JP4474876B2 - Heavy duty pneumatic tire - Google Patents

Description

  The present invention relates to a heavy duty pneumatic tire. In particular, the present invention improves the uneven wear resistance of the tire tread shoulder portion, maintains steering stability, and lacks the tread shoulder end when excessive lateral force is applied to the tire during turning. The present invention relates to a heavy-duty pneumatic tire capable of suppressing soot.

  In conventional heavy-duty pneumatic tires, the larger the ground contact area, the better the wear resistance and handling stability, so the tread shoulder end has an edge shape to effectively use the tread width as the ground contact area. A so-called square shoulder type is often used. In addition, in order to increase the contact area, the tread width tends to be widened. When the tread width is increased in this manner, wear resistance and steering stability are improved, while the ground contact pressure at the end of the tread shoulder is extremely high particularly during turning, which may cause uneven wear.

  Therefore, some conventional heavy-duty pneumatic tires are provided with a groove or the like around the tread shoulder end portion to prevent the contact pressure at the tread shoulder end portion from increasing (see, for example, Patent Document 1). . There are various shapes of grooves provided in the end portion of the tread shoulder. However, in Patent Document 1, the grooves are formed by providing a plurality of grooves in a buttress portion formed outward in the tire width direction of the tread portion. The load applied to the tread shoulder end is deformed to reduce the contact pressure.

JP-A-11-151910

  However, when an excessive load is applied to the end portion of the tread shoulder of the heavy duty pneumatic tire in which the groove is formed in the buttress portion, the buttress portion including the groove is deformed and the wall surfaces of the groove are separated from each other. When contact is made, the groove cannot be further deformed, and the ground pressure cannot be reduced. For this reason, when an excessive load is applied as described above at the time of turning and an excessive lateral force or twist is applied to the heavy duty pneumatic tire, there is a possibility that the tread shoulder end portion may be chipped or bald. Thus, when chipping or baldness occurs at the end of the tread shoulder, the original effect of preventing uneven wear that is effective when the ground contact area is increased cannot be obtained. In addition, when reducing the contact pressure when a large load as described above is applied, by increasing the width of the groove, the amount of deformation of the groove increases, so the load that is dispersed increases, and the contact pressure increases. However, if the width of the groove is simply increased, the amount of deformation at the end of the tread shoulder due to the load during turning increases, and steering stability is reduced.

  Accordingly, the present invention has been made in view of the above, and is a heavy-duty air that can suppress chipping or baldness at the end of the tread shoulder due to an excessive load during turning while maintaining steering stability. An object is to provide a tire entering.

In order to solve the above-described problems and achieve the object, the heavy-duty pneumatic tire according to the present invention is provided with a groove portion in the tire circumferential direction in a buttress portion formed outward in the tire width direction of the tread portion. In the heavy-duty pneumatic tire, the groove portion is formed continuously or discontinuously, and an opening is formed in the buttress portion , and an opening is formed at the bottom of the main groove. And a sub-groove formed in the depth direction of the groove portion from the opening thereof, and the sub-groove has a shape of a center line of a bottom portion of the sub-groove, and a shape of a center line of the opening portion of the main groove. The bottom of the sub-groove is different from the shape and is formed in a periodic waveform in the width direction of the sub-groove, and the waveform forming the sub-groove is W1 as the width of the main groove. When the pitch is P, W1 × 2 ≦ P ≦ It is formed so as to be 1 × 15, characterized in that is.

  In this invention, by forming the groove portion to be formed in the buttress portion with two or more steps, the large load applied to the tread shoulder end portion during turning is dispersed in the plurality of grooves, and the ground contact to the tread shoulder end portion is achieved. Pressure can be reduced. Thereby, the chipping of the end part of a tread shoulder due to an overload, a baldness, etc. can be controlled. Further, since the load is distributed by the plurality of grooves, the concentration of force on one groove bottom can be suppressed. Thereby, since stress concentration can be suppressed, the crack of the groove bottom part by stress concentration can be suppressed. Furthermore, when dispersing a large load, the wide groove is not greatly deformed and dispersed, but is dispersed by a plurality of grooves, and each of the grooves is deformed to reduce the above-mentioned ground pressure, The amount of deformation at the end of the tread shoulder can be reduced. Thereby, the steering stability when a load is applied to the tread shoulder end can be maintained. Furthermore, by forming the groove portion with a plurality of grooves, the area of the wall surface of the groove increases, so that it is easy to release heat generated during traveling. As a result, even when a large load is applied to the tread shoulder end during turning, the load can be distributed by the groove and the contact pressure can be reduced, so that the tread shoulder end can be prevented from being chipped or burned during turning. be able to. Furthermore, since the amount of deformation at the end portion of the tread shoulder is small even at that time, steering stability can be maintained. Furthermore, since heat dissipation improves by the increase in the area of the wall surface of a groove | channel, durability can be improved.

  Further, in the heavy load pneumatic tire according to the present invention, the groove portion includes the heavy load pneumatic tire from a tread shoulder end portion which is an end portion in a tire width direction of a tread surface of the tread portion toward an inner side in a tire radial direction. It is provided in the position within the range of 80%-150% of the depth of the longitudinal groove provided in the tire circumferential direction in the tread portion of the tire.

  In the present invention, the position of the groove formed in the buttress portion is provided at a position that is 80% or more of the depth of the vertical groove formed in the tread portion from the tread shoulder end toward the inside in the tire radial direction. As a result, even when the tread portion wears down and the thickness of the tread portion decreases, the groove portion provided in the buttress portion can maintain the shape before the tread wears. Can also achieve the above effects. Further, the position where the groove portion is provided is also a position of 150% or less of the depth of the vertical groove formed in the tread portion from the tread shoulder end toward the inside in the tire radial direction. Here, in the heavy duty pneumatic tire as in the present invention, when the tread is worn as described above, the tread portion may be scraped off and buffed, and a new tread portion may be joined and rehabilitated. There are many. When buffing during rehabilitation when the groove is formed at a position of 150% or more of the depth of the longitudinal groove formed in the tread, inward of the tire radial direction from the tread shoulder end, In addition, the groove portion is present on the buff line, and the joining surface may have a shape different from the original joining surface depending on the groove portion. Therefore, there is a possibility that problems such as a mismatch in width with the joining surface of the new tread portion may occur. is there. Further, when the groove is formed at this position, it is difficult to obtain the effect of dispersing the load applied to the tread shoulder end because it is too far from the tread shoulder end.

