JPH06234305A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To suppress the change of conicity with the lapse of time so as to attain travel stability over a long period of time and reduce passing noise. CONSTITUTION:In this pneumatic tire, the tread face 2 is provided with longitudinal main grooves 3 continuous in the circumferential direction of the tire. A longitudinal groove wall 5 facing the longitudinal main groove 3 is provided with a longitudinal groove base wall part rising from the groove bottom, and a longitudinal groove curved wall part provided outward in the radial direction of the longitudinal groove base wall part and formed into a circular arc with a radius r1 being 0.3mm to 3mm, continuous from the tread face 2.

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 suppressing running noise for a long period of time by suppressing the fluctuation of conicity over time and preventing an increase in one-way flow. Regarding

[0002]

2. Description of the Related Art In recent years, with the improvement of highways, passenger cars and light vans have become faster and faster, and tires used in these vehicles are required to have stable running and improved durability. In response to these requests, the tread pattern has been improved. In addition, there is a tendency for passing noise generated from tires to increase as speed increases,
There is a need to reduce such noise.

An important requirement for improving the running stability is to reduce the one-way flow of the vehicle. Also, conicity control is necessary to prevent this one-way flow. Conicity refers to the force generated in a certain direction regardless of the rotation direction, of the lateral force that acts when the tire is rotated. It is also known that the conicity and the flow of the vehicle are approximately linearly proportional as shown in the graph of FIG.

In the conventional tire, the groove portion a forming the tread pattern has a corner portion c where the groove wall surface b and the tread surface f sharply intersect each other as shown in FIG.

[0005]

In the tire thus formed, the one-way flow changes as the vehicle runs, that is, the conicity changes, and when the tire is new, the one-way flow was able to run without problems. Even with tires, the conicity increased over time as the vehicle traveled, and there were many cases where one-sided flow occurred.

When observing the tire whose conicity changes with time as described above, the edge of the wall portion where the groove wall surface and the tread surface intersect is rounded and worn, and the radius of the roundness is equal to that of the tread surface. I knew that it was different for each position.

[0007]

It has also been found that the groove edges in the direction in which the conicity changes greatly are rounded with a larger radius. For new tires,
By rounding the edges of the groove by buffing,
It was also possible to reproduce the fact that the same degree of fluctuation that conicity changed due to running appeared.

On the other hand, the vertical main groove provided on the tread surface discharges water adhering to the tread surface when running in the rain and the like to make the contact between the tread surface and the road surface close and to increase the friction resistance between the surfaces. , Grip performance in rainy weather,
The braking performance, that is, the wettability was improved. Such an effect is particularly noticeable during high-speed running, and as the vehicle speed increases, the vertical main groove is formed with a pattern configuration as shown in FIG. Therefore, the vertical main groove shown in FIG.
Corner c where the groove wall surface b and the tread surface f sharply intersect with each other
Was formed.

The formation of such vertical main grooves causes air compressed between the tread surface and the road surface to be rapidly discharged through the columnar vertical main grooves during traveling. Air column resonance noise, so-called air pumping noise, increases tire passing noise.

As a result of repeated trial manufacture and experiments for reducing the air column resonance sound, the inventors have found that the cross-sectional shape of the groove is changed from square to non-square, and that the noise reduction is remarkable as the distance from the square increases. It was.

The present invention is based on the above experimental results.
Fluctuations in conicity due to running of the tire, based on the provision of a vertical groove curved wall part that uses an arc that is continuous with the tread surface and has a restricted radius on the groove wall of the vertical main groove formed on the tread surface. It is an object of the present invention to provide a pneumatic tire capable of maintaining stable running for a long period of time and suppressing passing noise by suppressing the increase of one-way flow by suppressing the above.

[0012]

SUMMARY OF THE INVENTION The present invention is a pneumatic tire having a tread surface provided with vertical main grooves continuous in the tire circumferential direction, wherein the vertical groove wall facing the vertical main groove is a groove. A vertical groove base wall portion that rises from the bottom, and a vertical groove curved wall portion that is provided radially outward of the vertical groove base wall portion and that has an arc that connects the tread surface and has a radius of 0.3 mm or more and 3 mm or less. It is a pneumatic tire characterized by comprising

When a lateral groove intersecting with the vertical main groove is provided on the tread surface, the lateral groove wall facing the lateral groove has a lateral groove base wall portion rising from the groove bottom and the lateral groove base wall portion. It is preferable to provide a lateral groove curved wall portion that is provided radially outward and that uses a circular arc having a radius of 0.3 mm or more and 3 mm or less that is continuous with the tread surface.

