JP5109481B2 - Heavy duty pneumatic tire - Google Patents

Description

  The present invention relates to a heavy-duty pneumatic tire used for trucks, buses, and the like, and more particularly to a heavy-duty pneumatic tire with improved wear resistance.

  Conventionally, a heavy duty pneumatic tire having a rib pattern in which ribs are formed between main grooves extending in the tire circumferential direction on a tread surface and a sipe is provided on the ribs is known (for example, Patent Document 1). 2). By devising the sipe placement method on the ribs formed on the tread surface, traction is improved and steering stability is improved.

Such heavy-duty pneumatic tires with rib patterns are also used for steered wheels (driven wheels) of long-distance trucks and buses that are mainly driven at high speeds. There was a tendency for wear to proceed quickly, thereby leading to an early replacement of the tire and a short tire life.
JP-A-5-69704 JP-A-6-80002

  An object of the present invention is to provide a heavy-duty pneumatic tire capable of improving wear resistance and improving tire life without causing deterioration of uneven wear resistance and tear resistance of ribs between main grooves. There is to do.

In the heavy duty pneumatic tire of the present invention that achieves the above object, four main grooves extending in the tire circumferential direction are arranged on the tread surface, and three land portions are formed between the main grooves. A heavy load in which at least one of the land portions of the book is formed as a rib, and a first sipe extending in the tire width direction and communicating with the main groove at both ends is arranged at a predetermined pitch P1 in the tire circumferential direction. In the heavy duty pneumatic tire, the ratio P1 / W between the pitch P1 of the first sipe and the width W of the rib on which the first sipe is arranged is in the range of 0.80 to 0.95, A second sipe that intersects with one sipe extends in the tire circumferential direction, and the first sipe has a width of 0.5 to 1.0 mm and is disposed in the rib width direction with a shallow depth and a depth. Is formed of a deep portion, and the shallow portion is partially present in the rib width direction, Said There portion in ground contact shape of the tread surface obtained under the conditions of air pressure corresponding to the load and said maximum load capacity corresponding to the maximum load capacity described in JATMA by occupying 40 to 80% of the first sipe second One sipe is configured to be in an open state on the tread surface.

  According to the present invention described above, the ratio P1 / W between the pitch P1 of the first sipe provided on the rib and the width W of the rib on which the first sipe is arranged is defined in the above range, and each first sipe By extending the intersecting second sipe in the tire circumferential direction and further opening the first sipe without closing when it contacts the ground, slippage of the rib during tire rotation can be suppressed. The tire life can be prolonged by improving the property, while the uneven wear resistance and tear resistance of the ribs are not lowered.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  1 and 2 show an embodiment of a heavy-duty pneumatic tire of the present invention used for trucks, buses, etc., 1 for a tread portion, 2 for a sidewall portion, 3 for a bead portion, and 100 for a tire equatorial plane. It is.

  A carcass layer 4 is extended between the left and right bead portions 3, and both end portions 4 a are folded back from the inner side in the tire axial direction so as to sandwich the bead filler 6 around the bead core 5 embedded in the bead portion 3. Yes. On the outer peripheral side of the carcass layer 4 of the tread portion 1, a plurality of belt layers 7 in which steel cords are inclined and arranged with respect to the tire circumferential direction TC are provided. The plurality of belt layers 7 include a first belt layer 7A disposed adjacent to the carcass layer 4, a second belt layer 7B disposed on the outer peripheral side of the first belt layer 7A, and an outer periphery of the second belt layer 7B. The third belt layer 7C is disposed on the side, and the fourth belt layer 7D is disposed on the outer peripheral side of the third belt layer 7C. The steel cord of the second belt layer 7B and the steel cord of the third belt layer 7C intersect with each other with the inclination direction with respect to the tire circumferential direction TC reversed. The plurality of belt layers 7 are arranged symmetrically with respect to the tire equatorial plane 100.

