JP2815944B2 - 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)

As for construction vehicle tires, radial structures have begun to spread, but bias tires are still mainstream because of the high initial cost and the conditions under which radial merits are hardly utilized, such as loaders. 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. Therefore, the balance between the durability of the tread portion and the beat portion has been lost, and the failure of the beat portion has increased.

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, while the traction is achieved by adopting a flat tire having a flatness of 65%. As described above, the balance between the wear life and the durability of the bead portion is lost, and the failure of the bead portion is increasing.

The main cause of bead failure is CB due to bead fatigue.
U, that is, the cord is broken, and the main cause is insufficient rigidity 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 increase, and it is impossible to 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, as shown in FIG. 9, a structure in which the code filler 52 is disposed in the bead portion 50 is provided. What is Code Filler 52?
It is a filling material that is the same as carcass ply or that is stronger or has more or less number of shots than carcass ply cords.

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 includes a carcass that straddles a pair of bead cores including a plurality of bead cores and is formed by stacking rubber-coated organic fiber cord layers so as to cross each other. A pneumatic bias tire for heavy load vehicles, having a carcass sectional height
30% of the carcass cross-sectional thickness is inserted between at least one of the inside and outside of the tire based on a line that is inserted between the adjacent plies of the carcass in the region from 1/2 to the bead core group and that bisects the carcass cross-sectional thickness It is characterized in that it has an additional reinforcing layer in which the organic fiber cords arranged at a distance above are covered with rubber.

[Action]

According to the analysis by the inventors, as shown in FIG. 2, when the tire 12 receives a load in the direction of arrow A in FIG. 2, the bead portion 18 bends and deforms so as to fall outward. At this time, compressive strain is generated on the outer surface side of the bead portion 18, and tensile strain is generated 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 fatigue fracture caused by the compressive strain of the cord is reduced. (Especially, when the cord is made of an organic fiber, the fatigue due to the repeated tensile strain is slight, but the fatigue rupture is much more likely to occur with the repeated compressive strain.) On the other hand, the present inventors have found that, In addition to the bending stiffness that influences the bending deformation, as shown in FIG. 3, the compression distortion of the organic fiber cord 22A or 22B of the bead portion 18 due to the driving and braking torque transmitted through the rim 20. This means that the driving torque from the rim 20 is transmitted to the entire tire 12 through the bead portion 18, and the braking force from the tire tread surface 24 is transmitted to the rim 20 through the tread surface 24 to the bead portion 18, and Because it stops.

Particularly in the case of a bias tire, a compressive force is added to the cord 22A extending from the vicinity of the tread end to the side wall to the bead portion in the same direction as the driving torque (conversely, a tensile force is added to the cord 22B in the opposite direction to the torque). ). Accordingly, the above-described compressive force is further applied to the cord 22A on the outer surface side of the bead portion 18 which has received a greater compressive strain than other portions due to bending deformation or the like, and accelerates the fatigue fracture of the cord. On the other hand, under the use condition in which braking is performed more frequently than driving, a compression force is applied to the cord 22B. The magnitude of the compressive force input to the bead portion code by the driving and braking torques depends on the shear rigidity of the bead portion.

Therefore, in order to reduce the bead failure, it is necessary to increase the bending rigidity and the shearing rigidity at the same time, and the additional reinforcing layer according to the present invention can efficiently improve the shearing rigidity due to such torque. .

As described above, it was confirmed by analyzing a conventional tire that rigidity was effective in improving the durability performance of the bead portion. Here, the bending rigidity and the shear rigidity contribute to the rigidity, and it has been found that increasing the shear rigidity as the lamination rigidity is particularly effective in improving the bead portion durability.

As an additional reinforcing layer inserted and arranged to increase the rigidity of the carcass ply in which the bead portion is laminated, particularly the shearing rigidity, for example, a sheet-like one direction in which cords are buried in parallel in rubber rather than an isotropic material such as rubber. Reinforcements are effective. This is because the increase in thickness is small and the rigidity effect is large. In addition, simply inserting the one-way reinforcing material has no effect, and the neutral axis of the deformation divided by the bisector of the carcass thickness (the cross section of the carcass when the tire is cut along the plane including the rotation axis of the tire). A great effect can be obtained by arranging as far as possible inside and outside the tire from the geometric center line (medium line) and inserting it between plies.

If an additional reinforcing layer is inserted near the media line, the function of the filler to open the carcass ply is mainly used, and the original function of the reinforcing layer can hardly be exhibited, and the desired shear rigidity cannot be obtained. Also, when inserted between the folded back ply around the bead core and the unfolded toroidal carcass ply, the direction of the force applied to the inner and outer surfaces of the additional reinforcing layer is different. The effect is greatly reduced, and the desired bending and shear rigidity cannot be obtained.

