JP2011057183A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem wherein wear of rubber easily advances and lowering of wear resistance of a tire tread is not avoided since a shape holding effect becomes large during high and heavy load due to high rigidity of a peripheral direction belt, thereby the movement of the rubber itself of the tire tread is increased, and the problem wherein deterioration of wear balance between a tread center part and a tread shoulder part is generated. <P>SOLUTION: The pneumatic tire includes a belt layer 12 composed of at least one layer of a peripheral direction belt ply 15 and at least two layers of crossing belt plies 14, and the tread 13 composed of a cap rubber layer 17 and a base rubber layer 16. The cap rubber layer 17 has a larger elastic modulus than that of the base rubber layer 16. The base rubber layer 16 is formed so that a tire equatorial plane CL side region including a tire equatorial plane CL may be thinner than a tire shoulder part SH side region. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a heavy-duty pneumatic radial tire that employs a circumferential belt and is suitable for use in trucks and buses.

  Conventionally, a heavy-duty radial tire with a cap (CAP) / base (BASE) structure, for example, an ultra flat truck / bus, which employs a circumferential belt that is layered along the tire circumferential direction on the outside of the carcass A pneumatic tire such as a radial tire is known.

  In recent years, in large trucks and buses, there are many examples of adopting a single tire mounting structure for reducing fuel consumption and weight of the vehicle, and corresponding to this single mounting structure, the tire has a low flatness ratio. And the tread base is becoming wider. In general, a pneumatic tire having a low flatness has a belt layer composed of a pair of cross belt plies and a circumferential belt ply for circumferential reinforcement, thereby maintaining the tire shape under a high internal pressure load. In addition, the anti-centrifugal force and the heat resistance during running of the vehicle are improved, thereby improving the tire durability performance.

The cap / base structure has a two-layer structure in which the tire tread includes a cap rubber layer disposed on the outer side in the tire radial direction and a base rubber layer disposed on the inner side in the tire radial direction.
As a radial tire for heavy loads having such a structure, for example, there is a “radial tire for heavy loads” (see Patent Document 1).

JP 2003-127613 A

  However, in conventional heavy duty radial tires that use a circumferential belt, the circumferential belt is highly rigid, so the shape retention effect under load is great, and the tire side shape during tire rotation is close to a perfect circle. Become. For this reason, since the contact length of the tire contact portion is shortened, the contact pressure increases, and the increase in the contact pressure causes the rubber of the tire tread to be easily subjected to compressive deformation, and the rubber is greatly deformed. As a result, since the movement of the rubber of the tire tread itself becomes large, the wear of the rubber tends to proceed, and the wear resistance performance of the tire tread is inevitably lowered.

In addition, since the wear speed at the center of the tread in the tire tread is faster than that at the shoulder of the tread, the wear balance between the center of the tread and the shoulder of the tread has also deteriorated.
The object of the present invention is a pneumatic structure that has a structure to which a circumferential belt is applied, improves the wear resistance performance of the tire tread, prevents the wear balance of the tread center portion and the tread shoulder portion from deteriorating, and extends the wear life. Is to provide tires.

  In order to achieve the above object, a pneumatic tire according to the present invention comprises a belt layer comprising at least one circumferential belt ply and at least two intersecting belt plies, and a tread comprising a cap rubber layer and a base rubber layer. The cap rubber layer has a larger elastic modulus than the base rubber layer, and the base rubber layer is formed to be thinner in the tire equatorial plane side region including the tire equatorial plane than in the tire shoulder side region. Has been.

In the pneumatic tire according to another aspect of the present invention, the base rubber layer has a thickness difference of 5 mm or less in the tire equatorial plane side region, and a difference in thickness between the tire equatorial plane side region and the tire shoulder side region. 3 mm or more.
In the pneumatic tire according to another aspect of the present invention, the outer surface of the shoulder-side land portion located on the outermost side in the tire width direction in the land portion partitioned by the circumferential groove in the tire shoulder-side region. To the center in the tire width direction of the first inner land portion located on the inner side of the shoulder side land portion.
In the pneumatic tire according to another aspect of the present invention, the flatness is 60% or less.