  As shown in FIG. 2, the tread surface 11 of the tread portion 1 is provided with four main grooves 12 extending linearly in the tire circumferential direction TC. The four main grooves 12 are composed of two main grooves 12A and 12B arranged on both sides of the tire equatorial plane 100 and main grooves 12C and 12D arranged on both outer sides in the tire width direction of the main grooves 12A and 12B. The intervals in the tire width direction between the adjacent main grooves 12 are substantially equal. A rib 13 is formed between the adjacent main grooves 12 in the center region 11C of the tread surface 11 between the main grooves 12C and 13D located on the outermost side. The outer side in the tire width direction of the outermost main grooves 12C and 12D is a shoulder region 11S of the tread surface 11, and ribs 14 are also formed in the shoulder region 11S.

  On the tread surface 31 of the three ribs 13 formed between the main grooves 12, the first sipes 15 extending in the tire width direction and communicating with the main groove 12 at both ends are provided with a predetermined pitch in the tire circumferential direction TC. It is arranged at P1. Further, the ratio P1 / W between the pitch P1 of the first sipe 15 and the width W of the rib 13 on which the first sipe 15 is arranged is in the range of 0.80 to 0.95.

  In the central region 32 (see FIG. 3) in the tire width direction of the tread surface 31 of the rib 13, one annular ring extending in a zigzag shape along the tire circumferential direction TC so as to intersect the first sipe 15. A second sipe 16 is provided. A portion 61 of the second sipe 16 overlaps with the first sipe 15.

  As shown in FIG. 3, the first sipe 15 includes a shallow portion 51 and a deep portion 52, and partially includes the shallow portion 51. The deep portion 52 is located in the tire width direction central region 32 of the tread surface 31 and the end regions 33 on both sides in the tire width direction, and the shallow portion 51 is located in the intermediate region 34 between the central region 32 and each end region 33. The shallow portions 51 are arranged symmetrically.

  In this way, by configuring the first sipe 15 to have a portion 51 having a partially shallow depth, the load corresponding to the maximum load capacity described in JATMA (2006 YEAR BOOK) and the maximum load capacity can be obtained. In the ground contact shape of the tread surface 11 obtained under the corresponding air pressure conditions, the first sipe 15 can be kept open on the tread surface 11 without being closed. In addition, the state where the 1st sipe 15 said here is open with respect to the width | variety of the 1st sipe 15 (solid line) in the tire of the no load state which added the air pressure corresponding to a maximum load capability as shown in FIG. That is, the state in which the opening 15x of the first sipe 15 is 1/4 or more opened.

  As shown in FIG. 5, the second sipe 16 extends in the tire circumferential direction TC while periodically changing the depth, and the depth is partially at the center position between the first sipe 15. It is getting shallower.

  Between each adjacent first sipe 15 in both end regions 33 (both ends in the tire width direction) of the tread surface 31 of each rib 13, a third sipe 17 having only one end communicating with the main groove 12 is a tire circumferential direction. The TC is arranged at a predetermined pitch P3.

  In the end region 42 facing the main groove 12 of the tread surface 41 of the rib 14 of the shoulder region 11S, the fourth sipes 18 having only one end communicating with the main groove 12 are arranged at a predetermined pitch P4 in the tire circumferential direction TC. ing. The pitch P4 of the fourth sipe 18 is larger than the pitch P3 of the third sipe 17.

  An end region 43 on the outer side in the tire width direction of the tread surface 41 of the rib 14 is provided with one narrow groove 19 extending linearly in the tire circumferential direction TC. The fourth sipe 18 having one end opened in the narrow groove 9 is also arranged at a predetermined pitch P4 in the tire circumferential direction TC in the region 44 of the tread surface 41 on the inner side in the tire width direction from the narrow groove 19.

  When the present inventor used a heavy duty pneumatic tire having a rib pattern formed by four main grooves as a steered wheel (driven wheel) for a long-distance truck or bus mainly for high-speed continuous running. As a result of intensive studies on the point where the wear of the ribs between the main grooves progresses quickly and repeated experiments, the following was found.

  That is, by specifying the relationship between the pitch of the first sipe extending in the tire width direction on the rib between the main grooves and the width of the rib provided with the first sipe, the second sipe further intersecting each first sipe. By extending the sipe in the tire circumferential direction and keeping the first sipe open without closing at the ground contact portion of the tread surface when the tire is grounded, the progress of wear of the ribs between the main grooves is slow. I found out that This is presumably because slippage at the rib portion provided with the first sipe is suppressed, and the rigidity of the rib becomes more uniform on the tire circumference than before.

