JP2008221964A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress failure by improving heat generation resistance while preventing a pneumatic tire with main grooves extending in a tire circumferential direction and lug grooves extending from tread ends from lowering its eccentric wear resistance. <P>SOLUTION: Land part rows 20, 21 are formed by providing the tread part 2 with three main grooves 10, 11 extending in a zigzag shape in the tire circumferential direction and the plurality of lug grooves 13 extending from a tread end TE in the tire width direction and ending in a shoulder land part row 21 are provided at the shoulder land part row 21 between the tread end TE and the outside main groove 11 in the tire circumferential direction with a predetermined interval. A plurality of widthwise grooves 15 extending from the outside main groove 11 in the tire width direction and ending in the shoulder land part row 21 are provided along an edge part at the outside main groove 11 side of the shoulder land part row 21. The respective widthwise grooves 15 are formed to be narrower than the lug grooves 13 and provided near a center between adjacent respective lug grooves 13 in the tire circumferential direction. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a pneumatic tire provided with a main groove extending in a tire circumferential direction in a tread portion, and more particularly to a pneumatic tire that improves heat resistance and suppresses occurrence of a failure.

  In general, a pneumatic tire includes a plurality of belt layers on the outer peripheral side of the carcass layer of the tread portion, and increases the coefficient of friction between the tire and the road surface on the outer peripheral surface (tread surface) in contact with the road surface of the tread portion. In order to ensure steering stability or improve drainage performance to improve wet performance, a tread pattern including various grooves, sipes, and the like is formed. As a typical example of this tread pattern, conventionally, a plurality of land portion rows (ribs) are formed by a plurality of main grooves extending in the tire circumferential direction, and a plurality of portions extending in the tire width direction are formed in a part of the land portion rows. A so-called rib lug pattern provided with a plurality of lug grooves is widely known.

  Although FIG. 2 is not described in patent documents, it is a top view which expands and shows an example of the tread pattern of such a conventional pneumatic tire, and shows the part of the tire circumferential direction typically. .

  As shown in the figure, the pneumatic tire 80 includes a plurality of (three in the figure) main grooves 10 and 11 extending in a zigzag manner in the tire circumferential direction (vertical direction in the figure) in the tread portion 2. A plurality of (four rows in the figure) land portion rows 20 and 21 defined by the main grooves 10 and 11 are provided. Further, the pneumatic tire 80 has a plurality of sub-grooves 12 extending across the tire width direction (left-right direction in the drawing) in both center land portion rows 20 arranged with the tire equatorial plane CL interposed therebetween. Both shoulder land portions located between the outer main groove 11 on the tire width direction outer side and the tire width direction outer end (tread end) TE of the tread portion 2 and located on the outermost side in the tire width direction (shoulder portion side) The row 21 has a plurality of lug grooves 13 extending from the tread end TE in the tire width direction and terminating in the shoulder land portion row 21.

  Since such a tread pattern of the pneumatic tire 80 is excellent in driving / braking performance, turning performance, and the like, it is widely used in various tires, for example, heavy duty tires such as buses and trucks. However, in this conventional pneumatic tire 80, depending on use conditions and the like, separation may occur due to heat generation of tread rubber and the like accompanying use, and the pneumatic tire 80 may fail. Such separation, especially when used at high speeds and high loads, is located near the outer edge in the tire width direction of the second and third belt layers from the inner side in the tire radial direction and at the end. The generated heat tends to be accumulated in the tire as the depth of the main grooves 10 and 11 of the tread portion 2 in the initial stage of use (from the beginning of wear to the initial stage of wear) and the like increases as the depth increases. Therefore, the occurrence probability tends to increase.

  Therefore, conventionally, each lug groove 13 formed in the shoulder land portion row 21 is enlarged, and the volume occupied by each lug groove 13 is relatively increased with respect to the volume of the shoulder land portion row 21. It has been done to deal with. According to this, since the surface area of the shoulder land portion row 21 can be increased, the heat radiation property (heat radiation effect) is increased, and the heat resistance of the shoulder land portion row 21 and the pneumatic tire 80 can be secured. Can be suppressed to some extent.

