JP2568502B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to air that has sufficient heat endurance performance and wear resistance performance for practical use, and has significantly improved driving performance, braking performance and steering performance on ice and snow road surfaces. It is related to a tire with a tire.

(Prior art and its problems) Conventionally, a pneumatic tire has a drive performance, a braking performance and a steering performance (hereinafter, simply referred to as “ice and snow performance”) when traveling on an icy and snowy road surface. He frequently uses spiked tires with spike pins driven into the tread surface. However, dust pollution, in which these fine powders are scattered due to wear of the spike pins and roads, and damage to the roads due to the spike pins occur, causing a great social problem.

In order to cope with these problems, the amount of spike pins protruding, the number of driving spikes, the material of the spike pins, and the like have been studied, but such social problems have not yet been fundamentally solved.

On the other hand, in so-called studless tires that do not use spike pins, tire tread patterns or tread rubber quality have been studied, but there is a problem that ice and snow performance equivalent to that of spike tires cannot be exhibited. Especially,
For tread rubber, a polymer with a low glass transition point may be used to ensure rubber elasticity at low temperatures, and a softening agent with a low melting point may be used to secure a coefficient of friction with the road surface at low temperatures. It has been studied, but there is a problem that the ice and snow performance is not sufficient.

Further, a tire using a rubber having closed cells for a tread is disclosed in Japanese Patent Publication No. Sho-46-41, U.S. Pat. No. 4,249,588.
And JP-A-56-154304.

However, the one described in Japanese Patent Publication No. 40-4641 uses a synthetic rubber having a large hysteresis loss in the tread portion of the tire and uses a porous material to further increase the hysteresis loss. As a synthetic rubber having a large hysteresis loss, a high styrene rubber is used as described in Japanese Patent Publication No. 40-4641 as a synthetic rubber having a large hysteresis loss as well as an increase in friction coefficient and a porous structure. To use
This increases the glass transition temperature of the rubber, and therefore increases the hardness of the rubber at a low temperature, which is not preferable for securing ice and snow performance.

U.S. Pat. No. 4,249,588 discloses an attempt to improve the riding comfort and the like of tires for the road or golf cart. It is not an improvement.

Further, Japanese Unexamined Patent Publication No. Sho 56-154304 discloses an attempt to reduce the weight of a tire by using a foamed rubber to obtain the same hardness as that of a non-foamed rubber. It does not improve.

An object of the present invention is to solve the above-mentioned problems of the conventional spike tire and studless tire, and in particular, a pneumatic tire for practical use in which ice snow performance, abrasion resistance and heat generation durability are highly compatible. It is an object of the present invention to provide a new pneumatic tire that can sufficiently withstand the pressure.

(Means for Solving the Problems) The present inventors have conducted various studies to solve the above-mentioned problems, and as a result, contain the closed cells having a predetermined foam and a predetermined average cell diameter as described in detail below. While applying the foamed rubber layer to the tread of the pneumatic tire, and as appropriate, by using a rubber component having a low glass transition temperature, it has been confirmed that the above problem can be solved, and based on this fact,
Further studies from the structural point of view have led to the completion of the present invention.

Here, as the rubber component of the tread foamed rubber layer,-
Polymers having a glass transition temperature of 60 ° C. or less, for example, natural rubber, polyisoprene rubber, polybutadiene rubber, butyl rubber alone, or a mixture of two or more of these polymers, and styrene having a styrene content of 30% or less Mixtures of up to 40 parts by weight of butadiene rubber are preferred. In addition,
As the rubber component of the tread, a vulcanized rubber having a glass transition temperature of -60 ° C or lower is also included in the present invention. The reason for setting the rubber component of the tread as described above is that by using these polymers, the tread can maintain sufficient rubber elasticity even at a low temperature.

Further, the foamed rubber layer has at least a total volume of the tread.
It is desirably 10% or more, preferably 10-70%, and more preferably 40-60%. The reason why the foamed rubber layer is at least 10% or more of the total volume of the tread is that if it is less than 10%, the effect of improving the ice and snow performance is small. Further, the entire tread may be composed of a foamed rubber layer (foamed rubber layer 100%).

