JP2021138314A - Tire for heavy load - Google Patents

Abstract

To suppress rising up in a tread end at high-speed travelling and improve high-speed durability performance even on a wide and low-flat tire for heavy load.SOLUTION: A tire for heavy load includes: a belt layer 7 including first to third belt plies 7A-7C arranged from a tire radial inside; and a reinforcement ply 20 extending outside in a tire axial direction while being held between the first and third belt plies 7A, 7C on an outside in a tire axis direction of the second belt ply 7B and having a reinforcement cord 20c arranged at a cord angle smaller than 10 degrees relative to a tire circumferential direction.SELECTED DRAWING: Figure 1

Description

The present invention relates to a heavy-duty tire with improved high-speed durability.

In Patent Document 1 below, in a large radial tire provided with two or more layers, mainly three or more layers, the lifting of the tread end due to centrifugal force during high-speed running is suppressed, and uneven wear of the tire is prevented. Tires that have been prevented and have improved durability have been proposed.

In the proposed tire, reinforcing cord layers made of steel cords having a cord angle of 10 ° or less with respect to the tire circumferential direction are arranged on both sides of the belt layer outside the second belt. In particular, the case where the reinforcing cord layer is arranged on the outer side in the radial direction of the third belt and on both outer sides in the tire axial direction of the fourth belt is described. The reinforcing cord layer suppresses the lifting of the tread end due to centrifugal force during high-speed driving.

Japanese Unexamined Patent Publication No. 05-69702

On the other hand, in heavy-duty tires for trucks, buses, etc., it has been desired in recent years to reduce the weight and rolling resistance of the tires. Therefore, it is required to replace the conventional double tire with a single wide and low flat tire having a flatness of 60% or less, which is a so-called wide single tire.

However, since the wide, low and flat heavy-duty tire has a wide tread width, the binding force of the belt layer on the tread portion is significantly reduced in the tread shoulder region. Moreover, the bottom of the shoulder main groove that divides the tread shoulder region becomes a weak point of rigidity, and it is easy to bend in the tire radial direction.

Therefore, even when the technique of Patent Document 1 is applied to a wide, low and flat heavy load tire, it is difficult to sufficiently suppress the lifting of the tread end portion during high-speed running. As a result, high-speed durability performance could not be sufficiently improved, such as inducing delamination at the outer end of the belt layer.

The present invention has been devised in view of the above circumstances, and is for heavy loads that can suppress the lifting of the tread end at high speeds and enhance high speed durability performance, especially even for wide, low and flat heavy load tires. Its main purpose is to provide tires.

The present invention is a heavy-duty tire provided with a belt layer composed of a plurality of belt plies in which belt cords are arranged at a cord angle of 10 to 50 degrees with respect to the tire circumferential direction in a tread portion.
The plurality of belt plies include a first belt ply arranged on the innermost side in the tire radial direction, a second belt ply arranged on the outer side of the first belt ply in the tire radial direction, and the first belt ply. Including the third belt ply arranged outside the tire radial direction of the second belt ply,
It is sandwiched between the first and third belt plies on the outside in the tire axial direction of the second belt ply and extends outward in the tire axial direction, and the reinforcing cord extends 10 degrees with respect to the tire circumferential direction. Reinforcing plies arranged at smaller cord angles are arranged.

In the heavy-duty tire according to the present invention, the outer end of the reinforcing ply in the tire axial direction is located outside the tire axial direction of the outer end of the first and third belt plies in the tire axial direction. preferable.

In the heavy-duty tire according to the present invention, the tread portion includes a shoulder main groove continuously extending in the tire circumferential direction, and the reinforcing ply is arranged outside the shoulder main groove in the tire axial direction. preferable.

In the heavy-duty tire according to the present invention, the outer end of the first belt ply in the tire radial direction, the outer end of the second belt ply in the tire radial direction, and the third belt ply in the tire radial direction. It is preferable that the outer end and the outer end of the reinforcing ply in the tire radial direction are different from each other in the tire axial position.

