JP4769540B2 - Pneumatic tire - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a pneumatic tire that is excellent in both traction performance and braking performance on ice and snow with extremely low road surface μ, and has secured uneven wear resistance equivalent to that of a conventional product, and in particular, a tread pattern of a studless tire for heavy loads. About.

  Patent Document 1 describes a tread pattern of a conventional heavy duty studless tire.

  FIG. 7 shows a similar tread pattern 501 of a pneumatic tire. In the tread pattern 501, two rows of block rows 509 and 511 are formed in the circumferential direction by three circumferential main grooves 503, 505, and 507, which respectively have a center surface 513 (a central circumferential main portion). The grooves 505 are distributed on the both sides in the width direction from the center in the tire width direction).

  In each of the block rows 509 and 511, a block 519 is defined by a lug groove 517 and a sipe 515 in the width direction connecting between the closest lug grooves 517.

  In addition, by dividing the central portion of each block 519 in the width direction by a narrow groove 521 in the circumferential direction, two small blocks 523 and 525 are partitioned, and each small block 523 and 525 has the length of each block. The phase is shifted in the circumferential direction by approximately 50% to 60%.

Each circumferential narrow groove 521 is mainly composed of a circumferential component 527, and the width thereof is set to 2.5 mm or more.
JP 2002-362114 A

  The tread pattern 501 of the conventional pneumatic tire is provided with three circumferential main grooves 503, 505, and 507 so that the circumferential main groove 505 is disposed at the center in the width direction (center) of the tire ground contact surface. Since the circumferential main groove 505 greatly improves water removal performance, the performance in wet weather (Wet performance) is excellent.

  However, on icy and snowy roads, especially on road conditions where the road surface μ is extremely low, called black ice burn, in order to obtain a large tangential force (force generated in the tire rotation direction) that improves startability and running performance, tire contact Although it is known that it is more effective to arrange an edge component in the tire width direction at the center of the ground, in the case of the conventional tread pattern 501, the amount of circumferential phase shift between the small blocks 523 and 525 is small. It is set to a large value of about 50% to 60% of the length, and on normal icy and snowy roads, if the circumferential shift amount between the small blocks is set to such a large value, the edge component will move within the ground plane as the tire rotates. Although the average tangential force characteristic is obtained and a continuous tangential force is obtained, on an extremely low μ road such as black ice burn, such an average and continuous tangential force characteristic provides sufficient braking performance and drivability. There is a is not a problem to obtain.

  Further, the circumferential narrow groove 521 mainly composed of the circumferential component 527 and having a width set to 2.5 mm or more has a function of suppressing the deformation by actively causing the small blocks 523 and 525 to interfere with each other (decrease in rigidity). It is impossible to expect uneven wear resistance.

  The present invention has been made in view of the above-described problems of the prior art, and has excellent traction performance and braking performance on an extremely low μ road, while providing air wear resistance equivalent to that of conventional products. The purpose is to provide tires.

The pneumatic tire according to claim 1 is provided along the circumferential direction, and has at least three main grooves that divide a land portion, and one end of the circumferential main is between the two circumferential main grooves. a lug groove opening to the other end terminating within the land portion to the groove, in the pneumatic tire forming a block partitioned by the sipes connecting between the lug grooves closest, the central portion of the block, the circumferential The zigzag-shaped circumferential sipe that forms an angle of 10 ° to 30 ° with respect to the direction is divided in the width direction to form two small blocks, and the phase of these two small blocks is set to a small block length. The small block is shifted by 30 to 40% in the circumferential direction, and the width direction sipe for dividing the small block in the circumferential direction is formed in the small block, and each portion of the small block divided by the width direction sipe is formed. Is a jig for the circumferential sipe Wherein the grayed shape meet.

  A third aspect of the invention is the pneumatic tire according to the first or second aspect, wherein the circumferential sipe has a width of 0.7 mm to 2.5 mm.

  Invention of Claim 4 is the pneumatic tire described in any one of Claims 1-3, Comprising: The sipe of the said width direction which divides | segments the said small block to the circumferential direction forms 1-4 pieces It is characterized by being.

  A fifth aspect of the present invention is the pneumatic tire according to any one of the first to fourth aspects, wherein the depth of the width direction sipe is 50% to 80% of the depth of the circumferential main groove. It is characterized by%.

  A sixth aspect of the present invention is the pneumatic tire according to any one of the first to fifth aspects, wherein the four circumferential main grooves are provided and are partitioned by the four circumferential main grooves. Of the three block rows, the phases of the two block rows adjacent to the central block row are shifted in the circumferential direction by 0% to 5% of the block length of each of the two block rows. It is characterized by that.

