JP2011201364A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which enables run-flat traveling and has improved riding comfort in traveling at normal internal pressure without spoiling run-flat durability.SOLUTION: The pneumatic tire 10 includes: a carcass 4 comprising at least one ply extending in a toroidal shape from a tread part 1 over a pair of bead parts 3 via a pair of side walls 2; a belt 5 comprising at least one belt layer arranged at the outer circumferential side of the crown part of the carcass 4; and reinforced rubber layers 7 provided at the inside circumferential side of the carcass 4 of the parts corresponding to at least the side walls 2. Under ground-contact condition in which predetermined air pressure and predetermined load are applied with the tire 10 mounted on an applicable rim, foamed rubber is arranged at least a part of first areas A of the tread part 1 divided by a first plane P1, which includes end edges of the belt 5 and intersects tire surface perpendicularly, and a second plane P2, which includes a ground-contact end and intersects the tire surface perpendicularly.

Description

  The present invention relates to a pneumatic tire capable of run-flat traveling, and more particularly to a pneumatic tire with improved riding comfort during normal internal pressure traveling without impairing durability during run-flat traveling.

  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, the side-reinforcement type run-flat tires with improved rigidity of the sidewalls of the tire have a large amount of tire deflection when running with the tire's internal pressure lowered (during run-flat running), and side reinforcement Since the rubber layer is easily cracked, there is a problem that the distance in which the run-flat traveling is possible is short.

  Therefore, by increasing the thickness and rigidity of the side reinforcing rubber layer, or adding a fiber reinforcing layer to the outer side of the sidewall in the tire radial direction, the durability of the tire during run flat running (run flat durability) ) Has been proposed (see, for example, Patent Document 1).

JP 2006-76374 A

  However, run-flat tires with increased thickness and rigidity of the conventional side-reinforced rubber layer and run-flat tires with a fiber reinforcement layer added to the outer side in the tire radial direction of the sidewall portion ensure run-flat durability. However, there is a problem that the longitudinal spring constant of the tire at the time of using the normal internal pressure where the internal pressure of the tire is not lowered is increased, and the riding comfort at the time of running at the normal internal pressure is deteriorated.

  Therefore, there has been a demand for a pneumatic tire capable of run-flat running with improved ride comfort during normal internal pressure running without impairing run-flat durability.

  As a result of intensive studies to solve the above problems, the present inventor has found that the rigidity of a predetermined portion of the tread portion greatly affects the longitudinal spring constant of the tire when using normal internal pressure. The present inventors have also found that the portion hardly bears a load necessary for ensuring tire durability during run-flat running. Therefore, the present inventor arranges foamed rubber in the predetermined portion of the tread portion, and reduces the rigidity of the portion, thereby reducing the vertical spring constant of the tire when using normal internal pressure without impairing run-flat durability. The present invention was completed with the idea of lowering.

  That is, the present invention aims to advantageously solve the above-described problems, and the pneumatic tire of the present invention extends at least in a toroid shape from a tread portion to a pair of bead portions via a pair of sidewall portions. A carcass composed of one ply, a belt composed of at least one belt layer disposed on the outer peripheral side of the crown portion of the carcass, and disposed on the inner peripheral side of the carcass at least at a portion corresponding to the sidewall portion. A pneumatic tire comprising a reinforced rubber layer, wherein the tire is mounted on an applied rim, and includes a belt edge and a first orthogonal to the tire surface under a grounding condition applying a predetermined air pressure and a predetermined load. The foam rubber is disposed in at least a part of the first region of the tread portion defined by the flat surface and the second flat surface including the ground contact edge and perpendicular to the tire surface. The features. Thus, if foam rubber is arrange | positioned in a 1st area | region, the longitudinal spring constant of the tire at the time of normal internal pressure use can be reduced, and the riding comfort at the time of normal internal pressure driving | running | working can be improved. In addition, if the location of the foam rubber is at least part of the first region of the tread portion, run-flat durability can be ensured.

  Here, in the present invention, the “applied rim” is an industrial standard effective in the region where tires are produced and used. In Japan, JATMA (Japan Automobile Tire Association) YEAR BOOK is used, and in Europe, ETRTO (European Tire) is used. and Rim Technical Organization) In the United States, it refers to a rim specified in TRA (THE TIRE and RIM ASSOCIATION INC.) YEAR BOOK, etc. Further, in the present invention, “a grounding condition in which a tire is attached to an applicable rim and a predetermined air pressure and a predetermined load are applied” means that the tire is attached to the applicable rim and the tire of the standard of JATMA or the like in an applicable size tire The air pressure (maximum air pressure) corresponding to the load capacity is used, and it refers to a state in which a load that is 75% of the maximum tire load capacity of a standard such as JATMA is applied and grounded. Furthermore, in the present invention, the “edge of the belt” refers to an edge located most outward in the tire width direction among the edges of the belt layer when the belt is composed of a plurality of belt layers. .

