JPH08164712A - Pneumatic radial tire - Google Patents

Abstract

PURPOSE: To improve drain performance on a wetting road surface, a traveling noise preventive characteristic and maneuvering stability on a dry road surface by arranging respective inclined grooves whose start end does not each a pattern center in a plurality in the tire circumferential direction, and specifying an angle to a tire equatorial surface, the total number and a length of the inclined grooves. CONSTITUTION: In a tire where respective inclined grooves 4 and 5 whose start end does not reach a pattern center f-f are arranged in a plurality in the tire circumferential direction, an angle α to a tire equatorial surface X-X of the inclined grooves 4 arranged on one side tread surface part 1 from the pattern center f-f in a central area of the tread surface part 1, is set larger than an angle 13 to the equatorial surface X-X of the inclined grooves 5 arranged in the other side tread surface part 1 from the pattern center f-f. The total number of the inclined grooves 4 occupied on the tire circumference is set in 1.5 times or 2.5 times the total number of the inclined grooves 5, and a length up to the tail end from the start end of the inclined grooves 5 is set in 1/2.5 or 1/1.5 times a length of the inclined grooves 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-flat high performance pneumatic radial tire which is particularly mounted on a high speed and high performance vehicle to reduce pattern noise and to have excellent steering stability on both wet and dry road surfaces. Regarding

[0002]

2. Description of the Related Art Conventionally, as a tire mounted on a high-speed and high-performance passenger car that runs at high speed with high horsepower, the drainage property of the central portion of the ground contact surface is improved in order to avoid the hydroplaning phenomenon on a wet road surface. Thus, a linear groove in the tire circumferential direction has been arranged in this portion. However, since it has been found that such a linear groove in the circumferential direction causes a so-called air column resonance phenomenon in the groove at the time of grounding to generate high frequency noise (noise), it has been hesitated to be adopted recently. Then
Japanese Patent Laid-Open No. 4-193608 and Japanese Patent Laid-Open No. 4-193608
As shown in No. 224403, there is no linear groove in the circumferential direction in the pattern center portion, and a groove inclined with respect to the tire equatorial plane is arranged in a divergent manner from the tire rotation direction toward the rear. The directional pattern has been attracting attention. In such a directional pattern, the generation of noise due to the air column resonance is prevented, and in general, when the tire is running and rotating, the central portion of the ground contact surface is grounded first and the end portion is delayed and grounded. Therefore, the water in the ground contact surface is rapidly discharged from the center surface of the ground contact surface toward the end of the ground contact surface so that the running performance on the wet road surface can be maintained excellently.

Here, the definitions of the main terms used in this specification will be given. * Pattern center; In a pair of inclined grooves extending in one direction on the tire circumference with an inclination angle in the opposite direction to the tire equatorial plane, the ridgeline on the tire surface of each inclined groove is
Two tire circumferential tangents (c) contacting the parts (a and b in FIG. 1) closest to each other in the direction parallel to the tire rotation axis.
Bisecting line (f-f) of the distance between -c and d-d). * Grounding surface: For convenience, the tire is assembled on the regular rim based on the ETRTO standard, the regular internal pressure is filled, and the maximum load of 7 is designed on the flat plate.
The area is grounded when 0% is added. * Tread tread portion: a tread portion that serves as a ground contact surface and a pattern of the tread portion that is provided on both sides of the tread portion.
The part of the pattern that is substantially continuous with the pattern. * Inflection part: The part where the inclined groove is bent almost at right angles to the equatorial plane of the tire. * Central area of the tread tread; the area of the tread tread sandwiched between the inflections of the pair of inclined grooves. * Tread tread side area: Area from the inflection part to the end of the tread tread. * Negative rate: In the unit area of the tread tread surface, patterns such as grooves, sipes and slits within the unit area
The ratio of the area (A) of the notch forming the tread surface of the tread and the area (B) of the so-called land tread excluding the notch, expressed as A / (A + B). * Flatness; ratio of tire cross-section height to total tire width.

