JP2012153293A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of executing the run-flat run by reducing the weight and the longitudinal spring constant of the tire while suppressing occurrence of dispersion of the longitudinal spring constant and the load sustaining capacity and degradation of the run-flat durability.SOLUTION: The pneumatic tire includes a radial carcass 5 constituted of a carcass body part 51 extending in a toroidal manner, and locked to a bead core embedded in a bead part, and a carcass return part 52 extending from the carcass body part 51 and returned around the bead core. The carcass return part 52 is returned inwardly from the outer side in the tire width direction around the bead core 4, and further provided with a reinforced rubber layer 7 disposed on the inner circumferential side of the carcass body part 51 and on the outer side in the tire radial direction of the bead core 4 at a part corresponding to at least a bead part 3 and a side wall part 2. An outer end 52a in the tire radial direction of the carcass return part 52 is located on the inner side in the tire radial direction from the virtual line P passing through the outer end in the tire radial direction of the bead core 4 and extending in the tire width direction.

Description

  The present invention relates to a pneumatic tire capable of run-flat travel, and more particularly to a pneumatic tire capable of run-flat travel suitable for a passenger car.

  Conventionally, as a so-called run-flat tire that can safely travel a certain distance without losing load support capability even when the internal pressure of the tire is reduced by puncture or the like, on the inner surface of the carcass of the sidewall portion of the tire, A side-reinforcing rubber layer with a relatively high modulus in the cross section is arranged to improve the rigidity of the sidewall, so that the load can be borne without excessively increasing the deformation of the sidewall when the tire internal pressure decreases. Various types of side-reinforced run-flat tires have been proposed.

  Here, in the run flat tire in which the side reinforcing rubber layer is disposed on the inner surface of the carcass in the side wall portion, for example, as shown in the tire width direction cross section in FIG. 3, the carcass 5 ′ is the inner side in the tire width direction around the bead core 4. The side reinforcing rubber layer 91 that bears the load when the tire internal pressure is reduced (during run flat running) and the bead core 4 embedded in the bead portion 3 are disposed outside the tire in the tire radial direction. The bead filler 92 that reinforces the portion 3 is formed separately. Therefore, in the run flat tire 30 in which the side reinforcing rubber layer 91 is disposed on the inner surface of the carcass 5 ′, a deviation occurs in the relative position between the side reinforcing rubber layer 91 and the bead filler 92 in the green tire manufacturing process or the vulcanizing process. Variations in the longitudinal spring constant and load bearing capacity may occur in the tire.

  Therefore, a run-flat tire has been proposed in which the side reinforcing rubber layer and the bead filler are integrated to suppress the occurrence of variations in the longitudinal spring constant and load bearing capacity of the tire. Specifically, a carcass main body portion that extends in a toroidal shape from the tread portion to a pair of bead portions via a pair of sidewall portions and is locked to a bead core embedded in the bead portion, and a bead core that extends from the carcass main body portion. A carcass folded portion that is folded from the inner side to the outer side in the tire width direction around the belt and extends the carcass folded portion to the outer end in the tire width direction of the belt disposed on the outer peripheral side of the crown portion of the carcass In addition, there has been proposed a run flat tire in which a rubber in which a side reinforcing rubber layer and a bead filler are integrated is disposed in a region surrounded by a carcass main body and a carcass folding portion (for example, Patent Documents 1 to 3). 3).

JP 2005-271794 A Japanese Patent Laid-Open No. 11-115421 U.S. Pat. No. 4,142,567

  However, in the conventional run flat tire in which the rubber in which the side reinforcing rubber layer and the bead filler are integrated is disposed in the region surrounded by the carcass main body portion and the carcass folded portion, the carcass folded portion of the carcass folded portion is run during run flat running. In order to prevent the separation from occurring at the end edge, the carcass folded portion extends to the outer end of the belt in the tire width direction. Therefore, in the above conventional run flat tire, although it is possible to suppress variations in the vertical spring constant and load bearing capacity of the tire and a decrease in durability during run flat running (run flat durability), the carcass folded portion has There is a problem that the tire becomes longer and the weight of the tire and the longitudinal spring constant increase.

