JPH01153306A - Pneumatic tire and its formation mold - Google Patents

Abstract

PURPOSE:To improve maintainability of outside appearance at a tire having a side design by forming smooth portions and rough surface portions both of which have specified average roughness of a center line, with the interposition of projections so as to express the design. CONSTITUTION:A smooth portion 1 whose center line average roughness is 1.6a and a rough surface portion 2 whose center line average roughness is 3.2-25a are formed with a projection 3 interposed, and a design is expressed by the difference of the surface roughness of both surfaces. The height of this projection 3 is made to be 0.2-3.0mm. Also, designing can be done, too, by administering hard quality chrome plating of 5mum-50mum thickness, or the like on a smooth formation surface 20 and by forming a cavity 22 whose cavity depth is 0.2mm-0.3mm, between the smooth formation surface 20 and a rough surface formation surface 21. As a result, the design dan be retained under an excellent condition over a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a pneumatic tire having a design such as a graphic on the surface of a sidewall portion, and a mold for molding the pneumatic tire.

[Prior art]

BACKGROUND ART Conventionally, as the demands of automobile users have become more diverse, tires with various designs such as graphics on the surface of the sidewall portion have come to be desired.

As a result of various studies on such a design, the inventors of the present invention have found that by giving the sidewall surface a difference in surface roughness between a smooth surface and a rough surface, it has an extremely new feel and a good appearance. I came up with a new design.

It has been found that the design based on this difference in surface roughness is largely dominated by the smooth surface, and that the closer the surface is to a mirror surface, the better the appearance can be obtained.

However, in such a design, the closer the smooth surface is to a mirror surface, the more the center line average roughness becomes 1.
When the surface is in a state of 6a, dirt easily adheres to the surface compared to a rough surface, causing a problem that the appearance deteriorates at an early stage. That is, when the smooth surface contacts a curb or the like, dirt easily adheres to it, making it difficult to maintain a good appearance for a long time.

In addition, since the molding surface of a mold has a smooth surface and a rough surface adjacent to each other, when plating a smooth surface or etching a rough surface, the boundary between the two is important for appearance. The drawback of blurring lines was also a major issue that needed to be resolved.

Therefore, the present inventors solved these problems by simply processing the molding surface of the sidewall portion of the mold, and achieved the present invention.

[Purpose of the invention]

The present invention prevents dirt from adhering to a smooth surface when a side design is expressed by a difference in surface roughness.
Another object of the present invention is to provide a pneumatic tire that can maintain good appearance over a long period of time. Another object of the present invention is to provide a mold that can efficiently produce such pneumatic tires.

[Structure of the invention]

For this reason, the present invention forms a design represented by the difference in surface roughness between a smooth part with a centerline average roughness of 1.6a and a roughened part that is rougher than this on the surface of the sidewall part, The gist of the present invention is a pneumatic tire characterized in that a protrusion is provided at the boundary between the smooth portion and the rough surface portion. Moreover, the present invention forms a designed molding surface consisting of a smooth molding surface with a center line average roughness of 1.6a and a rough molded surface rougher than this on the molding surface of the sidewall portion, and The gist of the present invention is a pneumatic tire molding die, characterized in that the surface is plated with a hard metal and a depression is provided at the boundary between the smooth molding surface and the rough molding surface.

The pneumatic tire of the present invention may be either a radial tire or a bias tire, but it can be particularly preferably applied to a radial tire. In addition, in the present invention, the design applied to the sidewall portion mainly refers to shapes such as patterns and brands, but if necessary, it may include letters such as English letters, Japanese letters, numbers, or a combination thereof. shall also be included.

Hereinafter, the configuration of the present invention will be explained in detail with reference to the drawings.

FIG. 1(A) is an explanatory plan view showing an example of the design formed on the surface of the sidewall portion of the pneumatic tire of the present invention, FIG. 1(B) is a partially enlarged view thereof, and FIG. It is a planar view explanatory drawing which shows another design.

In these figures, 1 is a smooth part, 2 is a rough part,
A protrusion 3 is provided at the boundary between the smooth portion 1 and the rough surface portion 2.