[0004]

However, the directional pattern as described above is provided in the wide tread ultra-flat shape required for high speed and high performance vehicles (a tread width corresponding to the ground contact surface of 250 mm or more and an oblateness of 50). %), The width of the ground contact surface becomes extremely wide according to the total width of the wide tire, so that it is necessary to further increase the drainage amount in the ground contact surface. Therefore, a sufficient drainage effect cannot be obtained only by the inclined groove, and the negative ratio must be increased by adding many grooves in the pattern.
As a result, the area of the land portion in the pattern is reduced, the effective ground contact area is reduced, the frictional force with the road surface is reduced, and the cornering force of the tire is reduced. In particular,
On a dry road surface, and with tires mounted on the drive wheels, the driving torque lowers the frictional force of the ground contact surface and lowers the cornering force, causing dust and causing a problem of drastically reducing the steering stability performance of the vehicle. .

In view of the above situation, an object of the present invention is to provide a pneumatic radial tire which is excellent in running noise prevention property without lowering drainage property on wet road surface and which improves steering stability on dry road surface. Is to provide.

[0006]

In order to achieve the above object, in the pneumatic radial tire of the present invention, as described in claim 1, the pattern center of the tread tread portion is used.
The land portion is provided with a continuous land portion in the tire circumferential direction, and on both sides of the land portion, the pattern center portions are used as starting points to separate the land portions in the tire circumferential direction toward the respective ground contact surface end portions. A tire in which a plurality of inclined grooves are provided in the tire circumferential direction so that the starting end does not reach the pattern center even though the end extends to the end of the tread surface. In the central area of the tread surface, the angle of the inclined groove arranged on the tread surface on one side from the pattern center with respect to the tire equatorial plane is arranged on the tread surface on the other side from the pattern center. Greater than the angle of the inclined groove to the tire equatorial plane,
The total number of inclined grooves arranged on the tread tread portion on the one side on the tire circumference is 1.5 to 2.5 times the total number of inclined grooves arranged on the tread tread portion on the other side. The length from the start end to the end of the inclined groove arranged on the tread tread portion on the one side is 1 / 2.5 to 1 of the length of the inclined groove arranged on the tread tread portion on the other side. /1.5 times, and further, in both areas of the tread tread, there is a lug groove formed by bending the inclined groove almost at right angles to the tire equatorial plane at the inflection portion near the end of the ground contact surface. It is characterized in that it is arranged and the lug groove is opened at the end of the tread tread portion.

Further, in order to adjust the rigidity of the land portion partitioned by the adjacent inclined grooves in the both side areas of the tread tread portion and to further enhance the drainage property, both sides of the tread tread portion are set as described in claim 2. In the area, a sub-lug groove that is substantially parallel to the lug groove is provided in a land portion that is partitioned in the tire circumferential direction by the adjacent lug groove, and further, the sub-lug groove that is arranged on the tread tread portion on the other side. The pneumatic radial tire according to claim 1, wherein the number of tires is 2 to 4 times the number of the auxiliary lug grooves arranged on the tread surface of the one side.

Further, in particular, in order to prevent uneven wear of a side area of the tread tread portion on the other side, as described in claim 3, a plurality of sub-lugs arranged on the tread tread portion on the other side. The pneumatic radial tire according to claim 2, wherein the grooves have different lengths in the direction parallel to the tire rotation axis.

Further, in order to adjust the rigidity of the land portion defined by the inclined grooves, as described in claim 4, in the central area of the tread tread portion, in the land portion defined by the adjacent inclined groove, A plurality of dividing grooves or sipes that divide the land portion and extend in a direction substantially perpendicular to the extending direction of the inclined groove are provided, and further, the width of the dividing grooves or sipes arranged on the tread tread portion on the other side is the The pneumatic radial tire according to any one of claims 1 to 3, wherein the width is at least equal to or larger than the width of the dividing groove or the sipe arranged on the tread tread portion on one side.

Further, in order to preferably balance the performance on the wet road surface and the performance on the dry road surface, the negative ratio of the pattern arranged on the grounding surface on the other side as described in claim 5 Is a pattern arranged on the ground plane on the one side.
The pneumatic radial tire according to any one of claims 1 to 4, which is 5 to 20% larger than the negative ratio of the pneumatic radial tire.

