JP2006205824A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of improving hydraulic performance and braking performance on a wet road while ensuring draining performance of a main groove. <P>SOLUTION: This pneumatic tire 1 includes a main groove 2 independently placed from other grooves 3 and straightly extended in a plan view of a tread section and a depression portion 21 formed on a side wall of the main groove 2. Moreover, a cross-sectional area of the main groove 2 is expanded by the depression portion 21, and the depression portion 21 is formed in a streamline shape in the plan view of the tread section. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve hydro performance and braking performance on a wet road while ensuring drainage performance of a main groove.

  In a pneumatic tire, in order to improve braking performance and hydro performance on a wet road, a configuration in which the area ratio of the main groove in the tread portion is increased is adopted. On the other hand, in such a configuration, there is a possibility that the braking performance and the maneuverability on the dry road may be lowered, and thus a device for suppressing this is required.

  A technique described in Patent Document 1 is known for such a conventional pneumatic tire. In a conventional pneumatic tire, by not providing a groove that is substantially continuous in the tire circumferential direction in addition to one main groove that is continuous in the tire circumferential direction and extends in a zigzag shape in the tread portion. The tread portion is divided into tread side portions on both sides of the main groove, the main groove has a groove width GW of 35 mm or more, and an average amplitude S at which the groove edge where the main groove and the upper surface of the tread side portion intersect is zigzag. And the groove width GW to a ratio (S / GW) larger than 0 and 0.4 or less, and the groove edge is convex toward the groove center line side of the main groove of the groove edge. In the tire meridian section passing through the apex of the convex portion, an arc portion having a curvature radius Ra of 2 to 15 mm is formed.

  Here, when traveling at high speed, a water flow having a high flow velocity is generated in the main groove. However, in the configuration in which the main groove extends in a zigzag shape in the tire circumferential direction as in a conventional pneumatic tire, there is a problem that turbulent flow is generated in the main groove and the drainage performance of the main groove is reduced.

JP-A-11-301212

  Then, this invention is made in view of the above, Comprising: It aims at providing the pneumatic tire which can improve the hydro performance and braking performance in a wet road, ensuring the drainage performance of a main groove. .

  In order to achieve the above object, a pneumatic tire according to the present invention is formed in a main groove that extends in a straight shape in a plan view of a tread portion and is independent from other grooves, and a side wall of the main groove. And a groove cross-sectional area of the main groove is expanded by the recess, and the recess has a streamline shape in a plan view of the tread portion.

  In this pneumatic tire, since the straight main groove is formed in the tread portion, there is an advantage that drainage performance of the main groove is improved when traveling at high speed on a wet road. In addition, a recess is formed on the side wall of the main groove, and the groove cross-sectional area of the main groove is expanded by the recess, so that the drainage performance of the main groove is improved, and the braking performance and hydro performance of the tire on a wet road Has the advantage of improving. Moreover, since the hollow part has a streamline shape in a plan view of the tread part, there is an advantage that drainage performance of the main groove is improved due to the formation of the hollow part.

  Further, in the pneumatic tire according to the present invention, when the ground contact surface of the tire is viewed in plan view, at least one of the hollow portions exists in each main groove.

  In this pneumatic tire, there is an advantage that drainage performance in each main groove is ensured at the time of tire contact because there is at least one hollow portion in each main groove when the ground contact surface of the tire is viewed in plan. .

  In the pneumatic tire according to the present invention, when the ground contact surface of the tire is viewed in plan, only one depression is present in each main groove.

  In this pneumatic tire, when the ground contact surface of the tire is viewed in plan, the number N of the recessed portions arranged in one main groove uses the contact length Lc and the circumferential length L of the recess. 1 ≦ N ≦ Lc / 2L, so that the drainage performance of the main groove is improved as compared with a configuration in which a large number of depressions are continuously arranged in one main groove in the ground plane. There are advantages.

  In the pneumatic tire according to the present invention, the groove width D of the main groove, the radius of curvature R of the recessed portion, and the recessed width d satisfy D ≦ R and d ≦ D / 2.

