JPH02179506A - Pneumatic tire - Google Patents

Abstract

PURPOSE:To improve deflected abrasion resistance while suppressing the occurrence of rib tear by forming a pair of circumferential grooves halving a land part divided by a main groove, thereby forming a different level area, and disposing a plurality of platform parts in the circumferential grooves. CONSTITUTION:A tire 1 has a plurality of circumferentially extending continuous main grooves formed on the outer surface of a tread part 5, or a wheel tread 6. Thus, the wheel tread 6 is divided into a plurality of circumferentially extending land parts, namely a center rib 8a on the tire equatorial face 9 and side ribs Bb on the both sides thereof. In this case, at least a pair of circumferential grooves 11 extending continuously in the circumferential direction are formed on the wheel tread 6 of the side ribs 8b, whereby a different level area 12 independent from the side ribs 8b is formed. On each circumferential groove 11, a plurality of platform parts 16 protruded in the radial direction from the bottom to partly bury the inside of the circumferential groove 11 are disposed. The side walls of the land part 8 and the different level area 12 is mutually connected by the platform parts.

Description

[Detailed description of the invention]

The present invention provides a pneumatic tire having a main groove continuously extending in the circumferential direction and a land portion divided by the main groove on the road surface.

[1] In general, the wear phenomenon that occurs in pneumatic tires depends on the road surface conditions, but when driving for long periods of time on expressways that have recently been significantly improved, the wear phenomenon that occurs in pneumatic tires generally occurs when the tire treads on the road surface. The shape of the road surface changes depending on the external force (tire input) that acts on it, and this causes a difference in the speed and slowness of wear, leading to accelerated cumulative acceleration in the two parts where wear is faster, resulting in uneven wear of river wear, rib punches, etc. It becomes. In order to reduce such uneven wear, various proposals have been made in the past. For example, U.S. Pat. No. 4,155,313 proposes reducing uneven wear by changing the crown shape.
There is a method described in the specification of No. 2, and there is a method described in the specification of US Pat. No. 3,550,865 that reduces uneven wear by arranging the sizes at both ends of the rib. However, such conventional tires cannot prevent uneven wear itself, but merely delay its occurrence, so there is a problem in that uneven wear inevitably occurs after driving. Also, if the above suggestions are implemented,
There is a problem in that the burden of tire input is shifted to other parts, and uneven wear may occur in those parts. As a result of intensive research to solve these problems,
Because we were able to establish an effective uneven wear prevention +h measure1
The present applicant is Japanese Patent Application No. 82-285248 (1988).
A heavy-duty pneumatic tire having a main groove that extends continuously along the circumference of the tread surface of the tire, and a land area separated by this main groove, wherein the above-mentioned land area is The land section is divided into two by a pair of narrow grooves or sizes that descend from the cross-sectional contour of the tread and are continuous along the circumference of the tread. We have proposed a pneumatic tire for heavy loads that prevents uneven wear and is characterized by having an uneven wear sacrifice part that makes sliding contact with the road surface within the tread area that supports the applied load. This thing is
When the tire runs, the surface of the step area slides into contact with the road surface within the tread surface area, so an extremely large shearing force in the braking direction is generated in the step area, and as a result, the shear force on the land on both sides of the step area is driven. As a result, a shearing force in the driving direction is applied to all land parts. Here, the wear rate of the road surface receiving shear force in the driving direction is significantly slower than the wear rate of the road surface receiving shear force in the braking direction, so only the step area receiving shear force in the braking direction is sacrificed and wears out. Therefore, wear of the land portion is prevented. Here, when the circumferential groove is formed on the road surface as described above, the area of the land portion decreases and the negative ratio increases, resulting in a decrease in the wear resistance of the pneumatic tire. For this reason, it is better that the yt width of the circumferential groove is as narrow as possible;
When the groove width of the circumferential groove is narrowed, the radius of curvature of the groove bottom of the circumferential groove becomes small, making it easier for stress to concentrate. As a result, when the land portion and the step area are relatively displaced (opening of the circumferential groove) due to lateral force while driving, the bottom of the circumferential groove easily cracks, resulting in rib tears. There is. The present invention aims to solve such problems, and is directed to a pneumatic tire that has a main groove that extends continuously in one circumferential direction and a land section that is divided by this main groove on the road surface. By forming at least a pair of circumferential grooves on the tread surface that extend continuously in the direction and bisect the land portion,
