JP2009208597A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire achieving both braking performance on ice and turning performance on ice. <P>SOLUTION: In this pneumatic tire, a tread section 1 is partitioned into a center area Ce including a tire equator CL and shoulder areas Sh positioned on both outer sides in the width direction of the center area Ce by two peripheral narrow grooves 3. Land portions arranged in the shoulder areas Sh are composed of blocks partitioned by a plurality of transverse grooves 4. The blocks are formed with a plurality of width direction sipes 5. At least more than one peripheral sipe 6 is formed in at least one area partitioned between the width direction sipes 5. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, the tread portion is divided into a center region including the tire equator by two circumferential narrow grooves, and a shoulder region located on both outer sides in the width direction of the center region, and ice braking performance and ice turning performance It relates to a pneumatic tire that balances

  Conventionally, in order to improve the ice performance of a studless tire, there is known one in which a plurality of sipes are formed in each region (center region and shoulder region) of a tread portion. For the purpose of improving ice braking performance, many sipes extending in the tire width direction have been formed to enhance the edge effect in the front-rear direction. Further, in order to improve the ice turning performance, the sipe component having an angle approaching the tire circumferential direction is increased to enhance the lateral edge effect.

  Conventionally, as a method for improving both ice braking performance and ice turning performance, it has been generally performed to form a wave-shaped sipe in the tire width direction instead of a straight sipe. However, when the corrugated sipe is formed in the tire width direction, the ice turning performance can be improved as compared with the straight sipe, but the effect of improving the ice turning performance due to the increase of the sipe component in the tire circumferential direction is not sufficient. In addition, when a sipe having a length substantially equal to the tire circumferential length of the block is formed in the tire circumferential direction, the sipe component in the tire circumferential direction increases and the edge effect in the lateral direction is enhanced, thereby improving the ice turning performance. improves. However, in such a configuration, the block rigidity is likely to be reduced, and the ice braking performance is deteriorated due to the reduction in the contact area, and uneven wear such as step wear is generated. Thus, in the studless tire, it is very difficult to achieve both ice braking performance and ice turning performance.

  In the following Patent Document 1, a sipe extending from one block end is connected to an intermediate portion of a sipe extending from the other block end, and a sipe extending from the other block end is connected to a central region of the block. A pneumatic tire including a tread pattern in which a pseudo sipe extending substantially along the tire circumferential direction is formed by being connected to an intermediate portion is described. In such a pneumatic tire, by increasing the sipe density in the central region of the block than in the peripheral region of the block and enhancing the edge effect, the ice braking performance is improved, and a pseudo sipe along the tire circumferential direction is formed, The purpose is to improve the ice turning performance.

However, in such a pneumatic tire, each of the blocks constituting the land portion disposed in the center region and the shoulder region of the tread portion is provided with pseudo sipes extending in the tire circumferential direction, and further in the circumferential direction of each block. Since a circumferential sipe (pseudo sipe) having a length substantially equal to the length is provided, it is not possible to sufficiently achieve both ice braking performance and ice turning performance.
JP 2000-225815 A

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

  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 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 narrow grooves. In the pneumatic tire, the land portion disposed in the shoulder region is configured by a block partitioned by a plurality of lateral grooves, and the block is formed by a plurality of widthwise sipes and is partitioned between the widthwise sipes. It is characterized in that two or more circumferential sipes are formed in at least one region formed.

  In the pneumatic tire of the present invention, the land portion disposed in the shoulder region is constituted by a block, and the block is formed with a plurality of widthwise sipes and at least one region partitioned between the widthwise sipes. A circumferential sipe is formed on the surface. According to this configuration, two or more circumferential sipes are formed in the shoulder region where the force generated in the turning direction is large. Thereby, the edge effect of a horizontal direction acts effectively and ice turning performance can be improved. In addition, since the lateral edge effect acts effectively, slipping in the lateral direction during ice braking can be suppressed. As a result, stability in the lateral direction during ice braking can be ensured, so that the edge effect in the front-rear direction of the width direction sipe acts effectively, and the ice braking performance can be improved. Further, according to such a configuration, in the central region of the block that is partitioned between the widthwise sipes and has little movement, that is, in the block region other than the region that is partitioned into the widthwise sipes and the lateral grooves at the front and rear end portions of the block A circumferential sipe is formed. Thereby, the movement in the braking direction of the block area in which the circumferential sipe is formed can be supported by the block area located on both sides in the front-rear direction of the block area and in which the circumferential sipe is not formed. It is possible to suppress a decrease in rigidity in the block in which the sipe is formed. As a result, it is possible to suppress a decrease in the contact area in the block, to ensure a good ice braking performance, and to prevent uneven wear such as step wear.

  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.

