JP2010274801A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire compatibly satisfying wear resistance performance and low rolling resistance performance. <P>SOLUTION: The pneumatic tire 6 includes a belt constructed by sequentially disposing two inclined belt layers 3a and 3b in which a cord extending in an inclined direction with respect to an equatorial plane O of the tire 6 is rubber coated radially outside a crown section of a carcass 2; and at least one circumferential belt layer 4 in which a cord extending in the circumferential direction of the tire is rubber coated radially outside these inclined belt layers 3a and 3b; and includes a tread disposed radially outside the belt. In a cross section in a width direction of the tire, the ratio of a radial difference BD between a central part in the width direction and an end part in the width direction in the outermost layers of these inclined belt layers 3a and 3b, to a width BW of these outermost layers, namely, BD/BW is ≥0.01 and ≤0.04. The residual tension of the circumferential belt layer 4 in a center region CR of a tread section 5 is larger than the residual tension of the circumferential belt layer 4 in a shoulder region SR of the tread section 5. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a pneumatic tire having excellent uneven wear resistance and low rolling resistance.

In recent years, development of products with a smaller environmental load has been actively conducted. This is due to environmental problems such as global warming, and tires are no exception. With respect to this tire, in order to cope with the environmental problem, it is important to secure performance that contributes to reducing fuel consumption of the automobile. One means for achieving this is to reduce the rolling resistance of the tire, and various technical developments have been made in the past.
The following introduces some conventional improvements.

  First, it is known that a large amount of tire rolling resistance occurs in the rubber of the tread portion. As a direct improvement method, it is effective to change the rubber used for the tread portion to one having a small loss tangent. However, it is also known that this method sacrifices other performance of the tire, such as wear resistance. On the other hand, a method of reducing the tread thickness can be easily considered in order to reduce the rubber that is a source of increasing rolling resistance. However, in this case, the problem is that the wear life of the tire cannot be ensured.

  As means for solving the above problems, Patent Document 1 proposes reducing the rolling resistance by devising the cross-sectional shape of the tire. This proposal surely reduces the rolling resistance. Patent Document 2 proposes a pneumatic tire that devise the cross-sectional shape of the tire to achieve not only rolling resistance, but also other performance, particularly excellent wear resistance.

JP 2006-327502 Japanese Patent Application No. 2007-325279

  However, the pneumatic tire described in Patent Document 2 is difficult to obtain a tire having an actual arrangement of belt layers because the shape of the tire is deformed following the expansion of the bladder during manufacture. It was. Accordingly, an object of the present invention is to propose the details of the tire shape in order to provide a tire having excellent wear resistance and low rolling resistance.

  Inventors are able to improve the expected performance by regulating the shape of the tire in detail, especially in the case of shape design, not only the shape of the outer surface of the tire but also the reinforcement that becomes the skeleton of the tire Since the shape of the structure has a great influence on the tire performance, we have learned that it is effective to regulate it individually. In other words, suppressing the shear deformation in the tire width direction cross section, particularly in the tread on the outer side in the width direction, reduces the rolling resistance as a result of energy loss due to this deformation, and the shear force and slip resulting from this deformation. Thus, the present inventors have completed the present invention by finding that the wear often described can be improved at the same time, and that the belt structure can be optimized and the belt layer can be arranged as expected.

  The gist configuration of the present invention is as follows.

(1) With a carcass straddling a toroidal shape between a pair of bead portions, a large number of cords extending in a direction inclined with respect to the equatorial plane O of the tire are coated with rubber on the radially outer side of the crown portion of the carcass A belt formed by sequentially arranging at least two inclined belt layers, and at least one circumferential belt layer, which is rubber-coated with a cord extending in the tire circumferential direction on the radially outer side of the inclined belt layer, A pneumatic tire in which a tread is arranged on the outer side in the radial direction of the belt, and in the cross-section in the width direction of the tire, the width direction central portion and the width of the outermost layer with respect to the width BW of the outermost layer of the inclined belt layer In the tire in which the ratio BD / BW of the diameter difference BD from the direction end is 0.01 or more and 0.04 or less,
A pneumatic tire characterized in that a residual tension of the circumferential belt layer in the center region of the tread portion is larger than a residual tension of the circumferential belt layer in a shoulder region of the tread portion. The “residual tension” here refers to a value obtained by multiplying the residual tension (F) per cord by the number of cords to be driven (n) and the total number of spirals (residual tension = F × n × total number of spirals (N / cm)). The residual tension (F) per cord was measured as follows. Remove the rubber from the shoulder of the new tire that has not traveled until it reaches around the belt layer cord. The tire used for the test is a round tire that is not cut on the circumference. Cut tires or tire sections cannot be used because the residual stress changes. In order to make an accurate measurement, when peeling off, it is important to keep the rubber layer on the belt layer cord as much as possible, and at the same time pay the latest attention not to damage the cord. For a total of 10 cords, the length of 300 mm is accurately measured on the tire and the portion is marked. The cord is cut at points separated by 200 mm or more outside from the marking point. Thereafter, the cords are taken out one by one and the residual stress is measured. In this case, since the taken-out cord immediately shrinks due to the release of residual stress, if left as it is, the cord further shrinks due to the influence of humidity in the air. Within a minute), the cord sample is set on a chuck with a chuck interval of 450 mm of an autograph (S-500) made by Shimadzu with the sample immediately after being collected from the tire, and contracted at a speed of 10 mm / min. The cord sample is pulled until the mark point of the cord sample becomes 300 mm, the tension at that time is measured, and the average value of the ten cords is defined as the residual tension (F) per cord.