The road surface between these pairs of circumferential grooves is independent from the land, and its radially outer end surface is located radially inward from the cross-sectional contour line of the road surface, and during normal driving, the radially outer end surface is located in the tread area. A step area is defined as an uneven wear sacrifice part where the end surface slides into contact with the road surface, and. A plurality of platform portions spaced apart in the circumferential direction are provided in at least the narrow side circumferential groove of the pair of circumferential grooves, and the platform portions connect the side wall of the land portion and the side wall of the stepped region to each other. It is a pneumatic tire. JanuaryAs mentioned above, if the groove width of each circumferential groove is made as narrow as possible, the radius of curvature at the groove bottom of the circumferential groove will become smaller, so when lateral force etc. are applied, a large stress concentration will occur at the groove bottom of these circumferential grooves. is thought to occur. However, in this invention, a platform portion is provided in at least the circumferential groove on the narrow side, and the platform portion connects the side wall of the land portion and the side wall of the step area to each other, so that it is subjected to lateral force etc. At this time, the land portion and the stepped region are displaced by approximately the same amount in the same direction, and the relative displacement amount between the two becomes small. As a result, stress concentration at the groove bottom of the circumferential groove due to the lateral force etc. is reduced, and rib tear is suppressed. here,
As mentioned above, the platform portion is provided at least in the circumferential groove on the narrow side because the radius of curvature of the bottom of the circumferential groove on the narrow side is smaller than that of the circumferential groove on the wide side. This is to prevent the generation of cracks in the circumferential groove on the narrow side for the time being, since stress is more concentrated at the bottom of the circumferential groove on the narrow side when a lateral force or the like is applied. In addition, in this invention, the platform part may be provided also in the circumferential groove on the wide side, and if the groove widths are the same, it may be provided in either one or both circumferential grooves. Since the step region is connected to the land portion via the platform portion, the bending rigidity of the step region is improved, and thereby the effect as the uneven wear sacrifice portion described above is also improved. In addition, if this platform part is continuous in the circumferential direction and the groove depth of the circumferential groove is made shallow, the step area will no longer function as an uneven wear victim part in the later stages of wear, so in this invention, the platform is separated in the direction A plurality of such platforms are provided, and a circumferential groove of the original groove depth is left between these platforms, so that it can sufficiently function as a sacrificial part for uneven wear even during and in the later stages of wear. EMBODIMENT OF THE INVENTION Hereinafter, one embodiment of the present invention will be described based on the drawings. In Figure 1.2.3, 1 is a pneumatic radial tire for heavy loads that is installed on the driven wheels or idle wheels of buses, trucks, etc. The outer surface of the tread portion 5 of this tire 1, that is, the tread surface θ, has a A plurality of (two in this embodiment) continuous main grooves 7 extending in the circumferential direction are formed. As a result, the tread B has three land portions 8 extending in the circumferential direction by these main grooves 7, that is, a central rib 8a located on the tire equatorial plane θ.
and side ribs 8b located on both sides of the central rib 8a. Here, the main groove 7 is a straight groove in the circumferential direction parallel to the tire equatorial plane 9, but the main groove 7 may be a known zigzag groove. The land portion 8 may be a so-called block further divided by horizontal grooves or auxiliary grooves, or a rib-block composite including the same.The tread surface 6 of the side rib 8b At least one pair of circumferential grooves 11 (in this embodiment, a pair of circumferential grooves 11 in this embodiment) are formed that extend continuously in the circumferential direction, and these pairs of circumferential grooves 1 divide the side force rib 8b into two in the axial direction at the relevant position. . These circumferential grooves 11 form the land portion 8. That is, in order to increase the negative ratio of the side ribs 8b and reduce the wear resistance of the tire 1,
It is preferable that the groove width W of these circumferential grooves 11 is narrower, that is, 10 mm or less, and in this embodiment, the average groove width W of the pair of circumferential grooves 11 is the same, 41 mm. Here, each circumferential groove 11 is a circumferential straight groove parallel to the tire equatorial plane 8, but these circumferential grooves 11 may be a known zigzag groove.
