JP2011246002A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire having superior cornering power in vehicle turning.SOLUTION: The pneumatic tire has, on a tread surface 1 of the tire, a plurality of land parts 3a divided by: grooves 2a provided at least one by one on each of both tread half parts bordering on the tire equatorial plane and extending to a tread circumferential direction; and a tread end. The pneumatic tire is provided with a plurality of projection parts 4a, 4b extending in a groove in a direction inclined in a tread width direction from each of side walls 3f, 3g with a certain interval in the tread circumferential direction, on both side walls 3f, 3g dividing one groove 2a of circumferential directional grooves adjacent to the tread end in the circumferential directional grooves. In the plurality of projection parts 4a, 4b provided on both side walls 3f, 3g, two projection parts 4a, 4b each in a position opposed to each other in a tread width direction are not abutted on each other in non-grounded time, and are abutted on each other in grounded time.

Description

The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that improves cornering power when turning a vehicle by suppressing buckling.

In a pneumatic tire, a buckling phenomenon may occur in which a part of the tread surface is lifted from the road surface.
This buckling phenomenon occurs when the compressive stress in the tire radial direction exceeds a critical point due to an external force from the side with respect to the tread when the vehicle turns.
When the buckling phenomenon occurs, the area where the tire is in contact with the road surface is reduced, or the contact pressure at the portion where the tire is in contact with the road surface is reduced, which may reduce the cornering power.

  Here, as a method for suppressing buckling, for example, it is conceivable to increase the out-of-plane bending rigidity by forming a belt layer with a metal material. However, this method has a problem of increasing the weight of the tire. .

  On the other hand, in Patent Document 1, the relationship between the curvature of the tread and the curvature of the outermost belt layer is a predetermined one, the shape of the tread at the time of load is flattened, and the belt is formed in a convex shape outward in the tire radial direction. Therefore, a method for suppressing buckling has been proposed.

JP H5-185807

  However, with the technique described in Patent Document 1, buckling cannot be sufficiently suppressed, and when a vehicle equipped with the tire described in Patent Document 1 is actually run, cornering power is insufficient particularly when turning the vehicle. Turned out to be.

  Therefore, an object of the present invention is to solve the above-described problems, and an object thereof is to provide a pneumatic tire that effectively suppresses buckling and improves the cornering power of the tire. It is in.

The inventor has intensively studied to solve the above problems.
As a result, it has been found that the decrease in cornering power in the technique described in Patent Document 1 results from the fact that the magnitude of the compressive stress in the tire radial direction differs depending on the position in the tire width direction. That is, although it is preferable that the portion of the tread where the compressive stress is maximum is reinforced, in the method described in Patent Document 1, since the center of curvature of the outermost belt layer is in the center portion of the tread contact width, The reinforcement effect by the outermost layer belt is greatest at the tread ground width central portion, and the reinforcement effect is smaller as compared to the tread ground width central portion toward the outer side in the tire width direction. However, in reality, the maximum point of the compressive stress in the tire width direction is not in the center portion of the tread contact width, so that the rigidity against the compressive stress is not effectively increased, and buckling is sufficiently suppressed. I found that it was not done.
The inventor found that the position where the compressive stress is maximum is near the center of the outer half of the tread width direction when the tire is mounted on the vehicle, and in particular, at least 1 in both tread halves bounded by the tire equatorial plane of the tread. It has been found that in tires having circumferential grooves one by one, the outer circumferential groove adjacent to the tread end is the outer groove when the vehicle is mounted, that is, the vicinity of the outermost groove when the vehicle is mounted.
Then, the inventor provides a protrusion in the outermost groove that does not contact when not in contact with the ground but contacts when in contact with the ground, thereby improving the rigidity near the outermost groove and suppressing the occurrence of buckling. Thus, new knowledge has been obtained that the cornering power at the time of turning of the vehicle can be improved.