  In the pneumatic tire of claim 1, the edge component concentration rate is increased by setting the phase shift amount between the small blocks to a range of 30% to 40%, which is less than 50% to 60% in the conventional example. Because the locations where the edge component concentration rate is high (dense state) and low locations (sparse state) appear repeatedly along the circumferential direction, intermittent and peaky tangential force can be obtained, like black ice burn Large startability and running performance can be obtained even on extremely low μ roads.

  Here, the edge portion refers to the total length in the tread width direction of the step-side edge of the land portion of the tread surface divided by the grooves and sipes.

  The pneumatic tire of claim 2 can achieve the same effect as the structure of claim 1.

  Further, in this configuration in which the circumferential sipe is formed in a zigzag shape having an angle of 10 ° to 30 ° with respect to the circumferential direction, the block is different from the conventional example in which the circumferential sipe is mainly composed of the circumferential component 527. When deformed, the walls of the sipe interfere (contact) each other to suppress deformation and decrease in rigidity is suppressed, so heel and toe uneven wear (uneven wear in which the block kick-out side is greatly worn) is kept low. be able to.

  Further, since the edge component is increased by making the circumferential sipe a zigzag shape at an angle of 10 ° to 30 °, the startability and running performance on an extremely low μ road are further improved.

  In this configuration, the sipe angle is set to 30 ° for sharpening of the end shape of the small block that occurs when the sipe angle is extremely large, chipping of the block end due to sharpening, and uneven wear with this end as the core. By limiting so as not to exceed, such a problem is prevented in advance.

  The pneumatic tire of claim 3 can obtain the same effect as that of the structure of claim 1 or claim 2.

  In addition, this configuration, which limits the width of the circumferential sipe to a range of 2.5 mm or less, suppresses deformation due to interference between the walls of the sipe compared to the conventional example in which the width of the circumferential narrow groove is set to 2.5 mm or more. This improves the heel-and-toe uneven wear suppression function.

  Note that if the width of the circumferential sipe is 0.7 mm or less, the water removal effect is lost, and a water film (water film) is formed between the tread and the road surface, making it slippery. Such a problem is suppressed by limiting the width to 0.7 mm or more.

  The pneumatic tire of claim 4 can achieve the same effects as the configurations of claims 1 to 3.

  Moreover, in the case of the studless tire which the pneumatic tire of this invention intends, it is necessary to arrange | position an edge component effectively in the block which gave moderate rigidity.

  For example, if an independent fine block without a sipe is provided, the rigidity of each block may be lower than a desired value. Therefore, in the present invention, an appropriate size is given to the block to obtain a desired rigidity, By providing sipes in the block, it is possible to suppress a decrease in the rigidity of the block during deformation as described above.

  Further, regarding the decrease in block rigidity due to the provision of sipes, in this configuration, the number of sipes is limited to the range of 1 to 4, thereby minimizing the decrease in rigidity.

  The pneumatic tire of claim 5 can achieve the same effects as the configurations of claims 1 to 4.

  In this configuration, the depth of the sipe in the width direction is limited to a range of 50% to 80% of the depth of the circumferential main groove, thereby suppressing the block rigidity.

  The pneumatic tire of claim 6 can achieve the same effects as the configurations of claims 1 to 5.

  Further, in this configuration in which four circumferential main grooves are provided, a block row is formed at the center in the width direction of the tire contact surface, so that edge components in the tire width direction are concentrated on the center of the contact surface. Unlike the conventional example in which the circumferential main groove 505 is arranged at the center, intermittent and peaky tangential force is obtained on an extremely low μ road such as a black ice burn, and the startability and running performance are improved. This effect is particularly noticeable when the tread is only in contact with the center of the tread.

  In addition, in order to obtain intermittent and peaky tangential force by centrally arranging the edge components, it is desirable that there is no circumferential phase shift between the block rows. However, if the phase shift is set to zero, pattern noise occurs. This may facilitate heel and toe uneven wear.

  Therefore, in this configuration, the circumferential phase shift between the central block row and the adjacent block row is limited to a small amount of 0% to 5% of each block length, thereby obtaining an intermittent and peaky tangential force. And a reduction effect of pattern noise and heel and toe uneven wear.

<One Embodiment>
The pneumatic tire 1 (one embodiment of the present invention) will be described with reference to FIGS.

