JPH04345502A - Pneumatic bias tire for construction vehicle - Google Patents

Abstract

PURPOSE:To provide a tire suitable for a construction vehicle such as a wheel loader, restrain the occurrence of buckling without any harm to the lightweight design of the tire, and improve the durability thereof by specifying a positional relationship between the buttresses section and tubular protector of the tire. CONSTITUTION:In a pneumatic tire having a tread section 1 and a side wall section 5 with a tubular protector 7 at the outside of an organic fiber cord bias carcass comprising four or more plies, a line AC drawn from a tread end A to a radial inner direction, and another line BC drawn from the apex B of the protector 7 in a radial outer direction to a tire inner direction are caused to intersect each other at a point C. In addition, the inclination angle of the line AC with a vertical line X-Y passing the point C is taken at beta in a radial outer direction, and the inclination angle of the line BC in a radial inner direction is taken at alpha respectively. In this case, relationships are so established as to satisfy beta>=6 degrees, 20 degrees >=alpha>=35 degrees and 0.27<=beta<=0.45. In addition, relationships are so established as to satisfy of 0.06<=h1/h2<=0.15 and 0.02<=h1/SH<=0.03.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention is a pneumatic bias tire for construction vehicles, particularly a pneumatic tire used for wheel loaders mainly used for loading. This invention relates to a tire that maintains a light weight and has good stability against rolling, etc.

0002

[Prior Art] Pneumatic tires for construction vehicles operating on rough ground such as civil engineering sites and quarries are
If a stump or a chunk of rock rubs the side of the tire,
Or, it often pierces this side part, causing cuts and cracks. Therefore, in order to protect the side parts of tires for vehicles used in this type of work, an annular protector that protrudes outward in the width direction of the tire is installed slightly inside the shoulder part in the direction of the rotational axis. It is common to form the
No. 1). Such an annular protector is intended to minimize cuts and cracks on the side portion of the tire due to contact with rock lumps, etc., and to protect the side portion of the tire by scattering these. However, in recent years, there has been a demand for lighter tires in order to save energy, and pneumatic tires for construction vehicles are no exception. In order to reduce weight, there is a trend to make the entire tire thinner, and from the tire side, one of the targets is changing the shape of the annular protector. 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 tire's appearance.

[0003] The present inventors, while conducting intensive research to meet the above-mentioned requirements, developed an air compressor for construction vehicles, which reduced the overall tire structure by making it thinner and lighter in weight, and formed a conventional annular protector thereon. It has become clear that there are new problems with tires that have never been seen before. For example, in the case of a loader with a bucket, it has been found that during tapping loading, the rolling of the vehicle body, especially the bucket portion, increases and at the same time, the loader becomes difficult to fit. When the cause of this was investigated, it was found that when the bucket tilted to its maximum, a type of buckling phenomenon appeared near the confluence of the surface of the tire buttress and the aforementioned annular protector. did. That is, especially for loader tires, the width of the tread portion is made wide in order to improve the overall wear resistance and prevent rocks from getting stuck, i.e., cut, and the tread width accounts for about 85 to 95% of the maximum width of the tire. It becomes. For this reason, the side surface of the tire from the shoulder portion toward the beat portion, that is, the buttress portion, has a substantially vertical shape. With this tire shape, if the entire tire is thinned and an annular protector is formed radially inside the buttress, a constriction will occur at the intersection of the buttress and the annular protector. When a large unbalanced load is applied to one side of the tread of a tire during tipping, such as with a loader with a bucket, compressive strain is concentrated on this constricted part, resulting in a buckling phenomenon. It was found that this occurs.

0004

SUMMARY OF THE INVENTION The present invention addresses the need to reduce the weight of tires by attaching an annular protector that is clearly distinguishable from the outside. It is an object of the present invention to provide a pneumatic bias tire for construction vehicles that does not cause partial buckling phenomena. In other words, the tire has the same low weight as a tire before weight reduction or an OR tire without side annular protectors.
The problem to be solved is to reduce the size of the ring and obtain equivalent rolling convergence characteristics.

