JP2009126262A - Run flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve rim removal resistance while effectively suppressing the deterioration of rim assembling/releasing properties of a run flat tire. <P>SOLUTION: Since a distance M from an intersection point P to the center of Figure G is configured to be 0.45D or lower, a distance from a point of application of a resultant force given from a bead core 27 to rubber positioned between a bead core 27 and a rim 45, to the center of rotation near a bead toe 51 (the arm length of moment) becomes longer. Thereby, a total value of moment that resists the moment based on a lateral force becomes large, so that rim removal is effectively suppressed. Since the distance M is configured to be 0.25D or more, the rubber thickness from the outer end in the axial direction of the bead core 27 to the outside surface in the axial direction of a bead portion 28 is made to have a predetermined thickness. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

    The present invention relates to a run-flat tire in which reinforcing rubber layers having a crescent cross section are disposed on both sidewall portions.

    As conventional run flat tires, for example, those described in Patent Document 1 below are known. As shown in FIG. 6, the run-flat tire 11 includes a pair of bead portions 13 in which bead cores 12 are embedded, a pair of sidewall portions 14 that extend from the bead portions 13 substantially outward in the radial direction, Equipped with a tread portion 15 that connects the outer ends in the radial direction of the sidewall portion 14 and a reinforcing rubber layer 16 with a crescent-shaped cross section disposed on the inner surface side of the carcass layer in both sidewall portions 14, and the internal pressure is reduced by puncture etc. In this case, the reinforcing rubber layer 16 bears a load so that the vehicle can continue to travel safely over a predetermined distance.

JP 2005-297876 A JP 2000-185503 A "ETRO STANDARDS NANUAL 2005" Chapter 11.4 EXTENDED HUMP ‘EH2’ Published by The European Tire and Rim Technical Organization

    When turning (here, turning left) while running on a flat run with the tire 11 as described above, lateral force inward of the turning acts on the tire 11 from the road surface 17 due to centrifugal force. In the tire 11 in the vicinity of the ground contact area, the outer side 18 attached away from the vehicle center largely slides on the rim 19 toward the inside of the turn due to the lateral force, and the side wall 14 turns due to the moment based on the lateral force. While the inner core collapses greatly, the bead core 12 rotates while twisting around its own centroid around the bead toe 20, so that the bead portion 13 of the attached outer portion 18 falls into the well portion 21 of the rim 19 and falls off the rim. There was a problem that occurred.

  At this time, with respect to the moment based on the lateral force described above, a torsional moment due to the torsion of the bead core 12 and a resultant force such as a compressive force and a bending force applied to the rubber between the bead core 12 and the bead core 12 and the rim 19 (bead core 12 The resistance is the total moment of the moment obtained from the intersection point between the radial line passing through the centroid and the radial inner surface of the bead core 12 and the distance from the center of rotation near the bead toe 20 to the force point. Works.

  Here, in order to suppress the rim disengagement as described above, as described in Patent Document 2 and Non-Patent Document 1 described above, the protrusion continuously extending in the circumferential direction between the well portion of the rim and the bead seat portion. Providing a large amount of hump has been proposed, but if a hump with such a large amount of protrusion is provided, the hump becomes a hindrance at the time of rim assembly and rim unraveling, and the rim unraveling property will deteriorate. is there. It is also conceivable to suppress the rim disengagement by increasing the cross-sectional area of the bead core or reducing the inner diameter of the bead core to improve the torsional rigidity of the bead core or the fastening force by the bead core. In this case, as described above, the rim assembly and the rim unwinding property are deteriorated.

  An object of the present invention is to provide a run-flat tire capable of improving the rim detachment resistance while effectively suppressing deterioration of tire rim assembly and rim unwindability.

    Such a purpose is to connect a pair of bead portions each having a bead core embedded therein, a pair of sidewall portions extending from the bead portions toward the outside in a substantially radial direction, and radially outer ends of the sidewall portions. In a run flat tire provided with a tread portion and provided with reinforcing rubber layers having a crescent cross section on both side wall portions, a straight line L passing through the centroid G in the meridian section of the bead core and parallel to the tire axis, and outside of the bead portion in the axial direction The distance M from the intersection point P to the centroid G, where P is the intersection point with the side surface, Q is the intersection point between the straight line L and the axially inner side surface of the bead portion, and D is the distance from the intersection point P to the intersection point Q. Can be achieved by setting the value within the range of 0.25D to 0.45D.