In the heavy-duty tire according to the present invention, the tire axial distance La between the outer end of the first belt ply in the tire radial direction and the outer end of the reinforcing ply in the tire radial direction, and the third belt ply. The tire axial distance Lb between the outer end in the tire radial direction and the outer end in the tire radial direction of the reinforcing ply is preferably in the range of 3.0 to 8.0 mm, respectively.

In the heavy-duty tire according to the present invention, the cord angles θ2 and θ3 of the second and third belt plies are 10 to 16 degrees, and the cord angles θ1 of the first belt ply are from the cord angles θ2 and θ3. It is preferably large and 50 degrees or less.

In the heavy-duty tire according to the present invention, the tire flatness is preferably 60% or less.

In the present specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified in a no-load normal internal pressure state in which the tire is rim-assembled on a normal rim and the normal internal pressure is filled. A "regular rim" is a rim defined for each tire in the standard system including the standard on which the tire is based. For example, "standard rim" for JATTA and "Design Rim" for TRA. If it is ETRTO, it is "Measuring Rim". "Regular internal pressure" is the air pressure defined for each tire in the standard system including the standard on which the tire is based. For JATMA, "maximum air pressure", for TRA, the table "TIRE LOAD LIMITS AT" The maximum value described in "VARIOUS COLD INFLATION PRESSURES", or "INFLATION PRESSURE" for ETRTO.

In the heavy-duty tire of the present invention, the reinforcing plies in which the reinforcing cords are arranged at a cord angle smaller than 10 degrees with respect to the tire circumferential direction are arranged outside the tire axial direction of the second belt ply. Therefore, even in a tire having a wide, low and flat tread width, the region up to the tread end can be restrained with a high tag effect, and the lift of the tread end at high speed can be suppressed.

Moreover, the reinforcing ply is sandwiched between the first and third belt plies and extends outward in the tire axial direction. Therefore, the peeling between the plies between the reinforcing ply and the first belt ply and the peeling between the plies between the reinforcing ply and the third belt ply can be suppressed.

Here, when there is no reinforcing ply and the first to third belt plies are adjacent to each other as in the conventional case, as is well known, the cord angles of the belt cords are different from each other between the adjacent plies. As a result, shear strain occurs between the plies. Then, starting from the outer end of the ply, peeling between the plies is induced. That is, peeling between plies tends to occur between the first belt ply and the second belt ply, and between the second belt ply and the third belt ply. This peeling between plies is more likely to occur as the difference in cord angle between adjacent plies is larger.

However, in the present invention, the reinforcing ply and the first belt ply are adjacent to each other, and the reinforcing ply and the third belt ply are adjacent to each other. Since the cord angle of the reinforcing ply is smaller than 10 degrees, the difference in the cord angle between the reinforcing ply and the first belt ply and the difference in the cord angle between the reinforcing ply and the third belt ply. Is small. Therefore, the shear strain between the reinforcing ply and the first belt ply and the shear strain between the reinforcing ply and the first belt ply are suppressed to a low level, and the peeling between the plies is suppressed.

Although shear distortion occurs between the second belt ply and the first belt ply, and between the second belt ply and the third belt ply, the outer end of the second belt ply is the first, It is sandwiched between the third belt plies and restrained. Moreover, since the outer end of the second belt ply itself is closer to the equator side of the tire than in the conventional case, the influence of lifting during high-speed running is small. Therefore, peeling between plies in the second belt ply can be suppressed.

It is sectional drawing of the heavy-duty tire of one Embodiment of this invention. It is an enlarged cross-sectional view of the tread shoulder area of FIG. It is a development view which shows the arrangement state of the cord in a belt ply and a reinforcement ply in a concept. It is sectional drawing which conceptually shows the outer end position of the belt ply and the reinforcing ply in the tire axial direction.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a cross-sectional view of the tire meridian including the rotation axis of the heavy-duty tire (hereinafter, may be simply referred to as “tire”) 1 of the present embodiment in a normal internal pressure state.

