Pneumatic tire

Abstract

To provide a pneumatic tire capable of improving cut resistance performance in a side wall part while suppressing an increase in tire weight.SOLUTION: Provided is a pneumatic tire, the pneumatic tire including a tread part and a first sidewall part. The first sidewall part includes a plurality of protectors 10 and a gap part. The length of each protector 10 in the tire circumferential direction thereof is greater than that of the gap part adjacent to one side in the tire circumferential direction of the protector 10. Each of the plurality of protectors 10 includes a top surface 14 and a side surface 15. In a front view of the first sidewall part, at least a portion of the side surface 15 includes an undercut surface 18 continuous to a reference plane 9 on the central side of the top surface 14 from an outer edge 14e of the top surface 14.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to pneumatic tires.

Background Art

[0002] Patent Document 1 below proposes a pneumatic tire in which a side protector is formed in a sidewall portion. The side protector helps to improve the cut resistance performance of the sidewall portion.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In recent years, further improvement in the above-described cut resistance performance has been demanded. As a method, it is conceivable to arrange the above-described protectors densely in the tire circumferential direction. However, such a method may cause an increase in tire weight.

[0005] In view of the above actual situation, the present invention has been devised, and the main object is to provide a pneumatic tire that can improve the cut resistance performance of the sidewall portion while suppressing an increase in tire weight.

Means for Solving the Problems

[0006] The present invention relates to a pneumatic tire including a tread portion and a first sidewall portion extending radially inward in the tire radius direction from the tread portion. The first sidewall portion bulges outward in the tire axial direction from a reference plane and includes a plurality of protectors arranged in the tire circumferential direction and gap portions formed respectively between the protectors adjacent to each other in the tire circumferential direction. The length of each of the protectors in the tire circumferential direction is larger than the length of the adjacent gap portion in the tire circumferential direction on one side in the tire circumferential direction of the protector. Each of the plurality of protectors includes a top surface facing outward in the tire axial direction and a side surface connecting the outer edge of the top surface and the reference plane. In a front view of the first sidewall portion, at least a part of the side surface includes an undercut surface continuous with the reference plane on the center side of the top surface rather than the outer edge of the top surface, and it is a pneumatic tire.

Advantages of the Invention

[0007] By adopting the above configuration, the pneumatic tire of the present invention can improve the cut resistance performance of the sidewall portion while suppressing an increase in tire weight.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Although the drawings describe the features of the present invention, they may include exaggerated expressions or expressions different from the dimensional ratios of actual structures in order to assist in understanding the present invention. Also, throughout each embodiment, the same or common elements are denoted by the same reference numerals, and redundant descriptions are omitted.

[0010] FIG. 1 shows a cross-sectional view of a pneumatic tire 1 (hereinafter sometimes simply referred to as "tire 1") showing an embodiment of the present invention. FIG. 1 is a diagram showing a meridian section including the tire rotation axis of tire 1 in the normal state. As shown in FIG. 1, the tire 1 of the present embodiment is, for example, a pneumatic tire for a passenger car. The tire 1 of the present embodiment can cope not only with paved roads but also with rough terrain driving on unpaved roads such as gravel roads and roads with relatively large stones. Therefore, the tire 1 of the present embodiment is preferably used for SUVs. Such a tire 1 is required to have cut resistance performance in the sidewall portion.

[0011] The "normal state" means that in the case of a pneumatic tire for which various standards are defined, the tire is rim-mounted on a standard rim and filled with a standard internal pressure, and moreover, it is in a no-load state. In the case of a tire for which no various standards are defined, the normal state means a standard use state according to the purpose of use of the tire, which means a state where the tire is not mounted on a vehicle and is in a no-load state. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values measured in the normal state.

[0012] The "standard rim" is the rim defined for each tire in a standard system including the standards on which the tire is based. For example, in the case of JATMA, it is the "standard rim", in the case of TRA, it is the "Design Rim", and in the case of ETRTO, it is the "Measuring Rim".

[0013] The "normal internal pressure" is the air pressure determined for each tire in the standard system including the standards on which the tire is based. For JATMA, it is the "maximum air pressure"; for TRA, it is the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and for ETRTO, it is the "INFLATION PRESSURE".

