JPH0825918A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve heel-and-tow wear resistance while maintaining traveling performance on an icy road. CONSTITUTION:In a pneumatic tire, the block surface of which is provided with at least two sipings 10 extended at an angle of 88-90 deg. to the tire circumferential direction, each siping 10 is disposed at an angle beta in a range of 92-94 to the block surface 5, and the groove bottom 11 is inclined toward the later arrival side. In the first arrival wall 6 of a block, the groove bottom edge 13A is positioned on the first arrival side, and in the later arrival wall 7, the groove bottom edge 13A is positioned on the later arrival side. In the circumferential cross section, an angle r1 between the first arrival wall 6 and a tire radius line R1, an angle r2 between the later arrival wall 7 and a tire radius line R2, and the angle beta of the siping are to satisfy beta-90 deg.<=r2<r1<30 deg..

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of improving wear resistance, particularly heel and toe wear resistance, while maintaining running performance on icy and snowy roads.

[0002]

2. Description of the Related Art A so-called studless tire, which has improved running performance on ice and snow, mainly adopts a block pattern in which a tread surface is divided into a plurality of blocks, and the block has a narrow groove width. A plurality of sipings are spaced along the tire axial direction, and the edges thereof increase the coefficient of friction with the road surface.

As is apparent from FIG. 4, which is a partially enlarged view of a circumferential cross section of the block parallel to the equatorial plane of the tire, the block a has a substantially trapezoidal cross section and a wall surface c facing the lateral groove b.
In general, the angles γ1 and γ2 formed by 1 and c2 and the tire radial line d are set to be equal, and the angle β formed between the block surface e and the siping groove f is set to about 90 °.

[0004]

By the way, since the rotation speed of the ground contact portion of the tire tread becomes slower than the traveling speed of the road surface during braking, as shown in FIG. Shearing force F facing backward
Works. Therefore, in the block of the block pattern described above, when the tire rotates, the block a
The first-arriving portion g that first arrives on the road surface tends to float up from the road surface as it is rotated by the shearing force F, and the ground contact pressure of the second-arriving portion h that arrives later on the road surface of the block a becomes large.
This causes so-called heel-and-toe wear, in which the amount of wear of the rear landing portion h is larger than that of the first landing portion g,
This will deteriorate the ground contact property of the block surface and will significantly deteriorate the running performance on ice and snow roads.

As a result of intensive studies conducted by the present inventors in view of the above problems, the angles γ1 and γ2 formed by the wall surface of the block facing the lateral groove and the tire radial line and the block surface and the siping groove are formed. By prescribing the angle β formed with f in relation to each other, the rigidity of the first-arriving portion of the block is increased while maintaining the running performance on the snowy road, and the lifting of the first-arriving portion from the road surface during braking is suppressed. That is, the present invention has been completed. That is, it is an object of the present invention to improve wear resistance, more specifically heel and toe wear resistance, while maintaining running performance on ice and snow roads.

[0006]

The present invention provides a tread surface, a plurality of substantially rectangular block surfaces, and a plurality of vertical grooves extending in the tire circumferential direction and lateral grooves extending substantially in the tire axial direction. It is divided into blocks having a first-arrival wall surface that first reaches the road surface when the tire rotates facing the lateral groove, and a second-arrival wall surface that later arrives on the road surface, and extends on the block surface at an angle of 88 to 90 ° with respect to the tire circumferential direction. A pneumatic tire provided with at least two sipes, wherein the siping has a range of 92 ° to 94 ° with respect to the block surface from a block surface to a groove bottom of the siping in a circumferential cross section parallel to the tire equatorial plane. Angle β of the groove bottom, the groove bottom is inclined toward the rear-end side, the first wall surface of the block has the groove bottom edge positioned on the first side, and the rear-end wall surface is the groove bottom edge. On the side It causes the location in the circumferential cross section, arrival wall makes with the tire radial line angle γ1
And the angle γ2 formed by the rear wall surface with the tire radius line and the siping angle β satisfy the following equation. β-90 ° ≦ γ2 <γ1 <30 °

[0007]

According to the present invention, the siping has an angle β in the range of 92 ° to 94 ° with respect to the block surface from the block surface to the groove bottom of the siping in the circumferential cross section parallel to the tire equatorial plane, and By inclining the groove bottom toward the rear end side, it is possible to increase the thickness of the front end wall surface and the root portion of the front end portion sandwiched by siping, and to increase the rigidity of the front end portion.

