JPH06191227A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce the noise of a tire while maintaining dry grip and wet grip performance. CONSTITUTION:The center part of a tread part is provided with one longitudinal groove 7 continuous in the circumferential direction of a tire. In the reference state of the tire being mounted on a normal rim, charged with air pressure equivalent to 70% of the maximum air pressure chargeable in the specifications and loaded with 88% of the maximum load, the groove grounding width ratio Wg/Sw of the tire axial width Wg of the longitudinal groove 7 to the grounding width Sw which is the maximum length in the tire axial direction of the tread is to be 0.20 to 0.35, and the groove-land ratio Ss/SL of the groove part area Ss to the land part area SL in the tread S is to be 0.30 to 0.50.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a pneumatic tire, particularly while maintaining dry grip and wet grip performance,
The present invention relates to a pneumatic tire that reduces tire noise and can be suitably used as a passenger vehicle tire.

[0002]

2. Description of the Related Art As the speed of vehicles increases with the development of automobile technology in recent years, vehicle noise also increases and it is desired to reduce it.

The contribution ratio of tire noise to vehicle noise (the ratio of tire noise energy to the noise energy of the entire vehicle) is determined by the progress of vehicle noise countermeasures (silence of drive system, exhaust system, intake system, etc.). 60 to 70 by the hour
%, The value has been increasing in recent years to 10 to 30% even during accelerating traveling, and particularly during accelerating traveling, the noise energy of the entire vehicle is large, so that it is necessary to reduce the noise of tires.

A plurality of vertical grooves having a width of about 10 to 20 mm which are continuous in the tire circumferential direction are arranged on the tread of the tire.
Wet grip performance is maintained by eliminating water between the tread surface and the road surface when driving in the rain. However, the vertical grooves cause tire noise while improving drainage.

One of the noises generated by the vertical groove is air column resonance. In this air column resonance, the air in the air column formed between the vertical groove and the road surface on the tire contact surface resonates due to the excitation force by the tire pattern during tire rolling and the input from the road surface, A sound having a wavelength, that is, a wavelength about twice the length of the air column is generated.

This phenomenon is called air column resonance, and in the case of tires for passenger cars, it becomes a main sound source of noise of 800 Hz to 1 kHz which is offensive to the ears. The wavelength of the air column resonance sound has a substantially constant frequency regardless of the speed of the tire, increasing the vehicle interior sound and the vehicle exterior sound.

As a means for preventing this air column resonance, it is known to reduce the number of vertical grooves and the volume thereof. This is a wet grip performance, especially a hydroplaning phenomenon which occurs when traveling at high speed on a wet road surface. This leads to a decrease in performance.

[0008]

On the other hand, in order to improve the wet grip performance, conversely, the number of vertical grooves and the volume may be increased. However, as described above, this causes an increase in tire noise. Was being considered. It has also been considered that the increase of these causes a decrease in dry grip performance due to a decrease in the ground contact area and a decrease in steering stability performance due to a decrease in rigidity of the tread pattern.

Therefore, conventionally, such contradictory performances have been adjusted according to the performance required for the tire.

In order to improve the wet grip performance, JP-A-63-34204 proposes a technique of forming a depression in the center of the tread and forming the tread surface on both sides of the depression with an arc having a small radius. ing. This is 2
With two small radius arcs, water is discharged to both sides to improve wet grip performance, but since the ground contact area of the entire tread is reduced, it is easy to cause deterioration of dry grip performance and steering stability performance,
In addition, the noise cannot be reduced significantly.

European patent publication EP 50340
4, EP503405, EP503406, EP503
407 discloses a tire having a linear recess or groove extending in the tire circumferential direction at the center of the tread.
However, these vertical grooves have a relatively small groove width and are considered insufficient for reducing tire noise due to air column resonance.

According to the present invention, a vertical groove having a wider width than that of a conventional tire is arranged, and the ratio of the land area and the sea area is specified together to maintain wet grip performance and dry grip performance. It is intended to provide a pneumatic tire capable of reducing tire noise.

