JP2005047397A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress deterioration of cornering performance on snow while exhibiting excellent on-ice performance. <P>SOLUTION: A rib width RW is partitioned in a plurality of rib-like land part 4 containing the rib-like land part 6 having the width of 0.1 to 0.3 times of the tread contact land width TW by a peripheral main groove 3 larger having a groove width W1 of larger than 4 mm. The wide width rib-like land part 6 is partitioned into narrow rib parts 6A, 6B at both sides by a peripheral narrow groove having the groove width W2 of 1.0 to 4.0 mm. The lug grooves 9 having a pitch interval P of 1.5 to 4.0 times of the rib width RW are provided on at least one narrow rib part. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire that is suitable as a studless tire and that can improve performance on snow while maintaining excellent performance on ice.

  Studless tires have conventionally formed a large number of sipings in the block pattern, mainly due to the action of adhesive frictional force caused by contact between the block surface and the ice surface, and road surface digging frictional force (edge effect) caused by the edge of the block or siping. , Ensuring on-ice performance.

  On the other hand, in recent years, in order to further improve the performance on ice, there is a method of replacing some block rows with wide circumferential ribs and forming a large number of sipings on the wide circumferential ribs. It has been adopted. In this method, both the improvement of the adhesion friction force due to the increase in the contact area and the improvement of the frictional force caused by the excavation of the road surface due to the increase in the total length of the siping are exhibited. It is done.

However, when such a wide circumferential rib is used, there is a problem that the pattern rigidity becomes too high, the rib is less likely to bend or twist, and the cornering performance on snow is deteriorated.
JP-A-6-199111 JP-A-6-297918 JP-A-8-1831312 JP 2000-225814 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a pneumatic tire that suppresses a decrease in cornering performance on snow while exhibiting excellent on-ice performance substantially equivalent to the above-described method using a wide circumferential rib.

In order to achieve the above object, the invention of claim 1 of the present application divides the tread portion into a plurality of rib-like land portions by a circumferential main groove having a groove width W1 larger than 4.0 mm, and each rib-like land. A pneumatic tire in which a siping in a direction crossing the rib-like land portion is provided in the tire circumferential direction;
The rib-like land portion includes a rib-like land portion whose rib width RW is 0.1 to 0.3 times the tread grounding width TW, and the wide rib-like land portion has a groove width W2. It is divided into narrow ribs on both sides by circumferential narrow grooves of 1.0 to 4.0 mm,
A lug groove extending from the circumferential main groove to the circumferential narrow groove and having a pitch interval P in the tire circumferential direction of 1.5 to 4.0 times the rib width RW is provided in at least one narrow rib portion. It is a feature.

  In the invention of claim 2, the lug groove has a groove width Wy of 2.5 to 8.0 mm, and the groove depth Hyc of the lug groove at the intersection with the circumferential narrow groove is It is characterized by being larger than the groove depth Hys at the intersection with the direction main groove.

  Further, the invention of claim 3 is characterized in that the lug groove disposed in one of the thin rib portions and the lug groove disposed in the other thin rib portion are alternately disposed in the circumferential direction. .

According to a fourth aspect of the present invention, the rib-shaped land portion includes an inner rib-shaped land portion closest to the tire equator, an outer rib-shaped land portion along the tread grounding edge, and an intermediate rib-shaped land portion disposed therebetween. And forming a rib-like land portion in the wide rib-like land portion,
This wide rib-shaped land portion is characterized in that the rigidity of the thin rib portion on the tire equator side is larger than the rigidity of the thin rib portion on the tread ground edge side.

  Since the present invention is configured as described above, it is possible to suppress a decrease in cornering performance on snow while exhibiting excellent on-ice performance substantially equivalent to that using a wide circumferential rib.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a development view of a tread pattern when the pneumatic tire of the present invention is formed as a studless tire for a passenger car.

  In FIG. 1, a pneumatic tire 1 divides a tread portion 2 into a plurality of rib-like land portions 4 by a circumferential main groove 3, and each rib-like land portion 4 has a direction across the rib-like land portion 4. A plurality of sipings 5 are spaced apart in the tire circumferential direction.

  In this example, the circumferential main groove 3 has an inner circumferential main groove 3a extending on the tire equator C, an inner circumferential main groove 3b arranged on the outer side, and an outer outer arranged on the outer side. The case where it consists of five with the circumferential direction main groove 3c is illustrated. As a result, the tread portion 2 has six rib-like land portions 4, that is, rib-like land portions 4i between the circumferential main grooves 3a and 3b and rib-like land portions between the circumferential main grooves 3b and 3c. 4 m, and the outer circumferential main groove 3c and the outer rib-shaped land portion 4o outside the tire axial direction.

