JP4696145B2 - Pneumatic tire - Google Patents

Description

  In the present invention, the tread portion is divided into a center region including the tire equator and a shoulder region located on both outer sides in the width direction by two circumferential main grooves located on the outermost side in the width direction. Related to pneumatic tires.

  In general, since new pneumatic tires have almost no fine irregularities on the tread surface, the frictional force with the ice road surface tends to be insufficient. In particular, there is a problem that ice braking performance and ice turning performance are not sufficiently exhibited.

  Conventionally, as a means for improving the ice performance in the initial use of a tire, there is a method of arranging a shallow groove having a groove depth shallower than that of a sipe in a land portion of a tread portion. In the following Patent Documents 1 to 3, a pneumatic tire is described in which shallow grooves that form an angle of 0 to 40 ° with the tire circumferential direction are arranged in the tire width direction in the ground contact portion of the tread. However, in the pneumatic tires described in these documents, shallow grooves are provided for the purpose of discharging water to the outside of the contact land when traveling on an ice road surface. Ice performance will not improve.

  In the following Patent Document 4, a pneumatic tire is described in which a shallow groove having an angle of 42 to 60 ° with the tire circumferential direction is provided on the tread surface. However, the pneumatic tire described in this document is intended to quickly wear out the shallow groove based on the frictional force that the land portion receives during braking and turning while removing the water film, The edge effect of the shallow groove is not sufficiently exhibited during ice braking and ice turning.

In the following Patent Document 5, a pneumatic tire is described in which shallow grooves extending in the tire width direction are arranged side by side in the tire circumferential direction on the tread surface. However, although the shallow groove provided in the pneumatic tire described in this document contributes to the improvement of the ice braking performance in the initial use of the tire, it does not contribute to the improvement of the ice turning performance.
JP 07-186633 A JP 2006-151221 A JP 2006-151222 A JP 2004-34903 A JP 09-323511 A

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a pneumatic tire that achieves both ice braking performance and ice turning performance at the initial use of the tire.

  In order to achieve the above object, the present inventors applied braking to a tire on a low μ road surface (corresponding to an ice road surface) in each region (center region and shoulder region) of the tread pattern until the tire starts to slip. We studied earnestly about the braking force sharing. As a result, the force generated in the lateral direction (turning direction) is large in the shoulder region due to the effect of in-plane contraction force (force acting toward the center within the ground contact surface when the tire is grounded) It was found that the force generated in the front-rear direction (braking direction) was smaller than that in the center region. On the other hand, in the center region, the force generated in the braking direction is large, but the force generated in the turning direction is found to be smaller than that in the shoulder region. The present invention has been made as a result of the above-described studies, and achieves the above-described object with the following configuration.

  That is, in the pneumatic tire according to the present invention, the tread portion is positioned on the outer side in the width direction of the center region and the center region including the tire equator by the two circumferential main grooves positioned on the outermost side in the width direction. In the pneumatic tire partitioned into a shoulder region, the land portion disposed in the center region is provided with a shallow groove having an angle between a longitudinal direction and a tire circumferential direction of 75 to 90 °, and the shoulder The land portion disposed in the region is characterized in that a shallow groove with an angle between the longitudinal direction and the tire circumferential direction of 0 to 15 ° is disposed.

  In the pneumatic tire described above, the land portion disposed in the center region is provided with a shallow groove having an angle between the longitudinal direction and the tire circumferential direction of 75 to 90 °. According to such a configuration, the edge effect of the shallow groove is effective during braking in the center region where the force generated in the braking direction is large, and the ice braking performance at the initial use of the tire can be improved. Further, in the above pneumatic tire, the land portion disposed in the shoulder region is provided with a shallow groove in which an angle formed between the longitudinal direction and the tire circumferential direction is 0 to 15 °. According to this configuration, in the shoulder region where the force generated in the turning direction is large, the edge effect of the shallow groove acts effectively during turning, and the ice turning performance in the initial use of the tire can be improved.

