DE102018216403B4 - Pneumatic tire - Google Patents

Abstract

A pneumatic tire (1) having a main groove (10) extending in a tire circumferential direction and a rib (24, 26) extending in the tire circumferential direction, characterized in that the main groove (10) has a a main groove (10) which extends in a zigzag manner and which is provided with slanting surfaces (16) expanding a width of an opening end to a contact surface on both sides of the main groove (10) in a zigzag manner in a width direction, that an angle of the opening end to the contact surface with respect to the tire circumferential direction is smaller than an angle of a groove bottom with respect to the tire circumferential direction at least in a part of the main groove (10) extending in a zigzag manner that fine grooves (28) are provided extending from the main groove (10) towards a contact end (22), that the fine grooves (28) open to the main groove (10) at one end and that they at another Close the end in the rib (24) that the fine grooves (28) are straight, and that the fine grooves (28) have a slanted surface (29) widening toward the contact surface at an opening end.

Description

technical field

The invention relates to a pneumatic tire.

State of the art

For example, as described in Patent Literature 1 and Patent Literature 2, a pneumatic tire has a main groove extending in a circumferential direction of the tire and ribs on both sides of the main groove. Such a pneumatic tire has high longitudinal rigidity (rigidity in the tire circumferential direction) because the ribs extend in the tire circumferential direction without being divided.

Patent Literature 3 also discloses a pneumatic tire having a main groove extending in the circumferential direction of the tire and land portions on both sides of the main groove, in which a chamfered surface is provided at the land portion at an end adjacent to the main groove.

• Patent Literature 1: JP 5 781 566 B2
• Patent Literature 2: WO 2014/037 165 A1
• Patent Literature 3: U.S. 9,079,459 B2

The DE 10 2008 037 498 A1 discloses a pneumatic tire which has a profiled tread strip with at least one circumferential groove running in the circumferential direction of the tire, the groove flanks of which delimit rows of blocks or profile ribs with block-like profile elements extending over the circumference of the tire, and the circumferential groove having circumferential sections which run at an acute angle to the circumferential direction , wherein inclined surfaces are formed on the tread surface along the circumferential sections of the circumferential groove by chamfering on the profile elements delimiting the circumferential groove on both sides, which extend to a maximum depth of 30% of the profile depth, the delimiting edges of which run at least essentially in the circumferential direction on the profile surface and the boundary edges of which run at least substantially parallel to the extent of the peripheral sections to the flanks of the groove.

Summary of the Invention

Incidentally, a pneumatic tire is required to have not only longitudinal rigidity but also lateral rigidity (rigidity in the tire width direction) and drainage performance. In general, water drainage performance is improved by increasing the number of grooves or by making the grooves wider. However, the longitudinal stiffness and the lateral stiffness deteriorate as a result. It is therefore difficult in the prior art to ensure the longitudinal rigidity, the lateral rigidity and the drainage performances in a balanced manner.

An object of the present invention is to provide a pneumatic tire which ensures the longitudinal rigidity, the lateral rigidity and the drainage performance in a balanced manner.

A pneumatic tire of an embodiment has a main groove extending in a tire circumferential direction and a rib extending in the tire circumferential direction, and is characterized in that the main groove is a main groove extending in a zigzag shape manner and which is provided with slanting surfaces that widen a width of an opening end to a contact surface on both sides of the main groove, which extends in a width direction in a zigzag manner, and that an angle of the opening end to the contact surface with respect to the circumferential direction of the tire is smaller than an angle of a groove bottom with respect to the circumferential direction of the tire at least in a part of the main groove extending in a zigzag manner. Fine grooves are provided extending from the main groove toward a contact end, the fine grooves opening into the main groove at one end and closing into the rib at another end, the fine grooves being straight, and the fine grooves having a tapered surface that widens toward the contact surface at an opening end.

