JP4743754B2 - Tire durability test method - Google Patents

Description

  The present invention relates to a tire durability test method including a deterioration accelerating step capable of accurately reproducing a state in which a tire has deteriorated with time in a short time.

  When a tire is used over a long period of time, the rubber or tire cord or the like deteriorates with time due to various factors such as ultraviolet rays, oxygen, moisture, and / or temperature. Conventionally, when evaluating the durability of a pneumatic tire, a durability test is performed on the deteriorated tire in order to take into account the deterioration over time as described above (see, for example, Patent Documents 1 and 2 below). However, actually degrading a tire over a long period of time is inefficient and has a drawback that it takes a long time to develop a tire.

JP 2004-132847 A Japanese Patent Laid-Open No. 2004-233218

  The present invention has been devised in view of the above circumstances, and in a tire lumen surrounded by a pneumatic tire and a rim, high oxygen air having an oxygen concentration of 30% or more, 10 to 3000 cc of water, And a second step of leaving the tire assembly in a high-temperature and high-humidity atmosphere at a temperature of 50 to 100 ° C. and a humidity of 70 to 100% for at least three days, It is an object of the present invention to provide a tire durability test method that is useful for reproducing a state of deterioration of a tire over time in a short time and for performing a performance test or the like with higher accuracy.

Invention of Claim 1 among this invention is a durability test method of the pneumatic tire including the deterioration promotion process which accelerates | stimulates deterioration of a pneumatic tire, Comprising: The said deterioration acceleration process encloses a pneumatic tire and a rim. A first step of preparing a tire assembly filled with high oxygen air having an oxygen concentration of 30% or more and 10 to 3000 cc of water in a tire lumen; ℃ and saw including a second step of standing at least 3 days in a high-temperature, high-humidity atmosphere of a humidity 70% to 100%, after the second step, the load of 100% or more standard maximum load on the pneumatic tire Is a durability test method for a pneumatic tire characterized in that a durability test is performed by traveling at a speed of 20 km / h or more .

Here, the oxygen concentration of air (gas) is calculated by the following equation (1).
Oxygen concentration (%) = (Po / Pt) × 100 (1)
The “Pt” is the total pressure (Pa) of the target air, and “Po” is the oxygen partial pressure (Pa) with respect to the total pressure.

  The invention according to claim 2 is the pneumatic tire durability test method according to claim 1, wherein, in the second step, the tire assembly is left in the high-temperature and high-humidity atmosphere for 3 to 70 days. .

  In the present invention, the tire lumen of the tire assembly is filled with high oxygen air and water, and the assembly is left in a high temperature and high humidity atmosphere for at least three days. For this reason, the tire can be sufficiently deteriorated from the inside and the outside in a short period of time.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
The tire testing method of the present invention includes a deterioration promoting step of accelerating the deterioration of a pneumatic tire using oxygen and water. By performing this deterioration accelerating step, it is possible to obtain a pneumatic tire having deteriorated in a relatively short time without actually deteriorating over time by running the pneumatic tire over a long time. A durability test is performed on the deteriorated pneumatic tire. Thereby, the tire durability performance after deterioration with time can be analyzed efficiently and in a short time.

  In the present invention, the deterioration promoting step includes a first step and a second step.

  In the first step, as shown in FIG. 1, in the tire lumen i surrounded by the pneumatic tire 1 and the rim 2, high oxygen air having an oxygen concentration of 30% or more, and 10 to 3000 cc of water. Is prepared.

  The pneumatic tire 1 includes a tread portion 1a, sidewall portions 1b and 1b extending inward in the tire radial direction from both sides thereof, and a bead provided at an inner end of the sidewall portion 1b and attached to the rim 3. In this embodiment, a radial tire for trucks and buses is exemplified.

  The pneumatic tire 1 is provided with a toroidal carcass 4 and a belt layer 5 disposed on the outer side in the tire radial direction of the carcass 4 and inside the tread portion 1a. In the present embodiment, the carcass 4 is composed of a single carcass ply 4A. The carcass ply 4A is made of, for example, an organic fiber cord or a steel cord. The main body portion 4a extends in a toroidal manner between the bead portions 1c and 1c; And a folded portion 4b folded back from the inner side in the direction. Further, the belt layer 5 of the present embodiment is configured by superposing a plurality of belt plies 5A to 5D made of a metal cord.

