JPH06316203A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To reduce the passage noise of a pneumatic tire while the running performance in the wet condition is well maintained. CONSTITUTION:At the tread surface of a pneumatic tire, a longitudinal main groove 3 is provided which is continued in the circumferential direction, and a grounding surface pattern S is generated when the tread surface 2 is grounded, wherein the ratio Wo/L is made ranging between 0.25-0.40, where Wo is the intermediate groove width in the middle in circumferential direction of the grounding surface pattern having a main groove width W and L is the grounding length in the circumferential direction of the pattern S. The ratio H/Wo is made ranging 0.15-0.30, where H is the max. groove width, while the ratio SA/S is ranged 0.5 to 0.7 where SS is the rectangular groove section area SS as expressed by the product WoxH, H being max. groove depth, and SA is the actual area of the longitudinal main groove at the tire meridian section in the middle position of the grounding surface pattern.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire capable of reducing running noise while maintaining running performance when wet.

[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.) and steady running. 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 groove width of about 10 to 20 mm, which are continuous in the tire circumferential direction, are arranged on the tread of the tire to eliminate water between the tread surface and the road surface when running in the rain. Maintains the wet grip performance.
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 and volume of vertical grooves, and further to provide partition walls in the grooves. This is to improve wet grip performance, particularly wet road surface. This leads to a reduction in the performance of preventing the hydroplaning phenomenon that occurs when traveling at high speed.

[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.

The inventors of the present invention have conducted further research and experiments to find that the tire noise due to the air column resonance is caused by the length of the air column, that is, the circumferential length at the contact surface of the tire and the groove width of the vertical groove. Focusing on the relationship and the relationship between the groove width and groove depth of the vertical groove, and the cross-sectional shape of the vertical groove all affect the noise level, by restricting these values, various running conditions during wet The inventors have found that it is possible to reduce the passing noise of the tire while maintaining the performance, and have completed the present invention.

An object of the present invention is to provide a pneumatic tire capable of reducing the passing noise of the tire while maintaining the wet running performance, particularly the aquaplaning performance.

[0014]

According to the present invention, a tread surface is provided with a vertical main groove extending continuously in the tire equator in the circumferential direction, and a load corresponding to a normal internal pressure filled in a regular rim is filled. A contact length L, which is the maximum length in the circumferential direction of the contact surface pattern obtained by the contact of the tread surface with the ground, and a tire shaft of the vertical main groove appearing in the contact surface pattern in a normal state with a load of 85% applied. Of the groove width W, which is the length in the directional direction, in the intermediate groove width Wo at the intermediate position in the circumferential direction of the ground surface pattern, and the ground long groove width ratio Wo with this intermediate groove width Wo.
/ L is 0.25 or more and 0.40 or less, the intermediate groove width W
Groove depth ratio H / W of maximum groove depth H in normal condition with respect to o
o is 0.15 or more and 0.30 or less, and a rectangular groove cross-sectional area SS that is a product Wo × H of the intermediate groove width Wo and the maximum groove depth H, and a tire meridian at an intermediate position of the ground contact surface pattern. The pneumatic tire has a ratio SA / SS of 0.5 or more and 0.7 or less with respect to the actual area SA of the vertical main groove in the cross section.

The groove width W is the difference between the minimum groove width Wm and the maximum groove width WM (WM-
Ratio of intermediate groove width Wo to (Wm) (WM-Wm) / Wo
Is preferably 0.1 or less.

[0016]

[Operation] Groove width Wo at the middle position in the circumferential direction of the ground plane pattern
By setting the ground contact long groove width ratio Wo / L to 0.25 or more and 0.40 or less, air column resonance due to vibration in the air column surrounded by the vertical main groove and the road surface can be prevented. . This is a tire with a tire size of 205 / 55R15, installed on an actual vehicle, and at a speed of 60 km / H, JAS
It is based on the result of the passage measurement based on O.C606, and as shown in FIG. 4, when the groove depth H is set to a constant value of 8.0 mm and the groove width Wo is varied, the ratio Wo
When / L is around 0.2, the passing noise becomes maximum, and at 0.25 or more, the effect of noise reduction is recognized. However, 0.
Noise will not be suppressed even if it exceeds 4 and the actual contact surface in the contact surface pattern is reduced, resulting in excessive ground contact pressure resulting in poor dry grip and large wear and uneven wear. Therefore, durability will be impaired.

