JPH06171311A - Pneumatic tire provided with directional tread - Google Patents

Abstract

PURPOSE:To prevent lowering of the driving performance and abrasion in an early stage on a hard road by inclining a groove bottom of a tread main groove part. at an angle in the specific inclination angle range to the radius directional plane and shifting a pattern pitch to the tread center in the lateral circumferential direction by the specific % so as to increase a pattern land rate by the specific %. CONSTITUTION:A pattern unit is formed of a center block 4, the first main block 5, and the second main block 6, and a shift amount S is set to be 40-60% of one pitch P of the unit In a cross section A-A line, a width directional groove 10 is shallower than a main groove 1, and an inclination angle alpha of a groove 11 is set in the 60 deg.>alpha>30 deg. range. In this way, mud drainage performance is improved by angling the groove bottom between the blocks to the tread end direction deeply, so that a tread pattern land rate can be increased to 40-59% and tread width can be increased, and consequently, reduction in driving performance on a hard road is prevented while abrasion resistance is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire having a tread pattern in which a rotation direction is designated and suitable for running on a dirt road, and more particularly to a pneumatic tire having a directional tread exhibiting good performance on a mud road. .

[0002]

2. Description of the Related Art Conventionally, a tread for a competition tire on a dirt road, particularly a tire that exhibits good performance on a mud road, is formed by a groove a extending in the width direction of the tread T ₁ as shown in FIG. 3 as an example. A block pattern composed of blocks c formed by ridge lines in the width direction and ridge lines in the circumferential direction formed by the grooves b extending in the circumferential direction of the tread T ₁ is orthogonal to each other. A tire suitable for such a mud road has a smaller ground contact width W ₁ than a general tire and a smaller land ratio (ratio of the total area of the block ground contact surface to the total area of the tread) of the tread pattern. The required grip and side grip are obtained by preventing the decrease of the grip force due to the tire floating on the road, and the groove side wall and the kick side (the rear side in the tire rotation direction) on the stepping side (the front side in the tire rotation direction) of each block. The inclination angles γ of the groove wall and the groove walls on both sides in the width direction are the same (see FIG. 4).

Further, for example, in Japanese Patent Application Laid-Open No. 3-65407, a plurality of grooves extending in the circumferential direction of the tread, and an arrow-shaped widthwise groove extending obliquely from the central portion of the tread to the tread end are used to define the center of the tread. A central block row arranged in the circumferential direction, a shoulder block row arranged in the circumferential direction along the tread edge, and an intermediate block row arranged in the circumferential direction between the two block rows. The inclination angle of the groove wall of the circumferential groove located between the block and the block of the intermediate block row is changed from the stepping side to the kicking side, and in each block, it extends in the circumferential direction in the substantially straight line of the circumferential groove. It is described that the drainage at the time of high-speed running is improved by shifting the groove bottom toward the tread end side from the stepping side to the kicking side with respect to the groove opening having a constant width.

[0004]

However, in the pneumatic tire provided with the conventional directional tread described above,
When traveling on a hard road surface, there were problems such as insufficient grip force due to insufficient ground contact surface and early wear due to a small ground contact width and a small land ratio of the tread pattern. Also, on mud roads, sufficient traction and side grip cannot be obtained unless the mud under the tire contact surface is quickly discharged and the tire is brought into contact with the road surface of the mud lower layer, which is effective for digging up. In general, the mud flows in the front-rear direction with respect to the tire traveling direction as well as the water on the wet road, but this is not enough, and it is more effective to discharge the mud from the ground contact surface by flowing it in the tire width direction as well. However, since the mud's viscosity is higher than that of water, it is difficult to slip out in the tire width direction,
There is a problem in that dirt tends to be clogged in the groove of the tread, particularly in the groove in the width direction of the tread, and when the mud is dug up to obtain traction, the tire deeply dives, the running resistance is larger, and the fast running is prevented. Further, in each block, in the case where the groove bottom is shifted to the tread end side from the stepping side to the kicking side with respect to the groove opening of the constant width which is substantially straight in the circumferential groove and extends in the circumferential direction, in the circumferential groove, It does not mention the groove in the width direction that is effective for running on dirt road, and the width of the opening of the groove in the circumferential direction is constant, so it will be clogged in the groove when running on mud road. There was a problem that the running performance on the mud road was not high due to the lack of ability to discharge soil naturally.

