JP2019127109A - Pneumatic tire - Google Patents

Abstract

To provide a pneumatic tire that can make both uneven wear resistance and low-heat-generation performance compatible.SOLUTION: A plurality of lug main grooves 11 inclining symmetrically at both sides of a tire equator are formed in a tread part 1; inclination angles α of the lug main grooves are in a range shown by a relational expression of 15°≤α≤45°; and end parts at the equator side thereof are in a range of 5%-20% of a tread width TW from the tire equator. In the tread part are formed shoulder inclined grooves 12 inclined in the opposite direction of the direction of the lug main grooves, through which the lug main grooves are connected to each other. Center positions of the shoulder inclined grooves are arranged in a range of 15%-35% of the tread width from the tire equator and the center lines of the shoulder inclined grooves intersect with the lug main grooves at both sides, at two intersection points P1 and P2. A difference between distances L1 and L2 from the tire equator to the intersection points P1 and P2 satisfies a relational expression of TW×0.03≤|L1-L2|≤TW×0.2. A center groove 13 continuously extending in a circumferential direction is arranged in a range of 20% or less of the tread with from the tire equator, whose groove width W3 is 2%-10% of the tread width.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire suitable for use in construction vehicles, and particularly suitable for use in scraper vehicles, and more particularly to a pneumatic tire capable of achieving both uneven wear resistance and low heat buildup.

  In pneumatic tires applied to construction vehicles typified by scraper vehicles, since traction performance is important, a plurality of lugs extending in the tire width direction on both sides of the tire equator in the tread portion and opening at the tread end A tread pattern having a groove is generally employed (see, for example, Patent Document 1).

  In particular, a directional tread pattern is effective to ensure traction performance (see, for example, Patent Documents 2 to 4). However, in the pneumatic tire for construction vehicles as described above, when the directional tread pattern is adopted, the traction performance is significantly reduced if the rotational direction is changed by rotation when uneven wear occurs. Therefore, in the pneumatic tire of this type, there is a problem that it is difficult to secure good uneven wear resistance when trying to secure traction performance based on a directional tread pattern. In addition, in the pneumatic tire for construction vehicles as described above, since long-distance travel is performed under severe conditions, low heat buildup is required from the viewpoint of durability.

JP, 2006-215661, A JP, 2001-63319, A JP2013-159321A JP 2014-234091 A

  An object of the present invention is to provide a pneumatic tire capable of achieving both uneven wear resistance and low heat buildup.

A pneumatic tire according to the present invention for achieving the above object comprises a tread portion extending in the circumferential direction of the tire to form an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and these sidewall portions A pneumatic tire comprising a pair of bead portions disposed on the inner side in the tire radial direction of
A plurality of lug main grooves extending in the tire width direction on both sides of the tire equator and opening at the tread end are formed in the tread portion, and the lug main grooves are symmetrically inclined with respect to the tire width direction on both sides of the tire equator The end of the lug main groove on the tire equator side is disposed in the range of 5% to 20% of the tread width TW from the tire equator, and the inclination angle α of the lug main groove with respect to the tire width direction is the tread width from the tire equator It is set in a range of 15 ° ≦ α ≦ 45 ° at a position of 25% of TW,
A plurality of shoulder inclined grooves are formed in the tread portion to connect the lug main grooves adjacent to each other in the tire circumferential direction, and the shoulder inclined grooves are inclined in the opposite direction to the corresponding lug main grooves. Center position of the shoulder is arranged in the range of 15% to 35% of the tread width TW from the tire equator, and the center line of the shoulder inclined groove intersects with the lug main groove on both sides at two intersection points P1 and P2 The difference between the distance L1 from the tire equator of the intersection point P1 of the tire and the distance L2 from the tire equator of the other intersection point P2 with respect to the tread width TW is TW × 0.03 ≦ | L1-L2 | ≦ TW × 0.2 Satisfied with the relationship
A center groove extending continuously in the circumferential direction of the tire without being communicated with the main groove is formed between the main grooves of the lug on both sides of the tire equator in the tread portion, and the center groove is a tread from the equator of the tire It is arranged within a range of 20% or less of the width TW, and the groove width W3 of the center groove is 2% to 10% of the tread width TW.

  In the present invention, in the tread portion, a plurality of lug main grooves extending in the tire width direction and opening at the tread end, a plurality of shoulder inclined grooves connecting the lug main grooves adjacent to each other in the tire circumferential direction, and the tire equator And a center groove extending continuously in the tire circumferential direction without communicating with the lug main groove between the lug main grooves located on both sides of the lug, and in the inclination direction of the lug main groove, the tire of the lug main groove Tires at intersections P1 and P2 where the end position on the equator side, the inclination angle α of the lug main groove, the inclination direction of the shoulder inclination groove, the center position of the shoulder inclination groove, and the center line of the shoulder inclination groove intersect the main lug groove By defining the difference between the distances L1 and L2 from the equator (| L1−L2 |), the position of the center groove, and the groove width W3 of the center groove, the traction performance is ensured based on the directional tread pattern. In the pneumatic tire, while improving the low heat buildup and sufficient heat dissipation during tire running, it is possible to improve the uneven wear resistance. Also, ensuring low heat build-up contributes to improved durability.