  Here, the circumferential main groove 3 is defined as a circumferential groove having a groove width W1 larger than 4.0 mm, and the groove width W1 changes, for example, like the inner circumferential main groove 3b. Is defined as an average value (W1max + groove width W1min) / 2 of the maximum groove width W1max and the minimum groove width W1min. The upper limit of the groove width W1 is preferably 15 mm or less from the viewpoint of securing a ground contact area.

  The groove depth D1 (shown in FIG. 3) of the circumferential main groove 3 is not particularly limited in the present application, but is the same depth as that of a conventional studless tire, for example, a groove depth D1 in a passenger car tire. In the range of 8 to 12 mm, it can be suitably employed. In this example, the case where the groove depth D1 is 10 mm is illustrated. The circumferential main groove 3 may be a straight groove extending linearly in the tire circumferential direction or a zigzag groove extending in a zigzag shape. In this example, the circumferential main groove 3a is a straight groove. In addition, the inner and outer circumferential main grooves 3b and 3c are formed by zigzag grooves, respectively.

  Next, out of the six rib-like land portions 4i, 4m, and 4o divided by the circumferential main groove 3, in this example, the rib-like land portion 4m of the inner rib-like land portion 4m has a tread grounding width TW. It is formed as a rib-like land portion 6 that is 0.1 to 0.3 times as wide as. The rib width RW of the other rib-like land portions 4i, 4o is naturally less than 0.1 times the tread ground contact width TW.

  In the present application, the “rib width RW” is the maximum distance in the tire axial direction (on the tread surface) between one side edge e1 and the other side edge e2 of the rib-like land portion 4 as shown in FIG. Measured in). Therefore, for example, when the side edges e1 and e2 are substantially straight, it is the distance in the tire axial direction between the side edges e1 and e2, and in the case of a zigzag shape (in the case of the rib-like land portion 4m), This is the distance in the tire axial direction between the zigzag protruding corner of one side edge e1 and the zigzag protruding corner of the other side edge e2.

  The “tread grounding width TW” is a tread grounding surface where the tire is assembled to a normal rim determined by standards such as JATMA, TRA, ETRTO, etc. Means the maximum width in the tire axial direction. The regular rim means a standard rim for JATMA, “Design Rim” for TRA, and “Measuring Rim” for ETRTO. The regular internal pressure is the maximum air pressure for JATMA, the maximum value described in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO, but it is a tire for passenger cars. In this case, it is set to 180 KPa. The regular load means the maximum load capacity for JATMA, the maximum value listed in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” for TRA, and “LOAD CAPACITY” for ETRTO. In some cases, the load is equivalent to 88%.

  And in this embodiment, as shown in FIG. 2, while the said wide rib-shaped land part 6 is divided into the thin rib part 6A, 6B of a tire axial direction both sides by the circumferential direction fine groove 7, and at least one, Preferably, a lug groove 9 extending from the circumferential main groove 3 to the circumferential narrow groove 7 is formed in both the thin rib portions 6A and 6B.

At this time, the important thing is
The groove width W2 of the circumferential narrow groove 7 is 1.0 to 4.0 mm.
-The pitch interval P in the tire circumferential direction of the lug grooves 9 is secured relatively long to 1.5 to 4.0 times the rib width RW.

  As a result, while the wide rib-like land portion 6 has substantially the same on-ice performance as the circumferential rib that is continuous in the circumferential direction, the rigidity is moderately moderated and the cornering performance on the snow is deteriorated. Can be suppressed.

  That is, by making the rib-like land portion 6 wide, the contact area is increased and the adhesive frictional force is improved. Further, since the total length of the siping 5 provided on the rib-like land portion 6 is also increased, the road surface excavation frictional force by the edge can be improved, and further improvement in performance on ice can be achieved.

  The circumferential narrow groove 7 plays a role of relaxing the lateral rigidity of the rib-like land portion 6 while ensuring a ground contact area. When the groove width W2 exceeds 4.0 mm, the ground contact area is reduced. It cannot be ensured, and the merit of widening the rib-like land portion 6, that is, the effect of improving the performance on ice cannot be maintained. On the other hand, if the groove width W2 is less than 1.0 mm, the circumferential narrow groove 7 is closed at the time of grounding, and the effect of reducing the lateral rigidity is not exhibited. Therefore, the groove width W2 is more preferably in the range of 2.0 to 3.5 mm. In addition, it may be a circumferential narrow groove 7 blade, a straight groove or a zigzag groove.