  As a result of experiments and examinations focusing on the in-plane contraction force of the tread portion, the present inventors have divided the tread portion into a center region and a shoulder region by two circumferential narrow grooves. In this case, the position in the width direction where W2 / W1 = 0.45 ± 0.03 is used as a boundary line, and the force generated in the braking direction is larger on the center side (center area) than the boundary line. It was also found that the force generated in the turning direction is large on the shoulder side (shoulder region).

  Therefore, when the tread portion is divided into the center region and the shoulder region by two circumferential narrow grooves, the circumferential narrow groove is at the width direction position where W2 / W1 = 0.45 ± 0.03. A plurality of width sipes are formed in a block on the outer side in the width direction (shoulder region) than the circumferential narrow groove, and a circumferential sipe is formed in at least one region partitioned between the width direction sipes. The pneumatic tire can further improve the ice turning performance while ensuring the ice braking performance well.

  In the above, the land portion disposed in the shoulder region is further divided by a circumferential main groove into a first shoulder portion located on the outer side in the width direction and a second shoulder portion located on the inner side in the width direction, When the sipe interval between the circumferential sipe formed in the block constituting the one shoulder portion is C1, and the sipe interval between the circumferential sipe formed in the block constituting the second shoulder portion is C2, It is preferable that C1> C2. According to this configuration, it is possible to improve the ice turning performance and the uneven wear resistance performance while ensuring the ice braking performance satisfactorily.

  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, in the pneumatic tire of the present embodiment, the tread portion 1 is formed by two circumferential narrow grooves 3, a center region Ce including the tire equator CL, and both outer sides in the width direction of the center region Ce. Is partitioned into a shoulder region Sh. The land portion disposed in the shoulder region Sh is further divided into a first shoulder portion Sh-1 positioned on the outer side in the width direction and a second shoulder portion Sh-2 positioned on the inner side in the width direction by the circumferential main groove 2. The land portion disposed in the center region Ce includes the first center portion Ce-1 including the tire equator CL and the first center portion Ce-1 by two circumferential main grooves 2 extending on both sides of the tire equator CL. It is divided into a second center portion Ce-2 located on both outer sides in the width direction of the center portion Ce-1. In addition, the first shoulder portion Sh-1 and the second shoulder portion Sh-2 disposed in the shoulder region Sh are configured by blocks partitioned by a plurality of lateral grooves 4. In the present embodiment, the first center portion Ce-1 and the second center portion Ce-2 disposed in the center region Ce are configured by blocks partitioned by a plurality of lateral grooves 4. Here, although it does not specifically limit as a groove width of the circumferential direction fine groove 3, For example, a 0.5-2 mm thing is mentioned. In addition, 1st shoulder part Sh-1 may include the part extended in the width direction outer side across the grounding end 7 (illustration omitted).

  In the pneumatic tire according to the present embodiment, a plurality of width-direction sipes 5 are formed in a block constituting the first shoulder portion Sh-1 and the second shoulder portion Sh-2 disposed in the shoulder region Sh. Yes. As described above, the force generated in the braking direction of the shoulder region Sh is smaller than that of the center region Ce, but the plurality of width-direction sipes 5 constitute the first shoulder portion Sh-1 and the second shoulder portion Sh-2. By forming the block, an edge effect in the front-rear direction acts, leading to an improvement in ice braking performance. The interval between the width-direction sipes 5 is not particularly limited as long as the edge effect in the front-rear direction is suitably acted while securing the block rigidity, and examples thereof include those of 3 to 6 mm. Moreover, it does not specifically limit about the sipe width of the width direction sipe 5, For example, a 0.2-0.5 mm thing is mentioned. The width direction sipe 5 may be inclined with respect to the tire width direction.

  In the present embodiment, an example in which the width direction sipes are formed also in the blocks constituting the first center portion Ce-1 and the second center portion Ce-2 disposed in the center region Ce is shown. . A pneumatic tire having such a configuration is preferable because the edge effect in the front-rear direction by the width-direction sipe acts more effectively in the center region Ce where the force generated in the braking direction is large, and the ice braking performance is further improved.

  Moreover, in the pneumatic tire according to the present invention, between the widthwise sipes 5 formed in the blocks constituting the first shoulder portion Sh-1 and the second shoulder portion Sh-2 disposed in the shoulder region Sh. Two or more circumferential sipes 6 are formed in at least one partitioned area. According to such a configuration, since the circumferential sipe 6 is formed in the shoulder region Sh where the force generated in the turning direction is large, the lateral edge effect acts effectively and the ice turning performance can be improved. In addition, since the edge effect in the lateral direction acts effectively, it is possible to suppress the slip in the lateral direction during ice braking. As a result, stability in the lateral direction during ice braking can be ensured, so that the edge effect in the front-rear direction of the width direction sipe acts effectively, and the ice braking performance can be improved.

