JP2742363B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a pneumatic tire, in particular, to a dry grip and a wet grip while maintaining the performance.
The present invention relates to a pneumatic tire which reduces tire noise and can be suitably used as a tire for a passenger car.

[0002]

2. Description of the Related Art With the recent development of automobile technology, the speed of vehicles has been increased, and the noise of automobiles has been increased.

The contribution rate of tire noise to vehicle noise (the ratio of tire noise energy to the noise energy of the entire vehicle) has been steadily increased due to the progress of vehicle noise measures (quiet drive system, exhaust system, intake system, etc.). Sometimes 60-70
%, And even during accelerated driving, the value is increasing to 10-30% in recent years. Especially during accelerated driving, the noise energy of the whole vehicle is large.

On the tread of the tire, a plurality of longitudinal grooves having a width of about 10 to 20 mm which are continuous in the tire circumferential direction are arranged,
Wet grip performance is maintained by eliminating water between the tread surface and the road surface during rainy weather running. However, these flutes cause tire noise while improving drainage.

[0005] One of the noises generated by the flutes is caused by air column resonance. In the air column resonance, the air in the air column formed between the vertical groove and the road surface is resonated by the excitation force by the tire pattern during the rolling of the tire and the input from the road surface on the tire contact surface, and is specified. A sound having a wavelength, that is, a wavelength of about twice the length of the air column is generated.

[0006] This phenomenon is called air column resonance, and in the case of tires for passenger cars, it is the main source of unpleasant 800 Hz to 1 kHz noise. The wavelength of the columnar resonance sound becomes a substantially constant frequency irrespective of the speed of the tire, and increases the inside sound and outside sound.

As means for preventing the air column resonance, it is known to reduce the number and volume of the longitudinal grooves. This is due to the wet grip performance, particularly the hydroplaning phenomenon that occurs when the vehicle travels at high speed on a wet road surface. This leads to a reduction in the performance of preventing.

[0008]

On the other hand, in order to improve the wet grip performance, on the other hand, it is necessary to increase the number and the volume of the vertical grooves. However, as described above, this may cause an increase in tire noise. Was thought. It has been considered that such an increase causes a decrease in dry grip performance due to a decrease in the contact area and a decrease in steering stability performance due to a decrease in rigidity of the tread pattern.

Therefore, conventionally, such conflicting performance has been adjusted according to the performance required for the tire.

In order to improve the wet grip performance, Japanese Patent Application Laid-Open No. 63-34204 proposes a technique in which a depression is formed in the center of the tread, and the tread surface on both sides is formed by a small radius arc. ing. This is 2
Two small radius arcs drain water on both sides to improve wet grip performance.However, since the tread area of the entire tread is reduced, dry grip performance and steering stability performance are likely to be reduced,
Also, noise cannot be reduced much.

Also, European Patent Publication EP 50340
4, EP503405, EP503406, EP503
No. 407 discloses a tire having a linear recess or groove extending in the tire circumferential direction at the center of the tread.
However, these flutes have a relatively small groove width and are considered to be insufficient for reducing tire noise due to air column resonance.

According to the present invention, by arranging a vertical groove having a width wider than that of a conventional tire and specifying the ratio of land area to sea area, the wet grip performance and the dry grip performance can be maintained. It is intended to provide a pneumatic tire that can reduce tire noise.

[0013]

SUMMARY OF THE INVENTION According to the present invention, a single longitudinal groove is provided in the center of a tread in the tire circumferential direction, and the maximum air pressure which can be assembled to a regular rim and filled by a standard is set to 70 p.m. % In the tire axial direction between the outer end lines passing through the outer end in the tire axial direction of the ground contact surface S in the reference state where the tire is filled with 88% of the maximum load and is filled with the air pressure of 90%. The groove ground contact width ratio Wg / Sw with respect to the axial width Wg is 0.20 or more and 0.35 or less, and the land / land ratio Ss / Sr between the land area Sr and the sea area Ss on the contact surface S is set to 0. 30 or more and 0.50 or less, and the tread is substantially in addition to the flutes.
Equipped with a wide vertical groove that has a groove width and is continuous in the tire circumferential direction
And on both sides of the flute, in a direction crossing the flute
And starting at a position away from the longitudinal groove in the tire axial direction.
With a lateral groove extending beyond the outer end line of the ground plane S
In addition, the angle of the side groove on the acute side that forms the tire circumferential direction
The minimum at the starting point and the larger as it goes outward in the tire axial direction
By setting the outer end line to 90 °, the outer end
Pneumatic tires that are curved with projections at the position of the line
is there.

