JP6567397B2 - tire - Google Patents

Description

  The present invention relates to a tire having a protective film on an outer surface.

  Conventionally, the surfaces of the tread portion, sidewall portion, and bead portion of the tire are formed of a rubber member. Since the rubber member deteriorates when it comes into contact with ozone in the air, minute cracks due to the deterioration are likely to occur on the outer surface of the tire, and the appearance of the product may be impaired. In particular, this crack is likely to occur on the outer surface of the groove portion, sidewall portion, and bead portion of the tread portion that does not contact the road surface and is not easily worn during traveling. On the outer surface of the sidewall portion, an information display portion (convex portion) is formed in which characters, symbols, figures, etc. indicating various information are engraved. Among the outer surfaces, cracks tend to easily occur at the end of the groove (concave portion) and at the end of the information display portion (convex portion).

  As a technique for suppressing the occurrence of cracks on the outer surface of the tire, a technique for providing a thin film with excellent crack resistance on the outer surface of the tread part where the groove part is formed (for example, Patent Document 1), or urethane on the sidewall part. A technique (for example, Patent Document 2) for providing a film mainly composed of is known.

Microfilm of Japanese Utility Model No. 59-125702 (Japanese Utility Model Application No. 61-039604) JP 2004-58752 A

  When a protective film that suppresses the generation of cracks is simply provided on the outer surface of the tire, the basic performance inherent to the tire may be affected and deteriorated by the protective film. When the tread portion has a protective film, the wet friction coefficient (μ) of the ground contact surface in the tread portion may decrease. If the friction coefficient (μ) when the ground contact surface is wet is lowered, it may be considered that the braking distance is increased.

  The present invention can suppress the occurrence of cracks due to ozone in the air on the outer surface of the sidewall portion and the tread portion, and further suppress the decrease in the friction coefficient (μ) during the wet of the contact surface, It is an object of the present invention to provide a tire capable of early recovery to a good value of the coefficient of friction (μ).

(1) A tire according to the present invention includes a tread portion, a pair of sidewall portions connected to both ends of the tread portion, and a pair of bead portions connected to the sidewall portion, and the tread portion and the sidewall portion. The bead portion is formed of a rubber member. In the tire according to the present invention, a non-rubber-based protective film having resistance to ozone is provided on the outer surfaces of the tread part and the sidewall part, and the sidewall part has a more protective film than the protective film of the tread part. The protective film is characterized in that the average thickness is thicker.
(2) The tire according to (1), wherein the protective film is formed using urethane.
(3) In the tire according to (1) or (2) above, the average thickness of the protective film of the tread portion is 50 μm to 150 μm, and the average thickness of the protective film of the sidewall portion is 100 μm to It is characterized by being 200 μm.
(4) The tire according to (1) or (2), wherein the protective film is provided on an outer surface of the bead part, the protective film of the bead part, the protective film of the tread part, and the sidewall part The average thickness increases in the order of the protective films.
(5) In the tire according to (4) above, the average thickness of the protective film of the bead part is 30 μm to 100 μm, the average thickness of the protective film of the tread part is 50 μm to 150 μm, The average thickness of the protective film in the sidewall portion is 100 μm to 200 μm.

  The present invention can suppress the occurrence of cracks due to ozone in the air on the outer surface of the sidewall portion and the tread portion, and further suppress the decrease in the friction coefficient (μ) during the wet of the contact surface, It is possible to provide a tire capable of achieving early recovery to a good value of the friction coefficient (μ).

FIG. 1 is a cross-sectional view in the width direction of a tire according to the first embodiment. FIG. 2 is a cross-sectional view in the width direction of the tire according to the second embodiment.

  Hereinafter, a tire according to an embodiment of the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals.

  FIG. 1 shows a cross-sectional view in the width direction of the tire according to the first embodiment. The tire 10 includes a tread portion 11, a pair of sidewall portions 12 that are continuous with both ends of the tread portion 11, and a pair of bead portions 13 that are continuous with the sidewall portion 12. The tread portion 11, the sidewall portion 12, and the bead portion 13 are formed of a rubber member. Here, the tread portion 11 is defined as a contact surface side with respect to the position 31 corresponding to the division position of the side mold of the vulcanization mold used at the time of tire manufacture. Further, the side wall portion 12 is defined between the position 31 corresponding to the side mold dividing position and the rim line 32. A portion opposite to the position 31 corresponding to the division position of the side mold from the rim line 32, that is, a region between the rim line 32 and the bead heel is defined as a bead portion 13.