An object of the present invention is to provide a directional tread capable of improving running performance on a mud road and preventing deterioration of running performance and premature wear on a hard road surface by increasing a ground contact width and a land ratio. It is to provide a pneumatic tire.

[0006]

A pneumatic tire provided with a directional tread according to the present invention has a tread, a tread circumferential direction from the center of the tread to the tread width direction (hereinafter, simply referred to as width direction) to a tread end (hereinafter, referred to as a tread circumferential direction). Simply called the circumferential direction)
A plurality of main grooves (lug grooves) extending obliquely with respect to each other and a plurality of blocks divided by a plurality of sub-grooves extending in the circumferential direction, and a center block row arranged in the circumferential direction substantially in the center of the tread, Equipped with a plurality of main block rows arranged in the circumferential direction at intervals from the center block row in order in the width direction, and provided with a directional tread whose rotation direction is the direction in which the angle formed by the circumferential direction and the main groove is an obtuse angle. In the pneumatic tire, the ridge line in the tread width direction of the blocks of each main block row has a ridge line angle θ that is an inclination angle with respect to the circumferential direction, and the tread end side is sequentially arranged from the main block row closest to the center block row. The ridgeline angle θ is decreased as it goes to the main block row, and the ridgeline angle θ _F on the stepping side is made larger than the ridgeline angle θ _R on the kicking side (θ _F > θ _R ), that is, From the center block row to the tread edge direction, with the ridge angle θ _F1 on the stepping side of the block of the main block row on the first row and the ridge angle θ _R1 on the kicking side, and the ridge angle θ _F2 on the step side of the block in the second main block row. Ridge side ridge angle θ _R2 , ... Between the step side ridge angle θ _Fn and the kick side ridge angle θ _Rn of the block in the n-th main block row, θ _F1 > θ _F2 > ... > Θ _Fn θ _F1 > θ _R1 , θ _F2 > θ _R2 , ..., θ _Fn > θ _Rn . Further, the stepping side main groove wall angle β which is an inclination angle formed by the stepping side main groove wall of each block and a plane including the stepping side ridgeline and the tire rotation axis (hereinafter, simply referred to as a radial plane)
_{Make F1} larger than the kick-side main groove wall angle β _R, which is the angle of inclination of the kick-side main groove wall with the radial plane (β _F >
β _R ), that is, the main groove wall angle β _F1 on the stepping side and the kicking side main groove angle β _R1 of each block in the first block row, and the main groove wall angle β _F2 on the stepping side of each block in the first block row and kicking Main side groove angle β _R2 , ... Between the stepping side β _Fn of the block in the n-th main block row and the main side groove angle β _{Rn of the start} side, β _F1 > β _R1 , β _F2 > β _R2 , ... β _Fn > β _Rn holds, and in the groove in the width direction between each block of the center block row, the groove bottom of the portion facing the main groove from the tread center has an inclination angle α with respect to the radial plane. The bottom of the other part is formed shallower than the main groove by making it inclined and continuous with the main groove, and the inclination angle α is in the range of 60 to 30 degrees (60
°>α> 30 °). Furthermore, the main groove formed symmetrically with respect to the center of the tread has a pattern pitch of 40 to 40
The land rate of the tread pattern is shifted by 60%.
It is 40 to 50%. In addition, each of the above blocks
170 ° to 10 with respect to circumferential and widthwise ridgelines and circumferential direction
It is advisable to provide a ridgeline inclined with a ridgeline angle θ in the range of 0 °. Further, it is preferable to provide five block rows arranged in the circumferential direction, and at least one block row should be provided with two sipes in each block to divide the block surface area into three equal parts. And an inclined portion inclined in the range of 170 ° to 100 ° with respect to the circumferential direction.

