JP2011148375A - Pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pneumatic tire further improving on-ice/snow performance including on-snow braking/driving performance while securing pattern block rigidity of the tire. <P>SOLUTION: Narrow grooves 18 extending in the direction orthogonal to the tire circumferential direction and crossing a center land part 15 are formed in the center land part 15 positioned in the center part in the tire width direction, flat sipes (sipes 19) not opening in main grooves 12B, 12C are arranged in the groove bottom of the narrow grooves 18, wave-shape sipes (sipes 20p, 20q) are arranged in shoulder blocks 16A, 16B which are parts outside in the tire width direction and in intermediate blocks 17A, 17B, and the length of the sipes 19 is narrower as it goes further in the depth direction of a tread 11. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a tread pattern capable of improving braking / driving performance and steering stability performance on an icy snow road in a pneumatic tire used for a snow tire or the like.

Conventionally, in a snow tire, sipes extending in a direction intersecting the tire circumferential direction are uniformly arranged on the land portion of the tread. This is because the sipe opens and closes when the land of the tread contacts the tire tread, ensuring the straight running performance and braking performance on the snowy road surface and the icy road surface due to the scratching effect (edge effect) and the snow biting effect on the snowy road surface It is to do.
Increasing the amount of sipe can be considered to improve the performance on ice and snow, but simply increasing the amount of sipe reduces the stiffness of the pattern block of the tire, resulting in a decrease in steering stability performance on dry road surfaces. There was a problem such as.

  Therefore, a plurality of circumferential grooves are provided in the tire tread, and a plurality of rib-like land portions defined by the circumferential grooves are provided. A method of improving the performance on ice and snow while securing the rigidity of the pattern block of the tire by forming a sipe opening in the circumferential groove is proposed (for example, see Patent Document 1).

JP 2000-168317 A

  However, with the conventional method described above, Sipe can improve the stability of driving on ice and snow while ensuring the rigidity of the pattern block of the tire, but with regard to the improvement of snow braking and driving performance such as snow acceleration performance and snow braking performance, It was not always enough.

  The present invention has been made in view of the conventional problems, and an object of the present invention is to provide a pneumatic tire in which the performance on ice and snow including the on-snow braking / driving performance is further improved while securing the pattern block rigidity of the tire. .

  As a result of intensive studies by the present inventors, in snow tires, narrow grooves and sipes provided in the land have a large contribution to straight running performance and braking / driving performance on icy and snowy road surfaces. It has been found that if the extending direction of the narrow groove and sipe is a direction perpendicular to the tire circumferential direction, the straight running performance and braking / driving performance on the snowy and snowy road surface can be further improved, and the present invention has been achieved. .

That is, the present invention includes a plurality of circumferential grooves extending along the circumferential direction of the tire on the tread surface of the tire, and a plurality of land portions defined by the circumferential grooves, and is located at the center in the tire width direction. In the pneumatic tire in which the center land portion is a rib-like land portion that is continuous in the tire circumferential direction, the center land portion is divided into two pieces that cross the center land portion in the tire width direction and demarcate the center land portion. A transverse groove that opens in the circumferential groove is formed, and a sipe that does not open in any of the two circumferential grooves is formed in the groove bottom of the transverse groove.
The transverse groove is usually a narrow groove whose groove width is narrower than that of the circumferential groove or lug groove.
The pattern block rigidity refers to the rigidity of a pseudo block defined by a lug groove or a sipe that terminates in the land portion in the case of a block pattern.

In this way, if a transverse groove that crosses the center land portion in the tire width direction and opens to the circumferential groove is formed, and a sipe that does not open to any of the circumferential grooves is formed at the groove bottom of the transverse groove, In the center of the tire width direction, the edge effect and snow biting effect in the front-rear direction can be exerted intensively, ensuring on-snow acceleration performance including on-snow acceleration performance and on-snow brake performance while ensuring tire pattern block rigidity. Can be improved.
The transverse groove is usually a narrow groove whose groove width is narrower than that of the circumferential groove or lug groove.
Moreover, since the sipe provided at the groove bottom of the transverse groove is not opened in the circumferential groove, a decrease in the pattern block rigidity is suppressed, so that sufficient dry steering stability performance can be maintained.

