JP4639872B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire designed to achieve both ground contact and lateral rigidity.

  As a pneumatic tire, there is a racing tire used on a circuit course. In recent years, for competition tires, in order to further shorten the lap time, both lateral rigidity that greatly affects cornering and ground contact that greatly affects gripping force are strongly demanded.

  In general, the lateral rigidity is increased by increasing the rigidity of the sidewall part by extending the end of the carcass layer to the sidewall part to the outside in the tire radial direction, or by arranging a reinforcing layer on the sidewall part. Can do. However, if the rigidity of the sidewall portion is increased, the longitudinal rigidity also increases, so that the tire becomes difficult to bend and the grounding property is impaired, thereby reducing the grip force particularly at a low load and worsening the steering stability. .

Therefore, various proposals have been made to use a special compound for the tread rubber in order to ensure gripping force (see, for example, Patent Document 1). A proposal was desired.
JP 2002-79808 A

  An object of the present invention is to provide a pneumatic tire capable of ensuring lateral rigidity without impairing grounding performance and achieving both grounding performance and lateral stiffness.

The pneumatic tire of the present invention that achieves the above object is disposed around an annular bead core in which both end portions of a carcass layer extending between the left and right bead portions are embedded in the bead portion, and arranged annularly on the outer peripheral side of the bead core. In the pneumatic tire folded back so as to sandwich the bead filler, a recess extending along the tire circumferential direction is provided on the inner surface in the tire width direction of the bead filler, and the carcass layer is bent along the recess extend to Rutotomoni extends to the outer side in the tire radial direction beyond the outer peripheral edge of each end bead filler of the carcass layer, the edge length from said bead core to the end edge of the carcass layer The tire has a length of 60 to 95% of the tire cross-section height .

  According to the above-described present invention, the tension of the reinforcing cord of the carcass layer is lowered at the bent portion inside the bead filler, so that the sidewall portion is liable to fall to the outside, but hardly falls to the inside. As a result, since it becomes easy to bend in the vertical (diameter) direction, it is possible to reduce the vertical rigidity. On the other hand, it is difficult to bend in the horizontal direction, so it is possible to obtain high lateral rigidity. Therefore, even if the rigidity of the sidewall portion is increased, high lateral rigidity can be ensured without impairing the grounding property.

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

  1 and 2 show a racing tire used on a circuit course, which is an embodiment of the pneumatic tire of the present invention, wherein 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion.

  An annular bead core 4 is embedded in each of the left and right bead portions 3, and a bead filler 5 having a triangular cross section extending to the sidewall portion 2 is annularly disposed along the bead core 4 on the outer peripheral side of each bead core 4. ing. The height h of the bead filler 5 has a length of 10 to 70% of the tire cross-section height SH.

  Between the left and right bead portions 3, two carcass layers 6 in which reinforcing cords extending in the tire radial direction are arranged at predetermined intervals in the tire circumferential direction and embedded in the rubber layer are extended, and an inner carcass layer 6 </ b> A is provided. Both end portions 6A1 are folded around the bead core 4 from the tire inner side to the outer side. Both end portions 6B1 of the outer carcass layer 6B are folded back from the inner side of the tire so as to sandwich the bead filler 5 around the bead core 4, and further extend beyond the outer peripheral end 5a of the bead filler 5 to the outer side in the tire radial direction. is doing.

  A plurality of belt layers 7 are disposed on the outer peripheral side of the carcass layer 6 of the tread portion 1, and a plurality of belt cover layers 8 are provided on the outer peripheral side of the belt layer 7. An inner liner layer 9 is disposed inside the carcass layer 6. Both end portions 6B1 of the outer carcass layer 6B extending beyond the outer peripheral end 5a of the bead filler 5 to the outer side in the tire radial direction are extended to the inner peripheral side of the belt layer 7 of the tread portion 1.