According to the pneumatic tire of the present invention, the cap rubber layer has a larger elastic modulus than the base rubber layer, and the base rubber layer is thicker in the tire equatorial plane side region including the tire equatorial plane than in the tire shoulder side region. Since it is thinly formed, it has a structure with a circumferential belt applied to improve the wear resistance performance of the tire tread, prevent deterioration of the wear balance between the tread center and tread shoulder, and extend the wear life. Can do.
In the pneumatic tire according to another aspect of the present invention, the base rubber layer has a thickness of 5 mm or less in the tire equatorial plane side region, and a difference in thickness between the tire equatorial plane side region and the tire shoulder side region is 3 mm. Since it has made it above, the said effect can be show | played more effectively.

Moreover, according to the pneumatic tire which concerns on the other aspect of this invention, the outer side surface of the shoulder side land part located in a tire width direction outermost part in the land part divided by the circumferential groove | channel on the tire shoulder side area | region To the center in the tire width direction of the first inner land portion located inside the row on the shoulder side land portion, the above effect can be more effectively achieved.
Moreover, according to the pneumatic tire which concerns on the other aspect of this invention, since the flat rate is 60% or less, the said effect can be show | played more effectively.

1 is a cross-sectional view along a tire width direction schematically showing a configuration of a pneumatic tire according to an embodiment of the present invention. 1 shows a tire shoulder region in the pneumatic tire of FIG. 1, (a) is a conceptual explanatory diagram when there are three circumferential grooves, (b) is a conceptual explanatory diagram when there are four circumferential grooves, (c) ) Is a conceptual explanatory diagram when there are five circumferential grooves, and (d) is a conceptual explanatory diagram when there are six circumferential grooves.

Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view along a tire width direction schematically showing a configuration of a pneumatic tire according to an embodiment of the present invention. As shown in FIG. 1, a pneumatic tire 10 includes a carcass layer 11 constituting a tire skeleton, a belt layer 12 disposed on the outer side in the tire radial direction of the carcass layer 11, and an outer side in the tire radial direction of the belt layer 12. For example, it is an ultra-flat radial heavy-duty tire such as a truck / bus radial tire (TBR).

The carcass layer 11 is bridged in a toroidal shape between a pair of left and right bead cores (not shown) having an annular structure.
The belt layer 12 is laminated having at least two layers of cross belt plies 14 and at least one circumferential belt ply 15. These belt plies 14 and 15 are formed, for example, by rolling a plurality of belt cords made of steel fiber material or organic fiber material.

  The cross belt ply 14 is arranged so that the fiber direction of the belt cord is inclined with a predetermined belt angle with respect to the tire circumferential direction, and the fiber direction of the belt cord is inclined in different directions with respect to the tire circumferential direction. Are stacked. The circumferential belt ply 15 is disposed so that the fiber direction of the belt cord is substantially parallel to the tire circumferential direction. The circumferential belt ply 15 is preferably formed of a cord belt or a high elongation belt that is brazed in a wave shape.

  The tread 13 has a two-layer structure of a base (BASE) rubber layer 16 disposed on the inner side in the tire radial direction and a cap (CAP) rubber layer 17 disposed on the outer side in the tire radial direction. A tire tread is formed by 17. The cap rubber layer 17 has three or more circumferential grooves 13a extending in the tire circumferential direction. Sidewall rubber that forms the sidewall portion 18 of the tire is disposed on the outer side in the tire width direction of the carcass layer 11 following the tread 13.

  The base rubber layer 16 and the cap rubber layer 17 have different elastic moduli, and the elastic modulus of the cap rubber layer 17 is larger than that of the base rubber layer 16 (CAP elastic modulus> BASE elastic modulus). Is formed. Further, the base rubber layer 16 has a thickness (gauge) of the tire equatorial plane CL side region including the tire equatorial plane CL, that is, the central portion of the tread 13 through which the tire equatorial plane CL passes, based on the thickness (gauge) of the tire shoulder SH side area. ) Is thinner (CL gauge <SH gauge) (see FIG. 1).

Further, the thickness of the base rubber layer 16 in the tire equatorial plane CL side region including the tire equatorial plane CL is 5 mm or less, and the difference in thickness (gauge difference) between the tire equatorial plane CL side region and the tire shoulder SH side region is 3 mm or more. It is desirable to be.
Here, the tire shoulder SH side region S will be described.
FIG. 2 shows a tire shoulder region in the pneumatic tire of FIG. 1, (a) is a conceptual explanatory diagram when there are three circumferential grooves, and (b) is a conceptual description when there are four circumferential grooves. FIG. 4C is a conceptual explanatory diagram when there are five circumferential grooves, and FIG. 4D is a conceptual explanatory diagram when there are six circumferential grooves.

