JPH07237407A - Tire for all-landform vehicle - Google Patents

Abstract

PURPOSE:To reduce the weight of a tire without marring the running performance by constituting a region ranging from the tread part of a tire for an all-landform vehicle to the sidewall part out of a rubber composition in inner and outer double layers, and using severally restricted rubber compositions for this inner rubber layer and outer rubber layer. CONSTITUTION:In the cross section along some meridian of a tire, which is used with inside pressure of 0.5kgf/cm<2> or under and charged with air into regular inside pressure, the tire is made in a smooth curve from the equator C of the circular tread part 2 to the roughly middle level of the sidewall part 3, and tread rubber 9 and the sidewall rubber 10 are made each in inner and outer double layer structure continuous in the direction of the meridian of the tire. The inner rubber layer 12 consists of rubber composition 65-75 deg. in JISA hardness, 74-90kgf/cm<2> in complex modulus of elasticity, and 0.25-0.35 in loss tangent (tan delta, and the outer rubber layer 11 consists of rubber composition 60-63' in JISA hardness, 55-60kgf/cm<2> in complex modulus of elasticity, and 0.20-0.25 in loss tangent (tan delta').

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an all-terrain vehicle tire capable of reducing tire weight without impairing running performance.

[0002]

2. Description of the Related Art Generally, all terrain vehicle (ATV) tires are
It is used on relatively rough roads such as rocks, sands, and mud with relatively low load and low speed. Therefore, unlike the conventional tires for passenger cars, it is necessary to secure the ground contact property and impart a levitation force to the tire, and it is usually used at a low internal pressure of 0.5 kgf / cm ² or less.

As described above, tires for all-terrain vehicles are used at a low internal pressure, and as a result, the rubber compositions of the treads and sidewalls of the tires have a greater effect on the running performance of the tires than tires for passenger vehicles. At present, a large amount of rubber is used.

[0004]

By the way, in recent years, resource saving is desired as a countermeasure for global environmental problems, and it is important to reduce the weight of tires in order to reduce fuel consumption of vehicles. Has become.

From this point of view, the tire weight for all-terrain vehicles is also reduced by reducing the amount of rubber used, but it cannot be denied that the traveling performance is impaired accordingly.

On the other hand, it is considered that the amount of rubber can be reduced and the rubber hardness and elastic modulus can be increased to prevent a decrease in tire strength. However, good treading performance cannot be obtained in the tread portion, and the tread portion cannot be obtained. In the wall portion, the crack resistance is deteriorated and it cannot be expected to maintain satisfactory running performance.

In view of the above problems, the present invention has conducted extensive studies, and as a result, formed a region from the tread portion to the sidewall portion from a rubber composition having two layers of inner and outer layers and the inner rubber layer. The inventors have found that the weight of the tire can be reduced without deteriorating the running performance by using the regulated rubber composition for the outer rubber layer, respectively, and have completed the present invention.

It is an object of the present invention to provide an all-terrain vehicle tire capable of reducing the tire weight without impairing the running performance.

[0009]

The present invention provides 0.5 kgf /
In a tire meridian section in a normal state in which the tire is used at a low internal pressure of cm ² or less, is assembled to a regular rim, and is filled with the regular internal pressure, the tread surface has an arc shape and the tire cross section from the tire equator at the center of the tread surface to the tire section height. A tire for an all-terrain vehicle in which the outer surface of the tire between the points of the tire maximum total width of the sidewall portion located approximately at the intermediate height can be continuously connected by a smooth curve, and the tread portion and the sidewall portion are The tread rubber and the sidewall rubber, respectively, are formed into a two-layer structure of an outer rubber layer that is continuous in the tire meridian direction and forms a tire outer surface, and an inner rubber layer that overlaps on the inner side, and the inner rubber layer is JISA hardness is 65 °
Or more and is at 75 ° or less, and complex elastic modulus (E *) is 74kgf / cm ² or more and 90 kgf / cm ² or less, yet the loss tangent (tan [delta]) is 0.25 or more and 0.35 or less of the rubber composition while consisting the outer rubber layer is JISA hardness of 60 ° or more and 63 ° or less, and complex elastic modulus (E *) is 55 kgf / cm ² or more and 60 kgf / cm ² or less, yet the loss tangent (tan [delta] ) Is 0.20 or more and 0.
An all-terrain vehicle tire characterized by comprising a rubber composition of 25 or less.