[0014]

The groove contact width ratio LWg / Sw between the width Wg of the longitudinal groove continuous in the tire circumferential direction at the center of the tread and the contact width Sw under the standard condition is set to 0.20 or more and 0.35 or less. Accordingly, it is possible to prevent air column resonance due to vibration in the air column surrounded by the vertical groove and the road surface. FIG. 3 shows the shape of the ground contact surface S of the tire of the present invention under the reference condition, and FIG. 4 shows the cross section of the contact center line AA, and the vertical groove 7 indicated by the solid line under the reference condition. The bottom 8 is curved outward in the radial direction by 1 to 1.5 mm on the equatorial plane CO, as compared to the groove bottom 8n in an unloaded state indicated by a broken line. As a result, it is presumed that the air column formed by the longitudinal groove 7 and the road surface has an orifice shape in which both ends in the axial direction of the tire are widened and the center is narrowed, that is, the air flow is obstructed and air column resonance is reduced. You.

Further, the land / land area ratio Ss / Sr of the land area Sr and the groove area Ss on the ground contact surface S under the reference condition is expressed by:
By setting 0.30 ≦ Ss / Sr ≦ 0.50, it is possible to help suppress noise while maintaining wet grip performance and dry grip performance.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings. FIG. 1 shows a tire of the present invention mounted on a regular rim R,
In addition, FIG. 3 shows the shape of the tire when the internal pressure of 70% of the maximum air pressure that can be normally filled is applied, and FIG. 3 shows the shape of the ground contact surface in the reference state where 88% of the maximum load is applied.

In this specification, the normal rim used in the reference state is a standard rim according to the JATMA standard, TR
A and ETRTO standard measurement rims (Mesuring R
im), and the maximum air pressure and the maximum load are defined as the maximum air pressure and the air pressure and the load specified as the maximum load in each standard.

Pneumatic tire (hereinafter referred to as tire) 1
Is a radially arranged carcass 3 which is wound around the bead core 2 of the bead portion B from the tread portion T to the sidewall portion S from the inside in the tire axial direction to the outside and locked.
And a belt layer 4 inside the tread portion T and outside the carcass 3, and a bead apex 6 extending radially outward from the bead core 2 is disposed between the carcass main body portion and the rewind portion, The shape and rigidity of the bead portion are maintained.

The surface of the tread portion T is formed of a circular arc having a single radius of curvature or a curved surface monotonically convex outward in the radial direction in which circular arcs having plural radii of curvature are smoothly connected. Formed by using a central arc surface having a radius of curvature R1 forming a portion and an outer arc surface inscribed in the center arc surface and having a radius of curvature R2 smaller than the curvature radius R1 and forming both sides of the tread. You.

The tire 1 is formed as a wide flat tire having a relatively poor drainage property, in particular, a tire cross section height / tire width of about 0.4 to 0.6, particularly a radial tire for a passenger car. You.

The belt layer 4 is formed by plying a plurality of plies using cords having high tensile rigidity such as steel or aromatic polyamide by 15 to 30 ° with respect to the tire circumferential direction so that the cords intersect each other. Are formed at relatively small angles. When the carcass 3 is a tire for a passenger car, an organic fiber cord such as nylon, rayon, or polyester can be used.

In the present embodiment, the tread portion T is provided with a wide vertical groove 7 extending continuously in the tire circumferential direction with the tire equator CO as a center. Tread sides 9, 9 for grounding are formed.

