JP2012148623A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire sufficiently improved in the durability of a bead part by reducing distortion generated between a hard bead filler and a carcass body portion.SOLUTION: The pneumatic tire has a bead filler 15 composed of two kinds of hard and soft rubbers, a radial directional outer end 15c of the hard bead filler 15a of high hardness extended from a bead core 3 is disposed in the inner side in a tire radial direction from a carcass folding end 11c, a radial directional outer end 15d of the soft bead filler 15b of low hardness is disposed in the outer side in the tire radial direction from the carcass folding end 11c, and a rubber layer 17 having the same physical properties as the ply rubber is disposed between a carcass body part 11a and the hard bead filler 15a and between the radial directional outer end 15c and the radial directional inner end of the hard bead filler.

Description

  The present invention relates to a pneumatic tire used for improving durability of a bead part in a pneumatic tire used under high internal pressure and high load, such as a tire for a subway or a monorail.

  When a pneumatic tire rolls with a load, it receives the reaction force of the load from the road surface, and the side wall portion on the grounding side is bent and deformed, and the deformation is also transmitted to the bead portion and falls toward the outside in the tire width direction. This causes a so-called falling phenomenon. Due to this phenomenon, a large reaction force is applied to the bead portion from the rim, causing a failure of the bead portion.

  That is, stress is concentrated on the outer end in the tire radial direction of the carcass folded portion existing inside the bead portion due to a difference in rigidity with the adjacent rubber member, and distortion occurs. When the tire rolls, strain repeatedly works and rubber fatigue progresses, so that there is a problem that cracks are generated starting from the outer end in the tire radial direction of the carcass folded portion and progresses to a separation failure.

  In view of the problem of the failure of the bead part as described above, various measures have been taken so far, for example, for the purpose of increasing the rigidity of the entire bead part and suppressing deformation / distortion in the bead part, the bead core is enlarged. In addition, the height of the bead filler and the carcass folding portion is increased in the tire radial direction, and a reinforcing member such as a wire chafer is disposed along the carcass.

  Further, for example, as described in Patent Document 1, as a method of relaxing the strain acting on the bead portion and preventing separation, a bead filler disposed between the carcass main body portion and the carcass folded portion is hardened in contact with the bead core. The bead filler and a soft bead filler disposed on the outer side in the tire radial direction of the hard bead filler are also used.

JP-A-10-76820

  However, particularly in subway and monorail tires used under the action of high internal pressure and high load, as described in Patent Document 1, even if the bead filler is composed of two types of hard and soft rubbers, Since the force is large, shear strain acts between the hard bead filler and the carcass main body part, and if it continues to run, peeling may occur between the hard bead filler and the carcass main body part, which may eventually progress to separation. Therefore, further improvement in bead durability is desired.

  Therefore, the present invention relates to a tire in which the bead filler is composed of two kinds of rubbers having different hardnesses, and the distortion generated between the hard bead filler and the carcass is reduced and the durability of the bead portion is sufficiently improved. An object is to provide a tire entering.

  The present invention has been made to solve the above problems, and the pneumatic tire according to the present invention extends between each bead core embedded in a pair of bead portions, and the bead portion, the sidewall portion, and the tread portion. A carcass main body portion that reinforces each part of the carcass, a carcass folding portion that extends from the carcass main body portion around the bead core from the tire inner side to the outer side and extends in the tire radial direction, along the carcass main body portion, A hard bead filler extending outward in the tire radial direction from the bead core between the carcass folded portion and a soft bead filler extending further outward in the tire radial direction from the hard bead filler and having a lower hardness than the hard bead filler. A pneumatic tire comprising a bead filler; A rubber layer is provided between the carcass body portion and the bead filler, and an outer end in the tire radial direction of the hard bead filler is radially inward with respect to an outer end in the tire radial direction of the carcass folded portion. And the outer end in the tire radial direction of the soft bead filler is arranged on the outer side in the tire radial direction with respect to the outer end in the tire radial direction of the carcass folded portion, and the rubber layer An outer end in the tire radial direction is disposed on the inner side in the tire radial direction with respect to the outer end of the hard bead filler, and an inner end in the tire radial direction of the rubber layer is positioned on an inner side in the tire radial direction of the hard bead filler. It arrange | positions at the radial direction outer side. Here, “the outer end in the tire radial direction of the hard bead filler is disposed on the inner side in the tire radial direction and the inner side in the tire width direction with respect to the outer end in the tire radial direction of the carcass folded portion”, “ The outer end in the tire radial direction of the bead filler is disposed on the outer side in the tire radial direction with respect to the outer end in the tire radial direction of the carcass folded portion ”,“ the tire radial outer end of the rubber layer is disposed on the hard bead. "Pneumatic tire" means that the inner side in the tire radial direction of the rubber layer is arranged on the inner side in the tire radial direction of the outer end of the filler, and the outer side of the inner side in the tire radial direction of the hard bead filler. Means a configuration in a state in which a normal rim is assembled, normal internal pressure is filled, and no load is applied. The regular rim means “standard rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The normal internal pressure means “maximum air pressure” defined by JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined by TRA, or “INFLATION PRESSURES” defined by ETRTO. Further, “the outer end in the tire radial direction of the carcass folded portion” means the outer end in the tire radial direction of the carcass folded portion in the carcass ply closest to the bead core when the carcass is composed of a plurality of carcass plies. It shall be pointed out (hereinafter also referred to as carcass folded end).

  In such a pneumatic tire, the pneumatic tire is assembled to the rim, filled with internal pressure, and when a load is applied, the sidewall portion is bent and deformed, and when the load is large, the bead portion collapses and deforms. The force applied to the bead portion is dispersed by the two types of hard and soft bead fillers, and the distortion at the carcass folded end is reduced. At this time, the outer end of the hard bead filler in the tire radial direction (hereinafter also referred to as the outer end of the hard bead filler) is set on the inner side in the tire radial direction from the carcass folded end, and is closer to the flange portion of the rim. Since the shear strain of the bead filler is reduced, a rubber layer is provided between the bead filler and the carcass main body portion, and the rubber layer is disposed between the outer end and the inner end of the hard bead filler, the rim The shear strain generated between the hard bead filler and the carcass main body portion due to the reaction force from is absorbed and alleviated by the rubber layer. Further, since the outer end of the soft bead filler in the tire radial direction (hereinafter also referred to as the outer end of the soft bead filler) is arranged on the outer side in the tire radial direction with respect to the carcass folded end, it is added to the bead portion when a load is applied. The force can be surely shared by the bead filler, the concentration of strain at the folded end of the carcass can be more reliably prevented, and the durability of the bead portion can be more reliably improved.

  Therefore, according to the present invention, the shear strain at the folded end of the carcass can be reduced, and the local shear strain generated between the hard bead filler and the carcass main body portion can be reduced. Thus, the durability of the bead portion can be improved.

  In the pneumatic tire according to the present invention, the thickness of the rubber layer is preferably 0.4 mm or more and 0.8 mm or less. According to this, the rubber layer is generated between the hard bead filler and the carcass main body part. The shear strain can be absorbed and relaxed with certainty.

  In the pneumatic tire of the present invention, the physical properties of the rubber constituting the rubber layer are preferably the same as the ply rubber covering the carcass ply cord. It is possible to contribute to distortion reduction without hindering.

  Furthermore, in the pneumatic tire according to the present invention, the pneumatic tire is mounted on a predetermined rim, and a state in which a normal internal pressure is applied and no load is applied is defined as a predetermined state. The center of curvature of the curved portion formed by the flange portion is defined as a point P, a straight line passing through the point P and virtually drawn parallel to the tire rotation axis is defined as a straight line A, and the straight line A from the point P toward the bead portion. When a straight line that is virtually drawn at an angle of 45 ° to the straight line B is a straight line B, the rubber layer is preferably arranged so as to intersect the straight line B under the predetermined state. The shear strain generated between the hard bead filler and the carcass main body portion can be reliably absorbed and alleviated.

  According to the present invention, for a tire in which the bead filler is composed of two kinds of rubbers having different hardnesses, distortion generated between the hard bead filler and the carcass is reduced, and the durability of the bead part is sufficiently improved. It is possible to provide a pneumatic tire.

It is sectional drawing which shows the tire width direction cross section of the pneumatic tire of embodiment according to this invention. It is sectional drawing which expands and shows the bead part of the pneumatic tire of FIG. It is sectional drawing which expands and shows the bead part of the pneumatic tire of a prior art example. 3 is an enlarged cross-sectional view showing a bead portion of the pneumatic tire of Comparative Example 1. FIG. It is sectional drawing which expands and shows the bead part of the pneumatic tire of other embodiment according to this invention.

  Embodiments according to the present invention will be described below in detail with reference to the drawings. In the figure, symbol R indicates a rim that can be used as the above-described regular rim for assembling a pneumatic tire, symbol RF indicates a flange portion of the rim, and the flange portion of the rim has a predetermined curvature. It has a curved part. FIG. 1 shows a state where the pneumatic tire is assembled to the regular rim R, filled with the regular internal pressure, and no load is applied (hereinafter referred to as “predetermined state”).

  As shown in FIG. 1, a pneumatic tire (hereinafter referred to as “tire”) 1 according to this embodiment is connected to a pair of bead portions 5 in which bead cores 3 are embedded, and to the outside in the tire radial direction of the bead portions 5. It consists of a pair of sidewall portions 7 and a tread portion 9 straddling between the pair of sidewall portions 7. In the tire 1, the bead portion 5, the sidewall portion 7, and the tread portion 9 extend in a toroidal manner, and the bead portion 5, the sidewall portion 7, and the tread portion 9 are reinforced, and the end portion is connected to the bead core 3. A moored carcass 11 made of at least one (here, one) carcass ply and a belt 13 made of at least one belt layer disposed on the outer peripheral side of the carcass 11 of the tread portion 9 are provided. ing. The carcass 11 includes a carcass main body portion 11 a extending to the bead portion 5, the sidewall portion 7, and the tread portion 9, and a carcass folded portion that is wound up from the inner side in the tire width direction around the bead core 3 and ends in the bead portion 5. 11b. Here, the carcass 11 is composed of a single carcass ply formed by covering a ply cord with a ply rubber, but a plurality of carcass plies may be overlapped. The ply cord constituting the carcass ply is preferably made of a steel cord here.

  Furthermore, the tire 1 of this embodiment includes a bead filler 15 that is disposed between the carcass main body portion 11a and the carcass folded portion 11b and reinforces the bead portion 5, and the bead filler 15 is, as shown in FIG. From the vicinity of the upper surface (tire radial direction outer side surface) of the bead core 3 to the tire radial direction outer side, the hard bead filler 15a extending tapered along the carcass main body portion 11a and the side surface of the hard bead filler 15a on the outer side in the tire width direction from the carcass It consists of a soft bead filler 15b extending outward in the tire radial direction along the folded portion 11b. The rubber hardness of the hard bead filler 15a is higher than the rubber hardness of the soft bead filler 15b. The rubber constituting the hard bead filler 15a is preferably within a range of ± 15% of 5.5 MPa of 50% modulus, and the rubber constituting the soft bead filler 15b is ± 20 of 100% modulus of 2.0 MPa. % Should be within the range.

  The tire 1 also includes a rubber layer 17 provided between the carcass main body portion 11a and the bead filler. The rubber layer 17 has a lower hardness than that of the hard bead filler 15a, and the rubber physical properties of the rubber layer 17 are within a range of ± 20% where the 300% modulus at normal temperature (25 degrees) is 19.0 MPa. Good. The rubber layer 17 preferably has the same rubber hardness as the ply rubber of the carcass 11 or has the same physical properties as the ply rubber of the carcass 11. Here, in the above-mentioned predetermined state, the center of curvature of the curved portion formed by the flange portion of the rim is defined as a point P, and a straight line passing through the point P and virtually drawn parallel to the tire rotation axis is defined as a straight line A. When a straight line that is virtually drawn at an angle of 45 ° with respect to the straight line A from the point P toward the bead portion is defined as a straight line B, the rubber layer 17 intersects the straight line B under the predetermined state. Has been placed. More specifically, it is 20 degrees with respect to the straight line A (in FIG. 2, the angle between the straight line D and the straight line A virtually connecting the point P and the tire radial direction inner end 17b of the rubber layer is 40 degrees). It is preferably arranged within a range of ˜80 degrees (in FIG. 2, the angle formed by the straight line C and the straight line A virtually connecting the point P and the tire radial direction outer end 17a of the rubber layer is 70 degrees). Further, it is preferable to arrange the rubber layer 17 so that the center position thereof substantially coincides with the straight line B.