Further, the ratio H / Wo of the maximum groove depth in a normal state to the intermediate groove width Wo is 0.15 or more and 0.30.
I am trying. This is based on the result of measuring the passing noise by varying the H / Wo ratio while keeping the groove cross-sectional area constant as shown in FIG. 5, and when H / Wo is a rectangular groove with a constant groove cross-sectional area. When the value is less than 0.3, the effect of noise reduction appears. However, the H / Wo ratio is 0.15
If it is made too small, the groove depth becomes extremely shallow, and the tire life due to wear of the tread surface is reduced.

In addition, the rectangular groove cross-sectional area SS which is the product Wo × H of the intermediate groove width Wo and the maximum groove depth H, and the actual area SA of the vertical main groove in the tire meridional cross section at the intermediate position of the ground contact surface pattern. Ratio SA / SS of 0.5 or more and 0.
7 or less. The cross section of the groove has a triangular shape or a semicircular shape, that is, the larger the deviation from the quadrangular shape, the more the air flow through the vertical main groove is obstructed, and the passing noise can be reduced. In this way, the ratio SA / SS represents the deviation of the shape, and as shown in the graph of FIG. 6, when the ratio SA / SS is 0.7 or less, the effect of reducing noise appears. However, if it is made smaller than 0.5, the drainage property of the vertical main groove becomes poor and the wet grip property is deteriorated.

As described above, in the present invention, the regulation values of the groove width, the groove depth and the shape of the vertical main groove are organically integrated so that the tire noise is maintained while maintaining the wet performance. Can be reduced.

When the tread surface is in a normal state, the ground contact surface pattern has a maximum ground contact pressure at an intermediate position in the circumferential direction, and the ground contact pressure gradually decreases in the circumferential direction about the intermediate position. Therefore, due to such a distribution of the ground pressure, the vertical main groove has a so-called orifice shape in which the width in the vicinity of the intermediate position is narrowest and the both ends in the circumferential direction are narrowed. With such an orifice shape,
Although it inhibits air column resonance and reduces air column resonance, the ratio (WM-Wm) / Wo of the intermediate groove width Wo to the difference between the minimum groove width Wm and the maximum groove width WM exceeds 0.1. If it becomes large, the drainage property in the vertical main groove is deteriorated, and there is a risk that the wet grip property of the tire and the wet performance such as hydroplaning resistance are deteriorated.

[0021]

An embodiment of the present invention will be described in detail below with reference to the drawings. 1 shows the tire of the present invention mounted on a regular rim J,
In addition, the tire shape when filled with the regular internal pressure is shown, and FIG. 2 shows the shape of the ground contact surface pattern S in a normal state in which 85% of the maximum load is applied.

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).

Pneumatic tire (hereinafter referred to as tire) 1
Is a carcass 16 in a radial arrangement that is wound around the bead core 15 of the bead portion 14 from the tread portion 12 to the sidewall portion 13 from the inner side in the tire axial direction to the outer side, and the inner side of the tread portion 12 and Carcass 16
A bead apex 18 having an outer belt layer 17 and extending from the bead core 15 to the outer side in the tire radial direction is disposed between the carcass main body portion and the rewinding portion to maintain the shape and rigidity of the bead portion 14. There is.

The tread surface 2 forming the surface of the tread portion 12 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 monotonically convex outward in the radial direction.

In this embodiment, the tire 1 is 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 a radial tire for passenger cars. Formed as a tire.

The belt layer 17 comprises a plurality of plies using cords having a high tensile rigidity such as steel and aromatic polyamide, and the cords are crossed between the plies so that the cords cross each other by 15 to 30 ° with respect to the tire circumferential direction. Are formed by arranging at a relatively small angle. When the carcass 16 is a tire for passenger cars, organic fiber cords such as nylon, rayon, polyester, etc. can be used.

In the present example, the tread portion 2 is provided with a wide vertical main groove 3 extending linearly continuously around the tire equator C in the tire circumferential direction.

On both sides of the vertical main groove 3, as shown in FIG. 2, the tread portion 12 extends substantially in the tire axial direction.
A lateral groove 20 that is open at the edge of is provided, and the vertical main groove 3 and the lateral groove 20 form a tread pattern on the tread surface 2.

As described above, the tread surface 2 has
A ground plane pattern S obtained by grounding the tread surface 2 in a normal state is formed.