In the case where the outer tread layer is made of a foamed rubber layer and the tread layer on the radially inner side of the tire (hereinafter simply referred to as “inner tread layer”) is made of non-foamed rubber, the inner tread layer has no The hardness of the foamed rubber (solid rubber) is preferably 50 degrees or more in JIS hardness, more preferably 50 to 70 degrees, and more preferably greater than the hardness of the foamed rubber of the outer tread layer.

Further, as in the tire 21 shown in FIG. 4, a foamed rubber layer is formed only on a part of the outer tread layer 23 in contact with the road surface of the tread 25.
22 may be used, or a structure as shown in FIGS. 5 (a) to 5 (c) may be used.

The average cell diameter of the closed cells of the foamed rubber is desirably 1 to 120 µm, preferably 10 to 120 µm. To make the average cell diameter of the closed cells of the foamed rubber 1 to 120 μm, 1 μm
If it is less than the above, the flexibility of the foamed rubber at a low temperature or the effect of eliminating a water film between the tread and the road surface cannot be obtained, and if it exceeds 120 μm, the abrasion resistance performance is reduced, and the distortion restoring force of the foamed rubber is further reduced. This is because it is difficult to obtain a stable shape due to the deterioration of so-called set resistance and the decrease in permanent set property even during manufacturing.

Foaming ratio Vs as described above is expressed by the following equation _{Vs = {(ρ 0- ρ 9} ) / (ρ 1- ρ 9) -1} × 100 (%) ...... (1), ρ 1 is the foamed rubber density ^{(g / cm 3), ρ} 0 is the density of the rubber solid phase portion of the foamed rubber ^{(g / cm 3), ρ} 9 is the density of the gas portion in cells of the foamed rubber (g / cm ^3). The foamed rubber is composed of a rubber solid phase portion and a cavity (closed cell) formed by the rubber solid phase portion, that is, a gas portion in the air bubble.

By the way, since the density ρ _{9 of the} gas part is extremely small, almost close to zero, and extremely small with respect to the density ρ ₀ of the rubber solid part, the equation (1) is expressed by the following equation: Vs = (ρ ₀ / ρ ₁ -1) × 100 (%) (2)

The foaming ratio Vs is desirably in the range of 1 to 100%, preferably 2 to 50%. The ratio of foaming Vs to 1 to 100% is 1%
If it is less than 100%, the effect of improving the ice and snow performance will not be obtained, and if it exceeds 100%, the wear resistance will be reduced, and the strain restoring force of the foamed rubber will be reduced. This is because it is difficult to obtain a stable shape during manufacturing.

When a foamed rubber layer is applied to the outer tread layer in the tread including the outer tread layer and the inner tread layer in contact with the road surface, the foaming ratio Vs is desirably in the range of 2 to 50%.

The foamed rubber used for the tread of the pneumatic tire according to the present invention is formed when a foaming agent is added to a usual rubber compound and heated and pressed according to a usual tire manufacturing method.

As the foaming agent, for example, azodicarbonamide, dinitrosopentamethylenetetraamine, azobisisobutyronitrile, toluenesulfonylhydrazide derivative, toluenesulfonylhydrazide, aromatic succinyl todrazide derivative and the like are used. Can be

Hereinafter, details of the present invention will be described based on examples. In addition, the test of the property of the foamed rubber and the tire performance was performed by the following methods.

(Test method)

(1) Average cell diameter and foaming ratio Vs The average cell diameter was determined by cutting out a block-shaped sample from the foamed rubber layer of the tread of the test tire, photographing a photograph of the cross section of the sample with an optical microscope with a magnification of 100 to 400, and measuring 200 or more. Was measured and expressed as an arithmetic mean value. Also,
The foaming ratio Vs is the density ρ ₁ (g / cm ³ ) of the sample on the block.
Was measured, and the density ρ ₀ of the non-foamed rubber (solid rubber) was measured, and the density ρ ₀ was obtained by using the above equation (2).

