JP4658736B2 - Run flat tire - Google Patents

Description

  The present invention relates to a run-flat tire that can continuously travel a fixed distance at a relatively high speed even during puncture.

  2. Description of the Related Art Conventionally, a run-flat tire that can continuously travel a fixed distance at a relatively high speed even when punctured is known. As a typical run flat tire, as shown in Patent Document 1 below, a side reinforcing rubber layer having a substantially crescent-shaped cross section having a high load supporting capability is provided on a sidewall portion. Such a run-flat tire can support a load with a reinforced sidewall portion in a punctured state in which the air pressure in the tire lumen is substantially equal to the atmospheric pressure, and can continue to travel, for example, about 100 km. .

  However, even in the case of run-flat tires, when running in a puncture state (hereinafter, such running may be simply referred to as “run-flat running”), periodic bending strain generated in the sidewall portion is normal running. It becomes big compared to. Therefore, in the run-flat running, as the distance and / or speed increases, the side wall portion generates heat, and as a result, the internal rubber material may be peeled off or the cord material may be thermally destroyed, resulting in a running failure.

  In order to increase the run-flat travel distance, a run-flat tire in which a large side reinforcing rubber layer is arranged on a side wall portion is known. However, in such a run-flat tire, the fuel economy performance deteriorates due to the increase in the weight of the tire and the heat resistance of the sidewall portion deteriorates, and the effect corresponding to the reinforcement is not sufficiently obtained at present. .

JP 2005-126555 A

  The present invention has been devised in view of the above circumstances, and is based on the provision of a plurality of heat-dissipating grooves on the outer surface of the sidewall portion, while minimizing the increase in tire weight. The main object is to provide a run-flat tire that can increase the flat travel distance.

  The invention according to claim 1 is a toroidal carcass extending from the tread portion through the sidewall portion to the bead core of the bead portion, and a substantially crescent cross section disposed on the inner side in the tire axial direction of the carcass and in the sidewall region. A run-flat tire having a reinforced rubber layer in the form of a plurality of heat-dissipating grooves arranged at intervals in the tire circumferential direction on the outer surface of the sidewall portion. The groove-shaped portion is characterized by extending in and / or out of the tire radial direction including at least the tire maximum width position.

  Here, the tire maximum width position refers to the outer surface of the sidewall portion (characters, symbols or rims provided on the sidewall portion) in a normal state in which the tire is assembled on a regular rim, filled with a regular internal pressure, and unloaded. The surface is the same as the surface excluding the protector, etc., and the same shall apply hereinafter)).

  In addition, the “regular rim” is a rim determined for each tire in a standard system including a standard on which a tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, For ETRTO, use “Measuring Rim”. The “regular internal pressure” is the air pressure defined by each standard for each tire in the standard system including the standard on which the tire is based. The maximum air pressure is JATMA, and the table “TIRE LOAD” is TRA. The maximum value described in LIMITS AT VARIOUS COLD INFLATION PRESSURES is "INFLATION PRESSURE" if it is ETRTO, but it is uniformly 180 kPa if the tire is for passenger cars.

In the present invention, the thickness of the side reinforcing rubber layer is formed to be 1.5 to 4.0 times the thickness from the outer surface of the sidewall portion to the side reinforcing rubber layer at the maximum tire width position.

Furthermore, in the present invention, the groove depth from the outer surface of the sidewall portion of the heat radiating groove is 0.5 to 0 of the thickness from the outer surface of the sidewall portion to the side reinforcing rubber layer at the maximum tire width position. .8 times .

The invention of claim 2, the groove length in the tire radial direction of the radiating groove-shaped portion is a run-flat tire according to claim 1, wherein 20 to 50% of the tire section height.

The invention according to claim 3 is the run flat tire according to claim 1 or 2 , wherein the groove width of the heat radiating groove is 5 to 10 mm.

The invention according to claim 4 is the run flat tire according to any one of claims 1 to 3 , wherein 60 to 80 of the groove portions for heat dissipation are arranged on at least one side wall portion.

