JP4687342B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire that simultaneously satisfies the contradictory characteristics based on a tire profile and a cap compound. More specifically, the present invention reduces rolling resistance during straight traveling and also provides steering stability and braking during cornering. The present invention relates to a pneumatic tire that can improve performance.

  In recent years, in order to reduce the impact on the environment, there is an increasing demand for low fuel consumption tires with reduced rolling resistance. Conventionally, as a method for reducing the rolling resistance of a pneumatic tire, it has been proposed to use a low exothermic cap compound having a low loss tangent tan δ at the tread portion. However, when using a low heat-generating cap compound, there is a problem that the braking distance at the time of braking is extended, and a side slip is likely to occur when turning a road curve, and the steering stability at cornering is lowered. is there.

On the other hand, in order to achieve both reduction of rolling resistance and improvement of steering stability and braking performance, a low tan δ cap compound is used at the center side portion of the tread portion, and a high tan δ cap at the shoulder side portion. It has been proposed to use a compound (see, for example, Patent Document 1). However, even when multiple types of cap compounds are used as described above, since both cap compounds are grounded during normal driving, the effect of reducing rolling resistance is not always sufficient, and there is relatively wear. There is a problem in that uneven wear tends to occur because the cap compound of fast high tan δ wears first.
JP 2005-22622 A

  An object of the present invention is to provide a pneumatic tire that reduces rolling resistance during normal running, improves steering stability and braking performance during cornering, and avoids the occurrence of uneven wear. It is in.

  In order to achieve the above object, the pneumatic tire of the present invention has a load profile of 130 at an internal pressure of 230 kPa specified by the standard in a tire profile in which the internal pressure is 230 kPa by fitting to a standard rim specified by the standard. A profile change point P1 in which the tread surface is concave is provided in the tread contact width TW when a load of% is applied, and a tire axial distance Da from the profile change point P1 to the tread center position P2 is defined as TW / 2 ×. The angle α formed by the straight line L1 extending in the tire axial direction through the tread center position P2 and the straight line L2 passing through the profile change point P1 and the tread center position P2 is 8 ° to 12 °. , An angle β formed by a straight line L3 passing through the profile change point P1 and the ground contact end position P3 when the 130% load is applied and the straight line L2. The first cap compound layer on the center side and the second cap compound layer on the shoulder side are arranged in the tread portion, and the tread surface of these first and second cap compound layers is set to 0 ° to 5 °. The distance Db in the tire axial direction from the boundary position P4 to the tread center position P2 is TW / 2 × 65% to 90%, and the ratio of tan δ of the second cap compound layer to tan δ of the first cap compound layer is It is characterized by being 1.5 to 3.0.

  In the present invention, the low tan δ first cap compound layer is disposed on the center side of the tread portion, the high tan δ second cap compound layer is disposed on the shoulder side of the tread portion, and the first cap during normal running The tire profile is set so that only the compound layer is grounded, and the second cap compound layer is grounded in addition to the first cap compound layer when a 130% load is applied during braking or cornering. Therefore, the rolling resistance during normal running can be reduced based on the physical properties of the first cap compound layer, and the steering stability and braking performance during cornering can be improved based on the physical properties of the second cap compound layer. . In addition, since the second cap compound layer is grounded only during high loads such as during braking and cornering, it is possible to avoid the occurrence of uneven wear due to the difference in physical properties between the first and second cap compound layers.

  In the present invention, it is preferable that the first and second cap compound layers are arranged so that the boundary thereof becomes the outer side in the tire axial direction as the inner side in the tire radial direction. Thereby, the uneven wear prevention effect can be further enhanced.