  In the present embodiment, the rim 2 is a normal rim, and it is desirable that the air pressure filled in the tire lumen is set to a normal internal pressure. This is useful for deteriorating the pneumatic tire 1 in a state closer to the environment where the tire is actually used. In the present specification, the “regular rim” is a rim determined for each tire in a standard system including a standard on which the tire is based. For example, a standard rim for JATMA and a “Design Rim” for TRA. "If ETRTO," Measuring Rim ". In addition, “regular internal pressure” is the air pressure that each standard defines for each tire in the standard system including the standard on which the tire is based. The maximum air pressure for JATMA and the table “TIRE LOAD LIMITS AT for TRA” The maximum value described in “VARIOUS COLD INFLATION PRESSURES”, “INFLATION PRESSURE” for ETRTO, but 200 kPa for tires for passenger cars.

  The high oxygen air and water filled in the tire lumen i deteriorate the pneumatic tire 1 from the inside. For this reason, when the oxygen concentration is less than 30%, deterioration from the inside of the pneumatic tire 1 cannot be promoted in a short period of time. The high oxygen air is not particularly limited as long as the oxygen concentration is 30% or more, but by increasing the concentration, oxygen can be diffused more quickly into the tire 1 and the deterioration promoting process time can be increased. Can be reduced. From such a viewpoint, the oxygen concentration of the high oxygen air is preferably 40% or more, more preferably 50% or more. On the other hand, even if the oxygen concentration of the high oxygen air is too high, it becomes difficult to maintain or adjust the oxygen concentration. For example, the oxygen concentration is desirably 95% or less, and more desirably 90% or less. For example, as shown in FIG. 2, such high oxygen air is filled into the tire lumen i from a predetermined air cylinder 6 through the tire valve 7.

  The tire lumen i is filled with 10 to 3000 cc of water. By including the amount of water exceeding the moisture in the air in the tire lumen i, the corrosion of the internal cords of the tire, particularly the metal cords such as the belt plies 5A and 5B, is promoted, and the tire is deteriorated in a shorter period. Can be reproduced. Here, when the water injected into the tire lumen is less than 10 cc, there is a tendency that the corrosion promotion effect of the metal cord or the like is not sufficiently obtained. Conversely, when it exceeds 3000 cc, the rim assembly is not leaked from the tire. Tend to be difficult to do. From such a viewpoint, the amount of water filled in the tire lumen i is particularly preferably 50 cc or more, more preferably 100 cc or more, further preferably 300 cc or more, and the upper limit is preferably 2000 cc or less. Preferably it is 1000 cc or less.

  The water may be pure water, for example, saline. When salt water is used, corrosion of the metal cord inside the tire can be further promoted. The salt concentration of the saline is not particularly defined, but preferably about 5 to 20%. In addition, the water can be injected in advance into the inner surface of the pneumatic tire 1 before assembling the rim.

  In the second step, the tire assembly 3 prepared in the first step is left in a high-temperature and high-humidity atmosphere at a temperature of 50 to 100 ° C. and a humidity of 70 to 100% for at least three days. The second step is preferably performed in a steam oven chamber or the like capable of temperature and humidity management. Thereby, the temperature and humidity in a high-temperature, high-humidity atmosphere can be freely controlled.

  The inventors have found that when a pneumatic tire 1 as shown in FIG. 1 is subjected to an endurance test using, for example, a drum tester, different results are obtained when it is new and when it deteriorates with time.

First, when a durability test is performed on a new tire, most of the damage that occurs in the tire is the separation starting from the end portion of the folded portion 4b of the carcass ply 4A or the interface separation between the tread rubber 8 and the belt layer 5. It is. On the other hand, when a durability test is performed on a tire that has actually deteriorated over time, damage concentrates on the tread portion instead of the bead portion. The breakdown is roughly divided into the following damages (i) to (c).
B) Damage on the side wall 1b of the carcass 4 b) Interfacial peeling between the belt plies 5A and 5B c) Interfacial peeling between the carcass 4 and the belt layer 5

  Therefore, in order to accurately reproduce the deterioration over time of the tire by the deterioration promoting step, it is necessary to reduce the adhesive strength at the interface A to C in a short time. The inventors performed the deterioration accelerating step under various conditions. As a result, the tire assembly in which the pneumatic tire 1 is filled with high oxygen air and water can be reproduced in a short period of time by leaving the tire assembly in a high humidity atmosphere. I found it.

  That is, for example, even when the atmospheric temperature is maintained at a high temperature of 50 to 100 ° C., if the humidity is less than 70%, the damage of a to c cannot be sufficiently reproduced in the pneumatic tire 1. However, by setting the humidity to 70% or more, the pneumatic tire 1 is deteriorated from the outside, and particularly, corrosion or deterioration of the metal cord disposed inside the tread portion 1a or the sidewall portion 1b is efficiently promoted. Can be. In particular, since the tire 1 is more efficiently deteriorated as the humidity is higher, the humidity is preferably 80% or more, more preferably 90% or more.

