JP5953937B2 - Pneumatic radial tire for passenger cars - Google Patents

Description

  The present invention relates to a pneumatic radial tire for passenger cars.

  More specifically, air for passenger cars that can maintain high altitude without deteriorating steering stability and can significantly reduce rolling resistance, thereby reducing fuel consumption and having an excellent effect on reducing environmental impact. Related to radial tires.

  In general, a pneumatic radial tire for a passenger car has a carcass layer including a carcass cord oriented in the tire radial direction between a pair of bead portions, and is inclined with respect to the tire circumferential direction on the outer peripheral side of the carcass layer in the tread portion. And a belt layer including a plurality of steel cords.

  In recent years, automobile tires have been required to further reduce fuel consumption due to social demands for reducing environmental impacts such as resource saving and energy saving. In response to this, the realization of pneumatic radial tires for passenger cars with reduced rolling resistance has been realized. It is desired.

  One means for reducing rolling resistance is to reduce the weight of the tire. For example, it is considered to review the configuration of the belt cord used in the belt layer and reduce it.

  For example, as a belt cord, a single wire (monofilament) steel wire is used instead of a stranded wire cord in which a plurality of filaments are twisted together, and a plurality of pairs of the two steel wires which are spirally shaped are specified. A proposal has been made to use a spiral diameter, a spiral pitch, a diameter of the single wire, etc. to reduce the thickness of the belt layer, to reduce the tire weight, to reduce rolling resistance, and to reduce fuel consumption (Patent Document 1).

  However, when the belt cord is reduced in this way, a decrease in steering stability becomes a new problem. In the above proposal, the in-plane bending rigidity of the belt portion is lowered, and the steering stability is lowered.

JP-A-8-300905

  In view of the above-described points, an object of the present invention is to provide a pneumatic radial tire for a passenger car that can maintain high steering stability even when the belt cord is reduced by reducing rolling resistance. There is.

The pneumatic radial tire for passenger cars of the present invention that achieves the above-described object has the following configuration (1).
(1) A main belt layer in which two belt plies in which steel cords are embedded at an angle of 15 to 45 ° with respect to the tire circumferential direction on the outer side in the tire radial direction of the carcass layer in the crown region are overlapped in a direction crossing each other. In a pneumatic radial tire for a passenger car having a ply in which steel cords are embedded at an angle of 80 to 90 ° with respect to the tire circumferential direction as a belt auxiliary layer, from both ends in the width direction of the narrow main belt layer, respectively. It is arranged between the carcass layer and the inner main belt layer so that a part of the belt auxiliary layer is located 30 mm away from the tire equator side. The belt auxiliary layer has a width of 30 mm or more and an initial rigidity value of the belt auxiliary layer. A pneumatic radial tire for a passenger car having a larger initial rigidity value than the main belt layer.

Moreover, in the pneumatic radial tire for passenger cars of this invention, Preferably, it consists of the structure in any one of the following (2)-(8).
(2) The belt auxiliary layer has an initial stiffness value of 1.03 times to 1.5 times the initial stiffness value of the main belt layer. Radial tire.
(3) The pneumatic radial tire for passenger cars according to (1) or (2) above, wherein the steel cord constituting the main belt layer is a steel monofilament.
(4) The steel cord constituting the main belt layer is disposed in the belt layer as a bundle of wires composed of 2 to 5 steel monofilaments as a set. Pneumatic radial tires for passenger cars.
(5) The pneumatic radial tire for a passenger car according to (1) or (2), wherein the steel cord constituting the belt auxiliary layer is a steel cord formed by twisting two or more steel wires.
(6) the main the cord end count product of per cross-sectional area and 50mm width of the steel cord belt layers constituting the is 4.4 mm ² or more, above, wherein the at 6.8 mm ² or less (1) - (5) The pneumatic radial tire for passenger cars according to any one of (5).
(7) a product of the coding end count per cross-sectional area and 50mm wide steel cord constituting the main belt layer is 4.4 mm ² or more and 6.1 mm ² or less, the steel cord constituting the main belt layer The pneumatic radial tire for a passenger car according to any one of the above (1) to (6), wherein the strength of the tire is 3200 MPa or more.
(8) the product of the coding end count per cross-sectional area and 50mm wide steel cord constituting the main belt layer is 4.4 mm ² or more and 5.5 mm ² or less, the steel cord constituting the main belt layer The pneumatic radial tire for a passenger car according to any one of the above (1) to (7), wherein the strength of the tire is 3500 MPa or more.