[0005]

[Means for Solving the Problems] 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 or more plies made of organic fiber cord, a tread having lug grooves on the outside of the carcass ply,
In a pneumatic tire equipped with a sidewall having an annular protector projecting outward from the tire, when viewed from the meridional section of the tire, ■ a line AC pointing radially inward from the tread edge A and a radial direction of the protector. A line BC extending from the outer vertex B toward the inside of the tire intersects at point C, and the lines AC and BC are approximated by a straight line. Let β be the radially outward inclination angle of line BC, and α be the radially inward inclination angle of line BC, then β≧6 degrees, 20 degrees≦α≦35 degrees, and
0.27≦β/α≦0.45, ■ Tire cross-sectional height is SH, distance from vertex B to straight line XX is h1,
The distance from vertex B to point A measured parallel to straight line XX is h
2, 0.06≦h1 /h2 ≦0.15, and 0.02
≦h1 /SH≦0.03 The pneumatic bias tire for construction vehicles is characterized in that the position where the bottom of the lug groove opens to the buttress portion is located radially outward from the intersection C. This is a pneumatic bias tire for vehicles.

[0006]

[Function] Fig. 1 is a sectional view of the tire of the present invention, in which 1 is a tread portion, 2 is a lug groove formed in this tread portion 1 from both sides toward the center obliquely and taperingly, and 3 is a lug groove formed in this tread portion 1 from both sides toward the center. These lugs are divided by lug grooves 2. The side surface of the tire continues from the end of the tread portion 1 to a buttress portion 4, a sidewall portion 5, and a bead portion 6.
An annular protector 7 having a trapezoidal or triangular cross section is formed between the sidewall portion 5 and the sidewall portion 5. 8 in the figure is a carcass part. C is the intersection point between the buttress portion 4 extending radially inward from the end A of the tread portion 1 and a line extending inward from the radially outer apex B of the annular protector 7. Note that a somewhat curved surface may be formed at this intersection C portion.

For example, when the loader bucket is lifted and the vehicle is driven on an uneven road surface, the vehicle body rolls left and right, and a large unbalanced load acts on the vicinity of the end A of the tread portion 1. As mentioned above, in conventional loader tires, the buttress portion 4 is formed nearly perpendicular to the surface of the tread portion 1 in order to make the width of the tread portion 1 as wide as possible. . Therefore, due to the large unbalanced load generated at the end A of the tread portion 1, the buttress portion 4 has a small bending component protruding outward from the tire, while a large radial compression component almost perpendicular to the road surface is applied to the buttress portion 4. As a result, a buckling phenomenon occurs at the intersection C between the buttress portion 4 and the annular protector 7.

[0008] The present invention specifies the positional relationship between the buttress portion 4 and the annular protector 7, thereby making it difficult for the buckling phenomenon to occur without compromising the demand for reducing the weight of the tire. That is, by minimizing the change in bending rigidity from the buttress portion 4 to the annular protector 7, when a large unbalanced load is applied to the end portion A of the tread portion 1, the intersection point C that causes a buckling phenomenon can be avoided. By increasing the bending component from the sandwiched end A to the apex B of the annular protector 7 and adding a large tensile strain component, concentrated radial compressive strain near the intersection C is reduced. This is because the inside of the tire is a carcass that is originally subjected to tensile force, so increasing the tensile strain inside the tire due to bending makes it difficult for buckling to occur. More specifically, the present invention further improves the bending rigidity by allocating a portion of the rubber obtained by reducing the weight of other parts near the intersection C and distributing it. This leads to improved vehicle stability.

