JP2003335110A - Pneumatic tire for heavy load - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the rolling resistance. <P>SOLUTION: This pneumatic tire for heavy load comprises a carcass 6 from a tread part 2 to a bead core 5 of a bead part 4 through a sidewall part 3, and a belt layer 7 mounted outside of the carcass 6 and inside of the tread part 2. The tire is provided with the cushion rubber mounted between an outer end part in the tire axial direction of the belt layer 7 and the carcass 6, and stretched in the approximately triangular shape, and an inner reinforcement rubber 10 holding the carcass 6 with the cushion rubber 9 by being stretched between a tread shoulder part SH and a tire maximum width position M at the inside of the carcass 6. The inner reinforcement rubber 10 is made out of a rubber material having a maximum thickness T of 3.0-10 mm, and the viscoelastic characteristic substantially same as that of the cushion rubber 9. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy duty pneumatic tire capable of reducing rolling resistance.

[0002]

2. Description of the Related Art In recent years,
From the perspective of protecting environmental resources, improvement of fuel efficiency is drawing attention as an important issue for vehicles, and it is effective to achieve low fuel consumption in heavy-duty vehicles such as trucks and buses, which consume a lot of fuel. Is. In view of such a situation, even in a heavy duty pneumatic tire used for a heavy duty vehicle, further reduction of rolling resistance is desired.

As a method for reducing the rolling resistance, it is known to use a rubber material having a low heat generation for a tread rubber which is grounded to a road surface, for example. However, in general, in rubber materials, low heat generation performance and abrasion resistance performance are antithetical performances. Therefore, if a rubber material having a low heat generation is used, the wear resistance performance and the uneven wear resistance performance required for a heavy duty pneumatic tire cannot be sufficiently obtained, and it is not possible to meet the market demand such as reducing the tire life.

As another method, the amount of vertical deflection of the tire is reduced by increasing the rubber thickness of the sidewall portion, increasing the diameter of the carcass cord, and increasing the number of carcass cords to be driven. Attempts to reduce rolling resistance have also been proposed. However, in such a method, the weight of the tire is likely to be significantly increased, and the rolling resistance increase margin due to the weight increase is larger than the rolling resistance reduction margin due to the reduction in the vertical deflection amount, and thus the rolling resistance is reduced. Does not contribute enough to.

The present invention has been devised in view of the above problems, and a carcass is provided with a cushion rubber arranged between the carcass and the belt layer and an inner reinforcing member arranged inside the carcass. Provided is a pneumatic tire for heavy loads, which is sandwiched between rubbers and is basically made of a rubber material having the same viscoelastic properties as the cushion rubber for the inner reinforcing rubber to reduce the vertical deflection of the tire to reduce rolling resistance. Is intended.

[0006]

According to a first aspect of the present invention, the carcass extending from the tread portion to the bead core of the bead portion through the sidewall portion and the carcass outside the carcass and inside the tread portion are arranged. A heavy-duty pneumatic tire including a belt layer, the cushion rubber being arranged between an outer end portion of the belt layer in the tire axial direction and the carcass, and extending in a substantially triangular cross section, and the carcass. An inner reinforcing rubber sandwiching the carcass with the cushion rubber by extending at least between the tread shoulder portion and the tire maximum width position inside, and the inner reinforcing rubber has a maximum thickness of 3.0 to 10 mm. Moreover, it is characterized by being made of a rubber material having substantially the same viscoelastic characteristics as the cushion rubber.

The invention according to claim 2 is the pneumatic tire for heavy load according to claim 1, wherein the inner reinforcing rubber is made of a rubber material having a loss tangent tan δ of 0.035 to 0.065. is there.

The "loss tangent tan δ" of the rubber material is
Cut a strip-shaped sample of 4 mm width x 30 mm length x 1.5 mm thickness and measure it using a viscoelasticity spectrometer manufactured by Iwamoto Manufacturing Co., Ltd. under the conditions of temperature 70 ° C, frequency 10 Hz, dynamic strain ± 2%. Value.

