JP3532995B2 - Studless pneumatic tires - Google Patents

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art Spikes protruding from the surface of a tread,
Since the use of spiked tires has been banned to eliminate dust pollution caused by studs, various developments have been made with the aim of developing tires that do not have spikes and have excellent running performance on snowy and snowy roads. These are collectively called studless tires. As a common feature of this studless tire, the tread surface is divided into a number of blocks,
Each of the divided blocks is provided with a large number of vertical lateral sipes extending straight in the depth direction.
Blocking the land of the tread improves grip on snow, and subdividing the blocks by lateral sipes improves the coefficient of friction on the ice (edge effect) due to the numerous block corners formed by the subdivisions. It was intended.

[0003]

The tread having such a structure requires a more precise control of the latter from the viewpoint of safety in driving and braking when traveling on ice, which is particularly slippery, regardless of the performance on snow. Since the lateral sipes to the block are simply provided vertically, there is no change in the edge effect when the driving force and the braking force in the opposite directions are applied, and the frictional force on the ice during braking is insufficient, that is, the ice burn. Accidents due to the lack of braking on the eroded streets are endless. The present invention has been made in view of the above problems, and is provided with a tread including a block having a plurality of sideways sipes, and when an external force that opposes the direction orthogonal to the sipes acts, blocks corresponding to those forces. It is an object of the present invention to provide a studless pneumatic tire having different edge effects.

[0004]

SUMMARY OF THE INVENTION The present invention includes a plurality of main grooves extending in the circumferential direction and a block-shaped land portion divided by a large number of lug grooves intersecting with the main grooves, each of which is a plurality of land portions. In the tire provided with the tread having the lateral sipe, the sipe extends substantially perpendicularly to the surface of the land portion and is located close to the first vertical portion and the second end portion on the other end side.
Connect the vertical part and both vertical parts to the first vertical part
The studless pneumatic tire is characterized in that the sipe has a bent portion inclined to the side of, and the sipe arranged in the land portion has a different tilt angle of the bent portion.

The tread includes a block-shaped land portion having at least three lateral sipe arranged side by side, and the refraction inclination angle is sequentially increased or decreased from one of the sipe.
That it is preferable.

[0006]

According to the present invention, a plurality of lateral sipe provided on the block-shaped land portion is provided with a first vertical portion which extends substantially perpendicularly to the surface of the land portion and is located close to the surface, and a first vertical portion which is located on the other end side. 2 It consists of a vertical part and a bent part that connects both vertical parts and is inclined to one side. The sipe arranged on the land part is provided so that the tilt angle of the bent part is different. Therefore, with respect to the shearing force acting on the block in the direction orthogonal to the sipe, the direction following the inclination of the sipe bending part has a greater rigidity than the direction against the inclination, and therefore a large shearing force is applied. There is little loss of edge effect when is applied. Therefore, by using the tire by designating the rotation direction so that the braking force acts in a direction that follows the inclination of the sipe refraction portion during braking, effective ice running performance can be obtained.

In this case, if at least three lateral sipes are arranged on the block-shaped land portion and the refraction inclination angle is sequentially changed from one of the sipes, the refraction portion and the second refraction portion in the sipes having the maximum refraction inclination angle are arranged. Since the shear rigidity is further improved by receiving the support of the enlarged part of the land part formed by the vertical part, even when a large braking force acts on the moment, only the flexion of the land part is advantageously suppressed,
It is possible to obtain an effective edge effect. On the other hand, the driving force in the opposite direction is always mildly applied, so that it is not necessary to consider only the softness of the land portion, so that the loss of the edge effect does not substantially occur.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given below with reference to the drawings. 1a is a plan view of a tread showing an embodiment of the present invention, and FIG. 1b is a sectional view taken along the line AA in FIG. 1a. In the present invention, the studless tire includes a plurality of main grooves 2 extending in the circumferential direction and a block-shaped land portion 4 divided by a large number of lug grooves 3 intersecting with the main grooves, and each of the land portions 4 has a plurality of laterally extending sides. A tire with a tread 1 having a sipe 5,
The sipe 5 includes a first vertical portion 6 that extends substantially perpendicularly to the land surface F and is located close to the surface F, and a second end portion 2
Vertical part 7 and a bent part that connects both vertical parts and is inclined to one side
It is characterized in that the inclination angle of the refraction portion is different between the sipes 5 arranged in the land portion 4.

Although not shown, the studless tire according to the present invention has a crown portion provided with a tread 1 straddling the left and right side walls and both side walls and connected in a toroidal manner, and one side wall is provided. From the other side through the crown, nylon,
A carcass consisting of at least one fiber cord radial ply (typically two) represented by polyester, or one steel cord radial ply, and placed between the carcass and the tread 1. Known structures reinforced by a non-stretchable belt layer including a plurality of steel cord layers can be applied.

