JP2003165311A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reconcile and improve wandering performance and on-ice performance. <P>SOLUTION: This pneumatic tire is provided with a shoulder block row R0 constituted of shoulder blocks 10 having a plurality of sipings 20. A tread grounding width Ws is made 0. 8 to 0.9 times of a tire sectional width Wt. A width W0 of a tire shaft direction of each shoulder block 10 is made substantially the same. In the shoulder blocks 10 arranged in a peripheral direction, a side edge 10a on the shoulder side and a side edge 10b on a tire equator side are arranged by being positionally deviated in the tire shaft direction. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire suitable as a studless tire and capable of improving the performance on ice while exhibiting excellent wandering performance.

[0002]

2. Description of the Related Art In a studless tire, generally, a large number of sipings are formed in a block pattern having excellent traction property, and the adhesion frictional force mainly due to the contact between the block surface and the ice surface and the road digging caused by the edge of the block or the siping By the action of frictional force (edge effect),
The performance on ice is secured.

In recent years, in order to further improve the performance on ice, the tread contact width is set to 0.
Widening has been performed to increase the range to 8 to 0.9 times. This is because by increasing the tread contact width, it is possible to increase the contact area and increase the adhesive frictional force, and further increase the contact area to increase the number of sipes formed.
This is because it is possible to dig up the road surface and increase the frictional force.

[0004]

However, the widening of the tread ground contact width causes the flattening of the contour of the tread, that is, the increase of the tread radius, which causes a problem that the wandering performance is deteriorated.

Particularly, in recent years, in order to increase the actual ground contact area, as described in Japanese Patent Laid-Open No. 2001-105808,
It has been proposed to employ a rib block pattern in which the block rows are replaced by circumferential ribs in the central region of the tread. However, in such a case, the adoption of this circumferential rib increases the lateral rigidity of the tread central region,
The deterioration of the wandering performance becomes more remarkable.

Therefore, according to the present invention, the shoulder block row along the tread ground contact edge is constituted by shoulder blocks having substantially the same width in the tire axial direction, and the shoulder blocks are arranged to be displaced inward and outward in the axial direction of the tire. Based on this, it is an object of the present invention to provide a pneumatic tire capable of exhibiting excellent wandering performance while increasing the tread contact width and achieving both wandering performance and ice performance.

[0007]

In order to achieve the above object, the invention of claim 1 of the present application is provided with a shoulder block row in which shoulder blocks are arranged in the circumferential direction on the tread grounding edge side in the tread portion, and each shoulder block is provided. A pneumatic tire in which a plurality of sipings are provided in a block, wherein a tread ground contact width Ws is 0.8 to 0.9 times the tire cross-sectional width Wt, and each of the shoulder blocks has a width in the tire axial direction substantially. The shoulder blocks which are the same and are arranged in the circumferential direction are characterized in that the shoulder side edges and the tire equator side edges are displaced in the tire axial direction.

According to the invention of claim 2, the shoulder side edge of one shoulder block and the shoulder side edge of a shoulder block adjacent to this shoulder block in the circumferential direction are displaced in the tire axial direction. The quantity d1 is
The tire equatorial side edge of the one shoulder block and the tire equatorial side edge of a shoulder block adjacent to the shoulder block in the circumferential direction are approximately the same as the tire axial deviation amount d2. , And each deviation d
1, d2 are 0.01 to 0.
It is characterized by being 03 times.

Further, in the invention of claim 3, the tread portion has, together with the shoulder block row, an intermediate block row composed of an intermediate block arranged in the circumferential direction between the tire equator and the shoulder block row, Each of the intermediate blocks has substantially the same width in the tire axial direction, and the intermediate blocks lined up in the circumferential direction have their shoulder side edges and tire equator side edges displaced in the tire axial direction. It is characterized by being distributed.

In the invention of claim 4, the shoulder side edge of one intermediate block and the shoulder side edge of the intermediate block circumferentially adjacent to the intermediate block in the axial direction are displaced in the tire axial direction. The amount d3 is substantially the same as the deviation amount d4 in the tire axial direction between the side edge on the tire equator side of the one intermediate block and the side edge on the tire equator side of an intermediate block circumferentially adjacent to the intermediate block. They are the same, and the deviation amounts d3 and d4 are 0.
It is characterized in that it is 01 to 0.03 times.

