JP4518639B2 - Pneumatic tire - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pneumatic tire, and more particularly to a pneumatic tire capable of improving drainage performance and maintaining good performance on an icy and snowy road surface over a long period of time.
[0002]
[Prior art and problems to be solved by the invention]
In order to improve drainage performance, as shown in FIG. 9, a pneumatic tire including a tread having a block with chamfered corners is known. In such a pneumatic tire, the reduction rate of the groove volume between the blocks due to wear is much larger than that in the case of a pneumatic tire having blocks whose corners are not chamfered.
[0003]
By the way, the volume of the groove greatly affects the on-snow performance of the tire, and the larger the groove volume, the better the performance on snow. The initial performance on the snow of the tire having the block shown in FIG. 9 is better than that of the tire whose corners are not chamfered. However, as described above, the decrease rate of the groove volume due to wear is large. The rate of decline is significantly large.
[0004]
Since the snow and snow road surface tire is required to maintain a certain level of performance for a certain period of time, a pneumatic tire having a block as shown in FIG. 9 should be used as a snow and snow road surface tire, no matter how good the initial snow performance is. I can't.
[0005]
The present invention has been made in view of the above facts, and an object of the present invention is to provide a pneumatic tire capable of suppressing a decrease in performance on snow and a decrease in performance on ice and improving drainage performance.
[0006]
[Means for Solving the Problems]
The present invention comprises a tread having a plurality of blocks chamfered so that at least a part of the corner is gradually lowered toward the apex of the corner, and the chamfered corner includes the corner. Provided is a pneumatic tire in which a sipe extending substantially parallel to the edge of the chamfered portion of the upper surface of the block is formed from one block end surface forming the corner toward the other block end surface forming the corner. To do.
[0007]
In the pneumatic tire of the present invention, when a part of the chamfered corner portion comes into contact with the road surface due to wear, the sipe formed on the chamfered corner portion comes into contact with the road surface. When the sipe is opened by grounding, snow enters the sipe and can grip the snow, so that a decrease in performance on snow due to a decrease in groove volume can be offset.
[0008]
Further, when a part of the chamfered corner portion comes into contact with the road surface due to wear, not only the volume of the groove is reduced due to the wear, but also the area of the tread surface (surface contacting the road surface of the tire) is increased. The area of the tread is related to the performance of the tire on ice, and the larger the area of the tread, the better the performance on ice. Accordingly, a decrease in performance on ice due to deterioration of the tread rubber can be suppressed by increasing the tread area. Furthermore, the sipe that has come into contact with the road surface due to wear cuts the water film on the frozen road surface to bring the block into contact with the road surface. As a result, a frictional force and a force for gripping the road surface can be obtained, and a drop in performance on ice can be prevented.
[0009]
The number of sipes formed at the chamfered corner may be at least one, but a plurality is preferred. As the degree of wear progresses, the volume of the groove decreases. However, when there are multiple sipes, the number of sipes that effectively act on the snowy and snowy road surface also increases. It is maintained for a longer period of time.
[0010]
The pneumatic tire of the present invention also has good drainage performance, which is an effect obtained by chamfering corners.
[0011]
Sipes can also be formed on portions other than the chamfered corners of the plurality of blocks, and in this case, the height of the lower end of the sipe formed on the portion other than the chamfered corners (the inner end in the tire radial direction) The height is preferably the same as the height of the lower end of the sipe formed at the corner. If it does in this way, the sipe formed in the chamfered corner | angular part can work | work effectively until the last stage of wear.
[0012]
The tread can have an inclined groove that is inclined with respect to the tire circumferential direction. In this case, the angle between the inclined groove and the tire circumferential direction is preferably more than 45 °. In this way, many edge components effective in the tire circumferential direction when traveling on a snowy road surface, in other words, effective in driving and braking can be obtained.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the pneumatic tire of the present embodiment will be described in detail.
[0014]
FIG. 1 shows a part of the tread of the pneumatic tire of the present embodiment. As shown in this figure, a plurality of main grooves 12 extending along the tire circumferential direction are formed at equal intervals in the tread 10 of the pneumatic tire of the present embodiment. Further, a V-shaped inclined groove 14 extending from one end of the tread to the other end is formed in the tread 10, and a plurality of blocks 16 are partitioned by the main groove 12 and the inclined groove 14.
