JPS5822702A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To eliminate a possibility of gripping stones or the like in grooves and to improve the cracking resistance of the tire by a method wherein the zigzag grooves arranged in a tread part is so formed that a step part having a predetermined depth and width is provided on one side wall part, and in this case the step width is decreased gradually from a circumferential rib stretching part toward a rib corner part. CONSTITUTION:The step part 13 having a height H' of a value within a range of 30'60% of the maximum groove depth H is formed on one of the side wall parts 11 and 12 of the zigzag grooves 2-5. As to the width W' of the step part 13, a groove width expansion part 16 is formed which becomes narrower continuously and gradually from the stretching part 14 of the circumferential ribs 6-10 toward the corner part 15 thereof within a width value of 20-0% of the maximum groove width W. With this construction f the tire groove, the stone gripped in the groove can easily come out. Further, the frictional wear resistance of the tread part 1 is not decreased from an initial stage of friction to a final stage, and also the cracking resistance of the tire can be much improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pneumatic tire, and more specifically, the present invention relates to a pneumatic tire, and more specifically, by improving the shape of the zigzag grooves of a tire in which circumferential ribs are formed by a plurality of zigzag grooves arranged in the tread portion, The present invention relates to a pneumatic tire that prevents stones and the like from getting caught in the grooves and improves the crack resistance of the tire.

Conventional measures have been taken to prevent stones from getting stuck in the grooves arranged in the tread of tires as described above.
Forming the cross-sectional structure of the groove in a V-shape as shown in A),
Alternatively, forming it into a funnel shape as shown in FIG. 1(B) has been proposed.

However, as mentioned above, the countermeasure against stone encroachment by forming the cross-sectional structure of the groove in a V-shape or funnel-shape is similar to tires for trucks and buses, which have a wide tread width.
For large tires where the groove width can be widened, Celsius can be expected to have some effect, but for small truck tires, the tread width is relatively narrow and when considering the wear resistance of the tread, the groove width Small tires that cannot be made very wide have the disadvantage that, when loaded, especially when traveling on rough roads, piling occurs, which can lead to group cracks.

In addition, for large bias tires such as those for trucks and buses, tires with stepped grooves (relief steps) formed at every half pitch of the zigzag groove, as shown in Figure 1 (C''), have also been proposed. For tires with a small tread width, such as the light truck tires mentioned above,
Currently, since it is not possible to arrange wide grooves in the tread portion, it is not possible to expect an effect of preventing stone build-up.

The object of the present invention is to solve the above-mentioned problems.

The tread width is relatively narrow, such as tires for small trucks.
To provide an excellent pneumatic tire which can prevent stone build-up without impairing the wear resistance of tires in which the groove width cannot be widened, and which can improve crack resistance caused by the stone build-up.

The feature of this feature is that one side wall of the zigzag groove is provided with a stepped portion having a depth of 30% to 60% of the maximum groove depth, and the width of this stepped portion is equal to the maximum groove width. against 2
The groove width expansion portions are alternately provided on both edges of the groove, with the groove width gradually narrowing from the projecting portion of the circumferential rib toward the corner of the rib in the range of 0% to 0%.

Hereinafter, the present invention will be explained in detail by way of examples with reference to the drawings.

Fig. 2 is a developed view of the tire tread of a pneumatic tire according to an embodiment of the present invention, Fig. 3 (A) is a sectional view taken along arrows 1-1' in Fig. 2, and Fig. 3 (B) is a sectional view taken from Fig. 2 -n' arrow sectional view, Figure 3 (C)
The figure shows the test results for the anti-rock-blocking effect of tires, and FIG. 5 shows the test results for the wear resistance of tires.

In the figure, reference numeral 1 indicates the tread portion of a tire according to an embodiment of the present invention, and ``C5'' is shown in FIG. 2.

A plurality of zigzag grooves 2, 3° 4.5 are arranged in the circumferential direction of the tire, and these grooves form a zigzag circumferential rib 6.
．． 7, 8, 9.10 are formed. Each of the zigzag grooves 2, 3° 4.5 has a maximum groove depth H of 3° on one side wall portion 11.12, as shown in FIGS. 2 and 3.
Step part 1 is placed at a position having a depth H' in the range of 0% to 60%.
3 is provided, and @w' of this stepped portion 13 is within a range of 20% to θ% of the maximum groove width W, starting from the projecting portion 14 of the circumferential rib, and reaching the corner 15 of the circumferential rib. It has a groove width expanding portion 16 that continuously becomes gradually narrower.

