JP2992454B2 - Pneumatic tire - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire which can be suitably used as a tire for a passenger car by simultaneously improving wet performance, particularly hydroplaning performance, and reducing tire noise.

[0002]

2. Description of the Related Art In recent years, with the improvement in quietness of vehicles, the contribution rate of noise generated by tires to the noise of the entire vehicle has been increased, and reduction of the noise is desired. In particular, it is desired to reduce noise in a region near 1 kHz which is easy for a human to hear. One of the main sound sources in such a high frequency region is a so-called air column resonance.

[0003] On the other hand, a plurality of longitudinal grooves which are generally continuous in the tire circumferential direction are arranged on the tire tread in order to maintain a wet grip.

In such a tire, a kind of air column is formed by the road surface and the vertical groove when the tire is in contact with the ground, and air flows into the air column due to deformation of the tire tread during rolling, thereby causing a specific wavelength. That is, a sound having a wavelength twice that of the air column is generated.

[0005] This phenomenon is called air column resonance, and in a tire having a vertical groove, it becomes a main sound source of noise of 800 to 1.2 kHz. 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.

[0006]

In order to prevent this air column resonance, it is known that the number of flutes or the volume of the flute is reduced. Invite.

On the other hand, in order to improve the wet grip performance, it is necessary to increase the number of vertical grooves and the groove volume, but the mere increase is due to the increase in the tire noise and the decrease in the contact area. This leads to a decrease in dry grip performance and a decrease in steering stability performance due to a decrease in rigidity of the tread pattern.

Heretofore, tire performance has been adjusted at the expense of any of these conflicting performances.

It is an object of the present invention to provide a pneumatic tire capable of achieving both wet grip performance, in particular, improved anti-hyperplaning performance and tire noise, without impairing dry grip performance and steering stability performance.

[0010]

SUMMARY OF THE INVENTION According to the present invention, there is provided a tread portion having two circumferentially continuous tire equatorial sides.
By providing the vertical grooves, the tread portion is formed between the pair of shoulder portions outside the groove bottom edge of the vertical groove in the tire axial direction and the center portion between the groove bottom edges of the vertical groove in the tire axial direction. In a pneumatic tire that has been divided, the central portion has an inner groove wall surface extending inward in the tire axial direction along a curve that projects radially outward from the inner groove bottom edge in a tire meridional section, and the inner groove wall surface. A central tread surface with a series of curves consisting of a central tread area that smoothly joins between the tread edges, the tread area substantially abutting the virtual tread edge joining the tread areas of the shoulders At the same time, in the tire meridional section, the central portion has an asymmetric profile shape that is asymmetrical with respect to the tire equatorial plane CL. A pneumatic tire, wherein a groove width GW of the circumferential groove is a distance in the tire axial direction is less than 0.35 times the ground contact width of 35mm or more and a tread portion between the outer edge of the surface area.

In the center portion, the center plane KL passing through the middle in the tire axial direction may coincide with the tire equatorial plane CL.
Further, the position may be shifted with respect to the tire equatorial plane CL.

Further, the two vertical grooves may have different groove widths.

[0013]

In the surface shape of the central portion, the inner groove wall surface and the central ground contact surface area are formed by convex curved surfaces, so that the groove depth of the vertical groove gradually increases outward in the tire axial direction. By making the groove width GW of at least 35 mm wide, the drainage property is improved, and the hydroplaning phenomenon is reduced to improve the wet grip property.

Further, by setting the groove width GW of the vertical groove to 35 mm or more, preferably 40 mm or more, and further gradually increasing the groove depth of the vertical groove at the central portion by a series of convex curves, FIG.
As shown in FIG. 5, before and after the contact center Q of the tire contact surface F which is a footprint (before and after in the tire traveling direction), a widened portion in which the width of the groove in the contact surface F increases in a trumpet shape is formed. Drainability is enhanced and wet grip is further improved. In the drawing, Fc indicates the shape or area of the grounding surface in the central grounding surface area, and Fs indicates the shape or area of the grounding surface in the grounding surface region of the shoulder portion.

