JP3367846B2 - Pneumatic tire - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a pneumatic tire capable of reducing road noise without impairing cornering performance.

[0002]

2. Description of the Related Art Road noise is one of the noises associated with tires. This road noise is an unpleasant "going" sound generated in the vehicle compartment when the vehicle travels on a relatively rough road surface.
As for this road noise, the unevenness of the road surface vibrates the tire,
Further, this vibration is sequentially propagated to the rim, the axle, the suspension, the vehicle body, etc., and is heard in the passenger compartment.

In order to reduce this road noise, it is necessary to damp the vibration transmitted to the tire. Conventionally,
As a method of damping vibration in the tread part, for example,
It has been proposed to use soft rubber with excellent vibration absorption for the tread rubber, and to increase the thickness of the tread rubber gauge.However, in the former case, wear resistance deteriorates, and in the latter case, tire weight increases and rolling resistance increases. Defects such as deterioration of the product appear strongly, and the practical effects have not yet been achieved.

Further, the vibration of the tread portion can be reduced by increasing the out-of-plane bending rigidity of the belt layer. For this reason, it has been proposed to provide a reinforcing layer composed of plies and the like reinforced with fiber cords on the outer side in the tire radial direction of the belt layer, but with this method, road noise is increased in spite of an increase in tire manufacturing cost and weight. There is a problem that the reduction effect is small.

Further, there has been proposed a method of adopting a structure having low rigidity in the carcass in order to damp the vibration in the process of transmitting the tire. However, although this method is effective in reducing road noise, the problem that the cornering performance is significantly deteriorated as a result of the lateral rigidity of the tire being reduced becomes prominent.

The present inventor has conducted various studies in view of the above problems, and as a result, the deformation of the belt layer during tire running,
In particular, paying attention to the large amount of deformation at the tire axial end of the belt layer, which has a lower rigidity than the central part, and this deformation is one of the factors that result in vibration and worsen road noise. I found out.

The present inventor, in contrast to the conventionally proposed method, that is, from the viewpoint of suppressing the deformation by reinforcing the end portion of the belt layer with a reinforcing layer, the end portion of the belt layer having a low rigidity is applied. From the viewpoint of reducing the vibration input itself as much as possible, the tread part is composed of a small ground contact area having a small length from the tire equator and a wide ground contact area having a large length from the tire equator repeated in the circumferential direction. However, it has been found that the deformation of the end portion of the belt layer can be reduced without impairing the cornering performance by specifying the grounding end portion of each of these grounding regions in relation to the width of the belt layer.

As described above, the object of the present invention is to provide a pneumatic tire capable of reducing road noise without deteriorating various performances of the tire, and particularly to reduce road noise without deteriorating cornering performance. The purpose of the invention is to provide a pneumatic tire.

[0009]

According to a first aspect of the present invention, there is provided a carcass which is folded and locked around a bead core of a bead portion from a tread portion through a sidewall portion, and an inner side of the tread portion. A pneumatic tire comprising a belt layer arranged on the outer side in the tire radial direction of the carcass, and further comprising a belt layer in which cord plies in which the cords are arranged at a small angle with respect to the tire equator are overlapped in the tire radial direction, The tread portion has a length from the tire equator to the ground contact end, which is an axial distance from the tire equator to the outermost end where the belt plies overlap in the radial direction, 0.70 to 0.85 times the belt half width BW. And the length from the tire equator to the ground contact end is 0.95 of the belt half width BW.
1.10 times the distance TW2 and a wide ground contact area extending in the tire circumferential direction, and a wide ground contact area which is repeated in the circumferential direction, and the ground area is formed on both sides of each tread surface divided by the tire equator. Moreover, the total sum LH of the lengths of the wide contact area in the tire circumferential direction is 35 to 65% of the total length of the tire.

Further, the invention according to claim 2 is characterized in that the belt half width BW is 0.75 times or more of a tire half width SW which is an axial distance from the tire equator to the tire total width position.

Here, the "ground contact end" means the ground contact end in a state where the tire is assembled on a standard (JATMA) dimensional measurement rim and a standard internal pressure and a load of 88% of the standard maximum load capacity are applied. Part.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.