[Features of pneumatic tire 1]
As shown in FIG. 1, the pneumatic tire 1 includes four circumferential main grooves 9, 11, 13, 15 that divide the block rows 3, 5, 7 (land portions), and one circumferential end of the circumferential main groove 9, Pneumatic air dividing the block 21 by a lug groove 19 that opens to 11, 13, 15 and terminates in the block rows 3, 5, and 7 and a widthwise sipe 17 that connects between the closest lug grooves 19 In the tire, the central portion of each block 21 is divided by the circumferential sipe 23 in the tire width direction to form two small blocks 25 and 27, and between these two small blocks 25 and 27, As shown in FIG. 2, a circumferential phase shift (B / A) is given within a range of 30% to 40% of each block length (A).
The circumferential sipe 23 has a zigzag shape with an angle α of 10 ° to 30 ° with respect to the circumferential direction,
The width H of the circumferential sipe 23 is 0.7 mm to 2.5 mm,
Two width direction sipes 17 for dividing the small blocks 25 and 27 in the circumferential direction are formed.
The depth of the width direction sipe 17 is 50% to 80% of the depth of the circumferential main grooves 9, 11, 13, and 15.
Of the three circumferential block rows 3, 5, and 7 defined by the four circumferential main grooves 9, 11, 13, and 15, two block rows 3 adjacent to the central block row 5 respectively. , 7 are shifted in the circumferential direction by 0% (in the range of 0% to 5%) of each block length of the block rows 3 and 7.

[Evaluation test results]
Next, the performance of the pneumatic tire 1 having the above characteristics will be described with reference to FIGS. 3, 4, 5, and 6.

(1) Edge component measurement (Fig. 3)
FIG. 3 shows a distribution state of edge components along the width direction, a graph 51 shows the result of the pneumatic tire 1 (invention product), and a graph 53 shows a result of the conventional pneumatic tire (conventional product). Indicates.

  In the pneumatic tire 1, the in-plane edge components at the time of loading and emptying are 120 and 155 as compared with the conventional product, respectively, and both the contact width 55 when loading and the grounding width 57 when empty are compared with the conventional product. In comparison, the edge component is increased, and this increase is significant when the ground contact surface is gathered in the center when the vehicle is empty.

  As described above, the pneumatic tire 1 generates intermittent and peaky tangential force due to the increased number of edge components, and excellent startability and running performance can be obtained even on an extremely low μ road such as a black ice burn.

(2) Peak μ measurement on ice (Figure 4)
FIG. 4 shows a result of measuring a friction coefficient (μ) when the tire is run on a turntable on which ice (temperature 2 °) is arranged, and a graph 61 shows the pneumatic tire 1 (invention product). The graph 63 shows the result of the conventional pneumatic tire (conventional product).

  In the pneumatic tire 1, the fluctuation range of μ is widened and the peak μ is high by distributing the edge components densely along the circumferential direction as described above. Even on extremely low μ roads, this high peak μ provides excellent starting and running performance.

(3) Traction test (Fig. 5)
As shown in FIG. 5, 11R22.5 14PR W970 (conventional pneumatic tire) and pneumatic tire 1 (invention) were attached to a rim of size 7.50 and applied with air pressure of 900 kPa, respectively. The traction test on ice and the traction test on snow were performed with a 2-D4 truck in a fixed-load vehicle and an empty vehicle loaded with a constant load. The engine speed was constant.

as a result,
In (a) traction test on ice
Fixed time When empty
Conventional product 100 100
Invention product 108 118
In the snow traction test of (b)
Fixed time When empty
Conventional product 100 100
Invention 105 105
In both cases, as described above, the pneumatic tire 1 (invention product) having a large edge component and a high peak μ has obtained a traction larger than that of the conventional product on an extremely low μ road. It is remarkable.

(4) Measurement of level difference due to uneven heel and toe wear (Figure 6)
FIG. 6 shows the measurement results of the tire wear rate and the heel and toe level difference, where graph 71 is an invention product and graph 73 is a conventional product.

  As can be seen from the fact that there is almost no difference between the graph 71 and the graph 73, in the pneumatic tire 1, the block rows 3, 5, 5 are provided by providing the four circumferential main grooves 9, 11, 13, 15. Although the width of 7 is narrow, the angle α of the circumferential sipe 23 is limited to 10 ° to 30 ° and the width H is set to 2.5 mm or less, so that a large traction on the extremely low μ road as described above. The amount of uneven heel-and-toe wear is suppressed to almost the same level as the conventional product.

[Effect of pneumatic tire 1]
The pneumatic tire 1 has the following effects.

  By setting the phase between the small blocks 25 and 27 within the range of 30 to 40%, which is less than 50% to 60% in the conventional example, the edge component concentration rate increases and the edge component concentration rate in the circumferential direction increases. Appearing sparsely and densely, intermittent and peaky tangential force is generated, and excellent startability and running ability can be obtained even on extremely low μ roads such as black ice burn.