Due to the characteristics described above, the pneumatic tire of the embodiment ensures the longitudinal rigidity, the lateral rigidity, and the drainage performance in a well-balanced manner.

character list

• The 1 14 is a cross-sectional view of a pneumatic tire 1 according to an embodiment in a width direction.
• The 2 Fig. 14 is a tread pattern of the embodiment.
• The 3 Fig. 14 is a view of a center main groove 10 when viewed from the outside in a radial direction of the tire (at omission sen of the third fine grooves 28 for ease of illustration).
• The 4 12 is a view of the center main groove 10 when viewed in a direction tangential to a tire equator E (omitting the third fine grooves 28 for ease of illustration).
• The 5 FIG. 14 is a cross-sectional view of the center main groove 10 taken along a line AA of FIG 3 .
• The 6 12 is a view of the first fine grooves 30 and the second fine grooves 40 when viewed from the outside in the radial direction of the tire.
• The 7A FIG. 14 is a cross-sectional view of a slit portion 32 of the first fine groove 30 taken along line BB of FIG 6 ; and the 7B FIG. 14 is a cross-sectional view of a fin portion 33 of the first fine groove 30 taken along line CC of FIG 6 .
• The 8A FIG. 14 is a cross-sectional view of a slit portion 42 of the second fine groove 40 taken along a line DD of FIG 6 ; and the 8B FIG. 14 is a cross-sectional view of a fin portion 43 of the second fine groove 40 taken along a line EE of FIG 6 .
• The 9 Fig. 14 is a view of a shoulder rib 26 when viewed from the outside in the radial direction of the tire.
• The 10 FIG. 14 is a cross-sectional view of a fourth fine groove 50 taken along a line FF of FIG 9 .
• The 11 Fig. 12 is a view of a three-dimensional lamina 55 wherein the 11A the fourth fine groove 50, when viewed from a tire surface, shows the 11B shows a wall surface of the fourth fine groove 50 and the 1 1C shows a cross section of the fourth fine groove 50 parallel to a contact surface along a line GG of FIG 11B shows.

Mode for carrying out the invention

An embodiment is described with reference to the drawings. It goes without saying that the following exemplary embodiment only represents an example and in no way limits the scope of the invention.

In the following description, the term "widths of a groove and a slanted surface provided on the groove" means a length in a direction perpendicular to an extending direction of a center line of a groove bottom of the groove in a plane parallel to a tire contact surface. A term “load condition” means a condition in which a pneumatic tire attached to a normal rim is inflated with a normal internal pressure under a normal load. The term "a normal rim" means a standard rim defined according to the JATMA, TRA, or ETRTO standards. The term "a normal load" means a maximum load defined according to the above standards. The expression "a normal internal pressure" means an internal pressure corresponding to the maximum load.

1. Cross-sectional structure of the pneumatic tire 1

Like in the 1 As shown as an example, bead portions 2 are provided on both sides of a pneumatic tire 1 in a tire width direction. The bead portion 2 has a bead core 2a formed of a circularly wound steel wire and a bead filler 2b made of a rubber and provided on an outside of the bead core 2a in a radial direction. A carcass ply 5 is bridged between the bead portions 2 on both sides in the tire width direction. The carcass ply 5 is a sheet-like member formed by covering a large number of ply cords aligned in a direction orthogonal to the circumferential direction of the tire with a rubber. The carcass ply 5 not only forms a frame shape of the pneumatic tire 1 between the bead portions 2 on both sides in the tire width direction, but also wraps the bead portions 2 by being folded outward around the bead portions 2 in the tire width direction. A sheet-like inner liner 6 made of a rubber having a low air permeability is laminated on an inner side of the carcass ply 5 . One or more belts 7 are provided on an outside of the carcass ply 5 in a radial direction of the tire. The belt 7 is a member formed by covering a large number of steel-made cords with a rubber. A tread rubber 3 having a contact area with a road surface (hereinafter referred to as a contact area) is provided on an outer side of the belt 7 in the radial direction of the tire. In addition, sidewall rubbers 4 are provided on both sides of the carcass ply 5 in the tire width direction. Besides the above elements, elements such as an underbelt pad and a chafer are provided if a functional need of the pneumatic tire 1 arises.

