JPH03182811A - Pneumatic tire for truck and bus - Google Patents

Abstract

PURPOSE:To provide improved performance especially on an icy and snowy road, in a tire with block patterns, by forming tread parts from rubber with dynamic elastic coefficient in a particular region and forming two kinds of sipes whose intervals are different at respective blocks in the tread parts. CONSTITUTION:The tread patterns of a tire are formed from a large number of blocks 3 which are partitioned by plural main grooves 1 extending in a circumferential direction of the tire and plural sub-grooves 2 which cross the main grooves 1. Sipes 4 extending in a tire cross direction are disposed in the respective blocks 3 respectively. With this constitution, the intervals W1, W2 of the above respective sipes 4 are made to become different respectively, and either interval W1 is set within the region of 7-10mm, and the other interval W2 is set within the region of 11-15mm. Besides, the tread parts are formed from rubber with 80-110kgf/cm<2> dynamic elastic coefficient E'. It is thus possible to maintain stable friction on an icy and snowy road all the time regardless of any change in load weight.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a pneumatic tire for trunk buses that has improved performance on snowy and icy roads.

[Conventional technology]

In general, pneumatic tires for snowy roads have a block pattern tread and use relatively soft rubber for the tread rubber, which increases the frictional force of the tread against the snowy and icy road surface and provides great traction performance. I have to. However, according to research conducted by the present inventor, the above-mentioned frictional force is caused by the dynamic elastic modulus E of the tread rubber.
It was found that the influence of ground pressure was very large. Therefore, in pneumatic tires for trucks and buses, which have a significantly larger difference in load weight between loaded and unloaded than passenger car tires, the change in ground pressure on the tread surface is significantly large.
There was a problem that the frictional force was not stable, and as a result, the traction performance was also unstable.

[Problem to be solved by the invention]

The purpose of the present invention is to stabilize the frictional force on snowy and icy roads regardless of the size of the load weight, such as tires for trucks and buses, and to improve excellent performance on snowy and icy roads. Our goal is to provide truck and bus tires that can.

[Means to solve the problem]

An object of the present invention is to provide a pneumatic tire having a flock pattern in which blocks divided by grooves are formed on the torso surface and sipes in the width direction of the tire are formed in the blocks. is made of rubber with a dynamic elastic modulus E of 80 to 110 Kgf/cm2, and is the sipe provided on the flock, and the intervals in the tire circumferential direction are in the range of 7 to 10 mm θ) and 11 to 15 m, respectively.
This can be achieved by mixing a range of m sipes.

In the present invention, dynamic elastic strength is a value measured using a viscoelastic spectrometer (for example, manufactured by Harumoto Seisakusho) under the conditions of a temperature of 0°C, a frequency of 2011°C, and an amplitude of 10±2''A. say.

Furthermore, in the tire of the present invention, the interval between sipes in the tire circumferential direction refers to the distance between the sipes and the distance between the sipes and the edge of the Pro 7 square measured in the tire circumferential direction.

FIG. 1 shows one example of the tread pattern of the truck/lotus tire of the present invention.

As shown in the figure, the tread pattern consists of a large number of flocks 3 divided by a plurality of main grooves 1 extending in the circumferential direction of the tire and a plurality of sub-grooves 2 that intersect with these main grooves 1. , and the second figure 1 block 3 are formed with a →''-eve 4 in the tire width force direction, respectively.

In addition, FIG. 2 shows block 3 in FIG. 1 at A in the tire circumferential direction.
- It is a figure shown in the A cross section. As shown in the figure, the intervals W between the sipes 4 formed on the block 3 are not the same, but have different lengths. Moreover, these sipe intervals W,, W2 are not only different in interval, but also in the range of 7 to 1 Onon, and W2B
:J: is within the range of 11 to 15 mm, and is characterized in that at least both of them are mixed in Pro and Ri 3.

By mixing at least two types of sipes with different sipe spacings, the frictional force on the snow and ice road due to the brake can be maximized regardless of the load weight.
It becomes possible to stabilize it. The reason for this is as explained below.For truck and bus tires, for example, the tire size is 10.001? The average ground pressure εJ' is approximately 10 hf/cm2 when a load of 2,700 Kgf is applied to the 20 tires. On the other hand, when the unloaded load is 800 Kgf, the average ground pressure is about 5 to 7 Kgf/cm2, and the difference is 3 to 7 h.
f/cm”.

