JP5298787B2 - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire which, even with a number of small holes formed in a land portion of its tread, reduces damage by a stone caught in a small hole, thereby providing improved durability. <P>SOLUTION: The pneumatic tire includes a plurality of small holes 4 in land portions 3 divided by lug grooves 2; wherein each of the land portions is provided with a plurality of small holes 4, two sipes 5 are arranged side by side in a line between two small holes 4 adjacent to each other so as to interconnect both of their side edges, and a minor land portion is formed between the two sipes 5 connecting the two small holes 4. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire in which damage caused by stone biting on a small hole provided in a land portion of a tread is reduced.

  Some tire tread surfaces are provided with small holes for various purposes in the land divided into lug grooves. For example, in Patent Document 1, road noise is reduced by providing a large number of small holes along the tire circumferential direction in the shoulder portion of a tread of a pneumatic tire to reduce the rubber rigidity of the shoulder portion. . Further, in Patent Document 2, a block in a studless tire having a block pattern is divided into a plurality of small blocks by a plurality of sipes in the tire width direction, a plurality of small holes are provided in the small blocks, and the gaps between these small holes are siped. By connecting, drainage and performance on ice and snow are improved.

However, in both cases, the small holes provided in the tread tend to bite pebbles etc. on the road surface during traveling, and there is a problem that the tread surface is damaged by clogging the small holes with the pebbles and the durability of the tire decreases. .
JP 2004-90766 A Japanese Patent Laid-Open No. 2006-7882

  The object of the present invention is to solve the above-mentioned problems, and even when a large number of small holes are provided in the land portion of the tread, damage caused by stone biting on the small holes is reduced and durability is improved. It is to provide a pneumatic tire.

In order to achieve the above object, the pneumatic tire of the present invention is provided with a plurality of lug grooves extending in the tire width direction on the tread surface so as to be arranged in the tire circumferential direction, and a plurality of land portions partitioned by the lug grooves are provided. In the pneumatic tire provided with small holes, a plurality of the small holes are provided per one land portion, and two sipes that connect these outer edges are arranged between two adjacent small holes. And a small land portion was formed between the two small holes and the two sipes connecting them, and the height of the small land portion was made lower than the upper edge of the small hole. It is characterized by.

Moreover, in the structure mentioned above, it is preferable to comprise as described in the following (1)- (4) .
(1) The opening area of the small hole is 7 mm2 to 31 mm2, and the depth is 60% to 100% of the depth of the lug groove.
(2) The nearest interval between the two adjacent small holes is set to 2 mm to 10 mm.
(3) The width of the sipe is 0.2 mm to 1.0 mm, and the depth is 60% to 100% of the depth of the small hole.
(4) widthwise sectional shape of the upper end of the front SL small land portion so as a semicircular convex outwardly.

  According to the present invention, a plurality of small holes are provided for each land portion, and two sipes that connect both side edges between two small holes adjacent to each other are provided side by side. A small land is formed between each small hole and the two sipes connecting them, so even if a stone is bitten, it is surrounded by two small holes and two sipes. Further, since the small land portion is deformed when the tire rolls and is discharged so as to push out the stone, damage due to the stone biting can be reduced.

FIG. 1 is a front view of a tread surface of a pneumatic tire according to an embodiment of the present invention.
In FIG. 1, a large number of lug grooves 2 extending in the tire width direction are formed in the shoulder portion of the tread 1 so as to be arranged in the tire circumferential direction. The plurality of land portions 3 are divided by the large number of lug grooves 2 so as to be arranged in the tire circumferential direction. Two small holes 4 are arranged at predetermined intervals in the tire circumferential direction in each of the divided land portions 3. The two small holes 4 formed in the land part 3 are provided with two sipes 5 in parallel so as to connect both side edges thereof. As described above, the plurality of small holes 4 and the sipes 5 that connect the small holes 4 are provided in the land portion 3 of the shoulder portion, thereby reducing the rigidity of the land portion 3 and reducing road noise.

  FIG. 2 is an enlarged view showing a shoulder portion in FIG. Two small holes 4 are formed in the land portion 3 so as to be aligned in the tire circumferential direction, and two sipes 5 that connect both side edges between the small holes 4 are provided in parallel. The small holes 4 do not protrude from the extended line 5. As shown in FIG. 2, when the opening shape of the small hole 4 is circular, the sipe 5 is formed so as to circumscribe these two small holes 4.

  By connecting the two small holes 4 with two sipes 5, a small land portion 6 surrounded by the two small holes 4 and the two sipes 5 is formed. This small land portion 6 is a tire. By deforming at the time of rolling and changing the opening area of each small hole 4, the stones caught in the small holes 4 can be easily discharged.

