JP4783336B2 - studless tire - Google Patents

Description

  The present invention relates to a studless tire. Specifically, the present invention holds good performance on snow and ice and wear resistance in a well-balanced manner in a studless tire, and is particularly suitable for a passenger car.

Studless tires have been developed so that they can run safely on snowy and icy roads without studs (spike pins), and are now widely used in cold areas in winter instead of spiked tires.
As shown in FIG. 3, for example, in JP 2001-130228 A (Patent Document 1), a studless tire is formed by forming a deep tread pattern 1 by recessing a deep groove 2 on the grounding surface side of a tread portion. In addition, a large number of slit-shaped sipings 4 are formed in the block 3 surrounded by the groove 2. With such a configuration, not only adhesion and adhesion frictional force due to contact between the surface of the block 3 and the road surface, but also digging frictional force due to the edges of the groove 2 and the siping 4 can be increased. Performance on snow and ice can be improved.

  Furthermore, in the said patent document 1, the glass fiber is orientated in the thickness direction of the tread part as tread rubber of a studless tire, and it can dig up with glass fiber and can raise a frictional force further.

However, if the amount of the glass fiber is increased in order to improve the performance of the studless tire on snow and ice, the wear resistance tends to deteriorate.
In addition, increasing the number of grooves 2 and siping 4 of the studless tire improves the performance on snow and ice of the studless tire. However, if the grooves 2 and siping 4 of the tread pattern are made finer, the block rigidity decreases, and in this case the wear resistance is also increased. There is a tendency to deteriorate.
That is, the studless tire has a problem that it is difficult to maintain a good balance between snow and ice performance and wear resistance.

JP 2001-130228 A

  This invention is made | formed in view of the said problem, and makes it a subject to provide the studless tire which hold | maintained favorable performance on snow and ice and abrasion resistance in good balance.

In order to solve the above-mentioned problem, the present invention is a studless tire having a tread pattern and siping on the contact surface side of the tread portion,
The tread part has a vulcanization accelerator of 0.5 to 5.0 parts by weight, sulfur of 1.0 to 3.5 parts by weight, and zinc oxide of 100 parts by weight of a rubber component containing at least a diene rubber. 0.5 to 5.0 parts by mass, calcium carbonate powder is 0.4 to 2.0 parts by mass , glass fiber is 1 to 4 parts by mass, oil is 5 to 25 parts by mass, and the average particle size is 20 to 26 nm. It comprises a tread rubber composition containing 33 to 55 parts by mass of carbon powder ,
The density of the groove that is an effective edge component in the tire traveling direction of the tread pattern is 0.012 mm / mm ^{2 to} 0.018 mm / mm ² , and the density of the siping that is an effective edge component in the tire traveling direction is 0 A studless tire characterized by having a rubber hardness Hs of 42 to 50 and a rubber hardness Hs of 0.051 mm / mm ^{2 to} 0.059 mm / mm ² is provided.

In the present invention, “a groove which is an effective edge component with respect to the traveling direction of the tire (siping)” refers to a groove formed in the tread portion (a siping consisting of a slit) into a tire circumferential direction component and a tire axial direction component. It means a groove (sipeing) of a tire axial direction component when disassembled, and an edge (edge) on the rear end side in the traveling direction of the groove and siping of the tire. Therefore, the length of the edge per contact unit area is defined as the density [mm / mm ² ] of the groove (sipeing) that becomes an effective edge component in the tire traveling direction.

Specifically, for example, when a longitudinal groove is formed parallel to the tire circumferential direction and a lateral groove is formed parallel to the tire axial direction, the groove serving as an effective edge component with respect to the tire traveling direction is: It means a lateral groove parallel to the tire axial direction and an edge of the lateral groove on the rear end side in the tire traveling direction.
For example, when the groove is formed at a predetermined angle with respect to the tire axial direction, the groove serving as an effective edge component with respect to the tire traveling direction is the tire circumferential component and the tire axial direction. It means a groove in the tire axial direction component when disassembled into components, and an edge on the rear end side in the tire traveling direction of the groove in the tire axial direction component.

