JP2819147B2 - Pneumatic bias tire for heavy loads - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heavy duty pneumatic bias tire having improved braking / driving performance on icy and snowy roads.

[Conventional technology]

Conventionally, in heavy load pneumatic bias tires for icy and snowy roads, a plurality of main grooves extending in the tire circumferential direction are provided on the tread surface and ribs are formed by these main grooves in order to secure braking performance and drivability on icy and snowy roads. A plurality of sub-grooves are arranged in the tire width direction on the surface of the rib, and a plurality of spike pins are implanted on the tread surface. However, these tires have caused social problems such as damage to the road surface due to spike pins when traveling on general roads.

Further, in the bias tire, the tread rigidity is generally smaller than that of the radial tire because the belt layer is not disposed outside the carcass layer as in the radial tire. For this reason, cracks are apt to be generated at the groove bottom of the sub-groove, so that there is a problem that the groove width of the sub-groove cannot be widened in order to enhance manufacturability and driveability on an icy road.

[Problems to be solved by the invention]

An object of the present invention is to provide a pneumatic bias tire for heavy load that has improved braking and driving performance on icy and snowy roads without implanting a spike pin on a tread surface and without providing a sub-groove. And

[Means for solving the problem]

The heavy-load pneumatic bias tire of the present invention has a plurality of left-down grooves extending from one shoulder to the other shoulder in the tire circumferential direction on the tread surface, and extends from the other shoulder to one shoulder. A plurality of right-down grooves are provided so that the intersection of the left-down groove and the right-down groove is at a position offset from the tire equator line, and the angles of these two grooves with respect to the tire circumferential direction are respectively set in the tire width direction. The groove width gradually increases from the center to the shoulder, and the groove width gradually increases from the center in the tire width direction to the shoulder,
Two or more kerfs are engraved on the surface of the block formed by these grooves in the tire width direction, and the contact area ratio of the tread surface is set to a range of 63 to 66%.

 Hereinafter, this means will be described in detail with reference to the drawings.

(1) In the present invention, as shown in FIG. 1, a plurality of left-down grooves 2 are provided on the tread surface T from one shoulder portion 1 to the other shoulder portion 1 ', and the other shoulder portion 1' is provided. A plurality of right-down grooves 3 are provided from one shoulder portion 1 to the right. The left-down groove 2 and the right-down groove 3 are respectively provided on the tread surface T over the entire circumference of the tire.

The reason why the left down groove 2 and the right down groove 3 are provided in the tire circumferential direction is to avoid providing a sub groove as in the conventional bias tire. In addition, when the left descent groove 2 and the right descent groove 3 are provided, a left turn on snow,
The steering stability of the right-handed circuit can be improved.

(2) The intersection M between the left-downward groove 2 and the right-downward groove 3 is offset from the tire equator line EE 'toward the shoulder.

FIG. 2 shows a schematic view of the tread surface. As can be seen from FIG. 2, the intersection point M does not ride on the tire equator line EE 'and is offset to one of the shoulder portions.

Since the bias tire has a smaller tread rigidity than the radial tire, when the intersection M rides on the tire equatorial line EE ', when the lateral force acts on the tire, the intersection M is on the tire equatorial line EE'. This is because a buckling phenomenon (wave phenomena) occurs on the ground, and the grounding property to the ground road surface is deteriorated.

(3) The angles α and β of the left-down groove 2 and the right-down groove 3 with respect to the tire circumferential direction W are determined from the center of the tire width direction F (near the tire equator line EE ′) to the shoulders 1, 1 ′. And the width of these grooves is gradually increased from the center in the tire width direction F toward the shoulders 1, 1 '.

This is because when snow and ice enter the grooves 2 and 3, it is easy to remove the ice and snow from these grooves and to enhance the effect of removing ice and snow.

(4) Two or more kerfs (narrow notch grooves) are cut in the tire width direction F on the surface of the block formed by the left-down groove 2 and the right-down groove 3.

This kerf may be a straight kerf 4 or a partially curved kerf 4 ', as shown in FIG.

When one kerf is engraved on one block surface, the bias tire has a lower tread stiffness than the radial tire, so the shearing force is concentrated on one kerf and cracks are generated at the bottom of the kerf. easy. Therefore, in the present invention, two or more kerfs are engraved to disperse the shearing force.