2. Summary of tread pattern

A tread pattern found in the 2 shown as an example is provided on a surface of the tread rubber 3 . The tread pattern has a center main groove 10 at a center in the tire width direction and shoulder main grooves 20 on both sides in the tire width direction, all provided as main grooves formed of wide grooves extending in the tire circumferential direction . The tread pattern also includes center ribs 24 located between the center main groove 10 and the shoulder main grooves 20 and shoulder ribs 26 located between the shoulder main grooves 20 and the contact ends 22 . Here, the ribs are land portions that continue in the tire circumferential direction, and the land portions are portions that are divided by the grooves and have the contact surface. In addition, the contact ends 22 are ends of the contact patch in the tire width direction in a loaded state.

First fine grooves 30 are provided on a shoulder main groove 20 side closer to a tire equator E, and second fine grooves 40 are provided on a shoulder main groove 20 side closer to the contact end 22 . Third fine grooves 28 are provided on both sides of the central main groove 10 in a width direction. Fourth fine grooves 50 are provided on the shoulder rib 26 . The respective fine grooves 20, 30, 40 and 50 are aligned in the tire circumferential direction at regular or substantially regular intervals. The structures of these fine grooves 20, 30, 40 and 50 will be described below.

3. Structure of the main grooves

As in the 2 until 4 As shown, the center main groove 10 extends in the circumferential direction of the tire in a zigzag manner. That is, the center main groove 10 is zigzag-shaped when viewed from the outside in the radial direction of the tire. More specifically, the center main groove 10 has long groove portions 11 extending at an angle with respect to the tire circumferential direction and short groove portions 12 extending at an angle with respect to the tire circumferential direction in a direction extending from the extending direction of the long groove portion 11 differs. The central main groove 10 is formed by arranging the long groove portions 11 and the short groove portions 12 alternately.

Since the center main groove 10 is zigzag-shaped as described above, protrusions 14 projecting into the center main groove 10 and depressions 15 opposing the protrusions 14 with the center main groove 10 therebetween are at the boundaries of the long groove portions 11 and the short groove portions 12 forming the central main groove 10 are formed.

In the present embodiment, as in the 4 As shown, a protrusion 14a on the right side of a center line of the center main groove 10 and a protrusion 14b on the left side have no overlap in the tire circumferential direction; and a distance L in the tire width direction remains between the protrusion 14a on the right side and the protrusion 14b on the left side. The presence or absence of the distance L is determined at a groove bottom 13 .

However, a top of the protrusion 14a on the right protruding into the center main groove 10 and a top of the protrusion 14b on the left protruding into the center main groove 10 may be located at a same position in the tire width direction and these tops may be aligned with a single circle in the circumferential direction of the tire. Alternatively, the protrusion 14a on the right and the protrusion 14b on the left may have an overlap in the circumferential direction of the tire (in other words, the protrusion 14a on the right and the protrusion 14b on the left may overlap in the circumferential direction of the tire tires overlap when viewed in the circumferential direction of the tire).

As in the 3 until 5 1, slanted surfaces 16 are provided on both sides of the center main groove 10 in the width direction. The chamfered surface 16 is a surface that continues from the contact surface to an inner depth side of the center main groove 10 . Like in the 4 As shown, the chamfered surface 16 is a surface having a shape that chamfers a corner of the center rib that is adjacent to the center main groove 10 . The chamfered surface 16 widens a width of the central main groove 10 at an opening end to the contact area. The beveled surface 16 can reach the contact surface. Like in the 5 As shown, however, a wall portion 17 with a small height (e.g. about 0.5 mm) can be provided between the beveled surface 16 and the contact surface. In a portion provided with the slanted surface 16, a width of the center main groove 10 gradually widens toward the contact surface. An angle of the beveled surface 16 with respect to the contact surface is in a range of, for example, 40° to 50° inclusive.

