JPH04197809A - Block of pneumatic radial tire - Google Patents

Abstract

PURPOSE:To enhance the life of a tire and performance of the tire on ice by forming blocks from upper and lower sides, and increasing the rigidity of a lower block portion located on the inside of the radial direction of the tire relative to the rigidity of the upper block portion, and also making proper the configuration and size of each block and those of a sipe. CONSTITUTION:A plurality of blocks 10 are defined by a plurality of main grooves 12 and a plurality of lateral grooves 14. In this case, the width W(mm) of each block is set at a relation of 0.13<=W<=0.2T wherein T represents the width of the tread of the tire. Each block is provided with a sipe 16 and the width (d) (mm) of the sipe is set at 0.5<=d<=2.0 and also the width by which the bottom portion of the sipe is enlarged is set within the range of 1.5 to 3.0(mm). The depth h2 of the sipe 16 is set at a relation of 0.5H<=h2<=1.0H wherein H represents the depth of the main groove 12. The distance h3 from a tire tread surface 18 to the lower end of an upper block 20 is 0.5 to 0.7 times the depth h2 of the sipe. In addition, the upper and lower blockes 20, 22 have their respective angles theta1, theta2 and length lU, lD specified.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a block of a pneumatic radial tire that is disposed on the tread portion of the tire and improves on-ice performance and running life.

(Prior art) The so-called block pattern, in which multiple blocks are arranged on the tread of a tire, has excellent driving force and braking force, and is therefore preferred for tires that are often driven on icy and snowy roads or unpaved roads. In addition, increasing the edge component of the block is advantageous in further improving running performance on such road surfaces. It has been attempted to increase the edge component by reducing the block geometry and increasing their number in the overall tire.

(Problem to be Solved by the Invention) However, in a block that receives forces in the driving and braking directions during tire transfer, the sipes disposed there are subjected to repeated opening and closing movements, resulting in distortion at the bottom of the block. There was a problem in that it was easy to concentrate, and eventually a crank was formed at the bottom, reducing the life of the tire. Also,
Blocks with a large number of sipes, or even blocks with relatively small dimensions, have the problem of excessively reducing the rigidity of the block, making it impossible to achieve the desired on-ice performance. be. This problem is particularly noticeable in heavy-duty pneumatic radial tires that have relatively high ground pressure and are used in buses, trunks, etc., and a solution has been sought.

The present invention was made in view of such problems,
The object is to provide a pneumatic radial tire block that can improve tire life and performance on ice.

(Means for Achieving the Object) In order to achieve this object, the blocks of the present invention are blocks arranged spaced apart from each other in the circumferential direction of the tire and forming at least one row of blocks on the tire tread. , these blocks include an upper block portion located on the outside in the tire radial direction and a lower block portion located on the inside in the tire radial direction, and when the tire tread width is T (mm), the block width W ( -m) from 0.13 to 0.
Select from within the range of 2T, and each block has a sipe width d of 0.5 to 2.0 (mm) when the bottom is enlarged, and a sipe width of at least 1.5 to 3.0 (+n+a). The groove depth of the main groove, which is divided in the tire circumferential direction by a single sipe and extends approximately in the tire circumferential direction and partitions the block rows, is H(
mm), the distance from the tire tread to the bottom of the sipe bottom is h20.5H to 1.0H, and the distance from the tire tread to the lower block part, (llII
ll) is 0.5h2 to 0.7hZ, and the angle θ1 formed by the side wall of the upper block portion extending in the tire width direction with the normal plane in the tire width direction erected on the tire tread.
is 0 to 8 (°), and the angle θ2 between the side wall of the lower block portion extending in the tire width direction and the normal plane is 4 to 8 (°).
15('), while the length Iu (I1m+) from the edge in the tire width direction of the upper block part to the sipe is 0.9
tlz < lu < 1.4hz, and the length I from the edge of the lower block part in the tire width direction to the sipe
n (mm), lI, ±kh, + (D-d)/2, (
However, k = 0.0874 to 0.365').

(Function) Since the block is divided in the tire circumferential direction by sipes,
The edge component of the block, which is effective for on-ice performance, can be increased.

