JP5986375B2 - Tire and tire mold - Google Patents

Description

  The present invention relates to a tire and a tire molding die, and more particularly, to a tire excellent in performance on ice and on snow, and a tire molding die used for manufacturing the tire.

Conventionally, various devices have been made for winter tires in order to improve performance on ice and performance on snow.
For example, in Patent Document 1, by providing a plurality of sipes in each block formed in the tread portion, the edge component in the ground contact surface is increased and the snow biting effect is improved, so that the snow / ice road surface (frozen road surface or Techniques for improving running performance on snowy road surfaces have been proposed.
Further, for example, in Patent Document 2, in a tire having a tread rubber having a so-called cap-and-base structure composed of a cap rubber and a base rubber, the water removal performance is greatly improved by using foamed rubber as the cap rubber. Technologies for improving the performance on ice and on snow have been proposed.

  Further, for example, in Patent Document 3, as shown in FIG. 1A, with respect to the surface property of the tread portion 1 of the tire, the surface roughness is obtained by providing a protruding portion 2 having a sharp tip on the surface of the tread portion. There has been proposed a technique for increasing the on-ice performance and on-snow performance of a tire by increasing the friction and increasing the frictional force between the tire surface and the road surface.

JP 2002-192914 A JP-A-11-301217 JP 2009-67378 A

However, in the technique of providing sipes in the block described in Patent Document 1, if the number of sipes is increased too much, the rigidity of the block decreases and the block collapses easily. There was a problem that performance on ice and performance on snow deteriorated.
Moreover, in the technique using foamed rubber for the cap rubber described in Patent Document 2, the rigidity of the entire block may be reduced due to the use of foamed rubber, and the tire wear resistance is not always sufficient.
Furthermore, in the technique of providing a protrusion with a sharp tip on the surface of the tread described in Patent Document 3, since the rigidity of the protrusion is low, the tire is particularly large when the load on the front wheel is increased due to the nose dive of the vehicle. When a load is applied, the projection may be crushed and desired performance may not be obtained. That is, in the technique in which the protruding portion having a sharp tip is provided on the surface of the tread portion, as shown in FIG. 1B, the protruding portion 2 is crushed by contact with the road surface T, and the volume of the water removal gap 3 is reduced. However, as a result of the reduction in water removal, desired performance on ice and performance on snow may not be obtained. Therefore, the technique described in Patent Document 3 has room for further improvement in performance on ice and performance on snow.
Furthermore, as a result of the inventor's repeated studies on tires employing the techniques described in Patent Documents 1 to 3, the cause of these conventional tires is not clear, but sufficient on-ice performance and on snow It was also found that there was a problem that performance could not be obtained. Therefore, the techniques described in Patent Documents 1 to 3 have room for improving the performance on ice and the performance on snow especially when the tire is new.

  An object of the present invention is to solve the above problems, and to provide a tire with improved performance on ice and performance on snow, and a mold for molding a tire used for manufacturing (molding) the tire. To do.

The inventor has intensively studied to solve the above problems.
As a result, the present inventor can further improve the on-ice performance and on-snow performance of the tire by suppressing a decrease in block rigidity and a decrease in water removal, if a predetermined fine structure is formed on the tread portion tread, and It has been found that sufficient performance on ice and performance on snow can be exhibited even when a tire is new, and the present invention has been completed.

This invention is made | formed based on said knowledge, The summary structure is as follows.
In the tire of the present invention, a large number of hemispherical protrusions are formed over the entire tread surface.
The diameter of the hemispherical protrusion gradually increases from the outside in the tire radial direction toward the inside,
The entire tread portion tread is formed by the hemispherical protrusions.
Rsk <0 and Rku ≦ 2
Have a surface roughness satisfying,
The protrusion is characterized in that an average interval S between local peaks of the protrusion is 5.0 to 100 mm .
Accordingly, it is possible to further improve the on-ice performance and the on-snow performance of the tire by further suppressing the decrease in water removal while further suppressing the decrease in block rigidity. That is, the skewness Rsk of the contour curve of the tread surface and the torque cis Rku of the contour curve of the tread surface are expressed as follows:
Rsk <0 and Rku ≦ 2
Therefore, the on-ice performance and the on-snow performance of the tire can be further sufficiently improved while further suppressing a decrease in block rigidity and a decrease in water removal. That is, since the tire has a surface property of Rsk <0 and Rku ≦ 2, even when a large load is applied to the tire, the protrusion has a highly rigid shape. Therefore, the block rigidity can be secured, and the water removal path can be secured.
Here, “Rsk” means the skewness Rsk (JIS B 0601 (2001)) of the contour curve of the tread surface. “Rku” means kurtosis Rku (JIS B 0601 (2001)) of the contour curve of the tread surface.