Further, in the invention of claim 5, the tread portion is 1 / th of the width of the tread portion centered on the tire equator.
It is characterized in that a circumferential rib that extends substantially continuously is provided in the central region of the range of 3.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below.
This will be described together with the illustrated example. FIG. 1 is a cross-sectional view illustrating a case where the pneumatic tire of the present invention is a studless tire, and FIG. 2 is a development view conceptually showing the tread pattern thereof. In FIG. 1, a pneumatic tire 1 includes a carcass 6 extending from a tread portion 2 having a shoulder block 10 to a bead core 5 of a bead portion 4 through a sidewall portion 3 and an inside of the tread portion 2 and an outside of the carcass 6. And a belt layer 7 disposed on the.

The carcass 6 is formed of at least one carcass ply 6A in which carcass cords are arranged at an angle of, for example, 70 to 90 ° with respect to the tire circumferential direction, and in this example, one carcass ply 6A. The carcass ply 6A includes ply folded portions 6b folded around the bead core 5 at both ends of a ply body portion 6a extending between the bead cores 5, 5, and the ply folded portion 6b and the ply body portion 6a.
A bead apex rubber 8 for bead reinforcement extending from the bead core 5 to the outside in the tire radial direction is provided therebetween.

The belt layer 7 has at least two belt plies 7A, 7 in which belt cords are arranged at an angle of, for example, 10 to 35 ° with respect to the tire circumferential direction.
It is formed from B. The belt plies 7A and 7B have a so-called cross structure in which cords cross each other between plies,
As a result, the tread portion 2 has high rigidity and is strongly reinforced.

Further, in this embodiment, the pneumatic tire 1 is
The tread contact width Ws is 0.8 of the tire cross-section width Wt.
The width is expanded to a range of up to 0.9 times, thereby increasing the ground contact area, that is, improving the performance on ice. In order to widen the tread contact width Ws, the radius of curvature RT (so-called tread radius) of the tread contact surface is set to a range of 2 to 10 times the tread contact width Ws to flatten the tread contour shape.

Here, the "radius of curvature RT" means the tread contact edges Te, T on the tread surface in a standard state in which the tire is assembled on the regular rim and filled with the regular internal pressure.
It means the radius of curvature of a single arc passing through three points, e and the equatorial point Ce of the tire. Further, the "tread ground contact width Ws" means the tire outermost edges Te, Te in the tire axial direction of the tread ground surface that can contact the tire in the standard state when a normal load is applied.
Means the width of the space, and this outermost edge Te is the tread ground edge T
I call it e. In this example, the tread ground edge Te is aligned with the side edge 10Aa of the shoulder block 10 by flattening the tread contour shape.

The "regular rim" is a rim defined by the standard in the standard system including the standard on which the tire is based. For example, in the case of JATMA, the standard rim, TR
"Design Rim" for A, or ETRTO
Means "Measuring Rim". The "regular internal pressure" is the air pressure defined by the standard for each tire, and J
Maximum air pressure for ATMA, table for "TRA"
LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES "
If it is ETRTO, the maximum value described in "INFLATION PRES
SURE "but 180kP for passenger car tires
a. Further, the "regular load" is a load defined for each tire in the standard, and is a maximum load capacity in the case of JATMA, and a table "TIRE LOAD LIMITS AT VARI in the case of TRA".
Maximum value stated in "OUS COLD INFLATION PRESSURES", ET
In the case of RTO, it is "LOAD CAPACITY", but in the case of passenger car tires, the load is equivalent to 80% of the above load.

Next, as shown in FIGS. 2 and 3, the tread portion 2 includes a shoulder block row R composed of the shoulder blocks 10 arranged in the circumferential direction on the tread ground edge Te side.
At least 0 is included.

In this example, the shoulder block row R0
In addition, this shoulder block row R0 and tire equator C
And an intermediate block row R1 composed of an intermediate block 11 arranged in the circumferential direction, and a circumferential rib 12 extending substantially continuously in the circumferential direction on the tire equator C side of the intermediate block row R1. A rib block pattern is illustrated. The circumferential ribs 12 are preferably formed in the central region Yc which is a range of 1/3 of the tread ground contact width Ws with the tire equator C as the center in order to ensure straightness on snow.

In this example, by adopting this rib block pattern, the so-called land ratio, which is the ratio of the block surface and the rib surface to the tread ground contact surface, is increased to the range of 60 to 70%, and the tread ground width Ws is increased. Together with the widening, the actual ground contact area is significantly increased to improve the performance on ice.