1 and 2, the pneumatic tire according to the present embodiment includes a carcass 6 which is folded back and locked around a bead core 5 of a bead portion 4 from a tread portion 2 through a sidewall portion 3 and a tread portion. 2 illustrates a radial tire for a passenger vehicle, which has a belt layer 7 arranged inside 2 and outside the carcass 6 in the tire radial direction. Figure 1
In Fig. 2, a cross section left of the equator of the tire shows a view X, and a cross section right thereof shows a view Y.

The carcass 6 is composed of one or more, in this example, one ply of a radial structure in which carcass cords are arranged at an angle of 75 ° to 90 ° with respect to the tire equator C.
As the carcass cord, an organic fiber cord such as nylon, rayon or polyester is adopted in this example, but a steel cord can also be adopted if necessary.

The carcass 6 has a bead core 5 of a bead portion 4 from a tread portion 2 through a sidewall portion 3.
And a folded-back portion 6b extending from the body portion 6a and folded back around the bead core 5. The end portion of the folded-back portion 6b is located outside the total width position M on the outermost side in the tire axial direction in the tire radial direction. As a result, the carcass 6 has a so-called high turn-up structure, which is preferable in that the lateral rigidity of the tire can be increased.

The body portion 6a of the carcass 6 and the folded portion 6
A bead apex 8 extending from the bead core 5 to the outer side in the radial direction of the tire and made of hard rubber is arranged between the b and b to reinforce the bead portion.

Next, the belt layer 7 has at least two belt plies 7 in which cords are arranged at a small angle of 10 to 35 ° with respect to the tire equator.
The cords A and 7B are superposed in a direction in which the cords intersect each other. As the belt cord, a steel cord is used in this example, but a highly elastic organic fiber cord such as aramid or rayon can also be used if necessary.

The belt ply 7A on the inner side in the radial direction
Is wider than the outer belt ply 7B.
In the belt layer 7, the belt half width BW, which is the axial distance from the tire equator C to the outermost end P where the belt plies 7A and 7B overlap in the radial direction, is the axis from the tire equator C to the tire total width position M. It is desired to be 0.70 times or more, preferably 0.75 times or more, of the tire half width SW which is the directional distance.

Next, on the tread surface of the tread portion 2, in this example, a central main groove G1 extending continuously on the tire equator, and on both sides of the main groove G1 are arranged continuously in the tire circumferential direction. The outer main grooves G2 and G2 extending outward are formed, and the left and right auxiliary grooves G extending in a direction intersecting with the tire circumferential direction.
L and GR are formed.

In the present embodiment, each of the main grooves G1 and G2 is a straight groove, and has a groove width of 4 for improving drainage.
A groove having a groove depth of up to 20 mm and a groove depth of around 5 to 15 mm can be preferably used, but a zigzag groove can also be formed. In addition, the left and right sub-grooves GL and GR in this example incline from the upper left to the lower right in FIG. 2, and the rotation directions arranged at substantially point symmetrical positions centered on the tire equator C are specified. 9 illustrates an example of a non-directional pattern that is not performed. On the tread surface, the left and right sub-grooves G are provided on the outermost main groove in the axial direction of the tire, that is, on the outer side in the axial direction of the outer main groove G2.
The blocks B divided by L and GR form a row of blocks arranged in the tire circumferential direction.

In the present invention, the tread portion 2 is
Is a narrow ground contact area 9 having a small length from the tire equator C.
And a wide ground contact area 10 having a large length from the tire equator C
One of the features is that it is formed from a grounding region 11 in which the above and are repeated in the circumferential direction.

In the narrow grounding area 9, the grounding end 9E is
From the tire equator C to the belt half width BW of 0.70 to 0.
They are separated by a distance TW1 of 85 times. In this example, the grounding end 9E is formed by forming the recess 13 in which the tread surface is recessed. Such a grounding end portion 9E of the small width grounding region 9 is located on the inner side in the tire axial direction from the outermost end P where the belt plies 7A and 7B overlap in the radial direction.

Therefore, when the small width ground area 9 is grounded on the road surface, the impact at that time is mainly input to a relatively high rigidity portion of the belt layer 7 where two plies overlap each other. The belt layer 7 is small in deformation against such an impact and can suppress the vibration of the tire. Therefore, the vibration transmitted to the vehicle is also small and the road noise is reduced.