  According to the first aspect of the present invention, even when the belt cord is reduced by reducing the rolling resistance, the driving stability is maintained at a high level, and the environmental load is reduced. Can achieve a pneumatic radial tire for passenger cars.

  According to the present invention according to any one of claims 2 to 8, it is possible to realize a pneumatic radial tire for a passenger car that has the effects obtained by the invention according to claim 1 more clearly and highly.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a tire meridian direction sectional view showing an embodiment of a pneumatic radial tire for passenger cars of the present invention. It is a tire meridian direction sectional view showing other examples of an embodiment of a pneumatic radial tire for passenger cars of the present invention. (A) is explanatory drawing explaining the positional relationship of the belt layer and belt auxiliary layer in the pneumatic radial tire for passenger cars shown in FIG. 1 in model, (b) is the pneumatic for passenger cars shown in FIG. It is explanatory drawing which modeled and demonstrated the positional relationship of the belt layer and belt auxiliary layer in a radial tire. It is a model sectional view explaining the cord arrangement in the main belt layer in the pneumatic radial tire for passenger cars of the present invention.

  Hereinafter, the pneumatic radial tire for passenger cars of the present invention will be described in more detail with reference to the drawings.

  1 and 2 each show a pneumatic radial tire for a passenger car according to the present invention, wherein 1 is a tread portion, 2 is a sidewall portion, 3 is a bead portion, and CL is a tire equator. A single 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 to the outside of the tire. A bead filler 6 having a triangular cross section made of rubber is disposed on the outer peripheral side of the bead core 5. On the outer side in the tire radial direction of the carcass layer 4 in the crown region, two main belt layers 10 (11, 12) are arranged over the entire circumference of the tire. The main belt layer 10 (11, 12) is configured by embedding belt cords 11a, 12a made of steel cords in rubber. The belt cords 11a and 12a are inclined at a low angle with respect to the tire circumferential direction, and in the present invention, the belt plies in which steel cords are embedded at an angle of 15 to 45 ° with respect to the tire circumferential direction intersect each other. The main belt 10 is formed by stacking two layers in the direction of movement.

  In the present invention, in particular, as the belt auxiliary layer 20, plies in which steel cords are embedded at an angle of 80 ° to 90 ° with respect to the tire circumferential direction are respectively connected from the width direction both end portions 11 b of the narrow main belt layer 11. The belt auxiliary layer 20 is disposed between the carcass layer 4 and the inner main belt layer 12 so that a part thereof is positioned at a position P 30 mm apart on the tire equator CL side, and the belt auxiliary layer 20 has a width W2 of 30 mm or more, and The initial stiffness value of the belt auxiliary layer 20 is larger than the initial stiffness value of the main belt layer 10 (11, 12).

  The difference between the one shown in FIG. 1 and the one shown in FIG. 2 is that the belt auxiliary layer 20 is divided into pieces 21 divided in the tire width direction across the tire equator CL in the one shown in FIG. 2 is formed as a single belt auxiliary layer 20 in the width direction across the tire equator CL. Note that the width W2 of the belt auxiliary layer described above refers to the width of each divided piece 21 in the case of a split type, and refers to the entire width in the case of a single sheet.

  FIG. 3A is an explanatory diagram schematically illustrating the positional relationship between the belt layer and the belt auxiliary layer (split type) in the pneumatic radial tire for passenger cars shown in FIG. 1, and FIG. FIG. 3 is an explanatory diagram that schematically illustrates the positional relationship between a belt layer and a belt auxiliary layer (one type) in the pneumatic radial tire for a passenger car illustrated in FIG. 2. In each of FIGS. 3 (a) and 3 (b), two figures are drawn up and down, but these figures do not correspond to each other in dimension on the drawing, and only the structure can be understood. It is easy to draw.

In the present invention,
(A) As the belt auxiliary layer 20, a ply in which a steel cord is embedded at an angle of 80 ° to 90 ° with respect to the tire circumferential direction is connected to the tire equator CL from the widthwise both ends 11 b of the narrow main belt layer 11. Disposed between the carcass layer 4 and the inner main belt layer 12 so that a part thereof is placed at a position P 30 mm apart on the side,
(B) The belt auxiliary layer 20 has a width W2 of 30 mm or more,
And,
(C) Use an initial stiffness value of the belt auxiliary layer 20 larger than the initial stiffness value of the main belt layer 10 (11, 12).
By satisfying these three requirements, the bending resistance in the main belt surface is improved without deteriorating the rolling resistance, and the effect of suppressing buckling outside the main belt surface is obtained. Excellent handling stability can be obtained.