The tire molding die of the present invention is a tire molding die having a tread surface molding surface for molding a tread surface of a tire, and the tread surface molding surface extends over the entire tread surface molding surface. Have many hemispherical recesses,
The diameter of the hemispherical recess gradually increases from the bottom side of the hemispherical recess toward the surface side of the tread surface molding surface,
The entire tread molding surface is formed by the hemispherical recess.
Rsk> 0 and Rku ≦ 2
Have a surface roughness satisfying,
The said recessed part is an average space | interval S of the local peak of this recessed part being 5.0-100 mm .
Thereby, the tire which has the above-mentioned surface roughness and excellent in performance on ice and performance on snow can be molded.

  ADVANTAGE OF THE INVENTION According to this invention, the tire mold which can shape | mold the tire which improved on-ice performance and on-snow performance, and this tire can be provided.

(A) It is a schematic sectional drawing which shows typically the tread part tread of the conventional tire. (B) It is a schematic sectional drawing which shows typically a mode that a tread part tread of a tire and a road surface contact at the time of load load of a tire. It is a tire width direction sectional view of the tire concerning one embodiment of the present invention. It is a figure which expands and shows typically the shape of a part of tread part tread of the tire shown in Drawing 2, (a) is a top view, and (b) is a tire width direction sectional view. It is a SEM image (scanning electron microscope image) of the tread part tread of an example of the tire of the present invention. 1 is a schematic partial perspective view schematically illustrating a part of a tire molding die according to an embodiment of the present invention. It is a figure which expands and shows typically the shape of a part of tread surface molding surface of the metal mold | die for tire shown in FIG. 5, (a) is a top view, (b) is a width direction sectional drawing. (A)-(c) is a reference example of the shape of a part of tread part tread of a tire.

  Hereinafter, the tire and the tire molding die of the present invention will be described. The tire according to the present invention is characterized in that a predetermined fine structure is formed on at least a part of a tread surface (surface that contacts the road surface), and a surface property (tread surface property) of the tread portion is a predetermined property. . The tire molding die according to the present invention is used for manufacturing the tire according to the present invention, and has a predetermined inner surface of the mold, specifically, at least a part of a tread surface molding surface for molding the tread portion tread surface of the tire. It is characterized in that a microstructure is formed and the surface texture of the tread surface is made predetermined.

<Tire>
FIG. 2 is a sectional view in the tire width direction of one embodiment of the tire of the present invention.
As shown in FIG. 2, the tire 20 of the present embodiment includes a pair of bead portions 4, a pair of sidewall portions 5 that extend outward from each bead portion 4 in the tire radial direction, and the sidewall portions 5. And a tread portion 6 extending across.
Further, the tire 20 of the present embodiment includes a carcass 7 straddling a toroidal shape between a pair of bead cores 4a embedded in the pair of bead portions 4, and a two-layer belt disposed on the outer side in the tire radial direction of the carcass 7. A belt 8 composed of layers 8a and 8b. Further, a tread rubber made of non-foamed rubber is disposed outside the belt 8 in the tire radial direction.

Here, in the tire 20, minute protrusions having a predetermined shape are formed on the entire tread surface. Specifically, FIG. 3A shows an enlarged plan view of the tread portion tread surface 6a, FIG. 3B shows an enlarged cross-sectional view along the tire width direction on the tread portion tread surface 6a side, and FIG. As shown in the SEM photograph of the tread, in the tire according to the present embodiment, a large number of minute protrusions 9 (having a hemispherical shape in the illustrated example) that are convex outward in the tire radial direction are formed on the entire tread surface 6a. At least a part of the tread surface 6a has a surface roughness such that Rku is 2 or less and Ra is 1 μm or more and 50 μm or less.
FIG. 3 shows a case where the protrusion 9 is a hemispherical protrusion, but in the tire of the reference example , the protrusion has a truncated cone shape, a truncated pyramid shape, etc. A trapezoidal cross section as shown in FIG. 7, a rectangular shape such as a cylinder or a prism, and a truncated hemispherical shape as shown in FIG. 7C. It can be of various shapes.

