JPH03136911A - 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:An approximately flat hexagonal block 20 is formed between peripheral sub-grooves 14 and 14 with lateral groove 18, thereby providing a sheeting 36. Also, blocks 28 and 30 are formed respectively with lateral grooves 24 and 26 between main and sub grooves 12 and 14, and between a main groove 12 and a sub-groove 16, thereby providing sheetings 38 and 40. In addition, a ratio gamma of the widthwise projection length of respective blocks 20, 28 and 30, to block surface for tread plane width (a) is taken as 0.05a < gamma< 0.2a. Furthermore, opposite sides of blocks 20, and 28 and 28 separated in a tire peripheral direction are respectively so formed as to have a sawtooth waveform. 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) This invention relates to improvements in heavy-duty pneumatic tires applied to trucks, buses, etc., and in particular,
Related to tires that exhibit excellent performance on ice and snow.

(Prior Art) As a conventional tire that is often applied as a snow tire to heavy-load vehicles, there is a tire having a tread pattern as shown in FIG. 8, for example. Two circumferential main grooves 52 are provided which extend in a zigzag pattern, and a circumferential sub-groove 54 is provided between these main grooves and extends in the circumferential direction parallel to the main grooves. Between the groove 54 and each circumferential main groove 52, there are two blocks 56 whose planar shape is approximately "<" shaped.
are arranged at a predetermined interval in the tire width direction, and each of the two blocks 56 is oriented in the opposite direction to that of the adjacent block pair in the tire circumferential direction. A block 58 having a substantially "L" shape in plan view is provided along the circumferential main groove on the outside of the circumferential main groove 52, and a substantially "H" shaped block 58 is provided on the outside in the tire width direction in opposite directions. A pair of lugs 6 with two bent in a shape
0 are divided into sections.

This tire has a flatness ratio of 100% and a negative ratio of 50%, and when applied to heavy-duty vehicles such as trucks and buses, it exhibits excellent on-snow traction performance under high ground pressure. has been confirmed.

(Problems to be Solved by the Invention) However, although such conventional tires can exhibit excellent on-snow performance due to their high negative rate, they do not have satisfactory performance due to their small ground contact area. There was a problem that it could not demonstrate its performance on ice.

Therefore, for the purpose of improving on-ice performance, it has been proposed to form sipes in the tread land area of tires such as tires with spikes driven into the tread land area or studless tires for passenger cars.

However, although spikes can ensure high performance on ice, there is a problem in that the spikes scrape the road surface, making it impossible to avoid the generation of dust from the asphalt that forms the road surface.

In addition, tires with sipes, for example, tires with 3 to 5 sipes formed in one block, have a ground pressure of 2 to 5.
For passenger car tires as small as 3 kg/ci, the improvement in on-ice performance is remarkable, but the ground pressure is only 7 to 9 kg/cd.
In heavy-duty tires that reach this level, the provision of these sipes causes a decrease in block rigidity, and there is a problem in that the tires are unable to exhibit not only their performance on ice but also their essential performance as a tire.

This invention solves the problems of the prior art, and while ensuring sufficient traction performance on snow, it significantly improves both braking performance on ice and anti-skid performance on ice and snow compared to conventional tires. Its purpose is to provide a pneumatic tire for heavy loads.

(Means for Achieving the Object) The heavy-duty pneumatic tire of the present invention has two circumferential main grooves continuous in a zigzag shape in the tire circumferential direction in the tread contact area, and a tire width of each circumferential main groove. On the inner and outer sides of the tire, there are approximately flattened grooves that alternately taper in the tire width direction between each circumferential minor groove that continues in a zigzag shape in the tire circumferential direction and the circumferential minor groove that is located inside the circumferential main groove. Hexagonal blocks are arranged in rows of blocks spaced apart in the circumferential direction of the tire, and between the circumferential main groove and the circumferential sub-groove located inside the circumferential main groove, and the hexagonal blocks are arranged opposite to the blocks and alternately tapered and tapered. Thick approximately hexagonal blocks are arranged in rows of blocks alternately spaced apart in the tire circumferential direction, and between the circumferential main groove and the circumferential minor groove located on the outside thereof, each having a tire width. A block pattern tire having generally hexagonal blocks that are alternately tapered and thickened toward the outside in a tire circumferential direction and block rows that are alternately spaced apart from each other in the tire circumferential direction. Each block is provided with one or two sipes, and the ratio T of the surface area of each block to the projected length in the tire width direction is 0.05a<γ<0 with respect to the tread contact width a. ．．
2a, and the adjacent opposing sides of each block spaced apart in the tire circumferential direction are each formed into a sawtooth shape.

