JP2700808B2 - Pneumatic tire - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire in which a large number of blocks are defined by forming a wide groove main groove and a lateral groove on a tread surface.

2. Description of the Related Art Generally, when a pneumatic tire having a large number of blocks on a tread is run and a circumferential shearing force acting on each block at the time of contact with the ground is measured, a driving direction shearing force is applied to the stepping side of each block, A shearing force in the braking direction acts on the kicking-out side, and the absolute values of these shearing forces are maximum near the stepped end and the kicked-out end. Here, since the wear speed of the tread surface receiving the braking direction shear force is significantly higher than the wear speed of the tread surface receiving the drive direction shear force, the region receiving the braking direction shear force during traveling, that is, each block, Only the kick-out side wears and the amount of wear increases toward the kick-out end, so that so-called heel and toe wear occurs.

Conventionally, in order to prevent such heel and toe wear, for example, a number of sipes are formed around each block,
It has been practiced to reduce the bending stiffness of each block.

Problems to be Solved by the Invention However, although such a device can prevent heel and toe wear to some extent, its effect was not sufficient.

An object of the present invention is to provide a pneumatic tire that can reliably prevent heel and toe wear of a block defined on a tread surface.

Means for Solving the Problems Such an object is to define a large number of blocks by forming a plurality of continuous wide main grooves extending in a circumferential direction on a tread surface and a plurality of wide horizontal grooves intersecting the main grooves. In the pneumatic tire, in the main groove near the kick-out end of each block, the radial outer end face is located radially inward from the cross-sectional contour of the block, and the radial outer end face when reaching the tread contact area. This can be achieved by providing a stepped region that comes into contact with the road surface and allowing the stepped region to come into sliding contact with the road surface during traveling to function as an uneven wear sacrifice portion.

Operation When a pneumatic tire having a block on the tread surface is run, a shear force in the braking direction acts on the kicking side of each block at the time of contact with the ground, and only the kicking side tends to wear. Here, the radially outer end face of the stepped area provided near the kick-out end of the block comes into contact with the road surface when reaching the tread contact area by the running, but the radially outer end face of this stepped area is formed by the block. Because it is located radially inward from the cross-sectional contour, the radially outer end surface of the stepped region makes sliding contact while being dragged by the road surface, and as a result, the pneumatic tire rolls on the radially outer end surface of the stepped region. A shearing force is generated in the braking direction, that is, in the braking direction. Here, since the total value of the driving and braking direction shear forces generated in the unit area is considered to be substantially constant, the braking direction shear force is newly generated in a part of the unit area, that is, in the step region as described above. As a result, the shearing force acting on the block near the step region (block on the kick-out side) is shifted up to the drive side as a result. When the step region functions as the uneven wear sacrifice portion, the shearing force acting on the kick-out side of the block is in the driving direction, and the wear is suppressed on the kick-out side. As a result, the wear of the block progresses substantially uniformly on the stepping side and the kicking side, and uneven wear, that is, heel and toe wear, is prevented. Here, it is conceivable to provide the above-mentioned step region in the wide lateral groove. However, such a lateral groove has a short axial distance of the tire, that is, because the opening area is small, the radial direction of the step region provided in the lateral groove is small. The area of the outer end face must be small, and as a result, even if the stepped region functions as an uneven wear sacrifice portion during running of the tire, it cannot exert much influence on the kick-out side of the block. For this reason, even if the step region is provided at such a position, the heel and toe wear is generated on the block after traveling for a long time. On the other hand, when the step region is provided in the wide main groove, since the main groove is a continuous wide groove extending in the circumferential direction, the area of the radially outer end face of the step region can be easily reduced to the required area. Thus, a large uneven wear preventing effect can be given to the kick-out side of the block, and heel and toe wear can be reliably prevented. For this reason, in the present invention, the step region is provided in the main groove.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