As shown in FIG. 3, the vertical groove 7 has a width Wg in the tire axial direction of the vertical groove 7 and an outer end passing through the outer end of the ground surface S in the tire axial direction.
The tangent is the axial length between the lines Y, Y (shown in FIG. 2).
The groove ground width ratio Wg / Sw to the ground width Sw (sometimes referred to as the maximum ground width Sw) is set to 0.20 or more and 0.35 or less.

The nominal size specified in JIS D4202 as a radial tire for passenger cars is 155.
/ 225 / tires, and tires corresponding to them, and in a tire of the above size, the groove ground contact width ratio Wg / Sw is equivalent to setting the width of the vertical groove 7 to a range of 30 to 70 mm. I have.

The relationship between the groove ground contact width ratio Wg / Sw and the noise is as follows. The groove depth W of the vertical groove 7 is kept constant, and eight kinds of tires having different groove widths Wg are manufactured by hand carving, and are mounted on the indoor stand. It depends on the result measured with a tester. Tire size is 205/5
5 R15, and the result is shown in FIG. 5 as the sound pressure level dB (L) at 800 Hz on the vertical axis.

The measurement is performed at a rotation speed corresponding to 50, 60, and 70 km / h, and the average value is shown for each groove contact width ratio Wg / Sw. Groove contact width ratio Wg / Sw is 0.2
It can be seen that the noise increases when the value is less than the above. As described above with reference to FIGS. 3 and 4, by setting the diameter to 0.2 or more, the constriction occurs at the center of the tire to impede the air flow, and the air in the groove is less likely to be compressed. Is considered to be able to be reduced.

If the ratio is less than 0.20, reduction of tire noise due to air column resonance cannot be expected, and the hydroplaning phenomenon is likely to occur. Even if it exceeds 0.35, the noise reduction effect is small, but on the other hand, the ground contact area occurs, the cornering force required for steering stability is insufficient, and the dry grip performance is reduced. Therefore, the groove ground width ratio Wg / Sw is set in the above range.

In the pneumatic tire of the present invention, since the cause of the occurrence of air column resonance is not increased, the pneumatic tire is continuous in the circumferential direction except for, for example, sipes having substantially no groove width other than the vertical grooves 7. It is better not to have a wide vertical groove.

Further, the vertical groove 7 is arranged in a region of 70% of the maximum contact width Sw around the tire equator CO.
If the vertical groove 7 protrudes from this area, the vibration mode of the belt increases the air column resonance sound, which is not preferable.

In the tread side portions 9 on both sides of the vertical groove 7, a lateral groove 10 extending substantially in the axial direction and opening at the periphery of the ground contact surface S can be arranged as shown in FIG.

The width w of the lateral groove 10 is relatively small as shown in FIG. 2, that is, about 5 to 15% of the width Wg of the vertical groove 7, and is separated from the vertical groove 7 outward in the tire axial direction. The starting point 12 extends outward in the axial direction of the tire from the starting position, thereby ensuring the steering stability performance while reducing the decrease in the rigidity of the ground contact portion. The lateral groove 10 extends to the tread end 13 beyond the outer end line Y of the ground plane S.

[0032] with the exclusion the lateral grooves 10 into the peripheral effectively grounded outside the area of water between the tread surface and the road surface in the circumferential groove 7 and the ground region other than the periphery by extending to the ground surface S, wet grip Ensure performance. The groove bottom 10 c of the horizontal groove 10 is formed substantially parallel to the outermost ply of the belt layer 4, similarly to the groove bottom 8 of the vertical groove 7.

Further, in the present embodiment, the lateral groove 10 is formed at an angle β between the tire circumferential direction and the starting point 12 of the axially innermost end of the lateral groove 10.
Is smaller (β1), and is set to be larger as it goes outward in the axial direction, and β2 is set to 90 ° at the outer end line Y, so that the outer end line Y is curved with the convex portion 10a at the position of the outer end line Y. Note that the lateral grooves 10, 10 on both sides of the tire equator CO have the curved directions reversed. The angle β between the tire circumferential direction is the starting point 1
2, the angle formed by the tangent at the edge of the groove wall of the side groove 10 on the acute angle side.