  In the run-flat tire of the present invention, a plurality of heat radiating groove-like portions are arranged on the outer surface of the sidewall portion at intervals in the tire circumferential direction. Further, the heat radiating groove-like portion extends in and / or out of the tire radial direction including the tire maximum width position where bending is largest and heat is easily generated. Therefore, during the run-flat running, the heat-dissipating groove-like portion can suppress the heat generation of the side wall portion, particularly the side reinforcing rubber layer, and thereby can suppress damage such as peeling of the internal structure for a long time. Accordingly, the run flat travel distance increases. Further, the heat-dissipating groove portion reduces the rubber weight of the sidewall portion, which in turn makes it possible to reduce the weight of the tire.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a right half cross-sectional view of a normal state of a run-flat tire (hereinafter sometimes simply referred to as “tire”) 1 of the present embodiment. 2 is a partially enlarged view of the sidewall portion 3 of FIG. 1, and FIG. 3 is a partial side view of the tire.

  The tire 1 includes a toroidal carcass 6 that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and a belt disposed outside the carcass 6 in the tire radial direction and inside the tread portion 2. A layer 7 and a side reinforcing rubber layer 9 having a substantially crescent-shaped cross section disposed on the side wall portion 3 are provided, and in this embodiment, one for a passenger car is shown.

  In the present embodiment, the carcass 6 is formed by spanning a single carcass ply 6 </ b> A between a pair of bead cores 5. The carcass ply 6A is formed by covering carcass cords arranged in parallel with a topping rubber. As the carcass cord, an organic fiber such as nylon, polyester, rayon, or aromatic polyamide is suitable. In this example, polyester is used. Further, the carcass cord is inclined at 75 to 90 degrees with respect to the tire equator C, for example.

  The carcass ply 6A includes a toroidal main body portion 6a that extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4, and both ends of the main body portion 6a and around the bead core 5 in the tire axial direction. And a folded portion 6b folded back from the inside to the outside. In this example, a high turn-up structure (HTU) in which the outer end 6be of the folded portion 6b is located on the outer side in the tire radial direction from the tire maximum width position M is shown. Such a high turn-up structure effectively reinforces the sidewall portion 3 with a small number of plies. However, the outer end 6be of the folded portion 6b may be positioned radially inward of the outer end of the flange of the rim J in order to reduce the weight of the tire. Furthermore, the carcass 6 can also be configured using a plurality of carcass plies 6A.

  Further, a bead apex 8 is disposed between the main body portion 6a and the folded portion 6b of the carcass ply 6A. The bead apex 8 is tapered from the outer surface of the bead core 5 to the outer side in the tire radial direction, and is made of, for example, hard rubber having a JISA hardness of 65 to 95 degrees, more preferably about 75 to 95 degrees. Thereby, the bending rigidity of the bead part 4 can be improved and the vertical bending of the tire 1 can be suppressed small.

  Further, the height ha of the bead apex 8 from the bead base line BL is not particularly limited, but if it is too small, the durability during run-flat running tends to decrease, and conversely, if it is too large, the tire weight is excessively increased. In addition, there is a risk of significant deterioration in ride comfort. From such a viewpoint, the height ha is desirably about 10 to 55%, more preferably about 30 to 45% of the tire cross-section height H.

  The belt layer 7 is composed of belt plies 7A and 7B on the inner and outer sides in the tire radial direction in which a belt cord made of steel is inclined with respect to the tire equator C at, for example, about 10 to 35 °. The belt plies 7A and 7B are overlapped so that the belt cords intersect each other. As the belt cord, in addition to the steel material, a highly elastic organic fiber material such as aramid, rayon or the like is employed as necessary.

  In the present embodiment, the band layer 11 is disposed outside the belt layer 7 in the tire radial direction. The band layer 11 is composed of at least one band ply in which organic fiber cords are arranged at a small angle so as to be, for example, 5 degrees or less with respect to the tire circumferential direction. In the present embodiment, it is composed of a full band ply 11A having a width equal to that of the belt layer 7 and a pair of edge band plies 11B covering only the shoulder portion. The band ply may be either a jointless band formed by winding a ribbon-shaped band ply in a spiral shape or a splice of a ply.

  Further, the tire 1 is provided with a side reinforcing rubber layer 9 for run-flat running on each of the side wall portions 3 on both sides (however, only one side is shown in FIG. 1). The side reinforcing rubber layer 9 is disposed on the inner side in the tire axial direction of the carcass 6 and in a sidewall region. The side reinforcing rubber layer 9 has a substantially crescent cross section as a whole by gradually decreasing the thickness from the central thick part 9a having the maximum thickness toward the inner end 9i and the outer end 9o in the tire radial direction. What is formed in the shape is shown. Such a side reinforcing rubber layer 9 supports the load of the tire during run-flat running, suppresses the vertical deflection of the tire 1, and thus enables continuous running.