In FIGS. 1, 2, and 3, reference numeral 1 denotes a pneumatic radial tire mounted on a driven wheel or a free wheel of a car, truck, bus, or the like. A plurality of continuous tires extending in a circumferential direction are provided on a tread surface 2 of the tire 1. A wide main groove 3 is formed. These main grooves 3 are arranged on a pair of inner main grooves 3 a arranged on both sides of the tire equatorial plane 4 close to the tire equatorial plane 4, and arranged on both sides of the tire equatorial plane 4 near the shoulder end 5. A pair of outer main grooves 3b, the inner main grooves
3a is bent in a zigzag shape, while the width of the outer main groove 3b increases and decreases in synchronization with the zigzag of the inner main groove 3a. The tread surface 2 between the inner main groove 3a, the tread surface 2 between the inner main groove 3a and the outer main groove 3b, and the tread surface 2 between the outer main groove 3b and the shoulder end 5 are respectively connected to the main groove 3. A plurality of wide transverse grooves 6a, 6b, 6c intersecting with each other are formed. The transverse grooves 6a, 6b, 6c are equally spaced in the circumferential direction and extend in the axial direction of the tire 1. The lateral grooves 6b and 6c are arranged in the same phase in the circumferential direction, and the lateral grooves 6a and 6b are shifted in phase in the circumferential direction by 1/2 pitch. As a result, on the tread surface 2 between the inner main grooves 3a, a plurality of inner blocks 7a which are equidistant in the circumferential direction are defined by the inner main grooves 3a and the lateral grooves 6a. The tread 2 between the main groove 3b and the inner main groove
3a, the outer main groove 3b and the lateral groove 6b define a plurality of intermediate blocks 7b spaced equidistantly in the circumferential direction.
The outer main groove 3b is provided in the tread 2 between the shoulder 3b and the shoulder end 5.
And the lateral grooves 6c define a plurality of outer blocks 7c which are spaced equidistantly in the circumferential direction. The inner and outer main grooves 3a and 3b described above
The lateral grooves 6a, 6b, and 6c as a whole constitute a wide wide groove 8 that does not close even when touching the ground, and the wide groove 8 forms the tread surface 2 with an inner block 7a, an intermediate block 7b, and an outer block 7c. A number of blocks 7 are defined. In each outer main groove 3b, at a position where the outer main groove 3b intersects with the lateral grooves 6b, 6c, a step region 9 having a shape similar to the intermediate block 7b and having a smaller area is formed, and these plural step regions are formed. Numeral 9 is separated from the intermediate block 7b and the outer block 7c by a predetermined distance, is independent of the intermediate block 7b and the outer block 7c, and is equally spaced from each other in the circumferential direction. Here, the average circumferential length of each step region 9 (the average value of the circumferential lengths when the circumferential length changes in the axial direction) is 30.
mm or more, and the average width B of each step region 9 (when the width changes in the circumferential direction, the average value of the width) B is preferably 5 mm or more. The reason is that if at least one of the average circumferential length L and the average width B is less than the above value, the rigidity of the step region 9 is reduced, and the function of the step region 9 as the uneven wear sacrificial portion is reduced. It is. And
If the width of the step region 9 is changed to be maximum near the kick-out ends of the middle and outer blocks 7b and 7c as in this embodiment, the influence on the kick-out sides of these middle and outer blocks 7b and 7c is large. And uneven wear can be reliably prevented. In this embodiment, the step region 9 is separated from the intermediate block 7b and the outer block 7c by a predetermined distance, and a wide groove is left between them. However, the step region 9 is located between the step region 9 and the intermediate block 7b or the step region. Either one of the outer block 9 and the outer block 7c may be formed as a narrow groove or a sipe that closes at the time of contact with the ground, and a wide groove may be left on the other. Also, the radially outer end faces of these step regions 9
9a is located radially inward from the sectional contour line 10 of the block 7 by a fixed distance a. Here, the distance a is preferably 1 to 5 mm. And, radially outer end faces of these step regions 9
9a, when it reaches the tread contact area by running of the tire 1, it comes into contact with the road surface together with the outer surface of the block 7; Since it is shorter than one connected circumference, the radial outer end face 9a comes into sliding contact with the road surface at the time of contact with the ground and receives a large shearing force in the braking direction.

Next, the operation of the first embodiment of the present invention will be described.