The inventors of the present invention made a plurality of tires by changing the distance TW1 from the tire equator C to the ground contact end (however, uniform over the entire circumference of the tire) with respect to the belt half width BW, and produced the following conditions. Road noise was measured at.

Road noise (OA) measurement test Test vehicle: Domestic 2000cc class passenger car (1 passenger) Tires: 195 / 65R15 (rim 6JJ, internal pressure 2.0)
kgf / cm ² ) Runway: Test course (hot roll road) Speed: 60km / H Microphone position: Center front seat

As is clear from the test results shown in FIG. 3, when (TW1 / BW) is 0.85 or less, a critical reduction effect of road noise can be obtained. However, (TW
If 1 / BW) is further less than 0.7, the ground contact pressure of the tread portion increases and it cannot be said to be preferable from the viewpoint of uneven wear.

As described above, in order to reduce the road noise critically without deteriorating the various performances required for the tire, the grounding end portion 9E of the narrow grounding area 9 having a small length from the tire equator C. Is from the tire equator C to the belt half width BW
It is necessary to position them with a distance TW1 that is 0.70 to 0.85 times. More preferably, the distance TW1 is 0.70 to 0.80 of the belt half width BW.

However, if the entire circumference of the tread is constituted by such a small width grounding area 9, the grounding width is reduced,
Since the lateral rigidity of the tire, particularly the lateral spring constant of the tire, decreases, cornering performance also deteriorates. Therefore, in the wide ground contact area 10, the ground contact end 10E is located at the tire equator C.
Therefore, it is necessary to position the belt with a distance TW2 that is 0.95 to 1.10 times the belt half width BW.

The present inventors have found that the distance TW2 from the tire equator to the ground contact end with respect to the belt half width BW (however,
A plurality of tires having different tires (uniformity over the entire circumference) were manufactured, and the lateral spring constants of the tires were measured under the following conditions.

Lateral spring constant (calculated from lateral force and lateral displacement when lateral force is applied) Tire: 195 / 65R15 (rim 6JJ, internal pressure 2.0)
kgf / cm ² ) Vertical load: 350kgf Lateral force: 0-50kgf

As is clear from the test results shown in FIG. 4, when (TW2 / BW) is 0.95 or more, the lateral spring constant is stable at a high level and excellent cornering performance is obtained. Even if (TW2 / BW) exceeds 1.10 times, the ground area where reinforcement by the belt layer cannot be obtained increases. Therefore, the deformation of the tread portion 2 becomes large, and road noise and wear resistance (shoulder resistance) are increased. Wear, heel & toe wear) are not preferable.

Therefore, the ground contact end portion 10E of the wide ground contact area 10 having a large length from the tire equator C is located at a distance TW2 from the tire equator C which is 0.95 to 1.10 times the belt half width BW. It is necessary.

The tread portion 2 has a small ground contact area 9 and a wide ground contact area 10 which are repeated in the tire circumferential direction.
Has 1. As a result, the small-width ground contact area 9 and the wide-width ground contact area 10 can be dispersedly arranged on the entire circumference of the tire, so that the reduction of the road noise is ensured without impairing the cornering performance. In the present embodiment, the tire equator C
On the left and right tread surfaces 2L, 2R divided by, the small width ground contact areas 9 and the wide width ground contact areas 10 are arranged on both sides of the tire equator C and substantially evenly arranged in the tire axial direction. It is shown as an example .

In either the left or right tread surface sectioned by the tire equator C, the number of repetitions of the ground contact area 11 on the tire circumference can be appropriately determined, but it is preferably at least 2 or more from the viewpoint of tire uniformity and the like. Is preferably 6 or more, more preferably 10 or more.

Further, the total length LH of the wide contact area 10 in the tire circumferential direction is 35 to 6 of the total tire circumferential length L.
It needs to be 5%. The ratio of the length LH of the wide contact area 10 in the tire circumferential direction to the total length L of the tire (L
When (H / L) is less than 35%, the lateral spring constant of the tire is significantly reduced, which impairs cornering performance and
When (LH / L) exceeds 65%, the small width ground area 9 becomes small, and it is impossible to expect a reduction in road noise. In addition, here, the tire entire circumference length is measured at the position of the ground contact end 10E of the wide ground contact area 10.

