JP2016055816A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire adopting pitch variation as tread pattern, which can reduce rolling resistance and suppress uneven wear while maintaining excellent drainage performance.SOLUTION: In the pneumatic tire, on a tread surface 10, a plurality of land part rows 12 are formed by a plurality of main grooves 11, a plurality of lug grooves 13 are provided in the land part rows 12 and the land part rows 12 are partitioned by the lug grooves 13 into blocks 15, and at least three kinds of pitch lengths in repeat units, which are constituted of a block 15 in one land part row 12 having the lug grooves 13 formed and lug grooves 13 adjacent to one side of the block 15, exist. Only in lug grooves 13 included in the repeat units having a pitch length equal to 70% of the maximum pitch length or less, of the lug grooves 13, are provided bottom raised parts 16 having groove bottoms of end parts thereof communicated with the main grooves 11 protruded.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a pneumatic tire in which pitch variation is adopted for a tread pattern, and more specifically, a pneumatic tire that can reduce rolling resistance while suppressing excellent drainage and suppress uneven wear. Regarding tires.

  Conventionally, a tread pattern employing a pitch variation for the purpose of reducing pattern noise caused by the tread pattern (for example, a tread pattern including a block row in which a plurality of blocks having different circumferential lengths are connected in the tire circumferential direction). May be provided. At this time, for example, in Patent Document 1, each block included in the block row is partitioned in the block row in order to prevent the circumferential block rigidity from becoming uneven due to different circumferential lengths. The bottom raised portion provided in the lug groove between the blocks having a smaller circumferential length than the bottom raised portion provided in the lug groove between the blocks having a large circumferential length is provided in the lug groove. This suggests that this is more rigid.

  However, such a raised bottom portion increases the rigidity of the block adjacent to the lug groove in which the raised bottom portion is formed and suppresses deformation of the block, thereby reducing rolling resistance and suppressing occurrence of uneven wear. Is effective, but there is a problem that the drainage performance originally desired for the lug groove is hindered. Therefore, in the tread pattern that adopts pitch variation, both maintaining excellent drainage performance and suppressing unevenness of block (land) rigidity (ie, reducing rolling resistance and suppressing uneven wear) are highly compatible. Is required.

JP 2006-044469 A

  An object of the present invention relates to a pneumatic tire in which pitch variation is adopted for a tread pattern, and it is possible to reduce rolling resistance while maintaining excellent drainage and to suppress uneven wear. .

  In order to achieve the above object, the pneumatic tire of the present invention is provided with a plurality of main grooves extending in the tire circumferential direction in a tread portion, and a plurality of land portion rows are formed by the main grooves. The row is provided with a plurality of lug grooves with at least one end communicating with the main groove and extending in the tire width direction, the land row is partitioned into a plurality of blocks by the lug grooves, and the lug grooves In the pneumatic tire in which three or more types of pitch lengths of the repeating unit including the block in one land portion row formed and the lug groove adjacent to one side of the block exist, the maximum pitch length of the lug grooves Only the lug groove included in the repeating unit having a pitch length of 70% or less is provided with a bottom raised portion in which the groove bottom of the end portion on the side communicating with the main groove is raised.

  In the present invention, a block included in a repeating unit with a small pitch length has lower rigidity and is more likely to be deformed than other blocks (blocks included in a repeating unit with a large pitch length). However, since the bottom-up part is provided only in the lug groove included in the repeating unit with a small pitch length, the block included in the same repeating unit (the block included in the repeating unit with a small pitch length) It can be selectively reinforced, rolling resistance can be reduced, and uneven wear can be suppressed. At this time, since the lug groove in which the bottom raised portion is formed is limited to only the lug groove included in the repeating unit having a small pitch length, deterioration of drainage performance is minimized and excellent drainage performance is maintained. be able to.

  In this invention, it is preferable that the bottom raising height of a bottom raising part is 20 to 40% of the groove depth of a lug groove. In this way, by limiting the height of the bottom to a predetermined range, it is possible to sufficiently obtain the effect of improving rigidity (reducing rolling resistance and suppressing uneven wear) while effectively suppressing deterioration of drainage performance. Can do.