  However, since the groove portion of the present invention is provided at the above position, the position is outward in the tire radial direction from the buff line, and the groove portion is all removed at the time of rehabilitation, so that the heavy duty pneumatic tire Does not cause problems such as the width of the new tread does not match during rehabilitation. Further, since the tread shoulder end portion and the groove portion are close to each other, the function of the tread shoulder end portion can be supplemented, for example, the load applied to the tread shoulder end portion is dispersed in the groove portion. As a result, the groove portion can obtain the above effect regardless of the wear on the tread surface, and can also prevent problems caused by the groove portion when the tread portion is rehabilitated. Furthermore, the above-described effect when providing the groove can be reliably obtained.

  In the heavy duty pneumatic tire according to the present invention, the groove portion is formed with a depth of 2 mm to 10 mm.

  In the present invention, the depth from the opening to the bottom of the groove is 2 mm to 10 mm. By forming the depth of the groove within this range, the handling stability is ensured while dispersing the load on the tread shoulder end during turning. That is, when the depth of the groove portion is 2 mm or less, the amount of deformation of the groove portion is small, so the load applied to the tread shoulder end portion cannot be dispersed, and a large load is applied to the tread shoulder end portion. Will cause chipping and baldness. Further, when the depth of the groove portion is 10 mm or more, the deformation of the groove portion when the load is applied to the tread shoulder end portion is too large, and the deformation amount of the tread shoulder end portion also increases, so that the steering stability is improved. It will decline. Therefore, by forming the entire depth of the groove portion from 2 mm to 10 mm, the load at the end of the tread shoulder during turning is distributed to reduce the ground pressure by reducing the ground contact pressure, while improving steering stability. Is maintained.

  Further, in the heavy duty pneumatic tire according to the present invention, the groove portion includes a main groove having an opening formed in the buttress portion, and an opening portion at a bottom portion of the main groove, and the opening portion includes the opening portion. The sub-groove is formed in the depth direction of the groove, and the shape of the center line of the bottom of the sub-groove is different from the shape of the center line of the opening of the main groove.

  In the present invention, the shape of the center line that is the center in the width direction of the opening portion of the main groove and the shape of the center line that is the center in the width direction of the bottom portion of the sub-groove are different. That is, for example, the main groove is formed as a circular groove along the tire circumferential direction, and the sub-groove is formed along the tire circumferential direction while being formed in a waveform having an amplitude in the tire radial direction, On the contrary, when the circular sub-groove is formed in the corrugated main groove, the shape of the main groove and the sub-groove is different. Thus, by forming the main groove and the sub-groove in different shapes, the area of the wall surface increases, so it becomes easy to disperse the load applied to the tread shoulder end, and at the same time from the outside by the increased area. Since the force can be received, the rigidity of the entire groove portion can be improved. As a result, even when a load is applied to the end portion of the tread shoulder during turning, it is possible to maintain steering stability while suppressing chipping and baldness at the end portion of the tread shoulder. Moreover, since the shapes of the main groove and the sub-groove are different, the area of the wall surface forming the groove portion increases. Thus, when the area of a wall surface increases, the heat dissipation from a wall surface further increases. As a result, the durability is further improved.

  In the heavy duty pneumatic tire according to the present invention, the length of the center line of the bottom portion of the sub-groove is longer than the length of the center line of the opening portion of the main groove.

  In this invention, the length of the center line of the sub-groove is longer than the length of the center line of the opening of the main groove, that is, the sub-groove is longer when making one turn in the tire circumferential direction than the main groove. It is formed by distance. Thereby, the area of the wall surface which forms a subgroove can be increased. As a result of increasing the area of the wall surface of the groove in this way, a larger load can be dispersed in the groove, so that the contact pressure at the end of the tread shoulder can be further reduced and chipping and the like can be easily suppressed. Furthermore, since the area of the wall surface is large, the load can be more dispersed when a load is applied, so that the amount of deformation of the entire groove portion is further reduced, and it is possible to easily maintain steering stability.

  The heavy duty pneumatic tire according to the present invention is characterized in that the sub-groove is formed such that the bottom of the sub-groove has a periodic waveform in the width direction of the sub-groove.

  In this invention, since the sub-groove is formed to have a periodic waveform, when the wall surface area is increased and the load is received as described above, the wall surface area is averaged in the tire circumferential direction. Can be increased. In addition, since the load is dispersed by forming the sub-groove in a waveform, it is possible to suppress the occurrence of cracks in the sub-groove when the load is applied. As a result, effects such as suppression of chipping at the end of the tread shoulder due to load absorption and securing of steering stability are not biased in the tire circumferential direction, and any position in the tire circumferential direction of the tread portion touches the road surface. Even in this case, the same effect can be obtained, and further, the breakage of the groove itself can be suppressed.

  In the heavy duty pneumatic tire according to the present invention, the waveform forming the sub-groove is W1 × 2 ≦ P ≦ W1 × when the width of the main groove is W1 and the waveform pitch is P. It is formed so that it may become 15.

  In the present invention, the pitch of the waveform is set to W1 × 2 ≦ P ≦ W1 × 15 (P = pitch, W1 = groove width of the main groove), thereby increasing the area of the wall surface of the sub-groove. Such an effect is obtained efficiently. That is, when the corrugated pitch is smaller than twice the groove width of the main groove, the area of the wall surface of the sub-groove is too large and the strength of the groove portion becomes too high. Further, since the groove portion is not deformed and the load cannot be dispersed, the tread shoulder end portion may be chipped. Further, when the pitch of the waveform of the secondary groove is larger than 15 times the width of the main groove, the strength of the groove cannot be improved due to the increase in the groove wall area of the secondary groove, and the steering stability may be reduced. There is. Therefore, by forming the corrugated pitch in the range of W1 × 2 ≦ P ≦ W1 × 15, it is possible to accurately obtain the effect due to the increase of the groove wall area of the sub-groove. By distributing the load of the part, it is possible to maintain steering stability while suppressing chipping and the like.

  Further, in the heavy-duty pneumatic tire according to the present invention, the wall surface forming the sub-groove is inclined and periodically changes in a range of 5 ° to 45 ° with respect to the normal line of the tire outer surface. Features.

  In the present invention, by forming the inclination angle of the wall surface of the sub-groove in the above range, the above-described effect due to the increase in the area of the wall surface of the sub-groove is efficiently obtained. That is, when the angle of the wall surface is out of the above range, the displacement amount of the amplitude of the sub groove with respect to the main groove is large. In this case, since the increase in the strength due to the increase in the wall surface is too large, the groove portion is not deformed, and the load at the end portion of the tread shoulder cannot be dispersed. Further, when the displacement amount of the amplitude of the sub-groove is large, formation becomes difficult, which leads to an increase in cost. Therefore, by forming the inclination angle of the wall surface of the sub-groove in the above range, as described above, the effect due to the increase in the area of the wall surface of the sub-groove is efficiently obtained, and the increase in cost at that time is prevented. .

