JP2012086824A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire capable of enhancing foreign matter biting resistance.SOLUTION: In this pneumatic tire 1, lug grooves 31 and 32 are tilted at a tilting angle γ with respect to a groove depth direction in a cross-sectional view of the lug grooves 31 and 32 in a tire peripheral direction. Here, the tilting angle γ of the lug groove 31 in one land portion 41 and the tilting angle γ of the lug groove 31 (32) in the other land portion 41 (42) have opposite directions to each other, of the land portions 41, 41 (41, 42) adjacent to each other across a peripheral direction main groove 21 (22). A groove wall angle of the peripheral direction main groove 21 (22) changes toward the tire peripheral direction. Right and left groove walls of the peripheral direction main groove 21 (22) held between the land portions 41, 41 (41, 42) include an overlapping portion in a perspective chart in the tire peripheral direction.

Description

  The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire that can improve the resistance to foreign matter biting.

  In a pneumatic tire mounted on a heavy-duty vehicle, there is a problem that stones are caught in the circumferential main groove and cannot be removed, and the durability performance of the tire is lowered by this stone biting. As conventional pneumatic tires relating to such problems, techniques described in Patent Documents 1 to 4 are known.

JP-A-5-338413 JP 2002-337514 A JP 2008-087628 A JP 2004-155382 A

  An object of the present invention is to provide a pneumatic tire capable of improving the resistance to foreign matter biting.

  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, the circumferential main groove, and A pneumatic tire including a land portion partitioned by the lug groove, wherein the lug groove is inclined at an inclination angle γ with respect to the groove depth direction in a cross-sectional view in the tire circumferential direction of the lug groove. In addition, the inclination angle γ of the lug groove in one of the land portions adjacent to the circumferential main groove and the inclination angle γ of the lug groove in the other land portion are mutually The groove wall angle is reversed and the groove wall angle of the circumferential main groove changes as it goes in the tire circumferential direction, and the groove wall facing the circumferential main groove overlaps in the projection view in the tire circumferential direction. It is characterized by having.

  In this pneumatic tire, when the tire is in contact with the ground, adjacent land portions fall in opposite directions with respect to the circumferential direction of the tire, thereby pushing up the foreign matter caught in the groove wall of the circumferential main groove to raise the circumferential main groove. To the outside. Thereby, there exists an advantage which the foreign-material biting performance of a tire improves.

  Further, in the pneumatic tire according to the present invention, in the projection view of the groove wall of the circumferential main groove in the tire circumferential direction, the area Sa of the overlapping portion of the opposed groove wall and the total projected shadow area S are Sa. /S≧0.15.

  In this pneumatic tire, since the area Sa of the overlapping portion is optimized, there is an advantage that the foreign matter biting performance of the tire is further improved.

  In the pneumatic tire according to the present invention, the inclination angle γ of the lug groove is in the range of 5 [deg] ≦ | γ | ≦ 45 [deg].

  In this pneumatic tire, since the range of the inclination angle γ is optimized, the movement of the land portion in the tire circumferential direction becomes good at the time of tire contact. Thereby, there is an advantage that the foreign matter biting performance of the tire is further improved.

  Further, in the pneumatic tire according to the present invention, the inclination angle θ with respect to the tire width direction of the lug groove in one of the land portions and the inclination angle φ with respect to the tire width direction of the lug groove in the other land portion are | θ−φ | <20 [deg].

  In this pneumatic tire, since the relationship between the inclination angles θ and φ of the lug groove with respect to the tire width direction is optimized, the falling direction of adjacent land portions at the time of tire contact is substantially reverse. Thereby, there exists an advantage which the anti-foreign material biting performance of a tire improves effectively.

  In the pneumatic tire according to the present invention, the groove depth h of the lug groove is in a range of h ≧ 6 [mm].

