JPH09133611A - Test method for durability of pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a test method, for a pneumatic tire, in which a secular change in an actual use is reproduced well and in which a durability evaluation in the secular change is performed properly and with good efficiency. SOLUTION: Oxygen at a high concentration in which an oxygen concentration (x) expressed by an expression mentioned below is at 3.0 or higher is injected into a tire, and the degradation of the tire due to the oxygen is promoted. The oxygen at the high concentration is injected into the tire. After the passage of time, the tire is kept as it is or the oxygen is discharged. The air is injected. An actual durability test process is performed. Expression: x=(PO/PT)×100 (%) In Expression, PT represents the total pressure (kgf/cm<2> ) of a filled gas after its filling, and PO represents the partial pressure (kgf/cm<2> ) of oxygen with reference to the total pressure.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire endurance test method, and more particularly to a pneumatic tire endurance test method capable of appropriately performing durability evaluation upon deterioration over time.

[0002]

2. Description of the Related Art Conventionally, as a tire durability test, J
Air is filled with a predetermined air pressure as specified in IS D4230, left at room temperature of 38 ± 3 ° C. for 3 hours to stabilize the air pressure, and then readjusted to the original air pressure to perform a durability test. In addition, JIS D4230-1978 refers to the humidity control performance test method for examining the deterioration of steel radial tires for passenger cars under high temperature and high humidity conditions as a countermeasure against the peeling of steel cord that often occurs in the summer at that time. Have been described. In this method, a tire not assembled on a rim is left at a temperature of 38 ° C. and a humidity of 95% for 20 days, and then a drum durability test based on a high speed durability test method of JIS D4230 is performed.

The warranty life expected of a pneumatic tire has become longer and longer in recent years as the reliability of the vehicle system has improved, and it is becoming indispensable to evaluate the durability against deterioration over time. However, JIS D4230-1978
As described in the explanation of the above, the humidity control performance test method is not such that the experimental conditions such as the condition of being left under high temperature and high humidity have not been fixed, and the aeration that has been aged over a long period of actual use It has also been found that some tire failures cannot be reproduced by a conventionally known indoor / outdoor durability test.

[0004]

Therefore, there has been a strong demand for a pneumatic tire test method capable of reproducing aging deterioration in actual use, that is, capable of appropriately and efficiently evaluating durability against aging deterioration.

[0005]

[Means for Solving the Problems] As a result of studies by the present inventors, the rubber member constituting the inside of a pneumatic tire that has deteriorated over time due to long-term actual use has the inherent soft and sticky nature of rubber. It was revealed that the loss caused the loss, and the oxygen deterioration of the rubber due to the oxygen contained in the air when the rim was assembled was significantly involved. Therefore, the present inventors pay attention to the oxygen deterioration of rubber, and by using high-concentration oxygen, failure in the market efficiently in a short period of time,
That is, it was found that aging deterioration in actual use can be reproduced,
The present invention has been completed.

(1) The durability test method for a pneumatic tire according to claim 1 of the present invention comprises injecting a high concentration of oxygen having an oxygen concentration x represented by the following formula (I) of 30 or more into the tire. , A step of promoting deterioration of the tire due to oxygen.

Formula (I) x = (PO / PT) × 100 (%) [In the formula, PT is the total pressure (kgf / c) of the filling gas after filling.
m ² ), PO is the partial pressure of oxygen (kgf) with respect to the total pressure.
/ Cm ² ). (2) The durability test method for a pneumatic tire according to claim 2 of the present invention is the test method according to (1), wherein the step of accelerating the deterioration of the tire by oxygen includes i) injecting oxygen into the tire. And ii) leaving or heating the tire, and iii) discharging oxygen, and injecting air into the tire after the step of promoting deterioration of the tire due to oxygen is completed. The actual durability test process is performed by applying a load.

(3) A durability test method for a pneumatic tire according to claim 3 of the present invention is the test method according to (1), wherein the step of accelerating the deterioration of the tire by oxygen is i) oxygen in the tire. And a step of ii) leaving or heating the tire, and after the step of accelerating deterioration of the tire due to the oxygen is completed, a load is applied in a state where high concentration oxygen is injected into the tire. And an actual durability test process is performed.