  In addition, the forming direction of the siping is preferably the tire axial direction, and the siping may be a straight shape (including one inclined to about 45 degrees from the tire axial direction) or a bent shape such as a waveform. When siping is the waveform, the tire axial direction component in the entire siping length of the waveform is an effective edge component with respect to the tire traveling direction.

As described above, the groove density which is an effective edge component with respect to the tire traveling direction of the tread pattern is in the range of 0.012 mm / mm ^{2 to} 0.018 mm / mm ² . If it is less than 012 mm / mm ² , the edge component of the groove is insufficient and the performance on snow and ice deteriorates. On the other hand, if the density of the groove exceeds 0.018 mm / mm ² , the tread pattern becomes too fine and the block rigidity decreases. For this reason, the wear resistance deteriorates.
In particular, in order to keep good performance on snow and ice and wear resistance in a well-balanced manner, the density of grooves as an effective edge component in the tire traveling direction is set to 0.013 mm / mm ^{2 to} 0.015 mm / mm ² . It is preferable.

In addition, as described above, the siping density that is an effective edge component in the tire traveling direction of the tread pattern is in the range of 0.051 mm / mm ^{2 to} 0.059 mm / mm ^2. If it is less than 0.051 mm / mm ² , the edge component of siping is insufficient and the performance on snow and ice deteriorates. On the other hand, if the density of the siping exceeds 0.059 mm / mm ² , the tread pattern becomes too fine and the block rigidity is low. This is because the wear resistance deteriorates due to the decrease.
In particular, in order to keep good performance on snow and ice and wear resistance in a well-balanced manner, the density of siping that is an effective edge component in the tire traveling direction is 0.053 mm / mm ^{2 to} 0.057 mm / mm ² . It is preferable to do.

In addition, as described above, the tread rubber composition forming the tread part is obtained by blending 0.4 to 2.0 parts by mass of calcium carbonate powder with respect to 100 parts by mass of the rubber component including at least the diene rubber. In addition, while maintaining good snow and ice performance, it is possible to improve wear resistance and driving stability on dry road surfaces.
When the compounding amount of calcium carbonate powder is less than 0.4 parts by mass with respect to 100 parts by mass of the rubber component, even when the density of grooves and sipings that are effective edge components in the tire traveling direction is set within the above range. On the other hand, sufficient performance on snow and ice may not be obtained. On the other hand, if the amount of calcium carbonate powder exceeds 2.0 parts by mass, the wear resistance may be deteriorated.
In particular, in order to keep good performance on snow and ice and wear resistance in a good balance, the blending amount of the calcium carbonate powder is 0.7 to 1.5 parts by mass with respect to 100 parts by mass of the rubber component. Is preferred.

  The average particle size of the calcium carbonate powder is preferably 20 μm to 70 μm. When the average particle size of the calcium carbonate powder is less than 20 μm, sufficient on-snow characteristics may not be obtained. On the other hand, when the average particle size of the calcium carbonate powder exceeds 70 μm, the wear performance may be deteriorated. There is.

  On the other hand, as described above, the rubber component constituting the tread rubber composition contains at least a diene rubber, and examples of the diene rubber include butadiene rubber, styrene-butadiene rubber, isoprene rubber, and ethylene-propylene-diene rubber. Chloroprene rubber, acrylonitrile-butadiene rubber and the like, which can be used alone or in combination of two or more.

  Especially, in this invention, it is preferable that the rubber component of the said tread rubber composition consists of a butadiene rubber and a natural rubber, and a butadiene rubber is 20-80 mass parts with respect to 100 mass parts of this rubber component.

  As described above, by blending 20 to 80 parts by mass of butadiene rubber with 100 parts by mass of a rubber component composed of butadiene rubber and natural rubber, the balance between performance on snow and ice and wear resistance can be kept better. Can do. In particular, it is more preferable to mix 30 to 70 parts by mass of butadiene rubber with respect to 100 parts by mass of the rubber component, and further preferable to mix 45 to 55 parts by mass.

