JP2004299670A - Run-flat tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a run-flat tire in which (specifically) run-flat durability is efficiently improved without sacrificing riding comfort at the time of normal driving with normal internal pressure. <P>SOLUTION: In the run-flat tire 1, a belt 8 consisting of at least a sheet of cord rubberized layer is provided between a crown section of a carcass 7 and a treads section 5, the carcass 7 consisting of at least one ply toroidally extending over each section of a bead section 3, a sidewall section 4 and the treads section 5, a reinforcing rubber 11 having a substantial crescent cross-section is provided on at least an internal side of a side wall section 4, and a ring-like rim guard section 13 protruding toward the external side of the tire width direction is provided on the external surface position of the tire immediately above a rim flange Rf. Also, the section 13 consists of hard rubber, a 100% modulus of the hard rubber is 3.0 MPa or more and is within a range of two-five times a 100% modulus of outer skin rubber 14 forming the section 4. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention effectively improves run flat durability when continuously running at a low internal pressure or a punctured run flat state without sacrificing other performance such as ride comfort when normally running at normal internal pressure. Regarding improved run flat tires.

  If the vehicle continuously travels in a low internal pressure or punctured run flat state, the sidewall portion of the tire bends and deforms more than in a normal design internal pressure state, and thus often leads to an early failure of the tire. Observation of the failure status of general tires shows that the inner surfaces of the tires repeatedly come into contact with each other due to the large amount of deformation at the sidewalls, leading to wear and tear, and the large amount of collapse deformation at the bead. The rim may come off.

  In order to improve these failures, for example, those in which the rigidity of a sidewall portion is enhanced or beads or rims are specially processed are known as run flat tires.

  Examining the failure mode of the run flat tire in more detail, it can be seen that even in a tire in which the rigidity of the tire can be increased and contact inside the tire can be avoided, the sidewall portion of the tire is compared with a normal design internal pressure state. It is inevitable that the amount of deflection or deformation of the tire is inevitably increased, and it has been found that stress concentrates at the tire maximum width position or in the vicinity thereof, thereby causing a failure nucleus.

As means for suppressing the occurrence of such a failure nucleus, it is proposed to stack rubber between a plurality of carcass plies, or to make the shape of a reinforcing rubber disposed on the inner surface side of the carcass specific. (For example, see Patent Documents 1 to 3). However, all of these measures are accompanied by an increase in weight and a decrease in production efficiency. In addition, when the vehicle is normally driven under normal internal pressure, rigidity in the tire radial direction, that is, a so-called vertical spring, is increased. Tends to worsen, and it is difficult to effectively improve run flat durability.
JP 2000-168319 A JP 2000-52724 A JP 2000-190715 A

  By the way, at the border between the so-called road where vehicles pass and the so-called sidewalk exclusively for pedestrians or the site for other uses adjacent to the road, sign lines or steps are usually provided to clarify the boundary. In the latter case, so-called curbs are often installed.

  When a vehicle moves in or out of the site from the roadway or stops on the roadside zone, the tire may come into contact with the curb, but in such a case, the greatly bent sidewall part will be between the curb and the rim. In the worst case, a puncture may occur due to a cut wound caused by being pinched. Further, in a flat tire, since the rim easily comes into direct contact with the curb, the outer surface of the rim may be damaged, the appearance may be greatly impaired, and the rim flange may be damaged.

  In order to prevent the tire and the rim from being damaged by contact with an obstacle such as a curbstone, the outer surface of the sidewall portion of the tire, particularly between the tire maximum width position and the bead portion, is called a rim guard. In many cases, a rim guard is provided.

  This rim guard portion is mainly intended to prevent the outer surface of the tire from directly contacting the curb described above in a state where the tire is used at normal internal pressure, and to improve the design such as improving the tire appearance. Is provided.

  The inventors pay particular attention to the above-described rim guard portion as a means for improving the run flat durability without increasing the vertical spring of the tire when running normally under normal internal pressure as much as possible. It was thought that it would be useful to try to make it.

Conventional tires provided with a rim guard portion for the purpose other than preventing cuts on the outer surface of the sidewall portion and damage to the rim flange include, for example, Patent Documents 4 to 6.
JP-A-11-1557311 JP-A-53-138106 JP 2002-59713 A

  The tire described in Patent Literature 4 uses a relatively soft rubber at a portion facing a rim flange upper portion of a rim guard portion for the purpose of improving running performance during run flat and improving bead portion durability. A rim shift prevention layer is provided, and the rubber portion of the other rim guard portion is made of hard rubber. However, in such a tire, the rubber that forms the rim guard portion is not specified in relation to the outer cover rubber that forms the sidewall portion. Run-flat durability is not sufficient for more severe run-flat driving conditions that involve force.

  The tire described in Patent Literature 5 is a high-rigidity reinforcing member that forms an annular shape in a rim guard portion for the purpose of maintaining sufficient load force and durability without running off the rim of the tire during run flat running. (Pseudo beads) are buried. However, the pseudo bead is not provided to suppress the bending of the side portion.In addition, since the rubber portion of the bead portion sandwiched between the rim flange and the pseudo bead during run flat running repeatedly deforms significantly. There is a problem that it easily becomes a failure nucleus. In addition, the vertical spring at the time of the normal internal pressure tends to increase and the ride comfort tends to deteriorate.