  Further, in the pneumatic tire according to another aspect of the present invention, the tread portion is formed in the center region including the tire equator by the two circumferential main grooves positioned on the outermost side in the width direction, and on both outer sides in the width direction of the center region In the pneumatic tire partitioned into the shoulder region located, the land portion disposed in the center region further includes a first center region and a width direction of the first center region by two circumferential narrow grooves. A land portion that is partitioned into second center regions located on both outer sides, and the land portion disposed in the first center region has a plurality of ribs partitioned by at least one circumferential main groove and the circumferential narrow groove And a shallow groove having an angle between the longitudinal direction and the tire circumferential direction of 75 to 90 ° is disposed, and the land portion disposed in the second center region is partitioned by a plurality of lateral grooves. 1st block The land portion disposed in the shoulder region is composed of a second block row partitioned by a plurality of lateral grooves, and the land portion disposed in the second center region and the shoulder region is A shallow groove having an angle of 0 to 15 ° formed between the longitudinal direction and the tire circumferential direction is provided.

  As a result of experiments and examinations focusing on the in-plane contraction force of the tread portion, the present inventors have found that the center region of the tread portion is divided between the first center region and the second center region by two circumferential narrow grooves. It was found that the force generated in the braking direction on the ice road surface is particularly large on the center side (first center region) than the circumferential narrow groove. On the other hand, in the second center region on the shoulder side of the circumferential narrow groove, the force generated in the turning direction on the ice road surface is relatively large, and in the shoulder region, the force generated in the turning direction on the ice road surface is particularly large. I found.

  In the above pneumatic tire, the edge effect of the shallow groove disposed on the rib located in the first center region effectively acts during braking, and the ice braking performance in the initial use of the tire can be improved. In addition, the edge effect of the shallow grooves disposed in the block rows located in the second center region and the shoulder region effectively acts at the time of turning, and the ice turning performance in the initial use of the tire can be improved.

  In the above, the total ground contact area of the tread portion is S, the total ground contact area of the ribs is S1, the total ground contact area of the first block row is S2, and the total ground contact area of the second block row is S3. In this case, it is preferable that 0.45S ≦ S1 ≦ 0.55S, 0.15S ≦ S2 ≦ 0.25S, and 0.20S ≦ S3 ≦ 0.35S. Here, “the total of the ground contact areas of the ribs” means the total of the ground contact areas of all the ribs disposed in the first center region. The “total ground contact area of the first block row” means the total ground contact area of the block rows located in the second center region. Similarly, “the total of the ground contact areas of the second block row” means the sum of the ground contact areas of the block rows located in the shoulder region.

  According to the above configuration, in the tread portion, the contact area of the block row (second block row) located in the shoulder region becomes relatively small, so that the in-plane contraction component becomes small and the force generated in the braking direction as a whole. Becomes larger. Furthermore, since the ground contact area of the rib in the first center region is relatively large, many shallow grooves extending in the width direction can be provided in the rib in the center region where the force generated in the braking direction is large. For this reason, the edge effect of the shallow groove acting in the braking direction is enhanced, and the ice braking performance in the initial use of the tire can be further improved.

  In the above description, it is preferable that W2 / W1 = 0.45 ± 0.03, where W1 is the distance from the tire equator to the ground contact edge and W2 is the distance from the tire equator to the circumferential narrow groove. Here, the “distance from the tire equator to the circumferential narrow groove” means the distance from the tire equator to the center line in the width direction of the circumferential narrow groove.

  The present inventors conducted experiments and examinations by paying particular attention to the in-plane contraction force of the tread portion and the width direction position of the circumferential narrow groove that divides the center region into the first center region and the first center region. As a result, when the circumferential narrow groove is disposed in the width direction position where W2 / W1 = 0.45 ± 0.03, the ice road surface is closer to the center side (first center region) than the circumferential narrow groove. It has been found that the force generated in the braking direction is even greater. On the other hand, in the second center region on the shoulder side of the circumferential narrow groove, the force generated in the turning direction on the ice road surface is relatively large, and in the shoulder region, the force generated in the turning direction on the ice road surface is particularly large. I found.