The initial stiffness value X of the belt auxiliary layer and the initial stiffness value Y of the main belt layer are values defined by the following equations, respectively.
・ Belt auxiliary layer initial stiffness value X = Ex × Sx × Nx
Here, Ex: initial elastic modulus of belt auxiliary layer cord (calculated from elongation at 5N to 50N load)
Sx: Sum of strand cross-sectional area of belt auxiliary layer cord
Nx: number of auxiliary layer cords driven per 50 mm width, initial stiffness value of main belt layer Y = Ey × Sy × Ny
Here, Ey: initial elastic modulus of the main belt cord (calculated from elongation at 5N to 50N load)
Sy: Sum of strand cross-sectional area of main belt cord
Ny: Number of main belt cords driven per main 50 mm width When there are two main belt layers, the initial stiffness value Y for each main belt layer is obtained and an average value is taken.

  When the initial rigidity value of the belt auxiliary layer 20 is smaller than the initial rigidity value of the main belt layer 10 (11, 12), the effect of improving the bending rigidity in the main belt surface and the suppression of buckling to the outside of the main belt surface are suppressed. Since the effect is not sufficient, the effect of improving the steering stability tends to be insufficient, which is not preferable.

  Preferably, the initial stiffness value of the belt auxiliary layer is 1.03 to 1.5 times the initial stiffness value of the main belt layer. When the initial stiffness value of the belt auxiliary layer is too small, the effect of improving the steering stability as seen in the present invention is reduced, and the expected effect obtained by the present invention is reduced. On the other hand, if the wire amount is increased more than necessary to increase the initial stiffness value of the belt auxiliary layer, the effect of improving the steering stability is saturated, while the thickness and mass of the belt auxiliary layer are significantly increased. Therefore, it is preferable that the initial rigidity value of the main belt layer is about 1.5 times or less.

  On the other hand, the steel cords 11a and 12a constituting the main belt layers 11 and 12 are preferably steel monofilaments. The steel monofilament can be braided in a spiral shape or a plane wave shape, but it is preferable to use a straight monofilament that has not been subjected to various undulations. By using a straight monofilament, the main belt layer can be made thinner, and the effect of reducing rolling resistance can be obtained more greatly. A cross-sectional model diagram of the main belt layer in this case is illustrated in FIG.

  On the other hand, it is also preferable that the steel cords 11a and 12a constituting the main belt layers 11 and 12 are formed by being arranged in the belt layer in a bundle unit in which 2 to 5 pieces of steel monofilaments form a bundle. It is possible to improve the riding comfort in the case of a rigid single-wire belt layer that tends to be inferior in riding comfort due to the vibration damping effect by fretting between cords by arranging it in the belt layer as a bundled wire. . Further, it is more preferable from the viewpoint of reducing rolling resistance by increasing the wire interval (between bundles) in the belt layer and reducing the shear strain of rubber in the layer in contact deformation. FIG. 4B illustrates a cross-sectional model diagram of the main belt layer in which the cord is constituted by one bundle unit of three steel monofilaments in this case.

  The steel cord constituting the belt auxiliary layer is preferably used as a steel cord obtained by twisting two or more steel wires. Improve the drawbacks of using a single-wire belt, which tends to be inferior in general, because it is rigid and difficult to attenuate by using a stranded wire that is superior in damping property due to friction between strands between the main belt layer and the carcass In particular, the preferable number of driving is 15 to 35/50 mm width.

  As shown in FIGS. 1 and 2, the belt auxiliary layer is configured by embedding a belt auxiliary cord 20a made of a steel cord in rubber. The belt auxiliary cord 20a is inclined at a high angle with respect to the tire circumferential direction, and the inclination angle is 80 ° to 90 °, preferably 87 ° to 90 °. That is, it should be said that it was arranged in the radial direction. By providing the belt auxiliary layer 20 in this way, buckling of the main belt layer cords 11a and 12a was suppressed, and a monofilament was used as the main belt layer cord. Even in such a case, it becomes possible to supplement the fatigue resistance against bending to be reduced. As a result, it is possible to achieve both reduction in rolling resistance and maintenance of excellent steering stability.