  The tire described in Patent Document 6 has a rim guard portion made of a rubber in which short fibers made of organic fibers are dispersed for the purpose of improving both fuel economy and side cut resistance without impairing ride comfort. It consists of. However, such a tire is a pneumatic tire used by applying a normal internal pressure, and does not improve run-flat durability by providing a rim guard portion.

  From the above, at present, in run-flat tires, by adjusting the rim guard part, the vertical spring of the tire during normal running under normal internal pressure is not increased as much as possible, and the tire There is no technology that effectively increases the number of springs to significantly improve run flat durability.

  The present invention relates to optimization of a rim guard portion called a rim guard provided on an outer surface of a sidewall portion of a tire for the purpose of preventing a tire or a rim from being damaged by contact with an obstacle such as a curb. In particular, the run flat durability when running continuously at a low internal pressure or a punctured run flat state without sacrificing other performance such as ride comfort when running normally at normal internal pressure is effective It is an object of the present invention to provide a run flat tire that has been improved.

  In order to achieve the above object, a first aspect of the present invention extends over a pair of bead portions in which a bead core is embedded, a pair of sidewall portions extending radially outward from both bead portions, and both sidewall portions. A belt made of at least one cord rubberized layer is provided between the crown portion and the tread portion of the carcass made of at least one ply extending in a toroidal shape over each portion of the tread portion, and at least an inner side of the sidewall portion is provided with a substantially crescent moon. Run-flat with a reinforcing rubber with a cross section in the shape of a ring, with a ring-shaped rim guard protruding outward in the tire width direction at the outer surface of the tire immediately above the rim flange with the tire mounted on the standard rim In the tire, the rim guard portion is made of hard rubber, the 100% modulus of the hard rubber is 3.0 MPa or more, and A run-flat tire characterized in that the thickness is in the range of 2 to 5 times the 100% modulus of the outer rubber constituting the wall portion.

  According to a second aspect, the basic configuration is the same as that of the first aspect, and at least one composite reinforcing layer made of a reinforcing element and a matrix rubber is provided at a position adjacent to at least a part of the peripheral surface of the rim guard portion. This is a run-flat tire.

  The third invention is a run-flat tire having the same basic configuration as the first invention, and having both the features of the first invention and the features of the second invention.

  In the second and third inventions, (i) the reinforcing element constituting the composite reinforcing layer is a nonwoven fabric, and (ii) the reinforcing element constituting the composite reinforcing layer has a fiber diameter of 0.01 to 1 mm and a fiber length of 1 mm or more. And / or (iii) the composite reinforcing layer is preferably disposed so as to surround the outer peripheral surface of the rim guard portion.

  In the first to third inventions, a pair of narrow reinforcing belts whose cords extend in parallel with the tire circumferential direction are arranged at positions covering both end portions of the belt, and the narrow reinforcing belt has inner ends in the tire width direction. It is preferable that the distance measured in the tire width direction from the tread width end position is equal to or more than 1/4 of the tread width. In addition, the tread portion has a plurality of circumferential main portions extending along the tire circumferential direction. When the grooves are provided, the narrow width reinforcing belt is such that the inner end in the tire width direction is located on the inner side in the tire width direction than the groove width center line of the circumferential main groove located on the outermost side in the tire width direction. It is more preferable to arrange so that

  Further, in the first to third inventions, a pair of beads having a bead core embedded therein, a pair of sidewalls extending outward in the tire radial direction from the both beads, and a tread extending across the sidewalls. In a pneumatic tire provided with a carcass consisting of at least one ply extending in a toroidal shape over each part of the tire, the tire is mounted on a prescribed rim, and a tire in a width direction cross section of a tire wheel in a no-load state where a predetermined air pressure is applied. A ring-shaped rim guard portion protruding outward in the tire width direction is provided in a specific region of the tire outer surface from the tire maximum width position on the outer surface to the highest position of the tire outer surface in contact with the rim flange outer surface, and the tire maximum width An arc is drawn so as to be in contact with both the position and the outer surface of the rim flange, and this arc is defined as a specific area on the outer surface of the tire (excluding the rim guard portion). When assuming a reference arc that approximates the contour shape, within the specific region, measured on a plurality of normals drawn to the reference arc, the tire thickness, which is the distance between the reference arc and the tire inner surface, with respect to the maximum value The ratio of the minimum value is in the range of 0.8 to 1.0 times, and the maximum height of the rim guard part, which is the distance between the reference arc and the top surface of the rim guard part, measured on the normal drawn to the reference arc, is the same method. It is preferably in the range of 0.52 to 1.40 times the tire thickness measured on the line.

  Here, the “specified rim” and “predetermined air pressure” mean the air pressure (maximum air pressure) corresponding to the standard rim and the maximum load capacity respectively specified in JATMA YEAR BOOK (2002).

  The maximum height of the rim guard portion is preferably limited to a range of 0.58 to 1.20 times the tire thickness measured on the same normal line and a range narrower than the above range.

  The average height of the rim guard part when the cross-sectional area of the rim guard part in the cross section in the tire width direction is divided by the base length of the rim guard part on the reference arc is 0.6 times or more and less than 1.0 times the maximum height of the rim guard part It is preferable that

  The rim guard portion preferably has a substantially trapezoidal or substantially triangular cross-sectional shape. In the former case, the top surface of the rim guard portion has a flat shape, and / or the rim guard portion has a cross section in the tire width direction cross section. More preferably, the top surface length is in the range of 0.14 to 0.90 times the base length.

