JP2009079312A - Pneumatic radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a pneumatic radial tire that suppresses occurrence of separation troubles due to core removal of a steel cord while suppressing a growth in an outer diameter. <P>SOLUTION: In the pneumatic radial tire in which the steel cord 10 as the reinforcing material of a tire constituent member, formed of one steel center wire 11 and a plurality of steel side wires 12 twisted around the circumference of the steel center wire 11, the steel center wire 11 is made straight without forming, each of the steel side wires 12 is spirally formed, the form ratio being the ratio of a form wave height Hf of the steel side wires 12 to the diameter Hc of the steel cord 10 is 70% or less and less than 100% and the revolution number of the residual stress in the fastening direction of the steel side wires 12 based on the residual stress applied to the steel side wires 12 is 2 times or more and 6 times or less based on 6 m of the steel cord. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic radial tire using a steel cord having a 1 + N structure as a reinforcing member for a tire constituent member. More specifically, the present invention suppresses the occurrence of a separation failure due to the centering of the steel cord while suppressing the outer diameter growth. The present invention relates to a pneumatic radial tire.

  Conventionally, an open cord having a 1 × N structure formed by twisting a plurality of steel wires is used as a steel cord for a belt layer of a pneumatic radial tire for trucks and buses. Such an open cord having a 1 × N structure has an advantage that it has excellent rubber penetration and is excellent in corrosion resistance and can be manufactured at low cost. However, since the 1 × N structure open cord has a large elongation at low load, it has a drawback of promoting the growth of the outer diameter of the tire and thus reducing the durability of the tire.

  On the other hand, various steel cords having a 1 + N structure in which a plurality of steel wire side wires are twisted around one steel wire core wire have been proposed (see, for example, Patent Documents 1 to 4). Among them, a steel cord with a 1 + N structure, in which the steel wire core wire is not typed, is very effective in terms of suppressing the growth of the outer diameter, but is easy to cause a core failure, resulting in a separation failure due to the core failure. There is a problem that it is easy to produce. In addition, when the corrugated or spiral mold is applied to the steel wire core wire, it is possible to suppress the core disengagement, but the effect of suppressing the outer diameter growth is reduced. For this reason, it is difficult to achieve both suppression of outer diameter growth and suppression of core loss.

JP 9-31874 A JP 2001-329476 A Japanese Patent Laid-Open No. 10-53982 JP-A-9-256282

  An object of the present invention is to provide a pneumatic radial tire that can suppress the occurrence of a separation failure due to a core fall of a steel cord while suppressing outer diameter growth.

  In order to achieve the above object, a pneumatic radial tire of the present invention comprises a steel cord comprising a steel wire core wire and a plurality of steel wire side wires twisted around the steel wire core wire. In the pneumatic radial tire used as a reinforcing material, the steel wire core wire is formed into a straight shape without being shaped, while each of the steel wire side wires is spirally shaped, and the steel wire side wire with respect to the diameter of the steel cord. And a residual stress rotational speed in the tightening direction of the steel wire side wire based on the residual stress applied to the steel wire side wire is 70% or more and less than 100%. It is characterized in that it is 2 times or more and 6 times or less per 6 m of the steel cord.

  In the present invention, the steel wire core wire constituting the steel cord is formed into a straight shape without molding so as to suppress the outer diameter growth of the tire. On the other hand, each steel wire side wire has a spiral shape. By applying the mold and setting the mold rate to 70% or more and less than 100%, it is possible to suppress the relative movement of the steel wire core wire with respect to the steel wire side wire, and to suppress the occurrence of separation failure due to the centering of the steel cord. it can. In addition, when the above-mentioned molding rate is simply set small, the steel cord is likely to be broken, but the residual stress rotational speed in the tightening direction of the steel wire side wire based on the residual stress applied to the steel wire side wire is set to the steel cord. By making it twice or more per 6 m, it becomes possible to suppress the variation. Furthermore, by restricting the residual stress rotation speed based on the residual stress applied to the steel wire side wire to 6 times or less per 6 m of the steel cord, the rotational stress does not remain in the entire steel cord. There is no inconvenience that the tire constituent member is warped when it is molded.

  In the present invention, the residual stress rotation speed based on the residual stress applied to the steel wire side wire is preferably 2 to 4 times per 6 m of the steel cord. Moreover, it is preferable that the molding rate of the steel wire side wire is 70% or more and 96% or less. Thereby, a more preferable effect can be obtained.

  Examples of the tire constituent member to which the steel cord is applied include a belt layer, a carcass layer, a bead portion reinforcing layer, and the like, and it is particularly preferable to apply the steel cord to the belt layer. This is because the steel cord constituting the belt layer is strongly required to suppress the growth of the outer diameter and the core.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows a pneumatic radial tire according to an embodiment of the present invention, where 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. A carcass layer 4 is mounted between the pair of left and right bead portions 3, 3, and an end portion of the carcass layer 4 is folded around the bead core 5 from the inside of the tire to the outside. A plurality of belt layers 6 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 6 are disposed such that the reinforcing cords are inclined with respect to the tire circumferential direction, and the reinforcing cords cross each other between the layers. As the reinforcing cord of the belt layer 6, a steel cord having a 1 + N structure (N = 3 to 8), more specifically, a steel cord having a 1 + 5 structure is used. Furthermore, if necessary, a belt cover layer formed by winding a reinforcing cord in the tire circumferential direction may be disposed on the outer peripheral side of the belt layer 6.

  FIG. 1 illustrates a pneumatic radial tire for trucks and buses, but the present invention can also be applied to a pneumatic radial tire for passenger cars or light trucks as shown in FIG.

  FIG. 3 is a plan view showing a steel cord having a 1 + 5 structure used for the belt layer of the pneumatic radial tire of the present invention, and FIG. 4 is a cross-sectional view of the steel cord shown in FIG. FIG. 5 is a plan view showing a steel wire side line separated from the steel cord of FIG.

  As shown in FIGS. 3 to 5, the steel cord 10 includes a single steel wire core wire 11 and five steel wire side wires 12 twisted around the steel wire core wire 11. The steel wire core wire 11 is not molded, and the steel wire core wire 11 is substantially linear. On the other hand, each of the steel wire side wires 12 is spirally shaped. As the belt cord, the wire diameters of the steel wire core wire 11 and the steel wire side wire 12 are preferably in the range of 0.15 mm to 0.45 mm.

  The molding rate R of the steel wire side wire 12 is set to 70% or more and less than 100%, more preferably 70% or more and 96% or less. Thereby, the relative movement of the steel wire core wire 11 with respect to the steel wire side wire 12 can be suppressed, and the occurrence of a separation failure due to the core removal of the steel cord 10 can be suppressed. If the molding rate R is too small, the steel cord 10 is likely to be broken, and conversely if the molding rate R is too large, the effect of suppressing the centering is insufficient.

The molding rate R of the steel wire side wire 12 can be obtained from the following equation (1) when the diameter of the steel cord 10 is Hc (mm) and the wave height of the steel wire side wire 12 is Hf (mm). .
R = Hf / Hc × 100 (%) (1)

On the other hand, the diameter Hc (ideal diameter) of the steel cord 10 is calculated from the following equation (2) when the diameter of the steel wire core wire 11 is ds (mm) and the diameter of the steel wire side wire 12 is ds (mm). be able to.
Hc = ds + 2ds (2)

  Moreover, the wave height Hf of the type | molding of the steel wire side line 12 cuts the steel cord 10 to suitable length, loosens all the steel wire side lines 12, and makes each steel wire side line 12 orthogonal to a code | cord | chord longitudinal direction with a projector. Projecting in the direction, the wave height Hf is measured at four points per line, and the measured values of all the steel wire side wires 12 are averaged.

  The following residual stress is given to the steel wire side wire 12. That is, after separating the steel wire side wire 12 from the steel cord 10 so that the residual stress is not released, when the rotation of the steel wire side wire 12 is allowed based on the residual stress, the tightening direction (twisting of the steel wire side wire 12 is not allowed. Residual stress is applied to the steel wire side wire 12 such that the residual stress rotational speed in the tightening direction) is 2 to 6 times, more preferably 2 to 4 times per 6 m of the steel cord 10.

  When the molding rate R of the steel wire side wire 12 is simply set small, the steel cord 10 is likely to be broken, but by setting the residual stress rotation speed based on the residual stress applied to the steel wire side wire 12 to 2 times or more. , It becomes possible to suppress the variation. Further, by limiting the residual stress rotational speed based on the residual stress applied to the steel wire side wire 12 to 6 times or less, more preferably 4 times or less, no rotational stress remains in the entire steel cord. There is no inconvenience that the tire constituent member is warped when the member is formed into a sheet shape.

  According to the pneumatic radial tire described above, the steel wire core wire 11 is formed into a straight shape without being molded, while the steel wire side wire 12 is spirally shaped, and the steel wire side wire 12 has a shaping rate R and residual stress. Since the steel cord 10 having a specified rotational speed is used as a reinforcing material for the belt layer 6, it is possible to suppress the occurrence of a separation failure due to the centering of the steel cord 10 while suppressing the outer diameter growth of the tire. Become.