(4) The durability test method for a pneumatic tire according to claim 4 of the present invention is the test method according to (3), which is represented by the formula (I) in the step of promoting deterioration of the tire by oxygen. The oxygen concentration x is 30 or more and 60 or less. Further, (5) the durability test method for a pneumatic tire according to claim 5 of the present invention comprises: i) injecting a high concentration of oxygen having an oxygen concentration x represented by the following formula (I) of 30 or more into the tire. And a step of ii) leaving or heating the tire, and iii) a step of discharging oxygen.
Injecting air into the tire, applying a load to perform an actual durability test step, and then exhausting air from the tire, i) injecting the high concentration oxygen into the tire, and ii) leaving the tire Alternatively, a secondary deterioration promoting step by oxygen including a heating step and iii) a step of discharging oxygen is performed,
Thereafter, air is injected into the tire, the high-concentration oxygen is injected therein, and a load is applied to perform the second actual durability test process.

Formula (I) x = (PO / PT) × 100 (%) [wherein, PT is the total pressure (kgf / c) of the filling gas after filling.
m ² ), PO is the partial pressure of oxygen (kgf) with respect to the total pressure.
/ Cm ² ). Further, in the pneumatic tire durability test method according to (1) to (5), some or all of the steps of promoting deterioration of the tire due to oxygen are performed in a temperature range of 20 ° C to 120 ° C. Ii) In the step of accelerating the deterioration of the tire due to oxygen, ii) the step of leaving or heating the tire is performed for at least 24 hours, and further, the step of accelerating the deterioration of the tire due to oxygen is 10 to 10 times.
It is preferable to perform the treatment in a state where 3000 cc of water is enclosed, from the viewpoint that the deterioration with time in actual use can be appropriately reproduced.

In the present invention, the actual durability test process under load includes, for example, all the drum durability tests including the drum durability test based on the high speed durability test method of JIS D4230, and further the actual vehicle durability test. I shall.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION A high-concentration oxygen having an oxygen concentration x of 30 or more is injected into a tire and a durability test is performed, so that the durability test can be performed in a shorter time than a conventional durability test method in which air is filled. Therefore, it is possible to more accurately reproduce the change with time when actually used. A known method can be applied to the method for adjusting the oxygen concentration represented by the formula (I). The oxygen concentration (or oxygen partial pressure) is preferably as high as possible from the viewpoint of accelerating the deterioration in a short time, but x is preferably about 30 to 99, and in consideration of handling property, x is 30 to 9
About 5 is more preferable. When x is less than 30, acceleration of deterioration is insufficient, and it is difficult to fill the tire with high-concentration oxygen exceeding 99, which is not preferable. Further, when the actual durability test is performed under the condition that the tire generates a large amount of heat and tends to burst, x is more preferably about 30 to 60.

The step of accelerating the deterioration of the tire by this oxygen is
i) a step of injecting oxygen into the tire, and ii) a step of leaving or heating the tire, and thereafter, iii) a step of discharging oxygen when a load is applied and an actual durability test step is performed. Ordinarily, normal air may be injected into the tire, or high-concentration oxygen may be injected into the tire without discharging oxygen.

As for these durability tests, the former one, in which the deterioration promoting process by oxygen → high-concentration oxygen (hereinafter simply referred to as oxygen) discharge → air injection → actual durability test process, is performed (A) ), And the latter one, in which the actual durability test step is performed in the oxygen injection state while the oxygen deterioration promotion step is referred to as the test (B). In the present invention, any test method can be adopted. For example, in the case of performing an actual durability test of a large tire which is likely to cause a burst failure due to high heat generation of the tire in the actual durability test, the test (A) is performed. It is preferable to adopt the test (B), which can more effectively accelerate deterioration, when the actual durability test is performed under the condition that there is no risk of burst failure.

Further, as described in claim 5 of the present invention, in the durability test step of the pneumatic tire, the step of i) injecting a high concentration of oxygen into the tire and ii) leaving or heating the tire. And a step of iii) discharging oxygen, a deterioration promoting step due to oxygen is performed, air is injected into the tire, a load is applied to perform an actual durability test step, and then the air is discharged from the tire. It is also possible to inject the high-concentration oxygen again into the tire, apply a load, and fill the tire with the high-concentration oxygen to perform the second series of steps. The first deterioration promoting process by oxygen → oxygen discharge → air injection → first actual durability test → air discharge → oxygen injection → second deterioration promoting process → oxygen discharge → air injection → second actual durability test What performs a process is hereafter called test (C).

In this test (C), when it is necessary to guarantee the durability after the secondary life of a recycled tire or the like, the acceleration of deterioration and the damage due to running are repeatedly given, so that the durability can be guaranteed. It is suitable for use in tests to determine the presence or absence.

