JPH03231001A - Tire for heavy load - Google Patents

Abstract

PURPOSE:To improve brake performance and traction performance by specifying a ratio between the length of a peripheral direction and the length in the direction of width of an earthing print and a relative relation between the length component in a peripheral direction and the length in the direction of width of each of sipings of each land part in an earthing region. CONSTITUTION:In a tire, an aspect ratio is set to a value in a range of 80-120% and a negative factor to a value in a range of 25-50%. A bent block 2 is disposed between peripheral main grooves 1, a different block 3 and a lug 4 are disposed, in order, outside the peripheral main groove 4, and siping 5 are formed therein. In this case, a ratio of a length (a) in the direction of the width of a tire to a length (b) in the peripheral direction of a tire of an earthing print is set so as to satisfy a formula of 0.8<=a/b<=1.5. A relative relation between a length component beta in the peripheral direction of a tire and a length component alpha in the direction of the width of a tire of each siping 5 at each land part in an earthing region is set so as to satisfy a formula described at the right.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a heavy-duty tire, and in particular improves braking performance and traction performance on muddy and icy road surfaces.

(Prior art) It has an aspect ratio of 80 to 120% and a flatness ratio of 25 to 50%.
In conventional heavy duty tires with a negative rate of %,
Generally, the ratio a/b of the tire width direction length a to the tire circumferential direction length of the ground contact print under normal internal pressure and normal load is less than 0.8. For example, it is possible to develop excellent braking performance and traction performance on wet road surfaces.

For example, when a tire rolls on a wet road surface where water already exists, as is clear from the side view of the tire shown in FIG. Because the tire approaches the underside of the tire in a wedge-like manner, the tire generates frictional force against the road surface mainly through its kick-out side.

Here, let b be the circumferential length of the tire contact print under normal internal pressure and normal load, and a be the widthwise length of the tire in the tire width direction (see Figure 8(b)). Of the circumferential length b, the length of the part in contact with water is bl
, when the length of the contact part with the road surface is b2, and when a In order to achieve this, it is preferable to increase b, or in other words, to narrow the trend width in order to reduce a/b, thereby achieving high went performance of the tire.

(Problem to be solved by the invention) By the way, when a tire rolls on an icy and snowy road surface,
As shown in FIG. 9(a), the melt water generated by the friction between it and the road surface is present in a nearly wedge-like shape on the tire kick-out side, contrary to what was described above, and in this case,
Mainly, the pedal side part of the tire generates the road friction force.

Therefore, in this case, the length of the contact print under the same conditions as described above in the tire circumferential direction is b, and the tire width direction is a (see Fig. 9(b)). Of the direction length b, the length of the part in contact with the road surface is b 1
1. When the length of the part in contact with water is b1□, in order to improve the braking performance and traction performance of the tire, it is necessary to increase b, , and Xa. As in the case of improvement, b,
When a/b is made smaller with the purpose of increasing Xa, under the condition that a It becomes impossible to provide performance and traction performance.

Therefore, the present invention aims to improve the braking performance on muddy and icy road surfaces by making the ratio of the tire widthwise length a to the tire circumferential length of the ground contact print larger than that of conventional tires. The present invention provides a heavy-duty tire with significantly improved traction performance.

(Means for Solving the Problems) The present invention provides a general heavy-duty radial or bias tire with an aspect ratio in the range of 80 to 120% and a negative ratio in the range of 25 to 50%, of the ground print under normal internal pressure and normal load,
The ratio of the tire width direction length a to the tire circumferential length is 0.8≦a/b≦1.5, and the tire circumferential direction of each sipe provided on each land portion in the ground contact area is The relative relationship between the length component β in the tire width direction and the length component α in the tire width direction is preferably set as follows, where N: the total number of sipes in the ground contact area.

(Function) In this heavy-duty tire, in particular, the contact length ratio a
By setting /b to 0.8 or more and making the width direction length a relatively longer than the circumferential direction length, braking performance and traction performance on muddy road surfaces and ice and snow road surfaces can be greatly improved.

On the other hand, if the ratio a/b is made too large and exceeds 1.5, the resistance to sideslip will decrease significantly. For the purpose of achieving both of these, the ratio a/b of the ground contact length is set to 0.8≦a/b≦1.5.