[0013]

According to the present invention, a single longitudinal groove continuous in the tire circumferential direction is provided in the central portion of a tread, and the maximum air pressure that can be rim-assembled to a regular rim and is normally filled is 70. % Air pressure and 88% of the maximum load in the reference state, the groove contact width ratio Wg of the contact width which is the maximum tire axial length of the contact surface S and the tire axial width Wg of the vertical groove. / Sw is 0.20 or more and 0.35 or less, and the land area S at the contact surface S is
The pneumatic tire has a sea-land ratio Ss / Sr between r and the sea area Ss of 0.30 or more and 0.50 or less.

[0014]

The groove contact width ratio LWg / Sw between the width Wg of the vertical 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. This makes it possible to prevent air column resonance due to vibration in the air column surrounded by the vertical groove and the road surface. This shows the shape of the ground contact surface S under the reference conditions of the tire of the present invention in FIG. 3 and the cross section of the ground contact center line AA in FIG. The bottom 8 is curved outwardly in the radial direction by 1 to 1.5 mm on the equatorial plane CO, as compared with the groove bottom 8n in the unloaded state shown by the broken line. As a result, the air column formed by the vertical groove 7 and the road surface has a so-called orifice shape in which both ends in the axial direction of the tire are widened and the center is narrowed, and it is presumed that the air column is obstructed and air column resonance is reduced. It

Further, the groove-land ratio Ss / Sr between the land area Sr on the ground contact surface S and the groove area Ss under the standard condition is
By setting 0.30 ≦ Ss / Sr ≦ 0.50, it can be useful for suppressing noise while maintaining wet grip performance and dry grip performance.

[0016]

An embodiment of the present invention will be described in detail below with reference to the drawings. FIG. 1 shows that the tire of the present invention is mounted on a regular rim R,
In addition, the tire shape when the inner pressure of 70% of the maximum air pressure that can be normally filled is filled is shown, and FIG. 3 shows the shape of the ground contact surface in the standard state in which 88% of the maximum load is loaded.

In the present specification, the regular rim used in the reference state is the standard rim in 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 load specified as the maximum load in each standard.

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

The surface of the tread portion T is composed of an arc having a single radius of curvature, or a curved surface which smoothly connects the arcs having a plurality of radii of curvature and which is convex outward in the radial direction. Is formed by using a central arcuate surface having a radius of curvature R1 that forms a portion and an outer arcuate surface that is inscribed in the central arcuate surface and that has a radius of curvature R2 that is smaller than the radius of curvature R1 and that forms both sides of the tread. It

The tire 1 is formed as a wide flat tire having a relatively poor drainage property with a flatness ratio of tire cross-section height / tire width of about 0.4 to 0.6, especially as a radial tire for passenger cars. It

The belt layer 4 comprises a plurality of plies using cords having high tensile rigidity such as steel and aromatic polyamide, and the cords intersect each other at 15 to 30 ° with respect to the tire circumferential direction. Are formed by arranging at a relatively small angle. When the carcass 3 is a passenger car tire, organic fiber cords such as nylon, rayon, polyester, etc. 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, whereby a road surface is formed on both axial sides of the vertical groove 7. Tread sides 9, 9 for grounding are formed.

As shown in FIG. 3, the vertical groove 7 is a groove having a width Wg in the tire axial direction of the vertical groove 7 and a maximum axial width Sw of the ground surface S in the tire as shown in FIG. The contact width ratio Wg / Sw is set to 0.20 or more and 0.35 or less.

This ratio range has a nominal size of 155 specified by JIS D4202 as a radial tire for passenger cars.
/ ~ 225 /, the tire corresponding thereto, and in the tire of the above size, the groove ground contact width ratio Wg / Sw is equivalent to setting the width of the vertical groove 7 in the range of 30 to 70 mm. There is.

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

Further, the measurement is carried out at a rotational speed corresponding to 50, 60 and 70 km / h, and the average value of the groove contact width ratio Wg / Sw is shown. Groove contact width ratio Wg / Sw is 0.2
It can be seen that the noise is increased below the range. By setting the ratio to 0.2 or more, as described above with reference to FIGS. 3 and 4, a constriction is generated in the center of the tire to impede the air flow, and the air in the groove is less likely to be compressed, resulting in air column resonance. It is thought that it can reduce.