As shown in FIG. 1, the tire 1 of the present embodiment has a toroid-shaped carcass 6 extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a tread outside the tire radial direction of the carcus 6. Includes a belt layer 7 arranged inside the portion 2.

In this example, the case where the tire 1 has a cross-sectional width W of 300 mm or more and a tire flatness of 60% or less and is suitable for a so-called wide single tire used for a light truck or the like is shown. The "cross-sectional width W" is the maximum width in the tire axial direction excluding the pattern and letters on the side surface of the tire 1 in the normal internal pressure state. The "tire flatness" is the ratio (H / W) of the cross-sectional height H to the cross-sectional width W of the tire 1. The “cross-sectional height H” corresponds to 1/2 of the difference between the outer diameter of the tire 1 and the rim diameter of the regular rim.

The tread portion 2 includes a shoulder main groove Gs that divides the tread portion 2 into a tread shoulder region Ye on the tread end Te side and a tread crown region Yc on the tire equator Co side. In this example, the case where the crown main groove Gc is further arranged in the tread crown region Yc is shown. The shoulder main groove Gs and the crown main groove Gc extend continuously in the tire circumferential direction.

The carcass 6 has at least one carcass ply 6A, in this example one carcass ply.

The carcass ply 6A preferably includes a main body portion 6a and a folded portion 6b. The main body 6a extends across the bead cores 5 and 5. The folded-back portion 6b is connected to the main body portion 6a and is folded back around the bead core 5 from the inside to the outside in the tire axial direction.

The carcass 6 of this example has a so-called ultra-high turn-up structure in which the outer end 6c of the folded-back portion 6b in the tire radial direction is located inside the tread portion 2 and between the main body portion 6a and the belt layer 7. Such a carcass 6 can secure high tire rigidity while being composed of one carcass ply 6A, and moreover, the outer end 6c of the folded-back portion 6b is unlikely to be a starting point of damage, and the durability can be improved.

The carcass ply 6A has a carcass cord arranged at an angle of, for example, 70 to 90 ° with respect to the tire circumferential direction. As the carcass cord, a steel cord having a cord diameter of 0.6 to 0.8 mm can be preferably adopted. The number of steel cords driven in the carcass ply 6A per 50 mm width is preferably 20 to 30.

In this example, a sheet-shaped rubber layer 10 is arranged between the main body portion 6a and the folded-back portion 6b. It is desirable that the inner end 10a of the rubber layer 10 in the tire radial direction is connected to the outer side of the bead apex rubber 12 in the tire radial direction. It is desirable that the rubber layer 10 extends outward in the radial direction of the tire to at least the outer end 6c of the folded-back portion 6b.

Generally, in a tire 1 having an ultra-high turn-up structure, the strain amplitude, which is the distribution of strain changes on the surface of the sidewall portion 3 when no load is applied and when a load is applied, tends to be large. The rubber layer 10 described above can alleviate the strain between the main body portion 6a and the folded-back portion 6b, and can reduce the strain amplitude in the sidewall portion 3.

The rubber layer 10 preferably has a sheet-like thickness of 1.0 to 2.0 mm. If the thickness of the rubber layer 10 is smaller than 1.0 mm, the strain between the main body portion 6a and the folded-back portion 6b may increase. If the thickness of the rubber layer 10 is larger than 2.0 mm, the main body portion 6a may be located inside in the tire axial direction, and the strain amplitude may increase.

The bead apex rubber 12 has a substantially triangular cross-sectional shape extending outward in the radial direction of the tire from the bead core 5. The outer end of the bead apex rubber 12 in the tire radial direction is connected to the inner end 10a of the rubber layer 10.