  In FIG. 2, reference numeral 19 denotes a wire chafer disposed along the carcass 11 between the carcass 11 and the tire surface, and a reinforcing layer made of organic fibers may be provided instead of the wire chafer. Or you may provide the reinforcement layer which consists of organic fibers in the outer side of a wire chafer.

  When a load is applied from the state in which the tire 1 thus configured is assembled to the rim R and the internal pressure is filled (the state shown in FIG. 1), the sidewall portion 7 is bent and deformed, and the bead portion 5 when the load is large. However, the force applied to the bead portion 5 is dispersed by the bead filler 15 made of two types of hard and soft rubber, and the distortion of the carcass folded end 11c is reduced. At this time, since the outer end 15c of the hard bead filler 15a is set on the inner side in the tire radial direction from the carcass folding end 11c, the shear strain of the hard bead filler 15a is reduced, and the hard bead filler 15a and the carcass main body portion 11a are reduced. Since the rubber layer 17 is provided between the outer end 15c and the inner end of the hard bead filler 15a in the tire radial direction, the hard bead filler is caused by the reaction force from the rim R. The shear strain generated between 15 a and the carcass main body portion 11 a is absorbed and relaxed by the rubber layer 17. Furthermore, since the outer end 15d in the tire radial direction of the soft bead filler 15b is arranged on the outer side in the tire radial direction with respect to the carcass folded end 11c, the force applied to the bead portion 5 is reliably shared by the bead filler 15 when a load is applied. In combination with the fact that the bead filler 15 is made of two types of hard and soft rubber, it is possible to more reliably prevent strain from concentrating on the folded end 11c of the carcass, and the durability of the bead portion 5 can be improved. It can improve more reliably.

  In this embodiment, it is preferable that the thickness of the rubber layer 17 is 0.4 mm or more and 0.8 mm or less. According to this, the shear strain generated between the hard bead filler 15a and the carcass main body portion 11a is reliably ensured. Can be absorbed and relaxed. In addition, it is difficult to manufacture the rubber layer 17 with a thickness of less than 0.4 mm. In addition, the rubber layer 17 is too thin to sufficiently absorb and relax the shear strain. If the thickness exceeds 0.8 mm, rubber creep occurs due to running, and the strain increases from the initial design.

  Further, in this embodiment, the physical properties of the rubber of the rubber layer 17 are preferably within the range of ± 20% where the 300% modulus is 19.0 MPa, and particularly the physical properties of the ply rubber covering the ply cord. preferable. According to this, as described above, it is possible to prevent the occurrence of a rigid step between the hard bead filler and the hindering of the adhesion with the steel cord.

  Further, in the tire 1 having the above structure, the reaction force from the rim R is concentrated and loaded near 45 degrees with respect to the straight line A as seen from the point P. Since it arrange | positions so that it may cross | intersect the straight line B under a state, the shear strain which arises between the hard bead filler 15a and the carcass main-body part 11a can be absorbed and relieved reliably.

  As mentioned above, although demonstrated based on the example of illustration, this invention is not limited to the above-mentioned example, It can change suitably in the description range of a claim. For example, the tip shape of the hard bead filler 15a is not tapered and may be rounded as shown in FIG.

  Next, a tire according to the present invention was prototyped and performance evaluation was performed, which will be described below. The tires of the conventional example, the comparative example, and the example all have a tire size of TBR E13.50 / 85R16, and the rim used is 16 × 9.50V.

  Further, the position of the carcass folding end of the conventional example, the comparative example, and the example is at a position of 25% of the maximum tire height when measured from the innermost end in the tire radial direction of the tire.