Like it in the 3 1, on both sides of the center main groove 10 in the width direction, a width of the tapered surface 16 gradually widens from a position of the recess 15 to a position of the projection 14 in the center main groove. Consequently, an angle θ1 of the opening end of the center main groove 10 to the contact surface with respect to the tire circumferential direction becomes smaller than an angle θ2 of the groove bottom 13 of the center main groove 10 with respect to the tire width direction.

The beveled surface 16 becomes deeper toward the groove bottom 13 as the width becomes wider. Therefore, the depth of the tapered surface 16 gradually increases from a position of the recess 15 to a position of the projection 14 in the central main groove 10 .

A depth of the slanted surface 16 at a deepest position is, for example, half the depth to the groove bottom 13 of the central main groove 10.

In the present embodiment, the slanted surfaces 16 are provided for both the long grooves 11 and the short grooves 12 as above.

Meanwhile, the shoulder main grooves 20 are not zigzag and extend straight in the tire circumferential direction.

4. Structures of fine grooves

Like in the 2 As shown, the first fine groove 30 extends from the straight shoulder main grooves 20 in a direction toward the tire equator E. The first fine groove 30 opens to the shoulder main groove 20 at one end and closes in the middle rib 24 at the other end

The first fine groove 30 bends in the radial direction of the tire when viewed from the outside. A bending section 31 creates an obtuse angle. Like in the 6 As shown, a portion of the first fine groove 30 closer to the shoulder main groove 20 than the bend portion 31 is a relatively wide slit portion 32. Meanwhile, a portion of the first fine groove 30 closer to a tip end than a bend portion 31 is , a narrow blade portion 33. In a loaded condition, the slot portion 32 does not close, whereas the blade portion 33 closes. A width of the slit portion 32 is in a range of, for example, 1.9 mm to 2.1 mm inclusive. A width of the fin portion 33 is in a range of, for example, 0.7 mm to 0.9 mm inclusive.

As in the 6 and 7 As shown, the fin portion 33 has a tapered surface 34 at a position on an inner side of the bend of the first fine groove 30 (on a side where the obtuse angle is formed). The slanted surface 34 widens a width of the fin portion 33 at an opening end to the contact surface. The slanted surface 34 is a surface that extends from the contact surface to an inner depth side of the fin portion 33 near the contact surface. The beveled surface 34 can reach the contact surface. Like in the 7B As shown, however, a wall portion 35 with a small height (e.g. about 0.5 mm) can be provided between the beveled surface 34 and the contact surface. The slanted surface 34 does not reach the bottom of the fin portion 33. By providing the slanted surface 34, a width of the fin portion 33 is gradually expanded toward the contact surface. An angle of the beveled surface 34 with respect to the contact surface is in a range of, for example, 40 degrees to 50 degrees inclusive. A width of the tapered surface 34 gradually widens from the tip end of the first fine groove 30 toward the bending portion 31 and reaches a maximum at the bending portion 31. As in FIG 7A 1, such a tapered surface is not provided in the slit portion 32. FIG. Therefore, the slanted surface 34 is provided only for the fin portion 33 in the first fine groove 30 .

Like in the 2 As shown, the second fine groove 40 extends in a direction toward the contact end 22 from the straight shoulder main groove 20. The second fine groove 40 opens into the shoulder main groove 20 at one end and closes in the shoulder rib 26 at the other end.

The second fine groove 40 bends in the radial direction of the tire when viewed from the outside. A bending section 41 creates an obtuse angle. Like in the 6 As shown, a portion of the second fine groove 40 that is closer to the shoulder main groove 20 than the bending portion 41 is a relatively wide slit portion 42. Meanwhile, a portion of the second fine groove 40 that is closer to a tip end than the bending portion 41 is , a narrow blade portion 43. In a load condition, the slit portion 42 does not close, whereas the blade portion 43 closes. A width of the slit portion 42 is in a range of, for example, 1.9 mm to 2.1 mm inclusive. A width of the fin portion 43 is in a range of, for example, 0.7 mm to 0.9 mm inclusive.