(2) JIS hardness and elastic modulus at 300% elongation Prepare a predetermined test sample in the same way as normal tread rubber, measure according to normal JIS hardness (JIS standard K6301),
Further, the rubber elastic modulus at 300% elongation was measured.

(3) Tread heating temperature After filling the test tire with the regular internal pressure, the outer diameter is 1.7m and the speed is
It was pressed against a 100 km / H drum test machine with a regular load and run for 3 hours, and the surface temperature at the center of the tread was measured.

(4) Abrasion resistance Two test tires were mounted on a drive shaft of a passenger car having a displacement of 150 cc, and the test course was run on a concrete road surface at a predetermined speed. The amount of change in the depth of the groove was measured and expressed as an index, taking the non-foamed tire (Comparative tire 1) as 100. The larger the value, the better the abrasion resistance performance.

(5) Braking performance on ice Four test tires were mounted on a 1500 cc passenger car,
The braking performance on ice at an outside temperature of -15 ° C was measured. The index was indicated by setting the case of the non-foamed tire (Comparative Example 1) to 100. The smaller the value, the better the braking performance.

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

(First to Fifth Examples, Comparative Examples 1 to 6) FIGS. 1 and 2 are views showing a first example of a pneumatic tire according to the present invention.

In FIG. 1, a pneumatic tire 1 includes a case 2,
And a tread 3 made of foamed rubber and covering the crown portion 2a of the case 2. The case 2 includes a pair of beat portions 5, a carcass portion 6 made of a rubberized cord disposed substantially radially between the bead portions 5, and a belt portion 7 circumferentially disposed on the crown portion 2 a of the carcass portion 6. And a side rubber 8 that covers the side of the carcass portion 6.

The tread 3 is formed of the composition 1 among the compositions shown in Table 1 and is made of foamed rubber manufactured by a normal manufacturing method. The tread 3 is formed of the foamed rubber and forms the crown portion 2a. The entire tread is covered with a foamed rubber layer 4 (foamed rubber layer 100%). The average cell diameter of the closed cells of the foamed rubber is 32 μm, and its foaming ratio Vs is 8%
The properties of the foamed rubber and the performance of the tire were each measured by the test method described above.

Further, the configuration of the pneumatic tire other than the tread 3 and the method of manufacturing the pneumatic tire are the same as those of a normal pneumatic tire and the method of manufacturing the same, and therefore detailed description is omitted.

Next, 11 types of test tires (tire size 165 SR 13) (5 types in Example and 6 types in Comparative Example) were prepared, and the effect of the present invention was confirmed. Details are shown in Tables 2 and 3.

The first embodiment is, as described above, a pneumatic tire having the structure shown in FIGS.

As shown in FIGS. 1 and 2, 100% of the volume of the tread 3, that is, the total volume of the tread 3, in the second to fifth examples and the comparative examples 3 to 6, as in the first example. Was formed of a foamed rubber layer, and the second to fifth examples and comparative example 4
As in the first example, the foaming ratio and the average cell diameter were changed by using the composition 1 and changing the amount of the foaming agent as in the first example. Comparative Example 5 had an average cell diameter within the range of the present invention, but had a foaming ratio outside the range of the present invention, and Comparative Example 6 had a foaming ratio outside the range of the present invention. It is within the scope of the present invention, but the average cell diameter is outside the scope of the present invention. In Comparative Example 3, the foaming ratio was out of the range of the present invention, and 90 parts by weight of a styrene-butadiene rubber (containing 23% of styrene) having a glass transition temperature of −50 ° C. was used as the rubber component (composition 4). is there.

Comparative Example 1 is a case where the composition 2 obtained by removing the foaming agent from the composition 1 was used for the tread, and Comparative Example 2 was soft without using the foaming agent, that is, the hardness was reduced (composition 3). It is.

These test tires are the same as the first embodiment except for the above.

Average cell diameter of tread rubber, foaming ratio Vs, JIS hardness, 300
The test for the elastic modulus at% elongation and the performance of the tire
The test was performed according to the test method described above. The test results are shown in Tables 2 and 3 below.

