JP4710556B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire. In particular, the present invention relates to a pneumatic tire in which circumferential grooves are formed.

  A pneumatic tire that is mounted on a vehicle and contacts the road surface while rolling while the vehicle is running may cause uneven wear on the tread surface depending on the running state of the vehicle. For this reason, in the conventional pneumatic tire, various methods are used in order to suppress this uneven wear. For example, in Patent Document 1, the groove wall of the circumferential groove extending in the tire circumferential direction is formed in a straight shape with the groove opening in the tire circumferential direction, and the groove wall is directed in the tire width direction while facing the tire circumferential direction. Reciprocating wave type. Furthermore, the circumferential groove has a portion protruding inward of the circumferential groove and a portion recessed in the groove width direction from the groove opening in the groove width direction by forming the groove wall in a wave shape. Yes. As a result, in the portion where the groove wall is recessed, flexibility can be provided in the vicinity of the groove opening, so that stress concentration in the vicinity of the circumferential groove can be suppressed. As a result, uneven wear can be suppressed.

Special table 2003-504268 gazette

  However, in addition to uneven wear, there is a possibility that the rib near the groove opening portion of the circumferential groove may be chipped or frayed due to the entry of foreign matter, particularly long foreign matters such as metal rails and side groove lids, into the circumferential groove. . Such rib chippings and so-called rib tears, so-called rib tiers, make it difficult for foreign matter to enter the circumferential groove by forming the entire circumferential groove in a zigzag shape that reciprocates in the tire width direction while facing the tire circumferential direction. Therefore, the occurrence of rib tear can be reduced. However, in this case, since the corner portion protruding in the tire width direction is provided in the groove opening portion, stress concentration occurs in this portion when the vehicle travels, and there is a possibility that uneven wear may occur.

  Such uneven wear can be suppressed to some extent by forming the entire circumferential groove in a straight shape along the tire circumferential direction without taking rib tears into consideration. That is, by making the circumferential groove opening straight, it is possible to make it difficult for stress concentration to occur, so that the occurrence of uneven wear can be suppressed. However, when the entire circumferential groove is formed in a straight shape, foreign matters are likely to enter the circumferential direction, which may cause rib tears. For these reasons, it has been difficult to suppress the occurrence of both uneven wear and rib tear.

  This invention is made | formed in view of the above, Comprising: It aims at providing the pneumatic tire which can suppress generation | occurrence | production of a rib tear, ensuring uneven wear resistance.

  In order to solve the above-described problems and achieve the object, a pneumatic tire according to the present invention is a pneumatic tire having a plurality of circumferential grooves formed in a tire circumferential direction on a tread surface which is a surface of a tread portion. Of the plurality of circumferential grooves, at least one of the circumferential grooves has a groove opening formed in a straight shape along the tire circumferential direction, and groove walls facing each other are both facing the tire circumferential direction. It is formed in a zigzag shape reciprocating in the tire width direction, and the circumferential groove is a portion of the projected intersection where the groove walls facing each other intersect when the circumferential groove is viewed in the tire circumferential direction. The height of the circumferential groove from the groove bottom is in the range of 0.45 to 0.7 times the groove depth of the circumferential groove.

  In this invention, since the groove opening of at least one circumferential groove among the plurality of circumferential grooves is formed in a straight shape, stress concentration occurs on the tread surface near the groove opening of the circumferential groove. This can be suppressed, whereby uneven wear can be suppressed. In addition, since the groove wall of the circumferential groove is formed in a zigzag shape, the foreign object easily comes into contact with the groove wall even when the foreign object enters the circumferential groove. Thereby, since it becomes difficult for a foreign material to enter the circumferential groove, the occurrence of rib tears can be suppressed.

  Further, the circumferential groove has a height at which the projected intersection of the opposing groove walls from the groove bottom is within a range of 0.45 to 0.7 times the groove depth of the circumferential groove. Therefore, uneven wear and rib tear can be more reliably suppressed. That is, when the height of the projected intersection from the groove bottom is less than 0.45 times the groove depth, the projected intersection is too close to the groove bottom, so when the foreign object enters the circumferential groove, There is a risk that it will penetrate too deeply into the circumferential groove, and rib tears may occur. Further, when the height of the projected intersection from the groove bottom is higher than 0.7 times the groove depth, the projected intersection is too close to the tread surface, that is, the inclination angle of the groove wall with respect to the groove depth direction is Too big. For this reason, the rigidity of the land part adjacent to the circumferential groove changes greatly depending on which part of the groove wall formed in a zigzag shape, and the rigidity difference of the land part increases. This may cause uneven wear.