In the present invention, the width of the vertical groove GW is set to 35 or more and 0.35 times or less the contact width TW of the tread portion. When regulating the groove width dimension in this way,
An experiment was conducted on the relationship between the groove width and the passing noise, and it was determined based on the results. Tire size is 205/5
In 5R15, as shown in FIG. 8A, when the groove width GW is 7 to 35 mm, the contribution to the reduction of the passing noise is small and the groove width GW is 7 mm or less or 35 mm or more, so that the passing noise is remarkably reduced. And it was confirmed that it was stable. In addition, the tire size is 225 / 50R16
As shown in FIG. 8B, substantially the same results as those described above were obtained with the tire of FIG.

In the test, the microphone position and the like were determined by J
The passing noise was measured in accordance with the ASO standard at a vehicle speed of 60 km / H with the engine off.

Based on this result, the groove width GW can be set to 35 mm or more, and the widened portion formed in the ground contact surface F can prevent air column resonance from occurring and achieve an effective reduction of passing noise. Since the passing noise is caused by the air column resonance as described above, the passing noise changes depending on the size of the groove width GW itself regardless of the tire size. Also, the groove width GW
However, when the contact width exceeds 0.35 times the contact width TW of the tread portion, the contact pressure becomes excessive, so that the dry grip property and the steering stability are reduced, and the wear resistance is poor and the durability is reduced.

The convex central portion surface shape is useful for increasing the rigidity of the central portion. In addition, since the profile of the central part is asymmetrical with respect to the tire equatorial plane, mounting the central part toward the outside of the vehicle increases the tread rigidity on the outside of the vehicle. A strong lateral force can be exerted under the limited ground contact area, dry grip performance can be improved, and straight running stability and turning stability can be enhanced.

[0019]

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 meridional section in a standard state mounted on a standard applicable rim R such as JATMA TRA or ETRTO and filled with a normal internal pressure determined by these standards.

In this embodiment, the pneumatic tire 1 is
As a passenger car tire, a flat tire having a flatness ratio of tire cross-sectional height / tire width of about 0.4 to 0.6 and relatively poor drainage is formed.

The tire 1 has two radially arranged carcass plies 16A which are wound around a bead core 15 of a bead portion 14 from an inner side to an outer side in the tire axial direction through a side wall portion 13 from a tread portion 2 and locked. , 16B
And a belt layer 17 disposed inside the tread portion 2 and radially outside the carcass 16. A carcass 16 extending between the bead cores 15
A bead apex 18 extending radially outward from the bead core 15 in the tire radial direction is disposed between the main body portion and the rewinding portions at both ends of the main body portion, and maintains the shape and rigidity of the bead portion 14.

In the present embodiment, the belt layer 17 comprises a plurality of plies using cords having high tensile rigidity such as steel, aromatic polyamide, etc. in the tire circumferential direction such that the cords intersect each other. , Formed at a relatively small angle of 15 to 30 °. When the carcass 16 is a passenger car tire, an organic fiber cord such as nylon, rayon, or polyester can be used.

The tread portion 2 has, on its surface, two wide grooves 5, 5 which are located on both sides of the tire equator and extend substantially continuously in the circumferential direction. 5 and 5, a position between a pair of shoulders 4, 4 outside the groove bottom edge 6 b of the groove bottom 6 in the tire axial direction and a groove bottom edge 6 a, 6 a inside the groove bottom 6 in the tire axial direction. The tread portion 2 is divided into a central portion 9 to be formed.

In this embodiment, the pair of vertical grooves 5, 5
It is formed at an asymmetric position with respect to the tire equatorial plane CL. As a result, the center plane KL passing through the middle of the central portion 9 in the tire axial direction is displaced with respect to the tire equatorial plane CL.

