JP2007276569A - Pneumatic safety tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic safety tire capable of maintaining at a high level the normal running performance (riding comfort etc.) when filled with the internal pressure, compared with a conventional safety tire having a reinforcing rubber layer, and equipped with a largely improved run-flat durability due to possibility of enhancing the tire crosswise spring when the internal pressure is 0 kPa. <P>SOLUTION: The pneumatic safety tire is equipped with a left and a right bead ring 14, a carcass layer 20 in which a plurality of cords are embedded parallel in a covering rubber, and a pair of side wall parts 18 arranged outside in the tire radial direction of the carcass layer 20, wherein rubber including short fibers is arranged in the reinforcing rubber layers 30 of the side wall parts 18, in which the short fibers are oriented in the tire circumferential direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic safety tire, and more particularly to a pneumatic safety tire in which a sidewall portion of a tire is reinforced and good run-flat running is possible.

Conventionally, run-flat tires have been developed in which when the tire punctures during traveling, the sidewall portion takes over the internal pressure and travels with full load.
This pneumatic tire can be run flat, that is, when the tire is running, it is punctured due to a foreign object such as a nail or a metal piece hitting the tire, and the internal pressure of the tire (hereinafter referred to as “internal pressure”). Tires that can continue to travel safely over a considerable distance and reach a desired location, for example, a service station where the tires can be changed (hereinafter referred to as “pneumatic safety tires”). ").

As such a pneumatic safety tire, for example, a core type in which an annular core made of metal or synthetic resin is attached to a rim portion in the air chamber of the tire, and from a bead ring of a sidewall portion to a shoulder area, A side reinforcement type in which a relatively hard rubber layer having a crescent cross section is disposed on the inner surface of the carcass layer is known.
Of these two types, the core type has a high load-bearing capacity when running on a run-flat, so it is suitable for use in luggage-carrying vehicles and military vehicles where ride comfort is not a problem. It is highly valued for passenger cars that place little burden and emphasize ride comfort.

Among these, the simplest and most effective measure is to place a reinforcing rubber layer with a crescent cross-section on the inner side of the carcass layer on the sidewall of the thinnest and most rigid part of a normal tire to support the wheel load. There are so-called side-reinforced run-flat tires.
This side-reinforced run-flat tire is intended to bear the load mainly by the tension of the reinforcing cord due to the internal pressure at the normal air pressure, and to support it with the member rigidity inherent to the side wall at the time of no puncture internal pressure. It is.

  As the rubber composition used for the reinforcing rubber layer having a crescent-shaped cross section of the side-reinforced run-flat tire, for example, a rubber composition containing a micro organic short fiber having specific physical properties (for example, see Patent Document 1), A fiber-reinforced rubber composition containing aramid fibers in the form of fibrillated discontinuous short fibers, wherein the aramid fibers are aligned in the longitudinal direction at an angle of 0 to 20 ° with respect to the radial direction of the tire (For example, see Patent Document 2), and further, those using rubber fiber composites composed of short fibers such as aromatic polyamide fibers and aliphatic polyamide fibers and a rubber composition (for example, see Patent Document 3) are known. It has been.

However, in the side-reinforced run-flat tire, the pneumatic safety tire using the short fiber-blended rubber composition described in each of the above documents needs to have a thick rubber reinforcing layer in order to improve the run-flat durability. For this reason, there are problems such as an increase in tire weight, an increase in tire vertical springs during internal pressure filling, and deterioration in riding comfort performance.
Furthermore, in recent years, with the reduction in fuel consumption of vehicles, there has been a strong demand for reducing the weight and rolling resistance of tires. To reduce the weight of tires, the thinning of tire sidewalls has been increasingly aimed at, and conventional reinforcing rubber layers There is a tendency to conflict with the use of. In addition, there is a contradictory requirement that run flat running when the internal pressure of the tire is reduced and performance in normal running when filling the internal pressure is naturally required.
JP-A-57-47205 (Claims, Examples, etc.) JP-A-7-32828 (Claims, Examples, etc.) JP-A-11-348512 (Claims, Examples, etc.)

  SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-described problems of the prior art and the current situation, and is a short fiber-containing rubber having specific physical properties in the reinforcing rubber layer of the sidewall portion that is the thinnest and has the lowest rigidity in the tire. Compared to a safety tire with a conventional reinforcing rubber layer, the weight of the reinforcing rubber layer is the same, and normal running performance (riding comfort etc.) when filling with internal pressure is maintained at a high level (the tire vertical length when filling with internal pressure) It is an object of the present invention to provide a pneumatic safety tire in which a lateral spring at an internal pressure of 0 kPa is improved and a run-flat running performance is greatly improved.

In order to solve the above-described conventional problems, the present inventors have intensively studied the relationship between the reinforcing rubber layer and the tire's run-flat running performance, and as a result, have found that the reinforcing rubber layer of the sidewall portion is oriented in a specific direction. It has been found that a pneumatic safety tire for the above purpose can be obtained by using a fiber-containing rubber, and the present invention has been completed.
That is, the present invention resides in the following (1) to (3).
(1) A pair of left and right bead rings, a carcass layer formed of a layer in which a plurality of cords are embedded in parallel in a covering rubber, and a pair of sidewall portions disposed on the outer side in the tire radial direction of the carcass layer A pneumatic safety tire comprising a short rubber compound rubber disposed in a reinforcing rubber layer of the sidewall portion, wherein the short fiber is oriented in the tire circumferential direction. Safety tire.
(2) The pneumatic safety tire according to (1), wherein the short fiber has an aspect ratio of L / d> 2.
(3) The pneumatic safety tire according to the above (1) or (2), wherein the short fiber has a tensile elastic modulus of 3 GPa or more.

  According to the present invention, compared with a safety tire having a conventional reinforcing rubber layer, normal running performance (riding comfort, etc.) at the time of internal pressure filling can be maintained at a high level, and the tire lateral spring at an internal pressure of 0 kPa can be improved. Therefore, a pneumatic safety tire is provided in which run-flat durability is greatly improved.

Hereinafter, embodiments of the present invention will be described in detail.
The pneumatic safety tire of the present invention includes a pair of left and right bead rings, a carcass layer including a plurality of cords embedded in parallel in a covering rubber, and a pair of carcass layers disposed on the outer side in the tire radial direction. A pneumatic safety tire comprising a sidewall portion, wherein a short fiber compound rubber is disposed in the reinforcing rubber layer of the sidewall portion, and the short fibers are oriented in the tire circumferential direction. For example, the pneumatic safety tire shown in FIG. 1 can be mentioned.
As shown in FIG. 1, a pneumatic safety tire 10 according to an embodiment of the present invention is a side in which a bead filler 16 and a bead ring 14 are embedded at a tip part from both ends of a cylindrical crown part 12 toward a radially inner side. The wall portion 18 is continuous, and is composed of one piece of radial ply reinforced with fiber cords from one of the sidewall portions 18 through the crown portion 12 to the other sidewall portion 18, and bead rings 14 at both ends thereof. A folded carcass layer 20 (carcass layer body 20a having a carcass layer folded portion 20b) fixed around the outer periphery in the axial direction, between the side wall 18 and the outside of the folded carcass layer 20 from the vicinity of the bead ring 14. And one more down carcass layer 22 and sidewall 18 in the vicinity of the other bead ring. A reinforcing rubber layer 30 having a crescent cross section, supporting the load on the inner peripheral surface of the folded carcass layer 20, an inner liner 28 inside the folded crucible reinforcing rubber layer, an inner liner 28, and a folded carcass. A plurality of belt layers 24 and a tread portion 26 are sequentially disposed on the outer periphery of the crown portion 12 of the layer 20 and are reinforced.

  In the pneumatic safety tire 10 of the present invention, the short-fiber blended rubber is disposed in the reinforcing rubber layer 30 having a crescent-shaped cross section of the sidewall portion 18, and the short fibers are oriented in the tire circumferential direction. It is installed. In the present invention, the orientation in the tire circumferential direction is the direction of the arrow shown in FIG.

