JP4511253B2 - Pneumatic tire - Google Patents

Description

  This invention provides a circumferential groove extending along the tire circumferential direction between the tire equatorial plane of the tread portion and the tread end, and is formed by defining a side land portion by the circumferential groove and the tread end. With regard to tires, in particular, steering stability and drainage performance are improved without deteriorating pattern noise and uneven wear characteristics.

  In consideration of drainage, a conventional pneumatic tire has a lateral groove (Patent Document 1) or a lateral sipe (patent document 1) extending from a tread end to a position in front of the circumferential groove or opening to the circumferential groove in consideration of drainage. It is common to arrange literature 2).

  Conventional tires with a tread pattern with the above-mentioned lateral grooves in the side land area increase the drainage efficiency of water that has entered the contact area to the side of the tire, so drainage performance during cornering and braking performance on wet road surfaces However, pattern noise, uneven wear characteristics, and cornering performance are inferior.

On the other hand, conventional tires with a tread pattern with lateral sipe in the side land part have good pattern noise and uneven wear characteristics because the land part divided by the side sipe is closed when the tire touches down. However, there is a problem that drainage performance at cornering and braking performance on a wet road surface cannot be obtained sufficiently.
JP-A-5-330314 Japanese Patent Laid-Open No. 11-189011

  An object of the present invention is to provide a pneumatic tire with improved handling stability and drainage performance without deteriorating pattern noise and uneven wear characteristics by disposing pseudo lateral grooves in the side land portion. is there.

In order to achieve the above object, according to a first aspect of the present invention, a circumferential groove extending along the tire circumferential direction is provided between a tire equatorial plane and a tread end of a tread portion, and a lateral land portion is formed between the circumferential groove and the tread end. In the pneumatic tire formed by partitioning, in the tire circumferential direction, pseudo lateral grooves formed by forming a plurality of small holes on an imaginary line extending in a direction crossing the side land portion from the tread end are formed in the side land portion. The pneumatic tire is provided with a predetermined interval, and the small hole has a substantially rectangular shape whose long side is substantially parallel to the virtual line at a tread opening position .

  The pseudo lateral groove is preferably disposed from the tread end to a position of at least 10% of the width of the side land portion, and even if it is an end opening lateral groove such as a lug groove, both ends open the block land portion. It may be an open groove.

  Here, the “pseudo lateral groove” means a shape extending from the tread end to the innermost small hole which is a small hole located on the side closest to the peripheral groove among the small holes formed on the imaginary line.

The number of small holes constituting the pseudo lateral grooves is 2 to 25 carbon atoms, an opening area of the small hole is in the range of 0.7～40Mm ^2, hole depth of small holes in the groove depth of the circumferential groove 15 to 100% More preferably, the number of small holes constituting the pseudo lateral groove is 3 to 10, the opening area of the small holes is within a range of 1.5 to 25 mm ² , and the hole depth of the small holes is It is in the range of 20 to 90% of the groove depth of the circumferential groove.

  The pseudo lateral grooves preferably extend at an angle of 30 to 90 ° with respect to the tire circumferential direction.

  The pseudo lateral groove preferably has a lateral sipe communicating between the tread end and the small hole, between the small hole and the small hole, and / or between the small hole and the circumferential groove.

  The pseudo lateral groove is more preferably provided at least in a side land portion located outside the vehicle in the vehicle mounting posture.

  According to the present invention, it is possible to provide a pneumatic tire with improved steering stability and drainage performance without deteriorating pattern noise and uneven wear characteristics by disposing pseudo lateral grooves in the side land portion.

FIG. 1 shows a tread pattern of a typical pneumatic tire according to a reference example of the present invention.

  The pneumatic tire shown in FIG. 1 is provided with circumferential grooves 4a and 4b extending along the tire circumferential direction C between the tire equatorial plane 2 of the tread portion 1 and both tread ends 3a and 3b, respectively. 4b and both tread ends 3a, 3b define both side land portions 5a, 5b and a tread pattern that partitions the central land portion 6 by both circumferential grooves 4a, 4b.

  Thus, by providing the pair of circumferential grooves 4a and 4b in the tread portion 1, it is possible to ensure the drainage performance and the straight running stability performance required as a high-performance tire.

  In FIG. 1, the central land portion 6 is separated into two small land portions 6 a between a pair of circumferential grooves 4 a and 4 b from the viewpoint of improving drainage efficiency of water that has entered the tire contact area to the front of the tire. Although the case where one auxiliary circumferential groove 8 partitioned into 6b is provided is shown, the presence / absence of this auxiliary circumferential groove 8 and the increase / decrease in the number of arrangement may be changed as necessary. it can.

The main structural features of the present invention are at least one of the lateral land portions 5a and 5b, preferably at least the vehicle outer side 7 _out in the vehicle mounting posture. Arrangement of the pseudo lateral groove 9 in the side land portion, more specifically, a plurality of imaginary lines m extending from the tread end 3b in the direction crossing the side land portion 5b are arranged on the side land portion 5b. The pseudo lateral grooves 9 formed with the small holes 10 are arranged at predetermined intervals in the tire circumferential direction C. By adopting this configuration, pattern noise and uneven wear characteristics are not deteriorated. Steering stability and drainage performance can be improved.

  That is, in the tire of the present invention, the pseudo lateral groove 9 disposed in the side land portion 5b is composed of a plurality of small holes 10 that are discontinuously formed at predetermined intervals on the virtual line m from the tread end 3b. Compared to conventional tires with normal transverse grooves (Fig. 5) extending continuously across the lateral land 5b, the rigidity of the land is increased, resulting in improved uneven wear performance and reduced pattern noise. In addition, the handling stability on the dry road surface is improved.

  Further, since the edge of the small hole 10 constituting the pseudo lateral groove 9 can sufficiently exhibit the effect as an edge, it is possible to ensure braking performance on a wet road surface equal to or higher than that of a conventional tire provided with a normal lateral groove.

  Further, the small holes 10 constituting the pseudo lateral groove 9 have a water absorption effect, and the arrangement of the small holes 10 is aligned in a line toward the tread end 3b, so that the water on the grounding surface portion extends along the pseudo lateral groove. In addition, since it has an effect of being discharged to the side of the tire that is outside the ground contact surface, it is possible to ensure drainage performance during cornering that is equal to or higher than that of a conventional tire provided with a normal lateral groove.

  Here, it is preferable that the pseudo lateral groove 9 is arranged from the tread end 3b to a position at least 10% of the width W of the side land portion 5b. This is because if the pseudo lateral groove 9 is disposed shorter than the position of 10% of the width W of the lateral land portion 5b from the tread end 3b, the effect as the lateral groove is not remarkably recognized. The pseudo lateral groove 9 is a lug groove in which the innermost small hole 10a exists in the side land portion, so that the innermost small hole 10a substantially communicates with the circumferential groove as shown in FIG. It may be a transverse groove.

The number of small holes 10 constituting the pseudo lateral groove 9 is 2 to 25, the opening area of the small holes 10 is in the range of 0.7 to 40 mm ² , and the hole depth of the small holes 10 is the groove depth of the circumferential groove 4b. The number of small holes constituting the pseudo lateral groove is preferably 3 to 10, and the opening area of the small holes is within a range of 1.5 to 25 mm ^2. The hole depth is in the range of 20 to 90% of the groove depth of the circumferential groove. This is because if the number of small holes 10 is one, sufficient drainage performance as a lateral groove may not be obtained. If the number of small holes 10 is exceeded, the hole interval is basically too close and normal continuous. This is because the same land portion rigidity as in the case of the lateral grooves may not be obtained. When it is less than 0.7 mm ² open area of the small hole 10, the edge effect and water effect by eyelet 10 is that both scarce, in 40 mm ² beyond, cause a decrease in block rigidity, thereby excessively reducing the steering stability risk Because there is. If the hole depth of the small hole 10 is less than 15% of the groove depth of the circumferential groove 4b, the water absorption capacity of the small hole 10 tends to be insufficient, and if the hole depth exceeds 100%, the depth becomes deeper. This is because the land portion rigidity tends to decrease significantly.

  The small holes 10 constituting the pseudo lateral groove 9 are preferably arranged at a constant interval, for example, 2 to 10 mm.

  The pseudo lateral grooves 9 preferably extend at an angle of 30 to 90 ° with respect to the tire circumferential direction C. In the case of a normal lateral groove, in order to suppress uneven wear, the lateral groove is disposed at a relatively large angle with respect to the tire circumferential direction C so that the corner of the land portion (block) does not become as acute as possible. In general, in the case of a pseudo lateral groove formed with small holes as in the present invention, a large land portion rigidity can be maintained. Therefore, the pseudo lateral groove 9 is arranged at a somewhat small angle with respect to the tire circumferential direction C. Even if installed, uneven wear hardly occurs. However, if the angle is less than 30 °, uneven wear tends to occur, so the lower limit of the angle is preferably 30 °.

In the pneumatic tire according to the present invention, the small hole 10 is formed in a substantially rectangular shape (FIG. 3) whose long side (preferably 2 to 10 mm) is substantially parallel to the virtual line. And, in the pneumatic tire according to the reference example of the present invention, the small hole 10 is not particularly limited as long as it has a shape that can obtain both the edge effect by the hole edge and the drainage performance to the side of the tire. Preferably, at the tread opening position, a substantially circular shape with a hole diameter of 1.5 to 5 mm (FIG. 1) or a long axis (preferably 2 to 10 mm) having a substantially elliptical shape substantially parallel to the imaginary line is formed. There are cases.

  Further, the pseudo lateral groove 9 is connected to the imaginary line m between the tread end 3b and the small hole 10, between the small hole 10 and the small hole 10, and / or between the small hole 10a and the circumferential groove 4b (FIG. 2). It is preferable to have both the edge effect and the drainage performance to the side of the tire.

  FIG. 4 shows a case in which the horizontal sipe 11 is disposed all over between the tread end 3b and the small hole 10, between the small hole 10 and the small hole 10, and between the small hole 10a and the circumferential groove 4b.

  2 to 4, in each case, a longitudinal sipe 12 extending in the tire circumferential direction C is provided between the circumferential groove 4b and the tread end 3b in view of optimization of rigidity (wearability) and wet brake performance. 2 and 3 extend across the side land portion 5b between the adjacent pseudo lateral grooves 9 and 9 in the same side land portion 5b until they open from the tread end 3b to the longitudinal sipe 12 in the same side land portion 5b. A first auxiliary sipe 13 is provided, and FIG. 4 shows a second auxiliary that extends across the lateral land portion 5b from the tread end 3b to the circumferential groove 4b with an inclination opposite to the pseudo lateral groove 9. Although the sipes 17 are disposed, these sipes 12, 13, and 17 can be appropriately disposed as necessary.

  1 to 4, the pseudo lateral groove 9 may be disposed only on one side land portion 5b or on both side land portions 5a and 5b, although not shown. However, in any case, in order to smoothly discharge the water present in the ground contact center area to the side of the tire, as shown in FIG. The tread groove 14 (including sipes) disposed in the land portion 6 and the pseudo lateral groove disposed in the side land portion are arranged so as to be sequentially grounded toward the one tread end 3b side. Is preferred.

  1 to 4 are all asymmetric patterns in which the tire mounting direction is limited, so that the tread pattern is arranged so as to be sequentially grounded from the other tread end 3a side to the one tread end 3b side. However, it is also possible to use a line symmetric pattern centered on the tire equatorial plane or the pattern center. In this case, each tread edge 3a from the tire equatorial plane 2 (or pattern center) side, It is preferable to arrange so as to be sequentially grounded toward the 3b side.

  Further, when the pseudo lateral groove 9 is disposed only on one side land portion 5b, it is necessary to provide the side land portion located outside the vehicle in a vehicle mounting posture to ensure block rigidity (maneuvering stability). Property) and wear resistance.

The above description merely shows an example and a reference example of the embodiment of the present invention, and various modifications can be made within the scope of the claims.

