JPH03136910A - Pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE:To improve the performance of a heavy load pneumatic tire for a bus or the like on an iced or snow-covered road by applying the constitution wherein a ratio of the widthwise edge component of a block to the peripheral edge component thereof with each sheeting is specified with a center block row and an adjacent block row respectively, and a ratio of each widthwise block projection length to a block surface area is further specified. CONSTITUTION:A center block row 4, an adjacent block row 6 and a shoulder block row 8 are respectively formed with main grooves 2 and sub-grooves 3. Also, sheetings 5, 7 and 9 are formed in the blocks 4a, 6a and 8a of each block row. Furthermore, a ratio alpha/beta of the widthwise edge components alpha of respective blocks 4a, 6a and 8a to the peripheral edge components beta thereof is taken as equal to or larger than 1.5 in the center block row 4. Also, alpha/beta is taken as 0.7 <= alpha/beta <= 1.0 in the block row 6, and as 0.5 <= alpha/beta <= 0.7 in the block row 8. In addition, a ratio gamma of widthwise block projection length to block surface area is taken between 0.05 times and 0.2 times of tread ground plane width (a). According to the aforesaid construction, a tire performance on an iced or snow-covered road can be improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the improvement of heavy-duty pneumatic tires applied to trucks, buses, etc., and provides particularly excellent ice and snow performance.

(Prior art) Conventional tires that are often used as snow tires for heavy-duty vehicles such as trucks and buses include, for example, °
Some tires have tread patterns as shown in FIGS. 6 and 7.

Here, the tire shown in FIG. 6 is provided with two circumferential main grooves 52 extending in a zigzag shape in the tire circumferential direction in the tread contact portion 51, and between these main grooves 14, which is also circumferential. A circumferential sub-groove 53 is provided which extends in parallel to the main grooves 52 in the direction, and between the sub-groove 53 and each main groove 52, the planar shape is approximately "<"-shaped. The blocks 54 that form the structure are aligned and partitioned mutually in the tire width direction, and the orientation of each of these blocks 54 located at intervals in the tire circumferential direction is opposite to that of the circumferentially adjacent blocks, and , on the outside of each of the circumferential main grooves 52, there are blocks 55 that are bent into an approximately "Lj" shape along each of the circumferential main grooves 52, and the further outside of these bending blocks 55 are bent in opposite directions. The tread pattern has a tread pattern formed by partitioning two lugs 56, each of which is bent in a substantially "H" shape in the direction.

Such a tire has an aspect ratio of 100% and a negative ratio of 5.
It has been confirmed that when applied to a heavily loaded vehicle at 0%, it exhibits excellent on-snow traction performance under high ground pressure.

Further, the tire shown in FIG. 7 has two circumferential main grooves 57, each of which has a chamfered shape, between the two circumferential main grooves 57 extending in a zigzag shape in the tire circumferential direction. The bending blocks 58 are disposed so as to be inserted into each other in the width direction of the tire with a circumferential sub-groove 59 in between, and pairs of such blocks are provided at a predetermined interval in the circumferential direction of the tire, and A block 60, which is also approximately "J-shaped" and has a larger intersection angle than the above-mentioned bending block 58, is located on the outside of each circumferential main groove 57 and along each circumferential main groove 57. The tread pattern includes blocks 61 located further outside these blocks 60 and having a substantially rectangular shape.

This tire also has an aspect ratio of 100% and a negative ratio of 3.
At 5.6%, it is said to exhibit excellent on-snow traction performance.

(Problem to be Solved by the Invention) However, among such conventional tires, the former tire shown in FIG. 6 has a high negative rate;
In addition, in the case of the tire shown in Figure 7, the ground pressure is high because the tread width is narrow, and the braking performance on ice is extremely low.
Since the circumferential edge component is small, there has been a problem in that the structure cannot exhibit satisfactory structural slip resistance on ice and snow.