  It is more preferable that the boundary between the outer surface of the tire and the outer surface of the rim guard is formed by a gentle curved surface.

  More preferably, the reinforcing rubber has a 100% modulus of 4 MPa or more.

  Further, among the plies constituting the carcass, at least one ply preferably has one organic fiber cord selected from 6 nylon, 66 nylon, polyethylene terephthalate, rayon, polyethylene naphthalate and aramid.

  The present invention effectively improves run flat durability when continuously running at a low internal pressure or a punctured run flat state without sacrificing other performance such as ride comfort when normally running at normal internal pressure. It has become possible to provide improved run flat tires.

  FIG. 1 shows a left half section in the width direction of a run flat tire according to a first invention.

  The run-flat tire 1 shown in FIG. 1 has a pair of bead portions 3 (only one side is shown) in which a bead core 2 is embedded, and a pair of side wall portions 4 (only one side is shown) extending outward from both bead portions 3 in the tire radial direction. And a carcass 7 composed of at least one ply (two plies 6a and 6b in FIG. 1) extending in a toroidal shape over each portion of the tread portion 5 extending across both sidewall portions 4.

  Further, between the crown portion of the carcass 6 and the tread portion 5, a belt 8 including at least one cord layer, in FIG. 1, two cord layers 8a and 8b is provided.

  In addition, at least between the inner surface of the carcass 7a extending from the bead portion 3 and immediately below the end 9 of the belt 8 to the inner liner 10 in FIG. Is provided, and has a configuration of a so-called side reinforcement type run flat tire.

  In addition, in the tire 1 shown in FIG. 1, the tread portion 5 is provided with four circumferential main grooves 12a and 12b (only two main grooves are shown) extending along the tire circumferential direction. The number of grooves 12a and 12b, and other tread grooves such as lateral grooves and inclined grooves (not shown) can be arranged in various modes as needed.

  In addition, a ring-shaped rim guard 13 protruding outward in the tire width direction is provided at a position on the outer surface of the tire immediately above the rim flange Rf with the tire mounted on the standard rim R.

  The main feature of the configuration of the present invention is to prevent the outer surface 4a of the sidewall portion 4 of the tire 1 from being damaged by contact with an obstacle such as a curb, etc. In order to optimize the rim guard portion 13 provided, more specifically, in the first invention, the rim guard portion 13 is made of hard rubber, the 100% modulus of the hard rubber is set to 3.0 MPa or more, and In the second invention, the reinforcing element is provided at a position adjacent to at least a part of the peripheral surface 15 of the rim guard portion 13 in a range of 2 to 5 times the 100% modulus of the outer cover rubber 14 constituting the wall portion 4. And at least one composite reinforcing layer 16 composed of a matrix rubber and the third invention is to combine these configurations.

  The first to third aspects of the present invention adopt the above-described configuration, in particular, without sacrificing other performances such as ride comfort when the vehicle normally travels at a normal internal pressure, without causing a low internal pressure or punctured run flat. It is possible to effectively improve run flat durability when the vehicle continuously travels in the state.

Hereinafter, the process of completing the present invention will be described together with the description of the operation.
First, the inventor analyzed in detail the failure state of the tire when the vehicle continued running in a low internal pressure or punctured run flat state.

  As a result, in the side reinforcement type run flat tire in which the rigidity of the sidewall portion is increased, a failure due to so-called detachment of the rim in which the bead portion falls off the rim hardly occurs, and a typical failure mode is described above. It was found that the fracture was at the tire maximum width position and its vicinity. And it is considered that this destruction is caused by a large amount of flexure or deformation of the sidewall portion of the tire as compared with a normal design internal pressure state.

  From the tread to the buttress, a high-rigidity belt is placed and the gauge is thick, so the rigidity is high.In the bead, reinforcement of chafer etc. in addition to the high-rigidity bead filler and carcass ply turn-up High rigidity due to the presence of members.

  However, the sidewall portion, particularly the tire maximum width position and its vicinity, have relatively low rigidity because the number of members is small and the gauge is thin. In a normal tire, the inner surfaces of the tire repeatedly come into contact with each other due to insufficient rigidity of the sidewall portion, which causes a failure.

  Moreover, in the run-flat tire of the side reinforcement type, although the contact between the tire inner surfaces can be avoided, the deformation amount is still large at the tire maximum width position and the vicinity thereof, so that it is still a failure point.

  Therefore, in order to improve the run flat durability while minimizing the increase in tire weight and deterioration in productivity, there are places where the rigidity becomes relatively small in the side portion of the tire from the buttress portion to the bead portion. It is important to increase the rigidity as a whole and reduce the amount of flexure and deformation at the tire maximum width position and its vicinity in the vicinity of the tire.

  Also, when considering deformation in the tire, the fixed part is considered to be the ground contact tread and the rim fitting part, but the inventor has studied to suppress the amount of deformation at the maximum width position of the tire. In practice, rather than directly increasing the gauge at the maximum width position of the tire to increase rigidity, by increasing the rigidity at the fixed part that is the root of deformation, deformation at the maximum width position of the tire is indirectly performed. As a result, the deformation amount at the tire maximum width position can be effectively suppressed, and in this case, the vicinity of the fixed portion includes a buttress portion and a bead portion near the tread portion, but among these, Therefore, it was considered that increasing the rigidity in the vicinity of the bead portion, which is the fitting portion with the rim having much higher rigidity than the tire, can effectively suppress the deformation at the maximum width position of the tire.