(2) The residual tension of the circumferential belt layer in the center region of the tread portion is in the range of 1.5 to 5.0 times the residual tension of the circumferential belt layer in the shoulder region of the tread portion. The pneumatic tire according to (1) above.

(3) The residual tension of the circumferential belt layer in the center region of the tread portion is in the range of 150 to 400 N / cm, and the residual tension of the circumferential belt layer in the shoulder region of the tread portion is 50 to 200 N / cm. The pneumatic tire according to (1) or (2), wherein the pneumatic tire is in a range.

(4) The rigidity of the cord constituting the circumferential belt layer in the center region of the tread portion is greater than the stiffness of the cord constituting the circumferential belt layer in the shoulder region of the tread portion. The pneumatic tire according to (1), (2) or (3).

(5) The thermal contraction rate of the cord constituting the circumferential belt layer in the center region of the tread portion is larger than the thermal contraction rate of the cord constituting the circumferential belt layer in the shoulder region of the tread portion. The pneumatic tire according to (1), (2) or (3), characterized in that it is characterized.

(6) When winding the cord constituting the circumferential belt layer around the forming drum at the time of tire manufacture, the tension of the winding of the cord in the circumferential belt layer portion arranged in the center area of the tread portion is as follows: The said (1), (2) or (3) characterized by being manufactured by making it larger than the tension | tensile_strength of the winding of the cord of the circumferential belt layer part distribute | arranged to the shoulder area of the said tread part. Pneumatic tires.

(7) The ratio CW / BW of the width BW of the outermost layer of the inclined belt layer to the width CW of the circumferential belt layer in the center region of the tread portion is 0.5 to 0.9, The pneumatic tire according to any one of (6) to (6).

  According to the present invention, it is possible to provide a tire having excellent wear resistance and low rolling resistance.

It is a figure which shows the cross section of the width direction of the tire according to this invention. It is a figure which shows the influence which BD / BW and CW / BW have on rolling resistance.

Hereinafter, the present invention will be specifically described with reference to the drawings.
FIG. 1 shows a cross section in the width direction of a tire according to the present invention. In the figure, reference numeral 1 denotes a pair of bead cores, and a carcass 2 made of a radial arrangement ply of a cord straddling the bead cores 1 in a toroidal shape is used as a skeleton, on the radially outer side of the crown portion of the carcass 2. At least two layers of the cords extending in a direction inclined with respect to the equator plane O are covered with rubber, and two inclined belt layers 3a and 3b in the illustrated example are disposed, and further radially outward of the inclined belt layer 3a. Further, at least one circumferential belt layer 4 in the illustrated example, in which a large number of cords extending along the equator plane O of the tire are covered with rubber, is disposed in the illustrated example, and the tread portion 5 is disposed on the outer side in the radial direction of these belts. It is arranged. Such a tire 6 is mounted on an applicable rim and used. Here, in the tire width direction cross section of the tire 6, as shown in FIG. 1, the width direction central portion (equatorial plane O) of the outermost layer 3 a with respect to the width BW of the outermost layer 3 a of the inclined belt layer, It is important that the ratio BD / BW of the diameter difference BD with respect to the end in the width direction is 0.01 or more and 0.04 or less. It is important that the residual tension of the circumferential belt layer 4 in the center region CR of the tread portion 5 is larger than the residual tension of the circumferential belt layer 4 in the shoulder region SR of the tread portion 5.