The groove depth D of the vertical groove 5 is 4 to 6% of the total contact width TW of the tread, for example, a tire size of 205/5.
In 5R15, it is 7.5 to 12.0 mm, and more preferably 8.2 mm.

Further, the surface of the central portion 9 extends inward in the tire axial direction along a curve protruding radially outward from the inner groove bottom edges 6a, 6a in the tire meridional cross section including the tire axis. It has a central part surface shape using a series of convex curves composed of inner groove wall surfaces 9A, 9A and a central ground contact surface area 9B smoothly connecting between the inner groove wall surfaces 9A, 9A.

The center contact surface area 9B is defined as the central portion 9
A surface area in the axial direction of the tire that contacts the ground when a normal load determined by the standard is applied in the standard state, and the shoulder ground surface area 10 of the shoulder part 4 is a normal load of the shoulder part surface. It refers to the width area in the axial direction of the tire that touches down. Also, the total contact width TW of the tread.
Means the distance between the outer edges e1, e1 of the shoulder contact surface areas 10 on the outside in the tire axial direction.

Also, the contact surface area 10 of the shoulder portion 4 intersects with the outer groove wall surface 8 rising from the outer groove bottom edge 6b of the vertical groove 5, and this intersection point is at the contact point area 10 of the shoulder portion 4.
The inner edge 12 located on the inner side in the tire axial direction is formed. Therefore, in the contact surface area 10 of the shoulder portion 4, the contact surface area width SW is defined by the distance between the outer edge e1 and the inner edge 12 in the tire axial direction.

Therefore, the vertical groove 5 is formed by the groove bottom 6 and the inner and outer groove wall surfaces 9A and 8, and the groove width GW of the vertical groove 5 is set to the ground surface area 1 of the shoulder portion 4.
0 is defined as the distance in the tire axial direction between the inner edge 12 in the tire axial direction and the outer edge 11 of the central ground contact surface area 9B adjacent to the inner edge 12. The ground contact surface width C of the central contact surface area 9B
W is defined by the distance between the outer edges 11, 11 in the tire axial direction.

The groove bottom edges 6a and 6b appear to be bent between the outer and inner groove wall surfaces 8 and 9A when the groove bottom 6 is substantially flat as in this embodiment, and the groove bottom 6 has a curved surface. Time, FIG. 5
As shown in (A) and (B), it appears as a bending point or an inflection point between the groove wall surfaces 8 and 9A.

In the present application, when the vertical groove 5 and the inner groove wall 9A are distinguished on the left and right, respectively, the vertical grooves 51 and 52 and the groove walls 91A and 9 are used.
2A, groove width GW, shoulder area width SW at shoulder
Are referred to as groove widths GW1 and GW2 and ground surface area widths SW1 and SW2.

The curve of the central surface shape is
The ground contact areas 10 and 10 of the shoulder portion 4 are extended to substantially contact the virtual tread wire 7 that smoothly connects the contact areas 10 and 10.

Here, "substantially in contact" means that the distance between the central tread area 9B and the virtual tread wire 7 is within 2% of the total tread width TW. At 2% or more, the difference in the ground pressure between the shoulder part 4 and the center part 9 increases,
The grip performance deteriorates and the wear resistance is impaired. Therefore, it is preferably at most 1%, more preferably at most 0.5%.

The imaginary tread wire 7 which smoothly joins between the contact patch areas is an arc curve having a single radius of curvature which is in contact with a tangent at the inner edge 12 of the shoulder contact patch area 10 and has both ends at the inner edges 12, 12. When the tangents are substantially parallel, a straight line connecting the inner edges 12, 12 is formed.

In the present invention, by forming the central portion 9 to have a central portion surface shape composed of the curve as described above, a sub-radius having a relatively small radius of curvature and a sufficiently small width compared to the tire width is provided at the center of the tire. A tread is provided to prevent the hydroplaning phenomenon and improve wet grip.