The complex elastic modulus E * ₁₀ of the rubber layer 10 is smaller than the complex elastic modulus E * _{12 of the bead apex rubber 12.} The complex elastic modulus E * ₁₀ is preferably 6 to 8 MPa. If the complex elastic modulus E * ₁₀ is smaller than 6 MPa, the strain between the main body portion 6a and the folded-back portion 6b may increase. If the complex elastic modulus E * ₁₀ is larger than 8 MPa, it may peel off due to an impact when the vehicle is running. The complex elastic modulus E * ₁₂ is preferably 50 to 80 MPa.

Reference numeral 13 in the drawing is a chafer rubber, which prevents the rim from shifting and reinforces the bead portion 4 in cooperation with the bead apex rubber 12. The complex elastic modulus E * ₁₃ of the chafer rubber 13 is larger than the complex elastic modulus E * _{10 and} smaller than the complex elastic modulus E * ₁₂ . The complex elastic modulus E * ₁₃ is preferably 10 to 15 MPa. Generally, in the tire 1 having an ultra-high turn-up structure, the influence of the strain on the outer side in the tire radial direction of the carcass ply 6A tends to be concentrated on the chafer rubber 13. The above-mentioned chafer rubber 13 can efficiently disperse the strain in the chafer rubber 13.

The complex elastic modulus of the rubber material constituting the tire 1 is a value measured using a viscoelastic spectrometer under the conditions of a temperature of 70 ° C., a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2%.

Next, the belt layer 7 and the reinforcing ply 20 are arranged on the tread portion 2.

The belt layer 7 is composed of a plurality of belt plies including a first belt ply 7A, a second belt ply 7B, and a third belt ply 7C. In this example, the case where the belt layer 7 further includes the fourth belt ply 7D is shown.

The first belt ply 7A is arranged on the innermost side in the tire radial direction among the plurality of belt plies. The second belt ply 7B is arranged outside the first belt ply 7A in the tire radial direction. The third belt ply 7C is arranged outside the second belt ply 7B in the tire radial direction. The fourth belt ply 7D is arranged outside the third belt ply 7C in the tire radial direction.

As shown in FIG. 3, the first to fourth belt plies 7A to 7D include a belt cord 7c made of, for example, a steel cord arranged at a cord angle θ of 10 to 50 degrees with respect to the tire circumferential direction.

If the cord angle θ exceeds 50 degrees, the binding force is inferior, and it is difficult to sufficiently suppress the lifting of the tread end portion during high-speed running. On the contrary, when the cord angle θ is less than 10 degrees, the in-plane rigidity of the belt layer 7 becomes insufficient, and the uneven wear resistance performance is deteriorated.

From the viewpoint of the binding force and the in-plane rigidity, the cord angles θ2 and θ3 of the second and third belt plies 7B and 7C are preferably in the range of 10 to 16 degrees. In the second and third belt plies 7B and 7C, the inclination directions of the belt cords 7c are different from each other, so that the belt cords 7c intersect each other between the second and third belt plies 7B and 7C.

The cord angles θ1 and θ4 of the first and fourth belt plies 7A and 7D are preferably larger than the cord angles θ2 and θ3. In particular, the code angles θ1 and θ4 are more preferably in the range of 18 to 50 degrees. In this example, the inclination directions of the belt cords 7c are different from each other in the first and second belt plies 7A and 7B, and the inclination directions of the belt cords 7c are different from each other in the third and fourth belt plies 7C and 7D. doing.

As a result, both the binding force and the in-plane rigidity can be improved at the same time.

As shown in FIG. 2, the reinforcing ply 20 is arranged outside the second belt ply 7B in the tire axial direction. In particular, the reinforcing ply 20 is preferably arranged outside the shoulder main groove Gs in the tire axial direction.

In this example, the outer end Be of the second belt ply 7B in the tire axial direction and the inner end of the reinforcing ply 20 in the tire axial direction are arranged so as to abut against each other. The reinforcing ply 20 is sandwiched between the first and third belt plies 7A and 7C and extends outward in the tire axial direction.