  The heavy-duty pneumatic tire according to the present invention has the effect of suppressing chipping and teasing of the tread shoulder end due to an excessive load during turning while maintaining steering stability. Moreover, the effect of suppressing the crack of the groove part formed in a buttress part is produced. Furthermore, there is an effect that deterioration due to heat is suppressed and durability is improved.

  The best mode for carrying out the heavy duty pneumatic tire according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to the best mode for carrying out the invention. 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 the following description, the tire width direction refers to a direction parallel to the virtual rotation axis of the heavy duty pneumatic tire, and the inner side in the tire width direction refers to the direction toward the equator line in the tire width direction and the outer side in the tire width direction. Means the direction opposite to the direction of the equator line in the tire width direction. Further, the tire radial direction refers to a direction orthogonal to the rotation axis. The tire circumferential direction is a circumferential direction with the rotation axis as a central axis. FIG. 1 is a partial sectional view showing a heavy duty pneumatic tire according to the present invention. FIG. 2 is a partial perspective view of the heavy duty pneumatic tire of FIG. 1. In the heavy load pneumatic tire 1, a tread portion 2 is formed on the outermost side in the tire radial direction, and an end portion in the tire width direction of the tread portion 2 is formed as a tread shoulder end portion 6. A longitudinal groove 3 and a lateral groove 4 forming a tread pattern are provided on the surface of the tread portion 2, and a belt layer 8 is provided on the inner side in the tire radial direction of the tread portion 2. Further, sidewall portions 9 are provided from both ends of the tread portion 2 in the tire width direction toward the inside in the tire radial direction. Further, a carcass 10 is provided on the inner side in the tire width direction of the sidewall portion 9 and on the inner side in the tire radial direction of the belt layer 8. A surface of the tread portion 7 formed outward in the tire width direction, or the vicinity of the tire radial direction outer peripheral portion of the sidewall portion 9, that is, the vicinity of the tread shoulder end portion 6 of the sidewall portion 9, is a buttress. Part 7 is formed.

  The tread portion 2 has a tread surface 5 that is a portion that comes into contact with the road surface, and is formed as a surface along the tire width direction and the tire circumferential direction, and the buttress portion 7 is a substantially outer surface in the tire width direction, that is, It is formed as a part of the side surface of the heavy duty pneumatic tire 1. For this reason, the buttress portion 7 is formed in the tire circumferential direction while facing substantially the outer side in the tire width direction. In this way, the tread portion 2 and the buttress portion 7 are treads that are the boundary between the two because the surfaces to be formed face in different directions, and are also the outer ends of the tread portion 2 in the tire width direction. The shoulder end 6 is formed in an edge shape.

  A groove portion 11 is formed in the buttress portion 7 along the tire circumferential direction, and is formed in such a direction that the depth direction of the groove is substantially the tire width direction. This groove portion 11 is formed of a main groove 12 and a sub-groove 13, and the sub-groove 13 is located behind the main groove 12, that is, in the direction of the equator line 25 or the inner side in the tire width direction from the main groove 12. Is provided. Further, in the groove portion 11, the main groove 12 is opened in the buttress portion 7 by the opening portion 14, and a pair of main groove wall surfaces 15 are formed from the opening portion 14 toward the inner side in the tire width direction. Has been. The pair of main groove wall surfaces 15 are provided substantially parallel to each other so as to face each other from the outer side or the inner side in the tire radial direction. Further, a main groove bottom portion 16 is formed on a surface substantially parallel to the buttress portion 7 inside the main groove wall surface 15 in the tire width direction.

The sub-groove 13 is provided inward in the tire width direction from the main groove bottom 16. The sub-groove opening 17 that is the opening of the sub-groove 13 is formed in the main groove bottom 16, and the center in the width direction of the main groove bottom 16 and the center in the width direction of the sub-groove opening 17 are They are formed at almost the same position. Two sets of sub-groove wall surfaces 18 are provided so as to face each other from the sub-groove opening 17 toward the inside in the tire width direction . Further, a sub-groove bottom portion 19 is formed on a surface substantially parallel to the buttress portion 7 inside the sub-groove wall surface 18 in the tire width direction. Since the sub-groove 13 has the sub-groove opening 17 provided in the main groove bottom 15 as described above, the groove width of the sub-groove 13 is narrower than the groove width of the main groove 12.

  The groove portion 11 composed of the main groove 12 and the sub-groove 13 has the above-described shape and is continuously provided over the entire circumference of the buttress portion 7 along the tire circumferential direction. The position is provided at a position that falls within the range of 80% to 150% of the depth of the longitudinal groove 3 from the tread shoulder end 6 toward the inside in the tire radial direction. Thereby, the groove part 11 is provided in the tire radial direction outward rather than the buff line 20 which is a line which scrapes off a tread part at the time of the tread part 2 renovation. Further, the groove 11 is formed so that the total depth of the main groove 12 and the sub groove 13 is in the range of 2 mm to 10 mm.

  When the heavy-duty pneumatic tire 1 is mounted on a vehicle such as a truck and travels, when turning, the tire width direction of the tread 5, which is a portion where the heavy-duty pneumatic tire 1 and the road surface are in contact with each other The load on the tread shoulder end portion 6 that is the end portion or the ground pressure increases. Since the heavy-duty pneumatic tire 1 is mainly mounted on a heavy truck or the like as described above, a large ground pressure is applied to the tread shoulder end portion 6 in such a case. Such pressure on the tread shoulder end portion 6 is mainly a force that compresses the tread shoulder end portion 6 inward in the tire radial direction. The groove 11 is provided. As described above, the main groove 12 and the sub-groove 13 are formed in the groove portion 11. When pressure is applied to the tread shoulder end portion 6, the groove portion 11 is provided in the same direction as the pressure direction. Therefore, the tread shoulder end portion 6 is deformed in a direction in which the groove portion 11 is crushed. The pressure is released by the groove 11. Moreover, since the said groove part 11 is formed of the main groove 12 and the subgroove 13 as mentioned above, since the said pressure is disperse | distributed, it does not concentrate on one place of the groove part 11, but, as a result Can receive large pressure.

  As a result, since the burden on the tread shoulder end 6 is reduced with respect to the large pressure applied to the tread shoulder end 6, the chipping and baldness of the tread shoulder end 6 due to the ground pressure during turning can be suppressed. Furthermore, since the pressure does not concentrate in one place of the groove portion 11 as described above, cracks in the groove portion 11 due to stress concentration can be suppressed.