[0011]

In the pneumatic radial tire according to the present invention, the circumferential groove that is continuous from the tread tread portion in the tire circumferential direction is removed, and it is possible to completely prevent generation of pattern noise due to air column resonance. When the tire is mounted on the vehicle by designating the rotation direction such that the start end of the inclined groove is the rotation direction of the tire, the tires extend in a direction separating from each other from the lower side to the upper side in a front view. Due to the drainage action of the inclined groove, deterioration of running performance (wet performance) on a wet road surface including anti-hydroplaning can be prevented very effectively. In addition, pattern noise, particularly pitch noise generated based on the number of pattern pitches due to impact input from the road surface caused by stepping on the road surface of the tire tread portion or kicking out of the road surface during tire rolling On the other hand, since the starting point of each inclined groove is set so as not to reach the pattern center, the continuous land extending in a tire circumferential direction on a substantially straight line in the central area of the tread tread portion, which has a great influence on the noise. The pattern noise can be effectively reduced by forming the portion. Furthermore, the responsiveness at the initial stage of steering is improved by the land portion which is continuous in the circumferential direction.

In the central area of the tread surface,
In the tire of the present invention, the inclination angle of the inclined groove arranged on the tread tread portion on one side from the pattern center with respect to the tire equatorial plane is determined by the inclination angle of the inclined groove arranged on the tread tread portion on the other side from the pattern center. The inclination angle is set to be larger than the inclination angle to enhance the pattern rigidity in the direction parallel to the tire rotation axis on the one side. Here, when the inclined groove is slightly bent in the extending direction in the pattern, an average line segment representing the extending direction of the groove (for example, line segment A- in FIG. 1).
The angle between A, BB) and the equatorial plane of the tire is the tilt angle. Furthermore, the inclination angle of the inclined groove arranged on the tread tread portion on the one side is set in a range of 20 to 45 degrees,
It is preferable to set the inclination angle of the inclined groove arranged on the tread surface of the other side in the range of 8 to 25 degrees in the opposite direction. In the method of mounting the tire on the vehicle of the present invention, the tire is mounted so that the tread surface of the one side is on the outside of the vehicle and the tread surface of the other side is on the inside of the vehicle. Therefore, if the inclination angle of the tread surface on the one side is 20 degrees or less, the pattern rigidity in the direction parallel to the tire rotation axis decreases, and the steering stability on the dry road surface of the tread surface outside the vehicle decreases. . On the other hand, when the angle is 45 degrees or more, the flow velocity of water in the inclined groove becomes slow, the wet performance deteriorates, and the pattern noise increases. Further, in the tread tread portion on the other side, when the inclination angle is 8 degrees or less, the width of the land portion between the inclined grooves becomes too narrow and uneven wear is easily induced,
On the other hand, if the angle is 25 degrees or more, the drainage property expected on the tread surface of the tread inside the vehicle decreases.

Moreover, the total number of the inclined grooves arranged on the tread tread portion on the one side on the tire circumference is 1.5 to 2 from the number of the inclined grooves arranged on the tread tread portion on the other side. .5 times, and the length from the start end to the end of the inclined groove arranged on the tread tread portion on the one side is 1 / 2.5 of the length of the tread tread portion on the other side. It is set to a short range of 1 to 1.5.

The present invention is particularly targeted when the number of the inclined grooves arranged on the tread tread portion on the one side with respect to the number of the inclined grooves arranged on the tread tread portion on the other side is 1.5 times or less. The wet performance is insufficient because the drainage capacity of the tread tread portion outside the vehicle, which is required for an ultra-flat tire having a wide contact surface, is insufficient. On the other hand, when the multiple becomes 2.5 or more, the rigidity of the land portion between the inclined grooves of the tread tread portion on the one side, which is outside the vehicle, decreases, and it becomes difficult to improve the steering stability on a dry road. Become.

Further, in the present invention, as described above, the length of the inclined groove of the tread tread portion on the one side is set shorter than the length of the inclined groove of the tread tread portion on the other side. When the ratio of the length of the inclined groove of the tread tread portion on one side to the length of the inclined groove of the tread tread portion on the other side becomes 1 / 2.5 (0.4) or less, As a result, the groove area of the inclined groove of the tread tread portion is reduced, which may result in insufficient drainage or high noise in this portion. Alternatively, when the groove length on the other side is increased, the groove area of this portion increases and the dry performance deteriorates. On the other hand, when the ratio becomes 1 / 1.5 (0.67) or more, it is constant. Relative to the width of the ground contact surface, the groove area of the inclined groove of the tread tread portion on the other side decreases to reduce drainage, or the groove area on one side increases to decrease the dry performance. Concern arises.

