JP6006745B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire capable of achieving both wet performance and steering stability on a dry road surface (hereinafter sometimes simply referred to as steering stability) at a higher level.

  As a pneumatic tire with improved steering stability, a tire described in Patent Document 1 below is known. In this tire, as shown in FIG. 5, a shoulder land portion rs and a middle land portion rm divided by a shoulder main groove a and a crown main groove b are formed as ribs continuous in the tire circumferential direction. Therefore, the pattern rigidity is increased, and the steering stability can be improved.

  In the shoulder land portion rs, a shoulder lug groove c extending from the ground contact end Te side and a shoulder sipe ss ss extending from the shoulder main groove a are alternately arranged in the circumferential direction, and the inner end of the shoulder lug groove c and the shoulder sipe The outer ends of ss are interrupted in the shoulder land portion rs. In the middle land portion rm, an outer middle sipe ms1 extending from the shoulder main groove a and an inner middle sipe ms2 extending from the crown main groove b are alternately arranged in the circumferential direction, and the inner end and inner end of the outer middle sipe ms1 are arranged. The middle end of the middle sipe ms2 is interrupted in the middle land rm. Therefore, it is possible to ensure wet performance by exhibiting drainage while maintaining the pattern rigidity high.

  However, in recent years, with improvement in performance of vehicles, further improvement in wet performance and steering stability is desired.

JP 2012-17001 A

  Accordingly, an object of the present invention is to provide a pneumatic tire that can achieve both wet performance and steering stability at a higher level.

The present invention provides a tread portion having a pair of shoulder main grooves extending in the tire circumferential direction on the ground contact end side, a crown main groove extending in the tire circumferential direction on the inner side in the tire axial direction of each shoulder main groove, the crown main groove, A pneumatic tire comprising a pair of middle ribs arranged between the shoulder main grooves and a pair of shoulder ribs arranged on the outer side in the tire axial direction of the shoulder main grooves,
The shoulder rib has a shoulder lug groove extending inward in the tire axial direction across the ground contact end and the inner end being interrupted without reaching the shoulder main groove, and an outer end extending from the shoulder main groove in the tire axial direction outward. With shoulder sipe that breaks without reaching the ground end,
The middle rib does not have a lug groove, extends from the shoulder main groove inward in the tire axial direction, and has an inner end that is interrupted without reaching the crown main groove, and extends from the crown main groove outward in the tire axial direction. And with the middle sipe that the outer end breaks without reaching the shoulder main groove,
A corner portion where the tread surface of the middle rib intersects with the groove wall surface of the shoulder main groove is provided with a triangular chamfered portion extending in the tire circumferential direction from the outer middle sipe, and the circumferential length of the chamfered portion is defined as the outer circumferential length. And larger than the circumferential length of the middle sipe,
The outer middle sipe extends along the virtual extension line within a range of a circumferential distance of 5 mm or less from a virtual extension line obtained by extending the shoulder sipe inward in the tire axial direction.
Moreover, the shoulder sipe and the outer middle sipe each include an inner lug groove portion having an angle of 70 to 80 degrees with respect to the tire circumferential direction, and the shoulder lug groove having an angle with respect to the tire circumferential direction of 70 to 80 degrees on the inner end side. It is characterized by that.

  In the pneumatic tire according to the present invention, it is preferable that an inner end in the tire axial direction of the outer middle sipe is positioned on an outer side in the tire axial direction from an outer end in the tire axial direction of the inner middle sipe.

  In the pneumatic tire according to the present invention, the shoulder lug groove includes the inner lug groove portion, and an outer lug groove portion extending outward from the inner lug groove portion in the tire axial direction and having a larger angle with respect to the tire circumferential direction than the inner lug groove portion. It is preferable that the outer end of the shoulder sipe in the tire axial direction is interrupted inside the outer lug groove portion in the tire axial direction.

  In the present invention, “sipe” means a notched or ultrafine groove having a groove width of 1.5 mm or less, and the groove wall surfaces come into contact with each other at the time of grounding to close the groove. On the other hand, the “lag groove” and the “main groove” mean wide grooves in which the groove wall surfaces do not contact each other at the time of grounding, and are distinguished from the sipes.

  The grounding end means the outermost end in the tire axial direction of the tread grounding surface that contacts the tire when a normal load is applied to a tire that is assembled with a normal rim and filled with a normal internal pressure. The axial width is called the ground contact width.

  The “regular rim” is a rim determined for each tire in the standard system including the standard on which the tire is based, for example, a standard rim for JATMA, “Design Rim” for TRA, or ETRTO means "Measuring Rim". The “regular internal pressure” is the air pressure defined by the standard for each tire. If JATMA, the maximum air pressure, if TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” Means "INFLATION PRESSURE", but in the case of passenger car tires, it is 180 kPa. The “regular load” is a load determined by the standard for each tire, and if it is JATMA, the maximum load capacity, and if it is TRA, the maximum value described in the table “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” If it is ETRTO, it is "LOAD CAPACITY".

  In the present invention, the land portion of the tread portion divided by the shoulder main groove and the crown main groove is formed as a rib (that is, a shoulder rib and a middle rib) continuous in the tire circumferential direction. Therefore, the pattern rigidity is increased, and the steering stability can be improved.

  In the shoulder rib, a shoulder lug groove extending from the grounding end side and a shoulder sipe extending from the shoulder main groove are alternately arranged in the circumferential direction, and the inner end of the shoulder lug groove and the outer end of the shoulder sipe are respectively provided. There is a break in the shoulder ribs. In the middle land, the outer middle sipes extending from the shoulder main grooves and the inner middle sipes extending from the crown main grooves are alternately arranged in the circumferential direction, and the inner ends of the outer middle sipes and the outer ends of the inner middle sipes However, there is a break in each middle rib. Therefore, it is possible to ensure wet performance by exhibiting drainage while maintaining high pattern rigidity due to the rib pattern.

  Furthermore, in the present invention, the outer middle sipe extends along the virtual extension line within a range in which the circumferential distance from the virtual extension line of the shoulder sipe is 5 mm or less. That is, the outer middle sipe and the shoulder sipe are arranged so as to be continuous with each other via the shoulder main groove. Thereby, drainage is further improved. In this case, the rigidity tends to be reduced by being connected to one, but the rigidity reduction is suppressed by the triangular chamfer extending from the other middle sipes.

  The chamfered portion suppresses the movement of rubber on the open end side of the outer middle sipe during grounding. For this reason, a reduction in rigidity due to the outer middle sipes is suppressed. In addition, since the water on the road surface is guided into the shoulder main groove through the chamfered portion, it is also useful for improving drainage.

  In the shoulder sipe, the outer middle sipe, and the inner lug groove portion of the shoulder lug, the angle with respect to the tire circumferential direction is set in the range of 70 to 80 degrees. Thereby, the lateral rigidity on the shoulder side can be maintained high, and the steering stability, particularly the turning performance can be improved.

  As a result of organically combining such effects, wet performance and steering stability can be made compatible at a higher level.

It is an expanded view which shows an example of the tread pattern of the pneumatic tire of this invention. FIG. It is a fragmentary perspective view which shows a chamfer part notionally. It is a top view which shows a chamfer part notionally. It is an expanded view which shows an example of the tread pattern of the conventional tire.

Hereinafter, embodiments of the present invention will be described in detail.
As shown in FIG. 1, the pneumatic tire 1 of the present embodiment includes a tread portion 2, a pair of shoulder main grooves 4 extending in the tire circumferential direction on the ground contact end Te side, and an inner side in the tire axial direction of each shoulder main groove 4. And a crown main groove 3 extending in the tire circumferential direction. Accordingly, a pair of middle ribs 6 disposed between the crown main groove 3 and the shoulder main groove 4 and a pair of shoulder ribs 7 disposed on the outer side in the tire axial direction of the shoulder main groove 4 are formed in the tread portion 2. Is done.

  In this example, two crown main grooves 3 are provided, and a center rib 5 extending on the tire equator Co is further formed between the crown main grooves 3 and 3.

  The shoulder rib 7, the middle rib 6 and the center rib 5 are formed as rib bodies extending continuously in the tire circumferential direction without being divided into a plurality of blocks by lug grooves. Since a rib pattern tire made of such a rib body has a higher pattern rigidity than a block pattern tire, steering stability can be improved.

  The crown main groove 3 and the shoulder main groove 4 are formed as straight grooves extending linearly in the tire circumferential direction. Such a straight groove is useful for improving the wet performance since the drainage resistance is small. Particularly in this example, as shown in FIGS. 2 and 3, the groove wall surface 4 </ b> S on the inner side in the tire axial direction of the shoulder main groove 4 has a flat surface portion 8 extending in the circumferential direction and a V that protrudes toward the inside of the groove at a small height. The case where it consists of the character-shaped protrusion part 9, and the plane part 8 and the V-shaped protrusion part 9 are repeated alternately in a tire peripheral direction is shown. The V-shaped protrusion 9 suppresses the falling of the groove wall surface 4S, and the rigidity of the middle rib 6 is further increased while maintaining high drainage. The protruding amount J of the V-shaped protrusion 9 from the flat surface 8 is preferably in the range of 10 to 30% of the groove width W4 of the shoulder main groove 4.

  Note that the groove widths W3 and W4 (the groove width measured in the direction perpendicular to the groove center line and the same applies to other grooves) and the groove depth in the crown main groove 3 and the shoulder main groove 4 are customary. Can be variously determined. However, from the balance of wet performance and steering stability, the groove widths W3 and W4 of the crown main groove 3 and the shoulder main groove 4 are 3.0 to 6.0% of the ground contact width TW (shown in FIG. 1), respectively. The groove depth is preferably in the range of 6 to 12 mm, for example.

  As shown in FIG. 2, the shoulder rib 7 includes a shoulder lug groove 10 and a shoulder sipe 11. The shoulder lug groove 10 extends inward in the tire axial direction across the ground contact end Te, and the inner end 10E is interrupted without reaching the shoulder main groove 4. On the other hand, the shoulder sipe 11 extends outward from the shoulder main groove 4 in the tire axial direction, and its outer end 11E is interrupted without reaching the ground contact Te. The shoulder lug grooves 10 and the shoulder sipes 11 are alternately arranged in the tire circumferential direction.

The shoulder lug groove 10 includes an inner lug groove portion 10A inclined at an angle α1 of 70 to 80 degrees with respect to the tire circumferential direction on the inner end 10E side. The shoulder lug groove 10 of this example is formed by the inner lug groove portion 10A and an outer lug groove portion 10B that is bent from the inner lug groove portion 10A and extends outward in the tire axial direction. The angle α2 of the outer lug groove portion 10B with respect to the tire circumferential direction is set larger than the angle α1 of the inner lug groove portion 10A. The length L10 of the shoulder lug groove 10 in the tire axial direction is preferably in the range of 15 to 20% of the ground contact width TW, and is preferably in the range of 70 to 90% of the shoulder rib width W7.

  The shoulder sipe 11 has the same inclination direction as the inner lug groove portion 10A, and an angle α3 with respect to the tire circumferential direction is set to 70 to 80 degrees. In this example, the outer end 11E of the shoulder sipe 11 is interrupted on the outer side in the tire axial direction from the inner end 10E and on the inner side in the tire axial direction from the outer lug groove portion 10B. That is, the shoulder sipe 11 overlaps only in the circumferential direction only with the inner lug groove portion 10A having substantially the same inclination. As a result, drainage is ensured over almost the entire area of the shoulder rib 7 while suppressing the occurrence of local weak areas of rigidity.

  The middle rib 6 includes inner and outer middle sipes 12 and 13, but does not include lug grooves. The inner middle sipe 12 extends outward from the crown main groove 3 in the tire axial direction, and its outer end 12E is interrupted without reaching the shoulder main groove 4. On the other hand, the outer middle sipe 13 extends inward in the tire axial direction from the shoulder main groove 4, and the inner end 13 </ b> E is interrupted without reaching the crown main groove 3. The inner and outer middle sipes 12, 13 are alternately arranged in the tire circumferential direction.

  The outer middle sipe 13 has an angle α4 with respect to the tire circumferential direction of 70 to 80 degrees, and is inclined in the same direction as the shoulder sipe 11. The inclination direction of the inner middle sipe 12 is different from that of the outer middle sipe 13. The angle α5 of the middle sipe 12 with respect to the tire circumferential direction is not particularly limited, but is preferably 45 degrees or more, more preferably 60 degrees or more.

  In the case of this example, the inner end 13E of the outer middle sipe 13 is positioned on the outer side in the tire axial direction than the outer end 12E of the inner middle sipe 12. That is, the inner and outer middle sipes 12 and 13 are spaced apart from each other in the tire axial direction by a gap K, whereby the rigidity of the middle rib 6 is further enhanced.

  When the virtual extension line obtained by extending the shoulder sipe 11 inward in the tire axial direction is X, the outer middle sipe 13 has an imaginary extension line X within a circumferential distance L from the virtual extension line X of 5 mm or less. Extend along. The distance L is preferably 4 mm or less, and more preferably 3 mm or less. As a result, the outer middle sipe 13 and the shoulder sipe 11 are arranged so as to be continuous with each other via the shoulder main groove 4. Thereby, although drainage property is improved, it becomes the fall tendency of rigidity by connecting to one. However, this reduction in rigidity is suppressed by forming a chamfered portion 15 described later.

  3 and 4, in this example, the side wall surface 13S of the outer middle sipe 13 and the one side surface 9S1 of the V-shaped protrusion 9 are aligned.

  A triangular chamfered portion 15 is formed at a corner portion P where the tread surface 6S of the middle rib 6 and the groove wall surface 4S of the shoulder main groove 4 intersect. The chamfered portion 15 includes a first chamfered portion 15A extending from the outer middle sipe 13 to one side in the tire circumferential direction and a second chamfered portion 15B extending to the other side.

  The first chamfered portion 15A of this example is provided at a corner portion PA of the flat surface portion 8 and the tread surface 6S, and includes a lower side A1 extending on the flat surface portion 8, an upper side A2 extending on the tread surface 6S, and a middle sipe 13. It has a triangular shape surrounded by the side A3 extending on the side wall surface 13S.

  The second chamfered portion 15B is provided at a corner portion PB between the V-shaped projecting portion 9 and the tread surface 6S, and has a lower side B1 extending on the other side surface 9S2 of the V-shaped projecting portion 9 and the tread surface 6S. The upper side B2 that extends and the side side B3 that extends on one side surface 9S1 (corresponding to the side wall surface 13S of the middle sipe 13) of the V-shaped protrusion 9 form a triangular shape.

  In this example, the upper side B2 extends along the tire circumferential direction. The upper side A2 extends parallel to the other side surface 9S2. Accordingly, the first and second chamfered portions 15A and 15B have substantially similar shapes in a top view. In the present example, the first and second chamfered portions 15A and 15B are continuous in the tire circumferential direction. However, a corner portion P that is not chamfered may be interposed between the first and second chamfered portions 15A and 15B.

  Such a chamfered portion 15 suppresses the movement of rubber on the opening end side of the outer middle sipe 13 at the time of grounding, and suppresses a decrease in rigidity due to the outer middle sipe 13. Moreover, since the water on the road surface is guided into the shoulder main groove 4 through the chamfered portion 15, it is useful for improving drainage. For this purpose, the circumferential lengths TA and TB of the first and second chamfered portions 15A and 15B need to be larger than the circumferential length T of the outer middle sipe 13, respectively. Below this value, the effect of the chamfered portion 15 is not sufficiently exhibited.

  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.

A pneumatic tire for a passenger car (235 / 55R20) based on the tread pattern of Fig. 1 was prototyped based on the specifications in Table 1, and the driving stability of each sample tire (driving stability on a dry road surface) ) And wet performance. The specifications are substantially the same except those described in Table 1, and the common specifications are as follows.
Crown main groove ・ Groove width: 10.4 mm
・ Groove depth: 8.1mm
Shoulder main groove ・ Groove width: 9.6 mm
・ Groove depth: 8.1mm
Shoulder lug groove ・ Groove width: 4.5mm
・ Groove depth: 6.8mm
・ Tire axial length / contact width: 17.5%
Depth of each sipe: 6.5mm
The test method is as follows.