According to a third aspect of the present invention, in the inner reinforcing rubber, the end portion on the tread shoulder portion side has a length L of 0.1 from the inner end of the cushion rubber in the tire axial direction. ˜1.0 times the distance A along the carcass on the tire equator side, and the end portion on the tire maximum width position side is 0.5 to 0.5 times the length L of the cushion rubber from the outer end of the cushion rubber. The heavy-duty pneumatic tire according to claim 1 or 2, wherein a distance B of 1.5 times is separated inward in the tire radial direction along the carcass.

The invention according to claim 4 is characterized in that the cushion rubber has an overlapping length in the tire axial direction which overlaps with the belt layer of 10 mm or more and less than a half width of the belt layer. The pneumatic tire for heavy loads according to any one of 1.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of a heavy duty pneumatic tire (hereinafter sometimes simply referred to as “tire”) 1. In this example, a tubeless type heavy duty radial tire used for trucks, buses and the like is illustrated. ing.

In the figure, a tire 1 has a tread portion 2
And a pair of sidewall portions 3 extending inward in the tire radial direction from both ends thereof, and a bead portion 4 located at an inner end of each sidewall portion 3 and seated on a rim (not shown). In the tire 1, a toroidal carcass extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3 and a belt layer 7 located outside the carcass 6 and inside the tread portion 2 are provided. It is distributed.

The carcass 6 has a main body portion 6a extending from the tread portion 2 through the side wall portion 3 to the bead core 5 of the bead portion 4, and a body portion 6a connected to the main body portion 6a. The carcass ply 6A includes one or more (in the present embodiment, one) carcass ply 6A having a folded-back portion 6b that is folded back from the inside to the outside in the direction. The carcass ply 6A is a sheet-shaped one in which both sides of a cord array in which carcass cords are arrayed in an angle range of 70 to 90 ° with respect to the tire equator C are covered with topping rubber. In this example, a steel cord is used as the carcass cord. The inner liner rubber layer 12 is provided on the inner surface of the carcass 6 with the bead portions 4, 4
It is distributed over the space. This inner liner rubber layer 1
No. 2 is made of a butyl-based rubber that contains butyl halide in an amount of 50 parts by weight or more and is excellent in air permeation resistance, and prevents air from leaking into the tire lumen.

In the belt layer 7 of this embodiment, the belt cord is inclined with respect to the tire equator C at an angle of, for example, about 60 ± 10 °, and the tire equator C.
Belt ply 7 inclined at a small angle of 30 ° or less
B, 7C and 7D are overlapped with each other by providing one or more places where the belt cords intersect each other between the plies 4
It has a layered structure. In this example, the width of the second belt ply 7B from the inner side is formed to be the largest, and this end portion forms the outer end 7e of the belt layer 7. In addition, the belt cord,
Although a steel cord is used in this example, a highly elastic organic fiber cord such as aromatic polyamide can also be used if necessary.

The bead portion 4 is provided with a bead apex rubber 8 which extends from the bead core 5 outwardly in the tire radial direction through a space between the main body portion 6a and the folded-back portion 6b. In the example, a reinforcing ply 15 having a substantially U-shaped cross section and arranged so as to surround the bead core is provided to appropriately reinforce the bead portion 4.

Further, in the tire 1, a cushion rubber 9 extending in a substantially triangular cross section is arranged between an outer end portion 7E of the belt layer 7 in the tire axial direction and the carcass 6, and inside the carcass 6, An inner reinforcing rubber 10 sandwiching the carcass 6 with the cushion rubber 9 by extending at least between the tread shoulder portion SH and the tire maximum width position M.
Are arranged.

In the tire 1 of the present invention, the cushion rubber 9 and the inner reinforcing rubber 10 thus sandwich the carcass 6 near the buttress portion to improve the vertical rigidity of the tire without changing the profile of the carcass 6. . Then, the vertical deflection of the tire is reduced. As a result, the amount of deformation of the tire near the buttress portion during running is reduced, and the rolling resistance at this portion can be reduced.