  In this pneumatic tire, since the groove width D of the main groove, the radius of curvature R of the recess, and the recess width d are configured to satisfy the predetermined relationship, the separation of water flow on the inner wall surface of the recess is reduced. There is an advantage that generation of turbulent flow is more effectively suppressed.

  In the pneumatic tire according to the present invention, the recess width d of the recess portion is smaller on the groove bottom side than the groove opening portion of the main groove.

  This pneumatic tire has an advantage that the rigidity of the land portion is maintained because the recess width of the recess portion is smaller on the groove bottom side than the groove opening portion of the main groove.

  In the pneumatic tire according to the present invention, the recess circumferential length L of the recess is smaller on the groove bottom side than the groove opening of the main groove.

  This pneumatic tire has an advantage that the rigidity of the land portion is maintained because the recess circumferential length L of the recess portion is smaller on the groove bottom side than the groove opening portion of the main groove.

  In the pneumatic tire according to the present invention, the radius of curvature RB of the recessed portion on the groove bottom side of the main groove is smaller than the radius of curvature RA of the recessed portion on the groove opening side of the main groove.

  In this pneumatic tire, the radius of curvature RB of the recess on the groove bottom side of the main groove is smaller than the radius of curvature RA of the recess on the groove opening side of the main groove, so that the drainage performance of the main groove is maintained. There are advantages.

  In the pneumatic tire according to the present invention, the groove width D of the main groove, the recess width d of the recess, and the recess circumferential length L of the recess in the longitudinal direction of the main groove are D ≦ L. And d ≦ D / 2 is satisfied, and the radius of curvature R2 of the recessed portion on the downstream side with respect to the water flow generated in the main groove is larger than the radius of curvature R1 on the upstream side.

  In this pneumatic tire, the groove width D of the main groove, the recess width d of the recess, and the recess circumferential length L of the recess in the longitudinal direction of the main groove satisfy a predetermined relationship, and Since the radius of curvature R2 of the depression portion on the downstream side with respect to the generated water flow is smaller than the curvature radius R1 of the depression portion 21 on the upstream side, the effect of suppressing the separation of the water flow by the depression portion is improved. Thereby, there exists an advantage by which generation | occurrence | production of a turbulent flow is suppressed more effectively.

  In the pneumatic tire according to the present invention, the pair of depressions are arranged to face both side walls of the main groove.

  In this pneumatic tire, since the pair of indentations are arranged to face both side walls of the main groove, the rigidity of the ribs is lower than the configuration in which the groove width of the main groove is adjusted by a single indentation. There is an advantage to be secured.

  In the pneumatic tire according to the present invention, the main groove is disposed at the center of the tread portion.

  In this pneumatic tire, since the main groove is arranged at the center of the tread portion, there is an advantage that drainage performance as the whole tread portion is improved.

  In the pneumatic tire according to the present invention, since the straight main groove is formed in the tread portion, there is an advantage that the drainage performance of the main groove during high speed traveling on a wet road is improved. In addition, a recess is formed on the side wall of the main groove, and the groove cross-sectional area of the main groove is expanded by the recess, so that the drainage performance of the main groove is improved, and the braking performance and hydro performance of the tire on a wet road Has the advantage of improving. Moreover, since the hollow part has a streamline shape in a plan view of the tread part, there is an advantage that the drainage performance of the main groove is improved.

  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 portion of a pneumatic tire according to an embodiment of the present invention. 2-4 is explanatory drawing which shows the main groove | channel of the pneumatic tire described in FIG. 5-7 is explanatory drawing which shows the modification of the pneumatic tire described in FIG. FIG. 8 is a table showing performance tests of pneumatic tires according to examples of the present invention.