And in this tire 20, since the roughness of the surface of the tread portion tread satisfies Rsk <0 and Rku ≦ 2, the on-ice performance of the tire is suppressed while suppressing a decrease in block rigidity and a decrease in slow water. The performance on snow can be sufficiently improved.
That is, in the tire 20, the surface property of the tread surface satisfies Rsk <0 and Rku ≦ 2, so that even when a large load is applied to the tire, the protruding portion has a highly rigid shape. Therefore, the protrusions are not easily crushed, so that the block rigidity can be ensured and the water removal path can also be ensured.
In the tire 20, the formation of the minute protrusions 9 having a predetermined shape achieves the suppression of the reduction in water removal and the improvement of the performance on ice and the performance on snow. Therefore, an excessive number of sipes are formed, There is no need to use foam rubber.
The cause of the tire 20 is not clear, but sufficient on-ice performance and on-snow performance can be exhibited even when it is new (unused state).

  Therefore, according to the tire 20, it is possible to further suppress the on-ice performance and the on-snow performance of the tire even when it is new by suppressing the decrease in block rigidity and the decrease in water removal.

Here, in the tire 20, the portion where the protruding portion 9 is formed is the same for the following reason.
Rsk <−0.1 and Rku ≦ 2
It is more preferable that the surface properties satisfy the above conditions.

Further, in the tire 20, the shape of the protrusions 9 is Ru hemispherical der. If the shape of the protrusions 9 is a hemispherical protrusion 9 does not easily collapse, Ru can ensure water drainage.

Furthermore, in the tire 20, it is preferable that the height H of the protrusion 9 formed on the tread surface is 1 to 50 μm. This is because if the height H of the protrusions 9 is 1 μm or more, a sufficient volume of the gaps between the protrusions 9 can be secured and water removal can be enhanced. Further, if the height H of the protrusion 9 is 50 μm or less, the rigidity of the protrusion 9 can be increased and sufficient water removal can be ensured.
Here, the height of the protrusion 9 is in contact with the first virtual plane orthogonal to the tire radial line extending through the tip (tire radial outer end) of the protrusion 9 and the outer contour of the protrusion 9 and It shall mean the distance along the tire radial direction between the second virtual plane closest to the first virtual plane among the virtual planes orthogonal to the tire radial direction line.
In addition, the height of the protrusion part 9 can be measured with SEM and a microscope.

  In addition, it is more preferable that the part where the protrusion is formed has a surface property such that the kurtosis Rku of the contour curve element has a surface roughness of 1.5 or less for the same reason.

Here, in the tire of the present invention, at least a part of the tread portion tread has the following relational expression:
50 μm ≦ RSm ≦ 250 μm
Rku ≦ 2
It is preferable to have a surface property satisfying the above.
In this way, if at least part of the tread surface (the surface that contacts the road surface when traveling) is set so that RSm is 50 to 250 μm and Rku is 2 or less, the decrease in block rigidity is further suppressed. However, the frictional force between the tire surface and the road surface can be further increased, and the on-ice performance and on-snow performance of the tire can be further improved. Moreover, the reduction of water removal can be further suppressed. Moreover, since the RSm of the tread surface is 50 to 250 μm and the Rku is 2 or less, the on-ice performance and on-snow performance of the tire are further improved while further suppressing the decrease in block rigidity and the dewatering performance. Can be made.
That is, since RSm of the tread surface is 50 μm or more and Rku is 2 or less, the outer diameter of the protrusion and the distance between the protrusions can be sufficiently increased. Therefore, at the time of ground contact with the road surface, both the removal of the water film on the road surface using the gap between the protrusions 9 and the improvement on the ice performance and the snow performance by increasing the frictional force between the tread surface and the road surface are achieved. Can be made.
Furthermore, since the RSm of the tread part tread is 250 μm or less, a sufficient number of protrusions are formed at a high density on the tread part tread to sufficiently increase the frictional force between the tread part tread and the road surface. Can do.
Further, since the Rku of the tread surface of the tread is 2 or less, the rigidity of the protrusion 9 can be ensured, and even when a large load is applied to the tire, the protrusion 9 is not easily crushed, and the water removal property Can be secured. Therefore, it is possible to further improve the on-ice performance and the on-snow performance of the tire even when new, while suppressing a decrease in block rigidity and a decrease in water removal performance.
In the tire of the present invention, it is preferable that RSm is 50 to 250 μm and Rku is 2 or less over a range of 90% or more of the area of the tread surface. If the RSm is 50 to 250 μm and the Rku is 2 or less over 90% or more of the tread surface area, the effect obtained by setting the surface properties within a predetermined range can be sufficiently increased. Because.
Here, in the tire 20, it is more preferable that the RSm of the tread surface is 60 to 150 μm. This is because, when the RSm of the tread surface is set to 60 μm or more, water removal can be sufficiently improved and the frictional force between the tread surface and the road surface can be sufficiently increased. Further, if the RSm of the tread part tread is set to 150 μm or less, the frictional force between the tread part tread and the road surface can be sufficiently increased.
Here, “RSm” means the average length (JIS B0601 (2001)) of the contour curve elements of the tread surface.