  Hereinafter, the manufacturing method of the steel cord used by this invention is demonstrated easily. FIG. 6 shows the overall configuration of the steel cord manufacturing apparatus, FIG. 7 shows a preformer (molding machine), and FIG. 8 shows a residual stress adjusting apparatus.

  As shown in FIG. 6, this steel cord manufacturing apparatus connects one steel wire core wire 11 supplied from a bobbin 21 and a plurality of steel wire side wires 12 supplied from a plurality of bobbins 22 via a guide roller 23. These are collected by the aggregator 24 and supplied to the twisting machine 25. The stranding machine 25 is configured to twist a plurality of steel wire side wires 12 around a steel wire core wire 11 and wind the obtained steel cord 10 around a bobbin 26. The structure of the stranded wire machine 25 is not particularly limited, and a known one can be used.

  A preformer 30 and a residual stress adjusting device 40 are disposed between the bobbin 22 for supplying the steel wire side wire 12 and the guide roller 23, and each steel wire side wire 12 passes through the preformer 30 and the residual stress adjusting device 40. It is like that.

  As shown in FIG. 7, the pre-former 30 includes three rotation pins 31 a, 31 b, and 31 c that are arranged so that the rotation axis is orthogonal to the supply direction of the steel wire side wire 12, and these rotation pins 31 a to 31 c. It is comprised from the cylinder 32 which hold | maintains rotatably. The steel wire side wire 12 is stretched around the rotating pins 31a to 31c in a zigzag shape. Then, when the steel wire side wire 12 passes through the rotary pins 31a to 31c, the steel wire side wire 12 is handled and is subjected to the typing. The molding rate can be adjusted as appropriate based on the distance between the rotation pins 31a to 31c, the arrangement position, and the like.

  The residual stress adjusting device 40 has a structure in which a hollow rotary shaft 41 is rotatably supported by a bearing 46, a cylindrical body 42 is fixed to one end of the hollow rotary shaft 41, and a pulley 43 is fixed to the other end of the rotary shaft 41. It has become. A belt 44 is wound around the pulley 43, and the power of a motor (not shown) is transmitted to the pulley 43 via the belt 44, thereby rotating the cylindrical body 42. Two rolls 45 a and 45 b arranged so that the rotation axis is orthogonal to the supply direction of the steel wire side wire 12 are rotatably mounted on the cylindrical body 42. The steel wire side line 12 passes through the side of the roll 45a in the cylindrical body 42, and is hung on the first groove of the roll 45b, and then hung on the first groove of the roll 45a. The steel wire side wire 12 is hung from the first groove of the roll 45a to the second groove of the roll 45b and the second groove of the roll 45a, and after passing through the side of the roll 45b, It is to be sent out.

  When the cylindrical body 42 rotates, the steel wire side wire 12 is twisted on the inlet side of the cylindrical body 42 and its twist is returned on the outlet side. By rotating the cylinder body 42 at a relatively high speed, the steel wire side wire 12 exceeds the elastic range (twisting to the extent that the twist is completely restored), and the plastic range (twisting is not completely restored). Twisting is applied until twisting is reached, and twisting is restored. Thereby, residual stress is given to the steel wire side wire 12. The magnitude of the residual stress can be adjusted based on the number of twists of the steel wire side wire 12 (the rotational speed of the cylindrical body 42). The rotating direction of the cylinder 42 is the same as the twisting direction of the twisting machine 25. As a result, the residual stress applied to the steel wire side wire 12 acts to rotate the released steel wire side wire 12 in the tightening direction.

  With a tire size of 295 / 75R22.5, a steel cord (1 × 0.32 + 5 × 0.37) comprising one steel wire core wire and a plurality of steel wire side wires twisted around the steel wire core wire In pneumatic pneumatic tires used as reinforcements for the second and third belt layers of the four belt layers from the carcass layer side, whether or not the steel wire core wire is shaped (wavy), Pneumatic radial tires of Examples 1 to 6, Comparative Examples 1 to 4, and Conventional Example 1 having different residual stress rotational speeds based on the molding rate and the residual stress of the steel wire side line as shown in Table 1 were manufactured.

  In addition, the molding rate of the steel wire side wire and the residual stress rotation speed of the steel wire side wire were measured by the following methods. Moreover, about each steel cord, the following method evaluated the crack and the core-losing.