As is clear from Tables 2 and 3, in the case of the first to fifth examples, the heat generation durability and the wear resistance of the tread are maintained to a level that can sufficiently withstand practical use as compared with those of the comparative examples 1 to 6. In addition, the braking performance on ice has been greatly improved.

Comparative Example 1 having a tread made of non-foamed rubber has very poor braking performance on ice and is not suitable for use on ice and snow road surfaces at all, and Comparative Example 2 also made of non-foamed rubber and having a soft tread However, the abrasion resistance performance is extremely deteriorated and is not practical.

In Comparative Example 3, the foaming ratio was out of the range of the present invention, and 90 parts by weight of a styrene-butadiene rubber having a glass transition temperature of -50 ° C (containing 23% of styrene) as a rubber component was used. The abrasion resistance is poor, and the braking performance on ice is very poor, so that it cannot be put to practical use.

In Comparative Example 4, the average bubble diameter and the foaming ratio were both out of the range of the present invention, and the braking performance on ice was satisfactory, but the heat generation durability was poor, and the wear resistance was very poor. It is getting worse, and this is not practical.

In Comparative Example 5, the average bubble diameter was within the range of the present invention, but the foaming ratio was out of the range of the present invention, and the braking performance on ice was satisfactory, but the heat generation durability was poor, and However, the abrasion resistance is extremely deteriorated, which is not practical.

In Comparative Example 6, the foaming ratio was within the range of the present invention, but the average cell diameter was out of the range of the present invention. The braking performance on ice was satisfactory, but the abrasion resistance was extremely deteriorated. This is also not practical.

As described above, in the first to fifth embodiments, the heat endurance performance, the abrasion resistance performance, and the braking performance on ice are highly compatible, while those in Comparative Examples 1 to 6 have these performances. Among them, any of them have extremely poor performance and cannot be used as a practical pneumatic tire.

A pneumatic tire in which a foamed rubber layer containing closed cells having a predetermined foaming rate and a predetermined average cell diameter as shown in the first to fifth examples is applied to the tread, Fine irregularities formed on the outer surface that is in contact with the road surface serve as a relief for a water film interposed between the tread surface and the road surface and eliminate the water film, so that the grip performance of the tire can be significantly improved, and such The edge effect is enhanced by the fine irregularities, and thus the ice and snow performance is greatly improved.

(FIGS. 6 and 7) FIG. 3 is a view showing the pneumatic tire 11 according to the sixth and seventh embodiments of the present invention. The tread 13 is composed of an outer tread layer 15 in contact with the road surface and an inner tread layer 16 on the inner side of the tread. The outer tread layer 15 is made of a foamed rubber layer (composition 1), and the inner tread layer 16 is a normal non-foamed rubber. The configuration of the pneumatic tire other than the above is the same as that of the first embodiment.

The pneumatic tire 11 having such a tread 13 is
It is suitable especially when considering the steering stability performance when traveling on a dry road surface while maintaining the ice and snow performance. That is,
Since the outer tread layer 15 that is in contact with the road surface is provided with a foamed rubber layer that is appropriately foamed, in addition to the ice and snow performance due to the foamed rubber layer, the rise in the heat generation temperature of the tread is slight, and the heat generation durability is sufficient. Further, the abrasion resistance is practically sufficient, and the ice and snow performance is also excellent.

The inner tread layer 16 has a hard solid phase rubber layer 18.
The tread 13 consisting of the outer tread layer 15 and the inner tread layer 16 having a high hardness is sufficient for the tread 13 even when a steering reaction force (lateral force) is received from the road surface when traveling on a dry road surface. It exerts rigidity and can have practically sufficient steering performance. Further, since the hardness of the solid phase rubber layer 18 of the inner tread layer 16 is high, the movement of the outer tread layer 15 is suppressed, and the wear resistance is improved.

Further, the sixth and seventh embodiments are excellent in steering stability on a dry road surface, and the use of a foamed rubber layer increases the vibration absorption capacity, thereby greatly reducing tire noise during running. And the weight of the tire can be reduced.

