JP2001150910A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimally restrain an increase of an amount of used rubber, and enhance stability. SOLUTION: Rigidity in the vicinity of a bead part 12 (tire rotating direction) is increased thereby increasing stability in forward/backward direction of the tire since a rubber layer 40 between plies (100% extension modulus is within a range of 2.5 Mpa to 8.0 Mpa and JIS A hardness is 50 to 85 degree) is provided in a parallel part between a main body 20A of a carcass ply 20 and a folded part 20B to thick a gage between plies. When vibration occurs, the rubber layer 40 between plies is deformed by shearing to absorb the vibration, whereby the vibration is easy to stop. As compared with a conventional tire in which an amount of rubber used is increased due to thickening of rubber layer outside a side wall and a carcass inner surface rubber layer, stability is efficiently enhanced by the rubber layer 40 between plies, and increase of the used rubber amount is minimally restrained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire for use in heavy vehicles such as construction vehicles and industrial vehicles. The present invention relates to a pneumatic tire suitable for a heavy-duty vehicle, which has improved performance.

[0002]

2. Description of the Related Art Construction vehicles, especially wheel loaders (tire-type loaders), generally have many opportunities to travel on rough terrain having irregularities, and at that time, rolling (rolling) and pitching (pitching) tend to occur in the vehicle. Therefore, a part of the earth and sand or crushed stone scooped into the bucket is likely to fall on the traveling road surface, or when loading these earth and sand or crushed stone on another heavy vehicle, for example, a dump truck, the loading efficiency of the wheel loader is improved. For this reason, it is usual to stop the vehicle quickly, and at that time, large pitching occurs in addition to rolling, which hinders loading, and sometimes the bucket hits the loading frame of the dump truck, and both may be damaged. .

[0003] Rolling and pitching of industrial vehicles, especially forklifts and the like, may cause the cargo to collapse.

[0004] Therefore, pneumatic tires used in construction vehicles and industrial vehicles are required to have excellent stability that does not cause severe rolling and pitching of the vehicles, that is, high stability performance.

[0005]

The conventional tires used for construction vehicles and industrial vehicles for improving the stability performance are provided with a reinforcing rubber or a reinforcing treat on the inner surface of the carcass ply from the vicinity of the hump to the vicinity of the bead. For example, the entire tire side portion is reinforced to increase the rigidity (increase the longitudinal spring constant), so that the amount of rubber used increases and the cost increases.

The present invention has been made in view of the above circumstances, and has as its object to provide a pneumatic tire capable of minimizing an increase in the amount of rubber used and improving stability.

[0007]

According to a first aspect of the present invention, there is provided at least one carcass ply in which a plurality of cords are arranged side by side and coated with a coating rubber, and one carcass ply is provided from one bead portion to the other bead portion. A carcass straddling in a toroidal form, and a carcass reinforcing layer provided on the tire radial direction outside of the carcass, and at least one of the carcass plies is connected to a main body from one bead part to the other bead part. A pneumatic tire having a folded portion for folding a bead core of the bead portion from the inside to the outside of the tire, the parallel portion having a parallel portion in which the main body portion and the folded portion are arranged substantially parallel to each other, Is the vicinity of the rim separation point of the bead portion at the time when the tire radially inner end is 100% loaded (with respect to the straight line parallel to the tire rotation axis and passing through the rim separation point, In the direction of ± 5 mm.), The outer end in the tire radial direction is located in the buttress area between the tire maximum width portion and the end of the carcass reinforcing layer, and the main body portion in the parallel portion Where d is the inner surface distance between the cord and the folded portion cord, and t is the width of the bead core measured in the tire axial direction, d ≧ 0.35t, and the parallel portion has 100% elongation. Modulus is in the range of 2.5 Mpa to 8.0 Mpa and JIS A
It has a rubber layer having a hardness of 50 to 85 degrees.

Next, the operation of the pneumatic tire according to the first aspect will be described.

The stability performance mainly has two factors of vibration reduction and stability during actual work. Particularly, in the case of a vehicle such as a loader that receives a load in front of a vehicle body, the greater the wobble at the time of loading, the more the driver is. Since the operation becomes difficult, the influence of the vibration reduction on the vehicle performance is great.