The gist configuration of the present invention for solving the above-described problems is as follows.
(1) The tread surface of the tire has a plurality of land portions defined by tread ends and grooves extending in the tread circumferential direction provided at least one in each tread half with the tire equatorial plane as a boundary,
On the side walls defining one of the circumferential grooves adjacent to the tread end of the circumferential grooves, protrusions extending into the grooves in a direction inclined in the tread width direction from each side wall are spaced apart in the tread circumferential direction. Set up multiple,
Of the plurality of protrusions provided on the both side walls, two protrusions at positions facing each other in the tread width direction are not in contact with each other at the time of non-grounding, but are contacted at the time of grounding. .

(2) The plurality of projecting portions extend inclining in the same direction in the tread circumferential direction,
The two protrusions at the opposite positions have different protrusion widths,
When the groove width of the one groove is W (mm), when not grounded, the protrusion width of the protrusion with the larger protrusion width is larger than W / 2, and the protrusion width in the tire radial section is The pneumatic tire according to (1) above, wherein the size of the tire is larger than the extension line of the side portion on the one-direction side of the smaller protruding portion.

  (3) The pneumatic tire according to (1) or (2), wherein the two protrusions extend in a direction crossing each other.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire excellent in the cornering power at the time of vehicle turning can be provided.

FIG. 3 is a schematic development view schematically showing a tread surface when the tire of the present invention is not in contact with the ground. It is the partial expanded view which showed a part of tread surface at the time of the non-grounding of the tire of this invention. It is a schematic sectional drawing of the tire width direction of one groove part of the circumferential direction groove | channel on the outermost side of a tire width direction at the time of the non-grounding of the tire of this invention.

  Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic development view schematically showing a tread surface of a pneumatic tire (hereinafter referred to as a tire) according to the present invention when not grounded.

  As shown in FIG. 1, the tire of the present invention has a tread tread surface 1, a plurality of two grooves 2a in the illustrated example with the tire equatorial plane CL as a boundary, and a total of four grooves 2a extending in the tread circumferential direction, 2b, 2c, 2d, and land portions 3a, 3b, 3c, 3d, 3e are defined by circumferential grooves 2a-2d and tread end TE.

Further, in the tire of the present invention, the projecting portions 4 are spaced apart in the tread circumferential direction on the side walls 3f, 3g of the land portions 3a, 3b defined by one groove 2a of the circumferential groove adjacent to the tread end TE. A plurality of them are provided (three on one side wall in the illustrated example, a total of six).
FIG. 2 is a partial development view of one groove 2a of the circumferential groove adjacent to the tread end and the land portions 3a and 3c on both sides thereof when the tire of the present invention is not in contact with the ground.
As shown in FIG. 2, the two projecting portions at positions facing each other in the tread width direction are not in contact with each other when not grounded, and are spaced apart. On the other hand, at the time of grounding, the two protrusions abut against each other.
Here, the “position facing each other in the tread width direction” means that at least a part of the protrusion provided on one side wall defining the groove is projected in the tire width direction on the protrusion provided on the other side wall. Means that they are in overlapping positions.

Also, “Two protrusions come into contact with each other when touching” means that the groove with two protrusions at the corresponding position is above the normal load when the tire is mounted on the standard rim and filled with the normal internal pressure. This means that the protrusions are in contact with each other at this time.
Here, the normal load is the maximum load (maximum load capacity) of a single wheel at the applicable size described in a given industrial standard, and the normal internal pressure is the single load at the applicable size described in the standard. The air pressure corresponding to the maximum load (maximum load capacity) of the wheel, and the standard rim is the standard rim (or “Approved Rim” or “Recommended Rim”) in the applicable size described in the same standard. is there. For such industrial standards, there are standards that are valid in each region where tires are produced or used. For example, in the United States, “The Tire and Rim Association Inc. Year Book” (including design guides) ) In Europe according to “The European Tire and Rim Technical Organization Standards Manual” and in Japan according to “JATMA YEAR BOOK” of the Japan Automobile Tire Association.
Furthermore, “the two protrusions do not come into contact with each other when not grounded” means that the groove having the two protrusions in the opposite position is in a plane where no load is applied, and at this time the protrusions come into contact with each other. It means not to.