  Moreover, since the said pressure is disperse | distributed to the main groove 12 and the subgroove 13, since each receives the said pressure by receiving small force, the groove part 11 whole receives a pressure with little deformation. be able to. As a result, the amount of deformation of the tread shoulder end portion 6 can be reduced, so that the steering stability when receiving the ground pressure can be maintained. Further, since the groove 11 is formed by the main groove 12 and the sub-groove 13, the surface area of the wall surface or the like that forms the groove 11 is increased. As a result, heat generated during traveling can be easily released, so that deterioration due to heat is suppressed and durability is improved.

  Further, when the vehicle equipped with the heavy load pneumatic tire 1 continues to travel and the tread surface 5 is worn, the distance between the tread shoulder end portion 6 and the groove portion 11 after wear becomes closer. Even in this case, the groove portion 11 is provided at a position of 80% or more of the depth of the longitudinal groove 3 of the tread portion 2 from the tread shoulder end portion 6 inward in the tire radial direction, so that the tread surface 5 is worn. Accordingly, even if the buttress portion 7 is worn inward in the tire radial direction, the portion where the groove portion 11 is formed is not worn. As a result, the shape of the groove portion 11 does not change even after the tire tread is worn, so that the above effect can be obtained regardless of the wear of the tread portion 2.

  In addition, when the wear of the tread portion 2 of the tread portion 2 progresses due to repeated running, the heavy load pneumatic tire 1 scrapes the tread portion 2 to the buff line 20 and attaches a new tread portion 2 thereto. Often rehabilitate. Even in this case, the groove portion 11 is provided at a position of 150% or less of the depth of the longitudinal groove 3 of the tread portion 2 from the tread shoulder end portion 6 toward the inner side in the tire radial direction, and is therefore scraped off. At this time, the groove portion 11 is not cut at a halfway position. Furthermore, after scraping off, the same effect as described above can be obtained by bonding the tread portion 2 in which the groove portion 11 as described above is formed. As a result, when the tread portion 2 is rehabilitated, it is possible to prevent inconveniences such as the shape of the portion where the tread portion 2 is scraped off and the joint surface of the new tread portion 2 do not match. Furthermore, by sticking the tread portion 2 in which the groove portion 11 is formed at the time of rehabilitation of the heavy load tire 1, the same effect as the above effect can be obtained even after rehabilitation. Furthermore, since the groove portion 11 is provided at the above position with respect to the tread shoulder end portion 6 and is not too far from the tread shoulder end portion 6, the ground pressure applied to the tread shoulder end portion 6 as described above can be reduced. Since it can disperse | distribute reliably, the burden by the grounding pressure to the tread shoulder end part 6 can be reduced.

  Moreover, since the total depth of the main groove 12 and the sub-groove 13 is 2 mm or more, the groove portion 11 can sufficiently disperse the ground pressure applied to the tread shoulder end portion 6 by the groove portion 11. As a result, as described above, the ground pressure applied to the tread shoulder end portion 6 during turning can be reduced, and chipping, baldness, and the like can be suppressed. Further, since the total depth of the main groove 12 and the sub-groove 13 of the groove portion 11 is formed to be 10 mm or less, even when turning, the ground pressure is increased at the tread shoulder end portion 6 and even when the pressure is dispersed. The groove 11 is deformed with an appropriate amount of deformation without being excessively deformed. For this reason, the said ground pressure is disperse | distributed with little deformation amount of the tread shoulder end part 6 at the time of turning. As a result, it is possible to maintain steering stability when the ground pressure of the tread shoulder end portion 6 increases as during turning.

  FIG. 3 is a partial cross-sectional view of a heavy duty pneumatic tire in which the sub-groove is formed of a plurality of stages of grooves. FIG. 4 is a partial perspective view of the heavy duty pneumatic tire of FIG. 3. 3 and FIG. 4 are the same as those in FIG. 1 and FIG. 2 except for the parts described below, and thus the description thereof is omitted and the same reference numerals are given. The heavy duty pneumatic tire of the present invention can be implemented in other forms than the above, and can also be implemented in the form as shown in FIG. That is, the sub-groove 13 in FIG. 1 is formed in one step, whereas the sub-groove 33 in FIG. 3 is formed in two steps. As a result, the entire groove portion 31 is formed of three stages of grooves. In the groove portion 31 of FIG. 3, the main groove 32 is formed of a single-stage groove as in the main groove 12 of FIG. 1, and the sub-groove 33 is formed of the first sub-groove 35 and the second sub-groove 39. .

  The first sub-groove 35 is formed at the bottom of the main groove in the same manner as described above, and is formed in substantially the same shape as the sub-groove 33 at a depth deeper than the main groove 32 in the groove portion 31. . That is, the first sub-groove opening 36 is formed in the main groove bottom 34, and the first sub-groove wall surface 37 further extends inwardly in the tire width direction from the first sub-groove wall surface 37. A first sub-groove bottom 38 is provided at the end. A second sub-groove opening 40 is formed in the first sub-groove bottom 37.

The relationship between the first sub-groove 35 and the second sub-groove 39 is the same as the relationship between the main groove 32 and the sub-groove 33 of the groove portion 31 described above. Two sub-grooves 39 are formed. For this reason, two sets of second sub-groove wall surfaces 41 face each other from the outer side or the inner side in the tire radial direction toward the inner side in the tire width direction from the second sub-groove opening 40. Sina has been kicked et al set. Further, a second sub-groove bottom portion 42 is formed on a surface substantially parallel to the buttress portion 7 on the inner side in the tire width direction of the second sub-groove wall surface 41. Since the second sub-groove 39 has the second sub-groove opening 40 provided in the first sub-groove bottom 38 as described above, the groove width of the second sub-groove 39 is the groove of the first sub-groove 35. It is narrower than the width. Further, since the first sub groove 35 is provided with the first sub groove opening 36 at the main groove bottom 34, the groove width of the first sub groove 35 is narrower than the groove width of the main groove 32. . As described above, the groove portion 31 including the main groove 32, the first sub-groove 35, and the second sub-groove 39 is continuously provided over the entire circumference of the buttress portion 7 along the tire circumferential direction. . The position is provided at a position that falls within the range of 80% to 150% of the depth of the longitudinal groove 3 from the tread shoulder end 6 toward the inside in the tire radial direction. Further, the groove 31 is formed so that the total depth of the main groove 32 and the sub-groove 33 falls within a range of 2 mm to 10 mm.