(5) The contact area ratio of the tread surface T is in the range of 63 to 66%.

In order to ensure braking performance on an icy road without implanting a spike pin on the tread surface T, the contact area ratio must be increased. However, if the ground contact area ratio is increased, the snow removal effect on icy and snowy roads deteriorates, which is disadvantageous for driveability. Therefore, in the present invention, as described above, the grooves are arranged obliquely with respect to the tire circumferential direction, and the angle of the grooves is gradually increased from the center in the tire width direction toward the shoulder, and the groove width of the grooves is increased. By gradually increasing the width from the center in the tire width direction to the shoulder, the braking performance and the driving performance on icy and snowy roads can be achieved while increasing the contact area ratio. For reference, the contact area ratio of the conventional heavy load pneumatic bias tire is about 55 to 60%.

If the ground contact area ratio is less than 63%, good braking performance on ice cannot be obtained. On the other hand, if it exceeds 66%, snow drive performance on snow deteriorates, so good driving and braking performance on snow can be obtained. Absent.

 Examples will be described below.

Examples For the following bias tires, braking performance, drivability, and crack resistance were evaluated by the following evaluation methods. Table 1 shows the results.

Tire of the present invention Tire size 10.00-20 14PR. Tread surface contact area ratio 65%. Groove angle at the center in the tire width direction: Left downward groove; Angle α = 35 ° with respect to tire circumferential direction, groove width
5.5mm.

Downward right groove; angle β = 40 ° with respect to tire circumferential direction, groove width
8mm.

Groove angle at shoulder: Downward left groove; Angle α = 90 ° with respect to tire circumferential direction, groove width
20mm.

Downward groove: Angle β = 90 ° with respect to tire circumferential direction, groove width
20mm.

Intersection between the left descent groove and the right descent groove: A distance of 8 mm from the tire equator line toward the shoulder. Number of linear kerfs arranged in one block: 2-3 in the tire radial direction.

Comparative tire 1 Tire size 10.00-20 14PR. Tread surface contact area ratio 60%. Groove angle at the center in the tire width direction: Left downward groove; Angle α = 35 ° with respect to tire circumferential direction, groove width
10mm.

Downward right groove; angle β = 40 ° with respect to tire circumferential direction, groove width
11mm.

Groove angle at shoulder: Downward left groove; Angle α = 90 ° with respect to tire circumferential direction, groove width
20mm.

Downward right groove; angle β = 90 ° with respect to tire circumferential direction, groove width
20mm.

Intersection between the left descent groove and the right descent groove: A distance of 8 mm from the tire equator line toward the shoulder. Number of linear kerfs arranged in one block: 2-3 in the tire radial direction.

Comparative tire 2 Tire size 10.00-20 14PR. Tread surface contact area ratio 65%. Groove angle at the center in the tire width direction: Left downward groove; Angle α = 35 ° with respect to tire circumferential direction, groove width
5.5mm.

Downward right groove; angle β = 40 ° with respect to tire circumferential direction, groove width
8mm.

Groove angle at shoulder: Downward left groove; Angle α = 35 ° with respect to tire circumferential direction, groove width
20mm.

Downward right groove; angle β = 40 ° with respect to tire circumferential direction, groove width
20mm.

Intersection between the left descent groove and the right descent groove: A distance of 8 mm from the tire equator line toward the shoulder. Number of linear kerfs arranged in one block: 2-3 in the tire radial direction.

Comparative tire 3 Tire size 10.00-20 14PR. Tread surface contact area ratio 65%. Groove angle at the center in the tire width direction: Left downward groove; Angle α = 35 ° with respect to tire circumferential direction, groove width
13mm.

Downward right groove; angle β = 40 ° with respect to tire circumferential direction, groove width
14mm.

Groove angle at shoulder: Downward left groove; Angle α = 90 ° with respect to tire circumferential direction, groove width
13mm.

Downward right groove; angle β = 90 ° with respect to tire circumferential direction, groove width
14mm.

Intersection between the left descent groove and the right descent groove: A distance of 8 mm from the tire equator line toward the shoulder. Number of linear kerfs arranged in one block: 2-3 in the tire radial direction.

Comparative tire 4 Tire size 10.00-20 14PR. Tread surface contact area ratio 65%. Groove angle at the center in the tire width direction: Left downward groove; Angle α = 35 ° with respect to tire circumferential direction, groove width
5.5mm.