  Examples of the rubber component of the short fiber-containing rubber used in the reinforcing rubber layer 30 of the present invention include natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), and the like. It is done. Of these, natural rubber and butadiene rubber are preferable from the viewpoint of effects.

The short fiber used in the present invention preferably has a tensile elastic modulus of 3 GPa or more from the viewpoint of providing rigidity in the tire circumferential direction when blended with rubber. In addition, in this invention (an Example etc. are included), the tensile elasticity modulus is based on JISL1017-2002, The load-elongation obtained by Shimadzu Corporation autograph in room temperature 25 +/- 2 degreeC and humidity 55% It was calculated from the slope of the tangent at the rise of the curve and the filament fineness.
If this tensile modulus is less than 3 GPa, the circumferential rigidity may not be selectively improved.

In addition, the short fibers used in the present invention preferably have an aspect ratio of L / d> 2 from the viewpoint that the short fibers are oriented in the tire circumferential direction. In the present invention (including examples), the aspect ratio means L / d when the fiber length is L and the fiber diameter is d.
When the short fiber has an aspect ratio of L / d ≦ 2, the short fiber may not be oriented in the tire circumferential direction.

  As the short fibers used in the present invention, those having the above-described tensile elastic modulus and aspect ratio are preferable. Specifically, aromatic polyamide (aramid) fibers having the above tensile elastic modulus and aspect ratio, aliphatic polyamide fibers, Examples include polyester fibers, polyimide fibers, polyvinyl alcohol fibers, polyolefin ketone (POK) fibers, polybenzoxazole (PBO) fibers, glass fibers, carbon fibers, steel fibers; and natural polymer fibers such as cotton, rayon, and cellulose. These short fibers may be used alone or in combination of two or more.

The length of these short fibers is preferably 0.5 to 10 mm, and more preferably 1 to 5 mm. If the length is less than 0.5 mm, the fibers are difficult to orient and difficult to develop circumferential rigidity. On the other hand, if the length exceeds 10 mm, the intended short fibers are tired due to entanglement between the fibers. The formation of the reinforcing rubber layer arranged in the circumferential direction tends to be difficult, which is not preferable.
Moreover, the cross-sectional shape of the short fiber may be a circular shape or a cross-sectional shape different from the circular shape.

The content of these short fibers is preferably 0.1 to 20 parts by mass, and more preferably 1 to 10 parts by mass with respect to 100 parts by mass of the rubber component of the short fiber compound rubber. When this content is less than 0.1 parts by mass, uniformity cannot be maintained, and rigidity as a reinforcing rubber layer is difficult to develop. On the other hand, when the content exceeds 20 parts by mass, the fiber ratio of the short fiber blended rubber is large. Thus, the durability of the reinforcing rubber layer tends to be lowered, and the durability as a tire tends to be lowered, which is not preferable.
In addition, if the short fiber is sufficiently bonded to the matrix rubber after vulcanization, the short fiber may not be subjected to an adhesion treatment in advance, but if the adhesion is insufficient, the short fiber may be subjected to an adhesion treatment. Good.

  The short fiber-blended rubber of the present invention can further contain various components usually used in the rubber industry as long as the object of the present invention is not impaired. For example, as various components, fillers (for example, inorganic fillers such as calcium carbonate and calcium carbonate); vulcanization accelerators; anti-aging agents; zinc oxide; stearic acid; softeners; An agent can be mentioned. As vulcanization accelerators, thiazole vulcanization accelerators such as MBTS (dibenzothiazyl disulfide) and CZ (N-cyclohexyl-2-benzothiazylsulfenamide); thiurams such as TT (tetramethylthiuram sulfide) And guanidine-based vulcanization accelerators such as DPG (diphenylguanidine).