  Therefore, in this circumferential groove, the height from the groove bottom of the projected intersection of the opposing groove walls is within the range of 0.45 to 0.7 times the groove depth of the circumferential groove. By forming, uneven wear and rib tear can be more reliably suppressed. As a result, the occurrence of rib tears can be suppressed while ensuring uneven wear resistance.

  Further, in the pneumatic tire according to the present invention, the circumferential groove having the projection intersection point is a shoulder side circumferential groove that is the circumferential groove located at an end portion in the tire width direction among the plurality of circumferential grooves. It is characterized by being.

  In the present invention, the shoulder-side circumferential groove is a circumferential groove having the projection intersection described above, that is, a circumferential groove having a groove opening formed in a straight shape and a groove wall formed in a zigzag shape. The shoulder side circumferential grooves are adjacent to both ends in the tire width direction, that is, land portions located on the shoulder side, among land portions formed on the tread surface, such as shoulder ribs. Since uneven wear is likely to occur in such land portions, uneven wear can be more reliably performed by forming the shoulder side circumferential groove, which is a land portion adjacent to the land portion where uneven wear is likely to occur, into the shape described above. Can be suppressed. Further, among the plurality of circumferential grooves, foreign matters are likely to enter the shoulder side circumferential grooves located at the ends in the tire width direction. For this reason, by making the shoulder side circumferential groove into the shape described above, it is possible to reduce the entry of the foreign material into the shoulder side circumferential groove in which the foreign material easily enters, and the occurrence of rib tears can be suppressed. As a result, it is possible to suppress the occurrence of rib tears more reliably while ensuring uneven wear resistance.

  In the pneumatic tire according to the present invention, the projection intersection may have a plurality of positions in the tire width direction within at least two pitches of the zigzag pitch that is the shape of the groove wall. Features.

  In the present invention, the groove is formed so that the projected intersection is at a position shifted in the tire width direction within at least two pitches of the zigzag pitch that is the shape of the groove wall. By making the easiness of contact with the groove wall when entering the interior nonuniform in the tire circumferential direction, foreign matters are easily removed. As a result, it is possible to more reliably reduce the entry of foreign matter into the circumferential groove, and to more reliably suppress the occurrence of rib tears.

  In the pneumatic tire according to the present invention, the groove wall is formed so that an angle with respect to a groove depth direction of the circumferential groove is within 45 °.

  In this invention, since the angle of the groove wall with respect to the direction of the groove depth of the circumferential groove is within 45 °, it is possible to suppress the rigidity difference of the land portion from becoming too large. That is, when the angle of the groove wall with respect to the direction of the groove depth is larger than 45 °, the rigidity of the land portion adjacent to the circumferential groove depends on which portion of the groove wall formed in a zigzag shape is adjacent to Although there is a possibility that it will change too much, by making this angle within 45 °, the difference in rigidity can be reduced. As a result, the uneven wear resistance can be improved more reliably.

  Further, in the pneumatic tire according to the present invention, the groove wall located on the outer side in the tire width direction among the groove walls facing each other is reciprocated in the tire width direction with a certain amount of displacement while facing the tire circumferential direction. Of the groove walls facing each other, the groove walls located on the inner side in the tire width direction change in the amount of displacement in the tire width direction while facing the tire circumferential direction. It is formed in the zigzag shape by reciprocating in the tire width direction.

  In this invention, the amount of displacement in the tire width direction of the groove wall located on the inner side in the tire width direction of the circumferential groove formed in a zigzag shape is constant, and the groove wall located on the outer side in the tire width direction is made constant. The groove wall located on the inner side in the width direction is changed. That is, the groove wall located on the inner side in the tire width direction changes the position of the groove wall in the tire width direction for each zigzag pitch. The land portion adjacent to the circumferential groove is more susceptible to uneven wear in the land portion located on the outer side in the tire width direction than on the land portion located on the inner side in the tire width direction. By making the amount of displacement of the groove wall located on the lateral side constant, it is possible to reduce the rigidity difference in the land portion adjacent to the outer side in the tire width direction of the circumferential groove. As a result, the uneven wear resistance can be improved more reliably.

  The pneumatic tire according to the present invention has an effect that it is possible to suppress the occurrence of rib tear while ensuring uneven wear resistance.

  Embodiments of a pneumatic tire according to the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiments. In addition, constituent elements in the following embodiments include those that can be easily replaced by those skilled in the art or those that are substantially the same. In addition, the tread pattern of the pneumatic tire includes a rib pattern, a block pattern, a rib lug pattern, and the like, but the following explanation is an example of the pneumatic tire according to the present invention in which the tread pattern is formed of a rib pattern. The entering tire will be described.