  In addition, increasing the thickness of the gage at the buttress portion, and particularly at the position of the maximum width of the tire, increases rigidity and inertia weight at the portion, thereby deteriorating ride comfort. However, these adverse effects are considered to be small.

  Then, the inventor studied to effectively increase the rigidity at the base (near) of the bead portion, which is the fixing portion, and found that the outer surface of the sidewall portion of the tire was in contact with an obstacle such as a curb and the like. By optimizing the rim guard portion 13 called a rim guard provided for the purpose of preventing the rim from being damaged, the bending rigidity of the bead portion 3 is remarkably increased, and the side wall during run flat running is improved. It has been found that the flexure and deformation of the portion 4 are effectively suppressed, and tire failure is less likely to occur.

  However, if the rim guard portion 13 is merely made of hard rubber in order to increase the rigidity of the bead portion 3, the vertical springs of the tire particularly when a normal internal pressure is applied increase, and the tire uniformity is deteriorated along with the riding comfort and vibration characteristics. Invite. Therefore, it is important to optimize the rim guard portion 13 so that the function of increasing the bending rigidity of the root portion of the bead portion 3 can be effectively exerted.

  For the sake of simplicity, a side portion (L in the tire radial direction) over a specific region 20 from the tire maximum width position 17 to the tire outermost surface highest position 19 in contact with the rim flange outer surface 18 is shown in FIG. Then, the side portion including the carcass ply and the bead filler in the specific area 20 is cut out by a unit length in the tire circumferential direction (for example, 10 mm), and is regarded as a uniform straight beam having a constant thickness t, as shown in FIG. Then, the rim guard portion 13 is provided with a thickness h over the entire region L of the straight beam, and as shown in FIG. 4, the volume of the rim guard portion 13 is made equal, and The bending stiffness will be considered for a case in which a thickness kh is provided over an area L / k times / k times (k is a number greater than 1).

Assuming that the respective beam portions are made of the same physical properties, the bending stiffness may be considered as the second moment of area. By approximating and simplifying the constitutive equations as appropriate, the moment of inertia of the beam in each superposed state is
I ₀ = (1/12) t ³
I ₁ = (1/12) t ³ + (1/12) h ³ + {(t + h) / 2} ² h
I ₂ = (1/12) t ³ + (1/12) (kh) ³ + {(t + kh) / 2} ² kh

When the tire undergoes a load load and undergoes flexural deformation, a bending moment M acts on the portion at the tire maximum width position, and the amount of swelling (falling amount) in the tire axial direction at that time is δ.
δ ₁ = (M / 2EI ₁ ) (L / k) ² + (M / 2EI ₀ ) (LL−k) ²
+ (M / EI ₁ ) (L−L / k) (L / k)
δ ₂ = (M / 2EI ₂ ) L ²
f (t, h, k) = δ ₁ −δ ₂
It becomes.

By rearranging this, the amount of deformation when the protruding portion (rim guard portion) is provided over the entire beam as shown in FIG. 3 while maintaining the same volume, and when the protrusion is partially provided as shown in FIG. Judging the magnitude of the deformation amount,
g (t, h, k) = (1 / k ² ) ｛I ₀ I ₂ +2 (k−1) + I ₁ I ₂
(K−1) ² −I ₀ I ₁ k ² ｝
It becomes.

  Here, the following findings were obtained by further dimensionlessly setting the thickness as j = h / t and performing numerical analysis.

  As shown in FIG. 3, it has been found that the narrow and thick rim guard portion 13B as shown in FIG. 4 suppresses the bending and the amount of deformation more than the wide and thin rim guard portion 13A is provided.

  The above are the estimation results derived from a simple model of the material of the side part of the tire in terms of material mechanics. Based on this concept, a prototype of the tire was tested and tested, and the volume of the limited rim guard part ( We have conducted intensive research to optimize the rim guard part, which can effectively suppress the deformation of the side part under the weight and improve the durability.

  As a result, as in the first invention, the rim guard portion 13 is made of hard rubber, the 100% modulus of the hard rubber is set to 3.0 MPa or more, and the 100% modulus of the outer rubber 14 constituting the sidewall portion 4 is 2%. By setting the range to about 5 times, as in the second invention, at least one composite reinforcing member composed of the reinforcing element and the matrix rubber is provided at a position adjacent to at least a part of the peripheral surface 15 of the rim guard portion 13. By arranging the layer 16 and further combining these configurations as in the third invention, it is possible to sacrifice other performances such as ride comfort when the vehicle normally travels at normal internal pressure. Thus, the present invention succeeded in effectively improving the run flat durability when the vehicle continued running in a low internal pressure or punctured run flat state.

  In the first invention, the reason why the 100% modulus of the hard rubber forming the rim guard portion 13 is set to 3.0 MPa or more is that the rim guard portion 13 is hardly deformed by setting it to 3.0 MPa or more. This is because it is possible to alleviate local deformation of the tire side portion at the time, in particular, circumferential shear deformation of the reinforcing rubber 11, and in addition, increase in rigidity of the rim guard portion 13 with respect to the vertical spring of the tire when normal internal pressure is applied. Since the contribution is lower than that of the reinforcing rubber 11, the vertical spring stiffness (tire radial stiffness) is lower in the normal running state at normal internal pressure than in the conventional tire having the same run flat durability, and the riding comfort is low. The properties are good.

