JP2013139180A - Tire, and mold for tire molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire having the improved on-ice performance and on-snow performance, and to provide a mold for tire molding used in manufacturing the same.SOLUTION: In the tire, a large number of protrusions having the height in predetermined ranges are formed in predetermined number density, on at least part of a tread surface. Additionally, in the mold for tire molding, a large number of recesses having the depth in predetermined ranges are formed in predetermined number density, on at least of a tread molding surface.

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 lowered due to the use of foamed rubber, and the wear resistance of the tire 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 performance especially when new. It was also found that there was a problem that 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.
The tire according to the present invention is characterized in that at least part of the tread surface is formed with protrusions having a height exceeding 20 μm at a number density of 80 pieces / mm ² or more. In this way, if protrusions with a height of more than 20 μm are formed at a number density of 80 pieces / mm ² or more on at least part of the tread surface (the surface that contacts the road surface during travel), the block rigidity can be reduced. The on-ice performance and on-snow performance of the tire can be sufficiently improved while suppressing a decrease in water removal performance. That is, with respect to the surface texture of the tread portion tread surface, by forming a protrusion having a height exceeding 20 μm, a space for water removal can be secured between the protrusions, while a height exceeding 20 μm. Since the projecting portions having a number density of 80 pieces / mm ² or more are formed, a ground contact area of the projecting portions can be secured. Here, the height of the protrusion is defined by the first imaginary plane perpendicular to the tire radial direction line extending through the tip of the protrusion (the outer end in the tire radial direction), the outer diameter of the protrusion, and the tire diameter. 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 direction line. In the present invention, the “number of protrusions” and the “height of protrusions” can be measured by, for example, enlarging the tread surface with a SEM or a microscope.
Here, in the present invention, the “projection part” includes, for example, a hemispherical shape, a truncated hemispherical shape, a truncated conical shape, a truncated pyramid shape, a cylindrical shape, and a prismatic shape.

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 part of the tread surface molding surface has a depth. Recesses exceeding 20 μm are formed at a number density of 80 pieces / mm ² or more. In this way, by forming recesses having a depth exceeding 20 μm at a number density of 80 pieces / mm ² or more on at least a part of the tread surface molding surface, at least a part of the tread part tread described above has a height. This is because protrusions exceeding 20 μm can be formed at a number density of 80 pieces / mm ² or more, and a tire having excellent performance on ice and performance on snow can be formed. Here, the depth of the concave portion is in contact with the third virtual plane perpendicular to the radial line extending through the deepest portion (radially inner end) of the concave portion and the outer contour line of the concave portion and perpendicular to the radial line. The distance along the radial direction between the virtual plane and the fourth virtual plane closest to the third virtual plane. Incidentally, the “radial direction” refers to a radial direction of an annular tread surface, that is, a direction corresponding to a tire radial direction of a tire molded using a mold.
In the present invention, the “number of recesses” and “depth of recesses” can be measured by, for example, enlarging the tread surface with a SEM or a microscope. In the present invention, the “concave portion” includes, for example, a hemispherical shape, a truncated hemispherical shape, a truncated conical shape, a truncated pyramidal shape, a cylindrical shape, and a prismatic shape.

  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 tire mold shown in FIG. (A)-(c) is another example of the partial shape of the 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 the microstructure of the tread surface molding surface is formed to have a predetermined property.

<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, microprojections having a predetermined shape are formed on at least a part (all in this embodiment) of the 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, the entire tread tread 6a is formed with protrusions having a height H of more than 20 μm at a number density of 80 pieces / mm ² or more.
FIG. 3 shows a case where the protrusion 9 is a hemispherical protrusion, but in the tire of the present invention, the protrusion is a truncated cone or truncated pyramid, as shown in FIG. 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 many protrusions 9 are formed on the tread surface of the tread, it is possible to sufficiently improve the on-ice performance and on-snow performance of the tire while suppressing a decrease in block rigidity and a decrease in water removal. Can do.
That is, since the tire 20 has a large number of protrusions 9, the water film on the road surface is removed using the gaps between the protrusions 9 at the time of contact with the road surface (water removal is demonstrated). be able to. Moreover, the frictional force between the tread portion tread surface and the road surface can be increased, and the on-ice performance and on-snow performance of the tire can be improved.
Furthermore, in this tire 20, since the protrusion 9 has formed a protrusion having a height exceeding 20 μm, a space for water removal can be secured between the protrusions, while a height exceeding 20 μm. Since the protrusions having a thickness are formed at a number density of 80 pieces / mm ² or more, the ground contact area of the protrusions can 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. 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).