Here, in the pneumatic tire of the present invention, the foaming ratio of the foamed rubber is preferably 0.2 or more. If the foaming ratio of the foamed rubber is 0.2 or more, the longitudinal spring constant of the tire when using normal internal pressure can be effectively reduced, and the riding comfort during normal internal pressure running can be improved effectively. Because. In the present invention, the “foaming ratio” refers to the following formula (1) by measuring the density (mass / unit volume) of rubber before and after foaming.
Foam ratio = 1- (Rubber density after foaming / Rubber density before foaming) (1)
It can ask for.

  In the pneumatic tire of the present invention, it is preferable that the foam rubber is disposed in the entire region of the first region. If foam rubber is placed throughout the first region of the tread, the vertical spring constant of the tire when using normal internal pressure can be effectively reduced, and the riding comfort during normal internal pressure running is effectively improved. Because it can be done.

  Furthermore, in the pneumatic tire according to the present invention, it is preferable that the foam rubber is disposed in a part of the first region. This is because if the foamed rubber is disposed in a part of the first region of the tread portion, run-flat durability can be reliably ensured.

  In the pneumatic tire of the present invention, it is preferable that the foamed rubber is disposed on the outer side in the tire width direction than the first plane.

  According to the present invention, it is possible to provide a pneumatic tire capable of run-flat running with improved ride comfort during normal internal pressure running without impairing run-flat durability.

1 is a tire width direction cross-sectional view of a typical pneumatic tire according to the present invention. It is tire width direction sectional drawing of the other pneumatic tire according to this invention. It is a tire width direction sectional view of another pneumatic tire according to the present invention. 2 is a graph showing a change in a longitudinal spring constant of the tire when the foaming ratio of foamed rubber disposed in a first region is changed in the pneumatic tire shown in FIG. 1.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a cross section in the tire width direction of an example of a pneumatic tire according to the present invention. A pneumatic tire 10 shown in FIG. 1 is a so-called run-flat tire that can safely travel a certain distance without losing load supporting ability even when the internal pressure of the tire is reduced due to puncture or the like, and has a tread portion. 1, a pair of sidewall portions 2 that extend inward in the tire radial direction from the side portion of the tread portion 1, and a bead portion 3 that extends inward in the tire radial direction of each sidewall portion 2.

  The pneumatic tire 10 includes a radial carcass 4 composed of two plies extending between a pair of bead portions 3, and the radial carcass 4 is paired from the tread portion 1 via a pair of sidewall portions 2. A first radial carcass ply 41 and a second radial carcass ply 42 extending around a bead core 31 having a circular cross section embedded in the bead portion 3 and extending in a toroidal shape. The position of the folding end 41 a of the ply 41 is located outward in the tire radial direction from the position of the folding end 42 a of the second radial carcass ply 42. Although FIG. 1 shows a case where the number of carcass plies is 2 plies, in the pneumatic tire of the present invention, the number of plies may be 1 ply or 3 plies or more as required. it can. 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 of the radial carcass 4 of the tread portion 1 (on the outer peripheral side of the crown portion), two inclined belt layers (inclined in a direction intersecting each other across the tire equatorial plane E) ( Cross belt layers) 51, 52 and wide circumferential belt layers arranged by covering the entire surfaces of these inclined belt layers 51, 52 and spirally winding the cord at an inclination angle of 5 ° or less with respect to the tire equator plane A belt 5 is provided in which 53 (cap layer) and a narrow reinforcing belt layer 54 (layer layer) that covers only both ends in the tire width direction of the circumferential belt layer 53 are sequentially disposed. A tread rubber 11 is disposed on the outer side of the belt 5 in the tire radial direction, and a tread groove 12 such as a circumferential groove extending in the tire circumferential direction is formed on the surface of the tread rubber 11. . In addition, a stiffener rubber 32 having a substantially triangular cross section whose thickness gradually decreases outward in the tire radial direction along the radial carcass 4 is disposed on the outer side in the tire radial direction of the bead core 31 of the bead portion 3. In addition, in FIG. 1, although the belt 5 has shown the case where it consists of a total of four belt layers 51, 52, 53, 54, in the pneumatic tire of the present invention, the number and arrangement positions of the belt layers are: Any number and location can be used as necessary.

