JP2021165109A - Pneumatic tire - Google Patents

Abstract

To improve on-ice braking performance, on-snow braking performance and dry steering stability performance in a well-balanced manner.SOLUTION: At least one land part (10) is formed in a divided manner on a tread surface. A plurality of short sipes (12), in which a length along an extension direction is 5% or less of a grounding width, are formed on the land part. The short sipe is terminated within the land part. In regard to the two short sipes (12a and 12b) between which the shortest distance is minimized, a distance (R) between the centers of minimum circumscribed circles (14a and 14b) including the two short sipes, respectively, is in the range of 1.00-1.15 times of the shortest distance (r) between the two short sipes.SELECTED DRAWING: Figure 1

Description

The present invention relates to a pneumatic tire in which braking performance on ice, braking performance on snow, and dry steering stability performance are improved in a well-balanced manner.

In general, a large number of sipes are formed on the land surface of a studless tire so that the studless tire can achieve excellent on-ice performance and on-snow performance.

For example, in Patent Document 1, a pair of blocks extend inward in the block width direction from the side of the block side edges on both sides which are the circumferential groove side or the tread end edge side, and the inner ends are cut off facing each other. Pneumatic including at least an annular sipe block comprising a sipe combination comprising a sipe piece and an annular sipe arranged between the inner ends of the pair of siping pieces and on a virtual line connecting the inner ends. Tires are disclosed.

Japanese Unexamined Patent Publication No. 2012-6559

However, in the pneumatic tire described in Patent Document 1, an annular sipe having no end is used. Therefore, it is hard to say that the drainage effect is high due to the difficulty of water entering and exiting, and various performances (ice braking performance, snow braking performance) for vehicle running on ice roads and snowy roads where excellent drainage effect is required. ), There is room for improvement.

Further, in the pneumatic tire of Patent Document 1, there is a possibility that the rigidity of the portion surrounded by the annular sipe is insufficient, and there is room for improvement in the dry steering stability performance.

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 in which braking performance on ice, braking performance on snow, and dry steering stability performance are improved in a well-balanced manner.

In the pneumatic tire according to the present invention, at least one land portion is formed on the surface of the tread, and a plurality of short sipes having a length along the extending direction of 5% or less of the contact width are formed on the land portion. The short sipe is terminated in the land, and for the two short sipe with the shortest distance, the distance between the centers of each minimum circumscribed circle containing the two short sipe is the shortest of the two short sipe. The distance is 1.00 times or more and 1.15 times or less.

In the pneumatic tire according to the present invention, on the premise that a short sipe having a relatively small length is formed on the land portion, improvements are made to the formation mode of the short sipe in the land portion and the positional relationship between the short sipe. .. Therefore, according to the pneumatic tire according to the present invention, the braking performance on ice, the braking performance on snow, and the dry steering stability performance can be improved in a well-balanced manner.

FIG. 1 is a plan view showing an example of the positional relationship between sipes formed on the land portion of the pneumatic tire of the present embodiment. FIG. 2 is a plan view showing a tire circumferential direction forming position of a short sipe in one land area. FIG. 3 is a plan view showing an example of a land portion applicable to the pneumatic tire of the present embodiment.

Hereinafter, embodiments of the pneumatic tire according to the present invention (basic embodiments and additional embodiments 1 to 3 shown below) will be described in detail with reference to the drawings. It should be noted that these embodiments do not limit the present invention. In addition, the components of the above-described embodiment include those that can be easily replaced by those skilled in the art, or those that are substantially the same. Further, the various embodiments included in the above-described embodiments can be arbitrarily combined within a range of self-evident by those skilled in the art.

