JP2944702B2 - Heavy duty pneumatic tires - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heavy-duty pneumatic tire capable of improving performance on ice without generating dust.

2. Description of the Related Art In general, when traveling on ice with a heavy-duty pneumatic tire on which a large load is applied, a high contact pressure acts on ice in an area in contact with the tire, so that the ice surface in the area melts. Out and the water film covers the ice surface,
The coefficient of friction of the ice surface is extremely reduced, and the performance of the tire on ice is significantly reduced.

For this reason, a so-called spike tire in which a spike pin is driven into tread rubber, for example, has been proposed, and such a spike tire improves the performance on ice by making the spike pin bite into ice.

Problems to be Solved by the Invention However, such a spiked tire has a problem that, when traveling on a pavement surface on which ice is not covered, dust is generated because the spike pins scrape the road surface, causing dust pollution.

An object of the present invention is to provide a heavy-duty pneumatic tire capable of improving performance on ice without generating dust.

Means for Solving the Problems An object of the present invention is to provide a heavy-duty pneumatic tire in which a belt layer composed of at least two belt plies composed of a metal cord is disposed between a carcass layer and a tread rubber. Width W from 1.3 times rim width R
An annular groove extending in the circumferential direction is arranged on both outer surfaces of the tire, and a radial distance A from the deepest portion of each annular groove to the tread end is set at a tire height H. Within the range of 0.025 times to 0.15 times the maximum depth B of each annular groove from 0.02 times the tread width W
It can be achieved by setting it within the range of 0.12 times.

In the present invention, the tread width W is set to the rim width R of 1.3.
The width is set to be at least twice as large as the tread width of a normal heavy duty pneumatic tire. As a result, the contact area is increased, the contact pressure is reduced as a whole, and even when traveling on ice with a tire under heavy load, the ice in the contact area in contact with the tire melts very slightly. Only. As a result, the surface of the ice is exposed, and the surface of the ice having a high coefficient of friction comes into direct contact with the tire, so that the performance on the ice is improved. Here, when the tread width W is widened as described above, when the tire is bent and deformed by receiving a lateral force due to cornering or the like, the contact pressure near the tread end on the lateral force entry side becomes considerably high. Uneven wear occurs in the vicinity of the tread edge from the beginning of travel, and once such uneven wear occurs, the difference in diameter between the vicinity of the tread end and the vicinity of the tire equatorial plane drags the vicinity of the tread end during straight running, causing uneven wear. Progress rapidly, and the effect of increasing the contact area is reduced. For this reason, according to the present invention, the annular groove is provided on both outer side surfaces of the tire continuously extending in the circumferential direction, and the arrangement position and the maximum depth are provided in the above-described range. Radial inward deformation near the tread end on the entry side is allowed, thereby uniforming the contact pressure and preventing uneven wear near the tread end.
As a result, it is possible to maintain good performance on ice while preventing uneven wear from the beginning to the end of traveling.

According to the second aspect of the present invention, the bubbles in the foamed rubber serve as a relief for a water film adhering to the ice surface, so that the ice surface is exposed and the performance on ice is further improved.

Furthermore, according to the third aspect of the invention, the air bubbles in the tread rubber (foam rubber) in the central region serve as a refuge for a water film as described above, so that the performance on ice is improved and the tread rubber in both side regions is improved. Has higher abrasion resistance than the tread rubber in the central region, so that uneven wear near the tread edge can be more reliably prevented.

Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a pneumatic radial tire for heavy loads. The tire 1 has a carcass layer 2 having a toroidal shape, and the carcass layer 2 has at least one carcass ply 3 in this embodiment. It is composed of
Numerous cords made of steel or the like are embedded in each carcass ply 3, and these cords extend in a direction substantially orthogonal to the tire equatorial plane 5, that is, in a radial direction. A tread rubber 6 is disposed radially outside the carcass layer 2, and a belt layer 7 is disposed between the tread rubber 6 and the carcass layer 2. The belt layer 7 is formed by laminating at least two layers of belt plies 8, and in this embodiment, laminating three layers of belt plies 8. Inside each belt ply 8, a reinforcing metal cord, in this embodiment, A steel cord is buried. Here, the cord of the innermost belt ply 8 closest to the carcass layer 2 intersects the tire equatorial plane 5 at a cord angle of 45 degrees or more. The tire 1 is mounted on a rim 11, and when the rim width of the rim 11 is R,
The tread width W of the tire 1 is 1.3 times the rim width R.
It is within the range of 1.7 times. Here, the conventional heavy-duty pneumatic tire had a small tread width W because the tread width W was in the range of 0.9 to 1.2 times the rim width R, but the tread width W of the tire 1 was reduced as in this embodiment. When the rim width R is 1.3 times or more, the contact area is increased, the contact pressure is reduced as a whole, and the performance on ice is improved. However, tread width W
Exceeds 1.7 times the rim width R, the gauge of the tread rubber 6 at the tread width 12 becomes too thick, and there is a risk of contact with the adjacent tire 1 when two or more wheels are mounted. Must be 1.7 times or less. Here, when the tread width W is widened as described above, when the tire 1 is bent and deformed by receiving a lateral force due to cornering or the like, the contact pressure in the vicinity of the tread end 12 on the side of the lateral force is considerably increased. Uneven wear occurs in the vicinity of the tread end 12 on the entry side from the beginning of traveling, and once such uneven wear occurs, the tread end 12 is near the tread end 12 during straight running due to the diameter difference between the tread end 12 and the tire equatorial plane 5. This leads to rapid uneven wear, which reduces the effect of increasing the contact area. For this reason, in this embodiment, annular grooves 15 extending continuously in the circumferential direction are formed on both outer surfaces of the tire 1. Here, the deepest portion 16 of each annular groove 15 is a region U in which the radial distance A from the deepest portion 16 to the tread end 12 is within a range from 0.025 to 0.15 times the tire height H, that is, the tread end. It is arranged in an area U radially inward of a point S that is 0.025 times the tire height H from 12 and radially outward of a point T that is 0.15 times the tire height H apart from 12. The reason is that if the distance A is less than 0.025 times the tire height H, the rigidity of the ring portion 18 located between the annular groove 15 and the outer surface of the tread rubber 6 becomes too low and almost bears the contact pressure. On the other hand, if the distance A exceeds 0.25 times the tire height H, the rigidity of the ring portion 18 becomes too high, and it hardly deforms even when a lateral force is input. The maximum depth B of each annular groove 16, that is, the axial distance from the outer surface of the tire 1 to the deepest portion 16 of the annular groove 16 is in the range of 0.02 to 0.12 times the tread width W. The reason is that the maximum depth B is the tread width W
If it is less than 0.02 times, the rigidity of the ring portion 18 becomes too high and is hardly deformed even when a lateral force is input. Conversely, if it exceeds 0.12 times the tread width W, the ring portion 18
This is because the stiffness becomes too low and almost no bearing pressure is borne. When the annular groove 15 having the arrangement position and the maximum depth B within the above-described range is provided on both outer side surfaces of the tire 1, when a lateral force acts on the tire 1, the vicinity of the tread end 12 on the lateral force entry side is provided. That is, the ring portion 18 is deformed radially inward by an appropriate amount, whereby the contact pressure at the tread portion is made uniform, and uneven wear near the tread end 12 is prevented.
As a result, good performance on ice is maintained while uneven wear is prevented from the beginning to the end of traveling. In this embodiment, since no spike pins like those of a conventional tire are driven into the tread rubber 6, dust pollution based on the spike pins does not occur.

FIG. 2 is a view showing a second embodiment of the present invention. In this embodiment, at least the radially outer portion of the tread rubber 20 is made of a foamed rubber having a foaming ratio of 5% or more over the entire width. By doing so, the air bubbles in the foamed rubber serve as a refuge for the water film adhering to the ice surface, so that the ice surface is exposed and the performance on ice is further improved. The foaming ratio of the foamed rubber is calculated by the following formula: V = (a / b-1) × 100 (%) Here, a is the density (g / cm ³ ) of the rubber solid phase portion of the foamed rubber, and b is the density (g / cm ³ ) of the foamed rubber.
In this embodiment, the cross section of the annular groove 21 is substantially L-shaped.

