JP4710500B2 - Tire durability test method - Google Patents

Description

  The present invention relates to a tire durability test method, and more particularly to a tire durability test method capable of reproducing a tire failure in a state closer to a tire failure on the market.

  A test defined in JIS D4230 is well known as a tire durability test for reproducing tire failures on the market and evaluating durability. In addition, a tire durability test method that improves the tire durability test defined in JIS has been proposed (see, for example, Patent Documents 1 and 2).

By the way, the failure of tires used in the market is mostly caused by a combination of a mechanical destruction factor and a thermal destruction factor due to an increase in internal temperature. However, in the tire endurance test method defined in the above-mentioned JIS and the like, thermal destruction factors act greatly, and the influence of mechanical destruction factors tends to be low. That is, when examining tires that failed in the market and tires that failed using the tire durability test method described above, the degree of thermal oxidation degradation of rubber tends to be lower in tires that fail in the market. The failure was not necessarily reproduced with high accuracy, leaving room for improvement.
JP 2003-161694 A JP 2004-37286 A

  An object of the present invention is to provide a tire durability test method capable of reproducing a tire failure in a state closer to a tire failure on the market.

The tire endurance test method of the present invention that achieves the above-mentioned object is the method of performing the drum endurance test in which a pneumatic tire is run on a drum at a predetermined test speed while applying a predetermined test load. At least one is increased stepwise, and at least one increased stepwise is periodically changed up and down in each step .

  According to the present invention described above, by periodically moving up and down the test speed and test load, it is possible to suppress an increase in internal temperature while increasing the maximum stress and strain in the pneumatic tire to be tested, The mechanical and thermal destruction factors can be made to act in a state closer to the market than before. As a result, the degree of thermal oxidative degradation of the rubber in the test approaches that of the market, and it becomes possible to reproduce the tire failure in a state closer to the tire failure in the market and evaluate the durability.

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 according to the present invention. 1 is a pneumatic tire (test tire) to be tested, 2 is an oven for heating the test tire 1, and 3 is a drum durability test. It is a drum for.

  The tire durability test method of the present invention shown in FIG. 1 shows an example in which a drum durability test is performed after dry heat pretreatment is performed. First, as shown in FIG. 1 (a), the test tire 1 is assembled on the rim of the wheel W and filled with gas. The gas to be filled may be air. However, in order to promote oxidative degradation and shorten the test period, it is preferable to fill an oxygen-containing gas whose oxygen partial pressure is higher than that of air. The proportion of oxygen partial pressure is preferably 30% or more, more preferably 60% or more. Since the higher the oxygen concentration is, the more the deterioration can be promoted, the upper limit value 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 at 300 kPa, oxygen content (20 kPa) contained in 1 atm (100 kPa) air in the tire is added, and the oxygen partial pressure in the tire is 320 kPa. The ratio of oxygen partial pressure is 80%. However, the amount of oxygen contained in the air is 20%.

  Next, as shown in FIG. 1B, dry heat pretreatment is performed in which the test tire 1 filled with gas is heated in an oven 2. The dry heat pretreatment performed here is performed in the same manner as in the past. For example, when an oxygen-containing gas with an oxygen partial pressure ratio of 80% is filled, heating is performed in the oven 2 at about 80 ° C. for about 5 days. After heating, the test tire 1 is taken out of the oven 2 and the gas in the test tire 1 is discharged.

  In the same manner as in the past, the test tire 1 that has been subjected to the dry heat pretreatment is subjected to air or oxygen partial pressure higher than air (oxygen partial pressure is 30% or more, more preferably 60% or more oxygen). The gas is contained in a drum testing machine installed indoors, and a tire failure (belt layer edge separation) occurs on the drum 3 rotating at a predetermined test speed while applying a predetermined test load to the test tire 1. A drum endurance test is performed until it is generated (see FIG. 1C).

  When testing high-speed durability, the test load is made constant while the test speed is increased stepwise. At that time, in the present invention, as shown in FIG. 2, the test speed at each stage is periodically changed up and down. The range to be varied up and down can be set as appropriate according to the situation and region (market) used. In general, the fluctuation range is constant even if the test speed increases, but the fluctuation range may be increased as the speed increases.

  When testing the load durability, the test load is increased stepwise while keeping the test speed constant. At that time, in the present invention, as shown in FIG. 3, the test load at each stage is periodically changed up and down. The width to be varied up and down can be set as appropriate according to the situation and region (market) used, similarly to the above. Generally, the fluctuation range is constant even when the test load increases, but the fluctuation range may be increased as the load increases.

  As shown in FIGS. 2 and 3, the method of periodic fluctuation is not limited to the one that fluctuates in a sine wave shape, and may be any one that repeats fluctuations at a constant cycle, such as a rectangular wave shape or a sawtooth wave shape.

  In both tests, it is advisable to secure at least 5 hours of running time at each stage. If this time is short, that is, if the test speed or test load is increased in a short time, the degree of deterioration of the rubber at the time of a tire failure is smaller than the level of aging deterioration (market level) in actual use, and high speed running or load Since tire failure occurs due to the accompanying thermal factors, the evaluation result tends to be different from the evaluation result in actual use.