Moreover, the block is composed of an upper block portion and a lower block portion, and the lower block portion located on the inner side in the radial direction of the tire has greater rigidity than that of the upper block portion located on the outer side in the tire radial direction. With,
Since the shapes and dimensions of these block portions and sipes are made appropriate, the deformation of the lower block portion is smaller than that of the upper block portion. Therefore, in combination with expanding the sipe bottom, distortion at the sipe bottom can be reduced and tire life can be improved.

(Example) Hereinafter, an example to which the present invention is applied will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing a preferred embodiment of a block to which the present invention is applied, in which a plurality of blocks 10 forming a block row spaced apart from each other in the tire circumferential direction are mutually spaced in the tire width direction. A plurality of main grooves 12 and -1 which are spaced apart and extend substantially in the tire circumferential direction are partitioned by a plurality of lateral grooves 14 which extend in the tire width direction and cooperate with the main grooves, and are separated in the tire width direction. The dimension, that is, the width W (mm) of the block is 0.13T≦W≦, where T is the tread width of the tire.
It is assumed that the relationship 0.2T is satisfied.

This means that when the length of the block 10 in the tire width direction, that is, the block width W becomes smaller than 0.13 times the tread width T,
Since the rigidity of the block 10 as a whole becomes too small, it is difficult to expect the edge effect of the block, and if the block width W exceeds 0.2 T, the ground pressure of each block decreases, which also makes it difficult to achieve the desired edge effect. This is because it cannot be obtained.

The on-ice performance of the tire is improved by providing each block with a sipe 16 to divide it in the tire circumferential direction and increasing the edge component of the block. In addition, Sipe 1
If the sipe width d of 6 is smaller than 0.5 m, manufacturing defects are likely to occur, and if it exceeds 2.0 mm, the rigidity of the block portion divided by the sipes will be too low. It is difficult to expect an edge effect due to the edges, and therefore the sipe width d (mm) of sipe 16
is selected from the range of 0.5≦d≦2.0.

Furthermore, the bottom of the sipe 16 is enlarged relative to the sipe width d in order to reduce distortion to the bottom of the sipe due to forces that repeatedly act in the driving direction and braking direction as the tire is rotated, and specifically, The length of the bottom of the sipe 16 in the cross section in the tire circumferential direction, that is, the expanded width, is set to 1.5 to 3.
Set to 0 (mm).

This is because if the expansion width is smaller than 1.5 mm, it will not be able to sufficiently buffer the distortion at the bottom of the sipe 16, and if it exceeds 3.0 llIn, the movement of the bottom of the sipe will increase. This is because the bottom surface of the sipe becomes sagging, and the distortion at the bottom of the sipe cannot be buffered. Incidentally, in this embodiment, the sipe 16 is formed so that the cross section of the bottom of the sipe in the tire circumferential direction is approximately semicircular, but the shape is not limited to this. It may also be an enlarged version.

Further, the depth of the sipe 16, that is, the distance h2 from the tire tread surface 18 to the bottom surface of the sipe is 0.5H when the depth of the main groove 12 that substantially partitions the block 10 in the tire width direction is H. It is assumed that the relationship ≦h2≦1.0H is satisfied. This means that the sipe depth h2 is 50% of the main groove depth H.
If it is less than %, the sipes will be lost in a relatively short period of time, making it difficult to expect the effect of sipes, and
This is because if the depth exceeds 100% of the main groove depth, the deformation of the block becomes large and the durability and uneven wear resistance of the tire are impaired. In addition, the groove depth of the horizontal groove 14.

shall be 70% to 100% of the groove depth H of the main groove 12.

By the way, as is clear from FIG. 1, the block 10 has an upper block portion 20 that is located on the outside in the tire radial direction, that is, constitutes the tread surface, and an upper block portion 20 that is located on the inside in the tire radial direction and has a length in the tire circumferential direction. The tire has a lower block part 22 with a longer length, and the length of the lower block part 22 in the radial direction of the tire is longer than that of the upper block part 20 located on the tire tread surface.

As described above, by forming the block 10 into a two-tiered shape consisting of the upper and lower block parts, the rigidity of the lower block part 22 located on the inside in the tire radial direction can be made higher than that of the upper block part 20. I can,
The deformation of the upper block portion 20 located on the tread side is
As schematically shown in the figure, while maintaining the edge effect to the same extent as that of the conventional single-stage block 24, the deformation of the lower block portion 22 is made small and the sipe 1 is
6 to suppress expansion in the tire circumferential direction. ), the distortion at the bottom can be made small. Therefore, in combination with expanding the sipe bottom, the occurrence of cracks at the sipe bottom can be sufficiently suppressed. In addition,
The upper block portion and the lower block portion shall be smoothly continuous to reduce concentration of stress on the continuous portion.

