JP2016055817A - 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, a plurality of lug grooves 13 are provided in a shoulder land part row 12S, the shoulder land part row 12S is partitioned by the lug grooves 13 into blocks 15n, and at least three kinds of pitch lengths in repeat units which are constituted of the block 15 and the lug grooves 13 adjacent to one side of the block 15 exist. In the lug grooves 13 are provided bottom raised parts 16, where lengths in a tire width direction of the bottom raised parts 16 are set to be 50%-150% of a main groove 11, while heights of the bottom raised parts 16 are set to as high as the bottom raised parts 16 of the lug grooves 13 included in repeat units whose pitch length is short.SELECTED DRAWING: Figure 3

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. A plurality of lug grooves with one end communicating with the main groove and extending in the tire width direction are provided in the shoulder land portion row located on the outermost side in the tire width direction of the row, and the shoulder land is provided by the lug groove. In a pneumatic tire in which a partial row is divided into a plurality of blocks and there are three or more types of pitch lengths of repeating units composed of the blocks and a lug groove adjacent to one side of the block, a raised portion is provided in the lug groove. The bottom raised portion of the lug groove included in the repeating unit having a small pitch length while the length of the bottom raised portion in the tire width direction is set to 50% to 150% of the groove width of the main groove. I made it bigger The features.

  In the present invention, since the blocks included in the repeating unit having a small pitch length have lower rigidity and are more likely to be deformed, attention is paid to the points that tend to cause deterioration of rolling resistance and uneven wear. With respect to the bottom raised portion provided in the lug groove, the bottom raised height of the lug groove included in the repeating unit having a small pitch length is increased so that the block that is more easily deformed is more reliably reinforced. As a result, the rolling resistance can be effectively reduced and uneven wear can be suppressed. On the other hand, a block included in a repeating unit having a large pitch length has sufficient rigidity, is not easily deformed, and does not need to be reinforced more strongly by a raised portion. The bottom raising height of the lug groove included is made smaller to secure the groove volume. As a result, excellent drainage performance can be sufficiently maintained. That is, by changing the block height as described above, appropriate reinforcement of each block according to the ease of deformation of the block and securing of the groove volume according to the difficulty of deformation of the block are balanced. It is possible to achieve both compatibility, effectively reducing rolling resistance and suppressing uneven wear and maintaining drainage performance. Furthermore, since the length in the tire width direction of the bottom raised portion is limited to 50% to 150% of the groove width of the main groove, it is possible to suppress deterioration of drainage performance and maintain excellent drainage performance also from this point. it can.

  In this invention, it is preferable that the bottom raising part is arrange | positioned at the edge part of the side connected to the main groove of a lug groove. By providing the bottom raised portion on the main groove side in this way, it is possible to effectively reinforce the corner portion of the block that is likely to be deformed, which is advantageous for reducing rolling resistance and improving uneven wear resistance. .

  In this invention, it is preferable that the bottom raising height of a bottom raising part is 10%-50% 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 this invention, it is preferable that ratio of the maximum bottom raising height of the bottom raising part and the minimum bottom raising height is 1.8-2.3. Thus, in making the bottom raising height of the bottom raising portion different depending on the lug groove, by setting the relationship between the maximum value and the minimum value of the bottom raising height within the above range, it is possible to maintain drainage performance, reduce rolling resistance, and It is possible to balance the uneven wear with a good balance.

  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. FIG. 3 is a schematic diagram showing an outermost main groove and a part of a shoulder land portion extracted according to 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 another 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 is a block having four sides defined by the main groove 11 and the lug groove 13 (and possibly the circumferential groove 14), and the main groove 11 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 shoulder lug groove 13S provided in the shoulder land portion row 12S, one end portion of the shoulder land portion 12S has the main groove 11 (outer side). If a shoulder lug groove 13S communicating with the main groove 11S) is provided, and the block 15 (shoulder block 15S) is partitioned by the shoulder lug groove 13S and there are three or more types of repeating units having a pitch length P, the tread The pattern is not limited to the above example.

