JP2883377B2 - Pneumatic bias tire for heavy-duty vehicles - Google Patents

Description

The present invention relates to a heavy-duty vehicle having a carcass formed by a rubber-coated organic fiber cord layer straddling a plurality of bead cores and intersecting and laminating with each other. It relates to a pneumatic bias tire.

(Prior art)

Heavy-duty vehicle tires, especially construction vehicle tires,
Although the radial structure has begun to spread, bias tires are still the mainstream because of the high initial cost and the fact that, for example, there are conditions such as a loader where the merit of radial can hardly be utilized. In particular, almost all industrial vehicles (particularly large forklifts and large truck cranes) are bias tires.

On the other hand, the performance of the vehicle was suppressed by the tire durability (especially the heat generation durability). However, due to the heat generation durability and the load capacity of the radial tire, the performance of the vehicle was improved, while The focus on high productivity, such as the pursuit of increased production efficiency, has been further increased, and the use conditions of high speed and high load have been increased.

Users who use bias tires choose operating conditions that do not cause heat separation (tear failure due to heat) in the tread section, or use radials if it is unavoidable, while tire manufacturers use bias tires. Although heat separation at the tread portion has been reduced as a result of the primary aim of improving the heat generation durability, any effective measures have been taken to improve the durability of the bead portion, which is the other major failure site of heavy duty tires. However, the balance between the durability of the tread portion and the bead portion has been lost, and the failure of the bead portion has increased.

Further, under the use conditions in which tire spin promotes wear as in the case of the loader described above, the wear life is greatly improved by improving the tread rubber and the tread pattern, and the flattening rate is reduced.
Since the traction and the wear life are improved by adopting a 65% flat tire or the like, the balance between the wear life and the bead part durability is lost as in the above, and the failure of the bead part is increasing.

The main cause of bead failure is CB due to bead fatigue.
U, that is, a broken cord, and the main cause is insufficient rigidity in absolute and relative values of the bead portion.

[Problems to be solved by the invention]

The following countermeasures can be considered to solve this.

First, the number of carcasses is increased. However, in this case, the thickness of the crown portion of the tire also increases, which is disadvantageous in terms of heat generation and increases the weight of the tire, which leads to an increase in cost. In addition, the overall performance is not as high as the cost-up, and cannot meet customer requirements.

Second, the thickness of the rubber layer over the entire carcass ply layer is increased. In this case, there is a certain effect under the conditions of use only with a simple heavy load, but under the conditions of use with the speed up of the vehicle, the increase in heat generation becomes large, and the effect on performance is weakened. Problems will arise.

Third, there is a structure in which a code filler is arranged in the bead portion. A cord filler is a filling material in which a cord having the same strength as a carcass or having a lower strength than a cord for a carcass is used in a coarser number of times. In this case, an effect corresponding to the thickness of the cord filler is expected, the mechanical action is not sufficiently considered, and the effect on the performance of the bead portion in the market is hardly found. That is, this structure is based on the idea that the bead portion may be simply thickened.

From the above, thickening the bead part means
It has been considered that it is not a fundamental improvement of direct bead failure.

In consideration of the above facts, the present invention minimizes the increase in the thickness of the bead portion, effectively reinforces only the bead portion, prevents bead failure, and balances heat durability and wear life. Accordingly, it is an object of the present invention to provide a pneumatic bias tire for a heavy load vehicle that can significantly improve the tire life.

[Means for solving the problem]

The pneumatic bias tire for a heavy load vehicle according to the present invention is a pneumatic bias tire for a heavy load vehicle including a carcass that straddles a pair of bead cores formed of a plurality of bead cores and has a rubber-coated cord layer stacked so as to cross each other. In a biased tire, a bisecting line of the carcass thickness is located in a region from the half height of the maximum height of the inner surface of the carcass to the bead core group in a cross section obtained by cutting the tire on a plane including the rotation axis of the tire and facing the bead core group. Carcass thickness in the inside and outside directions of the tire respectively as reference
100% between adjacent layers of carcass ply within 20%
% Modulus inserted an additional reinforcing rubber sheet of 10-40 kg / cm ² .