  This definition means that the inclined belt layer 3 has a small diameter difference in the width direction. That is, it shows that the belt is almost flat. That is, as described above, the rolling resistance is dominated by the energy loss generated in the rubber of the tire tread portion, and suppressing the shear deformation in the cross section in the width direction, which is one of the deformations, reduces the rolling resistance. It is effective for reduction. The cause of this shear deformation is a deformation in which a curved belt is stretched flat when touched. Further, in a normal radial tire, since the radius of the shoulder relative to the tire center is small and has a diameter difference, the belt near the shoulder is stretched in the tire circumferential direction. Then, the inclined belt layer in which the cords are arranged so as to cross each other is deformed into a pantograph shape and stretched in the circumferential direction, and as a result, contracts in the width direction, thereby promoting the shear deformation. In order to suppress this deformation most simply from the shape of the tire, it is necessary to make the belt as flat as possible. However, in actual tire design, it is necessary to consider the deformation component accompanying the deformation of the side part, the ground contact shape to prevent uneven wear, and the contact pressure distribution. It is important to set the range. The proper range is that the above-mentioned ratio BD / BW is 0.01 or more and 0.04 or less. More desirably, it is 0.02 or more and 0.035 or less. In particular, when the improvement for suppressing the above-described shear deformation is performed from the shape of the tread, the shearing force and the slip distribution in the contact surface change in a direction to be reduced, so that the wear resistance can be improved at the same time.

  When the tire 6 is manufactured by making the residual tension of the circumferential belt layer 4 in the center region CR of the tread portion 5 larger than the residual tension of the circumferential belt layer 4 in the shoulder region SR of the tread portion 5. In addition, it is possible to achieve the desired belt layer arrangement such that the ratio BD / BW is 0.01 or more and 0.04 or less even after the vulcanization molding process, and the rolling resistance is effectively reduced. Can be obtained.

  Further, in order to obtain the tire 6 having the expected performance as described above, the outermost layers of the inclined belt layers 3a and 3b with respect to the width CW of the circumferential belt layer 4 in the center region CR of the tread portion 5 are used. It is important that the ratio CW / BW of the width BW is 0.5 or more and 0.9 or less.

The experimental results that led to the above findings will be described in detail below.
That is, by using a radial tire of size 245/40 R18, the residual tension of the circumferential belt layer 4 in the center region CR of the tread portion 5 is made larger than the residual tension of the circumferential belt layer 4 in the shoulder region SR of the tread portion 5. The rolling resistance test was performed under the condition that the ratios BD / BW and CW / BW were variously changed while increasing. The rolling resistance is evaluated by converting it into an index (RRindex in the figure), and the smaller the value, the lower the rolling resistance is (see FIG. 2).

  As a result of the experiment, as shown in FIG. 2, it was recognized that the rolling resistance was significantly improved when the ratio CW / BW was in the range of 0.5 to 0.9. Note that if CW / BW is too small, BD / BW can be reduced, but only the belt layer in the center region CR is locally suppressed, so that only the belt layer in the center region CR becomes recessed. . Such a concave shape increases the generation of strain energy loss in the tread rubber and deteriorates the rolling resistance. Therefore, CW / BW is preferably 0.5 or more.

  Further, in order to obtain the belt layer arrangement as expected when the vulcanization molding is performed, the residual tension of the circumferential belt layer 4 in the center region CR of the tread portion 5 is the circumferential belt in the shoulder region SR of the tread portion 5. The residual tension of the layer 4 is preferably in the range of 1.5 to 5.0 times, specifically, the residual tension of the circumferential belt layer 4 in the center region CR of the tread portion 5 is 150 to 400 N / cm. The residual tension of the circumferential belt layer 4 in the shoulder region SR of the tread portion 5 is preferably in the range of 50 to 200 N / cm.

  As described above, as means for achieving the residual tension of the circumferential belt layer 4 in the center region CR of the tread portion 5 to be larger than the residual tension of the circumferential belt layer 4 in the shoulder region SR of the tread portion 5. Various methods are envisaged, and examples thereof include the following methods. For example, by making the rigidity of the cord 7a constituting the circumferential belt layer 4 in the center region CR of the tread portion 5 larger than the rigidity of the cord 7b constituting the circumferential belt layer 4 in the shoulder region SR of the tread portion 5 Achieved. Alternatively, the thermal contraction rate of the cord 7a constituting the circumferential belt layer 4 in the center region CR of the tread portion 5 is set to be higher than the thermal contraction rate of the cord 7b constituting the circumferential belt layer 4 in the shoulder region SR of the tread portion 5. This is achieved by increasing the size. Further, when the cord for constituting the circumferential belt layer is wound around the forming drum at the time of manufacturing the tire, the cord 7a of the circumferential belt layer portion arranged in the center region CR of the tread portion 4 is wound. This is achieved by making the tension of the belt 7 larger than the winding tension of the cord 7b of the circumferential belt layer portion disposed in the shoulder region SR of the tread portion 4.