<Basic form>
The basic form of the pneumatic tire according to the present invention will be described below. In the following description, the tire radial direction means a direction orthogonal to the rotation axis of the tire, the inner side in the tire radial direction is the side toward the rotation axis in the tire radial direction, and the outer side in the tire radial direction is the rotation axis in the tire radial direction. The side away from. Further, the tire circumferential direction refers to a circumferential direction centered on the rotation axis. Further, the tire width direction means a direction parallel to the rotation axis, the inside in the tire width direction is the side toward the tire equatorial plane (tire equatorial line) in the tire width direction, and the outside in the tire width direction is in the tire width direction. The side of the tire away from the equatorial plane. The tire equatorial plane CL is a plane that is orthogonal to the rotation axis of the tire and passes through the center of the tire width of the tire.

FIG. 1 is a plan view showing an example of the positional relationship between sipes formed on the land portion of the pneumatic tire of the present embodiment. In the figure, the groove forming the land area is not shown. In the pneumatic tire of the present embodiment, as shown in FIG. 1, at least one land portion 10 is formed on the tread surface, and the length of the land portion 10 along the extending direction is 5% or less of the ground contact width. A plurality of (six in the figure) short sipes 12 (12a, 12b, 12c, 12d, 12e, 12f) are formed.

In the present specification, the length along the extending direction of the sipe means the length of a line segment connecting the center points in the width direction of the sipe. When actually determining the extending direction of the sipe, select an arbitrary point (first point) on one edge of the sipe, and the point at the other edge where the distance from the first point is the shortest. (Second point) is defined, and the midpoint between the first point and the second point is set as the first midpoint. By performing such an operation a plurality of times, the second midpoint, the third midpoint, the fourth midpoint, etc. are determined, and the first midpoint to the second midpoint, the third midpoint, and the third midpoint are determined. The direction of the line segment connecting the midpoints of 4 and the like is defined as the extending direction of the sipe. In this case, when determining the extending direction of the sipe, the number of midpoints to be used shall be appropriately determined according to the shape of the sipe.

Further, in the present specification, the ground contact width is defined as follows. That is, the ground contact width is the maximum length of the ground contact surface in the tire width direction that occurs when a specified internal pressure is applied by incorporating it into a specified rim and a specified load is further applied.

Here, the specified rim means a "standard rim" specified in JATTA, a "Design Rim" specified in TRA, or a "Measuring Rim" specified in ETRTO. The specified internal pressure means the "maximum air pressure" specified by JATTA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or "INFLATION PRESSURES" specified by ETRTO. .. Furthermore, the specified load is the "maximum load capacity" specified by JATTA, the maximum value described in "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" specified by TRA, or the "LOAD CAPACITY" specified by ETRTO. say.

Under such a premise, in the pneumatic tire of the present embodiment, these short sipes 12 are terminated in the land portion. That is, the short sipe 12 does not communicate with other grooves forming the land portion 10.

Further, in the pneumatic tire of the present embodiment, for the two sipes having the shortest shortest distance (for example, sipes 12a and 12b in FIG. 1), the minimum circumscribed circles 14a including these two short sipes 12a and 12b, respectively. , 14b has a center-to-center distance R of 1.00 times or more and 1.15 times or less of the shortest distance r of the two sipes 12a and 12b. Here, the shortest distance between the two sipes is not only when measuring between the ends of the two sipes, but also when measuring between a portion other than the end of one sipe and the end of the other sipe. It also includes the case of measuring between parts that are not the ends of both sipes.

(Action, etc.)
Conventionally, a large number of sipes have been formed on the land surface of studless tires in order to achieve excellent on-ice performance and on-snow performance, but in recent years, in addition to these performances, improvement in steering stability performance has also been required. ing. Therefore, in the pneumatic tire of the present embodiment, as shown in FIG. 1, a short sipe 12 having a length along the extending direction of 5% or less of the contact width is formed to suppress a decrease in land rigidity. By doing so, it is decided to improve the steering stability performance (action effect 1).

However, if the length of the short sipe 12 along the extending direction is excessively small, the drainage property that affects the performance on ice and the performance on snow, which are the performances required for the studless tire in the first place, may deteriorate. It is desirable that the length of the short sipe 12 along the extending direction is 3% or more of the ground contact width.