As described above, if it is less than 0.20, it is not possible to expect a reduction in tire noise due to air column resonance, and a hydroplaning phenomenon is likely to occur. Even if it exceeds 0.35, the noise reduction effect is small, but the ground contact area phenomenon occurs, the cornering force required for steering stability is insufficient, and the dry grip performance deteriorates. Therefore, the groove ground contact width ratio Wg / Sw is set within the above range.

In the pneumatic tire of the present invention, since the cause of air column resonance is not increased, the pneumatic tire is continuous in the circumferential direction except for the vertical groove 7, which has substantially no groove width, for example, siping. It is better not to provide a wide vertical groove.

Further, the vertical groove 7 is arranged in a region of 70% of the maximum ground contact width Sw with the tire equator CO as the center.
When the vertical groove 7 extends out of this region, the vibration mode of the belt rather increases the air column resonance sound, which is not preferable.

The tread side portions 9 on both sides of the vertical groove 7 may be provided with lateral grooves 10 extending substantially in the axial direction and opening at the peripheral edge of the ground contact surface S, as illustrated in FIG.

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

The outer edge line Y is a circumferential line connecting the outer ends of the ground contact surface S in the tire axial direction in the standard state, and the lateral groove 10 extends to the peripheral edge of the ground contact surface S so that the vertical groove 7 and the periphery thereof are not included. The water between the tread surface and the road surface in the ground contact area is effectively removed to the outside of the ground contact area to ensure wet grip performance. The groove bottom 10c of the lateral groove 10 is the groove bottom 8 of the vertical groove 7.
Similarly to, the outermost layer ply of the belt layer 4 is formed substantially parallel to the ply.

Further, in the present embodiment, the lateral groove 10 forms an angle β with the tire circumferential direction at the starting point 12 of the innermost axial end of the lateral groove 10.
Is the minimum (β1), and is set larger toward the outer side 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. The lateral grooves 10 and 10 on both sides of the tire equator CO are curved in opposite directions. The angle β with the tire circumferential direction is the starting point 1
2 is an angle formed with a tangent line at the groove wall edge of the lateral groove 10 on the side having an acute angle.

Further, the width of the lateral groove 10 may be gradually increased toward the tread end 13. As a result, the drainage effect from the tread center to the tread edge can be enhanced. In the example shown in FIG. 2, the angle β1 at the starting point 12 of the lateral groove 10 with respect to the tire circumferential direction is approximately 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 / improved without using other vertical grooves in the shoulder portion.

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

In the ground contact surface S of the tire, the vertical groove 7
It is preferable that two or more and four or less lateral grooves are included on both sides of each. If the number is less than 2, the drainage effect of the lateral groove tends to be insufficient, and if the number exceeds 4, the tread rigidity is insufficient and the steering stability is impaired.

Further, the sea-land ratio Ss / S between 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, wet grip performance, particularly drainage at the time of cornering, is insufficient, and if it exceeds 0.50, the ground contact area is reduced and the cornering force required for steering stability is insufficient.

The land area Sr is the total area of the ground surface S that is actually in contact with the road surface, and the sea area Ss is the total area of the non-ground area due to the groove.

The depth D of the vertical groove 7 is 5 mm or more and 10 or more.
Set to mm or less. If it is less than 5 mm, the drainage property and wear resistance are poor, and if it exceeds 10 mm, the rubber thickness of the tread is increased and the tire weight is increased, which is not suitable especially for passenger car tires. Preferably, the vertical 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 form an angle α with the tire radial line X of 0 to 30.
By making it relatively steep and non-arcuate, for example, a straight line, preferably about 5 to 20 °, an edge effect with the road surface is exerted, lateral force is improved, cornering power is enhanced, and dry grip performance is maintained. To help. The groove bottom 8
The groove walls 7A and 7B are connected to each other by an arc having a curvature radius r of about 0.1 to 0.5 times the groove depth D, whereby the vertical groove 7 has a rectangular cross section or a trapezoid with an outward spread. .