  The lug groove 9 divides the rib-like land portion 6 into substantially vertically long blocks, and relaxes the circumferential rigidity and torsional rigidity of the rib-like land portion 6 while ensuring a ground contact area. Play a role. If the pitch interval P is less than 1.5 times the rib width RW, the ratio of the lug grooves 9 increases, and the contact area cannot be secured, and the effect of improving the performance on ice cannot be maintained. On the contrary, when the pitch interval P exceeds 4.0 times the rib width RW, the circumferential rigidity and torsional rigidity of the rib-like land portion 6 are still large, and the effect of suppressing deterioration of cornering performance on snow is exhibited. Disappear. Therefore, the pitch interval P is more preferably 1.8 to 3.0 times the rib width RW.

  Further, the lug groove 9 preferably has a groove width Wy (average value when the groove width changes) in the range of 2.5 to 8.0 mm, and if it exceeds 8.0 mm, the ground contact area is reduced. As a result, the performance improvement effect on ice is not maintained. Conversely, if it is less than 2.5 mm, the cornering performance on snow tends to deteriorate. Therefore, the groove width Wy is more preferably in the range of 4.0 to 6.0 mm.

  In this example, as shown in FIG. 3, the groove depth Hyc of the lug groove 9 at the intersection Qc where the lug groove 9 intersects the circumferential thin groove 7 is set to the intersection Qs where the lug groove 9 intersects the circumferential main groove 3. The groove depth is greater than Hys. In this example, the groove depth D2 of the circumferential narrow groove 7 is shallower than the groove depth D1 of the circumferential main groove 3, and the groove depth Hyc and the groove depth D2 are substantially the same depth. One case is illustrated.

  Thus, by providing a change in the groove depth of the lug groove 9, more uniform and appropriate rigidity can be secured. If the rigidity is non-uniform, i.e., there is a portion with high rigidity, for example, on a mirror-like road surface with a low friction coefficient, there is a possibility that the entire rib-like land portion 6 may slip and impair the performance on ice. Can be prevented.

  For the same purpose, in this example, lug grooves 9A arranged in one of the thin rib portions 6A and lug grooves 9B arranged in the other thin rib portion 6B are alternately arranged in the circumferential direction. Yes. As a result, uniform rigidity can be further exhibited. The lug grooves 9 are preferably formed at an angle of 30 degrees or less with respect to the tire axial direction, and the inclination directions of the lug grooves 9A and the lug grooves 9B may be different.

  Next, FIG. 4 shows another example of the wide rib-like land portion 6. In this example, the circumferential narrow groove 7 is offset to the tread grounding edge TE side, so that the width of the thin rib part 6A on the tire equator side is larger than the width of the thin rib part 6B on the tread grounding edge TE side. Also set to large. Thereby, the rigidity of the thin rib portion 6A is increased as compared with the rigidity of the thin rib portion 6B.

  This is because a relatively large frictional force can be expected because the ground contact pressure is high on the tire equator side. Therefore, by making the rigidity of the thin rib portion 6A on the tire equator side larger than the rigidity of the thin rib portion 6B on the tread grounding edge TE side, an optimal rigidity distribution is created and the maximum frictional force is exhibited. Can be expected.

In addition, as means for providing a rigidity difference between the thin rib portions 6A and 6B,
-The depth of the lug groove 9A is shallower than the lug groove 9B.
The siping 5 disposed in the thin rib portion 6A is shallower than the siping 5 disposed in the thin rib portion 6B or the number thereof is reduced;
-The lug groove 9B can be formed only in the thin rib portion 6B, and these can be combined.

  In addition, the siping 5 is preferably formed in a cut shape having a width of 1.0 mm or less (in this example, about 0.3 mm) and substantially perpendicular to the circumferential direction as in the prior art. In this example, in order to enhance the edge effect, an example in which a meandering portion extending zigzag in the tire axial direction is formed at an intermediate position of the siping 5 is used, and thereby the edge component length per siping is increased. It is increasing. As for the shape of the meandering portion, various shapes such as a saw blade shape, a rectangular uneven shape, and a wave shape can be adopted.