Therefore, for the purpose of improving on-ice performance, it has been proposed to drive spikes into the tread land area and to form sipes in the tread land area, such as in studless tires for passenger cars. However, although the former proposed technology of driving spikes can ensure high on-ice performance, it is unable to avoid the generation of dust, which is currently a major social problem, and it also causes the formation of sipes. According to the latter proposed technique, for example, 3 to 5 per block of -
This formed size has low ground pressure (2 to 3 kg/
cm2) For passenger car tires, ground pressure of 7 to 9 kg/cm can contribute extremely effectively to improving on-ice performance.
In heavy-duty tires that reach up to 100 lbs., another problem was that the block rigidity was reduced too much by such sipes, making it impossible to demonstrate not only the performance on ice but also the essential performance of the tire. .

This invention solves all of the problems of the prior art, and while ensuring sufficient traction performance on snow, it also improves braking performance on ice and structural slip resistance on ice and snow compared to conventional tires. The present invention provides a pneumatic tire for heavy loads with significantly improved performance.

(Means for Solving the Problems) The heavy-duty pneumatic tire of the present invention has four circumferential grooves continuous in the tire circumferential direction in the tread contact area, and a central block located at the center in the tire width direction. Each block in the row has an approximately flat polygonal profile that is long in the tire width direction, and each block in the block row located on each side of the central block row is shaped in the tire width direction. A block pattern tire having partially adjacent substantially step-like contours, wherein a block edge component α in the tire width direction of each block is
The ratio α/β to the tire circumferential block edge component β is set to 1.5 above α/β for each block in the center block row, and 0.7≦α/β≦ for each block in the block row adjacent to the center block row. 1.0 Shoulder block row blocks, 0.5≦α/β≦0.7, each block is provided with one or two sipes, and each block is projected in the tire width direction. The ratio T of the block surface area to the length is set in the range of 0, 05a < r < 0.2a with respect to the tread contact width a.

(Function) In the pneumatic tire of the present invention, each block of the central block row located at the center in the width direction of the tire has an approximately flat polygonal profile that is long in the width direction of the tire, and the block edge in the tire width direction By setting the ratio α/β of the component α to the tire circumferential block edge component β to 1.5 or more in each block of the central block row, the vehicle will always touch the ground when traveling straight, even if it is empty. Each of these blocks has a long block edge component in the width direction of the tire, which has a large effect on driving performance, resulting in improved braking and traction performance on ice and snow.

Here, if the block edge component ratio α/β is less than 1.5, the braking performance on ice and the traction performance on snow will decrease, and each block in the shoulder block row will have
By setting the similar block edge component ratio α/β to 0.5≦α/β≦0.7 and making the block edge component in the tire circumferential direction longer than the blocks in other block rows, the lateral direction of the tire is increased. When a force is applied, in other words, when a vehicle turns or tires skid, these blocks contact the ground particularly strongly, providing excellent structural slip resistance on ice and snow.

That is, when the block edge ratio α/β is less than 0.5,
If the width direction component becomes too short, braking performance and traction performance when a circumferential force is applied to the tire are forced to decrease significantly, and the ratio thereof becomes 0.
If it exceeds 7, the circumferential block direction component becomes too short, making it impossible to hope for an improvement in the structural slip resistance.

Furthermore, in this tire, each block in the block rows located on each side of the central block row has a substantially step-like profile that partially adjoins each other in the tire width direction, so that the block edge of the adjacent portion It is also possible to improve the structural slip resistance, and therefore, even if the number of circumferential grooves is set to four, which is relatively small, and a sufficient ridge area is secured, excellent structural slip resistance can still be achieved. performance.

And here, by setting the block edge component ratio α/β of each block to 0.7≦α/β≦1.0, the center block, which makes a particularly large contribution to straight-ahead running, and the corner block In addition, it has a moderate performance with the shoulder block that makes a particularly large contribution, that is,
It provides both braking and traction performance and structural slip resistance.

By the way, when the block edge component ratio α/β exceeds 1.0 orders of magnitude, the anti-slip performance of the structure on ice and snow deteriorates.

