JPS62103205A - Heavy load pneumatic tyre - Google Patents

Abstract

PURPOSE:To prolong life of a tyre by making the tread part with radii of curvature asymmetrical, large and small, about the tyre equator surface, giving that side of said asymmetrical members which is greater an area ratio smaller than that of the smaller radius side, and thereby causing even wear of the tread surface. CONSTITUTION:Radii of curvature R2, R3 of the contour of tread part 2 which appears on the profile of a tyre 1 including tyre rotation axis are asymmetrical, great and small, about the tyre equator surface. The area ratio of the groove portion on tread 2 surface which is off the ground (negative ratio) is 5-30% on the side R2 with greater radius of curvature, while the corresponding figure 10-40% on the side R3 with smaller radius of curvature. The area ratio on the side R2 with greater radius of curvature shall be smaller than the area ratio on the side R3 with smaller radius of curvature, and fitting is so made that the side R2 is situated outside. This arrangement assures that various types of uneven wear to be generated on the tread surface are prevented, and this uniform worn tread 2 should cause prolonged life of the tyre.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to the radius of curvature of the contour of the tread portion of a heavy-duty pneumatic tire, and relates to preventing partial sliding wear and one-side rim wear of the tire.

(Prior Art) In heavy-duty pneumatic tires, especially radial tires, uneven wear due to sliding often occurs on a portion of the outer shoulder of the front wheel.

In conventional heavy-duty pneumatic tires, in order to prevent uneven wear due to sliding, the radius of curvature of the tread profile is bilaterally symmetrical, and a method has been used to greatly increase the ground contact pressure at the edge of the seat tread in a symmetrical state. Furthermore, in order to increase the radius of curvature, a method of increasing the tread volume has usually been used.

(Problems to be Solved by the Invention) Uneven wear that occurs at the tread ends of the front wheels occurs not at both ends of the tread, but mainly at the outer tread ends. This is due to the fact that roads include not only straight sections but also curved sections. When a vehicle turns around a curve, the centrifugal force causes the vehicle to roll, causing an increase in load and concentration of lateral force on the tread edge of the tire mounted on the outside of the turn. Wear is more likely to occur. In conventional heavy-duty pneumatic tires, the radius of curvature of the tread profile is bilaterally symmetrical, and a method is used to greatly increase the contact/ground pressure at the edge of the tread in a symmetrical state. Prevented office wear 0
In order to increase the radius of curvature, the method of increasing tread volume has usually been used, but this increases the tread volume and causes faster wear on the outer side of the tire, resulting in one-sided wear, and the ground pressure on the tire tread surface is insufficient. This results in uniform wear and abnormal wear called rib punching as shown in Figure 16, resulting in a shortened tire life and no fundamental solution has been reached.

Therefore, the purpose of the present invention is to prevent the occurrence of abnormal wear such as sliding uneven wear, one-side edge wear, or rib punching that occurs on the tread surface, and to improve the life of the tire by uniformly wearing the tread portion. .

(Means for Solving the Problems) That is, the present invention provides that the radius of curvature of the tread contour appearing in the cross section of the tire including the rotational axis of the tire is asymmetrical in size with respect to the tire equatorial plane, and the groove portions on the tread surface that do not touch the ground are The area ratio (hereinafter referred to as negative ratio) is 5 to 30% on the side with the larger radius of curvature, 10 to 40% on the other side with the smaller radius of curvature, and the area ratio on the side with the larger radius of curvature is It consists of a heavy-duty pneumatic tire characterized by a smaller radius of curvature than the area ratio on the smaller side.

In order to more effectively prevent abnormal wear, the difference in the radius of curvature of the tread contour should be 0.75 to 1.50 times the maximum ground contact width in the rotational axis direction of the tread; It is preferable that the average of the larger and smaller values is 1° with respect to the maximum ground contact width in the rotational axis direction of the tread.

Further, the large radius of curvature of the tread contour is 2.90 to 3.70 times the maximum ground contact width in the direction of the rotational axis of the tread, and the small radius of curvature is 2.30 to 2.60 times. This is recommended as an implementation.

The negative ratio on the tread surface is preferably 12 to 25%, and the negative ratio on the side with a larger radius of curvature is desirably 0.3 to 0.8 times the negative ratio on the side with a smaller radius of curvature.