  However, when the volume of the lug groove 13 is increased in this way, the stress of the shoulder land portion row 21 decreases, and stress is concentrated when a lateral force is input during tire rolling. The edge part of the shoulder land part row | line | column 21 becomes easy to move centering | focusing on the zigzag convex part which protrudes in the direction of the outer main groove 11 which is easy. As a result, the slip on the road surface of the side end portion (especially near the front end portion of the convex portion) along the outer main groove 11 of the shoulder land portion row 21 becomes larger than other portions, and the wear in the vicinity thereof is promoted and the rail There is a risk that uneven wear resistance may be reduced, such as way wear is likely to occur. Therefore, conventionally, it has been proposed to form a plurality of sipes at the edge portion of the shoulder land portion row 21 to suppress the occurrence of uneven wear (see Patent Document 1).

FIG. 3 is a plan view of an essential part showing a developed tread pattern of this conventional pneumatic tire.
As shown in the figure, the pneumatic tire 90 includes a plurality of sipes extending in the tire width direction at the edge portion on the outer main groove 11 side of the shoulder land portion row 21 in addition to the tread pattern of the pneumatic tire 80 described above. 91 is provided. In this pneumatic tire 90, the plurality of sipes 91 are arranged at the tips of the zigzag convex portions of the shoulder land portion row 21 to alleviate the stress concentration on the convex portions, and the vicinity thereof is the center. The occurrence of uneven wear (particularly railway wear) is suppressed.

  However, in this conventional pneumatic tire 90, it is difficult to suppress other uneven wear associated with the rigidity reduction of the shoulder land portion row 21, and when the volume of the lug groove 13 is increased, the uneven wear resistance decreases. There is a risk that it cannot be sufficiently prevented. Further, in such a pneumatic tire 90, although the heat dissipation performance on the tread end TE side is mainly increased, the effect of improving the heat dissipation performance on the outer main groove 11 side is low, and the temperature in the vicinity thereof is increased to cause a failure. It is necessary to further improve the heat resistance, such as fears. As described above, in these conventional pneumatic tires 80 and 90, it is difficult to secure both a sufficiently large uneven wear resistance and heat resistance in the shoulder land portion row 21.

JP-A-6-286421

  The present invention has been made in view of the above-described conventional problems, and the object thereof is to prevent uneven wear resistance of a pneumatic tire provided with a main groove extending in a tire circumferential direction and a lug groove extending from a tread end in a tread portion. It is to prevent the occurrence of failure by improving the heat resistance while preventing the decrease.

According to a first aspect of the present invention, the tread portion includes a plurality of main grooves extending in the tire circumferential direction, and a plurality of land portion rows partitioned by the main grooves, and the outer main groove and the tread on the outermost side in the tire width direction. A pneumatic tire having a plurality of lug grooves extending in a tire width direction from the tread end and terminating in the shoulder land portion row on a shoulder land portion row disposed between the shoulder land portion row and the shoulder land portion row. The partial row has a plurality of widthwise grooves that extend in the tire width direction from one end opening in the outer main groove and are narrower than the lug groove that terminates in the shoulder land portion row. .
According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, at least one of the lug grooves adjacent to each other in the tire circumferential direction of the shoulder land portion row is disposed between the circumferential positions. It has the said width direction groove | channel.
The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, wherein the lug groove has a length in the tire width direction of 60 to 70% of a maximum width in the tire width direction of the shoulder land portion row. The width in the tire circumferential direction is 35 to 40% of the length in the tire width direction of the lug groove, and the depth in the tire radial direction is the depth in the tire radial direction of the outer main groove. 60 to 65% of the depth.
According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, the widthwise groove has a length in the tire width direction having a maximum width in the tire width direction of the shoulder land portion row. 20-30% in length, the width in the tire circumferential direction is 15-40% of the width in the tire circumferential direction of the lug groove, and the depth in the tire radial direction is in the tire radial direction of the outer main groove The depth is 10 to 15% of the depth of.
According to a fifth aspect of the present invention, in the pneumatic tire according to any one of the second to fourth aspects, the width of each of the lug grooves of the shoulder land portion row is one between the arrangement positions in the tire circumferential direction. A center position in the tire circumferential direction of one end portion that has a direction groove and opens to the outer main groove of the width direction groove, or the center position of the adjacent circumferential position of each lug groove in the tire circumferential direction. It is characterized by being within 7% of the distance in the tire circumferential direction between the arrangement positions from the center position of the positions.