In the present invention, first, regarding the inclination angle at the intersection C of the buttress portion 4 and the annular protector 7, a straight line perpendicular to the axis of rotation of the tire and passing through the intersection C is
-X, and the inclination angle β of the line AC outward in the tire radial direction with respect to the straight line XX is 6 degrees or more, preferably 10 degrees.
The inclination angle α of the line BC in the radial direction of the tire is 20 degrees or more and 35 degrees or less, and the ratio of the inclination angle β to the inclination angle α is in the range of 0.27 or more and 0.45 or less. It is optimal that

[0010] If the inclination angle β is less than 6 degrees, if the unbalanced load is large, buckling will occur at point C or the weight of the tire will increase, causing problems; if it exceeds 10 degrees, the tread width will become too narrow, causing rock formation. There is a risk that it may become easier to bite. On the other hand, if the inclination angle α is less than 20 degrees, the appearance of the annular protector will be impaired and the function of the protector will be insufficient. Moreover, if this angle exceeds 35 degrees, it is impossible to maintain weight reduction and prevent buckling at point C. Furthermore, if the ratio of β/α is less than 0.27, even if the ratio of β and α is within the above ranges, the balance of the bending rigidity from the buttress portion 4 to the annular protector 7 will be disrupted, that is, the change in the bending rigidity will be large, Buckling at point C becomes more likely to occur. On the other hand, if the ratio β/α exceeds 0.45, although the change in the bending rigidity is small, it becomes susceptible to side cuts and cannot be put to practical use. For this reason, it becomes important to simultaneously satisfy the ranges of β and α and the ratio of β/α described above.

On the other hand, the buttress portion 4 and the annular protector
7, the distance (width) from the vertex B of the annular protector 7 to the straight line X-X is h1, measured parallel to the straight line X-X from this vertex B. The distance to the edge A of the tread portion 1 is h2, and the tire cross-sectional height is SH.
Then, the ratio between h1 and SH is 0.02 or more, 0.
03 or less, and the ratio of h1 and h2 is 0.0
It is necessary to satisfy a condition in the range of 6 or more and 0.15 or less.

The height h1 of the annular protector should be determined based on appearance, side cut resistance and rolling stability, and in this respect it is appropriate to use the cross-sectional height SH as a reference. That is, when h1/SH is less than 0.02, problems are less likely to occur in terms of rolling stability, but the appearance is poor and the side cut resistance is insufficient. If it exceeds .03, the latter will be good, but problems will arise in rolling stability. Furthermore, it has been found that even if the value of h1 is appropriate, the rolling stability and side cut prevention effect vary depending on where the annular protector is attached. The value of h1 should be determined based on h2; if the ratio of h1/h2 exceeds 0.15, the change in rigidity from near point B to point A will become too large, causing buckling at point C. If the ratio of h1 /h2 is less than 0.06, the side cut prevention effect will be weakened and the appearance will be reduced. It will make you look inferior. In the present invention, point B needs to be located radially outward from the cross-sectional width of the tire.

On the other hand, in order to avoid the buckling phenomenon, ensure stability, and provide a good appearance, the tread width should be made as large as possible, and the cross-sectional area of the tire should be The ratio to width SW is 0.82 to 0.9
1, and in terms of tire stability, the difference h0 in the tire radial direction between the center of the tread portion 1 and the edge A of the tread portion 1 should be large, and in practical use. From above, it is desirable that the ratio to the tire cross-sectional height SH is within the range of 0.07 to 0.13, taking into account the wear life. Note that the bottom of the lug groove 2 is the buttress part 4.
The opening position is h3 outward in the tire radial direction from the intersection C.
If it is inward, it will promote the buckling phenomenon, which is not preferable.

[0014]

[Example] Taking the above conditions into account, the following test tires were prepared and tested. Tire size 26.5-25 20PR, off-the-road (rock pattern) tire Tire structure The tread part has a pattern in which lug grooves are arranged in two rows at an angle to the left and right in the circumferential direction of the tire. The carcass is 1 ply of nylon cord (1890 denier/2)
Four sheets were used. Also, the bead is triple bead ((4)-
(4)-(4)-2) was adopted. Additionally, the tire dimensions were as follows.