[0007]

With the above construction, since the stepping side ridgeline of the block that comes into contact with the ground first during running is greatly inclined with respect to the circumferential direction, a mud flow is formed in a direction close to the circumferential direction at the initial stage of grounding, It gradually changes to a flow in the direction of the tread end as it goes toward the tread end, making it easier to discharge the mud to the tire side from the tire contact surface, and with the main groove widening toward the tread end, it is extremely easy to discharge soil. I am raising. Also, by making the step side main groove wall angle β _F larger than the kick side main groove wall angle β _R , the step side main groove wall area of the block is increased, and high traction performance is achieved by pushing the mud on this surface. The obtained tire can be efficiently run without diving, and since the kick-side main groove wall angle β _R is small, a large groove volume can be secured and earth scavenging performance can be secured. Further, in the widthwise groove between the blocks of the center block row, the groove center of the portion facing the main groove from the tread center is inclined at an inclination angle α with respect to the radial plane, so that the tire center is first When it touches the road, it creates a trigger for the mud to flow toward the tread edge, further improving the soil removal effect. Furthermore, by increasing the land ratio,
The running performance of the hard road surface is secured and early wear can be prevented.

[0008]

Embodiments of the present invention will be described with reference to FIGS. In FIG. 1, a tread T includes a large number of main grooves (lug grooves) 1 extending in the width direction from the center of the tread and inclined with respect to the circumferential direction, and four auxiliary grooves 2 and 3 extending in a substantially straight line in the circumferential direction. And a large number of blocks divided by the main groove 1 and the sub-grooves 2 and 3, and the direction in which the main groove 1 forms an obtuse angle with respect to the circumferential direction (upward direction in the figure) is the direction of rotation. It is a sex tread. 1st located on the tread center side
A center block row 40 in which a large number of center blocks 4 are arranged in the circumferential direction including the tread center line CL is formed between the sub-grooves 2 and 2, and the first sub-groove 2 and the tread end side from the first sub-groove 2 are formed. A first main block row 50 in which a large number of first main blocks 5 are arranged in the circumferential direction is formed between the second sub-grooves 3 and the second main blocks. A second main block row 60 in which 6 are arranged in the circumferential direction is formed, and a pattern unit is formed by each one center block 4, the first main block 5 and the second block 6, and is arranged on the center line CL. On the other hand, the left and right patterns are formed symmetrically, and the left and right patterns are circumferentially shifted by a predetermined amount s.
The center blocks 4 of the left and right pattern units are alternately arranged on the center line CL to form five block rows by shifting by. The shift amount s is 40 to 60% of one pitch p of the pattern unit, particularly preferably 45 to
50%, and one pitch p of the pattern unit is 40 to 70 mm, particularly preferably 45 to 55 mm, although it depends on the contact width.
If the pitch p is too short, the required pattern stability cannot be obtained, and if it is too long, the earth removal efficiency decreases.

The pattern unit located in the right half of the figure will be described below. The center block 4 has a width direction ridge line 41 extending in one direction from a center line CL formed on the tip side in the rotation direction, that is, a stepping side, and a ridge line angle γ which is a tilt angle measured clockwise with respect to a circumferential direction extending in the other direction. Inclined ridge line 42 and circumferential ridge lines 43, 44 formed on both widthwise end sides
(Facing the first sub-grooves 2 and 2), a widthwise ridgeline 45 behind the inclined ridgeline 42 and a widthwise ridgeline 46 behind the widthwise ridgeline 41, which are formed on the rear end side in the rotation direction. The connecting ridge line 47 is provided, and the ridge line angle γ is set to 10 ° to 80 °. In the center block row 40, as described above, the center blocks 4 of the left and right pattern units are alternately arranged, and the width direction ridge line 41 on the front end side of the center block 4, the width direction ridge line 46 of the adjacent center blocks 4 and the connection. The width direction groove 10 is formed between the ridge line 47, the inclined ridge line 42 on the front end side of the center block 4, and the width direction ridge line 45 of the adjacent center block 4.
And a widthwise groove 11 that expands as it goes in the widthwise direction facing the main groove 1 is formed. The widthwise grooves 10 and 11 are continuous at the center of the tread, and are shown in FIG. As shown, the widthwise groove 10 is formed shallower than the main groove, and the widthwise groove 11
The groove bottom of is smoothly continuous to the groove bottom of the main groove 1 with an inclination angle α measured counterclockwise with respect to the radial plane,
The inclination angle α is set in the range of 60 ° to 30 ° (60 °>α>
30 °). With this configuration, when the tire center first comes into contact with the mud road, a trigger for flowing through the mud toward the tread end is created, and the soil discharging effect is further improved.