  In the present invention, it is preferable that the bottom raising height of the bottom raising portion gradually decreases toward the main groove. Thus, by changing the height of raising the bottom, the flow of water in the lug groove can be improved, and the drainage performance can be more effectively maintained.

1 is a meridian cross-sectional view of a pneumatic tire according to an embodiment of the present invention. It is a front view showing an example of the tread pattern of the pneumatic tire which consists of an embodiment of the present invention. It is an enlarged view which shows an example of the bottom raising part of this invention. It is an enlarged view which shows the other example of the bottom raising part of this invention.

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

  In FIG. 1, the symbol CL represents the tire equator. The pneumatic tire according to the present invention includes a tread portion 1, a sidewall portion 2, and a bead portion 3. A carcass layer 4 is mounted between the pair of left and right bead portions 3. The carcass layer 4 includes a plurality of reinforcing cords extending in the tire radial direction, and is folded back around the bead core 5 disposed in each bead portion 3 from the vehicle inner side to the outer side. A bead filler 6 is disposed on the outer periphery of the bead core 5, and the bead filler 6 is wrapped by the main body portion and the folded portion of the carcass layer 4. On the other hand, a plurality of layers (two layers in FIG. 1) of belt layers 7 and 8 are embedded on the outer peripheral side of the carcass layer 4 in the tread portion 1. Each of the belt layers 7 and 8 includes a plurality of reinforcing cords inclined with respect to the tire circumferential direction, and is disposed so that the reinforcing cords cross each other between the layers. In these belt layers 7 and 8, the inclination angle of the reinforcing cord with respect to the tire circumferential direction is set, for example, in a range of 10 ° to 40 °. Further, a belt reinforcing layer 9 is provided on the outer peripheral side of the belt layers 7 and 8. The belt reinforcing layer 9 includes an organic fiber cord oriented in the tire circumferential direction. In the belt reinforcing layer 9, the organic fiber cord has an angle with respect to the tire circumferential direction set to, for example, 0 ° to 5 °.

  The present invention is applied to such a general pneumatic tire, but its cross-sectional structure is not limited to the basic structure described above.

  As illustrated in FIG. 2, a plurality of (four in FIG. 2) main grooves 11 extending in the tire circumferential direction are formed on the outer surface (tread surface 10) of the tread portion 1 of the pneumatic tire of the present invention. A plurality of rows (5 rows in FIG. 2) of land portions 12 are formed by these main grooves 11. Of these main grooves 11, a pair located on the tire equator CL side is referred to as a center-side main groove 11C, and a pair located on the outer side in the tire width direction is referred to as an outer main groove 11S. Also, among the plurality of land portion rows 12, the one located between the pair of center side main grooves 11C is the center land portion row 12C, and the one located between the center side main groove 11C and the outer main groove 11S is the middle. The land portion row 12M and the outer main groove 11S located on the outer side in the tire width direction are referred to as a shoulder land portion row 12S. In the example of FIG. 2, lug grooves 13 extending in the tire width direction are provided in the intermediate land portion row 12M and the shoulder land portion row 12S excluding the center land portion row 12C. Of the lug grooves 13, those provided in the intermediate land portion row 12M are referred to as intermediate lug grooves 13M, and those provided in the shoulder land portion row 12S are referred to as shoulder lug grooves 13S. In the example of FIG. 2, the intermediate lug groove 13M communicates with both the center main groove 11C and the outer main groove 11S, and the shoulder lug groove 13S communicates with one end at the outer main groove 11S and the other end at the other end. It terminates in the shoulder land portion row 12S. In addition to the intermediate lug groove 13M, the intermediate land portion row 12M is provided with a circumferential narrow groove 14 having a groove width smaller than that of the main groove 11 and extending in the tire circumferential direction. The land portion rows 12M and 12S are partitioned into blocks 15 by the lug grooves 13 and the circumferential grooves 14, respectively. In the present invention, the block 15 refers to a block having four sides defined by the main groove 12 and the lug groove 13 (and possibly the circumferential groove 14), and the main groove 12 and the lug groove 13 in the rib-like land portion. (And in some cases, the circumferential groove 14) and a portion (part of which is connected to another portion). Specifically, the intermediate land portion row 12M is divided into two blocks 15 (intermediate blocks 15M) in the tire width direction and in the tire circumferential direction by the intermediate lug grooves 13M and the circumferential narrow grooves 14. On the other hand, the shoulder land portion 12S is partitioned into a large number of blocks 15 (shoulder blocks 15S) in the tire circumferential direction by shoulder lug grooves 13S. The shoulder blocks 15S are partially outside the tire width direction. It is connected to another shoulder block 15S adjacent to.