The first wall surface of the block has a groove bottom edge on the first side, and the rear wall surface has the groove bottom edge on the rear side. By setting the angle γ1 formed with the tire radial line and the angle γ2 formed by the rear wall surface with the tire radial line to be γ2 <γ1, the rigidity of the first-arrival portion is increased as compared with the rear-attached portion, and the angle β of the sipe is set. The rigidity of the first-arrival part can be further enhanced in combination with the regulation of.

The angle γ1 formed by the first wall surface and the tire radius line is smaller than 30 °. This angle γ1
Is 30 ° or more, the interval pitch between adjacent blocks becomes large in order to secure a constant lateral groove depth,
The number of blocks in one tire, and consequently the number of edges of siping, decreases, resulting in poor running performance on ice and snow roads.

The angle γ2 formed by the rear wall surface and the tire radius line is β-90 ° or more. This angle γ2 is β
When the angle is smaller than −90 °, the thickness of the root portion of the trailing portion sandwiched between the trailing wall surface and the siping becomes thinner than the block surface position, and cracks occur due to the shearing force due to driving and braking. It must be maintained parallel to the siping angle.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a developed tread pattern of the pneumatic tire of the present invention. A plurality of vertical grooves 2 extending in the tire circumferential direction, four vertical grooves 2 in this example, and a lateral groove 3 extending approximately in the tire axial direction are ...
The tread surface 4 is formed as a block pattern by dividing the tread surface 4 into a plurality of blocks 9.

The plurality of blocks 9 have a block width BW.
The first-arriving first-arriving road surface when the tire rotates while facing a block surface 5 having a substantially rectangular shape having a tread width TW of about 13 to 18% and a block length BL of about 17 to 22%. It has a wall surface 6 and a rear wall surface 7 to be mounted later on the road surface.
At least two sipes that extend at an angle of ~ 90 ° 1
0 ... is provided.

As described above, by providing a plurality of sipings 10 substantially along the tire axial direction, the friction coefficient can be increased by the edge effect of the sipings on the ice and snow road, and the running performance can be improved.

In the present embodiment, the siping 10 is composed of three pieces which divide the block surface 5 into four substantially equal parts, and along the tire equator C as shown in FIG. 2 which is a cross section taken along the line AA 'of FIG. In the circumferential cross section parallel to the cut tire equatorial plane, from the block surface 5 to the sipe groove bottom 11, an angle β in the range of 92 to 94 ° with respect to the block surface 5, and the sipe groove bottom 11 is attached to the rear part. Leaning towards 12.

By thus inclining the groove bottom 11 of the siping toward the rear end portion 12 of the block 9, the root thickness of the front end portion 14 of the block 9 sandwiched between the front end wall surface 6 and the siping 10 is increased. , Its rigidity can be increased.

If the angle β is less than 92 °, the rigidity of the first-arrival part 14 cannot be improved, while the angle β is 94 °.
If it exceeds the range, cracks occur at the groove bottom of the siping when the tire is taken out from the circumferentially divided mold after the tire molding step, which is not preferable. The groove depth of the siping 10 is preferably about 50 to 70% of that of the lateral groove 3 in order to ensure traveling performance on ice and snow roads.

The first wall surface 6 of the block is the bottom edge 1 of the groove.
By arranging 3A on the first-arrival side with respect to the groove upper edge 13B, the rigidity of the first-arrival part 14 can be increased in combination with the inclination angle β of the groove bottom of the siping. Similarly, the rear wall surface 7 of the block locates the groove bottom edge 13A on the rear side of the groove upper edge 13B to maintain the rigidity of the block portion on the rear side appropriately.

The first wall surface 6 and the second wall surface 7 are
Tire center (not shown) in the circumferential section of the tire
And the tire radial lines R1 and R2 that connect the groove upper edge 13B with
The angles γ1 and γ2 formed by and satisfy the following relationship in relation to the sipe angle β. β-90 ° ≦ γ2 <γ1 <30 °

That is, the first-arrival wall surface 6 has the tire radius line R
The angle γ1 formed with 1 is smaller than 30 °. If this angle γ1 is 30 ° or more, as described above, in order to secure a constant lateral groove depth, the pitch between adjacent blocks becomes large, and the number of blocks in one tire, and thus the number of edges of siping. Is reduced, resulting in poor running performance on ice and snow roads.