  Therefore, when the center region of the tread is divided into the first center region and the second center region by two circumferential narrow grooves, W2 / W1 = 0.45 ± 0.03. A circumferential groove is arranged at a position in the width direction, and the rib width at the inner side in the width direction (first center region) is set larger than the circumferential groove, and the shallow groove extends in the width direction with the rib. By disposing a large amount, the ice braking performance in the initial use of the tire can be particularly improved. Furthermore, by disposing a large number of shallow grooves extending in the circumferential direction in the block row located on the outer side in the width direction (second center region and shoulder region) than the circumferential narrow grooves, the ice turning performance in the initial use of the tire Can be particularly improved.

  In the above, the shallow groove preferably has a groove width of 0.3 to 1.5 mm and a groove depth of 0.2 to 1.0 mm. By setting the groove width and depth of the shallow groove as described above, the ice braking performance and ice turning performance in the initial use of the tire can be suppressed while suppressing the decrease in rigidity of the land portion where the shallow groove is disposed. Can be improved.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a development view showing an example of a tread pattern in the pneumatic tire of the present invention.

  As shown in FIG. 1, the pneumatic tire according to the present embodiment includes a center region Ce including a tire equator CL, and a center region with two circumferential main grooves 2 in which the tread portion 1 is located on the outermost side in the width direction. It is partitioned into a shoulder region Sh located on both outer sides in the width direction of Ce. In the center region Ce, a plurality of circumferential main grooves 2 may be further disposed. In the present embodiment, two circumferential main grooves 2 are disposed in the center region Ce. Further, in the present embodiment, the land portion disposed in the tread portion 1 is configured by a block partitioned by four circumferential main grooves 2 and a plurality of lateral grooves 3. The circumferential main groove 2 disposed in the tread portion 1 may be a zigzag groove in addition to a linear groove as shown in FIG. The groove width of the circumferential main groove 2 is 4.5 to 8 mm, and the groove width of the lateral groove 3 is 4 to 7 mm.

  In the pneumatic tire of the present embodiment, the land portion disposed in the center region Ce is provided with a shallow groove 4A in which an angle formed between the longitudinal direction and the tire circumferential direction (arrow S direction) is 75 to 90 °. In addition, the land portion disposed in the shoulder region Sh is provided with a shallow groove 4B in which an angle formed between the longitudinal direction and the tire circumferential direction is 0 to 15 °. According to such a configuration, the edge effect of the shallow groove 4A acts effectively in braking in the center region Ce where the force generated in the braking direction is large, and further in the shoulder region Sh where force generated in the turning direction is large, The edge effect of the groove 4B acts effectively. As a result, in the pneumatic tire of this embodiment, ice braking performance and ice turning performance in the initial use of the tire are improved. The angle formed between the longitudinal direction of the shallow groove 4A and the tire circumferential direction is preferably 80 to 90 °, and more preferably about 90 °, in order to further improve the ice braking performance. Further, the angle formed by the longitudinal direction of the shallow groove 4B and the tire circumferential direction is preferably 0 to 10 ° and more preferably substantially 0 ° in order to further improve the ice turning performance.

  The groove widths of the shallow grooves 4A and the shallow grooves 4B are preferably 0.3 to 1.5 mm. If the groove widths of the shallow groove 4A and the shallow groove 4B are less than 0.3 mm or more than 1.5 mm, the edge effect of the shallow groove may not be suitably exhibited. The groove width of the shallow groove 4A and the shallow groove 4B is 0.5 to 0.7 mm in order to suitably exhibit the edge effect of the shallow groove and further improve the ice braking performance and ice turning performance in the initial use of the tire. More preferably. Moreover, it is preferable that the groove depth of the shallow groove 4A and the shallow groove 4B is 0.2 to 1.0 mm. When the groove depth of the shallow groove 4A and the shallow groove 4B is less than 0.2 mm, the edge effect of the shallow groove may not be suitably exhibited. On the other hand, when the groove depth of the shallow groove exceeds 1.0 mm, the rigidity of the land portion where the shallow groove is disposed is likely to be reduced, and the ice braking performance and the ice turning performance are deteriorated due to a decrease in the contact area. There is. In order to suitably exhibit the edge effect of the shallow groove 4A and the shallow groove 4B and further improve the ice braking performance and the ice turning performance, the groove depth of the shallow groove 4A and the shallow groove 4B is 0.3 to 0.5 mm. It is more preferable that Furthermore, in the shallow groove 4A and the shallow groove 4B, the distance between the adjacent shallow grooves is not particularly limited as long as the edge effect of the shallow groove is suitably acted while securing the rigidity of the land portion. The thing of -2.5mm is illustrated.