  However, in the first invention, the above configuration alone is not sufficient in terms of durability.

  Therefore, in the first invention, while minimizing the risk of separation or the like resulting from the rubber physical properties of the outer cover rubber forming the side wall portion and the rubber forming the rim guard portion, furthermore, in order to sufficiently bring out the effects of the present invention, It is necessary that the 100% modulus of the hard rubber forming the rim guard portion is in a range of 2 to 5 times the 100% modulus of the outer rubber forming the sidewall portion.

  That is, by limiting the 100% modulus of the hard rubber constituting the rim guard portion to a range of 2 to 5 times the 100% modulus of the outer rubber constituting the sidewall portion, the ride comfort and the run flat under normal internal pressure are normally achieved. The balance with durability can be optimized.

  Further, in the second invention, as shown in FIG. 5, the rubber constituting the rim guard portion 13 is not restricted as in the first invention, but is positioned at at least a part of the peripheral surface 15 of the rim guard portion 13. In addition, at least one composite reinforcing layer 16 composed of a reinforcing element and a matrix rubber is provided.

  In other words, when the side portion is largely bent during run flat running, the rubber in the side portion undergoes a so-called bulging deformation, which tends to move to the outside of the tire outer skin and other portions due to compression. In addition, by disposing the composite reinforcing layer 16 on the peripheral surface 15 of the rim guard portion 13, the rubber swelling at the time of bending is suppressed, and the vertical deflection in the run flat state can be effectively suppressed. The same effect as the first invention can be obtained. It should be noted that the arrangement of the composite reinforcing layer 16 has almost no effect on the vertical spring in the normal running state where the normal internal pressure is applied, so that good ride comfort during normal running can be maintained.

  The “peripheral surface of the rim guard portion” here means both the outer peripheral surface 15a and the inner peripheral surface 15b of the rim guard portion 13, as shown in FIG.

  Further, as in the third invention, if both the appropriate adjustment of the 100% modulus of the hard rubber and the arrangement of the composite reinforcing layer 16 are satisfied, the run-flat durability is further improved by the synergistic effect of these. be able to.

  In addition, the reinforcing elements constituting the composite reinforcing layer 16 may be arranged along a specific direction like cords of a cord rubberized layer, but a nonwoven fabric having no anisotropy from a material point of view. It is preferable to use them in order to effectively increase bending rigidity and torsional rigidity.

  In addition, as the reinforcing element constituting the composite reinforcing layer 16, for example, it is preferable to use a filament fiber having a fiber diameter of 0.01 to 1 mm and a fiber length of 1 mm or more, for example, aramid fiber or polyethylene terephthalate (PET). In particular, it is more preferable to use aramid fiber having high rigidity.

  The composite reinforcing layer 16 may be provided at a position adjacent to at least a part of the peripheral surface 15 of the rim guard portion 13.

  For example, as shown in FIG. 5, the composite reinforcing layer 16 is provided so as to surround the outer peripheral surface 15 a of the rim guard portion 13, so that the rubber swelling deformation at the time of deflection during run flat running is effectively suppressed. Although it is preferable in terms of point, as shown in FIG. 6, it is arranged only on the upper outer peripheral surface of the rim guard portion 13, or as shown in FIG. 7, it is arranged only on the lower outer peripheral surface of the rim guard portion 13, or As shown in FIG. 8, the rim guard 13 may be provided only on the inner peripheral surface 15b.

  Note that the arrangement of the composite reinforcing layer so as to surround the outer peripheral surface 15a of the rim guard portion 13 means that the arrangement position of the reinforcing element of the composite reinforcing layer is more than 70% of the rim guard height hmax. Surface 15a, and between the position of the outer peripheral surface 15a and the position within the rim guard portion within 3 mm therefrom. In this case, the composite reinforcing layer 16 itself is located on the outer peripheral surface 15a of the rim guard portion 13. Or buried in the rim guard portion 13.

  When it is necessary to prevent the outer surface of the bead portion from being damaged by contact with the rim, the composite reinforcing layer 16 contacts the rim R from the peripheral surface 15 of the rim guard portion 13 as shown in FIGS. Extending over the outer surface of the bead portion.

  Further, when the composite reinforcing layer 16 is provided on the outer peripheral surface 15a of the rim guard portion 13 and it is necessary to improve the surface appearance and weather resistance of the tire, as shown in FIG. A rubber layer 21 may be provided to further cover the layer.

  From the viewpoint of improving high-speed durability and the like, at least one layer of the wide reinforcing belt 22 covering the entire outer surface of the belt 8 and at least one cord extending parallel to the tire circumferential direction at positions covering both end portions of the belt 8. A pair of narrow reinforcing belts, two pairs of narrow reinforcing belts 23a and 23b in FIG. 5 can be provided, but in this case, at least one pair of narrow reinforcing belts 23a and 23b has a narrow width. With respect to the reinforcing belt 23b, the distance X measured in the tire width direction from the tread width end position 25 to the inner end position 24 in the tire width direction is set to be equal to or more than ４ of the tread width W. Is preferable in terms of reducing stress.

