JP5506509B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire (hereinafter, also simply referred to as “tire”), and more particularly to a pneumatic tire according to an improvement in the shape of a bead portion.

  The bead portion of the pneumatic tire is a part that is in contact with the rim and maintains internal pressure and transmits driving and braking. In general, the bead portion 30 has a shape as shown in FIG. 3 and is fitted to the rim.

  On the other hand, as a method for reducing the tire uniformity index, such as RFV (Radial Force Variation) and LFV (Lateral Force Variation), conventionally, tire RFV, LFV, etc. are measured over the entire circumference, It has been widely practiced to assemble the rim by matching the position where the measured value is maximum with the position of the standard rim on which the tire is assembled with the smallest peripheral runout.

  Further, as a technique for improving the uniformity of the wheel by improving the bead part, for example, Patent Documents 1 and 2 provide a bead part with a bulging heel that satisfies a predetermined condition. In addition to prescribing a predetermined radius of curvature in the cross section in the tire width direction, an annular recess is provided in an adjacent portion of the bulging heel on the side of the sidewall, and the radius of curvature in the cross section in the tire width direction is A bead portion structure of a pneumatic tire having a predetermined magnification range of the radius of curvature is disclosed.

JP-A-6-40221 (Claims etc.) JP 2001-253216 A (Claims etc.)

  However, when the tire is actually assembled to the rim, the bead portion 30 is in a twisted state after filling because the bead portion 30 has a large resistance to get over the hump portion 21 (see FIG. 4) of the rim 20 when the air pressure is filled. It will fit the rim. That is, since the bead portion 30 rotates within the cross section in the width direction, the bead toe (tip) 31 and the back surface 32 of the bead portion 30 interfere with the rim 20, and the bead portion 30 is twisted. For this reason, as shown in the drawing, the angle of the bead portion 30, and hence the contact positions X ′ and Y ′ of the bead portion 30 with the rim 20 change in the tire circumferential direction depending on the degree of twist of the bead portion 30 (contact position). X ″ and Y ″), the assembly accuracy is lowered, and the uniformity of tires such as RFV and LFV is supposed to be deteriorated.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic tire that solves the above-described problems and prevents a decrease in tire uniformity associated with a rim assembly.

  As a result of intensive studies, the present inventors have found the following. That is, the deterioration of tire uniformity due to the rim assembly as described above is considered to be because the position of the bead core 1 in the tire radial direction and the tire width direction changes depending on the position in the tire circumferential direction. Therefore, in order to prevent the deterioration of uniformity, it is considered important that the position of the bead core 1, more specifically, the position of the center C of the bead core 1 is uniform in the tire circumferential direction.

  From this point of view, as a result of further studies, the present inventor has improved the cross-sectional shape of the bead portion in contact with the rim, and suppresses fluctuations in the tire circumferential direction of the center position of the bead core when the bead portion is twisted. Thus, the inventors have found that the above problems can be solved, and have completed the present invention.

That is, the present invention is a pneumatic tire having a carcass framed around a bead core embedded in each of a pair of bead portions and locked.
In the cross section of the bead portion, the region from the back surface to the base of the bead portion is an arc centered at the intersection of the neutral axis for bending in the tire radial direction and the neutral axis for bending in the tire width direction of the bead core cross section. The rim has a shape, and the region from the back surface to the base of the bead portion has a tire mounted on a standard rim and the bead portion holds the outer surface in the tire axial direction in a no-load state filled with the standard internal pressure. In a no-load state in which the bead portion includes at least a position Y that contacts the rim base that holds the bottom surface of the bead portion, and the tire is mounted on the standard rim and filled with the standard internal pressure. It is an end portion of the arc shape and is outside the position X and the position Y, and has a gap with the standard rim.

  Here, the standard is a standard determined by an industrial standard effective in an area where a tire is produced or used. For example, “The Tire and Rim Association Inc.'s Year Book” in the United States, “The European Tire and Rim Technical Institute's Japan in Japan” It is prescribed. Therefore, the standard internal pressure is an air pressure defined by the above standard, and the standard rim is a standard rim (or “AppliedRim” or “Recommended Rim”) in an applicable size described in the standard.