At that time, at the intersection point where the vertical main groove and the horizontal groove intersect, the ridge where the vertical groove wall and the horizontal groove wall intersect has a vertical groove wall between the groove bottom and the tread surface. More preferably, it is formed by a circular arc that smoothly connects with the lateral groove wall.

[0015]

The curved surface of the vertical groove has a radius of 0.
It is formed by using an arc of 3 mm or more and 3 mm or less.
As a result, the cross-sectional shape of the edge portion connected to the tread surface of the groove wall has a slight difference before and after the running, so that the conicity does not increase with the running of the tire, and therefore the one-way flow does not increase with time. Therefore, traveling stability can be maintained for a long period of time.

This fact is based on the experimental results described below.
For a new tire having a tire size of 205 / 50R15 and having the configuration and pattern shown in FIGS. 1 and 2 on the ground contact surface, the ends where the groove walls of the four vertical main grooves 3B, 3A, 3A, 3B intersect the tread surface. An arc surface was formed by buffing the edges. The radius of curvature of the arc is 0.3 mm to 5 mm
Up to multiple levels.

FIG. 6 is a graph showing the change in conicity per groove wall by buffing in relation to the radius of a circular arc. It can be seen from the graph of FIG. 6 that the conicity fluctuates greatly as the radius of the edge is increased in buffing.

FIG. 7 is a graph showing the change in conicity in all groove walls of the vertical main groove before and after running in relation to the radius of the edge arc, and the arc radius is 0.3 mm from the graph of FIG. By the above, it was confirmed that the temporal change of conicity can be reduced.

Further, FIG. 8 is a graph showing the relationship between the radius of the arc of the edge of the groove wall and the steering stability on the wet road surface in all the groove walls of the vertical main groove. From the graph of FIG. 8, it was found that the steering stability was significantly reduced when the radius of curvature exceeded 3 mm.

Regarding passing noise, when the tire touches the ground, as shown in FIG.
The contact pressure is highest at the intermediate point M in the circumferential direction, and the contact pressure gradually decreases from the intermediate point toward the rise side F and the rise side R. Therefore, the vertical main groove 3 has a cross-sectional shape in FIG. 10 on the rise side F (shown by a solid line).
Therefore, the state of the alternate long and short dash line changes to the state of the broken line at the intermediate point M. Further, the ground pressure gradually decreases from the intermediate point M toward the kicking side R, whereby the vertical main groove 2 is restored from the state of the broken line to the state of the solid line.

As a result, the vertical main groove in the ground area has the narrowest width at the intermediate point. Further, since the groove wall of the vertical main groove is provided with the curved surface wall portion of the vertical groove that is continuous with the tread surface, when compared with the conventional vertical main groove shown in FIG.
The change in groove cross-sectional area during non-grounding can be made large, and since the groove cross-sectional shape is further away from the rectangular shape, the air flow velocity through the vertical main groove can be markedly dissimilar. Noise can be suppressed, and passing noise is reduced to JASO C6.
In the test method described in 06B, 0.5 dB to 1.
It can be reduced by 0 dB.

If the radius of the arc forming the curved wall of the vertical groove is less than 0.3 mm, the fluctuation of the groove cross-sectional area at the time of grounding and non-grounding is scarce, and the vibration of the air column resonance sound becomes large, resulting in the noise suppression effect. However, if it exceeds 3 mm and becomes large, the contact area of the tread surface becomes small and the traction force and braking force during wet running become insufficient.

As described above, according to the present invention, the groove wall of the vertical main groove is provided with the curved surface wall portion of the vertical groove formed by the circular arc which is continuous with the tread surface and has the radius restricted to the range of 0.3 mm to 3 mm. As a result, it is possible to suppress the temporal change in conicity, prevent an increase in one-sided flow, maintain stable traveling for a long time, and reduce passing noise.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 to 5, a pneumatic tire 1 includes a tread portion 22 having a tread surface 2 as an outer peripheral surface and a sidewall portion 23 extending from both ends thereof toward a tire radial direction inner side.
And a bead portion 24 located at the tire radial inner end of the sidewall portion 23. Further, in the pneumatic tire 1, a carcass 26 is formed by folding back the bead core 25 of the bead portion 24 from the tread portion 22 through the sidewall portion 23 toward the outer side in the tire axial direction, and the tread portion 2
2 and a belt layer 27 arranged on the outer side in the radial direction of the carcass 26.

