JPH07237409A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve the running performance on a frozen road by possessing transverse sipes, which divide each block-shaped land, at the block-shaped lands of the tread being divided by a plurality of circumferential grooves and many lug grooves crossing them, and making a plurality of longitudinal slits apart in each division. CONSTITUTION:A tread 1 is constituted by providing a plurality of circumferential grooves 2 (five pieces) at approximately equal intervals and dividing lands together with many lug grooves 3 extending, crossing these circumferential grooves. The land 4 is provided, at the center 5 in its circumferential direction, with a transverse sipe 6 which divides itself into a front block and a rear block, extending in the direction orthogonal to the equator 0, and both blocks are provided with a plurality (four pieces at regular intervals) of longitudinal slits 9 extending in parallel with the equator 0. For this slit 9, there is necessity to retain space at least partially even if the land has received the external force in back and forth direction or right and left direction during running, so it is proper for the slit to be 1-4mm in width and it is desired that the slit should be 3-10mm in length.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire having excellent running performance on ice and snow roads.

[0002]

2. Description of the Related Art A so-called winter tire, which focuses on running on ice and snow roads in winter, has a plurality of circumferentially extending grooves (usually 3 to 5 at substantially equal intervals) on the tread pattern. The block type is generally made up of a land portion that extends from one end of the tread to the other end across the circumferential groove of the tread and is divided by a number of lug grooves. By providing a plurality of laterally extending sipes extending in the axial direction on the land portion, consideration has been given particularly to slip resistance during driving and braking on an icy road. It is because of the expectation for the edge effect due to the corner portion formed by the transverse sipe and the ground contact surface which are orthogonal to the driving / braking force acting thereon.

[0003]

When a large number of lateral sipes are arranged in order to enhance the edge effect of the land portion of the tread, the edge effect itself is surely increased, but the land portion subdivided by the sipes is the circumferential direction. The rigidity is reduced accordingly. As a result, the edge component of the heavy-duty tire increases, so that the frictional force with the road surface increases, but the deformation during braking / driving increases, resulting in block breakage. Further, in the case of tires for passenger cars, the actual ground contact area decreases due to the collapse of the block, and although the edge component increases, the frictional force with the road surface decreases on the contrary. In addition, steering stability on a dry road surface may be deteriorated.

On the other hand, the lateral sipe is effective in improving the driving / braking characteristics of the tire when used properly, but is not so effective in the cornering characteristics. Therefore, in order to obtain well-balanced running performance, it is important not only to arrange the lateral sipe but also to improve the cornering characteristics while maintaining the circumferential rigidity of the land portion. The present invention has been made in view of the above, and an object thereof is to provide a tire having excellent running performance on an icy road.

[0005]

SUMMARY OF THE INVENTION The present invention comprises a block-shaped land portion divided by a plurality of circumferential grooves and a number of lug grooves extending across these grooves, the lateral direction dividing the land portion. A pneumatic tire having a tread provided with sipes, characterized in that a plurality of vertically-oriented bag small grooves are provided at intervals in an area divided by laterally-facing sipes in a land portion of the tread. Here, the bag small groove means a small groove which is closed at both ends in the longitudinal direction and extends like a bag in the depth direction.

[0006]

In general, it is said that an amorphous ice layer called a pseudo liquid layer always exists on a road surface frozen in a temperature range of 0 ° C to -6 ° C. In the icy road in such a state, the surface of the icy road is easily melted due to frictional heat generated by traveling, and a water film is generated between the road surface and the land portion of the tread. And it is this water film that is generated that greatly affects the reduction in frictional force. The tire in the present invention has a block-shaped land portion divided by a circumferential groove and a lug groove,
A plurality of vertically oriented bag grooves are provided at intervals in an area separated by a lateral sipe. Therefore, while traveling on the ice road, these lateral sipe and the vertical bag groove break the water film interposed between the road surface and the land portion in the ground contact surface, and mainly take the bag groove to take in water, and This makes it possible to prevent the frictional force from decreasing.