  In the tire of the present invention, on both side walls defining one of the circumferential grooves adjacent to the tread end of the circumferential grooves, protrusions extending into the grooves in a direction inclined from each side wall in the tread width direction are provided. A plurality of protrusions provided at intervals in the tread circumferential direction, and of the plurality of protrusions provided on both side walls, the two protrusions that are opposed to each other in the tread width direction do not contact each other when not grounded, It is important to touch.

When such a tire is mounted on the vehicle so that the side on which the protruding portion is provided is on the outside of the vehicle, the protruding portions at corresponding positions in the tread width direction come into contact with each other and support each other at the time of ground contact.
For this reason, the rigidity against the compressive stress in the tire radial direction of the land portion defined by the outermost groove in the tread width direction when the vehicle is mounted is increased, buckling is suppressed, and cornering power is improved when the vehicle is turning.

In addition, as shown in FIGS. 1 and 2, the two projecting portions located at positions facing each other in the tread width direction do not contact each other when not in contact with the ground and contact when in contact with the ground as shown in FIGS. 4 are inclined in the same direction of the tread circumferential direction, in the illustrated example, in the direction of the arrow, and the two protrusions 4 at the opposite positions have different protrusion widths, and further, the groove 2a is provided with a protrusion. When the groove width when not grounded is W (mm), when not grounded, the projecting width L1 of the projecting portion 4a having the larger projecting width is larger than W / 2, and in the tire radial direction cross section, It is preferable that the protrusion 4b has a smaller protrusion width than the extension line l of the side part 4c on the one direction side (in the direction of the arrow in the extending direction of the protrusion in the circumferential direction) of the protrusion 4b.
Here, the `` protrusion width '' refers to the side wall 4d on the opposite side to the extending direction of the protrusion 4 in the tread circumferential direction of the protrusion 4a, 4b (in the direction of the arrow in the illustrated example), as shown in FIG. The lengths L1 and L1 ′ in the extending direction of the protrusions 4a and 4b of 4e.

Here, the two protrusions at the opposite positions in the tread width direction are in the plane where a load of 1/4 or more of the normal load is applied with the tire mounted on the standard rim and filled with the normal internal pressure. Even in some cases, it is preferable to contact.
Tire diameter caused by lateral force at the time of turning of the vehicle by abutting and supporting even when the projecting part is in the plane where the load of 1/4 of the normal load is applied in the tread circumferential direction This is because, before the compressive stress in the direction is maximized, the rigidity in the vicinity of the outermost groove when the vehicle is mounted can be increased, and buckling can be prevented more reliably.

Here, the width L2 ′ (mm) of the end face of the protruding portion 4b having the smaller protruding width is W (mm) when the groove width at the time of non-grounding of the groove 2a in which the protruding portion is provided is
0.4 × W ≦ L2 ′ ≦ 0.5 × W
It is preferable to be in the range.
This is because if it is less than 0.4 × W, protrusions are likely to be lost, and if it is greater than 0.5 × W, the drainage performance is reduced.
Further, the width L2 (mm) of the end surface of the protrusion 4a having the larger protrusion width can be set to L2 = L2 ′.
Furthermore, the protrusion width L1 ′ (mm) of the protrusion 4b with the smaller protrusion width is
1.2 × L2 '≦ L1' ≦ 2 × L2 '
It is preferable to set it as the range.
Because, if it is less than 1.2 × L2 ′, the protrusion width of the protrusion with the smaller protrusion width is too short, making it difficult for the protrusions to come into contact with each other. Because it will end up.

In addition, as shown in FIG. 1, the two protruding portions 4 that are in opposing positions in the tread width direction and have a pair are cycled at predetermined constant intervals L3 (mm) and L3 ′ (mm) in the tread circumferential direction. Therefore, L3 and L4 are preferably 20 to 50 mm when not grounded.
Here, it is possible to make the circumferential interval L3 (mm) between the protrusions 4a with the larger protrusion width equal to the circumferential interval L3 ′ (mm) between the protrusions 4b with the smaller protrusion width.
This is to always have a pair of protrusions in the ground plane, and if the interval is narrower than 20 mm, the drainage performance will deteriorate due to having two or more pairs of protrusions in the ground plane. On the other hand, if the interval is larger than 50 mm, there is a case where there is no projecting portion in the ground contact surface during rolling of the tire, and the effect of suppressing the above buckling cannot be achieved.