In the first main block row 50, the first main block 5 is continuous with the stepwise widthwise ridgeline 51 on the first sub-groove 2 side and the widthwise ridgeline 51 on the tip side, that is, the stepping side in the rotation direction. It has a stepping side inclined ridgeline 52 having a ridgeline angle θ _F1 which is an inclination angle measured clockwise with respect to the circumferential direction, and a stepping side widthwise ridgeline 53 on the second sub-groove 3 side. A circumferential ridge line 54 is provided at the groove 2 side end, and a circumferential ridge line 55 is provided at the second sub-groove 3 side.
And the first sub-groove 2 on the rear end side in the rotation direction, that is, on the kicking side.
Side kicking side widthwise ridgeline 56, a kicking side tilting ridgeline 57 having a ridgeline angle θ _R1 which is a tilting angle measured in a clockwise direction with respect to the circumferential direction in succession to the widthwise ridgeline 56, and a second auxiliary It has a kick-out side width direction ridge line 58 on the groove 3 side.

The ridgeline angle θ _F1 of the stepping side inclined ridgeline 52 is made larger than the ridgeline angle θ _R1 of the kicking side inclined ridgeline 57. Also, a cross-sectional view taken along line BB of FIG. 2b and CC of FIG. 2c.
As shown in the line sectional view, the stepping side main groove wall angle β _F1 , which is the inclination angle measured counterclockwise with respect to the radial plane of the side wall of the stepping side main groove 1 of the first main block 5, is kicked. It is set to be larger than the kick-out side main groove wall angle β _R1 which is the tilt angle measured counterclockwise with respect to the radial plane of the side wall of the main groove 1 on the protruding side (β _F1 > β _R1 ). With this configuration, the area of the main groove wall on the stepping side of the block is increased, and high traction performance is obtained by pushing the mud on this surface, so that the tire can run efficiently without diving and the main groove wall on the kicking side can be obtained. Since the angle β _R is small, it is possible to secure a large groove volume and ensure soil unloading performance.

In the second main block row 60, the second main block 6 has a stepwise side widthwise ridgeline 61 on the second sub-groove 3 side and a circumferential direction continuously with the widthwise ridgeline 61. It has a stepping side inclined ridgeline 62 having a ridgeline angle θ _F2 which is a tilt angle measured in the clockwise direction, and a stepping side widthwise ridgeline 63 on the tread end side, and a circumferential ridgeline at the side end of the second auxiliary groove 3.
64 has a circumferential ridge line 65 on the tread end side, a kicking side width direction ridge line 66 on the second auxiliary groove 3 side and a width direction ridge line 66 continuous on the kicking side with respect to the circumferential direction. Kick-side inclined ridge 67 having a ridge angle θ _R2 that is the inclination angle measured in the direction
And a kick-out side width direction ridgeline 68 on the tread end side.