In the tire 20, it is more preferable that the portion where the protrusions 9 are formed has a number density of protrusions having a height H exceeding 20 μm of 150 pieces / mm ² or more for the same reason. More preferably, the number density of protrusions having a height of more than 20 μm is more preferably 150 pieces / mm ² or more and 250 pieces / mm ² or less, thereby further suppressing a decrease in block rigidity. Further, it is possible to further improve the on-ice performance and the on-snow performance of the tire by suppressing the reduction of water removal performance.
Moreover, as a preferable height of the protrusions, it is desirable that the number of protrusions exceeding 30 μm is a number density of 100 pieces / mm ² or more. Also, it is desirable that the height of the protrusion is less than 50 μm, and if it is 50 μm or more, the rigidity of the protrusion will decrease, and the protrusion may be crushed when a large load is applied to the tire, so that the braking force cannot be expressed. Because there is sex.
Here, in the present invention, the “number of protrusions” and “height of protrusions” can be measured by, for example, enlarging the tread surface with a SEM or a microscope.

  Moreover, in this tire 20, it is preferable that the shape of the projection part 9 is hemispherical. This is because if the shape of the protrusion 9 is hemispherical, the protrusion 9 is not easily crushed and water removal can be ensured.

  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, in the tire of the present invention, it is preferable that at least a part of the tread surface has a surface roughness with a roughness motif upper limit length A of 5 μm to 100 μm. According to this configuration, since the surface roughness of the tread portion tread has a roughness motif upper limit length A of 5 μm or more and 100 μm or less, while further suppressing a decrease in block rigidity and a decrease in water removal performance, The performance and the performance on snow can be further improved sufficiently.
That is, with respect to the surface properties of the tread surface, the roughness motif upper limit length A is 5 μm or more, so a space for water removal can be secured, while the roughness motif upper limit length A is 100 μm. Therefore, the frictional force between the tire and the road surface can be ensured.
In addition, the part in which the protrusion part 9 is formed has the surface property that the roughness motif upper limit length A has a surface roughness of 20 μm or more and 80 μm or less for the same reason. preferable.
Here, the “roughness motif upper limit length A” means “roughness motif upper limit length A” defined in JIS B 0631 (2000), and is measured using a microscope or the like under no-load conditions. Is.

Furthermore, 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 the average height Rc of the contour curve element 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. Further, if the surface roughness of the tread portion tread surface is set such that the average height Rc of the contour curve element is 1 μm or more and 50 μm or less, the block rigidity and the dewatering performance are further suppressed, while the tire surface is on ice. The performance and the performance on snow can be further improved sufficiently. That is, with respect to the surface texture of the tread portion tread surface, if the average height Rc of the contour curve element is 1 μm or more, a water removal space can be secured, while the average height Rc of the contour curve element is If the thickness is 50 μm or less, the rigidity of the protrusion can be ensured. For the same reason, it is more preferable that the average height Rc of the contour curve element has a surface property having a surface roughness of 10 μm or more and 40 μm or less.
Here, “the average height Rc of the contour curve element” means “the average height Rc of the contour curve element” defined in JIS B 0601 (2001). As for the measurement conditions, Rc measures the height of a mountain existing in a unit length (1 mm), and takes the average by excluding the height of the mountain included in the upper and lower ranges of 10% on the basis of the height. Can be obtained.

Furthermore, 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 the maximum peak height Rp of the contour curve is 5 μm or more and 70 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. In addition, if the surface roughness of the tread surface is such that the maximum peak height Rp of the contour curve is not less than 5 μm and not more than 70 μm, the on-ice performance of the tire is further suppressed while further suppressing the decrease in block rigidity and the dewatering performance. In addition, the performance on snow can be further improved sufficiently. That is, regarding the surface texture of the tread surface, if the maximum peak height Rp of the contour curve is 5 μm or more, a space for water removal can be secured, while the maximum peak height Rp of the contour curve is 70 μm. If it is set as follows, the rigidity of the protrusion can be ensured. For the same reason, it is more preferable that the portion where the protrusion is formed has a maximum peak height Rp of the contour curve of 10 μm or more and 40 μm or less.
Here, the “maximum peak height Rp of the contour curve” means “maximum peak height Rp of the contour curve” defined in JIS B 0601 (2001). In addition, Rp can be calculated | required by measuring the height of the peak which exists in unit length (1 mm).

