JP5071924B2 - Pneumatic tire - Google Patents

Description

  The present invention relates to a pneumatic tire suitable for a heavy load studless tire, and in particular, by devising a phase shift amount between a plurality of blocks arranged in a tire circumferential direction of a tread portion, quietness is ensured. The present invention relates to a pneumatic tire with improved performance on ice and snow.

  In studless tires that can run on icy and snowy roads without providing spike pins on the tread surface, a groove (circumferential groove) extending in the tire circumferential direction is formed in the tread portion and intersects with the circumferential groove. Lug grooves are provided as described above, and sipes are formed in a plurality of blocks defined by the circumferential grooves and the lug grooves. Sipe absorbs melted water that causes a water film formed between the road surface and the tread surface, eliminates the water film, and tears the road surface water film by the edge to ensure contact with the road surface. It has the function of further improving traction (acceleration when starting on a snowy road) and improving running stability on snow.

  FIG. 7 is a partially developed plan view showing an example of a pattern of a tread portion of a studless tire (see Patent Document 1). In this figure, the X axis is the tire width direction (hereinafter referred to as the width direction), and the Y axis is the tire circumferential direction (hereinafter referred to as the circumferential direction).

  A central main groove 1 extending in the circumferential direction on the tire equator CL is formed in the tread portion of the studless tire, and outer main grooves 3 and 5 are continuously formed in the circumferential direction on the left and right sides of the tire equator CL, respectively. Is formed.

  By these three main grooves, two rows of land portions each having land portions 7 and 9 having substantially the same width are partitioned on the left and right sides of the equator CL. The land portion 7 has one end opened in the central main groove 1 and the other end terminated in the land portion, a lug groove 11 opened in the outer main groove 3 and the other end terminated in the land portion. The lug groove 11 and the auxiliary groove 15 connecting the lug groove 13 are divided into a plurality of blocks 70 that are continuous in the circumferential direction. The land portion 9 has one end opened in the central main groove 1 and the other end terminated in the land portion, and a lug groove one end opened in the outer main groove 5 and the other end terminated in the land portion. 19 and the sub-groove 21 connecting the lug groove 17 and the lug groove 19 are divided into a plurality of blocks 90 connected in the circumferential direction. Here, the lug grooves 11 and 13 are arranged at equal intervals in the circumferential direction and alternately in the circumferential direction.

  Further, each block 70 of the land portion 7 is divided into left and right small blocks 70a and 70b of the same size by a sub-groove 23 extending in the circumferential direction at the center in the width direction. A sub-groove 25 extending in the circumferential direction in the center in the width direction is divided into left and right small blocks 90a and 90b having the same size. Furthermore, two sipes 27 and 29 are formed in each small block and open in grooves on both sides in the width direction. In FIG. 7, hatching is given to one block in each land portion. Here, the small block on the left side of the block was given a right-up hatching, and the small block on the right side was given a left-up hatching.

  Here, assuming that the positive direction of the X axis is the front in the circumferential direction, the front end and the rear end in the circumferential direction of the block 70 are the rear end of the lug groove 11 and the front end of the lug groove 13, respectively. Further, the front end and the rear end in the circumferential direction of the block 90 are the rear end of the lug groove 19 and the front end of the lug groove 17, respectively. The circumferential position of the lug groove 11 and the circumferential position of the lug groove 19 are substantially the same, and the circumferential position of the lug groove 13 and the circumferential position of the lug groove 17 are substantially the same. In the block 90, the circumferential positions of the front ends and the rear ends are substantially the same. In other words, the circumferential phase shift between the block 70 and the block 90 is substantially zero.