In the tire of the present invention, it is preferable that at least a part of the tread surface has a surface roughness such that Rku is 2 or less and Ra is 1 μm or more and 50 μm or less.
Accordingly, it is possible to further improve the on-ice performance and the on-snow performance of the tire by further suppressing the decrease in water removal while further suppressing the decrease in block rigidity. Moreover, if the surface roughness of the tread surface is set to Rku of 2 or less and Ra is 1 μm or more and 50 μm or less, the on-ice performance of the tire is further suppressed while further suppressing the decrease in block rigidity and the decrease in water removal. In addition, the performance on snow can be further improved sufficiently. That is, as for the surface property of the tread part tread surface, Rku is 2 or less, so even when a large load is applied to the tire, the protruding part has a highly rigid shape, and the protruding part is not easily crushed. Since Ra is 1 μm or more, a water removal path can be secured. On the other hand, since Ra is 50 μm or less, the block rigidity can be maintained even at high loads. In addition, it is more preferable that the portion where the microprojection portion 9 is formed has a surface property such that Rku is 2 or less and Ra has a surface roughness of 10 μm or more and 40 μm or less.
Here, “Ra” means arithmetic mean roughness Ra (JIS B 0601 (2001)) of the tread surface.

Here, the ten-point average roughness Rz of the tread surface of the tire due to the hemispherical protrusion is preferably 1.0 to 50 μm.
This is because when Rz is 1.0 μm or more, a void for water removal can be secured, while when Rz is 50 μm or less, a contact area with the road surface can be secured. This is because the performance on the ice and the performance on the snow of the tire can be further improved.
Here, “ten-point average roughness Rz” is measured in accordance with the provisions of JIS B 0601 (1994), and the reference length is 0.8 mm and the evaluation length is 4 mm. Is.

The average spacing S between local peaks of the projections 9 formed on the tread surface of the tire, Ru 5.0~100μm der.
This is because when the distance S is 5.0 μm or more, it is possible to ensure a water removal gap, while when the distance S is 100 μm or less, it is possible to ensure a contact area with the road surface. This is because the performance on the ice and the performance on the snow of the tire can be further improved.
Here, “the average interval between the local peaks” is measured in accordance with JIS B 0601 (1994), and the reference length is 0.8 mm and the evaluation length is 4 mm.

  And the tire mentioned above can be manufactured using the following molds for tire molding, without being specifically limited. The tire molding using the following tire molding die can be performed according to a conventional method.