[0014] Tire 1 includes a tread portion 2, a first sidewall portion 3A, a second sidewall portion 3B, a first bead portion 4A, and a second bead portion 4B. The first sidewall portion 3A and the second sidewall portion 3B extend radially inward from the tread portion 2 in the tire radius direction. The first bead portion 4A is connected to the radially inner side of the first sidewall portion 3A in the tire radius direction. The second bead portion 4B is connected to the radially inner side of the second sidewall portion 3B in the tire radius direction. The second sidewall portion 3B has substantially the same configuration as the first sidewall portion 3A. The second bead portion 4B has substantially the same configuration as the first bead portion 4A. Therefore, the configuration of the first sidewall portion 3A described below may also be applied to the second sidewall portion 3B.

[0015] Further, tire 1 includes a carcass 6 and a tread reinforcement layer 7. The carcass 6 extends from the first bead portion 4A, through the first sidewall portion 3A, the tread portion 2, and the second sidewall portion 3B, to the second bead portion 4B. The tread reinforcement layer 7 is provided on the radially outer side of the carcass 6 in the tread portion 2. Known configurations are applied to the carcass 6 and the tread reinforcement layer 7, and detailed descriptions thereof are omitted here.

[0016] The tread portion 2 has two tread ends Te. The tread end Te corresponds to the end of the ground contact surface of the tread portion 2 during normal driving. The tread end Te forms the boundary between the ground contact surface of the tread portion 2 and the outer surface of the first sidewall portion 3A.

[0017] Figure 2 shows an enlarged perspective view showing a part of the first sidewall portion 3A. In the cross-section shown in FIG. 2, the tire internal member is omitted. As shown in FIG. 2, the first sidewall portion 3A includes a plurality of protectors 10. The protector 10 bulges outward in the tire axial direction from the reference plane 9 of the first sidewall portion 3A and is arranged in the tire circumferential direction. As a desirable aspect, in the present embodiment, a plurality of protectors 10 are arranged over the entire circumference of the tire. Further, the reference plane 9 of the first sidewall portion 3A is a plane that extends along the carcass 6 (shown in FIG. 1) and constitutes the contour of the first sidewall portion 3A, meaning that fine irregularities on the outer surface of the first sidewall portion 3A are excluded.

[0018] Figure 3 shows a front view of the protector 10. As shown in FIG. 3, the first sidewall portion 3A includes a gap portion 11 formed between each of the protectors 10 adjacent in the tire circumferential direction. In the present invention, the length L1 of each protector 10 in the tire circumferential direction is larger than the length L2 of the gap portion 11 adjacent to one side of the protector 10 in the tire circumferential direction in the tire circumferential direction. The length L1 is measured at the top surface 14 of the protector 10 described later and means the maximum length of the protector 10 in the tire circumferential direction in the front view of the first sidewall portion 3A. The length L2 is measured at the same position as the bulge height of the protector 10 and means the maximum length of the gap portion 11 in the tire circumferential direction in the front view.

[0019] Figure 4 shows a cross-sectional view taken along line A-A of Figure 3. In Figure 4, for ease of understanding the invention, the curved components included in the protector 10 are excluded from the drawing. As shown in Figure 4, each of the plurality of protectors 10 includes a top surface 14 facing the outer side in the tire axial direction, and a side surface 15 connecting the outer edge 14e of the top surface 14 and the reference surface 9. As shown in Figures 3 and 4, in a front view of the first sidewall portion 3A, at least a part of the side surface 15 includes an undercut surface 18 that continues to the reference surface 9 on the center side of the top surface 14 rather than the outer edge of the top surface 14. In Figure 3, the ridge line formed by the undercut surface 18 and the reference surface 9 is indicated by a dashed line. By having the above-described features, the tire 1 of the present invention can improve the cut resistance performance of the sidewall portion while suppressing an increase in tire weight. The reason is as follows.