Further, if the extending direction of the transverse groove and the extending direction of the sipe are both perpendicular to the tire circumferential direction, the edge component in the front-rear direction increases, so the edge effect and the snow biting effect are further improved. Can be improved. Here, the extending direction of the transverse groove refers to the extending direction of the center line of the width of the transverse groove, and the extending direction of the sipe refers to the extending direction of the center line of the width of the sipe.
Further, the groove width of the sipe is 50% to 70% of the groove width of the transverse groove in which the sipe is formed, or the length of the sipe in the tire width direction becomes narrower as it goes in the tread depth direction. By doing so, the sipes can be effectively opened and closed, so that the snow biting effect of the transverse grooves can be improved. At this time, by setting the inclination angle of the sipe in the depth direction within a range of 15 ° to 30 °, the sipe can be opened and closed more effectively, and an appropriate pattern block rigidity can be secured.
In addition, the sipe formed on the shoulder land located at the shoulder portion of the tire that greatly contributes to driving stability performance on ice and snow can be used as a wave-shaped sipe, so that an edge effect can be exerted on multi-directional inputs. Therefore, it is possible to provide a pneumatic tire having high snow handling stability performance in addition to excellent snow braking / driving performance.

  The summary of the invention does not list all necessary features of the present invention, and sub-combinations of these feature groups can also be the invention.

It is a figure which shows an example of the tread pattern of the pneumatic tire which concerns on embodiment of this invention. It is the principal part perspective view of the pneumatic tire of this invention, and AA sectional drawing of FIG. It is a figure which shows the tread pattern of the conventional tire used for the actual vehicle test.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram illustrating an example of a tread pattern of a pneumatic tire (hereinafter referred to as a tire) 10 according to the first embodiment.
In the figure, 11 is a tread, 12A to 12D are circumferential grooves provided on the tread 11 to extend along the tire circumferential direction, and 13A and 13B are lugs extending along a direction intersecting the tire circumferential direction. In the groove, CL indicated by a one-dot chain line in FIG.
Hereinafter, the left side of CL is referred to as the left side in the tire width direction, and the right side is referred to as the right side in the tire width direction. Of the circumferential grooves 12A to 12D, the circumferential grooves 12B and 12C located on the center side in the tire width direction are called main grooves, and the circumferential grooves 12A and 12D located on the outer side in the tire width direction are called shoulder grooves.
Further, in this example, the left and right lug grooves 13A, 13B are respectively lug grooves that start at the outer side in the tire width direction, cross the shoulder groove 12A or the shoulder groove 12D, and terminate at the main groove 12B or the main groove 12C. did.
Reference numeral 15 denotes a center land portion defined by the main grooves 12B and 12C. The center land portion 15 is a land portion that is located at the center in the tire width direction and extends continuously in the tire circumferential direction, that is, a so-called rib-shaped land portion.
Reference numeral 16A is a left shoulder block defined by the left shoulder groove 12A and lug groove 13A, reference numeral 16B is a right shoulder block defined by the right shoulder groove 12D and lug groove 13B, and reference numeral 17A is The left intermediate block defined by the shoulder groove 12A, the lug groove 13A, and the main groove 12B, and the reference numeral 17B, are the right intermediate block defined by the shoulder groove 12D, the lug groove 13B, and the main groove 12C.

The center land portion 15 includes a narrow groove 18 and a sipe 19.
As shown in FIGS. 2A and 2B, the narrow groove 18 has a groove width of about 1.0 mm to 2.0 mm and a groove depth of about 1.5 mm to 3.0 mm. Is a groove extending in a direction perpendicular to the center, crossing the center land portion 15 and having both ends open to the main grooves 12B and 12C. The narrow groove 18 is a groove corresponding to the transverse groove of the present invention.
The sipe 19 is a sipe formed on the groove bottom 18k of the narrow groove 18 so as to extend in a direction perpendicular to the tire circumferential direction, and is generally called a flat sipe. The groove width of the sipe 19 is about 50% to 70% of the groove width of the narrow groove 18, and the groove depth is about 4.5 mm to 3.0 mm. Further, both ends of the sipe 19 are not opened in the main grooves 12B and 12C. That is, the start end 19 a and the end end 19 b of the sipe 19 are both in the narrow groove 18.

Thus, the center land portion 15 of the tread 11 of the tire 10 forms a narrow groove 18 extending in a direction perpendicular to the tire circumferential direction and a sipe 19 formed on the groove bottom 18k of the narrow groove 18. The edge component in the tire circumferential direction can be increased while ensuring the pattern block rigidity at the center in the tire width direction. Further, the narrow grooves 18 extending in the direction perpendicular to the tire circumferential direction concentrate on the snow biting effect. Therefore, the performance on ice and snow including the acceleration performance on snow and the brake performance on snow can be remarkably improved.
In addition, since both the start end 19a and the end end 19b of the sipe 19 are in the narrow groove 18, the narrow groove 18 is not divided by the sipe 19, so that a decrease in the rigidity of the pattern block can be suppressed.

