JP3067224B2 - Pneumatic radial 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 for a passenger car, and more particularly to a radial tire capable of exhibiting high athletic performance when used for a high-performance vehicle.

[0002]

2. Description of the Related Art A plurality of circumferential grooves extending in a circumferential direction of a tire are provided on a tread surface of a tread, and a circumferential groove located on an outer side of the vehicle body when the tire is mounted on the vehicle body in a front view. The groove center line in the cross section in the tread width direction is inclined in a direction in which the radially outer portion of the tire is located closer to the tread central portion with respect to the radially inner portion. There are those described in JP-B-36-10752, French Patent No. 993870 and U.S. Pat. No. 3,860,086.

When the relationship between the slip angle and the cornering force of these tires is measured using a flat belt maneuverability tester, the cornering force changes as shown by a solid line in FIG. The groove center line in the cross section of the circumferential groove in the tread width direction is generated by a tire that is not inclined at all in the tread width direction inside and outside in the radial direction. It will be raised effectively enough.

[0004]

In the prior art, when a vehicle is turned by giving a slip angle to the tire, the tire mounted on the vehicle body, in particular, on the outer side of the vehicle body. As shown in the partial cross-sectional view of the tread width direction in FIG. 4, the obtuse-side corner C of each land portion B defined by the circumferential groove A is severely worn by the side force SF received by the tire from the road surface. On the other hand, the corner D on the acute angle side of the land portion B remains with little wear. Such a phenomenon is caused by the obtuse corner C of the land B.
Is directly supported by the side force SF under high rigidity, whereas the acute-angled corner D is caused by being largely deformed inside the circumferential groove A and rising from the road surface. In the actual vehicle running, if such a wear phenomenon occurs, the contact state of the land portion B becomes uneven, and the tread operation rate gradually decreases, so that the road surface grip force of the tire decreases over time. There was a problem.

The present invention advantageously solves the above-mentioned problems of the prior art, and maintains the advantage of the conventional tire that generates a high cornering force by improving the form of wear of the land portion in the tread width direction. Another object of the present invention is to provide a pneumatic radial tire that can effectively prevent the road surface grip force of the tire from decreasing over time.

[0006]

In a pneumatic radial tire according to the present invention, a plurality of circumferential grooves extending in the circumferential direction of the tire are provided on a tread tread portion, and a front view of a mounting posture of the tire on a vehicle body is provided. At least, a groove center line in a cross section in the tread width direction of a circumferential groove located on the outermost side of the vehicle body, and a radially outer portion of the tire at a tread central portion with respect to a radially inner portion. At the place where it is inclined in the direction located on the side, the groove wall on the tread end side of the inclined circumferential groove is inclined in the radially outer end portion of the tire in the direction of gradually expanding the groove width. is there.

[0007] More preferably, the angle of intersection between the groove center line of the inclined circumferential groove and the normal line drawn on the outer contour of the tread is set to an angle in the range of 5 to 35 °. Note that, here, the outer tread contour refers to a tread contour in a case where a circumferential groove is omitted in a cross section in the tread width direction. Therefore, the term "intersecting angle" used herein means an intersecting angle between a normal line formed in the inclined circumferential groove portion and the groove center line.

Preferably, the angle of intersection between the widened inclined surface of the groove wall on the tread end side of the inclined circumferential groove and the normal to the outer contour of the tread is in the range of 10 to 45 °. hand,
5% to 15% of the width of the expanded slope along the outer contour of the tread with respect to the width along the outer contour of the tread of the land portion defined by the inclined circumferential groove at the tread end side.
Range.

Preferably, in a front view of the mounting posture of the tire on the vehicle body, all of the circumferential grooves extending in the tread half portion on the outer side of the vehicle body are formed in a cross section in the tread width direction.
It is inclined in the same direction as the outer circumferential groove located on the outermost side of the vehicle body, and the groove wall on the tread end side of all the inclined circumferential grooves gradually increases in the radial outer end portion of the tire. Inclined in the opening direction, and more preferably, at least one, more preferably all, of the circumferential grooves extending in the tread half on the inner side of the vehicle body in a front view of the mounting posture of the tire on the vehicle body. In the cross-section in the tread width direction, while inclining to the opposite side to the circumferential groove extending to the tread half portion on the outer side of the vehicle body,
At the tread end side groove wall at the radial outer end of the tire,
The groove width is inclined in the direction of gradually expanding.