  In this pneumatic tire, the groove depth h of the lug groove is optimized, so that the collapse action of the adjacent land portions at the time of tire contact is properly obtained. Thereby, there exists an advantage which the anti- foreign material biting performance of a tire improves appropriately.

  The pneumatic tire according to the present invention is applied to a heavy duty radial tire.

  In the pneumatic tire according to the present invention, when the tire is in contact with the ground, adjacent land portions fall in opposite directions with respect to the circumferential direction of the tire, thereby pushing up the foreign matter caught in the groove wall of the circumferential main groove. Drain outside the direction main groove. Thereby, there exists an advantage which the foreign-material biting performance of a tire improves.

FIG. 1 is a plan view showing a tread surface of a pneumatic tire according to an embodiment of the present invention. 2 is a cross-sectional view taken along line AA showing the lug groove of the pneumatic tire depicted in FIG. 1. FIG. 3 is a cross-sectional view taken along the line B-B in the tire circumferential direction showing the lug groove of the pneumatic tire depicted in FIG. 1. FIG. 4 is a C-part perspective view illustrating a groove wall of a circumferential main groove of the pneumatic tire illustrated in FIG. 1. FIG. 5 is a projection view showing the groove wall of the circumferential main groove of the pneumatic tire shown in FIG. 1. FIG. 6 is an explanatory view showing the operation of the pneumatic tire shown in FIG. FIG. 7 is an explanatory view showing the operation of the pneumatic tire shown in FIG. FIG. 8 is an explanatory view showing a modification of the lug groove of the pneumatic tire shown in FIG. 1. FIG. 9 is an explanatory view illustrating a modified example of the pneumatic tire depicted in FIG. 1. FIG. 10 is a table showing the results of the performance test of the pneumatic tire according to the embodiment of the present invention.

  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. Further, the constituent elements of this embodiment include those that can be replaced while maintaining the identity of the invention and that are obvious for replacement. In addition, a plurality of modifications described in this embodiment can be arbitrarily combined within a range obvious to those skilled in the art.

[Pneumatic tire]
FIG. 1 is a plan view showing a tread surface of a pneumatic tire according to an embodiment of the present invention.

  The pneumatic tire 1 includes a plurality of circumferential main grooves 21 and 22 extending in the tire circumferential direction, lug grooves 31 and 32 extending in the tire width direction, and the circumferential main grooves 21 and 22 and lugs. Land portions 41 and 42 defined by grooves 31 and 32 are provided in the tread portion (see FIG. 1). For example, in this embodiment, three circumferential main grooves 21 and 22 are formed around the circumferential main groove 21 on the tire equator line CL. Further, a plurality of lug grooves 31 and 32 extending in the tire width direction and opening in the circumferential main grooves 21 and 22 are formed. The circumferential main grooves 21 and 22 and the lug grooves 31 and 32 define four rows of land portions (block rows) 41 and 42. Further, a tread pattern that is symmetrical with respect to the tire equator line CL is formed.

  In this embodiment, the land portion 41 on the inner side in the tire width direction of the tread portion with the circumferential main grooves 22 and 22 located on the outermost side in the tire width direction as a boundary is referred to as a center land portion, and on the outer side in the tire width direction. A certain land portion 42 is called a shoulder land portion. The circumferential main grooves 21 and 22 are circumferential grooves having a groove width of 6 mm or more and a groove depth of 10 mm or more at the deepest position.

[Stone chewing control structure]
2 and 3 are an AA cross-sectional view (FIG. 2) and a BB cross-sectional view (FIG. 3) showing the lug groove of the pneumatic tire shown in FIG. These drawings respectively show the lug grooves in the land portion adjacent to each other with the circumferential main groove interposed therebetween. FIG. 4 is a C-part perspective view illustrating a groove wall of a circumferential main groove of the pneumatic tire illustrated in FIG. 1. The figure shows a state of the groove wall angle per unit period changing in the tire circumferential direction. FIG. 5 is a projection view showing the groove wall of the circumferential main groove of the pneumatic tire shown in FIG. 1.

