JP5844539B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire having a sipe formed on a land portion of a tread surface, and is particularly useful as a studless tire.

  Conventionally, in studless tires, incisions called sipe are formed in the land such as blocks and ribs, and the edge effect of this sipe improves traction, driving performance on icy and snowy road surfaces (hereinafter referred to as ice performance) with a low coefficient of friction. Is called). However, as the number of sipes increases, the edge component increases, but the rigidity of the land portion tends to decrease and the deformation during driving tends to increase, and if the deformation of the land portion is excessive, the edge effect Will become smaller.

  On the other hand, as disclosed in Patent Document 1 below, for example, a method of forming a sipe in a zigzag shape or a wave shape in the depth direction is known. In such a structure, a convex portion formed on the other of the sipe wall surfaces engages with a concave portion formed on one of the sipe wall surfaces facing each other, thereby suppressing excessive deformation of the land portion. However, since the unevenness of the sipe extends in the lateral direction (longitudinal direction of the sipe), it is difficult to exert an engaging force when turning with a lateral force, and deformation of the land portion may not be sufficiently suppressed.

  In other words, not only the longitudinal force at the time of braking but also the vertical force due to grounding, the lateral force at the time of turning, or a composite force of them can act on the land part during traveling, In order to suppress the excessive deformation of the land portion and improve the ice performance, it is considered effective to exert the engagement between the sipe wall surfaces in various directions.

  The following Patent Document 2 describes a sipe wall surface 10a in which an arcuate recess 64 (narrow groove) as shown in FIG. 7 is formed, but the sipe wall surface facing this engages with the recess 64. The convex part is not formed. Even if such a convex portion is formed, the convex portion that has entered the concave portion 64 during running travels out of the tread surface 1a and side surface 1b of the land portion, and the sipe wall surfaces do not accurately engage with each other. It is difficult to sufficiently suppress deformation.

JP 2002-192916 A Japanese Patent Laid-Open No. 10-86612

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pneumatic tire capable of improving ice performance by suppressing excessive deformation of land portions.

  The above object can be achieved by the present invention as described below. That is, the pneumatic tire of the present invention is a pneumatic tire in which a sipe is formed in a land portion of a tread surface, and a concave portion formed by a closed loop that is not exposed on the tread surface and side surface of the land portion on one of sipe wall surfaces facing each other. And a convex portion constituted by a closed loop having a shape corresponding to the concave portion is formed on the other side of the sipe wall surface.

  In the pneumatic tire of the present invention, the sipe wall surfaces are engaged with each other by the concave portion and the convex portion entering the concave portion, and deformation of the land portion during traveling can be suppressed. Moreover, since the concave portion is formed by a closed loop that is not exposed to the tread surface and the side surface of the land portion, and the convex portion is formed by a closed loop having a shape corresponding thereto, the convex portion that has entered the concave portion escapes from the tread surface and side surface of the land portion. While preventing these, excessive engagement of the land portion can be suppressed by exerting their engagement in various directions.

In the pneumatic tire of the present invention, the concave portion is constituted by an annular closed loop . According to such a configuration, since the engagement between the concave portion and the convex portion is firmly exhibited in all directions, excessive deformation of the land portion can be satisfactorily suppressed.

In the pneumatic tire according to the first aspect of the present invention, the concave portion is constituted by a plurality of closed loops arranged in contact with each other or crossing each other . Accordingly, it is possible to form a recess by a correspondingly large number of closed loops and arrange the recess in a wide range of the sipe wall surface, so that excessive deformation of the land portion can be satisfactorily suppressed.

In the pneumatic tire according to the second aspect of the present invention, the convex portion has a relatively thick portion and a thin portion on the circumference of the closed loop . With such a convex part, the entire convex part can enter the concave part starting from a thin part that is relatively easily deformed, and the engagement between the concave part and the convex part can be smoothly expressed.

The expanded view which shows an example of the tread surface of the pneumatic tire which concerns on this invention Longitudinal sectional perspective view when sipe is divided along the longitudinal direction The figure which shows the sipe wall surface of the sipe of FIG. Cross section of the sipe of FIG. The figure which shows the sipe wall surface in another embodiment of this invention. The figure which shows the sipe wall surface in another embodiment of this invention. The figure which shows the sipe wall surface in the comparative example 1 The figure which shows the sipe wall surface in the comparative example 2 The figure which shows the sipe wall surface in Example 1,2.

  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 surface of a pneumatic tire according to the present invention. This pneumatic tire includes a tread pattern having a plurality of blocks 1 (an example of a land portion). The block 1 is divided into a main groove 3a extending in the tire circumferential direction (vertical direction in FIG. 1) and a lateral groove 3b extending so as to intersect therewith, and four block rows sandwiching ribs 2 extending in the tire circumferential direction. Is provided.