  Accordingly, the present invention provides a pneumatic tire capable of run-flat running with reduced tire weight and longitudinal spring constant while suppressing variations in longitudinal spring constant and load bearing capacity and decrease in run-flat durability. The purpose is to do.

  An object of the present invention is to advantageously solve the above-described problems, and the pneumatic tire of the present invention extends in a toroid form from a tread portion to a pair of bead portions via a pair of sidewall portions. A pneumatic tire provided with a carcass made of at least one ply, comprising a carcass main body portion locked to a bead core embedded in the portion, and a carcass folded portion extending from the carcass main body portion and folded around the bead core. The carcass folding portion of the carcass is folded back from the outside in the tire width direction around the bead core, and at least a portion corresponding to the bead portion and the sidewall portion on the inner peripheral side of the carcass main body portion And further comprising a reinforcing rubber layer disposed on the outer side of the bead core in the tire radial direction, wherein the tire is used as an applied rim. In an unloaded state where a predetermined internal pressure is applied, an outer end in the tire radial direction of the carcass folded portion is on the inner side in the tire radial direction from a virtual line extending in the tire width direction through the outer end in the tire radial direction of the bead core. It is characterized by being located. As described above, if a reinforcing rubber layer is disposed on the inner circumference side of the carcass main body portion and at the outer side in the tire radial direction of the bead core at least corresponding to the bead portion and the sidewall portion, the load is applied to the reinforcing rubber layer during run flat running. And the occurrence of variations in the longitudinal spring constant and load bearing capacity of the tire can be suppressed. Further, the carcass folded portion is folded from the outside in the tire width direction around the bead core to the inside, and the outer end in the tire radial direction of the carcass folded portion is passed through the tire radial direction outer end of the bead core from a virtual line extending in the tire width direction. If it is located inside the tire in the radial direction, the length of the carcass folding portion can be shortened while suppressing the decrease in run-flat durability, the tire can be reduced in weight, and the longitudinal spring constant of the tire can be reduced. The riding comfort performance of the tire can be improved.

  In the present invention, the “applicable rim” is an industrial standard effective in the area where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK is used. In Europe, ETRTO (European Tire and Land) is used. Rim Technical Organization) In the United States, it refers to the rim defined by TRA (THE TIRE and RIM ASSOCIATION INC.) YEAR BOOK, etc. Further, in the present invention, “the tire is mounted on the applied rim and the predetermined internal pressure is applied” means that the tire is mounted on the applied rim and the tire has a maximum tire load capacity of a standard such as JATMA in an applied size tire. This refers to the state with the corresponding internal pressure (maximum air pressure).

  Here, in the pneumatic tire according to the present invention, the reinforcing rubber layer is composed of at least two kinds of rubbers having different hardnesses, and is located on the inner side in the tire radial direction than the hardness of the rubber located on the outer side in the tire radial direction. It is preferable that the hardness of the rubber is large. Of the rubbers that make up the reinforcing rubber layer, if the rubber located on the inner side in the tire radial direction is harder than the rubber located on the outer side in the tire radial direction, the longitudinal spring constant of the tire is further reduced while ensuring run-flat durability. This is because the riding comfort performance of the tire can be further improved.

  In the pneumatic tire of the present invention, the reinforcing rubber layer has a first rubber portion and a second rubber portion that is harder than the first rubber portion. In the applied no-load state, the second rubber portion is located in a range of 45% or more of the tire cross-section height measured in the tire radial direction from the tire radial inner end of the reinforcing rubber layer, and the first rubber The portion is preferably located on the outer side in the tire radial direction of the second rubber portion. A second rubber portion, which is measured in the tire radial direction from the tire radial inner end of the reinforcing rubber layer and located in a range of 45% or more of the tire cross-section height, is a first rubber rubber positioned on the outer side in the tire radial direction of the second rubber portion. This is because if it is harder than the rubber part, the longitudinal spring constant of the tire can be further reduced and the riding comfort performance of the tire can be further improved while ensuring run-flat durability.