  The circumferential sipe 6 may be an open sipe that opens to the width direction sipe 5, or may be a closed sipe that is closed to the width direction sipe 5. The number of circumferential sipes 6 formed in each block is, for example, 2 to 4 in the block constituting the second shoulder portion Sh-2, and 2 to 6 in the block constituting the first shoulder portion Sh-1. Can be mentioned. Further, the circumferential sipe 6 may be inclined with respect to the tire circumferential direction.

  According to the above-described configuration, the block is divided between the width-direction sipes 5 and is located in a block area other than the area defined by the width-direction sipes 5 and the lateral grooves 4 at the front-rear direction end of the block. Thus, a circumferential sipe 6 is formed. Thereby, the movement in the braking direction of the block region in which the circumferential sipe 6 is formed can be supported by the block region that is located on both sides in the front-rear direction of the block region and in which the circumferential sipe 6 is not formed, It is possible to suppress a decrease in rigidity in the block in which the circumferential sipe 6 is formed. As a result, it is possible to suppress a decrease in the contact area in such a block, to ensure good ice braking performance, and to prevent uneven wear such as step wear. In order to effectively suppress the decrease in rigidity in the block region where the circumferential sipe 6 is formed and to further improve the ice braking performance, the circumferential sipe 6 is provided in a substantially central region in the front-rear direction of each block. Is preferably formed.

  On the other hand, as described above, the center region Ce generates a large force in the braking direction, but the force generated in the turning direction is smaller than the shoulder region Sh. Therefore, in the pneumatic tire according to the present invention, in order to more effectively balance the ice braking performance and the ice turning performance, only the blocks constituting the land portion where the circumferential sipe 6 is disposed in the shoulder region Sh are used. It is preferable to form only the width direction sipe in the land portion formed and disposed in the center region Ce.

  Here, as shown in FIG. 1, when the distance from the tire equator CL to the ground contact 7 is W1, and the distance from the tire equator CL to the circumferential narrow groove 3 is W2, W2 / W1 = 0.45 ±. The circumferential narrow groove 3 is disposed at a position in the width direction of 0.03, and the circumferential narrow groove 3 is used as a boundary line only around the blocks constituting the land portion disposed on the shoulder side (shoulder region Sh). It is preferable that the directional sipe 6 is formed because the lateral edge effect by the circumferential sipe 6 acts more effectively and the ice turning performance can be further improved. In addition, the block constituting the land portion disposed on the center side (center region Ce) with the circumferential narrow groove 3 as a boundary line is formed with only the width direction sipe 5, and the ice braking performance is improved. Further improvement is preferable.

  When the sipe interval between the circumferential sipe 6 formed in the first shoulder portion Sh-1 is C1, and the sipe interval between the circumferential sipe 6 formed in the second shoulder portion Sh-2 is C2, C1> C2 is preferred. According to this configuration, it is possible to improve the ice turning performance and the uneven wear resistance performance while ensuring the ice braking performance satisfactorily. Examples of the sipe interval C1 between the circumferential sipe 6 formed on the first shoulder portion Sh-1 include 2.1 to 6 mm, and the circumferential sipe 6 formed on the second shoulder portion Sh-2. The sipe interval C2 between is 2 to 5 mm, for example. Further, the sipe width of the circumferential sipe 6 is not particularly limited, and examples thereof include 0.2 to 0.5 mm.

In the present invention, it is preferable that the sipe density in the entire tread portion 1 is 0.1 to 0.2 mm / mm ^2, more preferably 0.13~0.16mm / mm ^2. Further, the sipe formed in the tread portion 1 is not limited to a straight sipe, and may be a wave sipe.

  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, an example in which the first center portion Ce-1 is configured by blocks as illustrated in FIG. 1 is illustrated, but the first center portion may be configured by rib rows. According to such a configuration, since the land portion rigidity in the center region can be increased, the widthwise sipe density in the center region can be increased. As a result, in the pneumatic tire having such a configuration, the ice braking performance can be further improved.

  (2) In the above-described embodiment, as shown in FIG. 1, the example in which the two circumferential main grooves 2 extending on both sides of the tire equator CL are disposed in the center region Ce is shown. One circumferential main groove may be disposed on the equator CL. According to this configuration, the land area in the center area is effectively ensured, and the land area rigidity in the center area can be increased. Thereby, since the sipe density in the width direction in the center region can be increased, the ice braking performance can be improved in the pneumatic tire having such a configuration.

  (3) In the above-described embodiment, as shown in FIG. 1, the example in which the circumferential main groove 2 is formed in a straight shape is shown, but the circumferential main groove may be formed in a zigzag shape. Good. According to such a configuration, the edge effect with respect to the front-rear direction and the lateral direction of the circumferential main groove acts effectively. Thereby, in a pneumatic tire provided with this structure, both ice braking performance and ice turning performance can be improved more.