When the circumferential grooves 11 are formed in the side ribs 8b in this manner, a step region 12 independent from the side ribs 8b is defined on the tread surface 8 between the pair of circumferential grooves 11. Here, each step area 12
is a linear thin rib that extends continuously in the circumferential direction, but this stepped region 12 may have a zigzag shape, or it may be divided into blocks by a horizontal groove extending in the axial direction, size, etc. The radially outer end surface 13 of each step region 12 is located radially inward from the cross-sectional contour line of the tread surface 6. The radial outer end surface 13 of each step region 12 comes into contact with the road surface in the same way as the land portion 8 when the tire l reaches the tread surface area due to running of the tire l, but one circumference of this radial outer end surface 13 is Since it is shorter than one circumference of the outer surface of the portion 8, the radially outer end surface 13 comes into sliding contact with the road surface and is subjected to a large shearing force in the braking direction. Further, among the circumferential grooves 11, at least a circumferential groove on the narrow side,
In this embodiment, a plurality of platform portions 1B are provided in both circumferential grooves 11, respectively, protruding from the groove bottom in the radial direction and filling a portion of the circumferential grooves 11, and these platform portions 113 are spaced equidistantly apart in the circumferential direction. It is placed. As a result, the side walls of the land portion 8, i.e., the central and lateral ribs 8a, 8b and the side wall of the step area 12 are connected to the platform portion IB.
are connected to each other by. The reason why the platform portion 18 is provided at least in the circumferential groove on the narrow side is that the radius of curvature of the bottom of the circumferential groove on the narrow side is smaller than the radius of curvature of the bottom of the circumferential groove on the wide side. This is to prevent the generation of cracks in the circumferential groove on the narrow side for the time being, since stress is more concentrated at the bottom of the circumferential groove on the narrow side when the same lateral force or the like is applied. Further, the platform section 1
The reason why a plurality of grooves 8 are provided spaced apart in the circumferential direction is that if these platform parts were provided continuously in the circumferential direction and the groove depth of the circumferential groove was made shallow as a result, the step area 12 would be formed at a later stage during wear.
This is because the circumferential groove 11 of the original groove depth will remain between the platform parts 18 as described above, so that it will not function as an uneven wear victim part even during wear and in the later stages. It can function. Here, it is preferable that the height H of these platform portions 1e from the groove bottom is within the range of 25% to 50% of the groove depth D of the circumferential groove 11. The effect of suppressing the relative displacement between the land portion 8 and the stepped region 12 when subjected to force, etc. is not sufficient, and on the other hand, if it exceeds 50%, it becomes difficult for water to move in the circumferential direction within the circumferential groove 11. This is because drainage performance deteriorates. Further, it is preferable that the circumferential length L of these platform portions 1B is 51 mm or more, because if it is less than 5 mm, the effect of suppressing the relative displacement between the land portion 8 and the stepped region 12 will not be sufficient. That's because there isn't. Next, the operation of one embodiment of the present invention will be explained. When the tire 1 described above is mounted on a truck, bus, etc. and driven, the tire 1 is crushed in the area where it makes contact with the road surface, forming a roughly rectangular tread area. Both the outer surface of the land portion 8 and the radially outer end surface 13 of the stepped region 12 contact the road surface. Here, the radially outer end surface 13 of the stepped region 12 is the tread surface 6.
Since it is located radially inward from the cross-sectional contour line of the step region 12, one circumference of the step region 12 at the radially outer end surface 13 is shorter than one circumference of the outer surface of the land portion 8; Since the radially outer end surface 13 and the outer surface of the land portion 8 touch the ground together when reaching the tread surface region, the radially outer end surface 13 of this stepped region 12 comes into sliding contact with the road surface while being dragged. As a result, an extremely large shearing force is generated in the one-step difference region 12 in the direction of braking the displacement of the tire 1, that is, in the braking direction. Here, when a large shearing force in the braking direction is unevenly distributed on a part of the tread 6 of the tire 1, that is, the step region 12, the shearing force on the remaining tread 6 of the tire 1, that is, the land portions 8 on both sides of the step region 12 is is shifted up to the drive side. As a result, the shearing force acting on the land portion 8 is in the driving direction in both halves of the land portion 8. Here, since the wear rate of the tread surface B receiving the shear force in the driving direction is significantly slower than the wear rate of the tread surface e receiving the shear force in the braking direction, as described above, the step area 12 receiving the shear force in the braking direction Only the land part 8 is sacrificed and worn out.