(Embodiment)
In the following description, the tire width direction refers to a direction parallel to the rotation axis of the pneumatic tire, the inner side in the tire width direction refers to the direction toward the equator in the tire width direction, and the outer side in the tire width direction refers to the tire. The direction opposite to the direction toward the equator in the width direction. Further, the tire radial direction refers to a direction orthogonal to the rotation axis, and the tire circumferential direction refers to a direction rotating around the rotation axis as a center of rotation. FIG. 1 is a view showing a tread portion of a pneumatic tire according to the present invention. In the pneumatic tire 1, a tread portion 10 made of a rubber material having elasticity is formed on the outermost side in the tire radial direction. The surface of the tread portion 10, that is, a vehicle on which the pneumatic tire 1 is mounted. When the vehicle travels (not shown), the portion that contacts the road surface is formed as a tread surface 11. Further, both end portions of the tread portion 10 in the tire width direction are shoulder portions 15. Further, the tread portion 10 is provided with a plurality of circumferential grooves 20 which are grooves formed in the tire circumferential direction. A plurality of the circumferential grooves 20 are formed substantially in parallel, and are provided side by side in the tire width direction. The tread surface 11 is formed with a plurality of ribs 30 which are land portions defined by the circumferential grooves 20. A plurality of the ribs 30 are formed substantially in parallel like the circumferential groove 20, and are provided side by side in the tire width direction.

  Among the plurality of circumferential grooves 20, the circumferential groove 20 located at the end in the tire width direction is a shoulder side circumferential groove 21. That is, the shoulder side circumferential groove 21 is located closest to the shoulder portion 15 among the plurality of circumferential grooves 20. Of the plurality of ribs 30 formed on the tread surface 11, the rib 30 located at the end in the tire width direction is a shoulder rib 31. The shoulder rib 31 is located between the shoulder side circumferential groove 21 and the shoulder portion 15. For this reason, the shoulder side circumferential groove 21 is adjacent to the shoulder rib 31 and is located on the equatorial plane 5 side of the shoulder rib 31.

  FIG. 2 is a detailed view of part A of FIG. 3 is a cross-sectional view taken along the line BB in FIG. 4 is a cross-sectional view taken along the line CC of FIG. Of the plurality of circumferential grooves 20, the shoulder-side circumferential groove 21 has a groove opening 22 that is a portion opened to the tread surface 11 formed in a straight shape along the tire circumferential direction. Moreover, the groove wall 23 which the shoulder side circumferential groove | channel 21 has is formed in the zigzag shape which the groove wall 23 which mutually opposes reciprocated in the tire width direction, facing the tire circumferential direction. In other words, the shoulder-side circumferential groove 21 has a groove width that narrows from the groove opening 22 toward the groove bottom 24, and the groove bottom 24 has a zigzag shape that reciprocates in the tire width direction while facing the tire circumferential direction. Is formed. The groove wall 23 has a bent planar shape that connects the groove bottom 24 thus formed and the groove opening 22 formed in a straight shape along the tire circumferential direction. For this reason, the groove walls 23 become closer to each other as they move from the groove opening 22 toward the groove bottom 24, and face each other as they move from the groove opening 22 toward the groove bottom 24. Inclined with respect to the direction of the groove depth of the shoulder side circumferential groove 21 in the direction toward the groove wall 23.

  In this way, the groove bottom 24 formed in a zigzag shape has a different groove width for each zigzag pitch. Similarly, the groove walls 23 formed in a zigzag shape have different distances between the groove walls 23 facing each other for each zigzag pitch, and the inclination angle θ of the shoulder side circumferential groove 21 with respect to the groove depth direction is different. ing. That is, the groove wall 23 is formed in a planar shape bent in a zigzag shape, and the distance between the opposing planes differs for each zigzag pitch, and the shoulder side circumferential groove for each zigzag pitch. The inclination angle θ with respect to the groove depth direction of 21 is different. For this reason, the shoulder-side circumferential groove 21 has a zigzag pitch at the position of the projection intersection 25 where the opposing groove walls 23 intersect when the shoulder-side circumferential groove 21 is seen in the tire circumferential direction. Every one is different. That is, the projection intersection point 25 differs in the position in the tire width direction and the position in the groove depth direction for each zigzag pitch.

  In addition, the groove wall 23 is different in the distance between the groove walls 23 facing each other for each zigzag pitch. In other words, the groove wall 23 changes the tire width while changing the position in the tire width direction while facing the tire circumferential direction. It is going back and forth in the direction. Furthermore, since the projection intersection point 25 has a different position for each zigzag pitch, the displacement amount of the change in the position of the groove wall 23 in the tire width direction differs for each pitch. The zigzag pitch here refers to the length in the tire circumferential direction of the portion of the groove wall 23 or the groove bottom 24 formed in a zigzag shape that forms one reciprocation in the tire width direction.

