JP2979243B2 - Studless pneumatic tires - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to friction on snow and ice road surfaces, particularly on snow and ice road surfaces with a water film, without impairing traveling performance on general roads (dry roads and wet roads). The present invention relates to a studless pneumatic tire having improved force (braking performance and driving performance).

[Conventional technology]

Conventionally, there has been proposed a tire for automobiles in which friction on ice is improved by uniformly dispersing and mixing metal short fibers in tread rubber (JP-A-63-34206). However, since the rubber hardness of the automobile tire is relatively high, the effect of improving friction on ice was insufficient. In addition, the short metal fibers are scattered in accordance with the wear of the tire, causing pollution, which is a major environmental problem.

On the other hand, there has been proposed a foamed rubber composition in which the tread rubber is composed of foamed rubber having closed cells and short fibers are randomly blended around the closed cells (Japanese Patent Laid-Open No. 63-89547).
No.). However, this foamed rubber composition has a problem that the effect of improving the friction on ice is small in spite of the incorporation of the short fibers because the short fibers are randomly blended.

[Problems to be solved by the invention]

An object of the present invention is to improve the frictional force (braking property and driveability) on snow and ice road surfaces, particularly on snow and ice road surfaces with a water film, without impairing the running performance on general roads (dry roads and wet roads). It is to provide a studless pneumatic tire.

[Means for solving the problem]

The studless pneumatic tire of the present invention has a fiber length of 10
Non-metallic hollow fibers having a fiber length / fiber diameter ratio of 10 to 1000 are compounded in the tread rubber, and the hollow fibers are oriented along the tire circumferential direction near the tread block's ground contact surface. The dynamic Young's modulus E _{1 in} the tire circumferential direction near the ground contact surface of the block and the dynamic Young's modulus E _{2 in} the tire circumferential direction near the center of the block are calculated by the following equations (1) and (2). It is characterized by satisfying the expression.

1.03 ≦ E ₁ / E ₂ … (1) 3 [MPa] ≦ E ₂ ≦ 20 [MPa] …… (2) Since the non-metallic hollow fiber is blended in the tread rubber as described above, the snow and ice road surface, particularly, When traveling on a snow-ice road surface with a water film, non-metallic hollow fibers can suck up water on the road surface and remove it.

In addition, since the non-metallic hollow fibers are oriented along the tire circumferential direction near the ground contact surface of the tread block, the tire circumferential block stiffness near the ground contact surface (that is, the dynamic Young's modulus in the tire circumferential direction) E ₁ ) can be increased. Further, the non-metallic hollow fiber has a tire circumferential block rigidity (ie, a tire circumferential dynamic Young's modulus E ₂ ) at the center of the block that is smaller than the tire circumferential block rigidity (E ₁ ) near the ground contact surface, In addition, since the formulas (1) and (2) are satisfied, the edge effect on the snow-ice road surface can be enhanced (the road surface caused by the edge of the block in the tire width direction side surface scratching the snow-ice road surface during running). With the improvement of the frictional force), the contact area of the contact surface of the block with the snow and ice road surface can be increased, so that the adhesion effect of the contact surface of the block on the snow and ice road surface is improved.

Therefore, since the edge effect and the adhesion effect can be enhanced in this way, the frictional force (frictional force on ice) on the snow and ice road surface can be greatly improved.

On the other hand, as described above, since the tire circumferential block rigidity near the ground contact surface is increased, the wear resistance is improved, so that the running performance on a general road (dry road, wet road) is not impaired.

Therefore, according to the present invention, water on the road surface can be eliminated as described above, and the edge effect and the cohesion effect can be enhanced, so that the frictional force on the snow and ice road surface (frictional force on ice) is greatly improved. And the running performance on a general road (dry road, wet road) is not impaired.

Here, as the hollow fiber, the average fiber length is 10 to 5000 μ
m, preferably 100 to 5000 μm,
It is more preferable that the thickness be 1000 to 3000 μm and that the ratio of fiber length / fiber diameter be 10 to 1000 times. If the fiber length of the hollow fiber is less than 10 μm, the dispersion in the rubber becomes random, so it is not possible to achieve a high level of compatibility between the block rigidity and the adhesion effect, and not only the ice and snow performance is insufficient, but also the performance on general roads Will also be insufficient.