The step of accelerating the deterioration of the tire by oxygen can be carried out at room temperature (for example, an ambient temperature of about 20 ° C.), but by further heating and carrying out in an atmosphere at a temperature higher than room temperature, the tire is constructed. It becomes possible to promote the diffusion of oxygen into the rubber composition. The working temperature in the test method of the present invention is preferably about 20 to 120 ° C. If the atmospheric temperature in the test is less than 20 ° C., the acceleration of deterioration is insufficient, and a long standing time is required to obtain a test result close to actual use.
If the temperature exceeds 120 ° C, the risk of bursting of the tire during the oxygen deterioration step increases, and thus both are not preferable.

When the test is carried out by heating to a temperature higher than room temperature, the heating may be continuously carried out in all steps of the step of promoting deterioration of the tire by oxygen and all steps of the actual durability test step. It may be carried out only in all the steps of the deterioration accelerating step, or, in the tire deterioration accelerating step, it may be carried out only in the step of ii) leaving or heating the tire injected with high concentration oxygen.

The heating method may be a method of raising the atmospheric temperature in the test process using a heating device, or a method of utilizing self-heating due to rolling of the tire in the durability test.
Even in the case of utilizing self-heating, it is preferable to control the temperature condition by combining with another temperature control device, which enables a stable test. Since high-concentration oxygen is used in the deterioration promoting step, it is preferable to use a highly safe steam oven or the like as the heating device.

From the viewpoint of sufficiently diffusing oxygen into the rubber composition constituting the tire, the step of promoting deterioration of the tire by oxygen is preferably performed for at least one day, that is, for 24 hours or more.

Moisture is often not contained in the oxygen gas used in the step of accelerating the deterioration of the tire, and the amount of water contained in the high concentration of oxygen injected into the tire in this step is the water contained in the air. Less than. For this reason,
Deterioration due to moisture, for example, the influence on the deterioration due to moisture of the steel composition used for the rubber composition and the carcass ply of the tire decreases, and there is a possibility that the deterioration over time in actual use cannot be efficiently reproduced in a short period of time. . For this reason, in the tire deterioration promoting step, it is preferable to simultaneously fill the tire with more water than is contained in the air. This water content is preferably about 10 to 3000 cc per tire. If the amount of water added is less than 10 cc, a stable test is difficult, and if it exceeds 3000 cc, water easily leaks from the tire when the tire is assembled on the rim, which is not preferable. Corrosion of steel cords is promoted by adding an appropriate amount of water, and changes over time can be efficiently reproduced in a short period of time.

[0022]

EXAMPLES The test method of the present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. Test tire Steel radial tire 185SR as a test tire
14 sizes (hereinafter referred to as PSR) and steel radial tires 12R22.5 sizes (hereinafter referred to as TBR) were prepared. Deterioration acceleration process The standard maximum air pressure of each tire is PM [kgf / c
m ² ], and the rim-assembled tire was filled and adjusted with oxygen so that the filling pressure PT [kgf / cm ² ] and the oxygen concentration x [%] in Table 1 below were obtained, and the tire was stored in a temperature-controlled room. The conditions are shown in Table 1. In the table, t [° C.] represents the temperature of the temperature-controlled room in which the tire with the above-mentioned rim is stored, and L [days] represents the period of storage in the temperature-controlled room. Actual durability test process For the actual durability test, (A) Degradation acceleration process by oxygen → Oxygen discharge → Air injection → Actual durability test process, (B) Degradation acceleration process by oxygen → Actual durability in the oxygen injection state Test process, (C) first deterioration promoting process by oxygen → oxygen discharge → air injection → first actual durability test → air discharge → oxygen injection → second deterioration promoting process → oxygen discharge → air injection → second Table 1 below shows which of the actual durability test steps was adopted. The results are shown in Table 1 as drum life. The closer the cracks are to those in actual use, the shorter the drum life is. Comparative evaluation with actual use The above-mentioned PSR tire and TBR tire were actually used under normal conditions for 2 to 4 years (running for 1 to 6 hours a day, average speed 40 km / hr) to determine the state of internal deterioration. ,
Each item of deterioration of rubber elasticity, occurrence of cracks and deterioration of steel cord was evaluated. With these,
Differences between the above-mentioned Examples and Comparative Examples were evaluated by 5 expert panelists according to the following criteria. The results are shown in Table 1.

◯: It is very similar to the state of the actually used tire. Δ: Slightly different from the state of the actually used tire.

X: completely different from the condition of the tire actually used. (Example 1) The standard maximum air pressure of the PSR tire is 2.4.
(Kgf / cm ² ), the total pressure of the filled gas after filling is 2.4 (kgf / cm ² ), and the high concentration oxygen is x = 40.
It is injected into the tire under the conditions that
Left for days. After that, the internal pressure was adjusted while the tire was filled with high-concentration oxygen, and the load was: standard maximum load × 1.
2. Under the condition of drum running speed: 90 km / hr, an actual durability test was conducted by an indoor drum durability test [test (B)]. 100 drum life in Comparative Example 1 below
As an index of drum life was displayed. Table 1 shows the results
Shown in

(Comparative Example 1) The standard maximum air pressure of a PSR tire was set to 2.4 (kgf / cm ² ), and the tire was filled with air without undergoing a deterioration promoting step due to high concentration oxygen.
An actual durability test was conducted under the same conditions as in Example 1. The results are shown in Table 1 with the drum life in Comparative Example 1 set to 100.
Shown in

(Comparative Example 2) The standard maximum air pressure of a PSR tire was set to 2.4 (kgf / cm ² ), and air (oxygen concentration corresponds to x = 21) was injected instead of high concentration oxygen, and 6
After storing in a thermostatic chamber at 0 ° C. for 14 days, an actual durability test was conducted under the same conditions as in Example 1. The drum life in Comparative Example 1 was set to 100, and the drum life index was displayed. Table 1 shows the results.

(Example 2) Except that the total pressure of the filled gas after filling the PSR tire was set to 4.8 (kgf / cm ² ), the deterioration acceleration process was conducted under the same conditions as in Example 1 A durability test was conducted [test (B)]. The drum life in Comparative Example 1 was set to 100, and the drum life index was displayed. Table 1 shows the results.

(Example 3) An actual durability test was conducted under the same conditions as in Example 1 except that high concentration oxygen was injected into the PSR tire under the condition of x = 76 to carry out the deterioration promoting step. Conducted [Test (B)]. The drum life in Comparative Example 1 was set to 100, and the drum life index was displayed. Table 1 shows the results.

(Example 4) An actual durability test was conducted through a deterioration promoting step under the same conditions as in Example 3 except that the temperature of the temperature-controlled room for storing the PSR tire was 40 ° C [test (test ( B)]. The drum life in Comparative Example 1 was set to 100, and the drum life index was displayed. Table 1 shows the results.

(Example 5) An actual durability test was conducted through a deterioration promoting process under the same conditions as in Example 1 except that the temperature of the temperature-controlled room for storing the PSR tire was 20 ° C [test (test ( B)]. The drum life in Comparative Example 1 was set to 100, and the drum life index was displayed. Table 1 shows the results.

(Embodiment 6) The standard maximum air pressure of a TBR tire is set to 8.0 (kgf / cm ² ), the total pressure of the filled gas after filling is set to 8.0 (kgf / cm ² ), and high concentration oxygen is set to x. It was injected into the tire under the condition of = 80 and left in a thermostatic chamber at 80 ° C for 3 days. Then, an actual durability test was conducted in the same manner as in Example 1 except that oxygen was discharged from the tire and air was filled therein (test (A)). The drum life in Comparative Example 3 below was set to 100, and the index of the drum life was displayed. Table 1 shows the results.

(Comparative Example 3) A TBR tire having a standard maximum air pressure of 8.0 (kgf / cm ² ) was subjected to an actual durability test under the same conditions as in Comparative Example 1 without passing through a deterioration promoting step due to high concentration oxygen. I went. The drum life in this Comparative Example 3 is 1
The results are shown in Table 1 as 00.

(Comparative Example 4) In a TBR tire, not high concentration oxygen but air (oxygen concentration is x = 21)
Was injected and stored in a thermostatic chamber at 80 ° C. for 12 hours (0.5 days), and then an actual durability test was conducted under the same conditions as in Example 6. The drum life in Comparative Example 3 was set to 100, and the drum life index was displayed. Table 1 shows the results.

(Example 7) A TBR tire was subjected to an actual durability test under the same conditions as in Example 6 except that the period of standing in a temperature-controlled room was 14 days [Test (A)]. The drum life in Comparative Example 3 was set to 100, and the drum life index was displayed. Table 1 shows the results.

(Embodiment 8) In a TBR tire, under the same conditions as in Embodiment 7, except that 300 cc of water was injected together with gas into the tire at the time of assembling the rim, and the period of standing in a temperature-controlled room was 14 days. A durability test was conducted [Test (A)]. The drum life in Comparative Example 3 was set to 100, and the drum life index was displayed. Table 1 shows the results.

