JP3074400B2 - Pneumatic bias tire for construction vehicles - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic bias tire for construction vehicles, and more particularly to a pneumatic tire used for a wheel loader mainly for loading, which has a small side cut and a tire. The present invention relates to a tire having good stability against rolling and the like while maintaining light weight.

[0002]

2. Description of the Related Art Pneumatic tires for construction vehicles operating on rough ground such as civil engineering sites and quarries are known as:
Stumps and rock masses rub the side of the tire,
Alternatively, cuts and cracks often occur due to sticking into the side portions. Therefore, in the case of a vehicle tire used for this type of work, an annular protector projecting outward in the width direction of the tire is provided slightly inward in the rotation axis direction from the shoulder portion to protect the side portion. It is generally formed beforehand (Japanese Patent Publication No. 61-1768).
No. 1). Such an annular protector is intended to minimize the cutting and cracking of the side portion of the tire due to contact with a rock mass or the like, and to protect the side portion of the tire by splashing them.

However, in recent years, reduction in weight of tires has been required for energy saving measures, and pneumatic tires for construction vehicles are no exception. In order to reduce the weight, there is a tendency that the entire tire is made thinner. When viewed from the tire side, the shape change of the annular protector is one of the objects. However,
On the other hand, a protector shape that allows the annular protector to be clearly identified is desired from the user's evaluation of the appearance of the tire.

[0004] The inventors of the present invention have been diligently studying to meet the above-mentioned demands, and have taken measures to reduce the weight of the tire by reducing the thickness of the entire structure, and to provide a conventional pneumatic vehicle with a conventional annular protector. It has been found that there is an unprecedented problem with tires containing tires. For example, in the case of a loader with a bucket, it has been found that, at the time of a tapping load, the rolling of the vehicle body, particularly the bucket portion, becomes large and the accommodation becomes poor. After investigating the cause, it was found that a kind of buckling-like phenomenon appeared near the confluence of the surface of the buttress portion of the tire and the surface of the annular protector when the bucket was tilted to the maximum. did. That is, the width of the tread portion is particularly wide in the tire for the loader in order to improve the wear resistance as a whole and to prevent the rock from being caught or cut, and the tread width is about 85 to 95% of the maximum tire width ratio. It has become.

[0005] For this reason, the side surface of the tire from the shoulder portion to the beat portion, that is, the buttress portion has a shape that is almost vertical. In this tire shape, while reducing the thickness of the entire tire and forming an annular protector radially inward of the buttress portion, constriction occurs at the intersection of the buttress portion and the annular protector portion,
Therefore, when a large eccentric load is applied to one side of the tread portion of the tire at the time of tapping of a loader with a bucket or the like, compressive strain is intensively applied to the constricted portion, thereby causing a buckling phenomenon. Was found to occur.

[0006]

SUMMARY OF THE INVENTION The present invention addresses the need for a lighter tire by providing an annular protector that is clearly identifiable in appearance, and furthermore, this constriction of an annular protector that is clearly identifiable in appearance. It is an object of the present invention to provide a pneumatic bias tire for a construction vehicle which does not cause a buckling phenomenon of a bent portion. That is, it is an object of the present invention to achieve the same rolling size as a tire before weight reduction or an OR tire having no side annular protector, and to obtain the same rolling convergence characteristics.

[0007]

In order to solve the above problems, the present invention employs the following characteristic tire structure. That is, the gist of the present invention is to provide a bias carcass ply of at least four plies made of an organic fiber cord, a tread having a lug groove outside the carcass ply, and a side wall having an annular protector projecting outward from the tire. In a pneumatic tire provided with a tire, a line AC extending radially inward from the tread end A and a line BC extending radially outward from the vertex B of the protector in the tire in a meridional section of the tire. Intersect at point C, the line AC
And BC are approximated by a straight line, and the total thickness of the normal from the points A, B and C to the inner surface of the carcass is T _A ,
Assuming that T _B and T _C , 2.2 ≦ T _A / T _C ≦ 3.0,
A pneumatic bias tire for construction vehicles, satisfying 1.0 ≦ T _B / T _C ≦ 1.2, preferably a straight line X passing through an intersection C perpendicular to a tire rotation axis from a point B. Assuming that the vertical distance to −X is h ₁ , the vertical distance from the point B to the line YY passing through the point A and parallel to the rotation axis is h ₂ , and the tire section height is SH, 0.02 ≦ h ₁ / SH ≦ 0.
03, 0.06 ≦ h ₁ / h ₂ ≦ 0.15,
In addition, assuming that the inclination angle in the tire where the line BC and the straight line XX intersect is α, the tire satisfies 20 degrees ≦ α ≦ 35 degrees. In particular, the bottom of the lug groove is open to the buttress portion. It is preferable that the point is located radially outward from the intersection point C.