The thickness of the side reinforcing rubber layer 9 is less likely sufficient reinforcing effect is not obtained when too small, there is a risk that too large conversely increase the weight of the tire. From such a viewpoint, at least at the tire maximum width position M, the thickness T of the side reinforcing rubber layer 9 is preferably 1.5 times or more the thickness ts from the outer surface of the sidewall portion to the side reinforcing rubber layer 9. The upper limit is preferably 2.0 times or more, and the upper limit is preferably 4.0 times or less, more preferably 3.5 times or less.

  The inner end 9 i of the side reinforcing rubber layer 9 is preferably located on the inner side in the tire radial direction than the outer end 8 t of the bead apex 8 and on the outer side in the tire radial direction than the bead core 5. Further, it is desirable that the outer end 9o of the side reinforcing rubber layer 9 terminates extending inward in the tire radial direction of the belt layer 7, that is, inwardly in the tire axial direction from the outer end 7e of the belt layer 7. Such a side reinforcing rubber layer 9 can increase the longitudinal rigidity of the tire in a wide region of the sidewall portion 3. Moreover, since each end part 9o and 9i is arrange | positioned in the area | region where distortion is small at the time of driving | running | working, generation | occurrence | production of the damage which originates in each said end part 9o and 9i can be suppressed.

  Further, if the JIS durometer A hardness is too small, the side reinforcing rubber layer 9 has a small reinforcing effect on the side wall portion 3 and cannot obtain a sufficient run-flat travel distance. There is a tendency to adversely affect riding comfort during normal driving. From such a viewpoint, the rubber composition constituting the side reinforcing rubber layer 9 has a JIS durometer A hardness of preferably 65 ° or more, more preferably 70 ° or more, and further preferably 75 ° or more, and About an upper limit, Preferably it is 99 degrees or less, More preferably, 95 degrees or less is desirable.

  Further, in order to define dynamic rubber hardness, the complex elastic modulus of the rubber composition of the side reinforcing rubber layer 9 is preferably 14 MPa or more, more preferably 18 MPa or more, and the upper limit is preferably 35 MPa or less. More preferably, 30 MPa or less is desirable. Further, in order to increase the run-flat travel distance, it is desirable that the side reinforcing rubber layer 9 itself is made of low heat-generating rubber. From such a viewpoint, the rubber composition preferably has a loss tangent tan δ of 0.05 to 0.07. The loss tangent and the complex elastic modulus were measured at a measurement temperature of 70 ° C., a frequency of 10 Hz, an initial elongation strain of 10% and a half amplitude of 1% using a viscoelastic spectrometer “VES F-3” manufactured by Iwamoto Seisakusho. The measured value.

  The rubber polymer used for the side reinforcing rubber layer 9 is not particularly limited. For example, diene rubber, more specifically, natural rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber, chloroprene rubber, or acrylonitrile butadiene rubber is desirable. . These are used alone or in combination of two or more.

  Further, an inner liner rubber 12 made of rubber that does not easily allow air to pass through is disposed on the tire lumen surface. Thus, in the non-punctured state, the air pressure in the tire lumen surrounded by the tire lumen surface and the rim J is maintained by the inner liner rubber 12.

  2 and 3, the tire 1 of the present embodiment includes a plurality of heat radiating groove portions 10 arranged on the outer surface of the sidewall portion 3 at intervals in the tire circumferential direction. Is provided. In this embodiment, the heat radiating groove 10 extends substantially along the radial direction.

