JPH03200405A - Pneumatic tire for heavy load - Google Patents

Abstract

PURPOSE:To improve wandering performance while shoulder drop abrasion is suppressed by forming shapes of both shoulders in an asymmetric tread in a round shape outside a vehicle and in a square shape inside the vehicle respectively. CONSTITUTION:With the tire, the maximum peripheral line position D of a tread T with respect to an equator line O is shifted in a direction to be an outer side when the tire is mounted to a vehicle with a predetermined distance L. Tread shoulder diameters d1, d2 and crown radii r1, r2 outside and inside the vehicle are mutually set in relations of d1>d2 and r1>t2. In such a constitution, a shape of a shoulder part S1 which is to be outside when the tire is mounted to the vehicle is formed in a round shape having a predetermined curvature radius while a shape of a shoulder part S2 to be inside similarly is formed in a square shape having a predetermined gradient angle. Thus wandering performance can be improved while shoulder drop abrasion is suppressed.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention relates to the improvement of a heavy-duty pneumatic tire, and more specifically, to a heavy-duty pneumatic tire with improved shoulder drop wear and wandering performance. It is related to tires.

(Prior art) For example, in heavy-duty pneumatic tires used under high internal pressure and high loads on trucks and buses, if the tread portion is configured symmetrically, shoulder drop wear occurs on the outside of the front wheels of the vehicle. There was a problem that occurred frequently.

In order to improve the above-mentioned drawbacks, there is a method of increasing the radius of curvature on the outer side of the tread attached to the vehicle, and decreasing the radius of curvature on the inner side of the tread attached to the vehicle, with the equator line of the tire as the boundary.
Although this method can improve shoulder drop wear, it tends to reduce the ground contact pressure at the ribs adjacent to the inside shoulder part of the vehicle, and this method causes railway wear called riverway. The disadvantage was that the trend was becoming stronger.

The present applicant has proposed a heavy-duty pneumatic tire with an asymmetric tread of the embodiment shown in FIGS. This was previously proposed as Japanese Patent Application Laid-Open No. 63-41204.

In other words, the conventional heavy-duty pneumatic tires with asymmetric treads shown in FIGS. Shift the distance in the outward direction,
Shoulder diameter d1 of the tread on the outside of the vehicle
Shoulder diameter d2 of the tread on the inside of the vehicle
By setting the relationship di>d2 and the relationship r2 between the crown radius r1 of the tread on the inside of the vehicle and the crown radius of the tread on the inside of the vehicle to r2, the rigidity of the outside tread installed on the vehicle is increased, and in this part In addition to improving shoulder drop wear, the structure also avoids river wear on the outside and inside of the tire.

(Problems to be Solved by the Invention) However, as a result of further detailed studies, it was found that the heavy-duty pneumatic tire with the asymmetric tread proposed by the applicant described above has poor wandering performance, that is, on rutted road surfaces. It has been discovered that there is still a problem with the steering wheel being removed when driving along a slope.

In other words, in the conventional heavy-duty pneumatic tire with an asymmetric tread, both shoulder portions S1 and S2 on the left and right sides of the tread are usually formed in a square shape (angular shape), as shown in FIG. However, in this case, there is a problem with the wandering performance at the vehicle-mounted outer shoulder portion S1, and because the diameter of the vehicle-mounted inner shoulder portion S2 is small, the ground pressure in that portion tends to decrease, resulting in shoulder drop wear. This will lead to undesirable effects.

On the other hand, in order to improve wandering performance,
As shown in the figure, both shoulder parts S1 on the left and right sides of the tread
It is conceivable to form both S2 and S2 in a round shape (rounded shape), but in this case, the ground contact pressure at the inner shoulder part attached to the vehicle will further decrease, so there is a concern that shoulder drop wear due to dragging etc. will worsen. There was a problem with being exposed.

The present invention aims to solve the above-mentioned problems of the conventional heavy-duty pneumatic tires with asymmetric treads.

Therefore, an object of the present invention is to provide a heavy-duty pneumatic tire that has balanced shoulder wear and wandering performance.