Next, a description will be given of the stability in the case of a vehicle mounted on the front area of the vehicle such as a loader.

As an example of the stability in actual work, there is a degree in which the vehicle body swings back and forth greatly when a brake or the like is applied during traveling of a load, and if it is large, the rear wheels float and the work performance is greatly deteriorated.

Further, since an extremely large load is applied to the front wheels, the durability of the front wheels is not preferable.

The stiffness near the bead of the front wheel has a large effect on the stability during actual work. When the stiffness of this portion is high, the stiffness in the tire rotation direction increases, so that the stability in the front-rear direction of the tire increases.

In the pneumatic tire of the present invention, the gauge between plies is made thicker by setting d ≧ 0.35t in the parallel portion.
The rigidity (tire rotation direction) in the vicinity of the bead portion is increased, and when used in a vehicle mounted on the front area of a vehicle body such as a loader, stability in actual work can be improved.

On the other hand, as an example of vibration settling in actual work,
There is a degree of the roll-down in loading operation, and if this is large, the vehicle may fall over. Therefore, the operator needs to wait until the vibration stops to some extent, and the working efficiency deteriorates.

The rubber gauge between the main body portion and the folded portion greatly affects the vibration.

When the tire is loaded, the rubber between the main body and the folded portion causes shear deformation (because the main body and the folded portion are relatively displaced in the radial direction) when the bead portion falls down to the outside of the tire.

When vibration occurs, the tire having a thick rubber gauge between the plies absorbs the vibration due to the shear deformation of the rubber between the plies, so that the vibration can be reduced well.

When the thickness of the outer rubber of the sidewall portion is increased as in a conventional tire, and when a reinforcing rubber layer having a crescent cross section is provided on the inner surface of the carcass, the rigidity of the entire side portion is increased. The outer rubber of the sidewall portion and the reinforcing rubber layer having a crescent-shaped cross section mainly undergo bending deformation, and have little shear deformation as in the present invention. For this reason, in order to improve the vibration reduction, it is necessary to set the outer rubber of the sidewall portion and the reinforcing rubber layer having a crescent-shaped cross section to be considerably thick, so that the amount of rubber used increases and the cost increases. On the other hand, in the present invention, since vibration can be effectively absorbed by the shear deformation of the rubber between the plies, a large vibration absorbing effect can be obtained with a minimum amount of rubber used.

By the way, in a tire having a thin rubber gauge between the plies, the shear rigidity between the plies is increased, so that the shear deformation between the plies becomes difficult, and the vibration control is not so good.

In the pneumatic tire of the present invention, since the rubber gauge between the plies is made thicker by setting d ≧ 0.35t in the parallel portion, vibration can be reduced.

If d <0.35t in the parallel portion, it becomes impossible to improve the vibration convergence.

Further, by disposing a highly rigid rubber layer between the plies, the rigidity near the bead portion can be increased, and the above-mentioned stability can be improved. However, if rubber having too high rigidity is used, vibration absorption due to shear deformation between plies deteriorates.

For this reason, 100% elongation modulus (JI
SK6301) from 2.5 Mpa to 8.0 Mpa
By providing a highly rigid rubber layer having a JIS A hardness (according to JIS K6301) of 50 degrees to 85 degrees in the parallel portion, both stability and vibration reduction can be improved.

When the 100% elongation modulus of the rubber layer is less than 2.5 MPa, the stability cannot be improved. On the other hand, when the 100% elongation modulus of the rubber layer exceeds 8.0 Mpa, it becomes impossible to improve the vibration mitigation.

When the JIS A hardness of the rubber layer is less than 50 degrees, the stability cannot be improved. On the other hand, if the JIS A hardness of the rubber layer exceeds 85 degrees, it becomes impossible to improve the vibration mitigation.

Here, the rim separation point of the bead portion at the time of 100% load is determined by filling the tire mounted on the rim with the internal pressure.
The point is that the outer surface of the bead portion of the tire is separated from the rim (flange) when the load is 00%.