[0015]
This pneumatic tire is a directional tire in which a rotation direction (arrow R direction) when the pneumatic tire is attached to a vehicle is designated. In each block 16, the tire equatorial plane CL side and the main groove 12 The corner 18 (the lower right corner in the block 16A in FIG. 1 and the lower left corner in the block 16B) having an acute angle formed with the inclined groove 14 is grounded first.
[0016]
As shown in FIGS. 2 and 3, this corner 18 is chamfered, its surface gradually decreases toward its apex 18A, and the top surface 20 of the block 16 (16B in FIGS. 2 and 3). The edge 20A of the chamfered portion depicts a loose curve. Further, the edges of the chamfered portions of the end faces 22 and 24 of the block 16 (only the edge 22A is shown in FIG. 2) also draw a loose curve.
[0017]
The block 16 is formed with a plurality of sipes 26 parallel to the end portions along the inclined grooves 14. Further, a plurality of sipes 28 and 30 are also formed in the corner portion 18.
[0018]
The lower end 26A of the sipe 26, the lower end 28A of the sipe 28, and the lower end 30A of the sipe 30 are located at the same height.
[0019]
As shown in FIGS. 4 and 5, when the pneumatic tire provided with such a block 16 is worn and a part of the corner 18 comes into contact with the road surface, the sipes 28 and 30 formed in the corner 18. Among them, the sipe 28 farthest from the vertex 18A comes into contact with the road surface. For this reason, the number of edge components (parts on both sides of the sipe of the block 16) increases, and it becomes easy to cut the water film on the frozen road surface. Further, even if the depth of the sipe 26 is reduced due to wear and the drainage effect of the sipe 26 is lowered, the drainage effect of the sipe 28 is newly obtained. For this reason, the fall of the performance at the time of drive | working on the slippery frozen road surface is prevented. Furthermore, a decrease in performance on ice is also suppressed by increasing the tread area. In addition, since snow enters not only the sipe 26 but also the sipe 28, a decrease in performance when traveling on a snowy road surface is prevented.
[0020]
As wear further progresses, the volume of the groove further decreases, but the effect of the sipe 30 is newly obtained. For this reason, in this Embodiment, the performance at the time of favorable icy and snowy road surface maintenance is maintained over a long term.
[0021]
In addition, the pneumatic tire of the present embodiment also has good drainage performance obtained by chamfering the corner 18 that contacts the first part of the block.
[0022]
In order to verify the effect of the present embodiment, the speed at which hydroplaning occurs and the traction performance during running on an icy road surface or a snowy road surface were evaluated. The tires of the present embodiment and comparative example having a size of 205 / 55R16 were assembled to a rim having a width of 6.5 J × 16, and the tire was filled with air so that the internal pressure was 200 kPa.
[0023]
Hydroplaning speed is achieved by mounting tires filled with air on the four wheels of the test vehicle, applying a load of 588 N with the driver, and gradually increasing the speed on a road surface with a depth of 10 mm, causing the wheels to idle. It was determined by measuring the speed at which it became. The results are shown in FIG.
[0024]
In FIG. 6, A is the result of the pneumatic tire of the present embodiment in which the sipe is formed at the chamfered corner, and B is the air of Comparative Example 1 in which the sipe is not formed at the chamfered corner. It is a result of an entering tire, and C is a result of the pneumatic tire of Comparative Example 2 in which corners are not chamfered. The angle between the inclined groove and the tire circumferential direction was 60 °. From FIG. 6, the pneumatic tire of the present embodiment with the corners chamfered and the pneumatic tire of Comparative Example 1 cause hydroplaning as compared with the pneumatic tire of Comparative Example 2 with no corners chamfered. It can be seen that it has a high speed and excellent drainage performance.
[0025]
In addition, the traction performance is that the pneumatic tire is mounted on four test wheels, the driver and the load of 588N are applied, the road is covered with snow or the road is frozen, and the slip rate is 0 to 100%. The integral value of the generated axial force was obtained, and the change of the integral value with respect to the wear amount was examined. The results are shown in FIGS. In the figure, ◯ is the result of the pneumatic tire of the present embodiment, Δ is the result of the pneumatic tire of Comparative Example 1, and x is the result of the pneumatic tire of Comparative Example 2.