Further, in the pneumatic tire of the present embodiment, since all the short sipes 12 are terminated in the land portion and do not communicate with other grooves forming the land portion 10, the decrease in the land portion rigidity is suppressed. By doing so, the steering stability performance can be improved (action effect 2).

Further, in the pneumatic tire of the present embodiment, as shown in FIG. 1, two center-to-center distances R of the minimum circumscribed circles 14a and 14b including the two short sipe 12a and 12b having the shortest shortest distance are set. The shortest distance r of the sipes 12a and 12b is 1.00 times or more. As a result, excellent rigidity is ensured by avoiding the occurrence of a region where the sipes are locally dense without making the distance between the sipes excessively small, and the ground pressure is leveled to control the steering. Stability performance can be improved (action effect 3).

On the other hand, by setting the center-to-center distance R to 1.15 times or less of the shortest distance r, it is possible to avoid a region where the sipes are locally sparse without excessively increasing the distance between the sipes. By ensuring excellent drainage and leveling the ground contact pressure, it is possible to improve all of the braking performance on ice, braking performance on snow, and dry steering stability performance (action effect 4).

When the center-to-center distance R is 1.02 times or more and 1.13 times or less the shortest distance r, it is desirable because the above actions 3 and 4 are performed at a higher level, and the center-to-center distance R is the shortest distance. When it is 1.04 times or more and 1.11 times or less of r, the above actions 3 and 4 are performed at an extremely high level, which is more desirable.

As described above, in the pneumatic tire of the basic form, on the premise that a short sipe having a relatively small length is formed on the land portion, the formation mode of the short sipe in the land portion and the positional relationship between the short sipe are described. By adding the improvement, the above-mentioned action effect 1 to action effect 4 can be combined to improve the braking performance on ice, the braking performance on snow, and the dry steering stability performance in a well-balanced manner.

Although not shown, the pneumatic tire according to the basic form shown above has the same meridional cross-sectional shape as the conventional pneumatic tire. Here, the meridional cross-sectional shape of the tire means the cross-sectional shape of the tire that appears on a plane perpendicular to the tire equatorial plane CL. The pneumatic tire according to the basic form has a bead portion, a sidewall portion, a shoulder portion and a tread portion from the inside to the outside in the tire radial direction in a cross-sectional view of the tire meridian. Then, for example, in the tire meridional cross-sectional view, the pneumatic tire extends from the tread portion to the bead portions on both sides and is wound around the pair of bead cores, and the carcass layer is outward in the tire radial direction. A belt layer and a belt reinforcing layer, which are sequentially formed, are provided.

Further, the pneumatic tire according to the basic form shown above is a normal manufacturing process, that is, a tire material mixing process, a tire material processing process, a green tire molding process, a vulcanization process, and a post-vulcanization inspection process. It is obtained through the above. When manufacturing a pneumatic tire of a basic form, for example, a convex portion corresponding to a sipe shown in FIG. 1 is formed on the inner wall of a vulcanization die, and vulcanization is performed using this die.

<Additional form>
Next, additional embodiments 1 to 3 which can be arbitrarily and selectively implemented with respect to the above-mentioned basic embodiment of the pneumatic tire according to the present invention will be described.

(Additional form 1)
In the basic form, it is preferable that the total length along the extending direction of the sipe in the ground contact surface is 3.3 times or more and 10.0 times or less the ground contact width (additional form 1). The sipe in this embodiment is a concept including all sipe included in the ground plane, and of course, the short sipe described in the basic embodiment is included, and the sipe other than the short sipe (along the extending direction). It is a concept that also includes a sipe whose length is more than 5% of the ground contact width.

By increasing the total length along the extending direction of the sipe in the ground plane (ratio of the total length of the sipe to the ground width) to 3.3 times or more with respect to the ground width, the drainage performance is further improved and the land area is further improved. It is possible to include more edges generated by sipe formation in 10. As a result, in particular, the braking performance on ice and the braking performance on snow can be further improved.