On the other hand, since the block-shaped land portion does not need to be provided with the sipes extending in the lateral direction excessively due to the arrangement of the small groove in the bag, the rigidity in the circumferential direction can be secured, and the block in the heavy load tire and the tire for passenger cars can be secured. The above-mentioned problems such as the reduction of the frictional force are not caused. In addition, when cornering, the vertically oriented small groove groove exerts an edge effect against the lateral force acting on the land. At that time, in both the front and rear areas of the land portion, since the peripheries of the bag small grooves are integrally connected, the collapse of the land portion against the lateral force is suppressed and the surface does not rise.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. 1 is a partial plan view of a tread showing a first embodiment of the present invention, and FIG. 2 is an enlarged view of a land portion in FIG. In FIG. 1, a tread 1 is formed by providing a plurality of circumferential grooves 2 (five) at substantially equal intervals and partitioning a land portion 4 with a large number of lug grooves 3 extending across these circumferential grooves. In the example shown in FIG. 1, the grooves 2 and 3 are shown as straight grooves, but when applied in practice, a zigzag circumferential groove is used, or a straight or curved lug that intersects at an angle to the circumferential direction is used. Of course, it is possible to divide the block-shaped land portions of various shapes by using the groove.

The land portion 4 is provided with a lateral sipe 6, which extends in a direction perpendicular to the equatorial plane O in this embodiment and divides into a front area and a rear area, in a central portion 5 in the circumferential direction thereof, and the equator is provided in both areas. A plurality of (four at regular intervals) vertically oriented bag grooves 9 extending parallel to the plane O are provided. The bag groove 9 is required to hold at least a part of the void even when the land portion receives an external force in the front-back direction and the left-right direction in the ground contact surface during traveling, and the width w for this is 1 to 4 mm. The range is appropriate. If the width exceeds 4 mm, the ground contact surface area of the land portion due to the provision of a plurality thereof is excessively reduced, which is not preferable. The above width w
It is desirable that the width of the sideways sipe that closes when an external force is applied is larger than the width of the sideways sipe even if the value is decreased. Next, the bag groove length l
Is preferably 3 to 10 mm, though it depends on the width w. Length l is 3
If the length is shorter than mm, a large number of small bag grooves will be provided more than necessary, which will limit the productivity in tire manufacturing.
On the other hand, when it exceeds 10 mm, the central portion in the longitudinal direction is closed when a lateral force is applied, which is not preferable from the aspect of space retention.

Next, the axial distance i from the block end and the intervals i and j between the bag small grooves are preferably 3 to 10 mm. The respective circumferential distances k and n from the longitudinal end of the bag groove to the circumferential end of the land portion and the lateral sipe are 1 to 5 mm. distance
For k and n less than 1 mm, the front and rear areas of the land 7,
Perimeter 10 that extends along 8 lug grooves and sideways sipes
It becomes difficult to maintain the rigidity, and if it exceeds 5 mm, the effect of the bag groove is reduced correspondingly, which is not preferable. The depth of the bag small groove and the depth of the lateral sipe are appropriately in the range of 25 to 75% of the depth of the groove 2.

FIG. 3 is a plan view of a land portion showing a second embodiment of the present invention. The feature of this embodiment is alternately extend to the central portion 5 of the land portion 4 from the land portion side end of the left and right in the axial direction, by approximately one-third of each other block O - Ba - lateral sipe ₆₁ ending in wrapped point , 6 ₂ to divide the front and back areas,
The point is that vertical bag small grooves 9 ₁ and 9 ₂ of _two lengths are provided in those areas. In this case the circumferential space - the wider portion of the scan, the longer the bag minor groove 9 ₁ a single, are arranged side by side three short Fukuromizo 9 ₂ the narrow portion.

FIG. 4 is a plan view of a land portion showing a third embodiment of the present invention. The feature of this embodiment is that the land portion 4 is divided into parallelograms by the circumferential groove and the slanted lug groove, and the trapezoidal front and rear area is further divided into two by the lateral sipe 6.
7 and 8 are provided with longitudinal bag grooves 9 ₁ , 9 ₃ and 9 ₂ having different lengths such as long, medium and short depending on the space in the circumferential direction.

FIG. 5 is a plan view of a land portion showing a fourth embodiment of the present invention. The feature of this embodiment is that a relatively short and wide chevron-shaped land portion 4 is divided into front and rear regions 7 and 8 by a V-shaped lateral sipe 6 that extends along the shape of the land portion, and the chevron-shaped land portion 4 is divided along these shapes. The vertical groove for each bag is provided. In this case, _two short bag small grooves 9 ₂ are arranged on both sides of the land, and a short and relatively wide bag small groove 9 ₄ is provided at the center.

