JPH1134617A - Pneumatic tire for construction vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance durability by improving anti-separating performance when a reinforcement layer is provided at a side wall. SOLUTION: In this tire, both ends 4A of a carcass layer 4 reinforced with a steel code are folded back from inside the tire around bead cores 5 arranged at right and left bead parts 2 and humps 7 protruding from the outside surface of the tire are formed at side walls 3. Each edge 4a of the ends 4A of the carcass layer 4 extends more than 40% of a cross-sectional height H of the tire toward the hump 7 from the bead part 2 and the reinforcement code can elongate in the folded-back side of the bead core 5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire for a construction vehicle which travels in rough terrain such as civil engineering and construction sites and off-roads, and more particularly, to a pneumatic tire for a construction vehicle having excellent cut resistance of a sidewall portion. For entering tires.

[0002]

2. Description of the Related Art A pneumatic tire for a construction vehicle running on a rough terrain is liable to cause cut damage on a sidewall portion upon contact with rocks or the like. Therefore, a hump portion protruding from the tire outer diameter side surface of the sidewall portion is provided to increase the thickness, and further, a side portion reinforcing layer is buried so that cut scratches do not easily penetrate into the inside. .

Conventionally, for example, there has been a proposal to use a side reinforcing layer in which reinforcing cords are arranged in a wave form so as to have extensibility. With the configuration in which the side portion reinforcing layer is extended in this manner, even if the sidewall portion is repeatedly subjected to large deformation, the side portion reinforcing layer can be deformed by following the deformation. The strain generated in the part is significantly reduced compared to the case of the side part reinforcing layer using the non-extensible reinforcing cord, and the cut resistance is prevented from penetrating into the inside, and the separation resistance of the side part reinforcing layer end is also increased. Like that.

However, since the inner end of the side portion reinforcing layer is located in the region where the rim flange reaction force, the tire internal pressure, and the shear strain are concentrated due to bending deformation, the inner end of the side portion reinforcing layer is similar to the side portion reinforcing layer using a non-stretchable reinforcing cord. In addition, there is a problem that a separation failure from the inner end side is likely to occur.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a pneumatic tire for a construction vehicle which can improve the separation resistance when a reinforcing layer is provided on a sidewall portion and can increase the durability. It is in.

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a carcass layer in which steel cords are arranged as reinforcing cords, and both ends of the carcass layer are turned from the inside of the tire to the outside around bead cores arranged in right and left bead portions, In a pneumatic tire for a construction vehicle provided with a hump portion protruding from a tire outer diameter side surface of a sidewall portion, both ends of the carcass layer are formed so that edges thereof have a tire sectional height H of 4 from the bead portion side.
The reinforcing cord of the carcass layer is configured to extend from 0% to the hump portion such that the reinforcing cord of the carcass layer is extensible on the turnback side of the bead core.

[0007] In order to extend the edges of the folded both ends of the carcass layer toward the outer diameter side of the tire so as to be within the above-described range and use it as a reinforcing layer of the sidewall portion,
While preventing the cut wound from penetrating into the inside, there is no inner end such as the side portion reinforcing layer separately arranged in the related art, so that separation failure does not occur due to the inner end.

In addition, since the reinforcing cord on the turn-back side of the carcass layer has an extensibility, it can be used when traveling on a rough terrain.
Even if a large deformation repeatedly acts on the sidewall,
Following this, the folded side of the carcass layer can be deformed, thereby reducing the distortion generated on the folded side of the carcass layer, so that separation at the edges of both ends of the carcass layer can be prevented from easily occurring. it can. Therefore, the durability of the tire can be improved.

Furthermore, since the folded side of the carcass layer is used as a reinforcing layer for the sidewall portion, and there is no need to separately arrange the side portion reinforcing layer as in the conventional case, the step of attaching the side portion reinforcing layer is omitted. The number of steps can be reduced.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows an example of a pneumatic tire for construction vehicles of the present invention, wherein 1 is a tread portion, 2 is a bead portion, and 3 is a sidewall portion. Outer side in the tire radial direction (outer diameter side) connected to the left and right bead sections 2
Left and right sidewall portions 3 are extended, and a tread portion 1 extending in the tire circumferential direction is provided between the left and right sidewall portions 3.