  Next, another embodiment according to the present invention will be described with reference to the drawings. FIG. 2 is a development view showing another example of a tread pattern in the pneumatic tire of the present invention.

  As shown in FIG. 2, the pneumatic tire according to the present embodiment includes a center region Ce including a tire equator CL, and a center region with two circumferential main grooves 2 in which the tread portion 1 is located on the outermost side in the width direction. It is partitioned into a shoulder region Sh located on both outer sides in the width direction of Ce. The land portion disposed in the center region Ce is further separated by the two circumferential narrow grooves 5 to the first center region Ce-1 and the second center located on both outer sides in the width direction of the first center region Ce-1. It is partitioned into a region Ce-2.

  The land portion disposed in the first center region Ce-1 is composed of a plurality of ribs defined by at least one circumferential main groove 2 and circumferential narrow grooves 5. In FIG. 2, the land portion disposed in the first center region Ce- 1 has the tire equator CL defined by the two circumferential main grooves 2 and the circumferential narrow grooves 5 that extend on both sides of the tire equator CL. The first center rib R1 including the first center rib R1 and the second center rib R2 located on both outer sides in the width direction of the first center rib R1 are partitioned. Further, the land portion disposed in the second center region Ce-2 is configured by a first block row B1 partitioned by a plurality of lateral grooves 3, and the land portion disposed in the shoulder region Sh is formed by a plurality of lateral grooves. 3 is composed of a second block row B2 partitioned by three. The circumferential main groove 2 disposed in the tread portion 1 may be a zigzag groove in addition to a linear groove as shown in FIG. The groove width of the circumferential main groove 2 is 4.5 to 8 mm, and the groove width of the lateral groove 3 is 4 to 7 mm.

  In the pneumatic tire of the present embodiment, the land portion disposed in the first center region Ce-1 has a shallow groove 4A in which an angle formed between the longitudinal direction and the tire circumferential direction (arrow S direction) is 75 to 90 °. In addition, the land portion disposed in the second center region Ce-2 and the shoulder region Sh is provided with a shallow groove 4B in which an angle between the longitudinal direction and the tire circumferential direction is 0 to 15 °. ing. According to such a configuration, in the first center region Ce-1 that generates a large force in the braking direction, the edge effect of the shallow groove 4A acts effectively during braking, and the second center region that generates a large force in the turning direction. In Ce-2 and the shoulder region Sh, the edge effect of the shallow groove 4B acts effectively during turning. As a result, in the pneumatic tire of the present embodiment, ice braking performance and ice turning performance in the initial use of the tire are improved. In addition, the preferable range of the groove width of the shallow groove 4A and the shallow groove 4B, the groove depth, and the space | interval of adjacent shallow grooves is the same as that of embodiment mentioned above.

  In the pneumatic tire according to this embodiment, the total contact area of the tread portion 1 is S, the total contact area of the ribs is S1, the total contact area of the first block row B1 is S2, and the contact area of the second block row B2 is When S3 is defined as S3, relationships of 0.45S ≦ S1 ≦ 0.55S, 0.15S ≦ S2 ≦ 0.25S, and 0.20S ≦ S3 ≦ 0.35S are established. When the rib of the tread portion 1 and the block row are in the above relationship, the contact area of the block row (second block row B2) located in the shoulder region Sh is relatively small, so the in-plane contraction component is small, As a whole, the force generated in the braking direction increases. Furthermore, since the ground contact area of the rib located in the first center region Ce-1 is relatively large, the rib located in the first center region Ce-1 that generates a large force in the braking direction extends in the width direction. Many shallow grooves 4A can be arranged. For this reason, the edge effect of the shallow groove acting in the braking direction is enhanced, and the ice braking performance in the initial use of the tire can be further improved.