[Structure of the Invention (Means for Solving the Problems) In other words, the heavy-duty pneumatic tire of the present invention is such that the maximum circumferential position of the tread with respect to the equator line of the tire is spaced in a direction toward the outside of the vehicle when the tire is mounted on the vehicle. When the shoulder diameter of the tread on the outside of the vehicle is di1, the crown radius is r1, the shoulder diameter of the tread on the inside of the vehicle is d2, and the crown radius is 2, the relationship is dl > d2, rl < r2. A pneumatic tire with an asymmetric tread is characterized in that the shape of the outer shoulder part to be mounted on the vehicle is rounded, and the shape of the inner shoulder part to be mounted to the vehicle is shaped like a square.

(Function) In the heavy-duty pneumatic tire of the present invention, both shoulder portions of the asymmetric tread are formed into a round shape on the outside of the vehicle and a square shape on the inside of the vehicle.
Wandering performance can be improved while effectively suppressing the occurrence of shoulder drop wear.

That is, by rounding the vehicle-mounted outer shoulder portion, wandering performance is improved, high ground contact pressure is effectively exerted, and shoulder drop wear is suppressed.

On the other hand, since the inner shoulder part attached to the vehicle originally has a small contribution to wandering performance, there is no risk that wandering performance will be hindered by making this part into a soft-wear shape.Furthermore, the ground pressure increases and the shoulder drops due to dragging. The occurrence of wear is effectively suppressed.

Therefore, the heavy-duty pneumatic tire of the present invention has well-balanced and excellent shoulder drop wear resistance and wandering resistance in both tread shoulder areas, and is suitable for pneumatic tires used under high loads and high internal pressures, especially for trucks. It has ideal performance as a tire for large vehicles such as cars and buses.

(Example) Examples of the heavy-duty pneumatic tire of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is an explanatory cross-sectional view of a tread portion of an embodiment of the heavy-duty pneumatic tire of the present invention.

In FIG. 1, the tread T of the pneumatic tire for heavy loads of the present invention has a maximum circumferential position of the tread with respect to the equator line O of the tire, which is separated by a distance in a direction toward the outside of the vehicle when the tire is mounted on the vehicle. When the shoulder diameter of the tread on the outside of the vehicle is d1, the crown radius is rlx, the shoulder diameter of the tread on the inside of the vehicle is d2, and the crown radius is r2, dl > d2, rl < r2. The tire has a tread profile consisting of a tread profile, and thereby has a structure in which shoulder drop wear of the vehicle-mounted outer shoulder portion S1 is improved.

Although other structures such as the radial carcass, reinforcing belt layer, and tread pattern in the tread portion T are not shown in the drawings, for example, the reinforcing width of the reinforcing belt layer may be different, or the negative structure of the vehicle-mounted outer shoulder portion S1 may be It goes without saying that it is possible to advantageously equalize the difference in rigidity on both sides of the tread by reducing the ratio.

In the heavy-duty pneumatic tire of the present invention, the distance from the equator line O of the tire at the maximum circumferential position of the tread is in the range of 0.05 to 0°3 times the total tread width, and d2 /di is In the range of 0.98 to 1°00, further r
It is preferable that l/r2 is in the range of 0.50 to 0.85.

Therefore, in the heavy-duty pneumatic tire of the present invention, in the asymmetric tread profile having the above structure, the shape of the vehicle-mounted outer shoulder portion S1 is rounded with a radius of curvature; An important requirement is to form the inner shoulder portion S2 into an angular square shape with an inclination angle to further strengthen the asymmetric structure.

By making the shape of the vehicle-mounted outer shoulder portion S1 into a round shape with a radius of curvature of 5 to 50 mm, it is possible to improve the wandering performance compared to the case where it is made into a sphere shape. The ground pressure inherent to the vehicle-mounted outer shoulder portion 81 is effectively exerted, and the occurrence of shoulder drop wear is also reduced.

In addition, since the vehicle-mounted inner shoulder part S2 originally has a small contribution to wandering performance, the shape of this part is
Wandering performance is not hindered even when the sphere shape has an inclination angle of 5 to 30 degrees, and on the contrary, the ground contact pressure increases, which reduces shoulder drop wear due to dragging, which has been a problem with the inside shoulder part S2 attached to the vehicle. can be effectively suppressed.

Therefore, according to the heavy-duty pneumatic tire of the present invention, wandering performance can be improved while avoiding shoulder wear caused by the mounting pattern on a vehicle.

Next, the structure and effects of the heavy-duty pneumatic tire of the present invention will be explained in more detail using test examples.