However, since it is undeniable that the sideslip resistance decreases with an increase in the contact length ratio a/b, here, in order to compensate for this decrease and improve the structural integrity,
The relative relationship between the length component β in the tire circumferential direction and the length component α in the tire width direction of each land portion in the ground contact area, for example, each sipe formed on a block, that is, the 1 existing in the ground contact area More preferably, the ratio of the average value of the widthwise length component to the average value of the circumferential length component for each of the ~N sipes is as follows.

If it exceeds 0.5b/a, the length component α in the width direction of the tire becomes too large to effectively generate sideslip resistance, and if it is less than 0.5b/a, the length component α in the tire circumferential direction becomes too large. This is because the braking performance is too high and sufficient braking performance cannot be achieved.

In other words, when the length component α of the sipe in the tire width direction increases, the edges of the small land area divided by the sipe can effectively contribute to improving braking performance and traction performance. It becomes impossible to exert sufficient resistance against sideslip, and conversely, when the length component β in the tire circumferential direction becomes large, the edges of the small land areas make it possible to exert sufficient resistance against sideslip, but braking performance deteriorates. and impede improvement in traction performance.

Thus, according to this heavy-duty tire, it is possible to ensure sufficient stability resistance and greatly improve braking performance and traction performance on muddy road surfaces and icy and snowy road surfaces.

(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 the area surrounded by imaginary lines in the figure shows the area corresponding to the ground contact print when the tire is rolled under normal internal pressure and normal load. Therefore, a in the figure is the same as described in the conventional example,
b represents the length of the contact print in the tire width direction, and b represents the length of the contact print in the tire circumferential direction.

The internal structure of this tire is a radial or bias structure, so illustration is omitted here.

In this tire, the aspect ratio can be selected within the range of 80% to 120% and the negative ratio within the range of 25% to 50%, as required. Between two circumferential main grooves 1 extending in the tire, a pair of bending blocks 2, each of which is chamfered and approximately in the shape of a letter L, are arranged so as to be inserted into each other in the width direction of the tire. At the same time, such pairs of blocks are provided at predetermined intervals in the circumferential direction of the tire, and the above-mentioned bending blocks are located outside of each circumferential main groove 1 and along each circumferential main groove 1. Blocks 3 having a larger intersecting angle than 2 are also approximately in the shape of a "C" shape, and lugs 4 located further outside these blocks 3 and having an approximately rectangular shape
A tread pattern is formed by forming a plurality of sipes 5 on each of these blocks 2.3 and lugs 4 with a groove width in the range of, for example, 0 to 1.0 mm. ing.

Here, the angles and extending directions of the respective sipes 5 formed on the blocks 2.3 and the lugs 4 with respect to the tire equatorial plane It can also be different for each land column.

Further, each sipe 5 may have both ends terminated within the land portion, or at least one end may open to the side wall of the land portion.

Here, the ratio of the tire width direction length a to the tire circumferential direction length of the ground contact print is 0.8≦a/b≦
1.5.

This is because, according to the test results, as shown in Figure 2, the braking performance of tires on muddy road surfaces increases significantly when a/b≧0.8, while the sideslip resistance of tires increases with a/b
This is based on the fact that the value decreases rapidly when the value exceeds 1.5.

Furthermore, here, in order to compensate for the decrease in sideslip resistance due to the increase in a/b, each block 2 in the contact area
, 3 and each sipe 5 formed on the lug 4, the relative relationship between the length component β in the tire circumferential direction and the length component α in the tire width direction, as illustrated in FIG. 3, is expressed as follows: N: Ground contact area It is preferable that the total number of sipes in .

In other words, by increasing the length component β in the tire circumferential direction, the structural slip resistance performance on muddy road surfaces shown in Figure 4 will greatly improve, but the braking performance on ice, shown in Figure 5, will sharply decrease. In addition, the length component α of the sipe 5 in the tire width direction becomes too large, making it impossible to ensure effective demonstration of sideslip resistance.

As described above, here, the ratio a/b of the tire width direction length a to the tire circumferential direction length of the ground contact print is specified, and each of the blocks 2.3 and the lugs 4 included in the ground contact area is determined. By specifying the relative relationship between the length component β in the tire circumferential direction and the length component α in the tire width direction of the sipes 5 formed in braking performance and traction performance can be sufficiently improved.

[Comparative example]

Comparative tests of the invention tire and the comparative tire regarding on-ice braking performance, on-snow traction performance, and on-ice double lateral skidding performance will be explained below.