[0008]

FIG. 1 is a cross-sectional view of a tire according to the present invention, in which 1 is a tread portion, 2 is a lug groove formed diagonally and tapered on the tread portion 1 from both sides toward the center, and 3 is a tread portion. The lug is divided by the lug groove 2. The side surface of the tire continues from the end of the tread portion 1 to the buttress portion 4, the side wall portion 5, and the bead portion 6.
An annular protector 7 having a trapezoidal or triangular cross-section is formed between the side wall portions 5 and 5. In the figure, reference numeral 8 denotes a carcass portion. And a buttress portion 4 extending from the end A of the tread portion 1 in the tire radial direction, and an annular protector 7.
A point of intersection with a line extending from the vertex B radially outward to the inward direction of the tire is denoted by C. Note that the intersection C may have a slightly curved surface.

For example, when the loader lifts a bucket and travels on an uneven road surface, the vehicle body rolls left and right, and a large unbalanced load acts near the end A of the tread portion 1. As described above, in the conventional loading tire, the width of the tread portion 1 is made as large as possible, so that the buttress portion 4 is formed substantially at right angles to the surface of the tread portion 1. . For this reason, due to the large uneven load generated at the end A of the tread portion 1, the buttress portion 4 has a small bending component projecting outward from the tire, while a large radial compression component substantially perpendicular to the road surface is added. As a result, a buckling phenomenon occurs at the intersection C between the buttress portion 4 and the annular protector 7.

According to the present invention, by specifying the positional relationship between the buttress portion 4 and the inner surface of the carcass of the annular protector 7, the occurrence of a buckling-like phenomenon is less likely to occur without compromising the demand for reducing the weight of the tire. It is particularly preferable that the remarkable effect is brought about by further specifying the positional relationship between the two. That is, when a large eccentric load is applied to the end A of the tread portion 1, the distribution of the bending component from the end A across the intersection C where a buckling phenomenon occurs to the vertex B of the annular protector 7 is made as uniform as possible. In particular, the bending rigidity step (drop) near the intersection C is reduced and the absolute value is increased. Therefore, the gage between the carcass inner surface near the intersection C is increased, and conversely, the gage between the point A and the carcass inner surface and the point B and the carcass inner surface is slightly reduced, so that the buckling occurs. This phenomenon is unlikely to occur.

In the present invention, the thickness of the tread portion 1 from the end A to the inner surface of the carcass with respect to the normal is T _A , and similarly, the point C
If the thickness from point B is T _C and the thickness from point B is T _B , T
The ratio of _A to T _C is within 2.2 to 3.0, and T _B and T _C
Is within 1.0 to 1.2, the compressive strain in the radial direction near the intersection C is greatly reduced, and the thicknesses of T _A and T _B are reduced, and the thickness of T _C is reduced. , The distribution of bending stiffness from point A to point B is made more uniform, making it difficult to cause a buckling phenomenon, and as a result, the weight of the tire can be reduced. It is. More, the distribution of bending composite value of the cross-section leading to T _B section from T _A portion becomes the minimum at T _C section sequentially decreases from T _A unit ,,
Is intended to suppress the occurrence of the seat屈状phenomenon be kept to a degree that almost the same or slightly increases further towards the T _B unit.

In particular, the ratio of T _A to T _B is set to 2.1 to 2.
A value of 6 is particularly effective because the bending component can be made uniform. Here, if the value of the ratio is less than 2.1, the buckling phenomenon at the intersection C is suppressed, but the desired T _A
If the value of T _C becomes large, the weight reduction of the tire, which is one of the problems, cannot be achieved.
If it is attempted to obtain T _C that can reduce the weight of the tire, T _A becomes too small, resulting in a remarkable decrease in the wear life, which is a basic characteristic of the tire, which is a problem. On the other hand, if the value of the ratio exceeds 3.0, it becomes difficult to absorb the load due to the outward bending of the tire, and especially at the time of overload or when a large uneven load is applied, the intersection C Compressive strain tends to concentrate, causing a buckling phenomenon, which is below the allowable level in terms of the size of the rolling and the resilience and convergence.

