JPH03135804A - Pneumatic tyre - Google Patents

Abstract

PURPOSE:To reduce stone bite against narrow channels without hindering abrasion resistance due to narrow channels by forming a step part on one side wall and a projection on the other side wall of the narrow channels formed on the surface of a tread. CONSTITUTION:Narrow channels 12 are formed on the surface of a tread 10 extendedly in the tyre circumferential direction. In this case, a step part 20 for dividing a wide upper channel part 14 opened on the surface of the tread 10 and a narrow lower channel part 18 going to the channel bottom part 16 is formed in one side wall of the narrow channel 12 extendedly in the tyre circumferential direction. A projection 22 projecting to the upper channel part 14 is formed on the other side wall extendedly in the tyre circumferential direction. Furthermore, the projection 22 is formed spacedly from the top 24 of the step part 20 in the tyre radial direction, and also a projecting length thereof is set larger than the channel width of the lower channel part 18 so that the tip thereof looks overlapped with the step part 20.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a pneumatic tire in which damage to the tire due to stone bite is reduced without impairing uneven wear characteristics.

(Prior Art) For the purpose of reducing or improving uneven wear of tire treads, many proposals have been made for adding innovations to tread patterns and crown shapes. One of them is a tire that has narrow grooves extending in the circumferential direction of the tire in order to suppress the occurrence and progression of uneven wear in the rib portion partitioned by the circumferential main groove extending in the tire circumferential direction. These narrow grooves not only impart desired uneven wear resistance to the tire, but also have the effect of improving wet performance, preventing wandering, and the like.

(Problem to be Solved by the Invention) Incidentally, in order to obtain good uneven wear resistance, the groove depth D of the narrow groove must be greater than a certain value, but the groove width W relative to the groove depth D must be When the ratio (W/D) becomes small, it becomes difficult for stones to be trapped in the narrow grooves, but it becomes difficult to discharge the trapped stones from the narrow grooves in accordance with the rotation of the tire. In addition, when a tire is transferred with stones trapped in this way, repeated loads are applied to the bottom of the narrow groove, which can easily damage the bottom of the narrow groove (in the worst case, the damage may progress to the inside of the tire). Note that such problems exist regardless of the internal structure of the tire.

The present invention has been made in view of such problems,
It is an object of the present invention to provide a pneumatic tire having narrow grooves extending in the circumferential direction of the tire, excellent in uneven wear resistance, and with little stone encrustation.

(Means for Solving the Problems) In order to achieve this object, the present invention provides a pneumatic tire comprising at least a circumferential main groove and a narrow groove extending substantially in the circumferential direction of the tire on the tread surface, wherein the narrow groove is , a step part provided on one side wall and forming a wide upper groove part opening to the tread surface and a narrow lower groove part reaching the groove bottom, and a step part that is spaced from the other side wall and protrudes into the upper groove part and extends around the tire circumference. and a protrusion extending in the direction.

Furthermore, instead of the protrusions extending in the circumferential direction of the tire, a plurality of protrusions that are spaced apart from each other in the circumferential direction of the tire may be formed, and the protrusion width of these protrusions or protrusions is such that the free end thereof is in the tread direction. Preferably, the dimensions are such that the narrow groove overlaps the stepped portion when viewed from above.

Now, FIG. 1(a) shows a narrow groove portion of a pneumatic tire to which the present invention is applied. In the figure, numeral 10 indicates a tread;
12 is a narrow groove formed to extend in the tire circumferential direction.

A stepped portion 20 extending in the tire circumferential direction defines a wide upper groove portion 14 opening to the surface of the tread 10 and a narrow lower groove portion 18 reaching the groove bottom 16 on one side wall of the narrow groove 12. On the other hand, a protrusion 22 is formed on the other side wall so as to protrude into the upper groove portion 14 and extend in the tire circumferential direction. This protrusion 22 is formed apart from the top 24 of the stepped portion 22 in the tire radial direction, and its protrusion length is larger than the groove width of the lower groove portion 18. Therefore, when viewed from the tread surface direction, The end portion appears to overlap the stepped portion 20.

In this embodiment, the protrusions 22 extend in the circumferential direction of the tire, but as clearly shown in FIG. It can also be a protrusion 26.

The internal structure of the pneumatic tire illustrated in FIGS. 1 and 2 is the same as that of a radial tire, and is not directly related to the present invention, so a description thereof will be omitted here.

(Function) In this way, by arranging the stepped portion 20 on one side wall of the narrow groove 12 to provide the upper groove portion 14 and the lower groove portion 18, and providing the protrusion 22 on the other side wall of the upper groove portion, While maintaining the ratio of the groove width to the groove depth of the narrow grooves 12 within a predetermined range capable of suppressing uneven wear of the tire, the upper groove portion, that is, the surface of the tread 10 that is substantially involved in stone-biting of the tire. Since the distance from the groove to the top 24 of the stepped portion can be made small, the stone bite characteristics can be improved without impairing the uneven wear resistance due to the narrow grooves.