On the other hand, however, since the above method causes a decrease in wandering performance, in this embodiment, the shoulder block row R0 is configured as follows.

That is, each shoulder block 10 is shown in FIG.
As shown in the enlarged view, the block width W0 in the tire axial direction is
Are substantially the same as each other, so that each block 10
The lateral rigidity of the wheel is made uniform, cornering performance is improved, and uneven wear is suppressed. Note that "the block width W0 is substantially the same" means the ratio of the difference between the width W0max of the widest block and the width W0min of the narrowest block (W
0max-W0min) / W0max is 0.05 or less, that is, 5
It means that the variation of% is allowed.

The shoulder block 10 is composed of an outer shoulder block 10A that is displaced outward in the tire axial direction and an inner shoulder block 10B that is displaced inward. Therefore, the shoulder side edge 10Aa of the outer shoulder block 10A and the tire equator side edge 10
Ab is displaced in the tire axial direction with respect to the shoulder side edge 10Ba of the inner shoulder block 10B and the tire equator side edge 10Bb.

In this way, at least the side edges 10Aa, 10Ba on the shoulder side are not aligned in a straight line and are displaced inward and outward in the tire axial direction, so that an external force applied when riding over a step on the road surface such as a rut. The wandering performance can be improved by suppressing the fluctuation of the vehicle body and steering wheel. Moreover, since the position shift can be the starting point for climbing over a step, it is possible to climb over more easily.

In order to improve the wandering performance, the outer and inner shoulder blocks 10A, 10B are used.
Are preferably arranged alternately in the circumferential direction.

At this time, of the outer and inner shoulder blocks 10A and 10B adjacent to each other in the circumferential direction, one side (for example, outer) side edge 10Aa of the shoulder block 10A and the other (for example, inner) shoulder Side edge 10B on the shoulder side of block 10B)
The amount of deviation in the tire axial direction from a is d1, the side edge 10Ab on the tire equator side of the one shoulder block 10A, and the other shoulder block 10
When the deviation amount in the tire axial direction between B and the side edge 10Bb on the tire equator side is d2, since the block width W0 is substantially the same, the deviation amounts d1 and d2 are also substantially the same. At this time, it is preferable that the deviation amounts d1 and d2 are 0.01 to 0.03 times the tread ground contact width Ws.

This is because the shift amounts d1 and d2 are 0.01
When it is less than × Ws, the improvement effect of the wandering performance cannot be sufficiently exerted, and conversely 0.03 × Ws.
When it exceeds the above range, the groove width between the circumferential rib 12 and the intermediate block 11 and / or the groove width between the intermediate block 11 and the shoulder block 10 becomes too small, and clogging due to snow is likely to occur. This is because the performance on snow tends to be impaired. For the same reason, the shift amount d1,
It is also preferable that d2 is 1.5 mm to 4.5 mm.

Next, in the intermediate block row R1, in order to suppress the influence on the snow performance and uneven wear due to the position shift of the shoulder block row R0, this intermediate block row R1 is similarly formed in each intermediate block row R1. The block widths W1 in the tire axial direction are made substantially the same as each other, and the intermediate block 11 is circumferentially shifted by shifting the shoulder side edge 11a and the tire equator side edge 11b in the tire axial direction. Are arranged.

It should be noted that "the block width W1 is substantially the same" means that the width W1max of the widest block is the same as described above.
Proportion of difference from width W1min of the narrowest block (W1ma
It means that x-W1min) / W1max is 0.05 or less, and thereby, uneven wear is particularly suppressed.

The intermediate block 11 is also composed of an outer intermediate block 11A which is displaced to the outside in the axial direction of the tire and an inner intermediate block 11B which is displaced to the inner side, and the inner and outer intermediate blocks 11A and 11B are also surrounded. Staggered in the direction. At this time, the outer shoulder block 10A and the inner intermediate block 11B do not partially overlap inside and outside in the tire axial direction, and the inner shoulder block 1
It is important that 0B and the outer intermediate block 11A do not partially overlap inside and outside in the tire axial direction.