  Further, the projection intersection point 25 has a height from the groove bottom 24 of the shoulder side circumferential groove 21 within a range of 0.45 to 0.7 times the groove depth of the shoulder side circumferential groove 21. Is located. That is, the shoulder-side circumferential groove 21 has h / D of 0.45 to 0.4 when the height from the groove bottom 24 of the projected intersection 25 in the groove depth direction is h and the groove depth is D. A groove wall 23 is formed so as to be within the range of 7. In addition, the ratio h / D of the height h from the groove bottom 24 of the projection intersection 25 to the groove depth D of the shoulder side circumferential groove 21 is formed to be in the range of 0.5 to 0.6. More preferably.

  Further, the projection intersection point 25 has a different position in the groove width direction for each adjacent zigzag pitch. For example, when the projected intersection point 25 located at a certain pitch of the shoulder side circumferential groove 21 is located at the groove width center 26 that is the center of the groove width W of the shoulder side circumferential groove 21 (see FIG. 3). The projection intersection 25 at a pitch adjacent to the pitch having the projection intersection 25 is separated from the groove width center 26 in the tire width direction by the amount of deviation α between the projection intersections 25 (see FIG. 4). As described above, the shoulder side circumferential groove 21 is formed so that the projection intersection point 25 is positioned so that the height from the groove bottom 24 is within the above range at any zigzag pitch. The height from the groove bottom 24 and the position in the groove width direction are different for each. In addition, it is preferable that the shift amount α in the tire width direction between the projection intersections 25 at adjacent pitches is 0.1 or more of the groove width W.

  Further, the groove wall 23 of the shoulder side circumferential groove 21 is preferably formed so that the angle θ with respect to the direction of the groove depth of the shoulder side circumferential groove 21 is within 45 °. That is, the groove wall 23 of the shoulder side circumferential groove 21 is inclined with respect to the direction of the groove depth in the direction toward the opposite groove wall 23 from the groove opening 22 toward the groove bottom 24. The groove wall 23 is preferably formed such that the inclination angle θ is within 45 °.

  When the pneumatic tire 1 is mounted on a vehicle and travels, the pneumatic tire 1 rotates while the tread surface 11 positioned below the tread surface 11 contacts the road surface (not shown). At that time, a large load acts on the tread surface 11, and a large load acts on the end portion of the rib 30 formed in the tread surface 11 in the tire width direction, that is, in the vicinity of the groove opening 22 of the circumferential groove 20. To do. This load also acts near the groove opening 22 of the shoulder side circumferential groove 21, but the groove opening 22 of the shoulder side circumferential groove 21 is formed in a straight shape along the tire circumferential direction. For this reason, there is no portion where stress is concentrated near the groove opening 22 of the shoulder-side circumferential groove 21 on the tread surface 11 because there is no unevenness in the tire width direction, and there is stress concentration near the groove opening 22. Generation | occurrence | production can be suppressed. Thereby, the partial wear resulting from the stress concentration of the tread surface 11 can be suppressed.

  Moreover, although there exists a possibility that foreign materials, such as the stone scattered on the road surface and the protrusion of a road surface, may enter into the circumferential groove | channel 20, the groove wall 23 of the shoulder side circumferential groove | channel 21 is formed in the zigzag shape. For this reason, when these foreign matter enters the shoulder side circumferential groove 21, the foreign matter is likely to come into contact with the groove wall 23. Thereby, it is suppressed that a foreign material enters into the groove bottom 24 of the shoulder side circumferential groove 21, and the foreign material that has entered the shoulder side circumferential groove 21 is easily discharged. Accordingly, it is difficult for foreign matter to enter the shoulder side circumferential groove 21, so that the occurrence of rib tears can be suppressed.

  Further, in the shoulder side circumferential groove 21, the ratio h / D of the height h from the groove bottom 24 of the projection intersection 25 to the groove depth D of the shoulder side circumferential groove 21 is in the range of 0.45 to 0.7. Since it is formed so as to be inside, uneven wear and rib tear can be more reliably suppressed. That is, by setting the height h of the projection intersection 25 from the groove bottom 24 to 0.45 times or more of the groove depth D, the projection intersection 25 can be prevented from coming too close to the groove bottom 24. When foreign matter enters the directional groove 21, it is possible to suppress the foreign matter from entering the shoulder side circumferential groove 21 too deeply. Thereby, since it can suppress that the rib 30 is chipped or peeled off by this foreign material, generation | occurrence | production of a rib tear can be suppressed more reliably.