  Here, the position of the rim line 32 extends parallel to the tire width direction through a position of 20.0 mm outward from the bead heel in the radial direction of the tire in an unloaded tire that is attached to the applied rim and applied with a predetermined internal pressure. The imaginary line is a position that intersects the outer surface of the tire. However, if the position where the imaginary line intersects the outer surface of the tire is located inward in the tire radial direction from the tire width direction line passing through the separation point between the tire and the rim, the "rim line position" The position where the tire width direction line passing through the separation point between the rim and the rim passes. Applicable rims are rims stipulated in industrial standards effective in the areas where tires are produced and used. For example, in Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK, in Europe, ETRTO (European) Tire and Rim Technical Organization (STANDARD MANUAL) In the United States, TRA (THE TIRE and RIM ASSOCIATION INC.) Refers to the rim defined in YEAR BOOK.

  A carcass 14 extending in a toroidal shape is provided between the pair of bead portions 13. The carcass 14 is locked around the bead core 15 embedded in the bead portion 13 by, for example, folding back from the inner side in the tire width direction toward the outer side.

  A belt 16 composed of a plurality of belt layers is disposed on the outer side of the crown portion 14a of the carcass 14 in the tire radial direction. Here, the belt layer is usually composed of a rubberized layer of a cord, preferably a rubberized layer of a steel cord, extending at an inclination with respect to the tire equatorial plane CL, and the plurality of belt layers constitute the belt layer. The belt 16 is formed by laminating the cords so as to cross each other with the equator plane interposed therebetween.

  A tread pattern formed by the groove 41 and the land portion 51 is provided on the outer surface side of the tread portion 11. On the outer surface of the sidewall portion 12, an information display portion is formed in which characters, symbols, figures, etc. indicating various information are engraved. As described above, in the groove 41 and the information display portion, cracks associated with deterioration of the rubber member due to ozone are particularly likely to occur.

  A non-rubber-based protective film 20 that is resistant to ozone and prevents cracking due to ozone is provided on the outer surfaces of the tread portion 11 and the sidewall portion 12 that come into contact with ozone. In the protective film 20, the outer surface portion of the tread portion 11 is a protective film 21, and the outer surface portion of the sidewall portion 12 is a protective film 22. The protective film 21 of the tread portion 11 is naturally formed also on the side wall portion and the bottom portion of the groove 41. The protective film 21 is also formed on the outer surface of the sipe 42 which is a fine groove provided in the land portion 51. The sipe 42 is formed, for example, in a direction slightly inclined from the tire circumferential direction on the ground contact surface. The protective film 22 of the sidewall portion 12 is naturally formed also on the outer surface portion of the information display portion.

  Since the outer surface of the bead portion 13 has fewer grooves and information display portions than the outer surfaces of the tread portion 11 and the sidewall portion 12, the amount of cracks generated is also small. Further, since the bead portion 13 is covered with a rim when the tire is used, cracks are hardly noticeable. In consideration of these points, the protective film 20 is not provided on the outer surface of the bead portion 13 in the present embodiment. Note that the protective film 22 of the sidewall portion 12 may extend from the sidewall portion 12 side in the vicinity of the boundary between the outer surface of the bead portion 13 and the sidewall portion 12.

  The protective film 20 is made of a thin film mainly composed of a non-rubber-based component that is resistant to ozone, is not damaged by ozone, has an effect of preventing cracking against ozone, and has excellent durability. Here, a urethane film, which is a protective film formed using urethane having resistance to ozone, was used. Some protective films 20 having durability against ozone, including urethane films, have higher hardness than the hardness of the outer surface side of the rubber member forming the tread portion 11, sidewall portion 12, and bead portion 13. Components having resistance to ozone used for the protective film 20 include polyethylene, polypropylene, and the like in addition to urethane.

  The protective film 20 can prevent ozone from contacting the outer surface of the rubber member that forms the tread portion 11 and the sidewall portion 12. Therefore, the tire according to this embodiment can prevent deterioration of the rubber member on the outer surface side due to ozone, can suppress the occurrence of cracks on the outer surfaces of the tread portion 11 and the sidewall portion 12, and maintain a good appearance. it can.

  The thickness of the protective film 20 for obtaining the effect of suppressing the occurrence of cracks is preferably about 30 μm to 200 μm. If it is smaller than 30 μm, the suppression effect is weak, and if it is 200 μm or more, the suppression effect hardly increases when it is substantially constant.