1. Tire outer diameter according to the present invention
OD...1738mm Section height S
H‥‥ 555mm cross-sectional width SW‥‥
694mm Crown radius CR...800mm Tread width TW...600mm Specified inclination angle
α‥‥ 27 degrees β‥‥
9 degree standard dimension h1 13
mmh2 ‥‥ 157mm h3 ‥‥ 3mm h0 ‥‥ 63mm

2. The tire is the same as the tire described above except for the numerical specifications below the conventional tire. It is expected that this tire will still have problems in terms of stability. Tire tread width TW...622mm Specified inclination angle β...4 degrees Specified dimension h1...25mmh2
‥‥ 152mm

(Experiment) Table 1 shows the indoor test results and the actual vehicle feeling test results for the tires of the above example and the conventional tire. Note that the tire weight was measured separately. The test conditions were a normal internal pressure of 3.5 kgf/cm2 and a load of 1 of the normal load.
The test was conducted with a large load applied at 60% (20.3 tons/piece). The amount of vertical deflection and static spring constant were collected using a normal indoor static load tester as supporting data for the actual vehicle feeling test results, and both are expressed as an index with the conventional tire set as 100. The smaller the value for the former, the larger the value for the latter, the better. In addition, the weight is similarly expressed with the conventional tire set at 100.

Next, in a feeling test on an actual vehicle (loader), the bucket of the loader was raised, and when this bucket was lowered from side to side, the amount of rolling of the vehicle body and the resilience/convergence were measured. The performance was evaluated on a five-point scale based on the operator's feeling. This actual vehicle feeling test was evaluated at 3.5
The above is the permissible range for an actual vehicle.

[0019]

[Table 1]

The results show that the tire having the shape of the present invention has a remarkable effect of improving rolling stability while ensuring side cut resistance and weight reduction.

[0021]

[Effects] As described above, the present invention limits each structure of the tire and organically combines them, thereby ensuring side cut resistance and meeting the demands of the times for tire weight reduction. However, it was able to provide a tire with good stability, and its contribution to industry was significant.

[Brief explanation of drawings]

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

[Explanation of symbols]

1. Tread section 2..Lug groove 3..Lug 4..Buttress section 5..Side wall section 6..Bead section 7..Annular protector 8..Carcass section A..Tread End B of the part... Radial outer vertex C of the annular protector... Intersection α between the buttress part and the annular protector... Straight line X-X
The inclination angle β of the line BC in the tire radial direction inward with respect to the straight line h1 Distance h2 from apex B of the annular protector to straight line XX h3 Distance from apex B to tread end A measured parallel to straight line X-X h3 The bottom of the lug groove to the buttress part Distance SH from the intersection point C to the release position...Tire cross-sectional height straight line X-X...A straight line perpendicular to the rotation axis of the tire and passing through the intersection C

Claims (2)

[Claims] Claim 1: At least four cords made of organic fiber cords.
In a pneumatic tire equipped with a bias carcass ply larger than the ply, a tread having a lug groove on the outside of the carcass ply, and a sidewall having an annular protector projecting outward from the tire, in a meridional section of the tire, Looking at it, ■ A line AC running radially inward from the tread edge A and a line BC running inward from the radially outer vertex B of the protector intersect at point C, and the lines AC and BC are almost straight lines. The inclination angle of the line AC toward the outside in the radial direction with respect to the straight line XX perpendicular to the tire rotation axis and passing through the intersection C is β.
, let α be the inclination angle of line BC in the radial direction, then β
≧6 degrees, 20 degrees≦α≦35 degrees, and 0.27≦β/
Satisfying α≦0.45, ■The tire cross-sectional height is SH, the distance from apex B to straight line XX is h1, and the distance from vertex B to point A measured parallel to straight line XX is h2. ,0.
06≦h1 /h2 ≦0.15 and 0.02≦h
A pneumatic bias tire for a construction vehicle, characterized in that it satisfies the following: 1/SH≦0.03. 2. The pneumatic bias tire for construction vehicles according to claim 1, wherein the position where the bottom of the lug groove opens to the buttress portion is radially outward from the intersection C.