[0010]

According to the present invention, the tread rubber and the sidewall rubber have a two-layer structure comprising an outer rubber layer which is continuous in the tire meridian direction and forms an outer surface of the tire, and an inner rubber layer which overlaps with the inner rubber layer.

The outer rubber layer has a JISA hardness of 60 ° or more and 63 ° or less and a complex elastic modulus (E *) of 5
5 kgf / cm ² or more and 60 kgf / cm ² or less, yet with the loss tangent (tan [delta]) consists of 0.20 or more and 0.25 or less of the rubber composition, and the inner rubber layer, JISA hardness of 65 ° or more 75 ° or less, and complex elastic modulus (E *) is 74kgf / cm ² or more and 90 kgf / cm ² or less, and yet the loss tangent (tan [delta) is 0.25 or more 0.
It is composed of a rubber composition of 35 or less.

As described above, the tread rubber and the sidewall rubber have a two-layer structure, and the outer rubber layer is made of a rubber composition which is soft and rich in elasticity and has a small loss tangent. It is possible to maintain a good grounding feeling in the portion and the crack resistance of the sidewall portion.

The inner rubber layer is harder than the outer rubber layer,
By using a rubber composition with a large loss tangent, the rigidity of the tire is supplemented, damping performance is maintained, and the vibration transmitted from the outer rubber layer is mitigated to prevent this vibration from propagating to the vehicle body. As a result, riding comfort can be maintained.

Further, by using a tread rubber and a sidewall rubber as a two-layer structure body, the rubber composition can have a thinner rubber gauge than that of a one-layer structure body.
As a result, the weight of the tire can be reduced.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. The all-terrain vehicle tire 1 of the present invention has a weight of 0.5 kgf / cm ^2.
The tread rubber 9 and the sidewall rubber 10 which are used at the following low internal pressures and are respectively arranged in the tread portion 2 and the sidewall portion 3 are provided with an outer rubber layer 11 and an inner rubber layer 12 which are continuous in the tire meridian direction. And a two-layer structure.

In the tread portion 2, the tread surface 2A is formed in an arc shape in the tire meridian section in a normal state in which the tire 1 for all-terrain vehicle is assembled on the regular rim J and the regular internal pressure is filled.

Further, the sidewall portion 3 is smoothly connected to the tread portion 2 so that the outer surface of the tire between the tread portion and the total width MW of the tire located approximately at the middle height of the tire section height H is smoothed. Is formed. BL
Is the bead baseline.

By forming the tread portion 2 and the sidewall portion 3 in such a shape, and in combination with a low internal pressure, the tire is deformed when it comes into contact with the ground to increase the ground contact area, and the traction force in soft soil. Has been secured.

Further, the tread portion 2 and the sidewall portion 3
Tread rubber 9 and sidewalls 10 respectively
Is JISA hardness, complex elastic modulus and loss tangent (tan δ)
Is formed as a two-layer structure including an outer rubber layer 11 and an inner rubber layer 12.

Regarding the JIS A hardness, the outer rubber layer 11
It was found that it is necessary to combine the rubber composition having a rubber composition of 60 ° or more and 63 ° or less and the inner rubber layer 12 as a rubber composition of 65 ° or more and 75 ° or less within this range.

That is, the outer rubber layer has a JIS A hardness of 60 °.
If it is less than the above, durability is deteriorated because of early wear especially in the tread portion, while if it exceeds 63 °, the rigidity of the surface portion of the sidewall portion 3 tends to be excessively increased, and the crack resistance performance is significantly deteriorated. Therefore, the functions of the tread portion 2 and the sidewall portion 3 cannot be sufficiently balanced and held.