  In the present invention, it is preferable that the shortest distance in the tire width direction between the end on the tire equator side of the lug main groove and the center groove be 0% to 15% of the tread width TW. As a result, the width of the center rib defined between the lug main groove and the center groove can be narrowed to reduce heat generation in the center rib.

  In the present invention, the position of the lug main groove is shifted in the tire circumferential direction on both sides of the tire equator, and the positional shift amount S1 of the lug main groove is 0.3 with respect to the pitch P of the lug main groove in the tire circumferential direction. While satisfying the relationship of ≦ S1 / P ≦ 0.5, the center groove has a zigzag shape, the cycle T in the tire circumferential direction of the center groove is the same as the pitch P in the tire circumferential direction of the lug main groove, The amount of misalignment S2 in the tire circumferential direction between the end of the lug main groove on the tire equator side and the center groove bending point farthest from the end in the tire width direction is the pitch P of the lug main groove in the tire circumferential direction. However, it is preferable to satisfy the relationship of S2 / P ≦ 0.1. By shifting the position of the main groove of the lug in the circumferential direction of the tire on both sides of the tire equator in this way, the contact pressure rise instantaneously and the sudden deformation of the block end during tire rotation are suppressed, and heat generation in the tread portion is realized. It can be reduced. Further, by reducing the amount of misalignment S2 in the tire circumferential direction between the end of the lug main groove on the tire equator side and the bending point of the center groove that is farthest from the end in the tire width direction, uneven wear resistance is reduced. The property can be maintained well.

  In the present invention, the center groove has a zigzag shape, and the overlapping distance X in the tire width direction of both wall surfaces of the center groove has a relationship of TW × 0.01 ≦ X ≦ TW × 0.3 with respect to the tread width TW. It is preferable to be satisfied. Thereby, the heat dissipation effect by the airflow flowing in the center groove can be sufficiently secured and the low heat generation property can be improved.

  The groove depth D2 of the shoulder inclined groove satisfies the relationship of 0.3 ≦ D2 / D1 ≦ 0.7 with respect to the groove depth D1 of the lug main groove at a position 25% of the tread width TW from the tire equator. preferable. Thus, by making the shoulder inclined groove shallower than the lug main groove, the rigidity of the land portion in the vicinity of the shoulder inclined groove can be secured, and both uneven wear resistance and low heat generation can be achieved.

  The groove depth D3 of the center groove preferably satisfies the relationship of 0.3 ≦ D3 / D1 ≦ 0.8 with respect to the groove depth D1 of the lug main groove at a position 25% of the tread width TW from the tire equator. . By making the center groove shallower than the lug main groove in this way, the rigidity of the land portion in the vicinity of the center groove can be ensured, and both uneven wear resistance and low heat generation can be achieved.

  At the bottom of the center groove, a narrow groove extending in the longitudinal direction of the center groove is formed, and the groove width W4 of the narrow groove is 0.1 ≦ W4 / W3 ≦ 0.5 with respect to the groove width W3 of the center groove. It is preferable to satisfy the relationship of By providing the narrow groove in the bottom of the center groove disposed in the center region of the tread portion where the contact pressure becomes high, the heat radiation efficiency can be enhanced and the low heat buildup can be effectively improved. In addition, since the narrow groove is narrower than the center groove, the rigidity of the center rib partitioned between the lug main groove and the center groove is not impaired, heat generation due to the movement of the center rib is suppressed, and uneven wear resistance is improved. be able to.

The groove depth D4 of the narrow groove with respect to the tread surface is 0.5 ≦ D4 / D1 ≦ 1.0 with respect to the groove depth D1 of the lug main groove at a position 25% of the tread width TW from the tire equator. It is preferable to satisfy the relationship of By defining the groove depth D4 of the narrow groove in this way, it is possible to achieve both uneven wear resistance and low heat generation without impairing the rigidity of the center rib.

  An additional lug groove extending in the same direction as the lug main groove and communicating with the center groove is formed between the center groove and the shoulder inclined groove, and the groove width W5 of the additional lug groove is smaller than the groove width W3 of the center groove. It is preferable to satisfy the relationship of 0.2 ≦ W5 / W3 ≦ 1.0. Traction performance can be improved by providing an additional lug groove in the center region of the tread portion where the contact pressure increases.

  The groove depth D5 of the additional lug groove satisfies the relationship of 0.3 ≦ D5 / D1 ≦ 0.7 with respect to the groove depth D1 of the lug main groove at a position 25% of the tread width TW from the tire equator. preferable. By thus defining the groove depth D5 of the additional lug groove, the rigidity of the center rib defined between the main groove of the lug and the center groove is not impaired, and both the uneven wear resistance and the low heat buildup are achieved. , Traction performance can be improved.

