JP4496945B2 - Tire durability test method - Google Patents

Description

  The present invention relates to a tire endurance test method, and more particularly, a tire endurance test method capable of accurately reproducing and evaluating an internal failure that tends to occur in a pneumatic tire mounted on a vehicle continuously running in a relatively hot area. About.

  In recent years, as a tire durability test, a tire durability test method has been proposed in which a pneumatic tire is subjected to deterioration promotion treatment with oxygen, and then the pneumatic tire is filled with air to perform a drum durability test (for example, , See Patent Document 1).

  Pneumatic tires that have deteriorated over a long period of actual use have suffered a failure due to the loss of the rubber's natural soft and sticky properties, and the internal failure was enclosed when the rim was assembled. Oxygen degradation of rubber due to oxygen in the air is greatly involved. In the above durability test method, by performing the deterioration promotion treatment with oxygen, it is possible to evaluate deterioration durability by reproducing internally aged deterioration efficiently in a short time in a new tire. .

However, pneumatic tires mounted on vehicles that run continuously in a relatively hot area have a problem that variations in test results are large and it is difficult to accurately reproduce and evaluate.
JP 2003-161694 A

  An object of the present invention is to provide a tire durability test method capable of accurately reproducing and evaluating an internal failure that tends to occur in a pneumatic tire mounted on a vehicle that continuously runs in a relatively hot area.

The tire endurance test method of the present invention that achieves the above-described object is the method of accelerating deterioration of a pneumatic tire with oxygen, filling the pneumatic tire with air, and applying a test load to the drum endurance at a predetermined test speed. In the tire durability test method for performing the test, the deterioration promoting treatment is performed while filling the pneumatic tire with an oxygen-containing gas having a ratio of oxygen partial pressure of 60% or more and heating the pneumatic tire in a dry state. in, with increasing test speed of the drum durability test stepwise, and maintains a test speed of each stage 6-120 hours.

According to the present invention described above, in a pneumatic tire that is mounted on a vehicle that continuously runs in a relatively hot area by gradually increasing the test speed of the drum durability test for at least 6 hours, Oxidation fatigue can be generated, and variations in high-speed durability test results can be kept small, so that it is possible to accurately reproduce and evaluate internal failures due to speed that tends to occur inside the tire.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an embodiment of a tire durability test method of the present invention. In the tire durability test method shown in FIG. 1, first, the inside of a pneumatic tire to be tested (test tire) is subjected to deterioration promotion treatment with oxygen. This treatment fills the rim-assembled test tire T with oxygen and fills the tire cavity with a gas containing a high concentration of oxygen.

The oxygen concentration of the oxygen-containing gas should be such that the oxygen partial pressure ratio is 60 % or more in order to efficiently promote the deterioration of the internal rubber. The higher the oxygen concentration, the better the deterioration, and the upper limit of the oxygen partial pressure ratio may be 100% if possible (actually less than 100%).

  In addition, the oxygen partial pressure said here shows the partial pressure of oxygen with respect to the total pressure of filling gas. For example, when a tire is rim-assembled in a normal manner and oxygen is filled with 300 kPa, oxygen contained in 1 atm (100 kPa) of air in the tire is added, and the oxygen partial pressure in the tire becomes 320 kPa. The pressure ratio is 80%. However, the amount of oxygen contained in the air is 20%.

  The pressure in the test tire after filling is generally in the range up to the JATMA maximum air pressure, but may be an air pressure exceeding the maximum air pressure after confirming the safety of the tire.

  The test tire T filled with a gas containing a high concentration of oxygen is then heated in the oven 1. Here, heating is performed in a dry state in the oven 1 without adding steam (dry heat treatment). The heating temperature in the dry heat treatment is set to 65 to 85 ° C., preferably 70 to 80 ° C., in order to efficiently perform the deterioration promoting treatment without adversely affecting the rubber of the test tire T. As a matter of course, it is possible to carry out at normal temperature (for example, ambient temperature around 20 ° C.), but dry heat treatment is effective for promoting the tire durability test by promoting the deterioration of rubber.

  The dry heat treatment time is appropriately selected depending on the oxygen concentration, the dry heat treatment temperature and the type of tire. For example, in a passenger car tire of 265 / 70R16, the oxygen partial pressure ratio is 80% and the dry heat treatment temperature is 80 ° C. If it does, it will be about 4-8 days depending on the assumed market.

  After performing the dry heat treatment, the gas in the test tire T taken out from the oven 1 is discharged, cooled to room temperature, and then filled with normal (20% oxygen) air in the test tire T. The filling pressure can conform to the high-speed performance test A of JIS D4230, but is not limited to this, and any air pressure at that level may be used.

Next, the test tire T is attached to the drum testing machine 2 installed in the room 3, and a drum durability test is performed in which the test tire T runs on the drum 2a rotating at a predetermined test speed while applying a test load. This test is a test for examining high-speed durability, and is performed while gradually increasing the test speed. What is important at this time is that the test speed of each step is maintained for at least 6 hours as it is stepped up.