The reinforcing ply 20 includes a reinforcing cord 20c made of, for example, a steel cord arranged at a cord angle α (shown in FIG. 3) smaller than 10 degrees with respect to the tire circumferential direction. In particular, the reinforcing cord 20c is preferably wound spirally in the tire circumferential direction. As the reinforcing cord 20c, the same cord as the belt cord 7c can be preferably adopted.

Such a reinforcing ply 20 is arranged outside the second belt ply 7B in the tire axial direction. Therefore, even in the case of a wide single tire having a wide low flatness, the region up to the tread end can be restrained with a high tag effect, and the lifting of the tread end at high speed can be effectively suppressed.

Moreover, since the reinforcing ply 20 is sandwiched between the first and third belt plies 7A and 7C, the ply separation between the reinforcing ply 20 and the first belt ply 7A and the reinforcing ply 20 and the third The peeling between the plies with the belt ply 7C can be suppressed.

Regarding the peeling between the plies between the second belt ply 7B and the first belt ply 7A and the peeling between the plies between the second belt ply 7B and the third belt ply 7C, the second belt The outer end Be of the ply 7B is sandwiched and restrained by the first and third belt plies 7A and 7C, and the outer end Be of the second belt ply 7B is close to the tire equator C side during high-speed driving. Since the effect of lifting is small, peeling between plies can be suppressed.

In order to suppress the lifting of the tread end and the suppression of peeling between plies, the outer end 20e of the reinforcing ply 20 in the tire axial direction is the outer end of the first and third belt plies 7A and 7C in the tire axial direction. It is preferably located outside the tire axial direction rather than Ae and Ce.

The distance K in the tire axial direction between the outer ends 20e and 20e is preferably about the same as the ply width of the second belt ply in the conventional heavy-duty tire. Specifically, the distance K is the tread width TW. The range of 85 to 95% of the above is preferable.

The ply width Wa of the first belt ply 7A is preferably in the range of 70 to 80% of the tread width TW. The ply width Wc of the third belt ply 7C is preferably in the range of 75 to 90% of the tread width TW, and is particularly larger than the ply width Wa. The ply width Wb of the second belt ply 7B is smaller than the ply widths Wa and Wc, and is particularly preferably in the range of 50 to 65% of the tread width Tw. The ply width Wd of the fourth belt ply 7D is preferably smaller than the ply widths Wa to Wc.

The outer end Ae of the first belt ply 7A in the tire radial direction, the outer end Be of the second belt ply 7B in the tire radial direction, the outer end Ce of the third belt ply 7C in the tire radial direction, and the reinforcing ply. It is preferable that the positions in the tire axial direction are different from those of the outer end 20e in the tire radial direction of 20. As a result, the stress acting on the outer ends Ae, Be, Ce, and 20e during traveling is widely dispersed. Therefore, peeling between plies with each outer end Ae, Be, Ce, 20e as a base point can be suppressed more effectively.

In particular, as exaggerated in FIG. 4, the distance La in the tire axial direction between the outer end Ae of the first belt ply 7A and the outer end 20e of the reinforcing ply 20 and the third belt ply 7C. The distance Lb in the tire axial direction between the outer end Ce and the outer end 20e of the reinforcing ply 20 is preferably in the range of 3.0 to 8.0 mm, respectively. If the distances La and Lb are less than 3.0 mm, the stress dispersion effect is not sufficiently exhibited. On the contrary, even if it exceeds 8.0 mm, the rigidity and the binding force at the outer end of the tread portion 2 are lowered, which adversely affects the suppression of peeling between plies.

The distance Lc in the tire axial direction between the outer end Ae of the first belt ply 7A and the outer end Be of the second belt ply 7B, and the outer end Be and the third belt ply of the second belt ply 7B. For the same reason, the distance Ld in the tire axial direction from the outer end Ce of 7C is also preferably in the range of 3.0 to 8.0 mm, respectively.