A carcass layer 4 of one layer arranged in the tire radial direction with a steel cord as a reinforcement cord is disposed inside the tire, and both ends 4A of the carcass layer 4 are disposed in the right and left bead portions 2 and have an annular hexagonal cross section. The tire is folded around the beat core 5 from the inside to the outside of the tire. A plurality of belt layers 6 are embedded on the outer peripheral side of the carcass layer of the tread portion 1. A hump portion 7 is provided on the tire outer diameter side surface of the sidewall portion 3 (on the tread portion 1 side from the tire maximum width position P) so as to project outward in a ring shape. Note that C
L is a tire center line.

According to the present invention, in the pneumatic tire for a construction vehicle having the above-described configuration, both ends 4 A of the carcass layer 4 are
The configuration is such that the edge 4a extends from the bead portion 2 side to at least 40% of the tire sectional height H and to the hump portion 7. In addition, both bead cores 5
The reinforcing cord portion of the carcass layer 4 extending therebetween is inextensible as in the related art, whereas the reinforcing cord portion (the folded portion 4) folded back from the bead core 5 is formed.
B) is configured to have extensibility.

As described above, the folded both ends 4A of the carcass layer 4 are extended to the tire outer diameter side in the above-mentioned range, and the folded portions 4B function as side part reinforcing layers which are conventionally separately disposed. In addition, since there is no inner end unlike the conventional side portion reinforcing layer, it is possible to avoid a separation failure occurring due to the cut end being prevented from penetrating to the inside.

Further, since the reinforcing cord of the folded back portion 4B has extensibility, the side wall portion 3B can be moved while traveling on a wasteland.
, The carcass layer folded portion 6B can be easily deformed following the large deformation, so that the distortion generated at both ends of the carcass layer 4 is small, and the edge separation easily occurs. There is no. As a result, the durability of the tire can be improved.

Furthermore, since the side portion reinforcing layer conventionally separately provided has an integrated structure using the folded side of the carcass layer 4, the step of attaching the side portion reinforcing layer can be omitted, and the number of steps can be reduced. Edge 4 of the carcass layer 4
If a is less than 40% of the tire cross-sectional height H, it cannot function sufficiently as a protector for the sidewall portion. Conversely, if it extends beyond the hump portion 7, the separation from the edge 4a will occur. There is a problem of failure.

As a configuration for making the reinforcing cord of the carcass layer 4 on the folded side from the bead core 5 extensible, for example,
By forming the reinforcing cords in a waveform arrangement, the reinforcing cords can be made extensible. Such a carcass layer 4 can be obtained by using an unvulcanized carcass layer in which wavy reinforcing cords are arranged as a whole. By lift at the time of vulcanization,
The bead-bead interval and the cord elongation are set so that the reinforcing cord between both bead cores 5 is extended. After vulcanization,
While the corrugated reinforcing cords are stretched straight and become inextensible, the portions of the reinforcing cords that are folded back from the bead core 5 are not affected by the lift, so they are present in the corrugated arrangement as they are and have extensibility. Become like In order to easily deform the folded portion B of the carcass layer, it is preferable to form the reinforcing cord into a corrugated shape so that the elongation of the reinforcing cord before vulcanization is 5 to 15%.

Further, a reinforcing cord of the carcass layer 4 is formed by twisting a plurality of wires twisted in a spiral shape.
It can also be composed of a single twisted steel cord having an n structure. This single twisted steel cord is also twisted so that the elongation of the reinforcing cord before vulcanization is 5 to 10%. The molding rate is 100 to 140 as a short pitch (3 to 10 mm).
It is good to set in the range of%. In the case of a single twisted steel cord, the elongation of up to 10% is the limit in tire molding, and beyond that, it deteriorates other characteristics (corresponding to a breakage of the cord due to an increase in the bending rigidity of the steel cord in order to increase the wire diameter). Not preferred.

