape (round shape) or a flat shape in which the center of curvature is located on the inner side in the tire radial direction with respect to the tire 1. Under this assumption, the tire radial cross section of the outer peripheral surface 2b of the tread portion 2 during inflation is rounded, and the outer diameter of the tire 1 is maximized at the central portion 2c. The pressure increases, and uneven wear tends to occur in this part.

  On the other hand, in the present embodiment, the outer circumferential surface of the outer circumferential surface 2b of the tread portion 2 is formed in an inverted round shape so that the outer circumferential surface of the tread portion 2 can be made nearly flat during inflation. Therefore, the rise in contact pressure at the central portion 2c of the tread portion 2 can be suppressed, and uneven wear at this portion can be prevented.

  If only the reverse round shape of the outer peripheral surface 2b of the tread portion 2 is used, the ground pressure at the end 2a of the tread portion 2 becomes excessively high. However, in the present embodiment, by providing the shoulder portion 16 with the groove 17 extending along the tire radial direction, the contact pressure at the end portion 2a of the tread portion 2 due to the outer peripheral surface 2b of the tread portion 2 having an inverted round shape. The excessive rise of can be suppressed. Specifically, in the portion where the groove 17 of the shoulder portion 16 is provided, the rubber volume is reduced as compared with other portions, so that the rigidity can be lowered. By appropriately adjusting the rigidity of the shoulder portion 16 according to the cross-sectional area and arrangement of the groove 17, it is possible to suppress an excessive increase in the contact pressure at the end portion 2 a of the tread portion 2.

  As described above, in the pneumatic tire 1 according to the present embodiment, the outer peripheral surface 2b of the tread portion 2 has an inverted round shape, and the shoulder portion 16 is provided with the grooves 17 extending along the tire radial direction, so that the contact pressure distribution is obtained. The uneven wear at the central portion 2c of the tread portion 2 can be suppressed.

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

[Equation 1]
0.05h ≦ P ≦ 0.2h (1)

  When the cross-sectional area S in the tire radial direction cross section of the groove 17 is excessively small, an excessive increase in the contact pressure at the end 2a of the tread portion 2 cannot be suppressed. On the other hand, when the cross-sectional area S of the groove 17 is excessively large, the strength of the shoulder portion 16 is reduced. For example, the shoulder portion 16 is chipped at a portion closer to the tread portion 2 in the tire height direction H than the groove 17. . In the cross section of the tread portion 2 in the tire radial direction, if the cross sectional area T of the region on the side of the end portion 2a from the imaginary line L extending from the central portion 2c of the tread portion 2 to the outer side in the tire width direction, The area T is preferably 0.8 to 1.2 times the area T. That is, in order to suppress an excessive increase in the contact pressure at the end 2a of the tread portion 2 while ensuring the necessary rigidity of the shoulder portion 16, the relationship of the following formula (2) is established between the cross-sectional areas S and T. It is preferable to be established.

[Equation 2]
0.8T ≦ S ≦ 1.2T (2)

  Next, a 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 (the tread part 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 part 16, The upper end 17f of the groove 17 is referred to. Further, the position on the innermost side in the tire radial direction (the most bead side in the tire height direction H) of the opening 17 b of the groove 17, in other words, the position where the side wall 17 d of the groove wall 17 a is connected to the outer peripheral surface of the shoulder portion 16. , Referred to as 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. Is set.

  First, the distance A is set to 1.0 to 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 be not less than 1.3 times and not more than 2.5 times the depth g. That is, there is the following relationship 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 a distance W in the tire width direction between the center 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 to 0.2 times. That is, there is the following relationship between the depth C and the distance W.

[Equation 5]
0.08W ≦ C ≦ 0.2W (5)

  The inclination angle θ of the groove 17, which is an angle between the direction in which the groove 17 extends and the tire width direction, is set in the range of 0 ° to 60 °. That is, there is the following relationship with respect to 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 (conceptually indicated by a broken-line circle in FIG. 1) is the maximum rubber thickness (maximum rubber) in the shoulder portion 16. (Thickness) 30% or more of E is set. That is, the following relationship exists between the shortest distance D and the maximum rubber thickness E.

[Equation 7]
D ≧ 0.3E (7)

  For the groove 17, the distance B, the depth C, and the inclination angle θ of the lower end 17g are set as shown in the equations (4), (5), (6), respectively, and the step product S is expressed as the equation (2) as described above. ), It is possible to more reliably suppress an excessive increase in the contact pressure at the end 2a of the tread portion 2 while ensuring the necessary rigidity of the shoulder portion 16. Further, by setting the distance A of the upper end 17f of the groove 17 as shown in the expression (3), there is an amount of rubber necessary for securing rigidity between the outer peripheral surface 2b of the tread portion 2 and the groove 17, Chipping of the shoulder portion 16 at the portion on the tread portion 2 side in the tire height direction H from the groove 17 can be prevented. Further, the shortest distance D from the end portions 11a to 13a of the belt plies 11 to 13 to the groove 17 is set as shown in Expression (7), so that the end portions 11a to 11a of the belt plies 11 to 13 are caused by manufacturing tolerances. It is possible to prevent 13 a from protruding into the groove 17.

(Second Embodiment)
In the tire 1 according to the second embodiment of the present invention shown in FIG. 2, the concave portion 21 and the convex portion 22 are provided on the entire groove wall 17 a of the groove 17, that is, on the entire side walls 17 c and 17 d and the inner wall 17 e.

  Since the amount of rubber is large in the shoulder portion 16, particularly in the vicinity of the end portions 11 a to 13 a of the belt plies 11 to 13, the amount of heat generated during traveling is larger than the other portions of the tire 1. Further, in the vicinity of the end portions 11a to 13a of the belt plies 11 to 13, repeated distortion is likely to occur with tire rolling. However, since the generated heat is dissipated through the groove 17, it is possible to prevent the thermal degradation in the vicinity of the end portions 11a to 13a of the belt plies 11 to 13 and the occurrence of a failure such as a separation due to the heat deterioration. By providing the concave portion 21 and the convex portion 22, the surface area of the groove wall 17 a of the groove 17, that is, the heat radiating area is expanded, so that heat generation in the shoulder portion 16 can be more effectively suppressed.

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

1 tire
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 reinforcing ply 15 padless portion 16 shoulder portion 17 groove 17a groove wall 17b opening 17c, 17d side wall 17e deep wall 17f upper end 17g lower end 18 main groove 18a bottom wall 21 concave portion 22 convex portion A, B, W distance C depth D shortest distance g depth h rubber thickness P distance S, T cross section θ inclination angle

Claims (5)

The outer peripheral surface of the tread portion has an inverted round shape in which the outer diameter at the end portion is larger than the outer diameter at the center portion,
A pneumatic tire provided with a groove provided along a tire circumferential direction in a padless portion which is a region from the end of the tread portion to a tire maximum width portion.   The distance of the tire height direction from the said center part of the said tread part to the said edge part is 0.05 times or more and 0.2 times or less of the rubber | gum thickness of the said tread part in the said center part. Pneumatic tires.   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 groove in the tire radial direction cross-section is 0. 0 of the cross-sectional area of the region on the end side with respect to the imaginary line extending from the central portion of the tread portion to the outer side in the tire width direction. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is 8 times or more and 1.2 times or less.

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