  Further, since the height h of the projected intersection point 25 from the groove bottom 24 is 0.7 times or less of the groove depth D, the projection intersection point 25 can be prevented from being too close to the tread surface 11, so that the groove wall 23 It is possible to prevent the inclination angle θ of the lens from becoming too large. The rigidity of the rib 30 adjacent to the shoulder-side circumferential groove 21 increases as the inclination angle θ of the groove wall 23 increases, decreases as the inclination angle θ of the groove wall 23 decreases, and the groove wall 23 becomes zigzag. And the inclination angle θ is changed. For this reason, it can suppress that the rigidity difference of the rib 30 becomes large by suppressing that inclination-angle (theta) becomes large too much. That is, the rigidity of the ribs 30 varies greatly depending on which part of the groove wall 23 formed in a zigzag shape, so that the inclination angle θ of the groove wall 23 is suppressed from becoming too large, and the difference in the inclination angle θ is suppressed. By suppressing the excessive increase in the rigidity, it is possible to suppress the rigidity difference of the ribs 30 from becoming excessively large. Thereby, uneven wear can be more reliably suppressed.

  Accordingly, in the shoulder side circumferential groove 21, the ratio h / D of the height h from the groove bottom 24 of the projection intersection 25 to the groove depth D of the shoulder side circumferential groove 21 is 0.45 to 0.7. By forming so as to be within the range, uneven wear and rib tear can be more reliably suppressed. As a result, the occurrence of rib tears can be suppressed while ensuring uneven wear resistance.

  Of the circumferential grooves 20 provided on the tread surface 11, the shape of the shoulder-side circumferential groove 21 that is the circumferential groove 20 located at the end in the tire width direction is the groove opening 22 as described above. The groove wall 23 is formed in a zigzag shape. The shoulder-side circumferential groove 21 is adjacent to the equator plane 5 side of the shoulder rib 31, but a large load is likely to act on the shoulder rib 31 when the vehicle is traveling. That is, when the vehicle is running, a load is easily applied to the end portion in the tire width direction of the tread surface 11 during cornering or the like. Therefore, uneven wear occurs at both ends of the plurality of ribs 30 in the tire width direction. It is easy to generate | occur | produce in the shoulder rib 31 located. For this reason, uneven wear can be more reliably suppressed by making the shape of the shoulder side circumferential groove 21 which is the circumferential groove 20 adjacent to the shoulder rib 31 where uneven wear is likely to occur into the shape described above.

  Further, when the vehicle rides on a step along the road shoulder, a stepped portion, that is, a foreign object, easily enters a shoulder side circumferential groove 21 located at an end in the tire width direction among the plurality of circumferential grooves 20. ing. For this reason, by making the shoulder side circumferential groove 21 into the shape described above, it is possible to reduce the entry of foreign matter into the shoulder side circumferential groove 21 where foreign matter easily enters, and the occurrence of rib tears can be suppressed. As a result, it is possible to suppress the occurrence of rib tears more reliably while ensuring uneven wear resistance.

  Further, by forming the groove wall 23 of the shoulder side circumferential groove 21 so that the inclination angle θ with respect to the groove depth direction of the shoulder side circumferential groove 21 is within 45 °, the shoulder side circumferential groove 21 It can suppress that the difference in rigidity of the rib 30 adjacent to 21 becomes too large. In other words, the groove wall 23 of the shoulder-side circumferential groove 21 is formed in a zigzag shape. By making the inclination angle θ of the groove wall 23 within 45 °, the groove wall 23 formed in a zigzag shape is formed. Of these, the difference in inclination angle between the greatly inclined portion and the less inclined portion can be reduced. The rigidity of the rib 30 adjacent to the shoulder side circumferential groove 21 varies greatly depending on which part of the groove wall 23 formed in a zigzag shape as described above. By making the inclination angle θ within 45 ° and reducing the angle difference between the inclination angles, the difference in rigidity between the ribs 30 adjacent to the groove wall 23 formed in a zigzag shape can be reduced. As a result, the uneven wear resistance can be improved more reliably.

  The opposing groove walls 23 of the shoulder-side circumferential groove 21 are both formed in a zigzag shape, and the projected intersection point 25 differs in the position in the tire width direction for each zigzag pitch. 25, the position in the tire width direction is not necessarily different for each adjacent pitch. The projection intersection point 25 may have a plurality of positions in the tire width direction within at least two pitches of the zigzag pitch that is the shape of the groove wall 23. In other words, when the groove wall 23 is formed so that the projected intersection point 25 is shifted in the tire width direction within at least two pitches of the zigzag pitch, the foreign matter enters the shoulder side circumferential groove 21. By making the ease of contact with the groove wall 23 uneven in the tire circumferential direction, foreign matter can be easily removed. As a result, entry of foreign matter into the shoulder side circumferential groove can be reduced, and the occurrence of rib tears can be more reliably suppressed.