The 100% load is the maximum load (maximum load capacity) of a single wheel in the applicable size (ply rating) described in the following standard, and the internal pressure is described in the following standard. The rim is the air pressure corresponding to the maximum load (maximum load capacity) of a single wheel in the applicable size, and the rim is the standard rim (or “Approved Rim”, “Recommende”) in the applicable size described in the following standards
d Rim ").

The standard is determined by an industrial standard effective in an area where the tire is manufactured or used. For example,
In the United States, "The Tire and Rim Association
Inc.'s Year Book, and in Europe, "European T
Standards Manu of ire and Rim Technical Organization
al "in Japan and the Japan Automobile Tire Association's" JATMA
The Year Book is specified.

According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the end of the folded portion is radially inward and outward with respect to a position where the carcass has a maximum width. Are arranged within a range of 20% of the tire section height.

The term "substantially parallel" as used herein includes up to a portion having a thickness within + 30% of the minimum distance between the main body portion and the folded portion.

Next, the operation of the pneumatic tire according to claim 2 will be described.

[0033] In the pneumatic tire according to the second aspect, the end of the turn-back portion is formed such that the center of the carcass becomes the maximum width portion and the tire cross-section height of the tire cross-section height is 2 inward and outward.
Since it is arranged within the range of 0%, it is strong against overload and durability can be secured.

If the position of the end of the folded portion is not located within 20% of the tire sectional height inside and outside in the tire radial direction around the position of the maximum width of the carcass, the folded portion is not placed. Separation may occur from the end of the part.

According to a third aspect of the present invention, in the pneumatic tire according to the first or second aspect, when the maximum width of the tire is W, t> 0.03 W and t> 20 mm
It is characterized by being.

Next, the operation of the pneumatic tire according to the third aspect will be described.

In the pneumatic tire according to the third aspect, the width t of the bead core is larger than 0.03 W and t> 2.
Since it is 0 mm or more, the bead portion can be securely fixed to the rim, and the bead portion is stabilized.

When the width t of the bead core is not more than 0.03 W, and the actual size is 2 even if it is larger than 0.03 W.
If it is less than 0 mm, the bead cannot be securely fixed to the rim.

According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects,
It is characterized in that 0.45t ≦ d ≦ 0.75t.

Next, the operation of the pneumatic tire according to claim 4 will be described.

In the pneumatic tire according to the fourth aspect, since the rubber gauge between the plies is optimized by setting 0.45t ≦ d ≦ 0.75t in the parallel portion, vibration can be reduced.

When d ≧ 0.75t in the parallel portion, the function and effect of the rubber layer tend to level off, and the amount of rubber used in the rubber layer in the parallel portion increases, resulting in an increase in cost.

[0043]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a pneumatic tire according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, the rim 11 (size: 1)
9.50 "(rim width) /2.00" (flange height) x
25 "(rim diameter) of the pneumatic tire 10 of the present embodiment (tire size: ORR 25 / 65R25)
VKT) has a pair of bead portions (only one side is shown).
A pair of sidewall portions 14 (only one side is shown);
A tread portion 16 is connected to the sidewall portion 14.

The pneumatic tire 10 has a structure in which one bead portion 12 is connected to the other bead portion 12 (only one side is shown in the figure).
And a carcass 18 that straddles in a toroidal shape and reinforces a pair of bead portions 12, a pair of sidewall portions 14, and a tread portion 16.

Although the carcass 18 of the present embodiment is composed of one carcass ply 20, it may be composed of two or more carcass plies 20.

A belt 22 for reinforcing the tread portion 16 is provided on the outer peripheral surface of the carcass 18 in the tire radial direction. The belt 22 is composed of two or more belt plies 24 in this embodiment.

The belt ply 24 of this embodiment is formed by coating a plurality of parallelly arranged steel cords with rubber, and is laminated such that the cords intersect with each other between the plies.

On the inner peripheral surface of the carcass 18, an inner surface reinforcing rubber layer 26 is provided at a portion substantially opposed to the sidewall portion 14. In addition, one bead portion 1 is provided on the innermost surface of the tire.
A thin inner liner 28 (see FIG. 2) that is continuous from 2 to the other bead portion 12 is provided.