(Function) As shown in Figure 3, changing the negative ratio of the tread changes the wear rate. In addition, if the negative ratio is equal on the side with a large radius of curvature and the side with a small radius of curvature, the external force (during cornering, etc.) on the side with a large radius of curvature will be greater and the wear will be faster.In this case, the radius of curvature of the tread contour The asymmetry cannot be maintained, and as wear progresses, the radius of curvature on the outside of the attachment becomes smaller than that on the inside.

The present invention combines the asymmetry of the radius of curvature and the control of the negative ratio that influences the wear rate to increase the ground pressure and ground rigidity of the outer tread, thereby preventing sliding wear and one-edge wear on the outer side of the tread. It is intended to improve.

In the tire of the present invention, if the negative ratio is too small, the drainage performance will be impaired, and if it is too large, the wear resistance will deteriorate, so the above-mentioned values of 5 to 30% and 10 to 40% were determined. Also, the difference in radius of curvature is at least 70 mm
The above measures are effective in preventing slips and falls.

Conventionally, it has been difficult to determine an appropriate value for the degree of asymmetry of the radius of curvature due to differences in driving conditions and the like. Through further research by the inventor, an appropriate value for the difference between a large radius of curvature and a small radius of curvature of the tread was determined. FIG. 15 shows the relationship between the ratio of the amount of wear on the outside and inside of the vehicle and the difference in the radius of curvature, which was obtained through simulation calculation. The vertical axis is the quotient of the larger amount of wear divided by the smaller amount of wear, and 1.0 is uniform wear. The horizontal axis is the difference in radius of curvature with respect to the maximum ground contact iJ of the tread in the rotational axis direction. 2-D4 tires
Attach to the front wheels of a car (2 front wheels, 2 drive wheels, 2 idle wheels) so that the side with the larger radius of curvature is on the outside of the vehicle. This is the case when the vehicle is mainly driven.

Table 1 shows the lateral force G applied to the tire on each road. The lateral force G is expressed as the ratio of the lateral force applied to the tire to the gravitational acceleration.

From Table 1, Figure 15, the difference in radius of curvature is the maximum tangent in the direction of the rotational axis of the tread, Ill! II] is found to be 0.75 to 1.50 times the best. If it is smaller than 0.75 times, the wear j11 on the outer side of the mounting will be too large compared to the inner side when driving on a mountain slope, and if it is larger than 1.50 times, the wear j11 on the inside will be too large when driving mainly on highways. The amount of wear is too large.

(Example) FIG. 1 shows a cross section of a tire according to the present invention, and FIG. 2 shows a cross section of a tire according to the prior art. The radius of curvature (R1) of the tread contour of the tire in Figure 2 is 580 mm, and the road surface is shown in Figure 4, where the negative ratio is 1 for both the inside and outside.
It is 2%. In addition, the radius of curvature (R2) of the tread contour on the outside of the installation in Fig. 1 is 690+sm, and that on the inside of the installation (R3) is 470■, and the difference in the radius of curvature is 22
The tread surface is shown in Figure 6, and the negative ratio is 12% on the outer side and 20% on the inner side.
It has become.

Other examples are shown in Figures 10a to 14b, and the negative ratios are listed in Table 2.

Further, in the IJI tire of the present invention, it is preferable that the outermost groove depth is deeper than the other groove depths. This is because the radius of curvature on the outer side of the tread is larger, and the tread gauge is thicker, so the tread depth can be made deeper than on the inner side, which has the advantage of extending wear life.

Table 2 Negative ratio (effect of the invention) Comparison example 1 between the embodiment shown in Fig. 1 (tread shown in Fig. 6) and Fig. 2 (tread shown in Fig. 4), and Fig. 1 (tread shown in Fig. 5) The tire of Comparative Example 2 was subjected to an actual running test to compare the uneven wear performance of the tread edge.