  In the tread surface 10 configured as described above, the shoulder lug groove 13S is provided with a bottom-up portion 16 as shown in FIGS. The bottom raising portion 16 is configured by raising the groove bottom of the shoulder lug groove 13S. The length L of the bottom raised portion 16 in the tire width direction is 50% to 150% of the groove width GW of the main groove 11 (outer main groove 11S). In addition, when the bottom raising part 16 is smoothly continuing with the groove bottom of the shoulder lug groove 13S as shown in the figure, the length L in the tire width direction of the bottom raising part 16 is measured on the basis of the starting point of the protrusion of the bottom raising part 16. Is done.

  On the other hand, the bottom raising height H of the bottom raising portion 16 changes according to the pitch length P of the repeating unit including the shoulder lug groove 13S provided with the bottom raising portion 16, and the pitch length P is included in the small repeating unit. The bottom raising height H of the bottom raising portion 16 provided in the shoulder lug groove 13S increases. Specifically, as illustrated in FIG. 3, the shoulder lug included in the repeating unit of the bottom raising height 16 of the bottom raising portion 16 provided in the shoulder lug groove 13 </ b> S included in the repeating unit of the pitch length P <b> 1 and the pitch length P <b> 2. The height of the bottom raising portion 16 provided in the groove 13S and the height H3 of the bottom raising portion 16 provided in the shoulder lug groove 13S included in the repeating unit of the pitch length P3 of the bottom raising portion 16 are related to the pitch lengths P1 to P3. Corresponding to (P1 <P2 <P3), the magnitude relationship is H1> H2> H3.

  In the present invention, the shoulder block 15S included in the repeating unit having a small pitch length P has a lower rigidity and is more likely to be deformed, and thus tends to cause deterioration of rolling resistance and uneven wear. For the bottom raised portions 16 provided in each shoulder lug groove 13S, the bottom raised portion H of the shoulder lug groove 13S included in the repeating unit having a small pitch length P increases the bottom raised height H, and the shoulder block 15S is more easily deformed. Is reinforced more reliably. As a result, the rolling resistance can be effectively reduced and uneven wear can be suppressed. On the other hand, the shoulder block 15S included in the repeating unit having a large pitch length P has a sufficient rigidity, the shoulder block 15S itself is not easily deformed, and reinforcement by the bottom raised portion 16 is not necessarily required. The bottom raised portion 16 of the shoulder lug groove 13S included in the repeating unit having a large length P is made smaller in height to secure the groove volume of the shoulder lug groove 13S. As a result, excellent drainage performance can be sufficiently maintained. In other words, in the present invention, by changing the raised height H for each shoulder lug groove 13S as described above, appropriate reinforcement of each shoulder block 15S according to the ease of deformation of the shoulder block 15S, and the shoulder block 15S. The shoulder lug groove 13S according to the difficulty of deformation can be ensured in a well-balanced manner, and the reduction of rolling resistance, the suppression of uneven wear and the maintenance of drainage performance can be effectively achieved at the same time. it can. Furthermore, since the length L in the tire width direction of the bottom raised portion 16 is limited to 50% to 150% of the groove width GW of the main groove 11, the deterioration of drainage performance is suppressed from this point as well, and excellent drainage performance is achieved. Can be maintained.

  At this time, the height of the bottom raised portion 16 is constant in all the shoulder lug grooves 13S regardless of the pitch length P, or the shoulder lug groove 13S included in the repeating unit having a smaller pitch length P is the height of the bottom raised portion 16 raised. When the height H is small, appropriate reinforcement according to the ease of deformation of the shoulder block 15S cannot be performed, so that the effect of reducing rolling resistance and suppressing uneven wear cannot be obtained. Further, if the length L of the bottom raised portion 16 in the tire width direction is smaller than 50% of the groove width GW of the main groove 11, a sufficient reinforcing effect by the bottom raised portion 16 cannot be obtained. If the length L is larger than 150% of the groove width GW of the main groove 11, the groove volume decreases and the drainage performance deteriorates.

