JPH0390404A - Tire for heavy load - Google Patents

Abstract

PURPOSE:To improve braking performance and the like against a muddy road and the like by respectively specifying ratio of respective lengths in the circumferential direction and in the width direction of a tire in the grounding print, and relation of respective edge component lengths in the circumferential direction and in the width direction of a tire on respective land parts in the grounding territory. CONSTITUTION:In a tire, oblateness is instituted in the range of 80-120%, and negative ratio is instituted is in the range of 25-50%. A plurality of blocks 2, 3 are arranged on both sides, inner and outer, of a plurality of main grooves in the circumferential direction, and a plurality of lugs 4 are arranged further outside the outside block 3. In this case, in the grounding print in the condition applied with the regular inner pressure and load, ratio of the circumferential length (b) to the width length (a) is instituted as follows: 0.8<=(a/b)<=1.5. On the respective land parts in the grounding territory, mutual relation between the edge component length beta in the circumferential direction of the tire and the edge component length alpha in the width direction of the tire is instituted as a formula elsewhere.

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 b of the ground contact print under normal internal pressure and normal load is less than 0.8. For example, it is possible to exhibit excellent braking performance and traction performance on wet road surfaces.

For example, when a tire moves on a wet road surface where water already exists, as is clear from the side view of the tire shown in Figure 9, water on the road surface flows to the underside of the tire at the treading side. Since the tire enters in a wedge shape, the tire mainly generates frictional force against the road surface by its kick-off side portion.

Here, let b be the length in the tire circumferential direction and a be the length in the tire width direction of the contact print of the tire under normal internal pressure and normal load. Of the circumferential length b, the length of the part in contact with water is b+
, when the length of the contact part with the road surface is b2, and a X b = A'v const b+ '= const, in order to increase b2 It is preferable to increase b, in other words, to narrow the tread width in order to reduce a/b. By doing so, high wet performance of the tire can be achieved.

(Question H that the invention seeks to solve) By the way, when tires roll on an icy and snowy road surface,
Melt water generated by friction between it and the road surface
As shown in the figure, contrary to what was described above, the tire is interposed in a nearly wedge-shaped part on the kick-out side, and in this case, the road friction force is mainly generated by the push-in side of the tire. Become.

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. 10(b)). Of the direction length b, the length of the part in contact with the road surface is 0
, 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, , Xa, and the above-mentioned wet performance improvement As in the case of b2X
When a / b is made smaller for the purpose of making a larger, a X b = A' = = constb 11 ”i
Under the condition of C0n5 i , b, , Xa become small and it becomes impossible to provide the desired braking performance and traction performance.

In view of this, the present invention particularly improves braking performance on muddy and icy road surfaces by setting the ratio of the tire width direction length a to the tire circumferential direction length b of the ground contact print to a value 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 direction length b is 0.8≦a/b≦1.5, and the edge component length of each land portion within the contact area in the tire circumferential direction More preferably, the relative relationship between β and the edge component length α in the tire width direction is as follows.

(Function) In this heavy-duty tire, the contact length ratio a/b is 0.
．． By making the width direction length a relatively longer than the circumferential direction length b, the 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, 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 as the ground contact length ratio a/b increases, we will introduce the following measures to compensate for this decrease and improve the structural slip resistance.
The relative relationship between the edge length β in the tire circumferential direction and the edge component length α in the tire width direction of each land portion in the ground contact area, for example, a block, that is, for each of 1 to N blocks. The ratio of the average value of the width direction edge component length to the average value of the circumferential direction edge component length is more preferably .

If it exceeds 0.5b/a, the edge component length α in the width direction of the tire becomes too long to effectively generate sideslip resistance, and if it is less than 0.5b/a, the land stiffness in the sideslip direction is low. This is because the sideslip resistance cannot be increased that much.

Thus, with this heavy-duty tire, it is possible to sufficiently ensure structural slip 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 rotated under normal internal pressure and normal load. Therefore, a in the figure is the same as described in the conventional example,
b indicates the length of the ground contact print in the tire width direction, and b indicates the length of the ground 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 the two circumferential main grooves 1 extending in the direction of The direction of each of the three blocks 2 placed is opposite to that of the circumferentially adjacent blocks,
Further, on the outside of each of the circumferential main grooves 1, there are blocks 3 that are bent into an approximately "L" shape along each of the circumferential main grooves 1, and blocks 3 that are located further outside of each of the bending blocks 3 and that are approximately "L" shaped. A tread pattern is formed by respectively providing lugs 4 that are bent in a ``F'' shape.

And here, the tire circumferential length b of the ground contact print
The ratio of tire width direction length a to 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, 3 in the ground contact area is
More preferably, the relative relationship between the edge component length β in the tire circumferential direction and the edge component length α in the tire width direction, as shown in FIG. 3, of the lug 4 is more preferably as follows.