  In the pneumatic tire 1, a main groove 2 and a lug groove 3 are formed in a tread portion, and ribs 4 and a shoulder block 5 are defined by these grooves 2 and 3 (see FIG. 1). The main groove 2 is a straight vertical groove extending in the tire circumferential direction, and mainly has a function of ensuring the drainage performance of the tire on a wet road. Further, the main groove 2 has a side wall constituted by a rib 4 and is not coupled to the lug groove 3. Therefore, the main groove 2 is independent of other grooves on the tread surface. A plurality (three) of main grooves 2 are formed in the tread portion. The number of main grooves 2 may be one or plural.

[Recessed part of main groove]
A plurality of depressions 21 are provided on the side wall of the main groove 2. However, the side wall of the main groove 2 is not provided with a cutout portion or an uneven portion other than the recessed portion 21. The groove cross-sectional area (channel cross-sectional area) of the main groove 2 is partially expanded by the recess 21. Specifically, the groove cross-sectional area of the main groove 2 is adjusted by the recess 21 so that the water flow in the main groove 2 is prevented from being separated from the groove wall surface during traveling with the wet. In addition, the some hollow part 21 may be arrange | positioned alternately with respect to the both side walls of the one main groove 2, and may be arrange | positioned only at one side wall.

  In addition, the recess 21 has an inner peripheral shape that is smoothly formed, and a boundary portion between the opening edge and the surrounding side wall surface is formed smoothly. For example, the recess 21 has a substantially arc shape, an airfoil shape (an outer peripheral shape of the blade when the blade is viewed in a cross-section in the airflow direction), and other streamline shapes in a plan view of the tread portion. Moreover, the hollow part 21 may have a shape formed by connecting a plurality of arcs in a plan view of the tread part.

[Function and effect]
In general, in a pneumatic tire, water in the ground contact surface is drained through a main groove when traveling at high speed on a wet road. At this time, in the main groove that is independent of other grooves on the tread surface (for example, not connected to the lug groove), the boundary layer develops on the groove wall surface of the main groove because the water flow velocity is high. Water flow separation occurs (see FIG. 4A). Then, a turbulent flow is generated in the main groove and the drainage performance of the main groove is deteriorated.

  In this respect, in the pneumatic tire 1, first, since the straight main groove 2 is formed in the tread portion (see FIG. 1), the main groove extending in a zigzag shape in the tire circumferential direction is formed in the tread portion. Compared with the formed structure (see Patent Document 1), there is an advantage that the drainage performance of the main groove 2 is improved when traveling at high speed on a wet road.

  Moreover, in this pneumatic tire 1, since the hollow part 21 is formed in the side wall of the main groove 2, and the groove cross-sectional area of the main groove 2 is expanded by this hollow part 21 (refer FIGS. 1-3), When a water flow is generated in the main groove 2, the boundary layer with the groove wall surface of the water flow becomes thin at the recess 21. Then, since separation of the water flow from the groove wall surface (side wall surface) is reduced, generation of turbulent flow in the main groove 2 is suppressed (see FIG. 4B). Thereby, since the drainage performance of the main groove 2 improves, there exists an advantage which the braking performance and hydro performance of the tire in a wet road improve.

  Moreover, in this pneumatic tire 1, since the hollow part 21 has a streamline shape in plan view of the tread part (see FIGS. 1 to 3), the occurrence of turbulent flow is suppressed in the main groove 2. Thereby, there exists an advantage which the drainage performance of the main groove 2 improves.

[Modification 1]
In the pneumatic tire 1, it is preferable that at least one hollow portion 21 exists in each main groove 2 when the ground contact surface of the tire is viewed in plan (see FIG. 1). Thereby, there exists an advantage by which the drainage performance in each main groove 2 is ensured at the time of tire contact.

  Further, when the ground contact surface of the tire is viewed in plan, the number N of recesses 21 disposed in each main groove 2 is 1 ≦ N ≦ Lc using the contact length Lc and the circumferential length L of the recess. It is preferable to satisfy the relationship of / 2L (see FIG. 1). Thereby, there exists an advantage which the drainage performance of the main groove 2 improves compared with the structure by which many hollow parts 21 are continuously arrange | positioned in the one main groove 2 in the grounding surface.