  There is one shoulder lug groove 13S on both sides in the circumferential direction with respect to the shoulder block 15S. Of these shoulder lug grooves 13S, the shoulder lug grooves 13S are inclined with respect to the tire width direction so that the corners of the shoulder block 15S are present. It is preferable that the shoulder lug groove 13S on the side where the portion is an acute angle is paired with the shoulder block 15S in the repeating unit. That is, since the portion of the shoulder block 15S that has an acute angle is more easily deformed, reinforcing this side with the raised bottom portion 16 is effective in reducing rolling resistance and suppressing uneven wear. If the bottom raised portions 16 are provided in both shoulder lug grooves 13S on both sides in the circumferential direction with respect to the shoulder block 15S, the bottom raised portions 16 increase, so that it is difficult to secure a sufficient groove volume, and the drainage performance is affected. is there.

  As described above, an acute angle portion of the corner portion of the shoulder block 15S is easily deformed, so that the bottom raised portion 16 on the side communicating with the main groove 11 of the shoulder lug groove 13S can be reliably reinforced. It is preferable to arrange at the end. Thereby, since the corner | angular part of the shoulder block 15S which is easy to produce a deformation | transformation can be effectively reinforced, it becomes advantageous in reducing rolling resistance and improving uneven wear-proof performance.

  In the present invention, the bottom raising height H of the bottom raising portion 16 varies depending on the shoulder lug groove 13S. However, in any bottom raising portion 16, the bottom raising height H is 10 which is the groove depth D of the shoulder lug groove 13S. It is preferable to be within the range of% to 50%. 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 10% of the groove depth D of the lug groove 13, the effect of improving the rigidity by providing the bottom raising portion 16 is not sufficiently obtained, and the groove depth D of the lug groove 13 is not obtained. If it is larger than 50%, it becomes difficult to sufficiently maintain the drainage performance.

  Considering the balance between maintaining drainage performance, reducing rolling resistance, and suppressing uneven wear, the difference between the raised height H between the raised portion 16 having the largest raised height H and the raised portion 16 having the smallest raised height H. It is not preferable that is extremely large. Therefore, the ratio (H1 / H3 in FIG. 3) of the maximum bottom raising height (H1 in FIG. 3) and the minimum bottom raising height (H3 in FIG. 3) of the bottom raising portion 16 is 1.8 to 2.3. Preferably there is. As described above, when the bottom raised height H of the bottom raised portion 16 is varied depending on the shoulder lug groove 13S, the relationship between the maximum value and the minimum value of the raised height H is set, thereby maintaining drainage performance and reducing rolling resistance. And suppression of uneven wear can be achieved in a balanced manner. At this time, if the ratio of the maximum bottom raising height and the minimum bottom raising height of the bottom raising portion 16 is smaller than 1.8, the bottom raising height H of the bottom raising portion 16 is substantially constant in all the shoulder lug grooves 13S. The appropriate reinforcement according to the ease of deformation of the shoulder block 15S cannot be sufficiently achieved. On the contrary, if the ratio of the maximum bottom raising height to the minimum bottom raising height of the bottom raising portion 16 is larger than 2.3, the difference between the maximum value and the minimum value of the bottom raising height H becomes large, so that the drainage performance is maintained and rolled. It becomes difficult to achieve a good balance between reducing resistance and suppressing uneven wear.