This is considered to be because when the radius of curvature of the central portion 9, particularly the radius of curvature R1 of the central ground contact surface area 9B, is small, drainage to both outer sides is enhanced, and the drainage effect on a wet road surface is improved.

The radius of curvature R2 of the virtual tread wire 7 is
When the distance is also reduced, the grip performance on a dry road surface due to the decrease in the ground contact area and the steering stability performance at the time of cornering are reduced. Therefore, the radius of curvature R2 of the virtual tread wire 7 is relatively large, preferably three times or more the total contact width TW, and the upper limit thereof is allowable until the shoulder contact surface area 10 approaches a straight line parallel to the tire axis. . The radius of curvature R2
Is located on the tire equatorial plane CL. The shoulder portion 4 has an arc portion smaller than the radius of curvature R2 near the outer end of the contact surface F.

FIGS. 1 and 2 show an example in which the entire central portion surface shape is formed by a curve formed of a single arc having a radius of curvature R1. This radius of curvature R1 is sufficiently smaller than the radius of curvature R2 of the virtual tread line 7, and in this example, this curve is inscribed in the virtual tread line 7 at the contact point K.
The center of the radius of curvature R1 is located on the center plane KL of the central portion 9 passing through the contact point K and parallel to the tire equatorial plane CL, and the center plane KL is separated from the tire equatorial plane CL. Although the profile of the central portion 9 is symmetrical with respect to the center plane KL, the central portion 9 is asymmetric about the tire equatorial plane CL because the center line plane KL is separated from the tire equatorial plane CL.

The radius of curvature R1 is 0.4 times the total contact width TW.
About 1.5 times, more preferably about 0.45 to 0.55 times. If it is smaller than 0.4 times, the width CW of the central contact surface area becomes too small, and the dry grip tends to be greatly reduced. If it is more than 1.5 times, the drainage effect is insufficient and the wet grip property is impaired.

In the shoulder portion 4, the vertical groove 6
The groove wall surface 8 on the outer side in the tire axial direction is preferably a relatively steep and non-circular, for example, a straight line having an angle α formed with the tire radial line X of 0 to 40 °, preferably 5 to 25 °. As a result, an edge effect of the shoulder portion 4 having a high contact pressure with the road surface at the inner edge 11 is exerted, thereby improving lateral force, increasing cornering power, and maintaining dry grip performance. The outer groove wall surface 8 may have a convex curve extending outward in the tire axial direction, similar to the inner groove wall surface 9A. The outer groove wall surface 8 may be connected to the ground surface area 10 of the shoulder portion 4 via an arc.

In the present embodiment, the center plane KL is shifted to the right in FIG. 1 with respect to the tire equatorial plane CL in the present embodiment, as described above. On the other hand, two inner edges 1 of the ground contact areas 10, 10 of the shoulder portions 4, 4 arranged on both sides
2 and 12 are equidistant from the tire equatorial plane CL, and therefore, the contact patch area widths SW1 and SW of the two shoulders 4 are provided.
W2 has equal length.

As a result, the groove width GW is different between the one vertical groove 51 and the other vertical groove 52. Further, in this embodiment, the inner groove wall surfaces 9A, 9A in both the vertical grooves 51, 52 are formed by the same convex curved surface, so that the length of the groove bottom 6 of one of the other vertical grooves 51, 52 is set. Are different.

Regarding the vertical groove 5, a total width 2GW of the groove widths GW of the vertical grooves 5 and 5, and a contact width TW of the tread portion.
It has been found that the total groove width ratio of 2 GW / TW, which is the ratio between the two, has an effect on cornering power and wet grip. The total groove width ratio between the tire having a single circular arc center portion surface shape shown in FIG. 1 and having a tire size of 205 / 55R15 (Example) and the conventional tire having four longitudinal grooves G shown in FIG. FIG. 6 shows the results of measuring the cornering power while changing ΣGW / TW. The total groove width ratio is
The value of 2 GW / TW was used for the example, and the value of (ΣGW) / TW was used for the conventional example. As for the cornering power, each tire was mounted on a regular rim, filled with a regular internal pressure, and measured with a drum tester on a room bench. It can be seen that the value is larger than that of the conventional tire. This is considered that when the total groove width ratio defined above is constant, the inner groove wall surface 9A forming a convex curved surface contributes to an increase in tire lateral rigidity.

