JP6488838B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire suitable for heavy loads, and more particularly to a pneumatic tire that can improve stone biting prevention performance.

  A heavy-duty pneumatic tire mounted on a heavy-duty vehicle such as a truck usually has a plurality of circumferential grooves extending in the tire circumferential direction in a tread portion, and a plurality of rows extending in the tire circumferential direction by these main grooves. The rib has a tread pattern with a basic tone.

  The heavy-duty pneumatic tire configured as described above may be used not only on road but also off road. However, when stone biting occurs in the circumferential groove, the stone sandwiched in the groove is grooved. It moves to the bottom side, and so-called stone drilling may occur. When such stone drilling occurs, a large crack is formed at the groove bottom of the circumferential groove, rust is generated on the belt layer made of steel cord, and the durability of the pneumatic tire is greatly reduced, or the tire becomes a base tire. There is a problem that rehabilitation cannot be performed due to damage of the part.

  In contrast, various techniques for preventing stone biting by devising the cross-sectional shape of the circumferential groove have been proposed (see, for example, Patent Documents 1 to 6). In other words, as a measure against stone biting, for example, on the groove bottom of the circumferential groove, for example, a protrusion that continuously extends at a certain height along the tire circumferential direction, or continuously while undulating along the tire circumferential direction It has been proposed to provide a plurality of protrusions that extend intermittently along the tire circumferential direction.

  However, although the above-described stone biting prevention measures have an effect of suppressing the stone from reaching the groove bottom, the effect of discharging the stone sandwiched in the groove to the outside is hardly obtained. Therefore, the stone is held in a state of being sandwiched in the groove, and in some cases, the stone is pushed to a deep position on the groove bottom side, and stone drilling occurs.

JP 2004-155382 A JP 2008-87628 A JP-A-6-239107 JP 2008-184053 A JP 2013-43614 A JP 60-92904 A

  An object of the present invention is to provide a pneumatic tire capable of improving the stone biting prevention performance.

In order to achieve the above object, a pneumatic tire according to the present invention is a pneumatic tire having a circumferential groove extending in a tire circumferential direction in a tread portion, and is arranged along a tire circumferential direction at a groove bottom of the circumferential groove. A plurality of protrusion rows including a plurality of protrusions are formed, the height of the protrusions is periodically changed along the tire circumferential direction, and the pair of adjacent protrusion rows overlaps in the tire circumferential direction. However, it is arranged so that the maximum height position of the protrusions is shifted in the tire circumferential direction, and one of the adjacent protrusion rows in one of the protrusion rows is an inclined surface on one side in the tire circumferential direction constituting the protrusion. The inclination angle of the inclined surface on the other side is smaller than the inclination angle of the inclined surface on the other side, and the inclination angle of the inclined surface on one side in the tire circumferential direction constituting the protrusion in the other protrusion row is larger than the inclination angle of the inclined surface on the other side. which is characterized in that also increased A.

  In the present invention, a plurality of rows of projections including a plurality of projections arranged along the tire circumferential direction is formed at the groove bottom of the circumferential groove, and the height of the projections is periodically changed along the tire circumferential direction. By changing and arranging the adjacent pair of protrusion rows so that the protrusions overlap in the tire circumferential direction and the maximum height position of the protrusions deviates in the tire circumferential direction, A pair of protrusions whose maximum height is shifted when entering the direction groove prevents the stone from moving toward the groove bottom, and based on the sliding force generated between the tread and the stone when kicking out The stone moves along the protrusion on the kicking side and is pushed out in the tire radial direction. Therefore, it is possible not only to prevent the stone sandwiched in the groove from being pushed to a deep position on the groove bottom side, but also to discharge the stone sandwiched in the groove to the outside as the pneumatic tire rolls. . Thereby, the stone biting prevention performance can be improved.

  In the present invention, of one pair of adjacent protrusion rows, the inclination angle of one inclined surface in the tire circumferential direction constituting the protrusion is made smaller than the inclination angle of the other inclined surface in one protrusion row, In this projection row, it is preferable that the inclination angle of one inclined surface in the tire circumferential direction constituting the protrusion is larger than the inclination angle of the other inclined surface. Thereby, while the movement to the groove bottom side of the stone pinched | interposed into the circumferential groove | channel is prevented effectively, discharge | emission of a stone can be performed smoothly.