  FIG. 5 is a view showing a modification of the pneumatic tire according to the embodiment. Further, the groove wall 23 of the shoulder-side circumferential groove 21 is formed in a zigzag shape reciprocating in the tire width direction while facing the tire circumferential direction, and further, the displacement amount of the change in the position of the groove wall 23 in the tire width direction. However, the amount of displacement does not have to be different for each pitch of the opposing groove walls 23. For example, as shown in FIG. 5, the shoulder side circumferential groove 40 has a shoulder side groove wall 42 that is a groove wall 41 that is located on the outer side in the tire width direction among the groove walls 41 that are opposed to each other in the tire circumferential direction. Alternatively, a zigzag shape may be formed by reciprocating in the tire width direction with a constant displacement amount. On the other hand, the equatorial plane side groove wall 43 which is the groove wall 41 located on the inner side in the tire width direction is the tire width direction while facing the tire circumferential direction in the same manner as the groove wall 23 of the shoulder side circumferential groove 21 described above. The zigzag is formed by reciprocating in the tire width direction while changing the displacement amount.

  In the rib 45 adjacent to both sides of the shoulder side circumferential groove 40 in the tire width direction, the tire 45 is more inward than the rib 45 on the inner side in the tire width direction, that is, the equatorial plane side rib 47 that is the rib 45 located on the equatorial plane side. The rib 45 on the outer side in the width direction, that is, the shoulder rib 46 is more likely to be subjected to a large load, so that uneven wear tends to occur. Therefore, the groove wall 41 of the shoulder side circumferential groove 40, the shoulder side groove wall 42 in this way has a constant displacement amount, and the equatorial plane side groove wall 43 changes the displacement amount. It is possible to reduce the difference in rigidity of the shoulder ribs for each zigzag pitch while suppressing the entry of foreign matter. As a result, the uneven wear resistance can be improved more reliably.

  FIG. 6 is a view showing a modification of the pneumatic tire according to the embodiment. Moreover, the groove wall of the shoulder side circumferential groove may be formed in a shape other than the planar shape. For example, as shown in FIG. 6, the groove wall 51 of the shoulder-side circumferential groove 50 may be formed from the groove opening 52 to the groove bottom 53 in a curved shape protruding in the direction of the opposite groove wall 51. Good. Even when the groove wall 51 of the shoulder-side circumferential groove 50 is formed in a curved shape, the groove wall 51 has a zigzag shape that reciprocates in the tire width direction while facing the tire circumferential direction, and the groove wall 23 described above, and What is necessary is just to form so that the distance of the groove walls 51 which oppose for every zigzag pitch may differ. As a result, the occurrence of rib tears can be suppressed while ensuring uneven wear resistance. Further, in this case, the angle of the groove wall 51 with respect to the direction of the groove depth of the shoulder side circumferential groove 50 is that of the virtual groove wall 54 that is a virtual groove wall connected in a plane from the groove opening 52 to the groove bottom 53. It is preferable that the inclination angle θ is formed within 45 °.

  Hereinafter, the performance evaluation test performed on the conventional pneumatic tire 1 and the pneumatic tire 1 of the present invention will be described. The performance evaluation test was conducted for two items, uneven wear resistance and rib tear resistance.

  The test method was performed by attaching the 11R22.5 size pneumatic tire 1 to a rim and mounting it on a vehicle. It is known that the test method for each item is frequently generated when the foreign matter enters the circumferential groove 20 and the direction of the pneumatic tire 1 is changed by operating the handle when the foreign material enters the circumferential groove 20. For this reason, the test for rib tear resistance is carried out by mounting the pneumatic tire 1 on the steering shaft of a 2-4D vehicle and moving the steering wheel in both the left and right directions at a low speed of 5 km / h or less on a road surface provided with several kinds of protrusions. The test was performed three times, each of which was cut up to 10 times. Further, in this rib tear resistance test, six pneumatic tires 1 are alternately mounted on the steering shaft of the vehicle for each of the present invention and each comparative example to be described later. The above test was conducted. In this evaluation method, rib tears generated in these six pneumatic tires 1 were observed, and the number of rib tears having a length of 5 cm or more in the tire circumferential direction was counted and evaluated. The smaller the number of rib tears generated, the better the rib tear resistance.

  The uneven wear resistance test was performed by measuring the degree of occurrence of uneven wear after traveling 100,000 km on the above vehicle. The evaluation result by this test is shown by an index with the uneven wear resistance of Comparative Example 1 described later as 100, and the larger the index, the better the uneven wear resistance. The uneven wear resistance is assumed to be 95 or more, and when the index is 95 or more, the uneven wear resistance is excellent.

