JPH11222013A - Pneumatic tire for passenger car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable the reception of rolling resistance, without deteriorating tire performance such as wet performance, wearing resistance, etc. SOLUTION: In a pneumatic tire for a passenger car with a carcass layer 2 mounted between a pair of right and left beads 1, 1 and a two-layer belt layers 7a, 7b arranged in a peripheral side of the carcass layer 2 in a tread part 4, a width Wb of the belt 7b second from a side of carcass layer 2 is set for 95 to 110% tread grounded width Wc. A hollowed part 9 is provided in a shoulder part, and a center position Pc of this hollowed part 9 is arranged in a 8 to 25% range of the belt width Wb toward a side of the bead part 1 from a belt end Eb of the second belt layer 7b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire that promotes low fuel consumption of a vehicle, and more particularly, to a pneumatic tire without impairing tire performance such as running performance on wet roads (wet performance) and wear resistance. And a pneumatic tire capable of reducing rolling resistance.

[0002]

2. Description of the Related Art Conventionally, in order to reduce the rolling resistance of a tire, a rubber having a low fuel consumption is mainly used for a cap tread. In other words, the cap tread has the largest volume as a single part, and rubber with a large hysteresis loss is generally used to ensure abrasion resistance. Dynamic resistance can be reduced.

[0003] However, when low-fuel-consumption rubber is used for the cap tread in order to reduce rolling resistance, there has been a problem that tire performance such as wet performance and abrasion resistance necessarily decreases. Also, reducing the thickness of the cap tread as a whole is effective in reducing the rolling resistance, but also in this case, the wear life is reduced according to the decrease in the cap tread thickness, and the groove depth is reduced. As a result, the wet performance deteriorates.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a tire without impairing tire performance such as wet performance and wear resistance.
It is an object of the present invention to provide a pneumatic tire for a passenger car that can reduce rolling resistance.

[0005]

In order to achieve the above object, a pneumatic tire for a passenger car according to the present invention has a carcass layer mounted between a pair of right and left bead portions, and is provided on an outer peripheral side of the carcass layer in a tread portion. In a pneumatic tire for a passenger car in which two belt layers are arranged, the width of the second belt layer counted from the carcass layer side is 95 to 1 of the tread contact width.
10% and a concave portion is provided in the shoulder portion, and the center position of the concave portion is set to 8 to 2 of the belt width from the terminal in the tire width direction of the second belt layer toward the bead portion.
It is characterized by being arranged in a range of 5%.

[0006] As described above, from the end of the second belt layer in the tire width direction to the bead portion side, 8 to 25% of the belt width is increased.
By providing a concave portion in the shoulder portion around the position, stress generated in the shoulder portion can be reduced, energy loss concentrated on this portion can be effectively suppressed, and rolling resistance can be reduced. Accordingly, it is not necessary to use a low fuel consumption rubber having a small hysteresis loss for the cap tread, so that rolling resistance can be reduced without impairing tire performance such as wet performance and wear resistance. In addition, even if the depression is provided in the shoulder portion as described above, the width of the second belt layer is specified with respect to the tread contact width, and the center position of the depression is determined by the tire width of the second belt layer. By specifying from the direction terminal, the steering stability, the durability of the belt end portion, and the uneven wear resistance of the shoulder portion are not reduced.

In the present invention, the tread contact width is defined as JA.
In the air pressure-load capacity correspondence table specified in the TMA Yearbook (1997 version), the air pressure was set to 200 kPa.
And the contact width when a load of 75% of the maximum load capacity corresponding to the air pressure is applied.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The configuration of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 illustrates a pneumatic tire for a passenger car according to an embodiment of the present invention. In the figure, a carcass layer 2 in which a plurality of reinforcing cords are arranged in a radial direction is mounted between a pair of left and right bead portions 1, 1, and both end portions of the carcass layer 2 in the tire width direction are each a bead core 3. Is wound up from the inside of the tire to the outside. A pair of left and right bead portions 1
The tread portion 1 and the tread portion 4 are connected to each other via left and right sidewall portions 5 and 5. A bead filler 6 is arranged on the outer peripheral side of the bead core 3, and the bead filler 6 is wrapped by the carcass layer 2.