◎Test tire size 10.0OR20° Invention Tire I In a tire with the tread pattern shown in Figure 1, a/b is 1.3, and the intersection angle of each sipe with respect to the tire equatorial plane XX is 30 By setting Σ (αi/βi)/N to 0.577 b/a - Invented tire ■ In a tire having the tread pattern shown in Fig. 6, by setting a/b to 0.95 and , the intersection angle of each sipe with respect to the tire equatorial plane XX is 60°, and Σ (αi/βi)/N is set to 1.73b/a ° Comparative tire I As shown in Fig. 7 (a) In a tire with a tread pattern, a/b is set to 0.7 and Σ(αi/β
i)/N was set to 1.73 b/a, which is the same as that of the invention tire (■). Comparative tire (■) In a tire having the tread pattern shown in FIG. 7(b), a/b was set to 0.95, and , by setting the intersection angle of each sipe to the tire equatorial plane XX to be 75°, Σ(αi/βi)/N is 3.73b/a
Comparative Tire■ In a tire with the tread pattern shown in Figure 7(c), a/b is set to 0.7, and Σ(αi
/βi)/N is 3.73b/a, which is the same as the comparative tire ■.
Toshichi's ◎ Test Method For each tire, the braking performance on ice and traction performance on snow were determined as follows under a constant average ground pressure.

Braking performance on ice was measured by measuring the distance from when the brakes were applied while driving at 20 km/h until it came to a complete stop.As for traction performance on snow,
The towing force at the moment the tires rotated was measured using a load cell connected to the vehicle.

In addition, the performance of the structure on ice was determined by measuring the ramp time when running on a 50m diameter sludge course.

◎Test Results The results of these performance tests are shown in the table below, with each performance of the comparative tire (■) as an index of 100.

It should be noted that the larger the index value is, the more sagging the result is.

According to the above table, it is clear that as the ratio of the contact width to the contact length increases, both the braking performance on ice and the traction performance on snow improve. , both the braking performance on ice and the traction performance on snow will be improved by approximately 30%.

In addition, the anti-slip performance on ice can be achieved by appropriately increasing the length component of each sipe in the tire circumferential direction in relation to the above-mentioned improvements in each performance.
It is clear that this can be extremely effectively improved compared to that of Comparative Tire (2).

(Effects of the Invention) Thus, according to the present invention, it is possible to sufficiently eliminate the risk of skidding on muddy and icy road surfaces, and greatly improve braking performance and traction performance.

[Brief explanation of drawings]

FIG. 1 is a tread pattern showing an embodiment of the present invention. FIG. 2 is a graph showing changes in braking performance and sideslip resistance. FIG. 3 is a graph showing changes in braking performance and sideslip resistance. FIG. Figure 4 is a graph showing changes in structural slip resistance; Figure 5 is a graph showing changes in braking performance on ice; Figure 6 is a graph showing changes in braking performance on ice; 7 is a tread pattern showing a comparative tire; FIG. 8 is a diagram showing the contact state of the tire on a wet road surface; FIG. It is a figure showing the ground contact state of a tire. 1... Circumferential main groove 2.3... Fronk 4... Lug 5... Sipe a... Tire width direction length b... Tire circumferential length α... Tire width direction Length component β...Length component in the tire circumferential direction Fig. 1 1--Circumference j1m Main groove 23--Pro, Wa 4--Lug 5--Wise 'a--...In the tire aj: J-direction length b...Tyre circumferential direction & Fig. 2% Fig. 3 Fig. 4 Kusunoki Fig. 5 (〆tA) Fig. 15 Fig. 7<a) Fig. 7 (b) Figure 7 (C) Figure 8 (a) (b) Figure 9 (a) (b)

Claims (1)

[Claims] 1. A tire having an aspect ratio in the range of 80 to 120% and a negative ratio in the range of 25 to 50%, which has a ground contact print under normal internal pressure and normal load. , the ratio of the tire width direction length a to the tire circumferential length is 0.8≦a/b≦1.5, and the tire circumference of each sipe provided on each land portion in the ground contact area is The relative relationship between the length component β in the direction and the length component α in the tire width direction is expressed by ▲Mathematical formulas, chemical formulas, tables, etc.▼ N: Heavy-duty tire expressed as the total number of sipes in the contact area.