Now, it is assumed that the tire 1 as described above is rotating and running in the direction of arrow A. At this time, when the block 7 reaches the tread contact area, that is, when the block 7 comes into contact with the road surface, a shear force in the driving direction is generated on the stepping side, and a shear force in the braking direction is generated on the kicking side. The absolute value is maximum near the stepping end 16 and the kicking end 17 of each block 7. Here, since the wear rate of the part receiving the braking direction shearing force is significantly higher than the wear rate of the part receiving the driving direction shearing force, the part receiving the braking direction shearing force, ie, kicking out of each block 7 Only the side is going to wear. Here, as described above, since the shear force in the braking direction has a maximum value in the vicinity of the kicking end 17, the wear progresses fastest in the vicinity of the kicking end 17 of each block 7. However, in this embodiment, the outer main groove 3b and the lateral groove 6
A step region 9 is provided at a position where b and 6c intersect, that is, near the kick-out end 17 (also near the stepping end 16) of each of the intermediate blocks 7b and the outer block 7c, and a radially outer end surface 9a of each step region 9 is formed. When the vehicle reaches the tread contact area, the outer surfaces of the intermediate block 7b and the outer block 7c are brought into contact with the road surface.
9a is a sectional contour of the intermediate block 7b and the outer block 7c.
Since it is located radially inward from 10, the step region 9
The outer end face 9a in the radial direction comes into sliding contact with the road surface while being dragged. When the vehicle is in contact with the road surface as described above, a shearing force is generated on the radially outer end surface 9a of the step region 9 in the direction of braking the rolling of the tire 1, that is, in the braking direction. Here, since the total value of the shearing forces in the driving and braking directions generated in the unit area of the tread surface 2 of the tire 1 is considered to be substantially constant, as described above, a part of the unit area, that is, the step region 9 When a braking direction shearing force is newly generated on the radially outer end surface 9a, the influence of the braking direction shearing force spreads around the step region 9 and kicks the intermediate block 7b and the outer block 7c located near the step region 9. The shear force near the projecting end 17 is shifted up to the driving side as a result. As a result, the shearing force acting on the kick-out side of each of the intermediate block 7b and the outer block 7c, particularly in the vicinity of the kick-out end 17 which has conventionally been subjected to a large braking force in the braking direction, is in the drive direction, and is based on the shearing force in the braking direction. Scuffing is prevented. On the other hand, the stepped region 9 is worn by the large shear force in the braking direction prior to the middle and outer blocks 7b and 7c, and functions as an uneven wear sacrifice portion. The influence of the shearing force in the braking direction in the step region 9 also spreads to the vicinity of the stepped end 16 of the intermediate block 7b and the outer block 7c, and further increases the value of the shearing force in the driving direction at the portion. Even if the value increases, the wear speed hardly changes because the value is in the driving direction. For this reason, the wear of the intermediate block 7b and the outer block 7c proceeds almost uniformly on the stepping side and the kicking side, and uneven wear, that is, heel and toe wear, is reliably prevented. Here, it is conceivable to provide the step region as described above in the lateral groove 6. However, such a lateral groove 6 is provided in the lateral groove 6 because the axial distance of the tire 1 is short, that is, the opening area is small. The area of the radially outer end face of the step region must be small, and as a result,
Even if the step region functions as an uneven wear sacrifice portion during running of the tire, it does not significantly affect the kick-out side of the block 7. For this reason, even if the step region is provided at such a position, the heel-and-toe wear occurs in the block 7 when the vehicle travels for a long time. On the other hand, when the step region 9 is provided in the main groove 3,
Is a continuous wide groove extending in the circumferential direction, so that the area of the radially outer end surface 9a of the step region 9 can be easily set to the required area, that is, as described above, the average circumferential length L is 30 mm or more, and the average width is B can be increased to 5 mm or more, whereby a large uneven wear preventing effect can be given to the kick-out side of the block 7, and heel and toe wear can be reliably prevented. For this reason, in the present embodiment, the step region 9 is provided in the main groove 3 as described above.