  According to the present invention, heat resistance is improved while preventing uneven wear resistance of a pneumatic tire provided with a main groove extending in the tire circumferential direction and a lug groove extending from the tread end in the tread portion. The occurrence of failure can be suppressed.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The pneumatic tire of the present embodiment is a pneumatic tire such as a heavy duty tire, for example, a bead core disposed in a pair of tire bead portions, at least one carcass layer extending in a toroidal shape therebetween, and a tread portion. It has a known pneumatic tire structure such as a belt layer disposed on the outer peripheral side of the carcass layer and a tread rubber having a predetermined tread pattern.

FIG. 1 is a plan view showing a developed tread pattern of the pneumatic tire 1 of the present embodiment, and schematically shows a part of the tire circumferential direction.
As shown in the figure, the pneumatic tire 1 includes a plurality of (here, three) main grooves 10 and 11 extending in a tread portion 2 extending in a tire circumferential direction, for example, in a straight line shape or a zigzag shape (here, zigzag shape). , And a plurality (four in this case) of land portion rows 20 and 21 extending in the tire circumferential direction defined by the main grooves 10 and 11. In addition, a plurality of sub-grooves 12, lug grooves 13, and width direction grooves 15 that extend in the tire width direction and are arranged in the tire circumferential direction are provided at predetermined positions of the land portion rows 20 and 21, respectively.

  In this pneumatic tire 1, the three main grooves 10, 11 bent and extended in a zigzag shape are arranged on the tire equatorial plane CL (central main groove 10) and on the outer side in the tire width direction (tread end TE side). It arrange | positions in each of the substantially intermediate position (outer side main groove 11) between tire equator surface CL and both tread edge TE. As a result, the tread portion 2 is partitioned, the two center land portion rows 20 positioned at the center portion with the tire equator plane CL disposed between the main grooves 10 and 11 being sandwiched, and the outermost side in the tire width direction ( Here, two rows of shoulder land portions 21 are formed between the outer main groove 11 on the outer side and the tread end TE, and are located on the outermost side in the tire width direction (the shoulder portion side).

  The main grooves 10 and 11 are, for example, tire circumferential direction while being bent in a predetermined shape including substantially linear or curved portions inclined in opposite directions alternately with respect to the tire circumferential direction according to the required tire performance and the like. However, here, it is formed in a zigzag shape consisting of a substantially linear portion. The main grooves 10 and 11 are formed so that the width, depth in the tire radial direction, zigzag (amplitude) width, pitch, phase, and the like are substantially the same or substantially the same, and are substantially the same in the tire circumferential direction. Bending in the same direction in the tire width direction at the same position.

  The land portion rows 20 and 21 extend in the tire circumferential direction while being bent in the tire width direction in a zigzag shape corresponding to the shapes of the main grooves 10 and 11, and the center land portion row 20 has a tire width. Both groove walls and edge portions on both sides (main grooves 10 and 11 side) in the direction are zigzag, and the shoulder land portion row 21 is zigzag only on the groove wall and edge portions on the inner side in the tire width direction (outer main groove 11 side). It is formed in a shape. Moreover, the tire of the bending position of each land part row | line | column 20,21, ie, the zigzag-shaped convex part or recessed part (henceforth a convex part or a recessed part) which protrudes in the main grooves 10 and 11 direction (it protrudes in the left-right direction in the figure). The circumferential position and the pitch length of the zigzag (the interval in the tire circumferential direction between the convex portions or concave portions on the same main groove 10, 11 side) are also substantially the same.

  Further, of these land portion rows 20 and 21, the center land portion row 20 has one kind of sub-groove 12, and the shoulder land portion row 21 has two kinds of lug grooves 13 and width direction grooves 15, respectively. A plurality of pieces are arranged at predetermined intervals in the circumferential direction.