As in the 6 and 8th As shown, the fin portion 43 has a tapered surface 44 at a location on an inner side of the bend of the second fine groove 40 (on a side where the obtuse angle is generated). The slanted surface 44 widens a width of the fin portion 43 at an opening end to the contact surface. The tapered surface 44 is a surface extending from the contact surface to an inner depth side of the fin portion 43 near the contact surface. The beveled surface 44 can reach the contact surface. However, as in the 8B As shown, a wall portion 45 with a small height (e.g. about 0.5 mm) can be provided between the beveled surface 44 and the contact surface. The slanted surface 44 does not reach a bottom of the fin portion 43. By providing the slanted surface 44, a width of the fin portion 43 is gradually expanded toward the contact surface. An angle of the beveled surface 44 with respect to the contact surface is in a range of, for example, 40 degrees to 50 degrees inclusive. A width of the slanting surface 44 gradually widens from the tip end of the second fine groove 40 toward the bending portion 41 and reaches a maximum at the bending portion 41. Such a slanting surface is not provided at the slit portion 42. FIG. Therefore, the slanted surface 44 is provided only for the fin portion 43 in the second fine groove 40 .

Like in the 6 As shown, the slit portion 32 of the first fine groove 30 and the slit portion 42 of the second fine groove 40 extend in the same direction at an angle with respect to the tire circumferential direction. Further, the slit portion 32 of the first fine groove 30 and the slit portion 42 of the second fine groove 40 are on the same straight line.

In addition, the first fine groove 30 and the second fine groove 40 bend toward a same direction with respect to the tire circumferential direction. That is, the sipe portions 33 and 43 respectively extend from the bending portions 31 and 41 of the fine grooves 30 and 40 toward a same direction with respect to the tire circumferential direction. The sipe portion 43 of the second fine groove 40 is directed more toward the circumferential direction of the tire than the sipe portion 33 of the first fine groove 30 . That is, the sipe portion 43 of the second fine groove 40 is inclined at a smaller angle than the sipe portion 33 of the first fine groove 30 with respect to the tire circumferential direction. The fin portion 43 is a kind of smaller groove. The minor groove is a groove narrower than a main groove and extends either continuously on a full circumference in the tire circumferential direction or intermittently in the tire circumferential direction as the sipe portions 43.

Like in the 2 1, both the first fine grooves 30 and the second fine grooves 40 are provided on both sides in the tire width direction. However, it should be noted that the first fine grooves 30 and the second fine grooves 40 on one side and the other side in the tire width direction are oppositely arranged in the tire circumferential direction. Also, both the first fine grooves 30 and the second fine grooves 40 on one side and the other side in the tire width direction are offset in the tire circumferential direction. That is, the positions of the first fine grooves 30 on one side in the tire width direction and the positions of the first fine grooves 30 on the other side in the tire width direction do not match in the tire width direction. Also, the positions of the second fine grooves 40 on one side in the tire width direction and the positions of the second fine grooves 40 on the other side in the tire width direction do not perfectly match in the tire width direction.

The third fine groove 28 extends in a direction toward the contact end 22 from the zigzag-shaped middle main groove 10. The third fine groove 28 opens to the middle main groove 10 at one end and closes in the middle rib 24 at the other end. The third fine groove 28 does not bend and extends straight.

The third fine groove 28 has a width corresponding to the width of the slit portions 32 and 42 more or less. Like in the 2 As shown, the third fine groove 28 has a tapered surface 29 widening at an opening end to the contact surface. The slanted surface 29 is a surface extending from the contact surface to an inner depth side of the third fine recess 28 in the vicinity of the contact surface. The beveled surface 29 can reach the contact surface. However, like the first fine groove 30, a wall portion with a small height (for example, about 0.5 mm) may be provided between the slanted surface 29 and the contact surface. The slanted surface 29 does not reach a bottom of the third fine groove 28. By being provided with the slanted surface 29, a width of the third fine groove 28 is gradually expanded toward the contact surface. An angle of the beveled surface 29 with respect to the contact surface is in a range of, for example 40 degrees up to and including 50 degrees. A width of the slanted surface 29 gradually narrows in a direction toward the contact end 22 from the central main groove 10 .

