JP2010036598A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which hardly receives external damage to a sidewall part without causing the increase of weight and the deterioration of durability. <P>SOLUTION: The pneumatic tire includes a carcass layer 4 extended between right and left bead parts 3 and a belt layer 7 arranged at the outside circumferential side of the carcass layer 4 of the tread part 1. With the tire attached to a standard rim and in an inside pressure filled state in which air is filled so as to become pneumatic pressure corresponding to the maximum load capacity, the tire maximum width position Pm of the sidewall part 2 is positioned in a range 2a to the outside the tire radial direction from the position P1 of 50% of the tire cross section height SH. In a state before the tire is attached to the standard rim, the cross sectional shape of the carcass layer 4 extending to the sidewall part 2 becomes straight at the sidewall part 2b to the bead part 2 side from the tire maximum width position Pm or curves outward in a concave shape. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that is less likely to be damaged by sidewalls.

  When traveling on rough terrain such as a desert, the tire pressure is made lower than when driving on a general asphalt road surface, thereby improving the envelope characteristics of the tread portion and making the tread surface easy to deform following the rough terrain. However, when the air pressure is lowered in this way, as shown in FIG. 3, the sidewall portion 21 of the tire 20 is greatly deformed further outward in the tire width direction upon contact with the ground, so the sidewall portion 21 is obstructed by an obstacle on the road surface. Becomes more susceptible to trauma.

Conventionally, as a technique for solving the problem of trauma in the sidewall portion of a pneumatic tire, for example, the thickness of the sidewall portion is increased, or a reinforcing layer is embedded in the sidewall portion to improve the trauma resistance. A technique is known (see, for example, Patent Document 1). However, these methods have a problem that the durability is reduced due to an increase in weight or local stress concentration on the reinforcing layer.
JP 2006-160106 A

  An object of the present invention is to provide a pneumatic tire that is less susceptible to side wall damage without causing an increase in weight or a decrease in durability.

  The pneumatic tire of the present invention that achieves the above object is a pneumatic tire in which a carcass layer is extended between left and right bead portions, and a belt layer is disposed on the outer circumferential side of the carcass layer of a tread portion. Mounted on the rim, with the internal pressure filling state filled with air so that the air pressure corresponds to the maximum load capacity specified by the standard, the tire maximum width position of the sidewall portion from the position of 50% of the tire cross-section height SH A curve in which the cross-sectional shape of the outer surface of the sidewall portion is linear or concave on the outer side of the tire maximum width position before being mounted on the standard rim while being positioned in the radially outer region. It is characterized by the shape.

  According to the present invention described above, the cross-sectional shape of the outer surface of the sidewall portion is linear or curved at the bead portion side from the tire maximum width position, while the tire maximum width position is the tire cross-section height. By positioning it in the region radially outside of the tire from the position of 50% of the SH, the cross-sectional shape of the outer surface of the sidewall part becomes a straight line or a curved line that is concave outward at the bead part side from the tire maximum width position. A sufficient area can be secured. As a result, when used at low air pressure, the bead portion side of the sidewall portion does not spread greatly outward in the tire width direction as in the prior art at the time of ground contact, so that the sidewall portion can be prevented from being greatly deformed outward in the tire width direction. . Therefore, the sidewall portion is not easily damaged. On the other hand, since there is no need to add a new reinforcing layer or increase the thickness of the sidewall portion, there is no problem that the durability is lowered or the weight is increased.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of the pneumatic tire of the present invention, where 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 extends between the left and right bead portions 3, and both end portions are folded back from the inner side in the tire axial direction so as to sandwich the bead filler 6 around the bead core 5 embedded in the bead portion 3. A plurality of belt layers 7 are provided on the outer peripheral side of the carcass layer 4 of the tread portion 1. The bead filler 6 having a triangular cross section disposed on the outer peripheral side of the bead core 5 extends toward the sidewall portion 2.

  The tire maximum width position Pm of the sidewall portion 2 is the tire cross-sectional height in the internal pressure filling state in which the air pressure is filled so as to be the air pressure corresponding to the maximum load capacity specified by the standard. The tire maximum width position Pm is arranged on the tread surface 8 side, located in the region 2a on the outer side in the tire radial direction from the position P1 of 50% of SH. The tire maximum width position Pm referred to here is a position where the tire has the maximum width in a state excluding decorative portions protruding from the surface such as letters and symbols on the surface of the sidewall portion 2, in other words, the carcass layer 4 Is the position with the maximum width.

  Further, in the state before being attached to the standard rim, that is, the state shown in FIG. 1, the cross-sectional shape of the outer surface 2m of the sidewall portion 2 is the portion 2b of the sidewall portion 2 on the bead portion 3 side from the tire maximum width position Pm. And has a curved shape consisting of a predetermined arc that is concave outward (convex inward).

  The standard referred to in the present invention is a tire corresponding to JATMA (Japan Automobile Tire Association) standard, and does not correspond to JATMA or JATMA standard, but conforms to TRA (American Tire and Rim Association) standard. If applicable, the TAR standard, and if applicable to the ETRTO (European Tire and Rim Technical Organization) standard, the ETRTO standard.

  The pneumatic tire configured as described above has a cross section of the outer surface 2m of the sidewall portion 2 by positioning the tire maximum width position Pm in the region 2a outside the tire radial direction from the position P1 of 50% of the tire cross-section height SH. It is possible to sufficiently secure a curved region whose shape is concave outward. Therefore, when the air pressure is lowered and used, as shown in FIG. 2, the bead portion 3 side of the sidewall portion 2 does not open outward in the tire width direction as in the conventional tire of FIG. 2 can be prevented from being greatly deformed outward in the tire width direction. Accordingly, it is possible to make the side wall portion 2 difficult to be damaged. Since it is not necessary to add a new reinforcing layer or increase the thickness of the sidewall portion, the durability is not lowered and the weight is not increased.

  In the present invention, as the range R1 of the region 2a where the tire maximum width position Pm is located, the upper limit value is particularly from the viewpoint of the above effect as long as it is a range radially outside the position P1 of 50% of the tire cross-section height SH. Although not limited, from the viewpoint of the actual tire structure, the position can be up to 70% of the tire cross-section height SH. When the tire maximum width position Pm is located on the inner side in the tire radial direction from the position P1 at 50% of the tire cross-section height SH, the region where the cross-sectional shape of the outer surface 2m of the sidewall portion 2 is concavely curved outward is insufficient. Therefore, it becomes difficult to effectively suppress the sidewall portion 2 from being greatly deformed outward in the tire width direction. Preferably, a range from a position of 55% of the tire cross-section height SH to a position P2 of 70% is good.

  The tread development width TDW should be 80% or more of the total tire width SW in the internal pressure filling state, so that the tire outer surface line from the shoulder portion to the sidewall portion is The possibility of injury is reduced. The upper limit value of the tread development width TDW is 100% or less of the total tire width SW. The tread development width TDW referred to here is the development width between the intersections of the line of the tread surface 8 and the lines of the outer surfaces 2a of both sidewall portions 2 in the tire meridian cross section. In the case of being formed by arc-shaped lines, it is a developed width between virtual points where an extension line of the arc line forming the tread surface 8 and an extension line of the line forming the sidewall portion outer surface 2a intersect.

  In the internal pressure filling state, the thickness of the sidewall portion 2 at the tire maximum width position Pm is a, the tire maximum width position Pm to the tread surface 8 (position on the tire equator surface TE), and the tire maximum width position Pm. Assuming that the thickness at the position B of 20% of the length L in the tire radial direction is b, and the thickness at the position C of 50% of the length L from the tire maximum width position Pm is c, a <b It is preferable that the relationship of <1.3a and a <c <1.3a is satisfied. When the thicknesses b and c are equal to or less than the thickness a, steering stability is lowered. When the thicknesses b and c are 1.3 times or more the thickness a, the buffer region becomes narrow, and it becomes difficult to ensure riding comfort performance.