  The heat radiating groove 10 includes at least the tire maximum width position M and extends in and / or out of the tire radial direction therefrom. The heat radiating groove 10 of the present embodiment extends from the tire maximum width position M to both the inside and outside of the tire in the radial direction of the tire. Such a heat radiating groove portion 10 has a width and a groove depth, and therefore increases the surface area of the sidewall portion 3. Moreover, the groove part 10 for heat radiation can reduce the rubber thickness of the side wall part 3 compared with the part in which it is not provided. Such a heat radiating groove 10 can efficiently dissipate the heat stored in the side reinforcing rubber layer 9 to the outside during run-flat running. Therefore, damage such as rubber peeling caused by heat generation of the side reinforcing rubber layer 9 that tends to occur due to continuous run-flat running can be suppressed over a long period of time, and the run-flat running distance can be increased. It is also conceivable to provide a groove extending in the circumferential direction in the sidewall portion. However, such grooves tend to increase the amount of vertical deflection of the tire side portion and reduce the run-flat performance. On the other hand, the groove-like portion 10 extending in the tire radial direction can exhibit a heat dissipation effect without increasing the amount of vertical deflection of the tire.

Wherein the groove depth GD and groove width GW of the radiating groove-shaped portion 9, these tends to heat dissipation effect is not sufficiently obtained too small, withstand of the sidewall portion 3 is too large in the opposite The trauma deteriorates and the durability tends to decrease.

  From this point of view, the groove depth GD from the outer surface of the sidewall portion of the heat radiating groove portion 10 is preferably a thickness ts from the outer surface of the sidewall portion to the side reinforcing rubber layer 9 at the tire maximum width position M. The upper limit is preferably 0.5 times or more, more preferably 0.55 times or more, and the upper limit is preferably 0.8 times or less, more preferably 0.75 times or less.

  The groove depth GD of the heat radiating groove 10 may be constant or variable, but preferably, as shown in FIG. 2, the inner end 10i of the heat radiating groove 10 in the tire radial direction. As for the outer end 10o, it is desirable that the groove depth GD be gradually reduced toward the end. Thereby, during run flat running, stress concentration due to bending can be relaxed at both end portions 10i, 10o of the heat radiating groove-like portion, and the occurrence of rubber chipping and cracking can be effectively prevented. Particularly preferably, as shown in the cross section of FIG. 2, the bottom surface of the groove connected to both end portions 10i and 10o of the heat radiating groove portion 10 is preferably an arc shape having a radius of curvature r centered on the outer side of the tire and smoothly recessed. .

  Further, the groove width GW of the heat radiating groove 10 is preferably 5 mm or more, more preferably 6.5 mm or more, and the upper limit is preferably 10 mm or less, more preferably 8.5 mm or less. The groove width GW of the heat radiating groove 10 is measured in a direction perpendicular to the longitudinal direction of the groove. Further, the groove width GW may be constant in one heat radiating groove 10 or may be changed.

  Further, the groove length hb in the tire radial direction of the heat radiating groove 10 is not particularly limited, but if it is too small, the above-described heat radiation effect tends not to be obtained sufficiently, and conversely if it is too large. Further, the damage resistance of the sidewall portion 3 is deteriorated and the durability is likely to be lowered. From such a viewpoint, the groove length hb in the tire radial direction of the heat radiating groove 10 is preferably 20% or more, more preferably 30% or more of the tire cross-section height H, and the upper limit is preferably Is preferably 50% or less, more preferably 40% or less.

  It is desirable that 60 to 80 of the heat radiating groove portions 10 are provided in at least one, preferably both of the sidewall portions 3. If the number is less than 60, a sufficient heat dissipation effect may not be obtained. Conversely, if the number exceeds 80, the disposition pitch in the tire circumferential direction of the heat radiating groove 10 is reduced, and the side wall 3 is not damaged. It becomes easy to fall.

  In addition, it is desirable that the disposing pitch of the heat radiating groove 10 in the tire circumferential direction is constant, but a so-called variable pitch in which this is changed can also be adopted. In this case, it is useful for making white noise from the wind noise of the heat radiating groove 10 during traveling.

  FIG. 4 shows another embodiment of the present invention. In this embodiment, the heat radiating groove 10 is inclined with respect to the radial direction. In the aspect of FIG. 3, when a driving force or a braking force is applied to the tire, the heat radiating groove 10 is greatly sheared and deformed by the shearing force acting on the sidewall portion 3 in the vicinity of the grounding portion. Rubber chipping due to the portion 10 is likely to occur. On the other hand, as shown in FIG. 4, when the heat radiating groove 10 is inclined by θ with respect to the radial direction D, for example, in the tire rotation direction R, the heat radiating groove 10 is mainly used during braking. The tensile deformation extending in the longitudinal direction is received, and the chance of occurrence of damage is reduced as compared with the shear deformation. The angle θ is not particularly limited, but preferably about 5 to 45 °.