In addition, in the above, the ratio of the tire circumferential direction edge component (including block edges and edges of small blocks divided by sipes) to the unit length in the tire circumferential direction, which acts against tire lateral slip, is When it is 7 or more, the structural slip resistance is further improved.

Furthermore, in this invention, by providing one or two sizes in each block, the block edges of small blocks divided by sipes can be adjusted without reducing the rigidity of the block in relation to the block dimensions. It functions effectively against ice and snow, and when it tends to extend in the tire width direction, it improves braking and traction performance, and when it tends to extend in the tire circumferential direction, it improves durability. The structural sliding performance can be advantageously improved.

In other words, if the block does not have any sipes, the above-mentioned improvements in braking and traction performance or structural slip resistance cannot be expected, and if there are three or more sipes, the block rigidity decreases. Since the block is completely crushed, it is also impossible to expect any improvement in the above-mentioned performances.

Moreover, here, the ratio γ of the block surface area to the projected length in the tire width direction of each block is set to 0,05a < r <0.2a with respect to the tread contact width a, so that in relation to the sipes, This further improves the tire's frictional force on ice.

This means that when the ratio T, that is, the distance equivalent to the tire circumferential length of each block, is less than 0.05a, the tire cannot be used even when two sipes are formed, or even when only one sipe is formed. If the block rigidity in the circumferential direction decreases too much, or if the ratio T exceeds 0.2a, frictional melting of ice due to the block's length in the tire circumferential direction will progress, resulting in sipes. In addition to not being able to guarantee that the small blocks divided by
This is based on the fact that if the sipe spacing becomes too large, the frictional force on the ice will decrease significantly.

Thus, according to the present invention, by specifying the arrangement state of each block and the block edge component ratio, it is possible to ensure sufficient braking and traction performance on ice and snow as well as structural slip resistance performance. I can do it,
In addition, by specifying the relative dimensions of each block with respect to the tread contact width and the number of sipes formed in each block, based on their mutual and synergistic effects with the specified items above, in particular, on-ice traction and Braking performance can be further improved.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a tread pattern showing an embodiment of the present invention, and this tire has an aspect ratio of 100% and an aspect ratio of 33.3%.
, respectively.

Note that the internal structure of the tire is the same as that of a general heavy-duty radial tire, so illustration thereof is omitted here.

In this example, the tread contact portion 1 is provided with two circumferential main grooves 2 that are spaced apart from each other in the tire width direction and extend in a zigzag shape in the tire circumferential direction, and are located between the two circumferential grooves. In this case, two circumferential minor grooves 3 extending in a zigzag manner in the circumferential direction are provided at a predetermined interval, and the groove width of each circumferential major groove 2 is adjusted to a tread contact width a = 224 mm. 1
0.5 mm, and the groove width of each circumferential minor groove 3 is 5.5 mm.

A central block row 4 consisting of blocks 4a that are long in the tire width direction and have a substantially flat hexagonal profile is provided between the side circumferential minor grooves, and each block 4a of this block row 4 is shown in FIG. As shown in a), the ratio α4/β4 of the block edge component α4 in the tire width direction to the block edge component β in the tire circumferential direction is α4/β4≧1.5, and in addition, each block 4a is A single sipe 5 is formed at approximately the center in the circumferential direction of the tire and tends to extend in the width direction of the tire.

Further, between each circumferential main groove 2 and each circumferential sub-groove 3, a block row 6 is formed partially adjacent to each other in the width direction of the tire and consisting of blocks 6a each having a substantially step-like outline. , the ratio α6/β6 of the block edge component α6 in the tire width direction to the block edge component β6 in the tire circumferential direction, as shown in FIG.
is 0.7≦α6/β6≦1.0, and each of these blocks 6a also has a single step extending in the shape of a step, located approximately at the center in the circumferential direction of the tire. Sipe 7 is provided. Here, this sipe 7 has a component in the tire circumferential direction and a slightly larger component in the tire width direction.