The outer and inner intermediate blocks 1 adjacent to each other in the circumferential direction.
Of 1A, 11B, the tire shaft between the shoulder side edge 11Aa of one (for example, the outer) intermediate block 11A and the shoulder side edge 11Ba of the other (for example, the inner block 11B). The deviation amount in the direction d3, the deviation amount in the tire axial direction between the tire equator side edge 11Ab of the one intermediate block 11A and the tire equator side edge 11Bb of the other intermediate block 11B.
4, since the block width W1 is substantially the same, the deviation amounts d3 and d4 are also substantially the same. At this time, the deviation amounts d3 and d4 are 0.01 times the tread ground width Ws. .About.0.03 times, and it is particularly desirable to set the deviation amount d1 and the deviation amount 3 to be equal.

As a result, the shoulder block 10 and
The intermediate block 11 and the intermediate block 11 can be uniformly dispersed and arranged, and uneven wear can be suppressed. Further, the groove width between the shoulder block 10 and the intermediate block 11 can be made uniform, and the snow performance can be maintained. Further, due to the positional displacement of the intermediate block 11, the block edge in the circumferential direction functions more effectively, and it can be expected to improve the performance on ice.

The deviation amounts d3 and d4 are 0.01 ×
If it is less than Ws, the above effect cannot be achieved, and conversely 0.03 × W.
When s is exceeded, the circumferential rib 12 and the intermediate block 11 inside
The groove width D between the groove B and the groove B becomes too small, and the snow performance is likely to be impaired, for example, snow is clogged. The groove width D is
From the viewpoint of snow performance, the tread contact width Ws is preferably 0.03 times or more.

Next, it is preferable that the circumferential ribs 12 are arranged on both sides of the tire equator C in order to improve straightness on snow. Also, the total width of the rib width Wr of the circumferential rib 12 is 2 ×
Wr is preferably 0.17 times or more of the tread grounding width Ws from the viewpoint of increasing the actual ground contact area and improving the performance on ice, and is preferably 0.3 times or less from the viewpoint of maintaining the snow performance.

Further, the siping 2 formed on the shoulder block 10, the intermediate block 11 and the circumferential rib 12 is provided.
0 is a so-called open sipe in which both ends of the sipe open at the side edges of the block or rib, and in order to improve the performance on ice, the center line L connecting both ends of the sipe is ± 45 ° or less with respect to the tire axial direction, and further, ± 30 ° or less, further ± 15
It is formed at an angle θ of not more than °.

Although the siping 20 has a straight shape in this example, in order to further enhance the edge effect, as shown in FIG. 4, the siping 20 has a zigzag shape or the like at an intermediate position. It is also preferable to form the meandering portion 20A. As the meandering portion 20A, other saw blades,
Various shapes such as rectangular uneven shape and wavy shape can be adopted.

In addition, in this example, in order to prevent the block rigidity and the rib rigidity from being excessively lowered by arranging a large number of sipings 20, one siping 20 is provided with a shallow bottom portion and a deep bottom portion. The depth is changing.

Further, in the present embodiment, the side edges of the shoulder block 10 in the tire axial direction and the circumferential direction, the side edges of the intermediate block 11 in the tire axial direction and the circumferential direction, and the side edges of the circumferential rib 12 are, in this example, Although a linear shape is disclosed in this example, it is also preferable to form it in a zigzag shape, a sawtooth shape, a rectangular uneven shape or the like in order to further enhance the edge effect, as illustrated in FIG.

Next, the outer shoulder block 10A and the outer intermediate block 11A are adjacent to each other in the tire axial direction, and the inner shoulder block 10B and the outer intermediate block 1 are arranged.
Since 1B is adjacent to each other in the tire axial direction, a pair of the outer shoulder block 10A and the outer intermediate block 11A, and a pair of the inner shoulder block 10B and the outer intermediate block 11B are respectively provided with tread patterns. It can be configured as a pitch element 21 for arranging a variable pitch.

At this time, the block lengths of the shoulder block 10 and the intermediate block 11 in the circumferential direction change based on the pitch length PL of the pitch element 21, but the block shape of each shoulder block 10 is the circumferential direction. The intermediate blocks 11 have substantially the same shape as they have been enlarged or reduced, and the block shapes of the respective intermediate blocks 11 also have substantially the same shape as they have been enlarged or reduced in the circumferential direction. Therefore, the knife blade, which is a mold for forming the siping 20, can be shared, and the tire of the present invention can be manufactured without causing an increase in cost.

Although a particularly preferred embodiment of the present invention has been described above in detail, the present invention is not limited to the illustrated embodiment and can be modified in various modes.