According to the present invention, since the inclined groove is configured as described above, noise such as air column resonance and pitch noise is prevented, and the tread surface outside the vehicle is parallel to the tire rotation axis. The rigidity of the land in the direction is moderately increased to improve the steering stability when driving on a dry curved road (hereinafter referred to as dry performance), while the inclined groove is located on the tire tread on the inside of the vehicle. Since the direction is appropriately approached, drainage is improved without causing uneven wear.

Next, in the regions on both sides of the tread surface, the inclined groove is bent near the end of the ground contact surface in a direction substantially parallel to the tire rotation axis and transformed into a lug groove. Here, the position where the inclined groove is bent is referred to as an inflection portion. By bending the inclined groove to form the lug groove in this manner, rigidity in the direction parallel to the tire rotation axis at the end of the ground contact surface is effectively increased to improve dry performance, and water in the inclined groove is contacted. Drains to the side of the ground quickly and smoothly.

Next, in the present invention, the sub-lug groove which is substantially parallel to the lug groove is installed in the land portion defined by the adjacent lug groove, so that the drainage is further improved. By separating the land part divided into the lug groove, the extreme difference in rigidity between the land part on both sides of the tread tread part and the land part in the central part of the tread tread part is eliminated to improve the grounding property and to prevent uneven wear. Bring about an improvement in sex.

Further, since the number of the inclined grooves of the tread tread portion on the other side is set to be small, the land portion defined by the adjacent lug grooves becomes too wide, and the land portion in the central area of the tread tread portion becomes too wide. Since the rigidity difference increases, uneven wear tends to occur in the land portion partitioned by the lug groove, so in order to prevent this, the number of sub-lug grooves of the tread tread portion on the other side is set. The land portion is narrowly divided by setting the number of auxiliary lug grooves on the tread surface portion on the one side to 2 to 4 times.

If the number of the sub-lug grooves in the tread surface of the other side is less than twice the number of the tread surface of the one side, the uneven wear of the land cannot be prevented. On the other hand, if it is four times or more, the rigidity of the land portion is extremely reduced, and another type of uneven wear may be induced.

Further, in the tread surface portion on the other side, in the land portion defined by the adjacent lug grooves, one of the ridges along the tire circumferential direction of the land portion is formed by the inclined groove, so that the land portion is formed. Is different along the tire circumferential direction and the rigidity in the land portion is circumferentially different, which tends to cause uneven wear. In the present invention, in order to prevent this uneven wear, the length of each of the plurality of sub-lug grooves arranged in the circumferential direction of the land portion is set longer at the wider width of each position of the land portion, The rigidity in the section is made uniform.

Next, according to the present invention, in the tread tread central portion, the land portion is divided into adjacent slender grooves in the tire circumferential direction, and the land portion is divided with respect to the extending direction of the slant groove. Providing a plurality of dividing grooves or sipes extending in a substantially perpendicular direction, and at least the width of the dividing groove or sipe of the tread tread portion on the other side is at least compared to the width of the dividing groove or sipe of the tread tread portion on the one side. Widely set equal or higher. By doing so, the rigidity in the tire circumferential direction of the land portion defined by the adjacent inclined grooves is suppressed from increasing, and the ground contact property of the entire tread contact surface is improved, and uneven wear resistance and straight running are improved. Driving performance is improved.
Further, since the width of the dividing groove of the tread tread portion on the other side is set wide, the circumferential rigidity of the elongated land portion of the tread tread portion on the other side is the land portion of the tread tread portion on the one side. Rigidity imbalance on both sides of the pattern center due to its large relative to the circumferential rigidity of the tire is corrected, and the negative ratio of the tread tread portion on the other side is increased to contribute to improvement of the wet performance of the tire. can do.

Further, according to the present invention, when the vehicle travels on a dry curved road, a sufficient frictional force can be obtained when the tire inclines due to centrifugal force and the center of contact with the ground moves toward the outer side of the vehicle. In order to widen the effective grounding area of the grounding surface on the one side, which is outside the vehicle, and to improve the drainability of the grounding surface on the other side in order to maintain good wet performance when traveling on a wet road surface, grooves in this area The area is increasing. Therefore, when the negative ratio of the entire ground surface is constant, the negative ratio of the pattern of the ground surface on the other side is 5 to 20% with respect to the negative ratio of the pattern of the ground surface on the one side. It is set large. If the difference in the negative ratio obtained by subtracting the negative ratio of the ground surface on the one side from the negative ratio of the ground surface on the other side is 5% or less, the improvement of the driving performance on a dry road surface is not sufficient, and this negative ratio If the difference is 20% or more, the rigidity of the land portion of the ground contact surface on the other side is extremely reduced, and uneven wear is likely to occur in this region.