  And as for the pneumatic tire of this invention, it is preferable that the durometer A hardness of the said 1st rubber part is 67-73, and the durometer A hardness of the said 2nd rubber part is 74-80. If the durometer A hardness of the first rubber portion is 67 or more, run flat durability can be sufficiently secured, and if it is 73 or less, the longitudinal spring constant of the tire is reduced and the riding performance of the tire is improved. It is because it can improve. Further, if the durometer A hardness of the second rubber portion is 74 or more, run-flat durability can be sufficiently secured, and if it is 80 or less, the longitudinal spring constant of the tire is reduced and the riding comfort of the tire is reduced. This is because the performance can be improved.

  In the present invention, “durometer A hardness” refers to the hardness measured in accordance with JIS K6253.

  According to the present invention, there is provided a pneumatic tire capable of run-flat running with reduced weight and longitudinal spring constant of the tire while suppressing variations in longitudinal spring constant and load bearing capacity and decrease in run-flat durability. can do.

It is a tire width direction sectional view shown about a tire half in the state where an example of a pneumatic tire according to the present invention was equipped in an application rim. It is a tire width direction sectional view shown about a tire half part in the state where a pneumatic tire according to the present invention was attached to an application rim. It is a tire width direction sectional view shown about a tire half part in the state where a conventional pneumatic tire was attached to an application rim.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a diagram showing a tire width direction cross section in an unloaded state in which a predetermined internal pressure is applied to an applied rim R with respect to an example of a pneumatic tire according to the present invention only for a tire half portion.

  Here, the pneumatic tire 10 shown in FIG. 1 is a run-flat tire that can safely travel a certain distance without losing the load supporting ability even when the internal pressure of the tire is reduced due to puncture or the like. Suitable for passenger cars without limitation.

  The pneumatic tire 10 includes a tread portion 1, a pair of sidewall portions 2 (only one side is shown) extending inward in the tire radial direction from the side portions of the tread portion 1, and the tire radial direction inside of each sidewall portion 2. And a bead portion 3 (only one side is shown).

  The pneumatic tire 10 also includes a radial carcass 5 made of one ply extending between the pair of bead portions 3. The radial carcass 5 extends in a toroid shape from the tread portion 1 to the pair of bead portions 3 via the pair of sidewall portions 2, and is locked to a bead core 4 having a substantially square cross section embedded in the bead portion 3. The carcass main body portion 51 and a carcass folding portion 52 that extends from the carcass main body portion 51 and is folded around the bead core 4 from the outer side in the tire width direction to the inner side. The outer end 52a in the tire radial direction of the carcass folded portion 52 is located on the inner side in the tire radial direction from the virtual line P that extends in the tire width direction through the outer end in the tire radial direction of the bead core 4. Although FIG. 1 shows a case where the number of carcass plies is 1 ply, in the pneumatic tire of the present invention, the number of plies can be 2 plies or more as required. In the pneumatic tire of the present invention, the carcass may be a bias carcass.

  Further, on the outer side in the tire radial direction (crown outer peripheral side) of the carcass main body 51 of the tread portion 1, two inclined belt layers (intersections) extending incline in a direction intersecting with each other across the tire equatorial plane. Belt layer) 61 and 62 and a belt 6 formed by sequentially arranging a circumferential belt layer 63 arranged by spirally winding a cord at an inclination angle of 5 ° or less with respect to the tire circumferential direction. Has been. A tread rubber is disposed on the outer side of the belt 6 in the tire radial direction, and a tread groove 8 such as a circumferential groove extending in the tire circumferential direction is formed on the surface of the tread rubber. In FIG. 1, the belt 6 includes a total of three belt layers 61, 62, and 63. However, in the pneumatic tire of the present invention, the configuration, arrangement position, and number of the belt layers are as follows. These can be changed as necessary.