  A method for forming the protective film 20 will be described. In the vulcanization process at the time of tire manufacture, sponge-like urethane (foamed urethane) is wound around a predetermined portion of the outer surface of the tire before vulcanization, and then vulcanized to reduce the thickness of the urethane to form a tread portion 11 and a sidewall portion. 12 is formed with a protective film 20 having a predetermined thickness. As another method, a liquid having the same composition as urethane is applied to a predetermined portion of the outer surface of the tire and dried to form a protective film 20 having a predetermined thickness on the tread portion 11 and the sidewall portion 12.

  Here, the hardness of the protective film 20 which is a urethane film is higher than the hardness of the outer surface side of the rubber member forming the tread portion 11 as described above. Therefore, depending on the thickness of the protective film 21 of the tread portion 11, the protective film 21 in the tread portion 11 may reduce the coefficient of friction (μ) when the ground contact surface is wet, which may increase the braking distance. Conceivable. Moreover, in the protective film 20 using the component which is not urethane, the hardness may be below the hardness of the outer surface side of the rubber member which forms the tread part 11. Even in the protective film 20 with low hardness, depending on the film thickness of the protective film 21 of the tread portion 11, the friction coefficient (μ) when the ground contact surface is wet may be similarly reduced by the protective film 21 in the tread portion 11. is there. Here, the protective film 21 on the ground contact surface of the tread portion 11 (mainly the surface of the land portion 51) is not worn away when the tire 10 is mounted on the vehicle and travels a certain distance. If the protective film 21 on the ground contact surface is not worn, the normal friction coefficient (μ) at the time of wet by the rubber member (tread rubber) of the tread portion 11 is restored. The protective film 21 formed on the side wall and bottom of the groove 41 of the tread portion 11 and the protective film 21 formed on the outer surface of the sipe 42 of the tread portion 11 remain even after traveling. Therefore, the thickness of the protective film 21 is determined in consideration of both the degree of suppression of crack generation in the groove 41 and the sipe 42 of the tread portion 11 and the period of decrease in the friction coefficient (μ) during wet. In the groove 41 and the sipe 42 of the tread portion 11, an effect of suppressing the occurrence of cracks of a predetermined level or more is obtained, and the wet friction coefficient (μ) is a good value when the protective film 21 is not present within a predetermined travel distance. The average thickness of the protective film 21 that recovers to 50 μm is preferably 50 μm to 150 μm.

  Further, in the present embodiment, the occurrence of cracks in the sidewall portion 12 where the information display portion is formed is further suppressed than the occurrence of cracks in the tread portion 11. For this reason, the average thickness of the protective film 22 of the sidewall portion 12 is made larger than the average thickness of the protective film 21 of the tread portion 11. Considering that the average thickness of the protective film 21 of the tread portion 11 is preferably in the range of 50 μm to 150 μm, the average thickness of the protective film 22 of the sidewall portion 12 is preferably 100 μm to 200 μm. The protective film 22 having this average thickness can ensure a good riding comfort.

  As described above, the tire according to the present embodiment can suppress the influence of the protective film 20 on the wet friction coefficient (μ) of the ground contact surface, and can further suppress the decrease period of the wet friction coefficient (μ) of the ground contact surface. .

  In the present embodiment, the average thickness of each part of the protective film 20 is a value measured as follows. First, a tire is cut | disconnected in a tire width direction, and a tire width direction cross section is image | photographed. In the obtained image, the two points a and b on the interface between the outer surface of the rubber member and the protective film 100 are determined so that the lengths of the line segments a and b are 1 mm, respectively. The average thickness of the protective film was measured.

  As described above, the tire according to the present embodiment suppresses the occurrence of cracks due to ozone in the air on the outer surfaces of the tread portion and the sidewall portion, and more particularly more effectively in the sidewall portion than in the tread portion. Generation of cracks can be suppressed and a good appearance can be maintained for a long time. Furthermore, the tire according to the present embodiment can suppress the influence of the protective film 20 on the basic performance of the tire, and can further suppress the period during which the wet friction coefficient (μ) of the contact surface is reduced. As a result, it is possible to achieve both suppression of occurrence of cracks and early recovery of the contact surface wet coefficient of friction (μ) to a good value.

  Next, a tire according to a second embodiment will be described with reference to FIG. FIG. 2 is a cross-sectional view in the width direction of the tire according to the second embodiment. In addition, the same code | symbol is attached | subjected to the part same as 1st Embodiment, and description of the part is abbreviate | omitted.

  The tire 10a of the second embodiment is resistant to ozone on the outer surface of the bead portion 13 as well as the outer surfaces of the tread portion 11 and the sidewall portion 12, and prevents the occurrence of cracks due to ozone. 20a is provided. In the protective film 20 a, the outer surface portion of the bead portion 13 is a protective film 23.