In the present embodiment, the carcass 26 comprises one or more carcass cords of a radial arrangement or a semi-radial arrangement inclined at an angle of 70 to 90 ° with respect to the tire equator C. An organic fiber cord made of nylon, polyester aromatic polyamide or the like is used as the carcass cord, which is composed of a single carcass ply.

In the present embodiment, the belt layer 27 is composed of two belt plies, and each belt ply is made of an organic fiber such as nylon, polyester, aromatic polyamide or a steel cord, and the belt cord is inclined with respect to the tire equator C. And they are installed side by side.

The pneumatic tire 1 is provided on the tread surface 2.
Is mounted on a standard rim J, and there is a grounding area S for grounding when a normal internal pressure and a normal load are applied, and the tread surface 2 is arranged on both sides of the tire equator C in this embodiment. A plurality of vertical main grooves 3 composed of inner vertical main grooves 3A, 3A and outer vertical main grooves 3B, 3B arranged between the inner vertical grooves 3A and the tread edge E are provided. To be done. The vertical main grooves 3 are formed as straight grooves that circulate substantially parallel to the tire equator C.

The inner and outer vertical grooves 3A and 3B have a groove width WH which is 0.06 to 0.16 times the tread width WT which is the distance between the edges E of the tread portion 2, and Groove depth WD
Is 0.08 to 0.18 times the tread width WT.

In this embodiment, the inner longitudinal main groove 3A and the outer longitudinal main groove 3B are traversed with the vicinity of the tire equator C as a starting point, and the lateral grooves 4 extending to the edge E of the tread portion 2 are provided. In this example, the center rib is formed between the inner longitudinal grooves 3A, 3A on both sides in the central portion, and the inner and outer longitudinal grooves 3A,
3B and between the outer vertical groove 3B and the tread edge E,
Out of these, a row of blocks consisting of a plurality of blocks B formed by the outer vertical grooves 3A and 3B and the horizontal groove 4 is arranged, so that the tread surface 2 forms a rib block pattern. Therefore, at the intersection point P where the vertical main groove 3 and the horizontal groove 4 intersect, the ridge portion 15 ...
Will be formed.

In this example, a siping 29 having a small width and extending in the circumferential direction is arranged near the tread edge E to enhance the side slip resistance in the wet state. Further, the lateral groove 4 has a groove width WH1 narrower than that of the vertical main groove 3 and a groove depth WD1.
Is substantially equal to the groove depth WD of the vertical main groove 4.

The vertical main groove 3 has a vertical groove wall 5 which rises from the groove bottom 9 through a small arc, and the vertical groove wall 5 is provided with the groove bottom 9.
The vertical groove base wall portion 6 that is continuous with the vertical groove base wall portion 6 and the vertical groove curved surface wall portion 7 that is provided radially outward of the vertical groove base wall portion 6 and that is continuous with the tread surface 2. Further, the vertical groove curved surface wall portion 7 is formed of an arc having a radius r1 of 0.3 mm or more and 3 mm or less, and is smoothly continuous by contacting the tread surface 2.

The vertical groove base wall portion 6 is preferably an inclined surface which is inclined outwardly at an angle of 2 to 15 ° with respect to the vertical line N perpendicular to the tread surface 2.

Even in the lateral groove 4, the lateral groove wall 10 is provided.
As shown in FIG. 5, similarly to the vertical main groove 3, the lateral groove curved surface wall portion 11 rising from the groove bottom 13 and the lateral groove curved surface wall portion 11 are formed.
And a lateral groove curved wall portion 12 formed of an arc r2 having a radius r2 of 0.3 mm or more and 3 mm or less, which is provided radially outward of the tread surface 2 and smoothly connects to the tread surface 2.

By forming the lateral groove curved surface wall portion 12 as described above, it is possible to suppress the temporal change in conicity due to the running of the tire, to stabilize the maneuverability for a long time, and to suppress the air flow through the lateral groove 4. As a result of the change, it is possible to suppress the vibration of the air column resonance sound and further reduce the passing noise.