As shown in FIG. 2, the tire shoulder SH side region S is outside the SH (shoulder side) land portion 19 a that is a land portion located on the outermost side in the tire width direction in the land portion defined by the circumferential groove 13 a. From the side surface to the center in the tire width direction of the first inner land portion 19b located on the inner side of the SH land portion 19a (that is, the entire region of the SH land portion 19a + the 50% region of the first inner land portion 19b).
Further, the flatness of the pneumatic tire 10 is desirably 60% or less.

Next, deformation of rubber in the pneumatic tire 10 having the above configuration will be described.
Deterioration of the tread wear resistance and deterioration of the tread center and shoulder wear balance in heavy duty radial tires using a circumferential belt are due to increased tread rubber deformation due to the application of the circumferential belt. Is the result of
Since the deformation of this tread rubber is proportional to the elastic modulus of the rubber, it has become clear from research results that the hard deformation of the tread rubber does not cause an increase in deformation. The effect, that is, the effect that the tire side surface shape is maintained in a substantially circular shape when a load is applied is large. There was found.

However, increasing the hardness of the rubber of the cap rubber layer to harden the rubber suppresses the deformation of the rubber, but the rigidity of the tread rubber is excessively increased, and the tread pattern block, that is, the land portion is peeled off. Inconveniences such as easy. In order to efficiently increase the elastic modulus without incurring these problems, the thickness of the base rubber layer at the center of the tread through which the tire equatorial plane CL passes may be reduced.
This is because the rubber of the base rubber layer is generally set soft for the purpose of improving the heat build-up, and by reducing the amount of soft rubber by reducing the thickness of the soft base rubber layer. The elastic modulus at the center of the tread through which the tire equatorial plane CL passes can be increased.

On the other hand, the exothermic property of the rubber in the tread is almost determined by the tire shoulder SH where the thickness of the rubber becomes thick, but this portion reduces the thickness of the rubber of the base rubber layer disposed for the exothermic property. In addition, since the shape retaining effect of the tire shoulder SH is not originally large, a phenomenon such as a tread center portion through which the tire equatorial plane CL passes is unlikely to occur.
Therefore, considering the wear balance between the tread center portion through which the tire equatorial plane CL passes and the tire shoulder portion SH, there is little need to change the thickness of the base rubber layer of the tire shoulder portion SH.

  From this, the rubber thickness of the base rubber layer 16 is set to the tread center portion through which the tire equatorial plane CL passes, that is, the tire equatorial plane CL side region including the tire equatorial plane CL without hardening the rubber of the cap rubber layer 17. In the flat truck bus radial tire to which the circumferential belt 15 is applied, the wear resistance of the tire can be improved and the wear life can be extended. .

Three types of pneumatic tires 10 according to the present invention (Invention Examples 1 to 3) were prototyped and subjected to a comparative test with two types of conventional examples (Conventional Examples 1 and 2) in terms of wear resistance and the like.
The prototype was an ultra-flat radial heavy-duty tire with a tire size of 495 / 45R225 and two layers each of the cross belt 14 and the circumferential belt 15 and has the following specifications.

Number of circumferential grooves: 6 in both the invention example and the conventional example Rubber thickness of the base rubber layer 16 in the center of the tread through which the tire equatorial plane CL passes (CL BASE Ga.): 10 mm in the conventional examples 1 and 2, and the invention example 1 , 2 is 5 mm, Invention Example 3 is 0 mm
Rubber thickness of the base rubber layer 16 of the tire shoulder SH (SH BASE Ga.): 10 mm for each of Conventional Examples 1 and 2 and Invention Examples 1 to 3
Cross belt 2 width: 220 mm for Conventional Example 1, 380 mm for Conventional Example 2, 220 mm for Invention Example 1, 380 mm for Invention Examples 2 and 3
Cross belt 1 width: 420 mm for Conventional Examples 1 and 2 and Invention Examples 1 to 3
The width of the circumferential belt 2: 370 mm in the conventional examples 1 and 2 and the invention examples 1 to 3
The width of the circumferential belt 1: 370 mm in the conventional examples 1 and 2 and the invention examples 1 to 3

  The prototype tire of the above size is assembled in a 17.00 inch wide applicable rim, mounted on the drive shaft of the tractor head at an internal pressure of 900 kpa, and the tire equatorial plane CL passes when the fixed trailer is pulled and travels 50000 km. The depth of the circumferential groove in the tread center and the tire shoulder SH was measured. The measurement results are shown below.