Next, a pneumatic tire according to the present invention was prototyped and performance evaluation was performed, which will be described below.
The tires of Example 1 and Reference Examples 1 and 2 have a tire size of 235 / 50R17, and their specifications are shown in Table 1. In addition, about the other tire structure, it comprised similarly to the normal run-flat tire for passenger cars (pneumatic radial tire).
For comparison, a comparative tire 1 (Comparative Example 1) and a comparative tire 2 (Comparative Example) in which normal lateral grooves and sipes that extend continuously from the tread end to the circumferential groove are disposed in the side land portion, respectively. 2) was also prototyped , and performance evaluation was performed together with Example 1 and Reference Examples 1 and 2 .

(Performance evaluation)
Each test tire is mounted on a standard rim (7 1/2 JJ), tire pressure: 230 kPa, tire load: wet brake performance, cornering drainage performance, driving on dry roads under conditions equivalent to two passengers Stability, pattern noise and uneven wear characteristics were evaluated.

(1) Wet brake performance Wet brake performance was evaluated from the measured distance by measuring the braking distance when full braking was performed from a state where the vehicle traveled at a speed of 80 km / h on a straight road with a water depth of 2 mm.

(2) Drainage performance during cornering The drainage performance during cornering is measured by measuring the critical lateral G where hydroplaning occurs at this time, passing through a wet road surface with a radius of 80 m and a water depth of 5 mm. evaluated.

(3) Steering stability on a dry road surface Steering stability on a dry road surface was evaluated by a test driver feeling by driving a dry circuit course in various driving modes.

(4) Pattern noise Pattern noise was evaluated by feeling by a test driver by running a dry general road in various driving modes. The pattern noise was measured for each tire when it was new and when the tread was worn 50%.

(5) Uneven wear characteristics Uneven wear characteristics were evaluated by confirming the amount of wear and the wear state when a tire was attached to a vehicle and the vehicle traveled 5000 km on a general road.
The results of the performance evaluation are shown in Table 1.

From the results shown in Table 1, Example 1 and Reference Examples 1 and 2 are all wet brake performance, drainage performance during cornering, steering stability on dry road surface, pattern noise and uneven wear characteristics. Compared to Comparative Examples 1 and 2, the performance is equivalent or better.

  According to the present invention, it is possible to provide a pneumatic tire with improved steering stability and drainage performance without deteriorating pattern noise and uneven wear characteristics by disposing pseudo lateral grooves in the side land portion.

It is a principal part expanded view (tread pattern) of the tread part tread of the typical pneumatic tire which concerns on the reference example of this invention. It is a principal part expanded view (tread pattern) of the tread part tread of the other pneumatic tire which concerns on the reference example of this invention. It is a principal part expanded view (tread pattern) of the tread part tread of the typical pneumatic tire according to this invention. It is a principal part expanded view (tread pattern) of the tread part tread of the other pneumatic tire which concerns on the reference example of this invention. 3 is a development view (tread pattern) of a main part of a tread part tread surface of a comparative tire 1. FIG. FIG. 3 is a development of a main part (tread pattern) of a tread surface of a comparative tire 2.

Explanation of symbols

1 tread 2 tire equator
3a, 3b tread edge
4a, 4b Circumferential groove
5a, 5b Side land part 6 Central land part 7out Vehicle outside 7in Vehicle inside 8 Auxiliary circumferential groove 9 Pseudo lateral groove
10 small hole
11 Horizontal sipe
12 Vertical sipe
13 Auxiliary sipes
14 Tread groove

Claims (1)

In the pneumatic tire formed by providing a circumferential groove extending along the tire circumferential direction between the tire equatorial plane of the tread portion and the tread end, and defining a side land portion by the circumferential groove and the tread end,
Pseudo lateral grooves formed by forming a plurality of small holes on an imaginary line (m) extending in a direction crossing the side land portion from the tread end are arranged in the side land portion at predetermined intervals in the tire circumferential direction. Set up
The pneumatic tire according to claim 1, wherein the small hole has a substantially rectangular shape whose long side is substantially parallel to the virtual line at a tread opening position .

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