[Modification 2]
In the pneumatic tire 1, it is preferable that the groove width D of the main groove 2, the radius of curvature R of the recess portion 21, and the recess width d satisfy D ≦ R and d ≦ D / 2. (See FIG. 2). Further, it is more preferable that the groove width D of the main groove 2 and the recess width d of the recess portion 21 are in the range of D / 10 ≦ d ≦ D / 2. In other words, the ratio d / D between the recess width d of the recess portion 21 and the groove width D of the main groove 2 is preferably in the range of 0.10 ≦ d / D ≦ 0.50 or less. Furthermore, the ratio d / D is more preferably in the range of 0.30 ≦ d / D ≦ 0.40.

  In such a configuration, since the groove width D (groove cross-sectional area or flow path cross-sectional area) of the main groove 2 gradually changes in the recessed portion 21, water flow separation on the inner wall surface of the recessed portion 21 is reduced. Thereby, there exists an advantage by which generation | occurrence | production of a turbulent flow is suppressed more effectively.

[Modification 3]
Moreover, in this pneumatic tire 1, the structure where the hollow width d of the hollow part 21 becomes small in the groove bottom side rather than the groove opening part of the main groove 2 is preferable (refer FIG. 2 and FIG. 3). Thereby, there exists an advantage by which the drainage performance of the main groove 2 is maintained. Moreover, there exists an advantage by which the rigidity of the rib 4 in the formation position of the hollow part 21 is ensured.

  Moreover, the structure where the hollow circumferential direction length L of the hollow part 21 becomes small in the groove bottom side rather than the groove opening part of the main groove 2 is preferable (refer FIG. 2 and FIG. 3). Thereby, there exists an advantage by which the drainage performance of the main groove 2 is maintained. Moreover, there exists an advantage by which the rigidity of the rib 4 in the formation position of the hollow part 21 is ensured.

  Further, it is preferable that the curvature radius RB of the recess 21 on the groove bottom side of the main groove 2 is smaller than the curvature radius RA of the recess 21 on the groove opening side of the main groove 2 (see FIGS. 2 and 3). . Thereby, there exists an advantage by which the drainage performance of the main groove 2 is maintained.

[Modification 4]
In the pneumatic tire 1, the groove width D of the main groove 2, the recess width d of the recess portion 21, and the recess circumferential length L of the recess portion 21 in the longitudinal direction of the main groove 2 are D ≦ L and d. ≦ D / 2 is satisfied, and the radius of curvature R2 of the depression 21 on the downstream side with respect to the water flow generated in the main groove 2 is smaller than the radius of curvature R1 of the depression 21 on the upstream side (R2 ≦ R1) is preferable (see FIG. 5). In other words, the recess 21 is preferably configured such that the upstream wall surface has a gentler curve than the downstream wall surface with respect to the water flow generated in the main groove 2.

  In such a configuration, the depression 21 has a substantially airfoil shape (streamline shape) in a plan view of the tread portion, so that water flow separation on the inner wall surface of the depression 21 is reduced. Thereby, there exists an advantage by which generation | occurrence | production of a turbulent flow is suppressed more effectively. Further, in such a configuration, an abrupt increase in the groove cross-sectional area of the main groove 2 is suppressed as compared with a configuration in which the recessed portion 21 has a single arc shape in plan view of the tread portion. Thereby, since the hollow width d of the hollow part 21 changes efficiently (slowly), there is an advantage that generation of turbulent flow is more effectively suppressed.

[Modification 5]
Moreover, in this pneumatic tire 1, a pair of hollow parts 21 and 21 may be arrange | positioned facing both the side walls of the main groove 2 (refer FIG. 6). The groove cross-sectional area of the main groove 2 is adjusted by the sum d of the recess widths d1 and d2 of the recess portions 21 and 21. In such a configuration, compared to a configuration in which the groove width of the main groove 2 is adjusted by the single recess portion 21, the recess widths d1 and d2 of the recess portions 21 and 21 are reduced. Thereby, since the rib width of the rib 4 in which the hollow part 21 is formed increases, there is an advantage that the rigidity of the rib 4 is ensured.