  In this embodiment, when the ground contact area of the first center rib R1 is S11 and the total ground contact area of the second center rib R2 is S12, 0.15S ≦ S11 ≦ 0.30S, 0.20S ≦ S12 ≦ 0. It is preferable that 32S, 0.7S11 ≦ (S12 + S2) /2≦1.2S11, and S2 <S12. It is preferable that the ribs of the tread portion 1 and the block row have the above relationship because ice braking performance in the initial use of the tire is particularly improved.

  Further, in the present embodiment, as shown in FIG. 2, the center region Ce of the tread portion 1 is divided into the first center region Ce-1 and the second center region Ce-2 by the two circumferential narrow grooves 5. W2 / W1 = 0.45 ± 0.00, where W1 is the distance from the tire equator CL to the ground contact edge 6 and W2 is the distance from the tire equator CL to the circumferential narrow groove 5. A circumferential narrow groove 5 is disposed at a position in the width direction that becomes 03. Thereby, the rib width in the rib on the inner side in the width direction (first center region Ce-1) is set larger than the circumferential narrow groove 5, and a large number of shallow grooves 4A extending in the width direction are arranged on the rib. Thus, the ice braking performance in the initial use of the tire can be particularly improved. Furthermore, by disposing a large number of shallow grooves 4B extending in the circumferential direction in the block rows B2 and B1 located on the outer side in the width direction (second center region Ce-2 and shoulder region Sh) than the circumferential narrow groove 5 The ice turning performance in the initial use of the tire can be particularly improved.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that it includes the tread pattern as described above, and any conventionally known material, shape, structure, manufacturing method, etc. can be employed in the present invention.

  The pneumatic tire of the present invention is particularly useful as a studless tire because it can achieve both ice braking performance and ice turning performance.

[Other Embodiments]
Hereinafter, other embodiments of the present invention will be described.

  (1) In the above-described embodiment, as illustrated in FIGS. 1 and 2, the example in which only the shallow grooves are provided in the land portions provided in the center region Ce and the shoulder region Sh has been described. It is preferable to further arrange a sipe having a groove depth deeper than the groove. In addition to the shallow groove, by arranging the sipe in the land part, the edge effect of the sipe works effectively not only in the initial use of the tire but also after the shallow groove disappears in the middle to the end of the tire, The ice braking performance and ice turning performance of the pneumatic tire can be further improved. The groove depth of such a sipe is preferably 2 to 7 mm, and more preferably 4 to 6 mm. Further, the sipe groove width is 0.2 to 0.5 mm, and the sipe interval of the sipe to be disposed is 3 to 6 mm.

  In order to further improve the ice braking performance and ice turning performance of the pneumatic tire, in the embodiment shown in FIG. 1, when the sipe is disposed on the land portion in addition to the shallow groove, the sipe is disposed in the center region Ce. In the land portion, a sipe having an angle between the longitudinal direction and the tire circumferential direction of 75 to 90 ° is disposed, and in the land portion disposed in the shoulder region Sh, the longitudinal direction and the tire circumferential direction are formed. It is preferable to arrange a sipe having an angle of 0 to 15 °. In the embodiment shown in FIG. 2, a sipe having an angle between the longitudinal direction and the tire circumferential direction of 75 to 90 ° is disposed in the land portion disposed in the first center region Ce-1. It is preferable to arrange sipes having an angle between the longitudinal direction and the tire circumferential direction of 0 to 15 ° in the land portions disposed in the second center region Ce-2 and the shoulder region Sh. The cross-sectional shape of the sipe that can be disposed is not limited to a linear shape, and may be a zigzag shape, a wave shape, or a rectangular wave shape.