  (4) In the above-described embodiment, as shown in FIG. 1, an example in which a plurality of circumferential main grooves 2 are disposed has been shown. However, as shown in FIG. An inclined main groove 14 that extends incline in the tire width direction across the groove 13 and constitutes a substantially V-shaped pattern in the center region Ce may be disposed. In the pneumatic tire having such a configuration, both ice braking performance and ice turning performance can be further improved.

  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 tires are mounted on the same actual vehicle as above, and the same road surface is run on the Remnis skate curve (8-shaped curve: R = 25m yen) under the load condition of one passenger, and the lap time is evaluated as an index. did. 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 shown in FIG. 1, W2 / W1 = 0.45 when the distance from the tire equator CL to the ground contact 7 is W1, and the distance from the tire equator CL to the circumferential narrow groove 3 is W2. The sipe interval C2 between the circumferential sipe 6 formed on the second shoulder portion Sh-2 is set to 4.5 mm, and the sipe interval C1 between the circumferential sipe 6 formed on the first shoulder portion Sh-1 is set to 5.0 mm. A pneumatic tire was manufactured. Table 1 shows the results of the above performance evaluations using such tires.

Example 2-3
A pneumatic tire was manufactured in the same manner as in Example 1 except that W2 / W1 = 0.42 in Example 1 (Example 2). In Example 1, a pneumatic tire was manufactured in the same manner as Example 1 except that W2 / W1 = 0.48 (Example 3). Table 1 shows the results of the performance evaluations described above using these tires.

Conventional product (Comparative Example 1)
In the tread portion shown in FIG. 3, W22 / W21 = 0.45 when the distance from the tire equator CL to the ground contact edge 17 is W21, and the distance from the tire equator CL to the circumferential narrow groove 13 is W22. A pneumatic tire was manufactured in the same manner as in Example 1 except that no circumferential sipe was provided in the part. Table 1 shows the results of the above performance evaluations using such tires.

Comparative Example 2-3
In Example 1, a pneumatic tire was manufactured in the same manner as Example 1 except that W2 / W1 = 0.41 (Comparative Example 2). In Example 1, a pneumatic tire was manufactured in the same manner as Example 1 except that W2 / W1 = 0.49 (Comparative Example 3). Table 1 shows the results of the performance evaluations described above using these tires.

  From the result of Table 1, in the pneumatic tire of Example 1-3, in the block which comprises 1st shoulder part Sh-1 and 2nd shoulder part Sh-2, it is a substantially center area | region in the front-back direction of a block, Since two or more circumferential sipes 6 are formed in the region partitioned between the width direction sipes, it can be seen that the ice turning performance is superior to the pneumatic tire of Comparative Example 1. Furthermore, since stability in the lateral direction during ice braking is ensured, it can be seen that the ice braking performance is excellent. On the other hand, in the pneumatic tire of Comparative Example 2, since the shoulder region is larger than that of the pneumatic tire of Example 1-3, the influence of the in-plane contraction force is further increased. As a result, ice braking performance deteriorated. Moreover, in the pneumatic tire of Comparative Example 3, since the shoulder region is smaller than that of the pneumatic tire of Example 1-3, the number of circumferential sipes formed is reduced. As a result, ice turning performance deteriorated.

The expanded view which shows an example of the tread pattern in the pneumatic tire of this invention The expanded view which shows the other example of the tread pattern in the pneumatic tire of this invention Development view showing a tread pattern of a conventional pneumatic tire employed in Comparative Example 1

Explanation of symbols

1: tread portion 2: circumferential main groove 3: circumferential narrow groove 4: transverse groove 5: width sipe 6: circumferential sipe 7: ground end Ce: center region Sh: shoulder region

Claims (3)

In the pneumatic tire in which the tread portion is partitioned by two circumferential narrow grooves 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,
The land portion disposed in the shoulder region is configured by a block partitioned by a plurality of lateral grooves, and the block is formed with a plurality of widthwise sipes and at least one partitioned between the widthwise sipes. A pneumatic tire characterized in that two or more circumferential sipes are formed in a region.   2. The pneumatic tire according to claim 1, 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. .   The land portion disposed in the shoulder region is further divided by a circumferential main groove into a first shoulder portion located on the outer side in the width direction and a second shoulder portion located on the inner side in the width direction, and the first shoulder portion C1> C2 where C1 is a sipe interval between the circumferential sipes formed in the blocks constituting the sipe, and C2 is a sipe interval between the circumferential sipees formed in the block constituting the second shoulder portion. The pneumatic tire according to claim 1 or 2.

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