  Each block 1 is provided with a plurality of sipes 10 that open linearly on the tread surface 1a in parallel with each other at a predetermined interval. From the viewpoint of enhancing the traction and braking performance on an icy and snowy road surface, the inclination angle of the sipe 10 with respect to the tire width direction (left-right direction in FIG. 1) is preferably 45 ° or less. Both ends of the sipe 10 are open to the side surface 1b of the block 1 and are provided as so-called both-side open sipes.

  As shown in FIGS. 2 to 4, of the sipe wall surfaces facing each other, one sipe wall surface 10 a is formed with a recess 4 constituted by a closed loop that is not exposed to the tread surface 1 a and the side surface 1 b of the block 1, and the other sipe wall surface. On the wall surface 10b, a convex portion 5 formed by a closed loop having a shape corresponding to the concave portion 4 is formed. In this embodiment, the recessed part 4 is comprised by the annular | circular shaped closed loop, and the convex part 5 is comprised by the annular | circular shaped closed loop corresponding to it.

  During traveling, the sipe wall surfaces are engaged with each other by the concave portion 4 and the convex portion 5 entering the concave portion 4, and deformation of the block 1 is suppressed. In addition, since the recess 4 is closed without being exposed to the tread 1a and the side surface 1b, and the recess 4 and the protrusion 5 are configured in a closed loop, the vertical force or lateral force on the block 1 or Even if a force that combines them acts, the convex portion 5 is prevented from slipping out of the tread surface 1a and the side surface 1b, and yet it is engaged in various directions along the sipe wall surface, and the block 1 is excessively deformed. Can be effectively suppressed.

  In addition, with such a sipe structure, the position of the recess 4 appearing on the tread surface 1a of the block 1 changes during the progress of wear, so the location where the force acts on the opening of the sipe 10 is not biased, and the heel There is also an advantage that generation of andtoe wear can be suppressed. The heel and toe wear is a form of partial wear, and is a form of wear in which the amount of wear differs between the stepping side and the kicking side.

  By the way, in the structure in which the disk-like convex part having the same outer diameter as the convex part 5 is engaged with the circular concave part having the same outer diameter as the concave part 4, the pair of concave and convex parts can be engaged only at one place in one direction. There is a possibility that the disk-shaped convex portion having high rigidity is difficult to be deformed and hardly enters the circular concave portion. On the other hand, in the structure in which the concave portion 4 and the convex portion 5 configured by a closed loop as described above are engaged, even if a single set of concave and convex portions can be engaged, the convex portion 5 can be compared at a plurality of locations in one direction. Since it is easily deformed, it can enter the recess 4 smoothly.

  The closed loop constituting the concave portion 4 may be any closed loop shape (endless shape, closed loop shape), and may be another shape such as a polygon or an ellipse as described later. The same applies to the convex portion 5. The convex portion 5 is formed of a closed loop having a shape corresponding to the concave portion 4 and is provided so as to enter and engage with the concave portion 4. Although FIGS. 2-4 shows the example in which the recessed part 4 is comprised by two closed loops, it is not restricted to this, It is also possible to comprise by one or three or more closed loops.

  The recess 4 is formed in a region A indicated by a broken line frame in FIG. 3 so as not to be exposed on the tread surface 1a and the side surface 1b. In this area A, the gap G1 from the tread surface 1a is 5% of the sipe depth D, which makes it easy to prevent the convex portion 5 from slipping out from the tread surface 1a and to process the sipe blade used for forming the sipe 10. Becomes easier. The gap G2 from the bottom of the sipe 10 is 5% of the sipe depth D, and the sipe blade can be easily processed in the same manner. The sipe depth D is set to 30 to 80% of the depth of the main groove 3a so that the edge effect by the sipe 10 can be sufficiently exhibited.

  Further, in the region A, the gap G3 from the left and right side surfaces 1b is 5% of the sipe length L, respectively, thereby preventing the protrusion 5 from coming out from the side surface 1b appropriately. In addition, by ensuring a region having no irregularities at both ends of the sipe 10, it is easy to pull out the sipe blade from the block 1 when the vulcanized tire is taken out from the mold, thereby preventing the occurrence of cracks. it can.

  From the viewpoint of securing the engaging force between the sipe wall surfaces, the dent amount d4 of the concave portion 4 with respect to the sipe wall surface 10a is set to 0.2 to 0.5 mm, for example, and the convex portion 5 with reference to the sipe wall surface 10b. The protrusion amount h5 is set to 0.1 to 0.4 mm, for example. For the same reason, the thickness T5 of the convex portion 5 is set to 0.5 to 2 mm, for example, and the thickness T4 of the concave portion 4 is set to a dimension that allows the convex portion 5 to enter and engage. In order to sufficiently express the edge effect, the sipe width W10 is preferably 0.2 to 0.8 mm.