FIGS. 1A and 1B are cross-sectional views of the tire 12. FIG. FIG. 1 (A) is an enlarged view of the vicinity of a bead portion of the tire of FIG. 1 (B).

As shown in FIG. 1 (A), the virtual tangents 10a and 10b near the ML passing through the cord surface of the reinforcing layer closest to the medium line ML among the additional reinforcing layers are respectively located at the carcass thickness T from the medium line ML of the tire 12. 30% or more away (t ≧
0.3T), and if it is less than 30%, it is insufficient to improve the shear rigidity. Here, 11a is a virtual tangent connecting the innermost carcass ply cord to the tire inner surface side, and 11b is a virtual tangent connecting the outermost carcass ply cord to the tire outer surface side. Here, the carcass thickness T is the distance between 11a and 11b after inserting the additional reinforcing layer. FIG. 1 (A) shows an additional reinforcing layer 10. The two-dot chain line is used because a virtual tangent passing through both sides of the cord of the additional reinforcing layer was used.

It is preferable to insert an additional reinforcing layer between the two plies furthest from the media line ML in order to increase the shearing rigidity, but it is used at relatively low air pressure and the tire bends greatly (the bead portion falls down greatly) ) Under conditions of use, separation from the upper end of the separation (separation) is a concern. In this case, avoid between the plies farthest from the media line ML and insert between the plies more inside the tire. is there. Even, as mentioned above, the limit is 30%.

The carcass ply layer to be inserted is not limited to an adjacent ply layer straddling from one bead core 14 or 16 to the corresponding bead core (not shown) in a toroidal manner.
The effect does not change even if the carcass ply is between the folded ply layers folded around the bead. It is significant to insert between different adjacent ply layers, and even if it is separated by 30% or more between the layers of the same ply, for example, the folded ply around the bead core 16 and the layer of the same carcass ply, it is not inserted. The upper end of the additional reinforcing layer is up to 1/2 of the carcass sectional height H, and if it is inserted up to 1 / 2H or more, the flexibility of the side wall, which originally requires flexibility, is impaired, The distortion input is undesirably high. Also,
The lower end of the additional reinforcing layer extends to near the upper end of the bead core.

The additional reinforcing layer 10 is preferably arranged substantially symmetrically with respect to the medium line, but may be arranged on one side (particularly on the tire inner surface side).
Only may be. The additional reinforcing layer 10 may be a single layer, and when a larger reinforcing effect is required, a plurality of layers are laminated so that the cords cross each other. It is preferable that the ply cord and the cord of the additional reinforcing layer facing the ply cord intersect.

The cord material used for the additional reinforcing layer 10 is preferably the same organic fiber as the carcass ply cord, for example, a nylon cord, and a polyester cord or a Kevlar cord may be applied in order to further enhance the reinforcing effect. The cord breaking strength of the additional reinforcing layer 10 is 1.
A range of 5 to 0.5 times is optimal. For example, if a nylon cord of 1890d / 2 is used for the carcass cord, the nylon cord of the additional reinforcing layer is 1890d / 3, 2520d / 2, 1890d / 2, 126
0d / 2, 840d / 3 etc. are suitable. If the breaking strength of the cord of the additional reinforcing layer exceeds 1.5 times that of the carcass cord, separation at the end of the cord tends to occur, and if it is 0.5 times or less, a sufficient reinforcing effect cannot be obtained.

[First Embodiment] Fig. 4 (A) shows a tire 30 according to a first embodiment. The type of the tire 30 of the present embodiment is OR 1800-25
32PR bias tire. For the carcass 32, a nylon 1890d / 2 cord is used (d: denier), the number of driving is 44 / 5cm, and the number of carcass plies 34 is 14
It is a sheet. Further, the tire 30 of the first embodiment is a double bead (bead cores 36 and 38), and the carcass configuration is
6-6-2. The meaning of this number is bead core 36,
The number of carcass plies 34 wound around 38 is 6
−6 ”, it is a double bead. The number of carcass plies 34 that do not wind up the bead core 36 or 38 is two, and this plies are usually located on the outermost side of the carcass plies. Hereinafter, the first ply, the second ply,..., The fourteenth ply are referred to in order from the inside of the tire 30 (see FIG. 5). FIG. 5 shows a simplified arrangement of the carcass ply 34.