(Function) According to the pneumatic tire of the present invention, there are two circumferential main grooves that continue in a zigzag shape in the circumferential direction, and four circumferential minor grooves that also extend in a zigzag shape. Since the number of circumferential grooves in the tire is six, the block edge component in the tire circumferential direction increases compared to conventional tires with five or less circumferential grooves, which increases the resistance to icy and snowy roads. Demonstrates skidding resistance. In addition, each block constituting each block row is alternately tapered or thickened in the tire width direction, and has a generally hexagonal shape.
The sides of these blocks that are spaced apart and facing each other in the tire circumferential direction have a sawtooth shape, so they exhibit greater skidding resistance.

Moreover, by having two main circumferential grooves, melt water generated on the ice by the friction energy of the tires can be drained extremely smoothly, and the groove width of these circumferential grooves is 3.0 mm or more. This prevents snow from clogging the grooves and ensures reliable skidding resistance.

By providing one or two sipes on the blocks constituting each block row, the sipes can be used to separate blocks without reducing block rigidity in relation to the dimensions of the blocks, especially their circumferential length. The block edges of the small blocks can be made to function sufficiently against the waterway surface, and the frictional force on the ice is also increased. In other words, if you do not form any sipes extending in the width direction of the tire, you cannot hope for a sufficient improvement in the frictional force on ice.On the other hand, if you have three or more sipes, the block Since the rigidity is reduced, the block is crushed as a whole, which not only increases the frictional force on ice but also prevents the tire from exhibiting its essential performance.

In addition, the ratio γ of the block surface area to the projected length in the tire width direction of each block is set to 0 for the tread contact width a.
．． By setting 05 a < 7 < 0.2 a, the on-ice friction force of the tire is more effectively improved in relation to the above-mentioned sipes. This is the ratio T of the block surface area to the projected length of each block in the tire width direction, that is, the distance equivalent to the length of each block in the tire circumferential direction is 0.05a.
If it is less than that, the block rigidity in the tire circumferential direction will be too low, and the frictional force on ice will be greatly reduced, not only when two sipes are formed, but even when only one sipe is formed. On the other hand, when the ratio T is larger than 0.2a, the frictional melting of the ice progresses due to the length of the block in the tire circumferential direction increasing, and the small blocks divided by the sipes reliably melt into the ice. Since it is not possible to guarantee penetration and the spacing between the sipes becomes large, the frictional force on the ice is greatly reduced.

Therefore, according to the present invention, the selected block shape and block size, the sipes formed on each block, and the sides of each block facing each other at a distance in the tire circumferential direction are made into a sawtooth shape, and the edge component is Under the synergistic effect of this increase, in particular, traction performance and braking performance on ice can be greatly improved.

Moreover, in this invention, the number of circumferential grooves is six and the number of blocks in the tire width direction is increased, thereby increasing the edge component of the blocks in the tire circumferential direction, thereby greatly improving skidding resistance on ice and snow. In addition, despite the six circumferential grooves, the decrease in snow traction performance due to the increased ground contact area can be reduced by increasing the number of blocks in the tire circumferential direction and by increasing the number of circumferential blocks in the tire. By making the opposing sides of each block spaced apart in the circumferential direction into a sawtooth shape and increasing the edge component in the width direction of the tire, the on-snow traction performance can be made superior to that of conventional tires. .

(Embodiments) Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a diagram showing a tread pattern of a tire showing an embodiment of the present invention, and the aspect ratio of this tire is 100.
%, and its negative rate is 35.0%. The internal structure of the tire is not shown here because it is similar to that of a heavy-duty radial tire for boat fishing.

