JP2007076594A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire with enhanced steering stability and braking property by reducing the rolling resistance. <P>SOLUTION: In the tire profile fitted to a standard rim with the internal pressure being 230 kPa, a first arc of the radius of curvature TRa, a second arc of the radius of curvature TRb, and a third arc of the radius of curvature TRc are formed on the tread ground contact width TW from the side A to the side B when applying the load of 130% thereto so that the distance Dtc in the axial direction from the tread center P0 to the shifting point P1 of the first arc and the second arc satisfies the inequality Dtc/TW≤0.15; the distance Da in the axial direction from the point P1 to the ground contact end P3 on the side B and the distance Db in the axial direction to the shifting point P2 of the second arc and the third arc satisfies inequalities 0.45 ≤Db/Da≤0.75; the angle α formed by the line L1 in the axial direction passing through the point P1 and the line L2 passing through the points P1 and P2 is set to be 8-12°; the angle β formed by the line L3 passing through the point P2 and the ground contact end position P3 on the side B and the line L2 is set to be 2-6°; and the angle γ formed by the line L4 passing through the point P1 and the ground contact end position P4 on the side A and the line L1 is set to be 5-9°; and the inequalities α>γ>β are satisfied. <P>COPYRIGHT: (C)2007,JPO&INPIT

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 capable of reducing rolling resistance during normal running and improving steering stability and braking performance during cornering.

  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. % Of the curvature radius TRa that protrudes outward in the tire radial direction from one (A) side in the tire axial direction to the other (B) side within the tread contact width TW when a load of% is applied. An arc, a second arc of curvature radius TRb that protrudes outward in the tire radial direction, and a third arc of curvature radius TRc that protrudes outward in the tire radial direction are formed, and the first arc changes to the second arc. The point P1 is arranged on the A side from the tread center position P0, and the point P2 where the second arc changes to the third arc is arranged on the B side from the tread center position P0, and from the tread center position P0 to the point P1. tire The distance Dtc in the direction is Dtc / TW ≦ 0.15, and the distance Da in the tire axial direction from the point P1 to the ground contact end position P3 on the B side and the distance Db in the tire axial direction from the point P1 to the point P2 are 0. .45 ≦ Db / Da ≦ 0.75, the angle α formed by the straight line L1 extending in the tire axial direction through the point P1 and the straight line L2 passing through the points P1 and P2 is 8 ° to 12 °, and B The ground contact end position P3 on the side is arranged on the outer side in the tire radial direction from the straight line L2, and the angle β formed by the straight line L3 passing through the point P2 and the ground contact end position P3 on the B side and the straight line L2 is 2 ° to 6 ° The angle γ formed by the straight line L4 and the straight line L1 passing through the ground contact end position P4 on the P1 and A side is set to 5 ° to 9 °, and the relationship of α> γ> β is satisfied. .

  In the present invention, only the region on the A side centering on the boundary point P1 between the first arc and the second arc is grounded during normal traveling, and the tread grounding width TW is set at 130% load assuming braking or cornering. The tire profile is set so that the entire area touches down. Therefore, during normal running, the ground contact width can be reduced to reduce rolling resistance, and the cornering width can be extended during cornering or braking to improve steering stability and braking performance.

  In the present invention, the first cap compound layer is disposed on the A side of the tread portion, and the second cap compound layer is disposed on the B side of the tread portion, and the tread surfaces of these first and second cap compound layers The distance Dc in the tire axial direction from the boundary position P5 to the point P1 in this case is 0.45 ≦ Dc / Da ≦ 0.90, and tan δ of the second cap compound layer is the tan δ of the first cap compound layer. It is preferably 1.5 to 2.5 times.

  Thus, when the first cap compound layer having a low tan δ is arranged on the A side of the tread portion and the second cap compound layer having a high tan δ is arranged on the B side of the tread portion, the first cap compound in normal driving Only the layer is grounded, and in addition to the first cap compound layer, the second cap compound layer is also grounded when a 130% load is applied assuming 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.