  In the present embodiment, not only the tread portion 11 and the sidewall portion 12 but also the bead portion 13 is used to suppress the occurrence of cracks on the outer surface of the tire due to ozone in the air over a long period of time, thereby maintaining a good appearance. is there.

  Since the outer surface of the bead portion 13 has fewer grooves and information display portions than the outer surfaces of the tread portion 11 and the sidewall portion 12, the amount of cracks generated is also small. Therefore, the crack generation suppression effect of the protective film 23 may be lower than the crack generation suppression effect of the protective film 21 of the tread portion 11 and further the crack generation suppression effect of the protective film 21 of the tread portion 11. Therefore, the average thickness of the protective film 23 of the bead part 13 is made smaller than the thickness of the protective film 21 of the tread part 11. Considering that the average thickness of the protective film 21 of the tread portion 11 is preferably in the range of 50 μm to 150 μm, the average thickness of the protective film 23 of the bead portion 13 is preferably 30 μm to 100 μm. In the present embodiment, the protective film 20a is formed in the order of the protective film 23 of the bead part 13, the protective film 21 of the tread part 11, and the protective film 22 of the sidewall part 12 so that the average thickness increases.

  The hardness of the protective film 20a using urethane is higher than the hardness on the outer surface side of the rubber member forming the bead portion 13 as described above. Therefore, depending on the thickness of the protective film 23 of the bead part 13, the rim fit property (fitting property to a rim) of the bead part 13 may be reduced. Moreover, in the protective film 20a using the component which is not urethane, the hardness may be below the hardness of the outer surface side of the rubber member which forms the bead part 13. FIG. Even in the protective film 20a having a low hardness, depending on the film thickness of the protective film 23 of the bead part 13, the rim fit property of the bead part 13 may be reduced. In the average thickness 30 μm to 100 μm of the protective film 23 of the present embodiment, a sufficiently good rim fit property is obtained.

  As described above, the tire according to the second embodiment suppresses the occurrence of cracks due to ozone in the air on all the outer surfaces of the tread portion 11, the sidewall portion 12, and the bead portion 13, and more particularly than the tread portion. It is possible to more effectively suppress the occurrence of cracks in the sidewall portion and maintain a good appearance over a long period of time. Furthermore, the tire of the present embodiment can suppress the influence of the protective film 20a on the basic performance of the tire, can quickly recover the contact surface wet coefficient of friction (μ) to a good value, and can have a good rim fit. Can be ensured.

Next, examples and comparative examples relating to the first and second embodiments will be described. The tire size of each example and comparative example is 195/65 R15.
Example 1 In the first embodiment, the average thickness of the protective film 21 of the tread portion 11 is 50 μm, and the average thickness of the protective film 22 of the sidewall portion 12 is 100 μm.
Example 2 In the first embodiment, the average thickness of the protective film 21 of the tread portion 11 is 100 μm, and the average thickness of the protective film 22 of the sidewall portion 12 is 150 μm.
Example 3 In the first embodiment, the average thickness of the protective film 21 in the tread portion 11 is 150 μm, and the average thickness of the protective film 22 in the sidewall portion 12 is 200 μm.
Example 4 In the first embodiment, the average thickness of the protective film 21 in the tread portion 11 is 30 μm, and the average thickness of the protective film 22 in the sidewall portion 12 is 100 μm.
Example 5 In the second embodiment, the average thickness of the protective film 21 in the tread portion 11 is 100 μm, the average thickness of the protective film 22 in the sidewall portion 12 is 150 μm, and the average thickness of the protective film 23 in the bead portion 13. The thickness is 30 μm.
Example 6 In the second embodiment, the average thickness of the protective film 21 in the tread portion 11 is 150 μm, the average thickness of the protective film 22 in the sidewall portion 12 is 200 μm, and the average thickness of the protective film 23 in the bead portion 13. The thickness is 100 μm.
[Comparative Example 1] A conventional tire in which the protective film 20 is not provided.
[Comparative Example 2] A tire having the same structure as that of the first embodiment except for the average thickness of each part of the protective film 20, the average thickness of the protective film of the tread portion 11 is 220 μm, and the protective film of the sidewall portion 12 The average thickness is 150 μm.
[Comparative Example 3] A tire having the same structure as that of the second embodiment except for the average thickness of the protective film 20a. The thickness is 150 μm, and the average thickness of the protective film 23 of the bead portion 13 is 220 μm.

