JP2018111360A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve wandering performance while suppressing shoulder drop wear. A shoulder land portion has a shoulder slot having a width Wa of 18 to 28% of a circumferential pitch Pa. The tread contour line intersects the first arc portion J1 with the radius of curvature R1 at the intersection Q and includes a second arc portion J2 with a radius of curvature R2 of 5 to 15% of the radius of curvature R1. The distance LQ from the tire equatorial plane Co to the intersection Q is 75 to 85% of the contact half width Tw, the tire radial distance L2 from the tire equatorial point Cp to the intersection Q is 1 to 3% of the contact half width Tw, and the tire equatorial point Cp. The tire radial direction distance L1 to the tread contact end TE is 4 to 6% of the contact half width Tw. [Selection diagram] FIG.

Description

  The present invention relates to a pneumatic tire with improved wandering performance while suppressing shoulder wear.

  In pneumatic tires for heavy loads and light trucks, so-called single radius tires in which the tread contour shape is formed by a single arc centered on the tire equator plane have been widely adopted. However, such a single radius tire has a large tire radius difference between the tire equatorial plane side and the tread end side. Therefore, there is a problem that slippage occurs between the tread surface on the tread end side and the road surface, and so-called shoulder drop wear occurs.

  For this reason, it has been proposed to form a tread contour shape by an arc portion on the equator side and an arc portion on the shoulder side having a larger radius of curvature than the arc portion on the equator side (see Patent Document 1 below). However, in the case of this proposed tire, when traveling on a road surface having a saddle, if the tread end comes into contact with the unevenness in the saddle, a large reaction force acts to cause the vehicle to fluctuate. Moreover, when getting out of the kite, the camber thrust required to get over the sloping surface of the kite is small and the reaction force against the kite slope is large. Thus, the wandering performance, which is the straight travel ability and the escape performance, and the shoulder fall wear are in a trade-off relationship.

  In Patent Document 2 below, in order to improve wandering performance while suppressing shoulder wear, the tread end is formed by a small arc portion with a small radius of curvature (so-called round shoulder), or the tire circumference is located near the tread end. It has been proposed to form a vertical narrow groove extending continuously in the direction, or to form a sipe extending outward in the tire axial direction from the vertical narrow groove.

  However, in view of the recent demand for higher performance of tires, it is strongly desired to achieve both higher levels of shoulder wear resistance and wandering performance.

JP 2004-203343 A JP-A-S63-258203

  Therefore, an object of the present invention is to provide a pneumatic tire that can achieve both a shoulder wear resistance and a wandering performance at a higher level.

The present invention provides the tread portion by providing a center main groove extending continuously in the tire circumferential direction and a pair of shoulder main grooves extending continuously in the tire circumferential direction on both sides of the center main groove. A pneumatic tire divided into a pair of center land portions between the shoulder main groove and the center main groove, and a pair of shoulder land portions between the shoulder main groove and the tread grounding end,
The shoulder land portion includes a plurality of shoulder slots extending across the tread grounding end from an inner end portion interrupted in the shoulder land portion to an outer end portion interrupted in the buttress portion,
Each of the shoulder slots has a tire circumferential width Wa of 18 to 28% of the shoulder slot tire circumferential pitch Pa.
In the meridional section of the tire in the 5% internal pressure state in which the rim is assembled to the normal rim and filled with the internal pressure of 5% of the normal internal pressure,
The tread contour line on the surface of the tread portion intersects the first arc portion of the curvature radius R1 having the arc center on the tire equator plane, and intersects the first arc portion at the intersection point Q, and is 5 to 15% of the curvature radius R1. It consists of a second arc part with a radius of curvature R2,
The tire axial distance LQ from the tire equator plane to the intersection point Q is 75 to 85% of the ground contact half width Tw that is the tire axial distance from the tire equator plane to the tread ground contact edge.
The tire radial distance L2 from the tire equator point where the tread contour line and the tire equator plane intersect to the intersection point Q is 1 to 3% of the ground contact half width Tw,
And the tire radial direction distance L1 from the tire equator point to the tread contact edge is 4 to 6% of the contact half width Tw.

  In the pneumatic tire of the present invention, the maximum depth of the shoulder slot is preferably 18 to 22% of the depth of the shoulder main groove.

  In the pneumatic tire of the present invention, the shoulder land portion has two or three shoulders extending across the tread grounding end between the shoulder slots from an inner end portion interrupted in the shoulder land portion to an outer end portion interrupted in the buttress portion. It is preferable to provide sipes.

  The tire shape in the “5% internal pressure state” is generally substantially the same as the tire shape in the vulcanization mold. Then, by specifying the shape of the mold surface of the vulcanization mold, the tire shape in the 5% internal pressure state can be controlled. In this specification, unless otherwise specified, the dimensions and the like of each part of the tire are values specified in the 5% internal pressure state.

  The “tread grounding end” is the position of the outermost end in the tire axial direction of the tread tread that contacts the road surface when a normal load is applied to a tire that is assembled with a normal rim and filled with a normal internal pressure. Defined.

  The “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based. For example, JAMMA is a standard rim, TRA is “Design Rim”, or ETRTO. Then means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. The maximum air pressure for JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for ETRA, Means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The “regular load” is a load determined by the standard for each tire. The maximum load capacity in the case of JATMA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” in the case of TRA, If it is ETRTO, it is "LOAD CAPACITY".

  Since the present invention is configured as described above, as described in the embodiment for carrying out the invention, it is possible to achieve both a high level of both shoulder-proof wear resistance and wandering performance.

It is sectional drawing which shows one Example of the pneumatic tire of this invention. It is an expanded view which expands and shows the surface of the tread part in a plane. It is a diagram which shows a tread outline.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the pneumatic tire 1 according to this embodiment includes a carcass 6 that extends from a tread portion 2 through a sidewall portion 3 to a bead core 5 of the bead portion 4, and the radial direction of the carcass 6 inside the tread portion 2. A belt layer 7 disposed on the outside. In this example, the case where the pneumatic tire 1 is a tire for a light truck is shown.

  The carcass 6 is formed of at least one carcass ply 6A, 6B in which the carcass cord is arranged at an angle of, for example, 70 to 90 ° with respect to the tire equator C, in this example, radially inward and outward. Is done. The inner carcass ply 6 </ b> A has a folded portion 6 </ b> A <b> 2 that is folded around the bead core 5 at both ends of the main body portion 6 </ b> A <b> 1 straddling the bead cores 5 and 5. Further, the outer carcass ply 6B is not folded around the bead core 5 and ends on the outer surface of the folded portion 6A2.

  The belt layer 7 includes at least two belt cords whose belt cords are arranged at an angle of, for example, 15 to 75 ° with respect to the tire equator C. In this example, the first to third belt plies 7A to 7A are arranged in order from the radially inner side. 7C. In this example, the belt cord angle of the first belt ply 7A is 45 to 75 °, for example, and the belt cord angles of the second and third belt plies 7B and 7C are 10 to 35 ° and the inclination direction, for example. Are different from each other. As a result, the belt cords cross each other between the plies, and the belt rigidity is increased.

  If necessary, the number of belt plies may be increased or decreased in the belt layer 7, and a band ply in which, for example, a band cord is spirally wound in the tire circumferential direction is provided on the outer side of the belt layer 7. You can also.

  Reference numeral 8 in FIG. 1 denotes a bead apex rubber for bead reinforcement, which extends between the body portion 6A1 and the folded portion 6A2 and extends radially outward from the bead core 5. Reference numeral 9 denotes a reinforcement cord layer for bead reinforcement, for example, one or more reinforcing cords made of steel, for example, arranged at an angle of 30 to 60 ° with respect to the tire circumferential direction. Formed from ply.

  As shown in FIG. 2, the tread portion 2 includes a center main groove 10 extending continuously in the tire circumferential direction and a pair of shoulder main grooves 11 extending continuously in the tire circumferential direction on both sides of the center main groove 10. Have. Accordingly, the tread portion 2 is divided into a pair of center land portions 12 between the shoulder main groove 11 and the center main groove 10 and a pair of shoulder land portions 13 between the shoulder main groove 11 and the tread grounding end TE. The

  In this example, the case where the center land portion 12 and the shoulder land portion 13 are rib bodies extending continuously in the tire circumferential direction is shown.

