JP2008144318A5 - - Google Patents

Description

Steel cord and pneumatic tire having the same

  The present invention relates to a steel cord in which a plurality of steel strands are twisted together and a pneumatic tire having the same.

  In a pneumatic tire, a steel cord (twisted cord) obtained by twisting a plurality of steel strands is used as a reinforcing cord (for example, see Patent Documents 1 and 2).

  By the way, in recent years, particularly for pneumatic tires for passenger cars, there is an increasing demand for being able to exhibit high steering stability and being lightweight, and countermeasures against this are demanded.

  In order to further improve the handling stability, the bell rod layer needs to have high in-plane rigidity, and it is necessary to densely drive the steel cord. However, as the number of driven wires increases, the cord interval becomes narrower, and separation tends to occur at the end of the bell ridge layer.

Further, in order to further reduce the weight, it is necessary to reduce the gauge by reducing the tire cord longitudinal direction diameter of the steel cord. However, when this is done, the flattening of the cord reduces the longitudinal diameter and at the same time increases the lateral diameter, so that the cord interval is narrowed and separation of the belt layer end portion is likely to occur.
JP 61-201091 A JP 61-201092 A

  In view of the above facts, the present invention provides a steel cord that enables high steering stability and light weight of the tire while effectively suppressing the progress of separation at the end of the steel cord of the tire, and It is an object to provide a pneumatic tire having the same.

The invention according to claim 1 is a steel cord for a tire having a structure of 1 × N, M + N, or L + M + N, and the number of strands constituting the outermost sheath is N or more. and, Ri Do from wire of different diameters d1, d2 from each other, a small towards the d2 than d1, wires constituting the outermost layer of the sheath satisfies the relationship of 3.0 ≧ dl / d2 ≧ 1.15 It is characterized by that.

The steel cord having the 1 × N structure is a steel cord in which a core is not provided and a sheath made of N strands is formed around the cord central axis. Steel cords with an M + N structure include a structure in which the core M is twisted, and an M in which the core is untwisted (non-twisted + N structure . 1 + 6 indicates a single-type (wave-type). 2 + 7, 2 indicates untwisted steel cord in which a sheath made of N strands is formed around a core made of M strands, and L + M + N structure steel cords are made of L strands This is a steel cord in which a sheath made of M strands is formed around a core made of two strands, and a sheath made of N strands is formed around the core.

  As described above, in the first aspect of the invention, the outermost sheath has a so-called different diameter structure. Therefore, in the tire having the steel cord according to the first aspect, the cord surface area increases and the cord surface becomes uneven, so that the contact area between the steel cord surface and the rubber material increases.

  As a result, if a crack occurs around the cord, the crack propagation path becomes longer, so the speed at which the crack generated at the belt end (steel cord end) propagates into the bell ridge layer (in the direction of the belt center) is slowed down. be able to. Therefore, it is possible to provide a steel cord that enables high steering stability and weight reduction of the tire while effectively suppressing the progress of separation at the end of the steel cord of the tire.

Here, if dl / d2 is larger than 3.0, when the steel cord is pulled, the tension acting on the strands (sheath filaments) constituting the sheath becomes non-uniform and the strength is likely to be insufficient.

  When dl / d2 is smaller than 1.15, the effect of increasing the steel cord surface area is reduced, and it is difficult to slow the crack growth rate.

Therefore, d2 is smaller than d1, and the strands constituting the outermost sheath satisfy the relational expression of 3.0 ≧ dl / d2 ≧ 1.15, so that the strength of the strands is suppressed and crack propagation is suppressed. A steel cord capable of sufficiently slowing the speed can be obtained.

The invention according to claim 2 is characterized in that the diameter of half or more of the strands constituting the outermost sheath is d2.

  Thereby, the concave part of surface unevenness | corrugation can be enlarged, and a code diameter contrast contact area can be enlarged.

The invention described in claim 3 is characterized by having a sheath in which strands having a diameter of d1 and strands having a diameter of d2 are alternately arranged.

  Thereby, surface unevenness | corrugation can be formed effectively.

According to a fourth aspect of the present invention, a pneumatic tire has the steel cord according to any one of the first to third aspects.

  Thereby, it can be set as the pneumatic tire which can achieve high steering stability and weight reduction, suppressing the progress of the separation in a steel cord end part effectively.