FIG. 7 shows the result of measuring the speed at which the hydroplaning phenomenon occurred in the same manner. Compared with the conventional tire, the embodiment has the same total groove width ratio,
It can be seen that the hydroplaning generation speed is high and the phenomenon is unlikely to occur. This shows the tire contact surface F when a regular load is applied, largely due to the fact that the tire has a grooved surface 9A on the inside that forms a convex curved surface in the central portion 9 of the raised small width of the tire of the present invention. As shown in FIG. 4, at the time of grounding, the vertical groove 5 forms a widened portion 5a that spreads like a trumpet before and after the grounding center Q, thereby improving drainage. Note that the total groove width ratioΣ
If the GW / TW exceeds 50%, as shown in FIG. 7, the improvement of the effect of suppressing hydroplaning is hardly expected, and the cornering power becomes insufficient. Therefore, the total groove width ratio ΔGW / TW is preferably 50% or less, more preferably 45% or less.

The widened portion 5a formed in this way also suppresses the occurrence of air column resonance in the vertical groove 5, and as described above, also helps to reduce tire noise.

In order to further enhance the effect of suppressing the columnar resonance, the groove width GW of the vertical groove 5 needs to be 35 mm or more, preferably 40 mm or more. In the range of 55 mm or more, the above-mentioned effect hardly changes.

This is (Tire size 205 / 55R1
5, 225 / 50R16 tires)
8 (A) and 8 (B) in which the passing noise was measured while keeping the groove depth constant and changing the groove width GW. The passing noise rapidly decreases after the groove width GW reaches a maximum in the range of 7.5 to 25 mm, and exhibits excellent low noise performance especially at 35 mm or more.

However, as shown in FIG. 6, although the tire of the present invention has a high cornering power, an increase in the groove width GW causes a decrease in the ground contact area, and a decrease in dry grip performance and steering stability. Further, the wear resistance is deteriorated due to the increase in the contact pressure. Therefore, the groove width GW is set to be equal to or less than 0.35 times the contact width TW from the viewpoint of such dry grip properties, steering stability and wear resistance.

In order to further enhance the steering stability and dry grip performance due to the increase in the groove width GW, as described above, the center plane KL of the center section 9 is displaced with respect to the tire equatorial plane CL, and the center ground plane area is adjusted. 9B is formed asymmetrically about the tire equatorial plane CL. This is because the tread stiffness on the outer side of the vehicle body is increased and a strong lateral force can be exerted by mounting the tire with the side where the central portion 9 is deviated to the outside of the vehicle body, and the steering stability, especially the turning stability Can be increased.

On the contrary, when the center 9 is mounted with the side deviated from the tire equatorial plane CL facing the outside of the vehicle body,
The occurrence of cornering force is small and the asymmetry is excessive, which tends to cause an obstacle that steering stability is reduced.

In order to maintain the dry grip property, abrasion resistance, steering stability, etc., the width CW of the central contact surface area is as follows:
Preferably, it is about 5 to 40%, more preferably 15 to 35% of the contact width TW of the tread portion 2. Further, the width 9W of the central portion 9, which is the distance between the inner bottom edges 6a, 6a,
It is preferable to set it to about 40 to 55% of the grounding width TW.

The central surface shape may be formed as an elliptical shape as shown in FIG. 12, or a curve approximated to an ellipse. Further, in this example, one of the other shoulder contact surface area widths SW1 and SW2 is 0.09 times or more of the contact width TW, for example, 1 in a tire size of 205 / 55R15.
It is preferable that it is 5 mm or more, and when it is smaller than 0.09 times, the contact pressure of the shoulder contact surface areas 10 and 10 increases and uneven wear occurs.