The inner rubber layer 12 has a JIS A hardness of 65 °.
If it does not meet the requirement, damping performance at the sidewall cannot be obtained due to low internal pressure, and the overall rubber gauge cannot be made thin. On the other hand, if it exceeds 75 °, the rigidity of the sidewall is excessively increased and riding It is not preferable because it may cause a separation of the rigidity and a large rigidity step between the rubber layer and the outer rubber layer.

[0023] The complex elastic modulus (E *) is an outer rubber layer 11 with a 55 kgf / cm ² or more and 60 kgf / cm ² or less, and the inner rubber layer 12 and 75 kgf / cm ² or more and 90 kgf / cm ² It has been found that it is necessary to use a combination of rubber compositions.

That is, the complex elastic modulus (E
If *) is less than 55 kgf / cm ² , the tread part will be greatly deformed and lack in steering stability.
If it exceeds f / cm ² , the rigidity of both the tread portion and the sidewall portion becomes too high, and the feeling of contact with the ground and the riding comfort cannot be maintained.

The complex elastic modulus (E *) of the inner rubber layer 12
However, if it is less than 70 kgf / cm ² , the deformation becomes too large to obtain sufficient damping property at the sidewall portion, and if it exceeds 90 kgf / cm ² , the rigidity is too high and the tire deformation is small. I can't maintain the ride comfort.

Regarding the loss tangent (tan δ), a rubber composition in which the outer rubber layer 11 is 0.20 or more and 0.25 or less and the inner rubber layer 12 is 0.25 or more and 0.35 or less is used. It has been found that it is necessary to use them in combination.

That is, the outer rubber layer 11 in direct contact with the road surface
It is desirable to use a rubber composition having a low heat buildup for the inner rubber layer 12 as well as a rubber composition having a large energy loss and capable of suppressing vibration.

In the outer rubber layer 11, the loss tangent (tan
If δ) is less than 0.20, the vibration absorbing effect cannot be expected sufficiently, while if it exceeds 0.25, heat generation during high-speed traveling becomes large, which is not preferable.

In the inner rubber layer 12, the loss tangent (ta
If n δ) is less than 0.25, the vibration generated in the outer rubber layer in the tread portion and the sidewall portion cannot be absorbed, and the riding comfort deteriorates. Fever tends to be large.

Such outer rubber layer 11 and inner rubber layer 1
Table 1 shows a typical formulation example of the rubber composition of No. 2.

[0031]

[Table 1]

The complex elastic modulus (E *) and the loss tangent (tan δ) are values measured at 70 ° C., frequency 10 Hz, and dynamic strain rate 1% using a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho.

Further, as shown in FIG. 2, the inner rubber layer 1 is
2 is the thickness t2 at the position M of the maximum total width MW of the tire
Is 0.4 times or more the thickness t1 of the outer rubber layer 11 and 1.
5 times or less is preferable, and the sum of the thicknesses of the outer rubber layer 11 and the inner rubber layer 12 at the position M (t1 + t)
It is desirable to carry out step 2) within the range of 3 to 5 mm.
The thickness t2 of the inner rubber layer 12 is equal to the inner liner 1
The carcass 6 composed of three or two carcass plies 6A and 6B is not included.

In this way, the sum of the thicknesses of the outer rubber layer 11 and the inner rubber layer 12 (t1 + t2) is set to a regulated range,
By varying the thickness ratio, a plurality of tires having different specifications can be manufactured while maintaining the running performances described above, and the overall rubber gauge can be reduced to reduce the weight of the tire.

The thickness t2 of the inner rubber layer 12 is
If it is less than 0.4 times the thickness t1 of the outer rubber layer 11, the tire rigidity tends to decrease, and if it exceeds 1.5 times, the tire rigidity is increased and the riding comfort tends to be impaired. Is preferred.

The inner rubber layer 12 may have a uniform thickness from the tread portion 2 to the sidewall portion 3.

A bead portion 4 fitted to the rim J is continuously provided on the sidewall portion, and a bead core 5 and a bead apex 7 made of hard rubber are provided on the bead portion 4, respectively. The layer 12 terminates at a substantially middle position of the bead apex 7.