<Tire molds>
FIG. 5 is a schematic partial perspective view showing a part of a tire molding die used for molding the tire of the present invention.
As shown in FIG. 5, the mold 10 has a molding surface 11 for vulcanizing and molding a tire.
This molding surface 11 has a tread surface molding surface 11a that forms a tread portion tread surface. In the illustrated example, a side wall molding surface 11b that molds the outer surface of the sidewall portion, and a bead portion that molds the outer surface of the bead portion. It also has a molding surface 11c.
Although this shaping | molding surface 11 is not specifically limited, For example, it can form with aluminum.
The tread portion tread surface having the above-described surface property of the tire of the present invention can be formed by the tire vulcanization mold 10 including the tread surface molding surface 11a having the surface property corresponding to the surface property. Specifically, FIG. 6A shows an enlarged plan view of the tread forming surface 11a, and FIG. 6B shows an enlarged cross-sectional view along the width direction on the tread forming surface 11a side of the mold 10. The tire molding die 10 according to the present embodiment has a large number of recesses 12 on the entire tread surface molding surface 11a for molding the tread portion tread surface of the tire. Further, at least a part (the entire surface in the illustrated example) of the tread surface has a surface roughness that satisfies Rsk> 0 and Rku ≦ 2. FIG. 6 shows the case where the concave portion 12 is a hemispherical concave portion. However, in the mold of the reference example , the concave portion 12 has a truncated hemispherical shape, a truncated cone shape, a truncated pyramid shape, and a cylindrical shape. Alternatively, it may be a prismatic recess.
That is, in the tire vulcanization process using this mold 10, the surface shape of the tread surface molding surface 11a of the mold 10 is transferred as the surface shape of the tread portion tread surface of the tire. A large number of protrusions 9 are formed on the tread portion tread of the manufactured tire, and the tread portion tread has a surface roughness satisfying Rsk <0 and Rku ≦ 2. Therefore, a tire excellent in performance on ice and on snow can be formed.
Hereinafter, a method for forming the tread surface molding surface 11a of the mold 10 will be described.

The tread surface molding surface 11a can be formed by a projection material projection process in which a projection material having a specific shape is projected and collided with the molding surface. And the mold for tire molding obtained through this projecting material projecting step has a tread surface molding surface having many recesses 12 as described above, and at least a part of the tread surface molding surface has Rsk> 0, and Since the tire has a surface roughness that satisfies Rku ≦ 2, the tread surface of the tire that is vulcanized using this mold has a surface that satisfies Rsk <0 and Rku ≦ 2 as described above. It will have roughness.
Here, in the projection material projecting step, it is preferable that the tread surface molding surface 11a (entire surface or part) is formed by projecting and colliding a spherical projection material having a sphericity of 15 μm or less.
This is because, by setting the sphericity of the projection material to 15 μm or less, it is possible to form a large number of concave portions having desired properties on the molding surface of the mold of the mold, and the tire molded using this mold This is because the tread surface can be formed into a desired surface shape.

The sphericity of the projection material is more preferably 10 μm or less.
If the sphericity of the projection material is set to 10 μm or less, it is possible to easily form a large number of concave portions having desired properties on the molding surface of the mold, so that the tread surface of the tire formed using the mold is used. This is because it is possible to form a tire having more excellent performance on ice and performance on snow by forming a large number of protrusions having a desired shape.
The sphericity of the projection material is more preferably 5 μm or less.
This is because a recess having a desired property can be more easily formed on the tread surface molding surface of the mold.

Here, it is preferable that the average particle diameter of the projection material used for a projection material projection process is 10 micrometers-1 mm.
Because, by setting the average particle size of the projection material to 10 μm or more, it becomes easy to obtain a mold having a desired concave shape on the tread surface molding surface, and in the projection material projection step, when projecting under high pressure, This is because the projection material can be prevented from being scattered around, and on the other hand, by setting the average particle size of the projection material to 1 mm or less, it is possible to suppress the wear of the mold surface early. .
For the same reason, the average particle diameter of the projection material is more preferably 20 μm to 0.7 mm, and further preferably 30 μm to 0.5 mm.
Here, the “average particle size” is a photograph of the projection material taken by SEM, and 10 projection materials are taken out arbitrarily, and the average of the diameter of the inscribed circle and the diameter of the circumscribed circle in contact with each of the projection materials is calculated. The value obtained by averaging these values with the ten projectiles shall be referred to.

Moreover, it is preferable that the Mohs hardness of a projection material shall be 2-10.
This is because by setting the Mohs hardness of the projection material to 2 or more, it becomes easy to obtain a mold having a desired concave shape on the tread surface molding surface. On the other hand, by setting the Mohs hardness of the projection material to 10 or less, it is possible to reduce the early pain of the mold.
For the same reason, the Mohs hardness of the projection material is more preferably 3.0 to 9.0, and even more preferably 5.0 to 9.0.
The Mohs hardness of the tire molding die is preferably 2.0 to 5.0, and the difference in Mohs hardness between the tire molding die and the projection material is 3.0 to 5.0. Preferably there is.