The central portion 9 has a central ground contact area 9B.
In addition, a narrow groove 20 formed of a straight groove continuous in the tire circumferential direction is provided. The narrow groove 20 has a groove width W1 of 7 mm or less, 1.5 mm or more, and a groove depth D1 of 0.4 to 0.9 times the groove depth D of the vertical groove 5. In this embodiment, the narrow groove 20 is provided on the center plane KL.

By providing such a narrow groove 20,
The drainage in the central portion 9 is further improved, the wet grip performance is further improved, and a necessary heat radiation effect is exhibited while maintaining pattern rigidity and low noise. When the groove width W1 is larger than 7.5 mm, and when the groove depth D
When 1 is greater than 0.9 times the groove depth D, air column resonance occurs and tire noise deteriorates. When the groove depth D1 is smaller than 0.4 times the groove depth D and when the groove depth D1 is smaller than 1.5 mm, the heat radiation effect becomes insufficient.

As shown in FIG. 3, in this example, a lateral groove 21 is formed in the shoulder portion 4 and a lateral groove 22 is formed in the central portion 9.
Are provided respectively. The lateral groove 21 extends axially outward from a position axially outward from the vertical groove 5 and closes in front of the tread end E. The lateral groove 25 communicates with the vertical groove 5 and opens beyond the tread end E. Including a lateral groove 26.
By arranging the lateral grooves 25 and 26 alternately,
The wet grip performance is improved while preventing a decrease in rigidity of the shoulder portion 4.

Only one end of the lateral groove 22 of the central portion 9 is open to the longitudinal groove 5, and the inner side in the axial direction is interrupted near the central plane KL. By not providing the lateral groove near the center plane KL, the rigidity of the central portion 9 is maintained, and the steering stability is secured. The lateral grooves 21, 22 have their groove bottoms substantially parallel to the belt layer 17, and the axial inner end faces 21b, 22b of the lateral grooves 21, 22 are parallel to the tire equatorial plane CL. Also, the inclination angle of the groove wall with respect to the tire radius line is set to 1
It is preferable that the angle be a small angle of less than 5 °.

Thus, it is possible to suppress a decrease in wet grip due to a decrease in the length of the lateral groove as the tire wears. Note that the circumferential pitch,
Other tire specifications such as depth can be selected according to the purpose.

Next, FIGS. 9 and 10 show another embodiment in which the profile of the central portion 9 is asymmetric with respect to the tire equatorial plane CL when the center plane KL deviates from the tire equatorial plane CL.

In this example, the center contact surface area 9 having a radius of curvature R1
B is symmetrical with respect to the tire equatorial plane CL, but the profiles of the respective groove wall surfaces 91A and 92A are different from each other. One inner groove wall surface 91A is formed by an arc having a radius of curvature R3a, and the other inner groove is formed. The wall surface 92A has the radius of curvature R
1 and a radius of curvature R3b larger than R3a. Furthermore, the width S of the contact patch area at both shoulders 4 and 4
W1 and SW2 are the same.
In order to make the respective groove widths GW1, GW2 equal to each other, the groove bottom lengths 61W, 62W which are the distances between the outer groove bottom edges 6a, 6b of the groove bottom 6 are different.

Accordingly, in this example, as shown in FIG. 16A, the shape of the contact surface F when new is symmetrical with respect to the tire equatorial plane CL. In this case, the tire is mounted so that the groove wall 92A faces the outside of the vehicle.

In a normal tire, when a lateral force is applied to the tire at the time of cornering or the like, the contact surface shape F greatly changes from FIG. 18A to FIG. They tend to be about the same or rather slightly reduced.

On the other hand, the tire having the tread profile shape shown in FIGS.
As shown in (B), from the straight running to the cornering state where a large lateral force is applied, the change in the total of the contact shape and the contact area is small, and the cornering power generated on the table is superior to the conventional tire of FIG. ing. And the tire of this example can exhibit the same or better steering characteristics in a real vehicle as compared with a conventional tire having a small ΔGW.

Further, in the tire shown in FIGS. 9 and 10, when the vehicle is mounted on the vehicle, the groove wall surface 92A on the side located on the outside of the vehicle has a radius of curvature R3b having a central portion 9 as shown in FIGS. As shown in FIGS. 16A and 16B, the contact area Fc of the central contact area 9B at the time of cornering is less than the lateral force at the time of cornering, as shown in FIGS. With the increase,
Rather, it will gradually increase. As a result, in addition to good steering characteristics, the maximum cornering force can be increased to obtain a high limit grip.

On the other hand, when the radius of curvature R3b of the inner groove wall surface 92A is simply increased and the width 62W of the groove bottom 6 is reduced, the groove width (GW) decreases with the progress of wear, and the groove depth increases. Along with the decrease in the wear, the hydroplaning resistance during the progress of wear deteriorates. Therefore, the curvature radius R3 of the groove wall surface 91A on the inner side when the vehicle is mounted is shown.
a, the groove widths GW1 'and GW in the middle period of wear
By substantially maintaining the sum of 2 ′, it is possible to ensure the same level of hydroplaning resistance during wear as in the case where the central portion 3 is formed with a single radius of curvature R1.

FIG. 11 shows still another embodiment. In this example, the center plane KL passing through the center of the central portion 9 in the tire axial direction coincides with the tire equatorial plane CL. In this example, the profile shape of the central portion 9 is changed by changing at least each profile shape of the groove walls 91A and 92A to the tire equatorial plane CL.
Is asymmetric with respect to The central portion 9 includes groove walls 91A and 92A having different radii of curvature R3a and R3b, and the central ground contact surface area 9B has a central surface JL.
Symmetric with respect to The center plane JL is a plane that bisects the central ground contact surface area 9B in the width direction and is separated from the tire equatorial plane CL in this example, but may be matched as shown in FIG.

The tire having the profile shape shown in FIG. 13 has a central ground contact groove Fc as the lateral force increases at the time of cornering, similarly to the tires shown in FIGS. 9, 10 and 11.
It has the effect of increasing smoothly, improving the limit grip and turning stability.

In the present invention, the center contact surface area 9B may be asymmetric with respect to the center plane JL (FIG. 14).
Due to this asymmetry, the profile shape of the central portion 9B may be asymmetric with respect to the tire equatorial plane CL.

(Specific example) Tire size 205 / 55R1
The tire No. 5 was manufactured according to the specifications shown in Table 1, and the passing noise, cornering power, and hydroplaning generation speed were measured, and these were compared. The results are shown in the same table.

[0069]

[Table 1]

[0070]

As described above, the pneumatic tire of the present invention having the above-described structure can improve wet performance, especially hydroplaning performance, and reduce tire noise. The grip performance can be enhanced and the tire can be suitably used as a passenger car tire.

[Brief description of the drawings]

FIG. 1 is a sectional view of a tire according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing the tread portion surface shape.

FIG. 3 is a partial plan view showing the tread pattern.

FIG. 4 is a plan view showing the tread contact surface shape.

FIGS. 5A and 5B are cross-sectional views showing another embodiment of the bottom of the vertical groove.

FIG. 6 is a graph showing a relationship between a total groove width ratio of vertical grooves and a cornering power.

FIG. 7 is a graph showing a relationship between a total groove width ratio of vertical grooves and a hydroplaning generation speed.

FIGS. 8A and 8B are graphs each showing a relationship between a groove width of a vertical groove and a noise level.

FIG. 9 is a cross-sectional shape of a tire according to another embodiment.