  Further, a belt cover layer is disposed on the outer peripheral side of the belt layer embedded in the tread portion, and the binding force based on the belt cover layer is relative to the B side region relative to the A side region with the tread central position P0 as a boundary. It is preferable to make it large. By relatively increasing the restraining force based on the belt cover layer in the region on the B side, the tire profile during inflation and running can be stabilized, and the change in the ground contact shape during turning and braking can be stabilized. As a result, the effect of preventing uneven wear can be further enhanced. In particular, a belt cover layer having a laminated structure may be 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 may be increased toward the end of the belt layer.

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 pair of bead portions 3 and 3, 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. 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 such 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 an 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, within the tread contact width TW when a load of 130% of the load capacity at the internal pressure of 230 kPa defined in the above standard is applied, from one side in the tire axial direction (A side in the figure) To the other side (B side in the figure), a first arc of curvature radius TRa that protrudes outward in the tire radial direction, a second arc of curvature radius TRb that protrudes outward in the tire radial direction, and the tire radial direction A third arc having a radius of curvature TRc that is convex outward is formed. The first arc and the second arc are joined so as to contact each other with a point P1 positioned on the A side from the tread center position P0 as a boundary. The second arc and the third arc are joined at a point P2 located on the B side from the tread center position P0. The second arc and the third arc may be directly joined, or may be smoothly joined via a fourth arc having a curvature radius TRd that protrudes inward in the tire radial direction. When the second arc and the third arc are smoothly joined via the fourth arc, the boundary point P2 means the intersection of the virtual extension line of the second arc and the virtual extension line of the third arc. Is.

  In any case, it is preferable that the relationship of TRc> TRa> TRb or TRc> TRa> TRb ≧ TRd is satisfied. In particular, the curvature radius TRa is 1.5 to 3.0 times the curvature radius TRb, the curvature radius TRc is 3.0 to 6.0 times the curvature radius TRb, and the curvature radius TRd is 0.5 times the curvature radius TRb. It is good to be -1.0 times. 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 Dtc in the tire axial direction from the tread center position P0 to the point P1 is set to Dtc / TW ≦ 0.15, more preferably 0.10 ≦ Dtc / TW ≦ 0.15. The distance Da in the tire axial direction from the point P1 to the ground contact end position P3 on the B side and the distance Db in the tire axial direction from the point P1 to the point P2 are 0.45 ≦ Db / Da ≦ 0.75, more preferably 0. .55 ≦ Db / Da ≦ 0.65 is set. An angle α formed by a straight line L1 extending in the tire axial direction through the point P1 and a straight line L2 passing through the points P1 and P2 is set to 8 ° to 12 °. By setting the positional relationship between the points P1 and P2 as described above, it is possible to suppress an increase in the grounding width at the time of low load.

  Further, the B-side contact end position P3 is disposed on the outer side in the tire radial direction from the straight line L2, and the angle β formed by the straight line L3 and the straight line L2 passing through the point P2 and the B-side contact end position P3 is 2 ° to 6 °. Is set to By setting the B-side contact end position P3 as described above, an increase in the contact surface pressure near the B-side shoulder during cornering can be suppressed. If the angle β is less than 2 °, that is, if the B-side contact end position P3 is in a direction away from the road surface, the contact area near the shoulder is reduced during braking, resulting in a reduction in braking performance.

  Further, the angle γ formed by the straight line L4 and the straight line L1 passing through the point P1 and the A-side grounding end position P4 is set to 5 ° to 9 °. The angles α, β, and γ are in a relationship of α> γ> β. By setting the A-side grounding end position P4 as described above, the A-side grounding area during normal traveling can be increased and the B-side grounding area can be reduced, so that an effect of reducing rolling resistance can be obtained.

  On the other hand, a cap compound layer 1A (first cap compound layer) is disposed on the A side of the tread portion 1, and a cap compound layer 1B (second cap compound layer) is disposed on the B side of the tread portion 1. Yes. The distance Dc in the tire axial direction from the boundary position P5 to the point P1 on the tread surface of these cap compound layers 1A and 1B is 0.45 ≦ Dc / Da ≦ 0.90, more preferably 0.60 ≦ Dc / Da. The relation of ≦ 0.70 is set. The tan δ (B) of the cap compound layer 1B is set to 1.5 to 2.5 times the tan δ (A) of the cap compound layer 1A.