  Of the region extending from the tire width direction end of the tread portion 1 to the bead core 4 of the bead portion 3 via the sidewall portion 2, the carcass main body portion 51 of the radial carcass 5 and the inner peripheral side of the carcass main body portion 51. A reinforcing rubber layer 7 having a substantially bowl-shaped cross section made of rubber having a relatively high modulus is disposed between the inner liner 9 and the inner liner 9. That is, in the pneumatic tire 10, the reinforcing rubber layer 7 extends from the outer side in the tire radial direction of the bead core 4 to the inner side in the tire radial direction of the belt 6 on the inner peripheral side of the carcass main body 51.

  In this pneumatic tire 10, since the reinforcing rubber layer 7 is disposed on the inner peripheral side of the carcass main body portion 51 corresponding to at least the sidewall portion 2, the rigidity of the sidewall portion 2 is improved. Even when the tire internal pressure is reduced, the load can be borne without excessively increasing the deformation of the sidewall portion. Therefore, according to the pneumatic tire 10, it is possible to safely travel a certain distance without losing the load supporting ability even when the internal pressure of the tire is reduced.

  In the pneumatic tire 10, the reinforcing rubber layer 7 extends from the outer side in the tire radial direction of the bead core 4, so that the bead portion 3 can be reinforced with the reinforcing rubber layer 7. That is, in this pneumatic tire 10, the reinforcing rubber layer 7 not only exhibits the same function as the side reinforcing rubber layer 91 in the conventional pneumatic tire (run flat tire 30) as shown in FIG. The same function as the bead filler 92 of the conventional run flat tire 30 is exhibited. Therefore, according to the pneumatic tire 10, it is possible to reduce the number of parts and simplify the tire manufacturing process and the like as compared with the conventional run flat tire in which the side reinforcing rubber layer and the bead filler are provided separately. In addition, it is possible to suppress the occurrence of variations in the longitudinal spring constant and load bearing capacity in the tire due to the relative positional deviation between the side reinforcing rubber layer and the bead filler.

  Further, in the pneumatic tire 10, the carcass folded portion 52 is folded around the bead core 4 from the outer side in the tire width direction to the inner side, and the tire radial direction outer end 52 a of the carcass folded portion 52 is connected to the tire radial direction outer end of the bead core 4. It is located on the inner side in the tire radial direction from the imaginary line P that passes through in the tire width direction. That is, when the sidewall 2 is bent and deformed, the radial carcass is not disposed in the inner portion in the tire width direction, which is subjected to compressive strain and shear strain when the internal pressure of the tire is reduced and the sidewall 2 is bent and deformed. A radial carcass is disposed on the outer portion in the tire width direction that receives tensile strain to bear the tension. Accordingly, the length of the radial carcass 5, particularly the carcass folding portion 52, can be shortened and the tire weight can be reduced while suppressing a decrease in run-flat durability. In addition, since the length of the carcass folded portion 52 can be shortened while suppressing a decrease in run flat durability, the rigidity of the sidewall portion 2 is prevented from becoming too high while ensuring the run flat durability. The longitudinal spring constant of the tire can be reduced (that is, the riding comfort performance during normal running can be improved).

  Therefore, according to the pneumatic tire 10, the weight of the tire and the vertical spring constant can be reduced while suppressing the occurrence of variations in the vertical spring constant and load bearing capacity and the decrease in run-flat durability.

  Here, in the pneumatic tire 10 of the above example, the reinforcing rubber layer 7 composed of one kind of rubber was used, but the pneumatic tire of the present invention is composed of at least two kinds of rubbers having different hardness, Further, a reinforced rubber layer in which the hardness of the rubber located on the inner side in the tire radial direction is larger than the hardness of the rubber located on the outer side in the tire radial direction may be used.

  Specifically, in FIG. 2, as for another example of the pneumatic tire according to the present invention, a cross section in the tire width direction in a tire-less state in which a predetermined internal pressure is applied to the applicable rim R is shown only for the tire half. The reinforcing rubber layer may be composed of two types of rubbers having different hardnesses.