  That is, in the conventional run flat tire, as shown in FIG. 13, buckling (lifting deformation) is likely to occur at the tread portion near the buttress portion near the reinforcing rubber during run flat running. By setting the inner end position 24 of the tire width direction 23b in the tire width direction from the tread width end position 25 so that the distance X measured in the tire width direction is equal to or more than ４ of the tread width W, such buckling is suppressed. And run flat durability is further improved.

  Further, in the case where a plurality of circumferential main grooves 12a and 12b extending along the tire circumferential direction are provided on the tread portion 5, the position of the circumferential main groove 12b located most outward in the tire width direction is determined. As a starting point, as shown in FIG. 13, bending deformation is likely to occur locally, but in such a case, the inner end 24 in the tire width direction of the narrow reinforcing belt 23b is set in the circumferential main portion located most outward in the tire width direction. By arranging the groove 12b so as to be located on the inner side in the tire width direction from the groove width center position 26, such bending deformation is less likely to occur, and the run flat durability is further improved.

  It is considered that the run-flat tire has a substantially uniform gauge distribution from the buttress portion to the bead portion with almost no difference from the buttress portion to the basic configuration of the tire.

  However, in order to improve the durability by further adding the rubber weight from the almost uniform gauge distribution state, the inventor does not increase the gauges all over the place but concentrates on key points. It has been found that the durability can be effectively improved by increasing the gauge.

  As a result, a ring protruding outward in the tire width direction from the tire maximum width position 17 on the tire outer surface 4a to a specific area 20 of the tire outer surface 4a from the tire outer surface 4a in contact with the rim flange outer surface 18 to the highest position 19. By providing the rim guard portion 13 having a maximum height hmax at a predetermined ratio with respect to the tire thickness t, the flexure and deformation of the side portion of the tire are suppressed, and the durability is effectively improved. Found to improve.

  That is, the tire thickness t in the specific region 20 is made as equal as possible. More specifically, as shown in FIG. 1, an arc is formed so as to contact both the tire maximum width position 17 and the rim flange outer surface 18. When this arc is assumed to be a reference arc C approximating the contour of the specific area 20 (excluding the rim guard portion 13) of the tire outer surface 4a, a plurality of arcs drawn to the reference arc C within the specific area 20 are drawn. Assuming that the ratio of the minimum value to the maximum value of the tire thickness t, which is the distance between the reference arc C and the tire inner surface 27, measured on the normal line, is in the range of 0.8 to 1.0 times, the reference arc C The maximum height hmax of the rim guard portion 13, which is the distance between the reference arc C and the top surface 28 of the rim guard portion 13, measured on the normal m drawn in It is preferably in the range of 0.52 to 1.40 times, and by this configuration, Durability is suppressed deflection and deformation of the ear of the side portion is further improved.

  If the maximum height hmax of the rim guard portion 13 is less than 0.52 times the tire thickness t, the effect of improving the durability is small, and if it exceeds 1.40 times, the flexure and deformation are hardly changed and the tire durability is inferior. This is because a case occurs.

In addition, when the volume of the rim guard portion 13 is constant, the maximum height hmax of the rim guard portion 13 is further limited to a range of 0.58 to 1.20 times the tire thickness t measured on the same normal line. Can be improved.
The cross-sectional area of the rim guard portion 13 is preferably 0.4 to 1.5 cm ² (0.4 × 10 ^{−4 to} 1.5 × 10 ⁻⁴ m ² ) when viewed in the cross section in the tire width direction.

  As shown in FIG. 16, the average height ha of the rim guard portion 13 when the sectional area S of the rim guard portion 13 in the cross section in the tire width direction is divided by the length B of the base 29 of the rim guard portion 13 on the reference arc C. However, it is preferable that the maximum height hmax of the rim guard portion 13 is 0.6 times or more and less than 1.0 times.

  In the present invention, it is also important to optimize the height (thickness) distribution of the rim guard portion 13. In order for the rim guard portion to directly contribute to an increase in bending rigidity, the height of the rim guard portion 13 must be adjusted. It is desirable to reduce the low-profile portion as much as possible. For this purpose, it is preferable that the average height ha of the rim guard portion 13 is at least 0.6 times the maximum height hmax of the rim guard portion 13. Further, since the effect of exhibiting rigidity is exhibited when the length B of the base 29 is made longer than the length T of the top surface 28 of the rim guard portion 13, the average height ha of the rim guard portion 13 is set to the maximum height of the rim guard portion 13. It is preferably less than 1.0 times the height hmax.

  The rim guard 13 preferably has a substantially trapezoidal (FIG. 15) or substantially triangular (FIG. 1) cross-sectional shape.

  When the rim guard portion 13 has a substantially trapezoidal cross-sectional shape, it is preferable that the top surface 28 of the rim guard portion 13 be flat, and in addition, the top surface length T of the rim guard portion 13 in the cross section in the tire width direction is More preferably, it is in the range of 0.14 to 0.90 times the base length B. If it is less than 0.14 times, the width of the upper side of the trapezoid is narrow and the effect of the beam is small, and if it exceeds 0.90 times, the outer skin line forming the rim guard part from the side part will not be smooth and cracks will occur This is because there is a fear.

  Since a boundary portion 30 between the tire outer surface 4a and the outer peripheral surface 15a of the rim guard portion 13 is a portion where stress tends to concentrate, it is preferable to form the boundary portion 30 with a gentle curved surface.