[Action]

It was confirmed by analyzing conventional tires that bending and torsional rigidity were effective in improving the durability of the bead portion. Further, as described above, it is inefficient to improve the bending and torsional stiffness by the conventional technique of thickening the rubber gauge between the ply layers as a whole, and the inventors limit the rubber gauge between the bead ply layers to an appropriate place. The arrangement has the effect of simultaneously increasing the bending rigidity and the torsional rigidity to the required values efficiently, and as a result, it has been found that the bead durability can be greatly improved.

In the present invention, in order to raise the bending stiffness and torsional stiffness of the bead portion to an expected level with a small number of members, it isotropically close to the medium line of the carcass in the region from 1/2 of the carcass sectional height to the bead core group. It has been found that a large effect can be obtained by arranging an additional reinforcing rubber sheet, for example, rubber having an appropriate elastic modulus (here, the carcass medium line is as shown in FIGS. 1 (A) and 1 (B)). It refers to the geometric center line of the carcass in a cut plane obtained by cutting the tire at a plane including the rotation axis of the tire (hereinafter simply referred to as a medium line).

In other words, if the reinforcing rubber sheets are arranged at the same volume, they are arranged almost uniformly within a range of 40% of the carcass thickness based on the medium line in the above-mentioned area (20% when divided in the tire inward and outward directions based on the medium line). By doing so, a large bending stiffness and torsional stiffness desirable for the bead portion can be obtained at the same time, and a great effect of the torsional stiffness more than the bending stiffness can be obtained.

Further, depending on the tire size described later, it is more preferable to arrange the reinforcing rubber sheet more narrowly and intensively without being restricted by arranging the reinforcing rubber sheet almost uniformly in the range of 40%. Can be

That is, as shown in FIG. 1 (A), the additional reinforcing rubber sheet 10 has a carcass thickness before the additional reinforcing rubber sheet is inserted from the medium line ML in the region from the carcass sectional height 1/2 H of the tire 12 to the bead core group. Inside and outside of T tires
Within 20% (the area between 10a and 10b in the figure,
(t ≦ 20%), preferably between ply layers.
%, It is insufficient to improve bending rigidity and torsional rigidity with at least the same amount of rubber. Where 10a and 1
0b indicates the position of t = 20%, 11a indicates the inner surface of the innermost carcass ply, and 11b indicates the outer surface of the outermost carcass ply.

According to the present invention, as shown in FIG. 2, when a load is applied to the tire 12, the bead portion 18 bends and deforms so as to fall outward. At this time, compressive strain occurs on the outer surface side of the tire 12, and tensile strain occurs on the inner surface side. If the bending stiffness of the bead portion 18 is increased, the amount of bending deformation is reduced, and the compressive strain is also reduced accordingly, so that the fatigue rupture caused by the compressive strain of the cord is reduced. Fatigue is slight, but fatigue rupture is much more likely to occur for repeated compressive strain.

On the other hand, in particular, the present inventors have found that, in addition to the bending stiffness affecting the bending deformation, the torsional stiffness has a great effect on bead durability. In particular, heavy-duty vehicles that repeat intense turning movements, such as loaders that perform loading work in narrow places with high frequency, large forklifts that also repeat transporting work, and ore and waste rock from open-pit mine with many sharp curves For large dump trucks to be transported, the magnitude of the torsional rigidity that affects the degree of torsion applied to the bead from the side wall of the tire during turning increases the durability of the bead under the above use conditions. (Of course, under such conditions of use, the bending deformation when traveling on a curve is greater than when traveling straight.) That is, the ply cords 22A and 22B in the side wall to the bead portion having the bias structure arranged as shown in FIG. 3 receive a large torsional force from the tire wheel due to steering in a curve. Also,
From a bead portion to a sidewall portion based on a slip angle (an angle of deviation between the rotating surface of the tire tread 24 and the vehicle, that is, the traveling direction of the wheel) that generates a centripetal force against the centrifugal force applied to the vehicle from the tire 12 while traveling on a curve. Torsion.

When the tire having the bias structure receives such a torsion, either of the cords 22A and 22B receives a compressive force depending on the torsion direction, so that it is necessary to increase the torsional rigidity.
Therefore, by inserting the additional reinforcing gorge sheet of the present invention, not only the bending stiffness but also the torsional stiffness is improved at the same time, and it is possible to solve the problems such as the early breakage of the cord due to the repeated compressive strain as described above. .

In order to quantify the effect of the present invention in the laboratory, as shown in FIG. 4, the rigidity of the two rigid plates was measured using a composite laminate 25 (four types) of a rectangular carcass ply material of 50 mm × 100 mm and an additional rubber sheet. A comparison experiment of values was performed.

(Carcass ply material 27) Carcass with rubber-coated nylon 1890d / 2 (d: denier) cords with 44 / 5cm in number of cords and when stacked, the gauge G between cords of adjacent plies is 0.5mm A ply material was used.

(Method of laminating the carcass ply material 27) The above 10 sheets are set to have an intersection angle of 70 ° (that is, the angle of the cord of one ply is 35 ° with respect to the cross-sectional direction, and 55 ° when viewed in the tire circumferential direction). ) Alternately stacked.

(Type of laminated board and method of inserting additional reinforcing rubber sheet 29) "Concentrated type": In the case of laminated plates A and B The rubber sheet was inserted around the neutral axis (surface) laminated plate of the laminated plate. Therefore, in the case of the laminate A, the rubber sheet is inserted between the fifth and sixth sheets, and in the case of the laminate B, the rubber sheet is inserted between the third and fourth, between four and five, between five and six, ~ 7, 7
~ 8 respectively.

"Dispersion type": In the case of the laminated plate D A rubber sheet was inserted and stuck on 10 layers uniformly (all over the entire surface).

All of the above have the same total gauge, and the 100% modulus of the rubber sheet is 22.2 kg / kg including the ply rubber.
It is cm ^2. In addition, a rubber sheet 1.7 mm x 3 to specify the range
Sheets were added to the centralized type (laminate C). The insertion positions are between 4 and 5, between 5 and 6, and between 6 and 7.

As described above, the rigidity value increases when the additional reinforcing rubber sheet 29 is arranged mainly on the neutral shaft. In particular, the torsional rigidity is remarkable. In the present invention, since it is an important subject to largely improve the torsional rigidity, it is most effective to concentrate the components on a neutral shaft.

In this experiment, the ratio of the distance from the neutral axis of the central 3-ply to the carcass ply cord was about 19% on one side (about 38% in total) without additional rubber sheet, up to the ply including rubber. Is 20% on one side.

It is not limited to inserting only one sheet in the center. For example, when a large tire requires an additional reinforcing rubber sheet 29 having a total thickness of 10 mm, a single 10 mm thick rubber sheet is inserted between the carcass plies of the medium line at the time of manufacturing. If there is a possibility that air pools are formed near the upper and lower ends of the rubber sheet, or the carcass ply undulates in the vicinity of the rubber sheet, there is a possibility of seriously affecting the durability of the product. This is because it is necessary to arrange them.

Here, it is preferable that the ratio of the total thickness T of the additional reinforcing rubber sheet 29 to the gauge G between cords of the ply be 1.7 ≦ T / G.

Tires for construction vehicles have a size range that is extremely wide compared to other tire types, and are generally classified as small, medium, large, and super large.The lower limit of 1.7 is mainly used for small to medium sized tires. , 1.7 or less, 10% improvement in bending and torsional rigidity
This is because there is little effect on improving the bead failure of the tire. The reason why the upper limit is not limited is that the intensity of use conditions is further increasing, and in the case of a very large size,
A situation exceeding 50 is assumed, and preferably the following range including the lower limit is optimal.