  Therefore, in the present invention, in a heavy duty pneumatic tire provided with rib patterns by the four main grooves 2, the ratio P1 between the pitch P1 of the first sipe 15 and the width W of the rib 13 on which the first sipe 15 is arranged. / W is defined in the above-described range, and a second sipe 16 that intersects each first sipe 15 is extended to the rib 13 in the tire circumferential direction TC, and a load corresponding to the maximum load capacity described in JATMA The first sipe 15 is configured to be in an open state on the tread surface 11 in the ground contact shape of the tread surface obtained under the condition of air pressure corresponding to the maximum load capacity. As a result, the wear resistance of the ribs 13 can be improved, the tire life can be extended, and the uneven wear resistance and tear resistance of the ribs 13 are not reduced.

  When the ratio P1 / W is smaller than 0.80, the end portion of the rib 13 facing the main groove 12 is easily broken, and the tear resistance is lowered. On the other hand, if the ratio P1 / W exceeds 0.95, uneven wear is likely to occur in the rib 13 and uneven wear resistance is reduced. When the first sipe 15 is closed on the tread surface 11 at the time of contact with the ground, it is impossible to obtain the effect of improving the wear resistance of the rib 13 and extending the tire life. The same applies when the second sipe 16 that intersects the first sipe 15 is not extended in the tire circumferential direction TC.

In the present invention, the shallow portion 51 and the deep portion 52 of the first sipe 15 are preferably arranged symmetrically as described above from the viewpoint of the rigidity balance of the ribs 13, but can also be arranged asymmetrically. is there. The proportion of the shallow portion 51, it accounts for 40% to 80% of the first sipes 15 in the rib width direction. When the proportion of the shallow portion 51 is smaller than 40%, the opening of the first sipe 15 is easily closed at the time of ground contact, and conversely, when it exceeds 80%, the compression relaxation ability of the rib at the time of ground contact is lowered, and uneven wear suppression effect is achieved. Decreases. In addition, the ratio for which the shallow part 51 occupies is a ratio for the rib width direction on the tread surface 31.

  As the depth D1 of the shallow portion 51, the ratio SW / D1 of the width SW to the depth D1 is preferably in the range of 0.25 to 1.00 in relation to the width SW of the first sipe 15. When the ratio SW / D1 is smaller than 0.25, the depth D1 of the shallow portion 51 becomes too shallow, and the compression relaxation ability of the ribs at the time of contact decreases, and the effect of suppressing uneven wear decreases. On the other hand, if the ratio SW / D1 exceeds 1.00, the first sipe 15 is easily closed at the time of grounding, which is not preferable.

  The ratio Wb / Wt between the width Wb of the fourth belt layer 7D located on the outermost side in the tire radial direction and the total tire width Wt is preferably in the range of 0.4 to 0.6. By setting the ratio Wb / Wt to be 0.4 or more, the wear resistance can be improved while improving the uneven wear resistance of the rib 15. When the ratio Wb / Wt exceeds 0.6, uneven wear resistance deteriorates.

  The third sipe 17 is in a relationship with the first sipe 15 so that the ratio P3 / P1 between the pitch P3 of the third sipe 17 and the pitch P1 of the first sipe 15 is in the range of 0.1 to 0.5. The arrangement is good from the viewpoint of uneven wear resistance of the ribs 13.

  As shown in the figure, the fourth sipe 18 disposed on the rib 14 in the shoulder region 1S has a pitch P4 larger than the pitch P3 of the third sipe 17 to improve the tear resistance between the sipe of the rib 14. Above is good.

  In the above-described embodiment, the first sipe 15 intersects with the annular second sipe 14 extending in a zigzag shape. Instead, as shown in FIG. 6, the first sipe 15 has a short length in the tire circumferential direction TC. The second sipe 20 extending in the above may be provided so as to intersect each first sipe 15.