  The bottom raised height H of one bottom raised portion 16 provided in one shoulder lug groove 13S does not need to be constant throughout the bottom raised portion 16 as shown in FIG. It is preferable that it gradually decreases toward the groove 11 side. 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 a bottom raised portion and a raised height (H1 to H3). ), The maximum / minimum ratio of the raised height, the length of the raised portion in the tire width direction (the length of the raised portion), and whether or not there is a change in the raised height as shown in Table 1, Comparative Example 1 and Comparative Example 16 types of pneumatic tires of 1-4 and Examples 1-11 were produced.

  Each example includes three types having different pitch lengths as a repeating unit, where the smallest pitch length P1 is 33 mm, the second smallest pitch length P2 is 28 mm, and the largest pitch length P3 is 22 mm. The raised heights H1 to H3 described above correspond to the pitch lengths P1 to P3, and the raised height of the raised portion provided in the lug groove included in the repeating unit of the pitch length P1 is H1 and the repeating unit of the pitch length P2. The raised height of the raised portion provided in the included lug groove is H2, and the raised height of the raised portion provided in the lug groove included in the repeating unit of the pitch length P3 is H3. Further, as described later, the bottom raising heights H1 to H3 when the bottom raising height gradually decreases toward the main groove are the maximum bottom raising heights of the respective bottom raising portions.

  In the column of “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 decreases toward the main groove. The thing to do is indicated as “Yes”.

  About these 16 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. In addition, if the index value is “98.5” or more, the drainage performance of the conventional level is maintained.

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.

Uneven wear resistance performance Each test tire is assembled on a wheel with a rim size of 15 x 6 J, mounted on a test vehicle with a displacement of 1.8 L with an air pressure of 230 kPa, and after running a 10,000 km test on the asphalt road surface, The amount of uneven wear generated in the part 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.

  As is clear from Table 1, Examples 1 to 11 all improved drainage performance, rolling resistance and uneven wear resistance in a well-balanced manner with respect to Conventional Example 1.

  On the other hand, Comparative Example 1 in which no bottom-up portion was provided had excellent drainage performance but deteriorated rolling resistance and uneven wear resistance performance. In Comparative Example 2 in which the relationship between the height of the bottom and the height of the pitch was reversed from that of the present invention, the drainage performance was maintained at the conventional level, but the rolling resistance and uneven wear resistance were deteriorated. In Comparative Example 3 in which the length of the bottom raised portion is too small, the drainage performance is slightly improved, but a sufficient reinforcing effect cannot be obtained, and the rolling resistance and uneven wear resistance performance deteriorate. In Comparative Example 4 in which the length of the bottom raised portion is too large, the conventional level of drainage performance could not be maintained, and the drainage performance deteriorated.

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 (5)

A plurality of main grooves extending in the tire circumferential direction are provided in the tread portion, a plurality of land portion rows are formed by the main grooves, and a shoulder land portion row located on the outermost side in the tire width direction of the land portion rows A plurality of lug grooves extending in the tire width direction and having one end portion communicating with the main groove, and the shoulder land portion row is partitioned into a plurality of blocks by the lug grooves. In a pneumatic tire in which there are three or more types of pitch lengths of repeating units composed of lug grooves adjacent to one side of
The lug groove is provided with a bottom raised portion, and the length in the tire width direction of the bottom raised portion is 50% to 150% of the groove width of the main groove, while the bottom raised height of the bottom raised portion is a repeating unit with a small pitch length. A pneumatic tire characterized in that the bottom raised portion of the lug groove included in the tire is enlarged.   The pneumatic tire according to claim 1, wherein the bottom raised portion is disposed at an end portion of the lug groove on a side communicating with the main groove.   3. The pneumatic tire according to claim 1, wherein the bottom raised height of the bottom raised portion is 10% to 50% of the groove depth of the lug groove. 4.   The pneumatic tire according to any one of claims 1 to 3, wherein a ratio of a maximum bottom raising height to a minimum bottom raising height of the bottom raising portion is 1.8 to 2.3.   The pneumatic tire according to claim 1, wherein a bottom raising height of the bottom raising portion gradually decreases toward the main groove side.

Images