[0042]

EXAMPLES A studless tire of tire size 175 / 80R14 having the structure shown in FIG. 1 and having the tread pattern of FIG. 4 was prototyped according to the specifications of Table 1, and the on-ice performance, wandering performance, and And the uneven wear resistance performance were tested and compared with each other.

(1) Performance on ice: The test tire was subjected to an internal pressure (1
80kpa), rim (14x5J), passenger car (F
F car: 1,800 cc) mounted on four wheels, run on an ice lane in an environment with an air temperature of 0 ° C at a constant speed of 40 km / H, and suddenly brake with a four-wheel lock until the car stops. The reciprocal of the braking distance of is displayed as an index. The index is
Comparative Example 1 was set to 100, and the larger the index value, the better the performance on ice.

(2) Wandering performance: Using the above-mentioned vehicle, the driver performs a sensory evaluation on the rutted road surface provided on the test course and how the steering wheel is taken on the rutted road surface, and the pass criterion is 6 points. Evaluation was made by a 10-point method. The larger the index, the better.

(3) Uneven wear resistance test tires were run on a test drum having a pseudo surface of a dry pavement, and the uneven wear state after running for 1000 km was
Sensory evaluation was conducted visually by an inspector, and evaluation was made by a 10-point method with a pass criterion of 6 points. The larger the index, the better.

[0046]

[Table 1]

[0047]

As described above, according to the present invention, the shoulder block row is composed of shoulder blocks having substantially the same width in the tire axial direction, and the shoulder blocks are arranged so as to be displaced inward and outward in the tire axial direction. Because
While increasing the tread contact width, it can exhibit excellent wandering performance, and can achieve both wandering performance and ice performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a development view showing the tread pattern.

FIG. 3 is a development view showing a tread pattern in a further enlarged manner.

FIG. 4 is a development view showing another example of the tread pattern of the present invention.

[Explanation of symbols]

2 tread section 10 shoulder block 10a, 11a Shoulder side edge 10b, 11b Side edge on tire equator side 11 Intermediate block 12 circumferential ribs 20 siping R0 shoulder block row R1 middle block sequence Te tread ground edge W0, W1 block width Yc central area

Claims (5)

[Claims] 1. A pneumatic tire having a shoulder block row in which shoulder blocks are arranged in the circumferential direction on the tread ground contact edge side in the tread portion, and each shoulder block is provided with a plurality of sipings. Tire cross-section width Wt of 0.8 to 0.
9 times, and the width of each of the shoulder blocks in the tire axial direction is approximately the same, and the shoulder blocks arranged in the circumferential direction have the shoulder side edge and the tire equator side edge in the tire axial direction. A pneumatic tire characterized in that it is arranged at a different position. 2. A displacement amount d1 in the tire axial direction between a shoulder side edge of one shoulder block and a shoulder side edge of a shoulder block circumferentially adjacent to the shoulder block is equal to The tire equatorial side edge of one shoulder block and the tire equatorial side edge of a shoulder block circumferentially adjacent to this shoulder block are approximately the same as the tire axial displacement amount d2, and The pneumatic tire according to claim 1, wherein the deviation amounts d1 and d2 are 0.01 to 0.03 times the tread ground contact width Ws. 3. The tread portion, together with the shoulder block row, has an intermediate block row composed of an intermediate block arranged circumferentially between the tire equator and the shoulder block row, and each intermediate block comprises: The width of the tire in the axial direction is approximately the same, and the intermediate blocks arranged in the circumferential direction are arranged with their shoulder side edges and tire equator side edges displaced in the tire axial direction. The pneumatic tire according to claim 1, wherein the pneumatic tire is a tire. 4. The shift amount d3 in the tire axial direction between the side edge on the shoulder side of one intermediate block and the side edge on the shoulder side of an intermediate block circumferentially adjacent to the intermediate block is the above-mentioned 1 A tire equatorial side edge of one intermediate block and a tire equatorial side edge of an intermediate block circumferentially adjacent to the intermediate block are substantially the same as the tire axial displacement amount d4, and The deviation amounts d3 and d4 are
The pneumatic tire according to claim 3, wherein the tread ground contact width Ws is 0.01 to 0.03 times. 5. The tread portion is provided with a circumferential rib that extends substantially continuously in a central region within a range of ⅓ of the tread ground width centering on the tire equator. The pneumatic tire according to any one of 1 to 4.