  The ratio Hmax / P between the maximum height Hmax of the protrusion and the length P of the protrusion in the tire circumferential direction is preferably 0.16 to 0.20. The ratio Hmax / D between the maximum height Hmax of the protrusion and the groove depth D of the circumferential groove is preferably 1.0 or less. Furthermore, the ratio P / D between the groove depth D of the circumferential groove and the length P of the protrusion in the tire circumferential direction is preferably 3-8. Thereby, while the movement to the groove bottom side of the stone pinched | interposed into the circumferential groove | channel is prevented effectively, discharge | emission of a stone can be performed smoothly.

  The ratio w / W between the groove width W of the circumferential groove and the total width w of the protrusions aligned in the groove width direction in the circumferential groove is preferably 0.3 to 1.0. As a result, the overall rigidity of the protrusion that receives the stone is sufficiently secured, so that the stone sandwiched in the circumferential groove is effectively prevented from moving to the groove bottom side, and the stone is smoothly discharged. It can be carried out.

  Each of the protrusion rows preferably includes at least 20 protrusions. Further, the ratio X / P between the overlapping amount X of the protrusions in the tire circumferential direction and the length P of the protrusions in the tire circumferential direction in a pair of adjacent protrusions is preferably 0.3 or more. Thereby, while the movement to the groove bottom side of the stone pinched | interposed into the circumferential groove | channel is prevented effectively, discharge | emission of a stone can be performed smoothly.

It is a meridian half section view showing a pneumatic tire according to an embodiment of the present invention. It is an expanded view which shows the tread pattern of the pneumatic tire which consists of embodiment of this invention. It is a perspective view which shows an example of the protrusion formed in the groove bottom of the circumferential groove | channel. It is a side view which shows an example of the protrusion formed in the groove bottom of the circumferential groove. It is a front view which shows an example of the protrusion formed in the groove bottom of the circumferential groove. It is explanatory drawing which shows the state at the time of the depression of the stone pinched | interposed into the circumferential groove | channel. It is explanatory drawing which shows the state at the time of kicking out of the stone pinched | interposed into the circumferential groove | channel. It is a perspective view which shows the modification of the protrusion formed in the groove bottom of the circumferential groove | channel. It is a perspective view which shows the other modification of the protrusion formed in the groove bottom of the circumferential groove. It is a perspective view which shows the further another modification of the protrusion formed in the groove bottom of the circumferential groove. It is a side view which shows the further another modification of the protrusion formed in the groove bottom of the circumferential groove. It is a side view which shows the further another modification of the protrusion formed in the groove bottom of the circumferential groove. It is a side view which shows the further another modification of the protrusion formed in the groove bottom of the circumferential groove. It is a side view which shows the further another modification of the protrusion formed in the groove bottom of the circumferential groove. It is a side view which shows the protrusion of the comparative example formed in the groove bottom of the circumferential groove | channel. It is a side view which shows the protrusion of the other comparative example formed in the groove bottom of the circumferential groove | channel.

  Hereinafter, the configuration of the present invention will be described in detail with reference to the accompanying drawings. 1 to 5 show a heavy duty pneumatic tire according to an embodiment of the present invention. Although FIG. 1 shows only a portion on one side of the tire center line CL, this pneumatic tire has a structure corresponding to the other side of the tire center line CL.

  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.

  A 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. A bead filler 6 made of a rubber composition having a triangular cross-section is disposed on the outer periphery of the bead core 5.

  On the other hand, a plurality of belt layers 7 (7A, 7B, 7C, 7D) are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. These belt layers 7A to 7D include a plurality of reinforcing cords that are inclined with respect to the tire circumferential direction, and are arranged such that the reinforcing cords intersect each other between the layers. In the belt layers 7A to 7D, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set in a range of 10 ° to 60 °, for example. Steel cords are preferably used as reinforcing cords for the belt layers 7A to 7D.

  As shown in FIG. 2, the tread portion 1 is formed with a plurality of circumferential grooves 11 extending in the tire circumferential direction. As a result, the tread portion 1 has a plurality of rows of land portions 12 extending in the tire circumferential direction. Although these land parts 12 have a rib structure continuous along the tire circumferential direction, lug grooves and sipes extending in the tire width direction can be provided as necessary.