  According to the present invention, with the above configuration, even when the bead portion is twisted, unevenness in the tire circumferential direction at the position of the bead core center can be suppressed. It has become possible to realize a pneumatic tire that prevents deterioration of uniformity.

It is an expanded fragmentary sectional view which shows the bead part of an example of the pneumatic tire of this invention. It is explanatory drawing which shows the state of the twist of the bead part at the time of assembling the rim | limb of the pneumatic tire of this invention. It is an expanded partial sectional view which shows the bead part of an example of the conventional pneumatic tire. It is explanatory drawing which shows the state of the twist of the bead part at the time of assembling the rim | limb of the conventional pneumatic tire.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
The present invention includes a tread portion and a pair of sidewall portions and bead portions continuous on both sides of the tread portion, and a carcass framed around a bead core embedded in the pair of bead portions. This relates to the improvement of the cross-sectional shape of the bead portion of the tire.

  FIG. 1 is an enlarged partial sectional view showing a bead portion of an example of the pneumatic tire of the present invention. As shown in the figure, in the pneumatic tire of the present invention, the region from the back surface 11 to the base 12 of the bead portion 10 in the cross section of the bead portion 10 is a neutral axis for bending in the tire radial direction of the cross section of the bead core 1. It has an arc shape centered at the intersection with the neutral axis for bending in the tire width direction. Here, the intersection of the neutral axes substantially means the center C of the bead core 1, for example, the bead core having a circular cross section coincides with the center of the circle, and the bead core having a rectangular cross section coincides with the intersection of diagonal lines. . Further, in the present invention, the region from the back surface 11 to the base 12 of the bead portion 10 refers to the bead portion 10 in a no-load state in which the tire is mounted on the standard rim 20 and filled with the standard internal pressure as shown in FIG. However, it means a region including at least the position X that contacts the rim flange 22 that holds the outer surface in the tire axial direction to the position Y that the bead portion 10 contacts the rim base 23 that holds the bottom surface.

  The tire of the present invention has gaps A and B between the standard rim 20 and the standard rim 20 at the end of the arc shape when mounted on the standard rim 20 and filled with standard internal pressure. By adopting such a bead portion shape, when the tire is assembled to the rim, the bead portion 10 comes into contact with the rim at the points X and Y by the arc-shaped portion in both the tire radial direction and the tire width direction. . Therefore, the position of the bead portion 10 is determined by the contact between the vertical portion of the rim flange 22 and the arc-shaped portion of the bead portion 10 in the tire width direction, and the rim base 23 and the arc-shaped portion of the bead portion 10 in the tire radial direction. Even if the bead portion is twisted, the position of the arc-shaped portion in the tire radial direction and the tire width direction is always constant with respect to the rim cross section over the entire bead.

  In the tire of the present invention, since the center of the arc shape of the bead portion 10 and the center of the bead core 1 coincide with each other, as shown in the drawing, even when the bead portion 10 is twisted, the center of the bead core 1 is centered. There is no change in position, and it is always located at a constant distance with respect to the cross-section of the rim 20 over the entire circumference of the bead, like the position of the arc-shaped portion. As a result, it is possible to prevent a decrease in tire uniformity due to the rim assembly by suppressing a decrease in rim assembly accuracy.

  If the gaps A and B are formed so that the bead portion 10 and the standard rim 20 do not come into contact with each other at the end of the circular arc shape when the tire is assembled to the rim, the gap amount is as follows. Is not particularly limited.