When the radius of the circular arc is less than 0.3 mm, the effect of suppressing the conicity variation with time is small, and the resonance sound generated by the air flow through the lateral groove 4 cannot be reduced, and conversely 3 mm. If it exceeds, the steering stability will be impaired and the traction force will be insufficient when wet. In addition, it is preferable that such a lateral groove curved wall portion is provided over substantially the entire area of the lateral groove wall 10.

Further, in this embodiment, at the ridge portion 15 where the vertical groove wall 5 and the horizontal groove wall 10 intersect at the intersection P where the vertical main groove 3 and the horizontal groove 4 intersect, as shown in FIG. The vertical groove wall 5 is provided between the groove bottom 9 and the tread surface 2.
And the lateral groove wall 10 are both formed by an arc that smoothly continues.

By forming in this way, when the tire touches the ground, the flow of the air flowing through the vertical main groove 3 and the horizontal groove 4, especially the merging and branching of the air at the intersection point P, is smoothed, and the vortex flow is generated. And the passing noise can be further reduced.

When the narrow angle formed by the vertical groove wall 5 and the horizontal groove wall 10 at the intersection point P is an acute angle of less than 90 °, the radius r3 of the arc is in the range of 1.5 to 5 mm, and 9
At a right angle or an obtuse angle of 0 ° or more, it is preferable that the radius r3 of the arc is in the range of 2 to 5 mm.

As described above, the vertical groove wall 5, the horizontal groove wall 10 and the ridge 15 are all formed by arcs,
In the ribs and blocks, stress concentration is reduced, cutting resistance during running is improved, tire durability is improved, and also in the mold for vulcanizing and molding such ribs and blocks, vertical main grooves and lateral grooves Since the projections for formation have roundness at their roots, the strength of the projections is significantly increased, and the durability of the expensive vulcanization mold is improved,
Tires can be provided more economically.

The pneumatic tire according to the present invention has a rib pattern composed of only vertical main grooves,
The present invention can also be applied to various aspects including a block pattern of blocks.

[0041]

【Concrete example】

1) Test A For a tire having a tire size of 205 / 55R15 and having the pattern configuration shown in FIG. 2, the edges of the four vertical main grooves 3B, 3A, 3A, 3B where the groove walls intersect the tread surface 2 The change in conicity per groove wall by buffing was investigated in relation to the radius of the arc.

The test conditions are as follows. 6 for each sample tire
It was mounted on a 1/2 JJ × 15 rim, an internal pressure of 2.2 kgf / cm ² was applied, and a test was carried out by the automobile tire uniformity test method specified in JISO C-607.

As a result of the test, as shown in the graph of FIG. 6, as the arc radius of the groove wall end edge is increased by buffing, the change amount of the conicity is larger than that of the arc radius of 0, and It was confirmed that the change in conicity becomes large when the arc radius exceeds 3 mm.

2) Test B With respect to the tire having the same structure as in Test A, the amount of change in conicity by running was investigated. The investigation was conducted on the entire vertical main groove under the same test conditions as the test A.

In the running test, the vehicle was mounted on the front wheels of a 2000 cc class front-wheel drive passenger car, and the running distance of 1000 km was run at a ratio of 50 on the expressway and 50 on the general road.

As a result of the test, as shown in the graph of FIG. 7, it was confirmed that the temporal variation of the community can be reduced by setting the arc radius to 0.3 mm or more.

3) Test C With respect to the tire having the same structure as in Test A, the steering stability on a wet road surface was investigated. 200 tires for trial
It was mounted on all wheels of a 0 cc class front-wheel-drive passenger car, and the sensory evaluation of the driver was performed on a wet paved road surface.

The results of the test are shown in FIG. It was confirmed that the steering stability was significantly reduced when the arc radius exceeded 3 mm.

4) Test D For a tire having the same tire size and the same tread pattern as in Test A, the same test as in Test C was carried out for a tire in which an arcuate surface was formed only in the lateral groove (no arcuate surface in the longitudinal groove). It was

The test results are shown in FIG. It was confirmed that the steering stability was significantly reduced when the arc radius exceeded 3 mm.

5) Test E Passing noise test A tire having the same structure as the test A (a tire having an arcuate surface only in the longitudinal groove) was quasi-compliant with JISO C-606, and the maximum peak frequency was 1150 Hz. The relationship between the sound pressure level and the radius of arc was investigated.