[0024]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a tread pattern of a radial tire having a tire size of 315 / 35ZR17 as an embodiment of the present invention, in which 1 is a tread tread portion and 2 is a tread tread portion overlapping the tire equatorial plane XX. -Center-
The land part continuous in the tire circumferential direction provided in the (f-f) part is shown. On both sides of the land portion 2, when viewed from the front of the tires that are erected, the tires extend in a direction in which the tires rotate in the direction of rotation (the direction of the arrow in FIG. 1) and are spaced apart from each other starting from the lower side of the tires. The inclined grooves 4 and 5 whose end is open to the tread tread end 3 are arranged. Moreover,
The positions of the starting ends of the inclined grooves 4 and 5 are designed not to reach the pattern center (f-f) in order to form the land portion 2 described above.

Here, in FIG. 1, the right side region as the tread tread portion on the other side from the pattern center is defined as the vehicle inside region as the portion which becomes the inside of the vehicle when the tire is mounted on the vehicle, and on the other hand, An area on the left side in FIG. 1 as a tread tread portion on one side from the pattern center is an area outside the vehicle as an area outside the vehicle. In the vehicle outer region, the inclined groove 4 is extended in the tire circumferential direction along a line segment A-A representing the inclined groove having an inclination angle (α) with respect to the tire equatorial plane of 35 degrees, while the vehicle inner side is provided. In the area, the inclined groove 5
Is extended along a line segment BB representing the inclined groove having an inclination angle (β) with respect to the equatorial plane of the tire of 15 degrees. Strictly speaking, in the vehicle outer region, the start end portion of the inclined groove 4 extends downward from the line segment AA, that is, in a tire circumferential direction with a shift in the tire rotation direction. On the other hand, in the vehicle inner region, the starting end portion of the inclined groove 5 is displaced downward from the line segment B-B and the starting end is communicated with the adjacent inclined groove so that each inclined groove extends in the tire circumferential direction. Are connected together. Then, the end portion thereof is extended from the line segment B-B with a large deviation.

Thus, the inclined grooves 4 and 5 are arranged, and the pattern center portion is provided with the land portion extending in the circumferential direction.
Since there is no so-called rib groove that is straight in the circumferential direction on the tread tread portion, air column resonance noise is not generated, and steering response is improved by the land portion. Moreover, the inclined groove ensures good drainage and maintains high wet performance. Further, in the vehicle outer region, the longitudinal direction of the narrow land portion sandwiched by the inclined grooves approaches the direction parallel to the tire rotation axis (hereinafter referred to as the radial direction), so the radial rigidity is increased and the dry performance is improved. . Further, in the vehicle inner region, the drainage is extremely high and the wettability is excellent due to the inclined groove having a small inclination angle and a long length. Therefore, with the above configuration, a tire base having low noise and excellent dry and wet performance as a whole tire is established.

Strictly speaking, since the inclined groove is not a perfect straight line in the longitudinal direction and the inclination angle changes in a partial portion, the ground contact length of the inclined groove changes with rotation,
The resonance frequency of the air column, which is the space formed by the groove and the ground plane, is different, and the frequency of the sound generated by the air column is dispersed, further increasing the noise reduction effect. Since water that has entered the ground contact surface during rolling of the tire has a characteristic of flowing out from the center of the ground contact surface toward both ends of the ground contact surface, the shape of the water located in the center of the ground contact surface and along the tire circumferential direction The inclined groove extending from the formed starting end portion toward both ends of the grounding surface can discharge water into the smooth in conformity with the outflow characteristics.

Further, in addition to the above-mentioned characteristics, in the tire size to which the present invention is applied, the flatness is as small as 35% and therefore the width of the tread portion is extremely wide, so that the drainage property is particularly improved in the vehicle outer region. Similarly, assuming that the number of inclined grooves in the vehicle outer region is 30, the number of inclined grooves in the vehicle inner region is 1
The number of inclined grooves is doubled to increase the drainage capacity, and the length of the inclined grooves in the vehicle outer region is about 1/2 of the length of the inclined grooves in the vehicle inner region. It is set short to prevent water from staying in the ground. By setting in this way, while maintaining the above-mentioned excellent tire base, the water in the ground contact surface, which increases due to the wide tread portion, is quickly discharged.

