JP2006327502A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire reducing rolling resistance while ensuring braking distance and wear resistance. <P>SOLUTION: On the cross section in the tread width direction, when the section height of the height from the intersection point L of a bead line BL passing through one side bead toe 11c with the other side bead toe 11c with a tire equator line CL to the surface M of the tread part 15 is made SH, and the tire maximum width is made SW, the height PH from the point P positioning at 0.8SW on the surface of the tread part 15 around the tire equator line CL to the bead line BL is not less than 0.93SH on the cross section in the tread width direction, and the height QH from the point Q positioning at outermost position in the tread width direction to the bead line BL is not less than 0.6SH on the tire maximum width SW. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a pneumatic tire including at least a pair of bead portions including at least a bead toe and a tread portion in contact with a road surface.

  In recent years, various proposals have been made on pneumatic tires that reduce rolling resistance generated on a tread contact surface in contact with a road surface in a tread portion, rolling resistance generated due to deformation of the pneumatic tire itself, and the like.

  For example, a method in which rubber having a smaller loss tangent (tan δ) than that used in a tread portion of a general pneumatic tire is used in the tread portion or a thickness of a tread portion of a general pneumatic tire is made thinner. A pneumatic tire that reduces rolling resistance and improves fuel consumption of a vehicle by using a method or the like is known.

  However, the method of using a rubber having a small loss tangent (tan δ) for the tread portion inevitably deteriorates maneuverability and the like. In addition, the method of reducing the thickness of the tread portion inevitably reduces wear resistance and the like.

Therefore, by configuring the carcass line to have two or more inflection points at the side portion of the carcass line which is the shape of the cross section in the tread width direction of the carcass layer provided in the pneumatic tire at the time of vulcanization molding, And a pneumatic tire that improves ride comfort and the like (see Patent Document 1).
Japanese Patent Laid-Open No. 8-40011 (pages 2 to 3 and FIG. 1)

  However, in the pneumatic tire configured to have two or more inflection points at the side portion of the carcass line described above, although the maneuverability and the ride comfort are improved, the carcass line near the inflection point is improved. When the unevenness is increased, the rubber flows to cause a problem during vulcanization, and the effect of reducing rolling resistance may be limited.

  In addition, it is conceivable to reduce the shear deformation in the tire circumferential direction by defining the carcass line in a predetermined shape and increasing the belt tension, but the tread portion in the rotational direction of the pneumatic tire and the road surface Since the contact length, which is the length of contact with the ground, is shortened, the ground contact area may be reduced, and the braking distance may be increased or the wear resistance may be reduced.

  Therefore, the present invention has been made in view of the above-described situation, and an object thereof is to provide a pneumatic tire that can reduce rolling resistance while ensuring braking distance and wear resistance.

  A first feature of the present invention is a pneumatic tire (pneumatic tire 1) including at least a pair of bead parts (bead part 11) including at least a bead toe (bead toe 11c) and a tread part (tread part 15) in contact with a road surface. In the tread width direction cross section, from the intersection (L) of the bead line (BL) passing through one bead toe and the other bead toe and the tire equator line (CL) to the surface (M) of the tread part When the height of the section is SH and the maximum tire width is SW, the height from the point P located at 0.8 SW on the surface of the tread portion around the tire equator line to the bead line in the cross section in the tread width direction. The height PH is 0.93 SH or more, and the height QH from the point Q located at the outermost position in the tread width direction on the maximum tire width to the bead line is 0.6 SH. And summarized in that a top.

  Here, the provisions of the present invention are those when a pneumatic tire is assembled on a predetermined rim standardized by JATMA or the like.

  According to such a feature, the height PH from the point P located at 0.8 SW on the surface of the tread portion around the tire equator line to the bead line is 0.93 SH or more, and is the highest in the tread width direction on the maximum tire width. When the height QH from the point Q located at the outer position to the bead line is 0.6 SH or more, the rolling resistance can be reduced while ensuring the braking distance and the wear resistance.

  Specifically, the tread portion and the belt layer of the pneumatic tire of the present invention are flat with respect to the road surface, and a portion having a small curvature radius is locally deformed outside the belt layer (that is, the belt end). The bending deformation of the belt layer is reduced. Therefore, the contraction in the tread width direction in the belt layer and the pushing of the rubber constituting the shoulder of the tread portion are alleviated, and the shear deformation in the tread width direction in the tread portion shoulder is reduced. Thereby, the pneumatic tire of the present invention can reduce rolling resistance while ensuring braking distance and wear resistance.

  If the height RH is lower than 0.93SH and the height QH is lower than 0.6SH, the radius of curvature at the shoulder of the tread portion becomes large, and the braking distance and wear resistance are ensured. I can't.

  In the present invention, the pneumatic tire further includes a carcass layer (carcass layer 12) serving as a skeleton of the pneumatic tire. In the carcass line having a cross-sectional shape in the tread width direction of the carcass layer, the tire is centered on the tire equator line. The height RH from the point R located at 0.9 SW on the radially outer side to the bead line is preferably 0.72 SH or more. If the height RH is lower than 0.72SH, the braking distance and the wear resistance may not be ensured.

  In the present invention, the pneumatic tire further includes at least two belt layers (the first belt layer 14a and the second belt layer 14b), and the width of the tread contact surface in contact with the road surface in the tread portion in the tread width direction cross section. The tread ground contact width is preferably wider than the belt intersection width, which is the width at which the two belt layers intersect in the tire radial direction. In the present invention, the term “tread grounding width is wider than the belt crossing width” includes the case where the tread grounding width and the belt crossing width are the same. As a result, the pushing of the rubber constituting the shoulder of the tread portion is further relaxed, and the shear deformation in the tread width direction at the shoulder of the tread portion becomes smaller, so that the braking distance and wear resistance are ensured and the effect is further improved. Thus, rolling resistance can be reduced.

  ADVANTAGE OF THE INVENTION According to this invention, the pneumatic tire which can reduce rolling resistance can be provided, ensuring a braking distance and abrasion resistance.

  Next, an example of the pneumatic tire 1 according to the present invention will be described with reference to the drawings. In the following description of the drawings, the same or similar parts are denoted by the same or similar reference numerals. However, it should be noted that the drawings are schematic and ratios of dimensions are different from actual ones. Accordingly, specific dimensions and the like should be determined in consideration of the following description. Moreover, it is a matter of course that portions having different dimensional relationships and ratios are included between the drawings.

(Composition of pneumatic tire)
FIG. 1 is a cross-sectional view in the tread width direction of a pneumatic tire 1 according to the present embodiment. In addition, since the structure of the pneumatic tire which concerns on this embodiment is object with respect to a tire equator line, about a drawing, it shall show only on one side from a tire equator line.

  As shown in FIG. 1, the pneumatic tire 1 has a pair of bead portions 11 including a bead core 11a, a bead filler 11b, and a bead toe 11c that contact a rim portion (not shown) of the wheel.

  The pneumatic tire 1 has a carcass layer 12 that is a skeleton of the pneumatic tire 1. Further, an inner liner 13 which is a highly airtight rubber layer corresponding to a tube is provided on the inner side in the tire radial direction of the carcass layer 12.

  A belt layer 14 is disposed outside the carcass layer 12 in the tire radial direction. Specifically, the belt layer 14 includes a first belt layer 14a located on the outer side in the tire radial direction of the carcass layer 12, and a second belt layer 14b located on the outer side in the tire radial direction of the first belt layer 14a. Has been. A tread portion 15 that is in contact with the road surface is disposed on the outer side of the belt layer 14 in the tire radial direction.

  Here, in the pneumatic tire 1, the section height which is the height from the intersection L between the bead line BL passing through one bead toe 11c and the other bead toe 11c and the tire equator line CL to the surface M of the tread portion is SH. When the tire maximum width is SW, the height PH from the point P located at 0.8 SW on the surface of the tread portion 15 around the tire equator line CL to the bead line BL is 0.93 SH or more ( PH ≧ 0.93SH).

  Further, in the pneumatic tire 1, the height QH from the point Q positioned at the outermost position in the tread width direction with the tire maximum width SW to the bead line BL is 0.6SH or more (QH ≧ 0.6SH).

  Further, in the pneumatic tire 1, in the carcass line that is the cross-sectional shape in the tread width direction of the carcass layer 12, from the point R located 0.9 SW outside the tire radial direction centering on the tire equator line CL to the bead line BL. The height RH is 0.72SH or more (RH ≧ 0.72SH).