uneven wear is prevented. In addition, as described above, each circumferential groove 11
When the groove @ (average groove width W) is made as narrow as possible, the radius of curvature at the groove bottom of each circumferential groove 11 becomes smaller, so when receiving a lateral force etc., these circumferential grooves 11! It is thought that a large stress concentration occurs at the groove bottom of the ill. However, in this embodiment, a plurality of platform parts 1B are provided in the double-layer groove 11, and these platform parts 16 connect the land parts 8,
Here, the side walls of the central and lateral ribs 8a, 8b and the side walls of the stepped region 12 are connected to each other. Therefore, when a lateral force or the like is applied to the tire l, the center and side ribs 8a, 8
b and the stepped region 12 are displaced by approximately the same amount in the same direction,
The relative displacement between the two becomes smaller. As a result, even if the received lateral force or the like is large, the stress concentration generated at the groove bottom of the circumferential groove 11 does not become too large, and rib tear is reliably suppressed. Furthermore, since the stepped region 12 and the center and side ribs 8a and 8b are connected via the platform portion 1B,
The bending rigidity of the stepped region 12 is improved, thereby increasing the effect of the stepped region 12 as a victim of uneven wear. Next, a test example will be explained. In this test, the test tire explained in the above example, the circumferential groove 11 of the test tire,
A comparison tire 1 as shown in FIG. 4.5 in which a main groove 21 similar to the main groove 7 was provided instead of the step region 12, and a tire No. 6.7 in which the platform portion was removed from the circumferential groove 11 of the test tire.
Comparison tire 2 as shown in the figure? fIllIshita. Here, the tire size of each tire was IIR22.5, and the rim used was 8.25X22.5.
After filling each tire with an internal pressure of 7°25Kg/cj and installing the tires on the front wheels of a 2D-4 vehicle (flat body truck) with a loading rate of 100%, the tires can be used on expressways and general roads. The tire was run for 80,000 km on a road with a ratio of 7:3 (all paved), and at the end of the run, the width of uneven wear at the tread edge of each tire was measured. The result was 10m for the test tire.
m, whereas it was 32 sm for comparative tire 1 and 18+sm for comparative tire 2. In addition, at the end of the three runs, the rib tear in the entire circumferential groove 11 of the test tire and comparative tire 2 was measured, and the total was determined. The result was 7 for the test tire. mm, whereas in comparison tire 2 it was 134 em. In this way, the test tire to which the present invention is applied can suppress rib tear while improving uneven wear resistance. As explained above, according to the present invention, uneven wear resistance and abrasion resistance can be improved while suppressing the occurrence of rib tears.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a tread portion of a pneumatic tire showing an embodiment of the present invention, and FIG. 2 is a meridian cross-sectional view thereof, wIJ
Figure 3 is a cross-sectional view taken along the line I-I in Figure 1, Figure 4 is a plan view of the tread portion of the comparative tire l used in the test, Figure 5 is a meridian cross-sectional view thereof, and Figure 6 is the tire used in the test. A plan view of the tread portion of comparative tire 2, and FIG. 7 is a meridian cross-sectional view thereof. l...Pneumatic tires 8...Road surface? ...Main groove
8...Land part 11...Surrounding groove
12... Step region 13... Radial direction outer end surface 16.
...Platform part patent applicant Brideston Co., Ltd. Agent Patent attorney Tadashi 1) Toshio Fig. 1 Fig. 3 12... Step region 13... Radial outer end surface 16... Plastic, platform part Fig. 1 figure

Claims (1)

[Claims] A pneumatic tire having a main groove extending continuously in the circumferential direction and a land section separated by the main groove on the tread surface,
By forming at least a pair of circumferential grooves on the tread surface that extend continuously in the circumferential direction and bisect the land portion, the tread surface between the pair of circumferential grooves has a radially outer end surface that is independent of the land portion. The step area is located radially inward from the cross-sectional contour line of the tread, and defines a step region as an uneven wear victim part where the radially outer end surface located in the tread surface area slides into contact with the road surface during normal driving, and A plurality of platform portions spaced apart in the circumferential direction are provided in at least the narrow side circumferential groove of the pair of circumferential grooves, and the platform portions connect the side wall of the land portion and the side wall of the stepped region to each other. A pneumatic tire characterized by: