JP2019119320A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire that is able to improve durability and uneven wear resistance without increasing a mass of a carcass layer.SOLUTION: In a pneumatic tire having a carcass layer stretched between a pair of beads, left and right, the carcass layer comprises a carcass ply in which a steel cord having 1×n structure (n=3 to 6) formed by twisting together an n number of filaments of identical diameters. Tensile strength of the filaments is in the range of 4000(MPa)-2000×filament diameter(mm)≤tensile strength≤5400(MPa)-2000×filament diameter(mm). Flexure hardness per steer cord is 100cN/cords and a steel cord diameter is equal to or smaller than 0.30 mm.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a pneumatic tire.

  Heretofore, in passenger car tires, an organic fiber cord made of rayon has been adopted as a reinforcing material of a carcass forming the frame, that is, a carcass ply cord.

  Organic fiber cords made of rayon have low strength, and in order to ensure the required durability, it is necessary to increase the cord diameter. However, when the cord diameter is increased, there is a problem that the thickness of the carcass ply increases and the tire mass increases. There is also a need for a tire that is excellent in uneven wear resistance.

  In order to ameliorate the problem of durability, Patent Documents 1 to 4 propose to apply a general-purpose steel cord to the carcass layer. However, there is no description about uneven wear resistance, and simply applying a steel cord to the carcass layer has the problem that the mass of the carcass layer will increase as compared with the case where an organic fiber cord is used for the carcass layer. there were.

JP, 2012-218627, A JP, 2010-95061, A JP 2003-136910 A Japanese Patent Application Publication No. 2001-32184

  An object of the present invention is to provide a pneumatic tire that can improve durability and uneven wear resistance without increasing the mass of the carcass layer.

  The pneumatic tire according to the present invention is a pneumatic tire having a carcass layer stretched between a pair of left and right bead portions, and the carcass layer is formed by twisting n filaments having the same diameter. A carcass ply on which a steel cord of a structure (n = 3 to 6) is disposed, wherein the tensile strength of the filament is 4000 (MPa)-2000 x filament diameter (mm) ≦ tensile strength ≦ 5400 (MPa)-2000 x filament It is in the range of the diameter (mm), the bending hardness per one steel cord is 100 cN / cord or less, and the steel cord diameter is 0.30 mm or less.

  The twist pitch of the above-mentioned steel cord can be 5.5 mm or more.

  The diameter of the steel filament may be 0.15 mm or less.

  According to the pneumatic tire of the present invention, excellent durability and uneven wear resistance can be obtained without increasing the mass of the carcass layer.

1 is a half sectional view of a pneumatic tire according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS The schematic cross section which shows the steel cord of 1x n structure which concerns on one Embodiment of this invention. Drawing explaining the measuring method of the bending hardness of a steel cord. The schematic cross section which shows the shape of the test path used for evaluation of riding comfort.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The pneumatic tire according to the embodiment shown in FIG. 1 has a pair of left and right bead portions 1 and sidewall portions 2 and radially outer end portions of the left and right sidewall portions 2 connected to each other between the sidewall portions. A carcass 4 is provided which is configured to include the provided tread portion 3 and extends between a pair of bead portions.

  The carcass 4 is composed of at least one carcass ply having its both ends locked by an annular bead core 5 embedded in the bead portion 1 from the tread portion 3 to the sidewall portion 2. The carcass ply is obtained by coating a carcass cord comprising a steel cord 20 (see FIG. 2) with a coating rubber, and the steel cord 20 is arranged substantially at right angles to the tire circumferential direction.