Width _{W 12} of the center land portion 12, 36 to 40% of the range of the ground half width Tw (shown in FIG. 1), the width _{W 13} of the shoulder land portion 13 is preferably 45 to 50% range of the ground half width Tw. The sum of the width W ₁₂ and the width W ₁₃ (W ₁₂ + W ₁₃ ) is preferably in the range of 80 to 85% of the ground half width Tw. Thereby, the balance between the wet performance and the steering stability performance on the dry road surface is optimized. When the sum (W ₁₂ + W ₁₃ ) is less than 80% of the ground contact half width Tw, the tread rigidity is reduced and the steering stability tends to be insufficient. On the other hand, if it exceeds 85%, the drainage is reduced and the wet performance tends to be insufficient. Further, when the width W ₁₂ is out of 36 to 40% of the ground contact half width Tw and when the width W ₁₃ is out of 45 to 50% of the ground contact half width Tw, the rigidity balance between the center land portion 12 and the shoulder land portion 13 is poor. Therefore, the steering stability performance is lowered, and the center wear and the shoulder wear tend to be induced.

  The “contact half width Tw” is defined as the distance in the tire axial direction from the tire equatorial plane Co to the tread contact end TE.

As the center main groove 10 and the shoulder main groove 11, a straight groove in which the groove side edges on both sides extend linearly and a zigzag groove in which at least one of the groove side edges extends in a zigzag shape (including a wave shape) can be adopted. In the case of a zigzag groove, the groove width and the width of each land portion are defined with the amplitude center at the zigzag groove side edge as the virtual groove side edge. The groove widths W ₁₀ and W ₁₁ of the center main groove 10 and the shoulder main groove 11 are appropriately set based on the range of the sum (W ₁₂ + W ₁₃ ). Further, the groove depths D ₁₀ and D ₁₁ (shown in FIG. 1) can be variously determined according to the custom. In this example, the same and the groove depth _{D 10} and the groove depth _{D 11,} is set in the range of 8 to 15 mm (e.g. 10.5 mm).

The center land portion 12 is provided with a horizontal sipe 15 that crosses the center land portion 12 and a vertical sipe 16 that continuously extends in the tire circumferential direction. However, at the time of grounding, each of the sipes 15 and 16 closes its opening, so that the center land portion 12 substantially constitutes a rib body. Note the depth of the sipe 15, 16, 40% to 60% of the groove depth _{D 10} of preferably.

  The shoulder land portion 13 is provided with a plurality of wide shoulder slots 20 extending across the tread grounding end TE.

  The inner end portion 20 a of the shoulder slot 20 is interrupted in the shoulder land portion 13, and the outer end portion 20 b is interrupted in the buttress portion 21. Further, the width Wa in the tire circumferential direction of the shoulder slot 20 is in a range of 18 to 28% of the tire circumferential pitch Pa of the shoulder slot 20. The shoulder slot 20 of this example extends along the tire axial direction line with a constant width Wa.

As shown in FIG. 1, the shoulder slot 20 has a maximum depth D ₂₀ near the tread edge TE, the depth is gradually reduced toward the inner end portion 22a and an outer end portion 22b from the maximum depth position . The maximum depth _{D 20} is preferably 18 to 22% of the groove depth _{D 11} of the shoulder main grooves 11.

As shown in FIG. 2, the shoulder land portion 13 has two or three (three in this example) shoulder sipes extending in parallel with the shoulder slot 20 across the tread grounding end TE between the shoulder slots 20, 20. 22 is arranged. The shoulder sipe 22 also has an inner end portion 22 a interrupted in the shoulder land portion 13 and an outer end portion 22 b interrupted in the buttress portion 21. The depth of the shoulder sipe 22 is the same as that of the shoulder slot 20, and the maximum depth D ₂₂ (not shown) is preferably 18 to 22% of the groove depth D ₁₁ of the shoulder main groove 11.

  Also, as shown in FIG. 3, in the tire meridional section in the 5% internal pressure state, the tread outline on the surface of the tread portion 2 includes a first arc portion J1 having a radius of curvature R1 having an arc center on the tire equatorial plane Co, It intersects with the first arc portion at the intersection Q and is composed of a second arc portion J2 having a curvature radius R2 of 5 to 15% of the curvature radius R1.

  The tire axial distance LQ from the tire equatorial plane Co to the intersection point Q is 75 to 85% of the ground contact half width Tw. A tire radial distance L2 (sometimes referred to as “camber amount L2”) from the tire equator point Cp where the tread contour line and the tire equator plane Co intersect each other to the intersection point Q is 1 to 3% of the ground contact half width Tw. In addition, the tire radial direction distance L1 from the tire equator point Cp to the tread ground contact end TE (sometimes referred to as “camber amount L1”) is 4 to 6% of the ground contact half width Tw.