[Modification 6]
Moreover, in this pneumatic tire 1, it is preferable that the main groove 2 is arrange | positioned in the center of a tread part (illustration omitted). Thereby, there exists an advantage which the drainage performance as the whole tread part improves.

[Modification 7]
Further, in this pneumatic tire 1, the main groove 2 is a vertical groove extending in the tire circumferential direction (see FIG. 1), but not limited to this, the main groove 2 is an inclined groove inclined in the tire circumferential direction. (See FIG. 7). Such a configuration also has the advantage that the same effects can be obtained.

[performance test]
In this performance test, tests on (1) hydro performance, (2) wet braking performance, and (3) driving performance were performed on a plurality of pneumatic tires with different conditions (see FIG. 8). In this performance test, a pneumatic tire having a tire size of 235 / 50R17 is assembled on a rim having a rim size of 8JJ, and a normal load and a normal air pressure specified by JATMA are applied to the pneumatic tire.

  Each pneumatic tire has a tread pattern similar to V103, and is configured such that the groove width D of the straight main groove is D = 10 [mm].

  (1) In the performance test related to hydro performance, evaluation is performed by the hydroplaning cornering method. Specifically, when the test vehicle equipped with a pneumatic tire travels on a test course with a water depth of 10 ± 1 [mm] and a turning radius of 100 R, and the maximum lateral acceleration of the test tire occurs, the traveling speed of the test vehicle is hydrostatic. Recorded as planing rate. Based on this, index evaluation is performed using the conventional pneumatic tire as a reference (100). An evaluation result is so preferable that the numerical value is large. Note that it is extremely difficult to improve the hydro performance, and it is recognized that a beneficial effect is obtained even if the index value is improved by 1 or more.

  (2) In the performance test for wet braking performance, evaluation is performed according to the conditions specified in the Japan New Car Assessment Program (J-NCAP). Specifically, a test vehicle equipped with a pneumatic tire enters under a condition where the approach speed is 100 ± 1 [km / h] and the pad temperature is 110 [deg] or less to perform a sudden braking, and the braking distance is measured. Is done. Based on this, index evaluation is performed using the conventional pneumatic tire as a reference (100). An evaluation result is so preferable that the numerical value is large.

  (3) In a performance test related to maneuverability (steering stability), a test vehicle equipped with a pneumatic tire travels on a test course having a flat circuit at 60 [km / h]. Then, index evaluation is performed with respect to the steering performance at the time of the race change and the cornering and the stability at the time of straight traveling, using the conventional pneumatic tire as a reference (100). An evaluation result is so preferable that the numerical value is large.

  In this performance test, the conventional example shows a conventional pneumatic tire that does not have the depression 21 on the side wall of the main groove 2, and the inventive examples 1 to 5 have the depression 21 on the side wall of the main groove 2. A tire 1 is shown. Moreover, in the pneumatic tire 1 of the invention example 1, the depression 21 on the side wall of the main groove 2 has a substantially arc shape in a plan view of the tread surface, and the curvature radius R of the depression 21 is R = 9 and the depression. The width d is 5 [mm]. In the pneumatic tire 1 of Invention Example 2, the recess 21 has a substantially arc shape in a plan view of the tread surface, the radius of curvature R of the recess 21 is R = 25, and the recess width d is d = 4 [ mm].

  In the pneumatic tire 1 of the invention example 2, the two hollow parts 21 and 21 are formed in the grounding surface, and these hollow parts 21 have a substantially circular arc shape in planar view of the tread surface. Moreover, the curvature radius R of these hollow parts 21 is R = 25, and the hollow width d is d = 4 [mm]. In the pneumatic tire 1 of Invention Example 4, the recess 21 has a substantially airfoil shape in plan view of the tread surface, and the radii of curvature R1, R2 of the recess 21 are R1 = 35, R2 = 15, and the recess. The width d is d = 5 [mm]. In the pneumatic tire 1 of Invention Example 5, the recess portion 21 has a substantially airfoil shape in a plan view of the tread surface, and the recess width d decreases from the groove opening of the main groove 2 toward the groove bottom. . Further, the radii of curvature RA and RB of the recess 21 are RA = 25, RB = 15, and the recess width d is d = 4 [mm] at the groove opening.