Furthermore, between each circumferential main groove 2 and the tread ground contact end, a shoulder block row 8 consisting of blocks 8a having an irregularly shaped contour close to a rectangle is provided, and each of these blocks 8a is
As shown in FIG. 2(C), the ratio α8/β8 of the tire width direction block edge component αB to the tire circumferential direction block edge component β8 is 0.5≦α8/β8≦0.7, and Each block 8a is provided with two sipes 9 extending in a zigzag shape in the tire circumferential direction.

According to a general heavy-duty tire with a radial structure formed with a tread pattern as described above, the center block row 4 is long in the tire width direction, and the block edge component ratio α, /β is 1. Block 4a that is greater than or equal to .5
In particular, under the action of the block edge component extending in the widthwise direction of the tire, as described above, it functions to effectively improve braking performance and traction performance both on ice and on snow.

In addition, each block 6a of the block row 6 functions to improve the structural slip resistance by the block edges of the respective block portions located adjacent to each other in the tire width direction. By setting the component ratio α6/β6 to 0.7≦α6/β6≦1.0, a center block 4a that particularly greatly contributes to improving braking performance and traction performance;
It functions to provide intermediate performance between the shoulder block 8a and the shoulder block 8a, which particularly contributes significantly to improving structural slip resistance.

Furthermore, the block 8a of the shoulder block row 8 has a block edge component ratio α, /β8 of 0.5≦αS.
By setting /β8≦0.7, as described above, it functions to provide particularly excellent structural slip resistance.

In addition, each block 4a, 6a, 8a of each block row 4.6.8 is provided with a sipe 5°7 as described above.
．． 9, the sipe 5 can further improve the braking performance and traction performance due to the center block 4a, and the sipe 7 can further improve the braking performance and traction performance and the anti-strike performance due to the block 6a. In addition, the two sipes 9 each function to further improve the structural slip resistance of the shoulder block 8a.

Moreover, in this tire, each block 4a.

The projected lengths of 6a and 8a in the tire width direction, as shown in FIG. 3, are length l, 1. , 12. The surface area of each block is also ^4 + A6 in Figure 3.
+^8. The ratio? ”41 r fin 78+, A</i4= r, =0.085a As/ Ils = r s =0.096 aAs/
12 s = Ta = 0.2 a, and both of these ratios γ and γ6 are larger than 0, 05a,
By making it smaller than 0.2a, the coefficient of friction on ice can be increased to 150 in terms of index value, as shown by the dashed line in Figure 4.
Maintain high values (higher values indicate better results).

Here, when the ratio γ is set to a low value of less than 0.05a, the block rigidity in the tire circumferential direction becomes too small and the block is crushed, resulting in the block edge not properly biting into the ice. If it is not possible to ensure the If the block length becomes too long, frictional melting of the ice will proceed, making it impossible for the block edge to function effectively, and in any of these cases, the coefficient of friction on the ice will inevitably decrease.

By the way, the black circles in Fig. 4 indicate the coefficient of friction on ice of the conventional tire shown in Fig. 6, and according to this, the conventional tire can only exhibit a friction coefficient of about 273 that of the tire of the example. I understand that. In addition, the solid line in the figure shows the friction coefficient when the sipes are omitted from the tire of the example, and in this tire, in the region of γ>0.058, when T>0.2a of the tire of the example This results in a decrease in the coefficient of friction due to almost the same phenomenon. Furthermore, the broken line in the figure shows the friction coefficient when two sizes are arranged in every block, and according to this, in the range of 0.05a < r < 0.2a, the on-ice friction coefficient is can be maintained at a high value of around 150, similar to the tire of the example. However, in this case, the size interval is closer than in the example, and the block rigidity is lower, so the ratio γ
In the above range, the curve becomes somewhat more specific than the one-dot chain line in the figure, and the friction coefficient is lower than that of the example in the vicinity of 0.05a, while it is lower than that of the example in the vicinity of 0.2a. The coefficient of friction becomes higher.