  The running time at the test speed or test load at each stage is preferably 6 hours or more in order to approach the thermal oxidation fatigue at the market level. The upper limit value is within 6 days, preferably within 5 days (120 hours) from the viewpoint of evaluation accuracy and test efficiency of the durability test.

  While periodically moving up and down at each stage, the test speed or test load is increased stepwise, and the drum endurance test ends when a tire failure occurs.

  FIG. 4 shows another embodiment of the tire durability test method of the present invention. Here, an example in which a drum durability test is performed without performing dry heat pretreatment is shown. First, as shown in FIG. 4 (a), the test tire 1 is assembled on the rim of the wheel W and filled with gas. In this case, the oxygen partial pressure ratio is 30% in order to promote oxidative degradation. Above, preferably 60% or more of oxygen-containing gas is filled. Next, a drum durability test is performed as shown in FIG. 4B, which is the same as described above.

  In the drum endurance test, when the test speed and the test load are increased, the stress / strain in the test tire increases. If the vehicle continues to run as it is, the internal temperature rises with an increase in the amount of heat generated by the tire, and the tire is liable to break down due to a thermal failure factor. By moving it, it is possible to suppress the rise in internal temperature while increasing the maximum stress / strain in the test tire 1, so that mechanical and thermal destruction factors are closer to the market than before. It becomes possible to act. Therefore, the degree of thermal oxidative degradation of rubber in the test approaches that of the market, and it becomes possible to reproduce the tire failure and evaluate the durability in a state closer to the tire failure in the market.

  In the present invention, during the drum durability test, it is preferable to give the test tire 1 a slip angle and / or a camber angle because it is close to the running environment in the market. More preferably, the slip angle and / or the camber angle is periodically changed in synchronization with the periodic change. When the slip angle and / or camber angle are changed synchronously, when the test speed is in the increase region, the slip angle and / or camber angle is set to one side (+ side in the figure) as shown in FIG. It can be directed (tilted), or can be directed (tilted) to the other side (the minus side in the figure) as shown in FIG.

  The present invention is not limited to the tire durability test method of the above-described embodiment, as long as a drum durability test for running on the drum 3 at a predetermined test speed while applying a predetermined test load to the test tire 1 is performed. It can be applied to both. For example, it may be an endurance test that is performed without increasing the test speed and the test load stepwise, and as a more severe tire endurance test, both the test load and the test speed are increased stepwise. It can also be used for the test method. In that case, it suffices to periodically vary at least one of the test load and the test speed.

  Each test tire having a common tire size of 265 / 70R16 112S was subjected to a tire high speed durability test under the conditions shown in Table 1, and the results shown in Table 1 were obtained. In addition, the standard maximum load described in Table 1 is the load of the maximum load capacity prescribed | regulated to JATMA. The slip angle and camber angle are each 0 °.

From Table 1, in Examples 1 and 2 adopting the method of the present invention, the degree of thermal oxidative fatigue of rubber at the time of failure can be made the same level as the level of aging (market level) in actual use, It can be seen that the tire failure can be reproduced in a state close to a tire failure on the market, as compared with Comparative Example 1 in which the conventional method is adopted. In addition, although the failure occurrence rate has decreased, this means that the mechanical destruction factor has increased.

  When the tire load endurance tests were performed on the test tires having the same tire size of 265 / 70R16 LT under the conditions shown in Table 2, the results shown in Table 2 were obtained. In addition, the standard maximum load described in Table 2 is the load of the maximum load capacity prescribed | regulated to JATMA similarly to Example 1. FIG. The slip angle and camber angle are also 0 °.

From Table 2, it can be seen that in Examples 3 and 4 employing the method of the present invention, the degree of thermal oxidation fatigue of rubber at the time of failure can be made the same level as the level of aging deterioration (market level) in actual use.

(A)-(c) is explanatory drawing which shows one Embodiment of the tire durability test method of this invention. It is a graph which shows the example of the test speed which fluctuates periodically. It is a graph which shows the example of the test load which fluctuates periodically. (A), (b) is explanatory drawing which shows other embodiment of the tire durability test method of this invention. (A), (b) is a graph which shows the example which changes a slip angle and / or a camber angle periodically synchronizing with a periodic change of a test speed or a test load.

Explanation of symbols

1 Pneumatic tire (test tire)
2 Oven 3 Drum W Wheel

Claims (6)

When performing a drum durability test in which a predetermined test load is applied to a pneumatic tire while running on a drum at a predetermined test speed, at least one of the test load and the test speed is increased stepwise and the stepwise increase. A tire durability test method in which at least one of the two is periodically moved up and down at each stage . Tire durability test method according to claim 1 running time at each stage is at least 5 hours. The tire durability test method according to claim 2 , wherein the running time at each stage is 6 to 120 hours. The drum endurance test is performed according to any one of claims 1 to 3 , wherein the drum endurance test is performed after performing a dry heat pretreatment in which the pneumatic tire is filled with an oxygen-containing gas whose oxygen partial pressure is higher than that of air and then heated. The tire endurance test method described. The tire durability test method according to any one of claims 1 to 4 , wherein the pneumatic tire is filled with an oxygen-containing gas having an oxygen partial pressure ratio of 30% or more during the drum durability test. The tire durability test method according to any one of claims 1 to 5 , wherein a slip angle and / or a camber angle of the pneumatic tire is periodically changed in synchronization with the periodic change.