Next, test examples will be described. Before starting this test, a comparative tire 1 having a tread pattern as shown in FIGS. 4 and 5 and a test tire 1 to which the present invention was applied with a tread pattern as shown in FIGS. 2 and the test tire 3 described in the first embodiment, that is, the tread pattern shown in FIGS. 1, 2, and 3 were prepared. The comparative tire 1 has a plurality of rectangular grooves spaced equidistantly in the circumferential direction by forming a plurality of lateral grooves 23, 24, 25 equidistant in the circumferential direction with two pairs of main grooves 21, 22 in the tread surface 20. This tire defines inner, middle, and outer blocks 26, 27, and 28, and has the inner block 26 and the middle and outer blocks 27, 28 shifted in the circumferential direction by 1/2 pitch. The test tire 1 is a tire in which a step region 29 is formed in the outer main groove 22 of the comparative tire 1, and each step region 29 is disposed at a position where the main groove 22 intersects the lateral grooves 24 and 25. That is, the rectangular lower portion 30 arranged near the kick-out end 35 of the block and the adjacent lower portions 30 are connected to each other, and the radially outer end surface 31 is intermediate with the radially outer end surface 32 of the lower portion 30. And a high portion 34 located between the outer block 27 and the sectional contour 33 of the outer block 27. As a result, each step region 29 extends continuously in the circumferential direction. In this test tire 1, the distance b between the radial outer end face 32 of the lower portion 30 and the middle and the cross-sectional contour line 33 of the outer blocks 27 and 28 is 2 mm, and the distance b between the radial outer end face 31 of the higher portion 34 and the middle. The distance c between the outer blocks 27 and 28 and the step contour 33 is 1 mm. In this way, each step region 29 is configured by alternately arranging the lower portion 30 and the higher portion 34 in the circumferential direction, and the lower portion 30 is disposed near the kick-out end 35 of the middle and outer blocks 27 and 28. The reason is that the shear force in the braking direction near the kicking end 35 is set to a large value,
This is to effectively prevent wear near the kick-out end 35 of the middle and outer blocks 27 and 28. The test tire 2 is substantially the same as the test tire 1, except that the distance between the radially outer end face of each step region and the cross-sectional contour of the middle and outer blocks is constant in the circumferential direction (1 mm). The only difference is that Here, the size of each tire described above was 185SR14, and the rim used was 5.5JJ-14. After filling each tire with an internal pressure of 1.7 kg / cm ² and mounting the tires on the front wheels of an FR passenger car with two passengers, the ratio between the highway and the ordinary road is 7: 3. The road (entire pavement) was traveled 40,000 km, and the amount of wear on the tread at the end of traveling was measured. When the measurement results are indexed and shown as wear resistance (the larger the index value, the better the wear resistance), the comparative tire has 100, the test tire 1 has 108,
In the test tire 2, it was 104, and in the test tire 3, it was 111. Thus, the test tires embodying the present invention have improved wear resistance. Here, the index 100 is 3.2 mm
It is. At the end of the running, the minimum abrasion amount near the stepping side of the middle and outer blocks and the maximum abrasion amount near the kick-out end were measured, and these measured values were indexed to determine uneven wear resistance. Here, the larger the index value, the better the uneven wear resistance. The comparative tire is 100, the test tire 1 is 123, the test tire 2 is 118,
The value was 125 in Test tire 3. Thus, the test tires embodying the present invention have improved uneven wear resistance,
In particular, it is preferable to provide a step region only near the kick-out end of each block. In addition, when the tire was run with the above-mentioned tires in a wet state, and the wet μ index of each tire was obtained, the index was 100 for the comparative tire and improved to 112 for the test tire 3, but 98 for the test tire 1 and 98 for the test tire. Tire 2 dropped to 94.