Furthermore, in the block of the present invention, the side wall 20a of the upper pro-7 portion 20 extending in the tire width direction and the plane extending in the tire width direction erected on the tire tread portion 18, that is, the normal plane. The angle θ1 (°) is selected so as to satisfy the relationship O≦θ1≦8. This means that when θ is smaller than Oo, the upper pro.

Since the upper block portion expands toward the outside in the tire radial direction, uneven wear is likely to occur in the block portion, and if θ1 exceeds 8°, the rigidity of the upper block portion 20 will decrease. This is because if the height becomes too high, the running performance on snow deteriorates, that is, the rigidity of the block becomes too high, and the edge effect due to the sipes decreases.

On the other hand, the angle θ2 (°) between the side wall portion 22a of the lower block portion 22 and the normal plane is 4≦θ2≦1.
Select from within the range of 5. This means that the angle θ2 is 4°
If it is smaller, it will be difficult to suppress the deformation of the block portion in the tire circumferential direction, and the distortion at the bottom of the sipe will increase,
Furthermore, when the angle θ2 exceeds 15°, the distance between blocks adjacent to each other in the tire circumferential direction increases, the sum of the edge components of each block provided on the tire tread decreases, and the tire on-ice performance decreases. This is because it decreases.

On the other hand, as shown in FIG. 1, the distance h3 from the tire tread surface 18 to the lower end of the upper block portion 20 is set to 0.5 to 0.7 times the sipe depth h2. This is because the distance h3 is smaller than 0.5 times the sipe depth h2 (if the distance h3 is smaller than 0.5 times the sipe depth h2, the rigidity of the block becomes too high and it is difficult to expect an edge effect due to the sipes, and if the distance h3 exceeds 0.7 times the sipe depth h2) This is because the deformation of the block becomes large and it is difficult to suppress the occurrence of distortion at the bottom of the sipe 16. In this embodiment, the sipe 16 extends substantially in the width direction of the tire. As shown in FIG. 3, the angle β (°) between the line segment extending in the tire width direction and the extending direction of the sipe 16 may satisfy the relationship 0≦β≦45.

That is, if the angle β exceeds 45°, the edge effect due to the edge of the block defined by the sipes will be reduced and the on-ice performance will be impaired.

Furthermore, the length lu from the tire width direction edge of the upper block portion 20 of the block to the sipe 16 is defined as the sipe depth h2.
By making it approximately 0.9 to 1.4 times the length lu
It is possible to avoid the deterioration in on-ice performance that becomes noticeable when the sipe depth exceeds 140% of the sipe depth h2, and to avoid the deterioration in uneven wear resistance that becomes a problem when the sipe depth becomes shorter than 90% of the sipe depth h2. can.

On the other hand, the length 1D (mm) from the edge of the lower block portion 22 in the tire width direction, that is, the edge located on the upper block portion side, to the sipe 16 is selected so as to satisfy the following formula.

In = 10 +k h2 + (D a) 2
m However, 0.0874< k <0.365 where,
k is a parameter determined by the usage conditions, and within the range of k, k is thicker (
, k is set small under running conditions with low traction.

When the length 1° becomes larger than the value given by equation (1), the difference between the length of the lower block portion 22 in the tire circumferential direction and that of the upper block portion 20 becomes large, so that the wear of the tire tread becomes large. This is because as the length progresses, the rigidity of the block increases, making it difficult to expect an edge effect from the block and sipe, and the performance on ice after the middle stage of wear deteriorates.If the length ID becomes smaller than the value given in (1) 2, the upper This is because as the difference between the block portion 20 and the lower block portion 22 becomes smaller, the rigidity of the block 10 decreases and becomes easily deformed, making it impossible to sufficiently alleviate distortion at the bottom of the sipe.

Another embodiment shown in FIG. 4 has almost the same configuration as the embodiment shown in FIG. 1, except that the sipes 16 extend in a zigzag shape in the width direction of the tire. Since the block shown in the example has sipes 16 extending in a zigzag pattern, it has not only an edge component in the tire width direction but also an edge component in the tire circumferential direction, so there is no cracking at the bottom of the sipe. It has excellent on-ice performance and even better handling stability.