  Based on the physical properties of the cap compound layer 1A during normal driving, a low tan δ cap compound layer 1A is used for the grounding part during normal driving and a high tan δ cap compound layer 1B is used for the grounding part during high load. It is possible to reduce rolling resistance and improve steering stability and braking performance during cornering based on the physical properties of the cap compound layer 1B. In order to reduce the rolling resistance during normal running, tan δ (A) at 60 ° C. of the A-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.

  In addition, a belt cover layer 7 is disposed on the outer peripheral side of the belt layer 6 embedded in the tread portion 1, and the restraining force based on the belt cover layer 7 is a region on the A side with the tread center position P0 as a boundary. It is better to make it relatively larger in the region on the B side. The binding force based on the belt cover layer 7 can be adjusted based on the number of stacked belt cover layers 7, the material, the cord driving density, and the cord tension. Thus, by relatively increasing the restraining force based on the belt cover layer 7 in the region on the B side, the tire profile during inflation and running can be stabilized, and the grounding shape during turning and braking can be stabilized. The change can be stabilized, and as a result, the effect of preventing uneven wear can be further enhanced.

  In particular, 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, and the number of laminated belt cover layers 7 is preferably increased toward the end of the belt layer 6. (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, only the region on the A side centering on the boundary point P1 between the first arc of the curvature radius TRa and the second arc of the curvature radius TRb is grounded during normal running, and is assumed at the time of braking or cornering. The tire profile is set so that the entire tread contact width TW contacts the ground when a 130% load is applied. Therefore, during normal running, the ground contact width can be reduced to reduce rolling resistance, and the cornering width can be extended during cornering or braking to improve steering stability and braking performance.

  Further, when the low tan δ cap compound layer 1A is arranged on the A side of the tread portion 1 and the high tan δ cap compound layer 1B is arranged on the B side of the tread portion 1, the cap compound layer is used during straight traveling under a low load condition. Only 1A is grounded, and the cap compound layer 1B is also 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. In the low load condition, only the low tan δ cap compound layer 1A is grounded, but in the high load condition, the high tan δ cap compound layer 1B is also sufficiently grounded.

  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. 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.

  When the pneumatic tire is mounted on the vehicle, either the A side or the B side may be disposed outside the vehicle, but it is preferable to select the mounting direction according to the suspension type of the vehicle. That is, in the above pneumatic tire, the ground contact width mainly extends to the B side under high load conditions, so that the characteristics can be effectively utilized.

  For example, when the suspension of the front wheels is a strut type, a higher braking effect can be obtained by attaching tires to the vehicle with the A side facing the outside of the vehicle. This is because if the strut suspension sinks during braking, the negative camber becomes larger and the B side can be easily grounded.

  On the other hand, when the front wheel suspension is of the double wishbone type, both the braking performance and the cornering performance can be achieved by attaching the tire to the vehicle with the B side facing the outside of the vehicle.

  Also, in racing tires that run on oval courses, when the course is counterclockwise, the tires are mounted on the vehicle with the B side facing the right side of the vehicle. It is possible to increase the maximum speed by reducing rolling resistance. Since there is almost no strong braking in oval course races, it is more important to improve cornering performance than to improve braking performance.

  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 the conventional tire, the tire profile within the tread contact width TW is configured by a single arc having a radius of curvature TR (see FIG. 4). The tread contact width TW was 150 mm and the curvature radius TR was 400 mm. In addition, 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 tires of Examples 1 to 3 and Comparative Examples 1 and 2, the tire profile within the tread contact width TW is configured by four types of arcs of curvature radii TRa, TRb, TRc, and TRd (see FIG. 1). The tread contact width TW was 145 mm, the radius of curvature TRa was 262.48 mm, the radius of curvature TRb was 142.97 mm, the radius of curvature TRc was 600 mm, and the radius of curvature TRd was 100 mm. The distance Dtc in the tire axial direction from the tread center position P0 to the point P1 was 10 mm (= TW × 0.07). The angle α defining the profile was 10 °, the angle β was 4.5 °, and the angle γ was 7 °. The distance Da in the tire axial direction from the point P1 to the B-side ground contact position P3 and the distance Db in the tire axial direction from the point P1 to the point P2 were set as shown in Table 1. A low tan δ cap compound layer was disposed on the A side of the tread portion, and a high tan δ cap compound layer was disposed on the B side of the tread portion, and the ratio of both tan δ was 2.0. The distance Dc in the tire axial direction from the boundary position P5 to the point P1 on the tread surface of both cap compound layers was 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 was conducted on a test course. The degree of uneven wear during running at 10,000 km was evaluated based on a five-point rating. A larger score means less uneven wear.