  The pneumatic tire 1 has the following structure in order to suppress stone biting in the circumferential main grooves 21 and 22 (see FIGS. 1 to 5).

  First, the lug grooves 31 and 32 are inclined at an inclination angle γ with respect to the groove depth direction in a sectional view of the lug grooves 31 and 32 in the tire circumferential direction (see FIGS. 1 to 3). Of the land portions 41, 41 (41, 42) adjacent to each other across the circumferential main groove 21 (22), the inclination angle γ of the lug groove 31 in one land portion 41 and the other land portion 41 (42). ) Of the lug groove 31 (32) in opposite directions (different signs). Further, the groove wall angle of the circumferential main groove 21 (22) changes as it goes in the tire circumferential direction (see FIGS. 1 and 4). Further, the left and right groove walls of the circumferential main groove 21 (22) sandwiched between the land portions 41, 41 (41, 42) have overlapping portions (area Sa) in a projection view in the tire circumferential direction. (See FIG. 5).

  For example, in this embodiment, the pair of left and right center land portions 41 and 41 and shoulder land portions 42 and 42 have a plurality of lug grooves 31 and 32, respectively (see FIGS. 1 to 3). The lug grooves 31 and 32 traverse the land portions 41 and 42 while being inclined at a predetermined inclination angle with respect to the tire circumferential direction. Further, in the left shoulder land portion 42 and the right center land portion 41 in FIG. 1, the lug grooves 32 and 31 are inclined in the tire circumferential direction and in one direction (the lower side in FIG. 1) with respect to the groove depth direction. Yes. On the other hand, in the center land portion 41 on the left side and the shoulder land portion 42 on the right side in FIG. 1, the lug grooves 31 and 32 are inclined in the tire circumferential direction and the other direction (upper side in FIG. 1) with respect to the groove depth direction. . Thereby, the lug grooves 31 and 31 (31 and 32) of the land portions 41 and 41 (41 and 42) adjacent to each other with the circumferential main groove 21 (22) interposed therebetween are inclined in opposite directions (circumferential). The direction of the inclination angle γ is reversed each time the direction main grooves 21 and 22 are straddled).

  Moreover, the groove bottoms of the circumferential main grooves 21 and 22 have a groove width narrower than the groove opening width and extend in a zigzag shape in the tire circumferential direction (see FIGS. 1 and 4). Further, due to the three-dimensional groove wall surface, the groove wall angle of the circumferential main grooves 21 and 22 changes as it goes in the tire circumferential direction. Further, the groove wall of the circumferential main groove 21 (22) on the one land portion 41 side and the groove wall of the circumferential main groove 21 (22) on the other land portion 41 (42) side are the tire circumference. In the projection view in the direction, there is an overlapping portion at the maximum groove depth position of the circumferential main groove 21 (22) (see FIG. 5).

  In this embodiment, the circumferential main grooves 21 and 22 are straight grooves (see FIG. 1). However, the present invention is not limited to this, and the circumferential main grooves 21 and 22 may be zigzag grooves (see FIG. 9).

  The groove width D at the groove bottoms of the circumferential main grooves 21 and 22 is D> 0 [mm]. Thereby, generation | occurrence | production of the crack in a groove bottom is suppressed.

  In addition, the inclination angle γ of the lug groove is a progress angle in the groove depth direction of the lug groove when the tire is mounted on the specified rim and applied with the specified internal pressure and is in an unloaded state. (See FIG. 2 and FIG. 3). First, in a cross-sectional view of the lug groove in the tire circumferential direction, a straight line connecting the midpoint of the groove opening width of the lug groove and the maximum groove depth position (midpoint of the groove bottom width) is drawn. The angle formed by this straight line and the groove depth direction (normal to the tread of the land portion) is defined as an inclination angle γ. This inclination angle γ is similarly defined in the configuration in which the groove wall surface of the lug groove is bent in the groove depth direction (see FIG. 8). In the configuration in which the inclination angle γ of the lug groove changes as it goes in the groove length direction (not shown), the inclination angle γ is calculated as an average value over the entire groove length of the lug groove.

  Further, the groove wall angle of the circumferential main groove refers to an angle formed by the groove wall surface of the circumferential main groove and the groove depth direction in a sectional view in the tire meridian direction. Moreover, the presence or absence of the duplication part of the groove wall of the circumferential direction main groove in the projection figure to a tire circumferential direction is judged based on the projection figure per contact length. Here, the contact length of the tire means that when the tire is mounted on the specified rim and applied with the specified internal pressure, and is placed perpendicular to the flat plate in a stationary state and a load corresponding to the specified load is applied. It means the length in the tire circumferential direction at the contact surface between the tire and the flat plate.

  The specified rim refers to “applied rim” defined in JATMA, “Design Rim” defined in TRA, or “Measuring Rim” defined in ETRTO. The specified internal pressure is the “maximum air pressure” specified by JATMA. However, in the case of tires for passenger cars, the specified internal pressure is an air pressure of 180 kPa, and the specified load is 88% of the maximum load capacity. is there. The maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “INFLATION PRESSURES” defined in ETRTO. The specified load means “maximum load capacity” defined in JATMA, the maximum value of “TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES” defined in TRA, or “LOAD CAPACITY” defined in ETRTO.

  6 and 7 are explanatory views showing the operation of the pneumatic tire shown in FIG. In these figures, the arrows in FIG. 6 indicate the direction in which the land portions 41 and 42 fall when the tire is in contact with the ground. Further, FIG. 7 shows a state in which the foreign matter X (for example, pebbles) caught in the circumferential main groove 21 (22) is discharged.

  In this pneumatic tire 1, when the ground pressure acts on the land portions 41 and 42 during tire rolling, the lug grooves 31 and 31 (31 and 32) of the adjacent land portions 41 and 41 (41 and 42) are in the reverse direction. Therefore, the adjacent land portions 41 and 41 (41 and 42) fall in opposite directions with respect to the tire circumferential direction (see FIG. 6). Then, the groove wall of the circumferential main groove 21 (22) is displaced in the tire circumferential direction and opposite to each other in conjunction with the movement of the adjacent land portions 41, 41 (41, 42). Then, since the circumferential main groove 21 (22) has a groove wall angle that changes as it goes in the tire circumferential direction, the opposing groove wall narrows the groove width from the groove bottom side to the groove opening side. Displace (see FIG. 7). As a result, the foreign matter X bitten by the opposing groove wall is pushed up and discharged to the outside of the circumferential main groove 21 (22).

  In the pneumatic tire 1, in the projection view of the groove wall of the circumferential main groove 21 (22) in the tire circumferential direction, the area Sa of the overlapping portion of the opposed groove wall and the total projected shadow area S are Sa. It is preferable to have a relationship of /S≧0.15, and it is preferable to have a relationship of Sa / S ≧ 0.25 (see FIG. 5). Thereby, the area Sa of the overlapping part is optimized.

  Here, the total projected shadow area S is a straight line connecting the edge portions of the opposing land portions (extension line of the tread surface of the land portions), and a perpendicular to the tread surface of the land portion respectively drawn from the edge portions of the opposing land portions. The area of a region surrounded by a straight line passing through the bottom of the groove and parallel to the tread of the land portion (see FIG. 5). The overlapping portion area Sa and the total projected shadow area S are similarly defined even in the configuration in which the circumferential main grooves 21 and 22 extend while being bent or curved in the tire circumferential direction (see FIG. 9). Further, the upper limit value of Sa / S is Sa / S = 0.25 for a straight groove, and maximum Sa / S = 1.0 for a zigzag groove having a large amplitude.