  The sub-groove 12 is a narrow groove that is narrower than the main grooves 10 and 11, and extends from the end on the side of one main groove 10, 11 of the center land portion row 20 in an inclined manner in the tire width direction. After being bent in the opposite direction to the tire width direction in the land portion row 20, it is formed so as to extend incline in the tire width direction to the end portion on the other main groove 10, 11 side. In this way, each sub-groove 12 traverses the center land portion row 20 in the tire width direction, and both ends thereof open to the main grooves 10 and 11, respectively, so that the center land portion row 20 is divided into a plurality of block-like portions. It is divided into two. Further, each sub-groove 12 is connected to the inner side in the tire width direction (the tire equatorial plane CL side) so as to connect between the convex portion and the distal end (bending position) of the concave portion at substantially the same tire circumferential direction position of the center land portion row 20. Are arranged in the vicinity of the concave portion on the central main groove 10 side, and the outer end portion is arranged in the vicinity of the convex portion on the outer main groove 11 side. The sub-grooves 12 of both the center land portion rows 20 are substantially point-symmetric with each other, and are arranged in each tire land portion row 20 in the tire circumferential direction at substantially the same interval as the zigzag pitch length. It is alternately arranged in each of the center land rows 20 along the direction.

  The lug groove 13 is formed to be relatively wide compared to the grooves 12 and 15 extending in the other tire width direction, and extends substantially linearly from the tread end TE of the shoulder land portion row 21 in the tire width direction. It terminates at a predetermined position in the shoulder land portion row 21 without penetrating to the main groove 11. The arrangement position of the plurality of lug grooves 13 in the tire circumferential direction is a position where the width in the tire width direction of the shoulder land portion row 21 is maximum, that is, in the vicinity of the protruding end position of each convex portion of the shoulder land portion row 21. The shoulder land portion row 21 is arranged in the tire circumferential direction at substantially the same interval as the zigzag pitch length. In the pneumatic tire 1, each of the lug grooves 13 has a length N in the tire width direction from the tread end TE to the inner end in the tire width direction, which is 60 of the maximum width W in the tire width direction of the shoulder land portion row 21. It is formed in a length of ˜70%. In addition, the width H in the tire circumferential direction excluding the gradually decreasing end portion side is 35 to 40% of the length N in the tire width direction, and the depth in the tire radial direction is the outer main groove 11. It is formed at a depth of 60 to 65% of the depth in the tire radial direction.

  The width direction groove 15 is a so-called hot water groove that is narrower than the lug groove 13, extends substantially linearly in the tire width direction from one end portion in the tire width direction that opens to the outer main groove 11, and reaches the tread end TE. It does not penetrate and terminates at a predetermined position in the shoulder land portion row 21. This width direction groove | channel 15 is each between the arrangement positions (arrangement position of the groove | channel center of a tire circumferential direction) of each lug groove 13 adjacent to the tire circumferential direction of the shoulder land part row | line | column 21, ie, each of these each At least one (here, one) is arranged in each of the tire circumferential direction ranges of the shoulder land row 21 divided by the arrangement position.

  In this pneumatic tire 1, the width direction groove 15 is located at the tire circumferential direction position where the lug groove 13 of the shoulder land portion row 21 is not formed, and at the approximate center of the tire circumferential direction arrangement position of each adjacent lug groove 13. The width direction groove | channel 15 is formed in the vicinity of a position, and is spaced apart from each lug groove | channel 13 by the substantially equal distance in the tire circumferential direction. Therefore, in this pneumatic tire 1 in which the lug groove 13 is disposed in the convex portion, the width direction groove 15 is disposed in the vicinity of the bending position of each concave portion of the shoulder land portion row 21, and the shoulder land portion in the tire circumferential direction. The zigzag pitch length of the row 21 is provided at substantially the same interval. Further, the width direction groove 15 is formed to have the same width as the sub groove 12 of the center land portion row 20 and is smaller than the lug groove 13, that is, the length L in the tire width direction, the tire circumferential direction. The width F and the tire radial depth are set to predetermined values smaller than those of the lug grooves 13.