  Further, when the temperature of the atmosphere in which the tire assembly 1 is left is less than 50 ° C., the pneumatic tire 1 cannot be deteriorated in a short period of time. Particularly preferably, the temperature in the high-temperature and high-humidity atmosphere is particularly preferably 60 ° C. or higher, more preferably 70 ° C. or higher, and still more preferably 80 ° C. or higher. When the temperature exceeds 100 ° C., the rubber layer (tread rubber 8, sidewall portion 1 b) of the pneumatic tire 1 causes rubber burning or the like. Therefore, the next test cannot be performed.

  The tire assembly 3 is left in a high-temperature and high-humidity atmosphere for at least 3 days, preferably 7 days or more, more preferably 10 days or more, and even more preferably 20 days or more. When the leaving time is less than 3 days (that is, 72 hours), the tire 1 is not sufficiently deteriorated. On the other hand, if the standing period is too long, the test efficiency of the tire is lowered, so that it is preferably within 70 days, more preferably within 60 days, and even more preferably within 50 days.

  Then, by promoting the deterioration of the pneumatic tire 1 through the first and second steps as described above, a deterioration state having a very good correlation with the actual aging deterioration can be obtained in a short time.

  In the present embodiment, when the second step is completed, a durability test of the pneumatic tire 1 is performed using, for example, a drum tester. In the pneumatic tire 1, deterioration or aging similar to actual aging has occurred. Therefore, by performing an endurance test using such a pneumatic tire 1, the performance after aging can be evaluated accurately and without actually aging the tire. Therefore, evaluation in a short period is possible. Although it does not specifically limit as an endurance test, For example, the high-speed endurance test method of JIS-D4230 etc. can be mentioned.

  The pneumatic tire 1 is not limited to the above-mentioned category of tires, for example, and can include various categories of tires such as passenger cars, trucks, and motorcycles. In addition, the present invention can be particularly effective for a pneumatic tire having a belt layer or a breaker layer made of a metal cord in the tread portion.

  In order to confirm the effects of the present invention, the process of promoting the deterioration of 20 pneumatic tires was performed on the basis of the specifications shown in Table 1. The tire is a pneumatic radial tire (size: 11R22.5) for trucks and buses shown in FIG. 1, and includes a belt ply and a carcass ply made of a metal cord. The rim is 22.5 × 8.25 and the internal pressure is 800 kPa.

  In addition, as an actually deteriorated tire, the same tire having been run for about one year and having completely worn out tread grooves was prepared. Then, 10 tires are disassembled, and the interface between the tread rubber and the belt layer (hereinafter referred to as “interface 1”), the interface between the belt plies (hereinafter referred to as “interface 2”), and the belt layer. Adhesive strength was measured for each of the interfaces (hereinafter referred to as “interface 3”) between the carcass and the average value. The adhesive force was measured with a tensile tester under the condition of a peel width of 25 mm.

Further, the remaining ten pieces were subjected to the high-speed durability test method of JIS-D4230, and the first damage occurrence site on the tire was examined.
Table 1 shows the test results.

  As a result of the test, it was confirmed that, in the tire of the example, damage was concentrated on the interfaces 2 to 3 as well as the actual aged tire, and the adhesive force at the interface was also highly correlated. On the other hand, in the tire of the comparative example, all the damage forms are similar to those of the new tire, and it can be confirmed that sufficient deterioration with time is not reproduced.

It is a schematic diagram explaining the 1st process of this embodiment. It is sectional drawing of a pneumatic tire.

Explanation of symbols

1 Pneumatic tire 2 Rim 3 Tire assembly

Claims (2)

A durability test method for a pneumatic tire including a deterioration promoting step for promoting deterioration of the pneumatic tire,
In the deterioration promoting step, a tire assembly is prepared in which a tire lumen surrounded by a pneumatic tire and a rim is filled with high oxygen air having an oxygen concentration of 30% or more and 10 to 3000 cc of water. And the process of
The tire assembly, viewed contains a second step of standing at least 3 days in a high temperature and high humidity atmosphere at 50 to 100 ° C. and humidity 70% to 100%,
A durability test method for a pneumatic tire, characterized in that after the second step, a durability test is performed in which a load of 100% or more of a standard maximum load is applied to the pneumatic tire to run at a speed of 20 km / h or more .   The durability test method for a pneumatic tire according to claim 1, wherein in the second step, the tire assembly is left in the high-temperature and high-humidity atmosphere for 3 to 70 days.

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