JP2002002231A - Pneumatic tire for heavy load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent degradation in traction performance and improve the traction performance by improving mud-removing performance in a lug groove. SOLUTION: A pneumatic tire for a heavy load is provided not only with a lug 4 partitioned by the lug groove 1 opening at a tread end and a circumferential groove 2 but also with a center block 6 partitioned by the circumferential groove 2 and a crossing groove 5. The width-direction-of-tread span WS of the lug 4 is taken not only as at least the similar span WC of the center block 6 but also as at least one quarter of tread width.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty pneumatic tire having a lug, which has improved mud-repelling properties and traction performance on rough roads.

[0002]

2. Description of the Related Art A conventional heavy duty pneumatic tire having a lug, for example, a pneumatic radial tire is shown in FIG.
Some have a tread pattern as illustrated in a development view.

[0003] The lug grooves 2 are linearly inclined at intervals in the circumferential direction of the tread, and open at the tread end.
1 and a circumferential groove 22 extending in a zigzag shape in the circumferential direction and communicating with the tip of the lug groove 21 to define a lug 23 whose opposing sides extend almost in parallel and bend in a substantially "H" shape. The center block 25 which is long in the extending direction of the lug groove 21 is defined by the respective circumferential grooves 22 and the inclined transverse grooves 24 connecting them.
5 is provided with a groove 26 extending substantially in parallel with the inclined transverse groove 24 at the center.

According to such a tread pattern, there is an advantage that heat accumulation due to heat generated by the lug during high-speed running can be effectively prevented by the heat radiation effect of the groove, as compared with the case where only the lug is provided in the tread portion. .

[0005]

However, in such a conventional technique, the relative or absolute shape and size of the lug 23 are set in order to realize excellent mud repellency and traction. It is not clear whether the lug 23 is suitable, and in the prior art, the area occupied by the lug 23 is smaller than that of the groove 21 as shown in FIG.
There is no significant difference, and the degree of deformation of the lug grooves 21 during load rolling is not so large, and therefore, the degree of opening of the lug grooves 21 is small. The mud is hard to fall off, and the lug 23 is set shorter in the tread width direction for design reasons, and the center block 25 is emphasized. Could not. Recent experiments have confirmed that the contribution ratio of the ribs on both shoulders is higher than that of the center block in terms of traction performance.

SUMMARY OF THE INVENTION An object of the present invention is to solve such problems of the prior art, and it is an object of the present invention to improve the traction performance by improving the mud-peeling property from a lug groove. Another object of the present invention is to provide a heavy-duty pneumatic tire that prevents a decrease in the traction performance and further improves traction performance.

[0007]

A heavy-duty pneumatic tire according to the present invention is provided with a lug groove which bends in a substantially "H" shape, opens at the tread end, and gradually decreases in width toward the tread center. , Is defined by a circumferential groove extending substantially linearly or zigzag in the circumferential direction of the tread, and has, for example, a lug in a substantially “H” shape, and is defined by the circumferential groove and the transverse groove. The lug has a total length (WS) of the lug in the tread width direction equal to or greater than the same overall length (WC) of the center block and equal to or greater than 1/4 of the tread width (TW). It is what it was.

According to this tire, by increasing the rigidity of the lug, it is possible to concentrate the external force input to the lug groove to increase the degree of deformation, thereby making it easier for the mud from the lug groove to drop.

[0009] In this case, the overall length of the lug in the tread width direction is specified as described above, and is made sufficiently longer than that of the prior art, so that when the tire is loaded on muddy ground, the tire can be rolled. The mud hold area on the side of the tread, which has a high contribution to traction performance, can be effectively expanded to ensure improved traction performance.

The reason why the overall length (WS) of the lug in the tread width direction is set to be equal to or longer than the overall length (WC) of the center block is to improve the traction performance. Length (WS), tread width (T
The reason why W is set to 1/4 or more is that if it is less than 1/4, it is not effective for improving traction performance.

Preferably, the groove width of the lug groove is gradually reduced toward the tread center. According to this, the circumferential rigidity of the tread portion is not uniform, and the circumferential rigidity of the lug tends to increase, so that the protrusion deformation of the tire at the time of load rolling is borne by the groove portion. Thereby, the groove is easily opened, and the mud-peeling property is improved.

That is, when the vehicle travels on muddy ground, mud splashing depends on the expansion deformation of the lug grooves at the time of protruding in the circumferential direction of the tread upon load rolling of the tire. In the prior art, the lug is symmetrical about its center line C, and the circumferential rigidity of the pattern becomes uniform,
Since the force tends to be uniformly applied to the lug and the lug groove, deformation at the time of protruding is also received by the lug portion, and the opening of the groove deteriorates, so that the mud-repelling property decreases.