  Here, the pneumatic tire 20 shown in FIG. 2 includes a first rubber portion 71 and a second rubber portion 72 located on the inner side in the tire radial direction of the first rubber portion. Except for this point, the other configurations are the same as those of the pneumatic tire 10 of the previous example. In FIG. 2, parts having the same configuration as the pneumatic tire 10 shown in FIG.

  The second rubber portion 72 of the pneumatic tire 20 is made of rubber harder than the first rubber portion 71.

  Therefore, according to the pneumatic tire 20 of this other example, similarly to the pneumatic tire 10 of the previous example, the vehicle can safely travel a certain distance without losing the load supporting ability even when the internal pressure of the tire is reduced. can do. In addition, compared with a conventional run flat tire in which the side reinforcing rubber layer and the bead filler are provided separately, the number of parts can be reduced and the tire manufacturing process can be simplified, and the side reinforcing rubber layer and It is possible to suppress the occurrence of variations in the longitudinal spring constant and load bearing capacity in the tire due to the displacement of the relative position with the bead filler. Furthermore, the weight of the tire and the longitudinal spring constant can be reduced by reducing the length of the radial carcass 5, particularly the carcass folding portion 52, while suppressing a decrease in run-flat durability.

  Further, in the pneumatic tire 20, the rubber of the second rubber portion 72 constituting the tire radial direction inner portion of the reinforcing rubber layer 7 'is harder than the rubber of the first rubber portion 71 constituting the tire radial direction outer portion. The longitudinal spring constant of the tire can be further reduced while ensuring the rigidity of the sidewall portion 2. Therefore, it is possible to further improve the riding comfort performance of the tire during normal running while ensuring run-flat durability.

  From the viewpoint of ensuring the rigidity of the sidewall portion 2 and sufficiently ensuring the run-flat durability, the tire radial dimension h of the second rubber portion 72 measured from the tire radial inner end of the reinforcing rubber layer 7 ′. Is preferably 45% or more, more preferably 50% or more of the tire cross-section height H (1/2 of the difference between the outer diameter of the tire and the rim diameter of the applied rim R). Further, from the viewpoint of preventing the rigidity of the sidewall portion 2 from being improved excessively and increasing the longitudinal spring constant of the tire and degrading the riding comfort performance during normal traveling, the tire radial dimension of the second rubber portion 72 is prevented. h is preferably 55% or less of the tire cross-section height H.

  Further, from the viewpoint of ensuring that the reinforcing rubber layer 7 ′ is made of a moderately hard rubber and securing the rigidity of the sidewall portion 2 to sufficiently ensure the run-flat durability, the durometer A hardness of the first rubber portion is set to 67. Preferably, the durometer A hardness of the second rubber portion is preferably 74 or more. Furthermore, from the viewpoint of preventing the rigidity of the sidewall portion 2 from being improved excessively, increasing the longitudinal spring constant of the tire, and reducing the riding comfort performance during normal running, the durometer A hardness of the first rubber portion is set to be low. 73 or less is preferable, and the durometer A hardness of the second rubber portion is preferably 80 or less.

  As mentioned above, although embodiment of this invention was described with reference to drawings, the pneumatic tire of this invention is not limited to the said example and another example, It changes suitably in the pneumatic tire of this invention. Can be added.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to the following Example at all.

Example 1
A pneumatic tire with a size of 165 / 55R15 having the configuration shown in FIG. And while measuring the weight of a tire, the longitudinal spring constant of the tire was evaluated by the following method. The results are shown in Table 1.

(Example 2)
A pneumatic tire with a size of 165 / 55R15 having the configuration shown in FIG. The tire was designed so that the run-flat durability was equivalent to the tire of Example 1. And while measuring the weight of a tire, the longitudinal spring constant of the tire was evaluated by the following method. The results are shown in Table 1.