  In this invention, the intersection of the straight line L passing through the centroid G in the meridian section of the bead core and parallel to the tire axis and the axially outer surface of the bead part is P, and the intersection of the straight line L and the axially inner surface of the bead part Q, and when the distance from the intersection P to the intersection Q is D, the distance M from the intersection P to the centroid G is set to 0.45 D or less, so that it is located between the bead core and the rim of the mounting outer portion described above. The distance r (the length of the arm of the moment) from the applied point K of the resultant force R applied to the rubber to the rotation center O in the vicinity of the bead toe becomes longer. As a result, the resultant force R and the applied point K to the rotation center O are increased. The moment value obtained from the distance r (the length of the arm of the moment) becomes larger.

  As a result, the value of the total moment in the opposite direction against the moment based on the lateral force, that is, the total of the torsional moment caused by the torsion of the bead core and the moment obtained from the resultant force R and the distance r increases, and the above-described rim detachment is prevented. It can be effectively suppressed. Further, since the angle of inclination of the straight line connecting the rotation center O and the force point K with respect to the radial line is large, the rotation angle of the bead core required until the rim disengagement becomes large, which also causes the rim disengagement. Can be effectively suppressed.

  At this time, a hump with a large protruding amount is not necessary, so that deterioration of rim assembly and rim unwinding can be effectively suppressed. In addition, since the distance M is set to 0.25D or more, the rubber thickness from the outer end in the axial direction of the bead core to the outer surface in the axial direction of the bead portion is easily determined to avoid contact between the bead core and the rim flange. The thickness can be as follows.

  Moreover, if comprised as described in Claim 2, the bead core which has the existing cross-sectional shape can be used, and, thereby, a pneumatic tire can be manufactured at low cost. Furthermore, if comprised as described in Claim 3, the circumferential bending rigidity of a bead core can be improved, ensuring the rubber gauge required in order to protect a bead core reliably. According to the fourth aspect of the present invention, it is possible to effectively prevent a situation in which stress concentration occurs in the bead core as compared with the bead core in which the cross-sectional height (radial thickness) of the bead core changes rapidly. As a result, the bead durability can be improved.

  Furthermore, if comprised as described in Claim 5, the rubber gage required in order to protect a bead core can fully be ensured, and the inhibitory effect of a rim | limb disengagement can be made sufficient. Further, if configured as described in claim 6, it is possible to more effectively suppress the rim disengagement while setting the rubber gauge necessary for protecting the bead core to a sufficient value.

Embodiment 1 of the present invention will be described below with reference to the drawings.
In FIGS. 1 and 2, reference numeral 25 denotes a pneumatic tire that can safely run continuously over a predetermined distance even when the internal pressure is reduced to atmospheric pressure due to puncture or the like, that is, a run flat tire 25. The run flat tire 25 is a bead wire. A pair of bead cores 27 each including a bead core 27 formed by spirally or spirally winding 26 in the circumferential direction, respectively, and extend outward from the bead portions 28 in a substantially radial direction. A sidewall portion 29 and a substantially cylindrical tread portion 30 that connects the radially outer ends of the sidewall portions 29 are provided.

  Here, the run flat tire 25 has a mounting inner portion 31 that is closer to the vehicle center (center in the width direction of the vehicle) than the tire equator S, and a mounting outer portion 32 that is the side farther from the vehicle center than the tire equator S. And can be divided into In this embodiment, the bead core 27 has a meridian cross-sectional shape of a quadrangle, but may have a hexagonal shape or a circular shape, for example.

  The run flat tire 25 has a carcass layer 35 extending in a toroidal shape between the bead cores 27 to reinforce the sidewall portions 29 and the tread portions 30, and both end portions in the width direction of the carcass layer 35 are the bead cores 27. It is folded around. Reference numeral 36 denotes a reinforcing rubber layer disposed on the inner surface side of the carcass layer 35 in both side wall portions 29. The reinforcing rubber layer 36 is thickest in the radial center portion, and radially inward from the thickest portion. In addition, the thickness gradually decreases with increasing distance from the outside, that is, a crescent-shaped cross section. Here, the reinforcing rubber layer 36 is preferably composed of a single type of rubber having a relatively high hardness, for example, a JIS A hardness of 60 to 85 degrees. You may laminate and comprise.