The type of the hollow fiber is not particularly limited as long as it is a non-metal, and a chemical fiber such as polyester, cellulose, polyether sulfone, polymethyl methacrylate (PMMA), and polyacrylonitrile (PAN) is used.

Further, the hollow fiber preferably has a large number of micropores on its peripheral surface. It is preferable that the fine hole penetrates through the hollow portion, but does not have to penetrate. Furthermore, the average diameter D of the hollow fiber and the average diameter d of the hollow portion are D / d ≧ 1.0
It is preferably 1. The average diameter of the micropores is 0.001.
It is preferably from 100 to 100 μm.

On the other hand, in the present invention, the tire circumferential direction of the dynamic Young's modulus E ₂ in the vicinity of the dynamic Young's modulus E ₁ and the block central portion in the tire circumferential direction in the vicinity of the ground contact surface of the block, the following equation (1) and (2 Satisfies the expression.

1.03 ≦ E ₁ / E ₂ … (1) 3 [MPa] ≦ E ₂ ≦ 20 [MPa] …… (2) When the ratio of dynamic Young's modulus is E ₁ / E ₂ <1.03, the friction performance on ice is poor. Will be insufficient. Furthermore, E ₂ is the provision outside of the equation (2), in particular, block rigidity is difficult to exhibit good performance as a tire when traveling on a general road.

By the way, from the viewpoint of mixing operability of hollow fibers, E ₁ / E ₂ ≦
Preferably it is 3.0. This is because it is difficult to give the orientation of E ₁ / E ₂ > 3.0 due to the mixing of rubber and hollow fibers.

Hereinafter, a pneumatic tire according to the present invention will be described with reference to the drawings.

FIG. 1 is a half-sectional view in the meridian direction of a pneumatic tire according to the present invention.

In this figure, a pneumatic tire A of the present invention includes a pair of left and right bead portions 11, a pair of left and right side wall portions 12 connected to the bead portions 11, and a pair of these side wall portions.
The tread portion 13 is formed between the tread portions 13. A carcass layer 14 is mounted between the pair of left and right bead portions 11, and a belt layer 15 is arranged in the tread portion 13 so as to surround the outer periphery. 10 is a tread surface.

2 is a plan view explanatory view of a tread portion of the pneumatic tire shown in FIG. 1, FIG. 3 is a sectional view taken along the line KK 'of FIG. 1, and FIG. 4 is a perspective view of hollow fibers. As shown in FIG. 2, the longitudinal direction of the hollow fibers 17 is generally oriented in the tire circumferential direction EE '. However, when focusing on the block 16, as shown in FIG. Are oriented vertically along the side surface b near the side surface b in the tire width direction in the block 16 and oriented along the tire circumferential direction EE 'near the ground contact surface a, and contact near the center of the block. It is oriented so as to draw a convex curve in the direction of the ground a.
Therefore, in the vicinity of the contact surface a, the tire circumferential circumferential rigidity is generated due to the orientation of the hollow fibers 17 along the tire circumferential direction EE ′, and the tire circumferential block rigidity is increased. Since the rigidity caused by the orientation is divided into the vertical direction and the tire circumferential direction, the tire circumferential block rigidity near the center of the block is smaller than the tire circumferential block rigidity near the ground contact surface a. And become smaller.

Since the hollow fibers 17 as a whole are oriented in the tire circumferential direction EE ′, the dynamic Young's modulus E ₁ , E
₂ is larger than the dynamic Young's modulus in the tire width direction (tire radial direction). Therefore, the rigidity in the tire circumferential direction of the block 16 is also greater than the rigidity in the tire radial direction. As the tread rubber, the content of carbon black is reduced, and the base rubber is made relatively soft to enhance the adhesion effect. The decrease in block rigidity due to this is compensated for by orienting the hollow fibers 17.