The inner surface reinforcing rubber layer 26 has a maximum width 3 of the tire.
The gauge near 0 is set to the largest, and the gauge gradually decreases outward (in the direction of arrow A) and inward (in the direction of arrow B) in the tire radial direction.

With reference to a tire rotation axis (not shown),
The position of the inner end in the tire radial direction of the inner surface reinforcing rubber layer 26 is substantially the same as the position in the tire radial direction of the rim separation point 32 of the bead portion 12 under load.

The outer end of the inner reinforcing rubber layer 26 in the tire radial direction is located near the end of the belt 22.

The inner reinforcing rubber layer 26 has a 100% elongation modulus of 2.0 Mpa and a JIS A hardness of 50 to 65 degrees.
Degree, and as shown in FIG.
And the gauge a measured on a straight line L parallel to the tire rotation axis is 13 mm.

As shown in FIG. 1, the vicinity of the end of the carcass ply 20 is folded back from the inside of the tire to the outside of the bead core 34 embedded in the bead portion 12. Hereinafter, one bead core 34 of the carcass ply 20 will be described.
Is connected to the other bead core 34 from the main body 20.
A, a portion that is folded outward from the bead core 34 and extends outward in the tire radial direction is referred to as a folded portion 20B.

Outside the bead core 34 in the tire radial direction, a stiffener 36 having an elongated triangular cross section is provided between the main body 20A and the folded portion 20B to secure the rigidity of the bead portion 12.

The folded portion 20B from the vicinity of the radially outer end of the stiffener 36 in the tire radial direction (in the present embodiment, slightly inward of the radially outer end of the stiffener 36 in the tire radial direction) is the carcass ply 2
0 are arranged in parallel along the main body 20A.

As shown in FIGS. 1 and 2, the main body 20A
A rubber layer 40 between plies is provided between the main body 20A and the folded portion 20B in a parallel portion where the and the folded portion 20B are arranged in parallel.

The rubber layer 40 between plies needs to have a 100% elongation modulus in the range of 2.5 Mpa to 8.0 Mpa and a JIS A hardness of 50 to 85 degrees.

The inter-ply rubber layer 40 of the present embodiment
The 0% elongation modulus is 2.0 MPa and the JIS A hardness is 55 degrees.

Further, the inner surface distance between the cord 42 of the main body 20A and the cord 42 of the folded portion 20B is d, and the width t of the bead core 34 measured in the tire axial direction (the direction of the arrow OUT and the direction of the arrow IN) (see FIG. 1). ), D ≧
It is necessary to satisfy the relationship of 0.35t.

In this embodiment, the code 4 of the main body 20A is used.
2 and the inner surface distance d between the cord 42 of the turn-back portion 20B is 7.5.
mm, the width t of the bead core 34 measured in the tire axial direction is 2
5 mm, and d / t = 0.600.

The parallel portion where the main body portion 20A and the folded portion 20B are arranged in parallel is the rim separation point 32 of the bead portion 12 when its radially inner end is 100% loaded.
And the tire radially outer end (in the present embodiment, the end portion 20B of the folded portion 20B).
C) is located in the curved buttress area between the tire maximum width 30 and the end of the belt 22.

The end portion 20C of the folded portion 20B is connected to the carcass 1
It is preferable that they are arranged within a range of 20% of the tire cross-sectional height D inside and outside the tire in the tire radial direction around the position where the maximum width portion 30 of FIG.

The end portion 20C of the folded portion 20B has the maximum width 3
With reference to 0, it is arranged at a position of 2% of the tire sectional height D (in the present embodiment, at a position of 10 mm from the maximum width portion 30) outside in the tire radial direction.

Further, when the maximum width of the tire is W, the pneumatic tire 10 has t> 0.03 W and t> 20 mm.
Is preferably satisfied. Note that 0.45t ≦ d ≦
More preferably, it is 0.75 t.

In this embodiment, the maximum tire width W is 640.
mm, and t / W = 0.039.

Further, the pneumatic tire 10 of the present embodiment
As shown in FIG. 3, a wire chafer 44 in which a plurality of steel cords are arranged in a ply shape on the outer peripheral surface of the carcass ply 20 near the bead core 34, and a first ply-shaped wire chafer in which a plurality of nylon cords are arranged. Nylon chafer 46 and second nylon chafer 4
8 are arranged for reinforcement.

Next, the operation of the pneumatic tire 10 of the present embodiment will be described.

The operation and effect when the pneumatic tire 10 of this embodiment is used, for example, in a loader will be described.

As an example of stability in actual work, there is a degree that the body of the loader swings back and forth greatly when a brake or the like is applied during traveling of a load, and when this is large, the rear wheels float and the work performance is greatly deteriorated. . Further, since an extremely large load is applied to the front wheels, the durability of the front wheels is not preferable.

In the pneumatic tire 10 of the present embodiment, the inter-ply rubber layer 40 is provided in a parallel portion of the carcass ply 20 with the main body portion 20A and the folded portion 20B to increase the thickness of the inter-ply gauge. The rigidity (tire rotation direction) increases, and the stability in the tire front-back direction increases.

On the other hand, as an example of vibration settling during actual work,
There is a degree of roll-slack during the loading operation, and if it is large, the loader may fall over, so the operator needs to wait until the vibration stops to some extent, and the working efficiency deteriorates.

In the pneumatic tire 10 of the present embodiment, as described above, the inter-ply rubber layer 40 is provided in the parallel portion of the carcass ply 20 with the main body portion 20A and the folded portion 20B to increase the thickness of the inter-ply gauge. 1 of rubber layer 40 between plies
Since the rigidity of the inter-ply rubber layer 40 was optimized by setting the 00% elongation modulus to 3.0 Mpa and the JIS A hardness to 60 degrees, when vibration occurred, the shear deformation of the inter-ply rubber layer 40 between the plies (see FIG. 3). The shear direction is the main body 20A.
And the radial direction of the folded portion 20B. For example, when the bead portion 12 falls down in the direction of arrow C, the rubber layer 40 between plies before the fall (note the rectangular portion) is sheared and deformed into a parallelogram by the fall. ) Absorbs the vibration and improves the vibration mitigation.

If d <0.35t in the parallel portion, it becomes impossible to improve the vibration mitigation.

If the 100% elongation modulus of the inter-ply rubber layer 40 is less than 2.5 MPa, the stability cannot be improved. On the other hand, if the 100% elongation modulus of the inter-ply rubber layer 40 exceeds 8.0 Mpa, it becomes impossible to improve the vibration mitigation.

If the JIS A hardness of the inter-ply rubber layer 40 is less than 50 degrees, the stability cannot be improved. On the other hand, if the JIS A hardness of the inter-ply rubber layer 40 exceeds 85 degrees, it becomes impossible to improve the vibration mitigation.

Further, the folded portion 20 of the carcass ply 20
The end 20C of B is centered on the maximum width portion 30 of the carcass,
Tire section height D of 20 inside and outside in the tire radial direction
%, The durability can be ensured. When the end 20C is arranged outside this range,
There is a possibility that separation occurs from the end 20C.

The width t of the bead core 34 is set to 0.03 W
And the width t> 20 mm or more of the bead core 34, the bead portion 12 can be securely fixed to the rim 11, and the bead portion 12 is stabilized.

The width t of the bead core 34 is 0.03 W
In the following cases, or when the actual size is larger than 0.03 W and the actual size is 20 mm or less, the bead portion 12 cannot be securely fixed to the rim 11. (Test Example) In order to confirm the effect of the present invention, a total of three types of tires, two types of tires of the example to which the present invention is applied and one type of tire of the comparative example, were prepared, mounted on an actual vehicle, and rocked back and forth ( Pitching) and rolling (rolling) were compared.

First, each test tire was mounted on a rim (size: 1).
9.50 ″ /2.00 ″ × 25 ″), and filled with the maximum air pressure of 500 kpa, which was mounted on four wheels of a wheel loader having a vehicle weight of 15 tons and a bucket capacity of 2.5 m ³ .

The method of the swing test will be described below. As shown in FIG. 4, the bucket 54 of the wheel loader 50 is fully loaded with sand 54 and lifted to the highest position. The hydraulic pressure of the hydraulic cylinder that moves the bucket 52 of the wheel loader 50 is released at once, and the bucket 52 is lowered rapidly. This causes the wheel loader 50 to swing back and forth. Therefore, the forward and backward swing is recorded by an accelerometer installed inside the wheel loader 50.