In the present invention, the center line average roughness of the smooth portion l is 1.6
Let it be a. Here, the center line average roughness indicating the surface roughness of the tire is defined by JIS B12O3-1982, and is indicated by the symbol Ra. 1, 6 which defines the smooth part according to this JIS regulation
"a" represents the maximum allowable value of the center line average roughness, and means that the surface roughness is within the following range.

QμmRa≦1.6a≦1.6 um Ra, that is,
The arithmetic mean value of center line average roughness Ra at several locations is 1.6 μm
This means that up to Ra can be tolerated.

On the other hand, the rough surface portion 2 provided in contrast to the smooth portion 1 has a center line average roughness of (3,2 to 25 )
It is preferable to set it in the range of a. This (3,2-25)
a represents the section of center line average roughness according to the above JIS regulations, and the lower limit of that section is 3.2 μm Ra
This means that the upper limit is 25 μm Ra.

In this way, the sharpness expressed by the difference in surface roughness between the smooth portion and the rough surface portion becomes even more remarkable as the center line average roughness of the smooth portion approaches 0 μm Ra as much as possible. On the other hand, if the smooth portion exceeds 1.6 μm Ra, the surface roughness approximates that of the rough surface portion, which impairs the visual effect and makes it difficult to recognize a clear design. Therefore, in order to further emphasize the sharpness of such a design, it is more preferable to make the smooth part 0.8
If the rough surface portion is set to (3,2 to 6.3) a, an even better appearance can be obtained.

In addition, the reason why the protrusions 3 are provided in the present invention is that even when the tire comes into contact with a curb, etc., only the protrusions 3 come into contact and guard the smooth parts, and since it is difficult to contact the smooth parts, it prevents dirt from adhering. This is because it can be prevented. The height of the protrusion 3 is 0.2 mm ~
Preferably, it is 3.0 mm. If it is less than 0.2 mm, the effect of providing the protrusion 3 will not be recognized, and if it exceeds 3.0 mm, when the unvulcanized tire is pressed against the depression of the mold molding surface corresponding to the protrusion 3 during tire vulcanization, This is because a vortex is generated in the depression due to the flow of the rubber, and there is a risk that dust, mold release agent, etc. adhering to the surface of the unvulcanized tire may be caught in this vortex.

In order to obtain the above-mentioned design, a smooth molding surface and a rough molding surface having the same surface roughness are processed on the molding surface of the sidewall part of the mold for molding this tire. What is necessary is just to provide a depression at the boundary with the surface forming surface.

FIG. 3 is an explanatory partial cross-sectional view of an example of the pneumatic tire molding mold of the present invention, that is, a two-split mold. Third
In the figure, 10 is a mold body, and this mold body 1
A part of the molding surface 11 of the sidewall part on the inner surface of 0 has a
A smooth molded surface and a rough molded surface are formed so as to correspond to the designs shown in FIGS. ing. Note that 12 is a bead ring attached to the mold body 10 with bolts 13.

The center line average roughness of the smooth molded surface is 1.6a. This smooth molded surface is plated with a hard metal such as hard chrome plating, hard nickel plating, hard rhodium plating, etc. This makes it possible to obtain a mirror surface with extremely high smoothness. The thickness of this hard metal plating is 5~50μ
The range is preferably 10 to 308 m, more preferably 10 to 308 m.
It is recommended to set it within the range of . If it is thinner than 5 μm, the molding surface of the mold will not be sufficiently covered, and the effect of providing this plating layer will not be sufficiently exhibited. Further, even if the plating layer is made thicker than 50 μm, no effect can be obtained and it is uneconomical. Note that, if necessary, the rough molded surface may also be plated with a hard metal. This plating layer improves durability against cleaning by sandblasting. That is, after the mold is used, it must be cleaned by sandblasting or the like every approximately 1000 uses to remove dirt adhering to the molding surface. Even when sandblasting involves blowing plastic particles with relatively low hardness using compressed air, if there is no plating layer, the molded surface will gradually become rougher and eventually become blurred. However, if the hard metal plating layer is formed by sandblasting, which has a relatively low hardness, it is possible to suppress wear and prevent the sharpness of the molded surface from deteriorating. In addition, this hard metal plating layer exhibits a mold release effect (easily peeling off the tire, etc. from the mold) and prevents the dirt and rust from adhering to it. The molding surface can be cleaned in a short time by using granular material). Further, by applying hard metal plating in this manner, a distinct luster is produced in a corresponding portion of the sidewall portion of the tire after vulcanization.