  The depth of the main groove 12 can be in the range of 10 to 20 mm, and can be appropriately selected depending on the tire size. The depth of the first sipe 15 and the second sipe 16 can be set to a range of 5 to 20 mm at a deep portion. Preferably, the depth is 0.5 to 1.0 times the depth of the main groove 12 at a deep portion.

  In addition, the sipe 15-18 said by this invention says the notch | incision whose width is 0.5-1.0 mm.

  In the above embodiment, the land portions formed between the four main grooves 12 are examples of the ribs 13, but at least one of the three land portions between the four main grooves 12 is a rib. The present invention can also be suitably used for the formed heavy duty pneumatic tire.

  The configuration shown in FIGS. 1 and 2 in which the tire size is the same for 11R22.5, the ratio P1 / W of the pitch P1 of the first sipe and the rib width W, and the state of the first sipe at the time of grounding are as shown in Table 1. Tires 1 and 2 (Examples 1 and 2), comparative tires 1 to 3 (Comparative tires 1 to 3), and tire 2 No comparative tire 4 (Comparative Example 4), the conventional tire 1 having the configuration shown in FIG. 7 in which only the second sipes extending in the tire circumferential direction are arranged at a predetermined pitch in the tire circumferential direction, and the depth is constant (only the deep part) The conventional tire 2 having the configuration shown in FIG. 8 in which only the first sipe was arranged was prepared as a test tire.

Each test tires both, the ratio Wb / Wt of the width Wb and the total tire width Wt of the fourth belt layer 0.5, the depth of the sipe is 10 mm, a width of 0.8 m m. Note that the sipe depth is the depth of a deep portion in the case of a sipe having a shallow portion and a deep portion. The ratio SW / D1 between the ratio of the shallow part of the first sipe and the depth D1 of the shallow part of the first sipe and the width SW of the first sipe is as shown in Table 1.

  Each of these test tires is assembled on a rim having a rim size of 14RP, and the air pressure is set to 700 kPa. The tire is used as a steering wheel of a truck (2-D car) having a load weight of 10 t. After that, the wear amount (wear resistance) and uneven wear amount (uneven wear resistance) of the ribs between the main grooves were measured, and the tearing state (tear resistance) of the rib ends was visually observed. The evaluation results are shown as index values with the conventional tire 1 being 100. The larger this value, the better the performance.

  From Table 1, it can be seen that the tire of the present invention can improve the wear resistance, that is, extend the life of the tire without causing a decrease in the uneven wear resistance and tear resistance of the ribs.

  The tire size is the same as in Example 1, the first sipe state at the time of contact is opened, the ratio P1 / W of the pitch P1 of the first sipe and the rib width W, the width Wb of the fourth belt layer, and the total tire width The present invention tires 3 to 5 (Examples 3 to 5) having the structure shown in FIGS. 1 and 2 except that the ratio Wb / Wt to Wt is as shown in Table 1, except for the third and fourth sipes, and the fourth sipes. The tire 6 (Example 6) of the present invention having the configuration shown in FIGS. 1 and 2 and the tire 7 (Example 7) of the present invention having the configuration shown in FIGS. Each was produced as a test tire.

  In the tires 6 and 7 of the present invention, the ratio P3 / P1 between the pitch P3 of the third sipe and the pitch P1 of the first sipe is 0.2. In the tire 7 of the present invention, the fourth sipe pitch P4 is larger than the third sipe pitch P3, and the ratio P4 / P3 is 1.3.

  Each test tire has a sipe depth of 10 mm and a width of 0.8 mm. Note that the depth of the sipe is the depth of a deep portion in the case of a sipe having a shallow portion and a deep portion. The ratio SW / D1 between the ratio of the shallow part of the first sipe and the depth D1 of the shallow part of the first sipe and the width SW of the first sipe is as shown in Table 1.

  When each of these test tires was subjected to an evaluation test for wear resistance, uneven wear resistance and tear resistance in the same manner as in Example 1, the results shown in Table 2 were obtained.

  From Table 2, it can be seen that Examples 4 and 5 having the ratio Wb / Wt of 0.4 to 0.6 can improve the wear resistance while improving the uneven wear resistance of the ribs.