Here, as shown in FIG. 3, the tire radial direction lengths L4 (mm) and L4 ′ (mm) of the protrusions 4 are 15% or more and 80% or less of the groove depth H (mm) when not grounded. It is preferable that
Further, the tire radial direction length L4 (mm) of the protrusion 4a having the larger protrusion width and the tire radial direction length L4 ′ (mm) of the protrusion 4b having the smaller protrusion width can be made equal.
That is, if it is less than 15%, the volume of the protrusions is too small, and when the protrusions come into contact with each other, they support each other, increase the rigidity near the outermost groove when mounted on the vehicle, and suppress the buckling This is because, if it is larger than 80%, the volume of the protruding portion is too large and the drainage performance decreases.
Note that FIG. 3 shows an example in which the groove bottom 2b is flat, but the “groove depth” in the case where the groove bottom is curved is the innermost radial position of the curved portion. This is the distance from the part to the opening.

In addition, as shown in FIG. 2, when not grounded, the direction in which the protrusion 4b with the smaller protrusion width extends is in one direction of the tread circumferential direction (the direction in which the protrusion extends, the direction of the arrow in FIG. 2). When the angle is α,
30 ° ≦ α ≦ 60 °
Is preferable.
This is because if it is less than 30 °, it will be difficult to come into contact with the protruding portion 4a having the larger protrusion width, while if it is larger than 60 °, the drainage will be reduced.
Furthermore, it is preferable that the two projecting portions at the opposing positions extend in directions intersecting each other so that the two projecting portions facing each other come into contact with each other at the time of ground contact and the drainage performance is not hindered.

In order to confirm that there is a difference in cornering power and drainage between the tire of the present invention and the conventional tire, a tire of size 170 / 70R14 was assembled on a rim of size 5.5J × 14 and the internal pressure was 210 kPa. A simulation was conducted to compare the cornering power and drainage performance of the test tire.
In addition, in order to confirm that the difference in cornering power is due to the buckling suppression effect, the ground contact area was obtained from the FEM simulation results.

Here, as tires according to the inventive tires 1 to 4, two projecting portions that do not come into contact with each other on the side walls defining one groove of the groove adjacent to the tread end but do not contact when not grounded but contact when grounded are arranged on the tread circumference. A plurality of pneumatic tires provided at intervals in the direction were prototyped.
Protrusions are provided periodically at regular intervals of 30 mm in the tread circumferential direction.
In addition, as the conventional tire 1, a tire having no protrusion was prepared.
Further, as a conventional tire 2, a tire described in Patent Document 1 was created.
The specifications of each tire are shown in Table 1 below.
In the following evaluation, each tire having a protruding portion in one of the grooves adjacent to the tread end is mounted on the vehicle so that the side on which the protruding portion is provided is on the outside of the vehicle.
In Table 1, W (mm) is the groove width of the outermost circumferential groove when mounted on the vehicle, H (mm) is the groove depth of the outermost circumferential groove when mounted on the vehicle, L1 (mm), L1 ′ ( mm) is the protrusion width of the protrusion, L2 (mm), L2 '(mm) is the width of the end face of the protrusion, L3 (mm), L3' (mm) is the circumferential distance of the protrusion, L4 (mm), L4 ′ (mm) is the length of the protruding portion in the tire radial direction, and α and β are one direction of the tread circumferential direction (the protruding portion is the direction in which the protruding portion with the smaller protruding width and the larger protruding portion extend, respectively. Extending direction), and the length and angle when not grounded, respectively. In Table 1, “exceed” means that the protrusion width of the protrusion with the larger protrusion width exceeds the extension line l of the side portion on the circumferential extension side of the protrusion with the smaller protrusion width. It means that. Furthermore, the angle of intersection between the protrusions is an angle at the time of non-grounding, and actually does not intersect, but the smaller one of the angles that intersect when the protrusion is virtually extended in the extending direction An angle.