  The position where the small hole 4 is provided on the tread 1 is not limited to the shoulder portion as in the embodiment of FIG. The center portion may be used depending on the purpose of providing the small holes. At any position, as defined by the present invention, by arranging two sipes 5 that connect both side edges between the two small holes 4 in parallel, the pebbles biting into the small holes 4 can be obtained. It can be easily discharged, and damage caused by stone chewing can be reduced.

  The arrangement of the plurality of small holes 4 provided per land portion is not limited to the arrangement in the circumferential direction as shown in FIG. 1, and even if arranged in the tire width direction as shown in FIG. As shown in FIG. 3B, the tires may be arranged so as to be inclined with respect to the tire circumferential direction. The number of small holes per land portion may be three or more as shown in FIG. Even when three or more small holes 4 are connected to each other, the sipe 5 connects the side edges between adjacent small holes so that the small holes 4 do not protrude from the extension line of the sipe 5.

  The arrangement of the small holes 4 is not limited to one row, and may be two or more rows. A plurality of rows may be provided depending on the purpose of providing the small holes 4. In any case, by connecting the both side edges of the two or more small holes 4 with the sipe 5 as described above, damage caused by stone biting can be reduced.

  The opening shape of the small hole 4 is not limited to the circular shape as shown in FIGS. 1 and 2, but may be any shape as long as it has an open state such as an ellipse, a polygon such as a triangle or a quadrangle. Absent. Regardless of the opening shape of the small hole 4, both side edges between two adjacent small holes are connected by two sipe 5, and the small hole 4 protrudes from the extension line of the sipe 5. Provide so that there is no. That is, both ends of the maximum width portion in the normal direction of the straight line connecting the centers of the small holes 4 may be connected to each other.

  Further, if the small land portion 6 surrounded by the two small holes 4 and the two sipes 5 can be deformed when the tire rolls, the shapes of the two sipes may be different from each other.

In the present invention, the opening area of the small hole 4 described above is preferably in the range of 7 to 31 mm ² . Moreover, it is preferable that the depth of the small hole 4 is 60 to 100% of the lug groove depth. When the opening area is smaller than 7 mm ^2, the rigidity of the land portion 3 is not lowered and the road noise is not reduced. When the opening area is larger than 31 mm ^2, the rigidity of the land portion 3 is excessively lowered and the maneuverability is deteriorated.

  The interval between the two small holes 4 adjacent to each other is preferably 2 to 10 mm. Here, the interval between the two small holes 4 means the closest (shortest) distance between the two small holes 4. When the interval between the small holes 4 is smaller than 2 mm, the width of the small land portion 6 in the direction parallel to the sipe 5 is thinned and easily chipped. If it is larger than 10 mm, the width of the small land portion 6 in the direction parallel to the sipe 5 becomes thick, so that the small land portion 6 cannot be sufficiently deformed and the bitten stone cannot be discharged.

  The width of the sipe 5 is preferably 0.2 mm to 1.0 mm. The depth of the sipe 5 may be 60% to 100% of the depth of the small hole 4. If the width is narrower than 0.2 mm, the small land portion 6 is not easily deformed, and it is difficult to discharge the bited stone. If the width is larger than 1.0 mm, the small land portion 6 is deformed too much to easily cause chipping, and the sipe may be bitten by stone. Moreover, if the depth is shallower than 60% of the depth of the small hole, the small land portion 6 is difficult to deform and it is difficult to discharge the stone, and if it is deeper than 100% of the depth of the small hole, the small land portion 6 is Deformation becomes too easy to cause chipping.

  The sipe 5 that connects the two small holes does not necessarily have to be completely continuous as long as the small land portion 6 can be sufficiently deformed. As shown in FIG. You may be interrupted along the way. When the sipe 5 is interrupted, the length of the interrupted portion is preferably 50% or less of the total length of the sipe to be connected. If it is 50% or less, the deformation of the small land portion can be maintained. If the length of the interrupted portion is longer than 50%, the small land portion 6 is difficult to deform.

In the present invention, as shown in FIG. 5, the upper edge portion of the height of the small hole 4 of the small land portions 6, i.e. you lower than the surface of the land portion 3. When the small land portion 6 and the surrounding land portion 3 have the same height, the small land portion 6 is easily lost as the tire wears. The vertical depth from the surface of the land portion 3 to the upper end of the small land portion 6 may be 1.0 mm to 4.0 mm, and preferably 1.0 mm to 3.0 mm. If the vertical depth is smaller than 1.0 mm, many chips are generated by chipping, and if it is larger than 4.0 mm, it is impossible to suppress stone biting.