  On the inner side surface 5b in the tire width direction of the bead filler 5, a recess 10 is provided that extends in an annular shape along the tire circumferential direction. The carcass layer 6 extends so as to bend along the recess 10. A rubber member 12 made of rubber having a hardness lower than that of the rubber constituting the bead filler 5 is disposed in the concave portion 11 in which the carcass layer 6 is bent.

  In the pneumatic tire described above, two carcass layers 6 are arranged, and both end portions 6B1 of one carcass layer 6B are extended to the tread portion 1 side so that the rigidity of both sidewall portions 2 is increased. However, the depression 10 is formed on the inner surface 5b in the tire width direction of each bead filler 5 made of rubber having a hardness higher than that of the surrounding rubber, and the carcass layer 6 is bent along the depression 10. Since the tension of the reinforcing cord of the carcass layer 6 is lowered at the bent portion inside the bead filler 5, the side wall portion 2 is likely to fall outside, but is difficult to fall inside.

  Accordingly, the sidewall portion 2 is easily bent in the vertical (diameter) direction, so that the vertical rigidity can be lowered. On the other hand, since the side wall portion 2 is hardly bent in the horizontal direction, high lateral rigidity can be obtained. Therefore, even if the rigidity of the sidewall portion 2 is increased, the tire is easily bent, so that high lateral rigidity can be ensured without impairing the grounding property, and both the lateral rigidity and the grounding property can be achieved.

  In the present invention, the depth d of the recess 10 can be in the range of 2 to 7 mm. When the depth d is less than 2 mm, the hollow portion 10 is too shallow to effectively reduce the longitudinal rigidity. Conversely, if it exceeds 7 mm, the bent portion of the carcass layer 6 may be rubbed by the tire internal pressure and cracks may occur.

  The width w of the recess 10 is preferably in the range of 1 to 20 mm. When the width w is narrower than 1 mm, the carcass layer 6 cannot be bent effectively. On the other hand, if the width is larger than 20 mm, the bent portion of the carcass layer 6 may be rubbed by the tire internal pressure and cracks may occur.

  As described above, it is preferable to dispose the rubber member 12 in the bending recess 11 of the carcass layer 6 in order to avoid the tire inner surface from becoming concave and to obtain a good appearance. However, the rubber member 12 is not necessarily disposed. do not have to.

  In the case where the rubber member 12 is arranged as described above, the rubber member 12 is made of rubber having a JIS A hardness of 5 or more at 20 ° C. lower than that of the rubber constituting the bead filler 5. It's okay. The upper limit of the difference is not particularly limited as long as it is a usable rubber. Incidentally, a rubber having a JIS A hardness (20 ° C.) of 70 or more is preferably used for the bead filler 5, and a rubber having a JIS A hardness (20 ° C.) of 65 or less is preferably used for the rubber member 12.

Both end portions 6B1 of the carcass layer 6B, by the extension to the inner peripheral side of the belt layer 7. As described above, it is possible to obtain a high lateral stiffness effectively increases the rigidity of the sidewall portion 2. Both ends 6B1 of the carcass layer 6B extends beyond the outer peripheral edge 5a of the bead filler 5, and end director which is measured along the edge portion 6B1 from the bead core 4 to the edge e of the end 6B1 of the carcass layer 6B is L is you to a length of 60% to 95% of the tire section height.

  If the end length L is shorter than 60% of the tire cross-section height SH, the rigidity of the sidewall portion 2 cannot be effectively increased. When the end portion length L is longer than 95% of the tire cross-section height SH, the longitudinal rigidity increases and the ground contact property is deteriorated.

  In the above embodiment, the depression 10 is provided at one place on the inner surface 5b of the bead filler 5 in the tire width direction. However, it may be provided at one or more places and at a plurality of places as required. The bead filler 5 may be provided at one place on the inner side surface 5b in the tire width direction.

Moreover, in the said embodiment, it was set as the structure which makes the rigidity of the sidewall part 2 high using the carcass layer 6, However, The tire which arrange | positions a reinforcement layer in the sidewall part 2 and makes the rigidity of the sidewall part 2 high. It may be.