Downward right groove; angle β = 40 ° with respect to tire circumferential direction, groove width
8mm.

Groove angle at shoulder: Downward left groove; Angle α = 90 ° with respect to tire circumferential direction, groove width
20mm.

Downward right groove; angle β = 90 ° with respect to tire circumferential direction, groove width
20mm.

Intersection of the left and right ditch: on the tire equator. Number of linear kerfs arranged in one block: 2-3 in the tire radial direction.

Comparative tire 5 Tire size 10.00-20 14PR. Tread surface contact area ratio 65%. Groove angle at the center in the tire width direction: Left downward groove; Angle α = 35 ° with respect to tire circumferential direction, groove width
5.5mm.

Downward right groove; angle β = 40 ° with respect to tire circumferential direction, groove width
8mm.

Groove angle at shoulder: Downward left groove; Angle α = 90 ° with respect to tire circumferential direction, groove width
20mm.

Downward right groove; angle β = 90 ° with respect to tire circumferential direction, groove width
20mm.

Intersection between the left descent groove and the right descent groove: A distance of 8 mm from the tire equator line toward the shoulder. Number of linear kerfs arranged in one block: One in the tire radial direction.

Evaluation method of braking performance (braking performance on ice, braking performance on snow): Each tire is mounted on all wheels of a large vehicle (2D), and braking is applied at 40 km / h on snowy roads and frozen roads. The evaluation was made based on the distance, and the result was represented by an index with the tire of the present invention being 100. The larger the value, the better the manufacturability.

Drivability evaluation method (hill climbing performance on snow): Each tire is mounted on the driving wheel of a large vehicle (2D), the hill on a snow-covered road is climbed from an initial speed of 20 km / h, and the evaluation is made based on the time required. The result was represented by an index with the tire of the present invention being 100. The larger the value, the better the driveability.

Evaluation method for crack resistance: After mounting each tire on the driving wheels of a large vehicle (2D) and driving 15,000km on a course where braking and driving are frequently performed,
Evaluation was made by measuring the number of cracks generated from each tire, and the results were expressed by an index with the tire of the present invention being 100. The larger this number is, the better.

As is clear from Table 1, the tires of the present invention were Comparative tire 1 (Tread surface contact area ratio 60%), Comparative tire 2 (The groove angle is the same at the center in the tire width direction and at the shoulder), Comparative tire 3 (The groove width is the same at the center portion in the tire width direction and the shoulder portion), the comparative tire 4 (the intersection of the left down groove and the right down groove is on the tire equator), and the comparative tire 5
It can be seen that all the performances are superior to any of the above (the number of kerfs arranged in one block is one).

〔The invention's effect〕

As described above, according to the present invention, in a heavy-load pneumatic bias tire, a left descending groove and a right descending groove are provided on the tread surface so that the intersection of these grooves does not fall on the tire equator line. In order to optimize the groove angle and groove width of the groove, carve two or more kerfs on the surface of the block formed by these grooves, and further to make the tread surface contact area ratio in the range of 63 to 66% In addition, it is possible to sufficiently improve the manufacturing and driving performance on ice and snow roads without implanting spike pins on the tread surface and arranging the sub-groove. The present invention is particularly suitable for a deep groove bias tire called extra heavy tread (EHT).

[Brief description of the drawings]

FIG. 1 is an explanatory plan view showing an example of a tread pattern on a tread surface of a heavy duty pneumatic bias tire of the present invention, and FIG. 2 is a schematic view thereof. 1, 1 '... shoulder part, 2 ... left down groove, 3 ... right down groove, 4, 4' ... calf, M ... intersection, T ... tread surface.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60C 11/12

Claims (1)

(57) [Claims] 1. A plurality of left-down grooves extending from one shoulder to the other shoulder in the tire circumferential direction on the tread surface, and a plurality of right-down grooves extending from the other shoulder to one shoulder. So that the intersection of these left-down grooves and right-down grooves is at a position offset from the tire equator line, and the angles of these two grooves with respect to the tire circumferential direction from the center in the tire width direction to the shoulder respectively. The groove width gradually increases from the center of the tire width direction toward the shoulder, and two or more kerfs are engraved on the surface of the block formed by these grooves in the tire width direction. And a pneumatic bias tire for heavy loads, wherein the contact area ratio of the tread surface is in the range of 63 to 66%.