In this embodiment, the tread contact portion 1o is provided with two circumferential main grooves 12 that are spaced apart from each other in the tire width direction and extend in a zigzag shape in the tire circumferential direction. And on the outside thereof, circumferential sub-grooves 14 and 16 which also extend in a zigzag shape in the tire circumferential direction are provided, and the number of circumferential grooves is six. Note that the circumferential main groove 12
The groove width of the groove is 10.9 mm, and the groove width of the circumferential minor groove is 4 and 6 mm.
mm, and the total width of the circumferential grooves is 17.2% of the tread contact width a (234 mm).

Circumferential minor groove 14.14 located inside the circumferential major groove 12
In between, the tire equator line x-x is spaced apart in the tire circumferential direction.
A plurality of tire width direction grooves 18 are provided which alternately intersect diagonally with respect to each other, thereby forming a plurality of flat substantially hexagonal blocks 2o which are alternately tapered in the tire width direction. These flat hexagonal blocks 20 are alternately arranged at a distance in the tire circumferential direction, and the block rows 22 are arranged in the circumferential minor grooves 14, 14.
form between.

Here, the groove width of the width direction groove 18 which cooperates with the circumferential direction minor groove 14 to form each block 20 having a substantially flat hexagonal shape is 6.7 mm in this embodiment, and is set relative to the tire equator line. Alternately extending diagonally in a zigzag shape in the tire width direction,
The opposing sides of the blocks 20 that are spaced apart and opposed to each other in the tire circumferential direction have a sawtooth shape.

On the other hand, between the circumferential main groove 12 and the circumferential sub-groove 14 located inside the circumferential main groove 12, and between the circumferential main groove 12 and the circumferential sub-groove 16 located outward in the tire width direction, Other width direction grooves 24 and 26 are provided which extend diagonally in a zigzag shape in the tire width direction alternately, and a generally hexagonal block 28 facing the block row 22 is tapered and thickened at the end.
The approximately hexagonal blocks 30 that taper and become thicker toward the outside in the tire width direction form block rows 32 and 34 that are alternately arranged in the tire circumferential direction, respectively.

In addition, in this embodiment, the circumferential main groove 12 and the circumferential sub-groove 1
The groove widths of the width direction grooves 24 and 26, which cooperate with each other to form the block rows 32 and 34, respectively, are 4.
．． 7 mm and 5.1 mm.

In each block row 22, 32, and 34, each block 2 forming the block row is
0.28 and 30, mutually 1/2 in the tire circumferential direction
They shall be arranged so that they are relatively shifted by the pitch to ensure the generation of sideslip resistance. Furthermore, the blocks 20, 28 and 30 that face each other in the tire circumferential direction and each side having a sawtooth shape also contribute to the generation of sideslip resistance.

Each block 20, 32, and 34 forming block rows 22, 32, and 34, respectively, is shown in FIG. 2(a).
As shown in ~(C), the ratio T of the surface areas A0, A2, and A3 of each block to the projected length l3.12 and l in the tire width direction is Assume that the relationship 0.05a < 7 < 0.2 a is satisfied.

In the embodiment shown in FIG. 1, A+/It −
T r = 0.063aAx/1g = 7 t =
0.064aAx/Is-r s = 0.063
It becomes a.

Each of the blocks 20, 32, and 34 is provided with one sipe 36, 38, and 40 extending in the width direction of the tire at approximately the center of the circumferential length of the tire. 22. The region b where 32 and 34 are formed is 80% or more of the tread ground contact width a centered on the tire equator line xx.

In a heavy-duty pneumatic tire with a radial structure like the one described above, the number of circumferential grooves is set to six and the block edge component in the circumferential direction of the tire is increased. As shown above, it is possible to sufficiently improve sideslip resistance on ice and snow. That is, according to FIG. 3, it can be seen that the anti-skid performance can be improved as the number of circumferential grooves increases, and when the number of circumferential grooves is increased from five to six, the anti-skid performance is particularly improved.