Such a pneumatic tire 1 is
(A) The shoulder land portion 13 is provided with a shoulder slot 20 having a width Wa of 18 to 28% of the circumferential pitch Pa;
(B) The tread contour line includes a second arc portion J2 that intersects the first arc portion J1 at the intersection point Q, and the second arc portion J2 has a curvature radius R2 of 5 to 15% of the curvature radius R1. Formed by an arc;
(C) A tire axial distance LQ of the intersection point Q is 75 to 85% of the ground contact half width Tw;
(D) The camber amount L2 of the intersection point Q is 1 to 3% of the ground contact half width Tw;
(E) The camber amount L1 of the tread grounding end TE is 4 to 6% of the grounding half width Tw:
By cooperating with each other, it is possible to achieve both a high level of shoulder wear resistance and wandering resistance.

  Specifically, making the second arc portion J2 a small arc is a premise for generating a large camber thrust. At this time, if the radius of curvature R2 of the second arc portion J2 is too small, the camber amount L1 of the tread grounding end TE becomes large, leading to a tendency for shoulder fall wear.

  Therefore, the camber amount L1 is set to 4 to 6% of the ground half width Tw and lower than the conventional one while restricting the curvature radius R2 to the range of 5 to 15% of the curvature radius R1. As a result, the contact length on the shoulder side is increased to reduce the amount of slip, and the shoulder fall wear resistance performance is improved, while the camber thrust is increased by the second arc portion J2 of the small arc to improve the wandering performance. Is possible. When the radius of curvature R2 is out of the range of 5 to 15% of the radius of curvature R1, it is less effective to increase the camber thrust and it is difficult to sufficiently improve the wandering performance. From such a viewpoint, the lower limit of the curvature radius R2 is preferably 7% or more of the curvature radius R1, and the upper limit is preferably 12% or less. If the camber amount L1 exceeds 6% of the ground contact half width Tw, the shoulder wear resistance tends to be reduced. If the camber amount L1 is less than 4%, the wandering performance is adversely affected.

  Further, the tire axial direction distance LQ of the intersection point Q is set to 75 to 85% of the ground contact half width Tw, and the second arc portion J2 of a small arc is limitedly provided in the vicinity of the ground contact end. Thereby, the influence on the contact length on the shoulder side by the second arc portion J2, that is, the influence on the shoulder drop wear resistance performance can be suppressed. When the tire axial distance LQ is less than 75% of the ground contact half width Tw, the second arc portion J2 tends to deteriorate the shoulder wear. On the other hand, if it exceeds 85%, the second arc portion J2 becomes local, and the effect of improving the wandering performance decreases. From such a viewpoint, the lower limit of the tire axial distance LQ is preferably 78% or more of the ground contact half width Tw, and the upper limit is preferably 82% or less.

  Further, if the camber amount L2 itself at the intersection Q is large, the contact length on the shoulder side is reduced. Therefore, it is necessary to regulate the camber amount L2 within a range of 1 to 3% of the ground half width Tw.

  On the other hand, there is a limit to the improvement of the wandering performance only by the second arc portion J2 due to the restriction of the shoulder wear resistance. Therefore, the shoulder land 20 is provided with a shoulder slot 20 and its width Wa is set to be as wide as 18 to 28% of the circumferential pitch Pa.

  Thereby, the rigidity of the periphery of the grounding end including the tread grounding end TE can be lowered. As a result, it is possible to reduce the reaction force when coming into contact with the slope or unevenness in the kite while traveling on the kite and improve the straight traveling performance of the kite. Also, the camber thrust is increased, and the heel escape performance can be improved in combination with the decrease in the reaction force. The shoulder sipe 22 functions similarly to the shoulder slot 20 and can further improve the wandering performance.

When the width Wa of the shoulder slot 20 is less than 18% of the circumferential pitch Pa, the rigidity of the periphery of the ground contact end is not sufficiently lowered, and the wandering performance tends to be insufficient. Conversely, if it exceeds 28%, the steering stability tends to be lowered. Similarly, the maximum depth D ₂₀ of the shoulder slot 20 is less than 18% of the groove depth D _11, the rigidity of the grounding end peripheral portion not decrease sufficiently, leading to insufficient tendency of wandering performance. Conversely, if it exceeds 22%, the steering stability tends to be lowered.