Thus, this tire can provide better on-ice traction and braking performance in addition to the above.

The embodiment of the present invention has been described above with respect to the case in which each of the blocks 4a and 6a is provided with one sipe, but it is also possible to provide a block with one sipe and a block with two sipes between the circumferential main grooves. In addition, it is also possible to provide two sipes for all blocks, and it is also possible to provide only one sipe for the shoulder block 8a. It is also possible for at least one end of the sipe to terminate within the block without opening into the circumferential groove.

[Comparative example]

Below is the braking performance on ice between the invented tire and the conventional tire.
Comparative tests regarding structural slip resistance performance on ice and snow and traction performance on snow will be explained.

◎Test tire size: 10.0OR20 ・Invented tire Tire with the tread pattern shown in Figure 1 ・Conventional tire with the tread pattern shown in Figure 6 ◎Test method The above various tires were placed on a 3 ton vehicle with a fixed load. The brakes were installed and driven on both ice and snow roads with constant internal pressure charging, and the braking performance on ice was evaluated at -3°C and speed of 20 km.
μ on ice was measured based on the full lock braking distance at /h, and regarding the structural slip resistance on ice and snow, R = 20 m.
The lap time during turning was measured, and the traction performance on snow was determined by installing a load cell at the rear of the vehicle and measuring the traction force.

◎Test results These test results are compared to those of conventional tires by index 100.
When expressed as , it becomes as shown in the radar chart in Fig. 5. Note that the larger the index value, the better the result.

Here, according to the chart shown in FIG. 5, the invented tire exhibited significantly superior performance than the conventional tire in each of the braking performance on ice and the structural slip resistance performance on ice and snow,
Moreover, it is clear that the traction performance on snow is also improved over that of conventional tires.

(Effects of the Invention) Thus, according to the present invention, compared to conventional tires, both the performance on ice and the stability performance on ice and snow can be significantly improved, and the traction performance on snow can also be improved. As a result, high driving, braking, and turning performance can be demonstrated on both icy and snowy roads.

[Brief explanation of the drawing]

FIG. 1 is a tread pattern showing an embodiment of the present invention; FIG. 2 is a diagram showing a block edge component in the tire width direction and a block edge component in the tire circumferential direction of the block; FIG. A diagram showing an example of calculation of the ratio of the block surface area to the projected length in the tire width direction, FIG. 4 is a graph showing the relationship between the relative length of the block in the tire circumferential direction and the ice friction coefficient index, and FIG. Figures 6 and 7, which are radar charts showing braking performance on ice, anti-slip performance on ice and snow, and traction performance on snow, respectively show tread patterns of conventional examples. a...Tread contact width 1...Tread contact area 2...Circumferential main groove 3...
・Circumferential minor grooves 4a, 6a, 8a...Block 5.7.9...Sipes Figure 2 (a) (b) (C) Figure 1 Figure 3 (a) (b) (C) Figure 4□r Figure 5

Claims (1)

[Claims] 1. Four circumferential grooves continuous in the tire circumferential direction are provided in the tread contact area, and each block in the central block row located at the center in the tire width direction is long in the tire width direction. , a block pattern having an approximately flat polygonal outline shape, and each block of the block rows located on each side of the central block row having an approximately step-like outline shape partially adjacent to each other in the tire width direction. A tire, in which a block edge component α in the tire width direction of each block is
The ratio α/β to the tire circumferential block edge component β is determined as follows: α/β≧1.5 for each block in the central block row; 0.7≦α/β≦ for each block in the block row adjacent to the central block row. 1.0 Shoulder block row blocks, 0.5≦α/β≦0.7, each block is provided with one or two sipes, and each block is projected in the tire width direction. A pneumatic tire for heavy loads in which the ratio γ of the block surface area to the length is in the range of 0.05a<γ<0.2a with respect to the tread contact width a.