FIG. 10 is a sectional view showing the tread portion surface shape.

FIG. 11 is a cross-sectional view illustrating a tread surface shape according to another embodiment.

FIG. 12 is a cross-sectional view illustrating a tread portion surface shape according to another embodiment.

FIG. 13 is a cross-sectional view showing a tread surface shape of another embodiment.

FIG. 14 is a sectional view showing a tread portion surface shape according to another embodiment.

FIG. 15 is a sectional view of a tread portion of a conventional tire.

16 (A) and (B) are cross-sectional views showing the shape of the ground contact surface of the tire of the present invention shown in FIGS.

17 (A) and 17 (B) are cross-sectional views showing the shape of the ground contact surface of the tire of the present invention shown in FIGS.

FIGS. 18A and 18B are cross-sectional views showing the shape of the ground contact surface of a conventional tire.

19 is a cross-sectional view of a tread portion of a comparative tire used in Table 1. FIG.

[Explanation of symbols]

 2 Tread part 4 Shoulder part 5 Vertical groove 6 Groove bottom 6a Inner groove bottom edge 6b Outer groove bottom edge 8 Outer groove wall surface 9 Central part 9A, 91A, 92A Inner groove wall surface 9B Central ground plane area 10 Shoulder part Tread area 11 Inner edge 12 Outer edge CL Tire equatorial plane GW, GW1, GW2 Groove width of vertical groove KL Center plane SW1 Tread area width of one shoulder SW2 TW width of the other shoulder TW Tread

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-7-232515 (JP, A) JP-A-7-276915 (JP, A) JP-A-5-147407 (JP, A) JP-A-6-275407 127215 (JP, A) JP-A-7-186628 (JP, A) JP-A-7-47808 (JP, A) JP-A-6-33706 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60C 11/00 B60C 11/04 B60C 11/06

Claims (7)

(57) [Claims] A tread portion is provided with two longitudinal grooves on both sides of the tire equator which extend substantially continuously in the circumferential direction, so that the tread portion can be made larger than a groove bottom edge of the longitudinal groove on the outer side in the tire axial direction. A pneumatic tire divided into a pair of outer shoulder portions and a central portion between groove bottom edges on the tire axial direction inside of the longitudinal grooves, wherein the central portion is a tire meridional section from the inner groove bottom edge. It has a central part surface shape using a series of curves consisting of an inner groove wall surface extending radially outward and extending inward in the tire axial direction and a central tread area smoothly connecting between the inner groove wall surfaces, and The central tread area substantially abuts a virtual tread edge connecting between the tread areas of the shoulder portion, and in a tire meridional section, the center has an asymmetric profile shape that is asymmetric with respect to the tire equatorial plane CL. , The groove width GW of the longitudinal groove, which is the distance in the tire axial direction between the inner edge of the shoulder contact area in the tire axial direction on the inner side in the tire axial direction and the outer edge of the central contact area on the side adjacent thereto, is 35 mm or more and the tread part A pneumatic tire characterized in that the width is not more than 0.35 times the contact width of the tire. 2. The pneumatic tire according to claim 1, wherein a center plane KL passing through the middle of the center portion in the tire axial direction coincides with a tire equatorial plane CL. 3. The pneumatic tire according to claim 1, wherein a center plane KL passing through the center of the center portion in the tire axial direction is displaced from a tire equatorial plane CL. 4. The profile shape of the central ground contact area is:
The tire according to claim 3, wherein the tire is symmetric with respect to the tire equatorial plane CL. 5. The profile shape of the central portion is symmetrical with respect to the central plane KL.
The described tire. 6. The pneumatic tire according to claim 1, wherein said two vertical grooves have different groove widths GW. 7. The contact surface area width SW1 of the contact surface area of the one shoulder portion in the tire axial direction in the tire axial direction is equal to the contact surface area width SW2 of the contact surface area of the other shoulder portion. Or the pneumatic tire according to 3.