(Test Example) The asymmetric tread profile shown in FIG. 1 above was formed on the tread portion of a radial tire of tire size: 650R1610PR.

That is, in Figure 1, Tire tread T width - 120 order, L-12 order, d1 = 736 mm% d2=732mm.

rl -230 fin, r2 = 370 mra, and the radius of curvature α1 = vehicle-mounted outer shoulder part S1.
15mm round shape, vehicle mounted inner shoulder part S2
The tire A of the present invention was obtained by making the tire into a square shape with an inclination angle of α2-15''.

On the other hand, for comparison, in the tire A of the present invention, a conventional tire B was obtained by making both side shoulder portions S1 and S2 round, or a conventional tire C was obtained by making both shoulder portions S1 and S2 square.

Note that, common to the above three types of tires, other conditions such as the carcass, reinforcing belt layer, and tread pattern were applied using well-known techniques as they were.

These three types of tires were evaluated for shoulder drop wear and wandering performance through an actual vehicle feeling test under the following conditions, and the results are shown in the following table.

Shoulder drop wear evaluation method, wear work amount (an index evaluation of the amount of product of the amount of movement of the road surface and the generated force, integrated from the time the tread hits the ground to the time the tread is kicked off).

(A low index means good) Test vehicle: Small truck, 2-ton road Surface: Paved rutted road Speed: 60-1100k/h Evaluation method: Handling feeling evaluation (A high index means good) (Hereafter on this page Margin) From the above results, the heavy-duty pneumatic tire of the present invention
It is clear that the material has a high level of balanced wear resistance and wandering resistance.

[Effects of the Invention] As described in detail above, in the heavy-duty pneumatic tire of the present invention, the shapes of both shoulder portions of the asymmetric tread are rounded on the outside of the vehicle and squared on the inside of the vehicle. Therefore, wandering performance can be improved while effectively suppressing the occurrence of shoulder drop wear.

That is, by rounding the vehicle-mounted outer shoulder portion, wandering performance is improved, high ground contact pressure is effectively exerted, and shoulder drop wear is suppressed.

On the other hand, since the inner shoulder part attached to the vehicle originally has a small contribution to wandering performance, making this part a soft-wear shape does not impede wandering performance, and it also increases ground pressure and causes drag. The occurrence of shoulder drop wear is effectively suppressed.

Therefore, the heavy-duty pneumatic tire of the present invention has well-balanced and excellent shoulder drop wear resistance and wandering resistance in both tread shoulder areas, and is suitable for pneumatic tires used under high loads and high internal pressures, especially for trucks. It has ideal performance as a tire for large vehicles such as cars and buses.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view of the tread portion showing one embodiment of the heavy-duty pneumatic tire of the present invention, and FIGS.
The figure is an explanatory cross-sectional view of a tread portion of a conventional heavy-duty pneumatic tire. T...Tread part Sl...Vehicle mounted outer shoulder part S2...
...Vehicle-mounted inner shoulder part D...
Tread maximum outer diameter circumferential line position d1...Vehicle-mounted outer shoulder diameter "l..."
Crown radius d2...Vehicle-mounted inner shoulder diameter r2...//Crown radius α1...Curvature radius (round shape) 3rd
Figure 33- T ・ Tread part SL ・ Part of the outer diameter of the vehicle installed 32 Part of the inner diameter of the vehicle installed D ・ Maximum outer circumference position of the tread d I , , , , , 11 Part of the diameter of the outer diameter of the vehicle installed rl ・Clara/radius d2
・Vehicle-mounted inner norda part d"2
Crown radius al Radius of curvature (square shape) α2 Inclination angle (round shape) Fig. 1 Fig. 2rM

Claims (1)

[Claims] The maximum circumferential position of the tread relative to the tire's equator line,
When the tire is installed on the vehicle, it is shifted at a distance in the direction toward the outside of the vehicle, and the shoulder diameter of the tread on the outside of the vehicle is set as d1, the crown radius is set as r1, the shoulder diameter of the tread on the inside of the vehicle is set as d2, and the crown radius is set as r2. In a pneumatic tire with an asymmetric tread in which d1>d2 and r1<r2, the shape of the outer shoulder portion to be mounted on the vehicle is round, and the shape of the inner shoulder portion to be mounted to the vehicle is square. A pneumatic tire for heavy loads featuring: