JP2008254670A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving wet performance in the tire. <P>SOLUTION: This pneumatic tire has on a tread surface a plurality of peripheral directional main grooves extending in the tire peripheral direction, a plurality of lug grooves 31-33 extending in the tire width direction, and a plurality of rows of land parts 42 and 43 partitioned by these peripheral directional main grooves and lug grooves 31-33. A tread pattern is formed by arranging a plurality of pattern elements A-C having mutually different pitches P1-P3 in the tire peripheral direction. In this pneumatic tire, the groove length Ln of the lug grooves 31-33 is uniformized by changing a plane shape of the lug grooves 31-33 arranged in the same land part 42 (43) in response to the pitches P1-P3 of the pattern elements A-C. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve the wet performance of the tire.

  Generally, a tire tread pattern is composed of two or more types of pattern elements having different pitches. However, in the configuration in which the pitch variation structure is adopted, the groove length and the groove volume (groove area) of the lug groove change on the tire circumference, so that the drainage of the tread portion becomes uneven on the tire circumference.

  For example, a pattern element having a small pitch usually has a shorter lug groove length than a pattern element having a large pitch. Then, since the drainage performance is reduced by the lug groove at the tread portion where the small pitch continues in the tire circumferential direction, the wet performance of the tire is reduced.

  In addition, the technique described in patent document 1 is known for the conventional pneumatic tire which employ | adopts a pitch variation structure.

Japanese Patent Application Laid-Open No. 2004-299652

  An object of the present invention is to provide a pneumatic tire capable of improving the wet performance of the tire.

  In order to achieve the above object, a pneumatic tire according to the present invention includes a plurality of circumferential main grooves extending in the tire circumferential direction, a plurality of lug grooves extending in the tire width direction, and these circumferential main grooves. And tread patterns formed by arranging a plurality of pattern elements having different pitches Pn in the tire circumferential direction and having a plurality of rows of land portions partitioned by lug grooves on the tread surface. In the tire, the planar shape of the lug grooves arranged in the same land portion changes according to the pitch Pn of the pattern elements, whereby the groove length Ln of the lug grooves is made uniform. It is characterized by that.

  In this pneumatic tire, since the groove lengths Ln of the lug grooves arranged in the same land portion are uniform, compared with the configuration in which the groove lengths of the lug grooves are different from each other, Drainage is made uniform. Thereby, there exists an advantage which the wet performance of a tire improves. Further, since the groove length Ln of the lug groove is adjusted by changing the planar shape of the lug groove, there is an advantage that the lug groove can be appropriately arranged regardless of the pitch Pn of each pattern element.

  In the pneumatic tire according to the present invention, the lug groove has a planar shape in which the lug groove is bent or curved, and the groove length Ln of the lug groove is adjusted according to the bending degree or the bending degree of the lug groove.

  In this pneumatic tire, the groove length Ln of the lug groove can be accurately adjusted by gradually changing the bending degree or bending degree of the lug groove for each pattern element. Accordingly, there is an advantage that the groove length Ln of the lug groove is appropriately uniformized and the wet performance of the tire is improved.

  In the pneumatic tire according to the present invention, the lug groove has a planar shape that is smoothly curved.

  In this pneumatic tire, since the lug groove is smoothly curved, water flows smoothly in the lug groove. Thereby, there exists an advantage which the drainage property of a lug groove improves and the wet performance of a tire improves.

  In the pneumatic tire according to the present invention, the length Ln of the lug groove is within a range of ± 5 [%].

  In this pneumatic tire, since the groove length Ln of the lug groove is appropriately uniformed, there is an advantage that the drainage performance of each lug groove is uniformed and the wet performance of the tire is improved.

  In the pneumatic tire according to the present invention, the groove volume Vn of the lug groove is made uniform.

  In this pneumatic tire, the drainage of the lug groove in each pattern element is made uniform. Thereby, there exists an advantage which the wet performance of a tire improves.

  In the pneumatic tire according to the present invention, the groove volume Vn of the lug groove is within a range of ± 5 [%].

  In this pneumatic tire, since the groove volume Vn of the lug groove is made uniform appropriately, there is an advantage that the drainage performance of each lug groove is made uniform and the wet performance of the tire is improved.

  In the pneumatic tire according to the present invention, the lug groove penetrates the land portion in the tire width direction.

  In this pneumatic tire, since the lug groove penetrates the land portion, drainage performance of the lug groove is improved. Thereby, there exists an advantage which the wet performance of a tire improves.

  In the pneumatic tire according to the present invention, since the groove lengths Ln of the lug grooves arranged in the same land portion are uniform, each of the lug grooves has a different groove length. The drainage of the lug groove is made uniform. Thereby, there exists an advantage which the wet performance of a tire improves. Further, since the groove length Ln of the lug groove is adjusted by changing the planar shape of the lug groove, there is an advantage that the lug groove can be appropriately arranged regardless of the pitch Pn of each pattern element.

  Hereinafter, the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. The constituent elements of this embodiment include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

  FIG. 1 is a plan view showing a tread surface of a pneumatic tire according to an embodiment of the present invention. FIG. 2 is an explanatory diagram showing lug grooves of the pneumatic tire depicted in FIG. 1. 3 and 4 are explanatory views showing a modified example of the pneumatic tire shown in FIG. FIG. 5 is a chart showing the results of the performance test of the pneumatic tire according to the example of the present invention.

[Pneumatic tire]
The pneumatic tire 1 includes a plurality of circumferential main grooves 21 and 22 extending in the tire circumferential direction, a plurality of lug grooves (width direction grooves) 31 to 33 extending in the tire width direction, and the circumferential direction thereof. The tread surface has a plurality of land portions 41 to 43 defined by the main grooves 21 and 22 and the lug grooves 31 to 33 (see FIG. 1).

  For example, in this embodiment, four circumferential main grooves 21 and 22 extending in the tire circumferential direction are formed on the tread surface (see FIG. 1). The circumferential main grooves 21 and 22 and the lug grooves 31 to 33 form five rows of land portions 41 to 43. Specifically, three rows of land portions 41 and 42 are partitioned in the tread portion center region, and one row of land portions 43 is formed in the left and right tread portion shoulder regions. A plurality of lug grooves 31 to 33 are formed in land portions (second land portions) 42 and 42 in the second row from the center line CL among the land portions 41 and 42 in the tread portion center region. These lug grooves 31 to 33 open the left and right circumferential main grooves 21 and 22 across the second land portion 42 in the tire width direction. Similarly, lug grooves 31 to 33 are formed in the land portion (shoulder land portion) 43 in the tread portion shoulder region. These lug grooves 31 to 33 cross the shoulder land portion 43 in the tire width direction and open to the outer circumferential main groove 22 and the tread portion outside. As a result, two block rows (second land portion 42 and shoulder land portion 43) are formed on the left and right sides of the tread surface. In addition, lug grooves 31 to 33 are not formed in the land portion (center rib) 41 on the center line CL among the land portions 41 and 42 in the tread portion center region.

  Further, in the pneumatic tire 1, a tread pattern is formed by arranging a plurality of pattern elements A to C having different pitches Pn (P1, P2, P3) in the tire circumferential direction (FIG. 1). reference). That is, a pitch variation structure is adopted. With such a tread pattern, pattern noise during tire rolling is reduced, and the noise performance of the tire is improved.

  For example, in this embodiment, a pattern element A having a pitch P1, a pattern element B having a pitch P2, and a pattern element C having a pitch P3 are arranged in the tire circumferential direction to form a tread pattern (see FIG. 1). Further, the pitches P1 to P3 of the pattern elements A to C are in a relationship of P1> P2> P3. In the second land portion 42 and the shoulder land portion 43, at least one lug groove 31 to 33 is arranged in each pattern element A to C.

[Lug groove length]
Here, in this pneumatic tire 1, the planar shape of the lug grooves 31 to 33 arranged in the same land portions 42 and 43 (groove shape in a plan view of the tread portion) is the pitch P1 of each pattern element A to C, By changing according to P2 and P3, the groove length Ln (L1≈L2≈L3) of the lug grooves 31 to 33 is made uniform (see FIGS. 1 and 2). That is, by adjusting the planar shape of each of the lug grooves 31 to 33, the groove lengths Ln of the lug grooves 31 to 33 in the same land portions 42 and 43 are set to be substantially equal. In addition, groove length L1-L3 of the lug grooves 31-33 is measured on the basis of the length of the groove centerline of the lug grooves 31-33.

  For example, in this embodiment, the second land portion 42 and the shoulder land portion 43 have three types of pattern elements A to C (see FIGS. 1 and 2). Further, a pitch variation structure is formed by sequentially arranging these pattern elements A to C in the tire circumferential direction at each land portion 43 (42). Further, the lug grooves 31 to 33 of the land portions 43 (42) have substantially the same groove length Ln (L1≈L2≈L3). At this time, the groove lengths L1 to L3 of the lug grooves 31 to 33 are uniform by changing the planar shape of the lug grooves 31 to 33 according to the pitch Pn (P1, P2, P3) of each pattern element A to C. It has become. Specifically, in the pattern element A having the largest pitch P1, the lug groove 31 has a linear shape. Further, in the pattern element B having the second largest pitch P2, the lug groove 32 has an S shape that is small and curved. Further, in the pattern element C having the smallest pitch P3, the lug groove 33 has an S shape that is greatly curved. The lug grooves 32 and 33 are adjusted so that the groove lengths L1 to L3 of the lug grooves 31 to 33 are substantially equal to each other due to the difference in curvature of the lug grooves 32 and 33.

[effect]
In this pneumatic tire 1, since the groove lengths Ln of the lug grooves 31 to 33 arranged in the same land portions 42 and 43 are uniform (L1≈L2≈L3), the groove length of each lug groove Compared with the structure which is different, the drainage of each lug groove is made uniform. Thereby, there exists an advantage which the wet performance of a tire improves. In addition, since the groove length Ln of the lug grooves 31 to 33 is adjusted by making the planar shapes of the lug grooves 31 to 33 different, the lug groove 31 regardless of the pitches P1 to P3 of the pattern elements A to C. There exists an advantage which can arrange | position ~ 33 appropriately. For example, in the configuration in which the planar shape and the groove length of the lug grooves are set to be the same in each of the pattern elements A to C, it is difficult to arrange the lug grooves in the pattern elements C having a small pitch P3.

  Note that the above-described configuration does not have to be applied to all the land portions, and it is sufficient that the groove lengths Ln of the lug grooves 31 to 33 are uniform for at least some of the land portions 42 and 43. That is, the whole tread pattern should just be comprised based on the structure by which the groove length Ln of the lug grooves 31-33 arranged in the same land part 42 and 43 is equalized.

[Additional matter 1]
In the pneumatic tire 1, the lug grooves 31 to 33 have a planar shape in which the lug grooves 31 to 33 are bent or curved, and the groove length Ln of the lug grooves 31 to 33 is adjusted by the bending degree or the bending degree of the lug grooves 31 to 33. It is preferable (see FIG. 2). In such a configuration, the groove length Ln of the lug grooves 31 to 33 can be accurately adjusted by gradually changing the bending degree or bending degree of the lug grooves 31 to 33 for each of the pattern elements A to C. Thereby, groove length L1-L3 of the lug grooves 31-33 is equalized appropriately, and there exists an advantage which the wet performance of a tire improves. Moreover, in this structure, the edge length of the lug grooves 31-33 increases compared with the structure by which only a linear lug groove is arrange | positioned. Thereby, there exists an advantage which the drainage property of a lug groove improves and the wet performance of a tire improves.

  Moreover, in said structure, it is preferable that the lug grooves 31-33 have the planar shape curved smoothly (refer FIG. 1 and FIG. 2). That is, the lug grooves 31 to 33 have a planar shape that is smoothly curved, and the groove length Ln of the lug grooves 31 to 33 is adjusted according to the degree of curvature. In such a configuration, since the lug grooves 31 to 33 are smoothly curved, water flows smoothly in the lug grooves 31 to 33. Thereby, there exists an advantage which the drainage property of a lug groove improves and the wet performance of a tire improves.

  For example, in this embodiment, the lug grooves 31 to 33 have a substantially S-shape that is smoothly curved, and the groove lengths L1 to L3 of the lug grooves 31 to 33 are adjusted according to the degree of curvature (see FIG. 1 and FIG. 1). (See FIG. 2). Specifically, in the pattern element A having the largest pitch P1, the degree of curvature of the lug groove 31 is substantially 0, and the lug groove 31 has a substantially linear shape. As the pitches P2 and P3 of the pattern elements B and C become narrower, the curvature of the lug grooves 32 and 33 gradually increases. As a result, the groove lengths L1 to L3 of the lug grooves 31 to 33 are made uniform (L1≈L2≈L3). In such a configuration, the groove lengths L1 to L3 of the lug grooves 31 to 33 are easily made uniform by adjusting the curvature (amplitude) of the S-shape.

  In addition, the lug grooves 31 to 33 are not limited to the above, and may have a substantially arcuate planar shape that is smoothly curved (see FIG. 3). That is, the curvature (curvature) of the lug grooves 31 to 33 is adjusted, and the groove lengths L1 to L3 of the lug grooves 31 to 33 are made uniform. For example, as the pitches P1 to P3 of the pattern elements A to C become smaller, the curvatures of the lug grooves 31 to 33 are set smaller.

  In addition, the lug grooves 31 to 33 are not limited to the above, and may have a bent planar shape such as a substantially Z shape or a substantially L shape (see FIG. 4). In such a configuration, for example, the inclination angles and bending positions of the lug grooves 31 to 33 are adjusted, and the groove lengths L1 to L3 of the lug grooves 31 to 33 are made uniform. In this way, by changing the planar shape of the lug grooves 31 to 33, it is possible to diversify the tread pattern variations.

[Additional matter 2]
Moreover, in this pneumatic tire 1, it is preferable that groove length L1-L3 of the lug grooves 31-33 exists in the range of +/- 5 [%]. The groove lengths L1 to L3 are more preferably within a range of ± 3 [%]. That is, if the groove lengths L1 to L3 are within a range of ± 5 [%], it can be said that the groove lengths L1 to L3 are substantially equal (uniform). In such a configuration, since the groove lengths L1 to L3 of the lug grooves 31 to 33 are appropriately uniformized, there is an advantage that the drainage performance of each lug groove is uniformized and the wet performance of the tire is improved.

  Moreover, the groove length L1-L3 of the lug grooves 31-33 should just be equalized about the lug grooves 31-33 in the same land part 42 (43) (refer FIG. 1). That is, it is only necessary that the groove lengths L1 to L3 are made uniform for the lug grooves 31 to 33 arranged in the tire circumferential direction. For example, the lug grooves 31 to 33 of the second land portion 42 and the lug grooves 31 to 33 of the shoulder land portion 43 may have different groove lengths L1 to L3.

  However, the groove lengths L1 to L3 of all the lug grooves 31 to 33 in the same land portion 42 (43) are not necessarily uniform. For example, an auxiliary lug groove having a different groove length may be arranged in a part of the land portion 42 (43) (not shown).

[Additional matter 3]
Moreover, in this pneumatic tire 1, it is preferable that the groove volume Vn of the lug grooves 31-33 is equalized (refer FIG. 2). That is, it is preferable that both the groove length Ln and the groove volume Vn of the lug grooves 31 to 33 arranged in the same land portions 42 and 43 are made uniform. As for the groove volume Vn of the lug grooves 31 to 33, for example, the groove depth and groove width of the lug grooves 31 to 33 are adjusted, and the groove volume Vn of the lug grooves 31 to 33 is made uniform. In such a configuration, the drainage of the lug grooves 31 to 33 in the pattern elements A to C is made uniform. Thereby, there exists an advantage which the wet performance of a tire improves.

  For example, in this embodiment, as the pitches P1 to P3 of the pattern elements A to C are decreased, the curvature of the lug grooves 31 to 33 is increased, and at the same time, the groove depth of the lug grooves 31 to 33 is increased. (See FIG. 2). At this time, by adjusting the groove depth of the lug grooves 31 to 33, the groove volumes V1 to V3 of the lug grooves 31 to 33 in the pattern elements A to C are made uniform.

  In the above configuration, it is preferable that the groove volume Vn of the lug grooves 31 to 33 is within a range of ± 5 [%]. The groove volume Vn is more preferably within a range of ± 3 [%]. That is, if the groove volume Vn is within the range of ± 5 [%], it can be said that the groove volume Vn is substantially equal (uniform). In such a configuration, since the groove volume Vn of the lug grooves 31 to 33 is appropriately uniformized, there is an advantage that the drainage performance of each of the lug grooves 31 to 33 is uniformized and the wet performance of the tire is improved.