[0020] As shown in Figure 3, in the present invention, since the length L1 of the protector 10 is greater than the length L2 of the gap portion 11, the plurality of protectors 10 are densely arranged in the tire circumferential direction. Thereby, the cut resistance performance of the first sidewall portion 3A can be improved. On the other hand, as shown in Figure 4, in the present invention, since the side surface 15 of the protector 10 includes the undercut surface 18, the rubber volume of the protector 10 can be reduced compared to a conventional protector whose side surface is composed of a non-undercut surface, and thus an increase in tire weight can be suppressed (hereinafter, this effect may be referred to as the "tire weight suppression effect").

[0021] Hereinafter, a more detailed configuration of the present embodiment will be described. Each configuration described below shows a specific aspect of the present embodiment. Therefore, it goes without saying that the present invention can exhibit the above-described effects even if it does not have the configurations described below. Further, even if any one of the configurations described below is applied alone to the tire of the present invention having the above-described features, an improvement in performance corresponding to each configuration can be expected. Furthermore, when some of the configurations described below are applied in combination, a combined improvement in performance corresponding to each configuration can be expected.

[0022] As shown in FIG. 1, the protector 10 is preferably disposed at a position in the first sidewall portion 3A that is likely to be damaged. From this perspective, the protector 10 is preferably disposed so as to include the maximum tire width position. Further, the tire radial distance L3 from the outer end of the tread portion 2 in the tire radial direction to the outer end of the protector 10 in the tire radial direction is, for example, 50 to 100 mm. Thereby, the cut resistance performance of the first sidewall portion 3A is further improved.

[0023] In addition, when numerical ranges of various parameters are described in this specification, unless otherwise specified, the numerical ranges mean numerical ranges for the average values of the parameters. For this reason, for example, the distance L3 means the average value of the distances measured at a plurality of positions in the tire circumferential direction with respect to the distance from the outer end of the tread portion 2 in the tire radial direction to the outer end of the protector 10 in the tire radial direction. The same applies to other parameters described later.

[0024] As shown in FIG. 3, the protector 10 of the present embodiment has a horizontally long rectangular shape having a short side extending in the tire radial direction and a curved long side extending in the tire circumferential direction when viewed from the front of the first sidewall portion 3A. Further, in the present embodiment, protectors 10 having substantially the same shape are disposed over the entire circumference of the tire. However, the present invention is not limited to such an aspect.

[0025] From the viewpoint of achieving a good balance between the tire weight reduction effect and the cut resistance performance, the length L4 of the protector 10 in the tire radial direction (measured at the top surface 14) is, for example, 15 to 35 mm, preferably 20 to 30 mm. From the same viewpoint, the length L1 of the protector 10 in the tire circumferential direction is, for example, 50 to 150 mm, preferably 80 mm to 120 mm. Further, the length L1 is preferably 3.0 to 5.0 times the length L4.

[0026] As shown in FIG. 4, in this embodiment, the protector 10 has a substantially constant raised height. The maximum raised height h1 of the protector 10 is, for example, 1.5 to 3.5 mm. Such a protector 10 can effectively protect the first sidewall portion 3A while suppressing an increase in tire weight.

[0027] As shown in FIG. 3, the side surface 15 of the protector 10 includes a pair of first side surfaces 16 extending in the tire radial direction and a pair of second side surfaces 17 extending in the tire circumferential direction. The first side surface 16 constitutes the inner wall of the gap portion 11. The outer edge 14e between the top surface 14 and the first side surface 16 extends, for example, at an angle of 10° or less with respect to the tire radial direction. The second side surface 17 faces the inside or the outside in the tire radial direction. The outer edge 14e between the top surface 14 and the second side surface 17 extends, for example, at an angle of 10° or less with respect to the tire circumferential direction.

[0028] The undercut surface 18 can be formed on a part of the side surface 15 to expect a tire weight reduction effect. However, forming the undercut surface 18 in as large a range as possible of the side surface 15 can further enhance the above-described effect. From this viewpoint, in this embodiment, at least one, preferably both, of the pair of first side surfaces 16 include the undercut surface 18. Similarly, at least one, preferably both, of the pair of second side surfaces 17 include the undercut surface 18. Further, in a more preferable aspect, the undercut surface 18 is formed over the entire first side surface 16 and the second side surface 17 of this embodiment. That is, in this embodiment, the side surface 15 is configured as the undercut surface 18 over the entire circumference of the protector 10. Thereby, an increase in tire weight can be reliably suppressed.