In the tire 30 of the first embodiment, additional reinforcing layers 40 are inserted between the first ply and the second ply and between the thirteenth ply and the fourteenth ply. The additional reinforcing layer 40
It is made of the same material as the carcass 32 and has a width of 120 mm and each
The sheets are stacked and inserted one by one. The lower end of the additional reinforcing layer 40 is substantially near the upper ends of the bead cores 36 and 38. 2
The additional reinforcing layers 40 are stepped from each other and have a step width of 15 mm.

The 100% modulus of the rubber covering the carcass ply 32 and the additional reinforcing layer 40 is 16 kg / cm ² .

As shown in FIG. 4 (A), the inner surface height dimension H of the carcass 32 (a dimension corresponding to the dimension H shown in FIG. 1 (B)) is
380 mm (only H / 2 is shown in FIG. 4 (A), and the dimension H / 2 is 190 mm). The inclination angle of the carcass ply cord with respect to the circumferential direction is the center of the crown, and
The code of the ply is about 36 °, that of the 14th ply is about 34 °, and the other ply cords are in between. Here, the cord angle of the carcass at the portion where the additional reinforcing layer 40 is inserted is in a range of about 55 to 60 °, and the cord angle of the additional reinforcing layer 40 is about 46 ° near the bead core, and on the opposite side. It is about 44 ゜. The cord directions of the two additional reinforcing layers intersect with each other and are arranged so as to intersect with the cords of the adjacent carcass ply.

The spacing between the additional reinforcing layers 40 is as follows. In FIG. 4 (A), illustration of the third to twelfth plies is omitted. First, near the upper end of the additional reinforcing layer 40 (at a position of about 140 mm in height of the medium line), the dimension T from the innermost carcass ply (first ply) cord surface to the outermost carcass ply (14th ply) cord surface is set. ₁ is 29mm. Further, the distance t ₁ of the additional reinforcing layer 40 from the medium line ML is 11.5 mm. In any case, the distance between the cords is measured according to FIG. 4 (B), and the same applies to the following. Therefore, (t ₁ / T ₁ ) × 100 = 39.7%.

Similarly, in the vicinity of the center of the additional reinforcing layer 40 (about 80 mm in height of the medium line), T ₂ = 41 mm and t ₂ = 17.5 mm, and (t ₂ / T ₂ ) × 100 = 42.7% The vicinity of the lower end of the additional reinforcing layer 40 (approximately 26 mm in height of the medium line) is T ₃
= 66 mm, is a t ₃ = 29 mm, the _{(t 3 / T 3) ×} 100 = 43.9%. As a result, the appropriate value (30%
Above).

Second Embodiment Hereinafter, a second embodiment of the present invention will be described. In addition, the type of the tire of the second embodiment, the material and configuration of the carcass ply,
The material, dimensions, configuration, and the like of the additional reinforcing layer are the same as those of the first embodiment, and the same components as those of the first embodiment are denoted by the same reference numerals, and description of the configuration is omitted.

As shown in FIG. 8, in the second embodiment, the additional reinforcing layer 40 is provided between the second ply and the third ply, and between the seventh ply and the eighth ply. It has been inserted. In addition, in FIG.
The illustration of the carcass plies 34 from the sixth ply to the ninth ply to the twelfth ply is omitted.

In the tire 42 of the second embodiment, as shown in FIG. 8, the distance between the additional reinforcing layers 40 is as follows. First,
Near the upper end of the additional reinforcement layer 40 (approx.
In 140mm position), the dimension T ₁ of the from the innermost carcass ply 34 (first ply) surface to the outermost carcass ply 34 (14 ply) plane is 29 mm. The dimensions t _IN1 and t _OUT1 from the media line ML of the additional reinforcing layer 40 are each 9.5 m.
m, 9.0 mm. That is, the distribution dimension from the medium line ML is slightly different, and the t _IN1 is a distance from the medium line ML to the cord of the reinforcement layer closer to the ML among the additional reinforcement layers 40 inserted inside the tire 42, The above-mentioned t _OUT1 is the same distance as that of the additional reinforcing layer 40 inserted outside the tire from the medium line ML. Therefore,
(T _IN1 / T ₁ ) × 100 = 32.8%, (t _OUT1 / T ₁ ) × 100 = 31.0
%.

Similarly, near the center of the additional reinforcing layer 40 (about 80 mm in height of the medium line), T ₂ = 41 mm, t _IN2 = 15 mm,
t _OUT2 = 14 mm, and (t _IN2 / T ₂ ) × 100 = 36.6
%, (T _OUT2 / T ₂ ) × 100 = 34.1%. Additional reinforcement layer 40
Near the lower end (about 26 mm at the height of the medium line)
T ₃ = 66 mm, t _IN3 = 27 mm, t _OUT3 = 26 mm, and (t _IN3 /
T ₃ ) × 100 = 40.9% and (t _OUT3 / T ₃ ) × 100 = 39.4%. As a result, the appropriate value (30%
Above).