The type ratio of the single-twisted 1 × n structure is n
Assuming that the cord outer diameter when the strands are twisted concentrically without any gap is 100, it is defined as the spiral outer diameter of the strand when the individual strand alone is taken out. In order to make the reinforcing cord of the carcass layer 4 folded back from the bead core 5 in this way, the entire reinforcing cord of the carcass layer before vulcanization is made extensible. By extending the reinforcing cord between the bead cores 5 to make it inextensible and the folded side to be extensible, there is also a problem of rubber flow on the folded side of the carcass layer that occurs in the vulcanization process when using a non-extensible steel cord. Can be improved.

In the above-described embodiment, an example in which one carcass layer 4 is provided is shown. However, the present invention is not limited to this, and a plurality of carcass layers may be provided. In this case, at least one carcass layer 4 is provided. May be configured as described above.

[0020]

EXAMPLE The tire of the present invention having the structure shown in FIG. 1 in which the tire size is made common to 18.00R25 and both ends of the carcass layer are extended, and in the structure of FIG. 1, instead of extending both ends of the carcass layer, A conventional tire having a side reinforcing layer on which extensible reinforcing cords were arranged was manufactured.

The tire of the present invention uses a single-stranded steel cord (corrugated steel cord?) As a reinforcing cord for the carcass layer, and extends its edge beyond the tire maximum width position from the bead portion side to a tire sectional height H of 56. %. Conventionally, corrugated steel cord is used for the side reinforcement layer of the tire. When a durability evaluation test was performed on each of these test tires under the following measurement conditions,
The results shown in Table 1 were obtained.

Durability Each test tire is rim size 25 × 13.00 (2.5)
Rim, and air pressure 400kPa (specific pressure 57
%), A load of 11100 kgf (specified 120% load), a speed of 20 km / h, and an indoor drum test. The running time until the sidewall portion breaks down is measured. The value was evaluated. The larger the value, the better the durability.

[0023]

[Table 1] As is clear from Table 1, it can be seen that the tire of the present invention can greatly improve the durability.

[0024]

As described above, according to the present invention, both ends of a carcass layer in which steel cords are arranged as reinforcing cords are turned from the inside of the tire to the outside around the bead cores arranged in the right and left bead portions, and the tire of the sidewall portion is provided. In a pneumatic tire for construction vehicles provided with a hump portion protruding from the outer diameter side surface, both edges of the carcass layer are positioned between the bead portion side and 40% or more of the tire section height H to the hump portion. And the reinforcement cord of the carcass layer is configured such that the folded side from the bead core has extensibility, so that the separation resistance when the reinforcement layer is provided on the sidewall portion is improved, and the durability is improved. Can be enhanced.

[Brief description of the drawings]

FIG. 1 is a tire meridian half sectional view showing an example of a pneumatic tire for a construction vehicle of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tread part 2 Bead part 3 Side wall part 4 Carcass layer 4A end part 4B Folded part 4a Edge 5 Bead core 6 Belt layer 7 Hump part P Tire maximum width position

Claims (3)

[Claims] 1. A hump in which both ends of a carcass layer in which steel cords are arranged as reinforcing cords are turned from the tire inner side to the outer side around bead cores arranged in right and left bead parts, and project from the tire outer diameter side surface of the sidewall part. In the pneumatic tire for a construction vehicle provided with a portion, both ends of the carcass layer are extended so that their edges are located between the bead portion side and 40% or more of the tire section height H and the hump portion, A pneumatic tire for a construction vehicle, wherein the reinforcing cord of the carcass layer is configured to have extensibility at a turn side from a bead core. 2. The pneumatic tire for a construction vehicle according to claim 1, wherein the reinforcing cord on the turn-back side of the bead core of the carcass layer is formed in a waveform. 3. The pneumatic tire for a construction vehicle according to claim 1, wherein the reinforcing cord on the turn-back side of the bead core of the carcass layer is formed of a single twisted steel cord obtained by twisting a plurality of wires twisted in a spiral shape.