  Further, there is a relatively high modulus between the radial carcass 4 in the region extending from the tire width direction end of the tread portion 1 to the bead portion 3 and the inner liner 6 disposed on the inner peripheral side of the radial carcass 4. A side-reinforcing rubber layer 7 having a substantially crescent-shaped cross section made of high-rubber rubber is disposed.

  In this pneumatic tire 10, the pneumatic tire 10 is mounted on an applicable rim, and an air pressure (maximum air pressure) corresponding to a tire maximum load capacity of a standard such as JATMA and a load of 75% of the tire maximum load capacity is applied. The first tread portion 1 defined by the first plane P1 including the edge 5a of the belt 5 and orthogonal to the tire surface and the second plane P2 including the ground end S and orthogonal to the tire surface is provided. One region A is composed of the first tread rubber 11A. Moreover, the 2nd area | region B of the tread part 1 divided between the 2nd 2nd planes P2 orthogonal to a tire surface including each contact edge S is comprised by the 2nd tread rubber 11B.

  The first tread rubber 11A needs to be foamed rubber having air bubbles inside and low rigidity, and the second tread rubber 11B can be a known rubber usually used for the tread portion. . Here, a known foamed rubber can be used as the foamed rubber. The foam rubber can be disposed by a known method.

  In the pneumatic tire 10 described above, the first tread rubber 11A made of foamed rubber is disposed in the first region A of the tread portion 1 which is a portion that has a great influence on the vertical spring constant during normal internal pressure traveling. Therefore, the rigidity of the first region A can be reduced to reduce the tire spring constant when using the normal internal pressure, and the riding comfort during normal internal pressure running can be improved.

  Moreover, in the pneumatic tire 10, since the rigidity of the sidewall portion 2 is improved by the arrangement of the side reinforcing rubber layer 7, even when the internal pressure of the tire is reduced due to puncture or the like, the sidewall portion 2 is deformed and deformed. It is possible to run safely in a flat run while bearing a load without increasing it extremely.

  Here, since the first region A is a portion that hardly bears a load during run-flat travel, the pneumatic tire 10 can ensure durability during run-flat travel.

In addition, the foaming ratio R (= 1- (rubber density after foaming ρ ₁ / rubber density before foaming ρ ₂ )) of the first tread rubber 11A is 0.2 or more and less than 1.0 (1.0> R ≧ 0. 2), more preferably 0.2 or more and less than 0.8. This is because when the foaming ratio is 0.2 or more, the vertical spring constant of the tire when using normal internal pressure can be further reduced, and the riding comfort during normal internal pressure running can be further improved. Moreover, it is because manufacture may become difficult when a foaming ratio is 0.8 or more. Incidentally, the foaming ratio of the foamed rubber can be controlled, for example, by adjusting the amount of foaming agent added to the unvulcanized rubber.

  Here, the pneumatic tire of the present invention is not limited to the above example, and can be appropriately changed. Specifically, for example, a configuration as shown in FIGS.

  In a pneumatic tire 20 according to another example of the present invention shown in FIG. 2, the first tread rubber 11A made of foamed rubber is arranged only in a part of the first region A (the central portion of the first region A in FIG. 2). In the first region A, the third tread rubber 11C made of the same rubber as the second tread rubber 11B is disposed in a portion where the first tread rubber 11A is not disposed. The pneumatic tire 10 has the same configuration as the pneumatic tire 10 of the previous example except that the configuration is different from the pneumatic tire 10.

  In the pneumatic tire 20, like the pneumatic tire 10, it is possible to improve the riding comfort during normal internal pressure traveling without impairing the run-flat durability.

  In the pneumatic tire of the present invention, when the first tread rubber (foamed rubber) is disposed only in a part of the first region, the position of the first tread rubber is limited to the central portion of the first region. It can also be arranged on the first plane side or the second plane side.

  In a pneumatic tire 30 of another example of the present invention shown in FIG. 3, the first tread rubber 11A made of foamed rubber is disposed only in a part of the first region A (the first plane P1 side in FIG. 3). A third tread rubber 11C made of the same rubber as the second tread rubber 11B is disposed in a portion of the first region A where the first tread rubber 11A is not disposed, and further, from the first plane P1. Further, the rubber 8 made of foamed rubber having the same foaming ratio as that of the first tread rubber 11A is continuously arranged on the outer side in the tire width direction with the first tread rubber 11A. Except that they are different from each other, they have the same configuration as the pneumatic tire 10 of the previous example.