  On the other hand, regarding the circumferential phase shift of the small blocks 70a and 70b constituting the block 70, the front end and the rear end in the circumferential direction of the small block 70a are the rear end of the lug groove 13 and the rear of the lug groove 13, respectively. The front end of the lug groove 13, the front end and the rear end in the circumferential direction of the small block 70b are the rear end of the lug groove 11, and the front end of the lug groove 13 one behind the lug groove 13, respectively. As shown in the figure, the circumferential phase shift of 70b is approximately 55% of the circumferential length of the small blocks 70a and 70b. The same applies to the phase shift in the circumferential direction of the small blocks 90a and 90b constituting the block 90.

  The protruding land portions 31 and 33 extending in the circumferential direction at the bottoms of the outer main grooves 3 and 5 are stepped so that the surfaces thereof are in sliding contact with the outer contour of the tire when the tire rolls. This is for concentrating the force that generates uneven wear on the protruding land portions 31 and 33 and suppressing the generation of the force on the other land portions.

  In this way, the pattern noise that is promoted when the phase shift of all the large and small blocks is made substantially zero by making the circumferential phase shift of the small blocks approximately 50 to 60% of the circumferential length of the small block. And heel and toe wear can be suppressed.

JP 2002-127716 A

  However, if the circumferential phase shift between the small blocks is set in the above range, edge components appear on average as the tire rotates, and the continuous tangential force (the tire attached to the drive wheel of the vehicle is in contact). The driving force generated on the ground can be obtained, but intermittent and peaky tangential force is more effective. On ice and snow road surfaces with extremely low friction coefficient μ such as black ice burn, sufficient braking performance and driving performance are obtained. There is a problem that can not be.

  The present invention has been made to solve the above-described conventional problems, and an object thereof is to reduce pattern noise and improve performance on ice and snow in a pneumatic tire having a block pattern in a tread portion. It is.

The invention of claim 1 is divided into at least two rows of blocks by at least three main grooves extending in the circumferential direction and a plurality of grooves intersecting with the main grooves, and the central portion in the width direction of the block is circumferential. A pneumatic tire having a tread pattern divided into two small blocks in the width direction by directional sipes or narrow grooves, wherein a circumferential phase shift of the two small blocks is a circumferential direction of the small blocks It is 5% or more and 25% or less of the length, and the phase shift in the circumferential direction of the blocks in the row adjacent in the width direction is 30% or more and 45% or less of the circumferential length of the small block.
According to a second aspect of the present invention, in the pneumatic tire according to the first aspect, the sipe or narrow groove extending in the circumferential direction has a zigzag shape that forms an angle of 10 ° or more and 30 ° or less with respect to the circumferential direction. .
The invention according to claim 3 is the pneumatic tire according to claim 1 or 2, characterized in that the width of the sipe or narrow groove extending in the circumferential direction is 0.4 mm or more and 2.5 mm or less.
According to a fourth aspect of the present invention, in the pneumatic tire according to any one of the first to third aspects, one or more and four or less width direction sipes are formed in the small block.
According to a fifth aspect of the present invention, in the pneumatic tire according to the fourth aspect, the depth of the width direction sipe is not less than 50% and not more than 80% of the depth of the main groove.

(Function)
On icy and snowy road surfaces with a very low friction coefficient μ such as black ice burn, intermittent and peaky tangential force is more effective than continuous and average tangential force. In order to obtain intermittent and peaky tangential force, it is necessary to reduce the phase shift in the circumferential direction of adjacent blocks and concentrate the edge components. However, when the phase shift of all the large and small blocks is set to 0, pattern noise and heel-and-toe wear are promoted. Conversely, when the phase shift is increased, the pattern noise is reduced, but the performance on the snowy and snowy road surface is degraded.
In the present invention, the performance on ice and snow is improved by minimizing the phase shift between the small blocks, and quietness is ensured by increasing the phase shift between the blocks to some extent.

  ADVANTAGE OF THE INVENTION According to this invention, in a pneumatic tire which has a block pattern in a tread part, while improving performance on ice and snow, pattern noise can be reduced and silence can be ensured.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a partially developed plan view of a pattern of a tread portion of a pneumatic tire according to an embodiment of the present invention. In this figure, the X axis is the width direction and the Y axis is the circumferential direction.