[0013] Next, cyclic protector if the ratio of T _B and T _C of less than 1.0 - not only becomes insufficient resistance to side cut of, appearance also User - The - to give confidence When this value exceeds 1.2, the distance between point B and point C is shorter than the distance between point A and point C, so that the gradient of the bending composite change becomes too large. Failure will be caused.

Tire size 26.5-25 20PR
(Nylon code 1890 denier / 2 14 ply)
The bending stiffness value of each OR tire was determined by FEM analysis. The results are shown in Table 1, and it was found that the bending stiffness value was improved by greatly reducing T _A and T _B and slightly increasing T _C with respect to the conventional OR tire. That, 13 mm at T _A portion, at T _B of 8mm gate -
In this case, the thickness is reduced by 4 mm in the _TC portion while the thickness is reduced. The gage-up at the _TC portion is such that the same rubber as the carcass is inserted outside the fifth to eighth plies at the center of the carcass.

On the other hand, the buttress portion 4, the annular protector
7, a straight line passing through the intersection C perpendicular to the rotation axis of the tire is XX.
And then, the straight line X-X and an inclination angle of the inner tire radial direction of the line BC alpha respect, h ₁ the distance to the straight line X-X from the apex B of the annular protector -7, through rotation of the point A from the apex B Assuming that the vertical distance to the line Y-Y parallel to the axis is h ₂ , and the tire section height is SH, α is 20 degrees or more and 35 degrees or less, and the ratio of h ₁ to h ₂ is 0.06 or more, Tires satisfying the condition of 0.15 or less, the ratio of h ₁ to SH is 0.02 or more and 0.03 or less, and the ratio of h ₂ to SH is 0.2 or more and 0.35 or less are effective. Is remarkable. Inclination angle α
When the angle is less than 20 degrees, the appearance of the annular protector is impaired, while the function of the protector becomes insufficient.
On the other hand, if it exceeds 35 degrees, it is not possible to prevent the buckling at the point C while maintaining the weight reduction. Also, the height h of the annular protector
₁ should be determined from the appearance, the resistance to side cuts and the stability of rolling, and in this regard, it is appropriate to use the section height SH as a reference. That is, when h ₁ / SH is less than 0.02, a problem does not easily occur in terms of rolling stability, but the appearance is poor and the side cut resistance is insufficient. If it exceeds, the latter becomes good, but causes a problem in rolling stability. On the other hand, the annular protector when the ratio between h ₂ and SH exceeds 0.2 and less than 0.35 - the position becomes unsuitable on preventing side cut.

On the other hand, in order to ensure the stability without causing the above-mentioned buckling-like phenomenon, and to improve the appearance, the tread width should be as large as possible. 0.82 to 0.9 as the ratio to the width SW
1, the difference h _{0 in} the tire radial direction between the center of the tread portion 1 and the end A of the tread portion 1 should be large in terms of tire stability.
From a practical point of view, taking into account the wear life, the tire section height S
The ratio with H is preferably in the range of 0.07 to 0.13. The position where the bottom of the lug groove 2 is opened to the buttress portion 4, there should be in the tire radial direction outwardly h ₃ than the intersection point C, which could be prompting the phenomenon of the seat屈状there inwardly Is not preferred.

[0017]

EXAMPLES Taking the above conditions into consideration, test tires were prepared and tested as follows. Tire size 26.5-25 20PR, OR tire Tire structure On the tread portion, a pattern is formed in which lug grooves are arranged in two rows in the tire circumferential direction, and the carcass is made of nylon cord. (1890 denier / 2) ply 1
Four sheets were used. The bead is a triple bead ((4)-
(4)-(4) -2) was adopted.

The tire dimensions were as follows.

[0019] Such a tire has a good appearance of the annular protector, but is expected to cause a problem in rolling stability. The tire weight is close to the target value but is still slightly heavy.