On the other hand, according to the research of the present inventors, -
There is a large correlation between -1 and the circumferential dimension of the tire. For example, for a block made of a rubber composition with a dynamic modulus of elasticity E90Kgf/cm2, when the tire circumferential dimension corresponding to the sipe spacing is varied, the ground pressure and the shear stress F/S are Examining the relationship between the two, it is as shown in Fig. 4. In the figure, curve A has a length of 12mm, which corresponds to the circumferential direction of the tire.
7 mn+
A block of 20 mm x 8 mm, the length of curve C corresponding to the tire circumferential direction is 4 mm.
207mm block [Represents one block. The block at the curve A shows the maximum shear stress F/S at a ground pressure of approximately 10 Kgf/(5 m2), and the block at the curve entrance shows a ground pressure of approximately 5 to 7 m2.
The maximum shear stress F/S is shown around Kgf/cm2. Furthermore, the block to the curve has a ground pressure of about 4 hf/cm
The maximum shear stress F/S is around 2.

Due to the correlation between the ground pressure and the tire circumferential dimension of the blocks, the tire circumferential length (sipe spacing) of the small blocks divided by the sipes provided on the blocks on the tread surface is in the range of 7 mm to 10 mm. and 11mm
If you mix it with ~15mm, the average ground pressure will be 10
When loading after hf/cm2iij, the sipe spacing is 11 to 15.
The small block of the hammer exerts the maximum frictional force, and the average ground pressure is 5 to 7 kgf/cm2 and the sipe spacing is 7 to 7 kgf/cm2 when unloaded.
A small block of 1.0+nm will exhibit the maximum frictional force.

In this way, the tire of the present invention can be used even when the difference in ground pressure of the tire changes significantly between when loaded and when unloaded.
This results in a stable and maximum frictional force, resulting in good performance on icy and snowy roads.

The truck/lotus tire of the present invention has a tread having a dynamic elastic modulus E' of 80 to 1 at 0°C.
It must be constructed from 10 Kgf/cm2 tread rubber. If the dynamic elastic modulus E of the tread portion is outside the above range, the block provided with sipes at the above-mentioned sipe intervals will not reach the ground pressure that exhibits the maximum frictional force when loaded (loaded), and will not have good traction performance. This is because it is not possible to obtain a tire that exhibits its full potential.

〔Example〕

The tread portion is made of rubber with a dynamic elastic modulus E' of 100 gf/cm", and is divided into a main groove and a minor groove each having a groove width of 10+ nm, and the length in the tire circumferential direction a = 58 mn+,
In a tire having the pattern shown in Fig. 1 consisting of blocks of width direction length b = 50 mm and height C = 20 mm,
Three types of tires were created: the present invention tire in which the number and spacing of sipes formed in each block were as shown in the table and FIG. 2, and comparative tires I and H in which the sipes were spaced uniformly as shown in FIG. 3. . The sizes of these tires were all the same, 10.00 R20.

2.700 for each of these three types of tires.
Braking performance on ice when a load of 800 Kgf and 800 Kgf was applied 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 exhibits stable braking performance on ice, regardless of whether it is loaded or unloaded, compared to the comparative tires (3) and (H).

Product sales track survey: A test tire was attached to a 10-ton flat body vehicle, and the braking distance was measured when driving at a speed of 20 km/hr on ice floes at -10°C in a temperature of -12°C. The reciprocal number was expressed as an index, with the measurement result of Comparative Tire I at a load of 2.700 Kgf being set as 100.

(Margins below on this page) [Effects of the Invention] As explained above, according to the present invention, in a trunk/bus tire having a block pattern, the tread portion thereof has a dynamic elastic modulus E'' within a specific range. The tread is made of rubber, and each block of the tread has at least two types of sipes with different spacing, so even when the load weight varies greatly, such as in truck and bus tires, Regardless of the situation, the frictional force on the snowy and icy road can be kept stable, and the performance on the icy and snowy road can be stabilized and improved.

[Brief explanation of drawings]

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

Claims (1)

[Claims] Forming blocks divided by grooves on the tread surface,
In a pneumatic tire having a block pattern in which sipes in the tire width direction are formed in the blocks, the tread portion is made of rubber having a dynamic elastic modulus E' of 80 to 110 Kgf/cm^2, and the sipes provided in the blocks include: The interval in the tire circumferential direction is in the range of 7 to 10 mm and 11, respectively.
Pneumatic tires for trucks and buses with mixed sipes in the range of ~15mm.