  When a vehicle such as a truck equipped with the heavy duty pneumatic tire 30 is traveling, the ground pressure at the tread shoulder end 6 increases when the vehicle turns. In such a case, in the groove portion 31, the sub-groove 33 is formed of a two-stage groove, and therefore the entire groove section 31 is formed of a three-stage groove. As a result, the ground contact pressure is distributed by the main groove 32, the first sub-groove 35, and the second sub-groove 39 of the groove portion 31, so that a larger pressure can be dispersed by the groove portion 31. As a result, even when an excessive grounding pressure is applied to the tread shoulder end 6 during turning, the pressure can be dispersed, so that chipping or baldness of the tread shoulder end 6 can be suppressed. Furthermore, since the force is further dispersed by the groove portion 31, the force transmitted to each portion of the groove portion 31 becomes smaller, and cracks due to stress concentration can be further suppressed.

  Further, since the groove portion 31 is formed by three stages of grooves, the ground contact pressure is distributed and received by each groove, so that the deformation amount of the entire groove portion 31 is further reduced. As a result, the amount of deformation of the tread shoulder end 6 is further reduced, and it becomes easier to maintain the steering stability when receiving an excessive ground pressure. In addition, by increasing the number of grooves forming the groove 31, the surface area such as the wall surface of the groove is further increased. As a result, since heat dissipation becomes further higher, deterioration due to heat is further suppressed, and durability is further improved.

  FIG. 5 is a partial cross-sectional view of a heavy duty pneumatic tire in which the secondary grooves are formed in a corrugated shape. 6 is a partial perspective view of the heavy duty pneumatic tire of FIG. FIG. 7 is a view taken along arrow AA in FIG. 8 is a cross-sectional view taken along the line BB in FIG. 9 is a cross-sectional view taken along the CC line in FIG. 5 to 9 are the same as those in FIG. 1 and FIG. 2 except for the parts described below, so the description thereof is omitted and the same reference numerals are given. The secondary groove of the groove portion provided in the heavy duty pneumatic tire of the present invention is not shaped along the tire circumferential direction of the buttress portion as described above, but also formed into a corrugated shape and shaped along the tire circumferential direction of the buttress portion. Can be implemented. In the groove 51 of FIG. 5, the main groove 53 is provided on the buttress portion 7 over the entire circumference in the tire circumferential direction, similarly to the main groove 12 of the groove 11 of FIG. 2. The main groove 53 has the same shape as that of the main groove 12 and has a main groove wall surface 55 and a main groove bottom portion 56 formed therein. The auxiliary groove 58 is formed inward of the main groove 53 in the tire width direction.

  The sub-groove 58 is provided over the entire circumference in the tire circumferential direction as in the main groove 53, but is not provided in a simple circle but is provided while forming a waveform in the tire radial direction. Yes. That is, the sub-groove wall surface 59 is formed with a predetermined inclination angle with respect to the normal line 52 on the outer surface of the tire. That is, when the groove 51 is viewed from the main groove opening 54 toward the sub-groove bottom 60, the sub-groove wall 59 has an angle of 5 ° toward the opposing sub-groove wall 59. It is formed in a range of an angle of ˜45 °.

  In other words, while the sub-groove wall surface 59 is formed so that the angle f and the angle g of the sub-groove wall surface 59 of the sub-groove wall surface 59 of FIGS. The bottom 60 is formed to have a constant width. Within this range, the sub-groove 58 is formed while the angle of the sub-groove wall surface 59 changes periodically. The period is a period that falls within the range of W1 × 2 ≦ P ≦ W1 × 15 when the width of the main groove 53 is W1 and the period is P, and the inclination angle of the sub-groove wall surface 59 is It has changed.

  That is, the pitch of the corrugation that the sub-groove 58, specifically, the sub-groove bottom 60 forms in the tire radial direction or the groove width direction is P, and P is in the range of W1 × 2 ≦ P ≦ W1 × 15. The sub-groove bottom 60 is formed so as to enter. As a result, the sub-groove center line 61 that is a line passing through the center of the sub-groove bottom 60 in the width direction has a waveform with the period of P. For this reason, the sub-groove center line 61 is longer between the sub-groove center line 61 and the main groove center line 57 that is a line passing through the center of the main groove opening 54 in the width direction. With this shape, the sub-groove 58 is formed in the buttress portion 7, and other shapes are the same as those of the groove portion 11.

  If the vehicle turns, such as a truck, to which the heavy duty pneumatic tire 50 is attached, the ground pressure at the tread shoulder end 6 increases when the vehicle turns. In this case, the groove 51 formed in the heavy-duty pneumatic tire 50 is formed of a main groove 53 and a sub-groove 58, and the sub-groove 58 is provided while forming a waveform in the tire radial direction. ing. Thereby, since the area of the sub-groove wall surface 59 increases, the force can be received in a more dispersed manner, and the excessive ground pressure applied to the tread shoulder end portion 6 can be further dispersed. As a result, chipping or baldness due to pressure applied to the tread shoulder end 6 during turning can be further suppressed. Moreover, since the area of the sub-groove wall surface 59 is formed large, the groove 51 is formed with high strength. For this reason, even when the ground contact pressure is dispersed, it can be dispersed with a smaller amount of deformation. As a result, the amount of deformation of the tread shoulder end 6 is also reduced, so that it is easy to maintain steering stability. Moreover, since the sub-groove wall surface 59 is formed in the waveform shape, the surface area is large. For this reason, the heat dissipation is higher. As a result, durability against deterioration due to heat is further improved.

  Further, since the waveform of the secondary groove 58 formed in the tire radial direction is provided on the entire circumference of the buttress portion 7 in the tire circumferential direction, the area of the secondary groove wall surface 59 can be increased in the tire circumferential direction on average. . Further, since the auxiliary groove wall surface 59 is formed in a corrugated shape, the force applied to the auxiliary groove 58 can be further dispersed. As a result, chipping and scalding can be more effectively suppressed with respect to the contact pressure of any part of the tread shoulder end portion 6 in the tire circumferential direction, and cracks can be further suppressed. Further, the corrugated pitch P of the sub-groove 58 is formed to be twice or more the groove width W 1 of the main groove 53. Thereby, the groove part 51 including the sub-groove 58 can disperse the excessive ground pressure to the tread shoulder end part 6. As a result, it becomes easier to suppress chipping and balding of the tread shoulder end portion 6 due to the contact pressure during turning. Further, the corrugated pitch P of the sub-groove 58 is formed to be not more than 15 times the groove width W 1 of the main groove 53. Thereby, the strength is reliably improved by the waveform of the sub-groove 58, and therefore the strength of the groove portion 51 including the sub-groove 58 can be reliably improved. As a result, it becomes easier to maintain the steering stability during turning.