Further, by setting the groove width of the sipe 19 to be in the range of 50% to 70% of the groove width of the narrow groove 18, the sipe 19 can be effectively opened and closed while ensuring the rigidity of the pattern block. The snow biting effect is improved. That is, when the groove width of the sipe 19 is less than 50% of the groove width of the narrow groove 18, the opening and closing effect of the sipe 19 is small, so that the snow biting by the narrow groove 18 is not sufficient. On the other hand, if the groove width of the sipe 19 exceeds 70% of the groove width of the narrow groove 18, the volume of the grooves (the narrow groove 18 and the sipe 19) provided in the center land portion 15 increases and the pattern block rigidity decreases, which is preferable. Absent.
In this example, the sipe 19 is further effectively tilted in the tread depth direction so that the length of the sipe 19 (length in the tire width direction) becomes narrower as it goes in the depth direction of the tread 11. The pattern block rigidity is ensured.
Also, at one end in the width direction of the sipe 19 shown in FIG. 2B, the upper end in the tire radial direction of the sipe 19 at the bottom of the narrow groove 18 and the lower end in the tire radial direction at the bottom of the groove of the sipe 19 are connected. When the angle formed by the straight line 19c and the straight line parallel to the depth direction of the sipe 19 (the -z direction in FIG. 2B) is the inclination angle θ in the depth direction of the sipe 19, the depth of the sipe 19 The range of the inclination angle θ in the vertical direction is preferably θ = 15 ° to 30 °. That is, when the inclination angle θ is less than 15 °, the narrow groove 18 is more easily moved than necessary, so that the pattern block rigidity is lowered. On the other hand, when the inclination angle θ exceeds 30 °, the sipe 19 becomes difficult to open and close. Therefore, the inclination angle of the sipe 19 in the depth direction is preferably in a range of θ = 15 ° to 30 °.

On the other hand, as shown in FIG. 1, corrugated sipes 20p and 20q are formed in the shoulder blocks 16A and 16B and the intermediate blocks 17A and 17B.
The extending directions of the corrugated sipes 20p and 20q are both directions intersecting the tire circumferential direction and the tire width direction. In this example, the extending direction of the sipe 20p provided in the shoulder blocks 16A and 16B is set to an angle close to the direction parallel to the tire width direction, and the extending direction of the sipe 20q provided in the intermediate blocks 17A and 17B is set as the extension direction of the sipe 20p. The direction is inclined in the circumferential direction from the extending direction. Since the wave-shaped sipe can exhibit an edge effect with respect to various inputs, it is possible to obtain high on-snow handling stability.

Thus, in the present embodiment, a narrow groove 18 that extends in the direction perpendicular to the tire circumferential direction and crosses the center land portion 15 is formed in the center land portion 15 located in the center portion in the tire width direction. A flat sipe (sipe 19) is disposed on the groove bottom 18k of the narrow groove 18, and a corrugated sipe (sipe 20p, 20q) is disposed on the shoulder blocks 16A, 16B and the intermediate blocks 17A, 17B which are the outer portions in the tire width direction. Therefore, it is possible to improve both straight running performance, braking / driving performance and steering stability performance on an icy and snowy road surface.
Moreover, since the sipe 19 is a sipe that does not open to the main grooves 12B and 12C, it is possible to suppress a decrease in pattern block rigidity.
Furthermore, since the groove width of the sipe 19 is in the range of 50% to 70% of the groove width of the narrow groove 18, and the length of the sipe 19 is made narrower in the depth direction of the tread 11, the sipe 19 Can be effectively opened and closed to improve the snow biting effect by the narrow groove 18, and the pattern block rigidity can be ensured. Therefore, braking / driving performance and steering stability performance on an icy and snowy road surface can be further improved.

In the embodiment, the outer portion in the tire width direction is configured by the shoulder blocks 16A and 16B and the intermediate blocks 17A and 17B, but may be configured by a block and a rib-shaped land portion or a rib-shaped land portion.
Further, the extending direction of the corrugated sipes 20p and 20q is not limited to the one described in the present embodiment, and may be, for example, a direction parallel to the tire width direction. In short, if a flat sipe perpendicular to the tire circumferential direction is arranged in the center land portion 15 located in the center portion in the tire width direction and a corrugated sipe is arranged in the outer portion in the tire width direction, the straight running performance on the icy and snowy road surface -It is possible to improve both braking / driving performance and steering stability performance.