5 and 6 show another embodiment of the present invention.

In the embodiment shown in FIG. 5, the narrow ground contact area 9 is provided.
Shows a block formed between the blocks B and B divided by the sub-groove. Also, the left and right tread surfaces 2L,
In 2R, the ground contact areas 11 arranged in the tire circumferential direction are arranged with a phase difference of about half a pitch.

Further, in the embodiment shown in FIG. 6, the central main groove G is
The block B is also formed between the outer main groove G2 and the outer main groove G2 in a row in the tire circumferential direction, and the other points are the same as in the embodiment of FIG.

As described above, in the pneumatic tire of the present invention, the shape, position, pattern, etc. of each main groove, sub-groove, etc. can be appropriately modified other than the illustrated embodiment.

[0040]

[Examples] A radial tire (Examples 1 to 8) having a tire size of 195 / 65R15 and a tread pattern as shown in FIG. 1 and a structure as shown in FIG. Comparative examples 1 to 5) were also prototyped, and the road noise and the lateral spring constant were measured under the above conditions, and the performances were compared.

The test results are shown in Table 1.

[0042]

[Table 1]

As a result of the test, it can be confirmed that the tires of the examples all reduce the road noise while keeping the lateral spring constant at a high level. Although Comparative Example 2 reduces road noise, it has a narrow grounding width (TW1, T
W2 is 0.65 times as large as BW), and the lateral spring constant is significantly reduced. Similarly, in Comparative Example 4, although the road noise is reduced, the lateral spring constant is reduced because the ratio of the wide ground contact area is less than 35%.

[0044]

As described above, according to the present invention, the ground contact end is located inside the outermost end where the belt plies overlap in the radial direction, and the outside in the axial direction of the small ground contact region. A wide contact area having a contact end is repeatedly provided in the tire circumferential direction to prevent the impact from the road surface from being input to the low rigidity portion of the belt layer while maintaining the lateral spring of the tire. As a result, road noise can be reduced without impairing cornering performance.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a pneumatic tire showing an embodiment of the present invention.

FIG. 2 is a plan view showing a developed tread pattern of the pneumatic tire of FIG.

FIG. 3 is a graph showing the relationship between road noise and TW1 / BW.

FIG. 4 is a graph showing a relationship between a lateral spring constant and TW2 / BW.

FIG. 5 is a plan view showing a developed tread pattern of another embodiment.

FIG. 6 is a plan view showing a developed tread pattern of another embodiment.

[Explanation of symbols]

2 tread part 3 sidewall part 4 bead part 5 bead core 6 carcass 7 belt layers 7A, 7B belt ply 9 small grounding area 9E small grounding area grounding end 10 wide grounding area 10E widening grounding area grounding end 11 grounding Region P Outermost end TW1 where belt plies overlap in the radial direction Distance from tire equator to ground contact end of small contact area TW2 Distance from tire equator to contact end of wide contact area BW Belt half width SW Tire half width C Tire equator

Claims (2)

(57) [Claims] 1. A carcass which is folded back and locked around a bead core of a bead part from a tread part through a side wall part, and a carcass which is arranged inside the tread part and outside of the carcass in a radial direction of a tire and has a cord at a tire equator. A pneumatic tire comprising a belt layer in which belt plies arranged at a small angle with respect to each other are stacked in the tire radial direction, wherein the tread portion has a length from the tire equator to the ground contact end portion. A small ground contact area extending in the tire circumferential direction that is a distance TW1 that is 0.70 to 0.85 times the belt half width BW that is the axial distance from the tire equator to the outermost end where the belt plies overlap in the radial direction. A wide ground contact area extending in the tire circumferential direction with a distance TW2 that is 0.95 to 1.10 times the belt half width BW, from the tire equator to the ground contact end. Together are formed from the ground area to be repeated in the circumferential direction, the ground area of the tread surface that is divided by the tire equator
The total width L of the wide ground contact area formed on both sides in the tire circumferential direction
A pneumatic tire characterized in that H is 35 to 65% of the entire circumference of the tire. 2. The pneumatic tire according to claim 1, wherein the belt half width BW is 0.75 times or more of a tire half width SW which is an axial distance from a tire equator to a tire total width position.