  FIG. 5 shows an example in which the concave portion 14 formed in the sipe wall surface 10a is constituted by a plurality of (four in the present embodiment) closed loops arranged in contact with or crossing each other. On the sipe wall surface 10b facing the sipe wall surface 10a, convex portions 15 formed of a plurality of closed loops having shapes corresponding to the concave portions 14 are formed. About a basic effect and a preferable aspect, since it is the same as the recessed part 4 and the convex part 5 which were mentioned above, the overlapping description is abbreviate | omitted. Examples of the number of closed loops constituting such a recess include 2 to 6.

  With the structure as shown in FIG. 5, compared to the case where the recess is formed by a plurality of closed loops separated from each other, the recess 14 is configured by a correspondingly large plurality of closed loops, and the recess 14 is formed on the sipe wall surface 10 a. Since it becomes possible to arrange | position in a wide range, the excessive deformation | transformation of the block 1 can be suppressed favorably. Further, by arranging the recesses 14 in a wide range in this way, it is possible to reduce the difference in rigidity in the sipe due to the presence or absence of the recesses, and to suppress the occurrence of uneven wear.

  The plurality of closed loops constituting the recess 14 may be arranged in contact with each other, but it is preferable that they are arranged so as to cross each other. The reason for this is that an engagement portion between the concave portion 14 and the convex portion 15 is increased by forming a remote island-shaped portion surrounded by the convex portion 15 in a region where the closed loops overlap.

  The recess 14 is preferably formed in the region A as described above. However, in disposing the concave portion 14 in a wide range of the sipe wall surface 10a, the shortest distance from the tread surface 1a to the concave portion 14 and the shortest distance from the bottom portion of the sipe 10 to the concave portion 14 are 5 to 5 of the sipe depth D, respectively. The shortest distance from the side surface 1b to the recess 14 is preferably 5 to 8% of the sipe length L.

  The convex part 15 has a relatively thick part and a thin part on the circumference of the closed loop. In the present embodiment, the thickness of the convex portion 15 gradually changes on the circumference of the closed loop, and the outer circumference circle and the inner circumference circle are displaced so as to be eccentric, and T15a> T15b. Yes. The thickness of the recess 14 changes to correspond to this. Thus, the structure which changes the thickness of a convex part is employable also for the convex part 5 shown in FIG.

  In such a convex portion 15, the entire convex portion 15 can enter the concave portion 14 starting from a thin portion that is relatively easily deformed, and the engagement between the concave portion 14 and the convex portion 15 can be smoothly expressed. it can. Further, in such a case, it is preferable that the closed loop near the corner portion of the block 1 (a peripheral portion of the ridge line between the tread surface 1a and the side surface 1b), which tends to be greatly deformed during traveling, is directed to a thin part, Thereby, the action of suppressing the deformation of the block 1 can be held at the thick part.

  When the concave portion is constituted by a plurality of closed loops, it is preferable that the closed loop is composed of a combination of large and small as in the example shown in FIG. Thereby, it becomes easy to pack and arrange a plurality of closed loops, and a recess can be formed in a wide range of the sipe wall surface 10a. In this case, a large closed loop is disposed on the tread surface 1a side of the block 1 and the small closed loop is disposed on the bottom side of the sipe 10 in order to enhance the engaging action between the sipe wall surfaces. It is preferable to do.

  The recess formed in the sipe wall surface 10a may have a shape as shown in FIG. 6, for example. Although illustration is omitted, a sipe wall surface facing this is formed with a convex portion constituted by a closed loop having a shape corresponding to each of the concave portions. (A) and (B) are examples in which the recesses 24 and 34 are configured by polygonal closed loops, respectively. (C) is an example in which the recess 44 is configured by a closed loop having a uniform size. (D) is the example which comprised the recessed part 54 by multiple types of closed loop.

  The tire having the sipe structure as described above is a modification in which a sipe blade inserted into the tread surface during vulcanization molding is provided with a protrusion corresponding to the concave portion and a recess corresponding to the convex portion. The tire can be manufactured in the same manner as the tire manufacturing process.

  The pneumatic tire of the present invention is the same as a normal pneumatic tire except that a sipe as described above is formed in a land portion such as a block, and all of the conventionally known materials, shapes, structures, manufacturing methods, etc. It can be employed in the present invention.

  The present invention can be applied to so-called summer tires and all-season tires, but is particularly useful as a studless tire (winter tire) because of its excellent ice performance.

