JP3105616B2 - Pneumatic tires 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 tire for a construction vehicle, and more particularly to a pneumatic tire for a construction vehicle having a pattern for improving running performance on a soft road.

[0002]

2. Description of the Related Art Conventionally, a pneumatic tire for a construction vehicle disclosed in Japanese Patent Application Laid-Open No. 1-254405 is known as an example of a pneumatic tire mounted on a construction vehicle that travels on both uneven terrain and terrain.

As shown in FIG. 5, in a pneumatic tire 70 for a construction vehicle, one pitch P between the circumferential centers of adjacent grooves 74 at the center of a tread 72 is divided into four equal parts. Among the negative ratios of the four areas of the tread 72, the negative comparison value that is the ratio between the maximum negative ratio and the minimum negative ratio is set to 1.22 or less.

As a result, the pneumatic tire 70 for a construction vehicle has sufficient traction, skidability, and sufficient tire life, and reduces the occurrence of chipping failure of the block land portion 76, so that it can be operated until the end of traveling. The ride comfort can be maintained well.

[0005]

However, in this pneumatic tire for construction vehicles 70, the groove depth, the groove width perpendicular to the groove, the inclination angle of the groove wall, the radius of the arc at the groove bottom, etc. are set in the groove 74. There is a constricted portion 78 in which
Serves as a weir, and mud (arrow F in FIG. 5) flowing in the groove 74 is blocked in the groove 74. Further, when mud is clogged in the constricted portion 78, the clogging proceeds with the mud as a core, and the entire groove 74 is filled with mud. Note that the mud is likely to be clogged in the lateral groove of the tread central portion 72B, which has a long distance to the tread end 72A serving as the mud discharge port, and is further likely to be clogged in the circumferential groove, that is, the lateral groove having a large angle λ with the towing direction.

Therefore, the pneumatic tire 7 for construction vehicles
0 was attached to the construction vehicle, and the original weight of the change in gravity after leaving 100 g of mud for 24 hours at room temperature and humidity was 10%.
When the vehicle travels on a mud with a high water content of 30% or more, for example,
4 easily clogged. For this reason, there has been a problem that the shear resistance with the ground contact surface due to the lug pattern is significantly reduced, the traction on muddy ground is greatly reduced, and the skidding is also greatly reduced.

[0007] In view of the above facts, the present invention improves traction and skidding on rough terrain with high moisture content while maintaining basic performance such as abrasion resistance and traction on rough terrain with low moisture content. It is an object to obtain a pneumatic tire for construction vehicles that can be used.

[0008]

According to a first aspect of the present invention, there is provided a pneumatic tire for a construction vehicle, wherein a plurality of lug grooves arranged at both ends of a tread in a substantially tire width direction and a bend connecting these lug grooves are provided. A circumferential groove, and a lateral groove extending from one circumferential groove to the other circumferential groove across the tread from the top of the circumferential groove near the tire equatorial plane, and the lateral groove has substantially the same inclination direction as the circumferential groove. In a pneumatic tire for construction forming a block pattern having at least a portion excluding a portion where the circumferential groove and the transverse groove intersect, a groove depth, a groove width orthogonal to the groove, a groove wall inclination angle and a groove. The radius of the bottom arc is the same, the inclination angle θ of the transverse groove with respect to the tread equatorial plane is 60 ° to 75 °, and the swing angle α1 of the circumferential groove with respect to the transverse groove is 0 ° to 25 ° in the tire circumferential direction. And the circumferential direction Oscillation angle of the lug groove with respect to α2
Is 25 ° to 55 ° in the tire width direction.

[0009]

[Function] In a pneumatic tire for a construction vehicle, in order to prevent muddy clogging in muddy ground with a high water content, when torque is applied to the tire to generate traction, mud in the groove is removed from the center of the tread. Move towards the end of the tread,
It is necessary to be exhaled from inside the groove.

Therefore, in the pneumatic tire for a construction vehicle according to the first aspect, the groove depth of the circumferential groove, the groove width orthogonal to the groove, the inclination angle of the groove wall, the radius of the arc of the groove bottom, and the groove depth of the lateral groove. The groove width perpendicular to the groove, the inclination angle of the groove wall, and the radius of the arc at the bottom of the groove were made the same, and the constriction was eliminated in the groove.

Further, in the pneumatic tire for a construction vehicle according to the first aspect, the inclination angle θ of the lateral groove with respect to the equatorial plane of the tread is 6 °.
0 ° to 75 °, the swing angle α1 of the circumferential groove with respect to the lateral groove is 0 ° to 25 ° in the tire circumferential direction, and the swing angle α2 of the lug groove with respect to the circumferential groove is 25 ° to 55 ° in the tire width direction. did.

[0012] Therefore, when a torque is applied to a tire to provide traction on uneven terrain having a high water content, mud in the groove is
It can be smoothly moved from the center of the tread to the end of the tread along the lateral groove, the circumferential groove, and the lug groove and can be discharged. For this reason, the mud does not become clogged in the ditch, and the traction property and the skidding property on the rough terrain having a high moisture content can be improved, and the wear resistance and the traction property on the rough terrain having a low moisture content can be improved. It is possible to maintain basic performance.