9 to 19 show another embodiment of the present invention. The second embodiment shown in FIGS. 9, 10, and 11 is almost the same as the first embodiment, but mainly includes three pairs of main grooves 42 and 4 in the tread surface 41.
The point where 3, 44 were formed, the blocks 45, 46 between the main grooves 42, 43 and between the main grooves 43, 44 were shifted by 1/2 pitch from each other, and the points were shaped like a rectangle, the blocks 47 between the main grooves 42 and Main groove 44
And a block 49 between the shoulder end 48 and the shoulder end 48. The third embodiment shown in FIGS. 12, 13, and 14 is almost the same as the test tire 1 except that the step region 51 is mainly composed of only a low portion and the radially outer end face 53 of the step region 51 is formed. High at the stepping end 54 and the kicking end 55,
The difference between them is that they are lowered in the middle, and that the inner blocks 56 are formed in a U-shape which is fitted to each other. Fifteenth, one
The fourth embodiment shown in FIGS. 6 and 17 is substantially the same as the test tire 1 except that the radially outer end face 62 of the stepped area 61 is wavy like a saw blade, that is, the middle and outer sides. The difference between the steps 63 and 64 is that the stepped area 61 near the kick-out end 65 is the highest, and the stepped area 66 is lowered as approaching the stepped end 66.In the initial stage of wear, only the highest part of the stepped area 61 is grounded, As the wear progresses, the contact area of the step region 61 is increased. In this way, uneven wear, such as rib punch, which occurs in the block in the middle to late stages of wear can be prevented. The fifth shown in FIGS. 18 and 19
The embodiment is substantially the same as the test tire 2 except that the intermediate block 75 is arranged to be shifted in the circumferential direction by 1/2 pitch with respect to the outer block 76, and the step region 77 is bent in a zigzag shape, and Bent part in the middle, outer block 75,
The difference is that it is close to the kicking end 78 of 76. When a part of the step region 77 is arranged close to the kick-out end 78 of each of the blocks 75 and 76 in this way, the influence on the kick-out end 78 of the step region 77 increases, and the wear near the kick-out end 78 is reduced. It can be effectively prevented.

Effects of the Invention As described above, according to the present invention, heel and toe wear of a block defined on a road surface can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a developed view of a tread showing a first embodiment of the present invention, FIG. 2 is a meridional cross-sectional view thereof, FIG. 3 is a cross-sectional view taken along a line I-I of FIG. 1, and FIG. FIG. 5 is a developed view showing a tread surface of the comparative tire, FIG. 5 is a meridional sectional view thereof, FIG. 6 is a developed view showing a tread surface of the test tire 1 used for the test, FIG. 7 is a meridian sectional view thereof, and FIG. 6 is a sectional view taken along the line II-II of FIG. 6, FIG. 9 is a developed view of the tread showing the second embodiment of the present invention, FIG. 10 is a meridional sectional view thereof, and FIG. 11 is III-III of FIG. FIG. 12 is a developed view of a tread showing a third embodiment of the present invention, FIG. 13 is a meridional sectional view thereof, and FIG.
FIG. 15 is a development view of a tread showing a fourth embodiment of the present invention, FIG. 16 is a meridional section thereof, and FIG.
FIG. 18 is a sectional view taken along the line VV of FIG. 18, FIG. 18 is a developed view of the tread showing the fifth embodiment of the present invention, and FIG. 19 is a meridian sectional view thereof. 1 ... Pneumatic tire, 2 ... Tread surface 7 ... Block, 8 ... Wide groove 9 ... Step region, 9a ... Radial outer end surface 10 ... Cross-sectional contour line, 17 ... Kick-out end

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-1-95909 (JP, A) JP-A-1-95911 (JP, A) JP-A-63-106110 (JP, A) JP-A-2- 20407 (JP, A) JP-A-58-4605 (JP, A) JP-A-63-162380 (JP, A) JP-A-62-181904 (JP, A) Actually open Hei 1-1147107 (JP, U)

Claims (1)

(57) [Claims] 1. A pneumatic tire in which a plurality of blocks are defined by forming a plurality of continuous wide main grooves extending in a circumferential direction on a tread surface and a plurality of wide horizontal grooves intersecting the main grooves. In the main groove near the kick-out end, the radial outer end face is located radially inward from the cross-sectional contour of the block, and the step area where the radial outer end face contacts the road surface when reaching the tread contact area. A pneumatic tire, wherein the stepped region is brought into sliding contact with a road surface to function as an uneven wear sacrifice portion during running.