Steel wire side mold rate:
The diameter Hc of the steel cord was determined by the equation Hc = ds + 2ds from the diameter ds of the steel wire core wire and the diameter of the steel wire side wire ds. For the wave height Hf of the steel wire side line, the steel cord is cut to an appropriate length to loosen all the steel wire side lines, and each steel wire side line is projected in a direction perpendicular to the longitudinal direction of the cord by a projector. The projected image was projected on a screen, and the wave height Hf was measured at four points per line. And the average value of the measured value of all the steel wire side lines was made into wave height Hf. The molding rate R of the steel wire side wire was determined by the equation R = Hf / Hc × 100 (%) from the diameter Hc of the steel cord and the wave height Hf of the steel wire side wire.

Steel wire side wire residual stress rotational speed:
Cut the steel cord (test object) to a length of 6m and rotate the entire steel cord in the direction opposite to the twisting direction so that the residual stress is not released, that is, the steel wire side wire itself does not rotate. Thus, the steel wire side wires were separated. When one end of the separated steel wire side wire is fixed and the other end of the steel wire side wire is opened, the steel wire side wire rotates in the tightening direction based on the residual stress. The number of rotations up to 1) was measured in 1/4 rotation units. This measurement was performed on all the steel wire side lines constituting the test object, and the average value was defined as the residual stress rotation speed (times / 6 m) of the steel wire side line of the test object. The residual stress rotational speed was also measured for the steel cord itself.

Barake:
About the variation of the steel cord (test object), four-stage evaluation from A determination to D determination was performed as follows. That is, the case where the cord was cut with pliers while being held at a distance of 50 mm from the cutting portion, and the result that no flaking occurred even if the cutting terminal was tapped lightly was indicated by “A”. . “B” indicates a case where a result that no separation occurs even when the cord is cut with pliers while being held at a distance of 50 mm from the cut portion is obtained three times in succession. When the cord was cut with pliers while holding the part adjacent to the cutting part and the holding was gently released, a case where the result that no breakage occurred was obtained twice in three times was indicated by “C”. When the cord is cut with pliers while holding the part adjacent to the cutting part and the holding is gently released, the case where the result that no breakage occurs cannot be obtained is indicated by “D”.

Centering:
About the core removal of the steel cord (test object), the presence or absence of the core removal was evaluated as follows. That is, prepare a steel cord of about several meters wound in a coil shape with a diameter of about 150 mm, and hold the coiled steel cord with both hands to repeatedly deform (for example, bring both hands close or separate). It was. And the presence or absence of the steel wire core wire jumping out from the end portion of the steel cord (core removal) was determined.

  About the pneumatic radial tires of Examples 1 to 6, Comparative Examples 1 to 4 and Conventional Example 1 described above, the molding workability was evaluated by the following method, and the belt edge separation and the peripheral growth amount were measured. Is also shown in Table 1.

Belt edge separation:
Each test tire is mounted on a vehicle, and after traveling 150,000 km on a general pavement, each test tire is disassembled, and the amount of separation at the edge of the third belt layer is measured over the entire circumference, and the maximum amount of separation (mm ) The smaller this value, the better the belt edge separation resistance.

Perimeter growth:
Each test tire is mounted on a standard rim, placed in an oven in an inflated state (air pressure 900 kPa), left to stand at a temperature of 70 ° C. for 120 days, and the tire outer circumference at the groove bottom is measured before and after deterioration. The peripheral growth amount (mm) was determined from the measured value. It means that it is excellent in the outer diameter growth inhibitory effect, so that this value is small.

Molding workability (flatness):
The spring-up state of the sheet-like member at the time of molding each test tire was evaluated. As a result of the evaluation, a relatively good state in which the belt member's jumping height is 0 to 3 mm is indicated by “◯”, and a slightly poor state in which the belt member is 4 to 5 mm is indicated by “Δ”, and a failure of 6 mm or more is indicated. The state is indicated by “x”.

  As is clear from Table 1, the tires of Examples 1 to 6 were excellent in belt edge separation resistance, outer diameter growth suppression effect, and molding workability. On the other hand, since the tire of Conventional Example 1 is molded on the steel wire core wire, the belt edge separation resistance and the outer diameter growth suppressing effect are insufficient. In the tire of Comparative Example 1, since the molding rate of the steel wire side wire was too small, the belt edge separation resistance was insufficient due to the variation of the steel cord. In the tire of Comparative Example 2, the steel wire side line has a too high molding rate, so that the belt edge separation resistance and the outer diameter growth suppression effect are insufficient due to the centering of the steel cord. In the tire of Comparative Example 3, since the residual stress rotational speed of the steel wire side wire was too small, the belt edge separation resistance was insufficient due to the variation in the steel cord. In the tire of Comparative Example 4, the number of residual stress rotations on the steel wire side line was too large, and the molding workability was insufficient due to the warping of the belt member.

  Next, with a tire size 165R14, a steel cord (1 + 5 × 0.25) comprising one steel wire core wire and a plurality of steel wire side wires twisted around the steel wire core wire is attached to a two-layer belt. Table 2 shows the residual stress rotation speed based on the presence / absence of molding (corrugated) to the steel wire core wire, the molding rate of the steel wire side wire, and the residual stress of the steel wire side wire Various pneumatic radial tires of Examples 11 to 16, Comparative Examples 11 to 14, and Conventional Example 11 were manufactured.

  About the pneumatic radial tires of Examples 11 to 16, Comparative Examples 11 to 14 and Conventional Example 11, the molding workability was evaluated by the following method, and the belt edge separation and the peripheral growth amount were measured. The results are also shown in Table 2.

Belt edge separation:
Each test tire is mounted on a vehicle, and after running on a general paved road for 50,000 km, each test tire is disassembled, and the amount of separation at the edge of the second belt layer is measured over the entire circumference, and the maximum amount of separation (mm ) The smaller this value, the better the belt edge separation resistance.

Perimeter growth:
Each test tire is mounted on a standard rim, placed in an oven in an inflated state (air pressure 475 kPa), left to stand at a temperature of 70 ° C. for 120 days, and the tire outer circumference at the groove bottom is measured before and after deterioration. The peripheral growth amount (mm) was determined from the measured value. It means that it is excellent in the outer diameter growth inhibitory effect, so that this value is small.

Molding workability (flatness):
The spring-up state of the sheet-like member at the time of molding each test tire was evaluated. As a result of the evaluation, a relatively good state in which the belt member's jumping height is 0 to 3 mm is indicated by “◯”, and a slightly poor state in which the belt member is 4 to 5 mm is indicated by “Δ”, and a failure of 6 mm or more is indicated. The state is indicated by “x”.

  As apparent from Table 2, the tires of Examples 11 to 16 were all excellent in belt edge separation resistance, outer diameter growth suppression effect, and molding workability. On the other hand, since the tire of Conventional Example 11 is molded on the steel wire core wire, the belt edge separation resistance and the outer diameter growth suppressing effect are insufficient. In the tire of Comparative Example 11, since the molding rate of the steel wire side wire was too small, the belt edge separation resistance was insufficient due to the variation in the steel cord. In the tire of Comparative Example 12, since the molding rate of the steel wire side wire was too large, the belt edge separation resistance and the outer diameter growth suppression effect were insufficient due to the core loss of the steel cord. In the tire of Comparative Example 13, the residual stress rotational speed of the steel wire side line was too small, and therefore the belt edge separation resistance was insufficient due to the variation in the steel cord. Since the tire of Comparative Example 14 had too many residual stress rotational speeds on the steel wire side wires, the forming workability was insufficient due to the warping of the belt member.

1 is a meridian half cross-sectional view showing a pneumatic radial tire according to an embodiment of the present invention. It is a meridian half sectional view showing a pneumatic radial tire according to another embodiment of the present invention. It is a top view which shows the steel cord of the 1 + 5 structure used for the belt layer of the pneumatic radial tire of this invention. It is sectional drawing of the steel cord shown in FIG. It is a top view which shows the steel wire side line isolate | separated from the steel cord of FIG. It is a side view which shows roughly the whole structure of the manufacturing apparatus of a steel cord. It is a side view which shows a preformer (molding machine). It is a side view which shows a residual stress adjustment apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Belt layer 10 Steel cord 11 Steel wire core wire 12 Steel wire side wire

Claims (4)

  In a pneumatic radial tire using a steel cord comprising one steel wire core wire and a plurality of steel wire side wires twisted around the steel wire core wire as a reinforcing member for a tire constituent member, the steel wire core wire includes: While making the straight shape without shaping, each of the steel wire side lines is spirally shaped, and the molding rate comprising the ratio of the wave height of the steel wire side lines to the diameter of the steel cord is 70% or more and 100 %, And the residual stress rotational speed in the tightening direction of the steel wire side wire based on the residual stress applied to the steel wire side wire is not less than 2 times and not more than 6 times per 6 m of the steel cord. A featured pneumatic radial tire.   2. The pneumatic radial tire according to claim 1, wherein the residual stress rotational speed is 2 to 4 times per 6 m of the steel cord.   The pneumatic radial tire according to claim 1 or 2, wherein the molding rate is 70% or more and 96% or less.   The pneumatic radial tire according to any one of claims 1 to 3, wherein the tire constituent member is a belt layer.

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