  In the pneumatic tire 1, the inclination angle γ of the lug grooves 31 and 32 is preferably in the range of 5 [deg] ≦ | γ | ≦ 45 [deg], and further 15 [deg] ≦ | γ. It is preferably within the range of | ≦ 25 [deg] (see FIGS. 2 and 3). Thereby, the inclination | tilt angle (gamma) of the lug grooves 31 and 32 is optimized.

  Moreover, in this pneumatic tire 1, the inclination with respect to the tire width direction of the lug groove 31 in one land part 41 among the land parts 41 and 41 (41, 42) adjacent on both sides of the circumferential main groove 21 (22). It is preferable that the angle θ and the inclination angle φ of the lug groove 31 (32) in the other land portion 41 (42) with respect to the tire width direction have a relationship of | θ−φ | <20 [deg]. It is more preferable that θ−φ | = 0 [deg]. Thereby, the inclination angles θ and φ of the lug grooves 31 and 32 with respect to the tire width direction are optimized.

  In the pneumatic tire 1, the groove depth h of the lug grooves 31 and 32 is preferably in the range of h ≧ 6 [mm], and more preferably in the range of h ≧ 8 [mm] ( 2 and 3). Thereby, the groove depth h of the lug grooves 31 and 32 is optimized. The upper limit of the groove depth h depends on the sub-groove gauge of the tread portion.

  Moreover, in this embodiment, the circumferential main grooves 21 and 22 are straight grooves, and the groove wall angles of these circumferential main grooves 21 and 22 change as they go in the tire circumferential direction (FIG. 1). reference). At this time, it is preferable that the period of the change of the groove wall angle of the circumferential main grooves 21 and 22 is an integral multiple (2 times or more) of the block length of the land portion 41. For example, in the configuration shown in FIG. 1, the two periods of the groove wall angles of the circumferential main grooves 21 and 22 are configured to match the block length of the land portion 41. In such a configuration, the openings of the lug grooves 31, 31 (31, 32) of the land portions 41, 41 (41, 42) sandwiching the circumferential main groove 21 (22), and the groove walls of the circumferential main grooves 21, 22 The angle change nodes can be easily matched. Thereby, the drainage of the lug grooves 31, 31 (31, 32) can be improved. In the configuration in which the block length of the land portion 41 changes in the tire circumferential direction, the period of change in the groove wall angle of the circumferential main grooves 21 and 22 may change in accordance with this change.

[effect]
As described above, in the pneumatic tire 1, the lug grooves 31 and 32 are inclined at an inclination angle γ with respect to the groove depth direction in a sectional view of the lug grooves 31 and 32 in the tire circumferential direction (see FIG. 1). At this time, of the land portions 41, 41 (41, 42) adjacent to each other across the circumferential main groove 21 (22), the inclination angle γ of the lug groove 31 in one land portion 41 and the other land portion 41 ( 42) and the inclination angle γ of the lug groove 31 (32) are opposite to each other (different signs) (see FIGS. 2 and 3). Further, the groove wall angle of the circumferential main groove 21 (22) changes as it goes in the tire circumferential direction (see FIGS. 1 and 4). Further, the left and right groove walls of the circumferential main groove 21 (22) sandwiched between the land portions 41, 41 (41, 42) have overlapping portions in a projection view in the tire circumferential direction (see FIG. 5). ).

  In such a configuration, when the tire is in contact with the ground, the adjacent land portions 41 and 41 (41 and 42) fall in opposite directions with respect to the tire circumferential direction, whereby the groove wall of the circumferential main groove 21 (22) is engaged. The inserted foreign matter X is pushed up and discharged to the outside of the circumferential main groove 21 (22) (see FIGS. 6 and 7). Thereby, there exists an advantage which the foreign-material biting performance of a tire improves.