FIG. 12 shows the relationship between the size (mm) of the arc radius formed in the vertical groove and the reduction amount of passing noise.

6) Test F Passing Noise Test Similar to Test D, the same test as Test E was carried out on a tire having an arcuate surface only in the lateral grooves. Figure 13
The relationship between the size (mm) of the arc radius formed in the lateral groove and the reduction amount is shown.

From the test results of the above-mentioned tests E and F, the passing noise is reduced as the arc radius of both the vertical groove and the horizontal groove becomes larger, and the noise reduction amount does not increase even if the arc radius exceeds 3 mm. I was able to confirm.

[0055]

As described above, the pneumatic tire of the present invention is
A vertical groove base wall portion that rises from the groove bottom on a vertical groove wall of a vertical main groove that is continuous in the tire circumferential direction, and a radius that is provided radially outward of the vertical groove base wall portion and that is continuous with the tread surface is 0.3. Since the gist is to have a vertical grooved curved wall part consisting of an arc of ~ 3 mm, it is possible to suppress changes in conicity over time, prevent one-way flow of the vehicle from changing over time, and allow long-term running. The stability can be maintained, and the vibration of the air column resonance sound can be suppressed to reduce the passing noise.

[Brief description of drawings]

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

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

FIG. 3 is a perspective view showing an intersection of a vertical main groove and a horizontal groove.

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

FIG. 5 is a cross-sectional view illustrating a lateral groove.

FIG. 6 is a graph showing a change in conicity due to buffing in relation to the forming arc radius.

FIG. 7 is a graph showing a change in conicity before and after traveling in relation to an arc radius.

FIG. 8 is a graph showing a relationship between a radius of an arc of a curved surface of a vertical groove and steering stability on a wet road surface.

FIG. 9 is a circumferential sectional view showing a state at the time of grounding.

FIG. 10 is a cross-sectional view schematically showing the deformation of the vertical main groove at the time of grounding.

FIG. 11 is a graph showing a relationship between an arc radius of a lateral groove curved surface wall and steering stability on a wet road surface.

FIG. 12 is a graph showing a relationship between an arc radius of a curved surface of a vertical groove and a reduction amount of passing noise.

FIG. 13 is a graph showing a relationship between an arc radius of a curved surface of a lateral groove and a reduction amount of passing noise.

FIG. 14 is a cross-sectional view showing a vertical main groove of a conventional tire.

FIG. 15 is a cross-sectional view showing the ground area.

FIG. 16 is a graph showing the relationship between vehicle flow and conicity.

[Explanation of symbols]

 2 tread surface 3 vertical main groove 4 horizontal groove 5 vertical groove wall 6 vertical groove base wall portion 7 vertical groove curved surface wall portion 9 vertical groove wall 10 horizontal groove wall 11 horizontal groove base wall portion 12 horizontal groove curved wall portion 13 groove bottom 15 ridge portion C tire equator P intersection points r1, r2 radius

Claims (5)

[Claims] 1. A pneumatic tire having a tread surface provided with vertical main grooves continuous in the tire circumferential direction, wherein a vertical groove wall facing the vertical main groove has a vertical groove base wall rising from a groove bottom. And a vertical curved surface wall portion that is provided radially outward of the vertical groove base wall portion and that uses a circular arc having a radius of 0.3 mm or more and 3 mm or less continuous with the tread surface. Pneumatic tires. 2. The pneumatic tire according to claim 1, wherein the vertical groove curved surface wall portion is smoothly connected to the tread surface. 3. The tread surface includes a lateral groove intersecting with the vertical main groove, and a lateral groove wall facing the lateral groove has a lateral groove base wall portion rising from a groove bottom and a lateral groove base wall portion of the lateral groove base wall portion. It is provided radially outward and has a radius of 0.3 mm connected to the tread surface.
The pneumatic tire according to claim 1 or 2, further comprising a lateral groove curved surface wall portion having an arc of 3 mm or less. 4. The pneumatic tire according to claim 3, wherein the lateral groove curved wall portion is smoothly continuous with the tread surface. 5. A ridge portion where a vertical groove wall and a horizontal groove wall intersect at an intersection point where the vertical main groove and the horizontal groove intersect with each other is a vertical groove wall between the groove bottom and the tread surface. 5. The pneumatic tire according to claim 1, wherein the pneumatic tire is formed by an arc that smoothly connects with the lateral groove wall.