Further, the tread rubber composition, relative to 100 parts by mass of the rubber component, it is preferable that grayed Las fiber is blended with 1 to 3 parts by weight.

  As described above, the balance between the performance on snow and ice and the wear resistance can be kept better by blending the glass fiber in an amount of 1 to 3 parts by mass with respect to 100 parts by mass of the rubber component. When the amount of glass fiber is less than 1 part by mass, the performance on snow and ice may be insufficient. On the other hand, when the amount of glass fiber exceeds 3 parts by mass, the wear resistance may be deteriorated. is there. In particular, it is preferable that about 2 parts by mass of the glass fiber is blended with respect to 100 parts by mass of the rubber component.

  The average fiber diameter of the glass fiber is preferably 20 μm to 50 μm. When the average fiber diameter of the glass fiber is less than 20 μm, it is difficult to obtain the effect of scratching and digging the snowy and snowy road surface. On the other hand, when the average fiber diameter of the glass fiber exceeds 50 μm, rubber adhesion and adhesion friction are hindered. Therefore, there is a possibility that sufficient adhesion and adhesion friction force between the tread portion and the road surface cannot be obtained.

  Moreover, it is preferable that the average fiber length of the said glass fiber is 0.3 mm-0.8 mm. When the average fiber length of the glass fiber is less than 0.3 mm, the glass fiber tends to fall off by running, whereas when the average fiber length of the glass fiber exceeds 0.8 mm, the processing of the tread rubber tends to be difficult. is there.

  The glass fiber is preferably oriented in the thickness direction of the tread portion. As a result, the glass fiber oriented in the thickness direction of the tread part pushes away the water film formed between the ice and snow road surface and the surface of the tread part, increasing adhesion and adhesion friction force, and digging friction force of ice and snow road surface And the performance on snow and ice can be further improved.

Moreover, as mentioned above, the hardness Hs suitable as a studless tire can be controlled by setting the blending amount of oil to 5 to 25 parts by mass with respect to 100 parts by mass of the rubber component. When the blending amount of the oil is less than 5 parts by mass, the hardness Hs increases and the performance on snow and ice tends to be insufficient. On the other hand, when the blending amount of the oil exceeds 25 parts by mass, the hardness Hs decreases, Abrasion tends to deteriorate.
In particular, the oil is preferably blended in an amount of 5 to 40 parts by mass with respect to 100 parts by mass of the rubber component. Examples of the oil include mineral oils such as paraffinic process oil, naphthenic process oil, and aromatic process oil. Is preferably used.

Also, as described above, the amount of carbon powder with an average particle diameter of 20～26Nm, the shall be the blended with 33 to 55 parts by mass with respect to 100 parts by mass of the rubber component, the carbon powder If the blending amount is less than 33 parts by mass, the wear resistance tends to deteriorate, whereas if the blending amount of the carbon powder exceeds 55 parts by mass, the hardness Hs of the tread rubber becomes too high and the performance on snow and ice tends to deteriorate. Because.
In particular, it is more preferable to mix 40 to 50 parts by mass of the carbon powder with respect to 100 parts by mass of the rubber component, and it is preferable to use carbon black such as ISAF as the carbon powder.

The siping is formed in the tire axial direction in each block surrounded by the longitudinal groove in the tire circumferential direction and the lateral groove in the tire axial direction of the tread pattern, and is formed at a pitch of 3 to 7 mm in the circumferential direction in the one block. It is preferable that
Further, in order to prevent a decrease in block rigidity, the area of one block is surrounded by the longitudinal grooves and transverse grooves preferably ² about 300～1600Mm, therein, the length 10~35mm about sipes It is preferable that the tires are formed at a substantially uniform pitch in the tire circumferential direction.
Further, the width and depth of the vertical and horizontal grooves of the tread pattern are not particularly limited. For example, the groove width is preferably about 4 to 9 mm, and the groove depth is preferably about 3 to 11 mm.

The studless tire of the present invention is preferably composed of a pneumatic tire having two steel belts and one ply structure.
In addition, the studless tire of the present invention is suitable for mounting on a passenger car because it has excellent wear resistance and excellent performance on snow and ice.