 In the present invention, the tread width means the contact width in the tire axial direction measured when a tire is rimmed on a regular rim and filled with a regular internal pressure and placed vertically on a plane and a regular load is applied. Do. The tread end means an axial end (grounding end) in the tire axial direction of the grounding region specified by the grounding width. The “regular rim” is a rim that defines the standard for each tire in the standard system including the standard on which the tire is based, for example, the standard rim for JATMA, “Design Rim” for the TRA, or ETRTO Then, “Measuring Rim” is set. The “normal internal pressure” is the air pressure specified by each standard in the standard system including the standard to which the tire is based, and in the case of JATMA, the maximum air pressure, in the case of TRA, the table “TIRE ROAD LIMITS AT VARIOUS In the case of ETRTO, the maximum value described in COLD INFLATION PRESSURES is "INFLATION PRESSURE". The “regular load” is a load defined by each standard in the standard system including the standard to which the tire is based, and in the case of JATMA, the maximum load capacity, in the case of TRA, the table “TIRE ROAD LIMITS AT VARIOUS In the case of ETRTO, the maximum value described in COLD INFLATION PRESSURES is "LOAD CAPACITY".

  Each dimension in the present invention is measured in a state in which a tire is assembled on a regular rim and filled with a regular internal pressure.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is a top view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is sectional drawing which shows the tread part of the pneumatic tire which consists of embodiment of this invention. The airflow which arises in a tread part is shown, (a) is a top view which shows the airflow which arises in the structure of this invention, (b) It is a top view which shows the airflow produced in the conventional structure different from this invention. It is a top view which shows the center area | region of the tread pattern of the pneumatic tire which concerns on other embodiment of this invention. It is the VI-VI arrow sectional drawing of FIG. It is a top view which shows the tread pattern of the pneumatic tire which consists of further another embodiment of this invention. FIG. 8 is a sectional view taken along arrow VIII-VIII in FIG. 7. It is a top view which shows the tread pattern of the pneumatic tire which consists of another embodiment of this invention.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the attached drawings. 1 to 3 show a pneumatic tire for a scraper vehicle according to an embodiment of the present invention. Although only the structure on one side in the tire width direction than the tire equator CL is depicted in FIG. 1, this pneumatic tire also has a symmetrical structure on the other side. In FIG. 2, in order to facilitate understanding of the tread structure, a portion in contact with the road surface at the time of running the tire is depicted as a hatched portion.

  As shown in FIG. 1, the pneumatic tire of the present embodiment includes a tread portion 1 that extends in the tire circumferential direction and has an annular shape, and a pair of sidewall portions 2, 2 disposed on both sides of the tread portion 1. And a pair of bead portions 3 and 3 disposed inside the sidewall portion 2 in the tire radial direction. The tread portion 1 has a square shoulder, and the shoulder edge is a contact end.

  At least one carcass layer 4 is mounted between the pair of bead portions 3 and 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded from the inside of the tire to the outside around the bead core 5 disposed in each bead portion 3. As a reinforcing cord of the carcass layer 4, a steel cord is preferably used, but it is also possible to use an organic fiber cord such as polyester.

  A plurality of belt layers 6a, 6b, 6c and 6d are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 6a to 6d include a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and are arranged so that the reinforcing cords cross each other between arbitrary layers. In the belt layers 6a to 6d, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of 10 ° to 40 °, for example. Steel cords are preferably used as reinforcing cords for the belt layers 6a to 6d.

  In addition, although the tire internal structure mentioned above shows the typical example in a pneumatic tire, it is not limited to this.

  As shown in FIG. 2, a plurality of lug main grooves 11 extending in the tire width direction on both sides of the tire equator CL are formed in the tread portion 1 at intervals in the tire circumferential direction. Each of the lug main grooves 11 ends at an inner end in the tire width direction at a position separated from the tire equator CL, while an outer end in the tire width direction opens at the tread end. The lug main grooves 11 are inclined symmetrically with respect to the tire width direction on both sides of the tire equator CL. That is, the lug main groove 11 is inclined toward one side in the tire circumferential direction (opposite to the rotational direction R) toward the outer side in the tire width direction. The end of the lug main groove 11 on the tire equator CL side is disposed in the range of 5% to 20% of the tread width TW from the tire equator CL. That is, the distance X1 from the tire equator CL to the end of the lug main groove 11 on the tire equator CL side is set in the range of 5% to 20% of the tread width TW. Further, the inclination angle α of the lug main groove 11 with respect to the tire width direction is set in the range of 15 ° ≦ α ≦ 45 ° at a position of 25% of the tread width TW from the tire equator CL. The inclination angle α is the inclination angle of the center line of the lug main groove 11.

  The tread portion 1 is formed with a plurality of shoulder inclined grooves 12 that connect the lug main grooves 11 and 11 adjacent to each other in the tire circumferential direction. The shoulder inclined groove 12 is inclined in the opposite direction to the corresponding lug main groove 11. In other words, the shoulder inclined groove 12 is inclined in the opposite direction to the tire width direction with respect to the lug main groove 11 to which the shoulder inclined groove 12 is connected. The center position of the shoulder inclined groove 12 is arranged in the range of 15% to 35% of the tread width TW from the tire equator CL. That is, the distance X2 from the tire equator CL to the center position in the longitudinal direction and the width direction of the shoulder inclined groove 12 is arranged in the range of 15% to 35% of the tread width TW. The center line of the shoulder inclined groove 12 intersects the lug main grooves 11 on both sides at two intersections P1 and P2. The difference between the distance L1 from the tire equator CL at one intersection P1 located on the front side in the rotational direction R and the distance L2 from the tire equator CL at the other intersection P2 located on the rear side in the rotational direction R is the tread width. The relationship of TW × 0.03 ≦ | L1-L2 | ≦ TW × 0.2 is satisfied with respect to TW. The difference between the distances L1 and L2 means the distance in the tire width direction of the intersection points P1 and P2. As a result, in the shoulder region of the tread portion 1, a plurality of shoulder blocks 22 are partitioned by the lug main grooves 11 and the shoulder inclined grooves 12.