Also, the code end counts the product of per cross-sectional area and 50mm wide steel cord constituting the main belt layer is 4.4 mm ² or more, it is preferable that 6.8 mm ² or less.

Alternatively, furthermore, the main code end counts the product of the belt layer per cross-sectional area and 50mm width of 10 steel cord constituting the is 4.4 mm ² or more and 6.1 mm ² or less, and the strength of the steel cord 3200 It is preferable that it is MPa or more.

If the product of the cross-sectional area of the steel cord constituting the main belt layer 10 and the number of driven wires per 50 mm width is smaller than 4.4 mm ² , the presence of the main belt layer cord 10a is present regardless of the strength range. This is not preferable because the amount is too small, the rigidity is insufficient and the durability is lowered. When the strength is 3200 MPa or more and the product of the cross-sectional area and the number of implantations is larger than 6.1 mm ² , or when the strength is 3500 MPa and the product of the cross-sectional area and the number of implantations is larger than 5.5 mm ² Since the amount of the main belt layer cord 10a is larger than the amount capable of sufficiently maintaining the durability in each strength range, the cord amount is too large, resulting in an increase in mass, and the cord interval is too narrow, so that the adhesiveness is increased. This is not preferable because the steering stability is rather lowered. Furthermore, since the energy loss of the belt rubber increases, the reduction of rolling resistance may be hindered, which is not preferable.

  In the pneumatic tire of tire size 195 / 65R15 91H, for the main belt layer, the belt cord type and initial stiffness of the main belt layer were changed as shown in Tables 1 to 3, respectively, and for the belt auxiliary layer, Tables 1 to 3 show the presence / absence of the belt auxiliary layer, the arrangement of the belt auxiliary cord, the arrangement of the belt auxiliary layer, the layer width, the presence / absence of overlap with the position P, and the number of driven belt reinforcing cords, respectively. 19 types of test tires of Conventional Examples 1-2, Comparative Examples 1-4, and Examples 1-13 were manufactured. The inclinations of the cords of the belt auxiliary layer are all 90 degrees with respect to the tire circumferential direction.

  With respect to these 19 types of test tires, actual vehicle handling stability and rolling resistance were evaluated by the following evaluation methods, and the results are also shown in Tables 1 to 3.

  Conventional Example 1 uses a normal main belt layer and is not provided with a belt auxiliary layer, and has a conventional general configuration.

  Conventional Example 2 is a reduction in the amount of wire in the main belt layer compared to Conventional Example 1, and it is clear that the rolling resistance is improved, but the actual vehicle handling stability is significantly deteriorated.

  In Comparative Example 2, it can be seen that even if the cord has the same rigidity and strength as the main belt layer, the actual vehicle handling stability deteriorates when the amount of the belt auxiliary layer used is small.

  As can be seen from Examples 1 to 3, the steering stability is remarkably improved by increasing the rigidity of the auxiliary layer, but the effect is saturated at about 1.5 times.

  As can be seen from Comparative Example 3, when the belt auxiliary layer is too inside, the buckling deformation of the surface of the main belt layer to the surface becomes easy, resulting in poor steering stability improvement effect.

  As can be seen from Comparative Example 4, if the width of the belt auxiliary layer is too narrow, a sufficient reinforcing effect cannot be obtained, so that the steering stability improving effect is poor as in Comparative Example 3.

  As can be seen from Examples 7-9, when the main belt layer cord is composed of a single wire, the belt gauge becomes thin and the rolling resistance is remarkably reduced. In particular, in Example 7, since it is composed of a single wire, the ride comfort is improved by reducing the gauge of the main belt, but it is considered that the good ride quality is offset by the rigidity of the wire. . In particular, in Example 8, since the two single wires are arranged together, it is considered that the good riding comfort is slightly offset by the attenuation due to the contact between the strands. In particular, in Example 9, two 90-degree stranded wires are arranged together, but it is considered that the good ride quality is slightly offset by attenuation due to contact between the strands.

  As can be seen from Examples 10-12, as a whole, in the structure having the auxiliary belt of 90 degrees, there is no change in the steering stability due to the change in the wire amount of the main belt layer. Further, due to a decrease in the amount of wire used as the strength of the wire increases, the static safety factor is equivalent and the rolling resistance can be reduced.

(1) Steering stability of a real vehicle A test tire consisting of a 6JJ × 15 rim and an internal pressure of 230kPa was mounted on a 1.8 liter FF passenger car, and the test course was run by five trained test drivers. The feeling of steering stability was evaluated.

