JP2769890B2 - Pneumatic tires for trucks and buses - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pneumatic tire for trucks and buses having improved performance on snow and ice roads.

[Conventional technology]

In general, pneumatic tires for snow and ice roads have a tread block pattern and a relatively soft rubber tread rubber to increase the frictional force of the tread on the snow and ice road surface, and to exhibit great traction performance. I have to. However, according to the investigation and research by the present inventors, it was found that the frictional force varies depending on the dynamic elastic modulus E 'of the tread rubber, and that the influence of the contact pressure is very large. Therefore, as in pneumatic tires for trucks and buses, when the difference in load weight between when loaded and when unloaded is significantly larger than that for passenger car tires, the change in the contact pressure on the tread surface is significantly large. There was a problem that the friction force was not stable, and the traction performance was not stable.

[Problems to be solved by the invention]

An object of the present invention is to stabilize the frictional force on snowy and icy roads and improve excellent snow and icy road performances regardless of the magnitude of the load weight, even when the load weight changes greatly like tires for trucks and buses. To provide truck and bus tires.

[Means for solving the problem]

An object of the present invention is to provide a pneumatic tire having a block pattern in which a block is formed on a tread surface by a groove and a sipe in a tire width direction is formed on the block, and the tread portion has a dynamic elastic modulus E. ′ Is 80
Constructed from rubber of ~ 110Kgf / cm ^2, the sipe provided in the block, the interval in the tire circumferential direction is 7 ~ 10mm
And a sipe in the range of 11 to 15 mm can be achieved.

In the present invention, the dynamic elastic modulus E 'refers to a value measured using a viscoelastic spectrometer (for example, manufactured by Iwamoto Seisakusho) under the conditions of a temperature of 0 ° C., a frequency of 20 Hz, and an amplitude of 10 ± 2%.

In the tire of the present invention, the sipe interval in the tire circumferential direction refers to the distance between the sipe and the distance between the sipe and the block edge end measured in the tire circumferential direction.

FIG. 1 shows an example of a tread pattern of a truck / bus tire according to the present invention. As shown in the figure,
The tread pattern includes a large number of blocks 3 divided by a plurality of main grooves 1 extending in the tire circumferential direction and a plurality of sub-grooves 2 intersecting the main grooves 1. In each of the blocks 3, a sipe 4 in the tire width direction is formed.

FIG. 2 is a diagram showing the block 3 of FIG. 1 in an AA cross section in the tire circumferential direction. As shown in the figure, the intervals W ₁ and W ₂ of the sipe 4 formed in the block 3 are not the same,
They have different lengths. Moreover, this sipe interval W _1, W ₂ is not just different spacing, W ₁ is in the range of 7 to 10 mm, W ₂ is in the range of 11-15 mm, at least two blocks 3 is characterized by being mixed.

By mixing at least two types of sipes having different sipe intervals, it is possible to maximize and stabilize the frictional force of the block on snow and ice roads regardless of the load weight. The reason is as described below.

In a truck / bus tire, for example, when a load of 2,700 kgf is applied to a tire having a tire size of 10.00 R20 by load, the average contact pressure is about 10 kgf / cm ² . On the other hand, the average contact pressure when the empty load is 800 kgf is about 5 to 7 kgf / cm ² , and the difference ranges from ³ to 7 kgf / cm ² .

On the other hand, according to the study of the present inventors, there is a large correlation between the contact pressure and the size of the block in the tire circumferential direction. For example, for a block made of a rubber composition having a dynamic elastic modulus E'90 Kgf / cm ² , when the dimensions in the tire circumferential direction corresponding to the sipe intervals are variously varied, the contact pressure and the shear stress F / S are determined. Is as shown in FIG. In the figure, curve A is a block of 12 mm × 20 mm × 12 mm whose length corresponding to the tire circumferential direction is 12 mm, and curve B is 7 mm × 20 whose length corresponding to the tire circumferential direction is 7 mm.
The mm × 8 mm block and curve C represent a 4 mm × 20 mm × 7 mm block whose length corresponding to the tire circumferential direction is 4 mm. The block of the curve a shows the maximum shear stress F / S around the contact pressure of about 10 kgf / cm ² , and the block of the curve b shows the contact pressure of about 5 kgf / cm ^2.
It shows the maximum shear stress F / S around 77 kgf / cm ² . Furthermore, the curve C shows the maximum shear stress F / S near the contact pressure of about 4 kgf / cm ² .