  A belt 6 is disposed between the carcass 4 and the tread rubber portion 7 on the outer peripheral side (that is, the outer side in the tire radial direction) of the carcass 4 in the tread portion 3. The belt 6 is provided on the outer periphery of the crown portion of the carcass 4 and can be constituted by one or a plurality of belt plies, usually at least two belt plies, and in the present embodiment, the carcass side The first belt ply 6A and the second belt ply 6B on the tread rubber portion side are composed of two belt plies. The belt plies 6A and 6B are formed by inclining steel cords at a predetermined angle (for example, 15 to 35 degrees) with respect to the tire circumferential direction and arranging the steel cords at predetermined intervals in the tire width direction. Each belt ply has a steel cord coated with a coating rubber. The steel cords are disposed to intersect each other between the two belt plies 6A and 6B.

  A belt reinforcing layer 8 is provided between the belt 6 and the tread rubber portion 7 on the outer peripheral side of the belt 6 (that is, on the outer side in the tire radial direction). The belt reinforcing layer 8 is a cap ply that covers the belt 6 with its entire width, and is made of an organic fiber cord arranged substantially parallel to the tire circumferential direction. That is, the belt reinforcing layer 8 has organic fiber cords arrayed along the tire circumferential direction, and the organic fiber cords have an angle of 0 to 5 degrees with respect to the tire circumferential direction so as to cover the entire width direction of the belt 6 Can be formed by spiral winding.

  The twist structure of the steel cord 20 used for the carcass 4 according to the present embodiment is a steel cord of a 1 × n structure in which a plurality of steel filaments 12 are twisted together as shown in FIG. By virtue of the 1 × n structure, surface strain due to bending and compressive deformation is difficult to increase, and excellent durability is easily obtained. The number (n) of the steel filaments 12 is three to six, preferably three to five, and more preferably three or four. By being three or more, it becomes easy to become a highly symmetrical circular cross-section cord, local stress concentration to bending and compression hardly occurs, and excellent durability is easily obtained. In addition, by being 6 or less, it is easy to suppress the increase of the tire mass, and the twist structure of the cord is not easily broken and the symmetry is easily maintained, so that the cord hardness becomes uneven in the longitudinal direction of the cord. Hard and easy to obtain excellent durability.

  The steel cord 20 used for the carcass 4 according to the present embodiment has a filament tensile strength in the range of 4000 (MPa)-2000 x filament diameter (mm) ≦ tensile strength ≦ 5400 (MPa)-2000 x filament diameter (mm) It is inside. By setting the tensile strength to 4000 (MPa)-2000 x filament diameter (mm) or more, the number of the number of pins required for obtaining the desired durability does not increase excessively, and the distance between the cords can be secured. Excellent durability can be obtained easily while suppressing the occurrence of code separation. Moreover, by being 5400 (MPa)-2000 x filament diameter (mm) or less, the ductility of a cord can be maintained, the fracture by embrittlement is suppressed, and excellent durability is easily obtained.

  The bending hardness per steel cord is 100 cN / wire or less, preferably 80 cN / wire or less, and more preferably 60 cN / wire or less. Moreover, it is preferable that it is 9 cN or more. By setting it to 100 cN / piece or less, the ground contact shape can be made to correspond to the road surface according to the ground contact pressure, and excellent uneven wear resistance can be easily obtained. Here, the "bending hardness per one steel cord" is a value defined by the maximum load when one steel cord is bent at its center portion at a distance between supporting points of 25.4 mm. Specifically, it can be measured as follows using a tensile tester. That is, at room temperature, as shown in FIG. 3, the steel cord 20 having a length of 50 to 80 mm is suspended in a state in which the central portion is suspended at a distance of 25.4 mm with both ends free. And the center point 20M is applied to the straight upper side 21A of the fixed U-shaped fixed jig 21 so as to intersect at a right angle from the lower side. Here, the upper side portion 21A has a bar shape having a circular cross section (diameter = 3.0 mm). From this state, the support 22 is pulled up at a tensile speed of 500 mm / min, and the load applied to the support 22 is measured while the steel cord 20 is bent by the jig 21. The maximum load at that time is the maximum bending load (cN) of the steel cord 20, and the average value of n = 5 is taken as the cord bending hardness.

  The diameter d of the steel filament 12 is not particularly limited, but is preferably 0.15 mm or less, more preferably 0.06 to 0.12 mm, and still more preferably 0.07 to 0.10 mm. . When the diameter d of the steel filament 12 is 0.15 mm or less, the filament is less likely to cause metal fatigue, the fatigue resistance of the carcass ply can be maintained, and the durability of the tire can be easily maintained.

  The cord diameter D of the steel cord 20 is not particularly limited as long as it is 0.30 mm or less, preferably 0.10 to 0.30 mm, and more preferably 0.15 to 0.25 mm. By being 0.30 mm or less, it is easy to suppress the increase in tire mass.

  The twist pitch is not particularly limited, but is preferably 5.5 or more, and more preferably 6.0 to 11.0 mm.

  The number of implanted steel cords 20 in the carcass ply (lines / inch) is not particularly limited, but is preferably 40 to 130 / inch, and more preferably 70 to 125 / inch.

  The number of carcass plies is not particularly limited, but is preferably one from the viewpoint of reducing the weight of the tire.

  The type of pneumatic tire according to the present embodiment is not particularly limited, and various types of tires such as tires for passenger cars, heavy duty tires used for trucks, buses and the like can be mentioned.

  Hereinafter, although the example of the present invention is shown, the present invention is not limited to these examples.

  A steel cord having a structure shown in Table 1 below was produced. The carcass ply of the conventional example was made into two carcass plies using a rayon cord of 1840 dtex / 2 as an organic fiber cord. The other steel cords are all 1 × n steel cords formed by twisting a plurality of steel filaments of the same diameter. In Table 1, “3” of “1 × 3 × 0.10” indicates that the number of filaments is three, and “0.10” indicates that the filament diameter is 0.10 mm.

  The diameter of each filament and cord diameter were measured with a predetermined thickness meter in accordance with JIS G 3510.

  Each cord having a structure shown in Table 1 and a filament were subjected to a tensile test in accordance with JIS G 3510 to measure the cord tensile strength and the tensile strength of the filament.

  Further, for each cord, the bending hardness of the cord was measured as follows. That is, at room temperature, as shown in FIG. 3, the steel cord 20 having a length of 80 mm is supported by the support 22 in a state in which the central portion is suspended at a distance of 25.4 mm with both ends free. At the same time, the middle point 20M is applied to the straight upper side 21A of the fixed jig 21 having the inverted U-shape so as to intersect at a right angle from the lower side. Here, the upper side portion 21A has a bar shape having a circular cross section (diameter = 3.0 mm). From this state, the support 22 is pulled upward at a tensile speed of 500 mm / min using a tensile tester (Autograph manufactured by Shimadzu Corp.), and the steel cord 20 is bent by the jig 21 to the support 22. The load was measured. The maximum load at that time was the maximum bending load (cN) of the steel cord 20, and the average value of n = 5 was taken as the cord bending hardness.

  In addition, the carcass ply using the rayon cord of the conventional example is divided by the strength per unit width of a carcass layer in which two sheets are stacked (cord tensile strength × number of punches × number of plies), tensile strength of each steel cord and number of punches The number of strikes was adjusted so that the product had the same value, and a calender apparatus was used to produce a carcass ply by setting the topping direction.

  For the obtained carcass ply, the cord occupancy rate and the thickness of the carcass ply were determined as follows.

・ Code occupancy rate (%) = (cord diameter (mm) × number of impacted pieces (piece / 25 mm)) × 100/25 (mm)

-Thickness of carcass ply: A thickness as a carcass ply obtained by coating a steel cord with a coating rubber, which was measured by a dial gauge (diameter of leg 9.5 mm, load 1670 mN).

  Further, using the obtained carcass ply, a tire having a tire size of 225 / 40R18 was vulcanized and formed according to a conventional method. All the components other than the carcass layer were common to each tire. The steel cord in the belt ply had a 2 + 2 × 0.25 structure, and the number of strikes was 18 / inch. The angle of the steel cord in the belt ply (6A) / (6B) was + 25 ° / -25 ° with respect to the tire circumferential direction. In the belt reinforcing layer, one cap ply was made of nylon 66 cords of 1400 dtex / 2, and the number of punches was 28/25 mm.