  Further, in the pneumatic tire 1, the tread ground contact width CW, which is the width of the tread ground contact surface in contact with the road surface in the tread portion 15, intersects (overlaps) the first belt layer 14a and the second belt layer 14b in the tire radial direction. It is configured wider than the belt crossing width BW which is the width (CW ≧ BW).

  In the following, the background to the adoption of the configuration of the pneumatic tire 1 described above will be described together with the operation. Most of the rolling resistance of the tire is due to strain energy loss of the rubber constituting the tread portion 15. The strain energy loss of the tread portion 15 is mainly caused by shear deformation in the tire circumferential direction in the vicinity of the tire equator line CL of the tread portion 15, and is caused by shear deformation in the tread width direction in the vicinity of the shoulder of the tread portion 15. We know that what happens is the main thing.

In order to suppress the shear deformation in the tire circumferential direction in the vicinity of the tire equator line CL of the tread portion 15, the bending rigidity of the tread portion 15 in the tire circumferential direction is increased, and the strain energy loss due to the shear deformation caused by the bending deformation is increased. It is effective to reduce. For this purpose, it is important to increase the belt tension (T ₀ ).

As shown in FIG. 2, this belt tension (T ₀ ) is expressed by 1/2 Pa (b−r ₀ sin θ). Therefore, in the pneumatic tire 1, as described above, QH ≧ 0.6SH and RH By setting ≧ 0.72 SH, θ and r ₀ become small, and the belt tension becomes large. For this reason, the pneumatic tire 1 of the present invention can prevent the braking distance from becoming long and the wear resistance from being lowered.

Here, as shown in FIG. 3, the conventional pneumatic tire 10 is configured such that the tread ground contact width CW is narrower than the belt crossing width BW (CW ≦ BW). That is, in the cross section in the tread width direction, the second belt layer 140b is configured wider than the tread ground plane. Further, the conventional pneumatic tire 10 is configured such that the radius of curvature r ₀ at the shoulder of the tread portion 150 is larger than that of the pneumatic tire 1 of the present invention.

Further, as shown in FIG. 4, the pneumatic tire 1 of the present invention has a tread contact width CW wider than the belt crossing width BW (CW ≧ BW). That is, in the cross section in the tread width direction, the second belt layer 14b is configured to be narrower than the tread ground plane. Further, the pneumatic tire 1 of the present invention is configured such that the radius of curvature r ₀ at the shoulder of the tread portion 15 is smaller than that of the conventional pneumatic tire 10.

  As a result of comparing the deformation state of the conventional pneumatic tire 10 shown in FIG. 3 and the pneumatic tire 1 of the present invention shown in FIG. 4, the conventional pneumatic tire 10 has a ground contact end that is an end portion on the tread contact surface. Since the second belt layer 140b is disposed on the inner side in the tire radial direction of the belt portion, the belt layer 140 (the first belt layer 140a and the second belt layer 140b) has a large bending deformation, and the tread generated within the belt crossing width BW. Large shear strain in the width direction.

  On the other hand, in the pneumatic tire 1 of the present invention, the second belt layer 14b is not disposed on the inner side in the tire radial direction of the ground contact end, and therefore the belt layer 14 (the first belt layer 14a and the second belt layer 14b). ) Near the shoulder of the tread portion 15 is locally deformed on the outer side in the tread width direction, the bending deformation of the belt layer 14 is small, and shear strain in the tread width direction generated within the belt crossing width BW can be suppressed.

  As described above, the pneumatic tire 1 of the present invention can reduce rolling resistance while ensuring braking distance and wear resistance.

  Next, in order to further clarify the effects of the present invention, the results of tests performed using pneumatic tires according to comparative examples and examples to which the present invention is applied will be described. In addition, the data regarding a pneumatic tire were measured on the conditions shown below.

・ Tire size: 235 / 35ZR19
・ Wheel size: 8.5J × 19
・ Internal pressure condition: 250kPa
・ Load condition: 4.0kN
Here, as shown in FIG. 5, the pneumatic tire 10 according to the comparative example satisfies PH ≧ 0.92SH, QH ≧ 0.54SH, RH ≧ 0.64SH, and CW ≦ BW. Moreover, as shown in FIG. 6, the pneumatic tire 1 according to the embodiment to which the present invention is applied has PH ≧ 0.94SH, QH ≧ 0.61SH, RH ≧ 0.74SH, and CW ≧ BW.