(Example 9) A TBR tire was subjected to a deterioration promoting step under the same conditions as in Example 6. The oxygen was then evacuated from the tire and air was infused. The first actual durability test was performed under the same conditions as in Example 6 with respect to the drum life 100 of Comparative Example 3 for a running time corresponding to an index of 30. Next, after exhausting air, inject high concentration oxygen into the tire under the same conditions as the previous deterioration promoting step, carry out secondary deterioration promoting step, discharge oxygen from the tire and inject air A second actual durability test was conducted under the same conditions as in Example 6 [Test (C)]. 1 drum life in Comparative Example 3
As 00, the index of the drum life in the second actual durability test was displayed. Table 1 shows the results.

[0037]

[Table 1]

According to the pneumatic tire testing method of Examples 1 to 9 including the step of accelerating the deterioration of the tire by oxygen of the present invention, it is possible to obtain a result very similar to the deteriorated state of an actual tire in a short period of time. I understood. In particular, in Example 8 in which water was enclosed in the tire, it was confirmed that not only the rubber composition of the tire but also the deteriorated state of the tire cord was very similar to actual use. Further, it was found that Example 9 in which the deterioration promoting step and the actual durability test are repeated twice each can reproduce the deterioration state over time in the recycled tire in an extremely short period of time. On the other hand, each comparative example that did not go through the deterioration promoting step due to high concentration of oxygen is significantly different from the state of the tire actually used, and it was confirmed that the durability evaluation that appropriately reproduces the deterioration with time in actual use cannot be performed. It was

[0039]

According to the durability test method of the pneumatic tire of the present invention, aging deterioration in actual use can be reproduced, that is, durability evaluation in aging deterioration can be appropriately and efficiently performed, which is excellent. Produce the effect.

Claims (8)

[Claims] 1. In a pneumatic tire durability test process, a high concentration of oxygen having an oxygen concentration x represented by the following formula (I) of 30 or more is injected into the tire to accelerate deterioration of the tire due to oxygen. A pneumatic tire durability test method comprising the steps of: Formula (I) x = (PO / PT) × 100 (%) [In the formula, PT is the total pressure (kgf / c) of the filling gas after filling.
m ² ), PO is the partial pressure of oxygen (kgf) with respect to the total pressure.
/ Cm ² ). ] 2. The step of promoting deterioration of a tire by oxygen includes i) injecting oxygen into the tire, ii) leaving or heating the tire, and iii) discharging oxygen. And, after the step of accelerating the deterioration of the tire due to the oxygen is completed, injecting air into the tire and applying a load to perform an actual durability test step, the pneumatic tire according to claim 1, Durability test method. 3. The step of accelerating deterioration of a tire due to oxygen includes i) the step of injecting oxygen into the tire, and ii) the step of leaving or heating the tire, and the deterioration of the tire due to the oxygen. After the acceleration step is completed, in a state where high concentration oxygen is injected into the tire,
The tire durability test method according to claim 1, wherein an actual durability test process is performed by applying a load. 4. The tire durability test method according to claim 3, wherein the oxygen concentration x represented by the formula (I) in the step of accelerating deterioration of the tire due to oxygen is 30 or more and 60 or less. . 5. In a durability test process of a pneumatic tire, i) a step of injecting a high-concentration oxygen having an oxygen concentration x represented by the following formula (I) of 30 or more into the tire, and ii) the tire A step of leaving or heating the tire, and a step of iii) discharging oxygen to accelerate deterioration by oxygen, and then inject air into the tire and apply a load to perform an actual durability test step. A step of exhausting air from the tire and injecting the high concentration of oxygen into the air; ii) leaving or heating the tire; and iii) exhausting oxygen. Performing a secondary deterioration accelerating step, and then injecting air into the tire and applying a load to perform a secondary actual durability test step. Formula (I) x = (PO / PT) × 100 (%) [In the formula, PT is the total pressure (kgf / c) of the filling gas after filling.
m ² ), PO is the partial pressure of oxygen (kgf) with respect to the total pressure.
/ Cm ² ). ] 6. The tire durability test method according to claim 1, wherein some or all of the steps of promoting deterioration of the tire by oxygen are performed in a temperature range of 20 ° C. to 120 ° C. . 7. The tire durability test method according to claim 2, wherein ii) the step of leaving or heating the tire in the step of promoting deterioration of the tire due to oxygen is performed for at least 24 hours. 8. The tire durability test method according to claim 1, wherein the step of accelerating the deterioration of the tire due to oxygen is performed in a state where the tire is filled with 10 to 3000 cc of water.