  If the 100% modulus of the reinforcing rubber 11 is 4 MPa or more, the gauge thickness of the reinforcing rubber can be made relatively thin, so that it is preferable in terms of securing ride comfort under normal internal pressure.

  In addition, at least one of the plies constituting the carcass 7 may have one organic fiber cord selected from 6 nylon, 66 nylon, polyethylene terephthalate, rayon, polyethylene naphthalate and aramid. This is preferable for preventing breakage of the carcass cord during run flat running.

  What has been described above is merely an example of the embodiment of the present invention, and various changes can be made within the scope of the claims. For example, in the present invention, since the local deformation of the reinforcing rubber is alleviated by optimizing the rim guard, it is possible to improve the riding comfort in a normal running state in which normal internal pressure is applied by using a softer reinforcing rubber than before. It is also possible to reduce the weight by reducing the thickness of the reinforcing rubber.

Next, a pneumatic tire according to the present invention was prototyped and its performance was evaluated, and will be described below.
(Test Example 1)
Each of the tires of the examples is a side-reinforced type run flat tire having a tire size of 215 / 45ZR17, and the specifications thereof are shown in Table 1. The carcass consists of one folded ply, and the belt consists of two cord rubberized layers in which the cords are cross-laminated at an inclination angle of 26 ° to the tire circumferential direction. The belt is composed of a belt and two pairs of narrow reinforcing belts, and four circumferential main grooves are provided in a tread portion. The pair of narrow reinforcing belts has a tire width direction inner end located at the width center of the circumferential main groove. It was arranged so as to be located inward in the tire width direction from the position. Other tire structures were configured in the same manner as ordinary run-flat tires for passenger cars (pneumatic radial tires).

(Performance evaluation)
Run flat durability was measured by mounting each of the above test tires on a standard rim, running on a rotating drum under the test conditions of tire pressure: 0 kPa (relative pressure), tire load: 4.17 kN, and running speed: 90 km / h. Then, the running distance when the tire broke down was measured and evaluated from the measured value.
The ride comfort in the normal running state to which the normal internal pressure was applied was evaluated by calculating a longitudinal spring constant at a tire internal pressure of 230 kPa and a load of 3.7 kN, and from the calculated values.
For reference, the tire weight was also measured.
Table 1 shows the evaluation results. The numerical values in Table 1 are shown as index ratios with the conventional tire set to 100, and the larger the numerical value, the better the run flat durability, and the smaller the numerical values, the better the ride comfort and weight. .

  From the results shown in Table 1, all of the examples are excellent in durability during run-flat running, riding comfort during normal running, and overall balance performance of tire weight.

  The present invention effectively improves run flat durability when continuously running at a low internal pressure or a punctured run flat state without sacrificing other performance such as ride comfort when normally running at normal internal pressure. It has become possible to provide improved run flat tires.

FIG. 1 is a left half sectional view in the width direction of a run flat tire according to a first invention. It is a schematic diagram when a specific area | region of the side part of a tire is considered as a straight beam. It is a schematic diagram when a specific area | region of the side part of a tire and the rim guard part provided in this whole area | region are regarded as a straight beam. It is a schematic diagram when a specific area | region of the side part of a tire and the rim guard part provided only in the fixed part side part of this area | region are considered as a straight beam. It is a width direction left half sectional view of the run flat tire according to a 2nd invention. It is a figure showing other embodiments. It is a figure showing other embodiments. It is a figure showing other embodiments. It is a figure showing other embodiments. It is a figure showing other embodiments. It is a figure showing other embodiments. It is a figure showing other embodiments. FIG. 4 is a diagram for explaining a deformed state of a tire when a conventional run flat tire is run flat. It is a figure for explaining an example of a modification state of a tire at the time of run flat run with a run flat tire of the present invention. It is a figure showing other embodiments. FIG. 16 is a cross-sectional view of a rim guard portion when a side portion of the run flat tire of FIG. 15 is developed. It is a width direction left half sectional view of the conventional tire (conventional example).

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 1 Run flat tire 2 Bead core 3 Bead part 4 Side wall part 5 Tread part
6a, 6b Ply 7 Carcass 8 Belt
8a, 8b Cord layer 9 End of belt
10 Inner liner
11 Reinforced rubber
12a, 12b Circumferential main groove
13 Rim guard
14 Skin rubber
15 Rim guard area
16 Composite reinforcement layer
17 Tire maximum width position
18 Rim flange outer surface
19 Highest position of tire outer surface that contacts rim flange outer surface
20 Specific area
21 Rubber layer
22 Wide belt
23a, 23b Narrow reinforcement belt
24 Inner end position in tire width direction
25 Tread width end position
26 Groove width center
27 Tire inner surface
28 Top of rim guard
29 Bottom
30 Boundary

Claims (18)