  As shown in this figure, this tread pattern is zigzag in the tire circumferential direction on the right side of the tire equator CL, and the central main groove 2 and the outer main groove 6 extending zigzag in the tire circumferential direction on the left side of the tire equator CL. A central main groove 4 and an outer main groove 8 are provided. The widths of these four main grooves are substantially the same, and the distance from the tire equator CL to the left and right central main grooves 2 and 4 and the distance to the left and right outer main grooves 6 and 8 are also substantially the same.

  By these four main grooves, the center land portion 10 sandwiched between the left and right central main grooves 2 and 4, and the second land sandwiched between the left central main groove 2 and the outer main groove 6. A portion 12 and a second land portion 14 defined by being sandwiched by the right central main groove 4 and the outer main groove 8 are formed. Here, three rows of land portions are formed by four main grooves, but at least two rows of land portions may be formed by at least three main grooves.

  The center land portion 10 has a lug groove 16 having one end opened in the central main groove 2 and the other end terminated in the land portion, and a lug groove 18 having one end opened in the central main groove 4 and the other end terminated in the land portion. And a sipe (narrow groove) 20 connecting the other ends of the lug groove 16 and the lug groove 18 is divided into a plurality of blocks 100 that are continuous in the circumferential direction. Further, the second land portion 12 on the left side of the tire equator CL has one end opened to the outer main groove 6, the other end terminated in the land portion, one end opened to the central main groove 2, and the other end The lug groove 24 that terminates in the land part and the sipe (narrow groove) 26 that connects the lug groove 22 and the other ends of the lug groove 24 are divided into a plurality of blocks 120 that are continuous in the circumferential direction. Further, the second land portion 14 on the right side of the tire equator CL has one end opened in the central main groove 4, the other end terminated in the land portion, one end opened in the outer main groove 8, and the other end A lug groove 30 that terminates in the land portion and a sipe (narrow groove) 32 that connects the lug groove 28 and the other end of the lug groove 30 are divided into a plurality of blocks 140 that are continuous in the circumferential direction. Here, the lug grooves 16 and 18 are arranged at equal intervals in the circumferential direction, and the circumferential positions are alternately (alternate). In addition, the lug groove 16 and the lug groove 18 to which the sipe (thin groove) 20 is connected open to different main grooves (the lug groove 16 is the central main groove 2 and the lug groove 18 is the central main groove 4), and the circumferential direction. Is the closest to. The same applies to the lug grooves 22 and 24 to which the sipe (thin groove) 26 is connected and the lug grooves 28 and 30 to which the sipe (thin groove) 32 is connected.

  Each block 100 of the land portion 10 is divided into left and right small blocks 100a and 100b having the same size by a sipe (narrow groove) 34 extending in the circumferential direction in the center in the width direction. 120 is divided into left and right small blocks 120a and 120b of the same size by a sipe (narrow groove) 36 extending in the circumferential direction in the center in the width direction, and each block 140 of the land portion 14 is divided in the center in the width direction. Are divided into left and right small blocks 140a and 140b of the same size by a sipe (thin groove) 38 extending in the circumferential direction. Furthermore, two sipes 40 and 42 are formed in each small block and open in grooves on both sides in the width direction. The widths of sipes (narrow grooves) 34, 36, 38 are the same. The relationship between the sipe 20 that partitions the block 100 and the sipe 34 that partitions the small blocks 100a and 100b is shown in FIG. Blocks 120 and 140 are configured similarly to block 100 in this figure.