As shown in an enlarged view in FIG. 2, the cushion rubber 9 has a substantially maximum thickness Ta in the vicinity of the outer end 7e of the belt layer 7, from which the inner end 9a and the outer end in the tire axial direction are formed. 9b has a substantially triangular cross section in which the thickness is gradually reduced, and the cross section is continuous in the tire circumferential direction. The maximum thickness Ta of the cushion rubber 9 is not particularly limited, but is preferably 5 to 15 mm, particularly preferably 7 to 13
mm is preferable. If the maximum thickness Ta of the cushion rubber 9 is too small, the ability to relieve and absorb the strain at the outer end 7e of the belt layer 7 tends to decrease, and the effect of reinforcing the carcass 6 tends to be poor. Too big,
This is not preferable because it tends to damage the shape of the outer end portion 7E of the belt layer 7 and further tends to distort the profile of the carcass 6.

The cushion rubber 9 has its inner end 9a located at the separation portion J where the innermost belt ply 7A of the belt layer 7 and the carcass ply 6A start to separate from each other, and the outer end 9b of the cushion rubber 9 has its outer end 9b. The taper extends inward in the tire radial direction along the carcass 6 beyond the outer end 7e of the. Also, the length L of the cushion rubber 9 along the carcass 6
Is not particularly limited, but is preferably 80 to 150 m
It is effective to set m, particularly preferably 95 to 120 mm. The overlapping length Wa of the cushion rubber 9 and the belt layer 7 in the tire axial direction is preferably set to 10 mm or more and less than the half width bw of the belt layer 7, particularly preferably 25 mm or more and less than the half width bw of the belt layer. Is.

The cushion rubber 9 fills a step between the outer end portion 7e of the flat belt layer 7 and the carcass 6 curved in an arc shape toward the sidewall portion 3, and at the same time, the carcass 6 is covered. By extending inward in the tire radial direction, it is useful for absorbing strain of the outer end portion 7E of the belt layer 7 which is easily deformed during load running and improving durability.

The cushion rubber 9 of this embodiment has a loss tangent tan δ of 0.035 to 0.065, more preferably 0.04 to 0.06, and still more preferably 0.04 to 0.06.
It is made of rubber material with low heat generation of 055. Such a rubber having low heat generation suppresses energy loss due to deformation during load running, helps reduce rolling resistance, and can reduce heat generation and prevent damage such as belt edge looseness, and can also improve durability. Further, since the cushion rubber 9 does not come into direct contact with the road surface, the problem of deterioration in wear resistance, which is apt to occur in rubber materials having low heat generation, does not occur.

The loss tangent ta of the cushion rubber 9 is
When nδ is less than 0.035, the energy loss can be reduced, but the reinforcing property is low, and there is a possibility that it is easily broken. On the contrary, when nδ exceeds 0.065, the energy loss is increased and the rolling resistance is deteriorated. And the durability tends to decrease.

As the viscoelastic property of the cushion rubber 9, the complex elastic modulus is, for example, 1.0 to 5.0 MPa, more preferably 2.0 to 4.0 MPa, and further preferably 2.
It is desirable that the pressure is 5 to 3.5 MPa. This preferably helps to reduce the vertical deflection of the tire.

In the tire 1, the cushion rubber 9 extends at least inside the carcass 6 between the tread shoulder SH and the tire maximum width position M.
An inner reinforcing rubber 10 sandwiching the carcass 6 is provided. The “tread shoulder portion” is the tread ground contact end E.
To 25% of the tread contact width TW.
Further, the "tread ground contact width" TW is a distance in the tire axial direction between the tread ground contact ends when the tire is assembled on a regular rim, filled with a regular internal pressure, and loaded with a regular load to be grounded on a flat surface.

The "regular rim" is a rim defined by each tire in the standard system including the standard on which the tire is based. For example, JATMA is a standard rim, and TRA is "Design Rim". , Or ETRTO
If so, use "Measuring Rim". Also, "regular internal pressure"
Is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based.
Maximum air pressure for TMA, and table "TIRE L for TRA.
Maximum value described in OAD LIMITS AT VARIOUS COLD INFLATION PRESSURES, or "INFLATION PRESSU for ETRTO
In addition, "regular load" is the load that each standard defines for each tire in the standard system including the standard on which the tire is based. If JATMA, maximum load capacity, if TRA Table "TIRE LOAD LIMITS AT VARIOU
Maximum value stated in "S COLD INFLATION PRESSURES", ETR
If it is TO, it will be "LOAD CAPACITY". Further, the "tire maximum width position" is defined as a position that protrudes to the outermost side in the tire axial direction except the marking of the sidewall portion and the like when the tire is assembled on a regular rim and filled with regular internal pressure without load.