Furthermore, the specific gravity of the projection material is preferably 0.5-20.
This is because by setting the specific gravity of the projection material to 0.5 or more, it is possible to improve the workability by suppressing the scattering of the projection material in the projection process. On the other hand, by setting the specific gravity of the projection material to 20 or less, energy for accelerating the projection material can be reduced, and early wear of the mold can be suppressed.
For the same reason, the specific gravity of the projection material is more preferably 0.8-18, and further preferably 1.2-15.

  Here, the material of the projection material is not particularly limited, but for example, it is preferable to use gyricon, iron, cast steel, ceramics, or the like.

Further, in the projecting material projecting step, it is preferable to project the projecting material onto the tread surface molding surface of the mold with high pressure air of 100 to 1000 kPa for 30 seconds to 10 minutes.
Because, by projecting the projection material at 100 kPa or more for 30 seconds or more, the tread surface can be uniformly formed into the desired shape described above, while the projection material is projected at 1000 kPa or less and 10 minutes or less. This is because it is possible to suppress damage to the tread surface molding surface.
In addition, it is preferable to set the projection speed of the projection material to 0.3 to 10 (m / s) by adjusting the specific gravity and the projection pressure of the projection material, and to 0.5 to 7 (m / s). More preferred.
At this time, the distance between the projection nozzle of the projection material and the tire molding die is preferably 50 to 200 (mm).
Here, the projection time of the above-mentioned projection material means the projection time per mold, for example, when molding a tire with nine molds, the tread of nine molds that mold one tire It is preferable to project on the molding surface for a total of 270 seconds to 90 minutes.
In addition, the projection of the projection material onto the tread surface molding surface of one mold can be performed while shifting the position projected by the operator while considering the shape of the mold. In this way, the projection material can be projected more uniformly.

  Here, in this mold 10, it is preferable that the tread surface has a surface roughness satisfying Rsk> −0.1 and Rku ≦ 2. The tire can be molded so that at least a part of the tread surface of the formed tire has a surface roughness satisfying Rsk <−0.1 and Rku ≦ 2, and the on-ice performance of the tire This is because it is possible to form a tire with even better performance on snow. In addition, Rsk of the tread forming surface can be controlled by adjusting the projection time of the projection material. Specifically, when the projection time of the projection material is increased, Rsk can be decreased. The Rku of the tread surface molding surface can be controlled by adjusting the projection time of the projection material. Specifically, when the projection time of the projection material is increased, Rku can be decreased.

Further, in the mold 10, the shape of the recess 12 is Ru hemispherical der. If hemispherical shape of the recess 12, Ru can form hemispherical projections 9 in the tread surface of the tire. In addition, the shape of the recessed part 12 can be controlled by adjusting the particle size, the injection speed, and the projection angle of the projection material.

Furthermore, in this mold 10, the depth h of the recess 12 is preferably 1 to 50 μm. This is because if the depth h of the recess 12 is 1 to 50 μm, the protrusion 9 having a height of 1 to 50 μm can be formed on the tread surface of the tire. Note that the depth h of the recess 12 can be controlled by adjusting the projection speed of the projection material. Specifically, the depth h can be increased by increasing the projection speed of the projection material.
Here, the depth of the concave portion 12 is in contact with the third virtual plane orthogonal to the radial line extending through the deepest portion (radially inner end) of the concave portion 12 and the outer contour line of the concave portion 12 and the radial line. A distance along the radial direction between the fourth virtual plane closest to the third virtual plane among the virtual planes orthogonal to the first virtual plane. Incidentally, the “radial direction” refers to a radial direction of an annular tread surface molding surface, that is, a direction corresponding to a tire radial direction of a tire molded using the mold 10.
In addition, the depth of the recessed part 12 can be measured with SEM and a microscope.