As in the 2 and 9 As shown, the fourth fine groove 50 extends in the tire width direction in the shoulder rib 26. The fourth fine groove 50 closes in the shoulder rib 26 at one end and opens from the contact end 22 to an outside in the tire width direction at the other end.

When viewed from the outside in the radial direction of the tire, the fourth fine groove 50 bends at a location at one end closer to the tire equator E. A specific position of the bending portion 51 is, for example, a position separated from the one end of the fourth fine groove 50 is offset toward the contact end 22 in the tire width direction by a length equal to or shorter than a quarter of the length of the fourth fine groove 50 in the tire width direction (a length from the one end to the contact end 22 in the tire width direction). The bending portion 51 creates an obtuse angle in a range of, for example, 140 degrees to 160 degrees inclusive.

Like in the 10 1, the fourth fine groove 50 is provided as a sipe that closes in a load condition. A width of the fourth fine groove 50 is in a range of, for example, 0.7 mm to 0.9 mm inclusive. A depth of the fourth fine groove 50 gradually decreases from the bending portion 51 toward one end.

As in the 9 and 10 As shown, a chamfered surface 54 is provided on the fourth fine groove 50 at a location on an inner side of the bend. The slanted surface 54 widens a width of the fourth fine groove 50 at an opening end to the contact surface. The slanted surface 54 is a surface extending from the contact surface to an inner depth side of the fourth fine groove 50 in the vicinity of the contact surface. The beveled surface 54 can reach the contact surface. Like in the 10 As shown, however, a wall portion 56 having a small height (e.g., about 0.5 mm) may be provided between the beveled surface 54 and the contact surface. The slanted surface 54 does not reach a bottom of the fourth fine groove 50. By providing the slanted surface 54, a width of the fourth fine groove 50 is gradually expanded toward the contact area. An angle of the beveled surface 54 with respect to the contact surface is in a range of, for example, 35 degrees to 45 degrees inclusive. A width of the slanting surface 54 gradually widens from the contact end 22 toward the bending portion 51 and reaches a maximum at the bending portion 51. The slanting surface 54 is also continuous from the bending portion 51 at a location of the fourth fine groove 50 closer to the Tire equator E as the bending portion 51 is provided.

A portion of the fourth fine groove 50 closer to the contact end 22 than the bending portion 51 forms a three-dimensional lamina 55 as shown in FIG 11 is shown as an example. The three-dimensional louver 55 is a louver whose shape changes in a depth direction. Like in the 11C As shown, the three-dimensional fin 55 of the embodiment has a wavy shape formed of ridges 57 and troughs 58 in a cross section parallel to the contact surface at a position lower than the contact surface. Like in the 11B As shown, the ridges 57 and the troughs 58 extend in a zigzag manner in the depth direction of the three-dimensional sipe 55.

Like in the 2 1, the fourth fine grooves 50 are provided on both sides in the tire width direction. The fourth fine grooves 50 on both sides in the tire width direction are oppositely arranged in the tire circumferential direction. However, it should be noted that the fourth fine grooves 50 may be provided only on one side in the tire width direction, in which case it is desirable to provide the fourth fine grooves 50 on an outside (AUS, vehicle outside) when the pneumatic Tire 1 is attached to a vehicle.

Like in the 9 As shown, in addition to the fourth fine grooves 50, the second fine grooves 40 described above are located in the shoulder rib 26. The fourth fine groove 50 and the sipe portion 43 of the second fine groove 40 have an overlap in the tire width direction. The one end of the fourth fine groove 50 is in close proximity to the fin portion 43 of the second fine groove 40 and closes short of the fin portion 43 and therefore does not communicate with the fin portion 43.