On the other hand, by setting the ground contact width ratio of the total length of the sipes to 10.0 times or less, it is possible to suppress the excessive reduction of the rigidity of the land portion 10 and further improve the steering stability performance.

When the ground contact width ratio of the total sipe length is 3.5 times or more and 7.0 times or less, the above effects are more preferably achieved at a higher level, which is more preferable, 3.7 times or more and 5.0. When the value is doubled or less, the above effects are exhibited at an even higher level, which is extremely preferable.

(Additional form 2)
FIG. 2 is a plan view showing a tire circumferential direction forming position of a short sipe in one land area. In the example shown in FIG. 2, the rotation direction is specified, and the short sipes 22, 24, 26 having the above-mentioned shapes are formed on the land portion 20 partitioned by the circumferential grooves G1 and G2 and the inclined grooves G3 and G4. 28, 30, 32, 34, 36 are formed, and long sipes 42, 44, 46, 48, 50, 52 other than short sipes are formed. Here, the long sipe means a sipe whose length along the extending direction is more than 5% of the ground contact width, and it does not matter whether or not it communicates with the groove forming the land portion. Further, the positional relationship between the long sipes is not particularly limited. As shown in FIG. 2, the short sipes 22 to 36 are formed in the kick-out area of the land portion, and the long sipes 42 to 52 are formed in the other regions of the land portion.

In the basic form or the form in which the additional form 1 is added to the basic form, as shown in FIG. 2, the tire circumferential direction forming position of the short sipe 22 to 36 in the land portion 20 is the tire circumferential stepping side end portion X1. Is set to the 0% position and the short sipe 22 to 36 is set to the tire circumferential position of 75% or more and less than 100% in the land portion 20 when the tire circumferential kick-out side end X2 is set to the 100% position. (Additional form 2) is preferable.

By setting the tire circumferential direction forming position of the short sipe 22 to 36 to a position of 75% or more and less than 100%, a short sipe having a relatively small length along the extending direction is formed near the kick-out side end. It is possible to increase the rigidity near the end portion and thus suppress heel-and-toe wear. When the tire circumferential direction formation position of the short sipes 22 to 36 is set to a position of 80% or more, heel and toe wear can be further suppressed, which is more preferable. When the position is 85% or more, heel and toe wear is caused. It is extremely preferable because it can be further suppressed.

On the other hand, if the tire circumferential direction forming position of the short sipe 22 to 36 is made too close to the 100% position, the short sipe 22 to 28 does not communicate with the groove G3 forming the land portion 20, even if it does not communicate with the land portion. There is a high possibility that the rigidity in the vicinity of the kick-out side end of 20 will decrease. Therefore, it is more preferable that the tire circumferential direction forming positions of the short sipes 22 to 36 are 95% or less, and 93% or less is extremely preferable. By separating the short sipes 22 to 28 from the inclined groove G3 to some extent in this way, the rigidity in the vicinity of the kick-out side end portion of the land portion 20 can be increased, and thus the steering stability performance can be further enhanced.

(Additional form 3)
In the basic form or a form in which at least one of the additional forms 1 and 2 is added to the basic form, the short sipe 12 shown in FIG. 1 and the short sipe 22 to 36 shown in FIG. 2 are acyclic sipes (additional). Form 3) is preferable. Here, the acyclic sipe means that the short sipe has at least two ends. There may be three or more ends.

By making the short sipe 12 a non-annular sipe, water flow is efficiently constructed from the stepping side to the kicking side and from the inside to the outside in the tire width direction, and within one sipe. It is possible to prevent water from staying. As a result, the drainage property is further improved, and by extension, the braking performance on ice and the braking performance on snow can be further improved.