As shown in FIGS. 1 and 3, the longitudinal main groove 3 has an inverted trapezoidal shape in which the groove width gradually decreases toward the groove bottom, and the tread surface 2 has a groove width W in the circumferential direction of the ground plane pattern S. The ground contact length L, which is the length, and the groove width W appearing in the ground contact pattern S
The ground contact long groove width ratio Wo / L, which is the ratio of the ground contact surface pattern S to the intermediate groove width Wo at the circumferential position M, is 0.25 or more and 0.40 or less.

Further, in the vertical main groove 3, the ratio H / Wo of the maximum groove depth H in the normal state to the intermediate groove width Wo is 0.15.
It is above and 0.30 or less.

Further, the maximum groove depth ratio H / Wo in the normal state with respect to the intermediate groove width Wo is set to 0.15 or more and 0.30 or less, and therefore the vertical main groove W has a groove depth larger than the groove width. Is formed as a shallow shallow groove. The cross-sectional shape of the groove is shown in FIG.
In addition to the flat trapezoidal shape as shown in FIG. 3, it may be formed in a flat triangular shape, or further as a flat truncated circle shape as shown in FIG.

Further, at the rectangular groove cross-sectional area SS which is the product (Wo × H) of the intermediate groove width Wo and the maximum groove depth H, and at the intermediate position M of the ground contact surface pattern S, the longitudinal main groove in the tire meridional cross section. Actual area SA of 3 (shown with diagonal lines in Fig. 3)
The ratio SA / SS is set to 0.5 or more and 0.7 or less. Therefore, it is advantageous to reduce noise when the vertical main groove 3 is formed in a trapezoidal shape, a triangular shape, a truncated circular shape, or the like.

The reason why the groove width W of the vertical main groove 3 is regulated by the intermediate groove width Wo which is the groove width at the circumferential intermediate position M of the ground plane pattern S is as follows.

Since the tire has an arc in the circumferential direction, the ground contact pressure acting on the tread surface 2 at the time of landing is not uniform with respect to the ground contact surface pattern S, and is maximum at the intermediate position M of the ground contact surface pattern S. And gradually decreases from the intermediate position M toward both the kicking side and the kicking side. In such a grounded state, the vertical main groove 3 receives the largest pressure at the intermediate position M, so that the groove width W becomes the minimum and the groove width W is gradually increased toward both sides of the ground plane pattern. Therefore, in the present application, a substantially maximum pressure is applied to the groove edge portion of the vertical main groove 3, and the groove width Wo at the intermediate position M, which has the worst condition for noise drainage, is defined as a reference.

The groove width W of the vertical main groove 3 has an orifice shape with a narrowed middle due to the distribution of the contact pressure in the contact surface pattern S. By such a shape, the air flow is obstructed and the air column is blocked. While reducing the resonance, if the ratio (WM-Wm) / Wo of the intermediate groove width Wo to the difference between the minimum groove width Wm and the maximum groove width WM exceeds 0.1 and becomes large, the drainage performance deteriorates. .

The vertical main groove 3 can be formed as a zigzag groove whose wave height is lower than the groove width in addition to the straight groove, and further, the groove width W itself is changed to a narrow width portion and a wide width portion. However, in these cases, it is preferable that the ratio (WM-Wm) / Wo is 0.1 or less in order to maintain the drainage property.

In the pneumatic tire of the present invention, since the cause of air column resonance is not increased, the vertical main groove 3 is used.
Besides, it is preferable not to provide a continuous vertical groove having a continuous width in the circumferential direction except for siping, which has substantially no groove width.

The horizontal groove 20 is arranged separately from the vertical main groove 3 in this example, starting from the vicinity of the groove edge of the vertical main groove 3.
The rigidity of the central portion of the tread surface 2 is increased. Note that FIG.
The horizontal groove 20 may be connected to the vertical main groove 3 as shown in FIG.

It is preferable that the groove width w of the lateral groove 20 is gradually increased toward the tread edge in order to improve drainage.

[0041]

SPECIFIC EXAMPLE A tire having a tire size of 205 / 55R15 and having the configuration shown in FIG. 1 was prototyped according to the specifications shown in Table 1 (Examples 1 and 2) and its performance was tested. A conventional tire with a normal specification (Comparative Example 1) and a conventional tire with a low noise countermeasure (Comparative Example 2) were also tested to compare their performances. The test conditions are as follows.