  The pneumatic tire to be tested is tested by the above method for five types of the present invention and five types of comparative examples to be compared with the present invention. Among these, in Comparative Example 1, the circumferential groove 20 formed in the tread surface 11 is a straight groove. That is, the groove opening 22 and the groove wall 23 of the circumferential groove 20 are both straight formed along the tire circumferential direction. In Comparative Example 2, the circumferential groove 20 is a zigzag groove. That is, the groove opening 22 and the groove wall 23 of the circumferential groove 20 are both formed in a zigzag shape that reciprocates in the tire width direction while facing the tire circumferential direction. In Comparative Examples 3 to 5, the groove opening 22 of the circumferential groove 20 is formed in a straight shape, and the groove wall 23 is formed in a zigzag shape. Among these, in Comparative Example 3, the ratio h / D of the height h from the groove bottom 24 to the projection intersection 25 with respect to the groove depth D of the circumferential groove 20 is 0, and the groove width of the groove opening 22 is The ratio α / W of the shift amount α in the tire width direction between the projected intersections 25 at adjacent pitches with respect to W is 0, and the inclination angle θ of the groove wall 23 is 20 °. In Comparative Example 4, h / D = 0.3, α / W = 0, and inclination angle θ = 25 °. In Comparative Example 5, h / D = 0.75, α / W = 0.2, and inclination angle θ = 25 to 30 °.

  On the other hand, according to the first to fifth aspects of the invention, like the comparative examples 3 to 5, the groove opening 22 of the circumferential groove 20 is formed in a straight shape, and the groove wall 23 is formed in a zigzag shape. Among these, in the present invention 1, h / D = 0.45, α / W = 0, and the inclination angle θ = 25 °. In the second aspect of the present invention, h / D = 0.5, α / W = 0, and the inclination angle θ = 30 °. In the third aspect of the present invention, h / D = 0.5, α / W = 0.1, and the inclination angle θ = 25 to 30 °. In the present invention 4, h / D = 0.7, α / W = 0.2, and the inclination angle θ = 25 to 30 °. In the present invention 5, h / D = 0.5, α / W = 0.2, and the inclination angle θ = 35 to 50 °.

  These pneumatic tires 1 to 5 of the present invention and Comparative Examples 1 to 5 are subjected to an evaluation test by the above-described method, and the obtained results are shown in Table 1-1 and Table 1-2. Among these Table 1-1 and Table 1-2, Table 1-1 has displayed the result of the evaluation test of Comparative Examples 1-5, and Table 1-2 is the result of the evaluation test of this invention 1-5. Is displayed.

  FIG. 7 is a performance curve diagram of uneven wear resistance and rib tear resistance. As is clear from the above test results shown in Table 1-1 and Table 1-2, when both the groove opening 22 and the groove wall 23 of the circumferential groove 20 are formed in a straight shape, the rib tear-resistant It becomes difficult to improve the property (Comparative Example 1). Further, when the groove opening 22 and the groove wall 23 of the circumferential groove 20 are formed in a zigzag shape, the uneven wear resistance is reduced (Comparative Example 2). Even when the groove opening 22 of the circumferential groove 20 is formed in a straight shape and the groove wall 23 is formed in a zigzag shape, when h / D is small, that is, with respect to the groove depth D of the circumferential groove 20. When the height h from the groove bottom 24 to the projection intersection 25 is low, it is difficult to improve the rib tear resistance (Comparative Example 3 and Comparative Example 4). On the contrary, when h / D is large, that is, when the height h from the groove bottom 24 to the projection intersection 25 is high, it is difficult to improve the uneven wear resistance (Comparative Example 5).

  That is, when the groove opening 22 of the circumferential groove 20 is formed in a straight shape and the groove wall 23 is formed in a zigzag shape, uneven wear resistance and rib tear resistance change depending on h / D. Here, the uneven wear resistance is improved when the rigidity difference between the ribs 30 adjacent to the circumferential groove 20 is smaller. Therefore, as shown in the uneven wear resistance curve 61 of FIG. Performance is improved. On the other hand, the rib tear resistance is improved by increasing the height h of the projection intersection 25 and making it difficult for foreign matter to enter the circumferential groove 20, as shown in the rib tear resistance curve 62 when the projection intersection is constant. , The performance improves as h / D increases. Therefore, in order to improve the rib tear resistance while ensuring the uneven wear resistance, the groove is so that the position of the projected intersection point 25 in the groove depth direction of the circumferential groove 20 is located near the center of the groove depth. A wall 23 is formed.

  Further, when the position of the projection intersection 25 of the groove wall 23 formed in a zigzag shape is changed for each zigzag pitch, foreign matter is less likely to enter the circumferential groove 20, so that when the projection intersection changes As shown in the rib tear resistance curve 63, the rib tear resistance can be further improved. Accordingly, when improving the rib tear resistance while ensuring uneven wear resistance, the circumferential groove 20 is formed so that h / D is in the range of 0.45 to 0.7.