  The surface of the small land portion 6 may have a cross-sectional shape at the upper end in the width direction as shown in FIG. By making it semicircular, chipping at the time of wear can be further suppressed than in the case of a flat surface. Since the cross-sectional shape in the width direction of the upper end surface only needs to be a semicircular shape, the shape of the upper end may be a spherical shape or a kamaboko type. Further, when the upper end is a flat surface, the shape may be chamfered with a radius of curvature R that is 1/2 or less of the cross-sectional width of the small land portion.

  The lug grooves 2 provided in the tread 1 are preferably arranged at a variable pitch in the tire circumferential direction. In this case, the number of small holes 4 provided in land portions having different pitch lengths depending on the variable pitch may be changed according to the pitch length. Specifically, the number of small holes 4 provided is increased as the pitch length is longer, and the number of small holes 4 provided is decreased as the pitch length is shorter. Furthermore, it is not necessary to provide a small hole in the land portion with the shortest pitch length. Further, the number of small holes to be connected may be changed according to the pitch length, or three or more small holes may be connected.

The tire size is 215 / 60R16 95H, the tread pattern is as shown in Fig. 1, and a small hole with a radius of 2.5mm is arranged in the shoulder part, the presence or absence of sipes, the cross-sectional shape in the width direction of the upper end of the small land part, small Four types of pneumatic tires of a conventional example, a comparative example 1, and examples 1 and 2 in which the height of the small land portion with respect to the hole groove depth was varied as shown in Table 1 were manufactured.

The conventional example is an example in which small holes are not connected by sipes. Comparative Example 1 and Examples 1 and 2 are examples in which the small holes are connected with a sipe having the same depth as the small holes and a width of 1.0 mm, and Comparative Example 1 is the width direction of the upper end of the small land portion. In this example, the cross-sectional shape is flat, and the height of the small land portion is the same as the groove depth of the small hole. Example 1 is an example in which the cross-sectional shape in the width direction of the upper end of the small land portion is flat as in Comparative Example 1 , but the height of the small land portion is 80% of the groove depth of the small hole. . Example 2 is an example in which the cross-sectional shape in the width direction at the upper end of the small land portion is a semicircular shape, and the height of the small land portion is 80% of the groove depth of the small hole.

  These four types of tires are assembled on a 16x61 / 2 rim, filled with air pressure of 230 kPa, each mounted on a 3000cc FR drive sedan, and the number of stone bites when traveling 5000km in the city, chipping resistance of the small land Sex was measured respectively.

  The smaller the number of stone bites in the measurement result, the greater the action of discharging the bite stones, and the better.

  The chipping resistance of the small land portion was evaluated by the presence or absence of chipping after traveling 20,000 km with the vehicle. Table 1 shows the case where chipping occurred as x and the case where chipping did not occur as ○.

It is a top view of the tread surface of the pneumatic tire by the embodiment of the present invention. It is a front view of the land part of the pneumatic tire of FIG. It is a front view of the land part of the pneumatic tire by other embodiments of the present invention. It is a front view of the land part of the pneumatic tire by other embodiment of this invention. FIG. 3 is an XX arrow view of FIG. 2. FIG. 6 is an XX arrow view according to another embodiment corresponding to FIG. 5.

Explanation of symbols

1 tread 2 lug groove 3 land part 4 small hole 5 sipe 6 small land part

Claims (5)

In a pneumatic tire in which a plurality of lug grooves extending in the tire width direction are arranged on the tread surface so as to be arranged in the tire circumferential direction, and a plurality of small holes are provided in a land portion divided by the lug grooves,
A plurality of the small holes are provided per one land portion, and two sipes for connecting these outer edges are provided in parallel between two adjacent small holes, so that the two small holes are provided. A pneumatic tire in which a small land portion is formed between the two sipe connecting them and the height of the small land portion is lower than the upper end edge portion of the small hole . The pneumatic tire according to claim 1, 7mm ² ~31mm ² the opening area of the small holes, the depth was 60% to 100% of the depth of the lug groove.   The pneumatic tire according to claim 1 or 2, wherein a distance between two small holes adjacent to each other is set to 2 mm to 10 mm.   The pneumatic tire according to claim 1, 2 or 3, wherein the width of the sipe is 0.2 mm to 1.0 mm, and the depth is 60% to 100% of the depth of the small hole. The pneumatic tire according to any one of claims 1 to 4 , wherein a cross-sectional shape in a width direction of an upper end of the small land portion is a semicircular shape protruding outward.

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