The rear wall surface 7 and the tire radius line R2
The angle γ2 formed by and is set to β-90 ° or more. When this angle γ2 becomes smaller than β-90 °, the thickness of the root portion of the rear attachment part 12 sandwiched between the rear attachment wall surface 7 and the siping 10 becomes thinner than the block surface, and cracking occurs due to shearing force due to driving and braking. Is likely to occur.

Further, the first-arrival wall surface 6 has a tire radius line R1.
The angle γ1 formed by the rear wall surface 7 is larger than the angle γ2 formed by the rear wall surface 7 with the tire radius line R2. Thus, the angle γ1
Is set to be larger than γ2 to increase the rigidity of the first-arrival portion 14 with respect to the rear-end portion 12 of the block 9, and the first-arrival portion 14 of the block during braking is lifted from the road surface by the shearing force F as shown in FIG. Can be suppressed, and the ground contact pressure on the block surface can be made substantially uniform even during the braking, and heel and toe wear can be reduced.

The above specified values are values in a normal state in which a pneumatic tire is assembled on a specified rim and filled with a normal internal pressure.

(Specific example) Tire size is 5.60R13
Further, the tire having the block pattern shown in FIG. 1 was prototyped by changing the angles β, γ1, and γ2 variously (Examples 1 to 6), and the performance was tested. Incidentally, a tire (comparative example) having a configuration other than that of the present application and β
A conventional tire (conventional example) in which 90 ° and γ1 = γ2 = 10 ° were also tested and their performances were compared.

The test was conducted in the following manner. 1) Braking performance on ice We measured the braking distance until the vehicle stopped while running a test road surface formed on an ice plate at a speed of 40 km / H and applying a sudden brake. The larger the value, the better the braking performance.

2) Braking Performance on Snow A test road on a snowy road surface was run at a speed of 40 km / H, and braking and evaluation were performed according to the above-mentioned braking performance on ice.

3) Heel and toe wear durability performance A test tire was mounted on the front wheels of an all-wheel drive vehicle, and on the test course, the vehicle was decelerated at a peak maximum of 0.45G every 800m at 100km / h, and this was repeated 500km. After running, the difference in the amount of wear at both edges of the block in the circumferential direction was measured, and displayed as an index with the conventional example being 100. The higher the value, the less the heel and toe wear and the better. The test results are shown in Table 1.

[0027]

[Table 1]

As a result of the test, each of the examples is a conventional example,
It was confirmed that the uneven wear resistance was improved while maintaining the running performance on ice and snow, especially the braking performance, as compared with the comparative example.

[0029]

As described above, the pneumatic tire of the present invention is
It is possible to reduce the occurrence of uneven wear such as heel-and-toe wear that deteriorates ground contact while maintaining snow running performance.

[Brief description of drawings]

FIG. 1 is a plan view showing a developed tread surface of a tire showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA ′ in FIG.

FIG. 3 is a side view for explaining the operation of the present invention.

FIG. 4 is a sectional view for explaining a block in a conventional block pattern.

FIG. 5 is a side view for explaining the operation of the conventional block.

[Explanation of symbols]

 2 Vertical groove 3 Horizontal groove 4 Tread surface 5 Block surface 6 First-arrival wall surface 7 Last-arrival wall surface 9 Block 10 Siping 11 Siping groove bottom 12 Rear-end portion 13 Groove bottom edge 14 First-arrival portion

Claims (1)

[Claims] 1. A tire tread with a plurality of vertical grooves extending in the tire circumferential direction and lateral grooves extending substantially in the tire axial direction, with the tread surface facing a plurality of substantially rectangular block surfaces and the lateral grooves. It is divided into blocks having a first-arrival wall surface that arrives first on the road surface and a second-arrival wall surface that arrives later on the road surface, and at least two sipes extending at an angle of 88 to 90 ° with respect to the tire circumferential direction are provided on the block surface. A pneumatic tire, wherein the siping has an angle β in the range of 92 ° to 94 ° with respect to the block surface from the block surface to the groove bottom of the siping in a circumferential cross section parallel to the tire equatorial plane, and With the front end wall surface of the block, the groove bottom edge is located on the first end side, and the rear end wall surface, the groove bottom edge is located on the rear end side, In the circumferential cross-section, the angle γ1 of arrival wall makes with the tire radial line, an angle γ2 which late-arriving wall makes with the tire radial line
And the angle β of the siping satisfy the following expression. β-90 ° ≦ γ2 <γ1 <30 °