  (2) In the above-described embodiment, as shown in FIGS. 1 and 2, the shallow grooves 4A and 4B are illustrated as having a straight cross-sectional shape, but the cross-sectional shape is a zigzag shape (FIG. 3A). It may be of a wave shape (FIG. 3B) or a rectangular wave shape (FIG. 3C). When a shallow groove having a rectangular wave cross-sectional shape is provided, as shown in FIG. 3C, a shallow groove 4A (a shallow groove in which the angle between the longitudinal direction and the tire circumferential direction is 75 to 90 °) is shallow. In the groove 4B (a shallow groove in which the angle between the longitudinal direction and the tire circumferential direction is 0 to 15 °), the period of unevenness (for example, the distance between the convex and convex tops) C and the amplitude (the distance between the tops on both sides) D Is preferably C / 2> D. In the shallow groove 4A, when the period C and the amplitude D are in a relationship of C / 2> D, the edge effect of the shallow groove can be achieved in a balanced manner not only in the braking direction but also in the turning direction. Similarly, in the shallow groove 4B, when the cycle C and the amplitude D are in a relationship of C / 2> D, the edge effect of the shallow groove can be achieved with a good balance not only in the turning direction but also in the braking direction. As a result, both the ice braking performance and the ice turning performance of the pneumatic tire can be improved in a balanced manner. On the other hand, if the period C and the amplitude D are in the relationship of C / 2 ≦ D in the shallow groove 4A, the ice braking performance of the pneumatic tire tends to be reduced. In the shallow groove 4B, the period C and the amplitude D are Is in a relationship of C / 2 ≦ D, since the ice turning performance of the pneumatic tire tends to decrease.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In addition, each performance evaluation of the tire was performed as follows.

(1) Ice braking performance A test tire (size 205 / 65R15) is mounted on an actual vehicle (domestic 3000cc class FR sedan), running on an ice road under the load conditions of one passenger, and braking force at a speed of 40km / h. The braking distance when the ABS was operated by applying an index was evaluated by an index. The evaluation is indicated by an index display when the conventional product (Comparative Example 1) is set to 100, and the larger the value, the better the ice braking performance.

(2) Ice turning performance The tire is mounted on the same actual vehicle as above, and the same road surface is run at a speed of 20 km / h on a lemniskate curve (eight curve: R = 25 m yen) under the load conditions of one passenger. Lap time was evaluated as an index. In addition, evaluation is shown by an index display when the conventional product (Comparative Example 1) is 100, and the larger the numerical value, the better the ice turning performance.

Example 1
In the tread portion 1 shown in FIG. 1, a shallow groove 4A (groove width 0.6 mm, groove depth) in which the angle between the longitudinal direction and the tire circumferential direction is 90 ° in the land portion disposed in the center region Ce. 0.3mm) and a shallow groove 4B (groove width 0.6mm, groove depth) in which the angle between the longitudinal direction and the tire circumferential direction is 0 ° at the land portion disposed in the shoulder region Sh. A pneumatic tire provided with 0.3 mm) was manufactured. Table 1 shows the results of the above performance evaluations using such tires.

Comparative Example 1
In the tread portion 1 shown in FIG. 1, in the same manner as in Example 1 except that the shallow portion is not provided in the land portion provided in the center region Ce and the land portion provided in the shoulder region Sh. A pneumatic tire was manufactured. Table 1 shows the results of the above performance evaluations using such tires.

Comparative Example 2-3
In the tread portion 1 shown in FIG. 1, in the land portion disposed in the center region Ce and the land portion disposed in the shoulder region Sh, the shallow groove in which the angle between the longitudinal direction and the tire circumferential direction is 0 °. A pneumatic tire was manufactured in the same manner as in Example 1 except that 4B (groove width 0.6 mm, groove depth 0.3 mm) was disposed (Comparative Example 2). Further, in the tread portion 1 shown in FIG. 1, the angle formed by the longitudinal direction and the tire circumferential direction is 90 ° in the land portion disposed in the center region Ce and the land portion disposed in the shoulder region Sh. A pneumatic tire was manufactured in the same manner as in Example 1 except that the shallow groove 4A (groove width 0.6 mm, groove depth 0.3 mm) was provided (Comparative Example 3). Table 1 shows the results of the performance evaluations described above using these tires.