  Moreover, in this pneumatic tire 1, in the projection figure to the tire circumferential direction of the groove wall of the circumferential direction main groove 21 (22), the area Sa and the total projection shadow area S of the overlapping part of an opposing groove wall are Sa. /S≧0.15 (see FIG. 5). In such a configuration, since the area Sa of the overlapping portion is optimized, there is an advantage that the foreign matter biting performance of the tire is further improved. For example, Sa / S <0.15 is not preferred because the foreign matter biting performance cannot be sufficiently obtained.

  In the pneumatic tire 1, the inclination angle γ of the lug grooves 31 and 32 is in the range of 5 [deg] ≦ | γ | ≦ 45 [deg] (see FIGS. 2 and 3). In such a configuration, since the range of the inclination angle γ is optimized, the movement of the land portions 41 and 42 in the tire circumferential direction becomes good at the time of tire contact. Thereby, there is an advantage that the foreign matter biting performance of the tire is further improved. For example, | γ | <5 [deg] is not preferable because the variation in the land portion in the tire circumferential direction becomes small when the tire is in contact with the ground, and the foreign matter biting performance cannot be sufficiently obtained. Further, when 45 [deg] <| γ |, there is a possibility that the fluctuation of the land portion becomes large and uneven wear (for example, heel and toe wear) may occur.

  In the configuration in which the inclination angle γ of the lug grooves 31 and 32 is reversed in the middle of the lug grooves 31 and 32 in the groove length direction (not shown), the region is 50% or more of the groove length of the lug grooves 31 and 32. Therefore, it is preferable that the lug grooves 31 and 32 of the adjacent land portions 41 and 42 are inclined in the predetermined direction described above. Thereby, since the falling directions of the adjacent land portions 41 and 42 at the time of tire contact are opposite to each other, there is an advantage that the foreign matter biting performance of the tire is appropriately improved.

  Moreover, in this pneumatic tire 1, the inclination with respect to the tire width direction of the lug groove 31 in one land part 41 among the land parts 41 and 41 (41, 42) adjacent on both sides of the circumferential main groove 21 (22). The angle θ and the inclination angle φ of the lug groove 31 (32) in the other land portion 41 (42) with respect to the tire width direction have a relationship of | θ−φ | <20 [deg]. In such a configuration, since the relationship between the inclination angles θ and φ of the lug grooves 31 and 32 with respect to the tire width direction is optimized, the inclining directions of the adjacent land portions 41 and 41 (41 and 42) at the time of tire contact are substantially reversed. Direction. Thereby, there exists an advantage which the anti-foreign material biting performance of a tire improves effectively. For example, when 20 [deg] ≦ | θ−φ |, since the falling direction of the adjacent land portion at the time of tire contact is not reversed, the operation of the groove wall of the circumferential main groove is reduced. Then, since the foreign matter biting performance cannot be sufficiently obtained, it is not preferable.

  In the above configuration, the inclination angles θ and φ of the lug grooves 31 and 32 are preferably in the range of 10 ≦ θ ≦ 40 and 10 ≦ φ ≦ 40, and 15 ≦ θ ≦ 30 and 15 ≦ φ ≦ 30. It is more preferable that it is in the range. In such a configuration, since the lug grooves 31 and 32 have appropriate inclination angles θ and φ with respect to the tire circumferential direction, the circumferential main grooves 21 (22) when the land portions 41 and 42 fall down at the time of tire contact. The groove wall surfaces facing each other are displaced so as to twist the groove shape. As a result, the bitten foreign matter is pushed out to the groove wall surface and easily discharged. Thereby, there exists an advantage which the anti-foreign material biting performance of a tire improves effectively.

  Moreover, in this pneumatic tire 1, the groove depth h of the lug grooves 31 and 32 is in the range of h ≧ 6 [mm] (see FIGS. 2 and 3). In such a configuration, since the groove depth h of the lug grooves 31 and 32 is optimized, the falling action of the adjacent land portions 41 and 42 at the time of tire contact can be appropriately obtained. Thereby, there exists an advantage which the anti- foreign material biting performance of a tire improves appropriately. For example, h <6 [mm] is not preferable because the amount of collapse of the adjacent land portions 41 and 42 when the tire is in contact with the ground is small, and the foreign object biting performance cannot be sufficiently obtained.