In the embodiment shown in FIG. 1a, the tread 1
Is one on the equatorial plane O and one on each side of it.
Are arranged in parallel with each other, and lug grooves 3 intersecting with these main grooves are provided at a predetermined interval in the circumferential direction, so that the main grooves 2
And the land part 4 of the independent block is divided between the main groove 2 and the tread edge E. The axial width of the land portion 4 is wider in the so-called shoulder block facing the tread edge. In FIG. 1a, both the main groove 2 and the lug groove 3 are straight, but the main groove 2 is a known groove such as a zigzag shape or a crank shape which is continuous in the circumferential direction with a predetermined amplitude on the left and right. Similarly, the lug groove 3 may be a crank-shaped groove, a V-shaped groove, or the like.

Next, a lateral sipe to be installed on the land,
In this example, the rectangular land 4 has three lateral sipes 5
Are provided at equal intervals. The sipe 5 corresponds to approximately 1/3 of the depth d _S , the first vertical part 6 close to the land surface F, the second vertical part 7 occupying the bottom side of the sipe, and the bending part connecting them. Consisting of 8. The refraction portion 8 is inclined to one side (on the right side in FIG. 1b), and the inclination angles are in the relationship of α>β> γ. Since the sipe has the bending portion 8 in this way, the deformation of the land portion when a shearing force acts on the land portion in the direction of the arrow A is significantly reduced by the support of the enlarged portion 9 formed by providing the bending portion. Of.

The offset 10 according to the maximum inclination angle α of the second vertical portion 7 with respect to the first vertical portion 6 is in the range of 3 to 5 mm, and the offset amount is gradually reduced from this position in correspondence with the angles β and γ. Is preferred. On the other hand, the sipe depth d _S is preferably 70 to 100% of the lug groove depth d _G , and the sipe depth d _S
Are not necessarily all the same as shown in FIG. 1b, but may be provided deeper within the above-mentioned depth range, for example, as the inclination angles α to γ are smaller.

In plan view (FIG. 1a), the extension of the sipe 5 is used not only for straightening but also for zigzag, and one end of the sipe does not cross the land 4 unlike the sipe shown in FIG. It is also possible to provide dead end sideways sipe staggered in a staggered manner, or to use cross sipe and dead end sipe together.

[0014]

[Effect] In order to confirm the effect of the tire of the present invention thus constituted, in the point of using the sipe extending vertically in the depth direction in the tire of the example of 185 / 70R13 size using the tread shown in FIG. Only the tires of Comparative Examples different from each other were used, and an actual vehicle driving on ice and a braking test were performed and evaluated.
In this case, in the tire of the example, the sipe depth d _S and the lug groove depth d _G are 8 mm and 9.5 mm, respectively, and the sipe offset 10 is set in the descending order of the inclination angles α to γ of the bending portion. 3
, 2, 1 mm.

The test tire was assembled on a 13 × 5 1 / 2J rim, and 1.
After filling the internal pressure of 9 Kgf / Cm ² , the driving test was carried out at full speed while driving the special ice course at a speed of 20 Km / H, and the time required to run a straight distance of 50 m from this acceleration point was used. It was measured. In the braking test, a brake was applied while the vehicle was traveling straight at a speed of 25 km / h (locked state), and the distance from that point to the stop was measured. The measurement results are each converted into the reciprocal number and shown in Table 1 by an index based on the tire of the comparative example.

[0016]

[Table 1]

[Brief description of drawings]

FIG. 1A is a plan view of a tread showing an embodiment of the present invention. (B) AA sectional view in FIG.

[Explanation of symbols]

1 dread 2 Circumferential main groove 3 lug groove 4 Land 5 Sideways sipe 6 1st vertical section 7 Second vertical part 8 Refraction part

Claims (2)

(57) [Claims] 1. A tread including a plurality of circumferentially extending main grooves and a block-shaped land portion divided by a plurality of lug grooves intersecting with the main grooves, each land portion having a plurality of lateral sipe. In a tire that
A first vertical portion extending substantially perpendicularly to the surface of the land portion and located close to the surface, a second vertical portion on the other end side, and both vertical portions are connected to each other and inclined to one side with respect to the first vertical portion . A studless pneumatic tire comprising a bent portion, wherein the angle of inclination of the bent portion is different between sipes lined up on the land. 2. The tread includes a block-shaped land portion having at least three lateral sipe arranged side by side, and the refraction inclination angle is sequentially increased or decreased from one of the sipe .
Studless pneumatic tire according to claim 1, wherein that.