Table 4 shows test results and the like of Examples (Sixth and Seventh Examples) in which the foamed rubber layer as described above was applied to the outer tread layer 15. Configurations other than those shown in this table are the same as in the first embodiment.

As can be seen from Table 4, the heat generation durability performance, the wear resistance performance and the braking performance on ice are both highly compatible to a practically sufficient level.

Table 4 shows the test tires (tire size 165 SR1
3) Details are shown in which three types (Example 2 and Comparative Example 1) were prepared, and the effects of the present invention and the like were confirmed by variously changing the arrangement of the foamed rubber layer and the foamed rubber conditions.

Comparative Example 1 was the same as that shown in Table 2, and these test tire configurations were the same as those of the first example except for the above, and were manufactured by the same manufacturing method. The test method is the same as in Tables 2 and 3.

In addition, as a result of performing correction by using a foamed rubber in each of the configurations shown in FIGS. 2 to 5 using a conventional method and confirming the results, the ice and snow performance was significantly improved also in these corrected tires.

(Effects of the Invention) As described above, according to the present invention, the snow performance such as the braking performance, the driving performance, and the steering performance on the snowy road surface can be improved without impairing the wear resistance performance and the heat generation durability performance of the pneumatic tire. It can be greatly improved.

In a pneumatic tire in which a foamed rubber layer containing a closed cell having a predetermined foaming ratio and a predetermined average cell diameter is applied to at least a surface of the tread that is in contact with a road surface, the pneumatic tire is formed on an outer surface that is in contact with a tread road surface by closed cells. The fine irregularities provided serve as an escape for the water film interposed between the tread surface and the road surface and eliminate the water film, so that the grip performance of the tire can be significantly improved, and the edge effect due to such fine irregularities. As a result, the braking performance or the driving performance on the icy and snowy road surface is greatly improved.

In addition, the fine irregularities formed on the outer surface of the tread in contact with the road surface by the closed cells allow new closed cells to appear on the tread surface even if the tire is worn, so that the ice and snow performance can be maintained for a long time. .

Furthermore, a pneumatic tire in which a foamed rubber layer containing a closed cell having a predetermined foaming rate and a predetermined average cell diameter is applied to at least a surface of the tread that is in contact with the road surface, the rubber does not become hard even at low temperatures, and the elasticity is low. Since the tire does not lose its performance, the grip performance of the tire at low temperatures is significantly improved.

Furthermore, by reducing the weight of the pneumatic tire accompanying the weight reduction of the tread and applying the foamed rubber layer, the noise of the tire can be significantly reduced.

[Brief description of the drawings]

FIGS. 1 and 2 show a first example of a pneumatic tire according to the present invention.
FIG. 1 is a partial cross-sectional view, and FIG. 2 is an enlarged cross-sectional view of a main part thereof. FIG. 3 is an enlarged sectional view of a main part of a sixth embodiment and a seventh embodiment of the present invention. 4 and 5 are views showing another embodiment of the foamed rubber layer of the present invention. FIG. 4 is a partial cross-sectional view thereof, and FIG.
(C) is an enlarged cross-sectional view of a main part of each of the parts using the foamed rubber layer as a part of the outer tread layer. 1, 11, 21 ... pneumatic tire 2, 12 ... case 2a, 12a ... crown part 3, 13, 25 ... tread 4, 15, 22 ... foam rubber layer 16 ... inner tread layer 15, 23 …… Outer tread layer 18 …… Solid phase rubber

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-56-154304 (JP, A) JP-B-40-4641 (JP, B1) US Patent 4,249,588 (US, A)

Claims (1)

(57) [Claims] 1. A pneumatic tire having a tire case and a tread covering a crown portion of the case, a foamed rubber layer containing closed cells is provided on at least a surface of the tread in contact with a road surface, and A pneumatic tire having an average cell diameter in a range of 10 to 120 μm and a foaming rate of the foamed rubber layer in a range of 2 to 50%.