表１から明らかなように、本発明のタイヤは、雪上実車操縦安定性能、雪上加速性能、雪上ブレーキ性能のいずれもが従来例よりも向上しているだけでなく、ドライ実車操縦安定性能も従来例より向上していることから、本発明によるタイヤは、パターンブロック剛性を確保しつつ、雪上性能を効果的に向上していることが確認された。 The tire (present invention) in which a narrow groove and a sipe extending in a direction perpendicular to the tire circumferential direction are formed in the center land portion shown in FIG. 1, and a main groove 52B and a main groove 52C as shown in FIG. A conventional tire 50 (conventional example) provided with a narrow groove 58 and a sipe 59 intersecting in both the tire circumferential direction and the tire width direction is prepared in the center land portion 55 divided by Table 1 below shows the results of evaluating the driving stability performance of dry vehicles, the driving stability performance of snow vehicles, the acceleration performance on snow, and the braking performance on snow.
The tire size is 245 / 45R17, the rim used is 8.0 J, and the internal pressure is 250 kPa.
The actual driving stability and the actual driving stability on snow are an index in which the driving time is recorded on the dry asphalt course and the snow road course of 3km each, and the time required is recorded, and the reciprocal number is taken as 100 in the conventional example. Is displayed. The higher the number, the higher the performance.
Acceleration performance on snow is an index based on the conventional example of 100, which measures the time (acceleration time) required for the vehicle speed to reach 40 km / h after driving on the accelerator at a vehicle speed of 5 km / h. evaluated. The higher the number, the shorter the acceleration time and the higher the acceleration characteristics on snow.
Brake performance on snow is evaluated using an index based on the conventional example of 100, measuring the time (deceleration time) required to apply the brake after braking on the vehicle at a vehicle speed of 40 km / h and then stop the vehicle. did. The higher the number, the shorter the deceleration time and the better the snow braking performance.

As is apparent from Table 1, the tire of the present invention has not only improved on-snow actual vehicle handling stability performance, on-snow acceleration performance, and on-snow brake performance, but also has improved dry actual vehicle handling stability performance. Since it was improved from the example, it was confirmed that the tire according to the present invention effectively improved the performance on the snow while ensuring the pattern block rigidity.

  As mentioned above, although this invention was demonstrated using embodiment, the technical scope of this invention is not limited to the range as described in the said embodiment. It will be apparent to those skilled in the art that various modifications or improvements can be added to the embodiment. It is apparent from the claims that the embodiments added with such changes or improvements can be included in the technical scope of the present invention.

  According to the present invention, it is possible to obtain a pneumatic tire having excellent performance on ice and snow while ensuring the rigidity of the pattern block of the tire. Therefore, it is possible to further improve the running stability performance of the vehicle on an ice and snow road.

10 Pneumatic tire, 11 tread, 12B, 12C main groove,
12A, 12D shoulder groove, 13A, 13B lug groove, 15 center land,
16A, 16B shoulder block, 17A, 17B intermediate block, 18 narrow groove,
18k narrow groove bottom, 19 sipe, 19a sipe start, 19b sipe end,
19c Both ends of the sipe.

Claims (6)

A tire having a center land portion located at a center portion in a tire width direction, the tire including a plurality of circumferential grooves extending along a tire circumferential direction on the tread surface of the tire and a plurality of land portions defined by the circumferential grooves. A pneumatic tire that is a rib-like land portion continuous in the circumferential direction,
The center land portion is formed with a transverse groove that opens in two circumferential grooves that cross the center land portion in the tire width direction and demarcate the center land portion,
The pneumatic tire according to claim 1, wherein a sipe that does not open to any of the two circumferential grooves is formed at a groove bottom of the transverse groove.   2. The pneumatic tire according to claim 1, wherein an extending direction of the transverse groove and an extending direction of the sipe are both perpendicular to the tire circumferential direction.   3. The air according to claim 1, wherein the sipe is inclined in a tread depth direction so that a length in a tire width direction becomes narrower in a tread depth direction. Enter tire.   The pneumatic tire according to claim 3, wherein an inclination angle of the sipe in a depth direction is 15 ° to 30 °.   The groove width of the sipe formed in the groove bottom of the transverse groove is 50% to 70% of the groove width of the transverse groove in which the sipe is formed. The pneumatic tire according to Crab.   The pneumatic tire according to any one of claims 1 to 5, wherein a corrugated sipe is formed in a shoulder land portion located in the tire shoulder portion.

Images