  In addition, the width direction groove | channel 15 of this embodiment has the width L of the tire circumferential direction in which the length L of the tire width direction is 20 to 30% of the maximum width W of the shoulder land portion row 21 in the tire width direction. However, the depth in the tire radial direction is 15 to 40% of the width H of the lug groove 13 in the tire circumferential direction, and the depth in the tire radial direction of the outer main groove 11 is 10 to 15%. Each is formed. Further, the width direction groove 15 has a tire circumferential direction center position in the tire circumferential direction of one end portion opened to the outer main groove 11 in the tire circumferential direction adjacent to each other in the tire circumferential direction. It is arranged at the center position S of the arrangement position or within a distance of 7% of 1/2 (half) of the distance P in the tire circumferential direction between the arrangement positions from the center position S. That is, the center position of the one end of the width direction groove 15 is arranged within a distance of 0 to 7% of the distance P from the center position S between the lug grooves 13 in both directions in the tire circumferential direction.

  The lug grooves 13 and the width direction grooves 15 are alternately arranged along the tire circumferential direction in each shoulder land portion row 21, and each of the shoulder land portion rows 21 located on the tread end TE side has a tire circumference. Alternatingly arranged along the direction. In addition, each width direction groove 15 has an opening to the outer main groove 11 opposed to an opening to the outer main groove 11 of the sub groove 12 formed in the center land portion row 20 with the outer main groove 11 interposed therebetween. Placed in position.

  In the pneumatic tire 1 of the present embodiment described above, since the plurality of width direction grooves 15 are formed on the outer main groove 11 side of the shoulder land portion row 21, the surface area of the shoulder land portion row 21 is increased, and the heat dissipation thereof. Can increase the sex. At the same time, since the air flow in the outer main groove 11 can be disturbed by the width direction groove 15 to generate a turbulent flow in the groove, the groove wall on the outer main groove 11 side and the periphery thereof can be used. Higher heat dissipation effect can be obtained. In addition, heat generated in the shoulder land portion row 21 is transferred to both sides in the tire width direction by a synergistic effect of heat radiation by the width direction groove 15 on the outer main groove 11 side and heat radiation by the lug groove 13 extending from the tread end TE. The heat dissipation can be effectively enhanced, such as being able to dissipate heat.

  Therefore, according to this pneumatic tire 1, the heat radiation property of the shoulder land portion row 21 can be enhanced without increasing the lug groove 13, and the separation due to the shoulder land portion row 21 and particularly heat generation is likely to occur. It is possible to suppress an increase in the temperature in the vicinity of the outer end in the tire width direction of the second and third belt layers from the inner side in the tire radial direction. Thereby, generation | occurrence | production of the breakdown resulting from heat_generation | fever of the pneumatic tire 1 can be improved, such as being able to suppress effectively that generation | occurrence | production of a separation can be suppressed.

  At the same time, since the width direction groove 15 is made relatively narrow by forming it narrower than the lug groove 13, the rigidity of the shoulder land portion row 21 is kept low compared to the case where the lug groove 13 is made larger. be able to. As a result, the shoulder land portion row 21 can be secured with sufficient rigidity that can suppress the occurrence of uneven wear due to a reduction in rigidity such as railway wear.

  Therefore, according to the present embodiment, it is possible to improve the heat resistance and prevent the occurrence of failure while preventing the uneven wear resistance from being lowered. Moreover, in this pneumatic tire 1, since at least one width direction groove 15 is formed between the positions where the lug grooves 13 are arranged, the portion between the lug grooves 13 where the heat dissipation of the shoulder land portion row 21 tends to be low. The heat dissipating property can be reliably ensured.

  Here, when the width direction groove 15 is disposed near the middle of each lug groove 13, which is the portion where the heat radiation performance of the shoulder land portion row 21 is most likely to be the lowest, the heat generated in the shoulder land portion row 21 is effective. It is possible to dissipate heat. Therefore, as in the present embodiment, it is desirable that the width direction groove 15 is disposed in the vicinity of the substantially center position of the position in the tire circumferential direction of each lug groove 13 adjacent in the tire circumferential direction. Further, the center position in the tire circumferential direction of one end portion opened to the outer main groove 11 of the width direction groove 15 is at or from the center position S of the adjacent circumferential position of the lug groove 13 in the tire circumferential direction. It is more desirable to locate within 7% of the distance P in the tire circumferential direction between the arrangement positions. When this range is exceeded, the width direction groove 15 approaches one of the adjacent lug grooves 13 and is the portion sandwiched between the other lug grooves 13 of the shoulder land portion row 21. This is because the heat radiation may be insufficient. In addition, when the width direction groove 15 is disposed within the above range, the width direction groove 15 is disposed at a position substantially evenly separated from both the lug grooves 13, and the heat dissipation effect by the width direction groove 15 is reduced. The heat dissipation can be further enhanced by substantially evenly and reliably exhibiting the same.