[Applicable to]
The pneumatic tire 1 is preferably a heavy duty radial tire. In a heavy duty radial tire, foreign matter tends to be caught in the circumferential main groove. Therefore, by using the heavy duty radial tire as an application object, there is an advantage that the foreign matter biting performance of the tire is more remarkably improved.

[performance test]
In this embodiment, a performance test regarding the resistance to foreign matter biting was performed on a plurality of pneumatic tires having different conditions (see FIG. 10). In this performance test, a pneumatic tire having a tire size of 11 / R22.5 is assembled to an applicable rim defined by JATMA, and a specified internal pressure and a specified load specified by JATMA are applied to the pneumatic tire. Eight pneumatic tires are mounted on the drive shaft of a 2-DD test vehicle. Then, after the test vehicle travels on a predetermined test course, the number of stones caught in the circumferential main groove is measured. Then, based on the measurement result, index evaluation is performed with the conventional example 1 as a reference (100). This index evaluation is preferable as the numerical value increases.

  In Conventional Example 1, the circumferential main groove is a straight groove, and the lug groove is not inclined with respect to the groove depth direction (inclination angle γ = 0). Further, the groove wall angle of the circumferential main groove is constant over the entire circumference in the tire circumferential direction. Therefore, the left and right groove walls of the circumferential main groove do not overlap in the projection view in the tire circumferential direction (Sa / S = 0).

  In Conventional Example 2, the circumferential main groove is a straight groove, and the lug groove is not inclined with respect to the groove depth direction (inclination angle γ = 0). Further, the groove wall angle of the circumferential main groove changes as it goes in the tire circumferential direction. For this reason, the left and right groove walls of the circumferential main groove have overlapping portions in the projection view in the tire circumferential direction (Sa / S = 0.20).

  In the comparative example, the circumferential main groove is a straight groove. Further, the lug grooves of the land portions adjacent to each other with the circumferential main groove interposed therebetween are inclined in directions opposite to each other with respect to the tire circumferential direction (inclination angle | γ | = 20 [deg]). Further, the groove wall angle of the circumferential main groove is constant over the entire circumference in the tire circumferential direction. Therefore, the left and right groove walls of the circumferential main groove do not overlap in the projection view in the tire circumferential direction (Sa / S = 0).

  In Conventional Example 3, the circumferential main groove is a zigzag groove, and the lug groove is not inclined with respect to the groove depth direction (inclination angle γ = 0). Further, the groove wall angle of the circumferential main groove is constant over the entire circumference in the tire circumferential direction. However, since the circumferential main groove is a zigzag groove, the left and right groove walls of the circumferential main groove have overlapping portions in the projection view in the tire circumferential direction (Sa / S = 0.40).

  Example 1-7 is the pneumatic tire 1 described in FIG. 1, and the circumferential main grooves 21 and 22 are straight grooves. In these Examples 1 to 7, the lug grooves 31 and 31 (31 and 32) of the land portions 41 and 41 (41 and 42) adjacent to each other across the circumferential main groove 21 (22) are in the tire circumferential direction. In contrast, they are inclined in opposite directions and at an inclination angle γ (see FIGS. 2 and 3). Further, the groove wall angle of the circumferential main groove 21 (22) changes as it goes in the tire circumferential direction (see FIGS. 1 and 4). In addition, the left and right groove walls of the circumferential main groove 21 (22) sandwiched between the land portions 41, 41 (41, 42) have overlapping portions (area Sa) in the projection view in the tire circumferential direction. (See FIG. 5).