[0020] This tire does not have an annular protector and is expected to have good rolling stability. However, it can be expected that the wear life is poor and the side cut resistance is inferior due to the absence of the annular protector. Also, the weight of the tire is heavy.

(Experiment) Measurement results, indoor test results, and actual vehicle data for the above-described embodiment, conventional tires and comparative tires
The ring test results are shown in Tables 1 and 2. All the test conditions were a normal internal pressure of 3.5 kgf / cm ² , and the load was 160% (20.3 tons / piece) of the normal load, and the test was performed with a large load applied. The amount of vertical deflection and static spring constant are taken as data supporting the actual vehicle filling test using a normal indoor static load tester, and are all indexed with the conventional tire as 100. The former is better when the numerical value is smaller, and the latter is better when the numerical value is larger. Incidentally, the weight of the conventional tire was similarly set to 100
Displayed as

Next, in the filling test of the actual vehicle (loader), when the loader bucket is raised and the bucket is lowered left and right, the size of the rolling of the vehicle body and the resilience and convergence. The sex was evaluated on a five-point scale by filling the operator. This actual vehicle filling test has an evaluation value of 3.5.
The above is the allowable range as a real vehicle.

[0023]

[Table 1]

[0024]

[Table 2]

From these results, it can be seen that in the tire having the shape of the present invention, the effect of improving the rolling stability while securing the side cut resistance and the weight reduction is remarkable.

[0026]

As described above, the present invention restricts the respective components of the tire as described above, and by organically combining these components, secures anti-sidecut performance and adapts to the demands of the age of lighter tires. In addition, a stable tire can be provided, and its industrial contribution is significant.

[Brief description of the drawings]

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

[Explanation of symbols]

1 tread part 2 lug groove 3 lug 4 buttress part 5 side wall part 6 bead part 7 annular protector 8 carcass part A tread part end B ‥‥ annular protector - vertex C ‥‥ buttress portion and the annular protector radially outward of - the intersection alpha ‥‥ linear X-X tilt angle of the tire radially inward of the line BC for h ₁ ‥‥ annular protector - from the apex B of the distance h ₃ ‥‥ lug groove from the distance h ₂ ‥‥ apex B to the straight line X-X to the straight line Y-Y bottom from the intersection C of position to open the buttress portion of Distance SH {Tire cross-section height Straight line XX} Straight line perpendicular to tire rotation axis and passing through intersection C Straight line YY {Line parallel to tire rotation axis and passing point A T _A } Point A Karaka - in the normal direction to Kas inner surface thickness T _B ‥‥ point B karaka - to Kas inner surface Linear direction of thickness T _C ‥‥ point C karaka - in the normal direction thickness of the Kas inner surface

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B60C 11/00-13/02

Claims (3)

(57) [Claims] 1. A bias carcass ply comprising at least four plies comprising an organic fiber cord, a tread having a lug groove outside the carcass ply, and a side wall having an annular protector projecting outward from the tire. In a pneumatic tire provided with a tire, a line C extending radially inward from the tread end A and a line BC extending radially inward from the vertex B of the protector toward the tire in the meridional section of the tire are point C. And the lines AC and BC are approximated by a straight line, and the total thickness of the normals from the points A, B, and C to the inner surface of the carcass is T _A , T _B , and T _C , respectively. _{, 2.2 ≦ T a / T C} ≦ 3.0, 1.0 ≦ T B / T C ≦ 1.2 construction vehicle pneumatic bias tire, characterized by satisfying the. 2. The vertical distance from point B to a line XX perpendicular to the tire rotation axis and passing through intersection C is h ₁ , and the vertical distance from point B to line YY passing through point A and parallel to the rotation axis. Where h ₂ is the height of the tire and SH is the height of the cross section of the tire, SH2 satisfies 0.02 ≦ h ₁ /SH≦0.03, 0.06 ≦ h ₁ / h ₂ ≦ 0.15, and the line BC and the line The pneumatic bias tire for construction vehicles according to claim 1, wherein the inclination angle inside the tire at which -X intersects is α: 20 ° ≦ α ≦ 35 °. 3. The pneumatic bias tire for a construction vehicle according to claim 1, wherein a bottom portion of the lug groove is radially outward from an intersection C that opens to the buttress portion.