  Further, the sub-groove wall surface 59 inclined to form the corrugation is inclined within a range of 5 ° to 45 ° from the normal line 52 of the tire outer surface. The ground pressure applied to the tread shoulder end portion 6 can be dispersed with an appropriate strength without excessively increasing the strength. As a result, by dispersing the ground pressure applied to the tread shoulder end portion 6 at the time of turning, it is possible to more surely suppress chipping, baldness, etc., and to further maintain the steering stability. Further, when the inclination of the sub-groove wall surface 59 is large, the formation of the sub-groove 58 becomes difficult. However, since the inclination is at the above-mentioned angle, it can be easily formed. As a result, an increase in cost when forming the sub-groove 58 in a waveform can be reduced.

  FIG. 10 is a partial cross-sectional view of a heavy duty pneumatic tire in which the auxiliary grooves are formed by combining substantially triangular pyramid shapes. 11 is a partial perspective view of the heavy duty pneumatic tire of FIG. FIG. 12 is a DD arrow view of FIG. 13 is a cross-sectional view taken along the line EE in FIG. 10 to 13 are the same as those shown in FIGS. 1 and 2 except for the portions described below, and therefore the description thereof is omitted and the same reference numerals are given. The secondary groove of the groove portion provided in the heavy-duty pneumatic tire of the present invention is not a shape along the tire circumferential direction of the buttress portion as shown in FIG. 2, but a shape approximating a triangular pyramid is combined, and the buttress portion has a combined shape. It can also be carried out along the tire circumferential direction. In the groove portion 71 of FIG. 10, the main groove 72 is provided over the circumference of the buttress portion 7 along the tire circumferential direction, similarly to the main groove 12 of the groove portion 11 of FIG. 2. The main groove 72 has a main groove wall surface 74 and a main groove bottom 75 having the same shape as the main groove 12. The sub-groove 76 is formed inside the main groove 72 in the tire width direction. The sub-groove 76 is provided over the entire circumference in the tire circumferential direction as in the case of the main groove 72. A plurality of triangular pyramids 80 are formed in combination such that the portion 77 has a direction in which the apex side 82 is at the back of the groove. Further, the sub-groove bottom portion 79 is formed to be parallel to the buttress portion 7 by removing the corner portion on the apex side 82.

  Specifically, the side a which is one side of the virtual bottom surface 81 of the triangular pyramid 80 is formed in a direction parallel to the main groove opening 73 of the main groove 72, and the side a parallel to the main groove opening 73 is A part of the sub-groove opening 77 is formed in the main groove bottom 75. Similarly, the triangular pyramid 80 adjacent to the triangular pyramid 80 is formed so that the side a, which is one side of the virtual bottom surface, is oriented in parallel with the main groove opening 73. The side a of the triangular pyramid 80 is formed as a part of the sub-groove opening 77 on the side facing the sub-groove opening 77 formed. Further, although the lengths of the two sides a are the same, the triangular pyramid 80 is formed so that the sides a are located at positions shifted by ½ of the length. Further, the end of each side a is in contact with the corner b of the virtual bottom surface 81 of the other triangular pyramid 80 facing the side a. That is, the virtual bottom surface 81 of the triangular pyramid 80 is formed in an isosceles triangle, and a side sandwiched between two sides of equal length is a side a that becomes a part of the main groove opening 73, The angle b sandwiched between equal lengths is in contact with the end of the side of the virtual bottom surface 81 of the adjacent triangular pyramid 80.

  Further, the virtual corners 83 that face the virtual bottom surface 81 of each triangular pyramid 80 and become the apex side 82 are inclined to the side a side that forms the main groove opening 73 of the self, respectively. When the sub-grooves 76 are viewed in the tire circumferential direction, the imaginary corner portions 83 are formed to be staggered. The surface of the triangular pyramid 80 other than the virtual bottom surface 81 is formed as a sub-groove wall surface 78. The imaginary corner 83 is removed as described above, and the shape after the removal is formed as a plane parallel to the imaginary bottom 81 of the triangular pyramid 80, and this portion becomes the sub-groove bottom 79. The sub-grooves 76 are formed such that the triangular pyramids 80 having such a positional relationship and shape are continuous in the tire circumferential direction. In the case of this groove portion 71, the surface of the apex side 82 is used as the sub-groove bottom portion 79, and the total depth of the main groove 72 and the sub-groove 76 is formed in the range of 2 mm to 10 mm as in the above-described groove portion 11 To do.

  When the groove portion 71 having the secondary groove 76 having such a shape is formed in the buttress portion 7 of the heavy duty pneumatic tire 70, the secondary groove wall surface 78 has irregularities not only in the tire radial direction but also in the tire width direction. Since it has, it can disperse | distribute the pressure with respect to the pressure from all directions concerning the tread shoulder edge part 6, and can also ensure intensity | strength. As a result, even when the contact pressure applied to the tread shoulder end 6 is applied not only in the tire radial direction but also from other directions, the pressure can be dispersed, so that the tread shoulder end 6 can be more reliably chipped. Can be suppressed. Furthermore, since the sub-groove wall surface 78 has irregularities also in the tire width direction, it has strength against pressure from the oblique direction to the tread shoulder end portion 6 and reliably maintains steering stability. Can do.

  14 and 15 are partial perspective views of a heavy duty pneumatic tire in which grooves are formed discontinuously. 14 and 15 are the same as those shown in FIGS. 1 and 2 except for the parts described below, so the description thereof is omitted and the same reference numerals are given. The groove provided in the heavy duty pneumatic tire of the present invention can be implemented not only in the shape of the buttress portion continuous along the tire circumferential direction as shown in FIG. 2, but also in the shape of being discontinuously formed in the tire circumferential direction. The shape of FIG. 14 is a shape in which the groove 11 of FIG. 2 is simply discontinuous. For this reason, each groove portion 91 is provided with a main groove 92 and a sub groove 93 as in the case of the groove portion 11 of FIG. Further, in FIG. 15, the groove portions 95 are arranged so as to be shifted in the tire radial direction, and further, the groove portions 95 different in the tire radial direction are arranged so as to overlap in the tire circumferential direction. In this case, all the groove portions 95 are provided at positions that fall within a range of 80% to 150% of the depth of the longitudinal groove 3 from the tread shoulder end portion 6 inward in the tire radial direction.

  Even in the case where the groove portions 91 and 95 are discontinuously formed in the tire circumferential direction of the buttress portion 7 in the heavy load pneumatic tire 90 as described above, the effect as described above can be obtained if it is formed discontinuously over one lap. Therefore, it is possible to suppress chipping of the tread shoulder end 7 during turning and maintain steering stability. In particular, like the groove portions 95 formed in the heavy duty pneumatic tire 90 of FIG. 15, the plurality of groove portions 95 are also shifted in the tire circumferential direction while being shifted in the tire radial direction. When the groove portion 95 is provided somewhere in the direction, chipping of the tread shoulder end portion 7 can be reliably suppressed, and steering stability can be maintained. Further, by forming the groove portions 91 and 95 discontinuously, the shape of the groove portions 91 and 95 and the degree of freedom of arrangement are improved. As a result, by devising the shape and arrangement, the groove portions 91 and 95 can be used as a design such as a pattern, so that the aesthetic appearance of the heavy duty pneumatic tire 90 can be improved.