FIG. 6 shows a tread pattern of another embodiment of the present invention. In this embodiment, the groove walls 7A and 7B of the vertical groove 7 are formed.
Has a zigzag shape centering on the equatorial plane CO and extends continuously in the tire circumferential direction. At this time, the groove width Wg of the vertical groove 7 is defined as the average value of the intermediate lines C, C passing through the middle of the zigzags of the groove walls 7A, 7B.

Further, the ridge lines 7a and 7b at which the groove walls 7A and 7B of the longitudinal groove 7 intersect the tread surface are displaced from the intermediate line C in the tire axially opposite directions by deflections D1 and D1 of equal length. The straight line portions 7s1 and 7s2 extending in the circumferential direction and the straight line portions 7s3 and 7s4 that are displaced in the opposite direction by the shake D2 larger than the shake D1 are repeated, and the straight line parts 7s1, 7i2, 7i3 and 7i4 are provided between them. It is connected.

In this example, the straight line portions 7s1 to 7s4 and the slanted portions 7i1 to 7i4 have substantially the same circumferential length L, and at least one straight line portion 7s1 and 7s1 is provided in the ground plane.
It is assumed that s2 and the straight line portions 7s3 and 7s4 appear. Such straight line portions 7s1 to 7s4 and diagonal portions 7i1 to 7i4
The ridge lines 7a and 7b are formed by repeating.

In the present example, there are two types of shake, and a zigzag shape that repeats every cycle is provided, but it may be one type or a greater number of types. Also, the lengths L can be changed from each other, and the cycle of repetition can be changed.

Further, the difference between the maximum and minimum lengths in the tire axial direction of the straightest line portion (the straight line portion 7s4 in this example) and the closest straight line portion (the straight line portion 7s3 in this example) with respect to the tire equator CO. A certain zigzag maximum fluctuation width DM (D in this example
(2 times the length of 2) and the fluctuation width ratio DM /
Sw is 20% or less. If it exceeds 20%, the drainage of the flutes is adversely affected. Further, the effect of suppressing the air column resonance and the effect of dispersing the frequency are not sufficient, and the rigidity of the rib is further lowered, so that steering stability and uneven wear resistance are likely to be adversely affected.

Further, by adopting the zigzag shape, when the edge portion of the vertical groove travels on a wet road surface, a so-called wiping effect is generated, which is to wipe out water between the road surface and the tread surface, thereby improving wet grip performance and air permeability. The effect of preventing column resonance occurs.

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

Further, by changing the lengths of the straight line portions 7s1 to 7s4, the air column resonance energy is dispersed, concentration at a specific frequency is avoided, and so-called white noise is generated to prevent the generation of jarring noise.

In this embodiment, the vertical groove 7 has a drainage effect by the vertical groove having a sufficient groove width and a wiping effect by the edge portion formed by forming the zigzag shape (effect of scraping out and removing water). ) And will be equipped.

FIG. 7 shows another embodiment having an asymmetric pattern. The vertical groove 7 has its vertical center line C1 at the equator plane CO
Is asymmetric with respect to the equatorial plane CO. This tire has a tread end 13a farther from the vertical groove 7 on the vehicle outer side and a tread end 13b closer to the vertical groove 7
By mounting so as to come to the inside of the vehicle, it is possible to enhance the rigidity of the tread region on the outside of the vehicle that receives a load during cornering, and improve the cornering performance.

Distance d between the vertical groove centerline C1 and the equatorial plane CO
Is preferably within 20% of the ground contact width Sw. Two
If it exceeds 0%, the ground contact area on the tread end 13b side becomes 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 enhanced.

Further, as shown in FIG. 8, the lateral groove 10 can have its axial length changed in accordance with the deflection of the longitudinal groove 7.

In this example, 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. The lateral groove 10a corresponds to the deflection of the ridgelines 7a and 7b of the vertical groove 7, and the ridgeline 7a, A long lateral groove 10a is provided at a position where 7b is close to the equatorial plane CO. As a result, the change in rigidity of the tread in the circumferential direction is reduced, stable running is possible, and uneven wear can be prevented.