These will be described more specifically with reference to FIG. Here, the tread tread 1
In the center of the tire, a narrow circumferential groove 2 extending linearly in the tire circumferential direction is provided, and circumferential grooves 3a, 3b and symmetrically positioned on each side of the narrow circumferential groove 2 are provided.
4a and 4b are sequentially formed toward the tread end side, and reach the respective tread ends from the respective circumferential grooves 3a and 3b. In the figure, where a plurality of substantially “F” -shaped width-direction grooves 5 are formed, two circumferential grooves located on the outer side of the vehicle body when viewed from the front of the tire mounted on the vehicle body as shown in the figure. As is clear from the cross-sectional view in the tread width direction shown in FIG. 1B, the groove center lines 6 and 7 of the respective circumferential grooves 3a and 4a in the cross-section of the cross-sections 3a and 4a are A method in which the tire radially outer portion is inclined toward the tread center portion side with respect to the radially inner portion, and the respective groove center lines 6 and 7 are set on the tread outer contour line 8. The angles of intersection α _and β with the lines N ₁ and N ₂ are both 15
°.

Here, each of the inclined circumferential grooves 3
The groove walls 9 and 10 at the tread end side of the tires a and 4a are inclined at the radially outer end portion of the tire in a direction in which the groove width is gradually expanded, and their respective expanded inclined surfaces 9a and 10a, The intersection angles γ and δ with the normals N _{3 and} N ₄ set on the outer contour line 8 of the tread are both set to 42 °, and the widths w ₁ and w of the expanding inclined surfaces 9 a and 10 a along the outer contour line 8 of the tread are further increased. ₂ is about 11.5% and 7% for a similar width of the respective land sections, blocks 11 and 12 in the figure, which are defined on the tread end side by respective inclined circumferential grooves 3a and 4a. . In addition, in the drawing, both the expanding inclined surfaces 9a and 10a are flat surfaces, but these inclined surfaces 9a and 10a may be curved or bent surfaces.

[0012]

In this pneumatic tire, the circumferential grooves 3a and 4a are formed as inclined circumferential grooves, so that when the tire is provided with a slip angle, each of the circumferential grooves 3a and 4a is defined by the inclined circumferential grooves 3a and 4a. The obtuse corners 13 and 14 of the land portion can directly support the side force and generate a large cornering force under the high rigidity against the side force as described in the related art.

Moreover, here, the inclined circumferential grooves 3a, 4a
The groove walls 9 and 10 on the tread end side are provided with flared slopes 9a and 10a, respectively, so that the respective groove walls 9 and 10 are opposed to the respective groove walls due to the input of the side force to the land portion. As shown in FIG. 2, one of the groove walls 9 is taken as an example when the radially inner end portion of the groove wall 9 is deformed to a position very close to the opposing groove wall, and even if it is severely contacted. ,
It is possible to effectively prevent the side end portion of the block 11 on the side of the groove wall 9 from entering the circumferential groove 3a, so that the block 11 can be grounded almost uniformly in the entire width direction. This can result in a further increase in cornering force in conjunction with uniform wear.

Here, normal lines N ₁ , N ₂ erected on the groove center lines 6, 7 of the inclined circumferential grooves 3 a, 4 a and the tread outer contour line 8.
When the angles of intersection α _and β with 5 to 35 °, and more preferably 10 to 20 °, the occurrence of a large cornering force can be ensured, and the ground contact property of the land can be effectively improved. it can. That is, if the angles of intersection α _and β are less than 5 °, the cornering force cannot be effectively increased. If the angle of intersection exceeds 35 °, even if the expanded slopes 9a and 10a are provided, The groundability cannot be sufficiently improved.

Further, the intersection angles γ _and δ between the widening inclined surfaces 9 a and 10 a and the normals N ₃ and N ₄ formed on the outer contour line 8 of the tread are set to 10 to
45 °, more preferably in the range of 15 to 35 °,
The above-mentioned functions and effects of the widened inclined surfaces 9a and 10a are sufficiently provided, and a required groove volume can be secured.
In other words, if the intersection angles γ _and δ are less than 10 °,
9a and 10a can hardly perform their original functions.If the angle exceeds 45 °, it will not be possible to secure a sufficient groove volume under a limited groove width,
Substantial significance of the provision of 9a and 10a will be lost.

In this case, in this case, the expanding slope 9
The widths w ₁ and w ₂ along the outer contour line 8 of the treads a and 10a are respectively defined by the inclined circumferential grooves 3a and 4a on the tread end side. 5-15% of the width of
The expanding inclined surfaces 9a and 10a can function more effectively. In other words, if the ratio is less than 5%, it is almost impossible for the expanding inclined surface to exhibit its original function, and if the ratio exceeds 15%, the expanding inclined surface reaches the groove bottom. It cannot do its original function.