Test conditions Vehicle: Nidrak...2 front wheels, 4 rear wheels Mounting position: Front wheels (The tire in the example was mounted with the side with the larger radius of curvature (R2) on the outside of the vehicle) Driving road: 30% general road, high speed Road 70% Tire size: 11R22,51BPR Internal pressure: 7.7
5 Kg/crn' loading rate: 100% Toe-in amount = 3 rises The test results are shown in Figures 7 to 9. Figure 7 shows the change in the radius of curvature due to running of the tire according to the example FIG. 8 shows Comparative Example 2, and FIG. 9 shows the difference in radius of curvature due to running. According to these figures, the radius of curvature on the outer side of the tire of the comparative example becomes smaller than the radius of curvature on the inner side of the tire due to sliding wear or one-sided wear as the tire of the comparative example is worn, while the radius of curvature on the outer side of the tire of the example decreases even as the tire is driven. The difference between the radius of curvature on the inner side and the inner side was almost unchanged, and no occurrence of sliding wear on the outer side was observed even after driving for 50,000 km.

Furthermore, in order to confirm the results shown in FIG. 15, tires A to F as shown in Table 3 a were prepared and a comparative test was conducted under the following test conditions.

Test conditions/Vehicle Nidrak...2 front wheels, 4 rear wheels, installation position: Front wheel Φ tire size: 11R22, 51flPR, internal pressure
: 7.75 Kg/loading rate:
100% Fist Toe-in amount: 3ml ・Attach the side with the larger radius of curvature to the outside of the vehicle.

The results are also shown in Table 3a, and the CR difference in the table refers to the difference between the tread with a large and small curvature diameter (R3-R2).
), and TW is the maximum ground contact in the rotational axis direction of the tread. In tires E and F, the difference in the radius of curvature of the tread is too small and too large for maximum ground contact in the rotational axis direction of the tread. It can be seen that tire E has severe uneven wear on the outside of the vehicle on the mountain plank road, and tire F has severe uneven wear on the inside of the vehicle on the highway. On the other hand, tires A, B, and C had almost no uneven wear.

Next, in order to confirm the optimal value of the negative ratio of the tread, the tires A-
A comparative test was conducted between Tire C and Tire G-Q. From these results, it can be seen that the negative ratio of the entire tread surface is preferably 25% or less, and the negative ratio on the side where the radius of curvature is larger is preferably 0.3 to 0.8 times that on the side where the radius of curvature is smaller. When the negative ratio of the entire tread surface exceeds 25%, the wear amount of the entire tread becomes extremely worse as in tire O.

Also, if the negative ratio on the side where the radius of curvature is larger is less than 0.3 times that on the side where the radius of curvature is small, uneven wear will occur on the inside of the vehicle, as in tires H or P, and conversely, it is larger than 0.8 times. And tires I and K.

As shown in L, uneven wear occurs on the outside of the vehicle, significantly shortening the life of the tire. On the other hand, tires A, B, C,
For I, J, M, N, and Q, the tread surface wears almost uniformly, the performance of the tire is maintained until the tread wears out, and the life of the tire is extended.

Furthermore, in order to confirm the relationship between negative ratio and wet performance, B of the tires in Table 3 was used.

A trailer towed by tires D, G, H, I, P.
The tire was mounted on a tire and run on a wet road at a speed of 60 km/h with an internal pressure of 7.75 kg/crn' and a 100% load, and W e t g (Pea
k) was measured. The results are expressed as an index with tire D set as 100, and the results are expressed as W e, t p.

is 0.46, and the larger the index, the better. From this result, it can be seen that the wet performance deteriorates extremely when the negative ratio becomes smaller than 12%.

FIG. 16 shows the results of comparing the degree of abnormal wear on the outside of the vehicle, as shown in FIG. 17, with respect to the average radius of curvature of the tread profile. Fig. 17a shows abnormal wear generally called sliding wear, and Fig. 17s shows abnormal wear called rib punching. In both cases, the difference in the amount of wear between the sigolder rib and the second rib was measured. The test method was the same as the uneven wear comparison test described above, and the test was carried out on a general road at 50
I ran it for m. The tires used in the test are shown in Table 4. Note that the tire W-Z has a negative ratio of 12% on the outside where it is mounted on the vehicle and 20% on the inside.

Table 4: Outside R2...Tread contour radius of curvature on the outside of the vehicle installed Inside R3...Average tread contour radius of curvature on the inside of the vehicle installed CR...Average of the radius of curvature of the outside tread contour and the radius of curvature of the inside tread contour This result Therefore, the average radius of curvature of the tread profile is
It is preferably 2.5 to 3 degrees 0 times the maximum ground contact 111 in the direction of the rotational axis. If it is outside this range, abnormal wear such as h1 drop wear or rib punching will be severe and the tire life will be deteriorated.