As described above, if the stepped portion 16 is provided at a position having a depth in the range of 30% to 60% of the maximum groove depth H of the groove, as will be described later, from the initial stage of wear of the tread portion 1 to near the final stage of wear,
It has the effect of preventing stone build-up without compromising wear resistance, but
If the depth H' of the stepped portion 13 is still not 30% of the maximum groove depth H, if the tread portion 1 is worn down to the depth H' of the stepped portion 13, the stone-cage prevention effect will be lost, and the stepped portion 16 This is because if the groove depth H' exceeds 60% of the maximum groove depth H, the effect of preventing stone build-up in the early stage of wear of the tread portion 1 will be reduced.

Further, since the width W' of the stepped portion 13 is continuously changed as described above, stones stuck in the groove can be easily removed.

Also, is the width W' of the stepped portion 16 20% of the maximum groove width W? If it exceeds the level, the remaining groove width becomes narrow when the tread portion 1 wears down to the stepped portion 13, and the drainage performance deteriorates, which is not desirable. ) is a diagram showing the test results of a comparative study of the rock-blocking prevention effect between the tire with stepped grooves formed at every half pitch shown in Figure 1 (A) and the tire shown in Figure 1 (A). Size 6.0OR15-8P
R tires were mounted on a 1.5 toH car (Toyoace manufactured by Toyota Motor Corporation), and after driving on a rough road test course for 4000 km, the number of stones caught per tire was determined.

As a result, as shown in Fig. 4, the conventional tire shown in Fig. 1(C), that is, the tire in which stepped grooves are arranged at every half pitch of each zigzag groove, has 25 stones, and the number of stones in Fig. 1(A) is 25. As shown in the previous figure, the number of stones in the tire was 35,
The number of stone bites in the tire of the present invention was 1, and it can be seen that the tire of the present invention has a remarkable effect of preventing stone bite.

FIG. 5 is a diagram showing test results comparing the wear resistance of the tire of the present invention described above and the conventional tire shown in FIG. 1(A).

This test was conducted using tire size 6.0OR15-8P.
R tires were mounted on a 1.5 ton automobile (Toyoace manufactured by Toyota Motor Corporation), and after driving on a good road test course for 20,000 km, the wear of the tires was expressed as a wear resistance index.

As a result, as shown in Fig. 5, the tire of the present invention is equivalent to the conventional tire in terms of wear resistance, and the C groove width expansion section was provided for the purpose of preventing stone build-up, so that Celsius also does not impair wear resistance. It is clear that there is no.

As described above, the present invention provides a stepped portion having a depth of 3θ% to 60% of the maximum groove depth on one side wall of the zigzag groove, and the width of this stepped portion is equal to the maximum groove width. 20%~
Starting from the protrusion of the rib in the circumferential direction within a range of 0%, groove width expansion portions are gradually narrowed toward the corners of the rib and are alternately provided on both edges of the groove. It is possible to improve the effect of preventing one-stone bite without impairing the wear resistance of a tire whose tread development width is relatively narrow and whose groove width cannot be widened, and to improve the resistance to cracks caused by one-stone bite.

[Brief explanation of drawings]

Figures 1 (A) to (C) are explanatory diagrams showing the cross-sectional shape of the grooves of a tire with conventional stone-blocking prevention measures, and Figure 2 is a developed view of the tire tread of a pneumatic tire according to an embodiment of the present invention. , FIG. 3(A) is a sectional view taken along arrows I-I' in FIG. 2, FIG. 3(B) is a sectional view taken along arrows n-n' in FIG. [1-DI' arrow sectional view, FIG. 4 is a diagram showing the test results of the stone-blocking effect of the tire, and FIG. 5 is a diagram showing the test results of the tire wear resistance. 1... Tire tread portion, 2, 3, 4, 5... Zigzag groove, 6, 7, 8, 9, 10... Circumferential rib, 11° 12... Grooved side wall part , 13... step part of the groove,
14... Projection of groove, 15... Corner of lip, 16
...Groove width expansion portion, H...Maximum groove depth, H'...Depth of stepped portion, W...Maximum groove width, W'...Width of stepped portion. Figure 1 (A) (B) (C) Figure 2 Figure 3 (A) (B) (C) Figure 5
Wear resistance index

Claims (1)

[Claims] In a pneumatic tire having a tire tread portion formed with a circumferential groove by a plurality of zigzag-shaped grooves arranged in the circumferential direction of the tire, a side wall portion on the - side of the groove,
A stepped portion having a depth of 30% to 60% of the maximum groove depth is provided, and the width of the stepped portion is in the range of 20% to 0% of the maximum groove width, starting from the projecting portion of the circumferential rib. A pneumatic tire in which groove width expansion parts that gradually narrow toward the corners of the ribs are provided alternately on both edges of the groove.