  When such a reinforcing rubber layer 36 is disposed on the sidewall portion 29 of the run-flat tire 25, even if the internal pressure of the run-flat tire 25 is reduced to atmospheric pressure due to puncture or the like, the reinforcement having high bending rigidity is provided. Since the rubber layer 36 supports the load, the bending of the sidewall portion 29 is suppressed to a considerable extent, and as a result, it is possible to continue traveling (run-flat traveling) safely for a predetermined distance.

  Reference numeral 37 denotes a belt layer disposed on the outer side in the radial direction of the carcass layer 35. A tread 38 made of rubber is disposed on the outer side in the radial direction of the belt layer 37. A plurality of main grooves 39 extending in the circumferential direction are formed on the outer surface (tread surface) of the tread 38, but a plurality of horizontal grooves extending in the width direction and the oblique direction may be formed. 40 is a belt reinforcing layer disposed so as to cover the belt layer 37 with the full width between the belt layer 37 and the tread 38, and 41 is disposed so as to straddle both ends of the belt layer 37 and the belt reinforcing layer 40 in the width direction. A pair of belt auxiliary layers.

  45 is a rim to which the run-flat tire 25 is mounted, and the rim 45 has a side closer to the vehicle center than the center in the width direction, that is, the inner bead seat portion 46 is spaced from the center in the width direction from the vehicle center. The outer side bead seat portions 47 are provided on the side, that is, the outer side of the mounting, respectively, and the inner and outer bead seat portions 46 and 47 are provided with substantially rim-shaped rim flanges 48 extending outward in the radial direction on the outer side in the axial direction. Yes. Reference numeral 49 denotes an annular well portion which is provided on the rim 45 between the inner bead seat portion 46 and the outer bead seat portion 47 and is recessed radially inward.

  The run-flat tire 25 is mounted on such a rim 45 to form a tire / rim assembly 50. At this time, the bead portion 28 in the mounting inner portion 31 of the run-flat tire 25 becomes the inner bead seat portion 46. The bead portions 28 in the mounting outer portion 32 are respectively seated on the outer bead seat portions 47, and the axially outer surfaces of the bead portions 28 are in surface contact with the axially inner surfaces of the rim flanges 48, respectively.

  When the vehicle is running with the tire / rim assembly 50 as described above mounted on the axle of the vehicle, if the internal pressure of any of the run flat tires 25 decreases due to puncture or the like, The flat tire 25 tends to be crushed by the load because the tension rigidity due to the internal pressure is reduced. At this time, the reinforcing rubber layer 36 supports the load, and the deflection of the sidewall portion 29 is suppressed to a considerable extent.

  Here, when the vehicle turns during run-flat running as described above, the run-flat tire 25 on the outer side of the turn has a large lateral force acting on the inner side of the turn due to centrifugal force. The bead portion 28 of the outer portion 32 slides on the rim 45 (outer bead seat portion 47) toward the inside of the turn by the lateral force. Also, at this time, the side wall 29 of the mounting outer portion 32 falls to the inside of the turn due to the moment based on the lateral force, so that the bead core 27 rotates while being twisted around its own centroid G, and near the bead toe 51, Then, as shown in FIG. 3, the maximum contact pressure position slightly separated from the bead toe 51 in the axial direction is rotated about the rotation center O, and the rim is likely to be detached.

  At this time, a resultant force R (bead core 27) such as a torsional moment caused by twisting of the bead core 27 and a compressive force or a bending force applied to the rubber between the bead core 27 and the bead core 27 and the rim 45 with respect to the moment based on the lateral force described above. Of the radial line passing through the centroid G and the inner surface in the radial direction of the bead core 27 is an application point K), and a moment obtained from the distance r from the rotation center O to the application point K in the vicinity of the bead toe 51. And the total moment acts as a resistance.