Table 1 shows the results regarding the braking distance, wear resistance, and rolling resistance of the pneumatic tires according to the comparative example and the example.

<Braking distance>
When each pneumatic tire is mounted on a vehicle and traveling at a speed of 100 km / h, the braking distance of the pneumatic tire 10 according to the comparative example is set to “100”, and the braking distance of the pneumatic tire 1 according to the embodiment is displayed as an index. did. Note that the smaller the index, the shorter the braking distance.

  As a result, it was found that the pneumatic tire 1 according to the example has a braking distance equivalent to that of the pneumatic tire 10 according to the comparative example.

<Abrasion resistance>
Each pneumatic tire is mounted on a drum tester, and the abrasion resistance of the pneumatic tire 10 according to the comparative example after running 2000 km is set to “100”, and the abrasion resistance of the pneumatic tire 1 according to the embodiment is displayed as an index. did. In addition, it shows that it is excellent in uneven wear resistance, so that an index | exponent is large.

  As a result, it was found that the pneumatic tire 1 according to the example has the same wear resistance as the pneumatic tire 10 according to the comparative example.

<Rolling resistance>
Each pneumatic tire is mounted on a drum testing machine, and the rolling resistance of the pneumatic tire 10 according to the comparative example when traveling at a speed of 80 km / h is set to “100”, and the rolling resistance of the pneumatic tire 1 according to the example is The index was displayed. In addition, it shows that rolling resistance is so small that an index | exponent is small.

  As a result, it turned out that the pneumatic tire 1 which concerns on an Example has small rolling resistance compared with the pneumatic tire 10 which concerns on a comparative example.

  Thus, it turned out that the pneumatic tire 1 which concerns on the Example to which this invention was applied can reduce rolling resistance, ensuring a braking distance and abrasion resistance.

It is a tread width direction sectional view of the pneumatic tire concerning this embodiment (the 1). It is a tread width direction sectional view of the pneumatic tire concerning this embodiment (the 2). It is a tread width direction sectional view when the conventional pneumatic tire is in contact with the road surface. It is a tread width direction sectional view when the pneumatic tire concerning this embodiment is in contact with the road surface. It is a tread width direction sectional view of the pneumatic tire concerning a comparative example. It is a tread width direction sectional view of a pneumatic tire concerning an example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,10 ... Pneumatic tire, 11 ... Bead part, 11a ... Bead core, 11b ... Bead filler, 11c ... Bead toe, 12 ... Carcass layer, 13 ... Inner liner, 14, 140 ... Belt layer, 14a, 140a ... 1st belt Layer, 14b, 140b ... second belt layer, 15,150 ... tread portion

Claims (3)

A pneumatic tire comprising at least a pair of bead portions including at least a bead toe and a tread portion in contact with a road surface,
In the cross section in the tread width direction, the section height, which is the height from the intersection of the bead line passing through the one bead toe and the other bead toe and the tire equator line to the surface of the tread part, is SH, and the maximum tire width is When SW
In the cross section in the tread width direction, a height PH from a point P located at 0.8 SW on the surface of the tread portion around the tire equator line to the bead line is 0.93 SH or more,
A pneumatic tire characterized in that a height QH from a point Q located at the outermost position in the tread width direction on the tire maximum width to the bead line is 0.6SH or more. It further includes a carcass layer that becomes the skeleton of the pneumatic tire,
In the carcass line having a cross-sectional shape in the tread width direction of the carcass layer, a height RH from a point R located at 0.9 SW on the outer side in the tire radial direction around the tire equator line to the bead line is 0.72SH. It is the above, The pneumatic tire of Claim 1 characterized by the above-mentioned. Further comprising at least two belt layers;
In the cross section in the tread width direction, the tread ground contact width that is the width of the tread ground contact surface in contact with the road surface in the tread portion is wider than the belt cross width that is the width in which the two belt layers intersect in the tire radial direction. The pneumatic tire according to claim 1 or 2.

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