(Conventional example 1)
A pneumatic tire with a size of 165 / 55R15 having the configuration shown in FIG. The tire was designed so that the run-flat durability was equivalent to the tire of Example 1. And while measuring the weight of a tire, the longitudinal spring constant of the tire was evaluated by the following method. The results are shown in Table 1. Incidentally, in FIG. 3, the same reference numerals are given to portions having the same configuration as the pneumatic tire 10 shown in FIG. 1. Further, reference numeral 51 ′ in FIG. 3 indicates a carcass main body portion, and reference numeral 52 ′ indicates a carcass folding portion.

<Vertical spring constant>
The prepared tire is mounted on an applied rim, filled with an internal pressure of 200 kPa, a load-deflection curve is measured, and the tangential slope at a certain load on the obtained load-deflection curve is set to a longitudinal direction relative to the load of the prepared tire. The spring constant was used. Then, the value of the longitudinal spring constant of the tire of the conventional example 1 was set as 100 and displayed as an index. The index indicates that the smaller the value, the lower the longitudinal spring constant, and the better the riding comfort.

  From Table 1, it can be seen that the pneumatic tires of Examples 1 and 2 can reduce the tire weight and the longitudinal spring constant while suppressing the decrease in run-flat durability as compared with the pneumatic tire of Conventional Example 1. . In the pneumatic tires of Examples 1 and 2, since the reinforcing rubber layer is used, the longitudinal spring constant and the pneumatic tire of Conventional Example 1 in which the side reinforcing rubber layer and the bead filler are separately formed are different. Variations in load bearing capacity are unlikely to occur.

  According to the present invention, there is provided a pneumatic tire capable of run-flat running with reduced weight and longitudinal spring constant of the tire while suppressing variations in longitudinal spring constant and load bearing capacity and decrease in run-flat durability. can do.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Bead core 5, 5 'Radial carcass 6 Belt 7 Reinforcement rubber layer 8 Tread groove 9 Inner liner 10 Pneumatic tire 20 Pneumatic tire 30 Run flat tire 51, 51' Carcass main-body part 52 , 52 ′ Carcass turn-up portion 52 a Tire outer ends 61, 62 Inclined belt layer 63 Circumferential belt layer 71 First rubber portion 72 Second rubber portion 91 Side reinforcing rubber layer 92 Bead filler

Claims (4)

A carcass body extending from the tread portion to a pair of bead portions via a pair of sidewall portions and being locked to a bead core embedded in the bead portion, and extending from the carcass body portion and folded around the bead core A pneumatic tire provided with a carcass composed of at least one ply,
The carcass folded portion of the carcass is folded from the outside in the tire width direction around the bead core to the inside,
A reinforcement rubber layer disposed at least on the inner circumference side of the carcass main body portion and on the outer side in the tire radial direction of the bead core, at least corresponding to the bead portion and the sidewall portion;
The tire radial direction outer end of the carcass folded-back portion passes through the tire radial direction outer end of the bead core and extends in the tire width direction in a no-load state in which a tire is mounted on the applied rim and a predetermined internal pressure is applied. A pneumatic tire characterized by being located on the inner side in the tire radial direction.   The reinforcing rubber layer is composed of at least two kinds of rubbers having different hardnesses, and the hardness of the rubber located on the inner side in the tire radial direction is larger than the hardness of the rubber located on the outer side in the tire radial direction. The pneumatic tire according to claim 1. The reinforcing rubber layer has a first rubber part and a second rubber part harder than the first rubber part,
In a no-load state in which a tire is mounted on an applied rim and a predetermined internal pressure is applied, the second rubber portion is measured in the tire radial direction from the tire radial inner end of the reinforcing rubber layer and is 45% of the tire cross-section height. Located in the above range,
3. The pneumatic tire according to claim 1, wherein the first rubber portion is located on the outer side in the tire radial direction of the second rubber portion. The durometer A hardness of the first rubber part is 67-73;
The pneumatic tire according to claim 3, wherein durometer A hardness of said 2nd rubber part is 74-80.

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