When the inclination angle θ of the lateral groove with respect to the equatorial plane of the tread is smaller than 60 °, the traction is reduced, and when the inclination angle θ is larger than 75 °, the mud tends to be clogged in the lateral groove. For this reason, the inclination angle θ of the lateral groove with respect to the tread equatorial plane is preferably 60 ° to 75 °.

Further, when the swing angle α1 of the circumferential groove with respect to the lateral groove is larger than 25 ° in the tire circumferential direction, mud is likely to be clogged at the connecting portion between the lateral groove and the circumferential groove. Therefore, the swing angle α1 of the circumferential groove with respect to the lateral groove is 0 ° to 25 ° in the tire circumferential direction.
° is preferred.

Further, the swing angle α2 of the lug groove with respect to the circumferential groove is
Is larger than 55 ° in the tire width direction, the mud is easily clogged in the lug groove, and the swing angle α2 of the lug groove with respect to the circumferential groove is increased.
Is smaller than 25 ° in the tire width direction, the traction is reduced. Therefore, the swing angle α2 of the lug groove with respect to the circumferential groove is preferably 25 ° to 55 ° in the tire width direction.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a pneumatic tire for a construction vehicle according to the present invention will be described with reference to FIGS.

As shown in FIG. 1, the pneumatic tire 10 for a construction vehicle has a tire size of 20.5R25 (outer diameter 1480 mm, maximum width 530 mm, tread width 456).
mm, crown R850 mm), and with respect to both ends of the tread 12, that is, the width TW of the tread 12,
A plurality of lug grooves 14 are formed on the outer side of the central 2/3 TW along a substantially tire width direction (horizontal direction in FIG. 1) in a tire circumferential direction (vertical direction in FIG. 1) on the left and right sides of the tire equatorial plane 16. They are arranged alternately.

The lug grooves 14 are formed at predetermined intervals in the tire circumferential direction, and are connected to each other by a circumferential groove 18. The circumferential groove 18 is bent in a wave shape,
The lug groove 14 is connected to the top 18A near the tread edge. Also, the top 1 of the circumferential groove 18 near the tire equatorial plane
8B, one circumferential groove 18 across the tread 12
And a lateral groove 20 communicating with the other circumferential groove 18 is disposed, and these lug grooves 14, the circumferential groove 18 and the lateral groove 2 are provided.
The block 22 is defined by 0, and a block pattern having substantially the same inclination direction as the circumferential groove 18 is formed.

The lug grooves 14 and the circumferential grooves 18
And the moving direction of the mud moving in the lateral groove 20 (arrow A in FIG. 1).
Direction) along the transverse groove 20 with respect to the tread equatorial plane 16.
The inclination angle θ of the circumferential groove 18 with respect to the lateral groove 20 is 0 ° to 25 ° in the tire circumferential direction (the direction of arrow B in FIG. 1). Further, the swing angle α2 of the lug groove 14 with respect to the circumferential groove 18 is 25 ° to 55 ° in the tire width direction (the direction of arrow C in FIG. 1).

As shown in FIGS. 2 (A) and 2 (B), the groove depths D1 and D2, and the groove width L orthogonal to the groove, except for the portion where the circumferential groove 18 and the lateral groove 20 intersect each other.
1, L2, the inclination angles β1, β2 of the groove walls, and the radii R1, R2 of the arc at the groove bottom are the same.

Note that, as shown in FIG.
A concave portion 24 is formed at a central portion of each of the two portions, the concave portion 24 being connected to the lateral groove 20 sandwiching the block 22, respectively, substantially in parallel with the circumferential groove 18.

Next, the operation of this embodiment will be described. In the pneumatic tire 10 for a construction vehicle of the present embodiment, the circumferential groove 18
The groove depth D1, the groove width L1 orthogonal to the groove, the inclination angle β1 of the groove wall, and the radius R1 of the arc of the groove bottom are the groove depth D2 of the lateral groove 20.
The groove width L2 perpendicular to the groove, the inclination angle β2 of the groove wall, and the radius R2 of the arc at the groove bottom are the same, and there is no constriction in the groove.

Further, the inclination angle θ of the lateral groove 20 with respect to the tread equatorial plane 16 is set to 60 ° to 75 °, and the swing angle α1 of the circumferential groove 18 with respect to the lateral groove 20 is set to 0 ° to 2 ° in the tire circumferential direction.
5 °, and the swing angle α2 of the lug groove 14 with respect to the circumferential groove 18 is 25 ° to 55 ° in the tire width direction.

Therefore, when a torque is applied to the pneumatic tire 10 for construction vehicles in order to exert traction on irregular terrain having a high water content, the mud in the groove is transferred to the lateral groove 20, the circumferential groove 18, and the lug groove 14. Along the tread 12 from the center of the tread 12
2 can be smoothly moved toward the end and discharged. Therefore, traction and skidding on rough terrain with high moisture content can be improved without mud clogging in the ditch, and basic characteristics such as wear resistance and traction on rough terrain with low moisture content are obtained. It is possible to maintain performance.