  The tire mass, the riding comfort, the uneven wear resistance, and the durability were evaluated for each of the obtained pneumatic tires. The evaluation method of each evaluation item is shown below.

Tire weight: The total weight of one tire, and the total weight of the tire of the conventional example was indexed as 100. The smaller the number, the lighter.

· Ride comfort: A test tire incorporated in a standard rim with an internal pressure of 200 kPa is mounted on the front wheel of a test vehicle, and a test road 40 having a cross-sectional shape shown in FIG. The sensory evaluation of the tire's rideability was carried out at. Those that can ride over the ridge smoothly are marked with "○", those that are difficult to ride slightly are marked with "△", and those that are very difficult to ride are marked with "×".

-Uneven wear resistance: The above tire was mounted on a 2000 cc car and traveled for 10000 km, and the remaining groove depths of the center and the left and right shoulders after traveling were measured. Of the remaining grooves on the left and right shoulders, the shallower depth divided by the depth of the center is determined and expressed as an index with the conventional example as 100. The larger the index, the better the uneven wear resistance. Indicates that there is.

Durability: Measured by a drum tester having a 1700 mm diameter rotating drum made of steel and having a smooth surface according to FMVSS 109 (UTQG) as follows. The test tire was attached to a standard rim specified by JIS at an internal pressure of 220 kPa (2.2 kgf / cm ² ), and the load was 88% of the maximum load specified by JATMA. After running-in at a speed of 80 km / h, it was allowed to cool once, and after the air pressure was adjusted again, main running was performed. The main run started from 120 km / h, and thereafter, the speed was increased by 8 km / h every 30 minutes, and the vehicle was run until a failure occurred. The total travel distance of the main run until the occurrence of a failure is indexed as 100 for the conventional example. The larger the index, the better the durability.

  The results are as shown in Table 1, and in all of Examples 1 to 5 the tire mass can be reduced compared with the conventional example, and excellent ride comfort, uneven wear resistance and durability It can be seen that

  In Comparative Example 1, the cord diameter of the steel cord exceeds 0.3 mm, the bending hardness is greater than 100 cN, and both the ride comfort, the partial abrasion resistance, and the durability are inferior to those of the conventional example. I understand that.

  Comparative Example 2 is an example in which the cord diameter of the steel cord exceeds 0.3 mm, and it can be seen from the comparison with the conventional example that the ride comfort and the partial abrasion resistance are inferior.

  In Comparative Example 3, although the tensile strength of the filament was out of the predetermined range, it was not possible to produce a tire.

T ... tire 1 ... bead portion 2 ... sidewall portion 3 ... tread portion 4 ... carcass 5 ... bead core 6 ... belt 6A ... first belt ply 6B ... second belt ply 7 ... tread rubber portion 8 ... belt reinforcement layer 12 ... steel filament 20 ... steel cord 21 ... jig 22 ... support d ... diameter of steel filament D ... diameter of cord

Claims (3)

A pneumatic tire having a carcass layer stretched between a pair of left and right beads,
The carcass layer comprises a carcass ply on which a steel cord of 1 × n structure (n = 3 to 6) is formed by twisting n filaments of the same diameter.
The tensile strength of the filament is in the range of 4000 (MPa)-2000 x filament diameter (mm)? Tensile strength? 5400 (MPa)-2000 x filament diameter (mm),
The bending hardness per steel cord is 100 cN / wire or less,
A pneumatic tire characterized in that a steel cord diameter is 0.30 mm or less.   The pneumatic tire according to claim 1, wherein a twist pitch of the steel cord is 5.5 mm or more. The pneumatic tire according to claim 1, wherein a diameter of the filament is 0.15 mm or less.

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