JP4057315B2 - Tire durability test method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a tire durability test method, and more specifically, a tire that can efficiently simulate in a short time the creep behavior associated with deterioration over time of a tire exposed to a high temperature environment, particularly in a crown portion. It relates to a durability test method.
[0002]
[Prior art]
As a conventional test method for evaluating durability against deterioration over time that occurs in a tire exposed to a high temperature environment, for example, it is described in JP-A-9-133611.
[0003]
In the tire durability test method described in the above publication, high-concentration oxygen is injected into the tire to promote deterioration of the tire due to oxygen, then air is injected into the tire, and a load is applied to the rotating drum. In this method, in order to evaluate the durability of a tire in a dynamic load state, for example, the tire deteriorates over time in a high-temperature actual use environment, Especially, the cord interlayer rubber constituting the belt deteriorates, tire diameter growth occurs, and finally the failure mode that leads to creep failure, as well as the failure mode due to other factors such as road surface conditions and load conditions Thus, the tire durability is comprehensively evaluated.
[0004]
For this reason, tires exposed to high-temperature environments will deteriorate over time and tire diameter growth will occur, and the durability of the tire will be evaluated only due to failure modes that ultimately lead to creep failure. It was not suitable as a method for evaluating only the durability of the tire itself without the influence of other factors.
[0005]
Further, as a means for evaluating only the durability of the tire itself exposed to a high temperature environment, it is useful to perform a durability test in a stationary and no-load state.
[0006]
As a conventional durability test method performed in a stationary and no-load state, for example, there is a so-called tire water pressure test method in which water is injected into a tire at normal temperature and evaluated by its breaking pressure (water pressure). In general, the test method was performed at normal temperature, and only the bead portion of the tire was often destroyed. Therefore, the test method was not suitable for evaluating the durability of the tire itself exposed to a high temperature environment.
[0007]
In addition, tires that are actually used in high temperature environments usually have a considerably long period of time before they are degraded and destroyed by creep, so if a method that can simulate such creep failure in a short period of time can be developed, the tire itself It is advantageous in that it can predict the quality of the durability.
[0008]
[Problems to be solved by the invention]
The object of the present invention is to prevent deterioration over time, particularly in a crown portion of a tire actually used in a high temperature environment, by appropriately setting a tire filling pressure and a tire heating temperature in a stationary and no-load tire. An object of the present invention is to provide a tire durability test method capable of effectively simulating the accompanying creep behavior in a short period of time.
[0009]
In order to achieve the above object, a tire durability test method according to the present invention includes a high internal pressure maintaining step in which a tire is filled with a gas, and a stationary and unloaded tire filling pressure is maintained at a constant filling pressure. heating at least the entire tread portion at a constant temperature above 50 ° C., possess a constant temperature holding step of holding at the heating temperature to at least the tire diameter growth, size growth of the tire, so as to face the tread of the tread portion It is to measure with a displacement meter .
[0010]
In addition, prior to the high internal pressure maintaining step, it is preferable to further include a step of filling the tire with a gas containing high-concentration oxygen to promote deterioration of the tire due to oxygen.
[0011]
Further, it is preferable that the filling pressure in the high internal pressure holding step is not less than the maximum air pressure and not more than 1500 kPa, and / or the gas filling into the tire in the high internal pressure holding step is performed by remote control.
The “maximum air pressure” here means the maximum air pressure (the air pressure corresponding to the maximum load capacity) specified in the JATMA YEAR BOOK (2001).
[0012]
Furthermore, the heating / holding temperature in the constant temperature holding step is preferably in the range of 50 to 120 ° C. and / or the tire heating / holding in the constant temperature holding step is preferably performed using a tire warmer.
[0014]
Also, by assembling the tire to the wheel and making it a tire wheel, by inserting a pair of fixed shafts into the center holes present on both sides of the wheel of the tire wheel, and fixing the tire wheel in a floating state, It is more preferable to place the tire in a stationary and no-load state.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Tires that have been exposed outdoors for a long time under high-temperature environments, for example, in hot weather, tend to cause creep due to deterioration of the rubber parts that make up the tire, resulting in a decrease in rubber adhesion between cord layers. Then, as shown in FIG. 1, the tire 10 will creep-destruct.
[0016]
In the water pressure test method described above, the bead portion often breaks before the belt breaks, and the durability of the tire itself due to the creep phenomenon cannot be accurately grasped. When the test is performed under the same conditions, it takes a long time, and none of the methods can accurately grasp the durability of the tire itself due to the creep phenomenon in a short time.
[0017]
In the tire durability test method according to the present invention, the tire 1 is filled with a gas to maintain the tire filling pressure at a constant filling pressure, and at least the tread portion 2 of the tire 1 in a stationary unloaded state. the whole 50 ° C. or higher, preferably heated to a constant temperature of 50 to 120 ° C., possess a constant temperature holding step of holding at the heating temperature to at least the tire 1 is the diameter growth, diameter growth of the tire 1, a tread This is to measure the creep behavior associated with the deterioration over time in a tire actually used in a high temperature environment by adopting this configuration. Can be simulated efficiently.
[0018]
In addition, when it is necessary to simulate the creep behavior efficiently in a shorter period of time, the tire 1 is filled with a gas containing high-concentration oxygen prior to the high internal pressure maintaining step to promote deterioration of the tire 1 due to oxygen. It is preferable to further include a step of causing
[0019]
The “gas containing high-concentration oxygen” mentioned here specifically has an oxygen concentration of preferably 30% or more, more preferably 30 to 99%. This is because if the oxygen concentration is less than 30%, the tire deterioration promoting effect may not be sufficiently obtained.
[0020]
Moreover, although the deterioration acceleration | stimulation process of the tire 1 can also be performed at normal temperature (for example, the atmosphere around 20 degreeC), it is further heated and performed in a temperature atmosphere higher than normal temperature, Preferably it is 20-120 degreeC, This is preferable in that the diffusion of oxygen into the rubber composition constituting the tire 1 is promoted.
[0021]
The filling pressure in the high internal pressure holding step is preferably not less than the maximum air pressure and not more than 1500 kPa. This is because the creep phenomenon is not promoted if the pressure is lower than the maximum air pressure, and if it exceeds 1500 kPa, there is a risk that the tire bursts instantaneously.
[0022]
The filling of the gas into the tire 1 in the high internal pressure maintaining step is preferably performed by remote control from the viewpoint of safety. As a method of filling the gas by remote operation, for example, a filling device may be installed in a place away from the tire.
[0023]
The heating and holding of the tire in the constant temperature holding step is preferably performed using a tire warmer 3 as shown in FIG. The tire warmer 3 is brought into contact with a heater heating section (not shown), and a fixing means such as a piercing probe 5 to the land portion 4 of the tread portion 2 as shown in FIG. A temperature controller (not shown) connected to the tire warmer 3 automatically controls the temperature of the probe 5 so as to reach a preset temperature.
[0024]
Further, when a creep phenomenon occurs in the tire 1, the tire 1 grows in diameter and eventually tends to burst. Therefore, it is preferable to determine the susceptibility of the creep phenomenon based on the diameter growth of the tire 1. .
[0025]
As shown in FIG. 4, the diameter growth of the tire 1 is measured by a displacement meter 7 arranged to face the tread surface of the tread portion 2 .
[0026]
In FIG. 4, a displacement measuring hole 8 is formed in a portion of the tire warmer 3 that is placed on the tire 1 at the center position of the tread portion 2, and the displacement meter 7 is connected to the tread portion of the tire 1. 2 shows a case where the magnetic stand 10 is positioned and fixed in contact with the land portion 2 and the measurement data from the displacement meter 7 can be read by a counter (not shown) installed at a separated position. However, the present invention is not limited to this configuration, and various modifications within the scope of the claims are possible.
[0027]
Further, as a method for bringing the tire 1 into a stationary and no-load state, for example, as shown in FIG. 2, the tire 1 is assembled to a wheel 11 to form a tire wheel, and the centers existing on both side surfaces of the wheel 11 of this tire wheel. It is preferable to insert a pair of fixed shafts 12 in the holes and fix the tire wheels in a state of floating in the air because the tire 1 can be easily set in a stationary and no-load state.
[0028]
In order to allow the fixed shaft 12 to be inserted into the center hole of the wheel 11 having a different size, the tip portion is preferably tapered, for example, conical, and the fixed shaft 12 and the wheel 11 are also tapered. In view of the relationship with the central hole, a ring-shaped spacer (not shown) may be provided between them if necessary.
[0029]
When the test was conducted using the tire durability test method according to the present invention, the test period was about 14 days, and the creep behavior similar to the creep behavior of the actual tire itself deteriorated over a long period of 6 years was simulated. We were able to.
[0030]
【The invention's effect】
According to the present invention, in a stationary and no-load tire, by appropriately setting the tire filling pressure and the tire heating temperature, it is possible to prevent deterioration over time, particularly in a crown portion of a tire actually used in a high temperature environment. It has become possible to provide a tire durability test method that can efficiently simulate the accompanying creep behavior in a short period of time.
[Brief description of the drawings]
FIG. 1 is a front view showing an example of a tire in which creep fracture has occurred.
FIG. 2 is a perspective view showing a main part of a test facility for performing a tire durability test method according to the present invention.
FIG. 3 is a diagram for explaining a method of measuring the temperature of a tread portion of a tire.
4 is an enlarged perspective view of the displacement meter shown in FIG. 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1, 10 Tire 2 Tread part 3 Tire warmer 4 Land part 5 Temperature control gauge 6 Wiring 7 Displacement gauge 8 Displacement measurement hole 9 Displacement gauge gauge
10 Magnetic stand
11 wheel
12 Fixed shaft