Further, the width of the lateral groove 10 may be gradually increased toward the tread end 13. Thereby, the drainage effect from the tread center portion to the tread edge can be enhanced. In the example shown in FIG. 2, the angle β1 with respect to the tire circumferential direction at the starting point 12 of the lateral groove 10 is substantially 60 °.

By changing the inclination in this way,
The effective length of the lateral groove 10 can be increased without lowering the tread lateral rigidity, and the wet grip performance can be maintained and improved without using another vertical groove for the shoulder portion.

Further, since the lateral groove 10 is not connected to the vertical groove 7, the lateral groove 10 can enhance the rigidity of the tread side portion 9 formed in the circumferential direction, thereby improving the steering stability.

In the contact surface S of the tire, vertical grooves 7
It is preferable that two or more and four or less horizontal grooves are respectively included on both sides of. If the number is less than two, the drainage effect of the lateral groove tends to be insufficient. If the number is more than four, tread rigidity is insufficient and steering stability is impaired.

Further, the land / land ratio Ss / S of the land area Sr and the sea area Ss on the ground contact surface S in the reference state.
r is 0.30 ≦ Ss / Sr ≦ 0.50. If it is less than 0.30, the wet grip performance, especially drainage during cornering, will be insufficient. If it exceeds 0.50, the contact area will decrease, and the cornering force required for steering stability will be insufficient.

Here, the land area Sr refers to the total area of the portion of the ground contact surface S that is actually in contact with the road surface, and the sea area Ss refers to the total area of the portion that does not contact the ground due to the groove.

The vertical groove 7 has a depth D of 5 mm or more and 10 mm or more.
mm or less. If it is less than 5 mm, the drainage and abrasion resistance will be poor. If it exceeds 10 mm, the rubber thickness of the tread will increase, and the weight of the tire will increase, which is unsuitable especially for passenger car tires. Preferably, the longitudinal groove width Wg of the tire
Is set to 10 to 20%.

Further, as shown in FIG. 4, the groove walls 7A and 7B of the vertical groove 7 have an angle α between the tire radial line X of 0 and 30.
°, preferably about 5 to 20 °, a relatively steep and non-circular straight line, for example, exerts an edge effect with the road surface, improves lateral force, increases cornering power, and maintains dry grip performance. Help. Groove bottom 8
And the groove walls 7A and 7B are connected by an arc having a radius of curvature r of about 0.1 to 0.5 times the groove depth D, so that the vertical groove 7 has a rectangular or trapezoidal cross-sectional shape. .

[0042] Figure 6 illustrates another tread pattern. In this example, the groove walls 7A and 7B of the vertical groove 7 form a zigzag shape around the equatorial plane CO and extend continuously in the tire circumferential direction.
At this time, the groove width Wg of the vertical groove 7 is defined as an average value of intermediate lines C and C passing through the middle of the zigzag of each of the groove walls 7A and 7B.

The ridge lines 7a, 7b where the groove walls 7A, 7B of the vertical groove 7 intersect the tread surface are displaced in the tire axial direction in opposite directions in the direction of deflection D1, D1 of the same length from the intermediate line C. It is a repetition of the linear portions 7s1 and 7s2 extending in the circumferential direction and the linear portions 7s3 and 7s4 that are displaced in the opposite direction due to the shake D2 larger than the shake D1, and the diagonal portions 7i1, 7i2, 7i3 and 7i4 interpose therebetween. Connected.

In this embodiment, the circumferential lengths L of the straight portions 7s1 to 7s4 and the oblique portions 7i1 to 7i4 are substantially the same, and at least one straight portion 7s1 and 7
s2, and the length where the straight line portions 7s3 and 7s4 appear. Such linear portions 7s1 to 7s4 and oblique portions 7i1 to 7i4
Are repeated to form ridge lines 7a and 7b.

In the present embodiment, there are two kinds of shakes and a zigzag shape which repeats every one cycle. However, the number of kinds may be one or more. Further, the lengths L can be changed with each other, and further, the repetition cycle can be changed.