Next, in FIG. 1, the inclined grooves 4 and 5 are connected to both side areas of the tread tread portion from the inflection portions 6 and 6'of the inclined grooves 4 and 5 to the end portion 3 of the tread tread portion. Edge e of the ground,
At the inflection portions 6 and 6'provided near the e ", lug grooves 7 and 7" formed by bending the tire equatorial plane XX at a substantially right angle are arranged. The sub lug grooves 8 and 8'are arranged in the land portion defined by the adjacent lug grooves. Since the length of the land portion divided by the lug grooves is short in the auxiliary lug grooves in the vehicle outer region due to the high number density of the inclined grooves, only one lug groove is arranged between the lug grooves. Since the number of inclined grooves is small and the length of the land portion is long in the vehicle inside region, three auxiliary lug grooves are arranged to divide the wide land portion to prevent uneven wear.

Further, in the land portion defined by the lug groove in the vehicle inner side region, one of the ridgelines in the tire circumferential direction is formed by the inclined groove, so that the width of the land portion is
In FIG. 1, the difference in rigidity is made wider from the upper side to the lower side. In the present invention, in order to prevent uneven wear that may occur due to this difference in rigidity, the lengths of the three auxiliary lug grooves are changed according to the width of each position in the land portion, and one of them is changed. The auxiliary lug groove of the book is connected to the inclined groove to assist the drainage effect of the inclined groove.

Next, in the central area of the tread tread between the left and right inflections 6 and 6 ', a dividing groove extending in a direction reverse to the direction of the inclined groove is formed in a land portion defined by adjacent inclined grooves. Nos. 9 and 10 are provided to prevent the rigidity of the land portion from becoming extremely large and the grounding property from being deteriorated. Moreover, since the land portion is long in the vehicle inside region, the dividing groove 10
The groove width is widened to achieve rigidity balance with the land portion in the vehicle outer region where the length is short. At this time, widening the width of the dividing groove in the vehicle inner region also contributes to enhancing the drainage effect in this region.

Further, in the present invention, the negative rate of the tread pattern in the vehicle inner area is set to be approximately 10% higher than the negative rate of the vehicle outer area,
The structure of the outer region of the vehicle is dusty, and both the dry performance and the wet performance of the entire tire are achieved.

In the above embodiment, the pattern center is aligned with the equatorial plane of the tire. However, for the purpose of the present invention, the pattern center is left from the equatorial plane of the tire regardless of this. Alternatively, it is possible to make the pattern shifted to the right by a certain distance.

Next, in order to verify the effect of the present invention, the actual vehicle comparison test conducted on the tire of the above-described embodiment according to the present invention and two conventional tires (comparative examples) shown in FIGS. 2 and 3 will be described below. Explained. The three test items compared were the steering stability on dry road surface, drainage performance on wet road surface, and pattern noise test. Test tire: tire size; 315 / 35ZR17. * Invention tires: Tires of the above-described example manufactured separately for the left and right wheels of a vehicle. * Tires of comparative examples; the following two types of tires in which the tire material, internal structure, and total groove area in the ground contact surface are the same as those of the examples. Comparative Example 1; As shown in FIG. 2, circumferentially straight rib grooves parallel to the tire equatorial plane are provided on the tire equatorial plane and on both sides thereof, and inclined grooves traversing the grooves extend rearward from the tire rotation direction toward the rear. Tires with patterns spread out on both sides of the equatorial plane. Comparative Example 2; As shown in FIG. 3, the tire equatorial plane is provided with a continuous land portion in the circumferential direction, and the same number of inclined grooves are provided in the tire circumferential direction on the left and right sides of the land portion from the tire rotation direction toward the rear. A tire with a pattern that spreads out toward the end. Test method: Tires filled with an internal pressure of 2.5 kgf / cm ² were mounted on a high-performance passenger car, and steering stability on a dry road surface under load conditions (50% of JIS regular load) with two passengers. Is evaluated by the comprehensive feeling by the test driver when various kinds of driving are performed on the dry skid. The drainage performance on the wet road surface is the hydroplaning phenomenon when running straight on a wet road surface with a water depth of 5 mm. The pattern noise test was carried out on a smooth straight road surface at a speed of 5 m from the installed microphone at a position of 7.5 m.
The noise when coasting from 5 km / h was measured and evaluated.