  Since the present invention has the above configuration, the following effects can be obtained.

According to the first aspect of the present invention, it is possible to provide a steel cord that enables high steering stability and weight reduction of the tire while effectively suppressing the progress of separation at the end portion of the steel cord of the tire. .
Moreover, it can be set as the steel cord which can suppress the intensity | strength shortage of a strand and can fully slow a crack growth rate.

According to the second aspect of the present invention, the concave portion of the surface unevenness can be increased, and the contact area with respect to the cord diameter can be increased.

According to invention of Claim 3 , surface unevenness | corrugation can be formed effectively.

According to invention of Claim 4 , it can be set as the pneumatic tire which can achieve high steering stability and weight reduction, suppressing the progress of the separation in a steel cord edge part effectively.

  Hereinafter, embodiments will be described and embodiments of the present invention will be described. In the second and subsequent embodiments, the same components as those already described are denoted by the same reference numerals, and description thereof is omitted.

[First Embodiment]
First, the first embodiment will be described. As shown in FIG. 1, the pneumatic tire 10 according to the present embodiment includes a belt layer 14, a tread portion 16 provided with a groove, and a belt layer 14 on the outer side of a crown portion 12 </ b> C of a carcass 12 extending in a toroidal shape. And a reinforcing layer 18 that reinforces the end portion of each. The reinforcing layer 18 is provided with a steel cord 20 (see FIG. 2) according to the present embodiment as a reinforcing cord.

  The steel cord 20 does not have a core wire (core filament), and a sheath 22 that is an outermost layer is configured by five strands (sheath filament) (1 × 5 structure). The five strands are composed of a strand S1 having a diameter d1 and a strand S2 having a diameter d2. In the present embodiment, d2 is smaller than d1.

  Thus, in the present embodiment, the outermost sheath 22 has a so-called different diameter structure. Therefore, in the pneumatic tire 10 having the steel cord 20, the cord surface area is increased and the cord surface is uneven, so that the contact area between the steel cord surface and the rubber material is increased.

  As a result, when a crack occurs around the cord, the crack propagation path becomes longer, so the speed at which the crack generated at the belt end (steel cord end) propagates into the bell ridge layer (in the belt center portion) is slowed down. can do.

  Note that a pneumatic tire in which the steel cord 20 is provided on the belt layer 14 may be configured without the reinforcing layer 18.

[Second Embodiment]
Next, a second embodiment will be described. As shown in FIG. 3, the steel cord 30 according to the present embodiment is composed of one strand (core filament) C serving as a core and six strands constituting a sheath 32 of the outermost layer. (1 + 6 structure). Note that the dotted lines in FIG. 3 and FIGS. 4 and 6 described later indicate the circumscribed surface of the core. The six strands constituting the outermost sheath 32 are composed of three strands S1 having a diameter d1 and three strands S2 having a diameter d2. As in the first embodiment, d2 is smaller than d1.

  Thus, in this embodiment, in addition to the outermost sheath 32 having a so-called different wire diameter structure, the diameter of half or more of the strands constituting the outermost sheath 32 is d2, which is smaller. . Therefore, in the pneumatic tire having the steel cord 30, in addition to the effect obtained in the first embodiment, the insufficient strength of the wire is suppressed and the progress speed of the crack generated at the belt end (steel cord end) is sufficiently slowed. Can do.

  Furthermore, the strands having the diameter d1 and the strands having the diameter d2 are alternately arranged. Thereby, surface unevenness | corrugation can be formed effectively.

[Third Embodiment]
Next, a third embodiment will be described. As shown in FIG. 4, the steel cord 40 according to the present embodiment is composed of two strands (core filaments) C serving as a core and seven strands constituting a sheath 42 of the outermost layer. (2 + 7 structure). The seven strands constituting the outermost sheath 42 include three strands S1 having a diameter d1 and four strands S2 having a diameter d2. Similar to the first embodiment and the second embodiment, d2 is smaller than d1.

  Thus, in the present embodiment, in addition to the outermost sheath 42 having a so-called different-diameter structure, the diameter of half or more of the strands constituting the outermost sheath 42 is the smaller d2. . Therefore, in the pneumatic tire having the steel cord 40, in addition to the effects achieved in the first embodiment, the insufficient strength of the strands is suppressed, and the progress rate of cracks generated at the belt end (steel cord end) is sufficiently slowed. Can do.