[0029] FIG. 5 shows a cross-sectional view of a non-undercut surface NCU employed on the side surface of a conventional protector P. The region formed by the non-undercut surface NCU has high rigidity around it, enabling the protector P to exhibit excellent protective performance. For this reason, in another embodiment, in the protector 10 shown in FIG. 3, both of the pair of first side surfaces 16 may be formed of the non-undercut surface NCU shown in FIG. 5, and both of the pair of second side surfaces 17 may be formed of the aforementioned undercut surface 18. In such an embodiment, the rigidity of the protector 10 in the tire circumferential direction is improved. Therefore, such an embodiment can enhance the durability when a circumferential stress in the tire acts on the protector 10, such as when the first sidewall portion 3A contacts a curb during driving on a paved road surface, while obtaining the effect of suppressing the tire weight.

[0030] In yet another embodiment, in the protector 10 shown in FIG. 3, both of the pair of second side surfaces 17 may be formed of the non-undercut surface NCU shown in FIG. 5, and both of the pair of first side surfaces 16 may be formed of the undercut surface 18. In such an embodiment, the rigidity of the protector 10 in the tire radial direction is improved. Therefore, such an embodiment can enhance the durability when a radial stress in the tire acts on the protector 10, such as when the first sidewall portion 3A contacts a stone during driving on a rubble road surface, while obtaining the effect of suppressing the tire weight.

[0031] As shown in FIG. 4, for at least one of the plurality of protectors 10, in a cross-section along the tire radial direction, the length L5 in the tire radial direction at the reference plane 9 of the protector 10 is 85% to 95% of the length L4 in the tire radial direction of the top surface 14. Thereby, while improving the mold release property during vulcanization molding, the above-described effects can be obtained.

[0032] The undercut surface 18 of the present embodiment is configured as a planar surface inclined at a certain angle. However, as will be described later, the undercut surface 18 may be curved. The angle θa between the reference surface 9 and the undercut surface 18 is, for example, 40 to 70°. Such an undercut surface 18 can exhibit excellent mold releasability and obtain a tire weight reduction effect.

[0033] When the angle θa is increased, the rigidity of the protector 10 can be maintained high. Also, when the angle θa is decreased, the tire weight reduction effect can be enhanced. For this reason, as shown in FIG. 3, when both the first side surface 16 and the second side surface 17 include the undercut surface 18, it is conceivable to make the above-described angle θa different for each side surface according to the desired performance. For this reason, in another embodiment, the angle θa1 (not shown) between the reference surface 9 and the undercut surface 18 on the first side surface 16 may be larger than the angle θa2 (not shown) between the reference surface 9 and the undercut surface 18 on the second side surface 17. Such an embodiment can relatively improve the rigidity of the protector 10 in the tire circumferential direction and enhance the durability of the protector 10.

[0034] In yet another embodiment, the angle θa2 may be larger than the angle θa1. Such an embodiment improves the durability of the protector 10 in a situation where a stress in the tire radial direction is likely to act on the protector 10, such as when driving on a potholed road surface.

[0035] As shown in FIG. 3, the gap portion 11 has a length in the tire circumferential direction that slightly expands toward the outer side in the tire radial direction. Further, in the present embodiment, the gap portions 11 having substantially the same shape are arranged over the entire circumference of the tire. The length L1 of each of the protectors 10 in the tire circumferential direction is set to be twice or more, preferably 4 to 10 times, the length L2 of the gap portion 11 adjacent to the protector 10 in the tire circumferential direction. Further, by defining the gap portion 11 as described above, the total ΣL1 of the lengths L1 of the plurality of protectors 10 in the tire circumferential direction is 70% or more of the virtual circumferential length Rv extending over the entire circumference of the tire through the plurality of protectors 10. Thereby, sufficient cut resistance performance is exhibited by the protector 10. Note that the total ΣL1 means the total of the maximum lengths of the protectors 10 in the tire circumferential direction. Further, the virtual circumferential length Rv corresponds to the length of the circumference of a virtual circle having the largest overlapping length with the plurality of protectors 10 in a front view of the first sidewall portion 3A.

[0036] FIG. 6 shows an enlarged cross-sectional view of the undercut surface 18 in another embodiment. As shown in FIG. 6, the undercut surface 18 of this embodiment includes a curved surface 21 recessed toward the center side of the top surface 14 (the side of arrow A1 in FIG. 6). In such an embodiment, the mold releasability can be further enhanced.

[0037] The raised height h1 of the protector 10 of this embodiment is, for example, 1.5 to 5.0 mm. Further, the maximum recess amount d1 of the undercut surface 18 (the recess amount from the outer edge 14e of the top surface 14) is, for example, 1.0 mm or more, preferably 1.0 to 3.0 mm. Such a protector 10 can enhance the tire weight reduction effect and the mold releasability in a well-balanced manner.

[0038] It is desirable that this curved surface 21 is separated from the outer edge 14e of the top surface 14 by a distance L6 that is 10% to 40% of the raised height h1. Also, it is desirable that the curved surface 21 is connected to the outer surface 23 extending in the height direction of the protector 10 from the outer edge 14e via an inverse R surface having a curvature radius of 2.0 to 5.0 mm. Further, it is desirable that this curved surface 21 is smoothly curved and connected to the reference surface 9. The curvature radius r1 of the connection portion 24 between the curved surface 21 and the reference surface 9 is, for example, 1.0 mm or more, desirably 1.0 to 2.0 mm. The undercut surface 18 formed by such a curved surface 21 can further enhance the mold release property.

[0039] As described above, the tire according to one embodiment of the present invention has been described in detail. However, the present invention is not limited to the above specific embodiments and can be implemented in various forms.

Example

[0040] As an example, a pneumatic tire of size 235 / 65R16C having the basic structure of FIG. 1 was prototyped. In the tire of the example, the entire circumference of the side surface of the protector is configured as an undercut surface. As Comparative Example 1, a tire without a protector provided on the sidewall portion was created. Also, as Comparative Example 2, a tire having a protector provided on the sidewall portion but with the entire circumference of the side surface of the protector configured as a non-undercut surface was prototyped. Comparative Examples 1 and 2 are substantially the same as the tire of the example except for the above matters. Also, Comparative Example 2 and each example have the same length in the tire radius direction of the top surface of the protector. The cut resistance performance and the tire weight reduction effect were tested for these test tires. The common specifications and test methods of each test tire are as follows. Mounting rim: 16×7.0J Tire internal pressure: 240 kPa Test vehicle: Displacement 2000 cc, four-wheel drive

[0041] <Cut resistance performance> The test vehicle equipped with the test tire was driven on a rubble road surface, and the degree of damage to the sidewall portion was scored. The results indicate that the higher the numerical value, the better the cut resistance performance is demonstrated.

[0042] <Tire weight reduction effect> The weight of each test tire was measured, and a comparison with Comparative Example 1 without a protector was conducted. The results are the reciprocal of the difference in tire weight from Comparative Example 1, and the larger the numerical value, the better the tire weight reduction effect is shown. The test results are shown in Table 1.

[0043]

Table 1

[0044] As shown in Table 1, Comparative Example 1 without a protector has low cut resistance performance. In contrast, Comparative Example 2 and Examples 1 to 5 have a protector, so the cut resistance performance is significantly improved. On the other hand, Comparative Example 2 with a conventional protector has a low tire weight reduction effect of 80 points, while Examples 1 to 5 have a tire weight reduction effect of 100 to 120 points. That is, it was confirmed that the tire of the present invention improves the cut resistance performance of the sidewall portion while suppressing an increase in tire weight.

[0045] [Appendix] The present invention includes the following aspects.

[0046] [Invention 1] A pneumatic tire, comprising a tread portion and a first sidewall portion extending radially inward in the tire radius direction from the tread portion, the first sidewall portion includes a plurality of protectors that bulge outward in the tire axial direction from a reference plane and gaps formed between the adjacent protectors in the tire circumferential direction. The length of each of the protectors in the tire circumferential direction is greater than the length of the gap portion adjacent to the protector on one side in the tire circumferential direction. Each of the plurality of protectors includes a top surface facing the outer side in the tire axial direction and a side surface connecting the outer edge of the top surface and the reference surface. In a front view of the first sidewall portion, at least a part of the side surface includes an undercut surface that is continuous with the reference surface on the center side of the top surface rather than the outer edge of the top surface. Pneumatic tire. [Inventive concept 2] The side surface includes a pair of first side surfaces extending in the tire radial direction. The pneumatic tire according to Inventive concept 1, wherein at least one of the pair of first side surfaces includes the undercut surface. [Inventive concept 3] The side surface includes a pair of second side surfaces extending in the tire circumferential direction. The pneumatic tire according to Inventive concept 1 or 2, wherein at least one of the pair of second side surfaces includes the undercut surface. [Inventive concept 4] The pneumatic tire according to any one of Inventive concepts 1 to 3, wherein in a cross-section along the tire radial direction of at least one of the plurality of protectors, the length of the protector in the tire radial direction at the reference surface is 85% to 95% of the length of the top surface in the tire radial direction. [Inventive concept 5] The pneumatic tire according to any one of Inventive concepts 1 to 4, wherein the maximum bulging height of the protector is 1.5 to 3.5 mm. [Inventive concept 6] The pneumatic tire according to any one of Inventive concepts 1 to 6, wherein the distance in the tire radial direction from the outer end of the tread portion in the tire radial direction to the outer end of the protector in the tire radial direction is 50 to 100 mm. [Inventive concept 7] The pneumatic tire according to any one of Inventive concepts 1 to 6, wherein the length of each of the protectors in the tire circumferential direction is at least twice the length of the gap portion adjacent to the protector in the tire circumferential direction. [Inventive concept 8] The undercut surface includes a curved surface recessed toward the center of the top surface, and the pneumatic tire according to any one of 1 to 7 of the present invention.

Explanation of Signs

[0047] 2 Tread portion 3A First sidewall portion 9 Reference plane 10 Protector 11 Gap portion 14 Top surface 14e Outer edge 15 Side surface 18 Undercut surface

Claims

1. A pneumatic tire comprising: a tread portion and a first sidewall portion extending radially inward in the tire radius direction from the tread portion, wherein the first sidewall portion bulges outward in the tire axial direction from a reference plane, and includes a plurality of protectors arranged in the tire circumferential direction and a gap portion formed between the protectors adjacent to each other in the tire circumferential direction, wherein the length of each of the protectors in the tire circumferential direction is greater than the length of the adjacent gap portion in the tire circumferential direction on one side of the protector in the tire circumferential direction, wherein each of the plurality of protectors includes a top surface facing outward in the tire axial direction and a side surface connecting the outer edge of the top surface and the reference plane, wherein in a front view of the first sidewall portion, at least a part of the side surface includes an undercut surface continuous with the reference plane on the center side of the top surface rather than the outer edge of the top surface, A pneumatic tire.

2. The side surface includes a pair of first side surfaces extending in the tire radius direction, wherein at least one of the pair of first side surfaces includes the undercut surface, and the pneumatic tire according to Claim 1.

3. The side surface includes a pair of second side surfaces extending in the tire circumferential direction, wherein at least one of the pair of second side surfaces includes the undercut surface, and the pneumatic tire according to Claim 1.

4. In a cross section along the tire radius direction of at least one of the plurality of protectors, the length of the protector in the tire radius direction at the reference plane is 85% to 95% of the length of the top surface in the tire radius direction, and the pneumatic tire according to Claim 3.

5. The maximum bulging height of the protector is 1.5 to 3.5 mm, and the pneumatic tire according to any one of Claims 1 to 4.

6. The distance in the tire radius direction from the outer end of the tread portion in the tire radius direction to the outer end of the protector in the tire radius direction is 50 to 100 mm, and the pneumatic tire according to any one of Claims 1 to 4.

7. The length of each of the protectors in the tire circumferential direction is at least twice the length of the adjacent gap portion in the tire circumferential direction, and the pneumatic tire according to any one of Claims 1 to 4.

8. The undercut surface includes a curved surface recessed toward the center of the top surface, and the pneumatic tire according to any one of Claims 1 to 4.

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