That is, the tire 42 of the second embodiment indicates the limit in the case where the additional reinforcing layer 40 is inserted closer to the medium line ML.

The effects of the first and second embodiments will be described below.

In order to clarify the effects of the pair of additional reinforcing layers 40, durability tests were performed on the tires 30 according to the first and second examples together with the tire having the following structure.

Conventional ply structure tire without reinforcement layer (conventional tire) 120m wide with same rubber as carcass instead of additional reinforcement layer
A tire having a structure in which a rubber sheet having a thickness of 2.5 mm and a thickness of 2.5 mm is inserted in the same place as the additional reinforcing layer 40 in FIG. 4 (comparative tire) A tire having a carcass structure of 8-6-2 (comparative tire) Tire of the first embodiment Tire of the second embodiment The test conditions were as follows. The tire was rotated by a drum of 5 mφ, the load was 1.5 times the normal load (9,690 kg), the speed was 10 km / h, and the bead portion was continuously driven. The vehicle was allowed to run until "bulging" occurred due to cord breakage on the surface, and the total running time was evaluated. The air pressure is 5.75 kgf / cm ² at a normal internal pressure. The timing of the occurrence of the “bulge” was determined to be the time at which the drum was stopped by the operation of the “bulge detector”.

As an additional confirmation test of the durability test of the drum, a test piece similar to the part where the additional reinforcing layer was inserted with the tire was prepared (10 cm × 10 cm, 14 ply laminated plus additional reinforcing layer)
did. The same was applied to the test pieces, except that the test piece was a 16-ply laminate, and a shear rigidity comparison test was performed. The experimental results are shown in FIG.

On the other hand, FIG. 7 shows the durability index of each tire. In the durability index, the tire (115), the tire (128), the tire (140), and the tire (13
5) Both are better than the current tires (the above tires), but the index that can handle the currently required performance is 130
This is necessary, and therefore, only the tires of the first and second embodiments are suitable. Moreover, the heat separation durability of the above tires is higher than that of other test tires.
Not suitable for 20% drop.

As can be understood from the above durability test, the additional reinforcing layer
By inserting 40 in the proper position, both the shear stiffness and the durability are improved with less material.

〔The invention's effect〕

As described above, the pneumatic bias tire for a heavy load vehicle according to the present invention can minimize the increase in the thickness of the bead portion, can reinforce only the bead portion, and can prevent bead failure. It has an excellent effect.

[Brief description of the drawings]

1A is a cross-sectional view showing the vicinity of a bead portion of the tire of the present invention, FIG. 1B is a cross-sectional view of the tire of the present invention, and FIG. , Third
FIG. 4 is a schematic view illustrating the compression and tension states of the cord by the driving torque, FIG. 4 (A) is a cross-sectional view showing a part of the tire according to the first embodiment, and FIG. 4 (B) is FIG. FIG. 5A is a partially enlarged view, FIG. 5 is an explanatory view showing a simplified arrangement of the carcass plies according to the first embodiment, and FIG. 6 is a diagram showing the shear stiffness of four types of tires including the tire of the first embodiment. FIG. 7 is a characteristic diagram showing the results of a durability test of four types of tires including the tire of the first embodiment, and FIG. 8 is a cross-section showing a part of the tire according to the second embodiment. FIG. 9 (however, hatching of rubber is omitted), and FIG. 9 is a cross-sectional view showing an example of the vicinity of a bead portion of a conventional tire. 10, 40 ... additional reinforcement layer, 12, 30, 42 ... tire, 34 ... carcass ply, ML ... medium line.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-52-116504 (JP, A) JP-A-52-131307 (JP, A) JP-A-1-106707 (JP, A) 15241 (JP, B2) JP 56-15322 (JP, B2) JP 60-18561 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60C 9/06 B60C 9 / 08 B60C 15/00 B60C 15/06

Claims (1)

(57) [Claims] 1. A pneumatic bias tire for a heavy-duty vehicle comprising a carcass which straddles a pair of bead cores composed of a plurality of bead cores and has a carcass formed by laminating organic fiber cord layers covered with rubber so as to cross each other. At least one of the inside and outside of the tire based on a line that is inserted between the adjacent plies of the carcass in the region from the half of the carcass cross-section height to the bead core group and bisects the carcass cross-section thickness A pneumatic bias tire for a heavy-duty vehicle, comprising an additional reinforcing layer formed by rubber-coating an organic fiber cord disposed at a distance of at least 30% of a carcass sectional thickness.