  Further, the depth of the siping 5 is generally not more than the groove depth D2 of the circumferential narrow groove 7 and not less than 0.5 times the groove depth D1 of the circumferential main groove 3.

  Next, the rib-like land portions 4i and 4o other than the wide rib-like land portion 6 will be described. In this example, the inner rib-shaped land portion 4 i is formed in a row of vertically long blocks by the lug groove 10 having substantially the same configuration as the lug groove 9. In this example, the lug groove 10 is different from the lug groove 9 in that the groove depth is substantially the same as the groove depth D1 of the circumferential main groove 3.

  Further, the outer rib-like land portion 4o is formed in a row of horizontally long blocks in this example by the lug groove 10, thereby enhancing the cornering force.

  In the present invention, it is sufficient that at least one wide rib-like land portion 6 described above is provided, and at this time, another rib-like land portion 3 can be formed as a circumferential rib.

  As mentioned above, although especially preferable embodiment of this invention was explained in full detail, this invention is not limited to embodiment of illustration, It can deform | transform and implement in a various aspect.

(Test 1)
A tire (size 195 / 65R15) having the specifications shown in Table 1 in which only the groove width W2 of the circumferential narrow groove 7 is changed based on the tread pattern of FIG. 5 (A) was prototyped, and its on-ice performance and on-snow cornering performance Tested. Other specifications are the same as follows. The groove width W1 (7.0 mm) and groove depth D1 (10 mm) of the circumferential main groove 3, the groove depth D2 (9 mm) of the circumferential narrow groove 7, and the rib width RW of the wide rib-like land portion 6 ( 34 mm; ratio RW / TW = 0.20), depth of siping 5 (8 mm) and pitch interval (3.0 mm).

On-ice performance:
A sample tire is mounted on the four wheels of a passenger car (FR vehicle: 2000cc) under the internal pressure (200kpa) and rim (15x6JJ), and runs on an icy road in an environment with a temperature of 0 ° C. Thus, evaluation was carried out by a 10-point method in which Comparative Example 1 was 7. The larger the value, the better the performance on ice.

Snow cornering performance:
Using the vehicle (1), the vehicle was run on a snowy circuit in an environment with a temperature of 0 ° C., and evaluation was performed by a ten-point method with Comparative Example 1 being set to 4 by sensory evaluation of the driver. The larger the value, the better the snow cornering performance.

表１の如く、溝巾Ｗ２が４．０ｍｍ以下の範囲で、周方向細溝７がない比較例１の場合と実質的に同レベルの優れた氷上性能が確保でき、又溝巾Ｗ２が１．０ｍｍ以上の範囲で、雪上コーナリング性能の低下の抑制効果が発生するのが確認できる。

As shown in Table 1, in the range where the groove width W2 is 4.0 mm or less, excellent on-ice performance substantially the same level as in the case of Comparative Example 1 without the circumferential narrow groove 7 can be secured, and the groove width W2 is 1 It can be confirmed that the effect of suppressing the decrease in cornering performance on snow occurs within a range of 0.0 mm or more.

(Test 2)
Next, on the basis of the tread pattern of FIG. 5 (B) in which the lug grooves 9 are further formed in FIG. 5 (A), a tire having the specifications shown in Table 2 in which only the pitch interval P of the lug grooves 9 is changed is prototyped, The on-ice performance and on-snow cornering performance were tested. Note that the groove width W2 (2 mm) of the circumferential narrow groove 7, the groove width Wy (5.0 mm) and the groove depth Hy (8.5 mm) of the lug groove 9, and other specifications are the same as those in Test 1. .

表２の如く、ピッチ間隔Ｐとリブ巾ＲＷとの比Ｐ／ＲＷが１．５以上で、前記比較例１の場合と実質的に同レベルの優れた氷上性能が確保できる。しかも比Ｐ／ＲＷが４．０以下の範囲では、表１の比較例６、７と実質的に同レベルまで雪上コーナリング性能を引き上げうることが確認できる。

As shown in Table 2, the ratio P / RW between the pitch interval P and the rib width RW is 1.5 or more, and excellent on-ice performance substantially the same level as in the case of the comparative example 1 can be secured. Moreover, in the range where the ratio P / RW is 4.0 or less, it can be confirmed that the on-snow cornering performance can be increased to substantially the same level as Comparative Examples 6 and 7 in Table 1.