The evaluation is represented by an index with the magnitude (maximum value) of the forward-backward swing when the tire of the comparative example is mounted being 100, and the smaller the index is, the smaller the forward-backward swing is.

The sway test method will be described below. As shown in FIG. 4, the bucket 52 of the wheel loader 50 is fully loaded with sand 54 and lifted to the highest position. Turn the handle of the wheel loader 50 to the right or left as far as it will go. Slightly advance the wheel loader 50 to apply the brake (brake after moving about 2 to 3 km / h, 30 cm). Since the wheel loader 50 rolls due to the braking, the vibration is recorded by an accelerometer.

The evaluation is represented by an index with the rolling convergence time when the tire of the comparative example is mounted as 100, and the smaller the index is, the shorter the time in which the rolling can be settled.

[0085]

[Table 1]

As a result of the test, it can be seen that the tires of Example 1 and Example 2 to which the present invention is applied are less swaying in the front-rear direction and excellent in the swaying in comparison with the comparative example tires.

[0087]

As described above, the pneumatic tire according to the first aspect has the above-described structure, so that an increase in the amount of rubber used can be minimized and stability can be improved. Has excellent effects.

The pneumatic tire according to claim 2 has the above-described configuration, and thus has an excellent effect that durability can be ensured.

[0089] The pneumatic tire according to claim 3 has the above-described structure, so that the bead portion can be stabilized.
It has an excellent effect.

Since the pneumatic tire according to the fourth aspect has the above-described configuration, it has an excellent effect that vibration reduction can be improved while reducing the amount of rubber used in the rubber layer.

[Brief description of the drawings]

FIG. 1 is a sectional view of a pneumatic tire according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view of the vicinity of a tire maximum width portion of the pneumatic tire according to one embodiment of the present invention.

FIG. 3 is a sectional view of a bead portion of the pneumatic tire according to one embodiment of the present invention.

FIG. 4 is an explanatory view illustrating a test method of a lateral swing settling test and a longitudinal swing test method of a wheel loader.

[Explanation of symbols]

 REFERENCE SIGNS LIST 10 pneumatic tire 12 bead portion 18 carcass 20 carcass ply 22 belt (carcass reinforcing layer) 20A main body portion 20B folded portion 20C end portion (of folded portion 20B) 30 tire maximum width portion 32 rim separation point 34 bead core 40 rubber layer 42 code

Claims (4)

[Claims] 1. A carcass having at least one carcass ply in which a plurality of cords are arranged and covered with a coating rubber, and extending from one bead portion to the other bead portion in a toroidal manner; and a tire of the carcass A carcass reinforcing layer provided radially outward, wherein at least one of the carcass plies is folded back from the inside of the tire to the outside of the bead core of the bead portion and a main body portion connected from one bead portion to the other bead portion. A pneumatic tire having a portion, wherein the main body portion and the folded portion have a parallel portion arranged substantially in parallel, wherein the parallel portion has a tire radially inner end when 100% load is applied. The bead portion is located near the rim separation point, and the tire radially outer end is located within the buttress region between the tire maximum width portion and the end of the carcass reinforcing layer. When the inner surface distance between the cord of the main body portion and the cord of the folded portion in the parallel portion is d, and the width of the bead core measured in the tire axial direction is t, d ≧ 0.35t, Within the parallel portion, the 100% elongation modulus is 2.5
A pneumatic tire having a rubber layer having a range of Mpa to 8.0 Mpa and a JIS A hardness of 50 to 85 degrees. 2. The end of the turn-back portion is arranged inside and outside in the tire radial direction within a range of 20% of the tire cross-section height around a position that is a maximum width portion of the carcass. The pneumatic tire according to claim 1, wherein: 3. When the maximum width of the tire is W, t>
The pneumatic tire according to claim 1 or 2, wherein 0.03 W and t> 20 mm. 4. The pneumatic tire according to claim 1, wherein 0.45t ≦ d ≦ 0.75t.