On the outer peripheral side of the carcass layer 2 in the tread portion 4, there are provided two belt layers 7a and 7b each having a plurality of reinforcing cords covered with coat rubber. These belt layers 7a and 7b are arranged such that the reinforcing cords are inclined with respect to the tire circumferential direction, and the reinforcing cords intersect each other between the layers. In the shoulder portion, a belt cover layer 8 in which an organic fiber cord such as nylon or polyester is disposed substantially parallel to the tire circumferential direction is embedded so as to cover at least both ends in the tire width direction of the belt layers 7a and 7b. You may.

In the above pneumatic tire, the belt width Wb of the second belt layer 7b counted from the carcass layer 2 side
Is set in the range of 95 to 110%, more preferably 97 to 105% of the tread contact width Wc. This belt width Wb
Is less than 95% of the tread contact width Wc, the stiffness near the contact end is reduced, and the movement of the tread at the time of contact increases, causing uneven wear to the shoulder portion. Belt end E at the center of bending deformation caused by grounding
Since b enters, the durability of the belt end portion is reduced.

The tread portion 4 and the side wall portion 5
The recess 9 is provided in the shoulder between them. The center position (center position in the meridian section) Pc of the recess 9 is the second position where the belt width Wb is set as described above.
It is necessary to arrange the belt layer 7b in the range of 8 to 25% of the belt width Wb from the belt end Eb toward the bead portion 1 side. By arranging the center position Pc of the depression 9 in such a range, the steering stability, the durability of the belt end portion,
It does not decrease curb resistance and uneven wear resistance of the shoulder.

More specifically, the starting point Ps on the crown center side of the depression 9 is set at a position separated from the ground end Ec by 1.5% or more of the ground width Wc toward the bead 1. By separating the depression 9 from the grounding end Ec in this manner, the grounding width does not decrease even at the time of cornering, so that a decrease in steering stability can be prevented. Further, by separating the depression 9 from the ground end Ec, the depression 9 is not affected by the compressive stress in the direction of the ground pressure.
The length of the depression 9 in the tire circumferential direction can be increased without increasing the compression strain, and the rolling resistance can be further reduced. Therefore, it is preferable that the depression 9 is continuous in the tire circumferential direction. The depression 9 may be discontinuous in the tire circumferential direction, but in that case, the depression 9
Is preferably 50% or more of the tire circumferential length.

The starting point Ps of the depression 9 on the crown center side is 3.5 to 7.5% of the belt width from the belt end Eb of the second belt layer 7b toward the bead 1 side. Set. By separating the depression 9 from the belt end Eb in this way, the center of the bending deformation caused by the contact with the ground during rolling can be shifted from the belt end where the failure is most likely to occur in the tire. Deterioration of durability can be prevented. In addition, by setting the starting point Ps of the depression 9 at the above-described position, it is conventionally the center of the bending deformation,
In addition, the center of the bending deformation is shifted from the belt end Eb of the second belt layer 7b having a large gauge and a large rubber volume, and the bending deformation at the time of rolling is effectively absorbed. Can be improved. In addition, the starting point Ps of the depression 9 is moved from the belt end Eb to the bead 1.
When the belt is disposed at a position exceeding 7.5% of the belt width toward the side, the effect of absorbing the bending deformation near the belt end becomes small, and the effect of reducing the rolling resistance becomes insufficient.

On the other hand, the end point Pe on the bead portion 1 side of the recess 9
Is set at a position closer to the crown center than a point at 80% of the tire section height SH. If the hollow portion 9 is extended to the bead portion 1 side from this position, the hollow portion 9 reaches the side portion, and the rubber gauge of the side portion becomes insufficient, so that the curb cut resistance is reduced. However, the width W of the depression 9
g is preferably 3 mm or more, more preferably 5 mm or more. If the width Wg of the recess 9 is less than 3 mm, the effect of reducing the rolling resistance becomes insufficient.

The maximum depth of the depression 9 is preferably set in the range of 30 to 80% of the average tire thickness at both ends of the depression. If the maximum depth of the depression 9 is less than 30% of the average tire thickness at both ends of the depression, the effect of reducing the rolling resistance becomes insufficient. Further, in the present invention, since the starting point Ps of the concave portion 9 is separated from the belt end portion Eb, the concave portion 9 can be formed deeply without worrying about the failure of the belt end portion. However, if the maximum depth of the depression 9 exceeds 80% of the average tire thickness at both ends of the depression, cracks and the like are easily generated at the bottom of the depression 9 and durability is reduced. Note that the average tire thickness is the starting point Ps of the depression 9.
And the end point Pe, the tire thickness is measured, and half of the sum of the two may be obtained.

As described above, the width Wb of the second belt layer 7b is set to 95 to 110% of the tread contact width Wc, and the width Wb of the second belt layer 7b is shifted from the belt end Eb toward the bead portion 1 side. By providing the recess 9 in the shoulder centered on the position of 8 to 25% of the belt width Wb, the steering stability, the durability of the belt end, and the uneven wear resistance of the shoulder are reduced in the shoulder. The generated stress can be relieved, the energy loss concentrated on this portion can be effectively suppressed, and the rolling resistance can be reduced. Accordingly, it is not necessary to use a low fuel consumption rubber having a small hysteresis loss for the cap tread, so that rolling resistance can be reduced without impairing tire performance such as wet performance and wear resistance.

In the present invention, it is preferable to provide a belt cover layer 8 made of an organic fiber cord so as to cover at least both end portions in the tire width direction of the belt layers 7a and 7b.
By providing the belt cover layer 8 in this manner, the rigidity of the belt end portion is improved, and the bending deformation of the belt end portion caused by the contact with the ground at the time of rolling can be effectively suppressed. The rolling performance can be improved and the rolling resistance can be reduced.

[0018]

EXAMPLE A tire having a tire size of 185 / 65R14, having the tire structure shown in FIG. 1, presence or absence of a depression (continuous in the tire circumferential direction) in a shoulder portion, a belt width Wb of a second belt layer, a depression Passenger cars of conventional examples, comparative examples 1 to 5 and examples 1 to 6 in which the center position Pc, the width Wg of the depression, the maximum depth of the depression, and the presence or absence of a belt cover layer covering the belt end are varied. Pneumatic tires were manufactured. The belt width Wb is a ratio (%) to the contact width Wc. The center position Pc of the concave portion is a position (%) when the belt width Wb is set to 100% from the belt end Eb toward the bead portion. The maximum depth of the depression is a ratio (%) to the average tire thickness at both ends of the depression.

For these test tires, rolling resistance, steering stability, durability of the belt end,
The uneven wear resistance and trauma resistance of the shoulder portion were evaluated, and the results are shown in Table 1. Rolling resistance: Each test tire has a rim size of 14 × 5 ・ 1 /
Attached to a 2JJ wheel and mounted on a drum tester at an air pressure of 200 kPa, controlling the ambient temperature to 23 ± 2 ° C., running the outer surface of a steel drum having a smooth surface and a diameter of 1707 mm at a speed of 80 km, The rolling resistance at that time was measured. The evaluation results were indicated by an index with the conventional example being 100. A smaller index value indicates a smaller rolling resistance.

Steering stability: Each test tire was rim size 1
Air pressure 200 by assembling to 4 × 5 1/2 JJ wheel
The vehicle was mounted on a 1.6-liter FF passenger car with a displacement of 1.6 liters and the feeling was evaluated by running on a test course by five trained test drivers. The evaluation result is
Based on a relative comparison with the conventional example, a score was given by a 5-point method based on the following criteria, and the score was expressed by an average score of three persons excluding the highest point and the lowest point. The larger this evaluation point, the better the steering stability. The criteria are 5: excellent, 4: excellent, and 3.
5: slightly excellent, 3: equivalent to standard, 2.5: slightly inferior (lower limit of practical use), 2: inferior, 1: significantly inferior.

Endurance of belt end: Each test tire was mounted on a rim size 14 × 5 ・ 1 / 2JJ wheel, and was mounted on a drum testing machine at an air pressure of 180 kPa. The ambient temperature was controlled at 38 ± 3 ° C. Smooth surface and diameter 1
The outer peripheral surface of a 707 mm steel drum was driven at a speed of 81 km with a load of 4.42 kN for 4 hours, and then with a load of 4.68.
The vehicle was run for 6 hours at kN and then for 24 hours under a load of 5.20 kN. Here, the running was temporarily stopped, and if there was no abnormality in the appearance of the tire, the vehicle was further run for 4 hours with a load of 5.98 kN, and then for 2 hours with a load of 6.76 kN. At this time, the case where a failure occurred was regarded as failed (x), and the case where no failure occurred was regarded as passed (合格). In the case of a pass, the load is further increased to 6.76 kN for 2 hours, and then to 7.28 kN for 4 hours.
The vehicle was driven for 4 hours at a load of 8.32 kN for 4 hours. At this time, the case where no failure occurred in the appearance or the inside was judged as acceptable (合格).