[Other Embodiments]
(1) The tread pattern of the pneumatic tire of the present invention is not particularly limited, and various block shapes such as a V shape, a polygonal shape, and a curve base tone can be adopted instead of a rectangular shape. Further, the sipe structure of the present invention can be applied to the sipe formed on the rib.

  (2) In the above-described embodiment, an example is shown in which the sipe extends linearly along the longitudinal direction. However, the present invention is not limited to this, and for a waved sipe extending in a wavy or zigzag shape along the longitudinal direction, The sipe structure of the present invention can be applied.

  (3) In the above-described embodiment, an example in which only the concave portion is formed on one of the sipe wall surfaces facing each other and only the convex portion is formed on the other is shown, but the present invention is not limited to this. That is, in the present invention, the concave portions as described above may be formed on both sipe wall surfaces, and convex portions having shapes corresponding to the concave portions may be formed on the opposing sipe wall surfaces.

  Examples that specifically show the structure 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 (an example of ice performance)
The reciprocal of the braking distance was evaluated when the tire was mounted on a real vehicle and traveled on an icy and snowy road surface, and the vehicle was fully locked by applying a braking force at a speed of 40 km / h. The result is expressed as an index when Comparative Example 1 is set to 100, and the larger the value, the better the performance.

(2) Ice turning performance (an example of ice performance)
The tire was mounted on a real vehicle and traveled on an icy and snowy road surface, and the reciprocal of the lap time when traveling on a Lemmy skate curve (eight curve: R = 25 m yen) was evaluated. The result is expressed as an index when Comparative Example 1 is set to 100, and the larger the value, the better the performance.

(3) Uneven wear resistance (heel and toe wear resistance)
The reciprocal of the heel and toe wear amount (the difference in wear amount between the sipe stepping-in side and the kicking-out side) after running a distance of 12000 km with the tire mounted on the actual vehicle was evaluated. The result is expressed as an index when Comparative Example 1 is set to 100, and the larger the value, the better the performance.

Comparative Examples 1 and 2
In the block of the tread surface shown in FIG. 1, the concave portions having the shapes shown in FIGS. Although not shown, a sipe wall surface facing the sipe wall surface 10a is formed with a convex portion constituted by a closed loop having a shape corresponding to the concave portions 64 and 74. The tire size is 11R22.5, the sipe depth is 10.0 mm, the sipe length is 30 mm, the recess dent amount is 0.25 mm, the protrusion protrusion amount is 0.25 mm, and the protrusion thickness is 1.0 mm. The sipe width was 0.6 mm.

Examples 1 and 2
In the block of the tread surface shown in FIG. 1, Examples 1 and 2 were obtained by forming concave portions formed of six annular closed loops shown in FIG. Although not shown, a sipe wall surface facing the sipe wall surface 10 a is formed with a convex portion constituted by a closed loop having a shape corresponding to the concave portion 84. The tire size and dimensions related to sipes are the same as those in Comparative Example 1. However, in Example 1, the thickness of the convex portion was uniformly set to 1.0 mm. However, in Example 2, the thickness of the convex portion was changed on the circumference of the closed loop, and the thickness became 1.4 mm. It was set as 0.6 mm in the part which becomes. The evaluation results are shown in Table 1.

  As shown in Table 1, in Examples 1 and 2, both ice braking performance and ice turning performance are superior to Comparative Examples 1 and 2, and ice performance is improved by suppressing excessive deformation of the block during travel. It is thought that it is made. Moreover, in Example 1, 2, the suppression effect of heel and toe wear is also show | played.

1 block (an example of land)
DESCRIPTION OF SYMBOLS 1a Tread surface 1b Side surface 4 Concave part 5 Convex part 10 Sipe 10a Sipe wall surface 10b Sipe wall surface 14 Concave part 15 Convex part

Claims (2)

In a pneumatic tire in which a sipe is formed on a land portion of a tread surface, a concave portion formed by a closed loop that is not exposed on the tread surface and the side surface of the land portion is formed on one side of the sipe wall surface facing each other, and on the other side of the sipe wall surface. A convex portion formed by a closed loop having a shape corresponding to the concave portion is formed;
The recess is constituted by an annular closed loop;
The pneumatic tire is characterized in that the recess is constituted by a plurality of closed loops arranged to cross each other. In a pneumatic tire in which a sipe is formed on a land portion of a tread surface, a concave portion formed by a closed loop that is not exposed on the tread surface and the side surface of the land portion is formed on one side of the sipe wall surface facing each other, and on the other side of the sipe wall surface. A convex portion formed by a closed loop having a shape corresponding to the concave portion is formed;
The recess is constituted by an annular closed loop;
A pneumatic tire wherein the convex portion, characterized in that it has a portion which becomes thin and portion which becomes relatively thick on the periphery of a closed loop.

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