Test results: The results of these tests are shown in the following table as an index. Incidentally, the index value is represented by setting the result of the conventional tire (Comparative Example 1) as 100, and the larger the index value is, the better the result is.

[Table 1] According to Table 1, the invention tires (Example tires) can significantly improve the steering stability on a dry road surface without sacrificing the drainage property and further effectively reduce the pattern noise. I know that

[0036]

With the pneumatic radial tire according to the present invention, while maintaining good steering stability on a wet road surface,
It is possible to improve the steering stability performance on a dry road surface and effectively reduce the pattern noise.

[Brief description of drawings]

FIG. 1 is a tread pattern according to an embodiment of the present invention.

FIG. 2 is a tread pattern of Comparative Example 1 including a plurality of straight grooves in the circumferential direction.

3 is a symmetrical tread pattern of Comparative Example 2. FIG.

[Explanation of symbols]

 1 tread tread 2 land 3 tread tread end 4 sloped groove (vehicle outside area) 5 sloped groove (vehicle inside area) 6, 6 "inflection part 7, 7" lug groove 8, 8 "auxiliary lug groove 9 Dividing groove (vehicle outside area) 10 Dividing groove (vehicle inside area) a Ridge line portion of the inclined groove closest to each other b b Ridge portion of the inclined groove closest to each other c-c Circumferential tangent line d-d Circumferential tangent line f -F Pattern center e, e `End of the contact surface α, β Inclination angle

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location B60C 11/04 11/117

Claims (5)

[Claims] 1. A pattern center portion of the tread surface is provided with a land portion continuous in the tire circumferential direction, and one side in the tire circumferential direction with the pattern center portion as a starting end is provided on both sides of the land portion. Each of the inclined grooves extending toward the respective ground contact surface end portions so as to be separated from each other, and the end ends open to the tread tread surface end portions, but the start ends do not reach the pattern center. A plurality of tires provided in the circumferential direction, wherein an angle of an inclined groove arranged on one side of the tread surface from the pattern center with respect to the tire equatorial plane in the central area of the tread surface is the pattern. Greater than the angle of the inclined groove arranged on the tread tread portion on the other side from the center with respect to the tire equatorial plane,
The total number of inclined grooves arranged on the tread tread portion on the one side on the tire circumference is 1.5 to 2.5 times the total number of inclined grooves arranged on the tread tread portion on the other side. The length from the start end to the end of the inclined groove arranged on the tread tread portion on the one side is 1 / 2.5 to 1 of the length of the inclined groove arranged on the tread tread portion on the other side. /1.5 times, and further, in both areas of the tread surface, there is a lug groove formed by bending the inclined groove at a bending portion near the end of the ground contact surface at a substantially right angle to the tire equatorial plane. A pneumatic radial tire, which is arranged and has the lug groove opened at an end of a tread surface portion. 2. A tread on the other side of the tread is provided with a sub-lug groove, which is substantially parallel to the lug groove, in a land portion divided in the tire circumferential direction by the adjacent lug grooves in both areas of the tread tread portion. The pneumatic radial tire according to claim 1, wherein the number of the auxiliary lug grooves arranged on the tread portion is 2 to 4 times the number of the auxiliary lug grooves arranged on the tread tread portion on the one side. 3. The pneumatic radial tire according to claim 2, wherein the plurality of sub-lug grooves arranged on the tread tread portion on the other side have different lengths in the direction parallel to the tire rotation axis. 4. A plurality of dividing grooves that divide the land portion into a land portion defined by adjacent inclined grooves in the central area of the tread tread portion and extend in a direction substantially perpendicular to the extending direction of the inclined groove. A sipe is provided, and the width of the dividing groove or sipe arranged on the tread tread portion on the other side is at least equal to or more than the width of the dividing groove or sipe arranged on the tread tread portion on the one side. The pneumatic radial tire according to any one of claims 1 to 3. 5. A pattern arranged on the grounding surface on the other side.
The pneumatic radial tire according to any one of claims 1 to 4, wherein the negative ratio of the engine is 5 to 20% higher than the negative ratio of the pattern arranged on the ground contact surface on the one side.