  Accordingly, as in the first to fifth aspects of the present invention, the groove opening 22 of the circumferential groove 20 is formed in a straight shape, the groove wall 23 is formed in a zigzag shape, and the position of the projected intersection point 25 in the groove depth direction is determined. Rib tier while ensuring uneven wear resistance by forming the circumferential groove 20 so as to be located near the center of the groove depth, that is, h / D is in the range of 0.45 to 0.7. Can be suppressed (Inventions 1 to 5). Further, by making the inclination angle θ of the groove wall 23 with respect to the depth direction of the circumferential groove 20 within 45 °, the rigidity difference between the ribs 30 adjacent to the circumferential groove 20 can be reduced, so that more reliably. Uneven wear resistance can be ensured (Inventions 1 to 4).

  In the above description, among the plurality of circumferential grooves 20 provided on the tread surface 11, only the shoulder side circumferential groove 21 has a groove opening 22 in a straight shape and a groove wall 23 in a zigzag shape. The circumferential groove 20 thus formed may be a circumferential groove 20 other than the shoulder side circumferential groove 21. For example, together with the shoulder side circumferential groove 21, the other circumferential groove 20 may be shaped as described above, or only the circumferential groove 20 other than the shoulder side circumferential groove 21 may be shaped as described above. In the above description, the pneumatic tire 1 having a rib pattern is described as an example of the pneumatic tire 1. However, the pneumatic tire 1 to which the present invention is applied may be other than the rib pattern. A pneumatic tire formed with a rib lug pattern may be used.

  As described above, the pneumatic tire according to the present invention is useful for a pneumatic tire having a circumferential groove, and is particularly suitable when both uneven wear resistance and rib tear resistance are achieved.

It is a figure which shows the tread part of the pneumatic tire which concerns on this invention. FIG. 2 is a detailed view of part A in FIG. 1. It is BB sectional drawing of FIG. It is CC sectional drawing of FIG. It is a figure which shows the modification of the pneumatic tire which concerns on embodiment. It is a figure which shows the modification of the pneumatic tire which concerns on embodiment. It is a performance curve figure of uneven wear resistance and rib tear resistance.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pneumatic tire 5 Equatorial surface 10 Tread part 11 Tread surface 15 Shoulder part 20 Circumferential groove 21 Shoulder side circumferential groove 22 Groove opening 23 Groove wall 24 Groove bottom 25 Projected intersection 26 Groove width center 30 Rib 31 Shoulder rib 40 Shoulder Side circumferential groove 41 Groove wall 42 Shoulder side groove wall 43 Equatorial plane side groove wall 45 Rib 46 Shoulder rib 47 Equatorial plane side rib 50 Shoulder side circumferential groove 51 Groove wall 52 Groove opening 53 Groove bottom 54 Virtual groove wall 61 Uneven wear resistance Characteristic curve 62 Rib tear resistance curve when projection intersection is constant 63 Rib resistance curve when projection intersection changes

Claims (5)

In the pneumatic tire having a plurality of circumferential grooves formed in the tire circumferential direction on the tread surface which is the surface of the tread portion,
Of the plurality of circumferential grooves, at least one of the circumferential grooves has a groove opening formed in a straight shape along the tire circumferential direction, and groove walls facing each other are both facing the tire circumferential direction. It is formed in a zigzag shape reciprocating in the tire width direction,
Further, the circumferential groove has a height from the groove bottom of the circumferential groove at a projected intersection that is a portion where the groove walls that face each other when the circumferential groove is viewed in the tire circumferential direction, A pneumatic tire characterized by being in a range of 0.45 to 0.7 times the groove depth of the circumferential groove.   The said circumferential groove | channel which has the said projection intersection is a shoulder side circumferential groove | channel which is the said circumferential groove located in the edge part in a tire width direction among these several circumferential grooves. The described pneumatic tire.   3. The projection intersection point has a plurality of positions in the tire width direction within at least two pitches of the zigzag pitch that is the shape of the groove wall. 4. Pneumatic tire.   The pneumatic tire according to any one of claims 1 to 3, wherein the groove wall is formed so that an angle with respect to a groove depth direction of the circumferential groove is within 45 °. Of the groove walls facing each other, the groove wall located on the outer side in the tire width direction is formed in the zigzag shape so as to reciprocate in the tire width direction with a certain amount of displacement while facing the tire circumferential direction,
Of the groove walls facing each other, the groove wall located on the inner side in the tire width direction reciprocates in the tire width direction while changing in the displacement amount in the tire width direction while moving in the tire circumferential direction to form the zigzag shape. The pneumatic tire according to any one of claims 1 to 4, wherein the pneumatic tire is formed.

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