As shown in FIG. 1, when the tire is mounted on the vehicle body, when viewed from the front, all the circumferential grooves 3a and 4a extending in the outer tread half of the vehicle body are both inclined circumferentially. Grooves, and on the respective groove walls 9 and 10 on the tread end side of the inclined circumferential grooves, both the expanded inclined surfaces 9a,
When 10a is provided, the circumferential grooves 3a and 4a become deformed as shown in FIG. 2 in response to the input from the road surface outside the turning of the vehicle, and each block on the outer side of the tread is placed on the block surface. The grounding can be increased over the entire area to increase the functionality and improve cornering force.

Further, when the tire is mounted on the vehicle body, when viewed from the front, the tire extends to the tread half on the inner side of the vehicle body.
Preferably, all the circumferential grooves 3b, 4b are inclined in the direction opposite to the outer circumferential grooves 3a, 4a of the vehicle body, and the groove walls of the inclined circumferential grooves 3b, 4b on the tread end side. By inclining the groove width gradually in the radially outer end portion of the tire in the direction in which the groove width gradually widens, it is possible to obtain the above-described effect also on the inner wheel of turning, and a higher cornering force can be increased. Can be brought without wear damage.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. Figure 1 shows a tire of size 225/50 VR 16
It is a tread pattern and tread width direction sectional view shown in front view of the mounting posture to a vehicle body, and here, the left side of the figure is the outside of the vehicle body. The internal reinforcement structure of the tire is
Since it is the same as that of a general radial tire, illustration is omitted.

Here, under normal internal pressure and normal load, 18
A tread 1 having a width of 6 mm has a narrow circumferential groove 2
With the center groove as the center groove, extending straight in the tire circumferential direction,
A total of five circumferential grooves 2, 3a, 3b, 4a, 4b are formed, and their respective groove widths are 4.5mm, 9.5mm, 9.5mm, 7.0mm
And 7.0 mm, and each circumferential groove 3a,
3b, the width direction grooves 5 extending in a substantially “F” shape from the tread end to the tread end are provided, and the width of each width direction groove 5 is set to 6.0 mm.
Further, a downwardly inclined groove 15 extending from each of the circumferential grooves 3a and 3b in the direction of the width circumferential groove 2 but ending without reaching the groove 2 is provided. As is apparent from FIG. 1 (b), the groove center lines 6 and 7 in the cross section in the tread width direction of the circumferential grooves 3a and 4a of the The outer portion is inclined in the direction located on the tread center portion side with respect to the tire radially inner portion, and the groove center lines 6 and 7 and the respective grooves are provided.
The intersection angles α _and β with the normals N ₁ and N _2, which are set on the outer contour line 8 of the tread at the positions corresponding to 3a and 4a _, are both set to 15 °, and the grooves on the tread end side of the circumferential grooves 3a and 4a. Walls 9 and 10
At the radially outer end portion of the tire, the groove width is inclined in such a direction as to gradually expand, so that their respective expanded slopes 9a, 10
The intersection angles γ _and δ between a and the normals N ₃ and N ₄ drawn on the outer contour line 8 of the tread are both set to 42 °.

Here, by setting the width w ₁ of the expanding inclined surface 9a along the outer contour line 8 of the tread to 3.0 mm,
A block 11 defined by the circumferential grooves 3a, 4a and the width grooves 5.
To the same width 26 mm, and about 11.5 percent ratio of the width w _1,
Then, the width w ₂ of the expanding inclined surface 10a measured in the same manner is calculated.
By a 2.0 mm, the width 28mm of block 12, and about 7% the ratio of width w _2. In this example, the intersection angle of each of the groove walls of the two circumferential grooves 3b and 4b located on the inner side of the vehicle body with the normal set on the outer contour line 8 of the tread is 5 °.

(Comparative Example) Hereinafter, the maximum cornering force, the maximum wear step of the tread land portion, and the difference between the comparative tire in which the groove center line in the cross section in the tread width direction of the circumferential groove is not inclined at all and the inventive tire are described. A comparative test on the change over time of the road surface grip force will be described. ◎ Test tire ・ Invented tire Tire having tread pattern and dimensions shown in FIG. 1 ・ Comparative tire Circumferential grooves 3a, 4a on the outer side of the vehicle body of tire shown in FIG.
With the same configuration as the circumferential grooves 3b, 4b on the inner side of the vehicle body ◎ Test method ・ Maximum cornering force Using a flat belt maneuverability tester, tire internal pressure 2.5kg
The test was performed under the conditions of / cm ² , load of 400 kg, and speed of 50 km / h, and the maximum cornering force was measured.・ Maximum wear level After running around a circuit course of about 2 km in one round, the level difference (corresponding to level difference S shown in FIG. 4) in the cross section between the shoulder block and the second block was measured.・ Change over time in grip force One lap was run continuously for 20 laps on a circuit course of about 2 km, and the delay of the lap time in the second half with respect to the lap time in the first half was measured.試 験 Test results Table 1 shows the results of the above tests. For the cornering force in the table, the test result of the comparative tire is set to an index of 100, and the larger the index value, the better the result. In addition, the maximum wear step is represented by an actually measured value, and the change in grip force with time is set to an index of 100 at the beginning of the lap, and the larger the index value, the larger the change with time.