5. Advantage of the embodiment

In the pneumatic tire 1 of the embodiment, since the center ribs 24 and the shoulder ribs 26 extend in the tire circumferential direction, the longitudinal rigidity (rigidity in the tire circumferential direction) is high, and the lateral rigidity (rigidity in the tire width direction) is high. is also high because the central main groove 10 changes to a zigzag moderate way. In addition, the chamfered surfaces 16, which widen a width of the opening end to the contact surface, are provided on both sides of the zigzag-shaped central main groove 10 in the width direction. Therefore, drainage performance is improved since an inner volume of the central main groove 10 is increased. In addition, since the corners of the center ribs 24 on both sides of the center main groove 10 in the width direction are chamfered, the rigidity of the center ribs 24 is increased.

Further, by providing the slanted surfaces 16, an angle θ1 of the opening end of the center main groove 10 to the contact surface with respect to the circumferential direction of the tire 1 is made smaller than an angle θ2 of the groove bottom 13 with respect to the tire circumferential direction. Accordingly, the water can flow more easily in the circumferential direction of the tire in the vicinity of the opening end of the center main groove 10 . The water drainage performance is thus improved. Due to the effect described above, the pneumatic tire 1 of the embodiment ensures the longitudinal rigidity, the lateral rigidity, and the drainage performance in a well-balanced manner.

As has been described, the protrusions 14 protruding into the central main groove 10 are formed, and the protrusions 14 may possibly block the water flowing through the central main groove 10. FIG. However, in the pneumatic tire 1 of the embodiment, a width of the slanted surface 16 gradually widens to a place where the protrusion 14 is formed. Therefore, a large amount of water can flow in the space between the projections 14 and the road surface. The performance of the water drainage is thus guaranteed.

The effect is exerted by providing the slanting surfaces 16 having the characteristics described above for at least a part of the zigzag central main groove 10 . However, it should be noted that the effect is significant when the slanted surfaces 16 having the above characteristics are provided at least on the long groove portions 11 in the central main groove 10, which are obtained by repeatedly arranging the long groove portions 11 and the short groove sections 12 is formed. It goes without saying that when the slanting surfaces 16 having the above characteristics are provided on both the long groove portions 11 and the short groove portions 12, the effect is excellent.

When a clearance is left in the tire width direction between the protrusion 14a on the right side and the protrusion 14b on the left side in the center main groove 10, the water can easily flow through the center main groove 10 in the circumferential direction. The water drainage performance is thus improved.

The rigidity at the center in the tire width direction has a significant influence on the running stability of the pneumatic tire 1 . The pneumatic tire 1 of the embodiment has satisfactory running stability because the rigidity is secured at the center in the tire width direction owing to the central main groove 10 which is formed in a zigzag shape and which is provided with the slanted surfaces 16 . Also, the pneumatic tire 1 of the embodiment has a particularly satisfactory drainage performance since the shoulder main grooves 20 straightly extend in the circumferential direction of the tire.

Further, the first and second fine grooves 30 and 40 ensure the rigidity of the center ribs 24 and the shoulder ribs 26, respectively, by bending. Thus, by combining the central main groove 10 and the first and second fine grooves 30 and 40, rigidity is secured for the entire tire. Meanwhile, the fourth fine grooves 50 ensure the rigidity of the shoulder ribs 26 by bending and also ensure the drainage performance by opening outward in the tire width direction. Therefore, by combining the central main groove 10 and the fourth fine grooves 50, rigidity and water drainage performance are secured for the entire tire.

6. Amendments

It is understood that various omissions, substitutions and modifications to the above embodiment may be made within the scope of the invention.

A main groove which extends in the circumferential direction of the tire in a zigzag manner and which is provided with the slanting surfaces having the same properties as the slanting surfaces 16 described above is not necessarily the center main groove 10. The longitudinal rigidity that lateral rigidity and water drainage performance can be ensured in a well-balanced manner as long as any of the main grooves, which extends in the circumferential direction of the tire, extends in a zigzag manner and is provided with the slanted surfaces having the same properties as the slanted surfaces described above.