  16 and 17 are partial cross-sectional views of the heavy duty pneumatic tire formed with the sub-grooves shifted from the main grooves. 16 and FIG. 17 are the same as those in FIG. 1 and FIG. 2 except for the parts described below, so the description thereof is omitted and the same reference numerals are given. The secondary groove of the heavy duty pneumatic tire of the present invention is not located at the same center position in the width direction of the main groove 12 as the secondary groove 13 in the groove portion 11 of FIG. , Even if they are out of place. For example, the groove 101 in FIG. 16 is formed by shifting the main groove 102 and the sub-groove 103, and the other shapes are the same as the groove 11 in FIG. In addition, the groove portion formed by shifting the grooves in this way is not limited to the case where the main groove and the sub-groove are misaligned, but the sub-groove 113 is the first sub-groove 114 and the second sub-groove as in the groove portion 111 of FIG. 115, and the first sub-groove 114 and the second sub-groove 115 are formed in a shifted manner. The groove 111 is formed by shifting the main groove 112, the first groove 114, and the second groove 115, and the other shapes are the same as the groove 31 of FIG. Moreover, even when the groove part 111 is formed by a groove having a higher number of stages, each groove can be formed by being shifted.

  As described above, when a plurality of grooves formed in the groove portion are shifted, one of the two sub-groove wall surfaces 105 is formed continuously with the main groove wall surface 104 of the two sub-groove wall surfaces 105. Becomes easier. As a result, the manufacturing cost can be reduced when the groove portion is formed by a plurality of grooves in order to obtain the effect of suppressing the chipping of the tread shoulder end portion 7 as described above or maintaining the steering stability. it can.

Hereinafter, we have heavy duty pneumatic tire Nitsu above will be described evaluation test performance conducted on the conventional heavy duty pneumatic tire and heavy-duty pneumatic tire of Reference Example. The evaluation test was conducted with respect to uneven wear resistance, crack resistance, steering stability, and heat dissipation against wear including chipping and baldness.

  The test method was performed by attaching 11R22.5 size tires to a 22.5 × 7.50 rim, attaching the tires to a vehicle type 2D-4 truck, and setting the internal pressure to 700 kPa. About uneven wear resistance and crack resistance, after running 50,000 km on the aforementioned track, the wear state of the tread shoulder end was checked, and the wear state of the heavy-duty pneumatic tire with no grooves formed was set to 100. Indicated by an index. The larger the index, the better the uneven wear. In addition, the crack confirmed the presence or absence of the crack of a groove part visually. Regarding steering stability, a test run was performed on the above-mentioned truck, and the feeling of each tire was scored by three test drivers. The larger the numerical value, the better the steering stability. Regarding heat dissipation, a heavy-duty pneumatic tire was loaded with a load of 2725 kg using an indoor drum tester, and the vehicle was run at a speed of 80 km / hr for a certain time, and the internal temperature at the end of the tread shoulder was measured. The measurement results are shown as an index with the heat dissipation of a heavy duty pneumatic tire having no groove formed in the buttress portion as 100. The larger the index, the better the heat dissipation.

Heavy duty pneumatic tire to be tested, the three as a comparative example to be compared with the reference example, three types as a reference example, tested in the above test methods. The shape of the buttress portion of each of the heavy duty pneumatic tires of Comparative Examples 1 to 3, which is a conventional example, is that Comparative Example 1 has no groove in the buttress portion, and Comparative Example 2 has a single groove in the buttress portion. In Comparative Example 3, two small grooves of one step are formed in the tire radial direction.

Moreover, the shape of the groove part formed in the buttress part of each heavy load pneumatic tire of Reference Examples 1 to 3 is the same as that of the groove part 11 in FIG. A groove portion 11 is formed, and the groove portion 11 is formed by two stages of a main groove 12 and a sub groove 13 . Ginseng Reference Example 2 is formed in the same shape as the groove 101 in FIG. 16, the same manner as in Reference Example 1, the groove 101 is formed by the main grooves 102 and the sub-grooves 103, but one of the main groove wall 104 and one sub-groove wall surface 105 are formed by a continuous surface. The reference example 3 is formed in the same shape as the groove portion 111 of FIG. 17, the groove portion 111 formed in the buttress portion 7 is formed by the main groove 112 and the sub groove 113, and the sub groove is formed by the two-stage groove. is doing. The Comparative Example 1-3 及 beauty of Reference Example 1-3 heavy duty pneumatic tire, and the evaluation test by the method described above, Table 1 shows the results obtained.

As shown in Table 1, the test results of the above-described evaluation tests for the respective heavy-duty pneumatic tires are as follows. In Comparative Example 1, comparative wear resistance and heat dissipation are based on Comparative Example 1. Both are 100. In addition, steering stability = 3. In Comparative Example 2, uneven wear resistance = 105, steering stability = 2.5, and heat dissipation = 105. Moreover, in this comparative example 2, the crack has generate | occur | produced in the groove bottom. In Comparative Example 3, uneven wear resistance = 102, steering stability = 3, and heat dissipation = 103. In Comparative Example 3, cracks are generated at the groove bottom. In Reference Example 1, uneven wear resistance = 108, steering stability = 3, and heat dissipation = 104. In the reference example 1, no crack is generated at the groove bottom. In Reference Example 2 , uneven wear resistance = 108, steering stability = 3, and heat dissipation = 104. In the reference example 2 , no crack is generated at the groove bottom. In Reference Example 3 , uneven wear resistance = 108, steering stability = 3, and heat dissipation = 104. In Reference Example 3 , no cracks are generated at the groove bottom.