The ridgeline angle θ _F2 of the stepping side inclined ridgeline 62 is made larger than the ridgeline angle θ _R2 of the kicking side inclined ridgeline 67, and the ridgeline angle θ _F2 of the stepping side inclined ridgeline 62 is set to the first main block 5.
Smaller than the ridge angle θ _F1 of the stepped side inclined ridge line 52 (θ _F1 >
θ _F2 ), and the ridge angle θ _R2 of the kick-side inclined ridge line 67 is set smaller than the ridge angle θ _R1 of the kick-side inclined ridge line 57 of the first main block 5 (θ _R1 > θ _R2 ). With the above configuration, the width of the main groove 1 becomes wider from the tread center line CL toward the tread end, which significantly improves the soil unloading property. Also,
As shown in the sectional view taken along the line DD of FIG. 2d and the sectional view taken along the line EE of FIG. 2e, the main groove 1 on the stepping side of the second main block 6 is shown.
Step side main groove wall angle β _F2 , which is the tilt angle measured counterclockwise with respect to the radial plane of the side wall of, is measured counterclockwise with respect to the radial plane of the side wall of the main groove 1 on the kicking side. The inclination angle is larger than the kick-side main groove wall angle β _R2 (β _F2 > β _R2 ).

Here, the stepped side inclined ridge line 62 of each block
Has a ridge angle θ of 170 ° to 100 °, particularly preferably 160 ° to
It is preferable that the angle is 100 °, and the ridge angle θ _F1 of the stepping side inclined ridge 52 of the first main block 5 is 170 ° to 135 °, particularly preferably 160 ° to 140 °. If the ridge angle is too large, the stability of the main block cannot be secured, and if it is too small, the mud flow will be poor and the soil unloading performance will deteriorate.

Further, the stepping side main groove wall angle β _F of each main block 5, 6 is 5 to 30 °, particularly preferably 15 to 25 °, and the kicking side main groove wall angle β _R is 0 to 15 °. Angle, particularly preferably 3 to 10 °, and the main groove wall angle β _F on the stepping side
When the angle becomes close to 45 °, the side wall of the main groove 1 acts to hit the mud, a force is generated in the direction of floating rather than the traction, good traction cannot be obtained, and the kicking side main groove wall angle β _R If it is too small, the stability of the main block will deteriorate and the main block will twist, making it impossible to obtain good traction.

The main blocks 5 of the first main block row 50 are provided with two sipes 7 which divide the surface area into three equal parts, and the main blocks 6 of the second main block row 60 are provided with two sipes which divide the surface area into three equal parts. 8 are provided respectively, and each of the sipings 7 and 8 is a width direction portion on the tread center side.
71, 81, inclined portions 72, 82 having an inclination angle δ measured counterclockwise with respect to the circumferential direction, and width-direction portions 73, 83 on the tread end side. Let be °.

Experimental results comparing the embodiment of the present invention with the conventional example are shown below. [Example tire] A tire having a size of 195 / 65R,
Tread width 127 mm, tread pattern land ratio 41%,
The pattern is symmetrical and shifts left and right in the circumferential direction by 1/2 pitch (to efficiently discharge the mud to the left and right), and has two main block rows on one side except the center block. In addition, the main groove wall angle β _{F1 of} the first main block on the step side β _F1 = 20 °, the main groove wall angle of the kicking side β _R1 = 5
And the main groove wall angle of the second main block on the stepping side β _F2 =
The main groove wall angle of the kicking side is β _R2 = 5 ° and the inclination angle α of the groove bottom of the groove facing the main groove between the center blocks is 53 °. [Conventional tire] A tire with a size of 195 / 65R, a tread width of 118 mm, a land ratio of a tread pattern of 37%, and a block side wall angle of 10 °.

Table 1 shows the results of the evaluation of the actual vehicle by mounting the above two kinds of tires on the high performance 4WD used for the dirt trial competition and assuming the actual competition by the professional driver on the course including the mud road. [Table 1] Actual vehicle evaluation result [Time index] [Feeling] [Abrasion] "Mad road""Hardroad" TR SG TR SG Conventional tire 100 100 100 100 100 100 100 Example tire 110 110 110 105 115 115 110 120 However, TR Is traction, SG is a side grip,
Each result is shown as an index with the performance of the conventional tire as 100, and the larger the index, the better. From the results of Table 1 above, it is clear that the performance of the example tire of the present invention exceeds that of the conventional tire.