Example 2
In the tread portion 1 shown in FIG. 2, a shallow groove 4A (groove width of 0.6 mm, groove angle of 90 ° formed by the rib formed in the first center region Ce-1 with the longitudinal direction and the tire circumferential direction is 90 °. In the block rows B2 and B1 disposed in the second center region Ce-2 and the shoulder region Sh, the angle formed between the longitudinal direction and the tire circumferential direction is 0 °. The shallow groove 4B (groove width 0.6 mm, groove depth 0.3 mm) is disposed, the total contact area of the tread portion 1 is S, the contact area of the first center rib R1 is S11, and the second center rib R2 is When the total grounding area is S12, the total grounding area of the first block row B1 is S2, and the total grounding area of the second block row B2 is S3, S11 = 0.22S, S12 = 0.26S, S2 = Set 0.22S and S3 = 0.30S. A pneumatic tire was manufactured by setting W2 / W1 = 0.45, where W1 is the distance from the tire equator CL to the ground contact edge 6 and W2 is the distance from the tire equator CL to the circumferential narrow groove 5. Table 1 shows the results of the above performance evaluations using such tires.

  From the results in Table 1, it can be seen that both the ice braking performance and the ice turning performance of the pneumatic tire of Example 1 are improved as compared with the pneumatic tire of Comparative Example 1. Moreover, in the pneumatic tire of Example 2, it turns out that the ice turning performance is further improved and the ice braking performance is remarkably improved as compared with the pneumatic tire of Comparative Example 1. On the other hand, the pneumatic tire of Comparative Example 2 improved the ice turning performance compared with the pneumatic tire of Comparative Example 1, but the ice braking performance hardly improved. On the other hand, although the ice braking performance of the pneumatic tire of Comparative Example 3 was improved as compared with the pneumatic tire of Comparative Example 1, the ice turning performance was hardly improved.

The expanded view which shows an example of the tread pattern in the pneumatic tire of this invention The expanded view which shows another example of the tread pattern in the pneumatic tire of this invention Diagram showing an example of the cross-sectional shape of the shallow groove

Explanation of symbols

1: tread portion 2: circumferential main groove 3: lateral groove 4A, 4B: shallow groove 5: circumferential narrow groove 6: ground contact Ce: center region Sh: shoulder region CL: tire equator

Claims (4)

In the pneumatic tire in which the tread portion is divided into a center region including the tire equator and a shoulder region located on both outer sides in the width direction of the center region by two circumferential main grooves positioned on the outermost side in the width direction. ,
The land portion disposed in the center region is further partitioned into two first circumferential regions by two circumferential narrow grooves, a first center region and a second center region located on both outer sides in the width direction of the first center region,
The land portion disposed in the first center region includes a plurality of ribs defined by at least one circumferential main groove and the circumferential narrow groove, and is formed by a longitudinal direction and a tire circumferential direction. A shallow groove with an angle of 75 to 90 ° is arranged,
The land portion disposed in the second center region is configured by a first block row partitioned by a plurality of lateral grooves, and the land portion disposed in the shoulder region is a second portion partitioned by a plurality of lateral grooves. The land portion, which is composed of block rows and is disposed in the second center region and the shoulder region, is provided with shallow grooves in which the angle between the longitudinal direction and the tire circumferential direction is 0 to 15 °. A pneumatic tire characterized by being. When the total ground contact area of the tread portion is S, the total ground contact area of the ribs is S1, the total ground contact area of the first block row is S2, and the total ground contact area of the second block row is S3. , 0.45S ≦ S1 ≦ 0.55S, 0.15S ≦ S2 ≦ 0.25S, and 0.20S ≦ S3 ≦ 0.35S pneumatic tire according to claim 1, wherein. The air according to claim 1 or 2 , wherein W2 / W1 = 0.45 ± 0.03, where W1 is a distance from the tire equator to the ground contact edge and W2 is a distance from the tire equator to the circumferential narrow groove. Enter tire. The pneumatic tire according to any one of claims 1 to 3 , wherein the shallow groove has a groove width of 0.3 to 1.5 mm and a groove depth of 0.2 to 1.0 mm.

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