  The circumferential phase of each block is determined by the positions of the front and rear ends in the circumferential direction of each block. Based on the circumferential phase of the block 100, the circumferential phase shift of the block 120 Is the difference between the front end or rear end of the direction and the front end or rear end of the block 120 in the circumferential direction. The circumferential phase shift of the block 140 is the difference between the front end or rear end of the block 100 and the circumferential direction of the block 140. It is a difference from the front end or the rear end. Here, assuming that the positive direction of the X-axis is the front in the circumferential direction, the front end and the rear end in the circumferential direction of the block 100 are the rear end of the lug groove 16 and the front end of the lug groove 18, respectively. Further, the front end and the rear end in the circumferential direction of the block 120 are the rear end of the lug groove 22 and the front end of the lug groove 24, respectively. Further, the front end and the rear end in the circumferential direction of the block 140 are the rear end of the lug groove 28 and the front end of the lug groove 30, respectively.

  The phase of each small block is determined by the positions of the front and rear ends in the circumferential direction of each block, and the phase shift between the small blocks (100a and 100b, 120a and 120b, 140a and 140b) divided in the width direction is Is the difference between the front ends or the rear ends of the small blocks that are divided into two. Here, the front end and the rear end in the circumferential direction of the small block 100a are the rear end of the lug groove 16 and the front end of the lug groove 16 one behind the lug groove 16, respectively, and the front end in the circumferential direction of the small block 100b, The rear ends are the rear end of the lug groove 18 and the front end of the lug groove 18 one behind the lug groove 18, respectively. Further, the front end and the rear end in the circumferential direction of the small block 120a are respectively the rear end of the lug groove 22, and the front end of the lug groove 22 just behind the lug groove 22, and the front end and the rear end in the circumferential direction of the small block 120b. The ends are the rear end of the lug groove 24 and the front end of the lug groove 24 one behind the lug groove 24, respectively. Further, the front end and the rear end in the circumferential direction of the small block 140a are the rear end of the lug groove 28 and the front end of the lug groove 28 one rear of the lug groove 28, respectively. The ends are the rear end of the lug groove 30 and the front end of the lug groove 30 one behind the lug groove 30, respectively.

  In the present embodiment, the phase shift between the small blocks (100a and 100b, 120a and 120b, 140a and 140b) divided into two in the width direction is 5% or more and 25% or less of the circumferential length of the small block. For example, the phase shift between the small blocks 100a and 100b will be described with reference to FIG. 2. Since the circumferential length of the small block is L0 and the phase shift is L1, L1 is 5% to 25% of L0. . Further, the phase shift between adjacent blocks in the width direction, that is, the phase shift between the block 100 and the block 120, and the phase shift between the block 100 and the block 140 are represented by the circumferential length of each small block (L0 in FIG. 2). 30% to 45%.

  Thus, the phase shift between the small blocks divided in the width direction is set to 5% to 25% of the circumferential length of the small block, and the phase shift between adjacent blocks in the width direction is set to the circumferential direction of the small block. By setting the length to 30% or more and 45% or less, the pattern noise can be suppressed, and the performance on an icy and snowy road surface with a very low friction coefficient μ can be improved. The reason will be described below.

  In order to reduce pattern noise, it is effective to mitigate the impact sound when the edge contacts the ground by shifting the edge part by shifting the phase between adjacent blocks and between the small blocks divided in the width direction. (See “Phase Shift vs. Pattern Noise Characteristics” shown in FIG. 3). However, when the edges are distributed, the edge component appears on average, and continuous tangential force cannot be obtained, so the total edge length of the entire tread portion is the same as compared to the case where the edges are concentrated. However, the performance on ice and snow will deteriorate. That is, reducing the pattern noise and improving the performance on ice and snow by the arrangement of the edges is in a trade-off relationship, and it is difficult to achieve both.