The center line average roughness of the rough molded surface is (3,2-25)a. This rough molded surface may be formed by etching. Etching depth is 0.1-0.3 mm
It is preferable that it is in the range of . This is because this range is favorable in terms of cost and durability.

The depression depth at the boundary between the smooth molded surface and the rough molded surface is 0.2, corresponding to the height of the protrusion 3 on the sidewall portion of the tire.
mm to 3.0 mm. Providing the depressions in this way has the advantage that, for example, when forming a rough molded surface by etching, the masking step can be easily carried out. Here, the masking process refers to a process of covering unnecessary parts in order to apply plating or etching only to desired parts.

Next, FIGS. 4A and 4B show the correspondence between the molding surface of the mold and the surface of the sidewall portion of the tire.

FIG. 4(A) shows the molding surfaces of the mold, where 20 is a smooth molding surface, 21 is a rough molding surface, and 22 is a depression. Figure 4 (B
) shows the surface of the sidewall portion of the tire, and the smooth molding surface 20, the rough molding surface 21, and the depression 22 of the molding surface correspond to the smooth portion 1, the rough surface portion 2, and the protrusion 3, respectively. h is the height of the protrusion 3;

Note that the mold of the present invention may be either a two-part mold or a sectional mold.

〔Effect of the invention〕

As explained above, according to the present invention, the design is formed by the difference in surface roughness of the sidewall portion of the tire, and since the protrusion is provided at the boundary between the smooth portion and the rough surface portion, the sidewall portion is The protrusions guard the smooth portion when it comes into contact with a curb or the like, thereby preventing dirt from adhering to the surface of the smooth portion. therefore,
It becomes possible to maintain a good appearance over a long period of time.

In addition, the mold for molding this tire has a concave boundary between the smooth molding surface and the rough molding surface, so when applying hard metal plating to the smooth molding surface or etching the rough molding surface, This has the advantage that the masking process is extremely easy to carry out.

[Brief explanation of the drawing]

FIG. 1(A) is a plan view explanatory diagram showing an example of the design formed on the surface of the sidewall portion of the pneumatic tire of the present invention, FIG. 1(B) is a partially enlarged view thereof, and FIG. FIG. FIG. 3 is a partial cross-sectional explanatory view of an example of the pneumatic tire molding mold of the present invention, and FIG. 4 (A). (B) is an explanatory diagram showing the correspondence between the molding surface of the mold and the surface of the sidewall portion of the tire. DESCRIPTION OF SYMBOLS 1... Smooth part, 2... Rough surface part, 3... Protrusion, 10
... Mold body, 11... Molding surface, 12... Bead ring, 13... Bolt, 20... Smooth molding surface, 2
1... rough molded surface, 22... depression. Agent Patent Attorney Nobuo Ogawa −

Claims (1)

[Claims] 1. The surface of the sidewall portion has a center line average roughness of 1.
6a, which has a design represented by a difference in surface roughness between the smooth part and a rougher surface part, and has a protrusion provided at the boundary between the smooth part and the rougher part. Included tires. 2. Set the protrusion height at the boundary between the smooth part and the rough part to 0.2 mm or more.
The pneumatic tire according to claim 1, which has a diameter of 3.0 mm. 3. The pneumatic tire according to claim 1, wherein the center line average roughness of the rough surface portion is (3.2 to 25)a. 4. The center line average roughness of the sidewall molding surface is 1.
．． A designed molding surface consisting of the smooth molding surface of 6a and a rough molding surface that is rougher than this is formed, and the smooth molding surface is plated with a hard metal, and the boundary between the smooth molding surface and the rough molding surface is formed. A mold for molding a pneumatic tire, which is characterized by having a recess. 5. The center line average roughness of the rough molded surface is (3.2 to 25)a
A mold for molding a pneumatic tire according to claim 4. 6. The depression depth at the boundary between the smooth molded surface and the rough molded surface is set to 0.
7. A pneumatic tire molding mold according to claim 4, in which the thickness of the hard metal plating layer is 5 μm to 50 μm. Mold for forming pneumatic tires.