  Moreover, if the length L of the width direction groove | channel 15 is less than 20% of the maximum width W of the shoulder land part row | line | column 21, there exists a possibility that the above-mentioned turbulent flow effect may become small and sufficient heat dissipation effect may not be acquired. On the contrary, if it exceeds 30%, the rigidity of the shoulder land portion row 21 is lowered, and uneven wear tends to occur. Therefore, the length L of the width direction groove 15 is desirably 20 to 30% of the maximum width W of the shoulder land portion row 21. From the viewpoint of suppressing the occurrence of uneven wear, 20 to 23% It is more desirable to make the length. Similarly, the width direction groove 15 has a width F of 15 to 40% of the width H of the lug groove 13, a depth in the tire radial direction, and a depth in the tire radial direction of the outer main groove 11 of 10%. It is desirable to form each at a depth of ˜15%. If these widths F and depths are not within the respective ranges, the turbulent flow effect may be reduced, and a sufficient heat dissipation effect may not be obtained. Rigidity decreases and uneven wear tends to occur.

  On the other hand, if the length N of the lug groove 13 is less than 60% of the maximum width W of the shoulder land portion row 21, the heat radiation by the lug groove 13 is reduced, and the shoulder land portion row 21 as a whole has sufficient heat dissipation. On the contrary, if it exceeds 70%, the rigidity of the shoulder land portion row 21 is lowered and uneven wear tends to occur. Therefore, the length N of the lug groove 13 is desirably 60 to 70% of the maximum width W of the shoulder land portion row 21. Similarly, the lug groove 13 has a width H of 35-40% of its own length N, a depth in the tire radial direction, and a depth in the tire radial direction of the outer main groove 11 of 60-65. It is desirable to form each at a depth of%. If these widths H and depths are less than the respective ranges, there is a risk that the heat radiation by the lug grooves 13 will be reduced and sufficient heat dissipation will not be obtained as the shoulder land portion row 21 as a whole. If it exceeds, the rigidity of the shoulder land part row | line 21 will fall, and it will become easy to generate | occur | produce uneven wear.

  In the present embodiment, each of the three main grooves 10 and 11 is formed in a zigzag shape, but these may be formed in other shapes extending in the tire circumferential direction, such as a linear shape or a wavy shape, or In the tread portion 2, two or four or more similar main grooves may be formed. Further, the positions of the lug grooves 13 and the width direction grooves 15 in the shoulder land portion row 21 are opposite to those of the present embodiment, and the width direction grooves 15 are formed in the convex portions of the shoulder land portion row 21 and the lug grooves 13 are formed in the recessed portions. May be arranged at other positions in the shoulder land portion row 21. Furthermore, two or more width direction grooves 15 may be arranged between the lug grooves 13, for example, two are arranged at substantially equal intervals between the arrangement positions of the lug grooves 13 adjacent in the tire circumferential direction.

(Tire test)
In order to confirm the effect of the present invention, the pneumatic tire 1 (hereinafter referred to as “implemented product”) of the embodiment having the tread pattern (see FIG. 1) described above, and the width direction groove 15 from the shoulder land portion row 21 thereof. A comparative example (conventional example) pneumatic tire 80 (hereinafter referred to as a comparative product) provided with the removed tread pattern (see FIG. 2) was prototyped, and a heat resistance test was performed under the following conditions. These implementation products and comparative products were all formed in the same manner except for the presence or absence of the width direction groove 15, and the heat resistance was evaluated by indoor and field tests, respectively.