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.

Moreover, it is preferable that the average space | interval S of the local peak of the projection part 9 formed in the tread part tread of a tire is 5.0-100 micrometers.
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 surface molding surface 11a, and FIG. 6B shows an enlarged cross-sectional view along the width direction on the tread surface molding surface 11a side of the mold 10, and this embodiment The tire molding die 10 according to the embodiment has 80 cavities / mm ^{2 with} a number density of 80 / mm ² or more on the entire tread molding surface 11a for molding the tread surface of the tire. It has a large number with a number density of ² or more. FIG. 6 shows the case where the recess 12 is a hemispherical recess, but in the tire of the present invention, the recess 12 has a truncated hemispherical shape, a truncated cone shape, a truncated pyramid shape, a cylindrical shape, 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. Then, on the tread portion tread of the manufactured tire, protrusions having a height H exceeding 20 μm are formed at a number density of 80 pieces / mm ² or more. Therefore, a tire excellent in performance on ice and on snow can be formed. In the mold of the present invention, the tread surface molding surface 11a for molding the tread portion tread surface may be formed with recesses whose depth does not exceed 20 μm. In that case, the number of recesses that do not satisfy the above conditions Is preferably 10% or less of the total number of recesses. This is because, if such a recess is 10% or less, a sufficient number of predetermined protrusions 9 can be formed on the tread surface of the tire.
Incidentally, the “number of recesses” can be measured by, for example, enlarging the tread molding surface with an SEM or a microscope.
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 the above-mentioned recesses 12 having a depth exceeding 20 μm at a number density of 80 pieces / mm ² or more. Therefore, the tread portion tread of a tire vulcanized and molded using this mold has the above-described protrusions 9 having a height H of more than 20 μm at a number density of 80 pieces / mm ² or more. Become.
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, the mold 10 is a mold for molding a tire, and has a tread surface molding surface for molding the tread portion tread surface of the tire, and the depth exceeds 20 μm in at least a part of the tread surface molding surface. It is preferable to form the recesses with a number density of 80 pieces / mm ² or more. The tire can be molded such that at least a part of the tread surface of the formed tire has protrusions with a height H of more than 20 μm at a number density of 80 pieces / mm ² or more. This is because it is possible to form a tire with even better performance on snow.
The number density of the recesses on the molding surface of the mold surface of the mold can be controlled by adjusting the particle diameter and the number of grains of the projection material. Specifically, the number density can be increased by increasing the number of grains of the projection material. Further, the number density can be reduced by increasing the particle size of the projection material. Further, the depth of the recess on the molding surface of the mold of the mold can be controlled by adjusting the projection speed of the projection material. Specifically, when the projection speed of the projection material is increased, the depth can be increased.
Here, in the present invention, “number density of recesses” and “depth of recesses” can be measured by, for example, enlarging the tread surface with a SEM or a microscope.

  Moreover, in this metal mold | die 10, it is preferable that the shape of the recessed part 12 is hemispherical. This is because if the shape of the recess 12 is hemispherical, the hemispherical protrusion 9 can be formed on 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. Specifically, when the projection speed is increased, the depth h can be increased.
In addition, the depth of the recessed part 12 can be measured with SEM and a microscope.