  Further, the tread portion 1 is formed with a center groove 13 that continuously extends in the tire circumferential direction without communicating with the lug main groove 11 between the lug main grooves 11 located on both sides of the tire equator CL. There is. The center groove 13 has a zigzag shape. The center groove 13 is disposed in the range of 20% or less of the tread width TW from the tire equator CL. That is, the distance X3 from the tire equator CL to the outermost position of the center groove 13 in the tire width direction is set to 20% or less of the tread width TW. The groove width W3 of the center groove 13 is set in the range of 2% to 10% of the tread width TW. As a result, in the center region of the tread portion 1, two rows of center ribs 23 are defined by the lug main groove 11, the shoulder inclined groove 12 and the center groove 13.

  In the pneumatic tire, in the tread portion 1, a plurality of lug main grooves 11 extending in the tire width direction and opening at the tread end and a plurality of shoulder slopes connecting the lug main grooves 11 adjacent in the tire circumferential direction to each other A groove 12 and a center groove 13 extending continuously in the tire circumferential direction without communicating with the lug main groove 11 between the lug main grooves 11 located on both sides of the tire equator CL are formed. The inclination direction of the groove 11, the end position of the lug main groove 11 on the tire equator CL side, the inclination angle α of the lug main groove 11, the inclination direction of the shoulder inclined groove 12, the center position of the shoulder inclined groove 12, the shoulder inclined groove 12 A difference (| L1−L2 |) between the distances L1 and L2 from the tire equator CL of intersections P1 and P2 at which the center line intersects the lug main groove 11, the position of the center groove 13, and the groove width W3 of the center groove 13 In the pneumatic tire that ensures traction performance based on the directional tread pattern, the heat dissipation effect during running of the tire is sufficiently secured to improve the low heat generation and the uneven wear resistance. It will be possible to improve.

  More specifically, the lug main grooves 11 are arranged to be symmetrically inclined on both sides of the tire equator CL, and the inclination angle α of the lug main grooves 11 with respect to the tire width direction is 25% of the tread width TW from the tire equator CL The lug main groove 11 extends from the center region of the tread portion 1 toward the outer side in the tire width direction by setting the range of 15 ° ≦ α ≦ 45 °, more preferably 25 ° ≦ α ≦ 35 °. The soil and sand inside can be effectively discharged and good traction performance can be exhibited. If the inclination angle α of the lug main groove 11 is too small, earth and sand are easily clogged in the lug main groove 11, and conversely if it is too large, the traction performance decreases.

  In addition, by arranging the end portion on the tire equator CL side of the lug main groove 11 in the range of 5% to 20% of the tread width TW from the tire equator CL, both traction performance and uneven wear resistance can be achieved. . If the distance X1 from the tire equator CL to the end of the lug main groove 11 on the tire equator CL side is too small, the uneven wear resistance deteriorates. If too large, the traction performance deteriorates.

  By adding a shoulder inclined groove 12 that connects the lug main grooves 11 and 11 adjacent to each other in the tire circumferential direction to the tread portion 1, the groove area can be increased and good traction performance can be exhibited. Moreover, since the shoulder inclined groove 12 is inclined in the opposite direction with respect to the lug main groove 11, a good heat dissipation effect can be secured based on the air flow generated in the tread portion 1.

  That is, as shown in FIG. 4A, in the structure of the present invention, when the pneumatic tire rotates in the rotation direction R, an air flow F1 is generated in the tread portion 1 and taken into the lug main groove 11. The air moves outward in the tire width direction along the lug main groove 11, a part of the air returns to the inner side in the tire width direction through the shoulder inclined groove 12, and such movement of air is repeated, whereby the tread portion 1. In this case, an effective heat dissipation effect can be obtained. Such a heat dissipation effect is also obtained when the pneumatic tire rotates in the reverse direction. On the other hand, as shown in FIG. 4B, in the structure in which the shoulder inclined groove 12X is inclined in the same direction as the lug main groove 11, the airflow F2 is applied to the tread portion 1 when the pneumatic tire rotates in the rotation direction R. The air taken into the lug main groove 11 moves outward in the tire width direction along the lug main groove 11, and part of the air moves outward in the tire width direction through the shoulder inclined groove 12X. In part 1, a sufficient heat dissipation effect cannot be obtained.

  In obtaining the heat dissipation effect as described above, the difference between the intersections P1 and P2 of the shoulder inclined grooves 12 from the tire equator CL is TW × 0.03 ≦ | L1−L2 with respect to the tread width TW. Since the relationship of | ≦ TW × 0.2, more preferably, the relationship of TW × 0.05 ≦ | L1-L2 | ≦ TW × 0.1 is satisfied, sufficient heat dissipation effect can be secured. it can. Here, if the difference between the distances L1 and L2 is too small, the heat dissipation effect becomes insufficient. Conversely, if the distance is too large, the movement of the block at the time of grounding increases due to the sharpening of the block, and the amount of heat generation increases.