However, even if the number is increased from six to seven,
Since the stiffness in the tire width direction of the ridge section defined by the circumferential grooves is reduced, the anti-skid performance cannot be further improved, so it is advantageous to have six circumferential grooves. . However, by setting the groove width of the circumferential grooves to 3.0ffiI11 or more, it is possible to prevent the circumferential grooves from being clogged with snow, thereby ensuring high anti-skid performance.

The cornering time on ice and snow when turning at a radius of 7 m is taken as the cornering performance on ice and snow.■ If the shape is simply a flat hexagon, ■The planar shape of each block forming each block row is approximately a flat hexagon. Along with making it square,
As it tapers and thickens towards one side in the tire width direction,
Fig. 4 shows the cases in which blocks are arranged alternately in the circumferential direction of the tire, and (ii) in which each side of each block facing each other in the circumferential direction of the tire is made into a sawtooth shape. Thus, cornering performance on ice can be improved compared to a hexagonal block having parallel opposing sides extending linearly in the width direction of the tire.

Furthermore, it can be seen that cornering performance on ice and snow can be further improved by making the adjacent and opposing sides of each block in the tire circumferential direction serrated.

Furthermore, in the tire shown in this embodiment, each block 20, 2
8 and 30, each block 20.28 is formed with -1 sipe extending in the tire width direction, and each block 20.28,
Then, by setting the ratio T of the block surface area to the projected length in the tire width direction of 30 to the tread contact width a, 0.05a < r < 0.2a, as shown by the dashed line in Fig. 5. To,
The coefficient of friction on ice can be maintained at a high value of around 150 in terms of index value. Note that the higher the index value, the better the result.

Here, when the ratio T is set to a low value of less than 0.05a,
If the block rigidity in the tire circumferential direction becomes too small and the block is crushed, it will not be possible to ensure that the block edge properly bites into the ice, and the ratio γ
When is set to a high value exceeding 0.2a, the block edge interval of small blocks divided by sipes becomes too large, and the block length in the tire circumferential direction also becomes too long, resulting in ice friction. As the melting progresses, the block edge cannot function effectively, and in either case, the coefficient of friction on ice decreases.

By the way, the black circles in FIG. 5 indicate the coefficient of friction on ice of the conventional tire shown in FIG. 8, and it can be seen that the conventional tire can only exhibit a friction coefficient of about 273 as compared to the tire of this example. . In addition, in the figure, the solid line indicates the friction coefficient when the sipes are omitted from each block of the tire of this example, and in the tire, 7> A decrease in the coefficient of friction occurs due to almost the same phenomenon as in the case of 0.2a.

On the other hand, the broken line in the figure indicates the friction coefficient when two sipes are respectively arranged in each block. According to such a tire, in the range of 0.05a<7<0.2a, the FJ friction coefficient (index) can be maintained at a high value of around 150, similar to the tire of this embodiment. However, on the other hand, the sipe spacing is denser than in the tire of this example, and the block rigidity is reduced, so within the above range of ratio γ, the curve becomes somewhat different from the dashed-dotted line in the figure. In the vicinity of 0.05a, the friction coefficient tends to be lower than that of this example, and in the vicinity of 0.2a, the friction coefficient tends to increase.

Thus, this tire can exhibit significantly superior performance on ice compared to conventional tires.

In addition, the area where each block row 22, 32, and 34 are formed is set to be 70% or more of the tread contact width a, centering on the tire equatorial plane x-x, to increase the area occupied by the block within the tread contact area. It is preferable to do this, and thereby, as shown in FIG. 6, the coefficient of friction on ice can be improved to a practical level. That is, the area where the block rows are formed is 7 of the tread contact width a.
If it is less than 0%, the coefficient of friction on ice will drop sharply, as shown in FIG.

The embodiments of the present invention have been described above with respect to the case where each block forming a block row is provided with one sipe size. It is also possible to have a mixture of sipes, or to provide two sipes in every block. Furthermore, at least one end of the sipe provided in each block can be terminated within the block without opening into the circumferential groove.