  The rubber layers used in the examples and comparative examples are disposed on the bead portions on the left and right sides of the tire, respectively, and extend over the entire circumference of the tire between the carcass and the hard bead filler. The physical properties are as follows: 300% modulus at normal temperature (25 degrees) is 19.0 MPa, and thickness is as shown in Table 1. Although the tire of Comparative Example 2 is not shown, the structure is the same as that of Examples 1 and 2, but the rubber layer is different from that of Examples 1 and 2 in that the rubber layer is thicker.

Each of the above test tires is assembled to a rim, a load of 6000 kgf and an internal pressure of 10 kg / cm ² is applied to a tire for a new transportation (subway, monorail), and a bead is used using an indoor rotating drum under a speed of 60 km / h. The distance traveled until the failure occurred was examined and evaluated. Here, the failure of the target bead portion is a separation failure at the end portion of the carcass ply. The evaluation results are shown in Table 1. In the durability test results in Table 1, the tire travel distance of Comparative Example 1 is set to 100, and other tires are indicated by indices. The larger the value, the better the durability of the tire.

  In Table 1, “the radial outer end position of the hard bead filler relative to the carcass folded end” indicates the positional relationship between the carcass folded end and the outer end of the hard bead filler, and “outer” is more than the carcass folded end. It indicates that the outer end of the hard bead filler is on the outer side in the tire radial direction, and “inner” indicates that the outer end of the hard bead filler is on the inner side in the tire radial direction with respect to the carcass folded end.

  From the test results shown in Table 1, both the tires of Examples 1 and 2 in which the radially outer end of the hard bead filler is set lower than the carcass folded end and the rubber layer is disposed at a predetermined position are used. It can be seen that is improved.

  Thus, according to the present invention, it is possible to provide a pneumatic tire that prevents separation failure in the bead portion and has sufficient durability.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 3 Bead core 5 Bead part 7 Side wall part 9 Tread part 11 Carcass 11a Carcass main-body part 11b Carcass return part 11c Carcass return end 13 Belt 15 Bead filler 15a Hard bead filler 15b Soft bead filler 17 Rubber layer 19 Wire chafer R rim RF rim flange

Claims (4)

A carcass body portion extending between the bead cores embedded in the pair of bead portions and reinforcing each of the bead portion, the sidewall portion, and the tread portion, and from the carcass body portion to the outside from the inside of the tire around the bead core A carcass having a carcass folded portion that is wound around and extending in the tire radial direction,
A hard bead filler extending from the bead core to the outer side in the tire radial direction along the carcass main body portion and between the carcass folded-back portion and lower than the hard bead filler extending from the hard bead filler to the outer side in the tire radial direction. In a pneumatic tire comprising a bead filler made of a soft bead filler having hardness,
A rubber layer is provided between the carcass main body portion and the bead filler,
The outer end in the tire radial direction of the hard bead filler is disposed on the inner side in the tire radial direction and on the inner side in the tire width direction with respect to the outer end in the tire radial direction of the carcass folded portion,
The outer end in the tire radial direction of the soft bead filler is disposed on the outer side in the tire radial direction with respect to the outer end in the tire radial direction of the carcass folded portion,
An outer end in the tire radial direction of the rubber layer is disposed on an inner side in the tire radial direction from the outer end of the hard bead filler, and an inner end in the tire radial direction of the rubber layer is an inner end in the tire radial direction of the hard bead filler. A pneumatic tire characterized by being arranged on the outer side in the tire radial direction.   The pneumatic tire according to claim 1, wherein the rubber layer has a thickness of 0.4 mm or more and 0.8 mm or less.   The pneumatic tire according to claim 1 or 2, wherein the rubber constituting the rubber layer has the same physical properties as the rubber covering the ply cord of the carcass. A state in which the pneumatic tire is mounted on a predetermined rim and a normal internal pressure is applied and a load is not applied is defined as a predetermined state, and in this predetermined state, the center of curvature of the curved portion formed by the flange portion of the rim is point P A straight line that virtually passes through the point P and is parallel to the tire rotation axis is defined as a straight line A, and is virtually drawn at an angle of 45 ° with respect to the straight line A from the point P toward the bead portion. When the straight line is a straight line B,
The pneumatic tire according to any one of claims 1 to 3, wherein the rubber layer is disposed so as to intersect the straight line B under the predetermined state.

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