  Therefore, in this embodiment, the balance between the reduction in pattern noise and the maintenance of performance on ice and snow is achieved by taking into account the distribution in the width direction of the contact surface of the tire. Generally, as shown in FIG. 4, the widthwise ground pressure distribution of the tire contact surface becomes maximum at the equator CL and decreases as the distance from the equator CL increases. Because of this characteristic, in order to reduce pattern noise while suppressing deterioration in performance on ice and snow, the phase shift between adjacent blocks near the equator CL is minimized, and the phase shift between blocks adjacent to the equator CL is increased. You can see that In the present embodiment, the phase shift of the small blocks 100a and 100b, which are adjacent blocks in the center land portion 10 having a relatively high contact pressure, is made as small as possible in consideration of the performance on ice and snow. On the other hand, since the second land portions 12 and 14 have a relatively low contact pressure, the effects of the phase shift change on the performance on ice and snow are less sensitive than those of the center land portion 10, and the blocks 100 and 120 And the phase shift between the blocks 100 and 140 are increased to some extent to reduce the pattern noise. In addition, the phase shift between the small blocks 120a and 120b and the phase shift between the small blocks 140a and 140b are desirably small in order to suppress deterioration in performance on ice and snow, so the phase shift between the small blocks 100a and 100b. As well as smaller. Here, if the phase shift between the small blocks is too small, the pattern noise will increase, and if the phase shift between the blocks 100 and 120 and the phase shift between the blocks 100 and 140 are too large, the performance on ice and snow will deteriorate. Therefore, the above numerical range was set.

  FIG. 5 shows a case where the phase shift between the small blocks is reduced and the phase shift between the blocks is increased, and conversely, the phase shift between the blocks is decreased and the phase shift between the small blocks is increased. It is a graph which shows the measurement result of the friction coefficient (mu) which is performance. Here, the broken line is the friction coefficient μ when the phase shift between the small blocks is 0 and the phase shift between the blocks is on the horizontal axis, and the solid line is the phase shift between the blocks and the small block is between the small blocks. Is the friction coefficient μ when the horizontal axis represents the phase shift. From this graph, in order to improve the performance on ice and snow, as in this embodiment described above, the phase shift between the small blocks is reduced and the phase shift between the blocks is larger than the opposite case, It turns out to be effective. The measurement conditions are the same as in the on-ice braking test of the examples described later.

  When a load is applied to the small blocks, the sipe 34, 36, and 38 contact each other with the small blocks facing each other across the sipe 34, 36, and 38 to suppress the deformation of the block. In order to exhibit the effect of ensuring braking performance on ice by suppressing the decrease, it is preferable to form a zigzag shape having an angle of 10 ° to 30 ° with respect to the circumferential direction. If this angle is less than 10 °, the above effect is insufficient, and if it exceeds 30 °, chipping at the end of the small block and uneven wear tend to occur. Therefore, the angle is preferably 10 ° or more and 30 ° or less with respect to the circumferential direction.

  Further, it is preferable that the widths of the sipes 34, 36, and 38 are 0.4 mm or more and 2.5 mm or less. If this width is less than 0.4 mm, the drainage effect cannot be obtained sufficiently, so that the performance on ice cannot be improved, and if it exceeds 2.5 mm, the effect of suppressing the deformation of the block cannot be obtained. Therefore, 0.4 mm or more and 2.5 mm or less is suitable.

  In each small block, two sipes 40 and 42 opened on both sides in the width direction are formed, but it is preferable that the number of sipes opened on both sides in the width direction is 1 or more and 4 or less. This is because the rigidity of the block is reduced when the number is five or more. The depth of the sipe is preferably 50% or more and 80% or less of the depth of the main grooves 2, 4, 6, and 8. If it is less than 50%, the drainage effect cannot be sufficiently obtained, so that the performance on ice cannot be improved, and if it exceeds 80%, the rigidity of the block is lowered.