  Further, Examples 6 and 7 in which the ratio P3 / P1 of the pitch P3 of the third sipe and the pitch P1 of the first sipe is in the range of 0.1 to 0.5 can further improve the uneven wear resistance of the ribs. I understand.

  In addition, it can be seen that the tear resistance of the rib can be further improved in Example 7 in which the fourth sipe whose only one end communicates with the main groove at the end of the rib in the shoulder region is arranged at a pitch larger than the pitch of the third sipe.

It is a tire meridian half section view showing one embodiment of a heavy-duty pneumatic tire of the present invention. FIG. 2 is a partial development view of a tread surface of the heavy duty pneumatic tire of FIG. 1. It is explanatory drawing of the 1st sipe which shows the state which projected the 1st sipe of FIG. 2 to the tire circumferential direction. It is an expanded sectional view explaining the open state of the 1st sipe at the time of grounding. It is explanatory drawing of the 2nd sipe which shows the state which projected a part of 2nd sipe of FIG. 2 to the tire width direction. It is a top view which shows the other example of the 2nd sipe which cross | intersects a 1st sipe. FIG. 4 is a partial development view of a tread surface showing a tread pattern of a conventional tire 1. 4 is a partial development view of a tread surface showing a tread pattern of a conventional tire 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 7 Belt layer 7D 4th belt layer 11 Tread surface 11S Shoulder area 12 Main groove 13, 14 Rib 15 1st sipe 16 2nd sipe 17 3rd sipe 18 4th sipe 20 Second sipe 51 Shallow part TC Tire circumferential direction

Claims (6)

Four main grooves extending in the tire circumferential direction are arranged on the tread surface, three land portions are formed between the main grooves, and at least one of the three land portions is formed as a rib. In the heavy load pneumatic tire, the first sipes extending in the tire width direction on the rib and having both ends communicating with the main groove are arranged at a predetermined pitch P1 in the tire circumferential direction.
The ratio P1 / W between the pitch P1 of the first sipe and the width W of the rib on which the first sipe is arranged is in the range of 0.80 to 0.95, while the rib intersects each first sipe. Two sipes are extended in the tire circumferential direction, and the first sipe has a width of 0.5 to 1.0 mm and is composed of a shallow part and a deep part arranged in the rib width direction. The shallow portion partially exists in the rib width direction, and the shallow portion occupies 40 to 80% of the first sipe, so that the load corresponding to the maximum load capability described in JATMA and the maximum load capability can be obtained. A heavy-duty pneumatic tire configured so that the first sipe is in an open state on the tread surface in a ground contact shape of the tread surface obtained under a corresponding air pressure condition.   The heavy-duty pneumatic tire according to claim 1, wherein the three land portions are formed on ribs, and the first sipe and the second sipe are arranged on each rib. The heavy duty pneumatic tire according to claim 1 or 2 , wherein a ratio SW / D1 between a depth D1 of a shallow portion of the first sipe and a width SW of the first sipe is in a range of 0.25 to 1.00. . A carcass layer is extended to the left and right bead portions, a plurality of belt layers are provided on the outer periphery side of the carcass layer of the tread portion, and the width Wb of the belt layer located on the outermost side in the tire radial direction among the plurality of belt layers and the tire The heavy duty pneumatic tire according to any one of claims 1 to 3 , wherein a ratio Wb / Wt to the total width Wt is in a range of 0.4 to 0.6. Between each first sipe adjacent to both ends in the tire width direction of each rib, a third sipe having only one end communicating with the main groove is arranged at a predetermined pitch P3 in the tire circumferential direction, and the pitch P3 of the third sipe The heavy duty pneumatic tire according to any one of claims 1 to 4 , wherein a ratio P3 / P1 to the pitch P1 of the first sipes is in a range of 0.1 to 0.5. A rib is formed in a shoulder region located on both outer sides in the tire width direction of the four main grooves, and a fourth sipe in which only one end communicates with the main groove at an end facing the main groove in the tire circumferential direction. The heavy-duty pneumatic tire according to claim 5 , wherein the heavy-duty pneumatic tire is arranged at a predetermined pitch P4 and the pitch P4 of the fourth sipe is larger than the pitch P3 of the third sipe.

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