[0019]

Since the present invention is constructed as described above, it has the following effects. By making the angle between the tread width direction ridgeline of the block and the circumferential direction smaller toward the tread edge direction from the tire center, when the tire touches the mud road, the mud is quickly discharged to both sides of the tire and good traction is achieved. And a side grip is obtained. In addition, the width of the main groove (lug groove) in the tread width direction increases toward the tread edge direction by decreasing the kick-out side ridge angle with respect to the stepped side ridge angle of the block, and a large amount of mud on the ground contact surface is obtained. And it can be discharged smoothly. Further, the area of the stepping side main groove wall can be increased by increasing the stepping side main groove wall angle, and the traction side main groove wall surface pushes out a large amount of the mud to the rear side, thereby obtaining good traction performance. On the other hand, by making the kick-out side main groove wall angle smaller than that on the stepping side, it is possible to prevent the decrease in groove volume, smooth the flow of the mud, and ensure good soil removal performance. Furthermore, by making an angle so that the groove bottom between the blocks of the center block row to be grounded at the initial stage becomes deeper as it goes toward the tread end, it is possible to make a cue for flowing the mud toward the tread end at the initial stage of grounding. The soil removal performance is improved. As described above, as the mud discharging performance is improved, the land ratio can be increased and the ground contact width can be increased, so that there is no performance deterioration when traveling on a hard road, and the wear resistance can be improved.

[Brief description of drawings]

FIG. 1 is a development view of a tread portion according to an embodiment of the present invention.

FIG. 2 is a view of AA, BB, CC, D- in FIG.
It is a D-EE sectional view.

FIG. 3 is a development view of a tread portion of a conventional tire.

FIG. 4 is a sectional view taken along line HH of FIG.

[Explanation of symbols]

T-tread, CL tread center line 1 main groove (lug groove), 2nd sub groove, 3 2nd sub groove, 4
Center block 5 1st main block, 6 2nd main block,
7,8 Siping 40 Center block row, 50 1st main block row 60 2nd main block row

Claims (4)

[Claims] 1. A tread having a plurality of blocks divided by a plurality of main grooves extending from the center of the tread in a width direction to a tread end with an inclination with respect to the circumferential direction and a plurality of sub grooves extending in the circumferential direction, The center block row is arranged substantially in the center of the tread in the circumferential direction, and a plurality of main block rows are arranged in the circumferential direction at intervals from the center block row in order in the width direction, and the angle between the circumferential direction and the main groove is formed. In a pneumatic tire provided with a directional tread whose direction is an obtuse angle, the ridgeline in the tread width direction of the blocks of each main block row is a ridgeline angle θ with respect to the circumferential direction.
The ridge line angle θ is gradually decreased from the main block line closest to the center block line to the main block line on the tread end side in order, and the ridge line angle θ _F on the stepping side is set.
Is larger than the ridgeline angle θ _R on the kicking side, and the stepping side main groove wall angle β _F that the stepping side main groove wall of each block forms with the radial plane is the kicking side main groove wall that forms the radial plane. It is set to be larger than the kick-side main groove wall angle β _R , and in the width direction groove between each block of the center block row, the groove bottom of the portion facing the main groove from the tread center is 60 degrees to 30 degrees with respect to the radial plane. The main groove, which is formed symmetrically with respect to the center of the tread by inclining with a tilt angle α of 40 degrees, shifts the left and right sides in the circumferential direction by 40 to 60% of the pattern pitch to make the land ratio of the tread pattern 40 to 50%. Pneumatic tire with a directional tread characterized by. 2. The directional property according to claim 1, wherein each block includes a width direction ridge line, a circumferential direction ridge line, and a ridge line inclined in the range of 170 ° to 100 ° with respect to the circumferential direction. Pneumatic tire with tread. 3. A block row arranged in the circumferential direction of 5 rows,
The pneumatic tire with a directional tread according to claim 1 or 2, wherein each block of at least one block row is provided with two sipes that divide the surface area into three equal parts. 4. The directional tread according to claim 3, wherein the siping has a width direction portion and a portion inclined in the range of 170 ° to 100 ° with respect to the circumferential direction. Pneumatic tires.