(Available land example)
The basic embodiment and the additional embodiments 1 to 3 have been described in detail above, but an example of a land portion that can be used for the pneumatic tire of the present embodiment will be described below.

FIG. 3 is a plan view showing an example of a land portion applicable to the pneumatic tire of the present embodiment. Although not shown, in each of FIGS. 3A to 3H, the horizontal direction of the paper surface is the tire width direction, and the vertical direction of the paper surface is the tire circumferential direction. Further, in each of the drawings, the lower part of the paper surface is the stepping side and the upper part is the kicking side.

In the example shown in FIG. 3A, a plurality of short sipes 52 are formed on the land portion 50, and no long sipes are formed. This example is an example in which the rigidity of the land part and the steering stability performance are improved.

In the example shown in FIG. 3B, a plurality of short sipes 56 and two types of long sipes 58 and 60 are formed on the land portion 54, and the short sipes 56 are formed in a region on the kicking side. This example is an example in which the rigidity on the kick-out side is particularly increased to suppress heel-and-toe wear.

In the example shown in FIG. 3C, a plurality of short sipes 64 and two types of long sipes 66 and 68 are formed in the land portion 62, and the short sipes 64 are formed in the central portion of the land portion 62 in the tire width direction. ing. This example is an example in which the rigidity of the central portion of the land portion 62 in the tire width direction is increased to improve the durability against fracture starting from a sipe.

In the example shown in FIG. 3D, a plurality of short sipes 72 and two types of long sipes 74 and 76 are formed on the land portion 70, and the short sipes 72 and the long sipes 74 and 76 alternate in the tire circumferential direction. Is formed in. This example is an example in which the ground contact pressure in the tire circumferential direction is leveled to improve the steering stability performance.

In the example shown in FIG. 3 (e), a plurality of short sipes 80 are formed on the land portion 78, and the short sipes 80 have the same overall length as the short sipes 52 in FIG. 3 (a) but are different in shape. In this example, the opening amount of the sipe (determined by the existing range in the tire width direction and the existing range in the tire circumferential direction) is particularly reduced to improve the durability against fracture starting from the sipe. ..

In the example shown in FIG. 3 (f), a plurality of short sipes 84 are formed on the land portion 82, and the short sipes 84 have a longer length along the extending direction than the short sipes 52 in FIG. 3 (a). .. This example is an example in which the drainage property, the braking performance on ice, and the braking performance on snow are particularly improved.

In the example shown in FIG. 3 (g), a plurality of short sipes 88 are formed on the land portion 86, and the number of short sipes 88 formed is twice the number of short sipes 84 formed in FIG. 3 (f). This example is an example in which the drainage property, and by extension, the braking performance on ice and the braking performance on snow are improved to an extremely high level.

In the example shown in FIG. 3H, a plurality of short sipes 92 and two types of long sipes 94 and 96 are formed in the land portion 90, and the short sipes 92 are formed in the central portion of the land portion 62 in the tire width direction. However, the number of formations is half the number of formations in FIG. 3C. This example is an example in which the rigidity is particularly increased to improve the steering stability performance.

The tire size was 205 / 55R16 91H, and the pneumatic tires according to the first to fourth inventions and the pneumatic tires of the conventional example were produced. The detailed conditions of these pneumatic tires are shown in Table 1 below. However, for each pneumatic tire, at least one land portion is formed on the surface of the tread, and a plurality of short sipes having a length along the extending direction of 5% or less of the ground contact width are formed in these land portions. It was formed.

In Table 1, the center-to-center distance, the shortest distance, the ground contact width ratio of the total sipe length, the tire circumferential formation position of the sipe, the short sipe, and the annular sipe are all based on the description described in this specification. To do.

The tires according to Invention Examples 1 to 4 and the tires of the conventional example produced in this manner are assembled to a 16 × 6.5J aluminum rim at 250 kPa, and each test tire is used as an FR test vehicle (displacement: It was mounted on 2000cc), and the braking performance on ice, braking performance on snow, dry steering stability performance, and uneven wear resistance performance were evaluated according to the following procedure.