Cornering Force:
The cornering force of the test tire was measured using a cornering force tester under the conditions of a slip angle of 3 ° and a load load of 7.8 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 dimensional requirements deviate from the specified range, good results were not obtained for some evaluation items.

It is meridian sectional drawing which shows the pneumatic tire which consists of embodiment of this invention. It is meridian sectional drawing which shows the pneumatic tire which consists of other embodiment of this invention. It is a top view which shows the contact shape of the pneumatic tire of FIG. It is meridian sectional drawing which shows the conventional pneumatic tire. It is a top view which shows the contact shape of the pneumatic tire of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 1A 1st cap compound layer 1B 2nd cap compound layer 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Belt layer 7 Belt cover layer P0 Tread center position P1 1st circular arc changes to 2nd circular arc Point P2 Point where the second arc changes to the third arc P3 B-side contact end position P4 A-side contact end position P5 Boundary position between the first and second cap compound layers R Standard rim TW Tread contact width

Claims (5)

  In the tire profile in which the internal pressure is set to 230 kPa by fitting to the standard rim specified by the standard, within the tread contact width TW when a load of 130% of the load capacity at the internal pressure 230 kPa specified by the standard is applied, A first arc of a curvature radius TRa that protrudes outward in the tire radial direction and a curvature radius TRb that protrudes outward in the tire radial direction from one (A) side to the other (B) side in the tire axial direction. A second arc and a third arc having a radius of curvature TRc that protrudes outward in the tire radial direction are formed, and a point P1 at which the first arc changes to the second arc is arranged on the A side from the tread center position P0. The point P2 at which the second arc changes to the third arc is arranged on the B side from the tread center position P0, and the distance Dtc in the tire axial direction from the tread center position P0 to the point P1 is Dtc / TW ≦ 0.15. Relationship and The distance Da in the tire axial direction from the point P1 to the ground contact position P3 on the B side and the distance Db in the tire axial direction from the point P1 to the point P2 have a relationship of 0.45 ≦ Db / Da ≦ 0.75. An angle α formed by a straight line L1 extending through the tire P1 in the tire axial direction and a straight line L2 passing through the points P1 and P2 is 8 ° to 12 °, and the ground contact end position P3 on the B side is radially outside of the straight line L2. The angle β formed by the straight line L3 and the straight line L2 passing through the point P2 and the B-side grounded end position P3 is 2 ° to 6 °, and the straight line L4 and straight line passing through the point P1 and the grounded end position P4 on the A side A pneumatic tire in which an angle γ formed by L1 is 5 ° to 9 ° and satisfies a relationship of α> γ> β.   The first cap compound layer is disposed on the A side of the tread portion, and the second cap compound layer is disposed on the B side of the tread portion, and the boundary positions of the first and second cap compound layers on the tread surface The distance Dc in the tire axial direction from P5 to the point P1 has a relationship of 0.45 ≦ Dc / Da ≦ 0.90, and tan δ of the second cap compound layer is 1.5 to tan δ of the first cap compound layer. The pneumatic tire according to claim 1, which is 2.5 times larger.   3. 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 an inner side in the tire radial direction.   A belt cover layer is disposed on the outer peripheral side of the belt layer embedded in the tread portion, and the binding force based on the belt cover layer is relatively greater in the B side region than in the A side region with the tread central position P0 as a boundary. The pneumatic tire according to claim 1, which is enlarged. 5. 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. Pneumatic tire described in 2.

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