  Moreover, Example 8 is the pneumatic tire 1 described in FIG. 10, and the circumferential main grooves 21 and 22 are zigzag grooves. In Example 8, the configurations of the circumferential main grooves 21 and 22 and the lug grooves 31 and 32 are the same as those of the pneumatic tire 1 of Examples 1 to 7.

  As shown in the test results, when Example 1 is compared with Conventional Examples 1 to 3, it can be seen that in the pneumatic tire 1 of Example 1, the foreign matter biting performance of the tire is improved. Moreover, when Example 1 is compared with the prior art example 2 and the comparative example, the lug grooves 31, 31 (31, 32) in the land portions 41, 41 (41, 42) adjacent to each other across the circumferential main groove 21 (22) are compared. ) In the tire circumferential direction is reversed, and at the same time, the groove wall angle of the circumferential main grooves 21 and 22 is changed.

  In addition, when Examples 1 and 2 are compared, it can be seen that the foreign matter biting performance of the tire is further improved by optimizing the area Sa of the overlapping portion. Moreover, when Examples 1, 3, and 4 are compared, it can be seen that the resistance to biting of the tire by foreign matter is further improved by optimizing the range of the inclination angle γ. Further, when Examples 1, 5, and 6 are compared, the relationship between the inclination angles θ and φ of the lug grooves 31 and 32 with respect to the tire width direction is optimized, so that the foreign object biting performance of the tire is effectively improved. I understand that In addition, when Examples 1 and 7 are compared, it can be seen that the foreign matter biting performance of the tire is effectively improved by optimizing the groove depth h of the lug grooves 31 and 32.

  Moreover, when Example 8 and Conventional Example 3 are compared, even when the circumferential main groove 21 (22) is a zigzag groove (see FIG. 9), the land adjacent to the circumferential main groove 21 (22) is sandwiched. The inclination angle γ of the lug grooves 31, 31 (31, 32) in the portions 41, 41 (41, 42) with respect to the tire circumferential direction is set in the opposite direction, and the groove wall angle of the circumferential main groove 21 (22) is changed. As a result, it can be seen that the foreign matter resistance performance of the tire is dramatically improved.

  As described above, the pneumatic tire according to the present invention is useful in that it can improve the foreign matter biting performance of the tire.

1 Pneumatic tires 21, 22 Circumferential main grooves 31, 32 Lug grooves 41 Center land portion 42 Shoulder land portion X Foreign matter

Claims (6)

A pneumatic tire comprising 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 land portion defined by the circumferential main grooves and the lug grooves. Because
In the cross-sectional view of the tire circumferential direction of the lug groove, the lug groove is inclined at an inclination angle γ with respect to the groove depth direction, and one of the land portions adjacent to each other across the circumferential main groove An inclination angle γ of the lug groove in the land portion and an inclination angle γ of the lug groove in the other land portion are opposite to each other, and
The groove wall angle of the circumferential main groove changes as it goes in the tire circumferential direction, and the opposed groove walls of the circumferential main groove have overlapping portions in a projection view in the tire circumferential direction. Pneumatic tires.   2. In the projection view of the groove wall of the circumferential main groove in the tire circumferential direction, the area Sa and the total projected shadow area S of the overlapping portions of the opposed groove walls are Sa / S ≧ 0.15. Pneumatic tire described in 2.   3. The pneumatic tire according to claim 1, wherein an inclination angle γ of the lug groove is in a range of 5 [deg] ≦ | γ | ≦ 45 [deg].   The inclination angle θ of one of the land portions with respect to the tire width direction of the lug groove and the inclination angle φ of the lug groove with respect to the tire width direction of the other land portion have a relationship of | θ−φ | <20 [deg]. The pneumatic tire according to any one of claims 1 to 3.   The pneumatic tire according to claim 1, wherein a groove depth h of the lug groove is in a range of h ≧ 6 [mm].   The pneumatic tire according to claim 1, which is applied to a heavy duty radial tire.

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