  If this time is short, the degree of rubber deterioration at the time of tire failure is smaller than the level of aging deterioration (market level) in actual use, and tire failure occurs due to thermal factors associated with high-speed driving, so the evaluation results are actually used. The result is different from the evaluation result in. Further, if the test speed is increased at a constant high speed without increasing the test speed step by step, the test results vary greatly and cannot be accurately reproduced and evaluated.

The duration of the test speed at each stage should be 6 hours or more to obtain market-level thermal oxidative fatigue. The upper limit value is preferably within 5 days (120 hours) from the viewpoint of evaluation accuracy and test efficiency of the durability test.

  The starting test speed is preferably about 120 km / h from the viewpoint of evaluation accuracy and test efficiency of the durability test.

  The test load is preferably equal to or less than the standard maximum load of the tire (the load with the maximum load capacity specified in JATMA). If the test load exceeds the standard maximum load of the tire, in the high-speed endurance test, the temperature rise of the test tire T is greatly increased, and the tire is likely to break down due to thermal factors. Moreover, it is preferable to make the test load constant so as not to complicate the test factors.

  The temperature of the room 3 where the drum durability test is performed (test room temperature) can be set to 20 degrees or more, which is the same as the high speed performance test A of JIS D4230. Preferably, the range of approximately 25 to 34 degrees may be adjusted according to the tire conditions used in a relatively hot area.

According to the present invention shown in FIG. 1 described above, in the process of performing the drum durability test, the test speed is increased stepwise, and the test speed of each stage is maintained for at least 6 hours, thereby continuously in a relatively hot area. Pneumatic tires mounted on traveling vehicles can generate thermal oxidation fatigue at the market level and can suppress variations in test results for high-speed durability, resulting in speeds that tend to occur inside the tires. It is possible to reproduce and evaluate internal failures with higher accuracy than before.

  Sixteen test tires A and B, each having a tire size common to 265 / 70R16112S and different tire specifications, were produced. There is no problem when the test tire A is mounted on a vehicle that continuously runs in a relatively hot area (passenger car that frequently travels at a high speed), but the test tire B is tired up to the wear limit when mounted on such a vehicle. It is a tire in which a failure is seen before it wears.

  When each of the two test tires A and B was subjected to a tire high speed durability test under the conditions shown in Table 1, the results shown in Table 1 were obtained.

  In Examples 1 to 4 of Table 1, the time for maintaining the test speed at each stage is sufficiently long (6 hours or more), but the rubber at the time of failure occurrence in such a long time is used. Examining the degree of deterioration, both the test tire A that has no problem and the test tire B that has a problem have both failed due to thermal oxidation fatigue at the same level as the level of aging in actual use (market level). It was possible to reproduce and evaluate the tires that were actually evaluated.

  On the other hand, in Comparative Example 1, the time for maintaining the test speed at each stage is shortened to 3 hours, but the degree of deterioration of the rubber at the time of occurrence of the failure when conducted in such a short time is examined. As a result, the degree of deterioration was smaller than the market level, and the failure was caused by the thermal factor of heat generated by high-speed driving.

  Comparative Example 2 was performed at a constant high speed. When high-speed durability was tested at a constant speed in this way, even with the same type of tire, there was a large variation in the tire failure time, and the accuracy was high. Reproduction evaluation could not be performed.

  In Comparative Example 3, the drum endurance test was also performed with a high oxygen concentration. When the drum endurance test was also performed under conditions of a high oxygen concentration, the degree of rubber degradation at the time of failure occurred in the market. Since the level was exceeded, it was still impossible to accurately reproduce and evaluate.

  Comparative Example 4 is a drum endurance test without performing the deterioration promotion process, but when the endurance test is performed without performing the deterioration promotion process, the degree of deterioration of the rubber at the time of failure is smaller than the market level, The tire failed due to heat generated during high-speed driving, and could not be accurately reproduced.

It is explanatory drawing which shows one Embodiment of the tire durability test method of this invention.

1 Oven 2 Drum Testing Machine 2a Drum 3 Indoor T Pneumatic Tire (Test Tire)

Claims (4)

After accelerated degradation process by oxygen pneumatic within the tire, the air is filled in the pneumatic tire, the tire durability test method of performing drum durability test at a predetermined test speed while applying the test load, the accelerated deterioration treatment While the pneumatic tire is filled with an oxygen-containing gas with an oxygen partial pressure ratio of 60% or more and heated in a dry state, the test speed of the drum durability test is increased stepwise. And a tire durability test method in which the test speed of each stage is maintained for 6 to 120 hours. The tire durability test method according to claim 1, wherein a heating temperature in the deterioration promotion treatment is set to 65 to 85 ° C. The tire durability test method according to claim 1 or 2 , wherein the test load is equal to or less than a tire standard maximum load. The tire durability test method according to claim 3 , wherein the test load is constant.

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