  Here, the applicable rim is an “applied rim” defined by JATMA (The Japan Automobile Tire Manufacturers Association, Inc.), a TRA (Design Rim) defined by THE TIRE AND RIM ASSOCIATION INC., Or ETRTO. “Measuring Rim” as defined in (THE European Tire and Rim Technical Organization). The normal internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. The specified load means “maximum load capacity” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “LOAD CAPACITY” defined by ETRTO.

The result of comparing the depth of the worn circumferential groove (the depth of the circumferential groove when a new article−the depth of the circumferential groove after traveling) is shown below.
Depth of circumferential groove worn at the center of the tread through which the tire equatorial plane CL passes (CL wear groove depth): Conventional Example 1 is 10.3 mm, Conventional Example 2 is 9.7 mm, Invention Example 1 is 5.2 mm, Invention Example 2 is 4.9 mm, Invention Example 3 is 4.1 mm
Depth of worn circumferential groove of tire shoulder SH (SH wear groove depth): Conventional example 1 is 3.4 mm, Conventional example 2 is 3.3 mm, Invention example 1 is 3.5 mm, Invention example 2 is 3 0.1 mm, Invention Example 3 is 3.3 mm

  As can be seen from the above results, the depth of the worn circumferential groove 13 at the center of the tread through which the tire equatorial plane CL passes, that is, the depth of the circumferential groove 13a after traveling from the depth of the circumferential groove 13a when new is used. The values obtained by subtracting 10 were 10.3 mm for Conventional Example 1 and 9.7 mm for Conventional Example 2, both of which were about 10 mm, while those of Invention Example 1 were 5.2 mm and Invention Example 2 was 4. 9 mm, Invention Example 3 was 4.1 mm, an average of about 4.73 mm, and a maximum of 5.2 mm, which was substantially halved compared to the conventional example.

  According to this invention, the cap rubber layer has a larger elastic modulus than the base rubber layer, and the base rubber layer is formed such that the tire equatorial plane side region including the tire equatorial plane is thinner than the tire shoulder side region. Because it has a structure that applies a circumferential belt, it can improve the wear resistance performance of the tire tread, prevent deterioration of the wear balance between the tread center and the tread shoulder, and extend the wear life. It is most suitable for pneumatic tires, particularly pneumatic radial tires for heavy loads suitable for trucks and buses, which employ circumferential belts.

DESCRIPTION OF SYMBOLS 10 Pneumatic tire 11 Carcass layer 12 Belt layer 13 Tread 13a Circumferential groove 14 Cross belt ply 15 Circumferential belt ply 16 Base rubber layer 17 Cap rubber layer 18 Side wall part 19a SH land part 19b First inner land part CL Tire equator Surface SH Tire shoulder S Tire shoulder SH side area

Claims (4)

A belt layer comprising at least one circumferential belt ply and at least two cross belt plies;
It has a tread consisting of a cap rubber layer and a base rubber layer,
The cap rubber layer has a larger elastic modulus than the base rubber layer, and the base rubber layer has a tire equator plane side region including a tire equator side region formed thinner than a tire shoulder side region. . The base rubber layer is
The pneumatic tire according to claim 1, wherein the tire equatorial plane side region has a thickness of 5 mm or less, and has a thickness difference of 3 mm or more between the tire equatorial plane side region and the tire shoulder side region. The tire shoulder side region is
In the land portion defined by the circumferential groove, the center in the tire width direction of the first inner land portion located on the inner side of the shoulder side land portion from the outer surface of the shoulder side land portion located on the outermost side in the tire width direction. The pneumatic tire according to claim 1 or 2, wherein   The pneumatic tire according to any one of claims 1 to 3, wherein the flatness is 60% or less.

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