In addition, it is more preferable that the tread surface molding surface of the mold has a surface property such that the kurtosis Rku of the contour curve element has a surface roughness of 1.5 or less. The tread surface of the formed tire can be formed as a surface property having a surface roughness such that the kurtosis Rku of the contour curve element is 1.5 or less, and a tire that is further excellent in performance on ice and on snow This is because it can be molded.
Note that the kurtosis Rku of the contour curve element on the molding surface of the mold surface of the mold can be controlled by adjusting the projected particle size, speed, number of particles, and the like. Specifically, when the speed is increased, the kurtosis Rku can be decreased.

Here, the tire molding die of the present invention is a tire molding die having a tread surface molding surface for molding the tread portion tread surface of the tire, and at least a part of the tread surface molding surface has the following relationship: formula:
50 μm ≦ RSm ≦ 250 μm
Rku ≦ 2
It is preferable to have a surface property satisfying the above.
Thus, if at least a part of the tread surface is RSm of 50 to 250 μm and Rku is 2 or less, at least a part of the tread part tread is RSm of 50 to 250 μm and Rku. This is because it is possible to form a tire having a surface property of less than 2 and excellent in performance on ice and on snow.
In addition, in the metal mold | die of this invention, it is preferable to satisfy | fill the said relational expression over the range of 90% or more of the area of a tread surface molding surface. If RSm is 50 to 250 μm over 90% of the area of the tread surface and Rku is over 4, the surface texture is within a predetermined range over 90% of the tread surface of the tire. Because it can be done.
Here, in this metal mold | die, it is further more preferable that RSm of a tread surface molding surface is 60-150 micrometers. This is because if the RSm of the tread forming surface is 60 to 150 μm, the RSm of the tread portion of the tire can be 60 to 150 μm. In addition, RSm of the tread surface molding surface can be controlled by adjusting the projected particle size. Specifically, when the projection time is increased, RSm can be increased.
Note that the Rku of the tread surface can be controlled by adjusting the projection time of the projection material. Specifically, when the projection time is increased, Rku can be decreased.
Here, in the present invention, “RSm” refers to the average length of the contour curve elements of the tread surface molding surface. In the present invention, “Rku” refers to the kurtosis of the contour curve of the tread surface. “RSm” and “Rku” can be measured in accordance with JIS B 0601 (2001) as described above.

The tire molding die of the present invention is a tire molding die having a tread surface molding surface for molding the tread portion tread surface of the tire, and at least a part of the tread surface molding surface has an Rku of 2. The surface roughness is preferably such that Ra is 1 μm or more and 50 μm or less.
As a result, at least a part of the tread surface can be molded with a surface roughness such that Rku is 2 or less and Ra is 1 μm or more and 50 μm or less, and is excellent in performance on ice and on snow. Because.
Here, it is more preferable that the mold surface of the mold has a surface property such that Rku is 2 or less and Ra is 10 μm or more and 40 μm or less. In this way, the tread portion tread of the formed tire can be molded as a surface property such that Rku is 2 or less and Ra is 10 μm or more and 40 μm or less, and a tire excellent in performance on ice and on snow can be obtained. This is because it can be molded.
Rku of the tread surface molding surface can be controlled by adjusting the projection time of the projection material. Specifically, when the projection time is increased, Rku can be decreased. Further, Ra of the tread surface can be controlled by adjusting the projection speed of the projection material. Specifically, Ra can be increased by increasing the projection speed.

Here, it is preferable that the ten-point average roughness Rz of the tread surface molding surface of the mold is 1.0 to 50 μm. This is because a tire having a 10-point average roughness Rz of the tread portion tread of 1.0 to 50 μm can be formed.
In addition, by setting the average particle size of the projection material used in the projection material projecting step to 50 to 400 μm, it is possible to obtain a tire molding die having a tread surface molding surface having a ten-point average roughness Rz in the above range. .

The average spacing of local peaks of the concave portion of the tread forming surface of the mold, Ru 5.0~100μm der. This is because the tire can be molded with an average interval S between the local peaks of the protrusions formed on the tread surface of the tire being 5.0 to 100 μm.
In addition, the tire molding die provided with the tread surface molding surface which has the average space | interval S of said range can be obtained by making the average particle diameter of the projection material used in a projection material projection process into 50-400 micrometers.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

(Manufacture of tire molds)
A projection material (ceramic system) is projected on the tread molding surface of an aluminum tire molding mold by changing the projection conditions (projection pressure, projection speed, etc.), and the tread molding surface having the surface properties shown in Table 1 is used. The tire molding dies 1 to 4 were produced. In addition, the surface property of the tread surface molding surface of the produced mold was measured using an SEM and a microscope.