(Brake performance on ice)
ABS braking was performed on the test vehicle from a running state at a speed of 20 km / h on a test course consisting of an icy road surface under load conditions equivalent to two passengers, the braking distance was measured, and the reciprocal of the measured value was calculated. Then, based on this calculation result, an index evaluation was performed using the conventional example as a reference (100). The evaluation results are also shown in Table 1. This evaluation indicates that the larger the index, the higher the braking performance on ice.

(Brake performance on snow)
ABS braking was performed on the test vehicle from a running state at a speed of 20 km / h on a test course consisting of a snowy road surface under load conditions equivalent to two passengers, the braking distance was measured, and the inverse of the measured values was calculated. Then, based on this calculation result, an index evaluation was performed using the conventional example as a reference (100). The evaluation results are also shown in Table 1. This evaluation indicates that the larger the index, the higher the braking performance on snow.

(Maneuvering stability performance)
A test driver evaluated the sensuality of a vehicle equipped with each test tire when driving on a test course on a dry road surface. Then, based on this result, an index evaluation was performed using the conventional example as a reference (100). The evaluation results are also shown in Table 1. This evaluation indicates that the larger the index, the higher the steering stability performance.

(Uneven wear resistance 1)
For the test vehicle, the amount of wear on land after running a pattern of 40,000 km (amount of wear near the tire contact end with respect to the amount of wear near the equatorial plane of the tire: shoulder wear amount / center wear amount) was measured, and the measured value was measured. The reciprocal was calculated. Based on this calculation result, an index evaluation was performed using the conventional example as a reference (100). The evaluation results are also shown in Table 1. This evaluation indicates that the larger the index, the smaller the amount of wear near the tire contact end.

(Uneven wear resistance 2)
For the test vehicle, the amount of wear on land (heel-and-toe wear) after running a pattern of 40,000 km was measured, and the reciprocal of the measured value was calculated. Based on this calculation result, an index evaluation was performed using the conventional example as a reference (100). The evaluation results are also shown in Table 1. This rating indicates that the higher the index, the less heel-and-toe wear.

According to Table 1, it belongs to the technical scope of the present invention (that is, on the premise that a short sipe having a relatively small length is formed on the land portion, the formation mode of the short sipe in the land portion, and the short sipe of each other. All of the tires of Invention Examples 1 to 4 (with improved positional relationship) have ice braking performance, snow braking performance, and dry maneuvering as compared with the tires of the conventional examples, which do not belong to the technical scope of the present invention. It can be seen that the stability performance is improved in a well-balanced manner.

10 Land 12 Short sipe 14a, 14b Minimum circumscribed circle R Distance between centers of minimum circumscribed circles 14a, 14b r Shortest distance between two sipe 12a, 12b

Claims (4)

A pneumatic tire in which at least one land portion is formed on the surface of the tread, and a plurality of short sipes having a length along the extending direction of 5% or less of the ground contact width are formed on the land portion.
The short sipe terminates in the land
For the two short sipe with the shortest shortest distance, the distance between the centers of each minimum circumscribed circle containing the two short sipe is 1.00 times or more and 1.15 times or less the shortest distance of the two short sipe. Pneumatic tires that are characterized by being. The pneumatic tire according to claim 1, wherein the total length along the extending direction of the sipe in the ground contact surface is 3.3 times or more and 10.0 times or less the ground contact width. The direction of rotation is specified,
Regarding the tire circumferential direction formation position of the short sipe in the land portion, when the tire circumferential step-on side end is set to 0% and the tire circumferential kick-out side end is set to 100%.
The pneumatic tire according to claim 1 or 2, wherein the short sipe is formed at a position in the tire circumferential direction of 75% or more and less than 100% in the land portion. The pneumatic tire according to any one of claims 1 to 3, wherein the short sipe is a non-annular sipe.

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