In order to orient the hollow fiber 17 in the block 16 as shown in FIG. 3, first, an unvulcanized rubber composition containing the hollow fiber is extruded to form a long unvulcanized tread member. Form. At the time of extrusion molding, since hollow fibers having a certain fiber length / fiber diameter ratio tend to be oriented in the flow direction of rubber, the longitudinal direction of the hollow fibers in the obtained tread member is the same as the longitudinal direction of the tread member ( (Corresponding to the tire circumferential direction).

Next, a tread portion of a green tire is formed with the tread member, and when the green tire is put into a mold and vulcanized, the tread portion is partially pressed by a protrusion in the mold and a groove is formed on the tread surface. At the same time, a block 16 composed of the ground plane a and the side surface b is formed. When the block 16 is formed, the tread portion is pressed by the protrusion in the mold, so that the hollow fiber 17 is directed vertically along the side surface b near the side surface b as shown in FIG. In the vicinity of the ground contact surface a, the tire is oriented along the circumferential direction of the tire, and near the center of the block, it is oriented so as to draw a curved line protruding in the direction of the ground contact surface a. However, if the length of the hollow fibers 17 is too short, they will not be oriented as shown in FIG. 3 since they are randomly arranged in the unvulcanized tread member. For this reason, the hollow fibers need to have an average length of 10 to 5000 μm, preferably 100 to 5000 μm, more preferably 1000 to 3000 μm, and a fiber length / fiber diameter ratio of 10 to 5000 μm.
It should be 1000.

As shown in FIG. 4, the hollow fiber 17 has a cylindrical shape, and is provided with a myriad of fine holes 18 on its peripheral surface. The fine hole 18 preferably penetrates the hollow portion, but does not have to penetrate.

Thus, the hollow fiber 17 is connected to the tread block ground plane a.
And the orientation along the side surface b, the dynamic Young's modulus inside and outside the block is set to the relationship of the above-mentioned equations (1) and (2), and the tire circumferential rigidity of the tread block 16 is thereby reduced in the tire radial rigidity. Can be larger than For this reason, at the time of rotation of the tire, the braking force and the driving force are increased due to the increase in the circumferential rigidity of the tire, and the rigidity in the vicinity of the contact surface a of the block 16 is greater than that in the vicinity of the center of the block 16 as described above. Since the contact surface becomes large, the deformation of the contact surface a becomes small and the entire surface of the contact surface a comes into contact with the ground (the contact property becomes large), so that an adhesion effect is generated and the frictional force on ice is improved.

Further, on a snow and ice road surface, particularly on a snow and ice road surface having a water film, the hollow fiber sucks up and removes water on the road surface to improve the frictional force.

 Hereinafter, conventional examples, examples, and comparative examples are shown.

Conventional Example, Example, Comparative Example Various tires having a tread portion and a tire size of 185/70 R13 85Q having the composition shown in Table 1 (parts by weight) were manufactured. 1, Comparative Examples 1 to
Regarding 3), the following evaluation was performed. This result is referred to as "1st
Table.

 The test vehicle used was a 1600cc FF vehicle.

Braking performance on icy road surface: The vehicle traveled on an ice floe at an initial speed of 30 km / h, and the braking distance when braking was measured. The reciprocal of the braking distance was expressed as an index with the conventional tire (conventional example) as 100. The larger the value, the better the braking.

Driving performance on snowy road surface: Repeated braking of a snow-covered road surface with a passenger car, and on a slippery snow-covered road surface with a slippery road surface, perform a 5% (2.9 ゜) gradient test, and use a zero-start method to accelerate 30m uphill. Was measured, and the reciprocal of the ascending acceleration time was represented by an index, with the case of the conventional tire being 100. The larger the numerical value,
It shows that the driveability is good.

Driving stability (dry road surface): The results (average value) obtained by scoring the feeling of each tire by five test drivers by a 10-point method are shown as indices with the score of the conventional tire being 100. The larger the numerical value, the better the steering stability.