Uneven wear resistance of the shoulder portion: Each test tire was mounted on a wheel having a rim size of 14 × 51 / 2JJ, mounted at an air pressure of 200 kPa, mounted on the front wheel of a small-sized passenger car with a displacement of 1.6 liters, and mounted on a test course. 10,000
After traveling km, the wear rate of the shoulder portion and the center portion (amount of wear with respect to the depth of a new groove) was measured, and the ratio was determined. The evaluation results were rejected (x) when the ratio of the wear rate of the shoulder portion to the wear rate of the center portion was 1.5 or more, and passed (o) when the ratio was less than 1.5. This test was not performed on test tires that failed the other tests.

Trauma resistance: Each test tire was rim size 14
200k air pressure by assembling to × 5 1/2 JJ wheel
It was mounted on a small passenger car with a displacement of 1.6 liters as Pa and passed over a steel curb with a height of 100 mm at an approach angle of 30 °. The speed at this time was changed in steps of 10 km / h to 1.0 km / h, the critical speed at which the tire did not burst was checked three times, and the average value was used to evaluate the scratch resistance. In the evaluation results, a case where the average value of the critical speed was lower than that of the conventional example was regarded as rejected (x), and a case where the average value was equal to or more than that of the conventional example was passed (o).

[0024]

[Table 1]

As is clear from Table 1, in Comparative Example 1, since the belt width Wb was narrow, the uneven wear resistance of the shoulder portion was deteriorated, and the steering stability was also lowered. In Comparative Example 2, since the belt width Wb was wide, the durability at the belt end was reduced. In Comparative Example 3, since the center position Pc of the depression was located at 6% of the belt width Wb from the belt end Eb, the steering stability was reduced. In Comparative Example 4, since the center position Pc of the recessed portion was located at a position 6% of the belt width Wb from the belt end Eb, the durability of the belt end was reduced. In Comparative Example 5, the center position Pc of the recess was 30% of the belt width Wb from the belt end Eb.
, The trauma resistance was reduced.

On the other hand, in the first to fifth embodiments, since the shoulder portion has a recessed portion having a predetermined size, the steering stability, the durability of the belt end portion, and the uneven wear resistance of the shoulder portion are impaired. And the rolling resistance was reduced. In addition, in the sixth embodiment, the shoulder portion has a concave portion with a predetermined size, and has a belt cover layer that covers the belt end portion.
The effect of reducing the rolling resistance was increased without impairing the steering stability, the durability of the belt end, and the uneven wear resistance of the shoulder.

[0027]

As described above, according to the present invention, the width of the second belt layer counted from the side of the carcass layer is 95 to 110% of the tread contact width, and the shoulder is provided with a depression. By arranging the center position of the recessed portion in the range of 8 to 25% of the belt width from the terminal in the tire width direction of the second belt layer toward the bead portion side,
Since it is not necessary to use a low fuel consumption rubber having a small hysteresis loss for the cap tread, rolling resistance can be reduced without impairing tire performance such as wet performance and wear resistance. Moreover, even if the recessed portion is provided in the shoulder portion as described above, the steering stability, the durability of the belt end portion, and the uneven wear resistance of the shoulder portion are not reduced.

[Brief description of the drawings]

FIG. 1 is a meridian half sectional view showing a pneumatic tire according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Bead part 2 Carcass layer 3 Bead core 4 Tread part 5 Side wall part 6 Bead filler 7a, 7b Belt layer 8 Belt cover layer 9 Depression

Claims (4)

[Claims] A carcass layer is mounted between a pair of left and right bead portions, and a carcass layer is provided on a tread portion on an outer peripheral side of the carcass layer.
In a pneumatic tire for a passenger car in which a plurality of belt layers are arranged, the width of the second belt layer counted from the carcass layer side is set to 95 to 110% of the tread contact width, and a recess is provided in a shoulder portion, A pneumatic tire for a passenger car, wherein a center position of the concave portion is arranged within a range of 8 to 25% of a belt width from a terminal in a tire width direction of the second belt layer toward the bead portion. 2. The pneumatic tire for a passenger car according to claim 1, wherein the recessed portion is continuous in a tire circumferential direction. 3. The pneumatic tire for a passenger car according to claim 1, wherein a maximum depth of the recess is 30 to 80% of an average tire thickness at both ends of the recess. 4. The pneumatic tire for a passenger car according to claim 1, wherein at least both ends in the tire width direction of the belt layer are covered with a belt cover layer made of an organic fiber cord.