  At this time, in one land portion row 12 (in the case of FIG. 2, each of the intermediate land portion row 12M and the shoulder land portion row 12S) in which the lug groove 13 is provided and the block 15 is partitioned, the block 15 and the block 15 Assuming that the lug groove 13 adjacent to one side is a single repeating unit, the circumferential length (pitch length P) of this repeating unit is not the same in all the repeating units, as shown in FIG. There are three or more (three types in FIG. 2) pitch lengths P (P1 to P3). At this time, the magnitude relationship between the pitch lengths P1 to P3 is P1 <P2 <P3. The pitch length P is measured at the position where the lug groove 13 communicates with the main groove 11 and is the distance from the edge of one lug groove 13 to the edge of the adjacent lug groove 13 (see the dotted line in FIG. 2). Moreover, in FIG. 2, although only the repeating unit in the shoulder land portion row 12S is illustrated, the intermediate lug groove 12M may have the same configuration.

  In the present invention, as will be described later, since the bottom raised portion 16 is provided in the predetermined lug groove 13 specified from the repeating unit and the pitch length P, the block 15 is divided by the lug groove 13 and is divided into three types. The tread pattern is not limited to the above example as long as the above repeating unit of the pitch length P exists.

  In the tread surface 10 configured as described above, the pitch length (P1 in the case of FIG. 2) of 70% or less of the maximum pitch length (P3 in the case of FIG. 2) of the lug grooves 13 included in one land portion row 12. Only the lug groove 13 included in the repeating unit having the bottom portion 16 is provided. As illustrated in FIG. 3, the bottom raising portion 16 is configured by raising the groove bottom at the end portion on the side communicating with the main groove 11.

  In the present invention, the block 15 included in the repeating unit with a small pitch length is less rigid than the other blocks 15 (blocks 15 included in the repeating unit with a large pitch length) and is likely to be deformed. Although it causes deterioration of resistance and uneven wear, the bottom raised portion 16 is provided only in the lug groove 13 included in the repeating unit having a small pitch length of 70% or less of the maximum pitch length, and therefore included in the same repeating unit. The block 15 (the block 15 included in the repeating unit having a small pitch length) can be selectively reinforced, rolling resistance can be reduced, and uneven wear can be suppressed. At this time, since the lug groove 13 in which the bottom raised portion 16 is formed is limited only to the lug groove 13 included in the repeating unit having a small pitch length, the deterioration of the drainage performance is minimized, and the excellent drainage performance is achieved. Can be maintained.

  At this time, if the raised portion 16 is also provided in the lug groove 13 included in the repeating unit having a pitch length P larger than 70% of the maximum pitch length, the groove volume is reduced in the entire tire, so that the drainage performance is sufficiently maintained. Can not do it.

  There are one lug groove 13 on both sides in the circumferential direction with respect to the block 15, but among these lug grooves 13, the lug groove 13 is inclined with respect to the tire width direction so that the corners of the block 15 become acute angles. It is preferable that the lug groove 13 on the opposite side is paired with the block 15 in the repeating unit. That is, since the portion of the corner portion of the block 15 which is acute is more easily deformed, reinforcing this side with the bottom raised portion 16 is effective in reducing rolling resistance and suppressing uneven wear. In addition, when the bottom raising part 16 is provided in both the lug grooves 13 on both sides in the circumferential direction with respect to the block 15, the bottom raising part 16 is increased, so that it is difficult to secure a sufficient groove volume, and the drainage performance is affected.