  Although this invention can be preferably used especially for the competition tire used on a circuit course, it is not limited to it, It can use suitably also for another pneumatic tire.

  The tire size is made common to 245 / 40R18, and a recess portion extending along the tire circumferential direction is provided on the inner surface of the bead filler in the tire width direction, and the carcass layer is extended so as to bend along the recess portion. The tire of the present invention having the configuration shown in FIG. 1 and the comparative tire having no recess in the tire of the present invention were manufactured.

  In the tire of the present invention, the depth of the recess is 3 mm, the width is 3 mm, the JIS A hardness of the rubber constituting the bead filler is 91, the JIS A hardness of the rubber constituting the rubber member is 60, and the height of the bead filler is the tire. The cross-sectional height is 60%, and the end length of the carcass layer is 83% of the tire cross-sectional height.

Each of these test tires was mounted on a standard rim, mounted on a racing vehicle with an air pressure of 200 kPa and a displacement of 3000 cc, and an evaluation test of lap time and steering stability was performed according to the following method. The result was obtained.
Lap time The lap time was measured when the lap time was 10 laps on the 4.5km racing course. Since the tire of the present invention and the comparative tire have substantially the same lateral rigidity, the shorter the lap time, the more stable the steering and the better the ground contact.
Steering stability A feeling test by a test driver was performed in parallel with the measurement of the lap time, and the evaluation result was shown as an index value with a comparative tire as 100. The larger this value, the better the steering stability, and thus the better the ground contact.

  From Table 1, it can be seen that the tire according to the present invention can shorten the lap tire by 1 second and improve the steering stability by 10 points, and can effectively improve the ground contact property compared with the comparative tire. Therefore, it is possible to ensure the lateral rigidity without impairing the grounding property.

It is a tire meridian principal part sectional view showing one embodiment of the pneumatic tire of the present invention. It is a principal part expanded sectional view of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5 Bead filler 5a Outer peripheral edge 5b Tire width direction inner surface 6, 6A, 6B Carcass layer 6A1, 6B1 End part 7 Belt layer 10 Recessed part 11 Recessed part 12 Rubber member L End part length SH SH Sectional height d Depth depth e Edge h Bead filler height w Depression width

Claims (7)

A pneumatic tire folded around an annular bead core in which both ends of a carcass layer extending between the left and right bead parts are embedded in the bead part so as to sandwich a bead filler arranged annularly on the outer peripheral side of the bead core. In
The bead filler along the tire circumferential direction in the tire width direction inner side of the provided recess extends, extended to be bent along the depressions viewed portion of the carcass layer Rutotomoni, each end of the carcass layer The portion extends beyond the outer peripheral edge of the bead filler to the outside in the tire radial direction, and the end length from the bead core to the edge of the end of the carcass layer has a length of 60 to 95% of the tire cross-section height. pneumatic tire you.   The pneumatic tire according to claim 1, wherein the depth of the recess is 2 to 7 mm and the width is 1 to 20 mm.   The pneumatic tire according to claim 1 or 2, wherein a rubber member having a JIS A hardness of 5 or more lower than that of the rubber constituting the bead filler is disposed in a concave portion of the carcass layer that is bent.   The pneumatic tire according to claim 1, 2 or 3, wherein a height of the bead filler has a length of 10 to 70% of a tire cross-sectional height. The pneumatic tire according to any one of claims 1 to 4 , wherein a belt layer is provided on an outer peripheral side of the carcass layer of the tread portion, and both end portions of the carcass layer are extended to an inner peripheral side of the belt layer. The inside of the carcass layer disposed other carcass layer, the pneumatic tire according to claim 5, wherein both ends of the other of the carcass layer was returned folded from the tire inside to the outside around the bead core. The pneumatic tire according to any one of claims 1 to 6 , wherein the pneumatic tire is a racing tire.

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