  As shown in the test results, in the pneumatic tires 1 of the inventive examples 1 to 5 having the depression 21 on the side wall of the main groove 2, the hydro performance and the wet performance are improved as compared with the conventional example, and the draft performance is conventional. It can be seen that it is maintained at the example level. Moreover, when the invention examples 1-3 are compared, it turns out that hydro performance and wet performance improve further by optimization of the curvature radius R of the hollow part 21, and the hollow width d.

  In addition, when Invention Example 1 and Invention Example 4 are compared, it can be seen that the hydro performance and the wet performance are further improved by the hollow portion 21 having a substantially airfoil shape (streamline shape). In addition, when Invention Example 1 and Invention Example 5 are compared, it is found that the hydro performance and the wet performance are further improved by narrowing the dent width d of the dent portion 21 in the groove depth direction of the main groove 2.

  As described above, the pneumatic tire according to the present invention is useful in that it can improve the hydro performance and the braking performance on the wet road while ensuring the drainage performance of the main groove.

It is a top view which shows the tread part of the pneumatic tire concerning the Example of this invention. It is explanatory drawing which shows the main groove | channel of the pneumatic tire described in FIG. It is explanatory drawing which shows the main groove | channel of the pneumatic tire described in FIG. It is explanatory drawing which shows the main groove | channel 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 explanatory drawing which shows the modification of the pneumatic tire described in FIG. It is a graph which shows the performance test of the pneumatic tire concerning the Example of this invention.

Explanation of symbols

1 Pneumatic tire 2 Main groove 3 Lug groove 4 Rib 5 Shoulder block 21 Recessed part

Claims (10)

A main groove that extends in a straight shape in a plan view of the tread portion and is independent from other grooves, and a recess formed in a side wall of the main groove, and
The pneumatic tire is characterized in that a groove cross-sectional area of the main groove is expanded by the recess, and the recess has a streamline shape in a plan view of the tread portion.   2. The pneumatic tire according to claim 1, wherein when the ground contact surface of the tire is viewed in plan, at least one of the recesses is present in each main groove.   When the ground contact surface of the tire is viewed in plan, the number N of the depressions arranged in one main groove is 1 ≦ N ≦ Lc / using the contact length Lc and the circumferential length L of the tire. The pneumatic tire according to claim 1 or 2, satisfying a 2L relationship.   The pneumatic tire according to any one of claims 1 to 3, wherein a groove width D of the main groove, a radius of curvature R of the recess, and a recess width d satisfy D≤R and d≤D / 2.   The pneumatic tire according to any one of claims 1 to 4, wherein a recess width d of the recess portion is smaller on a groove bottom side than a groove opening portion of the main groove.   The pneumatic tire according to any one of claims 1 to 5, wherein a hollow circumferential length L of the hollow portion is smaller on a groove bottom side than a groove opening portion of the main groove.   The curvature radius RB of the said hollow part in the groove bottom side of the said main groove becomes smaller than the curvature radius RA of the said hollow part in the groove opening side of the said main groove, It is any one of Claims 1-6 Pneumatic tire.   The groove width D of the main groove, the recess width d of the recess, and the recess circumferential length L of the recess in the longitudinal direction of the main groove satisfy the relationship of D ≦ L and d ≦ D / 2. The pneumatic tire according to any one of claims 1 to 7, wherein a radius of curvature R2 of the hollow portion on the downstream side with respect to the water flow generated in the main groove is smaller than a radius of curvature R1 on the upstream side. .   The pneumatic tire according to any one of claims 1 to 8, wherein the pair of hollow portions are arranged to face both side walls of the main groove.   The pneumatic tire according to any one of claims 1 to 9, wherein the main groove is disposed at a center of a tread portion.

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