  In the tire of the present invention, the points other than the bead portion shape are not particularly limited, and can be appropriately configured according to a conventional method. For example, although not shown, the tire of the present invention includes a carcass ply that reinforces a tread portion and a pair of sidewall portions and bead portions connected to both sides of the tread portion between a pair of bead cores 1 embedded in the bead portion. And at least one belt layer disposed on the outer side in the tire radial direction. Of these, the carcass ply is composed of rubber-coated cords arranged in parallel to each other, and it is necessary to arrange at least one layer, but it may be arranged in two or more layers, and usually around the bead core 1 from the inside to the outside of the tire. It is folded back and locked. Further, the belt layer is formed by rubberizing reinforcing cords arranged in parallel at a predetermined angle with respect to the tire circumferential direction, and is usually at least two layers and arranged so as to cross each other.

  Further, a tread pattern is appropriately formed on the surface of the tread portion, and an inner liner (not shown) is formed in the innermost layer. Furthermore, in the tire of the present invention, as the gas filled in the tire, normal or air having a changed oxygen partial pressure, or an inert gas such as nitrogen can be used.

Hereinafter, the present invention will be described more specifically with reference to examples.
<Example>
As shown in FIG. 1, in the cross section of the bead portion 10, the region from the back surface 11 to the base 12 of the bead portion is a neutral axis of the cross section of the bead core 1 with respect to the bending in the tire radial direction and the middle with respect to the bending in the tire width direction. A pneumatic tire having an arc shape centered at the intersection with the vertical axis was manufactured with a tire size of 245 / 40R18. This tire was mounted on a standard rim and had a gap between the tire and the standard rim at an arc-shaped end in an unloaded state filled with standard internal pressure.

<Conventional example>
A conventional pneumatic tire was produced in the same manner as in the example except that the cross-sectional shape of the bead portion was changed to the shape shown in FIG. Also in this tire, the region from the back surface 32 to the base 33 of the bead portion 30 is formed in an arc shape, and the center of the arc shape is a neutral axis of the cross section of the bead core 1 with respect to bending in the tire radial direction, It does not coincide with the intersection with the neutral axis for bending in the tire width direction.

  The results of evaluation according to the following for each test tire obtained are also shown in the table below.

<Measurement of RFV and LFV deterioration due to rim assembly>
Each of the obtained test tires was assembled on a rim and filled with an internal pressure of 220 kPa, and the amount of RFV and LFV deterioration associated with the rim assembly was measured. The results are shown as indices with the conventional tire as 100. The smaller the number, the better the uniformity.

<Measurement of deterioration of runout in tire radial direction and tire width direction with rim assembly>
Each obtained test tire was assembled on a rim and filled with an internal pressure of 220 kPa, and the amount of deterioration in runout in the tire radial direction and the tire width direction associated with the rim assembly was measured. The results are shown as indices with the conventional tire as 100. The smaller the numerical value, the smaller the deterioration amount and the better.

  As shown in the above table, in the test tire of the example having the bead portion shape according to the present invention, the tire radial direction associated with the rim assembly compared to the conventional test tire of the conventional bead portion shape In addition, the deterioration amount of the runout in the tire width direction was significantly reduced, and it was confirmed that the uniformity of tires represented by RFV and LFV was greatly improved.

DESCRIPTION OF SYMBOLS 1 Bead cores 10 and 30 Bead parts 11 and 32 Back surface 12 and 33 of bead parts 20 Base 20 of a bead part Rim 21 Hump part 22 Rim flange 23 Rim base 31 Bead toe

Claims (1)

In a pneumatic tire having a carcass framed around a bead core embedded in each of a pair of bead parts,
In the cross section of the bead portion, the region from the back surface to the base of the bead portion is an arc centered at the intersection of the neutral axis for bending in the tire radial direction and the neutral axis for bending in the tire width direction of the bead core cross section. The rim has a shape, and the region from the back surface to the base of the bead portion has a tire mounted on a standard rim and the bead portion holds the outer surface in the tire axial direction in a no-load state filled with the standard internal pressure. In a no-load state in which the bead portion includes at least a position Y that contacts the rim base that holds the bottom surface of the bead portion, and the tire is mounted on the standard rim and filled with the standard internal pressure. A pneumatic tire characterized by having a gap with the standard rim at the end of the arc shape and outside the position X and position Y.

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