  Moreover, it is preferable to embed a belt cover layer having a laminated structure so as to cover the belt layer in the arrangement region of the second cap compound layer, and to increase the number of laminated belt cover layers toward the end of the belt layer. By increasing the restraining force of the belt layer in the arrangement region of the second cap compound layer and suppressing the outer diameter growth during traveling and the ground contact shape change during turning and braking, the uneven wear prevention effect can be further enhanced.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a pneumatic tire according to an embodiment of the present invention. In FIG. 1, 1 is a tread portion, 2 is a sidewall portion, and 3 is a bead portion. As shown in FIG. 1, a carcass layer 4 is mounted between a bead portion 3 on one side and the other bead portion (not shown), and an end portion of the carcass layer 4 is wound around the bead core 5 from the inside to the outside of the tire. It has been. 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 include reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between the layers. Further, a belt cover layer 7 is disposed on the outer peripheral side of the belt layer 6 so as to cover the end of the belt layer 6 in the tire width direction. The belt cover layer 7 includes reinforcing cords oriented in the tire circumferential direction.

  The tire profile in a state in which the pneumatic tire is fitted to the standard rim R defined by the standard to have an internal pressure of 230 kPa is set as follows. However, the standard is, for example, the JATMA standard. The tire profile means the contour of the outer surface of the tire in the tire meridian cross section.

  In the tire profile, a profile change point P1 in which the tread surface is concave is provided in the tread contact width TW when a load of 130% of the load capacity at the internal pressure of 230 kPa specified in the standard is applied. More specifically, the tire profile has a first arc with a radius of curvature TRa that has a center on the inner side in the tire radial direction from the tread surface and defines a profile on the center side, and a shoulder that has a center on the inner side in the tire radial direction from the tread surface. And a second arc having a radius of curvature TRa that defines the profile on the side, and a junction point between the first arc and the second arc is a profile change point P1. The first arc and the second arc may be directly joined, or may be smoothly joined via a third arc having a radius of curvature TRc centered on the outer side in the tire radial direction from the tread surface. In the case where the first arc and the second arc are smoothly joined via the third arc, the profile change point P1 means the intersection of the virtual extension line of the first arc and the virtual extension line of the second arc. It is. In either case, it is preferable to satisfy the relationship of TRb> TRa or TRb> TRa ≧ TRc. In particular, the curvature radius TRb is preferably 4.0 to 6.0 times the curvature radius TRa, and the curvature radius TRc is preferably 0.5 to 1.0 times the curvature radius TRa. By defining the dimensions of these arcs, the ground contact shape near the shoulder at the time of braking or cornering is stabilized, and a good uneven wear prevention effect can be obtained.

  Here, the distance Da in the tire axial direction from the profile change point P1 to the tread center position P2 is set to TW / 2 × 35% to 65%, more preferably TW / 2 × 45% to 60%. An angle α formed by a straight line L1 extending in the tire axial direction through the tread center position P2 and a straight line L2 passing through the profile change point P1 and the tread center position P2 is set to 8 ° to 12 °. The angle β formed by the straight line L3 and the straight line L2 passing through the grounding end position P3 when the profile change point P1 and 130% load is applied is set to 0 ° to 5 °. By setting the distance Da to TW / 2 × 35% to 65% and the angle α to 8 ° to 12 °, it is possible to suppress an increase in the ground contact width at the time of low load. Further, by setting the angle β to 5 ° or less, it is possible to suppress an increase in contact pressure near the shoulder during cornering. When the straight line L3 is located on the inner side in the tire radial direction than the straight line L2, the contact area near the shoulder at the time of braking decreases, so that the braking performance deteriorates.

  On the other hand, a cap compound layer 1A (first cap compound layer) is disposed on the center side of the tread portion 1, and a cap compound layer 1B (second cap compound layer) is disposed on the shoulder side of the tread portion 1. Yes. The distance Db in the tire axial direction from the boundary position P4 to the tread center position P2 on the tread surface of these cap compound layers 1A and 1B is TW / 2 × 65% to 90%, more preferably TW / 2 × 70% to It is set to 85%. The ratio [tan δ (B) / tan δ (A)] of the tan δ (B) of the cap compound layer 1B to tan δ (A) of the cap compound layer 1A is set to 1.5 to 3.0. In order to reduce rolling resistance during normal running, tan δ (A) at 60 ° C. of the center-side cap compound layer 1A is preferably set to 0.10 to 0.15. Here, tan δ uses a vulcanized rubber sheet having a thickness of 2 mm and is measured with a rheometric viscoelasticity tester (RDS-2 type) at a measurement temperature of 60 ° C., a frequency of 20 Hz, and a strain rate of 0.05%. Loss tangent measured under conditions.