  Attach to a standard rim specified by the standard, fill with air to 30% of the air pressure corresponding to the maximum load capacity specified by the standard, and apply a load equivalent to 35% of the maximum load capacity In the tire meridian section, the angle θ with respect to the tire radial direction of the tangent line N drawn on the surface of the sidewall portion 2 at the tread deployed width position Pd in the tire meridian section is 15 ° or less. It is sufficient to further suppress deformation to the outer side in the tire width direction. The lower limit of the angle θ is preferably 0 ° or more from the viewpoint of wear resistance.

  The bead filler 6 using rubber whose hardness is higher than that of the surrounding tire constituent members is such that, in the internal pressure filling state, the outer peripheral end 6x is in the range R2 from the position P3 where the tire cross-section height SH is 35% to the position P4 where 55%. It is good to arrange so that it may be located in the tire radial direction inner side from tire maximum width position Pm. When the outer peripheral edge 6x is located on the inner side in the tire radial direction from the position P3 of 35% of the tire cross-section height SH, the bead filler 6 effectively suppresses the sidewall portion 2 from being greatly deformed outward in the tire width direction at the time of contact. It becomes difficult. When the outer peripheral edge 6x is located on the outer side in the tire radial direction from the position P4 of 55% of the tire cross-section height SH, a free deformation region that is not constrained by the bead filler 6 is narrowed. Further, peeling occurs at the interface of the bead filler 6 and the durability is deteriorated.

  Measured at the position corresponding to the rim width BW of the left and right bead parts 3 before being attached to the standard rim (the state of FIG. 1) than the width (rim width) of the left and right bead parts 3 when attached to the standard rim. When the rim is assembled by this, a residual stress is generated in the bead filler 6 toward the inner side in the tire width direction, and the cross-sectional shape of the outer surface 2m of the sidewall portion 2 is changed to the shape described above. Can be made easier.

  The difference between the width of the left and right bead portions 3 when attached to the standard rim and the width BW of the left and right bead portions 3 before being attached to the standard rim is preferably in the range of 12.5 to 40 mm. If the difference is smaller than 12.5 mm, the above-described residual stress is not sufficiently generated. If the difference is larger than 40 mm, a problem of vulcanization failure may occur.

  In the present invention, in the above embodiment, the cross-sectional shape (profile) of the outer surface 2m of the sidewall portion 2 is a curved shape that is concave outward at the portion 2b of the sidewall portion 2 on the bead portion 3 side from the tire maximum width position Pm. However, it may be linear instead.

  The present invention can be particularly preferably used for a pneumatic tire having an aspect ratio of 70% or more, and can be suitably used for a racing tire that travels on rough terrain such as a desert provided with at least three carcass layers 4. However, it is not limited to that.

  The tire size is the same for 315 / 80R17, and the configuration shown in FIG. 1 is such that the cross-sectional shape of the carcass layer in the side wall portion on the bead portion side from the tire maximum width position and the tire maximum width position in the sidewall portion is as shown in Table 1. The tires 1 to 4 (Examples 1 to 4), the comparative tire (Comparative Example), and the conventional tire (Conventional Example) having three carcass layers were produced.

  In the tire of the present invention and the comparative tire, the tread development width TDW is 90% of the total tire width SW, the thicknesses a, b, and c of the sidewall portions are 8.0 mm, 9.0 mm, 10.0 mm, and the angle θ is 15 respectively. The position of the outer peripheral edge of the bead filler is 45% of the tire cross-section height SH, and the difference in width between the left and right bead portions is 279 mm. In the conventional tire, the tread development width TDW is 75% of the total tire width SW, the thicknesses a, b, and c of the sidewall portions are 8.0 mm, 10.0 mm, 13.0 mm, the angle θ is 30 °, and the bead filler. The position of the outer peripheral edge is 30% of the tire cross-section height SH, and the difference between the widths of the left and right bead portions is 254 mm.