Moreover, according to this asymmetric structure, the rigidity of the lug is inevitably increased, and the force with which the lug catches the road surface is increased, so that the traction performance is also improved.

In such a tire, when a groove is provided in the center portion of the center block, traction performance can be further enhanced by trapping mud with the groove.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a developed view of a tread pattern showing an embodiment of the present invention. The internal structure of the tire is the same as that of a general heavy-duty radial tire, and is not shown.

Here, a lug groove 1 which opens at each tread end and is bent in a substantially “H” shape in the middle portion and gradually decreases in width toward the tread center side, and extends in a zigzag fashion in the circumferential direction of the tread. A lug 4 having a substantially “H” shape is defined by the circumferential groove 2 which is present and communicates with the lug groove 1, and the lug 4 is asymmetrical with respect to its center line C, The width of the lug 4 in the circumferential direction of the tread is gradually increased toward the bend in the middle thereof.

Further, a center block 6 is defined by a pair of circumferential grooves 2 and 2 extending in a zigzag shape and a transverse groove 5 between the circumferential grooves to connect their bent projections to each other. In the center of the center block 6, which has a substantially parallelogram shape as a whole, an upwardly-sloping groove 7 is provided, which extends, for example, in a diagonal direction of the center block.

When each of the lug 4 and the center block 6 is partitioned in this way, the overall length WS of the lug 4 in the tread width direction is set to be equal to or longer than the same overall length WC of the center block 6, and Tread width TW
１ ／ or more. Further, preferably, the maximum width DS of the lug 4 in the tread circumferential direction is set to 0.5 to 0.85 times the arrangement pitch P of the lug 4.

According to the tire configured as described above,
As the rigidity of the lug 4 increases, the degree of deformation of the lug groove 1 can be effectively increased to advantageously improve the mud repelling property on rough roads, and the overall length WS of the lug 4 can be increased. By increasing the area of action of the lug 4 against mud and the like, traction performance can be greatly improved.

In addition, the case where the groove width of the lug groove 1 is gradually reduced toward the tread center and the maximum width DS thereof
Is set to 0.5 to 0.85 times the lug arrangement pitch P and is made thicker than the conventional lug, the rigidity of the lug 4 is further increased to further improve the mud-repelling property and the traction performance. Can be realized.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A tire for trucks and buses having a size of 315 / 80R22.5, having the tread pattern shown in FIG. 1 and the tread pattern shown in FIG. ETRT STANDARD for each of the conventional tires that are the same as the tires
Under a load condition, an applied rim and air pressure in accordance with S MANUAL, a traction test and a mud-peeling test were performed on muddy ground. Table 1 shows the results.

Here, the traction force is indicated by an index value using a conventional tire as a control, and the larger the value is, the better the result is. The mud repellency is measured by measuring the volume of the mud remaining in the lug groove. The index value is shown by using the conventional tire as a control. The smaller the numerical value, the better the result.

[0023]

[Table 1] According to Table 1, in the example tire, compared to the conventional tire,
It is evident that both traction and mud release can be significantly improved.

[0024]

As described above, according to the present invention, it is possible to greatly improve the mud-repelling property when traveling on a rough road, to prevent a decrease in traction performance, and to directly improve the traction performance itself. .

[Brief description of the drawings]

FIG. 1 is a development view of a tread pattern showing an embodiment of the present invention.

FIG. 2 is a development view of a tread pattern showing a conventional tire.

[Explanation of symbols]

 Reference Signs List 1 lug groove 2 circumferential groove 4 lug 5 transverse groove 6 center block 7 groove portion WS lug overall length in tread width direction WC overall width of center block in width direction TW tread width C center line

Claims (4)

[Claims] 1. A tire having a lug defined by a lug groove opening at a tread end and a circumferential groove and a center block defined by a circumferential groove and a transverse groove. A heavy-duty pneumatic tire having an overall length (WS) in the tread width direction equal to or greater than the same overall length (WC) of the center block and equal to or greater than ４ of the tread width (TW). 2. The heavy duty pneumatic tire according to claim 1, wherein a groove width of the lug groove is gradually reduced toward a tread center side. 3. The maximum width (DS) of the lug in the tread circumferential direction is 0.5 to 0.85 of the lug arrangement pitch (P).
The heavy-duty pneumatic tire according to claim 1 or 2, which is doubled. 4. The pneumatic tire for heavy loads according to claim 1, wherein a groove is provided in a center portion of the center block.