In other words, according to the test results regarding the stability of the structure on a muddy road surface shown in Figure 4, the block and lug rigidity of the tire in the side-slip direction was too low, making it impossible to increase the side-slip resistance that much. , and the braking performance is lower than practical. In addition, the edge component length α of blocks and lugs in the tire width direction
becomes too long, and it is not possible to ensure effective exertion of sideslip resistance.

As described above, here, the ratio a/b of the tire width direction length a to the tire circumferential direction length b of the ground contact print is specified, and the block 2.
By specifying the relative relationship between the edge component length β in the tire circumferential direction and the edge component length α in the tire width direction of 3 and lug 4, structural slip resistance against muddy and icy road surfaces can be determined. It is possible to effectively ensure that braking performance and traction performance are sufficiently improved.

[Comparative example]

A comparative test of the inventive tire and the conventional tire in terms of braking performance on ice, traction performance on snow, and anti-slip performance will be described below.

◎Test tire size: 10.00 R20 - Invention tire I A tire having the tread pattern shown in Fig. 1, with the ratio a/b of the contact width to the contact length being 1.0, and the edge component length in the circumferential direction The ratio of the average value of the edge component length in the width direction to the average value of ・Invented tire■ A tire having the trend pattern shown in FIG. 5, with a/b ~ ・Conventional tire 0.92b/a A tire having a tread pattern shown in Fig. 6, with a/b 1, 43b/a - Comparative tire ■ A tire having a tread pattern shown in Fig. 7 (a), with a/b 1, 43b/a 1.1 Comparative Tire■ A tire with the tread pattern shown in Figure 7 (b), with a/b of 0.9 ◎Test Method For each tire, the braking performance on ice and the braking performance on snow were determined. Traction performance and structural resistance performance were determined as follows under a constant average ground pressure.

For braking performance on ice, we measure the distance from locking the brakes to a complete stop while driving at 20 km/h, and for traction performance on snow, we measure the traction force at the moment the tires rotate, which is measured by connecting the vehicle with the vehicle. Measured using a load cell.

The structural slip resistance performance was measured by lap time when running on a 50 m diameter muddy course.

◎Test results The measurement results of braking performance on ice, traction performance on snow, and anti-slip performance are shown in Figure 8 (a) and (b).
, (C) shows the performance of each conventional tire as an index of 10
As 0, it is displayed as an index in a graph.

Note that the larger the index value, the better the result.

According to the graphs shown in FIGS. 8(a) and 8(b), it is clear that as the ratio a/b of the contact width to the contact length increases, both the braking performance on ice and the traction performance on snow improve. In particular, the invented tire (2) has an approximately 30% improvement in braking performance on ice and an approximately 50% improvement in traction performance on snow compared to the conventional tire.

On the other hand, in the comparative tires I and It which exhibit structural slip resistance performance, the structural slip resistance performance is reduced to nearly half that of the conventional tire, whereas inventive tire 1. In II, Σ(α, /β,)/Nt=1 are 1.94b8 and 0.92b/a, respectively, and both are 3. It is clear that by keeping the value less than Ob/a, it is possible to extremely effectively prevent the deterioration of the structure's anti-slip performance.

(Effects of the Invention) Thus, according to the present invention, it is possible to sufficiently eliminate the risk of skidding on muddy road surfaces and icy and snowy road surfaces, and to 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 braking performance and sideslip resistance, and Fig. 3 is an edge component of the land portion within the contact area in the circumferential direction of the tire. FIG. 4 is a graph showing structural slip resistance performance; FIG. 5 is a graph showing another tread pattern according to the present invention; FIG. , Figure 7 is a diagram showing the tread pattern of a conventional tire, Figure 8 is a graph showing the tread pattern of a comparative tire, Figure 8 is a graph showing braking performance on ice, traction performance on snow, and anti-slip performance. FIG. 10 is a diagram showing the contact state of tires on a wet road surface. FIG. 10 is a diagram showing the contact state of tires on an icy and snowy road surface. 1... Circumferential main groove 2.3... Block 4.
・・Lug a・・・Tire width direction length b・
...Tire circumferential length αa8 αb, αC...Edge component lengths facing in the tire width direction βa, βb, βC...Edge component lengths facing in the tire circumferential direction

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 direction length b is 0.8≦a/b≦1.5, and the edge component length of each land portion in the tire circumferential direction in the tire circumferential direction A heavy-duty tire that expresses the relative relationship between the length β and the edge component length α in the tire width direction as follows: ▲There are mathematical formulas, chemical formulas, tables, etc.▼