At least one ply extending in a toroidal shape over each of a pair of beads having a bead core embedded therein, a pair of sidewalls extending radially outward from both beads, and a tread extending across both sidewalls. A belt comprising at least one cord rubberized layer is provided between a crown portion and a tread portion of a carcass made of, and at least on an inner surface side of a sidewall portion, a reinforcing rubber having a substantially crescent cross section is provided, and a tire is provided. In a run-flat tire provided with a ring-shaped rim guard protruding outward in the tire width direction at the tire outer surface position immediately above the rim flange with the
The rim guard is made of hard rubber,
A run flat tire having a 100% modulus of the hard rubber of not less than 3.0 MPa and a range of 2 to 5 times the 100% modulus of the outer cover rubber constituting the sidewall portion. At least one ply extending in a toroidal shape over each of a pair of beads having a bead core embedded therein, a pair of sidewalls extending radially outward from both beads, and a tread extending across both sidewalls. A belt comprising at least one cord rubberized layer is provided between a crown portion and a tread portion of a carcass made of, and at least on an inner surface side of a sidewall portion, a reinforcing rubber having a substantially crescent cross section is provided, and a tire is provided. In a run-flat tire provided with a ring-shaped rim guard protruding outward in the tire width direction at the tire outer surface position immediately above the rim flange with the
A run flat tire having at least one composite reinforcing layer made of a reinforcing element and a matrix rubber disposed at a position adjacent to at least a part of a peripheral surface of a rim guard portion. At least one ply extending in a toroidal shape over each of a pair of beads having a bead core embedded therein, a pair of sidewalls extending radially outward from both beads, and a tread extending across both sidewalls. A belt comprising at least one cord rubberized layer is provided between a crown portion and a tread portion of a carcass made of, and at least on an inner surface side of a sidewall portion, a reinforcing rubber having a substantially crescent cross section is provided, and a tire is provided. In a run-flat tire provided with a ring-shaped rim guard protruding outward in the tire width direction at the outer surface of the tire immediately above the rim flange in a state where the
The rim guard is made of hard rubber,
The 100% modulus of the hard rubber is 3.0 MPa or more, and is in the range of 2 to 5 times the 100% modulus of the outer cover rubber constituting the sidewall portion,
A run flat tire having at least one composite reinforcing layer made of a reinforcing element and a matrix rubber disposed at a position adjacent to at least a part of a peripheral surface of a rim guard portion.   The run-flat tire according to claim 2 or 3, wherein the reinforcing element constituting the composite reinforcing layer is a nonwoven fabric.   The run-flat tire according to claim 2, 3 or 4, wherein the reinforcing element constituting the composite reinforcing layer is a filament fiber having a fiber diameter of 0.01 to 1 mm and a fiber length of 1 mm or more.   The run-flat tire according to any one of claims 2 to 5, wherein the composite reinforcing layer is disposed so as to surround the outer peripheral surface of the rim guard portion.   At a position covering both ends of the belt, a pair of narrow reinforcing belts whose cords extend in parallel with the tire circumferential direction are arranged, and the inner end position of the narrow reinforcing belt in the tire width direction is shifted from the tread width end position. The run flat tire according to any one of claims 1 to 6, wherein a distance measured in the tire width direction is equal to or more than 1/4 of a tread width.   In the tread portion, a plurality of circumferential main grooves extending along the tire circumferential direction are provided, and the narrow width reinforcement belt has a tire width direction inner end, which is located at the outermost in the tire width direction. The run-flat tire according to claim 7, wherein the run-flat tire is disposed so as to be located inside the groove width center line in the tire width direction. Attach the tire to the standard rim and apply a predetermined air pressure in the width direction cross section of the tire wheel under no load,
The rim guard portion is in a specific region of the tire outer surface from the tire maximum width position on the tire outer surface to the highest position of the tire outer surface in contact with the rim flange outer surface,
When drawing an arc so as to be in contact with both the tire maximum width position and the rim flange outer surface, and assuming that this arc is a reference arc that approximates the contour shape of a specific region (excluding the rim guard portion) of the tire outer surface,
In the specific area, measured on a plurality of normals drawn to the reference arc, the thickness of the tire, which is the distance between the reference arc and the tire inner surface, the ratio of the minimum value to the maximum value is in the range of 0.8 to 1.0 times. Yes,
The maximum height of the rim guard, which is the distance between the reference arc and the top surface of the rim guard, measured on the normal drawn to the reference arc, is 0.52 to 1.40 times the tire thickness measured on the same normal. The run flat tire according to any one of claims 1 to 8, which is in a range.   The run-flat tire according to claim 9, wherein the maximum height of the rim guard portion is in a range of 0.58 to 1.20 times the tire thickness measured on the same normal line.   The average height of the rim guard part when the cross-sectional area of the rim guard part in the cross section in the tire width direction is divided by the base length of the rim guard part on the reference arc is 0.6 times or more and less than 1.0 times the maximum height of the rim guard part The run flat tire according to claim 9 or 10, wherein   The run flat tire according to claim 9, 10 or 11, wherein the rim guard portion has a substantially trapezoidal cross-sectional shape.   13. The run flat tire according to claim 12, wherein a top surface of the rim guard portion has a flat shape.   14. The run flat tire according to claim 13, wherein the top surface length of the rim guard portion in the cross section in the tire width direction is in a range of 0.14 to 0.90 times the base length.   12. The run flat tire according to claim 9, wherein the rim guard has a substantially triangular cross-sectional shape.   The run-flat tire according to any one of claims 1 to 15, wherein a boundary between the outer surface of the tire and the outer surface of the rim guard portion is formed with a gentle curved surface.   The run flat tire according to any one of claims 1 to 16, wherein the reinforcing rubber has a 100% modulus of 4 MPa or more.   18. The carcass according to claim 1, wherein at least one ply has one organic fiber cord selected from 6 nylon, 66 nylon, polyethylene terephthalate, rayon, polyethylene naphthalate and aramid. A run-flat tire according to any one of the preceding claims.

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