  Here, the above-described compressive force is generated when rubber is crushed by the bead core 27 because the diameter cannot be increased when the bead core 27 rotates around the rotation center O. Further, the force applied to the rubber from the bead core 27 is distributed over the entire inner surface in the radial direction of the bead core 27, but here, it is considered as a force acting on one point (applying point K) equivalent to these forces.

  For this reason, in this embodiment, the intersection of the straight line L passing through the centroid G in the meridian section of the bead core 27 and parallel to the tire axis and the axially outer surface of the bead portion 28 is P, and the straight line L and the bead portion 28 The distance M from the intersection P to the centroid G is conventionally about 0.48D to 0.52D, where Q is the intersection with the inner side surface in the axial direction and D is the distance from the intersection P to the intersection Q. Is set to 0.45 D or less. As a result, the distance r (the length of the arm of the moment) from the applied point K of the resultant force R applied to the rubber positioned between the bead core 27 and the rim 45 of the mounting outer portion 32 described above to the rotation center O in the vicinity of the bead toe 51. As a result, the moment value obtained from the resultant force R and the distance r (moment arm length) increases.

  Here, the moment obtained from the resultant force R and the distance r is a value obtained by multiplying the distance r by a component force F in a direction orthogonal to a straight line connecting the applied point K of the resultant force R and the rotation center O. As a result, the value of the total moment in the opposite direction against the moment based on the lateral force, that is, the sum of the moments obtained from the torsional moment to restore the torsion of the bead core 27 and the resultant force R and the distance r is obtained. It becomes large and the above-mentioned rim detachment can be effectively suppressed. Furthermore, since the inclination angle with respect to the radial line of the straight line connecting the rotation center O and the force point K is large, the rotation angle of the bead core 27 necessary until the rim disengagement is large, thereby The detachment can be more effectively suppressed.

  At this time, since a hump with a large protrusion amount as described in the prior art is not necessary, deterioration of the rim assembly and rim unwindability can be effectively suppressed. Further, since the distance M is set to 0.25D or more, a rubber gauge from the outer end in the axial direction of the bead core 27 to the outer surface in the axial direction of the bead portion 28 is set to a predetermined value necessary to avoid contact between the bead core 27 and the rim flange 48. The thickness can be as follows.

  Here, in this embodiment, in order to make the distance M within the range of 0.25D to 0.45D, the bead core 27 is maintained in the original cross-sectional shape, here, in the axial direction in parallel to the bead base 52 while maintaining the rectangle. It is shifted outward. Thus, if the distance M is set within the above-mentioned range by shifting the bead core 27 outward in the axial direction, it is not necessary to change the cross-sectional shape of the bead core 27, so a bead core having an existing cross-sectional shape is used. As a result, the run-flat tire 25 can be manufactured at low cost, and the rubber gauge on the radially inner side from the bead core 27 can be maintained as it is.

  A distance d from the intersection A to the intersection B, where A is the intersection of the straight line L and the outer end of the bead core 27 in the tire axial direction, and B is the intersection of the straight line L and the inner end of the bead core 27 in the tire axial direction. Here, the axial length (cross-sectional width) of the bead core 27 is preferably set to a value of 40% to 80% of the distance D. The reason is that when the distance d exceeds 80%, the rubber gauge (rubber thickness) between the bead core 27 and the rim 45 becomes too thin, and external forces such as load and lateral force act on the run-flat tire 25. The bead core 27 and the rim 45 may come into contact with each other. On the other hand, when the bead core 27 is less than 40%, the axial length of the bead core 27 is too short, and the fastening area by the bead core 27 is narrowed. Although it cannot be effectively suppressed, if the distance d is within the above-mentioned range, the rubber gauge necessary for protecting the bead core 27 is sufficiently secured, and the effect of suppressing the rim removal is sufficient. Because you can.

  If the distance M is in the range of 0.30D to 0.40D, the rubber gauge necessary for protecting the bead core 27 can be set to a sufficient value, and the rim can be more effectively suppressed. More preferably, M is in the range of 0.30D to 0.40D. The tire / rim assembly 50 (run flat tire 25) mounted on the left axle of the vehicle is turned right, and the tire / rim assembly 50 (run flat tire 25) mounted on the right axle is turned left. Each of the rims is likely to be detached as described above. However, if the bead cores 27 of the inner and outer portions 31, 32 are both configured as in this embodiment, any turn on the public road where the vehicle turns in the same direction in both the left and right directions. Even at times, it is possible to effectively prevent detachment of the rim.