Although the particularly preferable embodiments of the present invention have been described in detail above, the present invention is not limited to the illustrated embodiments and can be modified into various embodiments.

A size 315 / 45R22.5 heavy-duty tire having the basic structure shown in FIG. 1 was prototyped based on the specifications shown in Table 1. High-speed durability was tested for each test tire. Except as shown in Table 1, the specifications are substantially the same, and only the structure of the belt layer and the reinforcing ply is different. Comparative Example 1 is a tire corresponding to Patent Document 1, and reinforcing plies are provided on both outer sides of the third belt ply in the tire radial direction and on both outer sides of the fourth belt ply in the tire axial direction. In Comparative Example 2, no reinforcing ply is provided, and only the belt layer of the tread portion is formed.

(1) High-speed durability performance:
Using a drum tester, the speed of the test tire is changed from 80km / h to 10km / h every 120 minutes under the conditions of rim (22.5 x 9.75), internal pressure (900kPa), and load (5000kgf). I ran on the drum while increasing it. Then, the speed at which the outer end of the belt layer was damaged (damage generation speed) was compared. The test results are displayed with the damage occurrence rate in Comparative Example 1 as a reference (0). The case where the damage occurrence speed is 10 km / h higher than the standard is described as "+1", and the case where the damage occurrence speed is 20 km / h higher is described as "+2".

As a result of the test, it was confirmed that the tire of the example had improved high-speed durability performance.

1 Heavy load tire 2 Tread part 7 Belt layer 7A 1st belt ply 7B 2nd belt ply 7C 3rd belt ply 7c Belt cord 20 Reinforcing ply 20c Reinforcing cord Ae, Be, Ce, 20e Outer end α cord angle θ , Θ1, θ2, θ3 Code angle Gs Shoulder main groove

Claims (7)

A heavy-duty tire provided with a belt layer consisting of a plurality of belt plies in which belt cords are arranged at a cord angle of 10 to 50 degrees with respect to the tire circumferential direction in the tread portion.
The plurality of belt plies include a first belt ply arranged on the innermost side in the tire radial direction, a second belt ply arranged on the outer side of the first belt ply in the tire radial direction, and the first belt ply. Including the third belt ply arranged outside the tire radial direction of the second belt ply,
It is sandwiched between the first and third belt plies and extends outward in the tire axial direction to the outside of the second belt ply in the tire axial direction, and the reinforcing cord extends 10 degrees with respect to the tire circumferential direction. Heavy-duty tires with reinforced plies arranged at smaller cord angles. The heavy-duty tire according to claim 1, wherein the outer end of the reinforcing ply in the tire axial direction is located outside the outer end of the first and third belt plies in the tire axial direction. The heavy-duty tire according to claim 1 or 2, wherein the tread portion includes a shoulder main groove continuously extending in the tire circumferential direction, and the reinforcing ply is arranged outside the shoulder main groove in the tire axial direction. .. The outer end of the first belt ply in the tire radial direction, the outer end of the second belt ply in the tire radial direction, the outer end of the third belt ply in the tire radial direction, and the tire of the reinforcing ply. The heavy-duty tire according to any one of claims 1 to 3, wherein the outer end in the radial direction and the position in the tire axial direction are different from each other. The tire axial distance La between the outer end of the first belt ply in the tire radial direction and the outer end of the reinforcing ply in the tire radial direction, and the outer end of the third belt ply in the tire radial direction and the above. The heavy-duty tire according to any one of claims 1 to 4, wherein the tire axial distance Lb between the reinforcing ply and the outer end in the tire radial direction is in the range of 3.0 to 8.0 mm, respectively. .. The cord angles θ2 and θ3 of the second and third belt plies are 10 to 16 degrees, and the cord angles θ1 of the first belt ply are larger than the cord angles θ2 and θ3 and 50 degrees or less. Item 2. The heavy-duty tire according to any one of Items 1 to 5. The heavy-duty tire according to any one of claims 1 to 6, wherein the tire flatness is 60% or less.

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