FIG. 3 is a view showing a third embodiment of the present invention. In this embodiment, the tread rubber 25 is located at the center in the width direction and the width P is 80% or less of the tread width W.
And two side areas 27 located on both outer sides of the central area 26 in the width direction. And the tread rubber of the central area 26
25 is made of foamed rubber having a foaming rate of 5% or more, while the foaming rate of the tread rubber 25 in both side areas 27 is smaller than the foaming rate of the tread rubber 25 in the central area 26 (including the case where the foaming rate is zero). ing. As a result, the tread rubber 25 in the central region 26
As described above, the air bubbles in the (foamed rubber) serve as a refuge for the water film, so that the performance on ice is improved. In addition, the abrasion resistance of the tread rubber 25 in the both side regions 27 is higher than that of the tread rubber 25 in the center region 26. Uneven wear near the tread end 12 is more reliably prevented. In this embodiment, the annular groove 29
Has a substantially V-shaped cross section.

Next, test examples will be described. In this test, comparative tires 1 and 2 and test tires 1, 2, and 3 having specifications as shown in the attached table were prepared. Where the size of each tire is 1
At 0.00R20, the size of the rim on which the tire is mounted is 7.00T x
It was 20. Next, after each of such tires is mounted on a vehicle, a regular load is applied to the tires and the paved highway 70
%, 30% of the paved general road, travel 40,000 km, and measure the amount of tread rubber abrasion on the tire equatorial plane and the tread rubber abrasion at the tread edge at the end of traveling.
The uneven wear resistance performance was determined by indexing the ratio of these wear amounts.
The results are shown in a separate table. The test tires have improved uneven wear resistance compared to the comparative tire 2 with a wider tread width.
In particular, in the test tire 3 in which both sides of the tread rubber are made of a rubber having a low foaming rate, the uneven wear resistance is significantly improved. After the tires were mounted on the vehicle, the tires were driven at a speed of 20 km / h on ice at a temperature of -5 ° C. while applying a regular load to the tires. The distance from the stop point to the stop point was measured. The reciprocal of this measurement result is indexed to be the performance on ice, and the result is shown in a separate table. As can be understood from this separate table, the test tire has improved performance on ice compared to the comparative tire 1. In particular, the test tire 2 in which the tread rubber is made of foam rubber over the entire width has significantly improved performance on ice. ing. Here, the braking distance at the index of 100 was 42.2 m.

Effect of the Invention As described above, according to the present invention, performance on ice and uneven wear resistance can be improved without generating dust.

[Brief description of the drawings]

FIG. 1 is a meridian sectional view showing a first embodiment of the present invention, FIG. 2 is a meridian sectional view showing a second embodiment of the present invention, and FIG.
The figure is a meridian sectional view showing a third embodiment of the present invention. 1 ... pneumatic tire for heavy load 2 ... carcass layer, 6 ... tread rubber 7 ... belt layer, 8 ... belt ply 12 ... tread end, 15 ... annular groove 16 ... deepest part, 26 ... Central area 27 ... Both areas

Continuation of front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B60C 11/00 B60C 11/01

Claims (3)

(57) [Claims] 1. A heavy-duty pneumatic tire in which a belt layer comprising at least two belt plies having a metal cord embedded between a carcass layer and a tread rubber is disposed, the tread width W of the tire is set to a rim width R. 1.3 times to 1.7 times
In addition, annular grooves extending continuously in the circumferential direction are arranged on both outer surfaces of the tire, and a radial distance A from the deepest portion of each annular groove to the tread end is defined as a tire height H. While making it within the range of 0.025 times to 0.15 times,
The maximum depth B of each annular groove is from 0.02 times the tread width W to 0.12
A pneumatic tire for heavy loads, characterized in that the range is twice as large. 2. The heavy-duty pneumatic tire according to claim 1, wherein at least a radially outer portion of the tread rubber is made of a foamed rubber having a foaming ratio of 5% or more over the entire width. 3. The tread rubber is divided into a central region where the tread rubber is located at a central portion in the width direction and the width is 80% or less of the tread width W, and two side regions located on both outer sides in the width direction of the central region. 2. The heavy load air according to claim 1, wherein the tread rubber in the central region is made of a foamed rubber having a foaming ratio of 5% or more, and the foaming ratio of the tread rubbers in both side regions is smaller than the foaming ratio of the tread rubber in the central region. Containing tires.