  As described above, the block 15 includes the main groove 12 and the lug groove 13 (and the circumferential groove 14 in some cases) divided into four sides, the main groove 12 and the lug groove 13 (and In some cases, it includes both a part (partly connected to another part) defined by the circumferential groove 14). Therefore, as the lug groove 13 provided with the bottom raised portion 16, it is assumed that both ends communicate with the main groove 11 and only one end portion communicates with the main groove 11. 16 is provided, and the place where the bottom raising portion 16 is provided is provided at an end portion communicating with the main groove 11 regardless of the shape of the lug groove 13. That is, when both ends of the lug groove 13 communicate with the main groove 11, the bottom raised portions 16 can be provided at both ends. However, as described above, the sharp part of the corners of the block 15 is more easily deformed, so that at least the end part corresponding to the sharp part of the corners of the block 15 (in the case of FIG. It may be provided at the end of the equator CL side.

  As long as the land portion row 12 is divided into blocks 15 by the lug grooves 13 and there are three or more kinds of repeating units of the pitch length P, the bottom raised portions 16 are formed in the lug grooves 13 that satisfy the above-described conditions in any land portion row 12. However, since the rolling resistance and uneven wear due to the deformation of the land portion are large in the shoulder land portion row 12S, it is preferable to provide the bottom raising portion 16 at least in the shoulder land portion row 12S.

  As exemplified in FIG. 3, the bottom raising height H of the bottom raising portion 16 is preferably 20% to 40% of the groove depth D of the lug groove. By limiting the bottom raising height H to a predetermined range in this way, the effect of improving the rigidity by the bottom raising portion 16 (reducing rolling resistance and suppressing uneven wear) is sufficiently suppressed while effectively suppressing the deterioration of drainage performance. Can be obtained. At this time, if the bottom raising height H is smaller than 20% of the groove depth D of the lug groove 13, the effect of improving the rigidity by providing the bottom raising portion 16 cannot be sufficiently obtained, and the groove depth D of the lug groove 13 is not obtained. If it is larger than 40%, it is difficult to sufficiently maintain the drainage performance.

  The bottom raising height H of the bottom raising portion 16 does not need to be constant throughout the bottom raising portion 16 and is preferably gradually reduced toward the main groove 11 as illustrated in FIG. By changing the bottom raising height H in this way, the flow of water in the lug groove 13 can be improved and the drainage performance can be more effectively maintained. At this time, it is preferable that the bottom raising height of the bottom raising portion 16 closest to the main groove 11 is 50% or less of the maximum bottom raising height of the bottom raising portion.

  The tire size is 195 / 65R15 91H, has the cross-sectional shape illustrated in FIG. 1, is based on the tread pattern illustrated in FIG. 2, and the shoulder land portion row has the presence / absence of the raised portion and the lug groove provided with the raised portion Conventional example 1, comparative example 1 and examples 1 to 6 in which the types of pitches of repeating units including pitch (the pitch to be raised), the raised height H, and the presence or absence of changes in raised height are set as shown in Table 1, respectively. 8 types of pneumatic tires were produced.

  Each example includes three types having different pitch lengths as repeating units, and the pitch lengths are 33 mm (hereinafter referred to as large pitch), 28 mm (hereinafter referred to as medium pitch), and 22 mm (hereinafter referred to as small pitch). It is. That is, the small pitch is 67% of the large pitch, and the medium pitch is 85% of the large pitch. In the column of “pitch for raising the bottom” in Table 1, the pitch of the repeating unit including the lug groove provided with the raised portion is the above-described large pitch, medium pitch, or small pitch (the large pitch is represented by “ Large, medium pitch is abbreviated as “medium”, and small pitch is abbreviated as “small”).

  In addition, in the column “Presence / absence of change in bottom-up height” in Table 1, “no” indicates that the bottom-up height is constant over the entire bottom-up portion, and the bottom-up height gradually increases toward the main groove. Those that decrease are indicated as “Yes”.

  About these seven types of pneumatic tires, drainage performance, rolling resistance, and uneven wear resistance performance were evaluated by the following evaluation methods, and the results are also shown in Table 1.