  As described above, (A) to (E) cooperate with each other, so that it is possible to achieve both a high level of anti-shoulder wear resistance and wandering performance.

  The tire axial distance Lb (shown in FIG. 2) from the tread ground contact end TE of the inner end 20a of the shoulder slot 20 is preferably in the range of 4 to 7 of the ground contact half width Tw. If it exceeds 7%, the steering stability tends to be lowered, and if it is below 4%, the wandering performance tends to be insufficient.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

  A small truck tire (205 / 85R16) shown in FIGS. Each prototype tire was tested for wandering performance, handling stability, and anti-shoulder wear performance. The specifications are substantially the same except for Table 1.

(1) Wandering performance:
Prototype tires are mounted on all wheels of a small truck (loading capacity 3 tons) with a rim (16 x 5.5 J) and internal pressure (600 kPa), and run on a road surface with eaves, providing eaves straightness and eaves escape characteristics. It was displayed by the 10-point method based on the sensory evaluation of the driver. The result is better as the numerical value is larger, based on 6 points.

(2) Steering stability:
Using the above vehicle, the vehicle traveled on a dry asphalt road test course, and the steering stability was displayed by a 10-point method based on the sensory evaluation of the driver. The result is better as the numerical value is larger, based on 6 points.

(3) Shoulder drop wear resistance:
Using the above-mentioned vehicle, on a general road (100% general road) in the Kanto and west districts, running on 15000 km and wearing on the front, the wear amount δc in the center main groove and the wall surface outside the tire axial direction of the shoulder main groove The amount of wear δs was measured. Evaluation was made based on the wear amount ratio δc / δs. As a result, the closer the value is to 1.0, the more uniform the wear, and the lower the value, the worse the anti-shoulder wear performance.

  As shown in the table, it can be confirmed that the example products can achieve both a high level of anti-shoulder wear performance and wandering performance.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 10 Center main groove 11 Shoulder main groove 12 Center land part 13 Shoulder land part 21 Buttress part 20 Shoulder slot 20a Inner end part 20b Outer end part 22 Shoulder sipe 22a Inner end part 22b Outer end part Co Tire Equatorial plane Cp Tire equator point J1 First arc part J2 Second arc part TE Tread grounding end

Claims (3)

The tread portion is provided with a center main groove extending continuously in the tire circumferential direction and a pair of shoulder main grooves extending continuously in the tire circumferential direction on both sides of the center main groove. A pneumatic tire divided into a pair of center land portions between the groove and the center main groove and a pair of shoulder land portions between the shoulder main groove and the tread grounding end,
The shoulder land portion includes a plurality of shoulder slots extending across the tread grounding end from an inner end portion interrupted in the shoulder land portion to an outer end portion interrupted in the buttress portion,
Each of the shoulder slots has a tire circumferential width Wa of 18 to 28% of the shoulder slot tire circumferential pitch Pa.
In the meridional section of the tire in the 5% internal pressure state in which the rim is assembled to the normal rim and filled with the internal pressure of 5% of the normal internal pressure,
The tread contour line on the surface of the tread portion intersects the first arc portion of the curvature radius R1 having the arc center on the tire equator plane, and intersects the first arc portion at the intersection point Q, and is 5 to 15% of the curvature radius R1. It consists of a second arc part with a radius of curvature R2,
The tire axial distance LQ from the tire equator plane to the intersection point Q is 75 to 85% of the ground contact half width Tw that is the tire axial distance from the tire equator plane to the tread ground contact edge.
The tire radial distance L2 from the tire equator point where the tread contour line and the tire equator plane intersect to the intersection point Q is 1 to 3% of the ground contact half width Tw,
And the tire radial direction distance L1 from the said tire equator point to a tread grounding end is 4 to 6% of the said grounding half width Tw, The pneumatic tire characterized by the above-mentioned.   The pneumatic tire according to claim 1, wherein the maximum depth of the shoulder slot is 18 to 22% of the depth of the shoulder main groove.   The shoulder land portion includes two or three shoulder sipes extending across the tread grounding end from the inner end portion interrupted in the shoulder land portion to the outer end portion interrupted in the buttress portion between the shoulder slots. The pneumatic tire according to claim 1 or 2.

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