FIG. 6 is a plan view of a land portion showing a fifth embodiment of the present invention. The feature of this embodiment is that the front and rear areas of the parallelogram land portion 4 with both sides inclined are provided with vertical bag groove 9 ₅ inclined at a shallow angle α (α = 25 °) with respect to a line extending parallel to the equatorial plane. There are four staggered arrangements in the axial direction. The angle α shall apply within a range not exceeding 45 °.

FIG. 7 is a plan view of a land portion showing a sixth embodiment of the present invention. The feature of this embodiment is that a modified chevron-shaped land portion 4 is provided with a _V -shaped sipe, and the longitudinal front bag groove 9 ₅ is inclined at a shallow angle α in the divided front and rear areas 7 and 8.
If there bags small groove 9 ₆ inclined in the reverse direction at an angle β to the point where the addressed two right and left arrangement. In this case, α = β = 45 °.

FIG. 8 is a plan view of a land portion showing a seventh embodiment of the present invention. The feature of this embodiment is that two lateral sipes for dividing the land portion are provided in parallel in the central portion 5 of the land portion 4 at intervals, and four bag small grooves are arranged in each of the front and rear areas.

[0017]

[Effect] In order to confirm the effect of the tire of the present invention thus constituted, the tread shown in FIG. 1 was applied to 11R22.5 size to make a prototype, and the braking performance on ice, cornering performance on ice and block chipping property were evaluated. did. In performing the test, the width of the vertical bag groove of the tire according to the present invention is set to 1
mm is tire A, and the width of the bag groove is 2.5 mm
The tire B is a tire B, and the tires C and 3 each have one lateral sipe that is the same as the lateral sipe 6 in the center of the front and rear areas of the land, without using the bag groove as a comparative tire.
A tire D having only one sipe 6 was used. For tires A, B, C and D, the circumferential length of the land portion (block) is 24.5 mm, the land width is 30.0 mm, the circumferential groove depth is 20 mm, and the lug groove depth is 15 mm. Moreover, the depth of the sipe and the small groove of the bag was set to 10 mm. For the portion other than the tread portion, the carcass has a structure in which one sheet of steel cord radial arrangement ply and a rubberized layer of steel cord which is arranged as a belt layer at a shallow angle with respect to the tire equatorial plane are laminated. Was commonly applied.

The tire thus constructed was mounted on an actual vehicle, and a braking and cornering test was conducted on ice.
As a test condition, in the braking test, a sudden brake was applied while going straight at a speed of 20 km / h, and the distance from the point where the brake was applied to the stop point was measured. Also, the cornering test is
A disk-shaped course having a radius of 50 m was turned, and the maximum orbital speed (average speed during one revolution) that could be taken out was measured. In the block break test, the presence or absence of a block break in the tire was evaluated after the actual vehicle was run for 20,000 km. The test results are shown in Table 1 as an index based on tire D.

[Table 1]

As shown in Table 1, tires A and B according to the present invention
Are superior to the comparative tires C and D.

[Brief description of drawings]

FIG. 1 is a partial plan view of a tread according to the present invention.

2 to 7 are plan views of respective land portions showing the first to sixth embodiments.

[Explanation of symbols]

 1 tread 2 circumferential groove 3 lug groove 4 land 5 center 6 lateral sipe 7 front area 8 rear area 9 vertical bag groove

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[Procedure amendment]

[Submission date] September 30, 1994

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a plan view of a tread according to a first embodiment of the present invention.

FIG. 2 is an enlarged view of a land portion in the first embodiment.

FIG. 3 is a plan view of a land portion in the second embodiment.

FIG. 4 is a plan view of a land portion in the third embodiment.

FIG. 5 is a plan view of a land portion according to the fourth embodiment.

FIG. 6 is a plan view of a land portion in the fifth embodiment.

FIG. 7 is a plan view of a land portion according to the sixth embodiment.

FIG. 8 is a plan view of a land portion according to the seventh embodiment.

[Explanation of symbols] 1 tread 2 circumferential groove 3 lug groove 4 land 5 central part 6 lateral sipe 7 front area 8 rear area 9 vertical bag small groove

Claims (1)

[Claims] 1. A tire having a tread including a plurality of circumferential grooves and a block-shaped land portion divided by a plurality of lug grooves extending across these grooves, and having a lateral sipe dividing the land portion. A pneumatic tire comprising a plurality of vertically oriented bag small grooves provided at intervals in a region divided by a lateral sipe in the land portion of the tread.