Drainage performance Each test tire was assembled on a wheel with a rim size of 15 x 6 J, mounted on a test vehicle with a displacement of 1.8 liters with an air pressure of 230 kPa, and entered a pool with a water depth of 10 ± 1 mm on a straight road. The speed of entering the pool was gradually increased, and the critical speed at which the hydroplaning phenomenon occurred was measured. The evaluation results are shown as an index with Conventional Example 1 as 100. A larger index value means better drainage performance.

Rolling resistance Each test tire is assembled to a wheel with a rim size of 15 × 6J and mounted on a rolling resistance testing machine equipped with a drum having a radius of 854 mm, and the air pressure is 230 kPa, the load is 4.0 kN, and the speed is 80 km / h for 20 minutes. After the preliminary running, the rolling resistance was measured under the same conditions. The evaluation result was shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. The larger this index, the better the rolling resistance. If the index value is “98.5” or more, the excellent rolling resistance of the conventional example 1 is maintained.

Uneven wear resistance performance Each test tire is assembled to a wheel with a rim size of 15 × 6J and mounted on a test vehicle with a displacement of 1.8L with an air pressure of 230 kPa. The amount of uneven wear that occurred was measured. The evaluation results are shown as an index with the conventional example 1 as 100, using the reciprocal of the measured value. The larger the index value, the better the uneven wear resistance performance. When the index value is “98.5” or more, the excellent uneven wear resistance performance of the conventional example 1 is maintained.

  As is clear from Table 1, Examples 1 to 6 all improved the drainage performance while maintaining excellent rolling resistance and uneven wear resistance performance compared to Conventional Example 1, and balanced these performances in a well-balanced manner.

  In Comparative Example 1 in which no bottom raised portion was provided, the drainage performance was excellent, but the rolling resistance and uneven wear resistance performance deteriorated. Comparative Example 2 in which not only the lug groove included in the repeating unit of the small pitch but also the lug groove included in the repeating unit of the medium pitch is provided with a raised portion maintains excellent rolling resistance and uneven wear resistance performance. Although it was possible, the drainage performance could not be improved sufficiently. Comparative Examples 3 and 4 in which the bottom raised portion is provided only in the lug groove included in the large pitch or medium pitch repeating unit, not the lug groove included in the small pitch repeating unit, are improved most, although drainage performance is improved. The blocks included in the easy-to-repeat small pitch repeating unit could not be sufficiently reinforced, and the rolling resistance and uneven wear resistance could not be sufficiently maintained.

DESCRIPTION OF SYMBOLS 1 Tread part 2 Side wall part 3 Bead part 4 Carcass layer 5 Bead core 6 Bead filler 7, 8 Belt layer 9 Belt reinforcement layer 10 Tread surface 11 Main groove 11C Center main groove 11S Outer main groove 12 Land part row 12C Center land part row 12M Middle land row 12S Shoulder land row 13 Lug groove 13M Intermediate lug groove 13S Shoulder lug groove 14 Circumferential narrow groove 15 block 15M Middle block 15S Shoulder block 16 Bottom raised portion CL Tire equator

Claims (3)

A plurality of main grooves extending in the tire circumferential direction are provided in the tread portion, and a plurality of land portion rows are formed by the main grooves, and at least one end portion of the land portion rows communicates with the main grooves. A plurality of lug grooves extending in the width direction are provided, the land row is partitioned into a plurality of blocks by the lug grooves, and the blocks in one land portion row in which the lug grooves are formed and the blocks In a pneumatic tire in which there are three or more types of pitch length of repeating units composed of lug grooves adjacent to one side,
Only the lug groove included in the repeating unit having a pitch length equal to or less than 70% of the maximum pitch length among the lug grooves is provided with a bottom raised portion in which the groove bottom at the end communicating with the main groove is raised. Pneumatic tire characterized by.   2. The pneumatic tire according to claim 1, wherein the bottom raised height of the bottom raised portion is 20% to 40% of the depth of the lug groove.   3. The pneumatic tire according to claim 1, wherein a bottom raising height of the bottom raising portion gradually decreases toward the main groove side.

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