[Comparative Example] Comparative tests of the invention tire and the conventional tire regarding braking performance on ice, anti-skid performance on ice and snow, and traction performance on snow will be described below.

◎Test tire ・Size: 10.00 R20 ・Invented tire A tire having a tread pattern shown in FIG.

・Conventional tires Tires with the tread pattern shown in Figure 8 ◎Test method The above tires were installed on an 8-ton vehicle with a constant load, and for braking on ice at a constant internal pressure, the tires were tested at -3°C and a speed of 20km/h.
Measure μ on ice based on the full lock braking distance at h,
In addition, the anti-skid performance on ice and snow was determined by measuring the lap time when turning at R = 20 m, 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 When these test results are expressed as an index of 100 for the conventional tire's braking performance on ice, anti-skid performance on ice, and traction performance on snow, the results are as shown in the radar chart in Figure 7. Note that the larger the index value, the better the result.

According to the chart shown in FIG. 7, the tire of the present invention exhibits significantly better performance than the conventional tire in both braking performance on ice and anti-skid performance on ice and snow, and moreover, the traction performance on snow is also lower than that of the conventional tire. It has become clear that this is a clear improvement over that of tires.

(Effects of the Invention) According to the present invention, both the performance on ice and the anti-skid performance on ice and snow can be significantly improved compared to conventional tires, and the block edge component in the width direction of the tire is improved. By increasing the amount, traction performance on snow can also be improved, and high driving, braking, and turning performance can be exhibited on both ice and snow road surfaces.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a tread pattern of a preferred embodiment of the tire of the present invention, and FIGS. 2(a) to (C) are examples of calculating the ratio of the block surface area to the projected length of the block in the tire width direction. Figure 3 is a graph showing the relationship between the number of circumferential grooves and anti-skid performance on ice and snow. Figure 4 is a graph showing the relationship between the planar shape of the block and cornering performance on snow. Figure 5 is a graph showing the relationship between the relative length of the block in the tire circumferential direction and the ice friction coefficient index, Figure 6 is a graph showing the relationship between the ridge area and the ice friction coefficient, and Figure 7 is: Figure 8 is a radar chart showing the braking performance on ice, skid resistance performance on ice and snow, and traction performance on snow of the tire shown in Figure 1 and the conventional tire, respectively. 10--Tread contact area 14.16- Circumferential minor groove 20.28.30...-Block 36.38.40--Sipe Shows the tread pattern of a conventional tire 12-- Circumferential main groove 18--Width direction groove 22, 32.34--Block row 1B -=-1 notch l? 1. * Figure 4 Figure 5 □r Figure 2 (a) (C) (b) Figure 3 3 pots, 4 pots 5 no, 6 no p. 11.911F
l, II water? Fire (Tread JljjefM734tr+
ki) Figure 6 (Bro'/!'Ig;W-suke'smwa>
Figure 8n

Claims (1)

[Scope of Claims] 1. Two circumferential main grooves continuous in a zigzag shape in the tire circumferential direction in the tread contact area, and a zigzag pattern in the tire circumferential direction on the inner and outer sides of each circumferential main groove in the tire width direction. Approximately flat hexagonal blocks tapered in the tire width direction are spaced apart in the tire circumferential direction between each circumferential minor groove that continues in a shape and the circumferential minor groove located inside the circumferential main groove. Approximately hexagonal-shaped blocks that are alternately tapered and tapered opposite the block rows are arranged between the block rows arranged as shown in FIG. Block rows spaced apart in the tire circumferential direction;
Approximately hexagonal blocks that are alternately tapered and thickened toward the outside in the tire width direction are spaced apart in the tire circumferential direction between the circumferential main groove and the circumferential minor groove located outside of the circumferential main groove. A block pattern tire having a block row in which each block in the block row is provided with one or two sipes, and the ratio of the surface area of the block to the projected length of each block in the tire width direction. A heavy load characterized in that γ is within the range of 0.05a<γ<0.2a with respect to the tread contact width a, and the adjacent opposing sides of each block spaced apart in the tire circumferential direction are each shaped like a sawtooth. Heavy duty pneumatic tires.