Table 1 shows the results of the following evaluations on the test tires of these examples and comparative examples.
[Evaluation of crack suppression]
A test tire is mounted at an internal pressure defined by the vehicle and allowed to run for three years. The level of occurrence of cracks in the tread portion, side portion, and bead portion was visually evaluated. The evaluation was made on a 7-point scale from 0 (no cracking) to 6 (replacement of tires required). The lower the number, the higher the cracking suppression effect. In this case, it is assumed that a crack generation suppression effect equal to or higher than a predetermined level is obtained at a generation level of 4 or less. An occurrence level of 3 or less is more desirable.

[Evaluation of recovery of wet friction coefficient (μ)]
A test tire is mounted at an internal pressure specified by the vehicle, and a travel distance is measured until the protective film 21 on the contact surface of the tread portion 11 is not completely worn (until it is completely worn). If the mileage to complete wear is less than 500 km, it is judged as a good early recovery (determined that there is a good suppression effect on the period when the wet friction coefficient (μ) is reduced), and the mileage to complete wear is 500 km The above is determined as having difficulty in early recovery (determining that there is difficulty in suppressing the wet friction coefficient (μ) during the reduction period). In Table 1, those with a running distance of less than 500 km until completion are indicated by “◯”, and those with a running distance of 500 km or more until completion are indicated by “Δ”.

[Rim fit evaluation]
When the test tire was filled with the internal pressure after the rim assembly, the pressure when the rim was fitted was measured and evaluated. The fit level by pressure was evaluated in three stages: 1 (no problem at all), 2 (OK level), and 3 (somewhat difficult). In this case, it is assumed that a sufficiently good rim fit can be obtained if the fit levels are 1 and 2.

  As shown in Table 1, the tires of Examples 1 to 4 relating to the first embodiment suppress the occurrence of cracks due to ozone in the air on the outer surface, compared with the tire of Comparative Example 1, and in particular from the tread portion. In addition, the occurrence of cracks can be suppressed more effectively in the sidewall portion, and a good appearance can be maintained over a long period of time. Furthermore, the tires of Examples 1 to 4 can further suppress the reduction period of the wet friction coefficient (μ) of the contact surface due to the protective film 20 as compared with the tire of Comparative Example 2. As a result, it is possible to achieve both suppression of occurrence of cracks and early recovery of the contact surface wet coefficient of friction (μ) to a good value.

  Further, in the tires of Examples 5 and 6 relating to the second embodiment, cracks due to ozone in the air on all the outer surfaces of the tread part 11, the sidewall part 12, and the bead part 13, compared with the tire of Comparative Example 1. In particular, the occurrence of cracks can be suppressed more effectively in the sidewall portion than in the tread portion, and a good appearance can be maintained over a long period of time. Furthermore, the tires of Examples 5 and 6 can suppress the influence of the protective film 20a on the basic performance of the tire compared to the tire of Comparative Example 3, and the contact surface has a good wet friction coefficient (μ). It is possible to achieve early recovery to the value and secure good rim fit at the same time.

  As mentioned above, although embodiment of this invention was described, these embodiment is only the illustration described in order to make an understanding of this invention easy, and this invention is not limited to the said embodiment. The technical scope of the present invention is not limited to the specific technical matters disclosed in the above embodiment, but includes various modifications, changes, alternative techniques, and the like that can be easily derived therefrom.

DESCRIPTION OF SYMBOLS 10,10a Tire 11 Tread part 12 Side wall part 13 Bead part 14 Carcass 15 Bead core 16 Belt 20, 20a Protective film 21 Tread part protective film 22 Side wall part protective film 23 Bead part protective film 31 Side mold dividing position Position corresponding to 32 rim line 41 groove 42 sipe 51 land portion

Claims (3)

A tread portion, a pair of sidewall portions connected to both ends of the tread portion, and a pair of bead portions connected to the sidewall portion, wherein the tread portion, the sidewall portions, and the bead portion are formed of a rubber member. Tires,
Provided on each outer surface of the tread portion, the sidewall portion, and the bead portion is a non-rubber protective film having resistance to ozone, the bead portion protective film, the tread portion protective film, the side A tire having an average thickness that increases in the order of the protective film of the wall portion . The tire according to claim 1,
The tire characterized in that the protective film is formed using urethane. The tire according to claim 1 or 2 ,
The average thickness of the protective film of the bead part is 30 μm to 100 μm, the average thickness of the protective film of the tread part is 50 μm to 150 μm, and the average thickness of the protective film of the sidewall part is 100 μm to 200 μm. A tire characterized by being.

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