[0026]
In FIG. 7, that of the pneumatic tire of Comparative Example 2 is better than that of Comparative Example 1 and the initial on-ice performance of the pneumatic tire of the present embodiment. This is because the area is larger than the initial tread area of the pneumatic tire of Comparative Example 1 and the present embodiment. Although the performance on ice of these pneumatic tires decreases due to deterioration of the tread rubber, the rate of decrease in performance on ice of the pneumatic tires of Comparative Example 1 and the present embodiment is smaller than that of the pneumatic tire of Comparative Example 2. This is because in the pneumatic tire of Comparative Example 1 and the present embodiment, the area of the tread surface increases due to wear. Moreover, in the pneumatic tire of the present embodiment, when the sipe formed at the chamfered corner portion comes into contact with the road surface, the decrease in performance on ice is further suppressed.
[0027]
In FIG. 8, that of the pneumatic tire of the comparative example 1 and the pneumatic tire of the present embodiment is better than that of the pneumatic tire of the comparative example 2 than the initial snow performance of the pneumatic tire of the comparative example 2. This is because the comparative example 1 and the pneumatic tire of the present embodiment are larger than the volume. The on-snow performance of these pneumatic tires decreases as the groove volume decreases due to wear, but the decrease rate of the on-snow performance of the pneumatic tire of Comparative Example 1 with a large decrease rate of the groove volume is that of Comparative Example 2. Greater than that of a tire. In the pneumatic tire of the present embodiment, the initial rate of decrease is large, but when the sipe formed at the chamfered corner comes into contact with the road surface, the decrease in performance on snow is suppressed.
[0028]
As described above, in the present embodiment, it is understood that a constant ice / snow performance is maintained for a long time.
[0029]
In the above embodiment, the planar shape of the block is a parallelogram, but it may be a rhombus, other quadrangles, or a polygon other than a quadrangle.
[0030]
Furthermore, in the above embodiment, the planar shape of the sipes 28 and 30 is zigzag, but it may be corrugated, linear, or curved.
[0031]
Further, the number of sipes formed in the corner 18 may be 1 or an integer of 3 or more, and is appropriately determined according to the area of the corner 18 when viewed from above.
[0032]
Furthermore, the sipes 28 and 30 formed in the corner 18 may be disposed in the same direction as the sipes 26 or in different directions. Further, the distance between the sipes 28 and 30 may be the same as or different from the distance between the sipes 26.
[0033]
Moreover, the height of the lower end of the sipe formed in the corner | angular part 18 and the height of the lower end of the other sipe do not need to be the same.
[0034]
【The invention's effect】
According to the present invention, since the sipe is formed at the chamfered corner, it is possible to suppress a decrease in performance when traveling on an icy and snowy road surface and to improve drainage performance.
[Brief description of the drawings]
FIG. 1 is a plan view of a part of a tread of a pneumatic tire according to an embodiment.
2 is an enlarged perspective view of a block of the tread in FIG. 1. FIG.
FIG. 3 is a plan view of the block of FIG. 2;
FIG. 4 is a perspective view when the block of FIG. 2 is worn.
FIG. 5 is a plan view of the block of FIG. 4;
FIG. 6 is a graph showing the speed at which hydroplaning occurs.
FIG. 7 is a graph showing the relationship between the amount of wear and the traction performance when traveling on an icy road.
FIG. 8 is a graph showing the relationship between the amount of wear and the traction performance when running on a snowy road surface.
FIG. 9 is a perspective view showing a conventional block.
[Explanation of symbols]
10 tread 16 block 18 corner 18A vertex 28 sipe 30 sipe

Claims (4)

A tread having a plurality of blocks chamfered so that at least a part of the corner gradually lowers its surface toward the apex of the corner;
The chamfered corner extends substantially parallel to the edge of the chamfered portion of the upper surface of the block from one block end surface forming the corner toward the other block end surface forming the corner. A pneumatic tire with sipe formed.   The pneumatic tire according to claim 1, wherein a plurality of sipes are formed at the chamfered corners.   A sipe is formed at a portion other than the chamfered corner portion of the plurality of blocks, and a height of a lower end of the sipe formed at a portion other than the chamfered corner portion is a lower end of the sipe formed at the corner portion. The pneumatic tire according to claim 1, wherein the pneumatic tire is the same as the height of the pneumatic tire.   The pneumatic tire according to any one of claims 1 to 3, wherein the tread has an inclined groove inclined with respect to a tire circumferential direction, and an angle between the inclined groove and the tire circumferential direction exceeds 45 °.

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