3.0 ≦ T / G ≦ 60 (Physical property value of additional reinforcing rubber) When the 100% modulus is 10 kg / cm ² or less, there is little improvement in bending and torsional rigidity and little effect. When the 100% modulus is 40 kg / cm ² or more, the difference from the carcass coating rubber (100% modulus 10 to 35 kg / cm ² ) is large, so that separation easily occurs (strain energy becomes too large).

The upper end position of the additional reinforcing rubber sheet is at a position of 1 / 2H, where H is the carcass inner surface height obtained by subtracting 1/2 of the nominal rim diameter from 1/2 of the maximum inner diameter of the carcass ply, preferably 2 /
Up to 5H is good. This is because when inserted into the tire radial direction more than 1 / 2H, the rigidity of the sidewall becomes too high, the deflection of the sidewall decreases, and the strain input to the bead increases accordingly.

〔Example〕

FIG. 5 shows a tire 30 according to the present embodiment. The model of the tire 30 of the present embodiment is “OR 23.5-25 16P
R's bias tires. For the carcass 32, a nylon 1890d / 2 cord is used (d: denier), the number of punches is 44 / 5cm, and the number of carcass plies 34 is
10 ply. Further, the tire 30 of the first embodiment is
It is a double bead (beads 36 and 38), and the carcass configuration is 4-4-2. The meaning of this number is bead 36,
The number of carcass plies 34 that winds 38 from the inside of the tire toward the outside is 4-4 in each case,
The number of carcass plies 34 that do not wind up the beads 36 and 38 is two, and this ply usually comes to the outermost side of the beads 38.
Hereinafter, the first ply, the second ply, and the
Plies—referred to as a tenth ply (see FIG. 6) FIG. 6 shows a simplified arrangement of the carcass plies 34. In FIG. 5, the illustration of the second to fourth plies and the seventh to ninth plies is omitted.

In the tire 30 of the present embodiment, an additional reinforcing rubber sheet 40 is inserted between predetermined layers of the carcass ply. When the additional reinforcing rubber sheet 40 is inserted, it can be inserted at a plurality of places, and the following three types (tire 30, tire 30, tire 30)
30) Set the insertion location and explain individually.

First, as shown in FIGS. 5 and 6, the tire 30 has an additional reinforcing rubber sheet 40 having a thickness of 3 mm inserted between the fifth ply and the sixth ply. The additional reinforcing rubber sheet 40 has a width of 140 mm (arc length) and the lower end thereof is almost a bead 3.
It is near the upper end of 6, 38.

The 100% modulus of the rubber covering the carcass ply 32 is 16 kg / cm ² ,
The% modulus is 22 kg / cm ² .

As shown in FIG. 5, the inner surface height dimension H of the carcass 32
Is 430 mm (H / 2 = 215 mm).

Next, as shown in FIG. 7, the tire 30 has an additional reinforcing rubber sheet 40 having a width of 140 mm and a thickness of 1.5 mm between the fifth ply and the sixth ply, and between the sixth ply and the seventh ply.
Is inserted. The two additional reinforcing rubber sheets 40 are stepped from each other, and have a step width of 15 mm. The 100% modulus is the same as the additional reinforcing rubber sheet 40 applied to the tire 30.

Next, as shown in FIG. 8, the tire 30 is placed between the fifth ply and the sixth ply, between the sixth ply and the seventh ply, on the fourth ply side along the fifth ply (the tire inner side). ), Additional reinforcing rubber sheets 40 each having a width of 140 mm and a thickness of 1 mm are inserted. The distribution dimensions from the carcass medium line ML with respect to the carcass thickness at the insertion position of the three additional reinforcing rubber sheets 40 are 20% at the upper end for each of the inside and outside of the tire (the position where the ply is not folded back), and the epex rubber at the lower region. The carcass cross section that passes through the top end of 44 is about 11.1% inside and outside, respectively. The mutual step width of the rubber sheet and the modulus of 100% are the same as those of the tire 30.