Table 1 According to Table 1, according to the invention tire, the maximum cornering force can be greatly increased as compared with the comparative tire under the action of the inclined circumferential grooves 3a and 4a. Due to the presence of 9a and 10a, it is clear that the maximum wear step can be reduced to 1/3 or less of that of the comparative tire to effectively prevent the time-dependent change of the road surface grip force and, at the same time, further increase the cornering force. is there.

[0024]

As described above, according to the present invention, the maximum cornering force is sufficiently increased, and the maximum wear step on the tread land portion is effectively reduced, so that the change over time in the grip force of the tire is extremely effectively prevented. be able to.

[Brief description of the drawings]

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

FIG. 2 is a sectional view showing a deformed state of a circumferential groove.

FIG. 3 is a graph showing a cornering force of a conventional tire.

FIG. 4 is a partial cross-sectional view showing a worn state of a conventional tire.

[Explanation of symbols]

 Reference Signs List 1 tread tread portion 2 narrow circumferential groove 3a, 3b, 4a, 4b circumferential groove 5 width groove 6,7 groove center line 8 tread outer contour line 9,10 groove wall 9a, 10a widening inclined surface 11,12 Blocks 13, 14 obtuse corners

Continuation of the front page (56) References JP-A-2-270608 (JP, A) JP-A-63-222905 (JP, A) JP-A-3-295706 (JP, A) JP-A-2-179507 (JP) , A) JP-A-3-193505 (JP, A) JP-A-4-133804 (JP, A) JP-A-4-143105 (JP, A) Japanese Utility Model Application No. Sho 59-172004 (JP, U) 36-10752 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) B60C 11/04 B60C 11/11 B60C 11/06

Claims (5)

(57) [Claims] A plurality of circumferential grooves extending in a circumferential direction of a tire are provided in a tread tread portion, and at least a circumferential groove positioned at an outermost side of a vehicle body in a front view of a mounting posture of the tire on the vehicle body. A tire in which a groove center line in a cross section in a tread width direction of a directional groove is inclined in a direction in which a radially outer portion of the tire is located closer to a tread central portion side than a radially inner portion. Of the inclined circumferential groove,
At the tread end side groove wall at the radial outer end of the tire,
A pneumatic radial tire with a groove that is inclined in a direction that gradually widens. 2. The pneumatic radial tire according to claim 1, wherein an intersection angle between the groove center line of the inclined circumferential groove and a normal line formed on the outer contour of the tread is in a range of 5 to 35 °. 3. An intersection angle between a widening inclined surface of the groove wall on the tread end side of the inclined circumferential groove and a normal line drawn on the outer contour line of the tread is in a range of 10 to 45 °, and the widening thereof is performed. Of the slope,
The width along the outer tread line is set in a range of 5 to 15% of the width along the outer tread line of the land portion defined by the inclined circumferential groove on the tread end side. Or the pneumatic radial tire according to 2. 4. A front view of a tire mounted on a vehicle body,
All of the circumferential grooves extending in the tread half on the outer side of the vehicle body are inclined in the same direction as the circumferential groove located on the outermost side of the vehicle body in the cross-section in the tread width direction, and all the inclined circumferential surfaces thereof are inclined. The pneumatic radial tire according to any one of claims 1 to 3, wherein a groove wall on the tread end side of the direction groove is inclined at a radially outer end portion of the tire in a direction in which the groove width gradually increases. 5. A front view of a tire mounted on a vehicle body,
At least one circumferential groove extending in the tread half on the inner side of the vehicle body is inclined in a cross section in the tread width direction to the side opposite to the circumferential groove extending in the tread half on the outer side of the vehicle body. The tire according to any one of claims 1 to 4, wherein a groove wall on the tread end side of the inclined circumferential groove is inclined at a radially outer end portion of the tire in a direction in which the groove width gradually increases. Pneumatic radial tire.