  Further, in order to obtain the above-described heat radiation effect, the center position of the shoulder inclined groove 12 is disposed in the range of 15% to 35% of the tread width TW from the tire equator CL, so the heat radiation effect is sufficiently ensured. be able to. Here, when the center position of the shoulder inclined groove 12 is out of the above range, it becomes difficult to obtain the heat radiation effect in a well-balanced manner over the entire area of the tread portion 1.

  Further, a center groove 13 that continuously extends in the tire circumferential direction between the lug main grooves 11 is formed in the tread portion 1, and the center groove 13 is disposed in a range of 20% or less of the tread width TW from the tire equator CL. Since the groove width W3 of the center groove is 2% to 10% of the tread width TW, the heat dissipation of the center rib 23 can be improved, and the center rib 23 connected to the tire circumferential direction instead of the block is provided in the center region. By partitioning and ensuring sufficient rigidity, it is possible to achieve both uneven wear resistance and low heat generation. Here, if the center groove 13 deviates from the above range, the uneven wear resistance decreases. If the groove width W3 of the center groove 13 is too small, the heat radiation effect is reduced, and if it is too large, the uneven wear resistance is reduced.

  In the pneumatic tire, as shown in FIG. 3, a bottom raised portion 11 a is formed at a portion of the lug main groove 11 on the outer side in the tire width direction. Such a raised portion 11a contributes to improvement in uneven wear resistance.

  In the pneumatic tire, the shortest distance X4 in the tire width direction between the end of the lug main groove 11 on the tire equator CL side and the center groove 13 is preferably 0% to 15% of the tread width TW. Thereby, the width | variety of the center rib 23 divided between the lug main groove 11 and the center groove | channel 13 can be narrowed, and the heat_generation | fever in this center rib 23 can be reduced. If the shortest distance X4 between the end of the lug main groove 11 on the tire equator CL side and the center groove 13 in the tire width direction is too large, the center rib 23 is likely to generate heat.

  In the pneumatic tire, as shown in FIG. 2, the position of the lug main groove 11 is shifted in the tire circumferential direction on both sides of the tire equator CL, and the positional deviation amount S1 of the lug main groove 11 is It is preferable that the relationship of 0.3 ≦ S1 / P ≦ 0.5 be satisfied with respect to the pitch P in the tire circumferential direction. By shifting the position of the main groove 11 in the tire circumferential direction on both sides of the tire equator CL in this manner, the instantaneous increase in contact pressure and the rapid deformation of the block end at the time of tire rotation are suppressed. Heat generation can be reduced. If the ratio S1 / P of the misalignment amount S1 of the lug main groove 11 to the pitch P in the tire circumferential direction of the lug main groove 11 is out of the above range, the improvement effect of the low heat buildup is reduced.

  Further, the cycle T in the tire circumferential direction of the center groove 13 having a zigzag shape is the same as the pitch P in the tire circumferential direction of the lug main groove 11, and from the end of the lug main groove 11 on the tire equator CL side and the end thereof. The positional deviation amount S2 in the tire circumferential direction with respect to the bending point of the center groove 13 located farthest in the tire width direction has a relationship of S2 / P ≦ 0.1 with respect to the pitch P in the tire circumferential direction of the lug main groove 11. You should be satisfied. By reducing the amount of misalignment S2 in the tire circumferential direction between the end of the lug main groove 11 on the tire equator CL side and the bending point of the center groove 13 that is furthest from the end in the tire width direction, Abrasion can be maintained well. If the ratio S2 / P between the positional deviation amount S2 of the bending point of the center groove 13 and the pitch P in the tire circumferential direction of the lug main groove 11 is out of the above range, the end of the lug main groove 11 on the tire equator CL side and its end Since the distance from the bending point of the center groove 13 located closest to the tire width direction from the end portion is small and the block rigidity is lowered, the effect of improving uneven wear resistance is lowered.

  In the pneumatic tire, as shown in FIG. 2, the overlap distance X in the tire width direction of both wall surfaces of the center groove 13 having a zigzag shape is TW × 0.01 ≦ X ≦ TW × 0. It is good to satisfy the relationship of 3, more preferably, the relationship of TW × 0.03 ≦ X ≦ TW × 0.1. Thereby, the heat dissipation effect by the airflow flowing in the center groove 13 can be sufficiently ensured and the low heat generation property can be improved. If the overlapping distance X in the tire width direction of both wall surfaces of the center groove 13 is too small, the effect of improving the low heat build-up is reduced, and conversely if it is too large, the effect of improving the uneven wear resistance is lowered.