As is clear from the above test results, by forming a groove in the buttress 7, the ground contact pressure of the tread shoulder end 6 that increases during turning can be dispersed in the groove, so that the tread shoulder end 6 can be chipped and burned. Further, uneven wear resistance against wear is improved. Furthermore, as in Reference Examples 1 to 3, the groove portion is formed by a plurality of grooves, so that the ground pressure can be distributed among the individual grooves. Therefore, the deformation amount of the groove portion when the ground pressure is distributed can be reduced. Less. Thereby, since the deformation amount of the tread shoulder end portion 6 is also reduced, the steering stability when the groove portion is formed in the buttress portion 7 can be maintained. Further, as described above, since the ground pressure is dispersed in the plurality of grooves, the concentration of stress is relaxed, and the occurrence of cracks at the bottom of the groove can be suppressed. Furthermore, by forming the groove portion with a plurality of grooves, the area of the wall surface of the groove is increased, so that heat dissipation is improved. As a result, by forming a groove portion formed of a plurality of steps in the buttress portion 7, the tread shoulder end portion 6 that becomes large at the time of turning can be maintained while maintaining the steering stability of the vehicle equipped with the heavy duty pneumatic tire. Uneven wear including chipping and the like due to the ground contact pressure can be suppressed.

  In addition, although it is preferable to form the said groove part in the buttress part 7 over 1 round in a tire peripheral direction, you may form discontinuously. The effect similar to the groove part formed continuously can be acquired by making the length and space | interval of a groove part appropriate. Alternatively, the main groove may be formed in the buttress portion 7 over one circumference in the tire circumferential direction, and the sub-grooves may be formed discontinuously. Also in this case, by making the length and interval of the sub-grooves appropriate, it is possible to obtain the same effect as the groove portion in which the sub-grooves are continuously formed. Further, as described above, the shape of the sub-groove may be a combination of corrugated or triangular pyramid shapes, or other shapes. In short, by providing the buttress portion 7 with a groove portion composed of at least two or more grooves, the tread shoulder end portion 6 can be prevented from being chipped while maintaining the steering stability as described above. Furthermore, in order to obtain a more reliable effect, the number of grooves, the shape of the sub-groove, and the like may be determined according to the ground pressure applied to the tread shoulder end 6 and other usage conditions.

  As described above, the heavy-duty pneumatic tire according to the present invention is effective in suppressing chipping and baldness at the tread shoulder end, and in particular, suppressing chipping at the tread shoulder end as described above. However, it is suitable for maintaining steering stability.

1 is a partial cross-sectional view of a heavy duty pneumatic tire according to the present invention. FIG. 2 is a partial perspective view of the heavy duty pneumatic tire of FIG. 1. FIG. 3 is a partial cross-sectional view of a heavy duty pneumatic tire in which a secondary groove is formed by a plurality of stages of grooves. FIG. 4 is a partial perspective view of the heavy duty pneumatic tire of FIG. 3. It is a partial sectional view of a heavy duty pneumatic tire in which a minor groove is formed in a corrugated shape. FIG. 6 is a partial perspective view of the heavy duty pneumatic tire of FIG. 5. It is AA arrow line view of FIG. It is BB sectional drawing of FIG. It is CC sectional drawing of FIG. FIG. 2 is a partial cross-sectional view of a heavy duty pneumatic tire in which sub-grooves are formed by combining substantially triangular pyramid shapes. It is a partial perspective view of the heavy duty pneumatic tire of FIG. It is DD arrow line view of FIG. It is EE sectional drawing of FIG. It is a partial perspective view of a heavy duty pneumatic tire in which grooves are formed discontinuously. It is a partial perspective view of a heavy duty pneumatic tire in which grooves are formed discontinuously. FIG. 3 is a partial cross-sectional view of a heavy duty pneumatic tire formed with a sub-groove deviated from the main groove. FIG. 3 is a partial cross-sectional view of a heavy duty pneumatic tire formed with a sub-groove deviated from the main groove.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heavy load pneumatic tire 2 Tread part 6 Tread shoulder end part 7 Buttress part 11 Groove part 12 Main groove 13 Sub groove 14 Opening part 15 Main groove wall surface 16 Main groove bottom part 17 Sub groove opening part 18 Sub groove wall part 19 Sub groove bottom part 30 Heavy-duty pneumatic tire 31 Groove portion 32 Main groove 33 Sub groove 34 Main groove bottom portion 35 First sub groove 36 First sub groove opening portion 37 First sub groove wall surface 38 First sub groove bottom portion 39 Second sub groove 40 Second sub groove Groove opening 41 Second sub-groove wall 42 Second sub-groove bottom 50 Heavy load pneumatic tire 51 Groove 52 Tire outer surface normal 53 Main groove 54 Main groove opening 55 Main groove wall 56 Main groove bottom 57 Main groove center Wire 58 Secondary groove 59 Secondary groove wall surface 60 Secondary groove bottom 61 Secondary groove center line 70 Heavy load pneumatic tire 71 Groove portion 72 Main groove 73 Main groove opening portion 74 Main groove wall surface 75 Main groove bottom portion 76 Secondary groove 7 Sub groove opening 78 Sub groove wall 79 Sub groove bottom 80 Triangular pyramid 81 Virtual bottom surface 82 Apex side 83 Virtual corner 90 Heavy load pneumatic tire 91 Groove 92 Main groove 93 Sub groove 95 Groove 101 Groove 102 Main groove 103 Sub groove 104 Main groove wall surface 105 Sub groove wall surface 111 Groove portion 112 Main groove 113 Sub groove 114 First sub groove 115 Second sub groove

Claims (5)

In a heavy duty pneumatic tire in which a groove portion is provided in the tire circumferential direction in a buttress portion formed outward in the tire width direction of the tread portion,
The groove portion is formed continuously or discontinuously, and the opening has a main groove formed in the buttress portion, and has an opening at the bottom of the main groove, and from the opening to the groove portion. Formed by a sub-groove formed in the depth direction of
The sub-groove has a shape in which the center line of the bottom of the sub-groove is different from the shape of the center line of the opening of the main groove, and the bottom of the sub-groove is periodically corrugated in the width direction of the sub-groove. Formed with
The corrugations forming the sub-grooves are formed such that W1 × 2 ≦ P ≦ W1 × 15, where W1 is the width of the main groove and P is the pitch of the corrugations. Heavy duty pneumatic tire.   The groove portion is a longitudinal portion provided in the tire circumferential direction on the tread portion of the heavy duty pneumatic tire from the tread shoulder end portion, which is the end portion in the tire width direction of the tread portion, in the tire radial direction. The heavy-duty pneumatic tire according to claim 1, wherein the heavy-duty pneumatic tire is provided at a position within a range of 80% to 150% of a depth of the groove.   3. The heavy duty pneumatic tire according to claim 1, wherein the groove has a depth of 2 mm to 10 mm. The length of the central line of the bottom portion of the sub groove, heavy duty pneumatic tire according to claim 1, characterized in longer than the length of the center line of the opening of the main groove . The wall surface forming the secondary grooves, any one of the preceding claims, characterized in that it is periodically changed to tilt in the range of 5 ° to 45 ° with respect to the normal of the outer surface of the tire Heavy duty pneumatic tire as described in 1.

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