  In addition, since the circumferential sipe 23 is formed in a zigzag shape having an angle α of 10 ° to 30 ° with respect to the circumferential direction, the walls of the sipe 23 interfere (contact) with each other during deformation, unlike the conventional example. Since deformation is suppressed and rigidity reduction is suppressed, heel and toe uneven wear is suppressed.

  Moreover, the edge component increases by making the circumferential sipe 23 into a zigzag shape of 10 ° to 30 °, and the starting performance and running performance on an extremely low μ road are further improved.

  In addition, the sipe angle is set for sharpening of the end portions of the small blocks 25 and 27 generated when the sipe angle is extremely increased, chipping of the block end due to the sharpening, and uneven wear with this end as a core. By limiting so as not to exceed 30 °, such a problem is suppressed.

  Further, by limiting the width H of the circumferential sipe 23 to a range of 2.5 mm or less, the deformation suppressing function due to the interference of the wall portion of the sipe 23 is improved as compared with the conventional example, and heel and toe uneven wear suppression is suppressed. The function is further improved.

  Moreover, in the pneumatic tire 1, since the width of the circumferential sipe 23 is limited to 0.7 mm or more, a problem that a water film is generated between the tread and the road surface is suppressed.

  Further, the sipe 19 in the width direction is limited to two (1 to 4 ranges), and the depth of the sipe 19 is 50% to 80% of the depth of the circumferential main grooves 9, 11, 13, 15. By limiting to this range, the rigidity reduction of the small blocks 25 and 27 is suppressed.

  Further, by providing the four circumferential main grooves 9, 11, 13, and 15, the block row 5 is formed at the center of the tire ground contact surface, and the edge component (ground contact portion) is concentratedly disposed at the center of the ground contact surface. Therefore, unlike the conventional example, intermittent and peaky tangential force is generated on the extremely low μ road as described above, and startability and running performance are improved, and this effect is an empty vehicle in which only the center portion of the tread is grounded. Especially noticeable at times.

  The pneumatic tire 1 is intermittent because the circumferential phase shift between the block rows 3 and 7 on both ends is limited to a small value of 0% to 5% of the block length of the block rows 3 and 7. The effect of obtaining peaky tangential force and the effect of reducing pattern noise and uneven heel and toe wear are both achieved.

1 is a drawing showing a tread pattern of a pneumatic tire 1. It is the elements on larger scale of FIG. It is the graph which compared the distribution state of the edge component along the width direction with an invention product and a conventional product. It is the graph which compared peak μ on ice with an invention product and a conventional product. The results of measuring the traction on the ice and snow of the invention and the conventional product are shown. It is the graph which compared the heel and toe uneven wear with an invention product and a conventional product. It is drawing which shows the tread pattern of the conventional pneumatic tire.

Explanation of symbols

1 Pneumatic tire 3, 5, 7 Block train (land)
9, 11, 13, 15 Circumferential main groove 17 Width direction sipe 19 Lug groove 21 Block 23 Circumferential sipe 25, 27 Small block α Circumferential angle H of circumferential sipe 23 Width of circumferential sipe 23

Claims (5)

It is provided along the circumferential direction, and has at least three main grooves that divide the land portion. Between the two circumferential main grooves, one end opens into the circumferential main groove, and the other end is the land. In a pneumatic tire that is partitioned by a lug groove that terminates in a part and a sipe that connects the closest lug grooves to form a block,
The central part of the block is divided in the width direction by a zigzag-shaped circumferential sipe that forms an angle of 10 ° to 30 ° with respect to the circumferential direction to form two small blocks. Shift the block phase in the circumferential direction by 30-40% of the small block length ,
The small block is formed with two width direction sipes that divide the small block in the circumferential direction,
The pneumatic tire according to claim 1, wherein the zigzag shape of the circumferential sipe contacts each portion of the small block divided by the width sipe. The pneumatic tire according to claim 1 ,
A pneumatic tire characterized in that a width of the circumferential sipe is 0.7 mm to 2.5 mm. A pneumatic tire according to claim 1 or claim 2 ,
One to four sipes in the width direction for dividing the small block in the circumferential direction are formed. A pneumatic tire according to any one of claims 1 to 3 , wherein
The pneumatic tire according to claim 1, wherein a depth of the widthwise sipe is 50% to 80% of a depth of the circumferential main groove. A pneumatic tire according to any one of claims 1 to 4 , wherein
Four circumferential main grooves are provided, and the three rows of blocks divided by the four circumferential main grooves are a central block row and two rows of blocks adjacent to the central block row, respectively. A column, and
A pneumatic tire , wherein the central block row and a block row adjacent to the central block row are shifted in the circumferential direction by 0% to 5% of the central block length.

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