  In the pneumatic tire, as shown in FIG. 3, the groove depth D2 of the shoulder inclined groove 12 is 0. 0 relative to the groove depth D1 of the lug main groove 11 at a position 25% of the tread width TW from the tire equator CL. It is preferable that the relationship of 3 ≦ D2 / D1 ≦ 0.7 is satisfied. As described above, by making the shoulder inclined groove 12 shallower than the lug main groove 11, the rigidity of the land portion in the vicinity of the shoulder inclined groove 12 can be secured, and both the partial abrasion resistance and the low heat buildup can be achieved. Here, when the ratio D2 / D1 of the groove depth D2 of the shoulder inclined groove 12 to the groove depth D1 of the lug main groove 11 is too small, the improvement effect of low heat buildup is reduced, and conversely, when it is too large, uneven wear resistance The effect of improving sexuality is reduced.

  In the pneumatic tire, as shown in FIG. 3, the groove depth D3 of the center groove 13 is 0.3 with respect to the groove depth D1 of the lug main groove 11 at a position 25% of the tread width TW from the tire equator CL. It is preferable that the relationship of ≦ D3 / D1 ≦ 0.8 is satisfied. By making the center groove 13 shallower than the lug main groove 11 in this way, the rigidity of the land portion in the vicinity of the center groove 13 can be ensured, and both uneven wear resistance and low heat generation can be achieved. Here, if the ratio D3 / D1 of the groove depth D3 of the center groove 13 to the groove depth D1 of the lug main groove 11 is too small, the improvement effect of the low heat buildup is reduced, and if it is too large, uneven wear resistance The improvement effect of

  FIG. 5 shows a center region of a tread pattern of a pneumatic tire according to another embodiment of the present invention, and FIG. 6 shows a cross section of the main part thereof. 5 and 6, the same components as those in FIGS. 1 to 3 are denoted by the same reference numerals, and detailed description thereof is omitted. As shown in FIG. 5, at the bottom of the center groove 13, a narrow groove 14 extending in the longitudinal direction of the center groove 13 is formed. The narrow groove 14 extends along the longitudinal direction of the center inclined groove 13 at the center of the width of the center groove 13. The width W4 of the narrow groove 14 satisfies the relationship of 0.1 ≦ W4 / W3 ≦ 0.5, more preferably the relationship of 0.2 ≦ W4 / W3 ≦ 0.3, with respect to the groove width W3 of the center groove 13. It is good to be doing.

  Thus, by providing the narrow groove 14 at the bottom of the center groove 13 disposed in the center region of the tread portion 1 where the ground pressure becomes high, the heat dissipation efficiency can be improved and the low heat generation can be effectively improved. In addition, since the narrow groove 14 is narrower than the center groove 13, heat generation due to the movement of the center rib 23 can be suppressed without deteriorating the rigidity of the center rib 23, and the uneven wear resistance can be improved. Here, if the width W4 of the narrow groove 14 is too small, the effect of increasing the heat dissipation efficiency is lowered. Conversely, if the width W4 is too large, the rigidity of the center rib 23 is lowered and heat is likely to be generated.

  As shown in FIG. 6, the groove depth D4 of the narrow groove 14 based on the tread surface of the tread portion 1 is relative to the groove depth D1 of the lug main groove 11 at a position 25% of the tread width TW from the tire equator CL. It is preferable that the relationship of 0.5 ≦ D4 / D1 ≦ 1.0 is satisfied. By thus defining the groove depth D4 of the narrow groove 14, it is possible to achieve both the uneven wear resistance and the low heat buildup without impairing the rigidity of the center rib 23. Here, if the groove depth D4 of the narrow groove 14 is too small, the effect of increasing the heat dissipation efficiency is reduced. Conversely, if the groove depth D4 is too large, the rigidity of the center rib 23 is reduced and heat is likely to be generated.

  FIG. 7 shows a tread pattern of a pneumatic tire according to still another embodiment of the present invention. In FIG. 7, the same parts as those in FIGS. As shown in FIG. 7, an additional lug groove 15 that extends in the same direction as the lug main groove 11 and communicates with the center groove 13 is formed between the center groove 13 and the shoulder inclined groove 12. It is preferable that the groove width W5 of the additional lug groove 15 satisfies the relationship of 0.2 ≦ W5 / W3 ≦ 1.0 with respect to the groove width W3 of the center groove 13. By providing the additional lug groove 15 in the center region of the tread portion 1 where the contact pressure increases, the traction performance can be improved. Therefore, it is possible to exhibit good traction performance as a scraper pneumatic tire. Here, when the groove width W5 of the additional lug groove 15 is too small, the improvement effect of the traction performance is reduced, and when it is too large, the improvement effect of the uneven wear resistance is reduced.

  As shown in FIG. 8, the groove depth D5 of the additional lug groove 15 is 0.3 ≦ D5 / D1 ≦ with respect to the groove depth D1 of the lug main groove 11 at a position 25% of the tread width TW from the tire equator CL. It is good if the relationship of 0.7 is satisfied. By defining the groove depth D5 of the additional lug groove 15 as described above, the rigidity of the center rib 23 partitioned between the lug main groove 11 and the center groove 13 is not impaired, and uneven wear resistance and low heat generation are achieved. The traction performance can be improved while satisfying both. Here, if the groove depth D5 of the additional lug groove 15 is too small, the effect of improving the traction performance decreases, and conversely, if it is too large, the effect of improving the uneven wear resistance decreases.