  FIG. 5 shows still another embodiment of the present invention. In this embodiment, the heat radiating groove 10 includes an outer heat radiating groove 10A extending from the vicinity of the tire maximum width position M to the tire radial direction outer side, and an inner portion extending from the tire maximum width position M to the tire radial direction inner side. These heat-radiating groove portions 10B are alternately arranged in the tire circumferential direction. In such an embodiment, heat is dissipated from a wider range of the side reinforcing rubber layer 9 and the heat radiating groove portions 10 are dispersed and arranged in the tire radial direction, thereby reducing the strength of the sidewall portions 3. Can be minimized.

  FIG. 6 shows still another embodiment of the present invention. In this embodiment, the groove portion 10 for heat dissipation includes a plurality of types (three types of large, medium and small in this example) having different lengths in the tire radial direction. Further, the center of the length of each heat radiating groove 10 is provided at the tire maximum width position M, and is arranged such that the length changes periodically.

  As described above, the run-flat tire 1 of the present embodiment can increase the run-flat travel distance while reducing the weight of the tire. In the above embodiment, a passenger car tire has been described as an example, but the present invention is not limited to such an embodiment, and it goes without saying that the present invention can also be applied to tires of other categories. In addition to the linearly extending groove-like portion 10, various shapes such as a zigzag or curved one may be adopted.

A run flat tire of 235 / 55R18 was made on the basis of the specifications shown in Table 1. These run-flat mileage and tire weight were tested. Each tire was provided with a carcass using a belt layer made of two belt plies made of steel cord, a band layer of one ply made of aramid cord, and a polyester cord. Moreover, the side reinforcement rubber layer unified the cross-sectional shape, the arrangement | positioning area | region of a tire radial direction, and rubber hardness (JIS durometer A hardness: 86 degree | times).
The test method is as follows.

<Tire weight>
The weight per tire was measured and displayed as an index with the value of Conventional Example 1 being 100. The smaller the value, the lighter the weight.

<Runflat mileage>
Each test tire was assembled on a rim (18 × 7-JJ) from which the valve core was removed, and an assembly was prepared in which the internal pressure was atmospheric pressure. Each assembly was run on a drum tester having a diameter of 1.7 m, the running distance until the tire broke down was measured, and the conventional example 1 was displayed as an index of 100. The larger the value, the better. The traveling conditions were a speed of 80 km / h and a longitudinal load of 4.31 kN.
Table 1 shows the test results.

It is sectional drawing of the run flat tire which shows embodiment of this invention. FIG. It is a partial side view of a tire. It is a partial side view of the tire which shows other embodiment. It is a partial side view of the tire which shows other embodiment. It is a partial side view of the tire which shows other embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Run flat tire 2 Tread part 3 Side wall part 4 Bead part 5 Bead core 6 Carcass 7 Belt layer 8 Bead apex rubber 9 Side reinforcement rubber layer 10 Radiation groove part M Tire maximum width position

Claims (4)

Toroidal carcass from the tread part through the sidewall part to the bead core of the bead part,
A run-flat tire having a reinforcing rubber layer having a substantially crescent-shaped cross section disposed in the tire axial direction inner side wall region of the carcass,
The outer surface of the sidewall portion is provided with a plurality of heat radiating groove portions arranged at intervals in the tire circumferential direction, and the heat radiating groove portions include at least a tire maximum width position. Extend radially in and / or out ,
The thickness of the side reinforcing rubber layer is 1.5 to 4.0 times the thickness from the sidewall outer surface to the side reinforcing rubber layer at the tire maximum width position,
Moreover, the groove depth from the outer surface of the sidewall portion of the heat radiating groove is 0.5 to 0.8 times the thickness from the outer surface of the sidewall portion to the side reinforcing rubber layer at the maximum tire width position. A run-flat tire characterized by that. The run-flat tire according to claim 1, wherein a groove length in a tire radial direction of the heat radiating groove portion is 20 to 50% of a tire cross-sectional height . The run flat tire according to claim 1 or 2 , wherein the groove width of the heat radiating groove is 5 to 10 mm . The run-flat tire according to any one of claims 1 to 3 , wherein 60 to 80 of the heat dissipating groove portions are arranged on at least one of the sidewall portions .

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