In addition, 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 a depth. It is preferable to form recesses having a length exceeding 20 μm at a number density of 80 pieces / mm ² or more.
As a result, a tire excellent in performance on ice and in snow can be formed by forming protrusions having a height of more than 20 μm at a number density of 80 pieces / mm ² or more on at least a part of the tread surface. Because it can.
The number density of the recesses on the molding surface of the mold surface of the mold can be controlled by adjusting the particle diameter and the number of grains of the projection material. Specifically, the number density can be increased by increasing the number of grains of the projection material. Further, the number density can be reduced by increasing the particle size of the projection material. Further, the depth of the recess on the molding surface of the mold of the mold can be controlled by adjusting the projection speed of the projection material. Specifically, when the projection speed of the projection material is increased, the depth can be increased.
In addition, as for the part in which the recessed part 12 is formed, it is more preferable that the number density of the protrusion part whose depth exceeds 20 micrometers becomes 150 pieces / mm < ² > or more for the same reason. More preferably, the number density of protrusions having a depth exceeding 20 μm is more preferably 150 pieces / mm ² or more and 250 pieces / mm ² or less.
Further, as a preferable depth of the recesses, the number density of recesses exceeding 30 μm is desirably 100 / mm ² or more. Further, the depth of the protrusion is desirably less than 50 μm.

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 is rough. The motif upper limit length A preferably has a surface roughness of 5 μm or more and 100 μm or less.
Thereby, at least a part of the tread part tread described above has a surface roughness with a roughness motif upper limit length A of 5 μm or more and 100 μm or less, and a tire excellent in ice performance and snow performance can be formed. Because.
Here, it is preferable that the mold surface of the mold has a surface property such that the roughness motif upper limit length A is a surface roughness of 20 μm or more and 80 μm or less. The tread surface of the formed tire can be molded as a surface property having a roughness motif upper limit length A of 20 μm or more and 80 μm or less, and the tire performance on ice and snow performance are further improved. This is because the tire can be molded.
The roughness motif upper limit length A of the recess 12 can be controlled by adjusting the particle size of the projection material. Specifically, when the particle size of the projection material is increased, the roughness motif upper limit length A can be increased.

Further, 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 is a contour curve element. It is preferable to have a surface roughness with an average height Rc of 1 μm or more and 50 μm or less.
As a result, at least a part of the tread portion tread described above has a surface roughness with an average height Rc of the contour curve element of 1 μm or more and 50 μm or less, and molding a tire excellent in ice performance and snow performance. Because it can.
Here, it is more preferable that the tread surface molding surface of the mold has a surface property such that the average height Rc of the contour curve element is 10 μm or more and 40 μm or less. The tread portion tread of the formed tire can be formed as a surface property such that the average height Rc of the contour curve elements is 10 μm or more and 40 μm or less, and a tire excellent in performance on ice and on snow can be formed. Because it can.
The average height Rc of the contour curve element on the tread surface can be controlled by adjusting the projection speed. Specifically, when the projection speed is increased, the average height Rc of the contour curve element can be increased.

Furthermore, 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 is a contour curve. The maximum peak height Rp preferably has a surface roughness of 5 μm or more and 70 μm or less.
As a result, at least a part of the tread portion tread described above has a surface roughness with a maximum peak height Rp of the contour curve of 5 μm or more and 70 μm or less, and a tire having excellent on-ice performance and on-snow performance can be formed. Because.
Here, it is more preferable that the tread surface molding surface of the mold has a surface property such that the maximum peak height Rp of the contour curve is 10 μm or more and 40 μm or less. The tread surface of the formed tire can be formed as a surface property such that the maximum peak height Rp of the contour curve is 10 μm or more and 40 μm or less, and a tire excellent in performance on ice and on snow can be formed. Because.
The maximum peak height Rp of the contour curve of the tread surface can be controlled by adjusting the projection speed. Specifically, when the projection speed is increased, the maximum peak height Rp of the contour curve can be increased.

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. .

Moreover, it is preferable that the average space | interval of the local peak of the recessed part of the tread surface molding surface of a metal mold | die is 5.0-100 micrometers. This is because the tire can be molded with an average distance 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)
The projection condition (projection pressure, projection speed, etc.) is changed on the tread forming surface of the aluminum tire molding mold, and the projection material (ceramic system) is projected. The tire molding dies 1 to 4 were produced. In addition, the surface property of the tread forming 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 (2)

A tire having a number density of 80 pieces / mm ² or more formed on at least a part of a tread part tread with a height of more than 20 μm. A mold for tire molding,
It has a tread forming surface for forming a tread portion tread of a tire, and at least part of the tread forming surface is formed with a recess having a depth exceeding 20 μm at a number density of 80 pieces / mm ² or more. Tire mold.