Also, the difference between the maximum and minimum lengths in the tire axial direction of the linear portion farthest (linear portion 7s4 in this example) and the linear portion (linear portion 7s3 in this example) closest to the tire equator CO. A certain zigzag maximum fluctuation width DM (in this example, D
2) and the variation width ratio DM /
Sw is set to 20% or less. If it exceeds 20%, the drainage of the flute is adversely affected. In addition, the effect of suppressing the columnar resonance and dispersing the frequency is not sufficient, and the rigidity of the ribs is further reduced, so that steering stability and uneven wear resistance are likely to be adversely affected.

Further, by forming the zigzag shape, when the edge portion of the vertical groove runs on a wet road surface, a so-called wiping effect of scraping water between the road surface and the tread surface occurs, thereby improving wet grip performance and improving air grip. This has the effect of preventing column resonance.

In this embodiment, the straight portions 7s1 to 7s4 and the oblique portions 7i1 to 7i4 of the groove walls 7A and 7B face each other, but may be displaced in the circumferential direction.

By changing the length of the linear portions 7s1 to 7s4, the columnar resonance energy is dispersed to avoid concentration on a specific frequency.

In this example , the vertical groove 7 has a draining effect by a vertical groove having a sufficient groove width, and a wiping effect by an edge formed by being formed in a zigzag shape (an effect of scraping out water). Will be provided.

FIG. 7 shows another embodiment having an asymmetric pattern. The longitudinal groove 7 is formed by moving the longitudinal groove center line C1 to the equatorial plane CO.
, And is asymmetric with respect to the equatorial plane CO. The tread end 13a, which is far from the longitudinal groove 7 and the tread end 13b which is close to the longitudinal groove 7,
By mounting the so that it comes inside the vehicle, the rigidity of the tread region outside the vehicle that receives a load during cornering can be increased, and the cornering performance can be improved.

The distance d between the longitudinal groove center line C1 and the equatorial plane CO.
Is preferably within 20% of the contact width Sw. 2
If it exceeds 0%, the contact area on the tread end 13b side is insufficient. Further, in this example, the lateral groove 10 is different between the tread end 13b side and the tread end 13a side, and the asymmetry is increased.

As shown in FIG. 8, the length of the lateral groove 10 in the axial direction can be changed in accordance with the run-out of the vertical groove 7.

In the present embodiment, the lateral groove 10 is composed of a lateral groove 10a having an axial length K1 and a lateral groove 10b having a shorter axial length K2, and the ridge lines 7a, 7b In a place where 7b is located near the equatorial plane CO, a long transverse groove 10a is arranged. As a result, a change in rigidity of the tread in the circumferential direction is reduced, and stable running is possible, and uneven wear can be prevented.

[0055] FIGS. 9 to 12, to place the siping 12
Showing still another examples. The siping 12 has a width of 0.
This is a so-called notch in the range of 2 to 0.7 mm, which is completely closed on the ground contact surface and does not affect the ground contact area. The siping 12 may have a straight shape or a bent shape. Further, the siping 12 is disposed between the lateral grooves 10 to improve wet grip performance. As shown in FIG. 10, the siping 12 is not connected to the vertical groove 7, but is connected to the vertical groove 7 as shown in FIGS. 9 and 12, so that the wiping effect at the connecting portion between the siping 12 and the vertical groove 7 is obtained. Can also be improved. Further, as shown in FIG.
The sipings 12 that are connected to each other and the sipes 12 that are not connected can be mixed. Furthermore, the horizontal groove 10 can also be connected to the vertical groove 7.

Further, as shown in FIG. 13, a projection 14 is provided in the vertical groove 7 so that the tread and the belt layer can be prevented from being damaged due to having a vertical groove wider than the conventional one. At this time, the height of the projection 14 is preferably 50% or less and 15% or more of the vertical groove depth D. If it exceeds 50%,
The air column resonance effect due to the deformation of the groove bottom during the load is reduced, and the drainage performance is also reduced. For the same reason, the protrusions 14 may be continuous, but it is preferable to form a block with a gap in the circumferential direction of the tire in order to reduce noise, and it is preferable that at least two protrusions exist in the ground contact surface S. Good.