(Tire manufacturing)
Tires 1 to 4 having a tire size of 205 / 55R16 were produced using the produced tire molding dies 1 to 4 respectively according to a conventional method. And the surface property of the tread part tread of the produced tire was measured using SEM and a microscope. The results are shown in Table 2.
Further, the performance on ice and the performance on snow of each tire produced were evaluated by the following evaluation methods. The results are shown in Table 2.

<Performance on ice>
The tire immediately after fabrication was assembled into the applicable rim, filled with the regular internal pressure prescribed in JATMA and mounted on the vehicle. Then, the friction coefficient on ice was measured on a freezing road under the condition of a speed of 30 km / h with the load per front wheel being 4.3 kN. The friction coefficient on ice of each tire was indexed with the friction coefficient on ice of the tire 1 being 100. Table 2 shows the results. In Table 2, the larger the numerical value, the greater the coefficient of friction on ice and the better the performance on ice.
<Snow performance>
The tire immediately after fabrication was assembled into the applicable rim, filled with the regular internal pressure prescribed in JATMA and mounted on the vehicle. Then, the friction coefficient on the snow was measured on a snowy road under a condition of a speed of 30 km / h with a load per front wheel set to 4.3 kN. The tire friction coefficient on snow of the tire 1 was set to 100, and the friction coefficient on snow of each tire was evaluated as an index. Table 2 shows the results. In Table 2, the larger the numerical value, the greater the friction coefficient on snow and the better performance on snow.

  As shown in Table 2, it can be seen that the tire according to the example is superior in performance on ice and on snow than the tire according to the comparative example and the conventional example.

  ADVANTAGE OF THE INVENTION According to this invention, the tire mold which can shape | mold the tire which improved on-ice performance and on-snow performance, and this tire can be provided.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Protrusion part 3 Space | gap 4 Bead part 4a Bead core 5 Side wall part 6 Tread part 7 Carcass 8 Belt 8a, 8b Belt layer 9 Protrusion part 10 Mold 11 Molding surface 11a Tread surface molding surface 11b Side wall part molding surface 11c Bead Part molding surface 12 Recess 20 Tire T Road surface

Claims (9)

Many hemispherical protrusions are formed over the entire tread surface,
The diameter of the hemispherical protrusion gradually increases from the outside in the tire radial direction toward the inside,
The entire tread portion tread is formed by the hemispherical protrusions.
Rsk <0 and Rku ≦ 2
Have a surface roughness satisfying,
The tire is characterized in that an average distance S between local peaks of the protrusions is 5.0 to 100 mm . A mold for tire molding,
A tread surface for molding the tread surface of the tire, and the tread surface has many hemispherical recesses over the entire tread surface,
The diameter of the hemispherical recess gradually increases from the bottom side of the hemispherical recess toward the surface side of the tread surface molding surface,
The entire tread molding surface is formed by the hemispherical recess.
Rsk> 0 and Rku ≦ 2
Have a surface roughness satisfying,
The mold for molding a tire , wherein the concave portion has an average interval S between local peaks of the concave portion of 5.0 to 100 mm .   2. The tire according to claim 1, wherein an overall Rsm of the tread portion tread is 50 to 70 μm due to the hemispherical protrusion. 3.   3. The tire molding die according to claim 2, wherein an overall Rsm of the tread surface molding surface is 50 to 70 μm due to the hemispherical concave portion.   2. The tire according to claim 1, wherein the entire tread surface has a surface roughness such that Ra is 20 μm or more and 50 μm or less due to the hemispherical protrusion. 3.   3. The tire molding die according to claim 2, wherein the entire tread molding surface has a surface roughness such that Ra is 20 μm or more and 50 μm or less due to the hemispherical concave portion.   The tire according to claim 1, wherein the height of the hemispherical protrusion is not less than 1 μm and not more than 50 μm.   The tire molding die according to claim 2, wherein the depth of the hemispherical recess is 1 µm or more and 50 µm or less.   The tire according to claim 1, wherein the tread rubber on the tread surface is made of non-foamed rubber.