Then, as shown in FIG. 1(b), ;Iζ of the narrow groove 12
The depth is D, the groove width is W, the depth from the surface of the tread IO to the top 24 of the stepped portion is d8, the dimension in the groove width direction of the stepped portion is W, and the distance from the tread surface of the protrusion 22 to its lower surface. When the depth is d2, the thickness of the protrusion is a, and the dimension in the groove width direction is h, it is preferable that these values satisfy the following conditions.

dl = (0,2~0.6)XD, 2 (mm)≦(d, dz)≦5 (mm), w=
(0,3-0.7)XW.

h>(W-w) a=2 to 4 (mm) This means that when the tread contacts the road surface and the tread rubber including the narrow grooves 12 is deformed when the tire is transferred, the groove width of the lower groove portion 18 is exceeded. protrusions 22 or protrusions 26 that protrude
However, as shown by the solid line in FIG. 3(a), the lower groove portion 18
This is because the openings of the tread rubber including the narrow grooves 12 can be closed, which is essentially equivalent to setting a large value of W/D, and the stone bite resistance can be improved. When the tire moves out of contact with the road surface and returns elastically, the ridges 22 or projections 26 will also move radially outward in accordance with the return, so even if a stone is caught in the upper groove. Even so, the layer can be released outward as the tire is transferred, as shown in FIG. 3(b).

Moreover, by selecting the ratio of the groove width W of the lower groove portion 18 to the groove width W of the upper groove portion 14 of the narrow groove within the range of 30 to 70%, it is possible to ensure the uneven wear resistance property of the narrow groove 12. Because you can.

In order to ensure the ejection of stones based on the elastic return of the protrusions 22 or protrusions 26, the thickness a is 2 to 4 (
mm). The reason why the difference between the depth d+ of the top 24 of the stepped portion and the depth d2 to the bottom surface of the protrusion 22 is set to 2 to 5 (mm) is because the tread wear has progressed to a certain extent. This is to ensure the desired performance.

(Example) Test tires of size 11R22.5 were alternately mounted on the same vehicle and driven for 100,000 km, and the number of stones caught in each vehicle was determined every 20,000 km. The test results are shown in FIG.

Here, the invention tire subjected to the test had narrow grooves with a cross-sectional shape shown in FIG.
The tire has protrusions with a length of 6M arranged at intervals, the groove depth D of the narrow groove is 15.0 mm, and the groove width W is 1.0 mm.
5mm, and the depth d of the top of the stepped part is 8. Omm, the dimension W of the step in the groove width direction is 0.5M, the depth d2 to the bottom surface of the protrusion 26 is 7.0mm, the thickness a of the protrusion 26 is 1.2mm,
The tire has a groove width dimension of 1.2 mm, and the comparative tire has the shape shown in Figure 5, with a groove depth D of 15.0 mm and a groove width of 1. .5+
It is set as nm.

As is clear from FIG. 4, according to the tire according to the present invention, the number of stone bites per mile traveled is approximately 60% lower than that of conventional tires, and this trend continues as the mileage increases. It was found that this phenomenon persisted until the latter half of the thickness ratio progression.

(Effects of the Invention) Thus, according to the present invention, the stone-biting characteristics in the narrow grooves can be significantly improved without impairing the uneven wear resistance of the tire provided with the narrow grooves.

[Brief explanation of the drawing]

FIGS. 1(a) and (b) are explanatory diagrams showing the narrow groove shape and the dimensional relationship of the pneumatic tire according to the present invention. FIG.
Diagrams showing other embodiments of the present invention, FIGS. 3(a) and (b)
is an explanatory diagram showing the behavior of the tire shown in FIGS. 1 and 2, FIG. 4 is a diagram showing the results of a comparative test between the tire of the present invention and a conventional tire, and FIG. 5 is a diagram showing the details of the conventional tire. It is a figure which shows the groove shape. 10--Tread 12-Narrow groove 14-Upper groove portion 16-Groove bottom 1B-Lower groove portion 20-Step portion 22-Protrusion
24-Top 26-Protrusion Fig. 1 (a) (b) Fig. 2 Fig. 3 (a) (b) Fig. 4 Fig. 5

Claims (1)

[Claims] 1. A pneumatic tire comprising at least a circumferential main groove and a narrow groove extending substantially in the circumferential direction of the tire on the tread surface, wherein the narrow groove is provided on one side wall and opens on the tread surface. A stepped portion defining a wide upper groove portion and a narrow lower groove portion reaching the groove bottom, and a protrusion that is spaced apart from the other side wall to the stepped portion, projects into the upper groove portion, and extends in the tire circumferential direction. A pneumatic tire characterized by: 2. The pneumatic tire according to claim 1, wherein the protrusions protruding from the upper groove portion are a plurality of protrusions spaced apart from each other in the tire circumferential direction.