  In the pneumatic tire 30, like the pneumatic tire 10, it is possible to improve riding comfort during normal internal pressure running without impairing run-flat durability.

  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 having a size as shown in FIG. 1 and a size of 245 / 45RF19 having the configuration shown in FIG. The results are shown in Table 1 and FIG.

(Examples 2 to 4)
A pneumatic tire was made in the same manner as in Example 1 except that the foaming ratio of the first tread rubber (foam rubber) was changed, and performance evaluation was performed in the same manner as in Example 1. The results are shown in Table 1 and FIG.

(Example 5)
A pneumatic tire having a size as shown in FIG. 2 and having a size as shown in FIG. 2 and having a size as shown in FIG. The results are shown in Table 1.

(Example 6)
A pneumatic tire with a size of 245 / 45RF19 having the configuration shown in FIG. 3 having the specifications shown in Table 1 was prototyped, and performance evaluation was performed by the following method. The results are shown in Table 1.

(Comparative Example 1)
A pneumatic tire was prototyped in the same manner as in Example 1, except that the first tread rubber (foam rubber) was not used in the first region and only the second tread rubber that was not foam rubber was used as the tread rubber. The performance was evaluated in the same manner as in 1. The results are shown in Table 1 and FIG.

(Ride comfort)
The produced tire was filled with an internal pressure of 230 kPa, the load-deflection curve was measured, and the tangential slope at a certain load on the obtained load-deflection curve was defined as the longitudinal spring constant for the produced tire. Then, the value of the longitudinal spring constant of the tire of Comparative Example 1 was indicated as 100 and indicated as an index. The index indicates that the smaller the value, the lower the longitudinal spring constant, and the better the riding comfort.
(Run flat durability)
The produced tire is assembled with a rim at an internal pressure of 250 kPa, left in a room temperature of 38 ° C. for 24 hours, then the valve core is removed, the internal pressure is 0 kPa, the load is 585 kg, the speed is 80 km / hr, and the drum runs at a room temperature of 38 ° C. Tested. The distance traveled until the failure occurred was indexed with the tire of Comparative Example 1 as 100. The larger the index, the better the run flat durability.

  According to Examples 1 to 6 and Comparative Example 1 in Table 1 and FIG. 4, it can be seen that in the pneumatic tire of the present invention, the longitudinal spring constant of the tire can be reduced.

  According to the pneumatic tire of the present invention, it is possible to improve riding comfort during normal internal pressure running without impairing run-flat durability.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Radial carcass 5 Belt 5a Edge 6 Inner liner 7 Side reinforcement rubber layer 8 Rubber 10 Pneumatic tire 11 Tread rubber 11A 1st tread rubber 11B 2nd tread rubber 11C 3rd tread rubber 12 tread groove 20 pneumatic tire 30 pneumatic tire 31 bead core 32 stiffener rubber 41 first radial carcass ply 41a folded end 42 second radial carcass ply 42a folded end 51 inclined belt layer 52 inclined belt layer 53 circumferential belt layer 54 reinforcing belt Layer E Tire equatorial plane S Ground contact edge A First region B Second region P1 First plane P2 Second plane

Claims (5)

A carcass composed of at least one ply extending in a toroidal shape from the tread portion to a pair of bead portions via a pair of sidewall portions, and a belt composed of at least one belt layer disposed on the outer peripheral side of the crown portion of the carcass. A pneumatic tire comprising at least a reinforcing rubber layer disposed on the inner peripheral side of the carcass at a portion corresponding to the sidewall portion,
A first plane that includes the edge of the belt and is orthogonal to the tire surface and a first plane that includes the contact edge and is orthogonal to the tire surface under a grounding condition in which the tire is mounted on an application rim and a predetermined air pressure and a predetermined load are applied. A pneumatic tire characterized in that foamed rubber is disposed in at least a part of a first region of a tread portion partitioned by two planes.   The pneumatic tire according to claim 1, wherein the foaming ratio of the foamed rubber is 0.2 or more.   The pneumatic tire according to claim 1, wherein the foamed rubber is disposed throughout the first region.   The pneumatic tire according to claim 1, wherein the foamed rubber is disposed in a part of the first region.   The pneumatic tire according to any one of claims 1 to 4, wherein the foamed rubber is disposed on the outer side in the tire width direction than the first plane.

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