1) Passing noise A vehicle equipped with test tires was tested by an actual vehicle coasting test specified in JASO C606, and a passing speed was set to 60 km / H and a distance of 50 m was coasted along a straight test course. The passing noise was measured at a midpoint of the course by a stationary microphone placed laterally 7.5 m from the running center line and 1.2 m in height from the test road surface.

2) Aqua-Braining Performance A test tire was mounted on an actual vehicle, a straight distance of a water depth of 5 mm was entered at a speed of 100 km / H, only the front tire was subjected to lock braking, and the speed at which the frictional force was recovered was measured. It is indicated by an index of 100. The larger the value, the better. The test results are shown in Table 1.

[0044]

[Table 1]

As a result of the test, it can be confirmed that the examples can reduce the passing noise without impairing the aqua-blending performance.

[0046]

As described above, the pneumatic tire of the present invention is
In the ground plane pattern, the ground long groove width ratio Wo / L, the groove depth ratio H / Wo to the intermediate groove width, the rectangular groove cross-sectional area SS which is the product of the intermediate groove width Wo and the maximum groove depth H, and the actual vertical main groove Since the ratio SA / SS with respect to the area SA is regulated within the predetermined range, the passing noise of the tire can be reduced while maintaining the wet running performance, and the tire can be preferably used as a passenger car tire.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention.

FIG. 2 is a partial plan view showing the tread pattern.

FIG. 3 is an enlarged sectional view showing a vertical main groove.

FIG. 4A is a graph showing a relationship between a ground contact long groove width ratio Wo / L and passing noise, and FIG. 4B is a sectional view illustrating the shape of the vertical main groove.

FIG. 5A is a graph showing the relationship between the maximum groove depth H ratio H / Wo and the passing noise with respect to the intermediate groove width Wo,
(B) is a cross-sectional view illustrating the shape of the vertical main groove.

FIG. 6 is a graph showing a relationship between a ratio SA / SS of a rectangular groove cross-sectional area SS and an actual area SA of a vertical main groove and passing noise.

FIG. 7 is a cross-sectional view showing another aspect of the tread portion.

[Explanation of symbols]

 2 Tread surface 3 Vertical main groove H Maximum groove depth J Regular rim L Grounding length M Intermediate position S Grounding surface pattern SA Actual area SS Rectangular groove cross section W Groove width WM Maximum groove width Wm Minimum groove width Wo Intermediate groove Width

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] June 11, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0043

[Correction method] Change

[Correction content]

[0043] 2) wearing the aqua-flops training performance prototyped tires to the vehicle, the speed measured Comparative Example 1, the frictional force multiplied by the only lock braking front tire entering the straight line distance at a speed 100km / H of the depth of 5mm is restored It is indicated by an index of 100. The larger the value, the better. The test results are shown in Table 1.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0044

[Correction method] Change

[Correction content]

[0044]

[Table 1]

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0045

[Correction method] Change

[Correction content]

[0045] those results embodiment of the test was confirmed that was able to reduce the pass-by noise without compromising the aqua play <br/> training performance.

Claims (2)

[Claims] 1. A regular use in which a tread surface is provided with a vertical main groove extending continuously in the circumferential direction of the tire equator, and 85% of a load corresponding to a normal internal pressure filled by being assembled on a regular rim is loaded. In the state, the contact length L which is the maximum length in the circumferential direction of the contact surface pattern obtained by the tread surface contacting the ground, and the groove which is the length in the tire axial direction of the vertical main groove appearing in the contact surface pattern In the middle groove width Wo at the middle position in the circumferential direction of the ground surface pattern having the width W, the ground long groove width ratio Wo / L with the middle groove width Wo is 0.25 or more and 0.
40 or less, the groove depth ratio H / Wo of the maximum groove depth H in a normal state to the intermediate groove width Wo is 0.15 or more and 0.3 or more.
The rectangular groove cross-sectional area SS which is 0 or less and is the product Wo × H of the intermediate groove width Wo and the maximum groove depth H, and the actual area SA of the vertical main groove in the tire meridional section at the intermediate position of the ground contact surface pattern. A pneumatic tire having a ratio SA / SS of 0.5 or more and 0.7 or less. 2. The groove width W is the difference (WM) between the minimum groove width Wm and the maximum groove width WM in the entire area of the ground plane pattern in the circumferential direction.
-Wm) ratio of intermediate groove width Wo (WM-Wm) / W
The pneumatic tire according to claim 1, wherein o is 0.1 or less.