  Here, the rim diameter means a nominal diameter of the rim when the tire is mounted on the rim, and the rim is a standard rim (or “DESIGN RIM”, “ Recommended Rim "). The standards are determined by industrial standards that are valid for the region where tires are produced or used. For example, “The Tire and Rim Association Inc. Year Book” in the United States and “The European Tire and Rim Technical Organization's Standards Manual ”corresponds to“ JATMA Year Book of Japan Automobile Tire Association ”in Japan.

    FIG. 4 is a diagram showing Embodiment 2 of the present invention. In this embodiment, the bead core 55 embedded in the bead portion 28 is not shifted outward in the axial direction parallel to the bead base 52, but is inclined so as to incline radially outward from the inner end in the axial direction toward the outer side in the axial direction. 56 is formed on the outer periphery of the inner end in the axial direction and has a substantially pentagonal cross section so that the cross-sectional area of the bead core 55 on the outer side in the tire axial direction from the center in the tire axial direction is larger than the cross-sectional area on the inner side in the tire axial direction. The distance M is in the range of 0.25D to 0.45D.

  In this way, the radial thickness of the bead core 55 can be increased as compared with the case where the bead core 27 is shifted outward in the axial direction as described above, and the outside of the bead core 55 from the centroid G of the bead core 55 in the axial direction. The distance to the end can be shortened. As a result, a rubber gauge necessary to protect the bead core 55 can be reliably ensured, and the circumferential bending rigidity of the bead core 55 can be easily improved.

  When the distance M is set within the above-described range simply by changing the cross-sectional shape of the bead core 55 in this way, the radial height of at least a part of the bead core 55, here the axially inner portion, is set as the tire axis. It is preferable to gradually increase from the inner side in the direction toward the outer side in the tire axial direction. The reason is that the cross-sectional height (radial thickness) of the bead core 55 changes gently in this way, so that the cross-sectional height (radial thickness) changes abruptly, for example, in a stepwise manner. This is because it is possible to effectively prevent a situation in which stress concentration occurs in the bead core 55, thereby improving the bead durability.

  In this embodiment, the radial height at the inner side in the axial direction of the bead core 55 is gradually increased from the inner side in the tire axial direction toward the outer side in the tire axial direction. The radial height of the outer portion may be gradually increased from the inner side in the tire axial direction toward the outer side in the tire axial direction, and the radial height of the entire bead core may be increased from the inner side in the tire axial direction toward the outer side in the tire axial direction. You may make it increase gradually.

  In this embodiment, the bead core 55 has a substantially pentagonal cross section as described above. However, in this invention, the cross-sectional shape of the bead core may be a so-called eccentric polygon, and the centroid G of the bead core is the bead core. Any shape that deviates from the axial center to the axially outer side may be used. Other configurations and operations are the same as those of the first embodiment.

    FIG. 5 is a diagram showing Embodiment 3 of the present invention. In this embodiment, by shifting the bead core 55 whose cross-sectional area on the outer side in the tire axial direction from the center in the tire axial direction is larger than the cross-sectional area on the inner side in the tire axial direction, is shifted toward the outer side in the axial direction in parallel to the bead base 52. The distance M described above is in the range of 0.25D to 0.45D. In this way, the rubber gauge necessary for protecting the bead core 55 can be more reliably ensured. Other configurations and operations are the same as those of the second embodiment.

    Next, test examples will be described. In this test, the structure of the bead portion and the cross-sectional shape of the bead core are as shown in FIG. 6, and the conventional tire 1 and the cross-sectional shape of the bead portion and the bead core are as shown in FIG. Example tire 2 and Example tire 3 as shown in FIG. 5 were prepared. Here, the distance D (mm) from the intersection point P to the intersection point Q of these tires, the distance N (mm) from the intersection point A to the intersection point P, the distance C (mm) from the intersection point A to the centroid G, and the intersection point P The distance M (mm) from the centroid G to the centroid G and the distance d (mm) from the intersection A to the intersection B were values as shown in Table 1 below.