In the evaluation, first, the contact pressure distribution at a load of 4 kN was obtained by FEM simulation, and the contact area was obtained therefrom.
Moreover, the cornering power at that time was calculated | required on simulation.
These values are shown in Table 2 as indices with the evaluation result of the tire according to Conventional Example 1 as 100. The larger the index value, the better.

Next, the drainage was evaluated by measuring the critical speed until the hydroplaning phenomenon occurred by running a test course with an average water depth of 20 mm while accelerating the speed.
The results are shown in Table 2 as an index with the evaluation result of the tire according to Conventional Example 1 as 100.
In addition, it shows that drainage is excellent, so that a numerical value is large.

  As shown in Table 2, the tires according to Invention Examples 1 to 4 each have a larger ground contact area than the tires according to Conventional Examples 1 and 2, and thus cornering power is improved.

In addition, the tire according to Invention Example 1 in which the protrusion width and the extension mode of the projecting portion having the larger protrusion width are optimized by comparison between Invention Examples 1 and 2, 3 is the tire according to Invention Examples 2 and 3. The ground contact area is larger than that, which increases the cornering power.
Furthermore, the tire according to Invention Example 1 in which the crossing direction of the protrusions is optimized by comparison between Invention Examples 1 and 4, the ground contact area is larger than the tire according to Invention Example 4, and thereby the cornering power Is improved and drainage is also excellent.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which improved the cornering power at the time of vehicle turning can be manufactured, and can be provided to a market.

1 Tread
2a One of the circumferential grooves adjacent to the tread edge
2b, 2c, 2d circumferential groove
2e Groove bottom of one of the circumferential grooves adjacent to the tread edge
3a One of the land adjacent to the tread edge
3b One of the second land from the tread edge
3c, 3d, 3e Land
3f, 3g Side wall of one of the circumferential grooves adjacent to the tread edge
4 Protrusion
4a Projection with larger projection width
4b Projection with smaller projection width
4c Side part of one side (circumferential extending direction side) of the projecting part with the smaller projecting width
4d Side of the protruding part opposite to the circumferentially extending side
4e Side part of projecting part opposite to circumferentially extending side
CL tire equator
TE tread edge
W Groove width of one of the outermost grooves in the tread width direction
H Groove depth α of one groove of the outermost groove in the tread width direction Angle of the direction in which the protrusion extends to one direction of the tread circumferential direction (direction in which the protrusion extends) β in the direction in which the protrusion extends Angle relative to one direction of the tread circumferential direction (direction in which the protrusion extends)
L1, L1 'protrusion width of protrusion
L2, L2 'Projection end face width
L3, L3 'Spacing in the circumferential direction
L4, L4 'Projection length in the tire radial direction

Claims (3)

The tread surface of the tire has a plurality of land portions defined by tread ends and at least one groove extending in the tread circumferential direction provided on both tread halves with the tire equatorial plane as a boundary,
On the side walls defining one of the circumferential grooves adjacent to the tread end of the circumferential grooves, protrusions extending into the grooves in a direction inclined in the tread width direction from each side wall are spaced apart in the tread circumferential direction. Set up multiple,
Of the plurality of protrusions provided on the both side walls, two protrusions at positions facing each other in the tread width direction are not in contact with each other at the time of non-grounding, but are contacted at the time of grounding. . The plurality of protrusions extend in an inclined direction in the same direction in the tread circumferential direction,
The two protrusions at the opposite positions have different protrusion widths,
When the groove width of the one groove is W (mm), when not grounded, the protrusion width of the protrusion with the larger protrusion width is larger than W / 2, and the protrusion width in the tire radial section is 2. The pneumatic tire according to claim 1, wherein the pneumatic tire has a size exceeding an extension line of a side portion on the one-direction side of the protruding portion having a smaller diameter.   3. The pneumatic tire according to claim 1, wherein the two protrusions extend in directions that intersect each other.

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