Further, another embodiment shown in FIG. 5 has almost the same configuration as the embodiment shown in FIG. 1 except that two sipes are formed, and the tire width of each of the upper block portions 20 is The distance 1o and ID from the directional end to each of the corresponding sipes 16a and 16b are 1,=1.18h2, and satisfy the relationship shown in equation (1).

According to this embodiment, the block has two sipes 16a,
16b, the edge component of the block increases, resulting in better on-ice performance. Of course, the number of sipes can be increased or decreased as appropriate depending on the specifications of the block.

Further, in the embodiment shown in FIG. 6, the edge of the upper block portion 20 in the tire width direction is chamfered, and the other configurations are almost the same as the embodiment shown in FIG. In this way, by chamfering the edges of the upper block portion 20 in the tire width direction, it is possible to suppress the occurrence of localized uneven wear at the edges of the blocks at the initial stage of tire specifications, thereby improving the tire life. It happens.

In order to investigate the tire life and on-ice performance of such blocks, a comparative test was conducted using a test tire equipped with a block according to the present invention and comparative tires 1 and 2 equipped with a known comparative block shown in FIG. I did it. Table 1 shows the specifications of each tire block.

Table 1 The dimensions of the tires used in the comparative test are 10.0OR2014
PR, and 100% JIS regular internal pressure was applied. Here, tire life is determined by visually inspecting the presence or absence of cracks at the bottom of the sipe after 30,000 miles of tire life on an actual vehicle, and performance on ice is measured at a constant speed of 20 km/h through a waterway with an ice temperature of -2°C. This is an index evaluation of the distance it takes for a vehicle to brake and come to a stop.The smaller the index, the better the ice performance. The comparison results are shown in Table 2.

As is clear from Table 2, according to the block of the present invention, on-ice performance and tire life are improved.

(Effects of the Invention) Thus, according to the present invention, it is possible to provide a block that can improve on-ice performance and also extend tire life compared to conventional blocks.

[Brief explanation of the drawing]

FIG. 1 is a perspective view schematically showing the block of the present invention. FIGS. 2(a) and (b) are explanatory diagrams showing the difference in deformation behavior between the conventional block and the block shown in FIG. 3-6
The figures are perspective views showing other embodiments of the present invention, and FIG. 7 is a schematic diagram showing other blocks subjected to comparative tests. 10-Block 12-Main groove 14-Transverse groove 16-Sipe 18-Tread section
20 - Upper block part 22 - Lower block part Fig. 1 22b - One move, one hair Fig. 2 (a) (b) Diagonal Fig. 3 @ Fig. 4 Fig. 5 Fig. 6 Fig. 7

Claims (1)

[Scope of Claims] 1. Blocks arranged spaced apart from each other in the tire circumferential direction forming at least one block row on the tire tread, which blocks are arranged in an upper portion located on the outside in the tire radial direction. It consists of a block part and a lower block part located on the inside in the tire radial direction, and when the tire tread width is T (mm), the block width W (mm) is W = 0.13 to 0.2T. The sipe width d of each block is 0.5 to 0.5.
2.0 (mm), and the enlarged width D at the bottom is 1.5 to 3.0 (m).
When the groove depth of the main groove extending substantially in the tire circumferential direction that divides the block rows into blocks in the tire circumferential direction by at least one sipe (m) is H (mm), the tire tread surface area The distance h_2 from the tire tread to the bottom of the sipe is 0.5H to 1.0H, the distance h_3 (mm) from the tire tread to the lower end of the upper block part is 0.5h_2 to 0.7h_2, and the tire width direction of the upper block part is The angle θ_ between the side wall extending on the tire tread surface and the normal plane in the tire width direction
1 is 0 to 8 (°), and the angle θ_2 formed by the side wall extending in the tire width direction of the lower block portion with the normal plane is 4 to 15 (°), provided that θ_1≦θ_2, while the upper block The length 1_U (mm) from the edge of the tire width direction to the sipe is 0.9h_2≦1_U<1.4h_2
In addition, the length 1_D (mm) from the tire width direction edge of the lower block portion to the sipe is 1_D=1_U+kh_2+(D-d)/2, where k=0.0874 to 0.365. Features a pneumatic radial tire block.