Tread shoulder portion S of the inner reinforcing rubber 10
The end 10a on the H side may be located inside the inner end 9a of the cushion rubber, but in the present embodiment, the end 10a extends from the inner end 9a of the cushion rubber 9 to the length of the cushion rubber. The distance A that is 0.1 to 1.0 times the length L is separated along the carcass 6 on the equator side of the tire. In this way, by displacing the end portion 10a of the inner reinforcing rubber 10 from the inner end 9a of the cushion rubber 9, a large rigidity step is prevented from occurring near the end portion 10a, and the carcass 6 is filled at the time of filling with the internal pressure. Can suppress the deformation of the profile. In addition, the end portion 10 of the inner reinforcing rubber 10
By extending a toward the tire equator C side from the inner end 9a of the cushion rubber 9, it is useful to secure a large length for sandwiching the carcass 6 with the cushion rubber 9. When the distance A is less than 0.1 times the length L of the cushion rubber 9, a rigidity step is likely to occur in the vicinity of the inner end of the cushion rubber 9, and when it exceeds 1.0 times, the tire weight is increased. Is likely to increase.

The end portion 10b of the inner reinforcing rubber portion 10 on the tire maximum width position M side is the outer end 9 of the cushion rubber 9.
It is provided at a position which is separated from b by 1.0 to 1.5 times the length L of the cushion rubber 9 along the carcass 6 inward in the tire radial direction. As a result, in the present embodiment, the cushion rubber 9 and the inner reinforcing rubber 10 can sandwich the so-called buttress portion carcass 6 from the inside and outside with the length L of the cushion rubber 9.

The inner reinforcing rubber 10 is characterized in that it has a maximum thickness Tb of 3.0 to 10 mm and is made of a rubber material having substantially the same viscoelastic characteristics as the cushion rubber 9. As described above, the inner reinforcing rubber 10 has the maximum thickness Tb and the rubber material limited, so that the rolling resistance is reduced by reducing the vertical deflection amount of the tire while preventing the tire weight from significantly increasing and the riding comfort from decreasing. Can be reduced. Further, such a reinforcing structure of the carcass 6 hardly changes the carcass profile at the time of filling with internal pressure. That is, the carcass profile tries to approach a uniform arc due to the expansion deformation due to the filling of the internal pressure, but when the reinforcing rubber layer is arranged on the outside of the carcass, the carcass enters the inside by the rubber thickness and is biased toward the carcass. Tension is applied. On the other hand, when the reinforcing rubber 10 is provided inside the carcass 6, there is no such influence of the rubber thickness. For this reason, it is possible to prevent uneven tension on the carcass cord and prevent deterioration of tire durability.

The maximum thickness Tb of the inner reinforcing rubber 10 is
Is less than 3.0 mm, the bending rigidity of the carcass 6 sandwiched by the cushion rubber 9 cannot be increased, and the effect of reducing the amount of vertical deflection is reduced. On the contrary, if the maximum thickness Tb of the inner reinforcing rubber 10 exceeds 10.0 mm, the tire weight is significantly increased, which is not preferable. Particularly preferably, the maximum thickness Tb of the inner reinforcing rubber 10 is 4.0 to 10.0.
mm, and more preferably 5.0 to 8.0 mm. Like the cushion rubber 9, the inner reinforcing rubber 10 of the present embodiment also has a cross-sectional shape in which the thickness gradually decreases toward both ends, and strain is concentrated at the ends 10a and 10b. It's suppressed.

It is desirable that the inner reinforcing rubber 10 has substantially the same viscoelastic characteristics as the cushion rubber 9. For example, even in a run flat tire that can safely travel to a predetermined place even at the time of puncture, there is one in which such a reinforcing rubber layer is provided inside the carcass. In such a run flat tire, the reinforcing rubber layer is a cushion rubber. A harder rubber material is used, which is completely different from the present invention. By making the viscoelastic characteristics of the cushion rubber 9 and the inner reinforcing rubber 10 substantially the same,
The vertical deflection of the tire can be reduced while preventing a significant deterioration in riding comfort. In addition, it is possible to prevent an increase in the material of the compounded rubber and prevent an increase in tire cost. The “viscoelastic property” includes tan δ and complex elastic modulus. Also, "substantially the same" means that both tan δ and complex elastic modulus are ± 3, as they can have the same action and effect.
This is because a difference of about% can be tolerated.