(Specific Example) The tires shown in FIGS. 1 and 2 were experimentally produced in sizes 205 / 55R15, and the passing noise of an actual vehicle was measured together with the conventional tires of the same size shown in FIG.

FIG. 14 shows that these two types of tires have a displacement of 2
This is a result of measuring passing noise based on the JASO standard, mounted on a 000 cc domestic car, and analyzing the frequency of the passing noise. The broken line shows the result of the conventional tire, and the solid line shows the result of the tire of the present invention. The product of the present invention is
It can be seen that the level near 1 kHz is reduced by 5 to 7 dB (A). This is the result of a reduction in columnar resonance.

In the conventional tire, four longitudinal grooves 7A are arranged symmetrically with respect to the tire equator CO, and a plurality of transverse grooves 10A intersecting the longitudinal grooves 7A and extending in the axial direction are arranged in the tire circumferential direction.

Further, as a result of performing a wet grip test and a dry grip test on an actual vehicle, the product of the example was at the same level as the product of the comparative example. As dry grip properties, each tire was mounted on a regular rim, and the cornering force was measured with an indoor bench drum tester in the above-mentioned reference condition. As the wet grip property, the speed at which the hydroplaning phenomenon occurred was measured.

[0061]

According to the present invention, tire noise can be reduced while maintaining dry grip performance and wet grip performance.

[Brief description of the drawings]

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

FIG. 2 is a plan view illustrating the tread pattern.

FIG. 3 is a plan view illustrating a ground plane S;

FIG. 4 is a cross-sectional view illustrating a cross section of a vertical groove.

FIG. 5 is a diagram showing noise measurement results.

6 is a plan view showing another tread pattern.

FIG. 7 is a plan view showing a tread pattern of another embodiment.

FIG. 8 is a plan view showing another embodiment.

FIG. 9 is a plan view showing another example .

FIG. 10 is a plan view showing another example .

FIG. 11 is a plan view showing another example .

FIG. 12 is a plan view showing another example .

FIG. 13 is a plan view showing another example .

FIG. 14 is a diagram showing a result of testing a noise level.

FIG. 15 is a plan view illustrating a tread pattern of a conventional tire.

[Explanation of symbols]

 2 Bead core 3 Carcass 4 Belt layer 6 Bead apex 7 Vertical groove 10 Horizontal groove

Claims (3)

(57) [Claims] At the center of the tread, a single longitudinal groove is provided in the circumferential direction of the tire. The rim is assembled to a regular rim and filled with 70% of the maximum air pressure that can be filled according to the standard. In the reference state where 88% of the load is applied, the distance between the outer end lines passing through the outer end in the tire axial direction of the contact surface S is determined.
A groove contact width ratio Wg / Sw of a contact width Sw, which is a length in the ear axis direction, and a width Wg of the longitudinal groove in the tire axis direction is 0.20 or more and 0.35 or less, and a land area on the contact surface S Sr and sea area Ss
The land-to-land ratio Ss / Sr is not less than 0.30 and not more than 0.50, and the tread is substantially groove width in addition to the longitudinal groove.
With no longitudinal flutes continuous in the tire circumferential direction,
On both sides of the flute, in a direction crossing the flute and
Starting from a position away from the longitudinal groove in the tire axial direction,
A lateral groove extending beyond the outer end line of the ground S is provided, and the lateral groove has an acute angle with respect to the circumferential direction of the tire.
At the minimum and larger as it goes outward in the tire axial direction,
By setting the outer end line at 90 °, the position of this outer end line is
A pneumatic tire that has a convex portion and is curved . 2. The grounding surface S is provided on both sides of the vertical groove, respectively.
2. The method according to claim 1, wherein the lateral groove is always included.
The pneumatic tire as described . 3. The vertical groove has at least one of its groove walls.
It extends in the circumferential direction of the tire in a zigzag manner, and
From the ridgeline where the wall and tread surface intersect, to the tire equator
Zigzag, the difference between the maximum and minimum length in the tire axial direction
Ratio D of the contact width Sw to the maximum change width DM
2. The method according to claim 1, wherein M / Sw is set to 20% or less.
The pneumatic tire as described .