(1) Steering stability:
The driving stability when driving on a dry asphalt road test course in a test vehicle with sample tires on all wheels was evaluated by sensory evaluation of the driver. The result is better as the numerical value is larger, indicated by an index with Comparative Example 1 as 100.
Rims: 7.5J x 20
Internal pressure: 230kPa
Test vehicle: Domestic FF vehicle (displacement 2500cc)
Load condition: 2 passengers on the front side, 1 passenger on the rear side

(2) Wet performance:
Using a vehicle under the same conditions as described above, a front wheel at a speed of 50-80 km / h was entered by gradually increasing the speed on a test course with a water pool of 5 mm depth and 20 m length on an asphalt road surface with a radius of 100 m. And the average lateral acceleration of the rear wheels was measured. The result is better as the numerical value is larger, indicated by an index with Comparative Example 1 as 100.

  As shown in Table 1, in the tires of the examples, it is possible to raise the overall potential for wet performance and steering stability, and confirm whether wet performance and steering stability can be achieved at a higher level.

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Tread part 3 Crown main groove 4 Shoulder main groove 4S Groove wall surface 6 Middle rib 6S Tread 7 Shoulder rib 10 Shoulder lug groove 10A Inner lug groove part 10B Outer lug groove part 11 Middle sipe 13 in shoulder sipe 12 Outside middle sipe 15 Chamfering Part Te Grounding end P Corner part X Virtual extension line

Claims (3)

In the tread portion, wherein a pair of shoulder main grooves extending in the tire circumferential direction at the ground end, the crown main groove extending the circumferential direction of the tire in the tire axial direction inside each shoulder main grooves, and the crown main groove shoulder main grooves A pneumatic tire comprising a pair of middle ribs disposed between and a pair of shoulder ribs disposed on the outer side in the tire axial direction of the shoulder main groove,
The shoulder rib has a shoulder lug groove extending inward in the tire axial direction across the ground contact end and the inner end being interrupted without reaching the shoulder main groove, and an outer end extending from the shoulder main groove in the tire axial direction outward. With shoulder sipe that breaks without reaching the grounding end,
The middle rib is not equipped with a lug groove, moreover and outside Midorusaipu interruption without the and the end extending from the shoulder main groove inwardly in the tire axial direction reaches the crown main grooves, in the tire axial direction outer side from the crown main groove comprising NobiKatsu outer end and Midorusaipu of interruption without reaching the shoulder main grooves,
Wherein the tread surface and the corner portion intersects the groove wall surface of the shoulder main grooves of middle rib, triangular chamfered portion extending in the tire circumferential direction from Midorusaipu of the outer are provided, and the circumferential length of the chamfer, the While making it larger than the circumferential length of the outer middle sipe,
The outer middle sipe extends along the virtual extension line within a range of a circumferential distance of 5 mm or less from a virtual extension line obtained by extending the shoulder sipe inward in the tire axial direction.
Moreover the the shoulder sipes and the outside Midorusaipu, angle, respectively 70 to 80 degrees with respect to the tire circumferential direction, and the shoulder lug groove, the inner lug groove angle of 70 to 80 degrees with respect to the tire circumferential direction on the inner end A pneumatic tire characterized by including. The outer of the inner end of Midorusaipu, rather than the outer end of the Midorusaipu in the pneumatic tire according to claim 1, wherein the located axially outwardly. The shoulder lug groove includes the inner lug groove portion and an outer lug groove portion that extends outward from the inner lug groove portion in the tire axial direction and has a larger angle with respect to the tire circumferential direction than the inner lug groove portion. 3. The pneumatic tire according to claim 1, wherein the outer end is interrupted on the outer side in the tire axial direction from the inner end of the shoulder lug groove and on the inner side in the tire axial direction from the outer lug groove portion.

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