In the indoor test, the implementation product and the comparative product were respectively attached to the test rim and attached to the indoor drum test apparatus, pressed against the rotating drum, loaded with a load of 3350 kg, and rotated at a speed of 65 km / h for 20 hours. This was done by indoor drum evaluation, in which the temperature of each shoulder land row 21 was measured and compared.
Table 1 shows the measurement results obtained by measuring and averaging the temperatures of the shoulder land rows 21 of the comparative product and the implementation product.

  As a result, as shown in Table 1, the temperature during running for 20 hours was 100 ° C. in the comparative product, but it was as low as 90 ° C. in the implemented product, and the heat dissipation increased and the heat resistance increased. Was found to have improved.

In the field test, each of the 100 actual products and comparative products were each applied to a vehicle with 2-D · 4 (front wheel is one shaft with two wheels, rear wheel is two drive wheels and two wheels with two wheels). The mounting position was fixed and the tires were run on the ground, and the number of tires that had failed due to heat generation was measured and compared and evaluated.
Table 2 shows the number of occurrences and the occurrence rates of the comparison products and the implementation products.

  As a result, as shown in Table 2, in the comparative product, the number of failure occurrences was 5 and the occurrence rate was 5%, whereas in the implemented product, the number of failure occurrences was 2 and the occurrence rate was 2%. It was found that the occurrence of failures was reduced.

  From the above results, it was proved by the present invention that the uneven wear resistance of the pneumatic tire 1 can be prevented from being lowered and the heat generation resistance can be improved and the occurrence of failure can be suppressed.

It is a top view which expands and shows the tread pattern of the pneumatic tire of this embodiment. It is a top view which expands and shows an example of the tread pattern of the conventional pneumatic tire. It is a principal part top view which expand | deploys and shows the tread pattern of the conventional pneumatic tire.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Pneumatic tire, 2 ... Tread part, 10 ... Central main groove, 11 ... Outer main groove, 12 ... Sub groove, 13 ... Lug groove, 15 ... Width Direction groove, 20 ... center land portion row, 21 ... shoulder land portion row, CL ... tire equatorial plane, TE ... tread edge.

Claims (5)

The tread portion includes a plurality of main grooves extending in the tire circumferential direction and a plurality of land portion rows partitioned by the main grooves, and is disposed between the outer main groove on the outermost side in the tire width direction and the tread end. A pneumatic tire having a plurality of lug grooves extending in the tire width direction from the tread end to the shoulder land portion row and terminating in the shoulder land portion row,
The shoulder land portion row has a plurality of widthwise grooves extending in the tire width direction from one end portion opened in the outer main groove and narrower than the lug groove terminating in the shoulder land portion row. A featured pneumatic tire. In the pneumatic tire according to claim 1,
A pneumatic tire comprising at least one width direction groove between each of the circumferential positions of the lug grooves adjacent to each other in the tire circumferential direction of the shoulder land portion row. In the pneumatic tire according to claim 1 or 2,
The length of the lug groove in the tire width direction is 60 to 70% of the maximum width in the tire width direction of the shoulder land portion row, and the width in the tire circumferential direction is the length of the lug groove in the tire width direction. A pneumatic tire characterized by having a width of 35 to 40% of the width and a depth in the tire radial direction of 60 to 65% of a depth of the outer main groove in the tire radial direction. In the pneumatic tire according to any one of claims 1 to 3,
The length in the tire width direction is 20-30% of the maximum width in the tire width direction of the shoulder land portion row, and the width in the tire circumferential direction is the width in the tire circumferential direction of the lug groove. A pneumatic tire having a width of 15 to 40% of a width, and a depth in a tire radial direction being a depth of 10 to 15% of a depth of the outer main groove in a tire radial direction. In the pneumatic tire according to any one of claims 2 to 4,
Each of the lug grooves of the shoulder land portion row has one width direction groove between the arrangement positions in the tire circumferential direction;
The center position in the tire circumferential direction of one end opening to the outer main groove of the width direction groove is the center position of the adjacent circumferential position of the lug groove in the tire circumferential direction or the center position of the arrangement position. A pneumatic tire characterized by being within a distance of 7% that is 1/2 of a distance in the tire circumferential direction between the arrangement positions.

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