  Further, in the sheath 42 of the outermost layer, the strand having a diameter d1 is disposed between the strands having a diameter d2. Thereby, surface unevenness | corrugation can be formed effectively.

<Experimental example>
In order to confirm the effect of the present invention, the present inventor made an example of a pneumatic tire using the steel cord of the first embodiment (hereinafter referred to as Example 1) and a conventional steel cord having a 1 × 5 structure ( An example of a pneumatic tire (see FIG. 5; hereinafter referred to as Conventional Example 1) using a tire having the same outer diameter of the five strands constituting the outermost layer sheath was prepared, and a performance test was performed. The number of steel cords to be driven is 30/5 cm.

  As test conditions, each tire was mounted on a rim (5.5 J × 14), attached to a passenger car with an air pressure of 200 kPa, and after traveling 50,000 km, the length in the tire width direction of separation at the belt end was measured.

  As an evaluation method, an index of 100 was calculated for the conventional tire, and an index for relative evaluation was calculated for Example 1. The larger this index, the better the performance. Table 1 shows the code conditions and the above-described indices, which are performance test results.

As can be seen from Table 1, the performance in Example 1 was significantly improved as compared with Conventional Example 1.

  In addition, the present inventor configured three examples of pneumatic tires using the steel cord of the second embodiment (hereinafter referred to as Examples 2 to 4) and a conventional steel cord having a 1 + 6 structure (a sheath of the outermost layer). An example of a pneumatic tire (see FIG. 6, hereinafter referred to as Conventional Example 2) using the same diameter of the six strands to be prepared was prepared, and a performance test was performed. The number of steel cords driven, the test conditions, and the evaluation method are the same as described above. Table 2 shows the cord conditions and the above-mentioned indices, which are performance test results, for each tire.

As can be seen from Table 2, in Examples 2 to 4, the performance was greatly improved as compared with Conventional Example 2.

  Furthermore, the present inventors configured four examples of pneumatic tires using the steel cord of the third embodiment (hereinafter referred to as Examples 5 to 8) and conventional steel cords having a 2 + 7 structure (the outermost layer sheath is configured). An example of a pneumatic tire (see FIG. 7, hereinafter referred to as Conventional Example 3) using the same diameter of all the seven strands to be prepared was prepared, and a performance test was performed. The number of steel cords driven, the test conditions, and the evaluation method are the same as described above. Table 3 shows the cord conditions and the above-mentioned indices, which are performance test results, for each tire.

As can be seen from Table 3, in Examples 5 to 8, the performance was greatly improved as compared with Conventional Example 2.

  The embodiments of the present invention have been described above with reference to the embodiments. However, these embodiments are merely examples, and various modifications can be made without departing from the scope of the invention. It goes without saying that the scope of rights of the present invention is not limited to these embodiments.

It is tire radial direction sectional drawing of the pneumatic tire which concerns on 1st Embodiment. It is a typical sectional view of steel cord 1x5 concerning a 1st embodiment. It is typical sectional drawing of the steel cord 1 + 6 which concerns on 2nd Embodiment. It is typical sectional drawing of the steel cord 2 + 7 which concerns on 3rd Embodiment. It is typical sectional drawing of the conventional steel cord 1x5 used in the experiment example. It is typical sectional drawing of the conventional steel cord 1 + 6 used in the experiment example. It is typical sectional drawing of the conventional steel cord 2 + 7 used in the experiment example.

10 Pneumatic tire 20 Steel cord 22 Sheath 30 Steel cord 32 Sheath 40 Steel cord 42 Sheath

Claims (4)

A steel cord for a tire having a structure of 1 × N, M + N, or L + M + N,
Wires constituting the outermost layer of the sheath, the number N is equal to or greater than 2, and Ri Do from wire of different diameters d1, d2 from each other,
d2 is smaller than d1, and the strands constituting the outermost sheath are
3.0 ≧ dl / d2 ≧ 1.15
A steel cord characterized by satisfying the relational expression of The steel cord according to claim 1 , wherein a diameter of at least half of the strands constituting the outermost sheath is d2. The steel cord according to claim 2 , further comprising a sheath in which strands having a diameter of d1 and strands having a diameter of d2 are alternately arranged. A pneumatic tire comprising the steel cord according to claim 1 .