[0038]

[Specific example] The tire size is AT25 × 8-12 according to the JATMA (Japan Automobile Tire Manufacturers Association) standard,
A tire having the structure shown in FIG. 1 was prototyped (Examples 1 to 4), and a conventional tire (conventional example) in which the rubber composition of the tread portion 2 and the sidewall portion 3 had a single structure, a tread portion 2, and a sidewall portion. Although 3 has a two-layer structure, tires (Comparative Examples 1 to 4) having a configuration other than that of the present application were also prototyped and the performance was evaluated. In the tires of Examples and Comparative Examples, the sum of the thicknesses (t1 + t2) of the outer rubber layer 11 and the inner rubber layer 12 was unified to 4 mm at the position M of the maximum total width MW of the tire.

The test method is as follows. B) Tire weight The weight per tire was measured and displayed as an index with the conventional example being 100. The smaller the value, the smaller the tire weight.

(B) Riding comfort, steering stability, and damping performance Test tires were mounted on all four wheels of a 2000cc class all-terrain vehicle, and the test course was run in a swamp, and the sensory evaluation of the driver was used as a conventional example. Is shown as an index. The larger the value, the better.

(C) Sidewall crack resistance performance At the maximum total width position of the test tire, a cut having a width of 5 mm and a depth of 1.0 mm was made at an angle of 45 ° with respect to the tire meridian, and this tire was subjected to an indoor drum tester. The growth size of the cut after traveling 1000 km under normal load was evaluated by an index with the conventional example being 100. Table 2 shows the test results
Shown in.

[0042]

[Table 2]

As a result of the test, it was confirmed that the tires of the examples were lighter in weight while maintaining their running performances than the tires of the comparative examples. Further, in the tire meridional section, the tire of the example has a rubber gauge of 1 mm over the tread portion and the sidewall portion as compared with the tire of the conventional example.
I was able to confirm that it was reduced.

[0044]

As described above, according to the present invention, riding comfort,
It is possible to reduce the tire weight by making the rubber gauge thin without reducing the running performance such as steering stability, damping performance, and side wall crack resistance.

[Brief description of drawings]

FIG. 1 is a meridian sectional view of a tire showing an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view showing the vicinity of the maximum tire width.

[Explanation of symbols]

 2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 7 bead apex 9 tread rubber 10 sidewall rubber 11 outer rubber layer 12 inner rubber layer C tire equator MW maximum tire width M maximum tire width position

Claims (3)

[Claims] 1. A tread portion having a circular tread surface in a tire meridian section in a normal state in which the tire is used at a low internal pressure of 0.5 kgf / cm ² or less, is assembled to a regular rim, and is filled with the regular internal pressure. A tire for an all-terrain vehicle in which the outer surface of the tire between the tire equator at the center and the point of the maximum tire width of the sidewall portion located approximately at the middle height of the tire cross section can be continuously connected by a smooth curve. A tread rubber and a sidewall rubber that are respectively arranged in the tread portion and the sidewall portion, a two-layer structure of an outer rubber layer that is continuous in the tire meridian direction and forms a tire outer surface, and an inner rubber layer that overlaps on the inner side thereof. In addition, the inner rubber layer has a JISA hardness of 65 ° or more and 75
° or less and the complex elastic modulus (E *) is 74 kgf / cm
² or more and 90 kgf / cm ² or less, and loss tangent (tan
δ) is made of a rubber composition having a value of 0.25 or more and 0.35 or less, while the outer rubber layer has a JISA hardness of 60 ° or more and 63 ° or more.
Below, and the complex elastic modulus (E *) is 55 kgf / cm
² or more and 60 kgf / cm ² or less, and the loss tangent (tan
A tire for all-terrain vehicles, which is made of a rubber composition having δ) of 0.20 or more and 0.25 or less. 2. The inner rubber layer is at least 0.4 times the thickness of the outer rubber layer at the position of the maximum total width of the tire and 1.
It is 5 times or less, The tire for all-terrain vehicles of Claim 1 characterized by the above-mentioned. 3. The tire for an all-terrain vehicle according to claim 1, wherein the inner rubber layer has a uniform thickness from the tread portion to the sidewall portion.