In the present invention, the reinforcing rubber layer 30 serving as the crescent-shaped rubber layer in cross section has a function of suppressing compressive deformation inside the sidewall in order to suppress the deflection of the sidewall when the air of the pneumatic safety tire escapes (for example, The reinforcing rubber layer has a short fiber blended rubber partly or entirely disposed in the reinforcing rubber layer, and the short fibers in the short fiber blended rubber are arranged in the tire circumferential direction. is required.
By orienting the arrangement direction of the short fibers in the tire circumferential direction, rigidity in the tire circumferential direction is increased, so that the tire lateral spring at an internal pressure of 0 kPa can be improved. More preferably, the short fibers are aligned in the longitudinal direction at an angle of 0 to 40 ° with respect to the tire circumferential direction.
In addition, what has arranged the arrangement direction of a short fiber in the longitudinal direction at an angle of 0-20 degrees substantially in the radial direction cannot exhibit the effect of the present invention.
Moreover, although the arrangement | positioning position of the reinforcement rubber layer 30 is not specifically limited, It is preferable to arrange | position to the internal peripheral surface of a carcass layer.

  In the present invention, the short rubber compound rubber is disposed in part or all of the reinforcing rubber layer, but it is preferable that the reinforcing rubber layer is disposed in the entire rubber layer in terms of rigidity as the reinforcing rubber layer.

  As a method for orienting the short fibers in the short fiber compounded rubber in the tire circumferential direction, for example, when producing the short fiber compounded rubber to be used, the short fiber compounded rubber in which the short fibers are oriented in the extrusion direction is disposed. Can be done.

  Moreover, the pneumatic safety tire of the present invention may further include a second reinforcing rubber layer. For this second reinforcing rubber layer, only the rubber composition may be used, or the short fiber-containing rubber of the present invention may be used. When short fiber compound rubber is used for the second reinforcing rubber layer, the fiber may be a short fiber or a long fiber, and a woven fabric or a non-woven fabric may be used. The rubber components and fibers of the rubber composition used for the second reinforcing rubber layer can be the same as those described above. Further, the arrangement position of the second reinforcing rubber layer is not particularly limited, and may be disposed so as to reinforce part or all of the sidewall portion, and the positional relationship with the carcass layer is not limited.

  Furthermore, in the pneumatic safety tire of the present invention, it is preferable from the viewpoint of the durability of the tire that at least one of the down carcass layers is further disposed outside the folded carcass layer body of the carcass layer. Here, the folded carcass layer main body means a portion (carcass layer main body 20a in FIG. 1) passing from one bead portion through the crown portion to the other bead portion.

  The pneumatic safety tire of the present invention configured as described above includes a pair of left and right bead rings, a carcass layer composed of layers in which a plurality of cords are embedded in parallel in a covering rubber, and the outer side of the carcass layer in the tire radial direction. A pneumatic safety tire comprising a pair of sidewall portions disposed on the sidewall rubber portion, wherein a short fiber compound rubber is disposed on the reinforcing rubber layer of the sidewall portion, and the short fibers are in the tire circumferential direction. Since the rigidity in the tire circumferential direction increases, the tire lateral spring at an internal pressure of 0 kPa can be improved. If the tire lateral spring at an internal pressure of 0 kPa is high, input to the tire during run-flat running is possible. Can be suppressed, and the run-flat mileage can be extended. In addition, since the tire radial rigidity (tire vertical spring) does not increase during internal pressure filling, the riding comfort during normal running does not change, so normal running during internal pressure filling compared to conventional safety tires with a reinforced rubber layer Performance (riding comfort, etc.) can be maintained at a high level.

  EXAMPLES Next, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited to the following Example.

[Examples 1-6 and Comparative Examples 1-3]
A short fiber-blended rubber composition having the blend composition shown in Table 1 below was prepared.
The short fibers used in Examples 1 to 4 and Comparative Examples 2 and 3 were made of aramid having an aspect ratio of 200, a tensile elastic modulus of 59 GPa, a diameter of 10 μm, and a length of 2 mm.
The short fibers used in Examples 5 and 6 were made of PET, having an aspect ratio of 200, a tensile elastic modulus of 12 GPa, a diameter of 10 μm, and a length of 2 mm.