  The above description shows only a part of the embodiment of the present invention, and these configurations can be combined alternately or various changes can be made without departing from the gist of the present invention.

  A radial tire of size 245/40 R18 was manufactured according to the specifications shown in Table 1, and mounted on an applicable rim of 8.0 J of the standard size specified by JATMA, and a rolling resistance test was performed. The basic structure of the tire is the same, and a pair of bead portions in which bead cores are embedded, sidewall portions extending radially outward from these bead portions, and radially outer ends of these sidewall portions are connected to each other. A substantially cylindrical tread portion is provided. In addition, a carcass formed of two layers of carcass plies extending in a toroidal shape between the bead cores is provided. Such a carcass ply is formed by twisting polyethylene cords extending in a direction inclined by 90 ° with respect to the equator direction. Two inclined belt layers are provided on the radially outer side of the carcass ply, and at least one circumferential belt layer is provided on the radially outer side of the inclined belt layer.

  The rolling resistance was determined by using a drum tester having a steel plate surface having a diameter of 1.7 m, and under conditions corresponding to an internal pressure of 230 kPa, a load load of 4.80 kN, and a tire rotational speed of 80 km / hr. Evaluation was made by calculating the force, converting the result of the conventional example into 100, converting it into an index, and comparing the result with other tires. It shows that rolling resistance is reducing, so that the obtained numerical value is small. Excluding errors, an improvement of 5% or more was regarded as a significant difference, and a large effect was obtained particularly when an improvement of 10% or more was observed.

  As shown in Table 1, the results of the evaluation are shown in Table 1. The tire according to the present invention achieves an appropriate belt arrangement, a significant difference in rolling resistance from the conventional example and the comparative example is recognized, and Examples 1 to 12 roll. It turns out that it is excellent in resistance.

1 Bead core 2 Carcass 3a Inclined belt layer (outermost layer)
3b Inclined belt layer 4 Circumferential belt layer 5 Tread portion 6 Tire 7a (Constructs a circumferential belt layer in the center region) Cord 7b (Constructs a circumferential belt layer in the shoulder region) Cord

Claims (7)

A carcass straddling a toroidal shape between a pair of bead portions, and a large number of cords extending in a direction inclined with respect to the equatorial plane O of the tire are coated with rubber on the radially outer side of the crown portion of the carcass, A belt formed by sequentially arranging two inclined belt layers, and at least one circumferential belt layer coated with rubber on a cord extending in the tire circumferential direction on the outer side in the radial direction of the inclined belt layer, A pneumatic tire in which a tread is arranged on the radially outer side, and in the cross-section in the width direction of the tire, the width direction center portion and the width direction end portion of the outermost layer with respect to the width BW of the outermost layer of the inclined belt layer In a tire having a diameter difference BD ratio BD / BW of 0.01 to 0.04,
A pneumatic tire characterized in that a residual tension of the circumferential belt layer in the center region of the tread portion is larger than a residual tension of the circumferential belt layer in a shoulder region of the tread portion.   The residual tension of the circumferential belt layer in the center region of the tread portion is in a range of 1.5 to 5.0 times the residual tension of the circumferential belt layer in the shoulder region of the tread portion. Pneumatic tires.   The residual tension of the circumferential belt layer in the center region of the tread portion is in the range of 150 to 400 N / cm, and the residual tension of the circumferential belt layer in the shoulder region of the tread portion is in the range of 50 to 200 N / cm. The pneumatic tire according to claim 1 or 2.   The rigidity of the cord constituting the circumferential belt layer in the center region of the tread portion is larger than the stiffness of the cord constituting the circumferential belt layer in the shoulder region of the tread portion. The pneumatic tire according to one item.   The thermal contraction rate of the cord constituting the circumferential belt layer in the center region of the tread portion is larger than the thermal contraction rate of the cord constituting the circumferential belt layer in the shoulder region of the tread portion. 4. The pneumatic tire according to any one of 3.   When the cord constituting the circumferential belt layer is wound around the forming drum at the time of tire manufacture, the tension of the cord winding of the circumferential belt layer portion arranged in the center region of the tread portion is the tread portion. The pneumatic tire according to any one of claims 1 to 3, wherein the pneumatic tire is manufactured with a tension greater than that of a cord wound in a circumferential belt layer portion disposed in a shoulder region of the tire.   The ratio CW / BW of the width BW of the outermost layer of the inclined belt layer to the width CW of the circumferential belt layer in the center region of the tread portion is 0.5 or more and 0.9 or less. The pneumatic tire according to item.

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