Abrasion resistance (dry road surface): After running 20,000 km on a dry road surface under the conditions of design normal load and air pressure specified by JATMA, the reciprocal of the amount of wear of each tire was indicated by an index with the conventional tire as 100. . The larger the value, the better the wear resistance.

Dynamic Young's modulus (surface and inside) [MPa]: A sample is cut out from the surface and inside of the tread block of each test tire in the circumferential direction (same in the tire circumferential direction) with respect to the tire rotation axis, and manufactured by Toyo Seiki Co., Ltd. Using a viscoelastic spectrometer, the length between chucks is 20 mm and the width is
A sample having a thickness of 5 mm and a thickness of 2 mm was measured under the conditions of a frequency of 20 Hz, an initial strain of 10%, a dynamic strain of ± 2%, and a temperature of 0 ° C. The larger the numerical value,
Indicates high rigidity.

Note) * 1 Hollow fiber: Porous water-absorbing polyester fiber (average fiber length 2500 μm, average fiber diameter 125 μm, average hollow part diameter 55)
μm, diameter distribution of micropores, mainly 0.01 to 3 μm) * 2 Short fiber: short carbon fiber, average length 5 μm, diameter 1 μ
m.

* 3 Blowing agent: dinitrosopentamethylenetetramine (Cellular D manufactured by Eiwa Chemical Industry Co., Ltd.).

* 4 Urea auxiliaries: Urea compounds (Cell Paste K5 manufactured by Eiwa Chemical Co., Ltd.).

In Table 1, the conventional example is a conventional studless tire and does not include fibers.

Example 1 is a hollow fiber-containing tire according to the present invention, which can achieve both ice and snow performance and general performance.

Comparative Examples 1 and 2 contain ordinary short fibers, but since there is no hollow portion, the water film is not efficiently removed and the ice and snow performance is not improved. However, Comparative Example 2 is foam rubber + short fibers.

Comparative Example 3 is a tire which is softened without blending hollow fibers in comparison with Example 1, and has good ice and snow performance, but deteriorates performance on a general road.

〔The invention's effect〕

As described above, in the studless pneumatic tire of the present invention, a nonmetallic short fiber having a fiber length of 10 to 5000 μm and a fiber length / fiber diameter ratio of 10 to 1000 is mixed in the tread rubber, and the hollow fiber the, in the vicinity of the ground contact surface of the block of the tread portion so as to orient along the tire circumferential direction, the tire circumferential direction in the vicinity of the dynamic Young's modulus E ₁ and the block central portion in the tire circumferential direction in the vicinity of the ground contact surface of the block Since the dynamic Young's modulus E ₂ satisfies the above formulas (1) and (2), without impairing the running performance on general roads (dry roads, wet roads), snow and ice road surfaces, particularly, It has become possible to improve the frictional force (braking performance, driveability) on snow and ice road surfaces with a water film. Moreover, since non-metallic hollow fibers are used, there is no pollution problem.

[Brief description of the drawings]

FIG. 1 is a half sectional view of a pneumatic tire according to the present invention in the meridian direction, FIG. 2 is a plan view of a tread portion of the pneumatic tire according to the present invention, and FIG. FIG. 4 is a perspective view of the hollow fiber. 10 ... tread surface, 11 ... bead part, 12 ... sidewall, 13 ... tread part, 14 ... carcass layer, 15 ...
Belt layer, 16 blocks, 17 hollow fibers, 18 micropores.

Claims (1)

(57) [Claims] 1. A nonmetallic hollow fiber having a fiber length of 10 to 5000 μm and a fiber length / fiber diameter ratio of 10 to 1000 is compounded in a tread rubber, and the hollow fiber is mixed with a tread portion near a ground contact surface of a block. In the tire, the dynamic Young's modulus E _{1 in} the tire circumferential direction near the ground contact surface of the block and the dynamic Young's modulus E _{2 in} the tire circumferential direction near the center of the block are calculated as follows. A studless pneumatic tire satisfying the following formulas (1) and (2): 1.03 ≦ E ₁ / E ₂ (1) 3 [MPa] ≦ E ₂ ≦ 20 [MPa] (2)