[0031]

EXAMPLE A heavy duty pneumatic tire having a tire size of 11R22.5 14PR was prototyped according to the specifications shown in Table 1, and rolling resistance, vertical deflection amount, riding comfort, tire weight and the like were measured. The test method and test results are as follows.

A) Rolling resistance test load: 24.52 kN, air pressure: 700 kPa Room temperature: 25 ° C. ± 2 ° C. Speed: 80 km / H Drum diameter: 1707.6 mm Drum surface: Iron In addition, the amount of vertical deflection is from the unloaded state. It is the value when the tire was brought into contact with the drum and a load was applied during the rolling resistance test.

B) Riding comfort The test tires are mounted on all wheels of a flat body (2-DD vehicle) having a constant weight of 10 tons with the above-mentioned rim and internal pressure, and riding comfort when traveling on a paved road. Was evaluated by a five-point method according to the feeling of the driver. The higher the number, the better.

C) Durability Under a condition of internal pressure (700 kPa) and rim (22.5 × 7.50), using a drum tester, every 10 minutes, 10 km.
The vehicle was run at a speed of / H and the running time until tire destruction occurred was measured. The evaluation is 100 comparative examples.
It is indicated by an index, and the larger the value, the better.

[0035]

[Table 1]

[0036]

As described above, the heavy duty pneumatic tire of the present invention can reduce rolling resistance by reducing the amount of vertical deflection of the tire. When the loss tangent tan δ of the inner reinforcing rubber is limited to a certain range as in the second aspect of the invention, the rolling resistance can be more effectively reduced.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a heavy duty pneumatic tire of the present embodiment.

FIG. 2 is a partially enlarged view thereof.

[Explanation of symbols]

1 pneumatic tire 2 tread section 3 Side wall part 4 bead part 5 bead core 6 carcass 6A carcass ply 6a Carcass ply body 6b Carcass ply turns 7 Belt layer 9 cushion rubber 9a Inner end of cushion rubber 9b Outer end of cushion rubber 10 Inner reinforcement rubber 10a End of the inner reinforcing rubber on the tread shoulder side 10b End portion of the inner reinforcement rubber on the maximum tire width position side

Claims (4)

[Claims] 1. A heavy duty pneumatic tire comprising a carcass extending from a tread portion to a bead core of a bead portion through a sidewall portion and a belt layer arranged outside the carcass and inside the tread portion. A cushion rubber that is arranged between an outer end of the belt layer in the tire axial direction and the carcass and extends in a substantially triangular cross section; and at least between a tread shoulder portion and a tire maximum width position inside the carcass. A rubber material having an inner reinforcing rubber sandwiching the carcass with the cushion rubber by stretching, and the inner reinforcing rubber having a maximum thickness of 3.0 to 10 mm and having substantially the same viscoelastic properties as the cushion rubber. A heavy-duty pneumatic tire comprising: 2. The pneumatic tire for heavy loads according to claim 1, wherein the inner reinforcing rubber is made of a rubber material having a loss tangent tan δ of 0.035 to 0.065. 3. The inner reinforcing rubber has an end on the tread shoulder side which is 0.1 to 1.0 of the length L of the cushion rubber from the inner end of the cushion rubber in the tire axial direction.
A double distance A is separated along the carcass on the tire equator side, and the end portion on the tire maximum width position side is 0.5 to 1.5 times the length L of the cushion rubber from the outer end of the cushion rubber. 3. The heavy-duty pneumatic tire according to claim 1, wherein the distance B is separated inward in the tire radial direction along the carcass. 4. The load according to claim 1, wherein the cushion rubber has an overlapping length in the tire axial direction overlapping with the belt layer of 10 mm or more and less than a half width of the belt layer. Heavy duty pneumatic tire.