Reference List

E

tire equator,

1

pneumatic tire

2

bead section

2a

bead core

2 B

bead filler

3

tread rubber

4

sidewall rubber

5

carcass ply

6

inner lining

7

Belt

10

middle main groove

11

long groove section

12

short groove section

13

groove bottom

14

head Start

14a

ledge on the right

14b

ledge on the left

15

recess

16

beveled surface

17

wall section

20

shoulder major groove

22

end of contact

24

middle rib

26

shoulder rib

28

third fine groove

29

beveled surface

30

first fine groove

31

bending section

32

slot section

33

slat section

34

beveled surface

35

wall section

40

second fine groove

41

bending section

42

slot section

43

slat section

44

beveled surface

45

wall section

50

fourth fine groove

51

bending section

54

beveled surface

55

three-dimensional lamella

56

wall section

57

Comb

58

trough

Claims (6)

A pneumatic tire (1) having a main groove (10) extending in a tire circumferential direction and a rib (24, 26) extending in the tire circumferential direction, characterized in that the main groove (10) a main groove (10) extending in a zigzag manner and provided with slanting surfaces (16) expanding a width of an opening end to a contact surface on both sides of the main groove (10) in a zigzag manner in a width direction that an angle of the opening end to the contact surface with respect to the circumferential direction of the tire is smaller than an angle of a groove bottom with respect to the circumferential direction of the tire at least in a part of the main groove (10) extending in a zigzag manner that fine grooves (28) are provided extending from the main groove (10) towards a contact end (22), that the fine grooves (28) open at one end to the main groove (10) and that they at one close the other end in the rib (24) that the fine grooves (28) are straight, and that the fine grooves (28) have a slanted surface (29) widening toward the contact surface at an opening end. Pneumatic tire (1) after claim 1 wherein a protrusion (14) in the main groove (10) and a recess (15) facing the protrusion (14) are formed on both sides of the main groove (10) extending in a zigzag manner in the width direction due to a extends in a zigzag shape, and a width of the slanting surfaces (16) gradually widens from a place where the recess (15) is formed to a place where the projection (14) is formed in the part of the main groove (10) is formed extending in a zigzag manner. Pneumatic tire (1) after claim 1 or 2 wherein the main groove (10) extending in a zigzag manner is formed by repeatedly arranging a long groove portion (11) and a short groove portion (12) each extending in a different direction with respect to the tire circumferential direction and the part of the main groove (10) which extends in a zigzag manner is the long groove portion (11). Pneumatic tire (1) according to any of Claims 1 until 3 wherein a protrusion (14) in the main groove (10) and a recess (15) facing the protrusion (14) are formed on both sides of the main groove (10) which change to a zigzag shape in the width direction due to a zigzag shape manner, and a protrusion (14a) on the right side and a protrusion (14b) on the left side with respect to a center line of the main groove (10) extending in a zigzag manner have no overlap in the tire circumferential direction and having a distance in a tire width direction on the left between the protrusion (14a) on the right side and the protrusion (14b) on the left side. Pneumatic tire (1) according to any of Claims 1 until 4 wherein a center main groove (10) extending in the tire circumferential direction at a center in a tire width direction, and shoulder main grooves (20) extending in the tire circumferential direction on both sides in the tire width direction and the center main groove (10) is the main groove (10) extending in a zigzag manner and the shoulder main grooves (20) extend straight in the tire circumferential direction. Pneumatic tire (1) according to any of Claims 1 until 5 wherein the main groove (10) extending in a zigzag manner is formed by repeatedly arranging a long groove portion (11) and a short groove portion (12) each extending in a different direction with respect to the tire circumferential direction and the angle of the opening end to the contact surface with respect to the tire circumferential direction is smaller than the angle of the groove bottom with respect to the tire circumferential direction in both the long groove portion (11) and the short groove portion (12).

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