9 to 12 show another embodiment of the present invention in which the siping 12 is arranged. The siping 12 is a so-called notch that has a width of 0.2 to 0.7 mm and is completely closed on the ground contact surface and does not affect the ground contact area. You can use the ones that you have done. Further, the siping 12 is the lateral groove 10
It is placed between and improves wet grip performance.
The siping 12 is not connected to the vertical groove 7 as shown in FIG. 10, but is also connected to the vertical groove 7 as shown in FIGS. 9 and 12 to improve the wiping effect at the connecting portion between the siping 12 and the vertical groove 7. It can also be improved. Furthermore, as shown in FIG. 11, siping 12 connected to the vertical groove 7 and siping 12 not connected can be mixed. Furthermore, the lateral groove 10 can also be connected to the vertical groove 7.

Further, as shown in FIG. 13, a protrusion 14 may be provided in the vertical groove 7 to prevent the tread and the belt layer from being damaged due to the wide vertical groove. At this time, the height of the protrusion 14 is preferably 50% or less and 15% or more of the vertical groove depth D. When it exceeds 50%,
The air column resonance effect due to the deformation of the groove bottom when the load is applied 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 tire circumferential direction in terms of noise suppression, and at least two protrusions 14 should exist in the ground contact surface S. Good.

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

FIG. 14 shows that these two types of tires have a displacement of 2
It is a result of frequency noise analysis of a passing noise measured based on JASO standard, which is installed in a domestic passenger car of 000 cc. The solid line shows the result of the tire of the conventional product, and the alternate long and short dash line shows the result of the tire of the present invention. It can be seen that the product of the present invention reduces the level in the vicinity of 1 kHz by 5 to 7 dB (A) as compared with the conventional product. This is a result of the reduced air column resonance.

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

Further, as a result of conducting a wet grip test and a dry grip test in an actual vehicle, the example product was at the same level as the comparative example product. As the dry grip property, each tire was mounted on a regular rim, and cornering force was measured by an indoor bench drum tester in the standard state. 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 drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a tire of the first 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 a noise measurement result.

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

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 embodiment.

FIG. 10 is a plan view showing another embodiment.

FIG. 11 is a plan view showing another embodiment.

FIG. 12 is a plan view showing another embodiment.

FIG. 13 is a plan view showing another embodiment.

FIG. 14 is a diagram showing the results of testing the 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

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[Procedure amendment]

[Submission date] August 31, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 3

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 6

[Correction method] Change

[Correction content]

Claims (6)

[Claims] 1. A single longitudinal groove continuous in the tire circumferential direction is provided in the central portion of the tread, and a maximum of 70% of the maximum air pressure that can be assembled as a rim on a regular rim and is standardly filled. Groove contact width ratio Wg / of the contact width which is the maximum length in the tire axial direction of the contact surface S in the standard state in which 88% of the load is applied and the width Wg of the vertical groove in the tire axial direction Wg /
Sw is 0.20 or more and 0.35 or less, and the land-to-land ratio Sr of the land area Sr and the sea area Ss at the contact surface S is S.
A pneumatic tire having s / Sr of 0.30 or more and 0.50 or less. 2. The pneumatic tire according to claim 1, wherein, in addition to the vertical groove, the tread does not have a vertical groove having a substantial groove width and being continuous in the tire circumferential direction. tire. 3. The pneumatic tire according to claim 1, wherein the tread has lateral grooves extending on both sides of the vertical groove in a direction intersecting with the vertical groove and extending on an outer peripheral edge of the ground contact surface S. tire. 4. The pneumatic tire according to claim 3, wherein the lateral groove extends to the outer peripheral edge of the ground contact surface S starting from a position separated from the vertical groove in the tire axial direction. 5. The ground contact surfaces S are respectively provided on both sides of the vertical groove.
4. At least one lateral groove is always included.
Alternatively, the pneumatic tire according to item 4. 6. The lateral groove extends in the tire circumferential direction with at least one of its groove walls forming a zigzag, and has a maximum length in the tire axial direction from the ridgeline where the groove wall and the tread surface intersect to the tire equator. Fluctuation width ratio D of the contact width Sw to the zigzag maximum fluctuation width DM which is the difference from the minimum length
2. The M / Sw is set to 20% or less.
Pneumatic tire described.