Claims (7)

A high internal pressure holding step of filling the tire with gas and holding the tire filling pressure at a constant filling pressure;
A constant temperature maintaining step of heating at least the entire tread portion of the stationary unloaded tire to a constant temperature of 50 ° C. or higher, and holding at the heating temperature until the tire grows in diameter ,
A tire endurance test method, wherein the tire diameter growth is measured by a displacement meter arranged to face the tread surface .   The tire durability test method according to claim 1, further comprising a step of filling the tire with a gas containing high-concentration oxygen prior to the high internal pressure maintaining step to promote deterioration of the tire due to oxygen.   The tire durability test method according to claim 1 or 2, wherein the filling pressure in the high internal pressure maintaining step is not less than a maximum air pressure and not more than 1500 kPa.   The tire endurance test method according to claim 1, 2 or 3, wherein the filling of the tire with gas in the high internal pressure maintaining step is performed by remote control.   The tire durability test method according to any one of claims 1 to 4, wherein a heating / holding temperature in the constant temperature holding step is in a range of 50 to 120 ° C.   The tire durability test method according to any one of claims 1 to 5, wherein the heating and holding of the tire in the constant temperature holding step is performed using a tire warmer. The tire is assembled by attaching the tire to the wheel to form a tire wheel, and by inserting a pair of fixed shafts into the center holes on both sides of the wheel of the tire wheel, and fixing the tire wheel in a state of floating in the air, The tire durability test method according to any one of claims 1 to 6 , wherein the tire is in a stationary and no-load state.

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