Each of these test tires was assembled to a wheel having a rim size of 37 × 12.50R17, mounted on a four-wheel drive vehicle with an air pressure of 120 kPa, and the side wall portion was subjected to a trauma test by the following test method. The result was obtained.
Injury test In Galeva (2.1 km per lap, dedicated test circuit with hard road and rock), the number of flaws received on the outer surface of the side wall after running 15 laps at 80 km / h. It was measured. The evaluation result is shown as an index value with the conventional tire as 100. The larger the index value, the less likely it is to receive trauma.

表１から、本発明タイヤは、いずれも外傷試験において１０２以上あり、サイドウォール部に対する外傷を受け難くできることがわかる。

From Table 1, it can be seen that the tires of the present invention all have 102 or more in the trauma test and are less susceptible to trauma to the sidewall portion.

It is a tire meridian sectional view showing one embodiment of a pneumatic tire of the present invention. It is a section explanatory view showing the deformation state at the time of grounding of the pneumatic tire of the present invention. It is sectional explanatory drawing which shows the deformation | transformation state at the time of the grounding of the conventional pneumatic tire.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 2a Area | region 2b Part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 6x Outer peripheral edge 7 Belt layer 8 Tread surface R1, R2 Range P1, P2, P3, P4 position Pm Tire maximum width position

Claims (9)

  In a pneumatic tire in which a carcass layer is extended between the left and right bead parts and a belt layer is arranged on the outer periphery of the carcass layer in the tread, it is attached to a standard rim specified by the standard, and the maximum load capacity specified by the standard In the internal pressure filling state in which the air pressure is filled so as to correspond to the air pressure, the maximum tire width position of the sidewall portion is positioned in the region radially outside of the tire in the tire radial direction from the position of 50% of the tire cross-section height SH. A pneumatic tire in which the cross-sectional shape of the outer surface of the sidewall portion is a straight line or a curved shape that is concave outward at a portion closer to the bead portion than the maximum width position of the tire before being attached to the tire.   2. The pneumatic tire according to claim 1, wherein a range of a region on the outer side in the tire radial direction is from a position of 50% to a position of 70% of a tire cross-section height SH.   In the internal pressure filling state, the thickness of the sidewall portion 2 at the tire maximum width position Pm is a, and the tire radial length L between the tire maximum width position Pm and the tread surface and the tire maximum width position Pm is 20 % Where b is the thickness at the position B, and c is the thickness at the position C that is 50% of the length L from the tire maximum width position Pm, a <b <1.3a and a <c <1.3a The pneumatic tire according to claim 1 or 2 satisfying the relationship:   In the tire meridian cross-section with the standard rim attached, filled with air so that the air pressure is 30% of the air pressure corresponding to the maximum load capacity, and a load corresponding to 35% of the maximum load capacity is applied. The pneumatic tire according to any one of claims 1 to 3, wherein an angle θ with respect to a tire radial direction of a tangent N drawn on the surface of the sidewall portion at a tread deployed width position is set to 15 ° or less.   A bead core is embedded in the bead portion, a bead filler extending toward the sidewall portion is disposed on the outer peripheral side of the bead core, and in the internal pressure filling state, the outer peripheral end of the bead filler is set to a tire sectional height SH of 35. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is positioned in a tire radial direction inner side than a tire maximum width position in a range of a position of 55% to a position of 55%.   6. The width of the left and right bead portions before being attached to the standard rim is wider than the width of the left and right bead portions when attached to the standard rim, and the difference is 12.5 to 40 mm. The pneumatic tire according to item 1.   The pneumatic tire according to any one of claims 1 to 6, wherein in the internal pressure filling state, a tread development width TDW is 80% to 100% of a tire total width SW.   The pneumatic tire according to claim 1, wherein there are at least three carcass layers.   The pneumatic tire according to any one of claims 1 to 8, wherein the flatness is 70% or more.

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