[Example]
In order to confirm the effect of the present invention, Example tires and Comparative tires were prepared, and an indoor noise test and an on-ice braking test were performed. The sizes of the example tire and the comparative example tire are both 12R22.5. The tread pattern is the same as that shown in FIG. 1 for the example tire, and the phase shift between the small blocks (100a and 100b, 120a and 120b, 140a and 140b) is 18.2% of the circumferential length of the small block. The phase shift between the blocks (100 and 120, 100 and 140) is 37.8% of the circumferential length of the small block. On the other hand, as shown in FIG. 6, the tread pattern of the comparative example tire has a phase shift between the small blocks of 35.4% of the circumferential length of the small block and a phase shift between the blocks in the tread pattern shown in FIG. This is changed to 60.2% of the circumferential length of the small block. That is, the comparative example tire is obtained by enlarging the phase shift between the small blocks by approximately 1.9 times and the phase shift between the blocks by approximately 1.6 times compared to the example tire.

The test conditions for the indoor noise test and on-ice braking test are as follows.
Indoor noise test Rim size: 8.25 × 22.5
Internal pressure: 800kPa
The tire was pressed against a 3m diameter drum tester with a normal load, rotated at a speed of 60km / h, and the noise was measured with a microphone placed 50cm away from the tire.

Ice braking test Rim size: 8.25 × 22.5
Internal pressure: 800kPa
Load: 28.4kN
Vehicle: 2D4
Measures the distance to stop after braking from a speed of 20 km / h.

  The test results are shown in Table 1.

  The numerical values in this table are expressed as an index with the comparative tire set to 100. The smaller the noise test result, the better the ice braking test result. From the table, the example tires maintained the same quietness as the comparative tires, and the performance on ice was improved by 20%, and the effects of the present invention could be confirmed.

It is a partial expansion top view of the pattern of the tread part of the pneumatic tire of the embodiment of the present invention. It is a figure which shows the relationship between the sipe which divides the block of FIG. 1, and the sipe which divides a small block. It is a figure which shows a phase shift versus pattern noise characteristic. It is a figure which shows the width direction contact pressure distribution of the contact surface of a tire. Graph showing the performance on ice and snow when the phase shift between small blocks is reduced and the phase shift between blocks is increased, and conversely, the phase shift between blocks is reduced and the phase shift between small blocks is increased. It is. It is a partial expansion top view of the pattern of the tread part of the pneumatic tire of the comparative example of the present invention. It is a partial expansion top view of the pattern of the tread part of the conventional pneumatic tire.

Explanation of symbols

  2, 4, 6, 8 ... main groove, 10, 12, 14 ... land, 16, 18, 22, 24, 28, 30 ... lug groove, 20, 26, 32, 34, 36 , 38, 40, 42 ... sipes, 100, 120, 140 ... blocks, 100aa, 100b, 120a, 120b, 140a, 140b ... small blocks.

Claims (5)

At least three main grooves extending in the circumferential direction and a plurality of grooves intersecting the main grooves are divided into at least two rows of blocks, and the central portion in the width direction of the blocks is formed by circumferential sipes or narrow grooves. A pneumatic tire having a tread pattern divided into two small blocks in the width direction,
The phase shift in the circumferential direction of the two small blocks is not less than 5% and not more than 25% of the circumferential length of the small block, and the phase shift in the circumferential direction of the adjacent blocks in the width direction is the circumference of the small block. A pneumatic tire characterized by being 30% to 45% of the directional length. The pneumatic tire according to claim 1,
A pneumatic tire characterized in that the sipe or narrow groove extending in the circumferential direction has a zigzag shape with an angle of 10 ° or more and 30 ° or less with respect to the circumferential direction. In the pneumatic tire according to claim 1 or 2,
A pneumatic tire characterized in that a width of a sipe or narrow groove extending in the circumferential direction is 0.4 mm or more and 2.5 mm or less. In the pneumatic tire according to any one of claims 1 to 3,
A pneumatic tire characterized in that one or more and four or less width direction sipes are formed in the small block. The pneumatic tire according to claim 4,
The pneumatic tire according to claim 1, wherein the depth of the sipe in the width direction is 50% or more and 80% or less of the depth of the main groove.

Images