The pneumatic safety tire used has the same structure as that shown in FIG. 1 and has a tubeless structure with a size of 215 / 45ZR17. As the carcass layer (body ply), two layers (2P structure) obtained by driving a double-twisted rayon cord of 1840 dtex (dtex) at 50/5 cm were used. The shape, thickness, arrangement, composition, etc. of the reinforcing rubber layer are not particularly limited. Moreover, it consisted of the rubber composition containing the short fiber of the following Table 1, and produced so that the maximum thickness after a vulcanization might become the thickest part gauge of the following Table 1. The belt layer is a 1x5 structure, and a steel cord layer with a wire diameter of 0.25 mm is cut into two steel belt layers with a number of drivings of 40 / 5cm and a steel cord angle of 20 ° with respect to the tire circumferential direction. It has a structure.
About each of the obtained prototype tires, the tire longitudinal spring (index) at an internal pressure of 230 kPa, the tire lateral spring (index) at an internal pressure of 0 kPa, and run-flat durability (index) were evaluated by the weight and the following evaluation method.
These results are shown in Table 1 below. In addition, durability at the time of internal pressure filling of all the test tires was a level with no problem.

(Tire vertical spring evaluation method)
Each prototype tire is incorporated into a standard rim, the internal pressure is adjusted to 230 kPa, the tire is placed on a pseudo road surface, and a vertical displacement when a constant load of 4.17 kN in the vertical direction is applied to the tire is measured. It was expressed as an index when Comparative Example 1 was used as a control (100). A larger index indicates a larger vertical spring.

(Tire side spring evaluation method)
Each prototype tire is incorporated in the standard rim, the internal pressure is adjusted to 0 kPa, the tire is placed on the pseudo road surface, and the lateral displacement when a constant load of 4.17 kN in the vertical direction is applied to the tire is measured. It was expressed as an index when Comparative Example 1 was used as a control (100). A larger index indicates a larger lateral spring.

(Runflat durability evaluation method)
Each prototype tire is assembled with a rim at normal pressure, filled with 230 kPa of internal pressure, left in a chamber at 38 ° C. for 24 hours, then the valve core is removed, the internal pressure is atmospheric pressure, the load is 4.17 kN, and the speed is 89 km / hr. The drum running test was performed at room temperature of 38 ° C. The travel distance at which the failure occurred was defined as run-flat durability, and was expressed as an index when Comparative Example 1 was defined as control (100). The larger the index, the better the run flat durability.

  As is clear from the results of Table 1 above, the pneumatic safety tires of Examples 1 to 6, which are within the scope of the present invention, are compared with Comparative Examples 1 to 3, which are outside the scope of the present invention. The spring could be improved. Further, when the tire lateral spring at the internal pressure of 0 kPa is high, the input of the tire at the time of run-flat running can be suppressed, so that the run-flat running distance is extended. It has been found that the riding comfort during normal driving does not change because the rigidity in the tire radial direction (tire vertical spring) during internal pressure filling does not increase.

  The pneumatic safety tire of the present invention has high industrial utility value because the sidewall portion of the tire is reinforced and excellent run flat running can be achieved.

1 is a schematic cross-sectional view of a pneumatic safety tire showing an example of an embodiment of the present invention. It is the schematic which shows a tire peripheral direction.

Explanation of symbols

10 Pneumatic safety tire 14 Bead ring 18 Side wall part 20 Carcass layer 30 Reinforced rubber layer (short fiber compound rubber layer)

Claims (3)

  A pair of left and right bead rings, a carcass layer formed of a layer in which a plurality of cords are embedded in parallel in a covering rubber, and a pair of sidewall portions disposed on the outer side in the tire radial direction of the carcass layer A pneumatic safety tire, characterized in that a short fiber-containing rubber is disposed in the reinforcing rubber layer of the sidewall portion, and the short fibers are oriented in the tire circumferential direction.   The pneumatic safety tire according to claim 1, wherein the short fiber has an aspect ratio of L / d> 2.   The pneumatic safety tire according to claim 1 or 2, wherein the short fiber has a tensile elastic modulus of 3 GPa or more.

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