  The cap compound layers 1A and 1B are preferably arranged so that the boundary thereof is on the outer side in the tire axial direction as the inner side in the tire radial direction. In other words, it is preferable that the exposed area of the low tan δ cap compound layer 1A is increased as wear progresses. In this case, the effect of preventing uneven wear can be further enhanced.

  Further, when a belt cover layer 7 having a laminated structure is embedded in the arrangement region of the cap compound layer 1B so as to cover the belt layer 6, the number of laminated belt cover layers 7 is increased toward the end of the belt layer 6. Good (see FIG. 2). In the case of such a laminated structure, it is possible to prevent uneven wear by increasing the binding force of the belt layer 6 in the region where the cap compound layer 1B is disposed, and suppressing the outer diameter growth during running and the ground contact shape change during turning and braking. The effect can be further enhanced.

  In the pneumatic tire described above, the low tan δ cap compound layer 1A is disposed on the center side of the tread portion 1, the high tan δ cap compound layer 1B is disposed on the shoulder side of the tread portion 1, and the vehicle travels straight under low load conditions. A tire profile is set such that only the cap compound layer 1A is grounded during traveling, and the cap compound layer 1B is grounded in addition to the cap compound layer 1A during braking and cornering. Therefore, it is possible to reduce rolling resistance during normal running based on the physical properties of the cap compound layer 1A, and to improve steering stability and braking performance during cornering based on the physical properties of the cap compound layer 1B. In addition, since the cap compound layer 1B is grounded only at the time of braking or cornering, it is possible to avoid the occurrence of uneven wear due to the difference in physical properties between the cap compound layers 1A and 1B.

  FIG. 3 shows the ground contact shape of the pneumatic tire. In FIG. 3, C1 shows a grounding shape when a specified load is applied when the tire is used (low load condition), and C2 shows a grounding shape when a load of 130% of the standard load capacity is applied (high load condition). Show. As shown in FIG. 3, in the pneumatic tire having the tire profile, the difference between the contact width under the low load condition and the contact width under the high load condition is large. That is, only the low tan δ cap compound layer 1A is grounded under low load conditions, but the high tan δ cap compound layer 1B is sufficiently grounded under high load conditions.

  4 shows a conventional pneumatic tire, and FIG. 5 shows a ground contact shape of the conventional pneumatic tire. In FIG. 5, C1 shows a grounding shape when a specified load is applied when the tire is used (low load condition), and C2 shows a grounding shape when a load of 130% of the standard load capacity is applied (high load condition). Show. As shown in FIG. 5, in the pneumatic tire provided with the conventional tire profile, the difference between the contact width under the low load condition and the contact width under the high load condition is small. That is, as shown in FIG. 3, when the low tan δ cap compound layer 1A and the high tan δ cap compound layer 1B are provided in the tread portion 1, both the cap compound layers 1A and 1B are always grounded regardless of the load conditions. It will be in the state. Therefore, the characteristics of the cap compound layers 1A and 1B cannot be utilized depending on the situation.

  In the pneumatic tire of tire size 195 / 65R15 91H, tires of conventional examples, examples 1 to 3 and comparative examples 1 and 2 having different tire profiles and cap compounds were produced. In all the test tires, a low tan δ cap compound layer was disposed on the center side of the tread portion, and a high tan δ cap compound layer was disposed on the shoulder side of the tread portion, and the ratio of both tan δ was 2.0.

  In the conventional tire, the tire profile within the tread contact width TW is configured by a single arc having a curvature radius TR. The tread contact width TW was 150 mm and the curvature radius TR was 400 mm. Further, the distance Db in the tire axial direction from the boundary position on the tread surface of both cap compound layers to the center position of the tread was set to TW / 2 × 65%.