The measurement standard for this dimension is based on the raw gauge of the carcass ply, as shown in FIG. That is, when the total width of the carcass ply 32 is B and the upper limit width of the insertion range of the additional reinforcing rubber sheet 40 is A, A / B is 2
It becomes 0%. In addition, the gauge at the time of the product (after vulcanization) is a value obtained by multiplying the raw material by δ (the rate of change of the gauge from the raw material to the product), but since δ is offset, the value of A / B is δ Has nothing to do with. Further, the gauges G between the cords of the adjacent plies were all made of a raw material and 0.5 mm.

 The effects of the present embodiment will be described below.

In order to clarify the effect of inserting the additional reinforcing rubber sheet 40 at a predetermined location as described above, the tires 30,
Was tested for durability.

As a comparative example, a conventional tire in which a 0.3 mm-thick rubber sheet was inserted into all 10 plies was used as a tire to perform a durability test.

The test conditions were a bead endurance test using a drum with a diameter of 5 m. The load was 1.5 times the normal load (9,530 kg) and the speed was 10 km.
/ h, the bead was continuously driven until "bulging" due to a cord break occurred on the outer surface of the bead portion, and the total running time was evaluated. The air pressure is 3.25 kgf / cm ² at a normal internal pressure. In addition, the generation time of the above-mentioned “blistering” was set to be until the drum stops by a “blowing detector” provided in the drum. The results are shown in the table below. The larger the index (%), the better.

From the above results, when the conventional tires were set to 100, each of the tires passed the market required durability index of 130, and it was found that each of the tires was good.

As can be understood from the durability test described above, by inserting the additional reinforcing rubber sheet 40 at an appropriate position, it is possible to improve both the bending rigidity and the torsional rigidity by not only the test piece experiment but also the tire itself. Tests have also demonstrated this.

〔The invention's effect〕

As described above, the pneumatic bias tire for a heavy load vehicle according to the present invention minimizes the increase in the thickness of the bead portion or the weight of the tire, and can reinforce only the bead portion very efficiently. It has an excellent effect that a failure can be prevented.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (A) is a cross-sectional view showing the vicinity of a bead portion of the tire of the present invention, FIG. 1 (B) is a cross-sectional view of the tire of the present invention, and FIG. Sectional drawing explaining bending state, 3rd
The figure is a schematic diagram illustrating the compression and tension states of the cord due to bending and torsion, and FIG. 4 is an experimental sample for determining the insertion position of the additional reinforcing rubber sheet of the present invention. FIG. 5 is a cross-sectional view showing a part of a tire according to the present embodiment, FIG. 6 is an explanatory diagram showing a simplified arrangement of carcass plies according to the present embodiment, FIG.
The figure is an explanatory view showing the arrangement state of the carcass plies of the tire in a simplified manner, FIG. 8 is an explanatory view showing the arrangement state of the carcass plies of the tire in a simplified manner, and FIG. 9 defines the range in which the additional reinforcing rubber sheet is inserted. It is explanatory drawing which shows a dimension standard (however, hatching of rubber was omitted.). 10, 40… Additional rubber sheet, 12, 30… Tire, 34
…… Carcass ply, ML …… Medium line.

Continuation of the front page (56) References JP-A-62-194906 (JP, A) JP-A-52-15004 (JP, A) JP-A-56-39901 (JP, A) JP-A-52-16704 (JP) JP-A-58-30807 (JP, A) JP-A-62-4613 (JP, A) JP-A-1-262205 (JP, A) Japanese Utility Model Showa 63-125604 (JP, U) 47-42441 (JP, B1) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60C 15/00 B60C 15/06

Claims (1)

(57) [Claims] 1. A pneumatic bias tire for a heavy-duty vehicle comprising a carcass straddling a pair of bead cores composed of a plurality of bead cores and having a rubber-coated cord layer intersected and laminated. In the region toward the bead core group from the position of 1/2 of the maximum height of the carcass inner surface of the cross section of the tire cut in the plane including the rotation axis, and in the tire inward and outward directions, respectively, based on the bisector of the carcass thickness A pneumatic bias tire for heavy-duty vehicles, wherein an additional reinforcing rubber sheet of 100 to 40 kg / cm ² is inserted between adjacent layers of a carcass ply having a carcass thickness within a range of 20%.