  In the pneumatic tire, as shown in FIGS. 1 to 5, a plurality of rows (2 rows in FIGS. 1 to 5) of protrusion rows 20 (20 </ b> A, 20B), and each protrusion row 20 is composed of a plurality of protrusions 21 (21A, 21B) arranged along the tire circumferential direction C. The height of the protrusion 21 changes periodically along the tire circumferential direction C. More specifically, each protrusion 21 has a shape that is lowest at both ends in the tire circumferential direction C and highest at an intermediate portion between both ends (see, for example, FIG. 4). Yes. As shown in FIG. 4, the pair of adjacent protrusion rows 20A and 20B has the protrusions 21A and 21B overlapping in the tire circumferential direction C, and the maximum height positions of the protrusions 21A and 21B are in the tire circumferential direction C. It is arranged so as to be displaced.

  FIG. 6 shows a state when the stone sandwiched in the circumferential groove is depressed, and FIG. 7 shows a state when the stone sandwiched in the circumferential groove is kicked out. In the pneumatic tire described above, a plurality of rows of projections 20 including a plurality of projections 21 arranged along the tire circumferential direction C are formed at the groove bottom of the circumferential groove 11, and the height of the projections 21 is set to the tire. The pair of adjacent protrusion rows 20A and 20B is periodically changed along the circumferential direction C, and the protrusions 21A and 21B overlap the tire circumferential direction C while the maximum height position of the protrusions 21A and 21B is the tire. It has a structure arranged so as to be shifted in the circumferential direction C. Therefore, as shown in FIG. 6, when stepping on, when the stone S on the road surface R enters the circumferential groove 11, the pair of protrusions 21 </ b> A and 21 </ b> B whose maximum height positions are shifted are grooves of the stone S. Block movement to the bottom. On the other hand, as shown in FIG. 7, at the time of kicking, the stone S moves along the protrusion 21A on the kicking side based on the sliding force generated between the tread portion 1 and the stone S, and the tire diameter Extruded in the direction. As a result, the stone S sandwiched in the circumferential groove 11 is prevented from being pushed into a deep position on the groove bottom side, and further, the stone S sandwiched in the circumferential groove 11 is accompanied with the rolling of the pneumatic tire. It can be discharged to the outside. Thereby, the stone biting prevention performance can be improved as compared with the prior art.

  And it can prevent that a big crack is formed in the groove bottom of the circumferential direction groove | channel 11 resulting from stone drilling by improving the stone biting prevention performance as mentioned above. As a result, it is possible to avoid the inconvenience that the durability of the pneumatic tire is lowered due to the occurrence of rust in the belt layer 7 and the rehabilitation is impossible due to the damage to the portion that becomes the base tire.

In order to sufficiently obtain the effect of improving the stone biting prevention performance, as shown in FIG. 4, one of the adjacent protrusion rows 20A and 20B has one protrusion row 20A in the tire circumferential direction constituting the protrusion 21A. The inclination angle θ _A1 of the inclined surface on the side is made smaller than the inclination angle θ _A2 of the inclined surface on the other side, and the inclination angle θ of the inclined surface on one side in the tire circumferential direction constituting the protrusion 21B in the other protrusion row 20B. _B1 may be larger than the inclination angle θ _B2 of the other inclined surface. The inclination angles θ _A1 , θ _A2 , θ _B1 , and θ _{B2 mentioned} here are all inclination angles with respect to the groove bottom surface of the circumferential groove 11. By defining such a shape, the stone S sandwiched in the circumferential groove 11 can be effectively prevented from moving to the groove bottom side, and the stone S can be discharged smoothly. For example, the inclination angles θ _A1 and θ _B2 may be set in the range of 15 ° to 45 °, and the inclination angles θ _A2 and θ _B1 may be set in the range of 45 ° to 75 °.

  In the pneumatic tire, the ratio Hmax / P between the maximum height Hmax of the protrusion 21 and the length P of the protrusion 21 in the tire circumferential direction is preferably 0.16 to 0.20. Thereby, while the movement to the groove bottom side of the stone pinched | interposed into the circumferential groove | channel 11 is prevented effectively, discharge | emission of a stone can be performed smoothly. Here, when the ratio Hmax / P is out of the above range, the effect of improving the stone biting prevention performance decreases.

  The ratio Hmax / D between the maximum height Hmax of the protrusion 21 and the groove depth D of the circumferential groove 11 is 1.0 or less, more preferably 0.3 to 0.5. Thereby, while the movement to the groove bottom side of the stone pinched | interposed into the circumferential groove | channel 11 is prevented effectively, discharge | emission of a stone can be performed smoothly. Here, if the ratio Hmax / D is too large, the drainage performance may be hindered. On the other hand, if the ratio Hmax / D is too small, the effect of improving the stone biting prevention performance decreases.

