JP4673172B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a design / decoration applied to the bottom surface of a sidewall portion of a tire.

In general, in order to engrave a logo, characters, and the like on the surface of a sidewall portion of a pneumatic tire, a convex portion for displaying a mark is formed along the tire circumferential direction. In order to sufficiently appeal the product name of the tire, the product logo, the manufacturer name, the manufacturer logo, and the like, the device for displaying the mark has been proposed to improve the visibility of the mark. For example, in Patent Document 1, there is a technique for improving the visibility by making the surface of the sidewall and the outer surface contour line of a cross section with a mark such as a brand, type, character, number, symbol or figure not parallel. It is disclosed.
Japanese Patent Laid-Open No. 10-086615

  By the way, in recent years, design and the like have been applied also to the sidewall portion, and a land portion such as a rib may be applied to the sidewall portion continuously from the tread surface toward the bead portion side. However, in the sidewall portion, if such a land portion and a convex portion for displaying the mark overlap, the visibility of the mark deteriorates. The part which can give such a land part to the wall part was restricted.

  Even when the land portion as described above and the convex portion for displaying the mark overlap, in order to ensure the visibility of the mark, for example, by applying the technique of Patent Document 1, The outer surface contour line is parallel to the bottom surface of the sidewall portion, while only the outer surface contour line of the cross section with the convex portion is not parallel to the bottom surface of the sidewall portion, thereby improving the visibility of the mark. It is also possible to give it. However, even if the technique of Patent Document 1 is simply applied to the sidewall portion where both are mixed as described above, there is a problem that the volume of the convex portion increases, resulting in an increase in the weight of the tire. There is also a problem that cracks are likely to occur at the end bottom of the convex portion.

  That is, the problem to be solved by the present invention is, as described above, the land portion continuously extending from the tread surface to the bead portion side on the sidewall portion and the convex portion displaying the mark formed along the tire circumferential direction. In the case of a pneumatic tire having a portion where both overlap and a portion where they do not overlap, the visibility of marks such as letters, logos, etc. represented by the convex portions is reduced. If an attempt is made to secure the visibility by an easy method, other problems such as a tendency for cracks to occur on the bottom surface of the convex portion occur.

  As a result of intensive studies to solve the above problems, in the pneumatic tire according to the present invention, the convex portion in the overlapping portion protrudes from the land portion, and the convex portion and the land portion do not overlap. A radially outer end bottom portion and a radially inner end bottom portion of the convex portion of each part have a radius of curvature and are curvedly in contact with the bottom surface of the sidewall portion, and the radially outer end bottom portion of the convex portion. And the radius of curvature of the end bottom on the radially inner side, the radius of curvature of the end bottom on the higher end side from the bottom surface of the sidewall of the convex portion, and the radius of curvature of the end bottom on the other side The main solution is to make it larger.

  According to the pneumatic tire of the present invention, the land portion extending in the tire radial direction toward the bead portion side continuously from the tread surface and the mark formed along the tire circumferential direction are displayed on the sidewall portion. Even in a tire in which convex portions are mixed and they overlap each other, it is possible to suppress the occurrence of cracks at the bottom portion of the convex portion displaying the mark while ensuring sufficient visibility.

  Hereinafter, further description will be given with reference to the drawings. FIG. 1 is a view showing the surface of the sidewall portion. In the figure, the upper side is the tread surface direction (radially outer side), and the lower side is the bead portion side (radial inner side). 2 is a cross-sectional view taken along the line A-A ′ of FIG. 1 (radial cross-sectional view). FIG. 3 is a cross-sectional view taken along the line B-B ′ of FIG. 4 to 6 are A-A 'cross-sectional views (radial cross-sectional views) of Fig. 1 in another aspect. 2 and FIGS. 4 to 6 are cross-sectional views of a portion where the land portion and the convex portion do not overlap, and the BB ′ cross-sectional view of FIG. 3 is a cross-sectional view where the land portion and the convex portion overlap. FIG. On the other hand, FIG. 7 is a cross-sectional view (circumferential cross-sectional view) taken along the line C-C ′ of FIG. In the cross-sectional views of FIGS. 2 to 7, the solid line is the ridgeline that actually appears on the cross-sectional view, and the dotted line will appear as a ridgeline if the bottom surface of the land portion, the convex portion, or the sidewall portion extends to the cross-sectional portion. It is a virtual line.

  In FIG. 1, the streamline shape indicates the land portion 2 extending in the tire radial direction continuously from the tread surface toward the bead portion, and the italic N-shape indicates the tire circle. It is the convex part 3 which displays the mark formed along the circumferential direction. As shown in FIGS. 1 to 7, the pneumatic tire of the present invention does not overlap with the portion where the land portion 2 and the convex portion 3 are mixed in the sidewall portion, and the land portion 2 and the convex portion 3 overlap each other. Part. The surface that is neither the land portion 2 nor the convex portion 3 is the bottom surface 1 of the sidewall portion.

  In a portion where the land portion 2 and the convex portion 3 overlap, the convex portion 3 is projected beyond the land portion 2 as shown in FIGS. 3 and 7 in order to ensure the visibility of the mark. In FIG. 3 and FIG. 7, the protruding portion of the convex portion is shown as the protruding portion 32. The height of the protrusion is preferably about 0.3 to 2.0 mmmm. This is because if the protrusion height is too low, the visibility due to the convex portion 3 is reduced. Conversely, if the protrusion height is too high, cracks are likely to enter the end bottom surface of the convex portion 3, and the convex portion 3 is likely to be missing. Because it becomes.

  On the other hand, in a region where the land portion 2 and the convex portion 3 do not overlap, the height of the convex portion 3 can be made higher or lower than the virtual ridgeline of the land portion 2. This is because the visibility of the mark can be ensured in any case. 2 and 4 show a state in which the height of the land portion 2 is lower than the virtual ridgeline of the convex portion 3. On the other hand, in FIGS. 5 and 6, the land portion 2 is higher than the virtual ridge line of the convex portion 3.

  In the pneumatic tire according to the present invention, the radially outer end bottom portion 31 and the radially inner end bottom portion 31 of the convex portion 3 where the convex portion 3 and the land portion 2 do not overlap each other have a radius of curvature. It is in curved contact with the bottom surface 1 of the sidewall portion. This is because cracks are generated with the corner as a base point when it is in contact with the bottom surface 1 of the sidewall portion linearly with the corner.

  Further, in the pneumatic tire of the present invention, in the portion where the convex portion 3 and the land portion 2 do not overlap, the convex portion 3 has a radially outer end bottom portion 31 and a radially inner end bottom portion 31 of the convex portion. The radius of curvature of the end bottom 31 on the side of the side wall having the higher end height from the bottom surface 1 is made larger than the radius of curvature of the end bottom 31 on the other side. In other words, among the two ends in the radial direction of the convex portion 3 at the portion where they do not overlap, the curve of the end bottom surface with the higher height is made gentler than the curve with the lower one. That is, of the radial end portions of the convex portion 3, which of the end bottom portions 31 on the radially outer side and the radially inner side should be increased depends on the height of the end portions thereof, and therefore is uniquely defined on the outer side or the inner side. Is not decided. 2 and FIG. 5 are cross-sectional views along the radial outer radius of curvature, while the AA ′ sectional views of FIGS. 4 and 6 have a large radial inner radius of curvature. It is a mode. As can be seen from FIGS. 2 and 4, which radius of curvature increases is often dependent on the shape of the land portion 2 in the height direction.

  Moreover, in the pneumatic tire of this invention, it is preferable that the curvature radius of each end bottom part 31 of the said radial direction outer side and radial direction inner side of the convex part 3 shall be below the edge part height of each side. This is because, when the radius of curvature is larger than the end height, the visibility of the mark displayed on the convex portion 3 is lowered because the curve in contact with the bottom surface 1 of the sidewall portion becomes too gentle.

  Furthermore, in the pneumatic tire of the present invention, it is preferable that the upper surface of the convex portion 3 in the overlapping portion protrudes substantially parallel to the upper surface of the land portion 2 in the tire radial direction cross section. In other words, assuming the surface of the land portion 2 when it is assumed that the convex portion 3 does not exist, in the cross section in the tire radial direction, the surface is delimited by the ridge line on the upper surface delimited by the assumed surface of the land portion 2 and the surface of the convex portion 3. It is preferable that the ridgeline on the upper surface is parallel. Since the upper surface of the protrusion 3 protrudes substantially in parallel in the tire radial direction cross section, the processing curvature surface is not mixed and processing is easy, so that the protrusion amount can be kept low and the workability can be improved. it can. FIG. 3 shows a state in which the upper surface of the convex portion 3 is protruded substantially parallel to the upper surface of the land portion 2 in the tire radial direction cross section in the state of FIG.

  In addition to the tire radial cross-section, it is more preferable that the upper surface of the convex portion 3 protrudes substantially parallel to the upper surface of the land portion 2 in the tire circumferential cross-section. The parallelism between the portion 2 and the land portion 2 is preferably maintained not only on the top surface but also on the side surface. That is, it is preferable that the upper surface and the side surface of the convex portion 3 in the overlapping portion protrude substantially parallel to the cross section in the tire circumferential direction from the upper surface and the side surface of the land portion 2. In other words, assuming the surface of the land portion 2 when it is assumed that the convex portion 3 does not exist, the top surface and the ridge line of the side surface and the surface of the convex portion 3 that are separated by the assumed surface of the land portion 2 in the tire circumferential section. It is more preferable that the upper surface and the ridge line on the side surface separated by are parallel to each other. Thereby, the amount of protrusion can be further reduced, and the occurrence of cracks can be suppressed. FIG. 7 is a cross-sectional view in the tire circumferential direction in the embodiment of FIG. 2, and in FIG. 7, the upper surface and side surface of the protrusion 3 protrude substantially parallel to the upper surface and side surface of the land portion 2 in the tire circumferential cross section. The mode which protruded 32 is shown.

(Tire manufacturing)
The tire size is LT285 / 70R17, and tires that are mixed in the sidewall portion with the streamline ribs continuously extending from the tread surface toward the bead portion and the convex portion of the character mark (Examples 1-3, Comparative Example 1). The shape, size, etc. of the streamlined rib and the character mark convex part are as follows.

Example 1
The streamline rib of the tire of Example 1 was gradually lowered from the tread surface toward the bead portion side. The radial outer end height is 4.5 mm, the radial inner end height is 2 mm, and the curvature of the radial outer end bottom 31 is the portion where the streamline rib and the convex portion of the character mark do not overlap. The radius is 4 mm, the radius of curvature of the radially inner end bottom portion 31 is 2 mm, and the upper surface of the convex portion in the portion where the rib and the convex portion overlap protrudes 0.5 mm in parallel in the tire radial cross section from the upper surface of the rib. Tire. In the tire of Example 1, the mark displayed by the convex portion was sufficiently recognizable.

(Example 2)
The streamline ribs of the tire of Example 2 also gradually decreased in height from the tread surface toward the bead portion side. The radial outer end height is 4.5 mm, the radial inner end height is 2 mm, and the curvature of the radial outer end bottom 31 is the portion where the streamline rib and the convex portion of the character mark do not overlap. The radius is 4 mm, the radius of curvature of the radially inner end bottom 31 is 2 mm, and the upper surface of the convex portion at the portion where the rib and the convex portion overlap is projected 0.5 mm in parallel in the tire radial cross section from the upper surface of the rib. And the upper surface and side surface of the convex part in the part where a rib and a convex part overlap were set as the tire which protruded 0.5 mm in parallel in the tire circumferential direction from the upper surface and side surface of the rib. In the tire of Example 2, the mark displayed by the convex portion was sufficiently recognizable.

(Example 3)
The streamlined rib of the tire of Example 3 gradually increased in height from the tread surface toward the bead portion side. In the portion where the streamline rib and the convex portion of the character mark do not overlap, the end height on the radially outer side is 2 mm, the end height on the radially inner side is 4 mm, and the radius of curvature of the radially outer end bottom 31 is 2 mm, the radius of curvature of the radially inner end bottom portion 31 is 4 mm, and the upper surface of the convex portion in the portion where the rib and the convex portion overlap each other protrudes 0.5 mm in parallel in the tire radial cross section from the upper surface of the rib did. In the tire of Example 3, the mark displayed by the convex portion was sufficiently recognizable.

(Comparative Example 1)
The streamline rib of the tire of Comparative Example 1 was gradually lowered in height from the tread surface toward the bead portion side. The radial outer end height is 4.5 mm, the radial inner end height is 2 mm, and the curvature of the radial outer end bottom 31 is the portion where the streamline rib and the convex portion of the character mark do not overlap. Both the radius and the radius of curvature of the radially inner end bottom portion 31 were 4 mm, and the upper surface of the convex portion protruded from the upper surface of the rib by 0.5 to 4 mm in the overlapping portion. The protrusions of the convex portions of the ribs are not parallel to the ribs in both the tire radial cross section and the tire circumferential direction. In the tire of Comparative Example 1, the mark displayed by the convex portion was sufficiently recognizable.

(test)
A running test was performed using each of the tires manufactured above. The vehicle traveled 12,000 km on a rough road, and the crack generation ratio (character cracking property) generated at the bottom of the convex portion of the character mark was measured. The results are shown in Table 1. The evaluation vehicle was a 4000CC 4WD vehicle, and the tire pressure was 350 kPa.

  The index of character cracking property indicates that the larger the number, the more cracking is suppressed. In Example 1, the character cracking property was improved as compared with Comparative Example 1, and in Example 2, the character cracking property was further improved as compared with Example 1. Further, from Example 3, the effect is not recognized only when the streamline rib gradually decreases in height from the tread surface toward the bead portion side, but the streamline rib extends from the tread surface to the bead portion side. It can be seen that the same effect is observed even when the height gradually increases.

It is a figure showing the side wall part surface. It is A-A 'sectional drawing (radial direction sectional drawing) of FIG. FIG. 3 is a B-B ′ sectional view (radial direction sectional view) of FIG. 1 in the embodiment of FIG. 2. It is A-A 'sectional drawing (radial direction sectional drawing) of FIG. 1 in another aspect. It is A-A 'sectional drawing (radial direction sectional drawing) of FIG. 1 in another aspect. It is A-A 'sectional drawing (radial direction sectional drawing) of FIG. 1 in another aspect. FIG. 3 is a cross-sectional view (circumferential cross-sectional view) of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Bottom face of sidewall part 2 Land part 3 Convex part 31 End bottom part of convex part of the part which does not overlap 32 Protruding part of convex part

Claims (4)

In the sidewall portion, it has a land portion that extends continuously in the tire radial direction toward the bead portion side from the tread surface, and a convex portion that displays a mark formed along the tire circumferential direction,
The land portion and the convex portion are pneumatic tires having overlapping portions and non-overlapping portions,
The convex portion in the overlapping portion protrudes from the land portion,
The projecting portion where the projecting portion and the land portion do not overlap each other has a radially outer end bottom portion and a radially inner end bottom portion that each have a radius of curvature and curvedly contact the bottom surface of the sidewall portion. And
The radius of curvature of the end bottom portion on the higher end side from the bottom surface of the sidewall portion of the convex portion, of the radially outer end bottom portion and the radially inner end bottom portion of the convex portion, A pneumatic tire characterized by being larger than the radius of curvature of the end bottom on the side.   2. The pneumatic tire according to claim 1, wherein a radius of curvature of each end bottom portion on the radially outer side and the radially inner side of the convex portion is equal to or less than an end height on each side.   2. The pneumatic tire according to claim 1, wherein an upper surface of the convex portion in the overlapping portion protrudes substantially parallel to a cross section in the tire radial direction from an upper surface of the land portion. The pneumatic tire according to claim 3, wherein an upper surface and a side surface of the convex portion in the overlapping portion protrude substantially parallel to a cross section in the tire circumferential direction from the upper surface and the side surface of the land portion.

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