  FIG. 9 shows a tread pattern of a pneumatic tire according to still another embodiment of the present invention. In FIG. 9, the same parts as those in FIGS. In the embodiment of FIG. 2, the center groove 13 having a zigzag shape has a bent portion and a straight portion alternately arranged. However, in the embodiment of FIG. 9, the center groove 13 forms a smooth waveform. There is. Such a zigzag shape is also effective. Although the center groove 13 preferably has a zigzag shape, it may extend linearly along the tire circumferential direction in some cases.

  The pneumatic tire according to the present invention is applicable to various applications, but is suitable for construction vehicles, and particularly suitable for scraper vehicles.

  The tire size is 37.25R35, extends in the circumferential direction of the tire to form an annular tread portion, a pair of sidewall portions disposed on both sides of the tread portion, and the tire radial direction inner side of these sidewall portions In a pneumatic tire provided with a pair of arranged bead portions, the tire has a directional tread pattern (α = 30 °) as shown in FIG. 2 and the end position of the lug main groove, the center position of the shoulder inclined groove, The distance between the ends of the shoulder inclined groove, the inclination direction of the shoulder inclined groove, the communication state of the center groove with the lug main groove, the arrangement range of the center groove, the groove width of the center groove, the shortest distance between the lug main groove and the center groove, Position shift amount of lug main groove, position shift amount of center groove, overlap distance of both wall surfaces of center groove, groove depth of shoulder inclined groove, groove depth of center groove, groove width of narrow groove, groove depth of narrow groove Table The tires of Comparative Examples 1 to 10 and Examples 1 to 18 set as shown in Table 1 to 4 were produced.

  Regarding the end position of the lug main groove, the ratio (X1 / TW) between the distance X1 from the tire equator to the end of the lug main groove on the tire equator side and the tread width TW is described. For the center position of the shoulder inclined groove, the ratio (X2 / TW) of the distance X2 from the tire equator to the center position of the shoulder inclined groove and the tread width TW is described. Regarding the distance between the end portions of the shoulder inclined groove, the ratio (| L1-L2 | / TW) of the difference between the distances L1 and L2 and the tread width TW is described. About the inclination direction of the shoulder inclination groove | channel, the relationship with respect to a lug main groove | channel was described. Regarding the arrangement range of the center groove, the ratio (X3 / TW) of the distance X3 from the tire equator to the outermost position in the tire width direction of the center groove and the tread width TW is described. Regarding the groove width of the center groove, the ratio (W3 / TW) of the groove width W3 of the center groove to the tread width TW is described. For the shortest distance between the main groove and the center groove, the ratio (X4 / TW) of the shortest distance X4 in the tire width direction between the end of the main groove on the tire equator and the center groove was described. . As for the positional deviation amount of the lug main groove, the ratio (S1 / P) between the positional deviation amount S1 of the lug main groove and the pitch P of the lug main groove is described. Regarding the positional deviation of the center groove, the ratio (S2 / P) of the positional deviation S2 of the center groove to the pitch P of the lug main groove is described. Regarding the misalignment amount of the center groove, the ratio (X / TW) of the overlapping distance X of both wall surfaces of the center groove to the tread width TW is described. Regarding the groove depth of the shoulder inclined groove, the ratio (D2 / D1) of the groove depth D2 of the shoulder inclined groove and the groove depth D1 of the lug main groove is described. Regarding the groove depth of the center groove, the ratio (D3 / D1) between the groove depth D3 of the center groove and the groove depth D1 of the lug main groove is described. As for the groove width of the narrow groove, the ratio (W4 / W3) of the groove width W4 of the narrow groove to the groove width W3 of the center groove is described. Regarding the groove depth of the fine groove, the ratio (D4 / D1) of the groove depth D4 of the fine groove and the groove depth D1 of the lug main groove is described.

  For comparison, the tire of Conventional Example 1 having the same structure as Example 1 except that the center groove extends in the tire width direction and communicates with the main lug groove without the shoulder inclined groove, and the center groove A tire of Conventional Example 2 having the same structure as that of Example 1 except that it extends in the tire width direction and communicates with the lug main groove was prepared.

  These test tires were evaluated for uneven wear resistance and low heat buildup by the following evaluation methods, and the results are also shown in Tables 1 to 4.

Uneven wear resistance:
Each test tire was mounted on a rim, mounted on a scraper vehicle with an air pressure of 525 kPa, and a road laying operation was continuously performed under the same conditions, and then the amount of uneven wear produced in the tread portion was measured. The evaluation result was shown by using an inverse value of the measured value as an index value with Conventional Example 1 being 100. The larger the index value, the better the uneven wear resistance.

Low fever:
Each test tire was mounted on a rim, mounted on an indoor drum tester at an air pressure of 525 kPa, and traveled for 20 hours under a load of 231 kN and a speed of 10 km / h, and then the surface temperature of the tread portion was measured. The evaluation result was shown by using an inverse value of the measured value as an index value with Conventional Example 1 being 100. The larger the index value, the better the low heat buildup.

  As is clear from Tables 1 to 4, the tires of Examples 1 to 18 were excellent in uneven wear resistance and low heat build-up in comparison with Conventional Example 1. On the other hand, although the tire of Conventional Example 2 has improved low heat build-up due to the addition of a shoulder inclined groove having a specific structure, the uneven wear resistance has deteriorated accordingly. Further, in the tires of Comparative Examples 1 to 10, either one of uneven wear resistance and low heat build-up was deteriorated.