  Evaluation was based on the following criteria, based on a relative comparison with the reference tire, and scored by the five-point method, and expressed by the average score of the three people excluding the highest and lowest points.

  Evaluation criteria: 5 points: Excellent, 4 points: Excellent, 3.5 points: Slightly superior, 3 points: Equivalent to criteria, 2.5 points: Slightly inferior (practical lower limit), 2 points: Inferior, 1 point: Large Inferior,

(2) Ride comfort of a real vehicle A test tire consisting of a rim of 6 JJ x 15 with an internal pressure of 230 kPa is mounted on a FF passenger car with a displacement of 1.8 liters, and the test course is run by five trained test drivers. The feeling of steering stability was evaluated.

  Evaluation was based on the following criteria, based on a relative comparison with the reference tire, and scored by the five-point method, and expressed by the average score of the three people excluding the highest and lowest points.

  Evaluation criteria: 5 points: Excellent, 4 points: Excellent, 3.5 points: Slightly superior, 3 points: Equivalent to criteria, 2.5 points: Slightly inferior (practical lower limit), 2 points: Inferior, 1 point: Large Inferior,

(3) Rolling resistance A test tire incorporated in a rim having a rim size of 15 × 6 J at a test internal pressure of 200 kPa was used with a drum tester made of steel with a smooth drum surface and a diameter of 1707 mm. The rolling resistance was measured when running at a speed of 80 km / hr with a load corresponding to 85% of the maximum load load at the indicated air pressure being applied to the drum.

  The measurement results are shown as an index with the measured value of the conventional tire 1 being 100. A larger index value means lower rolling resistance and better resistance.

1: Tread portion 2: Side wall portion 3: Bead portion 4: Carcass layer 5: Bead core 6: Bead filler 10, 11, 12: Main belt layer 11a, 12a: Main belt cord 11b: Width of narrow main belt layer Directional end portions 20: Belt auxiliary layer 21: Divided pieces of belt auxiliary layer P: Positions 30 mm away from both ends 11b in the width direction of the narrow main belt layer 11 toward the tire equator CL side

Claims (8)

  A passenger car having a main belt layer in which two layers of belt plies in which steel cords are embedded at an angle of 15 to 45 ° with respect to the tire circumferential direction are overlapped with each other in a direction intersecting each other on the outer side in the tire radial direction of the carcass layer in the crown region In pneumatic radial tires, plies in which steel cords are embedded at an angle of 80 to 90 ° with respect to the circumferential direction of the tire as a belt auxiliary layer are respectively connected to the tire equator side from both ends in the width direction of the narrow main belt layer. The belt auxiliary layer has a width of 30 mm or more and an initial rigidity value of the belt auxiliary layer of the main belt. A pneumatic radial tire for passenger cars, characterized by being larger than the initial stiffness value of the layer.   2. The pneumatic radial tire for a passenger car according to claim 1, wherein the belt auxiliary layer has an initial stiffness value of 1.03 times or more and 1.5 times or less of an initial stiffness value of the main belt layer.   The pneumatic radial tire for a passenger car according to claim 1 or 2, wherein a steel cord constituting the main belt layer is a steel monofilament. 4. The passenger car air according to claim 3, wherein the steel cord constituting the main belt layer is disposed in the belt layer as a bundle of wires composed of 2 to 5 steel monofilaments. Entering radial tire. The pneumatic radial tire for a passenger car according to claim 1 or 2, wherein the steel cord constituting the belt auxiliary layer is a steel cord obtained by twisting two or more steel wires. The main the cord end count product of per belt layer cross-sectional area and 50mm wide steel cord constituting the 4.4 mm ² or more, any one of the preceding claims, characterized in that it is 6.8 mm ² or less Pneumatic radial tire for passenger cars described in 1. The main the cord end count product of the belt layer per cross-sectional area and 50mm wide steel cord constituting the is 4.4 mm ² or more and 6.1 mm ² or less, the strength of the steel cord constituting the main belt layer passenger car pneumatic radial tire according to any one of claims 1 to 6, characterized in that a 3200 MPa or more. The main the cord end count product of per cross-sectional area and 50mm width of the steel cord belt layers constituting the is 4.4 mm ² or more and 5.5 mm ² or less, the strength of the steel cord constituting the main belt layer passenger car pneumatic radial tire according to any one of claims 1 to 7, characterized in that a 3500 MPa or more.

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