  Further, the ratio P / D between the groove depth D of the circumferential groove 11 and the length P of the protrusion 21 in the tire circumferential direction C is preferably 3-8. Thereby, while the movement to the groove bottom side of the stone pinched | interposed into the circumferential groove | channel 11 is prevented effectively, discharge | emission of a stone can be performed smoothly. Here, when the ratio P / D is out of the above range, the improvement effect of the stone biting prevention performance is lowered.

  In the pneumatic tire, the ratio w / W of the groove width W of the circumferential groove 11 and the total width w (w = w1 + w2) of the protrusions 21 aligned in the groove width direction in the circumferential groove 11 is 0.3. -1.0, more preferably 0.5-1.0. As a result, the rigidity of the entire protrusion 21 for receiving the stone is sufficiently secured, so that the stone sandwiched in the circumferential groove 11 is effectively prevented from moving to the groove bottom side, and the stone is discharged. It can be done smoothly. Here, if the ratio w / W is too small, the effect of improving the stone biting prevention performance is lowered. When n rows of protrusions 21 are arranged in the groove width direction in the circumferential groove 11, the total width w is obtained from w = w1 + w2 +.

  In the pneumatic tire, each of the protrusion rows 20 preferably includes at least 20 protrusions 21. As described above, each protrusion row 20 includes at least 20 protrusions 21 arranged along the tire circumferential direction C, so that the effect of improving the stone biting prevention performance is sufficiently exhibited in a wide range in the tire circumferential direction. It becomes possible.

  Further, the ratio X / P between the overlapping amount X of the protrusions 21A, 21B in the tire circumferential direction C and the length P of the protrusions 21A, 21B in the tire circumferential direction C in a pair of adjacent protrusion rows 20A, 20B (FIG. 4) is preferably 0.3 or more. In FIG. 4, since the overlap amount X and the length P have the same value, X / P = 1.0. Thereby, while the movement to the groove bottom side of the stone pinched | interposed into the circumferential groove | channel 11 is prevented effectively, discharge | emission of a stone can be performed smoothly. Here, if the ratio X / P is too small, the effect of improving the stone biting prevention performance is lowered.

  8 to 10 each show a modification of the projection formed on the groove bottom of the circumferential groove. In FIG. 8, two rows of protrusions 20A and 20B are formed at the groove bottom of the circumferential groove 11, and these protrusion rows 20A and 20B are respectively a plurality of protrusions 21A and 21B arranged along the tire circumferential direction C. The overlapping amount X of the protrusions 21A and 21B in the tire circumferential direction C is smaller than in the case of FIG. 9, three rows of protrusions 20A, 20B, and 20C are formed on the groove bottom of the circumferential groove 11, and each of the protrusion rows 20A, 20B, and 20C is a plurality of protrusions arranged along the tire circumferential direction C. The body 21A, 21B, 21C is included. In FIG. 10, four rows of protrusions 20A, 20B, 20C, 20D are formed on the groove bottom of the circumferential groove 11, and these protrusion rows 20A, 20B, 20C, 20D are arranged along the tire circumferential direction C, respectively. A plurality of protrusions 21A, 21B, 21C, and 21D are included. As described above, the number of the array of the protrusion rows 20 can be appropriately increased.

  FIGS. 11-14 show the modification of the protrusion formed in the groove bottom of the circumferential groove, respectively. In FIG. 11, the protrusions 21 constituting the protrusion row 20 form a right triangle in a side view. In FIG. 12, the protrusions 21 constituting the protrusion row 20 are continuously formed. In FIG. 13, the protrusions 21 constituting the protrusion row 20 have equal inclination angles on the inclined surfaces on both sides. In FIG. 14, the protrusions 21 constituting the protrusion row 20 have a waveform in side view. Thus, the side view shape of the protrusions 21 constituting the protrusion row 20 can be appropriately selected.

  Although the use of the pneumatic tire according to the present invention is not limited, it is particularly suitable as a heavy duty pneumatic tire. In heavy-duty pneumatic tires, stone drilling due to stone biting is likely to occur, and tire failures associated therewith are likely to occur. However, by applying the present invention, such inconveniences can be effectively avoided.