Reference Signs List 1 tread portion 2 sidewall portion 3 bead portion 11 lug main groove 12 shoulder inclined groove 13 center groove 14 fine groove 15 additional lug groove 22 shoulder block 23 center rib

Claims (10)

A tread portion extending in the circumferential direction of the tire and forming an annular shape, a pair of sidewall portions disposed on both sides of the tread portion, and a pair of bead portions disposed on the tire radial direction inner side of the sidewall portions In the equipped pneumatic tire,
A plurality of lug main grooves extending in the tire width direction on both sides of the tire equator and opening at the tread end are formed in the tread portion, and the lug main grooves are symmetrically inclined with respect to the tire width direction on both sides of the tire equator The end of the lug main groove on the tire equator side is disposed in the range of 5% to 20% of the tread width TW from the tire equator, and the inclination angle α of the lug main groove with respect to the tire width direction is the tread width from the tire equator It is set in the range of 15 ° ≦ α ≦ 45 ° at the position of 25% of TW,
A plurality of shoulder inclined grooves are formed in the tread portion to connect the lug main grooves adjacent to each other in the tire circumferential direction, and the shoulder inclined grooves are inclined in the opposite direction to the corresponding lug main grooves. Center position of the shoulder is arranged in the range of 15% to 35% of the tread width TW from the tire equator, and the center line of the shoulder inclined groove intersects with the lug main groove on both sides at two intersection points P1 and P2 The difference between the distance L1 from the tire equator of the intersection point P1 of the tire and the distance L2 from the tire equator of the other intersection point P2 with respect to the tread width TW is TW × 0.03 ≦ | L1-L2 | ≦ TW × 0.2 Satisfy the relationship,
A center groove extending continuously in the circumferential direction of the tire without being communicated with the main groove is formed between the main grooves of the lug on both sides of the tire equator in the tread portion, and the center groove is a tread from the equator of the tire A pneumatic tire which is disposed within a range of 20% or less of the width TW, and the groove width W3 of the center groove is 2% to 10% of the tread width TW.   2. The pneumatic tire according to claim 1, wherein the shortest distance in the tire width direction between the end portion of the lug main groove on the tire equator side and the center groove is 0% to 15% of the tread width TW.   The position of the lug main groove is shifted in the tire circumferential direction on both sides of the tire equator, and the positional shift amount S1 of the lug main groove is 0.3 ≦ S1 / with respect to the pitch P of the lug main groove in the tire circumferential direction. Satisfying the relationship of P ≦ 0.5, the center groove has a zigzag shape, the period T in the tire circumferential direction of the center groove is the same as the pitch P in the tire circumferential direction of the lug main groove, The amount of misalignment S2 in the tire circumferential direction between the end of the lug main groove on the tire equator side and the bending point of the center groove located farthest from the end in the tire width direction is the tire circumferential direction of the lug main groove. The pneumatic tire according to claim 1 or 2, wherein a relationship of S2 / P ≦ 0.1 with respect to the pitch P is satisfied.   The center groove has a zigzag shape, and the overlap distance X in the tire width direction of both wall surfaces of the center groove satisfies a relationship of TW × 0.01 ≦ X ≦ TW × 0.3 with respect to the tread width TW. The pneumatic tire according to any one of claims 1 to 3.   The groove depth D2 of the shoulder inclined groove satisfies the relationship of 0.3 ≦ D2 / D1 ≦ 0.7 with respect to the groove depth D1 of the lug main groove at a position 25% of the tread width TW from the tire equator. The pneumatic tire according to any one of claims 1 to 4, wherein:   The groove depth D3 of the center groove satisfies the relationship of 0.3 ≦ D3 / D1 ≦ 0.8 with respect to the groove depth D1 of the lug main groove at a position 25% of the tread width TW from the tire equator. The pneumatic tire according to any one of claims 1 to 5.   A narrow groove extending along the longitudinal direction of the center groove is formed at the bottom of the center groove, and the groove width W4 of the narrow groove is 0.1 ≦ W4 / W3 ≦ 0. The pneumatic tire according to any one of claims 1 to 6, wherein the relationship of 5 is satisfied.   The groove depth D4 of the narrow groove with reference to the tread surface of the tread portion is 0.5 ≦ D4 / D1 ≦ with respect to the groove depth D1 of the lug main groove at a position 25% of the tread width TW from the tire equator. The pneumatic tire according to claim 7, wherein a relationship of 1.0 is satisfied.   An additional lug groove extending in the same direction as the lug main groove and communicating with the center groove is formed between the center groove and the shoulder inclined groove, and the groove width W5 of the additional lug groove is the groove width of the center groove. The pneumatic tire according to any one of claims 1 to 8, wherein a relation of 0.2? W5 / W3? 1.0 is satisfied with respect to W3.   The groove depth D5 of the additional lug groove satisfies the relationship of 0.3 ≦ D5 / D1 ≦ 0.7 with respect to the groove depth D1 of the lug main groove at a position 25% of the tread width TW from the tire equator. The pneumatic tire according to claim 9.

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