As shown in FIG. 3, when the inclination angle θ of the lateral groove 20 with respect to the tread equatorial plane 16 is smaller than 60 °, the traction property is reduced, and when the inclination angle θ is larger than 75 °, mud enters the lateral groove 20. It becomes easy to clog. For this reason, the inclination angle θ of the lateral groove 20 with respect to the tread equatorial plane 16 is preferably 60 ° to 75 °.

As shown in FIG. 4, when the swing angle α1 of the circumferential groove 18 with respect to the transverse groove 20 is larger than 25 ° in the tire circumferential direction, mud is likely to be clogged at the connecting portion between the transverse groove 20 and the circumferential groove. . Therefore, the swing angle α1 of the circumferential groove with respect to the lateral groove is preferably 0 ° to 25 ° in the tire circumferential direction.

Further, when the swing angle α2 of the lug groove 14 with respect to the circumferential groove 18 is larger than 55 ° in the tire width direction, mud is easily filled in the lug groove, and the swing angle α2 of the lug groove 14 with respect to the circumferential groove 18 is reduced. Is smaller than 25 ° in the tire width direction, the traction is reduced. For this reason, the swing angle α2 of the lug groove 14 with respect to the circumferential groove 18 is preferably 25 ° to 55 ° in the tire width direction. (Test Example) In order to confirm the mud-removing property, traction property, side-slip resistance and service life of the pneumatic tire for construction vehicles of the present example, Examples 1, 2 and a conventional example having the specifications shown in Table 1 were used. Were prepared for each construction vehicle. Except for the specifications shown in Table 1 of these construction vehicle pneumatic tires, the construction vehicle pneumatic tires 10 are the same as the construction vehicle pneumatic tires 10 of the present embodiment (Example 1).

Next, each of the pneumatic tires for construction vehicles was mounted on an actual vehicle, and was run on a Kanto loam layer having a water content of 7% and 35%. The results were measured, and the results are shown in Table 2 as an index with the conventional example being 100.

[0029]

[Table 1]

[0030]

[Table 2]

As a result, the pneumatic tire tire for a construction vehicle according to the first embodiment of the present invention has a traction property and a side-slip resistance when the water content is 7% as compared with the pneumatic tire tire for a conventional construction vehicle. , Life and life at 7% moisture content are almost the same, but mud spraying at 7% water content and mud spraying, traction and skid resistance at 35% water content. Is improving. Further, the pneumatic tire tire for a construction vehicle according to the second embodiment of the present invention has a water content of 7% as compared with the pneumatic tire tire for a construction vehicle of the conventional example, and has a mud-repelling property, a traction property, and an endurance. The sideslip property, the life and the life when the water content is 35% are almost the same, but the mud-peeling property, the traction property and the side slip resistance when the water content is 35% are improved.

[0032]

As described above, the pneumatic tire for a construction vehicle of the present invention has the above-mentioned structure, so that it maintains the basic performance such as abrasion resistance and traction on uneven terrain having a low water content, and has a high water content. It has an excellent effect that the traction property and the side slip property can be improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing a part of a tread of a pneumatic tire for construction vehicles according to one embodiment of the present invention.

2A is a sectional view taken along line AA of FIG. 1, and FIG.
FIG. 2 is a sectional view taken along line BB of FIG. 1.

FIG. 3 is a graph showing a relationship between an inclination angle θ of a lateral groove with respect to a tread equatorial plane of a pneumatic tire for a construction vehicle, and mud repelling property and traction property.

FIG. 4 shows a swing angle α1 of a circumferential groove with respect to a lateral groove or a swing angle α2 of a lug groove with respect to a circumferential groove of a pneumatic tire for construction vehicles.
It is a graph which shows the relationship between and mud repellency.

FIG. 5 is a plan view showing a part of a tread of a conventional pneumatic tire for construction vehicles.

[Explanation of symbols]

 Reference Signs List 10 Pneumatic tire for construction vehicle 12 Tread 14 Lug groove 16 Tire equatorial plane 18 Circumferential groove 20 Side groove

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-200406 (JP, A) JP-A-1-254405 (JP, A) JP-A-2-286405 (JP, A) JP-A-3-302 86603 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 11/00-11/13

Claims (1)

(57) [Claims] 1. A plurality of lug grooves arranged substantially in the tire width direction at both ends of a tread, a bent circumferential groove connecting these lug grooves, and a tread from a top of the circumferential groove close to the tire equatorial plane. A transverse groove that traverses from one circumferential groove to the other circumferential groove, and a pneumatic tire for construction that forms a block pattern having substantially the same inclination direction as the circumferential groove, wherein at least the circumferential groove Except for the portion that intersects with the lateral groove, the groove depth, the groove width orthogonal to the groove, the inclination angle of the groove wall and the radius of the arc of the groove bottom are the same, and the inclination angle θ of the lateral groove with respect to the tread equatorial plane Is 60
° to 75 °, the swing angle α1 of the circumferential groove with respect to the lateral groove is 0 ° to 25 ° in the tire circumferential direction, and the swing angle α2 of the lug groove with respect to the circumferential groove is 25 in the tire width direction. 35 ° to 55 °, a pneumatic tire for construction vehicles.