(Test 3)
Next, a tire having the specifications shown in Table 3 in which only the groove width Wy of the lug groove 9 was changed based on the tread pattern of FIG. 5B was prototyped, and its on-ice performance and on-snow cornering performance were tested. Note that the groove width W2 (2 mm) of the circumferential narrow groove 7 and the pitch interval P (2.0 × RW) of the lug groove 9 are the same as in Test 1.

表３の如く、溝巾Ｗｙが２．５〜８．０ｍｍの範囲において、氷上性能と雪上コーナリング性能とを高いレベルでバランス良く発揮しうるのがわかる。

As shown in Table 3, when the groove width Wy is in the range of 2.5 to 8.0 mm, it can be seen that the performance on ice and the cornering performance on snow can be exhibited at a high level with a good balance.

(Test 4)
Also, as shown in FIG. 6 (A), both the lug grooves 9A on both sides are formed in the same phase, and as shown in FIG. 6 (B), the thin rib portions 6A are eliminated to eliminate the lug grooves 9A and increase the rigidity. The on-ice performance and on-snow cornering performance were tested. The circumferential narrow groove 7 has a groove width W2 (2 mm), a lug groove 9 has a groove width Wy (5.0 mm), and a pitch interval P (2.0 × RW). The other specifications are the same as those in Test 1. is there.

表４の如く、ラグ溝９Ａを同位相としたものでは、剛性のかたよりが生じ、特に摩耗係数の低い氷上性能が若干悪化している。一方、タイヤ赤道側のラグ溝９Ａを排除したものは、接地圧力の高い赤道側の剛性が高いため、摩擦力の均一化により氷上性能と雪上性能がともにバランス良く向上しているのがわかる。

As shown in Table 4, when the lug grooves 9A have the same phase, rigidity is produced, and the performance on ice with a particularly low wear coefficient is slightly deteriorated. On the other hand, since the equatorial side with high contact pressure has high rigidity, the lug groove 9A on the tire equator side has high rigidity, and it can be seen that both the performance on ice and the performance on snow are improved in a well-balanced manner by making the frictional force uniform.

It is an expanded view which shows the tread pattern of the tire of one Example of this invention. It is a diagram which expands and shows a wide rib-like land part. It is sectional drawing of a wide rib-like land part. It is a diagram which shows the other example of the wide rib-shaped land part 6. FIG. (A), (B) is a diagram which illustrates the tread pattern used in tests 1-3. (A), (B) is a diagram which illustrates the tread pattern used in Test 4. FIG.

Explanation of symbols

2 Tread parts 3, 3a, 3b, 3c Circumferential main grooves 4, 4i, 4m, 4o Rib-like land part 5 Siping 6 Wide rib-like land parts 6A, 6B Narrow rib part 7 Circumferential narrow groove 9 Lug groove Qc , Qs intersection

Claims (4)

The tread portion is divided into a plurality of rib-like land portions by circumferential main grooves having a groove width W1 larger than 4.0 mm, and siping in a direction crossing the rib-like land portions is arranged on the tire circumference. A pneumatic tire spaced in a direction,
The rib-shaped land portion includes a rib-shaped land portion whose rib width RW is 0.1 to 0.3 times the tread grounding width TW, and the wide rib-shaped land portion has a groove width W2. It is divided into narrow ribs on both sides by circumferential narrow grooves of 1.0 to 4.0 mm,
A lug groove extending from the circumferential main groove to the circumferential narrow groove and having a pitch interval P in the tire circumferential direction of 1.5 to 4.0 times the rib width RW is provided in at least one narrow rib portion. A featured pneumatic tire.   The lug groove has a groove width Wy of 2.5 to 8.0 mm, and the groove depth Hyc at the intersection with the circumferential thin groove is at the intersection with the circumferential main groove. The pneumatic tire according to claim 1, wherein the groove depth is greater than Hys.   The air according to claim 1, wherein the lug groove disposed in one of the thin rib portions and the lug groove disposed in the other thin rib portion are alternately disposed in the circumferential direction. Enter tire. The rib-shaped land portion includes an inner rib-shaped land portion closest to the tire equator, an outer rib-shaped land portion along the tread grounding edge, and an intermediate rib-shaped land portion disposed therebetween, and While forming the rib-like land portion in the wide rib-like land portion,
4. The wide rib-like land portion according to claim 1, wherein the rigidity of the thin rib portion on the tire equator side is larger than the rigidity of the thin rib portion on the tread grounding edge side. Pneumatic tires.

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