From the correlation between the ground pressure and the tire circumferential dimension of the block, the tire circumferential length (sipe interval) of the small block divided by the sipes provided on the tread surface block is in the range of 7 mm to 10 mm. and if brought into mix and those 11Mm～15mm, when the average ground contact pressure of 10 Kgf / cm ² before and after the load exerts a small block is the maximum friction force of the sipe interval 11-15 mm, the average ground contact pressure is 5~7Kgf At empty load of / cm ² , small blocks with a sipe spacing of 7 to 10 mm will exert the maximum frictional force.

As described above, the tire of the present invention exhibits almost stable maximum frictional force even when the difference in the tire contact pressure between a loaded state and an unloaded state changes significantly, and good ice and snow performance can be obtained. It becomes.

Such a truck / bus tire according to the present invention has a tread portion having a dynamic elastic modulus E 'at 80C of 80 to 110 kgf.
It must be composed of / cm ² tread rubber. When the dynamic elastic modulus E 'of the tread portion is out of the above range, the block provided with the sipe at the above-mentioned sipe interval has a load (load load).
This is because the contact pressure sometimes does not reach the maximum frictional force, and a tire exhibiting good traction performance cannot be obtained.

〔Example〕

The tread portion is made of rubber having a dynamic elastic modulus E 'of 100 kgf / cm ² , and is divided into a main groove and a sub-groove having a groove width of 10 mm. = 50 mm and a height c = 20 mm in a tire having the pattern shown in FIG. 1, wherein the number of the sipes and the intervals formed in each block are as shown in the table and FIG. As shown in FIG. 3, three types of tires, comparative tires I and II, were prepared at uniform intervals. The size of these tires was the same 10.00 R20.

For each of these three types of tires, 2,700Kgf
And braking performance on ice when a load of 800 kgf is applied,
It was measured by the following method. The results are shown in the table.

From the table, it can be seen that the tire of the present invention always exerts stable braking performance on ice irrespective of the loaded state and the unloaded state as compared with the comparative tires I and II.

Braking performance on ice: Test tires were mounted on a 10-ton flat body car, and the braking distance was measured at a speed of 20 km / hr on a -10 ° C ice plate at a temperature of -12 ° C. The reciprocal is represented by an index with the measurement result of the comparative tire I under a 2,700 kgf load being 100.

[Effects of the Invention] As described above, according to the present invention, in a truck / bus tire having a block pattern, the tread portion is made of tread rubber having a dynamic elastic modulus E ′ in a specific range, Since at least two types of sipes with different intervals were formed in each block of the tread,
Even when the magnitude of the load weight is large, as in the case of truck and bus tires, the frictional force on snowy and icy roads can be constantly stabilized regardless of the magnitude of the load, and the performance of icy and snowy roads can be stabilized and improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a tread pattern of the tire of the present invention, FIG. 2 is a sectional view taken along line AA of the block in FIG. 1, and FIG. 3 is a sectional view corresponding to FIG. Show. FIG. 4 is a graph showing the relationship between the contact pressure and shear stress F / S of blocks having different dimensions in the tire circumferential direction. 1 ... Main groove, 2 ... Sub groove, 3 ... Block, 4 ... Sipe.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-59-96002 (JP, A) JP-A-63-103709 (JP, A) JP-A-61-285105 (JP, A) JP-A-1- 314607 (JP, A) JP-A 61-106403 (JP, U) JP-A 62-185602 (JP, U) Utility model registration 2514780 (JP, Y2) JP 3-23367 (JP, B2) JP Hei 1-27884 (JP, B2) Special Publication Hei-3-23367 (JP, B2) (58) Fields investigated (Int. Cl. ⁶ , DB name) B60C 11/00 B60C 11/12

Claims (1)

(57) [Claims] In a pneumatic tire having a block pattern in which a block is formed on a tread surface by a groove and a sipe in a tire width direction is formed in the block, a dynamic elastic modulus E 'of the tread portion is 80 to 80. Constructed from rubber of 110 kgf / cm ² , as a sipe provided in the block, the intervals in the tire circumferential direction are in the range of 7 to 10 mm and 11 to 15 mm, respectively.
Pneumatic tires for trucks and buses with a mix of sipes in the range.