  Here, the structure other than the bead portion of each tire is the same as in FIG. 1, and the carcass layer is configured by laminating two carcass plies embedded with a large number of rayon cords extending in the radial direction, The belt layer is constructed by laminating two belt plies embedded with steel cords with a cord angle of 60 degrees with respect to the tire equator so that the cord angles are opposite to each other. The auxiliary layer used was embedded with a nylon cord extending substantially in the circumferential direction. The maximum thickness of the reinforcing rubber layers was 12 mm for all tires, and the tire size was 225 / 60R17. In addition, the expansion force (fastening force) of the bead core in each tire is shown in Table 1 with the value of the conventional tire as an index of 100.

  Next, after each such tire is mounted on a standard rim prescribed in the above standard, the internal pressure is filled in each tire, and the air pressure when the bead portion is seated at the normal position of the bead seat portion of the rim. Was measured. As a result, the rim assembly property is shown in Table 1 with the value of the conventional tire as an index of 100. The smaller this value, the smaller the fitting pressure and the better the rim assembly property. Here, the index 100 was 62 kPa.

  Next, after attaching the tires to the front, rear, left and right four wheels of the domestic passenger car, the internal pressure was released from the tires attached to the right front wheel to obtain atmospheric pressure. Next, the J-turn test of the left turn was repeated while increasing the speed from the speed of 40km / h to 2.5km / h with the turning radius of 25m, and the rim was removed in the tire running on the run-flat. Lateral acceleration was calculated. The results are shown in Table 1 with the value of the tire implemented as an index of 100. The larger this value, the better the rim detachment resistance.

  The present invention can be applied to the industrial field of run-flat tires in which both sidewall portions are reinforced with a reinforcing rubber layer.

1 is a meridian cross-sectional view of a tire showing Embodiment 1 of the present invention. It is meridian sectional drawing of the bead part vicinity. It is meridian sectional drawing of the bead part vicinity in the mounting | wearing outer side part at the time of run-flat driving | running | working. It is meridian sectional drawing of the bead part vicinity which shows Embodiment 2 of this invention. It is meridian sectional drawing of the bead part vicinity which shows Embodiment 3 of this invention. It is meridian sectional drawing of the conventional run flat tire.

Explanation of symbols

25… Run flat tires 27, 55… Bead core
28 ... Bead part 29 ... Side wall part
30 ... Tread part 36 ... Reinforced rubber layer
52 ... Bead base A ... Intersection B ... Intersection D ... Distance G ... Center of centroid L ... Line M ... Distance P ... Intersection Q ... Intersection d ... Distance

Claims (6)

    A pair of bead portions each embedded with a bead core; a pair of sidewall portions extending substantially radially outward from these bead portions; and a tread portion connecting the radially outer ends of these sidewall portions; In a run-flat tire having a reinforcing rubber layer with a crescent cross section on both sidewalls, the intersection of a straight line L passing through the centroid G in the meridian section of the bead core and parallel to the tire axis is P When the intersection point between the straight line L and the inner side surface in the axial direction of the bead portion is Q, and the distance from the intersection point P to the intersection point Q is D, the distance M from the intersection point P to the centroid G is 0.25D to 0.45D. A run-flat tire characterized by being within the range.     The run-flat tire according to claim 1, wherein the distance M is set within a range of 0.25D to 0.45D by shifting the bead core in an axially outward direction parallel to the bead base.     The run according to claim 1, wherein the distance M is set within a range of 0.25D to 0.45D by making a cross-sectional area of the bead core on the outer side in the tire axial direction from a center in the tire axial direction larger than a cross-sectional area on the inner side in the tire axial direction. Flat tire.     The run-flat tire according to claim 3, wherein the radial height of at least a part of the bead core is gradually increased from the inner side in the tire axial direction toward the outer side in the tire axial direction.     When the intersection point between the straight line L and the outer end in the tire axial direction of the bead core is A, and the intersection point between the straight line L and the inner end in the tire axial direction of the bead core is B, the distance d from the intersection A to the intersection B is the distance The run-flat tire according to claim 1, wherein the value of D is 40% to 80%.     The run-flat tire according to claim 1, wherein the distance M is in a range of 0.30D to 0.40D.

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