  In the tires of Examples 1 to 3 and Comparative Examples 1 and 2, the tire profile in the tread contact width TW is configured by three types of arcs of curvature radii TRa, TRb, and TRc, and the tread surface is recessed in the tread contact width TW. A profile change point is provided. The tread contact width TW was 156 mm, the radius of curvature TRa was 150 mm, the radius of curvature TRb was 600 mm, and the radius of curvature TRc was 100 mm. The angle α defining the profile was 10 °, and the angle β was 2.5 °. The distance Da in the tire axial direction from the profile change point to the center position of the tread and the distance Db in the tire axial direction from the boundary position on the tread surface of both cap compound layers to the center position of the tread were set as shown in Table 1. .

  For these test tires, rolling resistance, braking performance, uneven wear characteristics, cornering force, and steering stability were evaluated under the conditions of a rim size of 15 × 6JJ and an internal pressure of 230 kPa according to the following test methods. The results are also shown in Table 1. It was.

Rolling resistance:
The rolling resistance of the test tire was measured using a rolling resistance tester. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. It means that rolling resistance is so small that this index value is large.

Braking performance:
The test tire was mounted on a 2000 cc class minivan, and the braking test on the test course was performed five times, and the average value of the braking distance was obtained. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. A larger index value means better braking performance.

Uneven wear characteristics:
The test tire was mounted on a 2000 cc class minivan and a wear test on a test course was conducted. A larger score means less uneven wear.

Cornering Force:
Using a cornering force tester, the cornering force of the test tire was measured under conditions of a slip angle of 3 ° and a load load of 8 kN. The evaluation results are shown as an index with the conventional example being 100. A larger index value means a larger cornering force.

Steering stability:
The test tire was mounted on a 2000 cc class minivan and a sensory evaluation of steering stability by a test driver was performed. The evaluation results are shown as an index with the conventional example being 100. The larger the index value, the better the steering stability.

  As shown in Table 1, in the tires of Examples 1 to 3, better results than the conventional example were obtained with respect to all evaluation items regarding rolling resistance, braking performance, uneven wear characteristics, cornering force, and steering stability. . On the other hand, in Comparative Examples 1 and 2 in which the distances Da and Db are out of the specified range, good results were not obtained for some evaluation items.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is a meridian half sectional view showing a pneumatic tire according to another embodiment of the present invention. It is a top view which shows the contact shape of the pneumatic tire of FIG. It is a meridian half sectional view showing a conventional pneumatic tire. It is a top view which shows the contact shape of the pneumatic tire of FIG.

Explanation of symbols

1 tread portion 1A center side cap compound layer 1B shoulder side cap compound layer 2 sidewall portion 3 bead portion 4 carcass layer 5 bead core 6 belt layer 7 belt cover layer P1 profile change point P2 tread center position P3 ground end position R standard Rim TW tread ground contact width

Claims (3)

  In a tire profile that is fitted to a standard rim specified by the standard and has an internal pressure of 230 kPa, the tread is within the tread contact width TW when a load of 130% of the load capacity at the internal pressure of 230 kPa specified by the standard is applied. A profile change point P1 having a concave surface is provided, and a distance Da in the tire axial direction from the profile change point P1 to the tread center position P2 is set to TW / 2 × 35% to 65%, and passes through the tread center position P2. An angle α formed by a straight line L1 extending in the tire axial direction and the straight line L2 passing through the profile change point P1 and the tread center position P2 is 8 ° to 12 °, and the ground at the time of loading the profile change point P1 and the 130% load. An angle β formed by the straight line L3 passing through the end position P3 and the straight line L2 is set to 0 ° to 5 °, and the center side first A cap compound layer and a second cap compound layer on the shoulder side are disposed, and a distance Db in the tire axial direction from the boundary position P4 on the tread surface of these first and second cap compound layers to the tread center position P2 Is a TW / 2 × 65% to 90%, and the ratio of tan δ of the second cap compound layer to tan δ of the first cap compound layer is 1.5 to 3.0.   2. The pneumatic tire according to claim 1, wherein the first and second cap compound layers are arranged such that a boundary thereof becomes an outer side in the tire axial direction toward the inner side in the tire radial direction. The belt cover layer having a laminated structure is embedded in the arrangement region of the second cap compound layer so as to cover the belt layer, and the number of laminated belt cover layers is increased toward the end of the belt layer. Alternatively, the pneumatic tire according to claim 2.

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