[Additional matter 4]
Moreover, in this pneumatic tire 1, it is preferable that the lug grooves 31-33 have penetrated the land part 42 (43) in the tire width direction (refer FIG. 2). That is, it is preferable that the lug grooves 31 to 33 open to the circumferential main grooves 21 and 22 (or the tread portion outside) across the land portion 42 (43). In this structure, since the lug grooves 31-33 have penetrated the land part 42 (43), the drainage property of the lug grooves 31-33 improves. Thereby, there exists an advantage which the wet performance of a tire improves.

  However, not limited to the above, the lug grooves 31 to 33 do not necessarily have to penetrate (cross) the land portion 42 (43). For example, one end of the lug grooves 31 to 33 may open to the circumferential main grooves 21 and 22 (or the tread portion outside), and the other end may be located in the land portion 42 (43) ( Closed drag groove). Specifically, the closed drag groove may be arranged depending on the design of the tire and the wear resistance.

[performance test]
In this example, a performance test on wet performance (braking stop performance) was performed on a plurality of pneumatic tires having different conditions (see FIG. 5).

  In this performance test, a pneumatic tire having a tire size of 205 / 55R16 is assembled to an applicable rim specified by JATMA, and a specified internal pressure and a specified load are applied to the pneumatic tire. Then, a test vehicle equipped with a pneumatic tire travels on a flooded course on an asphalt road surface, and a braking stop distance until the vehicle stops from an initial speed of 100 [km / h] is measured. Then, five measurements are performed, and three measurement values excluding the maximum value and the minimum value of the measurement values are adopted, and the average value of the braking stop distance is calculated. Then, based on this calculation result, index evaluation is performed using the conventional example as a reference (100). An evaluation result is so preferable that the numerical value is large.

  In the conventional pneumatic tire, the groove length Ln and the groove volume Vn of the lug groove change according to the pattern element pitch Pn (P1 to P5) (not shown). On the other hand, in the pneumatic tires 1 of Invention Examples 1 and 2, the groove lengths Ln of the lug grooves 31 to 33 arranged in the same land portion 42 (43) are made uniform (see FIGS. 1 and 2). . Moreover, in the pneumatic tire 1 of the invention example 2, the groove volume Vn of the lug grooves 31 to 33 arranged in the same land portion 42 (43) is further made uniform. In FIG. 5, the pitch Pn, the groove length Ln, and the groove volume Vn are shown with the pattern element having the largest pitch P1 as a reference (100).

  As shown in the test results, it can be seen that in the pneumatic tires 1 of Invention Examples 1 and 2, the wet performance (braking stop performance) of the tire is improved. Further, when Invention Example 1 and Invention Example 2 are compared, it can be seen that the wet performance of the tire is further improved by making both the groove length Ln and the groove volume Vn uniform.

  As described above, the pneumatic tire according to the present invention is useful in that the wet performance of the tire can be improved.

It is a top view which shows the tread surface of the pneumatic tire concerning the Example of this invention. It is explanatory drawing which shows the lug groove of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is a graph which shows the result of the performance test of the pneumatic tire concerning the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 21, 21 Circumferential main grooves 31-33 Lug grooves 41-43 Land part

Claims (7)

A tread composed of a plurality of circumferential main grooves extending in the tire circumferential direction, a plurality of lug grooves extending in the tire width direction, and a plurality of rows of land portions defined by the circumferential main grooves and the lug grooves. A pneumatic tire in which a tread pattern is formed by arranging a plurality of pattern elements having different pitches Pn on the surface and arranged in the tire circumferential direction,
An air characterized in that the length Ln of the lug grooves is made uniform by changing the planar shape of the lug grooves arranged in the same land portion in accordance with the pitch Pn of the pattern elements. Tires.   2. The pneumatic tire according to claim 1, wherein the lug groove has a planar shape that is bent or curved, and the groove length Ln of the lug groove is adjusted by the bending degree or the bending degree of the lug groove.   The pneumatic tire according to claim 2, wherein the lug groove has a planar shape that is smoothly curved.   The pneumatic tire according to any one of claims 1 to 3, wherein a groove length Ln of the lug groove is within a range of ± 5 [%].   The pneumatic tire according to any one of claims 1 to 4, wherein a groove volume Vn of the lug groove is uniformized.   The pneumatic tire according to claim 5, wherein a groove volume Vn of the lug groove is within a range of ± 5 [%].   The pneumatic tire according to claim 1, wherein the lug groove penetrates the land portion in the tire width direction.

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