Since the tire of this invention has a small inner tread radius of curvature, the ground contact pressure load there is reduced, so the ground contact pressure at the outer tread end is higher than in a symmetrical tread tire, slowing down the progression of uneven wear. This and the small negative ratio of the outer tread increase ground contact rigidity and effectively prevent uneven wear on one side. When using a tire, the usage conditions differ from one to another, so according to the present invention, the synergistic effect of the asymmetric combination of the curvature radius of the tread profile and the negative ratio as described above allows the tires to be biased regardless of the usage conditions. It becomes possible to almost prevent the occurrence of wear.

[2] In conventional symmetric tread tires, the radius of curvature was increased by increasing the tread volume, but in the asymmetric tread tire of this invention, the radius of curvature of the tread profile on the outer side of the tire is compared to that on the inner side of the tire. By increasing the size, uneven wear can be suppressed without significantly increasing the tread volume.

[Brief explanation of drawings]

Figure 1 shows the tire of the present invention, Figure 2 shows the tire of the prior art, Figure 3 shows the test results, Figure 4 shows the road surface of the tire of the prior art, Figure 5 shows the tread of the comparative tire, and Figure 6 7 to 9 are test results, 10a to 14b are other examples, 15 is a diagram showing the relationship between the difference in radius of curvature and uneven wear, and 16 is the road surface of the tire of the present invention. is an explanatory diagram of uneven wear, and FIG. 17 is a diagram showing the relationship between the radius of curvature and uneven wear. 1...Tire 2...Trend R1, R2
, R3...Tread contour radius Fig. 1 Fig. 3 Fig. 4 Fig. 5 Fig. 6 Fig. 9 Fig. 10a Fig. 10b Fig. 110 Fig. 12a Fig. 13b Fig. 14a Fig. 15 Shigeshiro #F with trendy contours! Maximum width of disturbance/tread/do Fig. 16 C Fig. 16 b 1, 2 Fig. 17

Claims (8)

[Claims] (1) The radius of curvature of the tread contour that appears in the cross section of the tire, including the axis of rotation of the tire, is asymmetrical in size with respect to the tire equatorial plane, and the area ratio of the groove portion that does not touch the ground on the tread surface is 5 to 30 on the side with the larger radius of curvature. %, the other side with a smaller radius of curvature is 10 to 40%, the area ratio on the side with a larger radius of curvature is smaller than the area ratio on the side with a smaller radius of curvature,
A heavy-duty pneumatic tire that is installed with the side with a larger radius of curvature facing the outside of the vehicle. (2) The heavy-duty pneumatic tire according to claim 1, wherein the difference in radius of curvature is 70 mm or more. (3) The heavy-duty pneumatic tire according to claim 1, wherein the groove depth of at least one of the grooves on the side with a larger radius of curvature is deeper than the groove depth on the side with a smaller radius of curvature. (4) The difference between the large and small radius of curvature of the red contour is 0.75 of the maximum ground contact width in the direction of the rotational axis of the tread.
Claim 1 characterized in that it is ~1.50 times
Heavy-duty pneumatic tires listed. (5) Claim 1, characterized in that the average of the large and small radius of curvature of the tread contour is 2.5 to 3.0 with respect to the maximum ground contact width in the rotational axis direction of the tread. pneumatic tires for heavy loads. (6) The large radius of curvature of the tread portion contour is 2.90 to 3.70 times the maximum ground contact width in the rotational axis direction of the tread,
The pneumatic tire for heavy loads according to claim 1, wherein the small radius of curvature is 2.30 to 2.60 times. (7) The heavy-duty pneumatic tire according to claim 1, wherein the area ratio of the groove portions that do not touch the ground on the entire tread surface is 12 to 25%. (8) A patent claim characterized in that the area ratio of the groove portion that does not touch the ground on the entire surface of the tread on the side with a larger radius of curvature is 0.3 to 0.8 times the area ratio on the side with a smaller radius of curvature. A pneumatic tire for heavy loads according to Range 1.