The rubber hardness Hs of the studless tire of the present invention is set to 42-50 .
The rubber hardness Hs is measured at 0 ° C. according to a method defined in JIS K6253.
When the rubber hardness Hs is less than 42, the rubber itself is too soft and the wear resistance tends to deteriorate. On the other hand, when the rubber hardness Hs exceeds 50, the ground contact between the tread portion and the snowy and snowy road surface deteriorates. In particular, there is a risk that the performance on snow and ice necessary for mounting a passenger car may not be obtained.

  Further, for example, when the groove depth of the tread portion is measured after running a real vehicle of 10,000 km, the travel distance when the groove depth of the tire is reduced by 1 mm is calculated, and the travel distance is used as an index of wear resistance, the present invention As the wear resistance of the studless tire, it is preferable that the travel distance is 2000 km or more.

  Furthermore, for example, when the stop distance on ice is measured from 30 km / hr per hour and the stop distance on the ice required to stop is measured and the stop distance is used as an indicator of the performance on snow and ice, the snow and ice of the studless tire of the present invention As an upper performance, it is preferable that the stop distance is 45 m or less.

As described above, according to the present invention, the groove density, which is an effective edge component with respect to the tire traveling direction of the tread pattern, is 0.012 mm / mm ^{2 to} 0.018 mm / mm ² , and the siping density is 0.051 mm. / with ^mm 2 and ～0.059Mm / mm ^2, with respect to 100 parts by mass of the rubber component containing a diene rubber, 0.4 to 2.0 parts by weight of calcium carbonate powder, grayed Las fibers 1-4 mass Part of a tread rubber composition containing 5 to 25 parts by mass of oil and 33 to 55 parts by mass of carbon powder having an average particle diameter of 20 to 26 nm. High performance and wear resistance can be maintained in a well-balanced manner, and steering stability on dry road surfaces can be improved.

  In addition, as described above, 20 to 80 parts by mass of butadiene rubber is blended with 100 parts by mass of a rubber component composed of butadiene rubber and natural rubber, and 1 to 1 glass fiber with respect to 100 parts by mass of the rubber component. By blending 3 parts by mass, it becomes possible to maintain a better balance between the performance on snow and ice and the wear resistance.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a studless tire 10 for mounting a passenger car according to an embodiment of the present invention, and shows a state in which the studless tire 10 is assembled to a regular rim 30 and filled with a regular internal pressure.
The studless tire 10 includes a carcass 15 that is folded back from the inside to the outside around the bead core 14 of the bead portion 13 through the sidewall portions 12 on both sides from the tread portion 11, and the inside of the tread portion 11 and the carcass. 15 and a belt layer composed of two steel belts 16 disposed on the outside of the belt 15.

  The carcass 15 includes a single carcass ply, and the carcass ply has carcass cords arranged at an angle of 75 to 90 degrees with respect to the tire equator C. As the carcass cord, an organic fiber cord such as aromatic polyamide, nylon, rayon, polyester, etc. can be used in addition to the steel cord.

FIG. 2 shows a tread pattern 17 of the tread portion 11 in the studless tire 10.
As shown in FIG. 2, a longitudinal groove 18 in the tire circumferential direction and a lateral groove 19 in the tire axial direction are provided in the tread portion 11 to form a tread pattern 17, and each block 20 surrounded by the longitudinal groove 18 and the lateral groove 19 is formed in each block 20. Forms a siping 21 in the tire axial direction.
The longitudinal grooves 18 and the lateral grooves 19 do not have to be provided in parallel with the tire circumferential direction or the tire axial direction, and as shown in FIG. 2, they are inclined at a predetermined angle with respect to the tire circumferential direction or the tire axial direction. (Bending shape) may be provided. Similarly, the siping 21 does not need to be provided in parallel with the tire axial direction, and may be provided with a predetermined angle with respect to the tire axial direction as shown in FIG. Further, the groove widths and groove depths of the vertical grooves 18 and the horizontal grooves 19 can be appropriately changed.

In the present embodiment, the area of each block 20 is about 370 to 1400 mm ^2, and sipings 21 having a length of 13 to 25 mm are provided in each block 20 at a pitch of about 5 mm in the tire circumferential direction.
Moreover, the groove width of the vertical groove 18 and the horizontal groove 19 is about 5-7 mm, and the groove depth is about 7-10 mm.

By forming the tread pattern 17 and the siping 21 as described above, the density of grooves as effective edge components in the tire traveling direction is set to 0.012 to 0.018 mm / mm ^2, and effective in the tire traveling direction. The density of siping as an edge component is set to 0.051 to 0.059 mm / mm ² .

  On the other hand, the tread rubber composition forming the tread portion 11 includes a rubber component composed of butadiene rubber and natural rubber, calcium carbonate powder, glass fiber, mineral oil, carbon powder ISAF carbon black, vulcanization accelerator, Contains sulfur and zinc oxide.

  The butadiene rubber is blended in an amount of 20 to 80 parts by mass, preferably 30 to 70 parts by mass, and more preferably 45 to 55 parts by mass with respect to 100 parts by mass of all rubber components.

The calcium carbonate powder is blended in an amount of 0.4 to 2.0 parts by mass, preferably 0.7 to 1.5 parts by mass with respect to 100 parts by mass of the rubber component.
Moreover, the average particle diameter of the said calcium carbonate powder shall be 20-70 micrometers, and in this embodiment, the calcium carbonate powder currently distributed over 5-150 micrometers by using 40 micrometers as a mode value is used.

The said glass fiber is mix | blended 1-3 mass parts with respect to 100 mass parts of said rubber components, Preferably 2 mass parts is mix | blended.
Moreover, the average fiber diameter of the said glass fiber shall be 27-39 micrometers, and the average fiber length shall be 0.5-0.8 mm.

  The said mineral oil is 5-40 mass parts with respect to 100 mass parts of said rubber components, Preferably, 20-30 mass parts is mix | blended.

The carbon black is blended in an amount of 33 to 55 parts by mass, preferably 40 to 50 parts by mass with respect to 100 parts by mass of the rubber component.
The average particle size of carbon black is 20 to 26 nm.

Examples of the vulcanization accelerator include compounds such as guanidine-based, aldehyde-amine-based, aldehyde-ammonia-based, thiazole-based, sulfenamide-based, thiuram-based, and dithiocarbamic acid-based compounds, and particularly sulfenamide is used. It is preferable.
The vulcanization accelerator is blended in an amount of 0.5 to 5.0 parts by mass, preferably 1.0 to 3.5 parts by mass with respect to 100 parts by mass of the rubber component.

  The sulfur is blended in an amount of 1.0 to 3.5 parts by mass, preferably 2 to 3 parts by mass with respect to 100 parts by mass of the rubber component.

  The zinc oxide is blended in an amount of 0.5 to 5.0 parts by mass, preferably 2 to 4 parts by mass with respect to 100 parts by mass of the rubber component.

  Furthermore, in addition to the above-mentioned components, it is preferable to add additives used for the production of the tread rubber composition, for example, anti-aging agent, wax, stearic acid and the like.

The tread rubber composition is a known method, for example, kneading the above components using a kneading machine such as a Banbury mixer at a kneading temperature of 120 to 180 ° C. and a kneading time of 3 to 10 minutes, and molding and vulcanizing this. Can be obtained.
In order to orient the glass fiber in the thickness direction of the tread portion, for example, the tread rubber composition containing the glass fiber is rolled with a calender roll, and the obtained sheet is repeatedly folded. Orientation in the direction is possible.

As described above, the groove density, which is an effective edge component with respect to the tire traveling direction of the tread pattern 17 of the studless tire 10, is 0.012 mm / mm ^{2 to} 0.018 mm / mm ² , and the siping density is 0.051 mm / mm. A tread part from a tread rubber composition in which 0.4 to 2.0 parts by mass of calcium carbonate powder is blended with respect to 100 parts by mass of a rubber component containing a diene rubber, with a thickness of mm ^{2 to} 0.059 mm / mm ^2. By forming 11, the studless tire 10 can be kept in good balance between the performance on snow and ice and the wear resistance, and the steering stability on the dry road surface can be improved.

  In addition, as described above, 20 to 80 parts by mass of butadiene rubber is blended with 100 parts by mass of a rubber component composed of butadiene rubber and natural rubber, and 1 to 1 glass fiber with respect to 100 parts by mass of the rubber component. By blending 3 parts by mass, it becomes possible to maintain a better balance between the performance on snow and ice and the wear resistance.

Next, Examples 1 to 10, 12 to 24 of the present invention , Reference Example 11 and Comparative Examples 1 and 2 will be described. In addition, this invention is not limited to a following example.

(Examples 1 to 24, Comparative Examples 1 and 2)
Studless tire for mounting a passenger car having a tread pattern and siping having the structure shown in FIG. 1 and having a groove density and siping density as effective edge components in the tire traveling direction as shown in Tables 1 to 3 (tires) A size of 195 / 65R15 91Q) was prototyped.
Each of the studless tires prototyped was tested for handling stability on a dry road surface, wear resistance, and performance on snow and ice.
The test results are shown in Tables 1 to 3 together with the rubber hardness Hs and cost index of each studless tire.
Moreover, the composition of the tread rubber composition used for each prototype tire is also shown in Tables 1 to 3.
In Tables 1 to 3, the numerical values indicating the blending amounts of various components represent parts by mass, and “groove density” and “sipe density” are “the density of grooves that are effective edge components in the tire traveling direction”. , “The density of siping as an effective edge component with respect to the tire traveling direction”.

Various components used in Examples and Comparative Examples are as follows.
・ Natural rubber; “TSR20” grade ・ Butadiene rubber; “BR150B” manufactured by Ube Industries, Ltd.
Carbon black; “Dia Black I N220 ISAF” manufactured by Mitsubishi Chemical Corporation
・ Glass fiber: Nippon Sheet Glass Co., Ltd. average fiber diameter 11μm, fiber length 3mm
・ Calcium carbonate powder; “ES powder” manufactured by Kewpie Tamago Co., Ltd.
・ Mineral oil: “Diana Process Oil” manufactured by Idemitsu Kosan Co., Ltd.
-Anti-aging agent: Seiko Chemical Co., Ltd. "Ozonon 6C"
・ Wax: “Sunknock Wax” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Stearic acid: “Kiri” manufactured by NOF Corporation
・ Zinc oxide: “Zinc oxide 2 types” manufactured by Mitsui Mining & Smelting Co., Ltd.
・ Sulfur: “Powder sulfur” manufactured by Karuizawa Sulfur Co., Ltd.
・ Vulcanization accelerator: “Noxeller CZ” manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

The measurement methods of rubber hardness Hs, dry road surface handling stability, abrasion resistance, performance on snow and ice, and cost index calculation method of the studless tire shown in Tables 1 to 3 are as follows.
(1) Rubber hardness Hs
The rubber hardness Hs (JIS-A) at 0 ° C. was measured according to the method defined in JIS K6253.

(2) Dry road surface handling stability The studless tires of the example and the comparative example are mounted on four wheels of a 2.0 L domestic FR vehicle at an internal pressure of 200 kPa and a rim of 15 × 6.0 JJ, and the driving stability on a dry road surface. (Feeling in braking / cornering) was evaluated, and Comparative Example 1 was set as 100 and displayed as an index. The larger the index, the better the dry road surface handling stability.

(3) Abrasion resistance The studless tires of the example and the comparative example are mounted on four wheels of a 2.0 L domestic FR vehicle at an internal pressure of 200 kPa and a rim of 15 × 6.0 JJ, and the tread groove after running 10000 km. The depth was measured, and the running distance when the groove depth of the tire was reduced by 1 mm was calculated.
The travel distance in Example 5 was set to 100, and the travel distances of other examples and comparative examples were displayed as indices. That is, the larger the index, the better the wear resistance.

(4) Performance on snow and ice The studless tires of the example and the comparative example are mounted on four wheels of a 2.0 L domestic FR vehicle at an internal pressure of 200 kPa and a rim of 15 × 6.0 JJ, and suddenly on an icy road from 30 km / hr. After stopping, the stop distance on ice required to stop was measured. The reciprocal of each stop distance was taken, 1 / (stop distance) in Example 1 was set to 100, and 1 / (stop distance) of other examples and comparative examples was displayed as an index. That is, the larger the index, the better the performance on snow and ice.

(4) Cost The reciprocal of the cost per unit weight of the tread rubber is taken, and 1 / (cost per unit mass) in Comparative Example 1 is taken as 100, and 1 / (cost per unit mass) in other examples and comparative examples. ) Is displayed as an index. That is, the larger the index, the lower the cost.

As is apparent from Tables 1 to 3, the density of the grooves that are effective edge components in the tire traveling direction is less than 0.012 mm / mm ² , and the density of siping is less than 0.051 mm / mm ² , and calcium carbonate In Comparative Example 1 in which no powder was blended, both the performance on snow and ice and the wear resistance were insufficient. Also, the dry road surface handling stability, wear resistance, snow / ice performance and cost index total [(2) + (3) + (4) + (5)] are lower than other studless tires. The overall evaluation on the four items was also low.

Further, in Comparative Example 2 in which calcium carbonate powder is not blended, even when the groove density and siping density, which are effective edge components in the tire traveling direction, are within the specified range of the present invention, the wear resistance and The dry road surface handling stability was insufficient and, as in Comparative Example 1, the overall evaluation was also low.
That is, in Comparative Examples 1 and 2, the studless tires could not keep good performance on snow and ice and wear resistance in a well-balanced manner.

On the other hand, the studless tires of Examples 1 to 10 and 12 to 24 generally had good snow and ice performance and wear resistance in a well-balanced manner, and were excellent in dry road surface handling stability. In addition, the cost could be kept relatively low, and the overall evaluation on the four items was higher than those of Comparative Examples 1 and 2.

1 is a cross-sectional view of a studless tire according to an embodiment of the present invention. It is a top view of a tread pattern. It is drawing which shows a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Studless tire 11 Tread part 12 Side wall part 13 Bead part 14 Bead core 15 Carcass 16 Steel belt 17 Tread pattern 18 Vertical groove 19 Horizontal groove 20 Block 21 Siping 30 Rim

Claims (5)

A studless tire having a tread pattern and siping on the ground surface side of the tread portion,
The tread part has a vulcanization accelerator of 0.5 to 5.0 parts by weight, sulfur of 1.0 to 3.5 parts by weight, and zinc oxide of 100 parts by weight of a rubber component containing at least a diene rubber. 0.5 to 5.0 parts by mass, calcium carbonate powder is 0.4 to 2.0 parts by mass , glass fiber is 1 to 4 parts by mass, oil is 5 to 25 parts by mass, and the average particle size is 20 to 26 nm. It comprises a tread rubber composition containing 33 to 55 parts by mass of carbon powder ,
The density of the groove that is an effective edge component in the tire traveling direction of the tread pattern is 0.012 mm / mm ^{2 to} 0.018 mm / mm ² , and the density of the siping that is an effective edge component in the tire traveling direction is 0 A studless tire characterized in that the tire hardness is 0.051 mm / mm ^{2 to} 0.059 mm / mm ² and the rubber hardness Hs is 42 to 50 .   The studless tire according to claim 1, wherein the rubber component of the tread rubber composition is composed of butadiene rubber and natural rubber, and butadiene rubber is 20 to 80 parts by mass with respect to 100 parts by mass of the rubber component. Studless tire before Symbol of the rubber component 100 parts by weight, the glass fibers according to claim 1 or claim 2 are blended at 1 to 3 parts by weight   The studless tire according to any one of claims 1 to 3, comprising a pneumatic tire having two steel belts and one ply structure.   The studless tire according to any one of claims 1 to 4, wherein the studless tire is used for mounting a passenger car.

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