  In a heavy duty pneumatic tire having a tire size of 11R22.5 and having a plurality of circumferential grooves extending in the tire circumferential direction at the tread portion, the tires are arranged along the tire circumferential direction at the groove bottom of each circumferential groove. Two rows of projections including a plurality of projections are formed, the height of the projections is periodically changed along the tire circumferential direction, and the projections overlap a pair of adjacent projection rows in the tire circumferential direction. However, the maximum height position of the protrusions is shifted in the tire circumferential direction, and the ratio Hmax / P between the maximum height Hmax of the protrusions and the tire circumferential length P of the protrusions, the circumferential groove The ratio P / D of the groove depth D to the tire circumferential length P of the protrusion, the groove width W of the circumferential groove, and the total width w of the protrusions aligned in the groove width direction in the circumferential groove. Tires of Examples 1 to 8 in which the ratio w / W was set as shown in Table 1 were produced.

  In Examples 1-8, the structure shown in FIG. 3 is adopted for the protrusions, each protrusion row is composed of 200 protrusions arranged in the tire circumferential direction, and the protrusion tires in a pair of adjacent protrusion rows The ratio X / P of the overlap amount X in the circumferential direction and the length P of the protrusion in the tire circumferential direction was set to 0.4.

  For comparison, a conventional example was prepared in which no protrusion was provided on the groove bottom of each circumferential groove. Further, Comparative Example 1 was prepared in which the protrusions 30 (see FIG. 15) that are intermittently arranged along the tire circumferential direction and have a certain height are provided at the groove bottoms of the circumferential grooves. Furthermore, the comparative example 2 which provided the protrusion 40 (refer FIG. 16) continuously arrange | positioned along the tire circumferential direction at the groove bottom of each circumferential groove | channel and the height changes periodically was prepared.

  About these test tires, the stone biting prevention performance was evaluated by the following evaluation method, and the results are also shown in Table 1.

Stone chewing prevention performance:
Each test tire was assembled on a wheel with a rim size of 22.5 × 8.25, mounted on all wheels of a 2-D4 vehicle under conditions of an air pressure of 800 kPa and a load of 26.7 kN, and a predetermined off-road driving was performed. Then, the number of stone bites in the circumferential groove in each test tire was measured. The evaluation results are shown as an index with the conventional example being 100, using the reciprocal of the measured value. The larger the index value, the better the stone biting prevention performance.

  As is clear from Table 1, the tires of Examples 1 to 8 were excellent in stone biting prevention performance in comparison with Conventional Example 1. On the other hand, although the tires of Comparative Examples 1 and 2 showed an improvement effect on the stone biting prevention performance, the effect was not always sufficient.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 11 Circumferential groove 12 Land part 20, 20A, 20B, 20C, 20D Protrusion row | line | column 21,21A, 21B, 21C, 21D Protrusion body

Claims (7)

In the pneumatic tire having a circumferential groove extending in the tire circumferential direction in the tread portion, a plurality of rows of protrusions including a plurality of protrusions arranged along the tire circumferential direction is formed at the groove bottom of the circumferential groove, The height of the projections is periodically changed along the tire circumferential direction, and the maximum height position of the projections in the tire circumferential direction while the projections overlap a pair of adjacent projection rows in the tire circumferential direction. Of one pair of adjacent protrusion rows, the inclination angle of one inclined surface in the tire circumferential direction constituting the protrusion is smaller than the inclination angle of the other inclined surface. In the other projection row, the inclination angle of the inclined surface on one side in the tire circumferential direction that constitutes the protrusion is made larger than the inclination angle of the inclined surface on the other side . 2. The pneumatic tire according to claim 1 , wherein a ratio Hmax / P between a maximum height Hmax of the protrusion and a length P of the protrusion in the tire circumferential direction is 0.16 to 0.20. . 3. The pneumatic tire according to claim 1, wherein a ratio Hmax / D between a maximum height Hmax of the protrusion and a groove depth D of the circumferential groove is 1.0 or less. . The air according to any one of claims 1 to 3 , wherein a ratio P / D between a groove depth D of the circumferential groove and a length P of the protrusion in the tire circumferential direction is 3 to 8. Enter tire. The ratio w / W between the groove width W of the circumferential groove and the total width w of the protrusions arranged in the groove width direction in the circumferential groove is 0.3 to 1.0. The pneumatic tire according to any one of 1 to 4 . Each of the said protrusion row | line | column contains at least 20 protrusion body, The pneumatic tire in any one of Claims 1-5 characterized by the above-mentioned. The ratio X / P between the overlapping amount X of the protrusions in the tire circumferential direction and the length P of the protrusions in the tire circumferential direction in a pair of adjacent protrusions is 0.3 or more. The pneumatic tire according to any one of 1 to 6 .

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